Production treatment system for efficient and comprehensive utilization of fully strong weathered material
By combining screening, crushing, and washing systems with fine sand recovery, the problem of efficient utilization of fully weathered materials has been solved, achieving low-cost, high-efficiency production and high-quality washed sand production, reducing resource waste and flocculant residue, and extending equipment life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-03
- Publication Date
- 2026-03-10
AI Technical Summary
The fully weathered material has not been effectively utilized in the construction of green mines, resulting in resource waste and land degradation. Existing processing technology has unstable costs and quality, and the finished washed sand has serious problems with moisture content, mud content and flocculant residue.
The system employs a screening and crushing system, a washing system, and a fine sand recovery system, including equipment such as a bar feeder, jaw crusher, circular vibrating screen, spiral sand washer, wheel sand washer, cyclone separator, and linear dewatering screen. Through flushing screening, closed-loop circulation of roller mills, double-stage spiral sand washing, and cyclone separator combination, it achieves efficient washing and fine sand recovery of fully weathered materials.
It has enabled low-cost, high-efficiency, and high-quality production of fully weathered materials, reducing production costs, improving product quality, reducing resource waste and flocculant residue, and extending equipment life.
Smart Images
Figure CN223980957U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of comprehensive utilization technology of fully weathered materials, and in particular relates to a production and processing system for efficient comprehensive utilization of fully weathered materials. Background Technology
[0002] The disposal of fully weathered surface material in green mine construction urgently needs to be addressed. As a crucial resource in green mines, directly dumping fully weathered material as waste requires vast amounts of land, leading to both resource waste and land degradation. Comprehensive utilization of fully weathered material to produce washed sand is a commonly used disposal method. Through crushing, screening, washing, and dewatering, the mud and fine particles in the raw material are removed, resulting in washed sand with higher economic value, turning waste into treasure. Currently, different mines have different disposal methods for fully weathered material. The composition of the raw material varies, leading to different production processes and procedures for producing washed sand, resulting in varying production costs and product quality. The moisture content, mud content, and flocculant residue of the finished washed sand directly affect production costs and quality.
[0003] This invention designs a production and processing system for the efficient and comprehensive utilization of fully weathered materials to solve the above problems. Utility Model Content
[0004] To achieve the above objectives, the present invention adopts the following technical solution:
[0005] A production and processing system for the efficient and comprehensive utilization of fully weathered materials includes: a screening and crushing system, a washing system, a fine sand recovery system, a receiving bin, a finished sand bin, a return bin, and a waste bin;
[0006] The screening and crushing system includes a bar feeder, a jaw crusher, a circular vibrating screen, a regulating silo, a roller mill, and a closed-circuit linear screen. The bar feeder can transport large-diameter sand and gravel discharged from the receiving silo to the jaw crusher. The circular vibrating screen receives small-diameter sand and gravel output from the receiving silo, the bar feeder, and the jaw crusher. The receiving silo divides the sand and gravel into three categories according to particle size and transports them to the return silo, the regulating silo, and the washing system, respectively. The regulating silo, the roller mill, and the closed-circuit linear screen form a closed-circuit crushing and screening cycle. The closed-circuit linear screen transports sand and gravel that meet the particle size requirements to the washing system.
[0007] The washing system includes a first-stage spiral sand washer, a second-stage spiral sand washer, a first-stage wheel sand washer, a second-stage wheel sand washer, and a first-stage linear dewatering screen. The first-stage spiral sand washer receives sand and gravel from the receiving bin and the closed-circuit linear screen. The first-stage spiral sand washer, the second-stage spiral sand washer, the first-stage wheel sand washer, and the second-stage wheel sand washer are used for sand washing operations. The first-stage linear dewatering screen is used to dewater the sand and gravel washed by the second-stage wheel sand washer.
[0008] The fine sand recovery system includes a primary recovery tank, a secondary recovery tank, a primary cyclone separator, a secondary cyclone separator, a tertiary cyclone separator, a secondary linear dewatering screen, a tertiary linear dewatering screen, and a tertiary wheel sand washer. The primary recovery tank and the secondary cyclone separator are used to recover fine sand from the production wastewater of the secondary and tertiary spiral sand washers. The secondary recovery tank and the secondary cyclone separator are used to recover fine sand from the production wastewater of the secondary and tertiary wheel sand washers and the secondary linear dewatering screen. The tertiary wheel sand washer is used to wash the fine sand recovered by the secondary cyclone separator. The secondary linear dewatering screen is used to dewater the sand and gravel washed by the secondary cyclone separator and the tertiary wheel sand washer. The secondary cyclone separator and the tertiary linear dewatering screen are used to recover and dewater the fine sand from the production wastewater of the secondary linear dewatering screen and the tertiary wheel sand washer.
[0009] The fine sand output from the first-stage and second-stage linear dewatering screens is transported to the finished sand bin. If the fine sand output from the second-stage cyclone separator meets the quality requirements, it is transported to the second-stage linear dewatering screen. If the fine sand output from the second-stage cyclone separator does not meet the quality requirements, it is transported to the waste bin. If the fine sand output from the third-stage linear dewatering screen meets the quality requirements, it is transported to the finished sand bin. If the fine sand output from the third-stage linear dewatering screen does not meet the quality requirements, it is transported to the waste bin.
[0010] As a preferred option, the system includes a clear water tank and a recycled water tank. The water used for the 2-stage wheel sand washing machine, 3-stage wheel sand washing machine, 1-stage linear dewatering screen, 2-stage linear dewatering screen and 3-stage linear dewatering screen is supplied by the clear water tank, while the water used for the circular vibrating screen, 1-stage spiral sand washing machine, 2-stage spiral sand washing machine and 1-stage wheel sand washing machine is supplied by the recycled water tank.
[0011] As a preferred solution, a wastewater treatment system is included. The wastewater treatment system supplies water to a recycled water tank. Wastewater from the first-stage spiral sand washer and the second-stage spiral sand washer will sequentially enter the wastewater treatment system through a first-stage recovery tank and a first-stage cyclone separator. Wastewater from the first-stage wheel sand washer, the second-stage wheel sand washer, and the first-stage linear dewatering screen will sequentially enter the wastewater treatment system through a second-stage recovery tank and a second-stage cyclone separator. Wastewater from the second-stage linear dewatering screen and the third-stage wheel sand washer will enter the wastewater treatment system after passing through a third-stage cyclone separator. Wastewater from the third-stage linear dewatering screen will be directly fed into the wastewater treatment system.
[0012] As a preferred option, a bar screen is installed inside the receiving silo, which divides the inside of the receiving silo into a small-diameter silo and a large-diameter silo. The small-diameter silo stores sand and gravel smaller than 30mm, while the large-diameter silo stores sand and gravel larger than or equal to 30mm.
[0013] As a preferred embodiment, the circular vibrating screen has two layers of screens, with the upper screen having a mesh size of 30mm and the lower screen having a mesh size of 3mm, and the closed-circuit linear screen having a mesh size of 4.75mm.
[0014] Compared with existing technologies, the advantages of this utility model are:
[0015] 1. This utility model adopts a water flushing and screening system, a closed-loop circulation system of roller mill, a double-stage spiral sand washing system, a double-stage bucket wheel sand washing system, a cyclone group and a linear dewatering screen that work together to achieve low-cost operation, high efficiency and high quality of production of fully weathered material water-washed sand system, and has the advantages of wide applicability.
[0016] 2. The roller mill crushing and closed-circuit linear screen screening process of this utility model not only solves the problem of undisintegrated mud clumps after screening and washing, but also allows for repeated crushing of some sand and gravel with low crushing values, thereby improving product quality and achieving efficient utilization of fully weathered materials.
[0017] 3. Based on the mud content of the material, this utility model allows for flexible selection of washing steps in the washing system, and flexible configuration of washing combinations of stage 1 spiral sand washing machine, stage 2 spiral sand washing machine, stage 1 wheel bucket sand washing machine, and stage 2 wheel bucket sand washing machine, thereby improving the system's adaptability and reducing production costs.
[0018] 4. The sand washing stage of this spiral sand washer is set before the fine sand stage of the wheel sand washer. Utilizing the kneading, stirring, and pushing capabilities of the rotating blades, it is suitable for the initial washing stage of fully weathered materials with high mud content, thereby improving the system's mud removal and sand washing effect.
[0019] 5. This utility model sets up a three-level recycling system. The fine sand recycled by the first-level cyclone group is the first-level recycled sand, the fine sand recycled by the second-level cyclone group is the second-level recycled sand, and the fine sand recycled by the third-level cyclone group is the third-level recycled sand. Different recycling methods are used for different levels of recycled sand to achieve efficient utilization of fully weathered material and reduce resource waste.
[0020] 6. In this invention, the washing and dewatering processes before the sand enters the finished sand bin use clean water that has not undergone wastewater treatment. This avoids the sand from clumping together, reduces the residue of flocculant, and improves product quality.
[0021] 7. In this utility model, all wastewater generated in the sand washing process is recycled through fine sand and then enters the wastewater treatment system, which reduces the content of fine particles in the production wastewater. This reduces the amount of flocculant used in the wastewater treatment system and also reduces the wear of fine particles on the downstream filter press equipment. Attached Figure Description
[0022] Figure 1 This is a flowchart illustrating the present invention.
[0023] Figure 2 This is a schematic diagram of the flow direction of sand and gravel materials according to this utility model.
[0024] Figure 3 This is a schematic diagram of the water flow direction of this utility model.
[0025] Figure 4 This is a schematic diagram of the flow direction of the recycled water in this utility model.
[0026] Figure 5 This is a schematic diagram of the wastewater flow direction of this utility model. Detailed Implementation
[0027] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings and examples. The following embodiments or drawings are used to illustrate this utility model, but are not intended to limit the scope of this utility model.
[0028] A production and processing system for the efficient and comprehensive utilization of fully weathered materials, such as Figures 1 to 5 As shown, it includes: a screening and crushing system, a washing system, a fine sand recovery system, a receiving silo, a finished sand silo, a return silo, and a waste silo;
[0029] The screening and crushing system includes a bar feeder, a jaw crusher, a circular vibrating screen, a regulating silo, a roller mill, and a closed-circuit linear screen. The bar feeder can transport large-diameter sand and gravel discharged from the receiving silo to the jaw crusher. The circular vibrating screen receives small-diameter sand and gravel output from the receiving silo, the bar feeder, and the jaw crusher. The receiving silo divides the sand and gravel into three categories according to particle size and transports them to the return silo, the regulating silo, and the washing system, respectively. The regulating silo, the roller mill, and the closed-circuit linear screen form a closed-circuit crushing and screening cycle. The closed-circuit linear screen transports sand and gravel that meet the particle size requirements to the washing system.
[0030] The washing system includes a first-stage spiral sand washer, a second-stage spiral sand washer, a first-stage wheel sand washer, a second-stage wheel sand washer, and a first-stage linear dewatering screen. The first-stage spiral sand washer receives sand and gravel from the receiving bin and the closed-circuit linear screen. The first-stage spiral sand washer, the second-stage spiral sand washer, the first-stage wheel sand washer, and the second-stage wheel sand washer are used for sand washing operations. The first-stage linear dewatering screen is used to dewater the sand and gravel washed by the second-stage wheel sand washer.
[0031] The fine sand recovery system includes a primary recovery tank, a secondary recovery tank, a primary cyclone separator, a secondary cyclone separator, a tertiary cyclone separator, a secondary linear dewatering screen, a tertiary linear dewatering screen, and a tertiary wheel sand washer. The primary recovery tank and the secondary cyclone separator are used to recover fine sand from the production wastewater of the secondary and tertiary spiral sand washers. The secondary recovery tank and the secondary cyclone separator are used to recover fine sand from the production wastewater of the secondary and tertiary wheel sand washers and the secondary linear dewatering screen. The tertiary wheel sand washer is used to wash the fine sand recovered by the secondary cyclone separator. The secondary linear dewatering screen is used to dewater the sand and gravel washed by the secondary cyclone separator and the tertiary wheel sand washer. The secondary cyclone separator and the tertiary linear dewatering screen are used to recover and dewater the fine sand from the production wastewater of the secondary linear dewatering screen and the tertiary wheel sand washer.
[0032] The fine sand output from the first-stage and second-stage linear dewatering screens is transported to the finished sand bin. If the fine sand output from the second-stage cyclone separator meets the quality requirements, it is transported to the second-stage linear dewatering screen. If the fine sand output from the second-stage cyclone separator does not meet the quality requirements, it is transported to the waste bin. If the fine sand output from the third-stage linear dewatering screen meets the quality requirements, it is transported to the finished sand bin. If the fine sand output from the third-stage linear dewatering screen does not meet the quality requirements, it is transported to the waste bin.
[0033] It also includes a control center with PLC control function. The control center is used to realize the linkage between equipment. The circular vibrating screen, roller mill, closed-circuit linear screen, various spiral sand washing machines, various wheel bucket sand washing machines, various linear dewatering screens, and various cyclone groups are all controlled by the control center. In addition, the water washing system controls the opening of the chute distribution channel according to the mud content and cleanliness of the sand and gravel materials through the control center, thereby realizing the selection of the number of sand washing stages and controlling the fine sand steps. The transportation of materials between equipment is mostly realized by belt conveyors.
[0034] like Figure 3 and Figure 4 As shown, the system includes a clear water tank and a recycled water tank. The water used by the 2nd-stage wheel sand washing machine, the 3rd-stage wheel sand washing machine, the 1st-stage linear dewatering screen, the 2nd-stage linear dewatering screen, and the 3rd-stage linear dewatering screen is supplied by the clear water tank. The water used by the circular vibrating screen, the 1st-stage spiral sand washing machine, the 2nd-stage spiral sand washing machine, and the 1st-stage wheel sand washing machine is supplied by the recycled water tank.
[0035] like Figure 5 As shown, the system includes a wastewater treatment system. The treated water is supplied to the reuse water tank. Wastewater from the first-stage spiral sand washer and the second-stage spiral sand washer will sequentially enter the wastewater treatment system through the first-stage recovery tank and the first-stage cyclone group. Wastewater from the first-stage wheel sand washer, the second-stage wheel sand washer, and the first-stage linear dewatering screen will sequentially enter the wastewater treatment system through the second-stage recovery tank and the second-stage cyclone group. Wastewater from the second-stage linear dewatering screen and the third-stage wheel sand washer will enter the wastewater treatment system after passing through the third-stage cyclone group. Wastewater from the third-stage linear dewatering screen will be directly fed into the wastewater treatment system.
[0036] The receiving hopper is equipped with a bar screen, which divides the hopper into a small-diameter hopper and a large-diameter hopper. The small-diameter hopper stores sand and gravel smaller than 30mm, while the large-diameter hopper stores sand and gravel larger than or equal to 30mm. The circular vibrating screen has two layers of screens: the upper screen has a 30mm aperture, and the lower screen has a 3mm aperture. The closed-circuit linear screen has a 4.75mm aperture. A level gauge is installed in the receiving hopper to achieve linkage control between the front-end material inventory and the equipment, thereby saving energy, reducing consumption, and lowering operating costs.
[0037] Work steps:
[0038] Step 1: Large-diameter sand and gravel discharged from the receiving hopper are screened by the bar feeder. Large-diameter sand and gravel with a diameter greater than or equal to 30mm are conveyed by the bar feeder to the jaw crusher for crushing. Small-diameter sand and gravel with a diameter less than 30mm discharged from the receiving hopper, bar feeder, and jaw crusher are conveyed to the circular vibrating screen.
[0039] Step 2: The circular vibrating screen washes the sand and gravel with high-pressure water and classifies the sand and gravel into three particle sizes: larger than 30mm, 30-3mm, and smaller than 3mm. The sand and gravel larger than 30mm is transported to the return hopper, while the sand and gravel smaller than 3mm is processed by the regulating hopper, roller mill, and closed-circuit linear screen for recycling and crushing. The closed-circuit linear screen transports the sand and gravel smaller than 4.75mm to the water washing system, and the sand and gravel smaller than 3mm is also transported to the water washing system.
[0040] The sand and gravel returned to the silo are transported back to the receiving silo by loaders and dump trucks for crushing and screening again.
[0041] Step 3: Based on the mud content of the sand and gravel, the sand and gravel are washed by the first-stage spiral sand washer, the second-stage spiral sand washer, the first-stage wheel sand washer, and the second-stage wheel sand washer in the water washing system. Finally, the sand and gravel after being fined by the second-stage wheel sand washer are dewatered by the first-stage linear dewatering screen and enter the finished product silo.
[0042] Step 4: The production wastewater from the first-stage spiral sand washer and the second-stage spiral sand washer enters the first-stage recovery tank for collection and recycling, and is then pumped to the first-stage cyclone group for fine sand recovery. The production wastewater from the first-stage wheel sand washer and the second-stage wheel sand washer, as well as the wastewater after dewatering by the first-stage linear dewatering screen, enters the second-stage recovery tank for collection and recycling, and is then pumped to the second-stage cyclone group for fine sand recovery. The production wastewater from the third-stage wheel sand washer and the second-stage linear dewatering screen enters the third-stage cyclone group for fine sand recovery.
[0043] In step three, the sand washing process is divided into three steps based on the mud content of the sand and gravel.
[0044] The first method involves sequentially performing water washing treatment using a first-stage spiral sand washing machine, a second-stage spiral sand washing machine, a first-stage wheel sand washing machine, and a second-stage wheel sand washing machine.
[0045] The second method involves sequentially washing the sand using a first-stage spiral sand washer, a first-stage wheel sand washer, and a second-stage wheel sand washer.
[0046] The third method involves sequentially washing the sand using a first-stage spiral sand washer and a second-stage wheel sand washer.
[0047] In step four, the fine sand recovered by the first-stage cyclone group is the first-stage recovered sand. After the first-stage cyclone group recovers the fine sand, the wastewater generated enters the downstream wastewater treatment system for treatment. The recovered fine sand enters the third-stage wheel bucket sand washing machine for sand washing, and then enters the finished sand bin after being dewatered by the second-stage linear dewatering screen.
[0048] The fine sand recovered by the two-stage cyclone separator is the second-stage recovered sand. After the fine sand is recovered by the two-stage cyclone separator, the wastewater generated is sent to the downstream wastewater treatment system for treatment. The fine sand recovered by the three-stage cyclone separator is the third-stage recovered sand. After the fine sand is recovered by the three-stage cyclone separator, the wastewater generated is sent to the downstream wastewater treatment system for treatment.
[0049] If the quality of the grade 2 and grade 3 recycled sand is good, the grade 2 recycled sand will be dewatered through a grade 2 linear dewatering screen and then enter the finished sand bin, and the grade 3 recycled sand will be dewatered through a grade 3 linear dewatering screen and then enter the finished sand bin. If the quality of the grade 2 and grade 3 recycled sand is poor, the grade 2 recycled sand will be directly transported to the waste bin, and the grade 3 recycled sand will be dewatered through a grade 3 linear dewatering screen without water and then enter the waste bin.
[0050] In the above process, all finished sand is rinsed with clean water from an untreated clean water tank before entering the storage facility to reduce flocculant residue and improve product quality. All production wastewater is treated by first-stage, second-stage, and third-stage cyclone separators to recover fine sand before entering the wastewater treatment system. This maximizes the value of the fully weathered material resources while reducing the content of fine particles in the wastewater, extending the service life of the filter press equipment in the downstream wastewater treatment system, and reducing operating costs.
[0051] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.
Claims
1. A production and treatment system for efficient comprehensive utilization of fully weathered material, characterized in that, The application relates to a sand washing and screening system. The screening and crushing system comprises a bar feeder, an eccentric crusher, a circular vibrating screen, an adjusting bin, a double-roller machine and a closed-circuit linear screen, the bar feeder can convey large-diameter sand and stones discharged from a receiving bin to the eccentric crusher, the circular vibrating screen receives small-diameter sand and stones output from the receiving bin, the bar feeder and the eccentric crusher, the receiving bin divides the sand and stones into three types according to particle size and respectively conveys the sand and stones to a returning bin, an adjusting bin and a water washing system, the adjusting bin, the double-roller machine and the closed-circuit linear screen form a closed-circuit crushing and screening cycle, and the closed-circuit linear screen conveys sand and stones meeting the particle size requirement to the water washing system. The water washing system comprises a first-stage spiral sand washer, a second-stage spiral sand washer, a first-stage wheel-bucket sand washer, a second-stage wheel-bucket sand washer and a first-stage linear dehydration screen, the first-stage spiral sand washer receives sand and stones output from the receiving bin and the closed-circuit linear screen, the first-stage spiral sand washer, the second-stage spiral sand washer, the first-stage wheel-bucket sand washer and the second-stage wheel-bucket sand washer are used for sand washing, and the first-stage linear dehydration screen is used for dehydrating sand and stones washed by the second-stage wheel-bucket sand washer. The fine sand recovery system comprises a first-stage recovery tank, a second-stage recovery tank, a first-stage cyclone group, a second-stage cyclone group, a third-stage cyclone group, a second-stage linear dehydration screen, a third-stage linear dehydration screen and a third-stage wheel-bucket sand washer, the first-stage recovery tank and the first-stage cyclone group are used for recovering fine sand in production wastewater of the first-stage spiral sand washer and the second-stage spiral sand washer, the second-stage recovery tank and the second-stage cyclone group are used for recovering fine sand in production wastewater of the first-stage wheel-bucket sand washer, the second-stage wheel-bucket sand washer and the first-stage linear dehydration screen, the third-stage wheel-bucket sand washer is used for washing fine sand recovered by the second-stage cyclone group, the second-stage linear dehydration screen is used for dehydrating sand and stones washed by the second-stage cyclone group and the third-stage wheel-bucket sand washer, and the third-stage cyclone group and the third-stage linear dehydration screen are used for recovering fine sand in production wastewater of the second-stage linear dehydration screen and the third-stage wheel-bucket sand washer and dehydrating the fine sand. Fine sand output from the first-stage linear dehydration screen and the second-stage linear dehydration screen is conveyed to a finished sand bin, fine sand output from the second-stage cyclone group is conveyed to the second-stage linear dehydration screen if the fine sand meets the quality requirement, the fine sand output from the second-stage cyclone group is conveyed to a waste bin if the fine sand does not meet the quality requirement, and fine sand output from the third-stage linear dehydration screen is conveyed to the finished sand bin if the fine sand meets the quality requirement, the fine sand output from the third-stage linear dehydration screen is conveyed to the waste bin if the fine sand does not meet the quality requirement. The system comprises a clean water tank and a recycled water tank, water used by the second-stage wheel-bucket sand washer, the third-stage wheel-bucket sand washer, the first-stage linear dehydration screen, the second-stage linear dehydration screen and the third-stage linear dehydration screen is supplied by the clean water tank, and water used by the circular vibrating screen, the first-stage spiral sand washer, the second-stage spiral sand washer and the first-stage wheel-bucket sand washer is supplied by the recycled water tank.
2. The production and treatment system for efficient comprehensive utilization of full-strong weathered materials according to claim 1, characterized in that: 3. The production processing system for efficient comprehensive utilization of full-strong weathered materials according to claim 2, characterized in that: The wastewater treatment system supplies water for the recycling pool, and the wastewater of the first-stage spiral sand washer and the second-stage spiral sand washer will sequentially pass through the first-stage recycling pool and the first-stage cyclone group to enter the wastewater treatment system, the production wastewater of the first-stage wheel bucket sand washer, the second-stage wheel bucket sand washer and the first-stage linear dehydration screen will sequentially pass through the second-stage recycling pool and the second-stage cyclone group to enter the wastewater treatment system, the production wastewater of the second-stage linear dehydration screen and the third-stage wheel bucket sand washer will pass through the third-stage cyclone group to enter the wastewater treatment system, and the production wastewater of the third-stage linear dehydration screen will directly enter the wastewater treatment system.
4. The production processing system for efficient comprehensive utilization of full-strong weathered materials according to claim 1, characterized in that: The grate sieve is installed in the receiving bin and divides the receiving bin into a small-particle-size bin and a large-particle-size bin, the small-particle-size bin is used to store sand and gravel with a size less than 30 mm, and the large-particle-size bin is used to store sand and gravel with a size greater than or equal to 30 mm.
5. The production processing system for efficient comprehensive utilization of full-strong weathered materials according to claim 4, characterized in that: The circular vibrating screen has two layers of screen meshes, the upper layer of screen meshes has a mesh size of 30 mm, the lower layer of screen meshes has a mesh size of 3 mm, and the screen mesh of the closed-circuit linear screen has a mesh size of 4.75 mm.