I have been setting up the tube furnace to work with inert atmosphere, i.e. H2 and N2 in order to anneal the iron-based metallic powders. The furnace is equipped with vacuum pump as well. The whole process can be described briefly:
1. Place the samples inside the furnace, seal, and vacuumize (10 ^ -3 mbar)
2. Turn the vacuum off and purge the furnace with nitrogen to get rid of oxygen remains
3. The heating begins and pure hydrogen is incorporated into the furnace
4. After the annealing finishes, the furnace is again purged with nitrogen and vacuumed. At last the air is blown into and the samples are ejected.
I'm using the bubbler solution at the gas outlet, as shown in picture, to control the gas flow. The first jar (called Dreschl washer) is filled with gas and the next one with water. This is also a protection against backflow of water into the furnace when vacuuming.
I am wondering if i could replace the water in the bubbler to something more dense, in order to increase the gas pressure inside the furnace. I was particularly thinkng about glycerine as it is cheap, widely available and non-toxic. I know the mercury bubblers are quite popular, but i would not practice this for the obvious reasons. Does the glycerine react with hydrogen? How much pressure can I get (in relation to atmospheric) if I use, lets say, 15 centimeters of glycerol? Is there someting better than glycerine that I could use?
I've been known to use a cold trap on the back of a tube furnace with a regulator in series, while using pressure-resistant fittings (e.g. heavy bubblers or steel vial bubblers. This can bring a tube reactor up to high operation PSI. Note that you should have emergency shutoffs for H2 use! Best of luck on experiments!
I would suggest putting an elastic pipe on the exhaust end of the tube and squeezing it with a Wirtz clamp, thereby regulating the gas flow rate and, consequently, the pressure in the reactor.
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Annealing