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Wood is burned underground to exclude oxygen. The volatile constituents are driven off, and the solid carbon and the minerals are fused into a grey solid. This is then sold to villagers for use in their jinkos, with reduced smoke. | Wood is burned underground to exclude oxygen. The volatile constituents are driven off, and the solid carbon and the minerals are fused into a grey solid. This is then sold to villagers for use in their jinkos, with reduced smoke. | ||
Mit einer blähender Population, die Wälder sind leidend von Mehrbedarf | |||
With ballooning populations, the forests are increasingly degraded by the demand for firewood. | With ballooning populations, the forests are increasingly degraded by the demand for firewood. | ||
Collecting [[firewood]] is a major imposition on women. And the toxic fumes were still a problem. | Collecting [[firewood]] is a major imposition on women. And the toxic fumes were still a problem. | ||
Revision as of 06:21, 24 February 2010
Hintergrundinformationen
Traditionelle kochende Methoden in Zentralafrika haben einem Keramiktopf benutzt auf einem Kaminfeuer oder einer Feuerstelle aus Stein.
Mit der Einführung des Eisens, Kochtöpfe aus Metall übliche Praxis wurden. Die Kochtöpfe waren auf Kerne oder Ziegel mit dem Feuer darunter.
Mit der Händler und der Kolonisten reisend aus Europa, gebrauchte Metall Fässer waren abkömmlich. Lokale Schmiede machten Blechverkleidung aus die Metall Fässer. Die Blechverkleidung war geprägt und genutzt in viele Wege. Einfache Herde, oder Jinkos, waren aus der Blechverkleidung machten. Jahrhundertelang diese Herde waren sehr gemein in Kenia. Jedoch, sind sie sehr ineffizient! Die Hitze der Herde ist nicht enthalten in. Das Metall ist auch nicht jahrelang.
Der Bedarf
Die Verbrennung vom Holz produziert vieles Rauch. Dieses Rauch ist schädlich in die kleine begrenzte Hütten in viele kenianische Dörfer. Das Rauch ist giftig beim Einatmen. Dadurch Petrolkoks war in viele Bereiche eingeführt. Holz ist Untergrund gebrannt.
Wood is burned underground to exclude oxygen. The volatile constituents are driven off, and the solid carbon and the minerals are fused into a grey solid. This is then sold to villagers for use in their jinkos, with reduced smoke.
Mit einer blähender Population, die Wälder sind leidend von Mehrbedarf With ballooning populations, the forests are increasingly degraded by the demand for firewood. Collecting firewood is a major imposition on women. And the toxic fumes were still a problem.
Meanwhile, back in Europe, the value of ceramics was known. The classic Victorian fireplace had a ceramic block behind the fire. This provided insulation, reducing heat loss to the back. It also protected the metal from heat, prolonging its life.
Thus a group of aid workers searched for a more efficient jinko. They received funding from local and overseas sources. They applied the European ceramic technology by making a liner. This went through an evolution, but a typical product is shown in Figs 3-5.
The new design
The metal structure is made from old oil drums, flattened, cut using a template, re rolled, and riveted. It consists of two truncated cones, in an “hour glass” configuration. The lower cone has a hinged door.
A ceramic liner is made by local potters. Local clay is formed, using a mold. The bottom is perforated, and it is then fired. This is placed in the upper cone.
The completed unit cost US$15 at first, but after decades of refinement and competition the prices is now $1 to 4.
In use, the coke is placed in the upper chamber and lighted. Three hinged lugs can be folded inwards to support the cooking pot. A regulate air flow comes through the perforations in the liner. After the fire is established, the hinged door can be closed to further regulate air flow.
The lumps of coke cannot fall until they are reduced to fine ash, which then falls through the holes. When it accumulates, it can be removed through the door.
The metal is not exposed to red heat, and so has a reasonable life. There are handles on the sides and also on the door, to allow handling.
Thermodynamic Principles
Engineers might recognise many engineering principles incorporated in the Kenya Ceramic Jinko.
The firebox is insulated on all nonworking surfaces. Radiation and convection from the fire impinges on the walls. The ceramic, being a poor thermal conductor, rises to red heat, radiating according to blackbody theory (flux proportional to absolute temperature to the fourth power). . It stabilizes at an equilibrium temperature, where the energy it radiates inwards, equals the energy it absorbs from the fire.
In other words, the wall looks like a mirror to thermal radiation. With less heat loss, the higher temperature allows more complete combustion.
The holes in the bottom retain the pieces of coke or wood. The carbon content is oxidized to carbon monoxide and carbon dioxide (this releases the heat energy). It burns eventually to a powdery ash (the mineral content of the coke), which then falls through to the lower section. This can be emptied with a scoop.
The air flow is limited by the hole size, and then further by closing the door. Thus the burning rate is limited and controlled by availability of oxygen (as in a slow combustion heater).
The best Western space heaters have an “afterburning chamber”, where new air is introduced to the gases away from the fuel. Thus the CO and other partial products have a second chance of further combustion to CO2, recovering more heat and being less toxic. Is this an opportunity for further improvement of the KCJ?
Performance
The KCJ reduces fuel use by 30-50%, with corresponding reduction in greenhouse gases. The average saving is $60 worth of coke or firewood per year. Women are spared some of the exertion of finding and collecting wood or coke. The fumes are much reduced, improving the confort of families.
In 1995, 700,000 were in use in Kenya, reaching 50% of households. Smaller numbers reached neighboring states.
References
See for more details :
http://www.solutions-site.org/kids/stories/KScat2_sol60.htm
http://www.tve.org/ho/doc.cfm?aid=429
Translated by User: SarahMcClelland