Raw Material Moisture Content For The Pellet Mill

If you have done any previous research into making pellets you should now know that wet materials cannot be used in the pellet mill.

However such a comment is very general, therefore more specifically on average a moisture content of 15% performs best in the pellet mill. This does change though depending on the raw material and the type and size of pellet mill. For instance a large pellet mill with high temperature steam injection maybe to produce a pellet of equal density with just 10% moisture. The amount of water in the raw material effects the compression within the pellet mill and also the temperature the material achieves for lignin melting. You need to achieve a high temperature to melt the natural lignin to bind the pellet together. You need a certain amount of moisture to generate heat, however too much moisture will stop you achieving the required temperature. You also cannot compress water, therefore if a raw material contains a lot of moisture its impossible to produce a high density pellet. Some people attempt to find pellet mills which can process high moisture content materials. However the important point to remember is that these pellets will be used for fuel. Even if pellets could be produced the moisture content would mean the pellets would burn very poorly and only generate a small amount of heat. In terms of reducing the moisture content down to the required percentage there are various options. Preferably you should use solar and wind energy as much as possible to remove moisture. If forced drying is required there are solutions such as pipe dryers and rotary dryers. In both instances hot exhaust gases pass over the raw material to carry away moisture. However you have to be careful with fire risks. Ideally you want to source a biomass raw material that is already dry.