A method for treating wastewater in the whole process of tungsten wire sawing silicon wafer

Abstract

The application discloses a kind of for tungsten wire wire cutting silicon wafer full-process wastewater treatment method, including cutting fluid wastewater into wastewater conditioning tank homogenization after entering anaerobic biological treatment unit, most of organic matter in wastewater is degraded and removed by anaerobic microorganism;Effluent enters fenton processing unit, part of refractory organic matter enters fenton reactor, and under the strong oxidation of hydroxyl radical, chain is broken, and fenton effluent enters comprehensive conditioning tank;At the same time, degumming and wafer cleaning wastewater adopts coagulation sedimentation and high-efficiency dissolved air flotation;Cutting fluid wastewater and degumming and wafer cleaning wastewater after respective pretreatment unit, with domestic wastewater and ROR concentrated water are mixed evenly and enter hydrolysis acidification tank;Finally, further reduce COD by aerobic microbial flora, and effluent is realized stable discharge after air floatation advanced treatment.This application has the advantages of simplifying process flow, saving investment and operating cost, improving wastewater treatment efficiency and effect, and ensuring the smooth discharge of wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cutting large-size silicon wafer wastewater treatment method, and particularly relates to a method for treating wastewater in the whole process of tungsten wire cutting silicon wafer. BACKGROUND

[0002] A large amount of wastewater is generated in the production process of silicon wafer. The COD contained in the cutting wastewater mainly comes from the cutting waste liquid generated in the cutting process of the cutting machine. The waste liquid has high COD and is difficult to be biodegraded. The SS concentration and the organic matter concentration in the post-debinding and wafer discharging wastewater are high. After the cutting waste water, the debinding waste water and the domestic wastewater, i.e. ROR concentrated water, are mixed, there are still some refractory organic matters. The general wastewater treatment device has great treatment difficulty and poor treatment effect, which is not conducive to the standard discharge of the wastewater in the whole process. SUMMARY

[0003] The present application aims to solve the problems of great treatment difficulty and poor treatment effect of the wastewater in the whole process of the existing silicon wafer production, and provides a method for treating wastewater in the whole process of tungsten wire cutting silicon wafer. The method simplifies the process flow, rationally arranges the equipment, has compact structure, reduces the floor area, saves investment and operation cost, improves the wastewater treatment efficiency and effect in the whole process, and ensures the smooth standard discharge of the wastewater.

[0004] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0005] A method for treating wastewater in the whole process of tungsten wire cutting silicon wafer, and the specific steps are as follows, comprising:

[0006] (1) Pretreatment: the cutting liquid wastewater enters the wastewater conditioning tank for homogenization, and then enters the anaerobic biological treatment unit. Most of the organic matters in the wastewater are removed by anaerobic microorganisms, and the COD content is reduced;

[0007] (2) Fenton treatment: the effluent enters the Fenton treatment unit. According to the change of the inflow COD, the COD is further removed, and the biochemical load is reduced. At the same time, part of the refractory organic matter enters the Fenton reactor, is broken under the strong oxidation of hydroxyl radicals, and the biodegradability of the wastewater is further improved. The Fenton effluent enters the comprehensive conditioning tank;

[0008] (3) Physicochemical treatment: the debinding and wafer discharging cleaning wastewater adopts coagulation sedimentation and high-efficiency dissolved air flotation. By adding reagents to form flocs, most of the SS is precipitated, and a small amount of suspended SS can be further treated by air flotation;

[0009] (4) Hydrolysis acidification: the cutting liquid wastewater and the debinding and wafer discharging cleaning wastewater pass through their respective pretreatment units, are mixed with domestic wastewater and ROR concentrated water, and then enter the hydrolysis acidification tank. Through the microorganism group of the hydrolysis biochemical system, the macromolecular organic matter is broken, and the biodegradability is improved;

[0010] (5) Discharge up to standard: COD is further reduced by aerobic microbial flora, and the effluent is treated by air floatation to achieve stable discharge up to standard.

[0011] Further, in the step (1), the anaerobic biological treatment unit comprises a dosing tank and a UASB anaerobic reactor. The wastewater is first warmed to a suitable temperature in the dosing tank, and after adding nutrients, it is pumped into the UASB anaerobic reactor, where, under the action of the highly active anaerobic sludge, hydrolysis and acidification are completed to produce acetic acid and methane, most of the organic matter in the wastewater is degraded and removed by anaerobic microorganisms, the COD load is greatly reduced, and the effluent COD is greatly reduced.

[0012] Further, in the step (1), the biogas produced by the anaerobic biological treatment unit is introduced into a normal-pressure boiler to recover heat.

[0013] Further, in the step (2), the Fenton process is flexibly started according to the water quality of the incoming water. When the COD of the incoming water is low, the water can be directly discharged to the comprehensive conditioning tank, or the amount of chemicals added can be reduced to save costs.

[0014] Further, in the steps (1) and (2), an accident tank and a small air floatation device can be additionally provided in the cutting fluid wastewater pretreatment unit to prevent high SS caused by abnormal large circulation of the cutting fluid in front. When the SS of the incoming water is high, the turbidimeter is set to switch to the accident tank, and the SS is reduced by air floatation treatment before the wastewater enters the anaerobic dosing tank for subsequent treatment.

[0015] Further, in the step (3), by adding coagulants and flocculants, the colloids and suspended solids in the wastewater will undergo compressed double-layer action, electric neutralization and adsorption bridge action within a reasonable PH value range. The coagulation and flocculation caused by the three actions become coagulation, and the flocculation after coagulation forms a sludge layer by gravity settling, thereby achieving the purpose of removing SS.

[0016] Further, in the step (3), the particles with a relatively light specific gravity in the water are subjected to solid-liquid separation. Through the reflux pump, the air supplied by the air compressor is mixed with the baffle and the jet device in the dissolved air tank under high pressure, and the air is dissolved in the water. The dissolved air water pressure is suddenly reduced by using the dissolved air water release device, fine bubbles are generated, the flocculation adheres to the small bubbles, and the overall specific gravity is less than water, so as to quickly float to the water surface and form scum, thereby achieving the removal of SS. The clear water flows into the next process, and the scum flows into the scum tank from the scum collection tank.

[0017] Further, in the step (3), the sludge generated by the materialization treatment unit is delivered to the diaphragm plate and frame filter press for maximum volume reduction treatment, and the degummed silica mud has an economic value, so the sludge generated by the Fenton system is treated separately, or mixed with the biochemical sludge for treatment, the biochemical sludge is dewatered by the stacked screw dewaterer, and the sludge cake generated by the system is transported out for comprehensive treatment and utilization.

[0018] In the technical scheme of the present application, different processes are used for treatment according to the characteristics of each type of wastewater, and then unified purification, which not only can realize that each item of the water quality index of the discharged water after treatment meets the discharge standard and the reuse water quality requirement of the construction unit, but also has simple process flow, reasonable equipment arrangement, compact structure, small land occupation, low investment and operation cost, in addition, convenient operation and management, simple technical requirement, maximum degree of automation control, and improved wastewater purification efficiency and treatment effect. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A flow chart of the method for treating the whole-process wastewater of tung wire cutting silicon wafer is provided.

[0020] Figure 2 A detailed flow chart of the method for treating the whole-process wastewater of tung wire cutting silicon wafer is provided. EMBODIMENT

[0021] EMBODIMENT

[0022] In order to make the present application clearer, the following further describes a method for treating the whole-process wastewater of tung wire cutting silicon wafer in combination with the drawings, and the specific embodiments described herein are only used to explain the present application, and do not limit the present application.

[0023] Referring to Figure 1 and Figure 2 A method for treating the whole-process wastewater of tung wire cutting silicon wafer, and the specific steps are as follows, characterized in that:

[0024] (I) cutting liquid wastewater pretreatment: the cutting liquid wastewater enters the wastewater conditioning tank for homogenization, and then enters the anaerobic biological treatment unit, most of the organic matters in the wastewater are degraded and removed by anaerobic microorganisms, and the COD content is reduced, as follows:

[0025] Anaerobic: the anaerobic biological treatment unit includes a dosing tank and a UASB anaerobic reactor, the wastewater is first warmed to a suitable temperature in the dosing tank, and after adding nutrient salt, it is pumped into the UASB anaerobic reactor, under the action of the high-efficiency active anaerobic sludge, hydrolysis and acidification are completed to produce acetic acid and methane, most of the organic matters in the wastewater are degraded and removed by anaerobic microorganisms, the COD load is greatly reduced, the effluent COD is greatly reduced, and the biogas generated by the anaerobic biological treatment unit enters the atmospheric pressure boiler to recover heat.

[0026] Fenton: effluent into Fenton treatment unit, according to the change of incoming water COD, further remove COD, for biochemical reduction, while part of the refractory organic matter into Fenton reactor, under the strong oxidation of hydroxyl radical, broken chain, further improve the biodegradability of wastewater, Fenton process according to the water quality of the incoming water, when the COD of the incoming water is low, it can be directly discharged to the comprehensive conditioning tank, or the amount of chemicals can be reduced to save cost, and the Fenton effluent enters the comprehensive conditioning tank.

[0027] In addition, in this embodiment, an accident pool and a small air floatation are also added in the cutting fluid wastewater pretreatment unit to prevent high SS caused by abnormal large circulation of the front cutting fluid. When the SS of the incoming water is high, the turbidimeter is set to switch to the accident pool, and after the SS is reduced by air floatation, it enters the anaerobic dosing tank for subsequent treatment.

[0028] (2) degumming wastewater physical and chemical treatment: degumming and piece cleaning wastewater adopts coagulation sedimentation and high-efficiency dissolved air floatation. By adding coagulant and flocculant, the colloidal and suspended substances in the wastewater will have compression double-layer effect, electric neutralization effect and adsorption bridge effect within a reasonable PH value range. The coagulation and flocculation caused by the three effects become coagulation. After coagulation, the flocs form a sludge layer by their own gravity, so as to remove SS.

[0029] In coagulation sedimentation, by adding coagulant and flocculant, the colloidal and suspended substances in the wastewater will have compression double-layer effect, electric neutralization effect and adsorption bridge effect within a reasonable PH value range. The coagulation and flocculation caused by the three effects become coagulation. After coagulation, the flocs form a sludge layer by their own gravity, so as to remove SS.

[0030] In high-efficiency dissolved air floatation, the particles with lower specific gravity in water are separated from the water. Through the reflux pump, the air supplied by the air compressor is mixed in the dissolved air tank through the baffle and the jet device. Under high pressure, the air is dissolved in water. The dissolved air water pressure is suddenly reduced by the dissolved air water release device, generating fine bubbles. The flocs adhere to the small bubbles, causing the overall specific gravity to be less than water, and quickly floating to the water surface to form scum, thereby removing SS. The clear water flows into the next process, and the scum flows into the scum tank from the scum collection tank.

[0031] In addition, in this embodiment, the sludge generated by the physical and chemical treatment unit is transported to the diaphragm plate and frame filter press for maximum volume reduction treatment. Considering the economic value of the degumming silicon mud, the Fenton system sludge is treated separately, or mixed with the biochemical sludge for treatment. The biochemical sludge is dewatered by the stacked screw dewaterer, and the sludge cake generated by the system is transported for comprehensive treatment and utilization.

[0032] (Three) biochemical treatment unit: cutting fluid wastewater and degumming and piece cleaning wastewater after the respective pretreatment unit, with domestic wastewater and ROR concentrated water mixed evenly into hydrolysis acidification tank, through the hydrolysis biochemical system microorganism group, the macromolecular organic matter chain is broken, and the biodegradability is improved;

[0033] In addition, the COD is further reduced by aerobic microorganism group, and the effluent is realized stable discharge after deep treatment by air flotation.

[0034] In the embodiment, the treated water quality and removal rate of each step are shown in the following table:

[0035]

[0036] The wastewater treatment process of the application is simple, the equipment is arranged reasonably, the structure is compact, the land occupation is small, the investment and operation cost are saved, and the cutting silicon wafer process wastewater treatment efficiency and treatment effect are improved.

[0037] In addition to the above embodiments, the application can also have other implementation manners. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the application.

Claims

1. A method for treating wastewater from the entire process of tungsten wire cutting silicon wafers, comprising the following specific steps, characterized in that: (1) Pretreatment: The cutting fluid wastewater enters the wastewater equalization tank for homogenization, and then enters the anaerobic biological treatment unit. Most of the organic matter in the wastewater is degraded and removed by anaerobic microorganisms, and the COD content decreases. The biogas generated by the anaerobic biological treatment unit enters the atmospheric pressure boiler to recover heat. (2) Fenton treatment: The effluent enters the Fenton treatment unit, and COD is further removed according to the change of COD in the influent, which reduces the burden on the biochemical process. At the same time, some recalcitrant organic matter enters the Fenton reactor, where it is broken down and its chains are broken under the strong oxidation of hydroxyl radicals. The Fenton effluent enters the comprehensive conditioning tank. The Fenton process can be flexibly started according to the quality of the influent. When the COD of the influent is low, it can be directly discharged to the comprehensive conditioning tank or the dosage can be reduced. (3) Physical and chemical treatment: The wastewater from degumming and sheet washing is treated by coagulation sedimentation and high-efficiency dissolved air flotation. Most of the suspended solids (SS) are settled by adding chemicals to form flocs. The small amount of suspended SS can be further treated by air flotation. (4) Hydrolysis and acidification: After the cutting fluid wastewater and degumming and sheet cleaning wastewater have passed through their respective pretreatment units, they are mixed evenly with domestic wastewater and ROR concentrate and then enter the hydrolysis and acidification tank. Through the microbial community of the hydrolysis biochemical system, the macromolecular organic matter is broken down. (5) Compliant discharge: COD is further reduced by aerobic microbial community, and the effluent is discharged stably after deep treatment by air flotation.

2. The method for treating wastewater from the entire process of tungsten wire cutting silicon wafers according to claim 1, characterized in that: In step (1), the anaerobic biological treatment unit includes a dosing tank and a UASB anaerobic reactor. The wastewater is first heated to a suitable temperature in the dosing tank, and nutrients are added. Then, it is pumped into the UASB anaerobic reactor. Under the action of its highly efficient activated anaerobic sludge, hydrolysis and acidification to produce acetic acid and methane are completed. Most of the organic matter in the wastewater is degraded and removed by anaerobic microorganisms, and the COD load is greatly reduced, resulting in a significant decrease in effluent COD.

3. The method for treating wastewater from the entire process of tungsten wire cutting silicon wafers according to claim 1 or 2, characterized in that: In steps (1) and (2), an emergency tank and a small air flotation unit can be added to the cutting fluid wastewater pretreatment unit to prevent high SS caused by abnormal large circulation of the cutting fluid. By setting a turbidity meter, when the SS of the incoming water is high, it can be switched to the emergency tank. After the SS is reduced by air flotation treatment, it can be put into the anaerobic dosing tank for subsequent treatment.

4. The method for treating wastewater from the entire process of tungsten wire cutting silicon wafers according to claim 1 or 2, characterized in that: In step (3), by adding coagulant and flocculant, within a reasonable pH range, the colloids and suspended solids in the wastewater will undergo compression double layer effect, charge neutralization effect and adsorption bridging effect with the agent. The coagulation and flocculation caused by the three effects become coagulation. After coagulation, the flocs settle down by their own gravity to form a sludge layer, thereby achieving the purpose of removing SS.

5. The method for treating wastewater from the entire process of tungsten wire cutting silicon wafers according to claim 1 or 2, characterized in that: In step (3), the lighter particles in the water are separated from the water into solid and liquid components. Through the return pump, the air supplied by the air compressor is mixed in the dissolved air tank by the ejector in the dissolved air tank through the baffle and the ejector. Under high pressure, the air is dissolved in the water. Using the dissolved air water release device, the dissolved air water pressure is suddenly reduced, generating microbubbles. The flocs are attached to the small bubbles, causing their overall specific gravity to be less than that of water, and they quickly float to the water surface to form scum, thereby achieving the removal of SS. The clean water flows into the next process, and the scum flows from the scum collection tank into the scum trough.

6. The method for treating wastewater from the entire process of tungsten wire cutting silicon wafers according to claim 1 or 2, characterized in that: In step (3), the sludge produced by the physicochemical treatment unit is transported by a sludge pump to a diaphragm plate and frame filter press to maximize volume reduction treatment. Considering that the degummed silica sludge has economic value for sale, the sludge produced by the Fenton system is treated separately, or it can be mixed with biochemical sludge for treatment. The biochemical sludge is dewatered by a screw press dewatering machine, and the sludge cake produced by the system is transported off-site for comprehensive treatment and utilization.

Images