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wool processing of carpet yarn and effluent treatment
1.	INRODUCTION

All the process which are applied to make the yarn ready for manufacturing of the carpet can be known as wool processing of carpet yarn. It includes several steps such as a.	Shearing of wool fibre from the skin of sheep. b.	Scouring c.	Carding d.	Gilling e.	Drafting f.	Spinning g.	dyeing and effluent treatment is the process of extracting all the contaminants which are contained in the scoured liquor to make the liquor free from the pollutant. 2.	WOOL PROCESSING OF CARPET YARN

a.	Shearing :- the wool is removed from the sheep by shearing on thefarm (annually, or every 6 – 8 months). It is then sorted by skilledclassers according to quality and type, packed into bales and sent to a wool store for sampling and storage until it is sold.

b.	SCOURING Of WOOL FIBRE 	Wool scouring objectives:- The principle objectives of wool scouring are 1. 	To produce clean wool free from dirt and as much vegetable matter as possible, with the least loss of fibre as possible. 2. 	To reduce wool wax to a recommended low level, usually no more than 0.4%. 3. 	To produce an open mass of fibres which are free from entanglement, which reduces fibre breakage and loss of fibre in later mechanical processes such as carding, gilling and combing.

	DUHAMEL SCOURING PROCESS:- This method of scouring was first used in France in the early 1920s. It was used because a water solution of suint has an approximate pH of 7.5. With this pH level, there is less chance of damaging the wool than with the old soap-soda method.

Suint is easily removed from wool. When removed, it forms a slight soapiness when combined with the wool grease in the water. This slight soapiness helps to cleanse and scour the wool. Because the suint solution is not as harsh as the soap-soda solution, it was thought to be better for the wool. No alkali was used in the process.

During scouring, the dirt and suint are separated and the suint solution is returned to the bowl. After scouring, the grease dirt and suint in the liquor can be separated and the suint solution can be reused.

The system works as follows:

Bowl 1:	A cold water bowl that removes suint and dirt. The liquor is constantly run off and separated. The suint solution returns to the bowl, and the dirt goes to waste.

Bowl 2:	A hot water bowl kept at about 55 °C. The remaining suint combines with grease to form the slight soap. The solution is again constantly run off and the suint solution is recycled. The grease and dirt are separated. Most of the dirt and grease have now been removed. Bowl 3: 	A rinse bowl. Bowl 4: 	A hot soap solution to scour the wool.

Bowl 5: 	The final rinse.

Smaller bowls were used to allow the suint solution to build up enough concentration to scour the wool efficiently.

	AQUEOUS SCOURING PROCESS During scouring, a lot of sludge sinks to the bottom of the bowl through a false bottom. The sludge is made up of emulsified grease and insoluble dirt. Most of the grease and dirt in the raw wool are removed in the first and second bowl. Less grease and dirt is removed in the second bowl than in the first bowl. To remove the sludge, the first and sometimes the second bowl had self-cleaning mechanisms.

The self-cleaning mechanism is a slowly revolving helical worm gear in the bottom of the bowl. The worm gear runs the length of the bowl. It moves the sludge to a dump valve that opens regularly to get rid of the sludge. Liquor that is lost from any bowl is replaced by liquor from the succeeding bowl. Fresh water is added to the last bowl.In figure a four-bowl system would replace waste water.

Waste     	Bowl      	Bowl	Bowl	Bowl	Fresh water	1	2	3	4	water

Four-bowl system of water replacement

c.	BLEACHING 	Objective of bleaching To remove natural and other  coloring matter from  fibres	wool yarn. 	Bleaching wool with hydrogen peroxide Hydrogen peroxide is the most widely used bleaching agent for wool. the whiteness produced is much more permanent than by other method. 	Recipe H2O2		-	0.55-1.1% FORMIC ACID     – 	2.5% pH   -   4-4.5 The treated wool is then squeezed to remove excess liqour and passed into a drier where bleaching takes place.Ageing is preferable because the colour of the wool continues to improve for 24-48 hours after drying. d.	CARDING:-Carding is a big machine about 20 metres long or longer with tooth rollers that tease the fibres, open them up and produce a nice even strand for the next stage. 	Objective of carding:-The card has three main functions: 1.	to open and disentangle the blend to a single fibre state and mix it homogeneously with minimal breakage of fibres 2.	to remove impurities 3.	deliver the carded material in an appropriate form for the next stage of processing (ie, as card sliver)

e.	GILLING:-Gilling is a process of aligning the wool fibres so they are parallel to one another. This is done using a coarse comb. At this stage, the sliver still contains particles of vegetable matter as well as short fibres. f.	DRAFTING The strand of fibres has to come from a fairly thick strand down to a very fine one, so there are steps that enable that to happen. We call them drafting. The drafting process enables the fibres to slip apart and become finer. Here is wool prior to making a yarn – it’s called a roving. Roving is the raw material for spinning, it’s a very uniform strand of fibres – even, straight fibres ready for spinning.

g.	SPINNING AND TWISTING The last step in producing yarn is what we call spinning, and the ring-spinning frame does that very efficiently. The strand is taken, it’s twisted, it’s drafted into a thinner entity and wound onto a package at high speed. And so you end up with what is called a singles yarn. The singles yarn is quite fine, relatively weak, particularly if it’s wool, so it’s common practice to combine two singles yarns together, by twisting them together to form say a two-fold yarn or higher aswell. And there you have your yarn. Woolen processing This is the simplest and cheapest method of yarn manufacture. It is a very versatile system as it has the ability to handle wool of any length, especially short wools. Woolen yarns generally have less twist and are more bulky than semi-worsted or worsted yarns. This system is preferred for making carpet yarns. It’s a very quick route – scouring, carding, spinning and twisting – basically four steps, Worsted processing:- This is a more involved system, and generally uses full-length fleece wools of better style than the wool for producing woolen yarn. Worsted yarns are firmer and smoother, less bulky, and have more twist than woolen yarns. They are mainly used for woven and knitted apparel fabrics. This is the most elaborate and expensive system of yarn manufacture. Semi-worsted system:This is a simplified version of the worsted system. It requires wool that is reasonably sound and no shorter than 75 mm in length. The yarn produced from this system is smoother than woolen yarn but bulkier than worsted yarn.

h.	DYEING OF WOOL

Types of dyes used for wool

Wool dyes are classified according to the method of application and chemical type. The current classes of dyes used in the dyeing of carpet wool are: •	Acid dyes (acid levelling to acid milling) •	Metal complex dyes (2:1 and 1:2 pre-metallised dyes) •	Chrome dyes

1.	ACID DYES :-

Acid dyes are water-soluble dyes that are applied in a neutral to acidic solution. Their light fastness varies. They have average to good fastness properties with wool. Selected acid dyes are also suitable for dyeing polyamide (nylon). Two different acid dyes are available that exhaust on to the fibre: 1. From a weakly-acid bath, with such weak acids as acetic acid buffered with sodium acetate or ammonium sulphate; or 2. From a strongly-acid bath, with such strong acids as sulphuric acid or formic acid.

Types of acid dyes 1.	Levelling acid dyes 2.	Milling acid dyes 3.	Super milling acid dyes

Dyeing recipe-

At 50 degree temperature 1.	 H2SO4 – 2% (to maintain pH) 2.	Na2SO4 (Glauber’s Salt) – 10 % (Levelling Agent) 3.	Dye – X gm 2.	CHROME DYES :- •	Chrome dyes are water-soluble dyes that are very fast to washing, perspiration, and light. Chrome dyes tend to give rather dull shades, so they tend to be used for the darker colours such as navy and black. However, they have very good wet fastness and light fastness properties. •	Chrome dyeing is a two stage process. The dye is first applied much like an acid dye. Secondly, a chrome compound is applied to the fibre. Chrome molecules combine with both dye and fibre, making the dye very fast. •	Because of the residual chrome in the dyeing effluent, many countries prohibit the use of chrome dyes.

Method of dyeing •	Omega Crome :-This is a two process in which wool is first mordanted in a sodium or potassium dichromate in the presence of sulphuric acid and then dyed. •	After Crome :-It is also a two bath process in which chroming is done as the second step. i.e. after dyeing. •	Meta Crome :- It is a single step dyeing process.

OMEGA CROME Dyeing Process :- 1.	mordanting- 2.	Dyeing –

RECIPE :-

•	mordanting process recipe (A)	Sodium dichromate – 1-3 % (B)	H2SO4 		- 1-3% •	dyeing recipe (C)	Dye – X % Glauber’s Salt		–	 5-10 % Acetic Acid/ HCOOH –	 1-3 % (D)	H2SO4			 -	1-2% Na2Cr2O7 – 2% (max.) AFTER CHROME

Dyeing Process :- 1.	Dyeing :- 2.	Mordanting:-

RECIPE :-

dyeing recipe (A) Acetic acid – 3-5 % Glauber’s Salt – 5-10 % Dye – X% (B) HCOOH / H2SO4 - 0.5 – 1% mordanting (C) Sodium dichromate – 1-3%

META CHROME

RECIPE

(A)	 Dye – x parts Sodium dichromate – 1-2% Ammonium Sulphate – 2-3% (6-8% for deep shade) 3.	METAL COMPLEX DYES

•	Metal complex dyes, also called premetallised dyes or premets, resemble chrome dyes in some respects. They produce very good fastness on wool and nylon fibres. Metal complex dyes differ from chrome dyes because the complex-forming metal ion is put in the dye molecule when it is made. This makes after chroming unnecessary. •	Metal-complex dyes have good fastness properties, however they are not as fast as chrome dyes. •	Metal-complex dyes are in two groups: •	1:1 metal complex dyes must be applied in a strongly acid bath. The 1:1 means that one dye molecule is combined with one metal molecule. •	2:1 metal complex dyes are to be dyed in a neutral to weakly acid bath. The 2:1 means that two dye molecules are combined with one metal ion.

metal complex dye ( strong polar dye)

RECIPE :-

metal complex dye - X% Sodium Acetate – 1.5 % Acetic Acid – 1% Glauber’s Salt – 10-15 gpl Lyogen SMKI – 1 % pH – 5-6, Temperature- 980C,Time – 45-60 min.

Dye type	Shade range	Levelling ability	Wash fastness	pH range	Relative cost Acid levelling	Bright pastels	Excellent	Poor	2 – 3.5	Cheap Acid milling	Bright pastels	Poor	Very good	6 – 7	More than levelling 1:1 Metal complex	Dull, dark	Good	Good	2	Moderate 1:2 Metal complex	Dull dark	Poor	Very good	6 – 7	More than 1:1

3.	EFFLUENT TREATMENT If scouring liquor is discharged without any treatment into a river or sea outfall near the shore, the components of the liquor create a pollution problem PURPOSE – 1.	To remove the water polluting elements from the discharge water. 2.	To reduce the temperature of the discharge up to considerable level. The main components of wool scour liquor 1.	Suint, made up of mainly potassium salts, which are soluble in cold water; 2.	Wool grease, an organic mixture, which can be divided into unoxidised and oxidised grease; and 3.	Dirt, which can vary from fine clay particles to coarse grit The minor components of scouring liquor are vegetable matter, faeces, wool fibre, and detergent. Different wools yield effluents with different ratios of components. Effect of Scour Effluents 1.	The lives of micro-organisms, plants, and fish can be affected in different ways. 2.	Some pesticides, even in very small quantities such as parts per billion, are toxic to fish. 3.	Detergents can affect the rate at which oxygen dissolves in the water. 4.	Any discharge of hot effluent can cause pollution and kill aquatic life. There are several types of effluent treatment systems a.	Primary treatments b.	Secondary treatments c.	Tertiary treatments d.	Total treatments

a. Primary treatments - Aim- 1. Reduce the amount and variability of the discharge, 2. Remove settle able solids and fibre, and 3. Recover as much wool grease and heat as possible.

Effect- 1. BOD5 reduced by 42% 2. Suspended solids (SS) reduced by 47% 3. Total effluent volume reduced from about 5 litre/kg of wool scoured to 1 litre/kg of wool scoured. This figure does not include the rinse water. Removal of different types of Pollutants 1.	Fibre removal 2.	Suspended solids (SS) removal 3.	Grease removal 4.	Heat removal Methods 1. Fibre removal 	It is done on hot liquors by wedge wire screens. 	Screen must be cleaned regular interval 	Depending on rate & Volume of Liquor WEDGEWIRE SCREEN 2. Suspended solids removal 1.	It is done by gravity in a settling tank. 2.	About 50% of the suspended solids (SS) are removed by this method. 3.	Adding flocculent to the liquor :- results coagulation of small particles to   	large particles. 3.Grease removal 	Major Pollutant 	About 45 - 50% of grease can be removed by centrifuging. 	Centrifuging should have adequate capacity for efficient removal. 4.	heat Removal 	Removed by heat exchangers 	Exchangers reduces heat of primary effluent.

b.Secondary treatments After primary treatment, the effluent still contains suint and reduced amounts of grease and dirt. Most of the secondary treatments remove the grease and dirt, leaving a suint solution. The treatments of the effluent include 1.	Chemical destabilisation by acid cracking or by use of alcohols. Acid cracking uses acid to separate the effluent into its separate parts so that they can be removed. 2.	Chemical flocculation. 3.	Biological processes, which involve the use of micro-organisms to break down the effluent. 4.	Ultrafiltration to remove grease and dirt. 5.	Evaporation of the effluent as part of a total system. 6.	Centrifuging and evaporation.

c.Tertiary treatments

After the secondary treatments, further processes may be used including 1.	Biological treatments, such as adding nutrients to the grease-free liquor obtained from acid cracking, 2. 	Incineration of the sludges left after the secondary treatment, and 3.	Solvent extraction of sludge, where a solvent is used to extract the grease and water from the effluent. This leaves a potassium rich dirt, which is suitable as a fertiliser.

d.Total treatments No treatment will reduce effluent to nothing. Something is always left, even if it is ash or air pollution. The methods of total treatment include 1.	Evaporating the effluent and incinerating the sludge at very high temperatures. 2.	The Sover wool scouring process, which involves cleaning the wool by solvent extraction of grease and suint instead of by emulsion scouring. The suint-rich effluent is then evaporated to leave dry dirt, rich in potassium salts. 3.	Land irrigation, which consists of discharging effluent on to open land and leaving it there. The site must be suitably chosen because odour problems occur in hot weather.

Comparison of effluent treatments Treatment	Pollution removed 	Capital costs  	Running costs

Primary	35 - 50%	low	low Secondary	75 - 96%	low - medium	low - high Tertiary	100%	high	medium Complete	100%	low - med - high   	low - high

By:- Er. Rahul Singh IICT,BHADOHI (U.P)