1
$\begingroup$

"LPG" is the term used here for a mixture of Propane & Butane sold for public use. The exact ratio varies depending on where you buy it and I think also with the season and is not known to me.

I am working on a personal project, I have a gas tank (Liquefied petroleum gas) with a pressure of 4-5 bar (about 50 to 80 psi). Gas in it is a combination of liquid and gas (you can hear the liquid inside if you shake it).

I need some kind of a device/filter that would convert it to gas at the output (instead of liquid) with a small pressure so I can burn it cleanly.

I tried using an industrial vaporizer that is designed to produce gas from LPG, but it gave me something stronger than I need, and when it burns it seems that it is "not clean". (Maybe the industrial gas that is used with the vaporiser is a different mix of gases than domestic LPG?)

Basically, what I need is to build something that works like a large version of a cigarette lighter, like this :

Cigarette lighter

As you can see, in a lighter like in the photo there is liquid and gas, and a wick that turns produce "clean" fire, without all the side effects that the vaporizer creates.

Now, I am missing a lot of knowledge here, and I would like to know if someone can guide me to how should I do this, what are the names and definitions for the stuff I need etc, Any knowledge regarding to what I should do, or how, or where can I find it will be mostly appreciated.

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

enter image description here

So, I'll try to re-describe my problem,

I want to get "clean slow flame" such as is produced by a cigarette lighter. Instead, what I am getting, regardless of the vaporizer pressure setting, burns like it's not clean - it acts as if some of the gas is not really burning or properly vaporising when it comes out.

| improve this question | |
$\endgroup$
  • $\begingroup$ @Matan Air to gas ratio will affect flame. Flow rate per thermal energy into the gas will affect degree of valorisation. I'd expect that more heat into the expanded gas before the burner would help. Dirtiness seems unlikely - more likely you are getting a degree of liquid remaining at the combustion point. Gas with a Propane-Butane mix will probably be harder to vaporise as Butane percentage increases - and cheaper gas tends to have more Butane content. Pressure per given temperature gives some clue. $\endgroup$ – Russell McMahon Apr 17 '15 at 0:04
  • $\begingroup$ @Matan - Can you refine the question to the extent that people with a poor ability to understand English that isn't EXACTLY like what they are used to can understand. They MAY then reopen the question, but don't count on it. $\endgroup$ – Russell McMahon Apr 17 '15 at 0:05
  • $\begingroup$ The terms Liquified Petroleum Gas and LPG may be less known or used in some counties or areas than others, but is widely recognised internationally. $\endgroup$ – Russell McMahon Apr 17 '15 at 0:15
  • $\begingroup$ what are the characteristics of the flame? is it yellow or blue? $\endgroup$ – niels nielsen Apr 24 '18 at 6:22
7
$\begingroup$

Lighters usually use Butane.
Gas bottles use some or all Propane.
Propane pressures are MUCH higher.
A plastic 'tank' filled with Propane would probably explode.
As size increases the container strength must be increased disproportionately.
As temperatures increase pressures rise FAR faster than changes in absolute temperature.

We understand from comments you have added that your source is a Propane or LPG tank - such as these.

From here and here

enter image description here

A plastic cigarette lighter MAY use all Butane or even "longer chain" hydrocarbons and will be designed to work at low pressures. Also, because they are only used briefly they do not need to take account of the large heat energy required to vaporise a liquified gas continuously. Without some means of providing thermal input the temperature of the vaporiser will drop until the liquid will no longer vaporise.

At some intermediate temperature the liquid may only partially vaporise and the output may contain a mixture of gas plus liquid droplets. As the liquid droplets enter the air they will absorb ambient heat energy and expand and may change the air:gas mixture ratio and make the flame unstable. If this happens you probably need an improved way of adding heat energy to the vapouriser.

If I was doing this I would TRY heating the gas feed as near the outlet as possible, bearing in mind the safety concern mentioned below. One method for testing would be to use a towel soaked in hot water, and/or a water bath containing hot water.

If the vaporiser you have tried works with the liquified gas that it is intended for and not with your gas then your gas may be different in some manner. The most likely difference is probably the Propane / Butane ratio. You may have 100% Propane, or 100% Butane, of some mix.

If cylinders used with eg barbecues are user with a Propane / Butane mix and are regularly refilled before being empty, there is a tendency for Propane to be released preferentially and for Butane to form an increasing fraction of the bas output. The 'cure' for such Butane concentration is to fully drain tanks occasionally.

WARNING: Note that 'playing with' a gas generator that you do not understand well is potentially dangerous and possibly even life threatening. People have died from unexpected release and subsequent ignition of quite small quantities of butane. (A friend of a friend of mine died from gas release from a small disposable butane gas cylinder that he thought was empty.)

Propane has the potential to be even more dangerous due to the higher potential pressures. Propane has a MUCH higher vapor pressure than Butane.
At room temperatures Propane pressure is about 500% of that for Butane.

At temperatures you may experience on a really hot day Propane pressures WILL be more than 10 x Butane pressure at room temperatures.

You say your gas is at 4 or 5 Bar pressure. If you put it in another container it MUST still be at the same pressure. If you put it somewhere hotter pressure could double. If you make a big "lighter" it will be even weaker than a small lighter BUT pressures will be much higher.

:-(

Propane / Butane & mixtures - pressure versus temperature.

enter image description here

| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.