Lime Production: A traditional kiln at Bounoura, Algeria
Practical Action
Mode of operation
Production is carried out on a batch basis with each cycle averaging 15 days. The cycle is as
follows:
3 days for loading
(4 persons required);
3 days for calcining;
4 days for cooling;
3 days for discharging;
1 day for cleaning the kiln.
On average 20 batches are produced per kiln per year. Each batch consists of 22 to 25 tons
of quicklime which is sold in units of 40 kgs or 50 kgs (in powder or crushed). A diesel-
powered hammer mill is used to crush the quicklime to improve the efficiency of hydration. It
is worth noting that little lime is produced during the hot season (summer) due to the high
temperature which reduces the pace of work.
Hydration is normally done manually at the construction site. Because Algeria is a relatively
hot and dry country the risk of premature hydration of the quicklime is reduced.
Comments
The present technique has the following disadvantages:
The burner is of basic design which does not allow any control or adjustment of the
flame. It concentrates the flame on the central part of the kiln, so lime in this part of
the kiln tends to be overburnt and that from the sides underburnt. The temperature
distribution across the kiln is far from uniform.
With improved burner design the present efficiency of the kiln of 32 per cent could
be improved.
The quarrying methods employed are very labour intensive.
The frequent breakdown of the truck holds up production and wastes the labourers'
time.
However, there are also some advantages:
This technique provides both permanent and casual employment opportunities.
The capital cost is low.
Operation of the kiln is very simple.
A fuel efficiency of 32 per cent is relatively high for a batch kiln because the kiln is well-
insulated. With small improvements, such as an improved oil-burner, and by improving airflow
through the kiln using measures such as addition of a chimney, the efficiency could be
improved further.
Light fuel oil is clean burning and leaves no ash or soot residue on the quicklime. Unlike solid
fuel, there is no solid residue from burning the oil so there is no need to have a grate at the
bottom of the kiln. This makes the kiln easier and less costly to construct and simplifies kiln
operation.
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