I would humbly add to the discussion, the clay that is removed may be discharged into a hopper where it could stick, or into some poor trucker that would have a sticking problem as well. One of our soul purposes at Horn Plastics Inc. is to provide Superslide plastic liners to eliminate sticking in hoppers and truck beds. And if abrasion causes wear problems on the other side we have liners for that purpose as well. Check http://www.superslide.com and these problems will be solved.

I think the idea of a log washer, attrition cell and trommel/scrubbers is to dis-agglomerate the feed material in water. All three methods agitate the pulp by mechanical means. All three methods are viable although one may be more efficient than the other depending on the properties of the feed material, volume, availability of water and feed method.

Note that the method of feed may be by monitoring the quarry face and pumping the resultant slurry from the pit to the process plant (in the absence of very large oversize material bigger than 25% of the pump suction). This method does help in dis-agglomerating the feed due to agitation at the pit face and shearing during pumping as well as residence time in the delivery pipeline.

Following dis-agglomeration, the sand fraction and fines are separated from the clay (now in suspension) and oversize material in several screening and classification stages depending on the desired product(s). It has been weighed-in with a valid point that certainly the feed end may well suffer from sticking and hang up due to clay and impact from oversize material; whereas the downstream end will need to be protected from sliding abrasion due to the aggressive nature of sand.

I think you can use the vibrating screen which have spraying system to remove the clay contamination.

Like any process equipment, you are quite entitled to suggest it thrown into the mix of likely equipment. However, it indicates that it is so important to do the appropriate test work before committing to any type of de-sliming process.

Before committing to any type of de-sliming process, our engineers need to know the relative parameters and the working situation etc., then may offer the solution accordingly.

There are many types of equipment for dis-agglomeration and desliming as suggested. Each has their own merits! Drum scrubbers are typically used to process clay bound ROM. This is done to aid the downstream processes like conveying, crushing and screening etc. It is not generally used to provide final specification products as it generally has issues with highly plastic material "balling" and passing through without being liberated.

Logwashers have a much more aggressive scrubbing action, so therefore can be used to produce a final grade clay free product. In my experience they use less water than Drum Scrubbers. They are also inherently more efficient than a drum scrubber due to the basic design of each unit. The main limitation within a logwasher is the feed size must be less than 100-150mm depending on the machine.

An Attrition Cell is a different matter. These are intensive scrubbing units that are used to scrub fine material! The feed material size to a cell is normally less than 4mm and they are very effective at liberating clays as well as reducing contaminates adhered to the surface of fine particles.

Is its imperative that you consider the correct machine for each application; feeding 100mm lumps to an attrition cell will be problematic to say the least!

Finally, it is important to know how to operate and control each unit to maintain its optimum efficiency. Two key factors are retention time and feed concentration. It is vital that each system has the ability to adapt and manage to changes in feed that is present in every process. Having the ability to adjust these factors is very hard if the system is not prepared as the control in each unit generally relates to upstream and downstream process!

Every application in its own right needs to be considered against various methods of process and reduction to gauge which is the most appropriate to your own. We have seen installations where log washers have failed due to the volume and hardness of the rock in the system and this combination of materials and the wrong equipment caused additional problems and increased costs down stream of the front end engineering design that was completed in isolation of the full 'bigger picture' of the total process system. We have seen trommels fail because they didn't see enough lump material.

Where any clays are involved irrespective of moisture content, consideration to wall and valley angles is of the utmost importance and to that of the transfer points between equipment.

In brief, do your homework on the materials to be handled and make sure that you understand any climatic conditions that could alter their 'behaviour' subsequent to being pulled from the ground or having fluids added? Visit a number of applications where the materials handled and processed are as alike to your own as is geologically possible and always wherever possible see the equipment you consider best in operation at another application. Engage the right people for the work you wish to have completed.