What Is an Exhaust Gas Treatment Device?
An exhaust gas treatment device is a generic term for equipment that detoxifies toxic gases (flammable gases, natural gases, corrosive gases, toxic gases, volatile organic compound gases, global warming gases, PFC, odor, white and purple smoke, soot and dust, mist, etc.) generated in factories.
In the past, only highly toxic gases and acidic gases among toxic gases were treated, while relatively weakly toxic gases such as global warming gases were generally released into the atmosphere.
In recent years, however, in order to prevent environmental pollution and protect the natural environment, it has become common practice to discharge weakly toxic gases after appropriate non-toxic treatment, and exhaust gas treatment devices have become indispensable equipment. New exhaust gas treatment methods and exhaust gas treatment devices are being developed, and demand for these devices is expected to increase further in the future.
Uses of Exhaust Gas Treatment Devices
Exhaust gas treatment devices are mainly used to treat toxic gases (flammable, natural, corrosive, toxic, and PFC) generated from factories and facilities such as semiconductor manufacturing, LCD manufacturing, solar cell manufacturing, research facilities, chemical plants, and plating factories.
In semiconductor and LCD manufacturing, thermal decomposition, combustion, and catalytic types are often utilized, including treatment of global warming gases, while in other plants, appropriate treatment equipment is generally selected and installed according to the gases emitted, as follows:
- Gases containing As, P, Se, and Cd: Dry abatement equipment
- Halogenated hydrogen and hydrolysable gases: Wet type abatement equipment
- Others: Thermal decomposition or combustion type detoxification equipment
In the case of non-toxic treatment of mixed gases that cannot be removed by general exhaust gas treatment devices, a specific exhaust gas treatment device is designed for that plant or facility to remove the toxic gases.
Principle of Exhaust Gas Treatment Devices
Although treatment methods differ depending on the type and amount of gas emitted, they all have one thing in common: they all use some kind of chemical reaction to detoxify toxic gases.
Exhaust gas treatment devices mainly use the following principles to remove toxic gases.
- Heating Decomposition Type
Gases are detoxified by heating oxidative decomposition reaction with electric heaters. - Combustion Type
The exhaust gas is heated by a combustion burner and oxidized by an oxidation reaction to remove toxic gases. - Dry Type
Gas is detoxified by adsorption, chemical reaction, and ion exchange with the treatment agent. - Wet Type
Gas is detoxified by dissolving in chemicals or water. - Catalyst Type
Catalytic agent is heated, and the reaction removes the gas. - Plasma Type
Gas decomposition is performed by plasma discharge, and then the gas is removed by wet type abatement equipment.
Depending on the type of toxic gas to be treated, exhaust gas treatment devices are used as follows:
- Global Warming Gases
Combustion type detoxification equipment, catalyst type detoxification equipment, plasma type detoxification equipment, etc. - Combustible Gases
Combustion type detoxification equipment, dry type detoxification equipment, thermal decomposition type detoxification equipment, plasma type detoxification equipment, etc. - Acid Gas
Combustion type detoxification equipment, dry type detoxification equipment, wet type detoxification equipment, etc.
Types of Exhaust Gas Treatment Devices
Exhaust gas treatment devices include pyrolysis type, combustion type, dry type, wet type, catalyst type, and plasma type devices.
1. Heating and Decomposition Type Detoxification Equipment
This device uses heat from an electric heater to cause a heating oxidative decomposition reaction to remove toxic gases. Compared to other exhaust gas treatment devices, the greatest advantage of this type is that it requires less electricity and water, and can be operated at a lower cost, as it does not require fuel costs or fuel facilities.
On the other hand, disadvantages include the need for warm-up operation to heat the heater before treatment begins, the need for periodic heater replacement depending on the type of toxic gas, and the need for large amounts of water and air to cool the treated hot gases.
2. Combustion Type Detoxification Equipment
This system uses the heat from burning fuel to cause an oxidation reaction to remove toxic gases. Compared to other exhaust gas treatment devices, this type has the advantages of being able to treat a large amount of toxic gases and not taking as long to start up as the thermal decomposition type (warm-up operation is not required).
On the other hand, the disadvantage is that fuel equipment must be installed at the same time, which increases the cost of installation and operation, along with the cost of fuel. Another disadvantage is that a large amount of water or air is required to cool the processed high-temperature gas.
3. Dry Detoxification Equipment
This equipment detoxifies toxic gases by chemical reaction and adsorption by adding a treatment agent to the toxic gases. The chemical reaction with the treatment agent changes the gas into a non-toxic compound, which is then adsorbed by the treatment agent and discharged.
The treatment agent discharged must be disposed of as industrial waste, which is a major difference from the thermal decomposition, combustion, and plasma types. Since heating facilities are not required, the system can be operated at low cost, but it generates industrial waste, which requires time and money for disposal.
4. Wet Type Detoxification Equipment
Wet detoxification equipment dissolves toxic gases by spraying chemicals or water, which easily dissolve toxic gases, in a shower-like manner and passing the toxic gases through the spray.
However, it requires time and cost to dispose of the water and chemical solution that dissolved the toxic gas, and the facility tends to be large if the amount of toxic gas to be disposed of is large.
5. Catalyst-Type Detoxification Equipment
Catalytic detoxification equipment detoxifies toxic gases by giving a heated catalyst to the toxic gases to cause a chemical reaction.
The advantage of this system is that it can be operated safely and at low cost because it does not require fuel or fuel equipment, and it can be operated with low electricity costs.
6. Plasma Type Detoxification System
This device uses plasma heat to cause a gas decomposition reaction to remove toxic gases.
Plasma heat is generated by the following methods:
- Micro-discharge
- RF discharge
- Arc discharge
Compared to other exhaust gas treatment devices, the greatest advantage is that it requires less electricity and water, but its disadvantages include the need for periodic parts replacement, the need for large amounts of water and air to cool the hot gases that have been treated, and the fact that it is a new treatment device and there are few examples of its use.