Home made propane kiln. Temps and Humidity?

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Tints123

ArboristSite Lurker
Joined
Nov 25, 2019
Messages
7
Reaction score
0
Location
NY
Hello all, long time lurker first time poster.

So I've built a home made kiln about 8x10x8 which is heated via direct forced hot air coming from a propane construction heater we have on the other side of the wall.

We have a rather large fan that moves the air 4000cfpm

We are able to easily reach temps of 200 fahrenheit with the relative Humidity in the room at 12%

Using a equilibrium moisture content calculator it shows the rooms EMC is below 5%

After running it for two days the red oak will be completely dry on the outside but when split open still be 30%. The firewood pieces are small resplits no longer than 16 inches about 2 inches thick.

Can someone give me rough ideas on drying times when it comes to kiln like this? Should we eliminate trying to dry Red Oak all together?

Also I know the relative humidity is low at 15 percent but I also know that hot of air holds a ton of moisture. Should I be periodically venting that high heat air off?

We are on a very redneck budget but hope to be able to stack the money we make from this adventure to buy a miniquick kiln or a nyle setup.

Thanks in advance.
 
If it is down to 30 percent after two days I would say run a batch for 3 days and see if that gets it at or below 20 percent MC. Oak is definitely notorious for holding onto it's moisture.

How much volume of wood do you have in there? Also do you know how many gallons of propane it takes per day to operate?
 
We ran a test with about a half of a cord give or take. Two days was about 50 gallons of propane.

We're we are at propane is cheap 100 gallon is only $40 bucks
 
That is an incredible price for propane! Retail here is 1.29

You may want to experiment. After you determine how long it takes to cure 1/2 cord try adding extra wood to see if it cures in the same time or if it takes more time.
 
Takes about 3 months in my green house kiln to get oak 24" splits down to 15%. Most of the other hard wood I burn it is about half that time. I am drying a much higher quantity though. I think the only way you know for sure is trial and error.
 
Mind if I ask your temps and Humidity in your green house. I really need to have a turn around time of about 24-48 hours.

I may end up scrapping red oak all together if it's going to be a pain and focus on ash, maple and cherry.
 
My temps vary just because it is based off the sun. Routinely see them over 120 which is as high as my hanging thermo goes to. I'd have to look but I think the highest I recorded with a different one was 153. I've never measured how humid it is as I know I have plenty of time for it to dry. I vent mine by running a box fan in the door. It runs from 1pm until 6pm daily. There is a noticeable difference once it runs with the humidity in the air. I also get very little condensation on my ceiling.

Oak is the toughest to dry by far.
 
We ran a test with about a half of a cord give or take. Two days was about 50 gallons of propane.
We're we are at propane is cheap 100 gallon is only $40 bucks

The price of propane here is well over $3 a gallon. So using propane would not help us here at all. I can put a steel storage container in a sunny spot and achieve 160 F with no problem, but we have to have sunny weather. During the summer we only need a few weeks to dry wood down to 20% anyway. Right now we are having 35 to 45 F with cloudy skies. With humidity at 60 to 70% getting wood dried out is not easy. However if we get some cool days and freezing nights the humidity drops to 15%. We have had our first snow storm, but not much freezing weather to go with it. This week we have a forecast for 3' of snow maybe a whit Christmas. Thanks
 
I have often wondered about the feasibility of using a wood stove to kiln dry wood, using splitter trash, dirty wood, punk, junk wood, shorts, uglies etc as fuel. I can see that feeding another heater could be a PITA and you'd need to be producing enough unwanted wood to fuel it.

Has anyone given it some serious thought or tried it?
 
This will be our next kiln. Once we figure out how to drop the wet bulb temp we should make piles of cash and then can go into some alternative routes.
 
I have often wondered about the feasibility of using a wood stove to kiln dry wood, using splitter trash, dirty wood, punk, junk wood, shorts, uglies etc as fuel. I can see that feeding another heater could be a PITA and you'd need to be producing enough unwanted wood to fuel it.

Has anyone given it some serious thought or tried it?
Here in the UK firewood producers can get a significant renewables grant called RHI if they heat a kiln with bio fuel (wood). It's very doable on production scales. I believe set ups vary but think most run their kilns for a few days to a week.

Op, if you've space could you air dry/sun sun dry any Oak for 2-4 weeks before finishing on the kiln? You may I suspect be producing 'burritos' if you are putting green wood straight in a
Kiln and longer residence times may be of no help. I can't remember the proper name but it's well known about in timber production, dry the wood too fast initially and yes you get the water that's around the cells/tubes out but the tubes then close at the ends and seal the moisture in. You need to do initial drying more slowly. Go over to h e a r t h .com and go to the firewood forum (the wood shed I think it's called). Do a search for 'poindexter' and 'solar kiln'. The guy is.... Thorough ... Or a nerd ... Obsessive..... But very knowledgeable and helpful. He's in Alaska somewhere I think and runs a series of home built solar kilns to get his wood to something like 14% in a couple of months. He was doing something like 7% but found it made his blaze king smoke. He leaves the poly tunnels half open to limit solar gain for a few weeks and only then does he seal and let them crank. Iirc, he had found (through a lot of research and heavily instrumented experimentation) once he seals high temp is important, ventilation only slightly (hot air holds an awful lot of water and he doesn't want to waste heat to get drier but much cooler and hence more humid air).
 

Latest posts

Back
Top