Emissions
Dry Sorbent Injection Systems for Air Pollution Reduction
When fossil fuels, such as coal, are burned, SO2 and SO3 form in the exhaust flue gas.
As these pollutants travel through duct work, they can cause corrosion and damage to
downstream equipment. When escaping into the atmosphere they can form a visible plume and
generate particulate emissions. They are also known for their detrimental effects on human
health and the environment, as they may cause smog, acid rain, and ozone depletion.
Increased awareness of these problems has led to more legislation and increasingly tighter
standards to regulate these harmful emissions.
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Injecting dry powdered sorbents (such as hydrated lime, Trona and powdered activated carbon)
directly into the ductwork by a controlled method assists in the mitigation of SO2, SO3, Hg
and resulting particulate emissions. The dry sorbent will react with SOX in the flue gas,
removing the pollutant from the gas stream via downstream electrostatic precipitators or bag
houses. In the case of hydrated lime, the result of the reaction is synthetic gypsum, which
is collected along with fly ash and can be sold to gypsum wallboard plants.
Nol-Tec Southeast has provided numerous control systems for these applications. These PLC and
HMI based systems include loss-in-weight feeders, pneumatic conveying and injector controls.
They have been installed in brick plants, coal-fired power utilities, municipal waste
incinerators and medical waste incinerators. The largest of these systems was recently
installed at a coal fired power plant and incorporated Allen-Bradley ControlLogix PLC’s,
RSView32 HMI’s and PowerFlex adjustable frequency drives.
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