ESPs are used in cement plants to control particulate emissions from cement kilns and clinker
coolers. In a cement plant, raw materials are crushed, ground, blended, and fed into a kiln,
where they are heated. The kiln is fired with coal, oil, or gas. The material is heated to a temperature
above 1595°C (2900°F), which causes it to fuse. The fused material is called cement
clinker. The temperature of the hot, marble-sized, glass-hard clinker is cooled by the clinker
cooler. The cooled clinker is then sent to the final grinding mills.
ESPs are frequently used to control kiln emissions because of their ability to handle high-temperature
gases. These ESPs are usually hot-side ESPs with collection plates that are rapped or
sprayed with water to remove collected dust. The dust generated in the cement kiln frequently
has high resistivity. High resistivity can be reduced by conditioning the flue gas with moisture.
Many of the newer cement plants send the high temperature kiln flue gas that contains particulate
matter through a cyclone and conditioning tower (uses water to cool the gas temperature)
prior to ducting the flue gas to the ESP. The ESP is then operated at a temperature of approximately
150°C (302°F).
A special problem arises during kiln startup due to the fact that the temperature of the kiln
must be raised slowly to prevent damage to the heat-resistant (refractory) lining in the kiln.
While kilns (especially coal-fired ones) are warming up and temperatures are below those for
steady-state operating conditions, complete combustion of the fuels cannot occur, giving rise
to combustible gases in the exhaust stream leading into the ESP. Electrostatic precipitators
cannot be activated in the presence of combustibles, because the internal arcing of the precipitator
could cause a fire or explosion. Use of a cyclone preceding the precipitator helps to minimize
the excessive emissions during startup. Periods of excessive emissions during startup,
malfunction, or shutdown are specifically exempted from the federal New Source Performance
Standards for cement kilns.
ESPs can also be used on clinker coolers. However, the ESP must be carefully designed to prevent
moisture in the flue gas from condensing. Condensed moisture can combine with clinker
dust to coat the ESP internals with cement. (A case history of an ESP used on a cement kiln is
given in Szabo et al. 1981.)
coolers. In a cement plant, raw materials are crushed, ground, blended, and fed into a kiln,
where they are heated. The kiln is fired with coal, oil, or gas. The material is heated to a temperature
above 1595°C (2900°F), which causes it to fuse. The fused material is called cement
clinker. The temperature of the hot, marble-sized, glass-hard clinker is cooled by the clinker
cooler. The cooled clinker is then sent to the final grinding mills.
ESPs are frequently used to control kiln emissions because of their ability to handle high-temperature
gases. These ESPs are usually hot-side ESPs with collection plates that are rapped or
sprayed with water to remove collected dust. The dust generated in the cement kiln frequently
has high resistivity. High resistivity can be reduced by conditioning the flue gas with moisture.
Many of the newer cement plants send the high temperature kiln flue gas that contains particulate
matter through a cyclone and conditioning tower (uses water to cool the gas temperature)
prior to ducting the flue gas to the ESP. The ESP is then operated at a temperature of approximately
150°C (302°F).
A special problem arises during kiln startup due to the fact that the temperature of the kiln
must be raised slowly to prevent damage to the heat-resistant (refractory) lining in the kiln.
While kilns (especially coal-fired ones) are warming up and temperatures are below those for
steady-state operating conditions, complete combustion of the fuels cannot occur, giving rise
to combustible gases in the exhaust stream leading into the ESP. Electrostatic precipitators
cannot be activated in the presence of combustibles, because the internal arcing of the precipitator
could cause a fire or explosion. Use of a cyclone preceding the precipitator helps to minimize
the excessive emissions during startup. Periods of excessive emissions during startup,
malfunction, or shutdown are specifically exempted from the federal New Source Performance
Standards for cement kilns.
ESPs can also be used on clinker coolers. However, the ESP must be carefully designed to prevent
moisture in the flue gas from condensing. Condensed moisture can combine with clinker
dust to coat the ESP internals with cement. (A case history of an ESP used on a cement kiln is
given in Szabo et al. 1981.)
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