The spherical PET pellet offers double the energy savings

A plant with a production capacity of 600 tons per day may achieve an almost unbelievable energy savings of 25 gigawatt hours of energy during one year of operation using the CrystallCut technology developed by BKG, Bruckmann & Kreyenborg Granuliertechnik, in place of existing pelletizing and crystallizing technology. This has been acknowledged by Plastic Technology China in cooperation the Vogel Media Advertising Co. Ltd and nominated for the prize of the „most innovative, energy-saving plastics processing equipment of the last decade (2002-2012). The prize was officially awarded to BKG on April 17th at a ceremony in Shanghai. CrystallCut is a pelletizing and crystallization process in which the crystallization of the PET is achieved using the latent heat energy already present in the pellets. The equipment line-up is similar to a traditional polymerization and extrusion line. However, the critical difference lies in the cooling of the polymer after it exits from the extruder die. During the first two seconds the plastic melt loses two-thirds of the latent heat energy. Because of this it is very important that the residence time of the pellets in the process water be kept to an absolute minimum in order to later attain the highest possible degree of crystallization. Therefore CrystallCut equipment is usually employed with an underwater pelletizing system. The pellets exit from the dryer and enter the crystallization conveyor at an average temperature of more than 135 degrees Centigrade. Here the superficially cooled pellets are kept in constant motion triggering the crystallization process which proceeds without the requirement of any additional energy. Only the latent heat energy present within the pellets is used, crystallizing from the core to the outside and resulting in a 40% degree of crystallization. With CrystallCut, compared to conventional extrusion equipment for the manufacture of PET pellets, an energy savings of around 20% is achieved. A further energy cost savings of around 5% is realized during the subsequent processing of the pellets in the injection molding machine. Because of the microstructure that results from the crystallization action in the conveyor, significantly less energy is required to re-melt the pellets. This results in an overall energy savings, when compared to conventional processes, of around 25-30%. In turn this accounts for about 25 gigawatt hours per year at a plant having a capacity of 600 ton-per-day.This 25 gigawatt hours of energy, corresponds to the amount of energy consumed by 4900 four-person households, per year in Germany. Finally, the CrystallCut technology provides yet another advantage during further processing in injection molding machines. The performance of the injection molding machine increases by 5% when working with spherical pellets due to the fact that this form of pellet is more readily re-melted when compared to conventional strand-cut granlulate. This is certainly one of the reasons for the ever-increasing demand world-wide, for spherical, thermoplastic pellets. In addition to the aforementioned advantages, a lower total capital investment is required for a CrystallCut system when compared to the conventional combination of pelletizer and crystallizer. Therefore when considering new plants , it makes good sense to equip these plants with the innovative BKG technology. Furthermore, an investment to retrofit an existing plant can also be worthwhile. The return on investment can be achieved in a short period of time due to savings in the cost of energy. Last but not least, the space required for the CrystallCut equipment is less than that required for conventional equipment. BKG has convinced not only the prize giver with its innovative technology for energy savings in the production of PET pellets. Since the global introduction of the CrystallCut system about 10 years ago, many systems have been installed in America, Europe, Asia and the Middle East, mainly in raw material production, but also in recycling plants. Today, 10,000 tons of PET pellets are produced daily using CrystallCut equipment built in Muenster, Germany, having outputs ranging from 250-20000 kg/hour.