References

Staged gasification: clean fuel through innovative coupling of existing thermochemical conversion systems, E. Leijenhorst, L. van de Beld, 17th European biomass conference and exhibition, 29 june – 3 july, 2009, pp. 847-854.

Entrained flow gasification of bio-oil for synthesis gas, R.H. Venderbosch, L. van de Beld, W. Prins, European Bio-energy conference, Amsterdam, June 17-21, 2002

Preliminary techno-economic analysis of large-scale synthesis gas manufacturing from imported biomass, Pyrolysis and gasification of Biomass and Waste, HP Calis, JP Haan, H Boerrigter, A Van der Drift, G Peppink, R Van den Broek, A Faaij, RH Venderbosch, 2002, Strasbourg, France, 403-418

Contact

For more information please contact Bert van de Beld.

Contact office@btgworld.com

Contact +31 (0)53 486 1186

Staged gasification

In BTG’s two-stage gasification process, biomass and residues are converted at low temperature in an organic vapour, and subsequently the vapour is catalytically reformed into a clean fuel gas. The low temperature stage is to a large extent based on BTG’s pyrolysis process (see fast pyrolysis). In the gasification stage a catalyst can be applied.

Staged gasification

Background

Biomass gasification systems are investigated and developed for a long period with some emphasis on tar and tar reduction. The presence of tar in the fuel gas hampers troublefree operation of prime movers. Additionally, it would be a significant advantage if systems can convert a wide range of possible feedstocks, i.e multi-fuel systems. Worldwide, huge amounts of biomass residues and waste streams are available like e.g. agricultural residues. Typically, these streams have a low bulk density and contain significant amounts of minerals. When used in conventional systems these minerals may cause ash melting problems or result in high emissions. For example, the gas phase concentrations of K and Cl significantly increase at temperatures above 700 °C .

In BTG’s two-stage gasification process biomass is “vaporized” at low temperatures, and in the second stage the vapours are reformed. In the second stage a catalyst may be applied. Typical features of the system are:

Staged gasification

  • Organic vapours do not contain minerals (i.e. catalyst poisons) and the use of catalysts becomes feasible;
  • Reforming of a vapor is much easier to control than gasification of solids;
  • Ammonia originating from fuel nitrogen will be converted to nitrogen and hydrogen in case a Ni catalyst is applied;
  • Due to the low temperature in the pyrolysis stage a high fuel flexibility is achieved
  • To some extend the system is self controlling with respect to the water content of the feedstock without affecting the gas quality of the fuel gas.

The charcoal produced in the pyrolysis stage is used to preheat the biomass and to evaporate the water. Charcoal is not used in the high temperature reforming stage. Minerals will not reach a high temperature in the process. Due to the application of a fast pyrolysis stage, the amount of charcoal is limited.

Staged gasification

Process Description

Biomass is fed to the fast pyrolysis reactor, where organic vapours are produced. Whereas in the pyrolysis process the vapours are condensed, in the two-stage gasifier the vapours are reformed into a clean fuel gas. In the top section of the ‘gasifier’ the vapours are mixed with (preheated) air to increase the temperature to 800 – 950 °C. The bottom part can be filled with a reforming catalyst to convert remaining tar and ammonia. In the last stage the gas is cooled to ambient. An overall, cold-gas efficiency in the range of 65-80% is expected.

Staged gasification

Process Description Biomass is fed to the fast pyrolysis reactor, where organic vapours are produced. Whereas in the pyrolysis process the vapours are condensed, in the two-stage gasifier the vapours are reformed into a clean fuel gas. In the top section of the ‘gasifier’ the vapours are mixed with (preheated) air to increase the temperature to 800 – 950 °C. The bottom part can be filled with a reforming catalyst to convert remaining tar and ammonia. In the last stage the gas is cooled to ambient. An overall, cold-gas efficiency in the range of 65-80% is expected.