Energy Efficiency:
Thermal Treatment of high
purity plastic granulate

Delivery of a Fluidized Bed Cooler and Heater with Air Processing System. 

In collaboration with the subsidiary JOEST China based in Peking, JOEST designed and manufactured a Vibrating Fluidized Bed Heater and Cooler for thermal processing of highly pure plastic granulate this year. Both machines fulfil different tasks and are located at different stages of the overall process. In the production process from LDPE to XLPE, granules must be heated in one processing step and cooled down in another.

The Vibrating Fluidized Bed Heater with 6 m² of surface area is discontinuously operated (batch operation) and is equipped with an energy-efficient Recirculating Air Processing System. The recirculated air is tempered by an electric heater, freed from dust after running through the Fluidized Bed Heater and recirculated in the process. The product is brought to a temperature of 80-85°C at a throughput rate of 4.000 kg per hour in two batches, before being passed on to the next processing step.

After the chemical process that follows the Fluidized Bed Heater, the resulting XLPE-granulate is cooled back down by the JOEST Vibrating Fluidized Bed Cooler with 4 m² surface area, using fresh air. The cooler is divided into two zones for energy efficiency and is operated in a continuous process. Ambient air is used in the first zone and conditioned cold air is used for the second zone. The used air is freed of dust and discarded into the environment. By dividing the cooler into two different zones, an optimal cooling efficiency is achieved, since the amount of conditioned cold air is reduced to the bare minimum.

The plastic granules underlie very high purity standards, setting high demands for the heater and cooler, as well as the processed air. Every contamination with foreign particles is to be avoided. Therefore, both the cooler and heater are engineered without dead spaces in an ultra-clean design with a surface roughness of Ra < 0.4 µm on parts in contact with the product.

The machines are each powered by two unbalanced motors that can be controlled through the JOEST frequency controller. The Fluidized Bed Heater and Cooler and the Air Processing System are designed and manufactured by JOEST in Germany.

In addition to engineering and manufacturing both Fluidized Bed Machines, JOEST designed a Vibrating Screen measuring 600 x 1,500 mm for the downstream process. Manufacturing and delivery of the screen were done by the JOEST subsidiary in China. The products were completed and shipped in mid 2022.