CN108726761B - Treatment method of catalyst production wastewater - Google Patents

Treatment method of catalyst production wastewater Download PDF

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CN108726761B
CN108726761B CN201710263288.5A CN201710263288A CN108726761B CN 108726761 B CN108726761 B CN 108726761B CN 201710263288 A CN201710263288 A CN 201710263288A CN 108726761 B CN108726761 B CN 108726761B
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evaporation
wastewater
treated
ammonia
kpa
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CN108726761A (en
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殷喜平
李叶
王涛
刘夫足
刘志坚
徐淑朋
高晋爱
安涛
吕伟娇
顾松园
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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

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Analytical Chemistry (AREA)
  • Heat Treatment Of Water, Waste Water Or Sewage (AREA)

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 + Introducing wastewater to be treated into an MVR evaporation device to perform first evaporation to obtain first ammonia-containing steam and first concentrated solution containing sodium chloride crystals, wherein the wastewater to be treated contains the catalyst production wastewater; 2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium chloride crystals, sequentially introducing a liquid phase obtained by the first solid-liquid separation into each effect evaporator of the multi-effect evaporation device for second evaporation, respectively obtaining second ammonia-containing steam in each effect evaporator, and obtaining a second concentrated solution containing the sodium sulfate crystals in the last effect evaporator; 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 method for treating wastewater containing NH 4 + 、SO 4 2- 、Cl - And Na + The method for treating wastewater from catalyst production.
Background
In the production process of the oil refining catalyst, a large amount of inorganic acid alkali salts such as sodium hydroxide, hydrochloric acid, sulfuric acid, ammonium salts, sulfates, hydrochlorides and the like are needed, and a large amount of mixed sewage containing ammonium, sodium chloride, sodium sulfate and aluminosilicate is generated. For such sewage, the common practice in the prior art is that firstly the pH value is adjusted to be within the range of 6-9, most of suspended matters are removed, then the biochemical method, the stripping method or the steam stripping method is adopted to remove ammonium ions, then the saline sewage is subjected to pH value adjustment, most of suspended matters are removed, the hardness, the silicon and part of organic matters are removed, then the saline sewage is subjected to ozone biological activated carbon adsorption oxidation or other advanced oxidation methods to remove most of organic matters, then the saline sewage enters an ion exchange device to further remove the hardness, and then the saline sewage enters a concentration device (such as reverse osmosis and/or electrodialysis) for concentration, and then the MVR evaporative crystallization or multiple-effect evaporative crystallization is adopted to obtain sodium chloride and sodium sulfate mixed miscellaneous salt 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 or expensive to treat, and the process of removing ammonium ions at the early stage adds additional cost to the treatment of wastewater.
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 problems are that the total nitrogen of the wastewater subjected to the biochemical deamination treatment often does not reach the standard (the contents of nitrate ions and nitrite ions exceed the standard), advanced treatment is required, 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 ammoniacal nitrogen in 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 is not greatly changed, the salt content in the wastewater is not reduced (20000 mg/L-30000 mg/L), the wastewater cannot be directly discharged, further desalting treatment is needed, the operation cost of wastewater treatment is high, a large amount of alkali remains in the treated wastewater, the pH value is high, the waste is large, and the treatment cost is up to 50 yuan/ton.
Disclosure of Invention
The purpose of the invention is to overcome the defects in the prior artContaining NH 4 + 、SO 4 2- 、Cl - And Na + The catalyst has high treatment cost of wastewater and can only obtain mixed salt crystals, and provides a low-cost and environment-friendly NH-containing catalyst 4 + 、SO 4 2- 、Cl - And Na + The method for treating the catalyst production wastewater can respectively recover the ammonium, the sodium chloride and the sodium sulfate in the catalyst production wastewater, and furthest recycle resources in the wastewater.
In order to achieve the above object, the present invention provides a method for treating wastewater from catalyst production containing NH 4 + 、SO 4 2- 、Cl - And Na + The method comprises the following steps of,
1) Introducing wastewater to be treated into an MVR evaporation device to carry out first evaporation to obtain first ammonia-containing steam and first concentrated solution containing sodium chloride crystals, wherein the wastewater to be treated contains the catalyst production wastewater;
2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium chloride crystals, sequentially introducing a liquid phase obtained by the first solid-liquid separation into each effect evaporator of the multi-effect evaporation device for second evaporation, respectively obtaining second ammonia-containing steam in each effect evaporator, and obtaining a second concentrated solution containing the sodium sulfate crystals in the last effect evaporator;
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 an MVR evaporation device; sending second ammonia-containing steam obtained by evaporation in the previous evaporator to the next evaporator for second heat exchange with the first concentrated solution to obtain second ammonia water, and carrying out cocurrent heat exchange between the first concentrated solution and the second ammonia-containing steam; the first evaporation prevents sodium sulfate from crystallizing out, and the second evaporation prevents sodium chloride from crystallizing out; relative to 1 mol of SO contained in the wastewater to be treated 4 2- Cl contained in the wastewater to be treated - 9.5 mol or more.
By the technical scheme, the method aims at the content of NH 4 + 、SO 4 2- 、Cl - And Na + The pH value of the wastewater is adjusted to a specific range in advance, then an MVR evaporation device is used for evaporation and separation to obtain sodium chloride crystals and concentrated ammonia water, and then a multi-effect evaporation device is used for evaporation again to obtain sodium sulfate crystals and dilute ammonia water. The method can respectively obtain high-purity sodium chloride and sodium sulfate, avoids the difficulty in the processes of mixed salt treatment and recycling, simultaneously completes the process of separating ammonia and salt, simultaneously heats the wastewater and cools the ammonia-containing steam by adopting a heat exchange mode without a condenser, reasonably utilizes the heat in the evaporation process, saves energy, reduces the wastewater treatment cost, recovers the ammonium in the wastewater in the form of ammonia water, respectively recovers the sodium sulfate and the sodium chloride in the form of crystals, does not generate waste residues and waste liquid in the whole process, and achieves the purpose of changing waste into valuable.
The second evaporation is carried out by using the multi-effect evaporation device, so that the second evaporation can be carried out at different temperatures, firstly at a higher temperature, the evaporation efficiency is improved, and finally at a lower temperature, the energy consumption is reduced.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic flow diagram of a method for treating wastewater from catalyst production according to an embodiment of the present invention.
Description of the reference numerals
1. Multiple-effect evaporation device 2 and MVR evaporation device
31. First heat exchange device 32 and second heat exchange device
33. The third heat exchange device 34 and the fourth heat exchange device
51. First ammonia water storage tank 52 and second ammonia water storage tank
53. Crystal liquid collecting tank 54 and mother liquid tank
61. First pH value measuring device 62 and second pH value 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, sixth circulating pump
77. Seventh circulating pump 78, eighth circulating pump
81. Vacuum pump 82 and circulating water pool
83. Tail gas absorption tower 91 and first solid-liquid separation device
92. Second solid-liquid separation device 10 and compressor
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The present invention will be described below with reference to fig. 1, but the present invention is not limited to fig. 1.
The invention provides a method for treating wastewater generated in catalyst production, which contains NH 4 + 、SO 4 2- 、Cl - And Na + The method comprises the following steps of,
1) Introducing wastewater to be treated into an 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, sequentially introducing a liquid phase obtained by the first solid-liquid separation into each effect evaporator of the multi-effect evaporation device 1 for second evaporation, respectively obtaining second ammonia-containing steam in each effect evaporator, and obtaining a second concentrated solution containing sodium sulfate crystals in the last effect evaporator;
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 MVR evaporation device 2, adjusting the pH value of the wastewater to be treated to be more than 9;
sending second ammonia-containing steam obtained by evaporation in the previous evaporator to the next evaporator for second heat exchange with the first concentrated solution to obtain second ammonia water, and carrying out cocurrent heat exchange between the first concentrated solution and the second ammonia-containing steam; 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.
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 the wastewater to be treated is passed into the MVR evaporation plant 2. The upper limit of the pH of the wastewater to be treated is not limited, and may be, for example, 14 or less, preferably 13.5 or less, and more preferably 13 or less.
The invention providesThe process may be directed to a catalyst containing NH 4 + 、SO 4 2- 、Cl - And Na + Except that it contains NH 4 + 、SO 4 2- 、Cl - And Na + In addition, the catalyst production wastewater is not particularly limited. From the viewpoint of improving the treatment efficiency of wastewater, the amount of SO contained in the wastewater to be treated is 1 mole per mole 4 2- Cl contained in the wastewater to be treated - 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 may be, for example, 10 to 20 moles. According to a preferred embodiment of the present invention, the SO contained in the wastewater to be treated is 1 mole relative to the SO contained in the wastewater 4 2- Cl contained in the wastewater to be treated - Is 10-13 mol. 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. Since the water content of the crystals after solid-liquid separation is different, the sodium sulfate content in the sodium chloride crystals obtained is usually 8 mass% or less (preferably 4 mass%), and in the present invention, it is considered that the sodium sulfate does not crystallize out when the sodium sulfate content in the sodium chloride crystals obtained is 8 mass% or less.
In the present invention, the second evaporation to prevent sodium chloride from crystallizing out means that the concentration of sodium chloride in the mixed system is controlled not to exceed the solubility under the second evaporation conditions (including but not limited to temperature, pH value, etc.), and sodium chloride carried by sodium sulfate crystals or adsorbed on the surface is not excluded. Since the water content of the crystals after solid-liquid separation is different, the sodium chloride content in the obtained sodium sulfate crystals is usually 8 mass% or less (preferably 4 mass%), and in the present invention, it is considered that sodium chloride is not crystallized when the sodium chloride content in the obtained sodium sulfate crystals is 8 mass% or less.
In the present invention, it is understood that the first ammonia-containing steam and the second ammonia-containing steam are both secondary steam as referred to in the art. The strong ammonia is only relative to the weak ammonia. The cocurrent heat exchange of the first concentrate and the second ammonia-containing vapor refers to the use of a cocurrent flow scheme in multi-effect evaporation. The pressures are all pressures in gauge.
In the present invention, the MVR vaporizing device 2 is not particularly limited, and may be various MVR vaporizing devices conventionally used in the art. For example, it may be one or more selected from the group consisting of an MVR falling film evaporator, an MVR forced circulation evaporator, an MVR-FC continuous crystallization evaporator, and an MVR-OSLO continuous crystallization evaporator. Among them, preferred are an MVR forced circulation evaporator and an MVR-FC continuous crystallization evaporator, and more preferred is a falling film + forced circulation two-stage MVR evaporative crystallizer.
In the present invention, the conditions of the first evaporation may be appropriately selected as needed, and sodium chloride may be crystallized without precipitating sodium sulfate. 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 to 60 ℃, and the pressure is-97.5 kPa to-87 kPa; in order to further improve the evaporation efficiency, preferably, the conditions of the first evaporation include: the temperature is 40 ℃ to 60 ℃, and the pressure is-97 kPa to-87 kPa; from the viewpoint of reducing the cost of equipment and energy consumption, it is more preferable that the temperature is from 45 ℃ to 55 ℃ and the pressure is from-95 kPa to-90 kPa.
In the present invention, the operation 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 adapted according to the capacity of the equipment to processWhen selected, it 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 conditions of the first evaporation, more than 90 mass percent (preferably more than 95 mass percent) of ammonia contained in the wastewater to be treated can be evaporated, and the first ammonia water can be directly recycled in the production process of the catalyst, or neutralized by acid to obtain ammonium salt for recycling, or mixed with water and corresponding ammonium salt or ammonia water for use.
According to the present invention, the first evaporation does not crystallize sodium sulfate (i.e., sodium sulfate does not become supersaturated), and preferably, the first evaporation is performed so that the concentration of sodium sulfate in the first concentrated solution is Y or less (preferably 0.9Y to 0.99Y, and more preferably 0.95Y to 0.98Y), where Y is the concentration of sodium sulfate at which both sodium chloride and sodium sulfate in the first concentrated solution become 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 while ensuring 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 the concentration of the first evaporation-derived liquid, and specifically, the concentration of the first evaporation-derived liquid is controlled within the above range so that the first evaporation does not cause precipitation of sodium sulfate crystals. The concentration of the liquid resulting from the first evaporation is monitored by measuring the density, which may be carried out using a densitometer.
According to a preferred embodiment of the present invention, before the wastewater to be treated is introduced into the MVR evaporation apparatus 2, the first ammonia-containing steam and the wastewater to be treated are subjected to a first heat exchange to obtain a first ammonia water. The first heat exchange method is not particularly limited, and may be performed by a conventional heat exchange method in the art. The number of heat exchanges may be 1 or more, preferably 2 to 4, more preferably 2 to 3, and particularly preferably 2. Through first heat exchange, the first aqueous ammonia of output carries out the heat exchange with pending waste water, and the aqueous ammonia of output is cooled off, and the heat at utmost is at processing apparatus internal recycle, rational utilization the energy, the waste has been reduced.
According to a preferred embodiment of the present invention, the first heat exchange is performed by a first heat exchange device 31 and a second heat exchange device 32, specifically, first ammonia-containing steam obtained by evaporation in the MVR evaporation device 2 passes through the second heat exchange device 32 and the first heat exchange device 31 in sequence, and the 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 as to heat the wastewater to be treated for evaporation, and simultaneously cool the first ammonia-containing steam to obtain first ammonia water, and the first ammonia water 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 fourth heat exchange device 34, specifically, the first ammonia-containing vapor obtained by evaporation in the MVR evaporation device 2 passes through the second heat exchange device 32 and the first heat exchange device 31 in sequence, and the second ammonia-containing vapor condensate (the second ammonia water with higher temperature) obtained by the multi-effect evaporation device 1 passes through the fourth heat exchange device 34; and one part of the catalyst production wastewater passes through a first heat exchange device 31, the other part of the catalyst production wastewater passes through a fourth heat exchange device 34, then the two parts of catalyst production wastewater are combined and mixed with a second mother liquor to obtain wastewater to be treated, and then the wastewater to be treated passes through a second heat exchange device 32, so that the wastewater to be treated is heated for evaporation through the first heat exchange between the first ammonia-containing steam and the wastewater to be treated, and simultaneously the first ammonia-containing steam is cooled to obtain first ammonia water. The first aqueous ammonia may be stored in the first aqueous ammonia tank 51.
In the present invention, the first heat exchange device 31, the second heat exchange device 32 and the fourth heat exchange device 34 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 made of duplex stainless steel, titanium alloy and hastelloy can be selected, and the heat exchanger made of plastic can be selected when the temperature is lower.
According to the present invention, in order to fully utilize the heat energy of the first ammonia-containing steam condensate, it is preferable that the temperature of the catalyst production wastewater after the first heat exchange by the first heat exchange device 31 is 29 to 84 ℃, more preferably 39 to 59 ℃, and still more preferably 44 to 59 ℃.
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 catalyst production wastewater after the first heat exchange is performed by the fourth heat exchange device 34 is 44 to 364 ℃, and more preferably 84 to 106 ℃.
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 purpose of adjusting the pH can be achieved. However, in order to reduce the amount of water used and further reduce the cost, it is preferable to use a saturated aqueous solution of an alkaline substance. In order to monitor the pH value of the wastewater to be treated, the pH value of the wastewater to be treated may be measured after the above-mentioned pH value adjustment.
According to a preferred embodiment of the present invention, the first evaporation process is performed in the MVR evaporation plant 2, and the first pH adjustment is performed by introducing and mixing an aqueous solution containing an alkaline substance into the pipe for feeding the catalyst production wastewater into the first heat exchange device 31 or the fourth heat exchange device 34 before feeding the catalyst production wastewater into the first heat exchange device 31 or the fourth heat exchange device 34 for the first heat exchange; and then mixing the catalyst production wastewater with a second mother liquor to obtain wastewater to be treated, feeding the wastewater to be treated into a second heat exchange device 32 for first heat exchange, and introducing and mixing the aqueous solution containing the alkaline substance into a pipeline for feeding the wastewater to be treated into the MVR evaporation device 2 to perform secondary pH value adjustment.
Through two pH value adjustments, the pH value of the wastewater to be treated is more than 9, preferably more than 10.8 before the wastewater is introduced into the MVR evaporation device 2. Preferably, the first pH adjustment is carried out to enable the pH value of the adjusted wastewater to be treated to be more than 7 (preferably 7-9), and the second pH adjustment is carried out to enable the pH value to be more than 9, preferably more than 10.8.
In order to detect the pH values after the first pH adjustment and the second pH adjustment, it is preferable that a first pH measuring device 61 is provided on a pipe for feeding the wastewater to be treated into the first heat exchanging device 31 or the fourth heat exchanging device 34 to measure the pH value after the first pH adjustment, and a second pH measuring device 62 is provided on a pipe for feeding the wastewater to be treated into the MVR evaporating device 2 to measure the pH value after the second pH adjustment.
In the present invention, in order to increase the solid content in the MVR evaporation device 2 and reduce the ammonia content in the liquid, it is preferable to return part of the liquid evaporated by the MVR evaporation device 2 (i.e., the liquid located inside the MVR evaporation device, hereinafter also referred to as circulating liquid) to the MVR evaporation device 2 for evaporation. The above process of returning the circulation liquid to the MVR evaporation device 2 is preferably that the circulation liquid is mixed with the catalyst production wastewater after the first pH adjustment and before the second pH adjustment and then returned to the MVR evaporation device 2, for example, the 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 heat exchanged by the second heat exchange device 32, and after the second pH adjustment, the mixture is sent to the MVR evaporation device 2. The ratio of the part of the liquid evaporated by the MVR evaporation device 2 to be refluxed to the MVR evaporation device 2 is not particularly limited, and for example, the reflux ratio of the first evaporation may be appropriately set as needed, and may be 10 to 200, preferably 40 to 120. The reflux ratio refers to: the ratio of the amount of reflux to the total amount of liquid fed to the MVR evaporator 2 minus the amount of reflux.
According to the present invention, preferably, the method further comprises compressing the first ammonia-containing vapor before the first heat exchange. The compression of the first ammonia-containing vapor may be performed by a compressor 10. Through right first ammonia vapor that contains compresses, for input energy among the MVR vaporization system, guarantee that waste water heaies up-evaporation-the process of cooling goes on in succession, need input when MVR vaporization process starts and start steam, only pass through compressor 10 energy supply after reaching continuous running state, no longer need input other energy. The compressor 10 may employ various compressors conventionally used in the art, such as a centrifugal fan, a turbine compressor, or a roots compressor, etc. After compression by the compressor 10, the temperature of the first ammonia-containing vapor is raised by 5 to 20 ℃.
In the invention, the first concentrated solution containing sodium chloride crystals is subjected to first solid-liquid separation to obtain sodium chloride crystals and a first mother solution. The method of the first solid-liquid separation is not particularly limited, and may be selected from one or more of centrifugation, filtration, and sedimentation.
According to the present invention, the solid-liquid separation of the first concentrated solution may be performed by using a first solid-liquid separation device (for example, a centrifuge, a belt filter, a plate filter, or the like) 91. After the solid-liquid separation, the first mother liquor obtained by the first solid-liquid separation device 91 is temporarily stored in the mother liquor tank 54, and may be sent to the multi-effect evaporation apparatus 1 by the fifth circulation pump 75 to be subjected to the second evaporation. In addition, it is difficult to avoid that the obtained sodium chloride crystals adsorb certain impurities such as chloride ions, free ammonia, hydroxide ions, etc., and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals, it is preferable that the sodium chloride crystals are first washed with water, the catalyst production wastewater, or a sodium chloride solution and dried.
Preferably, the first wash comprises elutriation and/or rinsing. In addition, it is preferable that the first washing liquid obtained in the above washing process is returned to the washing liquid before the second pH adjustment before the first evaporation by the eighth circulation pump 78; 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 eighth circulation pump 78, then heat exchange is performed in the second heat exchange device 32, and after the second pH adjustment, the first washing liquid is finally conveyed to the 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 elutriation and rinsing are not particularly limited, and may be performed by a method generally used 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 countercurrent manner when used as the elutriation liquid. Before the elutriation, a slurry containing sodium chloride crystals is preferably obtained by preliminary solid-liquid separation by sedimentation (the liquid content may be 35% by mass or less, and this step is preferably performed in an apparatus known in the art, such as a sedimentation tank or a sedimentation tank). In the elutriation process, 1 to 20 parts by weight of a liquid is used for elutriation per 1 part by weight of a slurry containing sodium chloride crystals. The rinsing is preferably carried out using an aqueous sodium chloride solution. 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. For the liquid resulting from the washing, it is preferably returned to the MVR evaporation device 2 before the second pH adjustment before evaporation.
According to a preferred embodiment of the present invention, after the first concentrated solution containing sodium chloride obtained by evaporation in the 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 respective evaporators of the multi-effect evaporation apparatus 1 are not particularly limited, and may be composed of various evaporators conventionally used in the art. For example, it may be selected from one or more of falling film evaporator, rising film evaporator, wiped film evaporator, central circulation tube multi-effect evaporator, basket evaporator, external heating type evaporator, forced circulation evaporator and lien type evaporator. Among them, a forced circulation evaporator and an external heating evaporator are preferable. The respective evaporators of the multi-effect evaporation apparatus 1 are composed of a heating chamber and an evaporation chamber, and may further include other evaporation auxiliary components as necessary, such as a demister for further separating liquid foam, a condenser for condensing all secondary steam, and a vacuum apparatus for pressure reduction operation. The number of evaporators included in the multi-effect evaporation apparatus 1 is not particularly limited, and may be 2 or more, preferably 2 to 5, and more preferably 3 to 5.
In the present invention, the conditions for the second evaporation may be appropriately selected as needed, and sodium sulfate may be crystallized without precipitating sodium chloride. The conditions of the second evaporation may include: the temperature is above 45 ℃ and the pressure is above-95 kPa. In order to improve evaporation efficiency, preferably, the conditions of the second evaporation include: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa; preferably, the conditions of the second evaporation include: the temperature is 60 ℃ to 365 ℃, and the pressure is-87 kPa to 18110kPa; preferably, the conditions of the second evaporation include: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa; preferably, the conditions of the second evaporation include: the temperature is 75-130 ℃, and the pressure is-73 kPa-117 kPa; preferably, the conditions of the second evaporation include: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa; preferably, the conditions of the second evaporation include: the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa. In the present invention, the second evaporation condition refers to the evaporation condition of the last one of the multiple-effect evaporation devices.
In order to fully utilize the heat in the evaporation process, the evaporation temperature difference of two adjacent evaporator is preferably 5-30 ℃; more preferably, the evaporating temperatures of two adjacent effect evaporators differ by 10 ℃ to 20 ℃. In the present invention, the operation 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.
In the invention, in order to sequentially feed the first mother liquor into each effect evaporator of the multi-effect evaporator 1, a circulating pump can be arranged between each effect evaporator, and the liquor evaporated in the previous effect evaporator is fed into the next effect evaporator through the circulating pump.
In the invention, the circulating pump among the selected evaporators can be various pumps which are conventionally used in the field, in order to uniformly evaporate materials, avoid generating a large number of fine crystal nuclei and prevent crystal grains in the circulating crystal slurry from colliding with an impeller at a high speed to generate a large number of secondary crystal nuclei, the circulating pump is preferably a low-rotating-speed centrifugal pump, and more preferably a high-flow low-rotating-speed guide pump impeller or a high-flow low-lift low-rotating-speed axial pump.
According to a preferred embodiment of the present invention, the second evaporation process is performed in a multi-effect evaporation apparatus 1, the multi-effect evaporation apparatus 1 being composed of a first effect evaporator 1a, a second effect evaporator 1b and a third effect evaporator 1 c. And (3) sequentially introducing the first mother liquor into the first effect evaporator 1a, the second effect evaporator 1b and the third effect evaporator 1c of the multi-effect evaporation device 1 through a fifth circulating pump 75 for evaporation to obtain a second concentrated solution containing sodium sulfate crystals. And introducing second ammonia-containing steam obtained by evaporation in the first effect evaporator 1a of the multi-effect evaporation device 1 into a second effect evaporator 1b for second heat exchange to obtain second ammonia water (namely second ammonia-containing steam condensate), and introducing second ammonia-containing steam obtained by evaporation in the second effect evaporator 1b into a third effect evaporator 1c for second heat exchange to obtain second ammonia water. More preferably, the second ammonia water is subjected to the first heat exchange with the wastewater to be treated through the fourth heat exchange device 34, so as to fully utilize energy. Heating steam (namely raw steam conventionally used in the field) is introduced into the first effect evaporator 1a, and the heating steam is condensed in the first effect evaporator 1a to obtain a condensate which can be used for preparing a washing solution after being used for preheating the wastewater to be treated entering the MVR evaporation device 2. The second ammonia-containing vapor evaporated by the third effect evaporator 1c is subjected to third heat exchange with cooling water (preferably, the catalyst production wastewater before being introduced into the MVR concentration and evaporation apparatus is used as cooling water) in a third heat exchange apparatus 33 to obtain ammonia water, and the ammonia water is stored in a second ammonia water storage tank 52. And (3) introducing the first mother solution into the first-effect evaporator 1a through a fifth circulating pump 75 for evaporation, introducing into the second-effect evaporator 1b for evaporation, and introducing into the third-effect evaporator 1c for evaporation to finally obtain a second concentrated solution containing sodium sulfate crystals.
According to the present invention, the second evaporation does not cause crystallization of sodium chloride (i.e., sodium chloride does not reach supersaturation), and preferably, the second evaporation causes the concentration of sodium chloride in the second concentrated solution to be X or less (preferably 0.999X or less, more preferably 0.95X to 0.999X, and still more preferably 0.99X to 0.9967X), where X is the concentration of sodium chloride at which both sodium 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 liquid obtained by the second evaporation, and specifically, the concentration of the liquid obtained by the second evaporation is controlled within the above range so that the second evaporation does not cause crystallization of sodium chloride. The concentration of the liquid resulting from the second evaporation is monitored by measuring the density, which may be carried out using a densitometer.
In the present invention, in order to prevent the 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 deg.c, preferably 20 deg.c, more preferably 35 deg.c to 70 deg.c 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 invention, the second ammonia-containing steam obtained by the evaporation in the multi-effect evaporation device 1 is subjected to third heat exchange with the cold medium in a third heat exchange device 33 to obtain second ammonia water. The third heat exchange device 33 is not particularly limited, and various heat exchangers conventionally used in the art may be used to cool the second ammonia-containing steam. Specifically, it may be a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, a spiral threaded tube heat exchanger, or the like. The material of the heat exchanger can be specifically selected according to the requirement, for example, the stainless steel spiral thread pipe heat exchanger is preferred because the secondary steam has no corrosivity to the stainless steel. The cold medium may be cooling water, glycol water solution, etc. When conventional cooling water is used, the cooling water is recycled, and when the catalyst production wastewater is used as the cooling water, the catalyst production wastewater after heat exchange is preferably directly returned to the treatment process (for example, returned to the first pH value adjustment process).
In the present invention, it can be understood that the second ammonia water includes both the second ammonia water obtained by sending the second ammonia-containing steam evaporated by the previous evaporator of the multi-effect evaporation device 1 to the subsequent evaporator for the second heat exchange, and the second ammonia water obtained by sending the ammonia-containing steam generated by the last evaporator of the multi-effect evaporation device 1 to the third heat exchange device for the third heat exchange. The above two portions of ammonia water are stored together in the second ammonia water tank 52.
According to the invention, the method can also comprise crystallizing the second concentrated solution containing sodium sulfate crystals in a crystallizing device to obtain crystal slurry containing sodium sulfate crystals. In this case, the evaporation conditions for the second evaporation need only be satisfied for the purpose of crystallizing sodium sulfate in the crystallization device without precipitating sodium chloride. The crystallization apparatus is not particularly limited, and may be, for example, a crystal solution tank, a crystal solution collecting tank, a thickener with stirring or a thickener without stirring, or the like. According to a preferred embodiment of the present invention, the crystallization is performed in the liquid crystal collecting tank 53. The conditions for the crystallization may be appropriately selected, and may include, for example: the temperature is above 45 ℃; preferably 85-107 ℃; more preferably 95 to 105 ℃. In order to fully ensure the crystallization effect, the crystallization time can be 5min to 24h, preferably 5min to 30min.
According to the invention, the crystallization of the second concentrated solution containing sodium sulfate crystals can also be carried out in a multi-effect evaporator with a crystallizer (e.g. a forced circulation evaporator crystallizer), wherein the crystallization temperature is the corresponding second evaporation temperature. According to the present invention, when a separate crystallization device is used for crystallization, it is further ensured that the second evaporation does not crystallize sodium chloride during crystallization (i.e. sodium chloride is not supersaturated), and preferably, the concentration of sodium chloride in the second concentrated solution is X or less, where X is the concentration of sodium chloride at which both sodium chloride and sodium sulfate in the second concentrated solution are saturated under the crystallization conditions.
In the present invention, the second concentrated solution containing sodium sulfate crystals (or the magma containing sodium sulfate crystals when crystallized in a separate crystallization device) 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). The method of the second solid-liquid separation is not particularly limited, and may be selected from one or more of centrifugation, filtration, and sedimentation, for example.
According to the present invention, the second solid-liquid separation may be performed by a second solid-liquid separation device (e.g., a centrifuge, a belt filter, a plate filter, etc.) 92. After the second solid-liquid separation, the second mother liquor obtained by the second solid-liquid separation device 92 returns to the MVR evaporation device 2 to be subjected to the first evaporation again, and specifically, the second mother liquor and the catalyst production wastewater may be mixed by the seventh circulation pump 77 to obtain the wastewater to be treated, and then the wastewater is sent to the 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 certain impurities such as sulfate ions, free ammonia, hydroxide ions and the like, and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness and improve the purity of the crystals, the sodium sulfate crystals are preferably subjected to secondary washing with water, catalyst production wastewater or a sodium sulfate solution and dried. In order to avoid the dissolution of sodium sulfate crystals during the washing, the sodium sulfate crystals are preferably washed with an aqueous sodium sulfate solution. More preferably, the concentration of the aqueous sodium sulfate solution is preferably such that the sodium sulfate and sodium chloride reach the concentration of sodium sulfate in the saturated aqueous solution at the same time at the temperature corresponding to the sodium sulfate crystals to be washed.
Preferably, the second wash comprises elutriation and/or rinsing. The second washing liquid obtained in the above washing process is preferably returned to the multi-effect evaporation device 1 by the sixth circulation pump 76 to be subjected to the second evaporation again.
The form of the second solid-liquid separation and the second washing is not particularly limited, and may be carried out, for example, by using a combination of an elutriation apparatus and a solid-liquid separation apparatus which are conventional in the art, or may be carried out on a staged solid-liquid separation apparatus such as a belt filter. The above-mentioned elutriation and rinsing are not particularly limited and may be carried out by a method conventional in the art. The number of elutriation and rinsing is not particularly limited, and may be 1 or more, and is preferably 2 to 4 times in order to obtain sodium 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, a slurry containing sodium sulfate 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, the liquid used for elutriation is 1 to 20 parts by weight relative to 1 part by weight of the slurry containing sodium sulfate crystals. The rinsing is preferably carried out using an aqueous sodium sulfate solution, the concentration of which is preferably the concentration of sodium sulfate in the aqueous solution at which the sodium sulfate and sodium chloride reach saturation simultaneously at the temperature corresponding to the sodium sulfate crystals to be washed. In order to further enhance the elutriation effect and obtain sodium sulfate crystals with higher purity, the elutriation may be preferably performed using a liquid obtained by rinsing. For the liquid produced by washing, it is preferred that the catalyst production wastewater elutriation liquid is returned to the multi-effect evaporation device 1 before the second pH adjustment before evaporation in the MVR evaporation device 2, and other washing liquids are returned.
According to a preferred embodiment of the present invention, after a preliminary solid-liquid separation by settling, a magma containing sodium sulfate crystals obtained by evaporative crystallization is subjected to a first elutriation in an elutriation tank using the catalyst production wastewater, then a second elutriation is performed in another elutriation tank using a liquid obtained when sodium sulfate crystals are subsequently washed, finally the magma subjected to the two elutriations is sent to a solid-liquid separation device for solid-liquid separation, the crystals obtained by the solid-liquid separation are washed again with an aqueous sodium sulfate solution (the concentration of the aqueous sodium sulfate solution is the concentration of sodium sulfate in an aqueous solution in which sodium sulfate and sodium chloride reach saturation at the same time at a temperature corresponding to the sodium sulfate crystals to be washed) and the liquid obtained by washing is returned to the second elutriation as an elutriation liquid. Through the washing process combining elutriation and leaching, the purity of the obtained sodium sulfate crystals is improved, washing liquid is not excessively introduced, and the efficiency of wastewater treatment is improved.
According to a preferred embodiment of the present invention, the 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 third heat exchange are discharged after ammonia removal. The first ammonia-containing steam is condensed by the first heat exchange to obtain the residual tail gas, i.e. the tail gas discharged from the second heat exchange device 32, and the second ammonia-containing steam is condensed by the third heat exchange to obtain the residual tail gas, i.e. the tail gas discharged from the third heat exchange device 33. The ammonia in the tail gas is removed, so that the pollutant content in the discharged tail gas can be further reduced, and the tail gas can be directly discharged.
As the method of removing ammonia, absorption may be performed by the off-gas absorption tower 83. The off-gas absorption column 83 is not particularly limited, and may be any of various absorption columns conventionally used in the art, such as a plate-type absorption column, a packed absorption column, a falling film absorption column, or an empty column. Circulating water is arranged in the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of the fourth circulating pump 74, water can be supplemented into the tail gas absorption tower 83 from the circulating water tank 82 through the third circulating pump 73, fresh water can be supplemented into the circulating water tank 82, and meanwhile the temperature of working water of the vacuum pump 81 and the ammonia content can be reduced. The flow of the off-gas and the circulating water in the off-gas absorption tower 83 may be in a counter-current or co-current flow, preferably in a counter-current flow. The circulating water can be supplemented by additional fresh water. In order to ensure the sufficient absorption of the tail gas, dilute sulfuric acid may be further added to the tail gas absorption tower 83 to absorb a small amount of ammonia and the like in the tail gas. The circulating water can be used as ammonia water or ammonium sulfate solution for production or direct sale after absorbing tail gas. The off gas may be introduced into the off gas absorption tower 83 by a vacuum pump 81.
In the present invention, theThe catalyst production wastewater is not particularly limited as long as it contains NH 4 + 、SO 4 2- 、Cl - And Na + The catalyst is produced by waste water. In addition, the method is particularly suitable for treating high-salinity wastewater. The wastewater from the catalyst production of the present invention may be specifically wastewater from the production of a molecular sieve, alumina or an oil refining catalyst, or wastewater from the production of a molecular sieve, alumina or an oil refining catalyst after the following impurity removal and concentration. It is 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 + 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.
The above-mentionedNH contained in catalyst production wastewater 4 + 、SO 4 2- 、Cl - And Na + The upper limit of (b) is not particularly limited. SO in the catalyst production wastewater from the viewpoint of easiness in starting 4 2- 、Cl - And Na + Respectively 200g/L or less, preferably 150g/L or less; NH in catalyst production wastewater 4 + Is 50g/L or less, preferably 30g/L or less.
From the viewpoint of improving the efficiency of the first evaporation and reducing the energy consumption of the treatment process, the amount of SO contained in the wastewater is relatively 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 catalyst production wastewater is 1 mol based on 1 mol of the SO 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, further preferably 30 mol or less, for example, 10 to 20 mol. By adding Cl contained in the catalyst production wastewater - And SO 4 2- The molar ratio of (b) is limited to the above range, most of the water can be distilled out in the first evaporation, the amount of the circulating liquid in the treatment system is reduced, the 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 rare earth element ion is preferably 100mg/LThe amount of the inorganic salt is more preferably 50mg/L or less, still more preferably 10mg/L or less, and particularly preferably no other inorganic salt ion. By controlling the other inorganic salt ions within the above range, the purity of the sodium chloride crystals and the sodium sulfate crystals finally obtained can be further improved. In order to reduce the content of other inorganic salt ions in the catalyst production wastewater, the following impurity removal is preferably performed.
The TDS of the catalyst production wastewater may be 1600mg/L or more, preferably 4000mg/L or more, more preferably 8000mg/L or more, further preferably 16000mg/L or more, further preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, further preferably 60000mg/L or more, further preferably 100000mg/L or more, further preferably 150000mg/L or more, further preferably 200000mg/L or more.
In the present invention, the pH value of the catalyst production wastewater is preferably 4 to 8, preferably 6.5 to 6.7.
In addition, since the COD of the catalyst production wastewater may block a membrane at the time of concentration, affect the purity and color of a salt at the time of evaporative crystallization, etc., the COD of the catalyst production wastewater is preferably as small as possible (preferably 20mg/L or less, more preferably 10mg/L or less), and is preferably removed by oxidation at the time of pretreatment, and specifically, it may be carried out by, for example, a biological method, an advanced oxidation method, etc., and it is preferably oxidized by an oxidizing agent such as fenton's reagent at the time of very high COD content.
In the invention, in order to reduce the concentration of impurity ions in the catalyst production wastewater, ensure the continuous and stable treatment process and reduce the equipment operation and maintenance cost, the catalyst production wastewater is preferably subjected to impurity removal before being treated by the treatment method. Preferably, the impurity removal is selected from one or more of solid-liquid separation, chemical precipitation, adsorption, ion exchange and oxidation.
As the solid-liquid separation, filtration, centrifugation, sedimentation, or the like may be mentioned; the chemical precipitation may be pH adjustment, carbonate precipitation, magnesium salt precipitation, or the like; the adsorption can be physical adsorption and/or chemical adsorption, and the specific adsorbent can be selected from activated carbon, silica gel, alumina, molecular sieve, natural clay and the like; as the ion exchange, either one of a strongly acidic cation resin and a weakly acidic cation resin can be used; as the oxidation, various oxidizing agents conventionally used in the art, such as ozone, hydrogen peroxide, and potassium permanganate, can be used, and in order to avoid introduction of new impurities, ozone, hydrogen peroxide, and the like are preferably used.
The specific impurity removal mode can be specifically selected according to the types of impurities contained in the catalyst production wastewater. For suspended matters, a solid-liquid separation method can be selected for removing impurities; for inorganic matters and organic matters, chemical precipitation, ion exchange and adsorption methods can be selected for removing impurities, such as weak acid cation exchange, activated carbon adsorption and the like; for organic matters, impurities can be removed by adopting an adsorption and/or oxidation mode, wherein an ozone biological activated carbon adsorption oxidation method is preferred. According to a preferred embodiment of the invention, the catalyst production wastewater is subjected to impurity removal by filtration, a weak acid cation exchange method and an ozone biological activated carbon adsorption oxidation method in sequence. Through the impurity removal process, most suspended matters, hardness, silicon and organic matters can be removed, the scaling risk of the device is reduced, and the continuous and stable operation of the wastewater treatment process is ensured.
In the present invention, the catalyst production wastewater having a low salt content may be concentrated to have a salt content within a range required for the catalyst production wastewater of the present invention before the treatment by the treatment method of the present invention (preferably after the above-mentioned impurity removal). Preferably, the concentration is selected from ED membrane concentration and/or reverse osmosis; more preferably, the concentration is performed by ED membrane concentration and reverse osmosis, and the order of performing the ED membrane concentration and 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 wastewater treatment can be improved, and energy waste caused by a large amount of evaporation is avoided.
In a preferred embodiment of the invention, the wastewater is wastewater obtained by performing chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation on wastewater generated in the molecular sieve production process to remove impurities, and performing ED membrane concentration and reverse osmosis concentration on the wastewater.
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 amount of the regenerant (calculated by 100%) was 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 rate is 15 m/h-30 m/h; as the acidic cation exchange resin, for example, there can be used a Tokusan Senno chemical Co., ltd., SNT brand D113 acidic cation exchange resin.
The conditions of the above-mentioned ozone biological activated carbon adsorption oxidation method are preferably: the retention time of the ozone is 50min to 70min, and the empty bed filtration rate is 0.5m/h to 0.7m/h.
The conditions for concentrating the ED membrane are preferably: the current 145A to 155A and the voltage 45V to 65V. The ED membrane may be, for example, an ED membrane manufactured by astone corporation of japan.
The conditions for the reverse osmosis are preferably: the operation pressure is 5.4MPa to 5.6MPa, the water inlet temperature is 25 ℃ to 35 ℃, and the pH value is 6.5 to 7.5. The reverse osmosis membrane is, for example, a seawater desalination membrane TM810C manufactured by Dongli corporation of Lanxingdong.
According to the invention, when the wastewater treatment is started, the catalyst production wastewater can be used for direct operation, and if the ion content of the catalyst production wastewater meets the conditions of the invention, the first evaporation can be carried out firstly and then the second evaporation can be carried out according to the conditions of the invention; if the ion content of the catalyst production wastewater does not meet the conditions of the invention, the first evaporation can be controlled to ensure that the concentration of sodium sulfate in the first concentrated solution is close to the precipitation concentration, then the first concentrated solution is subjected to second evaporation to obtain a second concentrated solution, the second concentrated solution is subjected to solid-liquid separation to obtain sodium sulfate crystals and a second mother solution, the second mother solution is mixed with the catalyst production wastewater to adjust the ion content of the wastewater to be treated to be within 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 Or NaCl, as long as the ion content of the wastewater to be treated is adjusted SO that the wastewater to be treated satisfies SO in the wastewater to be treated in the 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 156g/L, na) 2 SO 4 49g/L、NH 4 Cl 62g/L、(NH 4 ) 2 SO 4 19.8g/L, pH 6.7) by means of a first circulation pump 71 at a feed rate of 5m 3 The reaction mixture was fed into a line of a treatment system at a speed of/h, an aqueous sodium hydroxide solution having a concentration of 45.16 mass% was introduced into the line to perform a first pH adjustment, the adjusted pH was monitored by a first pH measuring device 61 (pH meter) (measurement value 7.4), and the pH adjusted by the first pH adjustment was measuredPart of the saved catalyst production wastewater (3 m) 3 H) sending the waste water into a first heat exchange device 31 (a plastic plate heat exchanger) to perform heat exchange with the recovered first ammonia-containing steam condensate to heat the catalyst production waste water to 54 ℃, sending the rest part of the waste water into a fourth heat exchange device 34 (a duplex stainless steel plate heat exchanger) to perform heat exchange with the recovered second ammonia-containing steam condensate to heat the catalyst production waste water to 70 ℃, combining the two parts of the catalyst production waste water, and mixing the combined waste water with the second mother liquor to obtain waste water to be treated (SO contained in the waste water is measured) to obtain the waste water to be treated 4 2- And Cl - In a molar ratio of 1:12.444 Then, the wastewater to be treated is sent into a second heat exchange device 32 (a titanium alloy plate type heat exchanger), first heat exchange is carried out between the wastewater to be treated and the recovered first ammonia-containing steam to heat the wastewater to be treated to 62 ℃, then the wastewater to be treated after two times of first heat exchange is sent into a pipeline of the MVR evaporation device 2 to be introduced with a sodium hydroxide aqueous solution with the concentration of 45.16 mass percent to carry out second pH value adjustment, the adjusted pH value is monitored through a second pH value measuring device 62 (a pH meter) (the measured value is 10.8), and the wastewater to be treated after the second pH value adjustment is sent into the MVR evaporation device 2 (a falling film and forced circulation two-stage MVR evaporation crystallizer) to be evaporated to obtain first ammonia-containing steam and a first concentrated solution containing sodium chloride crystals. Wherein the evaporation temperature of the MVR evaporation device 2 is 55 ℃, the pressure is-90.2 Pa, and the evaporation capacity is 4.63m 3 H is the ratio of the total weight of the catalyst to the total weight of the catalyst. The first ammonia-containing vapor obtained by evaporation is compressed by a compressor 10 (the temperature rises by 10 ℃) and then sequentially passes through a second heat exchange device 32 and a 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 a first ammonia water storage tank 51. In addition, in order to increase the solid content in the MVR evaporation device 2, part of the liquid evaporated in the MVR evaporation device 2 is returned to the second heat exchange device 32 as a circulation liquid by the second circulation pump 72, and then enters the MVR evaporation device 2 again for the first evaporation (the return ratio is 96.4). The degree of the first evaporation was monitored by a densimeter provided in the MVR evaporation apparatus 2, and the concentration of sodium sulfate in the first concentrated solution was controlled to 0.9707Y (66.25 g/L).
The first concentrated solution obtained by the evaporation of the MVR evaporation device 2 is addedAfter the first solid-liquid separation by the first solid-liquid separation apparatus 91 (centrifuge), 24.13m was obtained per hour 3 Containing NaCl 293.8g/L, na 2 SO 4 66.25g/L、NaOH 0.18g/L、NH 3 0.10g/L of first mother liquor is temporarily stored in a mother liquor tank 54, sodium chloride solid obtained by solid-liquid separation (sodium chloride crystal filter cake 1306.96kg with water content of 14 mass% is obtained per hour, wherein the content of sodium sulfate is below 3.9 mass%) is eluted by 293g/L sodium chloride solution with the same dry mass as the sodium chloride crystal filter cake, sodium chloride 1124kg (with purity of 99.4 wt%) is obtained per hour after drying, and the washing liquid is circulated to a second heat exchange device 32 through an eighth circulating pump 78 and then enters an MVR evaporation device 2 again for first evaporation.
The second evaporation process is carried out in a multi-effect evaporation device 1, and the multi-effect evaporation device 1 (all of which are forced circulation evaporators) consists of a first effect evaporator 1a, a second effect evaporator 1b and a third effect evaporator 1 c. And (3) sending the first mother liquor in the mother liquor tank 54 into the multi-effect evaporation device 1 through a fifth circulating pump 75, introducing the first mother liquor into a second-effect evaporator 1b for evaporation after the first mother liquor is evaporated in a first-effect evaporator 1a, and introducing the first mother liquor into a third-effect evaporator 1c for evaporation to finally obtain a second concentrated solution containing sodium sulfate crystals. Wherein the evaporation temperature of the first effect evaporator 1a is 128 ℃, the pressure is 103.53kPa, and the evaporation capacity is 0.41m 3 H; the evaporation temperature of the second effect evaporator 1b is 114 ℃, the pressure is 28.07kPa, and the evaporation capacity is 0.40m 3 H; the evaporation temperature of the third effect evaporator 1c is 100 ℃, the pressure is-22.83 kPa, and the evaporation capacity is 0.40m 3 H is used as the reference value. And (3) introducing second ammonia-containing steam obtained by evaporation in the first effect evaporator 1a of the multi-effect evaporation device 1 into a second effect evaporator 1b for second heat exchange to obtain first ammonia water, introducing second ammonia-containing steam obtained by evaporation in the second effect evaporator 1b into a third effect evaporator 1c for second heat exchange to obtain first ammonia water, and storing the ammonia water obtained from the second effect evaporator 1b and the first effect evaporator 1c in a second ammonia water storage tank 52 after heat exchange with catalyst production wastewater through a fourth heat exchange device 34. Heating steam (namely raw steam conventionally used in the field) is introduced into the first-effect evaporator 1a, and the heating steam is obtained after being condensed in the first-effect evaporator 1aAnd the condensate is used for preparing a washing solution after preheating the wastewater (raw material) to be treated entering the MVR evaporation device 2. The second ammonia-containing steam evaporated by the third effect evaporator 1c of the multi-effect evaporator 1 is subjected to third heat exchange with cooling water (catalyst production wastewater) in the third heat exchange device 33 to obtain second ammonia, and the second ammonia is stored in the second ammonia storage tank 52. The degree of the second evaporation is monitored by a densimeter arranged on the multi-effect evaporation device 1, and the concentration of sodium chloride in the second concentrated solution is controlled to be 0.99353X (307.1 g/L). After the first mother liquor is evaporated in the multi-effect evaporator 1, the finally obtained second concentrated solution containing sodium sulfate crystals is crystallized in the crystal liquid collecting tank 53 (the crystallization temperature is 100 ℃, and the crystallization time is 10 min) to obtain crystal slurry containing sodium sulfate crystals.
The crystal slurry containing sodium sulfate crystals is sent to a second solid-liquid separation device 92 (centrifugal machine) for solid-liquid separation, and 20.13m is obtained per hour 3 Contains NaCl 307.1g/L, na 2 SO 4 54.2g/L、NaOH 0.19g/L、NH 3 0.0053g/L of second mother liquor, circulating the second mother liquor to a wastewater introduction pipeline through a seventh circulating pump 77, mixing the second mother liquor with the catalyst production wastewater to obtain wastewater to be treated, performing solid-liquid separation to obtain sodium sulfate solid (sodium sulfate crystal cake with a water content of 15 mass% 407.7kg, wherein the sodium chloride content is 4 mass% or less is obtained per hour), washing the sodium sulfate solid with 54g/L of sodium sulfate solution which is equal to the dry basis mass of sodium sulfate, drying the sodium sulfate solid in a dryer to obtain 346.54kg of sodium sulfate (the purity is 99.5 wt%) per hour, and returning the washed second washing liquid to the multi-effect evaporation device 1 through a sixth circulating pump 76.
In addition, the tail gas discharged by the second heat exchange device 32 and the third heat exchange device 33 is introduced into a tail gas absorption tower 83 through a vacuum pump 81 for absorption, circulating water is introduced into the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of the fourth circulating pump 74, water is supplemented into the tail gas absorption tower 83 from a circulating water tank 82 through a third circulating pump 73, and fresh water is supplemented into the circulating water tank 82, so that the temperature and the ammonia content of the working water of the vacuum pump 81 are reduced. Dilute sulfuric acid is further introduced into the tail gas absorption tower 83 to absorb ammonia and the like in the tail gas.
In this example, 4.63m of ammonia water having a concentration of 2.56 mass% was obtained per hour in the first ammonia water tank 51 3 1.21m of 0.19 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.
In addition, the starting phase of the MVR evaporation was started by steam at a temperature of 143.3 ℃.
s 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 160g/L, na 2 SO 4 25g/L、NH 4 Cl 39g/L、(NH 4 ) 2 SO 4 6.2g/L, pH is 6.5, the temperature of the catalyst production wastewater subjected to heat exchange by the first heat exchange device 31 is 44 ℃, the temperature of the catalyst production wastewater subjected to heat exchange by the fourth heat exchange device 34 is 100 ℃, the temperature of the wastewater to be treated subjected to heat exchange by the second heat exchange device 32 is 52 ℃, and the obtained SO contained in the wastewater to be treated 4 2- And Cl - In a molar ratio of 1:14.438. the MVR evaporation device 2 has an evaporation temperature of 45 ℃, a pressure of-94.69 kPa and an evaporation capacity of 4.94m 3 H is used as the reference value. The first effect evaporator 1a has an evaporation temperature of 130 ℃, a pressure of 116.77kPa, and an evaporation capacity of 0.19m 3 H; the evaporation temperature of the second effect evaporator 1b is 117 ℃, the pressure is 41.92kPa, and the evaporation capacity is 0.19m 3 H; the evaporation temperature of the third effect evaporator 1c is 105 ℃, the pressure is-7.02 kPa, and the evaporation capacity is 0.18m 3 H is used as the reference value. The crystallization temperature was 105 ℃ and the time was 5min.
The first solid-liquid separation device 91 obtains 1198.31kg of sodium chloride crystal filter cake containing 15 mass% of water every hour, and finally obtains 1018.57kg of sodium chloride (the purity is 99.4 weight%); obtained 9.49m per hour 3 The concentration of NaCl is 291.8g/L, na 2 SO 4 67g/L、NaOH 0.16g/L、NH 3 0.07g/L of the first mother liquor.
The second solid-liquid separation device 92 produced 177.95kg of sodium sulfate crystal cake with a water content of 14 mass% per hour, and finally produced 153.04kg of sodium sulfate (purity 99) per hour5 wt%); obtained at 9.00m per hour 3 The concentration is NaCl 307.9g/L, na 2 SO 4 53.1g/L、NaOH 0.17g/L、NH 3 0.0031g/L of a second mother liquor.
In this example, 4.94m of ammonia water having a concentration of 1.38 mass% was obtained per hour in the first ammonia water tank 51 3 0.56m of 0.118 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 NaCl-containing 105g/L, na 2 SO 4 108g/L、NH 4 Cl 20g/L、(NH 4 ) 2 SO 4 20.91g/L, pH was 6.7 catalyst process wastewater, a portion (2.5 m) of catalyst process wastewater 3 H) the temperature after heat exchange by the first heat exchange device 31 is 49 ℃, the temperature after heat exchange by the other part by the fourth heat exchange device 34 is 85 ℃, the temperature after heat exchange by the wastewater to be treated by the second heat exchange device 32 is 57 ℃, and the obtained SO contained in the wastewater to be treated 4 2- And Cl - In a molar ratio of 1:11.333. the MVR evaporation device 2 has an evaporation temperature of 50 ℃, a pressure of-92.7 kPa and an evaporation capacity of 3.35m 3 H is used as the reference value. The evaporation temperature of the first effect evaporator 1a is 125 ℃, the pressure is 84.91kPa, and the evaporation capacity is 0.77m 3 H; the second effect evaporator 1b has an evaporation temperature of 110 deg.C, a pressure of 11.34kPa, and an evaporation capacity of 0.75m 3 H; the evaporation temperature of the third effect evaporator 1c is 95 ℃, the pressure is-36.37 kPa, and the evaporation capacity is 0.75m 3 /h。
The first solid-liquid separation device 91 obtains 745.41kg of sodium chloride crystal filter cake containing 15 mass% of water every hour, and finally obtains 633.59kg of sodium chloride (the purity is 99.5 weight%); the hourly product is 52.06m 3 The concentration is NaCl 294.6g/L, na 2 SO 4 65.7g/L、NaOH 0.22g/L、NH 3 0.056g/L of the first mother liquor.
The second solid-liquid separation device 92 yielded a sodium sulfate crystal cake 7 having a water content of 15 mass% per hour68.53kg, which finally gives 653.25kg of sodium sulfate (purity 99.4% by weight) per hour; yield 50.07m per hour 3 The concentration of NaCl is 306.2g/L, na 2 SO 4 55.3g/L、NaOH 0.229g/L、NH 3 0.0017g/L of second mother liquor.
In this example, 3.35m of ammonia water having a concentration of 1.63 mass% was obtained per hour in the first ammonia water tank 51 3 2.27m of 0.12 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.
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 can be made, and the same should be considered as the disclosure of the present invention as long as the idea of the present invention is not violated.

Claims (34)

1. Method for treating catalyst production wastewater containing NH 4 + 、SO 4 2- 、Cl - And Na + Characterized in that the method comprises the following steps,
1) Introducing the wastewater to be treated into an MVR evaporation device for first evaporation to obtain first ammonia-containing steam and first concentrated solution containing sodium chloride crystals;
2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium chloride crystals, sequentially introducing a liquid phase obtained by the first solid-liquid separation into each effect evaporator of the multi-effect evaporation device for second evaporation, respectively obtaining second ammonia-containing steam in each effect evaporator, and obtaining a second concentrated solution containing the sodium sulfate crystals in the last effect evaporator;
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 an MVR evaporation device;
sending second ammonia-containing steam obtained by evaporation in the previous evaporator to the next evaporator for second heat exchange with the first concentrated solution to obtain second ammonia water, and carrying out cocurrent heat exchange between the first concentrated solution and the second ammonia-containing steam;
the first evaporation prevents sodium sulfate from crystallizing out, and the second evaporation prevents sodium chloride from crystallizing out;
relative to 1 mole of SO contained in the wastewater to be treated 4 2- Cl contained in the wastewater to be treated - 9.5 mol or more;
the wastewater to be treated contains the catalyst production wastewater and a liquid phase obtained by the second solid-liquid separation; NH in the catalyst production wastewater 4 + Is more than 8mg/L, SO 4 2- 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 as claimed in claim 1, wherein the pH of the wastewater to be treated is adjusted to be greater than 10.8 before passing the wastewater to be treated to the MVR evaporation plant.
4. The method as claimed in claim 1, wherein the pH adjustment of the wastewater to be treated is carried out with NaOH.
5. The 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.
6. The process of claim 5, wherein the first evaporation provides a sodium sulfate concentration in the first concentrated solution of 0.9Y to 0.99Y.
7. The method of claim 1, wherein the second evaporation provides a sodium chloride concentration in the second concentrate of no greater than X, where X is the sodium chloride concentration at which both sodium chloride and sodium sulfate are saturated in the second concentrate under the conditions of the second evaporation.
8. The process of claim 7, wherein said second evaporation provides a concentration of sodium chloride in said second concentrate of 0.95X to 0.999X.
9. The method of any one of claims 1-8, wherein the conditions of the first evaporation comprise: the temperature is 30-85 ℃, and the pressure is-98 kPa-58 kPa.
10. The method of claim 9, wherein the conditions of the first evaporation comprise: the temperature is 35 to 60 ℃, and the pressure is-97.5 kPa to-87 kPa.
11. The method of claim 10, wherein the conditions of the first evaporation comprise: the temperature is 40-60 ℃, and the pressure is-97 kPa to-87 kPa.
12. The method of claim 11, wherein the conditions of the first evaporation comprise: the temperature is 45-60 ℃, and the pressure is-95 kPa to-87 kPa.
13. The method of claim 12, wherein the conditions of the first evaporation comprise: the temperature is 45-55 ℃, and the pressure is-95 kPa to-90 kPa.
14. The method of any one of claims 1-8, wherein the conditions of the second evaporation comprise: the temperature is above 45 ℃ and the pressure is above-95 kPa.
15. The method of claim 14, wherein the conditions of the second evaporation comprise: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa.
16. The method of claim 15, wherein the conditions of the second evaporation comprise: the temperature is 60-365 ℃, and the pressure is-87 kPa-18110 kPa.
17. The method of claim 16, wherein the conditions of the second evaporation comprise: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa.
18. The method of claim 17, wherein the conditions of the second evaporation comprise: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa.
19. The method of claim 18, wherein the conditions of the second evaporation comprise: the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa.
20. The method of claim 14, wherein in the second evaporation, the evaporation temperatures of adjacent two-effect evaporators differ by 5 ℃ to 30 ℃.
21. The method as claimed in claim 20, wherein the evaporation temperatures of adjacent two-effect evaporators differ by 10 ℃ to 20 ℃.
22. The method of claim 9, wherein the temperature of the first evaporation is more than 5 ℃ lower than the temperature of the second evaporation.
23. The method of claim 22, wherein the temperature of the first evaporation is 20 ℃ or more lower than the temperature of the second evaporation.
24. The method of claim 23, wherein the temperature of the first evaporation is 35 ℃ to 70 ℃ lower than the temperature of the second evaporation.
25. The method according to claim 1, wherein the first ammonia-containing vapor is subjected to a first heat exchange with the wastewater to be treated to obtain a first ammonia water before the wastewater to be treated is passed into an 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 method of claim 25, wherein the second ammonia-containing vapor produced by the last evaporator of the multi-effect evaporation device undergoes a third heat exchange in a third heat exchange device and produces a second ammonia water.
28. The method according to claim 27, wherein the first ammonia-containing steam is subjected to the first heat exchange to condense the remaining tail gas, and the second ammonia-containing steam obtained by evaporating the second ammonia-containing steam in the last evaporator is subjected to the third heat exchange to condense the remaining tail gas, and then ammonia is removed and discharged.
29. The method according to any one of claims 1 to 8, further comprising subjecting the first concentrated solution containing sodium chloride crystals to a first solid-liquid separation to obtain sodium chloride crystals.
30. The method of claim 29, further comprising washing the resulting sodium chloride crystals.
31. The process of any one of claims 1 to 8, further comprising subjecting the second concentrate comprising sodium sulfate crystals to a second solid-liquid separation to obtain sodium sulfate crystals.
32. The method of claim 31, further comprising washing the resulting sodium sulfate crystals.
33. The process of any one of claims 1 to 8, wherein the catalyst production wastewater is wastewater from a molecular sieve, alumina or refinery catalyst production process.
34. The method of claim 33, further comprising removing impurities and concentrating the catalyst process wastewater.
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