Chlorine Filter

[Ventsi]

Okay so I have been running my KClO3 for a bit now and I would like to make filtration system for the chlorine gasses comming out of it.

 

I'm thinking something like Lampblack or AF charcoal with some additives, at the end of the hose that directs the gasses awy from the power source, any inputs?

 

EIDT: I dont need it to be permanent I would much rather have a replacable one.

Edited May 28, 2009 by Ventsi

[homebrewed77]

Im not sure if it will work or not..But it is along the line you mention..Might want to think activated carbon? Kinda like a mini carbon scruber?

[asilentbob]

I think you might be better off running the chlorine through a sodium hydroxide solution.

 

NaOH + Cl2 --cool temp--> Na+ + ClO-

NaOH + Cl2 --hot temp--> Na+ + ClO3-

 

I'd just use 2 beer bottle style scrubbers... with dilute NaOH in water solution (don't know optimum concentration)... Then later you can boil the scrubber water and get a bit more chlorate...

 

But... if you do it outside... without a scrubber system the amount of escaped chlorine is probably comparable to a pool... so not too harmful... Just don't do it inside. Scrubber or not, its too dangerous in a confined space.

[Ventsi]

I'm not running it inside ,I just don't want complaints from my family ,"What is that bleach smell, get rid of it! , blah blah blah".

NaOH might work ,or KOH.

BTW ,what do you guys mean by *Scrubber*?

 

Edit: Nooo man my cell pumps H and Cl like a train for some reason, it gets quite stinky!

Edited May 29, 2009 by Ventsi

[asilentbob]

A gas scrubber is just a flask or bottle with some chemical in it that you pass a gas through to try to neutralize any nasty chemicals before they reach the ambient air, in this case Cl2 is the nasty gas.

 

Coal plants sometimes have SO2 scrubbers using sodium carbonate or something so that less SO2 escapes into the atmosphere and forms acid rain.

 

Here is a gas scrubber. Used either to dissolve a gas in the liquid in the jar, or to dry (remove moisture) from a gas passed through the liquid. IE passing freshly generated (H2O vapor present) chlorine gas through sulfuric acid.

http://images.absoluteastronomy.com/images...hing_bottle.jpg

 

You can improvise a scrubber with a beer bottle, cork, some glass and plastic tubing, or similar...

Edited May 29, 2009 by asilentbob

[Ventsi]

Sweet man, thanks ! I'll give this a go with some glassware and PVC tubing.

[Miech]

How about using ureum solution? Up to nine (!) chlorine molecules can adhere to a single ureum molecule, making it ideal for this purpose. Ureum costs near nothing and is reusable when boiled off, as this releases the chlorine (so do it outside and safely).

 

Hot KOH sounds nice and effective for absorbing chlorine, but keep in mind this stuff eats away nearly anything. I've had some lab glassware eaten away by nearly boiling KOH solution when making potassium iodate last year.

[Swede]

Ventsi, coupla thoughts...

 

I used to run the exhaust tube from my cell into a container full of water, outside. That helped a little. It reduced/diffused the chlorine smell. The problem is this... If you insert the tube to the bottom of a 12" tall water container, the gas must now overcome a pressure of 12" of water, or about 0.43 PSI. This means you are pressurizing your cell to about 1/2 PSI. It doesn't sound like much, but it is harder than it sounds to create a truly airtitght cell, and the 1/2 PSI will force the chlorine gas to vent through seams and cracks, AND it will create salt creep like crazy. You end up with a % of the waste gas being forced from the cell, rather than out the tube.

 

Even the restriction of a 1/4" vs 3/8" exhaust tube makes a difference.

 

Stupid ideas... first, use as wide a bore as you can for your exhaust, and make the run as short as practical. Get it outside, and as high as you can. Here's where it gets stupid: position a fan so that the air is blown vigorously over the exhaust outlet. The airflow will instantly diffuse the chlorine, and the stink factor will drop dramatically.

 

Scrubbers would work, though. I'm not sure about carbon, but some liquid chlorine scavenger will definitely help, just watch out for the back pressure.

Edited May 29, 2009 by Swede

[Arthur]

Depending on your diy skills, you could make a venturi suction unit to collect the gasses without passing them through a fan or motor.

 

Take a tall pipe say 4" bore, upright say 3 metres or more tall. drive air up the pipe with a fan (computer fan or scroll fan) Make a choke in the main pipe so that air passing upwards draws in the fumes from the cell and sends it on upwards, away from the fan.

 

Moderate the fan or the flow rate to control the suction to prevent the cell being sucked dry.

[Ventsi]

Swede:

 

I hate salt creep !!!!!!!!! Happened during my last run and it got EVERYWHERE!

I'll draw up some ideas for a scrubber maybe have the pipe finely perforated for 3" and have it dipping in 4 -1/2" Water NaOH solution ?

 

 

Arthur:

 

Thats a good idea but it sounds way too bulky, My cell is only 1 Litre so a small scrubber might be sufficient.

 

Thanks for the ideas!

Edited May 29, 2009 by Ventsi

[asilentbob]

Oh, I didn't think to mention it earlier... but surface area is everything here... so perhaps something like a few sponges soaked in NaOH solution packed in a pipe, and passing the Cl2 through that... NaOH absorbs moisture from the air, so they shouldn't dry out... on the other hand the NaOH will probably wreck havok on the sponge material. I'd say use glass wool, but again, NaOH attacks glass... :/... I don't suppose you have teflon wool... Need something inert to NaOH with high surface area... Some kinds of plastic might be resistant... i really don't know... perhaps use some sort of synthetic string or yarn packed into a pipe? You could still use a bottle and just replace the liquid with soaked high surface inert stuff...

 

I believe fine iron powder and steel wool ignite and burn in chlorine gas... and with hydrogen present that would be even worse...

[Arthur]

There is no reason for you not to scale the venturi exhaust to your needs, it's the simplest way of causing a small pressure reduction in a way that does not cause the chemical fumes to pass over the fan or motor.

 

You could use a venturi of smaller dimensions to draw the fumes through the scrubber.

 

Try this too;

 

Get a bucket of water/NaOH recirculated through an aspirator pomp by a small magnetically coupled pump. This creates a significant (but far from HiVac) depression so the fumes would be exhausted using the water as both pump media and scrubber media. Any fumes would be "scrubbed" into the water and you would end up with a bucket of bleach.

 

As a trivial detail any chlorine escaping is chloride not being converted to chlorate. With DIY cells not getting good process control the efficiency always suffers. Some effort at process control will reduce the chlorine you have to clean up AND increase the chlorate yield.

Vacuum aspirators come in metal, glass and plastic so something to chose for corrosion resistance.

Edited May 30, 2009 by Arthur

[Swede]

Arthur and Bob's ideas are excellent. If the chlorine is truly objectionable, it'd be worth exploring those options.

 

On the salt-creep thing - even in a cell with zero back pressure, there's going to be some, but I'm convinced that even miniscule pressure differentials (slightly higher in the cell than out) easily quadruple the creep. You wipe the salt creep with paper towels, typically, which have the potential to dry and become pyrotechnic objects all by themselves, being encrusted with chlorate. When I run a cell, I have a heavy plastic bag which I add a cup of water to, and hang that nearby. Into that goes any flammable paper products that are created in routine cell maintenance. Or, you can isolate them and burn them later. A flaming pile of chlorate-encrusted paper towels is fairly spectacular!

 

The venturi can be made to actually reduce the pressure in the cell to BELOW ambient, meaning salt creep will be inhibited somewhat; maybe completely.

 

One other thing... are you working on pH control? A cell at the proper pH (near 6.8) tends to evolve less gaseous chlorine, and what does evolve, mostly remains in solution as dissolved aqueous Cl2. You know your pH is too high if you add a tiny portion of HCl and you instantly see green chlorine gas evolve at the site of the acid injection. If you are not controlling pH, no worries, it will simply take a bit longer in a given run due to reduced efficiencies. But it'll still make chlorate.

 

By now you've dealt with (and smelled) the unbelievably noxious liquor at the end of the run. That stuff is flat--out--nasty. You might want to consider a large pan, tray, or bucket to place the cell into, which will prevent disaster if the cell ruptures or erodes. I use a huge rubber bin from Home Depot, half filled with water, which does two things - it helps keep the cell cool, and it can effectively help crash the cell contents if the cell leaks or ruptures.

 

Good luck, it's a fun and fascinating process.

Edited May 30, 2009 by Swede

[Arthur]

Any and all chlorine is objectionable! It was one of the war gasses in WWI

 

 

Remember also that ANY exhaust gasses will contain some drying aerosol chlorate so if you use an organic scrubber it will be fire sensitive.

 

Activated charcoal will simply become rather dirty H3 -sensitive and powerful.

 

It's also a good plan to ventilate the cell carefully to ensure that the electrics and electronics are uncontaminated and have a reasonable life.

Edited May 30, 2009 by Arthur

[Ventsi]

Ahh good point Arthur , I will go with the scrubber trough some PE wool that I will make with some fine fishing line and have perforated PVC tubing running through it.

 

 

 

I'm not looking for something to steer the gasses away from the power supply Arthur , I have ~ 10ft of cable between the cell and the PS

[asilentbob]

How about using ureum solution? Up to nine (!) chlorine molecules can adhere to a single ureum molecule, making it ideal for this purpose. Ureum costs near nothing and is reusable when boiled off, as this releases the chlorine (so do it outside and safely).

 

Hot KOH sounds nice and effective for absorbing chlorine, but keep in mind this stuff eats away nearly anything. I've had some lab glassware eaten away by nearly boiling KOH solution when making potassium iodate last year.

 

By ureum solution... do you mean urea solution? Carbonyl diamide CO(NH2)2 ? I wouldn't know anything about how it would react, but if that is so... Then this would be an excellent method in my opinion. Absorb excess Cl2 and later on you can release it for whatever other experiment!

 

EDIT: And that wasn't really what I meant by surface area... I meant the surface area of the liquid as the the area of the barrier between the liquid and gas phase. A damp t-shirt has a very high surface area, so liquid will evaporate off it faster than the same volume of liquid in a cup. Likewise a damp t-shirt would have a much greater surface area that a gas could interact and dissolve into the liquid than the much smaller surface area that a cup of water would have. So a design would have it so the gas could pass all the way through the absorber so that back pressure wouldn't be a problem... And the scrubber would have high enough surface area that most all of the chlorine would dissolve/react before escaping. You'd still have to be wary of hydrogen.

 

If the urea thing works, then this opens the field of high surface area inert things... to a lot more... possibly old rags and t-shirts... Though I'm un-sure of how the chlorine-urea compound(s) would react with cotton fibers.

Edited June 1, 2009 by asilentbob