Formulation, analysis and plant design for coal water slurry fuel blended with wastewater

Abstract

Coal is an important and vital fossil fuel. It has been underutilized due to its complex mining procedures, transportation constraints and environmental impacts. Pakistan has vast amount of coal reserves and at present these reserves are not yet fully exploited due to the complications in underground coal gasification and mining. The proposed innovative technology of coal water slurry fuel can make the utilization of coal more easy and environment friendly. Finely ground coal particles are blended with water and additives to formulate a liquid fuel having properties comparable to the heavy fuel oils. Another novel idea is to use industrial wastewater instead of fresh water in preparation of coal slurry fuel. Major industries in Pakistan are facing problems of energy curtailment and wastewater disposal. Both the challenges can be effectively addressed by employing the proposed concept of coal slurry fuel together with the wastewater. The effects of blending pulverized coal in wastewater and fresh water were investigated in terms of properties such as heating values, sulfur content and ash content. Pulverized coal was obtained from ―Pioneer Cement‖, having average particle size 90 μm, heating value of 6260cal/g, 16.22% ash content and 0.69% sulphur content. Wastewater was collected from Noon Sugar Mills distillery having a pH of 3.92, brix 13.2, COD 101000 mg/l and BOD 35000 mg/l. Two samples of coal slurry fuel were prepared, one using fresh water and other using wastewater of alcohol distillery. Heating values were analyzed on dry basis, in case of wastewater sample the heating value decreases by a non-noticeable margin, the new value is 6014 cal/g and in case of fresh water sample it was 6245 cal/g. Sulphur in the fuel is increased to 0.96 due to presence of sulfur containing compounds in wastewater but for fresh water sample it is 0.83%. Further, ash content of the wastewater coal slurry fuel was 17.86% as compare to the fresh water sample, which was 16.72%. Both sample slurries can be fired in boilers in replacement of expensive heavy fuel oils. But in case of wastewater some post treatment is suggested in order to reduce Sulphur contents. All the parameters are in normal ranges so no post treatment is required.