The application of various chemical finishing and dyestuff generally involves impregnation of textile materials with aqueous solutions. This impregnation is followed by removal of excess water (by padding) then drying. Finally, if required, curing/backing is done. Now Knit RMG is the highest foreign currency earning sector of Bangladesh. For knit fabric processing its involves many chemical process, so drying is an important operation. The production of various mechanical finishes on knitted fabric involve conditioning of the material to a certain moisture content and then drying by different means.

Various Drying System:Cylinder drying

• Float dryer/ Loop dryer

• Tensionless dryer/Shrink dryer

• Stenter machine

Hot air dryer

Radio frequency dryer

Pressure dryer

Infra-red dryer

General remarks on drying techniques

• The drying process aims at eliminatingexceeding water and achieving the naturalmoisture content of the fibre. Excessive dryingcan negatively affect the final appearance andthe hand of the textile. When choosing a dryingtechnique, the cost efficiency of the dryingsystem must be carefully evaluated.

• The cost-efficiency of a drying processincludes many factors such as:

The quantity of steam and energy required to evaporateone kilogram of water

The evaporation capacity of a machine, expressed inkilograms of water evaporated in one operating hour.

Heating of the drying unitThe drying units are usually heated bymeans of:

o Steam with an average thermal efficiency ofabout 64%.

o Better thermal efficiency is granted bydryers heated with thermal fluid (about80%).

o Highly efficient heating is obtained bymeans of direct gas combustion, with anefficiency of almost 95%. The operatingtemperature can be reached in very shorttimes and heating can be donesimultaneously.

Drying systemsThe water dispersed in a textile material by chemical-physical process is generally eliminated by the action of hot air, which makes the water evaporate; during the drying process, it is very important to carefully consider the way heat is directed on the fabric. The drying process can be carried out:

- By heat convection

- By contact with heated metal surfaces

- By infrared radiation

- By means of microwaves or high-frequency waves e.g. fabric and yarn package dryer

- By combustion

Yarns and textile materials in bulk are generally dried inside hot air compartments. For the drying of piece fabrics, manufacturers have designed different drying units, which apply different principles, briefly described here below.

Drying by heat convectionThe heat diffusion

onto the wet fabric is

carried out by means

of hot air circulating

inside the drying unit.

Employment:Relax

dryer for knit fabric,

Stenter.

Contact dryingBy this system, the fabric moves forward arranged on

several heated drums or cylinders. The drying temperature

ranges between 120-130° C and the cylinders are heated

by means of steam at a pressure of 1-3 atm. This efficient

and low-cost drying system is particularly suitable for flat

fabrics, which cannot be easily affected by tension during

feeding.

Employment: For Woven Fabric.

Infrared radiation dryingInfrared radiation (near and medium infrared field) can be absorbed by the fabric and transformed into heat which helps in drying of fabric.

Employment: Woven fabrics and Yarn package drying

Microwave dryingBy means of radio frequency waves, heat develops inside the materialin a quantity that is proportional to the water dispersed in it. RadioFrequency penetrates to the core of the product and heat every partevenly to dry the product especially used for yarn in package form.

Employment: Yarn Package drying.

DMS 05 Jumbo Air Relax Dryer

• Origin: Dilmenler Textile

Machinery Co. Istanbul, Turkey

• DMS 05 Jumbo Air Relax Dryer is

economically and ergonomically

designed with latest technological

achievements and it is with up to

72 - 85% of calorific efficiency.

• Process: Drying after dyeing and

impregnating process from wet or

dry fabric

• Working width: 1600-4200 mm,

knitted and woven fabric.

• No of Chamber: min 2 - max 6

chamber

• Heating system: Natural gas,

thermic oil, steam.

• Production speed: 5-80 m/min

Variations in Design:

DynAir 6500- Relaxation DryerOrigin: Monforts Fong’s Textile Machinery Co., Ltd. ("Monforts Fong’s") is the joint venture of

the leading German textile machinery manufacturer, A. Monforts Textilmaschinen GmbH & Co.,

KG Mönchengladbach and Fong’s Industries Co., Ltd., Hong Kong established in January

1999.

• Modular Design: The Montex DynAir relaxation drier is designed for both woven and knitted

fabrics with feed either open/wide or tubular form. The models,available in the common nomi-

nal widths, are of modular design. Up to 15% higher drying performance because of higher

number of nozzle elements. Also suitable for integration of a heat recovery unit.

• DynAir 6500 S:

o Single fabric passage

o Fabric inlet from the front

o Fabric delivery to the rear

o Fabric feed in either open/wide or tubular form with one or more webs

• DynAir 6500 D:

o Double fabric passage

o Fabric inlet and delivery at the front

o Fabric feed in either open/wide or tubular form with one or more webs

Heating Options

Energy input as required

• Direct gas heating

• Indirect gas heating

• Circulating oil heating

• Steam heating

• Combined electric/steam heating

• Hot water heating

• Electric heating

Nozzle System

“Lay-on-Air” fabric supporting properties

with bulking effect through increased volume.

Advantages

Attractive cost / benefit ratio is possible due to

faster air transport with microtumbler effect

Higher evaporation rates

Continuous fabric support even at the chamber

transition points.

Reduced energy input

Gentle heat treatment

CADstreamE

The air outlet openings of the nozzles can be adapted

in steps to the fabric width to be treated. Adjustment is

controlled manually or automatically from the central

control desk.

CADstream Slot:

Combined round and slot nozzles. The new

slot nozzle system for high-pile and terry cloth

fabrics. Also suitable for dyeing processes on

the stenter.Figure: Slot and round

nozzles

Figure: CADstreamE

Conticlean

Circulating air filter system

Belt sieve with automatic suction system and high-

pressure cleaning for constant optimum air

circulation conditions. No energy-consuming air

resistance with increasing sieve soiling. For

constantly high drying capacity, even at high fabric

speeds and extreme linting. For further relief of the

operating personnel from maintenance work and for

lower energy consumption. Figure: Conticlean

Lint filter

The lint filters can be removed and cleaned while

the unit is operating.

Integrated heat recovery

With the new integrated heat recovery system,

Monforts is once again underlining its pioneering role

with innovative concepts for more economy and more

ecology. The waste heat produced in the thermal

process and contained in the exhaust air is

discharged via the exhaust air ducts directly into the

air/air heat exchanger. The new Monforts heat

exchanger of space-saving rectangular design

(Koenig system) is integrated into the roof

construction of the stenter. The exhaust air heat is

converted in the heat exchanger to heat up the

process air. The heated fresh air enters the fresh air

inlets of the stenter via integrated fresh air ducts. Up

to 60% of the fresh air required by the stenter can be

preheated in this way. The energy saving lies

between 10% and 30%, depending on the production.

The fans for exhaust and fresh air have variable-

frequency motors.

Dryer/Puisetronic

effect

(Bulking phase)

Improvement of the

fabric hand with pulsed

air currents, variable

from 1 to 30 pulses

Fabric transport and counter-holding belts

Twenty to 80 mm stepless setting of the nozzle

and belt distance by motor in each drying

compartment (optional).

With fabric transport belt and driven counter-

holding belt for skew-free fabric transport with

multi-web fabric feed, particularly with tubular

materials.Special features

Standard design with teflon-coated glassfibre belts. Optionally with special

transport and counter-holding belts and special belt control for particularly delicate

fabrics such as e.g. lace, bobbinet, open Jacquard fabrics.

Advantages

All belt guide systems and the drive and control rolls are located outside the hot

treatment chamber. They are housed in separate frames in front of and behind the

treatment chamber.