[TheForge] Blast furnace (Was: microwave heavy metal session)

[Mike]

>  One question though: doesn't a blast furnace need the air
>  blast to oxidize away some of the impurities, or is the
>  blast solely for obtaining temperature?

As I understand it, in the blast furnace, the air feeds the burning
coke.  The carbon in the hot coke and the hot CO reduce the iron oxide
to iron and pass off as CO2.

In an open hearth furnace, an oxygen lance is/can be used to inject
oxygen that gradually burns off carbon to reduce the carbon content.

An interesting point about an oxygen lance: Stick a pipe into molten
steel and pump oxy through it to burn any available carbon and
fizzzzzzzz: the lance burns away.  So they make the lance a pipe
within a pipe.  Oxy goes through the inner pipe and propane through
the outer one.  The propane responds to hitting the hot melt with
catalytic cracking, which is an endothermic process.  So that reaction
takes up heat from the nearest thing: the lance tip.  Keeps it from
burning off (at least for a while longer).  The resulting methane or
ethane (?) then burns but by that time it's further away from the
lance tip and doesn't do any harm, maybe even helps to keep the melt
hot.

I don't know how widespread this trick is.  Or was, considering the
shift to electric arc mini-mills.  But I saw a rig that used it in
Sydney, NS in the 70s.

- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer@tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^

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