System and method for removing sulfate from polysilicon acidic production wastewater

Abstract

The application provides a system and method for removing sulfate in polysilicon acidic production wastewater, and relates to the technical field of polysilicon production. The method comprises the following steps: neutralizing the acidic wastewater to obtain neutralized recycling wastewater; sending the neutralized recycling wastewater to a waste gas washing section to generate waste washing effluent; sending the waste washing effluent to a high-boiling hydrolysis section of a polysilicon production line to generate hydrolysis recycling wastewater after the waste washing effluent is hydrolyzed with high-boiling substances in the high-boiling hydrolysis section; neutralizing the hydrolysis recycling wastewater; and sending the supernatant obtained after separation to a calcium chloride evaporation system. The system comprises a recycling water tank, a waste gas washing section, a high-boiling hydrolysis section, an acid water tank, a four-stage neutralization tank, an inclined plate sedimentation tank and a calcium chloride evaporation system. The hydrolysis reaction of the high-boiling substances and the neutralized acidic wastewater can reduce the sulfate in the acidic wastewater, thereby reducing the sulfate content of the water entering the calcium chloride evaporation system and alleviating the scaling phenomenon in the calcium chloride evaporation system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polysilicon production, in particular to a system and method for removing sulfate from polysilicon acidic production wastewater. BACKGROUND

[0002] In the polysilicon production process, acidic wastewater containing hydrogen chloride and silicic acid is generated, which needs to be neutralized by adding lime before being reused; because a large amount of calcium ions and part of sulfate ions are brought into the acidic wastewater during the neutralization process (after adding lime to adjust the PH, the sulfate in the acidic wastewater has increased significantly, indicating that sulfate ions are brought into the system during the lime addition process), in order to maintain the salt balance and water balance in the acidic wastewater, low-concentration calcium chloride solution needs to be concentrated through a calcium chloride evaporation system.

[0003] The calcium chloride evaporation system includes a MVR subsystem and a three-effect subsystem connected in sequence, wherein: the MVR subsystem adopts two-stage concentration, and the concentration effect reaches 4 times; the concentration effect of the three-effect subsystem reaches 2.1 times, and contains three effect bodies connected in series and running in sequence, namely a three-effect evaporator, a two-effect evaporator and a one-effect evaporator, wherein the one-effect evaporator has the highest concentration and is the terminal device for producing high-concentration calcium chloride solution.

[0004] The water entering the calcium chloride evaporation system contains about 70 mg / L of sulfate and about 15,000 mg / L of calcium ions, after 4 times concentration by the MVR subsystem, the sulfate in the water entering the three-effect subsystem reaches about 300 mg / L, and after 2.1 times concentration by the three-effect subsystem, the sulfate in the one-effect reaches 600 mg / L; because the sulfate of 600 mg / L has reached the saturation degree of calcium sulfate in a high-calcium environment, calcium sulfate scaling will be generated in the three-effect subsystem, so that the three-effect subsystem needs to be cleaned once every 2.5 months, affecting the long-period operation of the three-effect subsystem; in addition, because the MVR subsystem adopts two-stage concentration of 4 times, slight scaling will also occur in the MVR subsystem, and the MVR subsystem needs to be cleaned once a year.

[0005] If the sulfate in the acidic wastewater can be effectively removed, it will be beneficial to improve the scaling phenomenon of the calcium chloride evaporation system, but there is no effective method for removing the sulfate in the above-mentioned acidic wastewater at present.

[0006] The information disclosed in this BACKGROUND section is only intended to enhance the understanding of the general background of the present application, and should not be taken as recognition or admission that this information constitutes prior art with respect to any country. SUMMARY

[0007] In view of the above, the present application provides a system and method for removing sulfate from polysilicon acidic production wastewater, aiming to remove sulfate from acidic wastewater.

[0008] To achieve the above object, the present application provides the following technical solutions.

[0009] In the first aspect, the present application provides a method for removing sulfate from polysilicon acidic production wastewater, which can mainly include the following steps:

[0010] Step S1, neutralizing the acidic wastewater to obtain neutralized recycled wastewater;

[0011] Step S2, sending the neutralized recycled wastewater to the exhaust gas washing section of the polysilicon production line to generate waste washing effluent;

[0012] Step S3, sending the waste washing effluent to the high-boiling substance hydrolysis section of the polysilicon production line, and after the waste washing effluent is hydrolyzed with the high-boiling substance in the high-boiling substance hydrolysis section, hydrolyzed recycled wastewater is generated;

[0013] The high-boiling substance includes trichlorosilane;

[0014] Step S4, neutralizing the hydrolyzed recycled wastewater;

[0015] Step S5, separating to generate a precipitate and a supernatant;

[0016] Step S6, sending the supernatant obtained after the separation in step S5 to a calcium chloride evaporation system for concentration.

[0017] In some embodiments of the present application, step S1 includes the following steps:

[0018] Step S11, collecting acidic wastewater generated by the polysilicon production line;

[0019] Step S12, neutralizing the acidic wastewater collected in step S11 with alkali;

[0020] Step S13, separating to generate a precipitate and a supernatant;

[0021] Step S14, pressure filtering the precipitate obtained after the separation in step S13 to collect a pressure filtrate, and the neutralized recycled wastewater includes the pressure filtrate.

[0022] In some embodiments of the present application, step S12 includes the following steps:

[0023] First, the acidic wastewater in the acid pool is introduced into the fourth-stage neutralization pool, and then liquid alkali is added for neutralization before the acidic wastewater generates a precipitate due to standing.

[0024] In some embodiments of the present application, the liquid alkali includes a reduced magnetic ring cleaning alkali solution.

[0025] In some embodiments of the present application, step S13 includes the following steps:

[0026] The neutralized acidic wastewater of step S12 is sent to the inclined plate sedimentation tank for separation, to produce sediment and supernatant, and the sediment in the inclined plate sedimentation tank is discharged to the sludge tank.

[0027] In some embodiments of the present application, step S6 comprises the following steps:

[0028] The supernatant in the inclined plate sedimentation tank is buffered by the filter press water tank and then enters the calcium chloride evaporation system for concentration.

[0029] In some embodiments of the present application, step S14 comprises the following steps:

[0030] After the sediment in the sludge tank is sent to the filter press for filter pressing, filter pressing liquid is collected, and the filter pressing liquid is sent to the reuse water tank, and the neutral reuse wastewater comprises the filter pressing liquid in the reuse water tank.

[0031] In some embodiments of the present application, step S4 comprises the following steps:

[0032] Step S41, collecting hydrolysis reuse wastewater;

[0033] Step S42, first introducing the collected hydrolysis reuse wastewater into the fourth-stage neutralization tank, and then adding liquid caustic soda to the hydrolysis reuse wastewater for neutralization.

[0034] In some embodiments of the present application, step S5 comprises the following steps:

[0035] The neutralized hydrolysis reuse wastewater of step S42 is sent to the inclined plate sedimentation tank for separation, to produce sediment and supernatant, the sediment in the inclined plate sedimentation tank is discharged to the sludge tank, and the supernatant in the inclined plate sedimentation tank is buffered by the filter press water tank and then enters the calcium chloride evaporation system for concentration.

[0036] In a second aspect, the present application provides a system for removing sulfate radicals in polysilicon acidic production wastewater, which can mainly comprise, which are connected in sequence: a reuse water tank, a waste gas leaching section, a high-boiling hydrolysis section, an acid water tank, a fourth-stage neutralization tank, an inclined plate sedimentation tank, a filter press water tank, and a calcium chloride evaporation system; wherein:

[0037] The reuse water tank is used for introducing neutralized acidic wastewater;

[0038] The waste gas leaching section produces waste leaching effluent;

[0039] The high-boiling hydrolysis section produces hydrolysis reuse wastewater;

[0040] The acid water tank is used for introducing the acidic wastewater and the hydrolysis reuse wastewater;

[0041] The sludge tank is connected with a pressure filter, and the water outlet of the pressure filter is connected with the inlet of the reuse water tank.

[0042] The embodiments of the present application have at least the following advantages or beneficial effects:

[0043] I. The high-boiling substance produced by the polysilicon production line is subjected to hydrolysis reaction with the neutralized acidic wastewater, which can hydrolyze the high-boiling substance and reduce the sulfate in the neutralized acidic wastewater; the hydrolysis reaction of the neutralized acidic wastewater with the high-boiling substance produces hydrolysis reuse wastewater, and the removal rate of sulfate in the hydrolysis reuse wastewater can reach 99%, thereby reducing the sulfate content of the water entering the calcium chloride evaporation system, alleviating the scaling phenomenon in the calcium chloride evaporation system, and prolonging the cleaning cycle of the calcium chloride evaporation system.

[0044] II. The neutralized acidic wastewater is subjected to neutralization treatment to obtain neutral reuse wastewater, which can effectively remove the sulfate in the acidic wastewater and facilitate the hydrolysis reaction with the high-boiling substance, thereby further removing the sulfate in the acidic wastewater.

[0045] III. The neutral reuse wastewater is subjected to the exhaust gas washing section and then the high-boiling substance hydrolysis section, which has the advantages that, on the one hand, the hydrolysis reuse wastewater entering the acid water tank does not contain or basically does not contain sulfate, and on the other hand, there is no need to separately remove the sulfate in the exhaust washing effluent.

[0046] Other features and advantages of the present application will be described in the following description, and some will become apparent from the description, or will be understood by those skilled in the art from the description, or will be understood by those skilled in the art through implementation of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0048] Figure 1 Schematic diagram of a system for removing sulfate in polysilicon acidic production wastewater;

[0049] Figure 2 Flowchart of a method for removing sulfate in polysilicon acidic production wastewater;

[0050] Figure 3 Schematic diagram of test results of sulfate content of an acidic wastewater sample and mixed sulfate content;

[0051] Figure 4The test results of the sulfate content and the pH value are shown in the following diagrams. DETAILED DESCRIPTION

[0052] In the following, only certain exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the embodiments of the present application.

[0053] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0054] Embodiment 1

[0055] Referring to Figure 1 The embodiment provides a system for removing sulfate in acidic production wastewater of polysilicon, which mainly comprises a reuse water tank, a waste gas washing section, a high-boiling hydrolysis section, an acid water tank, a four-stage neutralization tank, an inclined plate sedimentation tank, a filter press water tank and a calcium chloride evaporation system connected in sequence.

[0056] The reuse water tank is used for guiding in the neutralized acidic wastewater.

[0057] The waste gas washing section receives the exhaust gas of normal operation of the whole plant (a polysilicon production enterprise), the exhaust gas containing silicon powder and the safety valve discharge gas. The above exhaust gas contains chlorosilane, hydrogen chloride, hydrogen and nitrogen, etc. The chlorosilane and hydrogen chloride cannot be discharged into the atmosphere. The waste gas washing section uses the characteristics that the chlorosilane and hydrogen chloride are easily soluble in water to absorb the chlorosilane and hydrogen chloride in the above exhaust gas by using a three-stage washing method. The washing water source is the neutralized acidic wastewater. The above exhaust gas is washed and absorbed to generate waste washing effluent. Only nitrogen and hydrogen are left in the exhaust gas, which can be discharged after reaching the standard.

[0058] The high-boiling hydrolysis section generates hydrolysis reuse wastewater. The drainage outlet of the high-boiling hydrolysis section is connected with the water inlet of the acid water tank.

[0059] The acid water tank is used for guiding in the acidic wastewater and the hydrolysis reuse wastewater.

[0060] The four-stage neutralization tank is neutralized by adding alkali.

[0061] The inclined plate sedimentation tank plays a separation role.

[0062] The sewage outlet of the four-stage neutralization tank and the inclined plate sedimentation tank is connected with a sludge tank. The outlet of the sludge tank is connected with a filter press. The drainage outlet of the filter press is connected with the inlet of the reuse water tank.

[0063] Embodiment 2

[0064] Referring to Figures 1 to 4 The embodiment provides a method for removing sulfate in acidic production wastewater of polysilicon, which mainly comprises the following steps:

[0065] Step S1, neutralizing the acidic wastewater to obtain neutralized recycled wastewater.

[0066] Step S2, sending the neutralized recycled wastewater to the exhaust gas washing section of the polysilicon production line to produce exhaust gas washing effluent.

[0067] Step S3, sending the exhaust gas washing effluent to the high-boiling substance hydrolysis section of the polysilicon production line, and after the exhaust gas washing effluent is hydrolyzed with the high-boiling substance in the high-boiling substance hydrolysis section, hydrolyzed recycled wastewater is produced.

[0068] The high-boiling substance includes trichlorosilane, silicon tetrachloride, and dichlorodisilane.

[0069] Step S4, neutralizing the hydrolyzed recycled wastewater.

[0070] Step S5, separating to produce a precipitate and supernatant.

[0071] Step S6, sending the supernatant obtained after the separation in Step S5 to a calcium chloride evaporation system for concentration.

[0072] In one specific implementation scenario, Step S1 can mainly include the following steps:

[0073] Step S11, collecting acidic wastewater produced by the polysilicon production line;

[0074] Specifically, the acidic wastewater produced by the polysilicon production line is collected into an acid pool.

[0075] Step S12, neutralizing the acidic wastewater collected in Step S11 with alkali;

[0076] Specifically, Step S12 can mainly include the following steps:

[0077] First, the acidic wastewater in the acid pool is introduced into a fourth-stage neutralization pool, and then liquid alkali is added for neutralization before the acidic wastewater is precipitated due to standing;

[0078] More specifically, the liquid alkali includes a reduced magnetic ring cleaning alkali. In the polysilicon production process, a reusable magnetic ring with a small amount of silicon material attached is produced. The magnetic ring is used to fix the polysilicon rod, and the magnetic ring needs to be cleaned with a cleaning solution when it is reused to remove the attached silicon material. The cleaning solution uses a sodium hydroxide solution (sodium hydroxide is dissolved and heated to 80°C), and the magnetic ring is soaked in the sodium hydroxide solution for cleaning. The cleaning solution needs to be replaced every day. Since the waste alkali produced after the cleaning solution is used does not contain sulfate, it can be used as the liquid alkali of the present embodiment to turn waste into treasure.

[0079] Step S13, separating to produce a precipitate and supernatant.

[0080] Specifically, Step S13 can mainly include the following steps:

[0081] The neutralized acidic wastewater of step S12 is sent to the inclined plate sedimentation tank for separation, to produce a sediment and supernatant. The sediment in the inclined plate sedimentation tank is discharged to the sludge tank, and the supernatant in the inclined plate sedimentation tank is buffered by the filter water tank and then enters the calcium chloride evaporation system for concentration.

[0082] Step S14, the sediment separated in step S13 is subjected to filter pressing, to collect a filter pressing liquid. The neutralized recycled wastewater includes the filter pressing liquid.

[0083] Specifically, step S14 can mainly include the following steps:

[0084] The sediment in the sludge tank is subjected to filter pressing by the filter press, to collect a filter pressing liquid. The neutralized recycled wastewater includes the filter pressing liquid in the recycled water tank.

[0085] In one specific implementation scenario, step S4 can mainly include the following steps:

[0086] Step S41, hydrolysis recycled wastewater is collected.

[0087] Specifically, the hydrolysis recycled wastewater is collected in the acid water tank.

[0088] Step S42, the hydrolysis recycled wastewater is subjected to alkali neutralization.

[0089] Specifically, step S42 can mainly include the following steps:

[0090] The hydrolysis recycled wastewater in the acid water tank is first introduced into the fourth-stage neutralization tank, and then liquid caustic is added to the hydrolysis recycled wastewater for neutralization. Colloidal impurities exist in the neutralized hydrolysis recycled wastewater.

[0091] In one specific implementation scenario, step S5 can mainly include the following steps:

[0092] The neutralized hydrolysis recycled wastewater is sent to the inclined plate sedimentation tank. A PAM flocculant is added at the water inlet of the inclined plate sedimentation tank, to increase the specific gravity of the colloidal impurities. Under the action of gravity, the colloidal impurities are separated into a sediment and a supernatant. The sediment in the inclined plate sedimentation tank is discharged to the sludge tank, and the supernatant in the inclined plate sedimentation tank is buffered by the filter water tank and then enters the calcium chloride evaporation system for concentration.

[0093] In combination with the above, the present embodiment has at least the following beneficial effects:

[0094] I. In this embodiment, high-boiling-point substances generated from the polysilicon production line are hydrolyzed with neutralized acidic wastewater (the high-boiling-point substances hydrolyze with water to generate substances such as hydrogen chloride and silicic acid). This not only hydrolyzes the high-boiling-point substances but also reduces sulfate ions in the neutralized acidic wastewater. The hydrolysis of the neutralized acidic wastewater with the high-boiling-point substances produces hydrolyzed recycled wastewater, which has a sulfate removal rate of up to 99%. This reduces the sulfate content in the influent of the calcium chloride evaporation system, alleviates scaling in the calcium chloride evaporation system, and extends the cleaning cycle of the calcium chloride evaporation system. To verify the above effects, the inventors conducted the following three sets of comparative experiments:

[0095] Group 1: Prepare acidic wastewater samples with sulfate content of 500-600 mg / L. Take 50 mL of acidic wastewater sample and 0.5 mL of trichlorosilane liquid and mix them in an Erlenmeyer flask.

[0096] Experimental phenomena: A distinct white solid precipitated out, accompanied by the emission of white smoke;

[0097] The sulfate content of the acidic wastewater sample and the sulfate content after mixing are as follows: Figure 3 As shown.

[0098] Group 2: Prepare acidic wastewater samples with sulfate content of 500-600 mg / L. Take 50 mL of acidic wastewater sample and mix it with 0.5 mL of silicon tetrachloride liquid in an Erlenmeyer flask.

[0099] Experimental phenomena: A small amount of white solid precipitated out, accompanied by a trace of white smoke.

[0100] The sulfate content of the acidic wastewater sample and the sulfate content after mixing are as follows: Figure 3 As shown.

[0101] Group 3: Prepare acidic wastewater samples with sulfate content of 500-600 mg / L. Take 50 mL of acidic wastewater sample and 0.5 mL of high-boiling liquid and mix them in an Erlenmeyer flask.

[0102] Experimental phenomena: A large amount of white solid precipitated out, and a slight cracking sound and a large amount of thick white smoke were heard coming out of the conical flask;

[0103] The sulfate content of the acidic wastewater sample and the sulfate content after mixing are as follows: Figure 3 As shown.

[0104] Based on the above experimental phenomena and such Figure 3 The test results of sulfate content show that tetrasilicon (silicon tetrachloride) is relatively stable and has little effect on the change of sulfate content in acidic wastewater samples; high-boiling substances containing trisilicon (trichlorosilane) and other impurities have a very significant effect on sulfate content in acidic wastewater samples, with a removal rate of up to 99%.

[0105] II. The neutralized wastewater has the advantages of removing sulfate in the acidic wastewater and facilitating the hydrolysis reaction with high-boiling substances.

[0106] III. Compared with the neutralization by adding lime, the neutralization by adding liquid alkali does not bring in sulfate, thereby reducing the sulfate content of the water entering the calcium chloride evaporation system, alleviating the scaling in the calcium chloride evaporation system, and prolonging the cleaning cycle of the calcium chloride evaporation system.

[0107] IV. The reduced magnetic ring cleaning alkali solution is used as the liquid alkali required in the embodiment, which is helpful for recycling the reduced magnetic ring cleaning alkali solution.

[0108] V. The neutralized wastewater is first subjected to the exhaust gas washing section and then subjected to the high-boiling substance hydrolysis section. The reason for this arrangement is that the neutralized wastewater cannot effectively remove the sulfate in the neutralized wastewater after being subjected to the exhaust gas washing section, and the sulfate in the waste washing effluent generated in the exhaust gas washing section also needs to be removed. Therefore, the neutralized wastewater is first subjected to the exhaust gas washing section and then subjected to the high-boiling substance hydrolysis section, which can make the acid water tank not contain or basically not contain sulfate, and does not need to separately treat the waste washing effluent to remove the sulfate in the waste washing effluent, thereby reducing the load of the corresponding treatment equipment.

[0109] VI. The supernatant in the inclined plate sedimentation tank is buffered in the filter press water tank and then enters the calcium chloride evaporation system for concentration, which can effectively adjust the water amount entering the calcium chloride evaporation system and make the calcium chloride evaporation system run stably.

[0110] VII. The neutralization by adding liquid alkali to the acidic wastewater without precipitation reduces the sulfate ions decomposed from the solid substances in the acidic wastewater. In order to verify the above effect, the inventors conducted the following three groups of comparison experiments:

[0111] 1st group: The supernatant of the precipitated acidic wastewater was taken as a blank sample to measure the sulfate content and PH value. The results are shown in Table 1. Figure 4

[0112] 2nd group: Liquid alkali was added to the supernatant in the 1st group to adjust the PH to neutral, and the supernatant was measured for the sulfate content and PH value. The results are shown in Table 2. Figure 4

[0113] 3rd group: Liquid alkali was added to the acidic wastewater without precipitation to adjust the PH to neutral, and the supernatant was measured for the sulfate content and PH value. The results are shown in Table 3. Figure 4

[0114] The analysis is shown in Table 4. Figure 4 ​​​The test results of the sulfate content and the pH value show that the sulfate removal rate of the supernatant of the acid wastewater in the first group after precipitation and pH adjustment by adding liquid alkali can reach 74.3%; the sulfate removal rate of the supernatant of the acid wastewater in the second group after precipitation and pH adjustment by adding liquid alkali can reach 75.7%. It can be seen that by using the method of directly adding alkali to neutralize the acid wastewater without precipitation, the solid substances in the acid wastewater are not easy to decompose sulfate in the alkaline environment, that is, the sulfate ions decomposed from the solid substances in the acid wastewater are reduced.

[0115] Eight, in the present embodiment, the hydrolysis of the reuse of wastewater and acid wastewater are treated by the same acid water pool, four-stage neutralization tank and inclined plate sedimentation tank, which is conducive to reducing the equipment investment cost.

[0116] Finally, it should be noted that: the above is only the preferred embodiments of the present application, and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes, and the embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other without conflict. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for removing sulfate from polysilicon acidic production wastewater, characterized in that, The method comprises the following steps: Step S1, neutralizing the acidic wastewater to obtain neutralized recycled wastewater; Step S2, sending the neutralized recycled wastewater to the exhaust gas washing section of the polysilicon production line to generate exhaust gas washing effluent; Step S3, sending the exhaust gas washing effluent to the high-boiling substance hydrolysis section of the polysilicon production line, and after the exhaust gas washing effluent is hydrolyzed with the high-boiling substance in the high-boiling substance hydrolysis section, hydrolyzed recycled wastewater is generated; The high-boiling substance comprises trichlorosilane; Step S4, neutralizing the hydrolyzed recycled wastewater; Step S5, separating to generate precipitate and supernatant; Step S6, sending the supernatant obtained after the separation in step S5 to the calcium chloride evaporation system for concentration; Step S1 comprises the following steps: Step S11, collecting the acidic wastewater generated in the polysilicon production line; Step S12, neutralizing the acidic wastewater collected in step S11 by adding alkali: first, the acidic wastewater in the acid water tank is introduced into the fourth-stage neutralization tank, and then liquid alkali is added for neutralization before the acidic wastewater is precipitated due to standing; the liquid alkali comprises reduced magnetic ring cleaning alkali; Step S13, separating to generate precipitate and supernatant; Step S14, filtering the precipitate obtained after the separation in step S13 to collect the filter liquor, and the neutralized recycled wastewater comprises the filter liquor.

2. The method for removing sulfate radicals in polysilicon acidic production wastewater according to claim 1, characterized in that, Step S13 comprises the following steps: The acidic wastewater after neutralization in step S12 is sent to the inclined plate sedimentation tank for separation to generate precipitate and supernatant, and the precipitate in the inclined plate sedimentation tank is discharged to the sludge tank.

3. The method for removing sulfate radicals in polysilicon acidic production wastewater according to claim 2, characterized in that, Step S6 comprises the following steps: The supernatant in the inclined plate sedimentation tank is buffered by the filter water tank and then introduced into the calcium chloride evaporation system for concentration.

4. The method for removing sulfate radicals in polysilicon acidic production wastewater according to claim 2, characterized in that, Step S14 comprises the following steps: After the precipitate in the sludge tank is filtered by the filter press, the filter liquor is collected, and the filter liquor is sent to the recycled water tank, and the neutralized recycled wastewater comprises the filter liquor in the recycled water tank.

5. The method for removing sulfate radicals in polysilicon acidic production wastewater according to claim 1, characterized in that, Step S4 comprises the following steps: Step S41, collecting the hydrolyzed recycled wastewater; Step S42, first introducing the collected hydrolyzed recycled wastewater into the fourth-stage neutralization tank, and then adding liquid alkali to the hydrolyzed recycled wastewater for neutralization.

6. The method for removing sulfate radicals in polysilicon acidic production wastewater according to claim 5, characterized in that, Step S5 comprises the following steps: The hydrolyzed recycled wastewater after neutralization in step S42 is sent to the inclined plate sedimentation tank for separation to generate precipitate and supernatant, the precipitate in the inclined plate sedimentation tank is discharged to the sludge tank, and the supernatant in the inclined plate sedimentation tank is buffered by the filter water tank and then introduced into the calcium chloride evaporation system for concentration.

7. A system for removing sulfate from polysilicon acidic production wastewater, which applies the method for removing sulfate from polysilicon acidic production wastewater according to any one of claims 1 to 6, characterized in that, The system for removing sulfate from acidic polysilicon production wastewater comprises, which are connected in sequence: a recycled water tank, an exhaust gas washing section, a high-boiling substance hydrolysis section, an acid water tank, a fourth-stage neutralization tank, an inclined plate sedimentation tank, a filter water tank, and a calcium chloride evaporation system; wherein: The recycled water tank is used to introduce the neutralized acidic wastewater; The exhaust gas washing section generates exhaust gas washing effluent; The high-boiling substance hydrolysis section generates hydrolyzed recycled wastewater; The acid water tank is used to introduce the acidic wastewater and the hydrolyzed recycled wastewater; The outlet of the sludge tank is connected with the filter press, and the drain port of the filter press is connected with the inlet of the recycled water tank.

Images