Slide 1

Law, Mujumdar - Energy Savings in Drying of FVF

Table 7.2. Recent research findings on applying mathematical modeling to improve

energy efficiency

Drying system / dryer Findings Reference

Plug flow fluidized bed
using mathematical
models in different dry-
ing periods

25 - 27.5% saving in thermal power

by upgrading insulation and ad-

justing inlet air temperature or

flow rate in order to avoid over-

drying.

Baker & Lababidi,

2010

Wood drying using mul-
tiscale computational
model

Vacuum drying of spruce using

suitable drying schedule could give

10% savings in total energy con-

sumption

Perre et al., 2007

Through drying of tissue
paper using a dynamic
model for through dry-
ing combined with static
model for air system

3.3% reduction in total operating

cost by reducing initial fabric

moisture ratio.

Weineisen &

Stenstro ̈m, 2008

Spray drying using si-
mulation program

14% of fuel oil saving if 60% of

exhaust air is recycled

Velic et al., 2003

7.4.5. Drying strategy for energy savings

Apart from heat recovery, heat integration and applying control scheme to drying,
there are several drying strategies which can be applied to improve energy utilization
and save energy cost:

• Use conductive heating or indirect heating (such as IR) to avoid loss of ener-
  gy in exhaust air, where possible and this strategy is generally cost-effective


• Use intermittent, multi-mode heating to optimize the heat input and mois-
  ture transport, where possible for batch drying


• Use less air and higher temperature where possible to avoid loss of energy in
  exhaust air


• Use waste heat, renewable energy (such as solar, wind energies etc.), where
  feasible


• Use mechanical means such as filtration, ultra-centrifugation to remove wa-
  ter without phase change, etc and use evaporation (for dilute liquids) to re-
  duce the water content prior to drying


• Use solvent with low heat of vaporization and high vapor presence to dis-
  place water from drying material


• Apply hybrid drying or multistage drying to intensify energy utilization dur-
  ing drying.
  A dryer type may have many different variants. Each dryer variant can involve dif-
  ferent levels of energy consumption, for example fluidized bed dryer has more 30 differ-
  ent variants. Reader may refer to Law and Mujumdar ( 2004 , 2007 ) for the descriptions
  of various types of fluidized bed dryer (FBD). Conventional FBD uses high airflow and
  thus it requires higher energy consumption. With the use of immersed heat exchanger, it
  can save ~30-50% of energy usage. Vibrated / pulsed fluid bed on the other hand, can
  save ~20-40% energy by using lower airflow rate. Whereas, spouted bed consumes