Decarbonisation pathways of the cement production process via hydrogen and oxy-combustion

Decarbonising cement production is of profound importance for meeting global greenhouse gas emission reduction targets and mitigating the impact of climate change. This study evaluates various technical options for achieving deep decarbonisation in a clinker production facility by utilising hydrogen (H2) as an alternative fuel to replace fossil fuels and by integrating an oxy-combustion technique with carbon capture and storage (CCS). Using Aspen Plus process simulations, we examined the extent of decarbonisation and assessed the thermal and electrical energy demands. This was achieved by incorporating an amine-absorption-based CO2 capture to a conventional natural gas fuelled reference plant, implementing oxyfuel-combustion of natural gas, and exploring four different scenarios for replacing fossil fuel with H2. In these scenarios, H2 was assumed to be produced through on-site water electrolysis, which also supplied oxygen for oxyfuel combustion, potentially eliminating the need for an air separation unit (ASU). The processes utilizing H2, except for the case of indirectly heated pre-calcination, employed oxyfuel combustion. The results indicate that the natural gas-fuelled oxyfuel-combustion process had the lowest total energy input at 4.92 GJ/t clinker, approximately 35% lower than that of the reference plant. Processes using H2 reduced energy demand by 11% in the H2-d scenario and 33% in the H2-a scenario. However, the process with indirect calcination required 6.24 GJ/t clinker, about 8% more H2 fuel than direct calcination but helped eliminate the need for an ASU. The results also reveal that greater H2 substitutions led to higher total process energy requirements due to the inefficiencies of the electrolysis process. While the H2-using processes could reduce the CO2 generation by up to 559 kgCO2/t clinker, this represents only about 27.6% of the CO2 reductions relative to the reference plant. These findings underscore the limitation of fuel substitution alone in cement production and emphasize the need for innovations in raw materials and the adoption of CCS to achieve deeper decarbonisation in cement industries.