Waste casting precoated sand recycling system and method

Abstract

The invention provides a waste casting precoated sand recycling system and method, and belongs to the technical field of reclaimed sand. The system comprises a pretreatment unit, a hot air erosion unit, a superheated steam pulping unit and a shaping treatment unit. The method comprises the following steps: carrying out crushing, magnetic separation and grading treatment on the waste casting precoated sand to obtain waste sand particles; waste sand particles and air are mixed into a waste sand gas-solid mixture, hot air flow and the waste sand gas-solid mixture are subjected to opposite jetting, and primary regenerated sand is obtained; mixing the superheated steam with the primary reclaimed sand, tangentially spraying into a tank, then carrying out air jet pulverization, standing, and carrying out solid-liquid layering, so as to obtain a uniform reclaimed sand wet material; the regenerated sand wet material and the aluminum silicate powder form mixed slurry, the compressed hot air collides with the stirred mixed slurry, and regenerated sand particles are obtained after rapid cooling. According to the method, hot air crushing, superheated steam wet regeneration and hot air shearing, drying and mixing are adopted, impurities which are doped in the waste sand and difficult to separate are effectively removed, and the purity, the fluidity, the mechanical property and other properties of the regenerated sand are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of regenerated sand preparation, and in particular relates to a system and method for recycling waste foundry coated sand. Background Art

[0002] Coated sand is a high-performance casting material. It consists of sand grains coated with a solid resin film. It is the primary raw material for sand molds and cores during the casting process. During sand casting, every ton of castings produced generates 1 to 7 tons of used sand, resulting in significant resource waste and severe environmental pollution.

[0003] The recycling and reuse of waste foundry coated sand is currently the primary method for treating waste sand. Impurities in waste sand primarily include metallic impurities, functional agents such as coal dust, and binders, which significantly impact the quality of waste sand recycling. Existing waste sand recycling processes primarily include wet regeneration, thermal treatment, and mechanical treatment. Wet regeneration involves soft scrubbing of the waste sand in a water-based emulsion to remove impurities; thermal treatment melts the waste sand to remove binders and other components from the coated sand; and mechanical treatment utilizes friction and collision to remove impurities from the coated sand.

[0004] Although the above method can remove adverse impurities in waste coated sand to a certain extent, it is difficult to effectively remove coal powder, attached binders and resins mixed in the waste sand. As a result, the performance of the regenerated sand produced is significantly reduced compared with the original sand, such as poor stability, high high-temperature expansion rate, and low strength of the sand core. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a system and method for recycling waste foundry coated sand, aiming to solve at least one technical problem in the background technology.

[0006] The present invention is achieved in that:

[0007] A first aspect of the present invention provides a method for recycling waste foundry coated sand, comprising the following steps:

[0008] The waste casting coated sand is crushed, magnetically separated and classified to obtain waste sand particles;

[0009] The hot air flow at a preset temperature is injected into the waste sand gas-solid mixture, and the hot air flow erodes the waste sand particles, removing impurities attached to the surface of the waste sand particles to obtain primary regenerated sand; the waste sand gas-solid mixture is a mixture of waste sand particles and air;

[0010] After the superheated steam is mixed with the primary regenerated sand, it is injected into the tank tangentially and then subjected to air flow crushing to remove organic impurities. After standing, the solid and liquid layers are separated to obtain uniform regenerated sand wet material;

[0011] The regenerated sand wet material and aluminum silicate powder form a mixed slurry, and the compressed hot air collides with the stirred mixed slurry, and after rapid cooling, dry, regular and uniform regenerated sand particles are obtained.

[0012] Preferably, when the hot air flow and the waste sand gas-solid mixture are sprayed against each other, the flow rate of the hot air flow is 10m / s to 20m / s; the flow rate of the waste sand gas-solid mixture is 5m / s to 10m / s;

[0013] The temperature of the hot air flow is 80°C to 150°C;

[0014] The gas-solid ratio of the waste sand gas-solid mixture is 1 to 2:1.

[0015] Preferably, the mass ratio of the hot steam to the primary regenerated sand is 1 to 10:1.

[0016] Preferably, during the process of the compressed hot air colliding with the stirred mixed slurry, the temperature of the hot air is 200°C to 300°C.

[0017] Preferably, the compressed hot air enters the container for mixing the slurry tangentially.

[0018] A second aspect of the present invention provides a waste foundry coated sand recovery and reuse system, comprising:

[0019] A pre-treatment unit is used to crush, magnetically separate and classify waste foundry coated sand to obtain waste sand particles;

[0020] A hot air erosion unit, which uses a hot air flow of a preset temperature to collide with the waste sand gas-solid mixture, and the hot air flow erodes the waste sand particles, separating impurities attached to the surface of the waste sand particles to obtain primary regenerated sand; the waste sand gas-solid mixture is a mixture of waste sand particles and air;

[0021] The superheated steam pulping unit mixes superheated steam and primary regenerated sand and injects it into the tank tangentially, followed by air flow crushing to obtain regenerated sand wet material;

[0022] In the shaping processing unit, the spirally stirred mixed slurry comes into contact with the injected hot air and is rapidly cooled to obtain dry, regular and uniform regenerated sand particles; the mixed slurry is a mixture of wet regenerated sand and aluminum silicate powder.

[0023] Preferably, the hot air erosion unit comprises an erosion tank, a solid-gas ejector and a hot air ejector connected to the erosion tank, and a dust collection assembly connected to the top of the erosion tank;

[0024] The solid-gas ejector and the hot gas ejector are arranged opposite to each other;

[0025] The solid-gas injector is used to inject a waste sand-gas-solid mixture of waste sand particles and air into the erosion tank;

[0026] The hot air flow ejector is used to eject a hot air flow at 80°C to 150°C into the erosion tank to form a counter-flow with the waste sand gas-solid mixture;

[0027] The dust collection component is used to discharge the separated impurities.

[0028] Preferably, the superheated steam pulping unit comprises a pulping tank and a solid-liquid ejector;

[0029] The solid-liquid ejector is connected to the outlet of the hot air erosion unit, and the primary regenerated sand produced by the hot air erosion unit enters the solid-liquid ejector and is mixed with the superheated steam, and then ejected into the pulping tank;

[0030] Spiral wings are arranged inside the pulping tank.

[0031] Preferably, the shaping processing unit includes a thermal drying system and a rapid cooling system, and a material receiving component connected to the thermal drying system and the rapid cooling system;

[0032] The thermal drying system includes a drying tank, a mixing chamber connected to the bottom of the drying tank, and a hot air conveying component, which is used to dry the mixed slurry to obtain regenerated sand;

[0033] The mixing chamber is used to mix the regenerated sand wet material with the aluminum silicate powder and transport them into the drying tank;

[0034] The hot air delivery assembly is used to heat, compress and spray air into the drying tank;

[0035] The bottom of the drying tank is provided with an agitator, the upper end is provided with a flow dividing assembly, and the top end of the drying tank is connected to the material receiving assembly;

[0036] The diversion component is used to prevent insufficiently dried regenerated sand from entering the material receiving component;

[0037] The rapid cooling system is used to rapidly cool the regenerated sand after heat drying to obtain regenerated sand particles; the rapid cooling system uses cold water or cold air as a heat exchanger for the cold fluid.

[0038] Preferably, the diversion assembly includes a connecting rod for fixing, and a conical drainage fan fixed below the connecting rod.

[0039] The conical guide fan includes at least three groups of ribs distributed in a circular array; the ribs are arranged upright and are in a triangular shape that is wide at the top and narrow at the bottom.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The present invention provides a method for recycling and reusing waste foundry coated sand, which uses a method of hot air flow crushing + superheated steam wet regeneration + hot air flow shear drying and mixing to effectively remove difficult-to-separate impurities mixed in the waste sand and improve the purity, fluidity and mechanical properties of the regenerated sand.

[0042] 2. The present invention uses a hot air flow to collide with the waste sand gas-solid mixture and spray it. The hot air flow erodes the waste sand particles and separates impurities such as coal powder, dust, and fine sand attached to the surface of the waste sand particles.

[0043] 3. The present invention uses superheated steam to slurry the mixture and sprays it at high speed to achieve solid-liquid homogenization, and effectively dissolve organic impurities or strip organic impurities from waste sand, thereby removing organic impurities and achieving effective impurity removal.

[0044] 4. The present invention uses high-temperature hot air tangent to heat dry the mixed slurry of regenerated sand + aluminum silicate powder. Under the action of wind shear, impact, mutual friction, etc., it is quickly dried and the particles are further refined and homogenized, making the surface of the regenerated sand smoother and promoting the fusion of the regenerated sand and aluminum silicate to produce regenerated sand particles with good stability, high fluidity and excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a structural schematic diagram of a waste foundry coated sand recovery and reuse system of the present invention;

[0046] Figure 2 Schematic diagram of the top view of the hot air erosion unit in the present invention;

[0047] Figure 3 Schematic diagram of the top view of the superheated steam pulping unit in the present invention;

[0048] Figure 4 Schematic diagram of the top view of the diversion component in the shaping processing unit of the present invention;

[0049] Illustration:

[0050] 110-crusher, 120-magnetic separator, 130-screening and classifying machine;

[0051] 210- solid gas ejector, 220- hot gas ejector, 230- erosion tank, 240- dust collection assembly;

[0052] 310-solid-liquid ejector, 320-slurrying tank, 330-spiral wing;

[0053] 410 - mixing chamber, 420 - agitator, 430 - hot air delivery assembly, 440 - drying tank, 450 - diversion assembly, 451 - connecting rod, 452 - fins, 460 - material receiving assembly, 470 - heat exchanger. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific implementation cases described herein are only used to explain the present invention and are not intended to limit the present invention.

[0055] Example 1

[0056] like Figures 1 to 4 As shown, a waste foundry coated sand recovery and reuse system includes a pretreatment unit, a hot air flow erosion unit, a superheated steam pulping unit and a shaping treatment unit.

[0057] A pre-treatment unit is used to crush, magnetically separate, and classify the waste casting coated sand to obtain waste sand particles; the pre-treatment unit includes a crusher 110, a magnetic separator 120, and a screening classifier 130 connected in sequence;

[0058] The crusher 110 adopts a mechanical crushing device permitted in the art, such as a roller crusher, a shear crusher, etc., which breaks up the discarded sand molds and sand cores into waste sand particles;

[0059] The magnetic separator 120 is used to remove magnetic impurities from waste sand. During the casting process, sand molds and sand cores may contain magnetic impurities such as metal fragments or powder, which are separated from the waste sand by magnetic separation.

[0060] The screening and classifying machine 130 is used to separate the waste sand after crushing and magnetic separation according to different sizes. The large pieces of waste sand are returned to the crusher 110 for processing; the small particles of waste sand enter the subsequent processing unit.

[0061] A hot air erosion unit, which uses a hot air flow of a preset temperature to collide with the waste sand gas-solid mixture, and the hot air flow erodes the waste sand particles, separating impurities attached to the surface of the waste sand particles to obtain primary regenerated sand; the waste sand gas-solid mixture is a mixture of waste sand particles and air;

[0062] Among them, the hot air flow erosion unit includes an erosion tank 230, a solid-gas injector 210 and a hot air flow injector 220 connected to the erosion tank 230, and a dust collection assembly 240 connected to the top of the erosion tank 230; the solid-gas injector 210 and the hot air flow injector 220 are arranged relative to each other, and the solid-gas injector 210 is used to inject a waste sand gas-solid mixture of waste sand particles and air into the erosion tank 230; the hot air flow injector 220 is used to inject a hot air flow of 80℃ to 150℃ into the erosion tank 230, and form a counter-flow with the waste sand gas-solid mixture; the dust collection assembly 240 is used to discharge the separated impurities.

[0063] During the specific casting process, coal powder is added to sand molds and sand cores as a reinforcing agent to improve surface quality and prevent defects such as sand sticking and pores during casting. In addition, impurities such as dust and fine sand are mixed in during manufacturing or use. The functions of the hot air erosion unit include the following aspects: (1) breaking the waste sand into more regular and uniform particles; (2) removing free moisture from the waste sand under the action of hot air flow; (3) under the impact of air flow, impurities such as coal powder, dust, and fine sand are stripped from the waste sand particles; (4) under the action of flowing gas, fine impurities such as coal powder, dust, and fine sand can be discharged from the dust collection component 240 above due to their low particle density, while the waste sand particles with high density settle downward and enter the subsequent processing unit.

[0064] In practice, compared to directly impacting waste sand particles with a hot air flow, the present invention mixes waste sand particles with air before impacting them with the hot air flow. This effectively controls the direction of the waste sand particles and maximizes impact efficiency. Furthermore, mixing waste sand particles with air and impacting them with the hot air flow increases contact time.

[0065] The superheated steam pulping unit mixes superheated steam and primary regenerated sand and injects it into the tank tangentially, then performs air flow crushing. After standing, the solid and liquid layers are separated to obtain uniform regenerated sand wet material.

[0066] The superheated steam pulping unit includes a pulping tank 320 and a solid-liquid ejector 310; the solid-liquid ejector 310 is connected to the outlet of the hot air erosion unit (i.e., the bottom of the erosion tank 230), and the primary regenerated sand produced by the hot air erosion unit enters the solid-liquid ejector 310 and is mixed with the superheated steam, and then injected into the sealed pulping tank 320; a spiral wing 330 is arranged inside the pulping tank 320, and the function of the spiral wing 330 is to improve the mixing effect of the material in the pulping tank 320.

[0067] The present invention replaces water with superheated steam, mixes it with primary regenerated sand, and then uses a solid-liquid ejector 310 to inject it into a closed pulping tank 320 at a tangential angle. During this process, due to the high-speed injection of the mixture, it collides with the inner wall of the pulping tank 320 to achieve solid-liquid homogenization; in addition, due to the high temperature and high energy density characteristics of superheated steam, combined with the injection operation, the superheated steam can effectively dissolve organic impurities or strip organic impurities from the waste sand, thereby removing organic impurities (such as binders, etc.).

[0068] In addition to removing impurities, the superheated steam pulping unit can also play the following roles: (1) further refine the size of the regenerated sand particles; (2) further promote the uniformity of the surface of the regenerated sand particles, making the particles more spherical, thereby improving the fluidity and stability of the product.

[0069] In the shaping unit, the spirally stirred mixed slurry comes into contact with the injected hot air, and after rapid cooling, dry, regular and uniform regenerated sand particles are obtained; the mixed slurry is a mixture of wet regenerated sand and aluminum silicate powder;

[0070] The shaping processing unit includes a thermal drying system and a rapid cooling system, and a receiving assembly 460 connecting the thermal drying system and the rapid cooling system; the thermal drying system includes a drying tank 440, a mixing chamber 410 connected to the bottom of the drying tank 440, and a hot air conveying assembly 430, which is used to dry the mixed slurry to obtain regenerated sand; the mixing chamber 410 is used to mix the wet regenerated sand material with aluminum silicate powder and convey it to the drying tank 440; the hot air conveying assembly 430 is used to heat, compress and spray air into the drying tank 440; an agitator 420 is vertically installed at the bottom of the drying tank 440, and a diverter assembly 450 is set at the upper end, and the top of the drying tank 440 is connected to the receiving assembly 460; the diverter assembly 450 is used to prevent insufficiently dried regenerated sand from entering the receiving assembly 460; the rapid cooling system is used to quickly cool the regenerated sand after thermal drying to obtain regenerated sand particles, and the rapid cooling system uses a heat exchanger 470 with cold water or cold air as the cold fluid. The diversion assembly 450 includes a connecting rod 451 for fixing, and a conical guide fan fixed below the connecting rod 451. The conical guide fan includes at least three groups of ribs 452 distributed in a circular array; the ribs 452 are arranged upright and are triangular in shape, wide at the top and narrow at the bottom.

[0071] Because recycled coated sand suffers from a decrease in mechanical properties, particularly strength, after recycling, the present invention improves the regenerated sand by adding aluminum silicate powder. Compared to directly mixing solid regenerated sand with aluminum silicate, the present invention combines wet regenerated sand with aluminum silicate and then heat-dries it, effectively doping the aluminum silicate into the regenerated sand and utilizing its reinforcing properties. The amount of aluminum silicate used is within the acceptable range in the art and is adjusted based on the composition of the coated sand. Typically, the amount is 2% to 10% of the waste sand particles, with 5% used in the following examples.

[0072] The present invention introduces hot air at a temperature of 200°C to 300°C tangentially into the bottom of the drying tank 440. Agitator 420 simultaneously stirs the mixed slurry, driving the hot air to form a rotating wind field. This subjects the solids in the mixed slurry to wind shear, impact, and friction. This rapidly evaporates the water in the mixed slurry (drying can be achieved within tens of seconds or minutes), further refines and homogenizes the solids in the mixed slurry, and promotes the fusion of regenerated sand and aluminum silicate. Regenerated sand particles with lower moisture content and smaller particle size rise with the rotating airflow, are transported to the receiving assembly 460, and then enter the heat exchanger 470 for cooling. Meanwhile, regenerated sand particles with higher moisture content continue to come into contact with the hot air due to gravity. During their ascent, some particles with a certain degree of moisture are impacted and intercepted by the diverter assembly 450, causing them to settle back to the bottom of the drying tank 440 and continue drying until their moisture content is further reduced.

[0073] In the present invention, the dried regenerated sand particles are rapidly cooled in heat exchanger 470. This rapid cooling helps reduce residual stress in the regenerated sand while also maintaining good bonding between the sand particles. Furthermore, the heat absorbed by heat exchanger 470 can be recovered and reused, for example, as a heat source for the hot air erosion unit, the superheated steam pulping unit, and the hot air delivery assembly 430.

[0074] In a specific implementation, the dust collection assembly 240, hot air delivery assembly 430, and material receiving assembly 460 employ components, connections, and structures permitted in the art. For example, the dust collection assembly 240 includes a motor for generating power, a connecting pipe for conveying dust, and a valve for controlling the size of the dust; the hot air delivery assembly 430 includes a fan, a heater, a compression pump, connecting pipes, and valves; and the material receiving assembly 460 includes a suction pump, connecting pipes, and valves, etc., without further specific limitations herein.

[0075] Example 2

[0076] The recycling system of Example 1 is used to process waste foundry coated sand to prepare regenerated sand, and the method steps are as follows:

[0077] S1. Using a crusher 110, a magnetic separator 120, and a screening and classifying machine 130, the waste foundry coated sand is sequentially crushed, magnetically separated, and classified to obtain waste sand particles with a particle size not exceeding 5 mm;

[0078] S2. Waste sand particles are mixed with air at a gas-to-solid ratio of 1:1 to form a waste sand gas-solid mixture. The mixture is then sprayed into the erosion tank 230 by the solid-gas ejector 210 at a flow rate of 5 m / s. Simultaneously, the hot air flow ejector 220 sprays a hot air flow at 80°C into the erosion tank 230 at a flow rate of 10 m / s. The waste sand gas-solid mixture and the hot air flow form a counteraction to remove impurities attached to the surface of the waste sand particles. The impurities are discharged by the dust collection component 240, and the primary regenerated sand is discharged from the bottom of the erosion tank 230.

[0079] S3, superheated steam is introduced into the primary regenerated sand obtained in step S2, with the mass ratio of superheated steam to primary regenerated sand being 1:1. After the superheated steam and the primary regenerated sand are mixed, the solid-liquid ejector 310 tangentially injects the mixed material into the slurrying tank 320 for air flow crushing to remove organic impurities. After standing, the solid and liquid layers are separated to obtain a uniform wet regenerated sand material;

[0080] S4. The regenerated sand wet material obtained in step S3 and the aluminum silicate powder are mixed in the mixing chamber 410 to form a mixed slurry, which is then transported to the drying tank 440 and stirred by the stirrer 420. The compressed 200°C hot air enters the drying tank 440 tangentially to collide with the stirred mixed slurry. The hot air forms a rotating wind field to drive the dry material to flow upward into the receiving component 460, and is transported to the heat exchanger 470 for rapid cooling to obtain dry, regular and uniform regenerated sand particles.

[0081] The mud content, moisture content, and compressive strength (wet compression) of the regenerated sand particles prepared in this embodiment were tested in accordance with GB / T 2684-2009 "Test Methods for Foundry Sand and Mixtures." The angular factor and high-temperature expansion rate of the regenerated sand particles prepared in this embodiment were tested in accordance with GB / T 9442-2024 "Silica Sand for Foundry."

[0082] In addition, the performance of the original sand (coated sand before use in casting) and the waste sand particles obtained after the treatment in step S1 were tested, and the results are shown in Table 1.

[0083] Table 1

[0084]

[0085] Example 3

[0086] In this embodiment, the temperature in step S2 is adjusted to 100°C, 120°C, 140°C, 150°C, and 160°C respectively on the basis of embodiment 2. The other steps and conditions are consistent with embodiment 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 2.

[0087] Table 2

[0088]

[0089] Comparison of the data in Table 2 with that in Table 1 shows that the regenerated sand prepared in this embodiment has significantly lower mud content, moisture content, angular factor, and high-temperature expansion rate than the waste sand particles, and significantly increased (wet pressure) compressive strength; and compared with the original sand, some properties are improved.

[0090] It can be seen from the data in Table 2 that as the temperature of the hot air flow in step S2 increases, the mud content in the finally obtained regenerated sand gradually decreases and the compressive strength gradually increases. When the temperature exceeds 150°C, the changes are not obvious. In addition, as the temperature rises, the angular factor and high-temperature expansion rate gradually decrease. When the temperature exceeds 140°C, the angular factor and high-temperature expansion rate do not change significantly. Based on factors such as cost, the temperature of the hot air flow in step S2 is set to 80°C to 150°C.

[0091] Example 4

[0092] In this embodiment, the flow rate of the hot air flow in step S2 is adjusted to 8 m / s, 15 m / s, 17 m / s, 20 m / s, and 25 m / s, respectively, based on Example 2. Other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 3.

[0093] Table 3

[0094]

[0095] Comparison of the data in Table 3 with that in Table 1 shows that the regenerated sand prepared in this embodiment has significantly lower mud content, water content, angular factor, and high-temperature expansion rate than the waste sand particles, and significantly increased (wet pressure) compressive strength; and compared with the original sand, some properties are improved.

[0096] The data in Table 3 show that as the flow rate of the hot air flow in step S2 increases, the mud content, angular factor, and high-temperature expansion rate of the regenerated sand gradually decrease, while the compressive strength gradually increases. When the flow rate exceeds 20 m / s, the changes are not obvious, and some properties rebound slightly. In view of this, the temperature of the hot air flow in step S2 is set to 10 m / s to 20 m / s.

[0097] Example 5

[0098] In this embodiment, based on Example 2, the flow rate of the waste sand gas-solid mixture in step S2 was adjusted to 4 m / s, 7 m / s, 9 m / s, 10 m / s, and 12 m / s, respectively. The other steps and conditions were consistent with those in Example 2. The relevant performance indicators of the regenerated sand particles were measured, and the results are shown in Table 4.

[0099] Table 4

[0100]

[0101] Comparison of the data in Table 4 with that in Table 1 shows that the regenerated sand prepared in this embodiment has significantly lower mud content, moisture content, angular factor, and high-temperature expansion rate than the waste sand particles, and significantly increased (wet pressure) compressive strength; and compared with the original sand, some properties are improved.

[0102] It can be seen from the data in Table 4 that as the flow rate of the waste sand gas-solid mixture in step S2 increases, the mud content, angular factor and high-temperature expansion rate of the regenerated sand finally obtained gradually decrease, and the compressive strength gradually increases. When the flow rate exceeds 10 m / s, the change is not obvious, and some properties have a small rebound. In view of this, the temperature of the waste sand gas-solid mixture in step S2 is set to 5 m / s~10 m / s.

[0103] Example 6

[0104] Based on Example 2, the present invention adjusts the gas-solid ratio of the waste sand gas-solid mixture in step S2 to 0.9:1, 1.2:1, 1.5:1, 2:1, and 2.2:1, respectively. The other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 5.

[0105] Table 5

[0106]

[0107]

[0108] Comparison of the data in Table 5 with that in Table 1 shows that the regenerated sand prepared in this embodiment has significantly reduced mud content, moisture content, angular factor, and high-temperature expansion rate compared to the waste sand particles, and significantly increased (wet pressure) compressive strength; and compared with the original sand, some properties are improved.

[0109] It can be seen from the data in Table 5 that as the gas-solid ratio of the waste sand gas-solid mixture in step S2 increases, the mud content, angular factor and high-temperature expansion rate of the regenerated sand finally obtained gradually decrease, and the compressive strength gradually increases. When the gas-solid ratio exceeds 2:1, the change is not obvious, and some properties have a small rebound; in view of this, the gas-solid ratio of the waste sand gas-solid mixture in step S2 is set to 1:1~2:1.

[0110] Example 7

[0111] In this embodiment, based on Example 2, the mass ratios of hot steam to primary regenerated sand in step S3 were adjusted to 3:1, 5:1, 8:1, 10:1, and 11:1, respectively. Other steps and conditions were consistent with those in Example 2. The relevant performance indicators of the regenerated sand particles were measured, and the results are shown in Table 6.

[0112] Table 6

[0113]

[0114] Comparison of the data in Table 6 with that in Table 1 shows that the regenerated sand prepared in this embodiment has significantly lower mud content, water content, angular factor, and high-temperature expansion rate than the waste sand particles, and significantly increased (wet pressure) compressive strength; and compared with the original sand, some properties are improved.

[0115] It can be seen from the data in Table 6 that as the mass ratio of hot steam to primary regenerated sand in step S3 increases, the moisture content, angular factor, and high-temperature expansion rate of the finally produced regenerated sand gradually decrease, and the compressive strength gradually increases. When the mass ratio exceeds 10:1, the change is not obvious, and some properties have a small rebound. In view of this, the mass ratio of hot steam to primary regenerated sand in step S3 is set to 1:1 to 10:1.

[0116] Example 8

[0117] In this embodiment, the hot air temperature in step S4 is adjusted to 220°C, 250°C, 270°C, 300°C, and 320°C, respectively, based on Example 2. Other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 7.

[0118] Table 7

[0119]

[0120] Comparison of the data in Table 7 with that in Table 1 shows that the regenerated sand prepared in this embodiment has significantly reduced mud content, moisture content, angular factor, and high-temperature expansion rate compared to the waste sand particles, and significantly increased (wet pressure) compressive strength; and compared with the original sand, some properties are improved.

[0121] It can be seen from the data in Table 7 that as the hot air temperature increases in step S4, the moisture content, angular factor and high-temperature expansion rate of the regenerated sand finally obtained gradually decrease, and the compressive strength gradually increases. When the hot air temperature exceeds 300°C, the changes are not obvious, and some properties have a small rebound. In view of this, the hot air temperature in step S4 is set to 200°C~300°C.

[0122] Comparative Example 1

[0123] In this comparative example, step S2 is deleted based on Example 2. Other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0124] Comparative Example 2

[0125] In this comparative example, step S2 is adjusted on the basis of Example 2. The waste sand particles are not mixed with air, and the waste sand gas-solid mixture is changed to waste sand particles. The other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0126] The specific process of comparative example S2 is as follows: waste sand particles are sprayed into the erosion tank 230 at a flow rate of 5 m / s by the solid-gas injector 210, and at the same time, a hot air flow at 80°C is sprayed into the erosion tank 230 at a flow rate of 10 m / s by the hot air flow injector 220. The waste sand particles and the hot air flow form a counter-action, and impurities attached to the surface of the waste sand particles are removed. The impurities are discharged by the dust collection component 240, and the primary regenerated sand is discharged from the bottom of the erosion tank 230.

[0127] Comparative Example 3

[0128] In this comparative example, step S2 is adjusted on the basis of Example 2, the hot air flow is deleted, and the waste sand gas-solid mixture is directly subjected to air flow crushing. The other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0129] The specific embodiment of comparative example S2 is as follows: waste sand particles are mixed with air at a gas-solid ratio of 1:1 to form a waste sand gas-solid mixture, which is then sprayed into the erosion tank 230 by the solid-gas injector 210 at a flow rate of 15 m / s to remove impurities attached to the surface of the waste sand particles. The impurities are discharged by the dust collection component 240, and the primary regenerated sand is discharged from the bottom of the erosion tank 230.

[0130] Comparative Example 4

[0131] In this comparative example, step S2 is adjusted on the basis of Example 2. The waste sand particles are directly mixed with the hot air flow to form a waste sand gas-solid mixture for air flow crushing. The other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0132] The specific steps of comparative example S2 are as follows: waste sand particles are mixed with 80°C hot air flow at a gas-to-solid ratio of 1:1 to form a waste sand gas-solid mixture, which is then sprayed into the erosion tank 230 by the solid-gas injector 210 at a flow rate of 15 m / s to remove impurities attached to the surface of the waste sand particles. The impurities are discharged by the dust collection component 240, and the primary regenerated sand is discharged from the bottom of the erosion tank 230.

[0133] Comparative Example 5

[0134] In this comparative example, step S3 is adjusted on the basis of Example 2, and superheated steam is replaced with saturated steam. Other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0135] Comparative Example 6

[0136] In this comparative example, step S3 is adjusted on the basis of Example 2, and the superheated steam is replaced with room temperature water. The other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0137] Comparative Example 7

[0138] In this comparative example, step S4 is adjusted on the basis of Example 2, and the aluminum silicate powder is deleted. The other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0139] Comparative Example 8

[0140] In this comparative example, step S4 is adjusted on the basis of Example 2, and the aluminum silicate powder is added after cooling. The other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0141] S4 of this comparative example is specifically as follows: the regenerated sand wet material obtained in step S3 is transported to the drying tank 440 and stirred by the stirrer 420, and the compressed 200°C hot air tangentially enters the drying tank 440 to collide with the stirred regenerated sand wet material, and the hot air forms a rotating wind field to drive the dry material to flow upward into the receiving component 460, and is transported to the heat exchanger 470 for rapid cooling, and then aluminum silicate powder is added and mixed evenly to obtain regenerated sand particles.

[0142] Comparative Example 9

[0143] In this comparative example, step S4 is adjusted on the basis of Example 2, and the rapid cooling is adjusted to natural cooling. The other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0144] Comparative Example 10

[0145] In this comparative example, step S4 is adjusted based on Example 2. The flow component is not provided in the drying tank 440. Other steps and conditions are consistent with Example 2. The relevant performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0146] Comparative Example 11

[0147] This comparative example is a conventional roasting method for preparing regenerated sand, which includes the following steps:

[0148] S1, same as Example 2;

[0149] S2, mechanically grinding into powder;

[0150] S3, calcination at 650℃ for 5h;

[0151] S4, after cooling, repeat steps S2 and S3;

[0152] S5. Screening to obtain regenerated sand. The relevant performance indicators of the regenerated sand were measured, and the results are shown in Table 8.

[0153] Table 8

[0154]

[0155]

[0156] Comparison of the data in Table 8 with that in Table 1 shows that the mud content, water content, angular factor, and high-temperature expansion rate of the regenerated sand obtained in this embodiment and the comparative example are significantly reduced, and the (wet pressure) compressive strength is significantly increased compared to the waste sand particles. In addition, the performance of the regenerated sand obtained in each comparative example is lower than that in Example 2 of the present invention.

[0157] By comparing Comparative Example 1 with Example 2, it can be seen that by deleting step S2 of hot air erosion, the mud content, angular factor, and high-temperature expansion rate all increase significantly, and the compressive strength decreases significantly. The reason is that without hot air erosion, impurities such as coal powder, dust, and fine sand in the waste sand with low density and insoluble in water are difficult to remove, affecting the performance of the regenerated sand.

[0158] Compared with Example 2, the performance of the regenerated sand prepared by counteracting waste sand particles + air and hot air flow is better than the regenerated sand prepared by counteracting waste sand particles and hot air flow, crushing waste sand particles + air, and crushing waste sand particles + hot air flow in Comparative Examples 2 to 4, respectively.

[0159] Comparative Examples 5 and 6 used saturated steam and room temperature water to prepare the slurry in step S3, while Example 2 used superheated steam. As shown in Table 8, in terms of angular factor and high-temperature expansion rate, Example 2 is less than Comparative Example 5 and less than Comparative Example 6; in terms of compressive strength, Example 2 is greater than Comparative Example 5 and greater than Comparative Example 6. This indicates that wet regeneration with superheated steam produces superior regenerated sand.

[0160] Comparative Examples 7 and 8, respectively, omitted aluminum silicate powder in step S4 or added aluminum silicate powder after heat treatment. As shown in Table 8, in terms of high-temperature expansion rate, Example 2 < Comparative Example 7 < Comparative Example 8; and in terms of compressive strength, Example 2 > Comparative Example 8 > Comparative Example 7. This demonstrates that aluminum silicate powder improves the performance of reclaimed sand, and its composite drying with the reclaimed sand mortar is superior to dry mixing of the two.

[0161] Comparison between Example 2 and Comparative Example 9 shows that rapid cooling of the heat-treated regenerated sand particles is more effective than natural cooling. The high-temperature expansion rate and angular factor of Example 2 are slightly lower than those of Comparative Example 9, and the compressive strength is slightly lower than that of Comparative Example 9.

[0162] Comparison of Example 2 with Comparative Example 10 shows that, in step S4, the drying tank 440 is not provided with a flow assembly, the moisture content is significantly increased, the high-temperature expansion rate is slightly increased, and the compressive strength is decreased to a certain extent.

[0163] Comparison of Example 2 with Comparative Example 11 shows that the mud content and high-temperature expansion rate of the regenerated sand prepared by the method of the present invention are slightly lower than those of the conventional roasting method, and the compressive strength and moisture content are slightly higher than those of the conventional roasting method, but the angular factor is much lower than that of the conventional roasting method. In addition, the method of the present invention takes less time and consumes less energy.

[0164] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for recycling and reusing waste foundry coated sand, characterized in that: The method comprises the following steps: The waste casting coated sand is crushed, magnetically separated and classified to obtain waste sand particles; The hot air flow at a preset temperature is injected into the waste sand gas-solid mixture, and the hot air flow erodes the waste sand particles, removing impurities attached to the surface of the waste sand particles to obtain primary regenerated sand; the waste sand gas-solid mixture is a mixture of waste sand particles and air; After the superheated steam is mixed with the primary regenerated sand, it is injected into the tank tangentially and then subjected to air flow crushing to remove organic impurities. After standing, the solid and liquid layers are separated to obtain uniform regenerated sand wet material; The regenerated sand wet material and aluminum silicate powder form a mixed slurry, and the compressed hot air collides with the stirred mixed slurry, and after rapid cooling, dry, regular and uniform regenerated sand particles are obtained.

2. The method for recycling waste foundry coated sand according to claim 1, characterized in that: When the hot air flow and the waste sand gas-solid mixture are sprayed against each other, the flow rate of the hot air flow is 10m / s to 20m / s; the flow rate of the waste sand gas-solid mixture is 5m / s to 10m / s; The temperature of the hot air flow is 80°C to 150°C; The gas-solid ratio of the waste sand gas-solid mixture is 1 to 2:

1.

3. The method for recycling waste foundry coated sand according to claim 1, characterized in that: The mass ratio of the hot steam to the primary regenerated sand is 1 to 10:

1.

4. The method for recycling waste foundry coated sand according to claim 1, characterized in that: During the process of the compressed hot air colliding with the stirred mixed slurry, the temperature of the hot air is 200°C to 300°C.

5. The method for recycling waste foundry coated sand according to claim 1, characterized in that: The compressed hot air enters the container for mixing the slurry tangentially.

6. A waste casting coated sand recovery and reuse system, characterized in that: The system is used to implement the method for recycling and reusing waste foundry coated sand according to claims 1 to 5, comprising: A pre-treatment unit is used to crush, magnetically separate and classify waste foundry coated sand to obtain waste sand particles; A hot air erosion unit, which uses a hot air flow of a preset temperature to collide with the waste sand gas-solid mixture, and the hot air flow erodes the waste sand particles, separating impurities attached to the surface of the waste sand particles to obtain primary regenerated sand; the waste sand gas-solid mixture is a mixture of waste sand particles and air; The superheated steam pulping unit mixes superheated steam and primary regenerated sand and injects it into the tank tangentially, followed by air flow crushing to obtain regenerated sand wet material; In the shaping processing unit, the spirally stirred mixed slurry comes into contact with the injected hot air and is rapidly cooled to obtain dry, regular and uniform regenerated sand particles; the mixed slurry is a mixture of wet regenerated sand and aluminum silicate powder.

7. The waste casting coated sand recovery and reuse system according to claim 6, characterized in that: The hot air erosion unit includes an erosion tank, a solid-gas ejector and a hot air ejector connected to the erosion tank, and a dust collection assembly connected to the top of the erosion tank; The solid-gas ejector and the hot gas ejector are arranged opposite to each other; The solid-gas injector is used to inject a waste sand-gas-solid mixture of waste sand particles and air into the erosion tank; The hot air flow ejector is used to eject a hot air flow at 80°C to 150°C into the erosion tank to form a counter-flow with the waste sand gas-solid mixture; The dust collection component is used to discharge the separated impurities.

8. The waste foundry coated sand recovery and reuse system according to claim 6, characterized in that: The superheated steam pulping unit includes a pulping tank and a solid-liquid ejector; The solid-liquid ejector is connected to the outlet of the hot air erosion unit, and the primary regenerated sand produced by the hot air erosion unit enters the solid-liquid ejector and is mixed with the superheated steam, and then ejected into the pulping tank; Spiral wings are arranged inside the pulping tank.

9. The waste foundry coated sand recovery and reuse system according to claim 6, characterized in that: The shaping processing unit includes a heat drying system and a quick cooling system, and a material receiving component connected to the heat drying system and the quick cooling system; The thermal drying system includes a drying tank, a mixing chamber connected to the bottom of the drying tank, and a hot air conveying component, which is used to dry the mixed slurry to obtain regenerated sand; The mixing chamber is used to mix the regenerated sand wet material with the aluminum silicate powder and transport them into the drying tank; The hot air delivery assembly is used to heat, compress and spray air into the drying tank; The bottom of the drying tank is provided with an agitator, the upper end is provided with a flow dividing assembly, and the top end of the drying tank is connected to the material receiving assembly; The diversion component is used to prevent insufficiently dried regenerated sand from entering the material receiving component; The rapid cooling system is used to rapidly cool the regenerated sand after heat drying to obtain regenerated sand particles; the rapid cooling system uses cold water or cold air as a heat exchanger for the cold fluid.

10. The waste foundry coated sand recovery and reuse system according to claim 9, characterized in that: The diversion assembly includes a connecting rod for fixing and a conical guide fan fixed below the connecting rod. The conical guide fan includes at least three groups of ribs distributed in a circular array; the ribs are arranged upright and are in a triangular shape that is wide at the top and narrow at the bottom.

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