A small kiln for batch & continuous firing
Practical Action
Table of costs
Item
Quantity/Size
Common (red) bricks
7 000
Locally made insulation
1 000
bricks
Fire bricks (refractories)
250
Fireclay mortar
3 x 50 kg
Cement
4 x 50 kg
Hydrated lime
12 x 50 kg
Brickforce
1 roll
(2.5mm steel mesh wire)
Dambo sand
5 m3
River sand
5 m3
Reinforcing bar
6mm round x 55m
200 litre oil drum
1
(ends removed)
Angle iron 40mm x 40mm x 3mm x 6m
(chimney frame)
Poles (platform, 20 x 5m x Ø120mm
handrail & scaffold)
Timber 12 x 3m planks
(scaffold & platform)
Total materials
Labour
Grand total
Cost (MK)
1 750.00
2 000.00
3 750.00
450.00
400.00
960.00
55.00
250.00
250.00
220.00
250.00
240.00
400.00
480.00
11 455.00
6 900.00
18 355.00
Operation
When used for batch burning, the kiln is loaded with alternate layers of firewood and
limestone. The size of limestone should be determined by local conditions. Slightly larger
stones can be used in the mid section of the kiln where it is hottest. Once limestone at the
top of the kiln is red hot and the charge has subsided, it is possible to top up the kiln with
small limestones to make use of this heat. The kiln is left to burn out and, when it is cool,
quicklime is removed from the bottom loading door and from the fireboxes. In continuous
production, quicklime is removed every thirty minutes or so. At Dedza quicklime is raked to
fall through to the fireboxes. Mixed fuel and limestone is loaded into the top of the kiln every
two or three hours. Though they are expensive, refractory bricks might be considered for the
inner skin when the kiln is used continuously as they will last much longer.
If firewood or charcoal is chosen as a fuel, then lime burners must consider planting trees to
provide for the future and counter environmental damage. Alternatives to firewood have been
tried. Charcoal does work well. Briquettes of waste material soaked in waste oil burn well but
produce unpleasant smoke before they catch fire. Waste oil ‘dripped’ into the inspection holes
also produces a lot of smoke and doesn’t work well. However, a system of spraying oil into the
kiln at mid height could work. Blowing sawdust into the kiln is also possible, but this requires
an electricity supply. Using coal would certainly work.
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