Two Methods of Scouring Process | Scouring Process Overview !

Scouring is the process to remove natural and foreign impurities from the fabric and to prepare the fabrics for the next subsequent process. This process makes the fabric hydrophilic so that they can absorb the chemicals and dyes properly. In this article we will discuss about the methods of scouring process.

The non-continuous scouring process consists essentially of circulating hot alkali liquor through the cloth in a vessel called kier.

The continuous scouring and bleaching in the J-Box has been established after 1960s. The continuous process is based on the impregnation of the fabric in an alkali solution followed by steam ageing stage, the fabric being either in rope form or open width form.

Kiers have given way to J-Boxes and J-Boxes are discarded in favor of open width scouring which requires only 2-15 min having very high production. In comparison kiers take 6-12 h depending upon the amount of impurities.

There are two methods of Scouring Process is available:

  • Continuous process: J-box machine
  • Dis-continuous process: Kier boiler, Winch or Jigger machine

Batch type or Discontinuous process

Batch type or discontinuous scouring process in (rope form) are carried out in:

  • Low pressure kier
  • High pressure kier
  • Jafferson-Walker’s kier
  • Gebauer kier

Batch Type Scouring Machine (Open Width Form) are carried out in:

  • Mather and Platt’s horizontal kier
  • Jackson kier
  • Jig process

Among all of these the most used process is high pressure kier boiler. In this article we will cover this type of kier boiling method.

Machine profile:

  • The prototype of modern high pressure kier with multi-tubular heater is often referred to as Walsh’s kier and considered to be the best.
  • This machine is about 9 inch high and 6.5 inch in diameter with a 2 tons capacity.
  • This machine is mounted on R.C.C columns.
  • The maximum working pressure for this machine is 40 lb/in2 (2.812 kg/cm 2) at 141°C and is composed of mild steel plates with countersunk rivet heads inside to give a smooth surface.
  • Various mountings and accessories like pressure gauge, safety valve, blow off valve for air and steam, steam trap, liquor level indicator, drain cock are provided with this machine.

Recipe for batch process scouring

Chemicals

Amount needed

·       Caustic soda

·       Soda ash

·       Wetting agent

·       Sequestering agent

·       Temperature

·       M:L

·       0.5-2.4 g/L

·       0.5-1.0 g/L

·       0.5-1.0 g/L

·       0.5-1.0 g/L

·       120-130°C

·       1:100

Process description:

  • Goods in rope form are piled either manually or by mechanical plaiting on the perforated false bottom.
  • The cloth can be saturated with alkaline solutions containing caustic soda (2 to 3%), sodium silicate (0.75 to 1%), sodium carbonate (0.5 to 1%) and wetting agent (0.1%) during piling.
  • Sufficient scouring liquor is then admitted to the kier from below.
  • This is done to sweep out entrapped air from the goods to avoid the formation of oxy-cellulose.
  • Then the lid is closed but keeping the air valve open.
  • Steam is turned on and liquor is circulated by centrifugal pump.
  • High pressure kier operates at about 130°C (2.109 kg/cm 2) for about 8 to 10 hours with a liquor ratio 5:1 to 6:1.
  • After scouring the drain cock is opened at reduced pressure (5 to 6 lb/in 2) and equivalent amount of hot water is admitted from the top.
  • After circulating cold water the goods are removed and washed in a rope washing machine.
  • The liquor is withdrawn from the bottom of the kier and forced through the heater and spread over the top of the load by the distributor.

Fabric that is to sell at white state are given two boils whereas the fabrics intended for printing are given single boil.

Advantages & Dis-advantages of Dis-continuous process

               Advantages

                   Dis-advantages

·       Suitable for small orders

·       Fabric can be scoured in both open width and rope form.

 

·       Not economical for large orders

·       Time requirement is more than continuous process

Continuous process

Continuous scouring process can be carried out by the following machines. Continuous process is rarely followed in the industry. But among all of these J-box machine is used mostly. So, we will cover j-box machine here.

  • Saturator- J-Box-rope washer
  • Open width roller steamer
  • Vaporloc system
  • High pressure Klienewefer roller steamer
  • Conveyer storage steamer system
  • Roller bed steamer with pre-swelling zone

Saturator- J-Box- rope washer

This procedure can be divided into 4 stages:

  • Saturator
  • Pre-heater
  • J-box
  • Washing unit

Recipe for Continuous process

           Chemicals

   Amount needed

·       Caustic soda

·       Wetting agent

·       Sequestering agent

·       Impregnation temperature

·       Storing time in J-box

·       J-box temperature

·       5 g/L

·       1-4.5 g/L

·       1-5 g/L

·       70-80°C

·       8-10 min (open width form)

40-60 min (rope form)

·       100-105°C

Process description:

  • Saturator: In continuous machines, scouring can be carried out through a series of J-Boxes or range type operations for progressive desizing and scouring. The desized and washed cloth is first saturated with scouring solution at about 70-80°C in a saturator.
  • Pre-heater: The cloth before entering J-Box is rapidly pre-heated by means of steam in a U-shaped heating tube. Where the temperature range is 110-120°C. In case of Becco system, there is no pre-heater and the cloth is directly heated in the J-Box which is used as a steamer
  • J-box:
  1. After padding the saturated cloth and passing through the pre-heater, it enters into Du Pont type J-Box where it remains for 40-60 min in plaited form at a temperature of about 100°C.
  2. The internal surface of the entire J-Box is very smooth to avoid any friction on the moving cloth.
  3. In-stead of rope form a multi-stage J-Box in open width form can also be used with a dwell time of 8-10 min in J-Box.

Washing unit: The scoured fabric is washed outside heaving a counter current arrangement at temperature of about 70-80°C.

Advantages & Dis-advantages of Continuous process

               Advantages

                  Disadvantages

·       Fabric is scoured in both open width and rope form.

·       Suitable for large orders

·       Less time required

·       Not economical for large orders

Scouring is a must procedure that should be carried out in case of natural fibers. Otherwise proper dyeing can’t be possible.

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