Techno-economic evaluation of significant CO2 emission reductions in the iron and and steel industry with CCS: Dissertation

The iron and steel industry is one of the largest emitters of industrial CO2, accounting for around 6% of global anthropogenic CO2 emissions each year. In Europe, the recently proposed stricter emission reduction targets for 2030 are likely to increase the price for CO2 emission allowances. Various different GHG emission mitigation alternatives have been considered to enable decarbonisation of the iron and steel industry, such as energy efficiency, biogenic reducing agents, hydrogen and CCS. However, not all of these can be deployed for the most important production route - the blast furnace and basic oxygen furnace route (BF + BOF) - and all the solutions have advantages and disadvantages. CCS is currently the only mitigation option available for significantly reducing emissions from this energy-intensive industry. A full chain assessment of carbon capture and storage (CCS) applications for the iron and steel industry was performed in order to screen technology options and build a development pathway to low carbon steelmaking for future carbonconstrained world. A techno-economic assessment of application of CCS with various technologies in the iron and steel industry was carried out to create a knowledge base for a Nordic steel producer. The assessment was conducted for two different CO2 capture alternatives, namely post-combustion carbon capture and oxygen blast furnaces (OBF) with flue gas circulation. Processes were assessed by technical modelling based on the Aspen Plus process simulator and the economic evaluation toolkit CC-SkynetTM using two indicators: the break-even price of CO2 emission allowances for CCS and the impact of CCS on steel production costs. With the whole chain approach, including CO2 capture, processing, transport and storage, the results show a significant reduction potential at an integrated steel mill for all carbon capture technologies assessed. The application of an OBF would require a larger modification of the processes of the existing steel mill than that required by the application of post-combustion capture. The staged construction and implementation of CCS in order to minimise the financial investment risk was considered and several pathways for implementation were analysed. Only transportation of CO2 by ship was considered due to the coast-line location of the installation far from other emission sources, pipeline infrastructures and storage sites. Results show the cost structure and feasibility of the studied technologies. Cost break-even points for CCS at an integrated steel mill, for the plant owner and costs for globally avoided emissions are calculated. The direct site emissions were reduced by 0.28-2.93 Mt CO2/a. The cases resulting in significant reductions represent 48-73% of direct site emissions. The net GHG impact of emission reductions are between 45-62% of the site emission reductions. The cost of emission reductions are estimated from the site owner perspective, with the costs in majority of the cases being between 40-70/t CO2. Oxygen blast furnace with top gas recirculation was estimated to be slightly cheaper than post-combustion capture of CO2. As presented in the results of this study, BePs (break-even prices) are very sensitive to several factors which are uncertain regarding the time frame of large investments. The results also showed that the costs for CCS are heavily dependent not only on the characteristics of the facility and the operational environment, but also on the chosen system boundaries and assumptions.