Evaluation of Calcium-Based Sorbents Derived from Natural Ores and Industrial Wastes for High-Temperature CO₂ Capture

Abstract

This study focuses on the investigation of potential calcium-based, low-cost sorbent materials for post-combustion CO2 capture via carbonate looping. Mineral limestone, carbide slag, and white mud were evaluated for their CO2 sorption activity, with the latter two being industrial wastes retrieved from chlor-alkali and paper pulp plants, respectively. Mineral magnesite was tested as a structural promoter in an attempt to improve the cyclic stability of the sorbents. Different methods consisting of hydration, acetic acid treatment, and a modified sol–gel autocombustion using glycerol as the combustion agent were applied to modify the structural and morphological characteristics of the mineral- and waste- derived CaO and improve their performance. Preliminary thermogravimetric analysis (TGA) tests proved the superiority of limestone and carbide slag treated with glycerol autocombustion over white mud. The addition of magnesite was considered more beneficial via the acetic acid treatment, since the promoted limestone and carbide slag presented adequate stability under 50 sorption/desorption TGA cycles, with a 43.2% and 34.2% deactivation, respectively. The most promising CaO-based sorbents were further evaluated in a bench-scale fluidized-bed reactor, with the promoted materials withstanding sintering more distinctly, even under more severe calcination conditions (880 °C, 50% CO2 concentration). Magnesite-promoted limestone exhibited an initial CO2 uptake of ∼11 mol CO2/kg of sorbent, which corresponds to ∼90% CaO conversion and <35% deactivation after 20 consecutive carbonation cycles, even under harsh calcination conditions. The superiority of the limestone promoted with magnesite was attributed to the enhancement of its pore network due to a reconstruction of its morphology in the presence of steam during the carbonation/calcination cycles.

CO2 Capture at Medium to High Temperature Using Solid Oxide-Based Sorbents: Fundamental Aspects, Mechanistic Insights, and Recent Advances

“…Several works have dealt with techno-economic aspects of the calcium looping process, and very early it was anticipated that it could have significant advantages over the amine-based process with regard to the price per ton of CO 2 captured (<20 USD t CO 2 –1 , which was less than half of the costs for an amine-based CO 2 capture process; note that correcting for inflation this is ∼26 USD t CO 2 –1 in 2021). − The sensitivity toward the cost of the sorbent for CO 2 capture and its rate of deactivation was relatively high in these early analyses, and indeed synthetic sorbents were predicted not to be competitive with natural limestone unless their long-term stability is significantly better under realistic process conditions. , Interestingly, although most of the literature has dealt with the development of novel, synthetic sorbents, estimates of the production costs are scarce and thus make it difficult to assess their suitability for a large-scale CO 2 capture process on economic grounds. Often sorbent costs had to be estimated based on values published decades ago. , Recently, many studies have utilized industrial waste products rich in species that are typically used to stabilize the CaO in a sorbent, e.g., Mg, Al, or Si, ,− or bioderived materials ,− to reduce the costs of sorbent production; a recent overview on sorbents based on waste products, covering also low-temperature adsorbents, has been given by Wang et al . Questions related to the recycling and reuse of spent sorbents or their processing (e.g., the separation of the inert phases and the Ca phase) have not been addressed in detail and thus offer potential for research (as, for example, in refs and in the context of chemical looping).…”

CO2 capture using solid sorbents: Fundamental aspects, mechanistic insights and recent advances

“…Recently, many studies have utilized industrial waste products rich in species that are typically used to stabilize the CaO in a sorbent, e.g. Mg, Al, or Si [544], [619]- [625], or bioderived materials [380], [626]- [629] to reduce the costs of sorbent production. Questions related to the recycling and reuse of spent sorbents or their processing (e.g.…”

Application of engineered natural ores to intermediate‐ and high‐temperature CO2 capture and conversion

“…Although considerable progress has been made on MgO-and CaO-based sorbents, [35][36][37][38][39][40][41] most studies have used commercial chemicals as Mg and Ca precursors, and only a few have applied natural ores such as magnesite and limestone as the precursors. [42][43][44][45] Apparently, natural ores are promising precursors for manufacturing cost-effective MgO-based and CaObased sorbents in view of their abundant availability and low cost. Among all Mg-and Ca-bearing ores, dolomite is the only one that is composed principally of Mg and Ca carbonates in a near equimolar ratio, which makes it a precursor candidate for MgO-and CaO-based sorbents simultaneously.…”