Investigation Of Multi-Effect Condensing Technology By Using Waste Heat Recovery Of Burned Gas

Energy is the basic driving force of the world development and economic growth, and also is the basis of human survival. Because of a series of characteristic, such as high quality, stable, efficient, safe, non-toxic and low pollution, natural gas becomes the world’s ideal energy. Reasonable and optimized utilization using of the natural gas has important significance in improving China’s energy structure, energy supply safety and the environment. There are two technical means to raise natural gas utilization efficiency—improving the combustion system efficiency and reducing heat loss of exhaust gas. Traditional gas thermal efficiency calculation method does not take into account the latent heat of vaporization contained in the water vapor generated by gas combustion. A large amount of water vapor is discharged directly from the thermal system, and that results in serious waste of energy.Multi-effect condensing technology by using waste heat recovery of burned gas is investigated. Heat losses, condensate and condensate rate are calculated and analyzed by using heat balanced method. The variation of flue gas condensation rate and released heat under different exhaust gas temperature are obtained. That are the flue gas condensation rate decreases with increasing exhaust gas temperature, and the exhaust gas temperature is higher when the reducing rate is faster. When the exhaust gas temperature is above the dew point temperature, the recovery heat of the flue gas is proportional to the exhaust gas temperature, and the recycled heat is increased while the exhaust gas temperature is reduced. When the exhaust gas temperature is below the dew point temperature, the recovery heat increased faster while the exhaust gas temperature is reduced. The inflection point occurs at the dew point temperature. A steam boiler energy-saving technology programs is designed and different forms of heat transfer are used. The reliability and economy of the flue gas use are improved, and it is proved that multi-effect condensing technology by using waste heat recovery of burned gas is feasible. All of that provide a basis for follow-up gas efficiency condensing waste heat recovery technology. The energy saving rate of the gas efficiency condensing waste heat recovery technology is analyzed. Energy-saving rate with different exhaust gas temperature under typical conditions is calculated, and it is pointed out that the technology is fully applicable to the gas hot water boiler heating system and gas steam boiler with a lower boiler feed water temperature. The environmental superiority of multi-effect condensing technology is described from the gas itself, waste heat recovery energy and condensate purification, and the advantages of this technology used in protecting the environment are pointed out.