burning efficiency : coal vs wood pellet

burning efficiency : coal vs wood pellet

PostBy: evilstevie On: Wed Dec 14, 2011 12:29 am

I've noticed in comparing the amount of ash that I get per unit volume of burned coal, vs. % ash from wood pellet stoves, that coal seems to come out on the short end of the stick. I'd throw out a rough estimate that I get 15 pounds of ash per 100 lbs burned coal, vs 1 lb ash per 100 lbs burned wood pellets. Those estimates are very rough, as I don't even own a wood pellet stove, and it's not like I'm out there weighing my coal ash pans on a bathroom scale or anything. I guess what I'm yammering on about is when we go to replace our coal stove - do we replace with another coal burner, or look to wood pellets? I'm well aware that coal has more btu's than wood pellets per unit volume burned, but if coal burns at 80% efficiency, and wood pellets burn at 95% efficiency, that would seem to even the two fuel sources out. Just random thoughts that pop into my head before I go to bed. Any input is appreciated.
evilstevie
 

Re: burning efficiency : coal vs wood pellet

PostBy: McGiever On: Wed Dec 14, 2011 12:47 am

evilstevie wrote:I've noticed in comparing the amount of ash that I get per unit volume of burned coal, vs. % ash from wood pellet stoves, that coal seems to come out on the short end of the stick. I'd throw out a rough estimate that I get 15 pounds of ash per 100 lbs burned coal, vs 1 lb ash per 100 lbs burned wood pellets. Those estimates are very rough, as I don't even own a wood pellet stove, and it's not like I'm out there weighing my coal ash pans on a bathroom scale or anything. I guess what I'm yammering on about is when we go to replace our coal stove - do we replace with another coal burner, or look to wood pellets? I'm well aware that coal has more btu's than wood pellets per unit volume burned, but if coal burns at 80% efficiency, and wood pellets burn at 95% efficiency, that would seem to even the two fuel sources out. Just random thoughts that pop into my head before I go to bed. Any input is appreciated.


Think it is by weight (lbs. or tons) burned...maybe that's what you meant. :)

Ash is not fuel...therefor not a factor for calculating efficiency. Carbon is fuel. ;)
McGiever
 
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Re: burning efficiency : coal vs wood pellet

PostBy: rockwood On: Wed Dec 14, 2011 1:45 am

Wood pellets are more expensive, even from efficiency perspective, compared to coal.
Where I live natural gas is more cost effective than wood pellets.
rockwood
 
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Re: burning efficiency : coal vs wood pellet

PostBy: Short Bus On: Wed Dec 14, 2011 2:04 am

Ash and efficiency are not related, ash is just none combustable material in the coal, the BTU per pound is the energy available, ash just comes along for the ride.
Check out the Fuel Comparison calculator at the top of the page, this compairs fuels and burning efficiencies of various fuels and burners.
Short Bus
 
Stoker Coal Boiler: Kewanee boiler with Anchor stoker
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Re: burning efficiency : coal vs wood pellet

PostBy: Richard S. On: Wed Dec 14, 2011 5:46 am

Short Bus wrote:Ash and efficiency are not related, ash is just none combustable material in the coal, the BTU per pound is the energy available, ash just comes along for the ride.


Exactly, and high ash content doesn't necessarily mean lower BTU's. The red ash fromm places like Superior Coal so many people are fond of is both high ash(comparatively to white ash) and high BTU. Anthracite is going to be about 24 million BTU's per ton on average and in the high range up around 28 million. Pellets will be about 16.5 million per ton.

The efficiency is determined by the the unit you are burning it in and how effectively it uses those BTU's.
Richard S.
 
Stoker Coal Boiler: Van Wert VA1200
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Re: burning efficiency : coal vs wood pellet

PostBy: watkinsdr On: Wed Dec 14, 2011 6:45 am

It's all about BTUs per dollar; and, Excel spreadsheets don't lie... Plug the numbers into the "Fuel Comparison Calculator" above; and, you'll see which fuels are cost effective. There are other intangibles to consider too...

1. The ratio of coal ~24 MBTUs/ton and pellets ~16.5 MBTUs/ton means you'll be slinging ~1.45 times as much product to get the equivalent heat. My 52 year old back gets really tired of slinging 40 lb bags...

2. If pellets get wet 'yer done. If coal gets wet---'ya just burn it. Pellets just don't store very well.

3. Pellet quality is extremely inconsistent. Some pellets are mostly bark; and, bark doesn't burn well producing more cresote than BTUs. Coal quality is typically consistent; however, some coal is better than others---your milage may vary...

4. Coal creates flyash which doesn't burn. The flyash requires constant cleaning; but, causes no fire hazard. Pellets create cresote (again depending on pellet quality) which will require constant burn pot cleaning.

5. Watch out for wood pellet allergies too---pellets are dusty. Coal can be dusty too; but, there are several ways to minimize coal dust.

I almost went with a Harmon PB105 pellet boiler a couple of years ago. I'm glad I didn't... After talking to some people who burned pellets I quickly changed my mind; plus, I would've needed two PB105 boilers to meet my current heat load. My AHS S260 just laughs at my heat load; and, she's one sweet running machine after getting her dialed in. The learning curve was a little steeper than I anticipated; but, well worth the effort now.
watkinsdr
 
Stoker Coal Boiler: AHS S260 Boiler

Re: burning efficiency : coal vs wood pellet

PostBy: Sting On: Wed Dec 14, 2011 1:59 pm

I will agree with point one and two
a portion of three
but you should have stopped there

Lets keep the facts straight and dispersions in check - regardless of fuel

Kind Regards
Sting
watkinsdr wrote:It's all about BTUs per dollar; and, Excel spreadsheets don't lie... Plug the numbers into the "Fuel Comparison Calculator" above; and, you'll see which fuels are cost effective. There are other intangibles to consider too...

1. The ratio of coal ~24 MBTUs/ton and pellets ~16.5 MBTUs/ton means you'll be slinging ~1.45 times as much product to get the equivalent heat. My 52 year old back gets really tired of slinging 40 lb bags...

2. If pellets get wet 'yer done. If coal gets wet---'ya just burn it. Pellets just don't store very well.

3. Pellet quality is extremely inconsistent. Some pellets are mostly bark; and, bark doesn't burn well producing more cresote than BTUs. Coal quality is typically consistent; however, some coal is better than others---your milage may vary...

4. Coal creates flyash which doesn't burn. The flyash requires constant cleaning; but, causes no fire hazard. Pellets create cresote (again depending on pellet quality) which will require constant burn pot cleaning.

5. Watch out for wood pellet allergies too---pellets are dusty. Coal can be dusty too; but, there are several ways to minimize coal dust.

I almost went with a Harmon PB105 pellet boiler a couple of years ago. I'm glad I didn't... After talking to some people who burned pellets I quickly changed my mind; plus, I would've needed two PB105 boilers to meet my current heat load. My AHS S260 just laughs at my heat load; and, she's one sweet running machine after getting her dialed in. The learning curve was a little steeper than I anticipated; but, well worth the effort now.
Sting
 
Other Heating: BurnHAM=NG-gas

Re: burning efficiency : coal vs wood pellet

PostBy: jrn8265 On: Wed Dec 14, 2011 2:25 pm

Sting, my brother in law burns pellets and he and I compare coal and pellets all the time and his observations are exactly the same as stated by Watskinr so what do you mean?

Is your esperience different?

I almost went with a pellet furnace myself and came to the same conclusions as Watskinr 4 years ago!

Using a Koker and the best decision I ever made!!
jrn8265
 
Stove/Furnace Make: Keystoker Koker
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Re: burning efficiency : coal vs wood pellet

PostBy: Sting On: Wed Dec 14, 2011 6:21 pm

I don't burn solid fuel anymore

so I am an idiot :lol:
Sting
 
Other Heating: BurnHAM=NG-gas

Re: burning efficiency : coal vs wood pellet

PostBy: evilstevie On: Wed Dec 14, 2011 7:14 pm

i guess what I was driving at here, is that it seems like all coal is not created equal. And I've seen lots of spreadsheets that lie - I just fixed one today, in fact. You need to know where the constants within the formulas come from, and that they are correct.
It seems to me that the coal that I've been gettng lately generates a lot more ash - and that means that there are more inert components in the coal that are not burning, and are not generating heat for me. I suppose I should probably quantify how much ash I get from a given amount of coal before I complain about it. Seems like I'm burning more rocks than I am coal sometimes. Thanks for all the feedback!
evilstevie
 

Re: burning efficiency : coal vs wood pellet

PostBy: McGiever On: Wed Dec 14, 2011 7:55 pm

Better re-read what was told here again:

Richard S. wrote:
Short Bus wrote:Ash and efficiency are not related, ash is just none combustable material in the coal, the BTU per pound is the energy available, ash just comes along for the ride.


Exactly, and high ash content doesn't necessarily mean lower BTU's. The red ash fromm places like Superior Coal so many people are fond of is both high ash(comparatively to white ash) and high BTU. Anthracite is going to be about 24 million BTU's per ton on average and in the high range up around 28 million. Pellets will be about 16.5 million per ton.

The efficiency is determined by the the unit you are burning it in and how effectively it uses those BTU's.


Nobody gets cheated when there is more or less ash left over...
it never was fuel before or after the combustion.

It all about HEAT, as in BTU's...ashes never contained any energy...you need to understand this. :)
McGiever
 
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Re: burning efficiency : coal vs wood pellet

PostBy: pconn171 On: Mon Dec 19, 2011 12:39 pm

I feel that I have to weigh in here because I keep seeing that this comment about ashes not being important. They are extremely important because if you take two 50 lb bags of coal and one burns off to 5 lbs of ash and the other burns off to 10 lbs of ash - which one is more efficient? Someone's going to jump out there and say that they're both the same, but that's not true. The truth is that we measure the heat output of coal in Btu's/pound so if you have coal that produces more ash - that ash component was there before it was burned, therefore the two bags of coal would contain 2 different amounts of combustible material based on weight. Now you just paid for 5 extra pounds of ash with one option.

On a side note, the real issue here is how many Btu's/pound do each fuel source (pellets and coal) put out on average and that's where the real comparison comes in. I believe the last time I read something on this coal was rougly twice the amount of heat output as pellets for the same weight. This basically says that one may burn more or less effiicient or complete than the other, but it isn't what we're measuring in terms of heat quantity.
pconn171
 
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Re: burning efficiency : coal vs wood pellet

PostBy: titleist1 On: Mon Dec 19, 2011 2:09 pm

oops...deleted...response in wrong thread... :oops:
titleist1
 
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Re: burning efficiency : coal vs wood pellet

PostBy: Rob R. On: Mon Dec 19, 2011 2:39 pm

pconn171 wrote:I keep seeing that this comment about ashes not being important. They are extremely important because if you take two 50 lb bags of coal and one burns off to 5 lbs of ash and the other burns off to 10 lbs of ash - which one is more efficient?


Do both bags have the same price tag? What is your definition of efficiency? If it is lbs of ash produced per million usable btu's, I see your point. If it is usable btu's for the dollar...the low ash coal might not be the best choice if it is priced at a premium.

pconn171 wrote:On a side note, the real issue here is how many Btu's/pound do each fuel source (pellets and coal) put out on average and that's where the real comparison comes in. I believe the last time I read something on this coal was rougly twice the amount of heat output as pellets for the same weight.


There are different ways to calculate the btu content as coal. I don't have a reference handy, but I believe the most common are "Moisture free", "Moisture and ash free", and "As received". I have only reviewed a few anthracite analysis sheets, but the ones I did see had the "As received" btu content at 12,000-12,500 btu's per lb. I wonder if the 8500 btu/lb figure for pellets takes the moisture and ash into account?
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
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Re: burning efficiency : coal vs wood pellet

PostBy: McGiever On: Mon Dec 19, 2011 2:43 pm

pconn171 wrote:I feel that I have to weigh in here because I keep seeing that this comment about ashes not being important. They are extremely important because if you take two 50 lb bags of coal and one burns off to 5 lbs of ash and the other burns off to 10 lbs of ash - which one is more efficient? Someone's going to jump out there and say that they're both the same, but that's not true. The truth is that we measure the heat output of coal in Btu's/pound so if you have coal that produces more ash - that ash component was there before it was burned, therefore the two bags of coal would contain 2 different amounts of combustible material based on weight. Now you just paid for 5 extra pounds of ash with one option.

On a side note, the real issue here is how many Btu's/pound do each fuel source (pellets and coal) put out on average and that's where the real comparison comes in. I believe the last time I read something on this coal was rougly twice the amount of heat output as pellets for the same weight. This basically says that one may burn more or less effiicient or complete than the other, but it isn't what we're measuring in terms of heat quantity.


Well, a least you're comparing coal to coal...the o.p. was stretching coal over to pellets for ashes vs. efficiency.

Go back above in this thread and re-read what member/the Mayor *Richard S* says...his assessment is pretty solid. :)
McGiever
 
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