Slide 1

Jangam, Mujumdar - Classification and Selection

Table 3.7. Comparison of conventional and innovative fluid bed dryers

Variant Conventional Innovative

Mode of heat transfer Only convection Convection + conduction
(immersed heaters in bed)

• radiative heat transfer
  (MW assisted fluid beds)

Gas flow Steady Pulsating; on/off

Mode of fluidization Pneumatic Mechanically agitated / vi-
brations

Drying media Air / flue gases Superheated steam / heat
pump assisted (even using
inert media)

Type of material dried Particulate material Drying of pastes / slurries
using bed of inert particles

Figure 3.6. Hybrid drying technologies

Fluidized bed

dryers

Combined

mode of heat

transfer

Convective / conduction

(Agitated fluid bed dryer)

Convective with MW/RF/IR

Continuous or intermittent

Each stage with same dryer type

(Two-stage fluid bed)

Different dryers at each stage

(Spray and fluid bed dryer or

flash and fluid bed dryer)

Multi-stage

drying

systems

Multiprocess

ing dryers

Different drying technologies

at each stage (superheated

steam drying / by air drying)

Filter cum dryer

Drying and agglomeration (spray

followed by fluid bed)

Drying & cooling (in plug flow

fluid bed dryer