ECS_NB_Chunk_1

• 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