A method and system for recovering and treating acidic ammonium sulfate waste liquid

Abstract

The present application provides a method for recycling and treating acidic ammonium sulfate waste liquid. To this end, the present application also provides a recycling and treating system for acidic ammonium sulfate waste liquid, which can reduce equipment corrosion, avoid the introduction of metal impurities during waste liquid treatment, and prevent pipelines and equipment from being blocked, thereby improving the quality and production efficiency of the recovered product, ensuring production safety, and reducing the difficulty and frequency of manual dredging. It includes the following steps: in a pretreatment kettle, adding alkali solution to the acidic ammonium sulfate waste liquid for neutralization pretreatment, adding a remover for oxidative decomposition of hydrogen peroxide; the pretreated material enters a three-effect evaporator for evaporation and concentration, and the pretreated material is also used as a flushing liquid to flush the three-effect evaporator; the concentrated material is initially separated by a cyclone separator and enters a crystallizer, and then the ammonium sulfate product is obtained by crystallization, centrifugal separation, and drying, and the separated mother liquor and the centrifuged mother liquor are respectively reused in the three-effect evaporator.

Description

Technical Field

[0001] The present application relates to the technical field of industrial wastewater treatment, and specifically to a method and system for recovering and treating acidic ammonium sulfate waste liquid. Background Art

[0002] The semiconductor and electronics industries generate a large amount of wastewater containing high ammonia nitrogen and sulfuric acid waste liquid containing hydrogen peroxide during their production process. In order to better store or recycle the wastewater, manufacturers will conduct preliminary treatment of the waste liquid. For example, the high ammonia nitrogen wastewater is separated by a stripping process, and the ammonia-containing waste gas generated enters the absorption tower and is absorbed by the sulfuric acid waste liquid containing hydrogen peroxide, thereby generating acidic ammonium sulfate waste liquid with a concentration of 20-40% and containing a small amount of hydrogen peroxide and free acid.

[0003] The traditional treatment method of ammonium sulfate waste liquid is to neutralize the acid and alkali, and then evaporate, crystallize, and centrifuge to obtain a solid ammonium sulfate product. However, the acidic ammonium sulfate waste liquid obtained by preliminary treatment of waste liquid in the semiconductor and electronics industries contains hydrogen peroxide. During evaporation, the equipment is easily corroded by hydrogen peroxide, thereby introducing metal ion impurities, which not only affects the quality of the ammonium sulfate product, but also reduces the service life of the equipment. In addition, for acidic ammonium sulfate waste liquid with an ammonium sulfate content of 20 wt% to 40 wt%, the concentrated ammonium sulfate solution is easily affected by the solubility saturation of ammonium sulfate during the evaporation process, and is easy to produce crystals and aggregate, thereby causing blockage of the evaporation equipment and pipelines, affecting production efficiency and production safety, and manual dredging is also troublesome. Summary of the invention

[0004] In view of the problems that the existing ammonium sulfate waste liquid treatment method is prone to equipment corrosion, affecting the quality of the finished product and the service life of the equipment when treating the acidic ammonium sulfate waste liquid, and the evaporation pipeline and equipment are prone to blockage, affecting the production efficiency and production safety, and artificial dredging is difficult, the present application provides a recovery and treatment method for the acidic ammonium sulfate waste liquid. To this end, the present application also provides a recovery and treatment system for the acidic ammonium sulfate waste liquid, which can reduce equipment corrosion, avoid the introduction of metal impurities during the waste liquid treatment, and prevent the blockage of pipelines and equipment, thereby improving the quality and production efficiency of the recovered product, ensuring production safety, and reducing the difficulty and frequency of artificial dredging.

[0005] The present application adopts the following technical scheme: a method for recovering and treating acidic ammonium sulfate waste liquid, which comprises the following steps:

[0006] S1: In the pretreatment kettle, alkali solution is added to the acidic ammonium sulfate waste liquid for neutralization pretreatment;

[0007] S2: The pretreated material enters the triple-effect evaporator for evaporation and concentration;

[0008] S3: The concentrated material enters the crystallizer for crystallization;

[0009] S4: The crystallized material enters the centrifuge for centrifugal separation;

[0010] S5: the crystals obtained by centrifugal separation are put into a dryer for drying to obtain the finished ammonium sulfate product, and the mother liquor is recycled to the three-effect evaporator;

[0011] The invention is characterized in that: in S1, after neutralization pretreatment to a pH of 5 to 7, a remover for oxidatively decomposing hydrogen peroxide is added, and the molar ratio of the hydrogen peroxide to the remover is 1:1 to 1.5; in S2, the pretreated material is also used as a flushing liquid to flush the triple-effect evaporator; in S3, the concentrated material is preliminarily separated by a cyclone separator before entering the crystallizer.

[0012] It is further characterized by:

[0013] In S1, 20 wt % to 40 wt % of ammonium sulfate, 0.1 wt % to 4 wt % of free acid and 0.1 wt % to 8 wt % of hydrogen peroxide are pre-treated by neutralization at normal pressure and 50 to 70° C.; the alkali solution is 10 wt % to 30 wt % of ammonia water;

[0014] The remover is an ammonium salt remover;

[0015] In S2, evaporation concentration is carried out at -0.06Mpa to -0.08Mpa and 80 to 100°C; the liquid phase solid content of the material after evaporation concentration is 10 to 25% (V / V); in S2, after the concentrated material is discharged, it is flushed for 20 seconds after running for 4 to 8 minutes and after discharging for 60 seconds.

[0016] A recycling and treatment system for acidic ammonium sulfate waste liquid comprises a pretreatment kettle, a three-effect evaporator, a crystallizer, a centrifuge and a dryer which are connected in sequence, characterized in that: the pretreatment kettle is respectively connected with an acidic ammonium sulfate waste liquid pipeline, an alkali liquid pipeline and a removal agent pipeline, the pretreatment kettle is also connected with the three-effect evaporator through a material flushing branch pipeline, and a cyclone separator is arranged between the three-effect evaporator and the crystallizer.

[0017] It is further characterized by:

[0018] The triple-effect evaporator is connected with a water flushing pipeline;

[0019] The crystallizer is provided with a stirrer, the stirrer is provided with a guide tube, and the crystallizer is provided with a baffle plate on both sides of the stirrer; there is a gap between the baffle plate and the inner wall of the crystallizer;

[0020] The water flushing pipeline is connected to the first effect separator in the triple effect evaporator through the first flushing pipeline, connected to the second effect separator in the triple effect evaporator through the second flushing pipeline, and connected to the third effect separator in the triple effect evaporator through the third flushing pipeline; the material flushing branch pipeline is connected to the first flushing pipeline;

[0021] The second-effect separator and the third-effect separator are respectively connected to the crystallizer through the cyclone separator; the second-effect separator and the third-effect separator also form a loop with the cyclone separator respectively;

[0022] The centrifuge is communicated with the triple-effect evaporator through a temporary storage tank.

[0023] The beneficial effects of this application are:

[0024] (1) By adding excess remover to oxidize and decompose hydrogen peroxide, hydrogen peroxide can be removed in the pretreatment stage, which can prevent the metal equipment in the subsequent treatment process from being corroded, avoid the introduction of metal ion impurities, improve product quality, and extend the service life of equipment;

[0025] (2) After a period of discharge, the three-effect evaporator can be flushed by flushing the material branch pipe and using the pretreated raw material as a flushing liquid, or by diluting the pretreated raw material through the water flushing pipe and the material flushing branch pipe and using it as a flushing liquid to flush the three-effect evaporator, so as to prevent the crystals generated during the evaporation and concentration of the ammonium sulfate solution from clogging the pipe by aggregation; at the same time, the three-effect evaporator and the process pipe can be flushed regularly with the condensed water of the material or pressurized water through the water flushing pipe alone, so as to further prevent the ammonium sulfate crystals from clogging the pipe by aggregation, improve the quality and production efficiency of the recovered product, ensure production safety, reduce the difficulty and frequency of manual dredging, and improve the utilization effect of the material;

[0026] (3) By connecting the triple-effect evaporator and the cyclone separator of the crystallizer, not only can the solid and liquid materials be initially separated, the moisture content of the crystals can be reduced, the crystallization effect of the crystallizer and the purity of the ammonium sulfate product can be improved, but the separated mother liquor can also be reused to improve the recovery rate of ammonium sulfate.

[0027] In addition, through the agitator, guide tube and baffle in the crystallizer, under the impetus of the agitator, the suspension can circulate and crystallize in the guide tube and the channel between the guide tube and the baffle, thereby accelerating the formation of large-diameter granular ammonium sulfate, improving the crystallization efficiency, and preventing dust and agglomeration during subsequent drying, which may affect the quality of the recovered ammonium sulfate product. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a process flow chart of this application.

[0029] Figure 2 This is a schematic diagram of the structure of the process system of this application;

[0030] Figure 3 for Figure 2 A schematic diagram of the enlarged structure at A in the middle;

[0031] Figure 4 for Figure 2 Schematic diagram of the enlarged structure at point B in the middle. DETAILED DESCRIPTION

[0032] The present application is further described below in conjunction with the accompanying drawings:

[0033] The present application provides a method for recovering and treating acidic ammonium sulfate waste liquid, which comprises the following steps:

[0034] S1: Preprocessing

[0035] In a pretreatment kettle 1, an acidic ammonium sulfate waste liquid containing 20 wt % to 40 wt % of ammonium sulfate, 0.1 wt % to 4 wt % of free acid and 0.1 wt % to 8 wt % of hydrogen peroxide is added with alkali solution at normal pressure and 50 to 70° C. for neutralization pretreatment; the alkali solution is 10 wt % to 30 wt % of ammonia water; after the neutralization pretreatment to a pH of 5 to 7, a remover for oxidative decomposition of hydrogen peroxide is added, and the molar ratio of hydrogen peroxide to the remover is 1:1 to 1.5; the remover is an ammonium salt remover, and preferably, the remover is ammonium sulfite, which can avoid the introduction of new impurities and improve the recovery purity and recovery rate of ammonium sulfate.

[0036] S2: Evaporation and concentration

[0037] The pretreated material enters the triple-effect evaporator and is evaporated and concentrated at -0.06Mpa to -0.08Mpa and 80 to 100°C; the liquid phase solid content of the material after evaporation and concentration is 10 to 25% (V / V); the pretreated material is also used as a flushing liquid. After a period of discharge, the triple-effect evaporator is flushed through the material flushing branch 2902. Preferably, when the material reaches the discharge concentration after evaporation and concentration, that is, the ammonium sulfate content is greater than or equal to 40%, the triple-effect evaporator is flushed for 20 seconds through the material flushing branch 2902 every 4 to 8 minutes of operation and 60 seconds of discharge, which can effectively prevent the evaporation equipment and evaporation pipeline from being blocked.

[0038] S3: Crystallization separation

[0039] The concentrated material is initially separated by the cyclone separator 8 and then enters the crystallizer 9 for crystallization.

[0040] S4: Centrifugal separation

[0041] The crystallized material enters the centrifuge 10 for centrifugal separation.

[0042] S5: The crystals obtained by centrifugal separation are dried in a dryer to obtain the finished ammonium sulfate product, and the mother liquor is recycled to the triple-effect evaporator.

[0043] like Figures 2 to 4 As shown, the present application also provides a recovery and treatment system for acidic ammonium sulfate waste liquid, which includes a pretreatment kettle 1, a triple-effect evaporator, a crystallizer 9, a centrifuge 10 and a dryer connected in sequence. Preferably, the pretreatment kettle 1 is a jacketed stirred reactor, a first stirring paddle 101 is installed in the kettle body, and a jacket 102 is provided outside the kettle body, which can reduce the reaction temperature error and make the reaction uniform and safe; the pretreatment kettle 1 is respectively connected to the acidic ammonium sulfate waste liquid pipeline 12, the alkali liquid pipeline 13 and the removal agent pipeline 14, the pretreatment kettle 1 is also connected to the triple-effect evaporator through a material flushing branch pipeline 2902, and a cyclone separator is provided between the triple-effect evaporator and the crystallizer 9; the triple-effect evaporator is connected to a water flushing pipeline 16, the water flushing pipeline 16 is connected to the first effect separator 2 in the triple-effect evaporator through the first flushing pipeline 1601, is connected to the second effect separator 4 in the triple-effect evaporator through the second flushing pipeline 1602, and is connected to the triple effect separator 6 in the triple-effect evaporator through the third flushing pipeline 1603.

[0044] Preferably, Figure 1 and Figure 4 As shown, the material flushing branch pipeline 2902 is a branch of the material conveying pipeline 29 that connects the pretreatment kettle 1 with the first-effect separator 2 in the triple-effect evaporator. The material flushing branch pipeline 2902 is connected to the first flushing pipeline 1601 and is connected to the first-effect separator 2 from the top through the first flushing pipeline 1601. The pretreated material enters the first-effect separator 2 in the triple-effect evaporator through the main route 2901 of the material conveying pipeline 29 in a downstream manner for evaporation and concentration; as a flushing liquid, by controlling the opening and closing of the valve 36, the pretreated material enters the first-effect separator 2 in a downstream manner through the material flushing branch pipeline 2902 to flush the evaporation equipment and pipelines, or After being mixed with the condensed water or pressurized water of the material, it enters the first-effect separator 2 through the first flushing pipe 1601 of the water flushing pipe 16 to flush the evaporation equipment and the pipeline, which can prevent the crystals generated during the evaporation and concentration of the ammonium sulfate solution from clogging the pipeline by aggregation; at the same time, the condensed water or pressurized water of the material can be used separately through the water flushing pipe 16 to regularly flush the three-effect evaporator and process pipeline through the first flushing pipe 1601, the second flushing pipe 1602 and the third flushing pipe 1603, respectively, to further prevent the ammonium sulfate crystals from clogging the pipeline, thereby improving the quality and production efficiency of the recovered product, ensuring production safety, reducing the difficulty and frequency of manual dredging, and improving the utilization effect of the material.

[0045] like Figure 2As shown, the first-effect separator 2, the second-effect separator 4, and the third-effect separator 6 in the triple-effect evaporator are respectively connected to the first-effect heater 3 through the first pipeline 27, the second-effect heater 5 through the second pipeline 25, and the third-effect heater 7 through the third pipeline 23, thereby forming a first-effect internal circulation pipeline, a second-effect internal circulation pipeline, and a third-effect internal circulation pipeline, thereby improving the evaporation concentration effect and reducing the loss of ammonium sulfate recovery products; preferably, the shell side of the first-effect heater 3 is connected to steam through the first steam pipeline, and the steam evaporated from the first-effect separator 2 can be used as a heat source for the second-effect heater 5 and connected to the shell side of the second-effect heater 5 through the second steam pipeline 34, and the second-effect separator The evaporated steam can be used as a heat source for the triple-effect heater 7 and connected to the shell side of the triple-effect heater 7 through the branch 3501 of the third steam pipeline 35. The evaporated steam of the triple-effect separator 6 can be used as a heat source for the pretreatment kettle 1 and connected to the jacket 102 of the pretreatment kettle 1 through the fourth steam pipeline 15. When the triple-effect separator 6 is not turned on, the evaporated steam of the second-effect separator 4 can also be used as a heat source for the pretreatment kettle 1 and connected to the fourth steam pipeline 15 through the branch 3502 of the third steam pipeline 35 so as to be passed into the jacket 102 of the treatment kettle 1, which can improve the utilization efficiency of the energy of the recovery treatment system, reduce the use of external steam in the treatment system, and thus effectively reduce energy consumption.

[0046] Preferably, the first-effect separator 2 in the triple-effect evaporator is connected to the second-effect separator 4 through the first branch 2801 of the first-effect evaporation pipeline 28, and is connected to the triple-effect separator 6 through the second branch 2802 of the first-effect evaporation pipeline 28, thereby forming a structure in which the second-effect separator 4 and the triple-effect separator 6 are connected in parallel. The waste liquid can be treated by opening the first-effect separator 2 and the second-effect separator 4 in the triple-effect evaporator and the first-effect internal circulation pipeline and the second-effect internal circulation pipeline connected to each other, or by opening the first-effect separator 2, the second-effect separator 4 and the triple-effect separator 6 in the triple-effect evaporator and the first-effect internal circulation pipeline, the second-effect internal circulation pipeline and the third-effect internal circulation pipeline connected to each other, so as to meet the waste liquid treatment needs of different working conditions and save energy and reduce consumption.

[0047] like Figure 2 and Figure 3 As shown, the crystallizer 9 is provided with an agitator 901, and the agitator 901 is provided with a guide tube 902. On both sides of the agitator 901, the crystallizer 9 is provided with a baffle plate 903. There is a gap between the baffle plate 903 and the inner wall of the crystallizer 9. Driven by the agitator, the suspension can circulate and crystallize in the guide tube and the channel between the guide tube and the baffle plate, thereby accelerating the formation of large-diameter granular ammonium sulfate, improving the crystallization efficiency, and preventing dust and agglomeration during subsequent drying, thereby affecting the quality of the recovered ammonium sulfate product. Preferably, the agitator 901 is a propulsion-type stirring paddle, which is simple and convenient to operate, runs smoothly, can achieve uniform stirring, and helps to promote the suspension to circulate and crystallize inside the crystallizer.

[0048] like Figure 2 and Figure 3 As shown, the second-effect separator 4 is connected to a cyclone separator 8a through a second-effect evaporation pipeline 19, and the triple-effect separator 6 is connected to another cyclone separator 8b through a triple-effect evaporation pipeline 24. The cone bottom outlets of the two cyclone separators 8a and 8b are respectively connected to the crystallizer 9, which can perform preliminary separation of the solid and liquid of the material, reduce the moisture content of the crystal, and improve the crystallization effect of the crystallizer and the purity of the ammonium sulfate product; the second-effect separator 4 and the triple-effect separator 6 also form a loop with the cyclone separator, that is, the separation mother liquor outlet of the cyclone separator 8a is connected to the second-effect separator 4 through the first recycling pipeline 17, and the separation mother liquor outlet of the cyclone separator 8b is connected to the triple-effect separator 6 through the second recycling pipeline 18, so that the separation mother liquor is recycled to the triple-effect evaporator, thereby improving the recovery rate of resource products; preferably, the first recycling pipeline 17 is also connected to the water flushing pipeline 16 through the pipeline 37, and the second recycling pipeline 18 is connected to the water flushing pipeline 16 through the pipeline 38. If the concentration of the recycled separation mother liquor is relatively high, it can be flushed to prevent the separation mother liquor from clogging the pipeline when the separation mother liquor is recycled and crystallized.

[0049] like Figure 2 As shown, the centrifuge 10 is connected to the triple-effect evaporator through the temporary storage tank 11 and the third recycling pipeline 22. Preferably, the outlet of the temporary storage tank 11 is connected to the third effect internal circulation pipeline through the first branch 2201 of the third recycling pipeline 22, that is, the first branch 2201 of the third recycling pipeline is connected to the third pipeline 23, and is connected to the first effect separator 2 through the second branch 2202 of the third recycling pipeline 22, that is, the second branch 2202 of the third recycling pipeline is connected to the material conveying pipeline 29. Under different working conditions, the centrifuged mother liquor can be reused in the triple-effect evaporator through the first branch 2201 and the second branch 2202, respectively, to further improve the recovery rate of resource products. Since there is a temperature difference between the centrifugal mother liquor and the material in the evaporation system after the evaporated and concentrated material is centrifuged, according to the heat transfer law, the greater the temperature difference, the more heat is lost in the material mixing. When the first-effect separator 2, the second-effect separator 4 and the third-effect separator 6 in the triple-effect evaporator are all turned on, the steam evaporated from the second-effect separator 4 is used as the heat source of the triple-effect heater 7, so the temperature in the triple-effect separator 6 is lower than that of the second-effect separator 4. Therefore, the centrifugal mother liquor is recycled to the third-effect internal circulation pipeline through the temporary storage tank 11 and the first branch 2201 of the third recycling pipeline 22, which can reduce heat loss, improve heat recovery efficiency, reduce production costs, and further save energy.

[0050] Preferably, the material crystallized in the crystallizer 9 enters the centrifuge 10 through the connecting pipe 21, the crystals obtained by centrifugal separation enter the dryer, and the dried ammonium sulfate product enters the automatic packaging system 26. The dryer and the automatic packaging system 26 can be controlled by an automated program to detect, weigh and package the dried ammonium sulfate product, thereby facilitating the transportation and sale of the recovered products and realizing the recycling of resources.

[0051] Figure 2 In the figure, 31 is a feed pump, 32 is a forced circulation pump; the vacuum pump 20 evacuates the first effect separator 2, the second effect separator 4, and the third effect separator 6 of the triple effect evaporator through the first branch 3001, the second branch 3002, and the third branch 3003 of the connecting pipe 30, respectively, to provide negative pressure reaction conditions for evaporation and concentration; preferably, as Figure 2 and Figure 3 As shown, the pipelines for conveying materials, such as the first-effect evaporation pipeline 28, the second-effect evaporation pipeline 19, and the third-effect evaporation pipeline 24, form the first pipeline 27, the second pipeline 25, and the third pipeline 23 of the first-effect internal circulation pipeline, the second-effect internal circulation pipeline, and the third-effect internal circulation pipeline, the material conveying pipeline 29, the fourth steam pipeline 15, the first steam pipeline, the second steam pipeline 34, the third steam pipeline 35, the connecting pipeline 21, and the third recycling pipeline 22 are respectively coated with the insulation layer 33, combined with Figure 3 As shown, the thermal insulation layer 33 is not shown in its entirety, but is illustrated as a segment of the thermal insulation layer, which can reduce heat loss and prevent material crystallization from clogging the pipeline.

[0052] Embodiment 1:

[0053] 100 t of acidic ammonium sulfate waste liquid containing 20 wt % of ammonium sulfate, 1 wt % of free acid and 1 wt % of hydrogen peroxide is pumped from a raw material storage tank into a pretreatment kettle 1 with a first stirring paddle 101, and after neutralizing to a pH of 5 by adding 30 wt % of ammonia water, ammonium sulfite is added in a molar ratio of hydrogen peroxide to ammonium sulfite of 1:1.5 to oxidatively decompose hydrogen peroxide; preferably, ammonium sulfite is configured to be added as a 5% ammonium sulfite solution to facilitate control of the reaction rate and the amount of reagent added.

[0054] The reaction solution can be preheated by heat exchange with steam transported from the triple-effect evaporator in the jacket 102 of the pretreatment kettle 1. The steam after heat exchange is called condensed water and discharged from the condensed water pipeline. The condensed water pipeline can also be connected to the water flushing pipeline 16 to flush the evaporation equipment and pipeline flushing liquid, thereby improving resource utilization and reducing energy consumption. The pretreated material flows downstream into the triple-effect evaporator through the feed pump 31 for continuous reduced pressure evaporation, wherein the first-effect separator 2, the second-effect separator 4 and the triple-effect separator 6 and the first-effect internal circulation pipeline, the second-effect internal circulation pipeline and the third-effect internal circulation pipeline connected to each other are all opened, the evaporation and concentration temperature is 80°C, the pressure is -0.08Mpa, and the material is discharged when the liquid phase solid content of the material after evaporation and concentration is 10% (V / V). After the material is discharged, it is flushed, that is, every 8 minutes of operation, the material is discharged for 60 seconds, and the triple-effect evaporator is flushed for 20 seconds through the material flushing branch 2902. The flushing liquid is the pretreated material, and the ammonium sulfate concentration is 25%.

[0055] The concentrated ammonium sulfate solution with a liquid solid content of 10% (V / V) is transported through an evaporation pipeline provided with an insulation layer 33, while still maintaining a flowing state, and enters the crystallizer 9 through a cyclone separator for cyclic crystallization for 20 minutes, and then is centrifuged, dried, and automatically packaged to obtain about 19.8 tons of sulfuric acid that meets the requirements of HG / T 5744-2020 industrial ammonium sulfate standard (see Table 1); the centrifuged mother liquor is recycled to the triple-effect evaporator through the temporary storage tank 11 and the first branch 2201 of the third recycling pipeline 22, and the impurities in the centrifuged mother liquor are accumulated to a certain extent in the temporary storage tank 11 and are discharged regularly.

[0056] Embodiment 2:

[0057] 50 t of acidic ammonium sulfate waste liquid containing 30 wt % of ammonium sulfate, 0.9 wt % of free acid and 2 wt % of hydrogen peroxide is pumped from a raw material storage tank into a pretreatment kettle 1 with a first stirring paddle 101, and after neutralizing to a pH of 6 by adding 20 wt % of ammonia water, ammonium sulfite is added in a molar ratio of hydrogen peroxide to ammonium sulfite of 1:1.2 to oxidatively decompose hydrogen peroxide. Preferably, ammonium sulfite is configured to be added as a 5% ammonium sulfite solution to facilitate control of the reaction rate and the amount of reagent added.

[0058] The reaction solution can be preheated by heat exchange with steam transported from the three-effect evaporator in the jacket 102 of the pretreatment kettle 1, and the steam after heat exchange is called condensed water and discharged from the condensed water pipeline; the pretreated material enters the three-effect evaporator downstream through the feed pump 31 for continuous reduced pressure evaporation, wherein the first effect separator 2, the second effect separator 4 and the three-effect separator 6 and the first effect internal circulation pipeline, the second effect internal circulation pipeline and the third effect internal circulation pipeline connected to each other are all opened, the evaporation concentration temperature is 90°C, the pressure is -0.07Mpa, and the material is discharged when the liquid phase solid content of the material after evaporation and concentration is 15% (V / V). After the material is discharged, it is flushed, that is, every 6 minutes of operation, the material is discharged for 60 seconds, and the three-effect evaporator is flushed for 20 seconds through the material flushing branch 2902. The flushing liquid is the pretreated material, and the ammonium sulfate concentration is 35%, or the material condensed water or pressurized water is mixed with the diluted ammonium sulfate solution and then the three-effect evaporator is flushed through the first flushing pipeline 1601.

[0059] The concentrated ammonium sulfate solution with a liquid solid content of 15% (V / V) is transported through an evaporation pipeline provided with an insulation layer 33, while remaining in a flowing state, and enters a crystallizer 9 through a cyclone separator for circulated crystallization for 15 minutes, and then is centrifuged, dried, and automatically packaged to obtain about 14.9 tons of sulfuric acid that meets the requirements of HG / T 5744-2020 industrial ammonium sulfate standard (see Table 1); the centrifuged mother liquor is recycled into the triple-effect evaporator through the temporary storage tank 11 and the first branch 2201 of the third recycling pipeline 22, and the impurities in the centrifuged mother liquor are accumulated to a certain extent in the temporary storage tank 11 and are discharged regularly.

[0060] Embodiment 3:

[0061] 100 t of acidic ammonium sulfate waste liquid containing 40 wt % of ammonium sulfate, 0.8 wt % of free acid and 3 wt % of hydrogen peroxide is pumped from a raw material storage tank into a pretreatment kettle 1 with a first stirring paddle 101, and after neutralizing to a pH of 7 by adding 10 wt % of ammonia water, ammonium sulfite is added according to a molar ratio of hydrogen peroxide to ammonium sulfite of 1:1.5 to oxidatively decompose hydrogen peroxide. Preferably, ammonium sulfite is configured to be added as a 5% ammonium sulfite solution to facilitate control of the reaction rate and the amount of reagent added.

[0062] The reaction solution can be preheated by heat exchange with steam transported from the three-effect evaporator in the jacket 102 of the pretreatment kettle 1. The steam after heat exchange is called condensed water and discharged from the condensed water pipeline. The pretreated material enters the three-effect evaporator downstream through the feed pump 31 for continuous reduced pressure evaporation. Since the initial treatment concentration of the acidic ammonium sulfate waste liquid is relatively high, only the first-effect separator 2 and the second-effect separator 4 and the first-effect internal circulation pipeline and the second-effect internal circulation pipeline connected to each other are opened. The evaporation concentration temperature is 100°C and the pressure is -0.06Mpa. When the liquid phase solid content of the material after evaporation and concentration is 20% (V / V), the material is discharged and flushed after the discharge, that is, every 4 minutes of operation, the material is discharged for 60 seconds, and the three-effect evaporator is flushed for 20 seconds through the first flushing pipeline 1601. Since the ammonium sulfate concentration in the pretreated material is 45%, the flushing liquid is the material condensed water, pressurized water, or a solution of the pretreated material mixed with condensed water and pressurized water.

[0063] The concentrated ammonium sulfate solution with a liquid solid content of 20% (V / V) is transported through an evaporation pipeline provided with an insulation layer 33, while still maintaining a flowing state, and enters the crystallizer 9 through a cyclone separator for cyclic crystallization for 10 minutes, and then is centrifuged, dried, and automatically packaged to obtain about 49.8 tons of sulfuric acid that meets the requirements of HG / T 5744-2020 industrial ammonium sulfate standard (see Table 1); the centrifuged mother liquor is recycled to the triple-effect evaporator through the temporary storage tank 11 through the second branch 2202 of the third recycling pipeline, and the impurities in the centrifuged mother liquor are accumulated to a certain extent in the temporary storage tank 11 and are discharged regularly.

[0064]

Claims

1. A method for recovering and treating acidic ammonium sulfate waste liquid, comprising the following steps: S1: In the pretreatment kettle, alkali solution is added to the acidic ammonium sulfate waste liquid for neutralization pretreatment; S2: The pretreated material enters the triple-effect evaporator for evaporation and concentration; S3: The concentrated material enters the crystallizer for crystallization; S4: The crystallized material enters the centrifuge for centrifugal separation; S5: the crystals obtained by centrifugal separation are put into a dryer for drying to obtain the finished ammonium sulfate product, and the mother liquor is recycled to the three-effect evaporator; The method is characterized in that: in S1, after the pretreatment by neutralization to a pH of 5 to 7, ammonium sulfite is added according to a molar ratio of hydrogen peroxide to ammonium sulfite of 1:1 to 1.5; in S2, the pretreated material is also used as a flushing liquid to flush the triple-effect evaporator; in S3, the concentrated material is preliminarily separated by a cyclone separator before entering the crystallizer; In S1, 20 wt % to 40 wt % of ammonium sulfate, 0.1 wt % to 4 wt % of free acid and 0.1 wt % to 8 wt % of hydrogen peroxide are pre-treated by neutralization at normal pressure and 50 to 70° C.; the alkali solution is 10 wt % to 30 wt % of ammonia water; In S2, evaporation concentration is carried out at -0.06Mpa to -0.08Mpa and 80 to 100°C; the liquid phase solid content of the material after evaporation concentration is 10 to 25% (V / V); in S2, after the concentrated material is discharged, it is flushed for 20 seconds after running for 4 to 8 minutes and after discharging for 60 seconds.

2. A system for recovering and treating acidic ammonium sulfate waste liquid, using the method for recovering and treating acidic ammonium sulfate waste liquid as claimed in claim 1, comprising a pretreatment kettle, a triple-effect evaporator, a crystallizer, a centrifuge and a dryer connected in sequence, characterized in that: The pretreatment kettle is respectively connected with an acidic ammonium sulfate waste liquid pipeline, an alkaline solution pipeline and a remover pipeline. The pretreatment kettle is also connected with the triple-effect evaporator through a material flushing branch pipeline. A cyclone separator is provided between the triple-effect evaporator and the crystallizer.

3. The acidic ammonium sulfate waste liquid recovery and treatment system according to claim 2, characterized in that: The triple-effect evaporator is connected with a water flushing pipeline.

4. The system for recovering and treating acidic ammonium sulfate waste liquid according to claim 2, characterized in that: The crystallizer is provided with a stirrer, and the stirrer is sleeved with a guide tube. On both sides of the stirrer, the crystallizer is installed with a baffle plate; and there is a gap between the baffle plate and the inner wall of the crystallizer.

5. The system for recovering and treating acidic ammonium sulfate waste liquid according to claim 3, characterized in that: The water flushing pipeline is connected to the first effect separator in the triple-effect evaporator through the first flushing pipeline, connected to the second effect separator in the triple-effect evaporator through the second flushing pipeline, and connected to the third effect separator in the triple-effect evaporator through the third flushing pipeline; the material flushing branch pipeline is connected to the first flushing pipeline.

6. The system for recovering and treating acidic ammonium sulfate waste liquid according to claim 5, characterized in that: The second-effect separator and the third-effect separator are respectively connected to the crystallizer through the cyclone separator; the second-effect separator and the third-effect separator also form a loop with the cyclone separator respectively.

7. The system for recovering and treating acidic ammonium sulfate waste liquid according to claim 2, characterized in that: The centrifuge is communicated with the triple-effect evaporator through a temporary storage tank.

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