Controlling Pollutants in Coal-Fired Power Plants in China - Mercury Emission and its Control in Chinese Coal-Fired Power Plants - page 6

shows that the circulating fluidized-bed coal combustion method is helpful in re-
ducing mercury emissions. In fact, only 4.5% of mercury in coal is emitted to the
atmosphere when burning high chlorine bituminous coal [17] . Incorporating the ad-
ditive during the burning process changes the distribution of mercury speciation in
the flue gas. Currently, brominated additive is used to control mercury emissions.
On-site application research shows that total mercury removal efficiency can reach
80% when 4 ppm bromine is added to the coal [18] .
Mercury control technology after burning refers to the removal of mercury from
the coal-fired flue gas. This technology can be divided into several methods ex-
plained below. First, it uses sorbent to adsorb mercury in flue gas. However, the
mechanism involved in adsorbing mercury is unclear, and there are many arguments
surrounding its effectiveness. The popular absorbents are activated carbon, coal fly
ash, calcium material, zeolite, and so on.
Second, it uses existing flue gas pollution control devices of coal-fired power
plants to reduce mercury emissions. At present, existing flue gas pollution control
devices include particle-control equipment (ESP or FF), NO x -control equipment
(SCR), and flue gas desulfurization equipment (WFGD). It can simultaneously
control mercury, particulates, SO 2 , and NO x pollutants using the existing pollutant
control devices.
Third, it develops new mercury pollution control technologies, such as corona
discharge plasma technology and electrocatalytic oxidization combined treatment
technology, for comprehensive control.
Currently, except for the mercury emissions control technology used in the la-
boratories, there is no particular technology being used for coal-fired power plants
in China. However, ESP, WFGD, and SCR pollutant control equipment that has
certain mercury control functions is widely used. The mercury removal efficiency
of such equipment depends on the speciation distribution of mercury in flue gas,
which is mainly affected by coal type. Table 1.1 shows the average mercury re-
moval efficiency rates of existing pollutant control technologies with different coal
types [19,20] .
Table 1.1 Mercury removal efficiency of existing pollution control technology with different coal
types

Mercury removal efficiency (%)

Existing pollution control technology

Bituminite Sub-bituminite Lignite

Particle control

Cold-ESP 46/36 16/3 0/04

Hot-ESP 12/9 13/6 -/-

FF 83/90 72/72 -/-

Wet dust removal 14/- 0/9 33/-

SO 2 control

Dry spray+FF 98/98 3/24 17/0

Hot-ESP+WFGD 55/49 33/29 -/-

Cold-ESP+WFGD 81/75 35/29 44/44

FF+WFGD 96/98 -/- -/-