Improving the flotation performance of an oxidized bituminous coal source

Numerous studies have been conducted describing the challenges with oxidized coal flotation. Common industrial collectors such as fuel oil are typically ineffective under natural conditions for the flotation of oxidized coal sources such as the Coalburg seam from the Central Appalachia coalfields of the U.S. Low plant flotation recovery values of less than 30% were realized in part due to the weak surface hydrophobicity and the clay coating that results from a reduced isoelectric point of the coal and low slurry pH values. Elevated pH values and the use of a model collector containing carboxylic groups improved flotation recovery values by nearly 45 absolute percentage points. Operating at pH values around 7.5 to disperse the clay slimes and provide more surface active dimer complexes produced from a carboxyl collector resulted in excellent flotation recovery values for a hard-to-float coal. Due to the frothing properties of the carboxyl collector, column flotation with froth washing was needed to provide product ash values as low as 7.5%.