Sulfur hexafluoride gas does not damage the ozone layer?- SF6在线监测系统_SF6检漏仪_SF6传感器_SF6密度继电器

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Sulfur hexafluoride gas does not damage the ozone layer?

发布时间：2014-11-09 来源：ydlcb 浏览次数：36次

The atmosphere surrounding the Earth can be divided into troposphere, stratosphere and ionosphere. The troposphere is closest to the ground. Various meteorological phenomena occur in this layer. Above the troposphere is the stratosphere, and the boundary between the troposphere and the stratosphere is called the layer interface. The height of the layer interface is about 16KM near the equator. About 9KM from the pole. Above the stratosphere is the ionosphere, and the ozone concentration in the stratosphere is relatively high at the height of 20~30KM.

Ozone (O3) is mainly formed by solar radiation with a wavelength below 242mm through a three-body process to decompose oxygen molecules and then attach the released oxygen atoms to the oxygen molecules.

Ozone is mainly generated over the equator and slowly moves towards the poles. Many processes cause ozone depletion, the main depletion is chemical and photochemical reactions in the stratosphere.

There is about 3.3 billion terabytes of ozone in the atmosphere. The formation and disappearance of ozone in the stratosphere is repeated, which determines the global ozone balance.

The ozone layer protects the human environment and human health from the effects of ultraviolet radiation from the sun. In the early 1970s, it was discovered that the ozone layer was being damaged by human activities. Studies have found that hydrofluorocarbons (CFCS) harm the ozone layer in the atmosphere, while

Hydrofluorocarbons (CFCS) are widely used as chemical raw materials in refrigeration industry. The chloride ions decomposed by it have a serious damage to the atmospheric ozone layer, resulting in the direct exposure the sun's ultraviolet rays to the Earth, threatening human survival, and adversely affecting the environment and human health.

This hydrochlorofluorocarbon is called freon. Freon is the generic name for a series of man-made chlorofluorocarbons in which ammonia atoms in hydrocarbons such as methane or ethane are replaced by chlorine or fluorine atoms. It was developed by Michli et al. in 1930. Because freon has a series of advantages such as chemical stability, heat resistance, non-flammable, non-toxic, non-corrosion and so on, it is an ideal substance in industry, widely used in air conditioning, refrigeration equipment refrigerant, spray agent, electronic device cleaning agent, fire extinguishing agent, blowing agent and synthetic resin raw materials.

The depletion of the ozone layer has been recognized by the international community as a cause of adverse effects on the environment and on human health.

In the CFC group, ozone is destroyed by the catalytic action of free chlorine atoms released when ultraviolet radiation breaks the bonds of CFC molecules. The reaction process is as follows:

Cfc-c1 + the remaining CFC (1)

C1 + O3—C1O + O2 ②

C1O + O3—C1 + O2 ③

O + O3—2O2F ④

The reaction pathways listed above show that ultraviolet radiation disconnects CFC molecules to produce free C1 (row 1). C1 then destroys ozone (O3) to produce C1O and O2 (row 2). The final products of this reaction chain are C1 and O2 (third row).

Once a free chlorine atom is present, it may immediately react with the O3 molecule again, thus for each C1 atom. By relying on the reactions of rows 2 and 3 several times and destroying one O3 molecule at a time, a repeating cycle is created.

This is called a catalytic cycle, and a C1 atom can go through tens of thousands of cycles before it is neutralized by other reactions. In the case of sulfur hexafluoride, the only halogen component is fluorine (F), for which the above-mentioned catalytic reaction is practically impossible for two reasons:

(1) Due to the structural reasons of its ultraviolet absorption spectrum, sulfur hexafluoride does not occur photolysis in the critical ozone-destroying height range between 32 and 44KM. Therefore, very little atomic fluorine is expected from sulfur hexafluoride.

(2) Because of fluorine's strong chemical affinity for hydrogen (which is abundant in the stratosphere), any atomic fluorine that might be produced from sulfur hexafluoride. The hydrogen atoms available from the water molecule (which exists in quantities of 10,000 *10-6) will be used to rapidly combine to form HF.

Considering that a C1 atom destroys 10,000 ozone molecules by catalytic action, while the content of sulfur hexafluoride is only 1/1000 of that of CFC, and no free fluorine is produced from sulfur hexafluoride, it is clear that sulfur hexafluoride has no destructive effect on stratospheric ozone.

According to the current understanding, the destruction of the ozone layer is mainly chlorine (C1), or bromine (BR) atoms, and sulfur hexafluoride molecules do not have C1 or BR atoms, so people do not have to worry about sulfur hexafluoride gas to destroy ozone.

The international ozone layer protection Treaty came into force in 1990. The treaty stipulates that after 1998, the consumption of freon should be controlled at 50% of the 1986 level, the production should be controlled below 65%, and the research of substitutes and the recycling of freon gas after use. Our Government has pledged to stop the use of CFCS in refrigerators by 2005.