This instructable will walk you through the basics of making your own nitrogen gas generator. Using pressure swing adsorption with carbon molecular sieve you can make an endless supply from the air without using any consumables. You can use this for filling your tires (nitrogen stays in tires much longer than oxygen, reducing the time you need to refill them), having a non-combustible gas or, in my case, to feed into a liquid nitrogen generator.

I won't go into any theory here. I'll just go over the basic construction. A unit of the size I will describe can go between $6000 to $8000. You can build this for a fraction of the price. If you are interested in this subject in more detail you can go to my nitrogen generator web tutorial. There you will find more pictures, animations and other information. There is also a video going over the nitrogen generator. You can also view my liquid nitrogen generator tutorial.

If you are ready to build this for your shop just click next.

Step 1: Basic Theory

This is a big project and will most likely need to stay in your shop or garage. The generator runs off of compressed air. It has two tower beds, each filled with CMS (carbon molecular sieve). Pneumatic valves control the airflow into one at a time. Under pressure, oxygen is preferentially trapped, while nitrogen passes through and out the bottom. The controller opens the next bed for filling, isolating it from the first one as it opens it to the atmosphere. During decompression, the first bed releases the oxygen back into the atmosphere, regenerating the CMS.

The picture above shows the CMS, which looks like chocolate sprinkles. They are approximately 0.5 x 2mm in size. Let's go over a basic materials list.

<p>great tutorial, I seem to be missing one thing. How do the tanks acquire pressure and release the nitrogen. It seems like the gas flows freely from the bottom of the tank and wouldnt build up to 100-ish psi.</p>
Visit www.homemadeliquidnitrogen.com/PSA for more information.<br><br>Each tank is isolated with a solenoid gas valve. Both tanks join at the bottom and feed to a flow valve that controls the amount of gas that exists. This allows the pressure to build since more gas is going in than coming out. See the diagrams at the above link.
ahhh, that makes much more sense. would that mean that while the tank builds pressure the gas coming out would have a higher oxygen concentration, or does it build quickly enough that most of the oxygen is trapped anyways? Thanks again
<p>Look at the videos on the link. O2 diffuses into the porous CMS due to the high pressure and N2 rich gas exists.</p><p>http://www.homemadeliquidnitrogen.com/PSA/CMS%20material.html</p>
<p>Can you review the throughput equations? It seems that 650g/l for CMS vs 2250g/l density of carbon puts your carbon &quot;fill&quot; at 28.9%. 40kg of CMS fills a volume of 61 liters. That means there is 43.7 liters of space for the gas. At 130psi this is 370 standard liters or 13.1 SCF. The cycle is one minute so you are processing 13.1 SCFM air. Air is 78% N2 so your input rate is 10.2 SCFM N2. The output of 1.05 SCFM N2 seems low in comparison to the input rate. Is there a theoretical maximum separation efficiency? </p>
<p>imsmooth,where did you get your carbon molecular sieves?</p>
I think I left the contact information on my website tutorial for the N2 generator.
<p>imsmooth, Great build! do you have any advice or links for designing the Arduino control circuit side of your PSA system? I'm building a PSA system like yours but for generating oxygen for my torches. Thanks!!</p>
I think if you go to my website tutorial the code is there.<br>http://homemadeliquidnitrogen.com/PSA
I see the schematic and cycle timing but no code. Maybe I'm missing somthing..
<p>Send me your email and I'll reply back with the arduino file you need for the build.</p>
<p>alimurtazamaxim@gmail.com please send me the mail </p><p>as my current experiance there need of ceramic balls layer and the activated aluminum to obtain 99.995% pure.</p>
<p>I currently have a matching pair of two brass Versa 1/4&quot; 3-way valves that I used for this project. If you are interested in them you can email me privately. They are $130 a piece or $240 for the pair. They are practically brand new and in perfect working condition.</p>
<p>Dear imsmooth,</p><p>Can you make it with one pipe and on a smaller scale?</p><p>Can you leave the versa pneumatic valves out if you don't want a continuous proces?</p><p> BTW: Nice design.</p>
<p>Where can one obtain CMS-200, I cant seem to find a US supplier and the shipping fees for shipping this out of china is a lot 9free sample of 500g casts $67 to ship)</p>
I got mine from Interra Global. See if Bill Wallace is there. He helped me.<br><br>Tell them Crystal Clear Solutions referred you. I don't get anything from it but I'd like them to keep track of this. Let me know if they can help.
<p>can this be done on a smaller scale? perhaps with pvc and at lower pressures?</p>
Smaller scale - yes.<br>With PVC? Not a good idea. With the given diameter of the tube and a pressure over 100psi you risk bursting the tube and getting shrapnel in your body.
<p>You can get a little more info at www.homemadeliquidnitrogen.com/PSA</p>
<p>well, I'd obviously be working with pipe that could handle the pressure, and some of the smaller pvc pipes out there can handle 120psi if i recall correctly.<br><br>How do you figure out the timing or is it just guess work?</p>
<p>The higher the pressure, the purer the outgas. I get over 98% pure with a pressure of 130psi. You can do 100psi and get about 95-93% with the same amount of material. If you use narrower tubing you will need very long pieces to hold enough material to get a reasonably concentrated gas.</p>
<p>actually taking a look at your site and finding that info there.<br><br>I assume you can get away with one tank, just with the disadvantage of having downtime</p>
<p>Yes, you can use one tank if you don't mind a non-continuous supply. You still need a means to cycle the pressure/depressurization.</p>
<p>having trouble locating a supplier (still looking), got any leads?</p>
<p>Hi, <br><br>Nice work! You said that to get a purer gas you need a second stage. I have read some papers and many of them said that the purity of the nitrogen, in a nitrogen generator by the psa method, is inversely proportional to the flow rate. Have you try that?</p>
<p>Good article on how PSA &amp; CMS works:</p><p><a href="http://www.peakscientific.com/blog/pressure-swing-adsorption-technology/" rel="nofollow">www.peakscientific.com/blog/pressure-swing-adsorption-technology/</a></p>
<p>WOW, impressive professional work.</p>
<p>would a mebrane be sutable like this?</p><p>http://www.peakscientific.com/products/genius/genius-nm32la-nitrogen-generator/</p>
<p>Thought. I just lucked into a very nice used oxygen concentrator for $20 along with a huge bag of hoses etc. My thought was to use to supply O2 for a small propane torch set instead of buying solid-ox tablets. Why not also capture the exhausted nitrogen gas at the same time?</p><p>The O2 concentrater is exactly this same principle and has the two sieves, compressor etc.</p><p>Before I spend a lot of time...has anyone here already done this? If so what is best way to collect and store the gas? ( both the Nitrogen and the O2 )</p>
<p>Hypothetically, could this work on Mars? Just wondering...</p>
<p>Hypothetically, could this work on Mars? Just wondering...</p>
<p>Hypothetically, could this work on Mars? Just wondering...</p>
Can I increase the purity of the N2 if I just make the tower larger and increase the amount of CMS
Were could I buy some CMS-H there are so many sellers don't know which one I can trust
<p>This took a while but I built it and it works great. Keep in mind the CMS will be the most costly and difficult to source part of the build. I also built mine 2x as big as the one inthe instructions due to nitrogen requirements for my application. Thanks for all the help.</p>
Very nice. I built my analyzer. However, I got the O2 electrode from an anesthesia machine. You will have to find that part. The rest just involved building a circuit that could sense the voltage generated by the electrode and convert that to a value between 0 and 100.
<p>i have been doing so much research since first seeing your video and your pressure swing absorption machine. great video very inspiring, especially all of your failures explained. i was initialy inspired to learn about the production of the gases. my concept before i started anywhere was to produce oxygen, to mix with fuel gas, eg propane, acetylene, gasoline, etc. to be able to build a cost effective welding ,brazing system. looked at lots of different zeolite products even to the point of how are they produced. not sure if i have missed something , or if someone has messed with your info . in your video it shows 13x whitey coloured balls with odd blue ones in,. however in another tutorial it states walnut or coconut shells processed, i am curious to which one is the most effective. how can i purchase it in small quantity 20 to 40 kilograms. the pressure swing machine you have built is well smart. but it also appears you have a rocket shape system where air flows through one upright zeolite sieve. you make it look fun and exciting, great choice of music on the vid.. ps . i am a carpenter by trade, done lots of creative building work. would appreciate your input to build, pressure swing absorption machine or similar. </p>
<p>I would like to know if there is any way to take the nitrogen from the generator and make liquid nitrogen. Can you create an instructable on that? I saw one already, but I am uncertan about it.</p>
I already did. Search liquid nitrogen generator.<br>You can also view my web tutorial at<br>homemadeliquidnitrogen.com
http://www.edmunds.com/car-care/should-you-fill-your-cars-tires-with-nitrogen.html<br> Although they differ with my opinion of pressure build up they conclude that nitrogen is expensive and not much of a benefit at all. Keep in mind that the air you breath is already 78% nitrogen. If you keep your tires properly inflated with nitrogen the cost comes to about $86. per year per tire. If you add air to nitrogen every time the pressure drops the cost would be less but the percentage of nitrogen would be less and less. The other point is that the dealers would have to flow quite a bit of nitrogen through the tire in the first place to displace the air already inside the tire. In other words nitrogen tires are pretty much nonsense.
<p>The whole point of this instructable is to produce nitrogen cheaply. </p>
<p>About how much did this cost? Super cool project, I might see if I can get my school to fund a student led version of this.</p>
<p>I am thinking about building one but am in Europe so will start to investigate how to source these parts. After that I can post a European sourcing list.</p><p>You mention in the video if you had a larger system you could get more pure gas? Isn't the purity based on how much time you allow the cms to absorb? I guess you meant that to keep the same flow rate at a higher purity you would need a larger system. I am making this for fiber laser cutter assist gas and need like 99.9% pure.</p>
<p>This is great. If I need to get up to 50L/min what needs to change? The specification I am looking to meet is 1.5 cfm normal flow, 5 cfm peak flow for purging a chamber all at 50 PSI.</p>
<p>Look up Interra Global</p><p>They sell the stuff.</p>
<p>I'd love to have one of these but the steel aspect makes it less desirable. Is there a reason to not use PVC that can hold at least 150PSI?</p>
While there is pac schedule 80 that should hold the pressure, I would feel more comfortable with steel. All of the commercial units use metal. You would not want pieces of plastic flying around. <br><br>However, if you wish to proceed, I get about 95-97% N2 at around 100psi at about 30 L/min output.
I've been looking around for the CMS and am not having much luck in finding it at a reasonable price. What should I expect to pay? Where should I look for it?
<p>Hi! This looks like an awesome project, I just have a couple of questions.</p><p>First, where did you get the 8&quot; pipes?</p><p>Second, where did you get the CMS?</p><p>Third, please correct me if I'm wrong, but don't you need 4 pairs of flanges for the top and bottom of each pipe, and not two? </p>
<p>So, the waste gas in this case is pure oxygen?</p>

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