A natural gas burner for brewing.

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A natural gas burner for brewing.

Postby Charlie » Tue Jun 29, 2010 7:15 pm

One of my pet peeves is running out of propane. Propane is a pain in other ways, because I have to drive to a part of town I usually don't go to in order to buy it, and then haul the smelly (and dangerous) cylinders back to the house. Propane is also, from my perspective, expensive. I have natural gas in various locations at the house, and have been wishing I could use that instead.

BB provided the burner which he got out of an old hot water heater somebody put on the curb. I modified it to use a pilot/burner valve from an old central heat unit (don't you dare say pack rat!) and, Viola!

Image

I installed a "T" fitting and a gas cutoff valve in the hot water heater closet on my carport. Bearing Service (North Market) provided 1/2" FPT quick-connects and 6 ft of 1/2" MPT flexible gas line.

My main concern is that the natural gas burner be at least as powerful as the 10" propane banjo burner I've been using, so last Sunday I mounted the burner and did some testing.

Prior to modifying the propane burner stand I measured 2.0 gal of tap water, put it in a 6 gal Vollrath stainless steel pot, took a temp reading and slapped on the lid. Then I fired up the propane banjo burner at my usual boil setting and let the water heat for 10.0 minutes. At T + 10 I turned off the gas, removed the lid, and took a second temp reading.

It took about an hour to dismount the propane banjo, fabricate the supports, and mount the NG burner. Then I repeated the above experiment. Here's the numbers:

Image

If you can decode the spreadsheet you will see that the NG burner is roughly 17% more powerful than the 10" banjo. I think I've got a winner!

Image

Charlie
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Postby thebuddrik » Wed Jun 30, 2010 7:00 am

That sounds like a plan. Good job, I know a lot of people will be trying that now that they saw your experiment. I would to see the same thing done but instead of time being the variable, $.
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Postby Charlie » Wed Jun 30, 2010 3:49 pm

budrockdiesel wrote:I would to see the same thing done but instead of time being the variable, $.

My cost for the conversion was about $20.00 on the house side for the "tee", the valve, and assorted fittings. Add another $50.00 on the burner side for the 1/2" quick connects, hose, end fittings, and the shop labor to attach them.

The cost of propane vs natural gas is another thing entirely. Propane is sold by the gallon, natural gas is sold by the hundred cubic feet (ccf), and the energy numbers are in Megajoules per kilogram. To find common ground it was necessary to convert both to cost per kg. Here's what I came up with:

Image

If I dropped no decimal points then a kilogram of propane costs $1.37 and a kilogram of natural gas costs $0.43. The figure in column "C", Mj/kg is the energy in megajoules per kilogram that each produces when burned, and natural gas is slightly superior giving 49 Mj/kg vs 46.5 for propane.

Don't forget the time and cost of car fuel (oil, insurance, wear and tear) to get the propane to your house, and the cost of cylinder maintenance.

If you can work with a location near a natural gas outlet then NG looks like a clear winner.

One of these days somebody's going to ask me an easy one! :D

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Postby yeastmeister » Wed Jun 30, 2010 8:09 pm

Ok, I'm working from a phone, so I can't really see the charts well, but if I'm reading it correctly, are you indicating that natural gas is more efficient than propane? Or just cheaper by volume used?

Even though propane is sold by the gallon, and natural gas is sold by the cubic foot, both are actually used in their vapor state.

Rough estimates from the web indicate:
1 cubic foot of propane contains 2,516 BTU
and
1 cubic foot of natural gas contains 1,030 BTU

Propane provides more energy per unit volume than does natural gas.

But granted, natural gas is cheaper than propane. I'd go with it if I didn't move my brew stand around all the time.
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Postby thebuddrik » Thu Jul 01, 2010 6:49 am

I have always understood it the way el presidente put it.
I do agree that it is a pain to go fill bottles. That is why when they install my 500 gallon propane tank for my house next month I will have them run a high pressure line to my back patio for my brewery, crawfish burner, and grill.
I would have gone with natural gas but atmos wanted $11,000 to bring it to my house.
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Postby Charlie » Thu Jul 01, 2010 9:05 am

yeastmeister wrote:...are you indicating that natural gas is more efficient than propane? Or just cheaper by volume used?

Even though propane is sold by the gallon, and natural gas is sold by the cubic foot, both are actually used in their vapor state.

Rough estimates from the web indicate:
1 cubic foot of propane contains 2,516 BTU
and
1 cubic foot of natural gas contains 1,030 BTU

I got my energy figures from Wikipedia. Both are per kilogram, so are not volume dependent.

Propane: 46.44 megajoules per kilogram[9] (91,690 BTU per gallon).
NG: 49 megajoules per kilogram (0.8 kg/m^3)

The object was to figure some sort of cost estimate for one vs the other. This isn't my field, so errors may have crept in, but the result looks about right.

*The $3.03/gal figure for propane is today's cost to fill your 20lb cylinder at U-Haul. Residential propane may be taxed at a lower rate, and therefore less expensive.

* The $0.97/ccf figure for NG came from last month's gas bill. I used 10ccf but paid $22.00 for it because of all the charges they tack on. I don't know if doubling the consumption doubles the bill or if the tacked on charges are fixed, so additional research is indicated.

My feeling is that NG is cheaper in the long run, but not drastically so. I did the conversion mainly to avoid running out of gas in the middle of a brew, and because I'm a habitual tinkerer.

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Postby yeastmeister » Fri Jul 02, 2010 6:23 am

I think wikipedia has it wrong. Not arguing, I would definitely go natural gas, but I like getting facts straight for folks.

Everywhere I look indicates propane has more energy per unit than natural gas.

For instance, this (and many other sources) all sort of indicate the same thing....

[url]http://www.esmagazine.com/CDA/Archives/6bd52e20deba8010VgnVCM100000f932a8c0____[\url]

"Propane contains about 2,520 Btu/scf compared to natural gas with about 1,000 Btu/scf. Liquefied propane (at 60°) contains a little more than 92,000 Btu per gallon. Thus, 11 gallons of propane contains about 1 MMBtu (or 1 dekatherm) or about as much energy as 1 Mcf of natural gas. While natural gas is difficult to store at a consumer site, propane's energy density makes storage reasonably simple."

Of course, this guy is talking about storing the fuel locally, so if your hooked into the city, I guess it makes a lot of sense, but if your still storing the natural gas, then maybe you would be better off with a much smaller propane tank.....
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Postby aleguy » Fri Jul 02, 2010 10:00 am

Bahh! :x If you want cheap and easy, the a wood-burning Rims is the way to go. If you build it based in a rocket stove design from Approvecho, the fuel is free and abundant in virtually every American neighborhood.
Then of course there is the solar option, though that has some obvious limitations in this climate.
Come on people! Think outside the tank! :wink:
BTW the charts aren't showing up at all on my computer, I just get little icons to show where they go.
Anyway, Good job Charlie. Anything that promotes more options for home-brewers is a good thing IMHO.
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Postby david79thomas » Fri Jul 02, 2010 12:01 pm

I found this online:
http://forum.northernbrewer.com/viewtop ... =5&t=79812
it says how to convert the banjo burner to natural gas
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Postby Charlie » Fri Jul 02, 2010 7:37 pm

yeastmeister wrote:I think wikipedia has it wrong....

Everywhere I look indicates propane has more energy per unit than natural gas.

And I think you're right. Natural gas is primarily methane (CH4). Propane (C3H8) should logically contain more energy per molecule because it has more hydrogen atoms, and therefore more potential to combine with oxygen.

First person to spot the error in my spreadsheet gets a kewpie doll. Click reload if the images don't show because our server (networksolutions) is slow. I'll work on it from my end tomorrow, but it seems obvious that something isn't right in the cost analysis.

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Postby aleguy » Fri Jul 02, 2010 7:43 pm

I think the problem here is the embodied energy per unit weight versus per unit volume. One mole of propane is much heavier than one mole of methane. I suspect that the energy per unit of weight is greater for methane while the energy per unit of volume is greater for propane. I think the real question here is energy as a function of volume per unit of weight.
id est: how much energy per ccf/ccf per kg?
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Postby triple-oh_six » Fri Jul 02, 2010 9:42 pm

aleguy wrote:
BTW the charts aren't showing up at all on my computer, I just get little icons to show where they go.

Charlie wrote: Click reload if the images don't show because our server (networksolutions) is slow.

He failed to tell you that he is a hippie working on a pre cold war era Mac, I beleive that the problem may lie on his end :P

Looks good brotha, nice work, I think it's great that you took the time to spreadsheet this out. We as homebrewers can all learn from each other, and this is a great example of taking the initiative to document your findings and share with your fellow brewers.

Thanks Charlie
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Postby yeastmeister » Sat Jul 03, 2010 6:26 am

Charlie wrote:
yeastmeister wrote:I think wikipedia has it wrong....

Everywhere I look indicates propane has more energy per unit than natural gas.

And I think you're right. Natural gas is primarily methane (CH4). Propane (C3H8) should logically contain more energy per molecule because it has more hydrogen atoms, and therefore more potential to combine with oxygen.

First person to spot the error in my spreadsheet gets a kewpie doll. Click reload if the images don't show because our server (networksolutions) is slow. I'll work on it from my end tomorrow, but it seems obvious that something isn't right in the cost analysis.

Charlie

The error is that you used gallons to kg. Gallon is a unit of volume whereas kg is a unit of mass.

So, your cost per kg should have been 0.279 ish....

You may have also done something odd if you used a 20 lb propane tank to come up with a cost. Some folks say 5 gallons in a 20 lb tank, but I believe its closer to 4.1 gallons...
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Postby redtail28 » Sat Jul 03, 2010 9:56 am

I like beer and pizza and that gives me gas :roll:
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Postby aleguy » Sat Jul 03, 2010 7:14 pm

A 20# tank will have 20#s of propane only if filled by a reputable dealer. The exchange tanks may only have 12#s of propane in them when you get them. It's always better to have your tanks refilled than to exchange them. Of course BTUs per Kg of wood is highly variable, depending on species, % water content etc. But in the end, thin sticks and prunings are free for the taking, so who really cares? They make the perfect fuel for brewing.
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