Estimate the cost of manufacturing (COMd) for the styrene process given in Project B.3 of Appendix B. Assume that the fixed capital investment (CTM) = $145 x 106. You are required to determine the remaining four components (COL, CRM, CUT, CWT) in order to estimate COMd. Clearly state assumptions, if any. Please show hand-calculations for all steps.

Hints:

1. For compressor drives, divide electricity load by equipment efficiency (from summary tables) to determine the actual load. Note that only the drive needed for the compressor needs to be included here. No need to add the compressor separately, in the context of utility cost.

2. Remember to take credit for steam wherever appropriate.

3. Use appropriate steam price assuming electricity is co-generated at the plant (i.e., with credit for power).

4. For heat exchangers, use kg/h of steam/water associated with the process (summary table B.3.2), and hence the $/kg version of the unit cost (Table 8.3).

5. E-402feed for this is hps (stream 25). Assume this steam becomes a condensate before being recycled back as bfw to the steam plant for regeneration. The remainder of the original hps coming into the process from stream 4 is diverted as inert feed for the reaction (via stream 6) and is lost as wastewater at the end of the process. Hence the cost associated with the reactor feed portion of the incoming hps may be considered as raw material cost instead of utility cost for the sake of clarity.

6. H-401: convert given heat duty in MW to GJ/h using conversion factor (1 MW =3.6 GJ/h). Also, since heater efficiency is not specified, assume 90%.

7. For pumps, since the summary tables directly give the actual load, there is no need to divide by the efficiency.

8. Assume stream factor = 8375 h/y

9. Assume average operator salary is $90,000/y. change answer key accordingly.

Styrene is the monomer used to make polystyrene, which has a multitude of uses, the most common of which are in packaging and insulated Styrofoam beverage cups. Styrene is produced by the dehydrogenation of ethylbenzene. Ethylbenzene is formed by reacting ethylene and benzene. There is very little ethylbenzene sold commercially, because most ethylbenzene manufacturers convert it directly into styrene. B.3.1 Process Description [1,2] The process flow diagram is shown in Figure B.3.1. Ethylbenzene feed is mixed with recycled ethylbenzene, heated, and then mixed with high-temperature, superheated steam. Steam is an inert in the reaction, which drives the equilibrium shown in Equation (B.3.1) to the right by reducing the 1292 Appendix B Information for the Preliminary Design of Fifteen Chemical Procesies concentrations of all components. Because styrene formation is highly endothermic, the superheated steam also provides energy to drive the reaction forward. Decomposition of ethylbenzene to benzene and ethylene, and hydrodealkylation to give methane and toluene, are unwanted side reactions shown in Equations (B.3,2) and (B,3.3). The reactants then enter two adiabatic packed beds with interheating. The products are cooled, producing steam from the high-temperature (hydrogen, methane, ethylene), organic liquid, and water exit in separate streams. The hydrogen stream is further purified as a source of hydrogen elsewhere in the plant. The benzene/toluene stream is currently returned as a feed stream to the petrochemical facility. The organic stream containing the desired product is distilled once to remove the benzene and toluene and distilled agein to separate unreacted ethylbenzene for recycle from the styrene product. C6H3C2H52122C6H3C2H1+H2C6H5C2H53C6H6+C2H4C6H5C2H3+H24C6H5CH3+CH4 The styrene product can spontancously polymerize at higher temperatures. Because product styrene is sent directly to the polymerization unit, experience suggests that as long as its tempersture is maintained at less than 125C, there is no spontaneous polymerization problem. Bectuse this is less than styrene's normal boiling point, and because low pressure pushes the equilibrium in Equation (B.3.1) to the right, much of this process is run at vacuum. Stream tables, utility summaries, and major equipment summaries are given in Tables B,3,1, B.3.2, and B.3.3, respectively. B.3.2 Reaction Kinetics The styrene reaction may be equilibrium limited, and the equibrium constant is given as Equation (B.3.4). K=(yiy10yjdP)lnK=15.5408T14,852.6 where T is in K and P is in bar. The equifibritum calcufation is given as C6H5C2H51x1x222C6H3C2H7+H20x0x total moles =N+1+x includes N moles of inert steam K=(1x)(N+1+x)x2P where P is in bar. Figure B.3.1 Unit 400: Styrene Process How Diagram 1294 Appendix B Information for the Preliminary Design of Fifteen Chemical Processes Table B.3.1 Stream Tables for Unit 400 Appendix B Information for the Preliminn... Temperature(C)Pressure(kPa)VapormolefractionTotalflow(kg/h)Tocalflow(kmol/h)ComponentFlowrates(kmol/h)WaterEthylbenzeneStyreneHydrogenBenzeneTolueneEthyleneMethane70.0200.000.00289.53.340.000.100.000.001.371.860.000.00 Table B.3.2 Utility Summary for Unit 400 appendix B Information for the Preliminary Design of Fiftesn a Information for the Preliminary Design of Fifteen Chemical Procmeco. Equation (B.3.5) can be used and N. The kinetic equations are adapted from Snyder and Subramaniam [3]. Subscripts on r refer to reactions in Equations (B.3.1)-(B,3.3), and the positive activation energy can arise from non- r2=20.965exp(RT7804)PsPhr3=7.2061011exp(RT49675)Pdr4=1.724106exp(RT26857)PPhwd (8.3.6) where p is in bar, T is in K,R=1.987cal/molK, and ri in mol/m3-reactors. It may be assumed that the catalyst has a bulk density of 1282kg/m1, an effective ciameter of 25mm, and a void fraction =0.4. B.3.3 Simulation (CHEMCAD) Hints Results for the simulation given here were obtained using SRK as the K-value and enthalpy options in the thermodynamics package. B.3.4 References 1. Shiou-Shan Chen, "Styrene," Kirk-Othmer Engelopedia of Chemial Technology, online version (New York: John Wiley \& Sons, 2006). 2. McKetta, J. J. (ed). "Styrene," Engydopedia of Chemizal Processing and Design, Vol. 55 New York: Marcel Dekker, 1984), 197-217. 3. Snyder. J. D., and B. Subramaniam, "A Novel Reverse Flow Strategy for Ethylbenzene Dehydrogenation in a Packed-Bed Reactor, "Cham. Engr. Sci. 49 (1994): 5585-5601. Table 8.3 Utilities Provided by Off-Sites for a Plant with Multiple Process Units (Costs Represem Charges for Utilities Delivered to the Battery Limit of a Process and Are Based on the Natural Cas 2 Cost and Electricity Price Listed in This Table) Standard conditions are 1.013 bar and 15C. "These values are used to determine the other utility costs given in this table. t Based on Tcexingwucf=10C. Cooling water return temperatures should not exceed 45C due to excess scaling at higher temperatures. Approximately equal credit is given for condensate returned from exchangers using steam. Based on lower heating value of natural gas of 950Btu/stdft3=0.0354G/ /std m3, where the definition of standard is 1atm and 25C. "For hazardous waste, the cost of disposal varies widely. Chemical analyses are required for all materials that cannot be thoroughly identified. This does not include radioactive waste. Table 8.2 Multiplication Factors for Estimating 2. Fixed Manufacturing Costs a. Depreciation b. Local taxes and insurance c. Plant overhead costs 0.1FCl+(0.0140.05)FCI(0.500.7)(Line1.D.+Line1.E+Line1.F)0.1FCl0.032FCl0.708Cool0.036FCl Total Fixed Manufacturing Costs 0.708COL+0.068FCI+ depreciation 3. General Manufacturing Expenses a. Administration costs 0.15(Line1.D.+Line1.E.+Line1.F.)(0.020.2)COM0.05COM0.177Cof0.009FC0.11COM0.05COM Total General Manufacturing Costs 0.177Cot+0.009FCI+0.16COM Total Costs CRM+CWT+CUT+2.215COL+ 0.190COM+0.146FCI+ depreciation * Costs are given in dollars per unit time (usually per year). 'Costs are evaluated from information given on the PFD and the unit cost. 'Depreciation costs are covered separately in Chapter 9. The use of 10% of FCl is a crude approximation at best. From references [13]. Raw Matcial Costs 235 fable 8.4f Costs of Some Common Chemicals* IVtridor uote. Reprinted by permission of the McGraw-Hill Companies [11]. Styrene is the monomer used to make polystyrene, which has a multitude of uses, the most common of which are in packaging and insulated Styrofoam beverage cups. Styrene is produced by the dehydrogenation of ethylbenzene. Ethylbenzene is formed by reacting ethylene and benzene. There is very little ethylbenzene sold commercially, because most ethylbenzene manufacturers convert it directly into styrene. B.3.1 Process Description [1,2] The process flow diagram is shown in Figure B.3.1. Ethylbenzene feed is mixed with recycled ethylbenzene, heated, and then mixed with high-temperature, superheated steam. Steam is an inert in the reaction, which drives the equilibrium shown in Equation (B.3.1) to the right by reducing the 1292 Appendix B Information for the Preliminary Design of Fifteen Chemical Procesies concentrations of all components. Because styrene formation is highly endothermic, the superheated steam also provides energy to drive the reaction forward. Decomposition of ethylbenzene to benzene and ethylene, and hydrodealkylation to give methane and toluene, are unwanted side reactions shown in Equations (B.3,2) and (B,3.3). The reactants then enter two adiabatic packed beds with interheating. The products are cooled, producing steam from the high-temperature (hydrogen, methane, ethylene), organic liquid, and water exit in separate streams. The hydrogen stream is further purified as a source of hydrogen elsewhere in the plant. The benzene/toluene stream is currently returned as a feed stream to the petrochemical facility. The organic stream containing the desired product is distilled once to remove the benzene and toluene and distilled agein to separate unreacted ethylbenzene for recycle from the styrene product. C6H3C2H52122C6H3C2H1+H2C6H5C2H53C6H6+C2H4C6H5C2H3+H24C6H5CH3+CH4 The styrene product can spontancously polymerize at higher temperatures. Because product styrene is sent directly to the polymerization unit, experience suggests that as long as its tempersture is maintained at less than 125C, there is no spontaneous polymerization problem. Bectuse this is less than styrene's normal boiling point, and because low pressure pushes the equilibrium in Equation (B.3.1) to the right, much of this process is run at vacuum. Stream tables, utility summaries, and major equipment summaries are given in Tables B,3,1, B.3.2, and B.3.3, respectively. B.3.2 Reaction Kinetics The styrene reaction may be equilibrium limited, and the equibrium constant is given as Equation (B.3.4). K=(yiy10yjdP)lnK=15.5408T14,852.6 where T is in K and P is in bar. The equifibritum calcufation is given as C6H5C2H51x1x222C6H3C2H7+H20x0x total moles =N+1+x includes N moles of inert steam K=(1x)(N+1+x)x2P where P is in bar. Figure B.3.1 Unit 400: Styrene Process How Diagram 1294 Appendix B Information for the Preliminary Design of Fifteen Chemical Processes Table B.3.1 Stream Tables for Unit 400 Appendix B Information for the Preliminn... Temperature(C)Pressure(kPa)VapormolefractionTotalflow(kg/h)Tocalflow(kmol/h)ComponentFlowrates(kmol/h)WaterEthylbenzeneStyreneHydrogenBenzeneTolueneEthyleneMethane70.0200.000.00289.53.340.000.100.000.001.371.860.000.00 Table B.3.2 Utility Summary for Unit 400 appendix B Information for the Preliminary Design of Fiftesn a Information for the Preliminary Design of Fifteen Chemical Procmeco. Equation (B.3.5) can be used and N. The kinetic equations are adapted from Snyder and Subramaniam [3]. Subscripts on r refer to reactions in Equations (B.3.1)-(B,3.3), and the positive activation energy can arise from non- r2=20.965exp(RT7804)PsPhr3=7.2061011exp(RT49675)Pdr4=1.724106exp(RT26857)PPhwd (8.3.6) where p is in bar, T is in K,R=1.987cal/molK, and ri in mol/m3-reactors. It may be assumed that the catalyst has a bulk density of 1282kg/m1, an effective ciameter of 25mm, and a void fraction =0.4. B.3.3 Simulation (CHEMCAD) Hints Results for the simulation given here were obtained using SRK as the K-value and enthalpy options in the thermodynamics package. B.3.4 References 1. Shiou-Shan Chen, "Styrene," Kirk-Othmer Engelopedia of Chemial Technology, online version (New York: John Wiley \& Sons, 2006). 2. McKetta, J. J. (ed). "Styrene," Engydopedia of Chemizal Processing and Design, Vol. 55 New York: Marcel Dekker, 1984), 197-217. 3. Snyder. J. D., and B. Subramaniam, "A Novel Reverse Flow Strategy for Ethylbenzene Dehydrogenation in a Packed-Bed Reactor, "Cham. Engr. Sci. 49 (1994): 5585-5601. Table 8.3 Utilities Provided by Off-Sites for a Plant with Multiple Process Units (Costs Represem Charges for Utilities Delivered to the Battery Limit of a Process and Are Based on the Natural Cas 2 Cost and Electricity Price Listed in This Table) Standard conditions are 1.013 bar and 15C. "These values are used to determine the other utility costs given in this table. t Based on Tcexingwucf=10C. Cooling water return temperatures should not exceed 45C due to excess scaling at higher temperatures. Approximately equal credit is given for condensate returned from exchangers using steam. Based on lower heating value of natural gas of 950Btu/stdft3=0.0354G/ /std m3, where the definition of standard is 1atm and 25C. "For hazardous waste, the cost of disposal varies widely. Chemical analyses are required for all materials that cannot be thoroughly identified. This does not include radioactive waste. Table 8.2 Multiplication Factors for Estimating 2. Fixed Manufacturing Costs a. Depreciation b. Local taxes and insurance c. Plant overhead costs 0.1FCl+(0.0140.05)FCI(0.500.7)(Line1.D.+Line1.E+Line1.F)0.1FCl0.032FCl0.708Cool0.036FCl Total Fixed Manufacturing Costs 0.708COL+0.068FCI+ depreciation 3. General Manufacturing Expenses a. Administration costs 0.15(Line1.D.+Line1.E.+Line1.F.)(0.020.2)COM0.05COM0.177Cof0.009FC0.11COM0.05COM Total General Manufacturing Costs 0.177Cot+0.009FCI+0.16COM Total Costs CRM+CWT+CUT+2.215COL+ 0.190COM+0.146FCI+ depreciation * Costs are given in dollars per unit time (usually per year). 'Costs are evaluated from information given on the PFD and the unit cost. 'Depreciation costs are covered separately in Chapter 9. The use of 10% of FCl is a crude approximation at best. From references [13]. Raw Matcial Costs 235 fable 8.4f Costs of Some Common Chemicals* IVtridor uote. Reprinted by permission of the McGraw-Hill Companies [11]