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Viscose Filament Yarn (VFY) manufacturing (This image is for illustration purpose only, not of the actual plant)

By Pushkar Shukla, Amit Kumar, Sanjeev Gupta and Hiten Mehta

In the present case study, A Viscose Filament Yarn (VFY) manufacturing unit is conducting dyeing operations using dispersed pigments in their plant. During the color change in yarn manufacturing, the existing pigment solution is drained from the tank.

This solution is collected in a sump and further sent to ETP along with acid wash effluent (pH= 2, Flow = 200 m3/h). The complete effluent management system of the plant is mentioned in Figure 1.

Figure 1: Layout of effluent management stream of VFY manufacturing plant | Figure 2 (A-F): Results of pre and post (left-right) treated samples during pilot trials

The effluent treatment plant comprises of 5 Streams, of which 3 streams (D1, D2, D3) are major streams: D3 stream is the color-rich stream which comprises of dye room effluent along with washing of pot spinning process. D3 stream merges with highly Acidic and Zinc-rich D2 stream. The presence of Zinc Sulphate and Sulphuric Acid make this an acidic and metal-rich stream with a pH ~2. The stream is taken to a clarifier where pH is adjusted with lime to alkaline to precipitate and remove suspended matter. However, color arising due to Pigment rich stream is not efficiently removed.

D1 Stream is Alkaline in nature arising from Caustic Soda Plant, Water Treatment Plant (WTP), Alkaline effluent of other manufacturing processes. The effluent of a power plant is also mixed into this stream. D1 Stream is neutralized and treated with Polyelectrolyte to remove suspended matter.

After conducting lab scale trials on combined (D2+D3) stream good color removal was observed. However, the doses and large volume were making the treatment process economically unfeasible. Hence, it was decided to segregate the color-rich dye room effluent from other effluents and treat it with VYTAL 641 on a batch scale, and then send the treated water to D2 stream. Though, this required additional piping in the current set-up, significant savings in terms of operating cost made it more viable.

To check the validity of the proposed system, a pilot-scale trial was planned for 2 days where dye room effluent was treated with VYTAL 641 in a 300 L clarifier and results were monitored.

From Table 2 and Figure 2 (A-F) it can be observed that VYTAL 641 was able to deliver consistent performance in the case of an individual as well as mixed pigment-containing effluent giving between 98 to 99.9 % color removal.

On the basis of the successful pilot trial, it was decided to segregate the high color dye room washing stream and treat it separately. As there were space constraints in the plant, it was decided to have 6 clarifiers of 1 m3 capacity each instead of one large clarifier. This can treat the incoming effluent from the dye room before discharge to the ETP. Another advantage of this scheme is that effluent can be treated batch-wise depending upon the quantity generated. The treatment scheme is described in Figure 3.

Figure 3: Proposed treatment scheme for dye room effluent with C.S of clarifier

The results obtained from commercial trials are tabulated in Table 3.

Good results of final implementation into plant led to the successful deployment of the treatment system. The persistent problem, for several decades, was solved by the novel Product (VYTAL 641).

Figure 4 (a-d): Results of pre and post (left-right) treated samples during implementation

In this study, we synthesized novel hybrid coagulants for the removal of dispersed pigment. VYTAL 641 shows significant removal efficiency for dispersed pigment (≥95 %), it also shows faster and larger floc formation compared to other coagulants which in turn will lead to better operational efficiency. It has shown good anti-dispersant properties to coagulate the suspended pigment particles, which the conventional treatment system was not able to achieve. The VYTAL 641 based treatment system was found to be robust across all dyes and mixed effluent.

Overall, it can be concluded that hybrid-coagulants can provide better color removal than conventional inorganic coagulants, in a single step.

About the Authors

Dr. Pushkar Shukla holds a Master’s degree in Organic Chemistry and Ph.D. in Chemistry from ICT, Mumbai. He has 10 years of research experience in water, wastewater treatment, adsorption, development of separation, and purification technologies and Environment Research. He presently leads the water product development team at Grasim Industries. He has 10 research papers and 3 patents to his name.
Amit Kumar holds Master’s degree in Chemical Engineering from IIT Roorkee. He is having 7 years of experience in specialty chemicals for water treatment and oil & gas industries. He is presently leading Industrial, new product, and application development at Grasim Industries Limited.
Dr. Sanjeev Gupta holds a Master of Science in Applied Chemistry and Ph.D. in Chemistry. He has 18 years of experience in industrial research. His expertise includes water & wastewater treatment, hybrid biochemical treatment, environmental management, Chemical recovery, New product development, etc. Dr. Gupta was awarded Mecaster Young Scientist Award for the year 2011.
Dr. Hiten Mehta holds a Master of Science in Organic chemistry and a Ph.D. in Chemistry. He has 17 years of experience in industrial research. His expertise includes process development, Intellectual properties, regulatory guidelines for various regions of API, specialty chemical, personal care actives, Aluminium chemistry, and applications focused product development.

This case study was published in the annual “Finest-50 Global Case Studies” Special Digital Edition, March-April 2022. Click here to read the complete e-Magazine issue.

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