Background: Simple water vapor can evaporate and rise into the atmosphere, and simple dust pollution can also fall to the ground. The desulfurized wet smoke is mixed with various polluting particles, resulting in water vapor not rising and pollutants not falling., floating about 3000 meters away from the ground, accumulating into smog. Taking the "GB 28662-2012 Emission Standards for Air Pollutants in the Steel Sintering and Pellet Industry" as an example, it requires that after 2015, NOx<200 mg, SO2<200 mg, particulate matter <50 mg, and a chimney with a smoke volume of 1 million m³/h. Based on the annual working time of 7000 hours, the total amount of solid particulate matter discharged into the air in a year is about 3850 tons and water vapor is about 600,000 tons. Countless chimneys across the country add up, and the data is amazing. At present, 99% of coal-fired boilers in my country have been desulfurized, and more than 90% of them use wet methods. Putting aside the issues of investment and operating costs, even if all coal-fired boilers in my country reach ultra-low emission levels, they cannot completely solve atmospheric smog pollution. The reason is that the humidity of the emitted flue gas is not controlled, which is precisely the root cause of smog. It can effectively solve the problem of dehumidification and bleaching of flue gas for wet desulfurization. It can not only eradicate haze pollution, but also achieve environmental protection standards at low cost, ultra-low near-zero emissions, and improve coal combustion efficiency, especially the recovery of moisture and waste heat in flue gas., can take into account the contradiction between environment and development.  

 Summary of the results: After wet desulfurization, a large number of "colored smoke plumes" appear at the exit of the chimney. The wet smoke not only contains a large amount of water, but also contains more soluble salts. These salts are discharged into the atmospheric environment, resulting in the atmosphere. The concentration of PM2.5 has increased significantly. This technology adds a media smoke-flue gas heat exchange system (MGGH) in front of the chimney entrance to dehumidify, desalinate and remove white gas, thereby achieving the goal of ultra-clean emission of PM2.5. This achievement applied for a national invention patent: a method for ultra-low emission of PM2.5 from combustion sources and integrated coupling technology (Patent Application No.: 201710370216.0, published).

 Technical advantages: 1. No leakage: The cooling side and heating side of GGH are completely separated, and there is no leakage of flue gas and fly ash between hot flue gas and cold flue gas, which is inevitable in rotary heat exchangers. Therefore,MGGH never affects the SO2 and fly ash removal efficiency of the FGD system.

2. Optimization design: The design of the cooling side and heating side of GGH can well adapt to various flue gas conditions. It has good economy and reliability.

3. Flexible layout: The cooling side and heating side of GGH are different from rotary heat exchangers, and there is no need to arrange the two adjacent to each other. In contrast, it has the advantages of easy layout and reducing the cost of the flue.

4. Control heat: Adjust heat by controlling the flow of circulating hot coal water, and keep the flue temperature higher than the acid dew point temperature to prevent SO2 corrosion.

5. High reliability: Rotary heat exchangers can easily cause dust deposition and fouling due to fluctuations in flue gas temperature and moisture, while MGGH does not have this problem, because it can reduce the fluctuations in flue gas temperature and moisture by controlling the circulation flow and temperature of hot coal water.

6. Variable heat medium: Water can be used as heat medium, others, such as organic liquids, can be used under special circumstances.