The document discusses carbonizing processes in the textile industry. Carbonizing uses sulfuric acid to destroy any remaining vegetable particles in scoured wool that mechanical processes could not fully remove. It can be done on loose fibers or fabrics. For loose fibers, the damp wool is soaked in an acid solution and dried. For fabrics, it is immersed in acid and passed through a carbonizing chamber to remove particles. A newer "Carbosol" process uses an organic solvent instead of water and has environmental and quality advantages over traditional methods.

1. Carbonizing in textile industry
Back to EFFICIENCY FINDER FOR TEXTILE INDUSTRY
1. OBJECTIVE
Sometimes scoured wool contains vegetable impurities
that cannot be completely removed through mechanical
operations. Sulphuric acid is the chemical substance used
for destroying these vegetable particles and the process is
called carbonizing (BAT for the Textiles Industry, July 2003).
2. FIELD OF APPLICATION
Carbonizing can be caried out on (BAT for the Textiles
Industry, July 2003):
floc/loose fibre
fabric
This operation is not applied in the carpet secto.

2. 3. DESCRIPTION OF TECHNIQUES, METHODS AND
EQUIPMENT
Loose fibre carbonizing: (BAT for the Textiles Industry
July 2003)
t is performed only on fibres that are later used to produce
fine fabric for garments (worsted fabrics) and usually takes
place at the scouring mill.
In typical equipment for carbonisation of loose fibre, the
stll damp scoured wool is soaked in a solution containing 6
-
9%of mineral acid (generally sulphuric acid). Excess acid
and water are removed by pressing or by centrifugation
until on average 5- 7.5 % of sulphuric acid and 50 65 %
of water remain. The fibres are then dried at 65 - 90 °C to
concentratethe acid and baked at 105 130 °c (cSIRO
method) (literature: IPPC- BAT). Dry and bake in the dryer at
140° (literature: H.K. Rouette: Encyclopedia on textile
finishing, Springer, 2001)
As soon as the wool is dried, it is fed into a machine, which
consists of two counter-rotating rolls. These rolls crush the
carbonised particles into very small fragments, which are
then easily removed. The addition of small quantities of
detergent to the sulphuric acid improves the yield and
reduces the attack on the wool. In order to prevent the fibre
from being gradually degraded, the pH is finally set to 6 by
neutralisation (bath) with sodium acetate or ammonia.
Sulphuric acid can be replaced by gaseous HCl or by
aluminium chloride.
After carbonizing, the fibre can be carded and then spun
before being dyed or it can be dyed directly in floc form.
Fabric carbonizing: (BAT for the Textiles Industry, July
2003)
It is typical of woollen fabrics. The operation can be carried
out by either the traditional or the more modern "Carbosol"
system.
The conventional procedure is substantially similar to that
used for loose fibre. The fabric can be previously soaked in
a water or solvent bath and squeezed, but this step is
optional. Then it is impregnated in a concentrated sulphuric
acid solution (acidification) and squeezed (hydro-
extraction) before passing through the carbonizing
chamber. The carbonised particles are then removed by
mechanical action and subsequent washing. In modern
carbonizing plants all these steps are carried out in
continuous mode.

3. The "Carbosol" process, licensed by SPEROTTO RIMAR,
uses an organic solvent instead of water. The equipment
consists of three units. In the first one the fabric is
impregnated and scoured with perchloroethylene, in the
second the material is soaked in the sulphuric acid solution
and in the third, carbonizing and solvent evaporation take
place. At this stage the perchloroethylene is recovered by
distillation in a closed loop.
The "Carbosol" system is reported to have several technical
advantages over the traditional process. The level of acidity
of the fabric after carbonizing is much lower and the risk of
damage to the wool fibre is reduced. Thanks to full recovery
of the organic solvent, the process can also be considered
more efficient from the environmental point of view.
Figure 2.13: Representation of a coRVentional carboaising instalation
, Boazetta, 197
ove pregnabon unit
4. COMPETITIVE TECHNOLOGIES AND ENERGY SAVING
POTENTIALS
a) Changes in the process
No information is available.
b) Changes in the energy distribution system
No information is available.
c)Changes in the heat supply system
No information is available.

4. Table 14.1. Characteristics of Different Biochars
11.
Feedstock Feedstock Biochar
H/C ojc HHV
(MJ/Kg)
H/C oc HHV
(M/Kg)
White pine 1.40 0.62 18.06 0.43 0.08 31.41
Fruit cuttings 1.61 0.77 17.27 0.12 0.09 29.02
Switchgrass 1.56 0.77 19.50 0.70 0.24 26.60
Barley straw 1.45 0.66 17.34 0.40 0.11 26.02
Safflower 1.68 0.62 24.80 0.43 0.21 30.27
seeds
Eucalyptus 1.47 0.71 16.69 0.81 0.27 26.19
sawdust
Barley straw 1.45 0.66 17.34 0.86 0.21 27.49
Corn stover 1.62 0.73 16.20 0.94 0.18 27.76
Spruce 1.49 0.65 19.94 1.24 0.49 22.50
Birch 1.56 0.68 20.42 1.24 0.49 22.50
Maize silage 1.58 0.55 22.30 1.13 0.09 35.70
Coconut fiber 1.41 0.71 18.40 0.66 0.15 30.60
Eucalyptus 1.59 0.72 18.90 1.01 0.22 29.40
leaves
Corn stalk 1.58 0.65 17.51 0.94 0.17 29.21
Wood 1.65 0.68 17.93 0.90 0.22 28.38
HHV, higher heating value.