Assessment on the Application of Commercial Medium-Grade Charcoal as a Substitute for Coke Breeze in Iron Ore Sintering

Abstract

The application characteristics of cost-effective commercial medium-grade charcoal (MG charcoal) in the sinter-making process were assessed in this paper. The results showed that, in comparison to high-grade charcoal (HG charcoal), MG charcoal was characterized by a lower fixed carbon content, a higher volatile content, and a higher porosity and specific surface area, which led to its even greater difference in thermochemical behaviors with coke breeze than HG charcoal. This property of MG charcoal resulted in a faster sintering speed, a lower bed temperature, and a shorter holding time above 1200 °C for adhesive mineral melting, which restrained its proper replacement percentage at 20%, while it was 40% for HG charcoal. To achieve a sintering performance similar to the HG charcoal, the combustion behavior of MG charcoal and coke breeze was regulated simultaneously by coating fine-grained iron ore concentrate and adhering CaO, respectively. It was found that coating concentrate was useful to reduce the combustion rate of MG charcoal for reduced probability to contact air directly, while adhering CaO helped to accelerate the combustion rate of coke breeze as a result of the potential catalytic effect, which finally exhibited a relatively matched combustion speed. Sinter pot trials verified that, after pretreating MG charcoal particles and coke breeze through the pregranulation process, MG charcoal replacing 40% coke breeze showed a comparable sintering performance to the case using 100% coke breeze. The emissions of CO2, SO2, and NO x achieved an obvious reduction by 21.70, 27.75, and 18.31%, respectively.

Formation of Nitrogen Mono Oxide (NO) during Iron Ore Sintering Process

“…In addition to the surrounding material, the combustion atmosphere also has an important influence on the burning of fuel. 25) For C in sintering process, there are the combustion reactions (2C + O 2 →2CO and C + O 2 →CO 2 ) and the gasification reaction (C + CO 2 →2CO). From the non-isothermal gasification thermogravimetric curve (Fig.…”

Effect of coating structure of granulated quasi‐fuel particles in iron ore sintering

“…Incomplete combustion leads to less heat released. Moreover, too fast combustion rate led to the mismatch between flame front and heat transfer front, which was not conducive to heat accumulation 11 …”

“…Currently, iron ore sintering consumes a large number of fossil fuels, accounting for 0.7% of global CO 2 emissions each year 6,7 . To reduce greenhouse gas emissions, various scholars have focused on using carbon‐neutral biomass fuels to gradually replace fossil fuels in the sintering process 8–11 . Furthermore, biomass fuels have significant advantages in reducing NO x and SO 2 emissions due to the low N and S contents 12,13 …”

“…For charcoal, Cheng et al 13 proposed that embedding charcoal inside the quasi‐particles can improve thermal conditions during sintering due to the slower speed of oxygen diffusion and smaller surface area for reaction. To match the combustion rates of charcoal and coke breeze, Ji et al 11 used iron ore concentrate to coat charcoal through pregranulation to slow combustion rate and used quicklime to coat coke to increase combustion rate. The sintering test results show that using the carefully prepared fuel granules can increase the replacement ratio of medium‐grade charcoal from 20% to 40% without compromising sinter quality.…”

“…Moreover, most of the predecessors used quicklime (CaO) and fine iron ore (Fe 2 O 3 ) as the adhesion layer during pregranulation. Almost no one has studied the effect of different adhesion layers covering fuel particles in pregranulation on sintering 11,16 …”