coal mill

Abstract

The application discloses a coal mill, belonging to the field of boilers, comprising a casing, a grinding assembly, an air supply pipeline and a separation assembly. The grinding assembly is arranged in the casing to grind raw coal, and the air supply pipeline supplies airflow carrying pulverized coal into the separation assembly. The separation assembly comprises a first cone and a second cone arranged in a vertical direction, and a lower end of the first cone extends into the second cone. The coal mill forms a continuous pneumatic separation path by using a first channel, a corner space and a second channel. During the turning process, large-size pulverized coal is affected by inertia and sedimentation and falls back to the inner wall of the second cone; small-size pulverized coal is more obviously affected by the carrying capacity of the airflow and can continue to rise with the airflow and be discharged from the upper outlet of the first cone. The separation resistance is reduced while the separation effect is ensured, and the coal mill is especially suitable for the preparation of relatively coarse-diameter pulverized coal required by a circulating fluidized bed boiler.

Description

Technical Field

[0001] This application relates to the field of boiler technology, and in particular to coal mills. Background Technology

[0002] Traditional pulverized coal boilers concentrate combustion in the lower part of the furnace, requiring high fineness of pulverized coal, with particle size controlled within the range of 0μm to 200μm. In contrast, the combustion of circulating fluidized bed boilers is distributed throughout the entire furnace. Relying on the heat storage effect of a large amount of high-temperature bed material, the fuel (taking relatively hard coal as an example) only needs to be crushed to a wide sieve particle size of 0mm to 8mm before it can be fed into the furnace.

[0003] The key feature of Powdered Coal-Circulating Fluidized Bed (PC-CFB) technology is that it reduces the feed fuel particle size from the traditional 0mm~8mm wide screening range of CFB to a narrower screening range of 0mm~1mm, 0mm~2mm, or 0mm~3mm. This reduction in feed coal particle size effectively improves the load change rate and operational flexibility of the circulating fluidized bed boiler.

[0004] Traditional crushing systems are not fine enough, while traditional pulverizing systems are energy-intensive and produce pulverized coal that is too fine to meet the requirements of PC-CFB boilers to maintain fluidization.

[0005] Therefore, how to prepare pulverized coal that meets the requirements of PC-CFB boilers has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This application proposes a coal mill for producing pulverized coal that meets the requirements of a PC-CFB boiler.

[0007] To achieve the above objectives, this application provides a coal mill, including a casing, grinding components, air supply pipeline, and separation components; The grinding assembly is disposed inside the casing and is used to grind raw coal to obtain pulverized coal. The separation assembly includes a first conical hopper and a second conical hopper arranged vertically. The first conical hopper is installed on the top wall of the housing and has a lower inlet and an upper outlet. The second conical hopper has an upper open end and a lower open end. The lower end of the first conical hopper extends into the second conical hopper through the upper open end, and the lower open end communicates with the grinding assembly. The air supply pipeline is used to supply airflow into the housing so that the airflow carries the pulverized coal through the first channel, the corner space and the second channel in sequence and enters the first cone hopper. Small-sized pulverized coal is discharged through the upper outlet, and large-sized pulverized coal returns along the inner wall of the second cone hopper and returns to the grinding assembly through the lower open end. The first channel is the channel formed between the side wall of the housing and the outer wall of the second cone; the corner space is the space enclosed by the side wall and the top wall of the housing; the second channel is the channel formed between the inner wall of the second cone and the outer wall of the portion of the first cone that extends into the second cone.

[0008] Optionally, in the above-mentioned coal mill, the grinding assembly includes a grinding disc and a grinder; The grinding disc is located below the lower open end, and a material dropping area is formed in the middle of the grinding disc; The grinder is located between the grinding disc and the lower open end, and the grinder is used to grind the raw coal on the grinding disc; The grinding disc is provided with a flow guide ridge, which extends from the edge of the material drop area to the edge of the grinding disc, and a flow guide channel is formed between two adjacent flow guide ridges. Multiple guide ridges are uniformly arranged along the circumference of the grinding disc, and the circumferential distance L between the tops of two adjacent guide ridges does not exceed the height H of the guide ridge. The grinding disc is connected to a drive component, which drives the grinding disc to rotate in a vertical direction so that the pulverized coal located in the guide channel leaves the grinding disc under the action of centrifugal force.

[0009] Optionally, in the above-mentioned coal mill, the guide ridge is arranged along the radial direction of the grinding disc; Along the radial direction of the grinding disc, the width of the guide ridge gradually increases along the circumferential direction of the grinding disc, so that the circumferential width of the guide channel between two adjacent guide ridges is equal at different radial positions; Along the radial direction of the grinding disc, at least one side of the guide ridge is provided with a guide slope.

[0010] Optionally, in the above-mentioned coal mill, the grinding assembly

[0011] It also includes an adjusting component, which is used to adjust the distance between the grinder and the grinding disc to adjust the loading force of the grinder on the raw coal.

[0012] Optionally, the above-mentioned coal mill also includes a controller, which is used to obtain a preset coal feed amount according to a coal feeding instruction, obtain the load change trend of the grinding component according to the coal feed amount difference between the preset coal feed amount and the current coal feed amount, and adjust at least one of the coal feeding rate and the grinding state of the grinding component according to the load change trend. The controller is also used to compare the real-time current of the drive component of the grinding assembly with a preset optimal operating current range, and to reduce the coal feed rate when the real-time current is higher than the upper limit of the preset optimal operating current range, and to increase the coal feed rate when the real-time current is lower than the lower limit of the preset optimal operating current range.

[0013] Optionally, in the above-mentioned coal mill, the controller can also obtain the inlet and outlet pressure difference based on the inlet and outlet air pressure of the casing, and compare the inlet and outlet pressure difference with the target particle size preset pressure difference range. When the inlet and outlet pressure difference is higher than the upper limit of the target particle size preset pressure difference range, the controller can reduce the loading force of the grinder on the raw coal, increase the ventilation volume of the air supply pipeline, and / or increase the rotation speed of the grinding disc. When the inlet and outlet pressure difference is lower than the lower limit of the target particle size preset pressure difference range, the controller can increase the loading force of the grinder on the raw coal, reduce the ventilation volume of the air supply pipeline, and / or reduce the rotation speed of the grinding disc.

[0014] Optionally, in the above-mentioned coal mill, the coal feed pipe of the coal mill passes through the upper outlet, the lower inlet and the lower open end in sequence and is connected to the grinding assembly.

[0015] Optionally, in the above-mentioned coal mill, a protrusion is provided at the lower end of the coal feed pipe, and the protrusion is arranged along the circumference of the coal feed pipe; Along the extension direction of the coal feed pipe, the cross-section of the protrusion is triangular.

[0016] Optionally, in the above-mentioned coal mill, a guide block is provided in the corner space formed by the side wall and the top wall, and the guide block is arranged along the circumference of the casing; On a cross section parallel to the axis of the housing, the cross section of the guide block is triangular. The guide block includes a first side wall, a second side wall, and a guide wall. The first side wall is connected to the side wall of the housing, and the second side wall is connected to the top wall of the housing. The guide wall is an inwardly concave arc-shaped guide surface facing the second cone.

[0017] Optionally, in the above-mentioned coal mill, the sidewall of the second cone bucket extends obliquely upward from bottom to top in a direction close to the corner space; In a cross-section parallel to the axis of the housing, the upper edge of the second cone is teardrop-shaped, the free end of the upper edge is arc-shaped, and the thickness of the upper edge is greater than the thickness of the sidewall of the second cone.

[0018] Optionally, in the above-mentioned coal mill, a plurality of baffles are provided in the corner space formed by the side wall and the top wall. The baffles extend from the inner wall of the casing toward the center of the casing, and the angle between the extension direction of the baffles and the radial direction of the casing is 15°~20°. The baffle includes a horizontal section and a vertical section, the horizontal section being connected to the vertical section and extending in a direction perpendicular to the plane containing the vertical section; The vertical section includes a first section connected to the side wall of the housing and a second section connected to the top wall of the housing, and the connection position of the first section and the second section is arc-shaped; On a cross-section perpendicular to the plane containing the vertical segment, the first segment has an airfoil shape with a rounded upper end and a tapered lower end, and the second segment has an airfoil shape with a rounded upper end and a tapered lower end.

[0019] This application provides a coal mill, including a casing, a grinding assembly, an air supply duct, and a separation assembly. The grinding assembly is located inside the casing, where raw coal enters and is ground to form pulverized coal. The air supply duct is connected to the casing and supplies airflow into the casing, which carries the pulverized coal into the separation assembly. The separation assembly includes a first conical hopper and a second conical hopper arranged vertically. A first channel is formed between the side wall of the casing and the outer wall of the second conical hopper; a corner space is formed between the side wall and the top wall of the casing; and a second channel is formed between the inner wall of the second conical hopper and the outer wall of the portion of the first conical hopper extending into the second conical hopper. The coal mill disclosed in this application utilizes the first channel, the corner space, and the second channel to form a continuous pneumatic separation path, and guides large-particle pulverized coal back through the inner wall of the second conical hopper. No impeller structure is provided on the pneumatic separation path, forming a fully open flow channel with a significantly increased flow area, reducing the resistance to the passage of coarse particles. Particle size classification is completed during the change of the pulverized coal's direction of movement and the redistribution of the flow field. Because large-particle pulverized coal has greater inertia and a settling tendency, it is easier for it to approach the inner wall of the second cone and fall back after passing through the corner space and the second channel. Small-particle pulverized coal is more significantly affected by the airflow carrying capacity and can continue to rise with the airflow and be discharged from the upper outlet of the first cone. This method reduces separation resistance while ensuring separation efficiency, and is particularly suitable for the preparation of coarser-sized pulverized coal required by circulating fluidized bed boilers, such as pulverized coal with particle sizes in the range of 0mm~3mm, 0mm~2mm, or 0mm~1mm. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort, and this application can be applied to other similar scenarios based on the provided drawings. Unless obvious from the linguistic context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0021] Figure 1This is a schematic diagram of the structure of the coal mill provided in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the separation component of the coal mill provided in the embodiments of this application; Figure 3 This is a schematic diagram of the structure of the separation component of the coal mill provided in this application embodiment after adding baffles; Figure 4 This is a schematic diagram of the structure of the grinding disc of the coal mill provided in the embodiments of this application; Figure 5 yes Figure 4 A partial sectional view along the center AA; Figure 6 This is a front view of the baffle provided in the embodiment of this application; Figure 7 This is a left view of the baffle provided in the embodiment of this application; Figure 8 This is a right view of the baffle provided in the embodiment of this application.

[0022] in: 100 - Casing; 200-Grinding assembly; 210-Grinding disc; 211-Feeding area; 212-Guide ridge; 220-Driver; 230-Grinder; 240-Adjusting component; 300 - Air supply duct; 400 - Separation assembly; 410 - First cone; 420 - Second cone; 421 - Upper edge; 430 - Baffle; 431 - Horizontal section; 432 - Vertical section; 4321 - First section; 4322 - Second section; 500 - First Channel; 600 - Corner space; 610 - Flow guide block; 700 - Second Channel; 800 - Coal feed pipe; 810 - Protrusion. Detailed Implementation

[0023] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. The described embodiments are only a part of the embodiments of the present application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without inventive effort are within the scope of protection of the present application.

[0024] It should be noted that, for ease of description, only the parts relevant to the application are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0025] It should be understood that the terms "system," "apparatus," "unit," and / or "module" used in this application are a method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0026] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "a," and / or "the" are not specifically singular and may include the plural. Generally, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements. An element defined by the phrase "comprising an..." does not exclude the presence of other identical elements in the process, method, product, or apparatus that includes the element.

[0027] In the description of the embodiments of this application, unless otherwise stated, " / " means "or", for example, A / B can mean A or B; "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, in the description of the embodiments of this application, "multiple" refers to two or more.

[0028] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0029] This application provides a coal mill, such as... Figure 1 As shown, it includes a housing 100, a grinding assembly 200, an air supply duct 300, and a separation assembly 400.

[0030] The grinding assembly 200 is disposed inside the casing 100. After the raw coal enters the casing 100, it is ground by the grinding assembly 200 to form pulverized coal. The grinding method of the grinding assembly 200 on the raw coal can be selected by those skilled in the art according to actual needs, and no specific limitation is made here.

[0031] The air supply duct 300 is connected to the casing 100 and is used to supply airflow into the casing 100. The airflow carries the pulverized coal formed by grinding into the separation component 400. The airflow provides power for the movement of the pulverized coal within the separation component 400, ensuring that small-particle pulverized coal can move to the outlet of the separation component 400.

[0032] The airflow can be hot air, cold air, or a mixture of hot and cold air. The airflow serves two purposes: firstly, it carries the ground pulverized coal towards the separation component 400; secondly, it dries the pulverized coal, thereby reducing its moisture content and improving subsequent conveying and combustion stability.

[0033] like Figures 1-3 As shown, in some embodiments of this application, the separation component 400 includes a first cone 410 and a second cone 420 arranged in a vertical direction.

[0034] The first conical hopper 410 is installed on the top wall of the housing 100, and has a lower inlet and an upper outlet. The second conical hopper 420 has an upper open end and a lower open end. The lower part of the first conical hopper 410 extends into the second conical hopper 420 through the upper open end, and the lower open end of the second conical hopper 420 communicates with the grinding assembly 200. Vertically, the first conical hopper 410, the second conical hopper 420, and the grinding assembly 200 are sequentially arranged inside the housing 100.

[0035] The first cone hopper 410 and the second cone hopper 420 form a nested separation structure. The outer wall of the part of the first cone hopper 410 that extends into the second cone hopper 420 forms an annular or near-annular channel for pulverized coal and airflow to pass through between the inner wall of the second cone hopper 420.

[0036] A first channel 500 is formed between the side wall of the housing 100 and the outer wall of the second cone 420; the side wall of the housing 100 and the top wall of the housing 100 form a corner space 600; a second channel 700 is formed between the inner wall of the second cone 420 and the outer wall of the portion of the first cone 410 that extends into the second cone 420.

[0037] The ground pulverized coal, under the action of the airflow supplied by the air supply duct 300, first moves upward along the first channel 500; after rising with the airflow to the upper part of the casing 100, the pulverized coal enters the corner space 600; the pulverized coal and the airflow turn in the corner space 600 and enter the second channel 700.

[0038] After being continuously guided by the first channel 500, the corner space 600, and the second channel 700, the large-particle pulverized coal, due to inertia, gravity, and wall-adhering motion, partially falls directly back to the grinding assembly 200 in the first channel 500, partially falls back to the grinding assembly 200 after colliding with the corner space 600, and partially enters the second channel 700 and moves downward along the inner wall of the second cone 420, returning to the grinding assembly 200 for further grinding through the lower open end of the second cone 420. Some large-particle and small-particle pulverized coal enter the first cone 410 with the airflow. Under the action of centrifugal force and aerodynamic force, the small-particle pulverized coal is discharged directly from the upper outlet, while the large-particle pulverized coal slides down the inner wall of the first cone 410 and falls back to the second cone 420 through the lower inlet of the first cone 410, finally returning to the grinding assembly 200 through the lower open end of the second cone 420.

[0039] Among them, small-particle-size pulverized coal refers to pulverized coal that meets the preset particle size range, while large-particle-size pulverized coal refers to pulverized coal that exceeds the preset particle size range.

[0040] In the coal mill disclosed in this solution, the separation component 400 adopts a pneumatically driven screening method, which, compared to mechanical centrifugal screening, can reduce separation resistance and improve the adaptability for preparing coarse-sized pulverized coal. The ventilation characteristics of the coal mill become the primary factor controlling the passage behavior of pulverized coal particles and the particle size of the final product. When the prepared pulverized coal particle size becomes coarser, the pressure of the conveying mixed gas (referred to as air pressure) is affected by the resistance of the separation component 400, the pulverized coal concentration, and the particle size, making the original system design unsuitable for current needs.

[0041] The coal mill disclosed in this scheme utilizes a continuous pneumatic separation path formed by the first channel 500, the corner space 600, and the second channel 700. Pulverized coal undergoes particle size classification during the change of its direction of movement and the redistribution of the flow field. Larger particles fall back along the inner wall of the second cone 420. Due to the greater inertia and settling tendency of large particles, they are more likely to approach the inner wall of the second cone 420 and fall back after passing through the corner space 600 and the second channel 700. Smaller particles are more significantly affected by the airflow carrying capacity and can continue to rise with the airflow and be discharged from the upper outlet of the first cone 410. This reduces separation resistance while ensuring separation efficiency, making it particularly suitable for the preparation of coarser-sized pulverized coal required for circulating fluidized bed boilers, such as pulverized coal with particle sizes ranging from 0 mm to 3 mm, 0 mm to 2 mm, or 0 mm to 1 mm.

[0042] Optionally, the first cone 410 and the second cone 420 are conical hoppers or conical guides with locally circular arc transition surfaces.

[0043] The coal mill disclosed in this solution, in order to meet the low-resistance and high-efficiency separation requirements of pulverized coal with a wide particle size of 0mm~3mm, does not have an impeller structure installed in the separation component 400 at the position where pulverized coal and airflow enter the second channel 700, forming a full-pass flow channel with a significantly increased flow area. Compared with the impeller-setting method in related technologies, the effective flow area of ​​the coal mill disclosed in this solution can be increased by more than 50% at the position where pulverized coal and airflow enter the second channel 700, which greatly reduces the resistance of the gas-powder mixture and thus reduces the resistance of coarse particles.

[0044] In some embodiments of this application, such as Figure 1 As shown, the grinding assembly 200 includes a grinding disc 210, a grinder 230, a drive component 220, and an adjustment component 240.

[0045] The grinding disc 210 is located below the lower open end of the second conical hopper 420, and the grinder 230 is located between the grinding disc 210 and the lower open end of the second conical hopper 420. Optionally, the grinder 230 is a grinding roller, pressure roller, grinding ball, or other structure that can cooperate with the grinding disc 210 to grind raw coal.

[0046] The drive unit 220 is mounted on the housing 100 and is connected to the grinding disc 210 for driving the grinding disc 210 to rotate around its axis.

[0047] Adjustment component 240 is installed on housing 100 and connected to grinder 230. It is used to adjust the distance between grinder 230 and grinding disc 210, thereby adjusting the grinding force of grinder 230 on raw coal.

[0048] After the raw coal falls onto the grinding disc 210, the rotation of the grinding disc 210 causes the raw coal to move from the center to the outer periphery under the action of centrifugal force. During the movement, it passes through the grinding area between the grinder 230 and the grinding disc 210 and is squeezed and crushed into pulverized coal.

[0049] The distance between the grinder 230 and the grinding disc 210 can be adjusted by adjusting the adjustment component 240 according to the hardness, moisture content, and target particle size of the raw coal, thereby adjusting the grinding intensity. Specifically, when it is necessary to prepare finer particle size pulverized coal, the distance between the grinder 230 and the grinding disc 210 can be reduced or the loading force can be increased to improve the crushing effect; when it is necessary to prepare coarser particle size pulverized coal, the distance between the grinder 230 and the grinding disc 210 can be appropriately increased or the loading force can be reduced to reduce over-grinding.

[0050] The low-resistivity particle size classification structure of the grinding component 200 and the separation component 400 in this scheme works together to make the particle size control of pulverized coal not solely dependent on the retention of the separation component 400, but determined by both grinding intensity and pneumatic separation, thereby reducing energy consumption and improving the flexibility of particle size adjustment.

[0051] The driving component 220 can be an electric motor, a hydraulic motor, or other rotary driving mechanism; the adjusting component 240 can be a hydraulic loading device, a spring loading device, an electric push rod, or a pneumatic loading device.

[0052] In some embodiments of this application, such as Figure 4 As shown, a material drop zone 211 is formed in the middle of the grinding disc 210, into which raw coal supplied by the coal feed pipe 800 falls. A guide ridge 212 is provided on the grinding disc 210, extending from the edge of the material drop zone 211 to the edge of the grinding disc 210. Multiple guide ridges 212 are evenly arranged along the circumference of the grinding disc 210, and the circumferential distance L between the tops of two adjacent guide ridges 212 does not exceed the height H of the guide ridge 212.

[0053] Pulverized coal falls into the material drop zone 211 of the grinding disc 210 through the coal feed pipe 800. The grinding disc 210 rotates and uses centrifugal force to throw the raw coal into the grinding area, where it is ground by the grinder 230. When the pulverized coal moves on the grinding disc 210, the guide ridges 212 can separate and guide the raw coal and pulverized coal. Smaller particles of pulverized coal can move towards the outer periphery of the grinding disc 210 through centrifugal force along the gap between adjacent guide ridges 212 without being further over-ground, and then flow upward under the action of airflow, entering the separation component 400.

[0054] By setting the guide ridge 212, the residence time of fine powder on the grinding disc 210 can be reduced, thus decreasing the probability of pulverized coal that has reached the target particle size being repeatedly crushed. For pulverized coal with a wide or coarse particle size required by circulating fluidized bed boilers, the guide ridge 212 can promote qualified pulverized coal to leave the grinding zone as soon as possible, reducing over-grinding.

[0055] At the same radial position, the circumferential distance L between the tops of two adjacent guide ridges 212 does not exceed the height H of the guide ridge 212; preferably, as Figure 5 As shown, the circumferential distance L between the tops of two adjacent guide ridges 212 is equal to the height H of the guide ridge 212. Under the action of centrifugal force and airflow, pulverized coal is more likely to migrate outward along the groove, while larger pieces of raw coal can still be guided to the working area of ​​the grinder 230 for further grinding.

[0056] The flow-guiding ridges 212 can be arranged in a straight line along the radial direction, or in an arc or spiral shape along the radial direction. The height, spacing, and number of the flow-guiding ridges 212 can be designed to match the target particle size range.

[0057] In some embodiments of this application, at least one side of the guide ridge 212 is provided with a guide slope along the length extension direction of the guide ridge 212.

[0058] In the embodiment where the guide ridge 212 is arranged along the radial direction of the grinding disc 210, guide slopes are provided on both sides of the guide ridge 212. In a cross section perpendicular to the extension direction of the guide ridge 212, the guide ridge 212 is trapezoidal.

[0059] Along the radial direction of the grinding disc 210, the width of the guide ridge 212 gradually increases along the circumferential direction of the grinding disc 210, so that the circumferential width of the guide channel between two adjacent guide ridges 212 remains consistent at different radial positions.

[0060] The trapezoidal cross-section guide ridge 212 has a wider bottom and a relatively narrower top. The bottom can improve the connection strength between the guide ridge 212 and the grinding disc 210, while the top can reduce the obstruction to the flow of pulverized coal. The guide channel formed between adjacent guide ridges 212 has a narrower bottom and a relatively wider top, which helps to restrict larger pieces of material from directly entering the guide channel and guides smaller pulverized coal particles to move outward along the guide channel.

[0061] When pulverized coal passes through guide ridge 212, the top of guide ridge 212 can act as a grinding surface. The trapezoidal sides of guide ridge 212 can form a gentle guide, reducing the risk of local accumulation and blockage.

[0062] The cross-section of the guide ridge 212 is not limited to a trapezoid, but can also be an approximate trapezoid, a rounded trapezoid, or a triangle, as long as it can form a guiding structure on the surface of the grinding disc 210 to guide the pulverized coal to move outward.

[0063] In some embodiments of this application, the coal feed pipe 800 of the coal mill passes sequentially through the upper outlet of the first cone 410, the lower inlet of the first cone 410, and the lower open end of the second cone 420, and is connected to the grinding disc 210.

[0064] The coal feed pipe 800 runs through the separation component 400 from top to bottom, and the raw coal can be directly fed to the material drop area 211 of the millstone 210.

[0065] In this scheme, the coal feed pipe 800 passes through the central area of ​​the first cone hopper 410 and the second cone hopper 420. The wall of the coal feed pipe 800 serves as the central guiding boundary for the airflow inside the separation component 400, reducing the risk of disordered backflow of pulverized coal in the central area and facilitating the separation of small-particle pulverized coal from large-particle pulverized coal.

[0066] Raw coal enters the mill 210 downwards along the coal feed pipe 800, and pulverized coal is discharged along the first channel 500, the corner space 600, the second channel 700 and the upper outlet of the first cone hopper 410 under the action of airflow. The two paths are opposite but do not interfere with each other, which can improve the utilization rate of the internal space of the coal mill to a certain extent.

[0067] The millstone 210 is also equipped with a slag discharge port to discharge impurities in the raw coal that cannot be crushed.

[0068] The housing 100 is also equipped with a sealing assembly, which is connected to the housing 100. Clean, cold air at a pressure higher than the air-coal pressure inside the grinding disc 210 is continuously introduced into the interior of the coal mill (especially the area of ​​the grinder 230), forming an "air curtain barrier" between the moving and stationary parts to prevent the high-temperature coal airflow from entering the bearing chamber of the grinder 230 and to prevent wear on the grinder 230.

[0069] Optionally, the coal feed pipe 800 can be coaxially arranged with the first cone hopper 410; the lower end of the coal feed pipe 800 can be equipped with a flared end, a constricted end, or a guide hood to adjust the falling range of raw coal.

[0070] In some embodiments of this application, the coal mill also includes a controller that is communicatively connected to the coal feed pipe 800 and the grinding assembly 200.

[0071] The coal feed pipe 800 can optionally be connected to a coal feeder, coal feed valve, or variable frequency conveying mechanism to adjust the coal feed rate. Optionally, an external boiler sends a coal command to the controller.

[0072] The controller is used to obtain a preset coal feed rate according to the coal feeding command and use the preset coal feed rate as a feedforward input parameter. The controller can also obtain the current coal feed rate and obtain the load change trend of the grinding component 200 based on the coal feed rate difference between the preset coal feed rate and the current coal feed rate.

[0073] When the preset coal feed rate is greater than the current coal feed rate, the controller determines that the load on the grinding assembly 200 is increasing. At this time, the controller can slightly adjust the coal feed rate to smoothly transition the coal feed rate from the current rate to the preset rate, rather than increasing it abruptly. The controller can also adjust the grinding state of the grinding assembly 200 according to the increasing load trend, such as adjusting the loading force of the grinder 230, the gap between the grinder 230 and the grinding disc 210, the rotational speed of the grinding disc 210, or the output power of the drive component 220, so that the grinding assembly 200 enters the adaptation state before or during the increase in coal feed rate.

[0074] When the preset coal feed rate is less than the current coal feed rate, the controller determines that the load on the grinding assembly 200 is decreasing. If the coal feed rate drops sharply, the material layer on the grinding disc 210 may thin rapidly, weakening the buffer between the grinder 230 and the grinding disc 210, which can easily cause vibration, unstable grinding, or fluctuations in the particle size of the pulverized coal. The controller can slightly reduce the coal feed rate and simultaneously adjust the grinding state of the grinding assembly 200, such as appropriately reducing the loading force, adjusting the rotation speed of the grinding disc 210, or changing the grinding gap, so that the grinding capacity of the grinding assembly 200 matches the slightly reduced coal feed rate.

[0075] The controller in this scheme does not passively adjust after the load changes, but anticipates the load change trend based on the difference between the coal feeding command and the current coal feeding amount, and then performs feedforward adjustment.

[0076] The controller can also compare the real-time current of the drive unit 220 of the grinding assembly 200 with the preset optimal operating current range.

[0077] The drive unit 220 can be selected as the main motor that drives the grinding disc 210 to rotate. The real-time current can reflect the grinding resistance and load status currently borne by the grinding assembly 200.

[0078] When the real-time current is higher than the upper limit of the preset optimal operating current range, it indicates that the material layer on the grinding disc 210 is too thick and the grinding load is too high. The coal feed rate will be automatically reduced slightly to slow down the material entry speed and avoid mill blockage, uneven grinding and excessive particle size.

[0079] When the real-time current is lower than the lower limit of the preset optimal operating current range, it indicates that the material layer on the grinding disc 210 is too thin. The coal feed rate will be automatically increased slightly to replenish the material and restore a stable material layer thickness, preventing the primary air from directly blowing through the material layer, which would cause equipment vibration, reduced output, and particle size fluctuations.

[0080] If the real-time current is within the preset optimal operating current range, the current coal feed rate and operating parameters will remain unchanged to maintain the stability of the material layer and continuous grinding.

[0081] This solution combines feedforward prediction of coal feeding instructions with closed-loop current regulation of the drive unit 220. Feedforward prediction of coal feeding instructions can adjust the coal feeding rate and grinding state in advance before load changes occur, reducing material layer fluctuations caused by sudden changes in coal feeding. Closed-loop current regulation of the drive unit 220 can correct the coal feeding rate according to the actual load of the grinding assembly 200, avoiding deviations from actual operating conditions caused by changes in coal quality, moisture content, or equipment wear.

[0082] The controller can be selected as PID control, segmented control, fuzzy control, model predictive control or multivariable coordinated control.

[0083] The controller can also obtain the inlet and outlet pressure difference based on the inlet and outlet air pressure of the coal mill or casing 100, and compare the inlet and outlet pressure difference with the preset pressure difference range of the target particle size.

[0084] The inlet air pressure can be obtained by a pressure sensor installed at the air supply duct 300, the air inlet of the casing 100, or the primary air inlet. The outlet air pressure can be obtained by a pressure sensor installed at the outlet of the first cone hopper 410, the powder outlet duct, or the outlet side of the casing 100.

[0085] For different target pulverized coal particle sizes, corresponding preset differential pressure ranges can be established in advance. The larger the target particle size, the lower the allowable differential pressure. When the target pulverized coal particle size is relatively coarse, the fine powder content inside the coal mill is relatively low, and the air-powder flow resistance is usually small, so a lower differential pressure range can be set. When the target pulverized coal particle size is fine, the fine powder content inside the coal mill increases, and the flow resistance and powder-carrying resistance of the air-powder mixture usually increase, so a higher differential pressure range can be set.

[0086] The controller compares the real-time inlet and outlet pressure difference with the preset pressure difference range of the target particle size to determine whether the current pulverized coal particle size is deviating from the target particle size.

[0087] When the pressure difference between the inlet and outlet exceeds the upper limit of the preset pressure difference range for the target particle size, it is determined that there is too much fine powder in the mill and there is over-grinding. The loading force of the grinder 230 is automatically reduced to weaken the grinding intensity. At the same time, the primary air volume is increased to enhance the carrying capacity of coarse particles, and the rotation speed of the grinding disc 210 is appropriately increased to speed up material flow, shorten the grinding residence time, reduce the proportion of fine powder, and make the particle size return to the target upper limit.

[0088] When the pressure difference between the inlet and outlet is lower than the lower limit of the preset pressure difference range for the target particle size, it is determined that there is too much coarse powder in the mill and the grinding is insufficient. The mill 230 loading force is automatically increased to enhance the crushing effect, the primary air volume is slightly reduced to prolong the grinding residence time, and the grinding disc 210 speed is appropriately reduced to slow down the material flow and increase the grinding contact time, thereby increasing the proportion of fine powder and causing the particle size to converge toward the target lower limit.

[0089] If the differential pressure is within the set range, all parameters remain unchanged, and the target narrow-screen pulverized coal is output stably.

[0090] This scheme uses the inlet and outlet pressure difference as an indirect parameter to characterize the particle size and flow state of pulverized coal inside the coal mill. Compared to relying solely on manual sampling to detect pulverized coal particle size, the pressure difference-based control response is more timely and can correct for coarser or finer particle sizes in advance.

[0091] The controller coordinates the grinding load, grinding speed and ventilation volume to match the grinding intensity, material residence time and airflow carrying capacity. This can improve the stability of pulverized coal particle size control, avoid increasing energy consumption or equipment wear due to simply increasing the grinding load, and avoid increasing the resistance of the separation component or the entrainment of coarse particles due to simply increasing the ventilation volume.

[0092] In an embodiment where the separation component 400 is a double-cone hopper, pulverized coal, under the influence of the airflow supplied by the air supply duct 300, sequentially passes through the first channel 500, the corner space 600, and the second channel 700, with larger pulverized coal particles falling back along the inner wall of the second cone hopper 420. Changes in the inlet and outlet pressure difference reflect changes in resistance along this flow path. When the pulverized coal is too fine, the circulating powder volume increases, or there is localized powder accumulation, the pressure difference typically increases; when the pulverized coal is too coarse, insufficiently ground, or the flow resistance is too low, the pressure difference typically decreases. By comparing the pressure difference with a preset pressure difference range for the target particle size, and then adjusting the loading force, grinding speed, and ventilation volume, the controller can maintain the small-particle pulverized coal output from the separation component 400 within the target particle size range, while simultaneously allowing the larger pulverized coal particles to return to the grinding component 200 for further grinding via the lower open end of the second cone hopper 420.

[0093] The feedforward control of coal feed rate, closed-loop control of current, and differential pressure particle size correction control operate in tandem. The controller can first determine the load change trend based on the coal feed command and the current coal feed rate difference, and then smoothly adjust the coal feed rate and grinding status; then, it can determine whether the grinding assembly 200 is within the optimal load range based on the real-time current of the drive component 220; at the same time, it can determine whether the pulverized coal particle size deviates from the target range based on the inlet and outlet pressure difference.

[0094] When load control objectives conflict with particle size control objectives, the controller can coordinate according to strategies such as safety priority, load stability priority, or particle size priority. For example, when the current of drive component 220 is too high and the inlet and outlet pressure difference is also too high, the controller can prioritize reducing the coal feed rate and the loading force to alleviate both overload and over-grinding. When the current of drive component 220 is too low and the inlet and outlet pressure difference is too low, the controller can increase the coal feed rate and the loading force to improve output and compensate for insufficient grinding. Thus, the coal mill can maintain stable, efficient, and low-wear operation under complex coal quality and variable load conditions.

[0095] In some embodiments of this application, such as Figure 2 As shown, a protrusion 810 is provided at the lower end of the coal feed pipe 800, and the protrusion 810 is arranged along the circumference of the coal feed pipe 800. Along the extension direction of the coal feed pipe 800, the cross-section of the protrusion 810 is triangular.

[0096] The protrusion 810 is located on the outside of the coal feed pipe 800 to change the airflow boundary near the lower end of the coal feed pipe 800, so that the gas-powder mixture will smoothly change direction when passing around the coal feed pipe 800.

[0097] Because of the airflow turning and pulverized coal falling inside the separation component 400, coal is prone to accumulate near the lower end of the coal feed pipe 800. The circumferential protrusion 810 can guide the pulverized coal and reduce the risk of blockage.

[0098] The cross-section of the protrusion 810 can also be a circular arc triangle, trapezoid, or teardrop shape, etc.; the protrusion 810 can be integrally formed with the coal feed pipe 800, or it can be fixed to the outer wall of the coal feed pipe 800 by welding, screwing, or wear-resistant bushing, etc.

[0099] The corner space of 600 is the area where the flow direction of pulverized coal changes most drastically. If this area has a right angle or abrupt change in structure, coarse pulverized coal particles are prone to accumulate due to inertial collisions, and fine pulverized coal particles may also repeatedly circulate due to local eddies, resulting in unstable separation efficiency.

[0100] like Figure 2 As shown, in this design, a flow guide block 610 is provided within the corner space 600 formed by the side wall and top wall of the housing 100. The flow guide block 610 is arranged circumferentially along the housing 100. In a cross-section parallel to the axis of the housing 100, the cross-section of the flow guide block 610 is triangular.

[0101] The guide block 610 includes a first sidewall, a second sidewall, and a guide wall. The first sidewall is connected to the sidewall of the housing 100, and the second sidewall is connected to the top wall of the housing 100. The guide wall is a concave arc-shaped guide surface facing the second cone 420.

[0102] After the pulverized coal and gas flow rise from the first channel 500 to the corner space 600, they need to change from an upward flow to a swirling flow towards the second channel 700. The concave arc-shaped surface of the guide block 610 can smoothly guide the gas-powder mixture, transforming the originally abrupt corner into an arc-shaped transition area, reducing turbulence, impact, and dead zones caused by sharp turns, allowing the gas-powder mixture to enter the second channel 700 more smoothly, thus reducing system resistance and minimizing wear and dust accumulation.

[0103] Optionally, the guide block 610 is a continuous annular structure, and the radius of curvature of the guide wall can be designed according to the diameter of the casing 100, the airflow velocity, and the particle size of the pulverized coal.

[0104] like Figure 2 As shown, the sidewall of the second cone 420 in this design extends obliquely upwards toward the corner space 600; on a cross section parallel to the axis of the housing 100, the upper edge 421 of the second cone 420 is teardrop-shaped, the free end of the upper edge 421 is arc-shaped, and the thickness of the upper edge 421 is greater than the thickness of the sidewall of the second cone 420.

[0105] The upper open end of the second cone hopper 420 is located near the corner space 600. Before entering the second channel 700, the pulverized coal and airflow pass through the upper edge 421 of the second cone hopper 420. The upper edge 421 of the upper open end of the second cone hopper 420 is set in a teardrop shape, so that the airflow forms a smoother streamline when it bypasses the edge, reducing separation vortices and particle scouring at the edge.

[0106] Coarse pulverized coal has greater inertia in this area, and wear at the edges is usually more severe. The arc-shaped free end of the teardrop-shaped upper edge 421 can reduce the direct impact between the gas-powder mixture and the edge of the second cone hopper 420. At the same time, by thickening and adopting a teardrop-shaped transition, the service life of the second cone hopper 420 can be extended.

[0107] Optionally, the teardrop-shaped upper edge 421 is integrally formed with the second cone 420, or it can be fixed to the upper end of the second cone 420 by a wear-resistant alloy part, a ceramic wear-resistant part, or a weld overlay; its outer surface can be set as a low-resistance shape with a rounded transition, an elliptical transition, or a round front and pointed back.

[0108] The first channel 500, the corner space 600, and the second channel 700 form a bend in the pulverized coal flow. The guide block 610 transforms the abrupt right-angle bend into an arc-shaped bend, and the teardrop-shaped upper edge 421 of the second cone 420 forms a teardrop-shaped low-resistance guiding contact surface. On the one hand, this reduces turbulence and dead zones in the pulverized coal and airflow mixture at sharp turns; on the other hand, it effectively guides the flow direction of the mixture and can also adapt to the increased wear conditions caused by the increased particle size of the pulverized coal.

[0109] In some embodiments of this application, such as Figure 3 As shown, multiple baffles 430 are installed within the corner space 600 formed by the side walls and top wall of the casing 100. These baffles 430 can be arranged at intervals along the circumference of the casing 100. The baffles 430 extend from the inner wall of the casing 100 towards its center, with an angle of 15° to 20° between their extension direction and the radial direction of the casing 100. This angle allows the baffles 430 to create a certain swirling or tangential guiding effect on the gas-pulverized coal mixture, enhancing the pulverized coal classification effect without significantly increasing resistance.

[0110] like Figure 6 As shown, the baffle 430 includes a horizontal section 431 and a vertical section 432. The horizontal section 431 is connected to the vertical section 432 and extends in a direction perpendicular to the plane of the vertical section 432. Optionally, the horizontal section 431 may be located on one or both sides of the plane of the vertical section 432 to improve the strength of the baffle 430 and improve the flow guiding area. Optionally, the horizontal section 431 is located on the side of the vertical section 432 near the inner wall of the housing 100, and the horizontal section 431 is connected to the inner wall of the housing 100.

[0111] like Figures 6-8 As shown, the vertical section 432 includes a first section 4321 connected to the side wall of the housing 100 and a second section 4322 connected to the top wall of the housing 100. The connection position of the first section 4321 and the second section 4322 is arc-shaped. Along the radial direction of the housing 100, the length of the first section 4321 is less than the length of the second section 4322. The vertical section 432 is also L-shaped as a whole, and the corner of the L-shape faces the second cone 420.

[0112] Along the direction perpendicular to the plane containing the vertical segment 432, the first segment 4321 has an airfoil shape with a rounded upper end and a tapering lower end, and the second segment 4322 also has an airfoil shape with a rounded upper end and a tapering lower end. The airfoil cross-section can reduce the wind resistance of the baffle 430, reduce the impact wear of pulverized coal, and allow the airflow to adhere and flow more smoothly on the surface of the baffle 430. The baffle 430 as a whole is a plate-shaped guide that extends radially, and the vertical segment 432 has an airfoil shape in the cross-section perpendicular to its plane.

[0113] Baffle 430 is suitable for applications requiring further improved separation precision, such as when the particle size of pulverized coal needs to be controlled within the range of 0mm~2mm or 0mm~1mm. Compared to traditional impellers, baffle 430 employs a short airfoil or low-resistance linear design, which can improve particle size control while reducing system pressure drop.

[0114] When the target particle size is 0~3mm and low resistance and large diameter are required, the baffle 430 can be omitted, so that the separation component 400 forms a full flow channel; when the target particle size is 0~2mm or 0~1mm, a lower airfoil baffle 430 can be set to enhance the classification.

[0115] When the coal mill is running, raw coal enters the material drop zone 211 in the middle of the grinding disc 210 through the coal feed pipe 800. The drive component 220 drives the grinding disc 210 to rotate, and the grinding disc 210 moves the raw coal outward. Under the action of the adjusting component 240, the grinder 230 forms an appropriate grinding gap and grinding force with the grinding disc 210. After being ground by the grinder 230 and the grinding disc 210, the raw coal is formed into pulverized coal. The pulverized coal moves upward under the action of the airflow supplied by the air supply pipe 300. The finer pulverized coal and some coarser pulverized coal rise along the first channel 500 to the corner space 600, and enter the second channel 700 under the guidance of the guide block 610 or baffle 430 and the teardrop-shaped upper edge 421 of the second cone hopper 420. After entering the second channel 700, larger-sized pulverized coal slides down the inner wall of the second cone hopper 420 due to inertia and gravity, and returns to the grinding disc 210 for further grinding through the lower open end; smaller-sized pulverized coal enters the first cone hopper 410 with the airflow and is discharged through the upper outlet. The controller can adjust the coal feed rate, grinding intensity, and primary ventilation volume according to the coal feed rate, the current of the drive component 220, and the pressure difference between the inlet and outlet air, so that the coal mill can stably output pulverized coal that meets the target particle size requirements.

[0116] The flow guide block 610 and the baffle 430 are flow guide structures in different embodiments, and can be selected according to the target particle size and system resistance requirements.

[0117] By eliminating the baffle 430 or reducing its height, the resistance of the separation component 400 is reduced. Based on the new system resistance characteristics, the primary air pressure is controlled to 40%-70% of the rated air pressure value of traditional pulverizing, which effectively overcomes the system resistance and avoids excessive air pressure from blowing through the material layer of the grinding disc 210 and causing equipment vibration.

[0118] Considering the needs of conveying and drying, the primary air volume is increased to 105%~130% of the traditional pulverizing volume, thereby improving the ability of the mixed gas to convey coarse particles. The primary air is divided into cold primary air and hot primary air. The hot primary air is heated to above 200°C by an air preheater. By adjusting the mixing ratio of cold and hot primary air, the outlet temperature of the coal mill is controlled to be 5°C to 15°C higher than the set value of traditional pulverization, in order to compensate for the decrease in drying capacity caused by the coarsening of coal particles and ensure that the moisture content of the output coal is qualified.

[0119] The loading force applied to the grinder 230 by the adjusting component 240 is reduced to 70%~85% of the traditional value. The larger the target particle size, the lower the loading force setting value should be. This allows the raw coal to be crushed to the target particle size, avoiding over-grinding and the generation of fine powder, thereby reducing the energy consumption and wear of the device.

[0120] The grinding disc 210 operates at 70% to 85% of its rated speed to ensure that the pulverized coal has sufficient grinding time but can be carried away in time.

[0121] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed, and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. The scope of this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described application concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A coal mill, characterized in that, Includes housing (100), grinding assembly (200), air supply duct (300) and separation assembly (400); The grinding assembly (200) is disposed inside the housing (100) and is used to grind raw coal to obtain pulverized coal; The separation assembly (400) includes a first cone (410) and a second cone (420) arranged vertically. The first cone (410) is mounted on the top wall of the housing (100) and has a lower inlet and an upper outlet. The second cone (420) has an upper open end and a lower open end. The lower part of the first cone (410) extends into the second cone (420) through the upper open end, and the lower open end communicates with the grinding assembly (200). The air supply duct (300) is used to supply airflow into the housing (100) so that the airflow carries the pulverized coal through the first channel (500), the corner space (600) and the second channel (700) in sequence and enters the first cone hopper (410). Small-sized pulverized coal is discharged through the upper outlet, and large-sized pulverized coal returns along the inner wall of the second cone hopper (420) and returns to the grinding assembly (200) through the lower open end. The first channel (500) is the channel formed between the side wall of the housing (100) and the outer wall of the second cone (420); the corner space (600) is the space enclosed by the side wall of the housing (100) and the top wall of the housing (100); the second channel (700) is the channel formed between the inner wall of the second cone (420) and the outer wall of the portion of the first cone (410) that extends into the second cone (420).

2. The coal mill according to claim 1, characterized in that, The grinding assembly (200) includes a grinding disc (210) and a grinder (230). The grinding disc (210) is located below the lower open end, and a material dropping area (211) is formed in the middle of the grinding disc (210). The grinder (230) is located between the grinding disc (210) and the lower open end, and the grinder (230) is used to grind the raw coal on the grinding disc (210); The grinding disc (210) is provided with a guide ridge (212), which extends from the edge of the material drop area (211) to the edge of the grinding disc (210), and a guide channel is formed between two adjacent guide ridges (212); A plurality of guide ridges (212) are uniformly arranged along the circumference of the grinding disc (210), and the circumferential distance L between the tops of two adjacent guide ridges (212) does not exceed the height H of the guide ridge (212); The grinding disc (210) is connected to the drive unit (220), which is used to drive the grinding disc (210) to rotate in the vertical direction so that the pulverized coal located in the guide channel leaves the grinding disc (210) under the action of centrifugal force.

3. The coal mill according to claim 2, characterized in that, The guide ridge (212) is arranged along the radial direction of the grinding disc (210); Along the radial direction of the grinding disc (210), the width of the guide ridge (212) along the circumferential direction of the grinding disc (210) gradually increases, so that the circumferential width of the guide channel between two adjacent guide ridges (212) is equal at different radial positions; Along the radial direction of the grinding disc (210), at least one side of the guide ridge (212) is provided with a guide slope.

4. The coal mill according to claim 2, characterized in that, The grinding assembly (200) It also includes an adjusting member (240) for adjusting the distance between the grinder (230) and the grinding disc (210) to adjust the loading force of the grinder (230) on the raw coal.

5. The coal mill according to claim 4, characterized in that, It also includes a controller, which is used to obtain a preset coal feed amount according to the coal feeding instruction, and obtain the load change trend of the grinding component (200) according to the coal feed amount difference between the preset coal feed amount and the current coal feed amount, and adjust at least one of the coal feeding rate and the grinding state of the grinding component (200) according to the load change trend. The controller is also used to compare the real-time current of the drive unit (220) of the grinding assembly (200) with a preset optimal operating current range, and when the real-time current is higher than the upper limit of the preset optimal operating current range, reduce the coal feed rate, and when the real-time current is lower than the lower limit of the preset optimal operating current range, increase the coal feed rate.

6. The coal mill according to claim 5, characterized in that, The controller can also obtain the inlet and outlet pressure difference based on the inlet and outlet pressure of the housing (100), and compare the inlet and outlet pressure difference with the target particle size preset pressure difference range. When the inlet and outlet pressure difference is higher than the upper limit of the target particle size preset pressure difference range, the controller can reduce the loading force of the grinder (230) on the raw coal, increase the ventilation volume of the air supply pipeline (300), and / or increase the rotation speed of the grinding disc (210). When the inlet and outlet pressure difference is lower than the lower limit of the target particle size preset pressure difference range, the controller can increase the loading force of the grinder (230) on the raw coal, reduce the ventilation volume of the air supply pipeline (300), and / or reduce the rotation speed of the grinding disc (210).

7. The coal mill according to claim 1, characterized in that, The coal feed pipe (800) of the coal mill passes through the upper outlet, the lower inlet and the lower open end in sequence and is connected to the grinding assembly (200).

8. The coal mill according to claim 7, characterized in that, The lower end of the coal feed pipe (800) is provided with a protrusion (810), which is arranged along the circumference of the coal feed pipe (800). Along the extension direction of the coal feed pipe (800), the cross section of the protrusion (810) is triangular.

9. The coal mill according to claim 1, characterized in that, A flow guide block (610) is provided in the corner space (600) formed by the side wall and the top wall, and the flow guide block (610) is arranged along the circumference of the housing (100); On a cross section parallel to the axis of the housing, the cross section of the guide block (610) is triangular. The guide block (610) includes a first side wall, a second side wall and a guide wall. The first side wall is connected to the side wall of the housing (100), and the second side wall is connected to the top wall of the housing (100). The guide wall is a concave arc-shaped guide surface facing the second cone (420).

10. The coal mill according to claim 1, characterized in that, The sidewall of the second cone (420) extends obliquely upward from bottom to top toward the corner space (600); On a cross section parallel to the axis of the housing, the upper edge (421) of the second cone (420) is teardrop-shaped, the free end of the upper edge (421) is arc-shaped, and the thickness of the upper edge (421) is greater than the thickness of the side wall of the second cone (420).

11. The coal mill according to claim 1, characterized in that, Multiple baffles (430) are provided in the corner space (600) formed by the side wall and the top wall. The baffles (430) extend from the inner wall of the housing (100) toward the center of the housing (100). The angle between the extension direction of the baffles (430) and the radial direction of the housing (100) is 15°~20°. The baffle (430) includes a horizontal section (431) and a vertical section (432), the horizontal section (431) is connected to the vertical section (432) and extends in a direction perpendicular to the plane in which the vertical section (432) is located; The vertical section (432) includes a first section (4321) connected to the side wall of the housing (100) and a second section (4322) connected to the top wall of the housing (100), and the connection position of the first section (4321) and the second section (4322) is arc-shaped; On a cross section perpendicular to the plane containing the vertical segment (432), the first segment (4321) has an airfoil shape with a rounded upper end and a tapered lower end, and the second segment (4322) has an airfoil shape with a rounded upper end and a tapered lower end.

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