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30% Propane, 70% Butane Mix, Any good?
Posted: Sun Jul 15, 2007 12:14 pm
by athoul
Taymar
A woman i do gardening for has a can of this in her shed for a small flamethrower thing that is meant to burn small path weeds.
Its mix is
30% propane
70% butane
Will this be any good to use as fuel?
Posted: Sun Jul 15, 2007 12:20 pm
by noname
Hell yes it will! It'll be hard to get right, but once you get the fueling down, you'll have the best spray and pray fuel there is!
Posted: Sun Jul 15, 2007 12:21 pm
by athoul
Hard to get right?
Do you mean the right amount of spray?
Posted: Sun Jul 15, 2007 12:23 pm
by th3p0p0
yes iv tride it and it and it works very good but hard to get the right amont.
Posted: Mon Jul 16, 2007 12:02 pm
by Binder17
GEt the chemical equation for the combustion of propane and butane with oxygen. Make sure there are no other chemicals in the can. Stoichiometry may be difficult to use in figuring this out so maybe just experiment.
Posted: Tue Jul 17, 2007 3:48 pm
by jimmy101
If the can really only contains propane and butane then the stoichiometry is pretty simple.
Method 1: Just take the weighted average of the fuel ratios for the two fuels;
30% butane which is used at 3.12% (squirt-and-screw method)
70% propane which is used at 4.02% (squirt-and-screw method)
Volume percent of fuel is;
(0.30)(3.12%)+(0.70)(4.02%) = 3.75%
(this is only approximately but close enough for most purposes)
Method 2: The balanced chemical equation is;
3C<sub>4</sub>H<sub>10</sub> + 7C<sub>3</sub>H<sub>8</sub> + (109/2)O<sub>2</sub> = 33CO<sub>2</sub> + 43H<sub>2</sub>O
or
6C<sub>4</sub>H<sub>10</sub> + 14C<sub>3</sub>H<sub>8</sub> + 109O<sub>2</sub> = 66CO<sub>2</sub> + 86H<sub>2</sub>O
For every 6+14=20 volumes of fuel we need 109 volumes of oxygen.
Since air is only 21% oxygen;
(20/109)*(0.21) = 3.85% fuel in air.