Reduction of Tar and Soot Formation from Entrained-Flow Gasification of Woody Biomass by Alkali Impregnation

Abstract

Tar and soot in product gas have been a major technical challenge toward the large-scale industrial installation of biomass gasification. This study aims at demonstrating that the formation of tar and soot can be reduced simultaneously using the catalytic activity of alkali metal species. Pine sawdust was impregnated with aqueous K2CO3 solution by wet impregnation methods prior to the gasification experiments. Raw and alkali-impregnated sawdust were gasified in a laminar drop-tube furnace at 900–1400 °C in a N2–CO2 mixture, because that creates conditions representative for an entrained-flow gasification process. At 900–1100 °C, char, soot and tar decreased with the temperature rise for both raw and alkali-impregnated sawdust. The change in tar and soot yields indicated that potassium inhibited the growth of polycyclic aromatic hydrocarbons and promoted the decomposition of light tar (with 1–2 aromatic rings). The results also indicated that the catalytic activity of potassium on tar decomposition exists in both solid and gas phases. Because alkali salts can be recovered from product gas as an aqueous solution, alkali-catalyzed gasification of woody biomass can be a promising process to produce clean product gas from the entrained-flow gasification process at a relatively low temperature.

Influence of In-Bed Catalysis by Ash-Coated Olivine on Tar Formation in Steam Gasification of Biomass

“…Homogeneous gas-phase catalytic interactions have so far attracted little attention in gasification literature, e.g. [12,13]. However, the mechanisms of polycyclic aromatic hydrocarbon (PAH) formation are understood in terms of the chemistry of gas-phase radicals [14][15][16], so it is likely that the ash-coated olivine can alter the gas-phase chemistry both indirectly, as a result of heterogeneous catalysis [11], as well as directly owing to the inhibitory effects of alkali on the formation of tar and soot [12,13].…”

“…[12,13]. However, the mechanisms of polycyclic aromatic hydrocarbon (PAH) formation are understood in terms of the chemistry of gas-phase radicals [14][15][16], so it is likely that the ash-coated olivine can alter the gas-phase chemistry both indirectly, as a result of heterogeneous catalysis [11], as well as directly owing to the inhibitory effects of alkali on the formation of tar and soot [12,13]. Based on the existing literature [11,12,[17][18][19], Figure 1 depicts the potential interplays between heterogeneous (lower box) and…”

An Assessment of Gasification of Lipid-Extracted Algae by Thermodynamic Simulation

“…Recent studies on alkali catalyzed gasification showed that as the total alkali (Na+K) to carbon ratio in char increases, the reactivity increases drastically during low temperature gasification (< 850 o C) [20]. On the other hand, at higher temperatures, part of the alkali is evaporated to exert other activities such as tar destruction and soot reduction [21,22]. In all scenarios, the lipid extracted algae species (Nannochloropsisgaditana) stands out as a suitable candidate for catalytic gasification.…”

Removal of phenol and chlorine from wastewater using steam activated biomass soot and tire carbon black

“…High soot formation is a major technical challenge in the entrained flow biomass gasification. Soot yields obtained in CO 2 gasification of biomass vary from 4 to 16 wt.% and depend mainly on the feedstock composition and heat treatment temperature [37,38]. In order to improve the economic performance and reliability of entrained flow gasification, biomass soot has the potential to be captured, activated and further used as an sorbent to remove a broad range of pollutants from wastewater.…”