Did you ever think you could make liquid nitrogen in your own garage? This is an industrial process so how can an individual do this? Still doubt me? Intrigued? Read on.
As a lover of science I tried to think of a challenging project that was out of the ordinary. After going through the internet web and Youtube I realized that no one had made liquid nitrogen in his home. Yes, I did see some videos where some would use a Stirling Cooler from a cryorefrigerator and use this to condense nitrogen on the exterior of the cold-head. While one is making liquified gas, this is done using a prefabricated machine. I wanted to make the machine that liquefies the gas. Furthermore, a cryocooler has a very low production rate. You will only get about 500 - 1000ml per day. On the following pages I will walk you through the basics of how to build your own liquid nitrogen generator. Using easily obtained materials you can liquefy nitrogen or air. The unit cools to -320F in under 50 minutes. The production rate is about 350 cc/hr.
A full tutorial and plans are at http://homemadeliquidnitrogen.com This page goes over theory, thermodynamics and more detail on where to get components and how to build this. This Instructable serves as a general introduction to how this baby is put together.
I have just added a new web tutorial on how to make your own N2 gas from the air. I will add this as a new Instructable in the next few days. You can get a link for it at the end of this one.
I have also built a high-precision cryogenic digital LCD thermometer for this project. I thinking of mass producing it and selling it far cheaper than commercial units. There is information on the first page of my tutorial for those interested.
Ok. The video above gives you a quick 3 minute overview of the project. At the end of this tutorial I briefly mention the PSA I made for making the pure N2 from the air for the generator. If you're ready for 320 degrees below zero we can begin...
The liquefication generator has a few basic components. Starting in order:
1. Scrubber - This removes CO2 and H20 from the gas stream. Without this the water and CO2 would freeze and clog the tubing and valves
2. Filter - We need to remove any micro-particles that can clog our compressor valves
3. Compressor - This compresses the gas to high pressure. Two important factors are the pressure and flow rate. This project uses an oil-free scuba compressor delivers a pressure of 3500 psi at a flow rate of 3 SCFM (I jacked it up to 4 SCFM). It is possible to use a regular refrigerator compressor, but the production rate will be significantly reduced
4. Pre-cooler - This cools the hot, compressed gas before entering the cooling tower.
5. Regenerative cooling tower - Hot compressed gas flows through a counter-current system to cool the gas to cryogenic temperatures. Expanded, non-liquid gas returns to get recompressed.
6. Throttle - This is a needle-valve that enables a controlled expansion of the gas without losing the pressure behind it.
7. Baffle - This reduces the velocity of the expanded gas so it does not dissipate the cooled liquid into the gas-stream. It also provides a larger surface area for condensation.
7. Reservoir- This is the collection system that collects the gas. Heat exchange with the environment is minimal.
Above is a picture of an early version of the generator using a recycle can. Later you will see an improved version.