Optimization and improvement of bio-ethanol production processes

Transcription

1 Optimization and improvement of bio-ethanol production processes Dr. Kang Qian Prof. Jan Baeyens Date: 17/03/2017

2 Contents 1. Characteristics and worldwide potential 2. The uses of bio-ethanol 3. Bio-ethanol production 4. Traditional process routes 5. Process improvements 6. General conclusions

3 1.1 Ethanol and its characteristics Ethanol (C 2 H 5 OH) Bio-ethanol Primary Properties of Ethanol Boiling Point K Flash Point K Auto-ignition temperature 698 K Heat of combustion 26,800 kj/kg Fermentation C C 6H12O6 CH 3CH 2OH 2 2 CO 12H 22O11 H 2O CH 3CH 2OH 4 4 CO 2 Flash points of ethanol-water mixtures Industrial Production C 2 H for glucose and fructose 2 4 H 2 0 for sucrose CH 3CH 2OH H PO 3 4

4 1.2 The recognized potential of bio-ethanol Literature ( ) concerning bio-ethanol SCOPUS with keywords ( Bio-ethanol General; Fuel-Application; Environment and Economics; Simulation and Separation; Membrane Technology; Very High Gravity (VHG))

5 1.3 The different generations of bio-ethanol production Food-based Vs. Corn, Wheat, Sugarcane (mostly Brazil, USA, China) Non-food Cassava, Sweet sorghum (mostly China) Biomass Algae Fair ethanol yield: 3 to 10 ton raw material/ ton bioethanol Very low ethanol yield (although improving), through: (1) aggressive pretreatment; (2) selected bacterial/yeast strains; (3) enzymatic hydrolysis. 10 ton raw material/ ton bio-ethanol

6 Contents 1. Characteristics and worldwide potential 2. The uses of bio-ethanol 3. Bio-ethanol production 4. Traditional process routes 5. Process improvements 6. General conclusions

7 Engine fuel and fuel additive Common ethanol-petrol mixtures Code Composition Countries Comments E5 E10 E15 E25 E85 E100 max. 5% anhydrous ethanol, min. 95% petrol max. 10% anhydrous ethanol, min. 90% petrol max. 15% anhydrous ethanol, min. 85% petrol max. 25% anhydrous ethanol, min. 75% petrol max. 85% anhydrous ethanol, min. 15% petrol hydrous ethanol (~ 5.3 wt% water) Western Europe, India USA, Europe, China, India, South Africa USA, cars >2000, South Africa Brazil USA, Europe Brazil Fuel and feedstock in chemicals' synthesis Blends for regular cars Flex-Fuel vehicles Conversion pathways of ethanol to different organic chemicals

8 Contents 1. Characteristics and worldwide potential 2. The uses of bio-ethanol 3. Bio-ethanol production 4. Traditional process routes 5. Process improvements 6. General conclusions

9 "Generations" of bio-ethanol production Sugar-based mostly Hexoses Cellulosic/algal-based Hexoses Pentoses Pretreatment needed Saccharification+ Fermentation

10 Contents 1. Characteristics and worldwide potential 2. The uses of bio-ethanol 3. Bio-ethanol production 4. Traditional process routes 5. Process improvements 6. General conclusions

11 4.1 Intergrated saccharification/fermentation processes versus two-step processes

12 Mass balance of the first generation Cofco process of cassava-based bio-ethanol

13 Contents 1. Characteristics and worldwide potential 2. The uses of bio-ethanol 3. Bio-ethanol production 4. Traditional process routes 5. Process improvements 6. General conclusions

14 5.1 Energy intergration within the current production processes After Before Energy Stream Mass Stream Production Steam Steam Before: 2.5 kg steam/kg ethanol After: ~ 1.8 kg steam/kg ethanol

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16 5.2 The use of VHG fermentation In traditional starch fermentation, Saccharomyces Cerevisiae is used as yeast and the ethanol concentrations ~12 vol% are acceptable to avoid inhibition; The use of specific yeasts or bacteria, such as Zymomonas mobilis, with higher inhibition levels, opened the way to very high concentration fermentation, referred to as very high gravity (VHG) fermentation. Heat duty of the distillation when using VHG fermentation VHG conditions 15 vol% 19 vol% C1501 C1502 C C C1501 C1502 C C Reboiler duty (kw) Condenser duty (kw) After: ~ 0.94 kg steam/kg ethanol

17 5.3 The development of hybrid (pervaporation) systems Drying of Ethanol Current molecular sieve dehydration of azeotropic ethanol-h 2 O mixtures

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19 Mass and energy balance of the molecular sieve process Mass balance Feed water concentration (wt%) 5.6 Product water concentration(wt%) 0.8 Total feed flow rate (kg/h) 27,160 Feed ethanol flow rate (kg/h) 25,638 Product mass flow rate (kg/h) 25,845 Water absorption (kg/h) 1,314 Energy balance Evaporator heat Product heat (kj/kg) 868 Heat content of steam (kj/kg) 2,061 Absorption column Steam consumption (kj/h) 23,563,127 Absorption column Steam consumption (kg/h) 11,434 Regeneration column Steam consumption (kj/h) 1,452,207 Regeneration column Steam consumption (kg/h) 705 Total steam (kg/h) 12,139 (kg steam/kg ethanol) 0.48

20 Novel approach: Schematic diagram of the process and lab Test Cell Unit Membrane Area : ~ 117 m 2

21 5.3.2 Hybrid pervaporation operation of the bio-ethanol fermentation FFIRST 0.75FFEED FRETENTATE kg / h COLUMN F RETENTATE kg / h F PREMEATE 7920 kg / h Membrane Area : ~ 1095 m 2 Summary results of the Cofco distillation process System Steam Consumption (kg steam/kg ethanol) Basic 2.50 Integrating reboilers and condensers 1.18 VHG (15%) 1.17 VHG (19%) 0.94 Pervaporation 1.13

22 5.3.3 Cross-flow microfiltration of bio-ethanol fermentation broth Bio-ethanol fermentation broth consists of mainly water and ethanol, together with solid residues of un-reacted feedstock and additives (mostly yeast). The current mechanical separation (belt filter or centrifuge) can only remove + 10 µm particles representing about 90% of the total solids content. The sintered metal fiber (SFM) fleeces are highly efficient for microfiltration and the removal of suspended solids largely exceeds 99%.

23 > 99% retention of > 1 μm particles flux: 5 to 10 m 3 /m 2 h at TMP of 1.5 bar protection of heat exchangers, pumps no need of 1 st separation column very small MF unit needed: 30 m 2 Size analysis of broth solids

24 5.4 Intergrated novel production process Fig.5 Schematics of the processes for bio-ethanol production (a) As currently applied; (b) With potential membrane applications (DDGS: Distillers Dried Grains with Solubles; 1+2+3: cellulosic materials; 2+3: starch or carbohydrate rich materials)

25 Contents 1. Characteristics and worldwide potential 2. The uses of bio-ethanol 3. Bio-ethanol production 4. Traditional process routes 5. Process improvements 6. General conclusions

26 General Conclusions Implementing the energy-pinch approach enables to integrate recycle condenser and reboiler heat duties; Steam duty: 2.50 to 1.8 kg steam/kg bio-ethanol VHG (19%) reduces the steam consumption to 0.94 kg steam/kg bioethanol, whilst operation in a hybrid mode (pervaporation of 33 % of the fermenter broth) achieves similar savings; Membrane dehydration can save 0.5 kg steam/kg bio-ethanol, in replacing molecular sieves Microfiltration can reduce fouling of heat exchangers, pumps,. An economic analysis reveals that the factory-gate price of cassavabased bio-ethanol could be reduced from ~820 /ton to ~730 /ton. Sugarcane- and corn-based bio-ethanol remain about 30 to 50 % more expensive, due to the higher raw material cost.

27 Thank you for your attention!