Transition pathways for the Belgian Industry: application to the case of the lime sector

Abstract

Faced with the climate emergency, it is crucial to reduce CO2 emissions, which can be a complex task for hard-to-abate industries such as lime production. This thesis therefore, under the framework of the TRILATE project, aims to evaluate different energy transition pathways for the lime sector in Belgium. Lime is an essential product, used in a wide variety of applications: construction, steelmaking, effluent treatment, production of chemicals, etc. However, this sector is a major emitter of CO2, accounting for 1% of global anthropogenic emissions. The calcination reaction in lime kilns (CaCO3 + heat ⇌ CaO + CO2) alone generates 0.786 t CO2/t lime and takes place at very high temperatures (typically 900-1100°C), currently achieved by burning fossil fuels. Overall, between 1 and 1.8 t CO2/t lime are emitted depending on the considered kiln technology. The obtained quicklime can then be milled or hydrated (CaO + H2O ⇌ Ca(OH)2 + heat) to produce hydrated lime or milk of lime, depending on the amount of water added. The objective of this study is to analyze various energy transition pathways for CO2 emissions reduction in the lime sector. For this purpose, the Blueprint (BP) model of lime sector is developed, consisting of detailed mass and energy balances, as well as economic considerations (i.e., annualized CAPEX and OPEX). Moreover, all the possible emission-reduction pathways for lime production (i.e., fuel switching towards hydrogen, biogas, biomethane or solid biomass; electrification of kilns using plasma torches; CO2 capture by chemical absorption with MEA or by oxycombustion) are included and a superstructure of pathways is developed. Furthermore, the OSMOSE Lua tool, developed at EPFL, is utilized for the evaluation of the superstructure of various alternatives for three different years (2030, 2040, 2050) and three different EnergyVille’s scenarios (electrification, clean molecules, central). Finally, a comparison between all alternative lime production routes and the base case ’NG’ (natural gas-fired lime kiln without CC) is performed on the basis of three key performance indicators: specific energy consumption (kWh/t lime), specific CO2 emissions (kg CO2/t lime) and specific total cost (€/t lime). In 2030, the specific total cost of the base case is €269–270/t. The results indicate that the optimum energy transition pathways are ’Biomass-CC’ and ’NGOxy-CC’, resulting in a reduction in specific total cost (STC) of 27–28% and 16–18% compared to the base case, respectively, depending on the scenario considered. The CO2 emissions reduction potential compared to the base case amounts to 115% for ’Biomass-CC’ and 90% for ’NGOxy-CC’. ’Plasma-CC’ comes 3rd, with a cost reduction of 12–18% and an emission reduction of 93% compared to a natural gas-fired kiln without CC. In 2040, firing a lime kiln with natural gas requires a specific total cost of €370/t. The economically optimal solution remains ’Biomass-CC’ (49% lower STC than ’NG’), followed by ’Plasma-CC’ (40–45% lower STC than ’NG’, depending on the scenario). ’NGOxy-CC’ and ’Biogas-CC’ both achieve a STC reduction of 40–41%. Compared to the base case, ’Biogas-CC’ configuration enables 124% lower CO2 emissions. In 2050, the STC of ’NG’ reaches €476/t. By implementing ’Biomass-CC’, ’Biogas-CC’, ’Plasma-CC’ or ’NGOxy-CC’, the specific total cost can be reduced by 60–61%, 53–54%, 51–62%, and 51–54% respectively, compared to ’NG’. The use of hydrogen in lime kilns, on the other hand, represents one of the most expensive transition pathways for the sector. Despite relatively low costs, the problems associated with biomass availability and the low TRL of plasma technology should not be overlooked. This study provides a comprehensive analysis of a wide variety of energy transition pathways for the lime sector, however, there is still room for improvement. Future researches should focus on investigation of other CO2 capture processes, use of more accurate economic data, consideration of acid gas removal prior to CO2 capture, and inclusion of scope 2 CO2 emissions.