Raw Materials and Wastes for Wool Scouring Mill Processes

Table 1: Wool Scouring Mill Basis: 1 tonne of scoured wool
  Raw materials Water Energy Liquid Solid Gas 
Sorting & blending
Wool 1300-4000 Kg (1)   Electricity      
Soap, Sodium Carbonate 30-50 m3 [8](3) Electricity, Steam pH 9.0-10.4, BOD 104.5-221.4 Kg [8], TS 1129-64448 ppm (2), FLOW 20-50 m3 (3) N.A.  
    Electricity, Steam     Vapours, Particulate 
Top making
    Electricity   N.A.  

(1) According to the literature reviewed, raw sheep wool contains from 25 to 75% suint, which includes water soluble excretions of the sheep such as urine, feces, blood, dirt, grease, etc. From this data, the amount of raw wool needed to obtain 1 tonne of scoured wool has been calculated.

(2) Due to the high amount of organic impurities present in raw wool, the scouring process contributes to more than half or even up to two-thirds of pollution load in terms of BOD [10]. From the scour liquor, lanolin can be recovered by acid cracking or centrifugation. Lanolin recovery reduces BOD by 20-30%. Also suint can be recovered and sold for detergent manufacture reducing BOD by another 20-30% [5].

(3) Tables 1.1 and 1.2 give the water consumption and pollution load for wool scouring mills as extracted from reference [10]. As can be seen, the water consumption range for the scouring stage given in reference [8] is consistent with the data from reference [10], but the BOD reported in the former is higher. Differences might be due to the recovery of lanolin from the scouring effluent. According to the flow diagrams presented in reference 10, it seems that lanolin recovery is included as a part of the process. However, whether lanolin recovery is considered or not in reference [8] it can not be assured from the description given.

Table 1.1: Amounts of water typically used in Wool Scouring Mills [10]
Units: m3/t of scoured wool
Minimum Median Maximum 
4.2 11.7 77.6
Table 1.2: 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 6000 30000 8000 5500 1.5 0.05 0.2 
Kg/t 41.8 128.9 43.1 10.3 N.A. N.A. N.A.