GAS-L: Re: Drying Hog Fuel

["Graeme Williams" <graeme@powerlink.co.nz>]

Dear Phil,

I've had a look through the files and unfortunately I don't have any written
record of the drying times at Long Ashton as it was a separate activity at
times when I wasn't there.  Much the same thing at RGL in Londonderry, as
the photographs were taken during the harvest demonstration for the Biomass
Energy Conference in Belfast, February 2000.

I do know that the moisture level drops dramatically within 3 days, but
that's all I remember other than just ambient air without heating still does
a good job.  My suggestion would be to do a trial in just one bunker using a
makeshift air system.  I guess you can obtain flexible 100mm plastic
drainage pipe in coils where you are, and lay a few rows out across the
bunker down one side and connecting into a simple wooden box phlenum at the
front.  Then you can fiddle around and see just what is possible before you
get really serious.

Make sure you do weight samples before you start, then measure hourly until
you get it down to 15% - 20% MC.  As for a fire in the pile, it's not
something I've experienced with dry piles.  Certainly wet chip will start
heating without the air flow and I can remember the piles at Long Ashton
steaming in the rain, 3 hours after they were cut.

Something we were told about drying timber here in New Zealand was that if
you can drop the MC below 10%, then the cells won't take up the water again
if it gets wet.  Whilst that may be true, it won't stop fungus or rot
forming in the long term.

It's not easy to communicate with the guy who actually runs the RGL
installation to get a quick answer about the drying times, but I should be
there again in September and will make a point of obtaining a lot more
specific details to add to the Fluidyne Archive.

There is nothing wrong with black scrubber water, unless it stinks of
phenols.  Carbon dust will turn it black, ash will tinge it purple, but all
you need to do is let it settle in a jar for a few days and see if the water
clears.  You can buy simple pH test strips or rolls, and you want the water
to test out at about 8 - 9 pH.  In our experience, if the water is alkaline
then the tar levels are minimal which causes the water to become acetic, and
I'm sure the local pharmacist (chemist) will have some test papers if you
ask.  Don't forget though, that these are very simple guides and don't
purport to be an analysis of the water.

When you burn the gas, if you are able to measure its temperature with
simple K wire thermocouples, again the tar if present will give you a
reading of over 1100 degrees Celsius.  You will also feel high heat
radiation and see a strong colouring of the flame.  Really clean tar and
dust free gas burns almost invisibly and hardly radiates heat, making it
easy to pass your hand quickly through the flame.  Again, these are simple
DIY tests as guides before you waste money on lab testing, but certainly
accurate enough to indicate what's happening in the gas making.  Please post
your results as you progress as this is an important part of making it all
work, everywhere.

Doug Williams
FLUIDYNE GASIFICATION






: RE: Drying Hog Fuel


> Doug:
>
> Thank you for your reply. Your system would be easy for us to duplicate
> since we already have the concrete bunker silos, would just have to add
the
> duct work. We had considered this method already but had discarded the
idea
> when it was suggested to us we might be creating a very large fire hazard.
> What are your thoughts / experience relating to fuel pile fire hazard?
>
> Secondly, how fast can we dry chips in this manner?  Our proposed fuel
> consumption will be about 1/2 MT of dry fuel per hour, requiring us to dry
> about 1 green tonne per hour. We could use two or three bunkers in
rotation
> with forced air and heat, but how long does it take to dry a pile 8 or 9
> feet in depth? We produce hog fuel at a steady rate of about 45 MT (green)
> per day, 5 days a week. We need enough of a buffer to carry us through
> week-ends and shut-downs.
>
> As to tar in our wash water, it is just an assumption on my part that some
> of this stuff will always get through. Our wash water gets a nice charcoal
> colour to it and it definitely has some fly ash in it. Since we are
running
> a small prototype for testing purposes, and certainly do not know a lot
> about gasification, we likely have technical problems that we are not even
> aware of! We can produce a combustible gas, but as to quality, at this
point
> we really have no idea.
>
> Phil Marsh
> Marsh Bros.
> Ph (250) 569-2795
> Fax (250) 569-2247
>



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