PRODUCTION | ENERGY MANAGEMENT
Right: Control HMI’s can provide invaluable
insight into the process and help take corrective action
energy. It also leads to build-up of carbon, which unnecessarily extends purging and clean out time and increases screw and barrel wear. ENTEK says it is also important to remember that
The co-rotating twin-screw extruder is an ineffi- cient pump – it is roughly 10-15% efficient. This means an energy loss in restrictive areas such as mixing zones and at the die. Using the best suited pumping elements will increase pump efficiency, minimise the SEI and reduce wasted specific energy. When screws and barrels start to wear, pumping efficiency is reduced. This can force the operator to run at higher screw speeds than necessary, or lower than desired feed rates.
Use your controller Using the machine’s HMI to trend processing under Industry 4.0 helps to maintain optimal running conditions and rapidly take corrective action against upset conditions. Leaving the extruder powered on and/or the screws turning for long periods of time when not producing, for example, results in wasted
Right: A
consumption map of
machines, utilities and other electrical power
consumers is a first step in optimising overall energy efficiency of a compounding plant
under-utilising equipment is not energy efficient and can cause unnecessary capital equipment expense. Understanding the limiting factors of the process and addressing them sometimes requires only a design change on an existing piece of equipment rather than buying a whole new system. Such options include: improving screw design by breaking up short aggressive mixing zones into longer less aggressive zones; improving moisture removal from the process by adding a vacuum stuffer or a larger vacuum pump or vacuum pump filtration system; adding a melt pump as a more efficient pump; and increasing the hole diameter on the die and/or using a larger mesh screen size if quality allows. The final area contributing to energy loss is maintenance, according to Entek. This can be minimised by following best practice. For screws and barrels, for example, it is advisable to learn and understand the amount of wear a specific process can tolerate to avoid replacement too early or too late. Meanwhile, the loss of a heater in a zone can result in greater dependence on frictional heating, which in turn effects the SEI. A jammed cooling system valve can allow water to pass through barrels constantly, which means more heat is required than necessary to maintain the set-point. A properly tuned heat/cool system will also provide better control – large temperature oscillation means wasted energy, ENTEK says.
Mapping consumption According to Markus Schmudde, Head of R&D Compounding & Extrusion, at Coperion, a good
22
COMPOUNDING WORLD | February 2020
www.compoundingworld.com
IMAGE: ENTEK
IMAGE: COPERION
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