Optimum temperatures for carbon deposition during integrated coal pyrolysis–tar decomposition over low-grade iron ore for ironmaking applications

Abstract

Carbon deposited within low-grade iron ore, which was produced using an integrated process of coal pyrolysis and tar decomposition, showed high reactivity as a reducing agent. Coal pyrolysis and tar decomposition were both highly sensitive to temperature and exhibited contrasting behaviours during carbon deposition. In these experiments, the optimum temperatures for pyrolysis and tar decomposition were determined to obtain maximum carbon deposition within porous iron ore. High-temperature pyrolysis generated large amounts of volatile matter (tar and gases), which caused high tar decomposition and produced large amounts of deposited carbon and gases. The deposited carbon was the major product of tar decomposition at lower temperatures (400-600 °C), whereas mainly gases were produced at higher temperatures (700-800 °C), because of gasification of carbon. However, sintering started at 800 °C, and it significantly diminished the BET surface area and pore size distribution. The highest amount of deposited carbon was obtained at a pyrolysis temperature of 800 °C and a tar decomposition temperature of 600 °C. Hamersley ore gave higher amounts of deposited carbon than Robe-river ore because of its large pore size less than 4 nm, which was suitable for carbon deposition. The pore size distribution was a more important factor than the surface area in the carbon deposition process. Based on these results, the proposed system could achieve maximum carbon deposition in porous iron ore and solve problems related to reducing agents, tar materials, and the use of expensive raw materials in the ironmaking industry.

Utilization of Low Grade Iron Ore (FeOOH) and Biomass Through Integrated Pyrolysis-tar Decomposition (CVI process) in Ironmaking Industry: Exergy Analysis and its Application

“…........................ (7) ............................... (8) .......... (9) ... (10) . The exergy loss (EXL) was calculated as the difference between the exergy of the input material (εin) and that of the output material (εout) in each unit of the system.…”

“…This value was calculated by using the remaining pore volume of the porous ore after the carbon deposition process. 7,9) Figure 6 shows the exergy losses and ore product for both conventional and proposed system with different amounts of deposited carbon. As the carbon deposition originated from tar decomposition, increasing the carbon deposition enhanced the ore product exergy and decreased the chemical tar exergy outflow.…”

“…However, it has been reported that the dehydration of goethite at 450°C with a heating rate of 3°C/min in an air creates micropores ranging from 2 to 4 nm in size and a BET specific surface area as high as 70 m 2 /g. 7) Because of these, Miura et al 8) proposed iron ore/carbon composite (IOC) by introducing carbonaceous material into the pores to enhance the reduction rate of iron ore. The reduction rate of an IOC sample prepared using FeOOH reagent and thermoplastic carbon resin is dramatically enhanced and proceeds at temperatures as low as 700°C.…”

Study of pyrolysis of ulin wood residues

“…Figure 5 shows that the biggest three compositions of gas yield are CO, CO2, and CH4. Main gases produced at highest temperature [10]. These main gases producted at 700 °C.…”

A novel slag carbon arrestor process for energy recovery in steelmaking industry

“…These temperatures were chosen based on the literature which suggests the optimum temperatures of coal pyrolysis and tar decomposition for achieving the maximum carbon deposition [28]. Table 1 gives the detailed compositions of the hot raw COG (excluding tar) and BOF slag used in this study.…”