The abundance of natural gas and biomass in the U.S. was the motivation to investigate the effect of adding methane to catalytic nonoxidative high-temperature biomass gasification. The catalyst used in this study was Fe− Mo/ZSM-5. Methane concentration was varied from 5 to 15 vol %, and the reaction was performed at 850 and 950 °C. While biomass gasification without methane on the same catalysts produced ∼60 mol % methane in the total gas yield, methane addition had a strong effect on the biomass gasification, with more than 80 mol % hydrogen in the product gas. This indicates that the reverse steam methane reformation (SMR) reaction is favored in the absence of additional methane in the gas feed as the formation of H 2 and CO shifts the equilibrium to the left. Results showed that 5 mol % additional methane in the feed gas allowed for SMR due to formation of steam adsorbates from oxygen in the functional groups of aromatic lignin being liberated on the oxophilic transition metals like Mo and Fe. This oxygen was then available for the SMR reaction with methane to form H 2 , CO, and CO 2 . This study was not a detailed catalytic activity evaluation, but it was exploratory research to ascertain the synergy presented in the co-gasification of biomass and natural gas.

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The production of synthetic gas (syngas) from renewable or carbon-neutral sources can significantly reduce greenhouse and other emissions associated with conventional fuels. One of the most promising technologies to efficiently convert carbonaceous feedstocks such as biomass, coal, or municipal waste into syngas for transportation, power, heat, electricity generation, and or production of added-value chemicals is the bubbling fluidized-bed gasifier (BFBG). However, the gasification process inside a BFBG is a very complex high-temperature multiphase flow phenomena still not well understood, particularly when binary mixtures are investigated. As a result, despite the numerous correlations in the literature developed to predict the hydrodynamics inside a BFBG, the results are inconsistent, particularly for the minimum fluidization velocity, Umf.As predicting the fluidization hydrodynamics is paramount for optimum gasification, this investigation observed the effect of some of the most important fluidization parameters such as the particle size and shape, fluidizing gas properties, moisture content, bed aspect ratio etc. This study designed and built two separate experimental platforms: a bench-scale BFBG with automated feeding and a cold flow model with the same geometry and dimensions as the BFBG. The experiments used well-characterized (i.e., known size and shape distribution, density, moisture content, initial mixing condition) inert material (sand, glass beads) and feedstock (biomass (sawdust) and coal). The cold flow investigation results showed that the initial mixing conditions for binary mixtures with biomass had a significant effect on the measured Umf. For example, the relative error in predicting Umf using the available correlation in the literature increased for segregated mixtures. Moreover, lower relative errors in Umf suggested that the fluidization quality was better if the mixture was initially well-mixed (premixed). In addition, a larger biomass moisture content decreased Umf of premixed binary mixtures but increased the relative error between the predicted and the experimental Reynolds number, Re. After reaching the minimum fluidization condition, the fluidization behavior and mixing at various flow rates were also recorded with a high-speed camera. The processed images were used to determine the interval for the fluidizing-gas superficial velocity that produced the best mixing for a particular mixture composition and initial conditions. The images showed that while segregated biomass mixtures did not mix if the bed aspect ratio was larger than five, coal mixtures did mix homogeneously along the reactor bed. Finally, experiments performed at temperatures up to 800 C showed a large increase in the bed pressure drop at minimum fluidization velocity with the bed temperature due to the large effect on the fluidizing gas density and viscosity. On the contrary, Umf decreased when the process temperature increased. Finally, preliminary biomass and coal gasification experiments in the BFBG setup produced...

Bubbling Fluidized Bed Gasifier (BFBG) technology is an efficient and economical way of producing syngas from various feedstocks, such as coal, biomass, and municipal waste. However, the prediction of the gasification process inside the BFBG is quite complex due to many factors, including multiphase flow hydrodynamics. This study analyzed the hydrodynamics of a bench-scale top-fed bubbling fluidized bed coal gasifier with sand or glass beads used as bed materials at different bed aspect ratios. Two separate test rigs were built with the same dimensions for cold flow (without reaction) and hot flow (with reaction) studies, respectively. The cold flow test rig was used to investigate the hydrodynamics of BFBG fluidization. Bed pressure drop, minimum fluidization velocity, and mixing were analyzed in the test room conditions. Following that, gasification tests were carried out in the hot flow BFBG test rig with a novel feeding system using the optimum hydrodynamical parameters determined from cold flow analyses. Results showed that syngas was successfully produced at an adequate composition. This study contributes to a better understanding of the fluidization hydrodynamics of the binary coal and bed material mixtures in a top-fed BFBG for a more optimum gasification process and easier operation of the BFBG.