Raw Materials and Wastes for Wool Finishing Mill Processes

Table 2a: Wool Finishing Mill. Fabric Finishing Basis: 1 tonne of wool fabric
  Raw materials Water Energy Liquid Solid Gas
Wool Top, Olive Oil (1) Electricity   (1)    
Carding & spinning
    Electricity   N.A.  
Starch See Table 2.1 Electricity See Table 2.2    
Knitting or weaving
  (2) Electricity Steam     Vapours

(1) Although the oiling step does not contribute directly to the waste water volume, the oil finds its way into the waste stream through the washing after fulling operation. According to Jones, [8], the traditional oiling agent is olive oil, which produces a high BOD that could contribute 10% of the total BOD load.

(2) Weaving is a dry process but it is normally done in buildings maintained at high humidity. Cooling water and humidifying water used in greige mills represent a substantial portion of the total water usage [10].

Table 2b: Wool Finishing Mill. Fabric Finishing Basis: 1 tonne of finished cloth
  Raw materials Water Energy Liquid Solid Gas
H2SO4 (1) 30 m3 [10]   (1) (1)Fine carbon particles (2), Fumes (SOx), Organic Decomposition Products
Na2CO3 N.A. (5)   pH 2-9, BOD 1.7-2.1 Kg [8], TS 1250-4800ppm (5), FLOW 50-65 m3   
(4) N.A. (5) N.A. (4)    
Soap Synthetic Detergent N.A. (5) Electricity Steam pH 7.3-10.3, BOD 31-94 Kg [8], TS 4800-19300 ppm (5), FLOW 160-400 m3  
SO2 or H2O2 N.A. (5)Electricity, Steam pH 6.0, BOD 1.4 Kg [8], TS 908 ppm (5), FLOW 1-11 m3    
Acid or Metalized dye (3) See Tables 9,10 N.A. (5) See Table 8 Electricity, Steam pH 4.8-8.0 BOD 9.0-34.3 Kg [8], TS 3800-8300 ppm (5), FLOW 8-11 m3  Vapours
Special finishing
(6)N.A. (5) N.A. (5),(6)   Vapours Particulate
Mechanical finishing
    N.A.     Particulate

(1) Carbonizing is applied only if the greige goods are 100% wool. According to reference [8], it produces some solid waste but little liquid waste.

(2) According to Lund [12], this process generates very fine carbon particles which appear as smoke, as well as some fumes and odors. These fumes probably include residual sulfur oxides, if sulfuric acid has been used for carbonizing, as well as organic decomposition products and are generally corrosive [12].

(3) In accordance with Jones [8], these are the two classes of dyes used on wool fibre.

(4) There are two common methods of fulling: alkali fulling and acid fulling. In the former case, soap or synthetic detergent, soda ash and sequestering agent are used in the fulling solution; in acid fulling, fabric is impregnated with an aqueous solution of H2SO4, H2O2 and minor amounts of metallic catalyst (chromium, copper and cobalt). In either case, the water is heated to a temperature of 30-45 degC. Acid fulling is always followed by alkali fulling [8]. Little waste is generated since the fulling solution remains in the cloth [8] [12].

(5)Data for water consumption in the different stages is not available. See Table 6.1 for water use in a Wool Finishing Mill.

(6) The only dry finishing operation of concern for waste generation is moth-proofing [10].Table 2.3 shows the wastewater discharged if a permethrin-based mothproofing agent is used.

Table 2.1: Amounts of Water Typically used in Wool Finishing Mills [10]
Units: m3/t of wool fabric
Minimum Median Maximum
110.9 283.6 657.2

Table 2.2: Characteristics of Wool Scouring Effluents and Amounts of Waste Load Generated (median values) [10]
Units BOD COD TSS O&G Phenol Cr Sulphide
mg/l 300 1040 130 - 0.5 4.0 0.1
Kg/t 59.8 204.8 17.2 N.A. N.A. N.A. N.A.

Table 2.3: Effluent Characteristics for Different Mothproofing Methods, using a Permethrin-based Mothproofing Agent. Basis: 1tonne of wool [21]
Method Permethrin Load (g) Wastewater discharge (m3)
Hank Dyebath 8.0 50
Conventional tape scour 30.0 0.75
Mini-bowl tape scour 4.0 0.1
Modified centrifuge 1.7 0.05