The main causes and management of smog
Recently, the air quality index of Beijing, Tianjin, Hebei and other cities has “exploded the table” with heavy smog and poor visibility. Beijing issued the first orange warning for this year yesterday. Since November 27, the process of serious air pollution in Beijing has been going on for 4 days, and PM2.5 at some monitoring stations is close to bursting. Beijing's environmental protection department said that this round of pollution is a serious pollution process this year.
Recently, smog has become one of the hot topics. Regardless of the people, related industries and governments have expressed frustration and even complained. But complaining is useless, and it is imperative to understand the main reasons for the formation of smog, and then talk about how to control it.
Haze is divided into "primary particles" and "secondary particles". The particles emitted directly from the exhaust of fossil fuels such as diesel are "PrimaryParticulates", accounting for about 24% of the total smog. The contribution to the haze is "secondary particles (SecondaryParticulates)" accounted for about 50% of its total. "Secondary particles" are gaseous pollutants (such as NOx, SOx) and volatile organic compounds (VOC) in the combustion exhaust gas of fossil fuels that enter the atmosphere and generate gas with ammonia and VOC in the air under certain water mist conditions. The particles formed by the sol reaction. Therefore, to remove smog, it is necessary to reduce the emissions of pollutants such as NOx, SOx and VOC.
my country consumed about 470 million tons of oil in 2010 to about 570 million tons of crude oil in 2014, while coal consumption in 2014 was about 3.6-3.8 billion tons. The energy structure dominated by coal cannot be changed in the short term, so the treatment of coal-fired pollution has become the primary issue of the moment. Large power plants are required to install desulfurization, denitrification and dedusting equipment in accordance with regulations, with a removal rate of over 90%. With concentrated coal burning, the pollutants in the tail gas can be controlled to be similar to or even lower than that of natural gas. The world's average coal utilization rate is about 60%. Europe, America, Japan, etc. can reach more than 90%, but my country's coal utilization rate is less than 50%. There are nearly 700,000 small and medium-sized boilers in China that have burned hundreds of millions of tons of coal in bulk. Accurate figures and statistics have discrepancies, but it is estimated that about 600 million tons of loose-burned coal; the cost of installing a desulfurization and denitration device behind each small and medium boiler is too high. No country or individual will do this. Pollution of one ton of coal is about 10-20 times that of large boilers after ultra-clean emission reduction; therefore, the emission of 600 million tons of coal is equivalent to the pollution of about 6-12 billion tons of concentrated combustion. Due to the large population base in China, the per capita energy consumption and emissions in China are much lower than those in Europe and the United States, which cannot explain the smog pollution problem, but the environmental capacity is determined by the emissions per square kilometer (or energy density) and has nothing to do with per capita emissions (It may live 10 people or 10,000 people per square kilometer); the air is flowing, so it is not meaningful to focus on the local city data for the smog problem. From a macro perspective, the total area of the entire Europe is similar to China, but the Chinese population is mostly concentrated in the area of about 2 million square kilometers in the east, while the European population is distributed on about 4 million square kilometers of land. Compared with China’s coal consumption of 3.6 billion tons, Europe’s total coal combustion is only about 580 million tons, and most of it is used for large power plants with pollutant emission control. Not only is China’s total coal consumption far greater than Europe’s, Many coals are burned in bulk, so China's emissions per square kilometer are much larger than those in Europe. This explains the main reason why there are a lot of cars on both sides, and there is smog in China, which is rare in Europe.
The author believes that the burning of scattered coal is the first culprit of smog. People naturally have to ask, if so, why not change the combustion of bulk coal to natural gas? This direction is correct, but China's total natural gas is not enough. Recently, the price of natural gas in China has fallen, and many people think that there is a surplus of natural gas in China. This is a misunderstanding. China's natural gas is not too much but too expensive (more than twice the US price). From the perspective of environmental protection and the management of smog, very limited natural gas should first be used to transform small and medium boilers, rather than converting coal from large power plants to gas. But even if all of China's natural gas is used for small and medium-sized boiler reconstruction, our natural gas is not enough. It is impossible for us to install desulfurization, denitrification and dedusting devices after each small and medium-sized coal-fired boiler. Therefore, in the foreseeable future, a realistic and feasible method is the classification of coal refining technology called by the author in recent years to develop "coal refining" "Industry, clean coal before supplying it to small and medium-sized boilers; at the same time "coal refining", by-product high-value cleaner oil and gas fuel; at the same time, we must strictly regulate the quality of coal burning in small and medium-sized boilers and formulate other specifications. Control pollution caused by small and medium boilers. As long as large power plants are willing to spend money, it is not surprising that emissions other than CO2 can be reduced to the same or even lower emission levels as natural gas. In recent years, the country has done a lot of work on pollution control in large power plants and it is worthy of recognition. Some companies even make big money to make ultra-clean coal power plants that are cleaner than natural gas power plants. In fact, these ultra-clean emissions of desulfurization, denitrification, and dedusting technologies are all readily available. The key is to see if it is worth the cost to remove the pursuit from 95% to 99% or even higher. The current problem is that on the one hand, small and medium-sized boilers with 100% emissions have no ability to change coal to gas due to the inability of small and medium-sized enterprises and individuals; while large power plants that have installed more than 90% of desulfurization have invested heavily to pursue lower than natural gas Emissions ultra-clean power plant. On the one hand, large state-owned enterprises are pursuing large prices to upgrade large power plants that have installed pollutant control in pursuit of ultra-clean emissions (lower than natural gas power plant emissions). On the one hand, no one has invested in solving the real culprit-small and medium-sized boilers. Controlled "coal refining" technology; so much so that the country has spent a lot of money to upgrade and upgrade large power plants, but the smog control effect is not obvious, because the real culprit of smog is to burn coal, not desulfurization, denitrification and dedusting Big power plant.
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