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Author: Subject: Building an Ostwald reactor
Magpie
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[*] posted on 12-2-2013 at 17:43


Omega is another good supplier for technochemistry projects. Here's what they have in small diameter ceramic tubes:

http://www.omega.com/ppt/pptsc.asp?ref=PTRA_PTRM&Nav=tem...

Also see:

http://www.seattlepotterysupply.com/Merchant2/merchant.mvc?S...

I know these suppliers' items may be outside of your budget. I'm just trying to give you some options and ideas.




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Magpie
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[*] posted on 12-2-2013 at 20:05


In my cursory reading of Ullman's I see that the ratio of ammonia to air is important (if not critical), which I think you have already discovered. How do you propose maintaining this ratio?

One advantage is that your liquid ammonia will exert a constant pressure as long as its temperature is kept constant. You could use rotameters to meter these 2 gases, but maybe there is a simpler and more elegant way. Will you use an air compressor to provide pressurized air?

One advantage of operating your reactor above atmospheric pressure is that you will have plenty of pressure to drive the NOx through the absorber. There are, I suppose many different ways an absorber could be made, cheaply or otherwise. Much room for creativity here, I think. ;)




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plante1999
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[*] posted on 13-2-2013 at 04:44


Well, the three absorber are mostly made, I only need to make a gas dispersor in them. They are made of cheap PVC, you can see them on the first page. The ammonia air ratio is very critic as showed by my experiments too. I had thought, that if ammonia can keep a constant pressure, and keep a constant air flow, the gas mix would probably be similar trough all the experiment. Yes, a 50 gallon air compressor, with variable pressure adjustment.

I don't see how I could afford rotameters. I guess I will have to rely on constant pressure. And thanks for your ideas, they are helpful.




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[*] posted on 13-2-2013 at 09:20


Quote: Originally posted by Magpie  
One advantage is that your liquid ammonia will exert a constant pressure as long as its temperature is kept constant. You could use rotameters to meter these 2 gases, but maybe there is a simpler and more elegant way. Will you use an air compressor to provide pressurized air?



As your liquid ammonia evaporates, the temperature of the liquid will decrease unless you constantly put in the Enthalpy of evaporation. At low flow rates (of ammonia gas) and provided you have a large mass of liquid ammonia this effect may be negligible. It would be worth calculating though...

[Edited on 13-2-2013 by blogfast25]




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Magpie
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[*] posted on 13-2-2013 at 17:16


Here's some ammonia flow regulation experience that should be useful:

http://ww2.chemistry.gatech.edu/~bostwick/stms/ammonia.txt

I especially thought the last comment appropo.

[Edited on 14-2-2013 by Magpie]




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plante1999
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[*] posted on 19-2-2013 at 09:15


Could anyone test for reactivity of nitric acid of various concentration on 304 and 316 stainless steel? Maybe 5,15 and 50% acid?

I should get most of the stainless tubing/valves in the list soon, a very generous donation by doctorofphilosophy. I only have the quartz tubing, relieve valves and meters to find now.
I will try to find others things this week-end.

[Edited on 19-2-2013 by plante1999]




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Magpie
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[*] posted on 19-2-2013 at 09:32


Quote: Originally posted by plante1999  
Could anyone test for reactivity of nitric acid of various concentration on 304 and 316 stainless steel? Maybe 5,15 and 50% acid?


Have you seen this:

http://www.coleparmer.com/Chemical-Resistance

Both are excellent, at least up to 72F.




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[*] posted on 19-2-2013 at 12:39


It's supposed to passivate iron, is it not? But strong HNO3 is needed for that, IIRW...



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[*] posted on 19-2-2013 at 12:53


Nitric acid is also used to passivate stainless steels.

Here's an even better supplier of quartz tubing. They will also do glassblowing. It may take some coaxing for small jobs, however.

http://www.quartz.com/quartz.html




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[*] posted on 19-2-2013 at 14:00


Thanks for the information. I will see what I can do for the quartz tubing, the sand, filter and others. This wee-end, I may try to condense ammonia with a calcium chloride/ice mixture. I will probably finish the absorbers too.

The ammonia tank will be made of stainless steel, 2 inch by 6 with cap and reducer. Magpie test showed iron impurity that could really harm the system, even with filtering of the gases.




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[*] posted on 19-2-2013 at 16:00


Since appropriate rotameters and pressure regulators are so expensive I understand if you are not going to have them. Are you planing to just tune the the ammonia/air ratio based on the color of the reaction products, or what?

burning ammonia is potentially explosive
ammonia is toxic

NOx can be toxic

You already know these things. And I'm sure you are sensitized due to your recent accident, of which I was sorry to hear. I just repeat this here to encourage you to be very careful.




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[*] posted on 19-2-2013 at 16:19


The color of the reaction product would be useful, and the product analysis as well. burning ammonia is explosive when above 12% in air, I'm planning to run way lower than that, because I need an oxygen excess. When nitrogen monoxide is formed, it need to be oxidized to NO2 (need air), when the NO2 is dissolved in water it release NO, which need to be oxidized back too. I will probably run at 2-5% ammonia, if I want a good yield. Lower ammonia also increase the yield, because ammonia react with nitrogen oxides, to make nitrogen.

Liquid ammonia is dangerous, and NO2 too, but they are not my main concerns to be honest. I have worked with stronger stuff, I assure you. If I can find these item for under 50$, I will buy them, but I do not feel like they are necessary. My main concern is bursting of the combustion tube for a reason or another. As such, I will use 1/4 steel shield on possibly dangerous parts.

What is funny with my accident, is that I got the burns with completely homemade nitric acid, which I was quite proud of. The nitrate ion had bean made with my Ostwald tries. These accident do not only left physical harm, but I assume you know that.

On a side note, the cooling of the absorbers will be performed by a ice-water bath. This same bath will Heat the cooling ammonia, to maintain a constant pressure.




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[*] posted on 19-2-2013 at 17:07


Even if you cannot make strong acid you can make nitrates. From these you can make strong acid, as you have already done.

This is a very interesting project and I wish I could be there to work on it with you. I look forward to your progress and hope to see some pictures. ;)




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[*] posted on 19-2-2013 at 17:49


That is what I'm thinking, but hopefully I will be able to make strong nitric acid directly. I can clearly see that you would like to work with me on this! Now that I have a camera, it is easier for me to take pictures, a lot easier. If you want me to take a picture, simply ask me, I would be glad to take a picture in the same day.

One interesting part of this project is the fact that the reactor is multi functional. I could make many chemical with it, by simply changing the catalyst, and the gas reacting together. Sulphuryl chloride, mercury , acetaldehyde etc...

I hope to make something good, I like the absorbers I made at the moment, they feel sturdy and hole are well made (centered).

[Edited on 20-2-2013 by plante1999]




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[*] posted on 4-3-2013 at 13:44


I got a good part of the stainless tubing in my mail today. In a few hour I should have finish to make the ammonia tank with teflon tape and some other part too, I will put pictures here. Sadly, the waiter is supposed to be hot during the week, as such only this weekend it will be tried to liquefy ammonia. In The main while I may try to fill it with sulphur dioxide to test for leaks.



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[*] posted on 4-3-2013 at 15:54


Quote:
the waiter is supposed to be hot during the week, as such only this weekend it will be tried to liquefy ammonia.


Serious mad scientists don't get distracted by a hot waiter so easily. Focus! Looking forward to your pictures though, especially if they also involve hot waitresses :)



[Edited on 4-3-2013 by phlogiston]




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[*] posted on 4-3-2013 at 16:33


If I want to keep the temperature of the freezing mixture down I must do it on a cold day. Here is the Tank, it is about 15 inch height and 3 inch diameter on the cylinder and 4.5 on the valve. I love the industrial look of the stainless pieces. I will work on other connections during the week.



I changed the design (no teflon yet) There is a ball valve on top of the tank to be able to fill it with liquid ammonia easily, There is also the air valve on the right. I tried to put in evidence the outlets where the quartz tube should be. Near the tank there is an outlet which is where the absorbers will be connected.





[Edited on 5-3-2013 by plante1999]




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[*] posted on 5-3-2013 at 16:03


So I continued to put teflon everywhere, then I tested with 100 PSI, at the valve there was some minimal leak, but at the tank the leak was huge, even at 30 PSI it was leaking badly, I re-added teflon tape, screwed it tightly and tested again but it was still leaking...

I guess I will need some sort of liquid sealant...





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[*] posted on 5-3-2013 at 16:11


What you can do is use silicone grease to plug the leak. You should be able to get a nice little tub of it for a few bucks. If you need to find where the leak is specifically, you can cover the sealed tank in a thin layer of a solution of soap in water (without bubbles) so that when air comes out through the leaks, it'll make bubbles in the solution.
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[*] posted on 5-3-2013 at 16:39


As you know, plante, I have built an ammonia storage capsule out of threaded steel pipe. I also encountered leaking threads. I ended up using a liquid sealant which did eventually give me a seal. I have described said adventures in a thread to which I previously alluded.

I would recommend first trying a TFE paste pipe thread compound. I eventually ended up with Leak Lock, a joint sealing compound made by Highside Chemicals. This was recommended to me by a pipefitter who had experience maintaining an ammonia refrigeration unit.

When building my autoclave I ended up backwelding all of the threaded joints that I could.

For the most part I don't think threaded joints are meant for gases, at least not at high pressure. I know that the natural gas line coming into my house is threaded black iron, but that is fairly low pressure (1-2 psi). I don't think that the installers used any kind of joint sealer - they just reefed like hell to make a metal-on-metal compression seal.

Edit: I was wrong here. My natural gas line has a white liquid sealant at the joints - no doubt it is TFE.

One of the problems you will learn with threaded joints is that the threads can permanently deform making it difficult to seal when you try to unscrew and then rescrew the joint.

Welcome to the wonderful world of threaded joints! At one of my previous employers in the nuclear industry all pipe joints were were socket welds.

[Edited on 6-3-2013 by Magpie]

[Edited on 6-3-2013 by Magpie]




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[*] posted on 5-3-2013 at 17:12


wow i didnt know that about threaded joints i would always suspect dirty threads and cleaned them with a thread chaser. thread chasers bigger than an inch can be pretty expensive though but if clean threads and teflon dont cut it,then??
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[*] posted on 5-3-2013 at 17:19


Here's the thread telling of my experience building an ammonia capsule:

http://www.sciencemadness.org/talk/viewthread.php?tid=4566

One extra problem with ss vs black iron, is that ss threads tend to gall, ie, "fret and wear away by friction" (Webster dictionary).
Fret = eroded.




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[*] posted on 5-3-2013 at 18:57


yes, yes of course it does sorry i forgot about ss threads and even some black steel as you called it back in 2005 will gall. if not oiled enough or threaded too fast one does get galling.my supervisor would chew my butt for causing shatter as he called galling when i threaded casing pipe.it was cool seeing that pipe with frost harnessing ammonia.
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[*] posted on 21-3-2013 at 19:09


I just got the leak lock, as reccomended by magpie. I'm away for three day, so I will only be able to work on it Monday.



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[*] posted on 25-3-2013 at 17:12


I started leak-locking everything, it should be dry tomorow. I should also got the quartz tube and gauges fairly soon.
Hopefully I will be able to make a pressure test soon.

Then I will try to liquefy ammonia.




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