Influence of controlled handling of solid inorganic materials and design changes on the product gas quality in dual fluid bed gasification of woody biomass

Abstract

Utilizing biomass feedstock in thermal conversion technologies to reduce greenhouse gas emissions is a promising way to substitute for fossil fuels. Gasification of biomass allows for the production of electricity, district heat, high-grade fuels for transportation and synthetic chemicals. Investigations at the HGA Senden industrial-scale dual fluidized bed gasification power plant have shown the potential for improving gas quality by the controlled handling of solid inorganic materials in the reactor. Two measures for optimization were implemented and investigated on-site. First, improving the bed material and ash loops in the system led to significant reduction of undesirable tars in the product gas. This was based on reutilizing used, layered, olivine particles with higher catalytic activity compared to that of fresh olivine. Second, improving the mixing of feedstock or char particles with catalytically active bed material in the gasification reactor, and also ensuring steam, as reaction medium, was available local to the area of the fuel input, led to further decrease of tars in the product gas. This was achieved by incorporating additional fluidization nozzles in the gasification reactor.In summary, the optimization measures for controlled handling of inorganic materials had a major influence on the product gas quality in the dual fluidized bed gasification of biomass. As a consequence, long-term operation at significantly higher capacity than before could be achieved at the HGA Senden industrial-scale power plant.