Recovered mixed alkali solution from production of indigo, and recovering method and use thereof

Abstract

The invention relates to the field of dye production, in particular to a method for recovering potassium and sodium mixed alkali solution in the production of indigo. The method comprises: introducing carbon dioxide gas into used mixed alkali solution in which the sodium ion molar ratio is slightly higher to form sodium carbonate, precipitating sodium carbonate and removing sodium carbonate to obtain the raffinate, namely the recovered mixed alkali solution in which the potassium ion molar concentration and the sodium ion molar concentration are closer. The recovered mixed alkali solution, after being concentrated and dehydrated, can be used as an alkali fusion solvent in the production of an indigo dye. In the recovering method, the ratio of potassium to sodium can be regulated by introducing tail gas of combustion of natural gas instead of supplying expensive potassium hydroxide, so the production cost is reduced greatly; and the ratio of potassium to sodium in the recovered mixed alkali solution is 1:(1-1.4), so the recovered mixed alkali solution is suitable to be used as the alkali fusion solvent in indigo production by various methods. When the recovering method is used, a large amount of sodium carbonate serving as an intermediate product can be obtained, and environmental protection performance is higher compared with directly discarding the excess mixed alkali solution in the past.

Description

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AI Technical Summary

Benefits of technology

This patented technology allows for efficient recoveries without requiring excessive amounts of expensive chemicals or producing unwanted products such as salt water during manufacturing processes. It achieves these benefits through utilizing naturally occurring gases from burning coal instead of traditional sources like lime kiln exhaust gas (LFG) or soda ash. By adding specific ratios between different metals, valuable materials are obtained while reducing environmental impact on disposal options.

Problems solved by technology

This patented technical problem addressed in this patents relates to improving the recovery or balancing of nitroblue dye products from wastewater treatment plants without adding any chemical agents like caustic soda during their production processes.