Although China's air pollution control technology for coal-fired power generation is at the world's leading level, and the three conventional pollutants (soot, SO2, NOx) have achieved the same cleanliness as gas-fired power plants, the future development of thermal power still faces challenges, mainly in the following six aspects.

 

1. Greenhouse gas emissions are huge

 

The CO2 emission of coal-fired power generation unit is about 0.76 ~ 0.92kg / (KWH), while the CO2 emission of gas-fired power generation unit is only 45% ~ 66% of coal-fired power generation. China's coal-fired power generation accounts for 93% of the thermal power generation, resulting in a huge amount of greenhouse gas emissions. Although it is doubtful whether CO2 is a pollutant, China is a staunch supporter of the Paris Agreement and will continue to fulfill its commitment to the international community. Therefore, in the future, on the one hand, China should further reduce coal consumption of coal-fired power generation through technology research and development. For example, China is implementing the "251 project" in Pingshan, Huaibei, Anhui Province (that is, the coal consumption of new coal-fired power generation units is less than 251g / (KWH)), which is higher than the current situation The national average coal consumption of power supply is 310G / (KWH), which is 19% lower, but the CO2 emission per unit of power generation is still about 25% higher than that of gas-fired units. Therefore, China needs to further reduce the coal consumption of power supply and vigorously develop renewable energy to meet the requirements of the Paris Agreement. In addition, it also needs to carry out research and demonstration in CO2 storage and utilization.

 

2. Environmental improvement needs further reduction of air pollutants in thermal power plants

 

In 2017, although the national ambient air quality has been further improved, the heavy pollution weather has been significantly reduced, and the goals set in the air pollution prevention and control action plan have been fully realized. The average annual concentration of PM2.5 in Beijing Tianjin Hebei, Yangtze River Delta and Pearl River Delta has been reduced to 64, 44 and 34 μ g / m3 respectively, but there is still a big gap with the ambient air quality standards set by developed countries and the World Health Organization.

 

The proportion of coal used for power generation (including cogeneration) in China has increased year by year, from 20.6% in 1980 to 51.3% in 2013. The coal consumption for power generation has increased from 126 million tons in 1980 to 2.18 billion tons in 2013. However, the proportion of coal used for power generation is far lower than that in the United States, Germany and other developed countries. In order to further improve the environmental air quality, we should increase the clean utilization of coal and further increase the consumption of coal The proportion of coal used for power generation.

 

According to the current technological development, the International Energy Agency (IEA) has set the emission targets of pollutants from coal-fired power plants in 2020 and 2030. The 2020 targets are: 1 ~ 2mg / m3 of smoke, 25mg / m3 of SO2 and 30mg / m3 of NOx; the 2030 targets are: 1mg / m3 of smoke, 10mg / m3 of SO2 and 10mg / m3 of NOx. At present, some power plants in China have achieved the goal of IEA in 2020, but there is still a gap with the goal of 2030. It can be seen that the control of air pollutants from coal-fired power generation in China still has a long way to go, and we need to continue to make breakthroughs in technology to further reduce the emission of air pollutants from thermal power plants.

 

3. Influence of wet desulfurization on ecological environment

 

According to statistics, the installed capacity of limestone gypsum wet desulfurization in China's thermal power industry accounted for 93% in 2016, and the annual limestone consumption was about 50 million tons, which was equivalent to that 150 limestone mountains with water cubic volume were razed to the ground every year. Limestone mining will have a certain negative impact on the ecological environment. The utilization rate of gypsum, the by-product of limestone gypsum wet desulfurization, is gradually decreasing with the shrinkage of the construction industry. The storage and disposal of waste gypsum will also have a certain negative impact on the ecological environment. Therefore, in the future, we should increase the research and development and demonstration of new technologies and methods of resource-based desulfurization.

 

4. Disposal of hazardous waste from waste denitration catalyst

 

SCR is the main method of flue gas denitration in China's thermal power industry. According to statistics, the installed capacity of SCR in the thermal power industry accounted for more than 95% in 2016, resulting in a large number of waste denitration catalysts, which are hazardous wastes. How to treat and dispose of waste denitration catalysts is a major challenge for the thermal power industry. We should actively develop the recovery of waste denitration catalyst and the research and development of resource utilization technology.

 

5. The control of unconventional pollutants needs new technological breakthroughs

 

In 2017, the average annual concentration of PM2.5 in Beijing Tianjin Hebei region dropped to 64 μ g / m3, and the goal of the air pollution prevention and control action plan was fully completed. The whole country is heartened. However, we must clearly see that there is still a big gap between 64 μ g / m3 and the ambient air quality standard of 35 μ g / m3, and between 64 μ g / m3 and the ambient air quality transition period target 2 (it-2) of 25 μ g / m3 and transition period target 3 of 35 μ g / m3 determined by the World Health Organization (it-3) 15 μ g / m3 and AQG 10 μ g / m3 are more different. With the continuous improvement of people's requirements for ambient air quality, we not only need to control the conventional pollutants in the flue gas of coal-fired power plants, but also need to control the heavy metals such as Hg and its compounds, the condensable particles such as SO3, the dissolved salt particles in the liquid water of wet flue gas, and the recovery and utilization of gaseous water in wet flue gas in environmentally sensitive areas and serious water shortage areas "White plume"). It is necessary to develop unconventional pollutant control technology and carry out engineering demonstration.

 

6. Optimization and energy saving of flue gas treatment facilities

 

The flue gas treatment facility of coal-fired power plant is a complex system engineering. The load fluctuation of boiler and low nitrogen combustion, flue gas denitration, dust removal, desulfurization, deep purification and other devices are independent and interrelated. At present, each device is basically in an independent operation state, and is operated by different professional operators, which does not reflect the connection between the devices. The potential of flue gas treatment facilities has not been fully exploited, especially the energy saving potential. It is necessary to train comprehensive talents for controlling pollutants in flue gas, strengthen the coordination of flue gas treatment facilities in power plants, and optimize the operation and management of flue gas treatment facilities by using Internet, Internet of things, big data and other technical means, so as to achieve a win-win situation of energy conservation and emission reduction.

 

7. Conclusion

 

The emission standard of air pollutants for thermal power plants in China has gone through seven stages of development. The increasingly stringent emission limits continue to promote the progress of treatment technology. At present, the level of flue gas treatment has been leading the world. The emission of conventional pollutants from coal-fired power plants is basically as clean as that from gas-fired power generation, which has made great contributions to the improvement of air quality in China. However, the air pollution of China's thermal power industry is still facing many challenges, and it is necessary to strengthen technology research and development and engineering demonstration in related fields.