A cracking furnace tube with coke cleaning and coking monitoring

Abstract

The present invention discloses a cracking furnace tube with coking removal and coking monitoring, which relates to the field of olefin production. One end of the cracking furnace tube has a cracking furnace tube inlet, and the other end has a cracking furnace tube outlet. Along the pipeline direction, the cracking furnace tube is provided with a plurality of decoking gas pipes and decoking gas outlet nozzles, and the decoking gas pipes introduce decoking gas to remove the coking inside the cracking furnace tube. The present invention can solve a series of problems such as real-time monitoring of coking in the cracking furnace tube, real-time coking removal, and fixed-point and positioning coking removal.

Description

Technical Field

[0001] The present invention relates to the field of olefin production, and particularly to a cracking furnace tube with coke cleaning and coking monitoring. Background Art

[0002] Light olefins such as ethylene and propylene are the basic raw materials in the petrochemical industry, and the production capacity of light olefins is one of the important indicators to measure the petrochemical development level of a country. Steam cracking is the most commonly used method for industrial production of ethylene. After the cracking furnace raw materials and steam are mixed, they are introduced into the high-temperature radiation furnace tubes of the cracking furnace, and cracking reactions occur inside the furnace tubes, generating hydrocarbon products such as ethylene and propylene. While the steam cracking reaction of hydrocarbons occurs in the radiation section of the cracking furnace, secondary reactions will accompany the cracking reaction, and coke will be deposited on the inner wall of the radiation section furnace tubes. The continuous deposition of coke powder in the furnace tubes ultimately leads to the coking phenomenon. The coking phenomenon will increase the thermal resistance of the tube wall and reduce the heat transfer coefficient of the tube wall. In order to reach the reaction temperature, it is necessary to increase the temperature of the furnace tube wall, resulting in local overheating of the furnace tube wall, which will reduce the service life of the furnace tube and increase the energy consumption during the reaction process. Under the continuous deposition of the coke layer, the inner diameter of the furnace tube will continue to shrink, increasing the pressure drop of the raw material fluid inside the furnace tube, reducing the amount of cracking raw materials participating in the reaction, and decreasing the yield of olefins. As the degree of coking increases, it will eventually even block the furnace tube, causing safety problems. Therefore, when the coking limit of a certain process requirement is reached, it is necessary to remove coke from the radiation furnace tubes of the cracking furnace; at the same time, the accumulation of coke on the inner wall of the furnace tube will cause carburization of the inner wall of the furnace tube, damage the superalloy, and reduce the service life of the furnace tube.

[0003] During the coke cleaning process, it is necessary to stop the furnace regularly for coke burning. The coke removal gas generally enters from the cracking inlet and cannot directly act on the coking site, and it is impossible to clean coke under the condition of partial coking during operation. There are also a series of problems such as the coking position cannot be monitored in real time.

[0004] Therefore, the existing technology urgently needs to be improved and developed. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention provides a cracking furnace tube with coke cleaning and coking monitoring, which can perform coke removal operations by introducing coke removal gas.

[0006] To achieve the above object, the present invention can adopt the following technical solutions:

[0007] A cracking furnace tube with coke cleaning and coking monitoring, one end of the cracking furnace tube has a cracking furnace tube inlet, and the other end has a cracking furnace tube outlet. Along the pipeline direction of the cracking furnace tube, there are several coke removal gas pipes and coke removal gas outlet nozzles. Among them, high-temperature flue gas generated after combustion enters the cracking furnace tube, and the coke removal gas pipes introduce coke removal gas to remove the coke deposited inside the cracking furnace tube.

[0008] As described above, for the cracking furnace tubes with coke cleaning and coking monitoring, further, a resistance monitoring unit and a temperature detection unit are also provided along the pipeline direction of the cracking furnace tubes. The resistance monitoring unit obtains real-time relevant data on the coking amount in the tubes by monitoring the change of the resistance value between sections, and the temperature detection unit detects the coking thickness during normal operation and the wall temperature during decoking through the temperature change on the surface of the furnace tubes.

[0009] As described above, for the cracking furnace tubes with coke cleaning and coking monitoring, further, a gas sensor is provided at the outlet of the cracking furnace tubes of the cracking furnace tubes.

[0010] As described above, for the cracking furnace tubes with coke cleaning and coking monitoring, further, a decoking gas valve is provided at the part of the decoking gas pipe outside the cracking furnace tubes.

[0011] As described above, for the cracking furnace tubes with coke cleaning and coking monitoring, further, a decoking gas outlet nozzle is provided at the part of the decoking gas pipe inside the cracking furnace tubes.

[0012] As described above, for the cracking furnace tubes with coke cleaning and coking monitoring, further, an outer insulation for the furnace tubes is provided on the outer layer of the cracking furnace tubes.

[0013] As described above, for the cracking furnace tubes with coke cleaning and coking monitoring, further, the decoking gas includes a mixed gas of oxygen and / or carbon dioxide and / or carbon dioxide and / or water vapor and / or inorganic salts.

[0014] As described above, for the cracking furnace tubes with coke cleaning and coking monitoring, further, the cracking furnace tubes are arranged in a spiral and curved manner in one or more layers.

[0015] As described above, for the cracking furnace tubes with coke cleaning and coking monitoring, further, the cracking furnace tubes are arranged horizontally or obliquely.

[0016] As described above, for the cracking furnace tubes with coke cleaning and coking monitoring, further, the gas sensor includes any one or any combination of a carbon monoxide gas sensor, a carbon dioxide gas sensor or an oxygen gas sensor.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. For the cracking furnace tubes with coke cleaning and coking monitoring in the embodiments of the present invention, by setting a plurality of resistance monitoring units and temperature detection units in the cracking furnace tubes, the reference data for real-time monitoring of coking of each section of the furnace tubes are measured after the equipment is newly built or after a major overhaul of the furnace and the coke on the furnace tubes is removed, and the position of the coking section of the furnace tubes can be found by comparing with the real-time data of coking of each section of the furnace tubes during equipment operation.

[0019] 2. The cracking furnace tube with coke removal and coking monitoring according to the embodiment of the present invention is provided with a coke removal gas valve outside the cracking furnace tube, so that coke removal can be carried out without stopping the furnace. By opening the corresponding coke removal gas valve, the coke removal gas can be directly introduced into the corresponding furnace tube for coke removal operation. The oxygen-containing gas in the coke removal gas reacts with coke to produce carbon monoxide and / or carbon dioxide. Carbon monoxide, carbon dioxide and the introduced water vapor generated during the coke removal process have a certain effect on cracking, which can increase the continuous operation time of the equipment, greatly reduce the product cost, improve the operation efficiency of the equipment, and also reduce the energy consumption during the furnace shutdown and restart process.

[0020] 3. When the cracking furnace tube with coke removal and coking monitoring according to the embodiment of the present invention is subjected to coke removal during furnace shutdown, the corresponding coke removal gas valve can be opened to directly introduce the coke removal gas into the corresponding furnace tube, so that the coke removal gas directly acts on the coke, which can reduce the oxidation of the furnace tube and at the same time reduce the time required for coke removal during furnace shutdown. At the same time, by comparing the real-time coking data of each section of the furnace tube during operation, the position of the coke removal gas inlet can be adjusted in time to effectively remove coke.

[0021] 4. The cracking furnace tube with coke removal and coking monitoring according to the embodiment of the present invention is provided with a coke removal gas valve outside the cracking furnace tube. By opening the coke removal gas valve at a suitable position and adjusting a suitable small flow rate to retain it as a long-term coke removal gas, the coke generated by the secondary reaction accompanied by the cracking reaction can be offset, which can slow down the formation of coke, extend the normal operation time of the equipment, reduce the operation cost of the product, and improve the operation efficiency of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a schematic structural diagram of the cracking furnace tube with coke removal and coking monitoring according to the embodiment of the present invention;

[0024] Figure 2 It is another schematic structural diagram of the cracking furnace tube with coke removal and coking monitoring according to the embodiment of the present invention.

[0025] Wherein: 1, cracking gas; 2, cracking furnace tube inlet; 3, coke removal gas; 4, coke removal gas valve; 5, coke removal gas pipe; 6, coke removal gas outlet nozzle; 7, resistance monitoring unit; 8, temperature detection unit; 9, external insulation of furnace tube; 10, cracking furnace tube outlet; 11, gas sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0027] Embodiment:

[0028] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned accompanying drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" in the embodiments of the present invention and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0029] It should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0030] In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In addition, unless otherwise clearly specified and limited, the terms "mounted", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0031] In the present invention, unless otherwise clearly specified or limited, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature has a higher horizontal height than the second feature. The first feature being "under", "below" and "beneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower horizontal height than the second feature.

[0032] See Figures 1 to 2 , the present invention provides a cracking furnace tube with coke removal and coking monitoring, and coke removal operation can be carried out by introducing a decoking gas 3. It may include: one end of the cracking furnace tube has a cracking furnace tube inlet 2, and the other end has a cracking furnace tube outlet 10. A plurality of decoking gas pipes 5 and decoking gas outlet nozzles 6 are arranged along the pipeline direction of the cracking furnace tube. Among them, high-temperature flue gas generated after combustion enters the cracking furnace tube, and the decoking gas pipe 5 introduces the decoking gas 3 to remove the coking inside the cracking furnace tube.

[0033] On the basis of the above embodiments, as an optional embodiment, the cracking furnace tube can monitor the real-time coking data of each section of the cracking furnace tube and timely discover the position of the coking section of the furnace tube. It may include: a resistance monitoring unit 7 and a temperature detection unit 8 are further arranged along the pipeline direction of the cracking furnace tube. The resistance monitoring unit 7 obtains real-time relevant data on the coking amount inside the tube by monitoring the change in the resistance value between sections, and the temperature detection unit 8 detects the coking thickness during normal operation and the wall temperature during coke removal through the temperature change on the surface of the furnace tube.

[0034] Specifically, the burner or heater corresponding to the equipment is turned on to provide the heat and temperature required for pyrolysis. The pyrolysis gas 1 enters the pyrolysis furnace tubes through the pyrolysis furnace tube inlet 2. The pyrolysis furnace tubes are provided with a number of resistance monitoring units 7 and temperature detection units 8. The resistance monitoring units 7 obtain real-time relevant data on the coking amount in the pyrolysis furnace tubes by monitoring the subtle changes in the resistance values between sections. Among them, the set resistance monitoring units 7 are resistance sensors, and the resistance sensors are mainly used to monitor the change of the resistance value, including the change of the current value under a constant voltage source, or the change of the voltage value under a constant current source for a small signal. The resistance monitoring units 7 represent the change of the coking amount in this section by detecting the resistance change in this section. The temperature detection units 8 are temperature sensors, and the temperature sensors are mainly thermocouples, and may include temperature sensors such as thermocouples, thermal resistors or thermosemiconductors. The temperature detection units 8 can detect the approximate coking thickness of the pyrolysis furnace tubes during normal operation and the wall temperature during decoking by detecting the temperature change on the surface of the furnace tubes, and represent the coking thickness at this point by detecting the temperature change during the stable operation under the same inlet conditions or the same outlet conditions. Among them, the number of temperature sensors can be more than the number of resistance sensors, and when monitoring the coking state of the pyrolysis furnace tubes in this embodiment, the resistance signal can be collected through the resistance monitoring units 7 for monitoring, or the temperature signal can be collected through the temperature detection units 8 for monitoring, or the resistance monitoring units 7 and the temperature detection units 8 can be used jointly for monitoring.

[0035] When the pyrolysis furnace tubes in this embodiment are in use, by comparing the reference resistance and temperature data for real-time monitoring of coking of each section of the furnace tubes measured during the initial operation after the equipment is newly built or after the furnace is shut down for major overhaul and the furnace tubes are defouled, with the real-time resistance and temperature data of coking of each section of the furnace tubes during operation, the position of the coking section of the furnace tubes can be found. Among them, the resistance data needs to be coupled with the temperature for processing to obtain the resistance value curve corresponding to each operating temperature condition under the initial operation, and then the calculated reference resistance value corresponding to the temperature at each detection point during the real-time operation is compared with the actually measured resistance value of each section to obtain the coking area. At the same time, the relative coking area can also be obtained through the temperature change at each detection point.

[0036] The pyrolysis furnace tubes with coke cleaning and coking monitoring according to the embodiment of the present invention are provided with a number of resistance monitoring units 7 and temperature detection units 8 in the pyrolysis furnace tubes. By comparing the reference data for real-time monitoring of coking of each section of the furnace tubes measured during the initial operation after the equipment is newly built or after the furnace is shut down for major overhaul and the furnace tubes are defouled, with the real-time data of coking of each section of the furnace tubes during equipment operation, the position of the coking section of the furnace tubes can be found. At the same time, the pyrolysis furnace tubes are provided with a number of coke removal gas pipes 5. By introducing the coke removal gas 3 into the number of coke removal gas pipes 5, the coking inside the pyrolysis furnace tubes can be removed. Compared with the prior art, the pyrolysis furnace tubes with coke cleaning and coking monitoring according to the embodiment of the present invention can timely find the position of the coking section of the furnace tubes, and perform the coke removal operation by introducing the coke removal gas 3, which can improve the service life of the furnace tubes.

[0037] Based on the above embodiments, as an alternative embodiment, a gas sensor 11 is provided at the outlet 10 of the cracking furnace tube of the cracking furnace tube. Specifically, the gas sensor 11 includes gas sensors such as carbon monoxide, carbon dioxide, and oxygen. In the embodiment of the present invention, the content of carbon dioxide and oxygen can be detected by the gas sensor 11 to obtain the final decoking effect. Exemplarily, the gas sensor 11 can be arranged at a place far from the cracking furnace tube, and even after other related equipment is spaced apart.

[0038] As an alternative embodiment, in some embodiments, a decoking gas valve 4 is provided on the part of the decoking gas pipe 5 outside the cracking furnace tube. Further, a decoking gas outlet nozzle 6 is provided on the part of the decoking gas pipe 5 inside the cracking furnace tube.

[0039] Specifically, in this embodiment, decoking can be carried out without stopping the furnace by setting the decoking gas valve 4. The specific operation is as follows: Open the corresponding decoking gas valve 4 to adjust the appropriate flow rate at each point, and introduce the decoking gas 3. After the decoking gas 3 enters the decoking gas pipe 5, it enters the decoking gas outlet nozzle 6. The decoking gas outlet nozzle 6 is beneficial to make the decoking gas 3 adhere to the wall and effectively act on the coke surface on the inner surface of the furnace tube. At the same time, the high-pressure gas of the decoking gas outlet nozzle 6 can also effectively blow open the blocked coke. Preferably, the decoking gas 3 can be preheated by an external heat exchanger before entering the furnace tube, so that it can react immediately after entering the furnace tube, thereby reducing the reaction time and better removing the coke on the inner surface of the furnace tube. In addition, when decoking is carried out by stopping the furnace, the corresponding decoking gas valve 4 can be opened, and the decoking gas 3 can be directly introduced into the corresponding furnace tube, so that the decoking gas 3 directly acts on the coke, which can reduce the oxidation of the furnace tube and at the same time reduce the time required for the decoking process of stopping the furnace. At the same time, by comparing the real-time coking data of each section of the furnace tube during operation, the entry position of the decoking gas 3 can be adjusted in time to effectively remove coke.

[0040] Based on the above embodiments, as an alternative embodiment, the decoking gas 3 can be a mixture of oxygen and / or carbon dioxide and / or water vapor and / or (inorganic salts) inhibitor. Specifically, the oxygen-containing gas in the decoking gas 3 reacts with coke to produce carbon monoxide and carbon dioxide. Carbon monoxide, carbon dioxide, and the introduced water vapor generated during the decoking process have a certain effect on cracking. At the same time, the amount of carbon dioxide and water vapor at the raw material inlet of the corresponding cracking furnace can be reduced, the continuous operation time of the equipment can be increased, the product cost can be greatly reduced, and the energy consumption during the process of stopping and restarting the furnace can also be reduced.

[0041] Based on the above embodiments, as an alternative embodiment, an outer thermal insulation 9 of the furnace tube is provided on the outer layer of the cracking furnace tube. Specifically, the outer thermal insulation 9 of the furnace tube can reduce the heat dissipation loss on the surface of the cracking furnace tube, so that the decoking gas 3 can better remove the coke on the inner surface of the furnace tube.

[0042] As an alternative embodiment, in some embodiments, the cracking furnace tubes may be arranged horizontally or obliquely. In another embodiment, the cracking furnace tubes may be arranged in one or more layers in a spiral and curved manner. Specifically, the cracking furnace tubes may be arranged horizontally (as shown in Figure 1 ), or the outlet may be arranged downward, or it may be arranged obliquely downward. The cracking furnace tubes may be arranged in a single-layer spiral (as shown in Figure 2 ), or a multi-layer spiral arrangement may be adopted. Referring to Figure 2 , when a single-layer spiral arrangement is adopted, the decoking gas valve 4, the decoking gas pipe 5, the decoking gas outlet nozzle 6, the resistance monitoring unit 7, and the temperature detection unit 8 are only arranged on the outer circle, and no equipment is arranged on the inner circle. The inner circle can receive high-temperature heat from convection and radiation, and is generally used for the case of cracking gas 1 heated by an external heat source, such as a cracking furnace with a convection coil structure.

[0043] In addition, the cracking furnace tubes of the embodiments of the present invention with decoking and coking monitoring can be operated under high-pressure conditions or under normal-pressure operating conditions. The cracking furnace tubes can be used for high-temperature cracking gas after being mixed with high-temperature flue gas, or for cracking gas 1 heated by an external heat source.

[0044] As an alternative embodiment, in some embodiments, during the stable operation of the cracking furnace tubes, the decoking gas valve 4 can also be kept open to maintain the decoking effect. The specific operation is as follows: Open the decoking gas valve 4 at a suitable position, and adjust a suitable small flow rate to be retained as the long-term decoking gas 3 to offset part of the coke generated by the secondary reaction accompanying the cracking reaction, and at the same time keep the decoking gas outlet nozzle 6 unobstructed. The flow rates of each section of the retained gas may be different according to the coking situation. Generally, more is in the middle part and less is in the starting section. At the same time, the flow rate of the decoking gas 3 in each section can be adjusted according to the data monitored by the resistance monitoring unit 7 and the temperature detection unit 8 to keep the tube furnace unobstructed for a long time. By operating in this way, it is possible to maintain for a long time without stopping the furnace for decoking. In this embodiment, by opening the decoking gas valve 4 at a suitable position and adjusting a suitable small flow rate to be retained as the long-term decoking gas 3 to offset part of the coke generated by the secondary reaction accompanying the cracking reaction, the formation of coke can be slowed down, thereby prolonging the normal operation time of the equipment, reducing the operation cost of the product, and improving the operation efficiency of the equipment.

[0045] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc., mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those ordinary skilled in the art to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the essence of the content of the present invention should be covered within the protection scope of the present invention.

Claims

1. A pyrolysis furnace tube with coke cleaning and coking monitoring, characterized in that, One end of the cracking furnace tube has a cracking furnace tube inlet, and the other end has a cracking furnace tube outlet. Along the pipeline direction, the cracking furnace tube is provided with a plurality of decoking gas pipes and decoking gas outlet nozzles. The decoking gas pipes introduce decoking gas to remove the coking inside the cracking furnace tube. Along the pipeline direction, the cracking furnace tube is also provided with a resistance monitoring unit and a temperature detection unit. The resistance monitoring unit obtains real-time relevant data on the coking amount inside the tube by monitoring the change of the resistance value between sections. The temperature detection unit detects the coking thickness during normal operation and the wall temperature during decoking through the temperature change on the surface of the furnace tube. At the cracking furnace tube outlet of the cracking furnace tube, there is a gas sensor, and the gas sensor includes any one or any combination of a carbon monoxide gas sensor, a carbon dioxide gas sensor or an oxygen gas sensor.

2. The pyrolysis furnace tube with coke cleaning and coking monitoring according to claim 1, wherein, A decoking gas valve is provided on the part of the decoking gas pipe outside the cracking furnace tube.

3. The cracking furnace tube with coke cleaning and coking monitoring according to claim 1, wherein, Decoking gas outlet nozzles are provided on the part of the decoking gas pipe inside the cracking furnace tube.

4. The cracking furnace tube with coke cleaning and coking monitoring according to claim 1, characterized in that, An outer insulation for the furnace tube is provided on the outer layer of the cracking furnace tube.

5. The cracking furnace tube with coke cleaning and coking monitoring according to claim 1, characterized in that, The decoking gas includes a mixture of oxygen and / or carbon dioxide and / or water vapor.

6. The cracking furnace tube with coke cleaning and coking monitoring according to claim 1, wherein The cracking furnace tube is arranged in a spiral and curved manner in one or multiple layers.

7. The cracking furnace tube with coke cleaning and coking monitoring according to claim 1, characterized in that, The cracking furnace tube is arranged horizontally or obliquely.

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