Limestone calcination under calcium-looping conditions for CO₂ capture and thermochemical energy storage in the presence of H₂O: an in situ XRD analysis

Abstract

This work reports an in situ XRD analysis of whether the calcination/carbonation behavior of natural limestone (CaCO) is affected by the addition of HO to the calciner at a very low concentration under relevant Calcium-Looping (CaL) conditions for CO capture in coal fired power plants (CFPP) and Thermochemical Energy Storage (TCES) in Concentrated Solar Power plants (CSP). Previous studies have demonstrated that the presence of steam in the calciner at a high concentration yields a significant increase in the reaction rate. However, a further undesired consequence is the serious deterioration of the CaO mechanical strength, which would lead to particle attrition and mass loss in any CaL process based on the use of circulating fluidized beds. The results presented in this manuscript on the time evolution of the wt% and crystallite size of the phases involved in the calcination/carbonation reactions indicate that the calcination rate is still notably increased by the presence of HO at very low concentrations whereas the reactivity toward carbonation and crystal structure of the formed CaO are not essentially affected, which suggests that the CaO mechanical strength is not impaired. Thus, the benefit of using steam for calcination in the CaL process could be still retained while at the same time particle attrition would not be promoted.

Effect of milling mechanism on the CO2 capture performance of limestone in the Calcium Looping process

“…The thermogravimetric apparatus employed in our study does not allow for the introduction of H 2 O due to its corrosiveness, thus we chose to use 70%CO 2 /30%air atmosphere to replicate the CO 2 concentration in the calciner. Expectedly, the presence of H 2 O would accelerate the reaction as reported in previous works[28].…”

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

“…Similar to He, steam was found to accelerate the calcination reaction and to lower the thermodynamic driving force for its initiation [181], [220]- [225]. Unlike He, steam does affect the physical (i.e.…”

“…Unlike He, steam does affect the physical (i.e. structural and morphological) properties of the CaO formed [182], [225], [226]. Champagne et al [227], [228] observed that the CO2 uptake was improved when the subsequent carbonation was performed under dry conditions.…”

Developments in calcium/chemical looping and metal oxide redox cycles for high-temperature thermochemical energy storage: A review

“…This undesirable effect may pose a serious problem for the practical application of steam in circulating fluidised beds (CFBs) during the CaL-CSP process, since fine particles (around 10 μm) generated due to fracturing are difficult to recover with commercial cyclones. Fortunately, recent in situ XRD results based on the time evolution of the weight change and crystallite size of the sorbent material, have demonstrated that the presence of SHS at small concentrations still results in remarkably improved calcination reaction rates while the mechanical strength of the CaO formed is not significantly reduced [76]. In addition to carbonation/calcination atmospheres and operating temperatures, another relevant issue is carbonation pressure, since process simulations have shown that the thermoelectric efficiency can be promoted with an increased carbonator pressure [53].…”