A foreign customer of ours used a “standard” watering pelletizer GRO for pelletizing HPDE and PP. The pelletizing was with success and satisfaction, nonetheless he had problems with the process water used to cool down and convey the pellets. In his area the water was, and is, very scarce.
Our foreign customer asked us to reduce the water waste and Filtec modified the standard water circuit by installing a water/water heat exchanger between pump and granulation chamber. The process water passes through the water/water heat exchanger cooled by plant water cooled by a chiller. In this way the dirtiness is not dumped away and only a small amount of fresh cold water gets into balance the small water leaks and the evaporation.
In our “standard” watering pelletizers GRO as the one of our customer, the process water is kept in the tank below the granulation chamber and the vertical drying centrifuge. The process water is sucked by a pump and sent to the granulation chamber in order to cool down the newly-cut pellets and convey them towards the vertical drying centrifuge. Eventually from the drying centrifuge the water falls back into the tank and the cycle starts again.
The newly-cut pellets are hot and the process water gets warm too. When the process water gets too hot, a temperature gauge opens a valve and fresh cold water gets in. So a continuous flow of fresh cold water is needed to balance the amount of too hot water dumped away through a spillway.
This arrangement for “standard” watering pelletizers GRO is called “throwaway/running water system” and is used where an inexhaustible and continuous source of cold and clean water (well, river …) is available. In this system a small amount of fines and dirtiness may pollute the dumped water.
In case of a “shell and tube” heat exchanger, the dirtiness does not make problems. While in case of a “plate” heat exchanger, as the one owned by our above foreign customer, we have installed a mechanical filtering sieve for process water.