Boiler equipment maintenance methods

Abstract

To provide a maintenance method for a boiler facility that can more appropriately maintain the boiler facility.SOLUTION: A maintenance method for a boiler facility including a boiler comprises a sample acquisition step of acquiring a sample tube by cutting a portion of a furnace wall tube constituting a furnace wall of the boiler within a first shutdown period that is a shutdown period of the boiler in which a scaffold is not installed inside a furnace of the boiler, an evaluation step of evaluating a condition of the sample tube, and a maintenance plan creation step of creating a maintenance plan of the furnace wall on the basis of an evaluation result of the condition of the sample tube.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] The present disclosure relates to a maintenance method for a boiler facility. [Background technology]

[0002] Boiler furnace wall tubes are prone to scale buildup on their inner surfaces and thinning due to corrosion on their outer surfaces. To prevent this, maintenance such as chemical cleaning and repair of furnace wall tubes is carried out to prevent deterioration of heat transfer performance and damage caused by scale buildup and thinning.

[0003] Patent Document 1 describes that in a thermal power plant or the like, samples of heat transfer tubes are taken when operation is stopped, the amount of scale adhesion on the taken heat transfer tube sample is measured, and if the measured amount of scale adhesion is equal to or greater than a threshold, chemical cleaning is carried out at the time of the next regular inspection. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-147797 Summary of the Invention [Problem to be solved by the invention]

[0005] In the past, in boiler facilities, taking samples of furnace wall tubes (removing tubes) and restoring them required the installation of scaffolding inside the furnace, a large-scale operation. For this reason, sample tubes were taken and analyzed during periodic inspections when scaffolding was installed inside the furnace, and the results of this analysis were used to determine whether or not to perform chemical cleaning, etc., at the next periodic inspection several years later.

[0006] However, with this maintenance planning method, the period between the acquisition and analysis of samples from the furnace wall tubes and the next periodic inspection is long, and as a result, the accuracy of the results of the analysis of the sample tubes in determining whether chemical cleaning or other procedures are necessary is sometimes not good.

[0007] Furthermore, for example, if the analysis of a sample tube reveals that the amount of scale buildup is unexpectedly high, chemical cleaning will be carried out immediately. However, since arranging for chemical cleaning takes time, there are cases where the period of regular inspection (the period during which the boiler equipment is shut down) must be extended.

[0008] In view of the above circumstances, at least one embodiment of the present invention aims to provide a maintenance method for boiler equipment that enables more appropriate maintenance of boiler equipment. [Means for solving the problem]

[0009] A method for maintaining boiler equipment according to at least one embodiment of the present invention includes: A maintenance method for boiler equipment including a boiler, comprising: a sample obtaining step of obtaining a sample tube by removing a part of a furnace wall tube constituting a furnace wall of the boiler during a first shutdown period, which is a shutdown period of the boiler during which no scaffolding is installed inside the furnace of the boiler; an evaluation step of evaluating the condition of the sample tube; a maintenance plan creation step of creating a maintenance plan for the furnace wall based on the evaluation result of the state of the sample tube; Equipped with. [Effects of the Invention]

[0010] According to at least one embodiment of the present invention, a method for maintaining a boiler facility is provided that enables more appropriate maintenance of the boiler facility. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a boiler facility to which a maintenance method according to an embodiment is applied; [Figure 2] FIG. 2 is a schematic diagram of a furnace wall of a boiler. [Figure 3A] 1 is a flowchart of a maintenance method for a boiler facility according to an embodiment. [Figure 3B] 1 is a flowchart of a maintenance method for a boiler facility according to an embodiment. [Figure 4A] 1 is a flowchart of a maintenance method for a boiler facility according to an embodiment. [Figure 4B] 1 is a flowchart of a maintenance method for a boiler facility according to an embodiment. [Figure 5] 1 is a flowchart of a maintenance method for a boiler facility according to an embodiment. [Figure 6] 1 is a schematic graph showing an example of the relationship between the operation time of a boiler and the amount of scale adhesion on a furnace wall tube. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0013] (Boiler equipment configuration) Fig. 1 is a schematic diagram of a boiler facility to which a maintenance method according to some embodiments is applied. Fig. 2 is a schematic diagram of a furnace wall of the boiler. The boiler may be a fossil fuel-fired boiler such as a coal-fired boiler, or may be another boiler (for example, a soda recovery boiler).

[0014] A boiler facility 100 according to some embodiments includes a boiler 1 shown in Fig. 1. The boiler 1 shown in Fig. 1 includes a furnace 2 formed by a furnace wall 3, a wind box 5 provided on the furnace wall 3 for supplying combustion air to the furnace 2, and a burner 4 for burning a carbon-containing fuel supplied to the furnace 2. In the boiler 1, a combustion gas flow path 11 is formed by a duct wall 40, through which combustion gas generated by combustion of fuel in the furnace 2 flows.

[0015] The boiler 1 includes heat exchangers 6a to 6d that are arranged in a combustion gas flow path 11 and heat the steam generated in the furnace 2 by heat exchange with the combustion gas. These heat exchangers 6a to 6d may be, for example, heaters, reheaters, economizers, etc. The heat exchangers 6a to 6d are configured by a group of heat transfer tubes.

[0016] Fig. 2 is a partial schematic diagram of the furnace wall 10 of the boiler 1 as viewed from outside the furnace of the boiler 1. As shown in Fig. 2, the furnace wall 10 includes a plurality of furnace wall tubes 12 spaced apart from one another and plate-like fins 14 connecting adjacent furnace wall tubes 12. A cooling fluid such as feedwater or steam may be circulated through the furnace wall tubes 12.

[0017] The furnace wall tubes 12 of the boiler 1 are prone to scale buildup on their inner surfaces and thinning due to corrosion of their outer surfaces. Therefore, in order to prevent deterioration in heat transfer performance and damage caused by scale buildup and thinning, maintenance such as chemical cleaning and repair of the furnace wall tubes 12 is carried out.

[0018] (Boiler equipment maintenance method flow) Hereinafter, a maintenance method for the boiler facility 100 according to some embodiments will be described.

[0019] 3A and 3B are flowcharts of a maintenance method for a boiler facility according to one embodiment. As shown in Fig. 3A and 3B, the maintenance method for a boiler facility 100 according to one embodiment includes the steps of: cutting a portion of a furnace wall tube to obtain a sample tube (S200); evaluating the condition of the sample tube obtained in step S200 (S300); and creating a maintenance plan for the furnace wall 10 based on the evaluation result of the condition of the sample tube in step S300 (S400).

[0020] In step S200, during the first shutdown period of the boiler 1 after the boiler 1 is shut down in step S100, a part of the furnace wall tube 12 is cut off (removed) and obtained as a sample tube.

[0021] Here, the first shutdown period of the boiler 1 is a period during which the boiler 1 is shut down without scaffolding being set up inside the furnace 2 of the boiler 1. Generally, when performing periodic inspections of the boiler 1 (every few years, etc.), scaffolding is set up inside the furnace 2 to inspect the furnace wall 10, etc. Setting up scaffolding is a large-scale job that takes a relatively long time. The above-mentioned first shutdown period is a relatively short shutdown period during which scaffolding is not set up inside the furnace 2 of the boiler.

[0022] In step S200, because no scaffolding has been installed inside the furnace 2, a portion of the furnace wall tube 12 is removed by work outside the furnace 2. After removing a portion of the furnace wall tube 12 to obtain a sample tube, work is performed to connect a new pipe to the removed portion of the furnace wall tube 12 and restore the furnace wall 10 before restarting operation of the boiler 1 in step S500. This restoration work is also performed by work outside the furnace 2. Note that the methods described in Japanese Patent Application Laid-Open No. 2021-107747 or Japanese Patent Application Laid-Open No. 2021-107748 can be used as a method for removing a portion of the furnace wall tube 12 by work outside the furnace 2 and as a method for restoring a furnace wall 10 from which a portion of the furnace wall tube 12 has been removed.

[0023] In step S300, the state of the sample tube acquired in step S200 is evaluated. In step S400, a maintenance plan for the furnace wall 10 is created based on the evaluation result of the state of the sample tube in step S300.

[0024] In step S300, the amount of scale adhered to the inner surface of the sample tube obtained in step S200 (scale adhesion amount) may be measured. In this case, in step S400, conditions for chemical cleaning of the furnace wall tube 12 may be determined based on the measurement value of the scale adhesion amount obtained in step S300. The conditions for chemical cleaning may include, for example, the timing of chemical cleaning, the type or concentration of the cleaning liquid, the temperature of the cleaning liquid, and the cleaning time.

[0025] In step S300, the scale adhering to the inner surface of the sample tube may be dissolved in a solvent or the like, the dissolved scale may be weighed, and the weight may be obtained as the amount of scale adhesion. Alternatively, in step S300, the thickness of the scale adhering to the inner surface of the sample tube may be measured, and the thickness may be obtained as the amount of scale adhesion.

[0026] Alternatively, in step S300, the amount of thinning on the outer surface of the sample tube obtained in step S200 may be measured using an ultrasonic method or microscopic observation of a cross section, or the state of damage on the outer surface of the sample tube obtained in step S200 (for example, the size or number of cracks) may be evaluated. In this case, in step S400, a repair plan for the furnace wall tube may be determined based on the measurement value of the amount of thinning on the outer surface of the sample tube obtained in step S300 or the evaluation result of the state of damage. The repair plan for the furnace wall tube may include, for example, the repair timing, repair method, and repair scope of the furnace wall tube 12.

[0027] After obtaining the sample tube in step S200, operation of the boiler 1 may be resumed (S500). Thereafter, maintenance work on the boiler facility 100 may be performed based on the maintenance plan created in step S400. Note that the evaluation of the state of the sample tube (S300) and the creation of the maintenance plan (S400) may be performed during a first shutdown period from when the boiler 1 is stopped in step S100 until when the operation of the boiler 1 is resumed in step S500, as shown in FIG. 3A, or may be performed after the operation of the boiler 1 is resumed in step S500 (i.e., after the first shutdown period), as shown in FIG. 3B.

[0028] In the above-described method, during a first shutdown period of the boiler 1 in which no scaffolding is installed inside the furnace 2 of the boiler 1, a portion of the furnace wall tube 12 is removed to obtain a sample tube, and a maintenance plan for the furnace wall 10 is created based on the evaluation results of the sample tube. In other words, since no scaffolding is installed during the period in which the boiler 1 is shut down to obtain and evaluate the sample tube, the period (first shutdown period) can be shortened. Therefore, such a relatively short shutdown period can be flexibly incorporated into the operation schedule of the boiler 1. Therefore, for example, by obtaining and analyzing sample tubes during a first shutdown period close to the next regular inspection (a relatively long shutdown period during which scaffolding is installed inside the reactor), it is possible to accurately determine whether maintenance work such as chemical cleaning is required at the time of the next regular inspection, and to appropriately determine the conditions for chemical cleaning. Also, if the evaluation results of the sample tubes indicate that maintenance work such as chemical cleaning is required earlier than the next regular inspection, more appropriate maintenance can be performed, such as by bringing forward the start of the next regular inspection. Thus, the above-described method allows for more appropriate maintenance of boiler equipment.

[0029] The above-mentioned first shutdown period may be a period established after the boiler 1 resumes operation after another shutdown period of the boiler 1 (such as the second shutdown period described below), or may be the first shutdown period after the boiler 1 is started up for the first time.

[0030] Figures 4A and 4B are flowcharts of a boiler facility maintenance method according to one embodiment. Steps S100 to S500 in Figures 4A to 4B are the same as steps S100 to S500 in Figures 3A and 3B, respectively. Also, steps S600 to S900 in Figures 4A to 4B are the same as steps S600' to S900'.

[0031] 4A and 4B, in some embodiments, during a second shutdown period (after the boiler 1 is shut down in step S600), which is different from the above-described first shutdown period (the period during which steps S200 to S400 are performed), scaffolding is set up inside the furnace 2 and maintenance of the furnace wall 10 (boiler equipment 100) is carried out (S700). After the maintenance of the furnace wall 10 in step S700 is completed, the scaffolding inside the furnace 2 is removed (S800), and then the operation of the boiler 1 is resumed (S900).

[0032] The second shutdown period includes the period for installing and removing scaffolding inside the furnace 2, and is a relatively long period because these operations are large-scale. The second shutdown period may be, for example, a shutdown period for the boiler 1 for a periodic inspection. The periodic inspection may be performed periodically every few years.

[0033] In one embodiment, as shown in Figures 4A and 4B, a sample tube is obtained by cutting a portion of the furnace wall tube 12 (S200) during a first shutdown period that follows the end of a second shutdown period (the previous second shutdown period; the period during which S700 to S800 are performed) and precedes the start of the next second shutdown period (the subsequent second shutdown period; the period during which S700' to S800' are performed). Before the subsequent second shutdown period begins, the condition of the sample tube obtained in step S200 is evaluated (S300), and a maintenance plan for the furnace wall 10 is created based on the evaluation result of the condition of the sample tube (S400). In one embodiment, during the subsequent second shutdown period, maintenance of the furnace wall 10 (S700') may be performed based on the maintenance plan created in step S400.

[0034] In the above-described embodiment, after the end of the second shutdown period (earlier second shutdown period) of the boiler 1 in which scaffolding is installed inside the furnace 2 of the boiler 1, a sample tube is obtained by removing a portion of the furnace wall tube 12 during the first shutdown period of the boiler 1 in which scaffolding is not installed inside the furnace 2 of the boiler 1, and a maintenance plan for the furnace wall 10 is created based on the evaluation results of the sample tube before the start of the next second shutdown period (later second shutdown period). In other words, since no scaffolding is installed inside the furnace during the period in which the boiler 1 is shut down to obtain and evaluate the sample tube, the period (first shutdown period) can be shortened. Therefore, such a relatively short shutdown period can be flexibly incorporated into the operation schedule of the boiler 1. Therefore, for example, by acquiring and analyzing sample tubes during a first shutdown period close to the next second shutdown period (a relatively long shutdown period during which scaffolding is installed inside the reactor), it is possible to accurately determine whether maintenance work such as chemical cleaning needs to be performed during the next second shutdown period and to appropriately determine the conditions for chemical cleaning. Therefore, if the evaluation results of the sample tubes indicate that maintenance work such as chemical cleaning needs to be performed earlier than the scheduled start of the next second shutdown period, more appropriate maintenance can be performed, such as by advancing the start of the next second shutdown period. In this way, the method according to the above-described embodiment enables more appropriate maintenance of the boiler facility 100.

[0035] In one embodiment, as shown in Figures 4A and 4B, multiple first stop periods may be set after the end of a previous second stop period and before the start of the second stop period, and during each first stop period, sample tubes may be obtained (S200), the status of the sample tubes may be evaluated (S300), and / or a maintenance plan may be created (S400). For example, as shown in Figures 4A and 4B, if the time length until the next second stop period after a first stop period is greater than a specified value (Yes in step S510), steps S100 to S500 may be repeated again.

[0036] According to the above-described embodiment, sample tubes are acquired multiple times after the previous second shutdown period and before the subsequent second shutdown period, and the condition of each of the sample tubes thus acquired is evaluated, thereby enabling the creation of a more appropriate maintenance plan.

[0037] The first shutdown period is relatively short because no scaffolding is installed inside the furnace. Therefore, even if multiple first shutdown periods are provided between an earlier second shutdown period and a later second shutdown period as in the above-described embodiment, problems in operation of the boiler 1 are unlikely to occur.

[0038] Fig. 5 is a more detailed flowchart of the above-mentioned steps S300 to S400 in a maintenance method according to one embodiment. In the embodiment shown in Fig. 5, in step S300, the amount of scale adhesion on the sample tube obtained in step S200 is measured, and in step S500, the conditions for chemical cleaning of the furnace wall tube 12 are determined based on the measured value of the amount of scale adhesion.

[0039] In the embodiment shown in FIG. 5, the above-mentioned step S300 includes step S310 of measuring the amount of scale adhesion in the sample tube, and predicting the amount of scale adhesion after the first stop period based on the measured value of the amount of scale adhesion obtained in step S310 (S312).

[0040] In step S312, the future amount of scale deposition can be predicted based on two or more measurement values ​​of the amount of scale deposition obtained up to now.

[0041] FIG. 6 is a schematic graph showing an example of the relationship between the operating time of the boiler 1 (horizontal axis) and the amount of scale adhesion to the furnace wall tube 12 (vertical axis). With respect to the operating time, the time when the furnace wall tube 12 is replaced with a new tube is time t0. In other words, the amount of scale adhesion at time t0 can be considered to be zero. For example, assume that measurement values ​​A1 and A2 of the amount of scale adhesion at times t1 and t2 after time t0 are obtained. In this case, the amount of scale adhesion in the future can be predicted by obtaining an approximation curve (the dashed line in FIG. 6) using, for example, the least squares method or the like based on the measurement values ​​of the amount of scale adhesion at two or more of the three points at each of times t0, t1, and t2 and the operating time of the boiler 1.

[0042] In some embodiments, measurement values ​​of the amount of scale adhesion may be obtained multiple times, and a predicted value of the amount of scale adhesion may be calculated using the multiple measurement values ​​obtained in this way. In this case, the accuracy of prediction of the amount of scale adhesion can be improved, and therefore, in the subsequent step S400, the conditions or timing of chemical cleaning can be more appropriately determined based on the predicted value.

[0043] In some embodiments, the predicted value of the amount of deposited scale may be calculated based on two measurements of the amount of deposited scale obtained immediately before the second stop period, which improves the accuracy of the prediction of the amount of deposited scale.

[0044] In some embodiments, the predicted value of the amount of scale adhesion may be calculated based on the amount of scale adhesion (typically zero) before the start of boiler operation and a measurement value of the amount of scale adhesion at one point. In this case, the predicted value of the amount of scale adhesion can be calculated more easily.

[0045] In step S312, the predicted value of the amount of scale adhesion may be calculated using the measured value of the amount of scale adhesion acquired in step S310, without using any parameters other than the amount of scale adhesion that indicate the operating state of the boiler 1. In this case, since no parameters other than the amount of scale adhesion that indicate the operating state of the boiler 1 are used, the predicted value of the amount of scale adhesion can be calculated relatively easily.

[0046] Returning to the description of the flowchart in Fig. 5, as described above, once the predicted value of the amount of scale adhesion has been acquired in step S312, the predicted value of the amount of scale adhesion up to the next second stop period (later second stop period) is compared with the first threshold value Th1 (S410).

[0047] As a result, if the predicted value of the amount of scale adhesion until the next second shutdown period is less than the first threshold value (Yes in S410), it is determined that there is not much scale adhesion on the furnace wall tubes 12, and therefore chemical cleaning of the furnace wall tubes 12 will not be performed during the next second shutdown period.

[0048] On the other hand, if the predicted value of the amount of scale adhesion until the next second stop period is equal to or greater than the first threshold value (No in S410), proceed to the next step S412, where the predicted value is compared with a second threshold value Th2 that is greater than the first threshold value Th1 (S412).

[0049] If the predicted value is equal to or greater than the first threshold and less than the second threshold (Yes in step S412), the amount of scale adhesion is greater than the reference value (first threshold), so it is decided to perform chemical cleaning of the furnace wall tubes 12 during the next second shutdown period. On the other hand, if the predicted value is equal to or greater than the second threshold (No in step S412), the amount of scale adhesion greatly exceeds the reference value (first threshold), so it is decided to perform chemical cleaning of the furnace wall tubes 12 before the start of the next second shutdown period (i.e., earlier than planned).

[0050] In this way, the amount of scale adhesion can be predicted and the conditions for chemical cleaning can be appropriately determined based on the comparison between the predicted value and the threshold value, thereby enabling more appropriate maintenance of the boiler facility 100.

[0051] The contents described in each of the above embodiments can be understood, for example, as follows.

[0052] (1) A maintenance method for a boiler facility (100) according to at least one embodiment of the present invention includes: A maintenance method for boiler equipment including a boiler (1), comprising: a sample obtaining step (S200) of obtaining a sample tube by removing a part of a furnace wall tube (12) constituting a furnace wall (10) of the boiler during a first shutdown period during which no scaffolding is installed inside the furnace (2) of the boiler; an evaluation step (S300) of evaluating the state of the sample tube; a maintenance plan creation step (S400) of creating a maintenance plan for the furnace wall based on the evaluation result of the state of the sample tube; Equipped with.

[0053] In the above method (1), during the first shutdown period of the boiler, when no scaffolding is installed inside the boiler furnace, a portion of the furnace wall tube is removed to obtain a sample tube, and a furnace wall maintenance plan is created based on the evaluation results of the sample tube. In other words, since no scaffolding is installed during the period when the boiler is shut down to obtain and evaluate the sample tube, this period (first shutdown period) can be shortened. Therefore, such a relatively short shutdown period can be flexibly incorporated into the boiler operation schedule. Therefore, for example, by obtaining and analyzing sample tubes during a first shutdown period close to the next regular inspection (a relatively long shutdown period during which scaffolding is installed inside the reactor), it is possible to accurately determine whether maintenance work such as chemical cleaning is required at the time of the next regular inspection, and to appropriately determine the conditions for chemical cleaning. Also, if the evaluation results of the sample tubes indicate that maintenance work such as chemical cleaning is required earlier than the next regular inspection, more appropriate maintenance can be performed, such as by bringing forward the start of the next regular inspection. Thus, according to the method (1) above, more appropriate maintenance of the boiler equipment is possible.

[0054] (2) In some embodiments, in the method of (1), In the evaluation step, the amount of scale adhesion to the sample tube is measured, In the maintenance plan creation step, conditions for chemical cleaning of the furnace wall tubes are determined based on the measured values ​​of the amount of scale adhesion.

[0055] According to the method (2) above, the amount of scale adhesion on the obtained sample tube is measured, and the conditions for chemical cleaning of the furnace wall tube are determined based on the measured value of the amount of scale adhesion, so that the conditions for chemical cleaning can be determined more appropriately, thereby enabling more appropriate maintenance of the boiler facility.

[0056] (3) In some embodiments, in the method (2), In the maintenance plan creation step, the timing for chemical cleaning of the furnace wall tubes is determined based on the measured value of the amount of scale adhesion.

[0057] According to the method (3) above, the amount of scale adhesion on the obtained sample tube is measured, and the timing of chemical cleaning of the furnace wall tube is determined based on the measured value of the amount of scale adhesion, so that the timing of chemical cleaning can be determined more appropriately. For example, it is possible to accurately determine whether chemical cleaning is necessary at the next periodic inspection, or to determine that chemical cleaning should be performed earlier than the scheduled start date of the next periodic inspection. This allows for more appropriate maintenance of the boiler equipment.

[0058] (4) In some embodiments, in the method of (1), In the evaluation step, a thickness reduction amount of the outer surface of the sample tube is measured; In the maintenance plan creation step, a repair plan for the furnace wall tube is determined based on the measured values ​​of the amount of wall thinning.

[0059] According to the method (4) above, the amount of wall thinning on the outer surface of the sample tube is measured, and a furnace wall tube repair plan is determined based on the measured amount of wall thinning, so that the repair timing and conditions of the furnace wall tube can be determined more appropriately, and therefore, more appropriate maintenance of the boiler equipment can be performed.

[0060] (5) In some embodiments, in the method (1), In the evaluation step, a damage state of the outer surface of the sample tube is evaluated; In the maintenance plan creation step, a repair plan for the furnace wall tube is determined based on the evaluation result of the damage state.

[0061] According to the method (5) above, the state of damage to the outer surface of the obtained sample tube is evaluated, and a furnace wall tube repair plan is determined based on the results of the evaluation of the state of damage, so that the repair timing and conditions of the furnace wall tube can be determined more appropriately, and therefore, more appropriate maintenance of the boiler facility can be performed.

[0062] (6) In some embodiments, in any of the methods (1) to (5) above, The boiler equipment maintenance method includes: a maintenance step (S700) of installing scaffolding inside the furnace of the boiler and performing maintenance on the boiler equipment during a second shutdown period different from the first shutdown period; In the sample obtaining step, a part of the furnace wall tube is removed to obtain the sample tube during the first shutdown period before the second shutdown period begins; In the evaluation step and the maintenance plan creation step, the state of the sample tube is evaluated before the second shutdown period begins, and the maintenance plan is created based on the evaluation result of the state of the sample tube.

[0063] (7) In some embodiments, in the configuration of (6), In the sample obtaining step, a part of the furnace wall tube is removed to obtain the sample tube during the first shutdown period after the end of the previous second shutdown period and before the start of the subsequent second shutdown period; In the evaluation step and the maintenance plan creation step, the state of the sample tube is evaluated before the subsequent second shutdown period begins, and the maintenance plan is created based on the evaluation result of the state of the sample tube.

[0064] (8) In some embodiments, in the method of (6) or (7), The length of the first stop period is shorter than the length of the second stop period.

[0065] In the above methods (6) to (8), after the end of an outage such as the second shutdown period (earlier second shutdown period) of the boiler in which scaffolding is installed inside the boiler furnace, or during the first shutdown period of the boiler in which scaffolding is not installed inside the boiler furnace after the initial startup of the boiler, a sample tube is obtained by removing a portion of the furnace wall tube, and a furnace wall maintenance plan is created based on the evaluation results of the sample tube before the start of the next second shutdown period (later second shutdown period). In other words, because no scaffolding is installed during the period in which the boiler is shut down to acquire and evaluate the sample tube, the period (first shutdown period) can be shortened. This allows such relatively short shutdown periods to be flexibly incorporated into the boiler operation schedule. Therefore, for example, by acquiring and analyzing sample tubes during a first shutdown period close to the next second shutdown period (a relatively long shutdown period during which scaffolding is installed inside the reactor), it is possible to accurately determine whether maintenance work such as chemical cleaning needs to be performed during the next second shutdown period and to appropriately determine the conditions for chemical cleaning. Therefore, if the evaluation results of the sample tubes indicate that maintenance work such as chemical cleaning needs to be performed earlier than the scheduled start of the next second shutdown period, more appropriate maintenance can be performed, such as by advancing the start of the next second shutdown period. In this way, the above methods (6) to (8) enable more appropriate maintenance of boiler facilities.

[0066] (9) In some embodiments, in any of the methods (6) to (8) above, In the evaluation step, the amount of scale adhesion in the sample tube is measured, and a predicted value of the amount of scale adhesion after the first stop period is calculated based on the measured value of the amount of scale adhesion; In the maintenance plan creation step, the conditions or timing of chemical cleaning of the furnace wall tubes are determined based on the predicted values.

[0067] According to the method (9) above, the amount of scale adhesion in the acquired sample tube is measured, and a predicted value of the amount of scale adhesion after the first shutdown period is calculated based on the measured value of the amount of scale adhesion, so that the conditions or timing of chemical cleaning can be more appropriately determined based on the predicted value, thereby enabling more appropriate maintenance of the boiler equipment.

[0068] (10) In some embodiments, in the method of (9), In the evaluation step, the predicted value is calculated using the measured value of the amount of adhered scale and without using any parameter other than the amount of adhered scale that indicates the operating state of the boiler.

[0069] According to the method of (10) above, the predicted value of the scale deposition amount is calculated using the acquired measurement value of the scale deposition amount on the sample tube, without using other parameters that indicate the operating state of the boiler, so that the predicted value of the scale deposition amount can be calculated relatively easily. Furthermore, since the scale deposition amount is predicted using only the actual measurement value of the scale deposition amount, without using highly uncertain parameters (for example, parameters such as temperature and water quality that have relatively low measurement accuracy or that vary relatively widely depending on the measurement position), the prediction accuracy is good.

[0070] (11) In some embodiments, in the method of (9) or (10), In the sample obtaining step, a part of the furnace wall tube is removed to obtain the sample tubes in each of the first shutdown periods before the second shutdown period begins; In the evaluation step, the scale deposition amounts of the plurality of sample tubes obtained during the plurality of first stop periods are measured, and a predicted value of the scale deposition amount after the plurality of first stop periods is calculated based on the measured values ​​of the scale deposition amounts of the plurality of sample tubes (S312).

[0071] According to the method (11) above, sample tubes are obtained multiple times before the second shutdown period (i.e., the second shutdown period following the first shutdown period), and a predicted value of the amount of scale adhesion is calculated based on the measured values ​​of the amount of scale adhesion for each of the multiple sample tubes obtained in this manner. This improves the accuracy of predicting the amount of scale adhesion. Therefore, the conditions or timing of chemical cleaning can be more appropriately determined based on the predicted value. This allows for more appropriate maintenance of the boiler equipment.

[0072] (12) In some embodiments, in the method of (11), In the evaluation step, a predicted value of the amount of scale adhesion is calculated based on measurement values ​​of the amount of scale adhesion in the sample tube acquired during two first stop periods immediately before the second stop period.

[0073] In boiler facilities, because operating conditions and fuel type (coal type, etc.) may change, it may be better to focus on the recent trend of increase in the amount of scale deposition. In this regard, according to the configuration of (12) above, the predicted value of the amount of scale deposition is calculated based on the measured values ​​of the amount of scale deposition at the two most recent points during the second shutdown period, thereby improving the accuracy of the prediction of the amount of scale deposition.

[0074] (13) In some embodiments, in the method of (9) or (10), In the evaluation step, a predicted value of the amount of scale deposition after the first shutdown period is calculated based on the amount of scale deposition before the boiler starts operating and a single measurement value of the amount of scale deposition on the sample tube obtained during the first shutdown period.

[0075] According to the configuration of (13) above, the predicted value of the amount of scale adhesion is calculated based on the amount of scale adhesion (typically zero) before the boiler starts operating and the measured value of the amount of scale adhesion at one point, so that the predicted value of the amount of scale adhesion can be calculated more easily.

[0076] (11) In some embodiments, in any of the methods (8) to (10) above, In the maintenance plan creation step, If the predicted value until the subsequent second shutdown period is less than a first threshold, it is determined that chemical cleaning of the furnace wall tubes will not be performed during the subsequent second shutdown period (S410, 414); If the predicted value until the later second shutdown period is equal to or greater than the first threshold, it is determined that chemical cleaning of the furnace wall tubes will be performed during the later second shutdown period at the latest (S410, S412, S416, S418).

[0077] According to the method (11) above, if the predicted value of the amount of scale adhesion until the next second shutdown period (later second shutdown period) is less than the first threshold, chemical cleaning of the furnace wall tubes is not performed during the next second shutdown period. This prevents chemical cleaning from being performed more than necessary, making it possible to effectively reduce costs associated with maintaining the boiler equipment. Furthermore, if the predicted value of the amount of scale adhesion until the next second shutdown period is equal to or greater than the first threshold, chemical cleaning of the furnace wall tubes is performed during the next second shutdown period at the latest. This makes it possible to remove scale before the amount of scale adhesion on the furnace wall tubes becomes excessively large. In this way, the boiler equipment can be maintained appropriately.

[0078] (12) In some embodiments, in the method of (11), In the maintenance plan creation step, if the predicted value up to the subsequent second shutdown period is equal to or greater than a second threshold value that is greater than the first threshold value, it is determined that chemical cleaning of the furnace wall tubes will be performed before the start of the subsequent second shutdown period (S412, S418).

[0079] According to the method (12) above, if the predicted value of the amount of scale adhesion until the next second shutdown period (later second shutdown period) is equal to or greater than the second threshold value that is greater than the first threshold value, chemical cleaning of the furnace wall tubes is performed before the scheduled start of the next second shutdown period, so that scale can be removed before the amount of scale adhesion on the furnace wall tubes becomes excessively large. In this way, the boiler equipment can be maintained more appropriately.

[0080] The above describes an embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and also includes forms in which the above-described embodiment is modified, or forms in which these forms are appropriately combined.

[0081] In this specification, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement strictly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent rectangular shapes or cylindrical shapes in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components. [Explanation of symbols]

[0082] 1 boiler 2 Furnace 3 Furnace wall 4 Burner 5 Wind box 6a~6d Heat exchanger 10 Furnace wall 11 Combustion gas flow path 12 Furnace wall tube 14 Finn 40 Duct Wall 100 Boiler equipment

Claims

1. A maintenance method for boiler equipment including a boiler, comprising: a sample obtaining step of obtaining a sample tube by removing a part of a furnace wall tube constituting a furnace wall of the boiler during a first shutdown period during which no scaffolding is installed inside the furnace of the boiler; an evaluation step of evaluating the condition of the sample tube; a maintenance plan creation step of creating a maintenance plan for the furnace wall based on the evaluation result of the state of the sample tube; a maintenance step of installing scaffolding inside a furnace of the boiler and performing maintenance on the boiler equipment during a second shutdown period different from the first shutdown period; Equipped with In the sample obtaining step, a part of the furnace wall tube is removed to obtain the sample tube during the first shutdown period before the second shutdown period begins; In the evaluation step and the maintenance plan creation step, a state of the sample tube is evaluated before the second stop period begins, and the maintenance plan is created based on the evaluation result of the state of the sample tube. How to maintain boiler equipment.

2. In the evaluation step, the amount of scale adhesion to the sample tube is measured, In the maintenance plan creation step, conditions for chemical cleaning of the furnace wall tube are determined based on the measured value of the amount of scale adhesion. The method for maintaining a boiler facility according to claim 1.

3. In the maintenance plan creation step, the timing of chemical cleaning of the furnace wall tube is determined based on the measured value of the amount of scale adhesion. The method for maintaining a boiler facility according to claim 2.

4. In the evaluation step, a thickness reduction amount of the outer surface of the sample tube is measured; In the maintenance plan creation step, a repair plan for the furnace wall tube is determined based on the measured values ​​of the amount of wall thinning. The method for maintaining a boiler facility according to claim 1.

5. In the evaluation step, a damage state of the outer surface of the sample tube is evaluated; In the maintenance plan creation step, a repair plan for the furnace wall tube is determined based on the evaluation result of the damage state. The method for maintaining a boiler facility according to claim 1.

6. In the sample obtaining step, a part of the furnace wall tube is removed to obtain the sample tube during the first shutdown period after the end of the previous second shutdown period and before the start of the subsequent second shutdown period; In the evaluation step and the maintenance plan creation step, a state of the sample tube is evaluated before the second subsequent shutdown period begins, and the maintenance plan is created based on the evaluation result of the state of the sample tube. The method for maintaining a boiler facility according to any one of claims 1 to 5.

7. The length of the first stop period is shorter than the length of the second stop period. The method for maintaining a boiler facility according to any one of claims 1 to 6.

8. In the evaluation step, a scale deposition amount of the sample tube is measured, and a predicted value of the scale deposition amount after the first stop period is calculated based on the measured value of the scale deposition amount; In the maintenance plan creation step, conditions or timing for chemical cleaning of the furnace wall tubes are determined based on the predicted values. The method for maintaining a boiler facility according to any one of claims 1 to 7.

9. In the evaluation step, the predicted value is calculated using the measured value of the amount of scale adhesion and without using any parameter indicating the operating state of the boiler other than the amount of scale adhesion. The method for maintaining a boiler facility according to claim 8.

10. In the sample obtaining step, a part of the furnace wall tube is removed to obtain the sample tubes in each of the first shutdown periods before the second shutdown period begins; In the evaluation step, the scale deposition amounts of the plurality of sample tubes obtained during the plurality of first stop periods are measured, and a predicted value of the scale deposition amount after the plurality of first stop periods is calculated based on the measured values ​​of the scale deposition amounts of the plurality of sample tubes. The method for maintaining a boiler facility according to claim 8 or 9.

11. In the evaluation step, a predicted value of the amount of scale adhesion is calculated based on measurement values ​​of the amount of scale adhesion in the sample tube acquired during two first stop periods immediately before the second stop period. The method for maintaining a boiler facility according to claim 10.

12. In the evaluation step, a predicted value of the amount of scale adhesion after the first shutdown period is calculated based on the amount of scale adhesion before the start of operation of the boiler and a single measurement value of the amount of scale adhesion on the sample tube acquired during the first shutdown period. The method for maintaining a boiler facility according to claim 8 or 9.

13. In the maintenance plan creation step, If the predicted value until the second shutdown period is less than a first threshold, determining not to perform chemical cleaning of the furnace wall tube during the second shutdown period; If the predicted value until the second shutdown period is equal to or greater than the first threshold, it is determined that chemical cleaning of the furnace wall tubes will be performed at the latest during the second shutdown period. The method for maintaining a boiler facility according to any one of claims 8 to 12.

14. In the maintenance plan creation step, if the predicted value until the second shutdown period is equal to or greater than a second threshold value that is greater than the first threshold value, it is determined that chemical cleaning of the furnace wall tubes will be performed before the start of the second shutdown period. The method for maintaining a boiler facility according to claim 13.

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