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DECEMBER 2018 I PCB007 MAGAZINE 69 while increasing the efficiency of subsequent milling or leaching operations. Recognizing the emerging needs in the electronics indus- try, Gannon & Scott designed a multistage ther- mal reduction system that essentially roasts combustible materials at temperatures around 1400°F. The company operates the TRu3Tec® thermal reduction system at processing plants on the West and East Coast—both of which are zero-discharge facilities (Figure 2). Following combustion, gross metallics and primarily steel are removed before sending out for base metal recovery. The process also yields organic ash entrained with a combina- tion of base and precious metals. The volume of organic content is much higher than high- temperature pyrolysis, which is evidence of much lower air emissions. The resulting ash is reduced to a powder by heavy ball milling, and the residue is screened by particle size. These two simple mechanical processes sep- arate organic ash fines (also called sweeps) from the metallic (oversize), typically copper and precious metal alloys. Precious metals are also contained in the ash fines, which are then blended, sampled, assayed, and sold as a com- modity. Metallics are melted, sampled, and poured into ingots. The TRu3Tec system features advanced pol- lution controls including quenching, cyclonic separation, wet scrubbing of exhaust gases, and dust collection [12] . Quenching reduces exhaust temperatures to decrease the formation of haz- ardous byproducts. Cyclonic separation then knocks down carbons and other heavy particu- late matter. Next, wet scrubbing removes acidic compounds, and the liquids are neutralized and air-dried in a separate process. Before exhaust is released to the air, it passes through a final series of filters which remove fine particles. All scrubber-solution entrapped solid salts from the air purification process and filtered dry particles are captured and converted on-site into sweeps. No hazardous waste is created. There are other advanced electronic recycling technologies on the horizon including elec- tromechanical and supercritical gas technol- ogies, and even biometallurgical methods [13] . However, what may work in the laboratory must also be tested at a commercial scale, and be economically viable, profitable, and ideally, sustainable. In the final analysis, the two current paths for PM recovery following primary recycling operations remain chemical (hydrometallurgy) and thermal (pyrometallurgy). Both are proven methods that exist today. Nevertheless, there can be wide variation in process equipment and efficiencies, and residual waste byproducts. In addition, market pressures can negatively im- pact recycling channels. For this reason, elec- tronic manufacturers and suppliers concerned about data security or environmental liability should carefully evaluate downstream process- es and relationships. Those who do will likely discover fresh opportunities for growth. PCB007 References 1. U.S. Congressional Budget Office. "An Update to the Eco- nomic Outlook: 2018 to 2028," August 2018. Note: CBO esti- mates 2.4% growth in 2019 GDP. 2. Bachman, D., & Majumdar, R. "United States Economic Forecast: 3rd Quarter 2018," Deloitte Insights, September 14, 2018. Note: Estimate is tariffs will trim 0.5% from GDP in 2019. 3. IPC—Association Connecting Electronics Industries. "North American PCB Sales Growth Continues While Orders Fal- ter: IPC Releases PCB Industry Results for September 2018," October 25, 2018. Note: Total North American PCB shipments in Figure 2: Lower temperature thermal reduction in combination with advanced environmental controls greatly reduces emissions. (Source: TRu3Tec system, Gannon & Scott Inc.)

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