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The hazards of VOCs exhaust gas and how they are produced in various industries

Views: 5     Author: Xicheng EP LTD     Publish Time: 2022-12-05      Origin: Xicheng EP LTD

VOCs exhaust gas introduction:

VOCs is English for volatile organic compounds, and generally refers 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. Generally speaking, the VOCs waste gas we usually refer to is mainly divided into alkanes, aromatics, esters, aldehydes and others. More than 300 species have been identified so far. The most common ones are benzene, toluene, xylene, styrene, trichloroethylene, chloroform, trichloroethane, diisocyanate (TDI), diisocyanocresyl, etc.


VOCs exhaust hazards:

When the concentration of the gas is too high, it is easy to cause acute poisoning. In mild cases, headache, dizziness, cough, nausea, vomiting, or drunkenness will 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 itchy 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 an environment polluted by volatile organic compounds have a much higher chance of causing fetal malformations than ordinary people, and may affect the child's future intellectual development. At the same time, volatile organic compounds in indoor air are important causes of children's nervous system, blood system, and children's acquired diseases.

How VOCs exhaust gas is generated in each line:

1. Painting industry (spraying workshop):

Generate exhaust gas: the main components are some volatile organic compounds such as acetone, xylene, butanol, toluene, ethyl acetate and butyl acetate.

Causes and processes: Process flow and pollution production links of paint workshops in the automotive industry: production processes and VOCs pollution production links in paint workshops in the automotive industry: body-in-white → degreasing → surface adjustment → phosphating → cathodic electrophoresis (unorganized emission) → electrophoretic baking Drying (exhaust pipe discharge) → strong cooling → coarse sealing (disorganized discharge) → bottom plate protection → fine sealing (disorganized discharge) → PVC drying (exhaust pipe discharge) → strong cooling → electrophoresis polishing → intermediate coating manual wiping Cleaning → ostrich feather automatic cleaning machine cleaning → artificial spraying intermediate coating (inner cavity) → automatic coating machine spraying intermediate coating (partial exhaust pipe discharge, part unorganized discharge) → drying → intermediate coating drying (incineration discharge )→intermediate coating strong cooling→intermediate coating grinding→finish topcoat cleaning→ostrich feather automatic cleaning machine wiping→artificial spraying paint (inner cavity) (exhaust pipe discharge)→drying→automatic coating machine spray color coating (partial exhaust pipe discharge, part fugitive discharge) → automatic spraying of metallic paint at the air station (partial exhaust pipe discharge, part fugitive discharge) → dry → automatic coating machine spray varnish (partial exhaust pipe discharge, Partial fugitive emission) → check paint repair → finish paint drying (incineration discharge) → strong cooling of finish paint → modification → inspection → decoration → final assembly.

spray painting process

2. Plastic industry

The main cause: polymer monomers volatilized from particles such as plastics and plastics after being heated. Many traditional industrial manufacturers engaged in the manufacture of plastic products will heat plastic materials (ABS, PP, PE) at high temperatures (150-250oC), and then process them through injection molding machines as semi-finished or finished plastic products. Plastics will diffuse through heating reactions 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.

10MM gray PP plastic sheet customization

3. Petrochemical industry (fragrance workshop, cosmetics workshop)

Exhaust gas generation: 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.

Causes 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 the exhaust gas of vehicles and internal combustion engine equipment, the flue gas of heating furnaces and boilers, and the combustion flue gas of pulverized coal in thermal power plants in oil fields and refineries; the other is oil and gas development, gathering and transportation, During storage, transportation and processing, gas volatilized, vented or blown out at the wellhead, gas leaked from oil pipelines and oil tanks, non-condensable gas, released gas and reaction by-product gas produced by production equipment in refineries and petrochemical plants, and waste water The stench and harmful gases emitted during the treatment and transportation of other wastes; the third is the gaseous wastes (volatiles of paint and coatings, etc.) from machinery factories and other processing plants (pipe stations, etc.) affiliated to oil and gas enterprises.

Petrochemical industry

4. Biopharmaceutical industry

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

Exhaust gas generation: VOCs produced in the pharmaceutical process of the pharmaceutical industry are mainly methanol, acetone, benzene, toluene, xylene, methylene chloride, ethyl acetate, triethylamine, dimethylformamide, butyl acetate, n-propanol, 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, methyl ethyl ketone, ether, dichloroethane, acetic acid, chloroform Etc.), volatilizes to form a gas with pungent smell and stench, and has a certain degree of toxicity. Long-term discharge will inevitably deteriorate the quality of the regional air environment and cause harm to the health of nearby residents. Therefore, effective treatment of VOCs waste gas in the pharmaceutical industry has become an important issue to be solved urgently.

Pharmaceutical factory exhaust

5. Packaging and printing industry

Cause: Printing, pre-press, and post-press processes involve the use of a large number of solvent-based raw and auxiliary materials.

The printing industry (printing waste gas treatment) uses ink, toluene, xylene, gasoline, alcohol and other organic solvents, causing environmental pollution. In the ink drying process of the gravure printing process, the pollution discharge is particularly serious. Organic solvents accounting for 30% to 70% of the total amount of ink are evaporated by the drying oven, producing a large amount of organic waste gases (VOCs), which seriously endanger human health and damage the atmospheric environment.

Printing House Exhaust

6. Chemical fiber textile industry

The finalized exhaust gas produced: the main components are aldehydes, ketones, hydrocarbons, fatty acids, alcohols, esters, lactones, heterocyclic compounds, and aromatic compounds.

Chemical fiber textile industry

Cause: During the weaving and dyeing process of textiles, various textile auxiliaries and solvents need to be added in order to improve the appearance and dyeing quality of the product. Dyeing and rinsing textiles carry a large amount of organic compounds such as moisture, oil, wax, etc., which are volatilized by heat during high-temperature treatment, resulting in vocs exhaust gas.

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