Process and treatment system for preparing white carbon black by utilizing photovoltaic cell wastewater

Abstract

The invention discloses a process and a treatment system for preparing white carbon black by utilizing photovoltaic cell wastewater, which are characterized in that concentrated alkali wastewater in a concentrated alkali regulating tank and part of concentrated acid wastewater in a concentrated acid regulating tank are mixed in a primary mixing tank, and then a primary gelation reaction is carried out through a primary gelation reactor; the method comprises the following steps: preparing concentrated acid wastewater from concentrated acid wastewater, dehydrating the concentrated acid wastewater by a primary dehydration device to obtain coarse gel particles, dissolving the coarse gel particles in an alkali dissolution tank by liquid alkali, mixing the coarse gel particles with the rest concentrated acid wastewater in a secondary mixing tank, feeding the mixture into a secondary gelation reactor for secondary gelation reaction, and supporting the fine gel particles by a secondary dehydration device to obtain fine gel particles. According to the method disclosed by the invention, the yield of silicon-containing sludge in subsequent fluorine removal is reduced, the purity of calcium fluoride sludge is favorably improved, silicon resources in the concentrated alkali wastewater are recycled, and resourceful treatment of the concentrated alkali wastewater is realized.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a process for preparing white carbon black by utilizing wastewater from photovoltaic cells. Background Art

[0002] In the process of surface texturing in the production of photovoltaic cells, alkaline solutions such as sodium hydroxide and potassium hydroxide are used to soak silicon wafers. The alkaline solution reacts with the surface of the silicon wafer, dissolving some of the surface materials to form pyramid-shaped microstructures. These structures help reduce reflection losses and increase the short-circuit current density of the battery. In this process, a certain amount of high-concentration alkaline wastewater (referred to as concentrated alkaline wastewater) will be produced. The characteristics of this wastewater are strong alkalinity and high concentration of soluble silicon (the concentration of soluble silicon can reach more than 3000mg / L).

[0003] At present, concentrated alkaline wastewater is usually mixed with other wastewaters from photovoltaic enterprises (concentrated acid wastewater, dilute acid wastewater, dilute alkaline wastewater, etc.) for comprehensive treatment, that is, the comprehensive wastewater is neutralized and defluorinated by adding lime solution, etc., to form calcium fluoride sludge that is precipitated and separated from the water, so that the pH and fluoride ions in the water meet the discharge standards. Although concentrated alkaline wastewater plays a role in neutralizing hydrogen ions, due to the large amount of silicon contained in concentrated alkaline wastewater, these soluble silicon will be converted into silica gel sludge under neutral conditions and enter the calcium fluoride sludge, which increases the output of fluoride-containing sludge on the one hand, and greatly reduces the purity of calcium fluoride on the other hand, increasing the difficulty of calcium fluoride reuse; at the same time, it causes a waste of silicon resources in concentrated alkaline wastewater.

[0004] As an important raw material for the production of chemical products, precipitated silica has a wide range of applications:

[0005] (1) Rubber industry: It can be used as a reinforcing agent for rubber to improve its mechanical properties and wear resistance;

[0006] (2) Coatings industry: It can be used as a filler for coatings to improve the leveling, anti-settling and weather resistance of coatings;

[0007] (3) Ceramic industry: Precipitated silica can be used to prepare ceramic materials and improve the density and mechanical properties of ceramics;

[0008] (4) Food industry: Precipitated silica can be used as a food additive to make candies, chocolates and other foods to improve the taste and texture of food. At present, the demand and output of precipitated silica are gradually increasing. Summary of the invention

[0009] In order to overcome the above-mentioned defects, the present invention provides a process for preparing white carbon black using photovoltaic cell wastewater. The process for preparing white carbon black using photovoltaic cell wastewater achieves effective recovery of silicon resources in concentrated alkaline wastewater and prepares a white carbon black product with high utilization value.

[0010] The technical solution adopted by the present invention to solve the technical problem is: a process for preparing white carbon black using photovoltaic cell wastewater, comprising the following steps:

[0011] Step 1: Send concentrated alkaline wastewater and part of concentrated acid wastewater into a primary mixing tank for mixing, and control the pH of the mixed wastewater in the primary mixing tank to be between 5.0 and 9.0;

[0012] Step 2: Send the mixed wastewater in the primary mixing tank into a primary gelling reactor for a gelling reaction. After the concentrated alkaline wastewater and the concentrated acid wastewater are combined, a gelling reaction will automatically occur to form a gel precipitate;

[0013] Step 3: the effluent from the primary gelation reactor enters a primary dehydration device to separate the coarse gel particles formed by the primary gelation reaction from the wastewater;

[0014] Step 4: putting the dehydrated coarse gel particles into an alkali dissolving tank, and adding liquid alkali into the alkali dissolving tank to dissolve the coarse gel particles;

[0015] Step 5: The effluent from the alkali dissolution tank is discharged into the secondary mixing tank, and part of the concentrated acid wastewater is discharged into the secondary mixing tank, and the pH of the mixed wastewater in the secondary mixing tank is controlled between 5.5-8.0;

[0016] Step 6: The effluent from the secondary mixing tank enters the secondary gelation reactor for secondary gelation reaction;

[0017] Step 7: The effluent from the secondary gelation reactor enters the secondary dehydration device to separate the fine gel particles formed by the secondary gelation reaction from the wastewater;

[0018] Step 8: Drying the fine gel particles formed by the secondary gel reaction using a drying device;

[0019] Step nine: crushing the dried gel particles with crushing equipment, and the crushed particles form white carbon black products.

[0020] After the concentrated alkaline wastewater and the concentrated acid wastewater are mixed in the primary mixing tank, a gelation reaction is carried out in the primary gelation reactor to form large coarse gel particles. The gelation reaction is to recover silicon from the concentrated alkaline wastewater through the gelation reaction. The coarse gel particles are then dissolved with a small amount of liquid alkali, mixed with the concentrated acid wastewater in the secondary mixing tank, and then enter the secondary gelation reactor for a secondary gelation reaction. The secondary gelation reaction generates small fine gel particles. At this time, the silicon content in the fine gel particles is much higher than that in the concentrated alkaline wastewater. The fine gel particles are dried to remove excess water. After separation, since some particles will agglomerate together, the dried gel is crushed by crushing equipment to finally obtain a more uniform fine particle product, which is the white carbon black product. Furthermore, the silicon in the concentrated alkaline wastewater generated in the production process of photovoltaic cells is removed, and the output of silicon-containing sludge in subsequent fluorine removal is reduced, which is helpful to improve the purity of calcium fluoride sludge. In addition, the photovoltaic concentrated acid wastewater is fully utilized, the silicon resources in the concentrated alkaline wastewater are recovered, and a white carbon black product with high utilization value is prepared, which effectively realizes the resource treatment of photovoltaic cell production wastewater.

[0021] As a further improvement of the present invention, in the step one, the concentrated alkali wastewater discharged from the photovoltaic cell production line is first discharged into the concentrated alkali regulating tank, and the discharged concentrated acid wastewater is discharged into the concentrated acid regulating tank, and then the concentrated alkali wastewater in the concentrated alkali regulating tank is sent to the primary mixing tank at a certain flow rate, and at the same time, the concentrated acid wastewater in the concentrated acid regulating tank is sent to the primary mixing tank at a certain flow rate ratio, the concentrated acid wastewater flow rate is controlled according to the pH value of the mixed wastewater in the primary mixing tank, and the mixing time of the concentrated alkali wastewater and the concentrated acid wastewater in the primary mixing tank is controlled to be between 10-60min; in step five, the concentrated acid wastewater in the concentrated acid regulating tank is sent to the secondary mixing tank at a certain flow rate ratio, the concentrated acid wastewater flow rate is controlled according to the pH value of the mixed wastewater in the secondary mixing tank, and the mixing time of the effluent from the alkali dissolution tank and the concentrated acid wastewater in the secondary mixing tank is controlled to be between 1-30min.

[0022] As a further improvement of the present invention, the wastewater mixed in the primary mixing tank enters the primary gelation reactor for a primary gelation reaction time of 0.5-20 hours, and the wastewater mixed in the secondary mixing tank enters the secondary gelation reactor for a secondary gelation reaction time of 0.5-10 hours.

[0023] As a further improvement of the present invention, the primary dehydration device and the secondary dehydration device are filter presses, screw dehydrators or centrifuges, and the moisture content of the coarse gel particles after primary dehydration is below 92%, and the moisture content of the fine gel particles after secondary dehydration is below 90%.

[0024] As a further improvement of the present invention, in step 4, the amount of liquid alkali added is 10%-40% of the total acid content of the concentrated acid wastewater, and the dissolution time is 1-20 hours.

[0025] As a further improvement of the present invention, the gel particles dehydrated in step seven are put into a cleaning tank, clean water is added for cleaning, and the cleaned gel particles are then dried by drying equipment. By cleaning the fine gel particles with clean water and removing residual waste water adhering to the surface of the fine gel particles, the quality of the white carbon black product is improved.

[0026] As a further improvement of the present invention, the gel particles dehydrated in step seven are washed in the washing tank for 5-30 minutes, and the amount of clean water used for washing is 5-20 times the amount of the gel particles. The amount of clean water and the washing time can be selected according to actual conditions.

[0027] As a further improvement of the present invention, in step eight, the temperature of the drying equipment is controlled at 105-150° C., and the moisture content of the gel particles after drying is controlled to be below 5%.

[0028] As a further improvement of the present invention, the effluent from the primary dehydration device, the secondary dehydration device and the cleaning tank is collected and discharged into the comprehensive regulating tank of the photovoltaic wastewater treatment plant for subsequent comprehensive treatment to meet standards.

[0029] A treatment system for preparing white carbon black material by using concentrated alkaline wastewater produced by photovoltaic cells, comprising a concentrated acid regulating tank, a concentrated alkali regulating tank, a primary mixing tank, a secondary mixing tank, a primary gelling reactor, a secondary gelling reactor, a primary dehydration device, a secondary dehydration device, an alkali dissolving tank, a cleaning tank, a drying device, a crushing device, a comprehensive regulating tank and a plurality of lifting pumps, wherein the concentrated acid regulating tank and the concentrated alkali regulating tank can respectively hold concentrated acid wastewater and concentrated alkali wastewater discharged from a photovoltaic cell production line, the concentrated alkali regulating tank is connected to the primary mixing tank through a pipeline, the concentrated acid regulating tank is connected to the primary mixing tank and the secondary mixing tank through pipelines, the concentrated alkali wastewater in the concentrated alkali regulating tank is discharged into the primary mixing tank at a set flow rate through the lifting pump, the concentrated acid wastewater in the concentrated acid regulating tank is respectively discharged into the primary mixing tank and the secondary mixing tank at a set flow rate through the lifting pump, the primary mixing tank is connected to the primary gelling tank through a pipeline The first and second dehydration devices are connected to the water inlet of the first dehydration device and the second dehydration device through a pipeline. The first and second gelation reactors can make the mixed wastewater therein undergo gelation reaction. The water outlets of the first and second gelation reactors are respectively connected to the water inlets of the first dehydration device and the second dehydration device. The first and second dehydration devices can separate the gel particles therein from the wastewater. The gel particle discharge outlet of the first dehydration device is connected to the alkali dissolution tank, and the gel particle discharge outlet of the second dehydration device is connected to the cleaning tank. The drainage outlets of the cleaning tank, the first dehydration device and the second dehydration device are all connected to the water inlet of the comprehensive regulating tank. The drying equipment can dry the gel particles washed in the cleaning tank, and the crushing equipment can crush the gel particles dried by the drying equipment to form white carbon black products.

[0030] The alkali dissolving tank is preferably provided with a liquid alkali dosing device, which can automatically and quantitatively dosing liquid alkali into the alkali dissolving tank, and of course, liquid alkali can also be added manually. It is best to set a stirrer in the primary gel reactor and the secondary gel reactor to stir the mixed wastewater therein, so that the concentrated acid wastewater and the concentrated alkali wastewater are fully mixed for gelation reaction. A stirrer can also be set in the primary mixing tank and the secondary mixing tank to stir, so that the wastewater is quickly mixed, and it is best to also set a pH detection device in the primary mixing tank and the secondary mixing tank, and the pH detection device detects the pH of the wastewater in the primary mixing tank and the secondary mixing tank in real time. At the same time, it is best to set an acidity meter in the concentrated acid regulating tank, and the acidity of the concentrated acid wastewater in the concentrated acid regulating tank is detected by the acidity meter. The pH detection device and the acidity meter transmit their detection data values ​​to the control system respectively, and the control system controls the start and stop of the lifting pump and the liquid alkali dosing device and the flow rate through calculation to realize intelligent processing.

[0031] The beneficial effects of the present invention are as follows: the present invention not only effectively removes silicon in alkaline water, reduces the output of silicon-containing sludge in subsequent fluorine removal, and helps to improve the purity of calcium fluoride sludge, but also makes full use of photovoltaic concentrated acid wastewater, recovers silicon resources in concentrated alkaline wastewater, prepares white carbon black products with high utilization value, and realizes the resource treatment of concentrated alkaline wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a system principle diagram of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Example: The concentrated alkaline wastewater discharged from a photovoltaic cell production line enters a concentrated alkaline regulating tank, and the concentrated acid wastewater discharged from the production line enters a concentrated acid regulating tank, wherein the volume of concentrated alkaline wastewater is 135m3 / d, the silicon concentration in the concentrated alkaline wastewater is 3000-10000mg / L, and the volume of concentrated acid wastewater is 60m3 / d.

[0035] The concentrated alkali wastewater in the concentrated alkali regulating tank enters the primary mixing tank at a flow rate of 135m3 / d, and the concentrated acid wastewater in the concentrated acid regulating tank enters the primary mixing tank at a flow rate of 40m3 / d. The pH in the primary mixing tank is controlled at 7.5-8.5. The flow rate of concentrated acid wastewater is controlled according to the above pH value, and the mixing time is controlled at 25min.

[0036] The effluent from the primary mixing tank enters the primary gelation reactor for a gelation reaction with a reaction time of 0.5 h.

[0037] The effluent from the primary gelation reactor enters the screw dehydrator to separate the formed coarse gel particles from the wastewater. The moisture content of the dehydrated coarse gel particles is 88%-90%. The dehydrated coarse gel particles are put into the alkali dissolution tank, and liquid alkali is added to the alkali dissolution tank to dissolve the coarse gel particles. The amount of liquid alkali added is 15% of the total acid content of photovoltaic acid water, and the dissolution time is 5 hours.

[0038] The effluent from the alkali dissolution tank enters the secondary mixing tank, and the concentrated acid wastewater in the concentrated acid regulating tank enters the secondary mixing tank at a certain flow rate ratio. The pH in the secondary mixing tank is controlled at 6.5-7.0. The flow rate of the concentrated acid wastewater is controlled according to the above pH value, and the mixing time is controlled at 25 minutes.

[0039] The effluent from the secondary mixing tank enters the secondary gelation reactor for secondary gelation reaction with a reaction time of 1.0 h;

[0040] The effluent from the secondary gelation reactor enters the plate-and-frame filter press to separate the fine gel particles formed by the reaction from the wastewater. The moisture content of the dehydrated fine gel particles is 83%-86%.

[0041] The dehydrated fine gel particles are put into a cleaning tank and cleaned with water for 20 minutes. The amount of water used for cleaning is 10 times the amount of sedimentation.

[0042] The cleaned fine gel particles are dried using a drying device, the temperature is controlled at 120°C, and the moisture content is controlled below 5%;

[0043] The dried gel particles are crushed by a ball mill, and the crushed particles can be used as white carbon black products filled with rubber;

[0044] The effluent from the screw dewatering machine, plate and frame filter press and cleaning pool is collected and discharged into the comprehensive regulating tank of the photovoltaic wastewater treatment plant for subsequent comprehensive treatment to meet the standards.

[0045] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A process for preparing white carbon black using photovoltaic cell wastewater, characterized in that: The steps include: Step 1: Send concentrated alkaline wastewater and part of concentrated acid wastewater into a primary mixing tank for mixing, and control the pH of the mixed wastewater in the primary mixing tank to be between 5.0 and 9.0; Step 2: sending the mixed wastewater in the primary mixing tank into a primary gelling reactor for a primary gelling reaction; Step 3: the effluent from the primary gelation reactor enters a primary dehydration device to separate the coarse gel particles formed by the primary gelation reaction from the wastewater; Step 4: putting the dehydrated coarse gel particles into an alkali dissolving tank, and adding liquid alkali into the alkali dissolving tank to dissolve the coarse gel particles; Step 5: The effluent from the alkali dissolution tank is discharged into the secondary mixing tank, and part of the concentrated acid wastewater is discharged into the secondary mixing tank, and the pH of the mixed wastewater in the secondary mixing tank is controlled between 5.5-8.0; Step 6: The effluent from the secondary mixing tank enters the secondary gelation reactor for secondary gelation reaction; Step 7: The effluent from the secondary gelation reactor enters the secondary dehydration device to separate the fine gel particles formed by the secondary gelation reaction from the wastewater; Step 8: Drying the fine gel particles formed by the secondary gel reaction using a drying device; Step nine: crushing the dried gel particles with crushing equipment, and the crushed particles form white carbon black products.

2. The process for preparing white carbon black using photovoltaic cell wastewater according to claim 1, characterized in that: In the step 1, the concentrated alkaline wastewater discharged from the photovoltaic cell production line is first discharged into the concentrated alkaline regulating tank, and the concentrated acid wastewater discharged is discharged into the concentrated acid regulating tank, and then the concentrated alkaline wastewater in the concentrated alkaline regulating tank is sent to the primary mixing tank at a certain flow rate, and at the same time, the concentrated acid wastewater in the concentrated acid regulating tank is sent to the primary mixing tank at a certain flow rate ratio, the concentrated acid wastewater flow rate is controlled according to the pH value of the mixed wastewater in the primary mixing tank, and the mixing time of the concentrated alkaline wastewater and the concentrated acid wastewater in the primary mixing tank is controlled to be between 10 and 60 minutes; in the step 5, the concentrated acid wastewater in the concentrated acid regulating tank is sent to the secondary mixing tank at a certain flow rate ratio, the concentrated acid wastewater flow rate is controlled according to the pH value of the mixed wastewater in the secondary mixing tank, and the mixing time of the effluent from the alkali dissolution tank and the concentrated acid wastewater in the secondary mixing tank is controlled to be between 1 and 30 minutes.

3. The process for preparing white carbon black using photovoltaic cell wastewater according to claim 1, characterized in that: The wastewater mixed in the primary mixing tank enters the primary gelation reactor for a primary gelation reaction for 0.5-20 hours, and the wastewater mixed in the secondary mixing tank enters the secondary gelation reactor for a secondary gelation reaction for 0.5-10 hours.

4. The process for preparing white carbon black using photovoltaic cell wastewater according to claim 1, characterized in that: The primary dehydration device and the secondary dehydration device are filter presses, screw dehydrators or centrifuges. The moisture content of the coarse gel particles after primary dehydration is below 92%, and the moisture content of the fine gel particles after secondary dehydration is below 90%.

5. The process for preparing white carbon black using photovoltaic cell wastewater according to claim 1, characterized in that: In the step 4, the amount of liquid alkali added is 10%-40% of the total acid content of the concentrated acid wastewater, and the dissolution time is 1-20 hours.

6. The process for preparing white carbon black using photovoltaic cell wastewater according to claim 1, characterized in that: The gel particles dehydrated in step seven are put into a cleaning tank, cleaned with water, and then dried with a drying device.

7. The process for preparing white carbon black using photovoltaic cell wastewater according to claim 6, characterized in that: The gel particles dehydrated in step seven are then washed in the washing tank for 5-30 minutes, and the amount of clean water used for washing is 5-20 times the amount of the gel particles.

8. The process for preparing white carbon black using photovoltaic cell wastewater according to claim 1, characterized in that: In step eight, the temperature of the drying equipment is controlled at 105-150° C., and the moisture content of the gel particles after drying is controlled to be below 5%.

9. The process for preparing white carbon black using photovoltaic cell wastewater according to claim 1, characterized in that: The effluent from the primary dehydration device, secondary dehydration device and cleaning pool is collected and discharged into the comprehensive regulating pool of the photovoltaic wastewater treatment plant for subsequent comprehensive treatment to meet standards.

10. A processing system for preparing white carbon black material using concentrated alkali wastewater produced by photovoltaic cells, used in the process of preparing white carbon black using wastewater from photovoltaic cells as claimed in claim 1, characterized in that: The invention comprises a concentrated acid regulating tank, a concentrated alkali regulating tank, a primary mixing tank, a secondary mixing tank, a primary gelling reactor, a secondary gelling reactor, a primary dehydration device, a secondary dehydration device, an alkali dissolving tank, a cleaning tank, a drying device, a crushing device, a comprehensive regulating tank and a plurality of lifting pumps. The concentrated acid regulating tank and the concentrated alkali regulating tank can respectively hold concentrated acid wastewater and concentrated alkali wastewater discharged from a photovoltaic cell production line. The concentrated alkali regulating tank is connected with the primary mixing tank through a pipeline. The concentrated acid regulating tank is connected with the primary mixing tank and the secondary mixing tank through pipelines respectively. The concentrated alkali wastewater in the concentrated alkali regulating tank is discharged into the primary mixing tank through a lifting pump at a set flow rate. The concentrated acid wastewater in the concentrated acid regulating tank is respectively discharged into the primary mixing tank and the secondary mixing tank through a lifting pump at a set flow rate. The primary mixing tank is connected with a water inlet of the primary gelling reactor through a pipeline. The combined pool is connected with the water inlet of the secondary gelation reactor through a pipeline. The primary gelation reactor and the secondary gelation reactor can make the mixed wastewater therein undergo gelation reaction. The water outlets of the primary gelation reactor and the secondary gelation reactor are respectively connected with the water inlets of the primary dehydration device and the secondary dehydration device. The primary dehydration device and the secondary dehydration device can separate the gel particles and the wastewater therein. The gel particle discharge outlet of the primary dehydration device is connected with the alkali dissolution pool, and the gel particle discharge outlet of the secondary dehydration device is connected with the cleaning pool. The drainage outlets of the cleaning pool, the primary dehydration device and the secondary dehydration device are all connected with the water inlet of the comprehensive regulating pool. The drying equipment can dry the gel particles cleaned in the cleaning pool, and the crushing equipment can crush the gel particles dried by the drying equipment to form white carbon black products.

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