A system and method for recycling used foundry coated sand

Abstract

The application provides a waste foundry coated sand recycling system and method, and belongs to the technical field of reclaimed sand. The system comprises a pretreatment unit, a hot gas flow erosion unit, a superheated steam pulping unit and a shaping treatment unit. The method comprises the following steps: crushing, magnetic separation and grading treatment of waste foundry coated sand to obtain waste sand particles; mixing the waste sand particles with air to form a waste sand gas-solid mixture, and jetting the mixture with a hot gas flow in a butt joint manner to obtain primary reclaimed sand; mixing superheated steam with the primary reclaimed sand, tangentially jetting into a tank and performing airflow crushing, and then performing solid-liquid separation after standing to obtain uniform reclaimed sand wet material; and mixing the reclaimed sand wet material with aluminum silicate powder to form a mixed slurry, colliding the stirred mixed slurry with compressed hot air, and obtaining reclaimed sand particles after rapid cooling. The method of hot gas flow crushing+superheated steam wet regeneration+hot gas flow shearing drying mixing can effectively remove the difficult-to-separate impurities mixed in the waste sand, and improve the purity, fluidity and mechanical properties of the reclaimed sand.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of regenerated sand preparation, and particularly relates to a waste foundry coated sand recycling system and method. BACKGROUND

[0002] Coated sand is a high-performance casting material, which refers to a layer of solid resin film on the surface of sand particles, and is the main raw material for sand molds and sand cores in the casting process. During sand mold casting, 1 ton to 7 tons of used waste sand are generated for every 1 ton of castings, thereby causing a large amount of resource waste and serious environmental pollution.

[0003] Waste foundry coated sand recycling is the main treatment method for waste sand at present. The impurities in the waste sand mainly include metal impurities, functional agents such as coal powder, and binders, which seriously affect the quality of waste sand recycling. In the existing waste sand recycling process, it mainly includes wet regeneration, heat treatment and mechanical treatment. Among them, the wet regeneration is to flexibly scrub the waste sand under water emulsion to remove impurities; the heat treatment melts the waste sand to remove the binders and the like in the coated sand; and the mechanical treatment uses mechanical friction and collision to separate the impurities from the coated sand.

[0004] Although the above method can remove the adverse impurities in the waste coated sand to a certain extent, it is difficult to effectively remove the coal powder mixed in the waste sand, the attached binders and the resin, and the performance of the regenerated sand prepared by the method is significantly lower than that of the original sand, such as poor stability, high high-temperature expansion rate, low strength of the prepared sand core and the like. SUMMARY

[0005] In view of this, the present application aims to provide a waste foundry coated sand recycling system and method, which aims to solve at least one technical problem in the background art.

[0006] The present application is implemented as follows:

[0007] The present application provides a waste foundry coated sand recycling method in the first aspect, which comprises the following steps:

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

[0009] The waste sand gas-solid mixture is obtained by colliding and spraying the hot gas flow at a preset temperature with the waste sand gas-solid mixture, the waste sand particles are eroded by the hot gas flow, the impurities attached to the surface of the waste sand particles are removed, and the primary regenerated sand is obtained; 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, the tangential injection into the tank is carried out for airflow crushing, the organic impurities are removed, and the solid-liquid layering is carried out after standing to obtain uniform regenerated sand wet material;

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

[0012] Preferably, when the hot gas flow and the waste sand gas-solid mixture are jetted in a face-to-face manner, the flow rate of the hot gas flow is 10 m / s to 20 m / s; and the flow rate of the waste sand gas-solid mixture is 5 m / s to 10 m / s.

[0013] The temperature of the hot gas flow is 80℃ to 150℃.

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

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

[0016] Preferably, in the process that the compressed hot air collides with the mixed slurry, the temperature of the hot air is 200℃ to 300℃.

[0017] Preferably, the compressed hot air enters the container of the mixed slurry in a tangent manner.

[0018] The second aspect of the present application provides a waste foundry coated sand recycling system, comprising:

[0019] A pretreatment unit is used for crushing, magnetic separation and grading treatment of the waste foundry coated sand, so as to obtain waste sand particles.

[0020] A hot gas flow erosion unit is used for jetting the hot gas flow with a preset temperature and the waste sand gas-solid mixture in a face-to-face manner, so that the hot gas flow erodes the waste sand particles and separates impurities attached to the surface of the waste sand particles, thereby obtaining primary regenerated sand; the waste sand gas-solid mixture is a mixture of the waste sand particles and air.

[0021] A superheated steam slurry preparation unit is used for tangentially jetting the superheated steam and the primary regenerated sand into a tank and performing airflow pulverization, thereby obtaining a regenerated sand wet material.

[0022] A shaping treatment unit is used for contacting the mixed slurry which is stirred in a spiral manner with the jetted hot air, so that dry, regular and uniform regenerated sand particles are obtained after rapid cooling; the mixed slurry is a mixture of the regenerated sand wet material and the aluminum silicate powder.

[0023] Preferably, the hot gas flow erosion unit comprises an erosion tank, a solid-gas sprayer and a hot gas flow sprayer which are in communication with the erosion tank, and a dust suction assembly which is connected to the top end of the erosion tank.

[0024] The solid-gas sprayer and the hot gas flow sprayer are oppositely arranged.

[0025] The solid-gas ejector is used for ejecting the waste sand particles and the waste sand gas-solid mixture into the erosion tank;

[0026] The hot gas flow ejector is used for ejecting the hot gas flow with a temperature of 80-150℃ into the erosion tank and colliding with the waste sand gas-solid mixture;

[0027] The dust suction assembly is used for discharging the separated impurities.

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

[0029] The solid-liquid jetor is connected with the outlet of the hot gas flow erosion unit, and the primary regenerated sand produced by the hot gas flow erosion unit enters the solid-liquid jetor and is mixed with the superheated steam, and then is re-injected into the pulping tank;

[0030] The pulping tank is internally provided with spiral fins.

[0031] Preferably, the shaping treatment unit comprises a hot drying system and a quick cooling system, and a material collecting assembly connected with the hot drying system and the quick cooling system;

[0032] The hot drying system comprises a drying tank, a mixing chamber connected with the bottom of the drying tank and a hot air conveying assembly, which is used for drying the mixed pulp to produce regenerated sand;

[0033] The mixing chamber is used for mixing the regenerated sand wet material with aluminum silicate powder and conveying into the drying tank;

[0034] The hot air conveying assembly is used for heating, compressing and ejecting air into the drying tank;

[0035] The bottom of the drying tank is vertically provided with an agitator, and the upper end is provided with a shunt assembly, and the top of the drying tank is connected with the material collecting assembly;

[0036] The shunt assembly is used for preventing the insufficiently dried regenerated sand from entering the material collecting assembly;

[0037] The quick cooling system is used for rapidly cooling the hot-dried regenerated sand to produce regenerated sand particles; and the quick cooling system adopts a cold water or cold air heat exchanger as a cold fluid.

[0038] Preferably, the shunt assembly comprises a connecting rod for fixation, a conical flow guide fan fixed below the connecting rod,

[0039] The conical flow guide fan comprises at least three groups of rib plates arranged in an annular array; the rib plates are vertically arranged and have a triangular shape with a wide upper end and a narrow lower end.

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

[0041] 1. The application provides a waste foundry coated sand recycling method, which is a method of hot gas flow breaking + superheated steam wet regeneration + hot gas flow shearing drying mixing, which effectively removes the difficult-to-separate impurities mixed in the waste sand, and improves the purity, fluidity and mechanical properties of the regenerated sand.

[0042] 2. The application is characterized in that the hot gas flow and the waste sand gas-solid mixture are jetted by opposing, and the hot gas flow erodes the waste sand particles to separate the impurities such as coal powder, dust and fine sand attached to the surface of the waste sand particles.

[0043] 3. The application is characterized in that the overheat steam is used to mix the mixture and is sprayed at high speed to realize solid-liquid homogenization, effectively dissolve or strip the organic impurities from the waste sand, and then remove the organic impurities to realize effective impurity removal.

[0044] 4. The application is characterized in that the high-temperature hot air is used to tangentially dry the mixed slurry of regenerated sand + aluminum silicate powder, which is quickly dried and further refined and homogenized under the action of wind shear and impact, mutual friction and the like, so that the surface of the regenerated sand is smoother, and the regenerated sand and aluminum silicate are fused to obtain regenerated sand particles with good stability, high fluidity and excellent mechanical properties. BRIEF DESCRIPTION OF DRAWINGS

[0045] Fig. 1 It is a structural schematic view of a waste foundry coated sand recycling system of the application;

[0046] Fig. 2 It is a top view structural schematic view of the hot gas flow erosion unit in the application;

[0047] Fig. 3 It is a top view structural schematic view of the overheat steam pulping unit in the application;

[0048] Fig. 4 It is a top view structural schematic view of the shunt assembly in the shaping treatment unit in the application;

[0049] ILLUSTRATIVE DESCRIPTION

[0050] 110 - crusher, 120 - magnetic separation impurity removal machine, 130 - screening classifier;

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

[0052] 310 - solid-liquid jet, 320 - pulping tank, 330 - spiral fin;

[0053] 410 - mixing chamber, 420 - stirrer, 430 - hot air conveying assembly, 440 - drying tank, 450 - shunt assembly, 451 - connecting rod, 452 - fin, 460 - material collecting assembly. DETAILED DESCRIPTION

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0055] Example 1

[0056] like Figs. 1 to 4 As shown, a waste casting coated sand recycling system includes a pretreatment unit, a hot air erosion unit, a superheated steam slurry preparation unit, and a shaping unit.

[0057] The pretreatment unit is used to crush, magnetically separate, and classify waste foundry coated sand to obtain waste sand particles; the pretreatment unit includes a crusher 110, a magnetic separator 120, and a screening and grading machine 130 connected in sequence.

[0058] The crusher 110 adopts a mechanical crushing device permitted in this field, such as a roller crusher or a shear crusher, which breaks down and crushes waste sand molds and sand cores into granular waste sand.

[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 powders. Magnetic separation is used to separate them from waste sand.

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

[0061] The hot air erosion unit uses a hot airflow at a preset temperature to spray a mixture of waste sand and gas-solid mixture. The hot airflow erodes the waste sand particles, separating impurities adhering to the surface of the waste sand particles to obtain primary recycled sand. The waste sand gas-solid mixture is a mixture of waste sand particles and air.

[0062] The hot air erosion unit includes an erosion tank 230, a solid-gas ejector 210 and a hot air jet ejector 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 ejector 210 and the hot air jet ejector 220 are arranged opposite to each other. The solid-gas ejector 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 jet ejector 220 is used to inject a hot air stream of 80℃~150℃ into the erosion tank 230 and form an anti-collision with the waste sand gas-solid mixture. The dust collection assembly 240 is used to discharge the separated impurities.

[0063] In a specific casting process, sand molds and sand cores can add coal powder as a reinforcing functional agent to improve surface quality, prevent sand sticking and produce pores and other defects; In addition, impurities such as dust and fine sand are mixed during the manufacturing or use process. The effects of the hot gas flow erosion unit include the following aspects (1) breaking the waste sand into more regular and uniform particles; (2) removing the free moisture of the waste sand under the action of the hot gas flow; (3) under the impact of the gas flow, the coal powder, dust, fine sand and other impurities are stripped from the waste sand particles; (4) under the action of the flowing gas, the coal powder, dust, fine sand and other small impurities can be discharged from the dust suction assembly 240 above due to the small particle density, and the waste sand particles have a large density and then sink downward into the subsequent processing unit.

[0064] In a specific implementation, compared with directly opposing the waste sand particles with the hot gas flow, the present application mixes the waste sand particles with air and then opposes them with the hot gas flow, which can effectively control the direction of the waste sand particles and maximize the opposing efficiency. In addition, mixing the waste sand particles with air and opposing them with the hot gas flow can increase the contact time.

[0065] The superheated steam pulping unit tangentially injects superheated steam and primary regenerated sand into the tank and performs jet milling, and then the solid-liquid layer is separated after standing, to obtain uniform regenerated sand wet material;

[0066] The superheated steam pulping unit includes a pulping tank 320 and a solid-liquid jet device 310; the solid-liquid jet device 310 is connected in communication with the outlet of the hot gas flow erosion unit (i.e. the bottom of the erosion tank 230), and the primary regenerated sand prepared by the hot gas flow erosion unit enters the solid-liquid jet device 310 and is mixed with the superheated steam, and then is injected into the sealed pulping tank 320; the inside of the pulping tank 320 is provided with a spiral fin 330, and the spiral fin 330 serves to improve the mixing effect of the material in the pulping tank 320.

[0067] The present application uses superheated steam instead of water, mixes it with primary regenerated sand, and then uses the solid-liquid jet device 310 to inject it into the sealed pulping tank 320 at a tangent angle. In this process, the mixed material is injected at high speed, collides with the inner wall of the pulping tank 320, and realizes solid-liquid homogenization. In addition, due to the high temperature and high energy density characteristics of the superheated steam, combined with the injection operation, the superheated steam can effectively dissolve or strip the organic impurities from the waste sand, and then remove the organic impurities (such as binders, etc.).

[0068] In addition to impurity removal, the superheated steam pulping unit can also serve the following functions: (1) further refining the size of the regenerated sand particles; (2) further promoting the uniformity of the surface of the regenerated sand particles, making the particles more spherical, and thus improving the flowability and stability of the product.

[0069] The shaping treatment unit is used for contacting the mixed slurry of spiral stirring with the hot air sprayed into the shaping treatment unit, and obtaining dry, regular and uniform regenerated sand particles after rapid cooling.

[0070] The shaping treatment unit comprises a hot drying system and a rapid cooling system, and a material collecting assembly 460 connected with the hot drying system and the rapid cooling system; the hot drying system comprises a drying tank 440, a mixing chamber 410 communicated with the bottom of the drying tank 440 and a hot air conveying assembly 430, which is used for drying the mixed slurry to obtain the regenerated sand; the mixing chamber 410 is used for mixing the regenerated sand wet material and the aluminum silicate powder and conveying the mixed slurry into the drying tank 440; the hot air conveying assembly 430 is used for heating, compressing and spraying the air into the drying tank 440; the bottom of the drying tank 440 is vertically provided with a stirrer 420, and the upper end of the drying tank 440 is provided with a shunt assembly 450, and the top of the drying tank 440 is communicated with the material collecting assembly 460; the shunt assembly 450 is used for preventing the regenerated sand which is not sufficiently dried from entering the material collecting assembly 460; the rapid cooling system is used for rapidly cooling the regenerated sand after hot drying to obtain the regenerated sand particles, and the rapid cooling system adopts a heat exchanger using cold water or cold air as a cold fluid. The shunt assembly 450 comprises a connecting rod 451 used for fixing, and a conical diversion fan fixed below the connecting rod 451, and the conical diversion fan comprises at least three groups of rib plates 452 arranged in an annular array; the rib plates 452 are vertically arranged and have a triangular shape with a wide upper end and a narrow lower end.

[0071] Since the mechanical properties, especially the strength, of the coated sand waste sand after recycling and reuse are decreased, the aluminum silicate powder is added to improve the regenerated sand. Compared with directly mixing the regenerated sand solid with the aluminum silicate, the regenerated sand wet material and the aluminum silicate are mixed and hot dried in the present application, so that the aluminum silicate can be effectively doped into the regenerated sand to play the effect of the reinforcing agent. The amount of the aluminum silicate is in the range permitted in the field, and is adjusted according to the composition of the coated sand waste sand, and generally, the amount of the aluminum silicate is 2% to 10% of the waste sand particles, and 5% is used in the following examples.

[0072] The hot air tangentially enters the bottom of the drying tank 440 at 200-300°C, and the stirrer 420 drives the hot air to form a rotating wind field while stirring the mixed slurry, so that the solids in the mixed slurry are subjected to wind shear, impact, mutual friction and other forces, on the one hand, the moisture in the mixed slurry is rapidly evaporated (drying can be achieved within tens of seconds or minutes), on the other hand, the solids in the mixed slurry are further refined and homogenized, and in addition, the regenerated sand and aluminum silicate are fused. The regenerated sand particles with low moisture content and small particle size rise with the rotating air flow and are transported to the material collection assembly 460 and then enter the heat exchanger for cooling. At the same time, the regenerated sand particles with high moisture content continue to contact with the hot air due to gravity, and part of the particles with certain humidity rise again and are intercepted by the flow dividing assembly 450, and then fall back to the bottom of the drying tank 440 for further drying until the moisture is further reduced.

[0073] The present application rapidly cools the regenerated sand particles after heat drying in the heat exchanger, which helps to reduce the residual stress in the regenerated sand, and also maintains good bonding between the sand particles. In addition, the heat exchanger absorbs heat for waste heat recovery and reuse, such as a hot gas flow erosion unit, a superheated steam slurry preparation unit, and a heat source in the hot air conveying assembly 430.

[0074] In specific implementation, the dust collection assembly 240, the hot air conveying assembly 430, and the material collection assembly 460 adopt components, connections and structures permitted in the art. For example, the dust collection assembly 240 includes a power generating motor, a dust conveying pipeline, a valve for controlling the size, etc.; the hot air conveying assembly 430 includes a fan, a heater, a compression pump, a pipeline, a valve, etc.; and the material collection assembly 460 includes a suction pump, a pipeline, a valve, etc., which are not specifically limited here.

[0075] Example 2

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

[0077] S1, the waste coated sand for casting is sequentially subjected to crushing, magnetic separation and classification treatment by using the crusher 110, the magnetic impurity removal machine 120 and the screening classifier 130 to obtain waste sand particles with a particle size of not more than 5 mm;

[0078] S2, the 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 sprayed into the erosion tank 230 by the solid-gas injector 210 at a flow rate of 5 m / s, and the hot gas stream is sprayed into the erosion tank 230 by the hot gas stream injector 220 at a flow rate of 10 m / s, the waste sand gas-solid mixture and the hot gas stream form a collision, the impurities attached to the surface of the waste sand particles are removed, the impurities are discharged by the dust collection assembly 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 prepared in step S2, the mass ratio of superheated steam to primary regenerated sand is 1:1, after mixing, the mixture is tangentially injected into the slurry tank 320 by the solid-liquid jet device 310 for jet milling, and the organic impurities are removed, and after standing, the solid-liquid is layered to obtain uniform regenerated sand wet material;

[0080] S4, the regenerated sand wet material prepared in step S3 is mixed with aluminum silicate powder 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, and the compressed hot air at 200℃ is tangentially introduced into the drying tank 440 to collide with the stirred mixed slurry, the hot air forms a rotating air field to drive the dry material to flow upward into the material collection assembly 460, and then is transported to the heat exchanger for rapid cooling to obtain dry, regular and uniform regenerated sand particles.

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

[0082] In addition, the performance of the raw sand (coated sand before casting) and the waste sand particles obtained after step S1 was detected, 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℃, 120℃, 140℃, 150℃ and 160℃ respectively, and other steps and conditions are the same as those in Example 2. The relevant performance indicators of the regenerated sand particles were measured, and the results are shown in Table 2.

[0087] Table 2

[0088]

[0089] As can be seen from the comparison of the data in Table 2 and Table 1, the regenerated sand prepared in this embodiment has significantly lower mud content, water content, angular factor and high-temperature expansion rate, and significantly higher (wet compression) compressive strength compared to the waste sand particles; and compared with the raw sand, some of the performances are improved.

[0090] From the data in Table 2, it can be seen that as the temperature of the hot gas flow in step S2 increases, the clay content in the regenerated sand gradually decreases, and the compressive strength gradually increases. When the temperature exceeds 150℃, the changes are not obvious. As the temperature increases, the angle factor and high-temperature expansion rate gradually decrease. When the temperature exceeds 140℃, the angle factor and high-temperature expansion rate change is not obvious. Considering factors such as cost, the temperature of the hot gas flow in step S2 is set to 80℃-150℃.

[0091] Example 4

[0092] In this example, the flow rate of the hot gas flow in step S2 is adjusted to 8m / s, 15m / s, 17m / s, 20m / s, and 25m / s, respectively, based on Example 2. 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 3.

[0093] Table 3

[0094]

[0095] From the comparison of the data in Table 3 and Table 1, it can be seen that the regenerated sand prepared in this example has significantly lower clay content, water content, angle factor, and high-temperature expansion rate compared to the waste sand particles, and the (wet compression) compressive strength is significantly increased. Compared with the original sand, some of the performance has been improved.

[0096] From the data in Table 3, it can be seen that as the flow rate of the hot gas flow in step S2 increases, the clay content, angle factor, and high-temperature expansion rate of the regenerated sand gradually decrease, and the compressive strength gradually increases. When the flow rate exceeds 20m / s, the changes are not obvious, and some of the performance has a small rebound. Therefore, the temperature of the hot gas flow in step S2 is set to 10m / s-20m / s.

[0097] Example 5

[0098] In this example, the flow rate of the waste sand gas-solid mixture in step S2 is adjusted to 4m / s, 7m / s, 9m / s, 10m / s, and 12m / s, respectively, based on Example 2. 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 4.

[0099] Table 4

[0100]

[0101] From the comparison of the data in Table 4 and Table 1, it can be seen that the regenerated sand prepared in this example has significantly lower clay content, water content, angle factor, and high-temperature expansion rate compared to the waste sand particles, and the (wet compression) compressive strength is significantly increased. Compared with the original sand, some of the performance has been improved.

[0102] From the data in Table 4, it can be seen that as the flow rate of the waste sand gas-solid mixture in step S2 increases, the clay content, the angle factor and the high-temperature expansion rate of the regenerated sand gradually decrease, and the compressive strength gradually increases, and when the flow rate exceeds 10 m / s, the changes are not obvious, and some performances have a small rebound. Therefore, the temperature of the waste sand gas-solid mixture in step S2 is set to 5 m / s to 10 m / s.

[0103] Example 6

[0104] In this embodiment, the gas-solid ratio of the waste sand gas-solid mixture in step S2 is adjusted to 0.9:1, 1.2:1, 1.5:1, 2:1 and 2.2:1 respectively, and other steps and conditions are consistent with those in Example 2. The related performance indicators of the regenerated sand particles are measured, and the results are shown in Table 5.

[0105] Table 5

[0106]

[0107] From the comparison of the data in Table 5 and Table 1, it can be seen that compared with the waste sand particles, the regenerated sand prepared in this embodiment has a significant decrease in clay content, water content, angle factor and high-temperature expansion rate, and a significant increase in (wet compression) compressive strength. Compared with the original sand, some performances are improved.

[0108] From the data in Table 5, it can be seen that as the gas-solid ratio of the waste sand gas-solid mixture in step S2 increases, the clay content, the angle factor and the high-temperature expansion rate of the regenerated sand gradually decrease, and the compressive strength gradually increases, and when the gas-solid ratio exceeds 2:1, the changes are not obvious, and some performances have a small rebound. Therefore, the gas-solid ratio of the waste sand gas-solid mixture in step S2 is set to 1:1 to 2:1.

[0109] Example 7

[0110] In this embodiment, the mass ratio of the hot steam to the primary regenerated sand in step S3 is adjusted to 3:1, 5:1, 8:1, 10:1 and 11:1 respectively, and other steps and conditions are consistent with those in Example 2. The related performance indicators of the regenerated sand particles are measured, and the results are shown in Table 6.

[0111] Table 6

[0112]

[0113] From the comparison of the data in Table 6 and Table 1, it can be seen that compared with the waste sand particles, the regenerated sand prepared in this embodiment has a significant decrease in clay content, water content, angle factor and high-temperature expansion rate, and a significant increase in (wet compression) compressive strength. Compared with the original sand, some performances are improved.

[0114] From the data in Table 6, it can be seen 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 prepared regenerated sand gradually decrease, and the compressive strength gradually increases. When the mass ratio exceeds 10:1, the changes are not obvious, and some performances have a small rebound. Therefore, the mass ratio of hot steam to primary regenerated sand in step S3 is set to 1:1-10:1.

[0115] Example 8

[0116] In this example, the hot air temperature in step S4 is adjusted to 220℃, 250℃, 270℃, 300℃ and 320℃ respectively based on Example 2, and other steps and conditions are consistent with Example 2. The related performance indicators of the regenerated sand particles are measured, and the results are shown in Table 7.

[0117] Table 7

[0118]

[0119] From the comparison of the data in Table 7 and Table 1, it can be seen that compared with the waste sand particles, the regenerated sand prepared in this example has a significant decrease in clay content, moisture content, angular factor and high-temperature expansion rate, and a significant increase in (wet compression) compressive strength. Compared with the original sand, some performances are improved.

[0120] From the data in Table 7, it can be seen that as the hot air temperature in step S4 increases, the moisture content, angular factor and high-temperature expansion rate of the finally prepared regenerated sand gradually decrease, and the compressive strength gradually increases. When the hot air temperature exceeds 300℃, the changes are not obvious, and some performances have a small rebound. Therefore, the hot air temperature in step S4 is set to 200℃-300℃.

[0121] Comparative Example 1

[0122] In this comparative example, step S2 is deleted based on Example 2, and other steps and conditions are consistent with Example 2. The related performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0123] Comparative Example 2

[0124] In this comparative example, step S2 is adjusted based on Example 2, and the waste sand particles are not mixed with air. The waste sand particles are changed from a waste sand gas-solid mixture to waste sand particles. Other steps and conditions are consistent with Example 2. The related performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0125] The comparative example S2 is specifically: the waste sand particles are sprayed into the erosion tank 230 by the solid-gas injector 210 at a flow rate of 5 m / s, and the hot gas stream injector 220 sprays the hot gas stream at 80°C into the erosion tank 230 at a flow rate of 10 m / s, the waste sand particles and the hot gas stream form a collision, remove the impurities attached to the surface of the waste sand particles, the impurities are discharged by the dust collection assembly 240, and the primary regenerated sand is discharged from the bottom of the erosion tank 230.

[0126] Comparative example 3

[0127] The comparative example is based on example 2, adjusting step S2, deleting the hot gas stream, directly performing air flow crushing by the waste sand gas-solid mixture, other steps and conditions are consistent with example 2, and the related performance indicators of the regenerated sand particles are measured, and the results are shown in table 8.

[0128] The comparative example S2 is specifically: the waste sand particles and air are mixed in a waste sand gas-solid mixture according to a gas-solid ratio of 1:1, and then sprayed into the erosion tank 230 by the solid-gas injector 210 at a flow rate of 15 m / s, to remove the impurities attached to the surface of the waste sand particles, the impurities are discharged by the dust collection assembly 240, and the primary regenerated sand is discharged from the bottom of the erosion tank 230.

[0129] Comparative example 4

[0130] The comparative example is based on example 2, adjusting step S2, directly mixing the waste sand particles and the hot gas stream to form a waste sand gas-solid mixture for air flow crushing, other steps and conditions are consistent with example 2, and the related performance indicators of the regenerated sand particles are measured, and the results are shown in table 8.

[0131] The comparative example S2 is specifically: the waste sand particles and the hot gas stream at 80°C are mixed in a waste sand gas-solid mixture according to a gas-solid ratio of 1:1, and then sprayed into the erosion tank 230 by the solid-gas injector 210 at a flow rate of 15 m / s, to remove the impurities attached to the surface of the waste sand particles, the impurities are discharged by the dust collection assembly 240, and the primary regenerated sand is discharged from the bottom of the erosion tank 230.

[0132] Comparative example 5

[0133] The comparative example is based on example 2, adjusting step S3, replacing the superheated steam with saturated steam, other steps and conditions are consistent with example 2, and the related performance indicators of the regenerated sand particles are measured, and the results are shown in table 8.

[0134] Comparative example 6

[0135] The comparative example is based on example 2, adjusting step S3, replacing the superheated steam with room temperature water, other steps and conditions are consistent with example 2, and the related performance indicators of the regenerated sand particles are measured, and the results are shown in table 8.

[0136] Comparative example 7

[0137] The comparative example is based on adjusting step S4 of example 2, deleting the aluminum silicate powder, and other steps and conditions are consistent with example 2. The related performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0138] Comparative example 8

[0139] The comparative example is based on adjusting step S4 of example 2, adding the aluminum silicate powder after cooling, and other steps and conditions are consistent with example 2. The related performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0140] S4 of the comparative example is: the regenerated sand wet material prepared in step S3 is transported to the drying tank 440 and stirred by the stirrer 420. The compressed hot air at 200°C is tangentially introduced into the drying tank 440 to collide with the stirred regenerated sand wet material. The hot air forms a rotating air field to drive the dry material to flow upward into the material collecting assembly 460, and then is transported to the heat exchanger for rapid cooling. The aluminum silicate powder is added and uniformly mixed to obtain the regenerated sand particles.

[0141] Comparative example 9

[0142] The comparative example is based on adjusting step S4 of example 2, adjusting the rapid cooling to natural cooling, and other steps and conditions are consistent with example 2. The related performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0143] Comparative example 10

[0144] The comparative example is based on adjusting step S4 of example 2, and the flow assembly is not arranged in the drying tank 440. Other steps and conditions are consistent with example 2. The related performance indicators of the regenerated sand particles are measured, and the results are shown in Table 8.

[0145] Comparative example 11

[0146] The comparative example is a conventional roasting method for preparing regenerated sand, which includes the following steps:

[0147] S1, same as example 2;

[0148] S2, mechanically grinding into powder;

[0149] S3, high-temperature calcination at 650°C for 5h;

[0150] S4, repeating steps S2 and S3 after cooling;

[0151] S5, screening to obtain regenerated sand. The related performance indicators of the regenerated sand are measured, and the results are shown in Table 8.

[0152] Table 8

[0153]

[0154] From the comparison of Table 8 and Table 1 data, it can be seen that the regenerated sand prepared by the embodiment and the comparative examples has a significantly reduced clay content, water content, angularity factor and high-temperature expansion rate compared with the waste sand particles, and the (wet compression) compressive strength is significantly increased, and the performance of the regenerated sand prepared by each comparative example is lower than that of the embodiment 2.

[0155] From the comparison of Comparative Example 1 and Embodiment 2, it can be seen that the clay content, angularity factor and high-temperature expansion rate are significantly increased, and the compressive strength is greatly decreased, if the hot gas flow erosion in step S2 is deleted, because the impurities such as coal powder, dust and fine sand in the waste sand are difficult to remove without hot gas flow erosion, and the performance of the regenerated sand is affected.

[0156] Compared with the performance of the regenerated sand prepared by using waste sand particles + air and hot gas flow in Comparative Example 2, the performance of the regenerated sand prepared by using waste sand particles and hot gas flow, waste sand particles + air for crushing, and waste sand particles + hot gas flow for air flow crushing in Comparative Examples 2 to 4 is better.

[0157] Comparative Example 5 and Comparative Example 6 use saturated steam and room temperature water to prepare the slurry in step S3, and Embodiment 2 uses superheated steam, from the data in Table 8, in terms of angularity factor and high-temperature expansion rate, Embodiment 2 < Comparative Example 5 < Comparative Example 6, and in terms of compressive strength, Embodiment 2 > Comparative Example 5 > Comparative Example 6. It can be seen that the performance of the regenerated sand prepared by using superheated steam for wet regeneration is more excellent.

[0158] Comparative Example 7 and Comparative Example 8 delete the aluminum silicate powder in step S4 or add the aluminum silicate powder after heat treatment, from the data in Table 8, in terms of high-temperature expansion rate, Embodiment 2 < Comparative Example 7 < Comparative Example 8, and in terms of compressive strength, Embodiment 2 > Comparative Example 8 > Comparative Example 7. It can be seen that the aluminum silicate powder is beneficial to improve the performance of the regenerated sand, and the effect after the aluminum silicate powder is compounded and dried with the regenerated sand slurry is better than that of dry mixing of the two.

[0159] From the comparison of Embodiment 2 and Comparative Example 9, it can be seen that the effect of rapid cooling of the regenerated sand particles after heat treatment is better than that of natural cooling, the high-temperature expansion rate and angularity factor of Embodiment 2 are slightly lower than those of Comparative Example 9, and the compressive strength is slightly lower than that of Comparative Example 9.

[0160] From the comparison of Embodiment 2 and Comparative Example 10, it can be seen that the water content is significantly increased, the high-temperature expansion rate is slightly increased, and the compressive strength is decreased to a certain extent, if the flow assembly is not arranged in the drying tank 440 in step S4.

[0161] Compared with the comparative example 11, it can be seen that the regenerated sand prepared by the method of the application has slightly lower clay content and high-temperature expansion rate, slightly higher compressive strength and water content, and far lower angular factor than the conventional roasting method, in addition, the method of the application has shorter time consumption and lower energy consumption.

[0162] The above examples only express several embodiments of the application, which are described in more detail and in more detail, but cannot be understood as limiting the scope of the patent of the application. It should be noted that for ordinary skilled in the art, without departing from the concept of the application, several modifications and improvements can be made, which belong to the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A method for recycling used foundry coated sand, characterized by, The method comprises the following steps: The waste foundry coated sand is broken, magnetically selected and classified to obtain waste sand particles; The waste sand particles are eroded by a hot gas stream to remove impurities attached to the surface of the waste sand particles, and primary regenerated sand is obtained; the waste sand gas-solid mixture is a mixture of waste sand particles and air; The superheated steam is mixed with the primary regenerated sand, and the mixture is tangentially injected into a tank for jet milling to remove organic impurities, and the mixture is then statically layered to obtain uniform regenerated sand wet material; The regenerated sand wet material is mixed with aluminum silicate powder to form a mixed slurry, and compressed hot air collides with the mixed slurry to obtain dry, regular and uniform regenerated sand particles after rapid cooling.

2. The method according to claim 1, wherein When the hot gas stream and the waste sand gas-solid mixture are jetted against each other, the flow rate of the hot gas stream is 10 m / s to 20 m / s; the flow rate of the waste sand gas-solid mixture is 5 m / s to 10 m / s; The temperature of the hot gas stream is 80℃ to 150℃; The gas-solid ratio in the waste sand gas-solid mixture is 1 to 2:

1.

3. The method according to claim 1, wherein The mass ratio of the superheated steam to the primary regenerated sand is 1 to 10:

1.

4. The method according to claim 1, wherein In the process of the compressed hot air colliding with the mixed slurry, the temperature of the hot air is 200℃ to 300℃.

5. The method for reclaiming and reusing the spent foundry coated sand according to claim 1, characterized in that, The compressed hot air is tangentially injected into the container of the mixed slurry.

6. A waste foundry coated sand recycling system characterized by, The system is used to implement the method for recycling waste foundry coated sand according to any one of claims 1 to 5, and comprises: A pretreatment unit for breaking, magnetically selecting and classifying the waste foundry coated sand to obtain waste sand particles; A hot gas stream erosion unit for jetting the hot gas stream against the waste sand gas-solid mixture to erode the waste sand particles and separate impurities attached to the surface of the waste sand particles, thereby obtaining primary regenerated sand; the waste sand gas-solid mixture is a mixture of waste sand particles and air; A superheated steam slurry preparation unit for mixing the superheated steam with the primary regenerated sand, jetting the mixture tangentially into a tank, and performing jet milling to obtain regenerated sand wet material; A shaping treatment unit in which the mixed slurry is stirred and contacted with the injected hot air, and dry, regular and uniform regenerated sand particles are obtained after rapid cooling; the mixed slurry is a mixture of the regenerated sand wet material and aluminum silicate powder.

7. The system for reclaiming and recycling used foundry coated sand according to claim 6, wherein The hot gas stream erosion unit comprises an erosion tank, a solid-gas injector and a hot gas stream injector connected to the erosion tank, and a dust suction assembly connected to the top end of the erosion tank; The solid-gas injector and the hot gas stream injector are oppositely arranged; The solid-gas injector is used to inject the waste sand gas-solid mixture of waste sand particles and air into the erosion tank; The hot gas stream injector is used to inject the hot gas stream with a temperature of 80℃ to 150℃ into the erosion tank and form a jet against the waste sand gas-solid mixture; The dust suction assembly is used to discharge the separated impurities.

8. The system for reclaiming and recycling used foundry coated sand according to claim 6, wherein The superheated steam slurry preparation unit comprises a slurry preparation tank and a solid-liquid jet injector; The solid-liquid jet injector is connected to the outlet of the hot gas stream erosion unit, the primary regenerated sand prepared by the hot gas stream erosion unit enters the solid-liquid jet injector, is mixed with the superheated steam, and is then injected into the slurry preparation tank; A spiral fin is arranged inside the slurry preparation tank.

9. The system for reclaiming and recycling used foundry coated sand according to claim 6, wherein The shaping treatment unit comprises a hot drying system and a quick cooling system, a material collecting assembly connecting the hot drying system and the quick cooling system; The hot drying system comprises a drying tank, a mixing chamber communicated with the bottom of the drying tank, and a hot air conveying assembly for drying the mixed slurry to produce the regenerated sand; The mixing chamber is used for mixing the regenerated sand wet material with aluminum silicate powder and conveying the mixed material into the drying tank; The hot air conveying assembly is used for heating, compressing and spraying air into the drying tank; The bottom of the drying tank is vertically provided with a stirrer, the upper end is provided with a shunt assembly, and the top of the drying tank is communicated with the material collecting assembly; The shunt assembly is used for preventing the insufficiently dried regenerated sand from entering the material collecting assembly; The quick cooling system is used for quickly cooling the hot dried regenerated sand to produce regenerated sand particles; the quick cooling system uses cold water or cold air as a heat exchanger of the cooling fluid.

10. The system for reclaiming and recycling used foundry coated sand according to claim 9, wherein The shunt assembly comprises a connecting rod for fixation, a conical flow guide fan fixed below the connecting rod, The conical flow guide fan comprises at least three groups of rib plates arranged in an annular array; the rib plates are vertically arranged and have a triangular shape with a wide upper end and a narrow lower end.

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