Combustion Purification and Dry Purification
Combustion purification is a pollution control technology used for continuous emissions of large amounts of particulate matter. A major advantage of the technology is the removal of combustible and non-combustible material, as well as the removal of other compounds that may be present in the exhaust system. The combustion process is usually conducted in a fluidized bed. In a fluidized bed, a predetermined amount of air is forced through a bed of sand and/or activated carbon. This air flow is such that the sand and/or activated carbon form a fluidized bed. When a combustible material, such as a solid waste, is introduced into the fluidized bed, it undergoes combustion and the particulate matter is oxidized. The products of the oxidation reaction are mainly carbon dioxide, water vapor and small particles of particulate matter.
Non-combustion purification can also be used for particulate matter emissions control. Non-combustion purification systems typically use a dry scrubber, wet scrubber or electrostatic precipitator to capture and remove particulate matter from the exhaust stream. A dry scrubber uses a series of paddles or a blower to move the exhaust stream up through a filter bed, where the particulate matter is captured. Wet scrubbers use either a spray of water droplets, a mist of water droplets or atomized water droplets to capture and remove particulate matter. An electrostatic precipitator uses a high voltage field to attract the particulate matter to metal plates, where it is collected and removed from the exhaust stream.
Dry purification is a process in which air is passed through a filtering media to capture and remove particulate matter from the air stream. In a dry purification system, the air is passed through a filter media, such as a HEPA filter, or a combination of filter media, to remove particulate matter from the air stream. The process is typically used for industrial ventilation systems, as well as for residential or commercial buildings. Dry purification is generally less expensive and more efficient than wet or electrostatic methods, but it can be affected by humidity levels, as the filters can become clogged with moisture.
Although combustion purification and dry purification are the most commonly used methods for controlling particulate matter emissions, other types of air pollution control technologies can also be used to reduce the pollution from particulate matter. For example, high efficiency particulate air (HEPA) filters, as well as biofilters, can be used to remove some of the smaller particles from the air stream. In addition, catalytic ceramic filters can be used to reduce the amount of particulate matter that is emitted into the air.
