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12AX7
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Doesn't persulfuric acid decompose on heating and form much better at low temperatures? How about some Mn? (Even better: use an MnO2 anode!)
The reason switching power supplies are so pervasive today is 1. they are much lighter and cheaper (materials and labor) than iron and copper power
transformers, and 2. they are far more efficient at producing a regulated voltage than a corresponding linear regulator.
Most SMPSs use a cap-input filter, giving them bad power factor. Some use PFC (Power Factor Correction) chips to provide a pre-regulated high voltage
supply without all the nastiness.
Power factor is NOT loss. Indeed, that it is imaginary "power" is exactly the reason it is a concern! The reason is, capacitors are only charged
during the voltage peaks. This causes huge spikes in current, leading to I^2R loss in the wires (from the rectifier and filter, through the
transformer, all the way back to the generator station). By integrating, it can easily be seen that this piecewise current draw dissipates more power
in the wiring than the same average current would if drawn by a pure resistive load. A transformer has limited heat dissipation capacity for its
wiring, so a limited amount of RMS current can be drawn from one. Since RMS current is higher (per DC current output compared to a resistive load),
the current output must be derated.
A choke input filter, as suggested, has a constant-current characteristic (when current draw is greater than the critical value). This will much more
fully utilize the available current output of the transformer (and associated wiring), allowing nearly the full rated output capacity.
And BTW, generators have slip-ring losses, wiring and other BS. Don't be a fool. The industrial answer is always to connect many cells in series
anyway.
Tim
[Edited on 11-5-2006 by 12AX7]
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Rosco Bodine
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Switching supplies are well done little pieces of engineering ,
but they are highly specialized too . You don't just grab the parts off the shelf and toss one together , at least not as easily as a line frequency
linear supply . The transformers
are ribbon wound ferrite core for example , and it just gets worse from there . So if you are manufacturing ten thousand units ....then build a
switching supply , most definitely . But if you are custom building one unit for personal use ....build a linear .
An yeah , a plurality of cells in series combined with polyphase rectification would be the industrial solution , along with building the
electrolysis plant on the river right next door to the power plant .
And brush losses are virtually nothing compared with
semiconductor losses , even Schottky rectifiers are
way more wasteful than a good old graphite brush on a DC generator ......
Precisely why they use brush commutation on locomotives
and other high current switching , even in the age of semiconductors ......some switching is still better done using
brushes . Vacuum tubes still rule in some areas too .
[Edited on 5-11-2006 by Rosco Bodine]
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12AX7
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Odd, I have the parts literally on my shelf. Including removed ferrite transformers, and various ones that I've since rewound. If I have suitable
ferrite, copper and MOSFETs, I would rather build an SMPS than a linear supply, because I don't have any transformers of that size around and damned
if I'm going to cough up a couple hundred bucks for one!
Tim
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Rosco Bodine
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You must have an interesting junk box .....but
how do you even know what is the rating of the
ribbon wound ferrite cored transformers that you
cannibalize from switchers that are proprietary
parts ? They don't exactly provide the details
on all those " no user servicable parts inside "
that we all love to reverse engineer and try
to guess about . Is it hook it up and try it ,
do the old burn / no burn test ?
Hey I found a little line filter choke which caught my eye .
Light as a feather no doubt .
http://cgi.ebay.com/Large-Northlake-inductor-reactor-choke-D...
About a dozen of these in parallel out to give decent filtering on a 20 Amp linear supply , of course a forklift
will be required for moving the power supply , unless
it was rail mounted , you know the rails like a train
travels along  May as well simply use a box car for
the cabinet .
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12AX7
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Doesn't look much different from about two MOT's worth, where MOTs are approximately free, as opposed to upwards of $50. That is a nice inductor,
though!
You'd be suprised how many schematics there are for commercial power supplies. But that doesn't bother me as the specs for a power supply such as
this are proprietary anyway. Is it really that much trouble to use some copper wire or strap and masking tape to make your own four-turn transformer?
Tim
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Rosco Bodine
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Basically what you have with a switching power supply
is a VLF transmitter from which you have disconnected
the long wire antenna , and rectified and filtered the output .
In fact if you were to be creative , you could probably attract a whole lot of government attention with a bit of amplification
and off label use , of an ordinary switching power supply ,
because it would play hell with the VLF band that is monitored to the depths of the deep blue sea for submarine
communications . A sweep frequency oscillator in that band
would be like an invitation for black helicopters .
http://en.wikipedia.org/wiki/Grimeton_VLF_transmitter
[Edited on 6-11-2006 by Rosco Bodine]
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12AX7
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That was...rather non-sequitur, unless you were trying to get at something, RFI perhaps? If your concern is RFI, please just say so.
If you're making an analogy to transmitters, please don't; the squarewave output of any switching supply would be illegal in any country, transmitted
at any noticable power. Harmonics must be a whole lot better than -3dB below the fundamental! Conversely, radiotransmitters (except possibly AM
transmitters, which aren't as efficient as a straight class D amplifiers) are not made to supply the kind of load (transformer and rectifier) demanded
of in switching supplies.
Also, the wavelength is such that very little LF or VLF would be transmitted. Much more likely is switching transients (from rise and fall times
under a microsecond) radiating into the tens of MHz region, which again can be attenuated with proper shielding and filtering practice.
Lastly, it takes a badly designed SMPS to produce a frequency sweep. They are PWM, not FM.
Tim
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SAM4CH
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chamber!!
What about the best material for combustion chamber? I tried to use stainless steel 316 but it was not very good!! I faced expansion in chamber and
there are some very very small pores in it!!
Sam
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ac-
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Hope this isnt posted, but just saw this on wikipedia, "The aqueous solution on boiling loses some ammonia and forms an acid sulfate." http://en.wikipedia.org/wiki/Ammonium_sulfate
And then I found this: CHEMICAL AND THERMAL DECOMPOSITION OF AMMONIUM SULPHATE INTO AMMONIA AND SULPHURIC ACID
http://www.freepatentsonline.com/20040234441.html
Wouldnt this be a good way for sulfuric acid?
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Aqua_Fortis_100%
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| Quote: | from the above patent:
(...)By this method it is achieved to decompose ammonium sulphate to a fully extent into ammonia gas and sulphuric acid liquid, where the ammonia gas
during processing is evaporated and separated out from a restsolution consisting of sulphuric acid.
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This is interesting..i think which this had been discussed before on this board(and the pre conclusions were that the ammonium sulphate is decomposed
(if heated alone, without H2SO4 covering it) into NH3 and H2SO4 which recombine in the air making a large white and irritating smoke (almost as same
which happen to heated ammonium chloride).
But this seems to be strange: this this really a feasible method to make (or recovery) sulphuric acid?
seems to me that heating ammonium sulphate, in anyway, lead this to decompose (chiefly) into NH3 ,and H2SO4 (and further H2O and
SO<sub>x</sub> ).. but heating ammonium sulphate into conc. H2SO4, i'm considering which can be possible..but , is the resulting sulfuric
acid a pure substance ? i assume which at least some of this NH3 (re)react which the sulphuric acid to form again the ammonium sulphate... but in
these conditions , i'm not really sure..
have anyone tried this?
thanks
edit: thanks ,ac- , by provide a such patent...some months ago i iniciate to searching on sulfuric acid subject, and certainly i will thrown this
also to my "drawing search board" .
[Edited on 11-6-2007 by Aqua_Fortis_100%]
"The secret of freedom lies in educating people, whereas the secret of tyranny is in keeping them ignorant."
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not_important
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The H2SO4 tends to oxidise the NH3, plus there is some decomposition of H2SO4 to H2O and SO3. The mix of SO2, SO3, H2O, and NH3 does make 'smoke',
what the gas+particulate phase composition is depends on heating and pumping rates. If you are pumping the NH3 off it does reduce the amount of
decomposition, but the yields still didn't seem to be that great.
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kelaniz
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Interesting thread. At the risk of my first post here being stupid, I have a question.
How quickly does a solution of H2SO3 oxidize to H2SO4 (if at all)?.
I've seen this recommended a few times as a viable and (presumably) safer method of producing H2SO4, i.e. bubbling SO2 into water instead of SO3. Yet,
nobody seems to do it, so I'm wondering what the catch is. 
-Kel
[Edited on 30-7-07 by kelaniz]
\"Despite what mom always said, nothing beats childish, stupid behavior like childish, stupid revenge.\"
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12AX7
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Oxidizing it isn't too great I guess. Certainly works in the environment (SO2 from burning things and volcanos is the primary source of sulfate
aerosol), but that's a far cry from the conditions and the patience a mad scientist might be up for.
Tim
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kelaniz
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That makes sense. After all, acid rain doesn't decompose a car overnight, so it can't be that efficient a process.
Thanks for the reply! Any info from someone named after my favorite combo of 6AV6 triodes gets automatic credibility with me.
-Kel
\"Despite what mom always said, nothing beats childish, stupid behavior like childish, stupid revenge.\"
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12AX7
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You're welcome.
Don't take acid rain lightly though -- you might study Sudbury, Ontario before the 1970s. 
Tim
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akbarnejad
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Manufacturing of sodium sulfate from “salt cake”
The Mannheim process is a well known process for manufacturing of sodium sulfate from sulfuric acid and salt as:
NaCl + H2SO4 NaHSO4 + HCl
NaHSO4+ NaCl Na2SO4+HCl
As the second reaction is done in very elevated temperature, in some factories that HCl is the main product, they do not raise the temperate as needed
to complete the second reaction because of high corrosion problems. The solid from these furnaces is about 50% Na2SO4 and 50% NaHSO4 known as salt
cake.
I tried to put this salt cake in direct fire to convert the NaHSO4 to Na2SO4 as follow:
2 NaHSO4 Na2S2O7 +H20
Na2S2O7 Na2SO4+SO3
The problem is that the SO3 does not evolve from the salt cake unless severe mixing which is not practical in direct fire system and the second
problem is the absorption of hot SO3 mixed with hot fuel gas. The gas is very pollutant and absorption or distillation is very hard because the high
temperature.
I tried heating salt cake for 5 hours in 700 C but the sodium sulfate content has risen just from 50% to 87%.
Can anyone help me with this problem? Is there any other way to recover sodium sulfate from salt cake?
Thank you
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Polverone
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Quote: Originally posted by kelaniz  | Interesting thread. At the risk of my first post here being stupid, I have a question.
How quickly does a solution of H2SO3 oxidize to H2SO4 (if at all)?.
I've seen this recommended a few times as a viable and (presumably) safer method of producing H2SO4, i.e. bubbling SO2 into water instead of SO3. Yet,
nobody seems to do it, so I'm wondering what the catch is.
-Kel
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I have found a fairly detailed answer, only 4 years later. Sulfuric acid from sulfur dioxide by autoxidation in mechanical cells, courtesy of the US Bureau of Mines.
Sulfur dioxide is oxidized to dilute sulfuric acid in aqueous solution using air as oxidant and iron or manganese sulfate (better yet, iron and
manganese together) as catalyst.
The bad news is that none of the tests went higher than about 15% sulfuric acid concentration, though it should be possible to go a bit higher, and
the resulting acid is of course mixed with metal sulfates which will need to be plated out or otherwise removed before the acid is used for most
purposes*.
The good news is that the process uses very inexpensive and very widely available materials. It operates at low temperature and atmospheric pressure.
Although the Bureau's laboratory and pilot plant studies used special equipment to optimize conversion efficiency and rate, it is easy to imagine
performing essentially the same chemistry with dirt-cheap equipment, and on a fairly large scale.
*But not for the purposes the Bureau of Mines considered, where metals were already ubiquitous.
PGP Key and corresponding e-mail address
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hissingnoise
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| Quote: | | The bad news is that none of the tests went higher than about 15% sulfuric acid concentration, though it should be possible to go a bit higher, and
the resulting acid is of course mixed with metal sulfates which will need to be plated out or otherwise removed before the acid is used for most
purposes*. |
A hard look at all the methods described brings one to that inescapable conclusion --- there's always a catch!
All that's required, however, is absolute desperation and total commitment . . .
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watson.fawkes
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| Quote: Originally posted by Polverone | | The bad news is that none of the tests went higher than about 15% sulfuric acid concentration, though it should be possible to go a bit higher, and
the resulting acid is of course mixed with metal sulfates which will need to be plated out or otherwise removed before the acid is used for most
purposes. |
Since you mentioned using dirt-cheap equipment, this seems like an interesting process to develop
a solar still for, to reduce monetary inputs even further. I'm convinced that one of the good uses for solar power is for direct process heat for
industrial processes, and this looks like an interesting starting point.
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AJKOER
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One way (which I have yet to perform, but its on my list) is to add sulfur (buy flowers of sulfur in the garden section and wash with distilled water)
to freshly prepared HClO (add vinegar to bleach and distill half off of the solution, which is 5/6 of the total available HClO vapor and the gaseous
anhydride of HClO, namely Cl2O. Repeat to further concentrate if needed).
Hypochlorous acid (HClO), per Watt's Dictionary of Chemistry, not only will oxidize (even dilute HClO) sulfur to H2SO4, but P to H3PO4, I to HIO3,
etc.
By adding H2O2 to HClO, you get HCl and O2. Heating HClO to around 70 C (or, let standing in sunlight) makes HCl and HClO3 via a disproportionation
reaction (actually, a two stage reaction that forms HClO2 first). Chloric acid, HClO3, is of course, the parent of all chlorate salts.
By the way, in most H2SO4 reactions, you can replace H2SO4 with NaHSO4 and run a safer reaction! So if you have NaHSO4, I will recommend you using it
before handling, boiling or exposing your lungs to SO3 fumes from any H2SO4!
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aliced25
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| Quote: Originally posted by kelaniz | Interesting thread. At the risk of my first post here being stupid, I have a question.
How quickly does a solution of H2SO3 oxidize to H2SO4 (if at all)?.
I've seen this recommended a few times as a viable and (presumably) safer method of producing H2SO4, i.e. bubbling SO2 into water instead of SO3. Yet,
nobody seems to do it, so I'm wondering what the catch is.
-Kel
[Edited on 30-7-07 by kelaniz] |
Extremely well if you add a halide (such as chlorine/bromine/iodine). The addition of SO2 to water is endothermic and the amount of SO2 that will
dissolve will surprise the piss out of you. Also, if you freeze, thaw, freeze, thaw, freeze & thaw the SO2/H2O solution and check it with litmus
each time, you'll note that the solution increases in acidity each time (the idea comes from a Japanese journal article [very little engrish] which
describes the reaction with dissolved oxygen) as the H2SO3 is oxidised to H2SO4.
Personally I prefer the halides, it is the only way I know of to make pure HCl/HBr/HI (not that I make HI that is illegal here) with pure sulphuric
acid as a by-product. I make the SO2 by dropping HCl onto sodium metabisulphite, its neater than burning and it can be done in glass (that SO2 smell
is something you'd prefer to avoid getting into everything).
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
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BromicAcid
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Regarding metal salt catalysis... from a post I made in June 2005:
| Quote: | IF... someone gets a good sulfur burner design that works. I found an interesting method to produce sulfuric acid that is simple and could easily be
made continuous. The premise is to bubble SO2 and oxygen into a collum filled with water (in the experiments they used 100 ml) with a small precentage
of manganese sulfate. The solutions can be made readily to concentrations of about 40% where the effectiveness of this procedure slacks off. Reading
though the article it looks fairly promising (but I cannot upload it because it is >1 M).
Recovery of Sulfur Dioxide as Dilute Sulfuric Acid
Raymond L. Copson, John W. Payne;
Ind. Eng. Chem.; 1933; 25(8); 909-916. |
http://www.destructve.com/bromicacid/SO2manganese.pdf
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AJKOER
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OK, I recall reading in a thread that a much respect member of this forum has tested this route to H2SO4 from H2SO3 with some success:
1. Saturate aqueous solution with SO2.
2. Treat with Cl2.
3. Cycle through Steps 1 and 2, ending at Step 1 to remove any residual Chlorine smell.
Chemistry:
Cl2 + H2O <---> HCl + HOCl
H2SO3 + HOCl --> HCl + H2SO4
Source: "Watts' Dictionary of Chemistry", Volume 2, Page 16, to quote the relevant section from Watts':
"Reactions.--1. HClOAq acts generally as an oxidiser; it easily parts with 0 while HClAq remains. Thus, As is rapidly oxidised with evolution of
light; P, S, Se, Br, I are converted to H3P04Aq, H2S04Aq, &c., even by dilute HClOAq; lower oxides or salts are converted into higher, e.g. SO2Aq
to H2SO4Aq, FeO to Fe203, As203Aq to As2O5Aq, FeS04Aq to Fe2(S04)3Aq, Fe2Cl6Aq, and Fe2O3, MnSO4Aq to MnO2; sulphides yield sulphates, c.g. H2SAq
gives" H2SO4,Aq and S; NH3 gives N,H2O,and NH4CLAq; HC1 forms H20 and Cl. The quantity of the acid expressed by the formula HClO oxidises the same
mass of an oxide"
Link to free Google online book:
http://books.google.com/books/reader?id=ijnPAAAAMAAJ&dq=...
Normally, just bubbling Chlorine through water is not very efficient, but in the presence of SO2, the reaction proceeds rapidly. Note, this process
consumes H2O (permitting the formation of a concentrated acid solution) and the volatile HCl is removable by heating, or by blowing it out with air
(or air and oxygen, see: http://www.sbioinformatics.com/design_thesis/Chlorine/Chlori... ).
I will defer any further comments and let the distinguished member comment if he so desires.
[Edited on 17-4-2012 by AJKOER]
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White Yeti
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How about oxidising sulphite (obtained by bubbling SO2 through water) with an enzyme.... say sulphite oxidase? Or you could use an acidophile that
produces this enzyme.
Not sure if this is a viable method, but hey, no one has mentioned it before so I thought I might throw it out there. You'd have to find a way of
removing the acid so it doesn't kill the bacteria, not a simple task.
"Ja, Kalzium, das ist alles!" -Otto Loewi
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weiming1998
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An alternative way that doesn't involve SO2 is on this thread: http://www.sciencemadness.org/talk/viewthread.php?tid=18963
Just react oxalic acid with MgSO4/FeSO4/CuSO4 in aqueous solution, and the insoluble oxalates should precipitate out, leaving you with a solution of
H2SO4.
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