How long would it take to burn 1lb of ti

[MightyJ]

Hello all,
I am estimating the time it will take to burn 1lb of commercially pure ti powder in oxygen (outside atmosphere)? Thanks

 

[metengr]

This sounds like a question asked in a materials class versus work-related.

 

[MightyJ]

Yes, it does, though it actually is part of a work-related experiment. Though, it is just an experiment not very important. Should be an easy calculation. I am having trouble just finding values, i think I found the combustion rate of ti being ~0.1g/cm^2.s, I can not seem to find things over the internet. I got around 75 min. for 1lb of ti powder to burn. Let me know if this is near correct since it does seem a little long. Thanks

 

[metengr]

MightyJ
Fair enough.

http://www.sciencedirect.com/scienc...serid=10&md5=dfc4370182937afddd2553d9b1c7b1d2

http://www.specialmetals.chemetall.com/pdf/Titanium_metal_powder_S_8_µm_dry.pdf

 

[arunmrao]

How about trying to burn a few grams of Ti powder experimentally? It will let you know how hazardous handling Ti is.


If you think education is expensive, try Ignorance.
- Andy McIntyre


_____________________________________

 

[metengr]

Sorry;
Forgot to include this publication from Special Metals that goes with my response to the OP;

http://www.specialmetals.chemetall.com/pdf/6F3991AED55D7B37C12571650071C2D5_3.pdf

You can perform the calculation based on density and combustion rate.

 

[arunmrao]

Will surface area not contribute to combustion rate? Also any aid like free air supply will be some other factors.


If you think education is expensive, try Ignorance.
- Andy McIntyre


_____________________________________

 

[metengr]

Good Evening arunmrao;
Yes, particle size plays a significant role and the two documents from Special Metals above highlight this fact and provide very specific test requirements for determination of combustion rate using a standard practice.

 

[IRstuff]

Time for most things is related to how the process is constructed. Given that your burn rate value is expressed per unit area, then your time is solely dictated by what you assumed the total area to be, and how big your powder particles are.

Just for giggles, say your 1 lb of powder was spread out over 1 ft^2 area, which would make a layer about 1.5 mm thick. Since that works out to be about 0.5 gm/cm^2, it should take about 1 second.

TTFN

FAQ731-376

 

[Wrenchbender]

I know enough about thermochemistry to be dangerous (no pun), but I think you have to define more variables than the ones given. Like any propellant, the rate of reaction depends on exposed surface area, temperature, and exponentially on pressure. Ignition source, packing density and bulk geometry are also factors. As an order of mag guesstimate, I think a range between 1 and 10 seconds seems reasonable at 1 atmosphere. Maybe the guys in the chemical forum can help or someone smart in chemical kinetics.

 

[MightyJ]

Thanks for responces,
I'm actually calculating after the experiment took place, so I didnt perform the experiment and do not have any of the powder. The only information I have is, "1lb. of commercially pure ti powder was mound up (cone shape) onto a Sn lid (from a drum) outside in a field and was ignited with a blow torch". I also have one picture of the set-up before the experiment. The reason I am calculating this is to determine if the result they got (~3 minutes) was correct. I am suspecting maybe the titanium oxidized and only the surface of this cone shaped mound was actually ignited. So here I am to experiment since I have no other information.

I found the density of ti to be 4.5g/cm^2. Now with powder, I assume it is ~50% dense and, therefore, the ti powder would have a density of 2.25g/cm^2?
I calculated the volume of the cone to be =~226.2. assuming the radius=~6cm height=~6cm (approximated from the picture taken before the experiment).
If my assumption is correct, I would guess only 1mm of the surface of the cone ignited so I end up with 160cm^2. I get ~5min. for this amount to burn. So I figure something did not go well since they got 3min.
I also figure the experiment did not go well because titanium's melting point is ~1668 °C and Sn is ~232°C, so titanium should melt right through the Sn lid, which it did not. Thanks again for the help so far

 

[Compositepro]

Where did you find a tin drum? You do indeed have a lot to learn. It would be best if you could find someone you work with discuss your questions. Ask yourself some questions. How would particle size affect things? Shape of the pile? Air velocity? Scattering of powder due to air velocity?

What if your question were "how long does it take to burn one pound of gasoline"?

 

[IRstuff]

Is this for school?

TTFN

FAQ731-376

 

[MightyJ]

I did not find a tin drum and wouldnt know who did. In my previous post, I listed all the information I was given. So again I did not perform the experiment.
And yes, I believe the particle size would definetly affect the rate, as would the air velocity, density, how intensly the torch was used to ignite the powder and maybe even where on the 'cone shaped mound' it was ignited..ect, all which I do not know.

All I would like to accomplish is a ball park figure given what I have. So unless these factors could affect the result to range from lets say ~3 min to ~75min then I guess I couldnt even come up with a resonable range to rule out the ~3min result they obtained. And I guess your telling me that?
Maybe this question is just too difficult, I wish I had some powder laying around :/

 

[IRstuff]

Titanium burns on its own, once it's started.

TTFN

FAQ731-376

 

[Compositepro]

By the way, drums are made from steel. Based on all the information available I would estimate that it takes 3 minutes to burn 1 pound of titanium. Why do you think differently?

 

[EdStainless]

If the powder is mounded and you are in air I think that a minute or two sounds right. I used to have to deal with fires of rare earth alloys. Heat and oxygen transfer end up limiting combustion.
If you blew the powder into a cloud and provided proper ignition the time would be more like 0.1 sec. You could blow a building up this way.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[unclesyd]

I was composing a reply with exactly the same concerns as posted EdStainless.
Though not directly involved we had 3 explosions while working with powdered Ti while doing pilot plant work on using Ti to photocatalytically decompose NOx. I don't have the pilot plant data on the physical parameters but do know that the powder was the finest that was available at the time. There was an extremely powerful UV lamp and air involved. The first explosion was relatively mild, only destroyed the reactor, a small horizontal kiln. The second was the big one that took out the small reactor building. I assume the third one was just to prove it would blow up.

We had another incident with Ti where a solid 3" x 5/16" thick disk was just starting to be heated in a vacuum when O2 enriched air was accidently introduced into the chamber. This explosion essentially took out the whole room along with a 8" thick brick tile wall.

I learned long ago that fine metal powders have no place in conditions where heat and air are involved except under carefully controlled condition. This holds true when involving fine powders in reactions.

Anecdotal:
Pilot plant operators were running the PP when the first explosion happened, evidently two PHD's had taken over when the second explosion happened. The operators in the PP said 10 minutes after the explosion the PHD's were wearing coveralls.

 

[MightyJ]

I see, knowing that 1lb of ti could burn in 3 min is helpful, thanks for the help. But now I wonder why it did not burn through the drum. Even if it was steel.

 

[Compositepro]

Perhaps because there was titanium powder between the drum lid and the burning titanium?