Investigations into the effects of volatile biomass tar on the performance of Fe-based CLC oxygen carrier materials

Abstract

process with ex situ gasification of biomass. Beech wood was pyrolysed in the first stage of the reactor at 773 K to produce a tar-containing fuel gas that was used to reduce the OCM loaded into the 2nd stage at 973 K. The presence of either OCM was found to significantly reduce the amount of biomass tars exiting the reactor by up to 71 wt% compared with analogous experiments in which the biomass tar compounds were exposed to an inert bed of sand. The tar cracking effect of the 60Fe40Al OCM was slightly greater than the 100Fe OCM although the reduction in the tar yield was roughly equivalent to the increase in carbon deposition observed for the 60Fe40Al OCM compared with the 100Fe OCM. In both cases, the tar cracking effect of the OCMs appeared to be independent of the oxidation state in which the OCM was exposed to the volatile biomass pyrolysis products (i.e. Fe 2 O 3 or Fe 3 O 4 ). Exposing the pyrolysis vapours to the OCMs in their oxidised (Fe 2 O 3 ) form favoured the production of CO 2 . The production of CO was favoured when the OCMs were in their reduced (Fe 3 O 4 ) form. Carbon deposition was removed in the subsequent oxidation phase with no obvious deleterious effects on the reactivity in subsequent CLC cycles with reduction by 3 mol% CO.

Pressurized In Situ CO2 Capture from Biomass Combustion via the Calcium Looping Process in a Spout-Fluidized-Bed Reactor

“…This suggests that the tars had a bimodal molecular size distribution (Figure a,b). The first peak (also known as the excluded peak) represents the elution of tar species with high molecular mass . These tar species were either partially or completely excluded from the column pores (and hence dropped through the SEC column faster).…”

Chemical Looping for Combustion of Solid Biomass: A Review

“…As regards tar formation in CLC systems, the literature is rather poor: Zheng et al 114 and Boot-Handford et al 115 investigated the effectiveness of some OCs for the conversion of volatile matter. Fe 2 O 3 (pure), Fe 2 O 3 (on alumina), CuO (on mayenite), and Cu 2 O (on mayenite) were used as OCs.…”

Negative CO2 emissions through the use of biofuels in chemical looping technology: A review

“…The compilation of all these advantages clearly shows that BCLG allows the conversion of biomass into high-quality syngas with an appropriate H 2 :CO ratio in a single step without the Chemical looping technology can also be used to reduce the tar content in the gasification products of biomass [174][175][176]. For this purpose, a selective oxygen carrier must be designed to convert the volatile organic compounds and tar, although the degree of combustion must be maintained at a low level in order to prevent a significant decrease in the heating value of the syngas.…”

“…Considering the presence of CO 2 in biogas, another possibility is the use of the chemical looping dry reforming (CLDR) process as a means of biogas valorization [188]. The syngas In addition, CLR can be used as a secondary tar-cleaning process for upgrading biomassderived gas [174][175][176][190][191][192][193][194][195][196][197][198][199]. The idea behind the tar-cleaning method is to reform tar components (C n H m ) into useful gas molecules.…”

“…Other works at laboratory scale includes the possible use of materials based on Fe [174], Cu and La, Sr and Fe [192,193,195].…”