Download - Sugar & Sweeteners

Sugar & Sweeteners

for Beet, Cane &

Special Sugars

Drying & Cooling Plant

P R O C E S S E N G I N E E R I N G

Few manufacturers offer a greater choice

of dryers and coolers for the sugar and

sweetener industry than Barr-Rosin,

with a range that includes:

• Rotary dryers

• Rotary dryer/coolers

• Rotary coolers

• Dryer/ conditioners

• Fluidised bed dryer/coolers (static)

• Fluidised bed dryer/coolers (vibro)

• Fluidised bed coolers

These are supplied for processing beet,

cane and special sugars, such as:

• dextrose (monohydrate & anhydrous)

• maltitol

• fructose

• other polyols

• coated sugars

• confectionary products

In a world of changingmarkets and new

products, being able to rely on a process

equipment supplier witha broad experience and wide choice of

technologies is essential.Welcome to Barr-Rosin.

Counter-Current Rotary Dryer (evaporative cooler)

This makes full use of the heat from the

incoming sugar for drying, while also

cooling the product. The system generally

requires the lowest airflow and needs

very little additional heat input. When

a very low final sugar temperature is

required (ie.below 25-35ºC), this system

also significantly reduces the duty of the

following ‘secondary’ cooler.

Combined Dryer/Cooler (two zone, central tube type)

This maintains the counter-current

principle throughout both the drying and

cooling zones. It also uses the heat from

the sugar for drying, as well as pre-

heated air from the cooling zone. The

latter is mixed with a small amount of

supplementary drying air, introduced

via a central tube. The system is typically

more suited to high ambient temperature

and humidity conditions (as in cane

sugar regions), where increased quantities

of cooling air may be necessary.

Dryers can be designed for either co-

current or counter-current configuration,

according to the type of sugar processed.

They can also be supplied as combined

units with drying and cooling zones.

The dryer internals are fitted with special

‘sawtooth’ lifting flights, louvres and/or

cross-shelf (cruciform) baffles, as required.

For some applications, surfaces in

contact with the product are ground

and polished.

Combined Dryer/Cooler (central exhaust type)

This combines co-current drying and

counter-current cooling, where the

converging airflows are exhausted from

the centre of the dryer/cooler. Although

the design may permit higher drying

temperatures, which can reduce drum

diameter, the total air flow and drum

length is generally increased. It may be

used for beet and cane as well as certain

‘special’ sugar applications.

Solutions for all

A choice of technologiesFor animal feeds, such as beet pulp,

corn /wheat fibre and DDG, direct fired

Rotary, Ring (flash) and closed circuit

pressurised ‘Steam’ dryers are also

supplied – all specifically designed to

suit the varying product characteristics

and local climatic conditions.

The Rotary Dryer Workhorse of the Industry

Long established as the traditional method

of drying sugar, the rotary dryer is today,

still widely recognised as the most effective

and reliable system available. The simple,

robust design requires less energy, yet

offers greater flexibility than other dryer

types. Because it is less prone to sticking /

caking and more readily accomodates

‘upset’ or variable feed conditions, it is

suitable for a wide range of sugars. An

additional feature is the low headroom

requirement, which often benefits

installation in existing sugar factories.


page 3

Beet and Cane Sugar Applications

Counter Current


page 5

These dryers are often used in

conjunction with fluidised bed coolers

(sometimes fitted with ‘in-bed’cooling

tubes) and are supplied with a range of

ancillaries, such as agitated feed vessels,

multi-stage and absolute filters, trommel

screens, cyclones, wet scrubbers and

bag filters.

Special attention is given to the design

and surface finish of product contact

areas, to minimise sticking/caking and

micro-biological contamination.

Rotary CoolerA simple counter-current design can

provide separate cooling or secondary

cooling. This low energy system is

sometimes an appropriate alternative

to a fluidised bed cooler.

Co-Current Rotary DryerThis design is generally more suited

to sugars and sweeteners such as starch

derivatives, coated and confectionary

sugars, which are typically fine and /

or sticky.

Such products often contain higher

moistures – yet are more heat sensitive

and generally supplied at feed

temperatures close to ambient. The

longer co-current design affords the

extended residence times needed for

diffusuion drying / conditioning and

permits the use of higher drying

temperatures, without causing heat

damage or discoloration.

Due to the hygroscopic nature of most

special sugars, air conditioning

equipment is usually required, to reduce

both the temperature and humidity of

the ambient (fluidising) air before it

enters the cooler. However, for certain

applications, the unit can also be

supplied with ‘in-bed’ tube bundles

(heat exchangers) providing additional

but indirect, contact cooling.

By using chilled water through the tubes,

the air volume and cooler size is

significantly reduced, which is

particularly beneficial when the ambient

temperature and humidity is high.

Fluidised Bed Dryer/CoolersFor special applications, such as those

designed for confectionary sugars and

smaller plant capacities, fluidised bed

combined dryer/coolers can be

provided. However, to overcome the

cohesive nature of the sugar at the feed

point, static type fluid bed dryers are

often fitted with a de-aglomerator or

stirring device. Alternatively, a vibrating

bed dryer can be supplied to maintain

the product in a ‘live’ state during the

initial drying phase. These units are

more suitable if there is a wide particle

size distribution, or if integral final

product screening is required.

Fluidised Bed CoolersThis is an efficient, well proven system,

whereby the sugar layer (or bed) is

suspended on a ‘cushion’ of air passing

up through the cooler, via a special

perforated distributor plate. Bubbles

continuously form and collapse within

the bed of material, creating a fluidising

effect that promotes intimate contact and

rapid heat transfer between the cooling

air and sugar. Whereas a fluid bed

system for drying sugar can be prone to

‘blinding and caking’, the vigorous but

gentle handling and cooling of dry sugar

in a fluidised state can actually enhance

the quality of the final product.

Through careful design of the fluid bed

housing and with allowance for

adjustment of the cooling air flow, the

‘fines’ can be removed from the surface

of the product (if required), to produce

a clean, bright crystal.

For most sugar and sweetener

applications these units are of the static

type, since the sugar is free-flowing in

the dry state.

page 4

Co-current

Developing markets

More optionsSpecial Sugar Applications Fluid Bed Systems


page 6

consumption, fire risk and final off-gas

volume. Alternatively, in a CHP system,

the dryer may operate on an open-circuit

basis, using turbine exhaust-gas (TEG),

also having the effect of depleting

oxygen to safer levels.

Since the bleed-off volume to

atmosphere is relatively low when

recycling dryer exhaust gases, the duty

of any odour treatment, whether by

scrubber/condenser or Regenerative

Thermal Oxidiser (RTO), is greatly

reduced. This minimises both the

installation and operating costs.

Feed DryersEngineered for Efficiency utilising:-

• Exhaust Gas Recycle

• Turbine Exhaust Gas

• Waste Heat Recovery

• Regenerative Thermal Oxidisers

• Steam drying

Rotary, Ring (or Flash) and closed circuit,

pressurised Steam dryers can be

supplied for a range of animal feeds,

including beet pulp, corn/wheat fibre

and Distillers Dark Grains (DDG).

Direct Fired Rotary DryersThese dryers are of the co-current,

cascade/‘cruciform’ (or cross-shelf) type,

designed for oil/ gas firing and

generally utilise exhaust gas-recycle.

By recycling and reheating a proportion

of the dryer exhaust, this self-inertising

system also reduces energy

Steam DryingHaving originally pioneered the ring

dryer, Barr-Rosin has since developed a

closed circuit system, which combines

the main features of the ring dryer, but

entirely replaces the heated air with

recirculated steam, generated by the

evaporation of water. Steam drying, at

pressures of up to 3 bar g can offer

significant advantages when compared

with direct fired systems, in particular:

• there is no exhaust (or odour)

to atmosphere

• steam is available for other purposes

• there is no potential for fire/explosion

• energy consumption is greatly reduced

• product quality is improved.

Ring DryersThe ring dryer employs the same basic

principle as the flash dryer, but

incorporates a centrifugal classifier. This

allows selective internal recirculation of

semi-dried solids, effectively increasing

the retention-time of larger particles in

the dryer, while finer material (which

dries more rapidly), exits with the

exhaust air. Widely used for animal

feeds, in particular DDGS, these dryers

produce a high quality product.

Again, they are direct fired and utilise

exhaust gas recycle to render the drying

system inert and increase efficiency.

Also, when appropriate, RTO’s are

supplied to treat the bleed-off gases.

By- Products

Different approaches

Sugar & Sweeteners


Drying & Cooling Plantfor Beet, Cane & Special Sugars

Barr-Rosin is a world leader in industrial

drying technology, combining over one

hundred years of drying experience.

Barr-Rosin is part of the Process

Engineering Division of the GEA Group.