PRODUCTION | ENERGY MANAGEMENT
Right: CPM’s RE Ring
Extruder has been shown to significantly reduce specific energy via elongational mixing
Effectively, a production increase is realised without any additional energy consumption,” he says. Farrel Pomini’s continuous mixing technology is claimed to offer low energy consumption and low processing temperatures. In part for those reasons, it is widely used in sensitive applications such process- ing virgin and recycled PVC, other recyclates, biodegradables and flame retardants, as well as highly filled and white masterbatch production. Features contributing to its energy efficiency include short overall length of its two counter-rotating mixing rotors, efficient flow of material over the feed flights, and high free volume in the mixing chamber. “I feel the current energy management trends will continue; however, they will become increas- ingly more critical,” Lloyd says. “Consumption and waste will become less tolerable to the entire supply chain, therefore energy conservation at all points will be essential. Increases in process feedback from intelligent machines — Industry 4.0 — will both highlight and assist the pursuit of lower energy processes.”
Low hanging fruit One reason that energy efficiency has not been a top priority in the development of compounding equipment and processes is that industry has become accustomed to relatively low energy costs, according to Adam Dreiblatt, Director of Process Technology at CPM Extrusion Group. “With the advent of higher energy costs in the future, there is some ‘low hanging fruit’ that has been promoted for many years but never given any serious attention,” he says. “For example, insulation of the compounding
extruder barrel can have a return on investment payback within weeks or months, yet most com- pounding extruders are not equipped with insulation covers. When they are provided, the insulated covers get removed once for mainte- nance, then put into storage. When asked about this, production managers say because the insulating covers make access to the heating/ cooling system cumbersome. As a result, the energy radiating from the barrel heaters goes to heating the plant because it is more ‘convenient’ when maintenance is needed,” he says. This type of thinking has to change, Dreiblatt
says, and that change starts with corporate manage- ment making energy efficiency a high priority. “We see this type of philosophy taking place already in China, where new compounding lines are evaluated in terms of energy efficiency,” he says. Dreiblatt says good energy management should begin with an audit. “This is the only way to develop strategies to minimise waste and reduce energy consumption wherever possible,” he says. “Managing the peak electrical loads is possible, but perhaps not practical. When the extruder is first heated to operating temperature from ambient conditions, the electrical heaters on the extruder barrel draw 100% amperage until the barrel reaches near the setpoint — during this time the extruder is not yet running — at which time the heating demand is dramatically reduced. If you have multiple lines starting-up on a Monday morning, for example, they will all draw 100% amperage at the same time. If the heat-up period for each line was sequenced using timers, the peak electrical demand can be reduced,” Dreiblatt says. Some steps towards energy efficient production
Figure 3: Grace curve comparing the lower dispersive energy requirement for elongational flow (in RE RingExtruder) with dispersive energy requirements in simple shear flow (in a twin-screw extruder) over a wide range of viscosity ratios Source: CPM Extrusion
36 COMPOUNDING WORLD | February 2021
require little more than a change in mindset, Dreiblatt says. “In most plants today, companies leave idle machines at operating temperature for extended periods of time - sometimes for days – rather than turn off the heaters until the line is ready to run. These are simply bad habits we have all developed over time.” As energy use becomes an ever more important element in business planning, some decision
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IMAGE: CPM EXTRUSION
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