Effect of SO₂and steam on CO₂capture performance of biomass-templated calcium aluminate pellets

Abstract

Four types of synthetic sorbents were developed for high-temperature post-combustion calcium looping CO capture using Longcal limestone. Pellets were prepared with: lime and cement (LC); lime and flour (LF); lime, cement and flour (LCF); and lime, cement and flour doped with seawater (LCFSW). Flour was used as a templating material. All samples underwent 20 cycles in a TGA under two different calcination conditions. Moreover, the prepared sorbents were tested for 10 carbonation/calcination cycles in a 68 mm-internal-diameter bubbling fluidized bed (BFB) in three environments: with no sulphur and no steam; in the presence of sulphur; and with steam. When compared to limestone, all the synthetic sorbents exhibited enhanced CO capture performance in the BFB experiments, with the exception of the sample doped with seawater. In the BFB tests, the addition of cement binder during the pelletisation process resulted in the increase of CO capture capacity from 0.08 g CO per g sorbent (LF) to 0.15 g CO per g sorbent (LCF) by the 10 cycle. The CO uptake in the presence of SO dramatically declined by the 10 cycle; for example, from 0.22 g CO per g sorbent to 0.05 g CO per g sorbent in the case of the untemplated material (LC). However, as expected all samples showed improved performance in the presence of steam, and the decay of reactivity during the cycles was less pronounced. Nevertheless, in the BFB environment, the templated pellets showed poorer CO capture performance. This is presumably because of material loss due to attrition under the FB conditions. By contrast, the templated materials performed better than untemplated materials under TGA conditions. This indicates that the reduction of attrition is critical when employing templated materials in realistic systems with FB reactors.

Calcium looping sorbents for CO2 capture

“…All the particles with biomass components displayed better results than those without biomass. Erans et al [137] studied flour as a biomass-templating material in both TGA and bubbling FB. The synthetic materials displayed better performance than limestone; however, BFB testing proved that the attrition and fragmentation in biomass-templating materials is higher than in calcium aluminate pellets.…”

Fragmentation of biomass-templated CaO-based pellets

“…Natural sorbents (limestone and dolomite) are attractive due to their low cost, ready availability and, in the case of limestones, the potential suitability of the CaL purge material for the cement industry [12,13]. However, significant research efforts are being made to modify limestone sorbents or create new synthetic sorbents using techniques such as sol-gel combustion [14][15][16][17][18], organic acid modifications [19][20][21][22][23], co-precipitation [24,25] and granulation [26][27][28][29][30][31][32]. Such materials exhibited higher CO2 uptake, in general, when compared to natural lime-based sorbents.…”

CO2 Capture Performance Using Biomass-Templated Cement-Supported Limestone Pellets

“…Granulation 10,12,15,16,[29][30][31][32] has been proposed recently as a promising method, which allows the addition of various dopants and using kaolin 30,33 and/or cement 34 as binders to support sorbents.…”