[TheForge] allstate oxy-propane torch

[terry l. ridder]

hello;

the chemistry is set by the elements themselves there is little that
anyone can do to change that.

my question is not about whether propane vs. acetylene saving on fuel
cost. it does. propane is less expensive than acetylene.

my question is concerning oxygen consumption. the chemistry dictates
that for "prefect" combustion propane requires 2 times as much oxygen as
acetylene. there is no way around that.

for "prefect" combustion of propane the oyxgen to propane ratio is going
to be 5.0 to 1.0.

that has to be considered when making the switch from acetylene to
propane. as fuel gas costs decrease to oxygen cost increases. the
chemistry requires that.

for sake of completeness i have included gasoline in the fuel gases
since both the petrogas and opetrol oxy-gasoline torches have been
mentioned.

there is no good formula for gasoline. please refer to 

Ask A Scientist©
Chemistry Archive
Gasoline
http://www.newton.dep.anl.gov/askasci/chem99/chem99658.htm

again please refer to

Ask A Scientist©
Chemistry Archive
Gasoline Combustion
http://www.newton.dep.anl.gov/askasci/chem99/chem99583.htm

i will use the above isooctane in the below tables.

isooctane == C8H18 == gasoline for this post.

the chemistry of combustion for various fuel gases are given below.

methane   == CH4
acetylene == C2H2
ethylene  == C2H4
ethane    == C2H6
propylene == C3H6
propane   == C3H8
butylene  == C4H8
butane    == C4H10
gasoline  == C8H18
hydrogen  == H2
oxygen    == O2

          fuel        oxygen         carbon      water
          gas                        dioxide     vapor
methane   CH4(g)   + ( 2.0)O2(g) = (1)CO2(g) + (2)H20(g)
acetylene C2H2(g)  + ( 2.5)O2(g) = (2)C02(g) + (1)H20(g)
ethylene  C2H4(g)  + ( 3.0)O2(g) = (2)CO2(g) + (2)H20(g)
ethane    C2H6(g)  + ( 3.5)O2(g) = (2)CO2(g) + (3)H20(g)
propylene C3H6(g)  + ( 4.5)O2(g) = (3)CO2(g) + (3)H20(g)
propane   C3H8(g)  + ( 5.0)O2(g) = (3)CO2(g) + (4)H20(g)
butylene  C4H8(g)  + ( 6.0)O2(g) = (4)CO2(g) + (4)H20(g)
butane    C4H10(g) + ( 6.5)O2(g) = (4)CO2(g) + (5)H20(g)
gasoline  C8H18(g) + (12.5)O2(g) = (8)CO2(g) + (9)H20(g)
hydrogen  H2(g)    + ( 0.5)O2(g) =             (1)H2O(g)

          oxygen to fuel gas ratios
methane        2.0:1
acetylene      2.5:1
ethylene       3.0:1
ethane         3.5:1
propylene      4.5:1
propane        5.0:1
butylene       6.0:1
butane         6.5:1
gasoline      12.5:1
hydrogen       0.5:1

if available oxygen is held constant at 2.5 the following amounts of
fuel gases can be burned.
methane       2.5 /  2.0 == 1.25
acetylene     2.5 /  2.5 == 1.0
ethylene      2.5 /  3.0 == 0.833333333333
ethane        2.5 /  3.5 == 0.714285714285
propylene     2.5 /  4.5 == 0.555555555555
propane       2.5 /  5.0 == 0.500000000000
butylene      2.5 /  6.0 == 0.416666666666
butane        2.5 /  6.5 == 0.384615384615
gasoline      2.5 / 12.5 == 0.200000000000
hydrogen      2.5 /  0.5 == 5.0

as shown above only 1/2 of much propane can be burned if the available
oxygen is held constant.

the all-states web sites gives no chemistry nor any qualitative analysis
of their oxy-propane torch. i want to see the chemistry and a
qualitative analysis of their oxy-propane torch.

using an oxy-gasoline cutting torch the oxygen consumption is going to
go up to roughly 5 times that of acetylene and roughly 2.5 times that of
propane. this provide a good explanation as to the cutting speeds being
faster with the oxy-gasoline torch than an oxy-acetylene torch. the
amount of oxygen being consumed. the oxy-gasoline torch is more like an
oxygen lance.

On Mon, 16 Aug 2004, Dave Brown wrote:

dave_brown> At 10:40 08/16/04, you wrote:
dave_brown> > >
dave_brown> > > Very simple, it just does.
dave_brown> >
dave_brown> >         Not much of an answer in terms of chemical science, though.
dave_brown> 
dave_brown> Sometimes experience is the best evidence.  Anyway, Clyde isn't a scientist 
dave_brown> or chemist .... Right Clyde?
dave_brown> 
dave_brown> I was going to get all involved in this discussion, but it doesn't seem to 
dave_brown> be worth it.  It's like the fairy tail about how you can't use an acet 
dave_brown> regulator for propane.  The gaskets and seals in fuel regulators were 
dave_brown> changed decades ago and the manufacturers use the same gaskets and seals in 
dave_brown> all of their fuel regulators.  But you can't dispell the myth in spite of 
dave_brown> the information received from the manufacturers.  So, it probably doesn't 
dave_brown> or won't matter what the AllStates people tell you or don't tell you, the 
dave_brown> pseudo-chemists will always claim it can't be.
dave_brown> 
dave_brown> So Clyde and Jerry will just have to live with the fact that they really 
dave_brown> don't know what they know, in spite of being the only ones in the 
dave_brown> discussion with actual experience with this torch.
dave_brown> 
dave_brown> It ain't worth my breath.
dave_brown> 
dave_brown> Dave Brown
dave_brown> Heritage Smithing
dave_brown> Green Bay, WI
dave_brown> 

-- 
terry l. ridder ><>