# idea for an inline dry scrubber



## delboy9891 (Jul 16, 2021)

Hi folks, I currently have a ductless fume hood with carbon filters and was advised that this was not good enough to filter out nox gases and that I should use ducting and a scrubber, I have had a look at several scrubber designs including 4metals designs and they are a bit complicated for me plus I dont have access to water in my shed unless I run a really long hose in which is not very practical so I have come up with an inline three stage scrubber idea to attach to my plastic ducting,, I am going to reactivate the carbon in my fume hood filters by placing the carbon in a kiln at 800° then add a 12" duct flange over the fume hood exhaust for the 12" ducting, the first filter will be bioballs washed in a solution of sodium bicarbonate and placed inside the first filter, this will be a removable filter so I can replace the media, the next filter will be prilled limestone granules, which will be removable as well these granules go a purple colour when they are used up so being able to remove the filter and replace with fresh granules is a must and the final filter will be another carbon filter just to be sure I have drawn a diagram showing what it will look like but dont know how to post it, I would love to hear everybodys opinion on my idea, especially 4 metals, am I on the right track? or is it a case of back to the drawing board, many thanks for any advice


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## Martijn (Aug 2, 2021)

A scrubber is generally used to scrub gases directly from reaction vessels. A fume hood is used to keep the accidental releases of gas away from you by airflow and dilution before venting it out to a safe location where it gets diluted more. This airflow can also be scrubbed. But that's another thing. Bag house filter, mist scrubber. 
Keeping the escaped gases to a minimum should suffice to keep the emission levels acceptable. 
A scrubber bottle setup with some lye or H2O2 can get most of the gases out. 
You'll need a vacuum pump or venturi driven vacuum for it to work. The beauty of a water powered venturi vacuum is a second scrubber effect.


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## nickvc (Aug 3, 2021)

You really do need running water in my opinion as when disaster strikes which it will at some point you will want water to mitigate the results of said disaster, if you can’t or do not want to have water connected at least have a large capped water tank or butt raised as high as possible so water can be accessed through gravity feed, downside is you need to keep it filled unlike a ready connected pressured water supply. 
For a scrubber to work well you need a spray of solution of water and lye to fall over the media balls to absorb the fumes and enough air pressure to push the fumes through, not enough pressure and the fumes will not be vented out of your hood and too much and the fumes will not be scrubbed. 
Any removable filter such as your carbon ones will be a pain to maintain and monitor so if the scrubber designs look to hard for you to home make them look at sealed reaction vessel refining with the scrubbing done within connected sealed vessels, I believe 4metals also detailed his set up, this can be done with more expense but if the vessels are of decent size you can process fairly large amounts.


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