Ultimate Analysis of Biomass Fuel 1

[macmet]

I would like to get some clarification here. I am working on a project where I received two separate ultimate analysis of a biomass fuel.

The first result has ash, sulfur, carbon, hydrogen, nitrogen and oxygen add up to 100%.

The second result has moisture, ash, sulfur, carbon, hydrogen, nitrogen and oxygen add up to 100%.

The difference being whether moisture is part of it or not. I believe the first one is right. I did a google search and I saw some pages that include moisture and some that don't...

I do not have access to ASTM standards.

 

[mbeychok]

macmet:

I would recommend you use the ultimate analysis that includes the moisture (assuming it is from a valid source).

The ultimate analysis of coal usually (if not always) includes moisture and I see no reason to ignore the moisture in biomass.

If you are going to use the analysis in some stoichiometric combustion calculations, you should definitely include the moisture content.

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

 

[macmet]

The reason I ask is because oxygen is found by subtracting the mass of the other elements from the original sample. If I take the moisture out my oxygen level will change.

Once I size everything up and put an engineering factor on it, it probably won't make much of a difference, but on wetter fuels it will so I'd like to know in the future.

 

[rmw]

Fuels analysis can be on an "as fired" basis which would include the moisture-which might be variable based on a variety of reasons or a "bone dry" basis which would be without the moisture considered. You obviously have both if it is the same fuel sample.

Now, if you ask me why, I am going to have to start clearing out some cob webs. If I remember, I think you need both for your combustion calculations.

Maybe someone who has done combustion calculations more recently than I have can answer that. (it has been almost 30 years for me and I don't think I want to remember why.

rmw

 

[danberry]

You want to use the "bone dry" analysis for combustion calculations as the fuel moisture does not participate in combustion. Naturally, the fuel moisture will need to be added to the flue gas constituents produced by the combustion of the dry fuel.

This being said, the fuel moisture must be evaporated and this will rob heat from the combustion. This lowers flame temperatures and, in practice, the amount of heat that can be recovered; the water vapor is lost up the stack.

The short answer: use the "as fired" analysis; the dry version doesn't tell the whole story.

 

[macmet]

I guess I wasn't completely clear with my question.

I have two results from two different labs. Both tests show "as received" results. This should be the equivalent to the "as-fired" condition.

The calculations themselves are not a problem for me but I'm curious as to which one is right, because I think the oxygen level in the one might be wrong.

I don't have the results in front of me, but to provide an example. In test result #1 I have (ball park numbers only) - 35% C, 30% H, 5% ash, 0% N, 0% S, and therefore 30% oxygen. The results submitted for this test list about 10% moisture separately.

In the second I have 35% C, 30% H, 5% ash, 10% moisture, 0% N, 0% S, and therefore 20% oxygen.

 

[Unotec]

Do you have to do it based on an elemental analysis rather than a component analysis? I am completely unfamiliar with the concept of ultimate fuel analysis. But this is what I see (take it lightly, as I mentioned I am not sure of what you're talking about)
- If what you want is to know how much fuel you have, an elemental analysis like this will include water. Substract it and you'll get the exact amount of fuel. This would be a quantitative analysis of the fuel.
-If you're evaluating heating capacity, or quality of the fuel, you have to include the water, as it will effect the ehating capacity of the fuel.

I think you should define what is your purpose for the analysis, what are you trying to achieve, and then decide if the water will play a factor or not.

as I said, 'ultimate analysis' might imply the purpose and I'm just putting my foot on my mouth with this post

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[danberry]

Oh! So you have two conflicting tests. The obvious solution is to get a third tiebreaker analysis done; but before you do this, why don't you post the two results you have and maybe someone cand figure out what is wrong.

Usually, a fuel analysis is clear enough that you don't have to deduct one species from the sum of the others.

I know your numbers are from memory but 20% O2 seems low for biomass. Pls provide more info.

 

[davefitz]

Its hard to believe that "as recieved " biomass has zero % moisture. 18-50% moisture seems to be the norm with as recieved biomass, unless it has been processed via "torrefaction" . But the treatment of biomass is different than that of coal, due to its widely varying moisture content.

On the other hand , it is easier to estimate the efficiency of a biomass-fired boiler if the fuel is evaluated on a moisture free basis.

See the following link <

http://www.woodgas.com/proximat.htm>

for an example of the way that other countries treat biomass fuels vis a vis ultimate analysis.

 

[rmw]

Biomass fuel can vary depending on the source. I am very familiar with wood. Bark and sawdust as debarked and sawed can vary from 40-55% based solely on whether or not it is raining when the log comes into the mill. Planer shavings, on the other hand, made from the same piece of lumber that produced the sawdust at 50% moisture can be 10% moisture as planed or higher if exposed to a humid atmosphere before burned.

Other biomass fuels have the same considerations that have to be taken into account. As davefitz notes, sorting all of that on an "as fired" basis would be a nightmare, so the basis for comparison is best done on a "bone dry" basis.

rmw

 

[chicopee]

Is it possible that test #1 forgot to mention moisture? As I see it, both tests have identical percentages with exception of moisture.

 

[macmet]

The numbers I gave were not exact. They were close but I didn't have the tests in front of me at the time.

Although, who knows, maybe that is where the discrepancy was.

 

[brlewis]

If any one is interested in MSW waste analysis a good source is the MSW FACTBOOK <

http://www.p2pays.org/ref/03/02064.htm>

It contains an ultimate analysis of MSW.
The first time you run it you may have to tell it to open the file with TBook, it will be in your Factbook folder.
It also shows the HHV of most types of MSW like paper, plastic, wood,and food etc.

 

[ccc8666]

It is possible that in the result of test 1, H and O include those in moisture (H2O). If (H1-H2)*16/(O1-O2)=2, then this is the case.