Gas-gas Heaters
The Howden rotary regenerative heat exchanger is widely used as a gas-gas heater in wet flue gas desulphurization processes. Prudent selection of materials, together with advanced design features, result in a heat exchanger with high performance and exceptional resistance to the cool moist conditions of flue gas desulphurization (FGD) plant, where fouling and corrosion are a constant challenge.
Our design of gas-gas heater (
GGH
) incorporates fixed “VN” sealing. This ensures that there is no leakage drift on the GGH over an extended period of operation and, hence, no corresponding increase in the
SO2 levels to the stack. If such leakage drift did occur, the
FGD system would have to work progressively harder to achieve the required SO2 removal efficiency.
The thermal performance of GGHs is critical, as the reheated gas outlet temperature must be kept above the minimum specified value to achieve adequate flue gas buoyancy and ensure plume dispersion.
Extensive site tests have confirmed the high thermal performance and sealing of our GGHs. We have developed efficient, fully retractable, combined cleaning devices, with the facility for normal sootblowing and both high and low pressure water washing, in order to maintain low-pressure drop. With these devices we can offer 'on-load' maintenance capabilities that are essential to maintaining GGH availability over extended operation.
The element profiles used for gas-gas heater applications are chosen to combine thermal and pressure drop performance with easy cleaning. They have been proven over many years of operation in a large number of GGH installations.
We use specially developed enamel coatings to protect the elements from corrosion and utilize the Howden SurePack
® Elements packing system to ensure that they remain tightly packed during operation and cleaning.