Design and Analysis of Hydrogen Based Direct Reduction Plant

Abstract

The steel industry account for 6-7% of CO2 emissions according to the IPCC. It was estimated that 1.90 ton CO2 is generated per ton crude steel. These emissions are mainly due to the energy needed to produce DRI. Although CO2 emissions has been drastically decreased to 0.54 ton per ton DRI through the current technologies, there is an urgent need to further reduce CO2 emissions. In this work, two cases of direct reduction plant shaft furnace were simulated, HYL III/MIDREX and hydrogen based shaft furnace in order to analyze the thermodynamic differences between the two cases. A parametric study were conducted using ASPEN PLUS. It was found that hydrogen gas flow rate need to increase by 16% in comparison to the syngas flowrate or increase the temperature up to 1200 C in order to maintain the metallization and carburization. This is because of the high endothermic reaction of pure hydrogen with iron ore.

A whole plant simulation was preformed by ASPEN PLUS V12 for 5 direct reduction plant configurations, HYL III, Modified HYL III, MIDREX, Modified MIDREX and hydrogen based plant. The objective was to optimize these configuration to minimize CO2 emissions and energy consumption. It was found that a modified HYL III process can reduce the CO2 emissions by 22%. While the modified MIDREX plant can reduce the CO2 emissions by 35%. In addition, it was found that 71 kg of hydrogen and 42 NCMH of natural gas are needed per ton of DRI to achieve >92% metallization and >2% carburization.

A techno-economical analysis was conducted for each configuration to estimate the levelized cost in UAE. The results suggest that the modified HYL III process could be a cost effective solution when carbon taxation is implemented. When the carbon tax reach 120 $/ton CO2 and natural gas price 8.75 $/MMBtu, this configuration can save 9 $/ton DRI in comparison to the original HYL III. In a such scenario, the levelized cost for HYL III and modified HYL III is 515 and 506 $/ton DRI respectively. The modified configuration of MIDREX is not economically viable even on carbon tax reaches 120 $/ton CO2. This is due to the high operational and capital cost in comparison to the original MIDREX. In a pessimistic scenario, when carbon tax is 120 $/ton CO2 and natural gas price 8.75 $/MMBtu, the levelized cost of MIDREX and the modified MIDREX is 571 and 580 respectively. Finally, hydrogen based plant shows ideal results for decarbonization. However, it is only economically viable when hydrogen cost drop below 1.30 $/kg for the business as usual scenario or 2.25 $/kg for the pessimistic scenario in 2030 when the carbon tax is 120 $/ton CO2 and natural gas cost above 8.75 $/MMBtu. Nonetheless, the carbon tax only affect the levelized cost by 2% when taxation change by 20%. Iron ore is the most impactful factor on the levelized cost.

Date of Award	Apr 2023
Original language	American English
Supervisor	ALI ALMANSOORI (Supervisor)