08-11-2012, 12:54 PM
Circulating Fluidized-bed Combustion Technology (CFBC)
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Features
The features of circulating fluidized-bed boilers are described
below.
Compatibility with wide range of fuels
Conventional boilers for power generation can use only fossil
fuels, such as high-grade coal, oil, and gas. The CFBC is also
capable of using low-grade coal, biomass, sludge, waste plastics,
and waste tires as fuel.
NOx and SOx emissions are significantly decreased without
special environmental modifications. In the case of fluidized-bed
boilers, desulfurization is carried out intrafurnace, using mainly
limestone as the fluidizing material. For denitration, PC boilers
operate at combustion temperatures from 1,400oC to 1,500oC,
whereas circulating fluidized-bed boilers operate at lower
temperatures, ranging from 850oC to 900oC, thereby suppressing
thermal NOx emissions as the generation of NOx is dependent
upon the combustion temperature. In addition, the operation of
circulating fluidized-bed boilers involves a two-stage combustion
process: the reducing combustion at the fluidized-bed section,
and the oxidizing combustion at the freeboard section. Next, the
unburned carbon is collected by a high-temperature cyclone
located at the boiler exit to recycle to the boiler, thus increasing
the denitration efficiency
Progress and development results
CFBC technology was introduced from abroad and used in coalfired
boilers. It is used by power producers, iron makers, paper
producers, and in other sectors. Plans exist to distribute CFBC
technology to China under the Green Aid Plan (GAP).
Outstanding CFBC-related issues include the further
investigation of and efforts to reduce the initial costs and to
improve the power generation efficiency for boilers using fuels
such as RDF, industrial waste, and wood-based biomass.