Multiple Hearth Furnaces are exclusively used for many
gas and solid reaction processes in extractive metallurgy industries.
Vertically oriented and cylindrically shaped, these furnaces are
refractory lined with a steel shell and comprised with plurality of
horizontal hearths varying from 4 to 14, placed one above the other. The
material which is processed in the furnace is supplied in the uppermost
hearth, then afterwards passed to the lowermost one from which the
finished product is extracted. Used for varied industrial applications,
these versatile devices are used to treat the material of different
sizes. Also, they are vastly demanded because of their ability to
process both, dry as well as the materials having high moisture content.
Construction
Multiple hearth furnaces comprise a steel shell lined with refractory
bricks and refractory lined hearths. Driven by an external drive
mechanism, the material in the furnace is moved by the rabble teeth
supported by rabble arms and attached to a central rotating shaft. These
are able to cope high temperature conditions. The design of these
furnaces assure the contact between solid and gases. The heated air is
recycled to the burner system by a fan for further use as combustion
air. Depending on the way of charging, these furnaces are fabricated as
out-hearths and in-hearths.
Characteristics
Highly flexible multiple hearth furnaces can accept the feed material
having moisture content upto 50%. They are highly capable to process
material of very small sizes. Apart from industrial applications, they
are also applicable for oxidation and reduction processes. Inspite of
very less cost maintenance, they are not affected by the changes to
fluctuations in chemical and physical properties and moisture content of
the feed.
Applications
Also considered as activating furnaces, multiple hearth
furnaces are used for various diversified applications and operations
like:
- Sewage sludge incineration
- Disposition of bio solids
- Carbon activation and regeneration
- Manufacturing of charcoal
- Widely used as oil refinery catalyst, in various roasting of
mineral ores and to remove the uranium from uranium yellow cake
dryers.
- Calcining filter cakes from synthetic MgO processes etc.
- Thermal treatment of ores, minerals, earths and sands.
- Calcination of industrial minerals like magnesite, dolomite,
limestone and clay.
