A Review on Biomass Torrefaction Process and Product Properties for Energy Applications
Torrefaction of biomass can be described as a mild form of pyrolysis at temperatures typically ranging between 200 and 300 C in an inert and reduced environment. Common biomass reactions during torrefaction include devolatilization, depolymerization, and carbonization of hemicellulose, lignin and cellulose. Torrefaction process produces a brown to black solid uniform product and also condensable (water, organics, and lipids) and non condensable gases (CO2, CO, and CH4). Typically during torrefaction, 70% of the mass is retained as a solid product, containing 90% of the initial energy content, and 30% of the lost mass is converted into condensable and non-condensable products. The system's energy efficiency can be improved by reintroducing the material lost during torrefaction as a source of heat. Torrefaction of biomass improves its physical properties like grindability; particle shape, size, and distribution; pelletability; and proximate and ultimate composition like moisture, carbon and hydrogen content, and calorific value. Carbon and calorific value of torrefied biomass increases by 15-25%, and moisture content reduces to <3% (w.b.). Torrefaction reduces grinding energy by about 70%, and the ground torrefied biomass has improved sphericity, particle surface area, and particle size distribution. Pelletization of torrefied biomass at temperatures of 225 C reduces specific energy consumption by two times and increases the capacity of the mill by two times. The loss of the OH group during torrefaction makes the material hydrophobic (loses the ability to attract water molecules) and more stable against chemical oxidation and microbial degradation. These improved properties make torrefied biomass particularly suitable for cofiring in power plants and as an upgraded feedstock for gasification.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- DOE - FE
- DOE Contract Number:
- DE-AC07-05ID14517
- OSTI ID:
- 1030679
- Report Number(s):
- INL/JOU-11-21712; IBWAE7; TRN: US201124%%451
- Journal Information:
- Industrial Biotechnology, Vol. 7, Issue 5; ISSN 0268-3024
- Country of Publication:
- United States
- Language:
- English
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A Review on Biomass Torrefaction Process and Product Properties
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Related Subjects
08 HYDROGEN
BIOMASS
CALORIFIC VALUE
CARBON
CARBONIZATION
CELLULOSE
COCOMBUSTION
DEPOLYMERIZATION
DEVOLATILIZATION
ENERGY CONSUMPTION
ENERGY EFFICIENCY
GASIFICATION
GRINDING
HEMICELLULOSE
HYDROGEN
LIGNIN
LIPIDS
MOISTURE
OXIDATION
PARTICLE SIZE
PHYSICAL PROPERTIES
POWER PLANTS
PYROLYSIS
SURFACE AREA
biomass torrefaction
off-gas composition
physical and chemical properties
torrefaction temperature and residence time