Investigation of removal of ash and sulfur from Kangal (Sivas/Turkey) lignite with the application of combined methods

Abstract

ABSTRACT Boric acid is a dilute or mild acid derived from boron, and it is available in a water-soluble form as a white powder. Strong acids are generally preferred to remove ash and sulfur from coal. However, consumption of these strong acids harms the environment. Therefore, it is necessary to improve the leaching possibilities of weak acids. Also, a combination of beneficiation methods may need to be used to achieve the desired quality and environmental compatibility of coal. In this study, a combination of bioleaching and chemical experiments was employed to eliminate ash and sulfur from Sivas Kangal lignite coal. Initially, bioleaching experiments were conducted on lignites with high ash and sulfur contents by bioreactor with Acidithiobacillus ferrooxidans. Following this, in the second phase of experiments, boric acid leaching was employed to beneficiate Sivas/Turkey lignites through chemical methods. Additionally, the effect of glycerol on the leaching efficiency of boric acid, which is a weak acid, was investigated. Experimental findings have shown that combination methods provide better results in ash and sulfur removal from lignite coal. Finally, a clean coal product with 19.80% ash and 2.89% S content was obtained by combination methods to the lignite coal (46.60% ash and 4.99% S).