Volatile Organic Compound (VOCs) is a common pollutant emitted from petroleum, rubber, printing, coating, pharmaceutical, light industry and other industries. Organic waste gas often contains hydrocarbons (aromatic hydrocarbons, alkanes, olefins, etc.), benzene compounds (toluene, xylene, etc.), nitrogen, and so on. Compounds such as sulfur and halogen. If these exhaust gases are not treated, the direct discharge into the atmosphere will cause serious pollution to the environment and endanger human health.
The difference between organic waste gas and inorganic waste gas:
Organic waste gas mainly contains formaldehyde, xylene, acetone, butanone, acetic acid, ethyl ester and other waste gas treatment. Organic waste gases are generally flammable, explosive, toxic and harmful, insoluble in water, soluble in organic solvents, difficult to treat.
Inorganic waste gas mainly contains inorganic pollutants, mainly from nitrogen fertilizer, phosphorus fertilizer (containing sulfuric acid), inorganic salts, H2S, NOX, dust-containing waste gas such as oxidized dust in the process of metal smelting, stone dust in the process of ore processing and so on.
Hazards of organic waste gas:
The harm of organic waste gas to human body is multifaceted, and the toxicity of organic waste gas from different trades is also different. Among them, the organic compounds of benzene often damage human central nervous system, which will cause nervous system obstacles. When the concentration of benzene vapor is too high (up to 2% in the air), it can cause lethal acute poisoning, polycyclic aromatic hydrocarbons have. The machine has strong carcinogenicity.
Organic waste gas treatment methods:
1. Condensation recovery method: Organic waste gas is directly introduced into the condenser through adsorption, absorption, stripping and separation, and valuable organic matter can be recovered. This method is suitable for high concentration, low temperature and low air volume of organic waste gas. It needs auxiliary refrigeration equipment, which is mainly used in pharmaceutical and chemical industries. Printing enterprises seldom adopt it.
2. Adsorption method:
(1) Direct adsorption method: organic waste gas adsorbed by activated carbon can reach more than 95% of the purification rate, simple equipment, investment is small, but the frequent replacement of activated carbon, increased loading and unloading, transportation, replacement and other work procedures, resulting in increased operating costs.
(2) Adsorption-recovery method: adsorbing organic waste gas with fibre activated carbon, desorbing and regenerating with superheated steam after approaching saturation, this method requires to provide the necessary amount of steam.
(3) Adsorption-catalytic combustion method: This method combines the advantages of adsorption method and catalytic combustion method. A new type of adsorption material (honeycomb-like activated carbon) is used to adsorb, and hot air is introduced to desorb and analyse near drinking and after desorption. After desorption, the exhaust gas is introduced into flameless combustion of catalytic combustion bed, which is thoroughly purified and the hot gas is recycled in the system. It will greatly reduce energy consumption. This method is characterized by stable and reliable operation, low investment, low operation cost and convenient maintenance. It is suitable for the treatment of waste gas with high air volume and low concentration. It is a mature and practical method for the treatment of organic waste gas in China.
3. Direct combustion method: using auxiliary fuels such as gas or fuel to burn, the mixture gas is heated to decompose harmful substances into harmless substances at high temperature; this method is simple in technology, low in investment, suitable for high concentration, small air volume of exhaust gas, but requires high safety technology and operation.
4. Catalytic combustion method: converting waste gas into harmless and odorless carbon dioxide and water by catalytic combustion; this method has low ignition temperature, energy saving, high purifying rate, convenient operation, less floor area and large investment, and is suitable for high temperature or high concentration organic waste gas.
5. Absorption method: Physical absorption is generally used, that is, waste gas is introduced into the absorption liquid for purification, after the absorption liquid is saturated, it is heated, analyzed and condensed for recovery; this method is suitable for atmospheric volume, low temperature, low concentration of waste gas, but it needs to be equipped with a heating and analytical recovery device, large equipment volume, high investment.
6. Nano-micro-electrolytic oxidation: Nano-micro-electrolytic purification technology uses nano-scale processing piezoelectric materials, in the case of a certain humidity, micro-electrolytic electric field can produce nano-micro-electrolytic materials of electrical adsorption and release a large number of hydroxyl anions to purify the aerobic pollutants in the gas, not only can Remove most of the organic matter in the air, and can also analyze inorganic odors such as ammonia nitrogen and hydrogen sulfide.
7. Thermodynamic Combustion Method: Using regenerative thermal oxidation furnace RTO to treat organic waste gas can achieve the dual effect of high efficiency and energy saving. It is suitable for treating organic waste gas with wide scope and high efficiency. RTO equipment has been widely used in coating, printing, spraying, medicine and other industries.
Activated carbon adsorption method
Activated carbon is the most widely used method to treat organic waste gas. It has good adsorption performance for benzene waste gas, but poor adsorption performance for hydrocarbon waste gas. The main drawback is that the running cost is high and is not suitable for the environment with high humidity. If it is necessary to treat organic waste gas with high humidity, the nanometer micro-electrolysis oxidation process should be adopted. The nanometer micro-electrolysis air purification process does not need to replace the filler, does not need electricity, and has no running cost in the use process. Since the 12th Five-Year Plan period, it has gradually replaced the high-consumption technology such as activated carbon.
At present, adsorptive activated carbon is mainly used in industry for tail gas adsorption and harmful gas adsorption. Most of them are columnar activated carbon. The lignin columnar activated carbon is widely used because of its good adsorption effect, and gradually replaces the old coal activated carbon adsorption method.
Scrubbing tower for organic waste gas
Washing tower for organic waste gas treatment is a waste gas treatment technology. It has obvious effect on industrial waste gas treatment such as acid fog waste gas treatment, alkali fog waste gas treatment and paint waste gas treatment, painting waste gas treatment, absorption and dissolution of organic waste gas treatment, chemical waste gas adsorption, oxidation and reduction, acid and alkali neutralization, and achieves national industrial waste gas discharge.