CN108726611B

CN108726611B - Treatment method of catalyst production wastewater

Info

Publication number: CN108726611B
Application number: CN201710265681.8A
Authority: CN
Inventors: 殷喜平; 李叶; 顾松园; 王涛; 苑志伟; 陈玉华; 张志民; 高晋爱
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: 2023-01-03
Anticipated expiration: 2037-04-21
Also published as: CN108726611A

Abstract

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

Description

Treatment method of catalyst production wastewater

Technical Field

The invention relates to the field of sewage treatment, in particular to a method for treating catalyst production wastewater, and especially relates to a catalyst containing 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 alkali salts such as sodium hydroxide, hydrochloric acid, sulfuric acid, ammonium salts, sulfates, hydrochlorides and the like are needed, and a large amount of mixed sewage containing ammonium, sodium sulfate, sodium chloride 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 sulfate and sodium chloride 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 salt of sodium sulfate and sodium chloride containing ammonium salt. However, these ammonium-containing mixed salts are currently difficult to treat or expensive to treat, and the process of removing ammonium ions at the early stage additionally increases the cost of wastewater treatment.

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

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

Disclosure of Invention

The invention aims to overcome the defect of NH content in the prior art ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ The wastewater treatment cost is high, and only mixed salt crystals can be obtained, thereby providing a low-cost and environment-friendly NH-containing catalyst ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ The method for treating wastewater can respectively recover ammonium, sodium sulfate and sodium chloride 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 a first MVR evaporation device for first evaporation to obtain first concentrated solution containing ammonia vapor and sodium sulfate crystals, wherein the wastewater to be treated contains the catalyst production wastewater;

2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium sulfate crystals, introducing a liquid phase obtained by the first solid-liquid separation into a second MVR evaporation device for second evaporation, and obtaining second ammonia-containing steam and a second concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals;

3) Carrying out low-temperature treatment on the second 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;

4) Carrying out second solid-liquid separation on the treatment liquid containing the sodium chloride crystals;

adjusting the pH value of the wastewater to be treated to be more than 9 before introducing the wastewater to be treated into a first MVR evaporation device; the first evaporation prevents sodium chloride from crystallizing out; relative to 1 mole of SO contained in the wastewater to be treated ₄ ^2- Cl contained in the wastewater to be treated ^- The amount is 14 mol or less.

By the technical scheme, the method aims at the content of NH ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ The wastewater is prepared by adjusting the pH value of the wastewater to be treated to a specific range in advance, then obtaining sodium sulfate crystals and stronger ammonia water by utilizing first evaporation separation, then obtaining concentrated solution containing sodium sulfate crystals and sodium chloride crystals and thinner ammonia water by utilizing second evaporation, finally dissolving sodium sulfate in the concentrated solution by utilizing low-temperature treatment, and further crystallizing and separating sodium chloride to obtain sodium chloride crystals. The method can respectively obtain high-purity sodium sulfate and sodium chloride, 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 without a condenser, 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, and respectively uses the sodium chloride and the sodium sulfate as crystalsThe form is recycled, no waste slag and liquid are generated in the whole process, and the aim of changing waste into valuables is fulfilled.

Furthermore, the method enables the second evaporation to be carried out at a higher temperature through the cooperation of the second evaporation and the low-temperature treatment, so that the solid content and the evaporation efficiency of the second 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. Second MVR evaporation plant 33, third heat transfer device

2. First MVR evaporation plant 34, fourth heat transfer device

31. The first heat exchange device 35 and the fifth heat exchange device

32. Second heat exchange device 51 and first ammonia water storage tank

52. Second ammonia storage tank 77, seventh circulating pump

53. First mother liquor tank 78, eighth circulating pump

54. Second mother liquor tank 79 and ninth circulating pump

55. Low temperature treatment tank 80, tenth circulating pump

61. First pH value measuring device 81 and vacuum pump

62. Second pH value measuring device 82 and circulating water tank

71. First circulating pump 83 and tail gas absorption tower

72. Second circulating pump 91 and first solid-liquid separation device

73. Third circulating pump 92 and second solid-liquid separation device

74. Fourth circulating pump 101 and first compressor

76. Sixth circulation pump 102, second compressor

Detailed Description

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

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

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

The 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 the wastewater to be treated into a first MVR evaporation device 2 for first evaporation to obtain first ammonia-containing steam and a first concentrated solution containing sodium sulfate crystals, wherein the wastewater to be treated contains the catalyst production wastewater;

2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium sulfate crystals, introducing a liquid phase obtained by the first solid-liquid separation into a second MVR evaporation device 1 for second evaporation, and obtaining second ammonia-containing steam and a second concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals;

before the wastewater to be treated is introduced into the first MVR evaporation device 2, adjusting the pH value of the wastewater to be treated to be more than 9; the first evaporation prevents sodium chloride from crystallizing out; relative to 1 mol of SO contained in the wastewater to be treated ₄ ^2- Cl contained in the wastewater to be treated ^- The amount is 14 mol or less.

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

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

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

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

The method provided by the invention can be used for the treatment of the compounds containing NH ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ Is treated except for containing 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 13.8 mol or less, more preferably 13.75 mol or less, still more preferably 13.5 mol or less, still more preferably 13 mol or less,more preferably 12 moles or less, still more preferably 11 moles or less, still more preferably 10.5 moles or less, preferably 2 moles or more, more preferably 2.5 moles or more, still more preferably 3 moles or more, and may be, for example, 1 to 10 moles. By reacting SO ₄ ^2- And Cl ^- The molar ratio of sodium sulfate in the first evaporation is controlled within the above range, so that sodium sulfate is precipitated without precipitating sodium chloride, and the purpose of efficiently separating sodium sulfate is achieved. In addition, as described above and below, it is also possible in the present invention to recycle the second mother liquor obtained in the second evaporation process to the first evaporation, and thereby to treat SO in the wastewater to be treated ₄ ^2- And Cl ^- The molar ratio of (a) to (b) is adjusted and the balance of sodium hydroxide can be maintained.

In the present invention, the 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 may be completed before the wastewater to be treated is introduced into the first MVR evaporation apparatus 2.

In the present invention, the first evaporation is performed so that sodium chloride does not crystallize out, which means that the sodium chloride concentration of the mixed system is controlled not to exceed the solubility under the first evaporation conditions (including but not limited to temperature, pH value, etc.), and sodium chloride entrained 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, the second evaporation needs to dissolve the sodium sulfate crystals in the low-temperature treatment, and specifically, the second evaporation obtains a second concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals, and the sodium sulfate crystals in the second evaporation can be completely dissolved in the low-temperature treatment. And (3) simultaneously crystallizing and separating out sodium sulfate and sodium chloride by controlling the evaporation amount of the second evaporation (namely, the second evaporation obtains a second concentrated solution containing sodium sulfate crystals and sodium chloride crystals), dissolving the sodium sulfate crystals in the second concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals by the low-temperature treatment, further crystallizing and separating out sodium chloride, and obtaining the 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 the solid-liquid separation is different, the sodium sulfate content in the sodium chloride crystals obtained is usually 8 mass% or less (preferably 4 mass%), and in the present invention, it is considered that the sodium sulfate is dissolved when the sodium sulfate content in the sodium chloride crystals obtained is 8 mass% or less.

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

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

In the present invention, the conditions of the first evaporation may be appropriately selected as needed, and sodium sulfate may be crystallized without precipitating sodium chloride. The conditions of the first evaporation may include: the temperature is above 35 ℃ and the pressure is above-95 kPa; in order to improve the efficiency of evaporation, and from the viewpoint of reducing equipment cost and energy consumption, it is preferable that the conditions of the first evaporation include: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa; preferably, the conditions of the first evaporation include: the temperature is 60-365 ℃, 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; particularly preferably, the conditions of the first evaporation include: the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa.

In the present invention, the operating pressure of the 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 carrying out the first evaporation under the above conditions, the sodium chloride is not crystallized while the crystallization of sodium sulfate is ensured, so that the purity of the obtained sodium sulfate crystal can be ensured.

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

According to the present invention, the first evaporation does not crystallize sodium chloride in the wastewater to be treated (i.e., sodium chloride does not reach supersaturation), and preferably, the first evaporation is performed so that the concentration of sodium chloride in the first concentrated solution is 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 first concentrated solution reach saturation under the condition of the first evaporation. By controlling the degree of the first evaporation within the above range, as much sodium sulfate as possible can be crystallized under the condition that sodium chloride is not precipitated. By crystallizing sodium sulfate 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 performed by monitoring the concentration of the first evaporation-derived liquid, specifically, by controlling the concentration of the first evaporation-derived liquid within the above range, so that the first evaporation does not cause crystallization of sodium chloride in the wastewater to be treated. The concentration of the liquid obtained in the first evaporation is monitored by measuring the density, which may be carried out using a densitometer.

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

According to a preferred embodiment of the present invention, the first heat exchange is performed by the first heat exchange device 31, the third heat exchange device 33, the fifth heat exchange device 35 and the second heat exchange device 32, specifically, the first ammonia-containing steam is sequentially passed through the second heat exchange device 32 and the first heat exchange device 31, the second ammonia-containing steam condensate is passed through the third heat exchange device 33, the second concentrated solution containing sodium sulfate crystals and sodium chloride crystals is passed through the fifth heat exchange device 35, and the wastewater to be treated is simultaneously passed through one or more of the first heat exchange device 31, the third heat exchange device 33 and the fifth heat exchange device 35 and then is subjected to the second first heat exchange with the first ammonia-containing steam by the second heat exchange device 32. By the first heat exchange, the wastewater to be treated is heated to be evaporated, and the first ammonia-containing steam is cooled to obtain first ammonia water which can be stored in a first ammonia water storage tank 51; simultaneously cooling the second ammonia-containing steam condensate to obtain second ammonia water, wherein the second ammonia water can be stored in a second ammonia water storage tank 52; simultaneously cooling the second concentrated solution to facilitate low-temperature treatment; the second concentrated solution may be subjected to a low-temperature treatment in a low-temperature treatment tank 55.

In the present invention, the first heat exchange device 31, the third heat exchange device 33, the fifth heat exchange device 35 and the second heat exchange device 32 are not particularly limited, and various heat exchangers conventionally used in the art may be used to achieve the purpose of performing the first heat exchange between the first ammonia-containing steam and the wastewater to be treated. Specifically, a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, or the like may be mentioned, with the plate heat exchanger being preferred. The material of the heat exchanger can be specifically selected according to the needs, for example, in order to resist the corrosion of chloride ions, the heat exchanger of duplex stainless steel, titanium and titanium alloy, hastelloy can be selected as the material, and the heat exchanger containing plastic material can be selected when the temperature is lower.

According to the present invention, in order to fully utilize the heat energy of the first ammonia-containing vapor condensate, it is preferable that the temperature of the wastewater to be treated is 40 to 364 ℃, more preferably 74 to 174 ℃, still more preferably 79 to 129 ℃, and still more preferably 94 to 104 ℃ after the first heat exchange is performed by the first heat exchange device 31.

According to the present invention, in order to fully utilize the heat energy of the second ammonia-containing vapor condensate, it is preferable that the temperature of the wastewater to be treated is 44 to 174 ℃, more preferably 79 to 99 ℃ after the first heat exchange is performed by the third heat exchange device 33.

According to the present invention, in order to fully utilize the heat energy of the second concentrated solution, the temperature of the wastewater to be treated is preferably 44 ℃ to 174 ℃, more preferably 79 ℃ to 129 ℃ 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 50 ℃ to 370 ℃, more preferably 72 ℃ to 182 ℃, still more preferably 85 ℃ to 137 ℃, and still more preferably 102 ℃ to 112 ℃ after the first heat exchange is performed by the second heat exchange device 32.

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

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

According to a preferred embodiment of the present invention, the first evaporation process is performed in the first MVR evaporation device 2, and the first pH adjustment is performed by introducing and mixing the aqueous solution containing the alkaline substance into the pipe for feeding the wastewater to be treated into the first heat exchange device 31, the third heat exchange device 33 or the fifth heat exchange device 35 before feeding the wastewater to be treated into the first heat exchange device for the first heat exchange; then the wastewater to be treated is sent to a second heat exchange device 32 for first heat exchange, and the aqueous solution containing the alkaline substance is introduced and mixed in a pipeline for sending the wastewater to be treated to the second heat exchange device 32 for second pH value adjustment. The pH of the wastewater to be treated is adjusted twice, so that the pH is greater than 9, preferably greater than 10.8, before the wastewater is passed into the first MVR evaporator 2. Preferably, the first pH adjustment is such that the pH of the wastewater to be treated is greater than 7 (preferably 7-9), and the second pH adjustment is such that the pH is greater than 9 (preferably greater than 10.8). According to the present invention, it is preferable that the pH of the wastewater to be treated is adjusted to be greater than 7 before the first heat exchange is performed.

In order to detect the pH values after the first pH adjustment and the second pH adjustment, it is preferable that a first pH measuring device 61 is provided on a pipe for feeding the wastewater to be treated into the first heat exchanging device 31, the third heat exchanging device 33, and the fifth heat exchanging device 35 to measure the pH value after the first pH adjustment, and a second pH measuring device 62 is provided on a pipe for feeding the wastewater to be treated into the second heat exchanging device 32 to measure the pH value after the second pH adjustment.

In the present invention, in order to increase the solid content in the first MVR evaporation device 2 and reduce the ammonia content in the liquid, it is preferable to return a part of the liquid evaporated by the first MVR evaporation device 2 (i.e. the liquid located inside the first MVR evaporation device, hereinafter also referred to as the first circulation liquid) to the first MVR evaporation device 2 for evaporation. The above-mentioned process of returning the first circulation liquid to the first MVR evaporation device 2 is preferably to return the first circulation liquid to the first MVR evaporation device 2 after mixing with the wastewater to be treated after the first pH adjustment and before the second pH adjustment, for example, the first circulation liquid may be returned to the wastewater delivery pipeline between the first heat exchange device 31 and the second heat exchange device 32 by the second circulation pump 72 to be mixed with the wastewater to be treated, and then after the second pH adjustment, the second heat exchange device 32 performs heat exchange, and finally the wastewater is sent to the first MVR evaporation device 2. There is no particular limitation on the ratio of the portion of the liquid evaporated by the first MVR evaporator 2 to be returned to the first MVR evaporator 2, as long as the first MVR evaporator 2 is able to evaporate the desired amount of water and ammonia at the given evaporation temperature, and for example, the ratio may be 10 to 200, preferably 40 to 100. Here, the first reflux ratio means: the ratio of the amount of reflux to the total amount of liquid fed to the first MVR evaporator 2 minus the amount of reflux.

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

In the invention, the first concentrated solution containing sodium sulfate crystals is subjected to first solid-liquid separation to obtain sodium sulfate crystals and a first mother liquor (namely, 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 first solid-liquid separation may be performed using a first solid-liquid separation device (e.g., a centrifuge, a belt filter, a plate filter, etc.). After the first solid-liquid separation, the first mother liquor obtained by the first solid-liquid separation device 91 is temporarily stored in the first mother liquor tank 53, and can be sent to the second MVR evaporation device 1 by the sixth circulation pump 76 for second evaporation. In addition, it is difficult to avoid that impurities such as chlorine ions, free ammonia, and hydroxide ions are adsorbed on the obtained sodium sulfate crystals, 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 first washed with water, the catalyst production wastewater, or a sodium sulfate solution and dried. In order to avoid the dissolution of sodium sulfate crystals during the washing, the sodium sulfate crystals are preferably washed with an aqueous sodium sulfate solution. More preferably, the concentration of the aqueous sodium sulfate solution is preferably such that the sodium chloride and the sodium sulfate reach the concentration of sodium sulfate in the saturated aqueous solution at the same time at the temperature corresponding to the sodium sulfate crystals to be washed.

The 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 sulfate 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 a preliminary solid-liquid separation by sedimentation to obtain a slurry containing sodium sulfate crystals (the liquid content may be 35% by mass or less, and this step is preferably performed in an apparatus known in the art such as a sedimentation tank or a sedimentation tank). 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, the liquid obtained by rinsing may be preferably used for washing, and water or a sodium sulfate solution is preferably used. The liquid resulting from the washing is preferably returned to the first MVR evaporator 2 before the first heat exchange before the first evaporation is completed, for example, after being returned to the second heat exchanger 32 by the eighth circulation pump 78 for heat exchange.

According to a preferred embodiment of the present invention, after the first concentrated solution containing sodium sulfate obtained by evaporation in the first MVR evaporation apparatus 2 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 in the subsequent sodium sulfate crystal washing is subjected to second elutriation in another elutriation tank, finally the slurry subjected to the two elutriations is sent to a solid-liquid separation apparatus for solid-liquid separation, the crystals obtained by the solid-liquid separation are subjected to elution again with an aqueous sodium sulfate solution, and the liquid obtained by the elution is returned to the second elutriation. Through the washing process, the purity of the obtained sodium sulfate crystal is improved, washing liquid is not excessively introduced, and the efficiency of wastewater treatment is improved.

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

In the present invention, the evaporation conditions of the second evaporation may be appropriately selected as needed, so that the evaporation amount of the second evaporation can be controlled to simultaneously crystallize and precipitate sodium sulfate and sodium chloride (that is, the second evaporation yields a second concentrated solution containing sodium sulfate crystals and sodium chloride crystals), and then the low-temperature treatment is performed to dissolve the sodium sulfate crystals in the second concentrated solution containing sodium sulfate crystals and sodium chloride crystals, thereby further crystallizing and precipitating sodium chloride, thereby obtaining a treated solution containing only sodium chloride crystals. The conditions of the second evaporation may include: the temperature is above 35 ℃ and the pressure is above-95 kPa; in order to improve the evaporation efficiency, and from the viewpoint of reducing the equipment cost and energy consumption, preferably, the conditions of the second evaporation include: the temperature is 45-175 ℃, and the pressure is-95 kPa-18110 kPa; preferably, the conditions of the second evaporation include: the temperature is 60-175 ℃, 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; particularly preferably, the conditions of the second evaporation include: the temperature is 105-110 ℃, and the pressure is-8 kPa-12 kPa.

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

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

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

According to the invention, the second evaporation is used for crystallizing and separating out sodium chloride and sodium sulfate in the wastewater to be treated simultaneously, and preferably, the concentration of sodium sulfate in the treatment solution is less than Y (preferably 0.9Y-0.99Y, and more preferably 0.95Y-0.98Y), wherein Y is the concentration of sodium sulfate when sodium sulfate and sodium chloride in the treatment solution reach saturation under the condition of low-temperature treatment. By controlling the degree of the second evaporation within the above range, it is possible to ensure that the precipitated sodium sulfate is completely dissolved under the low-temperature treatment conditions, and to crystallize and precipitate as much sodium chloride as possible. By crystallizing sodium chloride 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 evaporation amount of the second evaporation, that is, the amount of the liquid, and specifically, the concentration factor is controlled by controlling the evaporation amount of the second evaporation, that is, the amount of the second ammonia water, so that the sodium sulfate crystals precipitated in the second evaporation-concentrated solution can be dissolved during the low-temperature treatment. The degree of the second evaporative concentration is monitored by measuring the evaporation, and the flow can be measured by using a mass flow meter.

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

According to the invention, the second ammonia-containing steam and the liquid phase obtained by the first solid-liquid separation are subjected to second heat exchange to obtain second ammonia water. Preferably, the second ammonia-containing steam obtained by evaporation of the second MVR evaporation device sequentially performs second heat exchange with the liquid phase obtained by the first solid-liquid separation and the wastewater to be treated to obtain second ammonia water. The second heat exchange method is not particularly limited, and may be performed by a heat exchange method that is conventional in the art. The number of heat exchanges may be one or more, preferably 2 to 4, more preferably 2 to 3, and particularly preferably 2. Through the heat exchange, the output ammonia water is cooled, and the heat is circulated in the treatment device to the maximum extent, so that the energy is reasonably utilized, and the waste is reduced.

According to the present invention, preferably, the second heat exchange is performed by a fourth heat exchange device 34, specifically, a second ammonia-containing steam is passed through the fourth heat exchange device 34, and the mixed liquid of the first mother liquid and the second circulation liquid is passed through the fourth heat exchange device 34 to perform the second heat exchange, so as to condense the second ammonia-containing steam, and the temperature of the mixed liquid of the first mother liquid and the second circulation liquid is raised to facilitate evaporation, and at the same time, the second ammonia-containing steam is condensed to obtain a second ammonia water, and the second ammonia water may be further subjected to the first heat exchange in a third heat exchange device 33, and finally stored in a second ammonia water storage tank 52.

According to the present invention, after the second heat exchange, the temperature of the mixed liquid of the first mother liquid and the second circulating liquid is 35 ℃ or higher, more preferably 50 to 200 ℃, still more preferably 75 to 184 ℃, and still more preferably 85 to 139 ℃.

In the present invention, in order to increase the solid content in the second MVR evaporation device 1 and reduce the ammonia content in the liquid, it is preferable to return part of the liquid evaporated by the second MVR evaporation device 1 (i.e. the liquid located inside the second MVR evaporation device 1, also referred to as the second circulation liquid) to the second MVR evaporation device 1. The above process of returning the second recycle liquid to the second MVR evaporation device 1 is preferably performed by mixing the second recycle liquid with the first mother liquor, optionally the second scrubbing solution, and then performing the second heat exchange with the second ammonia-containing vapor. For example, the second recycle liquid and the optional second washing liquid can be mixed with the first mother liquid in a pipeline by a seventh recycle pump 77, and then introduced into the fourth heat exchange device 34 for second heat exchange, and then returned to the second MVR evaporation device 1. The ratio of the part of the liquid evaporated by the second MVR evaporator 1 to be returned to the second MVR evaporator 1 is not particularly limited, and it is sufficient to ensure that the second MVR evaporator 1 can evaporate the required amount of water and ammonia at the given evaporation temperature, and for example, the ratio may be 0.1 to 100, preferably 5 to 50. Here, the second reflux ratio means: the ratio of the amount of reflux to the total amount of liquid fed to the second MVR evaporator 1 minus the amount of reflux.

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

In the invention, the second concentrated solution containing the sodium sulfate crystals and the sodium chloride crystals is subjected to low-temperature treatment to dissolve the sodium sulfate crystals, so as to obtain the treated solution containing the sodium chloride crystals. By controlling the evaporation amount of the second 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 (where Y is the concentration of sodium sulfate at which both sodium sulfate and sodium chloride in the treatment solution are saturated under 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 second concentrated solution containing sodium sulfate crystals and sodium chloride crystals obtained by the second evaporation are dissolved at a temperature controlled appropriately. Preferably, the temperature of the low-temperature treatment is lower than that of the second evaporation, and specifically, the conditions of the low-temperature treatment may include: the temperature is 13 to 100 ℃, preferably 15 to 45 ℃, more preferably 15 to 35 ℃, still more preferably 17.9 to 35 ℃, and still more preferably 17.9 to 25 ℃. 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 may be 10min to 600min, preferably 20min to 300min, preferably 50min to 70min, and more preferably 55min to 65min.

In the invention, by controlling the conditions of the second evaporation and the low-temperature treatment, the second 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 by using various temperature reduction devices conventionally used in the art, and for example, the low-temperature treatment tank 55 may be selected. Preferably, a cooling part, specifically, a part for introducing cooling water, may be provided in the low temperature treatment tank 55. The second concentrated solution in the low-temperature treatment tank can be rapidly cooled by the cooling part. Preferably, the low-temperature treatment tank 55 may be provided with a stirring member, and the stirring member can make the solid-liquid phase distribution and the temperature distribution in the second concentrated solution uniform, thereby achieving the purpose of sufficiently dissolving the sodium sulfate crystals and precipitating the sodium chloride crystals to the maximum.

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

In the present invention, the sodium chloride crystal-containing treatment liquid obtained by the low-temperature treatment is subjected to a second solid-liquid separation to obtain sodium chloride 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, for example, one or more of centrifugation, filtration, and sedimentation.

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, or the like). After the second solid-liquid separation, the second mother liquor obtained by the second solid-liquid separation device 92 is temporarily stored in the second mother liquor tank 54, and may return to the first MVR evaporation device 2 to perform the first evaporation again, and specifically, the second mother liquor may be returned by the ninth circulation pump 79 to be mixed with the catalyst production wastewater before the first pH adjustment or before the second pH adjustment to obtain wastewater to be treated. In addition, it is difficult to avoid that the obtained sodium chloride 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 chloride crystals are subjected to secondary 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 sodium chloride aqueous solution is preferably the concentration of sodium chloride in the aqueous solution at which sodium chloride and sodium sulfate reach saturation simultaneously at the temperature corresponding to the sodium chloride crystals to be washed.

The form of the second solid-liquid separation and the second washing is not particularly limited, and may be carried out, for example, by using a combination of an elutriation apparatus and a solid-liquid separation apparatus which are conventional in the art, or may be carried out on a staged solid-liquid separation apparatus such as a belt filter. Preferably, the second wash comprises panning and/or rinsing. The above-mentioned elutriation and rinsing are not particularly limited and may be carried out by a method conventional in the art. The number of elutriation and rinsing is not particularly limited, and may be 1 or more, and is preferably 2 to 4 times in order to obtain sodium 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 second washing can be recycled in a countercurrent manner when used as the elutriation liquid. Before the elutriation, a slurry containing sodium chloride crystals is preferably obtained by preliminary solid-liquid separation by sedimentation (the liquid content may be 35% by mass or less, and this step is preferably performed in an apparatus known in the art, such as a sedimentation tank or a sedimentation tank). 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, the concentration of which is preferably the concentration of sodium chloride in an aqueous solution in which sodium chloride and sodium sulfate are simultaneously saturated at the temperature corresponding to the sodium chloride crystals to be rinsed. In order to further enhance the elutriation effect and obtain sodium chloride crystals with higher purity, it is preferable to wash the sodium chloride crystals with the liquid obtained by rinsing. For the liquid generated by washing, it is preferable that the water or aqueous sodium chloride solution elutriation liquid and elutriation liquid are returned to the second MVR evaporation device, for example, to the second MVR evaporation device 1 through the tenth circulation pump 80 for second evaporation, before the catalyst production wastewater elutriation liquid is returned to the first MVR evaporation device for second pH adjustment.

According to a preferred embodiment of the present invention, after performing a preliminary solid-liquid separation by settling on a treatment liquid containing sodium chloride crystals obtained by low-temperature treatment, a first elutriation is performed in an elutriation tank using the catalyst production wastewater, then a second elutriation is performed in another elutriation tank using a liquid obtained when sodium chloride crystals are subsequently washed, finally, a slurry obtained by the two elutriations is sent to a second solid-liquid separation device for solid-liquid separation, crystals obtained by the solid-liquid separation are eluted with an aqueous sodium chloride solution (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 sulfate are simultaneously saturated at a temperature corresponding to the sodium chloride crystals to be washed), and the eluted liquid is returned to the second elutriation as an elutriation liquid. Through the washing process combining elutriation and leaching, the purity of the obtained sodium chloride crystal is improved, washing liquid cannot be introduced too much, and the efficiency of wastewater treatment is improved.

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

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

In the present invention, the catalyst production wastewater is not particularly limited as long as it contains NH ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ The waste water is. 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 an oil refining catalyst, or wastewater from the production of a molecular sieve, alumina or an oil refining catalyst after the following impurity removal and concentration. It is preferable that the wastewater from the production of molecular sieves, alumina or refinery catalysts is subjected to the following impurity removal and concentration.

As NH in the catalyst production wastewater ₄ ⁺ It may be 8mg/L or more, preferably 300mg/L or more.

As Na in the wastewater from the catalyst production ⁺ May be 510mg/L or more, preferably 1g/L or more, more preferably 2g/L or more, further preferably 4g/L or more, further preferably 8g/L or more, further preferably 16g/L or more, further preferably 32g/L or more, further 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 more, further preferably 40g/L or more, further preferably 50g/L or more, further preferably 60g/L or more.

NH contained in the catalyst production wastewater ₄ ⁺ 、SO ₄ ^2- 、Cl ^- And Na ⁺ The upper limit of (b) is not particularly limited. SO in the wastewater from the viewpoint of easy access to wastewater ₄ ^2- 、Cl ^- And Na ⁺ Respectively, is 200g/L or less, preferably 150g/L or less; NH in wastewater ₄ ⁺ Is 100g/L or less, preferably 50g/L or less.

From the viewpoint of improving the efficiency of the first evaporation and reducing the energy consumption of the treatment process, the amount of SO contained in the wastewater is relatively small ₄ ^2- Cl in catalyst production wastewater ^- The lower the content, the better, for example, relative to 1 mole of SO contained in the catalyst production wastewater ₄ ^2- Cl contained in the catalyst production wastewater ^- Is 30 mol or less, preferably 20 mol or less, more preferably 15 mol or less, and still more preferably 10 mol or less. 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 0.1 mol or more, more preferably 0.5 mol or more, further preferably 1 mol or more, for example, 1 to 5 mol. By adding SO contained in the catalyst production wastewater ₄ ^2- And Cl ^- The molar ratio of (a) to (b) is limited to the above range, most of water can be evaporated in the first evaporation, the amount of circulating liquid in a treatment system is reduced, energy is saved, and the treatment process is more economical.

In the present invention, the inorganic salt ions contained in the catalyst production wastewater are other than 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, further preferably 10mg/L or less, and particularly preferably no other inorganic salt ion is contained. By controlling the other inorganic salt ions within the above range, the purity of the sodium sulfate crystals and sodium chloride crystals finally obtained can be further improved. In order to reduce the content of other inorganic salt ions in the catalyst production wastewater, the following impurity removal is preferably performed.

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

In the present invention, the pH of the catalyst production wastewater is preferably 4 to 8, for example, 6.2 to 6.6.

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

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

As the solid-liquid separation, filtration, centrifugation, sedimentation, or the like may be mentioned; as the chemical precipitation, pH adjustment, carbonate precipitation, magnesium salt precipitation, and the like may be mentioned; the adsorption can be physical adsorption and/or chemical adsorption, and the specific adsorbent can be selected from activated carbon, silica gel, alumina, molecular sieve, natural clay and the like; as the ion exchange, 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 catalyst production wastewater is subjected to impurity removal by filtration, a weak acid cation exchange method and an ozone biological activated carbon adsorption oxidation method in sequence. Through the impurity removal process, most suspended matters, hardness, silicon and organic matters can be removed, the scaling risk of the device is reduced, and the continuous and stable operation of the wastewater treatment process is ensured.

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

In a preferred embodiment of the invention, the catalyst production wastewater is wastewater generated by chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation of wastewater generated in the molecular sieve production process, and is concentrated by an ED membrane and a reverse osmosis method.

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 HCl concentration of 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 satisfy the conditions of the present invention, the first evaporation may be controlled so that the concentration of sodium chloride in the first concentrated solution approachesSeparating out the concentration, then carrying out second evaporation and low-temperature treatment on the first concentrated solution to obtain a treated solution, carrying out solid-liquid separation to obtain sodium chloride crystals and a second mother solution, mixing the second mother solution 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 carrying out first evaporation to obtain sodium sulfate crystals. Of course, sodium sulfate and sodium chloride may be used in the initial stage to adjust the ion content of the wastewater to be treated SO long as the wastewater to be treated satisfies the SO content of the wastewater to be treated in the present 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 figure 1, the catalyst production wastewater (containing NaCl 80g/L, na) ₂ SO ₄ 81g/L、NH ₄ Cl48g/L、(NH ₄ ) ₂ SO ₄ 49.4g/L, pH of 6.2) at a feed rate of 5m ³ Mixing the second mother liquor with the speed of/h to obtain the wastewater to be treated (containing SO) ₄ ^2- And Cl ^- In a molar ratio of 1:3.7487 Then, the mixed pH is monitored by a first pH measuring device 61 (pH meter) in the main pipe fed to the first heat exchanging device 31, the third heat exchanging device 33 and the fifth heat exchanging device 35 (all being titanium alloy plate heat exchangers) (measured value is 9.2), and a part (3 m) of the wastewater to be treated is treated by a first circulating pump 71 ³ H) sending the waste water to the first heat exchange device 31 to carry out first heat exchange with the first ammonia-containing steam condensate so as to heat the waste water to be treated to 99 ℃, and the other part (2 m) ³ H) sending the waste water to the third heat exchange device 33 to carry out first heat exchange with the second ammonia-containing steam condensate to heat the waste water to be treated to 99 ℃, sending the rest part of the waste water to the fifth heat exchange device 35 to carry out first heat exchange with the second concentrated solution obtained by second evaporation to heat the waste water to be treated to 102 DEG CThen the wastewater to be treated is converged and sent into a second heat exchange device 32; the wastewater to be treated is introduced into a main pipeline for conveying the wastewater to be treated into a second heat exchange device 32, a sodium hydroxide aqueous solution with the concentration of 45.16 mass% is introduced for carrying out second pH value adjustment, the adjusted pH value is monitored by a second pH value measuring device 62 (a pH meter) (the measured value is 10.8), then the wastewater to be treated is conveyed into the second heat exchange device 32 (a titanium alloy plate type heat exchanger) to carry out first heat exchange with the recovered first ammonia-containing steam so as to heat the wastewater to be treated to 107 ℃, and then the wastewater to be treated is conveyed into a first MVR evaporation device 2 (a falling film and forced circulation two-stage MVR evaporation crystallizer) to carry out evaporation, so that first ammonia-containing steam and a first concentrated solution containing sodium sulfate crystals are obtained. Wherein the evaporation temperature of the first MVR evaporation device 2 is 100 ℃, the pressure is-22.82 kPa, and the evaporation capacity is 3.82m ³ H is used as the reference value. The first ammonia-containing steam obtained by evaporation is compressed by the first compressor 101 (the temperature is raised by 12 ℃) and then passes through the second heat exchange device 32 and the first heat exchange device 31 in sequence to exchange heat with the wastewater to be treated, and is condensed to obtain first ammonia water which is stored in the first ammonia water storage tank 51. In addition, in order to increase the solid content in the first MVR evaporation device 2, part of the liquid evaporated in the first MVR evaporation device 2 is circulated as a first circulating liquid to the second heat exchange device 32 through the second circulating pump 72 for heat exchange, and then enters the first MVR evaporation device 2 again for first evaporation (the reflux ratio is 75.9). The degree of the first evaporation is monitored by a densimeter arranged on the first MVR evaporation device 2, and the concentration of the sodium chloride in the first evaporation concentrated solution is controlled to be 0.9935X (306.2 g/L).

Feeding the first concentrated solution into a first solid-liquid separation device 91 (centrifuge) for first solid-liquid separation to obtain 4.48 m/hr ³ Contains NaCl 306.2g/L, na ₂ SO ₄ 54.0g/L、NaOH 1.3.8g/L、NH ₃ 0.60g/L of the first mother liquor is temporarily stored in a first mother liquor tank 53, the sodium sulfate solid obtained by solid-liquid separation (15 mass% sodium sulfate crystal cake containing water 664.41kg is obtained per hour, wherein the content of sodium chloride is 5.0 mass% or less) is eluted with 54g/L of sodium sulfate solution equal to the dry basis mass of the sodium sulfate crystal cake, after drying, 664.41kg (the purity is 99.4 wt%) of sodium sulfate is obtained per hour, and the washing solution is passed through an eighth circulating pump78 is recycled to be mixed with the wastewater to be treated before the second pH adjustment, and then enters the first MVR evaporation device 2 again for the first evaporation.

The second evaporation process is carried out in a second MVR evaporation plant 1 (falling film + forced circulation two-stage MVR evaporator crystallizer). And (3) sending the first mother liquor in the first mother liquor tank 53 to the second MVR evaporation device 1 through a sixth circulating pump 76 for second evaporation to obtain second ammonia-containing steam and a second concentrated solution containing sodium sulfate crystals and sodium chloride crystals. Wherein the evaporation temperature of the second MVR evaporation device 1 is 105 ℃, the pressure is-7.02 kPa, and the evaporation capacity is 2.01m ³ H is used as the reference value. In order to increase the solid content in the second MVR evaporation device 1, part of the first mother liquor after evaporation in the second MVR evaporation device 1 is circulated as a second circulation liquid to the fourth heat exchange device 34 by the seventh circulation pump 77 for heat exchange, and then enters the second MVR evaporation device 1 again for second evaporation (reflux ratio is 42.3). The second ammonia-containing steam obtained by evaporation is compressed by the second compressor 102 (the temperature is raised by 12 ℃) and then sequentially passes through the fourth heat exchange device 34 and the third heat exchange device 33, and is respectively subjected to heat exchange with the first mother liquor and part of wastewater to be treated conveyed by the first circulating pump 71, cooled to obtain second ammonia water, and the second ammonia water is stored in the second ammonia water storage tank 52. The degree of the second evaporation is monitored through a mass flow meter arranged on the second MVR evaporation device 1, and the evaporation capacity of the second evaporation is controlled to be 2.01m ³ H (corresponding to the control of the sodium sulfate concentration in the treatment solution to 0.979Y, i.e., 91.6 g/L). After the first mother liquor is evaporated in the second MVR evaporation device 1, the obtained second concentrated solution containing sodium sulfate crystals and sodium chloride crystals is subjected to low-temperature treatment in a low-temperature treatment tank 55 at the temperature of 17.9 ℃ for 70min to obtain a treatment solution containing sodium chloride crystals.

The treated liquid containing sodium chloride crystals was sent to a second solid-liquid separation apparatus 92 (centrifuge) to conduct solid-liquid separation, yielding 2.58m per hour ³ Containing NaCl 277.6g/L, na ₂ SO ₄ 91.6g/L、NaOH 2.34g/L、NH ₃ 0.01g/L of a second mother liquor, temporarily stored in a second mother liquor tank 54. The second mother liquor is circulated to a wastewater leading-in pipeline through a ninth circulating pump 79 and is mixed with the wastewater to obtain wastewater to be treated, and the wastewater is solidifiedAfter the sodium chloride solid obtained by liquid separation (769.43 kg of sodium chloride crystal filter cake with the water content of 14 mass% is obtained per hour, wherein the content of sodium sulfate is less than 6.0 mass%) is subjected to spray washing by 277.6g/L of sodium chloride solution which is equal to the dry basis mass of sodium chloride, part of the sodium chloride crystal filter cake is used for preparing 277.6g/L of sodium chloride solution, the sodium chloride crystal filter cake is dried in a drying machine, 661.71kg of sodium chloride (the purity is 99.5 weight%) is obtained per hour, and a washing liquid returns to the fourth heat exchange device 34 through a tenth circulating pump 80 to exchange heat and then returns to the second MVR evaporation device 1.

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

In this example, 3.83m of ammonia water having a concentration of 3.45 mass% was obtained per hour in the first ammonia water tank 51 ³ 2.01m of ammonia water having a concentration of 0.137 mass% is 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 2

The treatment of the catalyst production wastewater was carried out in the same manner as in example 1, except that: for NaCl-containing 65g/L, na ₂ SO ₄ 130g/L、NH ₄ Cl 12g/L、(NH ₄ ) ₂ SO ₄ Treating the catalyst production wastewater with 24.4g/L, pH of 6.5 to obtain SO contained in the wastewater to be treated ₄ ^2- And Cl ^- In a molar ratio of 1:2.291. a portion (4 m) of the waste water to be treated ³ H) performing first heat exchange with the recovered first ammonia-containing steam condensate through a first heat exchange device 31 to heat the wastewater to be treated to 94 ℃, and enabling the other part (1 m) to be heated ³ H) by a third heat exchangeThe device 33 performs first heat exchange with the recycled second ammonia-containing steam condensate to heat the wastewater to be treated to 99 ℃, and the rest part of the wastewater to be treated is subjected to first heat exchange with the second concentrated solution through the fifth heat exchange device 35 to heat the wastewater to be treated to 99 ℃, and the temperature of the wastewater to be treated is 107 ℃ after heat exchange is performed through the second heat exchange device 32 after the wastewater to be treated is converged. The first MVR evaporation device 2 has an evaporation temperature of 95 ℃, a pressure of-36.36 kPa and an evaporation capacity of 4.31m ³ H is used as the reference value. The evaporation temperature of the second MVR evaporation device 1 is 100 ℃, the pressure is-22.83 kPa, and the evaporation capacity is 1.17m ³ H is used as the reference value. The low-temperature treatment temperature is 20 deg.C, and the retention time is 55min.

The first solid-liquid separation device 91 obtains 911.15kg of sodium sulfate crystal filter cakes containing 14 mass% of water per hour, and finally obtains 783.59kg of sodium sulfate (the purity is 99.5 weight%) per hour; obtained 2.68m per hour ³ The concentration of NaCl is 307.2g/L, na ₂ SO ₄ 54.5g/L、NaOH 1.83g/L、NH ₃ 0.35g/L of the first mother liquor.

The second solid-liquid separation device 92 obtains 456.76kg of sodium chloride crystal filter cake with the water content of 15 mass% per hour, and finally obtains 38.24kg of sodium chloride (the purity is 99.6 weight%) per hour; 1.67 m/hr ³ The concentration of NaCl is 279.5g/L, na ₂ SO ₄ 88.7g/L、NaOH 4.13g/L、NH ₃ 0.011g/L of the second mother liquor.

In this example, 4.31m of ammonia water having a concentration of 1.1 mass% was obtained per hour in the first ammonia water tank 51 ³ 1.17m of aqueous ammonia having a concentration of 0.085 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 3

The treatment of the catalyst production wastewater was carried out in the same manner as in example 1, except that: for the sample containing NaCl168g/L, na ₂ SO ₄ 35g/L、NH ₄ Cl 40g/L、(NH ₄ ) ₂ SO ₄ 8.47g/L, pH is 6.6, and the obtained SO contained in the wastewater to be treated ₄ ^2- And Cl ^- In a molar ratio of 1:9.3964. after heat exchange by the first heat exchange device 31The temperature of the wastewater to be treated is 99 ℃, the temperature of the wastewater to be treated after heat exchange by the third heat exchange device 33 is 99 ℃, the temperature of the wastewater to be treated after heat exchange by the fifth heat exchange device 35 is 105 ℃, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange device 32 is 112 ℃. The first MVR evaporation device 2 has an evaporation temperature of 105 ℃, a pressure of-7.02 kPa and an evaporation capacity of 2.36m ³ H is used as the reference value. The evaporation temperature of the second MVR evaporation device 1 is 110 ℃, the pressure is 11.34kPa, and the evaporation capacity is 3.16m ³ H is used as the reference value. The low-temperature treatment temperature is 25 deg.C, and the retention time is 50min.

The first solid-liquid separation device 91 obtains 251.35kg of sodium sulfate crystal cake containing 14 mass% of water every hour, and finally obtains 216.16kg of sodium sulfate (the purity is 99.6 weight%); 8.22 m/hr ³ The concentration of NaCl is 306.4g/L, na ₂ SO ₄ 52.5g/L、NaOH 2.64g/L、NH ₃ 0.18g/L of the first mother liquor.

The second solid-liquid separation device 92 obtains 1236.21kg of sodium chloride crystal cake with water content of 14 mass% per hour, and finally obtains 1063.14kg of sodium chloride (purity is 99.5 wt%) per hour; obtained 5.03m per hour ³ The concentration of NaCl is 279.5g/L, na ₂ SO ₄ 82.2g/L、NaOH 4.13g/L、NH ₃ 0.017g/L of second mother liquor.

In this example, 2.36m of ammonia water having a concentration of 3.0 mass% was obtained per hour in the first ammonia water tank 51 ³ 3.16m of aqueous ammonia having a concentration of 0.044% 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.

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 a first MVR evaporation device to carry out first evaporation to obtain first ammonia-containing steam and first concentrated solution containing sodium sulfate crystals;

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

the first evaporation prevents sodium chloride from crystallizing out;

the conditions of the second 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 ℃;

relative to 1 mole of SO contained in the wastewater to be treated ₄ ^2- Cl contained in the wastewater to be treated ^- 14 mol or less;

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 ^- Is 13.8 mol or less.

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

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

5. The method of claim 1, wherein the first evaporation is conducted such that the concentration of sodium chloride in the first concentrated solution is no greater than X, where X is the concentration of sodium chloride at which both sodium sulfate and sodium chloride in the first concentrated solution are saturated under the conditions of the first evaporation.

6. A process as claimed in claim 5, wherein the first evaporation provides a concentration of sodium chloride in the first concentrate of from 0.95X to 0.999X.

7. The method according to claim 5, wherein the second evaporation is performed so that the concentration of sodium sulfate in the treatment solution is Y or less, wherein Y is the concentration of sodium sulfate at which both sodium sulfate and sodium chloride in the treatment solution are saturated under the low-temperature treatment condition.

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

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

10. The method of claim 9, wherein the conditions of the first evaporation comprise: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa.

11. The method of claim 10, wherein the conditions of the first evaporation comprise: the temperature is 60-365 ℃, and the pressure is-87 kPa-18110 kPa.

12. The method of claim 11, wherein the conditions of the first evaporation comprise: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa.

13. The method of claim 12, wherein the conditions of the first evaporation comprise: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa.

14. The method of claim 13, wherein the conditions of the first evaporation comprise: the temperature is 95-110 ℃, and the pressure is-37 kPa-12 kPa.

15. The method of any one of claims 1-8, wherein the conditions of the second evaporation comprise: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa.

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

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

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

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

20. The method according to claim 9, wherein the temperature of the first evaporation is higher than the temperature of the low-temperature treatment by 5 ℃ or more.

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

22. The method of claim 21, wherein the temperature of the first evaporation is 35 ℃ to 90 ℃ higher than the temperature of the low temperature treatment.

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

24. A method according to claim 23, wherein the pH of the wastewater to be treated is adjusted to be greater than 7 prior to the first heat exchange.

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

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

27. The method according to claim 26, wherein the second ammonia-containing steam is discharged after ammonia removal from the tail gas remaining from the condensation of the second heat exchange.

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

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

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

31. The method of claim 30, further comprising washing the resulting sodium chloride crystals.

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

33. The method of claim 32, further comprising removing impurities and concentrating the catalyst process wastewater.