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Dryers: The latest efficiencies

If you were forced to sympathize with one plastics machinery manufacturing segment in particular during this...


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June 3, 2010 by Canadian Plastics

Wittmann's new Drymax Aton dryer.
Wittmann's new Drymax Aton dryer.

If you were forced to sympathize with one plastics machinery manufacturing segment in particular during this so-called Great Recession, it might just be the dryer suppliers. With plastics processors fighting a two-front war against resin-destroying shop floor moisture on the one hand, and increased competition on the other, they’re demanding more from their dryers than ever before: smaller footprint, easier cleanout, all-stainless construction, increased drying speed and efficiency, equipment for new markets like medical parts molding, topped off by–what else?–the constant craving for energy savings.

Rather than throwing up their collective hands, though, dryer manufacturers are digging deep to come up with new units designed to satisfy all of the above criteria.

IT’S THE ENERGY SAVINGS, STUPID

In any discussion of plastics processing, energy consumption isn’t the elephant in the room–it’s more like Godzilla: a major issue for PET processors, including drying, and a headache for everyone else. Not surprisingly, virtually every new dryer introduced today is designed to cut energy usage to some extent at least. For some units, slashing hydro bills is unequivocally the prime directive.

Case in point: Wittmann’s new Drymax Aton desiccant dryer. According to Rob Miller, president of Wittmann Canada Inc., the Drymax Aton has three separate processes that use existing heating energy of the drying process to cut energy consumption. “First, the dryers have a chamber in the centre of the drying wheel that takes the radiation of excess heat from the wheel and uses it for the pre-heating of regeneration air,” he said. “Second, the radiation of heat from the inner heater tube is used to pre-heat the regeneration air; and third, the wheel is regenerated by reverse flow process for efficient cooling of the desiccant, further minimizing the heat energy used.”

The units also come standard with the company’s ECO-Mode technology. “If the moisture load on the dryer is lessened, the wheel regeneration can automatically operate similarly to a tower dryer,” Miller explained. “The regeneration is done sequentially during operation, which creates a lower water load, further reducing energy consumption.”

Since January, Italy-based Piovan SpA has been shipping its new Genesys PET dryer in North America, billed as a self-adjusting system that delivers very low energy consumption. Genesys has an automatic airflow control and adjustment to cut energy use by 35 to 55 per cent below today’s conventional resin dryers, the company said. Another feature of Genesys is the capability to stabilize the airflow in the drying hopper for better optimization of the energy utilization. Genesys also recovers between 50 to 80 per cent of energy used during regeneration of the desiccant material. As a hypothetical, processing systems producing PET performs that consume resin at a rate of 1,000 kg/hr can save as much as 220,000 kW/h per year, the company said.

Universal Dynamics recently brought out its first desiccant wheel dryers, the Titan TR series, with throughputs of between 15 to 250 lbs/hr. The units are described as having a special wheel design that allows for high-temperature regeneration with dry air, resulting in lower dewpoint and energy savings of up to 30 per cent over conventional rotary wheel drying systems. Housed in a stainless steel enclosure, the series also features a heat recovery and filtration system designed to trim energy usage even further, allowing the dryers to run dust-free and cost-effectively for drying resins in small quantities for medical applications.

FROM LARGE TO SMALL

Available in sizes from 600 cfm to 3,000 cfm, Sterling’s SDA large dryers are also meant for energy efficiency. Improved thermal efficiency is said to lower energy costs by 10 to 15 per cent, and reduce regeneration time to less than one hour. Available in three temperature ranges and sizes up to 3,000 cfm, SDA dryers are said to operate effectively either centrally or beside the machine, achieving a -40°F dewpoint even in high humidity. For even greater energy efficiency, an SDAG version incorporates gas-fired heat exchangers for both process and regeneration.

Also from Sterling is the compact SCD10 series dryer, which can be located on the floor or directly on the drying hopper. Air enters through a solenoid and is filtered through a large-particle compressed-air filter before it moves through the heating element. Another new dryer, the SDF series dryer, delivers low dewpoint dehumidified air for medium throughput drying applications. An energy efficient conditioning cycle is said to reduce energy consumption up to 40 per cent over traditional carousel-style designs, and virtually eliminates temperature and dewpoint spikes.

AEC has also weighed in with a compact, energy efficient drying solution. The company’s HRS Heat Recovery System is said to save up to 30 per cent of the annual heating energy cost associated with high-temperature drying. “The process uses the hot air leaving the drying hopper to preheat the cool air leaving the dryer prior to it being heated by the process air heater,” said Tom Thompson, AEC’s technical sales manager. “The return air from the dryer gives up heat and becomes cooler by as much as 40 to 80°F, which reduces the cooling load necessary to cool the air entering the desiccant bed by up to 30 per cent.” The process air takes on heat and becomes warmer by as much as 40 to 80°F, he continued, which in turn reduces the load on the process air heater by up to 30 per cent. “The result is an exchange of energy that would otherwise have been lost,” Thompson said.

OTHER EFFICIENCIES, NEW MARKETS

If you haven’t guessed by now, energy efficiency is a high-ranking concern–but it isn’t the whole ball game for plastics processors looking maximize their dryer efficiencies. Here’s a different efficiency: The Conair Group’s TouchView dryer controls, available on the company’s larger Carousel Plus dryers, offer an autostart function that makes it possible to begin pre-drying material hours before the start of production. “Also, correct settings can be locked in and saved for instant recall,” said Jamie Jamison, Conair’s general manager for PET and packaging.

“Once set, the Optimizer Mode controls will automatically adjust air flow, temperature, and dewpoint to maintain a stable temperature profile in the hopper, regardless of changes in throughput, material temperature, or ambient conditions.”

And in case you’re wondering, there’s an energy efficiency component to the TouchView controls, too. “The controls fine-tune the air temperature, flow and dewpoint to consume just enough heat and mechanical energy to produce the optimum temperature profile,” Jamison said. “Too much air flow wastes energy, while too little air flow results in poor drying. Similarly with temperature, except that too much heat is not only wasteful but can overdry or degrade the material.”

Ask an ambitious processor about new market possibilities and medical parts molding is likely to top the list. Problem is, materials used within the medical industry have become more demanding to effectively process, to say nothing of the energy waste associated with running a high throughput machine for low throughput rates. Can newer dryers provide a more cost effective approach? You bet. The Precision Micro dryers line from Dri-Air Industries is designed specifically for medical parts molding. The units can handle from two pellets to 20 lbs/hr, the company said, with drying temperatures from 70 to 400°F. Configurations range from compact all-in-one drying systems that can fit on extruders or molding machines, to separate systems with two-ounce hoppers and stand-alone dryer packages.

Wittmann is also dipping a toe into the pool with the release of its new Drymax Micro F2 unit. “With a drying cap
acity of two lbs/ hr, the F2 is well suited for micro molding,” said Rob Miller. “The dryers have integrated compressed air feeding, two-stage silos for a wide range of residence time, and are easy to clean.”