Metal Shredder Application
Metal shredder emission control involves three steps: capture the exhaust from the shredder, destroy the volatile organic compounds (VOCs) in it, and remove the acid gases that form when those compounds burn. The plastics, paints, rubber, and fluid residues that enter a shredder with the scrap vaporize in the heat of the mill, and EPA test data indicates that typical shredding operations emit 20 to 200 pounds of VOCs per hour.
PCC has installed shredder systems at several locations, including Tacoma, Washington; Portland, Oregon; and Oakland, California. All systems are currently operating in compliance with applicable requirements. Its most recent installation features a dual regenerative thermal oxidizer (RTO) and dual acid gas scrubber system treating a combined 140,000 SCFM of shredder exhaust at 98.0% destruction removal efficiency (DRE) or greater.
Dual RTO and dual acid gas scrubber trains where the exhaust volume requires them
Guaranteed up to 99.5% VOC destruction efficiency
Up to 97% heat transfer in the RTO, which holds down fuel use on a dilute, high-volume exhaust
Modular RTO designed for ease of installation with integrated control panels, VFD panels, instrumentation, and wiring and tubing provided in a compact footprint for a crowded yard and quick installation
Heat recovery media selected for the application, including ultra low-pressure drop media, high TER materials, and versatile materials designed for bed bakeouts for applications with organic particulate.
Allen-Bradley PLC control panels featuring remote connectivity, enabling the PCC Service Department to provide prompt troubleshooting support
Integrated Train
Cyclone or venturi scrubber for particulate ahead of the oxidizer
RTO sized for the full enclosure exhaust volume
Materials that are able to resist the highly corrosive process gases
Acid gas scrubber for HCl and HF downstream of the RTO
Integrated controls across the oxidizer and scrubber
Contact us by phone at (412) 655-0955 or request an engineering consultation to discuss your shredder emission control needs.
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Why Shredder Permits Come First
VOC emissions from shredders are regulated because they contribute to ground-level ozone. The applicable requirements depend on the shredder’s location. Permit thresholds differ between areas that meet the ozone standard, areas that do not, and the Ozone Transport Region[BF1.1]. A new or modified shredder that exceeds the applicable thresholds may be subject to New Source Review (NSR) or Prevention of Significant Deterioration (PSD) review, while an existing one may fall under Reasonably Available Control Technology (RACT) rules. Some states set lower thresholds of their own.
EPA outlined these requirements in a 2021 enforcement alert addressing the more than 250 U.S. metal recycling facilities that operate shredders. The alert also notes that newer tests with better capture have measured emission rates above the 20-to-200-pound range, and that emissions vary with the size of the shredder and the material fed to it. The emission estimate is therefore a critical initial design input. It helps determine whether controls are required and how large they have to be.
The Shredder Emission Control Train, Stage by Stage
| Stage | What It Handles | Equipment | Design Point |
|---|---|---|---|
| Capture | Everything the shredder releases | Enclosure around the shredder, pick-up hoods, and fans holding negative pressure | The enclosure air volume sets the size of every stage after it |
| Particulate Removal | Metal particles, large and small | Cyclone, venturi scrubber, or fabric filter | Keeps metal particles and fume out of the RTO heat recovery media |
| VOC Destruction | Vaporized fuels, fluids, plastics, and coatings | Regenerative thermal oxidizer | Guaranteed up to 99.5% destruction; up to 97% heat transfer |
| Acid Gas Removal | HCl and HF formed from chlorinated and fluorinated material | Acid gas scrubber using an alkali solution | Placed last, because the acid gases form in the oxidizer |
What Does the EPA Require of Auto Shredders?
The Clean Air Act cases cited in EPA’s 2021 alert resulted in penalties ranging from $900,000 to $4.1 million. In each case, the operator was also required to install emission controls. The control trains described in the alert include enclosures and fans, particulate control, regenerative thermal oxidizers, and acid gas scrubbers.
EPA recommends that operators estimate hourly and annual VOC emissions, compare them with the applicable thresholds for the area, and contact EPA or the state agency to discuss a path forward if the estimates exceed the thresholds. Depolluting scrap before it’s shredded (removing fuel, oil, refrigerants, and batteries) can reduce the VOC load and fire risk, but it does not replace add-on controls where the thresholds are exceeded.
Shredding Operations the Train Applies To:
Automobile shredders
Large appliance shredders
Mixed scrap metal shredders at metal recycling facilities
Related metals and mining processes
What PCC Needs to Size a System
Shredder size and the scrap mix
Automobiles, appliances, or mixed material
Enclosure design and total exhaust flow
Or the capture approach if no enclosure exists
VOC emission test data or estimate
In pounds per hour, with peaks
Existing particulate equipment
Such as a cyclone or scrubber
Permit status and the VOC threshold that applies to the site
Any consent decree or compliance order that applies to the site
Available plot space, natural gas, power, and water
Where test data is limited or the operating cases are uncertain, an engineering study validates the emission estimate, the design flow, and the scope before equipment is specified. PCC’s metal shredding white paper covers the application in more detail, and the RTO calculator provides a preliminary operating cost estimate. Contact us today to schedule an on-site visit with a PCC Process Engineer. PCC can provide upfront design and engineering support for the required equipment, including the shredder enclosure, capture hood, and ductwork connecting to the emissions-control system.
