Purification of product gas is very important for all applications with the exception of direct combustion after the gasifier. In the case of direct combustion product gas purification must compete with combustion exhaust gas purification. Which gas purification steps are necessary and how efficient they should be dependents on:
- Feedstock (e.g. biomass, waste) and its chemical components
- Gasification technology & operational conditions of the gasifier
- The application & downstream equipment; how clean should the gas be?
In general we can identify the following gas treatment steps, summarised in their most logical order:
- Particulate removal Cyclones, filters, electrostatic filters
- Organic impurities, Tar removal is most important,
- Water removal
- Removal of inorganic impurities such COS, H2S, NH3 & HCN
- Removal of volatile (alkali / heavy) metals For example adsorption on a pre-coat filter
(1)Particulates and (2) tars can be removed by OLGA (see Tar removal), should large amounts of (1)particulates be present in the product gas a gas filter could be the right solution. The (3)water and (4)inorganics can be removed by an aqueous absorption scrubber.
Read more about filtration and scrubbing technology