Control system for reducing flash explosion risk of steam superheater

Abstract

The utility model discloses a control system for reducing the flash explosion risk of a steam superheater. The control system comprises a DCS (Distributed Control System), the pressure transmitter I, the oxygen content analyzer and the pressure transmitter III are electrically connected with the input end of the DCS, and the output end of the DCS is electrically connected with the pressure regulating valve I, the pressure regulating valve II, the stop valve II, the stop valve III, the stop valve IV and the stop valve VII. The method has the advantages that in the ignition process, through ignition condition judgment, the safety condition of ignition starting is judged by the DCS, the ignition success rate is increased, and misjudgment of an instrument is avoided by observing a DCS curve; through control of preheating ignition, full preheating of the furnace body and the pipeline is achieved, deformation of the furnace body and breakage of the pipeline are avoided, and meanwhile the flash explosion risk caused by excessive fuel gas and the inner leakage risk is reduced.

Description

Technical fields:

[0001] This utility model relates to the technical field of steam superheater equipment, and in particular to a control system for reducing the risk of flash explosion in steam superheaters. Background technology:

[0002] In the modern chemical industry, the frequent start-up and shutdown of steam superheaters in production enterprises poses a high safety risk factor. Currently, operation and control rely entirely on manual experience, which is a major concern for production enterprises. Steam superheaters provide precise temperature control during the production process, which plays a crucial role in ensuring the stable operation of subsequent processes.

[0003] In the actual interlock design of steam superheater furnaces, the lack of pre-ignition delay control poses four major hidden dangers: 1. Lack of safety condition judgment during equipment startup, including confirmation of the safety conditions of fuel gas pressure, furnace negative pressure, and fuel valve status parameters. Currently, condition confirmation relies entirely on the operator's work experience, leading to incomplete confirmation and subsequent ignition failure; 2. Insufficient preheating of pipelines before ignition: Operators lack a sense of time to control valve opening and closing to preheat pipelines. Currently, the superheater furnace body, pipelines, and related components are directly ignited from a cold state, resulting in uneven heating of pipelines. Local overheating can lead to furnace body deformation and pipeline rupture; 3. Avoiding misjudgment by monitoring instruments: During the initial stage of ignition, the rapid changes in parameters such as furnace temperature and flow rate can cause brief fluctuations or misjudgments in measuring instruments; 4. Excessive combustible gas in the steam superheater furnace before ignition: There is a risk of internal leakage in the fuel valve, leading to excessive methane and CO levels, which can easily cause flash explosions during ignition. Utility model content:

[0004] The purpose of this invention is to provide a control system that improves the ignition success rate and reduces the risk of flash explosion in a steam superheated furnace.

[0005] This utility model is implemented by the following technical solution: a control system for reducing the risk of flash explosion in a steam superheater, comprising a steam superheater, a DCS system, and a main fuel gas pipeline and branch fuel gas pipelines connected to the steam superheater; a pressure transmitter I and an oxygen content analyzer are installed in the furnace of the steam superheater, and a pressure transmitter III is installed at the inlet of the main fuel gas pipeline; a pressure regulating valve I, a shut-off valve IV, and a shut-off valve VII are installed on the main fuel gas pipeline; a pressure regulating valve II, a shut-off valve II, and a shut-off valve III are installed on the branch fuel gas pipelines; the pressure transmitter I, the oxygen content analyzer, and the pressure transmitter III are electrically connected to the input terminal of the DCS system, and the output terminal of the DCS system is electrically connected to the pressure regulating valve I, the pressure regulating valve II, the shut-off valve II, the shut-off valve III, the shut-off valve IV, and the shut-off valve VII.

[0006] Furthermore, a first vent line is connected to the main fuel gas pipeline between the shut-off valve IV and the shut-off valve VII, and a shut-off valve V is installed on the first vent line; a second vent line is connected to the branch fuel gas pipeline between the shut-off valve II and the shut-off valve III, and a shut-off valve I is installed on the second vent line; the output terminal of the DCS system is electrically connected to the shut-off valve V and the shut-off valve I.

[0007] Furthermore, it also includes a non-condensable gas pipeline connected to the steam superheater; a shut-off valve VI and a pressure transmitter IV are installed on the non-condensable gas pipeline, the pressure transmitter IV is electrically connected to the input terminal of the DCS system, and the output terminal of the DCS system is electrically connected to the shut-off valve VI.

[0008] Furthermore, a flow transmitter I is installed at the superheated steam inlet of the steam superheater, and a flow transmitter II is installed on the fuel gas main pipeline; the flow transmitter I and the flow transmitter II are electrically connected to the input terminal of the DCS system.

[0009] Furthermore, a temperature transmitter I is installed at the superheated steam outlet of the steam superheater, and a temperature transmitter II is installed at the bottom of the convection section inside the steam superheater; the temperature transmitter I and the temperature transmitter II are electrically connected to the input terminal of the DCS system.

[0010] Furthermore, a pressure transmitter II is installed on the main fuel gas pipeline, and a pressure transmitter V is installed on the branch fuel gas pipeline; the pressure transmitter II and the pressure transmitter V are electrically connected to the input terminal of the DCS system.

[0011] The advantages of this invention are: the safety conditions for ignition start are determined by the DCS system, which improves the ignition success rate; and by observing the DCS system curve, misjudgments by the instruments are avoided; and the first and third hidden dangers mentioned in the background art are solved.

[0012] By controlling the preheating ignition, the furnace body and pipelines are fully preheated, avoiding furnace deformation and pipeline rupture. At the same time, by analyzing the combustible gas concentration, the risk of flash explosion caused by excessive fuel gas and internal leakage is reduced, thereby solving the second and fourth hidden dangers in the background technology. Attached image description:

[0013] Figure 1 This is a schematic diagram of the structure of this utility model.

[0014] Figure 2 This is a schematic diagram of the electrical signal transmission structure of the DCS system of this utility model.

[0015] The components in the attached diagram are labeled as follows: 1. Steam superheater; 2. Fuel gas main pipeline; 3. Fuel gas branch pipeline; 4. Oxygen content analyzer; 5. First vent pipeline; 6. Second vent pipeline; 7. Non-condensable gas pipeline; 8. Flow transmitter I; 9. Flow transmitter II; 10. Temperature transmitter I; 11. Temperature transmitter II; 12. Pressure transmitter I; 13. Pressure transmitter II; 14. Pressure transmitter III; 15. Pressure transmitter IV; 16. Shut-off valve I; 17. Shut-off valve II; 18. Shut-off valve III; 19. Shut-off valve IV; 20. Shut-off valve V; 21. Shut-off valve VI; 22. Shut-off valve VII; 23. Pressure regulating valve I; 24. Pressure regulating valve II; 25. Detailed implementation method:

[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0017] like Figure 1 As shown, this embodiment provides a control system for reducing the risk of flash explosion in a steam superheater, which includes a steam superheater 1, a DCS system, a fuel gas main pipeline 2 and a fuel gas branch pipeline 3 connected to the steam superheater 1; wherein, the DCS system is a system manufactured by Yokogawa and model number CENTUM VP.

[0018] The signal input device of this utility model includes:

[0019] Flow transmitter I8: Used to monitor the inlet flow rate of superheated steam materials;

[0020] If the superheated steam material flow rate is too low, the upstream conveying volume needs to be increased; if the superheated steam material flow rate is too high, the upstream conveying volume needs to be reduced, so as to ensure sufficient steam supply to meet the needs of downstream processes.

[0021] Flow transmitter II9: Used to monitor the inlet flow rate of main fuel gas; a low main fuel gas flow rate will lead to an excessively low temperature inside the steam superheater 1, which in turn will affect the steam volume. In this case, it is necessary to increase the upstream delivery volume.

[0022] Oxygen content analyzer 4: used to monitor the oxygen content of flue gas inside steam superheater 1;

[0023] Temperature transmitter I10: Used to monitor the outlet temperature of superheated steam material; if the detected temperature is too low, it feeds back to the DCS system to increase the opening of pressure regulating valve I24 to increase the fuel gas intake and raise the temperature inside the steam superheater 1; if the temperature is too high, it reduces the fuel gas intake and lowers the temperature.

[0024] Temperature transmitter II11: Used to monitor the temperature at the bottom of the convection section inside the steam superheater 1;

[0025] Pressure transmitter I12: Used to monitor the negative pressure in the furnace of steam superheater 1;

[0026] Pressure transmitter II13: Used to monitor the main fuel gas pressure; when the monitored pressure is too high or too low, it controls and adjusts the pressure regulating valve I24 to maintain the pressure within the set range required by the process, thereby controlling the intake gas volume.

[0027] Pressure transmitter Ⅲ14: Used to monitor fuel gas pressure;

[0028] Pressure transmitter Ⅳ15: Used to monitor the pressure of non-condensable gases; if the pressure is too high or too low, the process personnel can adjust the upstream delivery pressure to ensure that the pressure is within the range required by the process.

[0029] Pressure transmitter V16: Used to monitor ignition exhaust gas pressure; if the pressure is too high or too low, process personnel can adjust pressure regulating valve II25 to control the intake air volume and maintain the pressure within a suitable range.

[0030] Signal output devices include:

[0031] Shut-off valve I17 and shut-off valve V21: used for fuel gas venting and on / off control; when ignition fails, during normal shutdown or abnormal operating conditions, it is necessary to discharge the fuel gas remaining in the pipeline. In these cases, the valve is opened and closed after all the fuel gas has been discharged.

[0032] Shut-off valves II18, III19, IV20, VI22, and VII23 are used for fuel gas on / off control. During ignition or under normal operating conditions, fuel gas enters the steam superheater 1 through the above valves, in which case the valves need to be opened. When the boiler is shut down, the valves are closed.

[0033] Pressure regulating valve I24 and pressure regulating valve II25: used for regulating fuel gas flow.

[0034] Specifically, a pressure transmitter I12 and an oxygen content analyzer 4 are installed in the furnace of the steam superheater 1, and a pressure transmitter III14 is installed at the inlet of the fuel gas main line 2; a pressure regulating valve I24, a shut-off valve IV20, and a shut-off valve VII23 are installed on the fuel gas main line 2; a pressure regulating valve II25, a shut-off valve II18, and a shut-off valve III19 are installed on the fuel gas branch line 3; the pressure transmitter I12, the oxygen content analyzer 4, and the pressure transmitter III14 are electrically connected to the input terminal of the DCS system, and the output terminal of the DCS system is electrically connected to the pressure regulating valve I24, the pressure regulating valve II25, the shut-off valve II18, the shut-off valve III19, the shut-off valve IV20, and the shut-off valve VII23.

[0035] A first vent line 5 is connected to the fuel gas main line 2 between shut-off valve IV 20 and shut-off valve VII 23, and a shut-off valve V 21 is installed on the first vent line 5; a second vent line 66 is connected to the fuel gas branch line 3 between shut-off valve II 18 and shut-off valve III 19, and a shut-off valve I 17 is installed on the second vent line 66; the output terminal of the DCS system is electrically connected to shut-off valve V 21 and shut-off valve I 17.

[0036] It also includes a non-condensable gas pipeline 7 connected to the steam superheater 1; the non-condensable gas pipeline 7 is equipped with a shut-off valve VI22 and a pressure transmitter IV15, the pressure transmitter IV15 is electrically connected to the input terminal of the DCS system, and the output terminal of the DCS system is electrically connected to the shut-off valve VI22; the non-condensable gas is used as a supplement to the main fuel gas. When the main fuel gas is insufficient, the feedback value of the pressure transmitter IV15 is observed. When the fuel gas quantity is sufficient, the shut-off valve VI22 is opened to supplement the gas intake.

[0037] A flow transmitter I8 is installed at the superheated steam inlet of the steam superheater 1, and a flow transmitter II9 is ​​installed on the fuel gas main line 2; the flow transmitters I8 and II9 are electrically connected to the input terminal of the DCS system.

[0038] Temperature transmitter I10 is installed at the superheated steam outlet of steam superheater 1, and temperature transmitter II11 is installed at the bottom of the convection section inside steam superheater 1; temperature transmitter I10 and temperature transmitter II11 are electrically connected to the input terminal of DCS system.

[0039] Pressure transmitter II13 is installed on fuel gas main line 2, and pressure transmitter V16 is installed on fuel gas branch line 3; pressure transmitter II13 and pressure transmitter V16 are electrically connected to the input terminal of DCS system.

[0040] like Figure 2 As shown, the electrical signal input process is as follows: Each temperature transmitter, flow transmitter, and pressure transmitter in the field converts its corresponding physical signal into a 4-20mA electrical signal, which is then transmitted to the AI ​​safety barrier in the external distribution cabinet between the cabinets. The safety barrier transmits the signal to the AI ​​card in the DCS system. The card uploads the signal to the CPU of the DCS system via the DP line for processing and displays it on the host computer. The feedback from each shut-off valve transmits the level signal to the DI safety barrier. The DI safety barrier transmits the signal to the DI card. The DI card transmits the signal to the CPU via the DP line. The CPU performs the processing and displays it on the host computer.

[0041] Electrical signal output process control: The operator sets the relevant pressure regulating valve opening command on the host computer DCS system. The CPU performs calculations and transmits a 4-20mA signal to the AO card via the DP line. The card transmits the signal to the AO safety barrier. The safety barrier transmits the signal to the field valve positioner via cable. The positioner performs calculations and acts on the valve to control the valve opening. When the operator presses the valve switch command on the host computer, the CPU performs calculations and transmits the control signal to the DO card. The DO card transmits the level signal to the field shut-off valve to control the valve action.

[0042] Ignition control process:

[0043] (1) Ignition condition determination:

[0044] a. Pressure regulating valve I 24 and pressure regulating valve II 25 are in the closed state;

[0045] b. The fuel gas pressure monitored by pressure transmitter Ⅲ14 is greater than 10 kPa;

[0046] c. Oxygen content analyzer 4 detected that the oxygen content in the flue gas inside the furnace was greater than 20%;

[0047] d. The negative pressure in the furnace monitored by pressure transmitter I12 is less than or equal to -5 Pa;

[0048] e. On-site staff took samples and analyzed the combustible gas (methane, CO) content, which was less than 0.2%;

[0049] When all five conditions above are met, the real-time values ​​of pressure transmitter I12, pressure transmitter III14, and oxygen content analyzer 4 can be observed by retrieving the DCS system curves. If the curves do not fluctuate drastically within the preset time, it can be determined that the instrument display is accurate, and ignition operation can then be performed.

[0050] This invention uses the transmission of the aforementioned electrical signals to allow the DCS system to determine the safety conditions for ignition startup, thereby improving the ignition success rate. Furthermore, by observing the DCS system curve, it avoids misjudgments by the instruments, thus resolving the first and third hidden dangers mentioned in the background art.

[0051] (2) The DCS system starts preheating and ignition (supplying fuel gas to the continuous lamps).

[0052] A. Ignition successful:

[0053] a. Open the fuel gas inlet valve (pressure regulating valve II 25, shut-off valve II 18, shut-off valve III 19), delay for 15 seconds (adjustable), and close the vent valve (shut-off valve I 17);

[0054] b. Turn on the DCS system ignition switch for 6 seconds (adjustable). Within 15 seconds (adjustable), confirm the ignition success by pressing the ignition success button through the flame detector and flame detector video to enter normal operation.

[0055] B. Ignition failure:

[0056] After 15 seconds of ignition, the operator needs to confirm the presence of a flame signal via the flame detector signal or video. If a flame signal is present, press the soft button on the host computer. If there is no signal, do not press the soft button on the host computer, and the operation is considered a failure.

[0057] If ignition fails, the following interlocking operation is performed: the vent valve (shut-off valve I17) is opened, and the feed valve (pressure regulating valve II25, shut-off valve II18, shut-off valve III19) is closed. None of the above valves can be operated within 5 minutes (adjustable).

[0058] Before ignition, staff will analyze the combustible gas concentration as a safety interlock condition, and then determine the internal leakage of the valve. If the combustible gas concentration is low, process replacement will be carried out. If the combustible gas concentration is high, venting measures will be taken, the valve will be taken offline for maintenance, and ignition will be prohibited. If the analysis is qualified, preheating can be restarted after 5 minutes.

[0059] By controlling the preheating ignition as described above, the furnace body and pipelines are fully preheated, avoiding furnace deformation and pipeline rupture. At the same time, by analyzing the combustible gas concentration, the risk of flash explosion caused by excessive fuel gas and internal leakage is reduced, thereby solving the second and fourth hidden dangers in the background technology.

[0060] (3) Ignite the main flame

[0061] After the DCS system preheating is successful, the main flame is ignited:

[0062] A. Main ignition condition check: When the fuel gas pressure (pressure transmitter Ⅲ14) is greater than 8.5 kPa, the fuel gas feed valve (pressure regulating valve Ⅰ24, shut-off valve Ⅳ20, shut-off valve Ⅶ23) is allowed to be opened;

[0063] B. Press the main fire switch to ignite the main fire.

[0064] Troubleshooting: During the delay and ignition process, the DCS system monitors key parameters in real time, such as heat source overload and pipeline leakage. Once an abnormality is detected, the DCS system immediately enters the safety interlock shutdown state, closes the steam valve, and opens the vent valve. At the same time, an alarm is sent to the operator through the host computer, indicating the fault type and handling suggestions.

[0065] Through the above technical solutions, the time delay control of the steam superheater 1 of this utility model can effectively improve the safety and stability of equipment operation, reduce energy consumption, and extend the service life of equipment, and has great application value and market prospects.

[0066] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A control system for reducing the risk of flash explosion in a steam superheater, comprising a steam superheater, characterized in that, It also includes a DCS system, and a main fuel gas pipeline and branch fuel gas pipelines connected to the steam superheater; A pressure transmitter I and an oxygen content analyzer are installed in the furnace of the steam superheater, and a pressure transmitter III is installed at the inlet of the fuel gas main pipeline. The main fuel gas pipeline is equipped with pressure regulating valve I, shut-off valve IV, and shut-off valve VII; the branch fuel gas pipeline is equipped with pressure regulating valve II, shut-off valve II, and shut-off valve III. The pressure transmitter I, the oxygen content analyzer, and the pressure transmitter III are electrically connected to the input terminal of the DCS system, and the output terminal of the DCS system is electrically connected to the pressure regulating valve I, the pressure regulating valve II, the shut-off valve II, the shut-off valve III, the shut-off valve IV, and the shut-off valve VII.

2. The control system for reducing the risk of flash explosion in a steam superheater according to claim 1, characterized in that, A first vent line is connected to the main fuel gas pipeline between the shut-off valve IV and the shut-off valve VII, and a shut-off valve V is installed on the first vent line; a second vent line is connected to the branch fuel gas pipeline between the shut-off valve II and the shut-off valve III, and a shut-off valve I is installed on the second vent line; the output terminal of the DCS system is electrically connected to the shut-off valve V and the shut-off valve I.

3. The control system for reducing the risk of flash explosion in a steam superheater according to claim 1, characterized in that, It also includes a non-condensable gas pipeline connected to the steam superheater; a shut-off valve VI and a pressure transmitter IV are installed on the non-condensable gas pipeline, the pressure transmitter IV is electrically connected to the input terminal of the DCS system, and the output terminal of the DCS system is electrically connected to the shut-off valve VI.

4. A control system for reducing the risk of flash explosion in a steam superheater according to any one of claims 1 to 3, characterized in that, A flow transmitter I is installed at the superheated steam inlet of the steam superheater, and a flow transmitter II is installed on the fuel gas main pipeline; the flow transmitter I and the flow transmitter II are electrically connected to the input terminal of the DCS system.

5. A control system for reducing the risk of flash explosion in a steam superheater according to claim 4, characterized in that, Temperature transmitter I is installed at the superheated steam outlet of the steam superheater, and temperature transmitter II is installed at the bottom of the convection section inside the steam superheater; temperature transmitter I and temperature transmitter II are electrically connected to the input terminal of the DCS system.

6. A control system for reducing the risk of flash explosion in a steam superheater according to claim 4, characterized in that, Pressure transmitter II is installed on the main fuel gas pipeline, and pressure transmitter V is installed on the branch fuel gas pipeline; pressure transmitter II and pressure transmitter V are electrically connected to the input terminal of the DCS system.

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