Agglomerators also called Densifiers, are doing nothing but to physically transform a light, fluffy material in something heavy enough to feed the hopper of the extruder or any other machine. It is a cylinder where two blades are spinning at the bottom creating friction and thus increasing temperature till material reach the softening point (not the melting point); operator then adds some water to cool the batch down and, after water evaporates, from discharge door material comes out in chips, like very little pop-corn.
Densifier don't care at all about the fact material is dry, wet or dripping water because before going to softening point it has to dry it first and then temperature will raise over 100° C and agglomerate it.
Densifier also doesn’t care if you put into a mixture of material, the same material with different MFI or melting point, it will do its job.
Chips can be therefore mixed into a silo, so pellets can be a steady quality as far as lab characteristics.
Densifier accepts scraps in any form, meaning film, ropes, nets, filaments, non woven and, you name it; result will be the same for everything, size of scraps don't matter much as long operator is safe handling it.
Maintenance as well is little to nothing because to replace blades takes 10 minutes for everybody.
As far as we know, a lot of people put this machine in a corner and buy a granulator and a cram-feeder thinking all the problems were gone. Today they have the densifier back in place.
There are quite many more reasons to use a densifier, like the fact this way fluffy material converted in chips can be accumulated and stored ready for extrusion so, if something happens to the washing line, for example, you are on the safe side and can continue to make pellets, while fixing the system.
Having material densified, if something goes wrong on recycling line and final product is not very first quality you can store it and add it at a certain % in the good material you'll do later so you don't have to throw it away, and so on.
When recycling plastics wastes from post-consumer collect and, especially, in the case of LLDPE-LDPE-HDPE thin film foils and packaging material having a low specific weight and bulky density, it is advisable and necessary to increase the density and weight in order to process further the material in the extrusion or pulverizing phases.
There are cases when the material has a bulk density of 18-20 kg/cbm and to make them suitable for further process they should be turned to a minimum 350-400 kg/cbm.
During the density increasing phase, a fairly good amount of humidity must be removed specially when coming from the washing line. To this purpose, agglomerators are used by recyclers.
This type of machine has reduced capacity when the thickness of the film, foils lowers (bigger volumes with low density) and the humidity on surface of the material at in-feed increases.
Purpose Of Melting:
1. Increase the bulk density of plastic waste from 20 kg/cbm up to a minimum of 400 kg/cbm.
2. Reduce humidity on the plastic waste.