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Biomass gasification and pyrolysis were studied in a laboratory-scale atmospheric pressure entrained flow reactor. Effects of operating parameters and biomass types on the syngas composition were investigated. In general, the carbon conversion during biomass gasification was higher than 90% at the optimal conditions of 1400°C with steam addition. The biomass carbon that was not converted to gas in the gasification process only appeared as soot particles in the syngas in all of the experiments, except for the two experiments performed at 1000°C, where a very small amount of char was also left. In comparison to pyrolysis, lower yields of soot, H 2 , and CO were produced during gasification. The yield of soot could be reduced by a longer residence time, larger feeder air flow, lower oxygen concentration, higher excess air ratio, higher steam/carbon ratio, and higher reactor temperature. Changes in residence time, feeder air flow, and oxygen concentration did not show a noticeable influence on H 2 and CO yields. Increasing the excess air ratio decreased both the H 2 and CO yields; increasing the steam/carbon ratio increased the H 2 yield but decreased the CO yield; and increasing the reactor temperature increased both the H 2 and CO yields. Wood, straw, and dried lignin had similar gasification behavior, except with regard to soot formation. The soot yield was lowest during straw gasification possibly because of its high potassium content.

Biomass gasification experiments were carried out in a bench scale entrained flow reactor, and the produced solid particles were collected by a cyclone and a metal filter for subsequent characterization. During wood gasification, the major part of the solid material collected in the filter is soot. Scanning electron microscopy (SEM) images coupled with energy dispersive spectroscopy (EDS) show agglomerated nanosize spherical soot particles (<100 nm) that are very rich in carbon. In comparison to wood gasification, the soot content in the filter sample from straw gasification is quite low, while the contents of KCl and K2SO4 in the filter sample are high. SEM images of the straw filter samples show that with steam addition during gasification, where the soot yield is lower, the filter sample becomes richer in KCl and K2SO4 and appears as irregular crystals, and the typical particle size increases from below 100 nm to above 100 nm. During gasification of dried lignin, the filter sample mainly consists of soot and nonvolatilizable inorganic matter. SEM images of the parent wood particles and the derived char samples show that they have similar structure, size, and shape but the derived char particle surface looks smoother indicating some degree of melting. The reactivity of the organic fraction of the samples was determined by thermogravimetry, and it was found that char was more reactive than soot with respect to both oxidation and CO2 gasification. The activation energy for the soot conversion is higher than for the char conversion. These results support the observation from gasification experiments that char is more easily converted than soot. Surprisingly, the soot produced at a higher temperature is more reactive than the soot produced at a lower temperature.

No abstract

CoFe@HNSs exhibited bifunctional oxygen electrocatalytic activity, and exhibit a high-power density of 131.3 mW cm−2 and long-term stability over 140 h.