Propane Vapor Barrier

[ericwalker]

I am hoping there might be a product, such as foam, that is a vapor barrier for propane while allowing water to seep though? Help...

[Steptoe]

What is the application?

[ericwalker]

I do special effects and use propane to light the top of a large block of clear ice. I core a hole down the middle of the ice. I pipe propane at the bottom of the ice block, it rises through pressure and I ignite it at the top of the ice block (full block is approx. 45") Of course some of the gas does fall along with melting water. I am trying to contain the gas vapor and allow the water to drain...

[bumpstart]

im thinking you might be able to make a water trap barrier by gravity draining the water in the ice block via a tube to the bottom of another vessel that is already half filled with water
thus the tube holds a level of liquid water in it and no propane will pass through ( or drain )
and the level in the tube will remain constant while the drained fluid will displace water in the water trap , raising the level there

[Steptoe]

I pipe propane at the bottom of the ice block, it rises through pressure and I ignite it at the top of the ice block (full block is approx. 45") Of course some of the gas does fall along with melting water.

I have seen this done a long time ago.
The block of ice was about 3 or 4 " diam where the gas came out
The hole was maybe 1/2".
down the center of the hole was a glass tube the gas came up and burnt off
The water that melted around the hole drained back down the hole around the glass tube.

Of course some of the gas does fall along with melting water

I dont understand this thu.. if the flow is adjusted corectly, not excessive, then why would all the gas not burn at the top?....

[franz]

The problem is that the relatively low ice temperature increases the relative density of propane where it starts to assume some of the properties of a liquid. Not yet a liquid but it begins to be "lazy" and wants to settle before ignition. Those in colder climates might relate to this better than I, where it seldom reaches freezing.

Franz

[Steptoe]

Which would be why

The block of ice was about 3 or 4 " diam where the gas came out
The hole was maybe 1/2".
down the centre of the hole was a glass tube the gas came up and burnt off

Not a glass tube frozen in the ice but rather having a air gap around it.. which means melted water caught between the tube and the ice hole sides, runs out the bottom... and maybe why the hole was so large.. rather than drilled that lager it had melted that large due to heat from the flame warming the glass tube???

[ericwalker]

Great feed back everyone, thanks:

I do not use a glass tube to feed fuel to the top...I try to limit the amount of mechanics needed, therefore, not seen to those viewing it.
Yes, the propane does get "lazy" therefore has a tendency to accumulate at bottom hence the need to add pressure, forcing it to rise to the top of the ice block.
The ice block is approx. 45" tall so the pressure needs to be higher to reach the top.

The water trap is a good thought, I might experiment with that. My other thought is to feed compressed, or fanned air (low pressure) to "push" the gas up, do you think this will disperse the gas vapor too much, not allowing it to ignite at the top?