March/April 1992
What has the federal government ever done for recyclers? For one thing, scientists at the DOE's Argonne National Laboratory have been working to develop new solutions to recycling problems.
BY ROBERT J. GARINO
Robert J. Garino is director of commodities for the Institute of Scrap Recycling Industries (Washington, D.C.).
Argonne National Laboratory (Argonne, Ill.), with its annual budget of $350 million and a staff of approximately 4,300 employees (including 1,650 scientists and technicians), conducts research on a mind-boggling array of topics, most—but not all—of which involve energy issues. Some 30 divisions are at work full-time conducting research and development on long-range nuclear, biological, and environmental projects. Argonne 's scientists publish more than 2,000 research papers annually.
While much of the lab's research work may appear esoteric, not all of its efforts are blue-sky projects. Many have led to advances in energy conservation, new material development, waste reduction, and recycling. For scrap processors and recyclers, Argonne , primarily funded by the Department of Energy (DOE), is an accessible resource that is seeking commercial solutions—and industry input—to problems facing the recycling industry today.
One principle Argonne scientists and technicians seem committed to is Design for Recycling(TM). The laboratory's Waste Materials Management Division, in fact, has two guiding objectives: identify, through industry interaction, impediments to the recycling of scrap metals, and collaborate with industry to develop the technology and information to remove those impediments. The waste division's efforts target problems related to the demand for high-performance materials, which by their nature may have ingredients that limit recycling.
The process evaluation section of Argonne 's Energy Systems Division also takes on projects that could directly affect the scrap recycling industry. Among the section's missions is the "evaluation of alternatives and development of cost-effective technologies for waste minimization/utilization applications, with emphasis on the secondary metals industries." The group also performs technical, economic, and market analyses, evaluating the commercial potential for applied research and determining potential market and economic impacts of new technologies.
Under this broad directive, the section is operating research programs designed to increase the consumption of scrap metals. According to Edward J. Daniels, who heads the process evaluation section, Argonne 's concerns include the growing use of elements in alloys and coatings that might limit a material's recyclability and increasing residual-waste-disposal costs that affect the commercial viability of the suppliers and consumers of recycled metals.
The process evaluation section at Argonne is pursing various projects targeting these issues with regard to scrap; here's a look at four of special interest.
Recovering Plastics From Fluff
According to Argonne researchers, every ton of steel recovered from shredding automobiles also results in the generation of about 250 pounds of auto shredder residue, which contains plastics, glass, fillers, and foams, as well as dirt, gravel, and sand. Fluff is also often contaminated with automotive fluids and may contain heavy metals, such as lead and cadmium, and polychlorinated biphenyls (PCBs). (Argonne experts believe, however, that the presence of PCBs will become less of a problem over time because their use has been limited by law.)
These facts spurred Argonne to research development of a commercially viable technology that would not only reduce the volume and mass of shredder residue going into landfills, but also cut the cost of recycling the plastic portion of fluff, which the lab estimates at 15 to 20 percent by weight. Researchers expect that growing use of plastics in automobiles will push this figure even higher in the future.
Argonne has been working on selectively dissolving and recovering thermoplastics from shredder fluff for several years. A "proof of concept" paper was published in December 1990 by Daniels B.J. Jody, and P.V. Bonsignore, detailing work the laboratory accomplished between October 1989 and September 1990.
What has set Argonne 's efforts apart from other research involving shredder residue is the laboratory's attempt to selectively recover thermoplastics for recovery and reuse as plastic feedstock. Most other attempts have involved using the plastics in secondary applications, such as production of wood-product substitutes or energy cogeneration.
In addition, very little research had been done to physically separate various plastics from other meaterials in fluff prior to the Argonne study. Furthermore, the lab's researchers found that most of the residue-handling alternatives previously identified were not cost-effective.
Argonne 's scientists have determined that it is technically possible to selectively extract certain thermoplastics from shredder residue, but the cost of the process remains in question. Industry members credit the technical work done by Argonne , but at the same time remain skeptical about successful commercial application of the process in today's marketplace. They also note that the process isn't a panacea for landfill woes: Thermoplastic removal using Argonne 's process would reportedly reduce the ASR by less than 10 percent. (Another benefit, however, is that the resulting residual fluff is reportedly a more acceptable supplemental fuel than the raw shredder residue.)
Argonne scientists are continuing to examine process operating costs as well as market values of the recovered products. Most scrap processors, however, believe thatArgonne has a long way to go before demonstrating feasibility beyond laboratory-size application of the technology.
Degalvanizing Steel Scrap
Argonne , in conjunction with Metal Recovery Industries Inc. (Hamilton, Ontario), has developed an electrolytic process to separate and recover both steel and zinc from galvanized steel scrap. About 15 percent of the steel produced in the United States is galvanized, according to Argonne , and recycling of untreated galvanized scrap lowers production yields and raises environmental compliance costs.
In the process, loose or baled galvanized scrap is placed in tanks of a hot, caustic solution. Zinc is electrolytically dissolved from the surface of the steel and deposited on a metal cathode for marketing to zinc consumers. The stripped steel scrap is then removed and sold to steel mills or foundries. The process is said to be environmentally sound, producing "no significant wastes."
Argonne scientists Daniels and Frederick Dudek believe that a principal benefit of the process may lie in reduced raw material costs to the iron and steel industries. They also point out that the method promises to substantially reduce steel production energy costs, as well as to cut zinc imports. In addition, degalvanizing steel scrap not only should increase reduces the potentially available supply of quality scrap but also should reduce the volume of baghouse dust generated in basic-oxygen and electric-arc furnace and foundry operations, the researchers say.
The electrolytic operation has been reported to be both technically and commercially feasible. According Daniels and Dudek, the process has been tested and found effective on all common types of galvanized coatings, and on loose, shredded, and densified, and baled scrap. (Bulk densities tested range from 60 to 245 pounds per cubic foot.)
By 2000, Argonne experts expect to see a market potential for "dezinced" galvanized scrap ranging from 4.6 to 7.7 million tons annually.
The first pilot plant to test the process boosted on a to commercial scale has been built in East Chicago, Ind., by Metal Recovery Industries and is expected to be operational by late this spring.
Recycling Aluminum Salt Cake
According to Argonne scientists, the secondary aluminum industry annually generates more than 1.1 million tons of salt cake, a process residue containing about 3 to 5 percent aluminum, 15 to 30 percent aluminum oxide, 30 to 40 percent sodium chloride, and 20 to 30 percent potassium chloride. Aluminum recyclers also generate another 500,000 tons of residue in the form of black dross, which is reportedly not economically recoverable in a rotary furnace.
Given the sheer volume of these salt-containing residues materials and their potential to pollute surface and groundwater, Argonne researchers have conducted a study of promising and existing aluminum- and salt-recovery technologies. Spurring the effort are increasing landfill disposal costs and the belief that environmental regulations will eventually restrict disposal of salt-containing wastes in conventional landfills.
In a paper presented at a waste materials conference in December, Argonne researchers Jody, Daniels, Bonsignore, and D.E. Karvelos reviewed innovative concepts developed to date to recycle black dross and salt cake, including new systems developed by two European firms, work conducted by the Bureau of Mines in the late 1970s, and other recovery proposals by U.S. and Canadian firms.
In discussing new processing concepts, Argonne 's experts concentrated on methods designed to leach chlorides from aluminum salt cake using water. This sort of "wet process" is believed to demonstrate potential to be a more efficient and economical method in treating salt-bearing residues.
If the aluminum concentration of a residue is greater than 10 percent, Argonne researchers determined the net revenue from the aluminum and salts recovered should be sufficient to offset operating and capital costs of existing recovery methods and new wet-process salt-recycling technologies. As the concentration of aluminum decreases, however, the economics become more dependent on avoided landfill costs. To date, Argonne research indicates that residue disposal costs would have to be in excess of $100 per ton to economically justify recycling black dross or salt cake with an aluminum concentration of only 3 to 5 percent, but research continues.
Getting the Lead Out
A new Argonne effort just under way this year is directed at a problem of special concern to copper scrap processors, brass and bronze ingotmakers, and the entire brass mill industry: the threatened ban on the use of lead-bearing material. Should proposed environmental regulations limiting the lead content of plumbing fixtures be enacted, an enormous resource of obsolete castings, radiators, and other scrap would no longer be available for recycling. Currently, the brass and bronze recycling industry does not use any technology geared specifically to lead removal.
Argonne, in cooperation with the Brass and Bronze Environmental Research Corp. (BOB CHECKING CITY), has begun an assessment of several techniques for removing lead from copper-based alloys. Processes now being examined in the project include liquation—a heat-based process—use of precipitation or fluxing reagents, and selective and vacuum distillation. The object of the research, according to Dudek, is to find a cost-effective technology that will selectively reduce, or remove, the lead from scrap to ensure the continued use of lead-bearing scrap in the brass and bronze industries.
* * *
These studies are just a taste of Argonne 's work in meeting an objective to "identify and resolve issues affecting the continued or increased use of scrap metals in industry." For reports on these Argonne projects, or further information on the laboratory's other efforts related to metal recycling, contact Edward J. Daniels at 708/252-5279. •
What has the federal government ever done for recyclers? For one thing, scientists at the DOE's Argonne National Laboratory have been working to develop new solutions to recycling problems.