Study on rewashing of crushed middling product of heavy medium separation system and related process renovation at Xinzhuang Coal Preparation Plant

The middling product produced by the plant’s heavy medium separation system has a relatively low ash and a high calorific value and contains some clean coal.To solve this problem, a study is made on the process for rewashing the middlings after being crushed to 6 mm, 1 mm, 0.5 mm, and minus 0.25 mm.The optimum technological process for rewashing the crushed middlings is determined based on screening, float-and-sink and timed-release flotation analysis.Study shows that the finer the crushed size, the higher the level of liberation and the more the recovery of clean coal.Through overall consideration of capital cost, space of workshop and other factors including operating cost, it is reckoned that the use of the process for rewashing the middlings crushed to a size of< 1 mm can yield the most favorable economic result.Practice shows the renovation work has led to an additional recovery of 19 300 tons of clean coal and creation of 9.49 million yuan revenues per year, yielding a remarkable economic benefit for the plant.