Installing Overhead Moving Rail
Installing Overhead Moving Rail -Provision of overhead moving rail with stirrer in colour kitchen so as to avoid print paste spillages, which is commonly encountered in situations when the stirrer is stationery and filled drums are moved for paste preparation. Reduced spillage (about 5-7 kg print paste per day is spilled while shifting drums). Ease of operation and reduced fatigue to workers. Reduced pollution load. Improved shop floor environment. iii aaa
This measure could be implemented in colour kitchens, where print paste is prepared. Space availability above the drums for installation of the overhead cranes has to be ensured before implementing this measure.
Reusing dye liquor
The spent dyeing bath, depending on type of dye used, contains residual dyes, auxiliary chemicals, thermal energy and water. Besides, the mentioned resources, discharged spent dye baths cost significant amounts in their treatment, before they get discharged. In practice, direct VAT, disperse and sulphur dyes spent bath can be recycled several times with proper filtration and storage. However, for recycling of spent bath, it is desirable to have circuit collection tanks with proper colour codes for pipings, preferably for different shades to avoid interference of colour mixing for synthetic and blended fibres. Where dyeing is done at higher temperatures, the spent liquor can be transported to storage tanks using the available pressure. Normally dyeing is done at 113°C having 2 Kg pressure, which is sufficient in transportation to storage tank without using additional energy. However, in case of reactive dyes, recycling is possible only after adsorption of residual hydrolysed dyes, using a suitable adsorption media like activated carbon or membranes to remove high molecular dye stuffs. The spent dye bath of reactive dyes contributes high inorganic emission load due to electrolyte and alkali. Moreover, reactive dyes are applied at low temperature which requires additional energy for transportation of spent bath to the storage tank in practice. Reuse of reactive dye spent bath is generally not acceptable. Therefore, care should be taken before practicing this.
In reusing and recycling of spent bath, one can prevent a major portion of the auxiliary chemicals from going down the drain, which also contributes to a high TDS and which hampers the biological activity for removal of organic pollutants. Reuse of spent dye bath, not only reduces the organic and inorganic pollution load, but also
Reuse of spent dye bath is very much feasible for synthetic and blended fibres using direct, VAT, disperse and sulphur dyes. The light shade and medium shade spent bath can also be used for dark shade application by optimising the make-up chemical requirement. For reactive dyes, the application is still techno-economically not feasible but environmentally desirable.
The investment for proper collection filtration and reuse of dye bath will vary from unit to unit, depending upon the type of shades mostly used and the space available for additional storage tanks and pipings. etc.
Investment for additional installation of 1 to 10 tanks, piping and control
This option is feasible and suitable, particularly for large orders for same shade or darker shades without affecting the product quality, provided proper elaboration of spent bath and addition of make-up chemicals are strictly controlled. In developed countries, it has been reported that spent dye baths are re-used up to 25 times, before being discharged to the wastewater treatment plant.