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What are the three ways to characterize biomass?
- 1) Biochemical (Protein, oil, starch, sugar, fiber)
- 2) Elemental (C,H,O,N,S,Cl,Ash)
- 3) Proximate (Volatile, fixed ash, fixed carbon)
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What are the constituents of fiber?
- 1) Cellulose
- 2) Hemicellulose
- 3) Lingin
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What are the three types of biomass conversion?
- 1) Thermochemical (Fast ->Combustion, gasification, methanol production.
- 2) Biochemical (Slow -> Digestion, ethanol production)
- 3) Chemical (Biodisel from seed oils, animal fats, and waste oils)
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What are three things that the government has done to encourage ethanol expansion?
- 1) Contingent loan guarantees.
- 2) Public awareness
- 3) Subsidies for production facilities
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What is the chemical mixture of ethanol and what percentage of heating value of gasoline does it have?
C2H6O
HHV = 0.75*HHV(gas)
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What blend with gasoline is required to be termed flex fuel?
85%
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Give the basics of the bio-refinery concept.
Biomass is used both to produce fuels (ethanol - biochemical) and gasification (Thermochemical). These are used for fuels, chemicals and materials, while the residue and waste material is used to supply combined heat and power requirements.
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What are the 5 steps in ethanol production?
- 1) Preprocessing
- milling, grinding, liquefying
- Get cellulose ready
- 2) Hydrolysis
- Enzymes are used to break cellulose chains into glucose
- 3) Fermentation
- C6H12O2 + yeast --> 2C2H6O + 2CO2
- 4) Distillation
- Remove impurities
- 5) Dehydration
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What do lignocellulose require before being converted to ethanol?
Ligno cellulose does has lignin which must be preprocessed. Steam explosions are used to make celloulose available for hydrolysis.
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What are the approximate heating values (MJ/kg) of some various fuels?
- Gasoline (44)
- Heating oil(45.5)
- Diesel (42)
- Ethanol (38)
- Bio-disel (37)
- Bio-oil (18-20)
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How is biodesil formed?
Oil + (A)CH3OH ---> (B)C17H33CO2CH3 + (C) C3H(OH)3
Oil + Methanol ---> FAME (biodisel) + Glycerol
**FAME stands for Fatty Acid Methyl esters
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What are some benefits of Bio-Diesel?
- 1) Burns more completely due to high O2 content.
- 2) Offers more lubrication.
- 3) Higher flash point
- 4) Reduced CO, Sulfate, soot.
**Has a smaller heating value but above bio-oils.
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Give some characteristics of torrefaction process.
- 1) Slow roasting between 200 - 300C.
- 2) Anaerobic environment.
- 3) Heating rate < 50C/min
- 4) Residence time ~ 30min at T>200C
- 5) Ambient pressure
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Describe the torrefaction process steps
- 1) 125C - Majority of moisture evaporates
- 2) 175C - Devolitisation of hemicellulose begins
- Wood is unbound
- 3) 240C - Hemicellulose, VOCs and extractants are burned off
- Wood becomes friable (40 on Hardgrove)
- 4) 470C - Final torrefaction occurs, wood becomes hydrophobic.
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Give some benefits of torrefaction.
- Lower transport cost
- Inert (no mold)
- Less moisture absorbing
- Brittle (80-90% easy to pulverize)
- Higher energy density
- More uniform than regular stock
- low moisture content (hydrophobic)
- does not get very wet when exposed to moisture (hydrophobic)
- No smoking during combustion
- Stable flame during combustion
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Give 6 different torrification technologies.
- 1) Rotary drying drum (Rotary kiln)
- 2) Screw convener
- 3) Multiple hearth furnace (In use and scalable)
- 4) Torbed flash (Fast 90s-5min, risk or carbonization and tar formation. Relatively new technology)
- 5) Compact moving bed
- 6) Belt dryer (Simple and proven, consistent)
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Give 7 difficulties in operating a coal boiler on biomass.
- 1) Changed emissions
- 2) Increased corrosion and fouling
- 3) Change in performance
- 4) Change in furnace heat absorption
- 5) Storage
- 6) Fuel pulverization is more difficult
- 7) More moisture
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What index is used to measure the grind ability of a fuel?
Hardgrove index
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Give 3 types of co-firing.
- 1) Direct - Simple, cheap
- 2) Indirect - Totally independent of main boiler
- 3) Parallel - Feed separate but burned together
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Describe lingan power plant
- 1) Coal is pulverized and sent to the boiler
- 2) Coal is fired generating steam. Particulates are removed and SO2 scrubber is used before exhaust goes to stack.
- 3) Steam drives a turbine generator then goes through a condensation pump, a feed pump and back to the boiler.
- 4) Electricity is generated. Ocean water is used to cool turbine when required.
**25% of NSP generating capacity and provides 40% of electricity generation.
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Give the 5 carbon abatement options outlined in class
- 1) Energy conservation (Manage the demand)
- 2) Efficient generation technology (e.g. Supercritical or IGCC)
- 3) Carbon free energy use (Electrical where energy comes from non carbon source)
- 4) Biomass combustion (or co-firing)
- 5) Carbon capture and sequestration
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Give the 3 types of carbon capture in increasing maturity.
- 1) Amine Scrubbing (NH4 or other amine solvent captures CO2)
- 2) Oxygen combustion
- 3) Chemical looping combustion
- 2 and 3 are in-situ techniques
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Give the 3 types of carbon sequestration (storage)
- 1) Ocean - Depth >1Km, Occurs naturally, very new
- 2) Coal mines - Pump in CO2, Methane comes out and can be used to generate energy
- 3) Oil and Gas Reserves - (Enhance oil recovery) CO2 disolves in oil and reduces its viscosity (increasing recovery by (30-60%). Reservoir acts as a storage site for future CO2. Mature Technology.
- 4) Geological Reservoir
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Give some disadvantages to CCS
- 1) 10 times larger plant required for 0.75 emissions
- 2) 1.5 c/kwh increase in generation cost
- 3) 10 to 15% reduction in efficiency
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