Output control system and method of direct-blowing steel ball mill with automatic compensation function

Abstract

The present invention provides a direct-blowing steel ball coal mill output control system and method with an automatic compensation function. The conventional method of controlling the primary air door opening to adjust the primary air flow at the coal mill inlet to achieve coal mill output control is changed to controlling the primary air fan motor frequency converter to adjust the primary air main pipe pressure to achieve coal mill output control, and the dynamic set value of the primary air pressure is adapted to the unit load command signal and the actual value of the boiler total air volume; the present invention adopts the unit load command change signal, the primary air total air volume change signal and the coal quality correction signal as the feedforward signal of the primary air pressure controller, realizes dynamic compensation of the coal mill primary air pressure control during the load change process or when the coal quality changes, and the coal mill output control is more accurate and timely, meeting the full-operation control needs of the direct-blowing steel ball coal mill.

Description

Technical Field

[0001] The present invention relates to the technical field of output control of a direct-blowing steel ball coal mill, and in particular to an output control system and method for a direct-blowing steel ball coal mill with an automatic compensation function. Background Art

[0002] The statements in this section merely provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Mill output refers to the amount of pulverized coal carried by the primary air in the mill. Direct-fired ball mills inherently require a constant coal charge during operation. Due to the hysteresis associated with coal charge, it's difficult to directly measure or calculate the instantaneous pulverized coal output from the mill in practice. Because the primary air volume entering the mill is directly proportional to mill output, conventional control schemes for direct-fired ball mills control the primary air volume by adjusting the opening of the primary air damper at the mill inlet, thereby adjusting the amount of pulverized coal delivered to the furnace and ultimately controlling mill output.

[0004] However, the inventors found that in the above control scheme, the differential pressure before and after the primary air damper is large during actual operation, especially when the air damper opening is not large, there is a large throttling loss, and the primary fan has a huge waste of electricity; in addition, since the primary air volume measuring device is installed in the primary air duct at the inlet of the pulverizer, the straight pipe is short and the measurement has a certain error. The closed-loop control of the air volume achieved by adjusting the primary air damper opening cannot match the demand for controlling the pulverizer output; even with the same primary air flow rate, the coal volume converted from the primary air volume may deviate from the actual operation due to changes in coal quality. Therefore, the conventional control scheme uses the primary air volume to convert the instantaneous coal powder volume to control the pulverizer output and cannot meet the actual operation requirements of the direct-blowing steel ball mill. Summary of the Invention

[0005] In order to address the deficiencies of the prior art, the present invention provides a direct-blowing steel ball mill output control system and method with an automatic compensation function, which effectively solves the problem of inaccurate load control response of the unit caused by inaccurate measurement of the primary air volume at the mill inlet in conventional control schemes, eliminates the throttling loss caused by adjusting the primary air door of the mill to control the primary air volume, and achieves the purpose of reducing the energy consumption of the primary fan; by designing the unit load command change signal, the total primary air volume change signal and the coal quality correction signal as the feedforward signal of the primary air pressure controller, it quickly responds to the needs of load and coal quality changes, and realizes dynamic compensation of the mill output control during variable load or when the coal quality changes.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a direct-blowing ball mill output control system with an automatic compensation function.

[0008] A direct-blowing steel ball mill output control system with an automatic compensation function includes: a primary air pressure controller, a small value selector, a large value selector, a first divider, a second divider, a limiter, and a fifth function generator;

[0009] The minimum value selector is used to select and output the maximum value of the first primary air pressure process set value and the second primary air pressure process set value as the primary air pressure set value, and the maximum value selector is used to select and output the maximum value of the first primary air pressure process feedforward signal and the second primary air pressure process feedforward signal, and the primary air pressure controller calculates and outputs the difference between the primary air pressure set value and the primary air pressure measured value;

[0010] The calorific value of the coal fed into the furnace and the amount of coal fed into the furnace are divided by the first divider to generate the actual calorific value per unit of coal type, which is then divided by the second divider to generate the calorific value correction coefficient. The fifth function generator receives the data of the calorific value correction coefficient after passing through the limiter.

[0011] The output of the primary air pressure controller, the output of the maximum value selector and the output of the fifth function generator are superimposed by the adder and used as the input of the primary fan motor inverter to perform frequency conversion control of the primary fan speed, ultimately achieving primary air pressure control.

[0012] As a further limitation of the first aspect of the present invention, it further includes a first filtering module and a first function generator, and the total air volume data of the boiler supply air is sequentially passed through the first filtering module and the first function generator to obtain a first primary air pressure process set value.

[0013] As a further limitation of the first aspect of the present invention, the system further includes a second filtering module and a second function generator, and the unit load instruction is sequentially processed by the second filtering module and the second function generator to obtain a second primary wind pressure process set value.

[0014] As a further limitation of the first aspect of the present invention, the present invention further includes a third filtering module, and the measured value of the primary wind pressure is obtained after the measured value of the primary wind pressure passes through the third filtering module.

[0015] As a further limitation of the first aspect of the present invention, it also includes a first differential controller, a fourth filtering module and a third function generator. The total air volume data of the primary air main pipe passes through the first differential controller, the fourth filtering module and the third function generator in sequence to obtain a first primary air pressure process feedforward signal.

[0016] As a further limitation of the first aspect of the present invention, it also includes a second differential controller, a fifth filtering module and a fourth function generator. The unit load instruction passes through the second differential controller, the fifth filtering module and the fourth function generator in sequence to obtain a second primary air pressure process feedforward signal.

[0017] In a second aspect, the present invention provides a method for controlling the output of a direct-blowing steel ball mill with an automatic compensation function.

[0018] A method for controlling the output of a direct-blowing steel ball mill with an automatic compensation function includes the following steps:

[0019] The minimum value selector selects and outputs the maximum value of the first primary air pressure process set value and the second primary air pressure process set value as the primary air pressure set value, the maximum value selector selects and outputs the maximum value of the first primary air pressure process feedforward signal and the second primary air pressure process feedforward signal, and the primary air pressure controller calculates and outputs the difference between the primary air pressure set value and the primary air pressure measured value;

[0020] The calorific value of the coal fed into the furnace and the amount of coal fed into the furnace are divided by the first divider to generate the actual calorific value per unit of coal type, which is then divided by the second divider to generate the calorific value correction coefficient. The fifth function generator receives the data of the calorific value correction coefficient after passing through the limiter.

[0021] The output of the primary air pressure controller, the output of the maximum value selector and the output of the fifth function generator are superimposed by the adder and used as the input of the primary fan motor inverter to perform frequency conversion control of the primary fan speed, ultimately achieving primary air pressure control.

[0022] As a further limitation of the second aspect of the present invention, the total air supply volume data is sequentially passed through the first filtering module and the first function generator to obtain the first primary air pressure process setting value; the unit load instruction is sequentially passed through the second filtering module and the second function generator to obtain the second primary air pressure process setting value.

[0023] As a further limitation of the second aspect of the present invention, the measured value of the primary wind pressure is obtained after passing through a third filtering module.

[0024] As a further limitation of the second aspect of the present invention, the total air volume data of the primary air main pipe is sequentially passed through the first differential controller, the fourth filtering module and the third function generator to obtain a first primary air pressure process feedforward signal, and the unit load instruction is sequentially passed through the second differential controller, the fifth filtering module and the fourth function generator to obtain a second primary air pressure process feedforward signal.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention innovatively proposes a direct-blowing steel ball mill output control strategy with automatic compensation function. The mill output is achieved by controlling the primary fan motor inverter to adjust the primary air main pipe pressure. The dynamic set value of the primary air pressure is adapted to the unit load command signal and the actual value of the boiler total air supply volume. The air supply volume required by the actual mill output is less than the actual boiler total air supply volume to prevent oxygen-deficient combustion in the boiler. This solves the problem of inaccurate unit load control response caused by inaccurate mill inlet air volume measurement in conventional control schemes, eliminates the throttling loss of the mill primary air door, and reduces the energy consumption of the primary fan.

[0027] 2. The present invention innovatively proposes a direct-blowing ball mill output control strategy with automatic compensation function. By designing the unit load instruction change signal and the primary air total air volume change signal as the feedforward signal of the primary air pressure controller, the coal mill output can be quickly responded to and controlled during the load change process.

[0028] 3. The present invention innovatively proposes a direct-blowing steel ball mill output control strategy with automatic compensation function, designs a calorific value correction coefficient as a feedforward signal for primary air pressure control, and realizes dynamic compensation of mill output control when coal quality changes.

[0029] 4. The present invention innovatively proposes an output control strategy for a direct-blowing ball mill with an automatic compensation function. The strategy is applicable to various boiler control systems, such as DCS (Distributed Control System) or PLC (Programmable Logic Controller). The strategy is easy to configure and has good application prospects.

[0030] Advantages of additional aspects of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0032] Figure 1 This is a structural diagram of the output control system of a direct-blowing ball mill with automatic compensation function provided in Example 1 of the present invention.

[0033] Among them, 1. primary air pressure controller; 2. first filter module; 3. first function generator; 4. second filter module; 5. second function generator; 6. minimum value selector; 7. third filter module; 8. first differential controller; 9. fourth filter module; 10. third function generator; 11. second differential controller; 12. fifth filter module; 13. fourth function generator; 14. maximum value selector; 15. first divider; 16. second divider; 17. limiter; 18. fifth function generator; 19. adder; 20. primary fan inverter. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0036] In the absence of conflict, the embodiments of the present invention and the features thereof may be combined with each other.

[0037] Example 1:

[0038] like Figure 1 As shown, embodiment 1 of the present invention provides a direct-blowing steel ball mill output control system with an automatic compensation function, comprising:

[0039] A primary air pressure controller 1, a first filter module 2, a first function generator 3, a second filter module 4, a second function generator 5, a small value selector 6, a third filter module 7, a first differential controller 8, a fourth filter module 9, a third function generator 10, a second differential controller 11, a fifth filter module 12, a fourth function generator 13, a large value selector 14, a first divider 15, a second divider 16, a limiter 17, a fifth function generator 18, an adder 19, and a primary fan frequency converter 20;

[0040] The minimum value selector 6 is used to select and output the maximum value of the first primary air pressure process set value and the second primary air pressure process set value as the primary air pressure set value, the maximum value selector 14 is used to select and output the maximum value of the first primary air pressure process feedforward signal and the second primary air pressure process feedforward signal, and the primary air pressure controller 1 calculates and outputs the difference between the primary air pressure set value and the measured primary air pressure value;

[0041] The calorific value of the coal fed into the furnace and the amount of coal fed into the furnace are divided by the first divider 15 to generate the actual calorific value per unit of the coal type. The actual calorific value per unit of the coal type is then divided by the second divider 16 to generate the calorific value correction coefficient. The fifth function generator 18 receives the data of the calorific value correction coefficient after passing through the limiter 17.

[0042] The output of the primary air pressure controller 1, the output of the maximum value selector 14 and the output of the fifth function generator 18 are superimposed by the adder 19 and used as the input of the primary fan motor inverter 20 to perform frequency conversion control of the primary fan speed, ultimately achieving primary air pressure control;

[0043] The total air volume data of the air supply is sequentially passed through the first filtering module 2 and the first function generator 3 to obtain the first primary air pressure process setting value;

[0044] The unit load instruction passes through the second filtering module 4 and the second function generator 5 in sequence to obtain the second primary air pressure process set value, and the primary air pressure measured value passes through the third filtering module 7 to obtain the primary air pressure measured value.

[0045] The total air volume data of the primary air main pipe is sequentially passed through the first differential controller 8, the fourth filter module 9 and the third function generator 10 to obtain the first primary air pressure process feedforward signal;

[0046] The unit load instruction passes through the second differential controller 11, the fifth filtering module 12 and the fourth function generator 13 in sequence to obtain a second primary air pressure process feedforward signal.

[0047] Example 2:

[0048] Embodiment 2 of the present invention provides a method for controlling the output of a direct-blowing steel ball mill with an automatic compensation function, comprising the following steps:

[0049] The primary air pressure controller 1 controls the primary fan inverter 20 to adjust the primary air main pipe pressure based on the deviation between the primary air pressure set value and the measured primary air pressure value. The total air volume data is filtered and then passed through the first function generator 3 to generate a first primary air pressure process set value. This is then combined with the unit load command function and passed through the second function generator 5 to generate a second primary air pressure process set value. The above two primary air pressure process set values ​​are passed through the minimum value selector 6 to be used as the primary air pressure set value.

[0050] The unit load command change signal, the total primary air volume change signal and the coal quality correction signal are used as the feedforward signal of the primary air pressure controller to realize dynamic compensation of the pulverizer output control during the load change process or when the coal quality changes.

[0051] Specifically, the control method includes:

[0052] The variation data of the total primary air volume is filtered and then passed through the third function generator 10 to generate a first primary air pressure process feedforward signal. The variation data of the unit load instruction is passed through the fourth function generator 13 to generate a second primary air pressure process feedforward signal. The above two process feedforward signals are passed through the maximum value selector and serve as the feedforward signals of the primary air pressure controller 1.

[0053] The calorific value of the coal fed into the furnace over a certain period of time and the amount of coal fed into the furnace are divided by the first divider 15 to generate the actual calorific value per unit of the coal type. The actual calorific value per unit of the coal type is then divided by the second divider 16 to generate the calorific value correction coefficient. The fifth function generator 18 receives the data of the calorific value correction coefficient after passing through the limiter 17. The output signal of the fifth function generator 18 serves as the feedforward signal of the primary air pressure controller 1.

[0054] The total primary air volume, primary air pressure measurement data, coal feeding amount, and designed unit calorific value of coal type are introduced into the DCS system. The calorific value data of coal feeding into the furnace comes from the performance calculation module within the DCS, and the output control logic of the direct-blowing steel ball mill with automatic compensation function is used.

[0055] Specifically, the process includes the following:

[0056] Keep the primary air damper at the coal mill inlet in the fully open position during operation;

[0057] The introduction of differential control can easily cause the regulation system to oscillate, causing the inverter to operate frequently and the primary air pressure to fluctuate. This design method takes into account the feedforward signal of the primary air pressure control, so the primary air pressure controller adopts a PI (proportional integral) controller;

[0058] The filtering time of the first filtering module and the third filtering module is set to 5 seconds; the filtering time of the second filtering module is set to 12 seconds; the filtering time of the fourth filtering module and the fifth filtering module is set to 2 seconds.

[0059] According to the above scheme, the output control logic of the direct-blowing steel ball mill with automatic compensation function is designed in the DCS configuration software;

[0060] After the control logic is compiled and checked by the DCS configuration software, it is downloaded to the DCS controller;

[0061] A primary air pressure controller is designed in the screen of the DCS operator station so that the unit operating personnel can manually correct the controller setting parameters, set the offset, and switch between manual / automatic states on the DCS screen.

[0062] When the primary air pressure is subjected to a disturbance test with a constant value of 10% of the rated pressure, the transition process attenuation rate ψ should be 0.9 to 0.95, and the stabilization time is required to be less than 20s.

[0063] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A direct-blowing ball mill output control system with automatic compensation function, It is characterized by: include: a primary air pressure controller, a small value selector, a large value selector, a first divider, a second divider, a limiter, and a fifth function generator; The minimum value selector is used to select and output the maximum value of the first primary air pressure process set value and the second primary air pressure process set value as the primary air pressure set value, and the maximum value selector is used to select and output the maximum value of the first primary air pressure process feedforward signal and the second primary air pressure process feedforward signal. The primary air pressure controller calculates and outputs the difference between the primary air pressure set value and the filtered primary air pressure measured value; The calorific value of the coal fed into the furnace and the amount of coal fed into the furnace are divided by the first divider to generate the actual calorific value per unit of coal type, which is then divided by the second divider to generate the calorific value correction coefficient. The fifth function generator receives the data of the calorific value correction coefficient after passing through the limiter. The output of the primary air pressure controller, the output of the maximum value selector and the output of the fifth function generator are superimposed and used as the input of the primary fan motor frequency converter to perform frequency conversion control of the primary fan speed, ultimately achieving primary air pressure control; The device further comprises a first filtering module and a first function generator, wherein the total air volume data of the air supply is sequentially passed through the first filtering module and the first function generator to obtain a first primary air pressure process set value; It also includes a second filtering module and a second function generator, and the unit load instruction is sequentially passed through the second filtering module and the second function generator to obtain a second primary air pressure process set value; The third filter module is further included, and the measured primary wind pressure value is filtered by the third filter module to obtain the measured primary wind pressure value; The system further includes a first differential controller, a fourth filtering module, and a third function generator. The total air volume data of the primary air main pipe is sequentially passed through the first differential controller, the fourth filtering module, and the third function generator to obtain a first primary air pressure process feedforward signal. It also includes a second differential controller, a fifth filtering module and a fourth function generator. The unit load instruction passes through the second differential controller, the fifth filtering module and the fourth function generator in sequence to obtain a second primary air pressure process feedforward signal.

2. A method for controlling the output of a direct-blowing steel ball mill with an automatic compensation function, characterized in that: The minimum value selector selects and outputs the maximum value of the first primary air pressure process set value and the second primary air pressure process set value as the primary air pressure set value, the maximum value selector selects and outputs the maximum value of the first primary air pressure process feedforward signal and the second primary air pressure process feedforward signal, and the primary air pressure controller calculates and outputs the difference between the primary air pressure set value and the filtered primary air pressure measured value; The calorific value of the coal fed into the furnace and the amount of coal fed into the furnace are divided by the first divider to generate the actual calorific value per unit of coal type, which is then divided by the second divider to generate the calorific value correction coefficient. The fifth function generator receives the data of the calorific value correction coefficient after passing through the limiter. The output of the primary air pressure controller, the output of the maximum value selector and the output of the fifth function generator are superimposed by the adder and used as the input of the primary fan motor frequency converter for frequency conversion control; The total air volume data of the air supply is sequentially passed through the first filtering module and the first function generator to obtain the first primary air pressure process setting value; The unit load instruction is sequentially passed through the second filtering module and the second function generator to obtain the second primary air pressure process set value; The measured value of the primary wind pressure is filtered by the third filtering module to obtain the measured value of the primary wind pressure; The total air volume data of the primary air main pipe passes through the first differential controller, the fourth filtering module and the third function generator in sequence to obtain the first primary air pressure process feedforward signal. The unit load instruction passes through the second differential controller, the fifth filtering module and the fourth function generator in sequence to obtain the second primary air pressure process feedforward signal.

Images