Study on Direct Reduction in Carbon-Bearing Pellets Using Biochar

Jianlong Wu, Shengli Wu, Gang An, Chengwei Ma, Zhaojie Teng, Kun Xu, Chuan Wang, Xiaojun Ning and Guangwei Wang ()
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Jianlong Wu: Shougang Group Research Institute of Technology, Beijing 100043, China
Shengli Wu: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
Gang An: Shougang Jingtang Iron and Steel Co., Ltd., Tangshan 063200, China
Chengwei Ma: Shougang Jingtang Iron and Steel Co., Ltd., Tangshan 063200, China
Zhaojie Teng: Shougang Jingtang Iron and Steel Co., Ltd., Tangshan 063200, China
Kun Xu: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
Chuan Wang: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
Xiaojun Ning: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
Guangwei Wang: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China

Sustainability, 2023, vol. 15, issue 24, 1-14

Abstract: As a renewable, carbon-neutral raw material, the application of biomass in steel production is conducive to reducing greenhouse gas emissions and achieving green and sustainable development in the steel industry. The heating and reduction process of a rotary hearth furnace was simulated under laboratory conditions to roast and reduce biochar carbon-bearing pellets with coke powder and anthracite carbon-bearing pellets as a comparison. This was conducted to investigate the impact of biochar as a reducing agent on the direct reduction in carbon-bearing pellets. Under various reduction temperatures, carbon/oxygen ratios, and reduction times, tests were conducted on the compressive strength and metallization rate of carbon-bearing pellets made using typical binder bentonite. Results show that with the increase in reduction temperature, the metallization rate of pellets increases, while the compressive strength initially decreases and then increases, reaching the lowest point at 900 °C and 1000 °C. When the ratio of carbon to oxygen is between 0.7 and 0.9 and the reduction time is between 15 and 25 min, carbon-bearing pellets meet the requirements of both the metallization rate and the strength, with the metallization rate above 80%. However, severe volume swelling and low strength were observed in biochar carbon-bearing pellets at 900 °C and 1000 °C, which negatively impacted multi-layered charging and heat transfer efficiency in the blast furnace. Therefore, a novel laboratory-prepared binder was introduced in the preparation process of biochar carbon-bearing pellets at an appropriate addition ratio of 5–8%. Without producing any swelling concerns, the inclusion of this binder considerably improved the compression strength and metallization rate of the pellets, enabling them to fulfill the standards for raw materials in the blast furnace.

Keywords: biomass; carbon-bearing pellets; rotary hearth furnace (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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