[Gasification] Sawdust in Fan TLUD

Thomas Koch tk at tke.dk
Sun Jun 5 10:29:06 CDT 2011

I 100 % agree with Tom - the same relations apply top straw dividers - you can get a farm designed thing that can produce 10 tons pr hour for 1 hours a day for 40.000 € - and you have to pay 250000 € for a chipper that can deliver 7 tons pr hour 24/7/12.

Concerning the physiscs of how to press biomass through holes i disagree with you on the basic mechanisms you describe.
If you measure the ration of Poisson for biomass with increasing moisture content you see an increase from 0,1-0,2 at 5 % dm to 1 at 50 % moist. 
You will also find that biomass with 45 % dm is vitually pumpable at high pressures but biomass at low moisturecontent are not. 
I think what is happening is that the water is leaving the back of the "plug" thus give raise to poissons ratio in the far end of the plug and thus giving force perpendicular to the direction of motion and thus getting stuck.
Thus the reason for water decreasing the friction in biomass in channels is that the water takes up some of the force - the friction biomass-steel is almost independent of moisturecontent 


Fra: gasification-bounces at lists.bioenergylists.org [gasification-bounces at lists.bioenergylists.org] på vegne af stoveslist at gmail.com [stoveslist at gmail.com]
Sendt: 5. juni 2011 15:58
Til: Discussion of biomass pyrolysis and gasification
Emne: Re: [Gasification] Sawdust in Fan TLUD

On Sunday 05 June 2011 14:30:37 Thomas Koch wrote:
> Yes it was a machine that created som puck like lumps out of straw - i
> think you are right - you need something like 2-500 MPa to form a
> stable densification in a very short time - thus if you have rollers
> you will get enourmous dimensions on the axels and bearings . You ca
> reduce this force if you increase the time - but then capacity drops.

I suppose speed is more important in a mobile plant, to keep up with the
harvest you'd need to process in the order of 50 tonnes/hour??

I could see the need for the diameter of the press wheels to be smaller
than the sprocket which leads to chain drives above and below the press
to spread the drive load around the periphery.
> Can you please explain the work of you mate once more for a viking
> tyhat are not familiar with all the abreviations?  (mc wbb ??)

It was very simple trials to squeeze whole (short) logs through a steel
plate with shallow conical holes drilled through it such that their edges
overlapped to produce a knife like series of ridges.

As fresh wood is full of water the forces necessary were too high to force
the wood through and collapse the cell structure. If the wood was dry (
10% moisture content on a Wet Weight Basis) then the wood could be
comminuted by forcing it through the pate and producing a wholle wood
pellet at the same time. It was not pursued as the throughput was low and
it looked like abrasion would be an issue with keeping the die sharp.


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