Boiler Tube Group Ash Adhesion Removal System

Abstract

The boiler tube group adhering ash removal system (1) has: a soot blower (3) disposed between a plurality of tube groups (2); an induced draft fan (13) guiding exhaust gas downstream of the tube group (2); and a control device (4) controlling the soot blower (3) and calculating the heat transfer coefficient of the boiler. When the heat transfer coefficient is equal to or greater than a specified value, the control device (4) starts the soot blower (3) once at a specified interval, and when the heat transfer coefficient is less than the specified value, it performs an adhering ash determination process and continuously starts the soot blower (3) according to the result. The adhering ash determination process is performed including at least one of four conditions: the main steam flow rate of the tube group (2), the pressure difference of the exhaust gas, the rotational speed of the induced draft fan (13), and the total amount of combustion air supplied to the furnace.

Description

Technical Field

[0001] The present invention relates to a system for removing ash adhering to a boiler tube bank. Background Art

[0002] In a thermal power plant equipped with a coal-fired boiler or a waste incinerator or a gasification melting furnace equipped with a waste heat boiler for power generation, the incineration ash contained in the exhaust gas generated by the combustion of coal or waste easily adheres to and accumulates on a tube bank (a tube bank of a boiler composed of a filter tube, a superheater tube, an evaporator tube, a water tube of an economizer, etc.). If the incineration ash accumulates on the tube bank, it may corrode the tube bank. In addition, it may cause deterioration of power generation efficiency. Therefore, generally, at a predetermined time interval (a certain cycle), a steam type or an impulse type soot blower is started to remove the ash (hereinafter referred to as "adhering ash") accumulated on the tube bank, that is, "removing the adhering ash" is performed.

[0003] However, when the amount of adhering ash accumulated on the tube bank is small, even if the soot blower is started, the amount of adhering ash removed is small. Therefore, the effect of removing adhering ash is small relative to the cost of electricity, steam, or gas consumed or utilized by the soot blower. On the other hand, when the amount of adhering ash accumulated on the tube bank is large, during the start of the soot blower at the above-mentioned certain cycle, the adhering ash cannot be sufficiently removed, and it is possible that the adhering ash remaining in the tube bank without being removed solidifies before the next start of the soot blower, making it difficult to remove the adhering ash by the soot blower.

[0004] Therefore, in order to appropriately remove the adhering ash on the tube bank using a soot blower, various systems for removing ash adhering to a boiler tube bank have been developed.

[0005] For example, in Patent Document 1, a system for changing the above cycle according to the degree of contamination of the tube bank, that is, the degree to which the adhering ash accumulates on the tube bank, is disclosed. And, in Patent Document 2, a system for starting the soot blower in consideration of conditions other than the degree of contamination of the tube bank is disclosed. And, in Patent Document 3, a system for separately measuring the pressures of the exhaust gas flowing through the upstream and downstream of the tube bank and starting the soot blower when the difference between these pressures is equal to or more than a predetermined value is disclosed.

[0006] In addition, regarding the soot blower, a steam type has been mainly used heretofore, but in recent years, an impulse type that does not use steam has been developed and put on the market.

[0007] When the steam type soot blower is started, it only sprays steam for a predetermined time and stops spraying steam after passing through the predetermined time.

[0008] On the other hand, an impact pulse type soot blower is also called a pressure wave type or shock wave type soot blower or a shock pulse generator (SPG: Shock Pulse Generator). When it is activated, the combustible gas filled inside the soot blower explodes, and an impact pulse (also called a "shock wave" or "pressure wave") is emitted. In addition, once the impact pulse type soot blower is activated, the gas needs to be refilled for the next activation. This filling usually takes about 1 minute to 10 minutes.

[0009] Prior art documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Laid-Open No. 62-210316

[0012] Patent Document 2: Japanese Patent Laid-Open No. 63-286609

[0013] Patent Document 3: Japanese Patent Laid-Open No. 2017-181007 Summary of the invention

[0014] Technical problems to be solved by the invention

[0015] The technologies disclosed in Patent Documents 1 to 3 all activate the soot blower only once after the establishment of specified conditions such as the arrival of the above cycle.

[0016] However, as described above, depending on the accumulation amount of the adhering ash, activating the soot blower only once may not sufficiently remove the adhering ash. Therefore, in the case where the adhering ash is not effectively removed despite activating the soot blower, in the technologies disclosed in Patent Documents 1 to 3, it is necessary to wait for the next cycle to arrive or for other re-specified conditions to be established and then activate the soot blower again. Therefore, in these technologies, when the adhering ash cannot be sufficiently removed by one activation of the soot blower, the heat exchange performance of the boiler cannot be restored early.

[0017] Therefore, when activating the soot blower, it is possible to consider continuous activation multiple times instead of just one activation.

[0018] However, even when the adhering ash can be sufficiently removed by one activation of the soot blower, it is uneconomical to activate the soot blower multiple times each time the above specified conditions are established.

[0019] Therefore, an object of the present invention is to provide a system for removing adhering ash from boiler tube bundles that can ensure economy while early and appropriately removing the adhering ash.

[0020] Means for solving the technical problems

[0021] The boiler tube group ash adhesion removal system of the present invention removes the ash adhesion on multiple tube groups of a boiler that recovers heat from the exhaust gas generated in the furnace, and is characterized by having: a soot blower disposed between the multiple tube groups; an induced draft fan disposed downstream of the multiple tube groups to guide the exhaust gas; and a control device that controls the start of the soot blower.

[0022] The control device performs the following processes: calculates the heat transfer coefficient of the boiler; when the calculated heat transfer coefficient is equal to or greater than a specified value, starts the soot blower only once at a specified interval, and then performs another start at the specified interval or a different interval; when the calculated heat transfer coefficient is less than the specified value, performs an ash adhesion determination process that makes an alternative determination between a first determination and a second determination; when the first determination is obtained in the ash adhesion determination process, continuously starts the soot blower multiple times without the specified interval; when the second determination is obtained in the ash adhesion determination process, performs the one-time start.

[0023] The ash adhesion determination process is performed including at least one of the following conditions: a first condition that the main steam flow rate of the multiple tube groups is equal to or greater than a first threshold value; a second condition that the pressure difference between the inlet and outlet of the exhaust gas of the multiple tube groups is equal to or greater than a second threshold value; a third condition that the rotational speed of the induced draft fan is equal to or greater than a third threshold value; and a fourth condition that the total amount of combustion air supplied to the furnace is equal to or greater than a fourth threshold value.

[0024] In the case where the ash adhesion determination process is performed based on only any one of the four conditions, when the one condition is satisfied, the first determination is obtained, and when the one condition is not satisfied, the second determination is obtained. In the case where the ash adhesion determination process is performed including any two, three, or four of the four conditions, when all the conditions including the two, three, or four conditions are satisfied, the first determination is obtained, and when any of the conditions including the two, three, or four conditions is not satisfied, the second determination is obtained.

[0025] Advantages of the Invention

[0026] According to the boiler tube group ash adhesion removal system of the present invention, one-time start and continuous start are used separately based on the heat transfer coefficient. In addition, when the heat transfer coefficient is less than the specified value, the ash adhesion determination process is performed, and it is possible to appropriately determine whether to continuously start the soot blower. Therefore, it is possible to ensure economy while removing the ash adhesion early and appropriately. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of the boiler tube group ash adhesion removal system according to the embodiment and the first modification.

[0028] Figure 2 This is an example of a flowchart for explaining control of starting a soot blower in a boiler tube ash removal system.

[0029] Figure 3 (a)~ Figure 3 (d) Yes Figure 2 An example of a specific processing flow of step S16 (dust adhesion determination processing) in FIG.

[0030] Figure 4 (a)~ Figure 4 (c) is a schematic configuration diagram showing a part of a boiler tube group ash adhering system according to a second modification.

[0031] Figure 5 It is a schematic structural diagram of a boiler tube group ash adhering system according to a third modified example.

[0032] Figure 6 It is a schematic configuration diagram of a boiler tube group ash attachment removal system according to a fourth modified example. DETAILED DESCRIPTION

[0033] Hereinafter, a boiler tube group ash removal system as an embodiment and a modified example will be described with reference to the accompanying drawings. The structures shown below are merely examples, and are not intended to exclude the application of various modifications or technologies not explicitly stated. The structures shown below can be implemented with various modifications within the scope of these purposes. Moreover, they can be selected or discarded as needed, or can be appropriately combined.

[0034] [1. Overview of the boiler tube ash removal system]

[0035] Figure 1 1 is a schematic diagram of a boiler tube ash removal system 1 (hereinafter referred to as “removal system 1”) according to the present embodiment. Figure 1 It also serves as a diagram showing a first modified example (removal system 1 ′) described later.

[0036] exist Figure 1 and the following Figures 4 to 6 In the figure, an orthogonal coordinate system consisting of an X-axis and a Y-axis is illustrated for explanation. The X-axis is a horizontal direction, and the Y-axis is a vertical direction. In addition, the arrow direction of the Y-axis is a vertical direction and points upward.

[0037] In this embodiment, as an example, a removal system 1 applied to a plant including a waste incinerator having a boiler for generating electricity is described. Of course, the boiler tube ash removal system of the present invention can be applied to other plants such as thermal power plants and gasification melting furnaces.

[0038] Boilers are roughly classified into a two-drum type with a steam drum and a water drum, and a one-drum type with a steam drum. However, the removal system 1 can use any boiler. Additionally, in Figure 1 Although the illustration of the steam drum is omitted, an example of a complete set of equipment for a waste incinerator with a one-drum type boiler is shown.

[0039] The removal system 1 is a system for removing the adhering ash from a plurality of tube bundles 2 of a boiler that recovers heat from the exhaust gas generated in the furnace. This system has a soot blower 3 disposed between the plurality of tube bundles 2, an induced draft fan 13 disposed downstream of the plurality of tube bundles 2 to guide the exhaust gas, and a control device 4 for controlling the start of the soot blower 3.

[0040] Although it will be described in detail later, the control device 4 calculates the heat transfer coefficient K of the boiler. When the heat transfer coefficient K is equal to or greater than a specified value α1, the soot blower 3 is started only once at a specified interval, and "one start" at this specified interval or a different interval is performed again.

[0041] Moreover, when the calculated heat transfer coefficient K is less than the specified value α1 and less than the specified value α2, the control device 4 performs an adhering ash determination process for making an alternative determination between the first determination and the second determination. When the first determination is obtained in the adhering ash determination process, the control device 4 basically performs "continuous start", that is, continuously starts the soot blower 3 a plurality of times without a specified interval. When the second determination is obtained in the adhering ash determination process, "one start" is performed.

[0042] The adhering ash determination process is performed including at least one of the following first condition to fourth condition.

[0043] First condition: The main steam flow rate Qs of the tube bundle 2 is equal to or greater than a first threshold value

[0044] Second condition: The pressure difference ΔPg of the exhaust gas at the inlet and outlet of the tube bundle 2 is equal to or greater than a second threshold value

[0045] Third condition: The rotational speed Qr of the induced draft fan 13 is equal to or greater than a third threshold value

[0046] Fourth condition: The total amount of combustion air Qc supplied to the furnace is equal to or greater than a fourth threshold value

[0047] According to the inventor's experience, each of these four conditions is as follows: When each condition is satisfied, there is a high possibility that a large amount of adhering ash accumulates in the tube bundle 2. Therefore, it is considered preferable to perform "continuous start" of the soot blower 3.

[0048] As described in detail later Figure 3Among them, as an example, only the above four conditions (the first condition, the second condition, the third condition, and the fourth condition) are used for illustration. However, according to the design, other conditions (for example, the fifth condition, the sixth condition, the seventh condition, the eighth condition, etc.) can be added to these four conditions.

[0049] These other conditions can include: for example, as the fifth condition, "the temperature of the main steam of the tube bank 2 measured by the outlet steam temperature measuring device 24b described later is less than the fifth threshold value"; for example, as the sixth condition, "the amount of water sprayed by the superheat cooler 17 (described later) is less than the sixth threshold value"; and for example, as the seventh condition, "the gas temperature of the exhaust gas at the outlet of the tube bank 2 measured by the gas temperature measuring device 15b (outlet gas temperature measuring device) described later is equal to or higher than the seventh threshold value".

[0050] Moreover, although not shown in the drawings, in the plant of the waste incinerator, it is possible to adopt the exhaust gas recirculation technology (Exhaust Gas Recirculation (EGR)), and the exhaust gas recirculation technology is to circulate a part of the exhaust gas downstream of the dust collector 11 to the vicinity of the coal feeder 7. At this time, the following conditions can also be added as these other conditions: for example, as the eighth condition, a gas flow measuring device that separately measures the gas flow of the circulated exhaust gas (circulated exhaust gas) is provided from the gas flow measuring devices 16a and 16b described later, and "the gas flow of the circulated exhaust gas is equal to or higher than the eighth threshold value" measured by this gas flow measuring device.

[0051] In addition, these other conditions are also divided into two according to the evaluation formula in the same way as the first condition to the fourth condition. Specifically, regarding these other conditions, when the conditions of the evaluation formula are satisfied, there is a high possibility that adhering ash accumulates in large amounts in the tube bank 2. Therefore, it is preferable to perform "continuous start" of the soot blower 3. When the conditions of the evaluation formula are not satisfied, conditions for selecting so-called "continuous start" of the soot blower 3 (therefore, it can be "one-time start") can be determined.

[0052] In the case where the adhering ash determination process is executed based on any one of the above four conditions of the first condition to the fourth condition, when this one condition is satisfied, the first determination is obtained. Moreover, when this one condition is not satisfied, the second determination is obtained.

[0053] Moreover, in the case where the adhering ash determination process is executed including any two, three, or four of the above four conditions (sometimes adding the fifth condition etc.), when all the conditions including these two, three, or four conditions are satisfied, the first determination can be obtained. Moreover, when any one of all the conditions including these two, three, or four conditions is not satisfied, the second determination is obtained.

[0054] Hereinafter, except for removing the above-described structure that the removal system 1 at least has, other structures will be described. Moreover, after the description of the structure, the control related to the activation of the soot blower 3 (including the adhesion ash determination process) will be described in detail.

[0055] [2. System Structure]

[0056] As Figure 1 shown, the removal system 1 includes: a hopper 5 for storing incinerated materials such as garbage; a feeder 6 for extruding the incinerated materials stored in the hopper 5 from below the hopper 5 (in the Y-axis direction and downward); a stoker 7 for burning while conveying the incinerated materials extruded by the feeder 6; and an ash trough 8 for discharging the residue incinerated by the stoker 7.

[0057] Moreover, the removal system 1 exchanges heat of the exhaust gas containing fly ash generated by burning the incinerated materials by the stoker 7 through a economizer 9 (a type of tube bank, also called a "coal economizer") disposed in each tube bank 2 and its downstream. Further, the removal system 1 passes through a desuperheater 10 for cooling the heat-exchanged exhaust gas, and further passes through a dust removal device 11 (e.g., a bag filter) for removing the coal dust from the cooled exhaust gas, and discharges the dust-removed exhaust gas from a chimney 12 to the atmosphere.

[0058] The path of the exhaust gas from the stoker 7 to the opening of the chimney 12 is formed by a water-cooled wall or a duct, etc., and is substantially sealed. In this path, the path extending upward in the Y-axis direction directly above the stoker 7 is called the "1st passage" ("passage" means "pass" in English), the end portion above the 1st passage is bent, and the path adjacent to the 1st passage and extending downward in the Y-axis direction is called the "2nd passage", the end portion below the 2nd passage is bent, and the path adjacent to the 2nd passage and extending upward in the Y-axis direction is called the "3rd passage". As Figure 1 indicated by the arrow in the figure, the exhaust gas generated by the stoker 7 flows in such a way that it rises in the 1st passage, descends in the 2nd passage, and rises in the 3rd passage. In addition, in order to guide the flow of the exhaust gas from the 1st passage to the chimney 12, a draft fan 13 is disposed on this path between the dust removal device 11 and the chimney 12.

[0059] The removal system 1 includes: a measuring device 14a (inlet pressure measuring device) disposed in the 1st passage for measuring the pressure of the exhaust gas; and a pressure measuring device 14b (outlet pressure measuring device) disposed in the exhaust gas path between the economizer 9 and the desuperheater 10 for measuring the pressure of the exhaust gas.

[0060] In addition, the arrangements of the respective pressure measurement devices 14a and 14b are not limited to these. According to the design of the plant, the inlet pressure measurement device 14a may be arranged at any location upstream of the tube bank 2 that is the most upstream in the plurality of tube banks 2 that are the objects of adhering ash removal in the exhaust gas path, that is, at the "inlet of the plurality of tube banks 2". According to the design of the plant, the outlet pressure measurement device 14b may be arranged at any location downstream of the tube bank 2 that is the most downstream in the plurality of tube banks 2 that are the objects of adhering ash removal in the exhaust gas path, that is, at the "outlet of the plurality of tube banks 2". However, these arbitrary locations are preferably as close as possible to the plurality of tube banks 2 that are the objects of adhering ash removal.

[0061] The removal system 1 includes: a gas temperature measurement device 15a (inlet gas temperature measurement device) arranged below the tube bank that is the most upstream (lower) in the plurality of tube banks 2 that are the objects of adhering ash removal in the three channels to measure the temperature of the exhaust gas; and a gas temperature measurement device 15b (outlet gas temperature measurement device) arranged in the exhaust gas path between the tube bank that is the most downstream (upper) in the plurality of tube banks 2 in the three channels and the economizer 9 to measure the temperature of the exhaust gas.

[0062] In addition, the arrangements of the respective gas temperature measurement devices 15a and 15b are not limited to these. According to the design of the plant, the inlet gas temperature measurement device 15a may be arranged at any location upstream of the tube bank 2 that is the most upstream in the plurality of tube banks 2 that are the objects of adhering ash removal in the exhaust gas path, that is, at the "inlet of the plurality of tube banks 2". According to the design of the plant, the outlet gas temperature measurement device 15b may be arranged at any location downstream of the tube bank 2 that is the most downstream in the plurality of tube banks 2 that are the objects of adhering ash removal in the exhaust gas path, that is, at the "outlet of the plurality of tube banks 2". However, these arbitrary locations are preferably as close as possible to the plurality of tube banks 2 that are the objects of adhering ash removal.

[0063] In other words, in the present embodiment and the deformation examples described later, the "plurality of tube banks 2" that are the objects of adhering ash removal refer to the tube banks arranged between the two pressure measurement devices 14a and 14b and between the two gas temperature measurement devices 15a and 15b.

[0064] In Figure 1 As an example, a structure in which a plurality of tube banks 2 are arranged in three channels is shown. In addition, the economizer 9 also includes a tube bank (refer to Figure 6 ) However, in Figure 1In the structure, the economizer 9 is arranged at a position more downstream than the outlets of the plurality of tube groups 2, that is, at a position more downstream than the outlet gas temperature measuring device 15b. Therefore, in the present embodiment, the tube groups included in the economizer 9 are not regarded as the tube groups to be the object of soot removal. In addition, although it will be described later, regarding the tube groups included in the economizer 9 as an example of the "plurality of tube groups 2" is the fourth modification example of the present embodiment.

[0065] In the three channels, a tube group 2 composed of hanging tubes (filter tubes) 21 is arranged at the most upstream (the lowermost in the Y-axis direction) in the flow direction of the exhaust gas. From this tube group towards the downstream (above in the Y-axis direction), tube groups 2 respectively composed of superheater tubes (superheaters) 22a, 22b, and 22c are arranged in sequence.

[0066] In Figure 1 As an example, a structure in which the soot blower 3 (3a) is arranged between a plurality of tube groups 2 of the same type is shown. That is, in the tube group composed of superheater tubes, the soot blower 3a is arranged between the tube group 2 composed of the most upstream superheater tube 22a and the tube group 2 (the tube group 2 composed of the superheater tube 22b) arranged adjacent to this tube group 2 downstream. In addition, the arrangement of the soot blower 3 (3a) is not limited to this. It can also be arranged between adjacent different types of tube groups among tube groups 2 composed of different types of tube groups 2 such as the filter tubes, superheater tubes, evaporator tubes, and economizer water tubes of a boiler. The soot blower 3 can be a steam type or an impact pulse type. Here, it will be described as an impact pulse type soot blower.

[0067] The removal system 1 includes at least any one of the gas flow measuring device 16a arranged in the two channels to measure the flow rate of the exhaust gas and the gas flow measuring device 16b arranged in the path of the exhaust gas between the dust removal device 11 and the induced draft fan 13 to measure the flow rate of the exhaust gas. As described above, the path of the exhaust gas from the coal feeder 7 to the opening of the chimney 12 is substantially sealed. Therefore, one gas flow measuring device is provided, and thus the information on the gas flow rate of the exhaust gas required for the calculation of the heat transfer coefficient K described later can be obtained.

[0068] In addition, the arrangements of the gas flow measuring devices 16a and 16b are not limited to these. At least one can be arranged in the path of the exhaust gas. From the viewpoint of reducing the cleaning frequency of the gas flow measuring device, it is preferable to arrange the gas flow measuring device at a position more downstream than the dust removal device 11. That is, when choosing any one of the gas flow measuring devices 16a and 16b, it is preferable to arrange the gas flow measuring device 16b.

[0069] Moreover, instead of arranging the gas flow measuring device 16a, the gas flow rate of the exhaust gas in the two channels can also be calculated and used for the calculation of the heat transfer coefficient K described later.

[0070] The ash removal system 1 includes a superheat cooler (desuperheater) 17 that sprays water inside the superheat tubes to appropriately cool the steam inside the tube bundle 2 composed of superheat tubes. In Figure 1 , the superheat cooler 17 is arranged in the tube bundle 2 composed of the superheat tubes 22c that are arranged in the most downstream among the four tube bundles 2 arranged in the 3 channels. The amount of water sprayed by the superheat cooler 17 is measured by a water spray amount measuring device 18.

[0071] The ash removal system 1 includes: a steam temperature measuring device 24a (inlet steam temperature measuring device), which is arranged inside the superheat tube 22a that is the most upstream among the superheat tubes included in the multiple tube bundles 2 that are the objects of ash adhesion removal to measure the temperature of the steam; and a steam temperature measuring device 24b (outlet steam temperature measuring device), which is arranged inside the superheat tube 22c that is the most downstream to measure the temperature of the steam. The steam temperature measuring devices 24a and 24b are arranged on the superheat tubes in the multiple tube bundles 2.

[0072] The ash removal system 1 includes a main steam amount measuring device 25 that measures the amount of main steam flowing through the inside of the superheat tubes. Here, the main steam amount measuring device 25 is arranged inside the superheat tube 22a that is the most upstream among the superheat tubes included in the multiple tube bundles 2.

[0073] The ash removal system 1 includes: a primary air supply device 26, which is located below the stoker 7; a secondary air supply device 27, which is located in the 1 channel above the stoker 7; and a combustion air amount measuring device 28, which measures the total amount of primary air and secondary air (total combustion air amount) supplied to the exhaust gas path from these air supply devices 26 and 27.

[0074] Various information measured by each pressure measuring device 14a, 14b, each gas temperature measuring device 15a, 15b, gas flow measuring devices 16a, 16b, water spray amount measuring device 18, each steam temperature measuring device 24a, 24b, main steam amount measuring device 25, and combustion air amount measuring device 28 is input into the control device 4. The control device 4 is an electronic control device (for example, a computer) possessed by the ash removal system 1, and is equipped with a processor, a timer, and a storage device (all are omitted from the illustration) that operate based on a clock.

[0075] [3. Control Structure (Flowchart)]

[0076] As described above, the control device 4 calculates the heat transfer coefficient K of the boiler, appropriately performs an ash adhesion determination process based on the heat transfer coefficient K, and causes the soot blower 3 to "start once" or "start continuously".

[0077] Hereinafter, using Figure 2 and Figure 3The flowcharts shown in (a) to (d) will describe in detail the control related to the start-up of the soot blower 3 (including the determination process of ash adhesion). In addition, the dust removal device 11 is described as a bag filter here.

[0078] First, the operator starts the operation of the plant such as the incinerator by operating a start switch or a control panel (not shown), and also starts the removal system 1, and executes each process after "Start" of the flowchart shown Figure 2 from the control device 4.

[0079] In addition, the initial values of the time t1, Tmin, Tmax, and Δt, the initial value of the dirty heat transfer coefficient Kd, the initial value of the flag F, and the respective specified values α1, α2, and the recovery threshold R that appear in this flowchart are set as follows, and are stored in the storage device in advance before "Start" of this flowchart.

[0080] The clean heat transfer coefficient Kc does not need to be set in advance before "Start" of this flowchart, because the value of the heat transfer coefficient calculated first after the start of the removal system 1 becomes the initial value.

[0081] The time t1 is the initial time when the timer counts down (the remaining time of the timer), and corresponds to the interval when the soot blower 3 is "started once". The initial value of the time t1 is a specified value that satisfies the relationship of "0 < Tmin < t1 ≤ Tmax". Tmin is the minimum value (the shortest interval) of the interval for starting the soot blower 3, and is set to 1 hour, for example. And, Tmax is the maximum value (the longest interval) of the interval for starting the soot blower 3, and is set to 3 hours, for example.

[0082] The initial value of the time t1 is set to the time obtained by "2 / 3 × Tmax - Δt (for example, Δt is 0.5 hour)", for example. In addition, for the sake of explanation, here, the values of Tmin and Tmax are set to integer multiples of Δt respectively. And then, through steps S7 and S19 described later, the time t1 is changed from the initial value.

[0083] The dirty heat transfer coefficient Kd is the heat transfer coefficient when it is considered that ash is accumulated and adhered on the tube group 2 that is the object of ash removal and is in a contaminated state.

[0084] The initial value of the dirty heat transfer coefficient Kd is set to a specified value that satisfies the relationship of "0 < Kd < α2" (for example, Kd = 0.5). In addition, then, through step S3 described later, the dirty heat transfer coefficient Kd is changed from the initial value.

[0085] The initial value of the flag F is set to F = 0 (the first value). Additionally, thereafter, through steps S9, S20, and S14 described later, the flag F changes to any one of F = 0 (the first value), F = 1 (the second value), and F = 2 (the third value).

[0086] The first specified value α1 and the second specified value α2 are, respectively, in each of steps S5 and S15 described later, the determination thresholds for comparing with the heat transfer coefficient K (net heat transfer coefficient Kc) to determine whether to set the soot blower 3 to "start once". Also, the second specified value α2 is, in step S15 described later, the determination threshold for comparing with the heat transfer coefficient K (net heat transfer coefficient Kc) to determine whether to perform the determination process for adhering ash. The relationship "0 < α2 < α1" is satisfied. Here, for the sake of convenience of explanation, it is assumed that the relationship "0 < α2 < 1 < α1" is satisfied and the explanation continues.

[0087] In addition, the net heat transfer coefficient Kc is the heat transfer coefficient calculated immediately after the soot blower 3 is started. In other words, the net heat transfer coefficient Kc is the heat transfer coefficient in a state where the adhering ash of the tube bank 2 is somewhat removed due to the start of the soot blower 3 just now, and it is considered that the heat exchange rate is improved.

[0088] The first specified value α1 is set to the following value, that is, if the net heat transfer coefficient Kc is α1 or more, the heat exchange of the tube bank 2 is significantly good, and it can be said that there is no accumulation of adhering ash or very little accumulation of adhering ash. Here, for the sake of convenience of explanation, the first specified value α1 is set to the following value, that is, immediately after the flag F changes to F = 2 in step S20 described later, a single start of the soot blower, that is, a single start of the soot blower, will not make the net heat transfer coefficient Kc reach α1 or more, and it is a value that can be achieved only by continuously starting the soot blower 3 at least 2 times or more as "continuous start". For example, the first specified value α1 is set to α1 = 1.2 (W / m 2 K).

[0089] And the second specified value α2 is set to the following value, that is, if the net heat transfer coefficient Kc is α2 or more and less than α1, although the heat exchange of the tube bank 2 is not significantly good, the accumulation of adhering ash will not have a great impact on the operation of the plant, so it can be said that a single start of the soot blower is sufficient. In other words, it is set to a value that requires the determination process for adhering ash described later if the net heat transfer coefficient Kc is less than α2. Here, for the sake of convenience of explanation, the second specified value α2 is also set to the following value, that is, immediately after the flag F changes to F = 2 in step S20 described later, a single start of the soot blower 3, that is, a single start of the soot blower, will not make the net heat transfer coefficient Kc reach α2 or more, and it is a value that can be achieved only by continuously starting the soot blower 3 at least 2 times or more as "continuous start". For example, the second specified value α2 is set to α2 = 0.8 (W / m 2 K).

[0090] Therefore, in the flowchart of Figure 2 described later, when the flag F is temporarily changed to F = 2 in step S20 described later, as long as it does not become the second determination in the soot blowing determination process described later, in principle, the soot blower 3 performs at least 2 consecutive "continuous startups" by the control device 4.

[0091] Here, for the sake of convenience of explanation, the values of α1 and α2 are set as described above to satisfy the relationship of "0 < α2 < 1 < α1", but as long as the relationship of "0 < α2 < α1" is satisfied, the values of α1 and α2 can be appropriately set according to the design. At this time, immediately after the flag F is changed to F = 2 in step S20 described later, the soot blower 3 basically performs "continuous startup", but does not necessarily perform "continuous startup", and there is also a case of performing "one startup".

[0092] The recovery threshold R is a threshold for determining the soot removal effect (the degree of increase in the heat transfer coefficient K) compared with the recovery rate (Kc / Kd), and its initial value is set to a specified value (for example, R = 1) that satisfies the relationship of "1 ≤ R". Here, the recovery rate is a variable indicating how much the heat transfer coefficient K has recovered (increased) before and after the startup of the soot blower 3, and is a value obtained by dividing the net heat transfer coefficient Kc by the dirty heat transfer coefficient Kd.

[0093] In addition, the first specified value α1, the second specified value α2, and the recovery threshold R are respectively constants that do not change from their respective initial values appropriately set according to the design. And the above-mentioned Tmin, Tmax, and Δt are respectively constants that do not change from their respective initial values appropriately set according to the design.

[0094] In step S1, the control device 4 determines whether a specified time has elapsed after the start of operation of the plant (for example, an incinerator). This is because if the specified time has not elapsed since the start of operation of the plant, the conditions (such as temperature, pressure, etc.) related to the environment inside the plant are unstable. The control device 4 repeatedly executes the process of step S1 from the start of operation of the plant until the specified time has elapsed, and executes the process of step S2 when the specified time has elapsed.

[0095] In step S2, the control device 4 calculates the heat transfer coefficient K based on the temperature information and the flow rate information. Moreover, after calculating the heat transfer coefficient K, the control device 4 executes the process of step S3.

[0096] The heat transfer coefficient K is represented by the following (Equation 1).

[0097] [Equation 1]

[0098]

[0099] However, each variable is as described below.

[0100] Q: Heat exchange [W] = (Tg out - Tg in ) × Cp g × W g}

[0101] A: Heat transfer area [m 2

[0102] LMTD: Logarithmic mean temperature difference [K] = (dT 1 - dT 2 ) / {ln(dT 1 / dT 2 )}

[0103] Tg in : Inlet gas temperature of superheater [K]

[0104] Tg out : Outlet gas temperature of superheater [K]

[0105] Ts in : Inlet steam temperature of superheater [K]

[0106] Ts out : Outlet steam temperature of superheater [K]

[0107] dT 1 : Tg in - Ts out

[0108] dT 2 : Tg out - Ts in

[0109] Cp g : Specific heat of gas [J / kgK]

[0110] W g : Gas flow rate [kg / s]

[0111] ​The temperature information and the flow rate information are measured and sent to the control device 4 in the following manner. That is, the inlet gas temperature Tgin of the superheater is measured by the inlet gas temperature measuring device 15a, and the outlet gas temperature Tgout of the superheater is measured by the outlet gas temperature measuring device 15b. The inlet steam temperature Tsin of the superheater is measured by the inlet steam temperature measuring device 24a, and the outlet steam temperature Tsout of the superheater is measured by the outlet steam temperature measuring device 24b. Also, the gas flow rate Wg is measured by any one of the gas flow rate measuring devices 16a and 16b, or obtained through calculation. In addition, the specific heat of the gas Cpg is the specific heat of the exhaust gas, a constant corresponding to the composition of the exhaust gas. And the heat transfer area A is the total of the heat transfer areas of the superheaters in the plurality of tube groups 2.

[0112] In step S3, the control device 4 stores the heat transfer coefficient K calculated in step S2 as either the net heat transfer coefficient Kc or the dirty heat transfer coefficient Kd in a storage device (not shown) according to the value of the flag F at the processing time point of step S3.

[0113] Specifically, when the flag F is the first value, here when F = 0, the control device 4 sets Kc = K, when the flag F is the second value, here when F = 1, the control device 4 sets Kd = K, and when the flag F is the third value, here when F = 2, the control device 4 sets Kd = K and stores it in the storage device.

[0114] After starting this flowchart, the flag F is at the initial value, that is, F = 0. Therefore, the control device 4 stores the just-calculated heat transfer coefficient K as the net heat transfer coefficient Kc in the storage device (that is, Kc = K).

[0115] Moreover, the control device 4 executes the processing of step S4.

[0116] In step S4, the control device 4 determines whether the flag F is F = 0. When the flag F is F = 0, that is, shortly after "start" of this flowchart, or shortly after the start of the soot blower 3 in step S13 described later, the control device 4 executes the processing of step S5.

[0117] When the flag F is not F = 0 (in the cases of F = 1 and F = 2), the processing flow proceeds to the start of the soot blower 3 in step S13 described later. Therefore, the control device 4 executes the processing of step S10.

[0118] In step S5, the control device 4 determines whether the value of the net heat transfer coefficient Kc stored in the above storage device is equal to or greater than the first specified value α1.

[0119] When the value of the net heat transfer coefficient Kc is equal to or greater than the first specified value α1, the heat exchange of the tube bundle 2 is significantly good, so it is considered that there is no or very little accumulation of adhered ash. Therefore, in order to promote the processing flow towards the process of lengthening the interval between activations of the soot blower 3, the control device 4 executes the processing of step S6.

[0120] When the value of the net heat transfer coefficient Kc is less than α1, the heat exchange of the tube bundle 2 may not be considered good, so the control device 4 executes the processing of step S15.

[0121] In step S6, the control device 4 determines whether the time t1 is less than Tmax which is the longest interval.

[0122] When the value of the time t1 is less than Tmax (here, 3 hours), the control device 4 executes the processing of step S7 to increase the value of the time t1 (lengthen the time t1).

[0123] When the value of the time t1 is Tmax, the time t1 cannot be further increased, so the control device 4 executes the processing of step S8 without changing the value of the time t1 (skipping step S7).

[0124] In step S7, the control device 4 changes the value of the time t1 to the value of "t1 + Δt". In other words, the control device 4 changes the value of t1 in the above storage device to t1 = t1 + Δt and stores it again in this storage device. That is, the control device 4 resets the interval to be longer than the immediately preceding set value.

[0125] When the net heat transfer coefficient Kc is equal to or greater than the first specified value α1, it is not preferable to activate the soot blower 3 too frequently from the perspective of cost performance, so the "first activation" of the soot blower 3 is performed at a longer interval than before.

[0126] Moreover, the control device 4 executes the processing of step S8.

[0127] In step S8, the control device 4 activates a timer (counter). The activated timer counts down from the time t1 towards 0 according to the clock of the control device 4. For example, when the time t1 at the activation time point is 2 hours, it counts for 2 hours (7200 seconds), and when the count value becomes 0, the timer stops. After the timer stops, the control device 4 executes the processing of step S9.

[0128] In step S9, the control device 4 changes the value of the flag F stored in the above storage device to F = 1 and stores it again in this storage device. Moreover, the control device 4 returns the processing flow to step S2 and executes the processing of step S2 again.

[0129] The processing of step S2, step S3, and step S4 has been described. Therefore, the following will briefly describe the processing from step S4 to step S10, which is the next step.

[0130] In short, the control device 4 calculates the heat transfer coefficient K at intervals through a timer (step S2). In the next step S3, since the flag F is F = 1, the just-calculated heat transfer coefficient K is stored as the dirty heat transfer coefficient Kd in the above storage device (i.e., Kd = K). Moreover, since the current flag F is F = 1, the control device 4 determines in step S4 that the flag F is not F = 0 and executes the processing of step S10 as the next processing.

[0131] In step S10, the control device 4 determines whether the bag filter of the dust removal device 11 is in backwashing. Since the control device 4 controls the execution of the "backwashing" of the bag filter, it can determine whether the bag filter is in backwashing.

[0132] When the control device 4 determines that the bag filter is in backwashing, it repeatedly executes the processing of step S10. When it determines that the bag filter is not in backwashing, it executes the processing of step S11. Thus, the control device 4 does not start the soot blower 3 during the backwashing of the bag filter and can start the soot blower 3 after the backwashing ends.

[0133] In addition, the reason why the control device 4 repeatedly performs the processing of step S10 when it determines that the bag filter is in backwashing is as follows.

[0134] The backwashing of the bag filter is usually carried out when the exhaust gas flow stops. Therefore, if the impact pulse type soot blower 3 is started during the backwashing of the bag filter, the internal pressure of the duct of the flue where the exhaust gas flows will rise significantly, which may cause a failure in the complete set of equipment. However, in the removal system 1, the control device 4 does not start the soot blower 3 during the backwashing of the bag filter and starts the soot blower 3 after the backwashing ends, so it can prevent the occurrence of the above-mentioned failure.

[0135] Here, since the soot blower 3 is described as an impact pulse type, step S10 is provided. However, when the soot blower 3 is a steam type, step S10 can be omitted. Therefore, at this time, the next step of step S4 becomes step S11.

[0136] In step S11, the control device 4 determines whether the value of the flag F stored in the above storage device is F = 1. When the flag F is F = 1, the control device 4 executes the processing of step S12. And when the flag F is not F = 1, that is, when F = 2, the control device 4 executes the processing of step S13.

[0137] Here, since the current flag F is F = 1, the control device 4 executes the process of step S12. In step S12, the control device 4 restores the count value of the timer to time t1, that is, resets it. Then, the control device 4 executes the process of step S13.

[0138] In step S13, the control device 4 starts the soot blower 3 only once.

[0139] Moreover, the control device 4 executes the process of step S14.

[0140] In addition, in step S11, when the flag F is not F = 1, that is, when F = 2, the control device 4 skips step S12 and executes the process of step S13, so the count value of the timer is not reset. In the case of F = 2, the control device 4 basically executes the "continuous start" of the soot blower 3 until the net heat transfer coefficient Kc becomes equal to or greater than the second specified value α2. However, at this time, one process is omitted to more quickly continuously start the soot blower 3.

[0141] In step S14, the control device 4 changes the value of the flag F stored in the above storage device to F = 0 and stores it in the storage device again. This is because the heat transfer coefficient K calculated in the process of the next step S2 is the value after the soot blower 3 is just started. Therefore, in the process of the next step S3, this value is stored in the above storage device as the net heat transfer coefficient Kc.

[0142] Moreover, the control device 4 returns the processing flow to step S2 and executes the process of step S2. The processes of steps S2, S3, S4, and S5 have been described, so the description is omitted here.

[0143] Thus, the case where the control device 4 executes the process of step S15 in the next step after step S5 (when the value of the net heat transfer coefficient Kc in step S5 is less than α1) is described.

[0144] In step S15, the control device 4 determines whether the value of the net heat transfer coefficient Kc stored in the above storage device is less than the second specified value α2.

[0145] When the value of the net heat transfer coefficient Kc is not less than the second specified value α2, that is, when α2 ≤ Kc < α1, although the heat conduction of the tube bank 2 is not significantly good, it is considered that the accumulation of attached ash will not have a great impact on the operation of the complete set of equipment. Therefore, in order to enter the processing flow of starting the soot blower 3 at intervals, the control device 4 executes the process of the above step S8.

[0146] When the value of the net heat transfer coefficient Kc is less than the second specified value α2, in order to determine whether the value of the net heat transfer coefficient Kc has decreased due to ash fouling, the control device 4 performs the process of step S16, that is, performs the ash fouling determination process.

[0147] In step S16, the control device 4 performs the ash fouling determination process. For an example of the specific process in the ash fouling determination process, use Figure 3 which will be described later.

[0148] The ash fouling determination process is a process of making an alternative selection determination for either "(the case where the amount of ash fouling accumulated in the plurality of tube groups 2 is large and the heat exchange between the exhaust gas and the boiler is not sufficiently performed)" (the first determination) or "(the case where although the amount of ash fouling is small and it has no adverse effect on heat exchange, but according to the operating environment or various conditions of the plant, the net heat transfer coefficient Kc is calculated to be less than the second specified value α2)" (the second determination).

[0149] When the first determination is obtained in the ash fouling determination process, in order to continuously start the soot blower 3 according to the recovery rate (Kc / Kd), the control device 4 performs the process of step S17.

[0150] When the second determination is obtained in the ash fouling determination process, in order to confirm the state of the plant or determine whether to stop the plant, the control device 4 performs the process of step S21.

[0151] In step S17, the control device 4 calculates the recovery rate (Kc / Kd) based on the net heat transfer coefficient Kc and the dirty heat transfer coefficient Kd stored in the above storage device, and determines whether the recovery rate is equal to or greater than the recovery threshold R stored in the above storage device.

[0152] When the recovery rate is less than the recovery threshold R, the possibility of increasing the heat transfer coefficient K even if the soot blower 3 is started more is low. Therefore, the control device 4 performs the process of step S21.

[0153] When the recovery rate is equal to or greater than the recovery threshold R, the effect of removing ash fouling can be expected by starting the soot blower 3. Therefore, in order to remove ash fouling early, the process flow is advanced toward the "continuous start" of the soot blower 3. Therefore, the control device 4 performs the process of step S18.

[0154] In step S18, the control device 4 determines whether the time t1 is greater than Tmin which is the shortest interval.

[0155] When the time t1 is greater than Tmin, in order to shorten the interval when the soot blower 3 is "started once", the control device 4 executes the process of step S19. This is because, according to the properties of the ash, the attached ash cannot be effectively removed at the interval of the initial "start once". Therefore, in view of obtaining the first determination in the attached ash determination process, after the "continuous start" ends, when the control device 4 starts the soot blower 3 "once", it starts the soot blower 3 "once" at a shorter interval than before (in other words, at an earlier time point than before).

[0156] In step S19, the control device 4 changes the value of the time t1 to the value of "t1 - Δt". In other words, the control device 4 changes the value of t1 in the above storage device to t1 = t1 - Δt, and then stores it in the storage device again. Moreover, the control device 4 executes the process of step S20.

[0157] When the time t1 is Tmin, the time t1 cannot be further reduced. Therefore, the control device 4 executes the process of step S20 without changing the value of the time t1 (skipping step S19).

[0158] In step S20, the control device 4 changes the value of the flag F stored in the above storage device to F = 2, and then stores it in the storage device again. Moreover, the control device 4 returns the process flow to step S2 and executes the process of step S2.

[0159] The processes of step S2, step S3, and step S4 have been described. Therefore, the following will briefly describe the processes from step S4 to step S10 as the next step.

[0160] In short, the control device 4 calculates the heat transfer coefficient K (step S2) when the recovery rate is above the recovery threshold R. In the next step S3, since the flag F is F = 2, the calculated heat transfer coefficient K is stored in the above storage device as the dirty heat transfer coefficient Kd (that is, Kd = K). Moreover, in the next step S4, since the current flag F is F = 2, the control device 4 determines that the flag F is not F = 0 and executes the next step S10. Moreover, in step S10, when the control device 4 determines that the bag filter is not in backwashing, it executes the process of step S11. In step S11, since the current flag F is F = 2, the control device 4 skips step S12 and executes the process of step S13.

[0161] That is, when the flag F is F = 2, in order not to reset the timer and immediately start the soot blower 3, the control device 4 executes the process of step S13.

[0162] After the soot blower 3 is started in step S13, as described above, the control device 4 changes the flag F to F = 0 in step S14 and returns the processing flow to step S2 again.

[0163] Here, in the next processing flow, when the control device 4 processes step S2, step S3, step S4, step S5, step S15, step S16, step S17, step S18, step S19 (skipped according to circumstances), and step S20 in sequence again, thereafter, the control device 4 processes step S2, step S3, step S4, step S10, step S11, and step S13.

[0164] Therefore, at this time, the processing flow of step S13 is executed without going through the timer start of step S8, so it becomes the "continuous start" of the soot blower 3.

[0165] Well, as Figure 2 Regarding the description of the flowchart, finally, in the case where the second determination is obtained in the attached ash determination process of step S16, or in the case where the recovery rate is less than the recovery threshold R in step S17, the step S21 executed by the control device 4 will be described.

[0166] In step S21, the control device 4 determines whether the status confirmation of the plant or the work for stopping the operation of the plant (for example, the operation of the control panel) has been started by the operator or the staff. Since the control device 4 controls the actions of various devices arranged in the plant, it can determine whether this work has been started.

[0167] When the control device 4 determines that this work has not been started, it executes the processing of step S8. That is, at this time, it is clear that even if the soot blower 3 is started in step S17, the attached ash cannot be effectively removed, so from the perspective of cost performance, the "continuous start" of the soot blower 3 is not performed, but in order to reduce more ash accumulation on the tube bank 2, the processing flow of performing the "one-time start" of the soot blower 3 is carried out.

[0168] On the other hand, when the control device 4 determines that this work has been started, thereafter, it does not execute any of the processing of steps S1 to S20, but executes the processing required in this work. Thereafter, the operation of the entire removal system 1 including the control device 4 ends, that is, the operation of the plant stops.

[0169] According to this flowchart, when the "one-time start" of the soot blower 3 is based on the timer at intervals, when the net heat transfer coefficient Kc is above the first specified value α1, the interval is set longer than the previous interval, and when the net heat transfer coefficient Kc is less than the first specified value α1, the interval is not changed from the previous interval or is shortened from the previous interval.

[0170] In addition, according to this flowchart, even in the case of "continuous start" of the soot blower 3 where the timer-based intervals are not separated, each time the soot blower 3 is started, the heat transfer coefficient K is calculated. Moreover, as long as the value of the recovery rate R of the calculated heat transfer coefficient K (net heat transfer coefficient Kc, dirty heat transfer coefficient Kd) rises, the control device 4 executes the "continuous start" of the soot blower 3 until the net heat transfer coefficient Kc becomes equal to or greater than the second specified value α2.

[0171] That is, the number of starts of the soot blower 3 during "continuous start" is variable. If the value of the rising speed of the recovery rate R is large (if the rising speed is fast), the number of times automatically becomes smaller. If the value of this rising speed is small (if the rising speed is slow), the number of times automatically becomes larger.

[0172] This rising speed can be calculated by the control device 4 storing the value of the recovery rate calculated each time step S17 is executed and the time information at the calculated time point in the above storage device in sequence, and using the currently calculated value of the recovery rate, the most recent value of the recovery rate, and the value of the difference (time interval or time difference) between the two time information. Specifically, the control device 4 calculates this rising speed through the formula [({currently calculated recovery rate} - {most recent recovery rate}) / (this time difference)]. If the refill time of the gas of the impulse soot blower is less than 3 minutes (3 min), for example, a fast rising speed is, for example, a case where the number of "continuous starts" ends at 2 times (less than 6 min) or 3 times (less than 9 min) with a rising speed of 0.04 ( / min) or more. A slow rising speed is, for example, a case where the number of times requires 4 times or more (12 min or more) with a rising speed less than 0.04 ( / min).

[0173] Next, regarding the detailed situation of the attached ash determination process, that is, step S16, Figure 3 (a) to Figure 3 (d) will be used to explain the processing flow.

[0174] Here, based on the inventor's experience, only the above 4 conditions are taken as objects, and according to which of these conditions are used, the following 4 modes will be explained. However, as described above, other conditions can be added according to the design in addition to the above 4 conditions.

[0175] In addition, in the following description, as Figure 2 the next process of step S15, the process of the control device 4 executing step S161 will be explained.

[0176] Then, starting from Figure 3 (a) will be explained in sequence.

[0177] Figure 3(a) is the processing flow (Mode 1) executed based on all of the above four conditions for the determination of adhered ash. In step S161, the control device 4 determines whether the main steam flow rate Qs measured by the main steam flow rate measuring device 25 is equal to or greater than the minimum main steam flow rate qsmin (first threshold) allowed during the operation of the equipment. When the main steam flow rate Qs is less than qsmin, the control device 4 deems that a "second determination" is obtained, and then executes the processing of step S21 of Figure 2 When the main steam flow rate Qs is equal to or greater than qsmin, the control device 4 executes the next step, which is the processing of step S162 here.

[0178] In step S162, the control device 4 uses the pressure information measured by the pressure measuring devices 14a and 14b to calculate the pressure difference of the exhaust gas at the inlets and outlets of the plurality of tube groups 2, that is, the furnace gas pressure difference ΔPg, and determines whether the furnace gas pressure difference ΔPg is equal to or greater than the minimum furnace gas pressure difference pgmin (second threshold) allowed during the operation of the equipment. When the furnace gas pressure difference ΔPg is less than pgmin, the control device 4 deems that a "second determination" is obtained, and then executes the processing of step S21 of Figure 2 When the furnace gas pressure difference ΔPg is equal to or greater than pgmin, the control device 4 executes the next step, which is the processing of step S163 here.

[0179] In step S163, the control device 4 determines whether the rotational speed Qr of the induced draft fan 13 is equal to or greater than the minimum rotational speed qrmin (third threshold) allowed during the operation of the equipment. When the rotational speed Qr is less than qrmin, the control device 4 deems that a "second determination" is obtained, and then executes the processing of step S21 of Figure 2 When the rotational speed Qr is equal to or greater than qrmin, the control device 4 executes the next step, which is the processing of step S164 here. In addition, since the control device 4 controls the rotational speed Qr of the induced draft fan 13, it knows the rotational speed Qr.

[0180] In step S164, the control device 4 determines whether the total combustion air flow rate Qc measured by the combustion air flow rate measuring device 28 is equal to or greater than the minimum total combustion air flow rate qcmin (fourth threshold) allowed during the operation of the equipment. When the total combustion air flow rate Qc is less than qcmin, the control device 4 deems that a "second determination" is obtained, and then executes the processing of step S21 of Figure 2 When the total combustion air flow rate Qc is equal to or greater than qcmin, the control device 4 executes the processing of the next step. Here, it is deemed that a "first determination" is obtained, and the processing of the next Figure 2 step S17 is executed.

[0181] In addition, the order of the processing flows of the four processes S161 to S164 is not limited to this, and can be replaced appropriately.

[0182] Figure 3 Execute the processing flow of (b) (Mode 2) Figure 3 Three determination elements, steps S161 to S163, among the four determination elements included in the processing flow of (a). Figure 3 (b) is an example of a flowchart in which the adhering ash determination process is executed based on any three of the above four conditions. Any three of the four determination elements S161 to S164 can be used, and the order of processing can also be any one first.

[0183] Figure 3 Execute the processing flow of (c) (Mode 3) Figure 3 Two determination elements, steps S161 and S162, among the four determination elements included in the processing flow of (a). Figure 3 (c) is an example of a processing flow in which the adhering ash determination process is executed based on any two of the above four conditions. Any two of the four determination elements S161 to S164 can be used, and the order of determination can also be any one first.

[0184] Figure 3 Execute only the processing flow of (d) (Mode 4) Figure 3 The determination element of step S161 among the four determination elements included in the processing flow of (a). Figure 3 (d) is an example of a flowchart in which the adhering ash determination process is executed based on any one of the above four conditions. Any one of the four determination elements S161 to S164 can be used.

[0185] In addition, even in any of the above Modes 1 to 4, it is preferable to include step S161 that uses information on the main steam flow rate Qs that is not used in the calculation of the heat transfer coefficient K.

[0186] [4. Effects]

[0187] As described above, in the removal system 1, the control device 4 selects "one-time start" and "continuous start" of the soot blower 3 based on the calculated heat transfer coefficient K, so that it is possible to ensure economy while removing adhering ash early and appropriately.

[0188] The adhering ash determination process includes conditions based on the inventor's experience, that is, it is executed based on at least one of the main steam flow rate Qs, the furnace gas pressure difference ΔPg, the rotational speed Qr of the induced draft fan 13, and the total combustion air volume Qc, so that it is possible to appropriately determine the accumulation state of adhering ash on the tube bank 2.

[0189] In the removal system 1, when a first determination is obtained by the adhered ash determination process, the recovery rate is calculated based on the dirty heat transfer coefficient Kd and the clean heat transfer coefficient Kc. When the recovery rate is equal to or higher than the recovery threshold R, the soot blower 3 is "continuously started", thereby enabling the adhered ash to be removed at an early stage.

[0190] Moreover, in the removal system 1, when the rising speed of the recovery rate is high, the control device 4 automatically reduces the start-up frequency of the soot blower 3 during "continuous start-up", and when the rising speed of the recovery rate is low, the control device 4 automatically increases the frequency. Therefore, according to the condition of the adhered ash, the control device 4 appropriately increases or decreases the start-up frequency of the soot blower 3 during "continuous start-up" for control. Therefore, compared with the case where the frequency is a fixed value, the adhered ash can be effectively removed, and economy can also be ensured.

[0191] According to the removal system 1, when the clean heat transfer coefficient Kc is equal to or higher than the first specified value α1, the control device 4 determines that the heat conduction of the tube bank 2 is extremely good (there is no accumulation or very little accumulation of adhered ash). Since the interval of "one-time start-up" is set longer, over-starting of the soot blower 3 cannot be avoided, and as a result, economy can be further ensured. On the other hand, when the recovery rate is equal to or higher than the recovery threshold R, the interval of "one-time start-up" continued after the end of "continuous start-up" is set shorter. Therefore, even for ash with strong adhesion that requires "continuous start-up", the soot blower 3 is "one-time started" at short intervals, so that the adhered ash can be removed before a thick layer of ash accumulates in the tube bank 2. Therefore, it is not necessary to frequently perform "continuous start-up", and as a result, economy can be further ensured.

[0192] According to the removal system 1, the control device 4 does not start the soot blower 3 during the period of backwashing the bag filter that is the dust removal device 11, and starts the soot blower 3 after the backwashing is completed, so that faults in the plant can be avoided.

[0193] The soot blower 3 can be either a steam type or an impact pulse type. However, since the steam type soot blower uses steam generated by heat exchange between the exhaust gas and the boiler, the amount of steam supplied by the boiler to the turbine for power generation decreases. As a result, the power generation in the plant can be reduced. Therefore, when the power generation of the plant is emphasized, it is preferable to arrange an impact pulse type soot blower that does not use steam.

[0194] The soot blower 3 is usually arranged on the wall surface of a conduit or the like that forms the path of the exhaust gas. Therefore, Figure 1 when the soot blower 3 is of the steam type, the direction in which the injection nozzle of the soot blower 3 extends and retracts is a direction on a plane that includes the X axis and is orthogonal to the Y axis, and steam is injected from the injection nozzle in the Y-axis direction.

[0195] On the other hand, in the case where the soot blower 3 is an impact pulse type, the ejection direction of the impact pulse is a direction on a plane that includes the X-axis and is orthogonal to the Y-axis.

[0196] Therefore, in the case of the removal system 1 equipped with the impact pulse type soot blower 3, in Figure 1 if the impact pulse is ejected toward the wall surface between the 3-channel and the 2-channel, the wall surface is vibrated, and not only the adhering ash on the tube bank 2 can be removed, but also the ash adhering to the wall surface can be removed.

[0197] [5. Modification Example]

[0198] Hereinafter, a modification example of the removal system 1 having a plurality of soot blowers 3 will be described. The first modification example is an example in which the soot blowers indicated by the symbols 3' and 3'' shown by the dotted lines are used in Figure 1 . The second modification example is as shown in Figure 4 (a) to Figure 4 (c), an example of the case where the number of tube banks 2 arranged in the 3-channel is larger than that in Figure 1 . The third modification example is an example of the case where the boiler structure of the plant is of the end type as shown in Figure 1 . The fourth modification example is an example of the case where the boiler structure of the plant is a double-drum boiler as shown in Figure 5 . Figure 6 .

[0199] In the following description, the same symbols are given to the same elements as those of the above-mentioned Figure 1 removal system 1, and repeated descriptions are omitted. In addition, in Figure 5 and Figure 6 , the illustration of the control device 4 and the signal lines (thin solid lines) input to or output from the control device 4 shown in Figure 1 is omitted.

[0200] [5-1. First Modification Example]

[0201] In Figure 1 , as an embodiment, the removal system 1 provided with one soot blower 3 has been described. Depending on the number of tube banks 2 or the design of the plant, the removal system 1' provided with a plurality of soot blowers 3 may be used.

[0202] The soot blower 3 generally effectively removes the adhering ash on the tube bank 2 arranged close to it. Therefore, in the structure of the removal system 1, the adhering ash on the two tube banks 2 (the tube bank 2 composed of the superheater tubes 22a and 22b respectively) close to the soot blower 3a is effectively removed. However, since the tube bank 2 composed of the superheater tube 22c located at the most downstream is arranged at a position separated from the soot blower 3a, the removal of the adhering ash on this tube bank 2 (22c) may become insufficient.

[0203] Therefore, asFigure 1 As shown by the mid-dotted line, in the removal system 1′, in addition to the soot blower 3a, soot blowers 3′ are respectively arranged at positions downstream of the tube bank 2 (22c) (beside the tube bank 2 (22c) and directly above in the Y-axis direction), whereby the adhered ash on the tube bank 2 (22c) can be effectively removed.

[0204] Further, at this time, when the soot blower arranged separately from the soot blower 3a is an impact pulse type soot blower, the soot blower can replace the soot blower indicated by the symbol 3′, or can be arranged at the position indicated by the symbol 3″ together with the soot blower indicated by the symbol 3′. Figure 1 The soot blower 3″ shown by the mid-dotted line indicates a soot blower arranged near the wall surface of the ceiling of the 3-passage. If it is arranged to emit impact pulses in the Y-axis direction and downward, not only can the adhered ash on the tube bank 2 (22c) be more effectively removed, but also the adhered ash on the tube bank 2 (22b) arranged upstream thereof can be more effectively removed.

[0205] Even when multiple soot blowers 3, 3′, 3″ are arranged in the removal system 1′, similar to the above-described structure in which only one soot blower 3 is arranged, the control device 4 performs Figure 2 processing on each soot blower.

[0206] However, in the processing of step S13, the control device 4 starts them one by one in sequence with the timings of starting staggered according to the arrangements of the respective soot blowers 3, 3′, 3″. That is, the control device 4 does not start the multiple soot blowers 3, 3′, 3″ simultaneously.

[0207] When multiple steam soot blowers are arranged and these are started simultaneously, the steam supplied from the boiler to the turbine is significantly reduced, so the power generation amount is significantly reduced and it is difficult to supply power stably. And when multiple impact pulse type soot blowers are arranged and these are started simultaneously, the pressure in the furnace or the pressure inside the conduit rises significantly, and there may be a failure in the equipment set.

[0208] Therefore, in the removal system 1′, the start of these soot blowers 3 is staggered in time and started in sequence.

[0209] The order in which the control device 4 starts the multiple soot blowers 3 in sequence is the same as that in the Figure 4 second modification example shown later, so the description thereof is omitted.

[0210] [5-2. Second Modification Example]

[0211] Figure 4 (a) to Figure 4In the removal systems 1A to 1C of the second modified example shown in (c), the number of tube bundles 2, the number of soot blowers 3, and the arrangement of the outlet steam temperature measuring devices 24b are different from those of the removal system 1. In the second modified example, a plurality of tube bundles 2 and a plurality of soot blowers 3 are arranged in the Y-axis direction, that is, the vertical direction. Figure 4 (a) is the removal system 1A in which Figure 1 four tube bundles 2 composed of superheater tubes 22a to 22d are arranged in the three channels of Figure 4 (b) is the removal system 1B in which Figure 1 five tube bundles 2 composed of superheater tubes 22a to 22e are arranged in the three channels of Figure 4 (c) is the removal system 1C in which Figure 1 six tube bundles 2 composed of superheater tubes 22a to 22f are arranged in the three channels of

[0212] In the second modified example, similarly to the first modified example, the control device 4 performs Figure 2 processing on each of the plurality of soot blowers.

[0213] In Figure 4 the removal system 1A shown in (a), in addition to the Figure 1 structure, a tube bundle 2 composed of superheater tube 22d is arranged adjacent to the downstream (in the Y-axis direction and above) of the tube bundle 2 composed of superheater tube 22c. And a soot blower 3b is arranged between the tube bundle 2 composed of superheater tube 22c and the tube bundle 2 composed of superheater tube 22d.

[0214] In Figure 4 the removal system 1C shown in (c), in addition to the Figure 4 structure of (a), a tube bundle 2 composed of superheater tube 22e is arranged adjacent to the downstream of the tube bundle 2 composed of superheater tube 22d; and a tube bundle 2 composed of superheater tube 22f is further arranged adjacent to the downstream (in the Y-axis direction and above) of the tube bundle 2 composed of superheater tube 22e. And a soot blower 3d is arranged between the tube bundle 2 composed of superheater tube 22e and the tube bundle 2 composed of superheater tube 22f.

[0215] As shown in Figure 4 (a) and Figure 4 (c), when the number of tube bundles 2 (here, the tube bundles 2 composed of superheater tubes) to which the soot is attached and removed by the soot blower 3 is multiple and even, the soot blower 3 is not arranged in the whole between the target tube bundles 2. In view of the cost performance of soot removal, the target tube bundles 2 are grouped into units of two tube bundles 2 in order from the upstream tube bundle 2, and one soot blower 3 is arranged in one unit. Therefore, the number of the plurality of arranged soot blowers 3 is half of the number of the target tube bundles 2.

[0216] On the other hand, in Figure 4In the removal system 1B shown in (b), different from Figure 4 (c), in the structure of Figure 4 (a), only the tube group 2 composed of the superheater tubes 22e is added, and this tube group 2 is arranged adjacent to the downstream (in the Y-axis direction and upward) of the tube group 2 composed of the superheater tubes 22d. Therefore, in Figure 4 (b), the number of tube groups 2 (tube groups 2 composed of superheater tubes) with adhering ash removed by the soot blower 3 is multiple and odd. At this time, a tube group 2 for which the above-mentioned "unit" cannot be manufactured is generated. In Figure 4 (b), for the tube group 2 composed of the superheater tubes 22e, the above-mentioned "unit" cannot be manufactured.

[0217] However, in the case where the adhering ash of the tube group 2 composed of the superheater tubes 22e cannot be ignored, a soot blower 3c is arranged downstream of this tube group 2.

[0218] In the above second modification example, the tube groups 2 that are the objects of adhering ash removal are arranged in a vertical direction (Y-axis direction). Moreover, an outlet steam temperature measuring device 24b is arranged inside the superheater tube constituting the tube group 2 located at the most downstream.

[0219] When starting a certain soot blower 3 to remove the adhering ash, two cases can be considered for the movement of the removed adhering ash: [1] the case of falling vertically downward due to gravity; [2] the case where the flow of the exhaust gas is strong and moving downstream along with the flow of the exhaust gas.

[0220] Therefore, in the case of [1], when the control device 4 performs "one-time start" or "continuous start" on the soot blower 3, starting from the soot blower 3 arranged at the most downstream towards the soot blower 3 arranged upstream, the start is staggered in sequence. That is, in Figure 4 (a), after starting the soot blower 3b, the soot blower 3a is started. And, in Figure 4 (b), after starting the soot blower 3c, the soot blower 3b is started, and after starting the soot blower 3b, the soot blower 3a is started. Similarly, in Figure 4 (c), after starting the soot blower 3d, the soot blower 3b is started, and after starting the soot blower 3b, the soot blower 3a is started.

[0221] By starting each soot blower 3 in this order, even when the adhering ash removed by the soot blower 3 in a certain tube group 2 falls downward due to gravity and re-adheres to other tube groups arranged upstream, the adhering ash including the re-adhered adhering ash can be reliably removed.

[0222] On the other hand, in the case of [2], when the control device 4 performs "one-time start" or "continuous start" on the soot blower 3, it starts the soot blowers 3 arranged downstream from the soot blower 3 arranged at the most upstream at staggered timings. That is, in Figure 4 in the case of (a), after starting the soot blower 3a, the soot blower 3b is started. And, in Figure 4 in the case of (b), after starting the soot blower 3a, the soot blower 3b is started, and after starting the soot blower 3b, the soot blower 3c is started. Similarly, in Figure 4 in the case of (c), after starting the soot blower 3a, the soot blower 3b is started, and after starting the soot blower 3b, the soot blower 3d is started.

[0223] By starting each soot blower 3 in this order, even if the adhering ash removed by the soot blower 3 in a certain tube group 2 moves downstream along with the exhaust gas flow and re-adheres to other tube groups arranged downstream, it is possible to reliably remove the adhering ash including the re-adhered adhering ash.

[0224] In addition, in the second modification example, the structures corresponding to the first tube group, the second tube group, the third tube group, the fourth tube group, the first soot blower, and the second soot blower in the present application are as follows.

[0225] That is, in Figure 4 (a) and Figure 4 (b), the tube group 2 composed of the superheater tube 22a corresponds to the first tube group, the tube group 2 composed of the superheater tube 22b corresponds to the second tube group, the tube group 2 composed of the superheater tube 22c corresponds to the third tube group, and the tube group 2 composed of the superheater tube 22d corresponds to the fourth tube group. And, the soot blower 3a corresponds to the first soot blower, and the soot blower 3b corresponds to the second soot blower. Figure 4 In (c), in addition to the same cases as Figure 4 (a) and Figure 4 (b), there are also cases where the tube group 2 composed of the superheater tube 22c corresponds to the first tube group, the tube group 2 composed of the superheater tube 22d corresponds to the second tube group, the tube group 2 composed of the superheater tube 22e corresponds to the third tube group, the tube group 2 composed of the superheater tube 22f corresponds to the fourth tube group, the soot blower 3b corresponds to the first soot blower, and the soot blower 3d corresponds to the second soot blower.

[0226] [5-3. Third Modification Example]

[0227] Next, Figure 5 the third modification example will be described.

[0228] In the removal system 1D of the third modification example, in Figure 1Between the three channels of [[ID=]] and the economizer 9, an exhaust gas flow path extending in the horizontal direction (X-axis direction) is added, and a plurality of tube groups 2 and a plurality of soot blowers 3 are also arranged in this horizontal flow path. The boiler structure of the equipment in the third modification is called the end type. Moreover, an outlet steam temperature measuring device 24b is arranged inside the superheater tube 22f that constitutes the tube group 2 located at the most downstream.

[0229] In one of the second modifications Figure 4 In the structure of (c), the third modification has the following structure. Including the soot blowers 3b and 3d, the tube groups 2 from the tube group 2 composed of the superheater tube 22c to the tube group 2 composed of the superheater tube 22f are arranged in the horizontal direction without changing the order from the upstream to the downstream. Additionally, here, it is considered that the tube group 2 composed of the superheater tube 22b and the tube group 2 composed of the superheater tube 22c are arranged adjacent to each other in the same manner as in the second modification.

[0230] Therefore, in the third modification, there are: a plurality of tube groups 2 arranged in the vertical direction in sequence from the upstream (Y-axis direction and downward) to the downstream (Y-axis direction and upward); and a plurality of tube groups 2 arranged in sequence in the horizontal direction toward one direction (X-axis direction).

[0231] In addition, in the third modification, similar to the first modification and the second modification, the control device 4 performs Figure 2 processing on each of the plurality of soot blowers.

[0232] Here, when focusing on the plurality of tube groups 2 arranged in sequence in the horizontal direction toward one direction (X-axis direction), that is, Figure 5 in the case of the tube group 2 composed of the superheater tube 22c, the tube group 2 composed of the superheater tube 22d, the tube group 2 composed of the superheater tube 22e, and the tube group 2 composed of the superheater tube 22f, if the soot blower 3b or 3d is started to remove the adhered ash, the removed adhered ash is highly likely to move downstream along with the exhaust gas flow.

[0233] Therefore, when the control device 4 performs "one-time start" or "continuous start" on the soot blower 3, it starts the soot blowers 3 in sequence with a time offset from the soot blower 3 arranged at the most upstream to the soot blower 3 arranged at the downstream. That is, the control device 4 starts the soot blower 3d after starting the soot blower 3b.

[0234] By starting each soot blower 3 in this order, even if the adhered ash removed by the soot blower 3 in a certain tube group 2 moves downstream along with the exhaust gas flow and re-adheres to other tube groups arranged downstream, it is possible to reliably remove the adhered ash including the re-adhered ash.

[0235] And, Figure 5In this case, considering the multiple tube groups 2 arranged in the horizontal direction and the multiple tube groups 2 arranged in the vertical direction, the situation described in [2] in the second modification may occur. Therefore, when the control device 4 performs "one-time start" or "continuous start" on the soot blower 3, it starts the soot blowers 3 in sequence with a time stagger from the soot blower 3 arranged at the most upstream to the soot blower 3 arranged downstream. That is, after starting the soot blower 3a, the control device 4 starts the soot blower 3b, and after starting the soot blower 3b, it starts the soot blower 3d.

[0236] By starting each soot blower 3 in this order, even if the attached ash removed by the soot blower 3 in a certain tube group 2 moves downstream along with the exhaust gas flow and reattaches to other tube groups arranged downstream, the attached ash including the reattached ash can be reliably removed.

[0237] In addition, in the third modification, the structures corresponding to the first tube group, the second tube group, the third tube group, the fourth tube group, the first soot blower, and the second soot blower in the present application are as follows.

[0238] That is, when focusing on the multiple tube groups 2 arranged in the horizontal direction, the tube group 2 composed of the superheater tubes 22c corresponds to the first tube group, the tube group 2 composed of the superheater tubes 22d corresponds to the second tube group, the tube group 2 composed of the superheater tubes 22e corresponds to the third tube group, the tube group 2 composed of the superheater tubes 22f corresponds to the fourth tube group, the soot blower 3b corresponds to the first soot blower, and the soot blower 3d corresponds to the second soot blower.

[0239] And, when comprehensively considering the multiple tube groups 2 arranged in the horizontal direction and the multiple tube groups 2 arranged in the vertical direction, in Figure 5 the tube group 2 composed of the superheater tubes 22a corresponds to the first tube group, the tube group 2 composed of the superheater tubes 22b corresponds to the second tube group, the tube group 2 composed of the superheater tubes 22c corresponds to the third tube group, the tube group 2 composed of the superheater tubes 22d corresponds to the fourth tube group, the soot blower 3a corresponds to the first soot blower, and the soot blower 3b corresponds to the second soot blower.

[0240] According to the removal system 1D of the third modification, in addition to the effects obtained by the above-described embodiment, the attached ash including the reattached ash can be reliably removed.

[0241] [5-4. Fourth Modification]

[0242] Next, Figure 6 the fourth modification will be described.

[0243] In the third modification, the removal system 1E of the fourth modification is configured as follows: The flow path of the exhaust gas extending horizontally between the 3-passage and the economizer 9 is removed, and a double-drum boiler having a steam drum 19 and a water drum 20 is provided between the 3-passage and the economizer 9. Since this flow path is removed, the tube bundle 2 (22c to 22f) and the soot blower 3 (3b, 3d) disposed in this flow path in the third modification are also removed.

[0244] Moreover, in the fourth modification, the suspension tube 21 and the soot blower 3a of the third modification are removed, the superheater tubes 22a and 22b are hoisted and disposed on the ceiling of the 3-passage, and the soot blower 3 (3e) is disposed adjacent to the upstream of the superheater tube 22a and adjacent to the superheater tube 22a.

[0245] In addition, in Figure 1 , the tube bundle 2 of the economizer 9 is not regarded as a tube bundle to be the object of soot adhesion removal, but in the fourth modification, a plurality of tube bundles 2 of the economizer 9 are also the objects of soot adhesion removal. Therefore, inside the economizer 9, a soot blower 3f is provided between a plurality of tube bundles 2 arranged in the vertical direction (Y-axis direction), that is, the tube bundle 2 composed of the water tubes 23a and the tube bundle 2 composed of the water tubes 23b disposed adjacent to the downstream of the tube bundle 2.

[0246] In addition, at this time, as described above, the "plurality of tube bundles 2" that are the objects of soot adhesion removal are arranged between the two pressure measuring devices 14a and 14b, and are also arranged between the two gas temperature measuring devices 15a and 15b.

[0247] Figure 6 In

[0248] , the tube bundle 2 that is the object of soot adhesion removal includes different types of tube bundles 2, that is, the tube bundle 2 composed of the superheater tubes 22a to 22b and the tube bundle 2 composed of the water tubes 23a to 23b. In addition, between the tube bundle 2 composed of the superheater tube 22b and the tube bundle 2 composed of the water tube 23a, no other tube bundle 2 that becomes a resistance to the flow of the exhaust gas is arranged.

[0248] Moreover, different from Figure 1 , the temperature measuring device 15b that measures the temperature of the exhaust gas at the "outlet" of the plurality of tube bundles 2 is arranged downstream of the tube bundle 2 composed of the water tubes 23b that is arranged at the most downstream among the plurality of tube bundles 2 that are the objects of soot adhesion removal. In Figure 6 , the temperature measuring device 15b is arranged at a position substantially the same as the pressure measuring device 14b of Figure 1 . Moreover, inside the superheater tube 22b that is the most downstream in the superheater tubes, an outlet steam temperature measuring device 24b is arranged.

[0249] In addition, in the fourth modification, similar to the first to third modifications, the control device 4 performs Figure 2 processing on each of the plurality of soot blowers.

[0250] In the fourth modification, when the control device 4 performs "single start" or "continuous start" on the soot blower 3, it starts the soot blowers 3 arranged downstream from the soot blower 3 arranged at the most upstream in a time-shifted manner in sequence. That is, after starting the soot blower 3e, the control device 4 starts the soot blower 3f.

[0251] By starting each soot blower 3 in this order, when the adhered ash removed by the soot blower 3 in the tube group 2 arranged upstream moves downstream along with the exhaust gas flow and re-adheres to other tube groups arranged downstream, it is possible to reliably remove the adhered ash including the re-adhered adhered ash.

[0252] In addition, in the fourth modification, the structures corresponding to the first tube group, the second tube group, the third tube group, the fourth tube group, the first soot blower, and the second soot blower in the present application are as follows.

[0253] That is, the tube group 2 composed of the superheater tubes 22a corresponds to the first tube group, the tube group 2 composed of the superheater tubes 22b corresponds to the second tube group, the tube group 2 composed of the water tubes 23a corresponds to the third tube group, the tube group 2 composed of the water tubes 23b corresponds to the fourth tube group, the soot blower 3e corresponds to the first soot blower, and the soot blower 3f corresponds to the second soot blower.

[0254] According to the removal system 1E of the fourth modification, in addition to the effects obtained by the above-described embodiment, it is possible to reliably remove the adhered ash including the re-adhered adhered ash.

[0255] As described above, the embodiments and modifications of the present invention have been described, but the technical scope of the present invention is not limited to the embodiments or modifications, and various changes can be made without departing from the gist of the present invention.

[0256] Reference Signs

[0257] 1, 1', 1A to 1E - Boiler tube bank ash removal system (removal system), 2 - Tube bank, 3, 3', 3'', 3a to 3f - Soot blower, 4 - Control device, 5 - Hopper, 6 - Feeder, 7 - Coal feeder, 8 - Ash chute, 9 - Economizer (a type of tube bank), 10 - Desuperheating tower, 11 - Dust removal device (bag filter), 12 - Chimney, 13 - Induced draft fan, 14a, 14b - Pressure measuring device, 15a, 15b - Gas temperature measuring device, 16a, 16b - Gas flow measuring device, 17 - Superheat desuperheater, 18 - Injection water flow measuring device, 19 - Steam drum, 20 - Water drum, 21 - Suspension tube (filter tube), 22a to 22f - Superheater tube (superheater), 23a, 23b - Water pipe, 24a, 24b - Steam temperature measuring device, 25 - Main steam flow measuring device, 26 - Primary air supply device, 27 - Secondary air supply device, 28 - Combustion air flow measuring device, K - Heat transfer coefficient, Kc - Net heat transfer coefficient, Kd - Dirty heat transfer coefficient, Kc / Kd - Recovery rate, ΔPg - Pressure difference, pgmin - Second threshold, Qc - Total combustion air volume, qcmin - Fourth threshold, Qr - Rotational speed of induced draft fan, qrmin - Third threshold, Qs - Main steam flow, qsmin - First threshold, R - Recovery threshold, α1 - First specified value, α2 - Second specified value.

Claims

1. A boiler tube group fouling removal system that removes the fouling on multiple tube groups of a boiler that recovers heat from the exhaust gas generated in a furnace. It is characterized in that it has: A soot blower disposed between the multiple tube groups; An induced draft fan disposed downstream of the multiple tube groups to guide the exhaust gas; and A control device that controls the startup of the soot blower, The control device performs the following processing: Calculate the heat transfer coefficient of the boiler; When the calculated heat transfer coefficient is equal to or greater than a specified value, start the soot blower only once at a specified interval, and then perform another startup at the specified interval or a different interval; When the calculated heat transfer coefficient is less than the specified value, perform a fouling determination process that makes an alternative determination between a first determination and a second determination; When the first determination is obtained in the fouling determination process, perform continuous startup of continuously starting the soot blower multiple times without separating the intervals; When the second determination is obtained in the fouling determination process, perform the one-time startup, The fouling determination process is performed including at least one of the following conditions: First condition, the main steam flow rate of the multiple tube groups is equal to or greater than a first threshold value; Second condition, the pressure difference between the inlet and outlet of the exhaust gas of the multiple tube groups is equal to or greater than a second threshold value; Third condition, the rotational speed of the induced draft fan is equal to or greater than a third threshold value; and Fourth condition, the total amount of combustion air supplied to the furnace is equal to or greater than a fourth threshold value. In the case where the fouling determination process is performed based on only any one of the four conditions, when the one condition is satisfied, the first determination is obtained, and when the one condition is not satisfied, the second determination is obtained. In the case where the fouling determination process is performed including any two, three, or four of the four conditions, when all the conditions including the two, three, or four conditions are satisfied, the first determination is obtained, and when any of the conditions including the two, three, or four conditions is not satisfied, the second determination is obtained.

2. The boiler tube group fouling removal system according to claim 1, It is characterized in that The control device performs the following processing: In the case where the first determination is obtained in the fouling determination process, calculate the recovery rate based on the dirty heat transfer coefficient indicating the heat transfer coefficient calculated before starting the soot blower and the net heat transfer coefficient indicating the heat transfer coefficient calculated after starting the soot blower. When the recovery rate is equal to or greater than a recovery threshold value, perform the continuous startup. When the recovery rate is less than the recovery threshold value, perform the one-time startup.

3. The boiler tube group fouling removal system according to claim 2, It is characterized in that When the net heat transfer coefficient is equal to or greater than the specified value, the control device resets the specified interval to be longer than the value set just before, and when the recovery rate is equal to or greater than the recovery threshold value, resets the specified interval to be shorter than the value set just before.

4. The boiler tube group fouling removal system according to claim 3, It is characterized in that When the control device performs continuous startup, if the rising speed of the recovery rate is high, the number of startups during continuous startup is reduced; if the rising speed of the recovery rate is low, the number of startups during continuous startup is increased.

5. The boiler tube group ash adhesion removal system according to claim 4, wherein: further comprising: a bag filter disposed downstream of the plurality of tube groups to remove coal dust from the exhaust gas, during the backwashing of the bag filter, the control device does not start the soot blower, and starts the soot blower after the backwashing is completed.

6. The boiler tube group ash adhesion removal system according to claim 5, wherein: the plurality of tube groups include: a first tube group; a second tube group disposed adjacent to the first tube group downstream of the first tube group; a third tube group disposed adjacent to the second tube group downstream of the second tube group; and a fourth tube group disposed adjacent to the third tube group downstream of the third tube group, the soot blower includes: a first soot blower disposed between the first tube group and the second tube group; and a second soot blower disposed between the third tube group and the fourth tube group, when the control device performs one startup or continuous startup of the first soot blower and the second soot blower, when the first tube group to the fourth tube group are arranged in the vertical direction from bottom to top in sequence, after starting the second soot blower, the first soot blower is started, or after starting the first soot blower, the second soot blower is started, when the first tube group to the fourth tube group are arranged in sequence in one direction in the horizontal direction, after starting the first soot blower, the second soot blower is started, when the first tube group and the second tube group are arranged in the vertical direction from bottom to top in sequence, and the third tube group and the fourth tube group are arranged in sequence in one direction in the horizontal direction, after starting the first soot blower, the second soot blower is started.

7. The boiler tube group ash adhesion removal system according to claim 5, wherein: the plurality of tube groups include: a first tube group; a second tube group disposed adjacent to the first tube group downstream of the first tube group; a third tube group disposed downstream of the second tube group; and a fourth tube group disposed adjacent to the third tube group downstream of the third tube group, the soot blower includes: a first soot blower disposed adjacent to the first tube group upstream of the first tube group; and a second soot blower disposed between the third tube group and the fourth tube group, when the control device performs one startup or continuous startup of the first soot blower and the second soot blower, after starting the first soot blower, the second soot blower is started.

8. The boiler tube group ash adhesion removal system according to any one of claims 1 to 7, wherein: the soot blower is a pressure wave type soot blower that generates a pressure wave by gas explosion.

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