Efficient CO2 capture from lime plants: techno-economic assessment of integrated concepts using indirectly heated carbonate looping technology

This work attempts to close the illustrated knowledge gap in the IHCaL process and delineate the economic implications of applying this technology in lime production. For this, a comprehensive process modelling of the IHCaL process is performed. Furthermore, the design of the heat recovery steam cycle (HRSC) is optimized and three alternative configurations are compared. Finally, the economics of the process are taken into consideration and a sensitivity analysis is performed.
In this work, five different scenarios were considered: (i) the base case of the lime plant as-built, without carbon capture; a retrofitting or “tail-end” configuration for lime production with carbon capture, using (ii) coal and (iii) waste-derived fuels; and a fully integrated solution, using (iv) coal and (v) waste-derived fuels. Fueling with waste-derived fuels allows for carbon dioxide removal (CDR) through negative emissions from the biogenic fraction of the feedstock.
Different steam cycle configurations were analysed to optimize the heat recovery from the IHCaL process and the efficiency of the power production, while keeping the steam cycle cost within an acceptable range (see, e.g., Figure 2). The optimal configuration considers feed-water preheating, and superheating of steam up to 565 °C and 130 bar. Heat is recovered from the carbonator cooling system, the carbonator flue gases, and the calciner flue gases. It was shown that recovering heat from the combustor flue gases is detrimental to the thermodynamics of the entire process, but it may be used to decrease the operation temperature of some components (e.g., filters and blowers) in order to reduce costs. From the heat input into the IHCaL process, around 80% can be recovered in a steam cycle to produce electricity with a net electric efficiency of 41–42%. The calculated specific primary energy consumption for CO2 avoided (SPECCA) is lower than 2.3 MJLHV/kgCO2,av for coal, and 1.83 MJLHV/kgCO2,av for waste-derived fuels.
The cost calculations assume a 25-year project lifetime and the year 2020 was taken as the reference for the price indexing. The capital cost estimation of the lime production systems shows that the total installed cost is 67 M€ for the reference plant (i.e., w/o CCS) rising to 85 M€ once contingency and interest payments are accounted for. For the tail-end case, the total installed cost is about 313 M€, rising to 395 M€. For the integrated case, the total installed cost is around 137 M€, rising to 173 M€.
The break-even selling price (BESP) of the lime produced was determined using the discounted cash flowrate analysis. The techno-economic results show that for the BESP increases by 56.2 % for the tail-end case, and 55.6 % for the fully integrated plant configuration. The CO2 avoidance costs relative to the corresponding reference (the lignite fueled lime plant without CCS) are 41.1 €/tCO2 and 40.1 €/tCO2 for the tail-end and fully integrated cases, respectively. When the hard coal is replaced by the solid recovered fuels (SRF) in the lime plant, the BESP decreases by 21.1 % for the tail-end case, and 19.0 % for the fully integrated plant configuration. The CO2 avoidance costs relative to the corresponding reference are 18.4 €/tCO2 and 20.3 €/tCO2 for the tail-end and fully integrated cases, respectively.
The results of this work reveal the high potential for the IHCaL process to decarbonize the cement and lime industry. The technology is cost-efficient, especially for economic scenarios with high electricity prices. Additionally, when firing with waste-derived fuels, the solution can enable CDR. The next step towards the industrial implementation of the technology by 2028 is the construction of a demonstration facility to capture CO2 from flue gases of a cement or lime facility (Ströhle et al. 2021). Such demonstrator is being designed within the ANICA project, using the input from the experimental campaigns and the process models discussed in this work.