"We are eager for a clear way out for waste salt by-product from waste water treatment." During the recent visit of the China Chemical News Agency's Yangtze River Economic Zone Dye and Intermediate Industry Development Research Group, many companies reported that mother liquor water treatment has become a constraint on dyes and intermediates. An urgent task for industrial development, how to dispose of waste salt by-products has always troubled them.

According to experts, a large amount of wastewater is discharged during the production of dyes and intermediates. The main characteristics of these wastewaters are "three highs and one difference", that is, high chroma, high COD, high salinity, and poor biodegradability. A large amount of high-concentration salt-containing organic wastewater or high-salt mother liquor, containing organic matter produced by evaporation and crystallization, is difficult to treat, and will cause environmental hazards and safety risks. The use of advanced pollution control technology to implement clean transformation of the dye and intermediate industry, and speed up the solution of the treatment and reuse of salty wastewater in the dye and intermediate industry is an important topic that has a contribution to the present and will benefit the future. In the process of investigation and visit, the investigation team can clearly feel that enterprises generally attach great importance to the problems of dye wastewater treatment and resource utilization, and have made progress to varying degrees. Green, clean, recycling, and energy-saving technologies and equipment have greatly reduced the production cost and energy consumption of dye companies. At the same time, the amount of "three wastes" has also been significantly reduced. However, where the waste salt goes has been perplexing everyone in recent years.

Some companies have reported that in recent years, my country has explored the characteristics of high acidity, high chroma, and high COD of dye mother liquor water, and believes that the substances in the mother liquor wastewater can be recycled to prepare a series of by-products such as ammonium sulfate and ammonium chloride. , So as to realize the utilization of waste resources. However, according to the revised content of the national standard GB535 No. 1, the by-product ammonium sulfate is excluded from the national standard, which makes the by-product no standard to follow. It is classified as a hazardous waste to a certain extent and lacks control of key indicators, leading to product market acceptance. Lower, sales to downstream users also have potential environmental risks.

Some companies are thinking about whether ordinary salt can return to nature. Because abroad, ordinary sodium salts such as pure sodium chloride and sodium sulfate that do not contain organic matter can be returned to the sea. In my country, many ordinary sodium salts are now landfilled as hazardous wastes. In fact, pure ordinary sodium salts can be obtained by burning at high temperature without organic matter.

Some companies believe that the co-processing of hazardous waste in cement kilns is an ideal method for the treatment of waste salt in the dye and intermediate industries, but it has encountered obstacles in the promotion of technology. Cement kiln co-processing means that solid waste that meets or meets the requirements of entering the kiln after pretreatment is put into the cement kiln, and the harmless treatment of solid waste is realized while cement clinker is produced. Hazardous waste treatment follows the principles of harmlessness and resource utilization, and cement kiln co-processing can meet the requirements. Dyestuff companies hope that the country can liberalize the promotion of cement kiln co-processing of hazardous waste, so that resources can be recycled and effectively used.

Some companies believe that even if the by-product waste salt from wastewater treatment is processed, it will still contain a certain amount of COD. It is not recommended to discharge it directly to the sea. The solid waste can be incinerated at a high temperature through an incinerator or other technology to solve the solid waste. Troubles.

It is understood that the dye industry is formulating the industry standard "Ammonium Sulfate by-product from Dye Wastewater Treatment", but the progress is relatively slow. According to the relevant person in charge of the China Dyestuff Industry Association, the industry standard of "Ammonium Sulfate by-product from Dye Wastewater Treatment" has entered the stage of toxicological experiment. After the toxicological experiment is passed, the introduction of the standard will be just around the corner.

Research Group of Dyestuff and Intermediate Industry Development in Yangtze River Economic Zone of China Chemical Industry News

The research content of this issue is written by Zhang Xiang, Wang Zhuofeng, Meng Jing, Pan Jiecai