Method for recycling marine deposition backflow sand

Abstract

The invention relates to the technical field of marine deposition backflow sand recovery, and discloses a marine deposition backflow sand recovery method which comprises the following steps: (1) backflow tail mud collection and concentration regulation and control: systematically collecting overflow tail mud from a mortar ore storage hopper and a hydraulic classifier in a marine deposition sand beneficiation process, pumping the backflow tail mud into a slurry mixing tank, and carrying out slurry mixing and concentration regulation and control on the overflow tail mud; the mass concentration is accurately regulated and controlled within the range of 32%-48%; the backflow tail mud generated in the marine sedimentary sand beneficiation process is collected through the system, a multi-step cooperative treatment technology is adopted, especially ultrasonic cavitation and mechanical cooperative dispersion, enhanced secondary scrubbing, precise hydraulic cyclone classification and other technical means are adopted, particle aggregates formed by wrapping of salt and fine mud are effectively dissociated, and the separation effect is good. Therefore, qualified quartz sand particles of + 0.15 mm which are lost in the tail mud originally are efficiently recovered, the overall recovery rate of the quartz sand is remarkably improved, waste of precious silicon resources is reduced, and the comprehensive utilization level of the resources is improved.

Description

Technical Field

[0001] This invention relates to the field of marine sedimentary backflow sand recovery technology, specifically a method for recovering marine sedimentary backflow sand. Background Technology

[0002] Marine sedimentary sand is an indispensable high-quality siliceous raw material for modern industries, especially the glass, ceramics and casting industries. Its typical beneficiation process usually includes core operations such as "washing-desliming-classification". In this process, equipment such as slurry storage hopper (desliming hopper), obstructed settling machine, and hydraulic classifier are widely used to separate the qualified particle size of +0.15mm quartz sand as the product and remove the -0.15mm fine mud (mainly composed of clay, mica, salt and other light impurities).

[0003] However, the ideal gradation state is difficult to maintain consistently in actual industrial production, resulting in the loss of a large amount of qualified quartz sand that should have become the product, along with the overflow of fine mud, forming so-called "return tailings" or "overflow tailings." The root cause of this serious resource loss problem lies in: 1. Marine sand itself contains soluble salts (such as NaCl, KCl, MgCl2). In mineral slurry water, these electrolytes compress the double electric layer on the surface of the particles, weakening the electrostatic repulsion between particles. Especially for fine clay and quartz powder, they are very likely to adhere to or coat the surface of coarser qualified quartz sand particles through the action of salt, forming solid particle agglomerates. The settling velocity of these agglomerates is between that of a single qualified sand particle and fine mud, and they are very likely to enter the overflow in the classification equipment, causing loss.

[0004] 2. Process fluctuations and operational instability: Insufficient scrubbing: If the scrubbing intensity or time in the previous stage is insufficient, the clay film on the surface of the quartz sand will not be completely removed. These residual films will become the medium for the binding of fine mud and sand particles in the subsequent grading. Slurry concentration and flow rate fluctuations: Classification equipment (such as desliming hoppers) is very sensitive to feed concentration and flow rate. Too high a concentration will cause settling interference, and fine mud cannot overflow effectively; too high a flow rate will shorten the settling time, causing some agglomerates to be lost before they can settle. Fluctuations in production are normal, which leads to a periodic decline in classification efficiency. Mismatched equipment parameters: If the parameters of the hydraulic classifier (such as rising water velocity and tilt angle) are not adjusted in time according to the changes in the properties of the original sand, it will also cause the boundary particle size to drift, allowing qualified particles to enter the tailings. Covering and entrainment of fine mud: Extremely fine clay particles (-0.01mm) form a stable colloidal system in the slurry. They can cover coarser sand particles, changing their apparent particle size and density. During settling, rising water flow or turbulence in the equipment can also easily entrain individual qualified sand particles into the overflow.

[0005] Traditional solutions often involve simply pumping these reflux tailings back into the pit for backfilling. This not only means the permanent loss of valuable silica resources, but also directly returning these salt-rich and fine-mud-rich tailings to the main process will worsen the slurry properties of the main process, creating a vicious cycle. Therefore, developing a technology that can specifically and efficiently recover qualified sand particles from reflux tailings is crucial for improving the overall technical and economic indicators and sustainable development of marine sand beneficiation. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an efficient method for recovering qualified-sized quartz sand from marine sedimentary sand recirculation tailings.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for recovering marine sedimentary backflow sand, comprising the following steps: Step (1) Collection and concentration control of reflux tailings: Systematically collect the overflow tailings from the slurry storage hopper and hydraulic classifier in the marine sedimentary sand beneficiation process, pump the reflux tailings into the slurry conditioning tank, and precisely control its mass concentration to the range of 32% to 48%. Step (2) Slurry preparation and primary sedimentation thickening: The slurry prepared in step (1) is transported to a mortar storage hopper or a high-efficiency thickener for gravity sedimentation and desliming. The sedimentation time is 1.5 to 3 hours, and the sedimentation bottom flow rich in solid particles is collected. Step (3) Ultrasonic cavitation and mechanical synergistic dispersion: The sedimentation underflow obtained in step (2) is pumped into a reactor that integrates an ultrasonic generator and a mechanical stirrer. The slurry is treated under the conditions of ultrasonic power of 220W to 480W and mechanical stirring speed of 300 to 600rpm for 5 to 15 minutes. Step (4) Enhance secondary scrubbing and surface modification: Send the slurry treated in step (3) into the scrubbing machine, add 0.08% to 0.3% of the total mass of the slurry into the scrubbing machine, and perform secondary scrubbing with clean water. The scrubbing time is controlled at 10 to 25 minutes. Step (5) Precision hydrocyclone grading: Pump the slurry washed in step (4) to the hydrocyclone group, control the feed pressure between 0.16MPa and 0.22MPa, and select a hydrocyclone with an overflow port diameter to underflow port diameter ratio of 1:1.8 to 1:2.2 to collect the underflow product of the hydrocyclone, which is the qualified particle size of the recovered +0.15mm quartz sand; Step (6) Closed-loop water treatment and reagent reuse: The overflow of the hydrocyclone in step (5), the overflow of the slurry storage hopper in step (2), and the drainage of the scrubbing machine in step (4) are collected together and transported to the plant water treatment system. After sedimentation and clarification, they are reused for slurry preparation in step (1) or scrubbing operation in step (4). At the same time, the residual dispersant in the water is monitored and replenished to achieve indirect reuse of reagents.

[0008] Preferably, the dispersant in step (4) is one or more of sodium hexametaphosphate, sodium citrate, sodium gluconate, polymaleic anhydride, and acrylic acid-maleic anhydride copolymer.

[0009] Preferably, the ultrasonic generator in step (3) has a frequency range of 20kHz to 40kHz, and the ultrasonic probe is placed below the surface of the slurry to ensure that the ultrasonic energy is evenly distributed in the slurry and generates an effective cavitation effect.

[0010] Preferably, the hydrocyclone in step (5) has a cone angle range of 15° to 20°.

[0011] Preferably, the overflow product of the hydrocyclone obtained in step (5) will be returned to the desliming stage of the main process or enter the tailings system. The main components of the overflow product are fine mud of -0.15mm and a small amount of undissociated micro-agglomerates.

[0012] Preferably, the bottom sedimentation flow of the mortar storage hopper in steps (1) and (2) is discharged by intermittent automatic control, and the discharge valve is automatically opened when the concentration of the bottom sedimentation slurry reaches 60% to 70%.

[0013] Preferably, the impeller linear velocity of the scrubbing machine in step (4) is controlled at 8-12 m / s to provide sufficient shearing force while avoiding excessive abrasion. Preferably, the ultrasonic generator and the mechanical stirrer in step (3) are started simultaneously to achieve synchronous stirring, so that the particle agglomerates in the slurry are fully disintegrated under the synergistic effect of ultrasonic cavitation and shear force.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. Significantly improves the recovery rate of quartz sand and reduces resource waste. This invention systematically collects the reflux tailings generated during the beneficiation process of marine sedimentary sand and employs a multi-step synergistic treatment process, particularly ultrasonic cavitation and mechanical synergistic dispersion, enhanced secondary scrubbing, and precision hydrocyclone classification, to effectively dissociate particle agglomerates formed by salt and fine mud encapsulation. This allows for the efficient recovery of +0.15mm qualified quartz sand particles that were originally lost in the tailings, significantly improving the overall recovery rate of quartz sand, reducing the waste of valuable silica resources, and enhancing the comprehensive utilization level of resources.

[0015] 2. Physicochemical synergistic depolymerization, breaking through traditional technological bottlenecks. This invention innovatively combines the physical dispersion method of ultrasonic cavitation effect with mechanical stirring, and then uses a dispersant for surface modification and scrubbing to form a powerful physical-chemical synergistic deagglomeration mechanism. This not only effectively removes the clay and salt coating layer attached to the surface of quartz sand, but also prevents particles from re-agglomerating, fundamentally solving the problem of heterogeneous agglomeration that is difficult to handle by traditional methods, thus improving sorting efficiency and product quality.

[0016] 3. Achieve closed-loop water resource recycling and chemical reuse, promoting environmental protection and energy conservation. This invention collects and transports hydrocyclone overflow, primary sedimentation overflow, and scrubbing wastewater to the plant's water treatment system. After sedimentation and clarification, the wastewater is reused for slurry preparation and scrubbing operations, forming a closed-loop water resource recycling system. At the same time, by monitoring and replenishing residual dispersants in the recycled water, the indirect reuse of chemicals is achieved. This not only significantly reduces the consumption of fresh water and chemical agents but also reduces the environmental impact of wastewater discharge, meeting the requirements of green mining and sustainable development.

[0017] 4. Improve product quality and ensure quality for industrial applications. By using a precision hydrocyclone for grading and multi-stage scrubbing and dispersion, this invention ensures that the recovered +0.15mm quartz sand particles have a clean surface and low mud content, meeting the quality requirements of siliceous raw materials in industries such as glass, ceramics, and casting. It effectively removes fine mud and impurities that affect product performance, improves the purity and usability of quartz sand, and enhances its market competitiveness.

[0018] 5. High degree of process integration, strong adaptability, and easy to promote industrialization. This invention organically integrates the collection, concentration control, sedimentation and concentration, ultrasonic dispersion, scrubbing and modification, cyclone classification and water and chemical reuse of reflux tailings into a coherent process flow. The parameters of each step are clear and the control is precise, which has strong operability and adaptability. It is not only suitable for the transformation and upgrading of existing marine sand beneficiation plants, but also can provide technical support for new projects, and has good prospects for industrial promotion and application. Attached Figure Description

[0019] Figure 1 This is a system flowchart of the present invention. Detailed Implementation

[0020] The embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings and examples. The detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of this disclosure by way of example, but should not be used to limit the scope of this disclosure. This disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0021] Please see Figure 1 A marine sedimentary sand alkaline scrubbing and recycling process includes the following steps: Step (1) Collection and concentration control of reflux tailings: Systematically collect the overflow tailings from the slurry storage hopper and hydraulic classifier in the marine sedimentary sand beneficiation process, pump the reflux tailings into the slurry conditioning tank, and precisely control its mass concentration to the range of 32% to 48%. This step is the starting point and foundation of the entire recycling process, and is designed to provide a stable and suitable feed for subsequent operations; Operation: In the process design of the concentrator, the overflow outlets of various classification equipment (such as slurry storage hoppers and hydraulic classifiers) are connected through channels or pipelines to collect the tailings into one or more return tailings collection tanks. Then, the tailings in the collection tanks are pumped into a slurry mixing tank with a stirring device using a slurry pump. Key control parameters: The slurry concentration is controlled between 32% and 48%. If the concentration is too low, the subsequent settling equipment will have a large processing capacity, which is uneconomical. If the concentration is too high, the slurry will have poor fluidity, which is not conducive to pumping and subsequent uniform dispersion. By monitoring the concentration with an online concentration meter and adding supplementary water or thickening underflow, the concentration can be precisely controlled to the target range to ensure fluidity and subsequent settling efficiency. Step (2) Slurry preparation and primary sedimentation thickening: The slurry prepared in step (1) is transported to a mortar storage hopper or a high-efficiency thickener for gravity sedimentation and desliming. The sedimentation time is 1.5 to 3 hours, and the sedimentation bottom flow rich in solid particles is collected. The purpose of this step is to pre-remove some of the finest, easily separable clay and increase the slurry concentration fed into the core dispersion operation to improve the efficiency of subsequent operations. Equipment: Mortar storage hopper (desliming hopper) or small high-efficiency thickener; Process: The slurry after conditioning is fed into the settling equipment. During the settling time of 1.5 to 3 hours, the relatively coarse aggregates, individual quartz sand particles and some medium-sized mud and sand will settle to the bottom by gravity, while the finest mud that forms colloids will be discharged with the upper overflow and the bottom settling flow will be collected. Function: This step removes some of the very fine mud and some moisture, significantly reducing the load on subsequent ultrasonic and scrubbing operations and increasing the processing capacity per unit time. Step (3) Ultrasonic cavitation and mechanical synergistic dispersion: The sedimentation underflow obtained in step (2) is pumped into a reactor that integrates an ultrasonic generator and a mechanical stirrer. The slurry is treated under the conditions of ultrasonic power of 220W to 480W and mechanical stirring speed of 300 to 600rpm for 5 to 15 minutes. This step is one of the core technologies of this invention, and aims to remove the muddy outer shell that surrounds the quartz sand particles. Equipment: A dedicated ultrasonic-mechanical co-processing reactor, which has a built-in ultrasonic transducer or probe and is equipped with a mechanical stirring paddle; Process Principle and Operation: The concentrated underflow is pumped into the reactor, and the ultrasonic generator (power 220W~480W) is started. It generates high-frequency pressure waves in the slurry, forming tens of thousands of microbubbles. When these cavitation bubbles collapse instantaneously, they generate local pressures of up to several thousand atmospheres and temperatures of over a thousand degrees, as well as strong micro-jets and shear forces. This huge energy is enough to break and shatter the muddy shell surrounding the quartz sand particles. Simultaneous mechanical stirring (300~600 rpm) ensures that the slurry is uniform, avoids solid sedimentation, and allows all agglomerates to be exposed to the ultrasonic action. At the same time, it also provides a certain shear dispersion force. The processing time is 5~15 minutes to achieve full dispersion. Step (4) Enhance secondary scrubbing and surface modification: Send the slurry treated in step (3) into the scrubbing machine, add 0.08% to 0.3% of the total mass of the slurry into the scrubbing machine, and perform secondary scrubbing with clean water. The scrubbing time is controlled at 10 to 25 minutes. Based on ultrasonic physical dispersion, this step prevents the dissociated particles from re-aggregating at the chemical and mechanical levels. Equipment: Scrubbing machine (such as spiral scrubbing machine or trough scrubbing machine); Process: The ultrasonically treated slurry is fed into a scrubbing machine. At the same time, a dispersant is added. The dispersant is one or more of the following: sodium hexametaphosphate, sodium citrate, sodium gluconate, polymaleic anhydride, and acrylic-maleic anhydride copolymer. The dispersant can be adsorbed on the surface of quartz sand and residual clay particles, enhance the negative charge of their surface, increase the electrostatic repulsion between particles, and chemically prevent them from agglomerating again. Synergistic effect: The powerful fluid shear force generated by the rotation of the scrubbing machine impeller works synergistically with the chemical dispersion effect of the dispersant to further peel off the attached substances that have been loosened by ultrasound but have not been completely removed, and scrub the surface of the particles for 10 to 25 minutes. Step (5) Precision hydrocyclone grading: Pump the slurry washed in step (4) to the hydrocyclone group, control the feed pressure between 0.16MPa and 0.22MPa, and select a hydrocyclone with an overflow port diameter to underflow port diameter ratio of 1:1.8 to 1:2.2 to collect the underflow product of the hydrocyclone, which is the qualified particle size of the recovered +0.15mm quartz sand; The qualified quartz sand has basically achieved monomer dissociation. The goal of this step is to accurately separate it from the complex system. Equipment: Hydrocyclone assembly (multiple units can be connected in parallel to adapt to the processing capacity); Process and parameter optimization: The scrubbed slurry is pumped into the hydrocyclone at a stable pressure of 0.16-0.22 MPa. Under this pressure, the slurry forms a strong rotating vortex in the hydrocyclone, and the particles mainly settle by centrifugal force. The ratio of the overflow port diameter to the underflow port diameter of the hydrocyclone is 1:1.8-2.2. This optimization makes the classification with 0.15 mm as the cutting point more accurate. The heavier, dissociated +0.15 mm quartz sand particles are thrown against the wall and spiral down to be discharged from the underflow port, becoming the final qualified product for recycling. The -0.15 mm fine mud and water are discharged from the central overflow pipe. Step (6) Closed-loop water treatment and reagent reuse: The overflow of the hydrocyclone in step (5), the overflow of the mortar storage hopper in step (2), and the drainage of the scrubbing machine in step (4) are collected together and transported to the plant water treatment system. After sedimentation and clarification, they are reused for slurry preparation in step (1) or scrubbing operation in step (4). At the same time, the residual dispersant in the water is monitored and replenished to achieve indirect reuse of reagents. This step embodies the circular economy and environmental protection concept of this invention, aiming to achieve zero wastewater discharge and maximum utilization of reagents; Operation: Collect the overflow of the hydrocyclone, the overflow of the mortar storage hopper in step (2), and the drainage of the scrubbing machine, and transport them to the central water treatment system of the plant (which may include sedimentation tanks, clarification tanks, etc.). Here, the remaining suspended solids are further removed to obtain clarified reclaimed water. Resource recycling: The recycled water is pumped back into the system for slurry preparation in step (1) or scrubbing in step (4), thus realizing a closed-loop recycling of water resources. Chemical reuse: Reclaimed water contains dispersants that have not been completely consumed. By monitoring their concentration, the amount of fresh dispersant added in subsequent operations can be appropriately reduced, thus achieving indirect reuse and conservation of chemicals.

[0022] As a further technical solution of the present invention, the ultrasonic generator in step (3) has a frequency range of 20kHz to 40kHz, and the ultrasonic probe is placed below the surface of the slurry to ensure that the ultrasonic energy is evenly distributed in the slurry and generates an effective cavitation effect.

[0023] As a further technical solution of the present invention, the hydrocyclone in step (5) has a cone angle range of 15° to 20° to meet the grading requirements of this particle size range.

[0024] As a further technical solution of the present invention, the overflow product of the hydrocyclone obtained in step (5) will be returned to the desliming stage of the main process or enter the tailings system. The main components of the overflow product are fine mud of -0.15mm and a small amount of undissociated micro-agglomerates.

[0025] As a further technical solution of the present invention, the bottom sedimentation flow of the mortar storage hopper in steps (1) and (2) is discharged by intermittent automatic control, and the discharge valve is automatically opened when the concentration of the bottom slurry reaches 60% to 70%.

[0026] As a further technical solution of the present invention, the impeller linear velocity of the scrubbing machine in step (4) is controlled at 8 to 12 m / s to provide sufficient shearing force while avoiding excessive abrasion.

[0027] As a further technical solution of the present invention, the ultrasonic generator and the mechanical stirrer in step (3) are started at the same time to achieve synchronous stirring, so that the particle agglomerates in the slurry are fully disintegrated under the synergistic effect of ultrasonic cavitation and shear force.

[0028] This invention improves the recovery rate of qualified +0.15mm quartz sand particles lost in the return tailings through innovative deagglomeration and separation technology; it provides a powerful physical-chemical synergistic deagglomeration scheme to address the core problem of heterogeneous agglomeration caused by salt and fine mud; it reduces tailings discharge while recovering high-value quartz sand, realizes the recycling of water resources within the process, and achieves a dual improvement in resource and environmental benefits; it ensures that the content of harmful fine mud in the recovered qualified quartz sand particles is sufficiently low to not affect its quality as an industrial raw material.

[0029] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for recovering marine sedimentary backflow sand, characterized in that, Includes the following steps: Step (1) Collection and concentration control of reflux tailings: Systematically collect the overflow tailings from the slurry storage hopper and hydraulic classifier in the marine sedimentary sand beneficiation process, pump the reflux tailings into the slurry conditioning tank, and precisely control its mass concentration to the range of 32% to 48%. Step (2) Slurry preparation and primary sedimentation thickening: The slurry prepared in step (1) is transported to a mortar storage hopper or a high-efficiency thickener for gravity sedimentation and desliming. The sedimentation time is 1.5 to 3 hours, and the sedimentation bottom flow rich in solid particles is collected. Step (3) Ultrasonic cavitation and mechanical synergistic dispersion: The sedimentation underflow obtained in step (2) is pumped into a reactor that integrates an ultrasonic generator and a mechanical stirrer. The slurry is treated under the conditions of ultrasonic power of 220W to 480W and mechanical stirring speed of 300 to 600rpm for 5 to 15 minutes. Step (4) Enhance secondary scrubbing and surface modification: Send the slurry treated in step (3) into the scrubbing machine, add 0.08% to 0.3% of the total mass of the slurry into the scrubbing machine, and perform secondary scrubbing with clean water. The scrubbing time is controlled at 10 to 25 minutes. Step (5) Precision hydrocyclone grading: Pump the slurry washed in step (4) to the hydrocyclone group, control the feed pressure between 0.16MPa and 0.22MPa, and select a hydrocyclone with an overflow port diameter to underflow port diameter ratio of 1:1.8 to 1:2.2 to collect the underflow product of the hydrocyclone, which is the qualified particle size of the recovered +0.15mm quartz sand; Step (6) Closed-loop water treatment and reagent reuse: The overflow of the hydrocyclone in step (5), the overflow of the slurry storage hopper in step (2), and the drainage of the scrubbing machine in step (4) are collected together and transported to the plant water treatment system. After sedimentation and clarification, they are reused for slurry preparation in step (1) or scrubbing operation in step (4). At the same time, the residual dispersant in the water is monitored and replenished to achieve indirect reuse of reagents.

2. The method for recovering marine sedimentary backflow sand according to claim 1, characterized in that, The dispersant in step (4) is one or more of sodium hexametaphosphate, sodium citrate, sodium gluconate, polymaleic anhydride, and acrylic acid-maleic anhydride copolymer.

3. The method for recovering marine sedimentary backflow sand according to claim 1, characterized in that, The ultrasonic generator in step (3) has a frequency range of 20kHz to 40kHz, and the ultrasonic probe is placed below the surface of the slurry to ensure that the ultrasonic energy is evenly distributed in the slurry and to generate an effective cavitation effect.

4. The method for recovering marine sedimentary backflow sand according to claim 1, characterized in that, The hydrocyclone in step (5) has a cone angle range of 15° to 20°.

5. The method for recovering marine sedimentary backflow sand according to claim 1, characterized in that, The overflow product of the hydrocyclone obtained in step (5) will be returned to the desliming stage of the main process or enter the tailings system. The main components of the overflow product are fine mud of -0.15mm and a small amount of undissociated micro-agglomerates.

6. The method for recovering marine sedimentary backflow sand according to claim 1, characterized in that, The mortar storage hopper in steps (1) and (2) uses intermittent automatic control for the discharge of the bottom sedimentation flow. When the concentration of the bottom slurry reaches 60% to 70%, the discharge valve is automatically opened.

7. The method for recovering marine sedimentary backflow sand according to claim 1, characterized in that, The impeller linear velocity of the scrubbing machine in step (4) is controlled at 8 to 12 m / s to provide sufficient shearing force while avoiding excessive abrasion.

8. The method for recovering marine sedimentary backflow sand according to claim 1, characterized in that, In step (3), the ultrasonic generator and the mechanical stirrer are started simultaneously to achieve synchronous stirring, so that the particle agglomerates in the slurry are fully disintegrated under the synergistic effect of ultrasonic cavitation and shear force.

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