A method for treating ammonium sulfate waste liquid and an evaporation and concentration device

Abstract

This invention discloses a method for treating ammonium sulfate waste liquid and an evaporation and concentration device. The treatment method includes the following steps: S1. Adding ammonia water to the ammonium sulfate waste liquid and then allowing it to settle; S2. Removing a portion of the supernatant from the settled ammonium sulfate waste liquid, denoted as R1, and the residue as R2. Adding an organic-inorganic composite flocculant or a used organic-inorganic composite flocculant to R2, followed by stirring and filtration. The filtrate is combined with R1 to obtain a purified liquid; the purified liquid is then evaporated and concentrated to obtain a concentrated liquid; the concentrated liquid is centrifuged, and the centrifuged solid is dried to obtain the ammonium sulfate product. This invention uses ammonia water to adjust the pH of the ammonium sulfate waste liquid to settle metallic impurities. However, because the particles are too fine to filter directly, this invention removes a portion of the supernatant and then uses an organic-inorganic composite flocculant to flocculate the residue before filtration, thus removing the metallic impurities by precipitation.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and in particular to a method for treating ammonium sulfate waste liquid and an evaporation and concentration device. Background Technology

[0002] The manufacturing process of semiconductor integrated circuits involves numerous complex chemical reactions and cleaning steps, often using ammonium sulfate as an etching agent or cleaning agent. With the expansion of production scale, the amount of ammonium sulfate wastewater generated also surges. This wastewater typically contains high concentrations of metal ions, organic matter, and unreacted ammonium sulfate. Due to its high content, direct discharge would result in resource waste. Most hazardous chemical recycling companies recover ammonium sulfate through a simple pH adjustment-evaporation concentration-crystallization separation method. However, this process leads to the accumulation of high concentrations of metal ions and organic matter in the solution.

[0003] Patent application CN202211343565.0 discloses a treatment system and method for lithium iron phosphate battery mother liquor wastewater. This invention uses sand filtration-ultrafiltration-ion exchange resin to precipitate solids, followed by concentration and crystallization to obtain ammonium sulfate. However, the ion exchange resin is difficult to recover and has high costs.

[0004] Patent application CN200510044734.0 discloses a method for producing ammonium sulfate using waste acid from titanium dioxide. This method removes impurities by adjusting the pH and allowing the solid to settle. However, the precipitated solid particles are too fine to be removed by simple solid-liquid separation. Summary of the Invention

[0005] The main objective of this invention is to provide a method for treating ammonium sulfate waste liquid that can effectively precipitate, filter and remove metal impurities and prepare ammonium sulfate products.

[0006] To achieve the above objectives, the present invention provides a method for treating ammonium sulfate waste liquid, comprising the following steps: S1. Adjust pH Add ammonia water to the ammonium sulfate waste liquid, and then let it stand to settle. S2. Settlement overflow A portion of the supernatant of the ammonium sulfate waste liquid after settling is overflowed and taken out. The supernatant is recorded as R1 and the residue is recorded as R2. An organic-inorganic composite flocculant or a used organic-inorganic composite flocculant is added to R2, followed by stirring and filtration. The filtrate is combined with R1 to obtain the purified liquid. The filter cake is dried to obtain the used organic-inorganic composite flocculant. The organic-inorganic composite flocculant is composed of polysilicate and acrylamide-based organic compounds; S3. Evaporation and Concentration The purified liquid is evaporated and concentrated to obtain a concentrated liquid; S4. Centrifugal drying The concentrate is centrifuged, and the centrifuged solid is dried to obtain ammonium sulfate product. 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 to make the pH value of the ammonium sulfate waste liquid reach 6.5-8.0, and the settling time is 1-2 hours.

[0008] Further, in step S2, the polysilicate is polyaluminum silicate, polyaluminum magnesium silicate, or polyaluminum calcium silicate, and the acrylamide organic compound is polyacrylamide or methacrylamide oxyethyltrimethylammonium chloride, with a mass ratio of polysilicate to acrylamide organic compound of 1:20-30.

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

[0010] Furthermore, in step S2, the stirring conditions are a stirring speed of 100–300 rpm and a time of 15–30 min.

[0011] Furthermore, in step S2, the supernatant removed accounts for 50-60% of the total volume of the ammonium sulfate waste liquid after settling.

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

[0013] Furthermore, in step S4, the drying process employs airflow drying at a temperature of 160–170°C for 1–4 seconds.

[0014] Furthermore, in step S3, the steam generated during the evaporation and concentration process is absorbed by spray water. This is used to reduce ammonia loss in subsequent evaporation and concentration processes, improve the recovery rate of ammonium sulfate, and reduce ammonium sulfate loss.

[0015] This invention also provides an evaporation and concentration apparatus for implementing the evaporation and concentration step of the above-mentioned treatment method. It includes a separator, a circulating pump, and a reboiler. The separator is connected to a material inlet pipeline and a material outlet pipeline. The inlet of the circulating pump is connected to the bottom of the separator, and the outlet of the circulating pump is connected to the reboiler. The reboiler is connected to the top of the separator via a circulating pipeline. A spray branch pipeline is connected to the circulating pipeline, extending to the top of the separator and connected to multiple nozzles. A packing layer is provided inside the separator below the nozzles. Since a small amount of ammonium sulfate decomposes under heating conditions, the residence time of ammonia gas is increased by adding packing material, and the decomposed ammonia gas is recovered through spraying, reducing the ammonia loss rate.

[0016] The beneficial effects of this invention are reflected in: This invention uses ammonia water to adjust the pH of ammonium sulfate waste liquid, which can settle metallic impurities, such as iron impurities that form ferric hydroxide. Because the ferric hydroxide particles are too fine, they are difficult to filter directly. This invention removes part of the supernatant and then uses an organic-inorganic composite flocculant to flocculate the remaining material before filtration, which can remove the metallic impurities by precipitation and filtration.

[0017] After settling, the metal impurities in the ammonium sulfate waste liquid settle at the bottom, while the supernatant is basically free of metal impurities. After removing part of the supernatant, the remaining solid content is high, which can reduce the amount of flocculant used. The less impurities introduced, the lower the cost of removing metal ions from the ammonium sulfate solution without increasing the metal ion content in the system, thus maximizing profits.

[0018] Meanwhile, this invention innovates an organic-inorganic composite flocculant composed of polysilicate and acrylamide-based organic compounds. This flocculant not only has a good flocculation effect, but also does not require treatment. After use, the flocculated metal impurities and precipitates can be directly used as new flocculants. The introduction of polysilicate improves the charge neutralization and adsorption bridging capabilities of acrylamide-based organic compounds, resulting in looser flocs. Although the charge neutralization capacity of the flocs gradually weakens with the increase of reuse times, the loose floc state greatly increases the probability of collision between total suspended particles in the water and the flocs. Therefore, the reuse of flocs still has a good water purification effect. It has been verified that it can be reused 10 to 15 times. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the ammonium sulfate waste liquid treatment method of the present invention.

[0020] Figure 2 This is a schematic diagram of the structure of an evaporation and concentration device provided in an embodiment of the present invention.

[0021] The attached diagram is labeled as follows: 1-Material feed line; 2-Separator; 3-Circulation pump; 4-Reboiler; 5-Circulation line; 6-Spray branch line; 7-Nozzle; 8-Packing layer; 9-Material discharge line. Detailed Implementation

[0022] The present invention will be further described clearly and in detail below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

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

[0024] The properties of ammonium sulfate waste liquid are shown in Table 1 below: Table 1 Example 1 Treatment of ammonium sulfate waste liquid See Figure 1 The specific operating steps are as follows: S1. Adjust pH Add 20wt% ammonia water to the ammonium sulfate waste liquid to adjust the pH value to 8.0, and then let it stand for 1 hour to settle. S2. Settlement overflow The supernatant, representing 55% of the total volume of the ammonium sulfate waste liquid after settling, is taken out by overflow and denoted as R1. The residue is denoted as R2. 0.0008% of an organic-inorganic composite flocculant (composed of magnesium aluminum silicate and polyacrylamide in a mass ratio of 1:30) is added to R2. The mixture is then stirred at 300 rpm for 15 minutes and filtered. The filtrate is combined with R1 to form the purified liquid. The filtered filter cake is dried to become the new flocculant. S3. Evaporation and Concentration The purified liquid was evaporated and concentrated to a solid content of 75wt% under the conditions of 60℃ and -0.09MPa to obtain a concentrated liquid. S4. Centrifugal drying The concentrate is centrifuged, and the centrifuged solid is dried by airflow at 165°C for 3 seconds to obtain ammonium sulfate product. The centrifuged liquid is then returned to the evaporation and concentration step.

[0025] Example 2 Treatment of ammonium sulfate waste liquid See Figure 1 The specific operating steps are as follows: S1. Adjust pH Add 15wt% ammonia solution to the ammonium sulfate waste liquid to adjust the pH value to 7.5, and then let it stand for 1.5 hours to settle. S2. Settlement overflow The supernatant, representing 50% of the total volume of the ammonium sulfate waste liquid after settling, is taken out by overflow and denoted as R1. The residue is denoted as R2. 0.001% of an organic-inorganic composite flocculant (composed of polyaluminum silicate and methacrylamide oxyethyltrimethylammonium chloride in a mass ratio of 1:25) is added to R2. The mixture is then stirred at 200 rpm for 20 minutes and filtered. The filtrate is combined with R1 to obtain the purified liquid. The filtered filter cake is dried to obtain the new flocculant. S3. Evaporation and Concentration The purified liquid was evaporated and concentrated to a solid content of 70 wt% under conditions of 70℃ and -0.08 MPa to obtain a concentrated liquid. S4. Centrifugal drying The concentrate was centrifuged, and the centrifuged solid was dried by airflow at 160°C for 4 seconds to obtain ammonium sulfate product. The centrifuged liquid was then returned to the evaporation and concentration step.

[0026] Example 3 Treatment of ammonium sulfate waste liquid See Figure 1 The specific operating steps are as follows: S1. Adjust pH Add 30wt% ammonia water to the ammonium sulfate waste liquid to adjust the pH value to 6.5, and then let it stand for 2 hours to settle. S2. Settlement overflow The supernatant, representing 60% of the total volume of the ammonium sulfate waste liquid after settling, is taken out by overflow and labeled as R1. The residue is labeled as R2. 0.0005% of an organic-inorganic composite flocculant (composed of calcium aluminum silicate and polyacrylamide in a mass ratio of 1:20) is added to R2. The mixture is then stirred at 100 rpm for 30 minutes and filtered. The filtrate is combined with R1 to form the purified liquid. The filtered filter cake is dried to become the new flocculant. S3. Evaporation and Concentration The purified liquid was evaporated and concentrated to a solid content of 85wt% under conditions of 80℃ and -0.07MPa to obtain a concentrated liquid. S4. Centrifugal drying The concentrate is centrifuged, and the centrifuged solid is dried by airflow at 170°C for 1 second to obtain ammonium sulfate product. The centrifuged liquid is then returned to the evaporation and concentration step.

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

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

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

[0030] Comparative Example 1 Treatment of ammonium sulfate waste liquid This comparative example was processed in the same way 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 waste liquid This comparative example was processed in the same way 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 waste liquid This comparative example was processed in the same way 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 waste liquid This comparative example was processed in the same way as Comparative Example 2, except that the organic-inorganic composite flocculant was replaced with an equal amount of the new flocculant obtained in step S2 of Comparative Example 2.

[0034] Analysis of the treatment effect of ammonium sulfate waste liquid The components of the ammonium sulfate products prepared in the above embodiments and comparative examples were analyzed, and the results are shown in Table 2 below: Table 2 The method described in Example 1 was repeated 11 times. After the second time, all flocculants used were newly generated flocculants from the previous operation, and the addition amount was 0.03% of the mass of R2. The composition of the final ammonium sulfate product was analyzed, and the results are shown in Table 3 below: Table 3 Example 4 This embodiment provides an evaporation and concentration apparatus for step S3 of the ammonium sulfate waste liquid treatment method of the present invention. The apparatus includes a gas-liquid separator 2, a circulating pump 3, and a reboiler 4. The separator 2 is connected to a material inlet pipeline 1 and a material outlet pipeline 9. The inlet of the circulating pump 3 is connected to the bottom of the separator 2, and the outlet of the circulating pump 3 is connected to the reboiler 4. The reboiler 4 is connected to the top of the separator 2 via a circulating pipeline 5. A spray branch pipeline 6 is connected to the circulating pipeline 5, extending to the top of the separator 2 and connected to multiple nozzles 7. A packing layer 8 (which can be ceramic packing) is provided inside the separator 2 below the nozzles 7. This evaporation and concentration apparatus, by adding a spray device and packing at the top of the separator, reduces ammonia loss during subsequent evaporation and concentration, improves the recovery rate of ammonium sulfate, and reduces ammonium sulfate loss.

[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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for treating ammonium sulfate waste liquid, characterized in that, Includes the following steps: S1. Adjust pH Add ammonia water to the ammonium sulfate waste liquid, and then let it stand to settle. S2. Settlement overflow A portion of the supernatant of the ammonium sulfate waste liquid after settling is overflowed and taken out. The supernatant is recorded as R1 and the residue is recorded as R2. An organic-inorganic composite flocculant or a used organic-inorganic composite flocculant is added to R2, followed by stirring and filtration. The filtrate is combined with R1 to obtain the purified liquid. The filter cake is dried to obtain the used organic-inorganic composite flocculant. The organic-inorganic composite flocculant is composed of polysilicate and acrylamide-based organic compounds; S3. Evaporation and Concentration The purified liquid is evaporated and concentrated to obtain a concentrated liquid; S4. Centrifugal drying The concentrate is centrifuged, and the centrifuged solid is dried to obtain ammonium sulfate product. The centrifuged liquid is returned to the evaporation and concentration step.

2. The method for treating ammonium sulfate waste liquid as described in claim 1, characterized in that, In step S1, the concentration of ammonia water is 15-30 wt%, and the amount of ammonia water added is such that the pH value of the ammonium sulfate waste liquid reaches 6.5-8.

0. The settling time is 1-2 hours.

3. The method for treating ammonium sulfate waste liquid as described in claim 1, characterized in that, In step S2, the polysilicate is polyaluminum silicate, polyaluminum magnesium silicate, or polyaluminum calcium silicate, and the acrylamide organic compound is polyacrylamide or methacrylamide oxyethyltrimethylammonium chloride. The mass ratio of polysilicate to acrylamide organic compound is 1:20-30.

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

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

6. The method for treating ammonium sulfate waste liquid as described in claim 1, 2, or 3, characterized in that, In step S2, the supernatant removed accounts for 50-60% of the total volume of the ammonium sulfate waste liquid after settling.

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

8. The method for treating ammonium sulfate waste liquid as described in claim 1, 2, or 3, characterized in that, In step S4, the drying process is carried out by airflow drying at a temperature of 160-170°C for 1-4 seconds.

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

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