# DIY Generator, Unique idea... Utilizes Solid CO2



## Coconutboy (Apr 13, 2007)

The most commonly used DIY generator I've seen is the one which involves a yeast/sugar water solution

(what I'm currently using)

What I'm thinking about is creating a system that utilizes (sp?) dry ice.

This theorized (sp?) system will use water with dry ice (CO2 in solid form)

Im hoping the water will rapidly dissolve the solid CO2 into gas, which will then be released at a constant rate via a control valve.

It would be MUCH cheaper than the compressed CO2 tank method, and it would be a step up from the yeast method... heres my idea:









Obviously thats a 15 minute sketch... but you guys get the point.

I'm thinking that the container can be made out of a high pressure pvc piping.

As for tubing, I'm thinking a stronger silicon will work, in fact, now that I think about it, any CO2 resistant tubing will work (as the control valve will only allow so much CO2 through the tube, thus eliminating the need for high pressure tubing such as copper).

I also understand dry ice is not readly avalible for many people (most stores like Ralphs and Walmart carry dry ice), but none the less- it makes an interesting concept.

I will probably try to start this project within a couple months (It's going to take some time to gather funds... not all that easy for a 14 year old to make money..:heh , will keep you guys updated as progression continues...

And please, feel free to comment :mrgreen:


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## Coconutboy (Apr 13, 2007)

The only draw backs I can see are:

1) Your working with moderatley-high pressured items-posses a possible risk

2) I'm not exactly sure that dry ice is completley and totaly CO2, there may be other components that I'm unaware of that may be harmful to the aquatic life.

3) Solid CO2 can give frost bite... yet... I'm nearly 100% sure only the stupid and mentally challenged 
would have problems with that... 

4) Total estimated price: I'm gonna take a guess that this will more than likley cost me about $50-$70

Can be good, Can be bad-take your pick.:mrgreen:

EDIT!!!!
_________________________

Dry ice is infact 100% (or close to 100%-the other .0000000000001% being oxygen) Carbon dioxide


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## Muirner (Jan 9, 2007)

I say good thinking the only draw back i see is the water needs to be warm for the dry ice to produce the gas. But since it is dry ice, it will cool the water quickly. After a short amount of time it'd need to be rewarmed. If there was a way to keep the water warm you'd be onto something! Last i knew dry ice was 100% CO2, but i could be wrong.


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## Coconutboy (Apr 13, 2007)

Muirner said:


> I say good thinking the only draw back i see is the water needs to be warm for the dry ice to produce the gas. But since it is dry ice, it will cool the water quickly. After a short amount of time it'd need to be rewarmed. If there was a way to keep the water warm you'd be onto something! Last i knew dry ice was 100% CO2, but i could be wrong.


Actually, dry ice goes through a process called sublimation (when a substance goes directly from a solid state to one of gas-thus skipping the liquid state), and will constantly produce gaseous CO2 ( I think about one pound of dry ice is equal to 8.5 cubic feet of gaseous CO2).

The only reason I stated to add water, was that water will initiate the phase change... (or so I think)

Also even if you were right, a simple "stick on tank bottom" heater should keep the water inside the container nice and warm...:heh:

I feel nerdy..

A 14 year old shouldn't know such things... :heh:


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## Coconutboy (Apr 13, 2007)

BTW people, I am gonna check this thread every day... so don't feel like I wont read your posts..


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## slickwillislim (Oct 11, 2005)

I don't understand the need to warm the dry ice. Even in a regular home freezer dry ice sublimes. I would worry about having to much co2 subliming and blowing your system. I would definetly install a weak point that would work as a safety valve.

I think the risks involved with this system far out way the benefits. 

More refills
?More money for refills(depending on dry ice prices)
DIY high pressure system=dangerous
Set up price is not much cheaper if any.
Can't shut off, same as Yeast

No offense but I don't see any advantages to this system over yeast or pressurized. I personally wouldn't sleep well at night if I had a DIY pvc high pressure tube under my tank. I could be over looking some advantages but from what I can see it is not worth the effort for cost, safety, or efficiency.

It might be worth try just for fun, but be careful. I blew up some droppers in chemistry class with dry ice.(sort of on purpose) It shattered the glass beaker.(accident) I can't imagine what an exploding pvc pipe could do.


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## Coconutboy (Apr 13, 2007)

slickwillislim said:


> I don't understand the need to warm the dry ice. Even in a regular home freezer dry ice sublimes. I would worry about having to much co2 subliming and blowing your system. I would definetly install a weak point that would work as a safety valve.
> 
> I think the risks involved with this system far out way the benefits.
> 
> ...


 I never was going to heat it, that was a suggestion by another user-in which i had the same opinion as you did.

And as for the PVC exploding part...

The amount of inputed dry ice should determine the pressure
inside the container... (About one pound of dry ice is equal to 8.5 cubic feet of gaseous CO2)... a simple equation should solve the problem( I'm no scientist, but the equation should be along the lines of this:RR[release rate]xV[volume of cylinder]-FL[ amount of pressure released=maximum out put pressure... I'll do more research and find the exact equation..) I'll make sure to keep the psi at least 50-100 below the PVC's maximum pressure capacity (with the help of a gauge -hopefully costing around $15-$20 USA)..

And an emergency quick release shouldn't be too hard to build...


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## redstrat (Apr 3, 2006)

Using some extremely rough chemistry calculations I remember from a chem course I took last spring... It sounds to me like pressure could be a problem here. I'm not positive about the size blocks of Dry Ice you can buy but it looks like if you were to place a 1lb block, in a 1' long 3"diam. PVC pipe and it were sealed nicely on each end, and the entire block were to sublimate into gas, it would create a pressure of roughly 150PSI at room temps, no garantees on that calculation I could definately be wrong here. Adding water would only work to speed up the sublimation initially and actually would take up precious volume on the inside of the container creating an even higher pressure. It really seems to be a lot of pressure to rely on a PVC cement connection. I'd defiantely be concerned about saftey here, unless you could find very small dry ice chunks of an ounce or less weight, and probably a much larger container. I'd try to keep the pressure as low as possible and even then. I definately have safety concerns though. 

I really could be way off on that calc though its really been a while since i've done any chem.


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## cwlodarczyk (Sep 18, 2005)

Don't forget the additional challenge posed by the fact that the dry ice will be -109°F or colder.


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## HeyPK (Jan 23, 2004)

Your problem is going to be that the dry ice will sublime from solid to gas too quickly and so much gas will be produced that it kills all your fish and probably your plants too. The challenge will be to insulate the dry ice sufficiently to slow down the production of gas to the rate you want. You will need an extremely well insulated container such as a thermos bottle. You could buy a thermos, fill it with dry ice and find out the rate at which the gas comes out. It may turn out that you still get gas produced too fast. Thermos bottles are delicate and can't take much pressure, and so you must not allow pressure to build up. If you have a very large aquarium or a number of small aquaria, perhaps a very good thermos bottle would produce the right amount. Remember, the rate of CO2 gas production is entirely dependent on the rate that heat gets to the dry ice. 
Another approach would be to put the dry ice in a container with very strong walls and let the pressure build up as it converts to gas and then bleed the gas in at the rate you want. Hey! That's a CO2 tank with a regulator! 

Here is another idea. The air you breathe in has only about 0.04% CO2, but the air you breathe out has about 3.5% CO2. That is an increase of 87.5 X. If you bubbled exhaled air in your tank, much of the CO2 would dissolve, producing around 30 PPM CO2, which is just the right level for good plant growth.


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## Coconutboy (Apr 13, 2007)

davis.1841 said:


> Using some extremely rough chemistry calculations I remember from a chem course I took last spring... It sounds to me like pressure could be a problem here. I'm not positive about the size blocks of Dry Ice you can buy but it looks like if you were to place a 1lb block, in a 1' long 3"diam. PVC pipe and it were sealed nicely on each end, and the entire block were to sublimate into gas, it would create a pressure of roughly 150PSI at room temps, no garantees on that calculation I could definately be wrong here. Adding water would only work to speed up the sublimation initially and actually would take up precious volume on the inside of the container creating an even higher pressure. It really seems to be a lot of pressure to rely on a PVC cement connection. I'd defiantely be concerned about saftey here, unless you could find very small dry ice chunks of an ounce or less weight, and probably a much larger container. I'd try to keep the pressure as low as possible and even then. I definately have safety concerns though.
> 
> I really could be way off on that calc though its really been a while since i've done any chem.


Small chunks of dry ice aren't that hard to find-they are made out of bigger chunks

And if your calculations are right-I found piping that can withstand up to 300PSI... (It's metal-also means I can weld the ends:mrgreen: )

As far as saftey goes... I'll leave the system running outside on it's own for a couple days/weeks
if it doesn't blow outside-hopefully it won't blow inside..


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## Coconutboy (Apr 13, 2007)

HeyPK said:


> Your problem is going to be that the dry ice will sublime from solid to gas too quickly and so much gas will be produced that it kills all your fish and probably your plants too. The challenge will be to insulate the dry ice sufficiently to slow down the production of gas to the rate you want. You will need an extremely well insulated container such as a thermos bottle. You could buy a thermos, fill it with dry ice and find out the rate at which the gas comes out. It may turn out that you still get gas produced too fast. Thermos bottles are delicate and can't take much pressure, and so you must not allow pressure to build up. If you have a very large aquarium or a number of small aquaria, perhaps a very good thermos bottle would produce the right amount. Remember, the rate of CO2 gas production is entirely dependent on the rate that heat gets to the dry ice.
> Another approach would be to put the dry ice in a container with very strong walls and let the pressure build up as it converts to gas and then bleed the gas in at the rate you want. Hey! That's a CO2 tank with a regulator!
> 
> Here is another idea. The air you breathe in has only about 0.04% CO2, but the air you breathe out has about 3.5% CO2. That is an increase of 87.5 X. If you bubbled exhaled air in your tank, much of the CO2 would dissolve, producing around 30 PPM CO2, which is just the right level for good plant growth.


Yes, I'm going towards the controled valve way. And as for a container, I found nice thick metal piping (means I can weld) that can withstand up to 300PSI-Ill try to keep the PSI at least 50-100 below the max psi on the piping.

As for your breath... It poses a pretty good Idea... though, you would have to stand and bubble the tank for at least 30 mins x2 a day... I guess its fine if you can withstand asphyxiation


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## JG06 (Nov 5, 2006)

Have you ever made a dry-ice grenade? If not, perhaps you should sometime because it demonstrates pressure vessel failure brought on by the rapid sublimation of dry ice. IM me if you want me to tell you how to conduct this experiment because I don't want to publish it on an open forum.

Now, to your idea: I believe your idea *could* work, but I also believe this may have too many variables stacked against it that could cause it not to work. Here are a few that come to mind:

Storing unused dry ice
Constructing a failure proof pressure vessel
Sealing the pressure vessel against leakage
Controlling CO2 gas output
Safety
First is the storage of your unused dry ice. Unless you wanted a really big (and expensive) PVC tube capable of storing a pound of sublimating dry ice, you'll need a place to put the rest of your supply. While storing it in a deep freeze may slow down the sublimation process, it won't stop it and what you may end up with is your supply of dry ice withering away while you have it in storage. The way to get around that is to load your entire supply of dry ice (which I do not recommend) into your pressure vessel. 
Next, you will need to calculate what you think is the maximum pressure you might encounter using dry ice and then add a some margin of safety to it. Then you'll need to build some type of container that can withstand all that pressure without failing and I am curious to see if heavy walled PVC could do it. Gas under pressure can do some weird things and I would leary of putting the CO2 under too much pressure in anything other than a gas bottle.
Once you've figured out how to store and contain the gas, you'll need to seal the fittings and lid to prevent the pressurized gas from leaking out. I don't know how to do this and can't offer any advice.
Then, once the gas is pressurized and sealed in, you need to control the container's output. For that there are several regulators available but none of them are inexpensive. You might be able to get away with a regular ball valve, but that's only if your system didn't build up too much pressure. What ever set of valves you use, you'll have to mount them on your container and you might have to get creative to do that. 
Lastly, you really need to think safety first. If something gives or your container ruptures, the whole thing is could possible explode and make a heck of a mess - if it didn't hurt someone. Rapidly escaping gas propels bullets out of gun barrels and drives CO2 powered race cars. I'd hate to think of what could happen if this got loose in your living room.

Don't get me wrong as I'm not trying to talk you out of this. However, if you're going to try to container pressurized CO2 under your aquarium, I would urge you to think the whole thing through first. There's bound to be a way to do it and I curious to see your finished results. Please keep us posted.


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## Coconutboy (Apr 13, 2007)

JG06 said:


> Have you ever made a dry-ice grenade? If not, perhaps you should sometime because it demonstrates pressure vessel failure brought on by the rapid sublimation of dry ice. IM me if you want me to tell you how to conduct this experiment because I don't want to publish it on an open forum.
> 
> Now, to your idea: I believe your idea *could* work, but I also believe this may have too many variables stacked against it that could cause it not to work. Here are a few that come to mind:
> 
> ...


Yes, those do pose as problems...

As for the container, I plan to use metal piping- Although metal does pose a greater threat (in case of failure), it has greater benefits such as: higher psi capabillities, and the ability to be welded (I have an arch welder).

As for how much Dry ice I am going to use: a conveinient store that carries dry ice is about a 15 min walk away... so for me-I shouldn't have too much of a problem ( I've yet to find out how long a peice of dry ice will last)

And as for the valve- I plan to keep the psi as low as possible... hopfully a ball valve will work.

To seal, I'm most likely going to use welding epoxy-coated over with sillicone.

For saftey... I'm planning to test the system outside for a couple weeks (depending on how long an ounce of dry ice will last). If the container fails-at least it will be outside.

I haven't yet the funds to start this project, so progression might be a bit slow.

EDIT
_______________-
As for the dry ice grenade... yes I've tried it... but obviously, a metal pipe will have a higher psi rating then a 2L soda bottle...


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## redstrat (Apr 3, 2006)

your essentially building a DIY pressurized system, your pressure valve is going to need to operate as a regulator and you will need a needlevalve to fine tune the output, which will be very difficult. your way better off in many ways to just put the money into a real pressurized system, the cost will probably end up being equal if not less than what your going to be putting into a diy version. CO2 tanks are tested up to 2000psi every couple years because things can change over time rendering the tank unsafe to use, your DIY version would not undergo this saftey testing. Wether or not the pipe itself can withstand the pressure is irrelevent because the connections between the pipe and the fittings, pressure gauge(regulator), welds, ect. will be your weak points. It just seems like a lot more trouble than its worth. Do you knwo how to cut dry ice into reasonable peices. How do you plan to refill the vessel, the threaded fitting could be a weak point and actually pose the biggest risk, because your constantly opening and closing it everytime it needs refilled, saftey woudl be compromised everytime. Your also looking at a very unsteady CO2 supply as I'm sure it woudl be like a CO2 tank near empty all the time, which can cause a huge dump of CO2 in a real pressurized system. It sounds like an interesting idea at first but the more I think about his the more it worries me. why not save up the $150-$200 and invest in a real pressurized system if DIY is to much trouble and then at least safety wont be to much of a concern. www.aquariumplants.com has great prices on tanks and the milwaukee regulator, which includes a needlevalve and bubble counter. put the two together with a diffusor and you'll be in great shape, and have peice of mind for your safety. Co2 fills cost $10-15 for most tanks and will last for months, its way cheaper and not to mention cleaner than DIY CO2 in the long run.


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## Coconutboy (Apr 13, 2007)

davis.1841 said:


> your essentially building a DIY pressurized system, your pressure valve is going to need to operate as a regulator and you will need a needlevalve to fine tune the output, which will be very difficult. your way better off in many ways to just put the money into a real pressurized system, the cost will probably end up being equal if not less than what your going to be putting into a diy version. CO2 tanks are tested up to 2000psi every couple years because things can change over time rendering the tank unsafe to use, your DIY version would not undergo this saftey testing. Wether or not the pipe itself can withstand the pressure is irrelevent because the connections between the pipe and the fittings, pressure gauge(regulator), welds, ect. will be your weak points. It just seems like a lot more trouble than its worth. Do you knwo how to cut dry ice into reasonable peices. How do you plan to refill the vessel, the threaded fitting could be a weak point and actually pose the biggest risk, because your constantly opening and closing it everytime it needs refilled, saftey woudl be compromised everytime. Your also looking at a very unsteady CO2 supply as I'm sure it woudl be like a CO2 tank near empty all the time, which can cause a huge dump of CO2 in a real pressurized system. It sounds like an interesting idea at first but the more I think about his the more it worries me. why not save up the $150-$200 and invest in a real pressurized system if DIY is to much trouble and then at least safety wont be to much of a concern. www.aquariumplants.com has great prices on tanks and the milwaukee regulator, which includes a needlevalve and bubble counter. put the two together with a diffusor and you'll be in great shape, and have peice of mind for your safety. Co2 fills cost $10-15 for most tanks and will last for months, its way cheaper and not to mention cleaner than DIY CO2 in the long run.


 Wow wall of text lol..

and yes... sadly-you are right...

As much as I would like to continue this project... it posses as unsafe-and more so uneccesary.

Though, if any one can think of better ways to use dry ice as a source of CO2, Feel free to post:mrgreen: I will still keep this thread updated-as I search for more ways to do this.


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## stcyrwm (Apr 20, 2005)

Coconutboy said:


> As for your breath... It poses a pretty good Idea... though, you would have to stand and bubble the tank for at least 30 mins x2 a day... I guess its fine if you can withstand asphyxiation


This has actually been done and there is a rumor that this has been an ongoing project for a member for years. He obviously hasn't been asphyxiated yet................


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## Coconutboy (Apr 13, 2007)

stcyrwm said:


> This has actually been done and there is a rumor that this has been an ongoing project for a member for years. He obviously hasn't been asphyxiated yet................


Tis was only a joke...

Yeah I heard about that... didn't he use bags or somthing?


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## epicfish (Sep 11, 2006)

How much is a pound of dry ice? Approximately.


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## Coconutboy (Apr 13, 2007)

epicfish said:


> How much is a pound of dry ice? Approximately.


Over here it is about $0.60 USD a pound

very cheap


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## HeyPK (Jan 23, 2004)

> > :
> > Originally Posted by Coconutboy View Post
> > As for your breath... It poses a pretty good Idea... though, you would have to stand and bubble the tank for at least 30 mins x2 a day... I guess its fine if you can withstand asphyxiation
> 
> ...


The rumored member is me, and, with tanks that have glass covers, I only do it every two days, and I get a good pearling rate during the intervals. I breathe into a garbage bag until it is full and then pump the contents into 3 15 gallons and a 29 gallon.


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## gacp (Sep 11, 2006)

Looks like you'll have all the problems that come with pressurised CO2, _plus_ the added problems of making your own equipment instead of buying or adapting off-the-shelf stuff, _plus_ the added problem of refrigeration (you HAVE to keep this at the sublimation temperature for CO2, I think ca. -45º at 1 atm, I don't know about how it will change when pressurising it.

So, *why*?!

Now, an acid-base reaction involving cheap organic acid, regulating by drop count, may be a sensible replacement for yeast culture.


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## imzadi (Apr 3, 2007)

Even though your idea to use dry ice seems to be unworkable in your current circumstances, I'm still really impressed with your ingenuity and willingness to research the possibilities of your idea. Please keep coming up with ideas like this!


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## rgrycki (Jun 13, 2005)

After reading all the replies I just had to reply to this one. Your initial idea of submerging the dry ice in the water seems to me like it would work best. The bigger the chunks the better. Let me explain. First, when you submerge the chunk of dry ice in the water, the water will rapidly freeze around the chunk, developing a thick layer of ice. This ice will limit the amount of heat transfer to the chunk of dry ice thereby slowing the rate of gas released. I learned this at 19 years old when I tried to make a dry Ice bomb by using a big chunk and warm water. It didn't work, the ice insulated the dry ice really well. The bigger the chunk the longer your system will last. I really don't think this will result in any critical pressures. Additionally you may need to consider the temperatures in your pressure vessel. If you go past the charpy transition temperature of the material the mode of failure will change from plastic to brittle = BAD this will severely weaken your vessel. Again in this case, the insulating layer of ice would be more beneficial. I think this idea might have a chance, just use a reliable pressure relief device for the initial trials though I don't know how this would work long term.


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## Muirner (Jan 9, 2007)

Schedule 40 pvc can withstand 810psi, I'm sure schedule 80 could handle much more...

Just giving an idea on pvc pressures.


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## Coconutboy (Apr 13, 2007)

Muirner said:


> Schedule 40 pvc can withstand 810psi, I'm sure schedule 80 could handle much more...
> 
> Just giving an idea on pvc pressures.


wow, did not know thatrayer:


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## slickwillislim (Oct 11, 2005)

Things are rated a lot lower than there maximum pressure. I believe you have to test to 8-10x the working pressure. This is just what I picked up from a random conversation with my dad who is stress guy for United launch alliance. He works with stuff like this all day. Why things fail, will things fail... 

There is a reason why people don't put 810 psi in a pvc pipe though. Of course your not going to be in that range unless you have liquid co2 in there and then its the same as regular pressurized so... 

I guess you could try it out but check the strength of the pvc cement you use too.


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## Coconutboy (Apr 13, 2007)

slickwillislim said:


> Things are rated a lot lower than there maximum pressure. I believe you have to test to 8-10x the working pressure. This is just what I picked up from a random conversation with my dad who is stress guy for United launch alliance. He works with stuff like this all day. Why things fail, will things fail...
> 
> There is a reason why people don't put 810 psi in a pvc pipe though. Of course your not going to be in that range unless you have liquid co2 in there and then its the same as regular pressurized so...
> 
> I guess you could try it out but check the strength of the pvc cement you use too.


yeah, that the thing, i will have alot of weak points... especially where the bonds are..

what if i insulated the whole thing with cement?:boxing:


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## slickwillislim (Oct 11, 2005)

Bigger bomb. I have no idea how strong concrete is, If its as strong as I assume I would think that could work. Of course I am imagining you placing this in a substantially bigger box filling it with concrete with a tube extending out to a control valve and a safety valve. 

The problem I see with this is you cant refill with dry ice. The opening used to refill it will then become the weak point. 

The cold will make everything brittle as well. Everything has a temperate where it turns into glass, brittle and even the thermal stresses from the different temperatures could cause it to fail. I believe pvc lists its working temperatures at room temp so that might be worth investigating. 

Some guys at my dads worked cracked a launch platform of 1.5" high strength steel with some liquid gas, that spilled out of a launch vehicle. (I can't remember the gas probably oxygen since they use that... sorry I remember it was really cold.)


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## Coconutboy (Apr 13, 2007)

slickwillislim said:


> Bigger bomb. I have no idea how strong concrete is, If its as strong as I assume I would think that could work. Of course I am imagining you placing this in a substantially bigger box filling it with concrete with a tube extending out to a control valve and a safety valve.
> 
> The problem I see with this is you cant refill with dry ice. The opening used to refill it will then become the weak point.
> 
> ...


Indeed... well- it was a thought...


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## M.K.A. (Mar 31, 2007)

Very impressive thought processes going on here, pvc pipe 40 or 80 will crack and fail under cold and pressure, have you thought about finding a used pressure cooker, aluminum, large area, pressure locking ring and you could drill and tap for the gauges and fitting, also using it submerged in a 40 gal rubbermaid tub would help to reduce shrapnel damage lol


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## Coconutboy (Apr 13, 2007)

M.K.A. said:


> Very impressive thought processes going on here, pvc pipe 40 or 80 will crack and fail under cold and pressure, have you thought about finding a used pressure cooker, aluminum, large area, pressure locking ring and you could drill and tap for the gauges and fitting, also using it submerged in a 40 gal rubbermaid tub would help to reduce shrapnel damage lol


OMG! a pressure cooker would be awesome!- after all their built to withstand pressure I'm guessing (as it is in the name PRESSURE cooker...)

The only problem is drilling holes... how would i seal those?

They'd deff. be weak points


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## Rex Grigg (Jan 22, 2004)

Pressure cookers are only designed to work at pressures around 20-30 psi.


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## Coconutboy (Apr 13, 2007)

Rex Grigg said:


> Pressure cookers are only designed to work at pressures around 20-30 psi.


Ahh... ok nvm


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## kimo (Apr 21, 2006)

"also using it submerged in a 40 gal rubbermaid tub would help to reduce shrapnel damage lol"

No it won't... water does not compress and any submerged explosion only gets magnified.


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## snickle (Apr 8, 2007)

The overall explosion might be look bigger, but the shrapnel damage would be reduced as mentioned and would have to move the extra mass of the water as well. Not saying it is a good idea, just clarifying a point.



kimo said:


> "also using it submerged in a 40 gal rubbermaid tub would help to reduce shrapnel damage lol"
> 
> No it won't... water does not compress and any submerged explosion only gets magnified.


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## slickwillislim (Oct 11, 2005)

40g of water is probably worse, financially not personal safety, than just keeping it under a sturdy enclosed wooden stand. 

Of course both of these scenarios can be prevented by not creating a giant compressed co2 bomb.


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## WntrMute2 (Aug 16, 2007)

What about combining ideas. Let a pound (or other appropriate amount sublime in a garbage bag and then pump that out w/ an air pump located inside the bag. Just a thought instead of exhaling into the bag. BTW an exploding garbage bag would be harmless but way cool.


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## modster (Jun 16, 2007)

Hi, I am a mechanical engineering student and i would say this thing would probably work if you work out the details carefully. However, the question is does it really worth it? Maybe you have mentioned it before but how big is your tank? If it's small enough, just get the paintball system. I got my setup for about 100 bucks. The 20oz CO2 tank for 20 bucks and the regulator+pin valve for 75 (yes i have to turn on my CO2 manually  ). I get my CO2 from ****'s sport for 3.99 each fill. Your system needs a regulator + pin valve as well. Plus a lot of calculation/design and money to make this thing. Anyways, since everyone is so excited about this, i will give you guys another DIY co2 idea. How about burning rubbing alcohol ?

EDIT ahh... i just realize they filtered out the word dic k. :-\


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## kwc1974 (Jan 4, 2006)

After reading this post, some problems have arisin in my head.
I work in the pressure vessel industry and both PVC and Metal pipe does have good pressure ratings. But those ratings are for nominal temperature ranges -20F~100F
After you cross this range , either above or below temp is then added to the equation for pressure holding capability.

In this case we are talking about -190F (or somewhere around there....someone above mentioned this temp.). PVC will become way too brittle to hold pressure, and Metal will probably do the same (this is why special low temp pipes are made, usually any thing below -20F. Also any welds done to the pipe would also have to be rated for this temp, PVC cement will fail at the required temps.

I do not know what kind of metal pipe you prepose on using (grade??) but standard off the shelf stuff will not work.


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## NoSvOrAx (Nov 11, 2006)

I know this thread is old but I thought I'd let you know how we applied physics majors at CSUSB unwind. We put a couple of ounces of dry ice in a 2 liter bottle taped to a trailer hitch and drop it in a 40 gallon trashcan full of water and a couple cinder blocks. The result is the trashcan coming 3-5 feet off the ground.


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## jmhart (Nov 13, 2007)

This seems a little superfluous. I recognize this was deemed a bad idea, but in case anybody else wants to try it, realize it's very bad idea.

First off, dry ice itself is at -78C. Therefore, in a water bath, it will freeze the water before all of the co2 sublimes without a heater. In my lab I use dry ice to prepare liquid baths at cold temperatures for degassing solvents. When I'm done with the dry ice, I melt it in water. I always have to remove "wet" ice(water) and top off the container with hot water in order to melt all of the dry ice in an appreciable amount of time. So, if you want to use a water bath, you want to heat it.

However, even this isn't the best idea. You want to control the rate at which co2 is sublimed. The best way to do this is to reduce the ambient temperature, not increase it. The best system for this would be a cooler, or some other type of insulated vessel. Without a compressor, the vessel would never stay -78, but it would stay cold, helping slow the rate of sublimation.

So, best bet: no water bath, no heater, add insulation.

Next: You have to build something that can withstand pressure. You have to build something that can contain gaseous co2 and regulate the rate at which it is released. Hmmmm, a container that is strong enough to contain high pressure yet able to regulate it's release....hmmm, if only there was something available that did that...oh, wait, it's called a gas cylinder. Sorry for the sarcasm, but what you would be building is a gas cylinder. To build it safe enough to even look at, you'd have to spend more money than it would cost to just by a gas cylinder.

Additionally, it may seem like buying dry ice is cheaper than co2. Somebody said $.60/pound for dry ice. To but 20 lbs, let's call it $12. Compare that to a 20 lb cylinder refill ~$20. Seems cheaper, however, with this "DIY" setup, you'll be putting highly concentrated bubbles of co2 into your reactor. Each bubble would go a long way to reach your 30 ppm co2 level. After that, all of that co2(input in high doses) either starts to affect your fish, or is just wasted by diffusion out of the water. You'll end up wasting the co2, and I'd be willing to bet you'd waste enough to make the gas cylinder worth it.

One more thing: just because the co2 is now gaseous doesn't mean it's room temperature. CO2 is only liquid at high pressures, so, under atmosphere, any co2 that is higher temp than -78 is gas. Point is, that co2 coming off your dry ice and going into your tank is going to cause a major temperature gradient.

Not to mention the fact that a "homemade" gas cylinder is a www.fark.com headline waiting to happen.


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## onemyndseye (May 12, 2006)

".....Here is another idea. The air you breathe in has only about 0.04% CO2, but the air you breathe out has about 3.5% CO2. That is an increase of 87.5 X. If you bubbled exhaled air in your tank, much of the CO2 would dissolve, producing around 30 PPM CO2, which is just the right level for good plant growth......"


I've actually tried this before and it does work.


1. Take a 55gallon trash bag and blow it up like a balloon (with your breath).
2. Drop in a Small aquarium air pump with enough tubing already attached. Leave the cord and tubing hanging out of the bag
3. Attach a small valve (Like a gang valve) to the end of your tubing to act as a regulator.
4. Attach a diffuser of some type (Airstone, glass diffuser, etc etc) and drop it in the tank.
5. Seal the bag around the airpump cord cord with a rubber band
6. Plug in and turn on air pump. Adjust your valve so the only a tiny bit at a time is getting through.

When the bag completely deflates, simply un-do the rubber band and re-inflate. This will last alot longer than you would think. ... Can last a couple days or more as long as your bag doesnt leak 

Now THATS CO2 at bargain basement prices 


Take care,
-Justin
One Mynds Eye


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## hoppycalif (Apr 7, 2005)

For a small tank you can just stick a straw into the water and blow bubbles for a couple of minutes. That got me about 10 ppm when I tried it. It's a good method for someone who just can't find anything to do all day.


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## dekstr (Oct 30, 2007)

If you use dry ice, aren't you essentially trying to build up a CO2 pressurized system at very low temp?

It seems like common sense that most containers aren't designed to handle pressure at very low temps which is why you'll need a specialized container that can do this. But that'll cost you more money.

Normal bottled C02 seems a lot safer, and I guess the extra amount of money you pay for that will make up for as insurance money.
You could try dry ice though! Maybe you're on to something.
LOL @ blowing air through a straw into the water!


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## saint27 (Mar 25, 2006)

Okay so I don't post here very often but I thought I would add. Keep in mind that this is primarly done tongue in cheek and I have no drive to actually try this but here it is.

I have seen dry ice used to flash freeze fresh fruits and veggies from the garden. This is done by smashing up a block of dry ice and mixing it together with the soon to be frozen produce in a large bowl. The bowl is then placed inside a cooler until all the dry ice has gone. If you slow open the cooler you not only have a frozen goodies but also a big box of co2 gas. Co2 gas is heavier then air and will displace the air inside the cooler. If you place an unopened zip bag into the cooler open it in the co2, place the frozen food in and then zip it shut there will only be co2 in the bag and it will prevent freezer burn in the long run.

So if we take that last part and place the dry ice in the cooler. Place and run an air compressor, like this, inside as it begins to sublimate. Then have the compressor fill one of these. Then you can hook it up to your tank with a needle valve and a bubble counter and be ready to go. I have no idea how long it would last but I think it is possible to use dry ice with this menthod. You could even go with something like this if you could find a big enough cooler it place it in.

It is kind of a DIY medium pressursized system. Pretty involved if you ask me and you might have trouble with the compressor freezing up, but if you were dead set on using dry ice this is how I would do it.


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## hoppycalif (Apr 7, 2005)

You could have a machine shop build a heavy steel container, sufficient to hold about 2000 psi pressure, with a large mouth opening, and big enough to hold more than 5 pounds of dry ice. Then you just purchase 5 pounds of dry ice, dump it into the container, close and seal it, and let it sit for a day for the temperature to rise to room temperature. You would then have a heavy steel container of liquid CO2, which you could use a standard regulator, needle valve, etc. on. But, if you do this you do need to have that container hydrostatically pressure checked to be sure it will safely hold 2000 psi.

Don't worry about the cost of all of this. Sure, it will cost about ten times what an ordinary 5 pound CO2 bottle costs, but it will be a new method, and one you DIYed. If you decide to try this, be sure to start a thread here telling us how it worked.


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## Squawkbert (Jan 3, 2007)

Rex once told me that CO2 liquifies at ~700PSI, so a 1000PSI rated tank should be adequate, as should any CG tank commonly available - problem w/ those is getting dry ice into them. I'll stick to liquid CO2 when I go pressurized.


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## hoppycalif (Apr 7, 2005)

If anyone DIY's a container to hold 700 psi, they better make sure it will hold 2000 psi, just to be safe. Dealing with that high a pressure requires very good engineering or a very big safety factor. And, if you overfill a CO2 bottle the pressure will go higher than 700 psi - how high I'm not sure. I hope everyone recognized that I was proposing that project with "tongue in cheek". High pressure containing vessels are definitely not DIY projects.


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## kwc1974 (Jan 4, 2006)

Hoppy

I guess that depends on you level of DIY. I have a pressure vessel designing background and have availability to a pressure vessel shop. But I am here to tell you that the cost difference between DIY & a bought CO2 is very different.

And yes, at least I was aware that your proposed comment was "tongue in cheek"

I think the person that started this thread had very good intentions, and like all DIYers he/she thought outside of the box to solve a problem. It just so happened that this solution had it's own problems. This thread has rambled on into something completely different. Same topic, different path. This thread has turned into a place to theorize various CO2 setups, and I have enjoyed the different ways people have looked at this question.

I would hope that anyone would have enough smarts to not try rig up something that would hold 700-2000psi.

my 2 cents


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## Coconutboy (Apr 13, 2007)

Wow... Im amazed that this thread kept on going.. lol


Anyways...

Paintball equipment=much more worth it.

I realized I had some old paintball equipment... 

the regulators for it actually works wonders..


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## manifresh006 (Jul 20, 2007)

Youtube moment waitin to happen....lmao


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## Coconutboy (Apr 13, 2007)

manifresh006 said:


> Youtube moment waitin to happen....lmao


ha ha, I know right?

Someone'll have a video of their aquarium exploding...

ugh >_<

poor plants...


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## aug4you (Feb 12, 2008)

The diameter of the pipe determines its stength unless you are working with 3/4 or smaller the burst strength is alot lower please see: 
http://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-d_796.html
You are building a bomb so a weaker container will make a smaller explosion so I would start there.
Great idea though I like outside the box thinking


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