Drying/ Humidification Flashcards
The vapor pressure exerted by the moisture contained in a wet solid depends upon the
Nature of the moisture
Temperature
Nature of the solid
ALL OF THE ABOVE
To remove all the moisture from a wet solid requires exposure to
Perfectly dry air
Milk is dried usually in a
Spray dryer
Equilibrium-moisture curves of different solids
are different
Detergent solution is dried to a powder in a
Spray dryer
If moisture content of a solid on a dry basis is X then the same on wet basis is
X/(X+1)
In paper industry, paper is dried in
Heated cylinder dryer
Moisture content of a substance when at equilibrium with a given partial pressure of the vapor is called
Equilibrium moisture
Calcium ammonium nitrate (fertilizer) is dried in a
Rotary dryer
Moisture in a substance exerting an equilibrium vapor pressure LESS than that of pure liquid at the same temperature is
Bound moisture
Rotary dryer cannot handle
Sticky materials
Moisture in a solid exerting an equilibrium vapor pressure EQUAL to that of the pure liquid at the same temperature is
Unbound moisture
Refractory bricks are usually dried in a
Tunnel dryer
Heat sensitive materials like certain pharmaceuticals and food stuff can be dried
By freeze drying
Moisture contained by a substance in excess of the equilibrium moisture is called
Free moisture
Flights in a rotary dryer are provided to
lift and shower the solids thus exposing it thoroughly to the drying action of the gas
In the constant rate period of the rate of drying curve for batch drying
Surface evaporation of unbound moisture occurs
The falling rate period in the drying of a solid is characterized by
Increasing temperatures both on the surface and within the solids
Dryer widely used in a textile industry is
Festoon dryer
Sticky material can be dried in a
Tray dryer
Drying of a solids involves
Both heat and mass transfer
A solid material shows case hardening properties while drying. Which of the following should be controlled to control the drying process
temperature of the solid
Capacity of a rotary dryer depends on
its rpm
its inclination with ground surface
Air at a particular humidity is heated in a furnace. The new dew point
Increases
The critical moisture content in case if drying indicates
Beginning of falling rate period
A slurry is to be dried to produce flaky solid. Which dryer would you recommend?
Spray dryer
For continuous drying of granular or crystalline material, the dryer used is
Rotary
All moisture in a non-hygroscopic material is … moisture
Unbound
During constant rate period, the rate of drying decreases with
decrease in air temperature
increase air humidity
