System for nitrogen liquefaction deep cooling powder of waste tire waste plastic solid waste

Abstract

This invention provides a system comprising: a material tank having first, second, and third chambers, the first and second chambers communicating with each other, the second and third chambers communicating with each other, the first chamber having a discharge port, and the third chamber having a feed inlet and an air inlet; a powder tank having a material inlet at its top; a first pipeline and a second pipeline, the two ends of which are respectively connected to the powder tank and the second chamber, the first pipeline having a first fan; a liquid nitrogen ball mill having a feed end and a discharge end, the feed end being connected to the discharge port of the first chamber via the third pipeline, the third pipeline having a feed hopper; wherein a fourth pipeline extends from the third pipeline and communicates with the first chamber, the fourth pipeline having a second fan, and the discharge end being connected to the material inlet of the powder tank via a fifth pipeline; wherein the connection between the first pipeline and the powder tank is located near the material inlet. The purpose of this invention is to at least improve the utilization rate of cold energy in the system.

Description

Technical Field

[0001] This invention relates to a system for cryogenic pulverization of solid waste such as waste tires and waste plastics using liquid nitrogen. Background Technology

[0002] Waste tires and waste plastics mainly contain organic compounds (plastics, rubber, etc.) and small amounts of fibers, steel wires, and inorganic materials. They are not easily decomposed and have a high wear resistance coefficient. In industry, they can be recycled through cryogenic crushing. The principle is to freeze the waste plastics and rubber to below their glass transition temperature, causing the molecular chains to become brittle and immobile, making them easy to crush. This produces fine plastic and rubber powder, which can be used directly or after modification in plastic and rubber products, chemical building materials, road transportation, and other fields.

[0003] In the cryogenic grinding and powdering process of waste plastics and waste rubber, liquid nitrogen and atomized nitrogen are generally used as carriers to carry cold energy to cool the materials. However, the cold energy of existing cryogenic powdering equipment is wasted after one application. Due to the high price of liquid nitrogen, the production cost increases significantly. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention proposes a system for cryogenic pulverization of waste tires and waste plastic solid waste with liquid nitrogen, so as to improve the utilization rate of cold energy.

[0005] According to one embodiment of the present invention, a system for cryogenic pulverization of waste tires and waste plastic solid waste using liquid nitrogen is provided, comprising: a material tank, wherein a first chamber, a second chamber, and a third chamber are arranged sequentially from bottom to top within the material tank, the first chamber communicating with the second chamber and the second chamber communicating with the third chamber, the first chamber having a discharge port and the third chamber having a feed port and an air inlet; a powder tank, wherein a material inlet is provided at the top of the powder tank; a first pipeline and a second pipeline, the two ends of the first pipeline and the second pipeline being respectively connected to the powder tank and the second chamber, and a first fan being provided on the first pipeline; a liquid nitrogen ball mill, wherein a feed end and a discharge end are provided on the liquid nitrogen ball mill, the feed end being connected to the discharge port of the first chamber through the third pipeline, and a feed hopper being provided on the third pipeline; wherein a fourth pipeline extending from the third pipeline and communicating with the first chamber is provided, the fourth pipeline having a second fan being provided, and the discharge end being connected to the material inlet of the powder tank through a fifth pipeline; wherein the connection between the first pipeline and the powder tank is located near the material inlet.

[0006] It is understandable that the nitrogen gas in the liquid nitrogen ball mill (formed by atomizing liquid nitrogen injected into the ball mill) still carries a large amount of cold energy after cooling the material in the ball mill. Therefore, by using a second fan to pump it to the first chamber of the feed tank through the third and fourth pipelines, the cold energy it carries can be used to continue cooling the material in the first chamber of the feed tank. In addition, during the production process, the material is transported from the feed tank to the liquid nitrogen ball mill through the third pipeline, while the flow direction of the nitrogen gas in the third pipeline is opposite to that of the material, that is, from the liquid nitrogen ball mill to the feed tank (first chamber) through the third pipeline. Since the material transportation and nitrogen gas flow occur simultaneously during the production process, not only can this part of the nitrogen gas be used to cool the material in the first chamber, but it can also further absorb cold energy during the material transportation process, thus improving the utilization rate of cold energy.

[0007] On the other hand, the rubber powder generated after the material is processed in the liquid nitrogen ball mill also carries a portion of cold energy, which is transported to the powder hopper along with the rubber powder. Since an air inlet is installed on the third chamber of the hopper, and the second chamber, which is connected to the third chamber, is connected to the powder hopper via a first and a second pipeline, and a first fan is installed on the first pipeline, the first fan can sequentially draw outside gas into the third and second chambers of the hopper through the air inlet, and then into the powder hopper through the first pipeline. This gas drawn into the powder hopper will exchange heat with the rubber powder, thus transferring the cold energy carried by the rubber powder to this gas. Subsequently, this gas carrying the cold energy of the rubber powder returns to the second chamber through the second pipeline. In other words, the first fan can draw this gas and its carried cold energy (i.e., the cold energy obtained from the rubber powder) back to the second chamber of the hopper through the first and second pipelines, continuing to be used for cooling the material in the second chamber, further improving the utilization rate of cold energy.

[0008] Specifically, the connection between the first pipeline and the powder tank is located near the material inlet. During production, the rubber powder enters the powder tank from the material inlet and falls under gravity. Simultaneously, the first blower draws outside gas into the powder tank through the first pipeline (as described above). Because the connection between the first pipeline and the powder tank is located near the material inlet, the rubber powder entering the powder tank comes into contact with the gas blown out of the first pipeline and undergoes heat exchange. In other words, the rubber powder comes into contact with and exchanges heat with the gas drawn into the powder tank from the first pipeline throughout its entire descent within the powder tank. The rubber powder will not be unable to fully transfer its cooling energy to the gas due to insufficient contact or difficulty in contacting the gas after settling at the bottom of the powder tank. This design further improves the cold energy recovery rate of the rubber powder.

[0009] Preferably, the connection between the second pipeline and the powder tank is set lower than the connection between the first pipeline and the powder tank. This is because the gas enters the powder tank through the first pipeline and its temperature decreases after heat exchange with the adhesive powder (cold energy is transferred from the adhesive powder to the gas). Since the low-temperature gas has a higher specific gravity, it tends to flow downwards. Therefore, setting the connection between the second pipeline and the powder tank at a lower position is beneficial for the low-temperature gas to return to the second chamber through the second pipeline.

[0010] In summary, after liquid nitrogen is atomized into gaseous nitrogen in the liquid nitrogen ball mill, it is first used to cool the material in the liquid nitrogen ball mill. Then, under the suction of the second fan, it reaches the first chamber of the material tank through the third and fourth pipelines, using the cold energy carried by the nitrogen (i.e., the remaining cold energy) to cool the material in the first chamber. In addition, external gas can be drawn into the powder tank through the air inlet by the first fan and exchange heat with the rubber powder in the powder tank, transferring the cold energy carried by the rubber powder to the material in the second chamber through the second pipeline. In particular, the connection between the first pipeline and the powder tank is located near the material inlet, which further improves the cold energy recovery rate of the rubber powder.

[0011] According to one embodiment of the present invention, the connection point between the first pipeline and the powder tank is located on the side of the powder tank near the top of the powder tank.

[0012] According to one embodiment of the present invention, annular air ducts are provided in both the first chamber and the second chamber of the material tank, a second pipe is connected to the annular air duct in the second chamber, and a fourth pipe is connected to the annular air duct in the first chamber. The annular air ducts are provided with a plurality of air outlets spaced apart from each other.

[0013] According to one embodiment of the present invention, the distance between the plurality of air outlets is equal.

[0014] According to one embodiment of the present invention, an annular duct is wound around and attached to the inner walls of the first and second chambers of the material tank.

[0015] It should be understood that in actual production, material tanks are generally large in size (usually, with a radius greater than 10m). If a fourth pipeline is directly opened in the first chamber and a connection port for the second pipeline is opened in the second chamber, that is, if the recovered cold energy is directly transported to the material in the first and second chambers through this connection port, the cold energy cannot diffuse evenly and in a timely manner in the first and second chambers due to the large size of the material tank. This will result in inconsistent cooling of the material.

[0016] Therefore, annular air ducts are installed in the first and second chambers. The annular air ducts are wrapped around and attached to the inner walls of the first and second chambers of the material tank. Multiple air outlets are also provided on the annular air ducts, which are spaced apart from each other at equal distances. The cold energy transported to the first and second chambers from the second and fourth pipelines can flow in the annular air ducts and be blown out from the multiple air outlets. Preferably, the distance between the multiple air outlets is equal, so that the cold energy can be diffused more evenly in the first and second chambers and can make more full contact with the material, ensuring the consistency of material cooling in the chambers.

[0017] According to one embodiment of the present invention, an air filter is provided on the air inlet. The gas drawn into the powder tank through the first pipeline and the first fan must not contain moisture (water vapor), otherwise, when it comes into contact with the adhesive powder containing a large amount of cold energy, water droplets will condense on the inner wall of the powder tank, thereby affecting the quality of the adhesive powder. Therefore, the air filter provided on the air inlet can at least filter out the moisture in the drawn-in gas. In this case, the air filter is also called a dehumidifier.

[0018] According to one embodiment of the present invention, the liquid nitrogen ball mill is arranged in an underground containment space, which is formed by a top plate, a bottom plate and a plurality of walls extending from the top plate to the bottom plate, provided on the surface of the ground. The top plate is provided with a heat insulation layer; wherein the top plate is also provided with an opening for the passage of a third pipeline and a fifth pipeline, and the liquid nitrogen ball mill is placed on the bottom plate by at least one fixed support.

[0019] According to one embodiment of the present invention, the liquid nitrogen ball mill is further provided with an isolation box, which includes a metal outer layer, a heat insulation inner layer, and a sound-absorbing layer between the metal outer layer and the heat insulation inner layer.

[0020] The liquid nitrogen ball mill, the source of vibration and noise, is placed in an underground enclosure. A roof plate separates the enclosure from the surface space, ensuring that vibration and noise primarily propagate underground. By utilizing the soil's ability to absorb vibration and noise, the amount of vibration and noise transmitted to the outside is significantly reduced. In addition, an isolation chamber is installed on the liquid nitrogen ball mill. This chamber includes a heat-insulating inner layer and a sound-absorbing layer, further absorbing and isolating vibration and noise from propagating outward, while also reducing cold energy loss and lowering production costs.

[0021] According to one embodiment of the present invention, the system further includes: a liquid nitrogen storage tank, a nitrogen pipeline connected to the liquid nitrogen storage tank, and a liquid nitrogen pump driven by a variable frequency motor installed on the nitrogen pipeline; a sixth pipeline, one end of which is connected to the nitrogen pipeline and the other end of which is connected to the feed hopper, and a first automatic temperature control valve installed on the sixth pipeline, the first automatic temperature control valve being preset to correspond to a first temperature corresponding to the initial cooling and embrittlement stage of waste tire and waste plastic solid waste; a seventh pipeline, one end of which is connected to the nitrogen pipeline and the other end of which is connected to the liquid nitrogen ball mill, and a second automatic temperature control valve installed on the seventh pipeline, the second automatic temperature control valve being preset to correspond to a second temperature corresponding to the ball milling and pulverizing stage of waste tire and waste plastic solid waste; and a controller, the controller being signal-connected to the variable frequency motor of the liquid nitrogen pump.

[0022] The controller is connected to the variable frequency motor driving the liquid nitrogen pump, enabling control of the motor and thus the total flow rate of liquid nitrogen pumped from the liquid nitrogen storage tank. Furthermore, since the first automatic temperature control valve is preset with a first temperature corresponding to the pulverizing stage, and the second automatic temperature control valve is preset with a second temperature corresponding to the initial cooling and embrittlement stage (it should be understood that the first and second temperatures are not necessarily exact values, but may be within a certain range), when the temperature around the automatic temperature control valve is lower than the preset temperature, the valve opening decreases, thereby reducing the flow of liquid nitrogen through the valve (i.e., the sixth and / or seventh pipeline); conversely, when the temperature around the automatic temperature control valve is higher than the preset temperature, the valve opening increases, thereby increasing the flow of liquid nitrogen through the valve. In short, the automatic temperature control valve can automatically adjust the valve opening size according to the ambient temperature, i.e., adjust the flow rate of liquid nitrogen through the valve, to achieve automatic temperature control of the sixth and seventh pipelines equipped with the automatic temperature control valve, thereby precisely maintaining the temperature of the feed hopper connected to the sixth pipeline and the liquid nitrogen ball mill connected to the seventh pipeline within a predetermined temperature (range).

[0023] According to one embodiment of the present invention, the material tank, powder tank, liquid nitrogen ball mill, first pipeline, second pipeline, third pipeline, fourth pipeline and fifth pipeline are all covered with an insulation layer made of nano-silica aerogel.

[0024] In summary, for the system of this invention, after liquid nitrogen is atomized into gaseous nitrogen in the liquid nitrogen ball mill, it is first used to cool the material in the liquid nitrogen ball mill. Then, under the pumping of the second fan, it reaches the first chamber of the material tank through the third and fourth pipelines, using the cold energy carried by the nitrogen (i.e., the remaining cold energy) to cool the material in the first chamber. In addition, external gas can be pumped into the powder tank through the air inlet under the action of the first fan and exchange heat with the rubber powder in the powder tank, transferring the cold energy carried by the rubber powder to the material in the second chamber through the second pipeline. In particular, the connection between the first pipeline and the powder tank is located near the material inlet, which further improves the cold energy recovery rate of the rubber powder. Attached Figure Description

[0025] Figure 1 A schematic diagram of a system for cryogenic pulverization of waste tires and waste plastic solid waste using liquid nitrogen is shown according to an embodiment of the present invention.

[0026] Figure 2 This is a cross-sectional schematic diagram of a tank according to an embodiment of the present invention, with particular emphasis on the annular duct arranged in the second chamber;

[0027] Figure 3 This is a cross-sectional schematic diagram of a tank according to an embodiment of the present invention, with particular emphasis on the annular air duct arranged in the first chamber;

[0028] Figure 4 A liquid nitrogen ball mill is schematically shown in an underground containment space according to an embodiment of the present invention. Detailed Implementation

[0029] In the following, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the following description is merely illustrative of the invention and does not constitute any limitation on the invention. Various embodiments may be combined with each other to form other embodiments not explicitly shown in the following description or the accompanying drawings.

[0030] In this context and below, "materials" refers to solid waste such as waste tires and waste plastics.

[0031] In this context and below, "cryogenic powdering" refers to the process of turning solid waste such as waste tires and waste plastics into micro-powdered rubber powder under operating conditions of -70℃ to -110℃. At this temperature, the molecular chains of rubber and plastics become brittle due to their inability to move, making them easy to crush.

[0032] Referring to the accompanying drawings, according to an embodiment of the present invention, a system 100 for cryogenic pulverization of waste tires and waste plastic solid waste using liquid nitrogen is provided, comprising: a material tank 12, wherein a first chamber 121, a second chamber 122, and a third chamber 123 are arranged sequentially from bottom to top within the material tank 12, the first chamber 121 communicating with the second chamber 122, the second chamber 122 communicating with the third chamber 123, a discharge port 124 being provided on the first chamber 121, and a feed port 125 and an air inlet 126 being provided on the third chamber 123; a powder tank 14, wherein a material inlet 141 is provided at the top of the powder tank 14; a first pipeline 20 and a second pipeline 22, wherein the two ends of the first pipeline 20 and the second pipeline 22 are provided with... The first pipeline 20 is connected to the powder tank 14 and the second chamber 122 respectively, and a first blower 200 is installed on the first pipeline 20; the liquid nitrogen ball mill 16 is provided with a feed end 161 and a discharge end 162. The feed end 161 is connected to the discharge port 124 on the first chamber 121 through the third pipeline 24, and a feed bin 241 is provided on the third pipeline 24; a fourth pipeline 26 extends from the third pipeline 24 and is connected to the first chamber 121, and a second blower 260 is installed on the fourth pipeline 26; the discharge end 162 is connected to the material inlet 141 of the powder tank 14 through the fifth pipeline 28; the connection between the first pipeline 20 and the powder tank 14 is located near the material inlet 141.

[0033] In production, the feed inlet 125 of the material tank 12 is connected to the shredder 1251 through the feed pipe 1250. Preferably, the shredder 1251 is a two-stage shredder. After the material enters the shredder 1251, it will be crushed into small pieces and then enter the feed pipe 1250. Driven by the elevator 1252 installed on the feed pipe 1250, the material enters the material tank 12 through the feed inlet 125.

[0034] It should be understood that, since the crushed material is lightweight (mainly composed of rubber and plastic) and the initially crushed particles are relatively large, three chambers are set in the material tank 12 to separate the crushed material entering the material tank 12, so as to avoid the crushed material at the bottom of the material tank 12 being compacted, which would reduce the fluidity of the material at the bottom and affect the uniformity of unloading.

[0035] Preferably, in one embodiment of the present invention, a variable frequency quantitative unloading machine is provided on the discharge port 124. The variable frequency quantitative unloading machine can accurately unload materials at a predetermined weight, thereby improving accuracy. In another embodiment of the present invention, a pressure reducing tank is also provided between the discharge port 124 and the variable frequency quantitative unloading machine to reduce the pressure in the material tank 12, making the material discharge more uniform and smooth, and preventing material from clogging the discharge port 124. Preferably, a screw feeder 242 is provided on the third pipeline 24.

[0036] It is understandable that the nitrogen gas in the liquid nitrogen ball mill 16 (formed by atomizing the liquid nitrogen injected into the liquid nitrogen ball mill 16) still carries a large amount of cold energy after cooling the material in the liquid nitrogen ball mill 16. Therefore, it is drawn to the first chamber 121 of the material tank 12 by the second fan 260 through the third pipe 24 and the fourth pipe 26, so that the cold energy it carries can continue to be used for cooling the material in the first chamber 121 of the material tank 12. In addition, during the production process, the material is transported from the material tank 12 to the liquid nitrogen ball mill 16 through the third pipe 24, while the flow direction of the nitrogen gas in the third pipe 24 is opposite to that of the material, that is, from the liquid nitrogen ball mill 16 to the material tank 12 (first chamber 121) through the third pipe 24. Since the material transportation and the flow of nitrogen gas are carried out simultaneously during the production process, not only can this part of the nitrogen gas be used for cooling the material in the first chamber 121, but it can also further absorb cold energy during the material transportation process, thereby improving the utilization rate of cold energy.

[0037] On the other hand, the rubber powder generated after the material is processed in the liquid nitrogen ball mill 16 also carries a portion of cold energy, which is transported to the powder tank 14 along with the rubber powder. Because an air inlet is provided on the third chamber 123 of the material tank 12, and the second chamber 122, which is connected to the third chamber 123, is connected to the powder tank 14 through the first pipe 20 and the second pipe 22, and a first fan is provided on the first pipe 20, the first fan can sequentially draw outside gas into the third chamber 123 and the second chamber 122 of the material tank 12 through the air inlet, and then draw it into the powder tank 14 through the first pipe 20. The gas drawn into the powder tank 14 will exchange heat with the rubber powder, so that the cold energy carried by the rubber powder is transferred to this part of the gas. Subsequently, this part of the gas carrying the cold energy of the rubber powder returns to the second chamber 122 through the second pipe 22. That is, the first fan can draw this part of the gas and the cold energy it carries (that is, the cold energy obtained from the rubber powder) into the second chamber 12 of the material tank 12 through the first pipe 20 and the second pipe 22, and continue to be used for the cooling treatment of the material in the second chamber 122, further improving the utilization rate of cold energy.

[0038] Specifically, the connection between the first pipeline 20 and the powder tank 14 is located near the material inlet 141. During production, the adhesive powder enters the powder tank 14 from the material inlet 141 and falls under the influence of gravity. Simultaneously, the first blower draws outside gas into the powder tank 14 through the first pipeline 20 (as described above). Because the connection between the first pipeline 20 and the powder tank 14 is located near the material inlet 141, the adhesive powder entering the powder tank 14 will come into contact with the gas blown out of the first pipeline 20 and exchange heat with it. In other words, the adhesive powder will come into contact with the gas drawn into the powder tank 14 from the first pipeline 20 and exchange heat throughout its entire descent within the powder tank 14. The adhesive powder will not be unable to fully transfer cold energy to the gas due to insufficient contact or difficulty in contacting the gas after settling at the bottom of the powder tank 14. This arrangement further improves the cold energy recovery rate of the adhesive powder.

[0039] Preferably, the connection between the second pipe 22 and the powder tank 14 is set lower than the connection between the first pipe 20 and the powder tank 14. This is because the gas enters the powder tank 14 through the first pipe 20 and its temperature decreases after heat exchange with the adhesive powder (cold energy is transferred from the adhesive powder to the gas). Since the low-temperature gas has a higher specific gravity, it tends to flow downwards. Therefore, setting the connection between the second pipe 22 and the powder tank 14 at a lower position is beneficial for the low-temperature gas to return to the second chamber 122 through the second pipe 22.

[0040] In summary, after liquid nitrogen is atomized into gaseous nitrogen in the liquid nitrogen ball mill 16, it will first be used to cool the material in the liquid nitrogen ball mill 16. Then, under the pumping of the second fan 260, it will reach the first chamber 121 of the material tank 12 through the third pipeline 24 and the fourth pipeline 26, using the cold energy carried by the nitrogen (i.e., the remaining cold energy) to cool the material in the first chamber 121. In addition, external gas can be pumped into the powder tank 14 through the air inlet 126 under the action of the first fan 200 and exchange heat with the rubber powder in the powder tank 14. The cold energy carried by the rubber powder will be transferred to the material in the second chamber 122 through the second pipeline 22. In particular, the connection between the first pipeline 20 and the powder tank 14 is located near the material inlet 141, which further improves the cold energy recovery rate of the rubber powder.

[0041] According to one embodiment of the present invention, the connection between the first pipeline 20 and the powder tank 14 is provided on the side of the powder tank 14 near the top of the powder tank 14.

[0042] For reference Figure 2 and Figure 3According to one embodiment of the present invention, annular air ducts are provided in both the first chamber 121 and the second chamber 122 of the material tank 12. The second pipe 22 is connected to the annular air duct 220 in the second chamber 122, and the fourth pipe 26 is connected to the annular air duct 210 in the first chamber 121. The annular air ducts 210 and 220 are provided with a plurality of air outlets 230 spaced apart from each other.

[0043] According to one embodiment of the present invention, the distances between the plurality of air outlets 230 are equal.

[0044] According to one embodiment of the present invention, annular ducts 210 and 220 are wound around and attached to the inner walls of the first chamber 121 and the second chamber 122 of the material tank 12.

[0045] It should be understood that in actual production, the material tank 12 is generally large in size (usually, the radius is greater than 10m). If a connection port for the fourth pipeline 26 is directly opened in the first chamber 121 and a connection port for the second pipeline 22 is opened in the second chamber 122, that is, if the recovered cold energy is directly transported to the material in the first chamber 121 and the second chamber 122 through the connection port, the cold energy cannot diffuse evenly and in a timely manner in the first chamber 121 and the second chamber 122 due to the large size of the material tank 12. This will result in inconsistent cooling of the material.

[0046] Therefore, annular air ducts 210 and 220 are provided in the first chamber 121 and the second chamber 122. The annular air ducts 210 and 220 are arranged around and attached to the inner walls of the first chamber 121 and the second chamber 122 of the material tank 12. The annular air ducts 210 and 220 are also provided with multiple air outlets 230 spaced apart from each other at the same distance. The cold energy transported from the second pipe 22 and the fourth pipe 26 to the first chamber 121 and the second chamber 122 can flow in the annular air ducts 210 and 220 and be blown out from the multiple air outlets 230. Preferably, the distance between the multiple air outlets 230 is equal, so that the cold energy can be diffused more evenly in the first chamber 121 and the second chamber 122, and can come into more full contact with the material, ensuring the consistency of material cooling in the chamber.

[0047] More preferably, in another embodiment of the invention, multiple turns of annular ducts 210 and 220 are attached to and wound around the inner walls of the first chamber 121 and the second chamber 122. That is, the annular ducts 210 and 220 are wound in a "spiral" shape around the inner walls of the first chamber 121 and the second chamber 122. This is because although the material tank 12 is arranged in layers (with three chambers), each chamber (especially the first chamber 121 and the second chamber 122) still has a large height (as mentioned above, the diameter of the material tank 12 is generally around 10m, while the height is usually greater than 10m). If only a single turn of annular duct 210 and 220 is wound in the chamber, it cannot be ensured that the material at each height in the chamber is cooled to a uniform degree. Therefore, it is easy to understand that setting the "number of turns" of the annular duct according to the specific height of the chamber can further ensure the uniformity of material cooling in the chamber.

[0048] According to one embodiment of the present invention, an air filter 1260 is provided on the air inlet 126. The gas drawn into the powder tank 14 via the first pipe 20 and the first fan 200 must not contain moisture (water vapor), otherwise, when it comes into contact with the adhesive powder containing a large amount of cold energy, water droplets will condense on the inner wall of the powder tank 14, thereby affecting the quality of the adhesive powder. Therefore, the air filter 1260 provided on the air inlet 126 can at least filter out the moisture in the drawn-in gas. In this case, the air filter 1260 is also called a dehumidifier.

[0049] refer to Figure 4 According to one embodiment of the present invention, the liquid nitrogen ball mill 16 is arranged in an underground containment space 402, which is formed by a top plate 404, a bottom plate 406 and a plurality of walls 408 extending from the top plate 404 to the bottom plate 406, provided on the ground surface. The top plate 404 is provided with a heat insulation layer. The top plate 404 is also provided with an opening for the passage of the third pipe 24 and the fifth pipe 28. The liquid nitrogen ball mill 16 is placed on the bottom plate 406 by at least one fixed bracket 410.

[0050] According to one embodiment of the present invention, the liquid nitrogen ball mill 16 is further provided with an isolation box 412, the isolation box 412 including a metal outer layer, a heat insulation inner layer, and a sound-absorbing layer between the metal outer layer and the heat insulation inner layer.

[0051] The liquid nitrogen ball mill 16, the source of vibration and noise, is located in an underground containment space 402. A roof plate 404 is installed between the containment space 402 and the above-ground space (i.e., the ground surface) to separate the two, so that vibration and noise can only be transmitted underground. By utilizing the soil's ability to absorb vibration and noise, the vibration and noise transmitted to the outside world are greatly reduced. In addition, an isolation box 412 is installed on the liquid nitrogen ball mill 16. The isolation box 412 includes a heat-insulating inner layer and a sound-absorbing layer, which further absorbs and isolates the vibration and noise from being transmitted to the outside, while also reducing cold energy loss and lowering production costs.

[0052] According to one embodiment of the present invention, the sound-absorbing layer is made of foam material, preferably polyurethane foam; the heat-insulating layer is made of nano-silica aerogel.

[0053] Preferably, a star-shaped unloader is provided on the discharge end 162 to transport the rubber powder generated in the liquid nitrogen ball mill 16 to the fifth pipeline 28, and then, driven by the elevator 282 provided on the fifth pipeline 28, it enters the powder tank 14 through the material inlet 141. Preferably, a magnetic separator 280 is provided on the fifth pipeline 28 to remove metal impurities such as those generated by steel wire.

[0054] Continue to refer to Figure 1 According to one embodiment of the present invention, the system 10 further includes: a liquid nitrogen storage tank 50, a nitrogen pipeline 501 connected to the liquid nitrogen storage tank 50, and a liquid nitrogen pump 503 driven by a variable frequency motor 502 installed on the nitrogen pipeline 501; a sixth pipeline 30, one end of which is connected to the nitrogen pipeline 501 and the other end of which is connected to the feed hopper 241, and a first automatic temperature control valve 310 installed on the sixth pipeline 30, the first automatic temperature control valve 310 being preset to correspond to a first temperature corresponding to the initial cooling and embrittlement stage of waste tire and waste plastic solid waste; a seventh pipeline 32, one end of which is connected to the nitrogen pipeline 501 and the other end of which is connected to the liquid nitrogen ball mill 16, and a second automatic temperature control valve 320 installed on the seventh pipeline 32, the second automatic temperature control valve 320 being preset to correspond to a second temperature corresponding to the ball milling and pulverizing stage of waste tire and waste plastic solid waste; and a controller 505, the controller 505 being signal-connected to the variable frequency motor 502 of the liquid nitrogen pump 503.

[0055] The controller 505 is signal-connected to the variable frequency motor 502 driving the liquid nitrogen pump 503, enabling control of the variable frequency motor 502 and thus controlling the total flow rate of liquid nitrogen pumped from the liquid nitrogen storage tank 505. Furthermore, since the first automatic temperature control valve 310 is preset with a first temperature corresponding to the pulverization stage, and the second automatic temperature control valve 320 is preset with a second temperature corresponding to the initial cooling embrittlement (it should be understood that the first and second temperatures are not necessarily exact values, but may be within a certain range), when the temperature around the automatic temperature control valve is lower than the preset temperature, the automatic temperature control valve reduces its opening, thereby reducing the flow rate of liquid nitrogen through the valve (i.e., the sixth pipe 30 and / or the seventh pipe 32); conversely, when the temperature around the automatic temperature control valve is higher than the preset temperature, the automatic temperature control valve increases its opening, thereby increasing the flow rate of liquid nitrogen through the valve. In short, the automatic temperature control valve can automatically adjust the valve opening size according to the ambient temperature, that is, adjust the liquid nitrogen flow through the automatic temperature control valve, so as to realize the automatic temperature control of the sixth pipeline 30 and the seventh pipeline 32 equipped with the automatic temperature control valve, thereby accurately maintaining the temperature of the feed hopper 241 connected by the sixth pipeline 30 and the liquid nitrogen ball mill 16 connected by the seventh pipeline 32 at a predetermined temperature (within a predetermined range).

[0056] It is understandable that in the cryogenic crushing process of waste tires and waste plastic solid waste, the material (waste tires and waste plastic solid waste) is usually cooled to -70℃ to -80℃ first. This step is carried out in the feed hopper 241 and is called the initial cooling and embrittlement stage of the material. Then the material is sent to the liquid nitrogen ball mill 16 and further cooled to -100℃ to -110℃ for crushing, which is the ball mill crushing stage of the material. The temperatures of these two stages need to be strictly controlled within the required range. Excessive cooling or heating will affect the quality of the produced micro powder. Therefore, the liquid nitrogen pump 503 driven by the variable frequency motor 502 and the controller 505 connected to it first control the liquid nitrogen flow rate of the nitrogen pipeline 501. Then, the liquid nitrogen flow rate through the sixth pipeline 30 and the seventh pipeline 32 is controlled by the first automatic temperature control valve 310 and the second automatic temperature control valve 320, so as to accurately control the temperature of the initial cooling and embrittlement stage in the feed hopper 241 at -70℃ to -80℃, and accurately control the temperature of the ball milling stage in the liquid nitrogen ball mill 16 at -100℃ to -110℃.

[0057] It should also be understood that the first temperature (or first temperature range) is not necessarily strictly within the range of -70℃ to -80℃, and the second temperature (or second temperature range) is not necessarily strictly within the range of -100℃ to -110℃. This is because the first automatic temperature control valve 310 and the second automatic temperature control valve 320 are not directly installed in the feed hopper 241 and the liquid nitrogen ball mill 16, but are installed on the sixth and seventh pipelines 30 and 32 that are connected to the feed hopper 241 and the liquid nitrogen ball mill 16. In other words, the first and second automatic temperature control valves 310 and 320 actually control the temperature of the sixth and seventh pipelines 30 and 32 at the valve body (by controlling the liquid nitrogen flow rate). It is understandable that, since there is a certain distance between the first automatic temperature control valve 310 and the feed hopper 241, and between the second automatic temperature control valve 310 and the liquid nitrogen ball mill 16 (as can be seen from the figure), the liquid nitrogen flowing through the first and second automatic temperature control valves 310 and 320 will lose some cold energy during the process of passing through this distance. Therefore, preferably, the first temperature is preset to be slightly lower than the lowest value of the temperature range corresponding to the initial cooling and embrittlement of the material in the feed hopper 241 (i.e., -70°C). Similarly, the second temperature is preset to be slightly lower than the lowest value of the temperature range corresponding to the ball milling and pulverizing of the material in the liquid nitrogen ball mill 16 (i.e., -110°C).

[0058] According to one embodiment of the present invention, the material tank 12, powder tank 14, liquid nitrogen ball mill 16, first pipeline 20, second pipeline 22, third pipeline 24, fourth pipeline 26, and fifth pipeline 28 are all covered with an insulation layer made of nano-silica aerogel. The insulation layer can significantly reduce the heat exchange between the flowing nitrogen and materials in these components and the outside environment, thereby saving cooling energy. Preferably, the sixth pipeline 30, seventh pipeline 32, liquid nitrogen storage tank 50, and nitrogen pipeline 501 are also covered with an insulation layer made of nano-silica aerogel.

[0059] In summary, for the system of this invention, after liquid nitrogen is atomized into gaseous nitrogen in the liquid nitrogen ball mill, it is first used to cool the material in the liquid nitrogen ball mill. Then, under the pumping of the second fan, it reaches the first chamber of the material tank through the third and fourth pipelines, using the cold energy carried by the nitrogen (i.e., the remaining cold energy) to cool the material in the first chamber. In addition, external gas can be pumped into the powder tank through the air inlet under the action of the first fan and exchange heat with the rubber powder in the powder tank, transferring the cold energy carried by the rubber powder to the material in the second chamber through the second pipeline. In particular, the connection between the first pipeline and the powder tank is located near the material inlet, which further improves the cold energy recovery rate of the rubber powder.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for cryogenic pulverization of solid waste such as waste tires and waste plastics using liquid nitrogen, characterized in that, include: The material tank has a first chamber, a second chamber, and a third chamber arranged sequentially from bottom to top. The first chamber is connected to the second chamber, and the second chamber is connected to the third chamber. The first chamber is provided with a discharge port, and the third chamber is provided with a feed port and an air inlet. A powder tank, wherein a material inlet is provided on the top of the powder tank; A first pipeline and a second pipeline are connected at both ends to the powder tank and the second chamber, respectively, and a first fan is installed on the first pipeline. A liquid nitrogen ball mill, wherein the liquid nitrogen ball mill is provided with a feed end and a discharge end, the feed end is connected to the discharge port on the first chamber through a third pipeline, and a feed bin is provided on the third pipeline; The third pipeline extends into a fourth pipeline that communicates with the first chamber. A second fan is installed on the fourth pipeline. The discharge end is connected to the material inlet of the powder tank through a fifth pipeline. The connection between the first pipeline and the powder tank is located near the material inlet.

2. The system according to claim 1, characterized in that, The connection point between the first pipeline and the powder tank is located on the side of the powder tank near the top of the powder tank.

3. The system according to claim 1, characterized in that, Both the first chamber and the second chamber of the material tank are provided with annular air ducts. The second pipe is connected to the annular air duct in the second chamber, and the fourth pipe is connected to the annular air duct in the first chamber. The annular air duct is provided with a plurality of air outlets spaced apart from each other.

4. The system according to claim 3, characterized in that, The distances between the multiple air outlets are equal.

5. The system according to claim 4, characterized in that, The annular duct is wound around and attached to the inner walls of the first and second chambers of the material tank.

6. The system according to claim 5, characterized in that, An air filter is installed on the air inlet.

7. The system according to claim 1, characterized in that, The liquid nitrogen ball mill is arranged in an underground containment space, which is formed by a top plate and a bottom plate set on the ground surface and multiple walls extending from the top plate to the bottom plate. The top plate is provided with a heat insulation layer. The top plate is also provided with an opening for the passage of the third and fifth pipelines, and the liquid nitrogen ball mill is placed on the bottom plate by at least one fixed bracket.

8. The system according to claim 7, characterized in that, The liquid nitrogen ball mill is also fitted with an isolation box, which includes a metal outer layer, a heat-insulating inner layer, and a sound-absorbing layer between the metal outer layer and the heat-insulating inner layer.

9. The system according to claim 1, characterized in that, The system also includes: A liquid nitrogen storage tank, on which a nitrogen pipeline is connected, and a liquid nitrogen pump driven by a variable frequency motor is installed on the nitrogen pipeline; The sixth pipeline, one end of which is connected to the nitrogen pipeline and the other end of which is connected to the feed hopper, is equipped with a first automatic temperature control valve, which is preset to correspond to the first temperature of the initial cooling and embrittlement stage of waste tire and waste plastic solid waste. A seventh pipeline, one end of which is connected to the nitrogen pipeline and the other end to the liquid nitrogen ball mill, is equipped with a second automatic temperature control valve. This second automatic temperature control valve is preset to a second temperature corresponding to the ball milling stage of the waste tire and waste plastic solid waste. The controller is connected to the variable frequency motor signal of the liquid nitrogen pump.

10. The system according to claim 1, characterized in that, The material tank, the powder tank, the liquid nitrogen ball mill, the first pipeline, the second pipeline, the third pipeline, the fourth pipeline, and the fifth pipeline are all covered with an insulation layer made of nano-silica aerogel.

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