Chemical Forums
Specialty Chemistry Forums => Citizen Chemist => Topic started by: Corvettaholic on April 13, 2004, 05:06:05 PM
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Hey everyone, first post here :)
My goal is this: I want to create a sustained thermite reaction. As I understand it, a thermite reaction involves a 3:1 ratio of powderized Al and Fe3O4 (or Fe2O3, rust, in a pinch). Also as I understand it, the resulting reaction puts out a ton of light (don't care about that) and about 2500C worth of heat (I do care about that). Also, as I understand it, when you apply enough activation energy and the reactions begins, the oxygen atom scoots over from the iron oxide over to the aluminum, resulting in aluminum oxide and pure iron. Which will be in a liquid state due to the amount of heat.
My question is this: What happens if I introduce water into the reaction? I want to make 2 seperate solutions, powderized aluminum in water for one, and powderised iron oxide in water for the other solution. The way I figure it, once the reaction is started, I can continually pump minute amounts of each solution in the proper ratio into the chamber where the reaction is occuring, and it should supply enough fuel to keep it sustained? But if I make a solution, there's water in it! Is this bad? I'm guessing that the reaction will sometimes pull an oxygen atom from the water molecule instead of the iron oxide molecule, but the result would be hydrogen gas. I have a way to handle this, but would this kill the reaction?
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First, I must ask, where did you come by this information? I hope not from the anarchists' crapbook or similar texts on the internet.
But, for your curiosity's sake, here's some details about thermite:
1. The thermite mixture must be kept extremely dry. Small amounts of moisture will prevent the reaction from occuring. Putting the iron oxide in water would completely prevent the reaction from occurring.
2. The aluminum must be of a certain mesh size. Too big and it won't light.
3. You say "When you apply enough activation energy", which is correct. Enough activation energy is around 1250oC. This is not easy to accomplish.
4. It does indeed result in molten iron. The thermite reaction is also called the Goldschmidt process, and used to be used to weld railroad rails together. It still has certain industrial uses. It is not just iron oxide and aluminum; other metals and oxides can be used as well.
5. Introducing water into the reaction in the way you imply, i.e., making a solution of one or the other first (more correctly a suspension), will simply cause the reaction not to function. However, introducing water into an ongoing thermite reaction (i.e., while it's burning) is a dangerous process. Explosions from superheated steam can occur, and depending on the amount, temp., etc., you can have explosions from the hydrogen and oxygen that comes off of water that has been separated by the energy released.
6. This reaction is over in 10-20 seconds. It is very fast, and can't be sustained for long, except when engineered to do so as in pyrotechnics (think fountains). This you should not do unless you are a trained pyrotechnician, because you can easily create big problems (explosions, etc.)
Why are you interested in this amount of heat? Is it just the heat? You can easily reproduce the heat output with an oxy-acetylene torch or the like.
Let us know of other questions and some of the reasons you are interested in this.
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Anarchist cookbook? Nope. Found it online from some classroom demonstration sites where they put some the two materials together in a block of dry ice, and lit with a magnesium strip. The internet has many wonderful things to teach, but I take it with a grain of salt sometimes. I figured it looked pretty cool, and I wondered if I could sustain it. So me and my buddies got to thinking, what if we could make a furnace by sustaining a thermite reaction? From what reading I could get my hands on, I learned that there are other kinds of compounds I could use, but all the rest sounded too dangerous for me. Like the production of flourine gas, no thanks. But the idea of the furnace. We always wondered if it was possible to create gaseous iron. Not sure what we'd do with it, we just want to see if its possible with our means. We were thinking of creating a housing for the whole thing, and attempting to create a firehose effect with molten iron, by using a powerful electromagnet to propel it out of a barrel. Figure we could plate little things in iron that way. As I understand it, if you increase the energy state, the element in question will lose electrons, thereby having a positive charge? My buddy is coming back to town with some electrical equipment his dad had back from the 60's that'll let us build an electromagnet that can handle 500 amps. Figure that should be enough kick.
Glad you told me about the water! Won't do that then. Can you think of anyway to sustain this reaction beyond half a minute? We're shooting for 5 minutes. Maybe a constant feed of the reactants? We can easily fab up a framework for this whole thing and we have the perfect place to test it. Out in the sandy outskirts of Phoenix. I'm not trained per se as a pyrotechnics guy, but I've had some experience in the past with it. I always make sure I have safety covered, as in I won't burn down anything or anybody.
We thought of the torch idea, but we wanted to try something original, and since the natural product is iron anyway, we figured we could kill two birds with one stone.
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Well, glad to hear that you're not finding this stuff in bad locations. I'm also glad to hear you're taking your internet stuff with a grain of salt, too. My thought is that even though I can write that I am the lord of all creation and can defy the laws of physics on the internet, it doesn't make it true. Lots of people write lots of dumb stuff on the internet.
The thermite reaction is pretty energetic and can be a real mess to deal with. You can't put it out once it gets going, except with extreme measures (like liquid nitrogen, and that's not very safe because of the temperature difference). The idea for the furnace may work, but would have to have a lot of engineering go into it and be very fuel-inefficient. To get it to burn for around 5 minutes, you'd probably need a compressed thermite stick, and then you need to get into presses. Of course, if you're interested in getting some rocketry going on, you might have one of these.
If you increase the energy state, yes, you can ionize the iron. That's not very easy to do through thermal heating alone. You might want to check if iron is still ferromagnetic in a molten state; I'm sure that it is much less magnetic--the hotter things get, the less magnetic they are.
The reactants can't be constant fed separately, but you might get them to be poured in pre-mixed; my guess is that this would be very tricky, especially if you want it to burn slowly. To make it burn slower, you might want to try a different type of thermite, one that uses a different fuel besides aluminum. A great source of thermite references is Shidlovsky's Principles of Pyrotechnics.
Also, if you're doing this in your garage, you need to know that if something ignites, you will most likely not be able to put it out--thermite is nearly impossible to put out once it's going. Also, you need to be aware that you need a LEUP from the ATF; that is, a low explosives users permit. You'll also need an explosives manufacturing license, and the ATF is coming down pretty hard on people now. There was a case in Maryland where a man with all the correct permits was charged with improper storage of chemicals for keeping commercial fire-starting logs in his house. It's BS, but he paid anyway.
In terms of plating iron onto things, have you looked into electroplating, CVD or sputtering?
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I thought themite was considered incendiary and not explosive? Suppose I'll contact the ATF to make sure everything is legal before I begin. About two seperate feeds for the reactants, now that I think about it that won't work. They have to be mixed very well, don't they? I remember digging into magnetics a couple weeks ago, and I totally forgot about the heat issue. It won't be magnetic, especially molten or gaseous.
If I sub out aluminum for another reactive metal, should I go more reactive or less reactive for a slower burn? As far as igniting it in my garage, I have a little area perfect for projects. Big sandbox, with a lot of sand in it. Should contain it just fine till it decides to stop reacting ;D
Here's a thought that occured to me late last night: Scientists are currently working on converting pig feces into crude oil. Just accelerate nature's process of heat and pressure from some million years to 30 minutes. That being the case, I think I might actually have a USE for a thermite furnace as opposed to educational value. The byproducts of a thermite reaction are both solid though, so there would be no pressure increase in a sealed environment. Also, since the oxygen atom just hops over, I won't need an external source of oxygen, right? Now you mentioned that water creates a LOT of pressure, so I was thinking about making a fancy pressure cooker with it. I realize this is extremely dangerous, so I want to know everything there is to know about this before I even consider building a working model. What happens to the hydrogen gas if its stuck in this pressure chamber? How much pressure would I be looking at, like enough to rupture a 2000-psi rated tank with internal heat shielding? Probably just going to leave the pressure idea alone, I value my internal organs way too much.
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I think before you go and make a thermite powered pig feces pressure cooker, there are plenty of cleaner,less dangerous, and more economical ways of getting high temperatures. Lets not go out there almost forcing ourselves to use thermite for the heck of it; I would think thermite's main pro for anytype of practical usage is the production of instant liquid iron; any other side effects of this reaction are better off produced in easier to control/cleaner/less expensive methods. Also, when dealing with high pressures, you have to be extremely careful. One of my relatives had a regular little pressure cooker in their kitchen and one day, I guess the blowoff value just malfunctioned all of a sudden, and the whole kitchen was obliterated... now imagine that with molten iron. Yes and hydrogen gas would immediately ignite at those high temperatures.
With the pig feces idea... I'm pretty sure the whole mechanism is generally understood and the problem probably doesn't lie in producing it in small batches, but producing it in large enough quanities to make fuel as competitive as regular crude oil.
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I would agree with Greg; thermite is a pretty low-efficiency method of heat production. There are much easier ways of producing heat. Like Greg said, if you want molten iron for say, military destruction of a structure, then sure, it's probably a good way to go. But the military isn't concerned about destroying things or the safety of those around it, as they generally want to kill them anyway. So, thermite is probably best left to specialty applications.
Also, I would not light it indoors. Thermite is reported to throw sparks 16' high and 25' to the sides. I have seen 80g batches of it go off indoors, and it was in a huge auditorium. The sparks nearly hit the ceiling which was about 20' up, and it produces a tremendous amount of heat. If you trap that much heat, the ceiling may ignite even if it is not touched by sparks. Even though the university I saw the thermite done at indoors was safe as you could be about it, there is a famous video from the demonstrations when the thermite got away from them and lit the projector screen on fire. Another incident there with thermite came from an explosion caused by molten iron dripping into water, and this caused a terrific explosion (and a lawsuit). It is spectacular, but if you don't do it outdoors, you're a moron.
Thermite is an incendary and not an explosive. However, that doesn't keep the ATF from classifying it as such. According to them, anything with aluminum powder and an oxidizer is considered flash powder, which makes thermite a high explosive by their definitions. They consider a lot of things explosives that aren't technically. According to their law, sparklers are flash powder. Kind of sad, really.
Yes, the components have to be mixed well to ensure ignition.
To get a slower burn, use a less reactive fuel. More reactive fuels will go faster and may approximate an explosion. I think this is the case with some magnesium thermites. Particle size has a lot to do with it, too, as nano-aluminum thermite is very quick burning.
You do not need an external source of oxygen for thermite. This is why when you smother it with sand, it keeps burning.
Do not stick this in a closed vessel. The heat will melt through damn near anything you could put it in, and even if it didn't, it would thermally stress the vessel to the point where you have a blowout at the hot area very quickly. The hot area will be a lot weaker. Any contained gasses will be bad news. The amount of pressure depends on the amount of gas built up. If you run a 0.5g thermite reaction in a 25gallon 2000psi container, it probably won't blow up. If you run a 500g thermite reaction in a 2L 2000psi container, it will blow. Heat, pressure and closed containers are not a good thing.
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I was going over some revisions to the design last night, and came to the conclusion that I don't want to die, therefore a closed container is right out. I never even considered thermal stress. So if I have a container with a vent built into it, the heat should vent out of there and not stress out the container too much? My buddies and I were considering using fire brick or ceramic or something. Also drill some safety blowout holes that point into a sand dune. Not concrete, cause I read some industrial safety stuff that concrete contains some water, and that would be bad all around. Oh, and I'll never light a sizable amount of this stuff indoors (over a couple grams being sizable). I value the integrity of my garage and the car it contains.
I only thought of a thermite reaction for heat because I really don't know about anything else that can produce that kind of heat. Is there something safer I should be using that will give me comparable results? As far as the ATF thing, so long as I use something other than aluminum, and less reactive, it won't be flash powder, right? I was reading Jdurg's articles on alkali metal reactions, but how much heat do they put out? Isn't a lot of the reaction energy wasted as light for both alkali metal reactions and thermite reactions? If there is this much light involved, will a welding mask protect my eyes?
Since doing the small batch of crude oil idea involves pressure, I'm going to scrap that for safety reasons. As neat as it would be. But with a ongoing furnace of such a high heat level, I should be able to use it for other stuff though besides seeing if it works. Some of the guys and I had the idea of playing around with metallurgy and seeing what kind of alloys we could make, figure dumping stuff into iron thats plenty liquid would work. Once it cools, the new material we added plus the iron should give us a different compound, so I think.
As for maintaining a sustained reaction, I was tossing around the idea of using a low powered sandblaster and a loooooong hose to keep it fueled. I'm a bit concerned about the stuff beginning to react while in the feed line though, that could follow its way back to the sandblaster and that would be good-bye sandblaster. This is all providing that I use thermite reactants of course, I would love to use something better (and safer) providing I can produce a lot of heat from it. Is there any danger of iron going to a gaseous state? That would be bad, lungs don't process iron so well.
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I'm thinking you're going about it all the wrong way... you're designing the crude oil maker even before you know how the thing works.
You need to do research first on how exactly the reaction works. Once you do that, you will then venture to assume a few things like more heat during less time is as good as low heat over a long time... now this is not necessarily true, nor may it be the most important thing in producing crude... these are things you need to find out. Once you find out can you start making design decisions that actually go towards improving production of your product.
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Good point. I'll spend tomorrow at working figuring that one out. Even if it isn't possible with my low-budget means, I still want to make the furnace anyhow just for the sake of doing it. Figure I can find something entertaining to do with it if my original plan doesn't work out. I've been kicking around the idea of backyard metallurgy, like trying to make my own alloys. I remember hearing that you need a lot of heat for that. Isn't it more or less dump something that'll stick with iron into molten iron, and when it cools you have a new compound? I thought thats how steel was made. Add chromium to make it more ductile, add carbon to make it stronger but more brittle, and I think it was zinc to make it stainless? There has to be more combinations out there, maybe none of them useful for industrial purposes but I figure I can find a use for anything.
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I used to work at a glassblowing facility, and their torches could achieve temperatures between 1800 and 3500 C depending on the fuel and torch used. If you get a good cutting flame with an oxy-acetyelene torch, you'll easily be able to melt iron.
No offense, but it seems that you're trying to build a rube goldberg machine. It's odd to me that you want to go through the motions of making an elaborate furnace construction just to melt iron, then assume that you'll get an alloy by dumping other metals into it. The easiest way to go about it is to understand how compounds are introduced into iron to make different alloys. Take a look at your local university or college library at the Kirk-Othmer encyclopedia of technology. It will tell you exactly how smelting is done and alloys are made. My instinct would be to take a ceramic bowl, dump in you iron and other compounds, then heat it directly with an oxy-acetylene torch. You'd have to stir it with something, but as long as you didn't oxidize the iron by hitting it with the torch, you could probably get away with it. Depending, you might crack the ceramic container, too.
As for thermite, or any big heat difference, it's more the difference in heat concentration locally that breaks things. If you heat one specific area of a ceramic, even if it's below the melting point, you'd probably still wind up with cracking. If you heated the whole thing evenly (think resistive heater), you'd probably be much less likely to have problems.
Also, a few grams of thermite is a lot. If you do this inside your garage, you may have problems. I've seen half a soda can vaporized with only 3 grams or so of thermite.
The aluminum thing--the ATF will kick your ass on this, regardless of the metal fuel being used. Magnesium is used in flash, and they'll nail you on something. Their guidelines are very vague, and they can really zap you if you're doing this in a residence. You do it in a tent in your backyard, much less problems, but you can still get in trouble. However, the oxy-acetylene torch melting metals? That's no big deal to them. You can get a torch at your local hardware store.
Don't bother with the alkali metals. They just explode. There's a lot of heat released there, but then again, there's a lot of heat released from a hand grenade exploding, too. :)
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Whats a rube goldberg machine? I'll look that up at work tomorrow too. As you can see, I really don't know jack about alloys, it was just a thought. I'm going to cruise by ASU this weekend and pick up some books. I won't ever build anything until I understand how it all works. As far as the cutting torch, well thats a really good idea... but I dont want to do it. Seems to be much easier than going through all this work, but I want to go through all the work just to see if it works. How can oxygen and acetylene get that? I mean, I know they DO get that hot, but I never really thought of acetelyne as something "hot". Can't you touch it while its burning (unless there's oxygen involved)? A buddy of mine at work mentioned a story, where he knew a guy who poured liquid oxygen on a match to light a grill... there wasn't much left afterwards.
If I remember and get time between computer orders, I'm gonna give the ATF a ring tomorrow and ask a lot of questions about this. The last thing I need is fines or jail, it would put a damper on further experimentation.
Even though this idea is kind of dumb, I still appreciate all your guys' help with this! If nothing else, I'm learning a LOT!
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Look for George Gobel's homepage. The official one is down, but some mirrors are still up. He holds the world record for burning charcoal and is the chemical engineer behind the liquid oxygen madness.
And, no, you can't touch the flame of oxy-acetylene. You'll burn your finger off. Acetylene by itself, unlit, is not hot. When it burns, it's hot. Real hot.
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I just found out what a Rube Goldberg machine is, and yes, my idea is kind of like that. Gives my brain something to do besides mindlessly swap out motherboards at work. So as soon as you light acetylene, it gets really hot. Add oxygen, and you get even hotter. Thats basically how it works, right? For purposes of generating heat, think an electrical solution as opposed to a thermite reaction could work any better? I've worked a little bit with capacitive discharge stuff before, had a lot of fun. The torch IS a good idea, but its just too easy! Just called my east coast buddy today, and he really wants me to build this thermite furnace cause he "wants to throw things in it and see what happens". Sounds like trouble. So long as you don't add anything with an oxygen atom attached, a thermite reaction should leave it alone, right?
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Your biggest problem with thermite is that it releases a ton of heat very quickly. Anything with moisture or some other low-boiling material (think plasticizing agent) is likely to superheat and explode if you dump it in. Rocks tend to explode if put in campfires, so just imagine what it would do if you managed to throw one into a thermite mix. The other major problem is that you've basically got a flamethrower even if you do get this oven going, because sparks will be thrown out all over the place. You asked how to make heat. The torch is the best idea, because it's easy and safe. Decades of experimentation have come up with a safe, easy way to generate high heats, which is the torch. If you want to do something else, you're on your own, and you can expect some very dangerous work. Try not to get killed.
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Well containing the sparks is easy. Its an enclosed housing with a bunch of holes drilled in it for pressure/heat vents. At this point, I don't plan on dumping anything in there, other than more reactants. Not getting killed is the idea, and I'm not dumb enough to try and build this on a normal scale before I do some really tiny simulations, like with 1g or something. When I do get it working, I'll let you guys know how it turns out. Still haven't had time to get a hold of the ATF (which I will do first) due to military duty.
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Well containing the sparks is easy. Its an enclosed housing with a bunch of holes drilled in it for pressure/heat vents. At this point, I don't plan on dumping anything in there, other than more reactants. Not getting killed is the idea, and I'm not dumb enough to try and build this on a normal scale before I do some really tiny simulations, like with 1g or something. When I do get it working, I'll let you guys know how it turns out. Still haven't had time to get a hold of the ATF (which I will do first) due to military duty.
If you want to melt iron in any quantity, why not build a small blast furnace or electric arc furnace? Look for a place that sells foundry supplies; there used to be one that regularly advertised in the Popular Science classifieds; I'm not sure if it still does.
Norm
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Blast furnace, electric arc furnace... please do tell. I have no idea how these things work, but I've heard of blast furnaces before. Gimmie a quick rundown of the process works, and I'll dig up what I can at work tomorrow. Then I'll be back with plenty of questions (as usual) ;D
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Blast furnace, electric arc furnace... please do tell. I have no idea how these things work, but I've heard of blast furnaces before. Gimmie a quick rundown of the process works, and I'll dig up what I can at work tomorrow. Then I'll be back with plenty of questions (as usual) ;D
I apologize for taking so long to get back to you. As you probably know, a blast furnace uses forced air from a blower to speed up combustion of the fuel (usually gas for a small casting furnace) to achieve a high temperature. The combustion chamber is well-insuated by a refractory lining. Here is a link to a company that supplies materials for small commercial and hobbyist foundries: <www.budgetcastingsupply.com>. Their site includes a link to a web ring of metal casting hobbyists which is the place to go for info on building small furnaces.
An electric arc furnace uses an arc between carbon electrodes to melt metals. This is probably the simplest way to generate the high temperature (1535 C) to melt iron. The carbons can be obtained at your local welding supply store, and an arc welder used to supply the current. I once built a simple furnace from two fire bricks hollowed out to form the melting chamber, and this easily melted a few ounces of scrap iron.
All this is probably too off-topic for a chemistry forum. If you have any further questions you can E-mail me at nfs@midcoast.com.
Norm
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Thought this might be an alternative
Coffee Can Foundry
http://www.visi.com/%7Edarus/foundry2
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Very good information! As soon as finish painting my house, I'm going to get started on this!
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Hey guys, im suppose to do a thermite reaction for chemistry at school. I have to do a demonstration in front of an audience. But i had to test it today, {edited for content}. The school couldn’t get me {edited for content}.
I then attempted to ignite it {edited for content}.
Any help would be greatly appreciated
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Hey guys, im suppose to do a thermite reaction for chemistry at school.
Somehow, I doubt this. However, that being said, we don't allow posts of dangerous compositions on these forums. What you describe could be very dangerous. So, here's some safety tips:
1. Don't go looking for information on the internet. It's nothing but a shortcut and it's not reliable.
2. You asked in your post about Al particle size (before it was edited); it seems that you're looking for shortcuts, because you didn't read the second post in this thread carefully--particle size is mentioned. Take the time to do this right, and look it up someplace. The thermite reaction is so common that you can find an abundance of information on it if you just go to the library.
3. Go to a college chemistry library. Even if you have to ask the desk clerk there what you're looking for, you'll wind up with more reliable information than the internet.
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[satire]I have this nuclear bomb my physics teacher wants me to demonstrate in class can you help me out? Where can I get some uranium, preferably weapon grade?[/satire]
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