Development of Pollution Control Technology During Coal Combustion - Simultaneous Multi-Pollutants Removal in Flue Gas by Ozone - page 3

1.2.1.1 Circulating Fluidized-Bed Technology
Fluidized-bed combustion (FBC) technology first appeared in the 1960s [8] ,
followed by circulating FBC. Limestone or dolomite is mainly used as
desulfurizer for this technology. During the coal combustion process, the
limestone or dolomite is decomposed into CaO, which reacts with O 2 and SO 2 in
the oxidizing atmosphere to form CaSO 4 . Circulating Fluidized-bed technology is
widely used in the world, because of the characteristics of fuel flexibility, high
combustion efficiency, and low pollution emissions.
1.2.1.2 Wet Flue-Gas Desulfurization Technology
Wet flue-gas desulfurization (WFGD) technology, which is based on using
limestone or lime as a reagent, is a wet scrubbing process and has been the most
frequently selected flue-gas desulfurization (FGD) technology for SO 2 reduction
from coal-fired utility boilers [9] . The WFGD flue gas treatment system is typically
located after removal of particulate matter from flue gas either by a baghouse or
an electrostatic precipitator (ESP). The cleaned flue gas is then discharged to the
stack. SO 2 is removed by scrubbing flue gas with either a limestone or lime
(reagent) slurry. Nowadays, WFGD, which is considered to be a commercially
mature technology, has been applied widely in coal-fired power plants globally.
In most WFGD systems, the quantity of liquid sprayed relative to flue gas is
related to the SO 2 collection efficiency needed and is referred to as liquid-to-gas
(L/G) ratio. Higher L/G ratios improve SO 2 removal by exposing the gas to more
absorbing liquid, implying that higher L/G ratios also consume more power.
Conclusively, the WFGD technology has such features as highly efficient
desulfurization (achieving more than 95% SO 2 cleanup) and high operation cost.
1.2.1.3 Spray Dry Flue-Gas Desulfurization Technology
Alkaline solution or hydrated lime emulsion is usually employed as desulfurizer
for the spray dry flue-gas desulfurization process [10] . Considering that the wet
desulfurization agent is used but the dry final product is generated, this method is
also called the semi-dry desulfurization technology. The rotary spray
desulfurization technology is currently widely adopted by most countries
especially municipal solid waste incineration power plants because of its reliable