阅读说明：本技术 一种从高盐水合肼溶液中回收并精制盐碱的方法 (Method for recovering and refining saline-alkali from high-salt hydrazine hydrate solution ) 是由 黄永明 郭如涛 徐冬华 杨骥 邱兆富 胡宗贵 朱桂生 马克和 于 2019-11-21 设计创作，主要内容包括：本发明公开了一种从高盐水合肼溶液中回收并精制盐碱的方法,具体步骤：(1)高温蒸发高盐水合肼溶液后,室温下结晶回收NaCl粗产品；(2)步骤(1)蒸发时产生的蒸汽经过冷凝后通过精馏分离回收水合肼,部分冷凝水则回流至步骤(1)蒸发结晶NaCl后过滤产生的滤液中得到含Na<Sub>2</Sub>CO<Sub>3</Sub>和NaCl的浓卤；(3)精制步骤(1)得到的NaCl粗产品得到高纯度NaCl成品；(4)冷冻结晶步骤(2)得到的浓卤回收高纯度Na<Sub>2</Sub>CO<Sub>3</Sub>成品；(5)步骤(4)冷冻结晶后剩余液体与原水混合后进行蒸发循环处理。本发明采用的方法可以实现高盐水合肼溶液中氯化钠和碳酸钠的分离及氯化钠和碳酸钠的高效提纯,且无废水排放,实现环保效益和经济效益双赢。(The invention discloses a method for recovering and refining saline from a high-salt hydrazine hydrate solution, which comprises the following steps: (1) after high-temperature evaporation of the high-salt hydrazine hydrate solution, crystallizing at room temperature to recover a NaCl crude product; (2) condensing steam generated in the evaporation in the step (1), then recovering hydrazine hydrate through rectification separation, refluxing part of condensed water to the filtrate generated in the evaporation and crystallization of NaCl in the step (1) and then filtering to obtain Na-containing sodium chloride 2 CO 3 And concentrated brine of NaCl; (3) refining the NaCl crude product obtained in the step (1) to obtain a high-purity NaCl finished product; (4) high-purity Na is recovered from concentrated halogen obtained in the step (2) of freezing crystallization 2 CO 3 Obtaining a finished product; (5) mixing the residual liquid after freezing crystallization in the step (4) with raw water and then carrying out evaporation circulation treatment. The method can realize the separation of sodium chloride and sodium carbonate in the high-salt hydrazine hydrate solution and the efficient purification of the sodium chloride and the sodium carbonate, does not discharge waste water, and realizes the win-win of environmental protection benefit and economic benefit.)

1. A method for recovering and refining saline from a high-salt hydrazine hydrate solution is characterized by comprising the following steps:

step 1, evaporating high-salt hydrazine hydrate solution, cooling, crystallizing and recovering NaCl crude product

Measuring the content of sodium chloride, sodium carbonate, sodium sulfate, total salt, TOC and hydrazine hydrate in the high-salt hydrazine hydrate solution, and ensuring that the concentration of NaCl in the high-salt hydrazine hydrate solution is far greater than Na ₂CO ₃The concentration, then inputting the raw water of the high-salt hydrazine hydrate solution into an evaporation device for evaporation, stopping heating when the evaporation amount reaches the optimal evaporation amount, cooling and crystallizing at room temperature, then separating crystals and the solution, drying the separated crystals at 105 ℃ and roasting at 300 ℃ to obtain a NaCl crude product, and using the separated filtrate for low-temperature freezing crystallization to recover high-purity Na ₂CO ₃Obtaining a finished product; the salt in the high-salt hydrazine hydrate solution is mainly NaCl and Na ₂CO ₃；

Step 2, rectifying, separating and recovering hydrazine hydrate

In the process of evaporating the high-salt hydrazine hydrate solution in the step 1, condensing the generated steam, separating and recovering hydrazine hydrate by rectifying equipment, refluxing part of the separated condensed water to the filtrate generated by filtering after NaCl is evaporated and crystallized in the step 1 to obtain the solution containing Na ₂CO ₃And NaCl thick brine, and the rest condensed water is used as production water;

step 3, refining the NaCl crude product

Putting the NaCl crude product into a crucible, adding concentrated hydrochloric acid with the mass fraction of 37 percent, then adding hydrogen peroxide with the mass fraction of 30 percent into the crucible, carefully stirring the mixture by using a glass rod, standing the mixture for 30min at room temperature, placing the mixture into a muffle furnace, and roasting the mixture at high temperature to obtain refined NaCl with the NaCl purity of 99.1 percent, the total organic carbon content of less than 10ppm and the ammonia nitrogen content of less than 5 ppm;

step 4, recovering high-purity Na ₂CO ₃Finished product

Freezing and crystallizing the concentrated brine obtained in the step 2 at-5 ℃ to recover sodium carbonate with purity higher than 95%;

step 5, circulating treatment of saturated sodium carbonate solution

And (4) refluxing the residual saturated sodium carbonate solution after the freezing crystallization in the step (4) to the high-salt hydrazine hydrate solution raw water which does not start to evaporate in the step (1) to obtain a mixed solution, and then starting a new round of evaporation to realize zero wastewater discharge.

2. The method for recovering and refining saline and alkali from high salt hydrazine hydrate solution as claimed in claim 1, wherein at the optimal evaporation amount in step 1, the mass percentage of sodium carbonate in NaCl crude product obtained by evaporation and crystallization is 6% -7%, and the loss amount of hydrazine hydrate in evaporation is less than 2% by mass fraction.

3. The method for recovering and refining saline and alkali from high-salt hydrazine hydrate solution as claimed in claim 1, wherein the temperature of the high-temperature roasting in step 3 is 600 ℃.

4. The method for recovering and refining the saline-alkali from the high-salt hydrazine hydrate solution according to claim 1, wherein the high-temperature roasting time in the step 3 is 3-5 h.

Technical Field

The invention belongs to the technical field of chemical industry, relates to the technical field of treatment and resource recovery of chemical industrial wastewater, and particularly relates to a method for recovering and refining saline and alkaline from a high-salt hydrazine hydrate solution.

Background

In recent years, with the rapid increase of the economy of China, the industrial scale is continuously enlarged, and the amount of wastewater generated in industrial production is rapidly increased, so that the treatment of industrial wastewater faces unprecedented challenges. The high-salinity wastewater is one kind of industrial wastewater, mainly comes from industrial production, seawater utilization, resident domestic sewage and the like, has high salt content (the mass fraction of total dissolved solids is more than or equal to 3.5 percent in general), and usually contains a large amount of Cl ^-、SO ₄ ^2-、Na ⁺、Ca ²⁺And the like, and some high-salinity wastewater also contains organic pollutants. China can generate a large amount of high-salinity wastewater every year. According to statistics, the total amount of the high COD and high salinity dye wastewater generated by the printing and dyeing industry only reaches 2.43 multiplied by 10 in 2009 ⁹m ³. Because the salt in the high-salinity wastewater can inhibit the growth of microorganisms to a certain extent, the untreated high-salinity wastewater is directly discharged to a downstream sewage treatment plant and impacts a biological treatment unit, and the pretreatment of the high-salinity wastewater in enterprises is very important. With the continuous enhancement of water environment management and protection of the country, theThe treatment of industrial high-salinity wastewater often requires "zero discharge". At present, the basic idea of the 'zero discharge' treatment process of industrial high-salinity wastewater is to separate salt and water to obtain recycled water and crystallized salt, but the separated salt is miscellaneous salt containing various inorganic salts, belongs to the category of dangerous wastes, has higher treatment cost, and causes environmental pollution due to improper treatment.

At present, the treatment technologies of high-salinity wastewater mainly include a membrane separation technology, a thermal concentration technology, a membrane distillation technology, a biological treatment technology and the like, wherein the thermal concentration technology includes a multi-effect evaporation technology, a thermal vapor recompression evaporation technology and a mechanical vapor recompression evaporation technology. When the membrane separation technology, the thermal concentration technology, the membrane distillation technology and the biological treatment technology are adopted to treat the industrial high-salt wastewater, the simple substance salt and resource utilization cannot be realized, so how to separate the salt in the industrial high-salt wastewater in the form of the simple substance salt becomes the key point and difficulty of the current high-salt wastewater treatment.

When the solubility of two inorganic salts contained in the high-salinity wastewater is greatly different along with the change of temperature, the two inorganic salts can be separated out respectively by adopting the processes of evaporative concentration, cooling crystallization and evaporative crystallization to achieve the purpose of separation. Gaohawa et al invented a method for purifying sodium chloride and sodium sulfate from high-salt wastewater (sodium chloride mass fraction of 2.28%, sodium sulfate mass fraction of 0.72%) and has been applied in production practice. Because the solubility of sodium chloride in water is not changed greatly along with the temperature, and sodium sulfate is sensitive to the temperature change, the wastewater is concentrated by an electrodialysis and mechanical vapor recompression evaporation device, and then concentrated solution is sent into a crystallizer for cooling and crystallization to obtain mirabilite; the concentrated solution from the freezing crystallizer is subjected to two-stage evaporation crystallization to obtain a sodium chloride product. The purity of the sodium chloride and the anhydrous sodium sulfate products obtained by the process can reach 99 percent, and the recovery rate of the sodium chloride and the anhydrous sodium sulfate products can reach more than 90 percent. The process has the following adaptive conditions: the content of inorganic salt with the solubility sensitive to temperature change in water is larger than that of inorganic salt with the solubility not changing much with the temperature, or the content of the inorganic salt and the content of high-salinity wastewater with the solubility not changing much with the temperature. For high-salt wastewater with the inorganic salt content of which the solubility in water does not change much with the temperature, which is far more than the inorganic salt content of which the solubility is sensitive to the temperature change, a practical salt separation process is not available at present.

Disclosure of Invention

In view of the shortcomings of the prior art, the present invention aims to provide a method for recovering and refining saline from a high-salt hydrazine hydrate solution, wherein the salt content of the high-salt hydrazine hydrate solution is mainly sodium chloride and sodium carbonate, and the concentration of the sodium chloride is far greater than that of the sodium carbonate. Evaporating high-salt hydrazine hydrate solution at high temperature, crystallizing at room temperature to recover NaCl crude product, and using concentrated HCl and H ₂O ₂Refining and roasting to obtain a high-purity NaCl finished product; low-temperature freezing crystallization for recovering high-purity Na ₂CO ₃Obtaining a finished product; and (3) recovering hydrazine hydrate by adopting a rectification method.

In order to achieve the purpose, the invention adopts the technical scheme that:

a method for recovering and refining saline from high-salt hydrazine hydrate solution comprises the following steps:

step 1, evaporating high-salt hydrazine hydrate solution, crystallizing at room temperature and recovering NaCl crude product

Measuring the content of sodium chloride, sodium carbonate, sodium sulfate, total salt, TOC and hydrazine hydrate in the high-salt hydrazine hydrate solution, and ensuring that the concentration of NaCl in the high-salt hydrazine hydrate solution is far greater than Na ₂CO ₃The concentration, then inputting the raw water of the high-salt hydrazine hydrate solution into an evaporation device for evaporation, stopping heating when the evaporation amount reaches the optimal evaporation amount, cooling and crystallizing at room temperature, then separating crystals and the solution, drying the separated crystals at 105 ℃ and roasting at 300 ℃ to obtain a NaCl crude product, and using the separated filtrate for low-temperature freezing crystallization to recover high-purity Na ₂CO ₃Obtaining a finished product; the salt in the high-salt hydrazine hydrate solution is mainly NaCl and Na ₂CO ₃；

Step 2, rectifying, separating and recovering hydrazine hydrate

In the process of evaporating the high-salt hydrazine hydrate solution in the step 1, after condensing generated steam (containing hydrazine hydrate and moisture), separating and recovering hydrazine hydrate by rectifying equipment, and refluxing partial condensed water after separation to filtrate generated by filtering after evaporating and crystallizing NaCl in the step 1To obtain Na-containing ₂CO ₃And NaCl thick brine, and the rest condensed water is used as production water;

step 3, refining the NaCl crude product

Putting the NaCl crude product into a crucible, adding concentrated hydrochloric acid with the mass fraction of 37 percent, then adding hydrogen peroxide with the mass fraction of 30 percent into the crucible, carefully stirring the mixture by using a glass rod, standing the mixture for 30min at room temperature, placing the mixture into a muffle furnace, and roasting the mixture at high temperature to obtain refined NaCl with the NaCl purity of 99.1 percent, the total organic carbon content of less than 10ppm and the ammonia nitrogen content of less than 5 ppm;

step 4, recovering high-purity Na ₂CO ₃Finished product

Freezing and crystallizing the concentrated brine obtained in the step 2 at-5 ℃ to recover sodium carbonate with purity higher than 95%;

step 5, circulating treatment of saturated sodium carbonate solution

And (4) refluxing the residual saturated sodium carbonate solution after the freezing crystallization in the step (4) to the high-salt hydrazine hydrate solution raw water which does not start to evaporate in the step (1) to obtain a mixed solution, and then starting a new round of evaporation to realize zero wastewater discharge.

Further, when the optimal evaporation amount is obtained in the step 1, the mass percentage of sodium carbonate in the NaCl crude product obtained by evaporation crystallization is 6-7%, and the loss amount of hydrazine hydrate in the evaporation process is lower than 2% by mass fraction.

Further, the temperature of the high-temperature roasting in the step 3 is 600 ℃.

Further, the high-temperature roasting time in the step 3 is 3-5 hours.

Has the advantages that:

compared with the prior art, the method for recovering and refining the saline alkali from the high-salt hydrazine hydrate solution has the advantages that the hydrazine hydrate is recovered from the high-salt hydrazine hydrate solution, and simultaneously, sodium chloride and sodium carbonate are recovered, so that the production cost is reduced, and the zero discharge of waste water is realized. The invention has the following main characteristics:

(1) the process is simple and easy to implement, and the operation and maintenance cost is low;

(2) the recovered sodium chloride finished product can meet the following requirements: the purity of NaCl is more than 99.1 percent, the TOC is less than 10ppm, and the ammonia nitrogen is less than 5 ppm;

(3) the purity of the recovered sodium carbonate (containing crystal water) finished product is more than 95 percent;

(4) the loss amount of hydrazine hydrate in the hydrazine hydrate solution during evaporation is less than 2% by mass fraction.

Drawings

FIG. 1 is a flow diagram of the process for recovery and refining of a salt and alkali from a high salt hydrazine hydrate solution according to the invention;

fig. 2 is the result of the cycle experiment in example 1 of the present invention.

Detailed Description

The invention is further described below with reference to the accompanying drawings and specific embodiments.