System and method for controlling coal seam thickness of coal mill in negative-pressure pulverizing process

Abstract

The invention discloses a system and a method for controlling the thickness of a coal seam of a coal mill in a negative-pressure pulverizing process. Comprising a programmable logic controller (PLC) and a core carrier used for receiving signals in a processing system; the constant feeder is used for supplying coal to the coal mill under the control of the PLC; the coal mill is used for milling the coal input by the constant feeder; the coal mill comprises a coal mill main body, a millstone is arranged in the coal mill main body, and a milling roller is arranged on the millstone through a carrier; the loading frame applies pressure to the grinding roller through the three hydraulic cylinders and the pull rod; the distance measuring device is used for measuring the distance between at least one pull rod and the ground; and the PLC is used for controlling the coal supply quantity of the constant feeder according to the measurement result of the distance measuring device. The laser range finder is used for detecting the position of the coal mill grinding roller to judge the coal seam thickness, and therefore automatic control over the coal seam can be achieved.

Description

Technical Field

[0001] The present invention relates to a system and method for controlling the coal bed thickness of a coal mill in a negative pressure coal powder preparation process. Background Art

[0002] Coal powder preparation is a key link in industrial fields such as cement plants and ironmaking plants, and the coal mill is the core equipment;

[0003] Existing coal mills, such as Figure 4 As shown, the motor drives the grinding table to rotate through the main speed reducer, and the rotation of the grinding table drives three evenly distributed grinding rollers (with a 120° angle) to rotate self - sufficiently. Raw coal enters the grinding table from the coal dropping pipe. Under the action of centrifugal force, it moves along the radial direction to the edge of the grinding table and evenly enters the grinding table roller path. Subsequently, under the interaction between the grinding roller and the grinding table tile, the raw coal is effectively ground. The grinding pressure is transmitted to the coal mill foundation through the loading frame above the grinding roller and three tie rods (hydraulic cylinders).

[0004] The coal bed control level of this kind of coal mill directly affects the grinding capacity and coal powder quality, and further affects the combustion efficiency and the operation stability of the production line. A reasonable coal bed thickness can ensure that the grinding components are evenly stressed, avoiding vibration of the mill caused by too thin a coal bed or overload and tripping of the high - voltage main motor caused by too thick a coal bed. At present, most coal powder preparation workshops mainly rely on manual experience or simple camera monitoring of the grinding roller scale to control the coal bed, making it difficult to adjust the coal bed thickness in real - time, resulting in severe grinding fluctuations and increased equipment wear. At the same time, the low automation level also increases the labor cost of production and the economic cost of stopping the mill for coal cleaning. Summary of the Invention

[0005] In order to overcome the above problems, the purpose of the present invention is to provide a system for controlling the coal bed thickness of a coal mill for negative pressure coal powder preparation process. It improves the intelligence and precision of coal bed control and provides a more efficient and stable solution for industrial production.

[0006] To achieve the above - mentioned purpose, the system for controlling the coal bed thickness of a coal mill for negative pressure coal powder preparation process of the present invention includes:

[0007] A programmable logic controller PLC, which is the core carrier for receiving and processing signals within the system;

[0008] A quantitative feeder, which is used to supply coal to the coal mill under the control of the PLC;

[0009] A coal mill, which is used to grind the coal input by the quantitative feeder;

[0010] The described coal mill includes a coal mill main body, a grinding table is arranged inside the coal mill main body, and grinding rollers are arranged on the grinding table through a loading frame; pressure is applied to the grinding rollers through three hydraulic cylinders and tie rods on the loading frame;

[0011] It further includes a ranging device for measuring the distance of at least one drawbar relative to the ground;

[0012] The programmable logic controller PLC controls the coal supply amount of the constant - rate feeder according to the measurement result of the ranging device.

[0013] Furthermore, it further includes:

[0014] The constant - rate feeder measures the difference between the current coal supply amount and the set coal supply amount through a dynamic scale, and controls the frequency change of the frequency converter of the constant - rate feeder.

[0015] Furthermore, a powder collector is arranged on the coal mill, and a variable - frequency tail - exhaust fan is arranged downstream of the powder collector to provide air volume and negative pressure for the system.

[0016] Furthermore, the ranging device includes a target mirror installed parallel to the ground at the L grinding roll drawbar, and a laser rangefinder is installed at the projection position.

[0017] Furthermore, a pressure transmitter is installed between the coal mill and the powder collector; an averaging pitot tube flowmeter and a differential pressure transmitter are installed in front of the hot air inlet of the coal mill and the regulating valve at the tail - exhaust inlet.

[0018] To achieve the above - mentioned purpose, the control method for the coal bed thickness of the coal mill in the negative - pressure powder - making process of the present invention includes the following steps:

[0019] S1: The HMI interface switches the coal mill, fan, and feeder to the automatic mode, sets the target coal bed thickness, target system air volume, and target negative pressure, and closes the tail - exhaust inlet regulating valve to an opening degree below 15%;

[0020] S2: After the high - voltage variable - frequency fan starts successfully, fully open the regulating valve, and the fan automatically adjusts the frequency according to the set target air volume until the actual air volume reaches near the target value;

[0021] S3: After the air volume is stable, switch the inlet regulating valve to the automatic mode, and the valve automatically adjusts the system negative pressure according to the set pressure;

[0022] S4: After the primary air volume and primary air pressure are established, the coal mill system and the constant - rate feeder are successively started automatically;

[0023] S5: The constant - rate feeder continuously adjusts the set coal supply amount according to the coal bed thickness measured by the laser rangefinder, and the dynamic scale then adjusts the frequency change of the frequency converter according to the difference between the set coal supply amount and the actual weighing value.

[0024] Furthermore, it further includes the following steps:

[0025] S6: When the radar level gauge on the top of the raw coal bunker shows that the raw coal is too little, the automatic feeding system starts to operate, replenishing the raw coal into the bunker, which includes the interlocking actions of a large-angle belt conveyor, two wide belt scales, and two vibrating motors in the ground bunker. And the automatic feeding system can be switched back to manual shutdown at any time. The beneficial effects of the present invention are as follows:

[0026] (1) The automatic adjustment of the coal bed control system enables the coal mill to operate at a more reasonable coal bed thickness, ensuring uniform stress on the grinding components, and avoiding vibration grinding caused by too thin a coal bed or overload trip of the high-voltage main motor caused by too thick a coal bed.

[0027] (2) Get rid of the high dependence on the technical level of operators in the current mainstream control method, and reduce the labor cost of production.

[0028] (3) Improve the real-time performance of the production line control, avoid or reduce violent grinding fluctuations and equipment wear, improve the combustion efficiency and production stability, and expand the economic benefits.

[0029] (4) Reduce the possibility of manual grinding cleaning due to sudden stop of the coal mill, greatly reduce the number of times personnel need to enter the coal mill during non-maintenance periods, and improve production safety.

[0030] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification. It will be obvious to those skilled in the art based on the following investigation and research, or can be inspired from the practice of the present invention. Brief Description of the Drawings

[0031] Figure 1 It is a system schematic diagram of the coal bed thickness control of the negative pressure powder grinding process coal mill of the present invention.

[0032] Figure 2 It is an installation schematic diagram of the laser rangefinder installed on the grinding roller of the present invention.

[0033] Figure 3(a) - Partial screenshot of the metering feeder and the tail exhaust fan

[0034] Figure 3(b) - Partial screenshot of the inlet regulating valve of the tail exhaust fan

[0035] Figure 3(c) - Partial screenshot of the automatic feeding system

[0036] Figure 4 It is a structural schematic diagram of an existing coal mill. Detailed Embodiments

[0037] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0038] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention.

[0039] The terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0040] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] In the description of the present invention, it should be noted that in actual working conditions, necessary lubrication stations, hydraulic stations, seal fans, nitrogen security systems, etc. for the operation of the coal mill, as well as the operation of the cooling fans necessary before the start of the high-pressure tail exhaust fan, and the like. For those of ordinary skill in the art, the operating conditions and processes are obvious and have little relevance to the present invention. Therefore, the present invention does not separately describe such devices or systems.

[0042] The following Figure 1 Figure 2 and embodiments further illustrate the present invention in detail.

[0043] A system for controlling the coal bed thickness of a coal mill in a negative pressure pulverizing process includes a programmable logic controller, a medium-speed vertical coal mill, a laser rangefinder, a metering feeder, an automatic feeding system, a variable-frequency tail exhaust fan and its inlet regulating valve, and also includes several detection instruments and an HMI interactive interface.

[0044] The installation method of the said laser rangefinder, as Figure 2As shown. A target mirror is installed parallel to the floor at the pull rod scale of the coal mill roller, and a laser rangefinder is installed perpendicular to the target mirror. The position of the target mirror is measured during the 10 cm travel of the roller. The difference between the lowest point of the target mirror and the measured value is used as the current coal seam thickness. If the equipment cost is not considered, the rangefinder can be installed at the three rollers of the vertical mill at an angle of 120 degrees to prevent or reduce the measurement error caused by the vibration of the coal mill. The average value can be used as the coal seam thickness in data processing.

[0045] The feeding port of the quantitative feeder is connected to the feeding port of the coal mill, and quantitative feeding is achieved by measuring the real-time weight with an instrument scale and then controlling the speed of the belt motor with a frequency converter.

[0046] The high-pressure tail exhaust fan is frequency-controlled, and the system air volume is automatically adjusted by changing the frequency setting. The regulating valve is connected to the fan inlet and used as a fan regulating damper to achieve stable changes in the system negative pressure.

[0047] The automatic feeding system is equipped with a wide belt scale at the discharge port of the pit, connected to a high-angle belt conveyor. When the material replenishment signal comes, the high-angle belt conveyor starts first, and then automatically starts the corresponding wide belt scale according to the pit selected for operation, and starts to run materials to the raw coal bin. When the radar level meter sends a full material signal, the belt scale stops first, and then the high-angle belt conveyor stops after a certain delay. If the high-angle belt stops suddenly due to an accident, the belt scale will stop urgently.

[0048] The several instruments mentioned above include a flange pressure transmitter installed on the DN2000 pipe at the mill outlet to measure the primary negative pressure at the mill outlet; an average-speed tube flowmeter and a micro-differential pressure transmitter are installed at the hot air inlet of the mill and in front of the tail exhaust inlet regulating valve to measure the system air volume. Generally speaking, the two values are approximate. The primary air volume of the mill is used as the automatic adjustment parameter of the tail exhaust fan, and the difference between the tail exhaust fan inlet air volume and the system primary air volume is used as an indication signal of whether the powder collector is blocked.

[0049] The programmable logic controller is Siemens PLC S7-1516, and the HMI interactive screen is drawn by WinCC7.5SP2.12.

[0050] The system for controlling the thickness of coal seam in a negative pressure pulverizing process coal mill is characterized by comprising the following steps:

[0051] S1: On the HMI interface, set the coal mill, fan and feeder to automatic mode, set the target coal seam thickness, target system air volume and target negative pressure, close the tail discharge inlet regulating valve to below 15% opening and click the system start button.

[0052] S2: After the high-pressure variable frequency fan is successfully started, the regulating valve is fully opened, and the fan automatically adjusts the frequency according to the set target air volume until the actual air volume reaches near the target value.

[0053] S3: After the air volume is stable, turn the inlet control valve to the automatic mode, and the valve automatically adjusts the system negative pressure according to the set pressure.

[0054] S4: After the primary air volume and primary air pressure are established, the coal mill system and the constant rate feeder are automatically started in sequence.

[0055] S5: The constant rate feeder continuously adjusts the set coal feeding amount according to the coal seam thickness measured by the laser rangefinder, and the dynamic scale adjusts the frequency change of the frequency converter according to the difference between the set coal feeding amount and the actual weighing value.

[0056] S6: When the radar level gauge on the top of the raw coal bunker shows that the raw coal is too little, the automatic feeding system starts to operate to supplement the raw coal into the bunker, which includes the interlocking actions of a large angle belt conveyor, two wide belt scales, and two ground bunker vibration motors. And the automatic feeding system can be switched back to manual shutdown at any time.

[0057] In the description of this specification, the specific features, structures, materials, or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0058] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A system for controlling the coal bed thickness of a coal mill in a negative pressure powder-making process, characterized in that, Including: A programmable logic controller (PLC), which is the core carrier for receiving and processing signals within the system; A constant feeder, which is used to supply coal to the coal mill under the control of the PLC; A coal mill, which is used to grind the coal input by the constant feeder; The described coal mill includes a coal mill body, a grinding table is arranged inside the coal mill body, and grinding rollers are arranged on the grinding table through a loading rack; pressure is applied to the grinding rollers through three hydraulic cylinders and tie rods on the loading rack; It further includes a ranging device, which is used to measure the distance of at least one tie rod relative to the ground; The described programmable logic controller (PLC) controls the coal supply amount of the constant feeder according to the measurement result of the ranging device.

2. The system for controlling the coal bed thickness of a coal mill in a negative pressure powder grinding process according to claim 1, wherein, Including: The described constant feeder weighs the difference between the current coal supply amount and the set coal supply amount through a dynamic scale, and controls the frequency change of the frequency converter of the constant feeder.

3. The system for controlling the coal bed thickness of a coal mill in a negative pressure powder grinding process according to claim 1, characterized in that, A powder collector is arranged on the coal mill, and a variable-frequency tail exhaust fan is arranged downstream of the powder collector to provide air volume and negative pressure for the system.

4. The system for controlling the coal bed thickness of a coal mill in a negative pressure powder grinding process according to claim 1, characterized in that, The described ranging device includes a target mirror installed parallel to the ground at the position of the tie rod of the L grinding roller, and a laser rangefinder is installed at the projection position.

5. The system for controlling the coal bed thickness of a coal mill in a negative pressure powder grinding process according to claim 1, wherein, A pressure transmitter is installed between the coal mill and the powder collector; an averaging pitot tube flowmeter and a differential pressure transmitter are installed in front of the hot air inlet of the coal mill and the regulating valve at the tail exhaust inlet.

6. A control method for the coal bed thickness of a coal mill in a negative pressure powder grinding process, characterized in that, Including the following steps: S1: The HMI interface switches the coal mill, the fan, and the feeder to the automatic mode, sets the target coal seam thickness, the target system air volume, and the target negative pressure, and closes the regulating valve at the tail exhaust inlet to an opening below 15%; S2: After the high-voltage variable-frequency fan is successfully started, fully open the regulating valve, and the fan automatically adjusts the frequency according to the set target air volume until the actual air volume reaches near the target value; S3: After the air volume is stable, switch the inlet regulating valve to the automatic mode, and the valve automatically adjusts the system negative pressure according to the set pressure; S4: After the primary air volume and the primary air pressure are established, the coal mill system and the constant feeder are successively automatically started; S5: The constant feeder continuously adjusts the set coal supply amount according to the coal seam thickness measured by the laser rangefinder, and the dynamic scale then adjusts the frequency change of the frequency converter according to the difference between the set coal supply amount and the actual weighing value.

7. The control method for the coal bed thickness of the coal mill in the negative pressure pulverizing process according to claim 6, characterized in that, It further includes the following steps: S6: When the radar level gauge on the top of the raw coal bunker shows that the raw coal is too little, the automatic feeding system starts to operate to supplement the raw coal into the bunker, which includes the interlocking operation of a large-angle belt conveyor, two wide belt scales, and two vibrating motors for the ground material pits. And the automatic feeding system can be switched back to manual shutdown at any time.

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