In zig-zag kiln technology, green bricks are arranged in a way that forces hot air to travel in a zigzag path. The length of the zigzag air path is about three times that of a straight line air path and this improves the heat transfer from the flue gases to the bricks, making the entire operation more efficient.
FCBTKS VS ZIGZAG KILNS TECHNOLOGY
Obviously, shifting from FCBTK to zigzag kiln technology is an attractive option in terms of energy consumed and emissions reduced. But how do other costs and benefits pan out?
The total cost incurred in retrofitting an FCBTK into a zigzag kiln ranges from Rs 17.5–
38.5 lakh (and depends on the size and condition of the kiln). Table 1: Techno-economic of retrofitting an FCBTK into zigzag brick kilns presents an overview of the gains and costs to be made from the transition. It is clear that the costs incurred can be recovered within a
In case of natural draft zigzag kilns, the same chimney can be used if the daily production is up to 30,000 bricks. However, since we are using a daily production of 44,000 bricks in our calculations, the chimney needs to be rebuilt. This translates into an additional cost of Rs
8–10 lakh and does not require any external source to create a draught, thereby not putting any extra burden on operational costs.
In the induced draft zigzag kiln, erratic power supply sometimes necessitates the use of an external power source to run the fan. This requires around 1.5 litres of diesel per hour. The
average daily cost of diesel comes to around Rs 2,160 (considering the diesel price of Rs 60
per litre). The operation and maintenance cost of the fan and the DG set is over and above this.
The savings on diesel and operation and maintenance cost per kiln during a single brick
the season would be around Rs 250,000, thus the cost incurred in making new chimneys will
be recovered in four seasons.
Timeline of conversion to a natural draft kiln
NATURAL DRAFT KILNS
For retrofitting an FCBTK and converting it into a natural draft kiln, the chimney needs to be rebuild
and for that, the older chimney needs to be dismantled. For dismantling the older chimney, the kiln
owners have two options
1-To carry out the dismantling in such
a way that they can extract the
maximum number of bricks from the
older chimney. This method is time-consuming and requires 10–15 days
2-To cut the chimney at the base and let
it falls like a tree. This saves time (takes
only about 3 days) but reduces the
number of bricks that can be recovered
After this, construction on the new chimney starts and takes around 30 days
For the safety of the workers, the rest of the work begins only once the chimney is completed
The entire process takes around 80–90 days, after which stacking and firing can commence
The rest of the process is similar to that of retrofitting an FCBTK and converting it into an induced
draft brick kiln; the only difference is that natural draft kilns do not need to be equipped with a fan
Zig zag kiln technology design
In a natural draft zigzag kiln technology, bricks are set in five lines in each chamber. A gap of five inches
is maintained between adjacent lines for the flow of air. The width of a column of green bricks
caries with the width of the trench and the production capacity of the kiln. For a trench
width of 33 feet and a daily brick production of 44,000 bricks (and triple zigzag pattern),
two columns of four bricks, two columns of 10 bricks, and 12 columns of six bricks are
In induced draft brick kilns, the size of each chamber is around six feet. Bricks are set in six lines in each chamber; the length of each line is equal to the length of a brick. A three-inch gap is maintained between adjacent lines to help airflow. Green bricks are stacked in columns, the width of which depends on the width of the trench and production capacity.
For a trench width of 33 feet and a daily brick production of 55,000, two columns of four bricks, four columns of six bricks, and 10 columns of seven bricks is recommended.