CHEMICAL CLEANING OF COAL USING PEROXYACETIC ACID-A STUDY OF DESULFURIZATION, ASH REDUCTION AND EFFECT ON GROSS CALORIFIC VALUE IN MIANWALI COAL

Abstract

Background: Leaching of Mianwali coal was carried out by using peroxyacetic acid as leaching agent. The effect of peroxyacetic acid concentration at different particle size of coal was investigated. The peroxyacetic concentration was varied from 80ml, 100ml, 140ml and 200ml and particle size of coal from 60 mesh, 100 mesh, 150 mesh and 200 mesh. The effect of peroxyacetic acid onto the particle size was determined by washing the coal with water and HCl respectively. The findings of this investigation have shown that acetic acid concentration has direct relation with sulfur reduction (%) and ash reduction (%). Accordingly, maximum reduction in sulfur and ash was obtained at 100ml and 200ml concentrations of peroxyacetic acid respectively and 200 mesh particle size. The total reduction in ash and sulfur contents after leaching was found to be 62% and 78% respectively. The clean coal can be used in various energy recovery

Objectives and scope of the study: Though many oxidative reagents have been used by different researchers, the selection of peroxyacetic acid is highly capable because this reagent is an excellent and essential chemical in the establishments of various industries. It is used for bleaching process of pulp (Borah [5] and wood chips in presence of acid, to form volatile substances, in sugarcane industry [6], in the paper making process. Therefore,  due to large utilizations of peroxyacetic acid in various industrial sector, and as an oxidizing reagent used by Palmer [7] to desulphurize coal, it is measured that it could be an excellent oxidizing reagent for the removal of sulfur and ash content present in Mianwali coal.

The objective of this study is to reduce the amount of sulfur and ash contents present in Mianwali coal by chemical cleaning of coal. Coal contains several trace elements and metals which may be related as mineral matter or bonded with organic matter. During desulphurization process some metals could be leached out from coal particles which may also affect sulfur and ash removal process. The presence of metal ions in the oxidative desulphurization of pyritic sulfur by hydrogen peroxide has been observed. The present investigation is an attempt to understand the possible pathways for the formation of oxidized sulfur species responsible for desulphurization. Moreover, the formation of silicates and aluminates of trace metals, present in the coal matrix which may be responsible for the addition of some extra ash content in the leached coal, have also been discussed.

Significance of work: Researches have been shown that Peroxyacetic Acid is a better oxidizing agent for the desulfurization of coal having high sulfur content than acetic acid and hydrogen peroxide. This is an upgraded technology in the field of chemical cleaning of coal for the improvement of coal technology because it is simple with low cost and easily available chemical, and therefore, has significant technological interest.