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Andy

Sat Mar 30 2013, 12:42AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

Hi, I'm researching a idea for a plasma furnace. My goal was to make a arc and have ether a induction coil or microwave magnetron heat the plasma.
Would a magnetron heat the plasma?, and would it be safe if I limit current to 8watt and have a 10nF cap(for testing). The full version will have amply shielding.
The induction heater way is probable beyond me, but if someone could build it I wouldn't mind buying it off you, say 1kw.

Is there any other way to heat the plasma,ideas welcome?

Ash Small

Sat Mar 30 2013, 02:18AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

The conventional solution is the vacuum induction furnace, usually purged with argon. What advantages do you envisage from a 'plasma furnace'?

Andy

Sat Mar 30 2013, 02:43AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

I think high temperatures, and should be easier to build, maybe more effective The induction furnaces I've seen can't seem to reach 1600C which i'm aiming for, without using lots of power.

klugesmith

Sat Mar 30 2013, 05:26AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

Andy wrote ...
... My goal was to make a arc and have ether a induction coil or microwave magnetron heat the plasma.

Uh, would it not be more efficient to make an arc
and then let the arc current x voltage heat the plasma?
Try googling DIY arc furnace.

Where have you been looking, if you are not finding any induction heaters that can reach 1600 degrees C?
I've seen sapphire melted in platinum crucibles by induction heat.

Andy

Sat Mar 30 2013, 06:38AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

Uh, would it not be more efficient to make an arc
and then let the arc current x voltage heat the plasma?
Try googling DIY arc furnace.

Not sure, i'm after 50% from watts to heat. Ages ago I tryed gouging rods and a arc welder, but I don't think that will mange >1kg with that setup, and the lectrode didn't last 10seconds.
I thought with induction heating the more resistive the work peice to a point the more it heats up ?, and plasma should be more. The magnetron idea was tieing into something else i'm working on, but yeah....

I will try the magnetron way, shouldn't need to many parts.

Thanks

Ash Small

Sat Mar 30 2013, 12:05PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'm still not sure what you're trying to do. Conventional arc furnaces will easily reach these temperatures as well. I've worked on two types, one which used the normal limestone based flux/slag for conventional steel (actually 'special steels' at Rotherham), and another which, I believe' runs under argon for stainless steel production.

I've also worked on vacuum induction furnaces (which had the capability of argon purging) which produce nimonics and other nickel based super-alloys which have very high melting points. The biggest of these were at Ross & Catherall at Killamarsh near Sheffield, who produce nickel and cobalt based superalloys

A company called Trucast (also part of Doncasters group) produces turbocharger rotors

and Rolls Royce at Derby have hundreds of small vacuum induction furnaces for turbine manufacture

(I've not worked at Trucast myself, although friends of mine work there. I've worked on/at all the others mentioned, though)

Andy

Sat Mar 30 2013, 07:30PM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

The below picture is of the designs. The reason for the microwave is what the tokmak reactor uses to reach high temperatures.

Theres a couple of design hurdles, it has to reach 1600C in max of 25min using kilowatt/second of power.

Ash Small

Tue Apr 02 2013, 05:43PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

The arc furnace for steels that I worked on was three phase (had it's own substation) and had three electrodes, but for single phase you'd probably want something like the sketch below:

I think the one for stainless steel may have had an arc between two electrodes above the melt, but I'm not sure, as it was working the whole time I was there, so didn't get really close to it.

You could add an induction coil to the sketch if you wanted, Induction coils serve two purposes, firstly, heating, and secondly, the eddy currents produced in the melt assist in agitation and mixing. I imagine something similar could occur in a directly heated arc furnace, but I'm guessing here.

klugesmith

Thu Apr 11 2013, 09:32PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

Hi Andy.
Still can't read your mind yet. In your drawings from March 30,
is the part that looks like "brief" style underpants
a hopper for stuff that will fall down through the arc?

You might be interested in this real "Plasma furnace" that I just stumbled upon
while looking for stuff about tube furnaces.

Andy

Fri Apr 12 2013, 12:05AM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

Hi klugesmith
The arc is in a chamber at the bottom, with a crucible above. The whole thing is sealed.It should heat the air up and convection to the crucible.
Thanks for the link, I'll see if they got some basic diagrams or patent application.

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