Purification treatment and pure-salt recovery process for strong-salt wastewater in coal chemical industry

Abstract

Provided is a purification treatment and pure-salt recovery process for strong-salt wastewater in the coal chemical industry. According to the purification treatment and pure-salt recovery process, a working procedure of absorption treatment is additionally conducted on organic matter macromolecules and heavy metals contained in high-concentration salt water after a wastewater reuse multistage reverse osmosis treatment process is carried out; working procedures of evaporation, freezing and desalination are additionally carried out to achieve the purposes of effective utilization of natural energy and industrial low-grade waste heat resources and effective removal of salt-containing wastewater after the working procedure of absorption treatment; a working procedure of chemical separation is added between the working procedure of absorption treatment and the working procedure of desalination to completely convert sulfate radical ions in the salt-containing wastewater into chloride ions and collect and reuse obtained solid, and a nitrate-rich mother solution subjected to crystallization and desalination is returned to a biochemical treatment stage for denitrification treatment. By means of the purification treatment and pure-salt recovery process, salt contained in the salt-containing wastewater is effectively separated out, meanwhile nitrate is returned for biochemical treatment, and secondary steam condensate is evaporated for recycle, so that the whole process achieves the purposes of zero discharge and effective resource utilization.

Description

technical field [0001] The present invention relates to a purification treatment of concentrated salt wastewater in coal chemical industry and a pure salt recovery process, in particular to a method for treating coal chemical industry by using physical adsorption, chemical separation, natural energy utilization, full phase change, direct heat exchange, evaporation crystallization, and freezing crystallization. Process for high concentration saline wastewater. Background technique [0002] Coal chemical process is a kind of industrial process that uses coal as raw material and converts coal into gas, liquid and solid fuels and chemicals through chemical processing, mainly including coal gasification, purification, synthesis, liquefaction, dry distillation, and tar processing and Carbide acetylene chemical industry and other processes. With the continuous reduction of world oil resources, a new generation of coal chemical industry led by coal gasification is emerging, but in ...

AI Technical Summary

Problems solved by technology

However, this method has defects such as high concentration of organic residues (100mg / L), difficult pretreatment, poor strength, serious brokenness of the adsorbent during use, and short service life.

In addition, for the purification and purification of salt in coal chemical wastewater, the traditional natural energy evaporation, freezing and crystallization desalination method has low requirements for influent water quality, large production capacity, high purity of produced water, and the required heat can not only use coal chemical plants. Low-grade heat, and it can also directly use natural energy as energy, and has the advantages of safety and environmental protection. It is very suitable for the surrounding environment where there is sufficient sunshine, large annual temperature difference, large temperature difference between day and night, drought, little rain, and windy places. Therefore, in recent years, People are paying more and more attention to it, but this technology is mainly used for the clean production of salt lake brine and the separation of sodium sulfate and sodium chloride salts, and has not been directly used for the treatment of salty wastewater from coal chemical industry. There is a "clean production process for plateau sulfate type boron-lithium salt lake brine" disclosed by CN102910652A, that is, using the temperature changes in summer and winter, sodium chloride and Glauber's salt solids are separated out in the sodium chloride pool and Glauber's salt pool respectively, However, this process is aimed at salt lake brine, and the processed raw materials do not contain heavy metals and organic substances

Furthermore, this kind of process has the following two disadvantages in the production process: one is that the production process is generally open-air operations, and the evaporated water is greatly affected by meteorological conditions, making continuous production difficult and requiring a large area of ​​land , thus causing unnecessary waste of resources; second, due to the characteristics of the process itself and the limitation of its own process principle, the solid salt obtained through this process is a compound salt of sodium chloride and Glauber's salt, resulting in solid phase products that cannot meet market demand , need to continue to separate, resulting in waste of resources and cost increases

Therefore, in view of the above two situations, people have improved this technology. For example, in the prior art CN102603023A, a kind of "method and equipment for evaporating and concentrating salt water using solar energy and air" has proposed the technology of using flash evaporation and cooling and concentrating Evaporation and concentration of brine improves the efficiency of salt treatment and shortens the treatment time. However, this patent does not separate the individual salts in the saline wastewater in detail, and the concentration of the high-concentration saline wastewater obtained from the final concentration Whereabouts is also not specified in detail; in the prior art CN1644504A disclosed "a method for drying salt in a salt field", it is proposed to add a support rod and a water spray head in the evaporation pool, which accelerates the precipitation rate of salt to a certain extent, but if it is When applied to coal chemical industry, due to the special properties of coal chemical industry salty wastewater, the pipeline may be blocked, and when the chemical plant encounters an emergency and needs to quickly process the salty wastewater, this method will take a long time and have no effect. Low shortcoming; the prior art CN101143730A discloses a kind of " process method for making salt by direct vacuum evaporation of bittern without re-sunning in beach field ", which can improve the quality of salt by 5 percent, but this process is complicated and maintains the Vacuum requires a lot of energy

In the prior art CN103754898B, it is stated that calcium chloride is used as the conversion agent, and the sodium sulfate in the waste water is converted into sodium chloride by utilizing the low solubility of calcium sulfate, so as to realize the purification and purification of salts. The field of application is the soda ash process, and its process route is significantly different from the treatment of salty wastewater in the coal chemical industry, and the patent does not give detailed process parameters

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