CN108726760B - Treatment method of catalyst production wastewater - Google Patents

Treatment method of catalyst production wastewater Download PDF

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Publication number
CN108726760B
CN108726760B CN201710263287.0A CN201710263287A CN108726760B CN 108726760 B CN108726760 B CN 108726760B CN 201710263287 A CN201710263287 A CN 201710263287A CN 108726760 B CN108726760 B CN 108726760B
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evaporation
wastewater
treated
kpa
temperature
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CN108726760A (en
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殷喜平
李叶
刘志坚
杨凌
伊红亮
苑志伟
刘夫足
高晋爱
安涛
顾松园
王涛
吕伟娇
蒋绍洋
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China Petroleum and Chemical Corp
Sinopec Catalyst Co
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China Petroleum and Chemical Corp
Sinopec Catalyst Co
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C1/00—Ammonia; Compounds thereof
    • C01C1/02—Preparation, purification or separation of ammonia
    • C01C1/022—Preparation of aqueous ammonia solutions, i.e. ammonia water
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D3/00—Halides of sodium, potassium or alkali metals in general
    • C01D3/04—Chlorides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/101—Sulfur compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/12—Halogens or halogen-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions

Abstract

The invention relates to the field of sewage treatment, and discloses a method for treating catalyst production wastewater, wherein the wastewater contains NH 4 + 、SO 4 2‑ 、Cl ‑ And Na + The method comprises the steps of 1) introducing wastewater to be treated into a first MVR 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 a second MVR evaporation device for second evaporation to obtain a second concentrated solution containing 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 NH 4 + 、SO 4 2- 、Cl - And Na + The method for treating wastewater from catalyst production.
Background
In the production process of the oil refining catalyst, a large amount of inorganic acid-base salts such as sodium hydroxide, hydrochloric acid, sulfuric acid, ammonium salts, sulfates, hydrochlorides and the like are needed, and a large amount of mixed sewage containing ammonium, sodium chloride, sodium sulfate and aluminosilicate is generated. For such sewage, the common practice in the prior art is that the pH value is adjusted to be within the range of 6-9, most of suspended matters are removed, then the biochemical method, the blow-off method or the steam stripping method is adopted to remove ammonium ions, then the salt-containing sewage is subjected to pH value adjustment, most of suspended matters are removed, hardness, silicon and part of organic matters are removed, most of organic matters are removed through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then the salt-containing sewage enters an ion exchange device for further hardness removal, enters an enrichment device (such as reverse osmosis or electrodialysis) for concentration, and then MVR evaporative crystallization or multiple-effect evaporative crystallization is adopted to obtain mixed miscellaneous salt of sodium chloride and sodium sulfate containing a small amount of ammonium salt; or is; firstly, adjusting the pH value to be within the range of 6.5-7.5, removing most suspended matters, then removing hardness, silicon and part of organic matters, removing most organic matters through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then entering an ion exchange device for further removing hardness, entering a thickening device (such as reverse osmosis and/or electrodialysis) for concentration, and then adopting MVR (mechanical vapor recompression) evaporative crystallization or multiple-effect evaporative crystallization to obtain the mixed miscellaneous salt of sodium chloride and sodium sulfate containing ammonium salt. However, these ammonium-containing mixed salts are currently difficult to treat or expensive to treat, and the process of removing ammonium ions at the early stage additionally increases the cost of wastewater treatment.
In addition, the biochemical deamination can only treat wastewater with low ammonium content, and can not directly carry out biochemical treatment due to insufficient COD content in the catalyst sewage, and organic matters such as glucose or starch and the like are additionally added in the biochemical treatment process, so that the 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 art 4 + 、SO 4 2- 、Cl - And Na + The problem that the treatment cost of the catalyst production wastewater is high and only mixed salt crystals can be obtained is solved, and the NH-containing catalyst with low cost and environmental protection is provided 4 + 、SO 4 2- 、Cl - And Na + The method can respectively recover ammonium, sodium chloride and sodium sulfate in the catalyst production wastewater, and furthest recycle resources in the wastewater.
In order to achieve the above object, the present invention provides a method for treating catalyst production wastewater containing NH 4 + 、SO 4 2- 、Cl - And Na + The method comprises the following steps of,
1) Introducing wastewater to be treated into a first MVR evaporation device for first evaporation to obtain first 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 a second MVR evaporation device for second evaporation to obtain a second concentrated solution containing ammonia vapor and sodium sulfate crystals;
3) Carrying out second solid-liquid separation on the second concentrated solution containing the sodium sulfate crystals;
adjusting the pH value of the wastewater to be treated to be more than 9 before introducing the wastewater to be treated into a first MVR evaporation device; 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 treated 4 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 NH 4 + 、SO 4 2- 、Cl - And Na + After the pH value of the wastewater is adjusted to a specific range in advance, a first MVR evaporation device is used for evaporation and separation to obtain sodium chloride crystals and stronger ammonia water, and then a second MVR evaporation device is used for evaporation again 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.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic flow diagram of a method for treating wastewater from catalyst production according to an embodiment of the present invention.
Description of the reference numerals
1. Second MVR evaporation plant 2, first MVR evaporation plant
31. First heat exchange device 32 and second heat exchange device
33. Third heat exchange device 34 and fourth heat exchange device
35. Fifth heat exchange device 4 and vacuum degassing tank
51. First ammonia water storage tank 52 and second ammonia water storage tank
53. First mother liquor tank 54 and second mother liquor tank
61. First pH measuring device 62 and second pH measuring device
71. First circulating pump 72 and second circulating pump
73. Third circulating pump 74 and fourth circulating pump
75. Fifth circulating pump 76 and sixth circulating pump
77. Seventh circulating pump 78, eighth circulating pump
79. Ninth 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
101. First compressor 102, second compressor
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.
The present invention will be described below with reference to fig. 1, but the present invention is not limited to fig. 1.
The invention provides a method for treating wastewater generated in catalyst production, which contains NH 4 + 、SO 4 2- 、Cl - And Na + The method comprises the following steps of,
1) Introducing wastewater to be treated into a first MVR 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 a second MVR evaporation device 1 to carry out 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 the first MVR evaporation device 2, adjusting the pH value of the wastewater to be treated to be more than 9; the first evaporation prevents the crystallization of sodium sulfate, and the second evaporation prevents the crystallization of sodium chloride; relative to 1 mol of SO contained in the wastewater to be treated 4 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 of the wastewater to be treated is adjusted to be greater than 10.8 before it is passed into the first MVR evaporation plant 2. The upper limit of the pH of the wastewater to be treated is not limited, and may be, for example, 14 or less, preferably 13.5 or less, and more preferably 13 or less.
The method provided by the invention can be used for the treatment of the compounds containing NH 4 + 、SO 4 2- 、Cl - And Na + In addition to containing NH 4 + 、SO 4 2- 、Cl - And Na + In addition, the wastewater to be treated is not particularly limited. From the viewpoint of improving the treatment efficiency of wastewater, the amount of SO contained in the wastewater to be treated is 1 mole per mole 4 2- Cl contained in the wastewater to be treated - The amount is 10 moles or more, preferably 50 moles or less, more preferably 40 moles or less, further preferably 30 moles or less, and for example, may be 10 to 15 moles, more preferably 11 to 14 moles. By reacting SO 4 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 treated 4 2- And Cl - The molar ratio of (a) to (b) is adjusted and the balance of sodium hydroxide can be maintained.
In the present invention, the 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. When the content of sodium sulfate in the obtained sodium chloride crystals is usually 8 mass% or less (preferably 4 mass% or less) because of the difference in the water content of the crystals after solid-liquid separation, it is considered that sodium sulfate is not crystallized out.
In the present invention, the second evaporation is performed so that sodium chloride does not crystallize out, which means that the sodium chloride concentration of the mixed system is controlled not to exceed the solubility under the second evaporation conditions (including but not limited to temperature, pH value, etc.), and sodium chloride entrained by sodium sulfate crystals or adsorbed on the surface is not excluded. When the content of sodium chloride in the obtained sodium sulfate crystals is usually 8 mass% or less (preferably 4 mass% or less) because of the difference in the water content of the crystals after solid-liquid separation, it is considered that sodium chloride is not crystallized out.
In the present invention, it is understood that the first ammonia-containing steam and the second ammonia-containing steam are secondary steam as referred to in the art. The pressures are all pressures in gauge pressure.
In the present invention, the first MVR evaporation device 2 is not particularly limited, and may be various MVR evaporation devices conventionally used in the art. For example, it may be one or more selected from the group consisting of an MVR falling film evaporator, an MVR forced circulation evaporator, an MVR-FC continuous crystallization evaporator, and an MVR-OSLO continuous crystallization evaporator. Among them, preferred are an MVR forced circulation evaporator and an MVR-FC continuous crystallization evaporator, and more preferred is a falling film + forced circulation two-stage MVR evaporative crystallizer.
In the present invention, the conditions for the first evaporation may be appropriately selected as necessary, and the purpose of crystallizing sodium chloride without precipitating sodium sulfate may be achieved. The conditions of the first 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 first evaporation include: the temperature is 35-60 ℃, and the pressure is-97.5 kPa to-87 kPa; more preferably, the conditions of the first evaporation include: the temperature is 40 ℃ to 60 ℃, and the pressure is-97 kPa to-87 kPa; further preferably, the conditions of the first evaporation include: the temperature is 45-60 ℃, and the pressure is-95 kPa to-87 kPa; particularly preferably, the conditions of the first evaporation include: the temperature is 45-55 ℃, and the pressure is-95 kPa to-90 kPa.
In the present invention, the operating pressure of the first evaporation is preferably the saturated vapor pressure of the evaporated feed liquid.
In the present invention, the flow rate of the first evaporation may be appropriately selected according to the capacity of the apparatus process, and may be, for example, 0.1m 3 More than h (e.g. 0.1 m) 3 /h～500m 3 /h)。
By carrying out the first evaporation under the above conditions, the sodium 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 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 crystallize sodium sulfate in the wastewater to be treated (i.e., sodium sulfate 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). 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. 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 monitored by monitoring the concentration of the first evaporation-yielded liquid, and specifically, the concentration of the first evaporation-yielded liquid is controlled within the above range so that the first evaporation does not crystallize out sodium sulfate in the first concentrated solution. 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 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 can be appropriately selected as required before the wastewater to be treated is introduced into the first MVR evaporation plant.
According to a preferred embodiment of the present invention, before the wastewater to be treated is introduced into the first MVR evaporation device 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 the first heat exchange may be 1 or more, preferably 2 to 4, and more preferably 2 to 3. Through after the first heat exchange, the output ammonia water is cooled, and the heat is circulated in the treatment device to the maximum extent, so that the energy is reasonably utilized, and the waste is reduced.
According to a preferred embodiment of the present invention, the first heat exchange is performed by a first heat exchange device 31 and a second heat exchange device 32, specifically, first ammonia-containing steam obtained by evaporation in the first MVR evaporation device 2 passes through the second heat exchange device 32 and the first heat exchange device 31 in sequence, and wastewater to be treated passes through the first heat exchange device 31 and the second heat exchange device 32 in sequence, and the first heat exchange is performed between the first ammonia-containing steam and the wastewater to be treated, so that the temperature of the wastewater to be treated is raised for evaporation, and the temperature of the first ammonia-containing steam is lowered to obtain first ammonia water, which can be stored in a first ammonia water storage tank 51.
According to another preferred embodiment of the present invention, the first heat exchange is performed by a first heat exchange device 31, a second heat exchange device 32 and a fifth heat exchange device 35, specifically, first ammonia-containing steam obtained by evaporation in the first MVR evaporation device 2 sequentially passes through the second heat exchange device 32 and the first heat exchange device 31, a second condensate containing second ammonia steam obtained by second evaporation (for example, a condensate obtained by second heat exchange of second ammonia-containing steam in the third heat exchange device 33 and the fourth heat exchange device 34) passes through the fifth heat exchange device 35, and a part of wastewater to be treated passes through the fifth heat exchange device 35, and simultaneously another part of wastewater to be treated passes through the first heat exchange device 31, and then the two parts of wastewater to be treated are merged and mixed with a second mother liquor to obtain wastewater to be treated, and then the wastewater to be treated passes through the second heat exchange device 32, so that the first heat exchange between the first ammonia-containing steam and the wastewater to be treated is heated for evaporation, and the first ammonia water is stored in the first ammonia storage tank 51.
In the present invention, the first heat exchange device 31, the second heat exchange device 32 and the fifth heat exchange device 35 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, it may be a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, or the like, 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 second ammonia-containing steam condensate, it is preferable that the temperature of the wastewater to be treated is 35 to 60 ℃, more preferably 40 to 60 ℃, and even more preferably 44 to 60 ℃ after the first heat exchange is performed by the fifth heat exchange device 35.
According to the present invention, in order to fully utilize the heat energy of the first ammonia-containing steam condensate, 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 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, the temperature of the wastewater to be treated is preferably 41 ℃ to 67 ℃, more preferably 47 ℃ to 62 ℃ 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 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 MVR evaporation device 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 wastewater to be treated into the first heat exchange device 31 or the fifth heat exchange device 35 before feeding the wastewater to be treated into the first heat exchange device 31 or the fifth heat exchange device 35 for the first heat exchange; then, the wastewater to be treated is sent to the second heat exchange device 32 to perform the first heat exchange, and the aqueous solution containing the alkaline substance is introduced and mixed in the pipe that sends the wastewater to be treated to the second heat exchange device 32 to perform the second pH adjustment. The pH of the wastewater to be treated is adjusted twice, so that the pH is greater than 9, preferably greater than 10.8, before the wastewater is passed into the first MVR evaporator 2. Preferably, the first pH adjustment is 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 adjusted pH value of the wastewater to be treated is greater than 9, preferably greater 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 to the first heat exchanging device 31 or the fifth heat exchanging device 35 to measure the pH value after the first pH adjustment, and a second pH measuring device 62 is provided on a pipe for feeding the wastewater to be treated to the second heat exchanging device 32 to measure the pH value after the second pH adjustment.
In the present invention, in order to increase the solid content in the first MVR evaporation device 2 and reduce the ammonia content in the liquid, it is preferable that a part of the liquid after evaporation by the first MVR evaporation device 2 (i.e. the liquid located inside the first MVR evaporation device, hereinafter also referred to as the first circulation liquid) is refluxed into the first MVR evaporation device 2 for evaporation. The above process of returning the first circulation liquid to the first MVR evaporation device 2 is preferably performed by mixing the first circulation liquid with the wastewater to be treated after the first pH adjustment and before the second pH adjustment, and then returning the mixture to the first MVR evaporation device 2, for example, the first circulation liquid may be returned to the wastewater conveying pipeline between the first heat exchange device 31 and the second heat exchange device 32 by the second circulation pump 72 to be mixed with the wastewater to be treated, and then after the second pH adjustment, the heat exchange is performed in the second heat exchange device 32, and finally the mixture is sent to the first MVR evaporation device 2. The ratio of the part of the liquid evaporated by the first MVR evaporation device 2 to be refluxed to the first MVR evaporation device 2 is not particularly limited, and for example, the first reflux ratio of the first evaporation may be appropriately set as needed, and may be 10 to 200, and preferably 40 to 120. Here, the first reflux ratio means: the ratio of the amount of reflux to the total amount of liquid fed to the first MVR evaporator 2 minus the amount of reflux.
According to the present invention, preferably, the method further comprises compressing the first ammonia-containing vapor before the first heat exchange. The compression of the first ammonia-containing vapor may be performed by a first compressor 101. Through right first ammonia vapor that contains compresses, for input energy among the MVR vaporization system, guarantee that waste water intensification-evaporation-cooling's process goes on in succession, need input start-up steam when MVR vaporization process starts, only need pass through first compressor 101 energy supply after reaching continuous running state, no longer need input other energy. The first compressor 101 may employ various compressors conventionally used in the art, such as a centrifugal fan, a turbine compressor, or a roots compressor. After compression by the first compressor 101, the temperature of the first ammonia-containing vapor is raised by 5 to 20 ℃.
In the invention, the first concentrated solution containing sodium 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 53, and can be sent to the second MVR evaporation device 1 through the sixth circulation pump 76 for second evaporation. In addition, it is difficult to avoid that the obtained sodium chloride crystals adsorb certain impurities such as chloride ions, free ammonia, hydroxide ions, etc., and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals, 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, it is preferable that the first washing liquid obtained in the above washing process is before the second pH adjustment by the return of the fifth circulation pump 75; more preferably, the first washing liquid obtained in the above washing process is returned to the wastewater conveying pipeline between the first heat exchange device 31 and the second heat exchange device 32 through the fifth circulation pump 75, and then subjected to the second pH adjustment, and then subjected to heat exchange in the second heat exchange device 32, and finally sent to the first MVR evaporation device 2 for evaporation.
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 is used for elutriation per 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 elutriation may preferably be performed using a liquid obtained by rinsing, and preferably using water or a sodium chloride solution. The liquid resulting from the washing is preferably returned to the first MVR evaporator 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 MVR evaporator 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 by subsequent washing of sodium chloride crystals is subjected to second elutriation in another elutriation tank, finally the slurry subjected to the two elutriations is sent to a solid-liquid separation device for solid-liquid separation, the crystals obtained by the solid-liquid separation are subjected to elution again with an aqueous sodium chloride solution, and the liquid obtained by the elution 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 second MVR evaporation device 1 is not particularly limited, and may be various MVR evaporation devices conventionally used in the art. For example, it may be one or more selected from the group consisting of an MVR falling film evaporator, an MVR forced circulation evaporator, an MVR-FC continuous crystallization evaporator, and an MVR-OSLO continuous crystallization evaporator. Among them, preferred are an MVR forced circulation evaporator and an MVR-FC continuous crystallization evaporator, and more preferred is a falling film + forced circulation two-stage MVR evaporative crystallizer.
In the present invention, the evaporation conditions of the second evaporation may be appropriately selected as needed, 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 ℃. In order to improve evaporation efficiency, 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; more preferably, from the viewpoint of reducing equipment cost and energy consumption, the conditions of the second evaporation include: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa, and further preferably, the conditions of the second evaporation comprise: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa; particularly preferably, the conditions of the second evaporation include: the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa.
In the present invention, the 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 the waste water to be treated, and may be, for example, 0.1m 3 More than h (e.g. 0.1 m) 3 /h～500m 3 /h)。
By 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.
According to the present invention, the second evaporation does not crystallize sodium chloride (i.e., sodium chloride does not reach supersaturation), and preferably, the second evaporation is performed such that the concentration of sodium chloride in the second concentrated solution is X or less (preferably 0.9X to 0.99X, more preferably 0.95X to 0.99X, and further 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 reach saturation 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 second evaporation-yielded liquid, and specifically, by controlling the concentration of the second evaporation-yielded liquid within the above range, the second evaporation does not crystallize out sodium chloride in the second concentrated solution. The concentration of the liquid resulting from the second evaporation is monitored by measuring the density, which may be carried out using a densitometer.
According to the invention, the second ammonia-containing steam and the first mother liquor are subjected to second heat exchange to obtain second ammonia water. Preferably, the second ammonia-containing steam carries out second heat exchange with the first mother liquor and the wastewater to be treated in turn to obtain second ammonia water. The second heat exchange method is not particularly limited, and may be performed by a heat exchange method that is conventional in the art. The number of heat exchanges may be 1 or more, preferably 2 to 4, and more preferably 2 to 3. Through the heat exchange, the output ammonia water is cooled, and the heat is at the maximum degree at the internal circulation of processing apparatus, rational utilization the energy, it is extravagant to have reduced.
According to a preferred embodiment of the present invention, the second heat exchange is performed by the third heat exchange device 33 and the fourth heat exchange device 34, specifically, the second ammonia-containing steam is sequentially passed through the fourth heat exchange device 34 and the third heat exchange device 33, the second heat exchange is performed with the mixed liquid of the first mother liquor, the second recycle liquid and the second rinse liquid in the fourth heat exchange device 34, the second heat exchange is performed with the first mother liquor in the third heat exchange device 33, and preferably, the first heat exchange is further performed in the fifth heat exchange device 35, so that the temperature of the second ammonia-containing steam condensate is further reduced, the heat energy utilization rate is improved, and the second ammonia water is obtained, and the second ammonia water is stored in the second ammonia water storage tank 52.
Preferably, after the second heat exchange is performed by the third heat exchange device 33, the temperature of the first mother liquor is 59-364 ℃, and more preferably 69-129 ℃; preferably, after the second heat exchange is performed by the fourth heat exchange device 34, the temperature of the first mother liquor is 67 ℃ to 370 ℃, and more preferably 75 ℃ to 137 ℃.
In the present invention, in order to increase the solid content in the second MVR evaporation device 1 and reduce the ammonia content in the liquid, it is preferable to return part of the liquid evaporated by the second MVR evaporation device 1 (i.e. the liquid located inside the second MVR evaporation device 1, hereinafter also referred to as a second circulation liquid) to the second MVR evaporation device 1. The process of refluxing the second circulating liquid to the second MVR evaporation device 1 is preferably that the first mother liquid is mixed with the second circulating liquid and optionally the second leachant, then subjected to the second heat exchange with the second ammonia-containing vapor, and finally refluxed to the second MVR evaporation device 1. For example, the second circulating liquid and the second eluting liquid may be mixed with the first mother liquid in the pipeline by the seventh circulating pump 77, and then introduced into the fourth heat exchanging device 34 for the second heat exchange, and then returned to the second MVR evaporating device 1. The ratio of the part of the liquid after evaporation by the second MVR evaporation device 1 to be refluxed to the second MVR evaporation device 1 is not particularly limited, for example, the second reflux ratio of the second evaporation may be 0.1 to 50, preferably 1 to 20, and more preferably 2 to 15. Here, the second reflux ratio means: the ratio of the amount of reflux to the total amount of liquid fed to the second MVR evaporator 1 minus the amount of reflux.
According to the present invention, preferably, the method further comprises compressing the second ammonia-containing vapor before the second heat exchange. The compression of the second ammonia-containing vapor may be performed by a second compressor 102. Through right the second contains ammonia steam and compresses, for input energy among the MVR vaporization system, guarantee that waste water intensification-evaporation-cooling's process goes on in succession, need input when MVR vaporization process starts and start steam, only need pass through second compressor 102 energy supply after reaching continuous running state, no longer need input other energy. The second compressor 102 may be any one of various compressors conventionally used in the art, such as a centrifugal fan, a turbine compressor, a roots compressor, or the like. After compression by the second compressor 102, the temperature of the second ammonia-containing vapor is raised by 5 to 20 ℃.
In the 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 times of evaporation satisfy: the temperature of the first evaporation is at least 5 ℃, preferably 20 ℃ and more preferably 35 ℃ to 70 ℃ lower than the temperature of the second evaporation. 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.
According to a preferred embodiment of the present invention, the second evaporation process is carried out in a second MVR evaporation device 1. And introducing the first mother liquor into the second MVR evaporation plant 1 through a sixth circulating pump 76 for second evaporation to obtain second ammonia-containing steam and a second concentrated solution containing sodium sulfate crystals.
In the present invention, the second concentrated solution containing sodium sulfate crystals is subjected to a second solid-liquid separation to obtain sodium sulfate crystals and a second mother liquor (i.e. a liquid phase obtained by the second solid-liquid separation), and the second mother liquor is temporarily stored in the second mother liquor tank 54. The method of the second solid-liquid separation is not particularly limited, and may be selected from, for example, one or more of centrifugation, filtration, and sedimentation.
According to the present invention, the second solid-liquid separation may be performed by a second solid-liquid separation device (for example, a centrifuge, a belt filter, a plate filter, 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 MVR evaporation device 2 to be subjected to the first evaporation again, and specifically, the second mother liquor may be returned to the second pH adjustment process by the eighth circulation pump 78 to be mixed with the catalyst production wastewater to obtain the wastewater to be treated, and then the wastewater is sent to the first MVR evaporation device 2 to be subjected to the first evaporation. 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 dissolution of sodium sulfate crystals during washing, preferably, the sodium sulfate crystals are 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 from the above washing process is preferably returned to the second MVR evaporation device 1 by the ninth circulation pump 79 for 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 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 preferred that the catalyst production wastewater elutriation liquid is returned to the first MVR evaporation device before the second pH adjustment before evaporation, and that other washing liquids are returned to the second MVR evaporation device.
According to a preferred embodiment of the present invention, after the first solid-liquid separation by settling, the second concentrated solution containing sodium sulfate crystals obtained by the second evaporative crystallization is subjected to 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 second elutriation in another elutriation tank, finally the slurry subjected to the two elutriations is sent to a solid-liquid separation device for solid-liquid separation, the crystals obtained by the solid-liquid separation are subjected to elution by an aqueous sodium 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 liquid obtained by the elution is returned to the second elutriation as an elutriation liquid. Through the washing process combining elutriation and leaching, the purity of the obtained sodium sulfate crystal is improved, washing liquid cannot be introduced too much, and the efficiency of wastewater treatment is improved.
According to a preferred embodiment of the present invention, the tail gas remaining after the first ammonia-containing steam is condensed by the first heat exchange and the tail gas remaining after the second ammonia-containing steam is condensed by the second heat exchange are discharged after ammonia removal. The first ammonia-containing steam is subjected to the first heat exchange to condense the remaining tail gas, i.e., the tail gas discharged from the second heat exchange device 32, and the second ammonia-containing steam is subjected to the second heat exchange to condense the remaining tail gas, i.e., the tail gas discharged from the fourth heat exchange device 34. The ammonia in the tail gas is removed, so that the pollutant content in the discharged tail gas can be further reduced, and the tail gas can be directly discharged.
As the method of removing ammonia, absorption may be performed by the off-gas absorption tower 83. The off-gas absorption column 83 is not particularly limited, and may be any of various absorption columns conventionally used in the art, such as a plate-type absorption column, a packed absorption column, a falling film absorption column, or an empty column. Circulating water is arranged in the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of the fourth circulating pump 74, water can be supplemented into the tail gas absorption tower 83 from the circulating water tank 82 through the third circulating pump 73, fresh water can be supplemented into the circulating water tank 82, and meanwhile the temperature of working water of the vacuum pump 81 and the ammonia content can be reduced. The flow of the tail gas and the circulating water in the tail gas absorption tower 83 may be countercurrent or cocurrent, and is preferably countercurrent. The circulating water can be supplemented by additional fresh water. In order to ensure the sufficient absorption of the tail gas, dilute sulfuric acid may be further added to the tail gas absorption tower 83 to absorb a small amount of ammonia and the like in the tail gas. The circulating water can be used as ammonia water or ammonium sulfate solution for production or direct sale after absorbing tail gas. The off gas may be introduced into the off gas absorption tower 83 by a vacuum pump 81.
In the present invention, the catalyst production wastewater is not particularly limited as long as it contains NH 4 + 、SO 4 2- 、Cl - And Na + The wastewater is obtained. In addition, the method is particularly suitable for treating high-salinity wastewater. The wastewater from the catalyst production of the present invention may be specifically wastewater from the production of a molecular sieve, alumina or 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 preferably a wastewater obtained by subjecting a wastewater from a molecular sieve, alumina or oil refining catalyst production process to impurity removal and concentration as described below.
As NH in the catalyst production wastewater 4 + It may be 8mg/L or more, preferably 300mg/L or more.
As Na in the wastewater from the catalyst production + May be 510mg/L or more, preferably 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 catalyst 4 2- May be 1000mg/L or more, preferably 2000mg/L or more, more preferably 4000mg/L or more, further preferably 8000mg/L or more, further preferably 16000mg/L or more, further preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, further preferably 60000mg/L or more, further preferably 70000mg/L or more.
As Cl in the catalyst production wastewater - May be 970mg/L or more, more preferably 2000mg/L or more, further preferably 4000mg/L or more, further preferably 8000mg/L or more, further preferably 16000mg/L or more, further preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, further preferably 60000mg/L or more.
NH contained in the catalyst production wastewater 4 + 、SO 4 2- 、Cl - And Na + The upper limit of (3) is not particularly limited. SO in the wastewater from the viewpoint of easy access to the wastewater 4 2- 、Cl - And Na + The upper limit of (b) is 200g/L or less, preferably 150g/L or less, respectively; NH in wastewater 4 + Is 50g/L or less, preferably 20g/L or less.
From the viewpoint of improving the efficiency of the first evaporation and reducing the energy consumption of the treatment process, the amount of SO contained in the wastewater is relatively small 4 2- Cl in catalyst production wastewater - The higher the content, the better, for example, relative to 1 mole of SO contained in the ammonium salt-containing wastewater 4 2- Cl contained in the catalyst production wastewater - Is 1 mole or more, preferably 2 moles or more, preferably 5 moles or more, more preferably 9.5 moles or more, and further preferably 10 moles or more. From the viewpoint of practicality, the amount of SO contained in the wastewater from the catalyst production is 1 mole 4 2- Cl contained in the catalyst production wastewater - Preferably 200 mol or less, more preferably 150 mol or less, further preferably 100 mol or less, further preferably 50 mol or less, and further preferably 30 mol or less. By adding Cl contained in the catalyst production wastewater - And SO 4 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 NH 4 + 、SO 4 2- 、Cl - And Na + In addition, it may contain Mg 2+ 、Ca 2+ 、K + 、Fe 3+ Inorganic salt ions such as rare earth element ions, mg 2+ 、Ca 2+ 、K + 、Fe 3+ The content of each inorganic salt ion such as a rare earth element ion is preferably 100mg/L or less, more preferably 50mg/L or less, further preferably 10mg/L or less, and particularly preferably no other inorganic salt ion is contained. By controlling the other inorganic salt ions within the above range, the purity of the sodium sulfate crystals and sodium chloride crystals finally obtained can be further improved. In order to reduce the content of other inorganic salt ions in the catalyst production wastewater, the following impurity removal is preferably performed.
The TDS of the catalyst production wastewater may be 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 present invention, the pH of the catalyst production wastewater is preferably 4 to 8, and more preferably 6.4 to 6.6.
In addition, since the COD of the wastewater may block a membrane during concentration, affect the purity and color of a salt during evaporative crystallization, etc., the COD of the wastewater from the catalyst production is preferably as small as possible (preferably 20mg/L or less, more preferably 10mg/L or less), and is preferably removed by oxidation during pretreatment, specifically, by biological method, advanced oxidation method, etc., and is preferably oxidized by an oxidizing agent such as Fenton's reagent when the COD content is very high.
In the invention, in order to reduce the concentration of impurity ions in the wastewater, ensure the continuous and stable treatment process and reduce the equipment operation and maintenance cost, the catalyst production wastewater is preferably subjected to impurity removal before being treated by the treatment method. Preferably, the impurity removal is selected from one or more of solid-liquid separation, chemical precipitation, adsorption, ion exchange and oxidation.
As the solid-liquid separation, filtration, centrifugation, sedimentation, or the like may be mentioned; as the chemical precipitation, pH adjustment, carbonate precipitation, magnesium salt precipitation, and the like may be mentioned; the adsorption can be physical adsorption and/or chemical adsorption, and the specific adsorbent can be selected from activated carbon, silica gel, alumina, molecular sieve, natural clay and the like; as the ion exchange, either one of a strongly acidic cation resin and a weakly acidic cation resin can be used; as the oxidation, various oxidizing agents conventionally used in the art, such as ozone, hydrogen peroxide, and potassium permanganate, can be used, and in order to avoid introduction of new impurities, ozone, hydrogen peroxide, and the like are preferably used.
The specific impurity removal mode can be specifically selected according to the types of impurities contained in the catalyst production wastewater. For suspended matters, a solid-liquid separation method can be selected for removing impurities; for inorganic matters and organic matters, chemical precipitation, ion exchange and adsorption methods can be selected for removing impurities, such as weak acid cation exchange, activated carbon adsorption and the like; for organic matters, impurities can be removed by adopting an adsorption and/or oxidation mode, wherein an ozone biological activated carbon adsorption oxidation method is preferred. According to a preferred embodiment of the invention, the catalyst production wastewater is subjected to impurity removal by sequentially carrying out filtration, a weak acid cation exchange method and an ozone biological activated carbon adsorption oxidation method. 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 catalyst production 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 wastewater of the present invention before the treatment by the treatment method of the present invention (preferably, after the above-mentioned removal of impurities). Preferably, the concentration is selected from ED membrane concentration and/or reverse osmosis; more preferably, the concentration is performed by ED membrane concentration and reverse osmosis, and the order of performing the ED membrane concentration and the reverse osmosis is not particularly limited. The ED membrane concentration and reverse osmosis treatment apparatus and conditions may be performed in a manner conventional in the art, and may be specifically selected according to the condition of wastewater to be treated. Specifically, as the concentration of the ED membrane, a one-way electrodialysis system or a reversed electrodialysis system can be selected for carrying out; as the reverse osmosis, a roll membrane, a plate membrane, a disc-tube membrane, a vibrating membrane or a combination thereof can be selected for use. Through the concentration, the efficiency of treating the catalyst production wastewater can be improved, and energy waste caused by a large amount of evaporation is avoided.
In a preferred embodiment of the invention, the catalyst production wastewater is wastewater generated by chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation of wastewater generated in the molecular sieve production process, and is concentrated by an ED membrane and a reverse osmosis method.
The conditions for the above chemical precipitation are preferably: sodium carbonate is used as a treating agent, 1.2 to 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 between 20 and 35 ℃, and the reaction time is between 0.5 and 4 hours.
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 to 5 mass percent; the dosage of the regenerant (calculated by 100%) is 50kg/m 3 ～60kg/m 3 Wet 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 speed 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 for the above-mentioned ozone biological activated carbon adsorption oxidation method are preferably as follows: the retention time of the ozone is 50min to 70min, and the empty bed filtration rate is 0.5m/h to 0.7m/h.
The conditions for the concentration of the ED membrane are preferably: the current 145A to 155A and the voltage 45V to 65V. As the ED membrane, for example, an ED membrane manufactured by easton corporation, japan can be used.
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 stage 2 SO 4 And NaCl to adjust the ion content in the wastewater to be treated as long as the wastewater to be treated satisfies SO in the wastewater to be treated in the present invention 4 2- 、Cl - The requirements are met.
The present invention will be described in detail below by way of examples.
In the following examples, the catalyst production wastewater is wastewater from a molecular sieve production process, which is subjected to chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation in sequence to remove impurities, and is subjected to ED membrane concentration and reverse osmosis concentration in sequence.
Example 1
As shown in figure 1, the catalyst production wastewater (containing NaCl 160g/L, na) 2 SO 4 50g/L、NH 4 Cl 39g/L、(NH 4 ) 2 SO 4 12.4g/L, pH 65) at a feed rate of 5m 3 The reaction mixture was fed to a vacuum degassing tank 4 at a rate of/h to be subjected to vacuum degassing, an aqueous sodium hydroxide solution having a concentration of 45.16 mass% was introduced into a pipe to adjust the pH value for the first time, the adjusted pH value was monitored by a first pH value measuring device 61 (pH meter) (measured value: 7.5), and a part (1 m) of the catalyst production wastewater having been adjusted by the first pH value was subjected to first pH value adjustment by a first circulating pump 71 3 H) sending the waste water into a fifth heat exchange device 35 (a titanium alloy plate heat exchanger) to perform first heat exchange with the recovered second ammonia-containing steam condensate so as to heat the waste water generated in the catalyst production to 48 ℃, and sending the rest of the waste water into a first heat exchange device 31 to perform first heat exchange with the recovered first ammonia-containing steam condensate so as to heat the waste water generated in the catalyst production to 49 ℃; then, the two portions of the catalyst production wastewater are merged and mixed with a second mother liquor to obtain wastewater to be treated (SO contained therein is measured) 4 2- And Cl - In a molar ratio of 1:12.656 Introducing a sodium hydroxide aqueous solution with the concentration of 45.16 mass% into a pipeline for conveying the wastewater to be treated into the second heat exchange device 32 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 11), conveying the wastewater to be treated into the second heat exchange device 32 (a titanium alloy plate type heat exchanger) to carry out first heat exchange with the recovered first ammonia-containing steam so as to heat the wastewater to be treated to 57 ℃, conveying the wastewater to be treated into a first MVR evaporation device 2 (a falling film and forced circulation two-stage MVR evaporation crystallizer) to carry out evaporation, and obtaining first ammonia-containing steam and a first concentrated solution containing sodium chloride crystals. Wherein the evaporation temperature of the first MVR evaporation device 2 is 50 ℃, the pressure is-92.7 kPa, and the evaporation capacity is 4.56m 3 H is used as the reference value. The first ammonia-containing steam obtained by evaporation is compressed by the first compressor 101 (the temperature is increased by 10 ℃) and then sequentially passes through the second heat exchange device 32 and the first heat exchange device 31, and is respectively subjected to heat exchange with wastewater to be treated and catalyst production wastewater, cooled to obtain first ammonia water, and the first ammonia water is stored in the first ammonia water storage tank 51. In addition, in order to increase the solid content in the first MVR evaporation device 2, part of the liquid evaporated in the first MVR evaporation device 2 is circulated to the second heat exchange device 32 through the second circulation pump 72 as the first circulation liquid, and then enters the first MVR evaporation device 2 again for first evaporationAnd (the first reflux ratio is 95.4). The degree of the first evaporation was monitored by a densimeter provided in the first MVR evaporation apparatus 2, and the concentration of sodium sulfate in the first concentrated solution was controlled to 0.9705Y (65.7 g/L).
The first concentrated solution was sent to a first solid-liquid separation apparatus 91 (centrifuge) to carry out first solid-liquid separation, and 20.87m per hour was obtained 3 Contains NaCl 294.6g/L, na 2 SO 4 65.7g/L、NaOH 0.22g/L、NH 3 0.11g/L of first mother liquor is temporarily stored in a first mother liquor tank 53, sodium chloride solids obtained by solid-liquid separation (15 mass percent of sodium chloride crystal filter cake 1196.17kg is obtained in each hour, wherein the content of sodium sulfate is below 3.9 mass percent) are leached by 295g/L of sodium chloride solution which is equal to the dry basis mass of the sodium chloride crystal filter cake, after drying, 1016.74kg (the purity is 99.5 weight percent) is obtained in each hour, and the washing liquor is circulated to mix with the wastewater to be treated before the second pH value adjustment by a fifth circulating pump 75, and then enters the first MVR evaporation device 2 again for first evaporation.
The second evaporation process is carried out in a second MVR evaporation device 1 (forced circulation evaporator). And (3) enabling the first mother liquor in the first mother liquor tank 53 to exchange heat with the second ammonia-containing steam condensate through a third heat exchange device 33 by a sixth circulating pump 76, then enabling the first mother liquor to exchange heat with the second ammonia-containing steam through a fourth heat exchange device 34, and finally sending the second mother liquor into a second MVR evaporation device 1 for second evaporation to obtain second ammonia-containing steam and a second concentrated solution containing sodium sulfate crystals. Wherein the evaporation temperature of the second MVR evaporation device 1 is 105 ℃, the pressure is-7.0 kPa, and the evaporation capacity is 1.05m 3 H is the ratio of the total weight of the catalyst to the total weight of the catalyst. In order to increase the solid content in the second MVR evaporation device 1, part of the first mother liquor after evaporation in the second MVR evaporation device 1 is circulated as a second circulation liquid to the fourth heat exchange device 34 by the seventh circulation pump 77, and then enters the second MVR evaporation device 1 again for second evaporation (the second reflux ratio is 4). The second ammonia-containing steam obtained by evaporation is compressed by a second compressor 102 (the temperature is raised by 12 ℃) and then sequentially passes through a fourth heat exchange device 34 and a third heat exchange device 33 to perform second heat exchange with the first mother liquor, and then passes through a fifth heat exchange device 35 to perform second heat exchange with part of catalyst production wastewater conveyed by a first circulating pump 71The first heat exchange is carried out, and the second ammonia water is obtained by cooling and stored in the second ammonia water storage tank 52. The degree of the second evaporation was monitored by a densimeter provided in the second MVR evaporation apparatus 1, and the concentration of sodium chloride in the second concentrated solution was controlled to 0.99355X (307.9 g/L). After the first mother liquor is evaporated in the second MVR evaporation device 1, a second concentrated solution containing sodium sulfate crystals is obtained.
The second concentrated solution containing sodium sulfate crystals was sent to a second solid-liquid separation apparatus 92 (centrifuge) for solid-liquid separation to obtain 20.21 m/hr 3 Contains NaCl 307.9g/L, na 2 SO 4 53.0g/L、NaOH 0.30g/L、NH 3 0.0035g/L of a second mother liquor, temporarily stored in a second mother liquor tank 54. And (3) circulating the second mother liquor to the position before the second pH value adjustment through an eighth circulating pump 78, and mixing the second mother liquor with preheated catalyst production wastewater to obtain wastewater to be treated. After solid-liquid separation, the obtained sodium sulfate solid (sodium sulfate crystal cake with a water content of 14 mass% 364.15kg, wherein the sodium chloride content is below 3.8 mass% is obtained per hour) is subjected to leaching by using 53g/L sodium sulfate solution which is equal to the dry basis mass of sodium sulfate, and then is dried in a dryer, so that 313.17kg (the purity is 99.5 wt%) of sodium sulfate is obtained per hour, and a second washing liquid obtained by washing is circulated to the second MVR evaporation device 1 through a ninth circulation pump 79.
In addition, the tail gas discharged by the vacuum degassing tank 4, the second heat exchange device 32 and the fourth heat exchange device 34 is introduced into a tail gas absorption tower 83 through a vacuum pump 81 for absorption, circulating water is introduced into the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of a 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, 4.56m of ammonia water having a concentration of 1.63 mass% was obtained per hour in the first ammonia water tank 51 3 1.05m of aqueous ammonia having a concentration of 0.21 mass% was obtained per hour in the second aqueous ammonia tank 52 3 The 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 170g/L, na 2 SO 4 27g/L、NH 4 Cl 27.9g/L、(NH 4 ) 2 SO 4 4.5g/L, pH is 6.6, and the obtained SO contained in the wastewater to be treated 4 2- And Cl - In a molar ratio of 1:13.727. the temperature of the catalyst production wastewater after heat exchange by the fifth heat exchange device 35 is 53 ℃, the temperature of the catalyst production wastewater after heat exchange by the first heat exchange device 31 is 54 ℃, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange device 32 is 62 ℃. The first MVR evaporation device 2 has an evaporation temperature of 55 ℃, a pressure of-90.2 kPa and an evaporation capacity of 4.87m 3 H is used as the reference value. The evaporation temperature of the second MVR evaporation device 1 is 95 ℃, the pressure is-36.4 kPa, and the evaporation capacity is 0.56m 3 /h。
The first solid-liquid separation device 91 obtains 1183.08kg of sodium chloride crystal filter cake containing 15 mass% of water every hour, and finally obtains 1005.62kg of sodium chloride (the purity is 99.6 weight%); yield 15.89m per hour 3 The concentration of NaCl 296.6g/L, na 2 SO 4 63.6g/L、NaOH 0.29g/L、NH 3 0.031g/L of the first mother liquor.
The second solid-liquid separation device 92 obtains 183.73kg of sodium sulfate crystal cake with a water content of 15 mass% per hour, and finally obtains 156.17kg of sodium sulfate (with a purity of 99.4 wt%) per hour; yield 15.04m per hour 3 The concentration of NaCl is 306.1g/L, na 2 SO 4 55.3g/L、NaOH 0.3g/L、NH 3 0.0013g/L of second mother liquor.
In this example, 4.87m of ammonia water having a concentration of 1.0 mass% was obtained per hour in the first ammonia water tank 51 3 0.56m of 0.08 mass% ammonia water was obtained per hour in the second ammonia water tank 52 3 The ammonia water can be reused in the production process of the molecular sieve.
Example 3
The treatment of the catalyst production wastewater was carried out in the same manner as in example 1, except that: for the NaCl-containing 81g/L, na 2 SO 4 79g/L、NH 4 Cl 32g/L、(NH 4 ) 2 SO 4 31.72g/L, pH catalyst production wastewater of 6.4 is treated, and SO contained in the obtained wastewater to be treated 4 2- And Cl - In a molar ratio of 1:11.123. the temperature of the catalyst production wastewater after heat exchange by the fifth heat exchange device 35 is 43 ℃, the temperature of the catalyst production wastewater after heat exchange by the first heat exchange device 31 is 44 ℃, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange device 32 is 52 ℃. The evaporation temperature of the first MVR evaporation device 2 is 45 ℃, the pressure is-94.7 kPa, and the evaporation capacity is 3.73m 3 H is used as the reference value. The evaporation temperature of the second MVR evaporation device 1 is 100 ℃, the pressure is-22.9 kPa, and the evaporation capacity is 1.99m 3 /h。
The first solid-liquid separation device 91 obtains 675.13kg of sodium chloride crystal filter cake containing 14 mass% of water every hour, and finally obtains 580.61kg of sodium chloride (the purity is 99.4 wt%) every hour; yield 36.26m per hour 3 The concentration of NaCl is 292.4g/L, na 2 SO 4 67.3g/L、NaOH 0.1g/L、NH 3 0.076g/L of the first mother liquor.
The second solid-liquid separation device 92 obtained 657.0kg of sodium sulfate crystal cake with a water content of 14 mass% per hour, and finally obtained 580.6kg of sodium sulfate (purity of 99.5 wt%); yield 34.52m per hour 3 The concentration is NaCl 307.1g/L, na 2 SO 4 54.3g/L、NaOH 0.105g/L、NH 3 0.0039g/L of a second mother liquor.
In this example, 3.73m of ammonia water having a concentration of 2.3 mass% was obtained per hour in the first ammonia water tank 51 3 1.99m of ammonia water having a concentration of 0.13 mass% is obtained per hour in the second ammonia water tank 52 3 The ammonia water can be reused in the production process of the molecular sieve.
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 foregoing embodiments may be combined in any suitable manner without contradiction. 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 (33)

1. Method for treating catalyst production wastewater containing NH 4 + 、SO 4 2- 、Cl - And Na + Characterized in that the method comprises the following steps,
1) Introducing wastewater to be treated into a first MVR 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 a second MVR evaporation device to carry out second evaporation to obtain second concentrated solution containing ammonia vapor and sodium sulfate crystals;
3) Carrying out second solid-liquid separation on the second concentrated solution containing the sodium sulfate crystals;
adjusting the pH value of the wastewater to be treated to be more than 9 before introducing the wastewater to be treated into a first MVR evaporation device;
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 treated 4 2- Cl contained in the wastewater to be treated - 9.5 mol or more;
the wastewater to be treated contains the catalystAgent production wastewater and a liquid phase obtained by the second solid-liquid separation; NH in the catalyst production wastewater 4 + Is more than 8mg/L, SO 4 2- 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 treated 4 2- Cl contained in the wastewater to be treated - Is 10 mol or more.
3. The method according to claim 2, wherein the SO contained in the wastewater to be treated is 1 mole relative to the SO contained in the wastewater to be treated 4 2- Cl contained in the wastewater to be treated - Is 10-15 mol.
4. The method as claimed in claim 1, wherein the pH of the wastewater to be treated is adjusted to be greater than 10.8 before passing the wastewater to be treated to the first MVR evaporation plant.
5. The method as claimed in claim 1, wherein the pH adjustment of the wastewater to be treated is carried out with NaOH.
6. The process of claim 1, wherein the first evaporation is conducted 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.
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. The process of claim 6, wherein the second evaporation provides a concentration of sodium chloride in the second concentrate of X or less, wherein X is the concentration of sodium chloride at which both sodium chloride and sodium sulfate in the second concentrate are saturated under the conditions of the second evaporation.
9. The process of claim 8, wherein the second evaporation provides a concentration of sodium chloride in the second concentrate of 0.95X to 0.999X.
10. The method of any one of claims 1-9, wherein the conditions of the first evaporation comprise: the temperature is 30-85 ℃, and the pressure is-98 kPa-58 kPa.
11. The method of claim 10, wherein the conditions of the first evaporation comprise:
the temperature is 35-60 ℃, and the pressure is-97.5 kPa to-87 kPa.
12. The method of claim 11, wherein the conditions of the first evaporation comprise:
the temperature is 40-60 ℃, and the pressure is-97 kPa to-87 kPa.
13. The method of claim 12, wherein the conditions of the first evaporation comprise:
the temperature is 45-60 ℃, and the pressure is-95 kPa to-87 kPa.
14. The method of claim 13, wherein the conditions of the first evaporation comprise:
the temperature is 45-55 ℃, and the pressure is-95 kPa to-90 kPa.
15. The method of any one of claims 1-9, wherein the conditions of the second evaporation comprise: the temperature is above 45 ℃ and the pressure is above-95 kPa.
16. The method of claim 15, wherein the conditions of the second evaporation comprise:
the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa.
17. The method of claim 16, wherein the conditions of the second evaporation comprise:
the temperature is 60-365 ℃, and the pressure is-87 kPa-18110 kPa.
18. The method of claim 17, wherein the conditions of the second evaporation comprise:
the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa.
19. The method of claim 18, wherein the conditions of the second evaporation comprise:
the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa.
20. The method of claim 19, wherein the conditions of the second evaporation comprise:
the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa.
21. The method of claim 10, wherein the temperature of the first evaporation is more than 5 ℃ lower than the temperature of the second evaporation.
22. The method of claim 21, wherein the temperature of the first evaporation is 20 ℃ or more lower than the temperature of the second evaporation.
23. The method of claim 22, wherein the temperature of the first evaporation is 35 ℃ to 70 ℃ lower than the temperature of the second evaporation.
24. The method of claim 23, wherein the temperature of the first evaporation is 50 ℃ to 59 ℃ lower than the temperature of the second evaporation.
25. The method of claim 1, wherein the first ammonia-containing vapor is subjected to a first heat exchange with the wastewater to be treated and a first ammonia solution is obtained before the wastewater to be treated is passed to a first MVR evaporation plant.
26. The method as set forth in claim 25, wherein the pH of the wastewater to be treated is adjusted to be greater than 7 prior to the first heat exchange.
27. The process of claim 1, wherein the second ammonia-containing vapor evaporated by the second MVR evaporation device is subjected to a second heat exchange with the liquid phase obtained by the first solid-liquid separation to obtain a second ammonia water.
28. The method according to any one of claims 1 to 9, further comprising subjecting the first concentrated solution containing sodium chloride crystals to a first solid-liquid separation to obtain sodium chloride crystals.
29. The method of claim 28, further comprising washing the resulting sodium chloride crystals.
30. The method according to any one of claims 1 to 9, further comprising subjecting the second concentrated solution containing sodium sulfate crystals to a second solid-liquid separation to obtain sodium sulfate crystals.
31. The method of claim 30, further comprising washing the resulting sodium sulfate crystals.
32. The process of any one of claims 1 to 9, wherein the catalyst production wastewater is wastewater from a molecular sieve, alumina or refinery catalyst production process.
33. The method of claim 32, further comprising removing impurities and concentrating the catalyst process wastewater.
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