Exergy analysis of hydrogen-reduction based steel production with coal gasification-shaft furnace-electric furnace process

Carbon-free energy utilization in steel production is an effective way for China's iron and steel industry to achieve low carbon development. Thus, coal gasification-shaft furnace-electric furnace (CSE) technology, which use hydrogen-enriched gas for steel production, has recently become a sustainable topic of great concern. In the current study, the material flow analysis (MFA) and exergy assessment of the CSE process are conducted to investigate the material consumption and energy efficiency of this new steelmaking process. The exergy efficiency of the CSE process is calculated to be 50.11%, indicating a great potential for energy-saving. The results indicate that the coal gasification & gas purification that responsible for hydrogen-enriched gas production is the system with the largest exergy loss (account for 23.13% of the total exergy input), while the pelletizing system has the lowest efficiency (13.33%) due to heat loss. The key to further improve the thermal performance of this process lies in the heat recovery of the coal gasifier and pelletizing. It is also found that when the H-2 content in reducing gas rise from 57.00% to 100.00%, the exergy efficiency of the shaft furnace is only increased by 1.58%, while the demand volume of reducing gas significantly increases from 1326.30 Nm(3)/t to 2201.50 Nm(3)/t. The environmental benefits of hydrogen reduction based steelmaking must be considered together with energy utilization and production cost. The present work should do helpful effort for the application and further improvement of the CSE process in China. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The utilization of carbon-free energy in steel production, specifically the coal gasification-shaft furnace-electric furnace (CSE) technology using hydrogen-enriched gas, has a great potential for energy-saving and low carbon development in China. Material flow analysis and exergy assessment have revealed areas for improvement in energy efficiency, with a focus on heat recovery in the coal gasification and pelletizing systems. Increasing the H-2 content in the reducing gas may lead to a slight increase in exergy efficiency of the shaft furnace, but at the cost of significantly higher demand volume of reducing gas. Balancing environmental benefits, energy utilization, and production cost is essential for the success of hydrogen reduction based steelmaking processes.