A high-efficiency recycling system for foundry sand

Abstract

The present application relates to the technical field of foundry sand recycling, and particularly relates to a high-efficiency recycling system for foundry sand, which comprises a feeding bin, a six-stage vibrating screen in communication with the feeding bin is arranged below the feeding bin, six discharge outlets of the six-stage vibrating screen are respectively in communication with a magnetic separation device, and a powder grinding device for grinding the excessively fine foundry sand into powder is further arranged. The present application is mainly used for comprehensive recycling of investment casting sand, and through the steps of crushing, screening, iron removal and powder grinding, the recycling rate of the foundry sand is higher than 95%, waste and environmental pollution are basically eliminated, the whole system is simple to operate, and the production cost is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of foundry sand recycling technology, and in particular to a high-efficiency foundry sand recycling system. Background Technology

[0002] Investment casting first requires the preparation of a wax model. Then, sand is repeatedly coated onto the surface of the wax model using a slurry. After drying, a multi-layered, tightly bonded sand shell is formed. The wax model is then melted at high temperature, creating a cavity within the sand shell that contains the product's shape and structure. Molten metal is poured in, and after cooling, the sand shell is removed to obtain the casting. It is clear that the sand model is the carrier in investment casting, and casting sand and slurry are essential and widely used raw materials. With the development of casting technology, the price of new casting sand is increasing, which will also increase the production cost of cast products, hindering the company's competitive development.

[0003] Therefore, recycling used foundry sand has become a trend, and the proportion of recycled sand in foundry sand is increasing, which can also reduce the environmental pollution caused by waste foundry sand. For example, the patent "CN201710696623 - A method for regenerating mixed used foundry sand" has a complicated process and is too costly; "CN202020765645 - A molding sand recycling device for investment casting" does not have many particle size levels for recycling investment casting sand, especially the fine surface sand cannot be further processed, and it is mixed with other sands, which reduces the quality of foundry sand. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-efficiency recycling system for foundry sand. This system is mainly used for the comprehensive recycling of molten foundry sand, aiming to achieve high-quality and high-utilization-rate recycling of foundry sand at a lower cost.

[0005] The technical solution adopted by the present invention to solve its technical problem is: a high-efficiency recycling system for foundry sand, including a feeding silo, a six-stage vibrating screen connected to the feeding silo below it, the six discharge ports of the six-stage vibrating screen being connected to a magnetic separator, and a grinding device for grinding excessively fine foundry sand into powder.

[0006] Preferably, the feed inlet at the bottom of the feed hopper is equipped with a waterfall-type diversion valve.

[0007] Preferably, the six-stage vibrating screen includes a vibrating chamber elastically connected to the base frame. The vibrating chamber is equipped with a vibrating motor. Inside the vibrating chamber, from top to bottom, there are 6-mesh, 14-mesh, 20-mesh, 40-mesh, and 80-mesh screens. The rightmost end of each of the six screening chambers formed by dividing the vibrating chamber by these five layers of screens is provided with a discharge port. Dust suction ports are provided at both ends of the top of the vibrating screen.

[0008] Preferably, the magnetic separator includes a housing, the top of which is connected to the discharge port of the vibrating chamber, and the bottom of which is provided with a sand recovery discharge port and an iron filings discharge port. Support shafts are fixed to the two side plates of the inner cavity of the housing, and a transmission shaft driven by a motor is rotatably connected to them. The support shafts and the transmission shaft are coaxial. A roller is provided inside the housing, with both ends of the roller rotatably connected to the support shaft. One end face of the roller is fixed to the transmission shaft. A coaxial semi-magnetic cylinder is provided inside the roller, and the semi-magnetic cylinder is fixedly connected to the support shaft via a support plate. Several permanent magnets are provided on the circumference of the semi-magnetic cylinder, and the central angle corresponding to the semi-magnetic cylinder with permanent magnets is 165° to 180°. A counterweight is provided on the other side of the support shaft opposite to the semi-magnetic cylinder.

[0009] Preferably, the central angle corresponding to the semi-magnetic cylinder is 180° to 200°, and the semi-magnetic cylinder is composed of several strip plates spliced ​​together. Each strip plate is provided with 7 permanent magnets, and the permanent magnets are N52 neodymium magnets.

[0010] Preferably, the grinding device includes a sand silo for storing recycled sand with a particle size of less than 80 mesh, a grinding mill, and a powder silo. The feed inlet of the grinding mill is connected to the bottom of the sand silo. A blower is connected to the bottom of the grinding mill. The air inlet of the blower is connected to the top of the powder silo. A cage classifier is installed on the top of the grinding mill. The grinding mill is connected to the powder silo through the cage classifier, and the connection point is lower than the top of the powder silo.

[0011] Preferably, the system is used for investment casting sand recycling, and the recycling steps are as follows: First, crushing, crushing the waste sand blocks and sand shells used in casting into sand of 6-80 mesh; Second, screening, feeding the sand into the feed hopper via an elevator, and then into the six-stage vibrating screen to obtain recycled sand of six particle sizes: larger than 6 mesh, 6-14 mesh, 14-20 mesh, 20-40 mesh, 40-80 mesh, and smaller than 80 mesh; Third, iron removal, feeding the six particle sizes of recycled sand obtained in the second step into six magnetic separators to remove iron filings from the recycled sand; Fourth, grinding, packaging the five types of recycled sand larger than 80 mesh obtained in the third step separately for use as investment casting sand, and feeding the recycled sand smaller than 80 mesh into the grinding device to obtain 200-320 mesh fine casting powder, which is used as a slurry ingredient during casting.

[0012] The beneficial effects of this invention are: a high-efficiency foundry sand recycling system, comprising a feeding silo, below which is a six-stage vibrating screen connected to the silo, and the six discharge ports of the six-stage vibrating screen are each connected to a magnetic separator; a grinding device is also provided to grind excessively fine foundry sand into powder. This invention is mainly used for the comprehensive recycling of investment casting sand. Through steps such as crushing, screening, iron removal, and grinding, the recycling rate of foundry sand is higher than 95%, essentially eliminating waste and environmental pollution. The entire system is also simple to operate, greatly reducing production costs. Attached Figure Description

[0013] Figure 1 This is a plan view of a high-efficiency recycling system for foundry sand according to the present invention;

[0014] Figure 2 This is a front view of the six-stage vibrating screen;

[0015] Figure 3 yes Figure 2 The right view;

[0016] Figure 4 yes Figure 3 A sectional view;

[0017] Figure 5 This is a perspective view of the magnetic separation device;

[0018] Figure 6 This is a front view of the magnetic separator;

[0019] Figure 7 yes Figure 6 A sectional view;

[0020] Figure 8 yes Figure 6 A partial sectional view.

[0021] Explanation of reference numerals in the attached figures:

[0022] 1 – Feed hopper, 11 – Waterfall diversion valve, 2 – Six-stage vibrating screen, 21 – Vibrating chamber, 22 – Vibrating motor, 23 – Dust suction port, 3 – Magnetic separator, 31 – Shell, 32 – Recycled sand discharge port, 33 – Iron filings discharge port, 34 – Support shaft, 35 – Drive shaft, 36 – Drum, 37 – Semi-magnetic cylinder, 38 – Permanent magnet, 39 – Counterweight, 4 – Grinding device, 41 – Sand hopper, 42 – Grinding mill, 43 – Powder hopper, 44 – Blower, 45 – Cage classifier. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0024] like Figures 1-8 As shown, this embodiment of a high-efficiency foundry sand recycling system includes a feeding silo 1. A six-stage vibrating screen 2, connected to the feeding silo 1, is located below it. The six outlets of the six-stage vibrating screen 2 are each connected to a magnetic separator 3. A grinding device 4 is also provided to grind excessively fine foundry sand into powder. This embodiment uses the recycling of waste sand generated from wax pattern casting as an example. During wax pattern casting, the high-temperature baking and pouring processes melt and evaporate the adhesive substances in the sand shell. Therefore, the waste sand generated from wax pattern casting contains very little or almost no adhesive substances, requiring no treatment and not affecting the reuse of the recycled sand.

[0025] During operation, waste sand is recycled through the following steps: First, crushing, where waste sand blocks and sand shells used in casting are crushed into sand of 6-80 mesh; Second, screening, where all sand is fed into the feed hopper 1 via an elevator, and then into the six-stage vibrating screen 2, to obtain recycled sand of six particle sizes: larger than 6 mesh, 6-14 mesh, 14-20 mesh, 20-40 mesh, 40-80 mesh, and smaller than 80 mesh; Third, iron removal, where the six particle sizes of recycled sand obtained in the second step are fed into six magnetic separators 3 to remove iron filings from the recycled sand; Fourth, grinding, where the five types of recycled sand larger than 80 mesh obtained in the third step are packaged separately for use as sand in investment casting, and the recycled sand smaller than 80 mesh is fed into the grinding device 4 to obtain 200-320 mesh fine casting powder, which is used as a slurry ingredient during casting.

[0026] As can be seen from the above, this embodiment achieves recycling and regeneration of wax mold casting sand through only four processes. Moreover, the entire system has a simple structure and is easy to operate. There is no material loss in the treatment of all waste sand, and the obtained iron filings and recycled sand can generate economic value. Even if the recycled sand is too fine to be used as sand material, it can be ground into powder and used as a slurry ingredient. The recycling rate of the entire system for waste sand is higher than 95%, eliminating waste and greatly reducing production costs.

[0027] A waterfall-type diversion valve 11 is installed at the feed inlet at the bottom of the feed hopper 1. The waterfall-type diversion valve refers to a row of multiple adjustable-opening baffle valves arranged at the bottom of the feed hopper 1, with the arrangement direction along the width direction of the six-stage vibrating screen 2. This allows adjustment of the feed quantity based on the vibration efficiency of the six-stage vibrating screen 2 in the width direction. Each baffle valve includes a baffle plate slidably connected to the bottom of the feed hopper 1 via a slot. A nut is fixed to the baffle plate. A seat plate is fixed to the side of the bottom of the feed hopper 1, and a screw is rotatably connected to the seat plate. The screw is threadedly connected to the nut. Thus, when the screw is rotated, because the screw is restricted by the seat plate from moving along its length, the nut is driven to move along the screw, thereby causing the baffle plate to seal or open the bottom of the feed hopper 1.

[0028] The six-stage vibrating screen 2 includes a vibrating chamber 21 elastically connected to a base frame. The base frame refers to the platform used to support the various devices of this system and determine their spatial relationship. Figure 1 The two-layer steel structure platform is shown; the vibrating chamber 21 is equipped with a vibrating motor 22, which drives the vibrating chamber 21 to vibrate. In addition, the vibrating chamber 21 is placed at an angle and the feed end is higher; the vibrating chamber 21 is equipped with a 6-mesh sieve, a 14-mesh sieve, a 20-mesh sieve, a 40-mesh sieve and an 80-mesh sieve from top to bottom, thereby dividing the space inside the vibrating chamber 21 into six screening spaces from top to bottom. The above five sieves are parallel to the bottom of the vibrating chamber 21, and the discharge port is set at the lowest end of the six screening spaces. Specifically, the discharge port of the screening space larger than 6 mesh is located on the rightmost side of the vibrating chamber 21; the discharge port of the screening space from 6 to 14 mesh is located on the rightmost side of the vibrating chamber 21, below the discharge port of the screening space larger than 6 mesh; and the discharge ports of the four screening spaces—14-20 mesh, 20-40 mesh, 40-80 mesh, and smaller than 80 mesh—are located at the bottom of the rightmost end of the vibrating chamber 21, arranged sequentially from right to left. Figure 4 As shown.

[0029] During screening, the sand first enters the uppermost screening space. Under high-frequency vibration, the sand is screened as it moves from left to right along a 6-mesh screen. Sand smaller than 6 mesh falls into the lower space and continues screening on a 14-mesh screen. Sand smaller than 14 mesh continues to fall into the lower space, and so on, thus achieving multi-stage screening of the sand through a single vibrating screen. This embodiment uses 5-stage screening to obtain sand of six particle sizes. In actual production, the screening stages of the vibrating screen can be set with different mesh sizes and different numbers of screens as needed. In addition, dust suction ports 23 are provided at both ends of the top of the vibrating chamber 21. The dust suction ports 23 are connected to a dust removal device through pipes to remove dust from the vibrating chamber 21, preventing pollution of the workshop environment and improving the quality of the recovered sand.

[0030] The magnetic separator 3 is a semi-magnetic permanent magnet separator, and its specific structure is as follows: The magnetic separator 3 includes a housing 31. The top of the housing 31 is connected to the discharge port of the vibrating chamber 21. The bottom of the housing 21 is provided with a sand recovery discharge port 32 and an iron filings discharge port 33. The inner side plates of the housing 31 are respectively fixed with a support shaft 34 and a drive shaft 35 driven by a motor. The support shaft 34 and the drive shaft 35 are coaxial. A roller 36 is provided inside the housing 31. The two ends of the roller 36 are rotatably connected to the support shaft 34. One end face of the roller 36 is fixed to the drive shaft 35. A coaxial semi-magnetic cylinder 37 is provided inside the roller 36. The semi-magnetic cylinder 37 is fixedly connected to the support shaft 34 through a support plate. Several permanent magnets 38 are provided on the circumference of the semi-magnetic cylinder 37. The central angle of the semi-magnetic cylinder 37 with permanent magnets 38 is 165° to 180°.

[0031] The recycled sand falls from the top of the housing 31 onto the rotating drum 36, which is made of stainless steel and has flanges at both ends. As the recycled sand continues to fall to one side, the semi-magnetic cylinder 37 and the permanent magnet 38 are positioned there, attracting iron filings from the recycled sand to the surface of the drum 36. The recycled sand then falls out of the recycled sand discharge port 32 without being attracted. The drum 36, having attracted the iron filings, continues to rotate to the other side. Because it is further away from the permanent magnet 38, the iron filings are no longer attracted to the surface of the drum 36 and fall out of the iron filings discharge port 33. The drum 36 continues to rotate, repeating the iron removal process. Furthermore, to ensure that the recycled sand falling onto the drum 36 is only carried to one side and not splashed to the other side, the bottom of the recycled sand inlet on the housing 31 is an inclined plate, forming a slide facing one side. After sliding along this slide, the recycled sand flows downwards towards the recycled sand discharge port. Meanwhile, the feed inlet on the housing 31 is also equipped with a filter plate to filter and recover impurities mixed in the sand.

[0032] The central angle of the semi-magnetic cylinder 37 is 180° to 200°. The semi-magnetic cylinder 37 is composed of several strip plates spliced ​​together. Each strip plate is provided with 7 permanent magnets 38. In this embodiment, there are a total of 49 permanent magnets 38. The permanent magnets 38 are N52 neodymium magnets.

[0033] The three rotating connections in the magnetic separator 3 described above—namely, the rotating connection between the drive shaft 35 and the housing 31, and the rotating connection between the roller 36 and both ends of the support shaft 34—refer to connections via bearings. Since the permanent magnet 38 does not need to rotate, in this embodiment, the support shaft 34 and the housing 31 are fixedly connected. In actual production, the support shaft 34 can also be rotatably connected to the housing 31 (without bearings). By providing a square head at the end of the support shaft 34 and an adjustable limit switch on the housing 31, the height of the permanent magnet 38 can be adjusted. Simultaneously, to balance the weight of the semi-magnetic cylinder 37, a counterweight 39 is provided on the other side of the support shaft 34 opposite to the semi-magnetic cylinder 37.

[0034] The grinding device 4 includes a sand silo 41 for storing recycled sand with a particle size of less than 80 mesh, a grinding mill 42, and a powder silo 43. The feed inlet of the grinding mill 42 is connected to the bottom of the sand silo 41. A blower 44 is connected to the bottom of the grinding mill 42. The air inlet of the blower 44 is connected to the top of the powder silo 43. A cage classifier 45 is installed on the top of the grinding mill 42. The grinding mill 42 is connected to the powder silo 43 through the cage classifier 45, and the connection point is lower than the top of the powder silo 43.

[0035] After iron removal, the recycled sand with a particle size smaller than 80 mesh is fed into the sand silo 41 via an elevator. The bottom of the sand silo 41 is connected to the inlet of the grinding mill 42, and the bottom outlet of the sand silo 41 is equipped with an openable and closable vibrating feeder that promotes material falling. The recycled sand is ground into a particle size of 200-320 mesh in the grinding mill 42. At the same time, the blower 44 blows air into the grinding mill 42 from the bottom, so that the ground powder is blown away by the rising airflow. The powder passes through the cage classifier 45 at the top of the grinding mill 42. Powder that meets the specified particle size enters the powder silo 43 through the cage classifier 45, while powder that does not meet the specified particle size falls to the bottom under gravity and continues to be ground. Because the powder silo 43 is constantly filled with gas, causing the air pressure to rise, a filter device is installed at the top of the powder silo 43 to filter the powder and allow only air to pass through, so that excess air in the powder silo 43 is sucked away by the blower.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and for the convenience of describing the technical solutions, the front, back, left, right, top, middle, and bottom orientations are based on the accompanying drawings and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high-efficiency recycling system for foundry sand, characterized in that: It includes a feeding hopper, below which is a six-stage vibrating screen connected to it. The six discharge ports of the six-stage vibrating screen are respectively connected to a magnetic separator. It also includes a grinding device for grinding excessively fine foundry sand into powder for use in slurry preparation during casting. The magnetic separator includes a housing. The top of the housing is connected to the discharge port of the six-stage vibrating screen. The bottom of the housing is provided with a sand recovery discharge port and an iron filings discharge port. The inner cavity of the housing has two side plates, each fixed with a support shaft and rotatably connected with a drive shaft driven by a motor. The support shaft and the drive shaft are coaxial. A drum is provided inside the housing. The two ends of the drum are rotatably connected to the support shaft. One end face of the drum is fixed to the drive shaft. A coaxial semi-magnetic cylinder is provided inside the drum. The semi-magnetic cylinder is fixedly connected to the support shaft through a support plate. Several permanent magnets are provided on the circumference of the semi-magnetic cylinder. The central angle of the semi-magnetic cylinder with permanent magnets is 165° to 180°. A counterweight is provided on the other side of the support shaft opposite to the semi-magnetic cylinder. The six-stage vibrating screen includes a vibrating chamber elastically connected to the base frame. The vibrating chamber is equipped with a vibrating motor. Inside the vibrating chamber, from top to bottom, there are 6-mesh, 14-mesh, 20-mesh, 40-mesh, and 80-mesh screens. The rightmost end of each of the six screening chambers formed by dividing the vibrating chamber by these five layers of screens is provided with a discharge port. Dust suction ports are provided at both ends of the top of the vibrating screen.

2. The high-efficiency recycling system for foundry sand according to claim 1, characterized in that: The feed inlet at the bottom of the feed hopper is equipped with a waterfall-type diversion valve.

3. The high-efficiency recycling system for foundry sand according to claim 1, characterized in that: The central angle of the semi-magnetic cylinder is 180° to 200°. The semi-magnetic cylinder is composed of several strip plates spliced ​​together. Each strip plate is provided with 7 permanent magnets, which are N52 neodymium magnets.

4. The high-efficiency recycling system for foundry sand according to claim 1, characterized in that: The grinding device includes a sand silo for storing recycled sand with a particle size of less than 80 mesh, a grinding mill, and a powder silo. The feed inlet of the grinding mill is connected to the bottom of the sand silo. A blower is connected to the bottom of the grinding mill. The air inlet of the blower is connected to the top of the powder silo. A cage classifier is installed on the top of the grinding mill. The grinding mill is connected to the powder silo through the cage classifier, and the connection point is lower than the top of the powder silo.

5. A method for recycling foundry sand using the high-efficiency recycling system for foundry sand as described in claim 1, comprising the following steps: First, crushing, crushing waste sand blocks and sand shells used in casting into sand material of 6-80 mesh; Second, screening, feeding the sand material into the feed hopper via an elevator, and then into the six-stage vibrating screen to obtain recycled sand of six particle sizes: greater than 6 mesh, 6-14 mesh, 14-20 mesh, 20-40 mesh, 40-80 mesh, and less than 80 mesh; Third, iron removal, feeding the recycled sand of the six particle sizes obtained in the second step into six magnetic separators to remove iron filings from the recycled sand; Fourth, grinding, packaging the five types of recycled sand greater than 80 mesh obtained in the third step separately for use as sand material in investment casting, and feeding the recycled sand less than 80 mesh into the grinding device to obtain fine casting powder of 200-320 mesh, which is used as a slurry ingredient during casting.

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