Process Integration Case Study for the Second Generation Ethanol Production July 22-25, 2014 Paulo Brito - Granbio Sophia Rouzinou, Vesa Pylkkanen American Process Inc
Objectives Increase the ethanol production by integrating 1 st and 2 nd generation plants with energy saving, without any additional biomass
Methodology Process Simulation Energy Saves Pinch Analysis Integration of 1 st and 2 nd Generation plants Increase ethanol production Improve process efficiency
Applications of Process Integration Pinch Analysis is integral part of Process Integration, when Integrating heat needs with waste heat Generating steam/heat appropriately, Reusing / recovering raw materials, Integrating many processes / Co-production / Technology synergies, Upgrading byproducts
Principle of Pinch Analysis
Pinch Analysis Example First Generation Sugar Cane Ethanol Plant 3 million tons crush during 180-day harvest
Sugarcane Ethanol Plant Sugarcane 16666 t/d Crushing and Milling Juice Treatment Juice 14.4% solids 22 % solids Evaporation Fermentation Distillation Dehydration 1.41 MMlit/d Anhydrous Ethanol Bagasse 2204 ODt/d Cogeneration Plant 219 t/h 40 t/h 20 MW 75 MW Steam to the Process Steam to the Cogen Plant Power to the Process Exported Power
Sugarcane Plant Main Heat Duties Description Heat demand, GJ/h Steam consumption, GJ/h Juice preheating before liming 87 24 Juice heating after liming 89 76 Imbibition and wash water heating 38 0 Juice evaporation 141 141 Wine preheating (to distillation) 79 0 Distillation (stripper column) 161 161 Distillation (rectifier column) 79 79 Molecular Sieves heating 7 3 Boiler Feed Water heating 41 76 Totals 723 560
Sugarcane Plant Composite Curves 350 300 Q HMIN =415 GJ/h INTERVAL Temperature T* (deg C) 250 200 150 100 Pinch Temperature=95 o C 50 Q CMIN =304 GJ/h COMPOSITE CURVES 0 0 200 400 600 800 1000 1200 Enthalpy Change (GJ/h)
Sugarcane Plant Pinch Results Pinch Temperature Minimum ΔΤ selected 95 o C 10 ο C Minimum heating utility(qhmin) 415 GJ/h Actual process steam consumption 554 GJ/h Maximum scope for heat recovery 139 GJ/h
Second Generation Ethanol Plant Cellulosic Ethanol and Acetic Acid from Bagasse Feedstock
Second Generation Ethanol Plant American Process has developed hemicellulose extraction process termed Green Power + Liquid Hot Water digestion of Bagasse Hemicelluloses are acid hydrolyzed to Pentose sugars and Acetic Acid Acetic Acid is separated by evaporation & purified The sugars are fermented to beer The beer is distilled to produce ethanol Unreacted solids material are concentrated and burned in the boiler.
Green Power+ 2 nd Gen. Plant Bagasse from sugarcane plant Digester Washing Residues Pressing Biomass To Boiler Extract Acid Hydrolysis Reactor Evaporation & HAc Removal Hydrolyza te Fermentation & Distillation Ethanol Acetic Acid Purification
GP+ Plant Main Heat Duties Description Heat Demand, GJ/h Power demand, MW Biomass presteaming 18 GP+ Digester heating 167 7.4 Biomass wash water heating 36 Hydrolysis reactor heating 37 Sugar solution evaporation (MVR) 33 5.8 Beer preheating 26 Distillation (beer column) 40 Distillation (rectifier column) 40 Acetic Acid plant (MVR) 38 3.6 Totals 436 16.8 The sugar solution evaporation and concentration of acetic acid is performed in Mechanical Vapor Compression (MVR) Evaporator
GP+ Plant Pinch Results Pinch Temperature Minimum ΔΤ selected 101 o C 10 ο C Minimum heating utility(qhmin) 103 GJ/h
Combined 1 st & 2 nd Generation Plants Host sugarcane ethanol plant Sugarcane crush, t/d 16666 16666 Anhydrous ethanol production, MMlit/d 1.41 1.65 Acetic Acid production, t/d - 123 Bagasse generated from process, ODt/d 2203 2203 Steam generated from Bagasse, GJ/h 1183 791 Steam generated from Bagasse, t/h 414 292 Specific steam generation from bagasse, t/t 2.16 2.61 Host ethanol plant combined with GP+ Steam consumed in the plant, t/h 259 259+47 (at least) =306 Steam consumed in the process, t/h 219 219+47 (at least)=266 Power consumption, MW 20 37 The steam consumption is more than available from leftover bagasse solids!
Pinch Analysis for the Integrated plant First Generation Sugarcane Ethanol Plant with Green Power+ Bagasse Extraction to Cellulosic Ethanol and Acetic Acid
Composite Curves for Integrated Plant 350 300 Q HMIN =526 GJ/h INTERVAL Temperature T* (deg C) 250 200 150 100 Pinch Temperature=101 o C 50 Q CMIN =493 GJ/h COMPOSITE CURVES 0 0 200 400 600 800 1000 1200 1400 1600 1800 Enthalpy Change (GJ/h)
Integrated Plant Pinch Results Pinch Temperature Minimum ΔΤ selected 101 o C 10 ο C Minimum heating utility(qhmin) 526 GJ/h
Grant Composite Curve 350 GRAND COMPOSITE CURVE 300 250 T*: Interval temperature (deg C) 200 150 100 50 0 0 100 200 300 400 500 600 sumdh-interval
Comparison of Performance before and after Integration of 2 nd Gen. Ethanol Host sugarcane ethanol plant Integrated plants with 2 nd generation ethanol Sugarcane crush, t/d 16656 16656 Anhydrous ethanol production, MMlit/d 1.41 1.65 Acetic Acid production, t/d - 123 Bagasse generated from process, ODt/d 2203 2203 Steam generated from Bagasse, GJ/h 1183 791 Steam generated from Bagasse, t/h 414 292 Specific steam generation from bagasse, t/t 2.16 2.61 Steam consumed in the plant, t/h 259 244 (306) Steam consumed in the process, t/h 219 233 (266) Steam consumed in the cogeneration plant, t/h 40 11 Process steam consumption per ton of cane, kg/t 316 336 Steam to the turbine condenser, t/h 158 51 Total Power generation, MW 95 54 Power consumption, MW 20 29 (37) Net exported power, MW 75 25 (17)
Simulation Model in apimax IMBIBITION WATER 181 t/hr 78 C 435 t/hr 120 C LP STEAM 22.0% WINE 391 t/hr EtOH 11.87 %w MP STEAM MOLE SIEVES SUGARCANE 2205 BDt/day 694 t/hr 13.2 % 21 C 29.8% KNIVES SHEDDERS ROLLER MILLS 37 C 681 t/hr 16.2% JUICE EVAPORATORS FERMENTORS 54 t/hr 100.0% ETHANOL VAPOR 191 t/hr 2204 BDt/day BAGASSE BEER 127 t/hr EtOH 6.13 %w WATER HP STEAM SOLIDS 112 t/hr 82 C 54.9% 1469 BDt/day GP+ DIGESTER 292 t/hr 520 C 91.0 bar(a) WASHERS EXTRACT HP STEAM Acid Hydrolysis Reactor LP STEAM POST HYDROLYSIS EVAPORATORS HEMI SUGAR FERMENTORS VAPOR 10.5% BOILER 53.9 MW 0.05 bar(a) 51 t/hr TURBINE 52 t/hr 3 t/hr 186 t/hr HP STEAM MP STEAM LP STEAM 269 t/hr MEMBRANES 143 t/hr 5.9% HAc EVAPORATORS CONCENTRATOR FILTER 5 t/hr 100.0% ACETIC ACID CONDENSER
Results Summary Pinch Analysis was applied to stand-alone sugarcane ethanol mill to find 25% steam energy savings The integration resulted in 17% increase in ethanol and by-product acetic acid production without any additional biomass
Conclusions Combination of two optimized plants can be improved by process integration Reducing steam consumption allows leveraging of existing boiler and turbines Common distillation system can be used for 17% incremental ethanol production Additional cellulosic ethanol can be made from bagasse without bringing additional biomass to the site Techno-economic evaluation is necessary to calculate trade-off with power sales and the investment payback