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Russell Davis
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A very modest centrifugal blower got the burn rate up , the close exhaust temp cherry red, exhaust clean, and dry steam generation working for efficient remote heat transfer of high temperature heat, & downdraft pump of clean exhaust working for nearby scavenge of low temp heat.
My eyeball calc of heat effectiveness was that the heat from 20# dry wood chips or dust approximates+-20% the heat from 20#propane of direct application flame.
The efficiency of heat application may bias that very rough observation.
Does anyone know a source of calorie bomb test specs comparing fuel heat contents that would include different woods?
 
Cj Sloane
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Here are two charts showing the weight and available heat content of one cord of firewood of various species, the first sorted by heat value, and the second sorted alphabetically for easy lookup.

I don't think 20lbs of propane = 20 lbs of wood.

From what I read, 20lbs of propane = 1/2 cord (probably 1-2000 lbs depending on the wood and dryness).

We haven't found anything yet with the energy density of fossil fuels. That's why peak oil will hurt so much.
 
Russell Davis
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Cj Verde wrote:
I don't think 20lbs of propane = 20 lbs of wood.


Dry Wood appears to already have about 40% oxygen. Propane 0%.
Air dried cord wood or wood chips have about 20% moisture and when burned produce 7,100 Btu/lb ( page 13 of http://cardi.cornell.edu/cals/devsoc/outreach/cardi/programs/loader.cfm?csModule=security/getfile&PageID=1118149 )
From page 16 I get that propane has 91,333 BTU per GALLON.
Now how many pounds of propane in an at sale temperature gallon of propane? 6? 91,333/6= 15,222 BTU/Lb propane?
I think my application of propane may have been less efficient. But not 50% less efficient. The wood dust fire was much bigger that the propane -> I guess more time for heat loss with my application of propane.
 
Cj Sloane
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It sounds like 20 lbs propane might equal 40 lbs wood best case scenario. Still, pound for pound may not be the best way to compare.
 
Russell Davis
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Cj Verde wrote: Still, pound for pound may not be the best way to compare.


Engineering-wise #/# rationality is good for estimating capacity and handling cost issues - when scaled by density and also rheology (or flow).
Then $/$ rationality is possible without wild guesses.
I buy propane at about $0.60/ lb and wood chips at about $0.04/lb.
My propane hardware cost (tank, regulator, hose burner) cost me about the same on a BTU burn rate as my 3cf wood dust batch burner -IF I price the wood dust burner parts at full retail rather than scrounge cost. I scrounge well on wood dust furnace parts - saved most of the cost by my scrounging.
When my process is out of test mode I think the burner labor management cost will be very close - that is assuming that my work heat * batch time requirents match the wood dust stoves capacity.
 
Cj Sloane
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I think BTU/$ is a better comparison but... it leaves out environmental issues.
Corn @ $2.05/bushel, 80% efficient, gives 200,000 BTU per dollar.
Propane (bulk) @1.25/gal, 92% efficient, gives 66,600 BTU per dollar.
Wood @$125/cord (local costs), 60% efficient, gives 60,480 BTU per dollar.
Electricity @ $0.08/kWh, 100% efficient, gives 42,700 BTU per dollar.
Propane @$11.60/20lb, 92% efficient, gives 34,100 BTU per dollar.


Based on those figures, corn is best in terms of BTUs / dollar but what a waste! Wood is the only renewable one but that's probably only if heating with masonry heaters/ RMH.

Also, those figures must be old!
 
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