Removal of Phosphorus and Other Impurities from Cokes by Heating and Leaching

Abstract

One of the means to produce low phosphorus stainless steel is the removal of phosphorus from ferrochromium, which is its main source into the steels. In view of the fact that 70% of phosphorus in ferrochromium comes from cokes used as the reducing agent, the technical possibility to remove phosphorus and other impurities from various cokes has been studied in the present work by heating at elevated temperatures under argon at atmospheric and reduced pressures and followed by leaching into various acid solutions.
It was found that as the temperature was raised, phosphorus, sulfur, and nitrogen originally incorporated in coke matrix were gradually eliminated, following the initial decomposition of those included in inorganic minerals. At the same time, aluminum, calcium, and iron were removed as metallic vapor, silicon remaining in cokes as silicon carbide to the last.
Acid solutions dissolved only inorganic phosphorus and sulfur.