Decoking device and decoking process for a cracking furnace

Abstract

A coking removal device and process for a cracking furnace, which belongs to the field of petrochemical industry, and the inlet end and outlet end of the furnace tube of the cracking furnace are connected with input electrodes and input end detection electrodes, output electrodes and output end detection electrodes, the electric coking controller loads voltage and current to both ends of the furnace tube through the input and output electrodes, the current passing through the furnace tube forms an electromagnetic field, and the voltage at both ends of the furnace tube is detected in real time through the detection electrodes and uploaded to a detector; the reaction material containing coke particles flows into the furnace tube from the inlet end and flows out from the outlet end during the thermal cracking reaction process, the coke particles carry positive charges during the movement of the reaction material, and other substances carry negative charges, and since the flow direction of the coke particles in the furnace tube is consistent with the flow direction of the current, the electromagnetic field will hinder the coke particles with positive charges from approaching the furnace tube wall. The application reduces the coke particle aggregation time, prolongs the operation cycle of the cracking furnace, improves the coking removal effect, expands the temperature range applicable to the device, and does not affect the yield and selectivity of the target product of the cracking product.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and in particular relates to a decoking device and a decoking process for a cracking furnace. Background Art

[0002] Over 85% of global ethylene production utilizes a tubular furnace steam cracking process. Hydrocarbons and dilution steam undergo a thermal cracking reaction within the cracking furnace tubes at temperatures around 850°C, producing small molecule target products such as ethylene and propylene. This reaction is accompanied by numerous side reactions, including the dehydrogenation of aromatic components, which produces large amounts of byproducts such as tar and coke (hereinafter referred to as "coke pellets"). These coke pellets accumulate and clog the cracking furnace tubes, leading to production interruptions and numerous adverse impacts on ethylene production, including reduced target product yields, decreased plant processing capacity, increased energy consumption, and shortened operating cycles. Therefore, minimizing coke pellet accumulation and expediting its passage through the cracking furnace tubes is crucial to the operational efficiency of ethylene cracking furnaces.

[0003] The mechanism of hydrocarbon thermal cracking coking and its influencing factors are very complex. Currently, the more recognized ones include: catalytic coking, gas phase coking and free radical coking. Among them, gas phase coking is the main form of coking, which refers to the coke generated in the main body of the gas flow. Al-bright and Amnek (Albright LF, Marek J C. Mechanistic model for formation of coke in pyrolysis units producing ethylene [J]. Industrial & Engineering Chemistry Research, 1988, 27 (5): 755-759) used advanced means such as electron microscopy and microphotography to conduct a detailed study of the gas phase coking process. They believe that coke particles are the main substance in gas phase coking. Some of these coke particles come from the cracking reaction itself, and some are generated through polymerization and polycondensation reactions. The coking process can be expressed as:

[0004]

[0005] Tar particles, referred to as coke particles, move at a high speed together with other gaseous hydrocarbon substances in the cracking furnace tube, and the speed is 50-100 m / s. Since the mass of the coke particles is much greater than that of the other gaseous hydrocarbon substances, the moving speed of the coke particles is also lower than that of the other gaseous hydrocarbon substances. The speed difference causes the other gaseous hydrocarbon substances to continuously wash and rub the coke particles. In this process, static electricity is generated by rubbing, and the coke particles are charged positively, and the other gaseous hydrocarbon substances are charged negatively. Since the cracking furnace tube is made of metal material, grounding measures are generally adopted. The coke particles charged positively are easily separated from the reaction materials under the attraction of the electrostatic force, and are adsorbed on the inner surface of the cracking furnace tube, continuously accumulate, and block the cracking furnace tube.

[0006] In recent years, various coking inhibition technologies have been developed for thermal cracking coking. Among them are methods such as changing the cracking reaction conditions, hydrogen thermal cracking, cracking feedstock pretreatment, furnace tube surface treatment, and adding coking inhibitors. The adoption of new cracking technologies and furnace tube surface treatment processes requires a large amount of investment to replace the cracking furnace and the furnace tube, which is difficult to achieve in a short time. Moreover, the chemical market price changes rapidly, and the investment income cannot be guaranteed. Changing the dilution ratio and steam of the cracking is beneficial to reducing coking, but the effect is limited, and the increased dilution steam affects the processing capacity and yield of the device and increases the energy consumption of the device. Adding coking inhibitors has good effect, but it is difficult to avoid the inclusion of inhibitors in the product, which affects the purity and impurity content of the product and causes unpredictable impact on subsequent separation and processing. How to inhibit and reduce the side reactions of aromatic hydrocarbons in the initial stage of the reaction and increase the main reaction of ring-opening is an important issue in the current ethylene industry.

[0007] Electrostatic decoking is a new technology that has developed rapidly in recent years, involving the field of chemical reaction and separation. At present, it is mainly applied to the tail gas and air purification process. Its electrostatic decoking device is a metal tube with a metal wire in the center. The metal tube is grounded as the precipitation electrode, and the metal wire is connected to a high-voltage power supply of 30-80 kV as the discharge electrode. When the coal gas carrying tar dust enters the electric field caused by the above two electrodes (i.e. the tubular metal shell), it receives the charge discharged by the discharge electrode, i.e. the tar dust has the same charge as the discharge electrode. The charged tar dust, on the one hand, attracts other uncharged particles and combines with them to form larger particles, which eventually fall from the gas stream due to gravity; on the other hand, the charged tar dust moves to the precipitation electrode under the action of the electric field force, loses its charge when it hits the precipitation electrode, and adheres to the inner wall of the metal tube, and finally falls due to gravity or mechanical vibration, and is discharged from the tar and dust discharge port. The electrostatic decoking device needs to build a new complex high-voltage electric decoking tower, which cannot be applied to ethylene cracking decoking operation containing oxygen and high temperature. Since electrostatic decoking requires the use of high-voltage electricity of 30-80 kV, a metal wire is installed in the center as a discharge electrode, which is unstable at a high temperature of 850°C. High-voltage discharge can cause explosion of coke and air in the cracking furnace, seriously threatening the safe operation of the device, and the center-mounted metal wire discharge electrode cannot adapt to the high temperature of 850°C and the high-speed airflow scouring of 150 m / s, and it will soon be damaged and fail.

[0008] For example, the electrostatic decoking device disclosed in Chinese Patent No. CN209093613U. The electrostatic decoking device needs to build a new complex high-voltage electric decoking tower, including a decoking device body and a direct current power supply. The inner cavity of the decoking device body is provided with a partition plate, the inner cavity of the partition plate is uniformly provided with air pipes, and the air pipes penetrate through the top and bottom of the partition plate. The inner cavity of each group of air pipes is provided with a high-voltage electric field negative wire, and the electric field negative wire is connected to the negative electrode of the direct current power supply to achieve the effect of removing impurities from the gas. The electrostatic decoking device only increases the partition plate, and essentially has no difference from ordinary electric decoking. High-voltage discharge cannot be used for cracking decoking, which can cause explosion of coke and air in the cracking furnace, seriously threatening the safe operation of the device.

[0009] For example, publication number CN2882795Y discloses a honeycomb-type high-voltage electrostatic detarring dust collector. This dust collector requires the construction of a complex high-voltage electric decoking tower, comprising a housing with a gas inlet, gas outlet, and sewage outlet. The upper end of the housing houses a high-voltage incoming line box, intermittent flushing pipes, and an upper frame. The upper frame is connected to a high-voltage DC generator via high-voltage insulators within the high-voltage incoming line box. Corona wires connected to the upper and lower frames are housed within a hexagonal cylinder. Together, the corona wires and the hexagonal cylinder form a strong high-voltage DC electric field. This dust collector simply divides a large cavity into smaller honeycomb-shaped cavities, essentially no different from conventional electric decoking. The high-voltage discharge cannot be used for cracking and decoking, and can cause explosions between coke and air within the cracking furnace, seriously threatening the safe operation of the device. Furthermore, the structure is complex. Summary of the Invention

[0010] The purpose of the present invention is to provide a cracking furnace decoking device and a decoking process to solve the problem of hydrocarbon thermal cracking coking in the existing tubular furnace steam cracking process.

[0011] The technical solutions adopted by the present invention to solve the technical problems are as follows:

[0012] A decoking process for a cracking furnace according to the present invention mainly comprises the following steps:

[0013] An input electrode and an input detection electrode are connected to the inlet end of the cracking furnace tube, and an output electrode and an output detection electrode are connected to the outlet end of the cracking furnace tube. A set voltage and current are applied to both ends of the cracking furnace tube by an electric decoking controller through the input electrode and the output electrode. When current flows through the cracking furnace tube, an electromagnetic field is formed in the cracking furnace tube. At the same time, the voltage at both ends of the cracking furnace tube is detected in real time by the input detection electrode and the output detection electrode and uploaded to a detector. During the thermal cracking reaction, a reaction material containing coke particles enters the inlet end of the cracking furnace tube and flows out from the outlet end of the cracking furnace tube. At the same time, as the reaction material moves at high speed in the cracking furnace tube together with other gaseous hydrocarbon substances, the coke particles are positively charged and the other gaseous hydrocarbon substances are negatively charged. Since the flow direction of the coke particles in the cracking furnace tube is consistent with the flow direction of the current, the electromagnetic field will prevent the positively charged coke particles from approaching the tube wall of the cracking furnace tube, thereby reducing the coke particle aggregation time and extending the operation cycle of the cracking furnace.

[0014] As a preferred implementation, the set voltage range is 12V to 36V.

[0015] As a preferred implementation, the set current range is 1 mA to 10 mA.

[0016] As a preferred embodiment, the electric decoking controller is connected to a power supply.

[0017] As a preferred embodiment, the electric decoking controller is used to adjust the voltage and current applied to both ends of the cracking furnace tube to adapt to different stages of the cracking furnace operation.

[0018] As a preferred embodiment, the input detection electrode, the output detection electrode and the detector are used to realize an audible and visual alarm when it is detected that the voltage at both ends of the cracking furnace tube exceeds a set range.

[0019] As a preferred embodiment, a cooling radiator is installed on the input electrode, output electrode, input end detection electrode and output end detection electrode, and the cooling radiator is selected from one or more of an air-cooled heat dissipation structure, a water-cooled heat dissipation structure, a fin heat dissipation structure and a microchannel heat dissipation structure.

[0020] As a preferred embodiment, the cross-sections of the input electrode, output electrode, input-end detection electrode and output-end detection electrode are selected from one of circular, square, triangular and polygonal shapes; the end faces of the input electrode, output electrode, input-end detection electrode and output-end detection electrode are flat or curved.

[0021] A cracking furnace decoking device of the present invention is used to implement the aforementioned quencher electric decoking process, and mainly comprises: a power supply, an electric decoking controller, an input electrode, an output electrode, an input end detection electrode, an output end detection electrode, and a detector; the power supply is connected to the electric decoking controller, the electric decoking controller is respectively connected to the input electrode and the output electrode, the input electrode and the output electrode are respectively connected to the inlet and outlet ends of the cracking furnace tube, the input end detection electrode and the output end detection electrode are respectively connected to the inlet and outlet ends of the cracking furnace tube, and the input end detection electrode and the output end detection electrode are both connected to the detector.

[0022] The beneficial effects of the present invention are:

[0023] The present invention connects an input electrode and an input-end detection electrode to the inlet end of a cracking furnace tube, and connects an output electrode and an output-end detection electrode to the outlet end of the cracking furnace tube. An electric decoking controller is used to load a set voltage and current to both ends of the cracking furnace tube through the input electrode and the output electrode. When current flows through the cracking furnace tube, an electromagnetic field is formed in the cracking furnace tube. At the same time, the voltage at both ends of the cracking furnace tube is detected in real time through the input-end detection electrode and the output-end detection electrode and uploaded to a detector. When the voltage at both ends of the cracking furnace tube is too low or too high, an audible and visual alarm is issued, thereby improving the safety of the cracking furnace decoking process and solving the problem of high-voltage discharge safety. Problem: During the thermal cracking reaction, the reaction material containing coke particles enters the inlet end of the cracking furnace tube and flows out from the outlet end of the cracking furnace tube. At the same time, the reaction material moves at high speed in the cracking furnace tube together with other gaseous hydrocarbon substances, causing the coke particles to be positively charged and other gaseous hydrocarbon substances to be negatively charged. Since the flow direction of the coke particles in the cracking furnace tube is consistent with the flow direction of the current, the electromagnetic field will prevent the positively charged coke particles from approaching the tube wall of the cracking furnace tube, reducing the coke particle aggregation time, extending the operation cycle of the cracking furnace, and improving the decoking effect, solving the problems of rapid coking, short operation cycle, short furnace tube service life, high energy consumption and low production efficiency in the cracking furnace.

[0024] In addition, the electrodes used in a cracking furnace decoking device of the present invention can withstand a high temperature of 1300°C, which expands the applicable temperature range of the device and makes it suitable for most high-temperature and low-temperature environments, including minus 100°C to plus 1300°C. This solves the problem that existing decoking devices are only used for low-temperature tail gas purification below 250°C and cannot operate under the high-temperature conditions of 850°C in the cracking furnace.

[0025] The decoking device and decoking process for a cracking furnace of the present invention can suppress the accumulation of coke particles in the furnace tubes without affecting the yield and selectivity of the target product of the cracking product, thereby extending the operating cycle of the cracking furnace and the economic benefits of the device, and complying with low-carbon green chemical technology specifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a cracking furnace decoking device of the present invention.

[0027] In the figure, 1. power supply, 2. electric decoking controller, 3. input electrode, 4. output electrode, 5. input end detection electrode, 6. output end detection electrode, 7. detector, 8. cracking furnace tube, 9. reaction material, 10. coke particle flow direction, 11. current flow direction. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings.

[0029] In a first aspect, the present invention provides a decoking device for a cracking furnace.

[0030] See also Figure 1 To illustrate, a decoking device for a cracking furnace according to the present invention can be installed in an explosion-proof control cabinet and specifically includes the following components:

[0031] Power supply 1, electric decoking controller 2, input electrode 3, output electrode 4, input end detection electrode 5, output end detection electrode 6 and detector 7.

[0032] Among them, the power supply 1 is connected to the electric decoking controller 2, and the electric decoking controller 2 is respectively connected to the input electrode 3 and the output electrode 4. The input electrode 3 and the output electrode 4 are respectively connected to the inlet and outlet ends of the cracking furnace tube 8, that is, the input electrode 3 is connected to the inlet end of the cracking furnace tube 8, and the output electrode 4 is connected to the outlet end of the cracking furnace tube 8; the input end detection electrode 5 and the output end detection electrode 6 are respectively connected to the inlet and outlet ends of the cracking furnace tube 8, that is, the input end detection electrode 5 is connected to the inlet end of the cracking furnace tube 8, and the output end detection electrode 6 is connected to the outlet end of the cracking furnace tube 8; the input end detection electrode 5 and the output end detection electrode 6 are both connected to a detector 7.

[0033] Specifically, the voltage range of power supply 1 can be 0.01V to 36V. While all voltages have a decoking effect, the decoking effect varies, with higher voltages providing relatively better decoking. Therefore, to comply with the national standard "Safety Voltage" GB3805-83 and ensure operational safety, in the present invention, power supply 1 is designed for a DC safety voltage of less than 36V. To balance decoking effectiveness and safety, the voltage range of power supply 1 is preferably 12V to 36V.

[0034] Furthermore, the power supply 1 can specifically have a current range of 0.01 mA to 10,000 mA. While different currents all have a decoking effect, the decoking effect varies with different currents, with higher currents providing relatively better decoking. Therefore, to comply with the national standard "Safety Voltage" GB3805-83 and ensure operational safety, in the present invention, the power supply 1 is designed to have a DC safety current of less than 10 mA. To balance decoking effectiveness and safety, the current range of the power supply 1 is preferably 1 mA to 10 mA.

[0035] The input electrode 3 and the output electrode 4 are respectively connected to the inlet and outlet ends of the cracking furnace tube 8, and the input detection electrode 5 and the output detection electrode 6 are respectively connected to the inlet and outlet ends of the cracking furnace tube 8. Specifically, the input electrode 3, the output electrode 4, the input detection electrode 5, and the output detection electrode 6 can be connected to the cracking furnace tube 8 via metal materials.

[0036] The connection mode between the input electrode 3, the output electrode 4, the input end detection electrode 5 and the output end detection electrode 6 and the cracking furnace tube 8 can be bolt connection or welding connection, preferably welding connection to realize seamless connection and prevent loss of current energy and attenuation of detection signal.

[0037] The input electrode 3, the output electrode 4, the input end detection electrode 5 and the output end detection electrode 6 can be made of high-temperature-resistant material and can withstand a high temperature of 1300°C.

[0038] The high-temperature-resistant material is preferably nickel-based high-temperature alloy, titanium-based high-temperature alloy or molybdenum-based high-temperature alloy, more preferably titanium-based high-temperature alloy, which has good corrosion resistance and good oxidation resistance, heat resistance, acid and alkali resistance and is not easily corroded by air, water and chemicals.

[0039] The input electrode 3, the output electrode 4, the input end detection electrode 5 and the output end detection electrode 6 are each provided with a cooling radiator, which can increase the heat dissipation area and optimize the heat conduction path to improve the heat dissipation effect and reduce the high temperature in the cracking furnace tube 8 to the tolerance temperature of the electrode cable.

[0040] The cooling radiator can be an active cooling structure or a passive cooling structure, preferably a passive cooling structure.

[0041] The active cooling structure can be an air-cooled cooling structure or a water-cooled cooling structure, preferably an air-cooled cooling structure.

[0042] The passive cooling structure can be a fin cooling structure or a micro-channel cooling structure, preferably a fin cooling structure.

[0043] The input electrode 3, the output electrode 4, the input end detection electrode 5 and the output end detection electrode 6 can have a circular, square, triangular or polygonal cross-section.

[0044] The input electrode 3, the output electrode 4, the input end detection electrode 5 and the output end detection electrode 6 can have a flat or curved end surface.

[0045] The input electrode 3, the output electrode 4, the input end detection electrode 5 and the output end detection electrode 6 preferably have a cylindrical structure.

[0046] The main function of the electric decoking controller 2 is to adjust the different working voltage and working current of the decoking device of the present application to adapt to different stages of the operation of the cracking furnace. For example, in the initial stage of the operation of the cracking furnace, the surface of the cracking furnace tube 8 is relatively clean, and the working voltage and working current can be low, and the preferred voltage range is 12V-30V, and the preferred current range is 1mA-5mA; in the final stage of the operation of the cracking furnace, the surface of the cracking furnace tube 8 is covered with coke, and the working voltage and working current should be increased, and the preferred voltage range is 24V-36V, and the preferred current range is 5mA-10mA.

[0047] The working power of the decoking device of the present application is 0.1W-1000KW, and the conversion efficiency is about 90%, and the preferred working power is 100W-10KW.

[0048] After the decoking device of the present application is started, the electric decoking controller 2 converts alternating current into direct current, the current output by the electric decoking controller 2 enters the cracking furnace tube 8 through the input electrode 3, and flows out through the output electrode 4 or the ground, forming a closed loop. According to Ampere's law of electromagnetism, the size and direction of the current in any conductor determine the size and direction of the magnetic field generated. This law shows that the current is essentially a moving charge, and a magnetic field is generated. Therefore, when there is current passing through the cracking furnace tube 8, an electromagnetic field will be formed in the cracking furnace tube 8. At the same time, an input end detection electrode 5 and an output end detection electrode 6 are arranged at the inlet end and the outlet end of the cracking furnace tube 8 respectively, and the voltage of the input end detection electrode 5 and the output end detection electrode 6 is detected in real time by the detector 7, that is, the voltage of the two ends of the cracking furnace tube 8 is detected in real time, and once the voltage is too low or too high, the detector 7 will sound and light alarm.

[0049] For a reliable and stable decoking device suitable for industry, the maximum output power can generally only reach about 20KW. In actual application, the rated power that can be stably operated for a long period of time is only about 10KW, so in order to enhance the effect of decoking and adapt to more decoking occasions, multiple groups of the decoking device of the present application can be arranged to work in parallel to obtain better and more ideal decoking effect.

[0050] In the second aspect, the present application provides a decoking process for a cracking furnace, which is mainly realized by using the decoking device for a cracking furnace provided in the first aspect.

[0051] The specific implementation steps of the decoking process for a cracking furnace of the present application are as follows:

[0052] During the thermal cracking reaction, the reaction material 9 containing coke particles moves at a high speed of about 50 to 100 meters per second in the cracking furnace tube 8 together with other gaseous hydrocarbon substances. Since the mass of the coke particles is much greater than that of other gaseous hydrocarbon substances, their movement speed is also lower than that of other gaseous hydrocarbon substances. This speed difference will cause other gaseous hydrocarbon substances to continuously wash and rub the coke particles. In this process, friction generates static electricity, causing the coke particles to have a positive charge and other gaseous hydrocarbon substances to have a negative charge. Since the cracking furnace tube 8 is made of metal, grounding measures are generally adopted. According to Coulomb's law of electromagnetism, there is an interaction force between different charges. Under the attractive force of electrostatic force, the positively charged coke particles are easily separated from the reaction material 9, adsorbed on the inner surface of the cracking furnace tube 8 and continuously aggregated, which may block the cracking furnace tube 8. At this time, when the cracking furnace decoking device of the present invention is started, current flows through the cracking furnace tube 8 and an electromagnetic field is formed on the surface of the cracking furnace tube 8; when the magnetic lines of force of the electromagnetic field reach a suitable direction and intensity, the electromagnetic field will hinder the positively charged coke particles from approaching the wall of the cracking furnace tube 8, thereby achieving the purpose of slowing down their accumulation on the wall of the cracking furnace tube 8, allowing them to pass through the cracking furnace tube 8 as much as possible, reducing their accumulation time on the wall of the cracking furnace tube 8, and extending the operation cycle of the cracking furnace.

[0053] Among them, when the coke particle flow direction 10 in the cracking furnace tube 8 is consistent with the current flow direction 11, that is, the current output by the electric decoking controller 2 enters the cracking furnace tube 8 through the input electrode 3 and flows out of the cracking furnace tube 8 through the output electrode 4 or grounding, and the reaction material 9 enters the cracking furnace tube 8 through the input electrode 3 end and flows out of the cracking furnace tube 8 through the output electrode 4 end, the coke particles in the cracking furnace tube 8 generate a repulsive force due to the electromagnetic field effect of the tube wall of the cracking furnace tube 8, and are not easily adsorbed on the tube wall of the cracking furnace tube 8 and then pass through the cracking furnace tube 8, thereby greatly reducing the amount of coking and extending the operation cycle of the cracking furnace.

[0054] Among them, when the coke particle flow direction 10 in the cracking furnace tube 8 is inconsistent with the current flow direction 11, that is, the current output by the electric decoking controller 2 enters the cracking furnace tube 8 through the input electrode 3, and flows out of the cracking furnace tube 8 through the output electrode 4 or the ground, and the reaction material 9 enters the cracking furnace tube 8 through the output electrode 4 end and flows out of the cracking furnace tube 8 through the input electrode 3 end, the coke particles in the cracking furnace tube 8 generate a deflection force due to the electromagnetic field effect of the tube wall of the cracking furnace tube 8. The coke particles are prone to radial movement during the forward movement, and then deflect toward the direction of the tube wall of the cracking furnace tube 8, and are easily adsorbed on the tube wall of the cracking furnace tube 8, which greatly increases the amount of coking, resulting in the operating cycle of the cracking furnace being shorter than the operating cycle under normal operating conditions.

[0055] The present invention operates by utilizing electric decoking in the thermal radiation tubes of a cracking furnace in a thermal reaction environment exceeding 1000°C. The thermal radiation-induced coking mechanism is free radical coking, whereby coking precursors, such as polycyclic aromatic hydrocarbons (PAHs) in the high-temperature gas, undergo further dehydrogenation to form solid coke particles. The cracking furnace tubes (8) are exposed to a 1100°C furnace flame, requiring high safety standards. According to cracking furnace safety design specifications, a DC current of 36V or less should be used. Therefore, the present invention applies a safety voltage electric field of less than 36V (national standard "Safety Voltage" GB3805-83) at both ends of the inlet and outlet of the cracking furnace tube 8, and sets a safety current. By effectively controlling the voltage and current of the electric field, a stable electromagnetic field can be formed in the cracking furnace tube 8. When the flow direction of the coke particles in the cracking furnace tube 8 is consistent with the direction of the electric field (that is, when the coke particle flow direction 10 is consistent with the current flow direction 11), the coke particles are more likely to pass through the cracking furnace tube 8 under the action of the electromagnetic field, rather than being adsorbed on the inner surface of the cracking furnace tube 8, thereby achieving the effect of slowing down carbon deposition in the cracking furnace tube 8, greatly reducing the amount of coking, and extending the operation cycle of the cracking furnace.

[0056] In summary, the decoking device and decoking process for a cracking furnace of the present invention do not require the construction of a complex high-voltage electric decoking tower, thereby resolving the technical problems of conventional decoking processes, such as the need for the construction of a complex and expensive electric capture tower or cylinder, the safety issues of high-voltage discharge, and the inability to be applied to ethylene cracking and coking operations involving oxygen and high temperatures.

[0057] Furthermore, conventional decoking processes are only suitable for low-temperature tail gas purification below 250°C, and their electrodes cannot operate at the high temperatures of 850°C found in cracking furnaces. The decoking device and decoking process for cracking furnaces of the present invention have a wider applicable temperature range, applicable to most high- and low-temperature environments, including temperatures from -100°C to 1300°C, thus resolving the high-temperature decoking issues inherent in conventional decoking processes.

[0058] The decoking device and decoking process for a cracking furnace of the present invention have been experimentally verified to have the advantages of not affecting the yield and selectivity of the target product of the cracking product, while being able to inhibit the aggregation of coke particles in the cracking furnace tube 8, thereby solving the problems of the traditional decoking process, such as rapid coking of the cracking furnace, short operating cycle, short service life, high energy consumption and low production efficiency.

[0059] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0060] Example 1

[0061] First, a blank test was performed in a simulated cracking pilot plant with a charge of 5 kilograms per hour without opening the cracking furnace decoking device. Before the thermal cracking reaction, the cracking furnace tubes 8 were removed and weighed separately. The weight M1 obtained was the empty tube weight of the cracking furnace tubes 8 (8220.00 grams).

[0062] Install cracking furnace boiler tube 8, the cracking raw material is selected as naphtha, and cracking temperature is 830 ℃, and cracking pressure is 0.18MPa, and cracking dilution ratio is 0.5, treats that other each process parameter reaches set value after, feeds naphtha raw material.After treating that cracking furnace is run 6 hours, stop feeding naphtha raw material, cracking furnace boiler tube 8 is purged and dried after, remove cracking furnace boiler tube 8 and weigh, drawing weight M2 is empty tube weight and blank coking amount sum (8222.50 gram), and weight M2 deduction weight M1 is blank coking amount (2.50 gram).

[0063] A decoking test was then conducted in a simulated cracking pilot plant with a feed rate of 5 kg per hour. Naphtha was selected as the cracking feedstock, the cracking temperature was set at 830°C, the cracking pressure was set at 0.18 MPa, and the cracking dilution ratio was set at 0.5. After all other process parameters reached their set values, the naphtha feedstock was introduced. The voltage and current output by the electric decoking controller 2 were set to 30 V and 0.3 mA, respectively. The decoking device of the present invention was activated. The current output by the electric decoking controller 2 entered the cracking furnace tube 8 through the input electrode 3 and exited the cracking furnace tube 8 through the output electrode 4, forming a closed loop. Current flowed through the cracking furnace tube 8, generating an electromagnetic field on its surface. This electromagnetic field prevented positively charged coke particles from approaching the tube wall of the cracking furnace tube 8, thereby slowing the accumulation of coke particles on the tube wall. This allowed coke particles to pass through the tube 8 as much as possible, reducing the time they remained coked on the tube wall and extending the cracking furnace's operating cycle. After the cracking furnace has been in operation for 6 hours, the feeding of the naphtha feedstock is stopped. After the cracking furnace tube 8 is purged and dried, the cracking furnace tube 8 is removed and weighed. Deriving weight M3 is the sum of the empty tube weight and the decoking amount (8220.46 gram). The weight M3 minus the weight M1 is the decoking amount compared to the coking amount (0.46 gram). Compared with the blank coking amount (2.50 grams), it has decreased by 2.04 grams, and the reduction ratio is 81.60%. The decoking effect is obvious.

[0064] Example 2 Decoking Test with Reverse Current

[0065] The coke removing test is carried out in the simulated cracking pilot plant with the feeding amount of 5 kg per hour, the cracking raw material is selected as naphtha, the cracking temperature is 830℃, the cracking pressure is 0.18 MPa, the cracking dilution ratio is 0.5, after the other process parameters reach the set values, the naphtha raw material is input. The voltage and current outputted by the electric coke removing controller 2 are set as 30V and 3mA respectively, the cracking furnace coke removing device is started, the current outputted by the electric coke removing controller 2 enters the cracking furnace tube 8 through the input electrode 3, flows out of the cracking furnace tube 8 through the output electrode 4, and the reaction material 9 enters the cracking furnace tube 8 through the output electrode 4 end and flows out of the cracking furnace tube 8 through the input electrode 3 end. After the cracking furnace runs stably for 6 hours, the input of the naphtha raw material is stopped, the cracking furnace tube 8 is purged and dried, and then the cracking furnace tube 8 is removed and weighed, the weight M4 is the sum of the empty tube weight and the coke removing amount (8224.40g), the coke removing amount is 4.40g compared with the coking amount (M4-M1), which is 1.90g more than the blank coking amount (2.50g), the increase rate is 76.00%, which not only has no coke removing effect, but also obviously increases the coking amount.

[0066] Example 3 Coke removing test of different voltages

[0067] The coke removing test is carried out in the simulated cracking pilot plant with the feeding amount of 5 kg per hour, the cracking raw material is selected as naphtha, the cracking temperature is 830℃, the cracking pressure is 0.18 MPa, the cracking dilution ratio is 0.5, after the other process parameters reach the set values, the naphtha raw material is input. The voltage and current outputted by the electric coke removing controller 2 are set as 30V and 3mA respectively, the cracking furnace coke removing device is started, the current outputted by the electric coke removing controller 2 enters the cracking furnace tube 8 through the input electrode 3, flows out of the cracking furnace tube 8 through the output electrode 4, and the reaction material 9 enters the cracking furnace tube 8 through the output electrode 4 end and flows out of the cracking furnace tube 8 through the input electrode 3 end. After the cracking furnace runs stably for 6 hours, the input of the naphtha raw material is stopped, the cracking furnace tube 8 is purged and dried, and then the cracking furnace tube 8 is removed and weighed, the weight M4 is the sum of the empty tube weight and the coke removing amount (8224.40g), the coke removing amount is 4.40g compared with the coking amount (M4-M1), which is 1.90g more than the blank coking amount (2.50g), the increase rate is 76.00%, which not only has no coke removing effect, but also obviously increases the coking amount.

[0068] Example 4 Coke removing test of high voltage above the safety voltage

[0069] A decoking test was conducted in a simulated cracking pilot plant with a feed rate of 5 kg per hour. Naphtha was selected as the cracking feedstock, with a cracking temperature of 830°C, a cracking pressure of 0.18 MPa, and a cracking dilution ratio of 0.5. After all other process parameters reached their set values, the naphtha feedstock was introduced. The voltage and current output by the electric decoking controller 2 were set to 48 V and 3 mA, respectively. The decoking device of the present invention was activated. The current output by the electric decoking controller 2 entered the cracking furnace tube 8 through the input electrode 3 and exited the cracking furnace tube 8 through the output electrode 4, forming a closed circuit. After the cracking furnace has been running for 6 hours, the introduction of naphtha feedstock is stopped, the cracking furnace tube 8 is purged and dried, and then the cracking furnace tube 8 is removed and weighed. The weight M6 is obtained as the sum of the empty tube weight and the decoking amount (8220.32 grams). The weight M6 minus the weight M1 is the decoking amount compared to the coking amount (0.32 grams). Compared with the blank coking amount (2.50 grams), the decoking effect is further improved with a decoking voltage of 48V.

[0070] Example 5 Decoking Tests at Different Currents

[0071] A decoking test was conducted in a simulated cracking pilot plant with a feed rate of 5 kg per hour. Naphtha was selected as the cracking feedstock, with a cracking temperature of 830°C, a cracking pressure of 0.18 MPa, and a cracking dilution ratio of 0.5. After all other process parameters reached their set values, the naphtha feedstock was introduced. The voltage and current output by the electric decoking controller 2 were set to 30 V and 5 mA, respectively, and the cracking furnace decoking device of the present invention was activated. The current output by the electric decoking controller 2 entered the cracking furnace tube 8 through the input electrode 3 and exited the cracking furnace tube 8 through the output electrode 4, forming a closed loop. After the cracking furnace has been running for 6 hours, the introduction of naphtha feedstock is stopped, the cracking furnace tube 8 is purged and dried, and then the cracking furnace tube 8 is removed and weighed. The weight M7 is the sum of the empty tube weight and the decoking amount (8220.31 grams). The weight M7 minus the weight M1 is the decoking amount compared to the coking amount (0.31 grams). Compared with the blank coking amount (2.50 grams), the decoking effect is further improved with a decoking current of 5 mA compared to a decoking current of 3 mA.

[0072] Example 6 Alternating Current Decoking Test

[0073] A decoking test was conducted in a simulated cracking pilot plant with a feed rate of 5 kg per hour. Naphtha was selected as the cracking feedstock, with a cracking temperature of 830°C, a cracking pressure of 0.18 MPa, and a cracking dilution ratio of 0.5. After all other process parameters reached their set values, the naphtha feedstock was introduced. The AC voltage and AC current output by the decoking controller 2 were set to 30 V and 5 mA, respectively. The decoking device of the present invention was activated. The current output by the decoking controller 2 entered the cracking furnace tube 8 through the input electrode 3 and exited the cracking furnace tube 8 through the output electrode 4, forming a closed loop. After the cracking furnace has been running for 6 hours, the introduction of naphtha feedstock is stopped, the cracking furnace tube 8 is purged and dried, and then the cracking furnace tube 8 is removed and weighed. The obtained weight M8 is the sum of the empty tube weight and the decoking amount (8222.49 grams). The weight M8 minus the weight M1 is the decoking amount compared to the coking amount (2.49 grams). Compared with the blank coking amount (2.50 grams), there is basically no change, which shows that the alternating current has no decoking effect.

[0074] Example 7 Decoking Comparative Test of Pyrolysis Product Yield

[0075] To investigate whether the decoking device for a cracking furnace according to the present invention affects the yield of cracking products while simultaneously suppressing coke production, a decoking test was conducted in a simulated cracking pilot plant with a feed rate of 5 kg per hour. Naphtha was selected as the cracking feedstock, with a cracking temperature of 830°C, a cracking pressure of 0.18 MPa, and a cracking dilution ratio of 0.5. After all other process parameters reached their set values, the naphtha feedstock was introduced. The AC voltage and AC current output by the decoking controller 2 were set to 30 V and 3 mA, respectively. The decoking device was activated. The current output by the decoking controller 2 entered the cracking furnace tube 8 through the input electrode 3 and exited the tube 8 through the output electrode 4, forming a closed loop. After the cracking furnace had been running for three hours, cracking products were collected at the outlet of the tube 8 and subjected to chromatographic analysis. Comparative data on the yields of the decoked products and blank samples were obtained, as shown in Table 1.

[0076] Table 1 Mass yield of decoked pyrolysis products and blank pyrolysis products, %

[0077]

[0078]

[0079] As can be seen from Table 1, the yields of cracking products in the blank group and the decoking group are very close, which indicates that the decoking device for a cracking furnace of the present invention does not affect the yield of cracking products while suppressing coke.

[0080] The present invention discloses a decoking device and decoking process for a cracking furnace. Those skilled in the art may refer to the present disclosure and appropriately modify the process parameters to implement the present invention. It is particularly important to note that all similar substitutions and modifications apparent to those skilled in the art are considered encompassed by the present invention. The present invention has been described using preferred embodiments. It is obvious that those skilled in the art will be able to modify, adapt, and combine the present invention to implement and apply the present technology without departing from the present disclosure, spirit, and scope.

Claims

1. A decoking process for a cracking furnace, characterized in that: The following steps are involved: An input electrode and an input detection electrode are connected to the inlet end of the cracking furnace tube, and an output electrode and an output detection electrode are connected to the outlet end of the cracking furnace tube. A set voltage and current are applied to both ends of the cracking furnace tube by an electric decoking controller through the input electrode and the output electrode. When current flows through the cracking furnace tube, an electromagnetic field is formed in the cracking furnace tube. At the same time, the voltage at both ends of the cracking furnace tube is detected in real time by the input detection electrode and the output detection electrode and uploaded to a detector. During the thermal cracking reaction, a reaction material containing coke particles enters the inlet end of the cracking furnace tube and flows out from the outlet end of the cracking furnace tube. At the same time, as the reaction material moves at high speed in the cracking furnace tube together with other gaseous hydrocarbon substances, the coke particles are positively charged and the other gaseous hydrocarbon substances are negatively charged. Since the flow direction of the coke particles in the cracking furnace tube is consistent with the flow direction of the current, the electromagnetic field will prevent the positively charged coke particles from approaching the tube wall of the cracking furnace tube, thereby reducing the coke particle aggregation time and extending the operation cycle of the cracking furnace.

2. A decoking process for a cracking furnace according to claim 1, characterized in that: The set voltage range is 12V to 36V.

3. A decoking process for a cracking furnace according to claim 1, characterized in that: The set current range is 1 mA to 10 mA.

4. A decoking process for a cracking furnace according to claim 1, characterized in that: The electric decoking controller is connected to a power supply.

5. A decoking process for a cracking furnace according to claim 1, characterized in that: The electric decoking controller is used to adjust the voltage and current applied to both ends of the cracking furnace tube to adapt to different stages of the cracking furnace operation.

6. A decoking process for a cracking furnace according to claim 1, characterized in that: The input end detection electrode, the output end detection electrode and the detector are used to realize sound and light alarm when it is detected that the voltage at both ends of the cracking furnace tube exceeds a set range.

7. A decoking process for a cracking furnace according to claim 1, characterized in that: The input electrode, output electrode, input end detection electrode and output end detection electrode are all equipped with cooling radiators, and the cooling radiators are selected from one or more of air cooling structure, water cooling structure, fin cooling structure and microchannel cooling structure.

8. A decoking process for a cracking furnace according to claim 1, characterized in that: The cross-sections of the input electrode, output electrode, input end detection electrode and output end detection electrode are selected from one of circular, square, triangular and polygonal; the end faces of the input electrode, output electrode, input end detection electrode and output end detection electrode are flat or curved.

9. A decoking device for a cracking furnace, used to implement the decoking process for a cracking furnace according to any one of claims 1 to 8, characterized in that: include: Power supply, electric decoking controller, input electrode, output electrode, input end detection electrode, output end detection electrode and detector; The power supply is connected to an electric decoking controller, and the electric decoking controller is respectively connected to an input electrode and an output electrode, and the input electrode and the output electrode are respectively connected to the inlet end and the outlet end of the cracking furnace tube, and the input end detection electrode and the output end detection electrode are respectively connected to the inlet end and the outlet end of the cracking furnace tube, and the input end detection electrode and the output end detection electrode are both connected to a detector.

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