In response to the current "coal to gas" after the gas boiler high cost, operating loss status quo, Langfang Jin Sheng Energy Conservation Technology Services Limited (hereinafter referred to as Jin Sheng Energy) joint scientific research institutions launched a gas boiler exhaust heat depth technology. The application of the technology shows that the exhaust gas temperature can be reduced below 30 ℃, and some can even reach about 15 ℃, which can greatly improve the energy efficiency of the boiler system. Unit heating area of ​​natural gas consumption reduced by 10% -25%, heating capacity can be increased by 25% or more, reducing the direct heat required equipment, direct investment, economic and environmental benefits significantly. It is understood that the main component of natural gas is methane (CH4), the flue gas emitted after combustion contains a large amount of water vapor, the vaporization latent heat of water vapor accounts for 10% -11% of the low calorific value of natural gas, at present basically no Utilize and discharge directly to the environment. In addition, the water vapor in natural gas flue gas is condensed into the atmosphere, resulting in white smoke, landscape pollution and PM2.5 emission index increase. Therefore, deep recovery of waste heat, including water vapor, is important for saving energy and reducing pollutant emissions. In order to make full use of the waste heat from the flue gas of the boiler, Jin Sheng Energy Conservation Co., Ltd., in light of the waste heat recovery technology of flue gas from gas boilers, has jointly developed and applied to the deep utilization of flue gas in gas boilers and conducted anti-corrosion and anti-corrosion on the heat exchanger materials Dirt treatment avoids material corrosion problems after the exhaust gas temperature is lowered. The test results of a 29MW gas boiler for deep recovery of flue gas show that the flue gas temperature can be reduced to 25 ℃, the average recovery of flue gas heat is about 3 MW in the heating period, and the average heating efficiency of the gas boiler is increased by 13.5% . NOx reduction rate of 12% or more. Measured amount of water condensation 3.5t / h, to eliminate the effect of white smoke. The experts concluded that the technology has the feasibility of large-scale application, effectively solve the problem of high heat backwater temperature and the difficulty of direct recovery of flue gas condensation heat.