what is our efficiency?

Has anyone done a combustion test on their boiler to determine burner efficiency, ie CO2/O2 to determine combustion %? I know with flyash and a little soot can reduce thermal efficiency in heat exchanger. We don't condense water on our flues so we cannot get into the mid 80% range. Just wondering... tnx Guy

It been talked about, but not sure if anyone has done it. If you SEARCH on Efficiency....There are also other threads about Efficiency too.

Measuring Combustion Efficiency

A friend of mine had his EFM checked. I seem to have lost the email with the individual values, but I remember that the final efficiency number was 81%. That was with a squeaky clean boiler & stoker.

staybolt wrote:I know with flyash and a little soot can reduce thermal efficiency in heat exchanger.

Keep the heat exchanger brushed out, and use the minimum amount of air necessary to burn the coal. Do not adjust the air purely on the appearance of the ashes, if you try and burn all trace amounts of coal out of the ash you are sending a greater amount of btu's up the chimney.

The AAs and AHSs have an advantage due to their design, they can run over 85%.

It would be interesting to know. But the only stat I really care about is it costs me 1/3 the cost of oil and my home is warm.

staybolt wrote:...8<.. We don't condense water on our flues so we cannot get into the mid 80% range. Just wondering... tnx Guy

The main combustion product of coal is CO2 and CO; carbon dioxide and carbon monoxide respectively (C+O2=CO or CO2). Since coal is mostly all carbon, the level of hydrocarbons (CH) in coal is low. The water vapor content of the combustion exhaust is low (CH+O2= CO2+H2O). You shouldn't see water condnsing and coming out of your chimney if burning anthracite, just heat waves

I own instruments to measure CO2, CO, O2, draft and temperature in the flue gas. This would allow me to calculate combustion efficiency. But other than draft I haven't measured a thing. There's nothing very adjustable on my boiler. And as "coalkirk" says all that really matters is how much I'm saving over oil. The savings are so great I don't really care about the numbers.

What is the blue flame caused by? Isn't that coal gas made of some hydro carbon? Burn the gasses out of it then you get glowing gravel then the ash coating starts. Just thinking of how to make my Kaa2 more efficient that's all. Tnx Guy

staybolt wrote:Just thinking of how to make my Kaa2 more efficient that's all.

Keep it clean and don't run it any hotter than necessary to heat your house.

staybolt wrote:What is the blue flame caused by? Isn't that coal gas made of some hydro carbon? Burn the gasses out of it then you get glowing gravel then the ash coating starts. Just thinking of how to make my Kaa2 more efficient that's all. Tnx Guy

Yup, that's mostly methane - coal gas. There isn't that much compared to the total carbon content and the gasses tend to be smaller chain molecules. Methane (nat gas), Propane and fuel oil are all hydrocarbon (gaseous and liquids) so there's a fair amount of water released as a combustion product.

The term efficiency is an often misused and misunderstood. What is being discussed here is combustion efficiency. How well the fuel is burned, compared to it's theoretical maximum. This has nothing to do with overall efficiency, the efficiency of the appliance burning the fuel. For example I could burn fuel at theoretical efficiency in a fireplace and it wouldn't heat my house very well.

All fuels consist mostly of atomic Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Sulfur (S), minerals (ash) and water (H2O). In fuel combustion the molecular Oxygen (O2) in air react with the combustible components of a fuel. As an example the fuel Carbon (C) reacts with O2 of the air to generate Carbon Dioxide (CO2). If the reaction is incomplete Carbon Monoxide (CO) is produced. The empirically determined formula for Anthracite coal is:


Perfect combustion is simply a mixture of fuel and oxygen, with both being completely consumed in the burning process. The ideal situation would be to provide just enough air in the combustion chamber to insure complete burning of the fuel. This would be true if it were physically possible to bring each atom of fuel in direct contact with the amount of air required to complete its combustion.

If we reduce the amount of oxygen, in a perfect mixture, we would have a fuel-rich condition. However, if we increase the amount of oxygen, in a perfect mixture, we now have excess, which does not contribute to the burning process. Having just the right amount of oxygen (no more, no less) is called the stoichiometric point, or stoichiometric combustion. The stoichiometric point is also called the 100% air point.
Anything above the 100% point is called excess. Excess air just goes out the chimney lower the amount of heat that heats your home.

The excess air is above theoretical is typically, 1.3-1.5 times for mechanical (stoker) firing and 1.5-2.5 times for hand firing.

Use the above Anthracite formula in combination with your amount of excess air to determine where you are operating you coal appliance.
Get out your high school chemistry books and just do it.

If you are up to it, here's the formula you need. Just match up the x's and y's of coal.


In all seriousness it would only be an academic exercise, because you couldn't possible expect your coal, a mineral, to be consistent load to load and the amount of air supplied would vary with the weather. What you can do is understand what changes how much heat goes up your chimney is dependent on excess air amount. This is the only thing you can control. The other is how well your coal appliance extracts the heat out of coal combustion and puts it into your home. This is designed into you coal appliance, and there is nothing you can do about it. That's why it's important to buy the right coal appliance and why for efficiency reasons you don't use your fireplace.

Yanche wrote:I own instruments to measure CO2, CO, O2, draft and temperature in the flue gas. This would allow me to calculate combustion efficiency. But other than draft I haven't measured a thing. There's nothing very adjustable on my boiler. And as "coalkirk" says all that really matters is how much I'm saving over oil. The savings are so great I don't really care about the numbers.

Yanche, I was really worried about you when I read this post.. who kidnapped Yanche?? and what have you done with him? Who's impersonating him on the
forum??

But now I see a much more 'Yanche-like' post, with all the pertinent mathmatical formulas and explainations..

My faith in you is restored..

Just teasing you..

Take care,
Greg L

staybolt wrote:What is the blue flame caused by? Isn't that coal gas made of some hydro carbon? Burn the gasses out of it then you get glowing gravel then the ash coating starts. Just thinking of how to make my Kaa2 more efficient that's all. Tnx Guy

The blue flame is mostly carbon monoxide burning along with a very very small amount of hydrocarbons.

Berlin wrote:

staybolt wrote:What is the blue flame caused by? Isn't that coal gas made of some hydro carbon? Burn the gasses out of it then you get glowing gravel then the ash coating starts. Just thinking of how to make my Kaa2 more efficient that's all. Tnx Guy

The blue flame is mostly carbon monoxide burning along with a very very small amount of hydrocarbons.

... CO on it's way to CO2.
Methane:

CH4+2(02)= (H2CO + H2O)+O2= CO2 + 2(H2O)

Carbon:

C+O2= CO+O = CO2

Edit: didn't mean to post but did in rush. finished later.

Vigpeaburner, I'm not clear on what you're trying to say; The blue flames from anthracite coal are almost entirely from CO, not methane.