axehandle
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Microwave question, possibly stupid.
I'm going to use a microwave oven as a sulfur burner (sulfur absorbs microwaves). However, the burner vessel will only fit if I place the
microwave on its side, i.e. rotate it 90 degrees to the right.
Now, does anyone know if the magnetron will dislike this position, considering that it's a big rotating moving part?
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rikkitikkitavi
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why on earth do you want to use the microwave oven as a burner, i e heat up the sulfur?
A magnettron doesnt care of the position of the item heated , as long as it absorbs the energy put out by the magnetron. If it rotates it will
probably absorb the microwaves better and more even.
I assume by you question that you will have the burner vessel moving on the rotating disk inside the oven, so that means that it is not possible to
make connections to the burner vessel? You will fill the oven by SO2?
/rickard
[Edited on 7-3-2004 by rikkitikkitavi]
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Organikum
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Doesnt matter. Works in any position.
Take care of leaks though.
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axehandle
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why on earth do you want to use the microwave oven as a burner, i e heat up the sulfur?
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Simplest way of ignition. No spinning disk, but inlet and outlet pipes going through holes drilled in the door. I have tried the merthod and it works.
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Organikum
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why on earth do you want to use the microwave oven as a burner, i e heat up the sulfur?
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Thats a good use for microwave heating I would say. By no way I would recommend to use a microwave for heating food - thats in my opinion a bad idea
as microwaves destroy valuable compounds in food and change some other compounds in a way it is by no way sure if this has no negative effects onto
the metabolism of the person who eats the stuff.
But putting sulfur for example in a micro - in a vessel which is transparent for microwaves like glass - and nuking it makes the sulfur heat up
selectivly - thats the hit, isnt it?
I cant see your problem here Rickard?
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axehandle
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I think the confusion is a result of me not mentioning that
1) The sulfur will be inside a glass vessel
inside the microwave oven with two tubes
leading to and from it through holes drilled
in the oven door.
2) My oven is so old that it doesn't have a
spinning disk.
I think this a the cleanest, simplest and safest way to burn sulfur. If one has to stop the burning, one simply turns off the oven and stops the air
inlet pump. And if the heating vessel should explode, there is the additional safety of this taking place inside the closed oven.
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Marvin
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If you are drilling/cutting holes in the case, what stops the microwaves leaving the oven?
Does solid sulphur absorb 2.5GHz microwaves well, or only liquid? If the solid doesnt you may well damage the oven each time you start it up from
cold. I'm more worried about microwave leaks though.
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Organikum
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If you are drilling/cutting holes in the case, what stops the microwaves leaving the oven?
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Physics I guess.
The holes he wants to drill are about 1cm diameter as told in another thread already. Microwaves hardly pass holes with a diameter smaller than 6cm
aka half wavelength.
Actually holes are much less dangeroous as slits are - this is also already covered here on the board.
So the answer what holds the bad bad microwaves insides is:
The laws of nature.
And it is utmost impossible to kill a microwave by overheating the magnetron as these devices carry an thermoswitch which simple cuts off the energy
when ther magnetron gets to hot. And after sopme minutes of cooling down it will work again. Works like the switch in a watercooker - is no rocket
science at all.
[Edited on 7-3-2004 by Organikum]
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axehandle
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Besides, I've already proven that solid sulfur, as well as liquid, absorbes microwaves. I created a nice little fire in a glass can, it smelled
like hell, but proved the concept.
So it works both in theory and in partice.
I'm more worried about the phosphate bonding cement I'm going to use a a plug (neither cork nor rubber would stand up long to the heat). I
am, of course, going to test using a small bit of hardened PBC, if it warms up I'll simply have to use a very tall E-flask, and use a new cork
every time. No big problem.
This is what I see as the essence of science. If you can't find the info, and nobody knows, try it! You can only fail, and you've learnt
something during the process.
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rikkitikkitavi
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ok, i understand. For some reason I was thinking about a whole microwave oven used as a combustion chamber for sulfur...
/rickard
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Marvin
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Organikum,
"The holes he wants to drill are about 1cm diameter as told in another thread already. Microwaves hardly pass holes with a diameter smaller than
6cm aka half wavelength. "
I wasnt aware he'd posted a measurement elsewhere but I'm particually disspointed you got this wrong, considering your view on microwaves.
They pass quite happily through gaps 1/4 of the wavelength, and when you restrict this the radiation gets noticibly cut off. 1/4, not 1/2. This
doesnt take into acount absorption/reradiation effects in the metal, effects of the shape of the hole or god forbid harmonics from the magnetron.
"So the answer what holds the bad bad microwaves insides is:
The laws of nature. "
No, not nature, not faith, not luck. Design and understanding, or lack of it. From current appearances, more so the latter than the former if at
all.
"And it is utmost impossible to kill a microwave by overheating the magnetron as these devices carry an thermoswitch "
Aside from the hefty thermal lag between the magnetron and its thermal cut out this is irrelavent, noone has suggested this, you can damage magnetrons
in so many other ways, like dielectric stresses, or arcing inside the vacuum chamber or damage inside the oven dumping the eneergy into a short.
axehandel,
", I've already proven that solid sulfur, as well as liquid, absorbes microwaves. "
Yes, strangly a lot of things behave this way while being bad absorbers initially. Naturally it wouldnt have occured to you to put a glass of water
and a glass of solid sulphur in the microwave att eh same time to see which heats up more would it? Bit too close to being scientific that.
"So it works both in theory and in partice. "
Id suggest you were misinterpreting the evidence, but in this case you seem to be misintepreting the evidence and the theory, so lets try
'delusional' instead.
What do we need for half decent microwave absorbtion?
Partially conductive medium would be good, much less than a metal or it reflects and several orders higher than a classical insulator (or it
transmits) and reap the benifits of resistive heating, or for molecular absorption...
Non zero dipole moment,
Ability to transit to other rotational (microwave region) states,
(Several other symmetry and QM controlled factors).
Ok, what do we have.
Solid sulphur. Good insulator. Molecules cant rotate becuase its a solid, so this cannot cross rotational energy levels and thus cant absorb.
Conclusion, probably transparent to microwaves generally.
Liquid sulphur. Good insulator. S8 symetric unit, free to rotate (thats a good thing) zero dipole moment (that kills it becuase a zero dipole moment
cannot couple to the electric field of the microwaves). Conclusion, probably pretty much transparent to microwaves.
Sulphur vapour. Insulator unless ionised. S2 symetric unit. Zero dipole moment, ergo probably pretty transparent to microwaves as well.
Lets examine water for comparason. H2O, bent linear molecule, large dipole moment, Expected to absorb well at microwave energies. Bad insulator,
particually in home circumstances, good resistive absorber.
.... and ice. Good dipole moment. Solid so cant change rotational states, bad absorber. Very resonable insulator, bad absorber. So we expect this
to be mostly microwave transparent.
What do we find in the real world? This effect is the basis for a party trick. You put water in a styrofoam cup on top of ice fresh from the freezer
and hit full power. The water boils and the ice doesnt melt.
"This is what I see as the essence of science. If you can't find the info, and nobody knows, try it! You can only fail, and you've
learnt something during the process. "
Strangly you wont find the info if you dont look for it (try a library), and surprisingly few people will tell you the answer until you ask the
question. The point of trying and failing is this frequently involves injury/death in chemistry. I like the call the DIY-and-see-if-you-die method
of experimentalism. Oddly enough, I'm not in favour of it.
For a moment though, lets get all thoughts of clueless people with cutting equipment mindlessly attacking microwave ovens in a stupidty versus the
laws of physics battle giving glory to the victor and cataracts/internal burns to the loser and examine the actual idea.
Assuming we have microwaves safely contained in the oven, we have the glass container, the tubing which will hopefully survive the temperature, some
molten sulphur we are supposed to be heating, we have air or oxygen coming into the flask and catching fire with the sulphur vapour and the idea, is
that even after we've wasted half of our power making the microwaves in the first place, we are heating the sulphur liquid rather than the glass
will make it a better system.
Oddly enough though, those microwaves wont put most of their power into the liquid sulphur, they'll put it into the FLAME!. What starts it?
Almost certainly dielectric breakdown of the air in the oven, and producing a fuel/microwave powered flame/arc. So the this method puts most of its
remaining energy into the gases inside the container shortly before they leave. Wonderful. Both much more dangerous and less effective than the idea
you were replacing.
Suggestion,
Why not put a wire through some rock wool (make it stand up) immerse it in molten sulphur in the flask to soak in, and when cool use it as a sulphur
candle. Light the tip, put the top on, feed oxygen/air in, get the SO2 out through an air condensor (to trap unburned sulphur) and use up no more
power than the sulphur gives out by burning.
Or use the oven. One or the other.
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axehandle
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Naturally it wouldnt have occured to you to put a glass of water and a glass of solid sulphur in the microwave att eh same time to see which heats up
more would it? Bit too close to being scientific that.
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At it again are we? Pray tell what I've ever done to you to deserve these unwarranted attacks.
OFCOURSE I'VE TESTED *WITH* a glass off water as well. OFFCOURSE I tested with the sulfur inside a glass jar. OFCOURSE I've tested all
materials I'm going to use in the microwave.
Why the hell are you always dissing my ideas, especially the ones I've proved working??? And what was that nonsense about glass tubing
"heating up" in the microwave?
And again you're trying to make me responsible for other people aping me, this time drilling holes in their microwaves. It may surprise you, but
I'm not responsible for what other people do. I only tell what works FOR ME.
I WILL NOT insert disclaimers and warnings everywhere. You're the kind of person who would sue McDonalds for not putting a "warning, boiling
coffee may burn your skin" label on their mugs everytime you spill some coffee in your crotch, yes?
Well, let me tell you something. At least I'm DOING stuff, MAKING IT WORK, TAKING ALL RISKS MYSELF, not sitting making ad hominem attacks.
Buy the way, me saying " DIY-and-see-if-you-die" was referring to FAILURE, not death. A child could see that. And English is only my second
language. I will not make apologies for you misinterpreting me.
Btw: "delusional"? I guess I must have hallucinated when I saw the sulfur burning and smelled the SO2 then. How silly of me. Guess I should
stop taking acid.
[Edited on 2004-3-9 by axehandle]
[Edited on 2004-3-9 by axehandle]
[Edited on 2004-3-9 by axehandle]
[Edited on 2004-3-9 by axehandle]
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Organikum
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Marvin:
Your statement on microwaves passing holes is plain WRONG and MISINFORMING.
Your statement on what materials adsorb microwaves speaks for a complete nonunderstanding of what microwaves are and how they work.
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Marvin
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axehandle,
"At it again are we?"
My thoughts exactly when I saw your thread.
"OFCOURSE I'VE TESTED *WITH* a glass off water as well. "
And your results for absorbed energy, naturally taking into account the differece in heat capacity between sulphur and water were?
"Why the hell are you always dissing my ideas, especially the ones I've proved working??? "
I only argue against ideas I think are wrong or dangerous. Maybe if you read up a little better before posting these ideas there wouldnt be so much
to argue over? In so much as bad ideas go, cutting open a microwave oven and using it to 'power' the burning of sulphur has to rank pretty
low. Doing this would be justifyable if there was a massive improvement in a process but so far neither of you have argued against the basic point.
Heating with microwaves is flawed becuase that isnt where the energy is going to go. Even assuming you need additional energy.
Ive made a what I think is a positive suggestion, Ive even managed to avoid tacking onto it anything related to the toxicity of sulphur dioxide, how
much more positive do you want me to be?
"And what was that nonsense about glass tubing "heating up" in the microwave? "
You are burning sulphur in air, supplying extra energy via microwaves and passing the gasses through glass tubing, now I would think that would heat
up the glass tubing. Make sense? If it were burning propane or other usual 'fuel' it would seem fairly obvios that might be hot enough to
melt glass.
"And again you're trying to make me responsible for other people aping me"
No, I'm not, I'm trying to make the thread as a whole as accurate as possible. Thats why I present an alternative view, so readers can have
more than one reference in addition to trying to lay road markers around badly thought out experiments. I hope other people will spot flaws I dont.
If you didnt want comments, why are you posting on a forum?
"I WILL NOT insert disclaimers and warnings everywhere."
My point exactly. You dont, so other people have to.
"...everytime you spill some coffee in your crotch..."
I am not the one spilling coffie on my crotch deliberatly, and then telling people that this is a massive improvement on what people normally use it
for.
"At least I'm DOING stuff, MAKING IT WORK, TAKING ALL RISKS MYSELF,"
Science is not just about taking risks, its also about understanding risks and minimising them. If there is a simpler, easier or safer method of
doing something, I will try to suggest it. If something isnt going to work properly, I will say so, and try and point out why. I consider this
constructive to the forum as a whole.
"Buy the way, me saying " DIY-and-see-if-you-die" was referring to FAILURE, not death"
You didnt say that at all, I did and I was refering to general injury resulting from working an information vacuum.
"Btw: "delusional"? I guess I must have hallucinated when I saw the sulfur burning and smelled the SO2 then."
Ive explained why this happened and I considering willfully misinterpreting events becuase you want the idea to work delusional. Perhaps you would
have prefered the term 'Experimenter bias coupled with insufficiant understanding of the events'.
Organikum,
"Your statement on microwaves passing holes is plain WRONG and MISINFORMING"
Perhaps you are thinking of the electric vector limit for waveguides?
I am thinking of the focal limit for EM radiation by diffraction.
I also forgot to mention that a 2D conductor, even a perfect one is an imperfect blocker for EM radiation when it has holes in of any size. It is
only a decent (Read safe) blocker when the holes are *very much* smaller than the wavelength.
"Your statement on what materials adsorb microwaves speaks for a complete nonunderstanding of what microwaves are and how they work."
I look forward to a detailed explanation of microwaves and how they interact with matter from you, the limitations of my treatment, and the
consequences to my argument about the microwave heating of sulphur. I in return will endever to reply with more than 2 sentances of inspecific
refutation without conjecture or proof.
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Organikum
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I already posted all necessary information on this topic here on the board with all links for selfeducation, you should use them Marvin.
Search for my name and "microwave".
Repeating what you already said with other words isnt really bright and bad style too.
And for clearification:
We are talking here about "keeping microwaves in the box to an extent the escaping radiation isnt harmful anymore" as everybody knows that
ALL electromagnetic apparati are leaking more or less - thats not to prevent by any practical means.
The engineer who had his head in the cavern of a microwave as it was powered up full power spoke of an warm strange but not unpleasant feeling in the
head. He is still happy and alive.
Not that I advise to repeat this experiment in anys way. 
Running a microwave "empty" is by no way dangerous. It will in the worst case kill your magnetron but most probably the thermoswitch on the
magnetron will shut it down before this is going to happen.
Marvin, your argumentation and your wording isnt backed up by any practical and just a little theoretical knowledge. But it is loaden with many mean
tricks of argumenting available.
Please stop this, feed your ego elsewhere.
Nobody knows everything.
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Texium
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