Mines and quarries that introduce water into their operations will at some point require that moisture to be removed, either for further processing of the material or product handling. Dewatering is a process that separates liquid-solid mixtures, such as slurries comprised of particles and process water, that are present in aggregate, minerals, coal and frac sand wet processing applications.
Dewatering most often occurs through processes such as wet classification, centrifugation, filtration or similar liquid-solid separation processes. McLanahan offers a broad range of dewatering equipment that uses these methods to process sands, coal, pulp and paper, concrete and other minerals and materials in the mining industry, as well as for dewatering stall bedding in the dairy industry.
Wet classification is the process of separating particles in a feed material depending on their settling rates in a fluid. Larger, heavier sized particles sink to the bottom, while smaller, lighter fractions float to the top and overflow weirs on the equipment. The top water is then free of particles and able to be reused in the processing plant.
With centrifugation, material is dewatered by centrifugal force — a force that draws particles in inertia away from the center of rotation. Solid particles in a slurry are separated from liquid particles by a rapidly rotating cylindrical bowl in the center of an enclosed frame. Denser particles of the slurry move away from the axis of rotation, while less-dense particles move closer toward the axis. The largest particles are discharged as a thick, dewatered underflow, while the water and fine material discharge separately.
Dewatering through filtration separates liquids from solids by introducing a medium through which only the liquid can pass. Water and other liquids are removed from the slurry, draining out through a permeable barrier or filter media, and leave a trapped cake of drier solids that are too large to pass through the barrier or filter media. Dewatering through filtration creates dry material as well as reusable process water.