Process Integration Case Study for the Second Generation Ethanol Production

Transcription

1 Process Integration Case Study for the Second Generation Ethanol Production July 22-25, 2014 Paulo Brito - Granbio Sophia Rouzinou, Vesa Pylkkanen American Process Inc

2 Objectives Increase the ethanol production by integrating 1 st and 2 nd generation plants with energy saving, without any additional biomass

3 Methodology Process Simulation Energy Saves Pinch Analysis Integration of 1 st and 2 nd Generation plants Increase ethanol production Improve process efficiency

4 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

5 Principle of Pinch Analysis

6 Pinch Analysis Example First Generation Sugar Cane Ethanol Plant 3 million tons crush during 180-day harvest

7 Sugarcane Ethanol Plant Sugarcane 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

8 Sugarcane Plant Main Heat Duties Description Heat demand, GJ/h Steam consumption, GJ/h Juice preheating before liming Juice heating after liming Imbibition and wash water heating 38 0 Juice evaporation Wine preheating (to distillation) 79 0 Distillation (stripper column) Distillation (rectifier column) Molecular Sieves heating 7 3 Boiler Feed Water heating Totals

9 Sugarcane Plant Composite Curves Q HMIN =415 GJ/h INTERVAL Temperature T* (deg C) Pinch Temperature=95 o C 50 Q CMIN =304 GJ/h COMPOSITE CURVES Enthalpy Change (GJ/h)

10 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

11 Second Generation Ethanol Plant Cellulosic Ethanol and Acetic Acid from Bagasse Feedstock

12 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.

13 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

14 GP+ Plant Main Heat Duties Description Heat Demand, GJ/h Power demand, MW Biomass presteaming 18 GP+ Digester heating Biomass wash water heating 36 Hydrolysis reactor heating 37 Sugar solution evaporation (MVR) Beer preheating 26 Distillation (beer column) 40 Distillation (rectifier column) 40 Acetic Acid plant (MVR) Totals The sugar solution evaporation and concentration of acetic acid is performed in Mechanical Vapor Compression (MVR) Evaporator

15 GP+ Plant Pinch Results Pinch Temperature Minimum ΔΤ selected 101 o C 10 ο C Minimum heating utility(qhmin) 103 GJ/h

16 Combined 1 st & 2 nd Generation Plants Host sugarcane ethanol plant Sugarcane crush, t/d Anhydrous ethanol production, MMlit/d Acetic Acid production, t/d Bagasse generated from process, ODt/d Steam generated from Bagasse, GJ/h Steam generated from Bagasse, t/h Specific steam generation from bagasse, t/t Host ethanol plant combined with GP+ Steam consumed in the plant, t/h (at least) =306 Steam consumed in the process, t/h (at least)=266 Power consumption, MW The steam consumption is more than available from leftover bagasse solids!

17 Pinch Analysis for the Integrated plant First Generation Sugarcane Ethanol Plant with Green Power+ Bagasse Extraction to Cellulosic Ethanol and Acetic Acid

18 Composite Curves for Integrated Plant Q HMIN =526 GJ/h INTERVAL Temperature T* (deg C) Pinch Temperature=101 o C 50 Q CMIN =493 GJ/h COMPOSITE CURVES Enthalpy Change (GJ/h)

19 Integrated Plant Pinch Results Pinch Temperature Minimum ΔΤ selected 101 o C 10 ο C Minimum heating utility(qhmin) 526 GJ/h

20 Grant Composite Curve 350 GRAND COMPOSITE CURVE T*: Interval temperature (deg C) sumdh-interval

21 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 Anhydrous ethanol production, MMlit/d Acetic Acid production, t/d Bagasse generated from process, ODt/d Steam generated from Bagasse, GJ/h Steam generated from Bagasse, t/h Specific steam generation from bagasse, t/t Steam consumed in the plant, t/h (306) Steam consumed in the process, t/h (266) Steam consumed in the cogeneration plant, t/h Process steam consumption per ton of cane, kg/t Steam to the turbine condenser, t/h Total Power generation, MW Power consumption, MW (37) Net exported power, MW (17)

22 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 %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

23 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

24 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