Electrostatic precipitators have been successfully used for many years to reduce particulate
emissions from municipal waste incinerators. Municipal incinerators, also commonly called
municipal waste combustors (MWCs) are used to reduce the volume of many different solid and liquid wastes. Generally, municipal wastes are composed of combustible materials (e.g.
paper, wood, rags, food, yard clippings, and plastic and rubber materials) and noncombustible
materials (e.g. rocks, metal, and glass). MWCs burn waste and produce ash residue that is disposed
of in landfills.
Both dry and wet plate ESPs are commonly used on municipal incinerators. Collected dust can
be removed from collection plates by rapping or by using water sprays. Plate ESPs having
rigid frame discharge electrodes are currently being used on MWCs (installed after 1982). The
designed collection efficiency is usually in the range of 96 to 99.6%. Dust resistivity can be a
problem, particularly if the refuse contains a large quantity of paper products. The dust in the
flue gas in this case usually has low resistivity. Resistivity can be adjusted by carefully controlling
the temperature and the amount of moisture in the flue gas.
Since the mid-1980s a number of large MWCs (plants having a capacity of 250 to 3000 tons
per day) with heat recovery devices have been built. More recent installations have been built
with acid gas control systems along with an ESP or baghouse. The ESP (or baghouse) collects
acid gas reaction products (mainly calcium chloride and calcium sulfate), unused sorbent
material, and fly ash. ESPs are typically designed with 3 to 5 fields and are capable of meeting
particulate emission limits of 0.015 gr/dscf and occasionally can achieve limits as low as 0.01
gr/dscf. These units have successfully reduced SO2 by 80% (24 hr avg) and HCl by 90 to 95%.
The acid gas is removed by using dry sorbent injection or spray dryer absorbers. In dry injection
systems sorbent is injected (usually hydrated lime) into the furnace or into the ducting
prior to the flue gas entering the ESP. Acid gas removal efficiencies of 50% for SO2 and 75%
for HCl are routinely achieved (Beachler 1992).
A more commonly used acid gas control system is a spray dryer absorber placed ahead of the
ESP. These systems have been able to achieve 80% removal (24 hr avg) for SO2 and 90%
removal for HCl. A wet calcium hydroxide slurry is injected into a spray dryer by a rotary
atomizer or two-fluid nozzle. The slurry is made by slaking pebble lime (CaO) with water in a
paste or detention slaker. The heat of the flue gas evaporates the liquid slurry in the spray dryer
and the dry acid gas reaction products along with the particulate matter are collected in the
ESP. Background information and data prepared as part of the promulgated NSPS and Emission
Guidelines (U.S. EPA 1991) shows very good acid gas removal and particulate emission
control for these systems.
emissions from municipal waste incinerators. Municipal incinerators, also commonly called
municipal waste combustors (MWCs) are used to reduce the volume of many different solid and liquid wastes. Generally, municipal wastes are composed of combustible materials (e.g.
paper, wood, rags, food, yard clippings, and plastic and rubber materials) and noncombustible
materials (e.g. rocks, metal, and glass). MWCs burn waste and produce ash residue that is disposed
of in landfills.
Both dry and wet plate ESPs are commonly used on municipal incinerators. Collected dust can
be removed from collection plates by rapping or by using water sprays. Plate ESPs having
rigid frame discharge electrodes are currently being used on MWCs (installed after 1982). The
designed collection efficiency is usually in the range of 96 to 99.6%. Dust resistivity can be a
problem, particularly if the refuse contains a large quantity of paper products. The dust in the
flue gas in this case usually has low resistivity. Resistivity can be adjusted by carefully controlling
the temperature and the amount of moisture in the flue gas.
Since the mid-1980s a number of large MWCs (plants having a capacity of 250 to 3000 tons
per day) with heat recovery devices have been built. More recent installations have been built
with acid gas control systems along with an ESP or baghouse. The ESP (or baghouse) collects
acid gas reaction products (mainly calcium chloride and calcium sulfate), unused sorbent
material, and fly ash. ESPs are typically designed with 3 to 5 fields and are capable of meeting
particulate emission limits of 0.015 gr/dscf and occasionally can achieve limits as low as 0.01
gr/dscf. These units have successfully reduced SO2 by 80% (24 hr avg) and HCl by 90 to 95%.
The acid gas is removed by using dry sorbent injection or spray dryer absorbers. In dry injection
systems sorbent is injected (usually hydrated lime) into the furnace or into the ducting
prior to the flue gas entering the ESP. Acid gas removal efficiencies of 50% for SO2 and 75%
for HCl are routinely achieved (Beachler 1992).
A more commonly used acid gas control system is a spray dryer absorber placed ahead of the
ESP. These systems have been able to achieve 80% removal (24 hr avg) for SO2 and 90%
removal for HCl. A wet calcium hydroxide slurry is injected into a spray dryer by a rotary
atomizer or two-fluid nozzle. The slurry is made by slaking pebble lime (CaO) with water in a
paste or detention slaker. The heat of the flue gas evaporates the liquid slurry in the spray dryer
and the dry acid gas reaction products along with the particulate matter are collected in the
ESP. Background information and data prepared as part of the promulgated NSPS and Emission
Guidelines (U.S. EPA 1991) shows very good acid gas removal and particulate emission
control for these systems.
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