Non-leakage Gas-gas Heater (GGH)

A wet FGD used at thermal power plants must heat up the exhaust gas after desulfurization in order to :

1. Get better diffusion of the exhaust gas.
2. Prevent the white smokes.
3. Prevent low-temperature corrosion of the duct and chimney.

As a means for meeting above requirements, the after burner method or regenerative gas-gas heater is usually used.
Large amount of fuel is required for reheat in the former method and leakage of untreated dirty gas to treated clean gas can not be avoided in the latter method. In order to resolve these problems, Babcock-Hitachi has developed the heat pipe-based non-leakage gas-gas heater and the heating medium forced circulation gas-gas heater.

The gas-gas heater consists of two heat exchangers - a heat recovery section and reheat section. In the heat recovery section, heat exchange is taken place from boiler flue gas to heating medium first. The heating medium is sent to the reheater section by the heat medium circulation pump. In the reheater section, desulfurized clean gas is heated up by this heating medium to a temperature level required to exit from chimney. The medium is then circulated again to the heat recovery section. As depicted in the right, heat exchanger between the boiler flue gas and desulfurized flue gas takes place indirectly via the medium. This arrangement, therefore, allows you to install the recovery section and reheat section apart.