Flue gas heat exchanger

I. overview

1. Function of Flue Gas Heat Exchanger

The function of flue gas heat exchanger is to use the original flue gas to heat the net flue gas after desulfurization, so that the exhaust gas temperature can reach above dew point, reduce the corrosion of the net flue and chimney, and improve the diffusion degree of pollutants. At the same time, the flue gas temperature entering the absorption tower is lowered, and the technical requirements for anticorrosion in the tower are reduced.

In the wet desulfurization process system, the flue gas from the boiler induced draft fan (the temperature is generally 120-150 degrees C) passes through the heat exchanger at the inlet flue of the absorption tower before it is washed and desulfurized. The temperature of the flue gas from the heat exchanger drops to about 90-100 degrees C, and then it is washed and desulfurized before entering the absorption tower. Its purpose is: (1) to protect the components and anticorrosive layer in the absorption tower; (2) to make the absorption tower inside. The flue gas reaches the temperature favorable for SO2 absorption. 3. Reduce the evaporation water quantity and water consumption in the absorption tower. The flue gas after scrubbing and desulfurization at the outlet of absorption tower is cooled to 45-55 degrees C. In order to ensure that the flue gas can fully diffuse, reduce the visibility of exhaust smoke, avoid droplets falling from chimneys, and avoid the corrosion caused by condensation of net flue gas during discharge, it is necessary to heat the flue gas to 75-80 degrees C.

There are two types of flue gas heat exchangers: regenerative and non-regenerative. Regenerative flue gas heat exchanger transfers heat from hot ground gas to cold flue gas through heat carrier or heat carrier. The main types of heat exchanger are rotary gas-gas heat exchanger (GGH), water-gas heat exchanger (MGGH) and evaporative tube heat exchanger (heat pipe) non-regenerative flue gas heat exchanger, which heates cold flue gas through steam or natural gas combustion. This heating method has low initial investment, but high power consumption and operation. The cost is large. Here, the regenerative heat exchanger is mainly introduced.