| Main knowledge bank page |
Recent additions |
Recent changes |
What links here |
Categories |
Category cloud How-to guides | Organisation profiles | Project profiles | |||||||||||||||||||||||||||||||
The better bonfire
In October 1992, IT-Kenya commissioned a one-year research exercise to assess and compare the costs and performances of the various techniques used in firing Upesi stoves. This was carried out by devising an appropriate testing method and applying it to a range of firing techniques to help design a better system. The Upesi stove producers in western Kenya have been using the traditional 'bonfiring' method to fire their stove liners. The potters spend many exhausting hours coaxing their fires to reach required temperatures when the weather is not conducive to firing, for example when it is damp and windy, and orders already overdue depend on successful firing. Bonfires can also cause 50% of the liners to crack, and they consume vast quantities of grass as fuel. The procedure used to test kilns requires 4 thermocouples probes to be placed amongst the liners. They are covered with a thin clay sheaths to protect them from being exposed to the flames which can cause temperature fluctuations. The probes are connected to a data logger which stores the readings at 10-minute intervals. At the end of the firing, the data logger is down-loaded into a computer so that the results can be analysed to show maximum/minimum temperatures, the rate of temperature increase and heat the distribution. Performance of the Better Bonfire Kiln.
The Better Bonfire is a simple kiln which is quick and easy to construct, taking only five days to build using 400 local bricks and local soil as the mortar. The firing chamber is 1.5 m diameter inside and has a retaining wall 0.72m high. It costs approximately KSh 6000, about one tenth of the price of an enclosed kiln. The liners are loaded via the top, and they sit astride 6 walls that form combustion channels where the fuel wood is placed. The liners are stacked higher in the centre than at the outside, forming a dome. They are covered with broken pots, then grass with a thin layer of mud smeared over it. This cover lasts for one firing, and serves the purpose of keeping the heat in. Small holes and cracks which appear in this cover during firing allow some smoke to escape, and create a small chimney effect necessary for combustion. Fires lit in the fire boxes are adjusted to maintain a steady burning rate and to give the desired maximum kiln temperature. Tests have shown that the Better Bonfire saves as much as two thirds to a half of the fuel used in a traditional bonfire and that liner losses are reduced to below 10%. The Wise Women group, who helped to construct the prototypes, are very happy with the better bonfire, and two other women's groups, Keyo and Ichingo, have also built them with supervision from IT staff. A simple manual detailing the method of construction and how to operate the better bonfire is being prepared for other organizations in East Africa who have expressed an interest in using it for traditional pots. For details of this manual, please write to IT-Kisumu, P.O. Box 284, Kisumu, Kenya. [top] [end]Contents: Boiling Point 33: Household Energy Developments in Asia
Categories: Boiling Point 33| Stove Manufacture | |||||||||||||||||||||||||||||||
Page created:
24 August 2007; Last edited:
24 August 2007; Version: 0 | |||||||||||||||||||||||||||||||
Pagename: TheBetterBonfire @HEDON: BYGA | |||||||||||||||||||||||||||||||
