Abstract
The manufacturing industry is the second largest emitter of CO2, with the cement industry being one of the main contributors (7-8 % of the global emissions). Carbon capture and utilization (CCU) technologies are promising decarbonization solutions for the cement industry, addressing both fossil fuel-related (40 %) and process-derived emissions (60 %). Within a cement plant, producing synthetic natural gas (SNG) from captured CO2 is particularly suitable, as it is sufficient to fully replace solid fuels in the rotary kiln. On the other hand, the use of zero-carbon fuels, such as green ammonia, is also recognized as a promising approach for decarbonization. In this work, a superstructure was developed to explore alternative routes for producing SNG and green ammonia from CO2 and N2 in cement plant flue gas, respectively. The routes were modelled in Aspen Plus® V14, and their economic viability was assessed. Currently, the most promising route, at a cost of 109 €/tonne of flue gas, involves CO2 capture (90% efficiency) and storage, with the N2-rich stream emitted. However, all the routes remain uncompetitive compared with the full emission of the flue gas (22 €/tonne). Routes for green ammonia production from N2 in flue gas were compared with those from atmospheric air but were found to be uncompetitive. Nevertheless, with future developments, the economic feasibility of integrating pathways for synthesizing high-value chemical products into the cement industry is expected to increase.