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Use of EN rinse water in fume scrubber

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We are a small plating company dealing with EN coating.I wonder if we could use the rinse water used in Electroless nickel plating process in fume scrubber so that we can reduce the amount of water treated and discharged.Is there any regulations involved in this.

Naveen Kumar
plating shop - Arlington, Texas


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Can you do it? Yes, but you do not want to. Consider slowing down the amount of water that you put into your scrubber so that you reduce the outflow of water by say 25 % to start. If you do this, you will want to add a pH control unit to the scrubber to maintain its effectiveness. If you reduce the water flow too far, you wild have a buildup that is a bitch to clean, so do not get greedy.

You might also want to put a centrifugal mist eliminator in the duct as far away from the scrubber ,but after the last joining duct to remove most of the larger mist particles. This will lighten the loat on the scrubber more than most people will believe. Here is one of the places that I agree with Freeman, who will quite probably reply to your letter also.

James Watts
- Navarre, Florida


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Hi Naveen,

Well, a Kudo from James Watts ... wonders will never cease, will they ... but miracles? Wow! Thank you James or is it Muchas Gracias as they say in your area, eh?

He hit the nail on the head ... but maybe you have a twofold problem. Firstly reducing/lessening the load into the scrubber and secondly reducing/lessening the load after the scrubber.

Normally, I'd use a horizontal inertial scrubber which does both these things ... the simple one is called an eliminator, the better one, which you don't need, the LMITS, requires 3" SP and is good for 3 micron capture.

Either way, please consider a l2 micron (@ full efficiency) blade type horizontal 'eliminator' whose pressure drop, clean, would be max. l". Very easy to clean, if made right.

For 'after' the scrubber, it could go anywhere ... if freeze up is not a problem, then right up to the fan ... ideally allow min. 4 x dia. of duct diameter as a clear inlet duct length to enhance efficiency, ie. NOT just after an elbow.

The LMITS are now being made in Australia which proves, perhaps, that this inertial route is the way to go.

freeman newton portrait Freeman Newton
- White Rock, British Columbia, Canada
freeman newton died


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Good comments, I'd like more info on that LMITS 3 micron removal blade.

Is the scrubber only serving the EN Tank(s)? If so, you may look at totally eliminating the scrubber and using a Composite Mesh Pad Mist Eliminator or even blade type to capture the Nickel Emissions, since they evolve off the process as 'mists'. The mist eliminator should have a wash down spray header to periodically clean the pad, and reclaim the captured EN into back into the bath.

This way you will have no discharge to waste treatment from a scrubber, and you only be using a small amount of water to periodically wash down the mist eliminator.

The downside though, is that the mist eliminator will not capture as much of the gaseous Ammonium Hydroxide (ammonia) Emissions.

But back to your idea, using rinse water for scrubber makeup water is not uncommon. But, I wouldn't do it if you were permitted by city or state for a certain removal efficiency of the EN constituents. You may want to filter it before you send it to the scrubber. It should make sense to the regulatory folks...saves water.

Kyle Hankinson
- Forest City, NC


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Kyle,

LMITS blade removal? Ah, that's a cinch. The blades are made in modules for either accessing sideways or from the top. On large units, the modules are cut into approx. 40 lb units to facilitate removal.

IMPORTANT !

Nearly all plating shop acidic emissions are NEITHER gases nor FUMES but invisible low micron sized droplets ...and surely an ordinary 'rain cloud' would not be a gas but also 'droplets' albeit much larger.

What's in a name? The word scrubber denotes to the hoi-polloi that it WILL scrub something or another ... but never gives out efficiences as there are too many variances especially with a mass transfer scrubber ie. packing type, packing size, packing depth, liquid req'd to neutralize, liquid gpm rates, airflow and design velocity and THEN at the end, one sincerely hopes, some type of eliminator... and if it's mesh, oh dear, sooner or later it could fail... and I've seen a well made scrubber operating at around 400 fpm with a mesh eliminator .... and odiferous water droplets being spewed to atmoshphere.

The LMITS is a scrubber ... but good for 3 micron capture at full efficiency ... or BETTER ... But the LMITS is also a sophisticated blade type eliminator .... and unlike mesh, doesn't plug up easily and, I'd imagine, would be A.OK for Ammonium Hydroxide.

Any failures? Yes, partial failure in some very strong nitric emissions. Also in an Assay lab (Placer, Vcr) Perchloric carry-over ... but that was a l2 year old LMITS AND they hadn't done any maintenance for all these years so it cost them $ 35.oo for some parts to fix it ... this amused me immensely & I sent them a letter to BUY 4 new ones or do some maintenance once or so in decade !

Freeman Newton
- White Rock, British Columbia, Canada
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