The Gas Gas Heater in a flue gas desulphurisation (FGD) system, used to remove sulphur dioxide from the flue gases, is a lower temperature version of the rotary regenerative heat exchanger.
Capital investment. There had been a tendency for FGD plants to be constructed without a gas gas heater to reduce capital investment. The environmental considerations of a visible wet plume with insufficient buoyancy, coupled to the considerable additional maintenance costs on the wet stack, have reversed this trend.
Low leakage level without drift. Most new gas gas heaters can achieve leakage levels that are close to their design values after initial commissioning or when set up correctly after an outage. However, after a period of operation of up to 2 or 3 years, the leakage can increase, causing increased SOx emissions. The Howden VN sealing concept maintains low design leakage between outages. Active sealing, (purge and scavenge) systems provide extremely low leakage levels.
Extensive choice of heat transfer elements. Howden have designed and developed an extensive range of heat transfer elements over the years including profiles which are amenable to vitreous enamelling. Elements are selected to optimise performance, pressure drop and cleanability.
Low maintenance. Conceptual and detailed design targets the achievement of simplicity and minimal maintenance. Fixed sealing surfaces and centre drive greatly reduces maintenance by removing actuators and pin racks.
High availability. The major cause of reduced availability in gas gas heaters is due to element fouling. Careful element selection to suit the application and the application of the correct cleaning system maintains very high availability.
Centre column or bottom girder support. Custom designed and optimised to suit arrangement and client preference.