Circulation Mill Main Machine

Abstract

The circulation mill main machine consists of a centrifugal fan and a first circulation tube (21). The centrifugal fan includes a casing and an impeller. The casing consists of a front cover, a scroll casing, and a rear cover. The scroll casing consists of an outer straight section (22), a curved section (24), and an inner straight section (23). The outlet of the centrifugal fan is located at the front cover, the outer straight section (22) of the scroll casing, the rear cover, and the inner straight section (23) of the scroll casing. The outer region, further enclosed and aligned with the axial projection line of the impeller on the front and rear covers of the impeller's outer edge inside the casing, is called the diffuser chamber. Here, a raw material outlet (20) is installed on the scroll casing, and the impeller inlet has a first circulation pipe joint (25) in the axial projection region of the front or rear cover. The raw material outlet (20), the inlet of the first circulation pipe (21), the outlet of the first circulation pipe (21), and the first circulation pipe joint (25) are connected in order to form a first circulation passage. The installation of the circulation passage reduces the rotational resistance of the impeller and thus reduces energy consumption by eliminating the source of high pressure in the circulation mill, and the installation of the curved section of the scroll casing improves the wall-sticking phenomenon.

Description

TECHNICAL FIELD

[0001] The present invention relates to a circulation mill main machine, and belongs to the fields of circulating fluidized bed technology, drying and pulverization technology, as well as energy conservation and environmental protection technology. BACKGROUND ART

[0002] In the present invention, the centrifugal fan is an important assembly. In order to clarify the related terms of the centrifugal fan in the present solution, the structure of the centrifugal fan is briefly introduced below. Referring to Fig. 1, a conventional centrifugal fan is generally composed of two components: a casing and an impeller. The impeller is generally composed of a front disk on the side close to the air intake, blades, a rear disk on the side close to the input shaft and a boss. The air intake of the impeller is a circular hole in the middle of the front disk. The rear disk is fixedly connected to the boss, and the boss is mounted on the input shaft. The casing is composed of a front cover provided with the inlet of the centrifugal fan, a volute casing and a rear cover on the side close to the input shaft. The volute casing is generally composed of an outer straight section, a curved section and an inner straight section. The intersection of the curved section and the inner straight section is called a volute tongue. The outlet of the centrifugal fan is enclosed by the front cover, the outer straight section of the volute casing, the rear cover and the inner straight section of the volute casing. The outer region along the axial projection line of the impeller on the front cover and the rear cover at the outer edge of the impeller inside the casing is called a diffuser chamber. The minimum distance between the outer straight section and the inner side of the inner straight section is called the outlet width of the centrifugal fan, and the inner distance between the front cover and the rear cover is called the outlet height of the centrifugal fan.

[0003] This proposal further relates to classification technology, and after classifying the material, two materials with different particle sizes are obtained. To facilitate description, this proposal refers to the two materials with different particle sizes obtained after classification as coarse material and fine aggregate, respectively. When classifying with a sieve, the material on top of the sieve is the coarse material, and the material below the sieve is the fine aggregate. The coarse material is discharged from the ash outlet of the cyclone classifier, and the fine aggregate is brought in by the exhaust airflow.

[0004] A circulation mill, also known as a fluidized bed or circulating mill, consists of a main machine and auxiliary equipment. The main machine is the primary location for achieving drying and grinding, while the auxiliary equipment performs functions such as separating material from gas. The circulation mill utilizes a centrifugal fan and the high-speed airflow it produces to form the material into a fluid state, achieving drying and grinding through a high-speed circulating flow process in the circulation passage. In the main machine, large particle materials are mainly ground by impact with the impeller, while ultrafine powders are mainly ground by friction between the blades and the scroll casing surface during the high-speed flow process of the material. Through the grinding action, the material is continuously dispersed and circulates at high speed in a fluid state, increasing the mass-energy exchange area geometrically, thinning the solid-gas boundary layer, maximizing the exchange rate of water (mass) and heat (energy) between the material and the airflow, and resulting in a very rapid drying rate for the material. The circulation mill focuses on the drying and milling of fresh agricultural products, exploring factors that affect drying and grinding efficiency. Because wall-clogging issues exist, these influencing factors are more easily exposed and can be addressed with clearer targeting, thereby enabling the creation of efficient drying and grinding solutions.

[0005] The three core technical problems in the drying and grinding of fresh agricultural products are reliability, economy, and classification. Fresh agricultural products are crushed by impact with an impeller and become a slurry, which adheres to the inside of the machine and does not circulate. This is called wall clogging. If wall clogging steadily grows, the circulation passage will eventually be blocked, the machine will not be able to operate, and the purpose of drying and grinding will not be achieved. Wall clogging basically corresponds to the reliability problem. Prior to this invention, the circulation mill solved the wall clogging problem by combining two technical means. First, wall clogging cannot be steadily generated by the impact of high-speed flowing material on the wall clogging material. Second, the moisture content of the material is reduced by mixing the dried powder returned from the auxiliary device, i.e., the return material, with the material inside the machine and the newly added material, thereby improving wall clogging performance. The former is the foundation, and the latter is the reinforcement means. With the help of the latter, even if liquid is added, increasing the amount of return material will surely solve the wall clogging problem. Economy is mainly the energy consumption problem, and classification is the separation and discharge of compliant material from the circulation passage.

[0006] The invention theme disclosed in CN107694135B and WO2020057617 is a circulation mill, in which the circulation mill main machine of CN107694135B achieves classification through the cooperation of centrifugal force and a classification airflow with tensile force applied to the particles. When the tensile force is greater than the centrifugal force, the particles are carried out by the classification airflow through the space between the classification blades, and when the tensile force is less than the centrifugal force, the particles enter the circulation pipe and arrive at the inlet of the mill for circulating drying and grinding. Given the determined rotational speed and impeller diameter, the centrifugal force is determined by the diameter and moisture content of the particles, the tensile force is determined by the velocity of the classified airflow, and the velocity of the classified airflow is determined by the differential pressure at the inlet and outlet of the circulation mill main machine. The magnitude and direction of this differential pressure are determined by the difference between the diameter of the outlet at the inner cover and the diameter of the inlet at the front cover. The larger this difference, the greater the differential pressure. When the difference is positive, the airflow flows from the inlet to the outlet of the main machine, and when the difference is negative, the airflow flows from the outlet to the inlet of the main machine. Regarding the problems present in CN107694135B, firstly, the classification airflow weakens the impact on the inner surface of the scroll casing corresponding to the classification blades of the flowing material, effectively turning this area into a blind spot, where wall buildup is more likely to occur stably. This drawback is caused by the solution to the classification problem. Secondly, the circulation pipe of a single circulation mill main machine is a bent pipe, which makes wall buildup more likely to occur within the bent pipe. Using four circulation mill main machines connected in series allows the circulation pipe to be made straight.

[0007] Invention patent WO2020057617 improves upon it and discloses six types of circulation mill main machines. A common feature of the six types of circulation mill main machines is that classification is achieved through the cooperation of the differential pressure at the inlet and outlet of the centrifugal fan and the cyclone classification effect in the supply pipe. In the first, second, third, and sixth types of circulation mill main machines, two main machines are connected in series to make the circulation pipe a straight pipe, improving wall contact in the circulation pipe and further eliminating the nearly blind spot area of ​​CN107694135B. However, the solution to the classification problem in WO2020057617 increases the pressure in the equipment, This hinders the rotation of the impeller and increases the energy consumption of the mill. This is because when the intake velocity of the feed pipe with the circulation mill outlet generally exceeds 50 meters / second, the resistance of cyclone classification becomes very large, and the sub-mill pressurizes again on the high-pressure foundation of the main mill outlet. A similar problem exists in CN107694135B, as the obstruction of the classification airflow by centrifugal force also increases the pressure in the mill. Furthermore, the kinetic energy recovery technology proposed by WO2020057617 is practically meaningless because the kinetic energy recovery device itself consumes energy, resulting in an extremely small amount of remaining recovered energy. Furthermore, while the solutions to the wall-clogging problem in WO2020057617 and CN107694135B are theoretically perfect, two practical problems still exist: firstly, if there is insufficient powder material to be used as return material at the beginning of the process, material with a moisture content exceeding 60% will always fail to work properly due to the wall-clogging problem; and secondly, a large amount of return material worsens the economics of the mill.

[0008] Airflow milling is an ultrafine grinding technology that uses compressed air to impact materials, causing them to collide and pulverize. Its most notable advantage is that the process of compressed air being ejected from the nozzle undergoes near-adiabatic expansion, consuming a large amount of heat, while keeping the operating temperature low. The disadvantages of airflow milling include difficulty in processing fibrous materials such as reishi mushrooms and plastics, limited capacity for single-machine production, and relatively high energy consumption. Both its advantages and disadvantages present a stark contrast to those of a circulation mill. [Overview of the project] [Problems that the invention aims to solve]

[0009] The object of the present invention is to invent a circulation mill main machine with lower energy consumption in response to the problems described in the background art, to improve the kinetic energy recovery device, to optimize the solution to the wall-clogging problem, and to combine airflow grinding and circulation milling into an airflow circulation mill, thereby compensating for the shortcomings of both. [Means for solving the problem]

[0010] The technical measures employed to achieve the objectives of the present invention are as follows: The first circulation mill main machine comprises a centrifugal fan and a first circulation pipe, the centrifugal fan having at least one outlet, a raw material outlet located on the scroll casing of the centrifugal fan, and the impeller inlet, with a first circulation pipe joint provided in the axial projection area of ​​the front cover and / or rear cover, and the raw material outlet, the inlet of the first circulation pipe, the outlet of the first circulation pipe, and the first circulation pipe joint are connected in order to constitute a first circulation passage.

[0011] The principle of the above proposed technology is that, as the fluid material in the diffuser chamber rotates at high speed, materials with sufficiently large particle sizes and / or sufficiently high water content gather on the inner wall of the scroll casing due to centrifugal force. This process is a classification process, and the first circulation passage sends the classified raw material back to the mill to complete the circulation operation.

[0012] To achieve a better classification effect, an additional classification region is installed within the diffuser chamber. This classification region is the outer region of the second curved section formed by the extension of the curved section of the centrifugal fan's scroll casing from the vortex tongue. The effect is further improved when the coarse material outlet is located at the intersection of the curved section and the outer straight section of the scroll casing.

[0013] When the first circulation pipe joint is located on the rear cover, if there is a circular hole in the middle of the rear disc of the impeller, the flowing material from the first circulation pipe joint can enter the inside of the impeller. Furthermore, if the inlet ends of the blades extend towards the center of the impeller to a boss and are fixed to the boss, the various assemblies of the impeller can be made into a single unit. The blade portion formed by the blade inlet ends extending towards the center of the impeller to a boss and being fixed to the boss is referred to in this section as the kinetic energy recovery blade. This is sometimes more convenient when the raw material outlet is located on the edge of the front or rear cover.

[0014] The second circulation mill main machine consists of a centrifugal fan and a second circulation pipe. The impeller inlet has a second circulation pipe joint in the axial projection area of ​​the front cover and / or rear cover. The centrifugal fan outlet, the second circulation pipe inlet, the second circulation pipe outlet, and the second circulation pipe joint are connected in sequence to form a second circulation passage. The material discharge port of the second circulation mill main machine is located outside the axial projection area of ​​the front cover where the impeller inlet is located, and / or the material discharge port of the second circulation mill main machine is located outside the axial projection area of ​​the rear cover where the impeller inlet is located, and the material discharge ports are distributed around the circumferential direction of the impeller inlet.

[0015] The second circulation mill main machine further includes an air collection cover, which concentrates the material discharge ports on the front or rear cover, and has at least one outlet on the air collection cover, the air collection cover on the front cover is composed of an inner plate, an outer plate and a lid, the inner plate is cylindrical, the shape of the outer plate is similar to the scroll casing of a centrifugal fan, the shape of the lid is similar to the front cover of a centrifugal fan, there is a hole in the middle of the lid, the hole in the middle of the lid is fitted onto one end of the inner plate, one end of the outer plate is connected to the outer edge of the lid, the other ends of the inner plate and outer plate are connected to the outer surface of the front cover and cover the exhaust port, the outlet of the air collection cover on the front cover is formed by the extended portion of the front cover of the centrifugal fan, the outer straight portion of the outer plate, the outlet portion of the lid and the inner straight portion of the outer plate The enclosed rear cover is composed of an inner plate, an outer plate, and a lid. The inner plate is cylindrical, the outer plate has the same shape as the scroll casing of a centrifugal fan, and the lid has the same shape as the front cover of a centrifugal fan. There is a hole in the middle of the lid, which is fitted onto one end of the inner plate. One end of the outer plate is connected to the outer edge of the lid. The other ends of the inner and outer plates are connected to the outer surface of the rear cover and cover the exhaust port. The outlet of the rear cover is enclosed by the extended portion of the rear cover of the centrifugal fan, the outer straight portion of the outer plate, the outlet portion of the lid, and the inner straight portion of the outer plate. The outlet of the front cover and the adjacent rear cover outlet are connected to a single circulation mill main machine outlet via an exhaust three-way joint.

[0016] A further classification region is provided within the air collection cover. The classification region in the front air collection cover is the outer region of a second curved section formed by the extension of the outer plate of the front air collection cover forward from the vortex tongue, and the classification region in the rear air collection cover is the outer region of a second curved section formed by the extension of the outer plate of the rear air collection cover forward from the vortex tongue.

[0017] The second circulation mill main machine further includes a third circulation pipe, the coarse material outlet is located on the outer plate of the air collection cover on the front or rear cover, the inlet of the impeller has a third circulation pipe joint in the axial projection area of ​​the front or rear cover, and the coarse material outlet, the inlet of the third circulation pipe, the outlet of the third circulation pipe, and the third circulation pipe joint are connected in order to form a third circulation passage.

[0018] Both of the above circulation mill main machines are based on different classification technology proposals and aim to eliminate the cause of high pressure in the circulation mill main machine described in the background technology, thereby reducing the pressure in the circulation mill main machine, decreasing the resistance to impeller rotation, and reducing energy consumption.

[0019] To enlarge the intake space and facilitate the connection of the circulation pipes, the front cover further includes an intake spinal tube, the larger end of which is connected to the inlet of a centrifugal fan, and the smaller end of which is the intake port of the circulation mill main machine, and the first, second, or third circulation pipe joint in the front cover is provided on the intake spinal tube.

[0020] In order to achieve kinetic energy recovery of the fluid material in the circulation passage and to reduce the energy consumption of the kinetic energy recovery device described in WO2020057617 to the maximum extent, the circulation pipe joint may be installed so as to assist in pushing the impeller so that the fluid material from the circulation pipe effectively impacts the inlet end of the blade and causes it to rotate, or the circulation pipe joint may be installed so as to assist in pushing the impeller so that the fluid material from the circulation pipe effectively impacts the aforementioned kinetic energy recovery blade and causes it to rotate.

[0021] Compared to the first, second, third, and sixth circulation mill main machines described in WO2020057617, the two circulation mill main machines described above have non-straight circulation pipes, which makes wall entanglement problems in the circulation pipes more serious. To more effectively solve the wall entanglement problem, additional air vents are installed on the circulation mill main machines. These air vents are connected to a high-pressure air source and are positioned so that the high-speed airflow ejected from the air vents can blow away wall entanglement material.

[0022] The air vents in the impeller are thus realized. The air vents are located at the exit ends of two symmetrical blades, and a kinetic energy recovery blade is located between the inlet ends of the two symmetrical blades and the boss. Gas is introduced into an air chamber enclosed by the shaft end cap, the boss and the input shaft end face via a rotary joint attached to the center of the shaft end cap, and then through airways in the boss, airways in the kinetic energy recovery blade and airways in the blades to the air vents at the exit ends of the two symmetrical blades.

[0023] Air vents installed on the circulation pipe solve the problem of wall entanglement in the circulation pipe becoming more severe due to the bending of the circulation pipe; air vents installed on the air collection cover can solve the wall entanglement problem in the air collection cover; and air vents installed on the front cover or rear cover can use the airflow ejected from the air vents to blow away wall entanglement material on the inner wall of the scroll casing or on the front and rear covers.

[0024] The present invention further provides an airflow circulation mill main machine, and the technical measures thereof are as follows. An air hole connected to high-pressure gas is provided on the centrifugal fan constituting the circulation mill main machine, the air hole is arranged such that the high-speed airflow ejected from the air hole can push or assist in pushing the impeller to rotate, the air hole may be provided on the front cover or / and the rear cover or / and the intake spinal canal, the air hole is arranged such that the high-speed airflow ejected from the air hole impacts the inlet end of the blade or the kinetic energy recovery blade to push or assist in pushing the impeller to rotate, and the air hole may also be arranged such that the high-speed airflow ejected from the air hole impacts the outlet end of the blade to push or assist in pushing the impeller to rotate. Effects of the Invention

[0025] The circulation mill main machine disclosed in the present invention, by constructing solutions for different classification problems in the circulation mill main machine, eliminates the cause of high pressure in the circulation mill main machine described in the background art, reduces the internal pressure of the circulation mill main machine, further reduces the rotational resistance of the impeller, and achieves the objective of reducing the energy consumption of the mill; by arranging the circulation pipe joint such that the fluidized material from the circulation pipe impacts the inlet end of the blade or the kinetic energy recovery blade to assist pushing the impeller to rotate, the present invention reduces the energy consumption of the kinetic energy recovery device to the maximum extent and increases the remaining amount of recovered energy; using high-pressure gas to blow off material adhered to the wall solves the wall-adhesion problem with high reliability; and the airflow circulation mill that uses high-pressure gas to push or assist pushing the impeller of the mill to rotate makes up for the defects of circulation mills and airflow pulverization. Brief Description of the Drawings

[0026] [Figure 1] It is a structural diagram of a conventional centrifugal fan. [Figure 2]This is the first circulation mill main machine in Example 1. [Figure 3] This is the first circulation mill main machine with the front cover of the centrifugal fan hidden in Example 1. [Figure 4] This is the first circulation mill main machine with an intake spinal canal in Example 2. [Figure 5] This is the first circulation mill main machine having two outlets in Example 3. [Figure 6] This is the second circulation mill main machine at the outlet in Example 4. [Figure 7] This is the second circulation mill main machine with an intake spinal canal in Example 5. [Figure 8] This is the second circulation mill main machine having an air collecting cover in Example 6. [Figure 9] This is the second circulation mill main machine where both the front cover and the rear cover are provided with an air collecting cover in Example 7. [Figure 10] This is an air hole in the impeller in Example 8. MODE FOR CARRYING OUT THE INVENTION

[0027] Regarding the first circulation mill main machine in Example 1, referring to Figures 2 and 3, Figure 2 shows the rear of the circulation mill main machine, and Figure 3 shows the front of the circulation mill main machine with the front cover of the centrifugal fan hidden. The circulation mill main machine consists of a centrifugal fan and a circulation pipe 21. The centrifugal fan includes two components: a casing and an impeller. The impeller consists of a front disc on the side approaching the intake port, blades, a rear disc on the side approaching the input shaft, and a boss. The intake port of the impeller is a circular hole in the middle of the front disc. The rear disc is fixed to the boss, which is mounted on the input shaft. The casing consists of a front cover on which the inlet of the centrifugal fan is provided, a scroll casing, and a rear cover on the side approaching the input shaft. The scroll casing consists of an outer straight section 22, a curved section 24, and an inner straight section 23. The intersection of the curved section 24 and the inner straight section 23 is called a vortex tongue 27, and the centrifugal fan A single outlet is provided in the fan, and the outlet of the centrifugal fan is surrounded by the front cover, the outer straight section 22 of the scroll casing, the rear cover, and the inner straight section 23 of the scroll casing. The outer region along the axial projection line of the impeller on the front and rear covers of the outer edge of the impeller inside the casing is called the diffuser chamber. The minimum distance between the inner surfaces of the outer straight section 22 and the inner straight section 23 is called the centrifugal fan outlet width, and the distance between the inner surfaces of the front cover and the rear cover is called the centrifugal fan outlet height. A raw material outlet 20 is provided on the scroll casing, and the inlet of the impeller has a circulation pipe joint 25 in the axial projection region of the rear cover. The raw material outlet 20, the inlet of the circulation pipe 21, the outlet of the circulation pipe 21, and the circulation pipe joint 25 are connected in order to form a single first circulation passage.

[0028] The raw material outlet may be provided on the edge of the front or rear cover as needed. In this embodiment, the circulation pipe joint 25 is provided on the rear cover, and a circular hole the same as the impeller inlet on the front cover is provided on the rear disc of the impeller so that material from the circulation pipe can enter the impeller. The blades extend towards the center of the impeller to a boss and are fixed to the boss to form a kinetic energy recovery blade.

[0029] A further classification region is provided within the diffuser chamber of the centrifugal fan. This classification region is the outer region of the second curved section 28 of the scroll casing, which is formed when the curved section 24 of the centrifugal fan's scroll casing extends forward from the vortex tongue 27. The rough material outlet 20 is located at the intersection of the curved section 24 and the outer straight section 22 of the scroll casing.

[0030] In this embodiment, the classification region reinforces the classification effect in the diffuser chamber of the centrifugal fan on the one hand, and on the other hand, because the pressure at the outlet of the centrifugal fan in the diffuser chamber is minimal, there is no centrifugal fan in the second curved section, and most of the airflow exits directly from the impeller outlet in front of the vortex tongue and arrives at the centrifugal fan outlet, becoming a short-circuit airflow. Although the short-circuit airflow does not adversely affect the centrifugal fan for ventilation, as a centrifugal fan that is a main component of the circulation mill main machine, the presence of short-circuit airflow reduces the number of non-short-circuit airflows and reduces the velocity of the non-short-circuit airflows. In non-short-circuit airflows, material is more likely to sink and stick to the wall, and the second curved section of the scroll casing significantly reduces the proportion of short-circuit airflows and improves the wall-sticking problem.

[0031] In Example 2, a first circulation mill main machine with an intake spinal tube, referring to Figure 4, the front cover of the casing in this embodiment further includes an intake spinal tube 30, the large end of which is connected to the inlet of the centrifugal fan, and the small end of which is the intake port of the circulation mill main machine, and a circulation pipe joint 29 is provided on the intake spinal tube 30, and the raw material outlet, the circulation pipe inlet, the circulation pipe outlet, and the circulation pipe joint 29 are connected in order to form a circulation passage.

[0032] Example 3, a first circulation mill main machine having two outlets, refers to Figure 5. The circulation mill main machine of this embodiment adopts a horizontal arrangement. Figure 5 shows the circulation mill main machine with the front cover of the centrifugal fan hidden. The centrifugal fan has two outlets and two circulation tubes. The scroll casing of the centrifugal fan is composed of two parts. The first part has an outer straight section 32, a curved section 37, an inner straight section 38, and a second curved section 43. The second part has an outer straight section 39, a curved section 44, an inner straight section 31, and a second curved section 35. One outlet of the centrifugal fan is the front cover, the outer straight section 32 of the first part of the scroll casing, the rear cover, and the scroll of the second part. Another outlet of the centrifugal fan is surrounded by the inner straight section 31 of the scroll casing, the outer straight section 39 of the second part of the scroll casing, the rear cover and the inner straight section 38 of the first part of the scroll casing, the front cover further includes an intake spinal tube 36, and two circulation pipe joints are provided on the intake spinal tube 36. One circulation passage is constructed by sequentially connecting the raw material outlet 33 in the first part of the scroll casing, the inlet of the circulation pipe 34, the outlet of the circulation pipe 34, and one circulation pipe joint in the intake spinal tube 36, and the other circulation passage is constructed by sequentially connecting the raw material outlet 41 in the second part of the scroll casing, the inlet of the circulation pipe 40, the outlet of the circulation pipe 40, and another circulation pipe joint in the intake spinal tube 36.

[0033] Regarding Example 4, the second circulation mill main machine, referring to Figure 6, the upper left and upper right diagrams of Figure 6 show the front and rear of the second circulation mill main machine. This circulation mill main machine consists of a centrifugal fan and a circulation pipe 50. The centrifugal fan includes two components: an impeller 57 and a casing. The impeller consists of a front disc on the side approaching the centrifugal fan inlet 58, blades, a rear disc on the side approaching the input shaft, and a boss. The intake port of the impeller is a circular hole in the middle of the front disc. The rear disc is fixed to the boss, which is mounted on the input shaft. The casing consists of a front cover 54 on which the centrifugal fan inlet 58 is provided, a rear cover 52 on the side approaching the input shaft, and a scroll casing 53. The outlet 51 of the centrifugal fan is surrounded by the front cover 54, the outer straight section of the scroll casing 53, the rear cover 52, and the inner straight section of the scroll casing 53. The outer region along the input axial projection line on the front and rear covers of the impeller outer edge inside the chamber is called the diffuser chamber, and the inlet of the impeller has a second circulation pipe joint 59 in the axial projection region of the front cover, and the outlet of the centrifugal fan 51, the inlet of the circulation pipe 50, the outlet of the circulation pipe 50, and the second circulation pipe joint 59 are connected in order to form a second circulation passage, the inlet of the impeller on the front cover 54 has a material discharge port 56 of the second circulation mill main machine outside the axial projection region of the front cover, and the inlet of the impeller on the rear cover 52 also has a material discharge port 55 of the second circulation mill main machine outside the axial projection region of the rear cover, and the material discharge ports 56 and 55 are distributed around the circumferential direction of the impeller inlet, and the circulation pipe joint 59 that constitutes the circulation passage is installed so that it can assist in pushing the impeller so that the flowing material from the circulation pipe effectively strikes the inlet end of the blades and rotates.

[0034] The centrifugal fan of the circulation mill main machine shown in the lower left of Figure 6 has two outlets and two circulation pipe joints on the front cover, and there are two second circulation pipes, and a kinetic energy recovery blade 60 is installed between the inlet end of the blade and the boss, and the circulation pipe joints 61 and 62 that constitute the circulation passage are installed so that the flowing material from the circulation pipe can help push the impeller so that it effectively impacts the kinetic energy recovery blade 60 and rotates, and the centrifugal fan of the circulation mill main machine shown in the lower right of Figure 6 has four outlets and four circulation pipe joints on the front cover, and there are four circulation pipes.

[0035] The circulation mill main machine described in this embodiment makes a new and constructive contribution to solving three core technological problems in the drying and milling of fresh agricultural products. By providing material discharge ports on the front and rear covers, the pressure inside the centrifugal fan is reduced, thereby reducing the rotational resistance of the impeller and achieving the objective of reducing energy consumption. At the same time, the decrease in the flow velocity of the fluid material in the diffuser chamber is reduced, and the impact force of the fluid material on the wall-hugging material in the scroll casing is increased, which is advantageous in solving the wall-hugging problem in the scroll casing. Furthermore, the material discharge port is installed on the front cover and / or rear cover, and a different classification problem solution is constructed compared to CN107694135B and WO2020057617. The pressure in the diffuser chamber is greater than the pressure outside the material discharge port, and the pressure difference between the two drives the airflow to flow out from the material discharge port. Materials with large particle sizes and high moisture content are concentrated on the inner wall of the scroll casing by the action of centrifugal force, flow along the direction of impeller rotation, and re-enter the centrifugal fan through the circulation passage to achieve circulation. Fine particles with a relatively small particle size and relatively low moisture content are less affected by centrifugal force and flow out from the material discharge port with the airflow to achieve classification.

[0036] Regarding Example 5, a second circulation mill main machine with an intake spinal tube, referring to Figure 7, it is constructed by adding an intake spinal tube 65 on the base of the circulation mill main machine having four second circulation tubes as described in Example 4. The large end of the intake spinal tube 65 is connected to the inlet 68 of the centrifugal fan, and the small end 66 of the intake spinal tube is the intake port of the circulation mill main machine. There are four circulation tube joints on the intake spinal tube 65, one of which circulation tube joints 67 is connected to the outlet of one of the second circulation tubes. The circulation passage is constructed by connecting the outlet of the centrifugal fan, the inlet of the second circulation tube, the outlet of the second circulation tube, and the circulation tube joints in that order.

[0037] Regarding Example 6, a second circulation mill main machine with a wind-collecting cover, referring to Figure 8, this embodiment has two second circulation pipes 76 and 83, the joint between the two second circulation pipes is located in the axial projection area of ​​the rear cover of the impeller inlet, and a wind-collecting cover is provided on the front cover, the wind-collecting cover on the front cover is composed of an inner plate 71, an outer plate 75 and a cover 72, the inner plate 71 is cylindrical and the shape of the outer plate 75 is the scroll of a centrifugal fan Similar to a casing, the shape of the lid 72 is the same as the front cover of a centrifugal fan, with a hole 73 in the middle of the lid 72, the hole 73 in the middle of the lid is fitted onto one end of the inner plate 71, one end of the outer plate 75 is connected to the outer edge 74 of the lid 72, the other ends of the inner plate 71 and the outer plate 75 are connected to the outer surface 77 of the front cover and cover the exhaust port, and the outlet of the air collection cover on the front cover is surrounded by the extended portion 79 of the front cover of the centrifugal fan, the outer straight portion 80 of the outer plate, and the inner straight portion 78 of the lid 72 and the outer plate. A classification region is further provided within the air collection cover on the front cover, and the classification region is the outer region of the second curved portion 70 formed by the curved portion of the outer plate of the air collection cover on the front cover extending forward from the vortex tongue. In this embodiment, a third circulation passage and an intake spinal tube are further provided. The raw material outlet 81 is located at the intersection of the curved portion and the straight portion of the outer plate, and a third circulation pipe joint is provided on the intake spinal tube. The raw material outlet, the inlet of the third circulation pipe 82, the outlet of the third circulation pipe 82, and the third circulation pipe joint are connected in order to form a third circulation passage.

[0038] In Example 1, the first circulation passage and material discharge port achieve classification by utilizing the centrifugal classification effect of the diffuser chamber itself, while the third circulation passage in this example achieves secondary classification by utilizing the centrifugal classification effect of the air collection cover itself. The classification differential pressure of the former is the differential pressure between the inside of the diffuser chamber and the outside of the material discharge port, and the classification differential pressure of the latter is the differential pressure between the outside of the material discharge port and the centrifugal fan intake port.

[0039] In Example 7, a second circulation mill main machine having air collection covers on both the front and rear covers, referring to Figure 9, it is constructed by adding air collection covers to the front and rear covers of the casing of the second circulation mill main machine with an intake spine tube as described in Example 5. The air collection cover on the front cover has four outlets 86, 88, 91 and 92, and a material discharge port is also provided on the rear cover. The air collection cover on the rear cover also has four outlets 85, 87, 89 and one outlet behind outlet 91 which is blocked. The air collection cover outlet 88 on the front cover and the adjacent air collection cover outlet 89 on the rear cover are concentrated at one second circulation mill main machine outlet via an exhaust three-way joint 90.

[0040] The circulation mill main machines described in the seven embodiments above suffer from severe wall entanglement within the circulation pipes when processing fresh produce with a moisture content exceeding 60% due to the bending of the circulation pipes. Therefore, they can generally only be used for processing materials with a moisture content of less than 60%.

[0041] Example 8, the third solution to the wall-hanging problem, is a high-pressure gas blowing system added to the base of the circulation mill main machine described in the seven examples above. The high-pressure gas blowing system is an air vent installed on the circulation mill main machine, and the high-pressure gas ejected from the air vent is used to blow off the wall-hanging material.

[0042] The newly formed wall-clogging material still maintains a soft adhesion state within 5 minutes, and the high-speed airflow ejected from the air vents easily blows it off and rejoins the circulation process. The original two wall-clogging problem solutions, with the help of the third wall-clogging problem solution described in this embodiment, thoroughly solve the wall-clogging problem present in the drying and milling of high-humidity, high-viscosity materials, offering cost advantages while also ensuring the reliability of a single main machine circulation mill that does not require a 180-degree bend in the circulation pipe, thereby making it feasible to use the circulation mill main machine described in this embodiment for the drying and milling of most fresh agricultural products.

[0043] Referring to Figure 10, the air vents installed on the impeller can be realized in this way, with air vents 95 and 104 installed at the outlet ends of two symmetrical blades 106 and 103, respectively. The inlet ends of these two symmetrical blades extend to a boss in the center of the impeller and are fixed to the boss to form kinetic energy recovery blades 105 and 102. The high-pressure gas is introduced into an air chamber 101 surrounded by the shaft end cap 100, the boss and the end face of the input shaft, via a rotary joint 99 attached to the center of the shaft end cap 100, and then connects to air vents 95 and 104 at the outlet ends of the two symmetrical blades 106 and blade 103 via an airway 98 in the boss, an airway 97 in the kinetic energy recovery blades and an airway 96 in the blades, respectively.

[0044] Based on different circulation mill main machine structures, the air vents may be installed on the first circulation passage described in Example 1, on the second circulation passage described in Example 4, on the air collection cover described in Examples 6 and 7, on the third circulation passage described in Example 6, or on the front cover and / or rear cover described in Examples 1 to 7.

[0045] Example 9, the airflow circulation mill main machine is configured by installing air vents on the centrifugal fan casing of the circulation mill main machine described in Example 1 or Example 4, wherein the air vents are positioned so as to be able to push or assist in pushing the impeller so that the high-speed airflow ejected from the air vents rotates. The air vents are positioned on the front cover or rear cover or on the intake spine tube described in Example 2 or Example 5, wherein the air vents are positioned so as to be able to push or assist in pushing the impeller so that the high-speed airflow ejected from the air vents impacts the inlet end of the blade and causes it to rotate, or the air vents are positioned so as to be able to push or assist in pushing the impeller so that the high-speed airflow ejected from the air vents impacts the kinetic energy recovery blade and causes it to rotate, or the air vents are positioned on the front cover or rear cover, wherein the air vents are positioned so as to be able to push or assist in pushing the impeller so that the high-speed airflow ejected from the air vents impacts the outlet end of the blade and causes it to rotate.

[0046] The airflow circulation mill main machine described in this embodiment retains the collision and friction grinding mechanism of a circulation mill, while also increasing the grinding mechanism unique to airflow grinding where material particles collide with each other. Furthermore, the process in which compressed air is ejected from the nozzle undergoes near-adiabatic expansion, consuming a large amount of heat and reducing the working temperature. This retains the advantages of both circulation mills and airflow grinding, overcomes the disadvantages of both, and offers broader applicability.

Claims

1. The first circulation mill main machine consists of a centrifugal fan and a first circulation pipe (21), the centrifugal fan includes two components, a casing and an impeller, the impeller consists of a front disc on the side approaching the intake port, blades, a rear disc on the side approaching the input shaft and a boss, the inlet of the impeller is a circular hole in the middle of the front disc, the rear disc is fixed to the boss, the boss is mounted on the input shaft, the casing consists of a front cover on which the inlet of the centrifugal fan is provided, a scroll casing and a rear cover on the side approaching the input shaft, the scroll casing consists of an outer straight section (22), a curved section (24) and an inner straight section (23), the curved section (24) and the inner straight section The intersection with (23) is called a vortex tongue (27), the outlet of the centrifugal fan is surrounded by the front cover, the outer straight section (22) of the scroll casing, the rear cover and the inner straight section (23), the outer region along the axial projection line of the impeller on the front and rear covers of the outer edge of the impeller inside the casing is called a diffuser chamber, a raw material outlet (20) is installed on the scroll casing, the inlet of the impeller has a first circulation pipe joint (25) in the axial projection region of the front or rear cover, and the raw material outlet (20), the inlet of the first circulation pipe (21), the outlet of the first circulation pipe (21), and the first circulation pipe joint (25) are connected in order to form a first circulation passage, characterized in that a first circulation mill main machine.

2. The first circulation mill main machine according to claim 1, characterized in that the raw material outlet is installed on the edge of the front cover or the rear cover.

3. The first circulation mill main machine according to claim 1, characterized in that a circular hole is provided in the middle of the rear disc of the impeller.

4. The first circulation mill main machine according to claim 1, wherein the front cover further includes an intake spinal tube (30), the first circulation tube joint (29) in the front cover is provided on the intake spinal tube, the large end of the intake spinal tube is connected to the inlet of a centrifugal fan, and the small end of the intake spinal tube is the intake port of the first circulation mill main machine.

5. The first circulation mill main machine according to claim 1, characterized in that a classification region is further provided in the diffuser chamber, the classification region is the outer region of a second curved portion (28) formed by the extension of the curved portion (24) of the scroll casing of the centrifugal fan forward from the vortex tongue (27), or the first circulation mill main machine according to claim 1, characterized in that a classification region is further provided in the diffuser chamber, the classification region is the outer region of a second curved portion (28) formed by the extension of the curved portion (24) of the scroll casing of the centrifugal fan forward from the vortex tongue (27), and the coarse material outlet is installed at the intersection of the curved portion (24) and the outer straight portion (22) of the scroll casing.

6. The second circulation mill main machine consists of a centrifugal fan and a second circulation pipe (50). The centrifugal fan includes two components: a casing and an impeller. The impeller consists of a front disc on the side approaching the intake port, blades, a rear disc on the side approaching the input shaft, and a boss. The inlet of the impeller is a circular hole in the middle of the front disc. The rear disc is fixed to the boss, which is mounted on the input shaft. The casing consists of a front cover where the centrifugal fan inlet is provided, a scroll casing, and a rear cover on the side approaching the input shaft. The scroll casing consists of an outer straight section, a curved section, and an inner straight section. The intersection of the curved section and the inner straight section is called a vortex tongue. The outlet (51) of the centrifugal fan is located between the front cover, the outer straight section of the scroll casing, the rear cover, and the inner part of the scroll casing. A second circulation mill main machine characterized in that the outer region enclosed by the side straight sections and along the axial projection line of the impeller on the front and rear covers of the impeller outer edge inside the casing is called a diffuser chamber, the inlet of the impeller has a second circulation pipe joint (59) in the axial projection region of the front or rear cover, the outlet of the centrifugal fan (51), the inlet of the second circulation pipe (50), the outlet of the second circulation pipe (50), and the second circulation pipe joint (59) are connected in order to form a second circulation passage, the material discharge port (56) of the second circulation mill main machine is located outside the axial projection region of the front cover of the impeller inlet on the front cover, and / or the material discharge port (55) of the second circulation mill main machine is located outside the axial projection region of the rear cover of the impeller inlet on the rear cover.

7. The second circulation mill main machine according to claim 6, wherein the front cover further includes an intake spinal tube (65), a second circulation tube joint (67) in the front cover is provided on the intake spinal tube (65), the larger end of the intake spinal tube (65) is connected to an inlet (68) of a centrifugal fan, and the smaller end (66) of the intake spinal tube is an intake port of the second circulation mill main machine.

8. The second circulation mill main machine according to claim 6, characterized in that the material discharge ports are distributed around the circumferential direction of the impeller inlet.

9. The second circulation mill main machine according to claim 6, wherein the casing further includes a wind-collecting cover on the front lid, the wind-collecting cover on the front lid concentrates the material outlets on the front lid and has at least one outlet on the wind-collecting cover on the front lid, and / or the casing further includes a wind-collecting cover on the rear lid, the wind-collecting cover on the rear lid concentrates the material outlets on the rear lid and has at least one outlet on the wind-collecting cover on the rear lid.

10. The second circulation mill main machine according to claim 6, characterized in that the air collection cover outlet on the front cover and the air collection cover outlet on the adjacent rear cover are concentrated via an exhaust three-way joint to a single second circulation mill main machine outlet.

11. The air collection cover on the front cover is composed of an inner plate (71), an outer plate (75), and a lid (72). The inner plate (71) is cylindrical, the outer plate (75) has the same shape as the scroll casing of a centrifugal fan, and the lid (72) has the same shape as the front cover of a centrifugal fan. There is a hole (73) in the middle of the lid (72), which is fitted onto one end of the inner plate (71). One end of the outer plate (75) is connected to the outer edge (74) of the lid (72). The other ends of the inner plate (71) and the outer plate (75) are connected to the outer surface (77) of the front cover and cover the exhaust port. The outlet of the air collection cover on the front cover is the extended portion (79) of the front cover of the centrifugal fan, the outer straight portion (80) of the outer plate, and the lid (72). The air collection cover on the rear cover is surrounded by the inner straight portion (78) of the outer plate, and the air collection cover on the rear cover is composed of an inner plate, an outer plate and a lid, the inner plate is cylindrical, the shape of the outer plate is the same as the scroll casing of a centrifugal fan, the shape of the lid is the same as the front cover of a centrifugal fan, there is a hole in the middle of the lid, the hole in the middle of the lid is fitted onto one end of the inner plate, one end of the outer plate is connected to the outer edge of the lid, the other ends of the inner plate and outer plate are connected to the outer surface of the rear cover and cover the exhaust port, and the outlet of the air collection cover on the rear cover is surrounded by the extended portion of the rear cover of the centrifugal fan, the outer straight portion of the outer plate and the inner straight portion of the lid and outer plate, as described in claim 9.

12. The second circulation mill main machine according to claim 9, further comprising a third circulation pipe (82), wherein a raw material outlet (81) is installed on the outer plate of the air collection cover on the front or rear cover, the inlet of the impeller has a third circulation pipe joint in the axial projection area of ​​the front cover, and the raw material outlet (81), the inlet of the third circulation pipe (82), the outlet of the third circulation pipe (82), and the third circulation pipe joint are connected in order to constitute a third circulation passage.

13. The second circulation mill main machine according to claim 9, characterized in that a classification region is further provided within the air collection cover of the front cover, and the classification region is the outer region of a second curved portion (70) formed by the curved portion of the outer plate of the air collection cover of the front cover extending forward from the vortex tongue, or a classification region is further provided within the air collection cover of the rear cover, and the classification region is the outer region of a second curved portion formed by the curved portion of the outer plate of the air collection cover of the rear cover extending forward from the vortex tongue.

14. A kinetic energy recovery device for a circulation mill main machine, characterized in that the first circulation pipe joint according to claim 1 is installed so as to be able to assist in pushing the impeller so that the flowing material from the first circulation pipe effectively impacts the inlet end of the blade and causes it to rotate, or the second circulation pipe joint according to claim 6 is installed so as to be able to assist in pushing the impeller so that the flowing material from the second circulation pipe effectively impacts the inlet end of the blade and causes it to rotate.

15. The kinetic energy recovery device for a circulation mill main machine according to claim 14, characterized in that the inlet end of the blade extends to a boss towards the center of the impeller and is fixed to the boss to constitute a kinetic energy recovery blade, the first circulation pipe joint is installed so as to assist in pushing the impeller so that the flowing material from the first circulation pipe effectively impacts the kinetic energy recovery blade and causes it to rotate, or the second circulation pipe joint is installed so as to assist in pushing the impeller so that the flowing material from the second circulation pipe effectively impacts the kinetic energy recovery blade and causes it to rotate.

16. The third solution to the wall-clogging problem in the circulation mill main machine is a circulation mill main machine consisting of a centrifugal fan and a circulation tube. The centrifugal fan includes two components: a casing and an impeller. The impeller consists of a front disc on the side approaching the intake port, blades, a rear disc on the side approaching the input shaft, and a boss. The intake port of the impeller is a circular hole in the middle of the front disc. The rear disc is fixed to the boss, which is mounted on the input shaft. The casing consists of a front cover where the centrifugal fan inlet is provided, a scroll casing, and a rear cover on the side approaching the input shaft. A third solution to the wall-clogging problem of a circulation mill main machine, characterized in that the casing is composed of an outer straight section, a curved section and an inner straight section, the intersection of the curved section and the inner straight section is called a vortex tongue, the outlet of the centrifugal fan is surrounded by a front cover, an outer straight section of the scroll casing, a rear cover and an inner straight section of the scroll casing, the outer region along the axial projection line of the impeller on the front and rear covers of the outer edge of the impeller inside the casing is called a diffuser chamber, and air vents are installed on the circulation mill main machine, the air vents are installed so that a high-speed airflow ejected from the air vents can blow off wall-clogging material.

17. The air holes are located at the exit ends of two symmetrical blades of the impeller, the inlet ends of the two symmetrical blades extend to a boss in the center of the impeller and are fixed to the boss to form a kinetic energy recovery blade, and gas is introduced into an air chamber surrounded by the shaft end cap, the boss and the input shaft end face via a rotary joint attached to the center of the shaft end cap, and then connects to the air holes at the exit ends of the two symmetrical blades via an airway in the boss, an airway in the kinetic energy recovery blade and an airway in the blade, characterized in that the air holes are located at the exit ends of two symmetrical blades of the circulation mill main machine according to 16.

18. The solution to the third wall-hanging problem of the circulation mill main machine according to claim 16, characterized in that the air vent is installed on the first circulation passage according to claim 1, or the air vent is installed on the second circulation passage according to claim 6, or the air vent is installed on the air collection cover according to claim 9, or the air vent is installed on the third circulation passage according to claim 12, or the air vent is installed on the front cover and / or rear cover.

19. The airflow circulation mill main machine consists of a centrifugal fan and a circulation tube. The centrifugal fan includes two components: a casing and an impeller. The impeller consists of a front disc on the side approaching the intake port, blades, a rear disc on the side approaching the input shaft, and a boss. The intake port of the impeller is a circular hole in the middle of the front disc. The rear disc is fixed to the boss, which is mounted on the input shaft. The casing consists of a front cover on which the centrifugal fan inlet is provided, a scroll casing, and a rear cover on the side approaching the input shaft. The main airflow circulation mill machine is characterized in that the sing consists of an outer straight section, a curved section and an inner straight section, the intersection of the curved section and the inner straight section is called a vortex tongue, the outlet of the centrifugal fan is surrounded by a front cover, an outer straight section of the scroll casing, a rear cover and an inner straight section of the scroll casing, the outer region along the axial projection line of the impeller on the front and rear covers of the outer edge of the impeller inside the casing is called a diffuser chamber, and air holes are installed on the centrifugal fan, the air holes are installed so that the high-speed airflow ejected from the air holes can push or assist in pushing the impeller to rotate.

20. The air vents are installed on the front cover or rear cover or on the intake spine tube according to claim 4 or claim 7, and the air vents are installed so that a high-speed airflow ejected from the air vents can push or assist in pushing the impeller so that it strikes the inlet end of the blade and rotates, or the air vents are installed so that a high-speed airflow ejected from the air vents can push or assist in pushing the impeller so that it strikes the kinetic energy recovery blade according to claim 15 and rotates, or the air vents are installed on the front cover or rear cover, and the air vents are installed so that a high-speed airflow ejected from the air vents can push or assist in pushing the impeller so that it strikes the outlet end of the blade and rotates, as described in claim 19.

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