Boiler flue gas heat energy recovery method

Abstract

The invention relates to a boiler flue gas heat energy recovery method. The method comprises the following steps that flue gas passes through an economizer, and water in the economizer absorbs part offlue gas heat energy to increase the temperature of water going into a boiler; the flue gas passes through an air preheater to heat air in the air preheater and increase the temperature of the air going into the boiler; the flue gas passes through the lower section of a heat exchanger, a heat exchange working medium in the heat exchanger absorbs heat and then flows to the upper section of the heat exchanger, and the upper section of the heat exchanger releases heat to heat condensed water; the temperature of flue gas in a flue and the temperature of a heated wall surface of the heat exchangerare detected to control the temperature of the heated wall surface to be higher than the temperature of an acid dew point. According to the boiler flue gas heat energy recovery method, the temperature of the air at an inlet of the air preheater is heated by absorbing heat of low-temperature flue gas of a tail flue so as to improve the heat efficiency of a boiler system; while reducing the flue gas temperature, the temperature of the low-temperature heated wall surface to be higher than a higher temperature level, and the low-temperature heated wall surface is kept away from the corrosion areaof the acid dew point to avoid the phenomena of condensation corrosion and ash deposition. The maintenance cost of equipment is substantially reduced.

Description

technical field [0001] The invention relates to the technical field of boilers, in particular to a method for recovering boiler flue gas heat energy. Background technique [0002] Boilers are important heat supply equipment in the national economy. It is widely used in electric power, machinery, metallurgy, chemical industry, textile, papermaking, food and other industries, as well as industrial and civil heating, which require boilers to supply a large amount of heat energy. Since fuels such as coal, oil, and natural gas contain sulfur, sulfur oxides are usually produced during combustion, and sulfuric acid vapor is formed when sulfur oxides combine with water vapor. When the temperature of the metal wall on the heating surface at the rear of the boiler is lower than the condensation point of sulfuric acid vapor (called acid dew point), liquid sulfuric acid will form on its surface (called condensation). For a long time, the air preheater, as the tail heating surface, has...

AI Technical Summary

Problems solved by technology

So much so that at present, when designing boilers, it is necessary to increase the exhaust gas temperature to alleviate condensation and corrosion, which does not fundamentally solve the problem

However, increasing the exhaust gas temperature will inevitably cause a lot of waste of low-temperature energy.

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