Flue gas bypass control system and control method suitable for full load process denitration

Abstract

The present application belongs to the technical field of power generation and peak regulation control, and particularly relates to a flue gas bypass control system and control method suitable for denitration during full load process. Before the unit is connected to the grid, the boiler flue gas is directly discharged from the flue gas straight-through pipe without passing through the denitration device, so as to prevent the denitration device from being blocked. When the flue gas temperature is too low to meet the operation condition of the denitration device under low load power working condition, the flue gas bypass valve can be opened to increase the flue gas temperature entering the denitration device, so that the denitration device is normally put into operation. When the flue gas temperature is extremely low during cold-state starting of the unit or the flue gas temperature is too high due to sudden change of the unit operation condition, the flue gas bypass valve, the flue gas tangential valve and the denitration device isolation valve can be closed, the flue gas bypasses the denitration device and directly enters the air preheater through the flue gas output pipe and the flue gas straight-through pipe, so that the denitration device is quickly cut out, thereby protecting the denitration device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power generation and peak regulation control, and particularly relates to a flue gas bypass control system and control method suitable for denitration in a full load process. BACKGROUND

[0002] In recent years, in the process of clean and low-carbon transformation in the power industry, large-scale grid-connected power generation of clean energy such as wind power and photovoltaic power generation, due to the fluctuating, intermittent and random characteristics of wind and light energy power, the power grid urgently needs coal-fired units to full-load peak regulation, and improving the flexibility of deep peak regulation of coal-fired units has become an urgent task for building a new power system. When the output of wind, light and other power resources fluctuates rapidly, coal-fired units are required to respond quickly to deep regulation operation, and the temperature of flue gas entering the denitration system drops or rises suddenly. When low-temperature flue gas enters the denitration device, ammonium bisulfate, a viscous material, will be formed, which will adhere to the denitration catalyst and the air preheater, and will adsorb dust, causing the denitration catalyst and the air preheater to be blocked, and the pressure difference of the denitration reactor and the air preheater slowly increases, thereby reducing the output of the induced draft fan and affecting the unit output; when the flue gas temperature is too high, the service life of the catalyst of the denitration device will be greatly reduced in a short time. In order to improve the flue gas temperature of the denitration system, the published patent applications “Coal-fired unit full-load denitration system and adjusting method” (application publication number CN114749019A), “Coal economizer bypass system for full-load denitration” (application publication number CN209229770U), and “System for realizing wide-load denitration by bypass staged coal economizer” (application publication number CN211716596U) all propose bypass flue gas solutions, which mix high-temperature flue gas from the bypass flue gas with low-temperature flue gas from the main flue gas to increase the flue gas temperature, and the flue gas directly flows into the denitration device after the temperature is increased. However, such a system cannot protect the denitration device when the flue gas temperature is too low or too high during the full-process operation of the unit, and there are still technical problems to be solved in terms of protecting the denitration device and automatically controlling the flue gas temperature. Therefore, in view of the problems existing in the boiler denitration of the boiler in the full-load operation condition, the present application proposes a flue gas bypass control system and control method suitable for denitration in a full load process. SUMMARY

[0003] In order to solve the above problems and realize boiler denitration in the full-load operation condition of the boiler, and improve the flexibility of coal-fired units participating in grid regulation, the present application provides a flue gas bypass control system and control method suitable for denitration in a full load process, and the specific technical solutions are as follows:

[0004] A flue gas bypass control system suitable for full load process denitration is applied to a boiler, comprising a first flue gas passage damper, a second flue gas passage damper, a flue gas bypass, a flue gas bypass valve, a flue gas temperature measuring device in a flue gas outlet pipe, a flue gas outlet pipe, a flue gas temperature measuring device at the inlet of a denitration device, a flue gas inlet pipe of the denitration device, a flue gas tangential valve, a flue gas tangential pipe, a flue gas straight pipe, a flue gas straight valve, a denitration device isolation valve, a flue gas outlet pipe of the denitration device, an air preheater, a denitration agent regulating valve, a denitration agent inlet pipe, a denitration device, a data acquisition and control module.

[0005] The furnace of the boiler is provided with two parallel first flue gas passages and second flue gas passages; the outlet of the first flue gas passage is provided with a first flue gas passage damper for controlling the flue gas flow in the first flue gas passage, and the second flue gas passage is sequentially provided with a low-temperature superheater, a second flue gas passage economizer and a second flue gas passage damper for controlling the flue gas flow in the second flue gas passage from the inlet to the outlet; the outlets of the first flue gas passage and the second flue gas passage are merged into a flue gas outlet pipe, and the flue gas outlet pipe is provided with a flue gas temperature measuring device; the outlet of the flue gas outlet pipe is in communication with the inlet of a flue gas straight pipe and the inlet of a flue gas tangential pipe, respectively.

[0006] The inlet of the flue gas bypass is in communication with the second flue gas passage and is arranged before the second flue gas passage economizer, and a flue gas bypass valve is arranged on the flue gas bypass for controlling the flue gas flow through the flue gas bypass.

[0007] The outlet of the flue gas bypass and the outlet of the flue gas tangential pipe are in communication with the inlet of a flue gas inlet pipe of a denitration device, respectively, and a flue gas tangential valve is arranged on the flue gas tangential pipe for switching control of whether the flue gas flows through the denitration device.

[0008] The outlet of the flue gas inlet pipe of the denitration device is in communication with the inlet of the denitration device, and a flue gas temperature measuring device at the inlet of the denitration device is arranged at the inlet of the denitration device; the outlet of a denitration agent inlet pipe is in communication with the inlet of the denitration device, and a denitration agent regulating valve is arranged on the denitration agent inlet pipe; the outlet of the denitration device is in communication with the inlet of a flue gas outlet pipe of the denitration device, the outlet of the flue gas outlet pipe of the denitration device is merged into an air preheater with the outlet of a flue gas straight pipe, a denitration device isolation valve is arranged on the flue gas outlet pipe of the denitration device, and a flue gas straight valve is arranged on the flue gas straight pipe.

[0009] The data acquisition and control module is connected with the flue gas temperature measuring device at the inlet of the denitration device, the flue gas temperature measuring device in the flue gas output pipe, the flue gas bypass valve, the flue gas tangential valve, the flue gas straight-through valve, the denitration device isolation valve, the denitration agent regulating valve and the flue gas baffle of the first flue gas passage and the second flue gas passage, respectively, for comparing the flue gas temperature at the inlet of the denitration device measured by the flue gas temperature measuring device at the inlet of the denitration device with the corresponding set value and the flue gas temperature at the inlet of the flue gas output pipe measured by the flue gas temperature measuring device in the flue gas output pipe with the corresponding set value, and controlling the opening degree of the flue gas bypass valve, the flue gas tangential valve, the flue gas straight-through valve, the denitration device isolation valve, the denitration agent regulating valve, the flue gas baffle of the first flue gas passage and the flue gas baffle of the second flue gas passage according to the comparison result, so as to adjust the flue gas temperature at the inlet of the denitration device or cut off the denitration device.

[0010] Preferably, the ash hopper, the ash hopper accumulated ash height measuring device, the ash hopper ash discharging valve and the ash hopper ash discharging pipe are further included; the outlet of the first flue gas passage and the outlet of the second flue gas passage are combined and communicated with the inlet of the ash hopper, the outlet of the ash hopper is communicated with the inlet of the ash hopper ash discharging pipe, the ash hopper accumulated ash height measuring device is arranged in the ash hopper, the ash hopper ash discharging valve is arranged on the ash hopper ash discharging pipe, and the ash hopper accumulated ash height measuring device and the ash hopper ash discharging valve are connected with the data acquisition and control module, respectively; the ash hopper accumulated ash height measuring device is used for measuring the height of the accumulated ash in the ash hopper and transmitting the measured data to the data acquisition and control module, and the data acquisition and control module is further used for comparing the measured data of the ash hopper accumulated ash height measuring device with the corresponding set fixed value, so as to control the opening and closing of the ash hopper ash discharging valve.

[0011] Preferably, the reheater and the first flue gas passage economizer are further arranged in the first flue gas passage; the flue gas flowing through the first flue gas passage first passes through the reheater to absorb heat and reduce temperature, and then passes through the first flue gas passage economizer to continue to reduce temperature; and the flue gas baffle of the first flue gas passage is arranged after the economizer.

[0012] Preferably, the flue gas temperature measuring device in the flue gas output pipe and the flue gas temperature measuring device at the inlet of the denitration device each adopt three E-type thermocouples, and the probes of the thermocouples are located at the center part of the pipe diameter.

[0013] Preferably, the ash hopper accumulated ash height measuring device adopts a material level transmitter, and outputs a 4-20 mA or 1-5 V standard signal connected with the data acquisition and control module.

[0014] A flue gas bypass control method suitable for full-load process denitration is applied to the control system, and includes the following steps:

[0015] In step S1, the temperature parameters of the denitration system alarm protection, i.e. the low I value, the low II value, the high I value and the high II value of the flue gas temperature at the inlet of the denitration device, are set, wherein the low II value < the low I value < the high I value < the high II value;

[0016] Step S2, before the unit is connected to the grid, the flue gas bypass system is not put into operation, the data acquisition and control module controls the full closing of the denitration agent regulating valve, the data acquisition and control module controls the full opening of the first flue gas passage flue gas damper and the second flue gas passage flue gas damper, the data acquisition and control module controls the full closing of the flue gas bypass valve, the flue gas tangential valve and the denitration device isolation valve, the data acquisition and control module controls the full opening of the flue gas straight-through valve, and the boiler flue gas enters the air preheater through the flue gas output pipe and the flue gas straight-through pipe;

[0017] Step S3, the unit is connected to the grid, the data acquisition and control module controls the full opening of the flue gas tangential valve, the data acquisition and control module controls the full opening of the denitration device isolation valve, the data acquisition and control module controls the gradual closing of the flue gas straight-through valve in the full opening state to the full closing, and the flue gas bypass valve is gradually opened, to ensure that the measurement value of the denitration device inlet flue gas temperature measuring device is higher than the low I value and lower than the high I value, at this time, the data acquisition and control module controls the opening of the denitration agent regulating valve, and the denitration device is put into operation;

[0018] Step S4, when the data acquisition and control module controls the full opening of the flue gas bypass valve, and the measurement value of the denitration device inlet flue gas temperature measuring device is still lower than the low I value, the data acquisition and control module controls the closing of the opening degree of the first flue gas passage flue gas damper and the second flue gas passage flue gas damper, the amount of flue gas flowing to the flue gas bypass will be increased, to ensure that the measurement value of the denitration device inlet flue gas temperature measuring device is higher than the low I value, and the automatic adjustment function of the flue gas bypass valve is put into operation;

[0019] Step S5, during the process of the unit running from low load to high load, as the load of the unit increases, the measurement value of the flue gas temperature measuring device in the flue gas output pipe gradually increases, the data acquisition and control module controls the flue gas bypass valve to be in the automatic adjustment state, the opening degree of the flue gas bypass valve will gradually close, the data acquisition and control module controls the gradual opening of the opening degree of the first flue gas passage flue gas damper and the second flue gas passage flue gas damper, when the measurement value of the flue gas temperature measuring device in the flue gas output pipe is higher than the low I value, and the flue gas bypass valve is fully closed, the flue gas bypass is out of operation;

[0020] Step S6, during the process of the unit running from high load to low load, as the load of the unit decreases, the measurement value of the flue gas temperature measuring device in the flue gas output pipe gradually decreases, when the measurement value of the flue gas temperature measuring device in the flue gas output pipe is lower than the low I value, the data acquisition and control module controls the flue gas bypass valve to be in the automatic state, the opening degree of the flue gas bypass valve will gradually open, the flue gas bypass is put into operation, and the operator gradually closes the opening degree of the first flue gas passage flue gas damper and the second flue gas passage flue gas damper according to the need, to ensure that the measurement value of the denitration device inlet flue gas temperature measuring device is higher than the low I value;

[0021] Step S7, the unit from low load operation to grid disconnection shutdown, the measured value of the denitration device inlet flue gas temperature measuring device is lower than the low II value, or the measured value of the denitration device inlet flue gas temperature measuring device is higher than the high II value, the data acquisition and control module controls the denitration agent regulating valve to be fully closed, the data acquisition and control module controls the first flue gas passage flue gas damper and the second flue gas passage flue gas damper to be fully opened, the data acquisition and control module controls the flue gas straight-through valve to be fully opened, the flue gas bypass valve, the flue gas tangential valve and the denitration device isolation valve are fully closed, and the boiler flue gas directly enters the air preheater through the flue gas output pipe and the flue gas straight-through pipe, so that the denitration device is cut off, and the protection of the denitration device is realized.

[0022] Preferably, the method further comprises step S8: when the data acquisition and control module controls the opening degree of the first flue gas passage flue gas damper to control the flue gas flow in the first flue gas passage to slow down, or the data acquisition and control module controls the opening degree of the second flue gas passage flue gas damper to control the flue gas flow in the second flue gas passage to slow down, the dust in the flue gas will deposit in the ash bucket; when the ash bucket ash deposition height measuring device measures that the ash deposition height of the ash bucket is higher than the ash discharge height setting value, the data acquisition and control module controls the ash bucket ash discharge valve to be opened to discharge the dust deposited in the ash bucket through the ash bucket ash discharge pipe; when the ash bucket ash deposition height measuring device measures that the ash deposition height of the ash bucket is lower than the ash discharge removal height setting value, the data acquisition and control module controls the ash bucket ash discharge valve to be closed to stop discharging ash.

[0023] Preferably, the automatic adjustment function of the flue gas bypass valve is specifically controlled by the data acquisition and control module controlling the switching switch, when the switching switch is set to 1, the automatic adjustment function of the flue gas bypass valve is put into operation, and when the switching switch is set to 0, the flue gas bypass valve exits the automatic adjustment function;

[0024] Specifically comprising the following steps:

[0025] The target temperature value of the automatic adjustment of the flue gas bypass valve is set, and the flue gas bypass valve operates according to the target temperature value + Ts, wherein Ts is an automatic adjustment bias given by an operator according to the operation requirement;

[0026] The measured value Te of the denitration device inlet flue gas temperature measuring device is compared with the target temperature value + Ts, and the deviation is input into a PID link, and the output instruction signal of the PID link is converted into the instruction signal of the opening degree of the flue gas bypass valve through K proportion , the instruction signal controls the opening degree of the flue gas bypass valve, and the deviation between Te and the target temperature value + Ts is zero.

[0027] Preferably, the flue gas temperature measuring device in the flue gas output pipe and the flue gas temperature measuring device at the inlet of the denitration device each adopt three E-type thermocouples, the probes of which are located at the center of the pipe diameter; when the measured values of two of the three E-type thermocouples are lower or higher than the corresponding temperature parameters, it is considered that the measured value of the flue gas temperature measuring device in the flue gas output pipe or the flue gas temperature measuring device at the inlet of the denitration device is lower or higher than the corresponding temperature parameters.

[0028] The present application has the following beneficial effects: the present application can improve the flexibility of thermal power generating units participating in fast and deep regulation of power grid, relieve the pressure of power grid peak regulation, and is suitable for the regulation of flue gas temperature during full load process of boiler operation of thermal power generating units and the protection of denitration devices. Before the unit is connected to the grid, the boiler flue gas is discharged directly from the flue gas straight-through pipe without passing through the denitration device, preventing the denitration device from being blocked. When the flue gas temperature is too low to meet the operation condition of the denitration device under low load power condition, the flue gas bypass valve can be opened to increase the flue gas temperature entering the denitration device, so that the denitration device can be normally put into operation, realizing the denitration function of flue gas before the unit is connected to the grid or under low load power condition, reducing environmental pollution, and meeting the requirement of deep peak regulation function of power grid. When the flue gas temperature is extremely low during cold start of the unit or the flue gas temperature is too high due to sudden change of unit operation condition, the flue gas bypass valve, the flue gas tangential valve and the denitration device isolation valve can be closed, the flue gas bypasses the denitration device and is directly discharged into the air preheater through the flue gas output pipe and the flue gas straight-through pipe, realizing rapid cut-off of the denitration device, thereby protecting the denitration device. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or prior art description will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale.

[0030] Figure 1 The system schematic diagram of the present application;

[0031] Figure 2 The control schematic diagram of the present application;

[0032] Figure 3 The control schematic diagram of the flue gas bypass valve automatic control of the present application;

[0033] Wherein, 1 -furnace (1), 2 -screen superheater, 3 -high temperature superheater, 4 -reheater, 5 -the first flue gas passage, 6 -the second flue gas passage economizer, 7 -the first flue gas passage economizer, 8 -the first flue gas passage flue gas damper, 9 -the second flue gas passage flue gas damper, 10 -ash bucket accumulated ash height measuring device, 11 -ash bucket ash discharge valve, 12 -ash bucket ash discharge pipe, 13 -low temperature superheater, 14 -the second flue gas passage, 15 -flue gas bypass, 16 -flue gas bypass valve, 17 -ash bucket, 18 -flue gas output pipe inner flue gas temperature measuring device, 19 -flue gas output pipe, 20 -de NOx device inlet flue gas temperature measuring device, 21 -de NOx device inlet flue gas pipe, 22 -flue gas tangential valve, 23 -flue gas tangential pipe, 24 -flue gas straight pipe, 25 -flue gas straight valve, 26 -de NOx device isolation valve, 27 -de NOx device flue gas discharge pipe, 28 -air preheater, 29 -de NOx agent regulating valve, 30 -de NOx agent introduction pipe, 31 -de NOx device, 32 -data acquisition and control module. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0035] It should be understood that, when used in the specification and the appended claims, the terms "comprise" and "include" indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0036] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, unless otherwise clearly indicated by the context, the singular forms "a", "an" and "the" are intended to include the plural forms as well.

[0037] It should be further understood that the term "and / or" used in the present application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations thereof.

[0038] The specific implementation of this invention takes a 350 MW coal-fired power unit boiler as an example. The boiler type is HG-1150 / 25.4-YM1, a once-through boiler with intermediate reheat and supercritical pressure variable operation. It features a single furnace, balanced ventilation, solid ash discharge, and a π-type open-air layout. The flue gas bypass system enables the unit to be equipped with the denitrification device upon grid connection. The main design parameters of the boiler are shown in Table 1, and the alarm protection parameters of the denitrification system are shown in Table 2.

[0039] Table 1 Main Design Parameters of Boiler

[0040]

[0041] Table 2 Alarm and protection parameters of the denitrification system

[0042]

[0043] like Figures 1-2 As shown, a specific embodiment of the present invention provides a flue gas bypass control system suitable for full-load process denitrification, applied to a boiler, including a first flue gas passage flue gas damper 8, a second flue gas passage flue gas damper 9, a flue gas bypass 15, a flue gas bypass valve 16, a flue gas temperature measuring device 18 in the flue gas output pipe, a flue gas output pipe 19, a denitrification device inlet flue gas temperature measuring device 20, a denitrification device inlet flue gas pipe 21, a flue gas tangential valve 22, a flue gas tangential pipe 23, a flue gas straight pipe 24, a flue gas straight valve 25, a denitrification device isolation valve 26, a denitrification device exhaust pipe 27, an air preheater 28, a denitrification agent regulating valve 29, a denitrification agent inlet pipe 30, a denitrification device 31, and a data acquisition and control module 32;

[0044] The boiler furnace 1 is equipped with two parallel flue gas passages, namely, the first flue gas passage 5 and the second flue gas passage 14. At the outlet of the first flue gas passage 5, a first flue gas passage baffle 8 is installed to control the flow rate of the flue gas in the first flue gas passage 5. From the inlet to the outlet, the second flue gas passage 14 is equipped with a low-temperature superheater 13, a second flue gas passage economizer 6, and a second flue gas passage baffle 9 for controlling the flow rate of the flue gas in the second flue gas passage 14. The first flue gas passage 5 is also equipped with a reheater 4 and a first flue gas passage economizer 7. The flue gas flowing through the first flue gas passage 5 first passes through the reheater 4 to absorb heat and cool down, and then passes through the first flue gas passage economizer 7 to continue cooling down. The first flue gas passage baffle 8 is installed after the economizer 7.

[0045] The outlets of flue gas passage 5 and flue gas passage 14 converge into flue gas output pipe 19, and flue gas output pipe 19 is equipped with flue gas temperature measuring device 18; the outlet of flue gas output pipe 19 is connected to the inlet of flue gas straight pipe 24 and the inlet of flue gas tangential pipe 23 respectively.

[0046] The inlet of the flue gas bypass 15 is communicated with the second flue gas passage 14 and is arranged before the second flue gas passage economizer 6, and the flue gas bypass valve 16 is arranged on the flue gas bypass 15 and is used for controlling the flue gas flow through the flue gas bypass 15;

[0047] The outlet of the flue gas bypass 15 and the outlet of the flue gas tangential pipe 23 are respectively communicated with the inlet of the denitration device inlet flue gas pipe 21, and the flue gas tangential valve 22 is arranged on the flue gas tangential pipe 23 and is used for realizing switching control of whether the flue gas flows through the denitration device 31;

[0048] The outlet of the denitration device inlet flue gas pipe 21 is communicated with the inlet of the denitration device 31, and the denitration device inlet flue gas temperature measuring device 20 is arranged at the inlet of the denitration device 31; the outlet of the denitration agent introduction pipe 30 is communicated with the inlet of the denitration device 31, and the denitration agent adjusting valve 29 is arranged on the denitration agent introduction pipe 30; the outlet of the denitration device 31 is communicated with the inlet of the denitration device exhaust flue gas pipe 27, the outlet of the denitration device exhaust flue gas pipe 27 is merged into the air preheater 28 with the outlet of the flue gas straight-through pipe 24, the denitration device isolation valve 26 is arranged on the denitration device exhaust flue gas pipe 27, and the flue gas straight-through valve 25 is arranged on the flue gas straight-through pipe 24;

[0049] The data acquisition and control module 32 is connected with the denitration device inlet flue gas temperature measuring device 20, the flue gas output pipe inner flue gas temperature measuring device 18, the flue gas bypass valve 16, the flue gas tangential valve 22, the flue gas straight-through valve 25, the denitration device isolation valve 26, the denitration agent adjusting valve 29, the first flue gas passage flue gas baffle 8 and the second flue gas passage flue gas baffle 9 respectively, and is used for comparing the flue gas temperature at the inlet of the flue gas output pipe 19 measured by the flue gas output pipe inner flue gas temperature measuring device 18 and the flue gas temperature at the inlet of the denitration device 31 measured by the denitration device inlet flue gas temperature measuring device 20 with corresponding set values, and controlling the opening degrees of the flue gas bypass valve 16, the flue gas tangential valve 22, the flue gas straight-through valve 25, the denitration device isolation valve 26, the denitration agent adjusting valve 29, the first flue gas passage flue gas baffle 8 and the second flue gas passage flue gas baffle 9 according to the comparison results, so as to adjust the flue gas temperature at the inlet of the denitration device 31 or cut off the denitration device 31.

[0050] The realization principle is that temperature parameters of the denitration system alarm protection, i.e. low I value, low II value, high I value and high II value of the flue gas temperature at the inlet of the denitration device 31 are set in the data acquisition and control module 32, and the low II value < the low I value < the high I value < the high II value;

[0051] Before the unit is connected to the grid, the flue gas bypass system is not put into operation, the data acquisition and control module 32 controls the denitration agent regulating valve 29 to be fully closed, the data acquisition and control module 32 controls the first flue gas passage flue gas damper 8 and the second flue gas passage flue gas damper 9 to be fully opened, the data acquisition and control module 32 controls the flue gas bypass valve 16, the flue gas tangential valve 22 and the denitration device isolation valve 26 to be fully closed, the data acquisition and control module 32 controls the flue gas straight-through valve 25 to be fully opened, and the boiler flue gas enters the air preheater 28 through the flue gas output pipe 19 and the flue gas straight-through pipe 24.

[0052] When the unit is connected to the grid, the data acquisition and control module 32 controls the flue gas tangential valve 22 to be fully opened, the data acquisition and control module 32 controls the denitration device isolation valve 26 to be fully opened, the data acquisition and control module 32 controls the flue gas straight-through valve 25 in the fully open state to be gradually closed to the fully closed state, and the flue gas bypass valve 16 is gradually opened at the same time, so that the measurement value of the denitration device inlet flue gas temperature measuring device 20 is higher than the low I value and lower than the high I value. At this time, the data acquisition and control module 32 controls the denitration agent regulating valve 29 to be opened, and the denitration device 31 is put into operation.

[0053] When the data acquisition and control module 32 controls the flue gas bypass valve 16 to be fully opened, and the measurement value of the denitration device inlet flue gas temperature measuring device 20 is still lower than the low I value, the data acquisition and control module 32 controls the opening degree of the first flue gas passage flue gas damper 8 and the second flue gas passage flue gas damper 9 to be closed, so that the amount of flue gas flowing to the flue gas bypass 15 is increased, and the measurement value of the denitration device inlet flue gas temperature measuring device 20 is ensured to be higher than the low I value. The automatic adjustment function of the flue gas bypass valve 16 is put into operation, and the measurement value of the denitration device inlet flue gas temperature measuring device 20 is automatically followed to maintain at the set target value.

[0054] During the process of the unit running from low load to high load, as the load of the unit increases, the measurement value of the flue gas temperature measuring device 18 in the flue gas output pipe gradually increases, the data acquisition and control module 32 controls the flue gas bypass valve 16 to be in the automatic adjustment state, the opening degree of the flue gas bypass valve 16 will gradually be closed, the data acquisition and control module 32 controls the opening degree of the first flue gas passage flue gas damper 8 and the second flue gas passage flue gas damper 9 to be gradually opened, and when the measurement value of the flue gas temperature measuring device 18 in the flue gas output pipe is higher than the low I value, the flue gas bypass valve 16 is fully closed, the flue gas bypass is out of operation.

[0055] During the process of the unit from high load to low load, as the unit load decreases, the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe gradually decreases. When the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe is lower than the low I value, the data acquisition and control module 32 controls the flue gas bypass valve 16 to be in the automatic state. The opening degree of the flue gas bypass valve 16 will gradually open, the flue gas bypass is put into operation, and the operator will gradually close the opening degree of the first I flue gas passage flue gas damper 8 and the second I flue gas passage flue gas damper 9 according to the need, to ensure that the measured value of the denitration device inlet flue gas temperature measuring device 20 is higher than the low I value.

[0056] When the unit is switched from low load operation to grid separation shutdown, the measured value of the denitration device inlet flue gas temperature measuring device 20 is lower than the low II value, or the measured value of the denitration device inlet flue gas temperature measuring device 20 is higher than the high II value, the data acquisition and control module 32 controls the denitration agent regulating valve 29 to be fully closed, the data acquisition and control module 32 controls the first I flue gas passage flue gas damper 8 and the second I flue gas passage flue gas damper 9 to be fully opened, the data acquisition and control module 32 controls the flue gas straight-through valve 25 to be fully opened, the flue gas bypass valve 16, the flue gas tangential valve 22 and the denitration device isolation valve 26 are fully closed, the boiler flue gas directly enters the air preheater 28 through the flue gas outlet pipe 19 and the flue gas straight-through pipe 24, so that the denitration device 31 is cut off, and the protection of the denitration device 31 is realized.

[0057] The system of the present application further comprises an ash bucket 17, an ash bucket accumulated ash height measuring device 10, an ash bucket ash discharge valve 11, and an ash bucket ash discharge pipe 12; the outlets of the first flue gas passage 5 and the second flue gas passage 14 are merged and communicated with the inlet of the ash bucket 17, the outlet of the ash bucket 17 is communicated with the inlet of the ash bucket ash discharge pipe 12, the ash bucket accumulated ash height measuring device 10 is arranged in the ash bucket 17, the ash bucket ash discharge valve 11 is arranged on the ash bucket ash discharge pipe 12, and the ash bucket accumulated ash height measuring device 10 and the ash bucket ash discharge valve 11 are respectively connected with the data acquisition and control module 32; the ash bucket accumulated ash height measuring device 10 is used for measuring the height of the accumulated ash in the ash bucket 17 and transmitting the measured data to the data acquisition and control module 32, and the data acquisition and control module 32 is further used for comparing the measured data of the ash bucket accumulated ash height measuring device 10 with a corresponding set fixed value to control the opening and closing of the ash bucket ash discharge valve 11. When the first flue gas passage damper 8 controls the flue gas flow in the first flue gas passage 5 to cause the flue gas to slow down or the second flue gas passage damper 9 controls the flue gas flow in the second flue gas passage 14 to cause the flue gas to slow down, the dust in the flue gas will be deposited in the ash bucket 17; the ash bucket accumulated ash height measuring device 10 measures the accumulated ash height of the ash bucket 17, when the accumulated ash height of the ash bucket 17 is higher than the ash discharge height set value, the data acquisition and control module 32 controls to open the ash bucket ash discharge valve 11 to discharge the dust deposited in the ash bucket 17 through the ash bucket ash discharge pipe 12; when the accumulated ash height of the ash bucket 17 is lower than the ash discharge relief height set value, the data acquisition and control module 32 controls to close the ash bucket ash discharge valve 11 to stop discharging ash.

[0058] In the present application, the flue gas temperature measuring device 18 in the flue gas output pipe and the flue gas temperature measuring device 20 at the inlet of the denitration device each adopt three E-type thermocouples, and the probes thereof are located at the center of the pipe diameter. The flue gas temperature measuring device 18 in the flue gas output pipe is installed at a position close to the ash bucket 17.

[0059] The ash bucket accumulated ash height measuring device 10 adopts a material level transmitter, and outputs a standard signal of 4-20 mA or 1-5 V and is connected with the data acquisition and control module 32. The data acquisition and control module 32 adopts an OVATION distributed control system, and converts the electrical signals such as temperature, valve opening degree, and flue gas damper opening degree accessed thereby into digital quantities to realize the functions of calculation and control. The ash bucket ash discharge valve 11 adopts an electric butterfly valve or a heavy hammer flap valve. The flue gas bypass valve 16, the flue gas tangential valve 22, the flue gas straight-through valve 25, and the denitration device isolation valve 26 adopt electric butterfly valves.

[0060] The specific embodiment of the present application further provides a flue gas bypass control method suitable for full-load process denitration, which is applied to the control system and comprises the following steps:

[0061] Step S1, set the temperature parameters of the denitration system alarm protection, that is, the low I value, low II value, high I value and high II value of the flue gas temperature at the inlet of the denitration device 31, wherein low II value < low I value < high I value < high II value;

[0062] Step S2, before the unit is connected to the grid, the flue gas bypass system is not put into operation, the data acquisition and control module 32 controls the denitration agent regulating valve 29 to be fully closed, the data acquisition and control module 32 controls the first flue gas passage flue gas damper 8 and the second flue gas passage flue gas damper 9 to be fully opened, the data acquisition and control module 32 controls the flue gas bypass valve 16, the flue gas tangential valve 22 and the denitration device isolation valve 26 to be fully closed, and the data acquisition and control module 32 controls the flue gas straight-through valve 25 to be fully opened. The boiler flue gas enters the air preheater 28 through the flue gas output pipe 19 and the flue gas straight-through pipe 24.

[0063] Step S3, the unit is connected to the grid, the data acquisition and control module 32 controls the flue gas tangential valve 22 to be fully opened, the data acquisition and control module 32 controls the denitration device isolation valve 26 to be fully opened, the data acquisition and control module 32 controls the flue gas straight-through valve 25 in the fully open state to be gradually closed to the straight-through valve 25, and the flue gas bypass valve 16 is gradually opened, so that the measurement value of the denitration device inlet flue gas temperature measuring device 20 is higher than the low I value and lower than the high I value. At this time, the data acquisition and control module 32 controls the denitration agent regulating valve 29 to be opened, and the denitration device 31 is put into operation. In this embodiment, the denitration device inlet flue gas temperature measuring device 20 adopts three E-type thermocouples, and the probes thereof are located at the center part of the pipe diameter. When the measurement values of two of the three E-type thermocouples are lower than or higher than the corresponding temperature parameters, it is considered that the measurement value of the denitration device inlet flue gas temperature measuring device 20 is lower than or higher than the corresponding temperature parameters. That is, when two of the three E-type thermocouples of the denitration device inlet flue gas temperature measuring device 20 have a measurement value higher than the low I value, it is considered that the measurement value of the denitration device inlet flue gas temperature measuring device 20 is higher than the low I value, and the same principle applies below.

[0064] Step S4, when the data acquisition and control module 32 controls the flue gas bypass valve 16 to be fully opened, and the measurement value of the denitration device inlet flue gas temperature measuring device 20 is still lower than the low I value, the data acquisition and control module 32 controls the opening degree of the first flue gas passage flue gas damper 8 and the second flue gas passage flue gas damper 9 to be closed, so that the amount of flue gas flowing to the flue gas bypass 15 is increased, and the measurement value of the denitration device inlet flue gas temperature measuring device 20 is ensured to be higher than the low I value. The automatic adjustment function of the flue gas bypass valve 16 is put into operation.

[0065] As Figure 3As shown, the automatic adjustment function of the flue gas bypass valve 16 is controlled by the data acquisition and control module 32 through the switching switch. When the switching switch is set to 1, the automatic adjustment function of the flue gas bypass valve 16 is turned on, and when the switching switch is set to 0, the automatic adjustment function of the flue gas bypass valve 16 is turned off.

[0066] Specifically, the following steps are included:

[0067] The target temperature value of the automatic adjustment of the flue gas bypass valve 16 is set, and the flue gas bypass valve 16 operates according to the target temperature value + Ts of the automatic adjustment, where Ts is the automatic adjustment bias, in units of ℃, which is given by the operator according to the operation needs, and can be 0-15℃. When the switching switch is set to 0, the flue gas bypass valve 16 exits the automatic adjustment function, and Ts = 0, at this time the flue gas bypass valve 16 is automatically fully closed; Figure 2 wherein Rc is the opening degree command signal of the flue gas bypass valve 16, in units of %; K is the conversion of the flue gas temperature command signal Tc to the opening degree command signal Rc of the flue gas bypass valve 16, in the case , in units of % / ℃.

[0068] When the switching switch is set to 1, the measured value Te of the denitration device inlet flue gas temperature measuring device 20 is compared with the target temperature value + Ts, and the deviation is input into the PID loop. The PID loop has a limiting function, and the limiting range is generally-10℃~+10℃, to prevent the output signal from changing greatly. The output command signal of the PID loop is converted to the opening degree command signal of the flue gas bypass valve 16 by K proportion, and the command signal controls the opening degree of the flue gas bypass valve 16, until the deviation between Te and the target temperature value + Ts is zero.

[0069] wherein the measured value Te of the denitration device inlet flue gas temperature measuring device 20 is the median value of the measured values of three E-type thermocouples.

[0070] Step S5, during the process of the unit from low load to high load, as the load of the unit increases, the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe gradually increases, and the data acquisition and control module 32 controls the flue gas bypass valve 16 to be in the automatic adjustment state, that is Figure 3the switch in the figure is set to 1, and the given Ts=0℃, the opening of the flue gas bypass valve 16 will gradually close, and the data acquisition and control module 32 controls the opening of the first flue gas passage flue gas damper 8 and the second flue gas passage flue gas damper 9 to gradually increase, when the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe is higher than the low I value, the flue gas bypass valve 16 is fully closed, and the flue gas bypass is out of operation. In this embodiment, the flue gas temperature measuring device 18 in the flue gas outlet pipe adopts three E-type thermocouples, and the probes are located at the center of the pipe diameter; when the measured values of two of the three E-type thermocouples are lower or higher than the corresponding temperature parameters, it is considered that the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe is lower or higher than the corresponding temperature parameters, that is, when two of the three E-type thermocouples of the flue gas temperature measuring device 18 in the flue gas outlet pipe have measured values higher than the low I value, it is considered that the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe is higher than the low I value, and the same principle follows.

[0071] Step S6, during the process of the unit from high load to low load operation, as the load of the unit decreases, the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe gradually decreases, when the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe is lower than the low I value, the data acquisition and control module 32 controls the flue gas bypass valve 16 to be in the automatic state, that is Figure 3 the switch in the figure is set to 1, and the given Ts=0℃, the opening of the flue gas bypass valve 16 will gradually close, and the data acquisition and control module 32 controls the opening of the first flue gas passage flue gas damper 8 and the second flue gas passage flue gas damper 9 to gradually increase, when the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe is higher than the low I value, the flue gas bypass valve 16 is fully closed, and the flue gas bypass is out of operation. In this embodiment, the flue gas temperature measuring device 18 in the flue gas outlet pipe adopts three E-type thermocouples, and the probes are located at the center of the pipe diameter; when the measured values of two of the three E-type thermocouples are lower or higher than the corresponding temperature parameters, it is considered that the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe is lower or higher than the corresponding temperature parameters, that is, when two of the three E-type thermocouples of the flue gas temperature measuring device 18 in the flue gas outlet pipe have measured values higher than the low I value, it is considered that the measured value of the flue gas temperature measuring device 18 in the flue gas outlet pipe is higher than the low I value, and the same principle follows.

[0072] Step S7, when the unit is switched from low load operation to grid separation shutdown, the measured value of the denitration device inlet flue gas temperature measuring device 20 is lower than the low II value, or the measured value of the denitration device inlet flue gas temperature measuring device 20 is higher than the high II value, the data acquisition and control module 32 controls the denitration agent regulating valve 29 to be fully closed, the data acquisition and control module 32 controls the first flue gas passage flue gas damper 8 and the second flue gas passage flue gas damper 9 to be fully opened, the data acquisition and control module 32 controls the flue gas straight-through valve 25 to be fully opened, the flue gas bypass valve 16, the flue gas tangential valve 22 and the denitration device isolation valve 26 are fully closed, and the boiler flue gas directly enters the air preheater 28 through the flue gas outlet pipe 19 and the flue gas straight-through pipe 24, so that the denitration device 31 is cut off, and the protection of the denitration device 31 is realized.

[0073] Further comprising step S8: the data acquisition and control module 32 controls the opening of the first flue gas passage flue gas damper 8, and further controls the flue gas flow in the first flue gas passage 5, so that the flue gas slows down, or the data acquisition and control module 32 controls the opening of the second flue gas passage flue gas damper 9, and further controls the flue gas flow in the second flue gas passage 14, so that the flue gas slows down, when the dust in the flue gas deposits in the ash bucket 17; when the ash bucket ash deposition height measuring device 10 measures that the ash deposition height of the ash bucket 17 is higher than the ash discharge height setting value, the data acquisition and control module 32 controls to open the ash bucket ash discharge valve 11 to discharge the dust deposited in the ash bucket 17 through the ash bucket ash discharge pipe 12; when the ash bucket ash deposition height measuring device 10 measures that the ash deposition height of the ash bucket 17 is lower than the ash discharge height setting value, the data acquisition and control module 32 controls to close the ash bucket ash discharge valve 11, and further stops the ash discharge.

[0074] Those skilled in the art can understand that the units of the examples described in combination with the embodiments disclosed herein can be realized in electronic hardware, computer software or a combination of both. In order to clearly illustrate the interchangeability of hardware and software, the components of the examples have been described in general terms in the above description. Whether the functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0075] In the embodiments provided in the present application, it should be understood that the division of units is only a logical functional division, and actual implementation can have another division manner, for example, multiple units can be combined as one unit, one unit can be split into multiple units, or some features can be ignored, etc.

[0076] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application.

Claims

1. A flue gas bypass control system suitable for full load process denitration, characterized in that, The application is applied to a boiler, comprising a first flue gas passage baffle (8), a second flue gas passage baffle (9), a flue gas bypass (15), a flue gas bypass valve (16), a flue gas temperature measuring device (18) in a flue gas outlet pipe, a flue gas outlet pipe (19), a flue gas temperature measuring device (20) at a denitration device inlet, a flue gas pipe (21) at the denitration device inlet, a flue gas tangential valve (22), a flue gas tangential pipe (23), a flue gas straight pipe (24), a flue gas straight valve (25), a denitration device isolation valve (26), a flue gas pipe (27) at a denitration device outlet, an air preheater (28), a denitration agent regulating valve (29), a denitration agent introduction pipe (30), a denitration device (31), a data acquisition and control module (32); A hearth (1) of a boiler is provided with two parallel first flue gas passages (5) and second flue gas passages (14); the first flue gas passage (5) is provided with a first flue gas passage baffle (8) at an outlet thereof for controlling flue gas flow in the first flue gas passage (5); the second flue gas passage (14) is sequentially provided with a low-temperature superheater (13), a second flue gas passage economizer (6) and a second flue gas passage baffle (9) for controlling flue gas flow in the second flue gas passage (14) from an inlet to an outlet; outlets of the first flue gas passage (5) and the second flue gas passage (14) are merged into a flue gas outlet pipe (19); the flue gas outlet pipe (19) is provided with a flue gas temperature measuring device (18) therein; an outlet of the flue gas outlet pipe (19) is in communication with an inlet of a flue gas straight pipe (24) and an inlet of a flue gas tangential pipe (23) respectively; An inlet of the flue gas bypass (15) is in communication with the second flue gas passage (14) and is arranged before the second flue gas passage economizer (6); a flue gas bypass valve (16) is arranged on the flue gas bypass (15) for controlling flue gas flow through the flue gas bypass (15); An outlet of the flue gas bypass (15) and an outlet of the flue gas tangential pipe (23) are in communication with an inlet of a denitration device inlet flue gas pipe (21) respectively; a flue gas tangential valve (22) is arranged on the flue gas tangential pipe (23) for switching control of whether flue gas flows through the denitration device (31); An outlet of the denitration device inlet flue gas pipe (21) is in communication with an inlet of the denitration device (31); a denitration device inlet flue gas temperature measuring device (20) is arranged at the inlet of the denitration device (31); an outlet of a denitration agent introduction pipe (30) is in communication with the inlet of the denitration device (31); a denitration agent regulating valve (29) is arranged on the denitration agent introduction pipe (30); an outlet of the denitration device (31) is in communication with an inlet of a denitration device flue gas pipe (27); an outlet of the denitration device flue gas pipe (27) is merged into the air preheater (28) with an outlet of the flue gas straight pipe (24); a denitration device isolation valve (26) is arranged on the denitration device flue gas pipe (27); a flue gas straight valve (25) is arranged on the flue gas straight pipe (24). The data acquisition and control module (32) is connected with the flue gas temperature measuring device at the inlet of the denitration device (20), the flue gas temperature measuring device (18) in the flue gas output pipe, the flue gas bypass valve (16), the flue gas tangential valve (22), the flue gas straight-through valve (25), the denitration device isolation valve (26), the denitration agent regulating valve (29), the flue gas baffle (8) of the first flue gas passage and the flue gas baffle (9) of the second flue gas passage, respectively, for comparing the flue gas temperature at the inlet of the flue gas output pipe (19) measured by the flue gas temperature measuring device (18) in the flue gas output pipe and the flue gas temperature at the inlet of the denitration device (31) measured by the flue gas temperature measuring device (20) at the inlet of the denitration device with corresponding set values, and controlling the opening degrees of the flue gas bypass valve (16), the flue gas tangential valve (22), the flue gas straight-through valve (25), the denitration device isolation valve (26), the denitration agent regulating valve (29), the flue gas baffle (8) of the first flue gas passage and the flue gas baffle (9) of the second flue gas passage according to the comparison results, so as to adjust the flue gas temperature at the inlet of the denitration device (31) or cut off the flue gas from the denitration device (31); The ash hopper (17), the ash hopper accumulated ash height measuring device (10), the ash hopper ash discharge valve (11) and the ash hopper ash discharge pipe (12) are further included; the outlets of the first flue gas passage (5) and the second flue gas passage (14) are combined and communicated with the inlet of the ash hopper (17), the outlet of the ash hopper (17) is communicated with the inlet of the ash hopper ash discharge pipe (12), the ash hopper accumulated ash height measuring device (10) is arranged in the ash hopper (17), the ash hopper ash discharge valve (11) is arranged on the ash hopper ash discharge pipe (12), and the ash hopper accumulated ash height measuring device (10) and the ash hopper ash discharge valve (11) are connected with the data acquisition and control module (32), respectively; the ash hopper accumulated ash height measuring device (10) is used for measuring the height of the accumulated ash in the ash hopper (17) and transmitting the measured data to the data acquisition and control module (32), and the data acquisition and control module (32) is further used for comparing the measured data of the ash hopper accumulated ash height measuring device (10) with a corresponding set fixed value, so as to control the opening and closing of the ash hopper ash discharge valve (11).

2. The flue gas bypass control system suitable for full load process denitration according to claim 1, characterized in that, The reheater (4) and the first flue gas passage economizer (7) are further arranged in the first flue gas passage (5), the flue gas flowing through the first flue gas passage (5) is first cooled by the reheater (4) and then further cooled by the first flue gas passage economizer (7), and the flue gas baffle (8) of the first flue gas passage is arranged after the economizer (7).

3. The flue gas bypass control system suitable for full load process denitration according to claim 1, characterized in that, The flue gas temperature measuring device (18) in the flue gas output pipe and the flue gas temperature measuring device (20) at the inlet of the denitration device each adopt three E-type thermocouples, and the probes thereof are located at the center of the pipe diameter.

4. The flue gas bypass control system suitable for full load process denitration according to claim 1, characterized in that, The ash hopper accumulated ash height measuring device (10) adopts a material level transmitter, outputs a standard signal of 4-20 mA or 1-5 V and is connected with the data acquisition and control module (32).

5. A flue gas bypass control method suitable for full load process denitration, characterized in that, The control system applied to any one of claims 1-4 comprises the following steps: Step S1, set the temperature parameters of the denitration system alarm protection, that is, the low I value, low II value, high I value and high II value of the flue gas temperature at the inlet of the denitration device (31), wherein low II value < low I value < high I value < high II value; Step S2, before the unit is connected to the grid, the flue gas bypass system is not put into operation, the data acquisition and control module (32) controls the denitration agent regulating valve (29) to be fully closed, the data acquisition and control module (32) controls the first flue gas passage flue gas damper (8) and the second flue gas passage flue gas damper (9) to be fully opened, the data acquisition and control module (32) controls the flue gas bypass valve (16), the flue gas tangential valve (22) and the denitration device isolation valve (26) to be fully closed, the data acquisition and control module (32) controls the flue gas straight-through valve (25) to be fully opened, and the boiler flue gas enters the air preheater (28) through the flue gas output pipe (19) and the flue gas straight-through pipe (24); Step S3, when the unit is connected to the grid, the data acquisition and control module (32) controls the flue gas tangential valve (22) to be fully opened, the data acquisition and control module (32) controls the denitration device isolation valve (26) to be fully opened, the data acquisition and control module (32) controls the flue gas straight-through valve (25) in the fully open state to be gradually closed to the fully closed state, and the flue gas bypass valve (16) is gradually opened, so that the measurement value of the denitration device inlet flue gas temperature measuring device (20) is higher than the low I value and lower than the high I value, at this time, the data acquisition and control module (32) controls the denitration agent regulating valve (29) to be opened, and the denitration device (31) is put into operation; Step S4, when the data acquisition and control module (32) controls the flue gas bypass valve (16) to be fully opened, and the measurement value of the denitration device inlet flue gas temperature measuring device (20) is still lower than the low I value, the data acquisition and control module (32) controls the opening degree of the first flue gas passage flue gas damper (8) and the second flue gas passage flue gas damper (9) to be closed, so that the amount of flue gas flowing to the flue gas bypass (15) is increased, the measurement value of the denitration device inlet flue gas temperature measuring device (20) is ensured to be higher than the low I value, and the automatic adjustment function of the flue gas bypass valve (16) is put into operation; Step S5, during the operation of the unit from low load to high load, as the load of the unit increases, the measurement value of the flue gas temperature measuring device (18) in the flue gas output pipe gradually increases, the data acquisition and control module (32) controls the flue gas bypass valve (16) to be in the automatic adjustment state, the opening degree of the flue gas bypass valve (16) is gradually closed, the data acquisition and control module (32) controls the opening degree of the first flue gas passage flue gas damper (8) and the second flue gas passage flue gas damper (9) to be gradually opened, when the measurement value of the flue gas temperature measuring device (18) in the flue gas output pipe is higher than the low I value, and the flue gas bypass valve (16) is fully closed, the flue gas bypass is out of operation; Step S6, during the process of the unit from high load to low load, as the unit load decreases, the flue gas temperature measuring device (18) in the flue gas output pipe gradually decreases, when the measured value of the flue gas temperature measuring device (18) in the flue gas output pipe is lower than the low I value, the data acquisition and control module (32) controls the flue gas bypass valve (16) to be in the automatic state, the opening degree of the flue gas bypass valve (16) will gradually open, the flue gas bypass is put into operation, according to the need of the operator, the opening degree of the first I flue gas passage flue gas damper (8) and the second I flue gas passage flue gas damper (9) is gradually closed, to ensure that the measured value of the denitration device inlet flue gas temperature measuring device (20) is higher than the low I value; Step S7, when the unit from low load operation to power grid split shutdown, the measured value of the denitration device inlet flue gas temperature measuring device (20) is lower than the low II value, or the measured value of the denitration device inlet flue gas temperature measuring device (20) is higher than the high II value, the data acquisition and control module (32) controls the denitration agent regulating valve (29) to be fully closed, the data acquisition and control module (32) controls the first I flue gas passage flue gas damper (8) and the second I flue gas passage flue gas damper (9) to be fully opened, the data acquisition and control module (32) controls the flue gas straight-through valve (25) to be fully opened, the flue gas bypass valve (16), the flue gas tangential valve (22) and the denitration device isolation valve (26) are fully closed, the boiler flue gas directly enters the air preheater (28) through the flue gas output pipe (19) and the flue gas straight-through pipe (24), so as to cut off the denitration device (31), and the protection of the denitration device (31) is realized.

6. The flue gas bypass control method for full load process denitration according to claim 5, characterized in that, Further comprising step S8: when the data acquisition and control module (32) controls the opening degree of the first I flue gas passage flue gas damper (8) to control the flue gas flow in the first I flue gas passage (5) to slow down, or the data acquisition and control module (32) controls the opening degree of the second I flue gas passage flue gas damper (9) to control the flue gas flow in the second I flue gas passage (14) to slow down, the dust in the flue gas will deposit in the ash bucket (17); when the ash bucket ash accumulation height measuring device (10) measures that the ash accumulation height of the ash bucket (17) is higher than the ash discharge height setting value, the data acquisition and control module (32) controls to open the ash bucket ash discharge valve (11) to discharge the dust deposited in the ash bucket (17) through the ash bucket ash discharge pipe (12); when the ash bucket ash accumulation height measuring device (10) measures that the ash accumulation height of the ash bucket (17) is lower than the ash discharge relief height setting value, the data acquisition and control module (32) controls to close the ash bucket ash discharge valve (11) to stop discharging ash.

7. The flue gas bypass control method for full load process denitration according to claim 5, characterized in that, The automatic adjustment function of the flue gas bypass valve (16) is specifically controlled by the data acquisition and control module (32) controlling the switching switch, when the switching switch is 1, the automatic adjustment function of the flue gas bypass valve (16) is put into operation, when the switching switch is 0, the flue gas bypass valve (16) exits the automatic adjustment function; Specifically comprising the following steps: The target temperature value of the automatic adjustment of the flue gas bypass valve (16) is set, and the flue gas bypass valve (16) operates according to the target temperature value of the automatic adjustment + Ts, wherein Ts is an automatic adjustment bias, which is given by the operator according to the operation needs; The measured value Te of the flue gas temperature measuring device (20) at the inlet of the denitration device is compared with the target temperature value + Ts, the deviation is input to the PID link, and the output instruction signal of the PID link is converted into the instruction signal for the opening degree of the flue gas bypass valve (16) through K proportion The instruction signal controls the opening degree of the flue gas bypass valve (16) until the deviation of Te from the target temperature value + Ts is zero.

8. The flue gas bypass control method for full load process denitration according to claim 5, characterized in that, The flue gas temperature measuring device (18) in the flue gas output pipe and the flue gas temperature measuring device (20) at the inlet of the denitration device each adopt three E-type thermocouples, and the probes thereof are located at the center part of the pipe diameter; when the measurement values of two of the three E-type thermocouples are lower than or higher than the corresponding temperature parameters, it is considered that the measurement value of the flue gas temperature measuring device (18) in the flue gas output pipe or the flue gas temperature measuring device (20) at the inlet of the denitration device is lower than or higher than the corresponding temperature parameters.

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