CN115803563A - Boiler tube group attached ash removing system - Google Patents

Abstract

A boiler tube group adhering ash removing system (1) is provided with: a soot blower (3) disposed between the plurality of tube groups (2); an induced draft fan (13) that guides exhaust gas downstream of the tube bank (2); and the control device (4) is used for controlling the soot blower (3) and calculating the heat transfer coefficient of the boiler. The control device (4) starts the soot blower (3) once at a predetermined interval when the heat transfer coefficient is equal to or higher than a predetermined value, executes an attached ash determination process when the heat transfer coefficient is lower than the predetermined value, and continuously starts the soot blower (3) according to the result. The ash deposition determination process is executed under at least 1 of 4 conditions including the main steam amount of the tube bank (2), the pressure difference of the exhaust gas, the rotation speed of the induced draft fan (13), and the total amount of combustion air supplied to the furnace.

Description

Boiler tube group attached ash removing system

Technical Field

The invention relates to a boiler tube group attached ash removal system.

Background

In a plant such as a thermal power plant including a coal-fired boiler or a refuse incinerator or a gasification and melting furnace including a waste heat boiler for generating electric power, incineration ash contained in exhaust gas generated by combustion of coal or refuse is likely to adhere to and accumulate in a tube block (a tube block of a boiler including a mesh tube, a superheater tube, an evaporator tube, an economizer water tube, and the like). If the incineration ash is deposited on the tube group, the tube group may be corroded, and in addition, the power generation efficiency may be deteriorated. Therefore, in general, a steam-type or impact-type soot blower is activated at predetermined time intervals (at a predetermined cycle) to remove ash (hereinafter referred to as "attached ash") accumulated in the tube bank, that is, to "remove attached ash".

However, when the amount of the adhering ash deposited on the tube group is small, the amount of the adhering ash removed by activating the sootblower is small, and therefore the effect of removing the adhering ash is small compared to the cost of using the electric power, steam, or gas consumed or used by the sootblower. On the other hand, when the amount of the adhering ash accumulated in the tube group is large, the adhering ash cannot be sufficiently removed in the activation of the sootblower every certain period, and the adhering ash remaining in the tube group without being removed may be solidified before the next activation of the sootblower, and the adhering ash may be difficult to be removed by the sootblower.

Therefore, in order to appropriately remove the attached ash of the tube group using the soot blower, various boiler tube group attached ash removal systems have been developed.

For example, patent document 1 discloses a system in which the above cycle is changed according to the degree of contamination of the pipe group, that is, the degree of deposition of adhering ash on the pipe group. Patent document 2 discloses a system for activating a sootblower in consideration of conditions other than the degree of contamination of the tube bank. Further, patent document 3 discloses a system in which the upstream and downstream pressures of the exhaust gas flowing through the tube group are measured, and the soot blower is activated when the difference between these pressures is equal to or greater than a predetermined value.

Further, as for the soot blower, a steam type has been mainly used, but in recent years, a pulse type impact type without using steam has been developed and put on the market.

When the steam sootblower is activated, the steam is continuously injected for a predetermined time, and when the predetermined time elapses, the steam injection is stopped.

On the other hand, the impact Pulse type sootblower is also called a pressure wave type, shock wave type sootblower or Shock Pulse Generator (SPG), and when activated, the combustible gas filled inside the sootblower explodes and emits a Shock Pulse (also called a "Shock wave" or a "pressure wave"). In addition, if the impact pulse type soot blower is once started, the gas needs to be refilled for the next start. The filling typically takes about 1 minute to 10 minutes.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. Sho 62-210316

Patent document 2: japanese patent laid-open publication No. Sho 63-286609

Patent document 3: japanese patent laid-open publication No. 2017-181007

Disclosure of Invention

Technical problem to be solved by the invention

In the techniques disclosed in patent documents 1 to 3, only 1 time of activation of the sootblower is performed after a predetermined condition such as the arrival of the above-described cycle is satisfied.

However, as described above, the soot blower is activated only 1 time depending on the deposition amount of the adhering ash, and the adhering ash is not necessarily removed sufficiently. Therefore, in the techniques disclosed in patent documents 1 to 3, when the soot blower is activated and the adhering ash is not effectively removed, it is necessary to wait for the soot blower to be activated again after a predetermined condition such as arrival of the next cycle is satisfied. Therefore, in these techniques, if the soot blower cannot sufficiently remove the adhering ash by 1 activation, the heat exchange performance of the boiler cannot be recovered early.

Thus, when starting a sootblower, it may be considered to start multiple times in succession, not just 1 time.

However, although the soot blower can sufficiently remove the adhering ash with 1 activation of the soot blower, it is not economical to activate the soot blower a plurality of times each time when the above-mentioned predetermined condition is established.

Accordingly, an object of the present invention is to provide a boiler tube bank adhering ash removing system that removes adhering ash early and properly while securing economy.

Means for solving the technical problem

The present invention provides a boiler tube group adhering ash removing system for removing adhering ash from a plurality of tube groups of a boiler for heat recovery from exhaust gas generated in a furnace, the boiler tube group adhering ash removing system comprising: a soot blower disposed between the plurality of tube groups; an induced draft fan disposed downstream of the plurality of tube banks and guiding the exhaust gas; and a control device for controlling the start of the soot blower,

the control device performs the following processing: calculating the heat transfer coefficient of the boiler; when the calculated heat transfer coefficient is equal to or greater than a predetermined value, starting the sootblower only 1 time at a predetermined interval, and thereafter starting the sootblower 1 time at the predetermined interval or at an interval different from the predetermined interval; executing an adhering ash determination process of performing an alternative determination on one of the first determination and the second determination when the calculated heat transfer coefficient is smaller than the predetermined value; executing continuous activation of the soot blower a plurality of times without the predetermined interval when the first determination is obtained in the soot adhesion determination processing; executing the 1-time activation when the second determination is obtained in the attached ash determination processing,

the adhering dust determination process is executed including at least 1 of the following conditions: a first condition that a main steam amount of the plurality of tube groups is a first threshold value or more; a second condition that a pressure difference of the exhaust gas at an inlet and an outlet of the plurality of tube groups is a second threshold value or more; in the third condition, the rotating speed of the induced draft fan is above 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.

The first determination is obtained when the 1 condition is satisfied in a case where the adhering gray determination process is performed only according to any 1 condition among the 4 conditions, the second determination is obtained when the 1 condition is not satisfied, the first determination is obtained when all conditions including the 2, 3, or 4 conditions are satisfied in a case where the adhering gray determination process is performed including any 2, 3, or 4 conditions among the 4 conditions, and the second determination is obtained when any condition including the 2, 3, or 4 conditions is not satisfied.

Effects of the invention

According to the boiler tube bank adhering ash removing system, 1 start and continuous start are distinguished and used based on the heat transfer coefficient. Further, the adhering ash determination process is executed when the heat transfer coefficient is smaller than the predetermined value, and whether or not the sootblower is continuously activated can be appropriately determined, so that the adhering ash can be removed early and appropriately while the economical efficiency is ensured.

Drawings

Fig. 1 is a schematic configuration diagram of a boiler tube bank adhering ash removal system according to an embodiment and a first modification example.

Fig. 2 is an example of a flowchart illustrating control of the boiler tube bank attached ash removal system to activate the soot blowers.

Fig. 3 (a) to 3 (d) are examples of a specific processing flow of step S16 (adhering dust determination processing) in fig. 2.

Fig. 4 (a) to 4 (c) are schematic configuration diagrams showing a part of a boiler tube bank adhering ash removing system according to a second modification.

Fig. 5 is a schematic configuration diagram of a boiler tube bank adhering ash removal system according to a third modification example.

Fig. 6 is a schematic configuration diagram of a boiler tube bank adhering ash removal system according to a fourth modification example.

Detailed Description

The following describes a boiler tube bank adhering ash removal system according to an embodiment and a modification thereof with reference to the drawings. The structures and the like shown below are merely examples, and are not intended to exclude various modifications or technical applications not explicitly shown. The following configurations and the like can be variously modified without departing from the scope of these embodiments. Further, the components can be selected as needed, or can be appropriately combined.

[1. Overview of boiler tube group adhering ash removal System ]

Fig. 1 is a schematic configuration diagram of a boiler tube bank adhering ash removal system 1 (hereinafter referred to as "removal system 1") according to the present embodiment. Fig. 1 is also a diagram showing a first modification (removal system 1') described later.

Fig. 1 and fig. 4 to 6 described later illustrate an orthogonal coordinate system including an X axis and a Y axis. The X-axis is the horizontal direction and the Y-axis is the vertical direction. The arrow direction of the Y axis is a vertical direction and a direction facing upward.

In the present embodiment, the removal system 1 applied to a plant including a waste incinerator provided with a boiler for generating electric power will be described as an example. It is needless to say that the boiler tube group-attached ash removal system according to the present invention can be applied to other plants such as a thermal power plant and a gasification and melting furnace.

The boiler is roughly classified into a double drum type (two drum type) having a steam drum and a water drum, and a single drum type (one drum type) having a steam drum, but any boiler may be used for the removal system 1. In fig. 1, although illustration of the steam drum is omitted, a plant of a garbage incinerator provided with a single-drum boiler is illustrated.

The removal system 1 is a system for removing ash adhering to a plurality of tube banks 2 of a boiler for recovering heat from exhaust gas generated in the furnace, and includes soot blowers 3 arranged between the plurality of tube banks 2, an induced draft fan 13 arranged downstream of the plurality of tube banks 2 and guiding the exhaust gas, and a control device 4 for controlling activation of the soot blowers 3.

Although described in detail later, the control device 4 calculates the heat transfer coefficient K of the boiler, and when the heat transfer coefficient K is equal to or greater than the predetermined value α 1, the soot blower 3 is activated only 1 time at a predetermined interval, and "1 activation" at the predetermined interval or at an interval different from the predetermined interval is executed again.

When the calculated heat transfer coefficient K is smaller than the predetermined value α 1 and smaller than the predetermined value α 2, the control device 4 executes an adhesion ash determination process of performing an alternative determination on either the first determination or the second determination. When the first determination is made in the attached ash determination process, the control device 4 basically performs "continuous start", that is, continuously starts the plurality of sootblowers 3 without a predetermined interval, and when the second determination is made in the attached ash determination process, performs "1 start".

The attached ash determination process is executed including at least 1 condition among the first to fourth conditions described below.

The first condition is that: the main steam amount Qs of the stack 2 is not less than a first threshold value

The second condition is that: the pressure difference Δ Pg between the exhaust gas at the inlet and the exhaust gas at the outlet of the tube group 2 is not less than a second threshold value

A third condition: the rotating speed Qr of the induced draft fan 13 is above a third threshold value

A fourth condition: the total amount of combustion air Qc supplied to the furnace is equal to or higher than a fourth threshold

According to the inventors' experience, each of these 4 conditions is as follows: when the conditions are satisfied, there is a high possibility that a large amount of adhering ash is accumulated in the tube group 2, and therefore it is considered that it is preferable to perform "continuous activation" of the sootblower 3.

In fig. 3 described in detail later, only the above-described 4 conditions (first condition, second condition, third condition, and fourth condition) are described as an example, but other conditions (for example, fifth condition, sixth condition, seventh condition, eighth condition, … …, and the like) may be added to these 4 conditions according to the design.

The other conditions may be: for example, as the fifth condition, "the temperature of the main steam of the tube group 2 measured by the outlet steam temperature measuring device 24b described later is less than the fifth threshold value," as the sixth condition, "the amount of water injected by the desuperheater 17 (described later) is less than the sixth threshold value," and as the seventh condition, "the gas temperature of the exhaust gas at the outlet of the tube group 2 measured by the gas temperature measuring device 15b (outlet gas temperature measuring device) described later is equal to or more than the seventh threshold value," for example.

Further, although not shown, in the plant of the garbage incinerator, there is a possibility that an Exhaust Gas Recirculation (EGR) technique of circulating a part of the Exhaust Gas downstream of the dust removing device 11 to the vicinity of the stoker 7 may be employed. In this case, the following conditions may be added as the other conditions: for example, as an eighth condition, a gas flow rate measuring device that measures the gas flow rate of the circulated exhaust gas (circulated exhaust gas) is provided separately from the gas flow rate measuring devices 16a and 16b described later, and "the gas flow rate of the circulated exhaust gas is equal to or higher than an eighth threshold value" measured by the gas flow rate measuring device.

These other conditions are also divided into two according to the evaluation formula, as in the first to fourth conditions. Specifically, regarding these other conditions, it is preferable to perform the "continuous start" of the soot blower 3 because a large amount of adhering soot is likely to be accumulated in the tube group 2 when the condition of the evaluation formula is satisfied, and a condition that the "continuous start" of the soot blower 3 is not required (therefore, it may be "1 start") may be selected when the condition of the evaluation formula is not satisfied.

In the case where the adhering dust determination process is executed based on only any 1 condition among 4 conditions of the above-described first to fourth conditions, the first determination is obtained when the 1 condition is satisfied. Also, the second determination is obtained when the 1 condition is not established.

When the attached ash determination process is executed while including any 2, 3, or 4 of the 4 conditions (the fifth condition or the like may be added), the first determination may be made when all the conditions including the 2, 3, or 4 conditions are satisfied. Further, the second determination is obtained when any of all the conditions including the 2, 3, or 4 conditions is not satisfied.

Hereinafter, the following description will be made of the configuration other than the above-described configuration of at least the removal system 1. After the description of the configuration, the control (including the attached ash determination process) related to the activation of the sootblower 3 will be described in detail.

[2. System Structure ]

As shown in fig. 1, the removal system 1 includes: a hopper 5 for storing an object to be incinerated such as garbage; a feeder 6 that extrudes the material to be incinerated stored in the hopper 5 from below (in the Y-axis direction and below) the hopper 5; a coal feeder 7 for feeding and burning the material to be burned pressed by the feeder 6; and an ash tank 8 for discharging the residue burned by the coal feeder 7.

The abatement system 1 exchanges heat of the exhaust gas containing the fly ash generated by burning the material to be incinerated by the stoker 7 with an economizer 9 (one of the tube banks, also referred to as an "economizer") disposed in each tube bank 2 and downstream thereof. The removal system 1 discharges the heat-exchanged exhaust gas from a stack 12 to the atmosphere via a desuperheater 10 that cools the heat-exchanged exhaust gas and further via a dust removing device 11 (for example, a bag filter) that removes soot of the cooled exhaust gas.

The path of the exhaust gas from the stoker 7 to the opening of the chimney 12 is formed by a water wall or a duct or the like, and is substantially sealed. Among these paths, a path extending from just above the coal feeder 7 in the Y-axis direction and upward is referred to as "1 pass" ("pass" is an english "pass"), a path extending from the upper end of the 1 pass to the lower end of the Y-axis direction is referred to as "2 pass", a path extending from the 2 pass to the upper end of the Y-axis direction is referred to as "3 pass". As shown by arrows in fig. 1, the exhaust gas generated in the stoker 7 flows in such a manner that it rises in the 1 st path, falls in the 2 nd path, and rises in the 3 rd path. Further, an induced draft fan 13 is disposed on the path between the dust removing device 11 and the stack 12 in order to guide the flow of the exhaust gas from the duct 1 to the stack 12.

The removal system 1 includes: a measuring device 14a (inlet pressure measuring device) disposed in the 1-channel to measure the pressure of the exhaust gas; and a pressure measuring device 14b (outlet pressure measuring device) that is disposed in the path of the exhaust gas between the economizer 9 and the temperature-reducing tower 10 and measures the pressure of the exhaust gas.

The arrangement of the pressure measuring devices 14a and 14b is not limited to these. According to the design of the plant, the inlet pressure measuring device 14a is only required to be disposed in the exhaust gas path becomes the adhesion of ash removal object of the multiple tube group 2 in the upstream of the tube group 2 arranged at the most upstream arbitrary place, namely "the entrance of the multiple tube group 2", according to the design of the plant, the outlet pressure measuring device 14b is only required to be disposed in the exhaust gas path becomes the adhesion of ash removal object of the multiple tube group 2 arranged at the most downstream tube group of the downstream arbitrary place, namely "the multiple tube group 2 outlet". However, these arbitrary fields are preferably as close as possible to the attached ash removal object of multiple tube sets 2.

The removal system 1 includes: a gas temperature measuring device 15a (inlet gas temperature measuring device) which is disposed below the tube group 21 positioned at the most upstream (lower) among the plurality of tube groups 2 to be subjected to the removal of the adhering ash disposed in the 3-pass and measures the temperature of the exhaust gas; and a gas temperature measuring device 15b (outlet gas temperature measuring device) that is disposed on a path of the exhaust gas between the economizer 9 and the tube group 22c located at the most downstream (upper) among the plurality of tube groups 2 arranged in the 3-pass, and measures the temperature of the exhaust gas.

The arrangement of the gas temperature measuring devices 15a and 15b is not limited to these. According to the design of the plant, the inlet gas temperature measuring device 15a is only required to be disposed in the exhaust gas path becomes the adhesion of ash removal object of the multiple tube group 2 in the upstream of the tube group 2 arranged at the most upstream arbitrary place, namely "the entrance of the multiple tube group 2", according to the design of the plant, the outlet gas temperature measuring device 15b is only required to be disposed in the exhaust gas path becomes the adhesion of ash removal object of the multiple tube group 2 arranged at the most downstream tube group 2 in the arbitrary place, namely "the multiple tube group 2 outlet". However, these arbitrary fields are preferably as close as possible to the attached ash removal object of multiple tube sets 2.

In other words, in the present embodiment and the modifications described later, "the plurality of tube groups 2" to be removed of the adhering ash are tube groups disposed between the 2 pressure measuring devices 14a and 14b and between the 2 gas temperature measuring devices 15a and 15 b.

Fig. 1 shows, as an example, a configuration in which a plurality of tube groups 2 are arranged in 3 channels. Further, although the economizer 9 is also provided with the tube group (see fig. 6), in the configuration of fig. 1, the economizer 9 is disposed downstream of the outlets of the plurality of tube groups 2, that is, downstream of the outlet gas temperature measuring device 15b, and therefore, in the present embodiment, the tube group provided in the economizer 9 is not regarded as a tube group to be subjected to the removal of the adhering ash. Although described later, the tube group provided in the economizer 9 is also regarded as an example of "a plurality of tube groups 2" and is a fourth modification of the present embodiment.

In the 3-pass, the tube group 2 including the suspension tube (screen tube) 21 is disposed at the most upstream (lowermost in the Y-axis direction) in the flow direction of the exhaust gas, and the tube groups 2 including the superheater tubes (superheaters) 22a, 22b, and 22c are disposed in this order from the tube group 21 toward the downstream (upward in the Y-axis direction).

Fig. 1 shows, as an example, a configuration in which the sootblowers 3 (3 a) are arranged between a plurality of tube groups 2 of the same type. That is, in the tube group composed of the superheater tubes, the sootblower 3a is disposed between the tube group 2 composed of the superheater tube 22a located at the most upstream and the tube group 2 (the tube group 2 composed of the superheater tubes 22 b) disposed adjacent to the tube group 2 at the downstream of the tube group 2. The arrangement of the sootblowers 3 (3 a) is not limited to this, and the sootblowers 3 may be arranged between different types of tube groups arranged adjacent to each other among tube groups formed of different types of tube groups 2, for example, a filter screen tube of a boiler, a superheater tube, an evaporator tube, a water tube of an economizer, and the like. The sootblower 3 may be of a steam type or an impulse type, and is described here as an impulse type sootblower.

The abatement system 1 includes at least one of a gas flow rate measurement device 16a disposed in the 2-pass duct and measuring the flow rate of the exhaust gas, and a gas flow rate measurement device 16b disposed in the exhaust gas path between the dust removal device 11 and the induced draft fan 13 and measuring the flow rate of the exhaust gas. As described above, since the path of the exhaust gas from the coal charger 7 to the opening of the stack 12 is substantially sealed, 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 by providing 1 gas flow rate measuring device.

The arrangement of the gas flow rate measuring devices 16a and 16b is not limited to these. At least 1 exhaust gas path may be provided. From the viewpoint of reducing the frequency of cleaning by the gas flow rate measuring device, it is preferable to dispose the gas flow rate measuring device downstream of the dust removing device 11. That is, when either of the gas flow rate measurement devices 16a and 16b is selected, the gas flow rate measurement device 16b is preferably provided.

Instead of providing the gas flow rate measuring device 16a, the gas flow rate of the exhaust gas in the 2-channel may be calculated and used for calculating the heat transfer coefficient K to be described later.

The removal system 1 includes a desuperheater (desuperheater) 17 for spraying water into the interior of the superheater tubes in order to appropriately cool the steam passing through the interior of the tube bank 2 including the superheater tubes. In fig. 1, the desuperheater 17 is disposed in the group 2 including the superheater tube 22c disposed at the most downstream of the four groups 2 disposed in the 3 passes. The amount of water sprayed by desuperheater 17 is measured by a sprayed water amount measuring device 18.

The removal system 1 includes: a steam temperature measuring device 24a (inlet steam temperature measuring device) which is disposed inside the uppermost superheater tube 22a among the superheater tubes included in the plurality of tube groups 2 to be subjected to ash removal, and measures the temperature of the steam; and a steam temperature measuring device 24b (outlet steam temperature measuring device) that is disposed inside the superheater tube 22c located at the most downstream side and measures the temperature of the steam. The steam temperature measuring devices 24a, 24b are provided on the superheater tubes in the plurality of tube groups 2.

The removal system 1 is provided with a main steam amount measuring device 25 that measures the amount of main steam flowing through the inside of the superheated pipe. Here, the main steam amount measuring device 25 is disposed inside the superheater tube 22a positioned at the most upstream of the superheater tubes included in the plurality of tube groups 2.

The removal system 1 includes: a primary air supply device 26 located below the stoker 7; a secondary air supply device 27 located in the 1 channel above the coal feeder 7; and a combustion air amount measuring device 28 that measures the total amount of the primary air and the secondary air (total amount of combustion air) supplied from the air supply devices 26 and 27 to the path of the exhaust gas.

Various information measured by the pressure measuring devices 14a and 14b, the gas temperature measuring devices 15a and 15b, the gas flow measuring devices 16a and 16b, the injection water amount measuring device 18, the steam temperature measuring devices 24a and 24b, the main steam amount measuring device 25, and the combustion air amount measuring device 28 is input to the control device 4. The control device 4 is an electronic control device (for example, a computer) included in the system 1, and is equipped with a processor operated by a clock, a timer, and a storage device (all of which are not shown).

[3. Control Structure (flow chart) ]

As described above, the control device 4 calculates the heat transfer coefficient K of the boiler, appropriately executes the attached ash determination process based on the heat transfer coefficient K, and causes the sootblower 3"1 to be activated" or "continuously activated" once.

The control (including the attached ash determination process) related to the activation of the sootblower 3 will be described in detail below with reference to flowcharts shown in fig. 2 and 3 (a) to (d). The dust removing device 11 will be described as a bag filter.

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

The initial values of the times t1, tmin, tmax, and Δ t, the initial value of the Dirty (Dirty) heat transfer coefficient Kd, the initial value of the flag F, the predetermined values α 1 and α 2, and the recovery threshold value R appearing in the flowchart are set as follows, and stored in the storage device in advance before "start" of the flowchart.

The net (clean) heat transfer coefficient Kc does not need to be set in advance before the "start" of the present flowchart because the value of the heat transfer coefficient calculated first after the start-up of the removal system 1 becomes the initial value.

The time t1 is the first time (remaining time of the timer) when the timer is counted down, and corresponds to the interval when the sootblower 3"1 is activated once. The initial value of the time t1 is a predetermined value satisfying a relationship of "0 < Tmin < t1 < Tmax". Tmin is the minimum value (shortest interval) of the intervals at which the sootblowers 3 are activated, and is set to 1 hour, for example. Tmax is the maximum value (longest interval) of the intervals at which the sootblowers 3 are activated, and is set to 3 hours, for example.

The initial value of the time t1 is set to a time obtained by "2/3 × Tmax- Δ t (for example, Δ t is 0.5 hour)", for example. For convenience of explanation, the values Tmin and Tmax are set to be integral multiples of Δ t. Then, the time t1 is changed from the initial value in steps S7 and S19 described later.

The dirty heat transfer coefficient Kd is a heat transfer coefficient when the tube group 2 to be removed of the adhering ash deposits adhering ash and the like and is in a contaminated state.

The initial value of the dirty heat transfer coefficient Kd is set to a prescribed value (for example, kd = 0.5) satisfying the relationship "0 < Kd < α 2". Subsequently, in step S3 described later, the dirty heat transfer coefficient Kd is changed from the initial value.

The initial value of the flag F is set to F =0 (first value). Thereafter, the flag F is changed to any one of F =0 (first value), F =1 (second value), and F =2 (third value) in steps S9, S20, and S14, which will be described later.

The first predetermined value α 1 and the second predetermined value α 2 are determination thresholds for determining whether or not the sootblower 3 is "activated 1 time" in comparison with the heat transfer coefficient K (net heat transfer coefficient Kc) in each of step S5 and step S15, which will be described later. The second predetermined value α 2 is also a determination threshold value for determining whether or not to execute the adhering ash determination process in comparison with the heat transfer coefficient K (net heat transfer coefficient Kc) in step S15 described later. Satisfies the relation of 0 < alpha 2 < alpha 1. For convenience of explanation, the description will be continued assuming that a relationship of "0 < α 2 < 1 < α 1" is satisfied.

The net heat transfer coefficient Kc is a heat transfer coefficient calculated immediately after the soot blower 3 is started. In other words, the net heat transfer coefficient Kc is a heat transfer coefficient in a state where the heat exchange rate is considered to be increased because the soot blower 3 is started and the ash adhered to the tube group 2 is removed to some extent.

The first predetermined value α 1 is set to a value at which the heat exchange of the tube group 2 is remarkably good, so to speak, if the net heat transfer coefficient Kc is not less than α 1There is a value at which the deposition of the adhering ash or the deposition of the adhering ash is extremely small. For convenience of explanation, the first predetermined value α 1 is set to a value that can be achieved by continuously activating at least 2 or more sootblowers 3 as "continuous activation" without causing the net heat transfer coefficient Kc to become α 1 or more only by "1 activation" of the sootblowers, i.e., by a single activation of the sootblowers immediately after the flag F is changed to F =2 in step S20 to be described later. For example, the first predetermined value α 1 is set to α 1=1.2 (W/m) ² K)。

Further, the second predetermined value α 2 is set to a value sufficient for executing "1 startup" of the soot blower, because the heat exchange of the tube group 2 is not apparently good but the deposition of the adhering ash does not largely affect the operation of the plant if the net heat transfer coefficient Kc is equal to or more than α 2 and less than α 1. In other words, if the net heat transfer coefficient Kc is smaller than α 2, the value is set to a value that requires the adhering ash determination process described later. For convenience of description, the second predetermined value α 2 is also set to a value that can be reached as "continuous start" by at least 2 or more successive starts of the sootblower 3 without making the net heat transfer coefficient Kc equal to or greater than α 2 by only "1 start of the sootblower 3, i.e., by a single start of the sootblower immediately after the flag F is changed to F =2 in step S20 described later. For example, the second predetermined value α 2 is set to α 2=0.8 (W/m) ² K)。

Therefore, in the flowchart of fig. 2 described later, when the flag F is temporarily changed to F =2 in step S20 described later, as long as the second determination is not performed in the attached ash determination process described later, the soot blower 3 is continuously "continuously activated" at least 2 times by the control device 4 in principle.

For convenience of explanation, the values of α 1 and α 2 are set as described above as satisfying the relationship "0 < α 2 < 1 < α 1", but the values of α 1 and α 2 may be set as appropriate by design as long as the relationship "0 < α 2 < α 1" is satisfied. At this time, immediately after the flag F is changed to F =2 in step S20 described later, the sootblower 3 basically performs "continuous start", but the "continuous start" is not necessarily performed, and "1 start" may be performed.

The recovery threshold value R is a threshold value for determining the effect of removing the adhering ash (the degree of improving the heat transfer coefficient K) as compared with the recovery rate (Kc/Kd), and its initial value is set to a predetermined value (for example, R = 1) satisfying the relationship of "1 ≦ R". Here, the recovery rate is a variable indicating how much the heat transfer coefficient K recovers (increases) before and after the start of the sootblower 3, and is a value obtained by dividing the net heat transfer coefficient Kc by the dirty heat transfer coefficient Kd.

The first predetermined value α 1, the second predetermined value α 2, and the recovery threshold value R are constants that do not change from their respective initial values set as appropriate by design. The Tmin, tmax, and Δ t are constants that do not change from the respective initial values set as appropriate by design.

In step S1, the controller 4 determines whether or not a predetermined time has elapsed after the start of the operation of the plant (for example, an incinerator). This is because, if a predetermined time has not elapsed since the start of the operation of the plant, the conditions (for example, temperature, pressure, and the like) relating to the environment in the plant become unstable. The control device 4 repeatedly executes the processing of step S1 from the start of the operation of the plant to the elapse of the predetermined time, and executes the processing of step S2 when the predetermined time has elapsed.

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

The heat transfer coefficient K is represented by (formula 1) below.

[ number 1]

However, the variables are as follows.

Q: exchange heat [ W]{＝(Tg _out -Tg _in )×Cp _g ×W _g }

A: heat transfer area m ² ]

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

Tg _in : superheater inlet gas temperature [ K ]]

Tg _out : superheater outlet gas temperature [ K ]]

Ts _in : superheater inlet steam temperature [ K ]]

Ts _out : superheater outlet steam temperature [ K ]]

dT ₁ ：Tg _in -Ts _out

dT ₂ ：Tg _out -Ts _in

Cp _g : specific heat of gas [ J/kgK ]]

W _g : gas flow rate [ kg/s ]]

The temperature information and the flow rate information are measured as follows and transmitted to the control device 4. That is, the superheater inlet gas temperature Tgin is measured by the inlet gas temperature measuring device 15a, and the superheater outlet gas temperature Tgout is measured by the outlet gas temperature measuring device 15 b. The superheater inlet steam temperature Tsin is measured by an inlet steam temperature measuring device 24a, and the superheater outlet steam temperature Tsout is measured by an outlet steam temperature measuring device 24b. The gas flow rate Wg is measured by any one of the gas flow rate measurement devices 16a and 16b, or is obtained by calculation. The gas specific heat Cpg is the specific heat of the exhaust gas and is a constant corresponding to the composition of the exhaust gas. The heat transfer area a is the sum of the heat transfer areas of the superheaters in the plurality of tube groups 2.

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

Specifically, the control device 4 sets Kc = K when the flag F is a first value, where F =0, sets Kd = K when the flag F is a second value, where F =1, sets Kd = K when the flag F is a third value, where F =2, and stores the flag in the storage device.

Immediately after the start of the flowchart, since the flag F is an initial value, that is, F =0, the control device 4 stores the heat transfer coefficient K that has just been calculated as the net heat transfer coefficient Kc in the storage device (that is, kc = K).

Then, the control device 4 executes the process of step S4.

In step S4, the control device 4 determines whether or not the flag F is F =0. When the flag F is F =0, that is, immediately after "start" in the present flowchart, or immediately after activation of the soot blower 3 in step S13 described later, the control device 4 executes the process in step S5.

When the flag F is not F =0 (F =1, F = 2), the process flow is directed to the activation of the soot blower 3 in step S13 described later, and therefore the control device 4 executes the process in step S10.

In step S5, the controller 4 determines whether or not the value of the net heat transfer coefficient Kc stored in the storage device is equal to or greater than a first predetermined value α 1.

When the net heat transfer coefficient Kc is equal to or greater than the first predetermined value α 1, the heat exchange of the tube group 2 is remarkably good, and it is considered that there is no or very little deposition of adhering ash. Therefore, the control device 4 executes the process of step S6 in order to advance the process flow to the process of increasing the interval of activation of the sootblowers 3.

When the value of the net heat transfer coefficient Kc is smaller than α 1, the heat exchange of the tube group 2 is not necessarily good, and therefore the control device 4 executes the process of step S15.

In step S6, the control device 4 determines whether or not the time t1 is less than Tmax, which is the longest interval.

When the value of time t1 is smaller than Tmax (here, 3 hours), the control device 4 executes the processing of step S7 to increase the value of time t1 (extend time t 1).

When the value of time t1 is Tmax, the time t1 cannot be further increased, and therefore the control device 4 executes the process of step S8 without changing the value of time t1 (skipping step S7).

In step S7, the control device 4 changes the value of time t1 to a value of "t1+ Δ t". In other words, the control device 4 changes the value of t1 in the storage device to t1= t1+ Δ t and stores it in the storage device again. That is, the controller 4 sets the interval to be longer than the value set immediately before.

When the net heat transfer coefficient Kc is equal to or greater than the first predetermined value α 1, it is not preferable from the viewpoint of cost performance to excessively start the sootblowers 3 at the current interval, and therefore the sootblowers 3 are started "1 time" at longer intervals than before.

Then, the control device 4 executes the process of step S8.

In step S8, the control device 4 starts a timer (counter). The started timer counts down the count value from time t1 toward 0 according to the clock provided in the control device 4. For example, when the time t1 at the time of turning on is 2 hours, 2 hours (7200 seconds) are counted, and when the count value becomes 0, the timer is stopped. After the timer is stopped, the control device 4 executes the process of step S9.

In step S9, the control device 4 changes the value of the flag F stored in the storage device to F =1, and stores the value again in the storage device. Then, the control device 4 returns the processing flow to step S2, and executes the processing of step S2 again.

Since the processing of step S2, step S3, and step S4 has been described, the following description will be simplified from step S4 to step S10 which is the next step.

In short, the controller 4 calculates the heat transfer coefficient K after the interval of the timer (step S2), and in the next step S3, since the flag F is F =1, the heat transfer coefficient K that has just been calculated is stored in the storage device as the dirty heat transfer coefficient Kd (i.e., kd = K). Further, 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 process of step S10 as the next process.

In step S10, the control device 4 determines whether or not the bag filter as the dust removing device 11 is backwashing. The control device 4 controls the execution of the "backwashing" of the bag filter, and therefore can determine whether or not the bag filter is backwashing.

The control device 4 repeatedly executes the process of step S10 when it is determined that the bag filter is under backwashing, and executes the process of step S11 when it is determined that the bag filter is not under backwashing. Thus, the control device 4 can start the soot blower 3 after the backwashing is finished without starting the soot blower 3 during the backwashing of the bag filter.

When it is determined that the bag filter is under backwashing, the controller 4 repeats the process of step S10 for the following reason.

Backwashing of the bag filter is usually carried out with the flow of exhaust gas stopped. Therefore, when the pulse-type sootblower 3 is started during the backwashing of the bag filter, the internal pressure of the duct, which serves as a flue through which the exhaust gas flows, is significantly increased, and there is a possibility that a failure may occur in the plant. However, in the removal system 1, the control device 4 does not activate the soot blower 3 during the backwashing of the bag filter, and activates the soot blower 3 after the backwashing is finished, so that the occurrence of the above-described failure can be prevented.

Here, the sootblower 3 is described as a pulse type, and therefore, the step S10 is provided, but when the sootblower 3 is of a steam type, the step S10 can be omitted. Therefore, in this case, the next step of step S4 becomes step S11.

In step S11, the control device 4 determines whether or not the value of the flag F stored in the storage device is F =1. When the flag F is F =1, the control device 4 executes the process of step S12. When the flag F is not F =1, that is, when F =2, the control device 4 executes the process of step S13.

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 resets the timer count value to time t 1. Next, the control device 4 executes the process of step S13.

In step S13, the control device 4 activates only 1 time of the sootblower 3.

Then, the control device 4 executes the process of step S14.

In step S11, if the flag F is not F =1, that is, if 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 performs "continuous start-up" of the sootblower 3 in principle until the net heat transfer coefficient Kc becomes the second prescribed value α 2 or more, but starts the sootblower 3 continuously more quickly because 1 more process is omitted at this time.

In step S14, the control device 4 changes the value of the flag F stored in the storage device to F =0, and stores the value again in the storage device. This is because the heat transfer coefficient K calculated in the processing of the next step S2 is a value immediately after the soot blower 3 is started up, and therefore, in the processing of the next step S3, the value is stored in the storage device as the net heat transfer coefficient Kc.

Then, the control device 4 returns the processing flow to step S2 and executes the processing of step S2. The processing of step S2, step S3, step S4, and step S5 has already been described, and therefore, the description thereof is omitted.

Thus, a description will be given of a case where the control device 4 executes the process of step S15 as a step subsequent to step S5 (a case where the value of the net heat transfer coefficient Kc is smaller than α 1 in step S5).

In step S15, the controller 4 determines whether or not the value of the net heat transfer coefficient Kc stored in the storage device is smaller than a second predetermined value α 2.

When the value of the net heat transfer coefficient Kc is not less than the second predetermined value α 2, that is, α 2 is not less than Kc < α 1, the heat conduction of the tube group 2 is not apparently good, but it is considered that the deposition of the adhering ash does not have a great influence on the operation of the plant, and therefore, in order to enter the process flow of starting the sootblower 3 at spaced intervals, the control device 4 performs the process of the above-described step S8.

When the value of the net heat transfer coefficient Kc is smaller than the second predetermined value α 2, the control device 4 executes the process of step S16, that is, the adhering ash determination process, in order to determine whether or not the value of the net heat transfer coefficient Kc is lowered by adhering ash.

In step S16, the control device 4 executes the attached ash determination process. A specific example of the adhering dust determination process will be described later with reference to fig. 3.

The adhering ash determination process is a process of selectively determining either "a case where the amount of adhering ash accumulated in the plurality of tube groups 2 is large and heat exchange between the exhaust gas and the boiler is not sufficiently performed" (first determination), or "a case where the net heat transfer coefficient Kc is calculated to be smaller than the second predetermined value α 2 in accordance with the operating environment of the plant or various operating conditions although the amount of adhering ash is small and does not adversely affect the heat exchange" (second determination).

When the first determination is made in the attached ash determination process, the control device 4 executes the process of step S17 in order to continuously start the sootblower 3 according to the recovery rate (Kc/Kd).

When the second determination is made in the attached ash determination process, the control device 4 executes the process of step S21 in order to confirm the state of the plant or determine whether to stop the plant.

In step S17, the control device 4 calculates a recovery rate (Kc/Kd) from the net heat transfer coefficient Kc and the dirty heat transfer coefficient Kd stored in the storage device, and determines whether or not the recovery rate is equal to or greater than the recovery threshold value R stored in the storage device.

When the recovery rate is less than the recovery threshold R, the possibility of increasing the heat transfer coefficient K is low even if the sootblower 3 is activated more than once, and therefore the control device 4 executes the process of step S21.

When the recovery rate is equal to or higher than the recovery threshold R, since the effect of removing the adhering ash can be expected by the activation of the sootblower 3, the control device 4 advances the flow of the process to the process of "continuous activation" of the sootblower 3 in order to remove the adhering ash early, and thus executes the process of step S18.

In step S18, the control device 4 determines whether or not the time t1 is greater than Tmin, which is the shortest interval.

When the time t1 is longer than Tmin, the control device 4 executes the process of step S19 in order to shorten the interval when the sootblower 3 is activated "1 time". This is because, since the adhering ash cannot be effectively removed at the initial interval of "1 startup" according to the ash properties, the control device 4 performs "1 startup" of the sootblower 3 at a shorter interval than before (in other words, at an earlier time point than before) when the sootblower 3 is "1 startup" after the "continuous startup" is finished, in view of the first determination made in the adhering ash determination process.

In step S19, the control device 4 changes the value of time t1 to a value of "t1 to Δ t". In other words, the control device 4 changes the value of t1 in the storage device to t1= t1- Δ t, and stores the value again in the storage device. Then, the control device 4 executes the process of step S20.

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

In step S20, the control device 4 changes the value of the flag F stored in the storage device to F =2, and stores the value again in the storage device. Then, the control device 4 returns the processing flow to step S2 and executes the processing of step S2.

Since the processing of step S2, step S3, and step S4 has been described, the following description will be simplified from step S4 to step S10 which is the next step.

In short, the control device 4 calculates the heat transfer coefficient K when the recovery rate is equal to or higher than the recovery threshold R (step S2), and since the flag F is F =2 in the next step S3, the calculated heat transfer coefficient K is stored as the dirty heat transfer coefficient Kd in the storage device (i.e., kd = K). Then, 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. In step S10, the control device 4 executes the process of step S11 when determining that the bag filter is not backwashing. In step S11, the current flag F is F =2, and therefore the control device 4 skips step S12 to execute the process of step S13.

That is, when the flag F is F =2, the control device 4 executes the process of step S13 in order to start the sootblower 3 immediately without resetting the timer.

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

Here, in the next processing flow, when the control device 4 performs the processing of step S2, step S3, step S4, step S5, step S15, step S16, step S17, step S18, step S19 (skipped as the case may be), and step S20 again in this order, the control device 4 performs the processing of step S2, step S3, step S4, step S10, step S11, and step S13 thereafter.

Therefore, at this time, the process flow of step S13 is executed without the timer of step S8 being turned on, and therefore, the sootblower 3 is "continuously activated".

Then, as an explanation of the flowchart of fig. 2, step S21 executed by the control device 4 when the second determination is made in the attached ash determination processing of step S16 or when the recovery rate is smaller than the recovery threshold R in step S17 will be explained finally.

In step S21, the control device 4 determines whether or not the confirmation of the state 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 worker. The control device 4 controls the operations of various devices disposed in the plant, and thus can determine whether or not the operation has been started.

If it is determined that the operation has not been started, the control device 4 executes the process of step S8. That is, in this case, it is clear that the soot blower 3 cannot be efficiently removed even when the soot blower 3 is activated in step S17, and therefore the "continuous activation" of the soot blower 3 is not performed from the viewpoint of cost performance, but a process flow of executing the "1-time activation" of the soot blower 3 is performed in order to reduce more soot accumulated in the tube group 2.

On the other hand, when determining that the operation has been started, the control device 4 does not execute any of the processes of steps S1 to S20 thereafter, and executes a process necessary for the operation. Thereafter, the operation of the entire removal system 1 including the control device 4 is completed, that is, the operation of the plant is stopped.

According to the flowchart, when the sootblower 3 is activated "1 time" at intervals by a timer, if the net heat transfer coefficient Kc is equal to or greater than the first predetermined value α 1, the intervals are set longer than the conventional intervals, and if the net heat transfer coefficient Kc is smaller than the first predetermined value α 1, the intervals are not changed from the conventional intervals or are shortened from the conventional intervals.

Further, according to the flowchart, even in the case of the "continuous activation" of the soot blower 3 without an interval by the timer, the heat transfer coefficient K is calculated every time the soot blower 3 is activated. Then, the control device 4 performs the "continuous start" of the sootblower 3 until the net heat transfer coefficient Kc becomes equal to or higher than the second predetermined value α 2, as long as the value of the recovery rate R increases based on the calculated heat transfer coefficient K (net heat transfer coefficient Kc, dirty heat transfer coefficient Kd).

That is, the number of times of activation of the sootblower 3 in the "continuous activation" is variable, and when the value of the recovery rate R is large (when the rising speed is fast), the number of times is automatically decreased, and when the value of the rising speed is small (when the rising speed is slow), the number of times is automatically increased.

The rising rate can be obtained by the control device 4 sequentially 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 storage device, and calculating using the value of the currently calculated recovery rate and the value of the latest recovery rate and the value of the difference (time interval or time difference) between the two pieces of time information. Specifically, the control device 4 calculates the rising speed by the equation [ { (based on the currently calculated recovery rate) - (the latest recovery rate) }/(the time difference) ]. If the refilling time of the gas impacting the pulse-type sootblower is less than 3 minutes (3 min), for example, the rising speed is fast, for example, when the rising speed at which the number of "continuous starts" ends 2 times (less than 6 min) or 3 times (less than 9 min) is 0.04 (/ min) or more, and when the rising speed is slow, for example, when the number of times requires 4 times or more (12 min or more), the rising speed is less than 0.04 (/ min).

Next, the flow of the attached ash determination process, i.e., step S16, will be described with reference to fig. 3 (a) to 3 (d).

Here, based on the experience of the inventors, the following 4 modes will be described based on the use of only the above 4 conditions. However, as described above, other conditions may be added according to design in addition to the above 4 conditions.

In the following description, the control device 4 executes the process of step S161 as the next process of step S15 in fig. 2.

Then, the description will be made in order from fig. 3 (a).

Fig. 3 (a) shows a process flow (pattern 1) in which the attached ash determination process is executed based on all of the above-described 4 conditions. In step S161, the control device 4 determines whether or not the main steam flow Qs measured by the main steam flow rate measuring device 25 is equal to or greater than a lower main steam flow qsmin (first threshold) that is an allowable lower limit for the plant operation. In the case where the main steam amount Qs is less than qsmin, the control device 4 regards that "second determination" is obtained, and then executes the process of step S21 of fig. 2. When the main steam flow Qs is qsmin or more, the control device 4 executes the next step, which is the process of step S162 here.

In step S162, the control device 4 calculates a furnace gas differential pressure Δ Pg, which is a pressure difference between exhaust gases at the inlet and the outlet of the plurality of tube groups 2, using information of the pressures measured by the pressure measuring devices 14a and 14b, and determines whether or not the furnace gas differential pressure Δ Pg is equal to or greater than a furnace gas differential pressure pgmin (second threshold value) which is a lower limit allowable in the operation of the plant. When the furnace gas pressure difference Δ Pg is smaller than pgmin, the control device 4 regards that "second determination" is obtained, and then executes the process of step S21 in fig. 2. When the furnace gas differential pressure Δ Pg is equal to or greater than pgmin, the control device 4 executes the next step, which is the process of step S163.

In step S163, the controller 4 determines whether or not the rotation speed Qr of the induced draft fan 13 is equal to or higher than a lower limit rotation speed qrmin (third threshold) allowable during the operation of the plant. When the rotation speed Qr is less than qrmin, the control device 4 determines that the "second determination" is obtained, and then executes the process of step S21 in fig. 2. When the rotation speed Qr is not less than qrmin, the control device 4 executes the next step, which is the process of step S164. Further, the controller 4 controls the rotation speed Qr of the induced draft fan 13, and thus grasps the rotation speed Qr.

In step S164, the controller 4 determines whether or not the total combustion air amount Qc measured by the combustion air amount measuring device 28 is equal to or greater than a lower total combustion air amount qcmin (fourth threshold) that is an allowable lower limit for the operation of the plant. When the total combustion air amount Qc is less than qcmin, the control device 4 determines that the "second determination" is obtained, and then executes the process of step S21 in fig. 2. When the total combustion air amount Qc is equal to or greater than qcmin, the control device 4 executes the process of the next step. Here, as a result of the "first determination", the processing of step S17 in fig. 2 is executed next.

The order of the processing flow of the four processes of steps S161 to S164 is not limited to this, and may be replaced as appropriate.

The processing flow (pattern 2) of fig. 3 (b) executes 3 determination elements of steps S161 to S163 among the four determination elements included in the processing flow of fig. 3 (a). Fig. 3 (b) is an example of a flowchart in which the adhering dust determination process is executed based on any 3 of the 4 conditions described above, and any 3 of the 4 determination elements of steps S161 to S164 may be used, and the order of the process may be set to precede any one.

The processing flow (pattern 3) of fig. 3 (c) executes 2 determination elements, which are steps S161 and S162, among the four determination elements included in the processing flow of fig. 3 (a). Fig. 3 (c) shows an example of a process flow in which the attached ash determination process is executed based on any 2 of the 4 conditions, and any 2 of the 4 determination elements of steps S161 to S164 may be used, and the order of determination may be preceded by any one.

The process flow (pattern 4) of fig. 3 (d) executes only the judgment element of step S161 out of the four judgment elements included in the process flow of fig. 3 (a). Fig. 3 (d) is an example of a flowchart in which the attached ash determination process is executed based on any 1 of the above-described 4 conditions, and any 1 of the four determination elements of steps S161 to S164 may be used.

In addition, even in the case of any of the above-described modes 1 to 4, it is preferable to include step S161 of using information on the main steam flow Qs that is not used for the calculation of the heat transfer coefficient K.

[4. Effect ]

As described above, in the removal system 1, the control device 4 selects "1 startup" and "continuous startup" for using the sootblower 3 based on the calculated heat transfer coefficient K, and thus, can remove the adhering ash early and appropriately while ensuring economy.

The deposited ash determination process is executed under conditions based on the experience of the inventors, that is, at least 1 of the main steam flow Qs, the furnace gas pressure difference Δ Pg, the rotation speed Qr of the induced draft fan 13, and the total combustion air amount Qc, and therefore the deposition state of deposited ash on the tube group 2 can be appropriately determined.

In the removal system 1, when the first determination is obtained by the adhering ash determination process, the recovery rate is calculated from the dirty heat transfer coefficient Kd and the net heat transfer coefficient Kc, and when the recovery rate is equal to or higher than the recovery threshold R, the soot blower 3 is "continuously activated", whereby the adhering ash can be removed early.

In the removal system 1, the control device 4 automatically decreases the number of times of activation of the sootblower 3 in the "continuous activation" when the rate of increase in the recovery rate is high, and automatically increases the number of times when the rate of increase in the recovery rate is low. Therefore, the control device 4 appropriately controls the number of times of activation of the sootblowers 3 in the "continuous activation" in accordance with the state of the adhering ash, and therefore, the adhering ash can be effectively removed and the economical efficiency can be ensured as compared with the case where the number of times is a fixed value.

According to the abatement system 1, when the net heat transfer coefficient Kc is equal to or greater than the first predetermined value α 1, the control device 4 determines that the heat conduction of the tube group 2 is extremely good (no deposition of adhering ash or very little deposition), and sets the interval of "1 start" longer, so that excessive start of the sootblower 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 greater than the recovery threshold R, the interval of "1 startup" continued after the end of the "continuous startup" is set to be shorter again, so even if the soot blower 3 has a property of ash having strong adhesion to the extent that the "continuous startup" is required, "1 startup" is performed at short intervals, and therefore, the adhering ash can be removed before the thick ash is deposited on the tube group 2. Therefore, it is not necessary to frequently perform the "continuous start", and as a result, the economy can be further ensured.

According to the removal system 1, the control device 4 does not start the soot blower 3 during the execution of the backwashing of the bag filter as the dust removing device 11, and starts the soot blower 3 after the backwashing is ended, so that it is possible to avoid a malfunction of the plant.

The sootblower 3 may be of any one of a steam type and an impulse type. However, since the steam sootblower uses steam generated by heat exchange between exhaust gas and a boiler, the amount of steam supplied to the turbine by the boiler for power generation is reduced, and as a result, the amount of power generation in the plant can be reduced. Therefore, when importance is attached to the power generation amount of the plant, it is preferable to arrange a pulse-type sootblower that does not use steam.

The sootblower 3 is generally installed on a wall surface such as a duct forming a path of the exhaust gas. Therefore, when the sootblower 3 of fig. 1 is of a steam type, the direction in which the injection nozzle of the sootblower 3 extends and contracts 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.

On the other hand, when the sootblower 3 is of a shock pulse type, the emission direction of the shock pulse is a direction on a plane including the X axis and orthogonal to the Y axis.

Therefore, in the case of the removal system 1 including the impact pulse type sootblower 3, when the impact pulse is emitted toward the wall surface between the 3-channel and the 2-channel in fig. 1, the wall surface is vibrated, and not only the ash adhering to the tube group 2 but also the ash adhering to the wall surface can be removed.

[5. Modification ]

A modification of the removal system 1 having a plurality of soot blowers 3 will be described below. The first modification is an example in which soot blowers denoted by the symbols 3' and 3 ″ shown by dotted lines are used in fig. 1. The second modification is an example in which, as shown in fig. 4 (a) to 4 (c), the number of tube groups 2 arranged in the 3-channel in fig. 1 is larger than that in fig. 1. The third modification is an example in which the boiler structure of the plant is of a tail-end type, as shown in fig. 5. The fourth modification is an example of a double-drum boiler of a boiler structure of a plant as shown in fig. 6.

In the following description, the same elements as those of the above-described removal system 1 of fig. 1 are denoted by the same reference numerals, and redundant description thereof is omitted. In fig. 5 and 6, the control device 4 shown in fig. 1 and signal lines (thin solid lines) input to and output from the control device 4 are not shown.

[5-1 ] first modification

In fig. 1, the removal system 1 in which 1 soot blower 3 is arranged is explained as an embodiment, but a removal system 1' in which a plurality of soot blowers 3 are arranged may be adopted depending on the number of tube groups 2 or the design of a plant.

The sootblowers 3 are generally effective in removing adhering ash of the tube banks 2 arranged in proximity thereto. Therefore, in the structure of the removal system 1, the adhering ash of the 2 tube groups 2 (the tube groups 2 each composed of the superheater tubes 22a and 22 b) adjacent to the sootblower 3a is effectively removed. However, since the tube group 2 including the most downstream superheater tubes 22c is disposed at a position separated from the sootblower 3a, there is a possibility that the removal of the adhering ash from the tube group 2 (22 c) becomes insufficient.

Therefore, as shown by dotted lines in fig. 1, in the removal system 1', the soot blowers 3' are arranged at positions downstream of the tube group 2 (22 c) in addition to the soot blowers 3a [ beside the tube group 2 (22 c) and directly above in the Y-axis direction ], whereby the adhering ash of the tube group 2 (22 c) can be effectively removed.

In this case, when the soot blowers arranged separately from the soot blowers 3a are impulse type soot blowers, the soot blowers may be arranged at positions indicated by reference numeral 3 ″ instead of the soot blowers indicated by reference numeral 3 'or together with the soot blowers indicated by reference numeral 3'. The sootblowers 3 ″ shown by broken lines in fig. 1 represent sootblowers provided in the vicinity of wall surfaces of the ceiling of the 3-duct, and when they are arranged to emit a shock pulse downward in the Y-axis direction, not only the soot adhering to the tube group 2 (22 c) but also the soot adhering to the tube group 2 (22 b) arranged upstream thereof can be removed more effectively.

Even when a plurality of soot blowers 3, 3', 3 ″ are arranged in the removal system 1', the control device 4 executes the processing of fig. 2 for each soot blower, similarly to the above configuration in which only 1 soot blower 3 is arranged.

However, in the processing of step S13, the control device 4 sequentially starts each of the sootblowers 3, 3', 3 ″ with a shift in the timing of the start of the sootblowers. That is, the control device 4 does not activate the plurality of sootblowers 3, 3', 3 "simultaneously.

When a plurality of steam sootblowers are arranged and these are simultaneously activated, the amount of steam supplied from the boiler to the turbine is greatly reduced, and therefore, the amount of power generation is greatly reduced, and stable power transmission is difficult. When a plurality of impact pulse type sootblowers are arranged and these are simultaneously activated, the pressure in the furnace or the pressure inside the conduit significantly increases, and a failure may occur in the plant.

Therefore, in the removal system 1', the activation of the sootblowers 3 is sequentially activated with a time shift.

The sequence of sequentially activating the plurality of sootblowers 3 by the control device 4 is the same as the second modification shown in fig. 4, which will be described later, and therefore, the description thereof will be omitted.

[5-2 ] second modification

The removal systems 1A to 1C according to the second modification shown in fig. 4 (a) to 4 (C) differ from the removal system 1 in the number of tube groups 2, the number of sootblowers 3, and the arrangement of the outlet steam temperature measuring devices 24b. In the second modification, the plurality of tube groups 2 and the plurality of sootblowers 3 are arranged in the Y-axis direction, i.e., the vertical direction. Fig. 4 (a) shows a removal system 1A in which 4 tube groups 2 each including a superheater tube 22 are arranged in 3 passes in fig. 1. Fig. 4 (B) shows a removal system 1B in which 5 tube groups 2 each including a superheater tube 22 are arranged in 3 passes in fig. 1. Fig. 4 (C) shows a removal system 1C in which 6 tube groups 2 each including a superheater tube 22 are arranged in 3 passes in fig. 1.

In the second modification as well, the control device 4 executes the processing of fig. 2 for each of the plurality of soot blowers, as in the first modification.

In the removal system 1A shown in fig. 4a, in addition to the configuration of fig. 1, a tube group 2 including a superheater tube 22d is disposed adjacent to and downstream (Y-axis direction and above) the tube group 2 including the superheater tube 22 c. Further, the sootblower 3b is disposed between the tube group 2 made of the superheater tubes 22c and the tube group 2 made of the superheater tubes 22 d.

In the removal system 1C shown in fig. 4 (C), in addition to the configuration of fig. 4 (a), the tube group 2 composed of the superheater tubes 22e is disposed adjacent to and downstream of the tube group 2 composed of the superheater tubes 22 d; and the tube group 2 composed of the superheater tubes 22f are disposed adjacent to each other further downstream (Y-axis direction and above) of the tube group 2 composed of the superheater tubes 22 e. Further, a sootblower 3d is disposed between the tube group 2 composed of the superheater tubes 22e and the tube group 2 composed of the superheater tubes 22 f.

As shown in fig. 4 (a) and 4 (c), when the number of the tube groups 2 (here, the tube groups 2 including the superheater tubes 22) for removing ash by the sootblowers 3 is even and large, the sootblowers 3 are not arranged in the entire space between the target tube groups 2. In view of cost performance for removal of the adhering ash, the group 2 of the target is constituted by 2 groups 2 in order from the upstream group 2, and 1 soot blower 3 is arranged in 1 unit. Therefore, the number of the plurality of soot blowers 3 arranged is half of the number of the target tube groups 2.

On the other hand, in the removal system 1B shown in fig. 4 (B), unlike in fig. 4 (c), only the tube bank 2 including the superheater tube 22e is added to the configuration of fig. 4 (a), and the tube bank 2 is disposed adjacent to the downstream (Y-axis direction and above) of the tube bank 2 including the superheater tube 22 d. Therefore, in fig. 4 (b), the number of the tube groups 2 (tube groups 2 including the superheater tubes 22) for removing ash by the sootblowers 3 is odd and plural. At this time, the tube group 2 in which the above-described "cell" cannot be manufactured is produced. In fig. 4 (b), the above-described "unit" cannot be manufactured for the tube group 2 composed of the superheater tubes 22 e.

However, if the ash adhering to the tube group 2 including the superheater tubes 22e cannot be ignored, the sootblower 3c is disposed downstream of the tube group 2.

In the second modification described above, the tube group 2 to be removed of the adhering ash is arranged in the vertical direction (Y-axis direction). Further, an outlet steam temperature measuring device 24b is disposed inside the superheater tubes 22 constituting the tube group 2 located at the most downstream side.

When a certain ash blower 3 is activated to remove adhering ash, 2 cases can be considered for the movement of the removed adhering ash: [1] a situation where the weight falls in the vertical direction and downward; [2] the flow of the exhaust gas is strong, and the exhaust gas moves downstream along with the flow of the exhaust gas.

Therefore, in the case of [1], when the sootblowers 3 are "activated 1 time" or "continuously activated", the control device 4 is sequentially activated with a timing shift from the sootblower 3 disposed furthest downstream to the sootblower 3 disposed upstream. That is, in the case of fig. 4 (a), after the soot blower 3b is activated, the soot blower 3a is activated. In the case of fig. 4 (b), the sootblower 3b is activated after the sootblower 3c is activated, and the sootblower 3a is activated after the sootblower 3b is activated. Likewise, in the case of fig. 4 (c), the sootblower 3b is activated after the sootblower 3d is activated, and the sootblower 3a is activated after the sootblower 3b is activated.

By sequentially activating the soot blowers 3 in this order, even when the adhering ash removed by the soot blower 3 in a certain tube group 2 falls downward by gravity and adheres to another tube group disposed upstream, the adhering ash including the adhering ash adhered again can be reliably removed.

On the other hand, in the case of [2], when the sootblowers 3 are "activated 1 time" or "continuously activated", the control device 4 is sequentially activated with a timing shift from the sootblower 3 disposed most upstream to the sootblower 3 disposed downstream. That is, in the case of fig. 4 (a), after the soot blower 3a is activated, the soot blower 3b is activated. In the case of fig. 4 (b), the sootblower 3b is activated after the sootblower 3a is activated, and the sootblower 3c is activated after the sootblower 3b is activated. Likewise, in the case of fig. 4 (c), the sootblower 3b is activated after the sootblower 3a is activated, and the sootblower 3d is activated after the sootblower 3b is activated.

By sequentially activating the soot blowers 3 in this order, even when the adhering ash removed by the soot blower 3 in a certain tube group 2 moves downstream along with the flow of the exhaust gas and is reattached to another tube group arranged downstream, adhering ash including reattached adhering ash can be reliably removed.

In a second modification, the structures corresponding to the first tube group, the second tube group, the third tube group, the fourth tube group, the first sootblower, and the second sootblower in claim 6 of the present application are as follows.

That is, in fig. 4 (a) and 4 (b), the tube group 2 including the superheater tube 22a corresponds to the first tube group, the tube group 2 including the superheater tube 22b corresponds to the second tube group, the tube group 2 including the superheater tube 22c corresponds to the third tube group, and the tube group 2 including the superheater tube 22d corresponds to the fourth tube group. The sootblower 3a corresponds to a first sootblower, and the sootblower 3b corresponds to a second sootblower. In fig. 4 (c), except for the case similar to fig. 4 (a) and 4 (b), there are also cases where 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 blowers 3b correspond to the first soot blowers, and the soot blowers 3d correspond to the second soot blowers.

[5-3 ] third modification

Next, a third modification will be described with reference to fig. 5.

In the removal system 1D of the third modification, a flow path of the exhaust gas extending in the horizontal direction (X-axis direction) is added between the 3-pass of fig. 1 and the economizer 9, and a plurality of tube groups 2 and a plurality of soot blowers 3 are further arranged in the flow path in the horizontal direction. The boiler structure of the plant of the third modification is called a tail-end type. Further, an outlet steam temperature measuring device 24b is disposed inside the superheater tubes 22f constituting the tube group 2 positioned at the most downstream side.

In the configuration of fig. 4 (c), which is one of the second modifications, a third modification is a configuration in which the tube groups 2 from the tube group 2 composed of the superheater tubes 22c to the tube group 2 composed of the superheater tubes 22f, including the sootblowers 3b, 3d, are arranged in the horizontal direction without changing the order from the upstream to the downstream. Here, it is considered that the tube group 2 including the superheater tube 22b and the tube group 2 including the superheater tube 22c are disposed adjacent to each other, as in the second modification.

Therefore, in the third modification, there are: a plurality of tube groups 2 arranged in this order from upstream (Y-axis direction and below) to downstream (Y-axis direction and above) in the vertical direction; and a plurality of tube groups 2 arranged in order in a horizontal direction toward one direction (X-axis direction).

In the third modification, the control device 4 executes the process of fig. 2 for each of the plurality of soot blowers, as in the first modification and the second modification.

Here, focusing on the plurality of tube groups 2 arranged in order in the horizontal direction toward the one direction (X-axis direction), that is, the tube group 2 composed of the superheater tubes 22c, the tube group 2 composed of the superheater tubes 22d, the tube group 2 composed of the superheater tubes 22e, and the tube group 2 composed of the superheater tubes 22f in fig. 5, when the soot blower 3b or 3d is activated to remove the attached ash, the removed attached ash is highly likely to move downstream along with the flow of the exhaust gas.

Therefore, when the control device 4 performs "1-time activation" or "continuous activation" of the sootblowers 3, the sootblowers 3 arranged at the most upstream are sequentially activated with a timing shifted from the sootblower 3 arranged at the most upstream to the sootblower 3 arranged at the downstream. That is, the control device 4 starts the sootblower 3d after starting the sootblower 3b.

By sequentially activating the soot blowers 3 in this order, even when the adhering ash removed by the soot blower 3 in a certain tube group 2 moves downstream along with the flow of the exhaust gas and is reattached to another tube group arranged downstream, adhering ash including reattached adhering ash can be reliably removed.

Further, in fig. 5, when the plurality of tube groups 2 arranged in the horizontal direction and the plurality of tube groups 2 arranged in the vertical direction are considered in combination, there may be a case of [2] described in the second modification, and therefore, when the sootblowers 3 are "activated 1 time" or "continuously activated", the control device 4 sequentially activates the sootblowers 3 arranged downstream with a timing shifted from the sootblower 3 arranged most upstream to the sootblower 3 arranged most downstream. That is, the control device 4 activates the sootblower 3b after activating the sootblower 3a, and activates the sootblower 3d after activating the sootblower 3b.

By sequentially activating the soot blowers 3 in this order, even when the adhering ash removed by the soot blower 3 in a certain tube group 2 moves downstream in accordance with the flow of the exhaust gas and reattaches to another tube group arranged downstream, the adhering ash including the reattached adhering ash can be reliably removed.

In a third modification, the structures corresponding to the first tube group, the second tube group, the third tube group, the fourth tube group, the first sootblower, and the second sootblower in claim 6 of the present application are as follows.

That is, when focusing on the plurality of 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 blowers 3b correspond to the first soot blowers, and the soot blowers 3d correspond to the second soot blowers.

When the plurality of tubes 2 arranged in the horizontal direction and the plurality of tubes 2 arranged in the vertical direction are considered in combination, in fig. 5, the tube 2 including the superheater tube 22a corresponds to a first tube, the tube 2 including the superheater tube 22b corresponds to a second tube, the tube 2 including the superheater tube 22c corresponds to a third tube, the tube 2 including the superheater tube 22d corresponds to a fourth tube, the soot blower 3a corresponds to a first soot blower, and the soot blower 3b corresponds to a second soot blower.

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

[5-4 ] fourth modification

Next, a fourth modification will be described with reference to fig. 6.

In a third modification, the abatement system 1E of the fourth modification is configured as follows: a flow path of the exhaust gas extending in the horizontal direction between the 3-way and the economizer 9 is removed, and a double-drum boiler including a steam drum 19 and a water drum 20 is provided between the 3-way and the economizer 9. Since the flow path is removed, the tube groups 2 (22 c to 22 f) and the sootblowers 3 (3 b and 3 d) arranged in the flow path in the third modification are also removed.

In the fourth modification, the suspending pipe 21 and the sootblower 3a of the third modification are removed, the superheater pipes 22a and 22b are suspended and arranged on the ceiling of the 3-pass, and the sootblower 3 (3 e) is arranged adjacent to the superheater pipe 22a upstream of the superheater pipe 22 a.

In fig. 1, the tube group 2 of the economizer 9 is not regarded as a tube group to be subjected to the adhering ash removal, but in the fourth modification, the plurality of tube groups 2 of the economizer 9 are also subjected to the adhering ash removal. Therefore, in the interior of the economizer 9, the sootblowers 3f are provided between the plurality of tube groups 2 arranged in the vertical direction (Y-axis direction), that is, the tube group 2 constituted by the water tubes 23a and the tube group 2 constituted by the water tubes 23b arranged adjacent to and downstream of the tube group 2.

In this case, as described above, the "plurality of tube groups 2" to be removed of the adhering ash are arranged between the 2 pressure measuring devices 14a and 14b and also between the 2 gas temperature measuring devices 15a and 15 b.

In fig. 6, the tube group 2 to be subjected to the removal of the adhering ash includes different types of tube groups 2, that is, a tube group 2 including a superheater tube 22 and a tube group 2 including a water tube 23. Further, between the tube group 2 composed of the superheater tube 22 (22 b) and the tube group 2 composed of the water tube 23 (23 a), no other tube group 2 that provides resistance to the flow of the exhaust gas is disposed.

Further, unlike fig. 1, the temperature measuring device 15b that measures the temperature of the exhaust gas at the "outlet" of the plurality of tube groups 2 is disposed downstream of the tube group 2 including the water tube 23b disposed most downstream of the plurality of tube groups 2 to be subjected to the removal of the adhering ash. In fig. 6, the temperature measuring device 15b is arranged at substantially the same position as the pressure measuring device 14b of fig. 1. Further, an outlet steam temperature measuring device 24b is disposed inside the superheater tube 22b positioned at the most downstream side of the superheater tubes 22.

In the fourth modification, the control device 4 executes the process of fig. 2 for each of the plurality of soot blowers, as in the first to third modifications.

In the fourth modification, when the sootblowers 3 are activated "1 time" or "continuously", the control device 4 is activated sequentially with time shifts from the sootblower 3 disposed at the uppermost stream to the sootblower 3 disposed at the downstream. That is, the control device 4 starts the sootblower 3f after starting the sootblower 3 e.

By sequentially activating the respective sootblowers 3 in this order, the adhering ash removed by the sootblower 3 in the tube group 2 disposed upstream moves downstream in accordance with the flow of the exhaust gas, and even when the adhering ash reattaches to another tube group disposed downstream, the adhering ash including the reattached adhering ash can be reliably removed.

In a fourth modification, the structures corresponding to the first tube group, the second tube group, the third tube group, the fourth tube group, the first sootblower, and the second sootblower in claim 7 of the present application are as follows.

That is, the tube group 2 made of the superheater tubes 22a corresponds to the first tube group, the tube group 2 made of the superheater tubes 22b corresponds to the second tube group, the tube group 2 made of the water tubes 23a corresponds to the third tube group, the tube group 2 made of the water tubes 23b corresponds to the fourth tube group, the sootblower 3e corresponds to the first sootblower, and the sootblower 3f corresponds to the second sootblower.

According to the removal system 1E of the fourth modification example, in addition to the effects obtained by the above-described embodiment, adhering ash including reattached adhering ash can be reliably removed.

While the embodiments and modifications of the present invention have been described above, the technical scope of the present invention is not limited to the embodiments and modifications, and various modifications can be made without departing from the scope of the present invention.

Description of the symbols

1. 1', 1A-1E-boiler tube bank adhering ash removal system (removal system), 2-tube bank, 3', 3 a-3 f-soot blower, 4-control device, 5-hopper, 6-feeder, 7-coal feeder, 8-ash groove, 9-economizer (one of tube bank), 10-temperature reduction tower, 11-dust removal device (bag filter), 12-chimney, 13-draught fan, 14a, 14 b-pressure measurement device, 15a, 15 b-gas temperature measurement device, 16a, 16 b-gas flow measurement device, 17-superheat cooler, 18-spray water amount measurement device, 19-steam drum, 20-water drum, 21-suspension tube (filter screen tube), 22a to 22f superheater tubes (superheaters), 23a and 23b water tubes, 24a and 24b steam temperature measuring devices, 25 main steam amount measuring devices, 26 primary air supply devices, 27 secondary air supply devices, 28 combustion air amount measuring devices, K-heat transfer coefficients, kc-net heat transfer coefficients, kd-dirty heat transfer coefficients, kc/Kd-recovery rates, delta Pg-pressure differences, pgmin-second threshold values, qc-total combustion air amount, qcmin-fourth threshold values, qr-rotational speed of a draught fan, qrmin-third threshold values, qs-main steam amount, qsmin-first threshold values, R-recovery threshold values, alpha 1-first specified values, and alpha 2-second specified values.

Claims (8)

1. A boiler tube bank adhering ash removing system that removes adhering ash of a plurality of tube banks of a boiler that recovers heat from exhaust gas generated in a furnace, comprising:

a soot blower disposed between the plurality of tube groups;

an induced draft fan disposed downstream of the plurality of tube banks and guiding the exhaust gas; and

a control device for controlling the start of the soot blower,

the control device performs the following processing:

calculating the heat transfer coefficient of the boiler;

when the calculated heat transfer coefficient is equal to or greater than a predetermined value, starting the sootblower only 1 time at a predetermined interval, and thereafter starting the sootblower 1 time at the predetermined interval or at an interval different from the predetermined interval;

executing an adhering ash determination process of performing an alternative determination on either one of the first determination and the second determination when the calculated heat transfer coefficient is smaller than the predetermined value;

executing continuous activation of the soot blower a plurality of times without spacing the interval when the first determination is obtained in the soot attachment determination processing;

executing the 1-time activation when the second determination is obtained in the attached ash determination processing,

the attached ash determination process is executed including at least 1 of the following conditions: a first condition that a main steam amount of the plurality of tube groups is a first threshold value or more; a second condition that a pressure difference of the exhaust gas at an inlet and an outlet of the plurality of tube groups is a second threshold value or more; in the third condition, the rotating speed of the induced draft fan is above a third threshold value; and a fourth condition that the total amount of combustion air supplied into the furnace is equal to or greater than a fourth threshold value,

in a case where the attachment gray determination process is executed only according to any 1 condition of 4 the conditions, the first determination is made when the 1 condition is satisfied, the second determination is made when the 1 condition is not satisfied,

in a case where the attachment gray determination process is executed while including any 2, 3, or 4 of the 4 conditions, the first determination is obtained when all the conditions including the 2, 3, or 4 conditions are satisfied, and the second determination is obtained when any of the conditions including the 2, 3, or 4 conditions is not satisfied.

2. The boiler tube bank adhering ash removal system of claim 1,

the control device performs the following processing:

calculating a recovery rate from a dirty heat transfer coefficient indicating the heat transfer coefficient calculated before the soot blower is activated and a net heat transfer coefficient indicating the heat transfer coefficient calculated after the soot blower is activated, when the first determination is obtained in the attached ash determination processing,

performing the continuous boot when the recovery rate is above a recovery threshold,

when the recovery rate is less than the recovery threshold, performing the 1-time boot.

3. Boiler tube bank adhering ash removal system according to claim 2,

the control device may reset the predetermined interval to be longer than a value set immediately before when the net heat transfer coefficient is equal to or greater than the predetermined value, and reset the predetermined interval to be shorter than a value set immediately before when the recovery rate is equal to or greater than a recovery threshold.

4. The boiler tube bank adhering ash removal system of claim 3,

the control device reduces the number of times of activation in the continuous activation when the rate of increase of the recovery rate is large, and increases the number of times of continuous activation when the rate of increase of the recovery rate is small.

5. The boiler tube bank attached ash removal system according to claim 4, further comprising:

a bag filter disposed downstream of the plurality of tube groups to remove soot of the exhaust gas,

and the control device does not start the soot blower during the backwashing of the bag filter, and starts the soot blower after the backwashing is finished.

6. Boiler tube bank adhering ash removal system according to claim 5,

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 sootblower arranged between the third tube group and the fourth tube group,

when the control device starts the first soot blower and the second soot blower for the 1-time startup or the continuous startup,

when the first tube group to the fourth tube group are arranged in this order from the lower side toward the upper side in the vertical direction, the first sootblower is activated after the second sootblower is activated, or the second sootblower is activated after the first sootblower is activated,

the second soot blower is activated after the first soot blower is activated in a case where the first to fourth tube groups are arranged in order in a horizontal direction toward a first direction,

the first and second pipe groups are arranged in this order from the lower side to the upper side in the vertical direction, and the third and fourth pipe groups are arranged in this order in the horizontal direction, and the second soot blower is activated after the first soot blower is activated.

7. Boiler tube bank adhering ash removal system according to claim 5,

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 sootblower arranged between the third tube group and the fourth tube group,

the control device starts the second soot blower after starting the first soot blower when the first soot blower and the second soot blower are started for the 1-time start or the continuous start.

8. The boiler tube bank attached ash removal system according to any one of claims 1 to 7,

the sootblower is a pressure wave sootblower that generates pressure waves by exploding gas.

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