Efficient and environmentally friendly mechanism of fine sand production method and application thereof

Abstract

The present application relates to a kind of high-efficiency environmental protection machine-made fine sand production method and its application, the method includes the following steps: (1) feed screening;(2) one-stage screen washing;(3) coarse crushing, medium crushing and screening;(4) two-stage sand washing;(5) fine crushing closed-circuit screening;(6) wet rod grinding sand and dehydration;(7) crushing, shaping and classification;(8) slurry dewatering.The present application adopts dry-wet combined sand making process, and the sand making rate is higher, the quality indexes such as mud content, moisture content, grading, stone powder content of finished sand can be better controlled in sand making process, the quality of finished machine-made fine sand is guaranteed, has the advantages of small one-time investment, low operation and management cost, coarse aggregate surface is clean, fine aggregate stone powder loss is less, etc., while dust pollution caused by dry sand making can be effectively reduced, stone powder and waste water can be recycled, the whole machine-made fine sand production is efficient and clean, and has strong popularization and application value.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization technology of solid waste resources, specifically relating to an efficient and environmentally friendly method for producing machine-made fine sand and its application. Background Technology

[0002] As a major component of building materials such as concrete and masonry, sand and gravel aggregates account for 60% to 75% of the volume. They are the largest and most indispensable raw materials used in infrastructure construction and can be widely used as filling materials in metallurgy and mining, as well as as aggregate building materials for highway asphalt, cement, hydropower concrete, and general building concrete.

[0003] Sand and gravel aggregates are mainly divided into two categories based on their source: natural sand and manufactured sand. However, with the continuous exploitation of natural sand, natural sand resources are rapidly decreasing, and in some areas they are nearing depletion. Over-exploitation has led to a decrease in river sediment, causing irreparable damage to river ecology, flood control, and navigation safety. Manufactured sand, on the other hand, is rock particles produced from inert stones such as rocks, pebbles, and mine waste rock through mechanical crushing and screening processes. It is an effective substitute for natural sand. Developing manufactured sand can solve the ecological balance problems of river embankments and dams caused by the over-exploitation of natural sand and also realize the comprehensive utilization of vast mine waste rock resources. Therefore, research on large-scale manufactured sand production technology is of great significance for the harmonious and sustainable development of humans and the natural environment.

[0004] Currently, the commonly used processes for producing manufactured sand are mainly dry and wet methods. The characteristics and limitations of these two processes are as follows: Dry sand making process refers to a sand making production line that uses virtually no water, except for a few dust removal processes involving spraying water for dust suppression. It is suitable for use in conjunction with a tower-type dry aggregate shaping and sand making system after medium and fine crushing. This process has high requirements for the content of impurities such as mud and organic matter in the raw materials. The content of impurities such as mud in the parent rock must be strictly controlled; otherwise, it is very easy to cause blockage of the production system and overload of the dust collection system, resulting in problems such as excessive stone powder content in the finished aggregate, high fineness modulus of fine aggregate, and serious dust pollution.

[0005] In the wet sand making process, water serves as both a working and dust-suppressing medium throughout all stages of sand and gravel aggregate production. This removes organic matter and other soluble impurities from the sand and gravel surface, resulting in a finished product with excellent appearance and high cleanliness. The process generates less dust, requiring less investment in dust collection facilities compared to the dry process, making it more environmentally friendly. However, the wet process leads to the loss of stone powder particles in the washing slurry, resulting in finished sand containing almost no stone powder. The fine aggregate does not meet the fineness modulus requirement of 2.4-2.8 for artificial sand as specified in the "Hydraulic Concrete Construction Code." Direct use of this material would increase the cement content in concrete. Furthermore, the slurry carrying a large amount of stone powder must be treated before discharge, inevitably increasing investment in wastewater treatment. Additionally, the finished sand has a high moisture content, failing to meet the requirement of less than 6% moisture content in the "Hydraulic Concrete Construction Code." Summary of the Invention

[0006] To address the aforementioned problems, this invention provides an efficient and environmentally friendly method, system, and application for producing refined sand. The aim is to overcome numerous issues in existing sand production processes, such as unreasonable gradation of finished sand, low sand yield, and dust or wastewater pollution associated with production, by employing a combined dry and wet sand-making process. This optimizes finished product quality, improves production efficiency, and avoids secondary pollution.

[0007] The specific technical solution is as follows: This invention provides a highly efficient and environmentally friendly method for producing manufactured fine sand, comprising the following steps: (1) Feeding and screening: High-pressure flushing water is used to wet the ore and disperse the ore slime. The material is screened by a bar feeder to obtain +60mm oversize material and -60mm undersize material. (2) First stage of washing: High pressure flushing water is used to wash the material under the -60mm screen to further disperse the ore mud and separate the ore mud and boulders to obtain material I over the +20mm screen and material I under the -20mm screen; (3) Coarse crushing, medium crushing and screening: The material on the +60mm screen is coarsely crushed in an open circuit. The coarsely crushed product is combined with the material on the +20mm screen I after a first-stage screen washing for medium crushing. After medium crushing, the medium crushed product is screened and washed with high-pressure flushing water to obtain material on the +20mm screen II and material under the -20mm screen II. (4) Second stage sand washing: The material under the -20mm screen of the first stage washing and the material under the -20mm screen of the medium crushing are combined for a second stage sand washing operation to separate mud and clean sand; (5) Fine crushing and closed-circuit screening: The material II on the +20mm screen of the medium crushing is finely crushed, and the finely crushed product is screened to obtain the material on the +15mm screen and the material under the -15mm screen; the material on the +15mm screen is returned to the fine crushing equipment for recycling and screening until all materials are finely crushed into qualified products of -15mm. (6) Wet rod milling and dewatering: The clean sand obtained from the two-stage washing and the part of the -15mm screened material obtained from the fine crushing are combined and subjected to wet rod milling. The rod milling product is dewatered and becomes 0.2~2.5mm finished washed sand. (7) Crushing, shaping and grading: The -15mm undersize material obtained from fine crushing is crushed, the particle shape is trimmed and then screened by a double-layer screen to obtain the product on the upper screen as 10~15mm finished coarse aggregate, the product on the lower screen as 4.75~10mm finished medium coarse aggregate, and the product undersize on the lower screen as 0~4.75mm machine-made fine sand; (8) Mud dewatering: The mud obtained from the second stage of sand washing and the slurry from the dewatered product of the rod mill are concentrated and filtered to obtain fine mud and overflow water. The overflow water can be recycled after sedimentation and clarification.

[0008] Furthermore, the high-pressure flushing water used in steps (1) to (3) is all of 0.3 to 0.5 MPa.

[0009] This invention also provides an equipment system for the above-mentioned efficient and environmentally friendly method of producing refined sand, including a bar feeder, wherein the feed inlet of the bar feeder is connected to a linear vibrating screen I, and the feed outlet of the bar feeder is connected to a jaw crusher; the feed outlet of the jaw crusher and the feed outlet of the linear vibrating screen I are connected to a medium-sized cone crusher, and the feed outlet of the medium-sized cone crusher is connected to a linear vibrating screen II. The underflow ports of both linear vibrating screen I and linear vibrating screen II are connected to a trough sand washing machine. The clean sand outlet of the trough sand washing machine is connected to a rod mill. The discharge port of the rod mill is connected to a high-frequency dewatering screen. The mud outlet of the trough sand washing machine and the slurry outlet of the high-frequency dewatering screen are connected in sequence to a high-efficiency thickener and a plate and frame filter press. The feed inlet of the linear vibrating screen II is connected to the fine crushing cone crusher, the discharge outlet of the fine crushing cone crusher is connected to the heavy-duty circular vibrating screen, the feed inlet of the heavy-duty circular vibrating screen is connected to the feed inlet of the fine crushing cone crusher, the discharge outlet of the heavy-duty circular vibrating screen is connected to the rod mill and the vertical shaft impact crusher, and the discharge outlet of the vertical shaft impact crusher is connected to the double-layer linear screen.

[0010] Furthermore, the jaw crusher's discharge port is connected to the medium-sized cone crusher's feed port, the linear vibrating screen's feed port is connected to the medium-sized cone crusher's feed port, and the heavy-duty circular vibrating screen's feed port is connected to the fine-sized cone crusher's feed port via belt conveyors and buffer bins.

[0011] Furthermore, the feed inlet of the linear vibrating screen II and the feed inlet of the trough sand washing machine, as well as the discharge outlet of the rod mill and the feed inlet of the high-frequency dewatering screen, are all connected by a slurry tank and a slurry pump.

[0012] Furthermore, a distribution bin is provided between the screen discharge port of the heavy-duty circular vibrating screen and the rod mill. The screen discharge port of the heavy-duty circular vibrating screen and the feed port of the distribution bin, as well as the discharge port of the distribution bin and the feed port of the rod mill, are all connected by belt conveyors. A buffer ore bin is also provided between the discharge port of the distribution bin and the feed port of the vertical shaft impact crusher.

[0013] Furthermore, the discharge port of the fine cone crusher and the feed port of the heavy-duty circular vibrating screen, as well as the discharge port of the vertical shaft impact crusher and the feed port of the double-layer linear screen, are all connected by belt conveyors.

[0014] This invention also provides the application of the above-mentioned efficient and environmentally friendly method and system for producing refined sand. The method and system are applied to the production of mud-containing parent rock, stone or waste rock with a clay plasticity index of 1 to 10 or less than 6% mud content and less than 16%.

[0015] The beneficial effects of this invention are as follows: This invention adopts a dry-wet combined sand making process with a high sand yield. The mud content is controlled by a "wet screening + two-stage sand washing" desliming process, the moisture content is controlled by a combination of mechanical dewatering and gravity dewatering, and the gradation and stone powder content of the machined fine sand are adjusted by a combination of three-stage crushing and "wet rod milling + dry crushing and shaping" sand making process. This allows for better control of the finished product's quality indicators, such as mud content, moisture content, gradation, and stone powder content, ensuring the quality of the finished machined fine sand. It has advantages such as low initial investment, low operating and management costs, clean coarse aggregate surface, and less stone powder loss from fine aggregate. At the same time, it can effectively reduce dust pollution caused by dry sand making and realize the recycling of stone powder and wastewater. The entire production of machined fine sand is efficient and clean, and has strong promotion and application value. Attached Figure Description

[0016] Figure 1 This is a flowchart of an efficient and environmentally friendly method for producing machine-made refined sand, as described in Example 1. Figure 2 This is an equipment diagram of an efficient and environmentally friendly machine-made fine sand production system, as shown in Example 2. In the diagram: 1-Bar feeder; 2-Linear vibrating screen I; 3-Trough sand washer; 4-High-efficiency thickener; 5-Plate and frame filter press; 6-Rod mill; 8-High-frequency dewatering screen; 9-Jaw crusher; 10-Medium cone crusher; 11-Linear vibrating screen II; 13-Fine cone crusher; 14-Heavy-duty circular vibrating screen; 15-Vertical shaft impact crusher; 16-Double-layer linear screen; 17-Distribution bin. Detailed Implementation

[0017] To make the technical problems and solutions solved by the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. Example 1

[0018] This embodiment provides a highly efficient and environmentally friendly method for producing manufactured fine sand, including the following steps: (1) Feeding and screening: Use high-pressure washing water of 0.3~0.5MPa to wet the ore and disperse the ore mud, and screen the material through a bar feeder to obtain +60mm oversize material and -60mm undersize material; (2) First stage of washing: Use high pressure washing water of 0.3~0.5MPa to wash the material under the -60mm screen in the first stage, so that the ore mud is further dispersed and the ore mud and boulders are separated to obtain material I over the +20mm screen and material I under the -20mm screen. (3) Coarse crushing, medium crushing and screening: The material on the +60mm screen is coarsely crushed in an open circuit. The coarsely crushed product is combined with the material on the +20mm screen I after a first-stage screen washing for medium crushing. After medium crushing, the medium crushed product is screened and washed with high-pressure flushing water of 0.3~0.5MPa to obtain material on the +20mm screen II and material under the -20mm screen II. (4) Second stage sand washing: The material under the -20mm screen of the first stage washing and the material under the -20mm screen of the medium crushing are combined for a second stage sand washing operation to separate mud and clean sand; (5) Fine crushing and closed-circuit screening: The material II on the +20mm screen of the medium crushing is finely crushed, and the finely crushed product is screened to obtain the material on the +15mm screen and the material under the -15mm screen; the material on the +15mm screen is returned to the fine crushing equipment for recycling and screening until all materials are finely crushed into qualified products of -15mm. (6) Wet rod milling and dewatering: The clean sand obtained from the two-stage washing and the part of the -15mm screened material obtained from the fine crushing are combined and wet rod milling is carried out. The rod milling product is 0.2~2.5mm finished washed sand after dewatering. (7) Crushing, shaping and grading: The -15mm undersize material obtained from fine crushing is crushed, the particle shape is trimmed and then screened by a double-layer screen to obtain the product on the upper screen as 10~15mm finished coarse aggregate, the product on the lower screen as 4.75~10mm finished medium coarse aggregate, and the product undersize on the lower screen as 0~4.75mm machine-made fine sand; (8) Mud dewatering: The mud obtained from the second stage of sand washing and the slurry from the dewatered product of the rod mill are concentrated and filtered to obtain fine mud and overflow water. The overflow water can be recycled after sedimentation and clarification.

[0019] This invention employs a combined wet and dry sand-making process. The sand washing and desliming process utilizes a "wet screening + two-stage sand washing" method, the stone crushing process employs a "coarse crushing - medium crushing - fine crushing" three-stage crushing process, and the sand making process employs a "wet rod mill + dry crushing and shaping" method. It can be applied to the production of mud-containing parent rock, stone, or waste rock that is free of mud, has a mud content of 6% < < mud content < 16%, or has a clay plasticity index of 1~10.

[0020] The control of key technical indicators in the production process of manufactured fine sand by this invention is as follows: (1) Control of mud content in finished sand and gravel and coarse aggregate Since the methylene blue (MB) value of manufactured sand is directly proportional to the clay content, when the MB value exceeds the critical value of 1.4, the workability of fresh concrete decreases significantly, the degree of early plastic cracking increases, and the flexural strength and 7-day compressive strength of hardened concrete are significantly reduced. Therefore, it is necessary to remove clay or fine mud from the manufactured sand and aggregate.

[0021] In response, this invention organically combines the "wet screening + two-stage sand washing" desliming process with the crushing process. The staged separator uses high-pressure water washing to separate the raw stone, coarse crushed stone, and medium crushed stone, thereby effectively removing clay or fine mud adhering to the surface of the product and making the mud content of each particle size product <1%, creating favorable conditions for the subsequent production of sand and gravel aggregates.

[0022] (2) Control of moisture content of finished sand and gravel and coarse aggregate This invention employs a "wet rod mill + dry crushing and shaping" process for sand production. While fine crushing and shaping utilize dry crushing, and the rod mill itself is a wet grinding process, the product is dewatered using a high-frequency dewatering screen. Therefore, the coarse aggregate, manufactured fine sand, and washed sand obtained from this sand production process have low moisture content, controllable to below 10%. Furthermore, during storage in the finished sand bin, gravity dewatering and natural ventilation further reduce the moisture content to meet relevant technical requirements.

[0023] (3) Optimization and control of particle size distribution Particle size distribution refers to the proportion of particles of various sizes in aggregates. A continuous gradation consists of uninterrupted levels of particle size, while a discontinuous gradation consists of only a few particle sizes. A reasonable particle size distribution is crucial for achieving low porosity or low air porosity in aggregate production. To address the problem of coarse gradations in dry sand making and unreasonable gradations due to low 0.16mm stone powder content in wet sand making, this invention employs a "wet rod mill + dry crushing and shaping" sand-making process to produce machine-made fine sand with different gradations and yields, which is then mixed. Of course, the finished aggregate gradation can be adjusted according to the specific requirements of downstream users by modifying the discharge openings of the medium crusher and fine crusher, the screen size of the linear screen, and adjusting and distributing the feed rates of the rod mill and crushing / shaping processes to achieve the production of aggregates of different particle sizes.

[0024] (4) Control of stone powder content Stone powder is a fine-grained powder with a particle size of -0.16mm (specific surface area 325m² / kg) produced during the crushing process of parent rock. Stone powder can replace fly ash as an admixture in concrete preparation. Distinguished from fine mud, it is defined as stone powder if its methylene blue (MB) value is <1.4. In this invention, coarse and medium crushing employ a wet process, during which a small amount of stone powder is incorporated into the slurry along with the fine mud during sand washing. Fine crushing and crushing / shaping employ a dry process, during which the stone powder produced can be directly added to the finished sand and gravel. Appropriate amounts of stone powder can effectively improve the impermeability, frost resistance, and durability of concrete, as well as its workability. Similarly, this invention can control the stone powder content in the finished sand by rationally adjusting and distributing the feed rates of rod mill sand making and crushing / shaping sand making.

[0025] (5) Control of particle shape of finished sand and gravel aggregate The particle shape of finished sand and gravel aggregates, especially coarse aggregates, is related to factors such as the structure of the parent rock, crushing process, and equipment performance, making it difficult to avoid the production of a certain amount of needle-like and flaky aggregates. This invention employs a jaw crusher for open-circuit crushing to -180mm for coarse crushing, and a cone crusher for medium and fine crushing with full feeding and layered closed-circuit crushing. The cone crusher offers good stability, produces uniform particle shape, has a wide discharge adjustment range, and provides significant flexibility in adjusting the product gradation. Wet screening is installed after medium crushing, and dry closed-circuit screening is installed after fine crushing, combining wet and dry processes. A portion of the -15mm fine-crushed particles are fed into a vertical shaft impact crusher for crushing and shaping (four-stage crushing). The feeding gradation is continuous, and the materials collide and shape each other throughout the crushing and shaping process, resulting in cubic particle shapes with few flaky and needle-like particles (content < 5%). The crushed product has a continuous gradation and is dry-screened by a double-layer linear screen to produce three finished products: 0~4.75mm fine sand, 4.75~10mm medium and coarse aggregate, and 10~15mm coarse aggregate.

[0026] (6) Treatment of sand washing mud This invention employs a combined dry and wet process, which overcomes the dust pollution problem of dry sand making while reducing water consumption in wet sand making. It is a green and environmentally friendly sand making process. After concentration and pressure filtration, the sand washing slurry is treated for drainage, and the overflow water can be returned to the sand washing water point for recycling after sedimentation and clarification, which can further reduce the consumption of fresh water and comply with national energy conservation and emission reduction policies.

[0027] In summary, this invention employs a combined dry and wet sand-making process with a high sand yield. The mud content is controlled through sand washing and desliming, and the moisture content is controlled by combining mechanical and gravity dewatering. The combined dry and wet sand-making process adjusts the fineness modulus and stone powder content of the finished sand, ensuring good control over the finished sand's quality indicators such as mud content, moisture content, gradation, and stone powder content. This guarantees the quality of the finished machine-made fine sand and offers advantages such as low initial investment, low operating and management costs, clean coarse aggregate surface, and minimal stone powder loss from fine aggregates. Simultaneously, it effectively reduces dust pollution caused by dry sand-making and enables the recycling of stone powder and wastewater. The entire process of producing machine-made fine sand is highly efficient and clean, possessing strong potential for widespread application.

[0028] Application Example 1

[0029] A certain sand and gravel aggregate plant has a processing capacity of 3000t / d. The stone material is waste rock stripped from open-pit mines, mainly limestone, with a crushing power index of about 14.70kW·h / t and a raw material sludge content of about 8%.

[0030] The above-mentioned stone was processed into sand using the method described in Example 1. The process employed a combination of wet screening and two-stage washing for desliming, three-stage crushing (coarse, medium, and fine crushing), and wet rod milling combined with dry crushing and shaping. The main equipment selected for the production process was as follows: one Metso Outotec C100 jaw crusher for coarse crushing, used to process mine waste rock with a particle size of +60mm to +650mm from the quarry; one Metso Outotec HP300 hydraulic cone crusher for medium crushing, used to process coarse crushed products of -180mm and material washed from the first-stage screening; one Metso Outotec HP300 fine-crushing hydraulic cone crusher; a Metso B6150SE vertical shaft impact crusher for crushing and shaping; and a BM2740 wet rod mill for wet sand making. The main technical indicators of the finished product are shown in Table 1. Table 1: Main Technical Indicators of Finished Sand Products

[0031] Of this, 0-0.2mm stone powder and fine mud account for about 16%, with a yield of about 480t / d.

[0032] The fineness modulus of the finished fine aggregate is between 2.3 and 3.0, with continuous gradation and a stone powder content between 10% and 18%. The moisture content upon entering the storage bin is controlled at around 10%, and after gravity dewatering and natural ventilation, the moisture content can be reduced to below 6%. The production water recovery rate is ≥80%, and the power consumption is approximately 3.5 kWh / t. The finished sand meets the requirements for sand and gravel aggregates for underground mine filling.

[0033] Application Example 2

[0034] A hydroelectric sand and gravel plant is located near the dam site of a hydroelectric power station. It has abundant water resources and processes mainly granite and limestone. The rock hardness is medium and the parent rock has moderate abrasiveness. The designed processing capacity is 550t / h.

[0035] The original production process used dry sand making, following a "pre-screening - coarse crushing - medium crushing - fine crushing" flow. Before coarse crushing, pre-screening removed raw ore up to -150mm. Coarse crushing used one Sandvik CJ612 jaw crusher with a discharge opening CSS=150mm. Medium crushing used one Sandvik CS440C cone crusher with an eccentricity of 36mm and a close-side discharge opening CSS=44mm. Before fine crushing, pre-screening produced -5mm fine aggregate. Fine crushing used two CH440MF fine-crushing cone crushers with an eccentricity of 44mm and a close-side discharge opening CSS=22mm. Two double-layer linear vibrating screens were used in conjunction with the fine crushing process to form a closed-circuit screening system. The material passing through the upper screen (+31.5mm) is returned for fine crushing. The material passing through the lower screen (20-30mm) is transferred to the finished product yard to produce 20-30mm coarse aggregate. The material passing through the lower screen (-20mm) is then transferred to a double-layer linear screen for secondary screening. The material passing through the secondary screen produces 10-20mm finished aggregate, which is then transferred to the yard for storage. The material passing through the lower screen (-10mm) is then crushed, shaped, and screened using two Sandvik SC2462 vertical shaft impact crushers and two linear screens. The crushed and shaped material passing through the upper screen (+5mm) is returned to the vertical shaft impact crusher. The material passing through the lower screen (-5mm) is processed by two air classifiers to adjust the fine sand and gravel content of the finished product, producing -5mm finished sand.

[0036] In actual production, due to the high mud content of raw materials, the use of dry sand making causes problems such as process obstruction during the rainy season, low sand production rate of finished sand (0~5mm), unbalanced gradation, and excessive mud content in finished products.

[0037] After sand making using the method described in Example 1, the fineness modulus of the finished sand is controlled at around 2.8, and the stone powder content is controlled at 14%. This solves the problems of process obstruction during the rainy season, excessive mud content in the finished product, gradation imbalance, and production dust that exist when using granite and limestone as raw materials for aggregate production. A comparison of the main technical indicators after implementing the two sand making methods is shown in Table 2. Table 2: Comparison of main technical indicators of the two sand making methods

[0038] As shown in Table 2 above, the method described in this invention can produce relatively ideal finished sand and gravel from parent rocks of different lithologies such as limestone, granite, and limestone. The finished sand and gravel has a continuous gradation and a reasonable stone powder content, which can meet the needs of concrete production. Example 2

[0039] This embodiment provides a high-efficiency and environmentally friendly production system for manufactured fine sand used in Embodiment 1 above, including a bar feeder 1, the underfeed port of the bar feeder 1 being connected to a linear vibrating screen I2, and the overfeed port of the bar feeder 1 being connected to a jaw crusher 9; the underfeed port of the jaw crusher 9 and the overfeed port of the linear vibrating screen I2 are both connected to a medium-sized cone crusher 10 via belt conveyors and a buffer bin, and the underfeed port of the medium-sized cone crusher 10 is connected to a linear vibrating screen II11; The undersize inlets of both linear vibrating screen I2 and linear vibrating screen II11 are connected to the trough sand washing machine 3, and the undersize inlet of linear vibrating screen II11 is connected to the feed inlet of the trough sand washing machine 3 through a slurry tank and a slurry pump; the clean sand outlet of the trough sand washing machine 3 is connected to the rod mill 6, and the discharge outlet of the rod mill 6 is connected to the high-frequency dewatering screen 8 through a slurry tank and a slurry pump; the mud outlet of the trough sand washing machine 3 and the slurry outlet of the high-frequency dewatering screen 8 are connected in sequence to the high-efficiency thickener 4 and the plate and frame filter press 5. The feed inlet of the linear vibrating screen II11 is connected to the fine crushing cone crusher 13. The discharge outlet of the fine crushing cone crusher 13 is connected to the feed inlet of the heavy-duty circular vibrating screen 14 via a belt conveyor. The feed inlet of the heavy-duty circular vibrating screen 14 is connected to the feed inlet of the fine crushing cone crusher 13 via a belt conveyor and a buffer ore bin. The discharge outlet of the heavy-duty circular vibrating screen 14 is connected to the rod mill 6 and the vertical shaft impact crusher 15. The discharge outlet of the vertical shaft impact crusher 15 is connected to the feed inlet of the double-layer linear screen 16 via a belt conveyor.

[0040] Furthermore, a distribution bin 17 is provided between the discharge port of the heavy-duty circular vibrating screen 14 and the rod mill 6. The discharge port of the heavy-duty circular vibrating screen 14 and the feed port of the distribution bin 17 are connected by belt conveyors, and the discharge port of the distribution bin 17 and the feed port of the rod mill 6 are connected by belt conveyors. A buffer ore bin is also provided between the discharge port of the distribution bin 17 and the feed port of the vertical shaft impact crusher 15.

[0041] It should also be noted that the above-mentioned equipment is all existing equipment, and this invention does not involve the modification of the equipment, but only the use of the existing equipment. Of course, the finished aggregate gradation can be achieved according to the specific requirements of the downstream user by adjusting the discharge port of the medium-sized cone crusher (10 discharge port), the discharge port of the fine-sized cone crusher (13 discharge port), the screen size of the linear vibrating screen, the heavy-duty circular vibrating screen, and the double-layer linear screen, and by adjusting and distributing the feed rates of the rod mill and the vertical shaft impact crusher. The control of the stone powder content in the finished sand can be achieved by reasonably adjusting and distributing the feed rates of the rod mill and the vertical shaft impact crusher.

[0042] Working principle: (1) Feeding and screening: feed the waste rock into the bar feeder 1, use 0.3~0.5MPa high pressure flushing water to wet the ore and disperse the ore mud for screening, to obtain +60mm screen material and -60mm screen material.

[0043] (2) First stage of screening and washing: The material under the -60mm screen of the bar feeder 1 is transferred to the linear vibrating screen I2 for first stage screening and washing, so that the sludge is further dispersed and the sludge and boulders are separated to obtain the material I under the +20mm screen and the material I under the -20mm screen.

[0044] (3) Coarse crushing, medium crushing and screening: The material on the +60mm screen of the bar feeder 1 is transferred to the jaw crusher 9 for coarse crushing. The coarse crushed product and the material on the +20mm screen of the first stage are transferred to the medium crushing cone crusher 10 for medium crushing via a belt conveyor and a buffer bin. After medium crushing, the material is transferred to the linear vibrating screen II 11. The medium crushed product is screened and washed with high-pressure flushing water of 0.3~0.5MPa to obtain the material on the +20mm screen II and the material under the -20mm screen II.

[0045] (4) Second stage sand washing: The material I under the first stage screen washing -20mm and the material II under the medium crushing screen washing -20mm are combined and transferred to the trough sand washing machine 3 for second stage sand washing operation, and mud and clean sand are separated.

[0046] (5) Fine crushing and closed-circuit screening: The material II on the +20mm screen is transferred to the buffer ore bin and then to the fine crushing cone crusher 13 for fine crushing. After fine crushing, it is transferred to the heavy-duty circular vibrating screen 14 by the belt conveyor to obtain the material on the +15mm screen and the material under the -15mm screen. The material on the +15mm screen is returned to the fine crushing cone crusher 13 by the belt conveyor for repeated fine crushing and screening until all materials are finely crushed into qualified products of -15mm.

[0047] (6) Wet rod milling and dewatering: The clean sand from the two-stage washing and the -15mm screened material from the fine crushing screening (passing through the distribution bin 17 and the belt conveyor) are transferred to the rod mill 6 for wet rod milling. The rod mill product is transferred to the high-frequency dewatering screen 8 through the slurry tank and slurry pump for dewatering. The dewatered product is the washed sand (0.2~2.5mm).

[0048] (7) Crushing, shaping and grading: The -15mm undersize material from the fine crushing and screening part is transferred to the vertical shaft impact crusher 15 through the buffer ore bin for crushing and particle shape trimming, and then transferred by belt conveyor to the double-layer linear screen 16 for double-layer screening. The product on the upper screen is 10~15mm finished coarse aggregate, the product on the lower screen is 4.75~10mm finished medium coarse aggregate, and the product undersize on the lower screen is 0~4.75mm machine-made fine sand.

[0049] (8) Mud dewatering: The mud from the second stage of sand washing and the slurry from the dewatering of the rod mill product are transferred to the high-efficiency thickener 4 for concentration. After concentration, the mud is filtered by the plate and frame filter press 5 to obtain fine mud and overflow water. The overflow water can be recycled after sedimentation and clarification in the recovery tank.

[0050] The production system described in this invention is designed according to the production method described in Example 1. It has supporting equipment corresponding to the "wet screening + two-stage sand washing" desliming process, the "coarse crushing - medium crushing - fine crushing" three-stage crushing process, and the "wet rod mill + dry crushing and shaping" sand making process. It can be applied to the production of mud-containing parent rock, stone or waste rock that does not contain mud, has a mud content of 6% < mud content < 16% or a clay plasticity index of 1~10.

[0051] This production system controls the mud content through sand washing and desliming equipment, controls the moisture content through a combination of mechanical dewatering and gravity dewatering, and adjusts the fineness modulus and stone powder content of the finished sand through a combination of dry and wet sand making equipment. This allows for better control of the finished sand's quality indicators, such as mud content, moisture content, gradation, and stone powder content, resulting in a high sand production rate and high-quality manufactured fine sand. It has advantages such as low initial investment, low operating and management costs, clean coarse aggregate surface, and minimal stone powder loss from fine aggregate. At the same time, it can effectively reduce dust pollution caused by dry sand making and realize the recycling of stone powder and wastewater. The entire manufactured fine sand production process is efficient and clean, and has strong promotion and application value.

[0052] The present invention has been described in detail above through specific and preferred embodiments. However, those skilled in the art should understand that the present invention is not limited to the embodiments described above. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A highly efficient and environmentally friendly method for producing manufactured fine sand, applicable to the production of mud-bearing parent rock, stone, or waste rock with a clay plasticity index of 1-10 or less than 6% mud content and less than 16%, characterized in that, Includes the following steps: (1) Feeding and screening: High-pressure flushing water is used to wet the ore and disperse the ore slime. The material is screened by a bar feeder to obtain +60mm oversize material and -60mm undersize material. (2) First stage of washing: High pressure flushing water is used to wash the material under the -60mm screen to further disperse the ore mud and separate the ore mud and boulders to obtain material I over the +20mm screen and material I under the -20mm screen; (3) Coarse crushing, medium crushing and screening: The material on the +60mm screen is coarsely crushed in an open circuit. The coarsely crushed product is combined with the material on the +20mm screen I after a first-stage screen washing for medium crushing. After medium crushing, the medium crushed product is screened and washed with high-pressure flushing water to obtain material on the +20mm screen II and material under the -20mm screen II. (4) Second stage sand washing: The material under the -20mm screen of the first stage washing and the material under the -20mm screen of the medium crushing are combined for a second stage sand washing operation to separate mud and clean sand; (5) Fine crushing and closed-circuit screening: The material II on the +20mm screen of the medium crushing is finely crushed, and the finely crushed product is screened to obtain the material on the +15mm screen and the material under the -15mm screen; the material on the +15mm screen is returned to the fine crushing equipment for recycling and screening until all materials are finely crushed into qualified products of -15mm. (6) Wet rod milling and dewatering: The clean sand obtained from the two-stage washing and the part of the -15mm screened material obtained from the fine crushing are combined and wet rod milling is carried out. The rod milling product is 0.2~2.5mm finished washed sand after dewatering. (7) Crushing, shaping and grading: The -15mm undersize material obtained from fine crushing is crushed, the particle shape is trimmed and then screened by a double-layer screen to obtain the product on the upper screen as 10~15mm finished coarse aggregate, the product on the lower screen as 4.75~10mm finished medium coarse aggregate, and the product undersize on the lower screen as 0~4.75mm machine-made fine sand; (8) Mud dewatering: The mud obtained from the second stage of sand washing and the slurry from the dewatered product of the rod mill are concentrated and filtered to obtain fine mud and overflow water. The overflow water can be recycled after sedimentation and clarification.

2. The efficient and environmentally friendly method for producing manufactured fine sand according to claim 1, characterized in that, The high-pressure flushing water used in steps (1) to (3) is all of 0.3 to 0.5 MPa.

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