TransForum Vol. 4, No. 3

AWARD-WINNING RESEARCHERS INTRODUCE WORLD'S FIRST CONTINUOUS, MULTISTAGE PLASTICS SEPARATION PLANT

Highly pure recycled plastic emerges from one of several separation tanks at the U.S. Department of Energy FreedomCAR and Vehicle Technologies Program's demonstration facility at Argonne for recycling end-of-life vehicles.

What is the future of plastics recycling? According to Argonne's Bassam Jody, "plastics use is on the rise, and because plastics are not biodegradable, the need to recycle them will become more pressing with time." Thanks to the ongoing innovations of Jody and his colleagues, Ed Daniels and Joe Pomykala, Argonne has the technology to address this need: a new six-stage plastics recycling plant that builds on Jody's award-winning foam recycling process. "As far as we know, this is the first continuous, multistage plastic separation plant in the world — our new recycling process works for just about all mixtures of plastics generated by industry."

Ed Daniels, who is justifiably proud of his group's work, anticipates that the new process will offer key benefits for industry, consumers, and the environment. "For industry," explained Daniels, "the new process provides lower-cost raw materials. As a result, consumers will pay less for the products made with recycled materials." In terms of the environment, the new process reduces the amount of waste going to the landfill. It also saves energy that otherwise would be used to make plastics that would be replaced by recycled material.

This advanced recycling technology didn't happen overnight. "The current plant represents extension and improvement," explains Jody. "We learned from the previous plant about what types of equipment work reliably and adapted them to the new plant." Jody and his colleagues have overcome a number of technical hurdles. For example, they have identified properties of solutions that are selective toward an individual plastic, thereby maximizing recycled product purity and yield. The new plant also has an eddy current separator and a large-scale granulator. "We have also reduced the cost of the equipment by using innovative designs to make the process economical," Jody added. Plus, the plant will be far more extensively automated than the first one — and eventually, it could be computerized.

Once it is fully operational, the plant will be able to recover four to five products from a single waste stream. The new plant advances the state of the art because it is the only one — at an industrial scale — that can be used to separate plastics with overlapping density ranges, which it can do cost-effectively. One of the most noteworthy features of the process is its design capacity: it is able to process 1,000 pounds of plastics per hour.

Separating high-purity plastics from the rest of the waste stream has been a challenge because many conventional separation methods depend on material density — until now, plastics that were similar in density could not be separated to a high enough purity — or they employ large quantities of organic solvents, which pose environmental risks. Argonne's process is the only technology that can successfully produce recycled ABS with a purity of greater than 99%.

The hallmark of the new process — the key feature that separates the complex waste — is froth flotation. The new froth flotation process involves a series of six tanks. Each tank in the continuous process has a specific function, depending on the plastic that is being recovered. "The only difference between the tanks is the chemical composition of their contents. We can choose the most appropriate chemical to be used in a given tank to obtain the product we need," Jody said. For example, the light plastics go into the first tank. The second tank is used to separate heavy plastics, like PVC, and residual metals.

Already, Argonne's froth flotation process has successfully recovered selected plastics from automobile shredder residue, disassembled car parts, industrial scrap plastics, and consumer electronics. The technology is both highly selective and effective: it achieves high purities and high yields for the recovered plastics, and so it should be attractive to industry worldwide. According to Daniels, a two-year payback is realistic. "Because of the potential cost-effectiveness of plastics recyling," explained Daniels, "industries in Europe are pursuing this process more aggressively than in the United States. "In Europe, it costs $100-$200/ton to dispose of waste in landfills, while in the United States, it costs $20-$40/ton. Given rising disposal costs, though, U.S. industry is showing increased interest.

Before Argonne's technology, nobody had a way to cost-effectively separate high-purity plastics from a waste stream of incompatible mixed plastics. And plastics lose their value if they cannot be separated completely. Jody and his colleagues continue to advance the state of the art by applying their expertise in mechanical separation and froth flotation to create ever-more sophisticated technology. If history is any indication, they will make complex plastics recycling as simple, cost-effective, and environmentally sensible as other forms of recycling.