This equipment is a flowing film type of concentrator consisting of a series of inverted conical concentration decks surmounted by conical distribution decks arranged in a vertical array and employing various combinations of double and single deck elements. A double cone, single cone concentrator is shown in next figure. The arrangements form the basis of virtually all the configurations for cone concentrators. In general, the configuration consists of two stages surmounting other stage.
Double cone-Single cone configuration
All cones are fitted with adjustable inserts in which by means of a handle, the inner section of the insert can be moved vertically in relation to the outer section. This arrangement enables the concentrate take to be varied while the cone is on stream. This provision can be automated if necessary so that the circuit can have flexibility which is needed to cater for variations in grade and throughput. All cones have facilities for the addition of dilution water to control independently the percent solids of the feed on individual single cones.
Cones are made of fiberglass and covered with rubber and mounted in circular self supporting frames over 19-21 feet. The slurry can feed the equipment at 50-60% solids. In general the unit is very efficient at recovering fine particles sizes such as 53 µm. During the operation the slurry is distributed around the periphery of the cone. The size of the particles can be controlled by coarse screening to remove tramp material and particles coarser than 2.5 mm. If the material has a high content of clays or fine material, a preliminary separation with hydrocyclones can be performed in order to avoid problems during the operation. The following feed material acts as a dense medium that hinders the settling of lighter particles. Heavy particles settle to the bottom of the flow. Separation efficiency is not very high and the concentration process must be repeated several times in the same unit.
Gravimetric circuit with Cone Concentrator and Shaking Table
The design of any gravimetric circuit with cones must consider the following aspects:
Thin steel flakes from broken grinding media, wires and other sources of steel are used to found their way through the slotted scalping screen ahead of the cone and form part of the cone feed. They could become cemented onto the surface of the cone by pyrite that had oxidized and probably any soft mineral like carbonates. These surface obstructions are used to act as traps for the liberated gold. For example five or more kilos could be trapped and lost.
The inspection hatches must be designed in the right size, otherwise they could be very small for the deck surfaces to be inspected or cleaned in the right way. Larger hatches could be cut and the feed distribution could be distorted leading to uneven feeding of the concentrating cones.
It is important to include water addition points in order to get the right pulp density; otherwise the density will not be adjusted at the optimum point. During the operation is very important to take density readings near of the feed pumps. The operator must be able to take samples and add the appropriate flow of water because is very easy to modify the stability of the circuit.
The election of single or double cones must be studied carefully due to the slots feeding the cones could be blocked with pieces of rubber, coarse particles, wood or steel, which prevent the operation of one section of the double cone. Under this consideration, the design should consider one or more singles cones with the appropriate pulp distributor.