CN108314113B - Method for treating waste water containing ammonium salt - Google Patents
Method for treating waste water containing ammonium salt Download PDFInfo
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- CN108314113B CN108314113B CN201710034900.1A CN201710034900A CN108314113B CN 108314113 B CN108314113 B CN 108314113B CN 201710034900 A CN201710034900 A CN 201710034900A CN 108314113 B CN108314113 B CN 108314113B
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- 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
Abstract
The invention relates to the field of sewage treatment, and discloses a method for treating wastewater containing ammonium salt, which comprises the steps of introducing the wastewater into an MVR evaporation device to carry out first evaporation to obtain first ammonia-containing steam and first concentrated solution, sequentially introducing the first concentrated solution into each effect evaporator of a multi-effect evaporation device to carry out second evaporation to obtain second ammonia-containing steam in each effect evaporator, and obtaining second concentrated solution in the last effect evaporator; before the wastewater is introduced into an MVR evaporation device, adjusting the pH value of the wastewater to be more than 9; before the wastewater is introduced into the MVR evaporation device and the multi-effect evaporation device, carrying out heat exchange on ammonia-containing steam and the wastewater to obtain ammonia water; the first evaporation is performed so that the solid content in the first concentrated solution is 50 mass% or less. The invention provides a low-cost and environment-friendly method for treating high-salinity wastewater containing ammonium, which can recover ammonium and salt in the wastewater, furthest recycle resources in the wastewater and realize near zero emission.
Description
Technical Field
The invention relates to the field of sewage treatment, in particular to a method for treating ammonium salt-containing wastewater, and particularly relates to a method for treating ammonium salt-containing wastewater.
Background
In the production process of the oil refining catalyst, a large amount of inorganic acid alkali salts such as sodium hydroxide, hydrochloric acid, sulfuric acid, ammonium salts, sulfates, hydrochlorides and the like are needed, and a large amount of mixed sewage containing ammonium, sodium sulfate, sodium chloride and aluminosilicate is generated. For such sewage, the common method in the prior art is that the pH value is adjusted to be within the range of 6-9, most of suspended matters are removed, then a biochemical method, a blow-off method or a steam stripping method is adopted to remove ammonium ions, then the salt-containing sewage is subjected to pH value adjustment, most of suspended matters are removed, hardness, silicon and part of organic matters are removed, most of organic matters are removed through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then the salt-containing sewage enters an ion exchange device for further hardness removal, enters an enrichment device (such as reverse osmosis or electrodialysis) for concentration, and then MVR evaporative crystallization or multiple-effect evaporative crystallization is adopted to obtain mixed miscellaneous salt of sodium sulfate and sodium chloride containing a small amount of ammonium salt; or is; firstly, adjusting the pH value to be within the range of 6.5-7.5, removing most suspended matters, then removing hardness, silicon and part of organic matters, removing most of organic matters through ozone biological activated carbon adsorption oxidation or other advanced oxidation methods, then entering an ion exchange device for further removing hardness, entering a thickening device (such as reverse osmosis and/or electrodialysis) for concentration, and then adopting MVR (mechanical vapor recompression) evaporative crystallization or multiple-effect evaporative crystallization to obtain the mixed salt of sodium sulfate and sodium chloride containing ammonium salt. However, these ammonium-containing mixed salts are currently difficult to treat or expensive to treat, and the process of removing ammonium ions at the early stage additionally increases the cost of wastewater treatment.
In addition, the biochemical deamination can only treat wastewater with low ammonium content, and can not directly carry out biochemical treatment due to insufficient COD content in the catalyst sewage, and organic matters such as glucose or starch and the like are additionally added in the biochemical treatment process, so that the ammoniacal nitrogen can be treated by the biochemical method. The most important problem is that the total nitrogen of the wastewater after the biochemical deamination treatment is not up to the standard (the contents of nitrate ions and nitrite ions exceed the standard), the wastewater needs to be deeply treated, the salt content of the wastewater is not reduced (20000 mg/L-30000 mg/L), the wastewater cannot be directly discharged, and the wastewater needs to be further desalted.
In order to remove ammonia nitrogen from wastewater by gas stripping deamination, a large amount of alkali is needed to adjust the pH value, the alkali consumption is high, the alkali in the wastewater after deamination cannot be recovered, the pH value of the treated wastewater is high, the treatment cost is high, the COD content in the catalyst wastewater after gas stripping does not change greatly, the salt content in the wastewater is not reduced (20000 mg/L-30000 mg/L), the wastewater cannot be discharged directly, further desalting treatment is needed, the operation cost of wastewater treatment is high, a large amount of alkali remains in the treated wastewater, the pH value is high, the waste is large, and the treatment cost is up to 50 yuan/ton.
Disclosure of Invention
The invention aims to solve the problem of high treatment cost of the ammonium-containing high-salt wastewater in the prior art, and provides a low-cost and environment-friendly method for treating the ammonium-containing high-salt wastewater, which can recover ammonium and salt in the wastewater, furthest recycle resources in the wastewater and realize near zero emission.
In order to achieve the purpose, the invention provides a method for treating wastewater containing ammonium salt, which comprises the steps of introducing the wastewater into an MVR evaporation device to carry out first evaporation to obtain first ammonia-containing steam and first concentrated solution, sequentially introducing the first concentrated solution into each effect evaporator of a multi-effect evaporation device to carry out second evaporation, respectively obtaining second ammonia-containing steam in each effect evaporator, and obtaining second concentrated solution in a last effect evaporator, wherein before introducing the wastewater into the MVR evaporation device, the pH value of the wastewater is adjusted to be more than 9; before the wastewater is introduced into an MVR evaporation device, carrying out first heat exchange on the first ammonia-containing steam and the wastewater to obtain first ammonia water; sending second ammonia-containing steam obtained by evaporation in the previous evaporator to the next evaporator for second heat exchange with the first concentrated solution to obtain second ammonia water, and carrying out cocurrent heat exchange between the first concentrated solution and the second ammonia-containing steam; the first evaporation is performed so that the solid content in the first concentrated solution is 50 mass% or less.
Through the technical scheme, after the pH value of the wastewater is adjusted to a specific range in advance, the MVR evaporation device and the multi-effect evaporation device are reused for carrying out first evaporation and second evaporation on the wastewater, the process of separating ammonia and salt is completed, the wastewater is heated and cooled by ammonia vapor by adopting a heat exchange mode, a condenser is not needed, the heat in the evaporation process is reasonably utilized, the energy is saved, the wastewater treatment cost is reduced, the ammonium in the wastewater is recovered in the form of ammonia water, the salt is recovered in the form of miscellaneous salt crystals without ammonium or containing a small amount of ammonium, no waste residue and waste liquid are generated in the whole process, the purpose of changing waste into valuable is realized, the value of the recovered resources is not counted, and the treatment cost of each ton of wastewater is lower than that of a steam air stripping deamination. In addition, according to the technical scheme, the wastewater is subjected to first evaporation and then second evaporation, so that ammonia water with higher concentration can be obtained in the first evaporation step, and the subsequent reutilization is facilitated.
Furthermore, the invention returns the waste water in the processes of crystal separation, crystal washing and the like to the evaporation process, and discharges the waste gas in the processes of heat exchange and the like after absorbing, thereby realizing near zero emission in the treatment process and reducing the environmental pollution to the maximum extent.
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 4 and vacuum degassing tank
51. Ammonia water storage tank 52 and ammonia water collection tank
53. Crystal liquid collecting tank 61 and first pH value measuring device
62. Second pH value measuring device 71 and first circulating pump
72. Second circulating pump 73 and third circulating pump
74. Fourth and fifth circulating pumps 75 and 75
81. Vacuum pump 82 and circulating water pool
83. Tail gas absorption tower 9 and solid-liquid separation device
10. Compressor with a compressor housing having a plurality of compressor blades
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The present invention will be described below with reference to fig. 1, but the present invention is not limited to fig. 1.
The method for treating the wastewater containing the ammonium salt comprises the steps of introducing the wastewater into an MVR evaporation device 2 to carry out first evaporation on first ammonia-containing steam and first concentrated solution, sequentially introducing the first concentrated solution into each effect evaporator of a multi-effect evaporation device to carry out second evaporation, respectively obtaining second ammonia-containing steam in each effect evaporator, and obtaining second concentrated solution in a last effect evaporator, wherein before introducing the wastewater into the MVR evaporation device 2, the pH value of the wastewater is adjusted to be more than 9; before the wastewater is introduced into an MVR evaporation device 2, carrying out first heat exchange on the first ammonia-containing steam and the wastewater to obtain first ammonia water; sending second ammonia-containing steam obtained by evaporation in the previous evaporator to the next evaporator for second heat exchange with the first concentrated solution to obtain second ammonia water, and carrying out cocurrent heat exchange between the first concentrated solution and the second ammonia-containing steam; the first evaporation is performed so that the solid content in the first concentrated solution is 50 mass% or less.
Preferably, the pH of the wastewater is adjusted to be greater than 10.8 before the wastewater is passed into the MVR evaporation plant 2.
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 concentrate and the second ammonia-containing vapor refers to the use of a cocurrent flow scheme in multi-effect evaporation.
According to the method, the pH value of the wastewater is adjusted to be strong alkaline, the first evaporation and the second evaporation are carried out through the MVR evaporation device 2 and the multi-effect evaporation device 1, ammonium ions contained in the wastewater are converted into ammonia and evaporated out, the obtained steam and the wastewater are subjected to heat exchange, the steam is cooled while the wastewater is heated to obtain ammonia water, the ammonia and salt are simultaneously recovered, and the heat in the evaporation process is fully utilized.
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 first evaporation condition of the MVR evaporation apparatus 2 is not particularly limited, and may be appropriately selected as needed. In order to improve the evaporation efficiency of the first evaporation, it is preferable that the conditions of the first evaporation include: the temperature is above 30 ℃, and the pressure in gage pressure is above-98 kPa; more preferably, the conditions of the first evaporation include: the temperature is 50 ℃ to 130 ℃, and the pressure measured by gauge pressure is-93 kPa to 117 kPa; further preferably, the conditions of the first evaporation include: the temperature is 60 ℃ to 130 ℃, and the pressure in gage pressure is-87 kPa to 117 kPa. The flow rate of the first evaporation may be appropriately selected depending on the capacity of the apparatus process, and may be, for example, 0.1m3More than h (e.g. 0.1 m)3/h～500m3/h)。
In the present invention, the first concentrated solution is not lost in fluidity by controlling the first evaporation so that the solid content in the first concentrated solution is 50 mass% or less (preferably 20 mass% or less, more preferably, no solid content), and the first concentrated solution can be directly sent to the multi-effect evaporation apparatus 1 by the circulation pump to perform the second evaporation. Preferably, the first evaporation does not make the first concentrated solution supersaturated (i.e. the solid content of the first concentrated solution is 0), and no crystallization occurs in the first concentrated solution, so that the first concentrated solution is more convenient to convey.
In the present invention, the degree of the first evaporation is not particularly limited, and the concentration ratio of the first evaporation is preferably 1.2 to 1.3 times, and more preferably 1.05 to 1.2 times, in order to obtain ammonia water having a high concentration. The concentration of the first aqueous ammonia solution obtained is preferably adjusted to 3 times or more the concentration of the ammonia in the wastewater before evaporation by appropriately adjusting the concentration ratio, and more preferably 5 to 20 times the concentration of the ammonia in the wastewater before evaporation by appropriately adjusting the concentration ratio. Through the adjustment concentration multiple of first evaporation, can adjust the concentration of first aqueous ammonia in certain extent, can be convenient for recycle of aqueous ammonia from this.
In the present invention, the method of adjusting the pH is not particularly limited, and the pH of the wastewater may be adjusted by adding an alkaline substance, for example. The alkaline substance is not particularly limited, and the purpose of adjusting the pH value may be achieved. In order not to introduce new impurities in the wastewater, the alkaline substance preferably has the same metal cation as the salt in the wastewater. For example, in the case where the wastewater contains a large amount of alkali metal cations, the alkali substance is preferably a hydroxide of an alkali metal (e.g., NaOH, KOH, etc.), and specifically, in the case where the wastewater contains a large amount of sodium ions, the alkali substance is preferably NaOH.
The alkaline substance may be added in a conventional manner in the art, but it is preferable to mix the alkaline substance with the wastewater in the form of an aqueous solution, and for example, an aqueous solution containing the alkaline substance may be introduced into a pipeline into which the wastewater is introduced and mixed. The content of the alkaline substance in the aqueous solution is not particularly limited as long as the above-mentioned purpose of adjusting the pH value can be achieved. However, in order to reduce the amount of water used and further reduce the cost, it is preferable to use a saturated aqueous solution of an alkaline substance. In order to monitor the pH of the wastewater, the pH of the wastewater may be measured after the pH adjustment described above.
According to the invention, before the wastewater is introduced into the MVR evaporation plant 2, the first ammonia-containing steam and the wastewater are subjected to first heat exchange to obtain ammonia water. The first heat exchange method is not particularly limited, and may be performed by a heat exchange method that is conventional in the art. The number of heat exchanges may be one or more, preferably 2 to 4, more preferably 2 to 3, and particularly preferably 2. Through the heat exchange, the output ammonia water is cooled, and the heat is circulated in the treatment device to the maximum extent, so that the energy is reasonably utilized, and the waste is reduced.
According to a preferred embodiment of the present invention, the first heat exchange is performed by a first heat exchange device 31 and a second heat exchange device 32, specifically, the first ammonia-containing steam obtained by evaporation in the MVR evaporation device 2 passes through the second heat exchange device 32 and the first heat exchange device 31 in sequence, and the wastewater passes through the first heat exchange device 31 and the second heat exchange device 32 in sequence, and the first heat exchange is performed between the first ammonia-containing steam and the wastewater, so as to heat the wastewater for evaporation, and simultaneously cool the first ammonia-containing steam to obtain a first ammonia water, which can be stored in an ammonia water storage tank 51.
According to a preferred embodiment of the present invention, the first evaporation process may be performed in the MVR evaporation apparatus 2, and the first pH adjustment may be performed by introducing and mixing the aqueous solution containing the alkaline substance in the pipe for feeding the wastewater to the first heat exchange apparatus 31 before feeding the wastewater to the first heat exchange apparatus 31 for the first heat exchange; and the second pH adjustment is performed by introducing and mixing the aqueous solution containing the alkaline substance into the pipe for feeding the wastewater into the second heat exchange means 32 before feeding the wastewater into the second heat exchange means 32 for the first heat exchange. The pH of the wastewater is adjusted by two pH adjustments to a value greater than 9, preferably greater than 10.8, before it is passed to the MVR evaporator 2. Further, it is preferable that the first pH adjustment is performed so that the pH of the wastewater after adjustment is more than 7 (preferably 7 to 9), and the second pH adjustment is performed so that the pH is more than 9, preferably more than 10.8.
In order to detect the pH values after the first pH adjustment and the second pH adjustment, it is preferable that a first pH measuring device 61 is provided on a pipe for feeding the wastewater to the first heat exchange 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 the second heat exchange device 32 to measure the pH value after the second pH adjustment.
In the present invention, in order to increase the salt concentration of the liquid in the MVR evaporation device 2 and to reduce the ammonia content of the liquid, it is preferable to return a portion of the wastewater evaporated by the MVR evaporation device 2 to the MVR evaporation device 2. The above process of returning part of the wastewater evaporated by the MVR evaporation device 2 to the MVR evaporation device 2 is preferably that part of the wastewater evaporated by the MVR evaporation device 2 is returned to the MVR evaporation device 2 after being mixed with the wastewater after the first pH adjustment and before the second pH adjustment, for example, part of the wastewater evaporated by the MVR evaporation device 2 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, and then after the second pH adjustment, heat exchange is performed in the second heat exchange device 32, and the wastewater is sent to the MVR evaporation device 2.
In the present invention, the first heat exchange device 31 and the second heat exchange device 32 are not particularly limited, and various heat exchangers conventionally used in the art may be used to perform the first heat exchange between the first ammonia-containing steam and the wastewater. 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 steam condensate, it is preferable that the temperature of the wastewater after the first heat exchange by the first heat exchange means 31 is 30 ℃ or higher, and preferably 49 to 129 ℃.
According to the present invention, in order to fully utilize the heat energy of the first ammonia-containing steam, the temperature of the wastewater after the first heat exchange by the second heat exchange device 32 is preferably 49 to 139 ℃, and preferably 59 to 139 ℃.
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 evaporation plant, guarantee that waste water intensification-evaporation-cooling's process goes on in succession, need input when MVR evaporation process starts and start steam, only through the compressor 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 present invention, the multi-effect evaporation apparatus 1 is not particularly limited, and may be composed of various evaporators conventionally used in the art. For example, it may be selected from one or more of falling film type evaporator, rising film type evaporator, scraped surface evaporator, central circulation tube type multi-effect evaporator, basket type evaporator, external heating type evaporator, forced circulation type evaporator and Leveng type evaporator. Among them, a forced circulation evaporator and an external heating evaporator are preferable. The respective evaporators of the multi-effect evaporation apparatus 1 are composed of a heating chamber and an evaporation chamber, and may further include other evaporation auxiliary components such as a demister for further separating liquid foam, a condenser for condensing all secondary steam, and a vacuum apparatus for pressure reduction operation, if necessary. The number of evaporators included in the multi-effect evaporation apparatus 1 is not particularly limited, and may be 2 or more, preferably 2 to 5, and more preferably 3 to 4.
In the present invention, the evaporation conditions of the multi-effect evaporation apparatus 1 are not particularly limited, and may be appropriately selected as needed. In order to improve the evaporation efficiency, it is preferable that the conditions of the second evaporation include: the temperature is above 40 ℃, and the pressure in gage pressure is above-97 kPa; more preferably, the conditions of the second evaporation include: the temperature is 50 ℃ to 180 ℃, and the pressure measured by gauge pressure is-93 kPa to 750 kPa; further preferably, the evaporation conditions include: the temperature is 60 ℃ to 155 ℃, and the pressure measured by gauge pressure is-87 kPa to 350 kPa.
According to the present invention, when the above-described evaporation conditions are satisfied, it is further preferable that the evaporation conditions of the respective evaporators satisfy: the evaporation temperature of the first-effect evaporator is 100-180 ℃, and the evaporation temperature of the latter-effect evaporator is 10-50 ℃ lower than that of the former-effect evaporator; more preferably, the evaporation temperature of the first effect evaporator is 130 ℃ to 155 ℃, and the evaporation temperature of the latter effect evaporator is 15 ℃ to 46 ℃ lower than that of the former effect evaporator.
In the present invention, the operating pressure of each effect evaporator is the saturated vapor pressure of the evaporated feed liquid.
Further, the evaporation amounts of the respective evaporators may be the same or different, preferably the same, and the total evaporation amount of the second evaporation may be appropriately selected depending on the capacity of the apparatus to treat and the amount of the waste water to be treated, and may be, for example, 0.1m3More than h (e.g. 0.1 m)3/h～500m3/h)。
In the present invention, preferably, in order to sequentially introduce the wastewater into each effect evaporator of the multi-effect evaporation apparatus 1, a circulation pump may be provided between each effect evaporator, and the wastewater evaporated in the previous effect evaporator is introduced into the next effect evaporator through the circulation pump.
In the invention, the circulating pump among the selected evaporators can be various pumps which are conventionally used in the field, in order to uniformly evaporate materials, avoid generating a large number of fine crystal nuclei and prevent crystal grains in the circulating crystal slurry from colliding with an impeller at a high speed to generate a large number of secondary crystal nuclei, the circulating pump is preferably a low-rotating-speed centrifugal pump, and more preferably a high-flow low-rotating-speed guide pump impeller or a high-flow low-lift low-rotating-speed axial pump.
According to the invention, the second ammonia-containing steam obtained by evaporation of the last evaporator of the multi-effect evaporation device 1 is preferably subjected to third heat exchange with cooling water in a third heat exchange device 33 to obtain ammonia water. The third heat exchange device is not particularly limited, and various heat exchangers conventionally used in the art can be used to exchange heat between the second ammonia-containing steam and the wastewater. 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. Preferably, the cooling water is the waste water. When the conventional cooling water is used, the cooling water is recycled, and when the waste water is used as the cooling water, the waste water after heat exchange is preferably directly returned to the treatment process.
According to a preferred embodiment of the present invention, before the wastewater is introduced into the MVR evaporation device, the ammonia-containing vapor obtained by evaporation in the last one-effect evaporator of the multi-effect evaporation device 1 is subjected to a third heat exchange with the wastewater to obtain ammonia water.
According to the invention, the method further comprises crystallizing the second concentrated solution in a crystallizing device to obtain crystal slurry. The crystallization apparatus is not particularly limited, and may be, for example, a crystal liquid collection tank, a thickener with stirring or a thickener without stirring, or the like. The crystallization conditions are not particularly limited, and may include, for example: the crystallization temperature is 20-107 ℃, and the crystallization time is 5 min-24 h; preferably comprising: the crystallization temperature is 65-85 ℃, and the crystallization time is 10-30 min.
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 sequentially introducing the first concentrated solution 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 to evaporate to obtain a second concentrated solution. Will the second that obtains in the first effect evaporimeter 1a of multiple-effect evaporation device 1 evaporates contains ammonia steam and lets in second effect evaporimeter 1b with first concentrate carries out the second heat exchange and obtains the aqueous ammonia, with the second that obtains in the second effect evaporimeter 1b evaporates contains ammonia steam and lets in third effect evaporimeter 1c with first concentrate carries out the second heat exchange and obtains the second aqueous ammonia, first concentrate with the second contains ammonia steam cocurrent flow heat exchange. Heating steam (namely raw steam conventionally used in the field) is introduced into the first-effect evaporator 1a, and condensate obtained after the heating steam is condensed in the first-effect evaporator 1a can be used for preparing washing brine. The second ammonia-containing vapor evaporated in the third effect evaporator 1c is subjected to third heat exchange with cooling water (preferably, the 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 an ammonia water collection tank 52. And (3) after the first concentrated solution is evaporated in the first effect evaporator 1a, introducing the first concentrated solution into the second effect evaporator 1b for evaporation, then introducing the first concentrated solution into the third effect evaporator 1c for evaporation, and finally crystallizing the obtained second concentrated solution in a crystal liquid collecting tank 53 to obtain crystal slurry.
In the invention, the crystal slurry is subjected to solid-liquid separation to obtain crystals and liquid obtained by the solid-liquid separation. The method of the solid-liquid separation is not particularly limited, and may be selected from one or more of centrifugation, filtration, and sedimentation.
In the present invention, preferably, at least a part or all of the liquid obtained by subjecting the crystal slurry to solid-liquid separation is returned to the MVR evaporation apparatus 2 to perform the first evaporation again.
According to a preferred embodiment of the present invention, as shown in fig. 1, the solid-liquid separation may be performed by using a solid-liquid separation device 9 (preferably, a centrifuge), and after the solid-liquid separation, all the liquid obtained by the solid-liquid separation is returned to the MVR evaporation device to perform the first evaporation again.
According to the present invention, it is difficult to avoid adsorption of impurities such as free ammonia, hydroxyl ions, etc. on the crystals, and in order to remove the adsorbed impurities, reduce the odor of solid salts, reduce corrosiveness, and increase the purity of the crystals, the crystals are preferably washed with water or brine and dried. The saline water is not particularly limited and may be appropriately selected as needed. In order to avoid dissolution of crystals during washing, it is preferred that the type of salt in the brine is selected according to the salt contained in the wastewater, preferably the same salt as the wastewater. More preferably, the brine is preferably saturated brine. To further reduce the cost of the process, the use of salt is reduced, the brine preferably being an aqueous solution of the wastewater or the crystals, more preferably a saturated aqueous solution of the crystals. In addition, the washed liquid may be returned to the multi-effect evaporation device 1 or the MVR evaporation device 2, preferably, all of it is returned to the multi-effect evaporation device 1.
In the present invention, it is preferable to perform vacuum degassing before the wastewater is treated. The vacuum degassing may be performed using a vacuum degassing tank 4. Through the vacuum degassing, gases dissolved in the wastewater, such as air, ammonia gas and the like, can be removed, so that air resistance can be prevented, stability and reliability of the system during normal operation can be ensured, aerobic corrosion of the system is reduced, and the service life of the equipment is prolonged. The vacuum degassing conditions include: the vacuum degree can reach-90 kPa to-70 kPa by gauge pressure, the processing speed of vacuum degassing is consistent with the feeding quantity of fresh raw materials of the system, and the processing speed can be 0.1m3More than h (e.g. 0.1 m)3/h～500m3/h)。
In the present invention, preferably, the tail gas obtained by vacuum degassing, the tail gas remaining after the first ammonia-containing steam is condensed by the first heat exchange, and the tail gas remaining after the second ammonia-containing steam is condensed by the third heat exchange are discharged after ammonia removal. The tail gas obtained by vacuum degassing is the tail gas discharged from the vacuum degassing tank 4, the first ammonia-containing steam is the tail gas discharged from the second heat exchange device 32 after passing through the first heat exchange condensation, and the second steam is the tail gas discharged from the third heat exchange device 33 after passing through the second heat exchange condensation.
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 wastewater is not particularly limited as long as it is an ammonium salt-containing wastewater. In addition, the wastewater of the invention is particularly suitable for treating the wastewater containing ammonium and high salt. The wastewater of the present invention may be specifically wastewater from a process for producing a molecular sieve, alumina or a refinery catalyst, or wastewater from a process for producing a molecular sieve, alumina or a refinery catalyst, which is subjected to the following impurity removal and concentration. It is preferable that the wastewater from the production of molecular sieves, alumina or refinery catalysts is subjected to the following impurity removal and concentration.
In the present invention, the inorganic salt ions contained in the wastewater are other than NH4 +In addition, Na may be contained+、SO4 2-、Cl-、NO3 -、NO2 -And (3) plasma.
As NH in said wastewater4 +May be 8mg/L or more, preferably 300mg/L or more.
As Na in the wastewater+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 said wastewater4 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 said wastewater-May be 970mg/L or more, more preferably 2000mg/L or more, further preferably 4000mg/L or more, further preferably 8000mg/L or more, further preferably 16000mg/L or more, further preferably 32000mg/L or more, further preferably 40000mg/L or more, further preferably 50000mg/L or more, further preferably 60000mg/L or more.
The TDS of the 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.
The upper limit of the inorganic salt ions contained in the wastewater is not particularly limited, and the treatment by the method of the present invention can be performed even when the inorganic salt ions contained in the wastewater are in a supersaturated state.
In the invention, the pH value of the wastewater is preferably 4-7.
In addition, since the COD of the wastewater may block a membrane at the time of concentration, affect the purity and color of salt at the time of evaporative crystallization, etc., the COD of the wastewater is preferably as small as possible, and is preferably removed by oxidation at the time of pretreatment, and specifically, it may be performed by, for example, a biological method, an advanced oxidation method, etc., and it is preferably oxidized by an oxidizing agent, which may be, for example, fenton's reagent, at the time of very high COD content. Preferably, the COD content is 20mg/L or less, more preferably 10mg/L or less.
In addition, the wastewater of the invention can also contain Mg2+、Ca2+、K+、Fe3+Rare earth element ions and COD, and the content of the impurities is usually 3mg/L to 50mg/L (preferably 10mg/L or less, more preferably 5mg/L or less), and the impurities can be removed by subsequent impurity removal.
In the invention, in order to ensure the continuous and stable operation of the treatment process and reduce the equipment operation and maintenance cost, the wastewater is preferably subjected to impurity removal before being treated by the treatment method. Preferably, the impurity removal is selected from one or more of solid-liquid separation, chemical precipitation, adsorption, ion exchange and oxidation.
As the solid-liquid separation, filtration, centrifugation, sedimentation, or the like may be mentioned; as the chemical precipitation, pH adjustment, carbonate precipitation, magnesium salt precipitation, and the like may be mentioned; the adsorption can be physical adsorption and/or chemical adsorption, and the specific adsorbent can be selected from activated carbon, silica gel, alumina, molecular sieve, natural clay and the like; as the ion exchange, any one of a strongly acidic cation resin and a weakly acidic cation resin can be used; as the oxidation, various oxidizing agents conventionally used in the art, for example, ozone, hydrogen peroxide, ammonium persulfate, fenton's reagent, potassium permanganate, and the like 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 wastewater. For suspended matters, a solid-liquid separation method can be selected for removing impurities; for inorganic matters and organic matters, chemical precipitation, ion exchange and adsorption methods can be selected for removing impurities, such as weak acid cation exchange, activated carbon adsorption and the like; for organic matters, impurities can be removed by adopting an adsorption and/or oxidation mode, wherein an ozone biological activated carbon adsorption oxidation method is preferred. According to a preferred embodiment of the invention, the wastewater is subjected to filtration, weak acid cation exchange method and ozone biological activated carbon adsorption oxidation method for removing impurities in sequence. Through the impurity removal process, most suspended matters, hardness, silicon and organic matters can be removed, the scaling risk of the device is reduced, and the continuous and stable operation of the wastewater treatment process is ensured.
In the present invention, the wastewater having a low salt content may be concentrated to have a salt content within a range required for the wastewater of the present invention before the wastewater is treated by the treatment method of the present invention (preferably, after the above-mentioned impurity removal). Preferably, the concentration is selected from ED membrane concentration and/or reverse osmosis; more preferably, the concentration is performed by ED membrane concentration and reverse osmosis, and the order of performing the ED membrane concentration and the reverse osmosis is not particularly limited. The ED membrane concentration and reverse osmosis treatment apparatus and conditions may be performed in a manner conventional in the art, and may be specifically selected according to the condition of wastewater to be treated. Specifically, as the concentration of the ED membrane, a one-way electrodialysis system or a reversed electrodialysis system can be selected for carrying out; as the reverse osmosis, a roll membrane, a plate membrane, a disc-tube membrane, a vibrating membrane or a combination thereof can be selected for use. Through the concentration can improve the efficiency of waste water treatment, avoid the energy waste that a large amount of evaporations caused.
In a preferred embodiment of the invention, the wastewater is wastewater obtained by performing chemical precipitation, filtration, weak acid cation exchange and ozone biological activated carbon adsorption oxidation on wastewater generated in the molecular sieve production process to remove impurities, and performing ED membrane concentration and reverse osmosis concentration on the wastewater.
The conditions for the above chemical precipitation are preferably: sodium carbonate is used as a treating agent, 1.2-1.4 mol of sodium carbonate is added relative to 1 mol of calcium ions in the wastewater, the pH value of the wastewater is adjusted to be more than 7, the reaction temperature is 20-35 ℃, and the reaction time is 0.5-4 h.
The conditions for the filtration are preferably: the filtering unit adopts a double-layer filtering material multi-medium filter consisting of anthracite and quartz sand, the grain diameter of the anthracite is 0.7 mm-1.7 mm, the grain diameter of the quartz sand is 0.5 mm-1.3 mm, and the filtering speed is 10 m/h-30 m/h. After the filter material is used, the regeneration method of 'gas back flushing-gas and water back flushing-water back flushing' is adopted to regenerate the filter material, and the regeneration period is 10-15 h.
The conditions for the weak acid cation exchange method are preferably: the pH value range is 6.5-7.5; the temperature is less than or equal to 40 ℃, the height of the resin layer is 1.5-3.0 m, the HCl concentration of the regeneration liquid is as follows: 4.5-5 mass%; the amount of the regenerant (calculated by 100%) was 50kg/m3～60kg/m3Wet resin; the flow rate of the regeneration liquid HCl is 4.5 m/h-5.5 m/h, and the regeneration contact time is 35 min-45 min; the forward washing flow rate is 18 m/h-22 m/h, and the forward washing time is 20 min-30 min; the running flow rate is 15 m/h-30 m/h; as the acidic cation exchange resin, for example, there can be used a Gallery Senno chemical Co., Ltd, SNT brand D113 acidic cation exchange resin.
The conditions of the above-mentioned ozone biological activated carbon adsorption oxidation method are preferably: the retention time of the ozone is 50min to 70min, and the empty bed filtration rate is 0.5m/h to 0.7 m/h.
The conditions for the concentration of the ED membrane are preferably: the current 145A to 155A and the voltage 45V to 65V. The ED membrane may be, for example, an ED membrane manufactured by astone corporation of japan.
The conditions for the reverse osmosis are preferably: the operation pressure is 5.4MPa to 5.6MPa, the water inlet temperature is 25 ℃ to 35 ℃, and the pH value is 6.5 to 7.5. The reverse osmosis membrane is, for example, a seawater desalination membrane TM810C manufactured by Dongli corporation of Lanxingdong.
The present invention will be described in detail below by way of examples.
In the following examples, the wastewater is obtained by sequentially removing impurities from wastewater generated in the production process of the molecular sieve by chemical precipitation, filtration, weak acid cation exchange method and ozone biological activated carbon adsorption oxidation method, and sequentially concentrating the wastewater by ED membrane concentration and reverse osmosis method.
Example 1
As shown in FIG. 1, wastewater (containing NaCl 150g/L, Na)2SO456g/L、NH4Cl 27g/L、(NH4)2SO410.24g/L) in terms of feed amountIs 120m3Introducing the wastewater into a vacuum degassing tank 4 at a speed of/h for degassing (vacuum degree is-70 kPa in gauge pressure), introducing a sodium hydroxide aqueous solution with the concentration of 45.16 mass% into a pipeline for feeding the degassed wastewater into a first heat exchange device 3 (titanium alloy plate heat exchanger) for carrying out first pH value adjustment, monitoring the adjusted pH value (the measured value is 8.0) by a first pH value measuring device 61 (a pH meter), feeding the wastewater subjected to the first pH value adjustment into a first heat exchange device 31 by a first circulating pump 71, and carrying out first heat exchange with the recovered first ammonia-containing steam condensate to heat the wastewater to 63 ℃; then, before the wastewater after the first heat exchange is sent to the second heat exchange device 32 (titanium alloy plate heat exchanger), the wastewater is separated from the liquid (containing NaCl288.3g/L, Na)2SO465.2g/L, NaOH 10.06.06 g/L, flow rate 28m3H), introducing a sodium hydroxide aqueous solution with the concentration of 45.16 mass percent into a pipeline for secondary pH value adjustment, monitoring the adjusted pH value through a second pH value measuring device 62 (a pH meter) (the measured value is 11), sending the wastewater with the second pH value adjustment into a second heat exchange device 32, carrying out first heat exchange with the recovered first ammonia-containing steam to heat the wastewater to 76 ℃, and then sending the wastewater into an MVR evaporation device 2 (a falling film and forced circulation two-stage MVR evaporation crystallizer) for first evaporation. Wherein the conditions of the first evaporation include: the temperature was 71 ℃, the pressure in gauge was-77.4 kPa, and the evaporation capacity was 25.2m3H is used as the reference value. The first ammonia-containing steam obtained by the first evaporation is compressed by the compressor 10 (the temperature is raised by 12 ℃) and then sequentially passes through the second heat exchange device 32 and the first heat exchange device 31 to exchange heat with the wastewater, and the ammonia water is obtained by cooling and stored in the ammonia water storage tank 5. In order to increase the salt concentration of the liquid in the MVR evaporation plant 2, part of the wastewater from the MVR evaporation plant 2 after the first evaporation is returned to the second pH adjustment process by the second circulation pump 72. MVR evaporator 2 gives 128m per hour3Containing NaCl 231.3g/L, Na2SO477.1g/L, NaOH 2.2.2 g/L NH30.841g/L (solid content: 0).
The second evaporation process is carried out in a multi-effect evaporation apparatus 1 (triple-effect evaporation apparatus), the multi-effect evaporation apparatus 1 being composed ofThe evaporator comprises a first effect evaporator 1a, a second effect evaporator 1b and a third effect evaporator 1c (all forced circulation evaporators). And (3) feeding the first concentrated solution into a first effect evaporator 1a, a second effect evaporator 1b and a third effect evaporator 1c of the multi-effect heat exchange device in sequence through a fifth circulating pump 75 for second evaporation to obtain a second concentrated solution. Wherein, the evaporation conditions of the first effect evaporator 1a include: the temperature was 130 ℃, the pressure in gauge was 116.8kPa, and the evaporation rate was 33.9m3H; the evaporation conditions of the second effect evaporators 1b include: the temperature was 106 ℃ and the pressure in gauge was 0kPa, the evaporation rate was 33.8m3H; the evaporation conditions of the third effect evaporator 1c include: the temperature was 60 ℃, the pressure in gauge was-87 kPa, and the evaporation rate was 33.8m3H is used as the reference value. Heating steam (raw steam) is introduced into a first effect evaporator 1a of the multi-effect evaporation device 1, second ammonia-containing steam obtained by evaporation in the first effect evaporator 1a is introduced into a second effect evaporator 1b to carry out second heat exchange to obtain ammonia water, and second ammonia-containing steam obtained by evaporation in the second effect evaporator 1b is introduced into a third effect evaporator 1c to carry out second heat exchange to obtain ammonia water. The second ammonia-containing steam evaporated in the third effect evaporator 1c is subjected to third heat exchange with the wastewater in a third heat exchange device 33 (titanium alloy plate heat exchanger) to obtain ammonia water, and the ammonia water is stored in an ammonia water collecting tank 52. And collecting the ammonia water obtained in each step. And (3) after the first concentrated solution is evaporated in the first effect evaporator 1a, introducing the first concentrated solution into the second effect evaporator 1b for evaporation, introducing the first concentrated solution into the third effect evaporator 1c for evaporation, and crystallizing the finally obtained second concentrated solution in a crystal liquid collecting tank 53 to obtain crystal slurry.
After the magma is subjected to solid-liquid separation by a solid-liquid separation device 9 (a centrifugal machine), crystals (namely mixed salt crystallization filter cakes) and liquid obtained by the solid-liquid separation are respectively obtained, the mixed salt crystallization filter cakes are washed by the saturated mixed brine, part of the mixed salt crystallization filter cakes are used for preparing the saturated mixed brine, 41.66 tons of the mixed salt crystallization filter cakes with the water content of 30 mass percent are obtained every hour, and the mixed salt crystallization filter cakes are dried in a drier, and 29.58 tons of mixed salt containing sodium chloride and sodium sulfate are obtained every hour; solid-liquid separation to obtain 28m per hour3Containing NaCl288.3g/L, Na2SO465.2g/L, NaOH 10.06.06 g/L of crystallization mother liquor, and separating the solid from the liquidCirculating the obtained crystallization mother liquor to the stage before the second pH value adjustment; washing water obtained by washing the filter cake is mixed with the waste water evaporated by the MVR evaporation device 2 and then enters the multi-effect evaporation device 1.
In addition, the tail gas discharged by the vacuum degassing tank 4 and the second heat exchange device 32 is introduced into a tail gas absorption tower 83 through a vacuum pump 81 for absorption, circulating water is introduced into the tail gas absorption tower 83, the circulating water circulates in the tail gas absorption tower 83 under the action of a fourth circulating pump 74, water is supplemented into the tail gas absorption tower 83 from a circulating water tank 82 through a third circulating pump 73, and fresh water is supplemented into the circulating water tank 82, so that the temperature and the ammonia content of the water for operating the vacuum pump 81 are reduced. Dilute sulfuric acid is further introduced into the tail gas absorption tower 83 to absorb ammonia and the like in the tail gas.
In this example, 25.2m of ammonia water having a concentration of 4.9 mass% was obtained per hour in the ammonia water tank 513The ammonia water with the concentration of 0.106 mass percent and the concentration of 101.5m is obtained every hour after the multiple-effect evaporation device 1 is merged with the dilute ammonia water in the ammonia water collecting tank 523The ammonia water can be reused in the production process of the molecular sieve.
In addition, the starting phase of the MVR evaporation was started by steam at a temperature of 143.3 ℃.
Example 2
The wastewater was treated in the same manner as in example 1 except that the wastewater contained NaCl 221g/L, NH4And treating the Cl 40g/L wastewater. The first evaporation conditions of the MVR evaporation device 2 include: the temperature was 90 ℃ and the pressure as a gauge pressure was-47.89 kPa and the evaporation rate was 26m3H is used as the reference value. The second evaporation conditions of the multi-effect evaporation device 1 include: the evaporation conditions of the first effect evaporator 1a include: the temperature was 140 ℃, the pressure in gauge was 193.83kPa, and the evaporation rate was 33.6m3H; the evaporation conditions of the second effect evaporators 1b include: the temperature was 125 ℃, the pressure in gauge was 130.69kPa, and the evaporation rate was 33.6m3H; the evaporation conditions of the third effect evaporator 1c include: the temperature was 85 ℃, the pressure as a gauge pressure was-57.65 kPa, and the evaporation rate was 33.8m3/h。
The solid-liquid separation was carried out per hour to obtain 44.12 tons of a sodium chloride crystal cake having a water content of 29 mass%, 30m per hour3The crystallization mother liquor containing NaCl312.4g/L, NaOH9.533g/L finally obtains 31.76 tons of sodium chloride per hour, and the ammonia water with the concentration of 0.121 mass percent is obtained per hour after the multi-effect evaporation device 1 is merged with the ammonia water in the ammonia water collecting tank 523。
Example 3
The wastewater was treated in the same manner as in example 1 except that Na-containing wastewater was treated2SO4130g/L、(NH4)2SO420g/L of wastewater is treated. The first evaporation conditions of the MVR evaporation device 2 include: the temperature was 120 ℃ and the pressure in gauge was 56.97kPa, the evaporation rate was 22.43m3H is used as the reference value. The second evaporation conditions of the multi-effect evaporation device 1 include: the evaporation conditions of the first effect evaporator 1a include: the temperature was 155 ℃, the pressure in gauge was 349.43kPa, and the evaporation rate was 33.1m3H; the evaporation conditions of the second effect evaporators 1b include: the temperature was 135 ℃, the pressure in gauge was 211.6kPa, and the evaporation rate was 33.1m3H; the evaporation conditions of the third effect evaporator 1c include: the temperature was 100 ℃ and the pressure, as a gauge pressure, was-22.82 kPa and the evaporation rate was 33.1m3/h。
The solid-liquid separation yielded 25.25 tons per hour of a sodium sulfate crystal cake having a water content of 28 mass%, yielding 18m per hour3Containing Na2SO4166.3g/L, NaOH 14.42.42 g/L of crystallization mother liquor, finally obtaining 18.18 tons of sodium sulfate per hour, and obtaining 99.3m of second ammonia water with the concentration of 0.049 mass percent per hour in the multi-effect evaporation device 1 and the ammonia water collecting tank 523。
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (30)
1. A method for treating wastewater containing ammonium salt is characterized in that the method comprises the steps of introducing the wastewater into an MVR evaporation device to carry out first evaporation to obtain first ammonia-containing steam and first concentrated solution, sequentially introducing the first concentrated solution into each effect evaporator of a multi-effect evaporation device to carry out second evaporation, respectively obtaining second ammonia-containing steam in each effect evaporator, and obtaining second concentrated solution in the last effect evaporator, wherein,
adjusting the pH value of the wastewater to be more than 9 before introducing the wastewater into an MVR evaporation device; before the wastewater is introduced into an MVR evaporation device, carrying out first heat exchange on the first ammonia-containing steam and the wastewater to obtain first ammonia water;
sending second ammonia-containing steam obtained by evaporation of the previous evaporator into the subsequent evaporator to perform second heat exchange with the concentrated solution sent into the subsequent evaporator to obtain second ammonia water, wherein the first concentrated solution and the second ammonia-containing steam perform cocurrent heat exchange;
and the first evaporation is performed so that the solid content in the first concentrated solution is 50 mass% or less;
the conditions of the first evaporation include: the temperature is above 30 ℃, and the pressure in gage pressure is above-98 kPa; the conditions of the second evaporation include: the temperature is above 40 ℃, and the pressure in gage pressure is above-97 kPa;
crystallizing the second concentrated solution in a crystallizing device to obtain crystal slurry, performing solid-liquid separation on the crystal slurry to obtain crystals and liquid obtained by the solid-liquid separation, and returning all the liquid obtained by the solid-liquid separation to the MVR evaporating device;
NH in the wastewater4 +Is more than 8mg/L, and TDS is more than 1600 mg/L;
the wastewater also contains Na+、SO4 2-And Cl-，Na+The content of (B) is more than 510mg/L, SO4 2-Has a content of over 1000mg/L and Cl-The content of (b) is more than 970 mg/L.
2. The method of claim 1, wherein the pH of the wastewater is adjusted to greater than 10.8 prior to passing the wastewater to the MVR evaporation plant.
3. The method according to claim 1, wherein the first evaporation is performed so that a solid content in the first concentrated solution is 20% by mass or less.
4. The method of claim 1, wherein the first evaporation does not supersaturate the first concentrate.
5. The method of claim 1, wherein the conditions of the first evaporation comprise: the temperature is 50 ℃ to 130 ℃, and the pressure in gauge pressure is-93 kPa to 117 kPa.
6. The method of claim 5, wherein the conditions of the first evaporation comprise: the temperature is 60 ℃ to 130 ℃, and the pressure in gage pressure is-87 kPa to 117 kPa.
7. The method of claim 1, wherein the conditions of the second evaporation comprise: the temperature is 50 ℃ to 180 ℃, and the pressure measured by gauge pressure is-93 kPa to 750 kPa.
8. The method of claim 7, wherein the conditions of the second evaporation comprise: the temperature is 60 ℃ to 155 ℃, and the pressure measured by gauge pressure is-87 kPa to 350 kPa.
9. The method of claim 1, wherein the conditions of the second evaporation comprise: the evaporation temperature of the first-effect evaporator is 100-180 ℃; the evaporation temperature of the latter evaporator is 10-50 ℃ lower than that of the former evaporator.
10. The method of claim 9, wherein the conditions of the second evaporation comprise: the evaporation temperature of the first-effect evaporator is 130-155 ℃, and the evaporation temperature of the latter-effect evaporator is 15-46 ℃ lower than that of the former-effect evaporator.
11. The method of claim 1, wherein the first heat exchange is performed by a first heat exchange device and a second heat exchange device.
12. The method according to claim 11, wherein the temperature of the wastewater after the first heat exchange by the first heat exchange means is 30 ℃ or higher.
13. The method of claim 12, wherein the temperature of the wastewater after the first heat exchange by the first heat exchange device is between 49 ℃ and 129 ℃.
14. The method of claim 11, wherein the temperature of the wastewater after the first heat exchange by the second heat exchange device is 49 ℃ to 139 ℃.
15. The method of claim 14, wherein the temperature of the wastewater after the first heat exchange by the second heat exchange device is 59 ℃ to 139 ℃.
16. The process of claim 11 wherein the pH of the wastewater is adjusted to greater than 7 prior to entering the first heat exchange means.
17. The method of claim 1, wherein the multi-effect evaporation device is more than 2 effects.
18. The method of claim 17, wherein the multi-effect evaporation device is 2-5 effects.
19. The method of claim 18, wherein the multi-effect evaporation device is 3-4 effects.
20. The method of claim 1, wherein the second ammonia-containing vapor evaporated by the last evaporator of the multi-effect evaporation device is subjected to a third heat exchange with cooling water in a heat exchange device to obtain ammonia water.
21. The method of claim 20, wherein the cooling water is the wastewater.
22. The method of claim 20, wherein the second ammonia-containing vapor evaporated from the last one of the multiple effect evaporation apparatuses is subjected to a third heat exchange with the wastewater and produces ammonia water before passing the wastewater to the MVR evaporation apparatus.
23. The method according to claim 20, wherein the first ammonia-containing vapor is discharged after the tail gas remaining after the condensation by the first heat exchange and the second ammonia-containing vapor is discharged after the ammonia removal after the condensation by the third heat exchange.
24. The process according to claim 1, wherein the process further comprises compressing the first ammonia-containing vapor prior to the first heat exchange.
25. The method of claim 1, wherein the wastewater is vacuum degassed prior to being passed to the MVR evaporation unit for treatment.
26. The process of claim 11, wherein the crystals are washed with water or brine and dried.
27. The method of claim 26, wherein the washed liquid is returned to the multi-effect evaporation device.
28. The method of claim 26, wherein the brine is an aqueous solution of the wastewater or the crystals.
29. The method of claim 26, wherein the water in the water or brine is a condensate resulting from condensation of heated steam by a first effect evaporator of the multi-effect evaporation device.
30. The method of any one of claims 1-29, further comprising removing impurities from the wastewater and concentrating the wastewater prior to passing the wastewater to an MVR evaporator.
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| JPS61234982A (en) * | 1985-04-09 | 1986-10-20 | Kawasaki Heavy Ind Ltd | Treatment of waste water containing ammonia, hydrogen sulfide, and so forth |
| CN101391799A (en) * | 2007-09-20 | 2009-03-25 | 深圳市东江环保股份有限公司 | Method for recovery processing of ammonia nitrogen from printed circuit board waste liquid |
| CN103241887A (en) * | 2013-05-27 | 2013-08-14 | 兰州节能环保工程有限责任公司 | Method and device for treating and recycling high salinity wastewater |
| CN106186501A (en) * | 2016-09-19 | 2016-12-07 | 江苏泫槿环境科技有限公司 | A kind of high concentration ammonia nitrogen wastewater treatment system and processing method |
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| JPS61234982A (en) * | 1985-04-09 | 1986-10-20 | Kawasaki Heavy Ind Ltd | Treatment of waste water containing ammonia, hydrogen sulfide, and so forth |
| CN101391799A (en) * | 2007-09-20 | 2009-03-25 | 深圳市东江环保股份有限公司 | Method for recovery processing of ammonia nitrogen from printed circuit board waste liquid |
| CN103241887A (en) * | 2013-05-27 | 2013-08-14 | 兰州节能环保工程有限责任公司 | Method and device for treating and recycling high salinity wastewater |
| CN106186501A (en) * | 2016-09-19 | 2016-12-07 | 江苏泫槿环境科技有限公司 | A kind of high concentration ammonia nitrogen wastewater treatment system and processing method |
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