Experimental investigation of char generated from co-pyrolysis of coal and Appalachian hardwoods

Abstract

In recent years, there has been increased interest in the co-combustion and co-gasification of coal and biomass materials in many industrial applications. The primary driving force behind this interest lays in the fact that co-combustion and co-gasification of coal biomass material are viewed to be a more carbon-neutral approach to processes typically used for power generation, as well as generation of syngas and other coal-derived chemicals. With the addition of renewable biomass materials to the coal used in these processes, the net amount of carbon dioxide released to the atmosphere is effectively reduced due to the assumption that replenishment of the biomass via replanting will lead to carbon dioxide removal via photosynthesis.The current study investigates co-pyrolysis of coal and biomass feedstocks, a precursor to the co-combustion or co-gasification reactions when both materials are fed together into the combustor or gasifier. Experiments have been conducted in which different mixtures of typical West Virginia power plant blend coals and Appalachian hardwoods have undergone pyrolysis using a tube furnace. Measurements were made with samples that contained 100% coal, 100% biomass as well as a 50% coal/50% biomass mixture. In addition, two different particle size ranges were used in order to examine the effect of particle size on the resulting pyrolysis products. In each experiment, the coal and biomass mixtures were heated to 500°C in a nitrogen atmosphere. Samples of the resulting solid char were collected and analyzed via ultimate and proximate analysis, and Fourier transform infra-red spectrometry (FT-IR).Numerous authors have debated whether or not the addition of biomass material to coal generates a synergistic, non-linear effect upon the resulting pyrolysis products. The data obtained during the current study suggests that varying the biomass content in the initial feed stock shows linearity with respect to the proximate and ultimate (elemental) analysis results of the produced chars; however, non-linearities can be seen in the tar and char yields, and in the functional group structure of the chars, as revealed by FT-IR analysis of the solid char samples.