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Tacho
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axehandle,
People use ammonium persulfate to corrode printed circuit boards. I tried it. I did absolutely nothing to aluminum, but almost nothing to copper
either, just a black coating. If there is any corrosion, it takes forever. But then, how can people claim it’s a good etching chemical for copper?
Heat? Acidic or basic medium? A special dance?
A quick search in google.groups made me believe it has to be heated. I'll try that tonight.
Pharmacies have hair discoloring cocotions that are basically ammonium persulfate.
I’ll try glacial acetic acid+H2O2 tonight too. Tomorrow I’ll post what happened.
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Al Koholic
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Maybe I'm off here on what you want at this point. First it was a clay heating element, then salt, then something, etc...I'm having trouble
keeping up here (maybe because I've been up for 26 hours straight now) but you also just mentioned air flow restriction. Are you going gaseous
heating now?
In that case...and with coppers excellent heat conduction, why not just leave the pipe in there? Just cast the aluminum around the copper pipe for a
great fit and good contact.
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axehandle
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Well, yes, yes and no. Copper is attacked by hot gaseous SO2, but probably only to a small extent. Perhaps I would be better off doing as you said,
just leaving the copper pipe in there and employ a post-heater filter. It somehow feels "wrong", however.... although I'm quite sure it
would work.
Come to think of it, I really don't want any CuSO4 in my product....
Bah, I'll have a couple of beers and think it through....
| Quote: |
Heat? Acidic or basic medium? A special dance?
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A dance plus stirring and heating, probably. Last I used it I just used boiling water to dissolve the
Na2S2O7(8?) in. Worked. Then again, persulfates (at least the sodium one) are said to attack aluminum as well. That, however, doesn't matter as
long as it attacks copper more.
Edit: I'm going to put two equally sized pieces of Cu and Al overnight in NaHSO4(aq) and see how that turns out.
| Quote: | '
Try a solution of NH4NO3, this shouldn't be hard so to get ...
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Worth a try, I've got about 50kg in stock.
[Edited on 2004-4-19 by axehandle]
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Magpie
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an alternative
Axehandle - I like your aluminum heater, and I can see the beauty of it - if it could just be fabricated!
I know you have invested a great deal of time, money, and psychic energy in this, so I will timidly offer an alternative:
Assuming you can buy aluminum tubing and bend it to a suitable radius, form a serpentine pattern as you have in your heater. Enclose this in a
rectangular metal box, open at top and bottom. Fire it from the bottom with your propane heater.
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Hermes_Trismegistus
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Yes.
| Quote: | Originally posted by axehandle
<b>Now, a serious question:</b>
Does anyone know of a common chemical, that chemical NOT being sulfuric acid, that corrodes copper but does not attack aluminum? I'm thinking of
embedding a copper pipe spiral inside an aluminum block, then pump some copper-destroying liquid through the system until only Al remains.
[Edited on 2004-4-18 by axehandle] |
Use an aluminum pipe spiral, put water in it, then pour the Al block. the Al will solidify around the pipe. Then only Al will remain.
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Tacho
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There is a hundred posts in the usenet saying how well ammonium persulfate etches copper. I could not make it work. Even boiling.
Since I used Pharmacy stuff, I believe something in the formula may prevent it. Or wrong dance steps.
I like Hermes idea. Fast running water maybe. Or paraffin.
edit: Curving Al tubes in small radius is a pain in the ass! Much much more difficult than Cu tubes. They break or bend easily. Pratice is required.
[Edited on 20-4-2004 by Tacho]
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axehandle
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| Quote: |
Use an aluminum pipe spiral, put water in it, then pour the Al block. the Al will solidify around the pipe. Then only Al will remain.
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At a first glance, this seems good. However, there are 2 problems, one small and one big.
1) Bending Al pipe (especially the alloys available as pipe) tends to lead only to cracks. The old trick of filling the pipe witrh sand and warming it
prior to bending might work. But my guts tell me it would be futile.
2) There would be a steam explosion in the mold, and I like my face not covered with molten Al.....
I'm afraid that copper is the only viable solution.
edit1: | Quote: | I like Hermes idea. Fast running water maybe. Or paraffin.
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With solidified, once molten NaCl, it could work.
edit2 | Quote: | | Assuming you can buy aluminum tubing and bend it to a suitable radius, form a serpentine pattern as you have in your heater. Enclose this in a
rectangular metal box, open at top and bottom. Fire it from the bottom with your propane heater. |
No propane. I'm gonna use electical heating (the Al block will be insulated within a block of refractory mix to avoid too great heat losses).
Apart from that, you've read my mind  .
edit3: | Quote: | | There is a hundred posts in the usenet saying how well ammonium persulfate etches copper. I could not make it work. Even boiling.
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Bubbling air through it might do the trick. Etching "machines" do this, if for stirring or for providing oxygen, I know not.
Edit4: <b>Hey!</b> What about.... electroplating the inside of the copper pipe with Al? This could work, with the right electrolyte.....
it's thinking time.
[Edited on 2004-4-20 by axehandle]
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axehandle
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Thinking done.
Ok. After reading up by thoroughly studying a paper on the contruction of contact plants, I've decided that an exhaust heater is not necessary.
The sulfur combustion process itself yields SO2 + air mix that's more than hot enough in itself. If anything, <b>cooling</b> the
exhaust may be needed. However, I'm quite sure this is applicable only when using a huge, industrial, sulfur burner. I should be able to optimize
the air flow through the burner so that the exhaust has exactly the right temperature for the catalyst. This is very good, since I can now finish the
burner and scrap the mechanically complex exhaust heater.
Now, I have to construct a rather tricky piece of equipment. A very small heating element, consisting of a NiCr coil embedded in ceramics. The purpose
being to have this heating element submerged in the molten sulfur, the former hot enough to achieve ignition (in English, it must glow dull red hot).
The leads will have to be constructed out of something resistant to burning molten sulfur slag. The only options are 1) Platinum 2) Gold 3) Aluminum
coated iron/copper 4) Ceramic coated iron. I'll go with (4) for temperature reasons (don't want to melt the Al coating).
Oh, the fun I have!
[Edited on 2004-4-20 by axehandle]
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BromicAcid
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Sulfur Burner Designs, US Patent Numbers:
2637630; 2622007; 3149916; 2285170; 1714657; 1458001; 1382343; 1364716; 1289417; 1254992; 996215; 788512; 700537; 698748 Sulfur Candle; 527881
Sulfur Candle; 462085 Sulfur Candle; 451651 Sulfur Furnace; 390314 Sulfur Candle; 234025 Sulfur Burner
To find many more just search the patent website with the CCL 422/160
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axehandle
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Some success.
Had I known that burning sulfur is this complicated, I would have killed myself instead of starting this project. Now I must succeed. Sigh.
Edit: One thing springs to mind though. It's probably best to separate the burner into two devices: A sulfur melter (giving molten sulfur at a
KNOWN temperature) and a sulfur burner.
The output from the burner can then be cooled to the right temperature in two ways: Water cooling to lower the temperature, increasing the rate of
molten sulfur entering the burner to increase the temperature.
Edit2: There's one thing I'm going to try right away. Heating molten sulfur to its auto ignition temperature and see if contact with a Pt
wire ignites it. If that works, I can keep my old design.
Damned, downscaling is HARD!
Edit3: Molten sulfur does not combust even at its auto-ignition temperature when exposed to Pt. Hah, my 1st real scientific result!
Edit4: It's 01:25 here and I just cast the lid for the melter/burner. How? I filled the cavity almost to the top with anhydrous NaCL, put two
copper pipes where they were supposed to be, and strapped copper sheet around the top of the vessel, forming an edge around the top. Then I just
poured Al in there. Only thing that remains is drilling and threading the refill nipple hole, and ofcourse flushing out the NaCl using water.
Pictures will follow as soon a the thing has cooled down. I love casting aluminum.
No fires this time though.... pity .
Edit5: <b>I'll keep my old design,</b> btw. One time throw-away NiCr igniters, screwed into the lid, will do just nicely.
[Edited on 2004-4-20 by axehandle]
[Edited on 2004-4-20 by axehandle]
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axehandle
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Nope, failure.
The lid isn't airtight. Probable cause: Thermal expansion of the bottom half as a result of the lid being poured, then thermal constriction as it
all cooled.
Tomorrow I'll do something fun (this is irony): I'll glue sandpaper onto a table and sand the edge of the bottom perfectly even. Then
I'll cast a circular aluminum plate with the same diameter and sand that one as well. Then I'll drill, thread, and put a hinge on, so that
the lid can be opened and closed easily. That <b>should</b> make an airtight, or almost airtight, seal. And it that doesn't work,
I'll <b>weld</b> the little fucker in place. Or perhaps make lots of holes around the edge, thread them and then
<b>bolt</b> the damned thing in place. I've never met a piece of Al that does not yield to a 8/8 M10 bolt.
Here's the vessel with failed the lid on:
and here you can see the failed lid (the depressions in the center are due to the NaCl crystals I filled the bottom with prior to casting:
Blast.
[Edited on 2004-4-21 by axehandle]
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Hermes_Trismegistus
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I don't mean to come off sounding like a dickhole...but...
With all due respect, I think you may be too close to this to continue to see clearly, the most intelligent way to the finish line.
You are like a man who is trying to get laid, and have starting looking for you're true love and shopping for wedding rings.
Fuck it, just rent a crackwhore.
You're not building a sulfuric acid generator, you are building a Swedish monument. You are building axehandle's first sculpture. Those
walls to that little pot are thick enough to withstand a direct hit from a mortar shell.
----------------------------------------------------------
Dow chemical made a crapload of money making more sulfuric acid than anyone else, they did it by completely ignoring conventional wisdom.
They built a cheap shack, stuck a woodstove in the middle, mopped and sloshed common tar all over the inside walls of the shack, and slapped a bucket
of sulphur on top of the woodstove. They sucked the fumes out of the top of the room and bubbled them through water.
VOILA!
Sulphuric acid. When the shack sprung leaks, they just sloshed more tar in it, and when the tar became hopelessly contaminated/vulcanized/polymerised
from the sulphur fumes after a couple years of use, they just burned the fucker down.
SO, a suggestion.
1. put the aluminum ingots away. and breathe deeply.
2. Try to get out of the "Old World Craftsmanship" frame of mind and start thinking "Quick and Dirty"
Make a square box, smear the walls with roofing tar and stick one of these in the middle.
http://www.allproducts.com/manufacture1/chuntai/ch050.html
and if that doesn't work, just use a cheap glass alchohol burner.
I don't want to come off looking like an assface(but I probably will), after all when I want a litre a HSO4 I just wander down to the store and
buy one.
But we've all been waiting around and watching you jerk off for long enough. It's not that we haven't been rooting for you, but stop
screwing around and close the deal.
The principle is simple, burn sulphur, collect fumes, bubble through water.
What is swedish for?
YOU CAN DO IT....PUT YOUR BACK INTO IT!
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Geomancer
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Amusing post, Hermes, but it won't work. Burning sulfur creates SO<sub>2</sub>, mostly. You want SO<sub>3</sub>.
While I disagree with some of axehandle's design choices, it's not the kind of project you can get done in a day, at least not if you
use the contact process. Remember, my sulfur burner (assembled in an hour or two) didn't work either. Much of this is due to the fact that my
so-called sulfur refused to behave like it should (I have yet to obtain good sulfur, which is why my experiments have stopped in this area.), but my
design had other flaws, and may have failed regardless.
Besides, axehandle's more grandiose creations are simply fun.
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BromicAcid
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| Quote: |
They built a cheap shack, stuck a woodstove in the middle, mopped and sloshed common tar all over the inside walls of the shack, and slapped a bucket
of sulphur on top of the woodstove. They sucked the fumes out of the top of the room and bubbled them through water.
Violla
Sulfuric Acid.
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Don't you mean Sulfurous Acid? Personally I think you could just go with a sulfur candle in a big jar with two tubes, one entering and
one exiting. That's why I threw up the patents for sulfur candles. Regardless, axehandle's design is very interesting and I admire his
perseverance, he is exceptionally mad and dedicated, sure there were easier ways but he wants to do it professionally.
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Hermes_Trismegistus
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I stand corrected on the matter of SO2/SO3.
and if it wasn't for my supreme respect for the importance of keeping the threads integrity, I would immediately delete/adjust my comments.
But I value the flow and understandabiliyt of the this thread more than any desire to avoid looking dumb.
(it helps that I'm certain my past voiced appreciation of axehandle's efforts and superior intelligence will not go unnoticed to him, and
that I believe my tongue in cheek humor is well known to all)
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axehandle
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I got the joke, and yes I'm mad. Or perhaps insane. But c'mon, there's a <i>reason</i> I'm using Al in huge quantites:
Lead would melt, stainless steel is a pain to work with, and most everything else is either 1) corroded by molten sulfur and/or SO2 or 2) ceramic (I
hate ceramics) or 3) expensive as gold. Literally.
And Hermes, I can't speak for all Swedes, but there's no way I'm going to put my <b>back</b> into it. My back is very bad.
I will put my arms into it though..... Masturbation works wonders as workout.
Edit1: I'll explain my design by stating the design goals later, right now I have to go and see my probation officer.
[Edited on 2004-4-21 by axehandle]
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vulture
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| Quote: |
Those walls to that little pot are thick enough to withstand a direct hit from a mortar shell.
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Amusing comparison, but that strength maybe necessary. An accident where hot SO3 vapor would come into contact with water would have the same power as
a direct hit from a mortar shell.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Al Koholic
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Indeed that would be something worth avoiding. Just wondering but have you thought about placing a trap between the output (SO3) and the burner.
Perhaps one would also help between output and catalyst tube. Traps are invaluble when working with reactive/soluble gases. Also, I think if
your're worried about the gas being too hot (which I can easily imagine), the trap between the burner and the catalys tube will definetly help
too cool your stream. You could even use a variable insulating jacket to help moderate the temp.
BTW, it looks like the holes you have in the lid up there are expanded as you said. Out of curiosity, why didnt you just drill the holes and thread
them? Al is so easy to machine!
[Edited on 21-4-2004 by Al Koholic]
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axehandle
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Design goals.
| Quote: | | BTW, it looks like the holes you have in the lid up there are expanded as you said. Out of curiosity, why didnt you just drill the holes and thread
them? Al is so easy to machine! |
Because I'm an idiot, albeit one with some degree of hindsight...
| Quote: |
Amusing comparison, but that strength maybe necessary. An accident where hot SO3 vapor would come into contact with water would have the same power as
a direct hit from a mortar shell.
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See design goals 1, 2, 3 and 12.
OK, here are my design goals:
1) Safety.
2) Safety.
3) Did I mention safety?
4) Compactness. The maximum allowable
size of the machine is 500x500x500mm.
5) Modularity. All parts should fulfill 1
function only, and be easy to replace.
6) Longevity. The parts should withstand
at least 1/2 year of continous use.
Notable exception: filters, which must be
easy to replace.
7) Automation. The machine should be able
to run unattended, shutting itself down
immediately if any alarm thresholds are
exceeded.
8) Availability of materials. With the
exception of the catalyst, anyone should
be able to duplicate the machine with a
minimum of raw materials. Other
catalysts can be employed, however. I
chose V2O5 because 1e06 chemical plant
engineers can't be wrong.
9) Minimization of ancilliary feeds. In English,
the machine must run only on water,
electricity, air and sulfur. Its only waste
products should be heat, air, water, SO2,
and H2SO4. The last one isn't technically
a waste product, but I list it here anyway.
10) Efficiency. At least 80% of the generated
SO2 must be converted to SO3.
11) Leaklessness. The machine must be able
to run indoors.
12) Safety. Didn't I mention this before...?
Those are the major design goals. I will take
no shortcuts, and under no circumstances
violate design goals 1, 2, 3 and 12.
Edit: Can't do much right now, lack these tools in M16 size, as well as Al round bar:
Will buy the tools and roundbar tomorrow (together with more Al plate to melt.... )
Yes, I'm going to make my own Al pipe sections. Only way to be sure the walls are thick enough. Gaseous SO3 at 500C would
be like gaseous chainsaw..... *shudder*.
[Edited on 2004-4-21 by axehandle]
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Hermes_Trismegistus
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In hindsight I did forget one thing
The Dow process did include one thing I forgot to mention, the addition of chilean saltpeter to the sulfur prior to burning in air.
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axehandle
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A small victory for mankind, but a great one for me.
| Quote: |
The Dow process did include one thing I forgot to mention, the addition of chilean saltpeter to the sulfur prior to burning in air.
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Just like in the lead chamber process. The NO catalyses the reaction according to:
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NO2 + SO2 --> SO3 + NO
NO + 1/2 O2 --> NO2
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I STILL can't find anything suitable for dissolving copper pipe while leaving the Al more or less intact. Not anything economically feasible at
least. I would need about 10kg of sodium persulfate (used for etching PCB boards) for my purpose, and the damned thing would cost a fortune.
Right now I have a piece of Al sheet and a piece of Cu sheet in a saturated sulotion of NaHSO4 (sodium bisulfate). Nothing seems to happening to
either of the metals. I'll give it a few hours.
Edit1: I have an idea though, that could eliminate the need for watercooling everywhere except for the SO3 stream and absorber tank: Heat sinks. Huge,
aluminum plate heatsinks. Now I have to calculate heat dissipation etc....
... which reminds my that I've forgotten how....
Could anyone with his/her physics in more recent memory provide me with a formula that gives the heat dissipation in W given a room temperature of
25C, the material Al, a temperature differential of about 600C, and a surface area of x?
Edit2: I still have to find some way of servo-controlling a water valve... this might be tricky. Actually, using oil and a heat exchanger may be less
suicidal.
Edit3: If all goes well, I can <b>test my catalyst tonight, since I found the threading tools! For cheap! !</b>
Edit4: Now I'm going to be a bad boy and go out and buy some NaOH. That should take care of both copper and aluminum. Better use a dilute
solution though.... wouldn't want the hydrogen developed to rupture the Al block.....
Edit5: Bah, the NaOH does a very good job on the aluminum. The copper erodes much more slowly. Grrrrrr.
[Edited on 2004-4-22 by axehandle]
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axehandle
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Aquisition.
What's in the picture, and a thermostatically controlled hotplate I just couldn't resist buying considering how much work it will spare me.
Plus 10kg of powdered SiO2, and 1kg of bentonite clay. Now I only need a bottle of motor oil, then it's sand-casting time.
The only problem is: What am I supposed to eat for the next 5 days? This set me back about 70 Euro.....
EDIT1: I'm considering returning the M16 sized cutters and get M20 instead. Better wall thickness. Perhaps even M22.
EDIT2: Nah, I'll keep them AND get M20 dies.
[Edited on 2004-4-22 by axehandle]
[Edited on 2004-4-22 by axehandle]
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Saerynide
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Whats the motor oil for?
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axehandle
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Keeping the SiO2/bentonite/water mix together.
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Hermes_Trismegistus
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How about powdered gypsum
considering in the extreme difficulty you have in getting acids, I think that trying to find enough of an acid to dissolve out the copper pipe from a
block of Al is not efficient....
Perhaps you may look again at the aluminum coil in aluminum block idea(it does seem elegant doesn't it?) , even if the aluminum pipe gets brittle
or cracked in the bending, the Al block should take care of any leaks, also there would be remelting on the surface of the pipe. It would actually be
annealed in the process.
Talk to your metal dealers about aluminum alloys that may be more flexible than others.
Filling the pipe with powdered gypsum might be the trick. then blowing the gypsum coud be blown out with compressed air at a local filling station.
Maybe looking at the caro's acid archive in this forum would help, I think it would attack both copper and aluminum but the dissolving would
actually be a timed "burn" anyway right?
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