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This paper presents a new solids looping process for capturing CO2 while generating hydrogen and/or electricity from natural gas. The process is based on the sorption enhanced reforming of CH4, employing CaO as a high temperature CO2 sorbent, combined with a second chemical loop of CuO/Cu. The exothermic reduction of CuO with CH4 is used to obtain the heat necessary for the decomposition of the CaCO3 formed in the reforming step. The main part of the process is completed by the oxidation of Cu to CuO, which is carried out with air diluted with a product gas recycle of this reactor at sufficiently low temperatures and high pressures to avoid the decomposition of a substantial fraction of CaCO3.

Post-combustion CO 2 capture based on Ca-looping process, CaL, is a promising technology under development based on the reversible reaction between CaO and CO 2 to form CaCO 3 and the regeneration of the CaO by calcination of CaCO 3 in a rich CO 2 atmosphere. This work is focused on the study of the calcination kinetics with typical solid conditions expected in these systems. Calcination rates of carbonated materials derived from two limestones have been measured at different number of carbonationcalcination cycles, as a function of temperature and CO 2 partial pressure. It has been observed that calcination reaction is chemically controlled for particles below 300 m of particle size, as internal mass transfer is negligible even under the presence of CO 2 in the reaction atmosphere. Calcination rate (expressed per mol of initial CaO) depends on calcination temperature and CO 2 partial pressure, whereas CaCO 3 content and/or particle lifetime do not affect the reaction rate. The basic kinetic model of Szekely et al. (1970) is shown to be valid to fit the new data. Based on these results it is shown that calcination temperatures between 880-920ºC could be sufficient to achieve nearly

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This work analyses a Ca looping system that uses CaO as regenerable sorbent to capture CO 2 from the flue gases generated in power plants. The CO 2 is captured by CaO in a CFB carbonator while coal oxycombustion provides the energy required to regenerate the sorbent. Part of the energy introduced into the calciner can be transferred to a new supercritical steam cycle to generate additional power. Several case studies have been integrated with this steam cycle. Efficiency penalties, mainly associated with the energy consumption of the ASU, CO 2 compressor and auxiliaries, can be as low as 7.5% p. of net efficiency when working with low-CaCO 3 make-up flows and integrating the Ca looping with a cement plant that makes use of the spent sorbent. The penalties increase to 8.3% p. when this possibility is not available. Operation conditions aiming at minimum calciner size result in slightly higher-efficiency penalties.

This work investigates the kinetics of the reaction of CO 2 with CaO particles partially carbonated that are forced to increase their carbonate content at high temperatures in an atmosphere of rich CO 2. This additional recarbonation reaction, on particles that have already completed their fast carbonation stage, is the basis of a novel process that aims to increase the CO 2 carrying capacity of sorbents in Calcium looping CO 2 capture systems. The CaO reaction rates and the maximum carbonation conversions after the recarbonation step were measured on a thermogravimetric analyzer and the results indicate that they are highly dependent on temperature and CO 2 partial pressure, steam also being a contributing factor. The reaction mechanism governing the reaction rates during the carbonation and recarbonation reactions is explained by the combined control of chemical reaction and CO 2 diffusion through the CaCO 3 product layer. An extension of the Random Pore Model adapted to multi cycled CaO particles was successfully applied to calculate the CaO molar conversion as a function of time and the recarbonation conditions, using kinetic parameters consistent with previous published results on carbonation kinetics under typical flue gas conditions.

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