[Gasification] Gasification Digest, Vol 8, Issue 6

[Rolf Uhle]

Hallo Dr. Karve,
thank you for your description.This sounds very convincing.
I shall soon be confronted by a similar problem, too and I am looking for a 
continuous process solution.
We are beginning to produce quality chip from brushwood and we want to sieve 
the fines away and use them for charcoal.

Also in our case, transport of the fines is prohibitive, so I want to make a 
mobile platform.
I have also thought about the  cold char acting as a filter for the tars in 
the destillation fumes so as to enrich the biochar with these, but so far I 
have never found any comments on this.
The filtered gases would go through an engine to be completely burnt.

What do you use as a binder?

best regards
Rolf Uhle
Spain





Am Freitag, 15. April 2011 05:28:48 schrieb Anand Karve:
> Improving the charcoal kiln
> By Dr.A.D.Karve
> President, Appropriate Rural Technology Institute,
> Maninee Apartments, Survey No. 13, Dhayarigaon,
> Pune 411 041
> 
> Because there was a good demand for charcoal from the general public,
> our Institute started looking at the process of charring in order to
> remove the drawbacks in the traditional system. On the one hand, we
> wanted to offer an alternative to wood as the raw source of  charcoal,
> and on the other, we wanted to eliminate, or at least reduce the
> atmospheric pollution that the traditional process leads to.
> The objective of saving wood was achieved by us by using agricultural
> waste as the source of charcoal. One can use all forms of dry
> agricultural waste, such as straw of cereal grains, and also stalks of
> plants like cotton, castor, pigeonpea, soybean, mustard, castor, etc.
> but in order to sustain a commercial operation, the raw material must
> be available throughout the year.  Agricultural waste is however
> available only seasonally, at the time of harvest. This problem was
> solved by us by using sugarcane leaves. India produces sugarcane on
> about 1.5 million hectares. It is harvested continuously, throughout
> the dry part of the year. After harvest, a hectare of sugarcane leaves
> about 10 tons of dry leaves lying in the field. Being highly lignified
> and silicified, they do not have any use for the farmer, and therefore
> the sugarcane leaves, called trash, are burned by the farmer in the
> field itself.  Leaf litter of plantation crops like rubber, mango,
> cashewnut and even the dry leaves from urban avenue trees can be used
> as raw material for this activity.
> In order to tackle the problem of atmospheric pollution, our Institute
> produced two improved models of the charcoal kiln. One of the models
> made use of the oven and retort process, whereas the other model was
> based on the top-lit, updraft gasifier stove that our Institute is
> propagating under the brand name “Agni”.  Agricultural waste is light
> in weight. Transporting such material from a large number of small
> farms to a centrally located kiln is costly. Therefore, both the kilns
> developed by ARTI are portable. It is the kiln that is moved around
> and only the char, representing just 20 to 30% of the original
> biomass, is transported to a central briquetting facility.
> The kiln based on the oven-and-retort principle consists of a
> cylindrical structure (about 150 cm wide and 100 cm tall), made of
> sheet iron. This structure is called the oven. It consists of two
> compartments, one above the other. About 5 kg trash is placed into the
> basal compartment of the oven. Cylindrical metallic containers, called
> retorts, filled with 3 kg trash each, are then placed into the upper
> compartment of the oven. The retorts are about 37.5 cm wide and 60 cm
> tall, and provided with a tightly fitting lid, which has a hole in its
> centre. The retorts are placed upside down into the oven and the
> spaces between the retorts are stuffed with trash. The oven is then
> closed with a sheet metal lid, which has a built-in chimney. The trash
> lying underneath the retorts (in the lower compartment of the oven) is
> ignited to heat the retorts. This action starts the process of
> pyrolysis of the material contained in the retorts. The pyrolysis gas
> generated inside the retorts emerges out of the holes in their lids.
> It too burns, adding to the process heat. The process of pyrolysis is
> over by the time the trash underneath and around the retorts has
> burned out. This process is free of pollution because the pyrolysis
> gases are burned inside the kiln itself and the formation of carbon
> monoxide is also avoided in this process.
>  The kiln designed after a top-lit, updraft gasifier stove, consists
> of a metallic barrel of 200 litre capacity. Its basal part is provided
> with a few air holes, similar to the traditional kiln, but there is
> also a long chimney placed on its top. Air gaps have been provided
> also at the base of the chimney. The barrel is loosely filled with
> biomass and the same is ignited from the top, and the lid with the
> chimney is placed over it. When fire is started in the barrel, the
> draft created by the chimney sucks not only primary air through the
> basal holes, but it also sucks secondary air into the chimney to cause
> complete combustion of the pyrolysis gas and also of carbon monoxide.
> Combustion of these gases takes place inside the tall chimney, so that
> none of the polluting gases enters the atmosphere.
> The char generated in both the kilns is powdery. Therefore, it has to
> be mixed with a binder and extruded into briquettes, which can then be
> used as fuel in a household brazier or in an industrial burner.
> 
> On Thu, Apr 14, 2011 at 11:29 PM, GF <gfwhell at aol.com> wrote:
> > I have always thought that a pile of leaves posses considerable
> > thermal energy, probably equaling the equivalent of 1kw per sw yard if
> > the surface area of each leaf were noted.
> > If this pile of leaves were compressed into pellets for pyrolization,
> > what gasifier design would be needed to extract this potential energy? I
> > have about 50 trees which have an ever increasing molting rate. I clear
> > up this crap and need somewhere sensible to put it. ( sensible comments
> > only please)
> > If all this debris can be gasified, there is surely a market for the
> > needed apparatus.
> >
> > GF
> 
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