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Fuel Value

Fuel Value

Fuel Value

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

RE: Fuel Value

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.

RE: Fuel Value

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

RE: Fuel Value

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.

RE: Fuel Value

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?

RE: Fuel Value

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.

RE: Fuel Value

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.

RE: Fuel Value

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

RE: Fuel Value

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

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