Raw Materials and Wastes for Wool Finishing Mill
Processes
Table
2a: Wool Finishing Mill. Fabric Finishing Basis:
1 tonne of wool fabric
| PROCESS |
INPUTS |
WASTES |
| |
Raw materials |
Water |
Energy |
Liquid |
Solid |
Gas |
| Oiling |
Wool Top, Olive Oil (1) |
Electricity |
|
(1) |
|
|
| Carding
& spinning |
|
|
Electricity |
|
N.A. |
|
| Sizing |
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,
, 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 .
Table
2b: Wool Finishing Mill. Fabric Finishing Basis:
1 tonne of finished cloth
| PROCESS |
INPUTS |
WASTES |
| |
Raw materials |
Water |
Energy |
Liquid |
Solid |
Gas |
| Carbonize |
H2SO4
(1) |
30 m3 |
|
(1) |
(1) |
Fine
carbon particles (2), Fumes (SOx), Organic
Decomposition Products |
| Neutralization |
Na2CO3
|
N.A. (5) |
|
pH 2-9, BOD 1.7-2.1 Kg ,
TS 1250-4800ppm (5), FLOW 50-65 m3
|
|
|
| Fulling |
(4) |
N.A. (5) |
N.A. |
(4) |
|
|
| Washing |
Soap Synthetic Detergent |
N.A. (5) |
Electricity Steam |
pH 7.3-10.3, BOD 31-94 Kg
, TS 4800-19300 ppm (5), FLOW 160-400 m3
|
|
|
| Bleaching |
SO2 or H2O2
|
N.A. (5) |
Electricity, Steam |
pH 6.0, BOD 1.4 Kg , TS
908 ppm (5), FLOW 1-11 m3 |
|
|
| Dyeing |
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
, 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 ,
it produces some solid waste but little liquid waste.
(2) According to Lund , 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 .
(3) In accordance with Jones, 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 . Little waste
is generated since the fulling solution remains in
the cloth .
(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 .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
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
| 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 |