Ammonium sulfate waste liquid treatment method and evaporation and concentration equipment

Abstract

The invention discloses an ammonium sulfate waste liquid treatment method and evaporation and concentration equipment, and the treatment method comprises the following steps: S1, adding ammonia water into ammonium sulfate waste liquid, and then carrying out standing sedimentation treatment; s2, overflowing and taking out part of supernate of the ammonium sulfate waste liquid after standing and settling, recording the taken-out supernate as R1, recording the remainder as R2, adding an organic-inorganic composite flocculant or a used organic-inorganic composite flocculant into R2, then stirring and filtering, and combining the filtered filtrate with R1 to obtain purified liquid; evaporating and concentrating the purified liquid to obtain a concentrated liquid; and performing centrifugal treatment on the concentrated solution, and performing drying treatment on a centrifugal solid to obtain an ammonium sulfate product. According to the method, ammonia water is added into the ammonium sulfate waste liquid to adjust the pH value, so that metal impurities can be settled, particles are too fine and are difficult to directly filter, after part of supernate is taken out, residues are flocculated by using an organic-inorganic composite flocculant, and then filtration is performed, so that the metal impurities can be settled, filtered and removed.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment, and in particular to a treatment method and evaporation concentration equipment for ammonium sulfate waste liquid. Background Art

[0002] The production process of semiconductor integrated circuits involves many complex chemical reactions and cleaning steps, among which ammonium sulfate is often used as an etchant or cleaning agent. As the scale of production expands, the amount of ammonium sulfate waste liquid generated also surges. These ammonium sulfate waste liquids usually contain high concentrations of metal ions, organic matter and unreacted ammonium sulfate. Due to their high content, direct discharge will cause a waste of resources. Most hazardous chemical recycling companies will recycle ammonium sulfate through a simple pH adjustment-evaporation concentration-crystallization separation method, but the high concentration of metal ions and organic matter in this process will be enriched in the solution.

[0003] Patent application CN202211343565.0 discloses a system and method for treating lithium iron phosphate battery mother liquor wastewater. The invention uses sand filtration-ultrafiltration-ion exchange resin to precipitate solids, and then obtains ammonium sulfate through concentration and crystallization. The ion exchange resin is difficult to recycle and has a high cost.

[0004] Patent application CN200510044734.0 discloses a method for producing ammonium sulfate using waste titanium dioxide acid. This method uses pH adjustment and static sedimentation to remove impurities, but the precipitated solids are fine particles and cannot be removed by simple solid-liquid separation. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for treating ammonium sulfate waste liquid which can effectively precipitate and filter out metal impurities and prepare an ammonium sulfate product.

[0006] To achieve the above object, the present invention provides a method for treating ammonium sulfate waste liquid, comprising the following steps: S1. Adjust pH Adding ammonia water to the ammonium sulfate waste liquid, and then allowing it to settle; S2. Sedimentation overflow The supernatant of the ammonium sulfate waste liquid after static sedimentation is overflowed and taken out, the taken out supernatant is recorded as R1, and the remainder is recorded as R2, an organic-inorganic composite flocculant or a used organic-inorganic composite flocculant is added to R2, followed by stirring, and then filtering, the filtered filtrate is combined with R1 to obtain a purified liquid, and the filtered filter cake is dried to obtain the used organic-inorganic composite flocculant; The organic-inorganic composite flocculant is composed of polysilicate and acrylamide organic matter; S3. Evaporation and concentration The purified liquid is evaporated and concentrated to obtain a concentrated liquid; S4. Centrifugal drying The concentrated liquid is centrifuged, and the centrifuged solid is dried to obtain the ammonium sulfate product, and the centrifuged liquid is returned to the evaporation and concentration step.

[0007] Furthermore, in step S1, the concentration of ammonia water is 15-30 wt %, the amount of ammonia water added is such that the pH value of the ammonium sulfate waste liquid reaches 6.5-8.0, and the static sedimentation treatment time is 1-2 h.

[0008] Furthermore, in step S2, the polysilicate is polyaluminum silicate, magnesium aluminum polysilicate or calcium aluminum polysilicate, the acrylamide organic matter is polyacrylamide or methacrylamideoxyethyltrimethylammonium chloride, and the mass ratio of polysilicate to acrylamide organic matter is 1:20-30.

[0009] Furthermore, in step S2, when the organic-inorganic composite flocculant is used, the amount of flocculant added is 0.0005-0.001% of the mass of R2; when the used organic-inorganic composite flocculant is used, the amount of flocculant added is 0.01-0.05% of the mass of R2.

[0010] Furthermore, in step S2, the stirring treatment is carried out at a stirring speed of 100 to 300 rpm and for a time of 15 to 30 min.

[0011] Furthermore, in step S2, the part of the supernatant liquid taken out accounts for 50-60% of the total volume of the ammonium sulfate waste liquid after static sedimentation.

[0012] Furthermore, in step S3, the conditions for evaporation concentration treatment are a temperature of 60 to 80° C., a pressure of -0.07 to -0.09 MPa, and a solid content of the concentrated solution of 70% to 85 wt %.

[0013] Furthermore, in step S4, the drying process adopts airflow drying at a temperature of 160-170° C. and a time of 1-4 seconds.

[0014] Furthermore, in step S3, the steam generated by the evaporation and concentration process is absorbed by spraying water, so as to reduce the loss of ammonia in the subsequent evaporation and concentration, improve the recovery rate of ammonium sulfate and reduce the loss of ammonium sulfate.

[0015] The present invention also provides an evaporation concentration device for implementing the evaporation concentration step of the above-mentioned treatment method, which includes a separator, a circulation pump, and a reboiler. The separator is connected with a material feed pipeline and a material discharge pipeline. The feed port of the circulation pump is connected to the bottom of the separator, and the discharge port of the circulation pump is connected to the reboiler. The reboiler is connected to the top of the separator through a circulation pipeline. The circulation pipeline is connected with a spray branch pipeline, and the spray branch pipeline extends to the top of the separator and is connected with a plurality of nozzles. A packing layer is provided below the nozzle in the separator. Since a small amount of ammonium sulfate will decompose under heating, the residence time of ammonia can be increased by adding packing, and the decomposed ammonia can be recovered by spraying to reduce the loss rate of ammonia.

[0016] The beneficial effects of the present invention are embodied in: The present invention adds ammonia water to ammonium sulfate waste liquid to adjust pH so as to precipitate metal impurities, such as iron hydroxide generated by iron impurities. Since the iron hydroxide particles are too fine, it is difficult to filter directly. After taking out part of the supernatant, the present invention uses an organic-inorganic composite flocculant to flocculate the remainder, and then filters it, so that the metal impurities can be precipitated and filtered to be removed.

[0017] After static sedimentation, the metal impurities in the ammonium sulfate waste liquid are precipitated at the bottom, and the supernatant is basically free of metal impurities. After taking out part of the supernatant, the solid content of the residue is high, which can reduce the amount of flocculant used. The less impurities are introduced, the metal ions in the ammonium sulfate solution can be removed at the lowest cost without increasing the metal ion content in the system, thereby maximizing benefits.

[0018] At the same time, the present invention innovates an organic-inorganic composite flocculant composed of polysilicate and acrylamide organic matter. The flocculant not only has a good flocculation effect, but also does not need to be treated. After use, it is directly used as a new flocculant together with the flocculated metal impurity precipitates. The introduction of polysilicate improves the electrical neutralization ability and adsorption bridging ability of acrylamide organic matter, and the generated flocs are looser. Although the electrical neutralization ability of the flocs gradually weakens with the increase in the number of reuses, the loose floc state will greatly increase the probability of collision between the total suspended particles in the water and the flocs. Therefore, the reuse of the flocs still has a good water purification effect. It has been verified that it can be reused 10 to 15 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a process flow chart of the method for treating ammonium sulfate waste liquid.

[0020] Figure 2 A schematic structural diagram of an evaporation concentration device provided in one embodiment of the present invention.

[0021] The figures are marked as follows: 1-material feed pipeline; 2-separator; 3-circulation pump; 4-reboiler; 5-circulation pipeline; 6-spray branch pipeline; 7-nozzle; 8-packing layer; 9-material discharge pipeline. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0023] The raw materials, reagents or devices used in the following examples and comparative examples, unless otherwise specified, can be obtained from conventional commercial sources, or can be obtained by existing known methods; unless otherwise specified, the methods used in the embodiments of the present invention are methods known to those skilled in the art. Among them, polyacrylamide was purchased from Zibo Lanerqing Polymer Materials Co., Ltd., pH 4-9, effective substance content 99%, brand Lanerqing.

[0024] The properties of ammonium sulfate waste liquid are shown in Table 1 below: Table 1 Example 1 Treatment of ammonium sulfate wastewater See also Figure 1 , the specific steps are as follows: S1. Adjust pH Add 20 wt% ammonia water to the ammonium sulfate waste liquid to adjust the pH value to 8.0, and then let it stand for 1 hour; S2. Sedimentation overflow The supernatant of 55% of the total volume of the ammonium sulfate waste liquid after static sedimentation is taken out by overflow, which is recorded as R1, and the remainder is recorded as R2. An organic-inorganic composite flocculant (composed of polysilicon aluminum magnesium and polyacrylamide in a mass ratio of 1:30) accounting for 0.0008% of the mass of R2 is added, and then stirred at a stirring speed of 300 rpm for 15 minutes, and then filtered. The filtered filtrate is combined with R1 to obtain the purified liquid, and the filtered cake is dried to obtain a new flocculant. S3. Evaporation and concentration The purified liquid was evaporated and concentrated to a solid content of 75 wt % at a temperature of 60° C. and a pressure of −0.09 MPa to obtain a concentrated liquid; S4. Centrifugal drying The concentrated liquid is centrifuged, and the centrifuged solid is dried by air flow at a temperature of 165° C. for 3 seconds to obtain an ammonium sulfate product, and the centrifuged liquid is returned to the evaporation and concentration step.

[0025] Example 2 Treatment of ammonium sulfate wastewater See also Figure 1 , the specific steps are as follows: S1. Adjust pH Add 15 wt% ammonia water to the ammonium sulfate waste liquid to adjust the pH value to 7.5, and then let it stand for 1.5 hours; S2. Sedimentation overflow 50% of the total volume of the ammonium sulfate waste liquid after static sedimentation is taken out by overflow, which is recorded as R1, and the remainder is recorded as R2. 0.001% of the mass of an organic-inorganic composite flocculant (composed of polysilicate aluminum and methacrylamide oxyethyl trimethyl ammonium chloride in a mass ratio of 1:25) is added to R2, and then stirred at a stirring speed of 200 rpm for 20 minutes, and then filtered. The filtered filtrate is combined with R1 to obtain a purified liquid, and the filtered cake is dried to obtain a new flocculant. S3. Evaporation and concentration The purified liquid was evaporated and concentrated to a solid content of 70 wt % at a temperature of 70° C. and a pressure of −0.08 MPa to obtain a concentrated liquid; S4. Centrifugal drying The concentrated liquid is centrifuged, and the centrifuged solid is dried by air flow at a temperature of 160° C. for 4 seconds to obtain an ammonium sulfate product, and the centrifuged liquid is returned to the evaporation and concentration step.

[0026] Example 3 Treatment of ammonium sulfate wastewater See also Figure 1 , the specific steps are as follows: S1. Adjust pH Add 30 wt% ammonia water to the ammonium sulfate waste liquid to adjust the pH value to 6.5, and then let it stand for 2 hours; S2. Sedimentation overflow 60% of the total volume of the ammonium sulfate waste liquid after static sedimentation was taken out by overflow, which was recorded as R1, and the remainder was recorded as R2. An organic-inorganic composite flocculant (composed of calcium aluminum polysilicate and polyacrylamide in a mass ratio of 1:20) accounting for 0.0005% of the mass of R2 was added, and then stirred at a stirring speed of 100 rpm for 30 minutes, and then filtered. The filtered filtrate was combined with R1 to obtain the purified liquid, and the filtered cake was dried to obtain the new flocculant. S3. Evaporation and concentration The purified liquid was evaporated and concentrated to a solid content of 85 wt % at a temperature of 80° C. and a pressure of −0.07 MPa to obtain a concentrated liquid; S4. Centrifugal drying The concentrated liquid is centrifuged, and the centrifuged solid is dried by air flow at a temperature of 170° C. for 1 second to obtain an ammonium sulfate product, and the centrifuged liquid is returned to the evaporation and concentration step.

[0027] Example 4 Treatment of ammonium sulfate wastewater This embodiment is treated in the same manner as in Embodiment 1, except that the organic-inorganic composite flocculant is replaced with the new flocculant obtained in step S2 of Embodiment 1, and the added amount is 0.03% of the mass of R2.

[0028] Example 5 Treatment of ammonium sulfate wastewater This embodiment is treated in the same manner as in Embodiment 2, except that the organic-inorganic composite flocculant is replaced with the new flocculant obtained in step S2 of Embodiment 2, and the added amount is 0.05% of the mass of R2.

[0029] Example 6 Treatment of ammonium sulfate wastewater This embodiment is treated in the same manner as in Embodiment 3, except that the organic-inorganic composite flocculant is replaced with the new flocculant obtained in step S2 of Embodiment 3, and the added amount is 0.01% of the mass of R2.

[0030] Comparative Example 1 Treatment of ammonium sulfate wastewater This comparative example was processed in the same manner as Example 1, except that the organic-inorganic composite flocculant was replaced with an equal amount of polyaluminum magnesium silicate.

[0031] Comparative Example 2 Treatment of ammonium sulfate wastewater This comparative example was processed in the same manner as Example 1, except that the organic-inorganic composite flocculant was replaced with an equal amount of polyacrylamide.

[0032] Comparative Example 3 Treatment of ammonium sulfate wastewater This comparative example was processed in the same manner as comparative example 1, except that the organic-inorganic composite flocculant was replaced with an equal amount of the new flocculant obtained in step S2 of comparative example 1.

[0033] Comparative Example 4 Treatment of ammonium sulfate wastewater This comparative example is processed in the same manner as comparative example 2, except that the organic-inorganic composite flocculant is replaced with an equal amount of the new flocculant obtained in step S2 of comparative example 2.

[0034] Analysis on the Treatment Effect of Ammonium Sulfate Wastewater The ammonium sulfate products obtained in the above embodiments and comparative examples were tested for components, and the results are shown in Table 2 below: Table 2 The method of Example 1 was repeated 11 times, and the flocculants used after the second operation were all new flocculants produced after the last operation, and the added amount was 0.03% of the mass of R2. The ammonium sulfate product obtained in the last operation was tested for its components, and the results are shown in Table 3 below: Table 3 Example 4 This embodiment provides a step S3 of the treatment method of ammonium sulfate waste liquid of the present invention. An evaporation and concentration device is provided, which includes a gas-liquid separator 2, a circulation pump 3, and a reboiler 4. The separator 2 is connected with a material feed pipeline 1 and a material discharge pipeline 9. The feed port of the circulation pump 3 is connected to the bottom of the separator 2, and the discharge port of the circulation pump 3 is connected to the reboiler 4. The reboiler 4 is connected to the top of the separator 2 through a circulation pipeline 5. The circulation pipeline 5 is connected with a spray branch pipeline 6. The spray branch pipeline 6 extends to the top of the separator 2 and is connected with a plurality of nozzles 7. A packing layer 8 (ceramic packing can be used) is provided below the nozzle 7 in the separator 2. This evaporation and concentration device is used to reduce the loss of ammonia in subsequent evaporation and concentration by adding a spray device and a packing at the top of the separator, thereby improving the recovery rate of ammonium sulfate and reducing the loss of ammonium sulfate.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for treating ammonium sulfate waste liquid, characterized in that: The following steps are involved: S1. Adjust pH Adding ammonia water to the ammonium sulfate waste liquid, and then allowing it to settle; S2. Sedimentation overflow The supernatant of the ammonium sulfate waste liquid after static sedimentation is overflowed and taken out, the taken out supernatant is recorded as R1, and the remainder is recorded as R2, an organic-inorganic composite flocculant or a used organic-inorganic composite flocculant is added to R2, followed by stirring, and then filtering, the filtered filtrate is combined with R1 to obtain a purified liquid, and the filtered filter cake is dried to obtain the used organic-inorganic composite flocculant; The organic-inorganic composite flocculant is composed of polysilicate and acrylamide organic matter; S3. Evaporation and concentration The purified liquid is evaporated and concentrated to obtain a concentrated liquid; S4. Centrifugal drying The concentrated liquid is centrifuged, and the centrifuged solid is dried to obtain the ammonium sulfate product, and the centrifuged liquid is returned to the evaporation and concentration step.

2. The method for treating ammonium sulfate waste liquid as claimed in claim 1, wherein: In step S1, the concentration of ammonia water is 15-30 wt %, the amount of ammonia water added is such that the pH value of the ammonium sulfate waste liquid reaches 6.5-8.0, and the static sedimentation treatment time is 1-2 h.

3. The method for treating ammonium sulfate waste liquid as claimed in claim 1, wherein: In step S2, the polysilicate is polyaluminum silicate, magnesium aluminum polysilicate or calcium aluminum polysilicate, the acrylamide organic matter is polyacrylamide or methacrylamide oxyethyl trimethyl ammonium chloride, and the mass ratio of polysilicate to acrylamide organic matter is 1:20-30.

4. The method for treating ammonium sulfate waste liquid as claimed in claim 1, 2 or 3, wherein: In step S2, when the organic-inorganic composite flocculant is used, the amount of flocculant added is 0.0005-0.001% of the mass of R2; when the used organic-inorganic composite flocculant is used, the amount of flocculant added is 0.01-0.05% of the mass of R2.

5. The method for treating ammonium sulfate waste liquid as claimed in claim 1, 2 or 3, characterized in that: In step S2, the stirring treatment conditions are a stirring speed of 100 to 300 rpm and a time of 15 to 30 min.

6. The method for treating ammonium sulfate waste liquid as claimed in claim 1, 2 or 3, characterized in that: In step S2, the part of the supernatant liquid taken out accounts for 50-60% of the total volume of the ammonium sulfate waste liquid after static sedimentation.

7. The method for treating ammonium sulfate waste liquid as claimed in claim 1, 2 or 3, characterized in that: In step S3, the conditions for evaporation concentration treatment are a temperature of 60 to 80° C., a pressure of -0.07 to -0.09 MPa, and a solid content of the concentrated solution of 70% to 85 wt %.

8. The method for treating ammonium sulfate waste liquid as claimed in claim 1, 2 or 3, characterized in that: In step S4, the drying process adopts air flow drying at a temperature of 160-170° C. for a time of 1-4 seconds.

9. The method for treating ammonium sulfate waste liquid as claimed in claim 1, 2 or 3, characterized in that: In step S3, the steam generated by the evaporation concentration process is absorbed by spraying water.

10. An evaporation concentration device for use in the treatment method according to any one of claims 1 to 9, characterized in that: It includes a separator, a circulation pump, and a reboiler. The separator is connected to a material feed pipeline and a material discharge pipeline. The feed port of the circulation pump is connected to the bottom of the separator, and the discharge port of the circulation pump is connected to the reboiler. The reboiler is connected to the top of the separator through a circulation pipeline. The circulation pipeline is connected to a spray branch pipeline, and the spray branch pipeline extends to the top of the separator and is connected to a plurality of nozzles. A packing layer is provided below the nozzle in the separator.

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