Waste heat recovery system of flue gas in power plant and recovery method thereof

Abstract

The invention relates to a waste heat recovery system of flue gas in a power plant and a recovery method thereof by using working medium phase-change technology. The system comprises a first flue gasheat exchanger for the heat exchange between a working medium and flue gas, a second flue gas heat exchanger for the heat exchange between the working medium and the flue gas, a condensed water heat exchanger, a heat network water heat exchanger and a liquid storage tank; and the recovery method using the recovery system adapts a heat exchange mode of working medium phase-change to absorb heat ofthe flue gas, at the same time of reducing the temperature of the flue gas, the heat is transferred to the heat network water in winter and the condensed water of a boiler unit in non-winter, the recovery method comprises three phase change heat transfer processes of heating generation, evaporation and condensation of the working medium, and according to the use of the working medium condensationheat, the method can be divided into two categories of " the boiler unit condensed water temperature rise " and " for winter heating ".

Description

technical field [0001] The invention relates to the field of waste heat treatment of flue gas in a power plant, and relates to a waste heat recovery system and recovery method for the flue gas in a power plant by using the phase change technology of working medium. Background technique [0002] Water-cooled low-temperature economizer technology has been widely used in the waste heat recovery process of flue gas in thermal power plants. However, after long-term operation, many problems appeared, and the main adverse effects include: [0003] ①. The water-cooled method mainly relies on the sensible heat of water, so the temperature rise of water directly affects the area of ​​heat exchanger and the amount of circulating water, and also affects the shape of water pipes and circulating pumps; [0004] ②. The dew point caused by the water-cooled heat exchanger in the low-temperature section causes serious compaction on the surface of the heat exchanger, which directly affects th...

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Problems solved by technology

[0003] ①. The water-cooling method mainly relies on the sensible heat of water, so the temperature rise of water directly affects the area of ​​heat exchanger and the amount of circulating water, and also affects the shape of water pipes and circulating pumps;

[0004] ②. The dew point caused by the water-cooled heat exchanger in the low-temperature section causes serious compaction on the surface of the heat exchanger, which directly affects the normal operation of the boiler and causes a decrease in power generation;

[0005] ③. The one-way fluid heat transfer coefficient of the water-cooled heat exchanger is low, especially the increase of internal scale, which leads to the decline of the heat transfer performance of the heat exchanger year by year;

[0006] ④. The heat transfer coefficient of the water-cooled heat exchanger is generally 30-40W / m 2 K, leading to high cost of heat exchanger and water circulation system

[0007] ⑤. The water-cooled method has poor adjustment ability and is difficult to adapt to the influence of boiler operation and coal type change factors

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