Propane, Water and Rust

[Bluechip]

Hi Troops

There has to be a chemist on this board ..
Last evening I got into what turned out to be a fairly heated discusion on the amount of water produced by burning propane, in a torch, for instance.
Years ago, I seem to remember, probably in the letters page of 'Model Engineer' a write up on the subject.
So ... If I burn, say, 1kg of propane, how many kg of water do I get. ??
I seem to remember it was quite a lot, but maybe my memory is not what it was. If it ever was ???
This stems from a friend who was complaining about rust on his machine tools, so I suggested using the torch outside. But I don't know how to get the answer. I seem to remember converting to mols etc., which is way outside my remit :

Dave

 

[cfellows]

Here's one answer...

http://poultryfurnace.com/uploads/Harmful_Effects_From_Using_Brooders.pdf

Other nasty side effects as well, at least if you're raising chickens!

Chuck

 

[Philjoe5]

1 kg of propane is 23 mol of propane and that will produce 91 mol of water under ideal conditions which is 1.64 kg of water, more than 1.5 liters. You are correct in thinking that burning a hydrocarbon will produce a significant amount of water.

Cheers,
Phil

 

[Lew Hartswick]

Well! C3 H8 + 5-O2 = 3-CO2 + 4-H2O (digits following the letter are subscripts)
Thats for each molecule of Propane.

By the time I got this far I see Philjoe5 already has it to liters. :-(
...lew...

 

[Bernd]

Doesn't it also produce sulfuric acid? I believe natural gas does.

Bernd

 

[Philjoe5]

Any hydrocarbon containing impurities of sulfur will produce sulfur dioxide (again, the ideal) and that eventually comes back to us in the form of acid rain as one of the sulfur acids, of which sulfuric acid is one.

Lew, you would have been welcome in my chem class. That's a nice balanced chemical reaction you've got there :bow:

Cheers,
Phil

 

[rake60]

My youngest boy is the chemist in the family.
He will be receiving his BS at a ceremony in two days from now.
Then he is off to George Washington University in D.C.
to begin work on his Doctorate.
He will be here for a celebratory dinner Sunday evening and I
will pose this question to him. If the distant stars of PhD are not
too blinding, we may get an answer! LOL

Rick

 

[bentprop]

I used to have an LPG cabinet heater,which I sold to a fellow to use in hie workshop.I told him to watch the condensation,because I had heard stories of tools rusting when the area was LPG heated.After 2 years he has had no rusting or other problems,so I'm guessing it has a lot to do with lack of ventilation.
Hans.

 

[AlfrowD]

This is Rick's son Andrew

Assuming complete combustion and no impurities the combustion of 1 kg of propane would evolve 1.63 kg of water.

Cheers

 

[Bluechip]

Hi folks

Many thanks for the replies. I remembered it was more the the weight of propane, but not the rest of it. My friend remarked that any water would be vapour and would dissipate (?).
I suggested the word he wanted was 'condensate', and we knew where that was happening . ;D
He occasionally does pre-heating prior to electric welding on cast iron, ancient m/cycle cylinders, heads etc. so there is a fair bit of gas used.
It may be the sulfur comes from the artificial stinks put into the propane, I remember some fuel gasses don't have much smell in the pure state. I cleaned my torch nozzles some weeks ago, there was a sticky residue in some.
Chuck may be onto something with the chickens, he has some, and they are red. Maybe they are rusty too ;D

Thanks again, I will tell him he's wrong, and I'm right. But then I knew that anyway ;D ;D

Best wishes to Andrew on his PhD .. I'm well on my way to mine, in Mental Confusion & Amnesia ..

Dave