Slide 1

Law, Mujumdar - Energy Savings in Drying of FVF

more energy but it is used when particles cannot be fluidized in a conventional fluidized
bed.

Table 7. 3 gives some of the recent research findings on energy saving of multi-stage
drying, hybrid drying, heat pump drying and application of heat recovery method

Table 7. 3. Please provide the caption here

Drying system /
dryer

Findings Reference

Two-stage zeolite
dryer

10 - 15% higher in energy efficiency than

single stage zeolite dryer

30% higher in energy efficiency compared

to conventional dryer

Djaeni et al., 2009

Two-stage freeze dry-
ing followed by mi-
crowave vacuum dry-
ing

54.02% saving in invalid energy. Invalid

energy is the portion of total energy (a large

portion) that is not used for removing mois-

ture.

Huang et al., 2009

Heat pump assisted
dryer

Specific moisture extraction rate (SMER) is

three times higher than hot air dryer

Lee & Kim, 2009

Fluid bed dryer and
hybrid fluid dryer

Fluid bed dryer gives high energy efficiency

for drying which occurs in constant rate pe-

riod. Fluid bed – conveyor may be used in

falling rate period

Menshutina et al.,

2004

Longan drying using
heat recovery method,
wood as fuel, applying
thermal insulation and
better temperature
and humidity control

20% improvement in thermal efficiency and

80% reduction in fuel cost

Tippayawong,

2008

Hybrid drying or multistage drying has been reported to reduce energy consump-
tion compared to conventional drying. For instances, hybrid 6 hour freeze drying fol-
lowed by microwave vacuum drying could reduce energy consumption by 54.02% com-
pared to conventional freeze drying (Huang et al., 2009). More information on energy
aspects in drying technology can be found in Strumillo et al. (2007).

7.5. CONCLUSION

Energy analysis and minimization of energy consumption should be performed on
the entire flowsheet of a process rather than targeting on an individual unit operation
such as a dryer alone. Pre-drying, such as mechanical dewatering, filtration and etc. as
well as post-drying such as cooling, granulation, blending and etc. should be considered
in the overall strategy to save energy. However, it should be noted that the best energy
option does not produce the optimal product quality. Therefore, optimization should be
conducted to obtain the best drying strategy to meet requirements from various aspects
such as energy and product quality.