Reduction of CO2 emissions by recycling low-potential heat from the Benfield CO2 removal process at a natural gas hydrogen production plant

The EU policies related to CO2 emission strictly define the stages of carbon neutrality achieving. According to these regulations, all production installations that emit carbon dioxide will be charged additional emission fees from 2026 to fully in 2035. Analysis of the increasing emission fees shows that in some industries incurring such additional costs will result in a lack of profitability of the products. Industries directly related to the food sector, such as nitrogen fertiliser production, are strategic in the economies of all countries. Nitrogen fertilisers are produced from ammonia, which is synthesised on a large scale from hydrogen and nitrogen. Hydrogen is produced by natural gas reforming with water vapour resulting in syngas (mixture of H-2, CO, CO2, H2O), which CO in the next step reacts with water vapour (water gas shift reaction) producing H-2 and CO2. CO2 is separated from hydrogen using the Benfield method. The analysis of the Benfield process (one process of hydrogen production) shows a possible way to reduce CO2 emission by optimising heat balance. It was shown that in the proposed technology the heat recovery reaches 89%, while the level below 30% was reported for other available technologies. The proposed solution is based on recirculation and reuse of heat, which is lost in other technologies. The analysis is for a process balance in a medium-sized hydrogen production installation. The analysis considers also the correlations with other installations thermally linked to hydrogen production. The economic balance showed the great financial benefits of this solution. In the scenario discussed, the CO2 emission factor was reduced by 20%.