Comparative Study on Red Mud Gasification of Coal/Biomass Mixtures

Comparative Study on Red Mud Gasification of Coal/Biomass Mixtures

O. Hietsoi, C. G. Nyendu, F. Battaglia,* and F. A. Agblevor

USTAR Bioenergy Center, Department of Biological Engineering, Utah State University, Logan, UT 84322

*Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

Abstract

Coal is one of the major sources of fossil fuels used for power generation in the USA. Being one of the most polluting of all fuels, its annual use significantly contributes to environmental pollution and greenhouse gas emissions. Therefore, coal gasification is an alternative to mitigate pollutant emissions. Syngas produced from coal gasification can be used for electricity generation, chemical feedstocks, or for production of synthetic natural gas. Moreover, blending coal with biomass allows to control the hydrogen to carbon monoxide ratio, which is critical in converting syngas into transportation fuels such as gasoline and diesel by the Fischer-Tropsch process. Herein, in this work, mixtures of sub-bituminous coal and biomass feedstocks were gasified at atmospheric pressure in a bubbling fluidized bed reactor at 700—900 °C on sand and red mud. Three types of biomass were used, mainly corn stover, switchgrass, and poplar. It was shown that gasification of coal improved with increase in temperature and addition of biomass feedstock. De-fluidization of the reactor bed was observed during coal/corn stover gasification on sand at 900 °C due to formation of clinker-like material. Notably, gasification using the red mud improved gasification of the mixture compared to the baseline. The addition of biomass to the coal appeared to suppress the production of hydrogen but carbon monoxide yield increased. Additionally, the effect of dry coal/biomass gasification on red mud has been investigated.