Enhancing energy efficiency and decarbonization of cement production through integrated calcium-looping and methane dry reforming (CaL-DRM) for in-situ CO2 conversion to syngas

Abstract

The cement industry is exceptionally energy-intensive and a major global carbon emitter, with CO₂ primarily arising from the calcination of carbonate raw meal and the combustion of fossil fuels. This study proposes a novel process integrating calcium looping and dry reforming of methane (CaL-DRM) based on an “in-situ carbon capture and conversion” strategy to enhance the energy efficiency and decarbonization in the cement production process. Models for both conventional cement production process model and the CaL-DRM processes were developed using Aspen Plus to compare the mass flow and process energy balances of conventional cement production with the CaL-DRM process. The modelling results were validated by the cement plant operating data and published results. Sensitivity analyses were performed to optimize key production parameters, including CH₄/O₂ = 1.37 and CaCO₃/CH₄ = 0.5, which resulted in the highest conversion efficiencies of CO₂ and CH₄. Subsequently, the optimization of the tertiary air volume and the proportion of hot raw meal entering the carbonator was carried out. The optimal tertiary air volume was found to be less than 28529 Nm³/h, and 13% of the hot raw meal was directed to the carbonator. With these conditions, the process thermal efficiency can be increased from 58 % to 86 %. CO₂ emissions were analyzed at key stages of cement production process, focusing on fuel combustion and carbonate decomposition at the calciner and rotary kiln, with a comparison of the conventional method and the CaL-DRM process to quantify emissions at each stage. The results indicate that 852.3 kg CO₂ per ton of cement clinker can be converted to produce 1680 kg of syngas per ton of cement clinker along with cement clinker. Additionally, up to 62.5 kg CO₂ per ton of cement clinker can be captured by the carbonator, reducing the CO₂ volume fraction in flue gas from 23.29 % to 0.24 %, thus eliminating the need for subsequent CO₂ purification and transport. These findings demonstrate the significant potential of this novel method for sustainable development in the cement industry.