Plastics Washing Systems by Mark Henricks

View the list of manufacturers at the bottom of the page

The best way to get answers about plastics washing systems, a preliminary step in recycling plastics that removes contaminants, is to flash the cash. In the grand scheme of things, as Tim Hanrahan of EREMA North America Inc. quips half seriously, “Nobody is trying to save the Earth. Everybody is just trying to make a buck.”

The larger companies will approach an engineer and design firm, or a washing system manufacturer—the majority of which are based across the Big Pond, in or within Eurail striking-distance from Italy—with a certain end-product in mind. “They are your bottle manufacturers who want to bring recycled materials into their bottles,” says Curt Cozart, U.S. representative of Italian-based Sorema Plastics Recycling Systems, “or the big plastic lumber producers who want to bring cheaper materials into their products.”

To realize savings in the end—as much as 10 cents per pound in the case of recycled versus virgin plastic film, that which makes up grocery bags, for instance—and to place plastics washing systems in the scope of the staged evolution that is plastics recycling, we begin at the beginning, using PET (Polyethylene Terephthalate) as an example.

We drink the soda and usually just toss the empty bottle away. A waste management company then comes into possession of many such bottles, many of them contaminated, all usually mixed with other, dissimilar plastics. The plastics must therefore be sorted and size-reduced.

“The universe breaks into sort and grinding operations which produce your flake,” says Gerry Fishbeck, vice president of operations at United Resource Recovery Corporation, “then your washing, then palletizing, extruding and, ultimately, solid-stating or crystallizing.” With this, a bottle has perished and will be born again, incorporating to some degree the recycled plastics created in the process.

Now, homing in on the cleaning stage of plastics: “You would wash in a hot water agitated scrubbing system that contains various chemicals to remove dirt and glues,” says Chuck Jones, an engineer and president of Advanced Plastic Systems, which offers plastics washing system consulting and design services. Think of them as a series of home washing machines on steroids. In the general sense, along the lines of treating a wine stain in a button down shirt using special stain-remover, you must pick the right chemical package to clean a given plastic.

“The real secrets in the washing are in temperatures and chemistry, and water,” says Hanrahan, the vice president of sales and marketing at EREMA, a company that, like many others—due to the financial burden of these systems and/or China’s unpredictable and often devastating sway over the U.S. plastics market—has shifted its focus away from manufacturing washing systems in favor of focusing more on designing and implementing turn-key systems. Often a company like Sorema will supply the washing system for an EREMA line.

Though washing systems are a “mechanical engineer’s dream” according to Cozart, the cleaning magic happens in the midst of the potions, those chemical cocktails guarded by washing system designers and manufacturers as fastidiously as a Bronx chef his secret marinara sauce recipe.

There are a few ways to approach a plastic flake, to make it spic and span, free and clear of contaminants that, as with the gasoline some misguided consumer squirted into a 7-Up bottle, may have penetrated deeper than the surface of the bottle, beyond the literal reach of mere scrubbing and agitation systems. Where one washing system might actually break polyester down to chemicals again, others utilize a different approach, ala EREMA.

“With our system,” says Tim Hanrahan, “we use a vacuum to literally suck out any moisture or chemicals in the flake,” to get them one step closer to turn around for end-use in, say, the fiber industry where FDA approval is unnecessary—for pillows, mattresses, jackets; or as pre forms for bottle making; or for the sheet-for-food-contact side of things that is URRC’s specialty, at the contracted bequest of an unnamed major bottler.

“Our claim to fame is our focus on materials suitable for food-grade quality bottles,” says Gerry Fishbeck. “What we produce is a plastic chip; not a flake, not a pellet, but something in between.” The URRC washing system is unique in that it accomplishes a typically three-step PET recycling process—the sorting, grinding and washing of bottles, then the palletizing and solid-stating—in one process.

Rather than using plain old “soapy water” to wash the surface of a flake, this system uses a proprietary process that, through chemical reactions, etches the surface of the flake away, a crucial step in dispensing with deep-seated contaminants. The need to palletize or solid-state is eliminated. The chip product emerges with the proper physical and safety characteristics to meet the needs of the bottler and the approval of Big Brother at the FDA.

Contamination is a big, broad word. It could be the residual juices once contained by plastics that have wound up in or on them. It could just as soon be a polymer concern, to reference the PET imposter known commonly as PVC and, despite its many positive uses, despised in this respect.

“PVC is one of the major contaminants of PET,” says Gerry Fishbeck. “The problem is that it is a PET look-alike, has the same physical characteristics, until someone melts it,” whereupon the PVC unleashes its wrath by turning the recycled PET brown, releasing billowing clouds of hydrochloric acid, rendering washing and every other process heretofore irrelevant.

With its systems, Sorema’s patented philosophy is to get rid of contamination quickly. “Contamination is what wears your machine,” says Curt Cozart. “What we do is wash the material before it goes through a granulator,” removing the vast majority of contamination on most bottles—the labels, glue, sand, glass and dirt. In this case the bottles then enter a wet granulator; the advantage being that as the granulator cuts and reduces the plastic, it also cleans, like a bonus car wash with a fill-up at Shell.

From here the material is further agitated, enduring various stages of cutting and washing; in the case of plastics bottles, steam and a hot caustic solution are the major cleaning agents. Float-sink tanks separate the plastics by densities, followed by a mechanical drying process that varies in nature dependant on the type of plastic.

“There is an issue when you get to the end of the line,” says Tim Hanrahan, “when the flake still has moisture. You have to dry before extrusion.” Any moisture, and any more than a little oxygen, present in plastic flakes upon meltdown will degrade the plastic. “If you are running water, even half of one percent, in the extruder, you will either lock it up like a steam engine or spit out lousy pellets.”

With its proprietary densifier attached to the system’s feed throat, utilizing frictional heat to pre-warm and dry the flake before extrusion, EREMA claims to shine in this department. But so do the other washing system designers and manufacturers, backed by their own special formulas. Unlocking their secrets will cost you.