Effect of Steam on Carbonation of CaO in Ca-Looping

Abstract

Ca-looping is an effective way to capture CO2 from coal-fired power plants. However, there are still issues that require further study. One of these issues is the effect of steam on the Ca-looping process. In this paper, a self-madethermogravimetric analyzer that can achieve rapid heating and cooling is used to measure the change of sample weight under constant temperature conditions. The parameters of the Ca-looping are studied in detail, including the addition of water vapor alone in the calcination or carbonation stage and the calcination/carbonation reaction temperatures for both calcination and carbonation stages with water vapor. Steam has a positive overall effect on CO2 capture in the Ca-looping process. When steam is present in both calcination and carbonation processes, it increases the decomposition rate of CaCO3 and enhances the subsequent carbonation conversion of CaO. However, when steam was present only in the calcination process, there was lower CaO carbonation conversion in the following carbonation process. In contrast, when steam was present in the carbonation stage, CO2 capture was improved. Sample characterizations after the reaction showed that although water vapor had a negative effect on the pore structure, adding water vapor increased the diffusion coefficient of CO2 and the carbonation conversion rate of CaO.

Catalytic Gasification of Petroleum Coke with Different Ratios of K2CO3 and Evolution of the Residual Coke Structure

“…It is hard to differ the reactivity of the residual coke increase or decrease as the carbon conversion increases. Based on the residual coke structure analyses, the graphitization degree decreased, and the surface area and pore volume increased, which would increase the reactivity, as reported [8,10,27]. Then, it could be concluded that the variation in the carbon and pore structure was not the key factor affecting the residual coke's reactivity.…”

Impact of Limestone Surface Impurities on Quicklime Product Quality

“…The thermal decomposition, or calcination, of calcite has been extensively studied. Ratelimiting processes have been defined [1], and the effects of steam [2], pressure [3], CO 2 partial pressure [4], heating rate [5], and impurities [6][7][8], among other parameters, have been identified. Of the proposed calcination mechanisms, a mechanism involving intermediate "activated lime" CaO*(s), originally proposed by Hyatt et al in 1958 [9], has received support in more recent studies [4,10].…”