[TheForge] hot portable atmospheric forges may need propylene

[David E. Smucker]

Interesting discussion.  At the industrial level the difference between a 
BOF (Basic Oxygen Furnace) and the Bessemer Process of old is replacing the 
blow air feed with oxygen.  Because you don't have to heat the nitrogen in 
the air (approx. 80 %) you can use that energy to melt scrap.  That is why 
for steel making today the BOF is "King".  It can use around 25 percent cold 
scrap as a feed the rest of the metal being hot high carbon iron from the 
blast furnace (i.e. pig iron).  Part of what made the BOF go was the WWII 
development of bulk oxygen by the Germans.  They developed this for rockets 
(V2) but post war it found it use in steel production.

Dave Smucker
----- Original Message ----- 
From: <Keporter at aol.com>
To: <theforge at mailman.qth.net>
Cc: <skipjack394 at verizon.net>
Sent: Tuesday, May 31, 2005 6:46 PM
Subject: Re: [TheForge] hot portable atmospheric forges may need propylene


>
> Yes, atmospheric burners are self limiting, but no, they aren't  limited 
> by
> the amount of oxygen they can draw in (any of these designs can  be tuned 
> to an
> oxidizing flame). The limit is the amount of nitrogen--not  oxygen--found
> within the intake air. Nitrogen contributes nothing to  combustion, and is
> therefore a drag on the flame's energy density. This is  the sole reason 
> that
> oxy/fuel flames are hottest. However, the theoretical limit  of an 
> air/propane flame
> is listed as 3600 degrees, so you might not want to  dismiss them out of
> hand.
>
> Liquid oxygen costs money to use. Quite a bit more money than the cost of
> many fuels. If you want to take the temperature of an existing forge 
> higher
> than you can get by using the best of tube burners (correctly tuned), the 
> best
> IR coating (water separated ITC #100), and the best exhaust system 
> (larger
> openings with exterior baffles), then the next logical step is the use  of
> propylene fuel gas, rather than oxygen enrichment. Propylene will cost you 
> about 40
> percent more than small amounts of propane, but it is still only  about 60
> percent of the cost of MAPP gas; at least in Seattle.  Propylene was rated
> between 25 and 50 degrees of the temperature of MAPP.  However, Air 
> Liquide has
> replaced the propane content in its formula with  propylene, so this can 
> no
> longer hold true. In fact, I'll have to write them now  and find out what 
> the new
> flame temperature of MAPP is supposed to be.
>
> I have done a study of oxygen enrichment, and it works great as an
> economical means of raising natural gas flame temperatures.  With twenty 
> percent
> enrichment, you receive about a 1000 degree boost.  That's an excellent 
> investment,
> when you factor in the low cost of NG. The  reason enrichment works so 
> well is
> two fold: First, you get the biggest  temperature increase for oxygen
> enrichment at the lower end of a sliding scale;  the upper end of that 
> scale shows
> only a 50 degree increase for the final  twenty percent oxygen invested.
> Secondly, the fuel it's commonly used  with (natural gas) requires the 
> least amount
> of added oxygen (1.5 to  1) of any fuel but acetylene (1.1 or 1.2 to 1
> depending on whose  figures you use). Using it with propane, you would 
> need 3.5 to 1
> of added  oxygen. Therefore, you can multiply the needed percent of added
> oxygen by the  difference between these figures; at this point switching 
> to
> propylene is  not only looking simpler, but cheaper too. Propylene uses 
> the same
> fittings and  regulators as propane. I have used it during burner tests, 
> and it
> will give the  same comparative heat increase over propane with top flight
> burners or  ancient designs. On the other hand, my interest in propylene 
> is for
> hand torches  and burners being used as hand torches, where ambient air 
> can help
> cool  the SS nozzle. When you start running internal forge temperatures up 
> to
> the  higher ranges for very long, you well most certainly melt the SS 
> nozzles
> right  off your burners, so you want to use a good grade of ceramic to 
> build
> a burner port, with the nozzle shape incorporated,  instead.
>
> I have not bothered with recuperative schemes, because the temperature 
> boost
> simply isn't worth the added building expense and lack of design
> flexibility, for ordinary forge work. Since, these higher temperatures are 
> needed for
> some projects, one of you might give them a second look.  There is the 
> Sandia
> forge with plans already existing, but I think an all  ceramic version 
> would be
> the best design. It would probably also work best  with the ceramic 
> nozzles
> everyone will need to operate at the desired  temperatures. However, it 
> will
> either need a tall stack or fan to suck hot air  down into the furnace, 
> and
> neither scheme sounds very compatible with the word  portable. In the 
> meantime
> propylene out on a demonstration site is a very  minor cost compared to 
> say a
> hot-work permit, or even just your  time and travel expenses :-)
> Mike P.
>
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