[Stoves] [Jatropha cake properties]

[Crispin Pemberton-Pigott]

Dear Jonathan

 

You are in for a journey of discovery which I hope you will share because I
think you are on the cutting edge of this J-fuels curve.

 

>The plan is to take J seedcake produced by an electric screw expeller, 

 

If it is a modestly priced Indian press you will have something like 10% oil
in the cake. It is not totally important to know (yet) but others trying to
reproduce the process will want to know.

 

Setting the press correctly is going to make a big difference to the oil
yield. I hope you don't get talked into running it through several times. If
you need to, you have the wrong press or are using it improperly.

 

along with rice hulls that have been chopped up by an electric hammer mill, 

 

I presume you are using something like a Hippo Mill (South Africa - really
well made) or an equivalent. It should have a 'full screen' and tripper bars
(which will wear out) because you are using a pretty small initial size. It
is quite possible that it should NOT be run to flour. That means a large
hole size in the screen. Richard should hopefully have an insight on this
score - about the fibre length and how to mill rice hull. What you want is
binding, not problems, and to pay extra money for milling it from a solution
into a problem.

 

mix them together thoroughly and run this mixture through an electric
pelletizer to produce fuel for use in a TLUD stove for household cooking.



Keep the pellets small (not 50mm) in that case, and no smaller than 7mm.
Probably an 8 to 10mm size would be ideal. Paul A may like to comment. There
is inevitable breaking of the pellets so the final mix in the stove will
actually be smaller than the nominal size.

 
The economic logic is that by first expelling the J oil, you get two fuels:
pellets based on the J seedcake plus the free waste produced by rice
dehulling, and J oil itself, which seems to have a ready market as a
biodiesel, for research, etc. 



Well, I presume you will have explored the possibility that the best
economics are achieved that way. In other words that the oil is worth as
much more than seeds compared with what you are paying to remove it. Never
assume anything. It might be a better business case to use the whole seed
and use the rice hull in a rice hull stove.

 
My request for now concerns any advice you can offer concerning: 
 
A) the mixing of J seedcake and chopped-up rice hulls as pelletized fuel 

 

It can all burn. Ash can be an issue: what is the Cl and K content? They are
fluxes and lower the melting temperature of the ash.


B) combustion of these pellets in a TLUD or other stove for household
cooking 



Make no assumption, no holds barred - you are on a quest which has multiple
answers. Downdraft, sidedraft, updraft, whole seeds, pellets, fuel blends,
the whole scene. For example, you might press the seeds in a low pressure
manual press, expelling whole seeds with a lot of oil still in it. That oil
may have much better characteristics for fuel than oil pressed really hard.
And the resulting 'natural pellet' may outperform anything you can make with
an (expensive) pelletizer.

 

Pelletizing is really finicky with close control of moisture being probably
the main challenge. You should have a back-up plan for what to do 'in the
meantime' as the pelleting operation is worked out.

 

C) whatever else we haven't thought about in designing this process that we
need to consider  



I think you should not be sucked into any 'vortex of the moment' regarding
any particular stove design. TLUD's are a good way to burn some fuels but
most have issues: they are hard or impossible to reload, and they can (not
all) make a great deal of smoke near the end of the burn. Both have
solutions on offer but they are really not a fully developed system. There
are large working examples of TLUD combustion of coal which can be refuelled
continuously but this has not been copied into the current stove offers.

 

Burning oily seeds in a downdraft stove has a big advantage which is that
'yielded oil'  falls directly into the fire instead of away from it so it
can be burned as it comes out of the seeds. That may interest you.

 

If the best business cases all involve getting the oil out first, you are
forced to make a plan to deal with the cake, not seeds. Where the seeds are
not oily (marginal land) you are probably best burning the seeds whole
instead of processing them. You may have to consider mixing dry and oily
seeds to get what you want.


This operation has yet to begin, so we have no performance data to present;
but it's certainly a good moment to seek advice of those who have dealt with
seedcake and/or pelletized fuels.



If you can, get an ultimate analysis of the fuels you will be blending and a
chemical analysis. You will be able to make projections in future. Actually
Frank at Compost lab will probably be a good source of advice on how to
characterise the materials before putting them into the pelletizer. As you
keep notes, you will observe certain characteristics that always give a good
result. That will be valuable to future generations of equipment and
producers still to come.

 

Good luck!

Crispin

 

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