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AssigneeConsejo Superior De Investigaciones Cientificas (Csic)
InventorsJuan Carlos ABANADES GARCÍA, Borja ARIAS ROZADA, José Ramón FERNÁNDEZ GARCÍA
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This invention discloses a calcination process to produce high purity CO2 from solids containing CaCO3 which operates cyclically and continuously on the solids, arranged in a packed or a moving bed, and wherein each cycle comprises a first step where the combustion at atmospheric pressure of a fuel in the bed of solids containing CaCO3 heats them up to 800-900° C. and a second step wherein a vacuum pressure between 0.05 and 0.5 atm is applied to extract pure CO2 from the solids containing CaCO3 while cooling them by 30-200° C. Said combustion can be carried out directly with air, oxygen enriched air or O2/CO2 mixtures when the process is applied to the calcination of a continuous flow of limestone in a moving bed shaft kiln. The process is also applied to calcine CaCO3 formed in reversible calcium looping processes comprising a carbonation reaction step to form CaCO3 from CaO.
Process to recover in high purity form the CO2 released from the calcination of solids containing CaCO3, with said solids being preheated to a temperature between 650-800° C. and arranged in a thermally insulated vessel (1) able to withstand vacuum swings, wherein the process is characterized by the continuous repetition, at least twice, of a sequence of at least the following consecutive steps:
The process of any one of the preceding claims wherein the fuel (8) is a hydrocarbon gas or hydrogen.
The process of any one of the preceding claims further comprising a step of introducing a batch of particles of solids containing CaCO3 (4) in the thermally insulated vessel (1) so that the solids are displaced downwards in each combustion step while extracting a batch of particles containing CaO (5).
The process of any one of the preceding claims wherein the combustion taking place in the thermally insulated vessel (1) during the step i) is a chemical looping combustion of the gaseous fuel (8) with air (9) by dividing the step i) in two sub-steps:
The process of any one of the preceding claims further comprising an additional carbonation step iii) of the CaO (5) generated in step ii) by feeding a combustion flue gas or any other gas containing CO2 to the packed bed of solids to increase the molar conversion of CaO to CaCO3 between 0.03 and 0.1 and restore the CaCO3 (4) in the bed of solids (1) that is at the beginning of step i).
The process of any one of the preceding claims, wherein the thermal power of the combustion during step i) is the result of the multiplication of the average power input in the equivalent kiln without CO2 capture and the ratio between the sum of the duration step i) and ii) divided by the duration of step i).
Dependencies are inferred from the claim text.