[Stoves] [Jatropha cake properties]

Fri Jan 28 19:37:25 CST 2011

Dear all of the Jatropa briquetting thread,

Ok so it is apparent that one wants to get as much oil out of the cake as possible, first.
If the oil hardens then it might well work in briquettes. As to room for moisture migration for drying and heating and migration of pyrolsis gasses, this is a pretty fine hole you are talking about. More chunky briquettes do not necessarily burn better than less chunky ones...Teh issue is nto so much partical size but partical variation that is the factor that determines porosity. As to the rate of migration,
or permeability, ït becomes a question of the viscosity of the migrating fluid and the pressure driving it thru the medium, larer pores being generally more permeable everythign else held equal. In the case of a briquette, in migrating aromatics and other gasses out to the surface very fine holes or very fine pores can be sustained (think of wood or charcoal for example) . 

The binding is not so much chemical as it is mechanical. We are looking for plastic deformation of the ganglia associated with well pulped /retted/partially decomposed ---or just hippo or other-- hammermilled  agro residues. These fibers are then blended with infilling-also combustible- materials in this case perhaps the jatropa cake.  It is not about pressure so much as it is about infilling material within a randomly arranged 3 d web of pliable fibers.

While one worries about lubricating the web with residual oils, if in fact they dry out, then it can't hurt. 
We made samples with the "foot of oils from a local oil expelling operation in Lilonger in the late 90's and found them unuseable...( I think they were using sunflower  and cotton though). 

The matrix remained soft: At least a month of drying attempted befrore we gave up . More interestingly, the oil itself retarded the potential heat from the biomass...We wound up using it as a quick dipping bath for making the briquettes easier to start. We dipped one flat end to a depth of about 10mm for about 5 seconds...I never actually measured the actual oil consumption by this process.

As to Hippo mills , great but these are to hammer mills what a series "A" Landrover to a Range Rover today. (Probably more rugged and easier to repair but one heck of a lot less efficient). Lots of smaller mills, hundreds of them  in fact are available all over the globe. I have not found some not being made in almost every nation we have ever worked in. The idea is the same however you simply smash the feedstock so violently that its pith is pulverised and its fibers torn apart--but not exactly cut.. thats why it works so well because it gives us instantly,  a collection of  ganglia (2 - 5 mm on average), which really binds up the briquette material well.   

But the hammer mill is capable of generating expremely high impact velocities to take advantage of what is otherwise such a very low mass, low density, hence low  moment-of-inertia material , as flakey stringy agroresidues.. As we are unable to replicate the high tip speeds of a hammer mill by simply -gearing up a  hand cranked rotor---the gearing alone would consume all one's human power-- what we have devised is a forced  tearing device using offset combs and wire brushes called the (TMC thresher -masher-chopper) but its not easly to build and replicate at the village level, or at least outside a fairly good workshop. 

Lee Hite of the Engineers without Borders Organisation (greater Cincinnati-Ohio-  chapter) is however making very good progress on a new type of hand operated stone mill will be very replicable at the village level . He is testing it on challenging bananna tree stalks.  It is made from wood and concrete and it . He/ through his  seems to be about ready to break the surface with it in the coming weeks. I mention this because no matter what fiber you are using it has to really be sheared to expose these fine fibers if you want a tight briquette in the low pressure wet process at least.

As to the emerging discussion about toxsicity, will wait int he wings on this one.. I dont see a lack of jatropa a a cause for not briqueting yet but who knows. In the meantime, biogas anyone ? 

Regards, 

Richard Stanley
www.legacyfound.org

PS., for Frank Shields, I am not clear on what you ar edoing with the spring via a vis briquete testing: Are you using the spring for   testing impact resistance hardmess, or shear,  or tensile strength, or ?? Thanks in advance

On Jan 24, 2011, at 10:54 AM, Frank Shields wrote:

> Dear Crispin, and stovers,
> 
> Other experiments using a Spring Tester
> http://paceperformance.com/i-6120778-heavy-duty-valve-spring-tester-proform-66775.html
> The price is not to bad if we can use the one that only goes to 700 lbs. But I suggest getting the $800+ one that goes to 1000lbs.
> 
> I use the model that goes to 1000 lbs for adobe bricks and now experimenting with biochar and clay mixtures to determine the amount of biochar needed to reduce clay turning into a brick. I'm thinking there may be a way to use the spring tester to test the glueing effect of oil and other materials on biomass fuel bricks. If we can develop a test method we can experiment to plot the strength using increasing amounts of oil (or other materials), change with different temperatures, change in texture, moisture etc. Using calibrated Spring Testers we can compare results between labs and set standards down the road. For the adobe bricks and biochar/clay mixes I use cardboard cylinders (like toilet paper roll) that I had made that are 1.5" diameter and 1.5" tall. Perhaps the spring tester of 1000 lbsF could also be used to -make- the fuel bricks (in addition to testing)? I am sure a screw press goes much higher, but perhaps the spring tester can simulate what Richard Stanley is doing(?)
> 
> I think we also need the surface area so we can calculate in lbs/sq inch. If the screw press makes much larger bricks the spring tester may work if we use it maker smaller diameter bricks(?). And if the screw press purpose is to extract the oil, is the pressed material left the bricks? or is the material broken up again and re-pressed into the fuel bricks of a different shape using a different (less pressure) machine?
> 
> After finding what mixes are needed to make the suitable bricks that will hold up to travel and handling, we need to test the bricks n the stoves. Finally we will get control over the data so we can move forward into making better fuel for specific stoves.
> 
> Frank
> fes
> 
> 
> Crispin Pemberton-Pigott wrote:
> 
>> Dear Christa and Paul and Others contributing to this interesting angle
>> 
>> As you may know I have been making oil presses for quite a long time and looking at quite a lot of seed cake (‘torteau’ in some countries). Cake left alone, when there is a reasonable amount of oil in it, hardens as the oil degrades and as the whole thing dries. Old oil usually it makes a blackish hard, dry scale on things. In other words it is a binder but a slow one. Marula kernel cake is way too valuable as a food to burn (presuming you have taken care not to allow /fusareum roseum/ to grow on the seeds). Sunflower cake is probably like the jatropha cake.
>> 
>> If you have a low(er) pressure press it leaves a fair bit of oil in the cake: often 15%, maybe 10% from a screw press, only 6% after solvent extraction. The higher numbers are enough to become a binder, not a problem, if the post-processing is patient and correct. Obviously the fibressness (fibrosity?) of the mix and the amount of pure powder and all sorts of physical properties affects the result, but in principle, it is not necessarily a negative to have an oily and powdery cake.
>> 
>> Perhaps it needs to be compressed gently and heated to accelerate the breakdown of something, to dry it, to get something to grip. It may need an additive to be the binding fibre, or a chemical that accelerates the conversion of an oil to a dry hard goo holding things together.
>> 
>> It sounds like the best way to burn the J-cake (J-torteau = Jorteau!) is to try combustion systems that do not try to pull air through the fuel. An angled downdraft would to (using a wire grate) as would some side draft approaches though they would require periodic feeding. My bet is downdraft will be best because it removes the ash and provides new fuel at a known/fixed place. In that case there would be no air pulled through the fuel – i.e. it is loaded into a sealed hopper.
>> 
>> If it is sticky/oily, the hopper should taper slightly larger towards the bottom.
>> 
>> If there is an approximate equivalent that is perhaps more accessible we could all try versions of ‘cake burners’ that can deal with, say, rolled oats and crushed wood pellets and sawdust – that sort of thing.
>> 
>> Regards
>> 
>> Crispin
>> 
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