Gasification Characteristics of Hydrothermal Carbonized Biomass in an Updraft Pilot-Scale Gasifier

Abstract

Biocoal pellets were gasified in an updraft high-temperature agent gasification (HTAG) unit with preheated air at 900 °C to study the performance of the air gasification of hydrothermal carbonized biomass. In comparison to raw biomass, hydrothermal carbonization increased the carbon content from 46 to 66% and decreased the oxygen content from 38 to 16%. As a result, the heating value of biomass on a dry basis was increased from 19 to 29 MJ/kg after hydrothermal carbonization. Thermogravimetric analysis (TGA) of biocoal featured early decomposition of hemicellulose and a shoulder attached to the cellulose peak corresponding to lignin decomposition. Char gasification demonstrated a peak near conversion of 0.2. Syngas with 7.9 MJ Nm −3 lower heating value (LHV) was obtained from gasification experiments performed in the pilot-scale gasifier. The maximum cold gas efficiency was 80% at the lowest equivalence ratio (ER) and also resulted in high-purity syngas. The LHV and cold gas efficiency were higher than that of the previously studied unpretreated biomass pellets. The fuel conversion positively correlated with the fuel residence time in the bed, and almost 99% conversion could be achieved for a residence time of 2 h. The superficial velocity (or hearth load) and specific gasification rate were higher than the reported values of updraft gasifiers because of the high-temperature operation and specific fuel used.

Primary and Photochemically Aged Aerosol Emissions from Biomass Cookstoves: Chemical and Physical Characterization

“…Primary aerosol emissions from the NDS and FDGS fall near the char region, consistent with the much greater EC/TC ratios and relatively small contributions from OA (Figures 1, 5). Fresh FDGS emissions appear to have substantially higher O:C ratios than those from other stoves possibly due to dominant contributions from high temperature carboxylation or oxidation reactions 93 .…”

“…The figure shows that emissions from the TSF are more similar to lignin than char or soot and fall between the raw and combusted/pyrolyzed oak, consistent with the large contribution of soot and less-oxygenated volatiles to the emitted aerosol. As combustion efficiency improves, H:C ratios decrease, presumably due to the enhanced role of dehydration and demethylation in the evolution of the fuelwood 91,93,94 . Primary aerosol emissions from the NDS and FDGS fall near the char region, consistent with the much greater EC/TC ratios and relatively small contributions from OA (Figures 1, 5).…”

Hydrothermal Carbonization: Modeling, Final Properties Design and Applications: A Review

“…On the other hand, Lin et al [65] found that HTC as a pretreatment improved the CO 2 gasification of municipal solid wastes (MSW), promoting a higher reactivity. Furthermore, Gunarathne et al [66] accomplished a study in a continuous updraft gasifier located in a pilot plant, gasifying HC from spent grains from a brewery. Despite their promising results (syn-gas with a calorific value of 7.9 MJ·Nm −3 ), the authors found some problems due to ash slagging, which suggests that special attention should be paid to these phenomena, as is also the case with combustion experiments.…”

Pyrolysis of Furfural Residues and Possible Utilization Pathway

“…Last but not least, fourth peak is attributed to lignin degradation in FR material at a broad temperature range of 369-416°C with a maximum decomposition rate of 6.53%/°C. This could be as a result of hemicellulose extraction that tampered with the lignin content or rather a hypothesis that lignin undergoes a phase transition [18]. Some studies have found that at high temperatures (>400°C) the aromatic rings of char matrix in lignin are rearranged [19,20].…”