For the case of fluidized bed boiler, the desulfurizationis intrafurnace desulfurization using mainly limestone as the fluidizing material. For thedenitration, ordinary boilers operate at combustion temperatures from 1,400OC to1,500OC, and the circulating fluidized bed boiler operates at lower temperaturesranging from 850OC to 900OC so that the thermal NOx emissions (generated NOxdepending on temperature) are suppressed.
The features of circulating fluidized bed boiler are described below.
1.Wide range of fuel adaptability
Conventional boilers for power generation can use only fossil fuel such as high gradecoal, oil, and gas. The CFBC also uses low grade coal, biomass, sludge, waste plastics,and waste tire as fuel.
Emissions of pollutants such as NOx and SOx are significantly decreased without addingspecial environment measures.
In addition, the operation of circulatingfluidized bed boiler is conducted by two stage combustion: the reducing combustion atthe fluidized bed section; and the oxidizing combustion at the freeboard section. Then,the unburnt carbon is collected by a high temperature cyclone located at exit of theboiler to recycle to the boiler, thus increasing the denitration efficiency.
3.High combustion efficiency
High combustion efficiency is attained by excellent combustion mechanism of circulating fluidization mode.
4.Space saving and high maintenance ability
Space saving is attained because there is no need of separate desulfurization unit,denitration unit, and fuel finely crashing unit. Accordingly, sections of troubleoccurrence become few, and maintenance becomes easy.