Optimization of CO2 Capture using Chemical Solvents from Steel Mill’s Works Arising Gases

Abstract

Based on the Paris Accord, various governments have agreed to a long- term goal of keeping the increase in global average temperature to well below 2°C above pre-industrial levels; The Netherlands has committed to reduce its CO2 emissions with 80% by 2050; in this plan, the Dutch government has set an ambitious target for the industry to reduce their emissions by 70 million tonnes of CO2 annually. In The Netherlands, the steel industry contributes to nearly 7% of the total greenhouse gas emissions inventory. To meet the Dutch Government target, Tata Steel IJmuiden is exploring various options to reduce its CO2 emissions. One of the options being considered is CO2 Capture, whereby the CO2 could be captured from the Works Arising Gases (WAGs). Currently, the use of chemical absorption is the most mature technology to capture CO2 from any gas. This study has evaluated the performance, equipment sizing and cost of capturing CO2 using MEA or MDEA/Pz solvents. The performance of the chemical absorption process capturing 90% of the CO2 from a mixture of Blast Furnace Gas and Basic Oxygen Furnace Gas has been evaluated. The process was modeled in ASPEN Plus® . For cases using MEA as solvent, the conventional configuration were evaluated. It could be concluded that the optimal lean loading is around 0.19 mol/mol resulting to a specific reboiler duty of around 3.95 MJ/kg CO2 captured. Different advanced process flow configurations were also assessed. The results showed that the use of intercoolers in combination with a flash split-flow or LVC could result in a reduction of the specific reboiler duty. For cases using of MDEA and Pz as solvent, the conventional configuration operating with 1 and 10 bara absorber pressure were modeled. Resulting to a specific reboiler duty of 3.56 and 2.70 MJ/kg CO2 for 1 and 10 bara operating pressure, respectively. Furthermore, different advanced configurations were also assessed. This consisted of the incorporation of intercoolers and 1-stage or 2-stage configurations. With intercooling, the specific reboiler duty could be lowered down to 2.85 and 2.43 MJ/kg CO2 for operating pressure at 1 bara and 10 bara, On the other hand, based on the UCARSOL 1-stage configurations operating at 10 bara, the specific reboiler duty could be reduced down to 2.34 MJ/kg CO2. A reduction in specific reboiler duty for the 2-stage configuration could be significantly lowered. Preliminary economic evaluations were undertaken in this study to obtain the specific CO2 capture cost – based on CAPEX and OPEX estimates using 8% discount rate and an economic lifetime of 25 years. For the MEA cases evaluated, the costs of CO2 captured are in the range of 52.7 to 65.8 €/tonne CO2; the lowest cost is achieved with the LVC configuration in combination with intercooling. On the other hand, the results for the MDEA/Pz cases indicated that the costs of CO2 captured are in the range of 54.1 to 67.3 €/tonne CO2; the lowest cost is given in the configuration with intercooling operating at 1 bara.