Effect of Impurities on the Decarbonization of Calcium Carbonate Using Aqueous Sodium Hydroxide

Abstract

Decarbonizing calcium carbonate (CaCO 3 ) is a crucial step for a wide range of major industrial processes and materials, including Portland cement (PC) production. Apart from the carbon footprint linked to fuel combustion, the process CO 2 embodied within CaCO 3 represents the main concern for the sustainability of production. Our recent works demonstrated that it is possible to avoid both the fuel and process CO 2 by reacting CaCO 3 with aqueous NaOH and obtain Ca(OH) 2 and Na 2 CO 3 · x H 2 O ( x = 0 and 1). This present study provides a further understanding of the process by testing different raw calcareous sources. A high decarbonization (∼80%) of CaCO 3 was achieved for silica-rich chalk, whereas a lower extent was obtained (∼50%) for limestone. To understand the difference in their reaction behavior, the effect of impurities was studied. The effects of the major impurities (Si, Al, and Fe) were found to be marginal, which is advantageous to process industrial grade materials, while the morphology of the raw materials presents a significant impact. The applicability of our decarbonization technology was also demonstrated on magnesite (MgCO 3 ).

Low-Temperature Electrochemical Cement Clinker Production

“…22 While conventional electrolyzers use gas or liquid reactants, only a few groups have reported on low-temperature, solid-fed electrolyzers, thus requiring a customized flowplate design to achieve optimal mass transport for the solid CaCO 3 . Moreover, CaCO 3 frequently contains acid-sensitive metal impurities, 27 and the released metal ions may electro-plate onto the cathode and contaminate the membranes. Impurities such as Ca 2+ , Mg 2+ , and Fe 3+ metal ions from water matrices can also influence the catalysts' selectivity and potentially poison the CEMs.…”

Synthesis of Ca(OH)2 and Na2CO3 through anion exchange between CaCO3 and NaOH: effect of reaction temperature

“…To do that, the concomitant by-production of soda ash Na 2 CO 3 was also considered, whose conventional manufacturing route through Solvay process requires a high energy supply. This early-stage investigation, together with other ones focusing on the processing conditions 14 and the nature of the raw materials used, 15 will provide a strong base to the potential scale-up of the process. In these terms, future work will aim to design a laboratory-scale process simulating the ideal industrial one, providing a stronger dataset to assess the effective energy requirements of the route, and therefore allowing for a proper techno-economic analysis.…”

“…To achieve this, the application of carbon capture and storage (CCS) technologies 11 and the use of alternative fuels 12 are expected to be the best candidates; however, both these solutions assume that the thermal calcination of limestone (and the process CO 2 ) is unavoidable. In contrast to this, recent investigations [13][14][15][16] highlighted the possibility for alternative decarbonisation routes which apply no-combustion approaches for the synthesis of the essential chemical CaO 17 from CaCO 3 . As far as we are aware, the chemical decarbonisation route here characterised represents the only alternative for the sustainable co-synthesis of Ca(OH) 2 and Na 2 CO 3 .…”

An Innovative Approach to Prepare Calcium Oxide from Calcium Carbide Slag Based on Sequential Mineral Transformation

“…Approximately 300 million tons of CO 2 are emitted every year in China alone. 1,2 Therefore, developing and recycling low-carbon calcium alternative resources is an important way to reduce CO 2 emissions.…”