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Johny Walker

kiln dryer

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Hi, I sell kiln dried logs. Some of the logs I have read 4% moisture when cut in half! I have a 34 acre green house and that seems to dry the logs out a treat!

 

http://www.woob-be.co.UK

 

I suggest you buy a more reliable moisture meter. For a meter reading of 4% you would expect it to be torrefied wood not kiln dried.

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It might be worth rewording your website. "Our logs are 0%-20% moisture content" might be an open invite for the more pedantic log buyers to have you over a barrel. :001_smile:

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It might be worth rewording your website. "Our logs are 0%-20% moisture content" might be an open invite for the more pedantic log buyers to have you over a barrel. :001_smile:

 

Do you think their 'wood be' more than 20% moisture content then?

 

:lol:

 

[note: works best when red out in broad Norfolk accent]

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Is it worth having logs that 'dry'? 20% MC seems about right to me as most species will burn well/cleanly. At 1-10% I can imagine it would burn far too quickly. Perhaps useful for a pizza ovens etc but you'd be getting through so much wood in a fireplace/stove I'm not sure its viable.

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I've just built a prototype dehumidifier kiln with about 2 tonnes of split green sycamore in it (45-50% moisture content). I only got it started 48 hours ago but the data is already looking interesting.

 

I designed it so the only heat input is the actual electrical power input coming from the dehumidifier unit (rated at 0.7 kw). Then I made it a closed system, totally airtight, with a recycle of air powered by the dehumidifier fan. Then I insulated it like mad.

 

I really tried to build it to make the air movement all useful, so at least 95% of the air is passing through the stack of logs, instead of around the outside. There is lots of baffles and restrictions to make the air go through.

 

The insulation is supposed to be thick enough that it will eventually operate at close to 35 degrees centigrade once it's warmed up. Its currently gaining about 5-6 degrees every day at the moment and it's already at 22 degrees so I reckon I'll be there in a few days.

 

I'm shooting for 700 kg of water removal to try and get the wood down to around 15% moisture (any drier than this and our boiler gets a bit hyperactive!). It's a slow start as the dehumidifier spent a lot of time in defrost mode while it was dealing with cold air, but it's chugging along now. I extracted 7.5 liters yesterday and 11 liters today. It's rated to extract 58 liters a day in optimum conditions which I'm hoping to get close to.

 

I was really surprised at how well the dehumidifier is at pushing the air through the stack, It's doing a nice steady breeze. Currently going in at 50% eRH and coming out the other end of the kiln at 98% eRH so it's definitely getting the water out!

 

I don't have a clue how long it's going to take to complete the cycle but the cost is so far extrapolated to be 12.6 pence per kg of final dry wood based on the electricity meter and water so far extracted. I'm hoping once it gets up to working temperature that this comes down a bit as right now a lot of the energy is going into raising the temperature of the mass of wood.

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No mate, sorry. Container had a false floor, the floor is full of holes, the heat is blown in and comes through the floor and rises through all the logs and vents out the top drying logs on the way, awesome!

 

ImageUploadedByArbtalk1391202027.254950.jpg.4bff84da544b329469648682b14e3661.jpg

I've just had this beast dropped at my yard to fill to go off for drying. Its a very impresive system.

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I've just built a prototype dehumidifier kiln with about 2 tonnes of split green sycamore in it (45-50% moisture content). I only got it started 48 hours ago but the data is already looking interesting.

 

I designed it so the only heat input is the actual electrical power input coming from the dehumidifier unit (rated at 0.7 kw). Then I made it a closed system, totally airtight, with a recycle of air powered by the dehumidifier fan. Then I insulated it like mad.

 

I really tried to build it to make the air movement all useful, so at least 95% of the air is passing through the stack of logs, instead of around the outside. There is lots of baffles and restrictions to make the air go through.

 

The insulation is supposed to be thick enough that it will eventually operate at close to 35 degrees centigrade once it's warmed up. Its currently gaining about 5-6 degrees every day at the moment and it's already at 22 degrees so I reckon I'll be there in a few days.

 

I'm shooting for 700 kg of water removal to try and get the wood down to around 15% moisture (any drier than this and our boiler gets a bit hyperactive!). It's a slow start as the dehumidifier spent a lot of time in defrost mode while it was dealing with cold air, but it's chugging along now. I extracted 7.5 liters yesterday and 11 liters today. It's rated to extract 58 liters a day in optimum conditions which I'm hoping to get close to.

 

I was really surprised at how well the dehumidifier is at pushing the air through the stack, It's doing a nice steady breeze. Currently going in at 50% eRH and coming out the other end of the kiln at 98% eRH so it's definitely getting the water out!

 

I don't have a clue how long it's going to take to complete the cycle but the cost is so far extrapolated to be 12.6 pence per kg of final dry wood based on the electricity meter and water so far extracted. I'm hoping once it gets up to working temperature that this comes down a bit as right now a lot of the energy is going into raising the temperature of the mass of wood.

 

thats intresting,any pics of set up :001_smile:

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It's a prototype so it's not pretty!

 

I built a load of stillages to hold the wood and set them end to end to get the path of air through the stack:

IMG_1947.jpg.6f8326805977e42d42097ef16f4efd9f.jpg

 

Then I wrapped it in standard builders merchant DPM to create a sausage and put the dehumidifier at one end with it's output entering through a taped on plant pot with it's bottom cut out (it was handy and I was running out of daylight!):

IMG_1950.jpg.2ca18ae7c54d18545fa23d7f7e9523fe.jpg

I created the recycle for the air on top of the stillages using some more dpm and wood spacers so it flows from the far end back to the dehumidifer. I then built a wood cage around the dehumidifier so it would be "inside" the system and sealed the dpm around that. All totally air tight and more Jaffa Tape than I was expecting to use.

 

You might just be able to see that the dpm in the picture above is ballooning out on the side! I'd got the dehumidifier switched on at this point and the positive pressure was making the air flow around the stillages, so I created a load of wooden straps to hold the DPM in against each stillage and force the air back though the wood stack.

 

Then I bought some cheap rockwool insulation from wickes and wrapped it up so now it looks like a brown sausage (I calculated I needed 20cm ish of insulation around the outside to get steady state heat loss at 38 degrees centigrade inside and about zero ambient outside):

IMG_1956.jpg.e2a8c5e3966ad4dd314c1f88ec2abe5b.jpg

I didn't bother insulating the base but I would do for the final design.

 

It's not easy to see, but there is a bucket on the right that the water is pumped into through a plastic tube from the dehumidifier (it has a purge cycle every 6 minutes) and I've placed two sample tubes for the eRH and temperature meters at the start (right in front of the dehumidifier exhaust) and at the end (just before it starts recycling back over the top)

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