4- Burning of Bricks
It imparts strength and hardness to the bricks and make it more durable and dense. Burning of bricks should be carried out properly. if bricks are over burnt they become brittle and break easily, and if they are under burnt they remain soft and weak and are not able to carry the required load.
Burning of the bricks takes place in the temperature range of 900 to 1200℃ at which Alumina and silica fuse with each other thereby imparting strength to the brick.
Burning of bricks can be carried out either in clamps or kilns.
 |
Burning of Bricks
|
1- Clamps-
👉In order to prepare the clamps, a suitable piece of land is selected which is generally trapezoidal in plan.
👉The shorter side is kept in excavation and the longer side is raised by an angle of 15°.
👉A brick wall in mud is constructed along the shorter side and a layer of locally available fuel of thickness 700 mm to 800mm is applied over the area which is further followed by the application of bricks over it in the layers of approximately 5 to 6 courses is further followed by the application of fuel over it. Hence the entire clamp consist of alternate layer of fuel and bricks.
👉The total height of clamp is in the range of 3 to 4 metre and when 1/3rd of the clamp is constructed, fuel in the lower layer is burnt along with the subsequent construction of the clamp in upper layer.
👉When the entire clamp is constructed, it is covered with mud lining in order to avoid the escape of heat through it.
👉Bricks are allowed to burnt in it for the period of 2 to 4 weeks and further followed by the cooling of the bricks for the same duration.
As gradual burning and cooling of the bricks ensured in this case, bricks obtain from the clams are comparatively stronger.
👉More skilled supervision is required in this case and locally available fuel is used due to which this process is comparatively economical.
👉Bricks obtained from the clamp are not regular shape and size.
👉As there is no control over the burning in this case quality of bricks obtained is not uniform.
👉It is the time consuming process.
2- Kilns-
Kilns are large ovens which are used for the burning of bricks. Depending upon the supply of the bricks obtain from this kilns, they are classified into two.
1- Intermittent kilns
2- Continuous kilns
1- Intermittent kilns-
These are the type of kilns in which the supply of the bricks is intermittent as all the operations of loading, burning, cooling and unloading are done one after the another.
These kilns are further classified into two-
A- Up- Draught kiln
B- Drown- Draught kiln
A- Up- Draught kiln-
👉These kilns are rectangular in plan, thick walled structure which are generally provided with two main doors used for the loading and unloading of the bricks.
👉Bricks are arranged in these kilns in the layers of 2-3 courses across the width and 6-8 courses across the height.
👉Space of 2-3 bricks is provided in between the two stacks of brick, which is used for the placing the fuel required for the burning of bricks.
When the fuel is burnt, gases formed rises to the top, thereby causing the burning of the bricks.
👉In order to avoid any interference caused by atmosphere disturbance, temporary roof may be provided over it.
👉Quality of the bricks obtained from these kilns are comparatively better than clamps.
B- Drown Draught kiln-
👉These kilns are same as that of up-draught kiln with the only difference that these are provide with the permanent roof and a central chimney.
👉Floor of this kiln is connected with the roof with the help of vertical flue channels that carries the hot gases formed during the burning of the fuel to the top from where it is further forced in the downward direction through chimney.
👉As more uniform burning of the bricks takes place in this case, quality of bricks obtain is comparatively better than up-draught kiln.
2- Continuous kilns-
These are the type of kilns in which supply of the bricks is ensured to be continuous as all the operations of loading, burning, cooling and unloading are carried out simultaneously.
These kilns are further of three types-
A- Bull trench
B- Hoffman kiln
C- Tunnel kiln
A- Bull trench-
👉These kilns are either rectangular, circular, oval in plan and are constructed in excavation either partially or fully.
👉In these kilns continuous supply of the bricks is ensured by carrying out all the operations of loading, burning, cooling and unloading simultaneously in different sections.
👉It consist of two sets of movable chimney's which are placed one section ahead of the section in which burning is to be carried out which ensures preheating of the bricks placed in the section over which chimney is kept.
B- Hoffman kiln-
👉These kilns are circular in plan, constructed above the ground.
In these kilns, supply of the bricks is ensured to be continuous by carrying out all the operation of the loading, burning, cooling and unloading simultaneously in different chambers by effectively closing and opening different sets of doors, provided in each chamber.
👉The capacity of these kilns is comparatively greater than bull trench kiln.
C- Tunnel kiln-
👉These kilns are in the form of tunnel which may either have straight, rectangular or circular plan.
👉This kilns consists of number of stationary zone in which all the operations of loading, burning, cooling and unloading is carried out simultaneously.
👉Bricks are placed over the trolleys or conveyor belts and passed through different zones in order to obtain the continuous supply of bricks.
.jpg)
0 Comments