Time to kiln dry firewood down to 20%

[arboriculturist]

There have been many posts on the Forum about kiln drying firewood to x% moisture content (MC) in x days in a shipping container, batch boiler setup.

A large proportion of customers want a quality product i.e. firewood with a MC 20% maximum.

I know there are several of you with commercial kiln setups and I am interested to learn how many days on average it takes to dry average hardwood/softwood down to 20%. (putting all the variables to one side as there are too many)

 

My research has given the following results:

Sweet Chestnut green 61% and some Larch green 65%.

Using 20% MC fuel to fire the boiler - my figure would be approx 3 1/2 days to reach 40% and a further 2 1/2 days to reach 20% MC.

Final MC tested by 'oven dry' method.

This is running with an internal kiln temperature of 70 degrees C.

 

How does this compare with your findings?

[briquette_seller]

Never seen Larch at 65%

[arboriculturist]

Apologies, typo - SB Larch 55%MC

[R5log]

There have been many posts on the Forum about kiln drying firewood to x% moisture content (MC) in x days in a shipping container, batch boiler setup.

A large proportion of customers want a quality product i.e. firewood with a MC 20% maximum.

I know there are several of you with commercial kiln setups and I am interested to learn how many days on average it takes to dry average hardwood/softwood down to 20%. (putting all the variables to one side as there are too many)

 

My research has given the following results:

Sweet Chestnut green 61% and some Larch green 65%.

Using 20% MC fuel to fire the boiler - my figure would be approx 3 1/2 days to reach 40% and a further 2 1/2 days to reach 20% MC.

Final MC tested by 'oven dry' method.

This is running with an internal kiln temperature of 70 degrees C.

 

How does this compare with your findings?

 

 

24 hours a day running?

[arboriculturist]

Yes 24 hours a day running.

[Duffryn]

There have been many posts on the Forum about kiln drying firewood to x% moisture content (MC) in x days in a shipping container, batch boiler setup.

A large proportion of customers want a quality product i.e. firewood with a MC 20% maximum.

I know there are several of you with commercial kiln setups and I am interested to learn how many days on average it takes to dry average hardwood/softwood down to 20%. (putting all the variables to one side as there are too many)

 

My research has given the following results:

Sweet Chestnut green 61% and some Larch green 65%.

Using 20% MC fuel to fire the boiler - my figure would be approx 3 1/2 days to reach 40% and a further 2 1/2 days to reach 20% MC.

Final MC tested by 'oven dry' method.

This is running with an internal kiln temperature of 70 degrees C.

 

How does this compare with your findings?

 

I think you will struggle to get 70 degrees in the kiln using a biomass boiler ( most are designed to run efficiently at 70-75 degrees). I loose 20 degrees in temperature from boiler temperature to kiln temperature and a further 5 degrees at the back of the kiln. On my 10ft kiln I can dry Larch to 20% in 1.5 days, most hardwood typically 3 days, Oak 4-5 days. Log size makes a big difference on drying times. My figures are based on no more than 12inch logs. Hope this helps

[briquette_seller]

whats wrong with air drying?

[Fentiger]

whats wrong with air drying?

 

My thoughts as well. I have to ask about how the environmental impact of drying the wood stacks up?

[arboriculturist]

That's interesting - I am surprised at the short drying times at such low temperatures 50-55 degrees and 45-50 degrees at the far end, with up to 12" logs also. I don't doubt your figures as I expect your container is insulated and or course you have the Rolls Royce of chip boilers.

 

Have you a view on optimum stillage spacing between crates horizontally and vertically for optimum air circulation?

[Duffryn]

That's interesting - I am surprised at the short drying times at such low temperatures 50-55 degrees and 45-50 degrees at the far end, with up to 12" logs also. I don't doubt your figures as I expect your container is insulated and or course you have the Rolls Royce of chip boilers.

 

Have you a view on optimum stillage spacing between crates horizontally and vertically for optimum air circulation?

 

Temperature is a key factor but airflow is also very important, as is the time in which the air in the kiln is changed. Stillage design is critical, mesh all round if possible, loose stacked logs and 6" gap between stillages.