High-temperature corrosion risk hierarchical control method and system based on flue gas CO distribution characteristics

Abstract

The invention discloses a high-temperature corrosion risk hierarchical control method and system based on flue gas CO distribution characteristics. The system comprises a distributed CO detection array, an embedded processor and an execution module. The distributed CO detection array collects the CO concentration of a hearth outlet in real time; the embedded processor runs a distribution function correction algorithm; the execution module adjusts the operation oxygen amount or the opening degree of a wall-attached air door and a secondary air door according to the risk level. At present, most units cannot realize online detection of the CO concentration in the adherent atmosphere, the system monitors the high-temperature corrosion risk level of the water cooling wall through the CO concentration of a hearth outlet, a differential control strategy is provided, the high-temperature corrosion problem of the water cooling wall of the boiler is effectively relieved, and the efficiency of the boiler is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal-fired boiler safety control, and particularly relates to a high-temperature corrosion risk grading control method and system based on flue gas CO distribution characteristics. BACKGROUND

[0002] The phenomenon of high-temperature corrosion of the boiler causes the water-cooled wall tube to be continuously corroded and thinned, and the average value of the thinning speed reaches 1.8-2.6 mm per year. When the water-cooled wall tube is thinned to a certain extent, a serious power plant accident of high-temperature tube burst of the water-cooled wall will eventually occur, which endangers the safe operation of the boiler. The high-temperature corrosion not only consumes materials, but also prolongs the maintenance time of the unit and increases the workload, resulting in economic losses. The high-temperature corrosion of the boiler water-cooled wall is mainly related to the sulfur content of the coal fed into the furnace, the atmosphere at the wall of the water-cooled wall, the high-temperature flue gas, and the erosion of the coal powder flow, etc. At present, the measures to prevent and control the high-temperature corrosion of the water-cooled wall mainly include the following aspects: reasonable air distribution, strengthening of turbulent mixing in the furnace; control of reasonable coal powder fineness to prevent large particles of unburned coal powder from directly eroding the water-cooled wall; adoption of wall-attached air technology to form an air protection film in the high-temperature corrosion area; adoption of anti-corrosion spraying and pipe material optimization technology, etc.

[0003] Although the wall-attached air technology can alleviate the corrosion, according to statistics, the coverage rate of the wall-attached air for the 330MW / 660MW unit is insufficient, and only the 1000NW unit has a high popularization rate, and there is a lack of differentiated control strategies for different capacity units. At the same time, most units cannot realize online detection of the CO concentration and H2S concentration in the wall-attached atmosphere, and cannot observe and monitor the high-temperature corrosion condition of the water-cooled wall.

[0004] There is a feature of "high on both sides and low in the middle" for the CO distribution at the outlet of the opposed-wall boiler furnace, and the average value of the traditional detection point cannot truly reflect the CO concentration at the outlet of the furnace. Therefore, the evaluation of the high-temperature corrosion of the furnace based on the average value of the traditional CO detection point is misleading and needs to be corrected.

[0005] In view of the above problems, it is necessary to propose a high-temperature corrosion grading control system that fuses the correction of CO distribution. SUMMARY

[0006] The present application aims at the deficiencies of the prior art, and proposes a high-temperature corrosion risk assessment method and grading control system based on the correction of flue gas CO distribution characteristics. The auxiliary monitoring of the wall-attached atmosphere is realized by correcting the CO concentration at the outlet of the furnace, the high-temperature corrosion grade of different units is evaluated, and a grading control system is established.

[0007] The purpose of the present application is achieved by the following technical scheme: a high-temperature corrosion risk grading control system based on flue gas CO distribution characteristics, which comprises: a distributed CO detection array, which is used to collect the CO concentration at the outlet of the opposed-wall boiler furnace in real time; embedded processor, for correcting the CO concentration collected by the distributed CO detection array based on the flue width and the unit characteristic coefficient; an execution module, for determining the high-temperature corrosion level of the boiler according to the corrected CO concentration, and adjusting the oxygen content, the wall-attached air or the secondary air door opening degree according to the risk level for different alarm units.

[0008] Further, the formula for correcting the CO concentration is: ; wherein CO is the basic CO concentration, L is the flue width, k and a are the unit characteristic coefficients, and the unit characteristic coefficients are obtained by fitting the CO concentration correction formula with the historical data of the measured CO concentration distribution at the furnace outlet of the unit.

[0009] Further, the distributed CO detection array identifies the distribution feature of the CO concentration at the furnace outlet of the opposed-wall boiler, i.e., high on both sides and low in the middle, and establishes the spatial distribution function of the CO at the furnace inlet of the opposed-wall boiler through multi-point sampling.

[0010] Further, the measured CO concentration distribution data at the furnace outlet are obtained through multi-point sampling, and then the unit characteristic coefficients k and a are fitted by substituting the data into the CO concentration correction formula, so as to correct the single-point detection average to the effective CO concentration at the furnace outlet in the representative wall-attached area.

[0011] Further, the high-temperature corrosion level includes yellow warning and red alarm; the yellow warning is 1000 ppm≤corrected CO concentration≤2000 ppm or there is a local high fluctuation area, and the red alarm is corrected CO concentration>2000 ppm.

[0012] Further, the specific control strategies for different units are as follows: For a 330MW supercritical unit, the furnace oxygen content is preferentially controlled, and the oxygen content at full load is ≥3.4%; For a 660MW ultra-supercritical unit, the furnace oxygen content is preferentially controlled and the wall-attached air is adjusted, and the oxygen content at full load is ≥3.0%; For a 1000MW ultra-supercritical unit, the wall-attached air is preferentially controlled and the secondary air door is adjusted, so as to realize the fine control of the wall-attached air branch pipe and the secondary air door opening degree.

[0013] The application provides a high-temperature corrosion risk grading control method based on the CO distribution feature of flue gas, which comprises the following steps: (1) measuring the CO concentration of the boiler flue gas based on the distributed CO detection array; (2) correcting the CO concentration based on the flue width and the unit characteristic coefficient; (3) According to the revised CO concentration, it is determined that the high temperature corrosion level of the boiler exists; (4) Based on the red alarm in the high temperature corrosion level, the oxygen content, the wall-attached air or the secondary air door opening degree are adjusted for different units.

[0014] Design concept of the present application: A distributed CO detection array, an embedded processor and an execution module are arranged; the CO concentration at the furnace outlet is collected in real time through the distributed CO detection array; the embedded processor runs the distribution function correction algorithm; and the execution module adjusts the oxygen content or the wall-attached air and the secondary air door opening degree according to the risk level. The present application solves the problem that most units cannot realize online detection of the CO concentration in the wall-attached atmosphere, monitors the high temperature corrosion risk level of the water wall through the CO concentration at the furnace outlet, and proposes a differentiated control strategy, which effectively alleviates the problem of high temperature corrosion of the boiler water wall, reduces the risk of pipe explosion of the boiler water wall, improves the operation safety, and improves the efficiency of the boiler.

[0015] The present application has the following beneficial effects: the present application monitors the high temperature corrosion risk level of the water wall through the CO concentration at the furnace outlet, proposes a differentiated control strategy, effectively alleviates the problem of high temperature corrosion of the boiler water wall, reduces the risk of pipe explosion of the boiler water wall, improves the operation safety, and improves the efficiency of the boiler. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0017] Figure 1 A high temperature corrosion risk assessment and grading control system block diagram based on the CO distribution characteristics correction of flue gas is provided. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described below in combination with the drawings and implementation examples. It should be understood that the specific implementation examples described herein are only used to explain the present application, and are not used to limit the present application.

[0019] As shown in Figure 1 An aspect provided by the present application provides a hedge boiler high temperature corrosion risk grading control system based on the CO distribution characteristics correction of flue gas, which comprises a distributed CO detection array, an embedded processor and an execution module. The distributed CO detection array obtains flue gas samples at the outlet of the boiler back pass; measures the CO concentration in the flue gas samples; identifies the "high on both sides and low in the middle" distribution characteristics of the CO concentration at the outlet of the opposed wall furnace, and establishes the spatial distribution function of the CO at the inlet of the opposed wall furnace through multi-point sampling; Five detection points (for example, located at 0, L / 4, L / 2, 3L / 4, and L) are arranged at equal intervals on the A and B sides in the width direction of the flue, forming a detection array.

[0020] The measured CO concentration data is in the form of CO concentration values measured at multiple positions (for example, five points), for example: ; The embedded processor fits the unit characteristic coefficients k and a according to the measured CO concentration distribution data at the outlet of the furnace, and corrects the single-point detection average to the representative effective CO concentration at the outlet of the furnace in the wall attachment area.

[0021] Specifically, the specific process of the embedded processor for correcting the CO concentration can be as follows: ; Wherein, C0 is the basic concentration, L is the flue width, k and a are the unit characteristic coefficients, which are fitted by substituting the historical data of the measured CO concentration distribution at the outlet of the furnace into the CO concentration correction formula; The execution module judges the risk level and executes the corresponding control strategy. Specifically, the operation process of the execution module can be as follows: According to the obtained corrected CO concentration, it is determined that the boiler has a high temperature corrosion level. It includes: Red alarm level: corrected CO concentration > 2000 ppm; Yellow pre-warning level: 1000 ppm ≤ corrected CO concentration ≤ 2000 ppm or there is a local high fluctuation area, wherein the high fluctuation area is that the CO concentration difference between adjacent measuring points exceeds 1000 ppm, or the CO concentration standard deviation in a certain area is greater than 500 ppm, which is regarded as a high fluctuation area.

[0022] The alarm unit is proposed with the hierarchical control logic shown in Table 1; Table 1 ; On the other hand, corresponding to the foregoing embodiment of the high temperature corrosion risk grading control system of the opposed wall furnace based on the correction of the flue gas CO distribution characteristics, the present application also provides an embodiment of a high temperature corrosion risk assessment method based on the correction of the flue gas CO distribution characteristics. The specific process of each step of the method is referred to the implementation process of the distributed CO detection array, the embedded processor and the execution module of the foregoing embodiment of the high temperature corrosion risk grading control system of the opposed wall furnace based on the correction of the flue gas CO distribution characteristics; specifically comprising the following steps, (1) Measure the CO concentration of the boiler flue gas based on a distributed CO detection array; (2) Correct the CO concentration based on the flue width and the unit characteristic coefficient; (3) Determine the high-temperature corrosion level of the boiler according to the corrected CO concentration; (4) Adjust the oxygen content, the wall-attached air or the secondary air door opening degree according to the red alarm of the high-temperature corrosion level.

[0023] The above examples are used to explain and illustrate the present application, but not to limit the present application, and any modification and change made to the present application within the spirit and protection scope of the claims of the present application, all fall into the protection scope of the present application.

Claims

1. A high-temperature corrosion risk classification and control method based on the CO distribution characteristics of flue gas, characterized in that, Includes the following steps: Step 1) Measure the CO concentration of boiler flue gas at the furnace outlet based on a distributed CO detection array; Step 2) Based on the measured CO concentration distribution data of boiler flue gas at the furnace outlet, substitute the CO concentration correction formula to fit the unit characteristic coefficients k and α, and correct the single-point detection mean to the effective furnace outlet CO concentration in the wall-adhering area. Step 2) specifically involves: The CO concentration is corrected based on the flue width and unit characteristic coefficients. The formula for CO concentration correction is as follows: ； Where C0 is the basic CO concentration, L is the flue width, and k and α are the unit characteristic coefficients. The unit characteristic coefficients are obtained by fitting the historical data of the measured CO concentration distribution at the furnace outlet of the unit into the CO concentration correction formula. Step 3) Determine the high-temperature corrosion level of the boiler based on the corrected CO concentration, where the high-temperature corrosion level includes yellow warning and red alarm. Step 4) Based on the red alarm in the high temperature corrosion level, adjust the operating oxygen level, wall-mounted air or secondary air damper opening for different units.

2. The high-temperature corrosion risk classification and control method based on the CO distribution characteristics of flue gas according to claim 1, characterized in that, Step 1) specifically involves: identifying the distribution characteristics of CO concentration at the furnace outlet of the counter-pressure boiler, using a distributed CO detection array to obtain measured CO concentration distribution data at the furnace outlet through multi-point sampling, and establishing a spatial distribution function of CO at the furnace inlet of the counter-pressure boiler based on the data.

3. The high-temperature corrosion risk classification and control method based on the CO distribution characteristics of flue gas according to claim 1, characterized in that, In step 3), the yellow warning and red alarm are respectively: a yellow warning is given when the corrected CO concentration is ≤1000ppm≤corrected CO concentration≤2000ppm or when there is a local high fluctuation area, and a red alarm is given when the corrected CO concentration is >2000ppm.

4. The high-temperature corrosion risk classification and control method based on the CO distribution characteristics of flue gas according to claim 1, characterized in that, In step 4), the specific control strategies for different generator units are as follows: For 330MW supercritical units, priority should be given to controlling the oxygen content in the furnace, with the oxygen content at full load operation being ≥3.4%; For 660MW ultra-supercritical units, priority is given to controlling furnace oxygen levels and adjusting wall-mounted air, with oxygen levels ≥3.0% during full-load operation; For 1000MW ultra-supercritical units, priority is given to controlling the wall-mounted air and adjusting the secondary air dampers to achieve precise control of the opening of the wall-mounted air branch pipes and secondary air dampers.

5. A high-temperature corrosion risk classification and control system based on the CO distribution characteristics of flue gas, used to implement the method as described in any one of claims 1-4, characterized in that, include: Distributed CO detection array, embedded processor and execution module; A distributed CO detection array is used to collect CO concentration data at the furnace outlet of a counter-current boiler in real time. An embedded processor is used to correct the CO concentration collected by the distributed CO detection array based on the flue width and unit characteristic coefficients; The execution module is used to determine the high-temperature corrosion level of the boiler based on the corrected CO concentration, and adjust the operating oxygen, wall-mounted air, or secondary air damper opening according to the risk level for different alarm units.

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