Low Energy, Wet Solvent Extraction

Transcription

1 Low Energy, Wet Solvent Extraction Jason C. Quinn 1 Robert Wills 2, Alex McCurdy 2, Lance Seefeldt 2, Leonard Pease 3 1 Mechanical and Aerospace Engineering, Utah State University 2 Chemistry and Biochemistry, Utah State University 3 Chemical Engineering, University of Utah 1

2 Acknowledgments Algae Biomass Organization SBI Sue Conroe Bioenergy Group (Bugbee, Seefeldt, Wood) BioEnergy Center Funded by DOE: DE-EE

3 Talk Outline Introduction Importance of Extraction Methods of Solvent Selection Microalgae Cultivation & Dewater Experimental Results Energetic Analysis Conclusion 3

4 Extraction/Conversion Methods Feedstock Production Dewatering Drying Extraction and Conversion Termed in situ transesterification, requires cellular material to be completely dry for complete conversion of precursors to FAME. Feedstock Production Dewatering Wet Extraction Conversion Extraction of wet materials with as little as 20% solids would reduce the energy requirement of the overall costs of the biofuels production process 4 Wahlen, B. D., Willis, R. M., and Seefeldt, L. C. (2011), Bioresource Technology 102,

5 Lifecycle Modeling System Boundary ENGR Outputs Results Net Energy Ratio (NER)* * (Energy In)/(Energy Out) Greenhouse Gases (GHG)** **(g CO 2-eq /(MJ BD)) 5 Quinn, J. C., Smith, T.G., Downes, C.M., Quinn, C. Microalgae to biofuels lifecycle assessment-multiple pathway evaluation Algal Research. (in review)

6 Extraction Assumptions Two step process: Homogenization Hexane extraction Wet process at 20% solids 95% efficient Includes solvent recovery loss of 5.3*10-3 g g-oil -1 6

7 g CO2-eq/mmBTU g CO2-eq/MJ LCA Results Microalgae Extraction De-water Growth AD CO2 Credit Extraction represents an import aspect of the process in terms of environmental impact Total Conv. Diesel Soy Bio-Diesel Total Total Quinn, J. C., Smith, T.G., Downes, C.M., Quinn, C. Microalgae to biofuels lifecycle assessment-multiple pathway evaluation Algal Research. (in review)

8 Growth and first dewater Remaining dewater Lipid extraction Anaerobic digester CO2 delivery Anaerobic Digester credit Conversion Transportation & Distribution Feedstock Input NER LCA Results Extraction represents an import aspect of the process in terms of energy consumption NER defined as energy out over energy in 8 Quinn, J. C., Smith, T.G., Downes, C.M., Quinn, C. Microalgae to biofuels lifecycle assessment-multiple pathway evaluation Algal Research. (in review)

9 Talk Outline Introduction Importance of Extraction Methods of Solvent Selection Microalgae Cultivation & Dewater Experimental Results Energetic Analysis Conclusion 9

10 ASPEN Modeling Screening parameters Selectivity coefficient Molecular weight Boiling point Health hazard Cost Modeling work focused on maximizing oil solubility with minimizing water Utilized selectivity coefficient (β) β = K i K C Resulted in 300 solvents # of Solvents narrowed to 14 through explosion risk and cost. 10

11 ASPEN Results Solvent Aspen Rank Health Hazard Cost per L Boiling Point ( C) Dimethyl sulfide 3 2 $ Allyl Chloride 7 2 $ n-propylmercaptan 8 2 $ Methyl-1,3-butadiene 12 1 $ Chlorobutane 17 1 $ Chloroform 22 2 $ Tert-butyl-chloride 27 1 $ Chlorobutane 29 0 $ Pentane 33 0 $ Isopropyl chloride 34 1 $ Diethyl ether 35 2 $ ,1-Dichloroethylene 42 2 $ n-hexane $ Methylene chloride $

12 Talk Outline Introduction Importance of Extraction Methods of Solvent Selection Microalgae Cultivation & Dewater Experimental Results Energetic Analysis Conclusion 12

13 Microalgae Cultivation Culture Conditions Chaetoceros gracilis (UTEX# LB 2658) 1% CO 2 in sparge air at 1 L min -1 (0.833 VVM) Cultured under 300 μmol s -1 m -2 fluorescent lights, 14:10 hour light:dark Harvest Conditions Centrifuge operated at 8000 rpm for 10 min 13

14 Culture & Harvest Conditions 14

15 Talk Outline Introduction Importance of Extraction Methods of Solvent Selection Microalgae Cultivation & Dewater Experimental Results Energetic Analysis Conclusion 15

16 Solvent Screening ASPEN resulted in 300 solvents Reduced to 14 solvents through selection criteria Experimental evaluation of 14 solvents Experimental evaluation of solvents Utilized 20% solid biomass 2:1 solvent to slurry ratio 16

17 Solvent Screening Solvent Aspen Rank Health Hazard Cost per L Boiling Point ( C) Extraction η Dimethyl sulfide 3 2 $ ± 1 Allyl Chloride 7 2 $ ± 1 n-propylmercaptan 8 2 $ ± 1 2-Methyl-1,3-butadiene 12 1 $ ± 2 1-Chlorobutane 17 1 $ ± 1 Chloroform 22 2 $ ± 1 Tert-butyl-chloride 27 1 $ ± 1 2-Chlorobutane 29 0 $ ± 1 Pentane 33 0 $ ± 1 Isopropyl chloride 34 1 $ ± 3 Diethyl ether 35 2 $ ± 1 1,1-Dichloroethylene 42 2 $ ± 2 n-hexane $ ± 1 Methylene chloride $ ± 1 17 Selection based on extraction η, ASPEN rank, and cost

18 Process Optimization Parameters Percent Solids Mixing Rate Mixing Time Amount of Solvent

19 Percent Solids Fixed Parameters: 2:1 solvent to slurry Fixed Reynolds # (8*10 6 ) 2 min mixing time Optimum of 20% solids for all solvents 19

20 Solvent Ratio Fixed Parameters: 20% Solids Fixed Reynolds # (8*10 6 ) 2 min mixing time Results: Choroform-4:1 Methylene Chloride-6:1 Tert-butyl chloride 2:1 20

21 Mixing Rate Fixed Parameters: 20% Solids 2:1 solvent ratio 2 min mixing time Results: Choroform-6*10 6 Methylene Chloride-6*10 6 Tert-butyl chloride-4*

22 Mixing Time Fixed Parameters: 20% Solids 2:1 solvent ratio Fixed Reynolds # (8*10 6 ) Results: Choroform-30 sec Methylene Chloride-30 sec Tert-butyl chloride-2 min 22

23 Talk Outline Introduction Importance of Extraction Methods of Solvent Selection Microalgae Cultivation & Dewater Experimental Results Energetic Analysis Conclusion 23

24 Systems Engineering Process Model Growth Dewater Extraction Conversion Variety of processing Options: Centrifuge Drying Solvent Intended to compare processing options for dewater and extraction step 24

25 Process Assumptions Dewater Dewatering/Drying Centrifugation from 0.1% to 20% solids Clara, Alfa Laval Drying from 20% to 99% solids Heat recover up to 40% solids Extraction Wet Extraction 85% efficiency Cell slurry 20% Solvent to slurry 4:1 Dry Hexane 95% efficiency 25:1 solvent to biomass 25

26 Net Energy Ratio Results Dewater Extraction

27 Net Energy Ratio Process Results extraction dewater dry hexane wet extraction NER<1 is desirable Results are limited to dewater and extraction Dry hexane not feasible for energetic favorability 27

28 Talk Outline Introduction Importance of Extraction Methods of Solvent Selection Microalgae Cultivation & Dewater Experimental Results Energetic Analysis Conclusion 28

29 Conclusions Identified 300 feasible solvents Experimentally evaluated 14 solvents Optimized process for three solvents Demonstrated energetically favorable wet extraction Optimized process as a function of mixing rate, solvent ratio, input solids, and mixing time 29