Presented by: AMNINDER SINGH SEKHON

(Batch-2014)Registration No. L2014DT03Bachelor 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

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

• 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

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

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…)

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

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.

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

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..)

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

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

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

a)Roller feed b) Nip feed.

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

large

production capacity

continuous operation

simple structure

easy to operate less failure

low maintenance

costs

ADVANTAGES OF DRUM DRYING

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

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…