The CFS Density Separator is a hydraulic classification device consisting of an upper paralleled-walled section of square or rectangular cross-section, and a lower section consisting of one or more pyramidal discharge units. A rising current of water is established over the entire area of the upper unit by injection of a pre-determined flow through a series of nipple style spray pipes located at the junction of the upper and lower sections. These nipple spray pipes are installed to direct the flow of water straight down.
A mineral slurry continuously introduced into the upper unit through one or more feedwells is expanded into a teetered state by the rising water current. The particles are classified, with the coarser material reporting to the bottom of the teetered mass while the progressively finer material is distributed in the upper portion. Pulp level is maintained by a continuous overflow of the unit.
Interstitial water velocity and pulp-specific gravity progressively increase with depth from the top overflow weir to the bottom of the upper unit. An electronic, force balance-pressure sensing device with transmitter is located in the wall of the upper unit, immediately above the rising current water piping. The proportional output signal from the transmitter is coupled to electronic pneumatically operated discharge valve with positioner through a process controller or PLC.
For a pre-set upward current of water, the specific gravity of the mineral suspension at the level of the force-balance instrument is indicative of the average particle size of material above the instrument. When a specific gravity value is set in the controller, the automatic discharge valve will operate to maintain the set value, and thereby maintain an equilibrium condition of the teetered mineral suspension. With a preset upward current water flow and specific gravity, the teetered mineral suspension becomes, in fact, an operating part of the machine: “the sand is the machine.”
Essential to the maintenance of the desired classification is a relatively constant-volume feed rate to the Density Separator, which is generally achieved in practice by feeding the unit with a constant-speed centrifugal pump operating with a constant suction head, or by conveyor with a metered feed. On the other hand, operation of the unit is not sensitive to the percentage of solids in the feed slurry, nor is it sensitive to changes in feed size gradation, up to a design maximum determined for the particular material to be classified.
The efficient operation of the Density Separator depends on the introduction of a constant rising current of water over the whole area of the tank. It is, therefore, essential that: 1) the water be supplied at a constant pressure and, 2) the water supplied is clean and free from trash that would plug the water distributing system.To meet these criteria, each Density Separator is supplied with a modulating pressure reducing valve for installation in the users’ water supply system. The valve supplied would maintain a discharge pressure within acceptable limits regardless of fluctuations in inlet pressure.
A water flow meters is supplied with each Density Separator to measure rising current water and permit establishment of a pre-determined flowrate for a given classification. A flowmeter can also be supplied to monitor compensating water flow if this feature is required for operation.