Gold Sluices And Their Application

Savana Mining Equipment LLCSLUICES AND THEIR APPLICATION

MEXICO

PERU

PANAMA CAMEROON

GUINEA

INDONESIA

CAMEROON

CAMEROON

EUROPE, 1556

Savana Mining Equipment LLC

WHAT IS A SLUICE?

• Sluices are effectively a form of “stirred bed”. In other words a container in which the feed is stirred or agitated at a rate insufficient to keep all the mineral grains and rock particles in suspension. This action is independent of the container in which the feed has been placed,

• The agitation results in reverse classification and gravitational stratification, the result being that the heaviest particles settle the most rapidly and form the base or basal layer in the container.

• In the case of a sluice it is the tumbling action imparted by the riffles coupled with the flow of the water across the riffles that effects separation and thus settling. The importance then of the riffles is that they:

Retard material moving over them and give it a chance to settle; Form pockets to retain gold and other heavy minerals which settle into them; and Form eddies which roughly classify the material in the riffle spaces.

WHAT FORM DO SLUICES TAKE??• Basically they are an inclined troughs or launders, usually on a slightly angled slope, into which the

feed ore is placed and washed down the trough by a rapidly running stream of water. The sluice may have no riffles (tin streaming box) or have riffles of which there are a wide variety that have been and are being used.


WHAT ARE THE DESIGN CRITERIA??

• Know the ground to be treated! The nature of the alluvium should be well documented, its lithology and size range analysis; The grade should be documented from reliable testing programs; The location of the deposit and position of available water supply and tailings disposal should be

documented; and The grain size range of the mineral sought should be documented.

• Determine Treatment Parameters! The size range of the feed to the sluice; Is the feed to be screened and pumped, pumped or hand delivered to the sluice; The economic feed rate to be used; Is adequate fresh water supply available; and Determine the most suitable design, riffle and matting.

• Sluice Design! The next slide sets out the main features of the modern sluice, the design should incorporate

those which are best suited to recovery from the deposit to be mined.


DESIGN:

GENERAL: The general sections and components of the sluice are depicted in the drawing below. They may be varied from place to place and operation to operation however all designs will be based on these components.


DESIGN:

WIDTH: The width of a sluice is governed by the required throughput per hour, the rule of thumb is:1” of sluice width for every 1 loose cubic yard per hour of operation, or35 mm of sluice width for every 1.0 loose cubic metres per hour of operation.

LENGTH: Most mineral is recovered in the upper 30% of the length of a sluice, length has, in larger applications, been based around 12’ or 4 metre sluice runs but a sluice can be any length or multiples of the above lengths.

WATER: This depends to a large degree on the material being treated, coarse bouldery ground will require more water to move larger particles down the sluice than will fine sandy ground. The general rule of thumb is: 10 to 25 gpm per cubic yard per hour (50 to 130 litres per minute per cubic metre per hour).

SLOPE: Is heavily dependent of size and type of feed, generally slope of the sluice is set at:Nugget Trap Sluice (0O to 15O);

Primary Sluice (Hungarian Riffled) (5O to 12O); and Expanded Mesh Sluice (2O to 10O)


DESIGN APPLICATION:

To apply these simple design rules to a proposed small scale operation of say 25 lcm / hour would indicate that the sluice would have the following design measurements and water requirements.These design parameters will also depend on the type of material being sluiced, a coarse “Long Range” feed will require the higher end water use and probably a wider sluice while a “Short range” size feed that has been screened to say – ¾” or 19 mm will require way less water and could be adequately treated by a sluice with the dimensions as set out below.


DESIGN APPLICATION (Continued):

So what will this sluice look like??The schematic below gives an overall idea of how this sluice would look, it should be noted that the sides will be somewhat higher than depicted.


THE SLUICE IN A MODERN FLOWSHEET:


WHY SLUICES IN THE ARTIC:

A modern jig based plant is a bulky item that normally has a number of rubber components such as belting and jig diaphragms, electric motors and multiple bearings. A sluice has no drives, no belting and no motors!!

The simple answer is that a sluice can be stripped of its carpet in about 30 minutes and literally left in the field unprotected for the duration of winter. On the other hand the jig plant has to be either moved or the weather susceptible components removed, this is a time consuming process and that time, where the summer working season is brief means money lost.

So it is really not a function of efficiency and recovery but of simple time vs money expediency.

In the warmer climates such as Central and South America, Australia and Africa most larger operations utilise the modern jig and it is becoming more rare to see larger sluice based recovery systems being installed. Further, the high clay tropical alluvials are not as suitable for sluice recovery. The sluice is attractive to artisanal miners mainly because of its low capital, installation and operating costs.


THE DO’S AND DON’T’S OF SLUICING:

To achieve the best efficiency and recovery from any sluice it is advised to: Keep the feed in a “Short Range” of sizes but with enough coarse fraction to help break up any

effort by flow to settle and compact on the sluice bed; Ensure a constant feed and flow rate, the pulp density MUST be kept constant: AVOID running the sluice on clear water for any length of time to avoid flushing of heavy mineral

to tails; Adjust slope to keep feed eddying and AVOID laminar flow or highly disturbed and agitated flow; AVOID starting and stopping the process, run the sluice right through the shifts without taking

“Lunch Breaks”; If security is an issue place locked mesh cages over sluice beds; AVOID manually disturbing the bed where possible, adjust water volume and slope should beds

start to become compacted; The riffles MUST sit flush on top of and be clamped down on to the matting and the matting

MUST be cut to exact sluice length and width, no overlaps or loose matting to flap in the water flow;and

ENSURE the sluice is level across the unit.

Gold Sluices And Their Application

Engineering

Transcript of Gold Sluices And Their Application