A deep recovery device for boiler flue gas waste heat

Abstract

The invention relates to a boiler flue gas waste heat deep recovery device, which is characterized in that the device comprises a boiler, a steam-water heat exchanger, a water-water heat exchanger and an N-level flue gas-air total heat heat exchange unit, each The flue gas-air total heat exchange unit of each stage includes a flue gas-water heat exchanger and an air-water heat exchanger, wherein, N≥2; A flue gas-water heat exchanger provided with N-1 liquid distributors and an air-water heat exchanger provided with N-1 water receiving trays, compared with the existing flue gas waste heat recovery device, the temperature The flue gas and the air of the same grade carry out full heat exchange respectively. By adjusting the spray water volume at all levels, the temperature of the flue gas outlet can be reduced to the lowest level, and the temperature of the air outlet can be raised to the highest level to achieve the state of flow matching, which solves the problem of water vapor saturation. The problem of linear nonlinearity, etc., significantly improves the total heat exchange efficiency between flue gas and air, and can be widely used in boiler flue gas waste heat recovery devices.

Description

technical field [0001] The invention relates to a deep recovery device for boiler flue gas waste heat, in particular to a boiler flue gas waste heat deep recovery device for recycling boiler flue gas waste heat and reducing nitrogen oxide emissions, belonging to the technical field of energy. Background technique [0002] Natural gas, oil, biomass and other fuels contain a large amount of hydrogen, and boiler combustion produces a large amount of water vapor, such as 1m 3 The combustion of natural gas will generate 1.55kg of water vapor, and the latent heat is about 3600kJ, accounting for 10% of the low-level calorific value of natural gas, but this part of the heat is often directly discharged into the atmosphere with the flue gas, causing waste of flue gas waste heat. Therefore, if the temperature of the flue gas can be lowered below the dew point and the part of the latent heat can be recovered, it will play an important role in saving fuel consumption. On the other hand,...

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Problems solved by technology

In order to improve the above-mentioned heating device, the prior art discloses a centralized heating system that utilizes an absorption heat pump to recover waste heat from flue gas, and uses a flue gas-water direct contact heat exchanger to replace the dividing wall condensing heat exchanger to solve the problem of The corrosion problem of the metal heat exchange surface is solved; the existing technology discloses a heating system that uses a compression heat pump to realize the deep recovery of boiler waste heat, and gradually reduces the exhaust gas temperature of the boiler through three-stage heat exchange. To cool down the high-temperature flue gas and avoid the flue gas dew point area, the second-stage partition wall heat exchanger adopts resin material or heat pipe, and the third-stage heat exchanger adopts a combination of direct type and partition type, so as to realize the deep recovery of flue gas and solve the problem. Corrosion of metal heat exchange surfaces, however, both of these methods are based on heat pump equipment, the device structure is complex, the equipment is bulky and the cost is high

The prior art discloses a condensing boiler flue gas waste heat recovery device. A flue gas packing heat exchange tower and an air packing heat exchange tower are installed at the flue gas outlet of the condensing boiler. The boiler flue gas enters the flue gas packing heat exchange tower to cool down and dehumidify and discharge. The air is heated and humidified by the air-filled heat exchange tower and then enters the burner for combustion support. The hot water in the flue gas-filled heat exchange tower enters the air-filled heat exchange tower to exchange heat with the air, and then returns to the flue gas dryer to exchange heat with the flue gas. The air humidification can Improve the dew point of boiler flue gas, and at the same time reduce the combustion temperature and reduce NO x However, due to the nonlinear physical properties of the water vapor temperature and the corresponding saturated vapor pressure, the air temperature and humidity cannot be significantly increased, and the exhaust gas temperature is limited.

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