[Gasification] Size of blower and tumbler required to dry chip in a solar kiln

Doug Doug.Williams at orcon.net.nz
Sun Feb 2 17:22:29 CST 2014

Hi David,

Not sure where all these exchanges are going, but so some cross posting and private comments are mixed up I think!

On Mon, 03 Feb 2014 06:50:28 +1100
David Coote <dccoote at mira.net> wrote:

> My question is aimed at using a solar kiln to dry chip for use in a 
> biochar system or gasifier/combustion bioenergy system, Doug. This would 
> use material from waste woody biomass streams in regional Australia. 
> Likely to be a mix of eucalypt, conifers, acacias and exotics.

>From a application perspective, anything is possible, but you need to sort your chip if you want the best result, and size does matter for most application of the final charcoal. Drying the chip before making charcoal would speed up the char making, but to include this activity internally to the timber kiln would not be beneficial if the main kiln timber being dried is hardwoods. You can boil water out of pine, but you need steady humidity and temperature for the hardwoods. The chip isn't so fussy as you say, but there is an advantage of adding hot humid air out of the chip drier into the kiln, and because your chip drying activity will require a considerable work space, and you have not even built the kiln at this point, I would suggest you consider sighting the chip tumblers in an enclosed plenum along the outside wall.

 >I don't have a feel for the size of electric drive required for a tumbler 
> handling perhaps several cubic metres hence my question.

You have been advised by Mark on the correct procedure, but "bush" engineering tends to be more the norm in rural Australia from my own experiences. As you were making big on PV generation, and applying this to solar kilns, I was thinking battery stored power. In that situation, I would just use a big engine starter motor with a couple of chain drive reductions on a timer.

>And I suspect a  blower would also be necessary but again I don't have a feel for what 
> size of fan would be suitable for this scale. Hence my query.

Again if you have battery power, using truck radiator fans is an option for the plenum
> If you're interested in drying timber in a solar kiln there's a 
> reasonable amount of literature I can point you at but that's perhaps a 
> bit off-topic for discussion on this list.

I'm not interested in any specific technologies related to drying timber, but come from an age of bush mills and air drying in open sheds. Most people in rural economies share the same problems of how to do things without grid power supplies, and can find it interesting to see how others solve problems, so not that far off topic, unless cross posting confuses the needs of it's readers(:-)

Given that I don't recall anyone pre-drying chips for charcoal production, it would seem a unnecessary step, unless the charcoal making system has this requirement. Have you identified a system to make the char?

Doug Williams,


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