FLUID-DYNAMIC INVESTIGATIONS IN A COLD MODEL FOR A DUAL FLUIDIZED BED BIOMASS STEAM GASIFICATION PROCESS: OPTIMIZATION OF THE CYCLONE

摘要

Gasification of biomass is an attractive technology for combined heat and power production. Although a great deal of research and development work has been carried out during the past decade the commercial breakthrough for this technology is still not in sight. The optimisation of the operation costs influences significantly the economic efficiency. Especially bed material consumption constitutes a major part of expenses in fluidised bed systems. Thus, cyclones for circulating fluidized beds need to be designed properly. A dual fluidized bed steam gasifier is in commercial operation at the biomass CHP (combined heat and power plant) in Gussing, Austria since 2002. Some erosion and caking in the cyclone of the CHP plant could be observed with increasing hours of operation. The influences of these effects as well as the influence of the solid circulation rate between the two units on the separation efficiency were investigated by fluid-dynamic investigations using a cold model. The results show that due to erosion and caking elutriation rates are increased, especially for smaller particles. However, the cyclone achieves fractional separation efficiencies of more than 99.9%.