CN108726607B - Method for treating catalyst production wastewater - Google Patents

Method for treating catalyst production wastewater Download PDF

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Publication number
CN108726607B
CN108726607B CN201710263284.7A CN201710263284A CN108726607B CN 108726607 B CN108726607 B CN 108726607B CN 201710263284 A CN201710263284 A CN 201710263284A CN 108726607 B CN108726607 B CN 108726607B
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evaporation
wastewater
treated
kpa
sodium chloride
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CN108726607A (en
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殷喜平
李叶
顾松园
王涛
周岩
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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
    • 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
    • C02F1/041—Treatment of water, waste water, or sewage by heating by distillation or evaporation by means of vapour compression
    • 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
    • C01D3/14—Purification
    • 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
    • C01D5/16—Purification
    • 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
    • C02F1/08—Thin film evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2201/00—Apparatus for treatment of water, waste water or sewage
    • C02F2201/002—Construction details of the apparatus
    • C02F2201/007—Modular design

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (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 + The method comprises the following steps of 1) introducing the wastewater to be treated into an MVR evaporation device for first evaporation to obtain first concentrated solution containing first ammonia vapor and sodium sulfate crystals; 2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium sulfate 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 chloride crystals in the last effect evaporator; 3) And carrying out second solid-liquid separation on the second concentrated solution containing the sodium chloride crystals. The method can respectively recover ammonium, sodium sulfate and sodium chloride in the wastewater, and furthest recycle resources in the wastewater.

Description

Treatment method of catalyst production wastewater
Technical Field
The invention relates to the field of sewage treatment, in particular to a method for treating catalyst production wastewater, and especially relates to a catalyst containing NH 4 + 、SO 4 2- 、Cl - And Na + Method for treating wastewater from catalyst production。
Background
In the production process of the oil refining catalyst, a large amount of inorganic acid-base salts such as sodium hydroxide, hydrochloric acid, sulfuric acid, ammonium salts, sulfates, hydrochlorides and the like are needed, and a large amount of mixed sewage containing ammonium, sodium sulfate, sodium chloride and aluminosilicate is generated. For such sewage, the common practice in the prior art is that the pH value is adjusted to be within the range of 6-9, most of suspended matters are removed, then the biochemical method, the blow-off method or the steam stripping method is adopted to remove ammonium ions, then the salt-containing sewage is subjected to pH value adjustment, most of suspended matters are removed, hardness, silicon and part of organic matters are removed, most of organic matters are removed through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then the salt-containing sewage enters an ion exchange device for further hardness removal, enters an enrichment device (such as reverse osmosis or electrodialysis) for concentration, and then MVR evaporative crystallization or multiple-effect evaporative crystallization is adopted to obtain mixed miscellaneous salt of sodium sulfate and sodium chloride containing a small amount of ammonium salt; or is; firstly, adjusting the pH value to be within the range of 6.5-7.5, removing most suspended matters, then removing hardness, silicon and part of organic matters, removing most organic matters through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then entering an ion exchange device for further removing hardness, entering a thickening device (such as reverse osmosis and/or electrodialysis) for concentration, and then adopting MVR (mechanical vapor recompression) evaporative crystallization or multiple-effect evaporative crystallization to obtain the mixed salt of sodium sulfate and sodium chloride containing ammonium salt. However, these ammonium-containing mixed salts are currently difficult 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 ammonia nitrogen can be treated by the biochemical method. The most important problem is that the total nitrogen of the wastewater after the biochemical deamination treatment is not up to the standard (the contents of nitrate ions and nitrite ions exceed the standard), the wastewater needs to be deeply treated, the salt content of the wastewater is not reduced (20000 mg/L-30000 mg/L), the wastewater cannot be directly discharged, and the wastewater needs to be further desalted.
In order to remove ammonia nitrogen from wastewater by gas stripping deamination, a large amount of alkali is needed to adjust the pH value, the alkali consumption is high, the alkali in the wastewater after deamination cannot be recovered, the pH value of the treated wastewater is high, the treatment cost is high, the COD content in the catalyst wastewater after gas stripping does not change greatly, the salt content in the wastewater is not reduced (20000 mg/L-30000 mg/L), the wastewater cannot be discharged directly, further desalting treatment is needed, the operation cost of wastewater treatment is high, a large amount of alkali remains in the treated wastewater, the pH value is high, the waste is large, and the treatment cost is up to 50 yuan/ton.
Disclosure of Invention
The invention aims to overcome the defect of NH content in the prior art 4 + 、SO 4 2- 、Cl - And Na + The 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 can respectively recover ammonium, sodium sulfate and sodium chloride in the catalyst production wastewater, and furthest recycle resources in the catalyst production wastewater.
In order to achieve the above object, the present invention provides a method for treating wastewater from catalyst production containing NH 4 + 、SO 4 2- 、Cl - And Na + The method comprises the following steps of,
1) Introducing the wastewater to be treated into an MVR evaporation device to carry out first evaporation to obtain first ammonia-containing steam and a first concentrated solution containing sodium sulfate crystals, wherein the wastewater to be treated contains the catalyst production wastewater;
2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium sulfate crystals, sequentially introducing a liquid phase obtained by the first solid-liquid separation into each effect evaporator of a multi-effect evaporation device for second evaporation, respectively obtaining second ammonia-containing steam in each effect evaporator, and obtaining a second concentrated solution containing sodium chloride crystals in the last effect evaporator;
3) Carrying out second solid-liquid separation on the second concentrated solution containing the sodium chloride 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; the first evaporation prevents sodium chloride from crystallizing out, and the second evaporation prevents sodium sulfate from crystallizing out; relative to 1 mole of SO contained in the wastewater to be treated 4 2- Cl contained in the wastewater to be treated - The molar ratio is 14 mol or less.
By the technical scheme, the method aims at the content of NH 4 + 、SO 4 2- 、Cl - And Na + The pH value of the wastewater to be treated is adjusted to a specific range in advance, then an MVR evaporation device is used for evaporation and separation to obtain sodium sulfate crystals and concentrated ammonia water, and then a multi-effect evaporation device is used for evaporation again to obtain sodium chloride crystals and dilute ammonia water. The method can respectively obtain high-purity sodium sulfate and sodium chloride, avoids the difficulty in the processes of mixed salt treatment and recycling, simultaneously completes the process of separating ammonia and salt, simultaneously heats the wastewater and cools the ammonia-containing steam by adopting a heat exchange mode without a condenser, reasonably utilizes the heat in the evaporation process, saves energy, reduces the wastewater treatment cost, recovers the ammonium in the wastewater in the form of ammonia water, recovers the sodium chloride and the sodium sulfate in the form of crystals respectively, does not generate waste residues and waste liquid in the whole process, and achieves the purpose of changing waste into valuable.
The second evaporation can be carried out at different temperatures by using the multi-effect evaporation device, the second evaporation is firstly carried out at a higher temperature, the evaporation efficiency is improved, and finally, the evaporation is carried out at a lower temperature, so that the sodium sulfate is not separated out, and meanwhile, the temperature is convenient to control.
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 wastewater treatment process according to one 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. Third heat exchange device 34 and 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 and 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 numerical ranges, each range between its endpoints and individual point values, and each individual point value can be combined with each other to give one or more new numerical ranges, and such numerical ranges should be construed as specifically disclosed herein.
The present invention will be described below with reference to fig. 1, but the present invention is not limited to fig. 1.
The invention provides a method for treating wastewater generated in catalyst production, which contains NH 4 + 、SO 4 2- 、Cl - And Na + The method comprises the following steps of,
1) Introducing the 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 sulfate crystals, wherein the wastewater to be treated contains the catalyst production wastewater;
2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium sulfate crystals, 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 the sodium chloride crystals in the last effect evaporator;
3) Carrying out second solid-liquid separation on the second concentrated solution containing the sodium chloride crystals;
before the wastewater to be treated is introduced into the MVR evaporation device 2, adjusting the pH value of the wastewater to be treated to be more than 9; the first evaporation prevents sodium chloride from crystallizing out, and the second evaporation prevents sodium sulfate from crystallizing out; relative to 1 mol of SO contained in the wastewater to be treated 4 2- Cl contained in the wastewater to be treated - The amount is 14 mol or less.
Preferably, the wastewater to be treated is the catalyst production wastewater; or the wastewater to be treated contains the catalyst production wastewater and a liquid phase obtained by the second solid-liquid separation.
More preferably, the wastewater to be treated is a mixed solution of the catalyst production wastewater and at least part of a liquid phase obtained by the second solid-liquid separation.
Further preferably, the wastewater to be treated is a liquid phase mixed solution obtained by the catalyst production wastewater and the second solid-liquid separation.
Preferably, the pH 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 method provided by the invention can be used for the treatment of the compounds containing NH 4 + 、SO 4 2- 、Cl - And Na + Is treated except for containing NH 4 + 、SO 4 2- 、Cl - And Na + In addition, the wastewater to be treated is not particularly limited. From the viewpoint of improving the treatment efficiency of wastewater, the amount of SO contained in the wastewater to be treated is 1 mole per mole 4 2- Cl contained in the wastewater to be treated - 13.8 moles or less, more preferably 13.75 moles or less, further preferably 13.5 moles or less, further preferably 13 moles or less, further preferably 12 moles or less, further preferably 11 moles or less, further preferably 10 moles or less, further preferably 9 moles or less, further preferably 8 moles or less, further preferably 7 moles or less; preferably 2 moles or more, more preferably 2.5 moles or more, further preferably 3 moles or more, and for example, may be 4 to 11 moles. By reacting SO 4 2- And Cl - The molar ratio of sodium sulfate in the first evaporation is controlled within the above range, so that sodium sulfate is precipitated without precipitating sodium chloride, and the purpose of efficiently separating sodium sulfate is achieved. In addition, as described above and below, it is also possible in the present invention to circulate 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 - Can be adjusted and the balance of sodium hydroxide can be maintained.
In the present invention, the first evaporation to prevent the crystallization of sodium chloride means that the concentration of sodium chloride in the mixed system is controlled not to exceed the solubility under the first evaporation conditions (including but not limited to temperature, pH, etc.), but sodium chloride carried by sodium sulfate crystals or adsorbed on the surface is not excluded. Since the water content of the crystals after the solid-liquid separation is different, the sodium chloride content in the obtained sodium sulfate crystals is usually 8 mass% or less (preferably 4 mass%), and in the present invention, it is considered that the sodium chloride does not crystallize out when the sodium chloride content in the obtained sodium sulfate crystals is 8 mass% or less.
In the present invention, the second evaporation is performed so that sodium sulfate does not crystallize out, which means that the concentration of sodium sulfate in the mixed system is controlled not to exceed the solubility under the second evaporation conditions (including but not limited to temperature, pH value, etc.), and sodium sulfate entrained by sodium chloride crystals or adsorbed on the surface is not excluded. Since the water content of the crystals after solid-liquid separation is different, the sodium sulfate content in the sodium chloride crystals obtained is usually 8 mass% or less (preferably 4 mass%), and in the present invention, it is considered that the sodium sulfate does not crystallize out when the sodium sulfate content in the sodium chloride crystals obtained is 8 mass% or less.
In the present invention, it is understood that the first ammonia-containing steam and the second ammonia-containing steam are secondary steam as referred to in the art. The cocurrent heat exchange of the first concentrated solution and the second ammonia-containing steam means that a cocurrent flow process in multi-effect evaporation is adopted. 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 necessary, and the purpose of crystallizing sodium sulfate without precipitating sodium chloride may be achieved. The conditions of the first evaporation may include: the temperature is above 45 ℃ and the pressure is above-95 kPa. In order to improve the evaporation efficiency, it is preferable that the conditions of the first evaporation include: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa; to further improve the evaporation efficiency, more preferably, the conditions of the first evaporation include: the temperature is 60 ℃ to 365 ℃, and the pressure is-87 kPa to 18110kPa; from the viewpoint of reducing the equipment cost and energy consumption, it is more preferable that the temperature of evaporation is from 75 ℃ to 175 ℃ and the pressure is from-73 kPa to 653kPa; further preferably, the conditions of the first evaporation include: the evaporation temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa; particularly preferably, the conditions of the first evaporation include: the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa.
In the present invention, the 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 appropriately selected according to the capacity of the apparatus process, and may be, for example, 0.1m 3 More than h (e.g. 0.1 m) 3 /h～500m 3 /h)。
By carrying out the first evaporation under the above conditions, sodium chloride is not crystallized and precipitated while sodium sulfate is crystallized, and the purity of the obtained sodium sulfate crystal can be ensured.
According to the invention, by controlling the evaporation condition of the MVR evaporation device 2, more than 90 mass percent (preferably more than 95 mass percent) of ammonia contained in the wastewater to be treated can be evaporated, and the first ammonia water can be directly reused in the production process of the catalyst, or neutralized by acid to obtain ammonium salt for reuse, or mixed with water and corresponding ammonium salt or ammonia water for use.
According to the present invention, the first evaporation does not crystallize sodium chloride in the wastewater to be treated (i.e. sodium chloride does not reach supersaturation), and preferably, the first evaporation makes the concentration of sodium chloride in the first concentrated solution be less than X (preferably less than 0.999X, more preferably 0.95X to 0.999X, and further preferably 0.99X to 0.9967X), where X is the concentration of sodium chloride at which both sodium sulfate and sodium chloride reach saturation in the first concentrated solution under the conditions of the first evaporation. By controlling the degree of the first evaporation within the above range, as much sodium sulfate as possible can be crystallized under the condition that sodium chloride is not precipitated. By crystallizing sodium sulfate in the first evaporation as much as possible, the wastewater treatment efficiency can be improved, and the energy waste can be reduced.
In the present invention, the degree of progress of the first evaporation is monitored by monitoring the concentration of the first evaporation-yielded liquid, and specifically, the concentration of the first evaporation-yielded liquid is controlled within the above range so that the first evaporation does not crystallize out sodium chloride in the first concentrated solution. The concentration of the liquid resulting from the first evaporation is monitored by measuring the density, which may be carried out using a densitometer.
In the invention, the sequence of the first heat exchange, the adjustment of the pH value of the wastewater to be treated and the preparation of the wastewater to be treated (the preparation of the wastewater to be treated needs to be performed in the case that the wastewater to be treated contains a liquid phase obtained by the solid-liquid separation of the catalyst production wastewater and the second solid-liquid separation) is not particularly limited, and can be appropriately selected as required before the wastewater to be treated is introduced into the first MVR evaporation device.
According to a preferred embodiment of the present invention, before the wastewater to be treated is introduced into the MVR evaporation apparatus 2, the first ammonia-containing steam and the wastewater to be treated are subjected to a first heat exchange to obtain a first ammonia water. The first heat exchange method is not particularly limited, and may be performed by a heat exchange method that is conventional in the art. The number of heat exchanges may be 1 or more, preferably 2 to 4, more preferably 2 to 3, and particularly preferably 2. Through after the first heat exchange, the output ammonia water is cooled, and the heat is circulated in the treatment device to the maximum extent, so that the energy is reasonably utilized, and the waste is reduced.
According to a preferred embodiment of the present invention, the first heat exchange is performed by a first heat exchange device 31 and a second heat exchange device 32, specifically, the first ammonia-containing steam obtained by evaporation in the MVR evaporation device 2 sequentially passes through the second heat exchange device 32 and the first heat exchange device 31, and the wastewater to be treated sequentially passes through the first heat exchange device 31 and the second heat exchange device 32, 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 the first ammonia water, which can be stored in a first ammonia water storage tank 51.
According to another preferred embodiment of the present invention, the first heat exchange is performed by a first heat exchange device 31, a second heat exchange device 32 and a 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 4; and passing a part of the catalyst production wastewater through a first heat exchange device 31, and passing the other part of the catalyst production wastewater through a fourth heat exchange device 34; and then combining the two parts of wastewater, mixing the combined wastewater with at least part of a liquid phase obtained by second solid-liquid separation to obtain wastewater to be treated, and then passing the wastewater to be treated through a second heat exchange device 32, so that the wastewater to be treated is heated for evaporation through first heat exchange between the first ammonia-containing steam and the catalyst production wastewater and the wastewater to be treated, and simultaneously cooling the first ammonia-containing steam to obtain first ammonia water. The first ammonia water may be stored in the first ammonia water 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, a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, or the like may be mentioned, with the plate heat exchanger being preferred. The material of the heat exchanger can be specifically selected according to the needs, for example, in order to resist the corrosion of chloride ions, the heat exchanger of duplex stainless steel, titanium and titanium alloy, hastelloy can be selected as the material, and the heat exchanger containing plastic material can be selected when the temperature is lower.
According to the present invention, in order to fully utilize the heat energy of the first ammonia-containing vapor condensate, it is preferable that the temperature of the wastewater to be treated is 40 to 364 ℃, more preferably 55 to 364 ℃, even more preferably 65 to 174 ℃, and even more preferably 79 to 129 ℃ after the first heat exchange is performed by the first heat exchange device 31.
According to the present invention, in order to fully utilize the heat energy of the 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 29 to 84 ℃, more preferably 44 to 65 ℃.
According to the present invention, in order to fully utilize the heat energy of the first ammonia-containing steam, it is preferable that the temperature of the wastewater to be treated is 50 ℃ to 370 ℃, more preferably 65 ℃ to 370 ℃, even more preferably 75 ℃ to 184 ℃, and even more preferably 85 ℃ to 139 ℃ after the first heat exchange is performed by the second heat exchange device 32.
In the present invention, the method of adjusting the pH is not particularly limited, and for example, the pH of the wastewater to be treated may be adjusted by adding an alkaline substance. The alkaline substance is not particularly limited, and 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, and to increase the purity of the crystals obtained.
The manner of adding the basic substance may be any manner known in the art, but it is preferable to mix the basic substance with the wastewater to be treated in the form of an aqueous solution, and for example, an aqueous solution containing the basic 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 the aqueous solution containing the 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; then mixing the catalyst production wastewater with at least part of the liquid phase obtained by the second solid-liquid separation to obtain wastewater to be treated, feeding the wastewater to be treated into a second heat exchange device 32 for first heat exchange, and then introducing and mixing the aqueous solution containing the alkaline substance into a pipeline for feeding the wastewater to be treated into the MVR evaporation device 2 to perform second pH value adjustment. The pH value of the wastewater to be treated is more than 9, preferably more than 10.8 before the wastewater is introduced into the MVR evaporation device 2 through two pH value adjustments. Preferably, the first pH adjustment is performed so that the pH of the adjusted catalyst production wastewater is greater than 7 (preferably 7 to 9), and the second pH adjustment is performed so that the pH of the wastewater to be treated is greater than 9, preferably greater than 10.8.
In order to detect the pH values after the first pH adjustment and the second pH adjustment, it is preferable that a first pH measuring device 61 is provided on a pipe for feeding the wastewater to be treated into the first heat exchanging device 31 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 that a part of the liquid evaporated by the MVR evaporation device 2 (i.e. the liquid located inside the MVR evaporation device, hereinafter also referred to as a circulating liquid) is heated and then refluxed to the MVR evaporation device 2 for evaporation. The above process of returning part of the liquid evaporated by the MVR evaporation device 2 to the MVR evaporation device 2 is preferably that the circulation liquid is mixed with the wastewater to be treated after the first pH adjustment and before the second pH adjustment, and then sent into 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 after the second pH adjustment, heat exchange is performed in the second heat exchange device 32, and then sent into the MVR evaporation device 2. As a ratio of refluxing a part of the liquid evaporated by the MVR evaporation device 2 to the MVR evaporation device 2, there is no particular limitation, and for example, the reflux ratio of the first evaporation may be 10 to 200, preferably 50 to 100. Here, the reflux ratio means: the ratio of the amount of reflux to the total amount of liquid fed to the MVR evaporator 2 minus the amount of reflux.
According to the present invention, preferably, the method further comprises compressing the first ammonia-containing vapor before the first heat exchange. The compression of the first ammonia-containing vapor may be performed by a compressor 10. Through right first ammonia vapor that contains compresses, for input energy among the MVR vaporization system, guarantee that waste water intensification-evaporation-cooling's process goes on in succession, need input start-up steam when MVR vaporization process starts, only need pass through compressor 10 energy supply after reaching continuous running state, no longer need input other energy. The compressor 10 may employ various compressors conventionally used in the art, such as a centrifugal fan, a turbine compressor, or a roots compressor, etc. After compression by the compressor 10, the temperature of the first ammonia-containing vapor is raised by 5 to 20 ℃.
In the invention, the first concentrated solution containing sodium sulfate crystals is subjected to first solid-liquid separation to obtain sodium sulfate crystals and a first mother solution. The method of the first solid-liquid separation is not particularly limited, and may be selected from one or more of centrifugation, filtration, and sedimentation.
According to the present invention, the solid-liquid separation of the first concentrated solution may be performed by using a first solid-liquid separation device (for example, a centrifuge, a belt filter, a plate filter, or the like) 91. After the solid-liquid separation, the first mother liquor obtained by the first solid-liquid separation device 91 is temporarily stored in the mother liquor tank 54, and can be sent to the multi-effect evaporation device 1 through the fifth circulation pump 75 to be subjected to the second evaporation. In addition, it is difficult to avoid that the obtained sodium sulfate 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, the sodium sulfate crystals are preferably subjected to first washing with water, the wastewater, or a sodium sulfate solution and dried. The first wash comprises a rinsing and/or elutriation. In addition, the first washing liquid obtained in the above washing process is preferably returned to the second heat exchange device 32 by the eighth circulation pump 78.
The manner of the first solid-liquid separation and the first washing is not particularly limited, and may be carried out by using, for example, a combination of an elutriation apparatus and a solid-liquid separation apparatus which are conventional in the art, or may be carried out on a staged solid-liquid separation apparatus such as a belt filter. The 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 sulfate crystals of higher purity. In the elutriation process, the waste water produced by the catalyst is generally not recycled when used as an elutriation liquid, and the washing liquid recovered by the first washing can be recycled in a counter-current manner when used as the elutriation liquid. Before the elutriation, it is preferable to perform a preliminary solid-liquid separation by sedimentation to obtain a slurry containing sodium sulfate crystals (the liquid content may be 35% by mass or less, and this step is preferably performed in an apparatus known in the art such as a sedimentation tank or a sedimentation tank). In the elutriation, 1 to 20 parts by weight of a liquid is used for elutriation per 1 part by weight of a slurry containing sodium sulfate crystals. In addition, the rinsing is preferably performed using an aqueous sodium sulfate solution. Preferably, the concentration of the aqueous sodium sulphate solution is such that the sodium chloride and the sodium sulphate reach the concentration of sodium sulphate in a saturated aqueous solution at the same time at the temperature corresponding to the sodium sulphate 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, and more preferably using water or a sodium sulfate solution. The liquid resulting from the washing is preferably returned to the MVR evaporation unit prior to the second pH adjustment prior to evaporation.
According to a preferred embodiment of the present invention, after the first concentrated solution containing sodium sulfate obtained by evaporation in the MVR evaporation apparatus 2 is subjected to preliminary solid-liquid separation by sedimentation, the catalyst production wastewater is subjected to first elutriation in an elutriation tank, then the liquid obtained by subsequent washing of sodium sulfate crystals is subjected to second elutriation in another elutriation tank, finally the slurry subjected to the two elutriations is sent to a solid-liquid separation apparatus for solid-liquid separation, the crystals obtained by the solid-liquid separation are subjected to elution with an aqueous sodium sulfate solution, and the liquid obtained by the elution is returned to the second elutriation. Through the washing process, the purity of the obtained sodium sulfate crystal is improved, washing liquid is not excessively introduced, and the efficiency of wastewater treatment is improved.
In the present invention, the 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 such as a demister for further separating liquid foam, a condenser for condensing all secondary steam, and a vacuum apparatus for pressure reduction operation, if necessary. The number of evaporators included in the multi-effect evaporation apparatus 1 is not particularly limited, and may be 2 or more, preferably 2 to 5, and more preferably 2 to 3.
In the present invention, the evaporation conditions of the second evaporation may be appropriately selected as necessary, so that sodium chloride is crystallized without precipitating sodium sulfate. The conditions of the second evaporation may include: the temperature is 30-85 ℃, and the pressure is-98 kPa to-58 kPa; preferably, the conditions of the second evaporation include: the temperature is 35-60 ℃, and the pressure is-97.5 kPa to-87 kPa; preferably, the conditions of the second evaporation include: the temperature is 40 ℃ to 60 ℃, and the pressure is-97 kPa to-87 kPa; preferably, the conditions of the second evaporation include: the temperature is 45-60 ℃, and the pressure is-95 kPa to-87 kPa; preferably, the conditions of the second evaporation include: the temperature is 45-56 ℃, and the pressure is-95 kPa to-89 kPa. In the present invention, the second evaporation condition refers to the evaporation condition of the last one of the multiple-effect evaporation devices.
Among them, in order to fully utilize the heat in the evaporation process, the evaporation temperature of the former evaporator is preferably higher than that of the latter evaporator by more than 5 ℃, preferably 5 ℃ to 30 ℃, and more preferably 10 ℃ to 20 ℃.
In the present invention, the operating pressure of the second evaporation is preferably the saturated vapor pressure of the evaporated feed liquid.
Further, the evaporation amount of the second evaporation may be appropriately selected depending on the capacity of the apparatus and the amount of the wastewater to be treated, and may be, for example, 100L/h or more (e.g., 0.1 m) 3 /h～500m 3 H). By carrying out the second evaporation under the above conditions, the sodium sulfate is not crystallized while the crystallization of sodium chloride is ensured, so that the purity of the obtained sodium chloride crystal can be ensured.
In the invention, in order to sequentially feed the first mother liquor into each effect evaporator of the multi-effect evaporation device 1, a circulating pump can be arranged between each effect evaporator, and the wastewater 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 chloride crystals. And introducing second ammonia-containing steam obtained by evaporation in a first effect evaporator 1a of the multi-effect evaporation device 1 into a second effect evaporator 1b to perform second heat exchange with the first concentrated solution to obtain second ammonia water, and introducing second ammonia-containing steam obtained by evaporation in the second effect evaporator 1b into a third effect evaporator 1c to perform second heat exchange with the first concentrated solution to obtain second ammonia water. More preferably, the second ammonia water is subjected to first heat exchange with the wastewater to be treated through the fourth heat exchange device, so that energy is fully utilized. Heating steam (namely raw steam conventionally used in the field) is introduced into the first-effect evaporator 1a, the heating steam is condensed in the first-effect evaporator 1a to obtain a condensate, and the condensate is used for preheating the wastewater to be treated or the catalyst production wastewater entering the MVR evaporation device 2 and then is used for preparing a sodium sulfate washing solution. 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) after the first mother liquor is evaporated in the first effect evaporator 1a, introducing the first mother liquor into the second effect evaporator 1b for evaporation, and then introducing the first mother liquor into the third effect evaporator 1c for evaporation, and crystallizing the finally obtained second concentrated solution containing sodium chloride crystals in a crystal liquor collecting tank 53 to obtain crystal slurry.
According to the present invention, the second evaporation does not crystallize sodium sulfate in the second concentrated solution (i.e., sodium sulfate does not reach supersaturation), and preferably, the second evaporation is performed such that the concentration of sodium sulfate in the second 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 sulfate and sodium chloride in the second concentrated solution reach saturation under the conditions of the second evaporation. By controlling the degree of the second evaporation within the above range, as much sodium chloride as possible can be crystallized out under the condition that sodium sulfate is not precipitated out. By crystallizing sodium chloride in the second evaporation as much as possible, the wastewater treatment efficiency can be improved, and the energy waste can be reduced.
In the present invention, the degree of progress of the second evaporation is performed by monitoring the concentration of the second evaporation-yielded liquid, and specifically, by controlling the concentration of the second evaporation-yielded liquid within the above range, the second evaporation is performed so as not to crystallize out sodium sulfate in the second concentrated solution. The concentration of the liquid resulting from the second evaporation is monitored by measuring the density, which may be carried out using a densitometer.
In the present invention, in order to prevent the first evaporation from crystallizing and precipitating sodium chloride and the second evaporation from crystallizing and precipitating sodium sulfate, it is preferable that the conditions of the two-time evaporation satisfy: the temperature of the first evaporation is at least 5 c, preferably 20 c, more preferably 35-70 c, and especially 50-60 c higher than the temperature of the second evaporation (with the evaporation thermometer of the last effect evaporator). And respectively crystallizing and separating out sodium sulfate and sodium chloride by controlling the first evaporation and the second evaporation to be carried out at different temperatures, so that the purity of the obtained sodium sulfate and sodium chloride crystals is improved.
According to a preferred embodiment of the invention, the second 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 means 33 is not particularly limited, and various heat exchangers conventionally used in the art may be used to cool the second ammonia-containing steam. Specifically, it may be a jacketed heat exchanger, a plate heat exchanger, a shell-and-tube heat exchanger, a spiral threaded tube heat exchanger, or the like. The material of the heat exchanger can be specifically selected according to the requirement, for example, the stainless steel spiral thread pipe heat exchanger is preferred because the secondary steam has no corrosivity to the stainless steel. The cold medium can be cooling water, glycol water solution and the like. When conventional cooling water is used, the cooling water is recycled, and when the catalyst production wastewater is used as the cooling water, the catalyst production wastewater after heat exchange is preferably directly returned to the treatment process (for example, returned to the first pH value adjustment process).
In the invention, it can be understood that the second ammonia water includes both that the second ammonia-containing steam obtained by evaporating the second concentrated solution in the first evaporator of the multi-effect evaporator is sent to the second evaporator to perform the second heat exchange with the first concentrated solution to obtain the second ammonia water, and the second ammonia water also includes that the second ammonia-containing steam generated in the last evaporator of the multi-effect evaporator is subjected to the third heat exchange in the third heat exchange device to obtain the second ammonia water. The above two parts of ammonia water are collected together in the second ammonia water storage tank 52.
According to a preferred embodiment of the invention, the second evaporation process is carried out in a multi-effect evaporation device 1. And introducing the first mother liquor into the multi-effect evaporation device 1 through a fifth circulating pump 75 to perform second evaporation to obtain second ammonia-containing steam and a second concentrated solution containing sodium chloride crystals.
According to the invention, the method can also comprise crystallizing the second concentrated solution containing sodium chloride crystals in a crystallizing device to obtain crystal slurry containing sodium chloride crystals. In this case, the evaporation conditions for the second evaporation are required to satisfy the purpose of crystallizing sodium chloride without precipitating sodium sulfate in the crystallization device. The crystallization apparatus is not particularly limited, and may be, for example, a crystal solution tank, a crystal solution collecting tank, a thickener with stirring or a thickener without stirring, or the like. According to a preferred embodiment of the present invention, the crystallization is performed in the liquid crystal collecting tank 53. The crystallization conditions are not particularly limited, and may include, for example: the temperature is above 30 ℃; preferably 40-60 ℃; more preferably from 45 ℃ to 55 ℃. The crystallization time may be 5min to 24h, preferably 5min to 30min.
According to the invention, the crystallization of the second concentrated solution containing sodium chloride crystals can also be carried out in a multi-effect evaporator with a crystallizer (e.g. a forced circulation evaporator crystallizer), wherein the crystallization temperature is the corresponding second evaporation temperature. According to the present invention, when a single crystallization apparatus is used for crystallization, it is further required to ensure that the second evaporation does not crystallize sodium sulfate in the second concentrated solution (i.e., sodium sulfate does not become supersaturated), and preferably, the second evaporation is performed such that the concentration of sodium sulfate in the second concentrated solution is Y or less, where Y is the concentration of sodium sulfate at which both sodium chloride and sodium sulfate in the second concentrated solution become saturated under the crystallization conditions.
In the present invention, the second concentrated solution containing sodium chloride crystals (or the magma containing sodium chloride crystals when crystallized in a separate crystallization device) is subjected to a second solid-liquid separation to obtain sodium chloride crystals and a second mother liquor (i.e., a liquid phase obtained by the second solid-liquid separation). The method of the second solid-liquid separation is not particularly limited, and may be selected from, for example, one or more of centrifugation, filtration, and sedimentation.
According to the present invention, the second solid-liquid separation may be performed by a second solid-liquid separation device (e.g., a centrifuge, a belt filter, a plate filter, etc.) 92. After the second solid-liquid separation, the second mother liquor (i.e., the liquid phase obtained by the second solid-liquid separation) 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 may be returned to the first pH adjustment process by the seventh circulation pump 77 to be mixed with the catalyst production wastewater 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 chloride crystals adsorb certain impurities such as sulfate ions, free ammonia, hydroxide ions, etc., and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and improve the purity of the crystals, it is preferable that the sodium chloride crystals are subjected to secondary washing with water, the catalyst production wastewater, or a sodium chloride solution and dried. In order to avoid dissolution of the sodium chloride crystals during washing, preferably the sodium chloride crystals are washed with an aqueous solution of sodium chloride. More preferably, the concentration of the sodium chloride aqueous solution is preferably the concentration of sodium chloride in the aqueous solution at which sodium chloride and sodium sulfate reach saturation simultaneously at the temperature corresponding to the sodium chloride crystals to be washed.
Preferably, the second wash comprises a rinsing and/or elutriation. The second washing liquid obtained in the above washing process is preferably returned to the 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 chloride crystals of higher purity. In the elutriation process, the catalyst production wastewater is not generally recycled when being used as an elutriation liquid, and is preferably returned to the MVR evaporation device before the second pH value adjustment; the washing liquid recovered from the second washing (i.e. the washing liquid produced by the elution) can be recycled in countercurrent 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 with respect to 1 part by weight of a slurry containing sodium chloride crystals. In addition, the rinsing is preferably carried out using an aqueous sodium chloride solution (the concentration of the aqueous sodium chloride solution is preferably the concentration of sodium chloride in an aqueous solution in which sodium chloride and sodium sulfate are simultaneously saturated at a temperature corresponding to the sodium chloride crystals to be rinsed). In order to further enhance the elutriation effect and obtain sodium chloride crystals with higher purity, the elutriation may be preferably performed using a liquid obtained by rinsing. For the liquid produced by the washing, it is preferred that the waste elutriation liquid is returned to the multi-effect evaporation device for evaporation before the second pH adjustment before evaporation in the MVR evaporation device.
According to a preferred embodiment of the present invention, after a preliminary solid-liquid separation is performed by settling on a crystal slurry containing sodium chloride crystals obtained by crystallization, a first elutriation is performed in an elutriation tank using the catalyst production wastewater, then a second elutriation is performed in another elutriation tank using a liquid obtained when sodium chloride crystals are subsequently washed, finally, the slurry subjected to the two elutriations is sent to a solid-liquid separation device for solid-liquid separation, crystals obtained by solid-liquid separation are washed again with an aqueous sodium chloride solution (the concentration of the aqueous sodium chloride solution is the concentration of sodium chloride in an aqueous solution in which sodium chloride and sodium sulfate are simultaneously saturated at a temperature corresponding to the sodium chloride crystals to be washed), and the liquid obtained by washing is returned to the second elutriation as an elutriation liquid. Through the washing process combining elutriation and leaching, the purity of the obtained sodium chloride crystal is improved, washing liquid cannot be introduced too much, and the efficiency of wastewater treatment is improved.
According to a preferred embodiment of the present invention, the tail gas remaining after the first ammonia-containing steam is condensed by the first heat exchange and the tail gas remaining after the second ammonia-containing steam is condensed by the second heat exchange are discharged after ammonia removal. The first ammonia-containing steam is subjected to the first heat exchange to condense the remaining tail gas, namely the tail gas discharged from the second heat exchange device 32, and the second ammonia-containing steam is subjected to the second heat exchange to condense the remaining tail gas, namely 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, the catalyst production wastewater is not particularly limited as long as it contains NH 4 + 、SO 4 2- 、Cl - And Na + The wastewater is obtained. In addition, the method is particularly suitable for treating high-salinity wastewater. The wastewater from the catalyst production of the present invention may be wastewater from the production of a molecular sieve, alumina or an oil refining catalyst, or may be wastewater from the production of a molecular sieve or aluminaOr the wastewater after the following impurity removal and concentration are carried out on the wastewater in the oil refining catalyst production process. It is preferable that the wastewater from the production of molecular sieves, alumina or refinery catalysts is subjected to the following impurity removal and concentration.
As NH in the catalyst production 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.
NH contained in the 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 + The upper limit of (b) is 200g/L or less, preferably 150g/L or less, respectively; 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 lower the content, the better, for example, relative to 1 mole of SO contained in the catalyst production wastewater 4 2- Cl contained in the catalyst production wastewater - Is 30 mol or less, preferably 20 mol or less, more preferably 15 mol or less, and still more preferably 10 mol or less. From the viewpoint of practicality, the amount of SO contained in the wastewater from the catalyst production is 1 mole 4 2- Cl contained in the catalyst production wastewater - Preferably 0.1 mol or more, more preferably 0.5 mol or more, further preferably 1 mol or more, for example, 1 to 8 mol. By adding SO contained in the catalyst production wastewater 4 2- And Cl - The molar ratio of (a) to (b) is limited to the above range, most of water can be evaporated in the first evaporation, the amount of circulating liquid in a treatment system is reduced, energy is saved, and the treatment process is more economical.
In the present invention, the inorganic salt ions contained in the catalyst production wastewater are other than NH 4 + 、SO 4 2- 、Cl - And Na + In addition, it may contain Mg 2+ 、Ca 2+ 、K + 、Fe 3+ Inorganic salt ions such as rare earth element ions, mg 2+ 、Ca 2+ 、K + 、Fe 3+ The content of each inorganic salt ion such as a rare earth element ion is preferably 100mg/L or less, more preferably 50mg/L or less, further preferably 10mg/L or less, and particularly preferably no other inorganic salt ion is contained. By controlling the other inorganic salt ions within the above range, the purity of the sodium sulfate crystals and sodium chloride crystals finally obtained can be further improved. In order to reduce the content of other inorganic salt ions in the catalyst production wastewater, the following impurity removal is preferably performed.
The TDS of the catalyst production wastewater may be 1600mg/L or more, preferably 4000mg/L or more, more preferably 8000mg/L or more, further preferably 16000mg/L or more, further preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, further preferably 60000mg/L or more, further preferably 100000mg/L or more, further preferably 150000mg/L or more, further preferably 200000mg/L or more.
In the present invention, the pH of the catalyst production wastewater is preferably 4 to 8, more preferably 6.3 to 7.
In addition, since the COD of the wastewater may block a membrane during concentration, affect the purity and color of a salt during evaporative crystallization, etc., the COD of the wastewater from the catalyst production is preferably as small as possible (preferably 20mg/L or less, more preferably 10mg/L or less), and is preferably removed by oxidation during pretreatment, specifically, by biological method, advanced oxidation method, etc., and is preferably oxidized by an oxidizing agent such as Fenton's reagent when the COD content is very high.
In the invention, in order to reduce the concentration of impurity ions in the wastewater, ensure the continuous and stable operation of the 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, any one of a strongly acidic cation resin and a weakly acidic cation resin can be used; as the oxidation, various oxidizing agents conventionally used in the art, such as ozone, hydrogen peroxide, and potassium permanganate, can be used, and in order to avoid introduction of new impurities, ozone, hydrogen peroxide, and the like are preferably used.
The specific impurity removal mode can be specifically selected according to the types of impurities contained in the catalyst production wastewater. For suspended matters, a solid-liquid separation method can be selected for removing impurities; for inorganic and organic substances, chemical precipitation, ion exchange, and adsorption can be selected to remove impurities, such as weak acid cation exchange, and activated carbon adsorption; 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 catalyst production wastewater treatment process is ensured.
In the present invention, the catalyst production wastewater having a low salt content may be concentrated to have a salt content within a range required for the wastewater of the present invention before the treatment by the treatment method of the present invention (preferably after the above-mentioned 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 treating the catalyst production wastewater can be improved, and energy waste caused by a large amount of evaporation is avoided.
In a preferred embodiment of the invention, the catalyst production wastewater is wastewater generated after wastewater generated in the molecular sieve production process is subjected to chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation for impurity removal, and is concentrated by an ED membrane and a reverse osmosis method.
The conditions for the above chemical precipitation are preferably: sodium carbonate is used as a treating agent, 1.2 to 1.4 mol of sodium carbonate is added relative to 1 mol of calcium ions in the wastewater, the pH value of the wastewater is adjusted to be more than 7, the reaction temperature is between 20 and 35 ℃, and the reaction time is between 0.5 and 4 hours.
The conditions for the filtration are preferably: the filtering unit adopts a double-layer filtering material multi-medium filter consisting of anthracite and quartz sand, the grain diameter of the anthracite is 0.7 mm-1.7 mm, the grain diameter of the quartz sand is 0.5 mm-1.3 mm, and the filtering speed is 10 m/h-30 m/h. After the filter material is used, the regeneration method of 'gas back flushing-gas and water back flushing-water back flushing' is adopted to regenerate the filter material, and the regeneration period is 10-15 h.
The conditions for the weak acid cation exchange method are preferably: the pH value range is 6.5-7.5; the temperature is less than or equal to 40 ℃, the height of the resin layer is 1.5-3.0 m, the HCl concentration of the regeneration liquid is as follows: 4.5 to 5 mass percent; the dosage of the regenerant (calculated by 100%) is 50kg/m 3 ～60kg/m 3 Wet resin; the flow rate of the regeneration liquid HCl is 4.5 m/h-5.5 m/h, and the regeneration contact time is 35 min-45 min; the forward washing flow rate is 18 m/h-22 m/h, and the forward washing time is 20 min-30 min; the running flow rate is 15 m/h-30 m/h; as the acidic cation exchange resin, for example, there can be used a Gallery Senno chemical Co., ltd, SNT brand D113 acidic cation exchange resin.
The conditions of the above-mentioned ozone biological activated carbon adsorption oxidation method are preferably: the retention time of the ozone is 50min to 70min, and the empty bed filtration rate is 0.5m/h to 0.7m/h.
The conditions for the concentration of the ED membrane are preferably: the current 145A to 155A, and the voltage 45V to 65V. The ED membrane may be, for example, an ED membrane manufactured by astone corporation of japan.
The conditions for the reverse osmosis are preferably: the operation pressure is 5.4MPa to 5.6MPa, the water inlet temperature is 25 ℃ to 35 ℃, and the pH value is 6.5 to 7.5. The reverse osmosis membrane is, for example, a seawater desalination membrane TM810C manufactured by Dongli corporation of Lanxingdong.
According to the invention, when the wastewater treatment is started, the catalyst production wastewater can be used for direct operation, and if the ion content of the catalyst production wastewater meets the conditions of the invention, the first evaporation can be carried out firstly and then the second evaporation can be carried out according to the conditions of the invention; if the ion content of the catalyst production wastewater does not meet the costAccording to the conditions of the invention, the first evaporation can be controlled to enable the concentration of sodium chloride in the first concentrated solution to be close to the precipitated concentration, then the first concentrated solution is subjected to second evaporation to obtain a second concentrated solution, solid-liquid separation is carried out to obtain sodium chloride crystals and a second mother solution, then the second mother solution is mixed with the catalyst production wastewater to adjust the ion content of the wastewater to be treated to be in the range required by the invention, and then the first evaporation is carried out to obtain sodium sulfate crystals; of course, the ion content of the wastewater to be treated can be adjusted by using sodium sulfate or sodium chloride in the initial stage as long as the wastewater to be treated satisfies SO in the wastewater to be treated in the present invention 4 2- 、Cl - The requirements are met.
The present invention will be described in detail below by way of examples.
In the following examples, the catalyst production wastewater is wastewater from a molecular sieve production process, which is subjected to chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation in sequence to remove impurities, and is subjected to ED membrane concentration and reverse osmosis concentration in sequence.
Example 1
As shown in FIG. 1, the catalyst production wastewater (containing NaCl 156g/L and Na) 2 SO 4 50g/L、NH 4 Cl60g/L、(NH 4 ) 2 SO 4 19.55g/L, pH 6.3) at a feed rate of 5m 3 The reaction mixture was fed into a line of a treatment system at a rate of/h, and a 45.16 mass% aqueous sodium hydroxide solution was introduced into the line to adjust the pH value for the first time, and the adjusted pH value was monitored by a first pH value measuring device 61 (pH meter) (measurement value: 7.5), and a part (2.5 m) of the catalyst production wastewater after the first pH value adjustment was fed into the line 3 H) sending the waste water into a first heat exchange device 31 (a plastic plate heat exchanger) to carry out first heat exchange with the first ammonia-containing steam condensate so as to heat the catalyst production waste water to 99 ℃, sending the rest part of the waste water into a fourth heat exchange device 34 (a duplex stainless steel plate heat exchanger) to carry out first heat exchange with the second ammonia-containing steam condensate so as to heat the rest part of the catalyst production waste water to 60 ℃, combining the two parts of waste water, and sending the combined waste water and the second mother liquid (the sending speed is 15.31 m) 3 H) mixing to obtain the wastewater to be treated (SO contained in the wastewater to be treated) 4 2- And Cl - In a molar ratio of 1: 10.356). Then, the wastewater to be treated is sent to a second heat exchange device 32 (titanium alloy plate heat exchanger), first heat exchange is carried out with the recovered first ammonia-containing steam to heat the wastewater to be treated to 113 ℃, then the wastewater to be treated is sent to a pipeline of an MVR evaporation device 2 (falling film + forced circulation two-stage MVR evaporation crystallizer), sodium hydroxide aqueous solution with the concentration of 45.16 mass% is introduced for second pH value adjustment, the adjusted pH value is monitored by a second pH value measuring device 62 (pH meter) (the measured value is 10.8), the wastewater to be treated after the second pH value adjustment is sent to the MVR evaporation device 2 for evaporation, and first ammonia-containing steam and a first concentrated solution containing sodium sulfate crystals are obtained. Wherein, the evaporation conditions of the MVR evaporation device 2 include: the temperature is 105 ℃, the pressure is-7.02 kPa, and the evaporation capacity is 2.53m 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 the compressor 10 (the temperature is raised by 14 ℃) and then passes through the second heat exchange device 32 and the first heat exchange device 31 in sequence, exchanges heat with the wastewater to be treated, is cooled to obtain ammonia water, and is stored in the first ammonia water storage tank 51. In addition, in order to increase the solid content in the MVR evaporation device 2, part of the liquid evaporated in the MVR evaporation device 2 is circulated as a circulation liquid to the second heat exchange device 32 by the second circulation pump 72, and then enters the MVR evaporation device 2 again for the first evaporation (reflux ratio is 56.2). The degree of the first evaporation was monitored by a densimeter provided on the MVR evaporation apparatus 2, and the concentration of sodium chloride in the first concentrated solution was controlled to be 0.99352X (307.0 g/L).
The first concentrated solution obtained by evaporation in the MVR evaporation device 2 is sent to a first solid-liquid separation device 91 (centrifugal machine) for first solid-liquid separation, and 18.43m is obtained every hour 3 Contains NaCl 307.0g/L and Na 2 SO 4 52.7g/L、NaOH 1.67g/L、NH 3 0.13g/L of the first mother liquor was temporarily stored in a mother liquor tank 54, and the sodium sulfate solid obtained by solid-liquid separation (407.73 kg of a sodium sulfate crystal cake containing 14% by mass of water and having a sodium chloride content of 6.8% by mass or less per hour) was eluted with 52.7g/L of a sodium sulfate solution equivalent to the dry basis mass of the sodium sulfate crystal cake and driedAfter drying, 350.64kg of sodium sulfate (purity of 99.4 wt%) is obtained per hour, and the eluted eluate is circulated to the second heat exchange device 32 by the eighth circulation pump 78 and then enters the MVR evaporation device 2 again for the first evaporation.
The second evaporation process is carried out in a multi-effect evaporation device 1, and the multi-effect evaporation device 1 consists of a first effect evaporator 1a, a second effect evaporator 1b and a third effect evaporator 1c (all of forced circulation evaporators). 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 chloride crystals. Wherein the evaporation temperature of the first effect evaporator 1a is 86 ℃, the pressure is-55.83 kPa, and the evaporation capacity is 1.08m 3 H; the evaporation temperature of the second effect evaporator 1b is 71 ℃, the pressure is-77.40 kPa, and the evaporation capacity is 1.07m 3 H; the evaporation temperature of the third effect evaporator 1c is 56 ℃, the pressure is-89.56 kPa, and the evaporation capacity is 1.06m 3 H is used as the reference value. 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 heat exchange to obtain second ammonia water, introducing second ammonia-containing steam obtained by evaporation in the second effect evaporator 1b into a third effect evaporator 1c for heat exchange to obtain first ammonia water, and storing the second ammonia water in a second ammonia water storage tank 52 after the second ammonia water exchanges heat with the 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 a condensate obtained after the heating steam is condensed in the first-effect evaporator 1a is used for preparing washing brine. The second ammonia-containing steam evaporated by the third effect evaporator 1c is subjected to third heat exchange with the cold medium in the third heat exchange device 33 to obtain second ammonia water, and the second ammonia water is stored in the second ammonia water storage tank 52. The degree of the second evaporation was monitored by a densimeter provided in the multi-effect evaporation apparatus 1, and the concentration of sodium sulfate in the second concentrated solution was controlled to 0.9693Y (63.1 g/L). After the first mother liquor is evaporated in the multi-effect evaporation device 1, the finally obtained second concentrated solution containing sodium chloride crystals is crystallized in a crystal liquid collecting tank 53 (the crystallization temperature is 55℃)Crystallization time is 30 min) to obtain crystal slurry containing sodium chloride crystals.
The crystal slurry containing sodium chloride crystals is sent to a second solid-liquid separation device 92 (centrifugal machine) for solid-liquid separation, and the solid-liquid separation can obtain 15.31m per hour 3 Contains 295.6g/L NaCl and Na 2 SO 4 63.1g/L、NaOH2.0g/L、NH 3 0.13g/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 chloride solid (1293.73 kg of sodium chloride crystal filter cake with the water content of 14 mass% per hour, wherein the content of sodium sulfate is less than 7.0 mass%), washing the sodium chloride solid with 295g/L of sodium chloride solution with the same dry basis mass as the sodium chloride, drying the sodium chloride solid in a drier, and obtaining 1112.6kg of sodium chloride (with the purity of 99.4 weight%) per hour, wherein the washing liquid obtained by washing is circulated 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 a fourth circulating pump 74, water is supplemented into the tail gas absorption tower 83 from a circulating water tank 82 through a third circulating pump 73, and fresh water is supplemented into the circulating water tank 82, so that the temperature of the water for operating the vacuum pump 81 and the ammonia content 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, 2.53m of ammonia water having a concentration of 4.44 mass% was obtained per hour in the first ammonia water tank 51 3 3.21m of 0.072 mass% ammonia water is obtained in the second ammonia water tank 52 every hour 3 The ammonia water can be reused in the production process of the molecular sieve.
In addition, the starting phase of the MVR evaporation was started by steam at a temperature of 143.3 ℃.
Example 2
The treatment of the catalyst production wastewater was carried out in the same manner as in example 1 except that: for the solution containing NaCl71g/L and Na 2 SO 4 132g/L、NH 4 Cl 16g/L、(NH 4 ) 2 SO 4 Treating the catalyst production wastewater with the concentration of 30.24g/L and the pH value of 7.0 to obtain SO contained in the wastewater to be treated 4 2- And Cl - In a molar ratio of 1:4.163. the temperature of the wastewater to be treated after heat exchange by the first heat exchange means 31 was 64 deg.c, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange means 32 was 102 deg.c. The evaporation conditions of the MVR evaporation device 2 include: the temperature is 95 ℃, the pressure is-36.36 kPa, and the evaporation capacity is 2.53m 3 H is the ratio of the total weight of the catalyst to the total weight of the catalyst. The evaporation conditions of the first effect evaporator 1a include: the temperature is 80 ℃, the pressure is-65.87 kPa, and the evaporation capacity is 0.43m 3 H; the evaporation conditions of the second effect evaporator 1b include: the temperature is 64 ℃, the pressure is-84.0 kPa, and the evaporation capacity is 0.43m 3 H; the evaporation conditions of the third effect evaporator 1c include: the temperature was 46 ℃, the pressure was-94.33 kPa, and the evaporation capacity was 0.42m 3 /h。
The first solid-liquid separation device 91 yielded 970.09kg of a sodium sulfate crystal cake containing 15% by mass of water per hour, and finally yielded 824.57kg of sodium sulfate (purity 99.5% by weight) per hour; yield 6.59m per hour 3 The concentration of NaCl is 305.6g/L and Na 2 SO 4 55.15g/L、NaOH 1.15g/L、NH 3 0.19g/L of the first mother liquor.
518.3kg of sodium chloride crystal cake with the water content of 15 mass% is obtained by the second solid-liquid separation device 92 every hour, and finally 440.5kg of sodium chloride (with the purity of 99.5 weight%) is obtained every hour; 5.42 m/hr 3 The concentration of NaCl 292.6g/L and Na 2 SO 4 67.4g/L、NaOH 1.4g/L、NH 3 0.012g/L of the second mother liquor.
In this example, 4.26m of ammonia water having a concentration of 1.46% by mass was obtained per hour in the first ammonia water tank 51 3 1.28m of aqueous ammonia having a concentration of 0.095 mass% was obtained per hour in the second aqueous ammonia tank 52 3 The ammonia water can be reused in the production process of the molecular sieve.
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 118g/L, na 2 SO 4 116g/L、NH 4 Cl 19g/L、(NH 4 ) 2 SO 4 Treating the catalyst production wastewater with the concentration of 18.99g/L and the pH of 6.8 to obtain SO contained in the wastewater to be treated 4 2- And Cl - In a molar ratio of 1:6.419. the temperature of the wastewater to be treated after heat exchange by the first heat exchange means 31 was 97 deg.c, and the temperature of the wastewater to be treated after heat exchange by the second heat exchange means 32 was 107 deg.c. The evaporation conditions of the MVR evaporation device 2 include: the temperature is 100 ℃, the pressure is-22.83 kPa, and the evaporation capacity is 3.52m 3 H is the ratio of the total weight of the catalyst to the total weight of the catalyst. The evaporation conditions of the first effect evaporator 1a include: the temperature is 86 ℃, the pressure is-55.83 kPa, and the evaporation capacity is 0.667m 3 H; the evaporation conditions of the second effect evaporators 1b include: the temperature is 71 deg.C, the pressure is-77.4 kPa, and the evaporation capacity is 0.666m 3 H; the evaporation conditions of the third effect evaporator 1c include: the temperature is 56 deg.C, the pressure is-89.56 kPa, and the evaporation capacity is 0.665m 3 /h。
The first solid-liquid separation device 91 produced 792.33kg of a sodium sulfate crystal cake containing 14 mass% of water per hour, and finally produced 681.41kg of sodium sulfate (purity 99.5 wt%) per hour; obtained 10.95m per hour 3 The concentration of NaCl is 305.8g/L and Na 2 SO 4 53.84g/L、NaOH 2.2g/L、NH 3 0.099g/L of the first mother liquor.
The second solid-liquid separation device 92 yielded 817.22kg of sodium chloride crystal cake with a water content of 14 mass% per hour, and finally 694.64kg of sodium chloride (purity 99.4 wt%) per hour; obtained 9.06m per hour 3 The concentration of NaCl is 293.3g/L and Na 2 SO 4 65g/L、NaOH 2.656g/L、NH 3 0.0072g/L of the second mother liquor.
In this example, 3.515m of ammonia water having a concentration of 1.5 mass% was obtained per hour in the first ammonia water tank 51 3 The second ammonia water tank 52 receives 1.998m of 0.051 mass% ammonia water per hour 3 The ammonia water can be reused in the production process of the molecular sieve.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various features described in the foregoing embodiments may be combined in any suitable manner without contradiction. The invention is not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims (35)

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 concentrated solution containing ammonia vapor and sodium sulfate crystals;
2) Carrying out first solid-liquid separation on the first concentrated solution containing the sodium sulfate 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 chloride crystals in the last effect evaporator;
3) Carrying out second solid-liquid separation on the second concentrated solution containing the sodium chloride 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;
the first evaporation prevents sodium chloride from crystallizing out, and the second evaporation prevents sodium sulfate 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 - 14 mol or less;
the wastewater to be treated contains the catalyst production wastewater and the secondLiquid phase obtained by 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 13.8 mol or less.
3. The method as claimed in claim 1, wherein the pH of the wastewater to be treated is adjusted to be greater than 10.8 before passing the wastewater to be treated to the MVR evaporation plant.
4. The method as claimed in claim 1, wherein the pH adjustment of the wastewater to be treated is carried out with NaOH.
5. The method of claim 1, wherein the first evaporation is conducted such that the concentration of sodium chloride in the first concentrated solution is no greater than X, where X is the concentration of sodium chloride at which both sodium sulfate and sodium chloride in the first concentrated solution are saturated under the conditions of the first evaporation.
6. A process as claimed in claim 5, wherein the first evaporation provides a concentration of sodium chloride in the first concentrate of from 0.95X to 0.999X.
7. The process of claim 1, wherein the second evaporation is carried out such that the concentration of sodium sulfate in the second concentrated solution is Y or less, wherein Y is the concentration of sodium sulfate at which both sodium sulfate and sodium chloride in the second concentrated solution are saturated under the conditions of the second evaporation.
8. The process of claim 7, wherein the second evaporation provides a sodium sulfate concentration in the second concentrated solution of 0.9Y to 0.99Y.
9. The method of any one of claims 1-8, wherein the conditions of the first evaporation comprise: the temperature is above 45 ℃ and the pressure is above-95 kPa.
10. The method of claim 9, wherein the conditions of the first evaporation comprise: the temperature is 45-365 ℃, and the pressure is-95 kPa-18110 kPa.
11. The method of claim 10, wherein the conditions of the first evaporation comprise: the temperature is 60-365 ℃, and the pressure is-87 kPa-18110 kPa.
12. The method of claim 11, wherein the conditions of the first evaporation comprise: the temperature is 75-175 ℃, and the pressure is-73 kPa-653 kPa.
13. The method of claim 12, wherein the conditions of the first evaporation comprise: the temperature is 80-130 ℃, and the pressure is-66 kPa-117 kPa.
14. The method of claim 13, wherein the conditions of the first evaporation comprise: the temperature is 95-105 ℃, and the pressure is-37 kPa to-7 kPa.
15. The method of any one of claims 1-8, wherein the conditions of the second evaporation comprise: the temperature is 30-85 ℃, and the pressure is-98 kPa-58 kPa.
16. The method of claim 15, wherein the conditions of the second evaporation comprise: the temperature is 35 to 60 ℃, and the pressure is-97.5 kPa to-87 kPa.
17. The method of claim 16, wherein the conditions of the second evaporation comprise: the temperature is 40-60 ℃, and the pressure is-97 kPa to-87 kPa.
18. The method of claim 17, wherein the conditions of the second evaporation comprise: the temperature is 45-60 ℃, and the pressure is-95 kPa to-87 kPa.
19. The method of claim 18, wherein the conditions of the second evaporation comprise: the temperature is 45-56 ℃, and the pressure is-95 kPa to-89 kPa.
20. The method of claim 15, wherein in the second evaporation, the evaporation temperature of the previous evaporator is more than 5 ℃ higher than the subsequent evaporator.
21. The method of claim 20, wherein in the second evaporation, the evaporation temperature of the former evaporator is 5 ℃ to 30 ℃ higher than that of the latter evaporator.
22. The method of claim 9, wherein the temperature of the first evaporation is more than 5 ℃ higher than the temperature of the second evaporation.
23. The method of claim 22, wherein the temperature of the first evaporation is more than 20 ℃ higher than the temperature of the second evaporation.
24. The method of claim 23, wherein the temperature of the first evaporation is 35-70 ℃ higher than the temperature of the second evaporation.
25. The method according to claim 1, wherein second ammonia-containing steam obtained by evaporation in a previous-effect evaporator is sent to a subsequent-effect evaporator to perform second heat exchange with the first concentrated solution and obtain second ammonia water, and the first concentrated solution and the second ammonia-containing steam are subjected to concurrent heat exchange.
26. The method according to claim 25, 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 passing the wastewater to be treated to an MVR evaporation plant.
27. The method as set forth in claim 26, wherein the pH of the wastewater to be treated is adjusted to be greater than 7 prior to the first heat exchange.
28. The method of claim 26, wherein the ammonia-containing steam generated by the last evaporator is subjected to a third heat exchange in a third heat exchange device to obtain a second ammonia water.
29. The method of claim 28, 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 the evaporation of the last evaporator is subjected to the third heat exchange to condense the remaining tail gas, and is discharged after ammonia removal.
30. The method according to any one of claims 1 to 8, further comprising subjecting the first concentrated solution containing sodium sulfate crystals to a first solid-liquid separation to obtain sodium sulfate crystals.
31. The method of claim 30, further comprising washing the resulting sodium sulfate crystals.
32. The method according to any one of claims 1 to 8, further comprising crystallizing the second concentrated solution in a crystallizing device to obtain a crystal slurry containing sodium chloride crystals, and subjecting the crystal slurry containing sodium chloride crystals to a second solid-liquid separation to obtain sodium chloride crystals.
33. The method of claim 32, further comprising washing the resulting sodium chloride crystals.
34. 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.
35. The method of claim 34, further comprising removing impurities and concentrating the catalyst process wastewater.
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1944256A (en) * 2006-10-25 2007-04-11 中国中轻国际工程有限公司 Process for producing sodium sulfate and sodium chloride in Na2SO4-NaCl-H2O system
CN103172088A (en) * 2013-04-11 2013-06-26 南风化工集团股份有限公司 Application of MVR (mechanical vapor recompression) crystallizing evaporator in sodium sulfate and sodium chloride separation technology
CN103408086A (en) * 2013-08-02 2013-11-27 天华化工机械及自动化研究设计院有限公司 MVR (Mechanical Vapor Recompression) vapor-stripping deamination system and application method thereof
CN104609633A (en) * 2015-02-16 2015-05-13 阮氏化工（常熟）有限公司 Method and device for utilizing sewage containing ammonia and sodium
CN105967208A (en) * 2016-05-05 2016-09-28 上海弘佳能源科技有限公司 Sodium sulfate and sodium chloride mixed wastewater separation method and separation apparatus thereof
CN205974126U (en) * 2016-06-12 2017-02-22 双良节能系统股份有限公司 Contain salt wastewater resource recycling processed system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1944256A (en) * 2006-10-25 2007-04-11 中国中轻国际工程有限公司 Process for producing sodium sulfate and sodium chloride in Na2SO4-NaCl-H2O system
CN103172088A (en) * 2013-04-11 2013-06-26 南风化工集团股份有限公司 Application of MVR (mechanical vapor recompression) crystallizing evaporator in sodium sulfate and sodium chloride separation technology
CN103408086A (en) * 2013-08-02 2013-11-27 天华化工机械及自动化研究设计院有限公司 MVR (Mechanical Vapor Recompression) vapor-stripping deamination system and application method thereof
CN104609633A (en) * 2015-02-16 2015-05-13 阮氏化工（常熟）有限公司 Method and device for utilizing sewage containing ammonia and sodium
CN105967208A (en) * 2016-05-05 2016-09-28 上海弘佳能源科技有限公司 Sodium sulfate and sodium chloride mixed wastewater separation method and separation apparatus thereof
CN205974126U (en) * 2016-06-12 2017-02-22 双良节能系统股份有限公司 Contain salt wastewater resource recycling processed system

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