Reuse of post neutralization washes as pre washes at pretreatment machine

Technical description

In woven fabric textile finishing industries, continuous pretreatment machines are employed to perform desizing washes, scouring and post scouring washes, bleaching and post bleaching washes, and subsequent neutralization of the alkaline fabric with acid. In this machine, there are three sections of wash boxes: washes for desizing, post-scouring washes, and post-bleaching washes. After post bleaching washes, the fabric is treated with acid for neutralization of the fabric and then washed in the post-neutralization wash boxes at about 60oC temperature. The post-neutralization wash water can be reused as pre-wash water by directing the discharge pipeline of the neutralization section wash water into the supply line of pre-wash boxes (see Figure 1). For pre-washing, high-quality water is generally not required and neutralization wash water can be a good option for such type of washing.

$Description: C:\Users\suman\Downloads\Untitled.png$

Figure 1: Reuse of washing water after neutralization for the desizing washing process

Achieved environmental benefits:

Water conservation
Reduction in thermal energy (hot water will not require less steam for heating)
Reduction in greenhouse gases
Reduction in a hydraulic load of the wastewater treatment plant

Operational data:

The typical quality of pre wash and post neutralization wash water of one industry is given in Table 1 below.

Table 1: Example for the typical quality pre wash and post neutralization wash water

Parameters	Pre wash water	Post neutralization washing water
pH	8.17	7.29
Total hardness as CaCO3 (mg/l)	880	840
Total dissolved solids (TDS) (mg/l)	5,682	6,696

The quantity of post-neutralization wash water will vary from industry to industry, depending upon the operational frequency of the pretreatment machine and the quantity of fabric bleached and neutralized. The water is in the range of 50 to 82 m3/d (12,500 to 20,500 m3/yr) which can be reduced in the pretreatment machine. Its value is USD 9,200 to 15,130/yr (Rs. 1.38 to 2.27 Million/yr).

The implementation of this option will reduce water and steam consumption in the pretreatment machine.

Cross-media effects:

No relevant cross-media effect is known.

Technical considerations relevant to applicability:

This measure is applicable to all woven fabric processing industries where open-width continuous pretreatment machines are used. This measure does not require any intervention in the process, no major infrastructure development, and no technical human resource requirement. The post-neutralization washing water will be directed to the pre-wash boxes of the machine (see Figure 1).

The implementation cost will be USD 1,330 to 2,660 (Rs. 200,000 to 400,000) for the collection sump, pipelines, and small pump (if required).

Economics:

Capital cost = USD 1,330 to 2,660 (Rs. 200,000 to 400,000)

Annual saving = USD 9,200 to 15,130 (Rs. 1.38 to 2.27 million)

Annual O&M cost = USD 660 to 1,330 (Rs. 100,000 to 200,000)

Simple payback period = 2 to 3 months

An additional benefit will be the reduction in hydraulic load and treatment cost of the wastewater treatment plant.

Driving force for implementation:

Financial benefits
Resource conservation
Sustainability of textile business

Reference industry:

This measure is applicable to all the woven fabric textile finishing industries where open-width continuous pretreatment machines are employed.

Back