Co-gasification of Biomass and Non-biomass Feedstocks: Synergistic and Inhibition Effects of Switchgrass Mixed with Sub-bituminous Coal and Fluid Coke During CO₂ Gasification

Abstract

Co-gasification of biomass, namely, switchgrass, with coal and fluid coke was performed to investigate the availability of the gasification catalysts to the mixed feedstock, especially alkali and alkaline earth elements, naturally present on switchgrass. Rates of CO 2 gasification of the single and mixed materials were measured at temperatures between 750 and 950 °C and atmospheric pressure by thermogravimetry. High interparticle mobility of the catalysts is indicated by a prompt and lasting effect on the mixed feed gasification rate when compared with the separate rates. The switchgrass−coal mixtures show a deactivation (antagonism), attributed to sequestration of the mobile alkali elements by reaction with aluminosilicate minerals in coal to form inactive alkali aluminosilicates, such as KAlSi 3 O 8 and KAlSiO 4 . Remaining catalytic activity is evident when excess alkali is present in the feed mixture to satisfy the stoichiometric requirements of these deactivation reactions. In co-gasification of switchgrass with fluid coke, which has little interfering inorganic matter, a synergism is noted in the gasification of the mixed feed. The results document the effects of fuel mixture, composition of the coal or coke ash, and the gasification temperature on this behavior.

Preliminary study on co-gasification behavior of deoiled asphalt with coal and biomass

“…The above experiments confirmed that adding biomass could significantly increase the gasification rate of DOA, and it could be deduced that the catalytic effect is caused by the potassium in biomass [11,17,[22][23][24][25][26]33,36]. But how does the catalytic reaction happen is not clear.…”

“…Namely, the blending of CC with DOA promotes the gasification rate of DOA. This could be attributed to the catalytic effect of the alkali metals contained in the biomass [23,29,34], and the detailed results and reasons will be discussed in the following part.…”

“…Recently, the co-utilization of coal and biomass has been studied and the possibility that use biomass as a catalyst in coal gasification has been reported [17,21,22]. However, few researches focused on the co-gasification of biomass and DOA [11,23].…”

A Review of Thermal Co-Conversion of Coal and Biomass/Waste

“…Blending biomass and coal takes advantage of both the high reactivity of biomass and its catalytic effect. However, some negative catalytic effects have been evidenced by Habibi et al [100].…”

Effect of briquette composition and size on the quality of the resulting coke

“…The sawdust from pine has a very low ash content (0.3 wt.% db) but the K content of the ashes is much higher than in SC (14 vs. 4 wt.%) and some authors have linked the K content to the catalytic effect of the biomass ashes [33]. The two sawdusts have the highest reactivity followed by the non-coking coal and the coal tar sludge and the tar.…”