CN108726757B

CN108726757B - Treatment method of catalyst production wastewater

Info

Publication number: CN108726757B
Application number: CN201710263275.8A
Authority: CN
Inventors: 殷喜平; 李叶; 顾松园; 王涛; 刘志坚; 陈玉华; 高晋爱; 安涛; 杨凌; 苑志伟; 王生吉; 伊红亮; 刘夫足
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: 2021-10-01
Anticipated expiration: 2037-04-21
Also published as: CN108726757A

Abstract

The invention relates to the field of sewage treatment, and discloses a method for treating catalyst production wastewater, wherein the wastewater contains NH₄ ⁺、SO₄ ^2‑、Cl^‑And Na⁺Introducing 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 a first concentrated solution containing sodium chloride 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 chloride 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 concentrated solution containing second ammonia vapor and sodium sulfate crystals; 3) and carrying out second solid-liquid separation on the second concentrated solution containing the sodium sulfate crystals. The method can respectively recover the ammonium, the sodium sulfate and the sodium chloride in the wastewater, and furthest recycle resources in the wastewater.

Description

Treatment method of catalyst production wastewater

Technical Field

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

Background

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

In addition, the biochemical deamination can only treat wastewater with low ammonium content, and can not directly carry out biochemical treatment due to insufficient COD content in the catalyst sewage, and organic matters such as glucose or starch and the like are additionally added in the biochemical treatment process, so that the ammoniacal nitrogen can be treated by the biochemical method. The most important problem is that the total nitrogen of the wastewater after the biochemical deamination treatment is not up to the standard (the contents of nitrate ions and nitrite ions exceed the standard), the wastewater needs to be deeply treated, 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 catalyst has high treatment cost of wastewater and can only obtain mixed salt crystals, and provides a low-cost and environment-friendly NH-containing catalyst₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The method for treating the catalyst production wastewater can respectively recover the ammonium, the sodium chloride and the sodium sulfate in the catalyst production wastewater, and furthest recycle resources in the catalyst production 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 ammonia-containing steam and a first concentrated solution containing sodium chloride 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 chloride 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 concentrated solution containing second ammonia vapor and sodium sulfate crystals;

3) carrying out second solid-liquid separation on the second concentrated solution containing the 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 the crystallization of sodium sulfate, and the second evaporation prevents the crystallization of sodium chloride; relative to 1 mole of SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-9.5 mol or more.

By the technical scheme, the method aims at the content of NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The pH value of the wastewater is adjusted to a specific range in advance, then the wastewater is evaporated and separated by using a first multi-effect evaporation device to obtain sodium chloride crystals and stronger ammonia water, and then the wastewater is evaporated again by using a second multi-effect evaporation device to obtain sodium sulfate crystals and thinner ammonia water. The method can respectively obtain high-purity sodium chloride and sodium sulfate, avoids the difficulty in the processes of mixed salt treatment and recycling, simultaneously completes the process of separating ammonia and salt, simultaneously heats the wastewater and cools the ammonia-containing steam by adopting a heat exchange mode 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, respectively recovers the sodium sulfate and the sodium chloride in the form of crystals, does not generate waste residues and waste liquid in the whole process, and achieves the purpose of changing waste into valuable.

The second evaporation is carried out by using the multi-effect evaporation device, so that the second evaporation can be carried out at different temperatures, firstly at a higher temperature, the evaporation efficiency is improved, and finally at a lower temperature, the energy consumption is reduced.

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

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

33. Third heat exchange device 51 and first ammonia water storage tank

52. Second ammonia storage tank 53 and second crystal liquid tank

54. First mother liquor tank 55 and first crystal liquid tank

56. Second mother liquor tank 61 and first pH value measuring device

62. Second 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 ammonia-containing steam and a first concentrated solution containing sodium chloride 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 chloride 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 concentrated solution containing second ammonia vapor and sodium sulfate 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 the crystallization of sodium sulfate, and the second evaporation prevents the crystallization of sodium chloride; relative to 1 mole of SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-9.5 mol or more.

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

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

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

Preferably, the pH 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⁺Is treated except for containing NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺In addition, the wastewater to be treated is not particularly limited. From the viewpoint of improving the treatment efficiency of wastewater1 mol of SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-The amount of the catalyst is 10 mol or more, preferably 50 mol or less, more preferably 40 mol or less, further preferably 30 mol or less, and for example, may be 10 to 20 mol, preferably 10 to 15 mol, more preferably 11 to 12 mol. By reacting SO₄ ^2-And Cl^-The molar ratio of (a) to (b) is controlled within the above range, and sodium chloride can be precipitated without precipitating sodium sulfate in the first evaporation, thereby achieving the purpose of efficiently separating sodium chloride. 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 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 first 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 solid-liquid separation is different, the sodium sulfate content in the sodium chloride crystals obtained is usually 8 mass% or less (preferably 4 mass%), and in the present invention, it is considered that the sodium sulfate does not crystallize out when the sodium sulfate content in the sodium chloride crystals obtained is 8 mass% or less.

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

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

In the present invention, the 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. Wherein, the first evaporation and the second evaporation both adopt a concurrent feeding mode preferably.

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.

In a preferred embodiment of the invention, the first evaporation and the second evaporation are carried out in a concurrent feeding mode, namely, the wastewater to be treated is sequentially fed into the effect evaporators of the first multi-effect evaporation device 2, and the liquid phase obtained by the first solid-liquid separation is sequentially fed into the effect evaporators of the second multi-effect evaporation device 1. Preferably, the first ammonia-containing steam obtained by evaporation in the former evaporator of the first multi-effect evaporation device 2 is introduced into the latter evaporator, and the second ammonia-containing steam obtained by evaporation in the former evaporator of the second multi-effect evaporation device 1 is introduced into the latter evaporator. Heating steam can be introduced into the first-effect evaporator 2a of the first multi-effect evaporation device 2 and the first-effect evaporator 1a of the second multi-effect evaporation device 1, and condensation liquid obtained after the heating steam is condensed in the first-effect evaporator 2a and the first-effect evaporator 1a 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 and a third effect evaporator 2c of a first multi-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, a third effect evaporator 1c and a fourth effect evaporator 1d 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 and the first effect evaporator 1a of the second multi-effect evaporation device 1. 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 subsequent effect evaporator to obtain first ammonia water, the first ammonia water obtained by evaporation of each effect evaporator is collected, and the first ammonia water is optionally stored in a first ammonia water storage tank 51 after exchanging heat with the wastewater to be treated in the first heat exchange device 31. In the second multi-effect evaporation device 1, the second ammonia-containing steam obtained by evaporation in the former evaporator exchanges heat in the latter evaporator to obtain second ammonia water, and the second ammonia water obtained in each 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 second ammonia water storage tank 52.

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 chloride may be crystallized without precipitating sodium sulfate. To improve the efficiency of evaporation, the conditions of the first evaporation may include: the temperature is 30-130 ℃, and the pressure is-98 kPa-117 kPa. In order to improve evaporation efficiency, preferably, the conditions of the first evaporation include: the temperature is 35 to 95 ℃, and the pressure is-98 kPa to-37 kPa; preferably, the conditions of the first evaporation include: the temperature is 46-95 ℃, and the pressure is-95 kPa to-37 kPa; preferably, the conditions of the first evaporation include: the temperature is 46-51 ℃, and the pressure is-95 kPa to-92 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 evaporation process, the difference of the evaporation temperature of two adjacent evaporator 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 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 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 vapor-containing condensate obtained in the first effect evaporator and/or the second effect evaporator can be collected separately, namely, the ammonia vapor-containing condensate obtained in the second effect evaporator and/or the third effect evaporator can be collected. The ammonia water generated by the first effect evaporator and the second effect evaporator can be collected independently or in a converging way according to the requirement. 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 does not crystallize sodium sulfate in the wastewater to be treated (i.e., sodium sulfate is not supersaturated), and from the viewpoint of precipitating sodium chloride as much as possible without precipitating sodium sulfate, the first evaporation preferably makes the concentration of sodium sulfate in the first concentrated solution be Y or less (preferably 0.9Y to 0.99Y, more preferably 0.95Y to 0.98Y), where Y is the concentration of sodium sulfate at which both sodium chloride and sodium sulfate in the first concentrated solution are saturated under the conditions of the first evaporation. By controlling the degree of the first 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 first evaporation as much as possible, the wastewater treatment efficiency can be improved, and the energy waste can be reduced.

In the present invention, the degree of progress of the first evaporation is performed by monitoring the concentration of the first evaporation-yielded liquid, specifically, by controlling the concentration of the first evaporation-yielded liquid within the above range, so that the first evaporation does not cause crystallization of sodium sulfate in the wastewater to be treated. The concentration of the liquid resulting from the first evaporation is monitored by measuring the density, which may be carried out using a densitometer.

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 a preferred embodiment of the present invention, before the wastewater to be treated is passed into the first multi-effect evaporation device 2, the first ammonia-containing steam and the wastewater to be treated are subjected to first heat exchange to obtain first ammonia water. The first heat exchange method is not particularly limited, and may be performed by a heat exchange method that is conventional in the art. The number of heat exchanges may be one or more, preferably 2 to 4, more preferably 2 to 3, and particularly preferably 2. Through first heat exchange, the aqueous ammonia of output is further cooled off, and the heat furthest has rationally utilized the energy at processing apparatus inner loop, has reduced the waste.

According to a preferred embodiment of the present invention, the first heat exchange is performed by a first heat exchange device 31 and a second heat exchange device 32, and specifically, the first ammonia water obtained from the first multi-effect evaporation device 2 is passed through the first heat exchange device 31, the second ammonia water obtained from the second multi-effect evaporation device 1 is passed through the second heat exchange device 32, and simultaneously, a part of the wastewater to be treated is passed through the first heat exchange device 31, and another part is passed through the second heat exchange device 32. Through first heat exchange, make pending waste water intensification is convenient for evaporate, makes the aqueous ammonia cooling simultaneously, first aqueous ammonia can be stored in first aqueous ammonia storage tank 51, the second aqueous ammonia can be stored in second aqueous ammonia storage tank 52.

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

According to the present invention, in order to fully utilize the heat energy of the first ammonia-containing vapor condensate (the first ammonia water having a relatively high temperature), it is preferable that the temperature of the wastewater to be treated is 29 to 84 ℃, more preferably 39 to 59 ℃, and still more preferably 44 to 59 ℃ after the first heat exchange.

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 first pH adjustment is performed by introducing and mixing the aqueous solution containing the alkaline substance in the pipe for feeding the catalyst production wastewater to the first heat exchange apparatus 31 or the second heat exchange apparatus 32 before feeding the catalyst production wastewater to the first heat exchange apparatus 31 or the second heat exchange apparatus 32 for the first heat exchange; and then mixing the catalyst production wastewater with at least part of the second mother liquor to obtain wastewater to be treated, introducing the aqueous solution containing alkaline substances into a pipeline for feeding the wastewater to be treated into the first multi-effect evaporation device 2, and mixing to perform secondary pH value adjustment. And (3) adjusting the pH value twice to ensure that the pH value of the wastewater to be treated is more than 9, preferably more than 10.8 before the wastewater is introduced into the first multi-effect evaporation device 2. Preferably, the first pH adjustment is carried out to enable the pH value of the adjusted wastewater to be treated to be more than 7 (preferably 7-9), and the second pH adjustment is carried out to enable the pH value to be more than 9, preferably more than 10.8.

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

According to the invention, the method can further comprise a first crystallization, and the first concentrated solution containing sodium chloride crystals is subjected to the first crystallization in the first crystallization device to obtain a crystal slurry containing sodium chloride crystals. The first crystallization apparatus 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 a first liquid crystal tank 55. According to the invention, the crystallization of the first concentrated solution containing sodium chloride crystals can also be carried out in a first multi-effect evaporator with a crystallizer, such as a forced circulation evaporator crystallizer, in which case 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 sulfate in the sodium chloride crystal-containing crystal slurry (i.e., sodium chloride does not reach supersaturation), and preferably, the first evaporation is performed so that the concentration of sodium sulfate in the first concentrated solution is 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 which both sodium chloride and sodium sulfate in the first concentrated solution reach saturation under the conditions of the first crystallization.

According to the present invention, the conditions for the first crystallization may be appropriately selected, 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 first crystallization is not higher than the temperature of the first evaporation, preferably the temperature of the first crystallization is 0 to 10 ℃ lower than the temperature of the first evaporation, more preferably 1 to 5 ℃ lower.

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

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

According to the present invention, the solid-liquid separation of the first concentrated solution may be performed by using a first solid-liquid separation device (for example, a centrifuge, a belt filter, a plate filter, or the like) 91. After the solid-liquid separation, the first mother liquor obtained by the first solid-liquid separation device 91 is temporarily stored in the first mother liquor tank 54, and can be sent to the second multi-effect evaporation device 1 through the fifth circulation pump 75 to be subjected to the second evaporation. In addition, it is difficult to avoid that the obtained sodium chloride crystals adsorb certain impurities such as chloride ions, free ammonia, hydroxide ions, etc., and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals, it is preferable that the sodium chloride crystals are first washed with water, the catalyst production wastewater, or a sodium chloride solution and dried.

Preferably, the first wash comprises panning and/or rinsing. In addition, the first washing liquid obtained in the above washing process is preferably returned to the pH adjustment stage before the first evaporation by the second circulation pump 72, and for example, the first washing liquid may be returned to the wastewater introduction line before the pH adjustment stage before the first evaporation by the second circulation pump 72, mixed with the wastewater to be treated, subjected to the second pH adjustment, and then sent to the first multi-effect evaporation apparatus 2 to be evaporated.

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 chloride crystals of higher purity. In the elutriation process, the waste water produced by the catalyst is generally not recycled when used as an elutriation liquid, and the washing liquid recovered by the first washing can be recycled in a counter-current manner when used as the elutriation liquid. Before the elutriation, 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 performed using an aqueous sodium chloride solution. Preferably, the concentration of the sodium chloride aqueous solution is the concentration of sodium chloride in the aqueous solution that is saturated at the same time with sodium sulfate at the temperature corresponding to the sodium chloride crystals to be washed. In order to further enhance the elutriation effect and obtain sodium chloride crystals with higher purity, the liquid obtained by rinsing may be preferably used for washing, and water or a sodium chloride solution is preferably used. The liquid 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, after the first concentrated solution containing sodium chloride obtained by evaporation in the first multi-effect evaporator 2 (optionally, after the first crystallization to obtain a magma containing sodium chloride crystals), is subjected to a preliminary solid-liquid separation by settling, the catalyst production wastewater is subjected to a first elutriation in an elutriation tank, and then the liquid obtained when sodium chloride crystals are subsequently washed is subjected to a second elutriation in another elutriation tank, and 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 washed with an aqueous sodium chloride solution, and the liquid obtained by the washing is returned to the second elutriation. Through the washing process, the purity of the obtained sodium chloride crystal is improved, washing liquid is not excessively introduced, and the efficiency of wastewater treatment is improved.

In the present invention, the respective evaporators of the multi-effect evaporation apparatus 1 are not particularly limited, and may be composed of various evaporators conventionally used in the art. For example, it may be selected from one or more of falling film type evaporator, rising film type evaporator, scraped surface evaporator, central circulation tube type multi-effect evaporator, basket type evaporator, external heating type evaporator, forced circulation type evaporator and Leveng type evaporator. Among them, a forced circulation evaporator and an external heating evaporator are preferable. The respective evaporators of the multi-effect evaporation apparatus 1 are composed of a heating chamber and an evaporation chamber, and may further include other evaporation auxiliary components 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 multi-effect evaporation apparatus 1 is not particularly limited, and may be 2 or more, preferably 2 to 5, and more preferably 3 to 5.

In the present invention, the evaporation conditions of the second evaporation may be appropriately selected as needed, and the purpose of crystallizing sodium sulfate without precipitating sodium chloride may be achieved. The conditions of the second evaporation may include: the temperature is above 45 ℃ and the pressure is above-95 kPa. In order to improve evaporation efficiency, preferably, the conditions of the second evaporation include: the temperature is above 45 ℃ and the pressure is above-95 kPa; preferably, the conditions of the second evaporation include: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa; preferably, the conditions of the second evaporation include: the temperature is 60-365 ℃, and the pressure is-87 kPa-18110 kPa; preferably, the conditions of the second evaporation include: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa; preferably, the conditions of the second evaporation include: the temperature is 97-145 ℃, and the pressure is-32 kPa-240 kPa; preferably, the conditions of the second evaporation include: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa; preferably, the conditions of the second evaporation include: the temperature is 97-115 ℃, and the pressure is-32 kPa-33 kPa; preferably, the conditions of the second evaporation include: the temperature is 97-106 ℃, and the pressure is-32 kPa to-3 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.

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～500m³H). By carrying out the second evaporation under the above conditions, the sodium chloride is not crystallized while the crystallization of sodium sulfate is ensured, so that the purity of the obtained sodium sulfate crystal can be ensured.

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

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

According to the present invention, the second evaporation does not crystallize sodium chloride in the wastewater to be treated (i.e., sodium chloride is not supersaturated), and from the viewpoint of precipitating sodium sulfate as much as possible without precipitating sodium chloride, the second evaporation preferably makes the concentration of sodium chloride in the second concentrated solution X (preferably 0.999X or less, more preferably 0.95X to 0.999X, and still more preferably 0.99X to 0.9967X), where X is the concentration of sodium chloride when both sodium chloride and sodium sulfate 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 sulfate as possible can be crystallized out under the condition that sodium chloride is not precipitated out. By crystallizing sodium sulfate in the second evaporation as much as possible, the wastewater treatment efficiency can be improved, and the energy waste can be reduced.

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

According to a preferred embodiment of the invention, the second evaporation process is carried out in a multi-effect evaporation device 1. And introducing the first mother liquor into the multi-effect evaporation device 1 through a fifth circulating pump 75 to perform second evaporation to obtain second concentrated solution containing second ammonia-containing steam and sodium sulfate crystals.

According to the invention, the method can further comprise a second crystallization, and the magma containing sodium sulfate crystals is obtained after the second crystallization of the second concentrated solution containing sodium sulfate crystals in the second crystallization device. The second crystallization apparatus 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 preferred embodiment of the present invention, the second crystallization may be performed in a second crystallization tank 53. According to the invention, the crystallization of the second concentrated solution containing sodium sulfate crystals can also be carried out in a second 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 the crystallization is performed using a separate crystallization apparatus, it is necessary to further ensure that the second evaporation is performed so that sodium chloride in the sodium sulfate crystal-containing magma does not crystallize out (i.e., sodium chloride does not reach supersaturation), and the second evaporation is performed so that the concentration of sodium chloride in the second concentrated solution is X or less (preferably 0.999X or less, more preferably 0.95X to 0.999X, and still more preferably 0.99X to 0.9967X), where X is the concentration of sodium chloride at which 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, and may include, for example: the crystallization temperature is from 85 ℃ to 107 ℃, preferably from 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 second crystallization is not higher than the temperature of the second evaporation, preferably the temperature of the second crystallization is 0 to 10 ℃ lower than the temperature of the second evaporation, more preferably 0 to 5 ℃ lower. Preferably, the temperature of the second crystallization is the natural temperature of the second evaporated concentrate entering the crystallizer.

In the present invention, in order to prevent the sodium sulfate from crystallizing out by the first evaporation and prevent the sodium chloride from crystallizing out by the second evaporation, it is preferable that the conditions of the two-evaporation (crystallization conditions when crystallization is performed using a single crystallization device) satisfy: the temperature of the first evaporation is lower 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 chloride and sodium sulfate by controlling the first evaporation and the second evaporation to be carried out at different temperatures, so that the purity of the obtained sodium chloride and sodium sulfate crystals is improved.

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

According to the present invention, the second solid-liquid separation may be performed by a second solid-liquid separation device (e.g., a centrifuge, a belt filter, a plate filter, etc.) 92. After the second solid-liquid separation, the second mother liquor obtained by the second solid-liquid separation device 92 returns to the first multi-effect evaporation device 2 to perform the first evaporation again, and specifically, the second mother liquor can be returned to the second pH adjustment process by the seventh circulation pump 77 and then sent to the first multi-effect evaporation device 2. In addition, it is difficult to avoid that the obtained sodium sulfate crystals adsorb impurities such as sulfate ions, free ammonia, and hydroxide ions to some extent, and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals, it is preferable that the sodium sulfate crystals are subjected to secondary washing with water, the catalyst production wastewater, or a sodium sulfate solution and dried. In order to avoid the dissolution of sodium sulfate crystals during the washing, the sodium sulfate crystals are preferably washed with an aqueous sodium sulfate solution. More preferably, the concentration of the aqueous sodium sulfate solution is preferably such that the sodium sulfate and sodium chloride reach the concentration of sodium sulfate in the saturated aqueous solution at the same time at the temperature corresponding to the sodium sulfate crystals to be washed.

Preferably, the second wash comprises panning and/or rinsing. 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 sulfate crystals of higher purity. In the elutriation process, the catalyst production wastewater is generally not recycled when being used as an elutriation liquid, and the washing liquid recovered by the second washing can be recycled in a counter-current manner when being used as the elutriation liquid. Before the elutriation, it is preferable to perform 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 sulfate and sodium chloride reach the concentration of sodium sulfate in a 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. For the liquid produced by washing, it is preferable that the catalyst production wastewater elutriation liquid is returned to the multi-effect evaporation device 1 before the second pH adjustment before the first multi-effect evaporation device 2 evaporates, and other washing liquid is returned.

According to a preferred embodiment of the present invention, after the primary solid-liquid separation by settling, the crystal slurry containing sodium sulfate crystals obtained by the secondary crystallization is subjected to a first elutriation in an elutriation tank using the catalyst production wastewater, then the liquid obtained by the subsequent washing of the sodium sulfate crystals 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, the crystals obtained by the solid-liquid separation are subjected to a elution with 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 sulfate and sodium chloride 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 as an elutriation liquid. Through the washing process combining elutriation and leaching, the purity of the obtained sodium sulfate crystals is improved, washing liquid is not excessively introduced, and the efficiency of wastewater treatment is improved.

According to the invention, preferably, the first ammonia-containing steam obtained by the evaporation of the last evaporator of the first multi-effect evaporation device 2 is subjected to second heat exchange with cooling water in a fourth heat exchange device 34 to obtain first ammonia water; preferably, the second ammonia-containing steam obtained by the evaporation of the last evaporator of the second multi-effect evaporation device 1 is subjected to third heat exchange with cooling water in a 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 first pH value adjustment process).

In the present invention, the third heat exchanger 33 and the fourth heat exchanger 34 are not particularly limited, and various heat exchangers conventionally used in the art may be used to cool the ammonia-containing steam. Specifically, it may be a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, a spiral threaded tube heat exchanger, or the like. The material of the heat exchanger can be specifically selected according to the requirement, for example, the stainless steel spiral thread pipe heat exchanger is preferred because the secondary steam has no corrosivity to the stainless steel.

According to a preferred embodiment of the present invention, the tail gas left after the condensation of the first ammonia-containing steam by the second heat exchange is discharged after ammonia removal; and discharging the tail gas which is remained after the second ammonia-containing steam is condensed by the third heat exchange after ammonia removal. The first ammonia-containing steam is subjected to the first heat exchange to condense the remaining tail gas, i.e. the tail gas discharged from the fourth heat exchange device 34. And the second ammonia-containing steam is subjected to the third heat exchange to condense the remaining tail gas, namely the tail gas discharged by the third heat exchange device 33. 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 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.

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 preferablyMore preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, and 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. SO in the wastewater from the viewpoint of easy access to wastewater from catalyst production₄ ^2-、Cl^-And Na⁺The upper limit of (b) is 200g/L or less, preferably 150g/L or less, respectively; NH in wastewater₄ ⁺Is 100g/L or less, preferably 50g/L or less.

From the viewpoint of improving the efficiency of the first evaporation and reducing the energy consumption of the treatment process, the amount of SO contained in the wastewater is relatively small₄ ^2-Cl in catalyst production wastewater^-The higher the content, the better, for example, relative to 1 mole of SO contained in the ammonium salt-containing wastewater₄ ^2-Cl contained in the catalyst production wastewater^-Is 1 mole or more, preferably 2 moles or more, preferably 5 moles or more, more preferably 9.5 moles or more, and further preferably 10 moles or more. From the viewpoint of practicality, the amount of SO contained in the wastewater from the catalyst production is 1 mole₄ ^2-Cl contained in the catalyst production wastewater^-Preferably 200 moles or less, more preferably 150 moles or less, further preferably 100 moles or less, further preferably 50 moles or less, further preferably 30 moles or less, for example, 10 to 20 moles. By adding Cl contained in the catalyst production wastewater^-And SO₄ ^2-The molar ratio of (a) to (b) is limited to the above range, most of water can be evaporated in the first evaporation, the amount of circulating liquid in a treatment system is reduced, energy is saved, and the treatment process is more economical.

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

The TDS of the catalyst production wastewater may be 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 6.3-6.9.

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

In a preferred embodiment of the invention, the 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; the temperature is less than or equal to 40 ℃, the height of the resin layer is 1.5-3.0 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 sulfate in the first concentrated solution is close to the precipitation concentration, then the first concentrated solution is subjected to second evaporation to obtain a second concentrated solution, the second concentrated solution is subjected to solid-liquid separation to obtain sodium sulfate crystals and a second mother solution, the second mother solution is mixed with the catalyst production wastewater to adjust the ion content of the wastewater to be treated to be in the range required by the invention, and then the first evaporation is carried out to obtain sodium chloride crystals. Of course, Na may be used in the initial stage₂SO₄Or NaCl, as long as the ion content of the wastewater to be treated is adjusted SO that the wastewater to be treated satisfies SO in the wastewater to be treated in the invention₄ ^2-、Cl^-The requirements are met.

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

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

Example 1

As shown in FIG. 1, the catalyst production wastewater (containing NaCl 48g/L, Na)₂SO₄ 89g/L、NH₄Cl 45g/L、(NH₄)₂SO₄84.8g/L, pH 6.9) by means of the first circulation pump 71 at a feed rate of 5m³The velocity of/h is fed into the pipes of the treatment system, into which the concentrate is introducedThe aqueous sodium hydroxide solution having a concentration of 45.16 mass% was subjected to a first pH adjustment, the adjusted pH was monitored by a first pH measuring device 61(pH meter) (measurement value: 7.6), and a part (2 m) of the catalyst production wastewater (which had been subjected to the first pH adjustment) was treated³H) sending the wastewater to a first heat exchange device 31 (a plastic plate heat exchanger) to perform first heat exchange with the recovered first ammonia-containing steam condensate (namely first ammonia water) SO as to heat the catalyst production wastewater to 73 ℃, sending the rest of the wastewater to a second heat exchange device 32 (a duplex stainless steel plate heat exchanger) to perform first heat exchange with the recovered second ammonia-containing steam condensate (namely second ammonia water) SO as to heat the catalyst production wastewater to 98 ℃, then converging the two parts of the catalyst production wastewater, and mixing the converged wastewater with a second mother liquor to obtain wastewater to be treated (the SO contained in the wastewater is measured) to be mixed with the second mother liquor₄ ^2-And Cl^-In a molar ratio of 1: 11.159), introducing a sodium hydroxide aqueous solution with the concentration of 45.16 mass percent into a pipeline for feeding the wastewater to be treated into the first multi-effect evaporation device 2 to carry out secondary pH value adjustment, monitoring the adjusted pH value through a second pH value measuring device 62 (a pH meter) (the measured value is 10.8), feeding the wastewater to be treated after the second pH value adjustment into the first multi-effect evaporation device 2 to carry out evaporation, and obtaining first ammonia-containing steam and first concentrated solution containing sodium chloride crystals. The first multi-effect evaporation device 2 consists of a first effect evaporator 2a, a second effect evaporator 2b and a third effect evaporator 2c (all of which are forced circulation evaporators). And (3) feeding the wastewater to be treated into a first multi-effect evaporation device 2, introducing the wastewater to be treated into a second-effect evaporator 2b for evaporation after the wastewater to be treated is evaporated in a first-effect evaporator 2a, and introducing the wastewater to be treated into a third-effect evaporator 2c for evaporation to finally obtain a first concentrated solution containing sodium chloride crystals. Wherein the evaporation temperature of the first effect evaporator 2a is 95 ℃, the pressure is-36.36 kPa, and the evaporation capacity is 1.11m³H; the evaporation temperature of the second effect evaporator 2b is 75 ℃, the pressure is-72.74 kPa, and the evaporation capacity is 1.0m³H; the evaporation temperature of the third effect evaporator 2c is 51 ℃, the pressure is-92.3 kPa, and the evaporation capacity is 1.0m³H is used as the reference value. Heating steam is introduced into a first-effect evaporator 2a of the first multi-effect evaporation device 2, and condensation liquid obtained after the heating steam is condensed in the first-effect evaporator 2a is used forAnd (5) preparing a washing solution. Introducing first ammonia-containing steam obtained by evaporation in a first effect evaporator 2a of the first multi-effect evaporation device 2 into a second effect evaporator 2b for heat exchange to obtain first ammonia water, introducing first ammonia-containing steam obtained by evaporation in the second effect evaporator 2b into a third effect evaporator 2c for heat exchange to obtain first ammonia water, introducing first ammonia-containing steam obtained by evaporation in the third effect evaporator 2c into a fourth heat exchange device 34 for heat exchange with cooling water (catalyst production wastewater) to obtain first ammonia water, and combining the first ammonia water and storing the first ammonia water in a first ammonia water storage tank 51. The degree of the first evaporation is monitored by a densimeter arranged on the first multi-effect evaporation device 2, and the concentration of sodium sulfate in the first concentrated solution is controlled to be 0.9705Y (294.7 g/L). After the wastewater to be treated is evaporated in the first multi-effect evaporation device 2, the finally obtained first concentrated solution containing sodium chloride crystals is crystallized in the first crystal liquid tank 55 (the crystallization temperature is 50 ℃, and the crystallization time is 10min) to obtain crystal slurry containing sodium chloride crystals.

The above-mentioned crystal slurry containing sodium chloride crystals was fed to a first solid-liquid separation apparatus 91 (centrifuge) to conduct a first solid-liquid separation, and 66.18m was obtained per hour³Contains 294.7g/L, Na NaCl₂SO₄ 65.7g/L、NaOH 0.14g/L、NH₃0.109g/L of first mother liquor is temporarily stored in the first mother liquor tank 54, sodium chloride solid obtained by solid-liquid separation (568.76 kg of sodium chloride crystal filter cake containing 15 mass% of water is obtained every hour, wherein the content of sodium sulfate is less than 3.9 mass%) is leached by 294.7g/L of sodium chloride solution with the same dry basis mass as the sodium chloride crystal filter cake, 483.44kg of sodium chloride (with the purity of 99.6 weight%) is obtained every hour after drying, and the washing liquid is circulated to the first multi-effect evaporation device 2 through the second circulating pump 72 before the second pH value adjustment, 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 device 1, and the second multi-effect evaporation device 1 is composed of a first effect evaporator 1a, a second effect evaporator 1b, a third effect evaporator 1c and a fourth effect evaporator 1d (all of forced circulation evaporators). The first mother liquor in the first mother liquor tank 54 is sent to the second multi-effect evaporator 1 by a fifth circulating pump 75, and the first mother liquor is sent to the first multi-effect evaporator 1aAnd after evaporation, introducing the solution into a second-effect evaporator 1b for evaporation, introducing the solution into a third-effect evaporator 1c for evaporation, and introducing the solution into a fourth-effect evaporator 1d for evaporation to finally obtain a second concentrated solution containing sodium sulfate crystals. Wherein the evaporation temperature of the first effect evaporator 1a is 145 ℃, the pressure is 239.9kPa, and the evaporation capacity is 0.78m³H; the second effect evaporator 1b had an evaporation temperature of 130 deg.C, a pressure of 116.77kPa, and an evaporation capacity of 0.77m³H; the evaporation temperature of the third effect evaporator 1c is 115 ℃, the pressure is 32.56kPa, and the evaporation capacity is 0.77m³H; the fourth effect evaporator 1d has an evaporation temperature of 101 ℃, a pressure of-19.86 kPa and an evaporation capacity of 0.77m³H is used as the reference value. Introducing second ammonia-containing steam obtained by evaporation in a first effect evaporator 1a of the second multi-effect evaporation device 1 into a second effect evaporator 1b for heat exchange to obtain second ammonia water, 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, introducing second ammonia-containing steam obtained by evaporation in the third effect evaporator 1c into a fourth effect evaporator 1d for heat exchange to obtain second ammonia water, storing the second ammonia water obtained from the second effect evaporator 1b, the third effect evaporator 1c and the fourth effect evaporator 1d in a second ammonia water storage tank 52 after heat exchange with catalyst production wastewater through a second heat exchange device 32, and introducing second ammonia-containing steam obtained by evaporation in the fourth-effect evaporator 1d into a third heat exchange device 33 to exchange heat with cooling water (catalyst production wastewater) to obtain second ammonia water. Heating steam (namely raw steam conventionally used in the field) is introduced into the first-effect evaporator 1a, the heating steam is condensed in the first-effect evaporator 1a to obtain a condensate, and the condensate is used for preparing a washing solution after preheating the catalyst production wastewater entering the first-effect evaporator 2a of the first multi-effect evaporation device 2. The degree of the second evaporation is monitored by a densimeter provided on the second multi-effect evaporation apparatus 1, and the concentration of sodium chloride in the second concentrated solution is controlled to be 0.99353X (54.3 g/L). After the first mother liquor is evaporated in the second multi-effect evaporator 1, the finally obtained second concentrated solution containing sodium sulfate crystals is crystallized in the second crystal liquid tank 53 (the crystallization temperature is 100 ℃, and the crystallization time is 10min) to obtain crystal slurry containing sodium sulfate crystals.

Sodium sulfate-containing crystalsThe resulting slurry was fed into a second solid-liquid separation apparatus 92 (centrifuge) to conduct solid-liquid separation, thereby obtaining 63.39m per hour³Contains 307.1g/L, Na NaCl₂SO₄ 54.3g/L、NaOH 0.15g/L、NH₃0.0056g/L of second mother liquor is temporarily stored in the second mother liquor tank 56, the second mother liquor is circulated to a wastewater introduction pipeline through a seventh circulating pump 77 and mixed with the catalyst production wastewater to obtain wastewater to be treated, sodium sulfate solids obtained by solid-liquid separation (1050.9 kg of sodium sulfate crystal filter cake with a water content of 14 mass% per hour, wherein the sodium chloride content is below 4 mass%) are subjected to washing with 54g/L of sodium sulfate solution with a mass equal to the dry basis mass of sodium sulfate, and are dried in a dryer to obtain 903.78kg of sodium sulfate (with a purity of 99.4 wt%) per hour, and the washing liquor is circulated to the second multi-effect evaporation device 1 through a sixth circulating pump 76.

In addition, the tail gas discharged by the third heat exchange device 33 and the fourth heat exchange device 34 is introduced into a tail gas absorption tower 83 through a vacuum pump 81 for absorption, circulating water is introduced into the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of the fourth circulating pump 74, water is supplemented into the tail gas absorption tower 83 from a circulating water tank 82 through a third circulating pump 73, and fresh water is supplemented into the circulating water tank 82, so that the temperature and the ammonia content of the working water of the vacuum pump 81 are reduced. Dilute sulfuric acid is further introduced into the tail gas absorption tower 83 to absorb ammonia and the like in the tail gas.

In this example, 3.11m of ammonia water having a concentration of 5.28 mass% was obtained per hour in the first ammonia water tank 51³The second ammonia water tank 52 was filled with 3.09m of 0.22 mass% ammonia water per hour³The ammonia water can be reused in the production process of the molecular sieve.

Example 2

The treatment of the catalyst production wastewater was carried out in the same manner as in example 1, except that: for NaCl-containing 169g/L, Na₂SO₄ 26g/L、NH₄Cl 30.1g/L、(NH₄)₂SO₄4.7g/L, pH of 6.6 catalyst process wastewater, a portion (4.9 m)³H) sending the condensate into a first heat exchange device 31 (plastic plate heat exchanger) to carry out first heat exchange with the recovered first ammonia-containing steam condensateHeating the catalyst production wastewater to 73 ℃, sending the rest part of the catalyst production wastewater into a second heat exchange device 32 (a duplex stainless steel plate type heat exchanger) to carry out first heat exchange with the recovered second ammonia-containing steam condensate, heating the catalyst production wastewater to 99 ℃, and obtaining SO contained in the wastewater to be treated₄ ^2-And Cl^-In a molar ratio of 1: 14.502.

the evaporation conditions of the first multi-effect evaporation device 2 are as follows: the evaporation temperature of the first effect evaporator 2a is 90 ℃, the pressure is-47.89 kPa, and the evaporation capacity is 1.65m³H; the evaporation temperature of the second effect evaporator 2b is 70 ℃, the pressure is-78.45 kPa, and the evaporation capacity is 1.64m³H; the evaporation temperature of the third effect evaporator 2c is 46 ℃, the pressure is-94.33 kPa, and the evaporation capacity is 1.64m³H is used as the reference value. The crystallization temperature was 45 ℃ and the crystallization time was 10 min.

The evaporation conditions of the second multi-effect evaporation device 1 are as follows: the first effect evaporator 1a had an evaporation temperature of 140 deg.C, a pressure of 193.83kPa, and an evaporation capacity of 0.14m³H; the evaporation temperature of the second effect evaporator 1b is 128 ℃, the pressure is 103.53kPa, and the evaporation capacity is 0.13m³H; the evaporation temperature of the third effect evaporator 1c was 117 deg.C, the pressure was 41.92kPa, and the evaporation capacity was 0.13m³H; the fourth effect evaporator 1d has an evaporation temperature of 106 ℃, a pressure of-3.57 kPa and an evaporation capacity of 0.13m³H is used as the reference value. The crystallization temperature was 105 ℃ and the crystallization time was 10 min.

The first solid-liquid separation device 91 obtained 1178.75kg of sodium chloride crystal cake containing 14 mass% of water per hour, and finally obtained 1013.73kg of sodium chloride (purity 99.5 wt%); obtained at 9.21m per hour³The concentration of NaCl is 292.4g/L, Na₂SO₄ 67.3g/L、NaOH 0.10g/L、NH₃0.029g/L of the first mother liquor.

The second solid-liquid separation device 92 obtained 177.89kg of a sodium sulfate crystal cake containing 15 mass% of water per hour, and finally 151.21kg of sodium sulfate (purity: 99.4 wt%) per hour; 8.74 m/hr³Concentration of NaCl 307.9g/L, Na₂SO₄ 53.1g/L、NaOH 0.105g/L、NH₃0.0009g/L of second mother liquor.

In the present embodiment4.93m of ammonia water having a concentration of 1.07 mass% was obtained per hour in the first ammonia water tank 51³0.53m of 0.049 mass% ammonia water was obtained per hour in the second ammonia water tank 52³The ammonia water can be reused in the production process of the molecular sieve.

Example 3

The treatment of the catalyst production wastewater was carried out in the same manner as in example 1, except that: for the NaCl-containing 158g/L, Na₂SO₄ 68g/L、NH₄Cl 32g/L、(NH₄)₂SO₄14g/L, pH of 6.3 catalyst production wastewater, a portion (3.55 m)³H) sending the wastewater to a first heat exchange device 31 (plastic plate heat exchanger) to perform first heat exchange with the recovered first ammonia water SO as to heat the catalyst production wastewater to 68 ℃, sending the rest of the wastewater to a second heat exchange device 32 (duplex stainless steel plate heat exchanger) to perform first heat exchange with the recovered second ammonia water SO as to heat the catalyst production wastewater to 98 ℃, and obtaining SO contained in the wastewater to be treated₄ ^2-And Cl^-In a molar ratio of 1: 11.957.

the evaporation conditions of the first multi-effect evaporation device 2 are as follows: the evaporation temperature of the first effect evaporator 2a is 82 ℃, the pressure is-62.76 kPa, and the evaporation capacity is 1.40m³H; the evaporation temperature of the second effect evaporator 2b is 67 ℃, the pressure is-81.38 kPa, and the evaporation capacity is 1.39m³H; the evaporation temperature of the third effect evaporator 2c is 51 ℃, the pressure is-92.22 kPa, and the evaporation capacity is 1.39m³H is used as the reference value. The crystallization temperature was 50 ℃ and the crystallization time was 10 min.

The evaporation conditions of the second multi-effect evaporation device 1 are as follows: the first effect evaporator 1a had an evaporation temperature of 145 deg.C, a pressure of 239.9kPa, and an evaporation capacity of 0.37m³H; the evaporation temperature of the second effect evaporator 1b is 130 ℃, the pressure is 116.77kPa, and the evaporation capacity is 0.36m³H; the evaporation temperature of the third effect evaporator 1c is 114 ℃, the pressure is 28.07kPa, and the evaporation capacity is 0.36m³H; the fourth effect evaporator 1d has an evaporation temperature of 97 deg.C, a pressure of-31.21 kPa, and an evaporation capacity of 0.36m³H is used as the reference value. The crystallization temperature was 95 ℃ and the crystallization time 10 min.

The first solid-liquid separation device 91 obtains 1 hour of water1125.27kg of a 4% by mass cake of crystallized sodium chloride, resulting in 967.72kg of sodium chloride (99.5% by weight purity) per hour; 32.99m is obtained in each hour³The concentration of NaCl 294.6g/L, Na₂SO₄ 65.7g/L、NaOH 0.22g/L、NH₃0.0828g/L of the first mother liquor.

The second solid-liquid separation device 92 obtained 479.73kg of a sodium sulfate crystal cake having a water content of 14 mass% per hour, and finally 412.57kg of sodium sulfate (purity of 99.4 wt%) per hour; yield 31.87m per hour³The concentration of NaCl is 306.2g/L, Na₂SO₄ 55.3g/L、NaOH 0.229g/L、NH₃0.0043g/L of a second mother liquor.

In this example, 4.18m of ammonia water having a concentration of 1.55 mass% was obtained per hour in the first ammonia water tank 51³1.45m of 0.18 mass% ammonia water was obtained per hour in the second ammonia water tank 52³The ammonia water can be reused in the production process of the molecular sieve.

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 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 chloride crystals, wherein the wastewater to be treated contains the catalyst production wastewater and a liquid phase obtained by second solid-liquid separation;

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 the crystallization of sodium sulfate, and the second evaporation prevents the crystallization of sodium chloride; the conditions of the first evaporation include: the temperature is 30-130 ℃, and the pressure is-98 kPa-117 kPa; the conditions of the second evaporation include: the temperature is above 45 ℃ and the pressure is above-95 kPa;

relative to 1 mole of SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-9.5 mol or more;

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 10 mol or more.

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 1, wherein the first evaporation is such that the concentration of sodium sulfate in the first concentrated solution is Y or less, wherein Y is the concentration of sodium sulfate at which both sodium chloride and sodium sulfate in the first concentrated solution are saturated under the conditions of the first evaporation;

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

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

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

9. The method of any one of claims 1-8, wherein the conditions of the first evaporation comprise: the temperature is 35-95 ℃, and the pressure is-98 kPa-37 kPa.

10. The method of claim 9, wherein the conditions of the first evaporation comprise: the temperature is 46-95 ℃, and the pressure is-95 kPa to-37 kPa.

11. The method of claim 10, wherein the conditions of the first evaporation comprise: the temperature is 46-51 ℃, and the pressure is-95 kPa to-92 kPa.

12. The method of any one of claims 1-8, wherein the conditions of the second evaporation comprise: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa.

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

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

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

16. The method of claim 15, wherein the conditions of the second evaporation comprise: the temperature is 97-115 ℃ and the pressure is-32 kPa-33 kPa.

17. The method of claim 9, wherein the temperature of the first evaporation is more than 5 ℃ lower than the temperature of the second evaporation.

18. The method of claim 17, wherein the temperature of the first evaporation is 20 ℃ or more lower than the temperature of the second evaporation.

19. The method of claim 18, wherein the temperature of the first evaporation is 35 ℃ to 70 ℃ lower than the temperature of the second evaporation.

20. The method of claim 18, wherein the temperature of the first evaporation is 50 ℃ to 59 ℃ lower than the temperature of the second evaporation.

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

22. The method of claim 21, wherein the first and second multi-effect evaporation devices are each 3-5 effects.

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

24. The method as claimed in claim 23, wherein the pH of the wastewater to be treated is adjusted to be greater than 7 before the first heat exchange is carried out.

25. The method of claim 1, wherein the first ammonia-containing vapor evaporated by the last evaporator of the first multi-effect evaporator is subjected to a second heat exchange to obtain a first ammonia water.

26. The method of claim 25, wherein the second ammonia-containing vapor evaporated by the last evaporator of the second multi-effect evaporator is subjected to a third heat exchange to obtain a second ammonia water.

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

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

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

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

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

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

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

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