Circulating fluidized bed

The circulating fluidized bed (CFB) is a developing technology for coal combustion to achieve lower emission of pollutants. By using this technology, up to 95% of pollutants can be absorbed before being emitted to the atmosphere.

Circulating fluidized bed is a relatively new technology with the ability to achieve lower emission of pollutants. Extensive research has been conducted on this technology for the past 10 years because pollution in the world is getting more serious by the day and clean practice will be very crucial for the sustainability of the earth. The importance of this technology has grown recently because of tightened environmental regulations for pollutant emission.

The Mercury and Air Toxic Standards (MATS) enacted in December 2011 by the EPA have forced all the countries in Europe and America to strictly adhere to this policy. This means that emissions such as metals, acid gases, organic compound, flue gas acids and other pollutants from power plants or industrial facilities have to meet the requirements set by EPA and upgrades have to be done for facilities that do not meet the standards. As a result, the demand for circulating fluidized bed technology will be predicted to sky rocket.

The industrial application of fluidized bed started long back. In 1923, Winkler's coal gasifier represented the first significant large-scale use of fluidized bed (Kunii and Levenspiel, 1991). Nowadays, the world's largest CFB unit is operating since 2009 at Lagisza, Poland, 460 MW supercritical CFB, Foster and Wheeler. Even though the cheap liquid and gaseous fuels have decelerated the coal and solid fuels R&D.; many sectors increasingly use CFB viz. electricity generation and industrial sectors, because of the CFB's advantages. The 1970th cries reactivated the interest to the solid fuel and coal again. Moreover, the increasing concern of GHGs, cheap cost of coal and its abundant sources motivate again the researches of CFB (IEA-CIAB, 2013). The CCS was considered as an important technology to mitigate GHGs. To apply CCS, novel techniques viz. pre-combustion, post-combustion, and oxy-combustion are raised. Subsequently, the R&D are undertaken for understanding the effects of new operation conditions like using gaseous mixture comparing with conventional units. This chapter is dedicated toward the detailed review of literature in the fields of CFB's hydrodynamic behaviour, oxy-fuel combustion and generations of oxy-fuel combustion. It also discusses the literature on lower or zero carbon energy sources (biofuel). The special focus on the biofuel usage for CFB is to service lower or zero carbon energy technology.

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