A fuel control method for a coal mill of a coal-fired generator set

Abstract

The present application relates to the field of automatic control technology, and more particularly to a fuel control method for a coal mill of a coal-fired generator set. The steps are as follows: S1: adjusting the total air volume of the primary air fan; S2: calculating the total primary air volume automatic instruction; S3: adjusting the air volume deviation of each mill and the main pipe pressure according to the total primary air volume control; and S4: after the coal type of the unit is restored, the primary air fan and the mill hot air door control are restored. The present application provides a fuel control method for a coal mill of a coal-fired generator set, which controls the total outlet air volume of the primary air fan to meet the total coal powder amount demand of each coal mill carrying coal powder for combustion, realizes the requirement of coordinated control of the coal-fired generator set for rapid peak regulation and frequency modulation, thereby overall improves the coordinated control variable load capacity of the unit, meets the peak regulation and frequency modulation demand of the current new power system under the vigorous development of new energy, and improves the adaptability and economy of the coal-fired generator set under various coal blending combustion conditions.

Description

Technical Field

[0001] This invention relates to the field of automatic control technology, and in particular to a fuel control method for a coal mill in a pulverized coal boiler generator set. Background Technology

[0002] In recent years, the supply and demand relationship in the domestic power industry has undergone significant changes. Power supply is facing a shortage. Traditional thermal power plants have taken advantage of the rebound in the annual power generation rate of their units to increase power generation, but they are also facing the dilemma of rising coal prices and shortages. Therefore, thermal power plants have tried every means to blend and burn cheaper coal, and many regions mainly use lignite.

[0003] Coal blending often deviates from the design operating conditions of thermal power units, leading to slow load regulation and impacting grid peak and frequency regulation, thus triggering performance evaluations by dispatching departments. The primary cause is that the coal mills in these units are operating with high moisture and impurity levels in the blended coal, causing the primary air dampers to be almost fully open. This results in the original design of controlling the amount of pulverized coal entering the furnace from the mill using hot air volume, which is now out of control. Consequently, the coordinated control of the boiler and turbine load regulation cannot be properly and stably implemented, severely affecting the unit's load regulation capabilities.

[0004] For example, patent (CN111142377B) discloses a fuel feedforward control method for a coordinated control system that takes into account the operating status of the coal mill. This method includes: for all coal mills with automatic coal feed, selecting representative values ​​for the ratio of current to coal feed rate, the ratio of primary air pressure to coal feed rate, and the coal feed rate of each coal mill; specifically, selecting the representative value of the ratio of current to coal feed rate of each coal mill. The second largest value of the ratio of primary air pressure to coal feed rate of each coal mill is selected as the representative value; the representative value of the ratio of primary air pressure to coal feed rate of each coal mill is selected as the representative value; the representative value of the coal feed rate of each coal mill is selected as the representative value; the inertial time of the AGC command corresponding to each of the above representative values ​​on the actual differential control action in the fuel feedforward link is calculated, and the maximum value is selected as the inertial time of the final actual differential link. The process includes: after obtaining the inertial time of the actual differential element, the following steps are also included: dividing the inertial time of the pulverizing system by the inertial time of the actual differential element and subtracting 1 to obtain an intermediate coefficient; dividing the actual AGC command signal of the unit by the value of the static gain of fuel quantity on power generation to obtain the static fuel quantity feedforward signal; subtracting the signal output by the first-order inertial module after the static fuel quantity feedforward signal has been passed through the inertial time set as the inertial time of the differential element, and then multiplying by the intermediate coefficient to obtain the value, and adding the static fuel quantity feedforward signal to obtain the feedforward signal of AGC command on fuel quantity. The fuel quantity feedforward control method of the coordinated control system of the present invention, which takes into account the operating state of the coal mill, is particularly suitable for thermal power units with complex coal quality and frequent fluctuations in AGC commands. The control system can coordinate the contradiction between the steam pressure control quality in front of the turbine and the operating safety of the pulverizing system during the load change process, maximize the ultimate performance of the equipment, and obtain the best control effect under the premise that the pulverizing system does not fail.

[0005] There is an urgent need to study a solution to the problem of unit coordination and control failure caused by co-firing, in order to meet the current higher requirements for deep peak shaving and rapid frequency regulation of thermal power units, and to better absorb the current construction status of new energy power generation.

[0006] To address this issue, a fuel control method for the coal mill of a pulverized coal boiler generator set is designed to provide a technical solution to the aforementioned technical problems. Summary of the Invention

[0007] Based on this, it is necessary to provide a fuel control method for the coal mill of a pulverized coal boiler generator set to address the above-mentioned technical problems. This method is intended to solve the problem that the design operating conditions of the current pulverized coal boiler generator set deviate after co-firing, and the hot primary air damper of the coal mill cannot quickly follow the fuel control system to adjust the boiler combustion rate when it is near the fully open position. This seriously affects the automatic control and commissioning of the unit's boiler load.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A fuel control method for the coal mill of a pulverized coal boiler generator set, comprising the following steps: S1: Adjust the total outlet air volume of the primary air fan; S2: Automatic command to calculate total primary air volume; S3: Adjust the air volume deviation of each mill and the main pipe pressure according to the total primary air volume control; S4: After the coal type of the unit is restored, the control of the hot air damper of the primary air fan and mill is restored.

[0009] In a preferred embodiment of the fuel control method for the coal mill of a pulverized coal boiler generator set provided by the present invention, in step S1, the total outlet air volume of the primary air fan is adjusted as follows: By controlling the distribution of the primary air fans in the unit, a general-purpose PID module is used to control the total primary air volume of the coal mill according to the coal quantity command. The expression is as follows: ; in, This is the final set value for the total primary air volume. For the total primary air volume, This is the deviation input value for the air volume PID; ; in, This is an automatic command for total primary air volume. This is the total primary air volume offset setting.

[0010] In a preferred embodiment of the fuel control method for the coal mill of a pulverized coal boiler generator set provided by the present invention, in step S2, the automatic command for calculating the total primary air volume is expressed as follows: ; in, This refers to the number of coal mill systems included in the unit. The operating status of coal feeder i is 1 when it is running and 0 when it is not running. For the coal feeder i, the coal feed rate command is given. The coal feeding command for mill i is represented by the primary air volume function curve of mill i.

[0011] In a preferred embodiment of the fuel control method for the coal mill of a pulverized coal boiler generator set provided by the present invention, in step S3, the air volume deviation of each mill and the main pipe pressure are adjusted according to the total primary air volume control, as follows: When the total primary air volume control is activated, the primary air volume control of each individual coal mill is simultaneously deactivated. Operators can fine-tune the airflow deviation of the corresponding mill by using the mill's hot air damper; The pressure of the primary air main pipe is fine-tuned by the operators through the hot air damper of the corresponding mill.

[0012] As a preferred embodiment of the fuel control method for the coal mill of a pulverized coal boiler generator set provided by the present invention, in step S4, after the coal type of the unit is restored to the design operating conditions, the control of the primary air fan and the hot air damper of the mill is restored to the original automatic control mode.

[0013] It is clear without a doubt that the technical solution described above in this application can solve the technical problem that this application aims to address.

[0014] Meanwhile, through the above technical solutions, the present invention has at least the following beneficial effects: 1. The present invention provides a fuel control method for the coal mill of a pulverized coal boiler generator set, which controls the total outlet air volume of the primary air fan to meet the total amount of pulverized coal carried by each coal mill for combustion, thereby realizing the requirements of rapid peak shaving and frequency regulation for coordinated control of the pulverized coal boiler generator set.

[0015] 2. This invention allows for adjustment of the total outlet air volume of the primary air fan to ensure that the pulverized coal carried into the furnace by the primary air follows the fuel command in a proportional manner, thereby improving the speed and linearity of the boiler combustion response. This enhances the overall coordination and load-changing capability of the unit, meets the peak-shaving and frequency regulation requirements of the current new power system under the vigorous development of new energy sources, and improves the adaptability and economy of pulverized coal boiler generator units in various coal co-firing conditions. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a block diagram for calculating the total primary air volume command of the present invention; Figure 2 This is the PID control block diagram for the total primary air volume of the present invention; Figure 3 This is a block diagram of the primary air volume switching control of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0020] As described in the background section, there is an urgent need to study a solution to the problem of unit coordination and control failure caused by co-firing, in order to meet the current higher requirements for deep peak shaving and rapid frequency regulation of thermal power units, and to further absorb the current construction status of new energy power generation.

[0021] To address this technical problem, the present invention provides a fuel control method for the coal mill of a pulverized coal boiler generator set.

[0022] For details, please refer to Figures 1-3 The fuel control method and steps are as follows: S1: Adjust the total outlet air volume of the primary air fan; S2: Automatic command to calculate total primary air volume; S3: Adjust the air volume deviation of each mill and the main pipe pressure according to the total primary air volume control; S4: After the coal type of the unit is restored, the control of the hot air damper of the primary air fan and mill is restored.

[0023] This invention provides a fuel control method for the coal mill of a pulverized coal boiler generator set. It controls the total outlet air volume of the primary air fan to meet the total amount of pulverized coal carried by each coal mill for combustion. This achieves the requirements for rapid peak shaving and frequency regulation of the pulverized coal boiler generator set through coordinated control of the boiler and generator. By adjusting the total outlet air volume of the primary air fan, it ensures that the pulverized coal carried into the furnace by the primary air follows the fuel command proportionally, improving the speed and linearity of the boiler's combustion response. This enhances the overall coordinated control and load-changing capability of the unit, meeting the peak shaving and frequency regulation needs of the current new power system under the vigorous development of new energy sources. Simultaneously, it improves the adaptability and economy of the pulverized coal boiler generator set operating under various coal blending conditions.

[0024] It should be noted that, unless otherwise specified, the embodiments and features and technical solutions in the present invention can be combined with each other.

[0025] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] Example 1 Reference Figures 1-3 A fuel control method for the coal mill of a pulverized coal boiler generator set.

[0027] The pulverized coal boiler generator set uses a primary air fan to control the total primary air volume entering the coal mill to meet the total primary air volume command setting requirements. This replaces the control failure caused by the coal mill primary air volume control damper being close to the fully open position due to the blending of coal types not designed for operation. This significantly enhances the large inertia and large delay characteristics of the unit's fuel control, affecting the unit's coordinated control and preventing high-quality commissioning.

[0028] The implementation steps are as follows: S1: Through the distribution control of the unit's primary air fan, a general-purpose PID module is used to realize the follow-up coal quantity command control of the total primary air volume of the coal mill. The expression is: ; in, This is the final set value for the total primary air volume. For the total primary air volume, This is the deviation input value for the air volume PID; ; in, This is an automatic command for total primary air volume. This is the total primary air volume offset setting value; S2: The calculation expression for the total primary air volume automatic command is: ; in, This refers to the number of coal mill systems included in the unit. The operating status of coal feeder i is 1 when it is running and 0 when it is not running. For the coal feeder i, the coal feed rate command is given. The coal feeding command of mill i is represented by the primary air volume function curve of mill i. S3: While putting the total primary air volume control into operation, the original primary air volume control of each coal mill is cut off. The air volume deviation of each mill is fine-tuned by the operator through the hot air damper of the mill. The pressure of the primary air main pipe is fine-tuned by the operator through the hot air damper of each mill. S4: After the coal type of the unit is restored to the design operating conditions, the hot air damper control of the primary air fan and mill can be restored to the original automatic control mode.

[0029] The specific working principle of the fuel control method for the coal mill of a pulverized coal boiler generator set provided by this invention is as follows: In operation, the distribution control of the unit's primary air fan is first implemented using a general PID module to control the total primary air volume of the coal mill in accordance with the coal quantity command. The total primary air volume command is automatically calculated. After the calculation is completed, the original primary air volume control of each coal mill is cut off while the total primary air volume control is activated. The air volume deviation of each mill is fine-tuned by the operator through the mill's hot air damper. The pressure of the primary air main pipe is also fine-tuned by the operator through the hot air damper of each mill. Then, after the unit's coal type returns to the design operating conditions, the control of the primary air fan and the mill's hot air damper can be restored to the original automatic control mode.

[0030] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A fuel control method for a coal mill in a pulverized coal boiler generator set, characterized in that, The steps are as follows: S1: Adjust the total outlet air volume of the primary air fan; S2: Automatic command to calculate total primary air volume; S3: Adjust the air volume deviation of each coal mill and the main pipe pressure according to the total primary air volume control; S4: After the coal type of the unit is restored, the hot air damper control of the primary air fan and coal mill is restored; In step S1, the total outlet air volume of the primary air fan is adjusted as follows: By controlling the distribution of the primary air fans in the unit, a general-purpose PID module is used to control the total primary air volume of the coal mill according to the coal quantity command. The expression is as follows: ； in, This is the final set value for the total primary air volume. For the total primary air volume, This is the deviation input value for the air volume PID; ； in, This is an automatic command for total primary air volume. This is the total primary air volume offset setting value; In step S2, the automatic command for calculating the total primary air volume is as follows: ； in, This refers to the number of coal mill systems included in the unit. The value represents the operating status of coal feeder i, with 1 for running and 0 for not running. For the coal feeder i, the coal feed rate command is given. The primary air volume function curve of the coal feeding command -i for coal mill i; In step S3, based on the total primary air volume control, the air volume deviation of each coal mill and the main pipe pressure are adjusted, as follows: When the total primary air volume control is activated, the original primary air volume control of each coal mill is simultaneously deactivated. Operators can fine-tune the airflow deviation of the coal mill by adjusting the hot air damper. The pressure of the primary air main pipe is fine-tuned by the operators through the hot air damper of the corresponding coal mill.

2. The fuel control method for the coal mill of a pulverized coal boiler generator set according to claim 1, characterized in that, In step S4, after the coal type of the unit is restored to the design operating conditions, the hot air damper control of the primary air fan and coal mill is restored to the original automatic control mode.

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