# How can I turn LPG from liquid to gas?

I am working on a personal project that involves a balloon filled with liquefied petroleum gas (LPG) at a pressure of $$\pu{4 - 5 bar}$$, and I need some kind of a device/filter that would convert it to gas (instead of liquid) at a low pressure. I used an industrial vaporizer, but it gave me something stronger than I need, and "not clean."

Basically, what i need is to build a very big lighter, like this:

As you can see, just gas, and wick that turns to a "clean" fire, without all the side effects that the vaporizer creates.

Now, as I am missing a lot of knowledge here, I would like to know if someone could guide me through how I should do this, where I can find the things I will need, what the names and definitions for the stuff needed, etc.

EDIT:

When I used the phrase "home gas," which is common in my state, I meant liquefied petroleum gas (LPG).

Here is the vaporizer I use now (it belongs to someone who knows what he is doing, I do not plan on killing myself :) )

So, I will try to re-describe my problem:

I want to get a "clean, slow flame" such as a lighter has. What I am getting, regardless of the vaporizer pressure, is an unclean flame, as though some gas is not really burning and just comes out as well, or as if something in the process makes the flame burn dirtier.

• You seem to have asked the question on the physics site too at physics.stackexchange.com/questions/176145/… – tom Apr 14 '15 at 22:30
• Please post your question on one site at a time. While @tom has been kind enough to answer it both places, had two separate people answered, you would have been wasting someone's time. – jonsca Apr 14 '15 at 22:42
• Hi, since it is not absolutely clear to which site this question would best fit, i assumed that posting on physics is good as well, since the visitors of both sites are not the same people, and maybe it would be best to approach this from both physics and chemistry. – Matan L Apr 16 '15 at 7:26
• The issue with not getting a "clean" flame is not about the content of the gas or its vaporisation: it is about how well the gas/air mixture being burned is controlled. You have to mix the LPG and air in the right ratio to get a clean flame. This isn't trivial and needs good design of the burner. Gas pressure isn't the issue, mixing the gas with air is. – matt_black Apr 13 at 21:29

You don't really need to do anything to get LPG vapour. It is a gas a room temperature and pressure so as long as you just want the clean gas not mixed with air (which would be dangerous as the mixture will be flammable and potentially explosive), all you need to do is allow the output of the canister to vent into a balloon.

LPG is mostly propane and butane which liquefy under mild pressure. Butane will liquefy at about 220 kPa at normal room temperature (this is a little over twice atmospheric pressure). This is what happens in a typical cigarette lighter like the one illustrated. There is no "wick" involved just a valve that allows the gas to vent to the atmosphere and a flint to create a spark and ignite it (which you can avoid doing by careful handling of the lighter activating just the valve and not the flint). Large cylinders are similar and it might be possible to vent directly into a balloon just by carefully controlling the exit valve on the cylinder.

It is possible that standard supplies of LPG for household use also contain stinky additives to make leaks easy to detect, but otherwise the gas should be similar to that found in a cigarette lighter.

• What would be the best/safest way to "let" the LPG go in to the room for lighting it? it sounds a bit dangerous, maybe there are some devices or filters that can help doing it without a vaporizer ? – Matan L Apr 16 '15 at 7:22
• And, from more than one search on the web, it seems that there is wick there, the white line is made of wick, here is one refference that says so, but others do as well - bizearch.com/trade/electronic_lighter_parts_5394_32569.htm – Matan L Apr 16 '15 at 7:29
• @MatanL It is just bad terminology. It is a hollow tube not a "wick" and just serves to ensure the nozzle is fed by liquid not gas. It isn't like the wick in a candle. – matt_black Apr 16 '15 at 19:44

What you are asking is potentially very dangerous - but it is also what happens inside many cars in the carburetor - this is really an engineering / chemical engineering problem and if you are serious about doing this you might want to look up the linked wikipedia page about carburetors. Hope this is useful....

Carburetor will premix fuel and air so make a potentially explosive mixture - better just to have a valve where you can regulate the flow of gas above you 'home gas' - this gas would be best burnt with a proper burner that is appropriate for the type of gas you have.