Definition of VOC

VOCs (volatile organic compounds) is the abbreviation of volatile organic compounds. Sometimes it is also called VOC, which refers to a VOC at this time, or a collective concept of volatile organic compounds. Both Chinese volatile organic compounds and English Volatile Organic Compounds are relatively long, so it is customary to use VOCs or VOCs for short. In terms of chemical definition, VOC refers to a large class of organic compounds that are easily volatile, covering a wide range, while in terms of environmental protection, it refers to a class of organic compounds that are active, volatile at room temperature, and participate in atmospheric photochemical reactions at the same time. compound. Whether VOCs, SVOCs or NVOCs are involved in atmospheric chemical and physical processes in the atmosphere, some of them can directly endanger human health, and they bring environmental effects including affecting air quality, weather and climate.

Types of VOCs

According to the chemical structure of volatile organic compounds (VOCs), they can be further divided into 8 categories: alkanes, aromatic hydrocarbons, olefins, halogenated hydrocarbons, esters, aldehydes, ketones and other compounds.

In the sense of environmental protection, it mainly refers to the type of volatile organic compounds with active chemical properties. Common VOCs are benzene, toluene, xylene, styrene, trichloroethylene, chloroform, trichloroethane, diisocyanate (TDI), diisocyanatotoluene, etc.

VOC source

VOCs mainly come from two natural and anthropogenic factors, namely forests, oceans, soils and human activities.

Industrial VOC emissions involve many industries. In painting and painting, packaging and printing, chemical industry, and electronics industries, volatile organic compounds will be generated due to the use of various organic solvents such as coatings, binders, and cleaning agents.

VOC hazards

The concentration of voc from natural sources is usually not high under normal circumstances, and it is almost harmless to humans.

The accumulation of VOCs caused by humans, such as VOCs produced by industrial emissions, mainly enters the human body through the respiratory tract, digestive tract and skin to cause harm, and has teratogenic, mutagenic and carcinogenic effects on the human body. VOCs have photochemical activity, causing photochemical smog, which affects the function of the human respiratory tract, causing symptoms such as chest tightness, nausea, and fatigue, and also causes damage to the plant system. The hazards of VOCs to the environment and the impact on human health are mainly manifested in:

(1) Irritability and toxicity: When VOCs exceed a certain concentration, they will stimulate people's eyes and respiratory tract, causing skin irritation, sore throat and fatigue; VOCs can easily pass through the blood-brain barrier and damage the central nervous system; VOCs can harm human liver , kidneys, brain and nervous system.

(2) Carcinogenicity, teratogenicity and reproductive system toxicity.

(3) Some VOCs are ozone precursors, and the photochemical reaction of VOC-NOx increases the ozone concentration in the troposphere and enhances the greenhouse effect.

(4) Under the action of sunlight and heat, it participates in the reaction of nitrogen oxides to form ozone, which leads to poor air quality and is the main component of photochemical smog and urban haze in summer.

(5) VOCs are important precursors for the formation of fine particles (PM2.5) and ozone. The proportion of VOCs in PM2.5 in the atmosphere is about 20% to 40%, and some PM2.5 is converted from VOCs. .

All in all, local ambient air has teratogenic, mutagenic and carcinogenic effects on human health, and has become the main driver of ozone pollution in large regional environments.

Governance VOC

Industrial VOC control is the top priority in the prevention of environmental pollution. To control the emission of VOC,

First, reduce from the source, use raw and auxiliary materials with low VOC content, coatings, adhesives, cleaning agents, etc., the VOCs content should meet the corresponding national restrictions on the content of harmful substances.

Secondly, in the process, high-efficiency, energy-saving and environmentally friendly equipment is used to reduce volatilization during use.

The last is terminal treatment. Common purification methods include combustion method, catalytic combustion method, adsorption method, absorption method, etc. Commonly used treatment equipment are TO, RTO, RCO, zeolite runner, Voc Scrubber, activated carbon adsorption box, etc.

For VOC waste gas with high concentration and large air volume, because most of its components are hydrocarbons, ethers, and alcohols, they are often treated by adsorption concentration + thermal combustion/catalytic combustion. The combustion generates water and carbon dioxide, which will not harm the environment. Air affects.

It is not difficult to control VOCs by selecting the appropriate treatment process according to the working conditions, but the difficulty lies in the awareness of control. Some common problems have been found in many enterprises. In order to reduce the operating cost of environmental protection equipment, some bypass pipes are set up to directly discharge organic waste gas. Or mix organic waste gas into the large air volume waste gas pipeline, reduce the VOC concentration and discharge it directly, and these opportunistic methods bring great environmental pollution and impact. It is recommended that everyone improve their environmental responsibility and awareness, and do a good job in environmental protection, so that the residents can have a good living environment.