A wall mounting solution for a recirculating mill main unit

Abstract

The application discloses a wall-hanging problem solution of a circulating mill main machine, wherein a high-speed airflow is sprayed from a gas hole arranged on the circulating mill main machine to blow off the wall-hanging material and solve the wall-hanging problem, and the reliability is higher; the wall-hanging problem solution overcomes the defects that the material with a water content of more than 60% cannot normally work due to the wall-hanging problem when there is not enough powder material as a return material at the beginning of work, and a large amount of return material deteriorates the economy of the mill.

Description

Technical Field

[0001] This invention relates to a solution to the wall adhesion problem of a circulating mill main unit, belonging to the fields of circulating fluidized bed technology, drying and grinding technology, and energy-saving and environmental protection technology. Background Technology

[0002] The centrifugal fan is an important component in this invention. To clarify the relevant terminology for the centrifugal fan in this case, a brief description of the centrifugal fan structure is provided below. (See attached image) Figure 1 It typically consists of two main parts: the casing and the impeller. The impeller generally consists of a front disc 9 (near the air inlet 7), blades 8, a rear disc 12 (near the input shaft 13), and a bushing 14. The air inlet 6 of the impeller is a circular hole in the middle of the front disc 9. The rear disc 12 is fixedly connected to the bushing 14, which is mounted on the input shaft 13. The casing consists of a front cover 10 with a centrifugal fan inlet 7, a volute 15, and a rear cover 11 (near the input shaft). The volute 15 generally consists of an outer straight section 4, a curved section 5, and an inner straight section. The section 2 is composed of curved section 5 and inner straight section 2, which is called vortex tongue 1. The outlet 3 of the centrifugal fan is surrounded by front cover 10, outer straight section 4 of the vortex shell, rear cover 11 and inner straight section 2 of the vortex shell. The area outside the projection line of the impeller outer edge inside the casing along the impeller axial direction on the front and rear covers is called the diffuser chamber. The minimum distance between the inner sides of the outer straight section 4 and the inner straight section 2 is called the outlet width of the centrifugal fan. The inner distance between the front cover 10 and the rear cover 11 is called the outlet height of the centrifugal fan.

[0003] This case also involves grading technology. After grading, the material is divided into two materials with different fineness. For ease of description, the two materials with different particle sizes obtained after grading are referred to as coarse material and fine material, respectively. When grading with a sieve, the material on the sieve is coarse material and the material under the sieve is fine material. The ash discharge port of the cyclone grading device discharges coarse material, and the exhaust airflow carries away fine material.

[0004] A circulating fluidized bed mill, also known as a circulating mill or circulating fluidized bed mill, consists of a main mill unit and auxiliary devices. The main mill unit is the primary site for drying and grinding, while the auxiliary devices perform functions such as material-gas separation. The circulating mill utilizes a centrifugal fan and its high-speed airflow to fluidize the material, achieving drying and grinding through high-speed circulation within the circulating channel. In the main mill unit, large particles are primarily crushed by impeller impact, while ultrafine powders are crushed mainly through friction between the material and the surfaces of the blades and volutes during high-speed flow. This crushing action continuously disperses the material into a fluidized state, resulting in a high-speed circulating flow. The mass-energy exchange area increases geometrically, the gas-solid boundary layer thins, and the exchange rate of water (mass) and heat (energy) between the material and the airflow is maximized, leading to rapid drying. This study focuses on the drying and grinding of fresh agricultural products, exploring factors affecting drying and grinding efficiency. Due to the presence of wall adhesion issues, these influencing factors are more easily identified and can be addressed specifically, aiming to develop a highly efficient drying and grinding solution.

[0005] The three core technical challenges in drying and grinding fresh agricultural products are reliability, economy, and grading. Fresh agricultural products, after being crushed by the impeller, become a slurry that adheres to the machine and stops circulating, a process known as "wall adhesion." Once this wall adhesion stabilizes, the circulation channel will eventually become blocked, causing equipment failure and preventing the drying and grinding process from being achieved. Wall adhesion is essentially a reliability issue. Before this invention, circulating mills used a combination of two techniques to address the wall adhesion problem: first, the impact of high-speed fluidized material on the wall adhesion material prevents its stable formation; second, the return of dry powder (recycled material) from auxiliary devices is mixed with the existing material and newly added material to reduce the moisture content and improve wall adhesion performance. The former is fundamental, while the latter is a strengthening measure. With the latter's support, even if liquid is added, increasing the amount of recycled material can definitely solve the wall adhesion problem. Economy mainly concerns energy consumption, and grading involves separating and discharging qualified material from the circulation channel.

[0006] The inventions disclosed in CN107694135B and WO2020057617 are related to circulating mills. The circulating mill in CN107694135B achieves classification by the combined action of centrifugal force and the drag force exerted on the particles by the classifying airflow. When the drag force is greater than the centrifugal force, the particles are carried out by the classifying airflow through the space between the classifying blades. When the drag force is less than the centrifugal force, the particles enter the circulating pipe and reach the mill inlet for circulating drying and grinding. Under the condition of a fixed rotational speed and impeller diameter, the centrifugal force depends on the particle diameter and moisture content, while the drag force depends on the velocity of the classifying airflow. The velocity of the classifying airflow, in turn, depends on the pressure difference between the inlet and outlet of the circulating mill main unit. The magnitude and direction of this pressure difference depend on the difference between the outlet diameter on the middle cover and the inlet diameter on the front cover. The larger this difference, the greater the pressure difference. When the difference is positive, the airflow flows from the main unit inlet to the outlet; when the difference is negative, the airflow flows from the main unit outlet to the inlet. The problems with CN107694135B are as follows: First, the staged airflow weakens the impact of fluidized material on the inner surface of the vortex shell corresponding to the staged blades, making this area a near dead zone, where wall deposits can easily and stably form. This defect is due to the solution to the staged problem. Second, the circulation pipe of a single circulating mill main unit is a bent pipe, which is more prone to wall deposit formation. Four circulating mill main units need to be used in series to make the circulation pipe a straight pipe.

[0007] Invention patent WO2020057617 improved upon this, disclosing six types of circulating mill main units. The common feature of these six circulating mill main units is that they rely on the pressure difference between the inlet and outlet of the centrifugal fan and the cyclone classification effect within the feed pipe to achieve classification. In the first, second, third, and sixth types of circulating mill main units, two main units are connected in series to make the circulation pipe a straight pipe, improving the wall adhesion within the circulation pipe and eliminating the near-dead zone area found in CN107694135B. However, the classification problem solution in WO2020057617 increases the internal pressure, hindering impeller rotation and increasing the mill's energy consumption. This is because... (The sentence is incomplete and ends abruptly.) The air velocity in the feed pipe generally exceeds 50 m / s, which greatly increases the resistance of the cyclone classification. The auxiliary mill pressurizes the main mill outlet on top of the high pressure. A similar problem exists in CN107694135B, where centrifugal force hinders the classification airflow and increases the pressure inside the mill. In addition, although the solutions to the wall adhesion problem in WO2020057617 and CN107694135B are theoretically complete, two practical problems still exist. First, when there is not enough powder for return material at the beginning of operation, materials with a moisture content of more than 60% often cannot operate normally due to wall adhesion. Second, a large amount of return material deteriorates the mill's economic efficiency. Summary of the Invention

[0008] The purpose of this invention is to address the wall adhesion problem existing in the current circulating mills described in the background art by proposing a solution to the wall adhesion problem of the circulating mill main unit.

[0009] The technical measures taken to achieve the purpose of this invention are as follows: a solution to the wall-hanging problem of a circulating mill main unit. The circulating mill main unit consists of a centrifugal fan and a circulating pipe. The centrifugal fan has at least one outlet. A coarse material outlet is provided on the volute of the centrifugal fan. The impeller inlet has a circulating pipe interface in the axial projection area on the front cover and / or rear cover. The coarse material outlet, the circulating pipe inlet, the circulating pipe outlet, and the circulating pipe interface are connected in sequence to form a first type of circulating channel. The circulating mill main unit is provided with air holes, which are connected to a high-pressure air source. The air holes are configured such that the high-speed airflow ejected from the air holes can blow off the wall-hanging material.

[0010] The principle of the above-mentioned circulating mill main unit technology is that, due to high-speed rotation, the fluidized material in the diffuser chamber, with sufficiently large particle size and / or sufficiently high moisture content, converges to the inner wall of the volute under the action of centrifugal force. This process is a classification effect. The circulation channel returns the classified coarse material to the mill to achieve circulation operation. The newly formed wall-attached material remains soft and sticky for 5 minutes, and the high-speed airflow from the vents easily blows it off and reintroduces it into the circulation process. This improves the wall-attaching problem when there is not enough powder for return material at the beginning of operation, and also reduces the amount of return material during normal operation, thus improving the mill's economy.

[0011] To achieve better grading results, a grading zone is also set up in the diffuser chamber. The grading zone is the outer area of ​​the second curved segment formed by the curved segment of the centrifugal fan casing extending forward from the vortex tongue. It will be more effective to set the coarse material outlet at the intersection of the curved segment of the vortex casing and the outer straight segment.

[0012] When the circulation pipe interface is located on the rear cover, a circular hole is required in the center of the impeller rear disc to allow fluidized material from the circulation pipe interface to enter the impeller. Furthermore, the blades need to extend towards the impeller center and be fixedly connected to the shaft sleeve so that all impeller components can function as a single unit. The blade portion formed by the blades extending towards the impeller center and being fixedly connected to the shaft sleeve is referred to as the kinetic energy recovery blade in this project. Sometimes, it is more convenient to locate the coarse material outlet on the edge of the front or rear cover.

[0013] The circulating mill host can also be implemented as follows: it consists of a centrifugal fan and a circulating pipe. The impeller inlet is provided with a circulating pipe interface in the axial projection area on the front cover and / or the rear cover. The centrifugal fan outlet, the circulating pipe inlet, the circulating pipe outlet, and the circulating pipe interface are connected in sequence to form a second type of circulation channel. The discharge port of the circulating mill host is located on the front cover, outside the axial projection area of ​​the impeller on the front cover; or / and the discharge port of the circulating mill host is located on the rear cover, outside the axial projection area of ​​the impeller on the rear cover. The discharge ports are distributed circumferentially around the impeller inlet.

[0014] The circulating mill main unit also includes an air collecting hood, which collects the discharge ports on the front or rear cover. The air collecting hood has at least one outlet. The air collecting hood on the front cover consists of an inner side plate, an outer side plate, and a cover. The inner side plate is cylindrical, the outer side plate is shaped like the volute of a centrifugal fan, and the cover is shaped like the front cover of a centrifugal fan. The cover has a hole in the middle, which fits over one end of the inner side plate. One end of the outer side plate connects to the outer edge of the cover, and the other ends of the inner and outer side plates connect to the outside of the front cover and cover the exhaust port. The outlet of the air collecting hood on the front cover is formed by the portion extending from the front cover of the centrifugal fan, the outer straight section of the outer side plate, the outlet portion of the cover, and the inner straight section of the outer side plate. The rear cover's air collecting hood consists of an inner side plate, an outer side plate, and a cover. The inner side plate is cylindrical, the outer side plate resembles the vortex casing of a centrifugal fan, and the cover resembles the front cover of a centrifugal fan. The cover has a hole in the middle, which fits onto one end of the inner side plate. One end of the outer side plate connects to the outer edge of the cover, and the other ends of the inner and outer side plates connect to the outside of the rear cover and cover the exhaust port. The outlet of the air collecting hood on the rear cover is formed by the portion extending from the rear cover of the centrifugal fan, the outer straight section of the outer side plate, the outlet portion of the cover, and the inner straight section of the outer side plate. The outlet of the air collecting hood on the front cover and the outlet of the air collecting hood on the adjacent rear cover are converged into a single circulating mill main unit outlet via an exhaust tee.

[0015] The air collection hood is also equipped with a grading zone. The grading zone inside the air collection hood on the front cover is the outer area of ​​the second curved segment formed by the curved segment of the outer side plate of the air collection hood on the front cover extending forward from the vortex tongue. The grading zone inside the air collection hood on the rear cover is the outer area of ​​the second curved segment formed by the curved segment of the outer side plate of the air collection hood on the rear cover extending forward from the vortex tongue.

[0016] The circulating mill main unit also includes a second type of circulating pipe. A coarse material outlet is provided on the outer side plate of the air collecting hood on the front or rear cover. The inlet of the impeller has a circulating pipe interface in the axial projection area on the front or rear cover. The coarse material outlet, the inlet of the circulating pipe, the outlet of the circulating pipe, and the circulating pipe interface are connected in sequence to form a third type of circulating channel. The third type of circulating channel is provided with air holes.

[0017] To expand the air intake space and facilitate the connection of the circulation pipe, the front cover also includes an air intake conical pipe. The larger end of the air intake conical pipe is connected to the inlet of the centrifugal fan, and the smaller end of the air intake conical pipe is the air inlet of the circulating mill main unit. The first, second, or third circulation pipe interface on the front cover is located on the air intake conical pipe.

[0018] In order to realize the kinetic energy recovery of fluidized material in the circulation channel and minimize the energy consumption of the kinetic energy recovery device described in WO2020057617, the circulation pipe interface is configured such that the fluidized material from the circulation pipe can effectively impact the inlet end of the blade to assist in driving the impeller to rotate; or, the circulation pipe interface can also be configured such that the fluidized material from the circulation pipe can effectively impact the aforementioned kinetic energy recovery blade to assist in driving the impeller to rotate.

[0019] The air holes on the impeller are implemented as follows: the air holes are set at the outlet ends of two symmetrical blades, and kinetic energy recovery blades are set between the inlet ends of the two symmetrical blades and the bushing. The gas is introduced into the air chamber formed by the shaft end cover, the bushing and the input shaft end face through a rotary joint installed in the center of the shaft end cover, and then connected to the air holes at the outlet ends of the two symmetrical blades through the air passages on the bushing, the air passages on the kinetic energy recovery blades and the air passages on the blades.

[0020] The air vents on the circulation pipe solve the problem of more severe wall adhesion inside the circulation pipe caused by the bending of the circulation pipe; the air vents on the air collecting hood can solve the problem of wall adhesion inside the air collecting hood; the air vents on the front or rear cover can use the airflow ejected from the air vents to blow off the wall material attached to the inner wall of the vortex shell or the wall material attached to the front and rear covers.

[0021] This invention discloses a solution to the wall adhesion problem of a circulating mill main unit. It utilizes high-speed airflow ejected from air holes on the circulating mill main unit to blow off the adhered material, thus solving the wall adhesion problem with higher reliability. It overcomes the shortcomings of the two existing wall adhesion problem solutions described in the background art, which often prevent normal operation when there is insufficient powder as return material at the beginning of operation, and when the material with a moisture content of more than 60% is adhered to the wall, as well as the problem that a large amount of return material deteriorates the mill's economic efficiency. Attached Figure Description

[0022] Figure 1 This is a structural diagram of an existing centrifugal fan;

[0023] Figure 2 It is the circulating mill host in Example 1;

[0024] Figure 3 The circulating mill main unit in Example 1 has a hidden centrifugal fan front cover;

[0025] Figure 4 It is the circulating mill main unit with air inlet conical tube in Example 2;

[0026] Figure 5 It is the circulating mill main unit with two outlets in Example 3;

[0027] Figure 6 It is the circulating mill host in Example 4;

[0028] Figure 7 It is the circulating mill main unit with air inlet conical tube in Example 5;

[0029] Figure 8 It is the circulating mill main unit with an air collecting hood in Example 6;

[0030] Figure 9 It is the circulating mill main unit with air collection hoods on both the front and rear covers in Example 7;

[0031] Figure 10 These are the air holes on the impeller in Example 8. Specific Implementation

[0032] Example 1: Circulating mill main unit, see Figure 2 and Figure 3 , Figure 2 This shows the back of the circulating mill main unit. Figure 3 The display shows the front of the circulating mill main unit, with the centrifugal fan front cover concealed. The circulating mill main unit consists of a centrifugal fan and a circulation pipe 21. The centrifugal fan comprises two main components: a casing and an impeller. The impeller consists of a front disc and blades on the side near the air inlet, a rear disc and a bushing on the side near the input shaft. The air inlet of the impeller is a circular hole in the center of the front disc. The rear disc is fixed to the bushing, which is mounted on the input shaft. The casing consists of a front cover with a centrifugal fan inlet, a volute, and a rear cover on the side near the input shaft. The volute is composed 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 the volute tongue 27. The centrifugal fan has an outlet, which is formed by the front cover, the volute... The outer straight section 22 of the casing, the rear cover, and the inner straight section 23 of the volute enclose the area outside the impeller outer edge projected along the impeller axial projection line on the front and rear covers inside the casing, which 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 outlet width of the centrifugal fan, and the distance between the inner surfaces of the front and rear covers is called the outlet height of the centrifugal fan. A coarse material outlet 20 is provided on the volute, and a circulation pipe interface 25 is provided in the axial projection area of ​​the impeller inlet on the rear cover. The coarse material outlet 20, the inlet of the circulation pipe 21, the outlet of the circulation pipe 21, and the circulation pipe interface 25 are connected in sequence to form a first type of circulation channel.

[0033] The coarse material outlet can also be located on the side of the front or rear cover as needed; in this embodiment, since the circulation pipe interface 25 is located on the rear cover, in order to allow the material from the circulation pipe to enter the impeller, the rear disc of the impeller is provided with the same round hole as the impeller inlet on the front cover, and the blades extend towards the center of the impeller and are fixedly connected to the bushing to form kinetic energy recovery blades.

[0034] The centrifugal fan's diffuser chamber is also equipped with a grading zone, which is the outer area of ​​the second curved section 28 of the centrifugal fan's volute, formed by the curved section 20 extending forward from the volute tongue 27; the coarse material outlet 20 is located at the intersection of the curved section 24 and the outer straight section 22 of the volute.

[0035] In this embodiment, the grading zone enhances the grading effect within the centrifugal fan diffuser chamber. Furthermore, since the pressure at the centrifugal fan outlet is lowest within the diffuser chamber, and there is no second curve section in the centrifugal fan, a large portion of the airflow directly exits from the impeller outlet in front of the vortex and reaches the centrifugal fan outlet, becoming short-circuit airflow. While short-circuit airflow does not negatively impact the centrifugal fan used for ventilation, as it is a major component of the circulating mill, the presence of short-circuit airflow reduces the amount and velocity of non-short-circuit airflow. Material in the non-short-circuit airflow tends to settle and adhere to the wall. The second curve section of the vortex significantly reduces the proportion of short-circuit airflow, thus improving the wall-adhesion problem.

[0036] Example 2: A circulating mill main unit with an air inlet conical tube, see [link / reference] Figure 4 In this embodiment, the front cover of the casing also includes an air inlet duct 30. The large end of the air inlet duct 30 is connected to the inlet of the centrifugal fan, and the small end of the air inlet duct is the air inlet of the circulating mill host. The air inlet duct 30 is provided with a circulation pipe interface 29. The coarse material outlet, the circulation pipe inlet, the circulation pipe outlet, and the circulation pipe interface 29 are connected in sequence to form a circulation channel.

[0037] Example 3: A circulating mill main unit with two outlets, see [link / reference] Figure 5 In this embodiment, the circulating mill main unit adopts a horizontal arrangement. Figure 5 The display shows the main unit of the circulating mill with the centrifugal fan's front cover concealed. The centrifugal fan has two outlets and two circulation channels. The centrifugal fan's volute consists of two sections: the first section comprises an outer straight section 32, a curved section 37, an inner straight section 38, and a second curved section 43; the second section comprises 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 formed by the front cover, the outer straight section 32 of the first volute section, the rear cover, and the inner straight section 31 of the second volute section. The other outlet of the centrifugal fan is formed by the front cover, the second volute section... The outer straight section 39 of the shell, the rear cover and the inner straight section 38 of the first volute shell are enclosed. The front cover also includes an air inlet cone 36. The air inlet cone 36 is provided with two circulation pipe interfaces. One circulation channel is formed by connecting the coarse material outlet 33 on the first volute shell, the inlet of the circulation pipe 34, the outlet of the circulation pipe 34, and one circulation pipe interface on the air inlet cone 36 in sequence. The other circulation channel is formed by connecting the coarse material outlet 41 on the second volute shell, the inlet of the circulation pipe 40, the outlet of the circulation pipe 40, and another circulation pipe interface on the air inlet cone 36 in sequence.

[0038] Example 4: Another circulating mill host, see Figure 6 , Figure 6The upper left and upper right figures show the front and rear of the circulating mill main unit. This main unit consists of a centrifugal fan and an internal circulation pipe 50. The centrifugal fan comprises two main components: an impeller 57 and a casing. The impeller consists of a front disc and blades on the side near the centrifugal fan inlet 58, and a rear disc and bushing on the side near the input shaft. The air inlet of the impeller is a circular hole in the center of the front disc. The rear disc is fixedly connected to the bushing, which is mounted on the input shaft. The casing consists of a front cover 54 with the centrifugal fan inlet 58, a rear cover 52 on the side near the input shaft, and a volute 53. The centrifugal fan outlet 51 is formed by the outer straight sections of the front cover 54 and volute 53, and the inner straight sections of the rear cover 52 and volute 53. The outer edge of the impeller inside the casing projects along the input axis onto the front and rear covers. The outer area of ​​the line is called the diffuser chamber; the impeller inlet on the front cover has a circulation pipe interface 59, a centrifugal fan outlet 51, a circulation pipe inlet 50, and a circulation pipe outlet 50. The circulation pipe interface 59 is connected in sequence to form a second type of circulation channel. The impeller inlet on the front cover 54 is provided with a discharge port 56 for the circulating mill outside the axial projection area on the front cover. The impeller inlet on the rear cover 52 is also provided with a discharge port 55 for the circulating mill outside the axial projection area on the rear cover. The discharge ports 56 and 55 are distributed circumferentially around the impeller inlet. The circulation pipe interface 59 that forms the circulation channel is set so that the fluidized material from the circulation pipe can effectively impact the inlet end of the blade to assist in driving the impeller to rotate.

[0039] Figure 6 The centrifugal fan of the circulating mill main unit shown in the lower left figure has two outlets, and there are two circulation pipe interfaces on the front cover. There are two circulation pipes. Kinetic energy recovery blades 60 are provided between the inlet end of the blade and the bushing. The inner circulation pipe interfaces 61 and 62 that form the circulation channel are set so that the fluidized material from the circulation pipe can effectively impact the kinetic energy recovery blades 60 to assist in driving the impeller to rotate. Figure 6 The centrifugal fan of the circulating mill main unit shown in the lower right figure has four outlets, and there are four internal circulation pipe interfaces on the front cover. There are four internal circulation pipes.

[0040] The circulating mill main unit described in this embodiment makes a new constructive contribution to solving the three core technical problems of drying and pulverizing fresh agricultural products. By setting the discharge port on the front and rear covers, on the one hand, the internal pressure of the centrifugal fan is reduced, thereby reducing the impeller rotation resistance and achieving the goal of reducing energy consumption; on the other hand, it also slows down the decrease in the flow velocity of fluidized material in the diffuser chamber, increases the impact force of fluidized material on the material adhering to the wall inside the vortex shell, and helps to solve the problem of adhering to the wall inside the vortex shell. Furthermore, setting the discharge port on the front cover and / or rear cover also creates a different solution to the classification problem than CN107694135B and WO2020057617. The pressure inside the diffuser is greater than the pressure outside the discharge port. The pressure difference between the two drives the airflow to flow out through the discharge port. Under the action of centrifugal force, the material with large particle size and high moisture content crosses the discharge port and gathers on the inner wall of the vortex shell, flowing along the impeller rotation direction. It then re-enters the centrifugal fan through the circulation channel to achieve circulation. Particles with a particle size and low moisture content are less affected by centrifugal force and flow out through the discharge port with the airflow to achieve classification.

[0041] Example 5: A circulating mill main unit with an air inlet conical tube, see [link / reference] Figure 7 The circulating mill host with four circulating pipes described in Example 4 is formed by adding an air inlet conical pipe 65. The large end of the air inlet conical pipe 65 is connected to the inlet 68 of the centrifugal fan, and the small end 66 of the air inlet conical pipe is the air inlet of the circulating mill host. There are four circulating pipe interfaces on the air inlet conical pipe 65, one of which, 67, is connected to the outlet of a circulating pipe. The circulation channel is formed by the outlet of the centrifugal fan, the inlet of the circulating pipe, the outlet of the circulating pipe, and the circulating pipe interface connected in sequence.

[0042] Example 6: A circulating mill main unit with an air collecting hood, see [link / reference] Figure 8In this embodiment, there are two circulation pipes 76 and 83. The interfaces of the two circulation pipes are located in the axial projection area of ​​the impeller inlet on the rear cover. The front cover is provided with an air collecting hood, which is composed of an inner side plate 71, an outer side plate 75 and a cover 72. The inner side plate 71 is a cylinder, the outer side plate 75 is similar to the volute of a centrifugal fan, and the cover 72 is similar to the front cover of a centrifugal fan. The cover 72 has a hole 73 in the middle, and the hole 73 in the middle of the cover is fitted onto one end of the inner side plate 71. One end of the outer side plate 75 is connected to the outer edge 74 of the cover 72. The other ends of the inner side plate 71 and the outer side plate 75 are connected to the outside 77 of the front cover and cover the exhaust port. The outlet of the air collecting hood on the front cover is formed by the part 79 extending from the front cover of the centrifugal fan, the outer straight section 80 of the outer side plate, the cover 72 and the inner straight section 78 of the outer side plate. The air collecting hood on the front cover also has a grading zone, which is the outer area of ​​the second curved segment 70 formed by the curved segment of the outer side plate of the air collecting hood extending forward from the vortex. This embodiment also has a third type of circulation channel and an air inlet conical pipe. The coarse material outlet 81 is located at the intersection of the curved segment and the straight segment on the outer side plate. The air inlet conical pipe has a second type of circulation channel interface. The coarse material outlet, the inlet of the second type of circulation pipe 82, the outlet of the second type of circulation pipe 82, and the second type of circulation pipe interface are connected in sequence to form the third type of circulation channel.

[0043] Example 7: A circulating mill main unit with air collection hoods on both the front and rear covers, see attached... Figure 9 The circulating mill main machine housing with air inlet conical pipe described in Example 5 is formed by adding air collecting hoods to the front and rear covers. The air collecting hood on the front cover has four outlets 86, 88, 91 and 92. The rear cover also has a discharge port. The air collecting hood on the rear cover also has four outlets 85, 87, 89 and the one behind outlet 91 is covered. The air collecting hood outlet 88 on the front cover and the air collecting hood outlet 89 on the adjacent rear cover are converged into a circulating mill main machine outlet by an exhaust tee 90.

[0044] The circulating mill main unit described in the above seven embodiments suffers from severe wall adhesion inside the circulating pipe when processing fresh agricultural products with a moisture content exceeding 60% due to the bending of the circulating pipe. It can generally only be used to process materials with a moisture content of less than 60%.

[0045] Example 8, the third solution to the wall adhesion problem, is to add a high-pressure gas jetting system to the circulating mill main unit described in the above seven examples. The high-pressure gas jetting system is a gas hole set on the circulating mill main unit, which uses high-pressure gas ejected from the gas hole to blow off the material adhering to the wall.

[0046] The newly formed material adhering to the wall remains soft and sticky for 5 minutes, and the high-speed airflow from the vents can easily blow it off and reintroduce it into the circulation process. With the support of the third solution to the wall adhesion problem described in this embodiment, the wall adhesion problem in the drying and pulverizing of high-moisture and high-viscosity materials is completely solved. The reliability of the single-main unit circulating mill, which has cost advantages but requires the circulation pipe to be bent 180 degrees, is also guaranteed. This also makes it feasible to use the circulating mill main unit described in this embodiment for the drying and pulverizing of most fresh agricultural products.

[0047] See Figure 10 The air holes on the impeller can be implemented as follows: air holes 95 and 104 are respectively located at the outlet ends of two symmetrical blades 106 and 103. The inlet ends of the two symmetrical blades extend towards the center of the impeller and are fixedly connected to the bushing to form kinetic energy recovery blades 105 and 102. High-pressure gas is introduced into the air chamber 101 formed by the shaft end cover 100, the bushing and the end face of the input shaft through the rotary joint 99 installed at the center of the shaft end cover 100. Then, the gas is connected to the air holes 95 and 104 at the outlet ends of the two symmetrical blades 106 and 103 through the air passage 98 on the bushing, the air passage 97 on the kinetic energy recovery blade and the air passage 96 on the blade.

[0048] Depending on the different circulating mill main unit structures, the air holes can be set on the first type of circulation channel in Embodiment 1, or on the second type of circulation channel in Embodiment 4; they can also be set on the air collecting hoods in Embodiments 6 and 7; they can also be set on the third type of circulation channel in Embodiment 6, or on the front cover or / and rear cover in Embodiments 1-7, as well as on the air inlet cones in Embodiments 2 and 5, and within the grading zones in Embodiments 1 and 6.

Claims

1. A solution to the wall-mounting problem of a circulating mill main unit, wherein the circulating mill main unit is composed of a centrifugal fan and a circulating pipe (21). The centrifugal fan includes two main components: a casing and an impeller. The impeller is composed of a front plate and blades on the side near the air inlet, a rear plate and a bushing on the side near the input shaft. The inlet of the impeller is a circular hole in the middle of the front plate. The rear plate is fixedly connected to the bushing, and the bushing is installed on the input shaft. The casing is composed of a front cover with a centrifugal fan inlet, a volute, and a rear cover on the side near the input shaft. The volute is composed 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 the volute tongue (27). The outlet of the centrifugal fan is surrounded by the front cover, the outer straight section (22) of the volute, the rear cover, and the inner straight section (23) of the volute. The area outside the projection line of the impeller axial direction on the front cover and the rear cover inside the casing is called the diffuser. The circulating mill main unit is equipped with air holes, which are designed so that the high-speed airflow ejected from the air holes can blow off the material attached to the wall.

2. The solution to the wall-mounting problem of a circulating mill main unit according to claim 1, characterized in that, The vortex shell is provided with a coarse material outlet (20), and the impeller inlet has a circulation pipe interface (25) in the axial projection area on the front or rear cover. The coarse material outlet (20), the inlet of the circulation pipe (21), the outlet of the circulation pipe (21), and the circulation pipe interface (25) are connected in sequence to form a first type of circulation channel. The air hole is provided on the first type of circulation channel.

3. The solution to the wall-mounting problem of a circulating mill main unit according to claim 1, characterized in that, The impeller inlet has a circulation pipe interface (59) in the axial projection area on the front or rear cover; the centrifugal fan outlet (51), the circulation pipe (50) inlet, the circulation pipe (50) outlet, and the circulation pipe interface (59) are connected in sequence to form a second type of circulation channel. The discharge port (56) of the circulating mill host is located on the front cover, the impeller inlet is outside the axial projection area on the front cover, and / or the discharge port (55) of the circulating mill host is located on the rear cover, the impeller inlet is outside the axial projection area on the rear cover, and the air hole is located on the second type of circulation channel.

4. A solution to the wall-mounting problem of a circulating mill main unit according to claim 2 or 3, characterized in that, The vents are located on the front cover and / or the rear cover.

5. A solution to the wall-mounting problem of a circulating mill main unit according to claim 2 or 3, characterized in that, The air holes are located at the outlet ends of two symmetrical blades of the impeller. The inlet ends of the two symmetrical blades extend towards the center of the impeller and are fixedly connected to the bushing to form kinetic energy recovery blades. The gas is introduced into the air chamber formed by the shaft end cover, the bushing and the input shaft end face through a rotary joint installed at the center of the shaft end cover. Then, the gas is connected to the air holes at the outlet ends of the two symmetrical blades through the air passages on the bushing, the air passages on the kinetic energy recovery blades and the air passages on the blades.

6. A solution to the wall-mounting problem of a circulating mill main unit according to claim 3, characterized in that, The housing also includes an air collecting hood on the front cover, which collects the discharge ports on the front cover. The air collecting hood on the front cover has at least one outlet. The air collecting hood on the front cover consists of an inner side plate (71), an outer side plate (75), and a cover (72). The inner side plate (71) is cylindrical, the outer side plate (75) is shaped like the vortex casing of a centrifugal fan, and the cover (72) is shaped like the front cover of a centrifugal fan. The cover (72) has a hole (73) in the middle, and the hole (73) in the middle of the cover fits inside the inner side plate. One end of the side plate (71) and one end of the outer side plate (75) are connected to the outer edge (74) of the cover (72). The other ends of the inner side plate (71) and the outer side plate (75) are connected to the outside of the front cover (77) and cover the exhaust port. The outlet of the air collection hood on the front cover is formed by the part (79) extending from the front cover of the centrifugal fan, the outer straight section (80) of the outer side plate, the cover (72) and the inner straight section (78) of the outer side plate. The air hole is set on the air collection hood on the front cover.

7. A solution to the wall-mounting problem of a circulating mill main unit according to claim 3, characterized in that, The housing also includes an air collecting hood on the rear cover, which gathers the discharge ports on the rear cover together. The air collecting hood on the rear cover has at least one outlet. The air collecting hood on the rear cover is composed of an inner side plate, an outer side plate, and a cover 1. The inner side plate is cylindrical, the outer side plate is shaped like the vortex casing of a centrifugal fan, and the cover is shaped like the front cover of a centrifugal fan. The cover has a hole in the middle, and the hole in the middle of the cover fits over one end of the inner side plate. One end of the outer side plate is connected to the outer edge of the cover. The other ends of the inner side plate and the outer side plate are connected to the outside of the rear cover and cover the exhaust port. The outlet of the air collecting hood on the rear cover is formed by the portion extending from the rear cover of the centrifugal fan, the outer straight section of the outer side plate, the cover, and the inner straight section of the outer side plate. The air hole is set on the air collecting hood on the rear cover.

8. A solution to the wall-mounting problem of a circulating mill main unit according to claim 6, characterized in that, The circulating mill main unit also includes a second type of circulating pipe (82). A coarse material outlet (81) is provided on the outer side plate of the air collecting hood on the front cover. The impeller inlet has a circulating pipe interface in the axial projection area on the front cover or the rear cover. The coarse material outlet (81), the inlet of the second type of circulating pipe (82), the outlet of the second type of circulating pipe (82), and the circulating pipe interface are connected in sequence to form a third type of circulating channel. The air hole is provided on the third type of circulating channel.

9. A solution to the wall-mounting problem of a circulating mill main unit according to claim 6, characterized in that, The circulating mill main unit also includes a second type of circulating pipe. A coarse material outlet is provided on the outer side plate of the air collecting hood on the rear cover. The impeller inlet has a circulating pipe interface in the axial projection area on the front cover or rear cover. The coarse material outlet, the inlet of the second type of circulating pipe, the outlet of the second type of circulating pipe, and the circulating pipe interface are connected in sequence to form a third type of circulating channel. The air hole is provided on the third type of circulating channel.

10. A solution to the wall-mounting problem of a circulating mill main unit according to claim 6, characterized in that, The front cover has a grading zone inside the air collecting hood. The grading zone is the outer area of ​​the second curved segment (70) formed by the curved segment of the outer side plate of the air collecting hood on the front cover extending forward from the vortex. Alternatively, the rear cover has a grading zone inside the air collecting hood. The grading zone is the outer area of ​​the second curved segment formed by the curved segment of the outer side plate of the air collecting hood on the rear cover extending forward from the vortex. The air vents are located within the grading zone.

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