Drying firewood with biomass boiler

[BARNSLEY BOB]

175 kw

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[ash_smith123]

Just had a look, looks good! Is that container insulated?

Do you know what sort of temperatures you get in there?

How does that fan system work?

Sorry for all the questions!

[Duffryn]

Ash, What temperature are you getting inside the kiln I would guess 40 degrees max ? You would be better off putting 100kw in to an insulated container getting the temperature up to 70 degrees and drying it in a Fraction of the time. Consider using Industrial Kingspan insulation on the outside of the container ( the type with a metal outer lining). You will need to increase the size of the vents as well. Hope this helps

[cornish wood burner]

You might consider running the hot water through pipes acting as radiators. We use this system in glasshouses. Possibly a little more expensive to install but the running costs would be much less. This could be in addition to fan unit which could then be smaller.

We also use polyprop pipes set in concrete or sand if you are installing a floor.

[Duffryn]

You might consider running the hot water through pipes acting as radiators. We use this system in glasshouses. Possibly a little more expensive to install but the running costs would be much less. This could be in addition to fan unit which could then be smaller.

We also use polyprop pipes set in concrete or sand if you are installing a floor.

 

The rad system works but you have to have a means of expelling the air once it reaches the optimum relative humidity temperature and then reheating it and repeating the process. Not an impossible task.

[ash_smith123]

Hi Ian! We have now insulated the roof (inside) and have ordered some insulation for the sides (100mm kingspan) so it should hopefully be alot better. We are getting between 60-70 at the top but only 40 at the bottom.

We are hoping the insulation on the sides will bring the heat down as the sides are boiling at the moment!

Right ok, how big do you think the vents need to be? We have tried playing around with the size but its difficult deciding what is best!

[Duffryn]

Hi Ian! We have now insulated the roof (inside) and have ordered some insulation for the sides (100mm kingspan) so it should hopefully be alot better. We are getting between 60-70 at the top but only 40 at the bottom.

We are hoping the insulation on the sides will bring the heat down as the sides are boiling at the moment!

Right ok, how big do you think the vents need to be? We have tried playing around with the size but its difficult deciding what is best!

 

You are loosing a huge amount of heat through the container, OK here goes. Knock your boiler up to its maximum output and make sure that the heat exchangers can handle that output (i.e take 100kw from the boiler). The vent size is critical. The key to drying logs is getting the temperature as high as possible yet still having an airflow that gets rid of the moisture. I have found that the optimum vents size is one that gives an element of back pressure whilst still maintaining a 70 degree temperature at the back of the kiln at floor level. I am afraid that is is a case of trial and error cutting a series of vents until you get it right.

 

Where are your heat exchangers located ? You really need to spread them out to ensure even heat distribution and ensure that there is space between the crates to get optimum airflow

Edited August 28, 2014 by Duffryn

[cornish wood burner]

The rad system works but you have to have a means of expelling the air once it reaches the optimum relative humidity temperature and then reheating it and repeating the process. Not an impossible task.

 

We have the option of that system in the glasshouses to reduce humidity but it is run by computers. Continuous slow air venting or on a timer might work. Alternatively a humidity sensor driving a vent fan

[Duffryn]

We have the option of that system in the glasshouses to reduce humidity but it is run by computers. Continuous slow air venting or on a timer might work. Alternatively a humidity sensor driving a vent fan

 

Yes basically the opposite of what a kiln needs to easy to reverse the logic. The slow airflow on a timer will not work as well as an RH sensor driving a powered vent because the temperature and thus RH will differ over time as the logs heat up.

[cornish wood burner]

Yes basically the opposite of what a kiln needs to easy to reverse the logic. The slow airflow on a timer will not work as well as an RH sensor driving a powered vent because the temperature and thus RH will differ over time as the logs heat up.

 

That what I was thinking but just threw it in as a cheap and simple option. All this is outside my normal field but I find it very interesting as I run large biomass boilers to heat glasshouses. Thanks for the reply.