A technical evaluation of CO2 capture technologies when retrofitted to a cement plant is performed. The investigated technologies are the oxyfuel process, the chilled ammonia process, membrane-assisted CO2 liquefaction, and the calcium looping process with tail-end and integrated configurations. For comparison, absorption with monoethanolamine (MEA) is used as reference technology. The focus of the evaluation is on emission abatement, energy performance, and retrofitability. All the investigated technologies perform better than the reference both in terms of emission abatement and energy consumption. The equivalent CO2 avoided are 73–90%, while it is 64% for MEA, considering the average EU-28 electricity mix. The specific primary energy consumption for CO2 avoided is 1.63–4.07 MJ/kg CO2, compared to 7.08 MJ/kg CO2 for MEA. The calcium looping technologies have the highest emission abatement potential, while the oxyfuel process has the best energy performance. When it comes to retrofitability, the post-combustion technologies show significant advantages compared to the oxyfuel and to the integrated calcium looping technologies. Furthermore, the performance of the individual technologies shows strong dependencies on site-specific and plant-specific factors. Therefore, rather than identifying one single best technology, it is emphasized that CO2 capture in the cement industry should be performed with a portfolio of capture technologies, where the preferred choice for each specific plant depends on local factors.

This paper presents an assessment of the cost performance of CO2 capture technologies when retrofitted to a cement plant: MEA-based absorption, oxyfuel, chilled ammonia-based absorption (Chilled Ammonia Process), membrane-assisted CO2 liquefaction, and calcium looping. While the technical basis for this study is presented in Part 1 of this paper series, this work presents a comprehensive techno-economic analysis of these CO2 capture technologies based on a capital and operating costs evaluation for retrofit in a cement plant. The cost of the cement plant product, clinker, is shown to increase with 49 to 92% compared to the cost of clinker without capture. The cost of CO2 avoided is between 42 €/tCO2 (for the oxyfuel-based capture process) and 84 €/tCO2 (for the membrane-based assisted liquefaction capture process), while the reference MEA-based absorption capture technology has a cost of 80 €/tCO2. Notably, the cost figures depend strongly on factors such as steam source, electricity mix, electricity price, fuel price and plant-specific characteristics. Hence, this confirms the conclusion of the technical evaluation in Part 1 that for final selection of CO2 capture technology at a specific plant, a plant-specific techno-economic evaluation should be performed, also considering more practical considerations.

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Achieving sustainable development while limiting environmental pollution is one of the main enormous challenges for chemical engineering at present. To develop and design a greener alternative to replace or retrofit a current polluted process, it is essential to establish a method for quantitatively evaluating the environmental impact of a chemical process so that its environmental performance can be improved by identifying and discovering the bottlenecks that cause the pollution. In this work, a green degree (GD) method is proposed to quantitatively evaluate the environmental impact of a chemical process and related energygeneration system. Definitions and calculation formulas of green degrees for a substance, a mixture, a stream, and a unit (process) are illustrated. The green degree is an integrated index that includes nine environmental impact categories (including global, air, water, and toxicological effects). Therefore, it is comprehensive for assessing and understanding the environmental performance of a complex multicomponent chemical system. Three illustrative case studies are presented to further describe and verify the applicability of the method: (1) solvent screening by comparing the green degree values of solvents, (2) process route screening for producing methyl methacrylate (MMA), and (3) green degree analysis of the methyl methacrylate process (i-C4 route) by integration with process simulation technology.