CN108726762B

CN108726762B - Treatment method of catalyst production wastewater

Info

Publication number: CN108726762B
Application number: CN201710265378.8A
Authority: CN
Inventors: 殷喜平; 李叶; 苑志伟; 吕伟娇; 周岩; 杨凌; 顾松园; 王涛; 刘志坚; 刘夫足; 高晋爱; 安涛
Original assignee: China Petroleum and Chemical Corp; Sinopec Catalyst Co
Current assignee: China Petroleum and Chemical Corp; Sinopec Catalyst Co
Priority date: 2017-04-21
Filing date: 2017-04-21
Publication date: 2021-08-27
Anticipated expiration: 2037-04-21
Also published as: CN108726762A

Abstract

The invention relates to the field of sewage treatment, and discloses a method for treating wastewater generated in catalyst production, wherein the wastewater generated in catalyst production contains NH₄ ⁺、SO₄ ^2‑、Cl^‑And Na⁺The method comprises the steps of 1) introducing wastewater to be treated into a first MVR evaporation device for first evaporation to obtain first ammonia-containing steam and a first concentrated solution containing sodium sulfate crystals and sodium chloride crystals, wherein the wastewater to be treated contains catalyst production wastewater; 2) carrying out low-temperature treatment on the first concentrated solution to dissolve sodium sulfate crystals to obtain a treatment solution containing sodium chloride crystals; 3) carrying out first solid-liquid separation on the treatment liquid containing the sodium chloride crystals, and introducing a liquid phase obtained by the first solid-liquid separation into a second MVR evaporation device for second evaporation to obtain a second concentrated solution containing ammonia vapor and sodium sulfate crystals; 4) and carrying out second solid-liquid separation on the second concentrated solution containing the sodium sulfate crystals. The method can respectively recover the ammonium, the sodium sulfate and the sodium chloride in the wastewater, and furthest recycle resources in the wastewater.

Description

Treatment method of catalyst production wastewater

Technical Field

The invention relates to the field of sewage treatment, in particular to a method for treating catalyst production wastewater, and especially relates to a catalyst containing NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The method for treating wastewater from catalyst production.

Background

In the production process of the oil refining catalyst, a large amount of inorganic acid alkali salts such as sodium hydroxide, hydrochloric acid, sulfuric acid, ammonium salts, sulfates, hydrochlorides and the like are needed, and a large amount of mixed sewage containing ammonium, sodium chloride, sodium sulfate and aluminosilicate is generated. For such sewage, the common method in the prior art is that the pH value is adjusted to be within the range of 6-9, most of suspended matters are removed, then a biochemical method, a blow-off method or a steam stripping method is adopted to remove ammonium ions, then the salt-containing sewage is subjected to pH value adjustment, most of suspended matters are removed, hardness, silicon and part of organic matters are removed, most of organic matters are removed through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then the salt-containing sewage enters an ion exchange device for further hardness removal, enters an enrichment device (such as reverse osmosis or electrodialysis) for concentration, and then MVR evaporative crystallization or multiple-effect evaporative crystallization is adopted to obtain mixed miscellaneous salt of sodium chloride and sodium sulfate containing a small amount of ammonium salt; or is; firstly, adjusting the pH value to be within the range of 6.5-7.5, removing most suspended matters, then removing hardness, silicon and part of organic matters, removing most organic matters through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then entering an ion exchange device for further removing hardness, entering a thickening device (such as reverse osmosis and/or electrodialysis) for concentration, and then adopting MVR (mechanical vapor recompression) evaporative crystallization or multiple-effect evaporative crystallization to obtain the mixed miscellaneous salt of sodium chloride and sodium sulfate containing ammonium salt. However, these ammonium-containing mixed salts are currently difficult to treat or expensive to treat, and the process of removing ammonium ions at the early stage additionally increases the cost of wastewater treatment.

In addition, the biochemical deamination can only treat wastewater with low ammonium content, and can not directly carry out biochemical treatment due to insufficient COD content in the catalyst sewage, and organic matters such as glucose or starch and the like are additionally added in the biochemical treatment process, so that the ammoniacal nitrogen can be treated by the biochemical method. The most important problem is that the total nitrogen of the wastewater after the biochemical deamination treatment is not up to the standard (the contents of nitrate ions and nitrite ions exceed the standard), the wastewater needs to be deeply treated, in addition, the salt content in the wastewater is not reduced (20 g/L-30 g/L), the wastewater cannot be directly discharged, and the wastewater needs to be further desalted.

In order to remove ammoniacal nitrogen from wastewater by gas stripping deamination, a large amount of alkali is needed to adjust the pH value, the alkali consumption is high, the alkali in the wastewater after deamination cannot be recovered, the pH value of the treated wastewater is high, the treatment cost is high, the COD content in the catalyst wastewater after gas stripping does not change greatly, the salt content in the wastewater is not reduced (20-30 g/L), the wastewater cannot be directly discharged, further desalting treatment is needed, the operation cost of wastewater treatment is high, a large amount of alkali remains in the treated wastewater, the pH value is high, the waste is large, and the treatment cost is up to 50 yuan/ton.

Disclosure of Invention

The invention aims to overcome the defect of NH content in the prior art₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The catalyst has high treatment cost of wastewater and can only obtain mixed salt crystals, and provides a low-cost and environment-friendly NH-containing catalyst₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The method for treating wastewater can respectively recover ammonium, sodium chloride and sodium sulfate in the wastewater, and furthest recycle resources in the wastewater.

In order to achieve the above object, the present invention provides a method for treating wastewater from catalyst production containing NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The method comprises the following steps of,

1) introducing wastewater to be treated into a first MVR evaporation device for first evaporation to obtain first ammonia-containing steam and a first concentrated solution containing sodium sulfate crystals and sodium chloride crystals, wherein the wastewater to be treated contains the catalyst production wastewater;

2) carrying out low-temperature treatment on the first concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals to dissolve the sodium sulfate crystals to obtain a treatment solution containing the sodium chloride crystals;

3) carrying out first solid-liquid separation on the treatment liquid containing the sodium chloride crystals, and introducing a liquid phase obtained by the first solid-liquid separation into a second MVR evaporation device for second evaporation to obtain a second concentrated solution containing ammonia vapor and sodium sulfate crystals;

4) carrying out second solid-liquid separation on the second concentrated solution containing the sodium sulfate crystals;

adjusting the pH value of the wastewater to be treated to be more than 9 before introducing the wastewater to be treated into a first MVR evaporation device; the second evaporation prevents sodium chloride crystals from crystallizing out; relative to 1 mole of SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-Is 7.15 mol or more.

By the technical scheme, the method aims at the content of NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺By pre-treating the waste waterAfter the pH value of the treated wastewater is adjusted to a specific range, a first MVR evaporation device is used for evaporation and separation to obtain concentrated solution containing sodium sulfate crystals and sodium chloride crystals and stronger ammonia water, then low-temperature treatment is used for dissolving sodium sulfate in the concentrated solution, sodium chloride is further crystallized and separated out to obtain sodium chloride crystals, and then a second MVR evaporation device is used for evaporation again to obtain concentrated solution containing sodium sulfate crystals and thinner ammonia water, so that sodium sulfate crystals are obtained. The method can respectively obtain high-purity sodium chloride and sodium sulfate, avoids the difficulty in the processes of mixed salt treatment and recycling, simultaneously completes the process of separating ammonia and salt, simultaneously heats the wastewater and condenses ammonia-containing steam by adopting a heat exchange mode, reasonably utilizes the heat in the evaporation process, saves energy, reduces the wastewater treatment cost, recovers the ammonium in the wastewater in the form of ammonia water, recovers the sodium sulfate and the sodium chloride in the form of crystals respectively, does not generate waste residues and waste liquid in the whole process, and achieves the purpose of changing waste into valuable.

Furthermore, the method combines the first evaporation and the low-temperature treatment, so that the first evaporation can be carried out at a higher temperature, the solid content and the evaporation efficiency in the first evaporation concentrated solution are improved, and the energy-saving effect can be achieved.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic flow diagram of a method for treating wastewater from catalyst production according to an embodiment of the present invention.

Description of the reference numerals

1. Second MVR evaporation plant 72, second circulating pump

2. First MVR evaporation plant 73, third circulating pump

22. Low-temperature treatment tank 74 and fourth circulation pump

31. First heat exchange device 76 and sixth circulating pump

32. Second heat exchanger 77, seventh circulating pump

33. Third heat exchange device 78, eighth circulating pump

34. Fourth heat exchange device 79 and ninth circulating pump

35. Fifth heat exchange device 80 and tenth circulating pump

51. First ammonia water storage tank 81 and vacuum pump

52. Second ammonia storage tank 82 and circulating water tank

53. First mother liquor tank 83 and tail gas absorption tower

54. Second mother liquor tank 91 and first solid-liquid separation device

61. First pH value measuring device 92 and second solid-liquid separation device

62. Second pH value measuring device 101 and first compressor

71. First circulation pump 102, second compressor

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The present invention will be described below with reference to fig. 1, but the present invention is not limited to fig. 1.

The present invention providesThe catalyst production wastewater containing NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The method comprises the following steps of,

Preferably, the wastewater to be treated is the catalyst production wastewater; or the wastewater to be treated contains the catalyst production wastewater and a liquid phase obtained by the second solid-liquid separation.

More preferably, the wastewater to be treated is a mixed solution of the catalyst production wastewater and at least part of a liquid phase obtained by the second solid-liquid separation.

Further preferably, the wastewater to be treated is a liquid phase mixed solution obtained by the catalyst production wastewater and the second solid-liquid separation.

Preferably, the pH of the wastewater to be treated is adjusted to be greater than 10.8 before it is passed into the first MVR evaporation plant 2. The upper limit of the pH of the wastewater to be treated is not limited, and may be, for example, 14 or less, preferably 13.5 or less, and more preferably 13 or less.

The method provided by the invention can be used for the treatment of the compounds containing NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺Except that it contains NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺In addition, the catalyst production wastewater is not particularly limited. From the viewpoint of improving the treatment efficiency of wastewater, the amount of SO contained in the wastewater to be treated is 1 mole per mole₄ ^2-Cl contained in the wastewater to be treated^-Is 7.15 moles or more, preferably 9.5 moles or more, preferably 10 moles or more, preferably 50 moles or less, more preferably 40 moles or less, further preferably 30 moles or less, and for example, may be 8 to 20 moles, preferably 8 to 12 moles, more preferably 10 to 12 moles. By reacting SO₄ ^2-And Cl^-The molar ratio of sodium chloride is controlled within the range, so that sodium chloride is precipitated and sodium sulfate is completely dissolved in the low-temperature treatment, and the aim of efficiently separating sodium chloride is fulfilled. In addition, as described above and below, it is also possible in the present invention to recycle the second mother liquor obtained in the second evaporation process to the first evaporation, and thereby to treat SO in the wastewater to be treated₄ ^2-And Cl^-The molar ratio of (a) to (b) is adjusted and the balance of sodium hydroxide can be maintained.

In the present invention, the first evaporation is required to dissolve the sodium sulfate crystals in the low-temperature treatment, and specifically, the first evaporation is required to obtain the first concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals, and the sodium sulfate crystals in the first evaporation are required to be completely dissolved in the low-temperature treatment. And (3) controlling the evaporation amount of the first evaporation to simultaneously crystallize and separate out sodium sulfate and sodium chloride (namely, the first evaporation obtains a first concentrated solution containing sodium sulfate crystals and sodium chloride crystals), dissolving the sodium sulfate crystals in the first concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals through the low-temperature treatment, and further crystallizing and separating out sodium chloride to obtain a treated solution only containing the sodium chloride crystals. With respect to the treatment liquid containing sodium chloride crystals, sodium sulfate entrained by or adsorbed on the surface of sodium chloride crystals is not excluded. Since the water content of the crystals after the solid-liquid separation is different, the sodium sulfate content in the sodium chloride crystals obtained is usually 8 mass% or less (preferably 4 mass%), and in the present invention, it is considered that the sodium sulfate is dissolved when the sodium sulfate content in the sodium chloride crystals obtained is 8 mass% or less.

In the present invention, the second evaporation to prevent sodium chloride from crystallizing out means that the concentration of sodium chloride in the mixed system is controlled not to exceed the solubility under the second evaporation conditions (including but not limited to temperature, pH value, etc.), and sodium chloride carried by sodium sulfate crystals or adsorbed on the surface is not excluded. Since the water content of the crystals after the solid-liquid separation is different, the sodium chloride content in the obtained sodium sulfate crystals is usually 8 mass% or less (preferably 4 mass%), and in the present invention, it is considered that the sodium chloride does not crystallize out when the sodium chloride content in the obtained sodium sulfate crystals is 8 mass% or less.

In the present invention, it is understood that the first ammonia-containing steam and the second ammonia-containing steam are secondary steam as referred to in the art. The pressures are all pressures in gauge pressure.

In the present invention, the first MVR evaporation device 2 is not particularly limited, and may be various MVR evaporation devices conventionally used in the art. For example, it may be one or more selected from the group consisting of an MVR falling film evaporator, an MVR forced circulation evaporator, an MVR-FC continuous crystallization evaporator, and an MVR-OSLO continuous crystallization evaporator. Among them, preferred are an MVR forced circulation evaporator and an MVR-FC continuous crystallization evaporator, and more preferred is a falling film + forced circulation two-stage MVR evaporative crystallizer.

In the present invention, the conditions of the first evaporation may be appropriately selected as needed, and the evaporation amount of the first evaporation may be controlled to simultaneously crystallize and separate out sodium sulfate and sodium chloride (that is, the first evaporation may obtain a first concentrated solution containing sodium sulfate crystals and sodium chloride crystals), and the low-temperature treatment may be performed to dissolve the sodium sulfate crystals in the first concentrated solution containing sodium sulfate crystals and sodium chloride crystals, thereby further crystallizing and separating out sodium chloride to obtain a treated solution containing only sodium chloride crystals. The conditions of the first evaporation may include: the temperature is above 35 ℃ and the pressure is above-95 kPa. In order to improve evaporation efficiency, preferably, the conditions of the first evaporation include: the temperature is 45-175 ℃, and the pressure is-95 kPa-18110 kPa; preferably, the conditions of the first evaporation include: the temperature is 60-175 ℃, and the pressure is-87 kPa-18110 kPa; preferably, the conditions of the first evaporation include: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa; preferably, the conditions of the first evaporation include: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa; preferably, the conditions of the first evaporation include: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa; preferably, the conditions of the first evaporation include: the temperature is 100-110 ℃, and the pressure is-23 kPa-12 kPa.

In the present invention, the operating pressure of the first evaporation is preferably the saturated vapor pressure of the evaporated feed liquid.

In the present invention, the flow rate of the first evaporation may be appropriately selected according to the capacity of the apparatus process, and may be, for example, 0.1m³More than h (e.g. 0.1 m)³/h～500m³/h)。

By allowing the first evaporation to proceed under the above conditions, the efficiency of evaporation can be improved and the energy consumption can be reduced. The method ensures that the sodium sulfate crystals are completely dissolved after the first concentrated solution is subjected to low-temperature treatment while ensuring the maximum evaporation capacity (concentration multiple), thereby ensuring the purity of the obtained sodium chloride crystals.

According to the invention, by controlling the evaporation conditions of the first MVR evaporation device 2, more than 90 mass% (preferably more than 95 mass%) of ammonia contained in the wastewater to be treated can be evaporated, so as to obtain the first ammonia water with higher concentration, and the first ammonia water can be directly reused in the production process of the catalyst, or neutralized by acid to obtain ammonium salt for reuse, or mixed with water and corresponding ammonium salt or ammonia water for use.

According to the present invention, the first evaporation dissolves sodium sulfate crystals in the low-temperature treatment, and preferably, the first evaporation makes the concentration of sodium sulfate in the treatment solution be Y or less (preferably 0.9Y to 0.99Y, preferably 0.95Y to 0.98Y), where Y is the concentration of sodium sulfate at which both sodium chloride and sodium sulfate in the treatment solution are saturated under the low-temperature treatment. By controlling the degree of the first evaporation within the above range, as much sodium chloride as possible can be crystallized under conditions that ensure that the low-temperature treatment can dissolve sodium sulfate. By crystallizing sodium chloride in the first evaporation as much as possible, the wastewater treatment efficiency can be improved, and the energy waste can be reduced.

In the present invention, the degree of progress of the first evaporation is determined by monitoring the evaporation amount of the first evaporation, that is, the amount of the liquid, and specifically, the concentration factor is controlled by controlling the evaporation amount of the first evaporation, that is, the amount of the first aqueous ammonia, so that the sodium sulfate crystals precipitated in the first evaporation-concentrated solution can be dissolved during the low-temperature treatment. The degree of the first evaporative concentration is monitored by measuring the evaporation rate, and the flow rate can be measured by using a mass flow meter.

According to a preferred embodiment of the present invention, before the wastewater to be treated is passed into the first MVR evaporation plant 2, the first ammonia-containing vapor is subjected to a first heat exchange with the wastewater to be treated and a first ammonia solution is obtained. The first heat exchange method is not particularly limited, and may be performed by a heat exchange method that is conventional in the art. The number of times of the first heat exchange may be one or more, preferably 2 to 4 times, and more preferably 2 to 3 times. Through after the first heat exchange, the output ammonia water is cooled, and the heat is circulated in the treatment device to the maximum extent, so that the energy is reasonably utilized, and the waste is reduced.

According to a preferred embodiment of the present invention, the first heat exchange is performed by a first heat exchange device 31, a fifth heat exchange device 35 and a second heat exchange device 32, specifically, the first ammonia-containing steam obtained by evaporation in the first MVR evaporation device 2 sequentially passes through the second heat exchange device 32 and the first heat exchange device 31, the first concentrated solution containing sodium sulfate crystals and sodium chloride crystals passes through the fifth heat exchange device 35, and the wastewater to be treated is subjected to the first heat exchange by the first heat exchange device 31 or the fifth heat exchange device 35 and then is subjected to the first heat exchange by the second heat exchange device 32. Through first heat exchange makes pending waste water intensification is convenient for evaporate, makes simultaneously the condensation of first ammonia-containing steam obtains first aqueous ammonia, first aqueous ammonia can be stored in first aqueous ammonia storage tank 51.

In the present invention, the first heat exchange device 31, the fifth heat exchange device 35 and the second heat exchange device 32 are not particularly limited, and various heat exchangers conventionally used in the art may be used to achieve the purpose of performing the first heat exchange between the first ammonia-containing steam and the wastewater to be treated. Specifically, a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, or the like may be mentioned, with the plate heat exchanger being preferred. The material of the heat exchanger can be specifically selected according to the needs, for example, in order to resist the corrosion of chloride ions, the heat exchanger of duplex stainless steel, titanium and titanium alloy, hastelloy can be selected as the material, and the heat exchanger containing plastic material can be selected when the temperature is lower.

According to the present invention, in order to fully utilize the heat energy of the first ammonia-containing steam condensate, it is preferable that the temperature of the wastewater to be treated after the first heat exchange is performed by the first heat exchange device 31 is 44 to 174 ℃, more preferably 59 to 174 ℃, still more preferably 79 to 129 ℃, and still more preferably 94 to 109 ℃.

According to the present invention, in order to fully utilize the heat energy of the first concentrated solution, it is preferable that the temperature of the wastewater to be treated is 44 to 174 ℃, more preferably 59 to 174 ℃, still more preferably 79 to 129 ℃, and still more preferably 94 to 109 ℃ after the first heat exchange is performed by the fifth heat exchange device 35.

According to the present invention, in order to fully utilize the heat energy of the first ammonia-containing steam, it is preferable that the temperature of the wastewater to be treated is 52 to 182 ℃, more preferably 67 to 182 ℃, still more preferably 87 to 137 ℃, and still more preferably 102 to 117 ℃ after the first heat exchange is performed by the second heat exchange device 32.

In the present invention, the method of adjusting the pH is not particularly limited, and for example, the pH of the wastewater to be treated may be adjusted by adding an alkaline substance. The alkaline substance is not particularly limited, and the purpose of adjusting the pH value may be achieved. The alkaline substance is preferably NaOH in order not to introduce new impurities in the wastewater to be treated, increasing the purity of the crystals obtained.

The manner of adding the alkaline substance may be any manner known in the art, but it is preferable to mix the alkaline substance with the wastewater to be treated in the form of an aqueous solution, and for example, an aqueous solution containing the alkaline substance may be introduced into a pipe through which the wastewater to be treated is introduced and mixed. The content of the alkaline substance in the aqueous solution is not particularly limited as long as the above-mentioned purpose of adjusting the pH value can be achieved. However, in order to reduce the amount of water used and further reduce the cost, it is preferable to use a saturated aqueous solution of an alkaline substance. In order to monitor the pH value of the wastewater to be treated, the pH value of the wastewater to be treated may be measured after the above-mentioned pH value adjustment.

According to a preferred embodiment of the present invention, the first evaporation process is performed in the first MVR evaporation device 2, and the first pH adjustment is performed by introducing and mixing the aqueous solution containing the alkaline substance in the pipe for feeding the wastewater to be treated into the heat exchange device before feeding the wastewater to be treated into the first heat exchange device 31 or the fifth heat exchange device 35 for the first heat exchange; then the wastewater to be treated is sent to the first heat exchange device 31 or the fifth heat exchange device 35 for first heat exchange, and then the aqueous solution containing the alkaline substance is introduced and mixed in the pipeline sending the wastewater to be treated to the second heat exchange device 32 for second pH value adjustment. The pH of the wastewater to be treated is adjusted twice, so that the pH is greater than 9, preferably greater than 10.8, before the wastewater is passed into the first MVR evaporator 2. Preferably, the first pH adjustment is such that the pH of the wastewater to be treated is greater than 7 (preferably 7-9), and the second pH adjustment is such that the pH is greater than 9 (preferably greater than 10.8). According to the present invention, it is preferable that the pH of the wastewater to be treated is adjusted to be greater than 7 before the first heat exchange is performed.

In order to detect the pH values after the first pH adjustment and the second pH adjustment, it is preferable that a first pH measuring device 61 is provided on a pipe for feeding the wastewater to be treated into the first heat exchanging device 31 and the fifth heat exchanging device 35 to measure the pH value after the first pH adjustment, and a second pH measuring device 62 is provided on a pipe for feeding the wastewater to be treated into the second heat exchanging device 32 to measure the pH value after the second pH adjustment.

In the invention, the sequence of the first heat exchange, the adjustment of the pH value of the wastewater to be treated and the preparation of the wastewater to be treated (the preparation of the wastewater to be treated is required in the case that the wastewater to be treated contains a liquid phase obtained by the separation of the catalyst production wastewater and the second solid-liquid) is not particularly limited, and can be appropriately selected as required before the wastewater to be treated is introduced into the first MVR evaporation plant.

In the present invention, in order to increase the solid content in the first MVR evaporation device 2 and reduce the ammonia content in the liquid, it is preferable that a part of the liquid evaporated by the first MVR evaporation device 2 (i.e. the liquid located inside the first MVR evaporation device, hereinafter also referred to as the first circulation liquid) is heated and then returned to the first MVR evaporation device 2 for evaporation. The above-mentioned process of returning the first circulation liquid to the first MVR evaporation device 2 is preferably to return the first circulation liquid to the first MVR evaporation device 2 after mixing with the wastewater to be treated after the first pH adjustment and before the second pH adjustment, for example, the first circulation liquid may be returned to the wastewater conveying pipeline between the first heat exchange device 31 and the second heat exchange device 32 by the second circulation pump 72 to be mixed with the wastewater to be treated, and then after the second pH adjustment, heat exchange may be performed in the second heat exchange device 32, and finally the wastewater is sent to the first MVR evaporation device 2. The ratio of the part of the liquid evaporated by the first MVR evaporation device 2 to be refluxed to the first MVR evaporation device 2 is not particularly limited, and for example, the first reflux ratio of the first evaporation may be appropriately set as needed, and may be 10 to 200, and preferably 40 to 150. Here, the first reflux ratio means: the ratio of the amount of reflux to the total amount of liquid fed to the first MVR evaporator 2 minus the amount of reflux.

According to the present invention, preferably, the method further comprises compressing the first ammonia-containing vapor before the first heat exchange. The compression of the first ammonia-containing vapor may be performed by a first compressor 101. Through right first ammonia vapor that contains compresses, for input energy among the MVR vaporization system, guarantee that waste water intensification-evaporation-cooling's process goes on in succession, need input start-up steam when MVR vaporization process starts, only need pass through first compressor 101 energy supply after reaching continuous running state, no longer need input other energy. The first compressor 101 may employ various compressors conventionally used in the art, such as a centrifugal fan, a turbine compressor, or a roots compressor. After compression by the first compressor 101, the temperature of the first ammonia-containing vapor is raised by 5 to 20 ℃.

In the invention, the first concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals is subjected to low-temperature treatment to dissolve the sodium sulfate crystals, so as to obtain the treated solution containing the sodium chloride crystals. By controlling the evaporation amount of the first evaporation so that the concentration of sodium sulfate in the treatment solution is Y or less, the sodium sulfate crystals can be completely dissolved in the low-temperature treatment.

According to the present invention, the low-temperature treatment may be carried out in a manner not particularly limited as long as the sodium sulfate crystals in the first concentrated solution containing sodium sulfate crystals and sodium chloride crystals obtained by the first evaporation are dissolved at a temperature controlled appropriately. According to the present invention, the temperature of the low-temperature treatment is lower than the temperature of the first evaporation, and specifically, the conditions of the low-temperature treatment may include: the temperature is 13-100 ℃, preferably 15-45 ℃, more preferably 15-35 ℃, and further preferably 17.9-35 ℃; for example, the temperature can be 18 ℃, 19 ℃, 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃, 30 ℃, 31 ℃, 32 ℃, 33 ℃, 34 ℃, 35 ℃, 36 ℃, 37 ℃, 38 ℃, 39 ℃, 40 ℃, 41 ℃, 42 ℃, 43 ℃, 44 ℃, 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 55 ℃ and 60 ℃. In order to ensure the effect of the low-temperature treatment, the residence time of the low-temperature treatment can be 10min to 600min, preferably 20min to 300min, and preferably 50min to 70 min.

In the invention, by controlling the conditions of the first evaporation and the low-temperature treatment, the first evaporation can be carried out at a higher evaporation temperature and an evaporation pressure closer to the normal pressure, so that the problem of low efficiency in evaporation at a lower temperature is solved, the evaporation efficiency is improved, the energy consumption in the evaporation process can be reduced, and the wastewater treatment speed is increased. On the basis, the temperature control of the low-temperature treatment is simpler and more convenient, and the low-temperature treatment temperature can be operated under the condition of being lower than the evaporation temperature (such as below 45 ℃), thereby being more beneficial to the dissolution of sodium sulfate and the precipitation of sodium chloride.

In the present invention, the low-temperature treatment may be performed using various temperature reduction devices conventionally used in the art, and for example, the low-temperature treatment tank 22 may be selected. Preferably, a cooling part, specifically, a part for introducing cooling water, may be provided in the low-temperature treatment tank 22. The first concentrated solution in the low-temperature treatment tank can be rapidly cooled by the cooling part. Preferably, the low-temperature treatment tank 22 may be provided with a stirring member, and the stirring member can make the solid-liquid phase distribution and the temperature distribution in the first concentrated solution uniform, thereby achieving the purpose of fully dissolving the sodium sulfate crystals and precipitating the sodium chloride crystals to the maximum.

In the invention, the treated liquid containing sodium chloride crystals is subjected to a first solid-liquid separation to obtain sodium chloride crystals and a first mother liquid (i.e. a liquid phase obtained by the first solid-liquid separation). The method of the first solid-liquid separation is not particularly limited, and may be selected from one or more of centrifugation, filtration, and sedimentation.

According to the present invention, the solid-liquid separation of the first concentrated solution may be performed by using a first solid-liquid separation device (for example, a centrifuge, a belt filter, a plate filter, or the like) 91. After the solid-liquid separation, the first mother liquor obtained by the first solid-liquid separation device 91 is temporarily stored in the first mother liquor tank 53, and can be sent to the second MVR evaporation device 1 by the sixth circulation pump 76 for second evaporation. In addition, it is difficult to avoid that the obtained sodium chloride crystals adsorb certain impurities such as chloride ions, free ammonia, hydroxide ions, etc., and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals, it is preferable that the sodium chloride crystals are first washed with water, the catalyst production wastewater, or a sodium chloride solution and dried. In order to avoid dissolution of the sodium chloride crystals during washing, preferably the sodium chloride crystals are washed with an aqueous solution of sodium chloride. More preferably, the concentration of the sodium chloride aqueous solution is preferably the concentration of sodium chloride in the aqueous solution at which sodium chloride and sodium sulfate reach saturation simultaneously at the temperature corresponding to the sodium chloride crystals to be washed.

The manner of the first solid-liquid separation and the first washing is not particularly limited, and may be carried out by using, for example, a combination of an elutriation apparatus and a solid-liquid separation apparatus which are conventional in the art, or may be carried out on a staged solid-liquid separation apparatus such as a belt filter. Preferably, the first wash comprises panning and/or rinsing. The above-mentioned elutriation and rinsing are not particularly limited and may be carried out by a method conventional in the art. The number of elutriation and rinsing is not particularly limited, and may be 1 or more, and is preferably 2 to 4 times in order to obtain sodium chloride crystals of higher purity. In the elutriation process, the waste water produced by the catalyst is generally not recycled when used as an elutriation liquid, and the washing liquid recovered by the first washing can be recycled in a counter-current manner when used as the elutriation liquid. Before the elutriation, it is preferable to perform preliminary solid-liquid separation by sedimentation to obtain a slurry containing sodium chloride crystals (the liquid content may be 35% by mass or less). In the elutriation process, 1 to 20 parts by weight of a liquid is used for elutriation with respect to 1 part by weight of a slurry containing sodium chloride crystals. The rinsing is preferably carried out using an aqueous sodium chloride solution. In order to further enhance the elutriation effect and obtain sodium chloride crystals with higher purity, the liquid obtained by rinsing may be preferably used for washing, and water or a sodium chloride solution is preferably used. The liquid generated by washing is preferably returned to the first MVR evaporation device for evaporation before the second pH adjustment, for example, after being mixed with the wastewater to be treated before being returned to the second pH adjustment by the eighth circulating pump 78, and after being subjected to the second pH adjustment and the heat exchange by the second heat exchange device 32.

According to a preferred embodiment of the present invention, after a treatment liquid containing sodium chloride obtained by low-temperature treatment is subjected to preliminary solid-liquid separation by settling, the catalyst production wastewater is subjected to first elutriation in an elutriation tank, then the liquid obtained by subsequent washing of sodium chloride crystals is subjected to second elutriation in another elutriation tank, finally the slurry subjected to the two elutriations is sent to a solid-liquid separation device for solid-liquid separation, the crystals obtained by the solid-liquid separation are subjected to elution with an aqueous sodium chloride solution, and the eluted liquid is returned to the second elutriation. Through the washing process, the purity of the obtained sodium chloride crystal is improved, washing liquid is not excessively introduced, and the efficiency of wastewater treatment is improved.

In the present invention, the second MVR evaporation device 1 is not particularly limited, and may be various MVR evaporation devices conventionally used in the art. For example, it may be one or more selected from the group consisting of an MVR falling film evaporator, an MVR forced circulation evaporator, an MVR-FC continuous crystallization evaporator, and an MVR-OSLO continuous crystallization evaporator. Among them, preferred are an MVR forced circulation evaporator and an MVR-FC continuous crystallization evaporator, and more preferred is a falling film + forced circulation two-stage MVR evaporative crystallizer.

In the present invention, the evaporation conditions of the second evaporation are not particularly limited, and may be appropriately selected as needed to achieve the purpose of concentrating the first mother liquor. The conditions of the second evaporation may include: the temperature is above 35 ℃ and the pressure is above-95 kPa. In order to improve the evaporation efficiency, it is preferable that the conditions of the second evaporation include: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa; preferably, the conditions of the second evaporation include: the temperature is 60-365 ℃, and the pressure is-87 kPa-18110 kPa; preferably, the conditions of the second evaporation include: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa; preferably, the conditions of the second evaporation include: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa; preferably, the conditions of the second evaporation include: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa; preferably, the conditions of the second evaporation include: the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa.

In the present invention, the operating pressure of the second evaporation is preferably the saturated vapor pressure of the evaporated feed liquid.

Further, the evaporation amount of the second evaporation may be appropriately selected depending on the capacity of the apparatus and the amount of the wastewater to be treated, and may be, for example, 100L/h or more (e.g., 0.1 m)³/h～500m³/h)。

By carrying out the second evaporation under the above conditions, the sodium chloride is not crystallized while the crystallization of sodium sulfate is ensured, so that the purity of the obtained sodium sulfate crystal can be ensured.

According to the present invention, the second evaporation does not crystallize sodium chloride in the wastewater to be treated (i.e., sodium chloride does not reach supersaturation), and preferably, the second evaporation makes the concentration of sodium chloride in the second concentrated solution be X or less (preferably 0.999X or less, more preferably 0.95X to 0.999X, and further preferably 0.99X to 0.9967X). Wherein X is the concentration of sodium chloride when sodium sulfate and sodium chloride in the wastewater to be treated are both saturated under the condition of the second evaporation. By controlling the degree of the second evaporation within the above range, as much sodium sulfate as possible can be crystallized out under the condition that sodium chloride is not precipitated out. By crystallizing sodium sulfate in the second evaporation as much as possible, the wastewater treatment efficiency can be improved, and the energy waste can be reduced.

In the present invention, the degree of progress of the second evaporation is performed by monitoring the concentration of the liquid obtained by the second evaporation, and specifically, by controlling the concentration of the liquid obtained by the second evaporation within the above range, the second evaporation does not crystallize out sodium chloride in the wastewater to be treated. The concentration of the liquid resulting from the second evaporation is monitored by measuring the density, which may be carried out using a densitometer.

According to a preferred embodiment of the present invention, the second ammonia-containing vapor is subjected to a second heat exchange with the first mother liquor and a second aqua ammonia is obtained. The second heat exchange method is not particularly limited, and may be performed by a heat exchange method that is conventional in the art. The number of times of the second heat exchange may be one or more, preferably 2 to 4 times, more preferably 2 to 3 times, and particularly preferably 2 times. Through the second heat exchange, the output ammonia water is cooled, and the heat is at the maximum degree at the internal circulation of processing apparatus, rational utilization the energy, waste has been reduced.

According to the present invention, preferably, the second heat exchange is performed by a third heat exchange device 33 and a fourth heat exchange device 34, specifically, the second ammonia-containing vapor obtained by evaporation in the second MVR evaporation device 1 passes through the fourth heat exchange device 34 and the third heat exchange device 33 in sequence, the first mother liquor passes through the third heat exchange device 33 and then is mixed with the second circulating liquid (part of the concentrated liquid in the second MVR evaporation device 1), and the obtained mixed liquid passes through the fourth heat exchange device 34 to perform the second heat exchange, so as to heat the first mother liquor to facilitate evaporation, and simultaneously, the second ammonia-containing vapor is condensed to obtain the second ammonia water, and the second ammonia water can be stored in the second ammonia water storage tank 52.

According to the present invention, the temperature of the mixed liquid of the first mother liquid and the second circulating liquid after the second heat exchange is 42 ℃ or higher, more preferably 52 to 372 ℃, still more preferably 82 to 182 ℃, and still more preferably 102 to 112 ℃.

In the present invention, in order to increase the solid content of the concentrated liquid in the second MVR evaporation device 1 and reduce the ammonia content of the liquid, it is preferable to return part of the liquid evaporated by the second MVR evaporation device 1 (i.e. the liquid located inside the second MVR evaporation device 1, hereinafter also referred to as a second circulation liquid) to the second MVR evaporation device 1. The above process of returning the second circulation liquid to the second MVR evaporation device 1 is preferably that the second circulation liquid is mixed with the second leacheate and the first mother liquid and then returned to the second MVR evaporation device 1. For example, the second circulating liquid and the second eluting liquid may be mixed with the first mother liquid in the pipeline by the seventh circulating pump 77, and then introduced into the fourth heat exchanging device 34, and after the second heat exchange, the mixture may be returned to the second MVR evaporating device 1. The ratio of the part of the liquid after evaporation by the second MVR evaporation device 1 to be refluxed to the second MVR evaporation device 1 is not particularly limited, for example, the second reflux ratio of the second evaporation may be 0.1 to 100, preferably 5 to 50. Here, the second reflux ratio means: the ratio of the amount of reflux to the total amount of liquid fed to the second MVR evaporator 1 minus the amount of reflux.

According to the present invention, preferably, the method further comprises compressing the second ammonia-containing vapor before the second heat exchange. The compression of the second ammonia-containing vapor may be performed by a second compressor 102. Through right the second contains ammonia steam and compresses, for input energy among the MVR vaporization system, guarantee that waste water intensification-evaporation-cooling's process goes on in succession, need input when MVR vaporization process starts and start steam, only need pass through second compressor 102 energy supply after reaching continuous running state, no longer need input other energy. The second compressor 102 may be any one of various compressors conventionally used in the art, such as a centrifugal fan, a turbine compressor, a roots compressor, or the like. After compression by the second compressor 102, the temperature of the second ammonia-containing vapor is raised by 5 to 20 ℃.

According to a preferred embodiment of the present invention, the second evaporation process is performed in the second MVR evaporation device 1, and the first mother liquor is passed into the second MVR evaporation device 1 through the sixth circulation pump 76 to perform the second evaporation, so as to obtain a second concentrated solution containing ammonia vapor and sodium sulfate crystals.

In the present invention, in order to prevent the sodium chloride from crystallizing and precipitating by the second evaporation and to allow the sodium sulfate crystals precipitated by the first evaporation to be dissolved in the low-temperature treatment, it is preferable that the conditions of the second evaporation and the low-temperature treatment satisfy: the temperature of the second evaporation is at least 5 ℃ higher than the temperature of the low-temperature treatment, preferably 20 ℃ higher, more preferably 35 ℃ to 90 ℃ higher, still more preferably 35 ℃ to 70 ℃ higher, and particularly preferably 50 ℃ to 60 ℃ higher. By controlling the temperature of the second evaporation and the low-temperature treatment, the sodium sulfate crystals separated out by the first evaporation in the low-temperature treatment and the sodium sulfate in the sodium chloride crystals can be dissolved, and the sodium sulfate in the second evaporation can be separated out by single crystallization, so that the purity of the obtained sodium sulfate and sodium chloride crystals is improved.

In the invention, the second concentrated solution containing sodium sulfate crystals obtained by the second evaporation is subjected to a second solid-liquid separation to obtain sodium sulfate crystals and a second mother liquor (namely, a liquid phase obtained by the second solid-liquid separation). The method of the second solid-liquid separation is not particularly limited, and may be selected from one or more of centrifugation, filtration, and sedimentation, for example.

According to the present invention, the second solid-liquid separation may be performed by a second solid-liquid separation device (e.g., a centrifuge, a belt filter, a plate filter, etc.) 92. After the second solid-liquid separation, the second mother liquor obtained by the second solid-liquid separation device 92 returns to the first MVR evaporation device 2 for the first evaporation again, and specifically, the second mother liquor can be returned to the second pH adjustment process by the ninth circulation pump 79. In addition, it is difficult to avoid that the obtained sodium sulfate crystals adsorb impurities such as sulfate ions, free ammonia, and hydroxide ions to some extent, and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals, it is preferable that the sodium sulfate crystals are subjected to secondary washing with water, the catalyst production wastewater, or a sodium sulfate solution and dried. In order to avoid the dissolution of sodium sulfate crystals during the washing, the sodium sulfate crystals are preferably washed with an aqueous sodium sulfate solution. More preferably, the concentration of the aqueous sodium sulfate solution is preferably such that the sodium sulfate and sodium chloride reach the concentration of sodium sulfate in the saturated aqueous solution at the same time at the temperature corresponding to the sodium sulfate crystals to be washed.

The form of the second solid-liquid separation and the second washing is not particularly limited, and may be carried out, for example, by using a combination of an elutriation apparatus and a solid-liquid separation apparatus which are conventional in the art, or may be carried out on a staged solid-liquid separation apparatus such as a belt filter. Preferably, the second wash comprises panning and/or rinsing. The above-mentioned elutriation and rinsing are not particularly limited and may be carried out by a method conventional in the art. The number of elutriation and rinsing is not particularly limited, and may be 1 or more, and is preferably 2 to 4 times in order to obtain sodium sulfate crystals of higher purity. In the elutriation process, the catalyst production wastewater is generally not recycled when being used as an elutriation liquid, and the washing liquid recovered by the second washing can be recycled in a counter-current manner when being used as the elutriation liquid. Before the elutriation, it is preferable to perform preliminary solid-liquid separation by sedimentation to obtain a slurry containing sodium sulfate crystals (the liquid content may be 35% by mass or less). In the elutriation process, the liquid used for elutriation is 1 to 20 parts by weight relative to 1 part by weight of the slurry containing sodium sulfate crystals. The rinsing is preferably carried out using an aqueous sodium sulfate solution. In order to further enhance the elutriation effect and obtain sodium sulfate crystals with higher purity, it is preferable to wash the sodium sulfate crystals with the liquid obtained by rinsing. For the liquid generated by washing, it is preferable that the catalyst production wastewater elutriation liquid is returned to the second MVR evaporation device 1 before being returned to the first MVR evaporation device 2 for the second pH adjustment, and other washing liquid is returned to the second MVR evaporation device 1 for the second evaporation again through, for example, the tenth circulation pump 80.

According to a preferred embodiment of the present invention, after the second concentrated solution containing sodium sulfate crystals obtained by the second evaporation is subjected to preliminary solid-liquid separation by settling, the catalyst production wastewater is subjected to first elutriation in an elutriation tank, then the liquid obtained by subsequent washing of sodium sulfate crystals is subjected to second elutriation in another elutriation tank, finally the slurry obtained by the two elutriations is sent to a second solid-liquid separation device for solid-liquid separation, the crystals obtained by the solid-liquid separation are washed with an aqueous sodium sulfate solution, and the liquid obtained by the washing is returned to the second elutriation as an elutriation liquid. Through the washing process combining elutriation and leaching, the purity of the obtained sodium sulfate crystals is improved, washing liquid is not excessively introduced, and the efficiency of wastewater treatment is improved.

According to a preferred embodiment of the present invention, the tail gas left after the condensation of the first ammonia-containing steam by the first heat exchange is discharged after ammonia removal; and discharging the tail gas which is remained after the second ammonia-containing steam is condensed through the second heat exchange after ammonia removal. The first ammonia-containing steam is subjected to the first heat exchange to condense the remaining tail gas, i.e., the tail gas discharged from the second heat exchange device 32, and the second ammonia-containing steam is subjected to the second heat exchange to condense the remaining tail gas, i.e., the tail gas discharged from the fourth heat exchange device 34. The ammonia in the tail gas is removed, so that the pollutant content in the discharged tail gas can be further reduced, and the tail gas can be directly discharged.

As the method of removing ammonia, absorption may be performed by the off-gas absorption tower 83. The off-gas absorption column 83 is not particularly limited, and may be any of various absorption columns conventionally used in the art, such as a plate-type absorption column, a packed absorption column, a falling film absorption column, or an empty column. Circulating water is arranged in the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of the fourth circulating pump 74, water can be supplemented into the tail gas absorption tower 83 from the circulating water tank 82 through the third circulating pump 73, fresh water can be supplemented into the circulating water tank 82, and meanwhile the temperature of working water of the vacuum pump 81 and the ammonia content can be reduced. The flow of the off-gas and the circulating water in the off-gas absorption tower 83 may be in a counter-current or co-current flow, preferably in a counter-current flow. The circulating water can be supplemented by additional fresh water. In order to ensure the sufficient absorption of the tail gas, dilute sulfuric acid may be further added to the tail gas absorption tower 83 to absorb a small amount of ammonia and the like in the tail gas. The circulating water can be used as ammonia water or ammonium sulfate solution for production or direct sale after absorbing tail gas. The off gas may be introduced into the off gas absorption tower 83 by a vacuum pump 81.

In the present invention, the catalyst production wastewater is not particularly limited as long as it contains NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The wastewater is obtained. In addition, the method is particularly suitable for treating high-salinity wastewater. The waste catalyst production water of the present invention may be specifically wastewater from a molecular sieve, alumina or oil refining catalyst production process, or wastewater from a molecular sieve, alumina or oil refining catalyst production process after the following impurity removal and concentration. It is preferable that the wastewater from the production of molecular sieves, alumina or refinery catalysts is subjected to the following impurity removal and concentration.

As NH in the catalyst production wastewater₄ ⁺May be 8mg/L or more, preferably 300mg/L or more.

As Na in the wastewater from the catalyst production⁺May be 510mg/L or more, preferably 1g/L or more, more preferably 2g/L or more, further preferably 4g/L or more, further preferably 8g/L or more, further preferably 16g/L or more, further preferably 32g/L or more, further preferably40g/L or more, more preferably 50g/L or more, and still more preferably 60g/L or more.

As SO in wastewater from the production of said catalyst₄ ^2-May be 1g/L or more, preferably 2g/L or more, more preferably 4g/L or more, further preferably 8g/L or more, further preferably 16g/L or more, further preferably 32g/L or more, further preferably 40g/L or more, further preferably 50g/L or more, further preferably 60g/L or more, further preferably 70g/L or more.

As Cl in the catalyst production wastewater^-It may be 970mg/L or more, more preferably 2g/L or more, further preferably 4g/L or more, further preferably 8g/L or more, further preferably 16g/L or more, further preferably 32g/L or more, further preferably 40g/L or more, further preferably 50g/L or more, further preferably 60g/L or more.

NH contained in the catalyst production wastewater₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The upper limit of (3) is not particularly limited. SO in the wastewater from catalyst production from the viewpoint of easy wastewater treatment₄ ^2-、Cl^-And Na⁺The upper limit of (b) is 200g/L or less, preferably 150g/L or less, respectively; NH in catalyst production wastewater₄ ⁺Is 100g/L or less, preferably 50g/L or less.

From the viewpoint of improving the efficiency of the first evaporation and reducing the energy consumption of the treatment process, the amount of SO contained in the wastewater is relatively small₄ ^2-Cl in catalyst production wastewater^-The higher the content, the better, for example, relative to 1 mole of SO contained in the ammonium salt-containing wastewater₄ ^2-Cl contained in the catalyst production wastewater^-Is 1 mole or more, preferably 2 moles or more, preferably 5 moles or more, more preferably 9.5 moles or more, and further preferably 10 moles or more. From the viewpoint of practicality, the amount of SO contained in the wastewater from the catalyst production is 1 mole₄ ^2-Cl contained in the catalyst production wastewater^-Preferably 200 mol or less, more preferably 150 molThe amount of the compound is preferably 100 mol or less, more preferably 50 mol or less, and still more preferably 30 mol or less. By adding Cl contained in the catalyst production wastewater^-And SO₄ ^2-The molar ratio of (a) to (b) is limited to the above range, most of water can be evaporated in the first evaporation, the amount of circulating liquid in a treatment system is reduced, energy is saved, and the treatment process is more economical.

In the present invention, the inorganic salt ions contained in the catalyst production wastewater are other than NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺In addition, it may contain Mg²⁺、Ca²⁺、K⁺、Fe³⁺Inorganic salt ions such as rare earth element ions, Mg²⁺、Ca²⁺、K⁺、Fe³⁺The content of each inorganic salt ion such as a rare earth element ion is preferably 100mg/L or less, more preferably 50mg/L or less, further preferably 10mg/L or less, and particularly preferably no other inorganic salt ion is contained. By controlling the other inorganic salt ions within the above range, the purity of the sodium chloride crystals and the sodium sulfate crystals finally obtained can be further improved. In order to reduce the content of other inorganic salt ions in the catalyst production wastewater, the following impurity removal is preferably performed.

The TDS of the catalyst production wastewater may be 1.6g/L or more, preferably 4g/L or more, more preferably 8g/L or more, further preferably 16g/L or more, further preferably 32g/L or more, further preferably 40g/L or more, further preferably 50g/L or more, further preferably 60g/L or more, further preferably 100g/L or more, further preferably 150g/L or more, further preferably 200g/L or more.

In the present invention, the pH of the catalyst production wastewater is preferably 4 to 8, for example 6.5 to 7.5.

In addition, since the COD of the wastewater may block a membrane during concentration, affect the purity and color of a salt during evaporative crystallization, etc., the COD of the wastewater from the catalyst production is preferably as small as possible (preferably 20mg/L or less, more preferably 10mg/L or less), and is preferably removed by oxidation during pretreatment, specifically, by biological method, advanced oxidation method, etc., and is preferably oxidized by an oxidizing agent such as Fenton's reagent when the COD content is very high.

In the invention, in order to reduce the concentration of impurity ions in the catalyst production wastewater, ensure the continuous and stable treatment process and reduce the equipment operation and maintenance cost, the catalyst production wastewater is preferably subjected to impurity removal before being treated by the treatment method. Preferably, the impurity removal is selected from one or more of solid-liquid separation, chemical precipitation, adsorption, ion exchange and oxidation.

As the solid-liquid separation, filtration, centrifugation, sedimentation, or the like may be mentioned; as the chemical precipitation, pH adjustment, carbonate precipitation, magnesium salt precipitation, and the like may be mentioned; the adsorption can be physical adsorption and/or chemical adsorption, and the specific adsorbent can be selected from activated carbon, silica gel, alumina, molecular sieve, natural clay and the like; as the ion exchange, any one of a strongly acidic cation resin and a weakly acidic cation resin can be used; as the oxidation, various oxidizing agents conventionally used in the art, such as ozone, hydrogen peroxide, and potassium permanganate, can be used, and in order to avoid introduction of new impurities, ozone, hydrogen peroxide, and the like are preferably used.

The specific impurity removal mode can be specifically selected according to the types of impurities contained in the catalyst production wastewater. For suspended matters, a solid-liquid separation method can be selected for removing impurities; for inorganic matters and organic matters, chemical precipitation, ion exchange and adsorption methods can be selected for removing impurities, such as weak acid cation exchange, activated carbon adsorption and the like; for organic matters, impurities can be removed by adopting an adsorption and/or oxidation mode, wherein an ozone biological activated carbon adsorption oxidation method is preferred. According to a preferred embodiment of the invention, the catalyst production wastewater is subjected to impurity removal by filtration, a weak acid cation exchange method and an ozone biological activated carbon adsorption oxidation method in sequence. Through the impurity removal process, most suspended matters, hardness, silicon and organic matters can be removed, the scaling risk of the device is reduced, and the continuous and stable operation of the wastewater treatment process is ensured.

In the present invention, the catalyst production wastewater having a low salt content may be concentrated to have a salt content within a range required for the catalyst production wastewater of the present invention before the treatment by the treatment method of the present invention (preferably after the above-mentioned impurity removal). Preferably, the concentration is selected from ED membrane concentration and/or reverse osmosis; more preferably, the concentration is performed by ED membrane concentration and reverse osmosis, and the order of performing the ED membrane concentration and the reverse osmosis is not particularly limited. The ED membrane concentration and reverse osmosis treatment apparatus and conditions may be performed in a manner conventional in the art, and may be specifically selected according to the condition of wastewater to be treated. Specifically, as the concentration of the ED membrane, a one-way electrodialysis system or a reversed electrodialysis system can be selected for carrying out; as the reverse osmosis, a roll membrane, a plate membrane, a disc-tube membrane, a vibrating membrane or a combination thereof can be selected for use. Through the concentration can improve the efficiency of waste water treatment, avoid the energy waste that a large amount of evaporations caused.

In a preferred embodiment of the invention, the wastewater is wastewater obtained by performing chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation on wastewater generated in the molecular sieve production process to remove impurities, and performing ED membrane concentration and reverse osmosis concentration on the wastewater.

The conditions for the above chemical precipitation are preferably: sodium carbonate is used as a treating agent, 1.2-1.4 mol of sodium carbonate is added relative to 1 mol of calcium ions in the wastewater, the pH value of the wastewater is adjusted to be more than 7, the reaction temperature is 20-35 ℃, and the reaction time is 0.5-4 h.

The conditions for the filtration are preferably: the filtering unit adopts a double-layer filtering material multi-medium filter consisting of anthracite and quartz sand, the grain diameter of the anthracite is 0.7-1.7mm, the grain diameter of the quartz sand is 0.5-1.3mm, and the filtering speed is 10-30 m/h. After the filter material is used, the regeneration method of 'gas back flushing-gas and water back flushing-water back flushing' is adopted to regenerate the filter material, and the regeneration period is 10-15 h.

The conditions for the weak acid cation exchange method are preferably: the pH value range is 6.5-7.5; the temperature is less than or equal to 40 ℃, the height of the resin layer is 1.5-3.0m, the HCl concentration of the regeneration liquid is as follows: 4.5-5 mass%; the dosage of the regenerant (calculated by 100%) is 50-60kg/m³Wet resin; the flow rate of the regeneration liquid HCl is 4.5-5.5m/h, and the regeneration is carried outThe contact time is 35-45 min; the forward washing flow rate is 18-22m/h, and the forward washing time is 2-30 min; the running flow rate is 15-30 m/h; as the acidic cation exchange resin, for example, there can be used a Gallery Senno chemical Co., Ltd, SNT brand D113 acidic cation exchange resin.

The conditions of the above-mentioned ozone biological activated carbon adsorption oxidation method are preferably: the retention time of the ozone is 50-70min, and the empty bed filtration rate is 0.5-0.7 m/h.

The conditions for the concentration of the ED membrane are preferably: current 145-155A, voltage 45-65V. The ED membrane may be, for example, an ED membrane manufactured by astone corporation of japan.

The conditions for the reverse osmosis are preferably: the operation pressure is 5.4-5.6MPa, the water inlet temperature is 25-35 ℃, and the pH value is 6.5-7.5. The reverse osmosis membrane is, for example, a seawater desalination membrane TM810C manufactured by Dongli corporation of Lanxingdong.

According to the invention, when the wastewater treatment is started, the catalyst production wastewater can be used for direct operation, and if the ion content of the catalyst production wastewater meets the conditions of the invention, the first evaporation and the low-temperature treatment can be carried out firstly and then the second evaporation can be carried out according to the conditions of the invention; if the ion content of the catalyst production wastewater does not meet the conditions of the invention, the first evaporation can be controlled to ensure that the concentration of sodium sulfate in the first concentrated solution is close to the precipitation concentration, then the first concentrated solution is subjected to low-temperature treatment and second evaporation to obtain a second concentrated solution, the second concentrated solution is subjected to solid-liquid separation to obtain sodium sulfate crystals and a second mother solution, the second mother solution is mixed with the catalyst production wastewater to adjust the ion content of the wastewater to be treated to be in the range required by the invention, and then the first evaporation is carried out to obtain sodium chloride crystals. Of course, Na may be used in the initial stage₂SO₄Or NaCl, as long as the ion content of the wastewater to be treated is adjusted SO that the wastewater to be treated satisfies SO in the wastewater to be treated in the invention₄ ^2-、Cl^-The requirements are met.

The present invention will be described in detail below by way of examples.

In the following examples, the catalyst production wastewater is wastewater from a molecular sieve production process, which is subjected to chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation in sequence to remove impurities, and is subjected to ED membrane concentration and reverse osmosis concentration in sequence.

Example 1

As shown in FIG. 1, the catalyst production wastewater (containing NaCl 159g/L, Na)₂SO₄ 48g/L、NH₄Cl 39g/L、(NH₄)₂SO₄12g/L, pH is 7) at a feed rate of 5m³Feeding the catalyst production wastewater into a treatment system at a speed of/h through a first circulating pump 71, introducing a sodium hydroxide aqueous solution with the concentration of 45.16 mass% into a main pipeline fed into a first heat exchange device 31 and a fifth heat exchange device 35 (titanium alloy plate heat exchangers) to carry out first pH value adjustment, monitoring the adjusted pH value through a first pH value measuring device 61(pH meter) (the measured value is 7.8), respectively feeding the catalyst production wastewater subjected to the first pH value adjustment into the first heat exchange device 31 and the fifth heat exchange device 35, and respectively carrying out first heat exchange with a first ammonia-containing steam condensate and a first concentrated solution containing sodium sulfate crystals and sodium chloride crystals obtained by first evaporation to heat the catalyst production wastewater to 102 ℃; then mixing with the second mother liquor to obtain the wastewater to be treated (containing SO)₄ ^2-And Cl^-In a molar ratio of 1: 11.346), introducing a 45.16 mass percent sodium hydroxide aqueous solution into a pipeline for conveying the wastewater to be treated into the second heat exchange device 32 to adjust the pH value for the second time, monitoring the adjusted pH value through a second pH value measuring device 62 (a pH meter) (the measured value is 11), conveying the wastewater to be treated into the second heat exchange device 32 (a titanium alloy plate heat exchanger) to perform first heat exchange with the recycled first ammonia-containing steam to heat the wastewater to be treated to 112 ℃, and then conveying the wastewater to be treated after the two times of first heat exchange to 476.5m³And/h, sending the mixture into a first MVR evaporation device 2 (a falling film and forced circulation two-stage MVR evaporation crystallizer) for evaporation to obtain first ammonia-containing steam and first concentrated solution containing sodium sulfate crystals and sodium chloride crystals. Wherein the evaporation conditions of the first MVR evaporation device 2 include: the temperature is 105 ℃, the pressure is-7.02 kPa, and the evaporation capacity is 4.82m³H is used as the reference value. The first ammonia-containing steam obtained by evaporation is compressed by a first compressor 101 (the temperature is raised by 18 ℃) and then sequentially passes through a second heat exchangeThe device 32 and the first heat exchange device 31 exchange heat with the wastewater to be treated, and the wastewater is cooled to obtain first ammonia water which is stored in a first ammonia water storage tank 51. In addition, in order to increase the solid content of the concentrated solution in the first MVR evaporation device 2, part of the liquid evaporated in the first MVR evaporation device 2 is circulated to the second heat exchange device 32 by the second circulation pump 72, and then enters the first MVR evaporation device 2 again for first evaporation (reflux ratio is 95.3). The degree of the first evaporation is monitored through a mass flow meter arranged on the first MVR evaporation device 2, and the evaporation capacity of the first evaporation is controlled to be 4.82m³H (corresponding to the control of the sodium sulfate concentration in the treatment solution to 0.978Y (88.9 g/L)).

And (3) carrying out low-temperature treatment on the obtained first concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals in a low-temperature treatment tank 22 at the temperature of 20 ℃ for 60min to obtain a treatment solution containing the sodium chloride crystals.

The treated solution containing sodium chloride crystals was sent to a first solid-liquid separation apparatus 91 (centrifuge) to conduct solid-liquid separation, and 7.17m per hour was obtained³Contains 279.8g/L, Na% NaCl₂SO₄ 88.9g/L、NaOH 2.64g/L、NH₃0.31g/L of first mother liquor is temporarily stored in a first mother liquor tank 53, sodium chloride solid obtained by solid-liquid separation (1190.32 kg of sodium chloride crystal filter cake containing 15 mass% of water is obtained every hour, wherein the content of sodium sulfate is less than 3.9 mass%), is leached by 279.8g/L of sodium chloride solution with the same dry basis mass as the sodium chloride crystal filter cake, is dried in a drier, 1011.78kg of sodium chloride (with the purity of 99.5 weight%) is obtained every hour, and washing liquid enters the first MVR evaporation device 2 again for first evaporation after being sent to the second heat exchange device 32 through an eighth circulating pump 78.

The second evaporation process is carried out in a second MVR evaporation plant 1 (falling film + forced circulation two-stage MVR evaporator crystallizer). And (3) sending the first mother liquor in the first mother liquor tank 53 to the third heat exchange device 33 and the fourth heat exchange device 34 in sequence through a sixth circulating pump 76, and then sending the mother liquor to the second MVR evaporation device 1 for second evaporation to obtain a second concentrated solution containing sodium sulfate crystals. Wherein the evaporation conditions of the second MVR evaporation device 1 include: the temperature was 105 ℃, the pressure was-7.02 kPa, and the evaporation capacity was 0.78m³H is used as the reference value. In order to increase the solid content of the concentrated solution in the second MVR evaporation device 1, part of the first mother solution after evaporation in the second MVR evaporation device 1 is circulated as a second circulation solution to the fourth heat exchange device 34 by the seventh circulation pump 77, and then enters the second MVR evaporation device 1 again for second evaporation (the reflux ratio is 9.6). The second ammonia-containing steam obtained by evaporation is compressed by the second compressor 102 (the temperature is raised by 18 ℃) and then sequentially passes through the fourth heat exchange device 34 and the third heat exchange device 33, and is subjected to heat exchange with the second ammonia-containing steam condensate and the second ammonia-containing steam respectively, and is cooled to obtain second ammonia, and the second ammonia is stored in the second ammonia storage tank 52. The degree of the second evaporation is monitored by a mass flow meter arranged on the second MVR evaporation device 1, and the concentration of the sodium chloride in the second evaporation concentrated solution is controlled to be 0.9935X (306.5 g/L).

Feeding the second concentrated solution containing sodium sulfate crystals into a second solid-liquid separation device 92 (centrifuge) for solid-liquid separation to obtain 6.70m per hour³Contains 306.5g/L, Na NaCl₂SO₄ 52.5g/L、NaOH 2.89g/L、NH₃0.01g/L of the second mother liquor is temporarily stored in the second mother liquor tank 54. And (3) circulating the second mother liquor to a wastewater pipeline between the first heat exchange device 31 and the second heat exchange device 32 through a ninth circulating pump 79, and mixing the second mother liquor with the catalyst production wastewater to obtain wastewater to be treated. After solid-liquid separation, the obtained sodium sulfate solid (349.84 kg of sodium sulfate crystal cake containing 14 mass% of water per hour, wherein the content of sodium chloride is 3.9 mass% or less) was washed with 52.5g/L sodium sulfate solution equivalent to the dry basis mass of sodium sulfate, and dried in a dryer to obtain 300.87kg of sodium sulfate (purity: 99.5 wt%) per hour, and the washing solution was circulated to the second MVR evaporator 1 by the tenth circulation pump 80.

In addition, the tail gas discharged by the second heat exchange device 32 and the fourth heat exchange device 34 is introduced into a tail gas absorption tower 83 through a vacuum pump 81 for absorption, circulating water is introduced into the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of the fourth circulating pump 74, water is supplemented into the tail gas absorption tower 83 from a circulating water tank 82 through a third circulating pump 73, and fresh water is supplemented into the circulating water tank 82, so that the temperature and the ammonia content of the working water of the vacuum pump 81 are reduced. Dilute sulfuric acid is further introduced into the tail gas absorption tower 83 to absorb ammonia and the like in the tail gas. In addition, the starting phase of the MVR evaporation was started by steam at a temperature of 143.3 ℃.

In this example, 4.82m of ammonia water having a concentration of 1.5 mass% was obtained per hour in the first ammonia water tank 51³0.78m of 0.28 mass% ammonia water was obtained per hour in the second ammonia water tank 52³The ammonia water can be reused in the production process of the molecular sieve.

Example 2

The treatment of the catalyst production wastewater was carried out in the same manner as in example 1, except that: for NaCl-containing 58g/L, Na₂SO₄ 120g/L、NH₄Cl 19g/L、(NH₄)₂SO₄40g/L, pH of 7.1 catalyst production wastewater is treated to obtain SO contained in the wastewater to be treated₄ ^2-And Cl^-In a molar ratio of 1: 8.665. the temperature of the catalyst production wastewater after heat exchange by the first heat exchange device 31 and the fifth heat exchange device 35 is 97 ℃, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange device 32 is 97.5 ℃. The evaporation conditions of the first MVR evaporation device 2 include: the temperature is 100 ℃, the pressure is-22.83 kPa, and the evaporation capacity is 3.47m³H is used as the reference value. The low-temperature treatment temperature is 25 deg.C, and the retention time is 55 min. The evaporation conditions of the second MVR evaporation device 1 include: the temperature is 95 ℃, the pressure is-36.36 kPa, and the evaporation capacity is 2.28m³/h。

The first solid-liquid separation device 91 obtained 454.10kg tons of sodium chloride crystal cake containing 14 mass% of water per hour, and finally obtained 390.53kg of sodium chloride (purity 99.6 wt%); obtained 25.59m per hour³The concentration of NaCl 280.6g/L, Na₂SO₄ 82.9g/L、NaOH 2.2g/L、NH₃0.12g/L of the first mother liquor.

The second solid-liquid separation device 92 gave 962.68kg of a sodium sulfate crystal cake having a water content of 15 mass% per hour, and finally gave 818.28kg of sodium sulfate (purity: 99.5% by weight) per hour to give 23.56m³The concentration is NaCl 303.2g/L, Na₂SO₄ 55.3g/L、NaOH 2.4g/L、NH₃0.005g/L of the second mother liquor.

In this example, 3.47m of 2.2 mass% ammonia water was obtained per hour in the first ammonia water tank 51³2.28m of aqueous ammonia having a concentration of 0.13% by mass per hour was obtained in the second aqueous ammonia tank 52³The ammonia water can be reused in the production process of the molecular sieve.

Example 3

The treatment of the catalyst production wastewater was carried out in the same manner as in example 1, except that: for NaCl-containing 80g/L, Na₂SO₄ 78g/L、NH₄Cl 29g/L、(NH₄)₂SO₄28.7g/L, pH of 6.6 catalyst production wastewater to obtain SO contained in wastewater to be treated₄ ^2-And Cl^-In a molar ratio of 1: 8.745. the temperature of the catalyst production wastewater after heat exchange by the first heat exchange device 31 and the fifth heat exchange device 35 is 105 ℃, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange device 32 is 117 ℃. The evaporation conditions of the first MVR evaporation device 2 include: the temperature is 110 ℃, the pressure is 11.34kPa, and the evaporation capacity is 4.26m³H is used as the reference value. The evaporation conditions of the second MVR evaporation device 1 include: the temperature is 100 ℃, the pressure is-22.82 kPa, and the evaporation capacity is 1.40m³H is used as the reference value. The low-temperature treatment temperature is 20 deg.C, and the retention time is 60 min.

The first solid-liquid separation device 91 obtained 657.86kg tons of sodium chloride crystal cake containing 15 mass% of water per hour, and finally obtained 559.18kg of sodium chloride (purity 99.4 wt%); yield 13.55m per hour³The concentration of NaCl is 280.2g/L, Na₂SO₄ 89.1g/L、NaOH 1.7g/L、NH₃0.18g/L of the first mother liquor.

The second solid-liquid separation device 92 obtained 632.55kg of a sodium sulfate crystal cake having a water content of 14 mass% per hour, and finally 543.99kg of sodium sulfate (purity of 99.5 wt%) per hour; obtained at an hourly rate of 12.39m³The concentration of NaCl is 306.1g/L, Na₂SO₄ 53.9g/L、NaOH 1.85g/L、NH₃0.0099g/L of a second mother liquor.

In the present embodiment, the first aqueous ammonia tank 51 is filled with the ammonia water every hourAmmonia water having a concentration of 1.8 mass% of 4.26m was obtained³1.40m of ammonia water having a concentration of 0.16 mass% is obtained per hour in the second ammonia water tank 52³The ammonia water can be reused in the production process of the molecular sieve.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. Method for treating catalyst production wastewater containing NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺Characterized in that the method comprises the following steps,

1) introducing the wastewater to be treated into a first MVR evaporation device for first evaporation to obtain first ammonia-containing steam and a first concentrated solution containing sodium sulfate crystals and sodium chloride crystals;

adjusting the pH value of the wastewater to be treated to be more than 9 before introducing the wastewater to be treated into a first MVR evaporation device;

the conditions of the first evaporation include: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa; the temperature of the low-temperature treatment is 15-45 ℃; the temperature of the second evaporation is higher than that of the low-temperature treatment by more than 20 ℃;

the second evaporation prevents sodium chloride crystals from crystallizing out;

relative to 1 mole of SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-7.15 mol or more;

the wastewater to be treated contains the catalyst production wastewater and a liquid phase obtained by the second solid-liquid separation, and NH in the catalyst production wastewater₄ ⁺Is more than 8mg/L, SO₄ ^2-Is more than 1g/L, Cl^-Over 970mg/L of Na⁺Is more than 510 mg/L.

2. The method according to claim 1, wherein the SO contained in the wastewater to be treated is 1 mole relative to the SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-9.5 mol or more.

3. The method according to claim 2, wherein the SO contained in the wastewater to be treated is 1 mole relative to the SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-Is 10 mol or more.

4. The method of claim 1, wherein the pH of the wastewater to be treated is adjusted to greater than 10.8 prior to passing the wastewater to be treated to the first MVR evaporation unit.

5. The method as claimed in claim 1, wherein the pH adjustment of the wastewater to be treated is carried out with NaOH.

6. The method according to claim 1, wherein the first evaporation is performed so that the concentration of sodium sulfate in the treatment solution is Y or less, where Y is the concentration of sodium sulfate at which both sodium chloride and sodium sulfate in the treatment solution are saturated under the low-temperature treatment condition;

and the second evaporation enables the concentration of sodium chloride in the second concentrated solution to be less than X, wherein X is the concentration of sodium chloride when the sodium chloride and the sodium sulfate in the second concentrated solution are saturated under the second evaporation condition.

7. The method of claim 6, wherein the first evaporation provides a sodium sulfate concentration in the treatment solution of 0.9Y to 0.99Y.

8. A process as claimed in claim 6, wherein the second evaporation results in a concentration of sodium chloride in the second concentrate of 0.95X to 0.999X.

9. The method of any one of claims 1-8, wherein the conditions of the first evaporation comprise: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa.

10. The method of claim 9, wherein the conditions of the first evaporation comprise: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa.

11. The method of any one of claims 1-8, wherein the conditions of the second evaporation comprise: the temperature is above 35 ℃ and the pressure is above-95 kPa.

12. The method of claim 11, wherein the conditions of the second evaporation comprise: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa.

13. The method of claim 12, wherein the conditions of the second evaporation comprise: the temperature is 60-365 ℃, and the pressure is-87 kPa-18110 kPa.

14. The method of claim 13, wherein the conditions of the second evaporation comprise: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa.

15. The method of claim 14, wherein the conditions of the second evaporation comprise: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa.

16. The method of claim 15, wherein the conditions of the second evaporation comprise: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa.

17. The method according to any one of claims 1 to 8, wherein the temperature of the cryogenic treatment is between 15 ℃ and 35 ℃.

18. The method of claim 17, wherein the cryogenic treatment is at a temperature of 17.9 ℃ to 35 ℃.

19. The method of claim 12, wherein the temperature of the second evaporation is more than 5 ℃ higher than the temperature of the low temperature treatment.

20. The method according to claim 1, wherein the temperature of the second evaporation is 35-90 ℃ higher than the temperature of the low-temperature treatment.

21. The method of claim 1, wherein the first ammonia-containing vapor is subjected to a first heat exchange with the wastewater to be treated and a first ammonia solution is obtained before the wastewater to be treated is passed to a first MVR evaporation plant.

22. The method as set forth in claim 21, wherein the pH of the wastewater to be treated is adjusted to be greater than 7 prior to the first heat exchange.

23. The method according to claim 21, wherein the first ammonia-containing vapor is discharged after ammonia removal from the tail gas remaining from the condensation of the first heat exchange.

24. The method of claim 1, wherein the second ammonia-containing vapor evaporated by the second MVR evaporation device and the liquid phase obtained by the first solid-liquid separation are subjected to a second heat exchange to obtain a second ammonia water.

25. The method according to claim 24, wherein the second ammonia-containing steam is discharged after ammonia removal from the tail gas remaining after the condensation of the second heat exchange.

26. The method according to any one of claims 1 to 8, further comprising subjecting the treatment liquid containing sodium chloride crystals to a first solid-liquid separation to obtain sodium chloride crystals.

27. The method of claim 26, further comprising washing the obtained sodium chloride crystals.

28. The method according to any one of claims 1 to 8, further comprising subjecting the second concentrated solution containing sodium sulfate crystals to a second solid-liquid separation to obtain sodium sulfate crystals.

29. The method of claim 28, further comprising washing the resulting sodium sulfate crystals.

30. The process of any one of claims 1 to 8, wherein the catalyst production wastewater is a wastewater body from a molecular sieve, alumina or refinery catalyst production process.

31. The method of claim 30, further comprising removing impurities and concentrating the catalyst process wastewater.