Abstract
The study aims at the assessment of the impact of geometrical parameters of spiral separators on the efficiency of density separation of fine-grained materials. Experiments were carried out on three spiral separators: Krebs 2.85, Reichert LD-4 and Reichert LG-7. Three materials were used for the tests: raw coal, coal waste and mix of sand and magnetite as the model material. Results of raw coal and coal waste upgrading showed that density separation was most efficient in Reichert LD-4 spiral. This is due to the fact that this device had the highest amount of coils, height of sluice as well as was equipped with additional dense product collector and additional water sluice for transport water. The lower slope of sluice and larger height made separation even more efficient. Analysis of separation of model material, that is the mix of sand and magnetite, showed that in this case the existence of additional water sluice does not have an impact on product separation and best results were obtained in the Reichert LG-7 spiral separator. The shape and width of sluices did not have a significant impact on the separation process.
Highlights
Spiral separators are commonly used for the separation of fine-grained materials with the particle size not exceeding 3 mm
Other forces act on the particles and these are: gravity where direction is always constant for each particle and the force depends on the particle density; centrifugal force which results from the spiral movement of the water stream; friction which is the result of the slide of the particle on the surface of the sluice [4,5]
There are two sluices with three coils each. - Reichert LD-4 spiral: height 2500 mm, spiral diameter 900 mm; number of coils 6; sluice slope 15°; sluice width 280 mm - including additional sluice for transporting water of 60 mm; shape of sluice – circular sector with flattened bottom; the outer part of the sluice is of 8,5 cm in height and bend 90°; additional sluice for transporting water is a flat shaped sluice 6 cm in depth; distance between separating cuts for heavy product, semi-product and light product is 100, 80, 80 mm respectively; heavy product collectors – underflow at the bottom of spiral separator and one additional collector in the middle of the spiral; spiral is made of plastic without liners
Summary
Spiral separators are commonly used for the separation of fine-grained materials with the particle size not exceeding 3 mm. Other forces act on the particles and these are: gravity where direction is always constant for each particle and the force depends on the particle density; centrifugal force which results from the spiral movement of the water stream; friction which is the result of the slide of the particle on the surface of the sluice [4,5]. These forces act on the particles and lighter particles move with a higher speed whereas centrifugal force pushes particles to the outer side of the spiral [6]. Dense particles tend to concentrate on the inner side of the sluice [7]
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