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From: Bob Eld on 21 May 2010 23:22 <lektric.dan(a)gmail.com> wrote in message news:75685fd0-c052-461e-a57c-e8b709677fc5(a)p17g2000vbe.googlegroups.com... On May 21, 4:25 pm, "Bob Eld" <nsmontas...(a)yahoo.com> wrote: > > 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 >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. 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.
From: Robert Baer on 21 May 2010 23:36 lektric.dan(a)gmail.com wrote: > (no, this isn't spam...) > My boss came to me with another brain-stretching problem. We're > looking at designs for a new microreactor. We need to heat a section > of 1/2" dia. quartz tubing to 1000 oC in 1 second (heating zone is > about 1 inch. How to go about this? Inductive coil? Radiant quartz > lamps? RF? Microwave? What else is out there? Would prefer > commercial to build-it-ourselves. > (the material that will be going through the reactor is the same > finely ground organic material that resembles pepper or oregano). 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.
From: Robert Baer on 21 May 2010 23:40 lektric.dan(a)gmail.com wrote: > On May 21, 1:16 pm, "Bob Eld" <nsmontas...(a)yahoo.com> wrote: > >> A thousand deg C in one second?? Have you calculated the power to do that? > > Yep. A "metric boatload" depending upon method and effeciency. > >> What's in the tube. Pepper or oregano? > > "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. > >> Organics will just carbonize. > > That's kinda the idea. Actually, they will pyrolyze (decompose by > heating in the absence of oxygen). > >> 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 > > 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? > >> How about using a silicon carbide tube and running current through the >> carbide to heat it? > > That's an idea...I'll pass it by the boss. > >> It would help to know what you are trying to do, with not only the rate but >> max temp and power required. > > 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). 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!
From: Winston on 22 May 2010 01:13 On 5/21/2010 7:30 PM, lektric.dan(a)gmail.com wrote: > On May 21, 4:59 pm, Winston<Wins...(a)bigbrother.net> wrote: >> On 5/21/2010 2:25 PM, Bob Eld wrote: > >> >> Sounds like a plasma torch.http://www.cogeneration.net/plasma_pyrolysis.htm >> >> --Winston > > 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. 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. http://en.wikipedia.org/wiki/Plasma_arc_waste_disposal --Winston
From: Archimedes' Lever on 22 May 2010 05:55
On Fri, 21 May 2010 21:48:03 +0100, "ian field" <gangprobing.alien(a)ntlworld.com> wrote: > >"Bob Eld" <nsmontassoc(a)yahoo.com> wrote in message >news:ht6ima$hj1$1(a)news.eternal-september.org... >> >> <lektric.dan(a)gmail.com> wrote in message >> news:6cb52649-d4f5-4c75-aff8-5d8d93340791(a)j9g2000vbp.googlegroups.com... >>> (no, this isn't spam...) >>> My boss came to me with another brain-stretching problem. We're >>> looking at designs for a new microreactor. We need to heat a section >>> of 1/2" dia. quartz tubing to 1000 oC in 1 second (heating zone is >>> about 1 inch. How to go about this? Inductive coil? Radiant quartz >>> lamps? RF? Microwave? What else is out there? Would prefer >>> commercial to build-it-ourselves. >>> (the material that will be going through the reactor is the same >>> finely ground organic material that resembles pepper or oregano). >> >> 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. > >Don't know about quarz, but glass becomes conductive at red heat. > Cite! |