Horizontal flue continuous soot blowing device based on flue gas recirculation and control method

Abstract

The invention belongs to the technical field of thermal power generation, and particularly relates to a horizontal flue continuous soot blowing device based on flue gas recirculation. The horizontal flue continuous soot blowing device comprises a flue gas extraction and dust removal module, a heat exchanger module, a double-tank type compressed flue gas charging and discharging module, an in-furnace soot blowing module and a control module. The flue gas extraction and dust removal module comprises a circulating fan and a cyclone separator; the heat exchanger module includes: a heat exchanger; the double-tank type compressed flue gas charging and discharging module comprises a first gas storage tank, a second gas storage tank and control valves arranged at the output end and the input end of the first gas storage tank and the output end and the input end of the second gas storage tank respectively. The control module is in two-way communication with a distributed control system of an existing boiler system. The control module collects safety signals from the distributed control system and reports soot blowing system state information to the distributed control system. And through the circulating fan, the pretreated flue gas is compressed and stored in the two gas storage tanks to realize alternation of gas charging and gas discharging, so that continuous gas supply is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal power generation, and in particular relates to a horizontal flue continuous soot blowing device based on flue gas recirculation and a control method. Background Art

[0002] With the widespread application of flexible power generation deep peak-shaving mode, thermal power units need to adapt to load fluctuations and the instability of renewable energy generation, especially when running at low load or low flow rate, the flue gas flow rate is significantly reduced, and the ash accumulation problem in the flue is becoming increasingly serious. Traditional soot blowing methods often cannot effectively clean the deposited fly ash in a low flow rate environment, resulting in flue blockage, equipment failure, and even unit shutdown. The following is a detailed analysis of the existing technology:

[0003] 1. Long rod steam soot blower

[0004] Working principle: Long rod steam soot blower usually consists of multiple soot blowers installed in the boiler flue, each soot blower is connected to the external steam source through a long rod. When the boiler needs to blow soot, high-pressure steam is introduced into the soot blower through the steam pipe. The steam is ejected at high pressure and high speed, and directly impacts the ash layer in the flue through the nozzle of the soot blower.

[0005] Advantages: Strong soot blowing ability: can effectively remove dust accumulation, especially in high flow rate environment; Strong adaptability: can clean up large areas of dust accumulation, especially suitable for cleaning under high temperature and high pressure conditions.

[0006] Disadvantages: Steam soot blowing has a great impact on the heating surface of the boiler, and long-term use will cause wear and damage to the boiler. In addition, the steam consumption is large and the economy is poor, especially when operating at low load, it cannot guarantee continuous and efficient operation, and it is not suitable for horizontal flue environments with low flow rate and low flue gas volume.

[0007] 2. Sonic soot blower

[0008] Working principle: The sonic soot blower uses the vibration effect of high-frequency sound waves to remove the accumulated dust in the flue. The sound waves are generated by a specific vibration source and transmitted to the soot blower through the pipeline. The frequency and intensity of the sound waves will be adjusted according to the soot accumulation in the flue. When the sound waves propagate in the flue, periodic oscillations will be generated. The oscillation waves can loosen and vibrate the dust particles attached to the flue wall.

[0009] Advantages: Good economy: It can blow soot at high frequency, suitable for large areas, and save energy; Not affected by flow rate: The vibration frequency of sonic soot blowing is high, and it can work continuously under low flow rate conditions.

[0010] Disadvantages: Due to the relatively small force of the sound wave, it is unable to generate a large enough airflow or pressure to remove the ash deposited in the horizontal flue, especially in areas where the ash is thick or has strong adhesion, and the effect is poor. Its cleaning effect is limited, especially in the case of low-velocity flue gas and deep ash deposition, the effect is obviously inferior to other soot blowing technologies.

[0011] 3. Compressed air high speed soot blower

[0012] Working Principle: Compressed air high-speed soot blowers rely on compressed air in the air tank, which is introduced into the soot blower through the pipeline system. When the released compressed air passes through the nozzle, it will be ejected at a high speed, generating a strong airflow impact force to remove the accumulated ash in the flue. Usually, the compressed air will be ejected under high pressure, and quickly disturb and carry away the accumulated ash in the flue.

[0013] Advantages: Better economy: Compared with steam soot blowing, compressed air soot blowing is more economical and can save energy when running at low load; Strong high-frequency soot blowing ability: Suitable for quickly removing ash accumulation, can clean the ash accumulation area in a shorter time, especially in the horizontal flue, can effectively remove light ash accumulation.

[0014] Disadvantages: The traditional compressed air sootblowing system relies on a gas tank with limited capacity, which means that the gas will be exhausted in a short time and continuous sootblowing cannot be achieved. In addition, the intensity and duration of the airflow are limited, which cannot cope with the situation of thick soot accumulation, especially in the cleaning of deep soot accumulation, the effect is not as good as the steam sootblower.

[0015] The existing soot blowing technology generally has the following problems in horizontal flues that operate at low load for a long time:

[0016] 1. Unable to achieve continuous and efficient soot blowing: Existing soot blowing technology is difficult to provide continuous soot blowing capabilities, especially in environments with low flow rates and severe soot accumulation. It is impossible to effectively remove the soot accumulation, resulting in flue blockage and equipment shutdown.

[0017] 2. Poor economy: Steam soot blowing and compressed air soot blowing have poor economy when running at low load, and the long-term use cost is high, which makes it difficult to meet the needs of large-scale or high-frequency cleaning.

[0018] 3. Poor adaptability: Existing technologies perform poorly when dealing with complex working conditions with low flow rate and low flue gas volume, and cannot meet the special needs of deep peak regulation of flexible power generation.

[0019] Therefore, there is an urgent need for a horizontal flue continuous sootblowing device and control method based on flue gas recirculation to achieve a flue gas recirculation sootblowing effect with strong low-load adaptability, stable continuous operation, excellent energy-saving economy, and high universality of operating conditions, effectively prevent flue blockage, and ensure long-term stable operation of the boiler. Summary of the invention

[0020] The object of the present invention is to provide a horizontal flue continuous soot blowing device based on flue gas recirculation, comprising: a flue gas extraction and dust removal module, a heat exchanger module, a double-tank compressed flue gas charging and discharging module, an in-furnace soot blowing module and a control module;

[0021] The flue gas extraction and dust removal module includes: a circulation fan and a cyclone separator;

[0022] The heat exchanger module comprises: a heat exchanger;

[0023] The double-tank compressed flue gas charging and discharging module comprises: a first gas storage tank, a second gas storage tank, and control valves respectively arranged at the output end and the input end of the first gas storage tank and the second gas storage tank;

[0024] The circulating fan is connected to the flue gas extraction port of the existing boiler system, and the flue gas in the existing boiler system is input to the input end of the cyclone separator; the output end of the cyclone separator is connected to the input end of the heat exchanger to adjust the temperature of the flue gas filtered by the cyclone separator; the output end of the heat exchanger pressurizes the compressor of the circulating fan, and the constant temperature flue gas filtered by the cyclone separator is pressed into the first gas storage tank and the second gas storage tank; the first gas storage tank and the second gas storage tank are connected in parallel with each other; the output end of the double-tank compressed flue gas charging and discharging module is connected to the input end of the in-furnace soot blowing module; the control module is connected to the distributed control system of the existing boiler system to obtain data from the ash accumulation monitoring sensor, pressure sensor, flow sensor and temperature sensor of the existing boiler system; the control module uses the horizontal flue continuous soot blowing control method based on flue gas recirculation to control the control valve between the input and output ends of the double-tank compressed flue gas charging and discharging module and the first gas storage tank and the second gas storage tank, so as to realize the horizontal flue continuous soot blowing control of flue gas recirculation.

[0025] Furthermore, the flue gas extraction port is arranged before or after the dust collector of the existing boiler system, or at the tail flue of the existing boiler system; the flue gas flow rate processed by the flue gas extraction port is 5% to 15% of the total flue gas volume of the boiler.

[0026] Furthermore, the compressor pressurization range of the circulating fan is: the circulating fan pressurizes the flue gas to 0.2-0.6MPa, and the design pressure of the circulating fan is 1.0MPa to 1.2MPa to meet the high-pressure pulse soot blowing requirements; the double-tank compressed flue gas charging and discharging module is equipped with a safety valve, which automatically exhausts the air when the pressure exceeds the upper limit to protect the tank and system safety.

[0027] Further, the step of adjusting the temperature of the flue gas after being filtered by the cyclone separator comprises:

[0028] When the flue gas temperature is >350℃, the flue gas temperature is cooled to between 150 and 250℃;

[0029] When the flue gas temperature is <130℃, the flue gas temperature is raised to >130℃;

[0030] An insulation layer is provided outside the gas storage tank and pipeline of the double-tank compressed flue gas charging and discharging module to maintain the flue gas temperature.

[0031] Furthermore, the in-furnace sootblowing module includes: an air intake pipe, a ball check valve, a filter, a pneumatic butterfly valve, a pressure switch and a sootblower; one end of the air intake pipe of the sootblowing module is connected to the outlet of the double gas storage tank system, and is sequentially connected to the ball check valve, the filter, the pneumatic butterfly valve and the pressure switch to ensure that the airflow can only flow in one direction to prevent backflow from causing system failure. The pneumatic butterfly valve and the pressure switch are connected to an external automatic control system, and finally the sootblowing connection sootblower is arranged equidistantly at the end of the pipe, and the sootblower is placed 150-200mm above the ash accumulation area.

[0032] Furthermore, the in-furnace sootblowing module is provided with a spare interface, and when the flue gas recirculation system is under maintenance, fails, or the boiler is shut down, the traditional gas source can still be used to ensure the continuity of sootblowing.

[0033] Furthermore, the dual-tank compressed flue gas charging and discharging module is provided with an expansion interface, which can realize expansion from dual tanks to multi-tank modular parallel connection.

[0034] Another object of the present invention is to provide a control method for a horizontal flue continuous sootblowing device based on flue gas recirculation, comprising the following steps:

[0035] The control module performs two-way communication with the distributed control system of the existing boiler system: the control module collects safety signals from the distributed control system and reports the soot blowing system status information to the distributed control system; the safety signals include: boiler load, flue gas flow rate, gas storage tank pressure, soot accumulation sensor, temperature, valve status; the soot blowing system status information includes: soot blowing status and abnormal information of gas storage tank pressure; when the distributed control system performs an emergency shutdown, the soot blowing system correspondingly shuts down the high-voltage pulse program and enters a safe waiting state;

[0036] The control module performs output control, including: fan frequency conversion adjustment, valve opening switching, setting of soot blowing strategy and execution of strategy logic.

[0037] Furthermore, the setting of the sootblowing strategy includes:

[0038] Divide the load interval according to the load L; the load interval includes:

[0039] High load range: L ≥ 80%;

[0040] Medium and high load range: 50%≤L<80%;

[0041] Medium and low load range: 30%≤L<50%;

[0042] Low load range: L < 30%;

[0043] Set the ash deposition height threshold, and set three thresholds: X1, X2, X3;

[0044] During boiler operation or testing, continue to set through on-line ash measurement and historical data, including:

[0045] X1 ≥ X2 ≥ X3

[0046] X1 corresponds to the upper limit of the allowable deposition thickness under high load conditions;

[0047] X2 is used for the "medium-high load" range of 50% - 80%

[0048] X3 corresponds to the lower ash deposition amount threshold that can be tolerated under medium-low load;

[0049] Set the soot blowing mode, including: timed soot blowing and immediate soot blowing;

[0050] Timed soot blowing: Conducted in a relatively gentle continuous low pressure or medium pressure manner, which can save energy and maintain the basic cleanliness of the flue; 3 - 5 minutes is the basic single soot blowing duration;

[0051] Immediate soot blowing: Once the ash layer exceeds the threshold, immediately trigger soot blowing to quickly impact and strip the accumulated ash; After the ash deposition drops below the threshold, the timed soot blowing mode can be switched back;

[0052] Set the ash deposition sensor layout strategy: Priority is given to setting ash deposition sensors in the horizontal flue, return zone, elbow, and turning section; If there are differences in the ash layer thickness measured at multiple points, trigger the immediate soot blowing mode according to the maximum value to avoid ignoring local severe ash accumulation.

[0053] Furthermore, the execution strategy logic includes:

[0054] For the high load range (L ≥ 80%):

[0055] If the ash deposition height < X1, timed soot blowing: once every 8 hours, 0.2 - 0.3 MPa;

[0056] If the ash deposition height ≥ X1, immediately start soot blowing until the ash deposition height drops below X1, then resume to the "8-hour timed soot blowing" mode; 0.4 - 0.6 MPa to quickly break up stubborn ash layers; Cooperate with short-cycle continuous spraying and multiple cycles until the monitored ash thickness returns to normal;

[0057] For the medium-high load range (50% ≤ L < 80%):

[0058] If the ash deposition height < X2, sootblowing is carried out regularly: once every 4 hours, at 0.25 - 0.4 MPa;

[0059] If the ash deposition height ≥ X2, sootblowing is immediately started, at 0.5 - 0.6 MPa. Pulse sootblowing is preferably used to enhance the effect, and the spraying duration is appropriately increased; medium-pressure continuous purging is superimposed to ensure that the dust does not accumulate again in the short term, continuing until the ash deposition height drops below X2;

[0060] For the medium and low load range: 30% ≤ L < 50%:

[0061] If the ash deposition height < X3, sootblowing is carried out regularly: once every 1 hour, at 0.3 - 0.5 MPa;

[0062] If the ash deposition height ≥ X3, sootblowing is immediately started, at 0.5 - 0.6 MPa. High-pressure pulses are mainly used, combined with short-cycle continuous spraying; dense pulses can peel off the thickened ash layer in a short time to avoid the risk of blockage; and inspections and re-sootblowing are carried out once every 1 hour until the ash deposition height < X3.

[0063] The beneficial effects of the present invention are as follows:

[0064] The purpose of the present invention is to propose a continuous sootblowing technology and method based on flue gas recirculation. By optimizing the flue gas flow and adopting a continuous sootblowing method, the problem that the existing technology cannot efficiently remove ash deposits under low flow rate and low load conditions is solved. Specifically, the present invention will solve the following technical problems:

[0065] 1. Provide a sootblowing device and method that can continuously operate in a low flow rate and low load environment, ensure the timely removal of ash deposits in the flue, and prevent flue blockage.

[0066] 2. Overcome the problem that the sootblowing equipment in the existing technology cannot operate continuously, and achieve continuous and efficient ash cleaning effects through flue gas recirculation technology.

[0067] 3. Reduce energy consumption, provide a more economical sootblowing technology, reduce the dependence on external energy, especially under the condition of flexible power generation and deep peak shaving.

[0068] 4. Provide a sootblowing technology that can adapt to different ash deposition situations and can operate stably under complex conditions, ensure the long-term stable operation of the boiler, and avoid unit shutdown caused by ash deposition. Description of the Drawings

[0069] Figure 1 It is a schematic structural diagram of a horizontal flue continuous sootblowing device based on flue gas recirculation of the present invention;

[0070] Figure 2It is a schematic diagram of the installation position of the horizontal flue continuous soot blowing device based on flue gas recirculation in an existing boiler system according to an embodiment of the present invention;

[0071] Figure 3 It is a structural schematic diagram of a cyclone separator according to an embodiment of the present invention;

[0072] Figure 4 This is a schematic structural diagram of a sootblowing module in a furnace according to an embodiment of the present invention;

[0073] Among them, 1. cyclone separator, 2. check valve, 3. heat exchanger, 4. check valve, 51. first gas storage tank, 52. second gas storage tank, 6. furnace soot blowing module, 7 circulation fan, 61. ball check valve, 62. filter, 63. pneumatic butterfly valve, 64. pressure switch, 65. soot blower, A. soot blowing point. DETAILED DESCRIPTION

[0074] The present invention provides a horizontal flue continuous soot blowing device and a control method based on flue gas recirculation, and the present invention is further described in detail below in conjunction with the accompanying drawings.

[0075] like Figure 1 The embodiment of the present invention shown discloses a horizontal flue continuous sootblowing device based on flue gas recirculation, comprising: a flue gas extraction and dust removal module, a heat exchanger module, a double-tank compressed flue gas charging and discharging module, an in-furnace sootblowing module 6 and a control module;

[0076] The smoke extraction and dust removal module includes: a circulating fan 7 and a cyclone separator 1;

[0077] The heat exchanger module comprises: a heat exchanger 3;

[0078] The double-tank compressed flue gas charging and discharging module comprises: a first gas storage tank 51, a second gas storage tank 52, and control valves respectively arranged at the output end and the input end of the first gas storage tank 51 and the second gas storage tank 52;

[0079] The circulating fan 7 is connected to the flue gas extraction port of the existing boiler system, and the flue gas in the existing boiler system is input to the input end of the cyclone separator 1; the output end of the cyclone separator 1 is connected to the input end of the heat exchanger 3 to adjust the temperature of the flue gas filtered by the cyclone separator 1; the output end of the heat exchanger 3 pressurizes the compressor of the circulating fan 7, and the constant temperature flue gas filtered by the cyclone separator 1 is pressed into the first gas storage tank 51 and the second gas storage tank 52; the first gas storage tank 51 and the second gas storage tank 52 are connected in parallel with each other; the output end of the double-tank compressed flue gas charging and discharging module is connected to the input end of the in-furnace soot blowing module 6; the control module is connected to the distributed control system of the existing boiler system to obtain the data of the ash accumulation monitoring sensor, pressure sensor, flow sensor and temperature sensor of the existing boiler system; the control module uses the horizontal flue continuous soot blowing control method based on flue gas recirculation to control the input and output ends of the double-tank compressed flue gas charging and discharging module and the control valve between the first gas storage tank 51 and the second gas storage tank 52, so as to realize the horizontal flue continuous soot blowing control of flue gas recirculation.

[0080] In this embodiment, a suitable position of the tail flue is selected according to the actual boiler structure, a flue gas extraction port is set, and part of the flue gas is led out by the corresponding pipeline. After passing through the cyclone separator 1 (i.e., fly ash cyclone separator), fly ash with larger particle size is removed to protect subsequent equipment. At this time, the flue gas temperature is detected. If the flue gas temperature is too high or too low, it enters the heat exchanger for adjustment. Through the circulating fan, the pretreated flue gas is compressed and stored in two gas storage tanks A and B to achieve the rotation of inflation / deflation, thereby ensuring continuous gas supply. After meeting the pressure requirements, the gas storage tank transports the compressed flue gas to the original soot blowing system through the pipeline and the control valve group. In the original soot blower (or nozzle) area, the ash accumulation in the heating surface, horizontal flue or exhaust pipe is cleaned. The system retains the original functions, and at the same time adds automatic switching or parallel gas supply mode for "flue gas recirculation" gas supply. The data is sent to the control system through load signals (connected to DCS), dust accumulation monitoring sensors, and pressure / flow / temperature sensors to comprehensively determine whether to trigger soot blowing and adjust the frequency and intensity of soot blowing.

[0081] This patent includes the following components: flue gas extraction and dust removal module, heat exchanger, compressor and double gas storage tank, furnace soot blowing module, control module. The components are introduced as follows:

[0082] 1. Flue gas extraction and preliminary dust removal module

[0083] In this embodiment, the horizontal flue continuous soot blowing device based on flue gas recirculation is installed at the existing boiler system. Figure 2 As shown in the figure, the position of the flue gas extraction port: arranged before or after the dust collector, or selecting a suitable position in the tail flue according to the actual boiler structure (pressure and temperature are stable, and dust concentration is relatively controllable); Figure 2 Point A in the middle represents the soot blowing point.

[0084] The flue gas extraction port is arranged before or after the dust collector of the existing boiler system, or at the tail flue of the existing boiler system; the flue gas flow rate processed by the flue gas extraction port is 5% to 15% of the total flue gas volume of the boiler.

[0085] In this embodiment, according to the unit scale and the required soot blowing gas volume, the flue gas flow rate is generally processed to be 5% to 15% of the total flue gas volume of the boiler; in this embodiment, the structure of the cyclone separator is as follows: Figure 3 shown.

[0086] 2. Heat exchanger

[0087] The step of adjusting the temperature of the flue gas after being filtered by the cyclone separator 1 comprises:

[0088] When the flue gas temperature is >350℃, the flue gas temperature is cooled to between 150 and 250℃;

[0089] When the flue gas temperature is <130℃, the flue gas temperature is raised to >130℃;

[0090] An insulation layer is provided outside the gas storage tank and pipeline of the double-tank compressed flue gas charging and discharging module to maintain the flue gas temperature.

[0091] In this embodiment, if the flue gas temperature is too high (>350°C), it can be cooled to about 150-250°C to protect the fan and gas tank; if the flue gas temperature is low, possibly below the acid dew point (such as <130°C), it needs to be raised to a safe temperature range. When the boiler burns coal with a high sulfur content, components such as SO2 / SO3 in the flue gas are prone to acid condensation when encountering low temperatures. The temperature can be controlled above the acid dew point (such as >130°C or higher, depending on the coal quality); an insulation layer is set outside the gas tank and pipeline to maintain the flue gas temperature.

[0092] 3. Circulation fan and double air tank

[0093] The compressor pressurization range of the circulating fan 7 is: the circulating fan pressurizes the flue gas to 0.2-0.6MPa, and the design pressure of the circulating fan 7 is 1.0MPa to 1.2MPa to meet the high-pressure pulse soot blowing requirements; the double-tank compressed flue gas charging and discharging module is equipped with a safety valve, which automatically exhausts the air when the pressure exceeds the upper limit to protect the tank and the system safety.

[0094] The in-furnace sootblowing module 6 is provided with a spare interface, and when the flue gas recirculation system is under maintenance, fails, or the boiler is shut down, the traditional gas source can still be used to ensure the continuity of sootblowing.

[0095] The dual-tank compressed flue gas charging and discharging module is provided with an expansion interface, which can realize expansion from dual tanks to multi-tank modular parallel connection.

[0096] In this embodiment, the circulating fan usually pressurizes the flue gas to 0.2-0.6MPa, and the dual channels ensure continuous gas supply to the sootblowing system to avoid intermittent gas supply or pressure fluctuations due to exhaustion of gas storage in a single gas storage tank. The effective volume V of each tank is usually determined based on the total gas consumption of sootblowing, sootblowing interval and other parameters, and can generally meet the continuous sootblowing requirements of several minutes to tens of minutes. The design pressure is generally designed to 1.0MPa or 1.2MPa to meet the high-pressure pulse sootblowing requirements; the safety valve can automatically exhaust when the pressure exceeds the upper limit to protect the tank and system safety. The system retains a spare interface (or quick switching valve) connected to traditional compressed air or steam. When the flue gas recirculation system is overhauled, fails or the boiler is shut down, the traditional gas source can still be used to ensure the continuity of sootblowing. If the unit is large in scale, it can be further expanded from "double tanks" to modular parallel connection of multiple tanks.

[0097] Another embodiment of the present invention further discloses a control method for the horizontal flue continuous sootblowing device based on flue gas recirculation according to the present invention, comprising the following steps:

[0098] The control module performs two-way communication with the distributed control system of the existing boiler system: the control module collects safety signals from the distributed control system and reports the soot blowing system status information to the distributed control system; the safety signals include: boiler load, flue gas flow rate, gas storage tank pressure, soot accumulation sensor, temperature, valve status; the soot blowing system status information includes: soot blowing status and abnormal information of gas storage tank pressure; when the distributed control system performs an emergency shutdown, the soot blowing system correspondingly shuts down the high-voltage pulse program and enters a safe waiting state;

[0099] The control module performs output control, including: fan frequency conversion adjustment, valve opening switching, setting of soot blowing strategy and execution of strategy logic.

[0100] The specific implementation process is as follows:

[0101] (1) Pipeline and valve layout

[0102] A diverter valve is arranged on the pipeline from the flue gas extraction end to the gas storage tank, so that the flue gas can selectively enter tank A or tank B. A switching valve is also arranged on the gas outlet pipeline from the gas storage tank to the soot blower, so that the high-pressure flue gas from tank A or tank B can be supplied to the soot blowing pipeline separately or in parallel.

[0103] (2) Rotation Logic

[0104] Inflating stage: Tank A is delivering pressurized flue gas to the soot blowing system (degassing stage). At the same time, Tank B extracts air from the flue gas circuit after dust removal through the circulating fan and stores it under pressure (inflating stage).

[0105] (3) Switching phase:

[0106] When the internal pressure of tank A drops to the preset lower limit, the intelligent control system issues a switching command; the air outlet valve of tank A is closed and the air outlet valve of tank B is opened; tank A switches to the inflation stage and tank B switches to the deflation stage; this process is repeated alternately to achieve a continuous and uninterrupted supply of sootblowing air.

[0107] (4) Automation and security protection

[0108] Pressure sensor: detects the pressure values ​​of tank A and tank B in real time; control system: automatically switches the valve when it detects that the pressure of the gas tank reaches the upper / lower threshold; safety drain valve: prevents the abnormal increase of the gas tank pressure and provides safety protection for the system (for example, automatically opens the drain valve when the high pressure exceeds the limit).

[0109] Design pressure (Pd): 1.0MPa

[0110] Safety valve setting: 1.0MPa (100% Pd)

[0111] High pressure alarm (PH): 0.8MPa (80% Pd)

[0112] Low pressure alarm (PL): 0.25MPa (slightly higher than the minimum effective soot blowing pressure)

[0113] 4. Sootblowing module in furnace

[0114] In this embodiment, the structure of the soot blowing module in the furnace is as follows: Figure 4 The sootblowing module 6 in the furnace includes: an air intake pipeline, a ball check valve 61, a filter 62, a pneumatic butterfly valve 63, a pressure switch 64 and a sootblower 65; one end of the air intake pipeline of the sootblowing module is connected to the outlet of the double gas storage tank system, and is sequentially connected to the ball check valve 61, the filter 62, the pneumatic butterfly valve 63 and the pressure switch 64 to ensure that the airflow can only flow in one direction to prevent the backflow from causing system failure. The pneumatic butterfly valve 63 and the pressure switch 64 are connected to the external automatic control system, and finally the sootblowing connection sootblower 65 is arranged at an equal distance at the end of the pipeline, and the sootblower 65 is placed 150-200mm above the soot accumulation part.

[0115] In this embodiment, the sootblowing module is mainly composed of an air intake pipeline, a ball check valve 61, a filter 62, a pneumatic butterfly valve 63, a pressure switch 64 and a sootblower 65. One end of the air intake pipeline of the sootblowing module is connected to the outlet of the dual gas storage tank system, and is connected in sequence to the ball check valve 61, the filter 62, the pneumatic butterfly valve 63 and the pressure switch 64 to ensure that the airflow can only flow in one direction to prevent backflow from causing system failure. The pneumatic butterfly valve 63 and the pressure switch 64 are connected to the external automatic control system. Finally, the sootblowing connection sootblower 65 is arranged at equal distances at the end of the pipeline, and the sootblower 65 is placed 150-200mm above the dust accumulation part. After the clean and constant temperature flue gas of the dual gas storage tank system passes through the pipeline from the check valve to the pressure switch 64, it is ejected at a high speed in the sootblower 65, generating a strong airflow impact force, quickly disturbing and taking away the dust accumulation in the flue.

[0116] 5. Control module

[0117] Collect signals: boiler load, flue gas flow rate, gas storage tank pressure, ash accumulation sensor, temperature, valve status, etc. Communicate with the boiler DCS system in two directions to obtain important safety signals (such as furnace negative pressure, furnace temperature, drum water level), and feed back information such as "soot blowing status" or "abnormal gas storage tank pressure" to DCS. When DCS executes an emergency shutdown, the soot blowing system will shut down the high-voltage pulse program accordingly and enter a safe waiting state.

[0118] Output control: fan frequency conversion adjustment, valve opening switching, soot blowing frequency and strategy execution.

[0119] Ash deposition sensor layout strategy: Ash deposition sensors are preferentially set in “weak areas” prone to ash accumulation, such as horizontal flues, return areas, elbows, and turning sections. If there are differences in the ash layer thickness measured at multiple points, the “instant ash blowing” can be triggered according to the maximum value to avoid local severe ash accumulation being ignored.

[0120] The soot blowing strategy setting includes:

[0121] Divide the load interval according to the load L; the load interval includes:

[0122] High load range: L ≥ 80%;

[0123] Medium and high load range: 50%≤L<80%;

[0124] Medium and low load range: 30%≤L<50%;

[0125] Low load range: L<30%;

[0126] Set the ash deposition height threshold, and set three thresholds: X1, X2, and X3;

[0127] During boiler operation or testing, settings are continued through online ash measurement and historical data, including:

[0128] X1≥X2≥X3

[0129] X1 corresponds to the upper limit of deposition thickness allowed under high load conditions;

[0130] X2 is used in the "medium to high load" range of 50% to 80%.

[0131] X3 corresponds to the lower ash deposition threshold that can be tolerated under low and medium loads;

[0132] Set the soot blowing mode, including: timed soot blowing and instant soot blowing;

[0133] Timed soot blowing: It is carried out in a relatively gentle continuous low-pressure or medium-pressure manner, which can save energy and maintain the basic cleanliness of the flue. The basic single soot blowing time is 3 to 5 minutes;

[0134] Instant soot blowing: Once the ash layer exceeds the threshold, soot blowing is triggered immediately to quickly impact and remove the accumulated ash; when the ash deposition drops below the threshold, the system can switch back to the timed soot blowing mode;

[0135] Set the ash deposition sensor layout strategy: ash deposition sensors should be set preferentially in horizontal flues, return areas, elbows, and turning sections; if there are differences in the ash layer thickness measured at multiple points, the immediate soot blowing mode will be triggered according to the maximum value to avoid local severe ash accumulation being ignored.

[0136] In this embodiment, the soot blowing strategy includes:

[0137] (1) Basic criteria

[0138] (1.1) Load range division

[0139] High load range: L ≥ 80%

[0140] Medium and high load range: 50% ≤ L < 80%

[0141] Medium and low load range: 30% ≤ L < 50%

[0142] (1.2) Ash deposition height threshold

[0143] Set three thresholds: X1, X2, and X3.

[0144] It is generally recommended that during boiler operation or testing, the following principles be determined comprehensively through online ash measurement or historical data:

[0145] X1≥X2≥X3 (example, specific settings can be made according to actual working conditions)

[0146] X1 corresponds to the upper limit of deposition thickness allowed under high load conditions;

[0147] X2 is used for the "medium to high load" range of 50% to 80%

[0148] X3 corresponds to the lower ash deposition threshold that can be tolerated under medium to low loads (since the ash accumulation is more likely to increase due to the low flow rate, the threshold is relatively stricter);

[0149] (1.3) Soot blowing mode

[0150] Timed soot blowing: It is carried out in a relatively gentle continuous low-pressure or medium-pressure manner, which can save energy and maintain the basic cleanliness of the flue. The basic single soot blowing duration is 3 to 5 minutes.

[0151] Immediate soot blowing: Once the ash layer exceeds the threshold, soot blowing is immediately triggered to quickly impact and strip the accumulated ash; after the ash deposition is reduced below the threshold, it can be switched back to the timed soot blowing mode.

[0152] The execution strategy logic includes:

[0153] For the high load range (L≥80%):

[0154] If the ash deposition height < X1, timed soot blowing: once every 8 hours, 0.2 - 0.3 MPa;

[0155] If the ash deposition height ≥ X1, immediate soot blowing is started until the ash deposition height drops below X1, and then it returns to the "8-hour timed soot blowing" mode; 0.4 - 0.6 MPa to quickly break up the stubborn ash layer; combined with short-cycle continuous spraying, multiple cycles are carried out until the monitored ash thickness returns to normal;

[0156] For the medium to high load range (50%≤L<80%):

[0157] If the ash deposition height < X2, timed soot blowing: once every 4 hours, 0.25 - 0.4 MPa;

[0158] If the ash deposition height ≥ X2, immediate soot blowing is started, 0.5 - 0.6 MPa, and pulse soot blowing is preferentially used to enhance the effect and the spraying duration is appropriately increased; superimposed with continuous purging at medium pressure to ensure that the dust does not accumulate again in the short term, and continue until the ash deposition height drops below X2;

[0159] For the medium to low load range: 30%≤L<50%:

[0160] If the ash deposition height < X3, timed soot blowing: once every 1 hour, 0.3 - 0.5 MPa;

[0161] If the ash deposition height ≥ X3, immediate soot blowing is started, 0.5 - 0.6 MPa, mainly with high-pressure pulses, combined with short-cycle continuous spraying; the dense pulses can strip the thickened ash layer in a short time to avoid the risk of blockage; and inspections and repeated soot blowing are maintained once every 1 hour until the ash deposition height < X3.

[0162] (2) Strategy Logic

[0163] 1. High load range (L≥80%)

[0164] Ash deposition height < X1, regular sootblowing: once every 8 hours, 0.2 - 0.3 MPa (continuous sootblowing at medium pressure).

[0165] Ash deposition height ≥ X1, start sootblowing immediately, until the ash deposition height drops below X1, then resume to the "regular sootblowing every 8 hours" mode. 0.4 - 0.6 MPa (high - pressure pulse or enhanced purging), to quickly break up stubborn ash layers; short - cycle continuous spraying (such as frequency of 2 - 3 minutes) can be combined, with multiple cycles, until the monitored ash thickness returns to normal.

[0166] 2. Medium - high load range (50% ≤ L < 80%)

[0167] Ash deposition height < X2, regular sootblowing: once every 4 hours, 0.25 - 0.4 MPa (medium pressure or pulse)

[0168] Reason: The flue gas velocity in this range is smaller than that in the high - load range, but still has a certain self - cleaning ability; compared with the high - load range, the sootblowing cycle needs to be shortened to prevent excessive dust accumulation.

[0169] Ash deposition height ≥ X2, start sootblowing immediately, 0.5 - 0.6 MPa (high - pressure pulse), preferably use pulse sootblowing to enhance the effect, and appropriately increase the spraying duration; continuous purging at medium pressure can be superimposed to ensure that dust does not accumulate again in the short term. Continue until the ash deposition height drops below X2.

[0170] 3. Medium - low load range: 30% ≤ L < 50%

[0171] Ash deposition height < X3, regular sootblowing: once every 1 hour, 0.3 - 0.5 MPa (relatively high medium continuous or pulse),

[0172] Reason: At this time, the flue gas velocity decreases significantly, and ash deposition is very easy; therefore, regular sootblowing with a higher frequency (once every 1 hour) is adopted to prevent the ash layer from quickly accumulating to a dangerous level.

[0173] Ash deposition height ≥ X3, start sootblowing immediately, 0.5 - 0.6 MPa (high - pressure continuous or pulse), mainly high - pressure pulse, combined with short - cycle continuous spraying; dense pulses can peel off the thickened ash layer in a short time to avoid the risk of blockage. And maintain the inspection and re - sootblowing once every 1 hour until the ash deposition height < X3

[0174] By implementing the above technical solutions, the present invention has the following technical effects:

[0175] 1. Realize continuous soot blowing and eliminate air shortage

[0176] Through flue gas recirculation and the rotation of double gas tanks for gas storage, a stable and long-term gas supply can be provided, overcoming the problem of traditional compressed air systems where the gas tanks are easily exhausted in a short period of time and soot blowing cannot be carried out continuously.

[0177] 2. Adapt to multiple load conditions and high flexibility

[0178] The system can automatically adjust the soot blowing pressure, frequency and mode (combination of timed soot blowing and instant soot blowing) according to the unit load (30% to 100% peak load range) and the soot accumulation in the flue. It can still maintain efficient soot cleaning under low load conditions to meet the needs of flexible power generation and deep peak load regulation.

[0179] 3. Reduce external energy consumption and improve economic efficiency

[0180] Directly use the flue gas at the tail of the boiler as the main gas source to reduce or replace the dependence on external compressed air or steam; compared with pure steam soot blowing and a separate compressed air system, energy consumption and operating costs are greatly reduced, and the overall economic benefits are higher.

[0181] 4. Reduce the risk of erosion and wear of the heated surface

[0182] Compared with high-pressure steam soot blowing, the use of pressure-regulated recirculated flue gas to perform timed and pulsed soot blowing in an appropriate pressure range can reduce the strong scouring of the heating surface and extend the service life of the equipment.

[0183] 5. High degree of intelligence and precise dust cleaning

[0184] With the help of ash layer thickness sensors, flow / pressure sensors and intelligent control algorithms, real-time monitoring and feedback of ash accumulation conditions can be carried out, and “blowing occurs when ash is seen, and less blowing occurs when there is no ash” can be achieved, thereby optimizing the energy consumption of soot blowing and improving the soot blowing effect.

[0185] 6. Easy to integrate with the original system, low transformation cost

[0186] Without changing the original soot blower 65, pipeline layout and control system, it is only necessary to add a flue gas extraction port, a heat exchange / dust removal device, a gas storage tank and a valve group at the tail of the boiler to achieve upgrading and transformation; the original steam or compressed air system can be used as a backup or coordination to improve system reliability.

[0187] 7. Reduce downtime and failure risks

[0188] By maintaining continuous and effective ash cleaning in the flue, the risks of flue blockage, poor circulation, equipment corrosion and shutdown caused by ash accumulation can be reduced, thereby improving the overall operating stability and safety of the unit.

[0189] 8. Give equal weight to environmental protection and energy conservation

[0190] Reusing it in the flue gas emission system at the tail end of the boiler can, on the one hand, fully recover and utilize part of the kinetic energy and thermal energy of the flue gas; on the other hand, it can avoid ineffective external discharge, save primary energy consumption, and meet the requirements of green energy conservation.

Claims

1. A horizontal flue continuous sootblowing device based on flue gas recirculation, characterized in that: include: A flue gas extraction and dust removal module, a heat exchanger module, a double-tank compressed flue gas charging and discharging module, an in-furnace soot blowing module (6), and a control module; The smoke extraction and dust removal module comprises: a circulation fan (7) and a cyclone separator (1); The heat exchanger module comprises: a heat exchanger (3); The double-tank compressed flue gas charging and discharging module comprises: a first gas storage tank (51), a second gas storage tank (52), and control valves respectively arranged at the output end and the input end of the first gas storage tank (51) and the second gas storage tank (52); The circulating fan (7) is connected to the smoke extraction port of the existing boiler system, and the smoke in the existing boiler system is input to the input end of the cyclone separator (1); the output end of the cyclone separator (1) is connected to the input end of the heat exchanger (3), and the temperature of the smoke after being filtered by the cyclone separator (1) is adjusted; the output end of the heat exchanger (3) pressurizes the compressor of the circulating fan (7), and the constant temperature smoke after being filtered by the cyclone separator (1) is pressed into the first gas storage tank (51) and the second gas storage tank (52); the first gas storage tank (51) and the second gas storage tank (52) are connected to each other. The output end of the double-tank compressed flue gas charging and discharging module is connected to the input end of the soot blowing module (6) in the furnace; the control module is connected to the distributed control system of the existing boiler system to obtain data from the soot accumulation monitoring sensor, pressure sensor, flow sensor and temperature sensor of the existing boiler system; the control module uses a horizontal flue continuous soot blowing control method based on flue gas recirculation to control the input and output ends of the double-tank compressed flue gas charging and discharging module and the control valves between the first gas storage tank (51) and the second gas storage tank (52), so as to realize the horizontal flue continuous soot blowing control of flue gas recirculation.

2. The horizontal flue continuous sootblowing device based on flue gas recirculation according to claim 1 is characterized in that: The flue gas extraction port is arranged before or after the dust collector of the existing boiler system, or at the tail flue of the existing boiler system; the flue gas flow rate processed by the flue gas extraction port is 5% to 15% of the total flue gas volume of the boiler.

3. The horizontal flue continuous sootblowing device based on flue gas recirculation according to claim 1 is characterized in that: The compressor of the circulating fan (7) has a pressurization range of: the circulating fan pressurizes the flue gas to 0.2-0.6 MPa, and the design pressure of the circulating fan (7) is 1.0 MPa to 1.2 MPa to meet the requirements of high-pressure pulse soot blowing; the double-tank compressed flue gas charging and discharging module is provided with a safety valve, and when the pressure exceeds the upper limit, the exhaust is automatically performed to protect the tank body and the system safety.

4. The horizontal flue continuous sootblowing device based on flue gas recirculation according to claim 1 is characterized in that: The step of adjusting the temperature of the flue gas after being filtered by the cyclone separator (1) comprises: When the flue gas temperature is >350℃, the flue gas temperature is cooled to between 150 and 250℃; When the flue gas temperature is <130℃, the flue gas temperature is raised to >130℃; An insulation layer is provided outside the gas storage tank and pipeline of the double-tank compressed flue gas charging and discharging module to maintain the flue gas temperature.

5. The horizontal flue continuous sootblowing device based on flue gas recirculation according to claim 1 is characterized in that: The in-furnace sootblowing module (6) comprises: an air intake pipeline, a ball check valve (61), a filter (62), a pneumatic butterfly valve (63), a pressure switch (64) and a sootblower (65); one end of the air intake pipeline of the sootblowing module is connected to the outlet of the double gas storage tank system, and is sequentially connected to the ball check valve (61), the filter (62), the pneumatic butterfly valve (63) and the pressure switch (64) to ensure that the airflow can only flow in one direction to prevent backflow from causing system failure; the pneumatic butterfly valve (63) and the pressure switch (64) are connected to an external automatic control system; finally, the sootblowing connection sootblower (65) is arranged at an equal distance at the end of the pipeline, and the sootblower (65) is placed 150-200 mm above the soot accumulation part.

6. The horizontal flue continuous soot blowing device based on flue gas recirculation according to claim 1 is characterized in that: The in-furnace sootblowing module (6) is provided with a spare interface, so that when the flue gas recirculation system is under maintenance, fails, or the boiler is shut down, a traditional gas source can still be used to ensure the continuity of sootblowing.

7. The horizontal flue continuous sootblowing device based on flue gas recirculation according to claim 1 is characterized in that: The dual-tank compressed flue gas charging and discharging module is provided with an expansion interface, which can realize expansion from dual tanks to multi-tank modular parallel connection.

8. The control method of the horizontal flue continuous sootblowing device based on flue gas recirculation according to any one of claims 1 to 7, characterized in that: The steps include: The control module communicates bidirectionally with the distributed control system of the existing boiler system: the control module collects safety signals from the distributed control system and reports the sootblowing system status information to the distributed control system; The safety signal includes: boiler load, flue gas flow rate, gas tank pressure, ash accumulation sensor, temperature, valve status; the soot blowing system status information includes: soot blowing status and gas tank pressure abnormality information; when the distributed control system performs an emergency shutdown, the soot blowing system will correspondingly shut down the high-voltage pulse program and enter a safe waiting state; The control module performs output control, including: fan frequency conversion adjustment, valve opening switching, setting of soot blowing strategy and execution of strategy logic.

9. The control method of the horizontal flue continuous sootblowing device based on flue gas recirculation according to claim 8 is characterized in that: The soot blowing strategy setting includes: Divide the load interval according to the load L; the load interval includes: High load range: L ≥ 80%; Medium and high load range: 50%≤L<80%; Medium and low load range: 30%≤L<50%; Low load range: L<30%; Set the ash deposition height threshold, and set three thresholds: X1, X2, and X3; During boiler operation or testing, settings are continued through online ash measurement and historical data, including: X1≥X2≥X3 X1 corresponds to the upper limit of deposition thickness allowed under high load conditions; X2 is used in the "medium to high load" range of 50% to 80% X3 corresponds to the lower ash deposition threshold that can be tolerated under low and medium loads; Set the soot blowing mode, including: timed soot blowing and instant soot blowing; Timed soot blowing: It is carried out in a relatively gentle continuous low-pressure or medium-pressure manner, which can save energy and maintain the basic cleanliness of the flue. The basic single soot blowing time is 3 to 5 minutes; Instant soot blowing: Once the ash layer exceeds the threshold, soot blowing is triggered immediately to quickly impact and remove the accumulated ash; when the ash deposition drops below the threshold, the system can switch back to the timed soot blowing mode; Set the ash deposition sensor layout strategy: ash deposition sensors should be set preferentially in horizontal flues, return areas, elbows, and turning sections; if there are differences in the ash layer thickness measured at multiple points, the immediate soot blowing mode will be triggered according to the maximum value to avoid local severe ash accumulation being ignored.

10. The control method of the horizontal flue continuous sootblowing device based on flue gas recirculation according to claim 8, characterized in that: The execution strategy logic includes: For the high load range (L ≥ 80%): If the ash deposition height < X1, perform regular sootblowing: once every 8 hours, 0.2 - 0.3 MPa; If the ash deposition height ≥ X1, immediately start sootblowing. After the ash deposition height drops below X1, resume the "regular sootblowing every 8 hours" mode; 0.4 - 0.6 MPa to quickly break up stubborn ash layers; cooperate with short - cycle continuous spraying and perform multiple cycles until the monitored ash thickness returns to normal; For the medium - high load range (50% ≤ L < 80%): If the ash deposition height < X2, perform regular sootblowing: once every 4 hours, 0.25 - 0.4 MPa; If the ash deposition height ≥ X2, immediately start sootblowing, 0.5 - 0.6 MPa. Give priority to pulse sootblowing to enhance the effect and appropriately increase the spraying duration; superimpose continuous purging at medium pressure to ensure that dust does not accumulate again in the short term, continue until the ash deposition height drops below X2; For the medium - low load range: 30% ≤ L < 50%: If the ash deposition height < X3, perform regular sootblowing: once every 1 hour, 0.3 - 0.5 MPa; If the ash deposition height ≥ X3, immediately start sootblowing, 0.5 - 0.6 MPa, mainly with high - pressure pulses, cooperate with short - cycle continuous spraying; intensive pulses can peel off the thickened ash layer in a short time to avoid the risk of blockage; And maintain inspections and re - sootblowing once every 1 hour until the ash deposition height < X3.

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