Clean products from coal gasification waste by flotation using waste engine oil as collector: Synergetic cleaner disposal of wastes

Synergetic cleaner disposal of coal gasification waste and waste engine oil is urgent, as the harmfulness to environment and lacks of clean and efficient technique. In this work, coal gasification fine slag was divided to two clean products without byproducts or wastes by flotation using waste engine oil as flotation collector, achieved the goals of "Carbons Recycle" and "Waste Disposal by Waste". The waste engine oil improved the flotation property of the -0.5 mm fraction coal gasification fine slag, thereby a flotation concentrate with a loss-on ignition of 88.86 wt% and recovery of 92.13 wt% was produced at the waste engine oil dosage of 3 kg/t. The main components of waste engine oil were hydrocarbons, esters, and heteroatom-containing species, as confirmed by gas chromatography/mass spectrometry. The mechanism of flotation using waste engine oil as a collector for the coal gasification fine slag particles was examined via the measurement of contact angles and wrap angles. The qualified tailings (i.e. flotation tailings and +0.5 mm fraction coal gasification fine slag) with loss-on ignition of less than 5 wt% were also obtained to the standard for direct utilization in building materials. Economic evaluation indicates that the net profit would reach 12309.46 USD/h, with a coal gasification fine slag raw capacity of 400 t/h. This work demonstrates that the application of waste engine oil in coal gasification fine slag flotation is feasible, efficient, economical, and eco-friendly, and it has potential industrial application prospects. (C) 2020 Elsevier Ltd. All rights reserved.