CN108726766B

CN108726766B - Method for treating catalyst production wastewater

Info

Publication number: CN108726766B
Application number: CN201710266192.4A
Authority: CN
Inventors: 殷喜平; 李叶; 王涛; 苑志伟; 刘志坚; 顾松园; 高晋爱; 安涛; 王生吉
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: 2022-11-25
Anticipated expiration: 2037-04-21
Also published as: CN108726766A

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 NH ₄ ⁺ 、SO ₄ ^2‑ 、Cl ^‑ And Na ⁺ The method comprises the steps of 1) introducing wastewater to be treated into an 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 solution containing the sodium chloride crystals, and sequentially introducing the liquid phase obtained by the first solid-liquid separation into each effect evaporator of the multi-effect evaporation device for second evaporation to obtain a second concentrated solution containing the 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 method for treating wastewater containing NH ₄ ⁺ 、SO ₄ ^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-base 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 practice 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 the biochemical method, the blow-off method or the 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 ammonia 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 art ₄ ⁺ 、SO ₄ ^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 catalyst ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ For the treatment of waste waterThe method can respectively recover the ammonium, the sodium chloride and the 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, the wastewater containing NH ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ The method comprises the following steps of,

1) Introducing wastewater to be treated into an 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 solution containing the sodium chloride crystals, and sequentially introducing the liquid phase obtained by the first solid-liquid separation into each effect evaporator of a multi-effect evaporation device for second evaporation to obtain a second concentrated solution containing the 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 an MVR evaporation device; introducing second ammonia-containing steam obtained by evaporation of a subsequent evaporator of the multi-effect evaporation device into a previous evaporator, and performing countercurrent heat exchange between a liquid phase obtained by the first solid-liquid separation and the second ammonia-containing steam; the first evaporation enables sodium sulfate crystals to be dissolved in low-temperature treatment, and the second evaporation enables sodium chloride not to be crystallized and separated out; relative to 1 mole of SO contained in the wastewater to be treated ₄ ^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 NH ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ The catalyst production wastewater is obtained by adjusting the pH value of wastewater to be treated to a specific range in advance and then utilizingAnd (3) carrying out evaporation separation by using an MVR evaporation device to obtain concentrated solution containing sodium sulfate crystals and sodium chloride crystals and stronger ammonia water, then dissolving sodium sulfate in the concentrated solution by using low-temperature treatment, and further crystallizing and separating out sodium chloride to obtain sodium chloride crystals. And then evaporating again by using a multi-effect evaporation device to obtain concentrated solution containing sodium sulfate crystals and thinner ammonia water to obtain sodium sulfate crystals. 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 cools the 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, respectively recovers the sodium sulfate and the sodium chloride in the form of crystals, does not generate waste residues and waste liquid in the whole process, and realizes the purpose of changing waste into valuable.

Furthermore, the method is matched with low-temperature treatment through the first evaporation, so that the first evaporation can be carried out at a higher temperature, the solid content and the evaporation efficiency of the first evaporation concentrated solution are improved, and meanwhile, 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. Multi-effect evaporation plant 2, MVR evaporation plant

22. Low temperature treatment tank 73 and third circulation pump

31. First heat exchanger 74 and fourth circulating pump

32. Second heat exchange device 76 and sixth circulation pump

33. Third heat exchange device 78 and eighth circulating pump

34. Fourth heat exchange device 79 and ninth circulating pump

35. Fifth heat exchange device 80 and tenth circulating pump

36. Sixth heat exchange device 85 and fifteenth circulating pump

51. First ammonia water storage tank 86, sixteenth circulating pump

52. Second ammonia storage tank 87 and seventeenth circulating pump

53. First mother liquid tank 81, vacuum pump

54. Second mother liquor tank 82 and circulating water tank

55. Crystal liquid collecting tank 83 and tail gas absorption tower

61. First pH value measuring device 91 and first solid-liquid separation device

62. Second pH value measuring device 92 and second solid-liquid separation device

71. First circulating pump 10 and compressor

72. Second circulating pump

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 preferred embodiment of the 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 numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed 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 invention provides a method for treating wastewater generated in catalyst production, which contains NH ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ The method comprises the following steps of,

1) Introducing wastewater to be treated into an MVR evaporation device 2 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;

3) Carrying out first solid-liquid separation on the treatment solution containing the sodium chloride crystals, and sequentially introducing the liquid phase obtained by the first solid-liquid separation into each effect evaporator of the multi-effect evaporation device 1 for second evaporation to obtain a second concentrated solution containing sodium sulfate crystals;

before the wastewater to be treated is introduced into the MVR evaporation device 2, adjusting the pH value of the wastewater to be treated to be more than 9; introducing second ammonia-containing steam obtained by evaporation of a subsequent evaporator of the multi-effect evaporation device 1 into a previous evaporator, and performing countercurrent heat exchange between a liquid phase obtained by the first solid-liquid separation and the second ammonia-containing steam; the first evaporation enables sodium sulfate crystals to be dissolved in low-temperature treatment, and the second evaporation enables sodium chloride not to be crystallized and separated out; relative to 1 mole of SO contained in the wastewater to be treated ₄ ^2- Cl contained in the wastewater to be treated ^- Is 7.15 mol or more.

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 the wastewater to be treated is passed into the 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 ammonia-containing gas containing NH ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ Except that it contains NH ₄ ⁺ 、SO ₄ ^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 mole ₄ ^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 9 to 20 moles, preferably 9 to 12 moles, more preferably 10 to 12 moles. By reacting SO ₄ ^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 circulate the second mother liquor obtained in the second evaporation process to the first evaporation, and thereby to treat SO in the wastewater to be treated ₄ ^2- And Cl ^- Can be 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 concentrated solution can 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. Sodium sulfate entrained by or adsorbed on the surface of the sodium chloride crystals is not excluded with respect to the treatment liquid containing sodium chloride crystals. Since the water content of the crystals after solid-liquid separation is different, the sodium sulfate content of the obtained sodium chloride crystals 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 of the obtained sodium chloride crystals 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 liquid phase obtained by the first solid-liquid separation and the first ammonia-containing steam are subjected to countercurrent heat exchange, which means that a countercurrent flow in multi-effect evaporation is adopted. The pressures are all pressures in gauge pressure.

In the present invention, the 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 evaporation 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 105-110 ℃, and the pressure is-8 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, 0.1m ³ More than h (e.g. 0.1 m) ³ /h～500m ³ /h)。

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

According to the invention, by controlling the evaporation condition of the 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 is prepared 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 introduced into the MVR evaporation device 2, the first ammonia-containing vapor obtained from the MVR evaporation device 2 is subjected to a first heat exchange with the wastewater to be treated to obtain a first ammonia solution. 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 heat exchanges may be one or more, preferably 2 to 4, more preferably 2 to 3. Through the heat exchange, the output ammonia water is further 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 the first heat exchange device 31, the fifth heat exchange device 35 and the second heat exchange device 32, specifically, a part of the wastewater to be treated is first heat exchanged with the first condensate containing ammonia vapor by the first heat exchange device 31, and another part of the wastewater to be treated is first heat exchanged with the first concentrate by the fifth heat exchange device 35, and then the wastewater to be treated is merged and is first heat exchanged with the first condensate containing ammonia vapor 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 made of duplex stainless steel, titanium alloy and hastelloy can be selected, and the heat exchanger made of plastic 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 by the first heat exchange device 31 is 44 ℃ to 174 ℃, more preferably 69 ℃ to 174 ℃, even more preferably 79 ℃ to 129 ℃, and even 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 69 ℃ to 174 ℃, even more preferably 79 ℃ to 129 ℃, and even 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 MVR evaporation plant 2, and the first pH adjustment is performed by introducing and mixing the aqueous solution containing the alkaline substance in the main pipe for feeding the wastewater to be treated into the first heat exchange unit 31 or the fifth heat exchange unit 35 before feeding the wastewater to be treated into the first heat exchange unit 31 or the fifth heat exchange unit 35 for the first heat exchange; then, after the wastewater to be treated is sent to the second heat exchange device 32 to be subjected to the first heat exchange, the second pH adjustment is performed by introducing and mixing the aqueous solution containing the alkaline substance into the pipe that sends the wastewater to be treated to the MVR evaporation device 2. The pH value of the wastewater to be treated is more than 9, preferably more than 10.8 before the wastewater is introduced into the MVR evaporation device 2 through two pH value adjustments. 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 of the wastewater to be treated 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 main pipe for feeding the wastewater to be treated into the first heat exchanging device 31 and the third heat exchanging device 33 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 MVR evaporating device 2 to measure the pH value after the second pH adjustment.

In the present 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 (in the case where the wastewater to be treated contains a liquid phase obtained by the separation of the catalyst production wastewater and the second solid-liquid, the preparation of the wastewater to be treated needs to be performed) is not particularly limited, and may be appropriately selected as needed, and 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 are completed before the wastewater to be treated is introduced into the MVR evaporation apparatus 2.

In the present invention, in order to increase the crystal content of the concentrated liquid in the MVR evaporation device 2 and reduce the ammonia content in the liquid, it is preferable that a part of the liquid (i.e., the liquid inside the MVR evaporation device, hereinafter also referred to as a circulating liquid) evaporated by the MVR evaporation device 2 is heated and then returned to the MVR evaporation device 2 for evaporation. The above-mentioned process of returning the circulation liquid to the MVR evaporation device 2 is preferably to return the circulation liquid to the 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 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, heat exchanged by the second heat exchange device 32, and then sent to the MVR evaporation device 2 after the second pH adjustment. The ratio of the part of the liquid evaporated by the MVR evaporation device 2 to be refluxed to the MVR evaporation device 2 is not particularly limited, and for example, the 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 reflux ratio means: the ratio of the amount of reflux to the total amount of liquid fed to the 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 10. 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 10 energy supply after reaching continuous running state, no longer need input other energy. The first compressor 10 may employ various compressors conventionally used in the art, such as a centrifugal fan, a turbine compressor, or a roots compressor, etc. After compression by the first compressor 10, the temperature of the first ammonia-containing vapor is raised by 5 to 20 ℃.

In the invention, the first concentrated solution containing sodium sulfate crystals and sodium chloride crystals is subjected to low-temperature treatment to dissolve sodium sulfate crystals, so as to obtain the treated solution containing 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 is 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: 13 to 100 ℃, preferably 15 to 45 ℃, more preferably 15 to 35 ℃, and further preferably 17.9 to 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 70min.

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 an agitation member, and the solid-liquid phase distribution and the temperature distribution in the first concentrated solution can be made uniform by the agitation member, so that the sodium sulfate crystals can be sufficiently dissolved, and the sodium chloride crystals can be precipitated to the maximum extent.

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 multi-effect 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, the sodium chloride crystals are preferably subjected to first washing 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 aqueous sodium chloride solution is preferably the concentration of sodium chloride in an aqueous solution in which sodium chloride and sodium sulphate 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 MVR evaporation device before the second pH value adjustment, for example, after being returned to the waste water to be treated by the eighth circulating pump 78 before the second pH adjustment and mixed with the waste water to be treated, and then returned to the first MVR evaporation device for evaporation after the second pH adjustment and the heat exchange of 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 respective evaporators of the multi-effect evaporation apparatus 1 are not particularly limited, and may be composed of various evaporators conventionally used in the art. For example, it may be selected from one or more of falling film type evaporator, rising film type evaporator, scraped surface evaporator, central circulation tube type multi-effect evaporator, basket type evaporator, external heating type evaporator, forced circulation type evaporator and Leveng type evaporator. Among them, a forced circulation evaporator and an external heating evaporator are preferable. The respective evaporators of the multi-effect evaporation apparatus 1 are composed of a heating chamber and an evaporation chamber, and may further include other evaporation auxiliary components as necessary, such as a demister for further separating liquid foam, a condenser for condensing all secondary steam, and a vacuum apparatus for pressure reduction operation. The number of evaporators included in the multi-effect evaporation apparatus 1 is not particularly limited, and may be 2 or more, preferably 2 to 5, and more preferably 3 to 4.

In the invention, in order to sequentially feed the first mother liquor into each effect evaporator of the multi-effect evaporator 1, a circulating pump can be arranged between each effect evaporator, and the wastewater evaporated in the former effect evaporator is fed into the next effect evaporator through the circulating pump.

In the invention, the circulating pumps among the evaporators with various effects can be pumps of various forms conventionally used in the field, in order to uniformly evaporate materials, avoid generating a large number of fine crystal nuclei and prevent crystal grains in circulating crystal slurry from colliding with an impeller at high speed to generate a large number of secondary crystal nuclei, the circulating pump is preferably a centrifugal pump with low rotating speed, and more preferably a guide pump wheel with large flow rate and low rotating speed or an axial pump with large flow rate, low lift and low rotating speed.

According to a preferred embodiment of the present invention, the first evaporation is performed in a multi-effect evaporation apparatus 1, the multi-effect evaporation apparatus 1 being composed of a first effect evaporator 1a, a second effect evaporator 1b, a third effect evaporator 1c and a fourth effect evaporator 1 d. And (3) introducing the first mother solution into a first-effect evaporator 1a of the multi-effect evaporation device 1 for evaporation, then sending the first mother solution into a second-effect evaporator 1b for evaporation through a seventeenth circulating pump 87, then sending the first mother solution into a third-effect evaporator 1c for evaporation through a sixteenth circulating pump 86, and then sending the first mother solution into a fourth-effect evaporator 1d for evaporation through a fifteenth circulating pump 85 to obtain a second concentrated solution containing sodium sulfate crystals. And introducing second ammonia-containing steam obtained by evaporation in the last-effect evaporator of the multi-effect evaporation device 1 into the previous-effect evaporator for heat exchange to obtain second ammonia water. More preferably, the second ammonia steam-containing condensed water exchanges heat with the wastewater to be treated in the fourth heat exchange device 34, so as to fully utilize energy. Heating steam (namely raw steam conventionally used in the field) is introduced into the fourth-effect evaporator 1d, the heating steam is condensed in the fourth-effect evaporator 1d to obtain condensate, and the condensate is used for preheating the first mother liquor entering the multi-effect evaporation device 1 and then is used for preparing a sodium sulfate washing solution. The second ammonia-containing steam obtained by evaporation in the first effect evaporator 1a exchanges heat with cooling water (preferably, the wastewater to be treated before being introduced into the MVR evaporation device 2 is used as cooling water) in the third heat exchange device 33 to obtain ammonia water, and the ammonia water is stored in the second ammonia water storage tank 52.

In the present invention, the evaporation conditions of the second evaporation may be appropriately selected as necessary, and the purpose of crystallizing sodium sulfate without precipitating sodium chloride may be achieved. 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 efficiency of evaporation, 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 second evaporation condition refers to the evaporation condition of the last one of the multiple-effect evaporation devices.

In the present invention, in the second evaporation, the evaporation temperature of the latter effect evaporator is higher than the former effect by 5 ℃ or more, preferably by 10 ℃ or more.

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 to be treated and the amount of the wastewater to be treated, and may be, for example, 0.1m ³ More than h (e.g. 0.1 m) ³ /h～500m ³ H). By allowing the second evaporation to proceed 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 the sodium sulfate and the sodium chloride in the second concentrated solution reach saturation 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, the concentration of the liquid obtained by the second evaporation is controlled within the above range so that the second evaporation does not cause crystallization of sodium chloride. 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 the invention, the method can also comprise crystallizing the second concentrated solution containing sodium sulfate crystals in a crystallizing device to obtain crystal slurry containing sodium sulfate crystals. In this case, the evaporation conditions of the second evaporation need only be satisfied in order to crystallize sodium sulfate without precipitating sodium chloride in the crystallization apparatus (the concentration of sodium chloride in the second concentrated solution is X or less in the second evaporation). The crystallization apparatus is not particularly limited, and may be, for example, a crystal solution tank, a crystal solution collecting tank, a thickener with stirring or a thickener without stirring, or the like. According to a preferred embodiment of the present invention, the crystallization is performed in the crystal liquid collecting tank 55. The crystallization conditions are not particularly limited, and may include, for example: the temperature is 45 ℃ or higher, preferably 95 to 107 ℃, and more preferably 85 to 105 ℃. The crystallization time may be 5min to 24h, preferably 5min to 30min. According to the invention, the crystallization of the second concentrated solution containing sodium sulfate crystals can also be carried out in a second evaporator with a crystallizer (e.g. a forced circulation evaporator crystallizer), wherein the crystallization temperature is the corresponding second evaporation temperature. In the present invention, the temperature of crystallization is preferably the same as the temperature of the second evaporation.

According to the invention, in order to fully utilize the heat energy of the second ammonia vapor-containing condensate, the first mother liquor and the second ammonia vapor-containing condensate obtained by the multi-effect evaporation device are preferably subjected to second heat exchange before the first mother liquor is introduced into the multi-effect evaporation device, and second ammonia water is obtained. More preferably, before the first mother liquor is introduced into the multi-effect evaporation device, the first mother liquor and the condensate obtained by heat exchange of the heating steam in the last evaporator of the multi-effect evaporation device are subjected to second heat exchange.

According to a preferred embodiment of the present invention, the second heat exchange between the first mother liquor and the second ammonia vapor-containing condensate obtained by the multi-effect evaporation device is performed by a fourth heat exchange device 34, specifically, the first mother liquor and the second ammonia vapor-containing condensate obtained by the multi-effect evaporation device are respectively passed through the fourth heat exchange device 34, so as to raise the temperature of the first mother liquor, and the second ammonia vapor-containing condensate obtained by the multi-effect evaporation device is cooled to obtain the second ammonia. According to the present invention, after the second heat exchange is performed in the fourth heat exchange unit 34, the temperature of the first mother liquor is 39 ℃ or higher, more preferably 74 to 124 ℃, and still more preferably 88 to 104 ℃.

According to a more preferred embodiment of the present invention, the second heat exchange between the first mother liquor and the condensate of the heating vapor is performed by a sixth heat exchange device 36, and specifically, the first mother liquor and the condensate of the heating vapor are respectively passed through the sixth heat exchange device 36 to further raise the temperature of the first mother liquor. According to the present invention, after the second heat exchange is performed in the sixth heat exchanger 36, the temperature of the first mother liquor is 41 ℃ or higher, more preferably 67 to 172 ℃, still more preferably 74 to 126 ℃, and still more preferably 90 to 106 ℃.

According to a preferred embodiment of the present invention, the second ammonia-containing vapor obtained in the last evaporator of the multi-effect evaporation device exchanges heat with the cold medium in the third heat exchange device 33 to obtain the second ammonia water. The two portions of the second ammonia are hydrated and stored in a second ammonia storage tank 52.

The third heat exchange device 33, the fourth heat exchange device 34 and the sixth heat exchange device 36 are not particularly limited, and various heat exchangers conventionally used in the art may be used to achieve the purpose of the second heat exchange. Specifically, it may be a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, a spiral threaded tube heat exchanger, or the like. The material of the heat exchanger can be specifically selected according to the requirement, for example, a stainless steel spiral threaded pipe heat exchanger is preferred because the secondary steam has no corrosivity to stainless steel. The cold medium in the third heat exchange device 33 can be cooling water, glycol aqueous solution, etc. When conventional cooling water is used, the cooling water is recycled, and when the catalyst production wastewater is used as the cooling water, the wastewater after heat exchange is preferably directly returned to the treatment process (such as to the first pH value adjustment process).

According to a preferred embodiment of the present invention, the second evaporation process is performed in the multi-effect evaporation device 1, and the first mother liquor is passed through the respective evaporators of the multi-effect evaporation device 1 by 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, preferably 20 ℃ higher, more preferably 35 ℃ to 90 ℃ higher, still more preferably 35 ℃ to 70 ℃ higher, and particularly preferably 50 ℃ to 60 ℃ higher than the temperature of the low-temperature treatment. By controlling the temperature of the second evaporation and the low-temperature treatment, the sodium sulfate crystals separated out in the first evaporation and the sodium sulfate in the sodium chloride crystals can be dissolved in the low-temperature treatment, and the sodium sulfate in the second evaporation is independently crystallized and separated out, 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 (i.e. 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 (for example, 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 MVR evaporation device 2 to perform the first evaporation again, and specifically, the second mother liquor can be returned to the place before the second pH adjustment by the ninth circulation pump 79. In addition, it is difficult to avoid that the obtained sodium sulfate crystals adsorb certain impurities such as sulfate 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 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 sulphate solution is such that the sodium sulphate and sodium chloride reach the concentration of sodium sulphate in a saturated aqueous solution at the same time at the temperature corresponding to the sodium sulphate 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 elutriation 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 obtain a slurry containing sodium sulfate crystals (the liquid content may be 35% by mass or less) by performing preliminary solid-liquid separation by sedimentation. 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 resulting from the washing, it is preferred that the catalyst production wastewater elutriation liquid is returned to the multi-effect evaporation device 1, for example, by the tenth circulation pump 80 to the multi-effect evaporation device 1 for the second evaporation, before being returned to the second pH adjustment before the evaporation in the MVR evaporation device 2.

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 after 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 subjected to elution with an aqueous sodium sulfate solution, and the liquid obtained by the elution 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 tail gas discharged from the second heat exchange device 32 after being condensed by the first heat exchange, and the second ammonia-containing steam is tail gas discharged from the third heat exchange device 33 after being condensed by the second heat exchange. 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 NH ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ The wastewater is obtained. In addition, the method is particularly suitable for treating high-salinity wastewater. The wastewater from the catalyst production of the present invention may be specifically wastewater from the production of a molecular sieve, alumina or a refinery catalyst, or wastewater from the production of a molecular sieve, alumina or a refinery catalyst which is subjected to 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 wastewater ₄ ⁺ May be 8mg/L or more, preferably 300mg/L or more.

As Na in the catalyst production wastewater ⁺ 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 preferably 40g/L or more, further preferably 50g/L or more, further preferably 60g/L or more.

As SO in wastewater from the production of said catalyst ₄ ^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 ^- 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 moreThe content is more preferably 40g/L or more, still more preferably 50g/L or more, and still more preferably 60g/L or more.

NH contained in the catalyst production wastewater ₄ ⁺ 、SO ₄ ^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 treatment ₄ ^2- 、Cl ^- And Na ⁺ The upper limit of (b) is 200g/L or less, preferably 150g/L or less, respectively; NH in catalyst production wastewater ₄ ⁺ Is 50g/L or less, preferably 30g/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 small ₄ ^2- Cl in catalyst production wastewater ^- The higher the content, the better, for example, the SO content in the ammonium salt-containing wastewater is relative to 1 mole ₄ ^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 mole ₄ ^2- Cl contained in the catalyst production wastewater ^- Preferably 200 moles or less, more preferably 150 moles or less, further preferably 100 moles or less, further preferably 50 moles or less, and further preferably 30 moles or less. By adding Cl contained in the catalyst production wastewater ^- And SO ₄ ^2- The molar ratio of (b) is limited to the above range, most of the water can be distilled out in the first evaporation, the amount of the circulating liquid in the treatment system is reduced, the 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 NH ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ In addition, it may contain Mg ²⁺ 、Ca ²⁺ 、K ⁺ 、Fe ³⁺ Inorganic salt ions such as rare earth element ions, mg ²⁺ 、Ca ²⁺ 、K ⁺ 、Fe ³⁺ 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, still more 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, preferably 6.7 to 6.9.

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 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, either 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 wastewater is subjected to filtration, weak acid cation exchange method and ozone biological activated carbon adsorption oxidation method for removing impurities 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 wastewater having a low salt content may be concentrated to have a salt content within a range required for the wastewater of the present invention before the wastewater is treated 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 a 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 0.5-4h.

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 10-30m/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 10-15h.

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 concentration of HCl in the regeneration liquid is as follows: 4.5-5 mass%; the dosage of the regenerant (calculated by 100%) is 50-60kg/m ³ Wet resin; the flow rate of the regeneration liquid HCl is 4.5-5.5m/h, and the regeneration contact time is 35-45min; the forward washing flow rate is 18-22m/h, and the forward washing time is 2-30min; the running flow rate is 15-30m/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 0.5-0.7m/h.

The conditions for the concentration of the ED membrane are preferably: the current is 145-155A, and the voltage is 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 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 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 stage ₂ SO ₄ Or 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 invention ₄ ^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 69g/L NaCl and Na) ₂ SO ₄ 75g/L、NH ₄ Cl 43g/L、(NH ₄ ) ₂ SO ₄ 47.5g/L, pH 6.9) at a feed rate of 5m ³ A rate of/h was fed to a pipeline of the treatment system, a 45.16 mass% sodium hydroxide aqueous solution was introduced into the pipeline before being fed to the first heat exchanger 31 and the fifth heat exchanger 35 (titanium alloy plate heat exchanger) to adjust the pH for the first time, the pH after mixing was monitored by a first pH measuring device 61 (pH meter) (measured value was 8.2), and a part of the catalyst production wastewater was fed by a first circulation pump 71Is divided into (4 m) ³ H) sending the wastewater into a first heat exchange device 31, carrying out first heat exchange with the recovered first ammonia steam-containing condensate to heat the catalyst production wastewater to 104 ℃, sending the rest of the wastewater into a fifth heat exchange device 35, carrying out first heat exchange with the first concentrated solution to heat the catalyst production wastewater to 104 ℃, converging the catalyst production wastewater, and mixing the catalyst production wastewater with a second mother solution to obtain wastewater to be treated (containing SO) ₄ ^2- And Cl ^- In a molar ratio of 1:9.005 And then the wastewater to be treated is sent into the second heat exchange device 32 to carry out first heat exchange with the first ammonia-containing steam, so that the temperature of the wastewater to be treated is raised to 114 ℃; then, a 45.16 mass% aqueous sodium hydroxide solution is introduced into a pipe for feeding the wastewater to be treated into the MVR evaporation apparatus 2 to perform a second pH adjustment, the adjusted pH is monitored by a second pH measurement apparatus 62 (pH meter) (measurement value 11), and the wastewater to be treated after the second pH adjustment is fed into the MVR evaporation apparatus 2 to be evaporated, thereby obtaining a first concentrated solution containing ammonia vapor and crystals containing sodium sulfate and sodium chloride. The first ammonia-containing steam obtained by evaporation is compressed by the first compressor 10 (the temperature rises by 17 ℃) and then sequentially passes through the second heat exchange device 32 and the first heat exchange device 31 to respectively exchange heat with wastewater to be treated and catalyst production wastewater, and is cooled to obtain first ammonia water which is stored in the first ammonia water storage tank 51. In addition, in order to increase the crystal content of the concentrated solution in the MVR evaporation device 2, part of the liquid evaporated in the MVR evaporation device 2 is circulated as a circulating liquid to the second heat exchange device 32 by the second circulating pump 72, and then enters the MVR evaporation device 2 again for the first evaporation (the reflux ratio is 82). The degree of the first evaporation is monitored through a mass flow meter arranged on the MVR evaporation device 2, and the evaporation capacity of the first evaporation is controlled to be 4.15m ³ H (corresponding to the control of the sodium sulfate concentration in the treatment solution to 0.977Y (84.7 g/L)). Wherein, the evaporation conditions of the MVR evaporation device 2 are as the following table 1:

TABLE 1

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 25 ℃ for 55min to obtain a treatment solution containing the sodium chloride crystals.

The treated liquid containing sodium chloride crystals was sent to a first solid-liquid separation apparatus 91 (centrifuge) to carry out first solid-liquid separation to obtain 17.01m per hour ³ Contains NaCl 280.4g/L and Na ₂ SO ₄ 84.7g/L、NaOH 2.68g/L、NH ₃ 0.37g/L of first mother liquor is temporarily stored in a first mother liquor tank 53, sodium chloride solid obtained by solid-liquid separation (674.91 kg of sodium chloride crystal filter cake with 14 mass percent of water is obtained per hour, wherein the content of sodium sulfate is below 4.1 mass percent), 280.4g/L of sodium chloride solution with the same dry basis mass as the sodium chloride crystal filter cake is used for leaching, drying is carried out in a drier, 580.42kg of sodium chloride (the purity is 99.4 weight percent) is obtained per hour, and washing liquid enters the MVR evaporation device 2 again for first evaporation after being sent into the second heat exchange device 32 through an eighth circulating pump 78.

The second evaporation process is carried out in the multi-effect evaporation device 1, and the multi-effect evaporation device 1 consists of a first effect evaporator 1a, a second effect evaporator 1b, a third effect evaporator 1c and a fourth effect evaporator 1d (all forced circulation evaporators). The first mother liquor in the first mother liquor tank 53 is sequentially sent to the fourth heat exchange device 34 and the sixth heat exchange device 36 for heat exchange through the sixth circulating pump 76, then is sent to the first effect evaporator 1a of the multiple effect evaporation device 1 for evaporation, then is sent to the second effect evaporator 1b for evaporation through the seventeenth circulating pump 87, then is sent to the third effect evaporator 1c for evaporation through the sixteenth circulating pump 86, and then is sent to the fourth effect evaporator 1d for evaporation through the fifteenth circulating pump 85, so as to obtain a second concentrated solution containing sodium sulfate crystals, wherein the evaporation conditions are as in table 1 above. And introducing second ammonia-containing steam obtained by evaporation in the previous-effect evaporator into the next-effect evaporator for heat exchange to obtain condensate, further performing heat exchange with the first mother liquor in a fourth heat exchange device 34 to obtain second ammonia water, performing heat exchange between the second ammonia-containing steam obtained by evaporation in the first-effect evaporator 1a and the catalyst production wastewater in a third heat exchange device 33 to obtain second ammonia water, and combining the second ammonia water in a second ammonia water storage tank 52 for storage. Heating steam (namely raw steam conventionally used in the field) is introduced into the fourth-effect evaporator 1d, and condensate obtained after the heating steam is condensed in the fourth-effect evaporator 1d is introduced into the sixth heat exchange device 36, and the first mother liquor is further preheated and then used for preparing a washing solution. The degree of the first evaporation is monitored by a densimeter arranged on the multi-effect evaporation device 1, and the concentration of the sodium chloride of the second evaporation concentrated solution is controlled to be 0.9935X (306.4 g/L). Crystallizing the second concentrated solution obtained by evaporation in the multi-effect evaporation device 1 in a crystal liquid collecting tank 55 at the crystallization temperature of 105 ℃ for 5min to obtain crystal slurry containing sodium sulfate crystals.

The crystal slurry containing the sodium sulfate crystals is sent to a second solid-liquid separation device 92 (centrifugal machine) for solid-liquid separation, and 15.54m is obtained per hour ³ Contains NaCl 306.4g/L and Na ₂ SO ₄ 52.4g/L、NaOH 2.93g/L、NH ₃ 0.016g/L of second mother liquor is temporarily stored in the second mother liquor tank 54. And circulating the second mother liquor to a wastewater introduction pipeline through a ninth circulating pump 79 to be mixed with the catalyst production wastewater to obtain wastewater to be treated. The sodium sulfate solid obtained by solid-liquid separation (732.84 kg of a sodium sulfate crystal cake having a water content of 14 mass% per hour, wherein the sodium chloride content is 4.5 mass% or less) was washed with a sodium sulfate solution of 52.4g/L equivalent to the dry basis mass of sodium sulfate, and then dried in a dryer to obtain 630.25kg of sodium sulfate (purity: 99.5 wt%) per hour, and the washing solution was circulated to the multi-effect evaporation apparatus 1 by a tenth circulation pump 80.

In addition, the tail gas discharged by the second heat exchange device 32 and the third heat exchange device 33 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, 4.03m of ammonia water having a concentration of 1.2 mass% was obtained per hour in the first ammonia water tank 51 ³ 1.55m of aqueous ammonia having a concentration of 0.16% by mass per hour was obtained in the second aqueous ammonia tank 52 ³ The 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 the solution containing NaCl 71g/L and Na ₂ SO ₄ 129g/L、NH ₄ Cl 17.5g/L、(NH ₄ ) ₂ SO ₄ 32.3g/L of catalyst production wastewater with the pH of 6.7 is treated to obtain SO contained in the wastewater to be treated ₄ ^2- And Cl ^- In a molar ratio of 1:9.073. 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 103 ℃, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange device 32 is 112 ℃. The evaporation conditions of the MVR evaporation device 2 and the multi-effect evaporation device 1 are as follows in table 2. The low-temperature treatment temperature is 30 deg.C, and the retention time is 50min.

TABLE 2

522.41kg tons of sodium chloride crystal filter cakes containing 14 mass percent of water are obtained by the first solid-liquid separation device 91 every hour, and 449.27kg of sodium chloride (with the purity of 0.994 weight percent) is finally obtained every hour; obtained 28.78m per hour ³ The concentration of NaCl is 283.8g/L and Na ₂ SO ₄ 80.1g/L、NaOH 1.66g/L、NH ₃ 0.09g/L of the first mother liquor.

The second solid-liquid separation device 92 obtained 965.02kg of a sodium sulfate crystal cake having a water content of 15 mass% per hour, and finally 820.27kg of sodium sulfate (purity of 99.5 wt%) per hour; yield 26.83m per hour ³ The concentration is NaCl 303.2g/L and Na ₂ SO ₄ 55.3g/L、NaOH 1.77g/L、NH ₃ 0.005g/L of the second mother liquor.

In the present embodiment, the first aqueous ammonia tank 51 is filled with the ammonia water every hourAmmonia water of 1.8 mass% concentration of 3.50m was obtained ³ 2.21m of 0.1 mass% ammonia water was obtained per hour in the second ammonia water tank 52 ³ The 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 142g/L, na ₂ SO ₄ 70g/L、NH ₄ Cl 36g/L、(NH ₄ ) ₂ SO ₄ Treating the catalyst production wastewater with the concentration of 18g/L and the pH value of 6.9 to obtain SO contained in the wastewater to be treated ₄ ^2- And Cl ^- In a molar ratio of 1:11.927. the temperature of the catalyst production wastewater after heat exchange by the first heat exchange device 31 and the fifth heat exchange device 35 was 107 ℃, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange device 32 was 117 ℃. The evaporation conditions of the MVR evaporation apparatus 2 and the multi-effect evaporation apparatus 1 are as follows in table 3. The low-temperature treatment temperature is 35 deg.C, and the retention time is 50min.

TABLE 3

The first solid-liquid separation device 91 obtained 1057.66kg of crystallized sodium chloride cake containing 14 mass% of water per hour, and finally 909.59kg of sodium chloride (purity 99.5 wt%) per hour; yield 31.89m per hour ³ The concentration of NaCl is 294.6g/L and Na ₂ SO ₄ 65.7g/L、NaOH 2.7g/L、NH ₃ 0.12g/L of the first mother liquor.

The second solid-liquid separation device 92 obtained 516.62kg of a sodium sulfate crystal cake having a water content of 14 mass% per hour, and finally obtained 444.30kg of sodium sulfate (purity of 99.6% by weight) per hour; 30.86 m/hr ³ The concentration is NaCl 305.5g/L and Na ₂ SO ₄ 53.7g/L、NaOH 2.8g/L、NH ₃ 0.39g/L of the second mother liquor.

In this example, 4.33m of ammonia water having a concentration of 1.7% by mass was obtained per hour in the first ammonia water tank 51 ³ In the second ammonia water tank 52Ammonia water having a concentration of 0.28 mass% was obtained in 1.35m ³ The 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 NH ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ Characterized in that the method comprises the following steps,

1) Introducing the wastewater to be treated into an 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;

3) Carrying out first solid-liquid separation on the treatment solution containing the sodium chloride crystals, and sequentially introducing the liquid phase obtained by the first solid-liquid separation into each effect evaporator of the multi-effect evaporation device for second evaporation to obtain a 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 an MVR evaporation device;

introducing second ammonia-containing steam obtained by evaporation of a subsequent evaporator of the multi-effect evaporation device into a previous evaporator, and performing countercurrent heat exchange between a liquid phase obtained by the first solid-liquid separation and the second ammonia-containing steam;

the conditions of the first evaporation include: the temperature is 60-175 ℃, and the pressure is-87 kPa-18110 kPa; the temperature of the low-temperature treatment is 15-45 ℃;

the first evaporation enables sodium sulfate crystals to be dissolved in low-temperature treatment, and the second evaporation enables sodium chloride not to be crystallized and separated out;

relative to 1 mole of SO contained in the wastewater to be treated ₄ ^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; NH in the catalyst production wastewater ₄ ⁺ Is more than 8mg/L, SO ₄ ^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 treated ₄ ^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 mol based on the total amount of the SO ₄ ^2- Cl contained in the wastewater to be treated ^- Is 10 mol or more.

4. The method as claimed in claim 1, wherein the pH of the wastewater to be treated is adjusted to be greater than 10.8 before passing the wastewater to be treated to the MVR evaporation plant.

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 a concentration of sodium sulfate at which both sodium sulfate and sodium chloride in the treatment solution are saturated under the low-temperature treatment 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. The method of claim 6, wherein the second evaporation is performed such that the concentration of sodium chloride in the second concentrated solution is X or less, wherein X is the concentration of sodium chloride at which both sodium sulfate and sodium chloride in the second concentrated solution are saturated under the conditions of the second evaporation.

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

10. The method of any one of claims 1-9, wherein the conditions of the first evaporation comprise: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa.

11. The method of claim 10, wherein the conditions of the first evaporation comprise: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa.

12. The method of claim 11, wherein the conditions of the first evaporation comprise: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa.

13. The method of any one of claims 1-9, wherein the conditions of the second evaporation comprise: the temperature is above 35 ℃ and the pressure is above-95 kPa.

14. The method of claim 13, wherein the conditions of the second evaporation comprise: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa.

15. The method of claim 14, wherein the conditions of the second evaporation comprise: the temperature is 60-365 ℃, and the pressure is-87 kPa-18110 kPa.

16. The method of claim 15, wherein the conditions of the second evaporation comprise: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa.

17. The method of claim 16, wherein the conditions of the second evaporation comprise: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa.

18. The method of claim 17, wherein the conditions of the second evaporation comprise: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa.

19. The method according to any one of claims 1 to 9, wherein the temperature of the cryogenic treatment is between 15 ℃ and 35 ℃.

20. The method of claim 19, wherein the cryogenic treatment is at a temperature of 17.9 ℃ to 35 ℃.

21. The method of claim 10, wherein the temperature of the second evaporation is more than 5 ℃ higher than the temperature of the low temperature treatment.

22. The method of claim 21, wherein the temperature of the second evaporation is more than 20 ℃ higher than the temperature of the low temperature treatment.

23. The method of claim 22, wherein the temperature of the second evaporation is 35 ℃ to 90 ℃ higher than the temperature of the low temperature treatment.

24. The method according to claim 1, wherein the first ammonia-containing vapor obtained from the MVR evaporation device is subjected to a first heat exchange with the wastewater to be treated to obtain a first ammonia water before the wastewater to be treated is passed into the MVR evaporation device.

25. A method as claimed in claim 24, wherein the pH of the wastewater to be treated is adjusted to be greater than 7 prior to the first heat exchange.

26. The method according to claim 24, wherein the first ammonia-containing vapor is discharged after ammonia removal from tail gas remaining from condensation of the first ammonia-containing vapor by the first heat exchange.

27. The method of claim 26, wherein the liquid phase from the first solid-liquid separation is subjected to a second heat exchange with a second ammonia vapor-containing condensate from a multi-effect evaporation plant prior to passing the liquid phase from the first solid-liquid separation to the multi-effect evaporation plant;

and carrying out second heat exchange on the second ammonia-containing steam obtained in the last evaporator of the multi-effect evaporation device and a cold medium.

28. The process according to claim 27, wherein the second ammonia-containing vapor is discharged after ammonia removal from the tail gas remaining from the condensation of the second ammonia-containing vapor by the second heat exchange.

29. The method according to any one of claims 1 to 9, further comprising subjecting the treatment liquid containing sodium chloride crystals to a first solid-liquid separation to obtain sodium chloride crystals.

30. The method of claim 29, further comprising washing the obtained sodium chloride crystals.

31. The method according to any one of claims 1 to 9, further comprising subjecting the second concentrated solution containing sodium sulfate crystals to a second solid-liquid separation to obtain sodium sulfate crystals.

32. The method of claim 31, further comprising washing the resulting sodium sulfate crystals.

33. The process of any one of claims 1 to 9, wherein the catalyst production wastewater is wastewater from a molecular sieve, alumina or refinery catalyst production process.

34. The method of claim 33, further comprising removing impurities and concentrating the catalyst production wastewater.