Hot! Hot! Hot!

A thousand deg C in one second?? Have you calculated the power to do that? What's in the tube. Pepper or oregano? Organics will just carbonize. You need to be more specific. Obviousy methods that require electrical conductivity wont work well if at all.

Most likely such a reactor would use resistance heating with nichrome or kanthal or other heating wire surrounding the quartz tube. Dump tons of power for a short time to get the required rate.

How about using a silicon carbide tube and running current through the carbide to heat it?

It would help to know what you are trying to do, with not only the rate but max temp and power required.

Don't know about quarz, but glass becomes conductive at red heat.

Yep. A "metric boatload" depending upon method and effeciency.

"A finely ground organic substance like pepper or oregano" is all I can tell you in a public newsgroup. It's legal, if that's what you're thinking.

That's kinda the idea. Actually, they will pyrolyze (decompose by heating in the absence of oxygen).

Could do that...it would have to be very high gauge wire to carry the current (power) needed to get that hot/quick. Why would this be better than a series of quartz lamps?

That's an idea...I'll pass it by the boss.

ut

If you promise not to tell anyone - we're designing a micropyrolysis reactor. You have the specs I have about reactor (section) design and heating requirements. The only other thing I can tell you is that we will probably use either nitrogen or argon as a carrier gas. Sorry I have to be so vague. I'm just looking for general ideas and suggestions for technology right now. Don't be upset you can't design the entire heating system for me (grin).

Yep. A "metric boatload" depending upon method and effeciency.

"A finely ground organic substance like pepper or oregano" is all I can tell you in a public newsgroup. It's legal, if that's what you're thinking.

That's kinda the idea. Actually, they will pyrolyze (decompose by heating in the absence of oxygen).

Could do that...it would have to be very high gauge wire to carry the current (power) needed to get that hot/quick. Why would this be better than a series of quartz lamps?

That's an idea...I'll pass it by the boss.

but

Here's a thought: Heat the carrier gas in a separate tube long enough to insure the gas easily gets to temp. That way you shouldn't have to dump so much instantaneous power to get the rate. Then inject the hot gas into the reactor stream. Now, the rate of temp change of the material only involves the carrier and the reactant and not the quartz, heating elements, etc. There would be much less thermal mass to worry about. Furthermore, you can control the temp and the ratio of reactants precisely

(...)

Sounds like a plasma torch.

--Winston

Or CO2 laser? Whatever is used, it is going to take a lot of power. What total mass will be heated to 1000 degC?

We do that with our pilot plant and mini-scale reactors. But they only go to 450-500 oC. I don't know what's goin on in the reactor prior to the heater zone. It might be that we *can't* pre-heat. But thanks, it's a good suggestion.

tm

That's an interesting web site. I notice the copyright date is 1999. Wonder if they've ever gotten any customers? No one I've spoken to has ever heard of them.

The problem there is temperature control. It's fairly easy to dump a bunch of energy in - we could just as easily set of dynamite, but we need to *control* the energy/heat.

The organic material is about 0.2 grams per cc. Carrier gas will be either nitrogen (and remember it's di-atomic), or argon. The heating zone is 1" long and 1/2" dia. I don't know what the flow rate of carrier gas will be.

I think we're getting too involved in details and not looking at what technologies could actually give realistic results.

What is the flow rate of the carrier gas? What is the flow rate of the reactants and what is their specific heats and conductivity? Maybe I'm asking too much but I am trying to ball park this thing. It sure seems that the carrier gas could easlily be heated to 1000 or 1200 deg C in a silicon carbide tube which is also the heating element under current contol. Sounds like a piece of cake to me.

You cannot (efficently) heat quartz inductively or with RF of any type (obviously that includes microwave). What is left? infra red heaters not unlike the radiant quartz lamps mentioned or a rather hot flame. You did not mention some critical parameters: LENGTH of tubing to be heated, and THICKNESS (or mass) as that 1/2 might be ID or there may be a rather small bore.

Take a look at wire-wound power resistors that have a (hollow) ceramic core and the wire is "wiggly" and on edge. Those resistors can be powered so that the ceramic itself turns red and the glaze melts off. But in one second?? Fergeddit!

My key takeaway is that these torches commonly produce instantaneous > 20,000 F plasma capable of vaporizing steel.

Oregano or even pepper should not pose too much of a challenge.

Experimental plasma torches are being used to degrade refuse into combustible gas, for example.

--Winston

Cite!

Well, no, not directly. There would have to be a heating element on the outside that would actually be heated. They're also kicking around the idea to use a stainless steel tube to be directly inductively heated. I *think* only magnetic-type stainless would work, and I'm not sure about the corrosion resistance of these alloys.

be

I think it will be rather thin wall. The wall thickness will, of course, be determined by the pressure. If the pressure is very high, thos won't work at all because the quartz will soften and blow out. Thermal shock make be a killer issue too.

iron isn't magnetic at 1000C.

if it is conductive it can be induction heated, induction brazing of copper tubing for example.

only a few stainless steels are rated for use at 1000C

Maybe Inconel?

-Lasse

If you are looking to heat the gaseous contents of the tube rather than the tube itself that makes quite a difference to the technologies available. The only one I can think of is a plasma induction heater.