System for generating low-pressure steam by utilizing flue gas waste heat

Abstract

The invention relates to a system for generating low-pressure steam by utilizing flue gas waste heat, comprising a boiler flue, a flue gas waste heat evaporator and a flue gas waste heat recycling device, wherein the boiler flue is provided with a multi-stage heated surface; the tail-stage heated surface is positioned at the tail part of the boiler flue; the flue gas waste heat evaporator is additionally arranged before the tail-stage heated surface in the boiler flue; the flue gas waste heat recycling device comprises a heat-absorbing section and a heat-release section which are connected; and the heat-absorbing section is additionally arranged behind the tail-stage heated surface in the boiler flue. Due to adoption of the system for generating the low-pressure steam by utilizing the flue gas waste heat, the low-pressure saturated steam is generated by utilizing the high-grade waste heat of flue gas, simultaneously, the heat transfer capacity for utilizing the low-grade waste heat of the flue gas to compensate the tail-stage heated surface of the original boiler system is reduced, and all equipment through which the flue gas flows is guaranteed not to be corroded by acid dew.

Description

technical field [0001] The invention relates to recovery and utilization of waste heat of boiler exhaust smoke, in particular to a system for generating low-pressure steam by using waste heat of flue gas. Background technique [0002] The flue gas discharged from the boiler contains acid gases. When the flue gas temperature is high, they will flow through the heating surfaces of the boiler in gaseous form until they are removed in the desulfurization tower. When the temperature of the flue gas is lower than a certain temperature, they will combine with the water vapor in the flue gas to form sulfuric acid and corrode the heat exchange equipment. Low temperature corrosion typically occurs in the cold end of air preheaters and in economizers where feedwater temperatures are low. When the temperature of the heating surface is lower than the dew point of the flue gas, the sulfuric acid formed by the combination of water vapor in the flue gas and sulfur trioxide (only a small pa...

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Problems solved by technology

[0007] Since the exhaust gas temperature of the boiler mentioned above is usually around 140-160°C, using the above-mentioned heat exchanger to heat the feed water of the boiler can have a good effect, but the process requirements of customers in various industries are different, and many customers These low-grade hot water are not needed and low-pressure steam is needed, but it is difficult to produce low-pressure steam at the above exhaust gas temperature

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