Boiler pulverized coal monitoring method

Abstract

The invention relates to the technical field of boiler pulverized coal monitoring, in particular to a boiler pulverized coal monitoring method which comprises the following steps: determining whether a separation mode of a pulverized coal separator is qualified or not according to a comparison result of a particle size distribution characterization value of pulverized coal in a pulverized coal pipe at an outlet of a coal mill and a preset distribution characterization value; under the condition that the separation mode of the pulverized coal separator is determined to be unqualified, the angle of a guide blade of the pulverized coal separator is adjusted according to the radial flow velocity difference value of the pulverized coal pipe at the outlet of the coal mill; whether airflow mixing of the thick pulverized coal phase and the thin pulverized coal phase is qualified or not is determined based on the ignition interval; under the condition that airflow mixing is determined to be unqualified, a plurality of air speed adjusting coefficients are set according to the uniformity characterization value of temperature gradient distribution of the hearth to adjust the air speed of secondary air, and the air speed adjusting coefficients are optimized according to the flame shape characterization value in the hearth; and optimizing the preset distribution characterization value according to the fluctuation intensity of the combustion efficiency curve. The combustion efficiency of the pulverized coal is guaranteed while generation of nitric oxide is inhibited.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of boiler coal powder monitoring, and particularly relates to a boiler coal powder monitoring method. BACKGROUND

[0002] In the process of coal powder combustion in a boiler, in order to effectively inhibit the generation of nitrogen oxides (NO X ), the coal powder concentration grading combustion technology is widely used in the industry, and the coal powder gas flow is divided into a dense coal powder area and a light coal powder area to realize the grading air supply: the dense coal powder area maintains stable ignition and reduces the local flame temperature by fuel-rich combustion, and the light coal powder area promotes the burnout by supplementing oxygen, thereby reducing the generation of thermal NO X . However, this grading method puts forward very high requirements for the matching of the coal powder concentration of the dense and light coal powder areas, the uniformity of the particle size distribution, and the air flow mixing effect. In actual operation, problems such as the fluctuation of the coal powder particle size distribution at the outlet of the coal mill, and the poor air flow mixing of the dense and light coal powder areas frequently occur, which easily leads to incomplete combustion caused by local oxygen deficiency in the dense coal powder area, and the difficulty in stable ignition of the light coal powder area due to the sparseness of the coal powder, not only causing the increase of the carbon content in fly ash and the significant decrease of the combustion efficiency, but also possibly causing safety hazards such as local slagging and high-temperature corrosion in the furnace, which seriously restricts the coordinated improvement of the safety and economy of the boiler and the environmental protection performance.

[0003] Chinese Patent Application Publication No. CN102680370A discloses a coal powder concentration online monitoring system, which comprises a control cabinet and a measuring device. The measuring device is installed on the air pipe connected with the boiler, and the output end of the measuring device is connected with the control cabinet. The measuring device comprises a measuring probe and a differential pressure transmitter. The measuring probe comprises a primary air speed probe and a primary concentration probe installed on the primary air pipe, a secondary air speed probe and a secondary concentration probe installed on the secondary air pipe, and a tertiary air speed probe and a tertiary concentration probe installed on the tertiary air pipe. The measuring probe is connected with the differential pressure transmitter through a pressure transmission pipe. Through the above manner, the coal powder concentration online monitoring system has strong anti-interference ability, stable signal, and can accurately provide the air speed and the coal powder concentration of the boiler. The system has high sensitivity and reliability in response to the changes of the coal powder concentration and the air speed, high accuracy of the measured data, and wide application range.

[0004] The existing technology also has the following problems: in order to effectively inhibit the generation of nitrogen oxides, the coal powder concentration grading combustion technology is widely used in the existing technology. The emission of nitrogen oxides (mainly including NO, NO2, collectively referred to as NO X ) will cause serious harm to the environment, ecology and human health, and is also one of the pollutants strictly limited by global environmental protection regulations. There is a potential contradiction between the inhibition of NO X and the coal powder combustion efficiency. The core of the combustion efficiency is the full burnout of the fuel, which needs to meet three conditions of sufficient temperature, sufficient oxygen and sufficient mixing time, and the inhibition of NO XThe key is to control the combustion temperature and reduce the local oxygen concentration, so if the coal powder concentration grading combustion process is not monitored in real time and accurately adjusted, the combustion efficiency of the coal powder will be lower. SUMMARY

[0005] To this end, the present application provides a boiler coal powder monitoring method to overcome the problem of low combustion efficiency of coal powder caused by the lack of real-time monitoring and accurate adjustment of the coal powder concentration grading combustion process in the prior art.

[0006] To achieve the above-mentioned purpose, the present application provides a boiler coal powder monitoring method, comprising: Obtaining a particle size distribution representation value of coal powder in a coal powder pipe outlet of a coal mill, to determine whether the separation mode of a coal powder separator is qualified based on a comparison result of the particle size distribution representation value and a preset distribution representation value; Under the condition that it is determined that the separation mode of the coal powder separator is unqualified, adjusting the angle of the guide vane of the coal powder separator according to the radial flow rate difference value of the coal powder pipe outlet of the coal mill; Under the condition that it is determined that the separation mode of the coal powder separator is qualified, determining the ignition interval of the dense coal powder phase and the light coal powder phase in the furnace, to determine whether the airflow mixing of the dense coal powder phase and the light coal powder phase is qualified based on the ignition interval; Under the condition that it is determined that the airflow mixing is unqualified, adjusting the air speed of the secondary air according to a plurality of air speed adjustment coefficients set according to the uniformity representation value of the temperature gradient distribution of the furnace, and optimizing the air speed adjustment coefficient according to the flame shape representation value in the furnace; Constructing a combustion efficiency curve of the coal powder, to optimize the preset distribution representation value according to the fluctuation intensity of the combustion efficiency curve.

[0007] Further, the determination process of the particle size distribution representation value comprises: Using a light scattering instrument to establish a particle size distribution histogram of the coal powder in the coal powder pipe outlet of the coal mill; Connecting the upper edge midpoint positions of any straight blocks to form a particle size distribution curve; Aligning the particle size distribution curve and the standard distribution curve with the horizontal coordinate scale as a reference to coincide; Determining the ratio of the overlapping area of the particle size distribution curve and the standard distribution curve to the area surrounded by the standard distribution curve and the coordinate axis as the particle size distribution representation value.

[0008] Further, the process of determining whether the separation mode of the coal powder separator is qualified based on the particle size distribution representation value comprises: Comparing the particle size distribution representation value with the preset distribution representation value; Determining that the separation mode of the coal powder separator is unqualified based on the comparison result that the particle size distribution representation value is less than the preset distribution representation value.

[0009] Further, the process of determining the radial flow rate difference value comprises: dividing a cross section of the pulverized coal pipe at the outlet of the coal mill into a plurality of concentric annuli with a geometric center as a reference point and a preset distance as an interval, and determining a plurality of flow rates of the plurality of concentric annuli; determining a difference between a maximum value and a minimum value of the plurality of flow rates as the radial flow rate difference value.

[0010] Further, the process of adjusting the guide vane angle of the pulverized coal separator based on the radial flow rate difference value comprises: comparing the radial flow rate difference value with a preset flow rate difference value; setting a plurality of angle adjustment coefficients based on a comparison result of the radial flow rate difference value and the preset flow rate difference value, and reducing the guide vane angle based on the plurality of angle adjustment coefficients.

[0011] Further, the process of determining whether the gas flow mixing of the dense phase and the dilute phase of pulverized coal is qualified based on the fire interval comprises: comparing the fire interval with a preset time length respectively; determining that the gas flow mixing of the dense phase and the dilute phase of pulverized coal is unqualified based on a comparison result that the fire interval is less than a first preset time length or greater than a second preset time length.

[0012] Further, the process of adjusting the wind speed of the secondary air according to the uniformity representation value under the condition that the gas flow mixing is determined to be unqualified comprises: obtaining image information of the furnace, and determining a plurality of temperature distribution gradients and corresponding temperature distribution ranges in the furnace after preprocessing the image information; determining a coincidence degree of any of the temperature distribution ranges and a corresponding standard temperature distribution range; determining a uniformity representation value as a ratio of a number of temperature distribution gradients with the coincidence degree greater than or equal to a preset coincidence degree to a total number of the temperature distribution gradients; comparing the uniformity representation value with a preset representation value; setting a plurality of wind speed adjustment coefficients based on a comparison result of the uniformity representation value and the preset representation value, and adjusting the wind speed of the secondary air based on the plurality of wind speed adjustment coefficients.

[0013] Further, the process of optimizing the wind speed adjustment coefficient according to a flame shape representation value in the furnace comprises: comparing the flame shape representation value with a preset shape representation value respectively; reducing the wind speed adjustment coefficient by a first wind speed optimization coefficient based on a comparison result that the flame shape representation value is less than a first preset shape representation value; Based on the comparison result of the flame shape characteristic value being greater than the second preset shape characteristic value, a second wind speed optimization coefficient is used to increase the wind speed adjustment coefficient.

[0014] Further, the determination process of the fluctuation intensity of the combustion efficiency curve comprises: Based on the combustion efficiency curve, a plurality of points with combustion efficiency lower than the preset efficiency are determined. A plurality of distances of any of the points relative to the straight line of the preset efficiency are determined. The standard deviation of the plurality of distances is determined as the fluctuation intensity.

[0015] Further, the process of optimizing the preset distribution characteristic value based on the fluctuation intensity comprises: The fluctuation intensity is compared with a preset intensity. Based on the comparison result of the fluctuation intensity and the preset intensity, a plurality of characteristic value optimization coefficients are set to increase the preset distribution characteristic value based on the plurality of characteristic value optimization coefficients.

[0016] Compared with the prior art, the present application has the beneficial effects that the present application determines whether the original separation mode of the coal powder separator is qualified by monitoring the particle size distribution of the coal powder in the coal powder pipe at the outlet of the coal mill in real time to determine whether the initial particle size distribution of the coal powder in the coal powder pipe at the outlet of the coal mill is uniform to determine whether the concentration of the coal powder in the dense coal powder area and the light coal powder area is qualified, and the core principle of the coal powder separator to distinguish the dense coal powder area and the light coal powder area is to use the centrifugal force, inertial force or gravity difference of the airflow to make the coal powder particles of different concentrations form a partition in the flow field, if the initial particle size distribution is uniform, most of the particles have similar particle sizes, the difference in centrifugal force and airflow resistance in the separator is small, and the motion trajectories are more consistent, fine particles will be more concentratedly carried by the airflow to the dense coal powder area, coarse particles will be separated in proportion, the concentration of the dense coal powder area is high and stable, the concentration of the light coal powder area is low and uniform, and the dense and light areas are clearly distinguished, if the initial particle size distribution is not uniform, the particle size difference is large, large particles have large inertia and are easily affected by gravity to deviate from the airflow trajectory, small particles flow freely with the airflow, at this time, part of the coarse particles may mix into the dense coal powder area due to ineffective separation, or fine particles may be brought into the light coal powder area due to airflow disturbance, resulting in dilution of the concentration of the dense coal powder area and abnormal increase of the concentration of the light coal powder area, and the dense and light areas are indistinct. Although the indistinction of the dense and light coal powder areas can reduce local hypoxia or hyperoxia, the coal powder and oxygen are more uniformly mixed, the unburned loss caused by hypoxia in the dense coal powder area is avoided, and the overall burnout rate is improved, but the indistinction of the dense and light areas leads to insufficient concentration of the coal powder in the dense coal powder area and relatively excessive oxygen, which is difficult to form a strong reducing atmosphere, and the thermal NO X The generated oxygen-enriched high-temperature condition is more easily met, resulting in an increase in NO X emission, and uniform mixing may increase the overall temperature of the combustion area without obvious low-oxygen cooling area, further promoting the formation of NOX NOx is generated, especially when the excess air coefficient is high X The emission risk is significantly increased, so whether to adjust the pulverized coal separator to increase the concentration difference of the thick and thin areas and accurately adjust the subsequent combustion process is determined according to the particle size distribution of the pulverized coal, so as to effectively inhibit the generation of nitrogen oxides while ensuring the combustion efficiency.

[0017] Further, the present application determines whether the airflow mixing is qualified by the ignition interval of the thick and thin pulverized coal phases in the furnace, and the key of the thick and thin staged combustion is to burn the thick pulverized coal phase first to create a low-oxygen reduction environment to inhibit the generation of NO X x, and the timing cooperation of the thick and thin pulverized coal phases and the subsequent combustion in the oxygen-rich environment realizes the dual goals of inhibiting the generation of NO X x and ensuring the efficiency. The ignition interval directly reflects whether the mixing time of the two is appropriate, if the interval is within a reasonable range, it means that the thick pulverized coal phase completes the preliminary combustion in the low-oxygen environment, and then the thin pulverized coal phase mixes timely to supplement oxygen, realizes full burnout, and the mixing state is qualified; if the interval is too short, it means that the thick and thin pulverized coal phases mix too early, the low-oxygen reduction environment of the thick pulverized coal phase is destroyed, which may lead to local oxygen-rich high temperature, and on the contrary, promotes the generation of thermal NO X x, and the concentrated heat release of the pulverized coal combustion is easy to cause local temperature to be too high, deviating from the temperature control target of the staged combustion; if the interval is too long, it means that the mixing of the two is delayed, the thin pulverized coal phase cannot supplement in time after the thick pulverized coal phase burns, which may lead to insufficient combustion of the thick pulverized coal phase due to lack of oxygen, or the thin pulverized coal phase burns in the rear part of the furnace, causing heat not to be fully utilized, and may also lead to unburned loss due to insufficient combustion time, therefore, whether the airflow mixing is qualified is determined according to the ignition interval, and the wind speed of the secondary air is adjusted in time to correct the influence caused by unqualified airflow mixing, so as to effectively inhibit the generation of nitrogen oxides while ensuring the combustion efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The flowchart of the boiler pulverized coal monitoring method of the embodiment of the present application; Figure 2 The flowchart of determining the particle size distribution characteristic value of the embodiment of the present application; Figure 3 The flowchart of determining whether the separation mode of the pulverized coal separator is qualified of the embodiment of the present application; Figure 4 The flowchart of determining whether the airflow mixing of the thick and thin pulverized coal phases is qualified of the embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to make the objects, technical schemes and advantages of the present application clearer, the following further describes the present application with reference to the embodiments; it should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0020] The preferred embodiments of the present application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application and not to limit the protection scope of the present application.

[0021] Please refer to Figures 1-4 as shown, Figure 1 the flow chart of the boiler coal powder monitoring method of the embodiment of the present application; Figure 2 the flow chart of determining the particle size distribution representation value of the embodiment of the present application; Figure 3 the flow chart of determining whether the separation mode of the coal powder separator of the embodiment of the present application is qualified or not; Figure 4 the flow chart of determining whether the airflow mixing of the dense coal powder phase and the light coal powder phase of the embodiment of the present application is qualified or not.

[0022] The boiler coal powder monitoring method of the embodiment of the present application comprises: Step S1, obtaining the particle size distribution representation value of the coal powder in the coal powder pipe at the outlet of the coal mill, and determining whether the separation mode of the coal powder separator is qualified or not based on the comparison result of the particle size distribution representation value and the preset distribution representation value; Step S2, under the condition that it is determined that the separation mode of the coal powder separator is unqualified, adjusting the angle of the guide vane of the coal powder separator according to the radial flow rate difference value of the coal powder pipe at the outlet of the coal mill; Step S3, under the condition that it is determined that the separation mode of the coal powder separator is qualified, determining the fire interval of the dense coal powder phase and the light coal powder phase in the hearth, and determining whether the airflow mixing of the dense coal powder phase and the light coal powder phase is qualified or not based on the fire interval; Step S4, under the condition that it is determined that the airflow mixing effect is unqualified, adjusting the air speed of the secondary air according to the uniformity representation value of the temperature gradient distribution of the hearth, and optimizing the air speed adjustment coefficient according to the flame shape representation value in the hearth; Step S5, constructing the combustion efficiency curve of the coal powder, and optimizing the preset distribution representation value according to the fluctuation intensity of the combustion efficiency curve.

[0023] It can be understood that, in the coal powder combustion process, the reason why the concentration grading combustion mode of the dense coal powder area and the light coal powder area can inhibit the generation of nitrogen oxides lies in that the coal powder concentration in the dense coal powder area is high and the air supply is relatively insufficient, which is in an oxygen-deficient or low-oxygen environment. The oxygen-deficient condition can reduce the peak value of the combustion temperature, and the generation of thermal NO X is in an exponential relationship with the combustion temperature, and the high temperature exceeding 1500℃ will promote the reaction of N2 and O2 in the air to generate NOX and the low-oxygen combustion in the dense coal zone can avoid local super-high temperature, thereby reducing the generation of thermal NO X , while the coal particles in the dense coal zone are dense, and the nitrogen elements in the fuel are more likely to react with the reducing components such as carbon and hydrogen in the coal to generate harmless gases such as N2 rather than being oxidized into NO X , and the low-oxygen environment inhibits the conversion of fuel nitrogen into NO X , and enhances the reduction reaction of NO X ; and the combustion in the sparse coal zone is sufficient and the secondary generation is reduced, the coal concentration in the sparse coal zone is low and the air supply is sufficient, and the main role is to further burn the coal that is not completely burned to avoid the decrease of combustion efficiency due to the overall hypoxia, but since the amount of coal in the sparse coal zone is small, even if the air is sufficient, the local temperature will not be too high, and at this time the main conversion of fuel nitrogen has been completed in the dense coal zone, so it will not significantly increase the secondary generation of NO X . At the same time, the oxygen-rich environment in the sparse coal zone can supplement the oxygen required for combustion to ensure the overall combustion efficiency and avoid the unburned loss caused by the hypoxia in the dense coal zone, so that the coal combustion efficiency is ensured while the generation of nitrogen oxides is inhibited according to the staged combustion mode according to the coal concentration.

[0024] Specifically, in the step S1, the determination process of the particle size distribution characteristic value includes: Step S11, using a light scattering instrument to establish a particle size distribution histogram of the coal in the coal mill outlet pipe; Step S12, connecting the upper edge midpoint position of any straight block to form a particle size distribution curve; Step S13, aligning the particle size distribution curve with the standard distribution curve as a reference with the horizontal coordinate scale; Step S14, determining the ratio of the overlapping area of the particle size distribution curve and the standard distribution curve to the area surrounded by the standard distribution curve and the coordinate axis as the particle size distribution characteristic value.

[0025] Specifically, the model of the light scattering instrument is not limited, as long as it meets the requirement of online detection of the coal particle size distribution in the coal pipe.

[0026] It can be understood that the standard distribution curve refers to a coal particle size distribution reference curve that can ensure the optimal separation effect of the coal classifier and meet the subsequent needs of the dense-sparse staged combustion under the normal operating conditions of the boiler.

[0027] Specifically, the process of determining whether the separation mode of the coal classifier is qualified based on the particle size distribution characteristic value includes: comparing the particle size distribution characteristic value with the preset distribution characteristic value; determine that the separation mode of the coal powder separator is unqualified based on a comparison result of the particle size distribution characteristic value being less than the preset distribution characteristic value; determine that the separation mode of the coal powder separator is qualified based on a comparison result of the particle size distribution characteristic value being greater than or equal to the preset distribution characteristic value.

[0028] Specifically, the preset distribution characteristic value is set to [0.7, 0.8], and the embodiment of the application preferably 0.75.

[0029] Specifically, the process of determining the radial flow rate difference value includes: Divide the cross section of the coal powder pipe at the outlet of the coal mill into a plurality of concentric circles with the geometric center as the reference point and a preset distance as the interval, and determine a plurality of flow rates of a plurality of the concentric circles. Determine the difference between the maximum value and the minimum value in the plurality of flow rates as the radial flow rate difference value.

[0030] Specifically, the coal powder is transported in the pipeline by airflow, the inertia of large-particle coal powder is large, and it is less affected by airflow drag, and it is more difficult to follow the airflow diversion. In the rotating airflow in the coal powder pipe, large particles are easily thrown to the vicinity of the inner wall of the pipeline due to centrifugal force, forming a high-concentration coarse particle aggregation in the edge area. Small-particle coal powder has small inertia and good flowability, and is more likely to move with the main airflow, and tends to concentrate in the central area of the pipeline, forming a high-concentration fine particle aggregation in the central area. In the edge coarse particle area, the particles frequently collide and rub, and the resistance effect of the particles on the airflow is enhanced, resulting in an increase in local airflow resistance. According to the momentum conservation of fluid mechanics, under the same pressure drop condition, the increase in resistance will reduce the flow rate in this area. In the central fine particle area, the resistance effect of the particles on the airflow is weak, and the airflow resistance is small, so the flow rate will correspondingly increase. Therefore, uneven distribution of coal powder particles will cause a radial flow rate deviation.

[0031] Specifically, the preset distance is determined according to the pipe diameter of the coal powder pipe at the outlet of the coal mill. For example, if the diameter of the coal powder pipe at the outlet of the coal mill is 50 cm, the preset distance can be set to 5 cm, and 5 concentric circles will be formed with the geometric center of the coal powder pipe as the reference point. The flow rates at multiple point positions in the same concentric circle are uniformly taken, and the average value of the multiple point flow rates is determined as the flow rate of the concentric circle.

[0032] Specifically, the process of adjusting the angle of the guide vane of the coal powder separator based on the radial flow rate difference value includes: Compare the radial flow rate difference value with a preset flow rate difference value; Set a plurality of angle adjustment coefficients based on the comparison result of the radial flow rate difference value and the preset flow rate difference value, and reduce the angle of the guide vane based on the plurality of angle adjustment coefficients.

[0033] Specifically, it is determined to reduce the guide vane angle by a first angle adjustment coefficient based on a comparison result that the radial flow rate difference is less than the preset flow rate difference; It is determined to reduce the guide vane angle by a second angle adjustment coefficient based on a comparison result that the radial flow rate difference is greater than or equal to the preset flow rate difference.

[0034] Specifically, the preset flow rate difference is set to a range of [1.5 m / s, 3 m / s], preferably 2 m / s in the embodiment of the application, the second angle adjustment coefficient is set to a range of [0.92, 0.96], preferably 0.94 in the embodiment of the application, and the first angle adjustment coefficient is set to a range of [0.97, 0.99], preferably 0.98 in the embodiment of the application.

[0035] It can be understood that the radial flow rate difference reflects the uniformity of the flow rate at different radial positions on the cross section of the coal mill outlet pulverized coal pipe, and the smaller the difference is, the more uniform the radial distribution of the coal powder gas flow in the pipe is, and the larger the difference is, the more turbulent the flow rate distribution is. Such non-uniform flow rate directly leads to the segregation of coal powder particles in the pipe, for example, the coal powder concentration is low in the area with high flow rate, and the coal powder accumulates in the area with low flow rate, thereby causing the imbalance of the coal powder concentration in the thick and thin coal powder areas in the subsequent furnace, and further affecting the combustion efficiency and NO X suppression effect, when the radial flow rate difference is too large, the uniformity of the gas flow at the outlet of the separator needs to be optimized by adjusting the vane angle, so that the concentration of the thick and thin coal powder areas of the coal powder separated from the coal powder separator is balanced.

[0036] Specifically, the process of determining whether the gas flow mixing of the thick coal powder phase and the thin coal powder phase is qualified based on the fire interval includes: Comparing the fire interval with a preset time length respectively; Based on the comparison result that the fire interval is less than a first preset time length or greater than a second preset time length, it is determined that the gas flow mixing of the thick coal powder phase and the thin coal powder phase is unqualified; Based on the comparison result that the fire interval is greater than or equal to the first preset time length and less than or equal to the second preset time length, it is determined that the gas flow mixing of the thick coal powder phase and the thin coal powder phase is qualified.

[0037] Specifically, the determination of the fire interval can be achieved by installing infrared / ultraviolet composite detectors in the water-cooled wall area corresponding to the injection ports of the burner thick coal powder area and the thin coal powder area, respectively, to accurately capture the radiation signal mutation at the fire moment by the difference in radiation spectrum, and processing the collected signals using an algorithm (such as Bayesian criterion) to output the fire interval. This is a prior art and will not be described in detail.

[0038] Specifically, the value range of the first preset time length is set to [0.5s, 1s], and the embodiment of the application preferably 0.5s, and the value range of the second preset time length is set to [1.1s, 2s], and the embodiment of the application preferably 1.5s.

[0039] Specifically, under the condition of determining that the gas flow mixing is unqualified, the process of adjusting the air speed of the secondary air according to the uniformity characteristic value includes: Obtaining image information of the furnace, determining a plurality of temperature distribution gradients and corresponding temperature distribution ranges in the furnace after pre-processing the image information; Determining the coincidence degree of any temperature distribution range and the corresponding standard temperature distribution range; Determining the ratio of the number of temperature distribution gradients with the coincidence degree greater than or equal to the preset coincidence degree to the total number of temperature distribution gradients as the uniformity characteristic value; Comparing the uniformity characteristic value with the preset characteristic value; Setting a plurality of air speed adjustment coefficients based on the comparison result of the uniformity characteristic value and the preset characteristic value, and adjusting the air speed of the secondary air based on the plurality of air speed adjustment coefficients.

[0040] Specifically, the air speed of the secondary air is increased by the first air speed adjustment coefficient based on the comparison result that the uniformity characteristic value is less than the first preset characteristic value; The air speed of the secondary air is increased by the second air speed adjustment coefficient based on the comparison result that the uniformity characteristic value is greater than or equal to the first preset characteristic value and less than the second preset characteristic value.

[0041] Specifically, when the pulverized coal combustion adopts a concentration grading method, the temperature distribution in the furnace under stable operation conditions presents a local high temperature and gradient distribution, the dense phase coal powder injection area is the main ignition and combustion core area, the dense phase coal powder area has high coal powder concentration, short ignition delay and high combustion intensity, forming a local high temperature core area, the dilute phase coal powder area has low coal powder concentration and high primary air ratio, the ignition lags behind the dense phase, the combustion intensity is relatively moderate, and the temperature is lower than that of the dense phase core area but higher than that of the low temperature area at the tail of the furnace. The temperature presents a smooth gradient decrease from the dense phase core area to the outside, and the standard temperature distribution range refers to the reasonable interval range of the temperature in each area in the furnace under the conditions of the boiler design coal, rated load and stable operation conditions, which can ensure the combustion efficiency, equipment safety and environmental protection emission standards.

[0042] Specifically, in the pulverized coal combustion, especially in the concentration staged combustion, the core role of the secondary air is to provide oxygen required for combustion, to strengthen the airflow disturbance and mixing, and the air speed directly affects the uniformity of the contact between the pulverized coal and the air. When the airflow mixing is unqualified, the stratification phenomenon of the over-concentration of pulverized coal in the dense pulverized coal area and the excess air in the light pulverized coal area is easy to form in the furnace. After the air speed of the secondary air is increased, the momentum carried by the secondary air is increased, the secondary air can penetrate the boundary layer of the pulverized coal airflow formed by the primary air, the turbulence disturbance is enhanced, the pulverized coal in the dense pulverized coal area is diffused to the light pulverized coal area, and the air in the light pulverized coal area is penetrated to the dense pulverized coal area, so that the state of local concentration unevenness is broken. At the same time, the pulverized coal combustion needs continuous oxygen supply. When the mixing is unqualified, the incomplete combustion is caused by the lack of oxygen in the dense pulverized coal area, and the temperature is low due to the lack of pulverized coal in the light pulverized coal area. Increasing the air speed of the secondary air can speed up the oxygen delivery speed to the pulverized coal concentration area, reduce the oxygen deficiency lag in the dense pulverized coal area, promote the high-temperature flue gas circulation, and improve the temperature level of the light pulverized coal area, so that the combustion reaction is more uniform. However, the air speed of the secondary air is not the higher the better. Too high air speed of the secondary air can cause the flame to be blown away, so that the ignition stability is reduced. Therefore, the air speed adjustment coefficient needs to be optimized according to the flame shape characteristic value to prevent the increase range of the air speed from being too large.

[0043] Specifically, the preset coincidence degree is set to [65%, 80%], and the embodiment of the present application preferably 70%.

[0044] Specifically, the first preset characteristic value is set to [0.6, 0.7], and the embodiment of the present application preferably 0.65. The second preset characteristic value is set to [0.71, 0.85], and the embodiment of the present application preferably 0.75. The first air speed adjustment coefficient is set to [1.3, 1.5], and the embodiment of the present application preferably 1.4. The second air speed adjustment coefficient is set to [1.1, 1.29], and the embodiment of the present application preferably 1.2.

[0045] Specifically, the process of optimizing the air speed adjustment coefficient according to the flame shape characteristic value in the furnace includes: Comparing the flame shape characteristic value with the preset shape characteristic value respectively; Based on the comparison result that the flame shape characteristic value is less than the first preset shape characteristic value, the first air speed optimization coefficient is used to reduce the air speed adjustment coefficient; Based on the comparison result that the flame shape characteristic value is greater than the second preset shape characteristic value, the second air speed optimization coefficient is used to increase the air speed adjustment coefficient.

[0046] Specifically, the flame shape characteristic value refers to the flame length, and the determination of the flame length is determined according to image information using an image algorithm, which is prior art and will not be described herein. It can be understood that good mixing of the thick and thin pulverized coal zones will make the flame length moderate, without washing the water-cooled wall and with clear profile without deflection. If the mixing is too slow, the flame will be elongated and the tail will be red, and the secondary air speed needs to be increased. If the mixing is too fast, the flame will be too short and the root will be unstable, and the secondary air speed needs to be reduced.

[0047] Specifically, the value of the preset shape characteristic parameter is related to the height of the furnace, for example, for a furnace with a height of 4m-8m, the value range of the first preset shape characteristic parameter is set to [2m, 3m], and the embodiment of the present application preferably 2m, and the value range of the second preset shape characteristic parameter is set to [3.1m, 6m], and the embodiment of the present application preferably 6m; for a furnace with a height of about 20m-30m, the value range of the first preset shape characteristic parameter is set to [8m, 11m], and the embodiment of the present application preferably 10m, and the value range of the second preset shape characteristic parameter is set to [17m, 20m], and the embodiment of the present application preferably 18m; for a furnace with a height of about 30m-40m, the value range of the first preset shape characteristic parameter is set to [13m, 16m], and the embodiment of the present application preferably 14m, and the value range of the second preset shape characteristic parameter is set to [21m, 24m], and the embodiment of the present application preferably 22m, and the specific value is not limited.

[0048] Specifically, the value range of the first wind speed optimization coefficient is set to [0.8, 0.9], and the embodiment of the present application preferably 0.85, and the value range of the second wind speed optimization coefficient is set to [1.1, 1.2], and the embodiment of the present application preferably 1.15.

[0049] Specifically, the determination process of the fluctuation intensity of the combustion efficiency curve includes: determining a plurality of points with combustion efficiency lower than the preset efficiency based on the combustion efficiency curve; determining a plurality of distances of any of the points from a straight line where the preset efficiency is located; determining the standard deviation of a plurality of the distances as the fluctuation intensity.

[0050] Specifically, the value of the preset efficiency is 95%, and it can be understood that the preset efficiency is a straight line parallel to the horizontal coordinate axis with a vertical coordinate value of 95% on the combustion efficiency curve. A plurality of points on the combustion efficiency curve below the straight line can be determined, the distance of any point from the straight line along the vertical coordinate axis is determined, and the standard deviation of a plurality of the distances is determined as the fluctuation intensity.

[0051] Specifically, the process of optimizing the preset distribution characteristic value based on the fluctuation intensity includes: comparing the fluctuation intensity with a preset intensity; setting a plurality of characteristic value optimization coefficients based on a comparison result of the fluctuation intensity and the preset intensity, to increase the preset distribution characteristic value based on the plurality of characteristic value optimization coefficients.

[0052] Specifically, it is determined to optimize the preset distribution characteristic value with a characteristic value optimization coefficient based on a comparison result that the fluctuation intensity is greater than the preset intensity; determining to increase the preset distribution characteristic value with a first characteristic value optimization coefficient based on a comparison result that a fluctuation intensity difference between the fluctuation intensity and the preset intensity is greater than a preset difference value; determining to increase the preset distribution characteristic value with a second characteristic value optimization coefficient based on a comparison result that the fluctuation intensity difference is less than or equal to the preset difference value.

[0053] It can be understood that the fluctuation intensity of the combustion efficiency curve reflects the stability of the combustion process, the greater the fluctuation intensity, the higher the dispersion degree of the combustion efficiency over time, and the worse the combustion stability, and the preset distribution characteristic value is one of the core factors affecting the combustion stability, and the uniformity of the coal powder particle size distribution directly determines the consistency of the combustion reaction, when the particle size is uniform, the ignition and combustion rate of the coal powder particles are more synchronous, the heat release and burnout degree are more stable, and the fluctuation of the combustion efficiency curve is small, if the particle size distribution is not uniform, it means that the preset distribution characteristic value is too low, which will lead to too coarse or too fine coal powder particles in local area, and then cause the sharp fluctuation of the combustion efficiency. Therefore, when the fluctuation intensity is too large, the preset distribution characteristic value needs to be increased to improve the requirement for the uniformity of the particle size, improve the consistency of the coal powder particle size distribution, and reduce the fluctuation of the combustion efficiency from the root to improve the combustion stability.

[0054] Specifically, the preset intensity is set to [0.2cm, 0.5cm], and the embodiment of the present application is preferably 0.3cm, the preset difference value is set to [0.1cm, 0.3cm], and the embodiment of the present application is preferably 0.2cm, the first characteristic value optimization coefficient is set to [1.11, 1.15], and the embodiment of the present application is preferably 1.12, and the second characteristic value optimization coefficient is set to [1.05, 1.1], and the embodiment of the present application is preferably 1.07.

[0055] So far, the technical scheme of the present application has been described in combination with the preferred embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Without deviating from the principles of the present application, those skilled in the art can make equivalent changes or replacements to related technical features, and the technical scheme after the changes or replacements will fall within the protection scope of the present application.

Claims

1. A method of boiler coal monitoring, characterized by, The method comprises the following steps: acquiring a particle size distribution characteristic value of the coal powder in the coal powder outlet pipe of the coal mill, and determining whether the separation mode of the coal powder separator is qualified based on a comparison result of the particle size distribution characteristic value and a preset distribution characteristic value; under the condition that the separation mode of the coal powder separator is determined to be unqualified, adjusting the guide vane angle of the coal powder separator according to a radial flow velocity difference value of the coal powder outlet pipe of the coal mill; under the condition that the separation mode of the coal powder separator is determined to be qualified, determining a firing interval of the dense coal powder phase and the dilute coal powder phase in the furnace, and determining whether the airflow mixing of the dense coal powder phase and the dilute coal powder phase is qualified based on the firing interval; under the condition that the airflow mixing is determined to be unqualified, adjusting the air velocity of the secondary air according to a uniformity characteristic value of the temperature gradient distribution of the furnace, and optimizing the air velocity adjustment coefficient according to a flame shape characteristic value in the furnace; constructing a combustion efficiency curve of the coal powder, and optimizing the preset distribution characteristic value according to the fluctuation intensity of the combustion efficiency curve.

2. The boiler coal fin monitoring method according to claim 1, characterized by, The determination process of the particle size distribution characteristic value comprises the following steps: establishing a particle size distribution histogram of the coal powder in the coal powder outlet pipe of the coal mill by using a light scattering instrument; connecting the upper edge midpoint positions of any histogram blocks to form a particle size distribution curve; aligning the particle size distribution curve with a standard distribution curve as a benchmark according to the horizontal coordinate scale; determining a ratio of an overlapping area of the particle size distribution curve and the standard distribution curve to an area surrounded by the standard distribution curve and the coordinate axis as the particle size distribution characteristic value.

3. The boiler coal fin monitoring method according to claim 2, characterized by, The process of determining whether the separation mode of the coal powder separator is qualified based on the particle size distribution characteristic value comprises the following steps: comparing the particle size distribution characteristic value with the preset distribution characteristic value; determining that the separation mode of the coal powder separator is unqualified based on a comparison result that the particle size distribution characteristic value is less than the preset distribution characteristic value.

4. The boiler coal fin monitoring method according to claim 3, characterized by, The determination process of the radial flow velocity difference value comprises the following steps: dividing the cross section of the coal powder outlet pipe of the coal mill into a plurality of concentric circular rings with a preset distance as the interval and with the geometric center as the benchmark point, and determining a plurality of flow velocities of the plurality of concentric circular rings; determining a radial flow velocity difference value as a difference between the maximum value and the minimum value of the plurality of flow velocities.

5. The boiler coal monitoring method according to claim 4, wherein The process of adjusting the guide vane angle of the coal powder separator based on the radial flow velocity difference value comprises the following steps: comparing the radial flow velocity difference value with a preset flow velocity difference value; setting a plurality of angle adjustment coefficients based on a comparison result of the radial flow velocity difference value and the preset flow velocity difference value, and reducing the guide vane angle based on the plurality of angle adjustment coefficients.

6. The boiler soot monitoring method according to claim 5, characterized by, The process of determining whether the airflow mixing of the dense coal powder phase and the dilute coal powder phase is qualified based on the firing interval comprises the following steps: respectively comparing the firing interval with a first preset time length and a second preset time length; determining that the airflow mixing of the dense coal powder phase and the dilute coal powder phase is unqualified based on a comparison result that the firing interval is less than the first preset time length or greater than the second preset time length.

7. The boiler soot monitoring method according to claim 6, characterized by, The process of adjusting the air velocity of the secondary air according to the uniformity characteristic value under the condition that the airflow mixing is determined to be unqualified comprises the following steps: acquiring image information of the furnace, determining a plurality of temperature distribution gradients and corresponding temperature distribution ranges in the furnace after preprocessing the image information; determining a degree of coincidence of any of the temperature distribution ranges with a corresponding standard temperature distribution range; determining a ratio of a number of temperature distribution gradients with a degree of coincidence greater than or equal to a preset degree of coincidence to a total number of the temperature distribution gradients as a uniformity representation value; comparing the uniformity representation value with a preset representation value; setting a plurality of wind speed adjustment coefficients based on a comparison result of the uniformity representation value and the preset representation value, to adjust a wind speed of the secondary air based on the plurality of wind speed adjustment coefficients.

8. The boiler soot monitoring method according to claim 7, characterized by, a process of optimizing the wind speed adjustment coefficients based on a flame shape representation value in the furnace includes: comparing the flame shape representation value with a preset shape representation value respectively; based on a comparison result that the flame shape representation value is less than a first preset shape representation value, setting a first wind speed optimization coefficient to reduce the wind speed adjustment coefficients; based on a comparison result that the flame shape representation value is greater than a second preset shape representation value, setting a second wind speed optimization coefficient to increase the wind speed adjustment coefficients.

9. The boiler soot monitoring method according to claim 8, characterized by, a process of determining a fluctuation intensity of the combustion efficiency curve includes: determining a plurality of points with combustion efficiency less than a preset efficiency based on the combustion efficiency curve; determining a plurality of distances of any of the points from a straight line where the preset efficiency is located; determining a standard deviation of the plurality of distances as the fluctuation intensity.

10. The boiler soot monitoring method according to claim 9, characterized by, a process of optimizing the preset distribution representation value based on the fluctuation intensity includes: comparing the fluctuation intensity with a preset intensity; based on a comparison result of the fluctuation intensity and the preset intensity, setting a plurality of representation value optimization coefficients to increase the preset distribution representation value based on the plurality of representation value optimization coefficients.

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