Lime kiln designs
Practical Action
Examples of oil-fired lime kilns
Below are described a number of kilns from Indonesia with a range of outputs between 6 and
16 tonnes per day. The numbers in brackets in the text refer to components of the kilns
highlighted on respective diagrams. Note that the technical details were taken from actual
kilns built and in production, so those illustrated may not be the only, or even the best,
methods of the type described.
6 Ton per Day Kiln
(Figure 1)
The casing of the kiln is a brick-built body reinforced by metallic rings (1), (4). The wall
thickness is approximately 1 metre on the lower part, and 0.5 metres on the upper. The
inside of the kiln is lined with refractory bricks, which are normally of fired clay, with
magnesite in the burning zone (2). Behind the refractory lining of the cylindrical portion,
lightweight insulating refractory bricks are located. It is recommended that aluminium foil is
placed behind the insulating layer.
Other kiln dimensions (in cm) are marked on the diagram. To obtain sufficient draught for a
naturally ventilated kiln, a chimney should be located on top of the kiln. This is normally
made of sheet metal. The kiln is charged by a chute (6) equipped with a cover, which is
closed during firing to maintain the draught. For 6 ton per day production, l0.5 tons of
limestone are required, or 438 kg per hour. The kiln can be said to be divided into three
zones: the preheating zone, the firing zone, and the cooling zone. In the preheating zone,
which occupies the top 3 metres of the kiln, the limestone is preheated up to around 900°C
by flue gases from the firing zone. The burning zone occupies the next 1.7 metres, where the
temperature reaches 1100°C. Typically the speed of limestone through the kiln is about 0.2
metres per hour, so it takes 8 to 9 hours for the stone to pass through the firing zone. The3
burners (7) are placed at 120 degrees to each other, and operate by the atomization of the
fuel oil with steam. Oil and water for the burners are stored in barrels (8) and (9). The
remaining portion of the kiln is the
cooling zone, where the quicklime
cools naturally before being
discharged.
Discharge is effected through 3
channels (10) by manually operated
scrapers. The quicklime is then taken
away for hydration or temporary
storage. The kiln is equipped with a
steel or timber structure (12) for
access (13), and is erected on a
substantial concrete foundation (11).
The energy consumption of the kiln
has been estimated as 1500 kcal/kg
of quick- lime, or 156 g of a typical
oil per kg of lime. This corresponds to
13 kg of fuel oil per burner per hour.
10 Ton per Day Kiln
(Figure 2)
This particular example of a kiln has a
rectangular cross section of lx2
metres, and is made of concrete (1)
reinforced with iron mats. The
insulation and refractory lining is 0.5
metres thick (2). A housing (3) made
of concrete is situated on top of the
Figure 2: 10 ton per day kiln.
3