INDIGO Dye Recovery Plant
Product Outline
In the production of denim fabric, yarn is impregnated in a series of reduced or soluble indigo dye baths.
After dyeing, the yarn is rinsed with water and the dilute dye solution is sent to the wastewater treatment plant.
If the dyeing process is not controlled properly, a large amount of indigo can be removed in washing. The wasted indigo then enters wastewater streams. This wastage generally results from the use of excessive concentrations of indigo in the boxes (> 3 g/L) or low sodium hydrosulfite concentrations. Large amounts of dilute dye solution of approximately 0.5 g/L are generated in the rinse process. The dilute dye stream imposes heavy load of organic matter to the wastewater treatment plant, and if not recovered, large amounts of valuable dye are lost.
The wasted indigo consists of:
(1) Indigo that was not reduced to the leuco form and
(2) Indigo that was reduced but did not attach to cotton fiber.
The unreduced indigo has the potential for recovery and reuse for cotton dyeing. The rinse water from the dyeing operation is insoluble indigo dye solution of approximately 0.5 g/L, which is then sent to a low temperature vacuum evaporation system for concentration and reuse.
RAFAE Engineering utilizes the unique waste heat evaporation systems to capture the insoluble indigo dye.
Advantages:
10-15% recovery of indigo dye.
Waste water treatment cost saving.
Water recovery.
Waste heat recovery.
If the dyeing process is not controlled properly, a large amount of indigo can be removed in washing. The wasted indigo then enters wastewater streams. This wastage generally results from the use of excessive concentrations of indigo in the boxes (> 3 g/L) or low sodium hydrosulfite concentrations. Large amounts of dilute dye solution of approximately 0.5 g/L are generated in the rinse process. The dilute dye stream imposes heavy load of organic matter to the wastewater treatment plant, and if not recovered, large amounts of valuable dye are lost.
The wasted indigo consists of:
(1) Indigo that was not reduced to the leuco form and
(2) Indigo that was reduced but did not attach to cotton fiber.
The unreduced indigo has the potential for recovery and reuse for cotton dyeing. The rinse water from the dyeing operation is insoluble indigo dye solution of approximately 0.5 g/L, which is then sent to a low temperature vacuum evaporation system for concentration and reuse.
RAFAE Engineering utilizes the unique waste heat evaporation systems to capture the insoluble indigo dye.
Advantages:
10-15% recovery of indigo dye.
Waste water treatment cost saving.
Water recovery.
Waste heat recovery.
How it works:
The rinse water containing 0.3 g/L indigo dye will be stored in storage tank after prefiltration and then sent to waste heat evaporator to be concentrated up to 20 g/L concentration. The source of waste heat may be:
Flash steam from condensate.
Boiler blow down flash.
CRP condenser heat
Any other
The concentrated indigo dye solution then sent to rope dyeing for reuse.