Process upgradation and kinetic modeling of high-ash non-coking coal flotation using bio-based collector for enhanced clean coal recovery

Abstract

The reduction of ash content, contributed by inorganic mineral matter, and recovery of carbon values in a high ash non-coking coal was studied in a laboratory-scale mechanical flotation cell using a biocollector (PSO) derived from the pumpkin seeds for clean coal recovery. Surface characterization of PSO (GCMS, FTIR) and untreated/PSOtreated coal (contact angle, FTIR) indicated potential interaction between PSO and the coal surface, enhancing its hydrophobicity, while XRD analysis confirmed successful rejection of ash-forming inorganic gangue minerals into tailings, signifying effective clean coal separation from the gangue. The input parameters, such as PSO dosage, frother MIBC dosage, and airflow rate (AFR), were enhanced to attain best process responses, i.e. yield, ash, and fixed carbon of the final clean coal. The use of PSO significantly reduced the ash content of feed coal from 32% to as low as 9.86% in the final clean coal while simultaneously increasing the fixed carbon content from 35% to 61.15% and the gross calorific value from 4966 Kcal/Kg to 6318 Kcal/kg. A clean coal product having high fixed carbon of 61.15% with 11.29% ash content and 70.14% yield was obtained at PSO dosage of 10.73 Kg/t, MIBC dosage of 0.93 Kg/t and at AFR of 2.5lpm. The kinetic study revealed a high recovery of combustible materials (~88%) and low ash recovery (~46%) at a flotation time of 480 seconds. Based on the kinetic model discrimination analysis, it was found that the first-order fits well with the experimental data for combustible and ash recovery. This study illustrates the efficacy of pumpkin seed oil (PSO) as a potential bio-collector for the flotation of non-coking coal, enhancing the coal quality by selectively reducing mineral matter content and leading to substantial economic and environmental advantages.