|The most energy efficient brick kiln|
ENERGY EFFICIENCY OF DIFFERENT KILNS
The energy consumption varies significantly between different types of kilns as is shown in the following table. Overall, one can say that between 11 and 70 tons of coal is needed to fire 100,000 bricks, or every brick (of 3 kg weight) consumes between 110 to 700 grams of coal.
Most brick kilns in Asia are still operating as traditional industries with very limited investments. Batch fired clamp kilns are the most widespread kilns in rural areas and in South Asia the continuous “Bull’s Trench Kiln” (BTK)s are very popular. It has either a moveable chimney or a fixed chimney and is a moving fire kiln i.e the fire moves through the brick stacking in an oval shaped Trench.
VSBK - THE MOST EFFICIENT KILN
In a Vertical Shift Brick Kiln the green bricks are loaded on the top platform and move slowly down to the central firing zone (see picture in Chapter 2): the fresh air coming from below cools the fired bricks before unloading. The kiln works as a counter-current heat exchanger, with heat transfer taking place between the upward moving air (continuous flow) and downward moving bricks (intermittent movement). The maximum temperature is achieved in the middle of the shaft where fire is maintained. At an interval of 2 to 3 hours, a batch of fired bricks is unloaded at the bottom. A batch of bricks consists of four or six layers of bricks.