Brick bargain

A FUEL-EFFICIENT and superior qualitybrick-making technology is now available in India. The first vertical shaftbrick kiln (VSBK) was built in 1996 atDatia in Madhya Pradesh by a group ofnational and international NGOS(Development Alternatives, Vol 7, No 3).

The VSBK is a kiln for firing construction bricks whose technology was first developed in China in 1958. Since then,the VSBK technology has undergonemany changes and now there are some50,000 VSBKs operating in China. Withassistance from the Swiss DevelopmentCooperation, a project was undertakenin Datia in 1994, to assess the energyefficiency of the VSBK and to evaluate itsenvironmental performance.

The construction of the first inIndia started on March 14, 1996 underthe guidance of a Chinese team. Duringthe test run of the kiln, it was found thatthe'quality of the bricks produced wasbetter than those produced in ordinarykilns. The kiln saved up to 30 to 60 percent of energy. The breakage of bricks isonly about two to four per cent andmuch less than that observed in VSBKs inNepal and Pakistan.

The kiln is made up of one or moreshafts located inside a rectangular brickstructure. The shaft is square or rectangular in shape - usually one metre inwidth and one to two metres in length.The inside surface is a brick wall usuallylined with one layer of firebricks in thehot firing zone. Clay or rice husk mixedwith clay is used for filling the gapbetween the shaft wall and the outer kiln wall.

The shaft is open at both ends.During continuous operation of thekiln, layers of dried bricks are loadedat the top of the shaft and arrangedin a predetermined pattern with gapsbetween them. These gaps are thenfilled with powdered coal which isspread uniformly on each layer. The kilnhas unloading tunnelsrunning across itswidth in line with theshafts. The bricks areunloaded with the helpof an unloading trolleywhich runs on railsalong the length of theunloading tunnel andthen sorted out andkept in the respective classified areas.

The unbaked bricksare carried up to theloading platform manually or by donkeys.The main operationalskill lies in positioningthe firing zone in themiddle of the shaft .The draught of airmoving up from thebottom of the shaft cools the fired bricksand itself gets heated. The central firingzone heats up to maximum temperatures of the order of 96'c to 99'c. Thehot gases moving upwards dry and heatup the unbaked bricks which movedown the shaft. The energy efficiency ofVSBK depends on this intensive use of theheat generated. The firing temperatureis controlled by the amount of coalwhich is spread in the space betweenunbaked bricks in each batch.