A system and method for improving the induced draft fan RB condition of a thermal power unit with two boilers and one turbine

Abstract

The present invention discloses a system and method for improving the induced draft fan (IDF) operating condition of a two-boiler, one-unit thermal power unit. The outlet of a first boiler is connected to one end of a first induced draft main pipe, the other end of which is connected to the input ends of the first and second induced draft fans. The outlet of a second boiler is connected to one end of a second induced draft main pipe, the other end of which is connected to the input ends of the third and fourth induced draft fans. One end of a connecting pipe is connected to the first induced draft main pipe, and the other end of the connecting pipe is connected to the second induced draft main pipe. An electric regulating valve is provided on the connecting pipe. A first pressure transmitter and a second pressure transmitter are respectively provided on the first and second boilers. A PID controller is respectively connected to the first and second pressure transmitters and the electric regulating valve. The present invention can effectively solve the induced draft fan (IDF) problem caused by a failure of only one boiler's induced draft fan in a two-boiler, one-unit unit.

Description

Technical Field

[0001] The present invention relates to the technical field of automatic control of thermal power plants, and in particular to a system and method for improving the RB operating condition of an induced draft fan of a two-boiler-one-unit thermal power plant. Background Art

[0002] The RB function allows the unit to rapidly respond to load commands and fuel levels in the event of an abnormality or failure in the operating auxiliary equipment. The unit's main automatic control systems work together to quickly and steadily reduce the unit's load to the unit's maximum allowable output, while ensuring continued safe operation. Most existing thermal power units are equipped with two induced draft fans (IDFs) operating at 60% of their rated output (because the induced draft fan and the desulfurization system's booster fan are combined into one). These fans serve as the primary power source for the boiler's air and smoke system and are crucial for maintaining normal operation under the boiler's slightly negative pressure. If an IDF fan fails and trips, losing its output capacity, the unit must shed 50% of its load and 50% of its solid fuel supply at the fastest rate it can withstand, rapidly restoring stable combustion. In the thermal power industry, this failure process is referred to as induced draft RNUBACK, commonly known as IDF RB. There are two situations for the RB operating conditions of the induced draft fans of a two-boiler-one-unit thermal power unit: First, the induced draft fan of one boiler fails and trips, triggering the RB operating condition of the induced draft fan of the unit. In order to ensure the consistent steam quality before the gas valve, the other boiler with an intact induced draft system must also follow the boiler with the induced draft fan system failure, at the same speed and with guaranteed steam quality, and reduce the output to the target load until the load of the entire unit is reduced to 50% of the rated load; Second, one induced draft fan of each of the two boilers fails and trips at the same time, triggering the RB operating condition of the induced draft fan of the entire unit.

[0003] During the induced draft fan RB process of the two-boiler-one-machine unit, the unit load controller will automatically and quickly get rid of the excess 50% load; the fuel systems of the two boilers will automatically and quickly reduce the excess 50% fuel at a similar rate (related to the characteristics of the boilers themselves, with the purpose of ensuring that the steam quality produced by the two boilers is within the deviation range allowed for normal operation of the unit); at the same time, matching the fuel reduction rate, the primary air volume of each boiler will be reduced by 50% at the same time; in order to maintain the furnace negative pressure unchanged, the furnace negative pressure control system of the two boilers should also quickly reduce the output of the blower of each boiler by 50%. The main function of the induced draft system is to ensure the flow of air and smoke within the boiler furnace, thereby ensuring that the high-temperature flue gas after the pulverized coal combustion passes through a series of environmental protection and efficiency-enhancing facilities arranged behind the furnace, such as the high-temperature superheater, low-temperature superheater, economizer, air preheater, electrostatic precipitator, and desulfurization system. This allows the heat released by the burned pulverized coal to be fully utilized, thereby improving the thermal efficiency of the boiler. At the same time, it provides sufficient power for the heat released by the pulverized coal combustion and the remaining smoke to smoothly leave the furnace, thereby maintaining the pressure in the furnace within the allowable range of the unit. Therefore, a significant reduction in the output of the induced draft system directly affects the stability of the negative pressure in the furnace. When an induced draft fan (IDF) failure occurs, the first thing to change is the furnace negative pressure. This pressure plummets as a single IDF fan in the IDF system trips. With the emergency tripping of a single IDF fan in the supply air system to compensate for the sudden loss of 50% of the furnace's flow capacity, the furnace negative pressure briefly drops. Then, due to the heat released by the combustion of excess fuel in the furnace that wasn't removed in time due to the sudden load reduction, the furnace negative pressure temporarily rises. This process poses a significant challenge to the rapid response of the IDF system. The IDF's rapid response is likely unable to keep up with the rapid change in furnace negative pressure, resulting in a unit trip due to excessive furnace negative pressure.

[0004] Secondly, it manifests itself in the instability of combustion in the furnace. When the induced draft fan RB occurs, the fuel system quickly exits the pre-selected operating grinding group system at a certain rate (the maximum rate is set according to the boiler characteristics) to adapt to the unit load instruction after the induced draft fan RB. As the grinding group system continues to exit, the fuel entering the furnace is rapidly reduced, and the heat released by the combustion of pulverized coal in the furnace is also decreasing. However, when the boiler induced draft fan has lost half of its output, it still has to maintain the violently fluctuating furnace negative pressure within the protection value. This causes the air flow field in the furnace to be extremely unstable, which in turn causes the temperature field in the furnace to change violently, which can easily cause all the running grinding groups in the furnace to lose ignition conditions and exit the operating state. Ultimately, the unit trips due to the furnace fire extinguishing signal.

[0005] After the induced draft fan RB occurs, the auxiliary combustion air supply system also trips one of the air supply fans along with the induced draft system, resulting in insufficient output of the auxiliary furnace combustion air supply system, causing a large area of unburned coal powder to remain in the furnace. However, the extremely unstable aerodynamic field at this time provides an opportunity for coal powder to remain in the boiler tail flue. As time goes by, the unburned coal powder in the tail flue accumulates more and more. When it reaches a certain level, it will instantly explode in the tail flue, damaging the heat exchange area of the boiler tail flue, causing irreparable economic losses to the power generation company.

[0006] In a two-boiler, one-unit, centrally controlled unit, consistent boiler outlet steam quality is a key parameter for safe operation. When the steam parameters at the outlets of the two boilers deviate beyond the permissible values for maintaining safe operation, the steam merging after the merging valves can cause severe vibration in the steam piping. In severe cases, this can rupture the steam piping, exposing high-temperature, high-pressure steam and causing significant damage to personnel and equipment. When an induced draft fan failure (IDF) occurs in a two-boiler, one-unit unit, both boilers, while ensuring unit safety, must maintain steam quality before the merging valves within the permissible range to ensure smooth RB operation. However, reducing both boilers to the target load for RB operation at a consistent maximum speed places a significant strain on all auxiliary equipment and the professional skills of the boiler operators. Improper operation at any stage can lead to unplanned unit downtime and, worse still, equipment damage or personal injury, resulting in unimaginable human and financial losses for the power generation company.

[0007] The existing RB type of induced draft fan in two-furnace-one-unit units has the following problems:

[0008] First, the workload and mental stress caused to the operators by the simultaneous rapid reduction of 50% load on all auxiliary equipment in the entire unit are obvious; the rapid response of the equipment is also a great test for the quality of the equipment materials, and the hidden damage caused to the equipment by multiple rapid and large-scale load changes cannot be ignored.

[0009] Second, when the induced draft fan RB occurs, the air supply system urgently trips one of the fans to match the lost flow capacity of the boiler air and smoke system. However, the significant reduction in the output capacity of the air supply system leads to a reduction in the amount of secondary air in the furnace that assists the combustion of pulverized coal, resulting in a large area of unburned pulverized coal being retained in the furnace. However, the extremely unstable aerodynamic field at this time provides an opportunity for pulverized coal to be retained in the boiler tail flue. As time goes by, the unburned pulverized coal in the tail flue accumulates more and more. When it reaches a certain level, it will instantly explode in the tail flue, damaging the heat exchange area of the boiler tail flue, causing irreparable economic losses to the power generation company.

[0010] Third, the induced draft fan (RB) causes the negative pressure in the furnace to fluctuate violently, which can even reach the boiler's limit protection value in an instant, or even exceed the limit value, causing unplanned shutdown of the unit; although the time exceeding the limit protection value is not long, frequent such over-limit operation is also a great test for the material life of the boiler.

[0011] Finally, when the induced draft fan RB occurs, the loads of the two boilers change drastically at the same time, which poses a huge challenge to the operating personnel's ability to maintain the consistency of steam quality before the air valve. At the same time, the workload brought to the operating personnel is also obvious. If they are not careful, the unit may be shut down unplanned at best, and the unit equipment may be seriously damaged at worst, causing immeasurable economic losses to the power generation company. Summary of the Invention

[0012] In response to the problems existing in the prior art, the present invention provides a system and method for improving the RB operating conditions of the induced draft fan of a two-boiler-one-machine thermal power unit, which can effectively solve the RB problem of the induced draft fan caused by the failure of only one boiler induced draft fan in the two-boiler-one-machine unit. It is of great significance to improve the RB stability of the induced draft fan of the two-boiler-one-machine thermal power unit, extend the life of key boiler equipment, reduce the number of unplanned shutdowns of the unit's main auxiliary equipment due to the induced draft fan RB, and reduce maintenance and repair costs.

[0013] In order to solve the above technical problems, the present invention is implemented through the following technical solutions:

[0014] A system for improving the induced draft fan (RB) operating condition of a two-boiler, one-unit thermal power unit, comprising a first boiler, a first induced draft main pipe, a first pressure transmitter, a first induced draft fan, a second induced draft fan, a second boiler, the second induced draft main pipe, a second pressure transmitter, a third induced draft fan, a fourth induced draft fan, a connecting pipe, an electric regulating valve, and a PID controller. The outlet of the first boiler is connected to one end of the first induced draft main pipe, the other end of the first induced draft main pipe is connected to the input ends of the first and second induced draft fans, the outlet of the second boiler is connected to one end of the second induced draft main pipe, the other end of the second induced draft main pipe is connected to the input ends of the third and fourth induced draft fans, one end of the connecting pipe is connected to the first induced draft main pipe, and the other end of the connecting pipe is connected to the second induced draft main pipe. The electric regulating valve is arranged on the connecting pipe, the first pressure transmitter and the second pressure transmitter are respectively arranged on the first boiler and the second boiler, and the PID controller is connected to the first pressure transmitter, the second pressure transmitter, and the electric regulating valve, respectively.

[0015] Furthermore, the electric regulating valve is located in the middle of the connecting pipe.

[0016] Furthermore, the connection position between the connecting pipe and the first induced air main pipe is close to the outlet position of the first boiler, and the connection position between the connecting pipe and the second induced air main pipe is close to the outlet position of the second boiler.

[0017] Furthermore, the input ends of the first induced draft fan and the second induced draft fan are respectively provided with a first valve and a second valve, and the input ends of the third induced draft fan and the fourth induced draft fan are respectively provided with a third valve and a fourth valve.

[0018] Furthermore, output ends of the first induced draft fan, the second induced draft fan, the third induced draft fan, and the fourth induced draft fan are all connected to chimneys.

[0019] Furthermore, the PID controller selects the ovation system or HNICS-T316.

[0020] A method for improving the operating condition of an induced draft fan (RB) of a two-boiler-one-unit thermal power plant, using the system, wherein when any one of the first induced draft fan, the second induced draft fan, the third induced draft fan, and the fourth induced draft fan fails, the induced draft fan (RB) of the two-boiler-one-unit thermal power plant is triggered, comprising:

[0021] The remaining three induced draft fans are controlled to operate normally. The PID controller controls and adjusts the opening of the electric regulating valve on the connecting pipe according to the boiler furnace pressure collected by the pressure transmitter installed on the boiler corresponding to the failed induced draft fan, so that the boiler furnace pressure corresponding to the failed induced draft fan is within a safe fluctuation range, thereby making the first boiler and the second boiler tend to a stable state.

[0022] Furthermore, before the induced draft fan RB of a two-boiler-one-unit thermal power unit is triggered, if the unit load is greater than 75% of the rated load, the remaining three induced draft fans will be controlled to adjust their output to the maximum;

[0023] After the first boiler and the second boiler tend to be in a stable state, the remaining three induced draft fans are controlled to operate at a rated load at a certain speed.

[0024] Furthermore, after the first boiler and the second boiler tend to be in a stable state, the remaining three induced draft fans are controlled to operate normally, so that the unit load is maintained at 75% of the rated load.

[0025] Furthermore, after the first boiler and the second boiler tend to a stable state, the unit load is reduced to 50% according to a preset load change rate until any induced draft fan corresponding to the boiler not connected to the failed induced draft fan is safely stopped. While reducing the unit load, the PID controller controls and adjusts the opening of the electric regulating valve on the connecting pipe based on the boiler furnace pressure collected by the pressure transmitter installed on the boiler corresponding to the failed induced draft fan, so that the boiler furnace pressure corresponding to the failed induced draft fan is within a safe fluctuation range, thereby allowing the first boiler and the second boiler to tend to a stable state.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects: When any of the first, second, third, and fourth induced draft fans fails and the RB of the induced draft fan of a two-boiler, one-unit thermal power unit is triggered, the remaining three induced draft fans are controlled to operate normally. A PID controller controls the opening of the electric regulating valve on the connecting pipe based on the boiler furnace pressure recorded by the pressure transmitter installed on the boiler corresponding to the failed induced draft fan, so that the boiler furnace pressure corresponding to the failed induced draft fan is within a safe fluctuation range, thereby allowing the first and second boilers to reach a stable state. During the RB process of the induced draft fan of the two-boiler, one-unit thermal power unit, the present invention increases the target value of the unit load command, improves the rate of decrease of the two-boiler, one-unit load command, shortens the RB process time of the induced draft fan of the two-boiler, one-unit thermal power unit, and thus delays the withdrawal of solid fuel from the unit's furnace. When an induced draft fan (IDF) failure occurs in a two-boiler, one-unit thermal power plant, the unit load does not need to be rapidly reduced, nor do all of the unit's auxiliary equipment need to coordinate with this rapid load reduction. Major unit parameters, such as furnace negative pressure, main fuel quantity, main steam pressure, main steam temperature, and main feedwater flow, no longer need to experience significant fluctuations, potentially causing unexpected losses. With the present invention, when an IDF failure occurs in a two-boiler, one-unit thermal power plant, the operator simply waits for the IDF failure to complete and the unit's operating conditions to return to normal. This invention minimizes the risk of equipment damage during an IDF failure in a two-boiler, one-unit thermal power plant and reduces the number of unplanned shutdowns caused by IDF failure. This indirectly creates economic benefits for power plants. Based on the existing thermal power plant system hardware structure, this invention eliminates the need for complex hardware modifications and only requires a set of electric control valves. This reduces the amplitude of furnace negative pressure fluctuations, reduces the likelihood of unplanned unit shutdowns, and even significantly reduces, or even eliminates, major accidents such as furnace implosion or explosions caused by unstable furnace negative pressure. Traditionally, the occurrence of induced draft fan RB in a two-boiler-one-unit thermal power unit can only be handled by the unit's coordinated control system, which quickly responds to rapid changes in the unit's load. However, when an induced draft fan RB occurs in a two-boiler-one-unit thermal power unit, the present invention can substantially improve the actual situation of the loss of ventilation power in the accident boiler through substantial means, while increasing the target load of the induced draft fan RB working condition of the two-boiler-one-unit thermal power unit, improving the coordinated control system to complete the induced draft fan RB process of the two-boiler-one-unit thermal power unit, and changing the history of the two-boiler-one-unit thermal power unit, which could only complete the induced draft fan RB process of the two-boiler-one-unit thermal power unit with the help of control means or human intervention. The present invention selects another boiler induced draft system to compensate for the missing ventilation power of the unit, considering that the two boiler induced draft systems are consistent, and the process is simple and easy to implement.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the specific embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 The present invention is a schematic diagram of a system for improving the RB working condition of the induced draft fan of a two-boiler-one-unit thermal power unit.

[0030] In the figure: 1-first boiler; 2-first pressure transmitter; 3-first valve; 4-first induced draft fan; 5-second valve; 6-second induced draft fan; 7-chimney; 8-PID controller; 9-electric regulating valve; 10-first induced draft main pipe; 11-second boiler; 12-second pressure transmitter; 13-third valve; 14-third induced draft fan; 15-fourth valve; 16-fourth induced draft fan; 17-second induced draft main pipe; 18-connecting pipe. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] As a specific embodiment of the present invention, Figure 1 As shown, a system for improving the induced draft fan (RB) operating conditions of a two-boiler, one-unit thermal power unit includes a first boiler 1, a first induced draft main pipe 10, a first pressure transmitter 2, a first induced draft fan 4, a second induced draft fan 6, a second boiler 11, a second induced draft main pipe 17, a second pressure transmitter 12, a third induced draft fan 14, a fourth induced draft fan 16, a connecting pipe 18, an electric regulating valve 9, and a PID controller 8. The outlet of the first boiler 1 is connected to one end of the first induced draft main pipe 10, and the other end of the first induced draft main pipe 10 is connected to the input ends of the first induced draft fan 4 and the second induced draft fan 6. Preferably, the input ends of the first induced draft fan 4 and the second induced draft fan 6 are respectively provided with a first valve 3 and a second valve 5. The outlet of the second boiler 11 is connected to one end of the second induced draft main pipe 17, and the other end of the second induced draft main pipe 17 is connected to the input ends of the third induced draft fan 14 and the fourth induced draft fan 16. Preferably, the input ends of the third induced draft fan 14 and the fourth induced draft fan 16 are respectively provided with a third valve 13 and a fourth valve 15. Preferably, the output ends of the first induced draft fan 4, the second induced draft fan 6, the third induced draft fan 14 and the fourth induced draft fan 16 are all connected to a chimney 7.

[0033] One end of the connecting pipe 18 is connected to the first induced air main pipe 10, and the other end of the connecting pipe 18 is connected to the second induced air main pipe 17. Preferably, the connection position of the connecting pipe 18 to the first induced air main pipe 10 is close to the outlet position of the first boiler 1, and the connection position of the connecting pipe 18 to the second induced air main pipe 17 is close to the outlet position of the second boiler 11.

[0034] The electric regulating valve 9 is arranged on the connecting pipe 18 . Preferably, the electric regulating valve 9 is located in the middle position of the connecting pipe 18 .

[0035] The first pressure transmitter 2 and the second pressure transmitter 12 are respectively arranged on the first boiler 1 and the second boiler 11 . The first pressure transmitter 2 is used to collect the furnace pressure of the first boiler 1 , and the second pressure transmitter 12 is used to collect the furnace pressure of the second boiler 11 .

[0036] PID controller 8 is connected to first pressure transmitter 2, second pressure transmitter 12, and electric regulating valve 9, respectively. PID controller 8 is used to control the opening of electric regulating valve 9 on connecting pipe 18 based on the boiler furnace pressure collected by the pressure transmitter installed on the boiler corresponding to the failed induced draft fan, so that the boiler furnace pressure corresponding to the failed induced draft fan is within a safe fluctuation range, thereby stabilizing the first boiler 1 and the second boiler 11.

[0037] In the present invention, the PID controller is selected from Emerson's ovation system or Huaneng Ruiwo's HNICS-T316. The electric regulating valve is selected from Sibos 2SA7321-2CE20-4BB4-Z or Shanghai Xingli LTCQ012.

[0038] The present invention provides a method for improving the RB operating condition of the induced draft fan of a two-boiler-one-unit thermal power plant. The method improves the RB operating condition of the induced draft fan of the two-boiler-one-unit thermal power plant by using compensation means. Taking the case where the first induced draft fan 4 connected to the first boiler 1 fails and trips, triggering the RB of the induced draft fan of the two-boiler-one-unit thermal power plant, while the other three induced draft fans are normal, the effect of the system of the present invention on the RB process of the induced draft fan of the two-boiler-one-unit thermal power plant is described as follows:

[0039] When the first induced draft fan 4 trips due to a fault and the induced draft fan RB of the two-boiler-one-unit unit is triggered, the second boiler 11 does not need to trip an induced draft fan at the same time, and will not trigger the induced draft fan RB working condition like the first boiler 1. After the first induced draft fan 4 trips, the first valve 3 at the input end of the first induced draft fan 4 is closed, and the electric regulating valve 9 on the connecting pipe 18 between the first induced draft main pipe 10 and the second induced draft main pipe 17 is opened to a certain degree (the opening degree is related to the unit load before the induced draft fan RB occurs, and the greater the load, the greater the opening degree instruction), and the output of the remaining three induced draft fans of the two boilers is adjusted to the maximum (the unit load before RB occurs is greater than 75%). When the rated load is less than 75% of the rated load before RB occurs, the output of the three induced draft fans needs to be adjusted to the maximum; when the unit load is less than 75% of the rated load before RB occurs, the output value of the three induced draft fans is determined according to the load before RB occurs. The greater the load, the greater the output of the three induced draft fans). The PID controller 8 assists the first induced draft fan 4 in automatically adjusting the furnace negative pressure of the first boiler 1 by opening and closing the electric regulating valve 9 between the two boiler induced draft main pipes based on the boiler furnace pressure collected by the first pressure transmitter 2 installed on the first boiler 1 at this time. At this time, the two induced draft fans of the second boiler 11 continue to maintain the furnace negative pressure fluctuation of the second boiler 11 within a safe range. The two induced draft fans of the second boiler, through the connecting pipe 18 between the two boiler induced draft main pipes, try to supplement the air and smoke flow power lost by the first boiler due to the tripping of the first induced draft fan 4. After the induced draft fan RB operating condition of the unit gradually stabilizes, the three induced draft fans are then slowly reduced to rated load at a certain rate based on the actual situation of the unit. During this process, the PID controller 8 between the two boilers always assists the first induced draft fan 4 to ensure that the negative pressure fluctuation in the furnace of the first boiler is within the range allowed for safe operation of the unit. Under the improved method of the present invention, after the induced draft fans RB of the two boilers and one unit are triggered, the induced draft system of the entire unit can be regarded as a whole. In the event of the loss of the output of one induced draft fan, the furnace ventilation power of the entire unit is provided by the remaining three induced draft fans. In other words, the entire unit still maintains 75% of the furnace ventilation capacity. Therefore, the target load of the induced draft fans RB of the two-boiler-one-unit thermal power unit can be fully optimized to 75% of the rated load. After the RB operating condition of the induced draft fan of the two-boiler-one-unit thermal power unit stabilizes, the unit operator has two options: one, the unit continues to operate normally at 75% of the rated load; the other, the operator safely reduces the unit load to 50% at the load reduction rate of normal operation of the unit until the induced draft fan of the other non-faulty boiler stops safely.During this process, the PID controller 8 constantly maintains the negative pressure in the furnace of the first boiler within the range permitted for safe operation of the unit through the electric regulating valve 9 on the connecting pipe between the two boiler induced draft fan main pipes, until one induced draft fan of the non-faulty boiler safely stops. At this point, after the output of the two boiler induced draft fan systems gradually balances, the opening of the electric regulating valve 9 on the connecting pipe between the two boiler induced draft fan main pipes gradually decreases until it is closed. At this point, the PID controller 8 also stops operating, indicating that the present invention has successfully helped the two-boiler-one-unit thermal power unit complete the induced draft fan RB operating condition. If the induced draft fan RB of the two-boiler-one-unit thermal power unit is caused by the tripping of the other three induced draft fans, the process is the same as the induced draft fan RB process described above.

[0040] Example

[0041] like Figure 1 As shown in the figure, taking the case where the first induced draft fan 4 trips due to a fault, triggering the RB of the induced draft fan of the two-boiler-one-unit unit, the unit is running at 100% of the rated load before RB is triggered, and the other three induced draft fans are all normal, the role of this pressure compensation system in the RB process of the induced draft fan of the two-boiler-one-unit thermal power unit is described.

[0042] When the first induced draft fan 4 fails and trips, and the induced draft fan RB of the two-boiler-one-machine unit is triggered, the second boiler 11 does not need to trip an induced draft fan at the same time, and will not trigger the induced draft fan RB working condition like the first boiler 1. After the first induced draft fan 4 trips, the first valve 3 at the input end of the first induced draft fan 4 is closed, and the electric regulating valve 9 on the connecting pipe 18 between the first induced draft main pipe 10 and the second induced draft main pipe 17 is directly opened to 80% (a certain adjustment means is reserved), and the remaining three induced draft fans of the two boilers are adjusted to maximum output (for general induced draft fan selection, the maximum output is greater than 50% of the rated load). At this moment, the PID controller 8 is adjusted according to the current first induced draft fan. The first pressure transmitter 2 installed on boiler 1 collects the fluctuation value of the boiler furnace negative pressure. Through the electric regulating valve 9 between the two boilers, it assists the second induced draft fan 6 to automatically adjust the fluctuation of the furnace negative pressure of the first boiler 1 to between -2000Pa and 2000Pa, thereby compensating for the ventilation power lost by the first boiler due to the tripping of the first induced draft fan 4. After the parameters of the two boilers gradually stabilize, the three induced draft fans are gradually reduced to rated load operation at 1% / min according to the actual situation of the unit. During this process, the PID controller 8 always maintains the furnace negative pressure of the first boiler between -2000Pa and 2000Pa. With the improved method of the present invention, after the RB of the two-boiler-one-unit induced draft fan is triggered, the entire unit's induced draft system can be considered as a single entity. Even if one induced draft fan loses power, the furnace ventilation power of the entire unit is provided by the remaining three induced draft fans. In other words, the entire unit still maintains 75% of its furnace ventilation capacity. Therefore, the target load of the RB induced draft fan of the two-boiler-one-unit thermal power plant can be optimized to 75% of the rated load. After the RB operating conditions of the two-boiler-one-unit thermal power plant stabilize, the unit operator has two options: 1. Continue normal operation at 75% of the rated load; 2. Operators can safely reduce the unit load to 50% at a rate of 1% of the rated load per minute until the second boiler's induced draft fan safely stops. During this process, the PID controller 8 always maintains the negative pressure in the furnace of the first boiler between -2000Pa and 2000Pa through the electric regulating valve 9 on the connecting pipe between the two boiler induced draft main pipes until one induced draft fan of the second boiler is safely stopped. At this time, after the output of the induced draft fan systems of the two boilers is slowly balanced, the opening of the electric regulating valve 9 on the connecting pipe between the two boiler induced draft main pipes is slowly closed until it is closed. At this time, the PID controller also stops working, indicating that the improvement method of the present invention has successfully helped the two-boiler-one-unit thermal power unit to complete the induced draft fan RB operating condition.

[0043] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for improving the RB working condition of the induced draft fan of a two-boiler-one-unit thermal power plant, characterized in that: A system for improving the RB working condition of the induced draft fan of a two-boiler-one-unit thermal power unit is adopted. The system comprises a first boiler (1), a first induced draft main pipe (10), a first pressure transmitter (2), a first induced draft fan (4), a second induced draft fan (6), a second boiler (11), a second induced draft main pipe (17), a second pressure transmitter (12), a third induced draft fan (14), a fourth induced draft fan (16), a connecting pipe (18), an electric regulating valve (9) and a PID controller (8). The outlet of the first boiler (1) is connected to one end of the first induced draft main pipe (10), the other end of the first induced draft main pipe (10) is connected to the input ends of the first induced draft fan (4) and the second induced draft fan (6), the outlet of the second boiler (11) is connected to the second induced draft fan (4), and the second induced draft fan (6) is connected to the second induced draft fan (4). One end of the induced draft main pipe (17) is connected, the other end of the second induced draft main pipe (17) is connected to the input ends of the third induced draft fan (14) and the fourth induced draft fan (16), one end of the connecting pipe (18) is connected to the first induced draft main pipe (10), and the other end of the connecting pipe (18) is connected to the second induced draft main pipe (17), the electric regulating valve (9) is arranged on the connecting pipe (18), the first pressure transmitter (2) and the second pressure transmitter (12) are respectively arranged on the first boiler (1) and the second boiler (11), and the PID controller (8) is respectively connected to the first pressure transmitter (2), the second pressure transmitter (12) and the electric regulating valve (9); The electric regulating valve (9) is located in the middle of the connecting pipe (18); The connection position of the connecting pipe (18) and the first induced draft main pipe (10) is close to the outlet position of the first boiler (1), and the connection position of the connecting pipe (18) and the second induced draft main pipe (17) is close to the outlet position of the second boiler (11); When any one of the first induced draft fan (4), the second induced draft fan (6), the third induced draft fan (14) and the fourth induced draft fan (16) fails and the induced draft fan RB of the two-boiler-one-unit thermal power unit is triggered, the method includes: The remaining three induced draft fans are controlled to operate normally. The PID controller (8) controls and adjusts the opening of the electric regulating valve (9) on the connecting pipe (18) according to the boiler furnace pressure collected by the pressure transmitter installed on the boiler corresponding to the failed induced draft fan, so that the boiler furnace pressure corresponding to the failed induced draft fan is within the safe fluctuation range, thereby making the first boiler (1) and the second boiler (11) tend to a stable state; after the first boiler (1) and the second boiler (11) tend to a stable state, the unit load is reduced to 50% according to a preset load change rate until any induced draft fan corresponding to the boiler not connected to the failed induced draft fan is safely stopped. While reducing the unit load, the PID controller (8) controls and adjusts the opening of the electric regulating valve (9) on the connecting pipe (18) according to the boiler furnace pressure collected by the pressure transmitter installed on the boiler corresponding to the failed induced draft fan, so that the boiler furnace pressure corresponding to the failed induced draft fan is within the safe fluctuation range.

2. The method for improving the RB working condition of the induced draft fan of a two-boiler-one-unit thermal power plant according to claim 1, characterized in that: The input ends of the first induced draft fan (4) and the second induced draft fan (6) are respectively provided with a first valve (3) and a second valve (5), and the input ends of the third induced draft fan (14) and the fourth induced draft fan (16) are respectively provided with a third valve (13) and a fourth valve (15).

3. The method for improving the RB working condition of the induced draft fan of a two-boiler-one-unit thermal power plant according to claim 1, characterized in that: The output ends of the first induced draft fan (4), the second induced draft fan (6), the third induced draft fan (14), and the fourth induced draft fan (16) are all connected to a chimney (7).

4. The method for improving the RB working condition of the induced draft fan of a two-boiler-one-unit thermal power plant according to claim 1, characterized in that: The PID controller (8) is selected from the Ovation system or HNICS-T316.

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