Fuel Value

[johngerhart]

Is there a reference that shows how to calculate BTU fuel value if you know the chemical make up of a material

 

[TD2K]

Oil or gas?

Gaseous fuel heating values are available in a whole range of sources, the GPSA Engineering data book is just one.

For liquid fuels, many liquids are also listed in the GPSA data book. If you are talking fuels like gasoline, diesel, fuel oil, they are all fairly constant around 18,500 BTU/lb on a gross heating value basis.

 

[johngerhart]

To TD2k , the fuel is solids plastic pellets . I am trying to assess its fuel value versus material cost , thanks

 

[TD2K]

Let me take a look at work, essentially PET is just CH2 in a long chain, should be able to estimate it from the paraffin compounds heating value.

But my guess is it's still going to be around the 18,500 BTU/lb. You basically get into the amount of Carbon and Hydrogen to be burnt and that ratio starts to level off.

 

[TD2K]

Assuming we are talking something like polyethyle which would have a C/H ratio of about 0.5, the heating value (higher) should be about 19,800 BTU/lb.

I charted the heating value of the paraffins against their C/H ratio and then extrapolated to 0.5 (for a very long chain polyethylene moleculate). If this is another type of plastic like styrene, this value might be off.

Did a quick search and gasoline was reported to range from 18,800 BTU/lb to 20,400 BTU/lb, diesel ranged from 19,200 to 20,000 BTU/lb (HHV). LHV were about 1000 BTU/lb less.

I guess my original 18,500 BTU/lb is a little low, anyone got any better ideas how to estimate this?

 

[TD2K]

One more link on plastics heating values I found

http://www.sperecycling.org/PDF Files/0805.PDF

 

[25362]

If we speak of PET (aka polyester) we have to take also into account the oxygen atoms that don't contribute to heating values. The repeating unit, in this case, would be C10 H8 O5. PET is not a polyethylene-type of chemical, rather it's a xylene derivative.


PVC, on the other hand, has Chlorine, and the repeating unit is C2 H3 Cl1. Polystyrene, has as a repeating unit : C8 H8.

Polyurethane's: C10 H11 O3 N1.

Thus, as you see, the combustion calorific values may differ.

Without entering into theoretical calculations of heats of formation, I'd advise to use a simple lab bomb calorimeter with a known heat capacity, and measure its temperature increase upon combustion (by an electrical spark) of a weighed sample in excess air. The liberated energy would be the product of the calorimeter's heat capacity by its temperature rise. Divide the result by the mass of plastic used, and voila, you get its calorific value.

I hope this satisfies the query.

 

[jmw]

If you are dealing with fuel oils then the specific energy calculation may help. This is commonly calculated using fuel blend calculators from the ash content, density and viscosity. Try DNV, Shell Marine Fuels or Exxon Mobil Marine fuels fot their free calculator programs, some of which are dpownloadable.

 

[jsummerfield]

Check with the BTU or Wobbe Index analyzer representatives. They use a spreadsheet that fits your description. I do not have this on this machine but may have it on the platform where I will be after Tuesday 11 November.

John

 

[jmw]

try this site for a calculator:

http://www.processassociates.com/process/property/hc_oil.htm

 

[jmw]

Try this site.... if you can't find the calculator you need here, i'll be surprised.

http://tigger.uic.edu/~mansoori/Thermodynamic.Data.and.Property_html

Try also

http://www.Cheresources.com

 

[jmw]

Got it! Process assoicates of merica ptrovide this calc for you:

http://www.processassociates.com/process/property/hc_gas.htm

 

[jsummerfield]

My Excel program obtained was from Cosa called CALC-IGT. Search for this or just IGT on the web to see if you find it. I can email at john.summerfield@halliburton.com if you still need it. Enter the components below to obtain the details:
ACETYLENE C2H2
AIR
ARGON AR
BENZENE C6H6
BUTYLENE C4H8
CARBON DIOXIDE CO2
CARBON MONOXIDE CO
ETHANE C2H6
ETHYLENE C2H4
HELIUM He
HEXANE C6H14
HYDROGEN H2
HYDROGEN SULFIDE H2S
ISO-BUTANE C4H10
ISO-PENTANE C5H12
METHANE CH4
N-BUTANE C4H10
N-PENTANE C5H12
NEO-PENTANE C5H12
NITROGEN N2
OXYGEN O2
PENTANE C5H10
PROPANE C3H8
PROPYLENE C3H6
TOLUOL C7H8
WATER VAPOR H2O

TOTAL



John