Pallets, Pallets Everywhere...
We all have them. Whether you buy, sell, ship or wherehouse, just about any business that handles merchandise in large quantities has pallets. They are the ideal tool for storing and moving myriad materials. But what happens when the pallets become broken, or are just no longer needed? All too often they become a costly waste handling problem. However, if we explore the possibility of recycling, this waste handling problem
becomes a saleable product.
The following illustration shows some of the possiblities:
Questions to Ask
Whenever comparing different methods of size reduction, certain general criteria must be considered:
- Required throughput
- Required finished particle size
- Size and uniformity of in-feed material
- Method of feeding and collecting
To achieve the majority of pallet grinding goals, a two-phase process is necessary to make the most valuable output product.
Phase One: Breaking Them Down
Given their dimensions and overall bulk, the ideal method for reducing both whole pallets and pallet scrap is the slow speed ram-fed grinder.
- The open "deck" design of the ram fed grinder allows for easy infeed of whole or partial pallets whether by hand, or stacked on a fork truck.
- The hydraulic ram forces the pallets into the grinding rotor which features four-way reversible tool-steel cutting teeth which are hard enough to cut through nails or other ferrous metals.
- The pallet material is continuously ground until it is able to pass the screen covering the grinder's discharge area.
Screen size can vary, and screens may be changed to correspond with production goals. However, it is not recommended that a screen smaller than 1" be used in this application. The smaller the screen, the longer the mill will need to work to produce the required size. Therefore, when processing a bulky product such as pallets or pallet scrap, use of a screen smaller than 1" will dramatically reduce the throughput of the ram fed grinder.
Phase Two: The Finish Grind
So, let's consider how we get to the finish line. For this phase, a finish grinding hammer mill is the best solution. Each of the items shown on the list of suggested end products require a specific finished particle size. The role of a finish grinding hammer mill is to produce the required finished size, anywhere from mulch to sawdust.
- The pre-ground pallets are fed into the grinding chamber of the hammer mill where a combination of hammer blows, particle on particle contact, and impact with the internal breaker plate work in unison to further reduce the material.
- The material remains in the grinding chamber until it is able to pass through the screen covering the mill discharge.
- Screens are available in a variety of sizes, and can be interchanged to correspond with the operator's production goals.
- If the finish grinding hammer mill is outfitted with an integral fan, the process is taken to the next level. The pneumatic suction pulls the material through the hammer mill, then conveys the finished material to storage.
Here's where it gets cool. Add the finish grinding hammer mill to the ram fed grinder and not only do you go from whole pallets to the exact desired finished particle size, but the throughput rate is increased as much as 400% over that of the ram fed grinder alone. Here's why:
- Since the finish grinding hammer mill is producing the finished particle size, the ram fed grinder doesn't need to be concerned with it. As a result, a larger screen (2" to 3") can be used on the ram fed grinder, thus providing less resistance and allowing material to flow through the system at a much higher rate while still liberating all metals from the wood.
Critical Middle Step
While the ram fed grinder and the finish grinding hammer mill are the stars of the show, it can't be overstated that the ideal set-up will also include two rotary magnet hump tunnels between the ram fed grinder and the finish grinding hammer mill. Anyone who handles pallets is aware that they contain metal fasteners, typically nails, which hold them together. All metals must be removed if the end product is to be saleable. And, while they are not hazardous to the initial grind, it is critical that all metals be removed prior to infeed into the finish grinding hammer mill to avoid a potentially explosive environment.
Putting it All Together
When you combine all of the essential elements, the system looks like this: