CM 4310, Green Engineering Fall 07 Homework #2 Mon. 03 Dec., '07 1. Atom and Mass Efficiencies Problem 1 of Chapter 7, page 198. 2. Criteria Pollutant Emissions from an Industrial Boiler (Chapter 8) Calculate criteria pollutant emissions (SO 2, NO x, CO, Filterable Particulate Matter) and CO 2 from an industrial facility using the following information. Low S No. 6 Oil (1% wt. Sulfur) Annual Energy Demand of 10 11 Btu/yr Heating Value of 150,000,000 Btu/10 3 gal Boiler Efficiency of 0.90 3. Life Cycle Assessment: Disposable versus Home Laundered Cloth Diapers Problem 2 from Chapter 13 of the text. Parts a) and b) only. Due Mon 10 Dec., '07
1. Atom and Mass Efficiency Calculations: Calculate mass and atom efficiencies a) (Addition reaction) Isobutylene + methanol methyl,tert-butyl ether C 4 H 8 + CH 3 OH (C 4 H 9 )-O-CH 3 Mass efficiency: Feedstocks 5(12) + 12(1) + 1(16) = 88 Product 5(12) + 12(1) + 1(16) = 88.. efficiency = 100% Carbon efficiency: Feedstocks 5(12) = 60 Product 5(12) = 60.. efficiency = 100% Hydrogen efficiency: Feedstocks 12(1) = 12 Product 12(1) = 12.. efficiency = 100% Oxygen efficiency: Feedstocks 1(16) = 16 Product 1(16) = 16.. efficiency = 100% b) (Substitution reaction) Phenol + ammonia aniline + water C 6 H 5 -OH + NH 3 C 6 H 5 -NH 2 + H 2 O Mass efficiency: Feedstocks 6(12) + 9(1) + 1(16) + 1(14) = 111 Product 6(12) + 7(1) + 0(16) + 1(14) = 93.. efficiency = 83.8% Carbon efficiency: Feedstocks 6(12) = 72 Product 6(12) = 72.. efficiency = 100% Hydrogen efficiency: Feedstocks 9(1) = 9 Product 7(1) = 7.. efficiency = 77.8% Oxygen efficiency: Feedstocks 1(16) = 16 Product 0(16) = 0.. efficiency = 0% Nitrogen efficiency: Feedstocks 1(14) = 14 Product 1(14) = 14.. efficiency = 100% c) (Elimination reaction) Ethylbenzene styrene + hydrogen C 6 H 5 -C 2 H 5 C 6 H 5 -C 2 H 3 + H 2 Mass efficiency: Feedstocks 8(12) + 10(1) = 106 Product 8(12) + 8(1) = 104.. efficiency = 98.1% Carbon efficiency: Feedstocks 8(12) = 96 Product 8(12) = 96.. efficiency = 100% Hydrogen efficiency: Feedstocks 10(1) = 10 Product 8(1) = 8.. efficiency = 80% d) Other industrially important examples of additions, substitutions, and elimination reactions (see Wittkcoff, H.A. and Reuben, B.G. Industrial Organic Chemicals, John Wiley & Sons, New York, 1996; and Weissermel, K. and Arpe, H.-J. Industrial Organic Chemistry, VCH Verlagsgesellschaft mbh a Wiley company, Weinheim Germany, 1997). Addition Reactions: Ethanol from ethene CH 2 =CH 2 + H 2 O C 2 H 5 OH (hydration of ethylene using a phosphoric acid catalyst, low per pass conversions on the order of 10%)
Mass efficiency: Feedstocks 2(12) + 6(1) + 1(16) = 46 Product 2(12) + 6(1) + 1(16) = 46.. efficiency = 100% Carbon efficiency: Feedstocks 2(12) = 24 Product 2(12) = 24.. efficiency = 100% Hydrogen efficiency: Feedstocks 6(1) = 6 Product 6(1) = 6.. efficiency = 100% Oxygen efficiency: Feedstocks 1(16) = 16 Product 1(16) = 16.. efficiency = 100% Ethylene oxide from ethene CH 2 =CH 2 + 0.5O 2 CH 2 CH 2 (silver catalyst, 15 bar and 250 C, yield > 80%) \ / O Mass efficiency: Feedstocks 2(12) + 4(1) + 1(16) = 44 Product 2(12) + 4(1) + 1(16) = 44.. efficiency = 100% Carbon efficiency: Feedstocks 2(12) = 24 Product 2(12) = 24.. efficiency = 100% Hydrogen efficiency: Feedstocks 4(1) = 4 Product 4(1) = 4.. efficiency = 100% Oxygen efficiency: Feedstocks 1(16) = 16 Product 1(16) = 16.. efficiency = 100% Vinyl chloride from acetylene CH CH + HCl CH 2 =CHCl Mass efficiency: Feedstocks 2(12) + 3(1) + 1(35.45) = 62.45 Product 2(12) + 3(1) + 1(35.45) = 62.45.. efficiency = 100% Carbon efficiency: Feedstocks 2(12) = 24 Product 2(12) = 24.. efficiency = 100% Hydrogen efficiency: Feedstocks 5(1) = 5 Product 5(1) = 5.. efficiency = 100% Chlorine efficiency: Feedstocks 1(35.45) = 35.45 Product 1(35.45) = 35.45.. efficiency = 100% Substitution Reactions: Vinyl chloride from ethene CH 2 =CH 2 + Cl 2 CH 2 ClCH 2 Cl CH 2 =CHCl + HCl Mass efficiency: Feedstocks 2(12) + 4(1) + 2(35.45) = 98.45 Product 2(12) + 3(1) + 1(35.45) = 62.45.. efficiency = 63.4% Carbon efficiency: Feedstocks 2(12) = 24 Product 2(12) = 24.. efficiency = 100% Hydrogen efficiency: Feedstocks 4(1) = 4 Product 3(1) = 3.. efficiency = 75% Chlorine efficiency: Feedstocks 2(35.45) = 70.9 Product 1(35.45) = 35.45.. efficiency = 50%
Chlorine from oxidation of HCl 4HCl + O 2 2H 2 O + 2Cl 2 Mass efficiency: Feedstocks 4(1) + 4(35.45) + 1(32) = 217.8 Product 2(70.9) = 141.8.. efficiency = 65.1% Hydrogen efficiency: Feedstocks 4(1) = 4 Product 0(1) = 0.. efficiency = 0% Chlorine efficiency: Feedstocks 4(35.45) = 141.8 Product 2(70.9) = 141.8.. efficiency = 100% Oxygen efficiency: Feedstocks 1(32) = 32 Product 0(32) = 0.. efficiency = 0% Vinyl chloride from ethylene using oxychlorination (By integrating the above two reactions, we can increase the mass efficiency of the overall production of vinyl chloride) 1.5CH 2 =CH 2 + 1.5Cl 2 1.5CH 2 ClCH 2 Cl 3CH 2 ClCH 2 Cl 3CH 2 =CHCl + 3 HCl 1.5CH 2 =CH 2 + 3HCl + 0.75O 2 1.5CH 2 ClCH 2 Cl + 1.5H 2 O Mass efficiency: Feedstocks 6(12) + 15(1) + 6(35.45) + 1.5(16) = 333.7 Product 6(12) + 15(1) + 6(35.45) + 0(16) = 309.7.. efficiency = 92.8% Carbon efficiency: Feedstocks 6(12) = 72 Product 6(12) = 72.. efficiency = 100% Hydrogen efficiency: Feedstocks 15(1) = 15 Product 15(1) = 15.. efficiency = 100% Chlorine efficiency: Feedstocks 6(35.45) = 222.7 Product 6(35.45) = 222.7.. efficiency = 100% Oxygen efficiency: Feedstocks 1.5(16) = 24 Product 0(16) = 0.. efficiency = 0% Elimination Reactions: Phenol from dehydrogenation of a cyclohexanone/cyclohexanol mixture =O + 2 OH OH + 9/2 H Mass efficiency: Feedstocks 12(12) + 11(1) + 2(16) = 187 Product 12(12) + 2(1) + 2(16) = 178.. efficiency = 95.2% Carbon efficiency: Feedstocks 12(12) = 144 Product 12(12) = 144.. efficiency = 100%
Hydrogen efficiency: Feedstocks 11(1) = 11 Product 2(1) = 2.. efficiency = 18.2% Oxygen efficiency: Feedstocks 2(16) = 32 Product 2(16) = 32.. efficiency = 100%
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3. Life-Cycle Assessment of Diapering Systems a) Diapers per baby per week for disposable diapers Equivalency of diapers 15.8 billion disposable diapers are sold annually 3,787,000 babies are born each year children wear diapers for the first 30 months disposable diapers are used on 85% of children. Number of babies in diapers = (3,787,000 babies born/yr)(30 mo. in diapers/12 mo/yr) = 9,467,500 Number of babies in disposable diapers = 9,467,500 babies(0.85) = 8,047,375 Number of disposable diapers per baby per year = (15.8x10 9 disposable diapers)/(8,047,375 babies) = 1,963.4 disposable diapers/baby Number of disposable diapers per baby per week = (1,963.4 disposable diapers/baby)/52 weeks = 39.3 Equivalence = (39.3 disposable diapers/baby/wk)/(68 cloth diapers/baby/wk) = 0.577 b) Complete the Table of Ratio of Impact to Home Laundered Impact Impact Disposable diapers Commercially laundered cloth Home laundered Cloth diapers diapers Energy requirements (million BTU) 0.52 0.55 1.0 Solid waste (cubic feet) 4.26 1.0 1.0 Atmospheric emissions (lb) 0.50 0.47 1.0 Waterborne wastes (lb) 0.14 0.95 1.0 Water requirements (gal) 0.28 1.26 1.0 c) Recycle Percentage for Disposable Diapers 20 Solid Waste per 1000 Diapers 16 12 y = -0.162x + 17.04 R 2 = 1 8 4 0 0 20 40 60 80 100 120 % Recycle
The recycle percentage needed for disposable diapers to equal the solid waste requirements of laundered cloth diapers (2.3 cubic feet) can be obtained from the best-fit equation in the figure above. Rearranging the trendline from able and solving for x, x = (17.04-2.3)/0.163 = 90.43%.