r PB-211 927 ENERGY CONSUMPTION: THE CHEMICAL INDUSTRY ENVIRONMENTAL PROTECTION AGENCY APRIL 1975 DISTRIBUTED BY: National Technical Information Service U. S. DEPARTMENT OF COMMERCE ------- PB 241 927 EPA-650/2-75-032-a April 1975 Environmental Protection Technology Series O :$:$:^§j§i$ :::::::::::::::::::::::x:::::::^^ ------- TECHNICAL REPORT DATA ( P1 1 ase rccd !aWlwlwns on the reverse bc/ore completing) REPORT NO 2 EPA-650/2-75 -032-a 3 RECIPIENT S ACCESSIOr.NO. 4 TITLE AND SU6TITLE Energy Consumption: The Chemical Industry 5 REPORT DATE 4pril 1975 6. PERFORMING ORGANIZATION CODE 7 AUTHORIS) John T. Reding and Burchard P. Shepherd 8. PERFORMING ORGANIZATION REPORT NO 9 PERFORMING ORGANIZATION NAME AND ADDRESS Dow Chemical, U.S.A. Texas Division Freeport, Texas 77541 10. PROGRAM ELEMENT NO. IABO13: ROAP 2IADE-010 11. CONTRACT/GRANT NO 68-02-1329, Task 5 12 SPONSORING AGENCY NAME AND ADDRESS EPA, Office of Research and Development NERC-RTP, Control Systems Laboratory Research Triangle Park, NC 27711 13 TYPE OF REPORT NO PER 00 COVERED IS SUPPLEMENTARY NOTES lb. A8STRACTP repori gives results of a study of energy consumption in the chemical industry. It analyzes energy-intensive steps or operations for manufacturing pro- cesses which produce 12 of the top 50 volume chemicals in the U. S. Results of the analyses are in the form of energy consumption block diagrams. energy-Intensive equipment schematic diagrams, and tables that indicate the causes of energy losses, as well as possible conservation approaches. The most common energy-intensive operations in this industry are furnace operation, distillation, compression, refri- geration, electrolysis, drying/calcining, and evaporation. Energy losses in these operations could be reduced by: design, operation, market, and process modification: better insulation and maintenance; process integration; waste utilization: and research and development. PRICES SUCh [ CT TO CHANCE 19 SECURITY CLASS (This Report) Unclassified 20 SECURITY CLASS (This page) Unclassified 17. KEY WORDS AND DOCUMENT ANALYSIS a DESCRIPTORS b IDENTIFIERS/OPEN ENDED TERMS C COSATI Field/Group Energy Compressors 13G Consumption Refrigerating Chemical Industry Electrolysis 07A, 07D Conservation Drying Furnaces Roasting 13A Distillation Marketing Evaporation Wastes l3H 05C 18 DiSTRIBUTION STATEMENT Unlimited EPA Forni 2220.1 ($.73J 21. NO. OF PAGES ------- EPA650/2-75-032-a ENERGY CONSUMPTION: THE CHEMICAL INDUSTRY by John T. Reding and Burchard P. Shepherd Dow Chemical, U. S. A. Texas Division Freeport, Texas 77541 Contract No. 68-02-1329, Task 5 Program Element No. IABO13 ROAP No. 21ADE-010 EPA Project Officer: Irvin A. Jefcoat Control Systems Laboratory National Environmental Research Center Research Triangle Park, North Carolina 27711 Prepared for U. S. ENVIRONMENTAL PROTECTION AGENCY OFFICE OF RESEARCH AND DEVELOPMENT WASHINGTON, D. C. 20460 April 1975 ------- EPA HE VIEW NOTICE This report has been reviewed by the National Environmental Research Center - Research Triangle Park, Office of Research and Development, EPA, and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Environmental Protection Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. RESEARCH REPORTING SERIES Research reports of the Office of Research and Development, U.S. Environ- mental Protection Agency, have been grouped into series. These broad categories were established to facilitate further development and applica- tion of environmental technology. Elimination of traditional grouping was consciously planned to foster technology transfer and maximum interface in related fields. These series are: 1. ENVIRONMENTAL HEALTH EFFECTS RESEARCH 2. ENVIRONMENTAL PROTECTION TECHNOLOGY 3. ECOLOGICAL RESEARCH 4. ENVIRONMENTAL MONITORING 5. SOCIOECONOMIC ENVIRONMENTAL STUDIES 6. SCIENTIFIC AND TECHNICAL ASSESSMENT REPORTS 9. MISCELLANEOUS This report has been assigned to the ENVIRONMENTAL PROTECTION TECHNOLOGY series. This series describes research performed to develop and demonstrate instrumentation, equipment and methodology to repair or prevent environmental degradation from point and non- point sources of pollution. This work provides the new or improved technology required for the control and treatment of pollution sources to meet environmental quality standards. This document is available to the public for sale through the National Technical Information Service, Springfield, Virginia 22161. Publication No. EPA-650/ 2 -75-032-a 11 ------- CONTENTS Page ii L18t of Figures v List of Tables vii Sections Conclusions II Recommendations 2 III Introduction 3 IV Energy Consumption within the Chemical Industry 5 A. Chlorine by Electrolysis of Brine 7 B. Caustic Soda Concentration by Evaporation of Water 7 C. Ethylene by Ethane Pyrolysis 13 D. Ethylbenzene by Alkylatlon of Benzene with Ethylene 21 E. Styrene by Dehydrogenation of Ethylbenzene 21 F. Phenol/Acetone by Oxidation of Cumene and Cleavage of Cumene Hydroperoxide 29 G. Cumene by Alkylation of Berizene with Propylene 37 H. Sodium Carbonate by the Solvay Process 37 I. Carbon Black by the Furnace Process 146 J. Oxygen/Nitrogen by Air Distillation 146 K. Operational and Design Problems of Energy Intensive Equipment 56 iii ------- CONTENTS (continued) Page L. Operational and Design Problems of Heat Transfer Equipment 56 M. Chemical Industry Energy Conser- vation Study Summary 56 V Bibliography 61 VI Glossary of Abbreviations 62 VII Appendix 63 iv ------- FIGURES No. Page 1 Chlorine Energy Consumption Diagram 8 2 Chlorine Energy Intensive Equipment Diagram — Electrolytic Cell 9 3 Caustic Soda Energy Consumption Diagram 1]. ii Caustic Soda Energy Intensive Equipment Diagram — Evaporators 12 5 Ethylene Energy Consumption Diagram 15 6 Ethylene Energy Intensive Equipment Diagram — Pyrolysis Furnace and Waste Heat Recovery Equipment 17 7 Ethylene Energy Intensive Equipment Diagram — Compressors 18 8 Ethylene Energy Intensive Equipment Diagram — Propylene and Ethylene Refrig- eration Systems 19 9 Ethylene Process Refrigeration 20 10 Ethylbenzene Energy Consumption Diagram 214 11 Ethylbenzene Energy Intensive Equipment Diagram — Distillation Columns 25 12 Styrene Energy Consumption Diagram 27 13 Styrene Energy Intensive Equipment Diagram — Superheater, Reactor, and Cooling Equipment 28 114 Styrene Energy Intensive Equipment Diagram — Distillation Columns 30 15 Phenol/Acetone Energy Consumption Diagram 32 16 Phenol/Acetone Energy Intensive Equipment Diagram — Air Compressors 33 V ------- FIGURES (continued) Page 17 Phenol/Acetone Energy Intensive Equipment Diagram — Cumene Hydroperoxide Distilla- tion Column 314 18 Phenol/Acetone Energy Intensive Equipment Diagram — Acetone Distillation Columns 35 19 Phenol/Acetone Energy Intensive Equipment Diagram — Phenol Distillation Columns 36 20 Phenol/Acetone Energy Intensive Equipment Diagram - Cracking Furnace 38 21 Cumene Energy Consumption Diagram 140 22 Cumene Energy Intensive Equipment Diagram - Distillation Columns 4l 23 Sodium Carbonate Energy Consumption Diagram 143 214 Sodium Carbonate Energy Intensive Equipment Diagram - Lime Kiln 1414 25 Sodium Carbonate Energy Intensive Equipment Diagram — Compressors 145 26 Sodium Carbonate Energy Intensive Equipment Diagram — Calciner 147 27 Carbon Black Energy Consumption Diagram 149 28 Carbon Black Energy Intensive Equipment Diagram - Reactor and Waste Heat Recovery Equipment 50 29 Carbon Black Energy Intensive Equipment Diagram - Dryer 51 30 Oxygen/Nitrogen Energy Consumption Diagram 53 31 Oxygen/NItrogen Energy Intensive Equipment Diagram - Compressors 514 32 Oxygen/Nitrogen Energy Intensive Diagram - Distillation Column 55 vi ------- TABLES ___ Page ]. Chlorine Energy Conservation Approaches 10 2 Caustic Soda Energy Conservation Approaches i 4 3 Ethylene Energy Conservation Approaches 22 4 Ethylbenzene Energy Conservation Approaches 26 5 Styrene Energy Conservation Approaches 31 6 Phenol Energy Conservation Approaches 39 7 Cumene Energy Conservation Approaches 8 Sodium Carbonate Energy Conservation Approaches 48 9 Carbon Black Energy Conservation Approaches 52 10 Oxygen/Nitrogen Energy Conservation Approaches 57 11 Operational and Design Problems In Energy Intensive Equipment 58 12 Operational Problems with Heat Transfer Equipment 59 13 Chemical Industry Energy Conservation Study Summary 60 vii ------- SECTION I CONCLUSIONS Most of the energy consumption within the chemical In- dustry is concentrated in a relatively few operations. These Include furnace combustion, distillation, com- pression, electrolysis, drying, and evaporation. Avoid- able energy losses occur in all of the above operations. Some of the losses can be eliminated by employing con- servation techniques. These Inlcude: • Design modifications to increase waste heat recovery from furnaces. • Design modifications to allow lower energy input Into distillation columns. • Proper maintenance practices to prevent losses in many places. • Process Integration to obtain maximum energy from steam. • Operation modifications to avoid losses in electrolytic cells. • Greater use of Insulation to limit heat losses. • Research and development to develop processes with Increased conversions or yields. • Waste utilization to prevent the loss of the fuel value of waste streams. 1 ------- SECTION II RECOMMENDATIONS The energy conservation approaches suggested in this report could be further defined and specified In more detail. Unanswered questions which should be considered include: • The economic feasibility of the conservation approaches. • The difficulty of implementing the approaches. 2 ------- SECTION III INTRODUCTION Purpose The purpose of the total task is to provide a breakdown of energy consumption within the six primary industrial categories — primary metals, chemicals, petroleum, food, paper, and stone, clay, glass, concrete. The purpose of the portion of the total task covered by this report is to provide a breakdown of energy consumption within the chemical industry only. This breakdown can give direction to subsequent conservation efforts. Scope This report analyzes high energy consumption operations in the chemical industry (SIC 28) and identifies the principal energy intensive equipment. It points out causes of energy losses In these operations, the approx- imate magnitude of the losses, and possible approaches to decrease these losses. General Background The National Academy of Engineering has been commissioned by the Environmental Protection Agency to conduct a com- prehensive assessment of the current status and future prospects of sulfur oxides control methods and strategies. The agreement between the Environmental Protection Agency and the National Academy of Engineering states explicitly that special data collection projects may be required to provide the National Academy of Engineering panel with the background necessary for viewing all aspects of the problem in perspective. This report is one segment of the data collection project associated with the National Academy of Engineering assessment. One method of limiting the amount of SO emissions arising from energy conversion is simply to decrease fuel use through energy conservation. In the year 1968, it has been reported that l.2 percent of the total energy con- sumption In the United States was in the industrial sector. More specifically, 28 percent of the national energy con- sumption was in the six industrial categories encompassed by this total task. Conservation efforts directed toward industries in these six categories should obtain the great- est impact. 3 ------- General 4pproach Ten chemical processes which result in the production of 12 of the top 50 volume chemicals were reviewed. These processes are: • Chlorine by electrolysis of brine • Caustic soda concentration by evaporation of wateD • Ethylene by pyrolysis of ethane • Ethylbenzene’ by alkylation of benzene with ethylene • Styrene by dehydrogenation of ethylbenzene • Phenol/acetone by oxidation of cumene and then cleavage of cumene hydroperoxide • Cumene by alkylation of benzene with propylene • Sodium carbonate by the Solvay process • Carbon black by the furnace process • Oxygen/nitrogen by distillation of air Energy consumption block diagrams have been drawn for each process. These diagrams indicate the operations within the processes where large amounts of energy are used. The energy intensive operations have been further analyzed. Schematic diagrams which show the physical and operational appearance of the energy consuming equip- ment have been prepared. Causes of energy losses in the energy intensive operations, the approximate magnitude of the losses, and possible conservation approaches have been determined. ‘4 ------- SECTION IV ENERGY CONSUMPTION WITHIN THE CHEMICAL INDUSTRY In order to analyze energy consumption within the chemical industry, it was necessary to select a specific manufac- turing process for each chemical in the study. Two decisions had to be made: • A production route or overall production process had to be chosen. This is net automatic becuase most chemicals are manufactured by more than one process. However, the obvious choice In each case wath to select the dominant process. • A certain level of production technology had to be chosen. Although energy consumption for many chemical manufacturing processes is high, the low cost of energy in the United States in the past made the use of a large amount of energy conser- vation technology uneconomical. The recent in- creases in energy costs, however, have led to the construction of plants that produce chemicals using less energy than older plants. The process technology level for this study is the best avail- able to the general public. Much proprietary information on more modern plants is not available. It is therefore believed that some of the energy conservation approaches suggested in this study may already be in use in new plants. Estimates of the total 1973 energy requirements to pro- duce each chemical studied are included on the energy consumption block diagrams. The estimates are divided into two portions: • Process energy consumption excluding feedstock energy. Feedstock energy refers to first use of fuel and petroleum products within the industrial chemicals group. • Feedstock or, sometimes, feedstock—plus—process energy consumption. Any fuel generation in the process is included in this figure as a negative number or if fuel generation is greater than feedstock consumption, it is so indicated. 5 ------- These estimates are approximate and are Intended only to show the order of magnitude of energy requirements to produce the chemicals, The type of energy used to produce the chemicals is also indicated on the energy diagrams. Different types of energy are not equivalent. Approximately 3 Btu of fuel energy are usually required to obtain 1 Btu of’ electrical energy. Approximately 1.1 to 1.3 Btu of fuel energy are required to obtain 1 Btu of’ steam energy. Energy values in all figures and tables are expressed In terms of energy per unit weight of product. In the cases of’ the phenol/acetone process and the oxygen/nitrogen process, phenol and oxygen are considered to be the products. In the case of the 50 percent caustic soda process, the energy Is expressed In terms of energy per unit weight of 100 percent caustic soda. The tables showing energy conservation approaches give estimates of losses or rejected heat In operations in the process and in the overall process. The losses or rejected heat listed In the operations are additive. The lo8ses listed in the overall process often overlap and are not additive. Energy conservation approaches Include: • insulation • design modification • maintenance • process integration • research and development • operation modification • market modification • process modification • waste utilization 6 ------- In many cases a more specific explanation of the conser- vation approach is listed along with the approach. An explanation of the conservation approaches is included in the appendix for those instances where the meaning of the term may be vague. A. Chlorine by Electrolysis of Brine Figure 3. shows the major steps In the chlorine manufac- turing process. The process uses dlaphram type electro- lytic cells. The major step from an energy consumption viewpoint is the electrolytic separation of the brine into chlorine, hydrogen, and cell liquor (dilute caustic solution). This operation accounts for 85 to 90 percent of the total energy consumption in the process. Figure 2 shows the general arrangement of the chlorine electrolytic cell. Chlorine is evolved from the cell anode while hydrogen and cell liquor come from the cathodic compartment. The cell diaphragm separates the anodic and cathodic compartments. Table 1 indicates the causes of energy losses in the electrolytic brine separation operation. It also shows the approximate magnitude of the losses and possible energy conservation approaches. B. Concentration of Caustic Soda by Evaporation of Water FIgure 3 shows the major steps in the manufacture of caustic soda. This process concentrates the cell liquor from the chlorine diaphragm cell by evaporating water from the dilute caustic solution. Approximately 80 percent of the total energy consumption occurs in the water evaporation operation which produces 50 percent caustic scda. Figure shows a typical caustic soda evaporation operation. Cell liquor enters the third effect of a three effect evaporation system and 50 percent caustic soda leaves the first effect. Sodium chloride In the cell liquor is separated from the caustic soda solution after the solution leaves the first and second effect evaporators. Steam Is the source of heat. 7. ------- Figure 1. Chlorine energy consumption diagram (1973 USA production: 9.35 X i0 kg (20.6 x iO ib)) [ 1973 energy consumption (primarily electricity): 3300 MW (100 x iO Btu)] [ 1973 fuel generation (112): 1000 MW (30 x 1012 Btu)) Energy input Meat rejection Brine feed Chemical treatments Electrolysis cell àHreac 6250 kJ/k (2700 Btu/lb) Endotherinia 2530 kJ/kg ( 1100 Btu/1b Radiation, convection, other Wet chlorine gas _____ Cooling and I drvinz Cell liquor to caustic soda process 1150 kJ/kg (500 330°K (135°F) 230 kJ/kg ( 100 B /1br 360°K (190°F) 10.200 kJ/kg (4L 20 Btuflb) Electricity 11 by—product Fuel valve 3500 kJ/kg (1500 Btu/lb) 45 kJ/kg . - (20 Btu/lb) 360°K (190°F) 1 Dry chlorine gas Compressing I I Liquefaction I Liquid I chlorine 8 ------- Figure 2. Chlorine energy Intensive equipment diagram — electrolytic cell (Rejected heat: Radiation, convection, other — 2530 kJ/kg (1100 Btu/lb) Hot H 2 by—product — 5 kJ/kg (20 Btu/lb) at 360°K (190°F) Hot Cl 2 product — 230 kJ/kg (100 Btu/lb) at 360°K (190°F) Warm cell liquor — 1150 kJ/kg (500 Btu/lb) at 330°K (135°F)] Rectifier Cl 2 H 2 ___ 1 Brine feed — Diaphragm Cell liauor Electrolytic cell 9 ------- Table 1. CHI 1 ORINE ENERGY CONSERVATION APPROACHES Approx imate Causes of magnitude of Energy conservation energy losses losses approaches 1. Electrolysis cell a. Anode over— ‘460 kJ/kg Operation modification voltage (200 Btu/lb) (lower current density) Research & development (improve anode material) b. Cathode over— i’4oo kJ/kg Operation modification voltage (600 Btu/lb) (lower current density) Research & development (Improve cathode material) c. Voltage drop 580 kJ/kg Design modification across (250 Btu/lb) (thinner diaphragm) diaphragm d. Voltage drop in ‘460 kJ/kg electrolyte (200 Btu/lb) e. Voltage drop in 280 kJ/kg Design modification anode—cathode (120 Btu/lb) assemblies f. Oxygen evolu— 230 kJ/kg Research & development tion on anode (100 Btu/lb) (improve anode material) g. Unaccounted 580 kJ/kg for (250 Btu/lb) 2. Overall process a. Lack of heat 1’425 kJ/kg Design modification recovery from (620 Btu/lb) (waste heat recovery) H 2 , Cl 2 , and cell liquor streams b. Radiatlon,con- 2530 kJ/kg Insulation vection, other (1100 Btu/lb) heat losses from electro- lysis cell c. Failure to use 3500 kJ/kg Waste utilization H 2 by—product (1500 Btu/lb) as fuel NOTE: Electrolysis cell losses are electrical. The fuel value of these losses would be approximately three times as large as the values listed. 10 ------- Figure 3.’ Caustic soda energy consumption diagram (1973 USA production: 9.70 x iO kg (2l. 4 x (1973 energy consumption (primarily steam): (80 x lO Btu)] 10 ib)] 2700 MW * Weight of products as 100% caustic soda. Energy values are in terms of energy per unit weight of caustic soda as 100% caustic soda. Energy Input Heat rejection Chlorine cell liquor 120 kJ/kg 355°K (180°F) (by—product) Anhydrous NaOH (by—product) 11 ------- Figure 4. Caustic soda energy intensive equipment diagram — evaporators [ Rejected heat: Radiation, convectIon, other - 120 kJ/kg (50 Stu/Ib) Water vapor — 5200 kJ/kg (2250 Btu/lb) at 320°K (120°F) Hot product — ‘160 kJ/kg (200 Btu/lb) at 355°X (180°F)] * Energy values are in terms of energy per unit weight of caustic soda as 100% caustic soda. Evaporators 1st effect evaporator To vacuum jet 12 ------- Table 2 shows the causes of energy losses in the evap- oration of water from cell liquor. It also shows the approximate magnitude of the losses and some possible energy conservation approaches. C. Ethylene by Ethane Pyrolysis Figure 5 shows major steps in an ethylene manufacturing process that uses ethane as the feedatock. Major steps from an energy consumption viewpoint are pyrolysis of the feed, compression of the gases from the pyrolysis furnace, and liquefaction of the gases before distilla- tion. Both the compression and liquefaction by refrig- eration are necessary to allow separation by distilla- tion of the components in the furnace exit stream. The pyrolysis, compression, and refrigeration operations ac- count for approximately 90 percent of the total energy consumption in the manufacture of ethylene. Figure 6 shows the furnace and associated waste heat recovery equipment In a modern ethylene plant. Waste heat is recovered from furnace stack gases and from hot process gases leaving the furnace. Figure 7 shows the compression of process gases from the pyrolysis furnace. Intercooling and gas—liquid separation are necessary between each stage of com- pression. Acetylene hydrogenation is shown between the third and fourth compression stages. Figures 8 and 9 show a refrigeration system for a modern ethylene plant. Figure 8 shows the compression of pro- pylene arid ethylene refrigerants. Various levels of com- pression arid expansion lead to a number of temperature levels that are needed in the distillation columns. The system is referred to as a cascade system because some of the propylene refrigerant is used to cool the ethylene refrigerant which is then used to cool several process streams. An energy saving feature of the scheme In Figure 8 is the use of the coldness in the bottom streams from the demethanizer and C 2 splitter distillation columns to cool a portion of the propylene refrigerant. Figure 9 shows the refrigeration of process gases by cold process streams leaving distillation columns, by propylene and ethylene refrigerants, and by the gases in the demethanizer overhead stream. The demethanizer overhead stream is usable as a coolant because it has been supercooled by passing through a turbo—expander. Figure 9 also shows 13 ------- Table 2. CAUSTIC SODA ENERGY CONSERVATION APPROACHES Approximate Causes of magnitude of Energy conservation energy losses losses approaches 1. ReJected heat a. Radiation, 120 kJ/kg Insulation convection (50 Btu/lb) Maintenance b. Water vapor 5200 kJ/kg Design modification from last (2250 Btu/lb) (waste heat recovery) effect c. Hot product ‘i60 kJ/kg Design modification (200 Btu/lb) (waste heat recovery 2. Overall process a. Use of excess l 400 kJ/kg Design modification steam (600 Btu/lb) (add additional effect to evaporation operation) b. Low NaOH 2300 kJ/kg Research & development concentration (1000 Btu/lb) (ionic membrane in cell liquor diaphragm) c. Production of 230 kJ/kg Market modification anhydrous NaOH (100 Btu/].b) (substitute 70-74% NaOH f or anhydrous) Note: Energy values are in terms of energy per unit weight of caustic soda as 100% caustic soda. 114 ------- Figure 5.’ Ethylene energy consumption diagram [ 1973 USA production: 10.1 x iO kg (22.t x 1O 9 lb)) [ 1973 process energy consumption (primarily natural gas plus H 2 , CH 1 . gases generated in the process): 9300 MW 8o x 10 12 Btu)] [ 1973 total energy consumption (feedstock plus process requirements) 23,000 MW (700 x 1012 Btu)] 0 U -’ ‘-4 aD .- ) 0 0 C— —s .0I. J - U) . U ) •... . 4.) GJ — ) mr-. . 0. 0 o O {) 0 C%J 043 . .-..i U) kJ/kg (2100 Btu/lb) High pressure St earn 5..s U) 0. O E O. ( aD ) I 1.) .—x 65% conversion of ethane in furnace with an 80% yield of ethylene. (continued on next page) Reclaimed energy Energy Input 20.900 kJ/kg St earn Meat rejection Feedstock — ethane uuI Recycle ethane (9000 Btuulb) Natural gas or H 2 ,CH gases from distilla- tion columns t 350 kJ/kg Pyrolvsis furnace . (endotherTnic) Aflreac 5150 kJ/k (2220 Btu 1b) t Hs1de reac = 930 kJ/kg I (1j Btu/lb) I 67140 kJ/kg 2900 Btu/lb ) High pressure steam 1 830 kJ/kg (150 Btu/lb) Radiation, convection Stack •gases 2160 kJ/kg Hot reaction products (2080 Btu/lb) Quench, water scrub, and cooling (930 Btu/lb) 1 48o°K (1400°F) 230 kJ/kg .0 5 .. ’ 4) 0 a’ U). Cool reaction products Compression 14870 (100 Btu/lb) 3 1 40°K (150°F) 145 kJ/kg — Acetylene removal I Compress ion F (20 Btu/lb) Radiation, convection 3250 ‘1 Condensate return to process Compressed reaction products (11400 Btu/lb) 380°K (220°F) 1750 kJ/kg (750 Btu/lb) 380°K (220°F) 15 ------- Figure 5. (ContInued). High pressure ____________ St earn 5H10 kJ/kg (2330 Btu/lb) This steam Is used along with additional steam (900 kJ/kg or 390 Btu/lb) at other points in the process H 2 , CH as fuel 15,300 kJ/kg (6600 Btu/lb) to distillation Compressed reaction 1’ products Compressed, purified reactor products Refrigerant $ recycle .‘ Refrigerant ‘ compression ndensate ecycle Refrigerant Ethylene product 25 kJ/kg (10 Btu/lb) Radiation, convection 2320 kJ/kg ( 1,000 Btu/] ’ ) 3 1 0°K (150°F) 580 kJ/kg (250 Btu/lb) Conduction, other Ethane recycle Ret’rigerant recycle Energy input Reclaimed energy Heat rejection Caustic and water wash. Drying ..— ‘-3 0 0 \ C ” ‘-4 .0 -l 4) 0 C 3500 IcJ/kg (1500 Btu/Ib) I 380°K (220°F) Cooling, dernethanizer, deethanizer, and C 2 L splitter distillation F -_columns J 16 ------- Figure 6. EthyIrn ‘-ni rgy intensive equipment diagrarn—pyrolysis furnace and waote heat recovery equipment tReiected heat: Radiation, convection — 350 kJ/kg (150 Btu/lb) Stack gases — 2160 kJ/kg (930 Btu/lb) at ll80 0 K ( 1100°F)] Fyratysto fu rn a c P Furnace energy balance Waste hrat recovery Quench exchanger Water ocrubhrr (9000 Btu/lb) Energy input to furnace 20,900 kJ/kg Heats of reaction Ethylene Side reactions 5150 930 kJ/kg kJ/kg (2220 ( 100 Energy Energy Energy change from transferred loot feed to product to steam 5570 67 110 2510 kJ/kg kJ/kg kJ/kg (21400 (2900 (1080 11830 kJ/kg 1160 kJ/kg Btu/ lb) Btu/lb) Btu/lb) Btu/lb) Btuflb) Condensate Reaction products Low pressure nteam Condensate CH + air 20 00 kJfk (9000 Btu/lb) condensate Quench Water exchanger scrubber (2080 Btu/lb) ( 200 Btu/1.b) 17 ------- Figure 7. Ethylene energy intensive equipment diagram — compressors [ Rejected heat: Radiation, convection — 115 kJ/kg (20 Btu/lb) Condensate (vapor) — 3100 kJ/kg (1350 Btu/ lb) at 380°K C 220°F) Hot compressed reaction products — 1850 kJ/kg (800 Btu/ lb) at 380°K (220° ?) ] Steam Reaction Condensttte 1st stage compressor Steam Input to earh turbine 1220 kJ/kg (525 Btu/lb) Acetylene hydrogenat ion reactor Products Condensate pa ia) Steam 2nd stage 3rd stage compressor compressor 1 1th stage compressor 18 ------- Figure 8. Ethylene energy intensive equipment diagram — propylene and ethylene refrigeration systems [ Rejected heat: Radiation, convection — 25 kJ/kg (10 Btu/lb) Condensate (vapor — 3500 kJfkg (1500 Btu/lb) at 380°K (220°F) Hot refrigerant streams — 2320 kJ/kg (1000 Btu/lb) at -3 4O°K ( -150°F)] Demethanizer reboiler 0 (j Dryer feed chiller Demethanizer feed C 2 splitter reboller Gj Ethylene refrigeration Deethanizer condenser C. splitter condenser Demethanizer condcns r 19 ------- Figure 9. Ethylelte process refrigeration Feed #6 Feed #5 Feed # Feed #3 Feed #2 Feed #1 * Burned in pyrolysis furnace. Reaction products Ethane from feed CH 4 ., H 3 dryer recycle Propylene Ethylene product Propylene Demethanizer feed #2 Ethylene Dernethanizer feed # I Demethanizer feed #6 Deme t han X4e r feed # Demethanizer Propylene To deethanizer 20 ------- the efficient practice of multi—feeding the demethanizer column. In effect the feed stream has been partially separated before it enters the demethanizer column. Table 3 shows the causes of energy losses in the pyrolysis operation, compression operation, refrigeration operation, and overall process. It also shows the approximate mag- nitude of the losses and some possible energy conserva- tion approaches. D. Ethylbenzene by Alkylatlon of Benzerie with Ethylene Figure 10 shows the major steps In the ethylbenzene man- ufacturing process. The process illustrated uses an A1C1 3 catalyst to promote alkylatlon of benzene with ethylene. The major step from an energy consumption viewpoint is the separation of the reaction exit stream Into components by distillation. This operation accounts for approximately 75 percent of the total energy consump- tion in the production of ethylbenzene. Figure 11 shows the distillation operation. Steam pro- vides energy for the three primary columns — the tar removal column, the benzene column, and the ethy].benzene C oluinn. Table 14 shows the causes of energy losses in the distil- lation operation and the overall process. It also shows the approximate magnitude of the losses and possible con- servation approaches. E. Styrene by Dehydrogenation of Ethylbenzene Figure 12 shows the major steps in the styrene manuf’actur— ing process. This process uses a metal oxide catalyst to promote the dehydrogenation of ethylbenzene at high temper- ature. Major energy consumption operations are the heating of reactants plus steam and the separation of the reacto exit stream into components by distillation. These opera- tions account for more than 90 percent of the total energy consumption In the manufacture of styrene. Figure 13 shows the steam superheating, reaction, heat recovery, and desuperheating operations. Steam, natural gas, and waste process gas are used to provide energy for the reaction. The large amount of steam Is also 21 ------- Table 3. ETHYLENE ENERGY CONSERVATION APPROACHES Causes of energy ]sse Approximate magnitude of losses Energy conservation aD roaches 1. Furnace losses a. Hot stack gases b. Radiant and convection heat losses 2. Heat rejection in compression operation a. Unavailability of latent heat in steam to drive the turbine b. Loss of heat imparted to compressed gases c. Radiation, convection a. Unavailability of latent heat in steam to drive the turbine b. Loss of heat imparted to compressed refrigerant c. Radiation, convection 2160 kJ/kg (930 Btu/lb) 350 kJ/kg (150 Btu/lb) 3250 kJ/kg (l i00 Btu/lb) 1750 kJ/kg (750 Btu/lb) 4 kJ/kg (20 Btu/lb) 3500 kJ/kg (1500 Btu/lb) 2320 kJ/kg (1000 Btu/lb) 25 kJ/kg (10 Btu/lb) Design modification (waste heat recovery) Insulation Maintenance Process integration (find use for the low pressure steam exiting the turbine) Design modification (waste heat recovery) Process integration (find use for the low pressure steam exiting the turbine) Design modification (waste heat recovery) Insulation 4. Overall process a. Low conversion of etharie to products 8100 kJ/kg (3500 Btu/lb) Research & development 3. Heat rejection in refrigeration operation Insulation 22 ------- Table 3 (continued). ETHYLENE ENERGY CONSERVATION APPROACHES Approximate Causes of magniti. de of Energy conservation energy losses losses approaches b. Low yield of 11600 kJ/kg Research & development ethylene from (2000 Btu/lb) ethane c. Non—isothermal 580 kJ/kg compression of (250 Btu/lb) process gases and refrigerants d. Non—Isentroplc 700 kJ/kg Maintenance compression of (300 Btu/lb) process gases and refrigerants e. Excessive tern— 1160 kJ/kg Design modification perature dif— (200 Btu/lb) (use more heat exchange ferences between surface) cold and hot Maintenance fluids in the Insulation refrigeration operation F. Non—optimiza— 460 kJ/kg Design modification tion of (200 Btu/lb) distillation— refrigeration— compression scheme 23 ------- Figure 10. Ethylbenzene’ energy consumption diagram [ 1973 USA production: 2.91$ x 10 kg (6.50 x iO ib)] [ 1973 process energy consumption (primarily steam): 1130 MW (13 x l0 2 Etu)] - [ 1973 total energ consumption (feedatock plus process): 3150 MW (911 x 10 2 Btu)] Energy input A1C 1 3 Heat rejection Dried catalyst benzene I Ethylene Reactor (exotherinic) Hreac = 1280 kJ/kg (550 Btu/lb) Recycle diethyl— Overhead I benzene ,vapors 1 t I 930 kJ/kg Cooling and scrubbing __________________________ ( i00 Btu/lbY 370°K (210°F) Liquid reaction products Aid 3 sludge g 370°K (210°F) recycle 50% NaOH I decanting I Neutralizing and 1 lus e Water p caustic wast 3720 kJ/kg Heat 3720 kJ/kg rej ected rom overhead (1 0 Btu lb _______________ 355— 1 $l0°K Steam Benzene •uI recycle I Tar (fuel value is (180—280°F) Diethylbenzene I 0 kJ/kg or 100 Btu/lb) Ethylbenzene product * 110% conversion of benzene to products. 95% selectivIty to ethylbenzene 99% conversion of ethylene to products 24 ------- Figure 11. Ethylbenzene energy intensive equipment diagram — distillation IFleiected heat: From overhead streams — 3720 kJ/kg (1600 Btu/lb) at 355— IlO°K (180—280°F)] React ion products I 1310 kJ/kg — (560 Btu/lb) Steam To diethylbenzene. column Wet benzene to benzene drvinz column 1180 kJ/l lb) team /(510 Bt Ethyl- berizene product 1230 (530 Steam kJ/kg Btu/lb) To gas scrubber Tar removal column Benzene column Ethy lbenzene column 25 ------- Table Lj• ETHYLBENZENE ENERGY CONSERVATION APPROACHES Approximate Causes of magnitude of Energy conservation energy losses losses approaches 1. Rejected heat a. Cooling of 1280 kJ/kg Design modification reactor exit (550 Btu/lb) (waste heat recovery) St reams b. Cooling of 3720 kJ/kg Design modification overhead (1600 Btu/lb) (waste heat recovery) streams from distillation columns 2. Overall process a. Failure to 230 kJ/kg Waste utilization use tar as (100 Btu/lb) fuel b. Low conversion 1850 kJ/kg Research & development of benzene (800 Btu/lb) c. High ref lux 700 kJ/kg Design modification ratios in (300 Btu/lb) (more plates) distillation columns 26 ------- Figure 12. Styrene 0 energy consumption diagram [ 1973 USA production: 2.72 x 10 kg (6.01 x io lb.)] [ 1973 energy consumption (primarily natural gas, steam): 2600 MW (78 x 1012 Btu)] (1973 fuel generation (waste gases, residue): 730 MW (22 x 10 1z Btu)] 5 50 kJ/kg (2350 Btu/lb) Natural gas, process waste gas 19jP0 kJ/kg (8500 Btu/lb) Steam 5560 kJ/kg (2J400 Btu/lb) St earn J (‘40 btuf].D) Radiation, convection Stack gas 835 kJ/kg (360 Btu/l Steam 530°K (500°F) 2300 kJ/kg ( 980 Btu/1 500°K (440°F) 20,100 kJ/kg Residue fuel kJ/kg (300 Btu/lb) Styrene product * 40% conversion of ethylbenzene to products 90% selectivity to styrene. Energy input Reclaimed energy Heat rejection 4 Steam I Heat exchange and superheater 3920 kJ/kg (1690 Btu/lb) Ethy lbenzene Steam 111.1 4230 kJ/kg 95 kJ/kg (1830 Btu/lb) bO ‘-3 0 ‘L ieat exchange & reactor 1 AH .eac herm1c T Wet reaction products 50 kJ/kg ( U 5 UfJ.O) Radiation, convection 1 Cooling I I I Desuperheater I and cno11n $Tar Decantation and gas separation H 2 , other gases as fuel 3360 kJ/kg (1450 Btu/lb) i-j iCondensate (8700 Btu/lb) 380°K (220°F) I Reaction products 1 Distillation luene Benzene r; ;ei: 5560 kJ/kg_ I ( d ’ 400btufj. 1 315-340°K ( 110—150° ?) Ethylbenzene recycle 27 ------- Figure 13. 3tyrene energy intensive equipment diagram — superheater, reactor, and cooling equipment [ Rejected heat: Radiation, convection — 1 5 kJ/kg (60 Btu/lb) Stack gases — 835 kJ/kg (360 Btu/lb) at 530°K (500°F) Hot reaction products — 2300 kJ/kg (980 Btu/lb) at 500°K (L1110°F) and 20,100 kJ/kg (8700 Btu/lb) at 380°K (220°F)) Steam Desuperheater Superheater Natural gas 2090 kJ/kg (900 Btu/lb) Air Waste gas oJ 3360 kJ/kg (1 450 Btu/lb) St earn t Hreac 1730 kJ/kg (750 Btu/lb) Reactor Reaction products J 3920 kJ/kg and steam U690 Btu/lb) 19100 kJ/kg (8500 Btu/lb) Heat exchanger Ethylbenzene [ ( ) ) Heat exchanger 1200 kJ/kg (520 Btu/lb) Heat exchanger Waste gas 30110 ser Conden (1310 Btu/lb) (8700 Btu/lb) 20100 kJ/kg l————Dec 2300 kJ/kg (980 BtU ar_ Heating value 50 kJ/kg (20 Btu/lb) Liquid reaction products Condensate To boiler 28 ------- provided as a diluent to lower the ethylbenzene partial pressure and thereby allow the reaction conversion to Increase. Figure ]. I shows the distillation operation. Steam pro- vides energy for the primary columns - the light ends columns, the ethylbenzene column, and the styrene column. Table 5 shows the causes of energy losses in the super— heating—reaction operation, the distillation operation, and the overall process. It also shows the approximate magnitude of the losses and possible conservation approaches. F. Phenol/Acetone by Oxidation of Cumene and Cleavage of Cumene H ydroperoxide Figure 15 shows the major steps In the phenol/acetone manufacturing process. Cuinene Is oxidized to cumene hydroperoxide which Is then split into phenol and acetone. Major energy consumption operations are air compression and separation of the reactor exit stream by distillation. These operations account for approximately 70 percent of the energy consumption In the manufacture of phenol! acetone. Figure 16 shows the compression of air which Is used to oxidize cumene. A two stage compression scheme with Intercooling is employed. Figure 17 shows the separation of unreacted cumene from cumene hydroperoxide by distillation. Steam Is used to provide energy for this operation. Figure 18 shows the separation of acetone from other reactor effluent components by distillation. Steam is the energy source for the three distillation columns — the crude acetone column, the light ends column, and the refined acetone column. Figure 19 shows the separation of phenol from other reactor effluent components by distillation. Steam Is the energy source for the four distillation columns — the heavy ends column, the cuznene column, the dehydro— genation column, and the phenol column. 29 ------- Figure 111. Styrene energy intensive equipment diagram — distUlation (Rejected heat: From overhead streams - 5560 kJ/kg (21100 Btu/lb) at 315—3 1 10°K (110—150°F)] 700 kJ/kg (300 Btu/lb) steam cw To waste gas at ream cw Liquid reaction products from condenser Ethylbenzene column steam Light ends column cw Styrene column Styrene Residue fuel 700 kJ/kg (300 Btu/lb) 30 ------- Table 5. STYRENE ENERGY CONSEHVATION APPROACHES Approximate Ca ses of magnitude of Energy conservation energy losses losses approaches 1. Superheater, reactor & cooling operations a. Heat in stack 835 kJ/kg Design modification gases (360 Btu/lb) (waste heat recovery) b. Radiation, ]i45 kJ/kg Insulation convection (60 Btu/lb) Maintenance a. Heat discarded 22, 0O kJ/kg Design modification from process (9680 Btu/lb) (waste heat recovery) stream 2. Rejected heat in 5560 kJ/kg Design modification distillation (2’400 Btu/lb) (waste heat recovery) operation 3. Overall process a. Low ethyl— i8,500 kJ/kg Research & development berizene (5000 Btu/lb) conversion b. Fuel value 50 kJ/kg Waste utilization of tar (20 Btu/lb) c. High reflux 930 kJ/kg Design modification ratios in (1 00 Btu/lb) (more plates) distillation Columns 31 ------- Figure 15. Phenol/acetone’ energy consumption diagram [ 1973 USA production: phenol 1.02 x 1O 9 kg (2.25 x iO ib) acetone 0.905 x kg (1.99 x iO ib) (1973 energy consumption (primarily steam): 530 MW (16 x l0’ Btu)] [ 1973 fuel generation (tar): 60 MW (1.8 x 1012 Btu)] I , 700 kJ/kg (300 Btu/lb) Electricity 11460 kJ/kg (630 Btu/lb) Steam 10,600 kJ/kg (14570 Btu/lb) Steam I Ac etopheno J Cumene recycle * 25% conversion of cumene. 92% selectivity to phenol and acetone. Energy values are in terms of energy per unit weight of phenol produced. 6140 kJ/kg (280 Btu/lb) Natural gas Air Oxidation reactor (exothermic) AHreac 1150 kJ/kg (500 Btu/lb) Reaction products Ion exchange neutralizers ] iieavies 4 phenol kcetone product product Stack gas Side reaction products to distillation 1390 kJ/kg (600 Btu/lb) 355°K (175°F) 2550 kJ/kg ( 1100 B Uflbr 350°K (165°F) 10,850 kJ/kg,, (14660 Btu/lb) 320— 1 400°K (115—260°F) 230 kJ/kg ( ..LUU Ufi0) Blo°K (1000°F) Energy input Compression Meat rejection Cumene recycl Cumeme Hot air - 270 kJ/k (115 Btu/lb) 380°K (220°F) 1390 kJ/kg - !2 , 0 I Gas separation (bOO Btu/lb) 385°K (230°F) 185 kJfkg 4 Concentration distillation column Cumene J ( 0 Btu/lb) — 385°K (230°F) I recyc.Le I Cumene hydroperoxide Cleavage mixer, cooler, flash drum A}I ac: 2700 kJ/kg (1160 Btu/lb) Exotherinic Primarily acetone Primarily phenol I Distillation — 4 Cracking furnace — 145 kJ/kg ( U Utu/lb) Radiation, convection Tar 370 kJ/kg j (160 Btu/lb) 535°K (500°F) Fuel value is 1850 kJ/kg (800 Btu/lb) 32 ------- tgurc a6. Phenol/acetone energy intensive equipment diagram — air compression [ Rejected heat: Hot compressed air — 270 kJ/kg (115 Btu/lb) at 380°K (220°F)] Air 100 kN/m 2 (1LI.7 psia) Cw I ________ to actor _ J 1 F650kN/m2 — ____________ psia) Compressor Compressor Note: Energy values are in terms of energy per unit weight of phenol produced. 33 ------- Figure 17. Phenol/acetone energy intensive equipment diagram - cumene hydroperoxide concentration distillation column [ Rejected heat: Overhead stream — 1390 kJ/kg (600 Btu/lb) at 355°K (175°F)] recycle cumene hydroperoxide Cumene hydroperoxide concentration column Note: Energy values are In terms of energy per unit weight of phenol produced. Unreacted cumene and cumene ide ‘I 1, 460 kJ/kg (630 Btu/lb) steam 31 ------- Figure 18. Phenol/acetone energy Intensive equipment diagram — acetone distillation columns (Rejected heat: Overhead streams — 1350 kJ/kg (580 Btu/lb) at 320—335°K (115—1 1 40°F)] Crude acetone column Re fined acetone column Note: Energy values are in of phenol produced. terms of energy per unit weight Primarily acetone from flash tank Light ends column 35 ------- Figure 19. Phenol/acetone energy intensive equipment diagram — phenol distillation column [ Rejected heat: Overhead streams — 9500 kJ/kg (i O80 Btu/lb) at 320-Ji00°K (115—260°F)] Heavy ends column Cumene column Dehydration column Phenol column Note: Energy values are In terms of energy per unit weight of phenol produced. Phenol and heavies from crude acetone column Heavy ends to cracking furnace 36 ------- Figure 20 shows the cracking of the bottoms from the heavy ends distillation column and from the acetophenone distillation column. Natural gas is used to provide heat for cracking of the bottoms material. Table 6 shows the causes of energy losses ir the compres— sj on operation, the distillation operation, the cracking operation, and the overall process. It also shows the approximate magnitude of the losses and possible con- servation approaches. Q, Cuinene by Alkylation of Benzene with Propylene Figure 21 shows the major steps in the cumene manufac- turing process. Phosphoric acid on alumina catalyzes the alkylatlon of benzene with propylene. The major energy consumption step is the separation of reactor effluent components by distillation. This operation accounts for approximately 90 percent of the total energy consumption in the process. Fj gure 22 shows the distillation scheme used to separate the reactor exit stream components. Dowthertn is used to provide energy for the three distillation columns — the propane column, the benzene column, and the cumene co 1 uxnn. Table 7 shows the causes of energy losses In the distil- lation operation and the overall process. It also shows the approximate magnitude of the losses and possible energy conservation approaches. H. Sodium Carbonate by the Solvay Process Figure 23 shows the major steps In the synthetic sodium carbonate manufacturing process. The Solvay process is used. Major steps from an energy consumption viewpoint are the lime kiln operation, the compression of carbon dioxide, and the calcining of sodium bicarbonate to podium carbonate. These steps account for mere than 70 percent of the total energy consumption In the process. Figure 2 4 shows the lime kiln operation. Coke supplies energy to convert calcium carbonate to calcium oxide and carbon dioxide. Figure 25 shows the corpresslori of c rbor dioxIde nitrogen from the lime kiln. Steam is used to provide energy to drive the compressors. 37 ------- Figure 20. Phenol/acetone energy intensive equipment diagram — cracking furnace [ Rejected heat: Radiation, conve&tlon — 115 kJ/kg (20 Btu/lb) Hot stack gases — 230 kJ/kg (100 Btu/lb) at 810°K (1000°F) Hot process streams — 370 kJ/kg (160 Btu/lb) at 535°K (500°F)) Cracking furnace plus dehydrator Note: Energy values are in terms of energy per unit weight of phenol produced. Heavy ends column and acetophenone column bottoms Cw Al 2 03 To Tar N, Air Natural gas To C ume n e column 38 ------- Table 6. PHENOL/ACETONE ENERGY CONSERVATION APPROACHES Approx iniat e Causes of magnitude of Energy conservation energy losses losses approaches 1. Rejected heat a. Hot compressed 270 kJ/kg Design modification air (115 Btu/lb) (waste heat recovery) b. Overhead 12,130 kJ/kg Design modification streams from (5260 Btu/lb) (waste heat recovery) distillation columns c. Other hot 1i500 kJ/kg Design modification process streams (19 4O Btu/lb) (waste heat recovery) d. Hot stack gases 230 kJ/kg Design modification (100 Btu/lb) (waste heat recovery) e. Radiation, 145 kJ/kg Insulation convection (20 Btu/lb) Maintenance 2. Overall process a. Low cumene 11460 kJ,’kg Research & development conversion to (630 Btu/lb) cumene hydro— peroxide b. Fuel value 1850 kJ/kg Waste utilization of tar (800 Btu/lb) c. Hig i reflux 20L 0 kJ/kg Design modification ratios in (880 Btu/lb) (more plates) distillation co]. uinns d. Non—isothermal 95 kJ/kg compression of (140 Btu/lb) air e. Non—isentropic 95 kJ/kg Maintenance compression of (1 10 Btu/lb) air Note: Energy values are in terms of energy per unit weight of phenol produced. Overall process losses d and e are electrical. The fuel value of these losses would be approximately three times the values listed. 39 ------- Figure 21. Cunene’ energy consumption diagram [ 1973 USA production: 1.21 i 10 kg (2.67 x iO ib)) [ 1973 process energy consumption (primarily natural ga I): 270 74W (8.1 x 10’ Btu)] [ 1973 total energy consumption (feedetock plus process): 1270 14W (38 x 10 Btu)] 100% propylene conversion 92% selectivity to cwnene 1 % benzerie conversion 97% selectivity to cumerie “ Natural gas is used to heat Dowtherma. Energy Input Reclaimed energy Benzene recycle 2100 kJ/kg Heat rejection Bensene propylene, and propane Heating t 115 kJ,’kg r (900 Btu/lb) Dowtherma 3370 kS/kg Propane recycle 4 6 0 ‘a 0 Reactor (exothermic Hreac 815 kS/kg (350 Btu/lb) .0 In I Reaction Cooling 1 (1q50 Btu/lb) Dowtherm (50 Stu/ib) Radiation, convection 6170 kS/kg I Distillation Propane recycle Benzene recycle_ (2650 Btu/lb) 320—Q10°K (120—280°F) Diiaopropy lbenzene Cumene product 40 ------- Figure 22 Cumene energy intensiie equipment d agraTn — distillation [ Rejected heat: Overhead distillation column streams — 5350 kJ/kg (2300 Btu/lb) at 320_L410°K (120—280°F)] Propane Benzene Cumene column column column Benzene recycle 2,fl50 kJ/kg (1,050 Btu/lb) Diisopropylbenzene as fuel or for ‘urther processing 41 ------- Table 7. CUMENE ENERGY CONSERVATION APPROACHES Approximate Causes of magnitude of Energy conservation energy losses losses approaches 1. ReJected heat a. Radiation, 115 kJ/kg Insulation convection (50 Btu/lb) Maintenance b. Overhead 6170 kJ/kg Design modification streams from (2650 Btu/lb) (waste heat recovery) distillation columns 2. Overall process a. Low benzene 3500 kJ/kg Research & development conversion (1500 Btu/lb) b. High reflux 700 kJ/kg Design modification ratio In (300 Etu/ib) (more plates) distillation columns Z 12 ------- Fljure 23. Sodium carbonate energy consumption cUa ram [ 1973 USA production: 6.80 x 10 kj (15.0 x io ib)] [ 1973 energy consumption (primarily steam, coke): 2,000 4W (60 x l0 Btu)] $ Air e Coke Limestone 1? NH 3 and 1120 from calciner NH 11 C1 solution Steam Co 2 gPlus $ I’ Prl’ ar1lj 12 to amm ia absorber mmonia stills PuriNed brine Mostly N 2 from e carbonation towers Ammonia absorber (exothermic) Carbcnation towers (exothermic) ANreac = 17110 kJ/kg (750 Btu/lb) sol’n + co 2 NH and 1i 2 0 to ammonia stills - Filter Tu dual Na 2 C0 product ash (li lit ash) plant I 1 U StU/ID) 535°K (500°F) iic kJJk - 700 kJ/kg (300 Btu/lb) 380°K (220°F) 1620 kJ/kg (700 Btu/lb 320°K (120°F) 230 kJ/k (100 Btu/1b1 L 180°K (H00° 1) 930 I J /k.’ ( 1100 Btu/1 1 175°K (110001. ) Energy input 2520 kJ/kg (1090 Btu/lb) Coke Heat rejection • Lime kiln (endothermic) AHreac = 1,690 kJ/kg 1 (7 0 I 1 23OkJ/kg CaO (100 Btu/lbT Radiation, convection Stack gases (primarily N 2 arid C0 2 ) 350 kJ/kg 1970 kJ/kg (1450 Btu/lb) SI cam atmosphere hCaC1 2 solution - ess Ion T50Btu/ lb) 1 180°K (1100°F) 25 kJ/kg N 2 plus Co 2 I NH n 1 us CO 2 ‘JH .C1, NH OH solution (10 Btu/Jb) Radiation, conv€ rtLon 1300 kJ/kr (560 BLu/ibT Condensate 38o°K (220°F) N 2 to V atmosphere $ NaHCOi + NH C1 solution 17110 kJ/kg I ( (5U tU/LU) 320°K (l20° ’) $ Crude NaHCO3 Calciner 211110 LJJkr’ (I t)5i1 -ii/ lb i,Ci 2 It carbonatiun towers I 115 kJ/k J (50 Btu/Lh) — fthd ill on, conv& :I nil 43 ------- Figure 2 . Limestone plus coke mixture Sodium carbonate energy intensive equipment diagram - lime kiln [ Rejected heat: Radiation convection — 230 kJ/kg (100 Btu/lb) Stack gases - Z18 5 kJ/kg (210 Btu/lb) at 535°K (500°F) Hot lime — 115 kJ/kg (50 Btu/lb) at J 4 8O°l( (L100°F)) Co 2 to compressors Recuperat ive heater CaO to slaker - 4 — Air Lime kiln ------- Figure 25. sodium carbonate energy intensive equipment diagram - compressors [ Rejected heat: Radiation, convection — 25 kJ/kg (10 Btu/lb) Condensate (vapor) — 1300 kJ/kg (560 Btu/lb) at 380°K (220°F) Hot compressed CO 2 and N 2 — 700 kJ/kg (300 Btu/lb) at 380°K (220°F)] CO 2 and N 2 f’rom the lime kiln Cw Ste am Cw Condensate Condensate To carbonator 145 ------- Figure 26 shows the calcining of sodium bicarbonate to sodium carbonate. Steam is the heat source. Table 8 shows the causes of energy losses in the lime kiln operation, the compression operation, and the cal— cining operation. It also shows the approximate mag- nitude of losses and possible energy conservation approaches. I. Carbon Black by the Furnace Process Figure 27 shows the major steps in the carbon black man- ufacturing process. The furnace process uses a heavy aromatic oil as feedstock. A variety of blacks with different properties can be obtained by altering conditions in the reactor. The major energy consumption steps are the reaction operation and the drying of the carbon black. These operations account for over 80 percent of the total energy consumption In the process. Figure 28 shows the reactor plus heat recovery equip- ment. Natural gas is the source of energy to heat the aromatic oil to the reaction temperature. Figure 29 shows the drying operation. Reactor effluent gases are used to heat the wet carbon black and remove moisture from it. Table 9 shows the causes of energy losses in the reaction operation, the drying operation, and the overall process. It also shows the approximate magnitude of the losses and possible energy conservation approaches. J. Q ygen/Nitrogen by Air Distillation Figure 30 shows the major steps In the oxygen/nitrogen manufacturing process. The compression of air accounts for almost 100 percent of the energy consumption In this process. However, the amount of compression required is dependent on the heat exchange between feed and product streams, and on the design of the distillation column. Figure 31 shows the compression of air before it .S cooled by product streams. Electricity is used to drive the compressor. Figure 32 shows the distillation column used in the oxygen/nitrogen process to separate the components in 46 ------- Igure 26. odium r arbonaf,e energy i.nt nsive equipment diagram — calciner [ Rejected heat: Radiation, convec .tion — 115 kJ/kg (50 Btu/lb) Hot product — 230 kJ/kg (100 Stu/ib) at ( 80°X) )400°F)] CO 3 + NH 3 + H 2 0 Rotary dryer a) 4 ) c j a) 0 U Crude NaHCO , Finned tubes Steam Na 2 CO 3 147 ------- Table 8. SODIUM CARBONATE ENERGY CONSERVATION APPROACHES Approximate Causes of magnitude of Energy conservation energy losses losses approaches 1. ReJected heat a. Radiation, 370 kJ/kg Insulation convection (160 Btu/lb) Maintenance b. Stack gases 350 kJ/kg Design modification (150 Btu/lb) (waste heat recovery) c. Uncondensed 1300 kJ/kg Process integration steam from (560 Btu/lb) compressor d. Process streams 53110 kJ/kg Design modification (2300 Btu/lb) (waste heat recovery) 2. Overall process a. Non—isothermal 115 kJ/kg compression (50 Btu/lb) b. Non—Isentropic 115 kJ/kg compression (50 Btu/lb) c. Gas for compres— 1150 kJ/kg Process modification slon is only (500 Btu/lb) (use higher oxygen 0% CC 2 content combustion air) d. Heat required 115 kJ/kg Design modification to dry limestone (50 Btu/lb) (enclosed storage) and coke e. Heat lost in 230 kJ/kg heating impuri— (100 Btu/lb) ties in limestone f. High water con— 3145 kJ/kg Design modification tent In (150 Btu/lb) calciner feed 48 ------- Figure 27. Carbon black energy consumption diagram [ 1973 USA production: 1.58 x l0 ’kg (3.50 x 10’ ib)] [ 1973 process energy consumption (primarily natural gas): 800 MW (211 x lO 12 Btu)] [ 1973 total energy consumption (feed stock oil minus generated reactor gas plus process): 2500 MW (75 x 1012 Btu)] Reclaimed energy Magnetic separat and screening Fuel value is 32,500 kJ/kg or 14,000 Btu/lb. Fuel value is 42,000 kJ/kg or 18,000 Btu/lb. Ener v inout $ Heat rejection Aromatic* oil (9450 gas 115 kJ/kg Hot, carbon black I * Aromatic oil fuel value 18 approximately 714,500 kJ/kg (32,000 Btu/lb) Carbon black product. Reactor gas as fuel. 49 ------- Figure 28. Carbon black energy—intensive equipment diagram — reactor and waste heat recovery equipment. [ Rejected heat: Radiatiofl, convection — 700 kJ/kg (300 Btu/lb)] Warm reactor gas and carbon black Additive for property c( Blower Feed aromatic oil ------- Figure 9. [ Rejected heat: Reactor gases Carbon black energy—intensive equipment diagram - dryer. Radiation, convection — 115 kJ/kg (50 Btu/lb) Hot effluent gases — 18,500 kJ/kg (8000 Btu/lb) at 395°K (250°F) Hot carbon black — 115 kJ/kg (50 Btu/lb) at 1 420°K (300°F)] Rotary dryer Wet carbon black Reactor gases Carbon black to magnetic separator 51 ------- Table 9. CARBON BLACK ENERGY CONSERVATION APPROACHES Approximate Causes of magnitude of Energy conservation energy losses losses approaches 1. ReJected heat a. Radiation and 810 kJ/kg Insulation convection losses (350 Btu/lb) b. Sensible heat in 2300 kJ/kg Design modification generated reactor (1000 Btu/lb) (waste heat recovery gases leaving when using reactor the process gas as fuel) c. Latent heat in 16,200 kJ/kg Design modification generated reactor (7000 Btu/lb) (waste heat recovery gases leaving when using reactor the process gas as fuel) d. Sensible heat 115 kJ/kg from carbon black (50 Btu/lb) product 2. Overall process a. Energy to heat 7000 kJ/kg Process modification inerts which are (3000 Btu/lb) (use higher oxygen lost in quench content gas to burn water natural gas) b. Fuel value of 142,000 kJ/kg Waste utilization reactor gas (18,000 Btu/lb) 52 ------- Figure 30. Oxygen/nitrogen energy consumption diagram* [ 1973 USA production (oxygen): 1 4.5 x i0 9 kg (31.9 x iO lb)] [ 1973 energy consumption (electricity): 530 MW (16 x 1012 Btu)] Reclaimed energy Heat rejection * Energy is expressed in terms of’ energy per unit weight of’ oxygen produced. Energy input Air (250°F) Oxygen Nitrogen 53 ------- Figure 31. Oxygen/nitrogen energy-intensive equipment diagram — compressors [ Rejected heat: Hot compressed air — 1150 kJ/kg (500 Btu/lb) at 395°K (250°F)] cw Air 585 kN/m 2 (85 psla) Note: Energy Is expressed in terms of’ energy per unit weight of oxygen produced. 514 ------- Figure 32. Oxygen/nitrogen energy—intensive equipment diagram — distillation column. Low pressure [ 100 N/rn 2 (l l.5 psia)) distillation column Liquid oxygen Nitrogen rich liquid High pressure :550 N/rn 2 (80 psia)) distillation column Oxygen rich liquid Secondary air previously cooled by expansion through turbo—expander Main air feed previously cooled by exiting nitrogen and oxygen streams Note: Energy is expressed in terms of energy per unit weight of oxygen produced. Nitrogen gas Liquid sub—cooler Liquid Nitrogen gas 55 ------- air. The design of this column along with the efficiency of heat exchange between feed and product streams plays a major role in determining the amount of air compression required. Table 10 shows the causes of energy losses in the compres- sion operation, the distillation operation, the heat exchange operation, and in the turbo—expander operation. It also shows the approximate magnitude of the losses and possible energy conservation approaches. K. Qperational and Design Problems of Energy Intensive Eaj4pment The analyses of the 10 chemical processes were made under the assumption that the plants were well designed and operated. In actual practice several operational and design problems commonly occur. Table 11 shows problems associated with three large energy consumers — furnaces, compressors, and distillation columns. L. Qperational and Design Problems of Heat Transfer Eguipment In addition to energy intensive operations a common energy wastage problem area is heat transfer equipment. Table 12 lists equipment where problems commonly occur along with some possible measures to overcome the problems. M. Chemical Industry Energy Conservation Study Summary Table 13 shows where the energy conservation approaches suggested in this report can be applied. All processes analyzed appear to have operations where energy losses could be decreased. However, a more detailed analysis of the processes and the approaches would be necessary to determine the economic feasibility of implementing the approaches. 56 ------- Table 10. OXYGEN/NITROGEN ENERGY CONSERVATION APPROACHES Approximate Causes of magnitude of Energy conservation energy losses losses pproaches 1. Re3ected heat in 1060 kJ/kg Design modification hot air from (460 Btu/lb) (waste heat recovery) compressors 2. Overall process a. Non-ideal flow 1 45 kJ/kg volume of liquid (20 Btu/lb) down column b. Temperature 145 kJ/kg differences in (20 Btu/lb) reboiler—condens er and liquid sub—coolers c. Temperature 350 kJ/kg differences be— (150 Btu/lb) tween fluids in main heat ex- change equipment d. Non—isothermal & 350 kJ/kg Maintenance non—isentropic (150 Btu/lb) compression losses Note: Energy Is expressed in terms of energy per unit weight of oxygen produced. All overall process losses are electrical. The fuel value of these losses would be approximately three times as large as the values listed. 57 ------- Table 11. OPERATIONAL AND DESIGN PROBLEMS IN ENERGY INTENSIVE EQUIPMENT Common operational and design problems in high Measures to overcome energy consumption equipment problems 1. Furnace combustion a. Improper air/fuel ratio Provide instrumentation to measure oxygen content in flue gas (automatic controls) b. Leaks in furnace stacks Maintenance 2. Compression a. Leaky compressor bypass Maintenance valves b. Overdesign of motor or Do not over design turbine c. Improper suction pressure Do not over design d. Increasing clearance to Reduce compressor speed to lower output lower output e. Use of less expensive and Realize the value of high less efficient turbines efficiency when selecting and compressors equipment 3. Distillation a. Erratic control of Automatic control columns b. Excessive reflux result— Produce minimum quality i.ng in excessive component material separation c. Improper feed tray Any change in process operation could result In a change in the optimum feed tray d. Non—optimum distillation Consider energy saving scheme possibilities such as multi—feeds, side product draw, or cascade distilla- tion schemes 58 ------- Table 12. OPERATIONAL PROBLEMS WITH HEAT TRANSFER EQUIPMENT Common problems with Measures to overcome heat transfer equipment heat transfer problems 1. Steam traps a. Faulty operation Monitoring required b. Leaking traps Maintenance c. Mis—design Need proper application and sizing 2. Steam tracing a. Leaks Maintenance b. Unnecessarily high Substitute another fluid such steam temperature as Dow SR—i® for steam 3. Heat exchangers a. Fouling Maintenance b. Higher than necessary Design for low temperature temperature separa— differences by Increasing tion between fluid heat transfer surface area streams c. Complete reliance Air cooling requires less on water cooling power than water cooling 59 ------- Table 13. CHEMICAL INDUSTRY ENERGY CONSERVATION STUDY SUMMARY Process Energy intensive operations Energy conservation approaches 1 ON 2 R&D 3 DM 14 I 5 N 6 P1 —r PM r MM T WU Chlorine Electrolysis I I / I Caustic soda Evaporation Overall process I I I 7 Ethylene Furnace combustion / / I rompression — i — — — [ efrigeration verall process I I I Ethylbenzene Distillation / verall process I I Styrene Furnace combustion I I I isti1lation I ‘erall process I I — — — Phenol/acetone Compression I I — istillation I — — urnace combustion — t —r — — verall process I I Cumene Distillation I verall process I Sodium carbonate Kiln calcining ompression alcining (drying) verall process SI / ,‘ I I Carbon black Furnace combustion I I ‘rying ‘verah process — T — — 7 Oxygen/nitrogen Compression I ._ )TSti llat ion OM — Operation modification R&D - Research and development DM - Design modification I — Insulation M - Maintenance P1 — Process integration PM — Process modification MM - Market modification WU — Waste utilization 60 ------- SECTION V BIBLIOGRAPHY Anderson, E. V. Growth Slows in Top 50 Chemicals’ Output. Chemical and Engineering News. 52:10—13, May 6, 1971!. Deutsch, Z. G., C. C. Brumbaug, and F. H. Rockwell. Alkali and Chlorine Industry. In: Kirk—Othmer Encyclopedia of Chemical Technology. 2nd Ed., Standen A. (ed.). New York, John Wiley & Sons, Inc., 1963 i:668—75 . Frank, S. M. Modern Ethylene Technology and Plant Design. In: Ethylene and Its Industrial DerivatIves, Miller, S. A. (ed.). London, Ernest Benn Limited, 1969. p. l03 l1i9. Klenholz, P. J. Outlook for Chlorine—Caustic Production. Chemical Engineering Progress. 70:59—63, March 1971!. Latimer, H. E. Distillation of Air. Chemical Engineering Progress. 63:35—59, February 1967. Ries, H. C. Carbon Black. Stanford Research Institute, Menlo Park, California. Process Economics Program, Report No. 90. May 19713. 3139 p Stokes, C. A. Carbon Black. In: Xirk—Othmer Encyclopedia of’ Chemical Technology 2nd edition, Standen, A. (ed.). New York, John Wiley & Sons, Inc., 1971. Supplementary Volume: 91—108. Takaoka, S. Ethylene. Stanford Research Institute, Menlo Park, California. Process Economics Program, Report No. 29. August 1967. 355 p. Yen, Y. C. Chlorine, Supplement A. Stan ’ord Research Institute, Menlo Park, California. Process Economics Program, Report No. 6lA. May 1971!. 256 p. Yen, Y. C. Phenol, Supplement A. Stanford Research Institute, Menlo Park, California. Process Economics Program, Report No. 22A. September 1972. 232 p. Yen, Y. C. Styrene. Stanford Research Institute, Menlo Park, California. Process Economics Program, Report No. 33. October 1967. 265 p. Yen, Y. C. and T. H. Vanden Bosch. Styrene, Supplement A. Stanford Research Institute, Process Economics Program, Report No. 33A. March 1973. 223 p. 6 ]. ------- SECTION VI GLOSSARY OF ABBREVIATIONS Etu British thermal unit cond condensate CW cooling water kg kilogram kJ kiloJoule kN klloNewton kw kilowatt lb pound m meter psia pounds per square inch absolute MW megawatt stm steam yr year 62 ------- SECTION VII APPENDIX ENERGY CONSERVATION APPROACHES Design modification - This term includes design changes in equipment or process. Insulation — This term implies that a review of the economics of additional insulation Is needed. Maintenance — This term implies that the economics of additional maintenance effort need review. Process integration — This term relates to the best use of steam by using the same steam in more than one process such as to produce electricity and then heat. Research and development - This term relates to the improve- ment of processes by future discoveries. Operation modification — This term includes changes In operating procedures or practices that do not require a design change. Market modification — This term relates to the substitution of a low energy consumption product for a high energy consumption product. Process modification — This term relates to a change in a process due to a change in process feedstock, raw materials, or process route. Waste utilization — This term relates to the use of fuel value of waste process streams or to the recycling of discarded materials. 63 ------- |