PM2.5 emissions involve multiple chemical fields

On December 5, Beijing experienced hazy weather, resulting in reduced visibility and air quality. The picture shows the square in the dense fog.

Sinochem’s new online news has seen the public’s attention to PM2.5 monitoring since October when many haze or haze days have occurred in Beijing and parts of the country. After nearly two months of disputes, PM2.5 monitoring finally appeared for the first time on the Ministry of Environmental Protection's second public exposure draft of the “Ambient Air Quality Standard” published to the whole society on November 16. The biggest adjustment in the second consultation draft was to incorporate PM2.5 into routine air quality assessments.

At 24:00 on December 5th, the "Ambient Air Quality Standard" (second exposure draft) was solicited for comments. According to the Ministry of Environmental Protection website, the Ministry of Environmental Protection will soon incorporate PM2.5 into the revised Ambient Air Quality Standard. The deadline for the implementation of the new standard is planned for 2016.

However, according to feedback from all sectors of society, it is generally agreed to implement in advance in key areas.

Is PM2.5 related to the chemical industry? After the revised "Ambient Air Quality Standard" is formally implemented, what impact will it have on the chemical industry?

PM2.5 enters public view PM2.5 is not a new term. Some domestic scholars began to study PM2.5 since the 1990s, but until recently the concept of PM2.5 was widely discussed by the public.

According to Professor Lin Zhangyu of the Department of Chemical Engineering at Tsinghua University, PM2.5 refers to particles in the atmosphere that are less than or equal to 2.5 microns in diameter, and are also referred to as lung-injectable particles. Its diameter is less than 1/20 of the thickness of human hair. Although PM2.5 is only a component of the Earth's atmospheric composition, it has an important effect on air quality and visibility. Compared with coarser airborne particles, PM2.5 has a small particle size, is rich in toxic and hazardous substances, has a long residence time in the atmosphere, and has a long transportation distance, and thus has a greater impact on human health and atmospheric environmental quality. PM2.5 can enter the bronchus, enter the alveoli in the lungs, and enter the bloodstream. Particles not only cause respiratory diseases, many studies have also shown that particulate matter also affects the cardiovascular system, immune system, reproductive system, nervous system, and genetic system.

Wu Xuefang, director of the Environmental Standard Research Institute of the Ministry of Environmental Protection, told reporters that PM2.5 in the ambient air mainly comes from two aspects. On the one hand, it directly discharges PM2.5, including dust, mining and concentrating, metal smelting, organic chemical production and catering. Industry fumes, etc.; on the other hand, secondary particles, mainly sulfur dioxide and nitrogen oxides, volatile organic compounds (VOC), etc., emitted from coal-fired power plants, are discharged into the air, and the salts produced by chemical reactions , sulfate, secondary organic aerosols, etc., resulting in increased PM2.5. Therefore, pollution sources or industries that directly and indirectly involve PM2.5 emissions include thermal power generation, petroleum refining, organic chemicals, iron and steel, non-ferrous metals, cement, ceramics, glass, paint, gas stations, dry cleaning, and catering.

Involving various chemical fields According to Wu Xuefang's introduction, it is not difficult to identify the chemical sub-sectors related to PM2.5, which mainly involve VOCs, oxides and nitrogen oxides.

Yuan Ying, deputy director of the Environmental Standard Research Institute of the Ministry of Environmental Protection, interviewed the reporter: “PM2.5 emissions have a lot to do with chemicals. Because the pollutants emitted by the chemical industry contain many substances related to PM2.5, such as VOCs. As long as it is VOC, it may eventually become PM2.5. Although some organic chemicals may not be PM2.5 in themselves, it may be a precursor of PM2.5 if the gas is oxidized with nitrogen in the air. When the materials work together in the sunlight, secondary pollutants form and become PM2.5."

It is understood that VOC is defined in the United States as any organic compound that can participate in atmospheric photochemical reactions. The World Health Organization is defined as the general name for volatile organic compounds with a melting point below room temperature and a boiling point between 50°C and 260°C. Whatever the definition, from the environmental protection point of view, it is a kind of active volatile organic matter. It contains a wide range of substances, including hydrocarbons, halogenated hydrocarbons, oxygenated hydrocarbons, and nitrogen hydrocarbons such as benzene series, organic chlorides, Freon series, organic ketones, amines, alcohols, ethers, esters, acids, and petroleum hydrocarbon compounds. There are hundreds of species.

Coatings are one of the key industries in terms of VOC emissions. Chemicals that are harmful to humans in paints are VOCs other than heavy metals. Environmental protection agencies have made the paint industry a key focus of VOC control.

Liu Guojie, senior engineer of the Industrial Development Department of China National Coatings Industry Association, said: "Since solvent-based coatings use organic solvents, these solvents almost volatilized into the atmosphere after they were used, becoming VOCs, polluting the environment and wasting a lot of resources. China's paint industry, solvent-based coatings accounted for 52.1% of the total output, much higher than the average level of 30% for solvent-based coatings in developed countries.The annual consumption of organic solvents in the coating industry accounts for 25% to 30% of the total domestic solvent consumption, ranking among pesticides. , pharmaceuticals, rubber, etc. use the first solvent industry."

Yuan Ying told reporters: “The oxides are also one of the sources of PM2.5. There are a lot of * oxides in the combustion of fossil fuels and in industrial waste gas. This involves the refinery of the chemical industry, coal-fired boilers, Coal-fired power plants, etc. For example, in the oil refining process, acid gases containing carbon dioxide are produced, and if they are discharged without treatment, they become a source of PM2.5, but if they are handled well, the production process is sealed. No volatilization will occur, and at the same time, the * resources will be recycled and no PM2.5 will be formed."

Wu Xuefang said: “Nitroxide is the source of micro-particles in the air. It is one of the precursors of photochemical reactions and one of the sources of PM2.5. Most of the nitrogen oxides come from the combustion process of fossil fuels; it also comes from production and use. The process of **, such as nitrogen fertilizer plant, organic intermediate plant, etc.; when processing inferior crude oil, the amount of nitrogen oxides generated in the regenerator flue gas of the catalytic cracking unit will increase; the motor vehicle is also a key emission source of nitrogen oxides. About 50% of the nitrogen oxide pollution in the top 40 cities with motor vehicle emissions comes from vehicle exhaust emissions. This puts forward new requirements for oil quality.”

Emission reduction requirements may be overweight. So it seems that once the new standard of “Ambient Air Quality Standard” is implemented, it will surely put forward higher emission reduction requirements for the chemical industry.

Yuan Ying told reporters that once the new standard is implemented, the impact of the chemical industry such as petroleum refining, coatings, and organic chemicals will be greater, and environmental protection such as de-nitrification and denitrification will be further promoted. The specific impact can be summarized as two aspects:

First, to promote the improvement of emission standards in related industries.

In the coatings industry, Yang Yuande, secretary-general of the China Coatings Industry Association, said: “To reduce PM2.5, VOC emission standards in the paint industry need to be tightened. The paint VOC standard must be developed both indoor and outdoor, not only focusing on quality standards, but also setting environmental standards. In this case, companies will face cost pressures and development difficulties, such as changing production processes, upgrading painting equipment, etc. Therefore, the coating companies' response to VOC emission reduction measures is to speed up the development of water-based industrial coatings and powder coatings, and vigorously develop high solids and no Solvent coating, at the same time, using low-toxicity ester solvents to replace hydrocarbon solvents.In addition, it is necessary to improve the paint production process, from open to fully enclosed integration;Improve the coating process, to achieve controllable, recyclable, can be recycled use."

Yang Yuande also listed a concrete action roadmap: By the end of this year, wood coating manufacturers have reached the existing national standards; from 2012 to 2013, they have reached the European Union “to limit the use of solvent volatile organic compounds in paints, varnishes, and interior trims. The 2007 indicator requirements of the Directive; by the end of 2015, the EU's 2010 target has been met. During the “Twelfth Five-Year Plan” period, the paint industry will also develop paint VOC emission standards and VOC testing method standards for waterborne coatings.

In terms of refined oil refining, Professor He Kebin, professor of the Department of Environmental Science and Engineering at Tsinghua University and an expert on air pollution and control in the study and formulation of the PM2.5 standard, said: “According to plan, China will implement the Oil IV standard on January 1 this year. , But now is the gasoline vehicle to do it, diesel cars have not yet done. One of the important reasons is that PetroChina and Sinopec failed to supply the diesel corresponding to the national IV standard on time, and the content of oil in the oil did not fall."

However, whether it is through strict standards to reduce the emissions of new diesel vehicles, or through the replacement of exhaust emission treatment devices to reduce the emissions of diesel vehicles in use, the use of low * diesel is the general trend. Beijing has already taken action. On December 7, the Beijing local standards "vehicle gasoline" and "vehicle diesel" were publicly solicited on the website of the Beijing Bureau of Quality Supervision. This draft of the consultation draft reduced the content of gasoline and diesel for vehicles from "not more than 0.005%" to "not more than 0.001%". The content of * is rigorously 5 times higher than the original standard, which means that after the vehicle has been added to the national standard V gasoline, the concentration of discharged sulphide content is reduced accordingly. In PM2.5, the smelter is an integral part of PM2. .5 The concentration of microparticles will be reduced accordingly.

Second, related industries must increase their emission reduction efforts. Dioxide* and nitrogen oxides have been listed as major pollutant control indicators. “The Comprehensive Work Program for Energy Saving and Emission Reduction in the 12th Five-Year Plan” shows that by 2015, the total amount of China’s total CO2 emissions will be controlled at 20.864 million tons respectively, which is 8% lower than in 2010; and the total amount of nitrogen oxide emissions in China will be separately controlled. At 204.62 million tons, a decrease of 10% from 2010. However, if the new PM2.5 standard is implemented, the future emission reduction plan for CO2 may have to be adjusted. In other words, the emission reduction efforts faced by the chemical industry may increase further.

During the oil refining process, acidic gases containing carbon dioxide* are produced, which can become a source of PM2.5 if discharged without treatment. The picture shows the atmospheric and vacuum installations of a refinery. (Photo by reporter Zhang Yushe)