A metallurgist must select a centrifuge concentrator such as the Knelson or Falcon unit under some considerations. The first point is to try to identify the advantages and disadvantages of each unit according to the results obtained in the testing program. It is important to indicate that for the Falcon, the batch and continuous units are tested independently. The Knelson is basically tested under batch operation. If the gold operation will have to face variability in ore types and operating conditions, the Knelson could be a good option. Nevertheless, the continuous Falcon yields good performance too.
Other important consideration is related to stream that will feed the centrifugal unit, because the stream may be a recycled from any intermediate point or from the final product of the grinding circuit. The former tends to favor the Knelson, and the second favors the Falcon. Regarding a specific application, the gold must be recovered as early as possible is the correct choice, to reduce smearing or accumulation within a primary grinding circuit. Other important point is that the gold rougher gravity concentrate, 0.4-4% of gold, must be easily upgraded to marketable grade (i.e. to feed the smelting process), approximately, 40-45% of gold. It is well known that this is difficult to obtain with fine gold recovered from the hydrocyclone overflow, especially on a shaking table.
Essentially, when a gold gravity concentrate comes from a hydrocyclone overflow or flotation concentrate with a falcon unit, further upgrading could only be optimum using another Falcon. Nevertheless, when gold is recovered from a recycled stream, upgrading is not difficult with any gravimetric equipment such a shaking table. It has been noted that gold recovery in the circulating load of a grinding circuit takes the advantage of the concentrating action of the hydrocyclones and gold’s own malleability. For cases of gold recovery, the Knelson may be the right choice when recovery can be done in the grinding circuit. The batch Falcon is best used as a lab unit when there are restrictions of water in the mine site. Applications for fine gold recovery when the presence of sulphides is not significant are also possible.
Probably, the continuous Falcon unit is a very versatile unit. It is considered a good scavenger of fines heavies from most streams, with the extra benefit of producing a very heavy concentrate when the process must produce it. Basically, the continuous Falcon unit is s good option for gravity separations in the fine range, including heavy gold concentrates. The batch unit is a good option for gold recovery for fine feeds when sulphide content is low such flotation concentrates and hydrocyclone overflow. The Knelson concentrator is a good option for gold and platinum recovery within grinding circuit and placers. The design of the gravity process must ser flexible in order to solve unexpected problems and the best laboratory of any centrifugal concentrator is the same plant.