A canister-type direct-fired furnace capable of autonomous combustion suppression and a control method thereof

Abstract

The present application relates to the technical field of fire tube heating furnace, in particular to a fire tube direct heating furnace capable of autonomous combustion inhibition and a control method thereof, comprising a combustion furnace chamber, a circle of outer water jacket is arranged outside the combustion furnace chamber, the outer water jacket is connected with a flash structure, the flash structure is connected with a steam exhaust inhibition structure and a temperature reduction inhibition structure, the outer water jacket is filled with softened water, an emergency cut-off electromagnetic valve is arranged in communication between the outer water jacket and the flash structure, the steam exhaust inhibition structure and the temperature reduction inhibition structure are in communication with the inside of the combustion furnace chamber, the emergency cut-off electromagnetic valve is electrically connected with a controller, the controller is electrically connected with a switch control end of a combustion generator, and is electrically connected with a signal delivery end of a flame detector, a temperature sensor and a pressure sensor. The present application solves the technical problems in the prior art that combustion inhibition depends on external gas source, cold gas injection causes thermal stress damage, and residual heat of the fire tube wall cannot be eliminated.

Description

Technical Field

[0001] This invention relates to the field of fire-tube type heating furnace technology, and more specifically, to a fire-tube type direct heating furnace with autonomous combustion suppression and its control method. Background Technology

[0002] Fire-tube direct heating furnaces are widely used in petroleum, chemical, and other fields. They generate high-temperature flames within the furnace chamber via a combustion generator. The heat penetrates the furnace walls to heat the medium (such as water) inside the cylinder, thereby heating crude oil or natural gas in the oil and gas pipeline to achieve temperature increase and viscosity reduction or process heating. However, such equipment has the following safety hazards during long-term operation:

[0003] First, the combustion temperature inside the furnace is typically above 800℃. Under prolonged high-temperature conditions, components such as the furnace wall and flue gas pipes are prone to localized overheating, cracking, or even media leakage due to thermal fatigue and corrosion. If fuel leakage or abnormal flame occurs inside the furnace and combustion is not effectively suppressed in time, it may lead to serious accidents such as deflagration or explosion, endangering equipment and personnel safety.

[0004] Secondly, in existing technologies, although some heating furnaces are equipped with combustion suppression systems, they typically use an external inert gas source (such as a nitrogen cylinder or nitrogen generator) to inject room-temperature inert gas into the furnace for fire extinguishing and air replacement. This approach has significant shortcomings: First, it relies on an external gas source, which poses a risk of gas depletion, pipeline blockage, or insufficient gas pressure in remote oil fields, offshore platforms, and other locations with limited conditions, leading to the failure of the suppression function. Second, when room-temperature inert gas is directly injected into a high-temperature, high-pressure furnace, the drastic temperature difference can cause enormous thermal stress on the furnace wall, easily leading to local shrinkage and deformation of the furnace wall and flue, or even cracks, which can exacerbate equipment damage. Third, this approach can only achieve temporary inertization and extinguishing, and cannot effectively reduce the high-temperature residual heat on the furnace wall. The fire tube wall may still become an ignition source for any remaining combustible gases, posing a risk of reignition. Summary of the Invention

[0005] The purpose of this application is to provide a fire-tube type direct heating furnace with autonomous combustion suppression and its control method, which solves the technical problems in the prior art of combustion suppression relying on external gas sources, thermal stress damage caused by cold gas injection, and the inability to eliminate residual hot spots on the fire tube wall.

[0006] To solve the above-mentioned technical problems, the solution adopted in this application is as follows:

[0007] A fire-tube type direct heating furnace with autonomous combustion suppression includes a hollow heating tube, a water injection assembly connected to the upper part of the heating tube, a combustion chamber inside the heating tube, a combustion generator connected to one end of the combustion chamber, and an oil and gas pipe assembly installed at the top inside the heating tube.

[0008] Preferably, the combustion furnace outer casing is provided with an outer water jacket, which is connected to a flash evaporation structure, and the flash evaporation structure is also connected to an exhaust steam suppression structure and a cooling suppression structure.

[0009] Preferably, the outer water jacket is filled with softened water.

[0010] Preferably, the flash evaporation structure includes a flash evaporation chamber, the steam exhaust suppression structure includes a steam pipe, and the cooling suppression structure includes a drain pipe.

[0011] Preferably, the top of the outer water jacket is connected to the flash chamber, an emergency shut-off solenoid valve is provided between the outer water jacket and the flash chamber, the flash chamber is fixed outside the heating cylinder, the top of the flash chamber is connected to a steam pipe, and the bottom of the flash chamber is connected to a drain pipe.

[0012] Preferably, the steam pipe is connected to the interior of the combustion furnace.

[0013] Preferably, the drain pipe connects to the interior of the combustion furnace, the drain outlet is positioned to match the annular wall of the combustion furnace, and the drain outlet faces in the same direction as the extension of the combustion furnace wall.

[0014] Preferably, the emergency shut-off solenoid valve is electrically connected to a controller, which is electrically connected to the switch control terminal of the combustion generator, as well as the signal transmission terminals of the flame detector, temperature sensor, and pressure sensor.

[0015] Preferably, the flame detector, temperature sensor, and pressure sensor are all located on the combustion furnace.

[0016] Preferably, the emergency shut-off solenoid valve is normally closed when the fire-tube type heating furnace is working normally.

[0017] The flame detector is installed at one end of the combustion furnace connected to the combustion generator, with the sensing end of the flame detector facing the ignition port of the combustion generator.

[0018] The temperature sensor is installed on the combustion end tube wall of the combustion furnace.

[0019] The sensing end of the temperature sensor is in contact with or close to the outer wall of the combustion furnace.

[0020] The pressure sensor is installed at the combustion end pipe wall of the combustion furnace, and the sensing end of the pressure sensor is located inside the combustion furnace.

[0021] A check valve is connected to the steam pipe.

[0022] A thermal stress condensate drain valve is connected to the drain pipe.

[0023] The fluids in the steam pipe and drain pipe flow towards the interior of the combustion furnace through the check valve and thermal stress drain valve, respectively.

[0024] One end of the drain pipe is connected to the hollow interior of the injection ring pipe, which is fixedly sleeved on the outside of the combustion furnace.

[0025] The injection ring tube has several nozzles arranged in a ring or a ring-shaped opening, and the nozzles or the ring-shaped opening are inserted into the combustion furnace.

[0026] A mesh sleeve is fixedly fitted onto the connection port between the flash evaporation chamber and the outer water jacket.

[0027] A method for controlling autonomous combustion suppression in a fire-tube type direct heating furnace includes the following steps:

[0028] S1: The fire-tube direct heating furnace starts up, the emergency shut-off solenoid valve is normally closed, and the controller collects flame signals, combustion generator switch status signals, combustion furnace wall temperature and combustion furnace internal gas pressure in real time.

[0029] S2: When the signal received by the controller triggers any combustion suppression condition, the controller controls the emergency shut-off solenoid valve to open.

[0030] S3: High-temperature, high-pressure saturated water vapor in the outer water jacket is introduced into the flash evaporation chamber, where flash evaporation occurs to generate separated water vapor and water flow.

[0031] S4: High-temperature steam is injected into the combustion furnace under high pressure, and the internal airflow is discharged from the flue gas outlet.

[0032] S5: High-temperature water jets are sprayed at high pressure to cover the inner wall of the combustion furnace. The water vaporizes and absorbs heat to form steam.

[0033] S6: When the signal received by the controller does not trigger all combustion suppression conditions at the same time, the controller controls the emergency shut-off solenoid valve to close.

[0034] The combustion suppression conditions specifically include:

[0035] The combustion generator sends a shutdown signal, while the flame detector sends a flame sensing signal.

[0036] The combustion generator sends an activation signal, but the flame detector does not send a flame detection signal.

[0037] The temperature sensor sends an over-temperature warning signal.

[0038] The pressure sensor emits an overpressure sensing signal.

[0039] The technical solution of this application has at least the following advantages and beneficial effects:

[0040] To address the problem that inert gas sources at normal temperature and pressure can easily exacerbate the risk of deformation and cracking in the combustion furnace during traditional combustion suppression processes, this invention employs an external water jacket over the combustion furnace, filled with softened water containing fewer impurities. The residual heat generated during normal furnace operation creates a high-temperature, high-pressure environment within the jacket where saturated water and saturated steam coexist. When combustion suppression is required, an emergency shut-off solenoid valve is activated, allowing the high-temperature, high-pressure saturated steam from the jacket to enter the flash chamber and flash, generating high-pressure steam and high-temperature water flow. This simultaneously exhausts and suppresses combustion within the combustion furnace, while simultaneously lowering the furnace wall temperature due to the low-temperature difference. This reduces the risk of thermal shock cracks caused by rapid cooling of the furnace wall during combustion suppression. Furthermore, the use of softened water with fewer impurities as the suppression medium reduces scale formation within the combustion furnace, minimizing thermal stress concentration during continued use, effectively protecting the furnace structure, and extending the furnace's service life.

[0041] This invention continuously flash-evaporates and discharges saturated water from the outer water jacket during the combustion suppression process, causing a decrease in pressure within the jacket. This promotes the continuous vaporization and heat absorption of the remaining water in the jacket, aiding in the absorption of heat from the furnace wall and creating a heat trap effect. This, combined with the water jet sprayed towards the furnace wall, simultaneously absorbs heat and cools the inside and outside of the furnace, reducing the temperature difference between the inside and outside of the furnace. Furthermore, even if some of the water used for combustion suppression remains in the furnace after the combustion suppression process is completed, it can be quickly evaporated and discharged by restarting combustion in the furnace, without affecting the heating function of the subsequent fire-tube direct heating furnace.

[0042] To address the problem of accurately judging and controlling combustion suppression, this invention uses flame detectors, temperature sensors, and pressure sensors to monitor the flame state, wall temperature, and internal gas pressure within the combustion chamber in real time. Combined with the on / off status of the combustion generator, the controller comprehensively determines whether combustion suppression conditions should be triggered. When any abnormal condition such as reignition, failure to ignite, over-temperature, or over-pressure is detected, the emergency shut-off solenoid valve automatically activates to initiate flash evaporation, introducing steam and water flow to suppress combustion. Only when no abnormal condition is detected simultaneously will the combustion suppression operation be shut off, achieving accurate detection and control of combustion suppression in a fire-tube direct heating furnace. (See attached figures.)

[0043] Figure 1 This is a structural schematic diagram of the first angle of the present invention.

[0044] Figure 2 This is a structural schematic diagram of the second angle of the present invention.

[0045] Figure 3 This is a cross-sectional structural diagram of the present invention.

[0046] Figure 4 This is a cross-sectional schematic diagram of the drainage suppression structure in this invention.

[0047] Figure 5 This is a schematic diagram of the structure of the present invention after the heating cylinder has been disassembled.

[0048] Figure 6 The control logic flowchart for combustion suppression in this invention is shown.

[0049] In the diagram: 1-Heating cylinder, 2-Water injection assembly, 3-Combustion furnace, 4-Combustion generator, 5-Flue gas exhaust pipe, 6-Oil and gas pipe assembly, 7-External water jacket, 701-Pump water pipe assembly, 8-Flash structure, 801-Flash chamber, 802-Pressure relief pipe, 803-Emergency shut-off solenoid valve, 804-Wire mesh sleeve, 9-Exhaust steam suppression structure, 901-Steam pipe, 902-Check valve, 10-Cooling suppression structure, 1001-Drain pipe, 1002-Injection ring pipe, 1003-Thermal stress drain valve, 11-Flame detector, 12-Temperature sensor, 13-Pressure sensor. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. The terms "center," "upper," "lower," "inner," and "outer," indicating orientation or positional relationships based on the orientation or positional relationships shown in the figures, or the orientation or positional relationships commonly used when the product is in use, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed or operated in a specific orientation, and therefore should not be construed as a limitation on this application. It should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0052] Example

[0053] Please refer to Figures 1-5This invention provides a fire-tube type direct heating furnace with autonomous combustion suppression, used to automatically suppress combustion in the fire-tube type direct heating furnace. It includes a heating cylinder 1, which is a sealed hollow cylinder. A water injection component 2 is fixedly connected to the upper part of the heating cylinder 1. The water injection component 2 injects water and other heat-absorbing media into the heating cylinder 1 through a water pipe and a water pump. A combustion furnace 3 is fixedly installed at the bottom of the heating cylinder 1. One end of the combustion furnace 3 is connected to a combustion generator 4, and the other end of the combustion furnace 3 is connected to a flue gas exhaust pipe 5. The flue gas exhaust pipe 5 is also located inside the heating cylinder 1. The outlet end of the flue gas exhaust pipe 5 extends to the outside of the heating cylinder 1 to discharge the flue gas after combustion. An oil and gas pipe assembly 6 is installed at the top inside the heating cylinder 1. The oil and gas pipe assembly 6 contains viscous crude oil, natural gas, etc.

[0054] The heating process of the entire fire-tube direct heating furnace is as follows: water is injected into the heating cylinder 1, with the water level lower than the oil and gas pipe group 6 inside the cylinder. The combustion generator 4 is started, igniting the fuel in the combustion furnace 3 to generate flames and heat. The heat passes through the wall of the combustion furnace 3 to the external water, heating the water. The residual flue gas and heat after the flame combustion are continued to be transported to the flue gas exhaust pipe 5. The water continues to absorb heat through the wall of the flue gas exhaust pipe 5, heating the water to generate steam. The high-temperature steam contacts the oil and gas pipe group 6, heating the oil and gas inside the oil and gas pipe group 6, increasing the flowability of the viscous oil and gas, and allowing it to flow smoothly in subsequent pipelines.

[0055] Because the direct temperature generated by combustion in the combustion furnace 3 is very high (generally above 800℃), during long-term combustion heating, some equipment components may be unable to withstand the high temperature and be damaged, resulting in local overheating or leakage within the equipment. In traditional technology, to address this situation, an external inert gas source (such as nitrogen) is connected to the combustion furnace 3. When overheating or leakage is detected in the combustion furnace 3, the external inert gas source is quickly injected into the combustion furnace 3 to extinguish the fire and remove air, thereby suppressing continued combustion in the combustion furnace 3.

[0056] However, in practical applications, overheating inside the combustion furnace 3 may be accompanied by pipe blockage (pipe blockage prevents timely removal of high-temperature flue gas, leading to heat accumulation and overheating). This results in the combustion furnace 3 being in a high-temperature and high-pressure environment. Inert gas sources are generally stored in the external ambient temperature environment, and for cost reasons, no additional temperature or pressure control structures are set up. Therefore, when the inert gas source for suppressing combustion is introduced into the combustion furnace 3, it is generally ambient temperature and pressure inert gas. When it is directly injected into the high-pressure furnace, firstly, the gas source pressure may be too low to enter the combustion furnace 3, thus failing to suppress combustion; secondly, the large temperature difference between the ambient temperature gas and the high-temperature furnace will cause the furnace wall temperature to drop sharply, generating huge thermal stress. This makes it easier for the local wall surface of the combustion furnace 3 and flue gas exhaust pipe 5 to shrink and deform, or even crack, which will increase the risk of leakage and damage to equipment components.

[0057] To solve the above problems, please refer to Figure 3 and Figure 4 In this embodiment, an outer water jacket 7 is also fitted around the outside of the combustion furnace 3. The outer water jacket 7 is filled with softened water and is located inside the heating cylinder 1. The upper part of the outer water jacket 7 is connected to the flash structure 8. The flash structure 8 is connected to the inside of the combustion furnace 3 through the exhaust suppression structure 9 and the cooling suppression structure 10. When the combustion furnace 3 overheats or leaks, high-pressure steam and high-pressure water mist are automatically injected into the combustion furnace 3 simultaneously through the flash principle of high-pressure high-temperature water vapor, and exhaust and cooling are carried out at the same time.

[0058] The flash structure 8 includes a flash chamber 801, a pressure relief pipe 802, an emergency shut-off solenoid valve 803, and a mesh sleeve 804.

[0059] The exhaust suppression structure 9 includes a steam pipe 901 and a check valve 902.

[0060] The cooling suppression structure 10 includes a drain pipe 1001, a jet ring pipe 1002, and a thermal stress drain valve 1003.

[0061] Specifically, the softened water filling the outer water jacket 7 is not completely filled, and a steam space (usually 70%-85% of the jacket volume) is left in the upper part of the outer water jacket 7. When the combustion in the combustion furnace 3 generates heat, the water in the outer water jacket 7 and the external heating cylinder 1 will absorb heat simultaneously and gradually rise to a saturated state, so that a balanced state of saturated softened water and saturated steam is formed in the outer water jacket 7, maintaining a relatively stable gas pressure in the outer water jacket 7. When the fire tube type direct heating furnace is working normally, the steam in the outer water jacket 7 will not be discharged. At this time, the outer water jacket 7 and the heating cylinder 1 have the same function, serving only as a high-pressure closed heat storage space.

[0062] Specifically, one end of the pressure relief pipe 802 is connected to the top of the external water jacket 7, and the other end of the pressure relief pipe 802 is connected to the flash chamber 801. An emergency shut-off solenoid valve 803 is connected to the pressure relief pipe 802. The emergency shut-off solenoid valve 803 is normally closed when working normally. The flash chamber 801 is fixed outside the heating cylinder 1. The top of the flash chamber 801 is connected to the steam pipe 901, and the bottom of the flash chamber 801 is connected to the drain pipe 1001.

[0063] Preferably, the emergency shut-off solenoid valve 803 is electrically connected to the internal sensing end and the switching end of the device. When the fire-tube direct heating furnace malfunctions and shuts down, or when there is an internal overheating leak, the emergency shut-off solenoid valve 803 receives a signal change from the sensing end or the switching end, and the solenoid valve changes from the normally closed state to the normally open state. This allows the space of the outer water jacket 7 to be connected to the steaming chamber through the pressure relief pipe 802. Since the flash steaming chamber 801 is in a normal pressure environment, while the outer water jacket 7 is in a high temperature and high pressure environment due to heating, the high temperature and high pressure saturated water vapor in the outer water jacket 7 will enter the flash steaming chamber 801 due to the instantaneous pressure drop and undergo violent flash steaming, generating a large amount of saturated water vapor and saturated water in the flash steaming chamber 801.

[0064] A mesh sleeve 804 is fixedly fitted on the pressure relief pipe 802 that is connected to the flash chamber 801. When the high-pressure water vapor in the outer water jacket 7 enters the flash chamber 801, it will impact the mesh surface of the mesh sleeve 804, thereby quickly separating the water vapor and water in the water vapor.

[0065] Preferably, the top of the flash chamber 801 is connected to one end of the steam pipe 901, and the other end of the steam pipe 901 is connected to the inside of the combustion furnace 3 and located at the end of the combustion furnace 3 connected to the combustion generator 4. This allows high-pressure, high-temperature steam to be injected into the furnace, diluting the oxygen in the furnace and discharging it. The high-pressure steam directly covers the end of the combustion furnace 3 where the flame is generated, further preventing the burner from continuing to ignite the flame. The temperature difference between the high-temperature steam (above 120°C) and the high-temperature combustion furnace 3 is also smaller, resulting in less cold-state thermal shock to the combustion furnace 3, making it less likely for thermal stress to accumulate and reducing the possibility of damage to the combustion furnace 3.

[0066] Preferably, the bottom of the flash chamber 801 is connected to one end of the drain pipe 1001, and the other end of the drain pipe 1001 is connected to the hollow interior of the injection ring pipe 1002. The injection ring pipe 1002 is fixedly sleeved on the outside of the combustion furnace 3, and several nozzles or a ring opening are arranged in a ring on the injection ring pipe 1002. The nozzles or the ring opening penetrate into the interior of the combustion furnace 3 and are close to the annular wall of the interior of the combustion furnace 3. The injection direction is towards the extension direction of the wall of the combustion furnace 3 (i.e., the length direction of the combustion furnace 3), so that the high-pressure and high-temperature water flow is sprayed onto the inner wall of the combustion furnace 3 through the nozzles or the ring opening. When the high-temperature water flow contacts the wall, it quickly vaporizes into water vapor, which quickly absorbs the heat of the furnace wall and cools the inner wall of the combustion furnace 3, gradually eliminating the overheating of the combustion furnace 3. The large amount of water vapor generated will further dilute the oxygen content in the furnace, making it more difficult for the combustion furnace 3 to burn and heat up.

[0067] Preferably, the combustion furnace 3 needs to be connected to both the steam pipe 901 and the drain pipe 1001 of the flash chamber 801 to achieve its own combustion suppression effect. Simply injecting steam into the combustion furnace 3 can only expel the air inside the furnace, and the cooling effect on the furnace wall is weak (the steam absorbs less heat), which cannot solve the overheating problem of the combustion furnace 3. Simply spraying water into the wall of the combustion furnace 3 can only cool the furnace, but without the high-speed jet of steam, it cannot quickly expel the oxygen inside the combustion furnace 3, and reignition may still occur.

[0068] It is worth noting that a check valve 902 is connected to the steam pipe 901, and a thermal stress condensate valve 1003 is connected to the drain pipe 1001. When the fire-tube direct heating furnace is working normally, the check valve 902 can block the steam pipe 901, and the thermal stress condensate valve 1003 can block the drain pipe 1001 to prevent the flame and flue gas from entering the pipe in reverse. When the fire-tube direct heating furnace is used for combustion suppression, the high-pressure steam in the steam pipe 901 can be unidirectionally introduced into the combustion furnace 3, and the high-pressure water in the drain pipe 1001 can be unidirectionally introduced into the combustion furnace 3. By utilizing its own steam blocking and drainage function, it is prevented that the gas mixed in the high-pressure water flow will be ejected from the ring pipe 1002, which would prevent the water flow from continuously covering the furnace wall for heat absorption and cooling. This reduces the occurrence of local thermal stress concentration in the furnace due to the non-directional discharge of gas.

[0069] It is worth noting that the outer water jacket 7 is also connected to a pump water pipe assembly 701, which enables the outer water jacket 7 to perform combustion suppression work. After the softened water stored inside is consumed, new softened water can be replenished through the pump water pipe assembly 701.

[0070] Although the emergency shut-off solenoid valve 803 is connected to the internal sensing and switching terminals of the device to detect whether the fire-tube direct heating furnace has overheating leakage or shutdown, and thus quickly start the flash evaporation of the external water jacket 7 to suppress combustion in the combustion furnace 3, the situation of overheating leakage and other faults in the fire-tube direct heating furnace in actual working scenarios is very complex. The problem of the fire-tube direct heating furnace cannot be directly determined by simple fault shutdown and temperature detection. A specific detection system is needed to control the opening and closing of the emergency shut-off solenoid valve 803.

[0071] To solve the above problems, please refer to Figure 1 , Figure 2 and Figure 5 In this embodiment, a flame detector 11, a temperature sensor 12, and a pressure sensor 13 are also fixedly installed in the combustion furnace 3 to specifically identify whether there is a problem with the fire tube type heating furnace by the change of the sensing signal.

[0072] Specifically, the flame detector 11, temperature sensor 12, and pressure sensor 13 are all located outside the heating cylinder 1 to avoid the influence of the temperature of the water inside the heating cylinder 1 on the sensing signal (all three sensors are used to detect the combustion furnace 3) and to reduce the damage of high temperature to the sensor body.

[0073] Specifically, the flame detector 11 is installed at one end of the combustion furnace 3 connected to the combustion generator 4. The sensing end of the flame detector 11 faces the ignition port of the combustion generator 4. If reignition occurs in the combustion furnace 3, the position with the highest probability of reignition should be at the ignition port in the combustion furnace 3 (where more fuel and air supplied by the combustion generator 4 will remain).

[0074] Specifically, the temperature sensor 12 is installed at the combustion end pipe wall of the combustion furnace 3. The sensing end of the temperature sensor 12 is in contact with or close to the outer pipe wall of the combustion furnace 3, so as to avoid being burned by the open flame in the combustion furnace 3. At the same time, it detects the highest temperature in the combustion furnace 3 by detecting the highest temperature at the tail of the combustion flame.

[0075] Specifically, the pressure sensor 13 is also located at the combustion end pipe wall of the combustion furnace 3. The sensing end of the pressure sensor 13 is located inside the combustion furnace 3. The flame at the combustion end of the combustion furnace 3 has basically disappeared, and only a large amount of flue gas remains. Therefore, the pressure sensor 13 is not easily burned out, and the flue gas pressure inside the combustion furnace 3 can be detected by the pressure sensor 13.

[0076] The emergency shut-off solenoid valve 803 is electrically connected to the controller, which is electrically connected to the switch control terminal of the combustion generator 4, as well as the signal transmission terminals of the flame detector 11, temperature sensor 12, and pressure sensor 13.

[0077] Preferably, when overheating occurs in the fire-tube direct heating furnace, the temperature sensor 12 will sense the overheating signal and send it to the control terminal to activate the combustion suppression mechanism; when overpressure occurs in the fire-tube direct heating furnace, the pressure sensor 13 will sense the overpressure signal and send it to the control terminal to activate the combustion suppression mechanism; when the combustion generator 4 is shut down and the combustion chamber 3 reignites, the flame detector 11 will sense the reignition signal and send it to the control terminal to activate the combustion suppression mechanism.

[0078] For preferred options, please refer to [the provided text]. Figure 6 Based on the above embodiments, a control method for autonomous combustion suppression of a fire-tube type direct heating furnace can be obtained, and the specific steps are as follows:

[0079] S1: The fire-tube type direct heating furnace starts, the emergency shut-off solenoid valve 803 is normally closed, and the controller collects flame signals, combustion generator 4 switch status signals, combustion furnace 3 wall temperature and combustion furnace 3 internal air pressure in real time.

[0080] S2: When the signal received by the controller triggers any combustion suppression condition, the controller controls the emergency shut-off solenoid valve 803 to change from the normally closed state to the open state.

[0081] The combustion suppression conditions specifically include:

[0082] The combustion generator 4 sends a shutdown signal, while the flame detector 11 sends a flame sensing signal. This indicates that reignition has occurred inside the combustion furnace 3, and combustion suppression is required.

[0083] The combustion generator 4 sends an activation signal, but the flame detector 11 does not send a flame detection signal. This situation indicates that there is an accumulation of combustible gas inside the combustion furnace 3 (the fuel input to the combustion generator 4 can be gas). It is necessary to suppress the steam exhaust to avoid a flash explosion.

[0084] Temperature sensor 12 sends an over-temperature sensing signal (it has a built-in safe temperature threshold; exceeding the threshold is considered over-temperature and a sensing signal is sent). This situation indicates that excessive combustion or heat accumulation has occurred inside the combustion furnace 3, and combustion suppression and temperature reduction are required.

[0085] Pressure sensor 13 sends an overpressure sensing signal (it has a built-in safety pressure threshold; exceeding the threshold is considered overpressure and a sensing signal is sent). This situation indicates that gas blockage has occurred inside the combustion furnace 3, and gas and heat have accumulated, requiring combustion suppression to avoid flash explosion.

[0086] S3: High-temperature and high-pressure saturated water vapor in the outer water jacket 7 is introduced into the flash evaporation chamber 801, where flash evaporation occurs to generate separated water vapor and water flow.

[0087] S4: High-temperature steam is injected into the combustion furnace 3 under high pressure to dilute the internal oxygen concentration and promote the internal airflow to be discharged from the flue gas outlet.

[0088] S5: High-temperature water jets and high-pressure injections cover the inner wall of the combustion furnace 3. The water vaporizes and absorbs heat, cooling the furnace wall. The vaporized water vapor further dilutes the oxygen concentration inside the furnace.

[0089] S6: When the signals received by the controller do not trigger all combustion suppression conditions at the same time, the controller controls the emergency shut-off solenoid valve 803 to close, the flash evaporation ends, and the combustion suppression operation stops.

[0090] The presence of any trigger signal indicates a malfunction in the current fire-tube direct heating furnace, necessitating continuous combustion suppression. Only when the controller fails to receive any trigger signal does it indicate that the internal problem of the fire-tube direct heating furnace has been resolved or suppressed, reducing the likelihood of the furnace still being damaged due to incomplete combustion suppression.

[0091] Preferably, during the combustion suppression process, as the softened water in the outer water jacket 7 is continuously flashed out, the pressure inside the outer water jacket 7 will gradually decrease. This will further promote the continuous vaporization and heat absorption of the saturated water in the outer water jacket 7, which will help absorb the heat from the inner combustion furnace wall 3 and convert it into water vapor for combustion suppression. As long as the temperature of the fire tube wall remains higher than the boiling point of water, the vaporization and heat absorption pressurization in the outer water jacket 7 can continue (at least for a few minutes) until the temperature of the fire tube drops below the boiling point of water or all the water in the outer water jacket 7 is vaporized and discharged. This process forms a heat trap effect, which can absorb heat from both inside and outside along with the water jet inside the combustion furnace 3, thereby further reducing the occurrence of excessive temperature difference between the inner and outer walls of the high-temperature metal wall (the wall of the combustion furnace 3) and overheating cracking.

[0092] Among them, the heat trap effect refers to the interfacial vaporization heat trap effect in heat transfer. It means that during the boiling process, the liquid micro-layer at the bottom of the bubble rapidly vaporizes, taking away a large amount of latent heat, which significantly reduces the local interface temperature, thereby forming a "heat trap" and producing the effect of enhancing the heat transfer rate.

[0093] Preferably, the water in the outer water jacket 7 is the main agent for flash evaporation and combustion inhibition. If commonly used natural water is used, because this natural water contains minerals or sand particles (hard water), it is easy for impurities to adhere to the walls of the various pipes under high temperature, high pressure and impact, causing scale to form on the inner wall of the flash chamber 801 and the combustion furnace 3. In this embodiment, after the water vapor and water flow formed by flash evaporation are used to inhibit combustion in the combustion furnace 3, the combustion furnace 3 will continue to be used for combustion. If local scale points are generated in the combustion furnace 3, due to the difference in thermal conductivity between the scale and the furnace wall, local thermal stress concentration on the furnace wall surface is easy to occur, which makes it easier for heat accumulation and cracking to occur, thereby reducing the service life of the combustion furnace 3. Therefore, it is necessary to use softened water with low mineral content (low hardness) to reduce the occurrence of scale during the combustion inhibition process.

[0094] It is worth noting that the safe temperature threshold and the safe gas pressure threshold built into the temperature sensor 12 and the pressure sensor 13 are technical common sense that must be mastered by those skilled in the art. These are used to quickly determine whether the fire-tube direct heating furnace is experiencing overheating or overpressure (e.g., the combustion temperature in the furnace exceeds 1200℃, which is abnormal overheating; the gas pressure in the furnace exceeds 0.6 MPa, which is abnormal overpressure). Therefore, no specific numerical limit is set for the safe temperature threshold and the safe gas pressure threshold in this embodiment.

[0095] The various embodiments of the present invention have now been described in detail. To avoid obscuring the concept of the invention, some details known in the art have not been described. Those skilled in the art will fully understand how to implement the technical solutions of this invention based on the above description, and the scope of the invention is defined by the appended claims.

Claims

1. A fire-tube type direct heating furnace with self-inhibiting combustion, comprising a hollow heating cylinder (1), a water injection assembly (2) connected to the upper part of the heating cylinder (1), a combustion chamber (3) provided inside the heating cylinder (1), a combustion generator (4) connected to one end of the combustion chamber (3), and an oil and gas pipe assembly (6) installed at the top inside the heating cylinder (1), characterized in that: The combustion furnace (3) is fitted with an outer water jacket (7), which is connected to a flash structure (8). The flash structure (8) is also connected to an exhaust suppression structure (9) and a cooling suppression structure (10). The outer water jacket (7) is filled with softened water; The flash structure (8) includes a flash chamber (801), the exhaust suppression structure (9) includes a steam pipe (901), and the cooling suppression structure (10) includes a drain pipe (1001). The top of the outer water jacket (7) is connected to the flash chamber (801), and an emergency shut-off solenoid valve (803) is provided between the outer water jacket (7) and the flash chamber (801). The flash chamber (801) is fixed outside the heating cylinder (1). The top of the flash chamber (801) is connected to the steam pipe (901), and the bottom of the flash chamber (801) is connected to the drain pipe (1001). The steam pipe (901) is connected to the interior of the combustion furnace (3); The drain pipe (1001) is connected to the inside of the combustion furnace (3), the drain outlet position matches the annular wall inside the combustion furnace (3), and the drain outlet orientation is consistent with the extension direction of the wall of the combustion furnace (3). The emergency shut-off solenoid valve (803) is electrically connected to the controller, which is electrically connected to the switch control terminal of the combustion generator (4), as well as the signal transmission terminals of the flame detector, temperature sensor (12) and pressure sensor (13); The flame detector (11), temperature sensor (12) and pressure sensor (13) are all installed on the combustion furnace (3); When the fire-tube type heating furnace is working normally, the emergency shut-off solenoid valve (803) is normally closed.

2. The fire-tube type direct heating furnace with self-inhibiting combustion as described in claim 1, characterized in that, The flame detector (11) is located at one end of the combustion furnace (3) connected to the combustion generator (4), with the sensing end of the flame detector (11) facing the ignition port of the combustion generator (4).

3. The fire-tube type direct heating furnace with self-inhibiting combustion as described in claim 1, characterized in that, The temperature sensor (12) is installed at the combustion end pipe wall of the combustion furnace (3); The sensing end of the temperature sensor (12) is in contact with or close to the outer wall of the combustion furnace (3).

4. The fire-tube type direct heating furnace with self-inhibiting combustion as described in claim 1, characterized in that, The pressure sensor (13) is located at the combustion end pipe wall of the combustion furnace (3), and the sensing end of the pressure sensor (13) is located inside the combustion furnace (3).

5. A fire-tube type direct heating furnace with self-inhibiting combustion as described in claim 1, characterized in that, A check valve (902) is connected to the steam pipe (901); A thermal stress condensate valve (1003) is connected to the drain pipe (1001). The fluids in the steam pipe (901) and drain pipe (1001) flow towards the interior of the combustion furnace (3) through the check valve (902) and thermal stress drain valve (1003), respectively.

6. A fire-tube type direct heating furnace with self-inhibiting combustion as described in claim 1, characterized in that, One end of the drain pipe (1001) is connected to the hollow interior of the injection ring pipe (1002), and the injection ring pipe (1002) is fixedly sleeved on the outside of the combustion furnace (3); The injection ring pipe (1002) has several nozzles arranged in a ring or a ring opening, and the nozzles or the ring opening are inserted into the combustion furnace (3).

7. A fire-tube type direct heating furnace with self-inhibiting combustion as described in claim 1, characterized in that, A mesh sleeve (804) is fixedly fitted on the communication port between the flash chamber (801) and the outer water jacket (7).

8. A control method for autonomous combustion suppression in a fire-tube type direct heating furnace, characterized in that, Includes the following steps: S1: The fire tube type direct heating furnace starts, the emergency shut-off solenoid valve (803) is normally closed, and the controller collects flame signals, combustion generator (4) switch status signals, combustion furnace (3) wall temperature and combustion furnace (3) internal air pressure in real time; S2: When the signal received by the controller triggers any combustion suppression condition, the controller controls the emergency shut-off solenoid valve (803) to open; S3: High-temperature and high-pressure saturated water vapor in the outer water jacket (7) is introduced into the flash chamber (801) and flash evaporation occurs to generate separated water vapor and water flow; S4: High-temperature steam is injected into the combustion furnace (3) under high pressure, and the internal airflow is discharged from the flue gas outlet; S5: High-temperature water jets and high-pressure jets cover the inner wall of the combustion furnace (3), and the water vaporizes and absorbs heat to form steam; S6: When the signal received by the controller does not trigger all combustion suppression conditions at the same time, the controller controls the emergency shut-off solenoid valve (803) to close.

9. The control method for autonomous combustion suppression in a fire-tube type direct heating furnace according to claim 8, characterized in that, The combustion suppression conditions specifically include: The combustion generator (4) sends a shutdown signal, while the flame detector (11) sends a flame sensing signal; The combustion generator (4) sends an activation signal, while the flame detector (11) does not send a flame detection signal; The temperature sensor (12) emits an over-temperature sensing signal; The pressure sensor (13) emits an overpressure sensing signal.

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