Dear Willi,
I think Bill might have had applications in mind other than HT pyrolysis
when he mentioned 2000C.
Also, having a furnace that will deliver a constant 1600/1700/1800C over
prolonged periods of time does not necessarily mean one has and wants to run
it at that temperature.
My private reasoning (and I think that's were Bill's coming from too) is if
I know I want to use a system at a certain set point for prolonged periods
of time, I would not buy a system for which said set point would equal max.
output or max. performance. Given a choice I would buy a system for which my
desired set point would equal, say 80% of its top performance.
Cheers,
Wolfram
> -----Original Message-----
> From: Stable Isotope Geochemistry
> [mailto:[log in to unmask]] On Behalf Of Willi A. Brand
> Sent: 30 May 2005 08:49
> To: [log in to unmask]
> Subject: Re: High temp oven burnouts?
>
>
> I have 2 points to contribute:
>
> 1. There is no advantage in going higher than 1600 C. The
> reaction of Al2O3 with the glassy carbon (production of CO)
> becomes rather prominent at this temperature and renders the
> isotopic measurement very difficult (figure 6 in Gehre et al,
> RCM 18; 2650 (2004); pls. drop me a mail if you need a copy).
>
> 2. We buy the elements from the OEM supplier (Kanthal). They
> are not cheap either (~400 Eu), and they vary quite a bit in
> dimension. So, there is a larger risk that the replacement
> element does not fit. Given the high currents going through
> the SiC element and, thus, the associated risks, we have the
> exchange made by an experienced electronics person in our
> workshop. Because of the possible health hazard I advised my
> coworkers not to try this themselves.
>
> Please be aware that a furnace with temperatures above 1200 C
> is not a trivial thing to produce. Below 1200C, heating wires
> are suitable for the job, but above SiC or MoSi_2 (see for instance
> http://www.schupp-ceramics.com/english_site/products/heating_e
> lements.htm)
> must be used that are more difficult to shape. Moreover, the
> heating zone cannot be made as homogeneous as in a densly
> wound wire furnace. Pulsed heating with an inductive furnace
> has problems, too, because the blanks are high and difficult
> to maintain at a constant level.
>
> Best regards Willi
>
>
> .....................................................................
>
> Willi A. Brand, Stable Isotope Laboratory [log in to unmask]
>
> Max-Planck-Institute for Biogeochemistry
>
> Beutenberg Campus
> Hans-Knoell-Str. 10, 07745 Jena, Germany Tel: +49-3641-576400
> P.O.Box 100164, 07701 Jena, Germany Fax: +49-3641-577400
>
> http://www.bgc-jena.mpg.de/
> http://www.bgc-jena.mpg.de/service/iso_gas_lab/
>
> GASIR 2005 in Jena, October 10-12:
> http://www.bgc-jena.mpg.de/service/iso_gas_lab/gasir2005/index.shtml
>
>
> .....................................................................
>
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