A method for comprehensive recovery and utilization of wastewater from alkaline washing process

Abstract

The invention discloses a comprehensive recovery and utilization method for alkali cleaning working procedure waste water. The method comprises the steps that 1, waste alkali water is pumped into a neutralization kettle to be neutralized with hydrochloric acid, the pH value is adjusted to range from 1 to 4, benzoic acid turbid liquid is generated and cooled by cooling water to normal temperature, the turbid liquid is pumped into a plate-and-frame filter press, and a filter cake, namely benzoic acid obtained after filtering and pressing is used for producing methyl benzoate; 2, filter liquor obtained after filtering and pressing in the step 1 is collected into a filter liquor collection groove, caustic soda flakes are added for neutralization, the pH value is adjusted to range from 9 to 10, then the filter liquor is pumped into an evaporator for vacuum concentration, heating is stopped after the volume is concentrated to be 1 / 10-1 / 5 of the original volume, the temperature is cooled to be normal temperature, kettle bottom residual liquor is placed into a filter groove for vacuum concentration, a filter cake, namely sodium chloride is obtained and recycled as industrial salt, and the filter liquor with sodium benzoate is collected into an alkaline water groove for next circulation. According to the comprehensive recovery and utilization method for alkali cleaning working procedure waste water, the salt content and COD content in waste water are effectively reduced, and therefore waste water up-to-standard release is facilitated.

Description

technical field [0001] The invention relates to a method for comprehensive recycling of alkali washing wastewater in the production process of chemical products, and in particular provides a method for recycling benzoic acid and sodium chloride from alkali washing wastewater containing by-product benzoic acid. This method is especially suitable for the production of diphenyl Comprehensive recovery and utilization of waste alkali water resources generated in the alkali washing process in the formylmethane process. Background technique [0002] Benzoic acid is also known as benzoic acid. Benzoic acid is generally used as a medicine or preservative to inhibit the growth of fungi, bacteria, and mold. It is usually applied on the skin when it is used as medicine to treat skin diseases such as ringworm. Used in synthetic fiber, resin, paint, rubber, tobacco industry. [0003] In the production process, if the by-product benzoic acid is not recycled, it will have a serious negativ...

AI Technical Summary

Problems solved by technology

The process of producing dibenzoylmethane is divided into condensation, pickling, alkali washing, water washing, concentration, crystallization and other processes. In the pickling process, some methyl benzoate will be hydrolyzed to produce benzoic acid. During alkali washing, benzoic acid and Alkali reacts to produce sodium benzoate. When the separated sodium benzoate is neutralized with hydrochloric acid to recover benzoic acid, the filtrate contains about 8% sodium chloride and some crystal escapes. If this part of waste water is not treated, it will be discharged to the sewage treatment system. It affects the normal operation of sewage treatment and increases operating costs. In serious cases, sewage treatment cannot operate normally, and it is forced to reduce or stop production. Therefore, this part of wastewater must be treated to ensure normal production order