ECS_NB1

• 1) Drying (>150C)
• 2) Pyrolysis (Heating in absence of oxygen, 150-700C)
• Products are:
• Liquid Tar ---> BioOil
• Solid Char ---> Gasification (800 -1100C)
• Gas Tar
• 3) Combustion (700 - 1500C)

• Combustion releases heat packed in chemical bonds while gasification
• packs more energy into the chemical bonds.

• 1) Water gas Rxn C + H20 -> H2 +CO
• 2) Boudard Rxn CO2 + C -> 2CO
• 3) Shift Rxn CO + H20 -> CO2
• 4) Methanation C + H2 -> CH4

5) Partial Combustion C + 0.502 -> C02

0.2 -> 0.3

• <0.2 - Incomplete gasification, excess char, low HV
• >0.4 - Too much combustion Excess CO2, H20, low HV

• 1) Chemical production (CO2, Methanol, Hydrogen, Amonia)
• 2) Syngas production (H2 and CO)
• 3) Electricity/heat production (IGCC)
• 4) Transport fuel production (Kerosene, Bio-disel)

• 1) Allows for use of high efficiency combined cycle over typical Rankine Cycle.
• 2) Generates less CO2, NOx, and particulates.
• 3) For high sulfer coal the elemental sulfer can be retained with limestone during gasification.
• 4) Gasification/compression may be cheaper than boiler, condenser, engine required for small scale Rankine Cycle
• 5) Requires less water.
• 6) Allows for cleaning of dirty fuels for applications like glass manufacturing.

**If heat is the only product desired combustion may be preferable, especially at small scale.

• As T increases
• CO2 Conc (up)
• CO Conc (down)

**s shaped curve

• As P increases
• CO2 Conc (up)
• CO Conc (down)

**exponential curve

• As ER increases CCE increase until approximately 0.27.
• It then decreases again.

• 1) Updraft (Medium in bottom, Gas flows out top)
• 2) Downdraft (Medium in top, Gas flowes out bottom
• Up and down are both considered moving bed.
• 3) Fluidized Bed (Best for Biomass)
• 4) Entrained (High Capacity)

• 1) Entrained (>100 MW)
• 2) Fluidized Bed (10 - 100 MW)
• 3) Updraft (<20 MW)
• 4) Downdraft (<5 MW)

• 1) Entrained (1000 - 1500 C)
• 2) Fluidized Bed (800 - 900 C)
• 3) Updraft (700 - 900)
• 4) Downdraft (700 - 1200)

• 1) Updraft (High)
• 2) Fluidized Bed (Medium)
• 3) Downdraft (Low)
• 4) Entrained (Absent)

• 1) Choose type
• 2) Design choices (medium and temperature)
• 3) Energy Balance (How much hydrocarbon is used for combustion?)
• 4) Process design (mass balance, equilibrium calculation)
• 5) Gasifier Sizing
• 6) Optimization (Kinetic modeling)

• 1) Air - Cheap, convenient, 4-7 MJ/nm3
• 2) Steam - Increased hydrogen, 10 - 18MJ/nm3
• 3) Oxygen - Expensive (Requires O2 Plant), 12 - 28MJ/nm3

• 1) Composition of gas.
• 2) Gasification efficiency.

**Hydrogen yield increase with temperature.

• 1) Tar effects are ignored.
• 2) Assume infinite speed.
• 3) Neglect heat and mass transfer losses.

• 1) Indicated by cold and hot gas efficiency.
• 2) Amount of unconverted tar and carbon concentration.
• 3) Composition and heating value of the product.

• 1) Hydrodynamic model of the reactor
• 2) Reaction kinetic models
• 3) Heat and mass transfer models

• 1) Hydrodynamic model of the reactor
• 2) Reaction kinetic models
• 3) Heat and mass transfer models

Prevents back mixing

• 1) Biochemical (Protein, oil, starch, sugar, fiber)
• 2) Elemental (C,H,O,N,S,Cl,Ash)
• 3) Proximate (Volatile, fixed ash, fixed carbon)

• 1) Cellulose
• 2) Hemicellulose
• 3) Lingin

• 1) Thermochemical (Fast ->Combustion, gasification, methanol production.
• 2) Biochemical (Slow -> Digestion, ethanol production)
• 3) Chemical (Biodisel from seed oils, animal fats, and waste oils)

• 1) Contingent loan guarantees.
• 2) Public awareness
• 3) Subsidies for production facilities

C2H6O

HHV = 0.75*HHV(gas)

85%

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.

• 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

Ligno cellulose does has lignin which must be preprocessed. Steam explosions are used to make celloulose available for hydrolysis.

• Gasoline (44)
• Heating oil(45.5)
• Diesel (42)
• Ethanol (38)
• Bio-disel (37)
• Bio-oil (18-20)

Oil + (A)CH3OH ---> (B)C17H33CO2CH3 + (C) C3H(OH)3

Oil + Methanol ---> FAME (biodisel) + Glycerol

**FAME stands for Fatty Acid Methyl esters

• 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.

• 1) Slow roasting between 200 - 300C.
• 2) Anaerobic environment.
• 3) Heating rate < 50C/min
• 4) Residence time ~ 30min at T>200C
• 5) Ambient pressure

• 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.

• 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

• 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)

• 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

Hardgrove index

• 1) Direct - Simple, cheap
• 2) Indirect - Totally independent of main boiler
• 3) Parallel - Feed separate but burned together

• 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.

• 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

• 1) Amine Scrubbing (NH4 or other amine solvent captures CO2)
• 2) Oxygen combustion
• 3) Chemical looping combustion
• 2 and 3 are in-situ techniques

• 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

• 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