Process Modeling and Life Cycle Assessment of Biomass Conversion

Transcription

1 Process Modeling and Life Cycle Assessment of Biomass Conversion Dr. Wen Zhou Department of Chemical Engineering Michigan Tech October 12, 2017

2 Conversion Pathways

3 Hemicellulose-Cellulosic Substrate Comparison with experimental data from Qing and Wyman (2011)

4 Optimal Enzyme Mixture Composition 72 Hr Hydrolysis of Cellulose for Max Glucose Yield Enzyme (mg/g glucan) EG1 CBH1 CBH2 EX BG BX Glucose Yield % % %

5 Thermochemical Conversions Torrefaction C mins. O 2 -free Primarily solid bio-coal Pyrolysis feedstock wt% yield Fast Pyrolysis C 1 sec. O 2 -free Primarily viscous bio-oil Hydrocarbon biofuels Feedstock wt% yield

6 Process Description Simplified schematic diagram for a two step pyrolysis system Combustion of gas to offset natural gas usage Conveyor feed hopper Dryer Non condensable gases 1 Torrefaction at temperatures of 290 o C, 310 o C and 330 o C Condensed liquid from torrefaction added to liquid from pyrolysis Conveyor Dryer Woody biomass chips, 25mm 8% MC Torrefaction unit Torrefier Hydrogen Non condensable gases 2 Bio-oil condenser Torrefier feed hopper Conveyor Cyclone Biocoal chips, 25mm 1000 DMT/day Hammer mill Bio-Oil Credits for char sales Biochar Fast Pyrolysis Unit Biocoal chips, 2mm Fast Pyrolysis unit Conveyor Pyrolysis unit feed hopper Hydrogen recycle 3 phase separator Light Gases PSA 1 Steam Stabilizer Upgrade Hydrotreater WWT Hydrocarbon Fuel Natural Gas Off gas 1 Pre-reformer Reformer PSA 2 Off gas 2 combusted t o provide process heat Water-Gas Shift Reactor Off gas 2 Hydrogen Production

7 Cost of production of hydrocarbon fuel (with heat integration) $ $ $6.00 $/gal $5.50 $5.00 $4.50 $ $3.50 Sc1 Sc1 One Step Sc1 Sc 1 Sc 3 Sc 3 Sc1 Sc 1 Sc 3 Sc 3 Sc1 Sc 1 290⁰C 310⁰C 330⁰C Two Step Conversion pathway Sc 3 Sc 3 Further reduction in cost of production observed with heat integration

8 Life Cycle Assessment: Carbon Footprint Cradle to grave system boundary Inputs Biomass supply logistics Outputs Energy Wood waste collection Chipping operation Truck Transport Loading operations Rail Transport Moisture effluents Biomass conversion Airborne emissions Biofuel Hydrogen Upgrade Fast Pyrolysis Size reduction (grinding) Torrefaction Drying of biomass Mass flow Energy flow Hydrogen production Char Off gas Combustion Vapors Functional unit: 1 MJ of biofuel Co-Product Allocation: System Expansion Electricity from US grid

9 LCA: GHG Emission with heat integration

10 Anaerobic Digestion of Food and Industrial Wastes Bio-chemical process system Solid Wastes & Inactive Microbes Physico-chemical process system Disintegration Hydrolysis Carbohydrates Monosaccharides Acidogenesis & Acetogenesis Methanogenesis Proteins Amino Acids Acetates & H 2 & CO 2 Fats Long Chain Fatty Acids Soluble & Solid Inerts Dead Microbes Extracellular Processes outside the microbes catalyzed by extracellular enzymes Intracellular Processes inside the microbes catalyzed by intracellular enzymes Not directly mediated by microbes Major processes Liquid-gas processes (i.e. liquid-gas transfer) Liquid-liquid processes (i.e. ion association/dissociation) Liquid-solid processes (i.e. precipitation/solubilization) Simultaneously occur with biochemical processes Affect other processes of anaerobic digestion Biogas (CH 4 & CO 2 )

11 Conversion Pathways