A corrosion assessment and control method for natural gas purification plants

Abstract

This invention discloses a corrosion assessment and control method for a natural gas purification plant, relating to the field of corrosion control in natural gas purification plants. The natural gas purification plant includes a desulfurization unit, which includes a reboiler. The method comprises the following steps: S1: Information verification, confirming corrosion-related data of the purification plant equipment, including information on the desulfurization unit, production parameters of the desulfurization unit, and design and operating parameters of the reboiler in the desulfurization unit; S2: Simulation evaluation, identifying corrosion-prone areas; S3: On-site corrosion monitoring; S4: Modeling and optimization. By combining indoor and on-site simulations, the corrosion assessment considers the influence of multiple factors, adapting to the complex operating conditions of the actual desulfurization process. Repeated experiments are conducted to model and optimize the desulfurization unit, and the assessment and testing method ultimately achieves accurate results.

Description

Technical Field

[0001] This invention relates to the field of corrosion control in natural gas purification plants, and particularly to a method for corrosion assessment and control in natural gas purification plants. Background Technology

[0002] Currently, the development and production of sulfur-containing natural gas worldwide relies on various desulfurization and decarbonization technologies, with the amine desulfurization process being the most widely used. The process mainly includes four parts: absorption, flash evaporation, heat exchange, and regeneration.

[0003] Natural gas, as a high-quality clean energy source, has received widespread global attention for its development and utilization. However, the natural gas in the Sichuan-Chongqing region contains sulfur and requires treatment before it can be used. The main desulfurization and decarbonization methods both domestically and internationally include wet absorption, dry desulfurization, wet oxidation, and biological desulfurization, among which wet absorption is the most widely used. Its main process flow consists of four parts: absorption, flash evaporation, heat exchange, and regeneration.

[0004] According to publicly available data from both domestic and international sources, ensuring the long-term stable operation of natural gas purification plants is one of the crucial prerequisites for increasing natural gas production. Corrosion control in these plants has become a significant factor hindering their long-term stability. In the Sichuan-Chongqing region, many sulfur-containing natural gas purification plants have repeatedly experienced equipment and pipeline corrosion failures during production, severely impacting their stable operation.

[0005] Currently, corrosion control in desulfurization units mainly relies on the selection of metal materials, daily process parameter control, and corrosion monitoring. Material selection refers to addressing failure issues in severely corroded areas through the application of corrosion-resistant materials. Daily process parameter control involves optimizing production process parameters such as throughput, circulation rate, and acid gas load to control corrosion. Corrosion monitoring utilizes galvanic plates and online monitoring technologies to track the corrosion status of the unit, providing a basis for corrosion control decisions. Theoretically, the comprehensive application of these three aspects can effectively control corrosion and ensure the long-term operation of the unit.

[0006] Chinese patent CN103870670A discloses a method and device for predicting the degree of corrosion in oil pipelines; Chinese patent CN105069486A discloses a method for predicting corrosion in petrochemical equipment based on extreme learning machines; Chinese patent CN109816133A discloses a method for predicting corrosion inside pipelines; Chinese patent CN108119761A discloses a method for predicting the degree of corrosion in natural gas pipelines with gas-liquid two-phase flow; and Chinese patent CN111177947A discloses a method for establishing a CO2 corrosion prediction chart considering multiple factors. These technologies primarily target single objects and cannot predict the corrosion of complex desulfurization systems in purification plants. This is because the desulfurization system in a purification plant involves dozens of pieces of equipment and countless pipelines, all of which influence each other. An malfunction in one piece of equipment will affect other equipment and even the entire system. Therefore, at the production level, a holistic and comprehensive approach is necessary.

[0007] Therefore, existing technologies still have many problems at the technical level. Although there is a large amount of research on the main controlling factors of corrosion in desulfurization equipment, most of the research is based on indoor simulation evaluation, which is difficult to reflect the complex operating conditions of the actual desulfurization process. Within a single regeneration tower, there is a complex distribution of key parameters such as medium, temperature, pressure, and flow rate, which is difficult to simulate under laboratory conditions. This often leads to the dilemma that laboratory evaluation data does not match the field measurement data.

[0008] Even disregarding the differences between laboratory and field conditions, extensive research suggests that numerous key parameters influence the corrosion behavior of desulfurization units, including at least temperature, pressure, circulation rate, acid gas load, carbon-to-sulfur ratio, desulfurization solution medium, and throughput. Theoretical research in the laboratory is insufficient to determine the primary factors affecting corrosion and cannot accurately guide the control of process parameters in the field.

[0009] A large amount of on-site monitoring data cannot be effectively utilized; typically, the monitoring results for one cycle can only reflect the corrosion status of the production unit within that cycle. Furthermore, changes in corrosion status do not allow technicians to promptly identify the causes from a production management perspective.

[0010] Because the quality of raw gas varies from region to region, many newly built purification plants lack mature standards and experience for design, and lack corresponding methods for guidance. Often, problems with corrosion occur later, and modifications are only made then, which consumes a lot of manpower and resources.

[0011] Therefore, the following application is submitted. Summary of the Invention

[0012] The technical problem to be solved by this invention is to improve the fact that existing corrosion research on desulfurization equipment is limited to indoor simulation evaluation, which makes it difficult to reflect the complex working conditions of the actual desulfurization process.

[0013] This invention is achieved through the following technical solution:

[0014] This application proposes a corrosion assessment and control method for a natural gas purification plant, which includes a desulfurization unit, said desulfurization unit including a reboiler, comprising the following steps:

[0015] S1: Obtain confirmation information: Confirm corrosion-related data of the purification plant equipment, including one or more of the following: information on the purification plant's desulfurization unit, production parameters of the desulfurization unit, design parameters of the reboiler in the desulfurization unit, and operating parameters.

[0016] S2: Simulation Evaluation: Based on the corrosion-related data, design an indoor corrosion evaluation test to obtain the corrosion behavior of the desulfurization unit's metallic materials and determine the areas prone to corrosion.

[0017] S3: On-site corrosion monitoring: Based on the simulation evaluation, select the equipment and pipelines of the desulfurization unit, conduct on-site corrosion monitoring, perform flow field numerical simulation inside the desulfurization unit, and obtain the calculation results of the corrosion-prone parts.

[0018] S4: Modeling and Optimization: Model and simulate the desulfurization device, and optimize the corrosion-prone parts of the desulfurization device based on the calculation results of S3.

[0019] Preferably, step S4 is followed by step S5; wherein, S5 is: comparing the results of S2 and S3 with the parameters of S1 to optimize the control parameters.

[0020] Preferably, the desulfurization device information in S1 includes one or a combination of information such as the name of the purification plant, the source of the raw gas for the purification plant, the composition of the desulfurization solution system, the scale of the device, and the operating parameters of the desulfurization device;

[0021] The production parameters of the desulfurization unit include one or a combination of parameters such as the composition of the raw gas medium, the throughput, the circulation rate, the acid gas load, the temperature, the pressure, the content of solution degradation products and thermally stable salts.

[0022] The design and operating parameters of the reboiler in the desulfurization unit include one or a combination of parameters such as medium inlet and outlet temperature, pressure, design structure, specifications and dimensions, and material.

[0023] Preferably, the environmental conditions for simulation evaluation in S2 include one or more of the following: temperature, pressure, medium composition, and flow rate.

[0024] The simulation evaluation method is an electrochemical corrosion research method, which studies the influence of environmental conditions and current density on corrosion results. The corrosion results include one or more of the following: rate, morphology of corrosion products, and composition of corrosion products.

[0025] Preferably, the on-site corrosion monitoring method in S3 includes online monitoring, which includes ultrasonic detection and / or probe monitoring. The monitoring process is verified using corrosion plates, and monitoring data is acquired periodically. The corrosion status of the desulfurization unit is then analyzed based on the monitoring data.

[0026] Preferably, the object of the flow field numerical simulation in S3 is a reboiler, and the simulation method includes the following steps:

[0027] S3.1: Selection and verification of thermodynamic methods: The calculation method is determined based on the compositional properties of the medium inside the reboiler;

[0028] S3.2: Compare the calculated data with the experimental data to determine the thermodynamic model;

[0029] S3.3: The influence law of temperature on the internal parameters of the reboiler is constructed by the calculation method and thermodynamic model, and the functional formula of the internal parameters of the reboiler is established, wherein the temperature range is 100-200℃.

[0030] Preferably, the internal parameters of the reboiler include one or a combination of multiple parameters selected from liquid density, liquid specific heat capacity, liquid thermal conductivity, liquid viscosity, liquid latent heat of vaporization, liquid surface tension, gas density, gas specific heat capacity, gas pressure, gas thermal conductivity, and gas viscosity.

[0031] Preferably, the formula for the liquid density as a function of temperature is constructed as follows:

[0032] ρ1=-2.06166×10 -8 t 4 +9.83596×10 -6 t 3 -0.003t 2 -0.48341t+1060.80697

[0033] Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃;

[0034] The formula for the specific heat capacity of the liquid as a function of temperature is constructed as follows:

[0035] c1 = 8.25646 × 10 -6 t 2 +5.23139×10 -4t+3.04307

[0036] Among them, the goodness of fit R 2 =0.99992, the unit of temperature t is °C;

[0037] The formula for the function of the liquid's thermal conductivity with temperature is constructed as follows:

[0038] k1 = -1.03941 × 10 -6 t 2 -7.39211×10 -7 t+0.31681

[0039] Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃;

[0040] The formula for the function of liquid viscosity versus temperature is constructed as follows:

[0041] μ1 = 2.35332 × 10 -8 t 2 -9.83395×10 -6 t+0.0012

[0042] Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃;

[0043] The formula for the latent heat of vaporization of the liquid as a function of temperature is constructed as follows:

[0044] L = -0.11562t 2 -23.09614t+51565.3274

[0045] Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃;

[0046] The formula for the function of liquid surface tension versus temperature is constructed as follows:

[0047] σ1=-2.146×10 -8 t 2 -1.42743×10 -4 t+0.056

[0048] Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃;

[0049] The formula for the gas density versus temperature is constructed as follows:

[0050] ρ g =2.10033×10 -5 t 2-0.01381t+4.46427

[0051] Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃;

[0052] The formula for the specific heat capacity of the gas as a function of temperature is constructed as follows:

[0053] c g =1.1754×10 -8 t 4 -7.66578×10 -6 t 3 +0.00187t 2 -0.2021t+10.00898

[0054] Among them, the goodness of fit R 2 =0.98816, the unit of temperature t is °C;

[0055] The functional formula for the gas pressure versus temperature is constructed as follows:

[0056] p g =3.19468×10 -8 t 4 -9.97553×10 -6 t 3 +0.00161t 2 -0.1205t + 3.55263

[0057] Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃;

[0058] The formula for the function of gas thermal conductivity with temperature is constructed as follows:

[0059] k g =6.31203×10 -8 t 2 +5.70598×10 -5 t+0.01463

[0060] Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃;

[0061] The formula for the gas viscosity as a function of temperature is constructed as follows:

[0062] μ g = -1.17069 × 10 -14 t 4 +7.46974×10 -12 t 3 -1.73688×10-9 t 2 +2.07238×10 -7 t+1.56529×10 -6

[0063] Among them, the goodness of fit R 2 =0.99888, the unit of temperature t is ℃.

[0064] Preferably, the inlet and outlet parameters of the reboiler are obtained through modeling and process simulation analysis in S4, and the axial temperature distribution law of the reboiler is obtained. The inlet and outlet parameters include one or a combination of multiple parameters such as flow rate, temperature and pressure. The reboiler is equipped with heat exchange tubes.

[0065] Numerical simulation is performed during the simulation process to obtain one or a combination of data from the following: temperature distribution data, phase distribution data, pressure distribution data, wall shear force distribution data, gas mass fraction distribution data, and vaporization rate distribution data inside the heat exchange tube;

[0066] The optimization process includes optimizing one or more parameters among the reboiler's operating conditions, operating temperature, operating pressure, and liquid level of the medium in the reboiler.

[0067] Preferably, the control parameters include one or a combination of parameters selected from acid gas load, temperature, throughput, and circulation rate.

[0068] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0069] (1) This invention combines indoor simulation and field simulation, and the corrosion assessment takes into account the influence of multiple factors. It can adapt to the complex working conditions of the actual desulfurization process. Furthermore, repeated experiments are conducted to model and optimize the desulfurization device. The evaluation and testing methods finally achieve accurate results.

[0070] (2) The corrosion assessment and control method of the present invention can promptly reflect the monitoring results on site, and the corrosion status and changes in the corrosion status can be promptly fed back to the technicians for timely repair. The present invention can be applied to purification plants and purification plant equipment with different information. Attached Figure Description

[0071] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0072] Figure 1 This is a curve showing the change of liquid density with temperature in an embodiment of the present invention;

[0073] Figure 2 This is a curve showing the change of the specific heat capacity of the volume as a function of temperature in an embodiment of the present invention.

[0074] Figure 3 This is a curve showing the change of the thermal conductivity of a liquid with temperature, fitted according to an embodiment of the present invention.

[0075] Figure 4 This is a curve showing the change in liquid viscosity with temperature, as fitted in an embodiment of the present invention.

[0076] Figure 5 A curve showing the change of latent heat of liquid vaporization with temperature in an embodiment of the present invention;

[0077] Figure 6 This is a curve showing the change of liquid surface tension with temperature in an embodiment of the present invention;

[0078] Figure 7 This is a curve showing the change of gas density with temperature in an embodiment of the present invention;

[0079] Figure 8 This is a curve showing the variation of gas specific heat capacity with temperature in an embodiment of the present invention;

[0080] Figure 9 This is a curve showing the change of gas pressure with temperature in an embodiment of the present invention;

[0081] Figure 10 This is a curve showing the change of gas thermal conductivity with temperature in an embodiment of the present invention;

[0082] Figure 11 This is a curve showing the change of gas viscosity with temperature in an embodiment of the present invention;

[0083] Figure 12 This is a diagram showing the temperature and steam release rate distribution of the reboiler in an embodiment of the present invention.

[0084] Figure 13 This is a cloud map showing the velocity and temperature distribution of the tube bundle.

[0085] Figure 14 Velocity distribution contour maps under different inlet pressure conditions. Detailed Implementation

[0086] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0087] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0088] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0089] This invention provides a method for corrosion assessment and control in a natural gas purification plant, comprising the following steps:

[0090] S1: Obtain Confirmation Information: Determine the information of the desulfurization unit in the purification plant, including: purification plant name, raw gas source, desulfurization solution system, unit scale (including throughput, unit capacity, etc.), and basic design and operating parameters (including desulfurization efficiency, reaction temperature, etc.). This information is mainly used to identify specific unit conditions, facilitating differentiation and comparison between different units. Specifically, purification plant name: used to uniquely identify the unit; raw gas source: understand the composition and source of the raw gas, as different gas compositions will have different corrosive effects on the unit; desulfurization solution system: determine the composition and concentration of the desulfurization solution.

[0091] Equipment production parameters acquisition: The composition of the feed gas medium, throughput, circulation rate, acid gas load, temperature, pressure, content of solution degradation products and thermally stable salts, etc., are key process parameters that may affect corrosion during the production process; specifically, feed gas medium composition: understand the composition of the feed gas, especially the content of harmful gases; throughput: refers to the amount of gas processed per unit time; acid gas load: refers to the load of acidic gases.

[0092] The design and operating parameters of the reboiler include: medium inlet and outlet temperatures, pressures, design structure, specifications, dimensions, and materials.

[0093] Based on the collected data, a corrosion assessment can be performed, including evaluating the likelihood, rate, and possible corrosion mechanisms. This data is then used to design indoor corrosion evaluation tests, as detailed in step S2.

[0094] S2: Simulation Evaluation: This involves indoor corrosion evaluation tests to obtain the corrosion behavior of metallic materials under service conditions. The evaluation environment includes temperature, pressure, media composition, and flow rate. The research method is electrochemical corrosion testing, and the data obtained include current density, corrosion rate, corrosion product morphology, and composition. The metallic material used is the same as that used in key components such as the reboiler tube bundle, tube sheet, and shell to ensure the practical reference value of the test results. The test results provide important information about the corrosion behavior of metals in simulated environments, leading to a better understanding of corrosion conditions in actual industrial equipment and the development of appropriate corrosion monitoring strategies and control measures. Furthermore, indoor tests can be used to evaluate the performance of different anti-corrosion materials and coatings to select the most suitable materials to extend equipment life.

[0095] S3: On-site Corrosion Monitoring: Monitoring points are identified based on simulation evaluation data, including the regeneration tower, reboiler, and inlet / outlet pipelines. Online monitoring (such as ultrasonic testing and probes) is the primary method, supplemented by corrosion testing strips for verification. Corrosion monitoring data is periodically acquired to assess the corrosion status of the regeneration tower and reboiler system.

[0096] In this embodiment of the invention, the internal flow field of the reboiler is numerically simulated to obtain the calculation results for areas prone to corrosion. Specifically, based on the properties of the medium components, calculation methods such as phase equilibrium constant, enthalpy, and transport parameters are selected. The deviations between the calculated data and experimental data of the working medium properties are compared. Typically, properties such as density, viscosity, and saturated vapor pressure are compared to verify the acquisition of the optimal thermodynamic model.

[0097] Calculation of working medium physical property data: Professional software is used to simulate and calculate the density, viscosity, specific heat, heat of vaporization, and saturated vapor pressure of the desulfurization solution components within a set temperature and pressure range, constructing a physical property database that substitutes for the components with temperature as the variable. The temperature range is 100-200℃.

[0098] The functional formula for liquid density versus temperature is constructed as follows:

[0099] ρ1=-2.06166×10 -8 t 4 +9.83596×10 -6 t 3 -0.003t 2 -0.48341t+1060.80697

[0100] ,like Figure 1 As shown, the goodness of fit R 2 ≈1, the unit of temperature t is ℃.

[0101] The formula for the specific heat capacity of a liquid as a function of temperature is constructed as follows:

[0102] c1 = 8.25646 × 10 -6 t 2 +5.23139×10 -4 t+3.04307

[0103] ,like Figure 2 As shown, the goodness of fit R 2 =0.99992, the unit of temperature t is ℃.

[0104] The formula for the thermal conductivity of a liquid as a function of temperature is constructed as follows:

[0105] k1 = -1.03941 × 10 -6 t 2 -7.39211×10 -7 t+0.31681

[0106] ,like Figure 3 As shown, the goodness of fit R 2 ≈1, the unit of temperature t is ℃.

[0107] The formula for the function of liquid viscosity versus temperature is constructed as follows:

[0108] μ1 = 2.35332 × 10 -8 t 2 -9.83395×10 -6 t+0.0012

[0109] ,like Figure 4 As shown, the goodness of fit R 2 ≈1, the unit of temperature t is ℃.

[0110] The formula for the latent heat of vaporization of a liquid as a function of temperature is constructed as follows:

[0111] L = -0.11562t 2 -23.09614t+51565.3274

[0112] ,like Figure 5 As shown, the goodness of fit R 2 ≈1, the unit of temperature t is ℃.

[0113] The formula for the function of liquid surface tension versus temperature is constructed as follows:

[0114] σ1=-2.146×10 -8 t 2 -1.42743×10 -4 t+0.056

[0115] ,like Figure 6As shown, the goodness of fit R 2 ≈1, the unit of temperature t is ℃.

[0116] The formula for the function of gas density versus temperature is constructed as follows:

[0117] ρ g =2.10033×10 -5 t 2 -0.01381t+4.46427

[0118] ,like Figure 7 As shown, the goodness of fit R 2 ≈1, the unit of temperature t is ℃.

[0119] The formula for the specific heat capacity of a gas as a function of temperature is constructed as follows:

[0120] c g =1.1754×10 -8 t 4 -7.66578×10 -6 t 3 +0.00187t 2 -0.2021t+10.00898

[0121] ,like Figure 8 As shown, the goodness of fit R 2 =0.98816, the unit of temperature t is ℃.

[0122] The functional formula for gas pressure versus temperature is constructed as follows:

[0123] p g =3.19468×10 -8 t 4 -9.97553×10 -6 t 3 +0.00161t 2 -0.1205t + 3.55263

[0124] ,like Figure 9 As shown, the goodness of fit R 2 ≈1, the unit of temperature t is ℃.

[0125] The formula for the thermal conductivity of a gas as a function of temperature is constructed as follows:

[0126] k g =6.31203×10 -8 t 2 +5.70598×10 -5 t+0.01463

[0127] ,like Figure 10As shown, the goodness of fit R 2 ≈1, the unit of temperature t is ℃.

[0128] The formula for the function of gas viscosity versus temperature is constructed as follows:

[0129] μ g = -1.17069 × 10 -14 t 4 +7.46974×10 -12 t 3 -1.73688×10 -9 t 2 +2.07238×10 -7 t+1.56529×10 -6

[0130] ,like Figure 11 As shown, the goodness of fit R 2 =0.99888, the unit of temperature t is ℃.

[0131] Specifically, numerical simulation methods are used to simulate the flow field inside the reboiler and obtain calculation results for areas prone to corrosion. Appropriate thermodynamic methods are selected to calculate the properties of the medium, such as phase equilibrium constant, enthalpy, and transport parameters. The consistency between simulated and experimental data needs to be verified to ensure an optimal thermodynamic model is obtained. This allows for the assessment of corrosion in the regeneration tower reboiler system, and the implementation of control measures to ensure the safe and reliable operation of the system, including optimizing operating parameters, material selection, corrosion monitoring, and maintenance. This embodiment of the invention combines experimental evaluation, digital simulation, and on-site monitoring to comprehensively understand the corrosion status of the system.

[0132] It should be noted that:

[0133] Liquid density: Liquid density refers to the mass per unit volume of the desulfurization solution. In this step, it is necessary to calculate the density of the desulfurization solution at different temperatures and pressures to understand its physical properties under different conditions.

[0134] Liquid specific heat capacity: Liquid specific heat capacity refers to the energy required for a desulfurization solution to be heated or cooled. It is based on the temperature change per unit mass, which is convenient for understanding heat transfer and temperature control.

[0135] Thermal conductivity of liquids: The thermal conductivity of liquids describes the ability of a liquid to transfer heat, that is, the rate at which a liquid transfers heat.

[0136] Liquid viscosity: Liquid viscosity describes the viscosity of the desulfurization solution, that is, its fluidity. High viscosity liquids have poor fluidity and have an important impact on the flow process.

[0137] Latent heat of vaporization of liquid: The latent heat of vaporization of liquid refers to the heat required to convert a liquid into a gas, which helps to understand the vaporization process and phase change process of desulfurization solution;

[0138] Liquid surface tension: Liquid surface tension describes the interfacial tension between a liquid and air, which helps to understand the behavior and phenomena of liquids at the contact interface;

[0139] Gas density, specific heat capacity, pressure, thermal conductivity, and viscosity: These parameters are also physical properties of the gas phase, used to describe the behavior of the gas.

[0140] These physical property parameters are calculated using specialized software, based on existing physical property models and data. The selection of the temperature range (100-200℃) is determined according to specific process requirements and applications. Accurate calculation of these parameters is beneficial for thermodynamic modeling and process optimization.

[0141] S4: Modeling and Optimization: This includes obtaining the heat transfer boundary conditions of the reboiler heat exchanger tubes. The reboiler is modeled using specialized software. Based on the inlet and outlet conditions in step S1, reboiler calculations are performed to obtain relevant process parameters, with a focus on obtaining the inlet and outlet pressures and the heat exchanger tube wall temperature distribution. Specifically, the reboiler process is modeled and simulated to obtain key parameters of the medium inlet and outlet, such as flow rate, temperature, and pressure. The obtained axial temperature distribution curve of the reboiler is shown below. Figure 12 The figure illustrates the temperature distribution of the sulfonylamine solution and heating steam as a function of the heat exchanger tube position (position expressed as a percentage of tube length). It also shows the rate of change of the steam flow rate generated at different positions with respect to the heat exchanger tube position. As can be seen from the figure, the steam released from the sulfonylamine solution gradually increases with increasing tube length. The temperature distribution of the sulfonylamine solution can be used as the boundary condition for subsequent fluid dynamics simulations to achieve decoupling and simplification of the heat and mass transfer process between heating steam, tube wall, and sulfonylamine.

[0142] It should be noted that, in the embodiments of the present invention, the following main operating parameters and working medium parameters of the reboiler are used for calculation, as shown in Table 1 and Table 2 respectively:

[0143] Table 1: Main Operating Parameters of Reboiler

[0144]

[0145] Table 2: Parameters of the working medium in the reboiler

[0146]

[0147] Flow field simulation inside heat exchanger tubes: such as Figure 13As shown, numerical simulation software was used to model the process, and mesh generation and optimization were completed. The model was used to numerically simulate the vaporization process of the liquid in the heat exchange tube, and the influence of the vaporization location on the flow field was obtained, including key data such as temperature distribution, phase distribution, pressure distribution, wall shear force distribution, gas mass fraction distribution, and vaporization rate distribution in the heat exchange tube.

[0148] like Figure 14 As shown, the corrosion status and corrosion-risk areas of the reboiler are evaluated and optimized based on the calculation results of S3. This includes optimizing the operating process parameters of the reboiler, such as temperature and operating pressure, and optimizing the liquid level height of the medium in the reboiler. The figure shows that with increasing inlet pressure, the velocity increases significantly, and the location where significant vaporization occurs increases. This is because with increased operating pressure, the unsaturation of the liquid entering the heat exchange tubes increases, the heat and pressure drop required for the fluid to reach saturation increase, and the tube wall needs to provide more heat and increase frictional resistance to the fluid, thus increasing the location where significant vaporization occurs. It should be noted that r represents the axial distance of the tube bundle, where r = 0 at the inlet, and z is the radial distance.

[0149] Specifically, reboiler process modeling involves using specialized software to model the reboiler and perform process simulation. This method can simulate and understand the fluid flow and heat transfer within the reboiler, obtaining key parameters such as flow rate, temperature, and pressure. Simultaneously, obtaining the axial temperature distribution curve of the liquid within the reboiler can serve as crucial for assessing corrosion risk.

[0150] The flow field simulation inside the heat exchange tubes of the reboiler involves establishing a numerical model: using numerical simulation software to model the heat exchange tubes inside the reboiler and completing mesh generation and optimization, which helps to simulate the liquid and gas flow inside the heat exchange tubes; numerical simulation: using the established model to perform numerical simulation of the liquid vaporization process inside the heat exchange tubes, and obtaining relevant data through simulation, such as temperature distribution, phase distribution, pressure distribution, wall shear force, gas mass fraction, vaporization rate, etc., which helps to understand the complex flow field inside the heat exchange tubes.

[0151] Based on the results of the preceding steps, the operating process parameters of the reboiler, such as temperature and operating pressure, can be optimized to reduce corrosion risk and improve system performance. The liquid level in the reboiler can also be adjusted to ensure operation under appropriate conditions, thereby reducing corrosion risk.

[0152] S5: Based on the results of S2 and S3, and the actual production parameters in S1, further optimize the control parameters, especially the acid gas load and circulation rate. Utilizing the actual production parameters and the results of previous steps to further optimize the control parameters helps determine the optimal operating range and improve production efficiency and stability.

[0153] In production applications, by accumulating and calculating a large amount of existing data, the optimal operating ranges for various actual process parameters can be clearly defined, such as the control ranges for acid gas load, temperature, and throughput. This method allows on-site technicians to immediately identify abnormal production conditions and make timely adjustments, and also allows them to monitor the corrosion status of on-site equipment, providing a technical basis for overhaul planning. Furthermore, it avoids discrepancies between laboratory data and actual production conditions. This invention involves engineering and analysis in multiple fields, including numerical simulation, experimental data analysis, and process optimization, ensuring the reliability of the reboiler system and reducing corrosion risks, thereby improving production efficiency and safety.

[0154] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for corrosion assessment and control in a natural gas purification plant, the natural gas purification plant including a desulfurization unit, said desulfurization unit including a reboiler, characterized in that, Includes the following steps: S1: Obtain confirmation information: Confirm corrosion-related data of the purification plant equipment, including one or more of the following: information on the purification plant's desulfurization unit, production parameters of the desulfurization unit, design parameters of the reboiler in the desulfurization unit, and operating parameters; S2: Simulation Evaluation: Based on the corrosion-related data, design an indoor corrosion evaluation test to obtain the corrosion behavior of the desulfurization unit's metallic materials and determine the areas prone to corrosion. S3: On-site corrosion monitoring: Based on the simulation evaluation, select the equipment and pipelines of the desulfurization unit, conduct on-site corrosion monitoring, perform flow field numerical simulation inside the desulfurization unit, and obtain the calculation results of the corrosion-prone areas; S4: Modeling and Optimization: Model and simulate the process of the desulfurization device, and optimize the corrosion-prone parts of the desulfurization device based on the calculation results of S3; The flow field numerical simulation described in S3 is applied to a reboiler, and the simulation method includes the following steps: S3.1: Selection and verification of thermodynamic methods: The calculation method is determined based on the compositional properties of the medium inside the reboiler; S3.2: Compare the calculated data with the experimental data to determine the thermodynamic model; S3.3: The influence law of temperature on the internal parameters of the reboiler is constructed by the calculation method and thermodynamic model, and the functional formula of the internal parameters of the reboiler is established, wherein the temperature range is 100-200℃; The internal parameters of the reboiler include one or a combination of multiple parameters such as liquid density, liquid specific heat capacity, liquid thermal conductivity, liquid viscosity, liquid latent heat of vaporization, liquid surface tension, gas density, gas specific heat capacity, gas pressure, gas thermal conductivity, and gas viscosity. The formula for the function of liquid density versus temperature is constructed as follows: Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃; The formula for the specific heat capacity of the liquid as a function of temperature is constructed as follows: Among them, the goodness of fit R 2 =0.99992, the unit of temperature t is °C; The formula for the function of the liquid's thermal conductivity with temperature is constructed as follows: Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃; The formula for the function of liquid viscosity versus temperature is constructed as follows: Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃; The formula for the latent heat of vaporization of the liquid as a function of temperature is constructed as follows: Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃; The formula for the function of liquid surface tension versus temperature is constructed as follows: Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃; The formula for the gas density versus temperature is constructed as follows: Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃; The formula for the specific heat capacity of the gas as a function of temperature is constructed as follows: Among them, the goodness of fit R 2 =0.98816, the unit of temperature t is °C; The functional formula for the gas pressure versus temperature is constructed as follows: Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃; The formula for the function of gas thermal conductivity with temperature is constructed as follows: Among them, the goodness of fit R 2 ≈1, the unit of temperature t is ℃; The formula for the gas viscosity as a function of temperature is constructed as follows: Among them, the goodness of fit R 2 =0.99888, the unit of temperature t is ℃.

2. The corrosion assessment and control method for a natural gas purification plant according to claim 1, characterized in that, Step S4 is followed by step S5; S5 is: to combine the results of S2 and S3 with the parameters of S1 to optimize the control parameters.

3. The corrosion assessment and control method for a natural gas purification plant according to claim 1, characterized in that, The desulfurization device information mentioned in S1 includes one or a combination of information such as the name of the purification plant, the source of the raw gas for the purification plant, the composition of the desulfurization solution system, the scale of the device, and the operating parameters of the desulfurization device; The production parameters of the desulfurization unit include one or a combination of parameters such as the composition of the raw gas medium, the throughput, the circulation rate, the acid gas load, the temperature, the pressure, the content of solution degradation products and thermally stable salts. The design and operating parameters of the reboiler in the desulfurization unit include one or a combination of parameters such as medium inlet and outlet temperature, pressure, design structure, specifications and dimensions, and material.

4. The corrosion assessment and control method for a natural gas purification plant according to claim 1, characterized in that, The environmental conditions for simulation evaluation described in S2 include one or more of the following: temperature, pressure, medium composition, and flow rate. The simulation evaluation method is an electrochemical corrosion research method, which studies the influence of environmental conditions and current density on corrosion results. The corrosion results include one or more of the following: rate, morphology of corrosion products, and composition of corrosion products.

5. The corrosion assessment and control method for a natural gas purification plant according to claim 1, characterized in that, The on-site corrosion monitoring method in S3 includes online monitoring, which includes ultrasonic detection and / or probe monitoring. The monitoring process is verified using corrosion plates, and monitoring data is acquired periodically. The corrosion status of the desulfurization unit is then analyzed based on the monitoring data.

6. The corrosion assessment and control method for a natural gas purification plant according to claim 1, characterized in that, Modeling and process simulation analysis in S4 are used to obtain the inlet and outlet parameters of the reboiler and the axial temperature distribution law of the reboiler. The inlet and outlet parameters include one or a combination of multiple parameters such as flow rate, temperature and pressure. The reboiler is equipped with heat exchange tubes. Numerical simulation is performed during the simulation process to obtain one or a combination of data from the following: temperature distribution data, phase distribution data, pressure distribution data, wall shear force distribution data, gas mass fraction distribution data, and vaporization rate distribution data inside the heat exchange tube; The optimization process includes optimizing one or more parameters among the reboiler's operating conditions, operating temperature, operating pressure, and liquid level of the medium in the reboiler.

7. The corrosion assessment and control method for a natural gas purification plant according to claim 2, characterized in that, The control parameters include one or a combination of parameters such as acid gas load, temperature, throughput, and circulation rate.

Images