Abstract: A process for treating coal to obtain lower ash content coal including: (i) pretreating high ash coal in a pretreatment unit with ultrasonic waves or microwaves, (ii) forming a slurry of coal fines in a solvent solution including N-Methyl-2-pyrrolidone (NMP) and one of Ethylenediamine (EDA) or Monoethanolamine (MEA), (iii) maintaining said slurry in a refluxed condition at a temperature of about 170-190° C. for a period of about 15 minutes to 2 hours; (iv) separating the refluxed slurry into two parts consisting of extract and residue by coarse filtration, (v) recovering up to 85% of the solvent solution by evaporation of the extract to form a concentrated extract, (v) precipitating the coal by adding water to the concentrated extract, (vi) separating the coal from the water-extract solution by filtration, and (vii) recovering the rest of the solvent by distillation of the water-extract solution.

Abstract: A process for treating coal to obtain lower ash content coal including: (i) pretreating high ash coal in a pretreatment unit with ultrasonic waves or microwaves, (ii) forming a slurry of coal fines in a solvent solution including N-Methyl-2-pyrrolidone (NMP) and one of Ethylenediamine (EDA) or Monoethanolamine (MEA), (iii) maintaining said slurry in a refluxed condition at a temperature of about 170-190° C. for a period of about 15 minutes to 2 hours; (iv) separating the refluxed slurry into two parts consisting of extract and residue by coarse filtration, (v) recovering up to 85% of the solvent solution by evaporation of the extract to form a concentrated extract, (v) precipitating the coal by adding water to the concentrated extract, (vi) separating the coal from the water-extract solution by filtration, and (vii) recovering the rest of the solvent by distillation of the water-extract solution.

Abstract: An improved beneficiation process to produce low ash clean coal from high ash coals, comprising: preparing a coal slurry from fine coal and water and discharging it to a first reactor; preparing an alkali solution of NaOH and water and discharging it to a first reactor; carrying-out a leaching reaction between the coal and the alkali solution inside the first reactor; transferring the reaction mixture to a second reactor for filtration and washing to produce a filter cake; preparing a diluted acid solution in a second tank and delivering it to a second reactor; preparing a diluted alkali solution in a third tank and delivering it to a second reactor; feeding a coal slurry prepared from the filter cake into the second reactor for washing and transferring to a second filtration unit; transferring the product after filtration to a third reactor; carrying-out different leaching reaction sequences in the first, second, and third reactors; and transferring to a fifth tank the treated coal filter cake for drying.