Gas-fired boiler flue gas latent heat recycling system

Abstract

The invention provides a gas-fired boiler flue gas latent heat recycling system. Flue gas of a gas-fired boiler body enters a flue gas / circulating water contact tower, the flue gas in the flue gas / circulating water contact tower and circulating water in a circulating water subsystem make direct countercurrent contact for heat exchange, gas-fired boiler flue gas latent heat recycling is achieved, the high-temperature part of latent heat recycled from the flue gas is used for heating boiler feed water, and the low-temperature part of the latent heat is used for heating and humidifying combustion air and fuel gas, so that emission of combustion NOx is reduced. According to the gas-fired boiler flue gas latent heat recycling system, the flue gas and the circulating water make direct contact for heat exchange in the flue gas / circulating water contact tower, the heat exchange area is greatly decreased, the cost is reduced, and meanwhile the acid corrosion problem of a heat exchanger is avoided; by adopting a multi-segment heat exchange mode, the purpose that multiple segments of towers make direct contact with one another for heat exchange on the basis of different water-gas ratios is achieved, therefore, heat release of the flue gas latent heat and heat absorption of the circulating water are matched with each other and combined with air and fuel heating and humidifying, the flue gas latent heat recycling rate is significantly increased, and the flue gas latent heat can be recycled to the maximum extent.

Description

technical field [0001] The invention relates to recovery and utilization of flue gas low-temperature waste heat and NO x The technical field of emission reduction, in particular, a gas boiler flue gas latent heat recovery and utilization system. Background technique [0002] my country has a large number of boilers that burn gas (natural gas, etc.), liquid and other hydrocarbon fuels to generate hot water / steam, providing heat for industry and life. The flue gas of hydrocarbon fuel combustion contains a large amount of water vapor, which is discharged with the flue gas, causing a large amount of energy and water loss. The flue gas burned by gas-fired boilers contains a large amount of water vapor, and the water vapor will release a large amount of latent heat during the condensation process. For example, the dew point temperature of the flue gas from pure methane combustion is close to 60°C, that is, starting from about 60°C, the flue gas continues to cool down, then The w...

AI Technical Summary

Problems solved by technology

The conventional latent heat recovery method is to use feed water and wet flue gas to exchange heat through a partition wall heat exchanger to reduce the exhaust gas temperature. This method has been widely used, but its disadvantages are that the heat exchange area of ​​the heat exchanger is large, In addition, the heat exchanger needs to withstand the corrosiveness of the flue gas condensate, and the cost is high; on the other hand, the maximum heat recovery is limited by the feed water temperature, and the exhaust gas temperature cannot be lowered below the feed water temperature. When the feed water temperature is high , the latent heat recovery rate is low

Aiming at the problem of high feed water temperature and low heat recovery rate, people have developed a method of combining latent heat recovery of flue gas with absorption or compression heat pump. The disadvantage of this method is that the cost of the heat pump and the operation are relatively high.

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