Air Pollution Control Devices

Electrostatic Precipitator (ESP)

ESP control devices ionize contaminated air flowing between the electrodes.  The charged particles (contaminants) travel to the oppositely charged plates. The particles on the plates are removed.  These particles can be dry dust or liquid droplets (liquid droplets is more efficient).  The particles that are removed from the plates are knocked off to the bottom of the ESP.  ESPs have high efficiency and low pressure drops.

These devices are used after the roller mill and after the cement kiln in the production of cement to reduce emissions of particulate matter such as cement kiln dust.  Often spray towers are used before the ESP in order to moisten the particulates, increasing ESP efficiency.

Baghouse Filters

In these control devices, polluted air is filtered through the bags. The bags are closed at the bottom, and are exposed to a clean air chamber at the top.  The bags are cleaned by short bursts of pressured air.  The bags contracts and snaps which releases the particulate layer.

Baghouses are used in cement production at the top of material storage silos and gas separators.  They help prevent any particulate matter escape the process.  Anything collected in the bag filters is simply release back into the process to be used in the cement making.

In-situ Monitoring Devices

SO2, NOx, and hydrocarbon emissions are monitored using in-situ monitors.  The readings are transmitted to the control room.  The control operator uses this information in order to adjust temperature or flow of the material in order to reduce emissions.  These devices are placed near the top of the cement kiln stack.

Selective Non-catalytic Reduction

At 900-1000C ammonia will reduce NOx concentrations to N2 without a catalyst.  The ammonia is injected into a boiler to reduce NOx concentrations in the boiler.  Proper temperatures must be achieved in order to create a fuel-rich reburn zone.  The hydrocarbon radicals react with NOx to reduce NOx to N2.  This system can be used to prevent NOx formation in the cement kiln.

            ESP at Cement Plant                           Baghouse at Cement Plant

   In-situ monitoring device attached to side of cement kiln stack

    Monitor that displays current emissions of SO2, NOx, and HCs