Biomass Technology
Electricity
Gasification for Biomass Conversion
Gasification incorporates a Pyrolysis process whereby wood chips enter a chamber heated to a very high temperature. The wood chips are disintegrated as they pass through the chamber as the carbon chain is broken down, resulting in the formation of syngas which provides the source of power for gas turbine engines. GE’s Jenbacher gas engine division is one of the world’s leading manufacturers of syngas-fuelled reciprocating engine.
Electricity is generated from using pyrolysis gasification, a chemical combustion process by which hydrocarbons or organic materials are converted into gas using a large reactor or “cracker”, combining high levels of heat and pressure with low oxygen levels and steam. The biomass (wood chips) disintegrate and produce synthesis gas (or “syngas”) which is then cleansed and used to fire electricity generating gas turbine power plants . The heat generated from the gas turbines can be recovered and used as the source of energy for operating the power plant. Charcoal is a by-product of this process.
Its high levels of efficiency and energy conversion creates a consistent source of electricity production without generating any carbon emissions from the process. Carbon is stored in the waste product (ash), which is less than 2% of the total volume of biomass processed. As a result, the fossil fuel displacement value of the energy produced generates a carbon emission credit (CERs).
Combustion Steam for Biomass Conversion
Biomass combustion is a carbon-free process because the resulting CO2 has been previously captured by the plants being combusted. The amount of carbon dioxide (CO2) emitted during the burning process is typically 90% less than when burning fossil fuel. Wood fuel contains minimal amounts of sulfur and heavy metals. It is not a threat to acid rain pollution, and particulate emissions are controllable.
Combustion steam has evolved as the industry standard for generating low emission electricity. The system works to a fixed format rather than a fermentation or chemical process. There is no need for added external components to break down the wood biomass. The requirements for drying the wood biomass are significantly reduced as the system can absorb a moisture content of up to 20%.
In a conventional biomass-fired combustion steam turbine, wood biomass is burned in a boiler to produce pressurized steam. The steam is expanded in a fully condensed turbine to generate electricity. These combustion methods will produce boiler efficiencies ranging from 65 to 75% with net plant efficiencies from 20 to 25%.
A second combustion design available for biomass is fluidized beds. In these designs wood biomass are injected into the combustion chamber through ports and burned in suspension. Air entering the boiler fluidizes a bed of hot, granular, inert material. The inert material heats the wood biomass quickly to ignition temperature, stores the thermal energy, and provides the appropriate residence time for full combustion.
Biomass Pelleting
Wood pellets can be utilized to produce clean electricity as a feedstock for biomass electric generating facilities. They are also combined with coal in coal electric generating facilities to reduce harmful emissions.
In the Biomass Pelleting process, different types of wood are passed through a hammer mill to create a uniform dough-like mass. The mass is then fed to a high-pressure press which significantly increases the temperature of the wood, while also plastifying the lignin to form a natural adhesive that holds the pellet together as it cools.
The process is advantageous in a number of respects: their low moisture content provides the pellets with very high combustion efficiency; their regular geometry and size enables automatic feeding with a very fine calibration; the pellets’ high density also allows for compact storage and efficient long-distance transport.
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Energy crops or processes for growing energy crops
Biomass conversion technologies for biofuels, electricity and other valuable products