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The harm of VOCs exhaust gas and how it is produced in various industries

Views: 11     Author: Xicheng Ep Ltd     Publish Time: 2022-03-21      Origin: Xicheng Ep Ltd

The harm of VOCs exhaust gas and how it is produced in various industries

Introduction of VOCs waste gas:

   VOCs is the English word for volatile organic compounds, generally referring to any organic solid or liquid that can volatilize under normal temperature and pressure. The popular point is that it exists in the form of gas at normal temperature and pressure. Under normal circumstances, the VOCs waste gas we usually call is mainly divided into alkanes, aromatic hydrocarbons, esters, aldehydes and others. More than 300 species have been identified so far. The most common are benzene, toluene, xylene, styrene, trichloroethylene, chloroform, trichloroethane, diisocyanate (TDI), diisocyanatotoluene, etc.

Air pollution in cities is getting worse

VOCs exhaust gas hazards:

   When the gas concentration is too high, it is easy to cause acute poisoning. In mild cases, headache, dizziness, cough, nausea, vomiting, or intoxication may occur; in severe cases, liver poisoning or even coma will occur soon, and some may be life-threatening . Long-term living indoors polluted by volatile organic compounds can cause chronic poisoning, damage the liver and nervous system, cause general weakness, drowsiness, and itching of the skin. Some may also cause endocrine disorders and affect sexual function; benzene and xylene can also damage the system and even cause leukemia.

Especially the impact on children's health: It has been confirmed by foreign medical research that pregnant women living in volatile organic compound-polluted environments have a much higher risk of fetal malformations than ordinary people, and may have an impact on the children's future intellectual development. At the same time, volatile organic compounds in indoor air are an important cause of children's nervous system, blood system, and children's acquired diseases.

How VOCs waste gas in each line is generated:

1. Painting industry (spraying workshop):

Production of waste gas: the main components are acetone, xylene, butanol, toluene, ethyl acetate and butyl acetate and other volatile organic compounds.

Cause and process: Process flow and pollution-producing link of spraying workshop in automobile industry: Production process and pollution-producing link of VOCs in coating workshop of automobile industry: Body-in-white → degreasing → surface conditioning → phosphating → cathodic electrophoresis (unorganized emission) → electrophoresis drying Drying (exhaust pipe discharge) → strong cooling → rough sealing (unorganized discharge) → bottom plate protection → fine sealing (unorganized discharge) → PVC drying (exhaust pipe discharge) → strong cooling → electrophoresis polishing → middle coating manual rubbing Cleaning → ostrich hair automatic cleaning machine cleaning → manual spraying of the middle coating (inner cavity) → automatic coating machine spraying the middle coating (part of the exhaust pipe discharge, part of the unorganized discharge) → drying → the middle coating drying (incineration emission) ) → medium coating strong cooling → middle coating grinding → topcoat cleaning → ostrich hair automatic cleaning machine cleaning → manual color spray paint (inner cavity) (exhaust pipe discharge) → drying → automatic coating machine spray color (Part of the exhaust pipe discharge, part of the unorganized discharge) → The air station automatically sprays metal paint (part of the exhaust pipe discharge, part of the unorganized discharge) → Drying → The automatic coating machine sprays the varnish (part of the exhaust pipe discharge, Partial fugitive emissions) → check and touch up paint → finish paint drying (incineration emission) → top paint strong cooling → decoration → inspection → decoration → final assembly.

2. Plastics and plastics industry

The main reason: the polymer monomer volatilized after the particles of plastic and plastic are heated. Many traditional industrial manufacturers engaged in the manufacture of plastic products will heat plastic materials (ABS, PP, PE) at high temperature (150-250oC), and then process them through injection molding machines. As semi-finished or finished plastic products, the plastic will diffuse through the heating reaction. A pungent plastic smell, this part of the smell is the smell produced by VOCs, and the produced smell can be divided into intermittent or continuous.

3. Petrochemical industry (fragrance workshop, cosmetic workshop)

Generated waste gas: sulfur dioxide, nitrogen oxides, soot, benzopyrene, non-methane total hydrocarbons, hydrogen sulfide, volatile phenols, amines, hydrocarbons, benzene, acrylonitrile, cyclohexane, ammonia, ethylene, styrene, butyl Diene, propylene, vinyl chloride, etc.

Cause and process: The petroleum industry, especially the petroleum refining process, will produce a certain amount of toxic and harmful gases. There are three sources of these exhaust gases: one is fuel combustion, such as exhaust gas from vehicles and internal combustion engine equipment, flue gas from heating furnaces and boilers, and combustion flue gas from coal-fired power plants provided by oilfields and refineries; During storage, transportation and processing, gas that is volatilized, vented or leaked at the wellhead, leaked gas from oil pipelines and oil tanks, non-condensable gas, released gas and by-product gas of reaction generated by production units in refineries and petrochemical plants, as well as gas in wastewater and other odors and harmful gases emitted from waste treatment and transportation; the third is gas waste (volatiles from paint and coatings, etc.) from machinery factories and other processing plants (pipe stations, etc.) affiliated to oil and gas companies.

4. Biopharmaceutical industry

   The exhaust gas in the pharmaceutical industry is relatively complex, the process of different products is quite different, and the same products also have different conditions. The best way is to design a targeted exhaust gas treatment plan according to the current situation to ensure that the exhaust gas meets the standard.

Waste gas generation: VOCs produced in the pharmaceutical process of the pharmaceutical industry are mainly methanol, acetone, benzene, toluene, xylene, dichloromethane, ethyl acetate, triethylamine, dimethylformamide, butyl acetate, n-propanol, and ethanol , isopropanol, acetonitrile, ethylene oxide, formaldehyde. Causes in the medical and chemical industry: a large number of organic solvents (such as DMF, benzene series, organic amines, ethyl acetate, dichloromethane, acetone, methanol, ethanol, butanone, ether, dichloroethane, acetic acid, chloroform) are used. Etc.), volatilization forms a gas with irritating odor and stench, which is toxic to a certain extent. Long-term emission will inevitably deteriorate the quality of the regional atmospheric environment and cause harm to the health of nearby residents. Therefore, the effective treatment of VOCs waste gas in the pharmaceutical industry has become an important problem to be solved urgently.

5. Packaging and printing industry

Cause: The use of a large number of solvent-based raw and auxiliary materials will be involved in the printing and pre-press and post-press processes.

The printing industry (printing waste gas treatment) uses organic solvents such as ink, toluene, xylene, gasoline, and alcohol, causing environmental pollution. The drying ink process of the gravure printing process has particularly serious pollution emissions. The organic solvent, which accounts for 30% to 70% of the total ink, is evaporated from the drying box, and a lot of organic waste gas (VOCs) is generated, which seriously endangers human health and damages the atmospheric environment.

6. Chemical fiber textile industry

The resulting stereotyped waste gas: the main components are aldehydes, ketones, hydrocarbons, fatty acids, alcohols, esters, lactones, heterocyclic compounds, and aromatic compounds.

Cause: In the process of weaving and dyeing of textiles, in order to improve the appearance and dyeing quality of products, it is necessary to add a variety of textile auxiliaries and solvents. Textiles after dyeing and rinsing carry a large amount of organic compounds such as moisture, grease, wax, etc., which are volatilized by heat during high-temperature treatment, resulting in VOCs waste gas.

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