A unit control system and method based on real-time online analysis of coal quality

Abstract

The present invention discloses a unit control system and method based on real-time online analysis of coal quality, the system includes a raw coal hopper, a raw coal hopper outlet pipeline, a coal feeder belt, a weighing instrument, a coal feeder variable speed motor, a coal feeder outlet pipeline, a coal mill, a coal mill inlet primary air pipeline, a primary air volume measuring element, a boiler furnace, a coal quality online monitoring module, a coal feeder controller, a blower, a blower variable output element, an air supply pipeline, a secondary air volume measuring element and a secondary air controller. The method uses the available online data of incoming coal that meets the needs of real-time operation control to achieve accurate fuel and air distribution of thermal power units, and has significant practical value.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal power station automatic control, and in particular relates to a unit control system and method based on real-time online analysis of coal quality. Background Art

[0002] At present, my country's thermal power units generally experience frequent and drastic changes in coal quality and even coal types. Coupled with the lag in coal quality measurement, this seriously affects the process control of thermal power units, especially the setting of key parameters of the fuel and air distribution systems.

[0003] In the existing coordinated control of thermal power units, simple closed-loop control is generally used for the calorific value correction of the fuel system. The actual total coal quantity is multiplied by the calorific value correction coefficient to obtain the corrected coal quantity as the regulated quantity, and the standard coal quantity corresponding to the unit load is used as the set value. The two are sent to the PID controller. Through deviation adjustment, the corrected coal quantity is made close to the standard coal quantity under the corresponding load. In this process, the calorific value correction coefficient is gradually corrected to meet the fuel demand under various loads, such as Figure 1 shown.

[0004] In traditional combustion control, a similar control concept is also used for oxygen correction in the air distribution link. The regulated quantity is the oxygen content of the flue gas at the economizer outlet. The PID controller is used to track different oxygen set values ​​under various loads, so as to try to find an oxygen correction coefficient that meets the actual oxygen demand, such as Figure 2 shown.

[0005] The above control process has the following problems:

[0006] 1. Poor real-time correction. In the calorific value correction, since it takes a long time for the fuel to be fully burned in the furnace and enter the turbine to do work, and the amount of fuel as the regulated quantity is also lagging for the unit load, the real-time deviation is an unavoidable problem when adjusting based on these two. In the oxygen correction, the oxygen content of the flue gas at the economizer outlet is used as the regulated quantity. The combustion process that produces the obtained oxygen value has already ended at the time of measurement. For the air distribution of the boiler, it is also a seriously lagging control process.

[0007] 2. Poor calibration matching. Poor calibration real-time performance will result in the calibration parameters obtained at a certain moment calibrating the operation process at another moment, which will inevitably lead to poor matching of the control system's coal supply and air distribution, and the actual operation will deviate from the optimal fuel demand and air-coal ratio. In addition, the hysteresis and inaccuracy of oxygen measurement also greatly reduce the effect of oxygen calibration.

[0008] 3. Continuous fluctuations in correction. Improper fuel and air ratios during real-time operation may cause a vicious expansion of deviations in the actual process, and the correction coefficient will also fluctuate for a long time, making it difficult to stabilize quickly.

[0009] 4. Impact on other indicators. Fuel and air distribution are important factors in the coordination of units and boiler combustion. Their accuracy and stability have a significant impact on key parameters of the unit such as main steam pressure and main steam temperature, as well as important indicators such as the unit's variable load capacity. The impact on denitrification and environmental protection indicators is also inevitable.

[0010] In summary, under the actual conditions of coal quality fluctuations and delayed coal quality measurement in my country's thermal power units, the control logic of the traditional coordination system and combustion system cannot fundamentally achieve real-time optimal correction of fuel and air distribution, and thus cannot obtain more accurate coordination and combustion control effects. This has become a key problem that needs to be solved urgently. Summary of the invention

[0011] In view of the above problems existing in the prior art, the present invention provides a unit control system and method based on real-time online analysis of coal quality. Through the available online data of coal quality entering the furnace that meets the needs of real-time operation control, accurate fuel and air distribution of thermal power units can be achieved, which has significant practical value.

[0012] The present invention is achieved by adopting the following technical solutions:

[0013] A unit control system based on real-time online analysis of coal quality, including a coal feeder belt, a weighing instrument, a coal feeder variable speed motor, a coal feeder outlet pipeline, a coal mill, a primary air pipeline at the coal mill inlet, a primary air volume measurement element, a boiler furnace, a coal quality online monitoring module, a coal feeder controller, a blower, a blower variable output element, an air pipeline, a secondary air volume measurement element and a secondary air controller; wherein,

[0014] A weighing instrument is installed under the coal feeder belt, the coal feeder variable speed motor is connected to the coal feeder belt, the coal feeder outlet pipe at the tail end of the coal feeder belt and the primary air pipe at the coal mill inlet are both connected to the coal mill, the primary air volume measuring element is arranged on the primary air pipe at the coal mill inlet, the blower is connected to the boiler furnace through the air pipe, the secondary air volume measuring element is arranged on the air pipe, and the blower variable output element is connected to the blower;

[0015] The output end of the coal quality online monitoring module and the output end of the weighing instrument of the coal feeder belt are both connected to the input end of the coal feeder controller, and the output end of the coal feeder controller is connected to the control end of the coal feeder variable speed motor, which is used to drive the coal feeder belt transmission;

[0016] The output end of the coal quality online monitoring module is also connected to the input end of the secondary air controller together with the output ends of the primary air volume measuring element and the secondary air volume measuring element. The output end of the secondary air controller is connected to the control end of the fan variable output element. The fan variable output element is used to change the air volume of the fan.

[0017] A unit unit control method based on real-time online analysis of coal quality, the method is based on the above-mentioned unit unit control system based on real-time online analysis of coal quality, comprising:

[0018] The variable speed motor of the coal feeder changes the speed of the variable speed motor according to the needs of the unit, drives the coal feeder belt to rotate, and sends the coal on the coal feeder belt to the coal mill. During this process, the weighing instrument on the coal feeder belt performs real-time weighing and records the actual coal feeding amount of the unit. The coal quality online monitoring module outputs the calorific value of the coal, compares it with the calorific value of the standard coal, and outputs real-time and accurate coal feeding correction parameters. Together with the actual coal feeding amount, it is sent to the coal feeding controller for correction of the coal feeding amount. The coal feeding controller obtains the calibrated coal feeder control instruction, guides the operation of the variable speed motor of the coal feeder, and realizes real-time control of the coal feeding according to the calorific value of the coal.

[0019] The variable output element of the blower changes the air volume according to the needs of the unit unit and sends it to the boiler furnace to provide an appropriate amount of combustion-supporting air for combustion. The primary air volume measurement element on the primary air duct at the inlet of the coal mill monitors the primary air volume entering the coal mill in real time. The coal quality online monitoring module outputs the calorific value of the coal entering the furnace, and uses it together with the primary and secondary air volumes as known parameters to perform the following calculations:

[0020] The calorific value of the coal entering the furnace is compared with the calorific value of the standard coal, and the amount of coal entering the furnace is corrected to the standard coal amount; the air volume required for the combustion of a unit of standard coal is calculated by dividing the total air volume required for combustion by the corrected standard coal amount, where the total air volume required for combustion is the total air volume of the primary and secondary air minus the air volume at the economizer outlet, and the air volume at the economizer outlet is reversed from the outlet oxygen concentration; using the rule that the excess air oxygen content before and after combustion is equal to the oxygen content at the outlet of the smoke exhaust, an equation is listed according to the target oxygen concentration to calculate the excess air volume; according to The corrected standard coal quantity, air volume required for combustion of unit standard coal, excess air volume, and primary and secondary air volumes measured by the air volume measuring element form the secondary air volume control feedforward; the calculated secondary air volume control feedforward is sent to the secondary air controller, and at the same time, the secondary air controller receives the primary and secondary air volumes sent by the primary and secondary air volume measuring elements, and the secondary air controller outputs the blower control instructions after feedforward correction, guiding the blower to operate at variable output, thereby realizing precise control of air distribution according to the calorific value of the coal entering the furnace.

[0021] A further improvement of the present invention is that the calorific value correction calculation method is: receiving the actual calorific value of coal sent by the coal quality online monitoring module, that is, the calorific value of coal at the outlet of the coal feeder, and performing a simple calculation with the calorific value of the standard coal to generate a calorific value correction coefficient C, as follows:

[0022]

[0023] The calorific value correction coefficient C and the actual coal feeding amount obtained by weighing the coal feeder belt weighing instrument are sent to the coal feeding controller together to form an optimized coal feeder instruction to control the coal feeder variable speed motor, thereby completing targeted correction of the coal feeding amount based on the real-time calorific value of the coal.

[0024] A further improvement of the present invention is that the air volume correction calculation method is: receiving the calorific value of the incoming coal sent by the coal quality online monitoring module, comparing it with the calorific value of the standard coal, and correcting the actual amount of coal entering the furnace to the standard coal amount F, as follows:

[0025]

[0026] Calculate the air volume K required for combustion of unit standard coal as follows:

[0027]

[0028] Calculate the excess air volume X as follows:

[0029] X×21%=(K×corrected standard coal quantity+X)×target oxygen quantity

[0030]

[0031] In the calculation process of the excess air volume X, the preset value of the target oxygen volume is introduced, and based on this, the excess air volume X that meets the oxygen demand of the unit is calculated.

[0032] A further improvement of the present invention is that the secondary air volume control feedforward FF is calculated from the air volume K required for unit standard coal combustion, the excess air volume X, the corrected standard coal volume and the measured primary air volume signal, as follows:

[0033] FF=K×F+X-primary air volume

[0034] The secondary air volume control feedforward FF is sent to the secondary air controller and added to the total air volume set value to perform real-time and accurate air volume correction on the ongoing combustion process, obtain optimized air supply instructions, and guide the variable output element of the blower to respond to the output according to the real-time needs of the unit to form the best air-coal ratio.

[0035] The present invention has at least the following beneficial technical effects:

[0036] 1. The present invention designs a calorific value correction calculation method based on the calorific value of coal, and provides more accurate calorific value correction parameters when the calorific value parameter of coal provided by the coal quality online detection module changes.

[0037] 2. The traditional calorific value correction method is to generate a correction coefficient by using the deviation between the standard coal supply obtained by converting the unit power provided by the large delay process of coal combustion and the real-time coal supply. This is a correction based on the parameters at the current moment for a completed process and a lag. In the present invention, the correction coefficient is obtained by comparing the real-time calorific value of coal supply with the standard coal calorific value. This is a correction based on the parameters at the current moment for an ongoing process and in real time.

[0038] 3. The present invention designs an air volume correction calculation method based on the calorific value of the coal entering the furnace, and provides more accurate air volume correction parameters when the calorific value parameters of the coal entering the furnace provided by the coal quality online detection module change.

[0039] 4. The traditional air volume correction method is based on the oxygen demand converted from the unit load as the benchmark, and the oxygen quantity at the economizer outlet after the combustion process is completed is made close to it through the PID algorithm to form a correction coefficient, which is an obvious lagging correction. In the present invention, according to the real-time calorific value of the coal entering the furnace, combined with the calorific value of the standard coal, the actual coal supply, the total air volume, and the target oxygen quantity signal, the appropriate secondary air volume control feedforward is calculated to correct the air distribution of the combustion process in real time.

[0040] 5. The real-time characteristics of the calorific value correction and air volume correction in the present invention make the correction parameters of the two match the combustion process in progress, so it will not have a deteriorating effect on the process that deviates from the optimal operating conditions of the system, and can effectively improve the steady-state and dynamic characteristics of the main steam temperature and main steam pressure, as well as the environmental protection indicators of the denitrification system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of traditional calorific value correction control;

[0042] Figure 2 This is a schematic diagram of traditional oxygen correction control;

[0043] Figure 3 The present invention is a structural block diagram of a unit control system based on real-time online analysis of coal quality.

[0044] Description of reference numerals:

[0045] 1. Raw coal hopper, 2. Raw coal hopper outlet pipe, 3. Coal feeder belt, 4. Weighing instrument, 5. Coal feeder variable speed motor, 6. Coal feeder outlet pipe, 7. Coal mill, 8. Coal mill inlet primary air duct, 9. Primary air volume measuring element, 10. Boiler furnace, 11. Coal quality online monitoring module, 12. Coal feeder controller, 13. Blower, 14. Blower variable output element, 15. Air supply duct, 16. Secondary air volume measuring element, 17. Secondary air controller. DETAILED DESCRIPTION

[0046] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0047] like Figure 3 As shown, the present invention provides a unit control system based on real-time online analysis of coal quality, including a raw coal hopper 1, a raw coal hopper outlet pipeline 2, a coal feeder belt 3, a weighing instrument 4, a coal feeder variable speed motor 5, a coal feeder outlet pipeline 6, a coal mill 7, a coal mill inlet primary air pipeline 8, a primary air volume measuring element 9, a boiler furnace 10, a coal quality online monitoring module 11, a coal feeding controller 12, a blower 13, a blower variable output element 14, an air supply pipeline 15, a secondary air volume measuring element 16 and a secondary air controller 17.

[0048] The coal in the raw coal hopper 1 falls onto the coal feeder belt 3 through the raw coal hopper outlet pipe 2. The coal feeder variable speed motor 5 changes the motor speed according to the needs of the unit unit, drives the coal feeder belt 3, and sends the coal on the coal feeder belt 3 to the coal mill 7. During this process, the weighing instrument 4 on the coal feeder belt 3 performs real-time weighing and records the actual coal feeding amount of the unit. The coal quality online monitoring module 11 outputs the calorific value of the coal, compares it with the calorific value of the standard coal, and outputs real-time and accurate coal feeding correction parameters, which are sent to the coal feeding controller 12 together with the actual coal feeding amount to correct the coal feeding amount instruction. The coal feeding controller 12 obtains the corrected coal feeder control instruction, guides the operation of the coal feeder variable speed motor 5, and realizes real-time control of the coal feeding according to the calorific value of the coal.

[0049] The variable output element 14 of the blower changes the air supply volume according to the demand of the unit set, and sends it to the boiler furnace 10 to provide an appropriate amount of combustion-supporting air for combustion. The primary air volume measuring element 9 on the primary air duct 8 at the inlet of the pulverizer monitors the primary air volume entering the pulverizer 7 in real time. The coal quality online monitoring module 11 outputs the calorific value of the coal entering the furnace, which is used as input together with the primary and secondary air volumes. The secondary air volume control feedforward is calculated, and the secondary air controller 17 outputs the blower control instruction after feedforward correction to guide the blower 13 to operate at variable output, thereby realizing precise control of the air distribution according to the calorific value of the coal entering the furnace.

[0050] The present invention provides a unit control method based on real-time online analysis of coal quality, comprising:

[0051] The coal quality online monitoring module 11 outputs the calorific value of coal, compares it with the calorific value of standard coal, outputs real-time and accurate coal correction parameters, and sends them to the coal controller 12 together with the actual coal quantity for correction of the coal quantity. The coal controller 12 obtains the corrected coal feeder control instruction to guide the operation of the coal feeder variable speed motor 5. The specific calculation process is:

[0052] The actual calorific value of the coal sent by the coal quality online monitoring module 11, that is, the calorific value of the coal at the outlet of the coal feeder, is compared with the calorific value of the standard coal to generate a calorific value correction coefficient C, as follows:

[0053]

[0054] The calorific value correction coefficient C and the actual coal feeding amount obtained by weighing the weighing instrument 4 of the coal feeder belt 3 are sent to the coal feeding controller 12 to form an optimized coal feeder instruction to control the coal feeder variable speed motor 5, so as to complete the targeted correction of the coal feeding amount according to the real-time calorific value of the coal. This method starts from the heating characteristics of the coal itself, and compared with the traditional calorific value correction based on the coal feeding amount deviation, the correction result is more accurate.

[0055] The coal quality online monitoring module 11 outputs the calorific value of the incoming coal, together with the primary and secondary air volumes, as input, and obtains the secondary air volume control feedforward through calculation. The secondary air controller 17 outputs the blower control instruction after feedforward correction to guide the blower to operate at variable output. The specific calculation process is:

[0056] The calorific value of the incoming coal sent by the coal quality online monitoring module 11 is compared with the calorific value of the standard coal, and the actual amount of coal entering the furnace is corrected to the standard coal amount F, as follows:

[0057]

[0058] Calculate the air volume K required for combustion of unit standard coal as follows:

[0059]

[0060] Calculate the excess air volume X as follows:

[0061] X×21%=(K×corrected standard coal quantity+X)×target oxygen quantity

[0062]

[0063] In the calculation process of excess air volume X, the preset value of target oxygen volume is introduced as a guide to calculate the excess air volume X that meets the oxygen demand of the unit. Compared with the traditional air volume correction that only introduces the actual oxygen volume, this method is more real-time and more accurate.

[0064] The secondary air volume control feedforward FF is calculated based on the air volume K required for unit standard coal combustion, the excess air volume X, the corrected standard coal volume, and the measured primary air volume signal, as follows:

[0065] FF=K×F+X-primary air volume

[0066] The secondary air volume control feedforward FF is sent to the secondary air controller 17 and added to the total air volume set value to perform real-time and accurate air volume correction on the ongoing combustion process, obtain optimized air supply instructions, and guide the blower variable output element 14 to respond to the output according to the actual needs of the unit, forming the best air-coal ratio and significantly improving the combustion efficiency.

Claims

1. A unit control method based on real-time online analysis of coal quality, characterized in that: The method includes: The speed-changing motor (5) of the coal feeder changes its speed according to the demand of the unit, drives the coal feeder belt (3) to rotate, and sends the coal on the coal feeder belt (3) to the coal mill (7). During this process, the weighing instrument (4) on the coal feeder belt (3) performs real-time weighing to record the actual coal feeding amount of the unit. The coal quality online monitoring module (11) outputs the calorific value of the coal, compares it with the calorific value of the standard coal, obtains the real-time and accurate coal feeding correction parameter, and sends it to the coal feeding controller (12) together with the actual coal feeding amount for correction of the coal feeding amount. The coal feeding controller (12) outputs the corrected coal feeder control instruction to guide the operation of the speed-changing motor (5) of the coal feeder, so as to realize the real-time control of the coal feeding according to the calorific value of the coal. The variable output element of the blower (13) changes the air volume according to the unit unit demand and sends it to the boiler furnace (10) to provide a suitable combustion-supporting air volume for combustion. The primary air volume measuring element (9) on the primary air duct (8) at the coal mill inlet monitors the primary air volume entering the coal mill (7) in real time. The coal quality online monitoring module (11) outputs the calorific value of the coal entering the furnace, and uses the primary and secondary air volumes as known parameters to perform the following calculations: The calorific value of the coal entering the furnace is compared with the calorific value of the standard coal, and the amount of coal entering the furnace is corrected to the standard coal amount; the air volume required for the combustion of a unit of standard coal is calculated by dividing the total air volume required for combustion by the corrected standard coal amount, where the total air volume required for combustion is the total air volume of the primary and secondary air minus the air volume at the economizer outlet, and the air volume at the economizer outlet is inferred from the outlet oxygen concentration; using the rule that the excess air oxygen content before and after combustion is equal to the oxygen content at the outlet of the smoke exhaust, an equation is listed based on the target oxygen concentration to calculate the excess air volume; based on the corrected standard coal The secondary air volume control feedforward is calculated based on the coal volume, the air volume required for unit standard coal combustion, the excess air volume, and the primary air volume and secondary air volume measured by the air volume measuring element, and sent to the secondary air controller (17). At the same time, the secondary air controller (17) receives the primary and secondary air volumes sent by the primary air volume measuring element (9) and the secondary air volume measuring element (16). The secondary air controller (17) outputs a blower control instruction after feedforward correction to guide the blower (13) to operate with variable output, thereby realizing precise control of air distribution according to the calorific value of the coal entering the furnace.

2. A unit control method based on real-time online analysis of coal quality according to claim 1, characterized in that: The calorific value correction calculation method is: The actual calorific value of the fed coal sent by the coal quality online monitoring module (11), i.e. the calorific value of the coal at the outlet of the coal feeder, is compared with the calorific value of the standard coal to generate a calorific value correction coefficient C, as follows: The calorific value correction coefficient C and the actual coal feeding amount obtained by weighing the weighing instrument (4) of the coal feeder belt (3) are sent to the coal feeding controller (12) to form an optimized coal feeder instruction, and the coal feeder variable speed motor (5) is controlled to complete the targeted correction of the coal feeding amount according to the real-time calorific value of the coal.

3. The unit control method based on real-time online analysis of coal quality according to claim 1 is characterized in that: The air volume correction calculation method is: The calorific value of the incoming coal sent by the coal quality online monitoring module (11) is compared with the calorific value of the standard coal, and the actual amount of coal entering the furnace is corrected to the standard coal amount F, as follows: Calculate the air volume K required for combustion of unit standard coal as follows: Calculate the excess air volume X as follows: X×21%=(K×corrected standard coal quantity+X)×target oxygen quantity In the calculation process of the excess air volume X, the preset value of the target oxygen volume is introduced, and based on this, the excess air volume X that meets the oxygen demand of the unit is calculated.

4. A unit control method based on real-time online analysis of coal quality according to claim 3, characterized in that: The secondary air volume control feedforward FF is calculated based on the air volume K required for unit standard coal combustion, the excess air volume X, the corrected standard coal volume, and the measured primary air volume signal, as follows: FF=K×F+X-primary air volume The secondary air volume control feedforward FF is sent to the secondary air controller (17) and added to the total air volume set value to perform real-time and accurate air volume correction on the ongoing combustion process, thereby obtaining an optimized air supply instruction and guiding the air supply fan variable output element (14) to respond to the output according to the real-time demand of the unit, thereby forming an optimal air-coal ratio.

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