Grantee Research Project Results

Final Report: Environmentally Conscious Electrochemical Machining for Zero Discharge and Metal Recycling

EPA Contract Number: EPD13040
Title: Environmentally Conscious Electrochemical Machining for Zero Discharge and Metal Recycling
Investigators: Lee, Katherine
Small Business: Faraday Technology, Inc.
EPA Contact: Richards, April
Phase: I
Project Period: May 22, 2013 through November 21, 2013
Project Amount: $80,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2013) RFA Text | Recipients Lists
Research Category: SBIR - Innovation in Manufacturing , Small Business Innovation Research (SBIR)

Description:

This SBIR program addresses the need for a manufacturing method for recovery and recycle of metal removed during electrochemical machining (ECM) of stainless steel alloys. Direct current (DC) ECM typically uses difficult-to-control electrolytes and generates environmentally hazardous waste (sludge) at low process yield. Sludge discard results in the loss of valuable waste metal, as well as loss of electrolyte retained within the sludge, which must be filtered, dried and shipped for expensive landfilling and/or recycling. FARADAYIC^® (R)ECM combines FARADAYIC^® ECM and Electrowinning to eliminate sludge and recover machined metal in compact, solid form, while maintaining the electrolyte for immediate return to the process. FARADAYIC^® (R)ECM employs electrolytes yielding soluble metals enabling: (1) recycling to reclaim valuable metals, thus eliminating landfill; (2) water conservation by elimination of sludge; and (3) energy minimization by elimination of filtration, centrifugation and shipping of the sludge.

In Phase I, stainless steel 316L (SS316L) alloy was dissolved by pulsed-waveform FARADAYIC^® ECM into an electrolyte previously identified as suitable for (R)ECM processing of other materials. A portion of these ECM tests were dedicated to testing the FARADAYIC^® electropolishing capability of the electrolyte. Component metals of SS316L then were recovered from this same electrolyte without intermediate processing by FARADAYIC^® Electrowinning. The operating conditions were varied to explore the range of achievable metal recovery rates and energy/process efficiencies. The electrowinning deposits were evaluated from the perspective of ease of collection/handling and suitability for transfer to offsite reclamation/reprocessing. Finally, a preliminary economic and capital cost analysis of the FARADAYIC^® (R)ECM system was undertaken.

Summary/Accomplishments (Outputs/Outcomes):

The work done in this Phase I program demonstrates the feasibility of an ECM process with integrated electrowinning recovery of dissolved metals, affording total internal recycle of the operating electrolyte, using pulsed FARADAYIC^® waveforms. A high-quality surface finish (R_a = 0.15 μm) was demonstrated in FARADAYIC^® Electropolishing ECM on multiple SS316L coupons, generating total dissolved metals concentrations in the range of 500–3500 mg L^-1. SS316L constituent metals were recovered consistently in all FARADAYIC^® Electrowinning configurations tested as a dry, compact, readily-collectable metallic powder. Capital and operating costs were estimated and compared to current ECM practice, against which FARADAYIC^® (R)ECM compares favorably.

Conclusions:

Based on the results of the Phase I effort, significant benefits compared to standard ECM practice have been demonstrated, namely, the ability to recover the value of the metals retained within the electrolyte, and to permit zero-discharge use of the electrolyte, reducing environmental impact and lowering manufacturing costs. The compact, solid, metallic powders obtained are considerably less hazardous than the sludges generated by conventional ECM and are easily collected and handled. Comparable performance to existing FARADAYIC^® ECM processes has been demonstrated with the electrowinning-capable (R)ECM electrolyte, ensuring seamless insertion of the (R)ECM technology into the operations of Faraday's existing customers. During the Phase I program, Faraday engaged several potential commercial partners for the FARADAYIC^® (R)ECM technology, including Swagelok Company, Boeing Research and Technology, Abel Metal Processing, Pulse Technologies, PEM Technologies and ECM Technologies. The first four companies are potential end-users of the FARADAYIC^® (R)ECM technology, while PEM Technologies and ECM Technologies are manufacturers of ECM systems and hardware with a potential interest in incorporating (R)ECM into their product lines. Per a Commercialization Assessment Report prepared by Dr. S. Ludmerer (Foresight Science & Technology), "There is an important need for the technology, as environmental issues associated with ECM have restricted its market penetration and, in turn, volume growth in sales and installation of ECM machines." Faraday Technology, Inc. anticipates ready market acceptance of the (R)ECM technology as its capabilities and advantages become recognized.

Supplemental Keywords:

electrochemical machining, electrowinning, recycling, electrolyte, waste reduction, electropolishing, sludge, water conservation, metals

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