Reduction Reactivity of Low Grade Iron Ore-Biomass Pellets for a Sustainable Ironmaking Process

Abstract

Currently, fossil fuels are still the primary fuel source and reducing agent in the steel industries. The utilization of fossil fuels is strongly associated with CO2 emissions. Therefore, an alternative solution for green steel production is highly recommended, with the use of biomass as a source of fuel and a reducing agent. Biomass’s growth consumes carbon dioxide from the atmosphere, which may be stored for variable amounts of time (carbon dioxide removal, or CDR). The pellets used in this study were prepared from a mixture of low-grade iron ore and palm kernel shells (PKS). The reducing reactivity of the pellets was investigated by combining thermogravimetric analysis (TGA) and laboratory experiments. In the TGA, the heating changes stably from room temperature to 950 °C with 5–15 °C/min heating rate. The laboratory experiments’ temperature and heating rate variations were 600–900 °C and 10–20 °C/min, respectively. Additionally, the reduction mechanism was observed based on the X-ray diffraction analysis of the pellets and the composition of the reduced gas. The study results show that increasing the heating rate will enhance the reduction reactivity comprehensively and shorten the reduction time. The phase change of Fe2O3 → Fe3O4 → FeO → Fe increases sharply starting at 800 °C. The XRD intensities of Fe compounds at a heating rate of 20 °C/min are higher than at 10 °C/min. Analysis of the reduced gas exhibits that carbon gasification begins to enlarge at a temperature of 800 °C, thereby increasing the rate of iron ore reduction. The combination of several analyses carried out shows that the reduction reaction of the mixture iron ore-PKS pellets runs optimally at a heating rate of 20 °C/min. In this heating rate, the reduced gas contains much higher CO than at the heating rate of 10 °C/min at temperatures above 800 °C, which encourages a more significant reduction rate. In addition, the same reduction degree can be achieved in a shorter time and at a lower temperature for a heating rate of 20 °C/min compared to 10 °C/min.

Comparison of Hydrochar and Anthracite as Reducing Agents for Direct Reduction of Hematite

“…Extensive research has been undertaken to investigate the possibilities to substitute fossil carbon with biocarbon in the CCA to further decrease fossil CO 2 emissions during its use. To date, researchers have tested different biomass material as carbon additions in CCA, including low-volatile biochar 5,[14][15][16][17][18][19][20][21] , high-volatile torrefied biomass [22][23][24] , and raw biomass 19,20,[25][26][27][28][29][30][31] .…”

“…Although the positive contributions of biomass volatiles to the direct reduction process are known, there is still very few study that quantitatively determined the RD of IO contributed by biomass volatiles ( ) and by biomass char when biomass is utilized in the form of CCA. For RD VM the studies that measured [25][26][27] , the values scattered widely between 2-41%, which depends RD VM on the reduction temperature, the type of biomass used, the amount of biomass added in the sample, the reducibility of the IO material, and the heating rate. Additionally, no study so far has used hydrochar, a type of high-volatile biocarbon produced from hydrothermal carbonization of organic feedstocks, for direct reduction of IO.…”

Transformación de las hojas de caña de azúcar en biocarbón para su uso como combustible y agente reductor en procesos de reducción directa de minerales de hierro

“…En el campo de nuevos materiales, se están realizando esfuerzos para incorporar fuentes de energía renovable, como la biomasa, a los procesos metalúrgicos en reemplazo del coque (Wei et al, 2017). Actualmente, la biomasa es considerada una opción atractiva por ser un combustible neutro en CO2 (Chen et al, 2015) pudiendo ser empleada como como combustible y agente reductor en los procesos de reducción del mineral de hierro (Zulkania et al, 2022. En este contexto se vienen realizando investigaciones en el uso de la biomasa en procesos de reducción directa para la producción de pellets de hierro esponja, producto que puede sustituir a la chatarra para la producción de acero en los hornos de arco eléctrico (Ramakgala y Danha, 2019).…”