Main unit of circulating mill

Abstract

A main unit of a circulating mill. The main unit is composed of a centrifugal fan and a first circulating pipe (21). The centrifugal fan comprises a casing and an impeller; the casing is composed of a front cover, a volute and a rear cover; the volute is composed of an outer straight section (22), a curved section (24) and an inner straight section (23); an outlet of the centrifugal fan is enclosed by the front cover, the outer straight section (22) of the volute, the rear cover and the inner straight section (23) of the volute; and the area outside the projection lines of the outer edge of the impeller on the front cover and the rear cover along the axial direction of the impeller inside the casing is referred to as a diffuser chamber. The volute is provided with a coarse material outlet (20); a first circulating pipe interface (25) is in the axial projection area of an inlet of the impeller on the front cover or the rear cover; and the coarse material outlet (20), an inlet of the first circulating pipe (21), an outlet of the first circulating pipe (21) and the first circulating pipe interface (25) are sequentially connected to form a first circulating channel. By providing a circulating channel, the cause of high pressure in the circulating mill is eliminated, thereby reducing the rotational resistance of an impeller, and reducing the energy consumption; and by providing a volute curved section, a wall-sticking phenomenon is improved.

Description

Circulating grinding machine Technical Field

[0001] The invention relates to a circulating mill host, and belongs to the technical fields of circulating fluidized beds, dry powder grinding, and energy-saving and environmental protection. Background Art

[0002] The centrifugal fan is an important component in the present invention. In order to clarify the relevant terms of the centrifugal fan in this case, the structure of the centrifugal fan is briefly introduced as follows. Referring to Figure 1, it is usually composed of two major components: a casing and an impeller. The impeller generally consists of a front disc 9 on the side close to the air inlet 7, blades 8, a rear disc 12 on the side close to the input shaft 13, and a shaft sleeve 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 shaft sleeve 14, and the shaft sleeve 14 is installed 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 on the side close to the input shaft. The volute 15 is generally composed of an outer straight segment 4, a curved segment 5 and an inner straight segment 2. The intersection of the curved segment 5 and the inner straight segment 2 is called the volute tongue 1. The outlet 3 of the centrifugal fan is surrounded by the front cover 10, the outer straight segment 4 of the volute, the rear cover 11 and the inner straight segment 2 of the volute. The outer area of ​​the impeller outer edge inside the casing along the axial projection line of the impeller on the front cover and the rear cover is called the diffusion chamber. The minimum distance between the outer side of the outer straight segment 4 and the inner side of the inner straight segment 2 is called the outlet width of the centrifugal fan, and 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 classification technology. After classification, two materials with different fineness are obtained. For the convenience of description, this case refers to the two materials with different particle sizes obtained after classification 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 cyclone classifier discharges coarse material from the ash outlet, and the exhaust airflow carries away fine material.

[0004] A circulating mill, also known as a Yunjie mill or circulating fluidized bed, consists of a main unit and auxiliary devices. The main unit is the primary site for dry grinding, while the auxiliary devices perform functions such as material-gas separation. The mill utilizes a centrifugal fan and the high-speed airflow it produces to fluidize the material, drying and grinding it through its high-speed circulation channel. Large particles are primarily crushed by the impeller's impact, while ultrafine powders are crushed by friction between the impeller and the volute during high-speed flow. This crushing action causes the material to be continuously dispersed and circulate in a fluidized state at high speed. This exponentially increases the mass-energy exchange area, thinning the gas-solid boundary layer, and maximizing the exchange rate of water (mass) and heat (energy) between the material and the airflow, resulting in rapid drying. This research examines the factors influencing dry grinding efficiency in the dry grinding process of fresh agricultural products. Due to the presence of wall adhesion, these influencing factors are more easily identified and addressed, aiming to develop a highly efficient dry grinding solution.

[0005] The three core technical issues in the drying and grinding of fresh agricultural products are reliability, economy, and grading. Fresh agricultural products will become slurry after being impacted and crushed by the impeller. The slurry adheres to the machine and no longer circulates, which is called wall hanging. Once the wall hanging grows stably, the circulation channel will eventually be blocked, causing the equipment to be paralyzed, and the purpose of dry grinding cannot be achieved. Wall hanging is basically equivalent to a reliability problem. Before this invention, the circulating mill used two technical means to solve the wall hanging problem. One is that the impact of high-speed fluidized material on the wall hanging material makes the wall hanging unable to be stably generated. The other is that the dry powder returned by the auxiliary device, that is, the return material, is mixed with the material in the machine and the newly added material to reduce the moisture content of the material and improve the wall hanging performance. The former is the basis, and the latter is a strengthening means. With the support of the latter, even if liquid is added, increasing the amount of return material will definitely solve the wall hanging problem. Economy is mainly an energy consumption issue, and grading is to separate and discharge qualified materials from the circulation channel.

[0006] The subject matter of the invention disclosed in CN107694135B and WO2020057617 is a circulating mill. The circulating mill main unit of CN107694135B relies on centrifugal force and the drag force exerted on the particles by the graded airflow to achieve classification. When the drag force is greater than the centrifugal force, the particles are carried out by the graded airflow through the space between the graded blades. When the drag force is less than the centrifugal force, the particles enter the circulation pipe and reach the mill inlet for cyclic drying and grinding. Under the conditions of fixed speed and impeller diameter, the centrifugal force depends on the particle diameter and moisture content, and the drag force depends on the graded airflow velocity. The graded airflow velocity 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 the difference, the greater the pressure difference. When the difference is positive, the airflow flows from the main unit inlet to the outlet, and when the difference is negative, the airflow flows from the main unit outlet to the inlet. The problems with CN107694135B are: first, the graded airflow weakens the impact of the fluidized material on the inner surface of the volute corresponding to the graded blades, turning this area into a near-dead corner, where wall hangings can easily and stably form. This defect is caused by the solution to the graded problem; second, the circulation pipe of a single circulating mill main unit is a curved pipe, in which wall hangings are more easily formed. Four circulating mill main units need to be used in series to make the circulation pipe a straight pipe.

[0007] The invention patent WO2020057617 has improved it and disclosed six types of circulating mill hosts. The common feature of the six circulating mill hosts is that they rely on the pressure difference between the inlet and outlet of the centrifugal fan and the cyclone classification effect in the feed pipe to achieve classification. In the first, second, third and sixth types of circulating mill hosts, two hosts are connected in series to make the circulation pipe a straight pipe, the wall hanging in the circulation pipe is improved, and the area close to the dead corner of CN107694135B is eliminated. However, the classification problem solution of WO2020057617 increases the pressure in the machine and affects the rotation of the impeller. This creates an obstruction and increases the energy consumption of the mill. This is because the air inlet speed of the feed pipe with a circulating mill outlet generally exceeds 50 meters per second, the resistance of the cyclone classification becomes very large, and the auxiliary mill is pressurized again on the basis of the high pressure at the outlet of the main mill; a similar problem also exists in CN107694135B, where the centrifugal force's obstruction of the graded airflow also increases the pressure inside the mill; in addition, the kinetic energy recovery technology proposed in WO2020057617 has almost no practical significance because the kinetic energy recovery device itself also consumes energy, making the net remainder of recovered energy extremely small. In addition, although the wall hanging problem solutions of WO2020057617 and CN107694135B are theoretically complete, there are still two practical problems. First, when there is not enough powder as return material at the beginning of the operation, materials with a moisture content of more than 60% often cannot operate normally due to the wall hanging problem. Second, a large amount of return material worsens the economic efficiency of the mill.

[0008] Air flow milling is an ultrafine grinding technology that uses compressed air to impact materials and crush them into pieces. Its most significant advantage is that the process of compressed air being ejected from the nozzle is similar to adiabatic expansion, which consumes a lot of heat and the operating temperature is not high. The disadvantages of air flow milling are that it is difficult to process fiber materials such as Ganoderma lucidum and plastics, and it is also difficult to expand the production capacity of a single machine. The energy consumption is relatively high. Its advantages and disadvantages are in sharp contrast to those of circulating mills. Summary of the Invention

[0009] The purpose of the present invention is to address the problems described in the background technology, invent two circulating mill main machines with lower energy consumption, improve the kinetic energy recovery device, optimize the solution to the wall hanging problem, and integrate air flow crushing and circulating milling into an air flow circulating mill to make up for the shortcomings of both.

[0010] The technical measures taken to achieve the purpose of the present invention are as follows: the first circulating mill main unit is composed of a centrifugal fan and a first circulating pipe. The centrifugal fan has at least one outlet. The volute of the centrifugal fan is provided with a coarse material outlet. The inlet of the impeller is provided with a first circulating pipe interface in the axial projection area on the front cover or / and the rear cover. The coarse material outlet, the inlet of the first circulating pipe, the outlet of the first circulating pipe, and the first circulating pipe interface are connected in sequence to form a first circulating channel.

[0011] The principle of the above technical solution is that the fluidized material in the diffusion chamber rotates at high speed, and the material with a large enough particle size and / or a high enough moisture content converges to the inner wall of the volute under the action of centrifugal force. This process is a classification effect, and the first circulation channel returns the classified coarse material to the mill to realize the circulation operation.

[0012] In order to achieve a better grading effect, a grading area is also provided in the diffuser chamber. The grading area is the outer area of ​​the second curved segment formed by the curved segment of the centrifugal fan volute extending forward from the volute tongue. The coarse material outlet is set at the intersection of the volute curved segment and the outer straight segment, which will have a better effect.

[0013] When the first type of circulation pipe connection 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 first type of circulation pipe connection to enter the impeller. Furthermore, the blade inlet must extend toward the center of the impeller to the sleeve where it is fixed, ensuring that all impeller components function as a single unit. The blade portion formed by the blade inlet extending toward the center of the impeller to the sleeve where it is fixed 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.

[0014] The second type of circulating mill host is composed of a centrifugal fan and a second type of circulating pipe. The inlet of the impeller is provided with a second type of circulating pipe interface in the axial projection area on the front cover or / and the rear cover. The outlet of the centrifugal fan, the inlet of the second type of circulating pipe, the outlet of the second type of circulating pipe, and the second type of circulating pipe interface are connected in sequence to form a second type of circulating channel. The discharge port of the second type of circulating mill host is arranged at the inlet of the impeller on the front cover outside the axial projection area on the front cover; or / and the discharge port of the second type of circulating mill host is arranged at the inlet of the impeller on the rear cover outside the axial projection area on the rear cover, and the discharge ports are distributed circumferentially around the impeller inlet.

[0015] The second type of circulating mill host also includes an air collecting hood, which brings together the discharge ports on the front cover or the rear cover, and there is at least one outlet on the air collecting hood; the air collecting hood on the front cover is composed of an inner plate, an outer plate and a cover, the inner plate is a cylinder, the outer plate is shaped like a centrifugal fan volute, the cover is shaped like a centrifugal fan front cover, there is a hole in the middle of the cover, the hole in the middle of the cover is sleeved on one end of the inner plate, one end of the outer plate is connected to the outer edge of the cover, the other ends of the inner plate and the outer plate are connected to the outside of the front cover and cover the exhaust port, the outlet of the air collecting hood on the front cover is composed of the part extending from the front cover of the centrifugal fan, the outer straight line segment of the outer plate, the outlet part of the cover, the inner straight line segment of the outer plate The air collecting hood on the rear cover is composed of an inner plate, an outer plate and a cover. The inner plate is a cylinder, the outer plate is shaped like a centrifugal fan volute, and the cover is shaped like a centrifugal fan front cover. There is a hole in the middle of the cover, and the hole in the middle of the cover is sleeved on one end of the inner plate, one end of the outer plate is connected to the outer edge of the cover, the other ends of the inner plate and the outer 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 surrounded by the part extending from the rear cover of the centrifugal fan, the outer straight section of the outer plate, the outlet part of the cover, and the inner straight section of the outer 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 gathered into a circulating mill main outlet by an exhaust tee.

[0016] A grading area is also provided in the air collecting hood. The grading area in the air collecting hood on the front cover is the outer area of ​​the second curved segment formed by the curved segment of the outer plate of the air collecting hood on the front cover extending forward from the vortex tongue; the grading area in the air collecting hood on the rear cover is the outer area of ​​the second curved segment formed by the curved segment of the outer plate of the air collecting hood on the rear cover extending forward from the vortex tongue.

[0017] The second type of circulating mill main unit also includes a third type of circulating pipe. A coarse material outlet is provided on the outer plate of the wind collecting hood on the front cover or the rear cover. The inlet of the impeller has a third type of circulating pipe interface in the axial projection area on the front cover or the rear cover. The coarse material outlet, the inlet of the third type of circulating pipe, the outlet of the third type of circulating pipe and the third type of circulating pipe interface are connected in sequence to form a third type of circulating channel.

[0018] The above two circulating mill hosts are based on different classification technology solutions, eliminating the cause of high pressure in the circulating mill host described in the background technology, reducing the pressure in the circulating mill host and reducing the resistance of impeller rotation, thereby achieving the purpose of reducing energy consumption.

[0019] In order to expand the air inlet space and facilitate the connection of the circulation pipe, the front cover also includes an air inlet conical pipe. The large end of the air inlet conical pipe is connected to the inlet of the centrifugal fan, and the small end of the air inlet 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 arranged on the air inlet conical pipe.

[0020] In order to achieve kinetic energy recovery of the 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 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; alternatively, the circulation pipe interface can also be configured so 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.

[0021] Compared with the first, second, third and sixth circulating mill hosts in WO2020057617, the above two circulating mill hosts have a more serious problem of wall hanging in the circulating pipe because the circulating pipe is no longer a straight pipe. In order to more effectively solve the problem of wall hanging, air holes are also provided on the circulating mill host. The air holes are connected to the high-pressure air source, and the air holes are configured so that the high-speed air flow ejected from the air holes can blow off the wall hanging material.

[0022] The air holes on the impeller are realized in this way. The air holes are arranged at the outlet ends of two symmetrical blades, and kinetic energy recovery blades are arranged between the inlet ends of the two symmetrical blades and the shaft sleeve. The gas is introduced into the air chamber surrounded by the shaft end cover, the shaft sleeve 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 duct on the shaft sleeve, the air duct on the kinetic energy recovery blade, and the air duct on the blade.

[0023] The air holes set on the circulation pipe solve the problem of more serious wall hanging inside the circulation pipe caused by the bending of the circulation pipe; the air holes set on the wind collecting hood can solve the problem of wall hanging inside the wind collecting hood; the air holes set on the front cover or the rear cover can use the airflow ejected from the air holes to blow off the wall hanging materials on the inner wall of the vortex casing or the wall hanging materials on the front cover and the rear cover.

[0024] The present invention also provides an air circulation mill main unit, the technical measure of which is to provide an air hole connected to the high-pressure gas on the centrifugal fan constituting the circulating mill main unit, the air hole being configured so that the high-speed airflow ejected from the air hole can drive or assist in driving the rotation of the impeller, the air hole can be provided on the front cover and / or the rear cover and / or the air inlet cone, the air hole being configured so that the high-speed airflow ejected from the air hole can impact the inlet end of the blade or the kinetic energy recovery blade to drive or assist in driving the rotation of the impeller, and can also be configured so that the high-speed airflow ejected from the air hole can impact the outlet end of the blade to drive or assist in driving the rotation of the impeller.

[0025] The circulating mill main unit disclosed in the present invention eliminates the cause of high pressure in the circulating mill main unit described in the background technology by constructing different solutions to the grading problems in the circulating mill main unit, thereby reducing the pressure inside the circulating mill main unit and further reducing the resistance to impeller rotation, thereby achieving the purpose of reducing the energy consumption of the mill. The circulating pipe interface is set so that the fluidized material from the circulating pipe can impact the blade inlet end or the kinetic energy recovery blade to assist in driving the impeller rotation, thereby minimizing the energy consumption of the kinetic energy recovery device and increasing the net margin of recovered energy. High-pressure gas is used to blow off the wall-hanging material to solve the wall-hanging problem, and the reliability is higher. The airflow circulating mill formed by using high-pressure gas to drive or assist in driving the mill impeller to rotate makes up for the shortcomings of the circulating mill and airflow crushing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a structural diagram of an existing centrifugal fan;

[0027] FIG2 is a first circulating mill main unit in Example 1;

[0028] FIG3 is a diagram of the first circulating mill main unit with the centrifugal fan front cover hidden in Example 1;

[0029] FIG4 is a first circulating mill main unit with an air inlet cone in Example 2;

[0030] FIG5 is a first circulating mill main unit with two outlets in Example 3;

[0031] Figure 6 is a second circulating mill main unit in Example 4;

[0032] FIG7 is a second circulating mill main unit with an air inlet cone in Example 5;

[0033] FIG8 is a second circulating mill main unit with an air collecting hood in Example 6;

[0034] FIG9 is a second circulating mill main unit having air collecting covers on both the front and rear covers in Example 7;

[0035] FIG10 shows the air holes on the impeller in Example 8. Specific embodiments

[0036] Example 1, the first type of circulating mill host, see Figure 2 and Figure 3, Figure 2 shows the back of the circulating mill host, and Figure 3 shows the front of the circulating mill host with the front cover of the centrifugal fan hidden. The circulating mill host consists of a centrifugal fan and a circulation pipe 21. The centrifugal fan includes two major components: a casing and an impeller. The impeller consists of a front disc on the side close to the air inlet, blades, a rear disc on the side close to the input shaft, and a sleeve. The air inlet of the impeller is a circular hole in the middle of the front disc. The rear disc is fixed to the sleeve, and the sleeve is installed on the input shaft; the casing consists of a front cover with a centrifugal fan inlet, a vortex shell and a rear cover on the side close to the input shaft. The vortex shell consists of an outer straight segment 22, a curved segment 24 and an inner straight segment 23. The intersection of the curved segment 24 and the inner straight segment 23 is called a vortex tongue 27. The centrifugal fan is provided with an outlet. The outlet of the centrifugal fan consists of the front cover, the vortex shell and the rear cover on the side close to the input shaft. The outer straight section 22 of the casing, the inner straight section 23 of the rear cover and the volute are surrounded by the outer edge of the impeller inside the casing. The outer area along the axial projection line of the impeller on the front cover and the rear cover is called the diffusion 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 cover and the rear cover 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 circulation channel.

[0037] The coarse material outlet can also be arranged on the edge of the front cover or the rear cover as needed; in this embodiment, since the circulation pipe interface 25 is arranged on the rear cover, in order to allow the material from the circulation pipe to enter the impeller, the impeller rear disk is provided with a circular hole that is the same as the impeller inlet on the front cover, and the blades extend toward the center of the impeller to the shaft sleeve and are fixedly connected to the shaft sleeve to form kinetic energy recovery blades.

[0038] A grading zone is also provided in the diffusion chamber of the centrifugal fan. The grading zone is the outer area of ​​the second curved section 28 of the volute formed by the curved section 24 of the volute of the centrifugal fan extending forward from the volute tongue 27; the coarse material outlet 20 is arranged at the intersection of the curved section 24 of the volute and the outer straight section 22.

[0039] On the one hand, the grading area of ​​this embodiment strengthens the grading effect in the diffusion chamber of the centrifugal fan. On the other hand, since the pressure at the centrifugal fan outlet in the diffusion chamber is the smallest, for the centrifugal fan without the second curved section, a large part of the airflow directly comes out from the impeller outlet in front of the vortex tongue and reaches the centrifugal fan outlet to become short-circuit airflow. The short-circuit airflow has no adverse effect on the centrifugal fan used for ventilation. However, for the centrifugal fan which is the main component of the circulating mill main unit, the existence of the short-circuit airflow reduces the amount of non-short-circuit airflow and reduces the speed of the non-short-circuit airflow. The material in the non-short-circuit airflow is easy to settle and hang on the wall. The second curved section of the volute greatly reduces the proportion of the short-circuit airflow and improves the wall hanging problem.

[0040] Example 2, the first type of circulating mill main unit with an air inlet cone, see Figure 4. The front cover of the casing of this embodiment also includes an air inlet cone 30. The large end of the air inlet cone 30 is connected to the inlet of the centrifugal fan, and the small end of the air inlet cone 30 is the air inlet of the circulating mill main unit. A circulating pipe interface 29 is provided on the air inlet cone 30. The coarse material outlet, the inlet of the circulating pipe, the outlet of the circulating pipe, and the circulating pipe interface 29 are connected in sequence to form a circulating channel.

[0041] Example 3, a first type of circulating mill main unit with two outlets, see Figure 5. The circulating mill main unit of this embodiment is arranged horizontally. Figure 5 shows the circulating mill main unit with the front cover of the centrifugal fan hidden. The centrifugal fan has two outlets and two circulation pipes. The volute of the centrifugal fan is composed of two sections. The first section is the outer straight section 32, the curved section 37, the inner straight section 38 and the second curved section 43. The second section is the outer straight section 39, the curved section 44, the inner straight section 31 and the second curved section 35. One outlet of the centrifugal fan is composed of the front cover, the outer straight section 32 of the first volute, the rear cover and the inner straight section 3 of the second volute. 1, the other outlet of the centrifugal fan is surrounded by the front cover, the outer straight section 39 of the second section volute, the rear cover and the inner straight section 38 of the first section volute, the front cover also includes an air inlet vertebral tube 36, and the air inlet vertebral tube 36 is provided with two circulation pipe interfaces. One circulation channel is composed of the coarse material outlet 33 on the first section volute, the inlet of the circulation pipe 34, the outlet of the circulation pipe 34, and a circulation pipe interface on the air inlet vertebral tube 36 connected in sequence, and the other circulation channel is composed of the coarse material outlet 41 on the second section volute, the inlet of the circulation pipe 40, the outlet of the circulation pipe 40, and another circulation pipe interface on the air inlet vertebral tube 36 connected in sequence.

[0042] Example 4, the second circulating mill host, see Figure 6, the upper left and upper right figures of Figure 6 show the front and back of the second circulating mill host, the circulating mill host consists of a centrifugal fan and a circulation pipe 50, the centrifugal fan includes two major components, an impeller 57 and a casing, the impeller consists of a front plate on the side of the centrifugal fan inlet 58, blades, a rear plate and a sleeve on the side of the input shaft, the air inlet of the impeller is a circular hole in the middle of the front plate, the rear plate is fixedly connected to the sleeve, and the sleeve is installed on the input shaft; the casing consists of a front cover 54 with a centrifugal fan inlet 58, a rear cover 52 on the side of the input shaft and a volute 53, the outlet 51 of the centrifugal fan is surrounded by the front cover 54, the outer straight section of the volute 53, the rear cover 52 and the inner straight section of the volute 53, the outer edge of the impeller inside the casing is on the front cover and the rear cover along the input shaft. The outer area of ​​the axial projection line is called the diffusion chamber; the inlet of the impeller has a second circulation pipe interface 59 in the axial projection area on the front cover, the outlet 51 of the centrifugal fan, the inlet of the circulation pipe 50, the outlet of the circulation pipe 50, and the second circulation pipe interface 59 are connected in sequence to form a second circulation channel, the inlet of the impeller on the front cover 54 is provided with a discharge port 56 of the second circulation mill host outside the axial projection area on the front cover, and the inlet of the impeller on the rear cover 52 is also provided with a discharge port 55 of the second circulation mill host outside the axial projection area on the rear cover. The discharge ports 56 and 55 are distributed circumferentially around the impeller inlet, and the circulation pipe interface 59 that constitutes the circulation channel is arranged 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.

[0043] The centrifugal fan of the circulating mill main unit shown in the lower left figure of Figure 6 has two outlets, two circulating pipe interfaces on the front cover, and two second-type circulating pipes. A kinetic energy recovery blade 60 is arranged between the inlet end of the blade and the shaft sleeve. The circulating pipe interfaces 61 and 62 that constitute the circulating channel are arranged so that the fluidized material from the circulating pipe can effectively impact the kinetic energy recovery blade 60 to assist in driving the impeller to rotate; the centrifugal fan of the circulating mill main unit shown in the lower right figure of Figure 6 has four outlets, four circulating pipe interfaces on the front cover, and four circulating pipes.

[0044] The circulating mill main unit described in this embodiment makes a new constructive contribution to the solution of the three core technical problems of drying and grinding fresh agricultural products. The discharge port is set on the front cover and the rear cover. On the one hand, it reduces the pressure inside the centrifugal fan and reduces the rotation resistance of the impeller, thereby achieving the purpose of reducing energy consumption; on the other hand, it also slows down the decline in the flow velocity of the fluidized material in the diffusion chamber, increases the impact force of the fluidized material on the wall material in the volute, and is conducive to solving the wall hanging problem in the volute. In addition, the discharge port is set on the front cover and / or the rear cover, which also constructs a classification problem solution different from CN107694135B and WO2020057617. The pressure in the diffusion chamber is greater than the pressure outside the discharge port. The pressure difference between the two drives the air flow out through the discharge port. Under the action of centrifugal force, materials with large particle size and high water content pass through the discharge port and gather on the inner wall of the volute and flow along the direction of rotation of the impeller. They re-enter the centrifugal fan through the circulation channel to realize circulation operation. Particles with a particle size small to a certain extent and a water content low to a certain extent are less affected by the centrifugal force and flow out through the discharge port with the air flow to realize classification.

[0045] Example 5, a second type of circulating mill main unit with an air inlet cone tube, see Figure 7, is formed by adding an air inlet cone tube 65 on the basis of the circulating mill main unit with four second type circulating tubes described in Example 4. The large end of the air inlet cone tube 65 is connected to the inlet 68 of the centrifugal fan, and the small end 66 of the air inlet cone tube is the air inlet of the circulating mill main unit. There are four circulating tube interfaces on the air inlet cone tube 65, one of which is connected to the outlet of a second type circulating tube. The circulation channel is composed of the outlet of the centrifugal fan, the inlet of the second type circulating tube, the outlet of the second type circulating tube, and the circulating tube interfaces, which are connected in sequence.

[0046] Example 6, a second type of circulating mill main unit with an air collecting hood, see Figure 8, this embodiment has two second type circulating pipes 76 and 83, the two second type circulating pipe interfaces are arranged in the axial projection area of ​​the impeller inlet on the rear cover, and a air collecting hood is provided on the front cover, the air collecting hood on the front cover is composed of an inner plate 71, an outer plate 75 and a cover 72, the inner plate 71 is a cylinder, the outer plate 75 is shaped like a centrifugal fan vortex, the cover 72 is shaped like a centrifugal fan front cover, there is a hole 73 in the middle of the cover 72, the hole 73 in the middle of the cover is sleeved on one end of the inner plate 71, one end of the outer plate 75 is connected to the outer edge 74 of the cover 72, the other ends of the inner plate 71 and the outer plate 75 are connected to the outside 77 of the front cover and cover the exhaust port, and the outlet of the air collecting hood on the front cover is surrounded by the part 79 extending from the front cover of the centrifugal fan, the outer straight section 80 of the outer plate, the cover 72 and the inner straight section 78 of the outer plate. The air collecting hood on the front cover also has a grading area. This grading area is the area outside of the second curved section 70 formed by the curved section of the outer panel of the air collecting hood extending forward from the vortex tongue. This embodiment also has a third circulation channel and an air inlet cone. The coarse material outlet 81 is located at the intersection of the curved section and the outer straight section of the outer panel. The air inlet cone is equipped with a third circulation pipe interface. The coarse material outlet, the inlet of the third circulation pipe 82, the outlet of the third circulation pipe 82, and the third circulation pipe interface are sequentially connected to form the third circulation channel.

[0047] The first circulation channel and discharge port of Example 1 utilize the centrifugal grading effect inherent in the diffusion chamber to achieve grading. The third circulation channel of this embodiment utilizes the centrifugal grading effect inherent in the wind collecting hood to achieve secondary grading. The grading pressure difference of the former is the pressure difference between the diffusion chamber and the outside of the discharge port, and the grading pressure difference of the latter is the pressure difference between the outside of the discharge port and the air inlet of the centrifugal fan.

[0048] Example 7, a second type of circulating mill main unit with air collecting hoods on both the front and rear covers, see Figure 9, is formed by adding air collecting hoods to the front and rear covers of the second type of circulating mill main unit with an air inlet cone described in Example 5. The air collecting hood on the front cover has four outlets 86, 88, 91 and 92, and 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 covered behind the outlet 91; the air collecting hood outlet 88 on the front cover and the air collecting hood outlet 89 on the adjacent rear cover are combined by an exhaust tee 90 to form a second type of circulating mill main unit outlet.

[0049] The circulating mill main unit described in the above seven embodiments suffers from severe wall buildup in the circulating pipe due to its curved circulation pipe when processing fresh agricultural products with a moisture content exceeding 60%. Generally, it can only be used to process materials with a moisture content less than 60%.

[0050] Example 8: The third solution to the problem of wall hanging is to add a high-pressure gas blowing system on the basis of the circulating mill main unit described in the above seven embodiments. The high-pressure gas blowing system is an air hole set on the circulating mill main unit, and uses the high-pressure gas ejected from the air hole to blow off the wall hanging material.

[0051] The newly formed wall-hanging material remains soft and sticky within 5 minutes, and the high-speed airflow ejected from the pores can easily blow it off and re-join the circulation process; the original two solutions to the wall hanging problem are combined with the third solution to the wall hanging problem described in this embodiment. The wall hanging problem existing in the dry powder processing of high-humidity and high-viscosity materials can be completely solved, and the reliability of the single-host circulating mill with cost advantages but the circulation pipe needs to be bent 180 degrees is also guaranteed, which also makes it feasible to use the circulating mill host described in this embodiment for the dry powder processing of most fresh agricultural products.

[0052] Referring to Figure 10, the air holes set on the impeller can be realized in this way. The air holes 95 and 104 are respectively set at the outlet ends of two symmetrical blades 106 and 103. The inlet ends of the two symmetrical blades extend toward the center of the impeller to the shaft sleeve and are fixedly connected to the shaft sleeve to form kinetic energy recovery blades 105 and 102. The high-pressure gas is introduced into the air chamber 101 surrounded by the shaft end cover 100, the shaft sleeve and the input shaft end face through the rotary joint 99 installed at the center of the shaft end cover 100, and then connected to the air holes 95 and 104 at the outlet ends of the two symmetrical blades 106 and 103 through the air duct 98 on the shaft sleeve, the air duct 97 on the kinetic energy recovery blade, and the air duct 96 on the blade.

[0053] According to different structures of the circulating mill main unit, the air holes can be set on the first circulation channel in Example 1, or on the second circulation channel in Example 4; they can also be set on the wind collecting hoods described in Examples 6 and 7; they can also be set on the third circulation channel described in Example 6, or on the front cover and / or rear cover described in Examples 1-7.

[0054] Example 9: An air circulation mill main unit, comprising air holes provided on the centrifugal fan housing of the circulating mill main unit described in Example 1 or Example 4, wherein the air holes are configured such that the high-speed airflow ejected from the air holes can propel or assist in the rotation of the impeller. The air holes are provided on the front cover or rear cover or on the air inlet cone described in Example 2 or Example 5, wherein the air holes are configured such that the high-speed airflow ejected from the air holes can impact the inlet end of the blades, thereby propel or assist in the rotation of the impeller; or the air holes are configured such that the high-speed airflow ejected from the air holes can impact the kinetic energy recovery blades, thereby propel or assist in the rotation of the impeller; or the air holes are provided on the front cover or rear cover, wherein the high-speed airflow ejected from the air holes can impact the outlet end of the blades, thereby propel or assist in the rotation of the impeller.

[0055] The air circulation mill main unit described in this embodiment retains the impact and friction crushing mechanism of the circulation mill, and also adds the crushing mechanism of material particles colliding with each other that is unique to air flow crushing. At the same time, the process of compressed air being ejected from the nozzle is approximately adiabatic expansion, which consumes a large amount of heat and reduces the operating temperature. It retains the advantages of the circulation mill and air flow crushing, overcomes the disadvantages of both, and has a wider adaptability.

Claims

1. A first type of circulating mill host, comprising a centrifugal fan and a first type of circulating pipe (21), wherein the centrifugal fan comprises two major components, a casing and an impeller, wherein the impeller comprises a front disc on the side close to the air inlet, blades, a rear disc on the side close to the input shaft, and a shaft sleeve, wherein the inlet of the impeller is a circular hole in the middle of the front disc, the rear disc is fixedly connected to the shaft sleeve, and the shaft sleeve is installed on the input shaft; the casing comprises a front cover provided with a centrifugal fan inlet, a volute, and a rear cover on the side close to the input shaft, wherein the volute comprises an outer straight segment (22), a curved segment (24), and an inner straight segment (23), wherein the intersection of the curved segment (24) and the inner straight segment (23) is called a volute tongue (27), wherein the outlet of the centrifugal fan is surrounded by the front cover, the outer straight segment (22) of the volute, the rear cover, and the inner straight segment (23) of the volute, wherein the outer edge of the impeller inside the casing is located outside the projection line of the impeller axis on the front cover and the rear cover, and is called a diffusion chamber; ... The volute is provided with a coarse material outlet (20), the impeller inlet has a first circulation pipe interface (25) in the axial projection area on the front cover or the rear cover, and the coarse material outlet (20), the inlet of the first circulation pipe (21), the outlet of the first circulation pipe (21), and the first circulation pipe interface (25) are connected in sequence to form a first circulation channel.

2. The first circulating mill main machine according to claim 1 is characterized in that: The coarse material outlet is arranged at the edge of the front cover or the rear cover.

3. The first circulating mill main machine according to claim 1 is characterized in that: A circular hole is arranged in the middle of the impeller rear disc.

4. The first circulating mill main machine according to claim 1, characterized in that: The front cover also includes an air inlet vertebral tube (30), and the first circulation pipe interface (29) on the front cover is arranged on the air inlet vertebral tube. The large end of the air inlet vertebral tube is connected to the inlet of the centrifugal fan, and the small end of the air inlet vertebral tube is the air inlet of the first circulation mill host.

5. The first circulating mill main machine according to claim 1 is characterized in that: The diffusion chamber is further provided with a grading zone, which is an outer area of ​​a second curved section (28) formed by the curved section (24) of the centrifugal fan volute extending forward from the volute tongue (27); or the diffusion chamber is further provided with a grading zone, which is an outer area of ​​a second curved section (28) formed by the curved section (24) of the centrifugal fan volute extending forward from the volute tongue (27), and the coarse material outlet is arranged at the intersection of the volute curved section (24) and the outer straight section (22).

6. The second type of circulating mill main machine is composed of a centrifugal fan and a second type of circulating pipe (50). The centrifugal fan includes two major components: a casing and an impeller. The impeller is composed of a front disc on the side close to the air inlet, blades, a rear disc on the side close to the input shaft, and a shaft sleeve. The inlet of the impeller is a circular hole in the middle of the front disc. The rear disc is fixedly connected to the shaft sleeve, and the shaft sleeve is installed on the input shaft. The casing is composed of a front cover provided with a centrifugal fan inlet, a volute, and a rear cover on the side close to the input shaft. The volute is composed of an outer straight segment, a curved segment, and an inner straight segment. The intersection of the curved segment and the inner straight segment is called a volute tongue. The outlet (51) of the centrifugal fan is surrounded by a front cover, an outer straight section of a volute, a rear cover and an inner straight section of the volute; the outer area of ​​the outer edge of the impeller inside the casing along the axial projection line of the impeller on the front cover and the rear cover is called a diffusion chamber; the inlet of the impeller has a second circulation pipe interface (59) in the axial projection area on the front cover or the rear cover; the outlet (51) of the centrifugal fan, the inlet of the second circulation pipe (50), the outlet of the second circulation pipe (50), and the second circulation pipe interface (59) are connected in sequence to form a second circulation channel, characterized in that: The discharge port (56) of the second circulating mill main machine is arranged at the inlet of the impeller on the front cover outside the axial projection area on the front cover; or / and the discharge port (55) of the second circulating mill main machine is arranged at the inlet of the impeller on the rear cover outside the axial projection area on the rear cover.

7. The second circulating mill main machine according to claim 6 is characterized in that: The front cover also includes an air inlet vertebral tube (65). The second circulation pipe interface (67) on the front cover is arranged on the air inlet vertebral tube (65). The large end of the air inlet vertebral tube (65) is connected to the inlet (68) of the centrifugal fan, and the small end (66) of the air inlet vertebral tube is the air inlet of the second circulation mill main unit.

8. The second circulating mill main machine according to claim 6 is characterized in that: The discharge openings are distributed circumferentially around the impeller inlet.

9. The second circulating mill main machine according to claim 6, characterized in that: The casing also includes an air collecting hood on the front cover, which collects the discharge openings on the front cover together, and the air collecting hood on the front cover has at least one outlet; or / and the casing also includes an air collecting hood on the rear cover, which collects the discharge openings on the rear cover together, and the air collecting hood on the rear cover has at least one outlet.

10. The second circulating mill main machine according to claim 6, characterized in that: The air collecting hood outlet on the front cover and the air collecting hood outlet on the adjacent rear cover are connected by an exhaust tee to form a second circulation mill main machine outlet.

11. The second circulating mill main machine according to claim 9, characterized in that: The air collecting hood on the front cover is composed of an inner plate (71), an outer plate (75) and a cover (72), wherein the inner plate (71) is a cylinder, the outer plate (75) is shaped like a centrifugal fan volute, the cover (72) is shaped like a centrifugal fan front cover, a hole (73) is provided in the middle of the cover (72), the hole (73) in the middle of the cover is sleeved on one end of the inner plate (71), one end of the outer plate (75) is connected to an outer edge (74) of the cover (72), the other ends of the inner plate (71) and the outer plate (75) are connected to the outside (77) of the front cover and cover the exhaust port, and the outlet of the air collecting hood on the front cover is formed by a portion (77) extending from the front cover of the centrifugal fan. 9), the outer straight section (80) of the outer plate, the cover (72) and the inner straight section (78) of the outer plate; the air collecting hood on the rear cover is composed of the inner plate, the outer plate and the cover, the inner plate is a cylinder, the outer plate is shaped like a centrifugal fan volute, the cover is shaped like a front cover of the centrifugal fan, there is a hole in the middle of the cover, the hole in the middle of the cover is sleeved on one end of the inner plate, one end of the outer plate is connected to the outer edge of the cover, the other ends of the inner plate and the outer 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 surrounded by the part extending from the rear cover of the centrifugal fan, the outer straight section of the outer plate, the cover and the inner straight section of the outer plate.

12. The second circulating mill main machine according to claim 9, characterized in that: The second type of circulating mill main machine further comprises a third type of circulating pipe (82); a coarse material outlet (81) is arranged on the outer side plate of the wind collecting cover on the front cover or the rear cover; the inlet of the impeller has a third type of circulating pipe interface in the axial projection area of ​​the front cover; the coarse material outlet (81), the inlet of the third type of circulating pipe (82), the outlet of the third type of circulating pipe (82), and the third type of circulating pipe interface are connected in sequence to form a third type of circulating channel.

13. The second circulating mill main machine according to claim 9, characterized in that: The wind collecting hood on the front cover is also provided with a grading area, which is the outer area of ​​the second curved section (70) formed by the curved section of the outer plate of the wind collecting hood on the front cover extending forward from the vortex tongue, or the wind collecting hood on the rear cover is also provided with a grading area, which is the outer area of ​​the second curved section formed by the curved section of the outer plate of the wind collecting hood on the rear cover extending forward from the vortex tongue.

14. A kinetic energy recovery device for a circulating mill main machine, characterized in that: According to claim 1, the first circulation pipe interface is configured so that the fluidized material from the first circulation pipe can effectively impact the inlet end of the blade to assist in driving the impeller to rotate; or according to claim 6, the second circulation pipe interface is configured so that the fluidized material from the second circulation pipe can effectively impact the inlet end of the blade to assist in driving the impeller to rotate.

15. The kinetic energy recovery device of a circulating mill main machine according to claim 14, characterized in that: The inlet end of the blade extends toward the center of the impeller to the sleeve and is fixedly connected to the sleeve to form a kinetic energy recovery blade. The first circulation pipe interface is configured so that the fluidized material from the first circulation pipe can effectively impact the kinetic energy recovery blade to assist in driving the impeller to rotate, or the second circulation pipe interface is configured so that the fluidized material from the second circulation pipe can effectively impact the kinetic energy recovery blade to assist in driving the impeller to rotate.

16. The third solution to the wall hanging problem of the main unit of the circulating mill. The main unit of the circulating mill consists of a centrifugal fan and a circulating pipe. The centrifugal fan includes two major parts: a casing and an impeller. The impeller consists of a front disc on the side close to the air inlet, blades, a rear disc on the side close to the input shaft, and a sleeve. The air inlet of the impeller is a circular hole in the middle of the front disc. The rear disc is fixedly connected to the sleeve, and the sleeve is installed 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 close to the input shaft. The volute consists of an outer straight segment, a curved segment and an inner straight segment. The intersection of the curved segment and the inner straight segment is called a vortex tongue. The outlet of the centrifugal fan is surrounded by the front cover, the outer straight segment of the volute, the rear cover and the inner straight segment of the volute. The outer edge of the impeller inside the casing is on the front cover and the rear cover along the outer side of the impeller axial projection line. The area is called a diffusion chamber; it is characterized by: The circulating mill main machine is provided with air holes, and the air holes are arranged so that the high-speed airflow ejected from the air holes can blow off the wall-hanging materials.

17. The third solution to the wall hanging problem of the circulating mill main machine according to claim 16 is characterized in that: The air holes are arranged at the outlet ends of the two symmetrical blades of the impeller, and the inlet ends of the two symmetrical blades extend toward the center of the impeller to the shaft sleeve and are fixedly connected with the shaft sleeve to form a kinetic energy recovery blade. The gas is introduced into the air chamber surrounded by the shaft end cover, the shaft sleeve and the end face of the input shaft through a rotating 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 channel on the shaft sleeve, the air channel on the kinetic energy recovery blade, and the air channel on the blade.

18. The third solution to the wall hanging problem of the circulating mill main machine according to claim 16, characterized in that: The air holes are arranged on the first circulation channel of claim 1, or the air holes are arranged on the second circulation channel of claim 6; or the air holes are arranged on the wind collecting hood of claim 9; or the air holes are arranged on the third circulation channel of claim 12, or the air holes are arranged on the front cover and / or the rear cover.

19. An airflow circulation mill main unit, the circulation mill main unit is composed of a centrifugal fan and a circulation pipe, the centrifugal fan includes two major parts: a casing and an impeller, the impeller is composed of a front disc on the side close to the air inlet, blades, a rear disc on the side close to the input shaft, and a sleeve, the air inlet of the impeller is a circular hole in the middle of the front disc, the rear disc is fixedly connected to the sleeve, and the sleeve 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 close to the input shaft, the volute is composed of an outer straight segment, a curved segment and an inner straight segment, the intersection of the curved segment and the inner straight segment is called a vortex tongue, the outlet of the centrifugal fan is surrounded by the front cover, the outer straight segment of the volute, the rear cover and the inner straight segment of the volute, the outer edge of the impeller inside the casing on the front cover and the rear cover along the outer side of the impeller axial projection line is called a diffusion chamber; it is characterized in that The centrifugal fan is provided with air holes, and the air holes are arranged so that the high-speed airflow ejected from the air holes can drive or assist in driving the impeller to rotate.

20. The air circulation mill main machine according to claim 19, characterized in that: The air holes are arranged on the front cover or the rear cover or on the air inlet cone described in claim 4 or claim 7, and the air holes are arranged so that the high-speed airflow ejected from the air holes can impact the inlet end of the blades to promote or assist the rotation of the impeller; or the air holes are arranged so that the high-speed airflow ejected from the air holes can impact the kinetic energy recovery blades described in claim 15 to promote or assist the rotation of the impeller; or the air holes are arranged on the front cover or the rear cover, and the air holes are arranged so that the high-speed airflow ejected from the air holes can impact the outlet end of the blades to promote or assist the rotation of the impeller.

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