power of a torch

[laserglass]

recently, i have started a new project and have been doing some research in support of it. i am making a natural gas powered micro-gloryhole which uses oxygen from a 5 l/m concentrator. so i wanted to calculate the heating power of the torch. natural gas which is mainly methane (CH4) requires 2 moles of oxygen for every mole of methane for complete combustion (only CO2 and H2O as byproducts). since my concentrator can only produce 5 l/m of oxygen (i am ignoring that it is not 100% O2 for this calculation), then 2.5 l/m of methane is required for complete combustion. after some calculations and using the fact that methane has ~1100 BTU/ft^3 of energy, i calculate that the maximum heating power that and torch using a 5 l/m concentrator can generate is around 5775 BTU/hour or ~1.69 KWatts of power. it does not matter what torch you use.

i also did the same calculation for propane. for propane, 5 moles of oxygen is required for complete combustion of 1 mole of propane, so only 1 l/m of propane is required. since propane has ~2516 BTU/ft^3, the same calculations showed that burning propane only yielded ~5284 BTU/hour or 1.55 KWatts of power. again it does not matter what torch you use. the flame temperature of propane will be higher than with natural gas, but the flame of a natural gas powered torch will be bigger, so both have about the same amount of heating power. i though that some of you might find this interesting, so i decided to post this result here.

[FlameFilly]

Wow I always thought propane had much more btu's available than NG. It seems they are closer than I thought. That is interesting to me!

When we were building our hotglass studio my Hubby crunched all the numbers and I think we were burning 110,000 btu's per hour (its been awhile so not so sure about that figure) w/propane and I think that was roughly 1 gallon per hour.

I 've been thinking about building a mini glory hole but with forced air and propane and a home built burner head.

Thanks for the info!

[laserglass]

propane does have more than double the BTU/ft^3 of natural gas. the calculations i made here were based upon the limitation of how much oxygen can be supplied by a small concentrator. with air instead of oxygen, you are not limited as much so getting BTU/hour in the 100,000 to 500,000 BTU/hour are possible. my main glory hole has a 100,000 BTU/hour burner and even my outdoor melter has a 100,000 BTU/hour burner. but with air, you will have more heating power, a bigger flame, but the flame temperature will be lower than with oxygen because you are blowing 4/5ths nitrogen into the flame which does not help with the burning of the gas, but it does cool down the flame a lot.

[FlameFilly]

Oh o.k. my brain does still work..lol...
Since I'm coming from a hotglass background I'm more used to blowers and burners rather than torches w/oxygen technology.

I'd like to do soft glass sculpture i.e.ornaments goblets, but with a mini glory hole rather than a big honkin' torch (I'd use the torch mostly for surface decoration)...Just in the dream stages now but fairly easy to implement if I find the space and motivation


Thanks for the clarification.

[jokersdesign]

I'm still not awake this morning, but does that mean with NG you would need a ratio of 2/1 parts oxygen to NG to get complete combustion and with propane you need a ratio of 5/1 parts oxygen to propane to get complete combustion?

[FlameFilly]

It looks like NG need less oxygen to fully combust that propane does....so with the addition of pure oxygen NG becomes in some ways is more effecient than propane? Wait no it takes more O2 to combust less Propane fully, and less O2 to combust more NG fully....

Hmmm...I need to go back to watching Barney w/my son. They're learning how to cross the street today..lol sorry I have mommy brain right now...lol...

[laserglass]

Originally Posted by jokersdesign

I'm still not awake this morning, but does that mean with NG you would need a ratio of 2/1 parts oxygen to NG to get complete combustion and with propane you need a ratio of 5/1 parts oxygen to propane to get complete combustion?

yes, but that is the fuel/oxygen ratio. somtimes people quote fuel/air ratio and then you need to factor the relative abundance of oxygen in air. here are some links for further clarification.

http://en.wikipedia.org/wiki/Methane

http://en.wikipedia.org/wiki/Propane

http://en.wikipedia.org/wiki/Combustion

[laserglass]

Originally Posted by FlameFilly

It looks like NG need less oxygen to fully combust that propane does....so with the addition of pure oxygen NG becomes in some ways is more effecient than propane? Wait no it takes more O2 to combust less Propane fully, and less O2 to combust more NG fully....

Hmmm...I need to go back to watching Barney w/my son. They're learning how to cross the street today..lol sorry I have mommy brain right now...lol...

NG needs less oxygen to fully combust, but you need ~2X more NG to get the same heating power when compared to propane. i did not know barney was still on!!!!!

[bhhco]

<delete> Too verbose ... I mean ME... I was too verbose so I deleted my comment.

Me

[laserglass]

i did not start this thread to support either propane or natural gas as to their applicability to lampworking, only to provide information to anyone who would be interested. bill is correct that there is no such thing as 100% efficiency in combustion, but it is close enough to 100% to be lost in the noise. in the past people have told me that this torch is more efficient than that one, but that is, for the most part, kind of like a religious issue. people believe what they want to believe, but the truth is, gas burns. it will find the oxygen it needs even if you do not supply enough for it. there really isn't any major difference in the heat output of any torch which is limited by the maximum flow rate of oxygen from a small concentrator. with tanked oxygen, or more conenctrators, you are not as limited, and then one torch might be better than another in its ability to handle the higher flow rates and higher heat loads.

as for natural gas vs propane, i think that natural gas is the clear winner every time, if it is availiable, just because of safety. both propane and natural gas can cause an explosion. but small leaks of natural gas will diffuse while small leaks of propane will pool in the basement where they can build up.

the thing i was suprised about is that the heat output that can be obtained from a 5 l/m oxygen concentrator, no matter what fuel is use, is so low. 5775 BTU/hour is not very much. i may have to redesign my micro-gloryhole to use a gas-air burner to get more heat.

[jokersdesign]

Ok, got another question. lets say we are using a redmax torch. if we are using either NG or propane, how do we know if we are getting the correct 2/1 or 5/1 ration for complete combustion?

[bhhco]

Originally Posted by jokersdesign

Ok, got another question. lets say we are using a redmax torch. if we are using either NG or propane, how do we know if we are getting the correct 2/1 or 5/1 ration for complete combustion?

'complete combustion' is another way of saying 'neutral flame'...

Got Neutral?...got Complete!

Me

[jokersdesign]

Originally Posted by bhhco

'complete combustion' is another way of saying 'neutral flame'...

Got Neutral?...got Complete!

Me

Gotcha, thanks.

This is one of the best threads in a long time.

so you control the ration on any torch by adjust the needle valves on the torch to the correct ratio to get a nuetral flame.

Then this brings up a different question for me. Why is it common pratice to set your regulators at 5 psi for gas and 20 psi oxygen?

what not just 10 psi to 10 psi and adjust the flow with the valves on the torch?

[ziggys]

Mark wrote: QUOTE] in the past people have told me that this torch is more efficient than that one, but that is, for the most part, kind of like a religious issue. [/quote]

Hi Mark, Hey! that makes sense! I could never figure out why one would be better than another, not that I understand the chemistry/math behind it.

there really isn't any major difference in the heat output of any torch which is limited by the maximum flow rate of oxygen from a small concentrator.

Can you tell by your calculations if any of this means a Mini CC, (or probably a lot of other torches for that matter) will run well with 5/lm???
I am getting conflicting information on this. But I don't know what the Mini CC needs to,....um.....can't think of the technical term here, sigh, to "power" it.
Padre/Me wrote something about how to figure it out once you knew the "power" needed for the particular torch. Is that with using the air/fuel ratio instead of oxygen/fuel? Not sure if my question is related to what you are writing but just in case (I swear the answer to this has been keeping me up at night !)

I am planning on buying the Mini CC but can't figure out what the LPM needs to be. I want to run the torch at what it is supposed to run best at. Not try and make it burn hotter.

as for natural gas vs propane, i think that natural gas is the clear winner every time, if it is availiable, just because of safety. both propane and natural gas can cause an explosion. but small leaks of natural gas will diffuse while small leaks of propane will pool in the basement where they can build up.

What if you don't have a basement? kidding!!!
I quit using a HH on bulk fuel because of the PSI being 200 or there-abouts. And I had my propane outside. But I did not have the hose shielded.
I just like the idea of a torch that runs at 4 PsI better.

the thing i was suprised about is that the heat output that can be obtained from a 5 l/m oxygen concentrator, no matter what fuel is use, is so low. 5775 BTU/hour is not very much.

Do you remember what the BTU/hour is for the Hot Head running on propane or Mapp? I'm curious what the difference would be compared to the Mini CC on propane with 5 l/m.
Thanks!
Angela
(This is way over my head but I am grasping a tiny edge of it.)

[laserglass]

i developed a model for my micro-gloryhole using heat transfer theory. the model seems to predict the results i am experimentally seeing in my studio. the bottom line is that i can never power my micro-glory hole with the oxygen concentrated by a 5 l/min concentrator. i guess i should have done more experiments before i bought the thing. anyway, i now plan to make a gas/air burner and i feel i can get a lot more power. the funny thing is that a hothead torch has way more heat output than a mini cc or minor using a 5 l/min concentrator. my calculations show that a minor or mini cc or what ever torch you want to name, cannot have more than 5800 BTU/hour output, while a hothead burning MAPP can have 10,000 BTU/hour. now before everyone tells me i am full of it, i need to point out the difference between heat and temperature, THEY ARE NOT THE SAME THING. a minor or mini cc torch running on gas or propane, and a 5 l/min concentrator, will have a much higher flame temperature than a hothead, but overall, the hothead had more heat output because, while the flame is cooler, it is a much bigger flame. so i plan to try an experiment and see how well my micro-gloryhole works using a hothead. that is not to say that this is a good solution, but it is easy to set up and get data from. my plan is to build a gas/air burner in the 30,000 to 50,000 BTU/hour range. while my micro-glory hole can get to 2000°F to melt glass, it will take too long, and the temperature inside the micro-gloryhole will crash quickly when i open the door to take a gather or to reheat a piece. 5800 BTU/hour is just too small of heat output to be useful for this application. i am attatching a plot i made of my model showing how the micro-gloryhole will work as the internal mass of the system increases. the top curve is for the crucible empty, and the bottom curve is for the crucible full of glass. most of my heat loss is out the door, but there is not much more i can do to improve that. when you melt with a burner, you have to expect to loose heat out the door because the hot gas has to be vented.

as for pressure, people do what they want to. i run my major/minor torch, my national 3a torch, and my 100,000 BTU/hour burner for my 12 inch glory hole off of 0.25 PSIA. so why do people set their pressures at 5 PSIA? just because, it is not a requirement. now there are lots of torches that need to operate at higher pressures because the torches were designed for that. i would not buy one of those torches because it forces you to have to get a g-tech pressure booster to operate off of standard natural gas. why have to buy an expensive booster just so that you can use a poorly designed torch. better to use a torch that can operate off of 0.25 PSIA natural gas without a booster.

[ziggys]

Mark,
Sorry so long since I viewed this thread but I had a hard time finding it again since I didn't know your user name.
The HH BTU output with Mapp is surprising! Maybe I missed it completely before, but if the Hot Head was using propane and not Mapp, would that make a difference in heat output? Maybe you don't need to know for what you are doing.
Please do keep us informed of your experiment with the Hot Head and micro gloryhole.
As far as only getting 5775/BTU per hour in the soft glass world, I am thinking that is more than enough. Other countries think we are crazy wanting so much heat for out torches.
Though that does not apply to anything you are trying to do.
Oh, and do you want to sell your concentrator by any chance?
Which one is it either way? I am looking to purchase one and am guessing you would only buy the best.
Angela