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Effects of equivalence ratio (ER = 0.15, 0.25, and 0.35 at 934 °C) and temperature (790, 934, and 1078 °C at 0.25 ER) were investigated in air gasification of pine for primary gases and contaminants. CO and H 2 increased while CO 2 and CH 4 decreased from 790 to 1078 °C. Opposite trends were observed for ER. Based on overall contaminant weight, tar was highest at all temperatures (7.81, 8.24, and 8.93 g/kg dry biomass) and ERs (13.08, 8.24, and 2.51 g/kg dry biomass). NH 3 varied from 1.63 to 1.00 g/kg dry biomass between 790 and 1078 °C and from 1.76 to 1.47 g/kg dry biomass between 0.15 and 0.35 ER. H 2 S ranged between 0.13 and 0.17 g/kg dry biomass from 790 to 1078 °C and between 0.154 and 0.18 g/kg dry biomass from 0.15 to 0.35 ER. Finally, HCl yields ranged from 13.63 to 0 mg/kg dry biomass and from 11.51 to 0.28 mg/kg dry biomass over the range of temperature and ER, respectively.

a b s t r a c tTorrefied biomass has higher C/O ratio, resulting in improved heating value and reduced hygroscopic nature of the biomass, thus enabling longer storage times. In the southeastern United States, pine is has been identified as a potential feedstock for energy production. The objective of this study was to understand the performance of torrefied pine as a gasification fuel in a bench-scale bubbling fluidized bed gasifier. The gasification of torrefied pine was carried out at 790, 935 and 1000 C and three equivalence ratios (ERs: 0.20, 0.25 and 0.30). The effect of process variables were studied based on i) products yield, ii) syngas composition iii) syngas energy content, and iv) contaminants. The mean concentration of CO increased with an increase in temperature, but was not statistically significant. On the other hand, H 2 concentration increased whereas CH 4 concentration decreased significantly with an increase in temperature from 790 to 935 C. Further, with an increase in ER from 0.20 to 0.30, only CO 2 concentrations increased in the syngas. Results from torrefied pine were compared with raw pine gasification, and it was observed that torrefied pine gasification led to much higher char yield (more than twice) than pine; however, it produced less than half as much tar.

The purpose of this study was to evaluate the effects of temperature and equivalence ratios (ERs) on the distribution of products (primary gases carbon monoxide [CO], H 2 , CH 4 , CO 2 ), gas phase contaminants (tar, NH 3 , HCN, H 2 S, HCl), char, carbon, and inorganics), and energy flows on an oxygen-blown bubbling fluidized bed gasifier system using loblolly pine. The goal and value of this study was to provide quantitative and qualitative performance analysis and data for process engineering and optimization of these fledgling biomass conversion systems. As temperature and ER increased, mass balance closures also increased from 94.73% to 96.72% for temperature and 89.82-96.93% for ER. In addition, the carbon closures ranged from 80.77% to 92.29% and from 79.09% to 87.13% as temperature and ER increased, respectively. Carbon conversion efficiency to gas product ranged from 72.26% to 84.32% as temperature increased and from 72.26% to 84.66% as ER increased. Carbon flow analysis showed that the char product streams retained 10.26-6.94% and 8.82-2.13% of the carbon fed to the gasifier as temperature and ER increased, respectively. The carbon content in the liquid condensate was minimal compared to the carbon in other product streams and accounted for less than 0.1% of the carbon input to the gasifier at all conditions. The cold and hot gas efficiencies increased from 56.12% to 67.45% and from 67.51% to 83.83% as temperature increased due to higher production of CO and hydrogen (H 2 ). In contrast, cold and hot gas efficiencies decreased from 63.85% to 52.84% and from 78.06% to 73.00% as ER increased, respectively, due to enhanced oxidation of gas products resulting in a net decrease in heating value. 257

The economic viability of heat and power generation from biomass gasification is strongly influenced by the supply radius due to the low energy density of biomass relative to fossil fuels. Consequently, localized production of heat and electricity from biomass gasification is expected to play an eminent role in the future. In this study, an economic analysis was performed on a micro‐scale heat and power generation plant using urban waste from the city of Fultondale in Alabama, USA. The plant economics of heat and power production from urban biomass waste collected in Fultondale were analyzed by using a modular economic model with drying, chipping, gasification, power generation, and grid connection modules. Three gasification systems – fluidized bed, downdraft and updraft – and three power generation systems – internal combustion, steam turbine, and gas turbine – were assessed resulting in nine plant configuration scenarios. The fluidized bed gasifier and internal combustion engine plant configuration resulted in the lowest cost of electricity at ¢14/kWh for a micro‐scale installed capacity of 100kWe for a plant operating at 85% capacity with an annual green waste processing capacity of 1811 tons. The equipment and installation costs made up the largest contribution to the total capital investment whereas the operating labor and plant overhead make the largest contribution to the total annual production cost. Sensitivity analysis revealed that the plant capacity factor and the rate of return of investment had the strongest effect on the levelized cost of electricity under the best configuration.

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