Sawdust powered kiln?

[mobile demensia]

Is there anyone out there using a sawdust powered boiler to dry lumber? I would like to use my mountain of sawdust from my Mobile Dimension to Power a kiln.

[jueston]

I went to a timber framing conference at north house school in grand marais MN, they had a presentation from a commercial sawmill in the area which had been around a long time, they burned all there waste slabs and sawdust for heat for the kilns. I don't remember the name of the outfit, if no one else posts them I will do a little research... that's a huge industrial plant though, not a small operation. but for a smaller investment you could buy a bioburner and burn your saw dust in that using the hot water to heat your kiln....

[mobile demensia]

I found a furnace built buy Hern Iron Works called the Conifer that is designed to burn sawdust with a moisture content of 40%. I would love to use my sawdust to power a kiln, I was hoping that there was someone out there already doing this.

[beenthere]

that is designed to burn sawdust with a moisture content of 40%.

Burning wet sawdust may be one thing, but getting heat from wet sawdust may be entirely different ballgame. Are there any numbers claimed for BTU's of heat from wet sawdust?

[mobile demensia]

Yes there are numbers for btu on there website. This unit was designed in the 1920's and was common for home heating. They have a large range of sizes from home heating(225000 btus per hour to much larger 8400000 btu per hour. For something that was so common years ago there is so little info out there.

[tyb525]

Whatever happened to the BioMizer?

[barbender]

Jueston, was that Hedstrom Lumber?

[Den Socling]

I don't know how big your mountain of dust is but you have to consider the fact that a boiler will be eating away at it 24/7. You also need a feed system that won't burn the mountain down. I've seen a few that used augers. Also, you need to vary the speed of the auger when the MC of the dust changes. I've done that with frequency drives.

[Paul_H]

My dad's house in Squamish was heated with sawdust when he was growing up.I remember playing in the sawdust room in the basement of my Grandparents house.

Found a link to the Conifer.


http://www.hernironworks.com/conifer.html

[GeneWengert-WoodDoc]

If you have two pounds of wood and water, with the dry wood being 1 pound and the water being 1 pound (we would call that 100% MC in the lumber business, but in the heating business it is called 50% MC), the dry wood will produce about 8600 BTUs.  However, it will take 1100 BTUs to evaporate 1 pound of water.  Plus the burner will have heat losses (1000 BTUs assumption).  So, we might get about 6500 BTUs from this two pounds of wet wood. 

If we dried the wood, it would take the same amount of energy to evaporate the water, as above, but if we air dry, then energy is free. 

So, if we air dry to 20% MC, then will will have 1.2 pounds of wood and water and require 220 BTUs for evaporation when the wood is burned.  Now, we will get 8600 - 220 - 1000 BTUs when the wood is burned or 7400 BTU.  So, by drying the original 2 pounds, we get 880 more BTUs of heat (the amount we actually used from the air to dry the fuel), or about 12% more energy.  (If we used heat from a boiler to dry the wood, then we would use up this 880 BTUS.  In other words, dry fuel does not give more heat per pound of dry wood.)

Of course, soaking wet fuel is often hard to light and keep burning without using excess oxygen.  This extra oxygen increases heating losses, which I did not include above.

Also, dry sawdust is very explosive, so it is seldom used as fuel.

If we need energy 24/7, but the mill only runs 5 days a week, then we need storage, as well as the feed that Den mentioned.  Also, many burners do not like varying particle size, so oftentimes the fuel is made more uniform in size.  Bottom line is that wood burning is not a cheap and easy as it seems and also drying dust before burning may not be a good idea.

Hopefully, these comments give you some ideas on what to look for when considering a burner.

[Sonofman]

We did in the commercial mill I used to work in, but that was a 5 mil BF a week operation in eastern NC. We burned the green sawdust and chipped ends and what bark they did not sell to the landscaping market. The dry sawdust and chipped dry wood went to the pulp plant down the road or to floor chicken houses, depending on the price for that week.

We could not burn the dry stuff in the furnace, it was designed for green chips and dust.