Waste heat recovery system, boiler system and waste heat recovery method

Abstract

The invention relates to a waste heat recovery system, a boiler system and a waste heat recovery method. The waste heat recovery system comprises a first heat exchanger and a second heat exchanger which are sequentially arranged in a flue, wherein the first heat exchanger is an air-water heat exchanger made of a common material; the second heat exchanger is an air-water heat exchanger made of a corrosion-resistant material; a plate-type third heat exchanger is arranged between the two heat exchangers; a first heat exchange medium sequentially flows through the second heat exchanger, the third heat exchanger and the first heat exchanger, exchanges heat with the flue gas in the second heat exchanger and the first heat exchanger and exchanges heat with steam introduced into the boiler system in the third heat exchanger; a temperature control module is arranged to control the temperature of a first heat exchange medium in the first heat exchanger to be within a set temperature range slightly higher than the dew point temperature, so that water vapor in the flue gas cannot be condensed on the surface of the first heat exchanger and can be concentrated on the surface of the second heat exchanger; and good corrosion resistance is achieved on the premise of efficient heat exchange, and the overall cost is low.

Description

technical field [0001] The invention relates to a waste heat recovery system, a boiler system and a waste heat recovery method. Background technique [0002] With the continuous deepening of my country's energy-saving and emission-reduction policies, the original coal-fired boilers that provide steam for enterprises or residents are gradually replaced by gas-fired boilers fueled by natural gas. Taking an industrial park as an example, 3 gas-fired boilers can generate 150 steam per hour. tons, its consumption capacity is huge, and the temperature of the exhaust gas after combustion is around 110-150°C. The main component of natural gas is methane CH4. According to its combustion chemical formula: CH4+2O2=CO2+2H2O, 1m 3 After the natural gas is fully burned, the calorific value is about 35.88MJ without considering the condensation. When considering the condensation heat release, because the water vapor will release a lot of heat when it condenses, the calorific value can be as...

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Problems solved by technology

[0005] However, the recovery efficiency of exhaust heat recovery in the prior art is low. If you want to improve the heat exchange efficiency, you need to reduce the temperature of the heat exchange medium, which will cause a large amount of water vapor in the exhaust gas to condense on the surface of the heat exchanger, thereby forming corrosion. The acidic solution will cause serious corrosion and rust on the outer surface of the heat exchanger, and the rusted oxide will also block the passage for the exhaust gas on the heat exchanger, making the ventilation not smooth; and if you want to solve the corrosion The problem will be a huge investment, resulting in poor economy. Considering the cost issue, the steam supply unit is not optimistic about the waste heat recovery system, which seriously limits the promotion of the waste heat recovery system

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