2.1.3.2 OXYGEN-BLOWN GASIFICATION

It is an alternative route for the production of a nitrogen-free product gas. To prevent local hotspots in the reactor, the oxygen is normally diluted with steam or CO2. The methane content drops with increasing steam/O2 and CO2/O2 ratio. The decrease on dry gas basis is mainly caused by the dilution by CO2 or H2 that is produced from steam by the CO shift reaction.

A low steam or CO2/O2 ratio produces a product gas with the highest CH4 content, which is desired for synthetic natural gas (SNG) production. A low amount of CO2 or steam also increases the gasifier efficiency, because less "inert" gas needs to be heated to the process temperature. A certain amount of oxygen dilution is required to prevent possible agglomera­tion of biomass (http://www. biosng. com/experimental-line-up/o2-blown-gasification/).