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.

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