Page 74 - Materials Chemistry, Second Edition

Ch002-P373623.qxd 3/22/07 5:27 PM Page 55
Cleaner Production
Around 24 tons of fabric per annum are dyed with sulfur black dyes 55
Annual savings on current production: $1,632
Annual benefits from increased production capacity: $3,684

AmirTex: Savings of $35.7 per ton were achieved; however, where hydrogen
peroxide was already used as the oxidant, the savings reduced to $8 per ton.
AmirTex processes 21.6 tons per year using sulfur black dyes. Due to improved
fabric quality AmirTex has increased production to 70 tons per year and reduced
the use of more expensive reactive dyes, a saving of approximately $86 per ton.

Annual savings on existing production: $419
Annual savings by reducing use of reactive dyes: $4,160

Improved fabric quality
Elimination of free sulfur now avoids the past problem: residual sulfur on
the fabric progressively oxidized to form sulfuric acid, which then attacks
and may eventually destroy the fabric.
At El-Nasr factory, fabric strength was improved by 5% by using glucose
instead of sodium sulfide.

Improved productivity
The modified process not only improved product quality but also reduced
wastage. In all factories, the modified process was shorter than the conventional
process, thereby saving on time and labor costs.

Environmental benefits
Concentrations of both hexavalent chromium and sulfur were significantly
reduced in the effluent coming from the dyeing line at the three factories. BOD
levels increased, as shown in Table 2.21 due to the use of glucose; however,
it is not likely to significantly increase either wastewater treatment costs or
the characteristics of the final effluent.

Savings on effluent treatment requirements
Elimination of sodium sulfide and acidified dichromate made the final efflu-
ent easier to treat, as it became less toxic and corrosive. At AmirTex savings
on wastewater treatment requirements were estimated to be around $10 per
ton of fabric processed.

Improved working conditions
Workers interviewed at the factory were very positive on the improvement
to working conditions. The bad odors and inhalation of sulfur fumes have
been removed and the substitute chemicals are much safer to handle.
A summary of benefits and achievements for the three factories is
shown in Table 2.22.