The evolution of spirals in the coal fine circuit: A review

Spiral concentrators are extensively employed in coal beneficiation for the processing of fine coal particles within the size range of 2000 to 100 microns. Spirals separate valuable minerals from gangue based on their density. Among the gravity separators, the spiral concentrator is one of the most efficient and simple unit operations. The main operating variables for a spiral concentrator are the feed rate, the solid concentration, and the position of the cutters or splitters used to separate the tailings, middling and concentrate streams. Traditional spirals are classified as highcut technologies with typical cut point between 1.7 and 1.8 specific gravity. Recent developments in spirals have seen the introduction of low-cut spirals to the markets, these spirals have been shown to produce specific gravity cut points in the range of 1.4 to 1.55. This paper aims to review the status of spiral development, understand current challenges associated with fines processing in the industry and to establish gaps that require addressing to make the spiral relevant in the fines circuit while solving challenges faced in the coal processing industry.