A pipelined flow electrochemical silicon mud impurity removal device and method

Abstract

The application discloses a pipeline flow type electrochemical silicon mud impurity removal device, which comprises a groove body for passing silicon mud, and a multistage electrode group arranged above the groove body and used for electrochemically treating the silicon mud passing through the groove body. The groove body is provided with a plurality of upward bending portions at the bottom, so that the groove body forms a bending flow guide structure, and at least one bending portion is arranged between each adjacent electrode in the multistage electrode group. The application realizes continuous and efficient impurity removal without shutdown and reagent, solves the problems of silicon mud deposition, electrode passivation and pipeline mismatch, and has an impurity removal rate of greater than or equal to 90%. The application is green, environmentally friendly and recyclable, and is suitable for industrial large-scale application.

Description

Technical Field

[0001] This invention belongs to the fields of wet purification of silica mud, resource utilization of industrial solid waste and electrochemical deposition for impurity removal. Specifically, it relates to a device and process method that can be embedded in an industrial production line to achieve electrochemical removal of transition metal impurities in silica mud under continuous flow conditions. Background Technology

[0002] Silica sludge is a large amount of solid waste generated from photovoltaic and semiconductor cutting and processing. It contains a large amount of high-purity silicon powder, but due to the presence of transition metal impurities such as copper, nickel, iron, and lead, its high-value reuse is severely limited. Existing silica sludge removal technologies mainly have the following defects: (1) Chemical acid washing / alkali leaching method: large consumption of reagents, high cost of waste acid treatment, easy corrosion of equipment, and environmental pollution. (2) Flocculation / filtration / physical separation method: low removal rate of ionic metals and limited improvement in purity. (3) Traditional electrochemical removal: all are static intermittent tank electrolysis, which requires batch shutdown, low processing efficiency, and is not compatible with continuous production line production. (4) Ordinary flowing electrolysis: mostly used in clean water systems, which cannot adapt to the working conditions of silica sludge with high solid content, easy deposition, easy tank blockage, and easy electrode encapsulation. At present, there is no publicly available technology that can directly embed electrodes and continuously dynamically electrodeposit to remove impurities on a continuous flow production line of silica sludge slurry. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an embedded, continuous flow, dynamic electrochemical impurity removal device and method for production lines, enabling continuous impurity removal of silica sludge during the transportation process.

[0004] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0005] A continuous flow electrochemical silica sludge removal device includes:

[0006] A tank for passing silica mud;

[0007] A multi-stage electrode assembly is disposed above the tank body and is used to electrochemically treat the silica sludge passing through the tank body.

[0008] The bottom of the tank is provided with several upward bends, so that the tank forms a bendable flow guiding structure. Each adjacent electrode in the multi-stage electrode group is provided with at least one bend.

[0009] Furthermore, the bending portion is a flow guide baffle.

[0010] Furthermore, the angle between the main flow direction of the tank and the horizontal plane is ≥5°.

[0011] Furthermore, the multi-stage electrode group includes at least a first-stage electrode, a second-stage electrode, and a third-stage electrode.

[0012] Furthermore, the cathodes of the first, second, and third electrodes are made of titanium mesh or stainless steel mesh, and the anodes are made of graphite plates or titanium-based precious metal coatings.

[0013] Furthermore, the cathode of the first-stage electrode is a titanium mesh, and the anode is a graphite plate; the cathode of the second-stage electrode is a stainless steel mesh, and the anode is a ruthenium-plated titanium anode; the cathode of the third-stage electrode is a titanium mesh, and the anode is a graphite plate.

[0014] Another aspect of the present invention discloses a method for removing impurities from the above-mentioned apparatus, comprising:

[0015] The silica mud slurry is continuously introduced at a speed of 0.1–0.5 m / s;

[0016] Potentials are applied in stages to selectively deposit copper, nickel, iron, and lead in steps.

[0017] Continuous discharge ensures uninterrupted impurity removal, ultimately yielding purified silica sludge.

[0018] Furthermore, the settings for the impurity removal are: single-stage voltage 1.5–3.5 V, current density 20–80 A / m², and pH 3–7.

[0019] Furthermore, the electrodes at each stage are arranged in order of increasing potential to remove copper, nickel, iron, and lead in sequence.

[0020] Furthermore, the solid content of the silica mud slurry is 10-25%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Continuous production: fully embedded in the production line, without stopping or batching, running 24 hours a day, improving processing efficiency by 5 to 10;

[0023] (2) Green and chemical-free: No acid, alkali or flocculant is used, there is no secondary pollution, and the operating cost is reduced by more than 60%;

[0024] (3) High impurity removal rate: The total removal rate of transition metals (Cu, Ni, Fe, Pb) is ≥90%, and the purity of silica mud is significantly improved (from 85% to 92% to over 98%).

[0025] (4) Anti-sludge and anti-passivation: Suspended electrode + turbulent self-cleaning, electrode life is extended by more than 3 times, and the groove is not clogged;

[0026] (5) Metals are recyclable: The cathode deposits high-purity metals (containing >60% copper and >20% nickel), which can be recycled and reused, increasing economic benefits. Attached Figure Description

[0027] Figure 1This is a schematic diagram of the overall structure of the device of the present invention;

[0028] Figure 2 This is a magnified view of a V-shaped flow guide plate.

[0029] Figure 3 This is a process flow diagram of the method of the present invention.

[0030] 1. Suspension beam; 2. Tank body; 3. First-stage electrode; 4. Second-stage electrode; 5. Third-stage electrode; 6. Flow guide plate. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] This invention discloses a continuous flow electrochemical silica sludge removal device, such as... Figure 1 As shown, it includes:

[0033] Tank 2, the tank 2 being used to pass silica sludge;

[0034] A multi-stage electrode assembly is disposed above the tank 2 and is used to electrochemically treat the silica sludge passing through the tank 2.

[0035] The bottom of the tank 2 is provided with several upward bends, so that the tank 2 forms a bendable flow guiding structure. In the multi-stage electrode group, at least one bend is provided between each adjacent electrode.

[0036] Among them, such as Figure 1 As shown, tank 2 is a flow-through tank. One end of tank 2 can be directly connected in series to a silica mud conveying pipeline. The tank is long and narrow, with no dead corners and a flow-through structure. The length-to-width ratio is preferably ≥5:1, allowing for controllable hydraulic residence time. Furthermore, a bend is provided at the bottom of tank 2 between each adjacent electrode, causing turbulence in the silica mud slurry during flow, which can wash over the electrode surfaces. Multi-stage electrode groups can be installed above tank 2 via a suspension beam 1.

[0037] This invention, through the inclusion of a tank 2, can be embedded into an assembly line for continuous processing without batching, enabling 24-hour operation and improving processing efficiency. Furthermore, by incorporating a bend, this invention allows silica sludge to form turbulence at the electrodes, using this turbulence to flush the electrode surface, preventing silica sludge accumulation, passivation, and tank clogging.

[0038] Optional, such as Figure 2 As shown, the bending part is a flow guide baffle 6.

[0039] Among them, the flow guide baffle 6 is located between the electrodes and is an inverted V-shaped or arc-shaped baffle with a height of 0.4 to 0.6 times the depth of the groove.

[0040] In this embodiment of the invention, the use of a flow guide baffle 6 creates turbulent flow (Reynolds number ≥ 4000) in the silica mud slurry, continuously scouring the electrode surface and inhibiting deposition and encapsulation.

[0041] Optionally, the angle between the main flow direction of the tank 2 and the horizontal plane is ≥5°.

[0042] The flow direction of the tank 2 is bent due to the bend at the bottom. However, the main flow direction of the tank 2 refers to the flow direction of the tank 2 excluding the influence of the bend. This flow direction is straight and has an angle of inclination ≥ 5 with the horizontal plane.

[0043] In this embodiment of the invention, by tilting the main flow direction of the tank 2 at an angle of ≥5° to the horizontal plane, an anti-deposition structure is formed. Newly flowing silica sludge will first impact the bottom of the tank 2 and then gradually flow upward, thus avoiding the accumulation and blockage of silica sludge.

[0044] Optionally, the multi-stage electrode group includes at least a first-stage electrode 3, a second-stage electrode 4, and a third-stage electrode 5.

[0045] Among them, such as Figure 1 As shown, the first-stage electrode 3, the second-stage electrode 4, and the third-stage electrode 5 are arranged adjacent to each other in sequence, and a flow guide baffle 6 is provided between each adjacent electrode.

[0046] Specifically, the cathodes of the first, second, and third electrodes are made of titanium mesh or stainless steel mesh, and the anodes are made of graphite plates or titanium-based precious metal coatings.

[0047] In this embodiment of the invention, the electrodes are arranged in stages along the flow direction, with 3 to 5 stages. The cathode is made of titanium mesh or stainless steel mesh (mesh size 2 to 5 mm, open area ≥ 40%), and the anode is made of graphite or titanium-based precious metal coating (such as titanium plated with ruthenium or titanium plated with iridium). The top of the electrode is installed through a suspension beam 1, and the bottom is suspended without support, forming an open structure without a base, which facilitates the passage of silica mud particles and avoids bottom accumulation.

[0048] Specifically, the cathode of the first-stage electrode is a titanium mesh, and the anode is a graphite plate; the cathode of the second-stage electrode is a stainless steel mesh, and the anode is a ruthenium-plated titanium anode; the cathode of the third-stage electrode is a titanium mesh, and the anode is a graphite plate.

[0049] By setting the cathode and anode materials for each electrode stage separately, each electrode stage can effectively perform electrochemical treatment for different metal types.

[0050] In particular, each stage of the electrodes in this embodiment of the invention uses a DC regulated power supply and is powered independently, making the potential of each stage adjustable and enabling selective stepwise deposition (Cu→Ni→Pb→Fe).

[0051] This invention also provides a method for removing impurities from silica sludge using a continuous flow electrochemical process, characterized by the following steps:

[0052] Step 1: Streamline integration. Connect the impurity removal device directly in series to the silica mud wet process production line. The silica mud slurry has a solid content of 5% to 25% and the pH is adjusted to 3 to 7 (fine-tuning with dilute sulfuric acid or lime water is not necessary and depends on the original slurry). The slurry flows continuously through the tank at a flow rate of 0.1 to 0.5 m / s.

[0053] Step 2: Staged electrolysis. Turn on the staged power supply, set the single-stage voltage to 1.5–3.5 V, the current density to 20–80 A / m², and the temperature to room temperature to 45 ℃. Specifically: First-stage electrode (low potential 1.5–2.2 V): preferentially deposits copper (Cu²⁺ + 2e⁻ → Cu); Second-stage electrode (medium potential 2.2–2.8 V): deposits nickel and lead; Third-stage and subsequent electrodes (higher potential 2.8–3.5 V): deposit iron.

[0054] Step 3: Dynamic self-cleaning. The flowing slurry, in conjunction with the guide plate, forms turbulence that continuously washes the electrode, preventing the adsorption and passivation of silica sludge. No mechanical cleaning is required on the electrode surface.

[0055] Step 4: Continuous discharge; after impurity removal, the high-purity silica sludge directly enters the next process (pressure filtration, drying, etc.); the cathode metal deposition layer is removed every 24 to 72 hours to recover mixed metals of copper, nickel, iron, and lead, or to recover them in stages.

[0056] To further illustrate the effects achievable by the embodiments of the present invention, specific embodiments are provided below:

[0057] Example 1

[0058] A flow-line electrochemical silica sludge removal device has the following structure:

[0059] The flow channel is 2.5 m long, 0.3 m wide, and 0.4 m deep, with a bottom inclination angle of 5°. Three stages of electrode groups are arranged sequentially along the flow direction: the first stage consists of a titanium mesh (3 mm mesh size) and a graphite plate for both cathode and anode; the second stage consists of a stainless steel mesh (2 mm mesh size) and a ruthenium-plated titanium anode; the third stage consists of a titanium mesh and a graphite plate. The electrodes are suspended from a crossbeam above the channel, with a spacing of 20 cm between electrodes and a bottom distance of 10 cm from the channel bottom. V-shaped flow guide baffles, 0.2 m high, are installed between each stage. The power supply for each stage is independently adjustable.

[0060] A silica mud slurry with a solid content of 15% (initial pH=5.2, containing 0.8% copper, 0.5% nickel, 1.2% iron, and 0.3% lead) was introduced into the tank at a flow rate of 0.3 m / s. The voltage was set as follows: first stage voltage 2.0 V, second stage voltage 2.8 V, third stage voltage 3.2 V, and current density 50 A / m. 2 The temperature was 35 ℃. After 48 hours of continuous operation, samples were taken for analysis (samples were taken every 2 hours, and the samples were mixed). The metal content was determined by ICP-OES.

[0061] Results: Copper removal rate 96%, nickel removal rate 92%, iron removal rate 89%, lead removal rate 88%, total impurity removal rate 91%. The metal layer deposited on the cathode surface was of uniform thickness (approximately 0.3–0.8 mm), with no visible siltation at the bottom of the tank and no silica sludge covering the electrode surface. Voltage fluctuations during continuous operation were <5%, requiring no shutdown for cleaning.

[0062] Example 2

[0063] Using the same apparatus as in Example 1, the same batch of silica mud slurry was treated, with only the flow rate and the combination of voltage levels changed. Each process was run continuously for 24 hours, and the results are shown in Table 1.

[0064] Test No. Flow velocity (m / s) Level 1 voltage (V) Secondary voltage (V) Level 3 voltage (V) Cu removal rate (%) Ni removal rate (%) Fe removal rate (%) Pb removal rate (%) 2-1 0.15 1.8 2.5 3.0 97 93 85 84 2-2 0.30 2.0 2.8 3.2 96 92 89 88 2-3 0.45 2.2 3.0 3.4 93 88 86 83

[0065] The results show that the device maintains good impurity removal performance within the range of 0.15–0.45 m / s. At low speeds, mass transfer is slightly worse but residence time is longer, while at high speeds, scouring is enhanced but residence time is shorter. 0.30 m / s is the optimal overall speed. No clogging or electrode passivation occurred in any of the tests.

[0066] Example 3

[0067] Using the apparatus and parameters of Example 1, the system was run continuously for 240 hours (10 days), with samples taken every 24 hours and the electrode status observed.

[0068] Results: The removal rate remained stable at 90%–92% for the first 48 hours of operation; from 48 to 120 hours, the removal rate slightly decreased to 87%–89%, but remained within an acceptable range; after 120 hours, the cathode was removed for observation, and the deposited metal layer thickness reached 2.1 mm, with some detachment, but the electrode substrate remained intact. After cleaning the deposited layer and reinstalling the cathode, the removal rate recovered to 91%. There was no corrosion on the anode and no sediment accumulation at the bottom of the tank.

[0069] This invention demonstrates that the device can operate stably for ≥5 days and requires cathode cleaning once, which is more than 10 times longer than traditional static electrochemical methods (which require shutdown for cleaning every 4-6 hours).

[0070] Comparative Example 1 (Compared with traditional static electrochemistry)

[0071] A traditional static intermittent electrolytic cell with a volume of 50 L was used. The same electrode materials (titanium mesh cathode, graphite anode) and the same silica slurry with a solid content of 15% were employed. The cell was static and non-flowing, with a voltage of 3.0 V, a current density of 50 A / m², and a temperature of 35 ℃. Electrolysis was stopped after 6 hours to clean the electrode surface coating before starting the next batch. The processing capacity was the same (based on 24 hours).

[0072] Results: Static electrolysis achieved a single-batch removal rate of 85% for copper, 72% for nickel, 60% for iron, and 55% for lead, with a total impurity removal rate of approximately 68%. Due to the rapid formation of silica sludge on the electrode surface, mass transfer was hindered, and the removal rate decreased rapidly with electrolysis time. Four shutdowns for cleaning were required within 24 hours (once every 6 hours), resulting in an effective operating time of only 18 hours and a total throughput only 60% of that of the device described in this invention. Severe clogging of the electrode mesh necessitated high-pressure water jet cleaning, and the electrode lifespan was approximately 30 days (compared to ≥120 days for the device described in this invention). These results demonstrate that this invention significantly outperforms traditional static electrochemistry in terms of impurity removal rate, continuous operation capability, and electrode lifespan.

[0073] Comparative Example 2 (Comparison without flow deflectors)

[0074] The same apparatus as in Example 1 was used, but all flow guide baffles were removed to allow the slurry to flow in a laminar flow (Reynolds number of about 800). All other parameters were the same, and the slurry was run continuously for 24 hours.

[0075] Results: After 4 hours of operation, localized silica sludge began to adhere to the cathode surface; after 12 hours, nearly half of the cathode area was covered by silica sludge, and the measured removal rate dropped below 65%; after 24 hours, the cathode was completely covered by silica sludge, with a removal rate of only 20%. Significant sediment accumulation was observed at the bottom of the tank. This indicates that the turbulence generated by the flow guide baffles is a crucial and indispensable structure for achieving self-cleaning and preventing passivation.

[0076] In summary, the embodiments of the present invention have the following beneficial effects compared with the comparative examples:

[0077] (1) The design of this embodiment of the invention can realize continuous production. The tank 2 can be fully embedded in the production line, realizing non-stop, non-batch, 24-hour operation, and improving the processing efficiency by 5 to 10.

[0078] (2) Green process without chemicals: As shown in Examples 1-3, the solutions of this invention do not use acids, alkalis, or flocculants, have no secondary pollution, and reduce operating costs by more than 60%;

[0079] (3) High impurity removal rate: As shown in Examples 1-3, the solution of the present invention has a total removal rate of transition metals (Cu, Ni, Fe, Pb) of ≥90%, and the purity of silica mud is significantly improved (from 85% to 92% to over 98%).

[0080] (4) Anti-accumulation and anti-passivation: The embodiments of the present invention adopt suspended electrodes + turbulent self-cleaning, which extends the electrode life by more than 3 times, does not clog the groove, and reduces the cleaning frequency;

[0081] (5) Metals are recyclable: The cathode deposits high-purity metals (containing >60% copper and >20% nickel), which can be recycled and reused, increasing economic benefits.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this application specification, they can still modify or make equivalent substitutions to the specific implementation of the present invention, but these modifications or changes do not depart from the protection scope of the pending claims of the present invention.

Claims

1. A continuous flow electrochemical silica sludge removal device, characterized in that, include: A tank for passing silica mud; A multi-stage electrode assembly is disposed above the tank body and is used to electrochemically treat the silica sludge passing through the tank body. The bottom of the tank is provided with several upward bends, so that the tank forms a bendable flow guiding structure. Each adjacent electrode in the multi-stage electrode group is provided with at least one bend.

2. The automated electrochemical silica sludge removal device according to claim 1, characterized in that, The bent section is a flow guide baffle.

3. The automated electrochemical silica sludge removal device according to claim 1, characterized in that, The angle between the main flow direction of the trough and the horizontal plane is ≥5°.

4. The automated electrochemical silica sludge removal device according to claim 1, characterized in that, The multi-stage electrode group includes at least a first-stage electrode, a second-stage electrode, and a third-stage electrode.

5. The automated electrochemical silica sludge removal device according to claim 4, characterized in that, The cathodes of the first, second, and third electrodes are made of titanium mesh or stainless steel mesh, and the anodes are made of graphite plates or titanium-based precious metal coatings.

6. The automated electrochemical silica sludge removal device according to claim 5, characterized in that, The cathode of the first-stage electrode is a titanium mesh, and the anode is a graphite plate; the cathode of the second-stage electrode is a stainless steel mesh, and the anode is a ruthenium-plated titanium anode; the cathode of the third-stage electrode is a titanium mesh, and the anode is a graphite plate.

7. A method for removing impurities from a flowing electrochemical silica sludge removal device as described in claims 1-6, characterized in that, include: The silica mud slurry is continuously introduced at a speed of 0.1–0.5 m / s; Potentials are applied in stages to selectively deposit copper, nickel, iron, and lead in steps. Continuous discharge ensures uninterrupted impurity removal, ultimately yielding purified silica sludge.

8. The method according to claim 7, characterized in that, The impurity removal settings are: single-stage voltage 1.5–3.5 V, current density 20–80 A / m², pH 3–7.

9. The method according to claim 7, characterized in that, Electrodes at each level are arranged in ascending order of potential to remove copper, nickel, iron, and lead in sequence.

10. The method according to claim 7, characterized in that, The solid content of the silica mud slurry is 10-25%.

Images