Costs and Potential of Carbon Capture and Storage at an Integrated Steel Mill

Abstract

In this study different possibilities and the feasibility of applying carbon capture at an integrated steel mill based on blast furnace process, in order to reduce carbon dioxide emissions were studied. Technologies considered for capturing of CO2 are post-combustion carbon capture (PCC) and oxygen blast furnace route (OBF). Post-combustion capture for the integrated steel mill was evaluated in an earlier study by Arasto et Al. and Tsupari et Al. [1,2]. Implications of different capture amounts, different solvents for post-combustion capture and process integration levels to the greenhouse gas balance and operation economics are compared to the steel production base case with varying costs of CO2 emission allowances. Furthermore the effect of reducing the carbon intensity of steel production on the final steel production cost is evaluated.Iron and steel industry is responsible of around 5% of the overall global CO2 emissions [3]. Steel production based on the blast furnace and basic oxygen furnace-based route is the main technology corresponding to the growth in global steel production [4] and this technology route is also the main source of CO2 emissions in the iron and steel industry.The assessment of potential and cost for carbon capture and storage in the iron and steel industry is based on a case study on Ruukki Metals Oy's steel mill in Raahe. The mill is situated on the northeastern coast of the Gulf of Bothnia. It is the largest integrated steel mill in the Nordic countries producing hot rolled steel plates and coils. It is also the largest CO2 point source in Finland emitting approximately 4 Mton of CO2/year. Raahe steel mill produces district heat for use in the town nearby as well as for use onsite for heating of the premises. The power plant is connected to the national electricity grid, and thus it is possible to buy and sell electricity across system boundary.In contrast to power plant applications of CCS, CO2 emission sources at an integrated steel mill are scattered around the industrial site and the flue gases are led to several stacks. Due to this, the capture process evaluation is much more complex and requires system level optimization. Carbon capture processes and process integration options were modeled using Aspen Plus process modeling software and the results were used to estimate CO2 emission reduction possibilities and carbon abatement costs at the integrated steel mill from an investor's point of view. Different heat integration options and heat utilization scenarios were investigated and optimized with a custom-built CC-Skynet™ economics toolkit. Heat available for solvent regeneration varies between these heat utilization scenarios and thus different capture amount are investigated depending on the heat available for solvent regeneration in different case studies. Also different technologies related to oxygen blast furnace were considered, both for oxygen production and for top gas treatment. The application of oxygen blast furnace effects directly e.g. to the coke consumption of process and power production on site, and thus a new design considering new heat and process gas integration opportunities is essential.With a whole chain approach, including CO2 capture, processing, transport and storage, results show significant reduction potential at an integrated steel mill with carbon capture technologies. Ship transportation of CO2 is considered due to the location of the installation. Results show also the cost structure and feasibility of the studied technologies. Cost breakeven points for carbon capture at an integrated steel mill, for the plant owner and costs for globally avoided emissions are calculated. The study also reveals some major technical restrictions of the application. Finally the pros and cons of the technologies are compared and the role and potential of CCS as a carbon abatement tool in the European steel industry is considered.