Attachment 5 - Plating Line Descriptions.pdf

Attachment 5 – Nickel and Chrome Plating Line Descriptions

BEP D‐200 Nickel Plating Line Summary Description:

Nickel electroforming/plating line for the manufacture of Intaglio printing plates, including six electroplating tanks and rectifiers.

The six nickel plating baths are similar in make, model, size, method of operation, and materials plated.

The baths use a solution of nickel sulphamate, sulphamic acid, and boric acid. The solution contains nickel sulphamate at a concentration of 383 grams/liter. BEP also adds sodium lauryl sulfate to the baths for use as a wetting agent. Direct current is supplied to each tank by a rectifier, so that metal ions are reduced onto the surface of the substrate. Nickel rounds or pellets provide the anode in the system and replenish the metal ions in the solution.

The nickel plating baths each have a capacity of 715 gallons and a maximum rectifier capacity of 2,500 amperes. The pH of the plating solution typically ranges from 4 to 4.5 and the typical operating temperature is 52 to 53 degrees Celsius (125.5 to 127.5oF).

During plating operations, currency plates are lowered into the plating bath. Each bath has plexiglass cover, and covers are kept closed while plating occurs to minimize air emissions. Two currency plates can be processed in each bath at one time. Thirty‐two subject plates are plated for approximately 17 hours, at an average plating current of 330 amps per plate. Fifty subject plates are plated for approximately 17 hours, at an average plating current of 440 amps per plate. At the completion of the plating process about 0.040 inches of nickel is deposited onto the surface of each plate.

Air emissions from the six (6) nickel plating baths are controlled with a common wet packed‐bed scrubber (nickel PBS). These encompass the affected source at BEP’s DCF facility. A process flow diagram for the nickel plating line is attached. The plating bath rectifiers are interlocked to the scrubber control panel, so that when the scrubber is shut off, the rectifiers are automatically shut off.

Classification of the Nickel Plating Line Under the National Emissions Standards for Hazardous Air

Pollutants (NESHAPS): Area Source Standards for Plating and Polishing Operations, 40 CFR Part 63

Subpart WWWWWW (6W):

BEP’s Washington, DC facility is categorized as an area source of HAPs.

The nickel plating line is used for nickel electroplating. BEP does not own or operate any other affected equipment or processes installed at this facility, as defined under 40 CFR 63 Subpart 6W. BEP does not conduct electroless or non‐electrolytic plating, or other non‐electrolytic metal coating processes.

The plating line was installed and commenced operation in 2009. Therefore, line is classified as a new rather than an existing affected source under 40 CFR 63 Subpart 6W. The tanks are batch tanks rather than continuous process tanks.

Nickel Plating Line Emission Control Strategy:

The six plating baths vent to a common wet packed bed scrubber (PBS 15000). No other equipment is connected to the scrubber. The plating baths are also equipped with covers that are kept closed while plating is occurring. BEP does not use wetting agent/fume suppressant (WA/FS) for emissions control.

BEP D‐200 Hard Chrome Plating Line Summary Description:

The chrome plating line consists of three electrolytic plating tanks and three electrolytic de‐chrome/de‐ greasing tanks. The chrome plating tanks are used to harden nickel plates that are used on currency production presses at BEP. The plates are flat metal sheets, which are produced for two different types of presses – I‐10 and SOI presses. Plate production is approximately a 50/50 mix of SOI and I‐10 plates.

Plates for SOI presses are slightly larger than I‐10 plates, and are plated at higher amperage (2,380 amps/plate vs.1,800 amps/plate). Aside from that difference, the two types plates are handled and produced similarly. Each chrome tank can hold one plate, and each plate is run for 40 minutes. The three plating baths use the same bath chemistry – 33 oz. chromium and 0.33 oz. H2SO4 per gallon. At the completion of the plating process about 0.003 inches of chromium is deposited onto the surface of each plate.

The dechrome/degreasing tanks use an electrochemical process, like the plating tanks. Each dechrome/degreasing tank includes a separate dechrome and degreasing bath. The dechrome baths use a solution of water and sodium hydroxide. Current is applied from the same rectifiers which are used for the plating tanks, at a rate of approximately 500 amps/plate. The degreasing baths use a solution of an alkaline chemical (Metal Cleaner 373) and water, and current is applied at a rate of 350 amps/plate. Each plate is degreased for approximately 15 minutes as part of plate preparation, before being put chrome plating bath. Plates are dechromed on an as needed basis.

The electrolytic plating, dechroming, and degreasing process are all electrochemical processes. Three rectifiers supply power to these tanks, with each rectifier powering one plating tank and one dechrome/degreasing tank. Each rectifier can supply power to either the chrome plating tank or the dechrome/degreasing tank, but cannot supply power to both tanks at the same time. Each rectifier operates independently the other rectifiers.

Classification of the Plating Line Under the Chromium Electroplating National Emissions Standards for

Hazardous Air Pollutants (NESHAPS), 40 CFR Part 63 Subpart N:

BEP’s Washington, DC facility is categorized as an area source of HAPs.

The chrome plating line is used for hard chromium electroplating. BEP does not own or operate any other affected equipment or processes installed at this facility, as defined under 40 CFR 63 Subpart N.

BEP does not conduct decorative chromium electroplating or chromium anodizing.

Under 40 CFR 63 Subpart N, the chrome plating tanks and associated rectifiers are considered affected sources, and the de‐chrome/de‐greasing tanks are considered non‐affected sources.

This chromium plating line is categorized as an existing affected source in accordance with 40 CFR

63.341(a), because it was installed prior to February 8, 2012. The plating tanks are open surface hard chromium electroplating tanks. The D‐200 chrome plating line is categorized as a small hard chrome plating facility under 40 CFR 63 Subpart N. BEP has accepted a permit limit on maximum annual ampere‐ hour use under permit 6378.

Chrome Plating Line Emission Control Strategy:

Packed bed scrubbers (PWS1500) are mounted on each chromium plating bath. Exhaust from each packed bed scrubber is ducted to a common 3 stage composite mesh pad scrubber (CMP6900). Exhaust from the 3 electrolytic de‐chrome/de‐greasing tanks is also ducted to the scrubber CMP6900. BEP does not use wetting agent fume suppressants or foam blanket fume suppressants to control emissions from the chrome plating tanks. The tanks are not covered, but polypropylene balls are added to the tank surface to reduce the area of the interface between ambient air and the plating bath solution.