CN108726604B

CN108726604B - Treatment method of catalyst production wastewater

Info

Publication number: CN108726604B
Application number: CN201710263273.9A
Authority: CN
Inventors: 殷喜平; 李叶; 顾松园; 周岩; 杨凌; 王涛; 苑志伟; 伊红亮; 刘夫足; 高晋爱; 安涛; 吕伟娇; 刘志坚
Original assignee: China Petroleum and Chemical Corp; Sinopec Catalyst Co
Current assignee: China Petroleum and Chemical Corp; Sinopec Catalyst Co
Priority date: 2017-04-21
Filing date: 2017-04-21
Publication date: 2021-09-17
Anticipated expiration: 2037-04-21
Also published as: CN108726604A

Abstract

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

Description

Treatment method of catalyst production wastewater

Technical Field

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

Background

In the production process of the oil refining catalyst, a large amount of inorganic acid alkali salts such as sodium hydroxide, hydrochloric acid, sulfuric acid, ammonium salts, sulfates, hydrochlorides and the like are needed, and a large amount of mixed sewage containing ammonium, sodium sulfate, sodium chloride and aluminosilicate is generated. For such sewage, the common method in the prior art is that the pH value is adjusted to be within the range of 6-9, most of suspended matters are removed, then a biochemical method, a blow-off method or a steam stripping method is adopted to remove ammonium ions, then the salt-containing sewage is subjected to pH value adjustment, most of suspended matters are removed, hardness, silicon and part of organic matters are removed, most of organic matters are removed through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then the salt-containing sewage enters an ion exchange device for further hardness removal, enters an enrichment device (such as reverse osmosis or electrodialysis) for concentration, and then MVR evaporative crystallization or multiple-effect evaporative crystallization is adopted to obtain mixed miscellaneous salt of sodium 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 of 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, the salt content of the wastewater is not reduced (20000 mg/L-30000 mg/L), the wastewater cannot be directly discharged, and the wastewater needs to be further desalted.

In order to remove ammonia 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 (20000 mg/L-30000 mg/L), the wastewater cannot be discharged directly, further desalting treatment is needed, the operation cost of wastewater treatment is high, a large amount of alkali remains in the treated wastewater, the pH value is high, the waste is large, and the treatment cost is up to 50 yuan/ton.

Disclosure of Invention

The invention aims to overcome the defect of NH content in the prior art₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The wastewater treatment cost is high, and only mixed salt crystals can be obtained, thereby providing a low-cost and environment-friendly NH-containing catalyst₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The method for treating the wastewater generated in the catalyst production 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 containing NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The method comprises the following steps of,

1) introducing wastewater to be treated into each effect evaporator of a first multi-effect 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, and introducing a liquid phase obtained by the first solid-liquid separation into each effect evaporator of a second multi-effect evaporation device for second evaporation to obtain second ammonia-containing steam and a second concentrated solution containing sodium chloride crystals;

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

before the wastewater to be treated is introduced into a first multi-effect evaporation device, adjusting the pH value of the wastewater to be treated to be more than 9; the first evaporation prevents sodium chloride from crystallizing out, and the second evaporation prevents sodium sulfate from crystallizing out; relative to 1 mole of SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-The molar ratio is 14 mol or less.

By the technical scheme, the method aims at the content of NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The pH value of the wastewater to be treated is adjusted to a specific range in advance, then a first multi-effect evaporation device is used for evaporation and separation to obtain sodium sulfate crystals and concentrated ammonia water, and then a second multi-effect evaporation device is used for evaporation again to obtain sodium chloride crystals and dilute ammonia water. 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, recovers the sodium chloride and the sodium sulfate in the form of crystals respectively, does not generate waste residues and waste liquid in the whole process, and achieves the purpose of changing waste into valuable.

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. A second multi-effect evaporation device 2 and a first multi-effect evaporation device

31. First heat exchange device 32 and second heat exchange device

33. Third heat exchange device 51 and first mother liquor tank

52. Second ammonia water storage tank 53, first ammonia water storage tank

54. First crystal liquid collecting tank 55 and second crystal liquid collecting tank

6. pH value measuring device 71 and first circulating pump

72. Second circulating pump 73 and third circulating pump

74. Fourth and fifth circulating

pumps

75 and 75

76. Sixth circulating pump 77 and seventh circulating pump

81. Vacuum pump 82 and circulating water pool

83. Tail gas absorption tower 91 and first solid-liquid separation device

92. Second solid-liquid separation device

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 NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The method comprises the following steps of,

1) introducing wastewater to be treated into each effect evaporator of a first multi-effect evaporation device 2 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, and introducing a liquid phase obtained by the first solid-liquid separation into each effect evaporator of the second multi-effect evaporation device 1 for second evaporation to obtain second ammonia-containing steam and a second concentrated solution containing sodium chloride crystals;

before the wastewater to be treated is introduced into the first multi-effect 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, and the second evaporation prevents sodium sulfate from crystallizing out; relative to 1 mole of SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-The molar ratio 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 value of the wastewater to be treated is adjusted to be greater than 10.8 before the wastewater to be treated is passed into the first multi-effect evaporation device 2. The upper limit of the pH of the wastewater to be treated is not limited, and may be, for example, 14 or less, preferably 13.5 or less, and more preferably 13 or less.

The method provided by the invention can be used for the treatment of the compounds containing NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺Except that it contains NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺In addition, the catalyst production wastewater is not particularly limited. From the viewpoint of improving the treatment efficiency of wastewater, the amount of SO contained in the wastewater to be treated is 1 mole per mole₄ ^2-Cl contained in the wastewater to be treated^-Is 13.8 mol or less, preferablyIs selected to be 13.75 moles or less, more preferably 13.5 moles or less, still more preferably 13 moles or less, still more preferably 12 moles or less, still more preferably 11 moles or less, still more preferably 10 moles or less, still more preferably 9 moles or less, still more preferably 8 moles or less, still more preferably 7 moles or less; preferably 2 moles or more, more preferably 2.5 moles or more, further preferably 3 moles or more, and for example, may be 1 to 10 moles, more preferably 4 to 9 moles. By reacting SO₄ ^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 treated₄ ^2-And Cl^-The molar ratio of (a) to (b) is adjusted and the balance of sodium hydroxide can be maintained.

In the present invention, the first evaporation is intended to precipitate sodium sulfate, but sodium chloride is not crystallized, so that sodium sulfate and sodium chloride can be separated well. In the first evaporation, the concentration of sodium chloride in the first concentrated solution is not more than the solubility of the first crystal under the conditions corresponding to the concentration of sodium chloride in the first concentrated solution, from the viewpoint of further precipitating sodium sulfate as much as possible without precipitating sodium chloride in the subsequent crystallization step.

In the present invention, the second evaporation is intended to precipitate sodium chloride without crystallizing sodium sulfate, so that sodium sulfate can be separated from sodium chloride well. In the second evaporation, the concentration of sodium sulfate in the second concentrated solution is not more than the solubility of sodium sulfate in the second crystal under the conditions corresponding to the second crystal, from the viewpoint of further precipitating sodium chloride as much as possible without precipitating sodium sulfate in the subsequent crystallization step.

In the present invention, the first evaporation to prevent the crystallization of sodium chloride means that the concentration of sodium chloride in 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 carried by sodium sulfate crystals or adsorbed on the surface is not excluded. Since the water content of the crystals after the solid-liquid separation is different, the sodium chloride content in the obtained sodium sulfate crystals is usually 8 mass% or less (preferably 4 mass% or less), and in the present invention, it is considered that sodium chloride is not crystallized when the sodium chloride content in the obtained sodium sulfate crystals is 8 mass% or less.

In the present invention, the second evaporation to prevent the crystallization of sodium sulfate means that the concentration of sodium sulfate in the mixed system is controlled not to exceed the solubility under the second evaporation conditions (including but not limited to temperature, pH, etc.), and sodium sulfate entrained by sodium chloride 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 sulfate content in the obtained sodium chloride crystals is usually 8 mass% or less (preferably 4 mass% or less), and in the present invention, it is considered that the sodium sulfate does not crystallize out when the sodium sulfate content in the obtained sodium chloride crystals is 8 mass% or less.

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

In the present invention, the feeding modes of the liquid to be evaporated for the first evaporation and the second evaporation may be the same or different, and a co-current, counter-current or advection mode conventionally used in the art may be adopted. The forward flow is specifically as follows: and sequentially introducing liquid to be evaporated into each effect evaporator of the multi-effect evaporation device, and introducing ammonia-containing steam obtained by evaporation of the former effect evaporator of the multi-effect evaporation device into the latter effect evaporator. The countercurrent is specifically: and sequentially introducing liquid to be evaporated into each effect evaporator of the multi-effect evaporation device, and introducing ammonia-containing steam obtained by evaporation of the latter effect evaporator of the multi-effect evaporation device into the former effect evaporator. The advection is specifically as follows: and independently introducing liquid to be evaporated into each effect evaporator of the multi-effect evaporation device, and introducing ammonia-containing steam obtained by evaporation of the former effect evaporator of the multi-effect evaporation device into the latter effect evaporator. Preferably, the first evaporation and the second evaporation adopt a concurrent feeding mode.

And the first multi-effect evaporation device 2 and the second multi-effect evaporation device 1 can be the same multi-effect evaporation device by means of serial connection and the like, as long as one part of the evaporators meets the conditions of the first evaporation and the other part of the evaporators meets the conditions of the second evaporation. When feeding is carried out in a forward flow or a reverse flow mode, the evaporation condition refers to the evaporation condition of the last evaporator of the multi-effect evaporation device; when advection feeding is adopted, the evaporation conditions include the evaporation conditions of each effect evaporator of the multi-effect evaporation device.

According to a preferred embodiment of the invention, the second ammonia-containing vapor evaporated by the last evaporator of the first multi-effect evaporation device 2 is passed into the first evaporator of the second multi-effect evaporation device 1. If the energy of the secondary ammonia-containing steam generated by the last evaporator of the first multi-effect evaporation device 2 is not enough to meet the requirement of the second multi-effect evaporation device 1, fresh steam can be supplemented from the first evaporator of the second multi-effect evaporation device 1.

According to a preferred embodiment of the invention, the first evaporation and the second evaporation are both performed in a concurrent feeding manner, that is, the wastewater to be treated is sequentially introduced into each effect evaporator of a first multi-effect evaporation device 2, the liquid phase obtained by the first solid-liquid separation is sequentially introduced into each effect evaporator of a second multi-effect evaporation device 1, the first ammonia-containing steam obtained by evaporation of the previous effect evaporator of the first multi-effect evaporation device 2 is introduced into the next effect evaporator, and the first ammonia-containing steam obtained by evaporation of the previous effect evaporator of the second multi-effect evaporation device 1 is introduced into the next effect evaporator; preferably, the first ammonia-containing steam obtained by evaporation in the last evaporator of the first multi-effect evaporation device 2 is introduced into the first evaporator of the second multi-effect evaporation device 1. Heating steam can be fed into the first-effect evaporator 2a of the first multi-effect evaporation device 2, condensate obtained after the heating steam is condensed in the first-effect evaporator 2a can be used for preheating liquid phase obtained by first solid-liquid separation of the first-effect evaporator 1a of the second multi-effect evaporation device 1, and the condensate can be used for washing filter cakes or preparing washing solution.

Specifically, the wastewater to be treated is sequentially introduced into a first effect evaporator 2a, a second effect evaporator 2b, a third effect evaporator 2c and a fourth effect evaporator 2d of a first multiple effect evaporation device 2; after the first solid-liquid separation, the liquid phase obtained by the first solid-liquid separation is sequentially introduced into a first effect evaporator 1a, a second effect evaporator 1b and a third effect evaporator 1c of a second multi-effect evaporation device 1. Heating steam is introduced into the first effect evaporator 2a of the first multi-effect evaporation device 2. In the first multi-effect evaporation device 2, the first ammonia-containing steam obtained by evaporation of the previous-effect evaporator exchanges heat in the next-effect evaporator to obtain first ammonia water, the first ammonia water obtained by each-effect evaporator is collected, optionally exchanges heat with the wastewater to be treated in the second heat exchange device 32, and then is stored in the first ammonia water storage tank 53. In the second multi-effect evaporation device 1, the first ammonia-containing steam obtained by evaporation of the previous-effect evaporator exchanges heat in the subsequent-effect evaporator to obtain second ammonia water, and the second ammonia water obtained by each-effect evaporator is collected and optionally exchanges heat with the wastewater to be treated in the first heat exchange device 31, and then is stored in the second ammonia water storage tank 52. The first ammonia-containing steam obtained by the evaporation of the fourth-effect evaporator 2d of the first multi-effect evaporation device 2 exchanges heat in the first-effect evaporator 1a of the second multi-effect evaporation device 1 to obtain second ammonia water. When the energy of the secondary ammonia-containing steam generated by the last evaporator of the first multi-effect evaporation device 2 is not enough to meet the requirement of the second multi-effect evaporation device 1, fresh steam can be supplemented from the first evaporator of the second multi-effect evaporation device 1.

In the present invention, the first multi-effect evaporation apparatus 2 is not particularly limited, and may be composed of various evaporators conventionally used in the art. For example, it may be selected from one or more of falling film type evaporator, rising film type evaporator, scraped surface evaporator, central circulation tube type multiple effect evaporator, basket type evaporator, external heating type evaporator, forced circulation type evaporator and lien type evaporator. Among them, a forced circulation evaporator and an external heating evaporator are preferable. The first multi-effect evaporation apparatus 2 includes a heating chamber and an evaporation chamber, and may further include other evaporation auxiliary components such as a demister for further separating liquid foam, a condenser for condensing all secondary steam, and a vacuum apparatus for pressure reduction operation, if necessary. The number of evaporators included in the first multi-effect evaporation device 2 is not particularly limited, and may be 2 or more, preferably 2 to 5, and more preferably 3 to 4.

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 45 ℃ and the pressure is above-95 kPa. In order to improve the evaporation efficiency, 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; from the viewpoint of reducing the cost of equipment and energy consumption, it is preferable that the temperature of evaporation is from 75 ℃ to 175 ℃ and the pressure is from-73 kPa to 653 kPa; preferably, the conditions of the first evaporation include: the temperature is 96-151 ℃, and the pressure is-34 kPa-303 kPa; preferably, the conditions of the first evaporation include: the temperature is 96-106 ℃, and the pressure is-34 kPa to-3 kPa.

In the invention, when the first evaporation adopts concurrent flow or countercurrent flow feeding, the condition of the first evaporation refers to the evaporation condition of the last evaporator of the multi-effect evaporation device; when advection feeding is adopted, the first evaporation conditions comprise evaporation conditions of each effect evaporator of the multi-effect evaporation device.

Wherein, in order to fully utilize the heat in the first evaporation process, the evaporation temperature difference of adjacent two-effect evaporators is preferably 5-30 ℃; more preferably, the evaporating temperatures of two adjacent effect evaporators differ by 10 ℃ to 20 ℃.

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

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

By carrying out the first evaporation under the above conditions, the sodium chloride is not precipitated while the precipitation of sodium sulfate crystals is ensured, and the purity of the obtained sodium sulfate crystals can be ensured.

According to the invention, by controlling the evaporation conditions of the first multi-effect evaporation device 2, more than 90 mass percent (preferably more than 95 mass percent) of ammonia contained in the wastewater to be treated can be evaporated, 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 prepared with water and corresponding ammonium salt or ammonia water for use. In the first evaporation, in order to obtain stronger ammonia water, the first ammonia-containing steam condensate obtained in the first effect evaporator and/or the second effect evaporator can be collected separately, that is, the first ammonia-containing steam condensate (first ammonia water) obtained in the second effect evaporator and/or the third effect evaporator can be collected. The first ammonia water generated by the first effect evaporator and the second effect evaporator can be collected independently or in a converging way according to requirements. In order to control the concentration of ammonia, the evaporation conditions of the individual evaporator effects can be appropriately adjusted.

According to the present invention, the first evaporation is performed so that the concentration of sodium chloride in the first concentrated solution is preferably X or less (preferably 0.999X or less, more preferably 0.95X to 0.999X, and even more preferably 0.99X to 0.9967X), from the viewpoint of not crystallizing sodium chloride in the wastewater to be treated (that is, not supersaturating sodium chloride), but precipitating sodium sulfate as much as possible without precipitating sodium chloride. 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 liquid obtained by the first evaporation, and specifically, the concentration of the liquid obtained by the first evaporation is controlled within the above range so that the first evaporation does not cause crystallization of sodium chloride. The concentration of the liquid resulting from the first evaporation is monitored by measuring the density, which may be carried out using a densitometer.

According to the invention, in order to fully utilize the heat in the first ammonia water and the second ammonia water, the wastewater to be treated is preferably subjected to first heat exchange with the first ammonia water and/or the second ammonia water before being introduced into the first multi-effect evaporation device.

According to the present invention, the first heat exchange may be performed before the catalyst production wastewater and at least a part of the second mother liquor are mixed to obtain wastewater to be treated, or may be performed after the catalyst production wastewater and at least a part of the second mother liquor are mixed to obtain wastewater to be treated. Wherein it is preferably performed before at least part of the catalyst production wastewater and the second mother liquor are mixed to obtain wastewater to be treated.

According to a preferred embodiment of the present invention, said first heat exchange is carried out by means of first heat exchange means 31 and second heat exchange means 32, respectively. Specifically, a part of the wastewater to be treated is sent to a first heat exchange device 31 to perform first heat exchange with second ammonia water; and sending the rest part of the wastewater to be treated into a second heat exchange device 32 to carry out first heat exchange with the first ammonia water. Preferably, after the first heat exchange is performed by the first heat exchange device 31, the temperature of the wastewater to be treated is 70-106 ℃; preferably, after the first heat exchange is performed by the second heat exchange device 32, the temperature of the wastewater to be treated is 50 ℃ to 60 ℃.

The first heat exchange device 31 and the heat exchange device 32 are not particularly limited, and various heat exchangers conventionally used in the art may be used to exchange heat between the 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. Preferably, a duplex stainless steel plate heat exchanger is used.

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 may be, for example, a hydroxide such as sodium hydroxide or potassium hydroxide for the purpose of adjusting the pH. 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 multi-effect evaporation apparatus 2, and the pH adjustment is performed by introducing and mixing the aqueous solution containing the alkaline substance in the pipe for feeding the wastewater to be treated into the first multi-effect evaporation apparatus 2 before feeding the wastewater to be treated into the first multi-effect evaporation apparatus 2, so that the pH of the wastewater to be treated is greater than 9, preferably greater than 10.8.

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

In order to detect the pH value after the pH value adjustment, it is preferable to provide a pH value measuring device 61 on a pipe for feeding the wastewater to be treated into the first heat exchange device 31 or the second heat exchange device 32 to measure the pH value after the pH value adjustment; a pH measuring device 62 is preferably provided on the pipe that feeds the wastewater to be treated to the first multi-effect evaporation device 2 to measure the pH after pH adjustment.

In the present invention, the sequence of the first heat exchange, the adjustment of the pH value of the wastewater to be treated, and the preparation of the wastewater to be treated (in the case where the wastewater to be treated contains a liquid phase obtained by the separation of the catalyst production wastewater and the second solid-liquid, the preparation of the wastewater to be treated needs to be performed) is not particularly limited, and may be appropriately selected as needed, and the first heat exchange, the adjustment of the pH value of the wastewater to be treated, and the preparation of the wastewater to be treated need to be performed before the wastewater to be treated is introduced into the first multi-effect evaporation apparatus 2.

According to the invention, the method can further comprise a first crystallization, and the first concentrated solution containing sodium sulfate crystals is subjected to the first crystallization in the first crystallization device to obtain the crystal slurry containing sodium sulfate crystals. The first crystallization is carried out in a first crystallization apparatus, which is not particularly limited, and may be, for example, a crystal liquid collection tank, a thickener with or without stirring, and the like. The first crystallization process may be performed by crystallizing the concentrated solution evaporated by each evaporator of the first multi-effect evaporator 2 in different crystallization devices; or the concentrated solution obtained by evaporation of each effect evaporator of the first multi-effect evaporation device 2 is combined and crystallized in a crystallization device, preferably the concentrated solution obtained by evaporation of each effect evaporator of the first multi-effect evaporation device 2 is combined and crystallized in a crystallization device. According to a preferred embodiment of the present invention, the first crystallization may be performed in the first crystallization liquid collection tank 54. According to the invention, the crystallization of the first concentrated solution containing sodium sulfate crystals can also be carried out in a first multi-effect evaporator with a crystallizer (e.g. a forced circulation evaporator crystallizer), wherein the crystallization temperature is the corresponding first evaporation temperature.

According to the present invention, when the crystallization is performed using a separate crystallization apparatus, it is further necessary to ensure that the first evaporation does not crystallize sodium chloride in the sodium sulfate crystal-containing magma (i.e., sodium chloride does not reach supersaturation), and preferably, the first evaporation is performed such that the concentration of sodium chloride in the first concentrated solution is X or less, where X is the concentration of sodium chloride at which both sodium chloride and sodium sulfate in the first concentrated solution reach saturation under the conditions of the first crystallization.

The conditions for the first crystallization may be appropriately selected as needed, and may include, for example, a crystallization temperature of 45 to 364 ℃, preferably 80 to 107 ℃, and more preferably 95 to 105 ℃. In order to fully ensure the crystallization effect, the crystallization time can be 5min to 24h, preferably 5min to 30 min.

According to a preferred embodiment of the present invention, the temperature of the first crystallization is not higher than the temperature of the first evaporation, preferably the temperature of the first crystallization is 0-10 ℃ lower than the temperature of the first evaporation, more preferably 0-5 ℃ lower. Preferably, the temperature of the first crystallization is the natural temperature of the first evaporated concentrate entering the crystallizer.

In the invention, the first concentrated solution containing sodium sulfate crystals (or crystal mush 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, for example, 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.) 91. After the solid-liquid separation, the first mother liquor obtained by the first solid-liquid separation device 91 is temporarily stored in the first mother liquor tank 51, and can be sent to the second multi-effect evaporation device 1 through the first circulating pump 71 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.

Preferably, the first washing means comprises rinsing and/or elutriation. In addition, the first washing liquid obtained in the above washing process is preferably returned to the pH value before the second pH adjustment by the second circulation pump 72.

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. 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. In addition, the rinsing is preferably carried out using an aqueous sodium sulfate solution (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 rinsed). In order to further enhance the elutriation effect and obtain sodium sulfate crystals with higher purity, the elutriation may be preferably performed using a liquid obtained by rinsing, and more preferably using water or a sodium sulfate solution. The liquid resulting from the washing is preferably returned to the first multi-effect evaporation device 2 before the second pH adjustment before evaporation.

According to a preferred embodiment of the present invention, a first concentrated solution containing sodium sulfate (or a magma containing sodium sulfate crystals) is subjected to a preliminary solid-liquid separation by settling, then the catalyst production wastewater is subjected to a first elutriation in an elutriation tank, then a liquid obtained in a subsequent sodium sulfate crystal washing is subjected to a second elutriation in another elutriation tank, finally the slurry subjected to the two elutriations is sent to a solid-liquid separation device for solid-liquid separation, crystals obtained by the solid-liquid separation are subjected to elution by an aqueous sodium sulfate solution (the concentration of the aqueous sodium sulfate solution is the concentration of sodium sulfate in an aqueous solution in which sodium chloride and sodium sulfate reach saturation at the same time at the temperature corresponding to the sodium sulfate crystals to be washed) and the eluted liquid 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 multi-effect evaporation apparatus 1 is not particularly limited, and may be composed of various evaporators conventionally used in the art. For example, it may be selected from one or more of falling film type evaporator, rising film type evaporator, scraped surface evaporator, central circulation tube type multiple effect evaporator, basket type evaporator, external heating type evaporator, forced circulation type evaporator and lien type evaporator. Among them, a forced circulation evaporator and an external heating evaporator are preferable. The respective evaporators of the second multi-effect evaporation apparatus 1 are composed of a heating chamber and an evaporation chamber, and may further include other evaporation auxiliary components such as a demister for further separating liquid foam, a condenser for condensing all secondary steam, and a vacuum apparatus for pressure reduction operation, if necessary. The number of evaporators included in the second multi-effect evaporation apparatus 1 is not particularly limited, and may be 2 or more, preferably 2 to 5, and more preferably 2 to 3.

In the present invention, the evaporation conditions of the second evaporation may be appropriately selected as needed, and the purpose of crystallizing sodium chloride without precipitating sodium sulfate may be achieved. In order to improve evaporation efficiency, the conditions of the second evaporation may include: the temperature is 30-96 ℃, and the pressure is-98 kPa-34 kPa; preferably, the conditions of the second evaporation include: the temperature is 35-85 ℃, and the pressure is-97.5 kPa to-85 kPa; preferably, the conditions of the second evaporation include: the temperature is 46-85 ℃, and the pressure is-95 kPa to-85 kPa; preferably, the conditions of the second evaporation include: the temperature is 46-60 ℃, and the pressure is-95 kPa to-87 kPa; preferably, the conditions of the second evaporation include: the temperature is 46-51 ℃, and the pressure is-95 kPa to-92 kPa.

In the invention, when the second evaporation adopts concurrent flow or countercurrent flow feeding, the condition of the second evaporation refers to the evaporation condition of the last one-effect evaporator of the multi-effect evaporation device; when advection feeding is employed, the conditions of the second evaporation include evaporation conditions of each effect evaporator of the multi-effect evaporation device.

Wherein, in order to fully utilize the heat in the second evaporation process, the evaporation temperature difference of adjacent two-effect evaporators is preferably 5-30 ℃; more preferably, the evaporating temperatures of two adjacent effect evaporators differ by 10 ℃ to 20 ℃.

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

Further, the evaporation amount of the second evaporation may be appropriately selected depending on the capacity of the apparatus to treat and the amount of wastewater to be treated, and may be, for example, 0.1m³More than h (e.g. 0.1 m)³/h～500m³/h)。

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

According to the present invention, the second evaporation does not crystallize sodium sulfate (that is, sodium sulfate does not become supersaturated), and from the viewpoint of precipitating sodium chloride as much as possible without precipitating sodium sulfate, the second evaporation preferably makes the concentration of sodium sulfate in the second concentrated solution be Y or less (preferably 0.9Y to 0.99Y, and more preferably 0.95Y to 0.98Y), where Y is the concentration of sodium sulfate at the time when both sodium sulfate and sodium chloride in the second concentrated solution are saturated under the conditions of the second evaporation. By controlling the degree of the second evaporation within the above range, as much sodium chloride as possible can be crystallized out under the condition that sodium sulfate is not precipitated out. 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 concentration of the liquid obtained by the second evaporation, and specifically, the concentration of the liquid obtained by the second evaporation is controlled within the above range so that the second evaporation does not cause crystallization of sodium sulfate. The concentration of the liquid resulting from the second evaporation is monitored by measuring the density, which may be carried out using a densitometer.

According to the invention, the second ammonia-containing steam obtained by evaporation in the last evaporator of the second multi-effect evaporation device 1 exchanges heat with the cold medium in the third heat exchange device 33 to obtain second ammonia water. The cold medium can be cooling water, glycol water solution and the like. When conventional cooling water is used, the cooling water is recycled, and when the catalyst production wastewater is used as the cooling water, the catalyst production wastewater after heat exchange is preferably directly returned to the treatment process (for example, returned to the second pH value adjustment process). After the second ammonia water obtained by the second multi-effect evaporation device exchanges heat with the wastewater to be treated in the first heat exchange device 31, the second ammonia water is hydrated with the second ammonia water obtained in the third heat exchange device 33 and stored in a second ammonia water storage tank 52.

The heat exchanger 33 is not particularly limited, and various heat exchangers conventionally used in the art may be used to perform heat exchange. 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. Preferably, a heat exchanger comprising a plastic material is selected.

In the present invention, in order to prevent the first evaporation from crystallizing and precipitating sodium chloride and the second evaporation from crystallizing and precipitating sodium sulfate, it is preferable that the conditions of the two-evaporation (conditions of crystallization when crystallization is performed using a single crystallization apparatus) satisfy: the temperature of the first evaporation is higher than the temperature of the second evaporation by 5 ℃ or more, preferably by 20 ℃ or more, more preferably by 35 to 70 ℃, and particularly preferably by 50 to 59 ℃. And respectively crystallizing and separating out sodium sulfate and sodium chloride by controlling the first evaporation and the second evaporation to be carried out at different temperatures, so that the purity of the obtained sodium sulfate and sodium chloride crystals is improved.

According to a preferred embodiment of the invention, the second evaporation process is carried out in a second multi-effect evaporation device 1. And (3) introducing the first mother liquor into the second multi-effect evaporation device 1 through a first circulating pump 71 to carry out second evaporation to obtain second ammonia-containing steam and a second concentrated solution containing sodium chloride crystals.

According to the invention, the method can further comprise a second crystallization, and the magma containing the sodium chloride crystals is obtained after the second crystallization of the second concentrated solution containing the sodium chloride crystals is carried out in the second crystallization device. The second crystallization is carried out in a second crystallization apparatus, which is not particularly limited, and may be, for example, a crystal liquid collection tank, a thickener with or without stirring, and the like. The second crystallization process may be performed by crystallizing the concentrated solution evaporated by each evaporator of the second multi-effect evaporation apparatus 1 in different crystallization apparatuses; or the concentrated solution obtained by evaporation of each effect evaporator of the second multi-effect evaporation device 1 is combined and crystallized in a crystallization device, preferably the concentrated solution obtained by evaporation of each effect evaporator of the second multi-effect evaporation device 1 is combined and crystallized in a crystallization device. According to a second preferred embodiment of the present invention, the second crystallization may be performed in a second crystal liquid collection tank 55. According to the invention, the crystallization of the second concentrated solution containing sodium chloride crystals can also be carried out in a multi-effect evaporator with a crystallizer (e.g. a forced circulation evaporator crystallizer), wherein the crystallization temperature is the corresponding second evaporation temperature.

According to the present invention, when a single crystallization device is used for crystallization, it is further required to ensure that the second evaporation does not crystallize sodium sulfate out of the crystal slurry containing sodium chloride crystals (i.e., sodium sulfate does not reach supersaturation), and preferably, the second evaporation is performed so that the concentration of sodium sulfate in the second concentrated solution is Y or less, where Y is the concentration of sodium sulfate when both sodium chloride and sodium sulfate in the second concentrated solution reach saturation under the conditions of the second crystallization.

According to the present invention, the conditions for the second crystallization may be appropriately selected as needed, and may include, for example: the crystallization temperature is 20 ℃ to 107 ℃, preferably 45 ℃ to 55 ℃. In order to fully ensure the crystallization effect, the crystallization time can be 5min to 24h, preferably 5min to 30 min.

According to a preferred embodiment of the present invention, the temperature of the second crystallization is not higher than the temperature of the second evaporation, and preferably the temperature of the second crystallization is 0 to 10 ℃ lower than the temperature of the second evaporation, more preferably 1 to 5 ℃ lower.

In order to ensure that the second crystallization is carried out under the above conditions, the second crystallization apparatus may be provided with a cooling means. Specifically, the second crystallization device may be cooled by introducing cooling water. By using the second crystallization device with a cooling part, the second concentrated solution containing sodium chloride crystals can be rapidly cooled to the temperature of the second crystallization, so that the second evaporation can be carried out at a higher temperature, and the efficiency of the second evaporation is improved. In order to ensure that the second concentrated solution containing sodium chloride crystals is crystallized at the second crystallization temperature, the second crystallization device is preferably provided with a stirring component. Through the even mixing of stirring part, make the inside temperature homogeneity of second crystallization device in the crystallization process to further ensure that sodium sulfate does not precipitate out in the second crystallization process.

In the present invention, the second concentrated solution containing sodium chloride crystals (or the crystal slurry containing sodium chloride crystals) 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 one or more of centrifugation, filtration, and sedimentation, for example.

According to the present invention, the second solid-liquid separation may be performed by a second solid-liquid separation device (e.g., a centrifuge, a belt filter, a plate filter, etc.) 92. After the second solid-liquid separation, the second mother liquor obtained by the second solid-liquid separation device 92 returns to the first multi-effect evaporation device 2 for the first evaporation again, and specifically, the second mother liquor can be returned to the seventh circulating pump 77 and mixed with the catalyst production wastewater before the second pH adjustment to obtain the wastewater to be treated, and then sent to the MVR evaporation device 2 for the first evaporation. 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.

Preferably, the second wash comprises a rinsing and/or elutriation. The second washing liquid obtained in the above washing process is preferably returned to the second multi-effect evaporation device 1 by the sixth circulation pump 76 for second evaporation again.

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. 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 catalyst production wastewater is generally not recycled when being used as an elutriation liquid, and the washing liquid recovered by the second washing can be recycled in a counter-current manner when being used as the elutriation liquid. Before the elutriation, 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 used for elutriation is used with respect to 1 part by weight of a slurry containing sodium chloride crystals. In addition, the rinsing is preferably carried out using 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 rinsed). In order to further enhance the elutriation effect and obtain sodium chloride crystals with higher purity, the elutriation may be preferably performed using a liquid obtained by rinsing. For the liquid produced by washing, it is preferred that the catalyst production wastewater elutriation liquid is returned to the second multi-effect evaporation device before pH adjustment before evaporation in the first multi-effect evaporation device.

According to a preferred embodiment of the present invention, after the second concentrated solution containing sodium chloride crystals (or the crystal slurry containing sodium chloride crystals) 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 washing of sodium chloride crystals is subjected to second elutriation in another elutriation tank, finally the slurry subjected to the two elutriations is sent to a solid-liquid separation device for solid-liquid separation, the crystals obtained by the solid-liquid separation are subjected to elution by an aqueous sodium chloride solution (the concentration of the aqueous sodium chloride solution is 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 washed), and the liquid obtained by the elution is returned to the second elutriation as an elutriation liquid. Through the washing process combining elutriation and leaching, the purity of the obtained sodium chloride crystal is improved, washing liquid is not excessively introduced, and the efficiency of wastewater treatment is improved.

According to a preferred embodiment of the present invention, the remaining tail gas of the third heat exchange device 33 is discharged after ammonia removal. The ammonia in the tail gas is removed, so that the pollutant content in the discharged tail gas can be further reduced, and the tail gas can be directly discharged.

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

In the present invention, the catalyst production wastewater is not particularly limited as long as it contains NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The wastewater is obtained. In addition, the method is particularly suitable for treating high-salinity wastewater. The 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 wastewater₄ ⁺May be 8mg/L or more, preferably 300mg/L or more.

As Na in the wastewater from the catalyst production⁺May be 510mg/L or more, preferably 1000mg/L or more, more preferably 2000mg/L or more, further preferably 4000mg/L or more, further preferably 8000mg/L or more, further preferably 16000mg/L or moreMore preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, and further preferably 60000mg/L or more.

As SO in wastewater from the production of said catalyst₄ ^2-May be 1000mg/L or more, preferably 2000mg/L or more, more preferably 4000mg/L or more, further preferably 8000mg/L or more, further preferably 16000mg/L or more, further preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, further preferably 60000mg/L or more, further preferably 70000mg/L or more.

As Cl in the catalyst production wastewater^-May be 970mg/L or more, more preferably 2000mg/L or more, further preferably 4000mg/L or more, further preferably 8000mg/L or more, further preferably 16000mg/L or more, further preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, further preferably 60000mg/L or more.

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

From the viewpoint of improving the efficiency of the first evaporation and reducing the energy consumption of the treatment process, the amount of SO contained in the wastewater is relatively small₄ ^2-Cl in catalyst production wastewater^-The lower the content, the better, for example, relative to 1 mole of SO contained in the catalyst production wastewater₄ ^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 the catalyst production wastewater is 1 mole per mole of the catalyst production wastewaterSO contained in₄ ^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 6 mol. By adding SO contained in the catalyst production wastewater₄ ^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 NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺In addition, it may contain Mg²⁺、Ca²⁺、K⁺、Fe³⁺Inorganic salt ions such as rare earth element ions, Mg²⁺、Ca²⁺、K⁺、Fe³⁺The content of each inorganic salt ion such as a rare earth element ion is preferably 100mg/L or less, more preferably 50mg/L or less, further preferably 10mg/L or less, and particularly preferably no other inorganic salt ion is contained. By controlling the other inorganic salt ions within the above range, the purity of the sodium 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 1600mg/L or more, preferably 4000mg/L or more, more preferably 8000mg/L or more, further preferably 16000mg/L or more, further preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, further preferably 60000mg/L or more, further preferably 100000mg/L or more, further preferably 150000mg/L or more, further preferably 200000mg/L or more.

In the invention, the pH value of the catalyst production wastewater is preferably 4-8, and more preferably 6.3-6.8.

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, any one of a strongly acidic cation resin and a weakly acidic cation resin can be used; as the oxidation, various oxidizing agents conventionally used in the art, such as ozone, hydrogen peroxide, and potassium permanganate, can be used, and in order to avoid introduction of new impurities, ozone, hydrogen peroxide, and the like are preferably used.

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

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

In a preferred embodiment of the invention, the 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 0.5-4 h.

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

The conditions for the weak acid cation exchange method are preferably: the pH value range is 6.5-7.5; temperature is less than or equal to 40 ℃, treeThe height of the lipid layer is 1.5 m-3.0 m, the HCl concentration of the regeneration liquid is as follows: 4.5-5 mass%; the amount of the regenerant (calculated by 100%) was 50kg/m³～60kg/m³Wet resin; the flow rate of the regeneration liquid HCl is 4.5 m/h-5.5 m/h, and the regeneration contact time is 35 min-45 min; the forward washing flow rate is 18 m/h-22 m/h, and the forward washing time is 20 min-30 min; the running flow rate is 15 m/h-30 m/h; as the acidic cation exchange resin, for example, there can be used a Gallery Senno chemical Co., Ltd, SNT brand D113 acidic cation exchange resin.

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

The conditions for the concentration of the ED membrane are preferably: the current 145A to 155A and the voltage 45V to 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 5.4MPa to 5.6MPa, the water inlet temperature is 25 ℃ to 35 ℃, and the pH value is 6.5 to 7.5. The reverse osmosis membrane is, for example, a seawater desalination membrane TM810C manufactured by Dongli corporation of Lanxingdong.

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

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

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

Example 1

As shown in FIG. 1, the catalyst production wastewater (containing NaCl 45g/L, Na)₂SO₄ 88g/L、NH₄Cl42g/L、(NH₄)₂SO₄83.49g/L, pH 6.3) by means of a fifth circulation pump 75 at a feed rate of 5m³The reaction mixture was fed into a line of a treatment system at a rate of/h, an aqueous sodium hydroxide solution having a concentration of 45.16 mass% was introduced into the line to adjust the pH value for the first time, the adjusted pH value was monitored by a first pH measuring device 61(pH meter) (measurement value: 7.4), and a part (4.7 m) of the catalyst production wastewater having been adjusted by the first pH value was treated³H) sending the wastewater to a second heat exchange device 32 (a duplex stainless steel plate type heat exchanger) to perform heat exchange with the recovered first ammonia water to heat the catalyst production wastewater to 99 ℃, sending the rest of the wastewater to a first heat exchange device 31 (a plastic heat exchanger) to perform heat exchange with the recovered second ammonia water to heat the catalyst production wastewater to 70 ℃, then combining the two parts of the catalyst production wastewater, and mixing the combined wastewater with a second mother liquor to obtain wastewater to be treated (SO contained in the wastewater is measured) to obtain₄ ^2-And Cl^-In a molar ratio of 1: 4.199), introducing a 45.16 mass% aqueous sodium hydroxide solution into the pipeline fed into the first multi-effect evaporation device 2 again to adjust the pH value, monitoring the adjusted pH value by a pH value measuring device 62(pH meter) (the measured value is 11), and feeding into the first multi-effect evaporation device 2 (each effect is a forced circulation evaporator) to evaporate, so as to obtain a first concentrated solution containing ammonia vapor and sodium sulfate crystals. Wherein, the evaporation conditions of the first multi-effect evaporation device 2 are as shown in the following table 1. Specifically, the wastewater to be treated is sequentially introduced into a first effect evaporator 2a, a second effect evaporator 2b, a third effect evaporator 2c and a fourth effect evaporator 2d of a first multi-effect evaporation device 2, and the former effect evaporation is carried outThe first ammonia-containing steam obtained by evaporation of the evaporator is subjected to heat exchange in the later-effect evaporator to obtain first ammonia water, and the first ammonia water obtained by each-effect evaporator is subjected to heat exchange with the catalyst production wastewater in the second heat exchange device 32 and then stored in the first ammonia water storage tank 53. And (3) introducing heating steam into the first-effect evaporator 2a, performing heat exchange to obtain condensate, wherein the condensate is used for preparing a washing solution after preheating the first mother liquor which is sent into the first-effect evaporator 1a of the second multi-effect evaporation device 1. The degree of the first evaporation is monitored by a densimeter provided on the first multi-effect evaporation device 2, and the concentration of the sodium chloride in the first concentrated solution is controlled to be 0.9935X (i.e., 305.8 g/L). After the wastewater to be treated is evaporated in the first multi-effect evaporation device 2, the first concentrated solution containing sodium sulfate crystals obtained finally undergoes first crystallization (crystallization temperature is 100 ℃, crystallization time is 5min) in the first crystal liquid collecting tank 54 to obtain crystal slurry containing sodium sulfate crystals.

The resulting slurry containing sodium sulfate crystals was fed to a first solid-liquid separation apparatus 91 (centrifuge) to carry out a first solid-liquid separation, whereby 7.13m per hour was obtained³Contains NaCl 305.8g/L, Na₂SO₄53.84g/L、NaOH 2.2g/L、NH₃0.48g/L of first mother liquor is temporarily stored in a first mother liquor tank 51, sodium sulfate solid obtained by solid-liquid separation (1034.79 kg of sodium sulfate crystal filter cake containing 14 mass% of water is obtained per hour, wherein the content of sodium chloride is less than 3.8 mass%) is eluted by 54g/L of sodium sulfate solution which is equal to the dry basis mass of the sodium sulfate crystal filter cake, 889.9kg of sodium sulfate (the purity is 99.4 weight%) is obtained per hour after drying, and the eluate is circulated by a second circulating pump 72 until the pH value is adjusted for the second time, and then enters the first multi-effect evaporation device 2 again for first evaporation.

The second evaporation process is carried out in a second multi-effect evaporation plant 1 (each effect is a forced circulation evaporator). And (3) sequentially sending the first mother liquor in the first mother liquor tank 51 to each effect evaporator of the second multi-effect evaporation device 1 through a first circulating pump 71 for second evaporation to obtain a second concentrated solution containing sodium chloride crystals. Wherein, the evaporation conditions of the second multi-effect evaporation device 1 are shown in the following table 1. Specifically, the first mother liquor is sequentially introduced into a first effect evaporator 1a, a second effect evaporator 1b and a third effect evaporator 1c of a second multi-effect evaporation device 1; introducing second ammonia-containing steam obtained by evaporation in the first-effect evaporator 1a into a second-effect evaporator 1b for heat exchange to obtain second ammonia water; and introducing second ammonia-containing steam obtained by evaporation in the second-effect evaporator 1b into a third-effect evaporator 1c for heat exchange to obtain second ammonia water. The second ammonia-containing steam obtained by evaporation in the third effect evaporator 1c exchanges heat with the catalyst production wastewater in a third heat exchange device 33 to obtain second ammonia water. And after the second ammonia water obtained by each effect of evaporator exchanges heat with the wastewater to be treated in the first heat exchange device 31, the second ammonia water is collected with the second ammonia water obtained by the third heat exchange device 33 and stored in a second ammonia water storage tank 52. The degree of the second evaporation is monitored by a densimeter provided on the first multi-effect evaporation device 2, and the concentration of sodium sulfate in the second concentrated solution is controlled to be 0.9701Y (i.e. 65 g/L). After the first mother liquor is evaporated in the second multi-effect evaporation device 1, the finally obtained second concentrated solution containing sodium chloride crystals is subjected to second crystallization (crystallization temperature is 50 ℃, crystallization time is 30min) in a second crystal liquid collecting tank 55 to obtain crystal slurry containing sodium chloride crystals.

Sending the crystal mush containing sodium chloride crystals into a second solid-liquid separation device 92 (centrifugal machine) for solid-liquid separation to obtain 5.94m per hour³Contains 293.3g/L, Na NaCl₂SO₄ 65g/L、NaOH 2.66g/L、NH₃0.023g/L of second mother liquor. The second mother liquor is circulated to a wastewater introduction pipeline through a seventh circulating pump 77 and is mixed with the catalyst production wastewater to obtain wastewater to be treated. Sodium chloride solid obtained by the second solid-liquid separation (533.87 kg of sodium chloride crystal cake with a water content of 15 mass% is obtained per hour, wherein the content of sodium sulfate is below 4.0 mass%) is subjected to leaching and washing by using 293g/L sodium chloride solution with the same dry mass as sodium chloride, the sodium chloride is dried in a drier, 453.78kg of sodium chloride (with a purity of 99.4 wt%) is obtained per hour, and the washing liquid is circulated to the second multi-effect evaporation device 1 through a sixth circulating pump 76 to be subjected to second evaporation again.

In this example, 4.70m of ammonia water having a concentration of 3.5 mass% was obtained per hour in the first ammonia water tank 53³The second ammonia water tank 52 receives ammonia water 1 having a concentration of 0.255 mass% per hour.30m³The ammonia water can be reused in the production process of the molecular sieve.

In addition, the tail gas discharged by the third heat exchange device 33 is introduced into the tail gas absorption tower 83 through the 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 the circulating water tank 82 through the 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.

TABLE 1

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 108g/L, Na₂SO₄ 100g/L、NH₄Cl 21g/L、(NH₄)₂SO₄19.76g/L, pH of 6.6 to obtain SO contained in the wastewater to be treated₄ ^2-And Cl^-In a molar ratio of 1: 6.371. the evaporation conditions of the first and second

multi-effect evaporation devices

2 and 1 are shown in table 2 below.

The first solid-liquid separation device 91 obtained 704.76kg of a sodium sulfate crystal cake containing 14 mass% of water per hour, and finally obtained 606.1kg of sodium sulfate (purity: 99.5 wt%) per hour; obtained 9.82m per hour³The concentration of NaCl is 305.6g/L, Na₂SO₄55.15g/L、NaOH 1.15g/L、NH₃0.119g/L of the first mother liquor.

The second solid-liquid separation device 92 obtained 770.66kg of sodium chloride crystal cake with a water content of 15 mass% per hour, and finally 655.05kg of sodium chloride (purity 99.4 wt%) per hour; 8.02m per hour³The concentration of NaCl is 292.6g/L, Na₂SO₄67.4g/L、NaOH 1.41g/L、NH₃0.0087g/L of second mother liquor.

In this example, 3.61m of ammonia water having a concentration of 1.57 mass% was obtained per hour in the first ammonia water tank 53³1.90m of ammonia water having a concentration of 0.058 mass% is obtained per hour in the second ammonia water tank 52³The ammonia water can be reused in the production process of the molecular sieve.

TABLE 2

Example 3

for NaCl-containing 160g/L, Na₂SO₄70g/L、NH₄Cl 30g/L、(NH₄)₂SO₄13.34g/L, pH of 6.8 catalyst production wastewater to obtain SO contained in wastewater to be treated₄ ^2-And Cl^-In a molar ratio of 1: 8.976.

the first solid-liquid separation device 91 obtained 494.65kg of sodium sulfate crystal cake containing 15 mass% of water per hour, and finally obtained 420.45kg of sodium sulfate (purity 99.4 wt%); obtained at 13.80m per hour³The concentration of NaCl is 306.4g/L, Na₂SO₄52.53g/L、NaOH 2.64g/L、NH₃0.0933g/L of the first mother liquor.

The second solid-liquid separation device 92 obtained 1135.71kg of sodium chloride crystal cake with a water content of 15 mass% per hour, and finally 965.35kg of sodium chloride (purity 99.6 wt%) per hour; yield 11.14m per hour³The concentration of NaCl is 292.9g/L, Na₂SO₄ 64.9g/L、NaOH 3.26g/L、NH₃0.0058g/L of the second mother liquor.

In this example, 2.72m of ammonia water having a concentration of 2.28 mass% was obtained per hour in the first ammonia water tank 53³2.8m of ammonia water having a concentration of 0.044% by mass per hour was obtained in the second ammonia water tank 52³The ammonia water can be reused in the production process of the molecular sieve.

In addition, unlike embodiment 1, a part of the fresh steam is replenished in the first effect evaporator 1a of the second multi-effect evaporation apparatus 1.

TABLE 3

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

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

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

Claims

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

1) introducing the wastewater to be treated into each effect evaporator of a first multi-effect evaporation device for first evaporation to obtain first ammonia-containing steam and first concentrated solution containing sodium sulfate crystals;

before the wastewater to be treated is introduced into a first multi-effect evaporation device, adjusting the pH value of the wastewater to be treated to be more than 9;

the first evaporation prevents sodium chloride from crystallizing out, and the second evaporation prevents sodium sulfate from crystallizing out; the conditions of the first evaporation include: the temperature is above 45 ℃ and the pressure is above-95 kPa; the conditions of the second evaporation may include: the temperature is 30-96 ℃, and the pressure is-98 kPa-34 kPa;

relative to 1 mole of SO contained in the wastewater to be treated₄ ^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, and NH in the catalyst production wastewater₄ ⁺Is more than 8mg/L, SO₄ ^2-Over 1000mg/L, Cl^-Over 970mg/L of Na⁺Is more than 510 mg/L.

2. The method according to claim 1, wherein the SO contained in the wastewater to be treated is 1 mole relative to the SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-Is 13.8 mol or less.

3. The method as recited in claim 1, wherein the pH of the wastewater to be treated is adjusted to be greater than 10.8 prior to passing the wastewater to be treated to the first multi-effect evaporation device.

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 first ammonia-containing steam obtained by evaporation in a previous evaporator of the first multi-effect evaporation device is introduced into a next evaporator for heat exchange to obtain first ammonia water, and second ammonia-containing steam obtained by evaporation in a previous evaporator of the second multi-effect evaporation device is introduced into a next evaporator for heat exchange to obtain second ammonia water.

6. The method of claim 5, wherein the first ammonia-containing vapor obtained by evaporation in the last evaporator of the first multi-effect evaporation device is passed into the first evaporator of the second multi-effect evaporation device for heat exchange to obtain the second ammonia water.

7. The method of claim 1, wherein the first evaporation is performed such that the concentration of sodium chloride in the first concentrated solution is X or less, wherein 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;

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

8. The process of claim 7, wherein the first evaporation provides a concentration of sodium chloride in the first concentrate of 0.95X to 0.999X.

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

10. The method of any one of claims 1-9, 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 96-151 ℃, and the pressure is-34 kPa-303 kPa.

14. The method of any one of claims 1-9, wherein the conditions of the second evaporation comprise: the temperature is 35-85 ℃, and the pressure is-97.5 kPa to-85 kPa.

15. The method of claim 14, wherein the conditions of the second evaporation comprise: the temperature is 46-85 ℃, and the pressure is-95 kPa-85 kPa.

16. The method of claim 15, wherein the conditions of the second evaporation comprise: the temperature is 46-60 ℃, and the pressure is-95 kPa to-87 kPa.

17. The method of claim 16, wherein the conditions of the second evaporation comprise: the temperature is 46-51 ℃, and the pressure is-95 kPa to-92 kPa.

18. The method of claim 1, wherein the first and second multi-effect evaporation devices are each 2 or more effects.

19. The method of claim 18, wherein the first and second multi-effect evaporation devices are each 3-5 effects.

20. The method of claim 1, wherein the wastewater to be treated is subjected to a first heat exchange with a first ammonia and/or a second ammonia prior to passing the wastewater to be treated to a first multi-effect evaporation device.

21. The method as claimed in claim 20, wherein the pH of the wastewater to be treated is adjusted to be greater than 7 before the first heat exchange.

22. The method of claim 1, wherein the second ammonia-containing vapor obtained at the last one-effect evaporator of the second multi-effect evaporation device is subjected to a second heat exchange and a second ammonia water is obtained.

23. The method of claim 22, wherein the second ammonia-containing vapor evaporated by the last evaporator of the second multi-effect evaporator is discharged after ammonia removal from the tail gas condensed by the third heat exchange.

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

25. The method of claim 24, further comprising washing the resulting sodium sulfate crystals.

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

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

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

29. The method of claim 28, further comprising removing impurities and concentrating the catalyst process wastewater.