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exhaust ventilation alkaline cleaner tank
2

exhaust ventilation alkaline cleaner tank

exhaust ventilation alkaline cleaner tank

(OP)
I have a small black oxide line in my plant.  The first (cleaner) tank is caustic soda heated to 140°F.  There are vapors coming off the tank that cause an unpleasant odor.  I had an air quality audit done a while back and the industrial hygienist recommended local exhaust ventilation on this tank.  The vapors consist of sodium hydroxide, sodium metasilicate and /or glycol ether.  He said I need 190 cfm/ft^2 of surface area or 956 cfm total (5.03 ft^2).  There is an overhead crane above the tank, so I can't put  a hood over the top.  I will have to install ductwork on the sides of the tank and draw the vapors underneath and then somewhere. Now my question:

What do I do with the air and vapors?  Can I filter it or condense it and then blow the air outside, or just blow it all outside?  If I blow it outside do I need to allow for makeup air to keep the doors from being sealed shut?  Unfortunately the guy that did the audit is no longer at my insurance company and I haven't been able to get in contact with anyone there that could help me.  Any ideas?

RE: exhaust ventilation alkaline cleaner tank

2
Nate2003:

The most usual solution to your problem is a push-pull system consisting of forced air outlets across one side of your tank with inlets (exhaust) on the other.  The system essentially functions as an air curtain over the tank to capture the fumes.  Given the contaminants in your airstream, you might want to put in a plain water scrubber to remove the contaminants before exhausting the air outside.  Depends on the concentrations, odor levels and your environmental permits.  Filtration might work, depends on the level of aerosol in your exhaust.  Aerosols tend to gum up dry filters, so you might want to avoid those.  The thing to do first is to determine the level you might have.  You can estimate these levels from algorithms for caustic baths found in literature from the EPA, AWMA and the American Association of Industrial Hygienists.  From there, you can determine what is then needed in the way of control before exhausting the airstream.  

RE: exhaust ventilation alkaline cleaner tank

The scrubber would work well. The scrubber will need to be bled at a low flow rate. make sure COD is not too high in the bleed stream for your local discharge.

RE: exhaust ventilation alkaline cleaner tank

The push-pull system would only require 75 CFM/ft2 (vs 190).  Normally, this system is desirable if your tank width is > 36".  The "Industrial Ventilation" published  by the ACGIH is well documented about this subject.

The major atmospheric contaminant will be an alkaline mist and/or steam that can be treated with a mist eliminator.  However, this equipment might not be necessary  - you might be able to blow it outside, check with your local authorities.  

RE: exhaust ventilation alkaline cleaner tank

(OP)
Thank you all for your help.  I am dealing with a fan company that specializes in handling this type of situation and they are designing a system for me.  Thanks again.

RE: exhaust ventilation alkaline cleaner tank

if you have more information about this specialized fans co. or their site is known please inform us this will be of a great help with many thanks.

RE: exhaust ventilation alkaline cleaner tank

(OP)
Hopefully I am not violating any policy by mentioning them here.  The name of the company is MAPCO (Midwest Air Products) at midwestair.com.

RE: exhaust ventilation alkaline cleaner tank

Once the air requirements have been established, what is the best method of determining blower size?

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