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CHAPTER 5
EQUIPMENT SIZING AND COSTING
5.1 Introduction
This section covered the chemical design of the equipment and unit operation
in the acrylic acid plant. The equipment and the unit operation used in the process
plant are listed as below :
Table 5.1: The Equipment List
UNIT QUANTITY
Compressor 2
Mixer 1
Heat Exchanger 1
Heater 1
Cooler 3
Reactor 2
Flash 1
Extraction Column 1
Pump 3
Distillation Column 3
Group 39 200,000 MTA Acrylic Acid
Chapter 5-1
Refrigeration System 2
Condenser 1
Reboiler 3
Storage Tank 3
In this chapter, the summary result of every equipment will be shown and the
detailed calculation can be found in Appendix E. The result of this chapter will be
used in the calculation of mechanical design in Chapter 8. The base cost of every
equipment is based on the methods in Systematic Methods of Chemical Process
Design (L.T Biegler, I.E. Grossmann and A.W. Westerberg, 1997) and A Guide to
Chemical Engineering Design & Economics (Gael D. Ulrich, 1984)
5.2 Compressor
5.2.1 Introduction
Compressor is used to compress gases from one point to another point. There
are three type of compressor widely used in the process industries namely,
centrifugal, reciprocating and axial flow compressor. Axial flow compressor used for
high flowrate and moderate differential pressure and centrifugal compressor for high
flowrate and by staging for high differential pressure. Reciprocating compressor can
be used over a wide range of pressures are required at relatively low flowrate. Each
compressor is generally a function of the gas capacity, action and discharge head.
The work of compressor and single stage compressor can be calculated by
assumed the compressor is operated ideally under adiabatic compressor with three
stage compressor.
Ws = ( (-1) ) RTinlet [ (Poutlet Pinlet( (-1) ) - 1]
With :
Ws = Compressor work (kJ/ hr)
Group 39 200,000 MTA Acrylic Acid
Chapter 5-2
= Molar gas flowrate (kmol/ hr)
= Cp / Cv = 1.4
R = Gas constant
= 8.314 kJ/ kmol K
Tinlet = Inlet temperature (K)
Poutlet = Outlet pressure (atm)
Pinlet = Inlet pressure (atm)
The actual compressor work is
Wactual = W / (c x m)
With :
Wactual = Actual compressor work (hp)
W = Compressor work (kW)
c = Compressor efficiency
m = Motor efficiency
5.2.2 Chemical Design and Costing Summary
Detailed calculation as shown in Appendix E
Identification Compressor 1 Compressor 11
Item no. 1 11
Function To provide system
pressure required
To provide system
pressure required
Material of construction Stainless Steel Stainless Steel
Type of equipment Air Compressor Centrifugal Motor
Flowrates (kmol/hr) 4937.6 753.3
Pressure inlet (atm) 1 0.0526
Pressure outlet (atm) 3 1.5
Group 39 200,000 MTA Acrylic Acid
Chapter 5-3
Temperature in (C) 25 12.4
Actual work (kW) 1218.8 3874.4
Equipment Cost (RM) 48423354.39 22533319.22
Total Cost 70,956,673.62
5.3 Mixer
5.3.1 Introduction
The function of mixer is to mix the different components from different
stream into one stream. Turbulent flow is important to make sure that the component
mix well. In theory, turbulent flow can be achieve when the Reynolds Number
>2000. Therefore, a space-time assumption of 60 seconds is made in the calculation
in order to achieve a Reynolds Number >2000.
5.3.2 Chemical Design and Costing Summary
Detailed calculation as shown in Appendix E
Identification Mixer 9
Item no 9
Function Mixed fresh ethyl
acetate with recycle
stream 20
Material Stainless Steel
Flowrates, kmol/ hr. 804.23
Volume, m3 1.0590
Pressure, atm 1.5
Temperature, C 30.0
Equipment Cost (RM) 560642.95
Group 39 200,000 MTA Acrylic Acid
Chapter 5-4
Total Cost 560642.95
5.4 Heat Exchanger
5.4.1 Introduction
Heat exchanger can be classified in a number of ways depending on their
construction or on how the fluid moves relatively to each other through the device.
The most common type is one in which the hot and the cold come separated by a
tube wall or a flat or curved device. For this chemical design, the heat exchanger
that transferred heat from the hot stream to the cold stream and from the cold stream
to hot stream will be considered.
5.4.2 Design Procedure
The design procedure follows as below :
i. Define the duty: heat transfer rate, fluids flow rate and temperature
ii. Collect the fluid physical properties required : density, viscosity and
thermal conductivity.
iii. Decide the type of heat exchanger to be used.
iv. Select the value for the overall coefficient, U.
v. Calculated the mean temperature different, Tlm
vi. Calculated the heat transfer area required
vii. Decide the heat exchanger layout
viii. Calculated the individual coefficient
ix. Calculated the overall coefficient and compare with the trial value. If the
calculate value is above the estimated value, than the overall coefficient is
satisfy
x. Calculated the heat exchanger pressure drop; if the pressure drop is less than
1 atm, this mean that the pressure drop for heat exchanger is acceptable.
Group 39 200,000 MTA Acrylic Acid
Chapter 5-5
5.4.3 Summary for Heat Exchanger Design
Detailed calculation as shown in Appendix E
Identification Heat Exchanger
Item no 19
Function Exchange Heat Between Stream
5 and Stream 9
Heat Duty, Q (kW) 14,155.16
Hot Fluid Properties
Flowrates (kg/s)
Inlet temperature (C)
Outlet temperature (C)
62.81
220
59.7
Cold Fluid Properties
Inlet temperature (C)
Outlet temperature (C)
149
315
Heat transfer area, A (m2) 721
Number of tubes, Nt 2350
Tube inside diameter, dI (mm) 16
Tube outlet diameter, do (mm) 20
Length of tube, L (m) 4.88
Bundle diameter, Db.(mm) 1.352
Shell diameter, Ds.(m) 1.448
Tube Pressure Drop (atm) 0.3
Shell Pressure Drop (atm) 3.1
Cost, RM 5,045,787
Total Cost, RM 5,045,787
Group 39 200,000 MTA Acrylic Acid
Chapter 5-6
5.4.4 Summary for Heater Design
Detailed calculation as shown in Appendix E
Identification Heater
Item no 4
Function Heating Stream 28
Heat Duty, Q (kW) 852.72
Hot Fluid Properties
Flowrates (kg/s)
Inlet temperature (C)
Outlet temperature (C)
16.16
321
295
Cold Fluid Properties
Inlet temperature (C)
Outlet temperature (C)
315
Heat transfer area, A (m2) 210.1
Number of tubes, Nt 685
Tube inside diameter, dI (mm) 16
Tube outlet diameter, do (mm) 20
Length of tube, L (m) 4.88
Bundle diameter, Db.(mm) 0.773
Shell diameter, Ds.(m) 0.867
Tube Pressure Drop (atm) 3.8
Shell Pressure Drop (atm) 3.7
Cost, RM 728,836.00
Total Cost, RM 728,836.00
Group 39 200,000 MTA Acrylic Acid
Chapter 5-7
5.4.5 Summary for Cooler Design
Detailed calculation as shown in Appendix E
Identification Cooler Cooler Cooler
Item no 6 8 12
Function Cooling
Stream 29
Cooling
Steam 7
Cooling
Stream 19
Heat Duty, Q (kW) 852.28 9708.97 2339.36
Hot Fluid Properties
Flowrates (kg/s)
Inlet temperature (C)
Outlet temperature (C)
36.61
59.7
50
62.73
325
220
14.50
131
30
Cold Fluid Properties
Inlet temperature (C)
Outlet temperature (C)
25
40
25
50
25
50
Heat transfer area, A (m2) 116.3 673.2 176.1
Number of tubes, Nt 379 2195 574
Tube inside diameter, dI (mm) 16 16 16
Tube outlet diameter, do (mm) 20 20 20
Length of tube, L (m) 4.88 4.88 4.88
Bundle diameter, Db.(mm) 0.592 1.311 0.714
Shell diameter, Ds.(m) 0.683 1.407 0.806
Tube Pressure Drop (atm) 2.4 0.5 0.0013
Shell Pressure Drop (atm) 0.0024 0.1 0.0029
Cost, RM 560,643 1,569,800 672,772
Total Cost, RM 2749215.00
Group 39 200,000 MTA Acrylic Acid
Chapter 5-8
5.4.6 Summary for Reboiler Design
Detailed calculation as shown in Appendix E
Identification Reboiler Reboiler Reboiler
Item no 10 14 17
Function Heating out
stream from
distillation 10
Heating out
stream from
distillation 14
Heating out
stream from
distillation 17
Equipment Type Kettle Reboiler Kettle Reboiler Kettle Reboiler
Heat Duty, Q (kW) 8142.750 6138.125 2932.708
Hot Fluid Properties
Flowrates (kg/s)
Inlet temperature (C)
Outlet temperature (C)
85.7718
150
100
664.6561
150
100
153.7625
150
140
Cold Fluid Properties
Inlet temperature (C)
Outlet temperature (C)
23.2
33.4
32.3
40.3
59.4
59.70
Heat transfer area, A (m2) 95.8293 79.0865 38.1778
Number of tubes, Nt 201 166 80
Tube inside diameter, dI (mm) 28.45 28.45 28.45
Tube outlet diameter, do (mm) 31.75 31.75 31.75
Length of tube, L (m) 4.8 4.8 4.8
Bundle diameter, Db.(mm) 723.2039 665.2634 0.714
Shell diameter, Ds.(m) 1.4464 1.3305 0.806
Cost, RM 688297.04 615844 398487.76
Total Cost, RM 1702628.80
Group 39 200,000 MTA Acrylic Acid
Chapter 5-9
5.4.7 Summary for Condenser Design
Detailed calculation as shown in Appendix E
Identification Condenser
Item no 17
Function Cooling out
stream from
distillation 17
Equipment Type Floating head
Heat Duty, Q (kW) 2530.8889
Hot Fluid Properties
Inlet temperature (C)
Outlet temperature (C)
28.5
28.3
Cold Fluid Properties
Flowrates (kg/s)
Inlet temperature (C)
Outlet temperature (C)
605.2007
25
26
Heat transfer area, A (m2) 979.8716
Number of tubes, Nt 839
Tube inside diameter, dI (mm) 22.10
Tube outlet diameter, do (mm) 25.40
Length of tube, L (m) 4.88
Bundle diameter, Db.(mm) 1079.4982
Shell diameter, Ds.(m) 1.1735
Cost, RM 2934318.96
Total Cost, RM 2934318.96
5.5 Refrigeration
Group 39 200,000 MTA Acrylic Acid
Chapter 5-10
5.5.1 Refrigeration system
If a process stream needs to operate below about 300 K, some sort of
refrigeration is required and a refrigeration cycle needs to be considered. Often,
refrigeration can be purchased from an off-site facility.
In designing a refrigeration system , we first consider the refrigeration cycle
and the pressure-enthalpy diagram. As with staged compression, there is a trade-off
between capital and operating costs in choosing the number of refrigeration cycles. A
single cycle requires the maximum work and cooling water while a large number of
cycles require minimum work and cooling water. To relate the work (W) and heat
rejected for refrigeration (Q), a coefficient of performance is defined, CP = Q/ W. As
with staged compression, CP~4 is selected for design purposes. Thus, in a typical
cycle :
W = Q/ 4
Qc = W + Q ~ 5/ 4 Q
And for the compressor driven with an electric motor,
Wb = W/ mc
= W/ 0.72
(Assume c = 0.8 and m = 0.9)
5.5.2 Designing a Refrigeration System
By using these simplified sizing relationship, the work requirements for each
refrigeration cycle will be evaluated. This is done by considering that CP is the same
for all N cycles, and T = 30K/ cycle. The simplified relationships are :
W = Q [(5/ 4)N – 1 ]
Qc = (5/ 4)N Q
Wb = W/ (mc)
Group 39 200,000 MTA Acrylic Acid
Chapter 5-11
The costing of a refrigeration system can be done by using the mechanical
refrigeration configurations which had been specified directly in Guthrie. The basic
configuration includes centrifugal compression, evaporators, condensers, field
erection, and subcontractor indirect costs.
5.5.3 Sizing and Costing Summary of Refrigeration System
Detailed calculation as shown in Appendix E
No. of
cycles
Qc (kW) Wb (kW) S (ton) Price
RM
Condenser 10 1 162.65 45.1801 37.00 1438590.40
Condenser 14 1 7554.17 2098.3796 1718.40 21124826.58
Total 22563416.98
5.6 Reactor
Group 39 200,000 MTA Acrylic Acid
Chapter 5-12
5.6.1 Introduction
In term of reactor design, decisions must be made due to the type of reaction,
concentration, temperature, pressure, phase and catalyst. Then a practical reactor is
selected, approaching as nearly as possible the ideal in order that the design can
proceed.
Practical reactor deviate from the three idealized models, which are idealized
batch model, continuous well-stirred model and plug-flow model. The practical
reactor can be classified to stirred tank reactor, tubular reactor, fixed bed catalytic
reactor, fixed bed non-catalytic reactor, fluidized bed catalytic reactor, fluidized bed
non catalytic reactor and kiln.
5.6.2 Chemical Design Summary
Detailed calculation as shown in Appendix E
Reactor First-stage (R-3) Second-stage (R-5)Type Fixed-bed Multi-Tubular Reactor
Operating conditions :Temperature, oC 325 220Pressure, atm 2.5 2.5Space velocity, h-1 1625 2160Residence time, s 2.22 1.67Volume, m3 124 93Diameter, m 3.4 3.1Length, m 13.6 12.4Cross-sectional area, m2 9.1 7.5Catalyst :Basic components Mo, Co, Ce, Ni oxidesAppearance Grey tablets with dimensions 5x5 mm Bulk density, kg/m3 1200 1200Total mass, kg 74296 55921Mass in tube, kg 15.6 14
Group 39 200,000 MTA Acrylic Acid
Chapter 5-13
Tube properties :Nominal size, in 2 2Outside diameter, mm 60 60Inside diameter, mm 42.25 42.25Wall thickness, mm 5.4 5.4Inside cross-sectional area, m2 0.001905 0.001905Number of tube 4776 3952Length, m 7 6Bundle diameter, m 5.34 4.89Shell inside diameter, m 5.4 4.94Baffle spacing, m 2.16 1.98Number of baffle 3 3Heat removal system :Heat transfer area, m2 3468.6 3005.1Cooling media Molten SaltCoolant flowrate, m3/h 411.4 698.9Total cost, RM 3,135,000 2,810,690
5.7 Flash Column
5.7.1 Introduction
Group 39 200,000 MTA Acrylic Acid
Chapter 5-14
The flash drums are simply a pressure vessel to phase-split between liquid
and vapor phase. The chemical engineering design of the flash drum are based on the
method found in Chemical Engineering Volume 6 (Sinnott, 1991).
5.7.2 Chemical Design and Costing Summary
Detailed calculation as shown in Appendix E.
Identification Flash
Item no. 7
Function Purge The Residual Gas
Material Stainless Steel
Temperature (C) 30
Pressure (atm) 1.5
Cross sectional Area (m2) 11.8417
Inside Diameter (m) 3.8827
Height for Vapor Phase (m) 3.8827
Light Liquid Height (m) 2.2414
Liquid Depth (m) 1.3862
Cost 2458203.71
Total Cost, RM 2458203.71
5.8 Pump
5.8.1 Introduction
Group 39 200,000 MTA Acrylic Acid
Chapter 5-15
Pump are devices for supplying energy or head to a flowing liquid in order to
overcome head losses due to friction and also if necessary, to raise the liquid to a
higher level. The different types of pump commonly employed in industrial
operations can be classified as follows :
Reciprocating or positive-displacement pump with valve action : piston pumps,
diaphragm pumps, plunger pumps.
Rotary positive-displacement pumps with no valve action:gear pumps, lobe
pumps, screw pumps, metering pumps.
Rotary centrifugal pumps with no valve action : open impeller, closed impeller,
volute pumps and turbine pumps.
Air-displacement systems : airlifs, acid eggs or blow cases, jet pumps, barometric
legs.
The centrifugal pumps are the major types that used in the chemical plant
nowadays. Centrifugal pumps are used so extensively and for such a wide variety of
services that need for standardization of dimensions and operating characteristic has
long been evident. Pump selection is made depending on the flow rate and head
required, together with other process considerations.
5.8.2 Chemical Design and Costing Summary
Detailed calculation as shown in Appendix E.
Group 39 200,000 MTA Acrylic Acid
Chapter 5-16
.
Identification Pump Pump Pump
Item no 15 16 18
Function Pump the effluent
to D-10
Pump the
effluent to D-14
Pump the fresh
solvent
Type Centrifugal Pump Centrifugal
Pump
Centrifugal Pump
Material of
construction
Stainless Steel Stainless Steel Stainless Steel
Inlet Flowrates,
(kmol/hr)
877.2 455.9 50.9
Outlet Flowrates,
(kmol/hr)
877.2 455.9 50.9
Pressure Inlet (C) 0.526 0.039 1
Pressure Outlet
(C)
1 1 1.5
Temp. Inlet (C) 33.4 40.3 30
Temp. Outlet (C) 33.3 40.3 30
Shaft power (kW) 1.3973 1090.3283 0.1346
Differential head
(m) 9.6917 9.7003 5.8351
Equipment Cost
(RM) 88552.84 2728.79 336.83
Total Cost 200106.41
5.9 Distillation Column
Group 39 200,000 MTA Acrylic Acid
Chapter 5-17
Industrial scale of production of chemical product concerns purity of the
product. Higher purity gives higher market price. In each operation, separator plays
a major and important task to separate products from side products in order to obtain
the desired specification. Chemical can be divided into miscible and immiscible
phases. Immiscible phase can be isolated using physical separation methods, while
separating of miscible phase mostly deals with surface contacting devices. Among
the equipment used are distillation column, absorption column and stripping column.
5.9.1 Introduction
Distillation is a process of heating a liquid until its more volatile constituents
pass into the vapor phase, and then cooling the vapor to recover such constituents in
liquid form by condensation. The main purpose of distillation is to separate a
mixture of several components by taking advantage of their volatilities, or the
separation of volatile materials from nonvolatile materials. The design of distillation
columns in this production of 200,000 MT/ year of acrylic acid has based on the
typical design procedures as stated in Chapter 11 of Chemical Engineering, Volume
6, by J.M Coulson and J.F Richardson.
For the column sizing and plate design, a trial and error approach has been
used to obtain an optimum and satisfactory design. Each design variable is set and
calculated from the design formula and based on the recommended values. By
checking the key performance factors, the design parameters have been revised or
other wise determined. Some designs parameters are obtained from the simulation
generate report by the ChemCAD Simulator. In addition, the design calculation is
done for above feed point and below separately.
5.9.1.1 Choosing A Plate or Packed Column
Group 39 200,000 MTA Acrylic Acid
Chapter 5-18
There are two common types of distillation column used in the industries that
are palate or packed column. It is important to choose the right type of distillation
column in order to obtain the most efficient and cost effective separation process.
The most suitable type of column must be determined for the desired separation
process because these two columns have their own uses. In this project, a sieve plate
has been selected.
5.9.1.2 Plate Spacing
Plate spacing is the important for determined the overall height of column.
Plates spacing from 0.15m to 1m are normally used. The spacing chosen depends on
the column diameter and operating conditions. For column above 1m diameter, plate
spacing 0.3 to 0.6m will normally be used, and 0.5m can be taken as initial. This
will be revised as necessary.
5.9.1.3 Column Diameter
The principle factor on determining the column diameter is the vapor flow
rate. The column diameter can be calculated by calculating the top and bottom net
area at its maximum volumetric flow rate. The velocity is normally between 70 to
90% of what which cloud cause flooding
5.9.1.4 Height of Column
The height of column in the distillation column is calculated by knowing the
number of actual stages. Theoretical stages is given by ChemCAD Simulator was
used to obtained the number of actual stages required. The height of column can be
calculated by multiplying the number of the actual stages with tray spacing value.
5.9.1.5 Design Procedure
Group 39 200,000 MTA Acrylic Acid
Chapter 5-19
The general outlines of the design procedures are as below;
i. Determine the vapor and liquid rate, based on the reflux ratio and feed
condition
ii. Collect or estimate the system physical properties
iii. Select a trial plate spacing
iv. Based on the flooding condition, the column diameter is determined.
v. Decided the liquid flow pattern on the plate.
vi. Try to make a plate layout with downcomer area, active area, hole diameter,
hole area, weir height, weir length and plate thickness.
vii. Check the weeping rate.
viii. Check the plate pressure drop.
ix. Check the down-comer backup.
x. Determine plate layout details.
xi. Confirm on the percentage flooding based on the chosen column diameter.
xii. Check for entrainment.
xiii. Optimize the design parameters for column diameter and plate spacing.
xiv. Determine the column wall thickness and column head selection.
xv. Finalize the design with the drawing and data specification sheet.
5.9.2 Chemical Design and Costing Summary
Group 39 200,000 MTA Acrylic Acid
Chapter 5-20
Detailed calculation as shown in Appendix E.
Identification Distillation Distillation Distillation
Item no. 10 14 17
Operating pressure, barg 0.0533 0.0935 0.0404
Column Sizing
a) Tray Spacing (m)
b) Diameter of column, Dc (m)
c) Area of column, Ac (m2)
d) Total height of column, HT (m)
0.61
3.93
12.1627
12.64
0.61
2.78
6.0884
23.49
0.61
2.31
4.2025
23.49
Provisional plate design
a) Plate thickness (mm)
b) Plate area
i. Downcomer area, Ad (m2)
ii. Net area, An (m2)
iii. Active area, Aa (m2)
iv. Hole area, Ah (m2)
3
1.4595
10.7031
9.2436
0.9244
3
0.7306
5.3578
4.6272
0.4627
3
0.5043
3.6982
3.1939
0.3194
Weir Design
a) Weir length, Iw (m)
b) Weir height, Hw (m)
c) Weir liquid crest
i. Maximum, how (mm liquid)
ii. Minimum, how (mm liquid)
2.9868
12
30.2929
23.8821
2.1128
12
21.9503
17.3051
1.7556
12
24.5746
19.3509
Weep Point
a) Minimum Uh (m/s)
b) Actual Ua (m/s)
30.0833
62.9164
52.9122
127.1840
37.5584
83.2073
Hole Design
a) Hole diameter (mm)
b) Hole area (m2)
c) Number of holes
5
1.964x 10-5
47066
5
1.964x 10-5
23561
5
1.964x 10-5
16263
Total plate pressure drop
(mm Liquid)
175.6899 169.2340 150.0615
Group 39 200,000 MTA Acrylic Acid
Chapter 5-21
Equipment Cost (RM) 4601987.36 5164815.38 4122882.02
Total Cost 13889684.76
5.10 Storage Tank Specification
5.10.1 Chemical Design and Costing Summary
Detailed calculation as shown in Appendix E.
Storage Tank Propylene (raw material)Day of inventory, days 3Vessel type Cylindrical (Bullet) TankNumber of Bullet 2Volume, m3 1383Pressure, bar 30.0Temperature, oC 40.0Stored materials LiquidDiameter, m 7.60Length, m 30.0Orientation Axis horizontalCorrosion allowance, mm 2.0Wall thickness, mm 6.0Material of construction Carbon SteelCost, RM 6,037,693
Storage tank Ethyl Acetate (solvent) Acrylic Acid (product)Day of inventory, days 5 5Vessel type Floating-roof Floating-roofVolume, m3 654 3190Pressure, atm 1 1Temperature, oC 25 25Stored materials Liquid LiquidDiameter, m 8.22 13.94Height of tank :
HS
4.11 6.97
HL 3.7 6.27HR 0.72 1.23
Group 39 200,000 MTA Acrylic Acid
Chapter 5-22
Orientation Axis vertical Axis verticalCorrosion allowance, mm 2 4Wall thickness, mm 12 21Material of construction Carbon Steel Stainless SteelCost, RM 306,485 1,707,805
Group 39 200,000 MTA Acrylic Acid
Chapter 5-23