Distillation Column Report 59z6z

CE 3003 Advanced Process Design – Individual Project EXECUTIVE SUMMARY: The main objective of this project was to carry out a design on the Propane distillation column for a process that produces 1,3 Butadiene. The raw materials used are Butane, Oxygen and Water and the process capacity is 100 000 tonnes per annum nominal. In the previous work it was stated that the plant is located in China. The main location of the plant is in the capital city of the Gansu Provence, Lanzhou. This was decided as the location over other provinces due to the excellent transport links and the availability of raw materials and cheap labour. The close proximity to suppliers, customers and skilled labour all make Lanzhou the ideal location for the plant to be located. The design of the distillation column consists of the packed type. The distillation is a multicomponent distillation involving separation of Propane from the other components at very high pressure. The number of theoretical stages chosen was 16 stages based on a reflux ratio of 0.608. The column diameter calculated was 0.61 at maximum pressure gradient possible for distillation columns and 0.66m for minimum pressure gradient, which was then scaled up to 0.65m. This was a reasonable decision as it may be helpful when the plant capacity increases. The column has a height of 8m. Feed location for the arrangement of packing is at stage 3 from the top of the column. Pall rings constructed out of stainless steel with a size of 25mm is used for packing. The vessel thickness of the column is around 5mm, constructed out of stainless steel also to avoid corrosion. A preliminary design on the condenser for this distillation column was also carried out. The type of condenser is a fixed plate with a 1 shell and 1 tube . The tubes are stainless steel, 119 in number, 2.44m in length, and with a square pitch arrangement. The overall heat transfer coefficient was also calculated as 486.026W/m2C. The pressure drop on the tube side was 7.306 N/m2 (almost negligible) as only one tube is used with a very short length. The pressure drop on the shell side was 46.64 N/m2 The next section details on the Piping and Instrumentation over the column. The control system used for better efficiency of the units is also featured in the same P and ID.. The control mainly used for this, is the cascade control for the temperature and product composition, also in the varying of the bottom product flow rate to control the level at the bottom of the column. The variables

Richie Gandhi SUN-075909279

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CE 3003 Advanced Process Design – Individual Project controlled are the top and bottom temperatures including product composition and the reflux drum and also the level at the base of the column. There were two group tasks performed in this term along with the individual design. The first group task performed was the HAZOP on the feed line of the propane distillation column. The aim of the HAZOP was to evaluate the selected process line and identify the possible deviations which could result into a hazard; the possible causes to the deviations, consequences and actions needed to avoid the consequences were also discussed. An improvised P and ID was then produced after Hazop was done. The Hazop was done with Dr. Titiloye as the Study Leader. The deviations discussed include no flow, less flow, less temperature due to weather conditions, more temperature likely to occur as a result of external fire and extra phase in an event of poor separation, presence of heat transfer fluids, presence of off gases, corrosion inside the pipe catalyst pellets in the pipe and excess residue due which leads ultimately to contamination. The second group work is the economic appraisal, which was useful in concluding that if this project were to be operational; the payback period would be two years which would leave 13 years of net profit. So, from a financial aspect, the project was found to be very viable and attractive. Both the group works are attached in the Appendix VI and VII


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CE 3003 Advanced Process Design – Individual Project Contents 1.0 Project Brief: ..................................................................................................................................... 5 1.1 Introduction to the product: ........................................................................................................ 5 1.2 Production: ................................................................................................................................... 6 1.3 Location [4] .................................................................................................................................... 7 2.0 Project Plan and Objectives:........................................................................................................... 10 2.1Technical Objectives:................................................................................................................... 10 2.2 Personal Objectives: ................................................................................................................... 12 2.3 Schedule ..................................................................................................................................... 13 2.3.1Project Schedule ................................................................................................................... 13 3 The Revised Process: ......................................................................................................................... 15 4 The Chemical Design: ........................................................................................................................ 17 4.1 Calculations: ............................................................................................................................... 20 4.1.1 Reflux ratio and the number of Theoretical Stages ............................................................ 21 4.1.2 Determination of the Diameter of the Column: ................................................................. 28 4.1.3Feed Location: ...................................................................................................................... 31 4.2 Choice of Plates and Packing: ..................................................................................................... 33 4.2.1 Types of Packing: ................................................................................................................. 34 4.3 Column Internals [21][22]: .............................................................................................................. 43 5.0 CONDENSER:................................................................................................................................... 48 5.1 Energy Balance Over the condenser: ......................................................................................... 49 5.2 Shell Side Coefficient: ................................................................................................................. 54 5.3 Tube Side Coefficient: ................................................................................................................ 55 5.4 Overall Heat transfer Coefficient U; ........................................................................................... 56 5.5 Shell side Pressure Drop: ............................................................................................................ 59 5.6Tube Side Pressure Drop: ............................................................................................................ 63 6.0 REBOILER: ....................................................................................................................................... 65 6.1 Heat Duty over the Reboiler:...................................................................................................... 66 6.2 Choice of type of reboiler used with the Propane Distillation: [28] ............................................. 67 7.0 Overall Energy Balance over the Distillation Column: ................................................................... 68 8.0 Piping and Instrumentation Diagram ............................................................................................. 69 Richie Gandhi SUN-075909279

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CE 3003 Advanced Process Design – Individual Project 8.1 Control Loop ............................................................................................................................... 72 8.2 Control Systems over the Distillation Column: .......................................................................... 73 9.0 Hazard and Operability Studies HAZOP.......................................................................................... 76 10.0 Conclusion: ................................................................................................................................... 77 11.0 References: ................................................................................................................................... 78 12.0 APPENDIX: ....................................................................................... Error! Bookmark not defined. Appendix I ............................................................................................ Error! Bookmark not defined. Appendix II ........................................................................................... Error! Bookmark not defined. Appendix III .......................................................................................... Error! Bookmark not defined. Appendix IV ......................................................................................... Error! Bookmark not defined. Appendix V .......................................................................................... Error! Bookmark not defined. Appendix VI ......................................................................................... Error! Bookmark not defined. Appendix VII ........................................................................................ Error! Bookmark not defined.


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CE 3003 Advanced Process Design – Individual Project

1.0 Project Brief:

1.1 Introduction to the product: Butadiene is a simple conjugated diene. It is an important industrial chemical used as a monomer in the production of synthetic rubber. Butadiene at most of the times refers to 1,3-butadiene. 1,2-butadiene, which is a cumulated diene is an isomer which is difficult to prepare and has no industrial significance.[1] 1, 3 Butadiene (CH2=CH-CH=CH2), is a colourless gas with mild aromatic odour. Butadiene is soluble in alcohol and ether, insoluble in water and polymerizes readily, particularly if oxygen is present. It is non-corrosive and has a molecular formula of 54.09. Its boiling point is -4.4C and its vapour pressure is 1,790 mm Hg (239kPa) at 20◦C. It is easily liquefied, with a density of 0.6211 g/ml at 20C. It is soluble with ethanol, diethyl ester, and organic solvents and very slightly soluble in water. 1, 3 Butadiene has a flash point of -76C and can slowly be dimerised and may form peroxides upon exposure to air. Because 1, 3 Butadiene is a highly volatile gas, it is expected to partition in the atmosphere and then undergo rapid destruction by photo-initiated reactions. [1] A table of properties can be seen in Appendix I section (a) In 1863, a French chemist isolated a previously unknown hydrocarbon from the pyrolysis of amyl alcohol.[1] This hydrocarbon was identified as butadiene in 1886, after Henry Edward Armstrong isolated it from amongst the pyrolysis products of petroleum.[1] In 1910, the Russian chemist Sergei Lebedev polymerized butadiene, and obtained a material with rubberlike properties. This polymer discovered was too soft to replace the natural rubber in many of its uses, especially automobile tires. The butadiene industry originated during the World War II. Many of the belligerent nations realized that in the event of war, they could be cut off from rubber plantations controlled by the British Empire, and sought to remove their dependence on natural rubber.


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CE 3003 Advanced Process Design – Individual Project In 1929,Eduard Tschunker and Walter Bock, working for IG Farben in , made a copolymer of styrene and butadiene that could be used in automobile tires. Worldwide production quickly ensued, with butadiene being produced from grain alcohol in the Soviet Union and the United States and from coal-derived acetylene in .[1]

Butadiene is the raw material used [2] in the making of various synthetic rubbers and polymer resins as well as a few chemical intermediates. It is mainly used to make styrene butadiene rubber (SBR) which is used to make automobile tyres. It is also used in adhesives, sealants, coatings and rubber article such as shoe soles. SBR is has a high molecular weight, as it has excellent resistance to abrasion, it is widely used in the automobile tyre industry. Various other uses of butadiene are detailed in the table attached in Appendix I Section (b).

Figure 2: Chart Showing Various Uses of different forms of 1,3 Butadienehttp://www.sriconsulting.com/WP/Public/Reports/pie_charts/Butadiene.gif

1.2 Production:

Butadiene is produced commercially by three main processes:[3] 

Steam Cracking of Paraffinic Hydrocarbons: In this process, butadiene is a co-product in the manufacture of ethylene (the ethylene co-product process).



Catalytic Dehydrogenation of n-Butane and n-Butene (the Houdry process).



Oxidative Dehydrogenation of n-Butene (the Oxo-D or O-X-D process).


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CE 3003 Advanced Process Design – Individual Project Each of these processes produces a stream commonly referred to as crude butadiene that is rich in 1,3-butadiene. In the United States, western Europe, and Japan, butadiene is produced as a by-product of the steam cracking process which is used to produce ethylene and other olefins. The quantity of butadiene produced depends on the hydrocarbons used as feed. Light feeds, such as ethane, give primarily ethylene when cracked, but heavier hydrocarbons favour the formation of heavier olefins, butadiene, and aromatic hydrocarbons. Butadiene can also be produced by the catalytic dehydrogenation of normal butane. The first commercial plant, producing 65,000 tons per year of butadiene, began operations in 1957 in Houston, Texas. In the previous project it was decided that Oxydehydrogenation Process would be employed to produce butadiene for the plant to be built in China, which uses Butene as the main raw material. Due to the easy availability of Butane from the nearby industries, it was decided to integrate the process, where butane was first decided to be catalytically dehydrogenated to Butnene and the OX-O D Process follows after that. The specification was not clearly illustrated in the project earlier, and hence it’s now detailed further in this project.

1.3 Location [4] Since 2002, the Global Butadiene industry has maintained relatively fast growth especially in Asia due to its variety of uses. The global annual butadiene output increased from 8.08 million tons in 2002 to 10.15 million tons in 2007, with an average annual growth rate of 4.68%. China is one of the fastest developing Asian countries in the world. Along with the rapid development of china butadiene industry, the national output of butadiene increased from 725,000 tons in 2001 to 1.36 million tons in 2007, with an average annual growth of 9.4%. Even after increase in production, China has to import huge quantities of butadiene from different countries. Korea is the biggest supplier of butadiene to china.


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Figure 3 : graph to show Production Capacity and Output of Butadiene in China, 2001-2008 (Unit: 10,000 tons)http://www.researchinchina.com/s/Article/2008112601.gif It was decided that the best place locate the butadiene plant in China which can satisfy the demands of its market in near future is in Lanzhou, the capital of the Gansu province which is in north western china.

Figure 4: Map of Gansu Province in China http://janetong.com/image_gallery/data/agansubest.jpg i

While deciding the plant location several factors were taken into consideration:

Productivity - Since 1949 Lanzhou has been transformed from the capital of a poverty-stricken province into the centre of a major industrial area. The GDP per capita of Lanzhou was 25,566 Yuan (RMB) (US$3,681) in 2008, ranked no. 134 among 659 Chinese cities. Richie Gandhi SUN-075909279

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River - Lanzhou is situated at the upper course of the Yellow River. The river can provide water to the plant as the process requires large quantities of water for scrubbing and cooling. Also the river provides hydropower to the industries and cities in Gansu. A large multipurpose dam has been built in the Liujia Gorge on the Yellow River above Lanzhou. The river also helps in transportation.

Natural Resources - Lanzhou has many natural resources which include coal, gold, silver, nickel, manganese, clay and dolomite. The Coal is obtained from Qinghai which provides thermal power. The catalyst for our process is nickel which will be cheaper to buy and will be available in large quantities.

Cheap Labour - Due to the presence of the Yellow river the site is a residential area for more than 3.3 million people. Cheap labour is available for the plant. There are many top ranked universities in this province which means qualified staff will be available at the site.

Industrial area - Gansu has one of the largest oil refineries in the country and Lanzhou itself is the centre of the province's petrochemical industry. The main industries include rubber, petrochemical, oil refinery and machinery industry. Butane which is the raw material for our process is readily available and also Butadiene (product) can be sold to the neighbouring industries. Also, the machinery parts will be available from the neighbouring industries which will reduce the cost of transportation and energy and time.

Transportation - Lanzhou is very well interconnected to various cities and provinces through highways, railways and airlines. There are 3 major national highways namely China National Highways 212,213 and312, connecting Lanzhou to different provinces of the country. Transportation is cheap and easy. The Lanzhou Sustainable Urban Transport Project in China aims at improving the transport infrastructure and urban road networks. The total Asian Development Bank contribution is estimated at US$150 million. This project is under planning and is expected to get its approval by 11th Dec; 2010.This will greatly enhance the transportation of our product to different provinces when our plant is ready for production.


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CE 3003 Advanced Process Design – Individual Project 2.0 Project Plan and Objectives: The Second part of this project aims at carrying out a design study on a selected process section for the production of 100 000 tonnes per year of 1, 3 Butadiene from Butane for a plant to be built in China. Project Supervisor: Dr. James Titiloye Project Author: Richie Gandhi The process development project aims to give third year Chemical Engineering students a chance to experience what working on a project in an industry might be like. Working in groups, they must cover all the major areas involved in deg a process. The main process unit which has been discussed in this project is a Distillation Column which separates Propane from 1,3 butadiene. Within this task other objectives have been set to ensure that the goal is met which are outlined below:

2.1Technical Objectives:  Chemical engineering design to achieve the following outcomes is to be done 

Understanding solving a complex engineering design problem



Design a distillation column according to the engineering standards



To design a distillation column to meet the desired criteria



Gain an understanding of chemical engineering unit operations

 Description of a control system for the distillation column for best possible results is to be done 

To study concepts of process control including principles of and feed forward, apply these concepts to the design of instrumentation and control system for a distillation column.



Propose a control system which will execute the desires of the process functionality

 Piping and Instrumentation Diagram for the distillation column is obligatory 

Exhibit an understanding of engineering codes, standards and regulations



Develop skills through use of computer software such as Microsoft Visio


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CE 3003 Advanced Process Design – Individual Project  Carry out a group study on the HAZOP for any one of the individual selected processes to achieve the following outcomes 

To be able to investigate how the chemical plant might deviate from the design intent



To be able to identify scenarios that would lead to the release of hazardous and flammable materials to the environment and also to determine whether a particular deviation would result into an hazard



Work effectively in a team to achieve the project goal

 Economic appraisal (group work) for the full process on production of 1,3 Butadiene in order to gain the following outcomes 

Work effectively in the group to enhance team work skills



To estimate the costs and benefits of production of products using the desired process route



To study the economic feasibility of the production of products

 Written report preparation based on the selected design to achieve the following 

Assemble and use relevant background information



Provide Complete Referencing



Appendices containing lengthy derivations, calculations, large drawing, computer printouts etc.


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CE 3003 Advanced Process Design – Individual Project 2.2 Personal Objectives:  Understanding how chemical process work: Upon completion of this project, a better understanding of the Butadiene process will be gained. Also technical skills in carrying out a detailed distillation column design study will be improved, which will help towards future projects as a chemical engineer.  Enhance organisational skills and keeping to deadlines: The tasks would be scheduled at regular meeting with the supervisor where the deadlines will be decided which have to be met for a successful project.  To utilize our initiative: Many decision making processes will be used in the undertaking a couple sections of this project. Each member will need to use their initiative to come to a sensible and reasonable conclusion, which will benefit the entire group.  Develop Communication Skills: Communication skills are enhanced both by meetings with the supervisor and the group meetings. This would provide and individual a platform to build his confidence and propose his ideas.

 Enhance Team-working Skills: HAZOP and Economic Appraisal have to be carried out as a group. The group are required to co-operate with each other, share and listen to ideas and take constructive criticism from group . This will encourage each member to provide advice and .  Professional report writing: At the end of our project I wish to able to deliver a professionally laid out report.


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CE 3003 Advanced Process Design – Individual Project 2.3 Schedule To me in achieving these objectives a schedule has been devised to plan the project and ensure that all required tasks are undertaken, within the time period set for the study to be completed. This can be seen below. A Gantt chart is also attached for assistance in the Section 3(b) in the Appendix II. This is the revised Gantt Chat according to with the schedule has actually been carried out. A Gantt chart which was made earlier to aid in maintain time is attached in Section 3(a) in the Appendix II 2.3.1Project Schedule Serial No.

Objective

Start Date

End Date

 Get on report/presentation and 1

mass and energy balance from Dr. Titiloye  Submit project plan.

2

19/01/10

22/01/10

 Tutor meeting and discussing the topic.  Gathering relevant information from 1st

25/01/10

29/01/10

term project

3

 Discuss findings with tutor  Put together a list of all the equations

01/02/10

07/02/10

08/02/10

19/02/10

22/02/10

5/03/10

required to design a Distillation Column for the process  Start Deg the Distillation Column in the Butadiene production process.

4

 Calculating diameter and size of Distillation Column along with the flow though them thereby completing the design  Review the mass balance and calculating other dimensions


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5

 Piping and instrumentation diagram

1/03/09

10/03/10

 Control and instrumentation research  Calculating cost and profit

6

 HAZOP

10/03/10

19/03/10

7

 Calculating cost and profit

01/03/10

15/03/10

 Completing referencing

25/01/10

17/03/10

 Executive summary

13/03/10

17/03/10

 Ensuring completion of all section

20/03/10

21/03/10

22/03/09

26/03/09

 Economic appraisal

8

9

 Submit report  Review with tutor  Make changes

10

 Proof read  Submit report

To complete the objectives of the project various sources would be utilised for research work. The main source of information used will be university library, Birmingham city library, Aston University’s access to online journals, internet and ing companies in relation to scope of the project. Discussions would be carried out with Dr. Titiloye to check the track of the work and to ensure correct research is carried out.


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3 The Revised Process: Phillips OXO-Process [3] The n-butene, steam and air react at 590-650°C on a fixed bed heterogeneous catalyst (probably a ferrite (iron or iron alloy) with Zn, Mn or Mg). Addition of steam controls the selectivity. With butane conversions between 75-80%, the butadiene selectivity reaches roughly 88-92%.

C4H8 + ½ O2

Magnesium ferrite C4H6 + H2O..................................(1) 1 bar / 590-650°C

It is a one step process, where Butene gets oxidised straight away, without the need of butane dehydrogenation. Since our plant is close to an oil refinery plant, where butane can be obtained at a cheaper price in abundance, a decision to integrate the conversion of Butane to Butene in our process was made. This reaction would take place in the first reactor and then the produced butene is fed into the second reactor for further processing. The catalytic dehydrogenation of Butane to Butene is not a part of our OXO process which we had considered in the previous report.[3] The same method was carried out in the first project, but it was not stated clearly stated in literature. Tubular Rector

C4H10 + O2

0

1Atms/590 C Cromina-Alumina

C4H8 + H2O.................................(2)

Equation (1) gives 100% completion; higher conversions at lower temperatures are possible with fewer side reactions and improved yields. It is also easier to remove the hydrogen as it is now present as water vapor and can be condensed out. It is an exothermic reaction; heat input to the reactor is thus eliminated as heat is recovered to generate high pressure steam. By feeding stream and air to the reactor it is possible to carry out continuous in-situ catalyst regeneration. The steam also absorbs some heat released by a small amount of hydrocarbon oxidation and has a beneficial effect on butene selectivity to butadiene. In general, the equipment used is smaller and utilities usage is reduced for a given throughout compared with the conventional dehydrogenation process. A typical flow goes from the feed stream, with a composition of butene feedstock, 90% n-butene, Richie Gandhi SUN-075909279

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CE 3003 Advanced Process Design – Individual Project 5% butane, 2% of small amounts of Hydrocarbon and 1% Butadiene. Air is compressed and mixed with steam before heating in a furnace at 480-590◦C. This mixture is then blended with butenes and ed over the oxidative dehydrogenation catalyst bed in the reactor. Three reactors are used in parallel (multitubular reactor) with a fixed bed of mixed oxide catalysts, feeding into a single stream recovery and purification train. The products from the reactor are cooled. Heat is recovered from reactor effluent with water sprays and can be used to generate process stream. After quenching, Stream is cooled to about 400◦C, by direct with cold water. Cooling the stream causes condensation, the condensate being removed by a simple phase separation. Washing and scrubbing occurs in order to remove all water-soluble impurities, the C4 fraction is recovered in an oil absorption section. The mineral oil absorber has the ability to absorb the hydrocarbon components of the stream, in this case the butadiene whilst rejecting gases such as nitrogen, carbon dioxide. The fat oil is stripped and crude butadiene is transferred to the final purification step. The product is then obtained from the tailing column which is then fed into the recovery unit. Small amounts of oxygenated compounds are also produced and these are separated and taken to a waste disposal unit. Water sprays are used to reduce fouling in the plant. The advantages for this process are that the catalyst life is long which lasts for around 1000 hours. The capital costs compared to the other oxidative dehydrogenation process routes are more favorable because of the low steam requirements for the mixture and the relatively high concentration of butadiene leaving the reactor. Reactors are set up to de-coke the catalyst and restore its activity, and to allow more effluent output of butadiene. At high temperatures (up to 6000C), oxygen acts to oxidatively regenerate the catalyst. Also there are a class of metal Vanadate catalysts that are newly being used, which has highly selectivity and high conversions and the formation of oxygenated by-products is suppressed. The feedstock raw materials are inexpensive in the United States; a major factor causing this is the trend towards greater usage of feedstock such as natural gas liquids (ethane, propane). However, there is a growing shortage of these raw materials, encouraging the use of heavy feedstock such as ethylene. During this process, various by products are produced. These by-products must be removed to produce butadiene, so it can be polymerised. One major by product is vinyl acetylene, which is a highly unsaturated compound, a poison for the catalysts that polymerise butadiene. Therefore there is a need to produce a purification process by providing a stream with distillation steps. This allows the process to be energy-conserving and simple. Richie Gandhi SUN-075909279

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A revised Flow Sheet is attached in Appendix III. A compressor is added after the extractive distillation column, in the new flow sheet that increases the pressure of the process before it can be sent to the Propane Distillation Column for further purification. I assume the mass balance to be correct as it was based on many assumptions which were acceptable. A Copy of the Mass Balance done in the previous project is attached in Appendix IV.

4 The Chemical Design: The design chosen for this project is a continuous distillation column. The separation of the liquid mixture by distillation depends on differences in volatility between the components. The separation becomes easier if the differences in the volatilities between the components are massive. Figure 5 shows a basic distillation column. The liquid mixture is heated up and routed into the distillation column. The feed when enters the column flows down. Heat is vaporise the volatile components is provided by the reboiler. The components with lower boiling points vaporise and rise to the top of the distillation column. Vapour flows up and the liquid flows counter currently down the column. These two phase come in with each other on a surface which can be trays or packing. The composition of the vapour above the liquid differs from the liquid composition. The vapour is then separated and condensed into a liquid; it becomes richer in the lower boiling component(s) of the original mixture. Part of the condensate from the condenser is returned to the top of the column which provides liquid flow above the feed point and part of the liquid from the base of the column is vaporised in the reboiler and returned to provide vapour floe rate. [5]


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Figure 5: Basic Distillation Column http://wpcontent.answers.com/wikipedia/commons/e/e0/Distillation_Column.png The highlighted distillation column in the flow sheet in Appendix III is the Propane/Butadiene distillation column which is considered to be designed. The main objective of this unit is to get rid of propane from the process. The distillation is a multi-component distillation thereby it involves more than two components. It operates at very high pressure of 13.5 bars and consists of three streams. The feed enters the distillation column at a temperature of about 350C. On distillation, the Propane vapour leaves the top of the column to the condenser and collected in the reflux drum. Partial amounts of 1,3 Butadiene is also lost at the top of the column. The bottom product majorly comprises of 1, 3-Butadiene, 1, 2-Butadiene and Pentane.


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CE 3003 Advanced Process Design – Individual Project The table below shows the preliminary Mass Balance over the Distillation Column Table 1 (a): FEED: Components

Flow rate (kg/h)

Kmols/hr

Kmols fraction

Propane

424.23

9.64

0.04

1,3 butadiene

11904.76

220.46

0.91

1,2 butadiene

500.00

9.26

0.038

Pentane

138.84

1.93

0.008

Total

12967.83

241.29

1

Table 1 (b): Distillate: Components

Flow rate (kg/h)

Kmols/hr

Kmols fraction

Propane

424.23

9.64

0.687

1,3 Butadiene

237.6

4.4

0.313

Total

661.83

14.04

1

Components

Flow rate (kg/h)

Kmols/hr

Kmols fraction

1,3 Butadiene

11667.16

216.06

0.951

1,2 Butadiene

500.00

9.26

0.041

Pentane

138.84

1.93

0.0085

Total

12306.00

227.25

1

Table 1 (c): Bottom:

The boiling points of the feed components at 1 atmospheric pressure are as below: Propane: −42.09 °C 1,3 Butadiene: -4.4 °C 1,2 Butadiene: 10.8 °C Pentane: 36.1 °C Looking at the temperature differences it can be said that the components can be separated easily by reducing the temperatures but since in tangible situations, it is very expensive to reduce down the temperatures in the plant for continuous process we have to increase the pressure inside the


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CE 3003 Advanced Process Design – Individual Project unit to separate it at reasonable costs. This is done by using compressors or pumps before the feed is fed into the unit. It is assumed that the distillate is at a temperature of 400C which is a reasonable assumption as chilled water can be used to cool down the components in the distillate. Taking this as our basis we can calculate the pressure and temperature for rest of our unit using Antoine’s Equation. Detailed calculations are attached in Appendix V; Section (a)

4.1 Calculations: Basis: 1hr Units: 1 Kg Propane boiling point: 40°C/313K @ 13.5 bars Specifications Feed condition: Cold Liquid under pressure Feed inlet temperature @35°C/308K Temperature of Top of distillation column @ 45°C/318K Temperature of Bottom of distillation column @ 95°C/368K Therefore column Temperature will be taken as the average @ 70°C/343K The detail distillation design was performed by using the main steps below -

Determination of reflux ratio and number of stages required for the distillation

-

Calculation of the column diameter and determining the type of column to be used, Packed or trays

-

Column design in detail


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CE 3003 Advanced Process Design – Individual Project 4.1.1 Reflux ratio and the number of Theoretical Stages The vapour reaching the top of the column is totally condensed and the resulting liquid is divided into two parts. One part, L (reflux), is returned to the column and the other part, D (distillate), is withdrawn as product. The reflux ratio is the ratio of L to D, that is R = L/D. [6] Smaller values of reflux ratios means less the number of theoretical stages in the distillation column increases, which reduces the energy costs as most of the vapour is condensed as distillate and only partial amounts of reflux is sent back to the column. The minimum reflux ratio and the infinite reflux ratio place a constraint on the range of separation operation. Any reflux ratio between Rmin and Total R will produce the desired separation, with the corresponding number of theoretical stages varying from infinity at Rmin to the minimum number (Nmin at Total R). The relationship between R and N is shown in the Figure below. The choice of reflux ratio to use is governed by cost considerations [7]

Figure 6: Generalised graph between number of theoretical stages V/S Reflux Ratio http://www.separationprocesses.com/Distillation/DT_Chp04n.htm

Calculations: The minimum reflux ratio is calculated by using Underwood method. [8]


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CE 3003 Advanced Process Design – Individual Project Since the minimum reflux is calculated for a distillation column which consists of four components, four variables are used in the above equation. For a multi-component mixture to be split into two streams (distillate and bottoms) by distillation, it is common to specify the separation in of two ‘’key components’’ of the mixture. Hence in this way multi components can be reduced to equivalent binary systems.

Light Key: Most Volatile component in the Bottom Product Heavy Key: Least Volatile component in the Top Product. [8] Hence, from the table 1 (b) and (c); Heavy Key (HK) – 1,3 Butadiene Light Key (LK) – 1,3 Butadiene This will cause a problem in the calculation, since both the HK and LK are the same component therefore an unreasonable reflux ratio will be obtained. Therefore to trounce this problem, a small amount of Propane was added to the bottom product, making Propane the LK. I assume that 99% mole of propane and 2% mole of 1,3 Butadiene is now in the Distillate and the remaining are the bottom product. Revised Balance over the distillation column is as follows: Table 2 (a); FEED Feed Flow rate Components

(kg/h)

Propane

424.23

1,3 butadiene

Kmol Fraction

9.64

0.04

220.46

0.91

9.26

0.04

11904.76

1,2


Kmols/hr

butadiene

500.00

Pentane

138.84

1.93

0.01

Total

12967.83

241.29

1

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CE 3003 Advanced Process Design – Individual Project Table (b); Distillate and Bottoms Distillate

Bottoms

Components

Kmols/hr

Kmol Fraction

Kmols/hr

Kmol Fraction

Propane

9.544

0.684

0.096

0.0005

1,3

4.41

0.316

216.05

0.95

-

-

9.26

0.041

Pentane

-

-

1.93

0.0085

Total

13.954

1

227.336

1

butadiene 1,2 butadiene

Therefore new key components are: HK – 1,3 Butadiene LK – Propane The next step is to find the relative volatilities of each component with respect to the HK which in this case is 1, 3 Butadiene. The calculations are attached in the Appendix V, Section (b) and are tabulated below: Table 3: Components

α

Propane

α =2.724

1,3 Butadiene

α= 1

1,2 Butadiene

α = .66

Pentane

α = .31

Using the UNDERWOOD EQUATION:

Where q ≠ 1 as the feed is cold liquid @ 35°C.


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CE 3003 Advanced Process Design – Individual Project Calculation of feed condition q[9]:

Therefore,

Table 4: Latent Heat of the Components inside the Column [9] Components

Latent Heat in

Relative

Calculation

KJ/Kg

Molecular

Latent Heat in KJ/Kmol

Mass Propane

229.93

44

229.93*44

10116.92

1,3 Butadiene

335.55

54

335.55*54

18119.7

1,2 Butadiene

387.38

54

387.38*54

20918.52

Pentane

333.24

72

333.24*72

23993.28

Latent Heat = (10116.92* 0.04) + (18119.7* 0.91) + (20918.52* 0.038) + (23993.28* 0.008) Latent Heat = 17880.454 J/mol or KJ/Kmol Table 5: Specific Heat of the Components inside the Column [9] Components

Specific Heat in KJ/KmolK


Propane

81.84

1,3 Butadiene

138.78

1,2 Butadiene

136.08

Pentane

182.88

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CE 3003 Advanced Process Design – Individual Project Specific Heat to Vaporize the 1 mol of feed = m∆T + mHvapuorisation => {[(81.84*0.04) + (138.78*0.91) + (136.08*0.038) + (182.88* 0.008)] * (70-35)] } + 17880.454 J/mol Specific heat to Vaporise 1 mol of feed to 70oC = 4766.79 J/mol + 17880.454 J/mol Therefore, Specific Heat = 22647.244 J/mol

q = 1.267 Using the above value of “q” in the Underwood Equation (1), θ is obtained;

θ

θ

θ

θ

Therefore; by using excel spread sheet: Θ= 2.67; which is acceptable as the value for Θ should lie between the values obtained for relative volatility of heavy key and light key. Next, proceed to calculate Rmin.

Rmin +1=1.468, therefore Rmin = 0.468. Reflux ratio is generally between 1.1 -1.5 times the minimum reflux ratio based on practical values but there is no relationship between Rmin and the optimum value.[8] R = 1.1*0.468= 0.515 To find the number of theoretical stages using FENSKE EQUATION [11]


Page 25


Therefore,

From CHART – Erbar-maddox correlation in the figure below we have,

Graph 1: Ebbar Maddox Correlation


Page 26

CE 3003 Advanced Process Design – Individual Project N= 20 theoretical stages Table 6: Number of theoretical stages at different Reflux Ratios R

R/R+1

Nm/N

N

1.1*0.468 = 0.515

0.34

0.4

20

1.2*0.468 = 0.562

0.36

0.42

19

1.3*0.468 = 0.608

0.39

0.49

16

1.4*0.468 = 0.655

0.4

0.53

15

1.5*0.468 = 0.702

0.41

0.55

15

1.6*0.468 = 0.749

0.43

0.58

14

From the above observations it is clear that increasing the reflux ratio reduces the number of stages. But it is seen that increasing the minimum reflux ratios by 1.4 to 1.5 does not changes the number of theoretical stages. There are two options available to decide which reflux ratios could be used in our design. Either a line can be drwan from the origin of the graph as shown below which means that the best available technique is a mid way between the number of stages and the reflux ratio or this can be debated on the basis of economic costs.

Figure 8: Selection of Reflux ratio and the number of stages http://www.separationprocesses.com/Distillation/DT_Chp04n.htm

The increase in the reflux ratio reduces the number of stages in a distillation column. But energy costs shoot up which has to be considered as well. Since the Distillation column is almost running


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CE 3003 Advanced Process Design – Individual Project for (350 days* 15 years) approximately, it is not a good option to run the column at high reflux ratios. But if very low reflux ratios are opted, the metal costs to build the column go up. The reflux ratio chosen for the process is 1.3 × Rmin. I have decided to use a reflux ratio of 0.608 which requires reasonable costs and the number of stages are also acceptable. [8]

If the Feed is assumed to enter the column at its boiling point there is a huge difference in the reflux ratios 4.1.2 Determination of the Diameter of the Column: FAIR CORELLATION (1961)[10] is used to calculate the diameter of the column. To find the diameter, velocity of the fluids has to be calculated. The calculations are detailed below: Internal Traffic [11]: L =RD ; 0.608*661.83 = 402.39kg/hr L’ = L + qF ; 402.39+(1.267*12967.83) = 16832.63 kg/hr V = L+D ; 402.39+661.83 = 1063.22 kg/hr V’ = V – (1-q)F ; 1063.22 – (1-1.267)* 12967.83= 4525.63 kg/hr FLV = L/G (ρV/ρL)0.5

[18]

where;

L = Liquid mass flow rate, kg/s G = Vapour mass flow rate, kg/s Vapour density, kg/m3 = ρV Liquid density, kg/m3 = ρL The calculation of ρL and ρv (see section (C) of Appendix V) ρL = 599.69 Kg/m3 and ρv = 30.324 kg/m3 The Flooding correlation is calculated at both the sides of the column because it can be a stepped column. Therefore, the flooding correlation above the feed


Page 28


Using the CHART –flooding velocity, sieve plates, in Graph 2 and taking a generalized plate spacing of 0.6m:

Graph 2: Flooding Velocity Sieve plates

K1 (top) = 0.1 The velocity can now be calculated by;

Hence,

Taking percentage flood @ 80% based on good design considerations, therefore velocity @ flooding: uf (top) = 0.8*0.4333 => 0.34664 m/sec


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Maximum Volumetric Flow Rate:

Net Area Required

Allowing 10% for down comer and 10% for rings; There total area = 0.028*1.1*1.1 = 0.034 m2 Hence column diameter above the feed point;

√

√

Similarly for the lower section of the column;

Using the CHART –flooding velocity, sieve plates in Graph 2; taking a generalized plate spacing of 0.6m: K1 (bottom) = 5*10-2 The velocity can now be calculated by;


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Taking percentage flood @ 80% based on good design considerations, therefore velocity @ flooding: uf (bottom) = 0.8*0.21665 => 0.17332 m/sec

Maximum Volumetric Flow Rate:

Net Area Required

Allowing 10% for down comer and 10% for rings; There total area = 0.237*1.1*1.1 = 0.288 m2

Hence column diameter below the feed point; √

√

4.1.3Feed Location: The number of stages is greatly affected by the subsequent position of the feed into the column. The feed should enter the column at a point that matches best with the composition of the feed. It is always a wise decision to provide two or three feed point nozzles around the predicted feed point which will for the changes in the feed compositions after the start up. The propane Distillation column is operating under high pressure. Hence, the feed is either compressed or pumped into the column. It can be made to compress to a slightly higher pressure Richie Gandhi SUN-075909279

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CE 3003 Advanced Process Design – Individual Project into the feed pipe, approximately 14 bars, so that when it enters the column which is slightly at a lower pressure than the pipe, some of the propane from the components will immediately expand and undergo a partial flash vaporisation resulting in vapour liquid separation as it enters the distillation column.

4.1.3 Calculation of the Feed Position: Krickbride(1994)[13] can a practical equation to calculate the feed point location

[

]

Where, Nr = number of stages above the feed, including any partial condenser Ns = number of stages below the feed, including the reboiler B = Molar Flow Bottom Product D = Molar Flow Top Product XfHK = concentration of the heavy key in the feed XfLK = concentration of the light key in the feed XbLK = concentration of the light key in the bottom product XdHK = concentration of the heavy key in the Distillate

Therefore, by substituting the values in the above equation;

[


]

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CE 3003 Advanced Process Design – Individual Project This can also be rewritten as; ......................(A)

Since the total number of stages being used is 16, Therefore;

Substitution the value of Nr from Equation (A) in equation (B), We get, Ns = 12.8 (≈ 13) which means, there are 13 stages below the feed position which includes the reboiler as well. Since, the feed location is almost at the top of the column leaving 3 stages, the design of a stepped column is pointless. It is made with an overall diameter of 0.6m.

4.2 Choice of Plates and Packing: The calculated value for the distillation column is approximately 0.6 m. The choice between packing and trays was made on the basis of advantages and disadvantages of each type, and it is concluded that a PACKING would be best for such small diameters. This decision was made because: [14] 

Plate columns are generally designed to handle wider range of vapour and liquid flow rates than packed columns. Since the gas flow rates in the top of the column is minor, plate installation would not be a good idea.



Packed columns are not suitable for very low liquid flow rates.



The pressure drop per equilibrium stage (HETP) is lower for packing than plates. Since, the column is operated at high pressures; it would be a better option to choose packed column rather than plates to avoid complications.



Packing should always be considered for smaller diameters, generally for column diameters >0.9m as it is very expensive and difficult to install plates in such columns.

After the decision is made, the design over the packed column has to be done. This includes the following procedures: [14] 

The type and packing size has to selected corresponding to the diameter of the column



Determining the height of the column required for the desired separation


Page 33

CE 3003 Advanced Process Design – Individual Project 

Calculation of the column diameter (capacity), to handle the liquid and vapour flow rates.



Selection of column internal features like; packing , liquid distributor, redistributors.

4.2.1 Types of Packing: A packing should always fulfil the following requirements: [14] 

Provide a large interfacial area between the gas and the liquid.



Should have an open structure for low resistance to gas flow.



Should provide consistent liquid distribution on the packing surface



Promote unvarying vapour gas flow across the column cross section

Hence, keeping the above requirements into consideration, the packing is broadly classified as  Structured Packing: These are packing with standard geometry made of wire mesh or perforated metal sheets which are folded and arranged together. Some metal structured packing commonly used in distillation columns are shown in the figure 10. They have low height of equivalent theoretical plates (HETP) and low pressure drops. They are generally used in difficult separations which require many stages, like separating isotopes or in high vacuumed distillation columns. Using structured packing can also used to increase the capacity and reduce the reflux ratio requirements.

Figure 10: Structured Packing http://img.alibaba.com/photo/50678452/Ceramic_Metal_Plastic_Structured_Packing.jpg


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CE 3003 Advanced Process Design – Individual Project  Random Packing: These are variously shaped in rings, saddles etc, and are dumped into the distillation column to take up a random shape. These structures can be made up of plastics, ceramics and metals. The various types of random packing are shown in figure 11 below. The packing manufacturers should be consulted for details for many special types of packing that are available for special applications.

Figure 11: Various kind of random packing http://img.alibaba.com/photo/50553772/Ceramic_Random_Packing.jpg

Raschig rings are the oldest types of random packing whose length is equal to the diameter. These are cheaper compared to any of the random packing structures but not as efficient as others. These were then modified to Pall rings which have openings made by folding strips of the surface into the ring. This increases the liquid distribution by increasing the surface area. Other types of random packing are, Berl Saddle Ceramic, Intalox Saddle Ceramic, Metal Hypac and Super Intalox Ceramics.


Page 35

CE 3003 Advanced Process Design – Individual Project Selection of Packing: Type and Material [15]: From the above information it would be cheaper to use Random Packing with Metallic (CarbonSteel) Pall Rings. This is because the column is operating at high pressures and has a very small diameter. Also the components inside the column are non-corrosive. It would require too much effort and capital to install structured packing inside the column which would separate the same amount of propane. Also Ceramic pall rings can be considered, but they are more expensive than the metallic ones.

Figure 12: Metallic Pall rings http://www.pall-ring.com/images/product/Chempack_metal_pall_ring_02.jpg

Packing Size [15]: The largest size of packing suitable for any size of column should not exceed more than 50mm. This is because the larger packing sizes would cause flooding due to poor liquid distribution. Very small sizes are also available but are much more expensive than the larger ones. The sizes recommended for different column diameters are: Table 7: Packing size depending on the Column Diameter Column Diameter

Packing Size

< 0.3m

< 25mm (1inch)

0.3 m to 0.9m

25mm to 38mm (1inch to 1.5 inches)

> 0.9m

50mm to 75mm (2 inch to 3 inches)

Hence, for the Propane distillation column Metallic Pall rings with a size of 25mm is used. Richie Gandhi SUN-075909279

Page 36


Column Diameter (capacity)[16]: A distillation column is always designed to operate at height economical pressure drop. This ensures good liquid and gas distribution. For random packing the pressure drop normally does not exceed more than 80mm of H2O/m of the packing column. A distillation column’s design values for pressure gradients are between 40 -80 mm Hg/m packing. [17]

These values are almost halved when the liquid starts to foam. The proposed design has a

diameter of 0.61m with trays. Since random packing is now considered a new diameter has to be calculated.

Pressure gradient over the enriching section using column diameter as 0.61m

A generalised pressure gradient/flooding correlation graph can be seen in Graph 3 below:

Graph 3: Graph to determine the Flooding Line


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CE 3003 Advanced Process Design – Individual Project Values for “x” and “y” axis can be calculated and the flooding line can be plotted in the figure above. √ Where, L = Liquid Rate per Area G= Gas Rate per Area Since the area remains same; the ratio can just be taken as the normal flow rates of vapours and liquids. Hence; √

Now,

Where, Fp = Wet Packing Factor; Appendix V; section (d) Ψ = Ratio; (density of water/Density of Liquid inside the column) μL = Liquid Viscosity of 1,3 butadiene is considered in the calculations, as major fraction of the liquid comprises of 1,3 Butadiene g = Gravitational constant

Hence;

From the Graph 3; the flooding line is calculated at 6, which is 81 mm Hg/meter. This result is acceptable since the pressure gradient calculated above, 6mm Hg, it is concluded that the system is expected to run at very extreme pressure gradients.


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CE 3003 Advanced Process Design – Individual Project The values of pressure gradients for the lower range over the distillation column can be used to calculate a new diameter. Any of the values between the two ranges can be used for the design.

From the same graph above a new value of “ ” is plotted at 40mmHg/m is now calculated. Hence the Flooding line would be,

As 13.6 mm Hg is the specific gravity of mercury. “ ” axis in now 0.015. Again using Equation on the Y axis in Graph 3; a new gas flow rate per area is calculated which would give the new diameter. √ Since,

Therefore,

Since the gas flow rate per area in decreased; the diameter has to be increased. Hence, √

√

Since, the change in diameter is not drastic the packing used can still be suitable for this diameter. The capacity of the column can be anything between 0.61m – 0.66m depending on the flooding line. Hence, it has been concluded that the capacity will be 0.65m; which can also be helpful when the production capacity of the plant increases. The flooding like can be changed accordingly.


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CE 3003 Advanced Process Design – Individual Project Packed Bed Height:[18] The heights of equivalent equilibrium stage or HTEP is the height of a single packing which gives the same amount of separation as an equilibrium stage in a trayed column. The HTEP is for a specific type of packing is usually constant and is independent of the physical properties of the components. This provides good liquid distribution and does not let the pressure drop fall below 17mm H 2O/m of the packing height.

Table 8: The recommended HETP’s for Pall rings Size of the Pall Ring in mm

HETP in m

25mm

0.4m – 0.5m

38mm

0.6m – 0.75m

50mm

0.75m – 1.0

Hence, HETP for the propane distillation column is 0.5m as the size for pall rings used is 25mm.

This means, one stage is 0.5m since there are 16 stages calculated earlier, total height of the column = 0.5*16 = 8m Flooding is prevented due to the tall height of the column. Since the feed stream is put after 3 stages; the position of the feed stream is (0.5m*3 stages) 1.5 m at the top and the length below it is 6.5 m.

Choice of material used for construction: The column is decided to be made up of stainless steel (18Cr/8Ni, Ti stabilised)(321). Steel is a very strong metal with high ductility and high malleability which can withstand high stress. Since the column has to with stand high pressures and high temperatures, poor choice of material should not be used. Also the column is very tall. Also stainless steel does not corrode. It is more expensive than carbon steel, but it one time investment is affordable. Also the column is required for purification purposes; hence any corroded metal in the product would not be appreciated.


Page 40

CE 3003 Advanced Process Design – Individual Project Thickness of the metal: It is assumed that the column is cylindrical in shape. The welds are fully radio-graphed. This column is operating at very high pressure of 13.5 bars. Hence, a pressure has to be designed in such a way that the column resists the increase in pressure due to equipment failure. Internal pressure is designed at 10% above operating pressure. = (13.5 – 1)* 1.1 => 13.75 bars (1.375N/mm2)

The thickness of the cylindrical section of the column can be calculated by a formula from British standards PD 5500:

Where, Pi = Internal pressure σs = Design Stress for stainless steel @ 1000C; Appendix V; section (e) e = minimum thickness of the material Hence,

Allow 1mm for corrosion; Hence the thickness of the cylindrical section should be 4mm.

The thickness of the Domed Section of the column can be calculated by:

A standard dished head (torisphere) is assumed;

Crown Radius, Rc = Di = 0.65 m


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CE 3003 Advanced Process Design – Individual Project Knuckle radius = 6%of Rc = 0.039m (

√

)

(

√

)

A head of this size would be formed by pressing: no ts, hence, J = 1

Substituting, correct values in the above equation;

A tank diameter of less than 15m should have a minimum allowable thickness of 5mm [16]. The thickness obtained from calculation would hold the weight of content in the vessel, but would not stand depression or dent. Therefore, a 5mm minimum allowable thickness was given for any vessel less than 1m because this can withstand depression. Hence, the results obtained are acceptable.

Diameter and Thickness of the Pipes: It is decided to use Pipes made of Stainless Less because they have high tensile strength and are ductile. These twp parameters are matter much as the system is operating at high pressures. The diameter is calculated by equation 19[20] and the thickness is calculated from equation 20[20] For Stainless steel;

The thickness of the pipe; t


Page 42




The Feed Pipe:

And;



Pipe to the Condenser:

And,



Pipe to the Reboiler:

And,

4.3 Column Internals [21][22]: The internal packing in a packed distillation column should be designed carefully, to ensure better performance. Generally, the standard fittings are developed by the packing manufacturers and its uses are specified. Some of the typical designs are discussed as follows.


Page 43


Packing : The plate carries the weight of the random structures inside the column. A poorly designed of the plates causes flooding or very high pressure drops inside the column. A simple Grid or a perforated plate can be used. The only disadvantage with such kind of systems is that the liquid and the gas have to vie through the same openings. Hence, wide spaced grids are used to avoid this problem and increase the flow area. The larger sizes packing are dumped into the column first if wider grids are used, which the smaller random packing. (As shown in Figure 13)

The best design for packing is the gas injection type of . The gas inlets are provided above the level where the liquid flows from the bed. The problem of local flooding and high pressure drops is solved with the application of these rings. These s are available in a variety of sizes and materials, like plastics, ceramics and metals. Figure 14; shows design for the gas injection s and Figure 15 shows the Principle of gas injection packing


Page 44


Liquid Distributors:

Uniform flow of liquid throughout the column and good initial liquid distribution is a very essential factor for good performance of a column. A central open feed pipe or a pipe with a spray nozzle is best suited for proper distribution of liquid in small diameter columns. But for larger diameters, more elaborate designs are required. The two most common type of distributors used are orifice type and weir type. The orifice type has holes in the plate which allows age for the liquid and it has short stand pipes, through which the gas flows. Sizing of gas pipes are compulsory as it provides sufficient area for the gas flow without letting the pressure to drop significantly. The holes should be of an appropriate size, neither too small nor too big so that at lowest liquid flow rate, there should be a level of liquid always present on the plate and at highest flow rates, the liquid distributor does not over flows. Figure 16 shows the C.S and the T.S of an orifice distributor.

In the Weir types the liquid flows over the notched weirs in the gas stand-pipes. These stand an upper grade over the orifice type in handling wider range of liquid flow rates. The column designed Richie Gandhi SUN-075909279

Page 45

CE 3003 Advanced Process Design – Individual Project uses Orifice type of distributor. A pipe manifold distributor shown in figure 17 is used when the liquid is fed to the column under pressure and the flow rate is reasonably constant. The distribution pipes and orifices are accurately sized for equal uniform distribution.

Orifice type is exploited in the propane distillation column.

Liquid Redistributors:

The main purposes of redistributors are to collect liquid that has moved to the column walls and redistribute it evenly over the packing also redistributors will even out any maldistribution that has occurred within the packing.

A full distributor shown in figure 18 combines the function of packing and liquid distributor. The maximum bed height that should be used without liquid redistribution lies solely on the type of packing and the process. The wall-wiper type is mainly used in small columns of less than 0.6m in diameter. This operates in a mechanism were a ring collects liquid from the column wall and redirects it into the centre packing.


Page 46

CE 3003 Advanced Process Design – Individual Project Hold Down Plates: Fluidisation of the top layer of packing can occurs due to high gas flow rates or surging effects due to mis-operation. The ceramic packing crushes during such circumstances but the metal and plastic packing can be wafted out of the column. Bed-Limiters are used for plastic and metal packing to prevent to prevent expansion of bed at higher pressure drops. These are similar to Hold Down plates. Such plates should have smaller grids to retain the packing but not too small to restrict the fluid flow.

Installing Packing: The column is filled with water and the packing is dumped into the water ensuring the level of water always being above the packing at all times. Metal and Ceramic packing are generally deserted into the column “WET”. This ensures random distribution and prevents any damage to the packing. In case of “DR ” packing the packing should be lowered into the columns in buckets or other containers.

Concept Drawing: The Concept Drawing Details the application of column internals more in detail. Bit-Map is used to create the column showing every possible detail and dimension. The non calculated values are assumed to British standards.


Page 47


5.0 CONDENSER: Condensers are units similar to heat exchangers, which are used to condense the vapours to their liquid state. Condensers vary in size ranging from hand handled units to large industrial scale units. For condensers used in distillation columns, the process fluid generally flows through the shell side and the cooling fluid is made to flow through the tube side. The two fluids never come in with each other. The diagram below shoes a one tube condenser.

Figure 20: One tube side condenser http://.wikimedia.org/wikipedia/commons/c/cd/Straight-tube_heat_exchanger_1.PNG Four condenser configurations are possible:[23] 

Horizontal, with condensation in the shell, and the cooling medium in the tubes



Horizontal, with condensation in tubes



Vertical, with condensation in shell



Vertical, with condensation in the tubes

Horizontal shell side and vertical tube side is widely used as condensers. The other two are usually used in arrangements for heaters and vaporisers using steam as the heating medium.


Page 48

CE 3003 Advanced Process Design – Individual Project Assumptions: 

It is assumed that a horizontal shell side condenser is used to cool the propane vapours.



It is a complete condenser. Hence all the vapours are cooled down.



There is one shell and one tube inside the condenser and the flow is counter current.



Since the top product mainly comprises of the propane, the physical properties of propane are used for all the calculations.



The cooling fluid chosen is chilled water that enters the tube side at 15 0C and leaves at 450C.



The tube layout for this particular design is arranged in a squared pitch.

Basis: 1 hour Flow rate entering the condenser; V V = L+D; 402.39 + 661.83 = 1063.22 kg/hr

5.1 Energy Balance Over the condenser: Q = (Vapour flow rate * latent heat of vaporisation of methanol) + m∆T

“mL” due to phase change, since it is a complete condenser where phase change occurs; and “m∆T” due to increase in the energy per degree rise in temperature.

Vapour Flow Rate;

Latent heat of Vaporisation of Propane (1,3 Butadiene is ignored as it would not bring a vast difference)= L = 322.76 kJ/Kg Therefore,


Page 49

CE 3003 Advanced Process Design – Individual Project Since the Heat lost by the condenser is calculated the flow rate of water required can also be calculated as relevant from the following formula;

It is assumed earlier that the chilled water enters the condenser @ 150C and leaves @ 450C. Hence ∆T = 300C Hence,

Water flows at a flow rate of 0.781Kg/sec inside the tubes.

Figure 21: My Diagram for better understanding of ∆T LM

From the diagram above it now becomes easier to ∆TLM. The Log mean temperature difference is given by:

Where, ∆TLM = log mean temperature TIN = inlet temperature of process fluid Richie Gandhi SUN-075909279

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CE 3003 Advanced Process Design – Individual Project TOUT = outlet temperature of process fluid tIN = inlet temperature of cooling water tOUT = outlet temperature of cooling water

To begin with the design, we assume an approximate overall coefficient. This is done in aid with Graph 4; where the fluid in the process side are classified as Paraffin and the fluid in the service side is taken as River, Well or Sea Water. Hence, the assumed overall coefficient = 600 W/m2 0C

Graph 4: Overall Coefficients ( process side to the service side and read U values from the centre line)


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CE 3003 Advanced Process Design – Individual Project Trial Area:

Where, Q= Heat Transfer per unit Time U= Heat Transfer Coefficient A= Area ∆TLM = Log Mean Temperature difference

Layout and Tube Size[24]:

Usually the plant standards require tubes of: 

The outer diameter is 20mm



The inner diameter is 16 mm



The length is taken to be 2.44 m (8 ft)



The tubes are made of arbitrary brass.



The arrangement is a squared pattern.

Hence, the surface area can now be calculated from the above data specified.

Therefore,


Page 52

CE 3003 Advanced Process Design – Individual Project Since there is slight condensation occurring, hence the number of tubes calculated is so less.

Since, it was decided to use a Square Pitch;

Tube Bundle Diameter; Db

Where, Nt = number of tubes K1 and n = constants obtained from table 9[25] Do = Outer diameter Table 9: K and n constants for square arrangements: Square pitch, Pt = 1.25 do Number of es

1

2

4

6

K1

0.215

0.156

0.158

0.0402

n1

2.207

2.291

2.263

2.617

Hence,

Number of tubes in the centre row:

We take it as 12 tubes as the number of tubes should be even and divisible by 4 as the arrangement is a square pitch.


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CE 3003 Advanced Process Design – Individual Project 5.2 Shell Side Coefficient: The Tube Wall temperature, Tw can be estimated if the condensing coefficient is assumed. The value for the condensing coefficient is assumed to be 1500W/m0C

Mean temperature:





Hence, the wall temperature is 350C. Table 10: Physical Properties of Propane @ 350C[26] Liquid Density (ρL) @ 350C

514.13 Kg/m3

Liquid Viscosity (μL) @ 350C

0.11321 centi-poise

Liquid Thermal Conductivity (kL) @ 350C

0.095W/m K

Vapour Density @ 40 0C mean vapour temperature (ρV) = 28.6 Kg/m3 Using Kern’s Method [27], the mean transfer coefficient for the tube bundle is given by: ρ (ρ [ μ

ρ )

( )

]

(

)

Where,

Wc = Flow rate of the distillate in Kg/sec L = Length of the tubes Nt = Number of tubes


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CE 3003 Advanced Process Design – Individual Project Hence,

Substituting the values in the Kerns Equation:

( )

[

]

(

)

The value obtained is close enough to the value assumed (1500W/m 2K), hence the estimated Tw is acceptable.

5.3 Tube Side Coefficient: Eagle and Ferguson (1930) adapted a much reliable formula for the heat transfer coefficient for water used in the tube side. This is stated as below:

Where, hi = inside coefficient for water t = mean water temperature ut = water velocity di = tube inside diameter

ut can be calculated from the internal diameter of the tube Tube Cross- Sectional Area;


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Density of water at 27.50C (mean water temperature in the tubes) = 995.65 Kg/m3

Tube Side Velocity, ut ρ

Hence, substituting the values of velocity, the heat transfer coefficient of water inside the tube is;

5.4 Overall Heat transfer Coefficient U;

Where, U = the overall coefficient based on the outside area of the tube, W/m 2 0C ho = outside fluid film coefficient, W/m 2 0C hi = inside fluid film coefficient, W/m 2 0C hod = outside dirt coefficient; fouling factor, W/m 2 0C hid = inside dirt coefficient; fouling factor, W/m 2 0C kw = thermal conductivity of the tube wall material, W/m0C di = tube inside diameter, m do = tube outside diameter, m

Fouling Factors: As neither of the fluid is heavily fouling, the dirt coefficient at both the sides has been assumed to be 6000 W/m 2 0C and kw is assumed to be 50 W/m0C


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CE 3003 Advanced Process Design – Individual Project Substituting all the values in the equation 31;

Hence, Overall Heat transfer coefficient;

The value obtained is significantly lower than the assumed value of 600 W/m2 0C The calculation has to be repeated using different values of Overall heat transfer coefficient by trial and error method; and the closest possible answer firms up the final design. The calculations are redone with a new value of 500 W/m2 0C

Hence, the number of tubes now changes,

Tube Bundle Diameter; Db


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Shell Side Coefficient: As already known, ρ (ρ [ μ

ρ )

( )

]

(

)

Where,

And

Therefore, substituting the values of Гh and Nr in equation 32

Tube Side Coefficient:

Again using Eagle and Ferguson’s (1930) formula tube side coefficient is calculated. But the velocity of the water in the tubes changes;

New Cross sectional Area


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Hence, the tube velocity,

Hence, the new calculated value for the Tube Side Coefficient;

Overall Heat transfer Coefficient;

Hence, Overall Heat transfer coefficient;

The results are satisfactory. The values obtained are close enough to the values assumed hence, the design is confirmed.

5.5 Shell side Pressure Drop: Specifications: 

Pull through Floating head is used, no close clearance is required.



35% cut of the Baffle Spacing



A condenser has wider baffle spacing, lB ≈ Ds


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Pressure Drop is given by;

Where, Jf = Friction factor L = Length of the tubes Lb = baffle Spacing All the unknowns are calculated below.

Shell internal Diameter; Ds

Clearance is = 89mm estimated from the graph 5

Graph 5: Shell- Bundle Clearance Hence,


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Cross Sectional Area As for the hypothetical row of tubes at the Shell Equator

Where, Pt = Tube Pitch Ds = shell inside diameter LB = baffle spacing

Shell Side mass Velocity Gs

Where, Ws = Fluid Flow Rate on the shell side in kg/sec

Linear Velocity us

Shell Side Equivalent Diameter; de The equivalent diameter for a square pitch arrangement is given by;

(


)

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Friction Factor; jf Friction factor is estimated from a graph in FIG; which is a correlation between Reynolds’s number and baffle cut. Hence,

Graph 6: Shell side Friction Factor; Segmental Baffles From the graph Friction Factor is determined to be 4.8 *10-2

Substituting all the above calculated values in the pressure drop equation;


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CE 3003 Advanced Process Design – Individual Project Ignoring the viscosity correlation;

The Pressure drop is negligible; hence more sophistication calculation is not justified.

5.6Tube Side Pressure Drop: The pressure Drop on the Tube side is given by,

[

(

)

]

The viscosity correlation is neglected; Jf ; Friction Factor is given by a graph 7 Where,

Hence,


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Graph 7: Tube side Friction Factor Hence from the graph below, Jf = 9*10-3 Substituting the values in the pressure drop equation;

The pressure drop is almost negligible due to the following reasons: 

The flow is laminar as Re < 2000



The velocity of the cooling water is very low



Only one tube is used, hence there is a straight pipe through which the pipe flows.


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6.0 REBOILER: Reboilers are used with the distillation column to vaporise a fraction of the bottom product. There are three different kind of reboilers used: [28] 

Forced Circulation; where the fluid is pumped through the exchanger. The vapour formed is separated and sent back to the bottom of the distillation column and rest is removed.

Figure 22: Forced Circulation Reboiler http://.wikimedia.org/wikipedia/commons/a/a7/ForcedCirculation.png 

Thermosyphon, unlike forced circulation it has natural circulation. The liquid circulation is maintained by the difference in densities of the two-phase mixtures of vapour and liquid. These kinds of Reboilers can have vaporisation on the tube side; when they are vertically placed or the vaporisation occurs on the shell side, when placed horizontally.

Figure 23: Thermosyphon http://.wikimedia.org/wikipedia/commons/5/57/Thermosyphon_Reboiler.png


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Kettle Reboilers, also called submerged bundle reboilers; where boiling takes place on the tubes immersed in a pool of liquid. The liquid does not circulate through the heat exchanger. These are the most expensive kind of Reboilers.

Figure 24: Kettle Reboiler http://www.spiraxsarco.com/images/resources/steam-engineeringtutorials/2/13/Fig_2_13_5.gif

6.1 Heat Duty over the Reboiler:

In the above equation, the ∆H® (Heat of Vaporisation) is considered only for 1, 3 Butadiene as major fraction of the component entering the Reboiler comprises of 1, 3 Butadiene. Minor fractions of propane, pentane and 1, 2 Butadiene is ignored. This would not affect the result drastically as the Heat of vaporisation of the other components somewhere lies in the same range.

Hence, Assuming; that the bottom product is liquid at boiling point which enters the Reboiler at 368K.

Amount of Steam Required:

Heat obtained by the process fluid is the heat lost by the steam entering the Reboiler. Richie Gandhi SUN-075909279

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CE 3003 Advanced Process Design – Individual Project Hence the “Q” remains same. Assuming steam entering the Reboiler at 2.6 bars, Hence, ∆H® for steam at 2.6 bars = 2177.42 KJ/Kg

6.2 Choice of type of reboiler used with the Propane Distillation:[28] The choice of the kind of reboiler used with a distillation column solely depends on the following: 

The viscosity and the propensity to fouling of the process fluid



The operating pressure



The headroom available to layout the equipment.

After careful judgement, it is concluded that a Horizontal Thermosyphon Reboiler would be used with this distillation column, since the horizontal reboilers require less headroom. These are most economical type of reboilers for most application and are not suitable for high viscous fluids. The fluids in the column have very low viscosity. Also these reboilers are suitable for high temperatures and high pressure which fulfil the demands for this unit. The only disadvantage with this kind of reboiler is that a hydrostatic head is required for the thermosyphon effect which requires elevation of the column base. This problem can be overcome by using ers at the distillation column is not huge.


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7.0 Overall Energy Balance over the Distillation Column:

The Energy Balance over the column could not be calculated in the first part of the assignment as the Reflux Ratios were unknown. The Heat Duty over the Condenser and the Reboiler is calculated. It is summarised in the table below. Units

Energy Required

Energy Released

Condenser

-

98.434 KW

Reboiler

- 421.826KW

-

Total

-323.392 KW

The Negative Sign shows that the Energy is required to run the unit.


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8.0 Piping and Instrumentation Diagram The Piping and Instrument diagram (P and ID) shows the engineering details of the equipment, instruments, piping, valves and fittings and their arrangements which is not detailed in the process Flow sheet. It should include the following. [29] [30] 

All process equipment identified by an equipment number. The equipment should be drawn roughly in proportion, and the location of nozzles shown.



All pipes, identified by a line number. The pipe size and material of construction should be shown. The material can be included as part of the line identification number.



All valves control and block valves, with an identification number. The type and size should be shown. The type may be shown by the symbol used for the valve or included in the code used for the valve number.



Pumps identified by a suitable code number.



All control loops and instruments, with an identification number.



For simple processes, the utility (service) lines can be shown on the P and I diagram. For complex processes, separate diagrams should be used to show the service lines, so the information can be shown clearly, without cluttering up the diagram.

Since the Process of Butadiene production is very complex which includes many units, the P and ID is only done over the Propane Distillation Column which is attached in Appendix, 6 (issue number 002) The basic units and symbols used in the P and ID are briefly described below: 

Control Valves [31]: The parameters such as temperature, pressure, flow and level are controlled by the control valve. Control Valves can be manual or automatic which are partially or fully open or closed. The action of the control valves are in response to the signals received from their respective controllers that compare the set-point to the process variables.


Figure25: Detailed Diagram of a Control Valve http://www.isa.org/Images/InTech/2005/April/20050415-3.gif



Gate Valve [32]: These valves are opens by lifting a round or rectangular wedge out of the path of the fluid. Gate valves are used when a straight-line flow of fluid and minimum restriction is desired. These valves should never be used as control valves unless those are specifically designed for it. Typical gate valves are designed to be fully opened or closed. There is very low frictional loss when the valve is fully open due to negligible obstruction. Gate valves are present before and after every control valve and pump which offers effortless maintenance during equipment failure.

Figure 26: Detailed diagram of a Gate Valve http://www.spiraxsarco.com/images/resources/steam-engineering-tutorials/12/1/fig_12_1_1.gif



Transmitters: These are sensors which monitor the changes in the process variables and simultaneously send signals to the controller. T

Richie Gandhi SUN - 075909279

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CE 3003 Advanced Process Design – Individual Project They are named as FT (flow Transmitter), PT (Pressure Transmitter), TT (Temperature Transmitter) and LT (Level Transmitter) respectively. They are Locally Mounted which means that the controller and the display are located in the plant where the sensing instrument is placed. 

Drain Valve: As the name suggests, these valves are used to drain the components from the unit or pipelines. These are generally closed and are in operation usually during site or unit maintenance.



Relief Valve: The relief valve is a type of valve used to control or limit the pressure in a system or vessel which can build up by a process upset, instrument or equipment failure, or fire. The pressure is relieved by allowing the pressurised fluid to flow from an auxiliary age out of the system. Since the distillation Column taken into consideration is operating under high pressures, a relief valve can act as a precautionary measure which would help to get rid out the extra pressure built up into the unit. It is built on the reflux drum, as building it over the column can lose its components in the vapour phase that is released. As it is the last stage the purified butadiene cannot be afforded to be wasted.

RV-1



Pneumatic Lines: The signals transmitted from a controller to the valve are generally shown by pneumatic lines on a P and ID.



Electric Lines: The dotted lines show the transmission of electric signal in the P and ID. The electric signal is send by the transmitter to the controller.


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High and Low Level Alarms: Alarms alert the operators of serious and potentially hazardous deviations in the process conditions. Key instruments are fitted with switches. If there is a delay or lack of response by the operator a hazardous situation can occur in a short span of time. Often drills are practiced to overcome such catastrophic situations. When this system turns on, a trip system automatically comes into action which includes, shutting down of pumps, closing valves, operating emergency systems etc.

8.1 Control Loop A chemical plant is composed of several processing units; these cannot be treated as simple systems working independently. They are integrated to form a systematic, rational and controlled process. This process must then satisfy many requirements in order to achieve its objective of converting raw material to the desired products. Control systems are employed to successfully satisfy the requirements of safety, product specifications, taking into , operational constraints, plant economics and environmental regulations. The control system is composed of an arrangement of equipment such as temperature / pressure indicators, pneumatic valves, process controllers linked with computers (U). The requirements of control are stated below:[33] Safety [33] A principal prerequisite of the plant is to operate safely for the well being of plant stakeholders and to continue satisfying the economic goal. To achieve this, temperature, pressures, flow rates etc need to be controlled within allowable limits. Operational Constraints [33] Different process equipment have variable process constraints i.e. tanks should not overfill, distillation columns should not be flooded and centrifugal pumps must maintain a certain net positive suction head, these need to be considered when determining the control system. Environmental Constraints [33] Involves ensuring discharges are within acceptable limits e.g. as prescribed under IPC. Richie Gandhi SUN - 075909279

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CE 3003 Advanced Process Design – Individual Project Economics [33] Plant operating conditions need to be controlled to ensure that the plant is operating at its optimum, thus ensuring maximum profitability. Although control is essential, it is known in industry that trying to tightly control absolutely every stream in the process is very costly and unrealistic and can result in total inflexibility and even destabilisation of the plant, (control loops may start to interfere with each other’s actions). Similarly measurement sensors and control valves are expensive, so unnecessary measurement is a loss of money. Therefore these factors will need to be taken into when deciding upon the control.

8.2 Control Systems over the Distillation Column: Various control measures have been taken into to meet the objectives of the plant such as safety, operation, environmental constraints and economics. Sensors have been installed at various process lines and equipments to make the operator aware of the situation with the equipment and the process. The sensors transfer signals to the controller which then send back commands to the respective valves to carry out the action. Control system of the process will be explained as we go along the PID from left to right.[34][35]

FC 1: the feed pipe is installed with a flow controller, which helps to control the flow throughout the pipe. The flow rate is received as input to the FT-1, which then sends output signals to the flow controller FC, which then sends on information to the automated control valve CV-1. This ensures a steady state and control flow rate of feed to the distillation column. PC 1: The distillation column is operating under high pressures. The pressure is a very crucial variable and has to be controlled to avoid flooding. The pressure is read by a pressure gauge and this input is received by a PT1 which sends signal to the PC 1 which then forwards the information to the control valve on the condenser. The condenser would reduce the flow rate of water if the pressure drops; this intern increases the temperature of the distillate entering the reflux drum as desired heat exchange was not possible; which increases the Richie Gandhi SUN - 075909279

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CE 3003 Advanced Process Design – Individual Project pressure back into the column. The reverse action is carried out if the pressure inside the column increases. There is a relief valve on the reflux drum which also operates when the pressure inside the column increases drastically.

LC 1: For desired separation to take place, it is important to maintain the ratio of the distillate to the reflux Liquid. Hence it is vital to maintain the level in the reflux drum. The level is read by a level indicator which sends the information to the LT 1 which further forwards the signal to the control valve on the pipe back to the condenser. If the level in the drum falls, the controller sends signal to close the valve which results in maintaining the level in the drum.

TC 1 and FC 2: The temperature should be well maintained inside the column to provide vaporisation of the volatile fluids for desired separation. Heat is provided by the steam flow in the reboiler. Hence a controller valve is installed on the pipe which carries steam to the reboiler. This controller receives signal from the flow transmitter (FT2) or the temperature transmitter (TT1). If the temperature inside the column reduces, the controller sends signal to the control valve to open slightly. This increases the flow rate of steam into the reboiler increasing the temperature of the column.

LC 2: Flooding is a problem commonly faced by distillation columns if the design is poor. Sometimes blockage in the systems inside the column can cause obstruction to the age of the liquid and the gases. This can increase the level in the column resulting in spillage of the valuable product. A level controller is installed in the pipe leaving the column at the bottom. This control valve receives signals from the level controller which gets its input from the level transmitter. If the level in the column falls down, the valve closes slightly to maintain the level and prevent it from becoming dry. Also when the level falls down too low or rises to high, the alarms blow up which would alert the operators to take serious actions immediately like evacuating the plant or shutting all the valves and stopping the flow rates.


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CE 3003 Advanced Process Design – Individual Project Indicators: There are three main indicators used in the P and ID. These are mainly to provide information of the operating conditions. There are two sample indicators SI (1-1) and SI (1-2), which provide information about the purity of the fluids entering and leaving the column. Since, the column’s top temperature is different from the bottom one, two temperature indicators are required.

A combination of automated valves, flow and temperature indicators along with controllers are used to control the process. Investment in these instruments and the control system is required and is necessary. The control system along with the PID is then checked by senior manager and engineers over a HAZOP meeting. Changes are made to the control and the PID before the system is installed, in such a way money is saved and at the same time safety of the operator is ensured. Since Hazop was carried out on this section of the process, there were certain changes made from the previously designed control loop system. Issue 001 in Appendix VI shows the draft copy of the previously designed P and ID which was then improvised to Issue 002


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CE 3003 Advanced Process Design – Individual Project 9.0 Hazard and Operability Studies HAZOP HAZOP is a procedure for critical, systematic examination of the operability of a process. Procedure of a Hazop involves taking a full description of a process, generally using a PID, and systematically questioning every part of it. This helps to establish deviations from the design intent. When the deviations are identified assessments are made on the consequences of the deviation and the required action which should be taken to prevent or control the hazard from taking place. The analysis of Hazop is carried out in a structured way by following the guidlines attached; it completely relies on the realising and imagination to discover the credible causes of the deviations by the Hazop team. In practise many of the causes will be very obvious such as pump failure. But putting a Hazop meeting encourages highlighting many causes which might be obvious in first consideration. In this way the study is carried out and becomes more rigorous and encourages the involvement of all the team . The result of the Hazop there is a good chance of identifying and recording relevant actions to be taken against failures and problems which have not been experienced before. More over a documented file of Hazop is required by legislation to confirm that preventive measures had been taken to ensure the safe working condition of the operators and the environment. In our study we carried out a Hazop with Dr. Titiloye on the Feed pipe entering the Propane Distillation column. (As highlighted Green in Figure attached in Appendix VII). General consequence of a Hazop leads to an updated version of the PID to be made after including all the safety features discussed during the meeting. Hence the slight deviation in the final P and ID (ISSUE no. 2) is due to Hazop done on the pipe. In practise Hazop should be carried out over the whole process, but due to time constraints and requirements of the project only one line of the process is looked at. Hazop discussions have also been added, this includes all the causes and their consequences looked at and also preventive actions have been highlighted. The Hazop is attached in Appendix VII.


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CE 3003 Advanced Process Design – Individual Project 10.0 Conclusion: The design project has been successful in its aims of providing a detailed knowledge a chemical process unit. This project was a learning process where different challenges were faced. At this stage, such a project is aimed to increase general design knowledge of a given operating unit in this case; a packed bed distillation column. As this was just a preliminary design, the amount of detail of the design and the accuracy of the final calculations might be questionable. However, it remains a fact that this project targets more than just design but also gives an idea of how to make reasonable assumptions and where data is not available, the use of values which can be used to make reasonable estimates. Overall the project enhances one’s ability to play around with available data in order reach a reasonable estimate.

After calculating all the values over my distillation column I conclude that one distillation column can be used to separate propane and recover 1,3 butadiene. A stepped column can be used as the diameter for the pentane distillation column, (the unit where the 1,3 butadiene is pumped to for further purification.) is 2 m as suggested my group mate. Since the diameter for the propane distillation column is 0.65m the top part of the column can have this diameter and the lower part of the column should have a diameter of 2m. This can reduce the operating costs and also a significant amount of raw material to build the column would be reduced. Also a separator can be used instead of a distillation column, but the temperature has to be reduced too low, to obtain such separation. This can be more expensive than providing high pressure inside the column.


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CE 3003 Advanced Process Design – Individual Project 11.0 References: [1]: http://www.wakefield.gov.uk/NR/rdonlyres/F456AD74-5BC2-4697-941455C32FCBE9E2/0/s1_13Butadiene.pdf,( (Part 1: Group Project on1,3 Butadiene Production) accessed date 28/11/09 [2]: http://www.icis.com/v2/chemicals/9075172/butadiene/uses.html; accessed date 07/02/10 [3]: http://www.dow.com/productsafety/pdfs/butadiene_guide.pdf accessed date 15/03/10 [4]: http://www.gansu.gov.cn/en/BasicDetail.asp?CID=50 (Part 1: Group Project on1,3 Butadiene Production) [5]: http://www.britannica.com/EBchecked/topic/166112/distillation-column; accessed date 13/02/10 [6]: http://www.websters-online-dictionary.org/re/reflux+ratio.html accessed date 13/02/10 [7]: http://www.separationprocesses.com/Distillation/DT_Chp04n.htm; accessed date 23/02/10 [8]: Dr. Bruce, 3rd year Chemical Engineering Advanced Separation Class Notes, Aston University, 2010; Lecture 1 [9]: http://www.processglobe.com/Liquid_Specific_Heat.aspx; accessed date 24/02/10 [10]: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 567-569, [11]: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 579 [12]: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 569 *13+: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 526 *14+ : Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 588-593 *15+: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 592 [16]: Dr. Bruce, 3rd year Chemical Engineering Advanced Separation Class Notes, Aston University, 2010; Lecture 3 Richie Gandhi SUN - 075909279

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CE 3003 Advanced Process Design – Individual Project [17]: http://www.tower-packing.com/metal/metal_pall_ring_tower_packing.htm, accessed date 29/02/10 [18]: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 593 *19+: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 812 *20+: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 216 and 221 [21]: http://www.zehua-chem.com/ [22]: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 609-616 *23+: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 709 [24]: http://www.alibaba.com/showroom/condenser-tube.html; assessed on 26/02/10 [25]: Dr. John Brammer, 2nd Year Chemical Engineering Heat transfers Notes, Aston University. [26] : http://www.processglobe.com/Liquid_Specific_Heat.aspx [27]: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 711 [28]: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 729 *29+: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 195-199 [30]: http://www.azom.com/Details.asp?ArticleID=863; accessed date 09/03/10 [31]: http://www.documentation.emersonprocess.com/groups/public/documents/book/cvh99.pd f ; accessed date 14/03/10 [32]: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 197 -198 [33]: Dr. Fletcher, 2nd Year Chemical Engineering Control Process Notes, Aston University *34+:Page S. Buckley, William L. Luyben and Joseph P. Shunta ‘’Design of Distillation Column Control Systems’’ Richie Gandhi SUN - 075909279

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CE 3003 Advanced Process Design – Individual Project [35] :http://www.see.ed.ac.uk/~jwp/control06/controlcourse/restricted/course/fourth/course/m odule3-1.html [36]: Dr. Drahun, 2nd Year Chemical Engineering Advanced Design Process, Aston University. [37]: Dr Brammer’s, 3rd Year Chemical Engineering Process Economics lecture notes, Section C, *38+: Dr Brammer’s, 3rd Year Chemical Engineering Process Economics lecture notes [39]: (ref: www.informaworld.com/index/778741608.pdfl); accessed date 24/03/10 [40]: Dr Brammer’s, 3rd Year Chemical Engineering Process Economics lecture notes, Section 4(a) [41]: Dr Brammer’s, 3rd Year Chemical Engineering Process Economics lecture notes, Section 4(b)

Graphs and Correlations: Graph 1 : Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 524 Grapgh 2: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 568 Graph 3: Dr, Bruce Davies; 3 year Chemical Engineering advanced Separation notes; Lecture 3 Graph 4: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 639 Graph 5: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 646 Graph 6: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 574 Graph 7: Coulson J.M & Richardson J.F ‘’Chemical Engineering Design’’, 4th ed., vol. 6, Pergamon, Oxford, 2005 page 668


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