Russell Davis

Dale Hodgins wrote:Fiddling with it and allowing it to drift over to the neighbours is shameful. Stop it if you've already begun. [/b]

Fiddling is unavoidable if you have any learning curve to travel. No fiddling = No progress. To avoid offending your neighbors with the inevitable physical manifestations of transient brain farts and the error the goes with trial-and-error and even a well tuned system's start-up I find that a propane torch weeder fired in my smokey exhaust stream gives a tertiary burn of my smoke while adding to my work output. Using the 55,000BTU torch for system start-up also makes my start-up brief. And for many reasons I usually start-up around sunset.

Jim Fisk wrote:Somehow we made it and the drying wood gave off lots of moisture

I recall it being said that 1 lb propane has about the same heat as 2 lb of air dry wood having 20% moisture. Does anyone know if those to points are true?
And that plus or minus 10% moisture is worth about 15% of the woods heat either way?
Does anyone know if those to points are true?
Seems that it can be a lot easier to force dry wood (to minus about 20 to 30% of the wood's moisture ) than it is to cut split and haul about a third more wood.
Does anyone know if those to points are true?

At about 62 cents a pound for propane and about $1.50 a pound for propane storage a well done wood heating system looks like a bargain to me.

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 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.

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?

Russell Davis wrote:Yesterday I cobbled together my first attempt at a rocket-wood-dust-stove for purposes of mass heating & dry steam generation:
quote]

Version 1.3 tested tonight.
Added a bit of kerosene to the slightly damp saw dust
added two more burn holes in the sawdust charge
added a red hot secondary burn plate raised 1/2" off the top of the 35 g dust charge dum where the plate had a down turned edge to trurn the flame down easier while being aided w by burnulli flow from 50g drum lid & plenum pressure between lid and burn plate
at that level the 50g drum got cherry red and no smoke was visible arround the cowled 50g barrel of water to be boiled.

then there were some problems that reduced the burn rate.

Next B-)

Yesterday I cobbled together my first attempt at a rocket-wood-dust-stove for purposes of mass heating & dry steam generation:
50g steel outer exhaust down flow drum,
30 g steel dust charge drum ot (wood dust compressed in place),
vertical burn hole formed with a 4.5"OD plastic pipe set in a
steel air supply & fire starting tube 7" ID, with rough fit sealed with earth false floor.
Assembly set on water leveled & stabilized ground (puddled foundation earth)

Test fired last night. Burned well initially without the lid on.
With the lid on the lid did not get hot enough to support secondary combustion of the flue gas and so power the pump of flue gasses downward.
I somewhat expected that since there is a 3" gap between the top of the 50g barrel and the open top of the 30g drum.
That space is needed for pipes to superheat and dry the steam (open flow system arising from a pressure cooker on top of the 50g drum lid) .
A bit of hot steel to facilitate the secondary burn appears necessary.
Just to test that I dropped a bit of screen over the top of the saw dust's burn hole - now the dust burnt clean and hot.
But the burn was not given its secondary burn by the lid so that the down flow of flue gas would be pumped ram-jet style.
Draw was not nearly enough to produce the burn rate my intended use required - even with the lid off.

A right-gapped lid on on the inner 30g drum may do the job of starting and concentrating the burn so that the outer rim of the lid and upper edge of the 50g drum will get hot enough to complete the secondary burn powering the down draft pump. Sound a bit like wishful thinking. I might test that tonight.

My compressed-to-form dust charge collapsed at about 2/3 burnt. That may have been prompted by weight of the screen I used.
I suspect that my saw dust also needs to be drier.

I would sure like to get it right for this evening test burn. Any insights or guesses will be greatly appreciated. TIA.

Since the burn face and its tube grows and the dust charge is consumed it seems like it should continually work better until its form remains collapse.
Does anyone know if this is true?