Herding^® dust extraction plants, mainly in the form of Herding ALPHA filters, are used in gasification systems - where wood or biomass is converted directly into energy or further processed into SNG (synthetic natural gas) - in order to protect the downstream gas treatment stages.

The dust extraction plant is required to minimize the dust load in the reactor gas, which leaves the reactor with a temperature of between 350 and 450° C, while simultaneously allowing an operating temperature of over 280° C in order to prevent condensation of the long-chain hydrocarbons (wood tar) in the reactor gas. Poor gas quality leads to short-term failure of the gas engines. The normally used wet gas cleaning method mostly produces unsatisfactory dust extraction results, and the disposal problem adds to the expense.

By contrast, the Herding^® ALPHA filter is a surface-coated candle filter which works by the surface filtration principle.

Special properties of the Herding^® ALPHA filters:

• A high rate of separtion of less than 2 mg/m³ guarantees the necessary quality of gas and protects the downstream units
• The permissible operating temperature of 450° C provides a good safety margin from the dew point of the long-chain hydrocarbons
• Base materials on an inorganic, mineral basis ensure chemical resistance and are non-cumbustible
• Precoating prevents sticky particles (wood tar) from landing directly on the filter surface and leading to agglutination

As the manufacturer of both the filter media and the filter plant, Herding can deliver gas-tight filter units complete with a factory acceptance inspection and test certificate all from a single source. The filters can be cleaned with inert gas.