Distillation Column Design

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1.0 Project Objectives

This section of the advanced process design module involves designing a product distillation column. It is a continuation from the group project which involved the production of 100000 tonnes per year of Methyl Ethyl Ketone to be located in China.

This report will focus on certain chemical engineering design features including calculations of length and diameter. Also, it will be important to consider materials of construction and other characteristics associated with designing a distillation column. Within this part of the report cost and economical appraisal of designing the distillation column will be included.

The type of alarms, trips and relief devices which will be used will be included in the control and instrumentation section of the report. When selecting the types of control and instrumentation devices for the distillation column it will be important to consider temperatures and pressures.

A piping and instrumentation drawing will be constructed for the product distillation column. This will include all alarms, control valves, pressure relief devices and utilities.

This report will also include a Hazard and Operability study (HAZOP). This will be carried out as a group with the group supervisor. Each member will select a process line and a HAZOP will be carried out.

Within this report a costing and economic optimisation of the product distillation column design will also be carried out. The last section of the report includes the economic appraisal for the process. Within this section the capital costs of the process will be determined. Standard correlations will be used to determine if the project is economically feasible. It will identify whether the project should be carried out in the real world.

2.0 Project Objectives

This is a continuation from the group project and the main aim is to design a product distillation column. The report will include detailed and constructive explanation of how the distillation column should be designed. The following objectives have been set:

2.1 Technical Objectives

The report is expected to complete by week 22. In order to meet this deadline technical objectives will be set. From the Gantt Chart start dates and end dates for each task can be seen. The following are the technical objectives which have been set:

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 Research in detail and evaluate the design of a distillation column. Including characteristics such as number of trays, column height, column diameter, efficiency and flooding parameters.

 Research the various types of control systems, instrumentation and monitoring systems for the safe operation of the distillation column.

 Construct a P +ID indicating clearly all equipment items, piping, process and utility lines, control loops, valves, instruments including alarms and trips, pressure relief devices. Include a key of symbols and ensure that the diagram is correctly numbered.

 Carry out the HAZOP with the group. This will include systems which are required for the safe operation of the distillation column and reduce the chance of any accidents occurring.

 An economic appraisal should be carried out. This will include an estimate of the overall capital costs and annual operating costs. Parameters including product price, construction time and interest rate should also be justified.

 References used throughout the project should be listed.

 All appropriate documents including the Gantt Chart, lengthy calculations and any large drawings should be placed in the appendices.

2.2 Personal Objectives

 It is important that there is efficient communication within group members.

 Important that the group works together as a team to put across ideas to ensure that the tasks are completed on time.

 Enhance communication, individual and team-working skills through the project timeline.

 Remain focussed and motivated to ensure that work is produced to a high grade.

 Organisation is a very important factor for the competition of this report.

 It will be important that the Gantt Chart is followed closely as time as been allocated to each task equally to ensure that the deadline is met.

 Allocate sufficient number of hours during the week to work on the project.

 Regular meetings should be held with the supervisor this will ensure that everything is on task and any changes that need to be made quickly and efficiently.

 Research is a major section of this report. It is therefore very important that enough time is allocated to carry out adequate research. Extensive research will be required to gain sufficient knowledge. It is important that various methods of research are utilised to ensure that a wide range of information is available.

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 Have complete and clear understanding of how a distillation column operates on completion of the report.

 Improve technical skills by carrying out a HAZOP and constructing a P +ID which may be useful in future projects.

 Proof read all work to correct any errors which may occur and to ensure that work is of a high standard.

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3.0 Introduction

One of the most important operation in the chemical and petroleum industry is the separation of liquid mixtures into several components. It is sometimes referred to as fractional distillation. It is one of the oldest unit operation processes. The technical publication of distillation was first developed in 1957, however, distillation had been practiced for many centuries prior to this. Distillation is one of the most common and widely used separation processes in the chemical industry. However, it is also an extremely energy intensive process. [1] It requires large amounts of energy for both cooling and heating. 50% of plants operating costs are produced from distillation. At present distillation is commonly used in the petroleum, chemical, petrochemical, beverage and pharmaceutical industries. Distillation is a process which is important in the development of new products and for the recovery and reuse of volatile liquids.[2] A great deal of research has been carried out into techniques of distillation due to the demand for purer products and a persistent requirement of greater efficiency.

When designing a distillation column it is essential to consider process control. Many distillation columns usually operate with the combination of many other separate units. [3] The correct design of a distillation column is not always a simple procedure as it is regarded as a specialised technology. [2] Compared to other types of processing equipment distillation columns have to be designed with a larger range in capacity with single columns varying from 0.3 to 10m in diameter and 3m to 75m in height. It is important that designers are able to provide the desired product quality at a minimum cost but also at a constant purity.

Distillation is usually used to separate liquid mixtures into two or more vapour or liquid products which have different compositions. [1] The separation of liquid mixtures is dependent on the differences in the volatility between the components. Separation is easier if the relative volatilities are larger. [3] There are two major types of distillation, this includes continuous distillation and batch distillation.[4]In continuous distillation the feed is supplied continuously. There are usually no interruptions however, problems may occur with the column or surrounding units. This type is the more common of the two types of distillation. However, in batch distillation the feed is supplied to the column batch-wise. The column is charged with a batch and the distillation process is then carried out. Once the desired task has been achieved the next batch of the feed is then introduced. [5]

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3.1 Components of Distillation Columns

The following section is a description of the components required for the operation of a distillation column. This includes a reboiler and a condenser.

3.1.1Reboiler

[5][6]

The main objective of a reboiler in distillation columns is to vaporise a fraction of the bottom product. They are used to provide the necessary vaporisation required for the distillation process.[5] There are three principal types of reboilers used in distillation columns. They are as follows:

1. Forced Circulation Reboiler: the fluid is pumped through the exchanger and the vapour which is formed is separated at the base of the column. Figure 1 shows a diagram of a forced circulation reboiler.

Figure 1: Forced Circulation Reboiler [6]

2. Thermosyphon Natural Circulation Reboiler: it is a vertical exchanger with vaporisation in the tubes or the shell. The difference in density between the two-phase mixture of vapour and liquid and the single phase liquid in the base of the column helps maintain the liquid circulation through the exchanger. The most frequently used reboiler is the shell and tube thermosyphon reboiler this is because it is the most economical type of reboiler for most applications. Figure 2 shows a diagram of a thermosyphon reboiler.

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3. Kettle type: in which boiling takes place on tubes which are immersed in a pool of liquid. In this type of reboiler there is no circulation of liquid. This type of reboiler is sometimes also called a submerged bundle reboiler. The bundle may also be stored in the base of the column in some applications. This helps save the cost of the exchanger shell. Figure 3 shows a diagram of a kettle type reboiler.

Figure 3: Kettle Type Reboiler [6]

The choice of the reboiler to be used for a given duty will depend on certain factors including [6]: 1. The nature of the process fluid i.e. the viscosity and propensity to fouling.

2. The operating pressure i.e. vacuum or pressure. 3. The equipment layout.

3.1.2 Condenser

[7]

A condenser is used in a distillation column to cool and condense the vapour leaving the top of the column. The vapour is cooled and condensed to its liquid state. The most common type of condenser used is the horizontal shell-side and vertical tube side. This means the processor has the option of condensing on either the shell side or the tube side. In condensers the use of cooling water as a medium to cool the substance is of vital importance.

Condensers are available in a range of designs and in many different sizes. Capital costs of condensers can be reduced by using a carbon steel shell. There are four possible condenser configurations which may occur as they. They are as follows:

1. Horizontal in design with condensation occurring in the shell and the cooling medium in tubes. 2. Horizontal in design with condensation in the tubes.

3. Vertical in design with condensation in the shell. 4. Vertical in design with condensation in the tubes.

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4.0 Chemical Engineering Design

4.1 Process Description

[8]

A mixture containing Methyl Ethyl Ketone and Secondary Butyl Alcohol is obtained from the solvent recovery column and this is fed to the product distillation column.

Figure 4: Process Description Diagram

The product distillation unit will be fed with a Methyl Ethyl Ketone (MEK)/ Secondary Butyl Alcohol (SBA) mixture. The mixture fed to the product distillation column is obtained from the distillate of the solvent recovery column. Before the mixture is fed to the product distillation column, the two streams are firstly mixed in an intermediate storage holding tank. Within the product distillation column cooling water is utilised, which enters the condenser at 24°C and leaves at 40°C. In the reboiler steam enters at 140°C and at a pressure of 2.0 bar.

4.2 Distillation Column Design

[9]

There are various stages in the design of a distillation column. They can be divided into the following steps:

 Firstly the degree of separation required is specified. The product specifications are set.

 The operating conditions are selected; i.e. batch or continuous, temperature and pressure.

 Select the type of contacting device which is required; i.e. tray design or packed column.

 Determine the stage and reflux requirements; i.e. the number of stages required for distillation using various correlations, calculating the minimum reflux ratio and the reflux ratio.

Methyl Ethyl Ketone

Secondary Butyl Alcohol to the recycle stream

Methyl Ethyl Ketone and Secondary Butyl Alcohol Mixture from Solvent Recovery Column

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 Size the column; i.e. diameter, height and number of real stages.

 Design the column internals; i.e. plates and packing supports.

 Consider the mechanical design.

 Design the condenser and reboiler.

4.3 Key Components

Before the design stage of a distillation column the designer must select the key components which are to be separated. The light key is described as the component that is desired to be kept out of the bottom product. The heavy key is described as the component that is desired to be kept out of the top product. Usually it is relatively easy to determine which the key components are. However, there may be situations in which close boiling isomers are present so judgement must be used in their selection. The light key is described as the most volatile component in the bottom product and the heavy key is described as the least volatile component in the top product. In this case the light and heavy keys are as follows:

 Light Key: Methyl Ethyl Ketone (A)

 Heavy Key: Secondary Butyl Alcohol (B)

4.4 Operating Conditions

It is assumed that the process operates at a steady state and the system is ideal. It is assumed that the inlet temperature of the feed to the column will be at the boiling point i.e. ‘boiling liquid feed’. At this point q=1, assuming that all of the feed to the column is in liquid phase.

It is assumed that the operating temperature of the column will be at an average temperature of 89°C (362K). This is because Methyl Ethyl Ketone has a boiling point of 79.79°C and Secondary Butyl Alcohol has a boiling point of 99°C. So the feed has been set to operate at a temperature in between the boiling points of the two components.

The column will be operated on a continuous basis and will be operated at atmospheric pressure at 89°C (362K).

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4.6 Packed Columns

[10]

Packed columns are used for a variety of processes including distillation, gas absorption and liquid-liquid extraction. In packed bed columns the gas liquid contact is continuous, however, in plate columns it occurs stage-wise. In packed columns the liquid flows down the column and over the packed surface and the vapour flows counter-currently up the column. The adequate operation and performance of a packed column relies greatly on the maintenance of good liquid and gas distribution throughout the packed bed.

Figure 5 shows a diagram of a packed column. Packed distillation columns and plate columns are similar. However, the difference being that in packed columns the plates are replaced with packed sections.

Figure 5: Schematic Diagram of a Packed Column[11]

4.6.1 Types of Packing

[10]

Packing is required for certain requirements. They are as follows:

 They provide a large surface area i.e. to provide a high interfacial area between the vapour and liquid.

 They should have an open structure.

 They should promote the uniform distribution of liquid on the packing surface.

 They should promote uniform vapour gas flow across the column cross-section.

Various types of packing have been developed with many shapes and sizes to satisfy the requirements. They are usually divided into two categories:

1. Random Packing 2. Structured Packing

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4.7 Plate Columns

[11]

In distillation columns cross-flow plates are the most common type used. In this type design the liquid flows across the plate and the vapour flows up through the plate. The liquid is passed from one plate to the next through vertical channels which are known as downcomers. Figure 6shows a diagram of a cross-flow plate. In certain occasions plates may be used which do not have any downcomers. They are known as non-cross-flow plates. This type of plate may be utilised when a particularly low pressure drop is required.

Figure 6: Diagram of a Cross-Flow Plate [13]

4.7.1 Types of Plate

[12] [13]

There are three principal cross-flow plate types which are used in plate columns. They are classified according to the method used to contact the vapour and liquid. They are as follows:

1. Sieve Plate also sometimes called perforated plate: This type of plate is the simplest type of cross-flow plate. The vapour passes the holes in the plate and the liquid is retained on the plate due to the vapour flow. In occasions when flow rates are low liquid weeps through the holes and this reduces plate efficiency. Usually the perforations are small holes however, in some cases larger holes and slots are also made use of.

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Figure 7: Diagram of a Sieve Plate [13]

2. Bubble-cap Plate: This type of plate is the most traditional and oldest type of cross flow plate. Various designs have been developed. For most applications the standard cap design would be specified. In this type of plate the vapour passes up pipes which are known as risers. The risers are enclosed by a cap with a jagged edge or slots. Risers ensure that a level of liquid is maintained on the tray at all vapour flow-rates.

Figure 8: Diagram of a Bubble-cap Plate [13]

3. Valve Plate also sometimes called floating cap plate: This type of plate is very much similar to sieve plates however, the only difference being that they have large diameter holes which are covered by movable flaps. When the vapour flow increases the movable flaps lift. Valves plates are able to operate more efficiently at lower flow rates in comparison to sieve plates. At low flow rates the valves in the valve plate’s close.

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Figure 9: Diagram of a Valve Plate [13]

It can be observed from the mass balancein section 4.8 that a plate column will be more suitable. This is because the flow rates in this process are large and these will require a large diameter. In cases when the diameter is large it is possible to have plates or trays.

When selecting the plate type many factors are considered including cost, capacity, operating range, efficiency and pressure drop. Of the three types sieve plates are the cheapest and are satisfactory for most applications. The operating costs of sieve plates are the pressure drop is lower compared to the other types of plates. For these reasons the selected type of plate for the distillation column is sieve plates.

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4.8 Mass Balance

Figure 10: Block Diagram of the Product Distillation Column

Previously in the group report it was assumed that hundred percent separation i.e. complete separation was achieved. However, this is not likely to occur to reality. The temperature difference between the components is only 20°C as Methyl Ethyl Ketone has a boiling point of 79.79°C and Secondary Butyl Alcohol (SBA) has a boiling point of 99°C. The distillate temperature is assumed to be the boiling point of Methyl Ethyl Ketone i.e. the desired product. A small amount of SBA is assumed to be present in the distillate. Also, a small quantity of MEK is also present in the bottom product. This means that the mass balance calculated in the previous report has to be adjusted.

The following table shows the summary of the compositions entering and leaving the product distillation column before recalculation.

Inlet Stream: 17 Components kg/hr kmol/hr wt% MEK 12276.78571 170.2744204 89.66 SBA 1416.08693 19.11048489 10.34 Hydrogen Water TCE Total 13692.87264 189.3849053 100

Table 1a: Inlet Flowrates of the product Distillation Column [8] Product Distillation

Column 17

18

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Outlet

Stream: 18 19

Components kg/hr kmol/hr wt% kg/hr kmol/hr wt%

MEK 12276.78571 170.2744204 99.0 SBA 124.00794 1.673521457 1.00 1292.07899 17.43696343 100 Hydrogen Water TCE Total 12400.79365 171.9479419 100 1292.07899 17.43696343 100

Total Outlet Mass flowrate = 13692.87264 kg/hr

Table 1b: Outlet Flowrates of the Product Distillation Column [8]

4.8.1 Adjusted Mass Balance

It was previously assumed in the group project that all the MEK is recovered in the distillate i.e. meaning that there would be no MEK in the bottom product stream. This does not usually occur. So it is assumed that there is a 99% separation. This means that 99% of the MEK from the feed is recovered in the distillate and therefore the remaining 1% is recovered in the bottom product. This will mean the previous mass balance will have to be adjusted. This is calculated in this section of the report.

The inlet stream to the distillation column does not change. This can be seen from table 2a below:

Inlet Stream: 17 Components kg/hr kmol/hr wt% MEK 12276.786 170.274 90 SBA 1416.0867 19.110 10 Total 13692.873 189.385 100

Table 2a: Inlet Flowrate of the Product Distillation Column [8]

Outlet

Stream: 18 (Distillate) 19 (Bottom Product)

Components kg/hr wt% kmol/hr wt% kg/hr wt% Kmol/hr wt%

MEK 12140.239 99.0 168.381 99.0 13.92 1.00 0.19 1.00

SBA 126.030 1.00 1.701 1.00 1416.09 99.0 19.11 99.0

Total 12266.269 100 170.082 100 1430.00 100 19.30 100

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4.9 Vapour Pressure Calculation

To determine the vapour pressure of the components the Antoine equation must be used. The relative volatility can then be calculated using this information.

Equation 1: Antoine Equation[14]

Where:

P = Vapour Pressure (bar) T = Temperature (K) A, B and C are constants

The following table shows the Antoine constants, the boiling point and latent heat of vaporisation for both MEK and SBA.

Component

A

B

C

B.P (°C)

ΔH

vap

(kJkmol

-1

)

Methyl Ethyl Ketone

(MEK)

3.9894

1150.207

-63.904

79.6

31.3 Secondary Butyl Alcohol

(SBA)

4.32943 1158.672 -104.683

99

40.75

Table 3: Anotine Constants for MEK and SBA [15][16] Methyl Ethyl Ketone (MEK)

= 0.131

P = P = 1.35bar

Secondary Butyl Alcohol (SBA)

= -0.1735

P = P = 0.67 bar

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4.9.1 Relative Volatility

From the calculated vapour pressure for each of the components the relative volatility can be determined.

Where: A = Light Key B = Heavy Key

Therefore Relative Volatility:

αAB = 2.015

4.10 Reflux Ratio

[17] The reflux ratio (R) is defined as:

The reflux ratio is a very important factor in the determination of the number of stages required for separation. An increase in the reflux ratio reduces the number of stages required for separation. This leads to a decrease in capital costs, however, operating costs and service requirements such as steam and water increases. The optimum reflux ratio will be the ratio at which the annual operating costs are its lowest. The minimum reflux ratio Rmin is calculated using the Underwood equation. It is assumed that the feed enters at its boiling point. Therefore q=1.

[

] (

)

Equation 2: Underwood Equation to calculate the minimum reflux ratio

Where:

Rmin : The minimum reflux ratio

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20 : The mole fraction of MEK in the Distillate = 0.99

: The mole fraction of MEK in the feed =0.90 Substitute in values:            ) . ( ) . ( . . . . min 1 090 99 0 1 015 2 90 0 99 0 1 015 2 1 R Rmin = 0.88

It is suggested that for many systems the optimum reflux ratio lies between 1.2 to 1.5 times the minimum reflux ratio.

Therefore: R= Rmin x 1.5

R= 0.88 x 1.5 R= 1.323

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4.11 Fenske Equation and Gilliland Correlation

[19]

The Fenske Equation and Gilliland correlation are used together to calculate the number of theoretical stages. The minimum number of stages required at the total reflux can be calculated using the Fenske equation. The number of theoretical plates required can then be estimated using the Gilliland correlation,

figure 11. The Gilliland correlation is a relationship between the reflux ratio, the minimum reflux ratio and

the minimum number of stages. [18]

[( ) ( ) ]

Equation 3: Fenske Equation [20]

Where:

: The relative volatility = 2.015

: The mole fraction of MEK in the distillate = 0.99 : The mole fraction of SBA in the distillate = 0.01

: The mole fraction of SBA in the waste (bottoms) = 0.99 : The mole fraction of MEK in the waste (bottoms) = 0.01

Substitute in values: *( ) ( ) + = 13.099

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Figure 11: Gilliland Correlation

Where:

R: The Reflux Ratio = 1.32

Rm: The Minimum Reflux Ratio = 0.88 Substitute in values:

From figure 11 it can be determined that the curve is intersected at 0.47 when the x-axis is 0.189.

Substitute in the values and rearrange to calculate n (theoretical number of stages).

Therefore,

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4.12 Erbar–Maddox Correlation

[21]

The Erbar–Maddox correlation is a different method which can also be used in the determination of the number of theoretical plates. This method gives the ratio of number of stages required to the number at total reflux. It is given as a function of the reflux ratio with the minimum reflux ratio. Figure 12 shows the Erbar-Maddox correlation.

Figure 12: Erbar-Maddox Correlation [22]

The following calculations have to be carried out in order to determine the number of stages:

Where:

R: The Reflux Ratio = 1.32 Substitute in values: Where:

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24 Substitute in values:

The Nm /N value can be obtained from the graph in figure 12.

Where Nm = 13.099

Therefore, substitute in the values and rearrange to obtain N. Where N is the number of theoretical plates.

The values obtained for the number of plates are only preliminary value. The actual number of stages cannot be determined at this point as the plate efficiency is not yet known. The plate efficiency will be calculated at a later stage of the report and that will be used to calculate the actual number of stages.

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4.13 Column Diameter

The number of stages is not required to calculate the diameter of the column. However, the liquid and vapour flowrates are required in order to calculate the diameter. The flowrate is the principal factor in determining the column diameter. It is important that the vapour velocity is lower than that velocity which would cause entrainment.[23] There are various steps which will be needed to calculate the column diameter for the distillation column. A number of calculations will be carried out in this section to determine the column diameter.

The chosen plate is a sieve plate. Certain specifications have to be put in place in order to calculate the diameter of the column. The following specifications were made:

 Hole Diameter – 5mm

 Tray Spacing – 600mm

 Plate Thickness – 5mm

 Hole Pitch – 15mm

4.13.1 Internal Traffic

[24]

The liquid and vapour flowrates will be calculated using the four following equations: 1. Lo = RD

2. V = Lo + D 3. L’ = Lo + qF 4. V = V’ + (1 – q) Where:

R: The reflux ratio = 1.323

D: The total distillate flowrate = 170.081 kmol/hr which is equal to 12266.269 kg/hr F: The total feed flowrate = 189.385 kmol/hr which is equal to 13692.873kg/hr q: The feed enters as liquid at its boiling point = 1

1. Lo = RD A) Lo = 1.323 x 170.08 = 225.028 kmol/hr B) Lo = 1.323 x 12266.269 = 16228.274 kg/hr 2. V = Lo + D A) V = 225.028 + 170.081 = 395.109 kmol/hr B) V = 16228.274 + 12266.269 =28495.543 kg/hr 3. L’ = Lo + qF

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26 A) L’ = 225.028 + (1 x 189.385) = 414.413kmol/hr B) L’ = 16228.274 + (1 x 13692.873) =29921.147 kg/hr 4. V = V’ + (1 – q) A) V=395.109 + (1 – 1) = 395.109 kmol/hr B) V = 28495.543 + (1 – 1) = 28495.543 kg/hr

4.13.2 Vapour Density

The ideal gas equation will be used to calculate the vapour density for both Methyl Ethyl Ketone and Secondary Butyl Alcohol.

PV=nRT [25] Where:

P: is the Pressure in Pa V: is the Volume

n: is the number of Moles R: is the gas constant

T: is the temperature in Kelvin PV=nRT

Where M is the mass of the feed.

Rearrange the above equation to make density (ρ) the subject:

The column pressure is assumed to be operating at atmospheric pressure. So the pressure will be taken as 101325Pa.

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Methyl Ethyl Ketone Vapour Density

P = 101325 Pa Mr = 72.1

R = 8314 m3PaK-1kmol-1 T = 362 K

Substitute the values into the above equation.

Secondary Butyl Alcohol Vapour Density

P = 101325 Pa Mr = 74.1

R = 8314 m3PaK-1kmol-1 T = 362 K

Substitute the values into the above equation.

4.13.3 Liquid Density

To calculate the liquid density for both Methyl Ethyl Ketone and Secondary Butyl Alcohol the following equation will be used:

n c T T L

A

B

       



1

*



Equation 4: Liquid Density [25]

Where:

A, B and n: are regression coefficients (shown in table 4) T: The operating temperature in Kelvin = 362k

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Component

A

B

n

Critical

Temperature,

T

c

(K)

Operating

Temperature

(K)

Methyl Ethyl Ketone

(MEK)

0.2676

0.2514

0.2857

535.5

362 Secondary Butyl Alcohol

(SBA)

0.2734

0.2635

0.2604

536.01

362

Table 4: Regression Coefficients for MEK and SBA [26]

Methyl Ethyl Ketone Liquid Density

Substitute the values into the above equation: 2857 . 0 5 . 535 362 1 2514 . 0 2676 . 0          



893 0 2514 0 2676 0.  . .   Convert to kg/m3

Secondary Butyl Alcohol

Substitute the values into the above equation: 2604 . 0 01 . 536 362 1 2635 . 0 2734 . 0          



902 . 0 2635 . 0 2734 . 0    Convert to kg/m3

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4.13.4 Flooding

Flooding occurs when the vapour flow is excessive and this causes liquid to be entrained in the vapour up the column. The excessive vapour flowrate also cause an increase in pressure and this backs up the liquid in the downcomer. This causes an increase in liquid holdup on the plate above. The maximum capacity of the column can be reduced severely depending on the degree of flooding. Flooding can be detected by a sharp increase in the column differential pressure and a significant decrease in the separation efficiency. [27] The following equation is used to calculate the Liquid-Vapour Flow (FLV) factor.

5 . 0

*

_

























L V LV

V

L

F



Equation 5: Liquid Vapour Flow Factor [28]

Where:

FLV: Liquid-Vapour Flow Factor L: Liquid molar flowrate V: Vapour molar flowrate ρv: Vapour Density ρL: Liquid Density

The Liquid-Vapour Flow Factor will be calculated for both the enriching (Top) section and the stripping (Bottom) section.

Enriching Section (FLVTOP)

5 . 0

*

_

























L V LV

V

L

F



FLV: Liquid-Vapour Flow Factor

L: Liquid molar flowrate = 225.028 kmol/hr V: Vapour molar flowrate = 395.109 kmol/hr ρv: Vapour Density = 2.427 kg/m3

ρL: Liquid Density = 780 kg/m3

Substitute the values into equation5:

( ) ( ) 0.0312

(30)

30 Assuming a tray spacing of 600m (0.6m) which is suitable for maintenance, inspection and cleaning. From the calculated FLV the corresponding K1 TOP value can be obtained. From figure13 it can be seen that the corresponding K1TOP value is 0.11.

Figure13: Flooding Velocity [28]

Stripping Section (FLVBOTTOM)

5 . 0

*

'



























L V LV

V

L

F



Equation 6: Liquid Flow Factor [28]

FLV: Liquid-Vapour Flow Factor

L’: Liquid molar flowrate = 414.413 kmol/hr V’’: Vapour molar flowrate = 395.109 kmol/hr ρv: Vapour Density = 2.495 kg/m3

ρL: Liquid Density =820 kg/m3

Substitute the values into equation 6

( ) ( ) 1.048856138 × 0.055155504 0.058

(31)

31 Assuming a tray spacing of 600m (0.6m) which is suitable for maintenance, inspection and cleaning. From the calculated FLV the corresponding K1BOTTOM value can be obtained. From figure13 it can be seen that the corresponding K1BOTTOM value is 0.1.

The flooding velocity is then calculated using the following equation:

5 . 0 1         V V L F K U   

Equation 7: Flooding Velocity Correlation [28]

Where:

UF: Flooding Vapour Velocity K1: A Constant

ρL: Liquid Density ρV: Vapour Density

Enriching Section Flooding Velocity

5 . 0 1         V V L F K U   

UF TOP: Flooding Vapour Velocity K1: A Constant = 0.11

ρL: Liquid Density = 780 kg/m3 ρV: Vapour Density = 2.427 kg/m3 Substitute the values into equation 7

[

]

UF TOP = 1.969 m/s

Stripping Section Flooding Velocity

5 . 0 1         V V L F K U   

(32)

32 UF TOP: Flooding Vapour Velocity

K1: A Constant = 0.1

ρL: Liquid Density = 820 kg/m3 ρV: Vapour Density = 2.495 kg/m3 Substitute the values into equation 8

[

]

UF BOTTOM = 1.81 m/s

The flooding condition fixes the upper limit of vapour velocity. For high plate efficiencies a higher vapour velocity is required, the velocity will be normally 79-90% of that which could flooding. In chemical engineering design a flooding velocity between 80-85% would be effective. [29]

4.13.5 Maximum Volumetric Flowrate

Taking 80% flooding the velocity at flooding is as follows:

Flowrate in the enriching section (UV,TOP) = 0.8 × 1.969 = 1.575 m/s Flowrate in the stripping section (UV,BOTTOM) = 0.8 × 1.81 =1.448 m/s

To calculate the area for the top and the bottom of the column the maximum volumetric flowrates are used. The maximum volumetric flowrate is calculated using the following equation:

Where:

Umax: Maximum Volumetric Flowrate V: Molar Vapour Flowrate

ρ: Vapour Density

(33)

33

Maximum Volumetric Flowrate in the Enriching Section

Where:

Umax: Maximum Volumetric Flowrate

V: Molar Vapour Flowrate = 395.109 kmol/hr ρ: Vapour Density = 2.427 kg/m3

Mr: Relative Molecular Mass = 72.1

Substitute values into the above equation:

Umax = 3.260 m3_/s

Maximum Volumetric Flowrate in the Stripping Section

Where:

Umax: Maximum Volumetric Flowrate

V: Molar Vapour Flowrate = 395.109 kmol/hr ρv: Vapour Density = 2.495 kg/m3

Mr: Relative Molecular Mass = 74.1

Substitute values into the above equation:

Umax = 3.260 m3/s

(34)

34

4.13.6 Calculation of Column Diameter

The following equation is used to calculate the column diameter of the distillation column:

√

Equation 9: Column Diameter

Where:

d: The diameter A: Area

Enriching Section (Top) Diameter

Area:

So the diameter is therefore calculated to be:

√

d = 1.623 m

Striping Section (Bottom) Diameter

Area:

So the diameter is therefore calculated to be:

√

d = 1.693 m

It can be seen that the both the top and bottom diameter are very similar. However, the largest diameter is selected to be the column diameter of the entire distillation column, i.e. Dc = 1.693 m.

(35)

35 From the diameter calculated it can be seen that the diameter is greater than 0.6m. Therefore, it would be suitable for the column to be designed as a tray design.

4.14 Plate Design

4.14.1 Provisional Plate Design

[30]

In section 4.13.6 the column diameter was determined. The area of the column is calculated as follows:

Equation 10 Area of the Column

Ac = 2.251 m2

The Downcomer area (Ad) is taken at 12% of the column area (Ac): Ad = 0.12 × 2.251 = 0.270 m2

Net Area (An) = Ac – Ad

(An) = 2.251 – 0.270 = 1.981 m2 Active Area (Aa) = Ac – 2Ad

(Aa) = 2.251 – (2 × 0.270) = 1.711m2

The Hole area (Ah) is taken at 10% of the Active area (Aa): Ah = 0.1 × 1.711 = 0.171m2

The Weir length (lw) is calculated using figure14.

Where:

Ad: Downcomer area = 0.270 m Ac: Column Area = 2.251 m Substitute in the values:

The corresponding value for can now be obtained from figure14. The value determined from the graph is 0.76.

(36)

36 Weir length (lw) = 0.755 × 1.693 = 1.278m.

Figure14: Correlation between downcomer area and weir length [31]

4.14.2 Weir Height (h

w

)

The volume of liquid on the plate is determined by the height of the weir. It is also an important factor in the determination of plate efficiency. Plate efficiency increases as the weir height increases. However, this is at the expense of a higher plate pressure drop. For distillation columns which require a vacuum lower weir heights are suggested as this reduces the pressure drop. Recommended weir heights are typically in the range of 6 to 12mm for vacuum operation. For columns which operate above atmospheric pressure weir heights are generally between 40mm and 90mm. It is recommended that weir heights of 40 to 50mm are used. In this case the selected weir height (hw) is 50mm. [31]

4.14.3 Weeping

Weeping occurs when the flowrate in the distillation column is low. Due to this the pressure exerted by the vapour is insufficient to hold up the liquid on the tray. As a result of this, liquid starts to leak through the perforations (holes). Dumping occurs as a result of excessive weeping. This will mean that the liquid on all the trays will crash through to the base of the column. This in turn results in a domino effect and the therefore the column will have to be re-started. Significant pressure drops and reduced separation efficiency indicate the presence of weeping. [27] The weep point occurs when liquid leakage through the plate holes

(37)

37 becomes excessive. The vapour velocity at the weep point is the minimum velocity required for stable operation. The vapour flow velocity at the lowest operating rate must be well above the weep point when specifying the hole area. The minimum design vapour velocity is given in equation 11.[32]

[ ] [ ] [ ]

Equation11: Minimum Design Vapour Velocity [32]

Where:

uh: The minimum vapour velocity through the holes dh: The hole diameter

K2: A constant, which is dependent on the depth of clear liquid on the plate (obtained from figure 15)

Weeping Check [33]

K2 in equation 11 is a constant value. In order to determine K2 the depth of the crest of liquid over the weir (how) must first be calculated. The Francis weir formula can be utilised to find the height of the liquid crest over the weir. The Francis weir formula is given in equation 12.

[ ]

Equation12: Francis weir equation [34]

Where:

how: Weir Crest Lw: Weir Length Lw: Liquid flow-rate

: Liquid Density

Firstly, the values required to determine the weir crest must be calculated. The maximum liquid rate ( L’):

The minimum liquid rate at 70% turn down: = 0.7 x 8.312

(38)

38 Maximum how: [ ] Minimum how: [ ]

At the minimum liquid rate: hw + how = 50 + 24.312 = 74.312 The K2 value can now be determined from figure15.

Figure15: Weep point correlation [35]

The corresponding K2 value at 74.312mm is 30.7.

Now the minimum design vapour velocity can be calculated from equation 11. Where:

dh: The hole diameter = 5 mm K2: A constant = 30.7

ρv: Vapour Density = 2.427 kg/m3 Substitute values into equation 11:

[ ] [ ]

(39)

39 It is important to calculate the actual minimum vapour velocity. This is calculated as follows:

It can be seen that the minimum operating rate is well above the weep point.

4.14.4 Plate Pressure Drop

In the design of distillation columns the pressure drop is an important aspect. There are two causes of pressure drop: as a result of vapour flow through the holes and due to the static head of liquid on the plate. The total pressure drop is the sum of the dry plate pressure drop (hd), the head of the clear liquid on the plate (hw + how) and residual losses (hr). Residual losses account for other minor sources of pressure losses which may occur. The residual loss is the difference between the experimental pressure drop and the sum of the dry plate drop and the clear-liquid height. [36]

4.14.4.1 Dry Plate Drop

[37]

The pressure drop through the dry plate is calculated using equation 13. [ ]

Equation 13: Pressure drop through the dry plate [38]

Where:

Uh: Maximum vapour velocity through the holes

Co: Orifice coefficient. It is a function of plate thickness, hole diameter and the hole to perforated area ratio (obtained from figure16).

ρv: Vapour Density ρL: Liquid Density

(40)

40

Figure16: Discharge Coefficient [38]

The maximum vapour velocity through the holes (Uh) is calculated as follows: To determine Co: Assuming from the graph:

The corresponding Co value can be obtained 0.84

Now the dry plate drop can be determined by substituting into equation 13. [ ]

(41)

41

4.14.4.2 Residual Head

[39]

Many methods have been developed to estimate the residual head which have been a function of liquid surface tension, froth density and height. As a result of the correction term being small the estimation is not justified. However, an equation by Hunt et al (equation 14) has been proposed to find the residual head.

Equation 14: Residual Head [39]

Where:

hr: The Residual Head ρL: Liquid Density

4.14.4.3 Total Drop

The total pressure drop can now be calculated. The total plate drop is given in equation 15.

Equation 15: Total Plate Drop [39]

Where: ht: Total Drop

hd: Dry Plate Drop = 81.673 mm

hw+how: Head of clear liquid on the plate = (50 + 30.840mm) hr: Residual Head = 16.026 mm

Substitute in the values:

ht = 81.673 + 50 + 30.840 + 16.026 = 178.539 mm liquid

The total plate drop is expressed in terms of millimetres however it can also be given in pressure units. This is given as follows:

(42)

42 Where:

ΔPt: Total Plate Pressure Drop (Pa(N/m2)) ht: Total Plate Pressure Drop (mm liquid) ρL: Liquid Density

Substitute in the values:

ΔPt = 9.81 x 10-3 x 178.539 x780 = 1366.149 Pa = 1.366 kPa

4.14.5 Downcomer Design

[40]

When designing the downcomer it is important to ensure that the level of the liquid and the froth in the downcomer is considerably below the top of the outlet weir on the plate above it. The column is likely to flood if the level rises above the outlet weir. The pressure drop over the plate and the resistance to flow in the downcomer may cause a backup of liquid in the downcomer. A diagram of the downcomer backup is shown in figure17.

Figure17: Downcomer Back-up [40]

The head loss in the downcomer can be estimated using the equation is equation 17.

[ ]

Equation17: Head loss in downcomer [40]

Where:

Lwd: Liquid flow rate in downcomer

(43)

43 is used.

ρL: Liquid Density

The clearance area under the downcomer (Aap): (Aap) = hapIw

hap is the height of the bottom edge of the apron above the plate. The height is usually set at 5 to 10mm. In this case it has been set to be 10mm. So:

hap = hw – 10 = 50 – 10 = 40mm = 0.04m

The clearance area under the downcomer (Aap): =0.04 x 1.278 = 0.051 m2

It can be seen that Ad = 0.270m2. It can therefore be concluded that the smallest value for Am in this case is equal to Aap. i.e. Am = Aap

Substitute the values into equation 17:

[

]

The downcomer backup can now be calculated:

hb = 50 + 30.840 + 178.539 + 7.248 = 266.627 mm

The downcomer back up height should be less than 0.5 times the plate spacing and weir height for a safer plate design. This is shown below:

[ ]

[ ] 0.266m < 0.325m

(44)

44

4.14.6 Residence Time

[41]

It is important to ensure that enough time is allowed in the downcomer for any entrained vapour to disengage from the liquid stream and prevent the liquid being carried under the downcomer. A time of at least 3 seconds is recommended.

Equation 18: Residence Time for the downcomer [41]

Where:

tr: Residence Time

Ad: Downcomer Area = 0.270 m hbc: Clear Liquid back-up = 0.266 m ρL: Liquid Density = 780 kg/m3

Lwd: Liquid flow rate in downcomer = 8.312 kg/s Substitute in the values:

It can be seen that the calculated residence time is greater than the recommended time of least 3 seconds.

4.14.7 Entrainment

[42]

Entrainment is a result of high vapour flow rates and refers to the liquid carried up by vapour to the tray above. It is unfavourable as tray efficiency is reduced. The lower volatile material is carried to a plate holding liquid of a higher volatility. High purity distillates can also become contaminated. In the event of excessive entrainment flooding can occur. [27] The correlation developed by Fair (figure18) can be used to estimate entrainment. It shows the fractional entrainment (ψ) as a function of the liquid-vapour factor (FLV), with the percentage of flooding as a parameter.

It can be seen from section 4.13.5 that the percentage flooding is taken to be 80%. FLV = 0.058

The corresponding fractional entrainment (ψ) can be obtained from figure18 below. The (ψ) is found to be 0.041.

(45)

45 It is important to ensure that the fraction entrainment is lower than 0.1. It can be seen that the value obtained is significantly lower than 0.1 and is therefore within a safe operating range.

(46)

46

4.14.8 Trial Layout

4.14.8.1 Perforated Area

[43]

Figure19: Relation between angle subtended by chord, chord height and chord length [44]

Obstruction caused by structural members such as support rings and beams and by the use of calming zones reduces the area available for perforation. Calming zones are referred to unperforated strips of plate at the inlet and outlet sides of the plate. The widths of each zone are usually made the same and have recommended values of below 1.5m, 75mm; above 100mm. For sectional plates the width of the support ring is usually between 50 to 75mm. It is important to ensure that the support rings do not enter into the downcomer area. Using figure19 the unperforated area can be calculated from the plate geometry. [43] From figure19:

From the y axis the corresponding value determined = 99°

The angle subtended at the plate edge by unperforated strip = 180 – 99 = 81° Mean Length of unperforated edge strips = Area of unperforated edge strips =

(47)

47 Area of calming zone = 2(1.328 x 50 x 10-3) = 0.133 m2

Total Area for perforations (Ap) = Active Area - Area of unperforated edge strips - area of the calming zone Ap = 1.711 – 0.116 – 1.328 = 0.267 m2

The distance between the hole centres i.e. the hole pitch should not be less than 2.0 hole diameters. The normal range falls between 2.5 to 4.0 diameters. From the range the pitch can be selected to give the number of active holes required for the total hole area. Usually square and equilateral triangular patterns are used. Of these two the equilateral triangular pattern is preferred. The total hole area as fraction of the perforated area Ap is expressed in the following equation.

[ ]

Equation 19: The total hole area as a fraction of the perforated area [43]

From figure 20 below the can be determined using the value calculated for above.

Figure 20: Correlation to show the relationship between hole area and pitch [45]

The value obtained for does not fall within the range. This means that the hole area is too large. Within the provisional plate design it was originally assumed that the hole area will be taken as 10% of the active area. However, now we shall assume a hole area as 3% of the active area:

(48)

48 Ah =0.03 x 1.711 m2_{= 0.051 m}2

Therefore, can now be recalculated:

The corresponding can now be obtained figure20:

4.14.8.2 Number of Holes

The diameter of hole = 5mm Therefore,

4.14.9 Liquid Flow Arrangement

(49)

49 The liquid flow-rate and column diameter are the factors which determine the choice of the plate type i.e. reverse, single pass or multiple pass. Figure21 can be used to find the liquid-flow arrangement. [46]

From figure21it can be seen that a cross –flow (single pass)can be used.

4.14.10 Hydraulic Gradient

The difference in liquid level which is needed to drive the liquid flow across the plates is referred to as the hydraulic gradient. On sieve plates no hydraulic gradient occurs because of small resistance to liquid flow. In sieve plate designs the hydraulic gradient is usually ignored. [43]

4.14.11 Actual Plate Efficiency

[47]

Van Winkle et al (1972) published a correlation for the determination of plate efficiency which can be used for binary systems. Dimensionless groups which affect plate efficiency are included within the correlation. The equation is as follows:

08 . 0 25 . 0 14 . 0 Re 07 . 0 Dg Sc Emv 

Equation 20: Van Winkle Correlation for plate efficiency [47]

Where:

(50)

50 σL: Liquid surface tension = 0.0213 N/m (calculation shown in appendix ##)

DLK: Liquid Diffsivity = (calculation shown in appendix ##) hw: Weir height = 50 mm

ρL: Liquid Density = 780 kg/m3 ρv: Vapour Density = 2.427 kg/m3

Calculating the unknowns from above:

Substitute all the values into the Van Winkles equation: Emv = 0.07 × (67.046)0.14 × (74.139)0.25 ×(10537.998)0.08 Emv = 0.776

(51)

51

4.14.12 Actual Number of Plates

Previously two methods were used to determine the theoretical number of plates. According to Gilliland and Fenske’s correlation 24 plates would be required. According to the Erbar-Maddox correlation 23 plates would be required. We must select the worst case scenario i.e. pick 24 plates.

Therefore, the actual number of plates required taking account of the calculated plate efficiency would be as follows:

In order to achieve effective distillation 31 stages would be required.

4.14.13 Height of Column

The equation below can be used to predict the height of the distillation column: Hc = (N+1)*Hs+∆H+plate thickness

Equation 21: Determination of Column Height

Where:

N: The actual number of plates (stages) required = 31 Hs: The tray spacing = 600mm (0.6m)

ΔH: The distance of liquid holdup and vapour disengagement = 1m Plate Thickness = 5mm (0.005m)

Substitution of all values gives a column height of: [(31 + 1) × 0.6] +1 + 0.005 = 20.205m ~ 21m The height of the column is therefore predicted to be approximately 21m tall.

(52)

52

5.0 Energy Balance

[48]

Process streams have kinetic and potential energies; however, they are neglected as they are small. In all systems a transfer of heat occurs between the inlet and outlet streams. This is shown in figure22.

Figure22: Transfer of Energy within a system [48]

Input of energy is provided by two means: from the feed (Hf) and the reboiler (Qb). So: Qb + feed sensible heat Hf

Output of energy occurs from the top (HD) and bottom (HW) products and from the condenser (QC). So: QC + top and bottom products sensible heat HD + HW

In order to calculate the condenser and reboiler heat load the following have to be calculated:

 Latent Heat of Vaporisation of the Components ( Calculations found in appendix ##)

 Specific Heat Capacity ( Calculations found in appendix ##)

5.1.1 Condenser Heat Load (Q

C

)

In order to determine QC the heat balance must be calculated around the condenser. The temperature of the column is 89°C (362 K), however the temperature at the top of the column must be lower than this. The inlet temperature to the condenser is assumed to be 79.98°C (352.98K) and the outlet temperature is assumed to be 60°C (333 K). From the mass balance in section 4.8 it can be seen that the distillate contains 99% MEK so the calculation will be based on the capacities of only MEK.

(53)

53

Figure23: Top of column and condenser diagram [49]

At a steady state as shown in figure 23 the following are true: INPUT = OUTPUT

And this can be rearranged to determine QC:

It is assumed that complete condensation occurs so: Enthalpy of vapour HV = Latent + Sensible

189.809 J/molK 1.591 J/molK [ ] Where: 189.809 J/molK 1.591 J/molK V’_{= 28495.543 kg/hr}

Substitute in all the values:

(54)

54 [ ]

QC = 6317039.579 kj/hr = 1754.733 KW

The top product and reflux will be at the same temperature so QC = HV

Cooling water required

The amount of cooling water required in the condenser will be calculated in this section. It is assumed that:

It is know that:

The above equation can be rearranged to calculate the amount of cooling water required. This is as follows:

Where:

Cp = 4.187 kj/kg.K

ΔT = From the process description in section 4.1 it can be seen that the cooling water enters the condenser at 24°C (297K) and leaves at 40°C (313 K).

Substitute the values in:

(55)

55

5.1.2 Condenser Design

This next focuses on the detailed design of the condenser.

There are certain specifications which are put in place in order to carry out the appropriate calculations. They are as follows:

 Outside Diameter (OD) of 25mm

 Internal Diameter (ID) of 20mm

 Tube length of 5m

 Baffle cut of 25% is optimum as this gives good heat transfer rates [50]

 The condensing material MEK will be located on the shell side as the shell side copes better with changes in density. The cooling water will flow on the tube side.

 Pipes are assumed to be arranged in a square arrangement. This is due to the ease of maintenance such as cleaning. [51]

 The recommended minimum clearance between the tubes is 25 inches (6.4mm) when using a square pattern. [51]

 The overall heat transfer coefficient (U) is assumed to be 850 W/m2 °C [52]

 Fouling Coefficient of 5000 W/m2 °K

5.1.2.1 Heat Transfer Area and Number of Tubes (NT)

Calculating the provisional Area:

Firstly the log mean temperature needs to be calculated using the following equation:

([ _[ ]_])

Equation 22: Calculation of log mean temperature [53]

Where:

ΔTLM: Log mean temperature difference T1: Inlet shell side fluid temperature = 79.98°C T2: Outlet shell side fluid temperature = 60°C t1: Inlet tube side temperature = 24°C t2: Outlet tube side temperature = 40°C

(56)

56 Substitute values into equation 22:

([ ]_{[ ] )}

We are aware that Q=UAΔT. This can be rearranged to obtain the area. This is shown below:

From the above assumptions and specification it can be seen that U is assumed to be 850 W/m2 °C. Therefore;

(

)

From this information the number of tubes can now be calculated:

Square pitch of 1.25do

Therefore pitch (Pt) = 1.25 x 25 = 31.25 mm

5.1.2.2 Tube Bundle Diameter (Db)

[54]

The diameter of the tube bundle depends on both the number of tubes and the number of passes. The tube bundle diameter can be estimated from equation 23. The constants are shown in table 5.

( )

Equation 23: Tube Bundle diameter page [54]

Where:

Db: Bundle Diameter

(57)

57 do: Outside diameter = 25mm

K1 and n1: Constants = assumed a square pitch with 2 passes (The constants are shown in table 5)

Table 5: Constants required for tube bundle equation[54] Substitute the values into equation 23:

( ) Where: Db: Bundle Diameter = 484.774 mm Pt: Tube Pitch = 31.25 mm Therefore:

5.1.2.3 Length of Condenser

The length of the condenser can be calculated as follows:

Equation 24: Length of Condenser

(58)

58 L: The length of the condenser

A: The heat transfer area = 54.391 m2 do: Outside diameter = 25 mm NT: The number of tubes

Substitute in the values into Equation 24:

5.2 Tube Side Coefficient

[55]

The tube side coefficient is calculated using equation 25 below. The equation has been adapted from data provided Eagle and Ferguson (1930).

Equation 25: Tube Side Coefficient [56]

Where:

hi: Inside coefficient for water

t: water temperature = 32°C - calculated below ut: Water Velocity - calculated below

di: Tube inside diameter = 20mm

Mean temperature of water:

Tube cross-sectional area:

Tube side water velocity:

(

)

(59)

59 Density of water = 998 kg/m3[57]

Substitute into Equation 25:

5.3 Shell Side Coefficient

[58]

Firstly the shell diameter has to be determined. The bundle diametrical clearance is found from figure24 below. Then this is used with the bundle diameter to calculate the shell diameter.

Choosing the pull through floating head the bundle diametrical clearance is found to be 90.5mm. Shell Diameter (DS) = 484.774 + 90.5 = 575.274 mm

Figure24: Shell-bundle Clearance [59]

In the shell’s baffles are used to direct the fluid stream across the tubes. They help to increase fluid velocity and therefore improve the rate of transfer. Single segmental baffles are the most common type of baffle used. This type of baffle is show in figure25.

Distillation Column Design

Contents

1.0 Project Objectives

2.0 Project Objectives

2.1 Technical Objectives

2.2 Personal Objectives

3.0 Introduction

3.1 Components of Distillation Columns

3.1.1Reboiler

3.1.2 Condenser

4.0 Chemical Engineering Design

4.1 Process Description

4.2 Distillation Column Design

4.3 Key Components

4.4 Operating Conditions

4.6 Packed Columns

4.6.1 Types of Packing

4.7 Plate Columns

4.7.1 Types of Plate

4.8 Mass Balance

4.8.1 Adjusted Mass Balance

4.9 Vapour Pressure Calculation

Component

A

B

C

B.P (°C)

ΔH

(kJkmol

)

Methyl Ethyl Ketone

(MEK)

3.9894

1150.207

-63.904

79.6

31.3

Secondary Butyl Alcohol

(SBA)

4.32943 1158.672 -104.683

99

40.75

4.9.1 Relative Volatility

4.10 Reflux Ratio

4.11 Fenske Equation and Gilliland Correlation

4.12 Erbar–Maddox Correlation

4.13 Column Diameter

4.13.1 Internal Traffic

4.13.2 Vapour Density

4.13.3 Liquid Density

A

B



*



Component

A

B

n

Critical

Temperature,

T

(K)

Operating

Temperature

(K)

Methyl Ethyl Ketone

(MEK)

0.2676

0.2514

0.2857

535.5

362

Secondary Butyl Alcohol

(SBA)

0.2734

0.2635

0.2604

536.01

362

_

_