《化学工程设计技术》课程教学资源（参考资料，英文版）15 Design 2 Input-Output Structure

DESIGN METHODOLOGY ILA INPUT-OUTPUT DECISIONS GOAL- Choose the process chemistry and feedstock most appropriate to the plant to be designed and determine the associated economic potential 1l/19/99 Input-Output Structure

11/19/99 Input-Output Structure 1 DESIGN METHODOLOGY II: INPUT-OUTPUT DECISIONS GOAL -- Choose the process chemistry and feedstock most appropriate to the plant to be designed and determine the associated economic potential

BASIC LEVEL II DECISIONS o Choice of reaction chemistry o Choice of raw material feedstocks o Determination of need for vapor recycle Evaluation ofeconomic potential for process 1l/19/99 Input-Output Structure

11/19/99 Input-Output Structure 2 BASIC LEVEL II DECISIONS u Choice of reaction chemistry u Choice of raw material feedstocks u Determination of need for vapor recycle u Evaluation of economic potential for process

CHOICE OF REACTION CHEMISTRY The choice of reaction chemistry involves the following considerations o Source of the chemistry to be employed E Developed in-house E Freely available patents expired) E Available only through a license ◆ Availability offeed stocks ◆ Choice ofprocess type Environmental considerations 1l/19/99 Input-Output Structure

11/19/99 Input-Output Structure 3 CHOICE OF REACTION CHEMISTRY The choice of reaction chemistry involves the following considerations: u Source of the chemistry to be employed ð Developed in-house ð Freely available (patents expired) ð Available only through a license u Availability of feed stocks u Choice of process type u Environmental considerations

EXAMPLE #1 Chemistries available to manufacture vinyl chloride ffrom Seider et al, Process Design Principles) 9 Direct chlorination of ethylene C2H4+Cl2-> C2H3Cl+ HCl (Only half the cl2 converted to vinyl chloride Thermal cracking of dichloroethane via Oxychlorination of ethyelene CH4+2HCl+1202-C2H4C12+H20 C2H4C12 -->C2H3C+HCl (Uses HCl instead of cl2, but requires two reaction steps) 1l/19/99 Input-Output Structure

11/19/99 Input-Output Structure 4 EXAMPLE #1 Chemistries available to manufacture Vinyl chloride (from Seider et al, Process Design Principles) uDirect chlorination of Ethylene C2H4 + Cl2 --> C2H3Cl + HCl (Only half the Cl2 converted to vinyl chloride) u Thermal cracking of Dichloroethane via Oxychlorination of Ethyelene C2H4 + 2HCl + 1/2 O2 --> C2H4Cl2 + H2O C2H4Cl2 --> C2H3Cl + HCl (Uses HCl instead of Cl2, but requires two reaction steps)

EXAMPLE #1(Contd.) o Balanced process for Chlorination ofof ethylene C2H4+C2->C2H4C2 CH4+2HC+1202->C2H4C2+H20 2 C2H4012->2 C2H3C +2 HC Converts all cl atoms to vinyl chloride 1l/19/99 Input-Output Structure 5

11/19/99 Input-Output Structure 5 EXAMPLE #1 (Cont’d.) u Balanced Process for Chlorination of of Ethylene C2H4 + Cl2 --> C2H4Cl2 C2H4 + 2HCl + 1/2 O2 --> C2H4Cl2 + H2O 2 C2H4Cl2 --> 2 C2H3Cl +2 HCl (Converts all Cl atoms to Vinyl Chloride)

EXAMPLE #2 Chemistries available for the manufacture of maleic anhydride ◆ From benzene C6H6+31202->0+2C0+2H20 C6H6+4102->6C02+3H20 ◆ From butane C4H10+31202->0+4H20 C4H1+41202->4C0+5H20 CH1+61202->4C02+5H20 1l/19/99 Input-Output Structure

11/19/99 Input-Output Structure 6 EXAMPLE #2 Chemistries available for the manufacture of maleic anhydride: u From benzene C6H6 + 3 1/2 O2 --> O + 2 CO + 2 H2O C6H6 + 4 1/2 O2 --> 6 CO2 + 3 H2O u From butane C4H10 + 3 1/2 O2 --> O + 4 H2O C4H10 + 4 1/2 O2 --> 4 CO + 5 H2O C4H10 + 6 1/2 O2 --> 4 CO2 + 5 H2O

EXAMPLE #2(Contd. ◆ Maleic anhydride from benzene E> High selectivity at almost complete conversion-no recycle required e Benzene is expensive and is a carcinogen o Maleic anhydride from Butane E Lower selectivity-cannot operate at complete conversion e Butane is relatively cheap almost all new plants use butane as the feedstock. 1l/19/99 Input-Output Structure

11/19/99 Input-Output Structure 7 EXAMPLE #2 (Cont’d.) u Maleic Anhydride from Benzene ð High selectivity at almost complete conversion - no recycle required ð Benzene is expensive and is a carcinogen u Maleic Anhydride from Butane ð Lower selectivity - cannot operate at complete conversion ð Butane is relatively cheap Almost all new plants use butane as the feedstock

CHOICE OF FEEDSTOCK ◆ Availability E What feedstocks are available at the potential plant ? E At what price? Purity E At what purities is are the feedstocks available? E Are the impurities > Inert? Affect reaction rates or separation system performance? Catalyst poisons or otherwise foul the process equipment? 1l/19/99 Input-Output Structure

11/19/99 Input-Output Structure 8 CHOICE OF FEEDSTOCK u Availability ð What feedstocks are available at the potential plant site? ð At what price? u Purity ð At what purities is are the feedstocks available? ð Are the impurities ÿ Inert? ÿ Affect reaction rates or separation system performance? ÿ Catalyst poisons or otherwise foul the process equipment?

PROCESS TYPE ◆Type E> All components in reactor effluent must be condensable at a reasonable temperature and pressure using cooling water or moderate refrigeration E Can assume that all components can be recovered and purified using distillation or liquid-liquid extraction E> Can further assume that all(100% of the limiting raw material fed to the process can be converted to products or byproducts as a good approximation. 1l/19/99 Input-Output Structure

11/19/99 Input-Output Structure 9 PROCESS TYPE u Type I ð All components in reactor effluent must be condensable at a reasonable temperature and pressure using cooling water or moderate refrigeration. ð Can assume that all components can be recovered and purified using distillation or liquid-liquid extraction. ð Can further assume that all (100%) of the limiting raw material fed to the process can be converted to products or byproducts as a good approximation

Products R aw Materials BⅤ products Type/ process 1l/19/99 Input-Output Structure

11/19/99 Input-Output Structure 10 Raw Materials Products Byproducts Type I Process