Smart questions
Smart answers
Smart people
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Member Login




Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips now!
  • 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!

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

Donate Today!

Do you enjoy these
technical forums?
Donate Today! Click Here

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

sspence (Electrical)
9 Dec 05 14:36
how do I calculate BTU of gas, with composition of CH4, C2H6, CO2, N2, etc.
macmet (Materials)
9 Dec 05 14:55
you have to have more information then that

?
sspence (Electrical)
9 Dec 05 15:17
was looking for how to calculate if I know individual gas compositions and properties of the gas.
in a simple formula, if I have 99.5% CH4, 0.5% CO, what would the btu level be?
Helpful Member!(3)  mbeychok (Chemical)
9 Dec 05 18:08
sspence:

HV of gas = Sum [ (x1) (HV1) + (x2) (HV2) + (x3) (HV3) + ... ]

If your percentages are volume percents or mole percents (which are completely equivalent), then:

HVn = heating value of gas component n, in kJ/m3
x = (percentage/100) of gas component n

If your percentages are weight perecents, then:

HVn = heating value of gas component n, in kJ/kg
x = (percentage/100) of gas component n

If you would rather use USA units than metric units, then:

Use Btu/ft3 and Btu/lb instead of kJ/m3 and kJ/kg

Also, be consistent. If you want the higher (or gross) heating value of the gas, then use the higher (or gross)  heating value of each gas component. If you want the lower (or net) heating value of the gas, then use the lower (or net) heating value of each gas component.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

sspence (Electrical)
9 Dec 05 18:58
Much appreciated!
I was under a mis-impression that some inerts (like CO2) had a negative impact to the Btu (i.e. if CO2=10%, CH4=90%) and drive the BTU to much less than the calculated 910Btu/Lb.
mbeychok (Chemical)
9 Dec 05 19:16
sspence:

Inerts such as carbon dioxide or nitrogen simply have a heating value of zero.  They should be included in the formula I gave you. Hence, they dilute the combustibles and do lower the heating value of the overall gas.

In other words, a gas containing 10% carbon dioxide and 90% methane will indeed have a lower overall heating value than a gas which is 100% methane. I guess you might consider that to be "negative impact", but that terminology really has no objective meaning.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

25362 (Chemical)
19 Dec 05 2:26

Sspence, don't confuse heating values with flame cooling effects which inert diluents may cause.

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!

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close