CN108726606B

CN108726606B - Treatment method of catalyst production wastewater

Info

Publication number: CN108726606B
Application number: CN201710263282.8A
Authority: CN
Inventors: 殷喜平; 李叶; 周岩; 王涛
Original assignee: China Petroleum and Chemical Corp; Sinopec Catalyst Co
Current assignee: China Petroleum and Chemical Corp; Sinopec Catalyst Co
Priority date: 2017-04-21
Filing date: 2017-04-21
Publication date: 2021-09-21
Anticipated expiration: 2037-04-21
Also published as: CN108726606A

Abstract

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

Description

Treatment method of catalyst production wastewater

Technical Field

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

Background

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

In addition, the biochemical deamination can only treat wastewater with low ammonium content, and can not directly carry out biochemical treatment due to insufficient COD content in the catalyst sewage, and organic matters such as glucose or starch and the like are additionally added in the biochemical treatment process, so that the ammoniacal nitrogen can be treated by the biochemical method. The most important problem is that the total nitrogen of the wastewater after the biochemical deamination treatment is not up to the standard (the contents of nitrate ions and nitrite ions exceed the standard), the wastewater needs to be deeply treated, the salt content of the wastewater is not reduced (20000 mg/L-30000 mg/L), the wastewater cannot be directly discharged, and the wastewater needs to be further desalted.

In order to remove ammonia nitrogen from wastewater by gas stripping deamination, a large amount of alkali is needed to adjust the pH value, the alkali consumption is high, the alkali in the wastewater after deamination cannot be recovered, the pH value of the treated wastewater is high, the treatment cost is high, the COD content in the catalyst wastewater after gas stripping does not change greatly, the salt content in the wastewater is not reduced (20000 mg/L-30000 mg/L), the wastewater cannot be discharged directly, further desalting treatment is needed, the operation cost of wastewater treatment is high, a large amount of alkali remains in the treated wastewater, the pH value is high, the waste is large, and the treatment cost is up to 50 yuan/ton.

Disclosure of Invention

The invention aims to overcome the defect of NH content in the prior art₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The 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 wastewater generated in the catalyst production can respectively recover ammonium, sodium sulfate and sodium chloride in the wastewater, and furthest recycle resources in the wastewater.

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

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

2) carrying out first solid-liquid separation on the first concentrated solution containing the sodium sulfate crystals, and carrying out flash evaporation on a liquid phase obtained by the first solid-liquid separation;

3) introducing the liquid phase obtained by flash evaporation into a single-effect evaporation device for second evaporation to obtain second ammonia-containing steam and second concentrated solution containing sodium chloride crystals;

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

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

By the technical scheme, the method aims at the content of NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The pH value of the wastewater is adjusted to a specific range in advance, then an MVR evaporation device is used for evaporation and separation to obtain sodium sulfate crystals and concentrated ammonia water, and then a single-effect evaporation device is used for evaporation again to obtain sodium chloride crystals and dilute ammonia water. The method can respectively obtain high-purity sodium sulfate and sodium chloride, avoids the difficulty in the mixed salt treatment and recycling process, 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, reasonably utilizes the heat and cold generated by a heat pump, saves energy, reduces the wastewater treatment cost, recovers the ammonium in the wastewater in the form of ammonia water, recovers the sodium chloride and the sodium sulfate in the form of crystals respectively, does not generate waste residues and waste liquid in the whole process, and achieves the purpose of changing waste into valuable.

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

Drawings

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

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

Description of the reference numerals

1. Single-effect evaporation device 2 and MVR evaporation device

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

33. Third heat exchange device 41, flash tank

42. Heat pump 51, first aqueous ammonia storage tank

52. Second ammonia storage tank 53, crystal liquid collecting tank

54. 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

78. Eighth circulating pump 81, vacuum pump

82. Circulating water tank 83 and tail gas absorption tower

91. First solid-liquid separator 92 and second solid-liquid separator

10. Compressor with a compressor housing having a plurality of compressor blades

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,

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.

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

The method provided by the invention can be used for the treatment of the compounds containing NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺Except that it contains NH₄ ⁺、SO₄ ^2-、Cl^-And Na⁺In addition, the catalyst production wastewater is not particularly limited. From the viewpoint of improving the treatment efficiency of wastewater, the amount of SO contained in the wastewater to be treated is 1 mole per mole₄ ^2-Cl contained in the wastewater to be treated^-13.8 mol or less, more preferably 13.75 mol or less, further preferably 13.5 mol or less, further preferably 13 mol or less, further preferably 12 mol or less, further preferably 11 mol or less, further preferably 10 mol or less, further preferably 9 mol or less, further preferably 8 mol or less, further preferably 7 mol or less, further preferably 6 mol or less; preferably 2 moles or more, more preferably 2.5 moles or more, further preferably 3 moles or more, and for example, may be 3 to 9 moles. By reacting SO₄ ^2-And Cl^-The molar ratio of sodium sulfate in the first evaporation is controlled within the above range, so that sodium sulfate is precipitated without precipitating sodium chloride, and the purpose of efficiently separating sodium sulfate is achieved. In addition, as described above and below, it is also possible in the present invention to recycle the second mother liquor obtained in the second evaporation process to the first evaporation, and thereby to treat SO in the wastewater to be treated₄ ^2-And Cl^-The molar ratio of (a) to (b) is adjusted and the balance of sodium hydroxide can be maintained.

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

In the present invention, the second evaporation to prevent the crystallization of sodium sulfate means that the concentration of sodium sulfate in the mixed system is controlled not to exceed the solubility under the second evaporation conditions (including but not limited to temperature, pH, etc.), and sodium sulfate entrained by sodium chloride crystals or adsorbed on the surface is not excluded. Since the water content of the crystals after 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, 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 MVR vaporizing device 2 is not particularly limited, and may be various MVR vaporizing devices conventionally used in the art. For example, it may be one or more selected from the group consisting of an MVR falling film evaporator, an MVR forced circulation evaporator, an MVR-FC continuous crystallization evaporator, and an MVR-OSLO continuous crystallization evaporator. Among them, preferred are an MVR forced circulation evaporator and an MVR-FC continuous crystallization evaporator, and more preferred is a falling film + forced circulation two-stage MVR evaporative crystallizer.

In the present invention, the conditions of the first evaporation may be appropriately selected as needed, and sodium sulfate may be crystallized without precipitating sodium chloride. The conditions of the first evaporation may include: the temperature is above 45 ℃ and the pressure is above-95 kPa. In order to improve the evaporation efficiency, it is preferable that the conditions of the first evaporation include: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa; in order to further improve the evaporation efficiency, it is preferable that the conditions of the first evaporation include: the temperature is 60-365 ℃, and the pressure is-87 kPa-18110 kPa; from the viewpoint of reducing the cost of equipment and the energy consumption, it is more preferable that the temperature of evaporation is 75 to 175 ℃ and the pressure is-73 to 653kPa, and it is further preferable that the conditions of the first evaporation include: the evaporation temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa; particularly preferably, the conditions of the first evaporation include: the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa.

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

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

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

According to the invention, by controlling the evaporation condition of the MVR evaporation device 2, more than 90 mass% (preferably more than 95 mass%) of ammonia contained in the wastewater to be treated can be evaporated, 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.

According to the present invention, the first evaporation does not cause crystallization of sodium chloride (i.e., sodium chloride does not reach supersaturation), and preferably, the first evaporation causes the concentration of sodium chloride in the first concentrated solution to be 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 sulfate and sodium chloride in the first concentrated solution reach saturation under the conditions of the first evaporation. By controlling the degree of the first evaporation within the above range, as much sodium sulfate as possible can be crystallized under the condition that sodium chloride is not precipitated. By crystallizing sodium sulfate in the first evaporation as much as possible, the wastewater treatment efficiency can be improved, and the energy waste can be reduced.

In the present invention, the degree of progress of the first evaporation is performed by monitoring the concentration of the liquid obtained by the first evaporation, and specifically, the concentration of the liquid obtained by the first evaporation is controlled within the above range so that the first evaporation does not cause crystallization of sodium chloride. The concentration of the liquid resulting from the first evaporation is monitored by measuring the density, which may be carried out using a densitometer.

According to a preferred embodiment of the present invention, before the wastewater to be treated is introduced into the MVR evaporation apparatus 2, the first ammonia-containing steam and the wastewater to be treated are subjected to a first heat exchange to obtain a 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 the heat exchange, the output ammonia water is cooled, and the heat is circulated in the treatment device to the maximum extent, so that the energy is reasonably utilized, and the waste is reduced.

According to 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, specifically, first ammonia-containing steam obtained by evaporation in the MVR evaporation device 2 passes through the second heat exchange device 32 and the first heat exchange device 31 in sequence, wastewater to be treated passes through the first heat exchange device 31 and the second heat exchange device 32 in sequence, the first heat exchange is performed between the first ammonia-containing steam and the wastewater to be treated, so as to heat the wastewater to be treated for evaporation, and simultaneously, the temperature of the first ammonia-containing steam is reduced to obtain first ammonia water, and the first ammonia water can be stored in a first ammonia water storage tank 51.

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, it is preferable that the temperature of the wastewater to be treated is 40 to 364 ℃, more preferably 55 to 364 ℃, even more preferably 65 to 174 ℃, and even more preferably 79 to 129 ℃ after the first heat exchange is performed by the first heat exchange device 31.

According to the present invention, in order to fully utilize the heat energy of the first ammonia-containing steam, it is preferable that the temperature of the wastewater to be treated is 50 ℃ to 370 ℃, more preferably 65 ℃ to 370 ℃, even more preferably 75 ℃ to 184 ℃, and even more preferably 85 ℃ to 139 ℃ after the first heat exchange is performed by the second heat exchange device 32.

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

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

According to a preferred embodiment of the present invention, the first evaporation process is performed in the MVR evaporation 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 before feeding the catalyst production wastewater to the first heat exchange apparatus 31 for the first heat exchange; and then mixing the catalyst production wastewater with a second mother liquor to obtain wastewater to be treated, sending the wastewater to be treated into a second heat exchange device 32 for first heat exchange, and then introducing and mixing the aqueous solution containing the alkaline substance into a pipeline for sending the wastewater to be treated into the MVR evaporation device 2 to adjust the pH value for the second time. The pH value of the wastewater to be treated is more than 9, preferably more than 10.8 before the wastewater is introduced into the MVR evaporation device 2 through two pH value adjustments. Preferably, the first pH adjustment is performed so that the adjusted pH value of the wastewater to be treated is greater than 7 (preferably 7-9), and the second pH adjustment is performed so that the pH value of the wastewater to be treated is greater than 9, preferably greater than 10.8. The wastewater to be treated after evaporation in the MVR evaporation apparatus 2 may be returned to the second pH adjustment process by the second circulation pump 72.

In order to detect the pH values after the first pH adjustment and the second pH adjustment, it is preferable to provide a first pH measuring device 61 on the pipe for feeding the wastewater to be treated into the first heat exchanging device 31 to measure the pH value after the first pH adjustment, and provide a second pH measuring device 62 on the pipe for feeding the wastewater to be treated into the MVR evaporating device 2 to measure the pH value after the second pH adjustment.

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

In the present invention, in order to increase the solid content in the MVR evaporation device 2 and reduce the ammonia content in the liquid, it is preferable that a part of the liquid evaporated by the MVR evaporation device 2 (i.e., the liquid located inside the MVR evaporation device, hereinafter also referred to as a circulating liquid) is heated and then returned to the MVR evaporation device 2 for evaporation. The above-mentioned process of returning the circulating liquid to the MVR evaporation device 2 is preferably to return the circulating liquid to the MVR evaporation device 2 after mixing with the wastewater to be treated after the first pH adjustment and before the second pH adjustment, for example, the circulating liquid may be returned to the wastewater delivery pipeline between the first heat exchange device 31 and the second heat exchange device 32 by the second circulating pump 72 to be mixed with the wastewater to be treated, and then after the second pH adjustment, the circulating liquid may be heat-exchanged in the second heat exchange device 32 and then sent to the MVR evaporation device 2. As a ratio of returning a part of the liquid evaporated by the MVR evaporating device 2 to the MVR evaporating device 2, there is no particular limitation, and for example, the reflux ratio of the first evaporation may be 10 to 200, preferably 50 to 100. Here, the reflux ratio means: the ratio of the amount of reflux to the total amount of liquid fed to the MVR evaporator 2 minus the amount of reflux.

According to the present invention, preferably, the method further comprises compressing the first ammonia-containing vapor before the first heat exchange. The compression of the first ammonia-containing vapor may be performed by a compressor 10. Through right first ammonia vapor that contains compresses, for input energy among the MVR vaporization system, guarantee that waste water intensification-evaporation-cooling's process goes on in succession, need input start-up steam when MVR vaporization process starts, only need pass through compressor 10 energy supply after reaching continuous running state, no longer need input other energy. The compressor 10 may employ various compressors conventionally used in the art, such as a centrifugal fan, a turbine compressor, or a roots compressor, etc. After compression by the compressor 10, the temperature of the first ammonia-containing vapor is raised by 5 to 20 ℃.

In the invention, the first concentrated solution containing sodium sulfate crystals is subjected to first solid-liquid separation to obtain sodium sulfate crystals and a first mother solution. 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 mother liquor tank 54, and can be sent to the single-effect evaporation device 1 by the fifth circulation pump 75 to be subjected to the second evaporation. In addition, it is difficult to avoid that impurities such as chlorine ions, free ammonia, and hydroxide ions are adsorbed on the obtained sodium sulfate crystals, and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals, it is preferable that the sodium sulfate crystals are first washed with water, the catalyst production wastewater, or a sodium sulfate solution and dried. The first wash comprises a rinsing and/or elutriation. In addition, the first washing liquid obtained in the above washing process is preferably returned to the second heat exchange device 32 by the eighth circulation pump 78.

The manner of the first solid-liquid separation and the first washing is not particularly limited, and may be carried out by using, for example, a combination of an elutriation apparatus and a solid-liquid separation apparatus which are conventional in the art, or may be carried out on a staged solid-liquid separation apparatus such as a belt filter. The above-mentioned elutriation and rinsing are not particularly limited and may be carried out by a method conventional in the art. The number of elutriation and rinsing is not particularly limited, and may be 1 or more, and is preferably 2 to 4 times in order to obtain sodium sulfate crystals of higher purity. In the elutriation process, the waste water produced by the catalyst is generally not recycled when used as an elutriation liquid, and the washing liquid recovered by the first washing can be recycled in a counter-current manner when used as the elutriation liquid. Before the elutriation, it is preferable to perform a preliminary solid-liquid separation by sedimentation to obtain a slurry containing sodium sulfate crystals (the liquid content may be 35% by mass or less, and this step is preferably performed in an apparatus known in the art such as a sedimentation tank or a sedimentation tank). In the elutriation process, the liquid used for elutriation is 1 to 20 parts by weight relative to 1 part by weight of the slurry containing sodium sulfate crystals. In addition, the rinsing is preferably performed using an aqueous sodium sulfate solution. Preferably, the concentration of the sodium sulfate aqueous solution is the concentration of sodium sulfate in the saturated aqueous solution obtained by simultaneously obtaining sodium chloride and sodium sulfate at the temperature corresponding to the sodium sulfate crystal to be washed. 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. The liquid resulting from the washing is preferably returned to the MVR evaporation unit prior to the second pH adjustment prior to evaporation.

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

In the present invention, the flash process is not particularly limited and may be performed in a manner conventional in the art, for example, by a flash tank 41. Through carrying out the flash distillation, make the temperature of first mother liquor descend and evaporate out part of water, the operation of the second evaporation of being convenient for is favorable to improving the solubility of sodium sulfate fast simultaneously, prevents to appear. The conditions of the flash may include: the pressure is-98 kPa to-58 kPa, and the temperature of the solution after flash evaporation is 30 ℃ to 85 ℃. Preferably, the conditions of the flash include: the pressure is-98 kPa to-87 kPa, and the temperature of the solution after flash evaporation is 35 ℃ to 60 ℃; more preferably, the conditions of the flash include: the pressure is-97 kPa to-87 kPa, and the temperature of the solution after flash evaporation is 40 ℃ to 60 ℃. Further preferably, the conditions of the flash evaporation include: the pressure is-95 kPa to-87 kPa, and the temperature of the solution after flash evaporation is 45 ℃ to 60 ℃.

In the present invention, the single-effect evaporation apparatus 1 is not particularly limited, and may be 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 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 single-effect evaporation apparatus 1 is composed of a heating chamber and an evaporation chamber, and may further include other evaporation auxiliary components as necessary, such as a demister for further separating liquid foam, a condenser for condensing all secondary steam, and a vacuum apparatus for pressure reduction operation.

In the present invention, the evaporation conditions of the second evaporation may be appropriately selected as needed, and the purpose of crystallizing sodium chloride without precipitating sodium sulfate may be achieved. The conditions of the second evaporation may include: the temperature is 30-85 ℃, and the pressure is-98 kPa-58 kPa. In order to improve evaporation efficiency, preferably, the conditions of the second evaporation include: the temperature is 35-60 ℃, and the pressure is-98 kPa to-87 kPa; preferably, the conditions of the second evaporation include: the temperature is 40 ℃ to 60 ℃, and the pressure is-97 kPa to-87 kPa; preferably, the conditions of the second evaporation include: the temperature is 45-60 ℃, and the pressure is-95 kPa to-87 kPa; preferably, the conditions of the second evaporation include: the temperature is 46-56 ℃, and the pressure is-95 kPa to-89 kPa.

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

Further, the evaporation amount of the second evaporation may be appropriately selected depending on the capacity of the apparatus and the amount of the wastewater to be treated, and may be, for example, 100L/h or more (e.g., 0.1 m)³/h～500m³H). By carrying out the second evaporation under the above conditions, the sodium sulfate is not crystallized while the crystallization of sodium chloride is ensured, so that the purity of the obtained sodium chloride crystal can be ensured.

According to the present invention, the second evaporation does not crystallize sodium sulfate (i.e., sodium sulfate does not reach supersaturation), and preferably, the second evaporation makes the concentration of sodium sulfate in the second concentrated solution to be Y or less (preferably 0.9Y to 0.99Y, and more preferably 0.95Y to 0.98Y), where Y is the concentration of sodium sulfate at which both sodium sulfate and sodium chloride in the second concentrated solution reach saturation under the conditions of the second evaporation. By controlling the degree of the second evaporation within the above range, as much sodium chloride as possible can be crystallized out under the condition that sodium sulfate is not precipitated out. By crystallizing sodium chloride in the second evaporation as much as possible, the wastewater treatment efficiency can be improved, and the energy waste can be reduced.

In the present invention, the degree of progress of the second evaporation is performed by monitoring the concentration of the liquid obtained by the second evaporation, and specifically, the concentration of the liquid obtained by the second evaporation is controlled within the above range so that the second evaporation does not cause crystallization of sodium sulfate. The concentration of the liquid resulting from the second evaporation is monitored by measuring the density, which may be carried out using a densitometer.

In the present invention, in order to prevent the first evaporation from crystallizing and precipitating sodium chloride and the second evaporation from crystallizing and precipitating sodium sulfate, it is preferable that the conditions of the two-time evaporation satisfy: the temperature of the first evaporation is at least 5 ℃, preferably 20 ℃ and more preferably 35 ℃ to 70 ℃ higher than the temperature of the second evaporation. And respectively crystallizing and separating out sodium sulfate and sodium chloride by controlling the first evaporation and the second evaporation to be carried out at different temperatures, so that the purity of the obtained sodium sulfate and sodium chloride crystals is improved.

According to a preferred embodiment of the present invention, the second ammonia-containing vapor obtained by evaporation in the single-effect evaporation device 1 undergoes second heat exchange with the cold medium in the third heat exchange device 33 to obtain second ammonia water. The third heat exchange means 33 is not particularly limited, and various heat exchangers conventionally used in the art may be used to cool the second 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. 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). The cold medium may also be a cold medium resulting from cold heat exchange generated by the heat pump 42.

According to a preferred embodiment of the present invention, the second evaporation process is carried out in a single-effect evaporation apparatus 1. And introducing the first mother liquor into the single-effect evaporation device 1 through a fifth circulating pump 75 for second evaporation to obtain second ammonia-containing steam and a second concentrated solution containing sodium chloride crystals. The second ammonia-containing steam and the cooling medium generated by the heat pump 42 perform the second heat exchange to obtain second ammonia, and the second ammonia is stored in the second ammonia storage tank 52. The heat pump 42 is not particularly limited as long as it can simultaneously perform cooling and heating, and may be, for example, an electrically driven heat pump unit. Specifically, the temperature of the cold medium before the heat pump 42 is introduced is 10 ℃ to 30 ℃, the temperature of the heat medium is 40 ℃ to 45 ℃, the temperature of the cold medium is 0 ℃ to 25 ℃ and the temperature of the heat medium is 45 ℃ to 55 ℃ after the treatment in the heat pump 42.

In the present invention, the heat pump 42 operates on the principle of ensuring that enough cold medium is obtained, and when the heating heat is insufficient, the heat can be supplemented by steam or electric auxiliary heating, and the auxiliary heating position is on the way of the heat medium from the heat pump to the heat exchanger. Preferably, the heat medium generated by the heat pump 42 is heat exchanged with the liquid phase obtained by flashing and with the washing liquid obtained by washing the sodium chloride crystals.

According to a preferred embodiment of the present invention, when heating is required in the single-effect evaporation device 1, a heat medium obtained by heat exchange by the heat pump 42 is circulated between the single-effect evaporation device 1 and the heat pump 42, and a cold medium generated by the heat pump 42 is circulated between the third heat exchange device 33 and the heat pump 42, so that when the heat quantity of the heat medium is insufficient, additional heat quantity can be further supplemented by auxiliary heating using steam or electricity, and the auxiliary heating position is on the way of the heat medium from the heat pump to the heat exchanger. By arranging the heat pump 42, the heating and cooling energy consumption of the single-effect evaporation device can be reduced, and the energy is saved.

According to the invention, the method can also comprise crystallizing the second concentrated solution containing sodium chloride crystals in a crystallizing device to obtain crystal slurry containing sodium chloride crystals. In this case, the evaporation conditions for the second evaporation are required to satisfy the purpose of crystallizing sodium chloride without precipitating sodium sulfate in the crystallization device. The crystallization apparatus is not particularly limited, and may be, for example, a crystal solution tank, a crystal solution collecting tank, a thickener with stirring or a thickener without stirring, or the like. According to a preferred embodiment of the present invention, the crystallization is performed in the crystal liquid collection tank 53. The crystallization conditions are not particularly limited, and may include, for example: the temperature is above 30 ℃; preferably 40-60 ℃; more preferably from 45 ℃ to 55 ℃. The crystallization time may be 5min to 24h, preferably 5min to 30 min.

According to the invention, the crystallization of the second concentrated solution containing sodium chloride crystals can also be carried out in a single-effect evaporator with a crystallizer (e.g. a forced circulation evaporator crystallizer), wherein the crystallization temperature is the corresponding second evaporation temperature. According to the present invention, when a single crystallization device is used for crystallization, it is further required to ensure that the second evaporation does not crystallize sodium sulfate (i.e., sodium sulfate does not reach supersaturation), and preferably, the second evaporation is performed so that the concentration of sodium sulfate in the second concentrated solution is Y or less, where Y is the concentration of sodium sulfate at which both sodium chloride and sodium sulfate in the second concentrated solution reach saturation under the crystallization conditions.

In the present invention, the second concentrated solution containing sodium chloride crystals (or the magma containing sodium chloride crystals when crystallized in a separate crystallization apparatus) is subjected to a second solid-liquid separation to obtain sodium chloride crystals and a second mother liquor (i.e., a liquid phase obtained by the second solid-liquid separation). The method of the second solid-liquid separation is not particularly limited, and may be selected from one or more of centrifugation, filtration, and sedimentation, for example.

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

Preferably, the second wash comprises a rinsing and/or elutriation. The second washing liquid obtained from the above washing process is preferably returned to the single-effect evaporation apparatus 1 by the sixth circulation pump 76 to be subjected to the second evaporation again.

The form of the second solid-liquid separation and the second washing is not particularly limited, and may be carried out, for example, by using a combination of an elutriation apparatus and a solid-liquid separation apparatus which are conventional in the art, or may be carried out on a staged solid-liquid separation apparatus such as a belt filter. The above-mentioned elutriation and rinsing are not particularly limited and may be carried out by a method conventional in the art. The number of elutriation and rinsing is not particularly limited, and may be 1 or more, and is preferably 2 to 4 times in order to obtain sodium chloride crystals of higher purity. In the elutriation process, the catalyst production wastewater is generally not recycled when being used as an elutriation liquid, and the washing liquid recovered by the second washing can be recycled in a counter-current manner when being used as the elutriation liquid. Before the elutriation, a slurry containing sodium chloride crystals is preferably obtained by preliminary solid-liquid separation by sedimentation (the liquid content may be 35% by mass or less, and this step is preferably performed in an apparatus known in the art, such as a sedimentation tank or a sedimentation tank). In the elutriation process, 1 to 20 parts by weight of a liquid used for elutriation is used with respect to 1 part by weight of a slurry containing sodium chloride crystals. In addition, the rinsing is preferably carried out using an aqueous sodium chloride solution (the concentration of the aqueous sodium chloride solution is preferably the concentration of sodium chloride in an aqueous solution in which sodium chloride and sodium sulfate are simultaneously saturated at a temperature corresponding to the sodium chloride crystals to be rinsed). In order to further enhance the elutriation effect and obtain sodium chloride crystals with higher purity, the elutriation may be preferably performed using a liquid obtained by rinsing. For the liquid produced by washing, it is preferred that the catalyst production wastewater elutriation liquid is returned to the single-effect evaporation device 1 before being returned to the pH adjustment before evaporation in the MVR evaporation device 2.

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

According to a preferred embodiment of the present invention, the first ammonia-containing steam is subjected to the first heat exchange to condense the remaining tail gas, the flash evaporation of the remaining tail gas, and the second ammonia-containing steam is subjected to the second heat exchange to condense the remaining tail gas, and then ammonia is removed and discharged. The first ammonia-containing steam is subjected to the first heat exchange to condense residual tail gas, namely tail gas discharged from the second heat exchange device 32, the flash evaporation residual tail gas is tail gas discharged from the flash tank 41, and the second ammonia-containing steam is subjected to the second heat exchange to condense residual tail gas, namely tail gas discharged from 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 catalyst is produced by waste water. 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/LMore preferably 40000mg/L or more, still more preferably 50000mg/L or more, yet more preferably 60000mg/L or more, and still more preferably 70000mg/L or more.

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

NH contained in the catalyst production wastewater₄ ⁺、SO₄ ^2-、Cl^-And Na⁺The upper limit of (3) is not particularly limited. SO in the wastewater from catalyst production from the viewpoint of easy wastewater treatment₄ ^2-、Cl^-And Na⁺Respectively 200g/L or less, preferably 150g/L or less; NH in catalyst production wastewater₄ ⁺Is 50g/L or less, preferably 30g/L or less.

From the viewpoint of improving the efficiency of the first evaporation and reducing the energy consumption of the treatment process, the amount of SO contained in the wastewater is relatively small₄ ^2-Cl in catalyst production wastewater^-The lower the content, the better, for example, relative to 1 mole of SO contained in the catalyst production wastewater₄ ^2-Cl contained in the catalyst production wastewater^-Is 30 mol or less, preferably 20 mol or less, more preferably 15 mol or less, and still more preferably 10 mol or less. From the viewpoint of practicality, the amount of SO contained in the wastewater from the catalyst production is 1 mole₄ ^2-Cl contained in the catalyst production wastewater^-Preferably 0.1 mol or more, more preferably 0.5 mol or more, further preferably 0.8 mol or more, for example, 0.8 to 6 mol. By adding SO contained in the catalyst production wastewater₄ ^2-And Cl^-The molar ratio of (A) to (B) is limited to the above range, most of water can be evaporated in the first evaporation, the amount of circulating liquid in a treatment system is reduced, energy is saved, and the treatment process is enabled to be carried outIs more economical.

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

The TDS of the catalyst production wastewater may be 1600mg/L or more, preferably 4000mg/L or more, more preferably 8000mg/L or more, further preferably 16000mg/L or more, further preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, further preferably 60000mg/L or more, further preferably 100000mg/L or more, further preferably 150000mg/L or more, further preferably 200000mg/L or more.

In the invention, the pH value of the catalyst production wastewater is preferably 4-8, and more preferably 6.7-7.

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

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

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

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

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

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

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

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

The conditions for the weak acid cation exchange method are preferably: the pH value range is 6.5-7.5; 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 chloride in the first concentrated solution is close to the precipitation concentration, then the first concentrated solution is subjected to the second evaporation to obtain a second concentrated solution, the solid-liquid separation is carried out to obtain sodium chloride crystals and a second mother solution, the second mother solution is mixed with the catalyst production wastewater to adjust the ion content of the wastewater to be treated to be within the range required by the invention, and then the first evaporation is carried out to obtain sodium sulfate crystals. Of course, the ion content of the wastewater to be treated can be adjusted by using sodium sulfate or sodium chloride in the initial stage as long as the wastewater to be treated satisfies the SO content in the wastewater to be treated in the present invention₄ ^2-、Cl^-The requirements are met.

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

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

Example 1

As shown in FIG. 1, the catalyst is formedProduction wastewater (containing NaCl 122g/L, Na)₂SO₄ 52g/L、NH₄Cl 45g/L、(NH₄)₂SO₄19.5g/L, pH of 7.0) at a feed rate of 5m³Feeding the wastewater into a pipeline of a treatment system at a speed of/h, introducing a sodium hydroxide aqueous solution with the concentration of 45.16 mass% into the pipeline to adjust the pH value for the first time, monitoring the adjusted pH value through a first pH value measuring device 61 (a pH meter) (the measured value is 7.5), feeding the catalyst production wastewater into a first heat exchange device 31 (a plastic plate heat exchanger) to perform first heat exchange with the first ammonia-containing steam condensate to heat the catalyst production wastewater to 68 ℃, and mixing the catalyst production wastewater with a second mother liquor to obtain wastewater to be treated (containing SO)₄ ^2-And Cl^-In a molar ratio of 1: 8.828). Then, the wastewater to be treated is sent into a second heat exchange device 32 (titanium alloy plate heat exchanger), first heat exchange is carried out with the recovered first ammonia-containing steam to heat the wastewater to be treated to 102 ℃, then the wastewater to be treated after two times of first heat exchange is sent into a pipeline of an MVR evaporation device 2, sodium hydroxide aqueous solution with the concentration of 45.16 mass percent is led in for second pH value adjustment, the adjusted pH value is monitored through a second pH value measuring device 62(pH meter) (the measured value is 11), and the wastewater to be treated after second pH value adjustment is 393.63m³And/h, sending the mixture into an MVR evaporation device 2 (a falling film and forced circulation two-stage MVR evaporation crystallizer) for evaporation to obtain first concentrated solution containing ammonia vapor and sodium sulfate crystals. Wherein, the evaporation conditions of the MVR evaporation device 2 include: the temperature is 95 ℃, the pressure is-36.36 kPa, and the evaporation capacity is 3.18m³H is used as the reference value. The first ammonia-containing vapor obtained by evaporation is compressed by a compressor 10 (the temperature is raised by 12 ℃) and then sequentially passes through a second heat exchange device 32 and a first heat exchange device 31 to exchange heat with the wastewater to be treated, and is cooled to obtain ammonia water, and the ammonia water is stored in a first ammonia water storage tank 51. In addition, in order to increase the solid content in the MVR evaporation device 2, part of the liquid evaporated in the MVR evaporation device 2 is circulated as a circulating liquid to the second heat exchange device 32 by the second circulating pump 72, and then enters the MVR evaporation device 2 again for the first evaporation (reflux ratio is 68.4). Through the densitometer pair arranged on the MVR evaporation plant 2The extent of the first evaporation was monitored and the concentration of sodium chloride in the first concentrate was controlled to 0.9935X (307.2 g/L).

The first concentrated solution obtained by evaporation in the MVR evaporation plant 2 is sent to a first solid-liquid separation device 91 (centrifugal machine) for first solid-liquid separation, and 12.13m is obtained per hour³Contains NaCl 307.2g/L, Na₂SO₄ 54.5g/L、NaOH 1.83g/L、NH₃0.158g/L of first mother liquor is temporarily stored in a mother liquor tank 54, sodium sulfate solid obtained by solid-liquid separation (427.25 kg of sodium sulfate crystal filter cake containing 15 mass% of water is obtained every hour, wherein the content of sodium chloride is below 6.9 mass%) is eluted by 55g/L of sodium sulfate solution which is equal to the dry basis mass of the sodium sulfate crystal filter cake, 363.16kg of sodium sulfate (the purity is 99.3 weight%) is obtained every hour after drying, and washing liquid obtained by washing is circulated to the second heat exchange device 32 through an eighth circulating pump 78 and then enters the MVR evaporation device 2 again for first evaporation.

The second evaporation process is carried out in a single-effect evaporator 1 (forced circulation evaporator). The first mother liquor in the mother liquor tank 54 is sent to the flash tank 41 for flash evaporation treatment through a fifth circulating pump 75, and then sent to the single-effect evaporation device 1 for second evaporation to obtain a second concentrated solution containing sodium chloride crystals. Wherein the flash conditions include: the pressure is-92.67 kPa, and the temperature of the solution after flash evaporation is 50 ℃; the evaporation conditions of the single-effect evaporation apparatus 1 include: the temperature was 46 ℃, the pressure was-94.32 kPa, and the evaporation capacity was 2.3m³H is used as the reference value. The second ammonia-containing steam obtained by evaporation in the single-effect evaporation device 1 performs second heat exchange with the cold medium generated by the heat pump 42 in the third heat exchange device to obtain second ammonia, and the second ammonia is stored in the second ammonia storage tank 52. Then the cold medium circulates to the heat pump 42 for heat exchange, the cold medium is cooled, and then the heat medium is introduced into the single-effect evaporation device 1 for heat exchange with the first mother liquor when needed. At this time, the cold medium circulates between the third heat exchanging device 33 and the heat pump 42, and the heat medium circulates between the heat pump 42 and the single-effect evaporation device 1. The temperature of the cold medium before being introduced into the heat pump 42 is 20 ℃, the temperature of the heat medium is 47 ℃, the temperature of the cold medium is 10 ℃ and the temperature of the heat medium is 52 ℃ after being treated in the heat pump 42. Passing through sheetThe density meter provided in the efficient evaporation apparatus 1 monitored the degree of the second evaporation, and the concentration of sodium sulfate in the second concentrated solution was controlled to 0.9711Y (67.2 g/L). After the first mother liquor is evaporated in the single-effect evaporator 1, the finally obtained second concentrated solution containing sodium chloride crystals is crystallized in the crystal liquid collecting tank 53 (the crystallization temperature is 45 ℃ and the crystallization time is 30min) to obtain crystal slurry containing sodium chloride crystals.

The crystal slurry containing sodium chloride crystals is sent to a second solid-liquid separation device 92 (centrifugal machine) for solid-liquid separation, and the solid-liquid separation can obtain 9.78m per hour³Contains 292.1g/L, Na NaCl₂SO₄ 67.2g/L、NaOH 2.26g/L、NH₃0.0078g/L of second mother liquor, feeding the second mother liquor into a wastewater introduction pipeline through a seventh circulating pump 77, mixing the second mother liquor with the catalyst production wastewater to obtain wastewater to be treated, carrying out solid-liquid separation to obtain sodium chloride solid (997.41 kg of sodium chloride crystallization filter cake with the water content of 14 mass% is obtained per hour, wherein the content of sodium sulfate is below 7.1 mass%), washing the sodium chloride solid with 293g/L of sodium chloride solution with the same mass as the dry basis of sodium chloride, drying the sodium chloride solid in a drier, obtaining 857.77kg of sodium chloride (with the purity of 99.5 weight%) per hour, and circulating the washing liquid obtained by washing to a single-effect evaporation device 1 through a sixth circulating pump 76.

In addition, the tail gas discharged by the second heat exchange device 32 and the third heat exchange device 33 is introduced into a tail gas absorption tower 83 through a vacuum pump 81 for absorption, circulating water is introduced into the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of the fourth circulating pump 74, water is supplemented into the tail gas absorption tower 83 from a circulating water tank 82 through a third circulating pump 73, and fresh water is supplemented into the circulating water tank 82, so that the temperature and the ammonia content of the working water of the vacuum pump 81 are reduced. Dilute sulfuric acid is further introduced into the tail gas absorption tower 83 to absorb ammonia and the like in the tail gas.

In this example, 3.18m of ammonia water having a concentration of 2.89 mass% was obtained per hour in the first ammonia water tank 51³And 2.3m of ammonia water having a concentration of 0.026% by mass per hour is obtained in the second ammonia water tank 52³The ammonia water can be reused in the production process of the molecular sieve.

In addition, the starting phase of the MVR evaporation was started by steam at a temperature of 143.3 ℃.

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 68g/L, Na₂SO₄ 170g/L、NH₄Cl 17g/L、(NH₄)₂SO₄43.2g/L, pH of 6.9 catalyst production wastewater to obtain SO contained in wastewater to be treated₄ ^2-And Cl^-In a molar ratio of 1: 3.288. the temperature of the wastewater to be treated after heat exchange by the first heat exchange device 31 was 92 deg.C, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange device 32 was 112 deg.C. The evaporation conditions of the MVR evaporation device 2 include: the temperature is 105 ℃, the pressure is-7.02 kPa, and the evaporation capacity is 4.45m³H is used as the reference value. The evaporation conditions of the single-effect evaporation apparatus 1 include: the temperature was 51 ℃, the pressure was-92.21 kPa, and the evaporation capacity was 1.16m³/h。

The first solid-liquid separation device 91 obtained 1260.63kg of a sodium sulfate crystal cake containing 14 mass% of water per hour, and finally obtained 1084.14kg of sodium sulfate (purity: 99.6 wt%) per hour; yield 6.10m per hour³The concentration of NaCl is 307g/L, Na₂SO₄ 52.73g/L、NaOH 1.67g/L、NH₃0.265g/L of the first mother liquor.

The second solid-liquid separation device 92 obtained 507.28kg of sodium chloride crystal cake with a water content of 15 mass% per hour, and finally 431.19kg of sodium chloride (purity 99.4 wt%) per hour; yield 4.98m per hour³The concentration of NaCl is 293.6g/L, Na₂SO₄ 65.2g/L、NaOH 2.06g/L、NH₃0.006g/L of a second mother liquor.

In this example, 4.45m of ammonia water having a concentration of 1.79 mass% was obtained per hour in the first ammonia water tank 51³1.16m of ammonia water having a concentration of 0.025 mass% 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 NaCl-containing 97g/L, Na₂SO₄ 99g/L、NH₄Cl 20g/L、(NH₄)₂SO₄20.75g/L, pH of 6.7 of catalyst production wastewater to obtain SO contained in the wastewater to be treated₄ ^2-And Cl^-In a molar ratio of 1: 6.844. the temperature of the wastewater to be treated after heat exchange by the first heat exchange device 31 was 80 deg.c, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange device 32 was 107 deg.c. The evaporation conditions of the MVR evaporation device 2 include: the temperature is 100 ℃, the pressure is-22.83 kPa, and the evaporation capacity is 3.79m³H is used as the reference value. The evaporation conditions of the single-effect evaporation apparatus 1 include: the temperature was 56 ℃, the pressure was-89.56 kPa, and the evaporation capacity was 1.58m³/h。

The first solid-liquid separation device 91 obtained 705.45kg of a sodium sulfate crystal cake containing 14 mass% of water per hour, and finally obtained 606.69kg of sodium sulfate (purity: 99.5 wt%) per hour; yield 11.03m per hour³The concentration of NaCl is 305.8g/L, Na₂SO₄ 53.84g/L、NaOH 2.2g/L、NH₃0.105g/L of the first mother liquor.

The second solid-liquid separation device 92 obtained 699.16kg of sodium chloride crystal cake with a water content of 15 mass% per hour, and finally 594.28kg of sodium chloride (purity 99.5 wt%) per hour; obtained 9.42m per hour³The concentration of NaCl is 295.2g/L, Na₂SO₄ 63g/L、NaOH 2.57g/L、NH₃0.0008g/L of second mother liquor.

In this example, 3.79m of ammonia water having a concentration of 1.8 mass% was obtained per hour in the first ammonia water tank 51³1.58m of ammonia water having a concentration of 0.006% by mass per hour was obtained in the second ammonia water tank 52³The ammonia water can be reused in the production process of the molecular sieve.

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

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

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

Claims

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

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

before the wastewater to be treated is introduced into an MVR evaporation device, adjusting the pH value of the wastewater to be treated to be more than 9;

the first evaporation prevents sodium chloride from crystallizing out, and the second evaporation prevents sodium sulfate from crystallizing out;

the conditions of the first evaporation include: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa; the flash conditions include: the pressure is-98 kPa to-87 kPa, and the temperature of the solution after flash evaporation is 35 ℃ to 60 ℃; the conditions of the second evaporation include: the temperature is 35-60 ℃, and the pressure is-98 kPa to-87 kPa;

relative to 1 mole of SO contained in the wastewater to be treated₄ ^2-Cl contained in the wastewater to be treated^-14 mol or less;

the wastewater to be treated contains the catalyst production wastewater and a liquid phase obtained by the second solid-liquid separation; NH in the catalyst production wastewater₄ ⁺Is more than 8mg/L, SO₄ ^2-Over 1000mg/L, Cl^-Over 970mg/L of Na⁺Is more than 510 mg/L.

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

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

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

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

6. The process of claim 1, wherein the first evaporation provides a concentration of sodium chloride in the first concentrate of 0.95X to 0.999X.

7. The process of claim 1, wherein the second evaporation results in a sodium sulfate concentration in the second concentrate of Y or less, wherein Y is the concentration of sodium sulfate at which both sodium sulfate and sodium chloride in the second concentrate are saturated at the temperature of the second evaporation.

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

9. The method of any one of claims 1-8, wherein the conditions of the first evaporation comprise: the temperature is above 45 ℃ and the pressure is above-95 kPa.

10. The method of claim 9, wherein the conditions of the first evaporation comprise: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa.

11. The method of claim 10, wherein the conditions of the first evaporation comprise: the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa.

12. The method of any one of claims 1-8, wherein the flash conditions comprise: the pressure is-97 kPa to-87 kPa, and the temperature of the solution after flash evaporation is 40 ℃ to 60 ℃.

13. The method of claim 12, wherein the conditions of the flashing comprise: the pressure is-95 kPa to-87 kPa, and the temperature of the solution after flash evaporation is 45 ℃ to 60 ℃.

14. The method of any one of claims 1-8, wherein the conditions of the second evaporation comprise: the temperature is 40-60 ℃, and the pressure is-97 kPa to-87 kPa.

15. The method of claim 14, wherein the conditions of the second evaporation comprise: the temperature is 45-60 ℃, and the pressure is-95 kPa to-87 kPa.

16. The method of claim 15, wherein the conditions of the second evaporation comprise: the temperature is 46-56 ℃, and the pressure is-95 kPa to-89 kPa.

17. The method of claim 9, wherein the temperature of the first evaporation is more than 20 ℃ higher than the temperature of the second evaporation.

18. The method of claim 17, wherein the temperature of the first evaporation is 35 ℃ to 70 ℃ higher than the temperature of the second evaporation.

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

20. The method as set forth in claim 19, wherein the pH of the wastewater to be treated is adjusted to be greater than 7 before the first heat exchange is performed.

21. The method according to claim 1, wherein the second ammonia-containing vapor obtained by evaporation in the single-effect evaporation device is subjected to second heat exchange with the cold medium generated by the heat pump to obtain second ammonia water.

22. A method according to claim 21, wherein the heat medium generated by the heat pump is heat exchanged with the liquid phase obtained by flashing and with the washing liquid obtained by washing the sodium chloride crystals.

23. The method according to claim 22, wherein the first ammonia-containing steam is subjected to the first heat exchange to condense the remaining tail gas, the tail gas produced by flashing and the second ammonia-containing steam is subjected to the second heat exchange to condense the remaining tail gas and is discharged after ammonia removal.

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

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

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

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

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

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