Venting control system and method to prevent boiler shutdown resulting in intake system pressure build-up

Abstract

The application discloses a venting control system and method for preventing air intake system pressure from being blocked due to boiler shutdown, and relates to the technical field of boiler safety control. The system comprises a DCS control system, a DCS tail gas pressure detection transmitter arranged on a tail gas pipeline and connected with the DCS control system in signal, a boiler air inlet pressure detection transmitter arranged on a boiler gas inlet pipeline and connected with the DCS control system in signal, and a boiler interlock protection sensor group connected with the DCS control system in signal. The power supply circuit of the tail gas venting valve is connected in series with the control relay of the gas supply valve, at the moment of the boiler shutdown, the control relay of the gas supply valve is disconnected, and the venting valve is synchronously operated due to the power supply interruption or conduction, so that the signal transmission delay and judgment delay caused by the pressure signal control of the venting valve opening are eliminated, the venting valve is immediately opened, and the tail gas can be immediately discharged through the venting valve when the boiler is unexpectedly shut down.

Description

Technical Field

[0001] This invention relates to the field of boiler safety control technology, specifically to a venting control system and method for preventing pressure buildup in the intake system caused by boiler shutdown. Background Technology

[0002] In chemical production, boilers often use combustible exhaust gas, a byproduct of the process, as fuel, forming a close process coupling with the upstream production system. That is, the operation of the boiler depends on the continuous gas supply from the upstream, and the stable operation of the upstream also depends on the continuous absorption of exhaust gas by the boiler.

[0003] Existing boilers are typically equipped with multiple interlocking protections: when any of the following trigger signals occur, such as high / low gas inlet pressure, high / low boiler drum liquid level, furnace pressure overpressure, steam pressure overpressure, or furnace flameout, the control system disconnects the gas supply valve control relay and closes the gas supply valve to shut down the boiler. Simultaneously, a vent valve is installed on the exhaust gas pipeline to release exhaust gas during boiler shutdown to prevent pressure buildup.

[0004] However, existing technologies have the following drawbacks:

[0005] First, pressure buildup detection is delayed. Existing systems typically rely on a single pressure measuring point to monitor the exhaust gas system pressure, lacking a redundant detection mechanism. Failure of a single measuring point or signal drift can easily lead to missed or false alarms, and the system fails to effectively correlate pressure detection with boiler operating status, making it difficult to achieve accurate early warning in the early stages of pressure buildup.

[0006] Secondly, the delayed action of the vent valve leads to the shutdown of the front-end system. The existing vent valve is controlled by a pressure signal to open. After the boiler is shut down, it must go through a serial link of "pressure increase → signal transmission → controller judgment → command issuance" before the vent valve can open. This process inevitably involves a time delay. During this delay, the front-end system continues to produce gas, and the inability to promptly absorb the exhaust gas causes a sudden pressure surge. This often triggers the front-end system's safety protection shutdown before the vent valve opens, causing production interruption and posing safety hazards.

[0007] Third, there is insufficient system integration. The boiler control system and the venting system operate independently, lacking a unified monitoring platform and coordinated control logic, resulting in insufficient response under abnormal operating conditions. Summary of the Invention

[0008] The purpose of this invention is to provide a venting control system and method to prevent pressure buildup in the intake system caused by boiler shutdown, thereby overcoming the aforementioned shortcomings in the prior art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a venting control system for preventing pressure buildup in the intake system due to boiler shutdown, comprising:

[0010] DCS control system;

[0011] The DCS exhaust gas pressure detection transmitter installed on the exhaust gas pipeline is connected to the DCS control system signal.

[0012] The boiler inlet pressure detection transmitter, installed on the boiler gas inlet pipe, is connected to the DCS control system signal.

[0013] A boiler interlock protection sensor group connected to the DCS control system signals;

[0014] A gas supply valve is installed on the gas inlet pipe of the boiler;

[0015] An exhaust vent valve is installed on the exhaust pipe and has a solenoid valve and a power supply circuit;

[0016] The gas supply valve control relay is electrically connected to the output terminal of the DCS control system, and includes a normally open contact for controlling the opening and closing of the gas supply valve, and an energized contact for controlling the opening and closing of the exhaust gas vent valve.

[0017] The normally open (only energized and conducting) contact of the gas supply valve control relay is connected in series in the power supply circuit of the exhaust gas vent valve.

[0018] When the DCS control system receives the interlocking trigger signal of the boiler interlocking protection sensor group, the DCS control system outputs a power-off command to de-energize and release the gas supply valve control relay, causing the energized contact to open instantaneously, the power supply circuit to be instantly disconnected, and the exhaust gas vent valve to be immediately de-energized and automatically opened.

[0019] Furthermore, there are two sets of gas supply valve control relays, each set of which has an energized contact, and the two energized contacts are connected in series in the power supply circuit.

[0020] Furthermore, the DCS exhaust gas pressure transmitter and the boiler inlet gas pressure transmitter are respectively connected to the analog input module of the DCS control system through independent shielded signal cables, and both pressure signals are 4-20mA DC standard signals.

[0021] Furthermore, the DCS control system has a built-in pressure stagnation identification algorithm module. The pressure stagnation identification algorithm module collects the tail gas pipeline pressure value P1 of the DCS tail gas pressure detection transmitter and the boiler inlet gas pressure value P2 of the boiler inlet gas detection transmitter in real time with a sampling period of 50~100ms, and performs moving average filtering on the collected raw signals.

[0022] The pressure buildup identification algorithm module is used to calculate the effective value of the exhaust gas pipeline pressure P1 and compare it with the first preset threshold T1, and to calculate the effective value of the boiler inlet gas pressure P2 and compare it with the second preset threshold T2, and calculate the difference ΔP=|P1-P2|. ΔP is then compared with the preset deviation threshold TΔ. When any one of the following conditions is met, P1>T1, P2>T2, or ΔP>TΔ is met, a pressure buildup warning state is determined, and an audible and visual alarm signal is issued through the operation interface of the DCS control system.

[0023] Furthermore, the valve body of the exhaust vent valve is made of C12A chromium-molybdenum alloy steel, and the sealing surfaces of the valve disc and valve seat are overlaid with tungsten carbide hard alloy. The sealing structure adopts a double sealing type of hard alloy and polytetrafluoroethylene. A balance hole is opened on the valve disc, and the valve stem packing adopts a self-sealing V-shaped structure. The overall explosion-proof rating of the exhaust vent valve is not lower than ExdⅡCT4, and the nominal pressure is not lower than PN1.6.

[0024] A venting control method to prevent pressure buildup in the intake system due to boiler shutdown includes the following steps:

[0025] S1. Under normal boiler operation, the DCS control system continuously outputs a holding current to keep the gas supply valve control relay energized and engaged, keeping the gas supply valve open. At the same time, the power supply circuit of the tail gas vent valve remains closed, keeping the tail gas vent valve closed.

[0026] S2. The DCS control system continuously monitors the status signals of the boiler interlock protection sensor group;

[0027] S3. When the DCS control system receives a chain trigger signal from any interlock protection sensor, the DCS control system immediately outputs a power-off command, causing the gas supply valve control relay to de-energize and release. After the gas supply valve control relay is de-energized, it simultaneously performs the following two parallel actions:

[0028] (a) When the normally open contact of the gas supply valve control relay is opened, the solenoid valve of the gas supply valve is de-energized and closed, the solenoid valve closes and cuts off the gas source of the instrument, thereby closing the gas supply valve and cutting off the gas supply.

[0029] (b) When the energized contact of the gas supply valve control relay is disconnected, the power supply circuit of the exhaust gas vent valve is momentarily disconnected, the solenoid valve of the exhaust gas vent valve is de-energized, and the exhaust gas vent valve is automatically opened immediately.

[0030] S4. After the fault is cleared, the operator performs a system reset operation. The gas supply valve control relay is re-energized and the gas supply valve is reopened. The power supply circuit of the exhaust vent valve is re-closed, and the solenoid valve of the exhaust vent valve is energized to supply the instrument gas source, so that the exhaust vent valve can return to the closed state.

[0031] Furthermore, S2 also includes a pressure buildup warning:

[0032] The tail gas pipeline pressure value P1 is collected in real time by the DCS tail gas pressure detection transmitter, and the boiler inlet gas pressure value P2 is collected in real time by the boiler inlet gas detection transmitter.

[0033] The effective value of the exhaust gas pipeline pressure P1 is calculated and compared with the first preset threshold T1. The effective value of the boiler inlet gas pressure P2 is calculated and compared with the second preset threshold T2. The difference ΔP = |P1-P2| is calculated and compared with the preset deviation threshold TΔ.

[0034] When any one of the following conditions is met—P1>T1, P2>T2, or ΔP>TΔ—the DCS control system determines that the pressure buildup warning state is in effect and issues an audible and visual alarm signal on the operation interface.

[0035] Furthermore, the DCS control system collects the exhaust gas pipeline pressure value P1 and the boiler inlet gas pressure value P2 with a sampling period of 50~100ms, and performs moving average filtering on P1 and P2, taking the arithmetic mean of the most recent N sampled values ​​as the corresponding current valid value, where the value of N ranges from 5 to 20.

[0036] The first preset threshold T1 is 1.2 to 1.5 times the upper limit of the normal operating pressure of the exhaust gas pipeline, the second preset threshold T2 is 1.2 to 1.5 times the upper limit of the normal operating pressure of the boiler gas inlet pipeline, and the preset deviation threshold TΔ is 5 to 10 kPa.

[0037] Furthermore, in S4, after the system is reset, the DCS control system re-outputs the holding current to energize and engage the gas supply valve control relay, and then starts the boiler ignition procedure. After the boiler resumes normal operation, the system returns to S1.

[0038] Compared with the prior art, the venting control system and method for preventing pressure buildup in the intake system due to boiler shutdown provided by the present invention have the following beneficial effects:

[0039] 1. By setting up a dual pressure detection channel consisting of a DCS exhaust gas pressure detection transmitter and a boiler inlet gas pressure detection transmitter, combined with the unified monitoring interface of the DCS control system and the pressure buildup identification algorithm, redundant monitoring and comprehensive judgment of the exhaust gas system pressure are realized, avoiding missed or false alarms caused by a single measuring point failure, and enabling rapid identification and accurate early warning in the early stage of pressure buildup.

[0040] 2. By connecting the power supply circuit of the exhaust gas vent valve in series with the control relay of the gas supply valve, at the moment the boiler shuts down, the gas supply valve control relay disconnects, and the vent valve operates synchronously due to power interruption (or conduction), forming a control link of "interlock trigger → relay de-energization → normally open contact disconnects (gas supply valve closes) → energized contact disconnects (vent valve power supply circuit disconnects) → vent valve opens". Compared with the existing control link of "interlock trigger → DCS detects signal → DCS software judges → DCS issues vent valve opening command → vent valve pneumatic drive device is energized → vent valve mechanically opens", this eliminates the signal transmission delay and judgment delay caused by the pressure signal controlling the vent valve to open, realizing the instantaneous opening of the vent valve, so that the exhaust gas can be released immediately through the vent valve when the boiler is unexpectedly shut down.

[0041] 3. By connecting the power supply circuit of the exhaust gas vent valve in series with the relay's energized contact (which only activates the circuit when energized), without any software judgment or communication links, even in extreme cases where the DCS control system is completely paralyzed or the power supply is interrupted, the vent valve can still automatically open when the relay loses power and the energized contact opens, further ensuring the stability of exhaust gas release when the boiler is unexpectedly shut down. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0043] Figure 1 A system structure block diagram provided for embodiments of the present invention;

[0044] Figure 2 The diagram illustrates the method steps provided in this embodiment of the invention. Detailed Implementation

[0045] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0046] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0048] Exemplary embodiments will be described more fully below with reference to the accompanying drawings; however, these exemplary embodiments may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will enable those skilled in the art to fully understand the scope of this disclosure.

[0049] Where there is no conflict, the various embodiments of this disclosure and the features thereof in the embodiments may be combined with each other.

[0050] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0051] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded.

[0052] The embodiments described herein can be described with reference to plan views and / or cross-sectional views using the ideal schematic diagrams of this disclosure. Therefore, the example illustrations can be modified according to manufacturing techniques and / or tolerances. Therefore, the embodiments are not limited to those shown in the drawings, but include modifications to configurations formed based on manufacturing processes. Therefore, the areas illustrated in the drawings are schematic in nature, and the shapes of the areas shown in the figures illustrate specific shapes of areas of an element, but are not intended to be limiting.

[0053] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having the same meaning as they have in the context of the relevant art and this disclosure.

[0054] Please see Figure 1 (Thick arrows indicate gas flow paths, thin arrows indicate electrical signal paths), a venting control system to prevent boiler shutdown from causing pressure buildup in the intake system includes:

[0055] DCS control system, exhaust gas pipeline, boiler gas inlet pipeline, DCS exhaust gas pressure detection transmitter, boiler inlet gas pressure detection transmitter, boiler interlock protection sensor group, gas supply valve, gas supply valve control relay and exhaust gas vent valve.

[0056] One end of the exhaust gas pipe is connected to the exhaust gas outlet of the upstream chemical production system (such as a formaldehyde production system), and the other end is connected to the boiler gas inlet pipe. The exhaust gas (gas) enters the boiler combustion chamber through the exhaust gas pipe and the boiler gas inlet pipe.

[0057] The power supply circuit of the exhaust gas vent valve is connected in series with the energized contact of the gas supply valve control relay. When the DCS control system receives the interlocking trigger signal from the boiler interlocking protection sensor group, the DCS control system outputs a power-off command to de-energize the gas supply valve control relay, causing the energized contact to open instantaneously, the power supply circuit to be disconnected instantaneously, and the exhaust gas vent valve to open immediately.

[0058] In a preferred embodiment, the gas supply valve control relays are in two sets, used to control the opening and closing of two sets of gas supply valves respectively. The energized contacts of the two sets of relays (which only engage when energized to connect the circuit) are connected in series in the power supply circuit. That is, the phase line of the power supply circuit of the exhaust vent valve passes through the energized contacts one after the other before being connected to the power input terminal of the solenoid valve of the exhaust vent valve. When either of the two energized contacts is de-energized, the power supply circuit is in an open circuit state, the solenoid valve of the exhaust vent valve cannot be energized, the spring force of the pre-installed return spring in the exhaust vent valve cylinder is released, and the valve disc is opened, causing the vent valve to open automatically. Only when both energized contacts are closed simultaneously does the power supply circuit form a complete electrical path, the solenoid valve of the exhaust vent valve can be connected to the instrument gas source, and the vent valve can overcome the spring force of the return spring and return to closure under the action of the instrument gas source pushing the cylinder. The design of two sets of relays connected in series ensures that the vent valve will not be accidentally closed if either set of relays fails to operate properly, thus improving the reliability of the system. At the same time, during normal shutdown, both sets of relays must be energized simultaneously to manually control the vent valve to close, avoiding abnormal closure of the vent valve caused by the malfunction of a single set of relays.

[0059] The DCS exhaust gas pressure transmitter is installed on the exhaust gas pipeline to detect the gas pressure in the pipeline in real time and convert the pressure signal into a standard electrical signal for transmission to the DCS control system. The boiler inlet gas pressure transmitter is installed on the boiler gas inlet pipeline to detect the gas pressure entering the boiler in real time and convert the pressure signal into a standard electrical signal for transmission to the DCS control system.

[0060] In this embodiment, the DCS exhaust gas pressure transmitter has a range of 0~0.02MPa and an accuracy class of not less than 0.5; the boiler inlet gas pressure transmitter has a range of 0~0.01MPa and an accuracy class of not less than 0.5. Both transmitters use a 4-20mA DC standard signal output and are connected to the analog input module of the DCS control system via independent shielded signal cables. Using independent shielded signal cables effectively avoids mutual interference between the two signals and the influence of the on-site electromagnetic environment on signal transmission, ensuring the accuracy and reliability of the detected signals.

[0061] The boiler interlock protection sensor group is connected to the DCS control system signal, including:

[0062] The gas inlet high-pressure transmitter is installed on the boiler gas inlet pipeline to detect the gas inlet pressure. When the pressure exceeds the preset high-pressure threshold, it sends a high-pressure interlock trigger signal to the DCS control system.

[0063] The low-pressure gas inlet switch is installed on the gas inlet pipe of the boiler to detect the gas inlet pressure. When the pressure is lower than the preset low-pressure threshold, it sends a low-pressure interlock trigger signal to the DCS control system.

[0064] The boiler drum liquid level electrode sensor is installed on the boiler drum to detect the liquid level in the drum. When the liquid level exceeds the preset high liquid level threshold or falls below the preset low liquid level threshold, it sends a liquid level interlock trigger signal to the DCS control system.

[0065] The furnace pressure transmitter is installed on the boiler furnace to detect the furnace pressure. When the pressure exceeds a preset threshold, it sends a furnace overpressure interlock trigger signal to the DCS control system.

[0066] A steam pressure transmitter is installed on the boiler steam outlet pipe to detect steam pressure. When the pressure exceeds a preset threshold, it sends a steam overpressure interlock trigger signal to the DCS control system.

[0067] An infrared flame detector is installed near the boiler furnace burner to detect the flame status in the furnace. When flameout is detected, it sends a flameout interlock trigger signal to the DCS control system.

[0068] When any of the aforementioned interlocking protection sensors is triggered, an interlocking trigger signal is sent to the DCS control system.

[0069] The DCS control system's user interface integrates both boiler operation monitoring and exhaust gas pressure monitoring interfaces. Operators can monitor boiler operating parameters such as steam pressure, furnace pressure, boiler drum liquid level, and flue gas temperature in real time, as well as exhaust gas system parameters such as exhaust gas pipeline pressure and boiler inlet gas pressure, through a unified DCS human-machine interface.

[0070] The DCS control system has a built-in pressure stagnation identification algorithm module. This module acquires the pressure values ​​P1 from the DCS exhaust gas pressure transmitter and P2 from the boiler inlet gas pressure transmitter in real time with a sampling period of 50-100ms (preferably 100ms). It then performs a moving average filtering process on the acquired raw signals, taking the arithmetic mean of the most recent N samples as the current valid measurement value. The value of N ranges from 5 to 20 (preferably N=10) to eliminate measurement fluctuations caused by electromagnetic interference and signal noise.

[0071] The pressure stagnation identification algorithm module compares the filtered effective value P1 with a first preset threshold T1, and the effective value P2 with a second preset threshold T2. It then calculates the difference between the two pressure detection values, ΔP = |P1 - P2|, and compares ΔP with a preset deviation threshold TΔ. When any one of the following conditions is met—P1 > T1, P2 > T2, or ΔP > TΔ—the pressure stagnation identification algorithm module determines a pressure stagnation warning state and issues an audible and visual alarm signal on the DCS control system's operating interface.

[0072] The first preset threshold T1 is 1.2 to 1.5 times the upper limit of the normal operating pressure of the exhaust gas pipeline, and further T1 = 5 kPa; the second preset threshold T2 is 1.2 to 1.5 times the upper limit of the normal operating pressure of the boiler gas inlet pipeline, and further T2 = 3 kPa; the preset deviation threshold TΔ is 5 to 10 kPa, and further TΔ = 8 kPa.

[0073] The gas supply valve consists of two sets, namely gas supply valve 1 and gas supply valve 2, which are connected in series on the gas inlet pipe of the boiler. The normally open contacts of gas supply valve control relay 1 and gas supply valve control relay 2 respectively control the opening and closing of the valves.

[0074] During normal boiler operation, the DCS control system continuously outputs a holding current, energizing the gas supply valve control relay. At this time, the normally open contact of the gas supply valve control relay closes, connecting the power supply circuits of both gas supply valves, and the gas supply valves are in the open position, allowing gas to enter the boiler for combustion. Simultaneously, the energized contact of the gas supply valve control relay closes, closing the power supply circuit of the exhaust gas vent valve, ensuring that the solenoid valve of the exhaust gas vent valve is energized to remain closed.

[0075] The solenoid valve of the exhaust vent valve is electrically connected to the power supply circuit. When the power supply circuit is on, the solenoid valve is energized and connects to the instrument air source, allowing the vent valve to overcome the return spring force and return to closed under the action of the cylinder driven by the instrument air source. The overall explosion-proof rating of the exhaust vent valve is not lower than ExdⅡCT4, meeting the explosion-proof requirements of exhaust gas (fuel gas) media; the nominal pressure is not lower than PN1.6, and the applicable temperature range is -29℃ to 250℃. The response time of the solenoid valve is not greater than 50ms.

[0076] When the DCS control system receives a trigger signal from any interlocking protection sensor, it simultaneously outputs a de-energizing command (i.e., stops outputting holding current) to the coils of the two gas supply valve control relays via its digital output module. Both gas supply valve control relays de-energize and release, their normally open contacts change from closed to open, closing the gas supply valves and cutting off the gas supply; simultaneously, their energized contacts change from closed to open, momentarily disconnecting the power supply circuit to the exhaust vent valve, causing the exhaust vent valve to open automatically.

[0077] Because the power supply circuit of the exhaust vent valve is connected in series with the energized contact of the gas supply valve control relay, in extreme fault conditions such as complete power failure of the DCS control system, communication interruption, or program crash, the gas supply valve control relay will also release due to coil de-energization. Its energized contact will momentarily disconnect due to de-energization, opening the power supply circuit of the exhaust vent valve and causing the vent valve to open automatically. Therefore, even if the control system is completely paralyzed, the vent valve opening mechanism of this invention still operates reliably, achieving intrinsically safe protection.

[0078] Please see Figure 2 The present invention also provides a venting control method for preventing pressure buildup in the intake system caused by boiler shutdown using the above-mentioned control system, comprising the following steps:

[0079] S1. Circuit status confirmation under normal operating conditions

[0080] During normal boiler operation, the DCS control system continuously outputs a holding current to keep the gas supply valve control relay energized and engaged. At this time: the normally open contact of the gas supply valve control relay is closed, the power supply circuit of the gas supply valve is connected, the gas supply valve remains open, and gas enters the boiler for combustion normally; the energized contact of the gas supply valve control relay is closed, the power supply circuit of the exhaust gas vent valve is closed, and the exhaust gas vent valve remains closed.

[0081] S2. Continuously monitor the boiler's interlock protection signals.

[0082] The DCS control system continuously monitors the status signals of the boiler interlock protection sensor group, including: the high-pressure trigger signal of the gas inlet high-pressure transmitter; the low-pressure trigger signal of the gas inlet low-pressure switch; the high or low liquid level trigger signal of the boiler drum liquid level electrode cell sensor; the overpressure trigger signal of the furnace pressure transmitter; the overpressure trigger signal of the steam pressure transmitter; and the flameout trigger signal of the infrared flame detector.

[0083] Furthermore, a pressure buildup warning step is also executed in parallel:

[0084] The tail gas pipeline pressure value P1 is collected in real time by the DCS tail gas pressure detection transmitter, and the boiler inlet gas pressure value P2 is collected in real time by the boiler inlet gas detection transmitter.

[0085] The DCS control system acquires two pressure signals with a sampling period of 50~100ms, performs moving average filtering on the acquired raw signals, and takes the arithmetic mean of the most recent N sampled values ​​as the current valid measurement value, where N ranges from 5 to 20.

[0086] The effective value P1 after filtering is compared with the first preset threshold T1, the effective value P2 is compared with the second preset threshold T2, and the difference between the two pressure detection values ​​ΔP=|P1-P2| is calculated. ΔP is then compared with the preset deviation threshold TΔ.

[0087] When any one of the following conditions is met, such as P1>T1, P2>T2, or ΔP>TΔ, the DCS control system determines that the pressure buildup warning state is in effect and issues an audible and visual alarm signal on the operation interface.

[0088] After receiving an alarm, operators can take manual intervention measures in advance (such as checking whether the pipeline is blocked, adjusting the load of the front-end system, etc.) to achieve early warning and proactive handling of pressure buildup.

[0089] The first preset threshold T1 is 1.2 to 1.5 times the upper limit of the normal operating pressure of the exhaust gas pipeline, and further T1 = 5 kPa; the second preset threshold T2 is 1.2 to 1.5 times the upper limit of the normal operating pressure of the boiler gas inlet pipeline, and further T2 = 3 kPa; the preset deviation threshold TΔ is 5 to 10 kPa, and further ΔT = 8 kPa.

[0090] S3, after interlocking triggering, the relay is de-energized and performs dual parallel actions.

[0091] When the DCS control system receives a trigger signal from any of the interlocking protection sensors in S2, the DCS control system immediately outputs a power-off command through its digital output module, causing the gas supply valve control relay to de-energize and release. After the gas supply valve control relay is de-energized, it simultaneously performs the following two parallel actions:

[0092] (a) When the normally open contact of the gas supply valve control relay, which controls the opening and closing of the gas supply valve, changes from closed to open, the solenoid valve of the gas supply valve is de-energized and closes. The solenoid valve closes and cuts off the gas supply to the instrument, thereby closing the gas supply valve, cutting off the gas supply, and the boiler enters the shutdown state.

[0093] (b) The energized contact of the gas supply valve control relay, which controls the opening and closing of the exhaust vent valve, changes from closed to open. Since these two energized contacts are connected in series in the power supply circuit of the exhaust vent valve, when they are simultaneously disconnected, the power supply circuit is momentarily disconnected, the solenoid valve of the exhaust vent valve is de-energized, the return spring in the cylinder drives the valve stem to push open the valve disc, and the exhaust vent valve opens automatically and immediately.

[0094] Actions (a) and (b) are directly driven by the same physical event—relay de-energization—and are completely synchronized, with no temporal sequence. The response time of the entire process depends solely on the inherent operating time of the relay itself, without involving any software judgment, data processing, or command output from the DCS control system. In this embodiment, the inherent operating time of the gas supply valve control relay is no greater than 20ms, and the response time of the exhaust vent valve from disconnection to full opening is no greater than 50ms.

[0095] S4. System reset, resume operation.

[0096] Once the cause of the cascading boiler shutdown is identified and eliminated, the operator performs a system reset on the DCS control system interface. The DCS control system re-outputs the holding current, energizing the gas supply valve control relay: the normally open contact of the gas supply valve control relay closes, the power supply circuit of the gas supply valve is reconnected, the gas supply valve reopens, and gas resumes entering the boiler; the energized contact of the gas supply valve control relay closes again, the power supply circuit of the exhaust vent valve is reconnected, the solenoid valve of the exhaust vent valve is energized and connects to the instrument gas source, and the vent valve closes again under the action of the cylinder driven by the instrument gas source. The boiler ignition procedure is then started. After the boiler returns to normal operation, the system returns to S1.

[0097] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A venting control system for preventing pressure buildup in the intake system due to boiler shutdown, characterized in that, include: DCS control system; The DCS exhaust gas pressure detection transmitter installed on the exhaust gas pipeline is connected to the DCS control system signal. The boiler inlet pressure detection transmitter, installed on the boiler gas inlet pipe, is connected to the DCS control system signal. A boiler interlock protection sensor group connected to the DCS control system signals; A gas supply valve is installed on the gas inlet pipe of the boiler and has a solenoid valve. An exhaust vent valve is installed on the exhaust pipe and has a solenoid valve and a power supply circuit; The gas supply valve control relay is electrically connected to the output terminal of the DCS control system, and includes a normally open contact for controlling the opening and closing of the gas supply valve, and an energized contact for controlling the opening and closing of the exhaust gas vent valve. The power supply circuit of the exhaust vent valve is connected in series with the energizing contact of the gas supply valve control relay. When the DCS control system receives the interlocking trigger signal of the boiler interlocking protection sensor group, the DCS control system outputs a power-off command to de-energize and release the gas supply valve control relay, causing the energized contact to open instantaneously, the power supply circuit to be instantly disconnected, and the exhaust gas vent valve to be immediately de-energized and automatically opened.

2. The venting control system for preventing pressure buildup in the intake system due to boiler shutdown as described in claim 1, characterized in that, There are two sets of gas supply valve control relays, and each set of gas supply valve control relays has an energized contact. The two energized contacts are connected in series in the power supply circuit.

3. The venting control system for preventing pressure buildup in the intake system due to boiler shutdown as described in claim 1, characterized in that, The DCS exhaust gas pressure transmitter and the boiler inlet gas pressure transmitter are respectively connected to the analog input module of the DCS control system through independent shielded signal cables. Both pressure signals are 4-20mA DC standard signals.

4. The venting control system for preventing pressure buildup in the intake system due to boiler shutdown as described in claim 1, characterized in that, The DCS control system has a built-in pressure stagnation identification algorithm module. The pressure stagnation identification algorithm module collects the tail gas pipeline pressure value P1 of the DCS tail gas pressure detection transmitter and the boiler inlet gas pressure value P2 of the boiler inlet gas detection transmitter in real time with a sampling period of 50~100ms, and performs moving average filtering on the collected raw signals. The pressure buildup identification algorithm module is used to calculate the effective value of the exhaust gas pipeline pressure P1 and compare it with the first preset threshold T1, and to calculate the effective value of the boiler inlet gas pressure P2 and compare it with the second preset threshold T2, and calculate the difference ΔP=|P1-P2|. ΔP is then compared with the preset deviation threshold TΔ. When any one of the following conditions is met, P1>T1, P2>T2, or ΔP>TΔ is met, a pressure buildup warning state is determined, and an audible and visual alarm signal is issued through the operation interface of the DCS control system.

5. The venting control system for preventing pressure buildup in the intake system due to boiler shutdown as described in claim 1, characterized in that, The valve body of the exhaust vent valve is made of C12A chromium-molybdenum alloy steel. The sealing surfaces of the valve disc and valve seat are overlaid with tungsten carbide hard alloy. The sealing structure adopts a double sealing type of hard alloy and polytetrafluoroethylene. The valve disc is provided with a balance hole. The valve stem packing adopts a self-sealing V-shaped structure. The overall explosion-proof rating of the exhaust vent valve is not lower than ExdⅡCT4, and the nominal pressure is not lower than PN1.

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6. A venting control method for preventing pressure buildup in the intake system due to boiler shutdown, applicable to the venting control system for preventing pressure buildup in the intake system due to boiler shutdown as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Under normal boiler operation, the DCS control system continuously outputs a holding current to keep the gas supply valve control relay energized and engaged, keeping the gas supply valve open. At the same time, the power supply circuit of the tail gas vent valve remains closed, keeping the tail gas vent valve closed. S2. The DCS control system continuously monitors the status signals of the boiler interlock protection sensor group; S3. When the DCS control system receives a chain trigger signal from any interlock protection sensor, the DCS control system immediately outputs a power-off command, causing the gas supply valve control relay to de-energize and release. After the gas supply valve control relay is de-energized, it simultaneously performs the following two parallel actions: (a) When the normally open contact of the gas supply valve control relay is opened, the solenoid valve of the gas supply valve is de-energized and closed, the solenoid valve closes and cuts off the gas source of the instrument, thereby closing the gas supply valve and cutting off the gas supply. (b) When the energized contact of the gas supply valve control relay is disconnected, the power supply circuit of the exhaust gas vent valve is momentarily disconnected, the solenoid valve of the exhaust gas vent valve is de-energized, and the exhaust gas vent valve is automatically opened immediately. S4. After the fault is cleared, the operator performs a system reset operation. The gas supply valve control relay is re-energized and the gas supply valve is reopened. The power supply circuit of the exhaust vent valve is re-closed, and the solenoid valve of the exhaust vent valve is energized to supply the instrument gas source, so that the exhaust vent valve returns to the closed state.

7. The venting control method for preventing pressure buildup in the intake system due to boiler shutdown as described in claim 6, characterized in that, S2 also includes a pressure stagnation warning: The tail gas pipeline pressure value P1 is collected in real time by the DCS tail gas pressure detection transmitter, and the boiler inlet gas pressure value P2 is collected in real time by the boiler inlet gas detection transmitter. The effective value of the exhaust gas pipeline pressure P1 is calculated and compared with the first preset threshold T1. The effective value of the boiler inlet gas pressure P2 is calculated and compared with the second preset threshold T2. The difference ΔP = |P1-P2| is calculated and compared with the preset deviation threshold TΔ. When any one of the following conditions is met—P1>T1, P2>T2, or ΔP>TΔ—the DCS control system determines that the pressure buildup warning state is in effect and issues an audible and visual alarm signal on the operation interface.

8. The venting control method for preventing pressure buildup in the intake system due to boiler shutdown as described in claim 7, characterized in that, The DCS control system collects the tail gas pipeline pressure value P1 and the boiler inlet gas pressure value P2 with a sampling period of 50~100ms, and performs moving average filtering on P1 and P2, taking the arithmetic mean of the most recent N sampled values ​​as the corresponding current valid value, where N ranges from 5 to 20. The first preset threshold T1 is 1.2 to 1.5 times the upper limit of the normal operating pressure of the exhaust gas pipeline, the second preset threshold T2 is 1.2 to 1.5 times the upper limit of the normal operating pressure of the boiler gas inlet pipeline, and the preset deviation threshold TΔ is 5 to 10 kPa.

9. The venting control method for preventing pressure buildup in the intake system due to boiler shutdown as described in claim 6, characterized in that, In step S4, after the system is reset, the DCS control system outputs a holding current again to energize and engage the gas supply valve control relay, and then starts the boiler ignition procedure. After the boiler returns to normal operation, the system returns to step S1.

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