Effect of Coal and Coke Ash on Blast Furnace Slag Properties: A Comparison Between Pulverized Coal, Charcoal, Fossil‐Based Coke, and Biocoke

Abstract

Blast furnace (BF) is the most used equipment for production of iron in the world. It is charged mainly with metallurgical coke and ferrous materials. When descending inside the BF, iron‐bearing materials start reducing and melting with other burden materials. This melting leads to the formation of so‐called primary slags from which the final slag is formed as materials descend inside the furnace. Each charge material has a unique effect on the total composition of the BF slag. Herein, the parts of the slag, which originate from ash of metallurgical coke and pulverized coal, and changes in the final slag compositions and properties are focused on. The global trend is to decrease the use of fossil‐based carbon by replacing it with bio‐based coal. Ash from coke and pulverized coal eventually dissolve in the final slag, affecting its properties. The purpose herein is to evaluate how BF slag composition changes when fossil‐based coke is replaced with biocoke and pulverized coal is replaced with charcoal. Based on mass balance calculations, these replacements have both increasing and decreasing effects on solidus and liquidus temperatures, viscosity, and CaO/SiO2 and MgO/Al2O3 ratios depending on the used replacement materials.

Optimising Carbon Type Differentiation Techniques to Reduce Dust Emissions in Blast Furnace Ironmaking

“…The ash content of the final blend of coal should be maintained between 7 and 9%. This was to prevent issues with residue after combustion clogging the furnace, or the ash constituents drawing on heat reserves of the furnace caused by high levels of ash content of the coal [110]. Coals A and B are low in ash content and are blended with high ash coals, to lower the ash content of the blend with high ash coals such as Coal E, which was above the limit for ash to be used in isolation.…”