Polyester dyeing machine
Polyester dyeing machine – The spent dye bath from polyester dyeing could be reused by adding make-up chemicals. The dye bath could be directly discharged into a storage tank kept at an elevated level (refer the enclosed picture), by the pressure of the machine itself and could be re-charged into the machine for the next batch by gravity. You can read Chemical Consumption for Dyeing Fabric
Figure showing the arrangement of piping and valves for dye reuse dyeing machines in polyester dyeing
This measure results in reduced water consumption, as well as reduced pollution load to the ETP (effluent treatment plant). In addition, reduced consumption of auxiliary chemicals in subsequent batches can also be achieved. Due to heat recovery, implementing this measure results in reduced energy consumption.
Applicable in the polyester, as well as wool dyeing, where acid dyes of dark shades are used. Number of times of re-use depends on the level of oil content in the fabric and also on the type of shade.
Savings of this option depends on the quantity of heat recovered and the reduction in quantity of auxiliary chemicals in subsequent dyeing operations, as well as the shade of dye used.
Substituting dyestuff for effective dyeing
Environmental problems surrounding the dyeing of fabrics can be reduced or even prevented in the materials procurement stage by means of a careful selection of chemicals, substitution of dyestuffs with more efficient ones and quality control of the raw materials.
Applying dyestuffs with a higher colour intensity (and, although with a lesser impact, with higher fixation rates) can reduce the amount of dyestuff disposed off through the wastewater considerably. Colour intense dyestuffs require less pigment to achieve the same colour intensity.
Reactive pigments contain one or more reactive groups, which increase the fixation rate of the dyestuff so less pigments are discharged with the wastewater. Reactive pigments can be used for dyeing materials such as cotton, polyamide and wool. Whenever possible, select reactive pigments with a stable fixation efficiency under variable process parameters such as liquor ratio, salt, pH level, temperature and time. Furthermore, selecting dyes with several reactive groups can result in a better fixation and resistance against hydrolysis. It is best to select pigments with a high colour intensity, combined with a high level of fixation and a low salt requirement. At the same time, the pigments should be easy to rinse out.
Substitution of pigments with a high metal content with pigments that are low in metals but with an equal or higher fixation level contributes to a reduction in the disposal of heavy metals into the wastewater. Apart from this, all other (auxiliary) materials necessary in the textile processing can also be screened as to their impact on the environment (e.g. formaldehyde, heavy metals, etc.).
A reduction in the emissions of polluting substances into the wastewater and air.
It is complicated to make such changes, and in the case of existing production processes with existing dyestuff recipes it is generally recommended not to make such changes. However, this measure is feasible in the case of new product designs or the optimization of existing production processes. Before implementing the substitution of chemicals, it is important to investigate the effects of the new materials on the quality of the end product and / or the production process. It is recommended to consult your materials supplier on this.
The investments related to materials screening and switching depend on the additional costs of the materials involved. Savings are possible by consuming less raw materials and auxiliary materials and a reduction of the wastewater fees.
