A gold trommel is a piece of mining equipment that is quite popular and is used all around the world on all different sized mining operations. Their purpose is to process gold bearing material by separating out the larger rocks and boulders, allowing the smaller material that contains the gold to be run through a sluice box. Depending on the quality of your trommel and the type of material that you are feeding into it, a grizzly may also be used prior to feeding the trommel in order to separate out the largest boulders. This will allow the system to operate at its optimum potential. Some larger wash plants have grizzlies set up directly over the hopper when the material is added.
When gold bearing material is added to the hopper, it is washed down by jets of water to break up the material and help release the gold. There are different designs and amounts of water jets used, but the ultimate goal is to completely break apart any clays and mud that could retain placer gold and prevent it from being caught in the sluice.
After gold bearing gravel is added to the hopper, it enters a rotating drum that further helps to break apart the material. There are generally also water jets inside the hopper, so that there is a combination of high pressure water and the rotating drum which break apart any clays and dirt as the slurry moves through the drum.
The rotating drum is constructed of screen material. This allows the smaller gravel and fines to fall through to a sluice or other processing system, while the bigger rocks will move through the drum and be discharged out the back. The ideal screen size will vary depending on the coarseness of gold found in the area, but ½” and ¾” is commonly used. If the trommel system is working properly, all of the fine material will drop through the screens to be processed, and the larger gravels and rocks will discharge out of the back, completely rinsed and without holding onto any dirt or gravel.
Trommels are quite simple to build and work excellent when they are constructed properly. The come in all different sizes from small units that can be used efficiently by one or two prospectors using shovels all the way up to huge commercial mining operations feeding them with loaders.
The trommel itself does not separate out the gold. It is simply used to help separate and classify out the material for further process. On larger operations, the trommel is generally incorporated into an entire wash plant setup, so that the smaller material that drops through the trommel is run through is simple sluice system to capture the heaviest materials and discharge the lighter sands.
To efficiently operate a trommel, it generally works best to have at least two people running the system. One miner feeds material into the trommel, while the other tends to the operation of the unit; making sure everything is working efficiently and clearing discharged waste material so more can be added.
Recovering the gold that has been processed is the same as for any other sluice box. Collect the concentrates and use some type of fine gold recovery system
to complete the final process and separate the gold.