Disclosed is an underground coal preparation process adopting a water medium, comprising: feeding exploited raw coal into a Φ25 mm raw coal classifying screen for screening; performing dry coal preparation on a classifying screen oversize product with a particle size greater than 25 mm and feeding a classifying screen undersize product with a particle size less than 25 mm into a special underground compact jigging machine for sorting to obtain jigging machine overflow clean coal, jigging middling coal and jigging gangue; screening and dewatering the jigging machine overflow clean coal to obtain a clean coal product, and screening and dewatering the jigging middling coal to obtain a middling coal product, sorting slime water to be sorted and generated during sorting to obtain coarse clean coal slime and coarse middling coal slime, and performing circulating water treatment on a final liquid.

A wide-size-fraction flotation system and process includes feeding coal slime to be floated into a stirrer, adding water to the floating coal slime in the stirrer, stirring, then feeding same into a grading cyclone through a first feeding pump for pre-grading; after grading of the coal slime in the grading cyclone, feeding overflow in the grading cyclone into a flotation column through a second feeding pump for flotation, discharging flotation tailings through an underflow port of the flotation column, collecting flotation concentrates through an overflow port of the flotation column and feeding same into a bubble generator through a fourth feeding pump, and the flotation concentrates passing through the bubble generator and being fed from the bottom of a hydraulic flotation machine; and feeding underflow in the grading cyclone into the hydraulic flotation machine through a third feeding pump, for flotation and recovery.

A clean coal production system and method for treating coal refuse (waste) resulted from coal mining or coal washing plants by extracting substantial remaining coal components from said coal refuse (waste) and turning them into clean (fine) coal products of much higher market value wherein the necessary water usage is recovered, recycled, and reused in a closed setting (ecosystem) to minimize environmental concerns.

A system for collecting mercury from feed material that can be tailings comprises: a water inlet for forming a slurry containing the tailings; at least one screen for separating tailings greater than ¼ inch in diameter from the slurry to form a screened slurry; a rotatable collection chamber containing a plurality of plates, a drive for rotating the collection chamber for collecting mercury on the plates to provide a discharge material comprising water and treated tailings, the treated tailings containing less mercury than in the feed material.

A system for collecting mercury from feed material that can be tailings comprises: a water inlet for forming a slurry containing the tailings; at least one screen for separating tailings greater than ¼ inch in diameter from the slurry to form a screened slurry; a rotatable collection chamber containing a plurality of plates, a drive for rotating the collection chamber for collecting mercury on the plates to provide a discharge material comprising water and treated tailings, the treated tailings containing less mercury than in the feed material.

An apparatus for processing magnetite iron ore, including an upstream cyclone and a mill for grinding particles, wherein the upstream cyclone is arranged to operate as a splitter by diverting material in an overflow of the upstream cyclone to bypass the mill and by feeding material in an underflow of the upstream cyclone to the mill.

An apparatus for processing magnetite iron ore, including an upstream cyclone and a mill for grinding particles, wherein the upstream cyclone is arranged to operate as a splitter by diverting material in an overflow of the upstream cyclone to bypass the mill and by feeding material in an underflow of the upstream cyclone to the mill.

A method for separating a calcite-rich low-grade fluorite barite paragenic ore, includes the following steps: S1, crushing; S2, performing classification on a crushed ore to obtain a fine-grained ore, a medium-grained ore and a coarse-grained ore; S3, performing jigging gravity separation on the medium-grained ore and the coarse-grained ore to obtain first barite concentrates and jigging tailings; S4, performing color sorting on the jigging tailings to obtain calcite minerals and color sorting tailings; S5, combining the fine-grained ore and the color sorting tailings, and then performing ore grinding to obtain feeding materials in flotation; S6, performing flotation on the feeding materials in flotation to obtain fluorite concentrates and flotation tailings; S7, performing chute gravity separation on the flotation tailings to obtain second barite concentrates and chute tailings. The method achieves an effect of obtaining high-quality acid-grade fluorite concentrates (CaF.sub.2≥98%).

A method for separating a calcite-rich low-grade fluorite barite paragenic ore, includes the following steps: S1, crushing; S2, performing classification on a crushed ore to obtain a fine-grained ore, a medium-grained ore and a coarse-grained ore; S3, performing jigging gravity separation on the medium-grained ore and the coarse-grained ore to obtain first barite concentrates and jigging tailings; S4, performing color sorting on the jigging tailings to obtain calcite minerals and color sorting tailings; S5, combining the fine-grained ore and the color sorting tailings, and then performing ore grinding to obtain feeding materials in flotation; S6, performing flotation on the feeding materials in flotation to obtain fluorite concentrates and flotation tailings; S7, performing chute gravity separation on the flotation tailings to obtain second barite concentrates and chute tailings. The method achieves an effect of obtaining high-quality acid-grade fluorite concentrates (CaF.sub.2≥98%).

A method of grading and washing sand including the steps of removing oversize material from a feed material to which water is added on a first grading screen, whereby the oversize material passes over a downstream end of an apertured deck of the first grading screen, undersize material and water passing through the apertured deck being collected in a sump of the first grading screen before being passed onto an apertured deck of a second grading screen having apertures of a smaller size than those of the deck of the first grading screen, oversize material passing over a downstream end of the second grading screen, pumping water and undersize material from a sump of the second grading screen to a washing stage to remove fine contaminants therefrom.