Co-firing power plant
Cofiring refers to the combustion of two different types of materials at the same time. In terms of bioenergy, it refers to the burning of a solid or gas biofuel along with a more traditional fuel. Cofiring power plants usually refer to coal power plants that burn solid biomass, wood, agricultural waste etc., along with coal. It can also refer to plants that use a mix of natural gas and biogas. Because burning biomass is carbon neutral, cofiring reduces the amount of greenhouse gases that are released. Also, cofiring can be used to lower the emission of some pollutants. For example, cofiring biomass with coal results in less sulfur emissions than burning coal by itself. The main advantage of cofiring is that it can be done in existing power plants with little or no modification, allowing for comparatively inexpensive and rapid reductions in greenhouse gases.
Types of Cofiring
There are basically three types of coal cofiring.
- Direct cofiring is simplest, cheapest and most common form. Biomass fuel and coal are burned together in the same furnace, using the same or separate mills and burners depending on the biomass fuel characteristics.
- Indirect cofiring, a biomass gasifier can be used to convert solid biomass into a clean fuel gas form, which can be burned in the same furnace as coal. The advantages of indirect cofiringa are that a wider range of biomass fuels can be used and impurities can be removed from the fuel gas before it is burned. Only a few plants of this kind are in use.
- Completely separate biomass boilers
- IEABCC Database of Biomass Cofiring Initiatives provides a list of biomass cofiring coal power plants around the world, what type of plant they are, and what feedstock they use.
- Biomass-coal Co-combustion: Opportunity for Affordable Renewable Energy (PDF) by Larry Baxter and Jaap Koppejan; IEA Biomass Combustion and Co-firing, published in EuroHeat & Power, January 2004.
- A life-cycle Assesment of Biomass Cofiring in a Coal-fired Power Plant (PDF) by M.K. Mann, P.L. Splath; US National Renewable Energy Labratories, June 2001.
- Repowering Options: Retrofit of Coal-Fired Power Boilers using Fluidized Bed Biomass Gasification (PDF), by Michael Murphy; Energy Products of Idaho, May 2001.
- Biomass Test Burn Report Polk Power Station Unit 1 (PDF); Tampa Electric Company, April 2002.
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