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)
What are the constituents of fiber?
1) Cellulose 2) Hemicellulose 3) Lingin
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)
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
What is the chemical mixture of ethanol and what percentage of heating value of gasoline does it have?
HHV = 0.75*HHV(gas)
What blend with gasoline is required to be termed flex fuel?
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.
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
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.
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)
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
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.
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
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.
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
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)
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
What index is used to measure the grind ability of a fuel?
Give 3 types of co-firing.
1) Direct - Simple, cheap 2) Indirect - Totally independent of main boiler 3) Parallel - Feed separate but burned together
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.
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
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
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
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