Gasification

Gasification is a thermochemical process in which a solid carbonaceous fuel (e.g. coal, biomass, or waste) is converted into a combustible gas called producer gas or syngas (depending on the gas composition) under sub-oxidizing conditions and medium-high temperatures (700-1200°C). The key feature of the gasification process is that the producer gas keeps 70-80% of the chemical energy initially contained in the initial solid fuel. The producer gas, in turn, is a versatile energy carrier which, after proper cleaning and upgrading, can be used in a number of applications: production of heat/power/mechanical energy, or feedstock for synthesis/recovery of fuels and chemicals.

Overview of applications of producer gas from gasification

Since biomass and waste gasification produces a gas with a significant amount of valuable compounds, high-value applications beyond the production of power and heat, e.g. synthesis of biofuels and chemicals, are getting increasing attention.

A low-value application like heat production requires minimal gas cleaning, and as the value of the application increases, so does the level of cleaning and upgrading required for the gas. Co-firing of producer gas in a boiler, as in the case of the Amer 9 power plant, is a relatively simple way of converting biomass for the production of heat and power. If the gas is fed to an engine or a turbine, the degree of gas cleaning (dust removal, tar removal) is higher. An example of this type of application is the Güssing plant in Austria, already in operation for several years. In case the producer gas is used as feedstock for biofuel production, additional gas upgrading besides dust and tar removal (e.g. acid gas removal, adjustment of the H2/CO ratio, compression…) is necessary. An example of this type of application is the recently commissioned GoBiGas plant in Sweden, where biomass is converted to Synthetic Natural Gas (SNG) via gasification. In this case, the green gas product offers the advantages of easy storage, existing infrastructure, and social acceptance.

Ethylene and benzene are the important ones. Although gasification developments at ECN primarily focused on energy production, the co-production of valuable chemicals is becoming more and more a target in itself. Developments therefore originally started with methods to avoid, remove or treat olefins and aromatics to improve energy production, but now are moving to finding ways to increase its yield. Developed energy technologies and process knowledge turn out to be a perfect platform and head start.