Research and application progress on combustion-based carbon capture technologies in cement industry

WANG Junjie; YANG Huawei; ZHU Zhiping; CAI Jun

doi:10.13226/j.issn.1006-6772.CBJ25012401

Abstract：Cement industry is one of the largest contributors to greenhouse gas emissions accounting for about 7％of global CO2 emissions.Carbon capture is considered a "fallback" technology,with combustion carbon capture offering several advantages such as strong capture capacity,low process energy consumption,and low costs.This article systematically reviews combustion carbon capture projects in the cement industry both domestically and internationally,including four projects for direct separation,twelve projects for oxyfuel combustion,and four projects for calcium looping.Direct separation technology captures CO2 produced from the decomposition of limestone through indirect heat exchange.Internationally,the LEILAC project is a key example,with its core being a direct separation reactor.The first phase of the project is designed to capture 25 000 tons of CO2 per year,and the second phase aims to capture 100 000 tons per year.Industrial trials of the first phase have shown that the separated CO2 purity is greater than 95％.Domestically,a company has developed an external combustion rotary kiln technology and is currently constructing a 50 000 tons per year carbon capture demonstration project.Oxyfuel combustion technology is divided into partial oxyfuel,first-generation full-sacale oxyfuel,and second-generation full-scale oxyfuel.Partial oxyfuel combustion achieves O2/CO2 combustion only in the calciner,capturing approximately 60％-75％of total carbon emissions.Due to the inhibition of raw material decomposition in the O2/CO2,industrial trial results indicate that the calciner temperature needs to be increased by 60 to 70 ℃ to achieve a higher decomposition rate.Two projects using partial oxyfuel combustion technology have been constructed domestically.Full-system oxyfuel combustion technology creates the O2/CO2 atmosphere both in the rotary kiln and calciner,with a CO2 capture capacity of 90％-95％.The first-generation full-scale oxyfuel combustion technology is based on flue gas recirculation to control flame temperature.Studies have shown that the O2/CO2 atmosphere has no significant impact on clinker quality,and parameter adjustments can achieve a similar temperature field in the rotary kiln with air combustion.Compared to the first generation,the second-generation full-scale oxyfuel combustion technology eliminates the flue gas recirculation system,with the rotary kiln temperature controlled by excess O2.Studies have shown that increasing the oxygen equivalence ratio provides an ideal temperature control effect,and several projects have been laid out.Several features,including CaCO3 and CaO being the main components of the raw meal and clinker respectively,an existing calciner in the production process,give calcium looping technology a natural advantage in the cement industry.This article focuses on the integrated calcium looping process layout and the industrial trial results of the CLEANKER project,which showed a capture efficiency of 20％-80％.Within the carbonator temperature range of 450 to 750 ℃,the CO2 capture efficiency significantly increases with temperature,rising from 0 to a maximum of 100％.A comparative analysis is conducted around carbon capture capacity,the scale of carbon capture projects,energy consumption and abatement costs,and technical risks.China's cement production accounts for about 45％of the global total.It is recommended to strengthen the research and development of new technologies,accelerate the engineering verification of these technologies,and improve related supporting facilities.