A method for detecting anti-carbon deposition performance of a cracking furnace tube coating

Abstract

The application provides a pyrolysis furnace tube coating anti-carbon deposition performance detection method. The pyrolysis furnace tube coating anti-carbon deposition performance detection method combines the magnetic suspension balance calibration result and the magnetic suspension balance operation data, filters the data, guarantees the effectiveness of the data, reduces the subsequent data operation processing calculation amount, and improves the coating anti-carbon deposition performance detection efficiency.

Description

Technical Field

[0001] This invention relates to the field of steam cracking technology in petrochemicals, specifically to a method for testing the anti-carbon deposition performance of cracking furnace tube coatings. Background Technology

[0002] Ethylene, propylene, butene, and butadiene, among other low-carbon olefins, are fundamental chemical raw materials. Ethylene production capacity, in particular, is often considered a marker of a country's or region's petrochemical development level and is hailed as the cornerstone of modern chemical industry. Currently, approximately 98% of the world's ethylene production processes utilize tubular furnace steam cracking. This process boasts high ethylene yields and co-produces essential chemical raw materials such as propylene, butadiene, benzene, toluene, xylene, C5, and C9, playing a crucial role in the petrochemical industry.

[0003] Cracking furnace tubes are the core equipment of tubular steam cracking processes. Due to prolonged contact with high-temperature (above 800°C) hydrocarbon steam, they inevitably accumulate a large amount of coke. This coke deposition on the inner wall of the cracking furnace tubes not only hinders heat transfer within the tubes, increasing pressure drop and even clogging the pipes, affecting normal operation of the cracking furnace, but also reduces low-carbon olefin production and increases energy consumption. Furthermore, coke enters the tube alloy in solid solution form and reacts with chromium atoms in the alloy to form chromium carbide deposits, a phenomenon known as carburization. This causes the tube alloy to lose its initial oxidation resistance, making it more susceptible to chemical attack, thus reducing the service life of the cracking furnace tubes, shortening the operating cycle of the cracking furnace, and severely impacting the long-term stable operation of the ethylene plant and its overall profitability.

[0004] To suppress coking and carbon buildup in pyrolysis furnace tubes, surface coating technology for furnace tubes has emerged. This technology involves coating the inner surface of the furnace tube with a substance that shields against catalytic coking and inhibits coke adhesion, thereby suppressing coking. The measurement and evaluation of the coating's carbon buildup rate has become a crucial indicator of coating quality. Steam pyrolysis experiments using coated furnace tubes can effectively evaluate coating performance; however, coated furnace tubes are difficult to process, have long production cycles, and high manufacturing costs. Furthermore, accurately measuring the carbon content on the coating surface is challenging. Therefore, developing convenient, rapid, and effective coating evaluation methods is a key aspect of furnace tube surface coating technology research.

[0005] Patent CN201910624426.7 discloses an apparatus and method for determining the carbon deposition rate of a catalytic reforming catalyst. The method first uses a suitable device to deposit carbon on the catalytic reforming catalyst, then introduces an oxidation gas source. The resulting tail gas is continuously analyzed online using instruments such as an online mass spectrometer. The carbon monoxide and carbon dioxide products are converted into carbon deposition mass to determine the amount and rate of carbon deposition. This method is simple to operate and has high accuracy, but it is only suitable for detecting carbon deposition after an experiment. The carbon deposition rate result is the average carbon deposition rate within the experimental period. Determining the carbon deposition rate under different reaction time conditions requires numerous experiments.

[0006] Patent CN201310431980.6 addresses the problem of carbon buildup in distilled gas passing through heat exchanger pipes by discharging carbon deposits. It discloses a system and method for detecting the carbon buildup characteristics of distilled gas. The detection system includes a distillation apparatus, a carbon buildup apparatus, and a carbon buildup analysis apparatus. Semi-coke or distilled gas feedstock is converted into distilled gas via the distillation apparatus, and the distilled gas then forms carbon deposits via the carbon buildup apparatus. By cutting a reaction tube and placing it in the carbon buildup analysis apparatus for heating, the carbon deposits are oxidized to carbon dioxide, and data such as the amount of carbon deposits can be obtained from the carbon dioxide data. This method is simple to operate and has high accuracy, but it is only suitable for detecting carbon buildup after an experiment. The carbon buildup rate result is the average carbon buildup rate within the experimental period. Determining the carbon buildup rate under different reaction time conditions requires numerous experiments.

[0007] Patent CN200810043493.1 addresses the problem of previous carbon deposition measurement techniques being unable to accurately determine the amount of carbon deposits on catalysts in real time by proposing an online detection method for catalyst carbon deposition. This patent uses an acoustic signal detection device to receive acoustic emission signals generated by the catalyst impacting the wall inside the reactor or regenerator. It selects the frequency f, amplitude A, energy N, and energy fraction Ei within each wavelet scale and / or wavelet packet scale as feature values, and uses the least squares method for function regression to achieve real-time measurement of catalyst carbon deposition. This method is based on function estimation and has good calculation results for a given catalyst; however, it requires re-establishing the estimation function for catalysts with different properties. Furthermore, the furnace tube coating and the carbon deposits on the coating cannot be impacted, making this method unsuitable for real-time measurement of coating carbon deposits.

[0008] Patent CN201310139615.8 proposes an instrument and method for detecting carbon deposits in hot carrier furnace pipes based on ultrasonic guided wave non-destructive testing. The instrument structure includes an arbitrary function signal generator, a power amplifier, an oblique-incidence piezoelectric ultrasonic transmitting sensor, an oblique-incidence piezoelectric ultrasonic receiving sensor, an oscilloscope, and a computer. In application, two frequency bands are used for detection, one high and one low. The results are compared with the critical value for carbon deposit thickness detection to obtain the carbon deposit thickness. This method has good measurement accuracy for both newly formed thin carbon layers and long-term accumulated thick carbon layers. While this method can determine the carbon deposit layer in pipes, it is difficult to calculate the carbon deposit amount for pipes with uneven carbon layer distribution. Furthermore, the high temperature of the pyrolysis furnace tubes and the presence of multiple bends and branching structures in the pipes make carbon deposit calculation difficult, and the instrument material is difficult to meet high-temperature requirements. In addition, ultrasonic waves may adversely affect the pyrolysis furnace tubes under high-temperature conditions, limiting the application of this method in real-time measurement of carbon deposits on pyrolysis furnace tube coatings.

[0009] Patent CN200710017429.1 discloses a dynamic online analysis system for chemical vapor phase reaction processes. In this design, a magnetic levitation balance is fixed directly above the gas-phase reactor. The hook of the magnetic levitation balance is connected to the substrate via a metal rope, enabling real-time weight measurement during the chemical vapor phase infiltration process. The reaction environment during the evaluation of the pyrolysis furnace tube coating is quite harsh, with complex and corrosive raw materials that can easily contaminate the precision components of the magnetic levitation balance, such as the levitation magnet. Furthermore, the high-temperature conditions required for evaluating the pyrolysis furnace tube coating far exceed the Curie temperature of general magnetic materials, which can cause demagnetization of the levitation magnet. In addition, fluctuations in the feed during the evaluation of the pyrolysis furnace tube coating can easily cause significant changes in the reading of the magnetic levitation balance, interfering with the measurement results. Summary of the Invention

[0010] The purpose of this invention is to provide a method for detecting the anti-carbon deposition performance of coatings in pyrolysis furnace tubes. This method enables real-time study of the carbon deposition process in coatings during steam pyrolysis. By combining the calibration results of a magnetic levitation balance with a constructed carbon deposition behavior calculation vector, carbon deposition data is detected and noise is reduced, abnormal data is filtered out, the computational load of subsequent data processing is reduced, and the efficiency, validity, and accuracy of the coating anti-carbon deposition performance detection results are improved. Furthermore, linear fitting of the data ensures the continuity of the data results and obtains a reliable trend of carbon deposition changes.

[0011] To achieve the above objectives, the present invention provides a method for testing the anti-carbon deposition performance of a pyrolysis furnace tube coating, wherein the apparatus for performance testing includes:

[0012] A pyrolysis reaction system, the pyrolysis reaction system including furnace tubes;

[0013] A magnetic levitation metering system includes a counter-current measuring tube communicating with the top of the furnace tube. The top of the counter-current measuring tube is closed, and a magnetic levitation balance body is located above the top. A magnetic float is located inside the counter-current measuring tube below the magnetic levitation balance body. A position sensing terminal and a load couple are connected sequentially from top to bottom to the bottom of the magnetic float via an inertial connecting line. The load couple includes a body with a hollow cavity and a plug built into the hollow cavity. The plug is connected to the magnetic float via the inertial connecting line. The bottom of the body is connected to a... The coating plate is located inside the counter-current measuring tube and the coating plate is located inside the furnace tube. A position sensor, a counter-current gas inlet pipe, and a limiter are also provided on the inner sidewall of the counter-current measuring tube. The position sensor is located in the upper part of the counter-current measuring tube and corresponds to the position sensing terminal, used to mark the working state of the magnetic float. The counter-current gas inlet pipe is located between the limiter and the position sensor, used to introduce inert protective gas into the counter-current measuring tube. The limiter is located below the load couple and has an opening in the middle, used to limit, support, and mark the state of the load couple.

[0014] The performance testing using the device includes the following steps:

[0015] S1, Calibrate the magnetic levitation balance:

[0016] (1) Weigh the mass m0 of the coated pad before carbon deposition using an analytical balance, and calculate the surface area S0 of the coated pad.

[0017] (2) Suspend the coated plate inside the device and weigh the initial total mass m of the suspended object using a magnetic levitation balance. c The furnace tube is heated, and inert gas is introduced into the counter-impact measuring tube. A mixture of water vapor and nitrogen is then introduced into the furnace tube. Once the pressure and temperature inside the furnace tube reach the preset reaction conditions and the device is operating stably, the mass of the suspended object is weighed again using a magnetic levitation balance as a blank test result. The measurement is performed for at least five measurement cycles. The results of the maximum positive offset, average positive offset, maximum negative offset, and average negative offset are statistically analyzed.

[0018] Measurement cycle: The spatial positions of the load couple and the limiter in the magnetic levitation balance mark the magnetic levitation balance as the zero-point calibration position, the measurement position, and the position to be measured. In the zero-point calibration position, the load couple body is located on the limiter, the plug of the load couple does not contact the body, and it is suspended inside the hollow cavity of the body. The magnetic levitation balance is zeroed and measured. In the measurement position, the plug of the load couple contacts the body, and the body is lifted away from the limiter. The magnetic levitation balance is weighed and measured. In the position to be measured, the load couple returns from the measurement position to the zero-point calibration position, but the magnetic levitation balance does not measure. The process of the magnetic levitation balance going through the zero-point calibration position - measurement position - position to be measured is one measurement cycle. In each measurement cycle, the zero-point calibration position is maintained for 20-60s, the measurement position is maintained for 40-150s, the measurement position reads measurement values ​​at a frequency of 4-8 times / s, and the position to be measured is maintained for 40-80s.

[0019] Maximum positive offset Z max : Maximum value of blank test results and m c The absolute value of the difference;

[0020] Average positive offset Z avg : The blank test results are greater than m c The average value of the numerical results and m c The absolute value of the difference;

[0021] Maximum negative offset F max Minimum value of blank test results and m c The absolute value of the difference;

[0022] Average negative offset F avg : The blank test results are less than m c The average value of the numerical results and m c The absolute value of the difference;

[0023] S2, switch the mixed feed gas of water vapor and nitrogen to hydrocarbon feed gas, and collect real-time carbon deposition data during the experiment. t ;

[0024] S3, Data Filtering and Results Acquisition: Real-time calculation of the average value D of all data within the current measurement period. avg If the carbon deposition data D collected in a single measurement cycle in the current measurement cycle t Satisfy D t >D avg And |D t -D avg |>Z max Or D t <D avg And |D t -D avg |>F avg If so, the carbon deposition data collected in that single instance will be discarded;

[0025] S4, using the carbon deposition behavior operation vector to detect the collected results, filtering out abnormal data again, and performing data processing to obtain coating carbon deposition data, specifically:

[0026] (1) After the experiment, the coated plate was removed and its mass m after carbon deposition was measured using an analytical balance. t ;

[0027] (2) Export the result data retained in step S3, calculate the average value D of the data collected in each measurement cycle, construct the carbon deposition behavior operation vector, and detect the result data retained in step S3 during the process of constructing the carbon deposition behavior operation vector to filter out abnormal data again.

[0028] The method for constructing the carbon deposition behavior operation vector is as follows:

[0029] i. Determine whether the average value D1 of the raw data results in the first measurement cycle satisfies m. c +(m t -m0)+Z max ≥D1≥m c If the condition is met, the original measurement value of the first measurement cycle is retained. If D1≥m c +(m t -m0)+Z max Then discard all data from the first measurement cycle and treat the second measurement cycle as the first measurement cycle. If D1 < m c Then, the data of the first measurement cycle is assigned a value based on the raw data result of the second measurement cycle, specifically as follows:

[0030] If the average value of the raw data results in the second measurement period, D2, is less than D1 or m c If D2 > D1, then m c The numerical value is assigned to the data result of the first measurement cycle;

[0031] If the average value of the raw data results in the second measurement period, D2, is greater than m c Then, for a single acquisition in the first measurement cycle, satisfying D... t >D1 and |D t -D1|>Z avg Or D t <D1 and |D t -D1|>F avg The data is discarded, and the average value D1′ of the data results for the first measurement period is recalculated. If D1′>m c If the data result of the first measurement cycle after processing is retained; if D1′<m c Then m cThe numerical value is assigned to the data result of the first measurement cycle;

[0032] ii. Determine the average value D of the raw data results in the (n+1)th measurement period. n+1 Is it greater than or equal to the average value D of the raw data results in the nth measurement period? n Let n be an integer greater than or equal to 2, if D n+1 ≥D n Then keep D. n+1 The original measured value; if D n+1 <D n Then, the result data of the nth period is assigned to the (n+1)th period (and all data in the nth and subsequent measurement periods that are greater than m are removed). c +(m t -m0)+Z max Data results;

[0033] (5) Perform linear fitting on the processed data, and the fitted curve satisfies:

[0034] i, the initial point coating pad mass is between m c -F avg With m c +Z avg between;

[0035] ii, the final coating pad mass is between m c +(m t -m0)-F avg With m c +(m t -m0)+Z avg between;

[0036] iii, time T in the fitted curve n The corresponding fitting result is less than or equal to time T. n+1 The corresponding fitting results;

[0037] (6) The obtained fitted curve y is then subjected to (ym) c The S0 transformation yields the carbon deposition changes of the coating over the corresponding time.

[0038] The method for testing the anti-carbon deposition performance of the pyrolysis furnace tube coating according to the present invention uses a magnetic levitation balance and an analytical balance with an accuracy of 10. -6 g.

[0039] The method for testing the anti-carbon deposition performance of the pyrolysis furnace tube coating of the present invention includes an insulation layer covering the outside of the counterweight measuring tube, and the temperature of the insulation layer is controlled at 50-80°C during the experiment.

[0040] The method for testing the anti-carbon deposition performance of the pyrolysis furnace tube coating of the present invention includes a hollow shell structure for the insulation layer. The temperature is controlled by introducing a cooling medium into the hollow shell structure. The cooling medium is one of water, mineral heat transfer oil, propylene glycol, and glycerol.

[0041] The method for testing the anti-carbon deposition performance of the pyrolysis furnace tube coating described in this invention involves introducing a gas at a temperature of 5-50°C that does not participate in the reaction inside the pyrolysis furnace into the counteracting gas inlet pipe during the experiment. The outlet of the counteracting gas inlet pipe is oriented downwards within the counteracting measuring pipe.

[0042] The method for testing the anti-carbon deposition performance of the pyrolysis furnace tube coating described in this invention uses one of nitrogen, argon, and carbon dioxide as the gas.

[0043] The method for testing the anti-carbon deposition performance of the coating of the pyrolysis furnace tube according to the present invention includes a lower main furnace tube and an upper enlarged section furnace tube. The maximum diameter of the enlarged section furnace tube is 1.5 to 3.0 times the diameter of the main furnace tube, and the ratio of the volume of the enlarged section furnace tube to the volume of the main furnace tube is ≤0.3.

[0044] Beneficial effects of this invention:

[0045] The present invention provides a method for testing the anti-carbon deposition performance of pyrolysis furnace tube coatings. This method combines magnetic levitation balance calibration results and operational data to filter the data, ensuring its validity and reducing subsequent computational load, thus improving the efficiency of coating anti-carbon deposition performance testing. By utilizing carbon deposition behavior computational vectors to detect and process the data acquisition results, abnormal data can be identified and valid data compensated in a timely manner, further reducing the impact of coating plate disturbance on the overall data and improving data validity and accuracy. Linear fitting correlation is performed by combining coating plate analysis results and real-time magnetic levitation balance measurement results to ensure the continuity of data results and obtain reliable carbon deposition change trends. The reactor used for measuring coating carbon deposition employs a magnetic levitation balance with an enlarged section furnace tube buffer structure and a self-protection structure, providing intuitive, accurate, and effective measurement results with convenient operation. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the apparatus used in the method for testing the anti-carbon deposition performance of the pyrolysis furnace tube coating according to the present invention;

[0047] Figure 2 This is a schematic diagram of the load couple of the present invention in the zero-point correction position / test position;

[0048] Figure 3 This is a schematic diagram of the load couple of the present invention in the measurement position;

[0049] Figure 4 This is the blank test result of Embodiment 1 of the present invention;

[0050] Figure 5 This is the original data result of Embodiment 1 of the present invention;

[0051] Figure 6 This is the processed data and its fitting result of Embodiment 1 of the present invention.

[0052] In the attached figures, the following labels are used:

[0053] 1. Raw material gas inlet; 2. Main furnace tube; 3. Coated hanging plate; 4. Enlarged section furnace tube; 5. Cooling medium inlet; 6. Insulation layer; 7. Counteracting gas inlet pipe; 8. Position sensor; 9. Magnetic float; 10. Main body of magnetic levitation balance; 11. Cooling medium outlet; 12. Position sensing terminal; 13. Counteracting measuring tube; 14. Load coupler; 141. Plug; 142. Hollow cavity; 143. Coupler body; 15. Limiter; 16. Product outlet; 17. Inertial connection line. Detailed Implementation

[0054] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0055] like Figure 1 The diagram shown is a structural schematic of the apparatus used in the method for testing the anti-carbon deposition performance of the pyrolysis furnace tube coating according to the present invention, including a pyrolysis reaction system and a magnetic levitation metering system.

[0056] like Figure 1 As shown, the pyrolysis reaction system includes furnace tubes, which consist of a lower main furnace tube 2 and an upper enlarged section furnace tube 4. In one specific embodiment, the maximum diameter of the enlarged section furnace tube 4 is 1.5 to 3.0 times the diameter of the main furnace tube 2, and the volume ratio of the enlarged section furnace tube 4 to the main furnace tube 2 is ≤0.3. The main furnace tube 2 has a raw material gas inlet 1 at its bottom, and the enlarged section furnace tube 4 has a product outlet 16 on its side wall.

[0057] The magnetic levitation metering system includes a counter-current measuring tube 13 connected to the top of the enlarged section furnace tube 4. The top of the counter-current measuring tube 13 is closed, and a magnetic levitation balance body 10 is located above the top. A magnetic float 9 is located inside the counter-current measuring tube 13, below the magnetic levitation balance body 10. A position sensing terminal 12 and a load couple 14 are connected sequentially from top to bottom to the bottom of the magnetic float 9 via an inertial connecting line 17. The load couple 14 includes a couple body 143 with a hollow cavity 142 and a plug 141 built into the hollow cavity 142. The plug 141 is connected to the magnetic float 9 via the inertial connecting line 17. A coated plate 3 is connected to the bottom of the couple body 141 via the inertial connecting line 14. The load couple 14 is located... Inside the counter-current measuring tube 13, the coated hanging plate 3 is located inside the main furnace tube 2. A position sensor 8, a counter-current gas inlet pipe 7, and a limiter 15 are also provided on the inner side wall of the counter-current measuring tube 13. The position sensor 8 is located in the upper middle part of the counter-current measuring tube 13, corresponding to the position sensing terminal 12, and is used to mark the working state of the magnetic float 9. The counter-current gas inlet pipe 7 is located between the limiter 15 and the position sensor 8, and is used to introduce inert protective gas into the counter-current measuring tube 13. The limiter 15 is located below the load couple 14 and has an opening in the middle, used to limit, support, and mark the state of the load couple 14. The outside of the counter-current measuring tube 13 is covered with an insulation layer 6, which can specifically be a hollow shell structure, such as... Figure 1 As shown, the hollow shell structure has a cooling medium inlet 5 at the bottom and a cooling medium outlet 11 at the top. The temperature inside the counter-measuring tube 13 is controlled by introducing a cooling medium into the hollow shell structure. Specifically, the cooling medium can be one of water, mineral heat transfer oil, propylene glycol, or glycerol.

[0058] The device is used to perform performance testing through the following steps:

[0059] S1, Calibrate the magnetic levitation balance:

[0060] (1) Weigh the mass m0 of the coated pad before carbon deposition using an analytical balance, and calculate the surface area S0 of the coated pad.

[0061] (2) Suspend the coated plate inside the device and weigh the initial total mass m of the suspended object using a magnetic levitation balance. c The furnace tube is heated, and inert gas is introduced into the counter-pressure measuring tube through the counter-pressure gas inlet pipe. A mixture of water vapor and nitrogen is introduced into the furnace tube through the raw material gas inlet. After the pressure and temperature inside the furnace tube reach the preset reaction conditions and the device operates stably, the mass of the suspended object is weighed again using a magnetic levitation balance as a blank test result. The number of measurements is greater than or equal to 5 measurement cycles. The results of the maximum positive offset, average positive offset, maximum negative offset, and average negative offset are statistically analyzed, among which:

[0062] Measurement Cycle: The spatial positions of the load couple and the limiter in the magnetic levitation balance are marked as the zero-point calibration position, the measurement position, and the position to be measured. In the zero-point calibration position, the load couple's body is located on the limiter, the load couple's plug is not in contact with the body, and it is suspended inside the hollow cavity of the body; the magnetic levitation balance performs zeroing measurement. In the measurement position, the load couple's plug contacts the body, and the body is lifted away from the limiter; the magnetic levitation balance performs weighing measurement. In the position to be measured, the load couple returns from the measurement position to the zero-point calibration position, but the magnetic levitation balance does not perform measurement. The process of the magnetic levitation balance going through the zero-point calibration position, measurement position, and position to be measured constitutes one measurement cycle. In each measurement cycle, the zero-point calibration position is maintained for 20–60 seconds, the measurement position for 40–150 seconds, and the measurement position reads measurement values ​​at a frequency of 4–8 times / second. The position to be measured is maintained for 40–80 seconds. The relative positions of the load couple, plug, and limiter within the measurement cycle are as follows: Figure 2 and Figure 3 As shown. Figure 2 A schematic diagram of the load couple and limit switch for the zero-point calibration position / the position to be measured; Figure 3 This is a schematic diagram of the load couple and limit switch for measuring the position.

[0063] Maximum positive offset Z max : Maximum value of blank test results and m c The absolute value of the difference;

[0064] Average positive offset Z avg : The blank test results are greater than m c The average value of the numerical results and m c The absolute value of the difference;

[0065] Maximum negative offset F max Minimum value of blank test results and m c The absolute value of the difference;

[0066] Average negative offset F avg : The blank test results are less than m c The average value of the numerical results and m c The absolute value of the difference;

[0067] S2, switch the mixed feed gas of water vapor and nitrogen to hydrocarbon feed gas, and collect real-time carbon deposition data during the experiment. t ;

[0068] S3, Data Filtering and Results Acquisition: Real-time calculation of the average value D of all data within the current measurement period. avg If the carbon deposition data D collected in a single measurement cycle in the current measurement cycle t Satisfy D t >D avg And |D t -D avg |>Zmax Or D t <D avg And |D t -D avg |>F avg If so, the carbon deposition data collected in that single instance will be discarded;

[0069] S4, using the carbon deposition behavior operation vector to detect the collected results, filtering out abnormal data again, and performing data processing to obtain coating carbon deposition data, specifically:

[0070] (1) After the experiment, the coated plate was removed and its mass m after carbon deposition was measured using an analytical balance. t ;

[0071] (2) Export the result data retained in step S3, calculate the average value D of the data collected in each measurement cycle, construct the carbon deposition behavior operation vector, and detect the result data retained in step S3 during the process of constructing the carbon deposition behavior operation vector to filter out abnormal data again.

[0072] The method for constructing the carbon deposition behavior operation vector is as follows:

[0073] i. Determine whether the average value D1 of the raw data results in the first measurement cycle satisfies m. c +(m t -m0)+Z max ≥D1≥m c If the condition is met, the original measurement value of the first measurement cycle is retained. If D1≥m c +(m t -m0)+Z max Then discard all data from the first measurement cycle and treat the second measurement cycle as the first measurement cycle. If D1 < m c Then, the data of the first measurement cycle is assigned a value based on the raw data result of the second measurement cycle, specifically as follows:

[0074] If the average value of the raw data results in the second measurement period, D2, is less than D1 or m c If D2 > D1, then m c The numerical value is assigned to the data result of the first measurement cycle;

[0075] If the average value of the raw data results in the second measurement period, D2, is greater than m c Then, for a single acquisition in the first measurement cycle, satisfying D... t >D1 and |D t -D1|>Z avg Or D t <D1 and |D t -D1|>F avgThe data is discarded, and the average value D1′ of the data results for the first measurement period is recalculated. If D1′>m c If the data result of the first measurement cycle after processing is retained; if D1′<m c Then m c The numerical value is assigned to the data result of the first measurement cycle;

[0076] ii. Determine the average value D of the raw data results in the (n+1)th measurement period. n+1 Is it greater than or equal to the average value D of the raw data results in the nth measurement period? n Let n be an integer greater than or equal to 2, if D n+1 ≥D n Then keep D. n+1 The original measured value; if D n+1 <D n Then, the result data of the nth period is assigned to the (n+1)th period, and data with values ​​greater than m in the results of the nth measurement period and subsequent measurement periods are removed. c +(m t -m0)+Z max Data results;

[0077] (5) Perform linear fitting on the processed data, and the fitted curve satisfies:

[0078] i, the initial point coating pad mass is between m c -F avg With m c +Z avg between;

[0079] ii, the final coating pad mass is between m c +(m t -m0)-F avg With m c +(m t -m0)+Z avg between;

[0080] iii, time T in the fitted curve n The corresponding fitting result is less than or equal to time T. n+1 The corresponding fitting results;

[0081] (6) The obtained fitted curve y is then subjected to (ym) c The S0 transformation yields the carbon deposition changes of the coating over the corresponding time.

[0082] In one specific embodiment, the accuracy of the magnetic levitation balance and the analytical balance is 10. -6 g.

[0083] The present invention will be further described below with reference to the accompanying drawings. The embodiments described are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0084] Example 1

[0085] The coating used in this invention is a composite barrier coating composed of Cr, Si and Al. The substrate is 310S stainless steel. The experimental conditions are: pyrolysis temperature 840℃, water-oil mass ratio 0.5, raw material residence time 0.3s, and reaction pressure 0.07MPa.

[0086] The raw material used in this invention is naphtha, and its composition analysis is shown in Table 1.

[0087] Table 1 Compositional Analysis of Naphtha

[0088]

[0089] The present invention provides a method for testing the anti-carbon deposition performance of a pyrolysis furnace tube coating, comprising the following steps:

[0090] (1) Measurement of coating pads. To facilitate the calculation of coating pads, this invention uses rectangular sheet-shaped coating pads, with an accuracy of 10... -6 The mass m0 of the coated pad before carbon deposition was measured using an analytical balance was 6.899060 g. The calculated surface area S0 of the coated pad was 5.2 cm². 2 .

[0091] (2) Conduct a blank test.

[0092] ① The coating sample is suspended inside the reactor for measuring the amount of carbon deposits in the coating. Weighing is performed using a magnetic levitation balance with an accuracy of 10 μm under conditions of no airflow interference. -6 g, after the value stabilizes, record the initial total mass m of the suspended object. c It weighs 8.700530g.

[0093] ② Start the reactor for measuring the amount of carbon deposits in the coating. According to the experimental evaluation requirements, set the pyrolysis temperature to 840℃ to heat the reactor. When the temperature inside the reactor reaches 300±5℃, introduce a mixture of steam and nitrogen into the reactor. The amount of steam used ensures the required water-to-oil mass ratio of 0.5 and the required residence time of the raw material of 0.3s. The amount of nitrogen used maintains the reaction pressure at 0.07 MPa. After the pressure and temperature inside the reactor reach the required set conditions and the reactor operates stably, perform measurements using a magnetic levitation balance. Perform at least five measurement cycles and statistically analyze the blank test results.

[0094] The statistical blank test results include the maximum positive offset, average positive offset, maximum negative offset, and average negative offset, which are as follows:

[0095] Maximum positive offset (Z) max ): Maximum value of blank test results and m c The absolute value of the difference;

[0096] Average positive offset (Z) avg ): The blank test results are greater than m c The average value of the numerical results and m c The absolute value of the difference;

[0097] Maximum negative offset (F) max ): Minimum value of blank test results and m c The absolute value of the difference;

[0098] Average negative offset (F) avg ): The blank test results are less than m c The average value of the numerical results and m c The absolute value of the difference.

[0099] like Figure 4 As shown, Figure 4 To obtain the blank test results of Embodiment 1 of the present invention, blank test results for 9 measurement cycles were collected, and the maximum positive offset (Z) was obtained. max The value is 0.000133g, and the average positive offset (Z) is 0.000133g. avg The value is 0.000043g, and the maximum negative offset (F) is 0.000043g. max The value is 0.000094g, and the average negative offset (F) avg The value is 0.00030g.

[0100] (3) Switch the mixed raw material gas of water vapor and nitrogen to naphtha raw material, adjust the feed parameters to a water to naphtha mass ratio of 0.5 and a raw material residence time of 0.3s, and collect magnetic levitation balance data in real time.

[0101] Figure 5 The original data results after switching to naphtha feedstock in Example 1 of this invention are presented in a total of 19 measurement cycles. The wide distribution of data within the same measurement cycle indicates that multiple data points are affected by experimental conditions.

[0102] (4) Perform preliminary filtering on the data results collected in step (3) to ensure the validity of the data and reduce the computational load of subsequent data processing. Specifically, calculate the average value D of all data results in the current measurement period. avg If the carbon deposition data D collected in a single measurement cycle in the current measurement cycle t Satisfy D t >D avg And |D t -D avg |>Zmax Or D t <D avg And |D t -D avg |>F avg Discard the carbon deposition data from a single collection (D). t .

[0103] (5) The carbon deposition behavior operation vector is used to detect the collected results after step (4), and abnormal data is filtered out again. Data operation is then performed to obtain the coating carbon deposition data, specifically:

[0104] ① After completing the experiment, remove the coating sample from the reactor for measuring the amount of carbon deposits in the coating, and measure it with a precision of 10. -6 The mass m of the coated pad after carbon deposition was measured using an analytical balance. t It weighs 6.902850g;

[0105] ② Export the data results in step (4), calculate the average value D of the data collected in each measurement cycle, construct the carbon deposition behavior operation vector, and detect the result data retained in step (4) in the process of constructing the carbon deposition behavior operation vector to filter out abnormal data again;

[0106] The method for constructing the carbon deposition behavior operation vector is as follows:

[0107] i. Determine whether the average value D1 of the raw data results in the first measurement cycle satisfies m. c +(m t -m0)+Z max ≥D1≥m c If the condition is met, the original measurement value of the first measurement cycle is retained. If D1≥m c +(m t -m0)+Z max Then discard all data from the first measurement cycle and treat the second measurement cycle as the first measurement cycle. If D1 < m c Then, the data from the first measurement cycle is assigned a value based on the data result of the second measurement cycle, specifically as follows:

[0108] If the average value of the raw data results in the second measurement period, D2, is less than D1 or m c If D2 > D1, then m c The numerical value is assigned to the data result of the first measurement cycle;

[0109] If the average value of the raw data results in the second measurement period, D2, is greater than m c Then, for a single acquisition in the first measurement cycle, satisfying D... t >D1 and |D t -D1|>Z avgOr D t <D1 and |D t -D1|>F avg The data is discarded, and the average value D1′ of the data results for the first measurement period is recalculated. If D1′>m c If the data result of the first measurement cycle after processing is retained; if D1′<m c Then m c The numerical value is assigned to the data result of the first measurement cycle;

[0110] ii. Determine the average value D of the raw data results in the (n+1)th measurement period. n+1 Is it greater than or equal to the average value D of the raw data results in the nth measurement period? n Let n be an integer greater than or equal to 2, if D n+1 ≥D n Then keep D. n+1 The original measured value; if D n+1 <D n Then, the result data of the nth period is assigned to the (n+1)th period, and data with values ​​greater than m in the results of the nth measurement period and subsequent measurement periods are removed. c +(m t -m0)+Z max Data results;

[0111] (6) Perform linear fitting on the processed data, and the fitted curve satisfies:

[0112] i, the initial point coating pad mass is between m c -F avg With m c +Z avg between;

[0113] ii, the final coating pad mass is between m c +(m t -m0)-F avg With m c +(m t -m0)+Z avg between;

[0114] iii, time T in the fitted curve n The corresponding fitting result is less than or equal to time T. n+1 The corresponding fitting results;

[0115] Figure 6 This shows the processed data and its fitting results from Embodiment 1 of the present invention. Figure 6It can be seen that after data filtering and carbon deposition behavior vector detection, the computational load of subsequent data processing is significantly reduced, improving the detection efficiency of coating anti-carbon deposition performance, and the accuracy of the data results is improved from 0.001g to 0.0001g. The fitting result is: y = 8.700480 + 3.61684 × 10⁻⁶ -6 x-4.29817×10 -9 x 2 +2.71665×10 -12 x 3 -7.48615×10 -16 x 4 +7.41339×10 -20 x 5 (y represents mass in g; x represents statistical time in seconds). This formula, after transformation by (y-8.700530) / 5.2, yields the carbon deposition change of the coating over the corresponding time (g / s·cm). 2 If the initial carbon deposition change result is negative, it indicates that there is no initial carbon deposition or very little carbon deposition, meaning that the amount of carbon deposition generated is far less than the disturbance effect of gaseous materials on the coating pads.

[0116] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for testing the anti-carbon deposition performance of a pyrolysis furnace tube coating, characterized in that, Devices used for performance testing include: A pyrolysis reaction system, the pyrolysis reaction system including furnace tubes; A magnetic levitation metering system includes a counter-current measuring tube communicating with the top of the furnace tube. The top of the counter-current measuring tube is closed, and a magnetic levitation balance body is located above the top. A magnetic float is located inside the counter-current measuring tube below the magnetic levitation balance body. A position sensing terminal and a load couple are connected sequentially from top to bottom to the bottom of the magnetic float via an inertial connecting line. The load couple includes a body with a hollow cavity and a plug built into the hollow cavity. The plug is connected to the magnetic float via the inertial connecting line. The bottom of the body is connected to a... The coating plate is located inside the counter-current measuring tube and the coating plate is located inside the furnace tube. A position sensor, a counter-current gas inlet pipe, and a limiter are also provided on the inner sidewall of the counter-current measuring tube. The position sensor is located in the upper part of the counter-current measuring tube and corresponds to the position sensing terminal, used to mark the working state of the magnetic float. The counter-current gas inlet pipe is located between the limiter and the position sensor, used to introduce inert protective gas into the counter-current measuring tube. The limiter is located below the load couple and has an opening in the middle, used to limit, support, and mark the state of the load couple. Performance testing using the device includes the following steps: S1, Calibrate the magnetic levitation balance: (1) Weigh the mass m0 of the coated pad before carbon deposition using an analytical balance, and calculate the surface area S0 of the coated pad; (2) Suspend the coated plate inside the device and weigh the initial total mass m of the suspended object using a magnetic levitation balance. c The furnace tube is heated, and inert gas is introduced into the counter-impact measuring tube. A mixture of water vapor and nitrogen is then introduced into the furnace tube. Once the pressure and temperature inside the furnace tube reach the preset reaction conditions and the device is operating stably, the mass of the suspended object is weighed again using a magnetic levitation balance as a blank test result. The measurement is performed for at least five measurement cycles. The results of the maximum positive offset, average positive offset, maximum negative offset, and average negative offset are statistically analyzed. Measurement cycle: The spatial positions of the load couple and the limiter in the magnetic levitation balance mark the magnetic levitation balance as the zero-point calibration position, the measurement position, and the position to be measured. In the zero-point calibration position, the load couple body is located on the limiter, the plug of the load couple is not in contact with the body, and it is suspended inside the hollow cavity of the body. The magnetic levitation balance is zeroed and measured. In the measurement position, the plug of the load couple is in contact with the body, and the body is lifted away from the limiter. The magnetic levitation balance is weighed and measured. In the position to be measured, the load couple returns from the measurement position to the zero-point calibration position, but the magnetic levitation balance does not measure. The process of the magnetic levitation balance going through the zero-point calibration position - measurement position - position to be measured is one measurement cycle. In each measurement cycle, the zero-point calibration position is maintained for 20~60 s, the measurement position is maintained for 40~150 s, the measurement position reads measurement values ​​at a frequency of 4~8 times / s, and the position to be measured is maintained for 40~80 s. Maximum positive offset Z max : Maximum value of blank test results and m c The absolute value of the difference; Average positive offset Z avg : The blank test results are greater than m c The average value of the numerical results and m c The absolute value of the difference; Maximum negative offset F max Minimum value of blank test results and m c The absolute value of the difference; Average negative offset F avg : The blank test results are less than m c The average value of the numerical results and m c The absolute value of the difference; S2, the mixed feed gas of water vapor and nitrogen is switched to hydrocarbon feed gas, and real-time carbon deposition data is collected during the experiment. t ; S3, Data Filtering and Results Acquisition: Real-time calculation of the average value D of all data within the current measurement period. avg If the carbon deposition data D collected in a single measurement cycle in the current measurement cycle t Satisfy D t >D avg And |D t -D avg |>Z max Or D t <D avg And |D t -D avg |>F avg If so, the carbon deposition data collected in that single instance will be discarded; S4, using the carbon deposition behavior operation vector to detect the collected results, filtering out abnormal data again, and performing data processing to obtain coating carbon deposition data, specifically: (1) After the experiment, the coated plate was removed and its mass m after carbon deposition was measured using an analytical balance. t ; (2) Export the result data retained in step S3, calculate the average value D of the data collected in each measurement cycle, construct the carbon deposition behavior operation vector, and detect the result data retained in step S3 in the process of constructing the carbon deposition behavior operation vector to filter out abnormal data again. The method for constructing the carbon deposition behavior operation vector is as follows: i. Determine whether the average value D1 of the raw data results in the first measurement cycle satisfies m. c +(m t - m0) + Z max ≥D1≥m c If the condition is met, the original measurement value of the first measurement cycle is retained. If D1≥m c +(m t - m0) + Z max Then discard all data from the first measurement cycle and treat the second measurement cycle as the first measurement cycle. If D1 < m c Then, the data of the first measurement cycle is assigned a value based on the raw data result of the second measurement cycle, specifically as follows: If the average value of the raw data results in the second measurement period, D2, is less than D1 or m c If D2 > D1, then m c The numerical value is assigned to the data result of the first measurement cycle; If the average value of the raw data results in the second measurement period, D2, is greater than m c Then, for a single acquisition in the first measurement cycle, satisfying D... t >D1 and |D t -D1|>Z avg Or D t <D1 and |D t -D1|>F avg The data is discarded, and the average value D1′ of the data results for the first measurement period is recalculated. If D1′>m c If the data result of the first measurement cycle after processing is retained; if D1′<m c Then m c The numerical value is assigned to the data result of the first measurement cycle; ii. Determine the average value D of the raw data results in the (n+1)th measurement period. n+1 Is it greater than or equal to the average value D of the raw data results in the nth measurement period? n Let n be an integer greater than or equal to 2, if D n+1 ≥D n Then keep D. n+1 The original measured value; if D n+1 <D n Then, the result data of the nth period is assigned to the (n+1)th period, and data with values ​​greater than m in the results of the nth measurement period and subsequent measurement periods are removed. c +(m t - m0) + Z max Data results; (5) Perform linear fitting on the processed data, and the fitted curve satisfies: i, the initial point coating pad mass is between m c - F avg With m c + Z avg between; ii, the final coating pad mass is between m c +(m t - m0) - F avg With m c +(m t - m0) + Z avg between; iii, time T in the fitted curve n The corresponding fitting result is less than or equal to time T. n+1 The corresponding fitting results; (6) The obtained fitted curve y is then subjected to (y-m) c The S0 transformation yields the carbon deposition changes of the coating over the corresponding time.

2. The method for testing the anti-carbon deposition performance of the coating on the pyrolysis furnace tube according to claim 1, characterized in that, The magnetic levitation balance and the analytical balance have an accuracy of 10. -6 g.

3. The method for testing the anti-carbon deposition performance of the coating on the pyrolysis furnace tube according to claim 1, characterized in that, The outer side of the counter-impact measuring tube is covered with a heat insulation layer. During the experiment, the temperature of the heat insulation layer is controlled at 50~80℃.

4. The method for testing the anti-carbon deposition performance of the pyrolysis furnace tube coating according to claim 3, characterized in that, The insulation layer has a hollow shell structure, and the temperature is controlled by introducing a cooling medium into the hollow shell structure. The cooling medium is one of water, mineral heat transfer oil, propylene glycol, and glycerol.

5. The method for testing the anti-carbon deposition performance of the coating on the pyrolysis furnace tube according to claim 1, characterized in that, During the experiment, a gas at a temperature of 5~50 ℃ that does not participate in the reaction in the pyrolysis furnace is introduced into the counteracting gas inlet pipe, and the outlet of the counteracting gas inlet pipe is oriented downward in the counteracting measuring pipe.

6. The method for testing the anti-carbon deposition performance of the coating on the pyrolysis furnace tube according to claim 5, characterized in that, The gas is one of nitrogen, argon, and carbon dioxide.

7. The method for testing the anti-carbon deposition performance of the coating on the pyrolysis furnace tube according to claim 1, characterized in that, The furnace tube includes a lower main furnace tube and an upper enlarged section furnace tube. The maximum diameter of the enlarged section furnace tube is 1.5 to 3.0 times the diameter of the main furnace tube, and the volume ratio of the enlarged section furnace tube to the main furnace tube is ≤0.3.

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