Wan Andy has organized ten methods below for your reference.
Treatment of exhaust gasA wide range of exhaust pollutants, different characteristics, for different types of exhaust, select the appropriate treatment. Common treatment methods include: condensation, absorption, combustion, catalytic, adsorption and so on.
1 condensation recovery method
The condensate recovery method is a method in which the exhaust gas is directly introduced into the condenser or absorbed first, and then the analyzed condensed exhaust gas is introduced into the condenser, and the condensate is separated to recover valuable organic matter.
Advantages: The condensation method is mainly used for the recovery of high-boiling and high-concentration VOC contaminated gases. The applicable concentration range is >5% (volume). The process is simple and the recovery rate is high.
Disadvantages: This method requires an attached refrigeration equipment. It has large investment, high energy consumption, and high operating costs. At the same time, the exhaust gas after condensation still contains a certain concentration of organic matter, causing serious secondary pollution. Therefore, this method is rarely used for the treatment of low-concentration exhaust gas.
2 absorption method
Absorption can be divided into chemical absorption and physical absorption. Since organic exhaust gas contains a large amount of "triphenylene" gas, the chemical activity is low, and chemical absorption cannot be generally used.
The physical absorption is that one or more components of the exhaust gas are dissolved in the selected liquid absorbent. This absorbent should have a high affinity with the absorption component, low volatility, and should also have a small volatilization. After the absorption solution is saturated, it is heated and desorbed and then cooled again for reuse.
The common process flow chart is as follows:
Advantages: Suitable for low temperature, medium and high concentration exhaust gas, can selectively absorb hydrogen sulfide and other exhaust gas, the process is simple, and does not require additional steam and other heat sources.
Disadvantages: need to be equipped with heating and analytical condensation recovery device, large installed capacity, large investment, but also the existence of secondary pollution, purification effect is not ideal.
3 direct combustion method
The direct combustion method utilizes the heat released from combustion of auxiliary fuel such as gas or fuel to heat the mixed gas to a certain temperature (700-800°C) and stays for a certain time (0.3-0.5 seconds), causing flammable hazardous substances to undergo high temperature decomposition. A method for harmless substances.
Advantages: Direct combustion method is simple, equipment investment is small, and it is suitable for the treatment of exhaust gas with high concentration and small air volume.
Disadvantages: large energy consumption, high operating costs; high operating technology requirements, not easy to control and grasp, has not been widely promoted in the country.
4 Thermal combustion
Thermal combustion refers to the process of increasing the temperature of exhaust gas to the temperature of flammable pollutants and allowing them to undergo full oxidative decomposition.
Advantages: It is suitable for the purification treatment of exhaust gas with low content of flammable organic substances. The combustion and purification technology has high thermal efficiency, long equipment life, anti-aging and corrosion resistance.
Disadvantages: Large equipment, inconvenient transportation; high equipment prices, high operating costs; poor treatment of waste gases containing sulfur and halogen organic compounds.
5 catalytic combustion method
Catalytic combustion is the process of completely oxidizing harmful combustible components in exhaust gas into carbon dioxide and water under the action of a catalyst.
Advantages: Catalytic burners have a high purification rate, a low operating temperature, low energy consumption, less restrictions on the concentration and calorific value of combustible components, simple operation and good safety.
Disadvantages: Some gas combustion conditions are harsh, requiring high temperature, high altitude and high partial pressure of steam, so the catalyst must have high activity, high thermal stability and high hydrothermal stability, as well as a certain resistance to poisoning.
6 activated carbon adsorption method
Activated carbon adsorption is to send organic exhaust gas to an adsorption bed by an exhaust fan. Organic exhaust gas is adsorbed on an adsorption bed by an activated carbon adsorbent to purify the gas, and the purified gas is discharged to the atmosphere to complete the purification process.
Advantages: high adsorption rate, low operating energy consumption, low cost, safety and reliability, applicable to explosive dangerous places, adsorbents can be recycled, energy saving and environmental protection.
Disadvantages: not high temperature, can not maintain a good adsorption capacity under humid conditions; flammable, quickly reach saturation adsorption and lose effectiveness; produce secondary solid or liquid contaminants.
7 biological methods
Biological methods are a way for microorganisms to use organic components as carbon sources and energy sources, and to decompose them into CO2 and H2O processes.
Advantages: Simple equipment, low investment, low operating costs, no secondary pollution, ideal for treating VOCs.
Disadvantages: The reaction device has a large area and a long reaction time.
8 plasma decomposition method
The plasma decomposition method is a kind of exhaust gas treatment method that causes pollutants to be degraded and removed by a large number of energetic electrons generated by the dielectric discharge to bombard contaminant molecules under the action of an external electric field and trigger a series of complicated physical and chemical reactions.
Advantages: simple process, low consumption and energy saving, strong anti-oxidation of equipment materials, anti-corrosion, long service life, can efficiently remove exhaust gas containing volatile organic compounds, inorganic substances, hydrogen sulfide, ammonia and other major pollutants.
Disadvantages: The vacuum technology required by plasma technology in the waste disposal process brings certain technical problems, and it is still in the research stage. At present, many researches only focus on single pollutants.
9UV UV
The UV-ultraviolet method utilizes a special high-energy and high-ultraviolet UV ultraviolet beam to irradiate the exhaust gas, change the molecular structure of the exhaust gas, and degrade the organic or inorganic polymeric exhaust gas molecular chain under irradiation with a high-energy ultraviolet light beam to a low molecular compound.
Advantages: Small footprint, low operating costs, low equipment investment.
Disadvantages: Low removal efficiency, less types of gases that can be processed.
10 biological trickling
The biological trickling method is to pass the exhaust gas through a pretreatment process such as dust removal and humidification or temperature reduction, and from the bottom of the filter bed through the filter bed composed of the filter material, the exhaust gas is transferred from the gas phase to the water-microbial mixed phase, and is fixed. A method of decomposition of microorganisms on the filter material.
Advantages: low processing cost, simple process flow, ecological protection.
Disadvantages: Large area, the need for regular replacement of the filler, the process is not easy to control, after a period of time prone to problems, the treatment of hydrophobic and difficult to biodegradable material there are still more difficult.
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