rotary dryer consists of a cylinder, rotated upon suitable bearings and
usually slightly inclined to the horizontal. The length of the cylinder
may range from 4 to more than 10 times its diameter, which may vary
from less than 0.3 to more than 3 m. Feed solids fed into one end of the
cylinder progress through it by virtue of rotation, head effect, and
slope of the cylinder and discharge as finished product at the other
end. Gases flowing through the cylinder may retard or increase the rate
of solids flow, depending upon whether gas flow is countercurrent or
cocurrent with solids flow.
Rotary dryers have been classified as
direct, indirect-direct, indirect, and special types. The terms refer to
the method of heat transfer, being “direct” when heat is added to or
removed from the solids by direct exchange between flowing gas and
solids and being “indirect” when the heating medium is separated from
physical contact with the solids by a metal wall or tube.
totally direct and totally indirect types will be discussed extensively
here, as it must be recognized that an infinite number of variations
between the two are possible. Their operating characteristics when
performing heat- and mass-transfer operations make them suitable for the
accomplishment of drying, chemical reactions, solvent recovery, thermal
decompositions, mixing, sintering, and agglomeration of solids. The
specific types included are the following:
Direct rotary dryer
(cooler). This is usually a bare metal cylinder, with or without
flights. It is suitable for low- and medium-temperature operations, the
operating temperature being limited primarily by the strength
characteristics of the metal employed in fabrication.
kiln. This is a metal cylinder lined on the interior with insulating
block and/or refractory brick. It is suitable for hightemperature
Indirect steam-tube dryer. This is a bare metal cylinder
provided with one or more rows of metal tubes installed longitudinally
in the shell. It is suitable for operation up to available steam
temperatures or in processes requiring water cooling of the tubes.
rotary calciner. This is a bare metal cylinder surrounded on the
outside by a fired or electrally heated furnace. It is suitable for
operation at medium temperatures up to the maximum which can be
tolerated by the metal wall of the cylinder, usually 650 to 700 K for
carbon steel and 800 to 1025 K for stainless steel.
Roto-Louvre dryer. This is one of the more important special types,
differing from the direct rotary unit in that true through circulation
of gas through the solids bed is provided. Like the direct rotary, it is
suitable for low- and medium-temperature operation.
This picture of rotary dryer for fertilizer
ROTARY DRYER FOR FERTILIZER INFORMASI HARGA ROTARY DRYER :