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6/25/2008 | 3 MINUTE READ

ETA Process®: High Thermal Efficiency through Utilization of the Return Air Offers Savings up to 40%

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Cost-efficiency is highly valued everywhere.

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Cost-efficiency is highly valued everywhere. In plastics processing, the drying of hygroscopic plastics is a cost factor which is not to be underestimated. At first glance, some conventional, low-priced drying systems reach an efficiency of less than 50%. Motan dryers with patented ETA-process® however, prove to be a great investment: drying costs are reduced by up to 40%. The drying of plastic granules before processing is the most important prerequisite for high quality products, efficient production and trouble-free manufacturing. With ever increasing competition and as well as cost pressure, the used raw materials, machinery and the energy must be optimally utilized. Motan took account of this with its ETA-process®, named after the designation for efficiency. Resulting from the process, the unused heat from the drying bin is directly returned to the bin via a heat exchanger. Depending on the material grade and consumption, this reduces the drying costs by up to 40%. For the drying process, four parameters (their correct settings as well as relations to each other) are essential for the drying process: drying temperature, air volume or air flow, dewpoint and drying time. Here, the intelligence of the ETA-process® comes into play. This means that the process works with the "ideal" parameters of each plastic material. Through the respective adaptation of air volume, drying temperature, dewpoint and drying time considerable energy savings are achieved. The technical starting point for the ETA-process® was the assumption that the drying parameters indicate "ideal" values and are also in an "ideal" relation to each other. The principle of the process is the optimum utilization of the waste heat from the drying bin and is characterized by two essential features. The heating for the drying air is arranged directly in front of the air inlet into the material to be dried. Thus, dry but "cold" air is led to the drying bin and only there brought to drying temperature. Temperature losses by radiation from the pipework are avoided and expensive insulation is no longer required. The resulting unused heat in the drying bins is utilized in a heat exchanger for pre-heating the process air (dry air) before the return air is dehumidified again in the dry air generator. The energy in the return air is made use of and at the same time the return air is cooled down to the low temperature required to achieve sufficient absorption by the molecular sieve and to ensure a low dewpoint for the dry air. Expensive water after-coolers in the return air process are not required. Motan engineers carried out series of measurements with different drying temperatures, material throughputs, bin sizes and heat exchangers. The tests showed that using ETA-process® in conventional systems, the commonly accepted energy loss in the drying circuit amounting to approx. 47%, could be reduced to 22% - cutting it in half. Exceptional energy savings are possible, particularly with materials dried at high temperatures - such as PET. With regard to cost efficiency, Motan ETA-process® should generally be used with drying temperatures as low as 170 °F, resulting in a savings of 10%. With drying temperatures over 200 °F, the cost benefit is more than 20% compared to conventional drying systems. Besides the energy potentials in the drying bin, as part of the ETA-process® concept, energy is also reclaimed through a heat exchanger in the regeneration process. Recooling the freshly regenerated cartridge in the closed loop mode avoids "preloading" the desiccant with moisture from the ambient air during the cooling phase. Therefore, the drying system can be used regardless of the weather and the season. In total, these measures secure energy savings of approx. 40% for the regeneration process. In addition, longer residence times of the material in the bin. For example due to smaller throughputs or down time do not result in material degradation, since the drying temperature is lowered automatically to a throughput-adjusted temperature (Motan DryingOrganizer). At the same time, a decrease in temperature means a decrease in heat output as well as the exhaust air heat resulting in considerable energy savings. So, Motan drying systems with ETA-process® are a smart investment.