As China's energy production for a long time to coal-based, coal-based power is also, so coal-fired power plant air pollution control has always been the focus of national requirements. Since reform and opening up, China's coal-fired power generation developed rapidly, compared with 1980, thermal power generation in 2015 increased by 16.5 times, coal consumption increased by 14.7 times, about 50% of coal for power generation.

China's coal-fired power plant air pollutant control is carried out in stages, which is also similar to the control process in developed countries. First, the high chimney diffusion to solve environmental pollution problems, and gradually through the installation of pollution control equipment to improve the efficiency of pollutant removal to reduce particulate matter in the flue gas, sulfur dioxide, nitrogen oxides emissions. According to the China Electricity Council, the power particulate matter (soot) emissions from 1980 to about 400 million tons per year (peak), down to 2015, 400,000 tons, down 90%; sulfur dioxide emissions from 2006 Of the total emissions of about 13.5 million tons in 2015 fell to about 2 million tons, down 85%, compared with 2.80 million tons in 1980 decreased by 18%; nitrogen oxide emissions from 2011 to about 10 million tons peak in 2015 Of the 1.8 million tons, down 82%. From the sum of the three pollutants, the peak period between 2006 and 2010 is about 80% lower than that of about 27 million tons, which is about 50% lower than the sum of 1980 emissions.

As the pollutants are the culprit of the formation of haze, from the above data, that power in recent years, haze formation and aggravation of the reasons is untenable. In addition to the large-scale use of combined heat and power generation units, pollution control technology has greatly improved, replacing a large number of urban heating boilers, improve the efficiency of coal use, greatly reducing the pollutant emissions, haze played an important role in governance.

An increase in flue gas humidity does not increase pollutant emissions

As China's "thermal power plant air pollutant emission standards" for the world's most stringent, and China's coal quality is relatively poor, require a higher level of pollution control technology to support. Over the past few decades, China's thermal power plant air pollutant control is mainly in the introduction of international advanced dust, desulfurization, denitrification technology based on digestion, absorption, re-innovation developed, of course, completely independent intellectual property rights of environmental technology, the overall point of view in the world Advanced level.

The efficiency of a specific unit's pollutant treatment facilities is determined by emission limits and environmental impact assessments, and the specific choice of technology is also subject to environmental, technical and economic feasibility studies. Generally speaking, the overall efficiency of flue gas denitrification is about 80% ~ 90%, the dust removal efficiency is above 99.9%, and the desulphurization efficiency is generally over 95% when using low NOx in the boiler combustion stage.

The size of pollutant emission is the core of environmental pollution control and environmental impact. Of course, the temperature and humidity of flue gas discharged from the chimney are also the necessary factors to consider the impact on the environmental quality. China's environmental impact assessment of coal-fired power plants actually began in the mid-80s of last century, especially 90 years after the implementation of environmental impact assessment of power plants almost 100 percent. Environmental impact assessment of each power plant will be the impact on the quality of atmospheric environment as a top priority. It is necessary to consider the influence of flue gas lift and air quality after diffusion. This is the basic content of atmospheric environmental assessment and the basic basis for environmental protection department to approve pollution prevention and control measures. Flue gas temperature is considered the core parameters of pollutant dispersion, in fact, the atmospheric environment assessment not only the flue gas temperature has been considered, the height of the coal-fired power plant chimney and so put forward specific requirements. The relatively little consideration is given to the humidity of the flue gas, mainly because there is not much need. After adopting the strict pollution control measures, the pollutant emission is greatly reduced, and the diffusion method meets the environmental quality requirements. Heating does not heat the flue gas only affects the diffusion of pollutants on a fixed point concentration changes and concentrations of contour changes in range, popular speaking, flue gas heating after lifting high, from the chimney around 2 to 5 km Of the local concentration of pollutants lower, but the impact of a large range, the situation is not the opposite of the gas is not heated. But for the PM2.5 this large-scale impact of environmental problems, the impact of flue gas heating or not negligible.

After the desulfurization does not heat the wet fog will increase the haze of the argument is wrong

First, the desulfurization desulfurization tower desulfurization chemical reaction is the absorption - redox reaction, rather than "adsorption and collection", adsorption and collection of physical methods such as activated carbon and other dry desulfurization process.

Moreover, after the wet desulfurization of flue gas to go through a very important equipment to remove water droplets and droplets - after the defogger into the chimney. After passing through the demister, the flue gas is saturated (for water) or slightly supersaturated flue gas, the water in the flue gas is mainly gaseous water and, of course, water mist. The so-called flue gas heating, whether using GGH or other means of heating are saturated after the desulfurization of flue gas heating. If heated, saturated flue gas discharged into the chimney, the discharge of flue gas - "white smoke" reduced, even in high temperature can not see the smoke, but the flue gas water content has not decreased, still Is discharged to the air.

While no heating of the flue gas, due to further cooling when the chimney, at this time, part of the water vapor and water is condensed into the water flow to the bottom of the chimney recycling, discharge of smoke in the chimney - "white smoke" is still obvious, but The total amount of water brought into the air by the flue gas is reduced. Therefore, regardless of the heating or not, no increase in pollutant emissions, not heated due to a part of the condensed water containing particulate matter, particulate matter discharged into the air but decreased.

Second, the standard for the exhaust gas temperature is mainly Germany, the last century, Germany in the large-scale combustion equipment regulations on the exhaust temperature of not less than 72 degrees Celsius requirements, but there is no temperature requirements for the emission of flue gas through the cooling tower, and Cooling tower displacement is much greater than the chimney, so later some of the German power plant using the cooling gas into the cooling tower of the way, that is, smoke tower in one technology. Smoke tower-in-one technology in China has a large unit in the application. Germany in the later implementation of the EU's unified emission standards, there will be no flue gas temperature requirements. And then the United States after the majority of wet flue gas desulfurization is not heated, the reason why China is not heating emissions to a large extent is to absorb the experience of the United States.

The removal of corrosion by heating is practically ineffective unless heated to above the acid dew point (above about 110 ° C) because the acid dew point of the sulfur trioxide is about 100 ° C or so and the effect of heating to 72 or 80 ° C is limited, Corrosion point has changed. Moreover, the flue gas heating is mainly used to solve the "white smoke" perception problems and the residents in the vicinity of the plant to solve the "chimney rain" problem, so the heating or not depends on the surrounding environment. Even if the flue gas is heated to 80 or even 100 degrees Celsius, the ambient temperature is below 10 degrees Celsius, or can see the obvious white plume, and not heating discharge almost.

Another point needs to be explained, under normal circumstances in addition to using GGH heating increases, the failure to increase, the rotary GGH air leakage, no desulfurization of flue gas in the hot and cold flue gas between the formation of short-circuit, there will be tens of per cubic meter Milligrams to hundreds of milligrams of direct emissions of sulfur dioxide, a direct impact on desulfurization efficiency.

It should be further explained that the study confirmed that the air humidity (water and more) to promote the formation of haze, so I also wrote a letter to the Beijing Municipal Government to remove the measures to control the water spray haze adopted (of course more important is that recycled water contains large Of the soluble salts, the drying and the formation of new particles), but the size of air humidity is mainly determined by natural factors, from the water vapor on the role of haze formation, wet power plant emissions of water and air compared to water It can be ignored.

Power industry in the management of haze made great contributions

In the EIA approval, the power plant chimney height is clearly defined. In the design specifications, the height of the chimney of coal-fired power plants is bound by various conditions, such as not less than 2.5 times the surrounding buildings, etc., China's coal-fired power plant chimney height is generally 240 meters, 210 meters, some projects to take desulfurization denitrification after the chimney Height has been reduced, but generally more than 210 meters.

On the issue of ammonia escape. SCR process denitrification, there are indeed ammonia escape, especially ultra-low emissions, due to increase the amount of ammonia reducing agent, ammonia escape problem is more serious, which is denitrification process, equipment selection and facilities construction difficulties, but not solved problem. The ammonia escape problem is mainly due to the excess of ammonia after denitrification or reaction with pollutants in the flue gas to form salts adhering to the downstream equipment, such as the formation of ammonium salt on the air pre-impact. So in accordance with the requirements of denitrification ammonia escape concentration is generally controlled at 3ppm or less. Long-term excessive ammonia escape is not sustainable for the pollution control system, because denitrification, dust removal, desulphurization and other equipment in series in the flue gas system, any one of the equipment a big problem, then the whole system will outage. For the short-term and a small amount of ammonia into the downstream equipment, because there are follow-up dust removal and desulphurization facilities, ammonia has a high efficiency of synergistic removal, so through the chimney emissions of ammonia is rarely, should not be a significant impact on environmental quality problem.

All human activities in production and practice are subjective to avoid disadvantages, try to increase the positive effect, reduce the negative effect. Although we still have some problems in the pollution control regulations, policies, technology and management, these problems can not erase the great achievements made by the power industry in air pollution control.

If we must evaluate the effects of desulphurization and denitrification on the control of haze and the side effects of the positive role, I think it should be 99 to 1 problem, that 99 results are overwhelming, a side effect will increase the haze, which may increase some difficult Removal of aerosol emissions, but this increase is minimal, the environmental quality of PM2.5 the impact of the ratio is almost negligible.

Electricity air pollution control is still a long way to go

In spite of the great achievements made in the control of pollution discharge, pollution control still has a long way to go. On the one hand, the current pollution control technology, process and equipment selection, construction and operation still have a lot of problems, such as lean coal, anthracite nitrogen oxide control problem, sulfur dioxide because of denitration catalyst selection problem is too much catalysis for sulfur trioxide, And then increase the downstream equipment failure and emissions of aerosol in the flue gas problem, the system energy consumption is too high, the effect of poor defogger and other issues; the other hand, the peak load increase due to coal-fired power plant at rated load The operation time is reduced, the low-load operation and the start-up frequency of the unit increase, which will affect the stable operation of the flue gas treatment system, especially when the flue gas temperature is low and the denitration catalyst can not work normally. There are some continuous monitoring system of flue gas methods, equipment, operation, data transmission problems. Some of these problems are new found in the application of ultra-low-emission technology, some of the characteristics of the original technology itself or a worldwide problem. These issues on the power companies, environmental protection industry and environmental regulation have raised new challenges, need to work together to gradually resolve. In general, these problems are at the level of high pollution control, the problem of excellence, environmental protection is a higher goal of the problem, but also the need to innovate and solve problems, but can not these problems and low pollution control Level or even no pollution control problems confused.

For power companies and industries, the current environmental protection in accordance with national requirements, strict self-discipline, continue to improve the reliability of environmental protection facilities, a comprehensive standard discharge. The environmental protection department shall further improve the discharge standard of pollutants according to the development of technology, the change of the role of coal power in the transformation of power industry and the change of running status and the need of environmental supervision and reform. The environmental protection industry shall, in accordance with the requirements of laws and regulations, adhere to scientific innovation and continuously improve the technical level, reliability and economy of pollution control facilities so as to minimize the generation of secondary pollution.