Natural Gas Question

When you introduce gas into air the concentration of gas is low (or not enough for implosion). If you introduce air into gas, concentration of gas is high and implosion is probably.

Hello lynlynch!

You excuse me for my English...

I don't mean a spontaneous combustion. I was thinking that ignition source is probably exist. Of course, there is a lower explosive limit, but while this limit is not reached, explosion is not being started.
I think, it is recomended reason why gas must been introduce into air. It my opinion only, probably it's wrong.

Thank you! Happy Winter Solstice, too! :-).

Hello Evgeny,

Excuse my rudeness for not giving you a welcome to CR4 greeting last time.

Your English is fine. At first, I agreed with your reasoning, but then I had doubts.

How about this: In introducing gas into air there would be less gas to burn in case of accidental ignition since you would have 100% air to begin with.

If introducing air into gas you would have 100% of gas available to burn during an accidental ignition.

OK, now I think I understand.

You are right, I believe. Stick around.

I think, our answer is true. Nevertheless, I don't know of practice usage for this answer - low limit of concentration will be reached, and if combustion is probably exist, it is danger. What reason, that must man introduce gas in air in dangerous concentration? When I've practiced explosion of gas, we have created air+gas in needed concentration and ignited it, but it was student laboratory work for researching aims.

lynlynch, what's point of your name?
And, what is it "another GA"?

"lynlynch, what's point of your name?" Since I'm not very creative, I just used a combination of letters from my name.
"And, what is it "another GA"?" GA refers to Good Answer. This can be given by anyone who participates and it can be for almost any reason. USUALLY GA's are given if the answer is technically correct, if the answer leads to resolution of the problem at hand, or for almost any reason that the person giving the GA wishes. Read the FAQ's for a better explaination.

Many participants place far too much emphasis on getting GA's and are sometimes offended if they think they should have been given a GA but were not.

Happy Holidays.

Gentlemen, I am not sure I fully understand the question. First, isn't an implosion a "negative" pressure catastrophic event? Normally when gas and air combust, the thermal reaction creates heat. Depending on the speed of the reaction, I would expect an explosion, not an implosion.

Second, the reacion would only occur between the lower explosive and upper explosive limits. (LEL and UEL). I am not certain that one is worse than the other, it would depend on the amount of fuel and oxygen that are available to react.

I think the OP (original poster) needs to clarify the question.

By the way, Seasons Greetings! In my case it will be Christmas with church and gift opening on the 24th! Skol!

I believe the discussion (air and gas?) is referring to the ignition of a combustible gas...e.g 2H2 (gas) + O2 (air) -> 2H20 (water). The exothermic composition reaction would cause a rapid reduction in volume thus an implosion due to the gases changing to a liquid. 48L of H2(g) + 24L of O2(g) produces 36g (36cc) of H20(l). Some of the H2O will vaporize, but still a huge reduction in volume will occur. Using the analogy above, the original statement is comparing adding oxygen (air) to hydrogen or hydrogen to oxygen (air). If H2 is released into the air, it will burn slowly. If air is quickly added to H2 (with the activation energy), an explosion then implosion will occur. The rate of both reactions depend on the concentrations of both gases. However, large amounts of oxygen (air) is available in our surroundings.

The answers here are mostly correct, however the important reason for the procedure , like the acid analogy, is one of safety. As also pointed by LynLynch.

This is ruining my Bah Humbug! Christmas. I have to give you another GA.

Sorry. Only 4 more days to go.

Cheers!

In my country the Christmas will in January 7, only. And, in our country Christmas is not main holiday. Main holiday is first day of new Year.
Happy Holiday and Mary Christmas for you!

I celebrate both Christmas Days. And our New Year and Chinese New Year. What good is life without holidays?

How 'bout Evgheny? I think he deserved the GA, not lynch!

Titi-the-rabbit.

Are you incapable of voting?

Do you mean me?

I have voted, but without any voting and rating I think you are good collaborator.

No. Note the numbers in the upper right hand corner. My #19 was directed toward the Guest in post #13.

Explosive limits vary with pressure at constant temperature, and with temperature at constant pressure.

Seasons Greetings to our new Russian friend. Welcome, we are always interested in new members. We discuss just about anything here, feel free to ask anything. From my avatar you can see I am interested in airships. We have members who carve archery bows, and many good engineers and researchers. If we don't have the answer right away, we will find it eventually. Enjoy the site. Mike k.

If the air is introduced from a point source and expands as a sphere through the gas would not the resultant shock wave from ignation first cause an implosion. The path of the compustions intial shock wave would be towards the airs point source and then bounce outward.

not unlike triggering a nuclear.... ahhh never mind

No.

I think the OP's use of implosion is a result of English not being their first language.

Implosions do not result from combustion of gasses inside an object. Implosions are caused by external pressure acting on an object such as a submarine being crushed by water.

Have you not experienced the effects of cavitation?

Implosions can also be caused by a decrease in internal pressure.

It's NEVER allowed to introduce gas into air, NEITHER introduce air into gas. For Pipelines, tanks and vessels one has to PURGE the equipment first (With Nitrogen) and then introduce the gas or air.

This prevents an explosive gas/air mixture occuring

Hope this helps

Stewie

Oh, yes... I think we need the topic-starter to solve the problem :-)

Why do you think that is never allowed mix air and gas (or gas and air). For nature gas is probably - I don't know and I doubt. And how about propane-air mix, which is produced and known as sinthetic nature gas?

On the other hand, if we will introduce gas into air, we can have concentration upper the high limit and we can transport this mix to any point of Earth while limit is not be reached. And this mix is have not explosion opportunity. And we can add air and combust our mix when we want it. Do you think so or not?

All transportation of fuels (natural gas, propane, oil, etc) is done with out any air present. There is to much chance of things going boom otherwise.

Propane and natural gas are similar. Propane is more dense and has a higher BTU content. If I am doing an natural gas application and it is not available I convert the equipment over to propane. The propane comes liquefied. I draw the vapor of the top of the storage tank.

Synthetic gas is from "coking" coal. This was common during the late eighteen hundreds and mid nineteen hundreds mainly in Europe and England.

Transporting a mixture of gas and air is a wast of money and dangerous. Air is always at the final user and that is were the air is mixed at combustion. Different equipment and applications require different mixes of air and gas. Even at the upper end of concentration, all you need is for a small amount to come out of mix and a bit of static electricity and your transportation system will vanish.

Synthetic gas may not be common many places, but here in Pittsburgh we have coke oven gas for industrial use. Of course, it helps that we have coke ovens.

China uses a fair amount of the stuff also, although I believe theirs is pretty low BTU.

The steel mills in Hamilton do the same. The Chinese are using a lower grade of coal, some where around the lignite range. Thats if they can get it out of the ground with out the miners dying. Real coking coal should be anthracite.

Oh, tongue sharper than a viper's tooth! You have wounded me with your slight of the Pittsburgh Seam. Just for that, we're gonna change Mario Lemieux's name to Billy DeNardo and claim he's from Uniontown.

I built a couple of gas analyzers for one Chinese coke industry maybe 8 years back. They provided me some sample analyses of what they were producing. Cripes! You could have used the stuff for fire suppressant.

HI All!

I mean propane-air mix. I am not a professional in HVAC, but I read about this with Google:

http://www.algas-sdi.com/propane-air.html

Can you comment this article?

The lower end of combustion for natural gas is 4% mixed with air and the upper end is 14%. That is a complete homogeneous mix or at the flame front. That said, I have seen where a major gas leak had managed to make its way to a building over a kilometer away, underground with explosive results.

As for mixing air with gas or gas with air, it is easier to regulate the gas flow. Some manufacturers need to supply a pre-mixed gas/ air supply to work stations. This means a very flammable mix in the supply line. To limit risk, back flash arrestors are installed in the lines in multiple locations.

I am curious as to why a premixed air/gas supply would need to be delivered in long pipe lines. It is not a safe practice even with flash backs there is a risk of it getting by same and causing explosions?

Surly it is possible to arrange the mixing at the point of delivery?

Notice that the OP has vanished?

Aye, they're a weak lot they are. Don't have the guts to slosh it out with the rest of us here in the trenches. But that's ok. We have new members showing up, willing to take up the banner and charge forward into infamy. AArgh. Onward!

yes lynlynch ... and he walked away without voting you a GA ;)

OK.

The OP used the troll term *implosion*... To me this signifies that the topic of the question had something to do with HHO or Brown's Gas which as we all know is a complete waste of bandwidth.

If the question was about anything reasonable, like controlled atmospheres, or regulating the volumetric BTU value of fuel, or purging a vessel/pipe, he'd have dropped one of those terms into the discussion.

Happy Solstice everyone -- The days are officially getting longer again ^_^

Sorry. I have an unavoidable Northern hemisphere bias... ;^)

Icarus (#18) makes a good point. I have observed several sites where a premix of gas/air is made with very specific calorific content controls to allow a specific temperature flame at the end use- and with over 150 end-uses at one time in the same plant.

Yes, there are inline flame arresters, but the systems have worked for many years with NO safety issues.

Gas is like everything else that is useful and plentiful- you need to know what you are doing and always keep one step ahead of the process to stay safe. And- if you forget either of those conditions, someone WILL get hurt.

I appreciate that gas & air mixtures can be perfectly safe so long as they are not in the ratio where they will support combustion, but mixtures which will support combustion should not be enclosed in any large containers or large volume pipes as the obvious result of a flash back {Murphy's Law] is a large explosion. It is not unknown for flash back valves to be faulty or have there integrity compromised by actually doing the job for which they were designed.

You might get away with it for a long time but sooner or later will come to grief. I personally would not recommend or design such a system.

My experience with mixed gases was for low volume, small diameter pipes employing flash back arrestors and pressure reliefs. The mixture had to be constant for quality control. A strict maintenance program ensured that safety was maintained.

Please note: Murphy was an optimist.

The following does occur, but I am making an educated guess on the reasoning...but it is related to three things coming together in the appropriate quantity: fuel, oxygen, and activation energy. Assume a container is filled with H2 and the cap is remove allowing the H2 (lower density) to slowly exit the container. If the fuel leaving is ignited, it will slowly burn. However, when the H2 leaves the container, some air (oxygen) will enter the container with the captured H2 but no activation energy is present because the denser air sinks to the bottom of the container prior to diffusing. Eventually, a large amount of the mixture of the two gases connects with the activation energy at the opening and an explosion then implosion will occur. (Exothermic reaction causes the explosion and reduction in volume ~ gases to liquid ~ causes the implosion). Reverse the gases, and the process is different.

"(Exothermic reaction causes the explosion and reduction in volume ~ gases to liquid ~ causes the implosion)."

Sorry, but I cannot agree with your statements. You have redefined the word implosion to mean creation of a vacuum inside some imaginary vessel.

What is there to implode?

vacuum: empty of matter implosion: a collapse inward. My statements never referred to a vacuum, but did imply a rapid reduction in internal pressure Using your example of submarine imploding...when the external pressure is significantly greater than the internal pressure, an implosion may occur. Likewise, when gases ignite in a closed container (or when the opening is not large enough to balance the rapid change in the two pressures), an implosion of the container may occur due to gases producing a liquid (a rapid reduction in volume e.g. 48L H2 (g) + 24L O2 (g) -> 36mL H20 (l)) thus a rapid decrease in internal pressure. I really don't like mean to get into a negative communication but do enjoy open discussions which I assume (hope) that was your intent. P.S. The hydrogen/air implosion described in my example was in several lab manuals when I taught in an engineering department. Also, texts refer to the classic implosions caused by condensation of water vapor (gas to liquid) in a closed container. Thanks for your comment though.

We have never established, and probably never will, that there is any container involved.

I am assuming, perhaps incorrectly, that the OP intended to say explosion which would be the result of the ignition of a flammable mixture of gas in the atmosphere.

It's anybody's guess and the OP is likely gone forever.

Cheers.

The OP stated air into gas (CH4) and implosion...implying the methane was segregated or contained which is typical in industry.

Of course, after reaction gas+air the products of reaction have small volume compared with gas+air before reaction, and if volume is constant the pressure will be reduced.

But if we will think so, is there is no any differences if we will introduce gas into air or introduce air into gas.

On the other hand if we assume OP mean "explosion". In this case opportunity of explosion depend from concentration of gas and there is differences if we will introduce gas into air or introduce air into gas.

Offtopic. I think OP has introduced air into gas (or gas into air) and vanished. I always tell to him - mixing gas and air is dangerous. :-).

Too bad the guest did not heed your warning! ; )

Evgeny, welcome to the site, and hope to see more of your posts.

Evgeny,

"I think OP has introduced air into gas (or gas into air) and vanished"

I think you're right! Maybe he had an implosion!

Cheers.

Just how cold would a stream of air have to be to bring about a change in phase of natural gas to a liquid.

The orginal question did refer to Natural Gas right so the gas was not say saturated steam. A change of phase to liquid would explain the implosion but not by adding air.

... and he didn't give you the G.A. ... so sad ...