Introduction of Rotary
Kiln:
The kiln is a cylindrical vessel, inclined slightly to the
horizontal, which is rotated slowly about its axis. The material to
be processed is fed into the upper end of the cylinder. As the kiln
rotates, material gradually moves down towards the lower end, and
may undergo a certain amount of stirring and mixing. Hot gases pass
along the kiln, sometimes in the same direction as the process
material (co-current), but usually in the opposite direction
(counter-current). The hot gases may be generated in an external
furnace, or may be generated by a flame inside the kiln. Such a
flame is projected from a burner-pipe (or "firing pipe") which acts
like a large bunsen burner. The fuel for this may be gas, oil or
pulverized coal.
Construction of Rotary
Kiln:
The basic components of a rotary kiln are the shell, the refractory
lining, support tyres and rollers, drive gear and internal heat
exchangers.
Kiln Shell of Rotary
Kiln:
This is made from rolled mild steel plate, usually between 15 and
30 mm thick, welded to form a cylinder which may be up to 230 m in
length and up to 6 m in diameter. This will be usually situated on
an east/west axis to prevent eddy currents.
Upper limits on diameter are set by the tendency of the shell to
deform under its own weight to an oval cross section, with
consequent flexure during rotation. Length is not necessarily
limited, but it becomes difficult to cope with changes in length on
heating and cooling (typically around 0.1 to 0.5% of the length) if
the kiln is very long.this is cylindrical.