Eco kiln Technology Improves
Quality
of Brick Production in Malawi
In Malawi in south-eastern Africa, use of bricks in the construction
industry comprises almost up to 90% as the cement and concrete are too
expensive in this country. Owing to the visibly poor state of brick
production in Malawi, the local entrepreneurs have opted for the ‘eco
kiln’ (vertical shaft brick kiln). This endeavour has been led by GIZ
under the technical supervision of TARA, India; with the aim of
imparting training in the construction and operation of the eco kiln to
local partners CCODE.
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For over three decades, TARA has been
transforming the landscape of rural economies across continents, by
creating new opportunities to build and support enterprises. The
technology transfer initiatives look at scalable solutions both
nationally and internationally, especially in the building materials,
renewable energy and waste utilisation sector. The training for this
focuses on local engineers, foremen and labourers in enhancing their
skills in their field of work and teaching them about the quality
standards of the product as it would prove to be a revolutionary
initiation in uplifting the standards of the brick production industry
in Malawi.
Before the eco kiln technology was
introduced the brick production was done locally with no adherence to
the dimensional tolerances. This leads to a variation in the quality of
the bricks which was directly related to the team, their method of
practice and the nature of the raw material used for the purpose. This
variation in the dimension leads to unnecessary usage of cement mortar
to fill up the joints and often to an unequal load distribution pattern
when the structure constructed is deemed serviceable. Such a non-uniform
load distribution has been found to be a prime cause of many structural
collapses all through the history of the construction done by mankind.
The eco kiln is basically a housing setup
for the combustion zones which are located in the central portions
surrounded by refractory bricks laid in refractory mortar so as to
sustain the high temperatures of the burning and processing of raw
bricks into quality products. The eco kiln has vertical shafts of
rectangular or square cross-section. The gap between shaft wall and
outer kiln wall is filled with the insulating materials – broken bricks
and burnt coal ash. The kiln works as a counter-current heat exchanger
with the heat transfer taking place between the air moving up and bricks
moving down.
Green bricks are loaded in batches from the kiln top. Bricks move down
the shaft through brick pre-heating, firing and cooling zones, and
unloaded from the bottom. The combustion of coal takes place in the
middle of the shaft before exiting from the kiln through the shaft or
chimney.
The brick setting in the kiln is kept on
support bars at the bottom of the shaft. Unloading of bricks is done
from bottom of the shaft using a trolley. The trolley is lifted with the
help of screw mechanisms till the iron beams placed on the trolley
touches the bottom of the brick setting and the weight of the bricks is
transferred on to the trolley. The trolley is then lowered batch wise
with the help of support bars. One batch of the fired bricks is usually
lowered after every two-three hours and another batch is replaced on the
top accordingly. The eco-kiln is provided with two chimneys in the shaft
to remove the flue gases from the kiln. A lid is also provided on the
shaft top which is kept closed during normal operations. Flue gases are
directed to pass through the chimney and therefore they do not pollute
the working area of the kiln. ■
Pratyush Malaviya
pmalaviya@devalt.org
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