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Science & Technology

Brick bargain

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Jun 15, 1997 | From the print edition
The vertical shaft brick kiln technology reduces energy consumption and breakage of bricks

The vertical shaft brick kiln< (Credit: Development Alternatives)A FUEL-EFFICIENT and superior quality
brick-making technology is now available in India. The first vertical shaft
brick kiln (VSBK) was built in 1996 at
Datia in Madhya Pradesh by a group of
national 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 undergone
many changes and now there are some
50,000 VSBKs operating in China. With
assistance from the Swiss Development
Cooperation, a project was undertaken
in Datia in 1994, to assess the energy
efficiency of the VSBK and to evaluate its
environmental performance.

The construction of the first in
India started on March 14, 1996 under
the guidance of a Chinese team. During
the test run of the kiln, it was found that
the'quality of the bricks produced was
better than those produced in ordinary
kilns. The kiln saved up to 30 to 60 per
cent of energy. The breakage of bricks is
only about two to four per cent and
much less than that observed in VSBKs in
Nepal and Pakistan.

The kiln is made up of one or more
shafts located inside a rectangular brick
structure. The shaft is square or rectangular in shape - usually one metre in
width and one to two metres in length.
The inside surface is a brick wall usually
lined with one layer of firebricks in the
hot firing zone. Clay or rice husk mixed
with clay is used for filling the gap
between the shaft wall and the outer kiln wall.

The shaft is open at both ends.
During continuous operation of the
kiln, layers of dried bricks are loaded
at the top of the shaft and arranged
in a predetermined pattern with gaps
between them. These gaps are then
filled with powdered coal which is
spread uniformly on each layer. The kiln
has unloading tunnels
running across its
width in line with the
shafts. The bricks are
unloaded with the help
of an unloading trolley
which runs on rails
along the length of the
unloading tunnel and
then sorted out and
kept in the respective classified areas.

The unbaked bricks
are carried up to the
loading platform manually or by donkeys.
The main operational
skill lies in positioning
the firing zone in the
middle of the shaft .The draught of air
moving up from the
bottom of the shaft cools the fired bricks
and itself gets heated. The central firing
zone heats up to maximum temperatures of the order of 96'c to 99'c. The
hot gases moving upwards dry and heat
up the unbaked bricks which move
down the shaft. The energy efficiency of
VSBK depends on this intensive use of the
heat generated. The firing temperature
is controlled by the amount of coal
which is spread in the space between
unbaked bricks in each batch.

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