[Stoves] Different stokes for different folks...

Wed Oct 31 15:07:39 CDT 2012

True Crispin on some points but not all; On one point its just the physics of the process: on the others, I think it has to do with the difference in the different type blends and diameters of briquettes we are both  speaking about.

For our own process we find that;
•  More water is generally better than less water : The water added is recovered usually by gravity and only periodically is it scooped up and poured into the bath of feedstock. The time saved by this  pouring,  as  opposed to hand stuffing is hands down a winner in production. 

•  Vertical stacking requires less pressure overall but in terms of total work being done, it's theoretically the same.  As you note, it requires a longer stroke to compress stacked briquettes  as opposed to a parallel alignment. Work = force x distance and all that… 
To our experience stacking gets a bit more complicated than that however, as stacking of briquettes and dividers in one cylinder  also requires some skill to get the size consistent ( although the variance is far wider with more easily compressed blends). This is due in part to the fact that the wall friction is accumulative,  such that the bottom most briquette in the stack tends to be the least least compressed). It gets more challenging where one is using two or three divider washers to build the stack in any one cylinder especially with the  more  compressible blends. (i.e. a leaf - paper blend will show far greater differences due to the above than say a charcoal-sawdust-paper blend) 

In looking at output of the parallel cylinder press designs,  Kevin Adair,  head of el Fuego del Sol in Haiti,  is reporting a press output of 25 square bqs in 82 seconds ~ 20 per minute in the 25 cylinder press I helped him design last year. (each of these briquettes is 10cm on a side and probably about 5cm tall with what looks like a 30mm dia.  hole in the  center). Each cylinder contains only one briquette and they are aligned cupcake tray-style, side by side, with a sliding tray for the bottom gate (a nifty idea borrowed from a briquette colleague, Sanu Kaji, of FoST Nepal several years ago). I  recon Fuego's Haiti bqs are the typical sg of .3 
which amounts to roughly 1.8kgs a minute.  Thats pretty amazing when you consider only one 2+ ton hand bottle jack powering it all.  

This is a case of different strokes for different folks eh ? 
Cheers, 

Richard 

On Oct 31, 2012, at 4:40 AM, Crispin Pemberton-Pigott wrote:

Dear Richard

I am not disputing the ease with which one can fill and balance the multiple cavities, the same holds for bricks however...

The water has to be added and then removed both of which require work. If you can avoid it, do so. 

The suggestion was to make a sort of pie-shaped briquette. As there is a 'parallelism' involved, it means the pressure in each briquette is additive. If there were 6, it would take 6 times the total pressure of one. 

Putting them in series as a stack would require the same pressure as 1 but make six at a time, using 6 times the stroke distance. It is much cheaper to build for a long stroike than additional pressure. 

As they are in a line, the need to fill thenm equally does not arise. 

Regards
Crispin
-----Original Message-----
From: Legacy Mail <rstanley at legacyfound.org>
Date: Tue, 30 Oct 2012 23:57:48 
To: crispinpigott at gmail.com<crispinpigott at gmail.com>; Discussion of biomass cooking stoves<stoves at lists.bioenergylists.org>
Cc: Stoves<stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] Plans and actions wedgies presses and invite to	Guatemala

Crispin , 
Beg to differ here. liquifying assures far faster filling (you set up the top surface of the cylinders with a flat sheet thibk cupcake mold with slightly raised 25-30mm high) sides. One then just pours the slurry in and  screeds/ squeegees  it over the cylinder tops and voila , near immediate filling . You need to make the cylinder more porous (2---2.5mm dia holes on 1 cm centers), to bleed off the fiber rich water which is recovered to feed stock . Drying time is about the same 4-5 days to ambient humidity under natural drying conditions.
Richard

Sent from my iPhone

On Oct 30, 2012, at 17:55, "Crispin Pemberton-Pigott" <crispinpigott at gmail.com> wrote:

> Dear R and P
> 
> Having faced this problem with our 2-Up brick machine albeit at much higher pressures I found the answer is a robust machine and operator training. After a time the operators just get good at loading the cavities. It was very important to our production process that the mix NOT be a slurry because of the extended drying needed, though it is a workable idea. 
> 
> In Lubumbashi 205 workers using 41 manual machines made 1.3 million bricks in one month (Oct 2010) using 11% moisture clay. The cavities are filled individually but compressed in pairs. I was as impressed as the frogged side of the bricks!
> 
> I concur that the mix is critical but people get very good at the art of batching...
> 
> Regards
> Crispin
> -----Original Message-----
> From: Richard Stanley <rstanley at legacyfound.org>
> Sender: "Stoves" <stoves-bounces at lists.bioenergylists.org>
> Date: Tue, 30 Oct 2012 16:38:29 
> To: Paul Anderson<psanders at ilstu.edu>
> Reply-To: Discussion of biomass cooking stoves
>   <stoves at lists.bioenergylists.org>
> Cc: Stoves and biofuels network<Stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Plans and actions wedgies presses and invite to
>   Guatemala
> 
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