×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

How long would it take to burn 1lb of ti

How long would it take to burn 1lb of ti

How long would it take to burn 1lb of ti

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

RE: How long would it take to burn 1lb of ti

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

RE: How long would it take to burn 1lb of ti

(OP)
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  

RE: How long would it take to burn 1lb of ti

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


_____________________________________
 

RE: How long would it take to burn 1lb of ti

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


_____________________________________
 

RE: How long would it take to burn 1lb of ti

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.
 

RE: How long would it take to burn 1lb of ti

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: Eng-Tips.com Forum Policies

RE: How long would it take to burn 1lb of ti

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.
 

RE: How long would it take to burn 1lb of ti

(OP)
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

RE: How long would it take to burn 1lb of ti

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"?

RE: How long would it take to burn 1lb of ti

(OP)
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 :/

RE: How long would it take to burn 1lb of ti

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?

RE: How long would it take to burn 1lb of ti

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

RE: How long would it take to burn 1lb of ti

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.    

RE: How long would it take to burn 1lb of ti

(OP)
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.

RE: How long would it take to burn 1lb of ti

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

RE: How long would it take to burn 1lb of ti

Titanium is supposedly relatively slow burning when not dispersed.  While there was presumably a lot of total energy in the burn, it would not have been until the last 1/2 minute or so that the steel would have been exposed to anything close to a melting temperature, and the exposure was probably too brief.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: How long would it take to burn 1lb of ti

If you just want to burn a hole in the lid use Thermite.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources