1. Advanced Drying Concepts: Superheated Steam and Adsorption
EFCE Working Party on Drying
Advanced Drying Concepts: Superheated Steam and Adsorption
Henk C. van Deventer

2. Challenges Remaining on Drying Processes
Decrease product degradation
Reduce high energy uses
Emissions control:
Odours
Solvents
Volatiles
Dust
Drying in controlled atmosphere
Oxygen free
Fire prevention
Explosion prevention
Intensify drying
Combining processes
Advanced drying concepts
11 April 2002

3. Advanced Drying Concepts
Drying with superheated steam
Drying with adsorptives, zeolites
Advanced drying concepts
11 April 2002

4. Superheated steam drying
Closed
steamdrying
process
Fan
Removal of
condensate
Energy recovery
via heat exchanger
Direct use
of steam
Purged steam
Slightly super-
heated steam
Recycled steam
Super-
heater
Advanced drying concepts
11 April 2002

5. Potential benefits of superheated steam drying
Latent heat comes available as slightly superheated steam, energy recovery on a relatively high temperature level
Energy saving potential: 50 to 75 %
No emission of odours, dust or hazardous components; pollutants in condensate
Evaporation rates can be higher; increasing drying speed
Product temperatures dependent on pressure
No oxygen, qualitative benefits for the product
Explosion and fire protection
Additional processing: sterilising, blanching, fixation
Advanced drying concepts
11 April 2002

6. Experimental set up Process variable Range Steam temperature
Steam flow rate
kg/h
Pressure
bar(a)
Evaporation capacity
100 kg/h
Advanced drying concepts
11 April 2002

7. Feasibility studies Experimental: Model calculations:
product qualities
drying rates
additional processing
Model calculations:
validated Micro- and macro scale models
heat and mass transfer in products
Quality influences
Advanced drying concepts
11 April 2002

8. Example: Drying of Pigments
Better quality products
Faster drying
Prevention of emissions
No fire risc
Stage: laboratory tests
Advanced drying concepts
11 April 2002

9. Example: Drying of Catalysts
Energy savings
Fluidised bed drying
Stage: laboratory tests
Advanced drying concepts
11 April 2002

10. Example: Superheated steam drying of biomass, chopped wood
Energy from biomass
Drying before burning
Better quality fuel
Lower overall energy uses
No emissions to the air
Pollutants in condensate
Stage: pilot scale tests
Advanced drying concepts
11 April 2002

11. Example: Steam Drying of Potato’s and Vegetables
Fast drying
High quality products
Combination of drying and blanching
Stage: laboratory tests
Advanced drying concepts
11 April 2002

12. Example: drying of cauliflower
Process variable
Range of values
Pressure
bar(a)
Steam temperature C
Residence time
min.
Advanced drying concepts
11 April 2002

13. Example: Sterilising / Drying of Herbs
Alternative for steam sterilising, followed by drying
No pressure differences
Odours and flavours in circulation
No odour emission
Stage: industrial tests, superheating steriliser
Advanced drying concepts
11 April 2002

14. Example: Drying and fixation
Samples of cotton cloth, printed with various kinds of dye
Best results for reactive dyes: drying and fixated in one step
Stage: laboratory tests
Advanced drying concepts
11 April 2002

15. Products for application of steam drying
Catalysts
Colouring agents
Inorganic chemicals
Chopped wood
Paper
(Coated) Textile
Vegetables
Potato fries
Herbs
Cacao beans
Advanced drying concepts
11 April 2002

16. Adsorption drying Water adsorption by zeolites Using adsorption heat
Low temperature drying
Fast drying
Direct or indirect
Advanced drying concepts
11 April 2002

17. Adsorption drying using Zeolites
Ideal drying process
Low temperature
Short duration
Free of oxygen
Good controlled process conditions
Predictable final moisture
Low energy consumption
No emissions
Compact equipment
Advanced drying concepts
11 April 2002

18. Adsorption Drying mixer separation device emission energy product
zeolite
regenerator
Advanced drying concepts
11 April 2002

19. Regeneration of zeolites used in adsorptive drying processes
Thermal swing
Temperature increase 200 °C – 300 °C (4200 kJ/kg water)
Small stream of purge gas
Advanced drying concepts
11 April 2002

20. Zeolites for drying Energy aspects
Advanced drying concepts
11 April 2002

21. Zeolites for drying sludge or manure
Raw material
Pretreatment &
Separation
Liquid fraction
Fibrous Fract.
Zeolite Drying
Product
Advanced drying concepts
11 April 2002

22. Adsorption drying PFD
Advanced drying concepts
11 April 2002

23. Adsorption drying Pilot
Advanced drying concepts
11 April 2002

24. Applications of Adsorption drying
Slurries
Lactic acid derivatives
Manure
Starch drying with a low energy consumption
Milk powder drying in a oxygen-free environment
Herbs
Fast drying of cocoa cake
Wheat flour with a low moisture content
Advanced drying concepts
11 April 2002

25. Further developments on steam drying
Challenges remaining:
Feasibility studies:
Product qualities
Quantify advantages
Equipment development
Different types and throughputs
Continuous operation
Steam tight in and output devices
Energetic process integration
Advanced drying concepts
11 April 2002

26. Further development of Adsorption drying
Feasibility studies:
Product qualities
Quantify advantages
Zeolite crushing strength and erosion resistance
Integration of unit operations
Regenerator optimisation
Different adsorbentia
Equipment development
Advanced drying concepts
11 April 2002