Singhasini Engineers & Consultants

In a chemical Industry, of all the Unit Operations Drying has the widest application and a proper appreciation of the mechanism of drying and the equipment available to resolve a drying problem on an industrial scale is correspondingly important.  Most manufacturing operations, particularly in the chemical and metallurgical fields, entail one or more stages where drying is one form or another is carried out.

 

Drying costs account for a large portion of the processing costs associated with the manufacture of Chemicals, Pharmaceuticals, Dye Stuff’s and other products.  A Filter Press or a Centrifuge is often used to remove as much water or solvent as possible, there by reducing the heat load in the drying process.  Mostly and unfortunately the cake is normally dried in a tray dryer, where the energy consumption is excessively high.  Apart from high energy costs, tray dryers also have high labor cost for loading and unloading of the product.  Product loss due to manual loading and unloading long drying time and generally dirty operating area.

 

SDC ROTARY VACUUM DRYER offers a clean, simple and very effective method of drying wet cake, powder and even the slurry.  The drying is under vacuum and hence it is possible to dry heat sensitive materials at temperatures well below 100(C without suffering the problem associated with very long drying periods.  Valuable organic solvents can also be conveniently condensed and recovered.  Thus production rate can be greatly increased and production bottle necks created by extended drying time can be brought down to minimum and with the result factory floor space can be put to the fullest possible use, minimum labor can be employed in view of the high cost of labor and maximum thermal efficiency can be achieved thus saving the rupees due to high fuel cost and hence over all profitability of an industry can be increased.

 

 

SDC ROTARY VACUUM DRYER consists of stationary cylindrical shell mounted horizontally in which a set of agitator blades mounted on a revolving central shaft stirs the solid being treated.  Heat is supplied by circulation of hot water, steam or dowtherm through a jacket surrounding the shell and, in larger units through the hollow central shaft having hollow paddles.  The agitator in case of blades is either a single discontinuous spiral or a double continuous spiral.  The outer blades are set as closely as possible to the wall without touching.  In case of hollow shaft having hollow paddles each paddle has specially designed scraper blades.  The scraper blades in both type of agitator design scrape the entire internal surface of the dryer and move the material longitudinally and also turns the material continuously so that the same particles do not remain in contact with hot surface for long time.

Heavy duty trunnions and bearings are provided along with reduction gear box and electric motor.  A helical gear pinion arrangement is provided to rotate the agitator by gear and motor at desired RPM.  Agitator is supported on bearings and bearing housing in such a manner that once alignment is done in shop floor during manufacture of the dryer it can never be disturbed later on.  In case of hollow shaft with paddles a provision is made of insert four breaker bars of approximately same length as dryer shell which can be used for size reduction of particles when drying is in progress.  These bars prevent the material from caking and keep the heat transfer surface clean.  It is necessary to use them only when the characteristics of material is such that during certain phase of drying, the material becomes distinctly sticky, but it is not possible to use them when the material becomes doughy or viscous.

 

 

Wet cake or slurry which is to be dried is charged through the feeding point  while agitator is rotating in the clock wise direction.  Vacuum is applied by starting the water ring type vacuum pump and the dryer comes under vacuum through receiver/condensing tank, condenser and dust catcher.  The heating medium is passed in to the jacket and cooling water is let into the condenser and condensing tank/receiver.  Vigorous evaporation of moisture takes place under vacuum, and vapor passes through the bag filter of dust catcher, goes in to condenser where it condenses and collected in the receiver.  Evaporation under high vacuum and low temperature result in faster recovery of maximum solvents.  After some time, sample can be drawn from inside the dryer and tested for its moisture content.  Two or three batches will give accurate idea regarding the exact time required for drying.  When the product gets dried, it is discharged by opening the Discharge Valve .