Drum dryers are indirect dryers that remove moisture from materials by spreading them in a thin film on a rotating steam-heated drum. As the drum rotates, a doctor blade scrapes the dried film off. Drum drying requires less space than spray drying and allows for continuous operation. While drum drying has advantages like large capacity and simple operation, it also has disadvantages such as high energy costs, long drying time for materials, and difficulty processing corrosive substances.

2. Presented by:
AMNINDER SINGH SEKHON
(Batch-2014)
Registration No. L2014DT03
Bachelor in Dairy Technology
Presented to:
ER . NARENDER KUMAR
ASSTT. PROF. (DAIRY ENGINEERING)
Department of Dairy Engineering , CODST,
Guru Angad Dev Veterinary and Animal Science University
(GADVASU), Ludhiana, Punjab,
India -141001
6 May, 2016
Drum dryers

3. The removal of nearly all the water present through
vaporization is known as drying or dehydration.
Removal of moisture to a very low moisture content
nearly to a bone dry condition
Bone dry material is the material from which all the
moisture has been removed
INTRODUCTION

4. • Drying is carried out for one or more of the following reasons:
 To eliminate moisture which may lead to corrosion and
decrease the product or drug stability.
 To improve the good properties of a material, e.g. flowability,
compressibility.
 To reduce the cost of transportation
 To make the material easy to handle
 to increase the shelf life
PURPOSES OF DRYING

5.  Minimal chemical and biochemical degradation reactions
 Selective removal of water over other salts and volatile
flavor and aroma substances
 Maintenance of product structure (for a structured food)
 Control of density
 Lack of contamination or adulteration
 Minimal product loss
GOALS OF DRYING

6.  Rapid rate of water removal
 Inexpensive energy source (if phase change is involved)
 Facility of continuous operation
 Noncomplex apparatus (reliable and minimal labor
requirement)
 Minimal environmental impact
DRYING SHOULD ACHIEVE
THESE GOALS (CONTD…)

7. 
 In drying processes, the main operation usually
carried out on solid materials, e.g. powders, or
products
 Drying in most of the cases means the removal
of relatively small amounts of water from solids .
 Evaporation include the removal of large
amounts of water from solutions.
DIFFERENCE BETWEEN DRYING
AND EVAPORATION

8. 
 In most cases, drying involves the removal of water at
temperatures below its boiling point, whereas evaporation
means the removal of water by boiling a solution.
 In drying , water is usually removed by circulating air over the
material in order to carry away the water vapour , while in
evaporation , water is removed from the material as pure water
vapour mixed with other gases.

9. 
The drum dryer is an indirect type dryer in which the
milk to be dried is maintained in a thin film on a rotating
steam heated drum.
The milk being dried is spread over the outside surface
of the dryer. Clinging to it and drying continues as the
hot drum rotates.
DRUM DRYING

10.  At the end of a revolution, the drum comes to a ‘doctor blade’
which scrapes the dried film from the drum, when the
product has made about three-quarter of a complete rotation
on the drum surface
 The process is also known as roller drying
 Drum drying requires less space and is more economical than
spray dryers for small volumes. The ratio of steam
consumption to water evaporation is from 1.2 to 1.6:1
Drum Drying(contd..)

11. 
 Diameter of typical drums ranges from 0.5m to 6m and the
length from 1m to 6m.
 In operation , steam at temperature up to 200 degree
Celsius heats the inner surface of the drum.
 The moist material is uniformly applied in a thin
layer(0.5mmñ2mm)on to the outer drum surface.
SYSTEM DESCRIPTION

12. 
 The energy consumption in a drum dryer may range between
1.1 kg steam per kg of evaporated water and 1.6kg steam per
kg of evaporated water , corresponding to energy efficiencies
of about 60%-90%.
 Under ideal conditions ,the maximum evaporation capacity of
a drum dryer is 80 kg H2O/hour m2

13. 
 Number of drums (a) single drum, (b) double drum, or (c) twin
drum.
 Pressure surrounding the product (a) atmospheric, and (b)
vacuum.
 Feeding arrangement: (a) nip feed, (b) splash feed, (c) dip
feed or (d) roller feed.
 Material of construction: (a) alloy steel, (b) stainless steel, or
(c) chrome, or nickel plate steel
CLASSIFICATION

16. a)Roller feed b) Nip feed.

20.  Freeze drying is a process used to dry extremely heat –
sensitive materials. It allows the drying , without excessive
damage
 In this process the initial liquid solution or suspension is frozen,
the pressure above the frozen state is reduced and the water
removed by sublimation.
 Thus a liquid –to-vapour transition takes place, but here three
states of matter involved: liquid to solid, then solid to vapour
FREEZE DRYING

21. 
large
production
capacity
continuous
operation
simple
structure
easy to
operate
less failure
low
maintenance
costs
ADVANTAGES OF DRUM
DRYING

22. 
The equipment
is large,
one-time
investment are
high;
installation and
removal are
difficult;
The heat loss is
large, thermal
efficiency is low
material in the
dryer stay for a
long time
DISADVANTAGES OF
DRUM DRYING

23.  Not able to process salty or other corrosive materials due
to potential pitting of drum surface
 High cost of changing drum surface because of the
precision machining that is required
 Some products ,especially those with high sugar content ,
may not be easily scrapped off from the drum
Continued…

24. 