Thursday, April 19, 2012: 11:41:43 AM

The BKG CrystallCut Process Receives Award for Innovative, Energy-Saving Technology

The spherical PET pellet offers double the energy savings. A plant with a production capacity of 600 tonnes 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 pelletising and crystallising technology.

This has been acknowledged by Plastic Technology China in cooperation with 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 17th April at a ceremony in Shanghai.

CrystallCut is a pelletising and crystallisation process in which the crystallisation of the PET is achieved using the latent heat energy already present in the pellets. The equipment line-up is similar to a traditional polymerisation 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 crystallisation. Therefore, CrystallCut equipment is usually employed with an underwater pelletising system. The pellets exit from the dryer and enter the crystallisation conveyor at an average temperature of more than 135 degrees centigrade. Here the superficially cooled pellets are kept in constant motion triggering the crystallisation process which proceeds without the requirement of any additional energy. Only the latent heat energy present within the pellets is used, crystallising from the core to the outside and resulting in a 40% degree of crystallisation.

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 realised during the subsequent processing of the pellets in the injection moulding machine. Because of the microstructure that results from the crystallisation 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 tonnes-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 moulding machines. The performance of the injection moulding 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.

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