A method of recovering mixed lye from indigo post-treatment washing process

Abstract

The invention relates to a method for recycling mixed alkali liquor from an after-treatment washing process of indigo. According to the method for recycling the mixed alkali liquor from the after-treatment washing process of the indigo, after an indigo oxidation process, mixed alkali liquor is sent to a filter press for filter pressing, tap water is filled for washing, washing liquid is divided into two paths, one path returns back to the filter press to serve as washing water, and the other path returns back to the indigo oxidation process to serve as diluting water of alkali fusion materials according to the amount of the diluting water of the alkali fusion materials of the indigo oxidation process after being cooled. According to the method for recycling the mixed alkali liquor from the after-treatment washing process of the indigo, the requirements of the indigo oxidation process are combined, the characteristics of a alkali fusion process are utilized, a method of recycling and reusing is utilized, the filter-pressed washed low-concentration mixed alkali liquor is collected and reused as washing water and the diluting water of the kali fusion materials, full recycling of the low-concentration mixed alkali liquor and the utilization of surplus low-concentration mixed alkali liquor can be achieved, and the aims of emission reduction and fresh water tap water consumption reduction can be achieved.

Description

technical field [0001] The invention belongs to the recycling technology of dye chemical raw materials, in particular to a method for recycling mixed lye in the post-treatment washing process of vat dyes such as indigo. Background technique [0002] Indigo is an environmentally friendly vat dye with a long history, which is widely used in the dyeing of cotton fabrics, especially the warp yarns of indigo denim products. [0003] The current industrial production is to prepare indigo through the oxidation of 3-indoxyl salt. The reaction process includes a certain amount of aniline acetate, sodium amide, and a mixed alkali of sodium hydroxide and potassium hydroxide at 220~250°C. Reaction to obtain 20-30% alkali melt of 3-indoxyl salt, dissolve the alkali melt in a large amount of water, oxidize with air, press filter, wash and dry to obtain indigo. [0004] In the alkali fusion, oxidation and post-treatment process of indigo synthesis, the use of alkali is mainly in the alkal...

AI Technical Summary

Problems solved by technology

According to tracking statistics and analysis, during the post-treatment and washing process of indigo, the filter cake washing causes a large amount of alkali loss, and a large amount of tap water is required to dilute and wash the material. After the lost alkali enters the sewage treatment device, a large amount of acid is required. For neutralization, the treatment cost and production cost are high, and the formed inorganic salt is difficult to biochemically treat, which wastes alkali resources and causes large environmental pollution

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