Ammonium hydrosulfide erosion simulation experiment device and test method for hydrocracking unit

Abstract

The invention belongs to the technical field of petrochemical engineering, particularly relates to an ammonium hydrosulfide erosion simulation experiment device for a hydrocracking unit and a testing method, and designs the ammonium hydrosulfide erosion simulation experiment device and method for the hydrocracking unit. Through the structure of the patent, simulation test research can be carried out on flow erosion conditions of high-risk corrosion media such as ammonium sulfide and ammonium hydrosulfide in a high-pressure heat exchanger of a hydrocracking unit, and erosion simulation under specific conditions is realized by controlling key corrosion erosion parameters such as flow velocity, temperature, spraying angle and medium concentration; self-circulation erosion of a corrosion medium is achieved through a circulating pump, the inclination angle of a corrosion sample table is remotely and accurately controlled, the spraying center of a nozzle can be automatically calibrated, accurate testing of a metal sample at different spraying angles can be achieved, the corrosion rate can be calculated in real time through an ultrasonic thickness measuring probe, and the experiment efficiency is greatly improved.

Description

Technical Field

[0001] This application belongs to the field of petrochemical technology, specifically relating to an experimental apparatus and testing method for simulating ammonium hydrosulfide erosion in a hydrocracking unit. Background Technology

[0002] As a key production unit for refinery feedstock impurity removal, oil product quality upgrading, and product structure optimization, hydrocracking units face prominent corrosion problems in high-pressure systems due to factors such as feedstock degradation and long-term equipment service, seriously threatening the safe operation of the unit. Corrosion problems are particularly severe in high-pressure heat exchangers and high-pressure air coolers, with the corrosion mechanisms mainly being ammonium salt crystallization, under-deposit corrosion, and scouring corrosion. Ammonium salt crystallization and under-deposit corrosion can be addressed by timely flushing of crystals through water injection. Scouring corrosion is difficult to avoid due to numerous influencing factors, such as flow rate, temperature, erosion angle, medium concentration, and substrate material. Furthermore, high-pressure heat exchangers / high-pressure air coolers operate in high-pressure, hydrogen-rich, variable-condition, multiphase flow, and highly corrosive environments. Their corrosion failure is the result of the coupling of flow, heat transfer, phase change, and corrosion processes, with complex influencing factors and unclear spatiotemporal evolution patterns. This leads to an unclear understanding of the patterns and characteristics of scouring corrosion, making effective control of scouring corrosion impossible. Summary of the Invention

[0003] This patent designs a simulation experimental device and method for ammonium hydrosulfide erosion in a hydrocracking unit. It simulates the flow erosion of ammonium hydrosulfide, a key medium inside a high-pressure heat exchanger. By controlling flow rate, temperature, erosion angle, and medium concentration, it achieves erosion simulation under specific conditions. The device enables self-circulating erosion of the corrosive medium and allows for automatic adjustment of the erosion angle, automatic nozzle alignment, and real-time measurement of the corrosion rate, greatly improving experimental efficiency. The technical solution is as follows:

[0004] An ammonium hydrosulfide erosion simulation experimental device for a hydrocracking unit includes a corrosion chamber, a circulating water pump, a pump speed controller, and a temperature controller. The circulating water pump is connected to the inlet and outlet of the corrosion chamber via connecting pipes. A spray nozzle is installed at the inlet. A heating element is installed on the connecting pipes and connected to the temperature controller. A flow meter is installed between the circulating water pump and the outlet of the corrosion chamber. The circulating water pump is connected to the pump speed controller, which is connected to external AC power via a power adapter.

[0005] Preferably, the corrosion chamber includes a chamber body, a sample stage, and a storage tank. The chamber body has a top cover and side ribs on both sides. The top cover has an exhaust gas treatment pipe. The sample stage and the storage tank are located inside the chamber body and are connected by a guide channel. The guide channel is located below the sample stage, and its tail end is sealed to the storage tank. The contact areas between the guide channel, the storage tank, and the chamber body are all sealed. The sample stage is connected to a rotating shaft, and a corrosion sample to be tested is placed on the sample stage. One end of the rotating shaft is axially connected to the side ribs, and the other end is connected to a driven component. The driven component is connected to a driving component, and the driving component is connected to a motor.

[0006] Preferably, the top cover is provided with a second motor, the second motor is provided with a transmission gear, the transmission gear meshes with a transmission rack, the transmission rack is located on a nozzle mounting plate, the nozzle mounting plate is mounted on the box body, located between the two side plates of the box body; the nozzle mounting plate is provided with a nozzle, the nozzle is connected to the liquid inlet of the corrosion box.

[0007] Preferably, an ultrasonic thickness gauge is installed on the back of the sample stage at the center position. The ultrasonic thickness gauge is located in a mounting groove, and a spring is provided in the mounting groove. The spring is in a pre-tightened state. The ultrasonic thickness gauge is fixed by inserting the corrosion sample plate into the mounting groove to compress the spring. An ultrasonic coupling agent is applied to the sample contact surface of the ultrasonic thickness gauge.

[0008] Preferably, the system includes a controller connected to an ultrasonic thickness gauge probe, a flow valve, a flow meter, a temperature controller, a water pump speed controller, a motor 1, and a motor 2. The controller controls the rotation of motor 1, causing the sample stage to rotate from 0 to 90 degrees. It also automatically controls motor 2 to rotate based on the rotation angle of the sample stage controlled by motor 1, ensuring the position of the nozzle erosion of the sample is within a set central area. While controlling motor 1 to rotate the sample stage at each set angle, the controller simultaneously controls motor 2 to automatically adjust the nozzle up and down for alignment. Furthermore, the controller collects ultrasonic thickness gauge probe data at different temperatures and flow rates for a duration t. Based on a hypothetical model, it calculates the thickness of the material eroded per unit time, which is denoted as the erosion rate E.

[0009] Preferably, the formula for calculating the erosion rate E is as follows:

[0010] E = k + a·v + b·T 2 +c·cos(θ)+d·log(ρ)

[0011] k is a constant term; v is the flow velocity, representing the speed at which the fluid erodes the surface of the corrosive sample.

[0012] T is temperature, representing the temperature of the ammonium hydrosulfide solution;

[0013] ρ is the concentration, representing the mass fraction or molar concentration of ammonium hydrosulfide in the solution;

[0014] θ is the erosion angle, which represents the angle between the direction of fluid impact and the surface of the corrosive spline;

[0015] a, b, c, and d are coefficients to be determined, representing the degree of influence of flow velocity, temperature, concentration, and erosion angle on the erosion rate, respectively.

[0016] Preferably, the parameters k, a, b, c, d in the model are estimated using the collected experimental data through multivariate nonlinear regression analysis; and the error between the predicted value and the actual measured value is calculated and minimized using the least squares method.

[0017] Preferably, the housing is made of corrosion-resistant transparent PVC material, which facilitates cleaning and observation of the liquid spraying state of the nozzle and the macroscopic morphological characteristics of the sample erosion; the nozzle is made of high corrosion-resistant alloy material, which can withstand long-term continuous erosion by high-velocity water flow.

[0018] The preferred testing method has the following steps:

[0019] S1. Move the entire experimental equipment into the laboratory ventilation box. Personnel wearing gas masks are isolated from the experimental equipment. Install the corrosion sample on the sample platform and adjust the spray angle between the sample platform and the nozzle to 90°.

[0020] S2. Slowly pour the prepared ammonium hydrosulfide solution of a certain concentration into the storage tank, cover it with the top cover, and connect the tail gas treatment pipe on the top cover to the tail gas treatment device (the tail gas is mainly hydrogen sulfide gas, and the absorption method mainly uses alkaline solution (such as ammonia water) to absorb hydrogen sulfide).

[0021] S3. Turn on the circulating water pump and use the pump speed controller to initially circulate the corrosive medium at the minimum flow rate. Set the temperature controller to the rated temperature of 50℃ for rapid heating. Once the actual temperature reaches about 20℃, change the rated temperature to 20℃ and maintain a constant temperature. Gradually increase the flow rate to v, and the erosion time is t hours.

[0022] S4. During the erosion process, every hour, the controller automatically calculates the erosion thinning rate (mm / h) of the material based on the real-time thickness data measured by the ultrasonic thickness gauge.

[0023] S5. After erosion is completed, turn off the circulating water pump, open the top cover, and take out the sample stage; replace with a new eroded sample, repeat steps S1-S4, change the flow rate v in step (S3), and calculate the corresponding erosion thinning rate.

[0024] Preferably, the flow rate in step S3 can be set to a constant value and the temperature can be set to a variable for the experiment; or the flow rate and temperature can both be set to constant values ​​and the erosion angle in step S1 can be set to a variable for the experiment; or the flow rate, temperature, and erosion angle can all be set to constant values ​​and the concentration of ammonium hydrosulfide solution in step S2 can be set to a variable for the experiment.

[0025] Preferably, when changing ammonium hydrosulfide solutions of different concentrations, the waste solution in the storage tank should first be discharged from the outlet at the bottom of the tank, and the pipeline and the residual solution inside the tank should be cleaned with distilled water and dried. Only after drying can the solution be added again for subsequent experiments.

[0026] Compared with the prior art, the beneficial effects of this application are as follows:

[0027] 1) This patented device enables continuous cyclic erosion analysis of samples made of different materials under varying conditions of different concentrations of ammonium hydrosulfide solution, at different temperatures, flow rates, and erosion angles. It allows for erosion experiments with toxic and corrosive media, real-time monitoring of corrosion rates, and multi-dimensional examination of material corrosion rates and erosion resistance. Furthermore, by utilizing the collected data, a corrosion model for a specific material can be rapidly fitted using nonlinear regression combined with the least squares method, providing theoretical guidance for material corrosion prediction.

[0028] 2) Design an automatic rotating sample stage and an automatic nozzle centering mechanism to achieve erosion analysis with an angle of 0-90° between the nozzle and the sample stage.

[0029] 3) The overall experimental setup is made of transparent and corrosion-resistant materials, which facilitates real-time observation of the erosion spraying status.

[0030] 4) The obtained erosion samples can be further analyzed in greater depth using scanning electron microscopy, energy dispersive spectroscopy, and other methods. This provides strong experimental equipment support for researchers to study the erosion mechanism of key corrosive media, and the analytical conclusions can provide theoretical guidance for the daily maintenance and repair work of on-site corrosion prevention operators, and provide experimental support for ensuring the long-term operation of the equipment. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the application.

[0032] Figure 2 This is a three-dimensional view of the corrosion chamber.

[0033] Figure 3 This is a three-dimensional view of the corrosion chamber.

[0034] Figure 4 This is a partial schematic diagram of the corrosion chamber.

[0035] Figure 5 This is a partial schematic diagram of the corrosion chamber.

[0036] Figure 6 This is a partial schematic diagram of the sample platform.

[0037] Figure 7 This is a screenshot of Example 1.

[0038] Figure 8 This is the result of Example 2.

[0039] Figure 9 This is the result of Example 3.

[0040] Figure 10 This is the result of Example 4.

[0041] In the diagram: 1-Temperature controller, 2-Heating belt, 3-Corrosion chamber, 4-Flow meter, 5-Circulating water pump, 6-Water pump speed controller, 7-Power adapter, 8-Exhaust gas treatment pipe, 9-Nozzle, 11-Sample stage, 12-Guide channel, 13-Storage tank, 14-Corrosion sample; 15-Ultrasonic thickness probe, 16-Spring, 17-Ultrasonic coupling agent;

[0042] 301-Box body, 302-Top cover, 303-Side rib plate, 304-Motor mounting platform, 305-Motor II, 306-Transmission gear, 307-Nozzle mounting plate, 308-Corrosion box outlet, 309-Driving component, 310-Driven component, 311-, 312-Transmission rack, 313-Rotating shaft. Detailed Implementation

[0043] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0044] An ammonium hydrosulfide erosion simulation experimental device for a hydrocracking unit includes a corrosion chamber, a circulating water pump, a pump speed controller, and a temperature controller. The circulating water pump is connected to the inlet and outlet of the corrosion chamber via connecting pipes. A spray nozzle is installed at the inlet. A heating element is installed on the connecting pipes and connected to the temperature controller. A flow meter is installed between the circulating water pump and the outlet of the corrosion chamber. The circulating water pump is connected to the pump speed controller, which is connected to external AC power via a power adapter.

[0045] The corrosion chamber includes a chamber body, a sample stage, and a flow storage tank. The top of the chamber body is equipped with a top cover, and side ribs are provided on both sides. An exhaust gas treatment pipe is provided on the upper part of the top cover. The sample stage and the flow storage tank are located inside the chamber body and are connected by a guide channel. The guide channel is located below the sample stage, and its tail end is sealed to the flow storage tank. The contact areas between the guide channel, the flow storage tank, and the chamber body are all sealed. The sample stage is connected to a rotating shaft, and a corrosion sample to be tested is placed on the sample stage. One end of the rotating shaft is axially connected to the side rib, and the other end is connected to a driven component. The driven component is connected to a driving component, and the driving component is connected to a motor.

[0046] The top cover is equipped with a second motor, which has a transmission gear that meshes with a transmission rack. The transmission rack is located on a nozzle mounting plate, which is mounted on the box body between the two side plates of the box body. The nozzle mounting plate is equipped with a nozzle, which is connected to the water inlet of the corrosion box.

[0047] An ultrasonic thickness gauge probe is installed on the back of the center of the sample stage. The ultrasonic thickness gauge probe is located in a mounting groove, which contains a spring that is in a pre-tightened state. The ultrasonic thickness gauge probe is fixed by inserting the corrosion sample plate into the mounting groove to compress the spring. An ultrasonic coupling agent is applied to the contact surface of the ultrasonic thickness gauge probe.

[0048] To enable real-time measurement of sample thickness corrosion, an ultrasonic thickness gauge probe and spring assembly are added to the center of the rotating sample stage. The ultrasonic thickness gauge probe's connecting wire passes through the center of the rotating shaft of the rotating sample stage and connects to the computer for real-time measurement of thickness changes. As shown in the figure below, during installation, the probe is lifted to compress the spring, and ultrasonic coupling agent is applied to the contact surface between the probe and the sample. After installing the sample, the probe is released to allow the spring to tighten.

[0049] The controller is connected to the ultrasonic thickness gauge probe, flow valve, flow meter, temperature controller, water pump speed controller, motor one, and motor two. The controller controls motor one to rotate, causing the sample stage to rotate 0-90 degrees, and controls motor two to rotate, so that the position of the erosion corrosion sample by the nozzle is within the set center area. When the controller controls motor one to drive the sample stage to rotate at each set angle, it simultaneously controls motor two to drive the nozzle to automatically adjust and center up and down. The controller also collects ultrasonic thickness gauge probe data at different temperatures and flow rates for a duration of t. Based on the assumed model, it calculates the thickness of the material eroded per unit time, which is marked as the corrosion rate E.

[0050] The corrosion model, i.e., the formula for calculating the corrosion rate E, is as follows:

[0051] E = k + a·v + b·T 2 +c·cos(θ)+d·log(ρ)

[0052] k is a constant term; v is the flow velocity, representing the speed at which the fluid passes through the surface of the corrosive spline;

[0053] T is temperature, representing the temperature of the ammonium hydrosulfide solution;

[0054] ρ is the concentration, representing the mass fraction or molar concentration of ammonium hydrosulfide in the solution;

[0055] θ is the erosion angle, which represents the angle between the direction of fluid impact and the surface of the corrosive spline;

[0056] a, b, c, and d are coefficients to be determined, representing the degree of influence of flow velocity, temperature, concentration, and erosion angle on the erosion rate, respectively.

[0057] Using the collected experimental data, the parameters k, a, b, c, and d in the model were estimated through multivariate nonlinear regression analysis. The least squares method was used to calculate and minimize the error between the predicted and actual measured values. Finally, relatively accurate corrosion model parameter values ​​were obtained, and a corrosion model specific to this material was established.

[0058] The enclosure is made of corrosion-resistant transparent PVC material, which facilitates cleaning and observation of the liquid spraying state of the nozzle and the macroscopic morphological characteristics of the sample erosion; the nozzle is made of high corrosion-resistant alloy material, which can withstand the continuous erosion of high-velocity water flow for a long time.

[0059] The testing method is characterized by the following steps:

[0060] S1. Move the entire experimental equipment into the laboratory ventilation box. Personnel wearing gas masks are isolated from the experimental equipment. Install the corrosion sample on the sample platform and adjust the spray angle between the sample platform and the nozzle to 90°.

[0061] S2. Slowly pour the prepared ammonium hydrosulfide solution of a certain concentration into the storage tank, cover it with the top cover, and connect the tail gas treatment pipe on the top cover to the tail gas treatment device.

[0062] S3. Turn on the circulating water pump and use the pump speed controller to initially circulate the corrosive medium at the minimum flow rate. Set the temperature controller to the rated temperature of 50℃ for rapid heating. Once the actual temperature reaches about 20℃, change the rated temperature to 20℃ and maintain a constant temperature. Gradually increase the flow rate to v, and the erosion time is t hours.

[0063] S4. During the erosion process, every hour, the controller automatically calculates the erosion thinning rate of the material based on the real-time thickness data measured by the ultrasonic thickness gauge.

[0064] S5. After erosion is completed, turn off the circulating water pump, open the top cover, and take out the sample stage; replace with a new eroded sample, repeat steps S1-S4, change the flow rate v in step S3, and calculate the corresponding erosion thinning rate.

[0065] In step S3, set the flow rate to a constant value and the temperature to a variable for the experiment; or set both the flow rate and temperature to constant values ​​and set the erosion angle in step S1 to a variable for the experiment; or set the flow rate, temperature, and erosion angle to constant values ​​and set the concentration of ammonium hydrosulfide solution in step S2 to a variable for the experiment.

[0066] When changing ammonium hydrosulfide solutions of different concentrations, first drain the waste solution in the reservoir from the outlet at the bottom of the tank, and clean the pipeline and the residual solution inside the tank with distilled water and dry them. Only after drying can the solution be added for subsequent experiments.

[0067] Example 1: Verification of the erosion behavior of ammonium hydrosulfide solutions at different flow rates on #10 carbon steel

[0068] Experimental conditions: The corrosion rate of 10# carbon steel was studied under the conditions of 20℃, 5% ammonium hydrosulfide solution without chloride ions, and erosion angle of 90°.

[0069] Experimental procedure:

[0070] (1) First, set up the experimental equipment according to Figure 1 The setup is carried out in the sequence shown. The entire equipment is operated inside a fume hood. The temperature controller and circulating water pump are powered on, the temperature controller is preheated, and the water pump is turned off. Personnel wear protective equipment such as gas masks, anti-corrosion gloves, protective clothing, and goggles in accordance with experimental safety requirements.

[0071] (2) Take a 10# steel corrosion sample with dimensions of 40mm×40mm×3mm, clean it with ethanol, dry it, and weigh it. Then install it on the sample table, weld the rotating shaft to the sample table, install side ribs on both ends of the rotating shaft, insert the side ribs into the box, tighten one end of the rotating shaft with a T-head structure, adjust the rotating shaft, fix the spray angle to 90°, and then fix the threaded end of the other end of the rotating shaft with a nut.

[0072] (3) As shown in the figure, when the spray angle is 90°, slowly pour 2L of 5% ammonium hydrosulfide solution into the storage tank, cover it with the top cover, connect the exhaust gas treatment pipe to the top of the top cover, and connect the pipe to the exhaust gas treatment device to prevent the leakage of toxic gas. The drain outlet at the bottom of the tank is connected to the circulation pipeline.

[0073] (4) After all equipment is connected, turn on the circulating water pump. Using the pump speed controller, initially circulate the corrosive medium at the minimum flow rate. Set the temperature controller to the rated temperature of 50℃ for rapid heating. Once the actual temperature reaches about 20℃, change the rated temperature back to 20℃ and maintain a constant temperature. Gradually increase the flow rate to 2m / s. The erosion time is 24 hours. During the erosion process, every hour, the controller automatically calculates the material erosion thinning rate based on the real-time thickness data measured by the ultrasonic thickness gauge.

[0074] (5) After the erosion is completed, turn off the circulating water pump, open the top cover, take out the sample platform, take out the corrosion sample, and use 500ml of hydrochloric acid with a concentration of 1.19m / mL and 3.5g of hexamethylenetetramine, add distilled water to make a 1000ml solution, soak for 10min for cleaning, drying, and weighing. The corrosion rate is calculated by the weight loss method and compared with the corrosion rate measured by the ultrasonic probe for reference analysis.

[0075] The experimental data statistics table is shown below:

[0076]

[0077] In the table above, the "corrosion rate calculated by ultrasonic thickness measurement" is obtained by dividing the measured thickness by the time difference using an ultrasonic thickness measuring probe. The "comprehensive average corrosion rate" is obtained by averaging the "corrosion rate calculated by ultrasonic thickness measurement" and then averaging it with the "corrosion rate measured by weight loss method".

[0078] (6) Replace with a new etched sample and repeat the above (2)-(5) process, changing the flow rate in step (4) to 4m / s, 6m / s, 8m / s, and 10m / s respectively, to obtain the corresponding experimental record data statistics table, as shown in the figure below:

[0079]

[0080]

[0081]

[0082] The graph showing the variation of the overall average corrosion rate under different flow rates is shown below. Figure 7 As shown.

[0083] Example 2: Verification of the erosion behavior of 10# carbon steel by ammonium hydrosulfide solutions of different concentrations.

[0084] Experimental conditions: At 20℃, a flow rate of 5m / s, and an erosion angle of 90°, the corrosion rate of No. 10 steel in an ammonium hydrosulfide solution with varying concentration and no chloride ions was investigated.

[0085] Experimental procedure:

[0086] (1) The experimental operation steps described above are the same as (1)-(5) in Example 1;

[0087] Replace the corrosion sample with a new one and repeat the process (2)-(5) in Example 1. Change the concentration of the solution prepared in step (3) to 1%, 3%, 7%, 9%, 11%, 13%, and 15%, respectively, and obtain the corresponding experimental record data statistics table (the style is as in Example 1, which will not be repeated here). The graph of the change of the comprehensive average corrosion rate under different solution concentrations is shown in the figure. Figure 8 As shown.

[0088] (2) When changing solutions of different concentrations, first discharge the waste solution from the outlet at the bottom of the tank, and clean the pipes and the remaining solution inside the tank with distilled water and dry them. Only after drying can the solution be added for subsequent experiments. The discharged waste liquid is collected and treated in a harmless manner.

[0089] Example 3: Verification of the erosion behavior of ammonium hydrosulfide solutions at different temperatures on 10# carbon steel

[0090] Experimental conditions: The corrosion rate variation was studied under different temperature conditions with a flow rate of 5 m / s, a solution concentration of 5%, and an erosion angle of 90°.

[0091] Experimental procedure:

[0092] (1) The experimental operation steps described above are the same as (1)-(5) in Example 1;

[0093] (2) Replace with a new corrosion sample and repeat the process (2)-(5) in Example 1. Change the rated solution temperature set in step (4) to 30℃, 40℃, 50℃, 60℃, 70℃, and 80℃ respectively, and obtain the corresponding experimental record data statistics table (the style is as in Example 1, which will not be repeated here). The graph of the change of the comprehensive average corrosion rate under different solution temperatures is shown in the figure. Figure 9 As shown.

[0094] Example 4: Verification of the erosion behavior of ammonium hydrosulfide solution at different erosion angles on 10# carbon steel

[0095] Experimental conditions: The variation law of corrosion rate under different erosion angles was studied under the conditions of flow velocity of 5 m / s, solution concentration of 5%, and temperature of 20℃.

[0096] Experimental procedure:

[0097] (1) The experimental operation steps described above are the same as (1)-(5) in Example 1;

[0098] (2) Replace with a new corrosion sample and repeat steps (2)-(5) of Example 1, changing the erosion angles set in steps (2) and (3) to 15°, 30°, 45°, 60°, and 75° respectively, to obtain the corresponding experimental record data statistics table (the style is as in Example 1, and will not be repeated here). The graph showing the change in the comprehensive average corrosion rate under different erosion angles is shown in the figure. Figure 10 As shown.

[0099] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] Example 5: Solving the corrosion model of #10 carbon steel

[0101] The corrosion model of 10# carbon steel is solved using the following steps:

[0102] ① Organize experimental data:

[0103] Experimental parameters with different temperatures, flow rates, erosion angles, and solution concentrations were randomly combined. During the calculation, the corrosion rate parameter under each condition was replaced by the "comprehensive average corrosion rate".

[0104] The collected data is shown in the table below:

[0105]

[0106] ② Define the error function:

[0107] In nonlinear regression analysis, the least squares method is used to minimize the sum of squared residuals. The error function (or sum of squared residuals) is defined as:

[0108]

[0109] Where n is the total number of data points, E i v i T i ρ i θ i These are the corrosion rate, flow rate, temperature, solution concentration, and erosion angle of the i-th data point.

[0110] ③ Estimating model parameters k, a, b, c, and d using nonlinear least squares involves an iterative solution process. Numerical optimization algorithms can be used, such as gradient descent, Newton's method, or more complex algorithms like the Levenberg-Marquardt method. Alternatively, the lsqcurvefit function in MATLAB can be used for nonlinear least squares fitting. This function automatically selects an appropriate algorithm to solve the minimization problem.

[0111] This case uses the lsqcurvefit function in MATLAB to solve for the parameters based on the above 6 sets of data. The calculation steps are as follows:

[0112] 1) Set the initial parameter values ​​m0 = [k0, a0, b0, c0, d0], estimate the initial parameter values ​​and assign them, let k0 = 0.004; a0 = 0.002; b0 = 0.005; c0 = 0.001; d0 = 0.0014.

[0113] 2) Set the minimum and maximum range of parameter values: mmin = 0.00001 * m0; mmax = 10000 * m0.

[0114] 3) The summary variable is X_data = [T_data; v_data; seata_data_2; rho_data].

[0115] 4) Define the regression formula: f=@(m,x)(m(1)+m(2)*x(1,:)+m(3)*x(2,:).^2+m(4)*cos(x(3,:))+m(5)*log(x(4,:))).

[0116] 5) Substitute the values ​​into the lsqcurvefit function to solve the formula:

[0117] [m,resnorm,residual] = lsqcurvefit(f,m0,Xdata,y_data,mmin,mmax). The output m is the optimal fit parameter value.

[0118] We obtain m = [0.000226 1.0e-06 0.000574 1.77e-07 1.43e-07]

[0119] 6) The final optimal corrosion model is:

[0120] E = (0.000226 + 10) -6 ·v+0.000574·T 2 +1.77·10 -7 ·cos(θ)+1.43·10 -7·log(ρ))

[0121] 7) Randomly substitute the second set of parameters for verification, and the fitted value is 0.0051. The error between the fitted value and the measured value of 0.0057 is small, and the model fit is successful.

Claims

1. A simulation experimental apparatus for ammonium hydrosulfide erosion in a hydrocracking unit, characterized in that, The system includes a corrosion chamber, a circulating water pump, a pump speed controller, and a temperature controller. The circulating water pump is connected to the inlet and outlet of the corrosion chamber via connecting pipes. A spray pipe is installed at the inlet. A heating element is installed on the connecting pipe and connected to the temperature controller. A flow meter is installed between the circulating water pump and the outlet of the corrosion chamber. The circulating water pump is connected to the pump speed controller, which is connected to external AC power via a power adapter.

2. The ammonium hydrosulfide erosion simulation experimental apparatus for a hydrocracking unit according to claim 1, characterized in that, The corrosion chamber includes a chamber body, a sample stage, and a flow storage tank. The top of the chamber body is equipped with a top cover, and side ribs are provided on both sides. An exhaust gas treatment pipe is provided on the upper part of the top cover. The sample stage and the flow storage tank are located inside the chamber body and are connected by a guide channel. The guide channel is located below the sample stage, and its tail end is sealed to the flow storage tank. The contact areas between the guide channel, the flow storage tank, and the chamber body are all sealed. The sample stage is connected to a rotating shaft, and a corrosion sample to be tested is placed on the sample stage. One end of the rotating shaft is axially connected to the side rib, and the other end is connected to a driven component. The driven component is connected to a driving component, and the driving component is connected to a motor.

3. The ammonium hydrosulfide erosion simulation experimental apparatus for a hydrocracking unit according to claim 2, characterized in that, The top cover is equipped with a second motor, which has a transmission gear that meshes with a transmission rack. The transmission rack is located on a nozzle mounting plate, which is mounted on the box body between the two side plates of the box body. The nozzle mounting plate is equipped with a nozzle, which is connected to the water inlet of the corrosion box.

4. The ammonium hydrosulfide erosion simulation experimental apparatus for a hydrocracking unit according to claim 2, characterized in that, An ultrasonic thickness gauge probe is installed on the back of the center of the sample stage. The ultrasonic thickness gauge probe is located in a mounting groove, which contains a spring that is in a pre-tightened state. The ultrasonic thickness gauge probe is fixed by inserting the corrosion sample plate into the mounting groove to compress the spring. An ultrasonic coupling agent is applied to the contact surface of the ultrasonic thickness gauge probe.

5. The ammonium hydrosulfide erosion simulation experimental apparatus for a hydrocracking unit according to claim 2, characterized in that, The system includes a controller connected to an ultrasonic thickness gauge probe, a flow valve, a flow meter, a temperature controller, a water pump speed controller, a motor 1, and a motor 2. The controller controls the rotation of motor 1, causing the sample stage to rotate 0-90 degrees, and controls the rotation of motor 2, ensuring that the erosion of the sample by the nozzle is within a set central area. When the controller controls motor 1 to rotate the sample stage at each set angle, it simultaneously controls motor 2 to automatically adjust the nozzle up and down for centering. The controller also collects ultrasonic thickness gauge probe data at different temperatures and flow rates for a duration of t. Based on the assumed model, it calculates the thickness of the material eroded per unit time, which is denoted as the erosion rate E.

6. The ammonium hydrosulfide erosion simulation experimental apparatus for a hydrocracking unit according to claim 5, characterized in that, The formula for calculating the erosion rate E is as follows: E=k+a·v+b·T 2 +c·cos(θ)+d·log(ρ) k is a constant term; v is the flow velocity, representing the speed at which the fluid erodes the surface of the corrosive spline. T is temperature, representing the temperature of the ammonium hydrosulfide solution; ρ is the concentration, representing the mass fraction or molar concentration of ammonium hydrosulfide in the solution; θ is the erosion angle, which represents the angle between the direction of fluid impact and the surface of the corrosive spline; a, b, c, and d are coefficients to be determined, representing the degree of influence of flow velocity, temperature, concentration, and erosion angle on the erosion rate, respectively.

7. The ammonium hydrosulfide erosion simulation experimental apparatus for a hydrocracking unit according to claim 6, characterized in that, Using the collected experimental data, the parameters k, a, b, c, d in the model were estimated by multivariate nonlinear regression analysis; the least squares method was used to calculate and minimize the error between the predicted value and the actual measured value.

8. The ammonium hydrosulfide erosion simulation experimental apparatus for a hydrocracking unit according to claim 7, characterized in that, The enclosure is made of corrosion-resistant transparent PVC material, which facilitates cleaning and observation of the liquid spraying state of the nozzle and the macroscopic morphological characteristics of the sample erosion; the nozzle is made of high corrosion-resistant alloy material, which can withstand the continuous erosion of high-velocity water flow for a long time.

9. The testing method for the experimental apparatus according to any one of claims 1-6, characterized in that, The steps are as follows: S1. Move the entire experimental equipment into the laboratory ventilation box. Personnel wearing gas masks are isolated from the experimental equipment. Install the corrosion sample on the sample platform and adjust the spray angle between the sample platform and the nozzle to 90°. S2. Slowly pour the prepared ammonium hydrosulfide solution of a certain concentration into the storage tank, cover it with the top cover, and connect the tail gas treatment pipe on the top cover to the tail gas treatment device. S3. Turn on the circulating water pump and use the pump speed controller to initially circulate the corrosive medium at the minimum flow rate. Set the temperature controller to the rated temperature of 50℃ for rapid heating. Once the actual temperature reaches about 20℃, change the rated temperature to 20℃ and maintain a constant temperature. Gradually increase the flow rate to v, and the erosion time is t hours. S4. During the erosion process, every hour, the controller automatically calculates the erosion thinning rate of the material based on the real-time thickness data measured by the ultrasonic thickness gauge. S5. After erosion is completed, turn off the circulating water pump, open the top cover, and take out the sample stage; replace with a new eroded sample, repeat steps S1-S4, change the flow rate v in step S3, and calculate the corresponding erosion thinning rate.

10. The test method according to claim 9, characterized in that, In step S3, set the flow rate to a constant value and the temperature to a variable for the experiment; or set both the flow rate and temperature to constant values ​​and set the erosion angle in step S1 to a variable for the experiment; or set the flow rate, temperature, and erosion angle to constant values ​​and set the concentration of ammonium hydrosulfide solution in step S2 to a variable for the experiment.

11. The test method according to claim 9, characterized in that, When changing ammonium hydrosulfide solutions of different concentrations, first drain the waste solution in the reservoir from the outlet at the bottom of the tank, and clean the pipeline and the residual solution inside the tank with distilled water and dry them. Only after drying can the solution be added for subsequent experiments.

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