A small kiln for batch & continuous firing
Practical Action
Design
The Dedza kiln was designed to test a more efficient and environmentally benign option for
small-scale lime burners. The kiln has been fired with softwood, charcoal, briquettes of waste
material, and combinations of these fuels. The kiln is relatively low-cost and easy to operate.
Because it can also be used as a continuous kiln, it has the potential for lime burners to
expand their operations. It is an intermediate stage between traditional production and
relatively capital intensive technology. Such a kiln could represent a step away from seasonal
lime burning towards a more full-time approach which does not, however, need a big
investment or major changes in operating practice.
The kiln is ‘tall and slim’ to reduce heat losses from the top. It is insulated to reduce heat
losses from the sides. Although a kiln with a round section would be more energy efficient,
this kiln is square because it is easier to build and to load when burning wood. Construction is
simple and uses inexpensive local materials; built using mainly common bricks and as little
cement as possible. Even though using these materials and this design, it does require a cash
outlay, whereas a traditional kiln does not. Nevertheless, the design described was developed
to minimise materials costs. An oil drum is used as a chimney to increase draught and take
smoke away from the loading area.
Design Considerations
Construction materials
• Foundation
Well burned bricks laid in mortar, 3:1 (river sand: hydrated lime).
• Fireboxes, firebars
Refractory bricks (fire bricks) laid with fireclay mortar.
• Outer skin, buttresses and inner skin
Common bricks laid in mud mortar, 2:1 (dambo sand: river sand)
• Reinforced ring beams and capping slab
Reinforced concrete beams as shown on drawing. Capping slab 1 brick thick. Mortar for
beams and slab, 4:2:1 (20 mm aggregate: sand: cement).
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