Natural gas purification plant corrosion evaluation and control method

Abstract

The invention discloses a corrosion assessment and control method for a natural gas purification plant, and relates to the field of corrosion control of the natural gas purification plant, the natural gas purification plant comprises a desulfurization device, the desulfurization device comprises a reboiler, and the method comprises the following steps: S1, information confirmation: confirming corrosion related data of equipment of the purification plant, comprising desulfurization device information of a purification plant, production parameters of the desulfurization device, and design parameters and operation parameters of a reboiler in the desulfurization device; s2, carrying out simulation evaluation, and determining a part where corrosion easily occurs; s3, on-site corrosion monitoring; and S4, modeling and optimizing. Indoor simulation and field simulation are combined, the influence of various factors is considered in corrosion evaluation, the method can adapt to the actual complex working condition of the desulfurization process, modeling and optimization of the desulfurization device are repeatedly carried out through repeated experiments, and the evaluation and test method finally achieves the accurate effect.

Description

Technical Field

[0001] The invention relates to the field of corrosion control in a natural gas purification plant, and in particular to a corrosion assessment and control method for a natural gas purification plant. Background Art

[0002] At present, the development and production of sour natural gas worldwide relies on various desulfurization and decarbonization process technologies, and the most widely used is the amine desulfurization process, which mainly includes four parts: absorption, flash evaporation, heat exchange and regeneration.

[0003] As a high-quality clean energy, the development and utilization of natural gas has attracted widespread attention from all over the world. However, natural gas in Sichuan and Chongqing contains sulfur and needs to be treated before it can be used. The main desulfurization and decarbonization methods at home and abroad are wet absorption, dry desulfurization, wet oxidation, biological desulfurization, etc. Among them, wet absorption is more widely used. Its main process flow includes absorption, flash evaporation, heat exchange and regeneration.

[0004] According to public data at home and abroad, ensuring the long-term stable operation of natural gas purification plants is one of the important prerequisites for natural gas production, and corrosion control of purification plants has become an important factor restricting long-term stable operation. In the Sichuan and Chongqing regions, many sulfur-containing natural gas purification plants have repeatedly experienced equipment and pipeline corrosion failure during production and operation, seriously affecting the smooth operation of the purification plants.

[0005] At present, the corrosion control of desulfurization equipment mainly depends on the selection of metal materials themselves, daily process parameter control and corrosion monitoring. Material selection refers to solving the failure problem of certain severely corroded parts through the application of corrosion-resistant materials. The control of daily process parameters refers to optimizing production process parameters such as processing volume, circulation volume and acid gas load in the hope of achieving the purpose of controlling corrosion. Corrosion monitoring uses hanging plates and some online monitoring technologies to track and monitor the corrosion status of the device to provide a decision-making basis for corrosion control. The comprehensive application of the three aspects can theoretically effectively control corrosion and ensure the long-term problem of the device.

[0006] Chinese patent CN103870670A discloses a method and device for predicting the degree of corrosion of oil pipes, Chinese patent CN105069486A discloses a method for predicting corrosion of petrochemical equipment based on extreme learning machines, Chinese patent CN109816133A discloses a method for predicting corrosion in pipelines, Chinese patent CN108119761A discloses a method for predicting the degree of corrosion of natural gas pipelines under gas-liquid two-phase flow, and Chinese patent CN111177947A discloses a method for establishing a CO2 corrosion prediction chart considering multiple factors. These technologies are mainly aimed at a single object, and cannot predict the complex desulfurization system of a purification plant. Because the desulfurization system of the purification plant involves dozens of equipment and countless pipelines, they affect each other, and the abnormality of one equipment will affect other equipment and even the entire system. Therefore, at the production level, an overall and comprehensive consideration must be made.

[0007] Therefore, there are still many problems in the existing technology at the technical level. Although there are a lot of studies on the main control factors of desulfurization device corrosion, most of the studies are based on indoor simulation evaluation, which is difficult to reflect the complex working conditions of the desulfurization process. In just one regeneration tower equipment, there is a complex distribution of key parameters such as medium, temperature, pressure and flow rate, which is difficult to simulate under laboratory conditions, which often leads to the dilemma that laboratory evaluation data is difficult to match with field measured data.

[0008] Even without considering the difference between laboratory and field conditions, we believe through extensive research that there are many key parameters that affect the corrosion behavior of desulfurization equipment, including at least temperature, pressure, circulation volume, acid gas load, carbon-sulfur ratio, desulfurization solution medium, processing volume, etc. It is difficult to determine the main factors affecting corrosion through laboratory theoretical research, and it is impossible to accurately guide the regulation of field process parameters.

[0009] A large amount of on-site monitoring data cannot be effectively used. Usually, the monitoring results of one cycle can only reflect the corrosion status of the production equipment in this cycle. In addition, the change of corrosion status cannot allow technicians to find the cause from the production management aspect in time.

[0010] Since the gas quality of raw gas in each region is different, the design of many newly built purification plants does not have relatively mature specifications and experience references, and lacks corresponding methods for guidance. Often, renovations are not carried out until problems with corrosion occur in the later stage, which will consume a lot of manpower and material resources.

[0011] Therefore, the following application is made. Summary of the invention

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

[0013] The present invention is achieved through the following technical solutions:

[0014] The present application proposes a corrosion assessment and control method for a natural gas purification plant, wherein the natural gas purification plant includes a desulfurization device, wherein the desulfurization device includes a reboiler, and the method includes the following steps:

[0015] S1: Obtain confirmation information: confirm the corrosion-related data of the purification plant equipment, including one or more combinations of information of the purification plant desulfurization device information, production parameters of the desulfurization device, design parameters of the reboiler in the desulfurization device, and operation parameters;

[0016] S2: Simulation evaluation: Based on the corrosion-related data, an indoor corrosion evaluation test is designed to obtain the corrosion behavior of the metal materials of the desulfurization device and determine the parts prone to corrosion;

[0017] S3: On-site corrosion monitoring: Select the equipment and pipelines of the desulfurization device according to the simulation evaluation, conduct on-site corrosion monitoring, perform numerical simulation of the flow field inside the desulfurization device, and obtain calculation results of the corrosion prone parts;

[0018] S4: Modeling and optimization: Modeling and process simulation of the desulfurization device are performed, and the corrosion-prone parts of the desulfurization device are optimized in combination with the calculation results of S3.

[0019] Preferably, step S4 further includes step S5, wherein S5 is: combining the results of S2 and S3 and comparing them 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 selected from the group consisting of the name of the purification plant, the source of the raw gas of 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 device include one or a combination of multiple parameters selected from the group consisting of raw gas medium composition, processing volume, circulation volume, acid gas load, temperature, pressure, solution degradation products and the content of thermally stable salts;

[0022] The design parameters and operation parameters of the reboiler in the desulfurization device include one or a combination of multiple parameters including medium inlet and outlet temperatures, pressure, design structure, specification size and material.

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

[0024] The simulation evaluation research 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 rate, corrosion product morphology and corrosion product composition.

[0025] Preferably, the method for on-site corrosion monitoring in S3 includes an online monitoring method, which includes ultrasonic detection and / or probe monitoring. The monitoring process is verified by corrosion coupons, and after periodically acquiring monitoring data, the corrosion condition of the desulfurization device is analyzed through the monitoring data.

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

[0027] S3.1: Selection and verification of thermodynamic methods: Determine the calculation method based on the properties of the medium components inside the reboiler;

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

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

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

[0031] Preferably, the function formula of liquid density and 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] , where the degree of fit R 2 ≈1, the unit of temperature t is °C;

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

[0036] c1=8.25646×10 -6 t 2 +5.23139×10-4 t+3.04307

[0037] , where the degree of fit R 2 =0.99992, the unit of temperature t is ℃;

[0038] The function formula of the liquid thermal conductivity and temperature is constructed as follows:

[0039] k1=-1.03941×10 -6 t 2 -7.39211×10 -7 t+0.31681

[0040] , where the degree of fit R 2 ≈1, the unit of temperature t is °C;

[0041] The function formula of liquid viscosity and temperature is constructed as follows:

[0042] μ1=2.35332×10 -8 t 2 -9.83395×10 -6 t+0.0012

[0043] , where the degree of fit R 2 ≈1, the unit of temperature t is °C;

[0044] The functional formula of the liquid vaporization latent heat and temperature is constructed as follows:

[0045] L=-0.11562t 2 -23.09614t+51565.3274

[0046] , where the degree of fit R 2 ≈1, the unit of temperature t is °C;

[0047] The functional formula of the liquid surface tension and temperature is constructed as follows:

[0048] σ1=-2.146×10 -8 t 2 -1.42743×10 -4 t+0.056

[0049] Among them, the degree of fit R 2 ≈1, the unit of temperature t is °C;

[0050] The function formula of gas density and temperature is constructed as follows:

[0051] ρ g =2.10033×10 -5 t 2-0.01381t+4.46427

[0052] , where the degree of fit R 2 ≈1, the unit of temperature t is °C;

[0053] The function formula of the gas specific heat capacity and temperature is constructed as follows:

[0054] c g =1.1754×10 -8 t 4 -7.66578×10 -6 t 3 +0.00187t 2 -0.2021t+10.00898

[0055] , where the degree of fit R 2 =0.98816, the unit of temperature t is ℃;

[0056] The function formula of gas pressure and temperature is constructed as follows:

[0057] p g =3.19468×10 -8 t 4 -9.97553×10 -6 t 3 +0.00161t 2 -0.1205t+3.55263

[0058] , where the degree of fit R 2 ≈1, the unit of temperature t is °C;

[0059] The function formula of gas thermal conductivity and temperature is constructed as follows:

[0060] k g =6.31203×10 -8 t 2 +5.70598×10 -5 t+0.01463

[0061] , where the degree of fit R 2 ≈1, the unit of temperature t is °C;

[0062] The function formula of gas viscosity and temperature is constructed as follows:

[0063] 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

[0064] , where the degree of fit R 2 =0.99888, the unit of temperature t is ℃.

[0065] Preferably, in S4, the inlet and outlet parameters of the reboiler are obtained by modeling and process simulation analysis, and the axial temperature distribution law of the reboiler is obtained, wherein the inlet and outlet parameters include one parameter or a combination of multiple parameters of flow rate, temperature and pressure, and a heat exchange tube is arranged in the reboiler;

[0066] During the simulation process, numerical simulation is performed to obtain one or a combination of multiple data of temperature distribution data, phase distribution data, pressure distribution data, wall shear force distribution data, gas mass fraction distribution data and gasification rate distribution data in the heat exchange tube;

[0067] The optimization process includes optimizing one or more parameters of the reboiler operation process conditions, the reboiler operating temperature, the reboiler operating pressure and the liquid level height of the medium in the reboiler.

[0068] Preferably, the control parameters include one or a combination of multiple parameters selected from the group consisting of acid gas load, temperature, processing volume and circulation volume.

[0069] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0070] (1) The present invention combines indoor simulation with field simulation. The corrosion assessment takes into account the influence of multiple factors and can adapt to the complex working conditions of the desulfurization process. Repeated experiments are performed to model and optimize the desulfurization device. The evaluation and testing methods finally achieve accurate results.

[0071] (2) The corrosion assessment and control method of the present invention can timely reflect the on-site monitoring results. The corrosion status and changes in the corrosion status can be fed back to the technical staff in a timely manner for timely repair. The present invention can be applied to purification plants and purification plant equipment with different information. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0073] Figure 1 This is a curve diagram showing the variation of liquid density with temperature according to an embodiment of the present invention;

[0074] Figure 2 This is a curve diagram showing the variation of specific heat capacity of a fitted body with temperature according to an embodiment of the present invention;

[0075] Figure 3 A curve diagram showing the variation of the thermal conductivity of liquid with temperature according to an embodiment of the present invention;

[0076] Figure 4 This is a curve diagram showing the variation of liquid viscosity with temperature according to an embodiment of the present invention;

[0077] Figure 5 A curve diagram showing the variation of the latent heat of vaporization of liquid with temperature according to an embodiment of the present invention;

[0078] Figure 6 This is a curve diagram showing the variation of liquid surface tension with temperature according to an embodiment of the present invention;

[0079] Figure 7 This is a curve diagram of the change of gas density with temperature fitted in an embodiment of the present invention;

[0080] Figure 8 This is a curve diagram showing the variation of specific heat capacity of a gas with temperature according to an embodiment of the present invention;

[0081] Fig. 9 This is a curve diagram of the change of gas pressure with temperature according to the embodiment of the present invention;

[0082] Fig.10 This is a curve diagram showing the variation of gas thermal conductivity with temperature according to an embodiment of the present invention;

[0083] Fig.11 This is a curve diagram of the change of gas viscosity with temperature according to the embodiment of the present invention;

[0084] Fig.12 The reboiler temperature and steam release rate distribution diagram of the embodiment of the present invention;

[0085] Fig.13 It is the cloud diagram of tube bundle velocity and temperature distribution;

[0086] Fig.14 Velocity distribution cloud diagram under different inlet pressure conditions. DETAILED DESCRIPTION

[0087] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0088] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0089] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0090] The embodiment of the present invention provides a method for corrosion assessment and control of a natural gas purification plant, comprising the following steps:

[0091] S1: Obtain confirmation information: determine the information of the desulfurization device in the purification plant, including: the name of the purification plant, the source of raw gas, the desulfurization solution system, the scale of the device (including the processing volume, the capacity of the device, etc.), and the basic parameters of the design and operation (including desulfurization efficiency, reaction temperature, etc.). This information is mainly used to identify the specific device conditions, so as to facilitate the distinction and comparison between different devices; specifically, the name of the purification plant: used to uniquely identify the device; the source of raw gas: understand the composition and source of the raw gas, because gases with different compositions will have different corrosive effects on the device; the desulfurization solution system, determine the composition and concentration of the desulfurization solution.

[0092] Acquisition of device production parameters: raw gas medium composition, processing volume, circulation volume, acid gas load, temperature, pressure, solution degradation products and thermal stability salt content as key process parameters that may affect corrosion in the production process; specifically, raw gas medium composition: understand the composition of the raw gas, especially the content of harmful gases; processing volume: refers to the amount of gas processed per unit time; acid gas load: refers to the load size of the acid gas.

[0093] The design parameters and operating parameters of the reboiler include: medium inlet and outlet temperature, pressure, design structure, specifications and dimensions, material, etc.

[0094] Based on the collected data, corrosion assessment can be performed, including assessment of the possibility, rate and possible corrosion mechanism of corrosion, and the design of indoor corrosion evaluation test can be carried out through these data, as shown in step S2.

[0095] S2: Simulation evaluation: The corrosion behavior of metal materials under service conditions is obtained through indoor corrosion evaluation tests. The test evaluation environment includes: temperature, pressure, medium composition, flow rate, and the research method is electrochemical corrosion test. The data results obtained include: current density, corrosion rate, corrosion product morphology and composition, etc. The metal material is the same material as the key parts such as the reboiler tube bundle, tube sheet, and shell to ensure that the test results have practical reference value. Through the test results, important information about the corrosion behavior of metals in simulated environments can be obtained, and the corrosion situation in actual industrial equipment can be better understood, and appropriate corrosion monitoring strategies and control measures can be formulated. At the same time, indoor tests can also be used to evaluate the performance of different anti-corrosion materials and coatings to select the most suitable materials to extend the life of the equipment.

[0096] S3: On-site corrosion monitoring: Confirm the monitoring points under the guidance of the simulation evaluation results data, and select the regeneration tower, reboiler, import and export pipelines, etc. The monitoring method is mainly online monitoring (such as ultrasound, probe, etc.), which can assist in verification by corrosion coupons. Periodically obtain corrosion monitoring data to evaluate the corrosion status of the regeneration tower reboiler system.

[0097] In the embodiment of the present invention, the flow field inside the reboiler is numerically simulated to obtain the calculation results of the corrosion prone parts. Specifically, according to the properties of the medium components, the calculation methods such as phase equilibrium constant, thermal enthalpy, and transport parameters are selected, and the deviation between the calculated data of the working medium properties and the experimental data is compared. Usually, the physical properties such as density, viscosity, and saturated vapor pressure can be compared to verify the optimal thermodynamic model.

[0098] Calculation of working medium physical property data: Professional software is used to simulate and calculate the density, viscosity, specific heat, heat of vaporization, saturated vapor pressure and other related physical property parameters of the desulfurization solution components within the set temperature and pressure range, and a physical property database of the replacement components with temperature as the variable is constructed. The temperature range is 100-200℃.

[0099] Among them, the function formula of liquid density and temperature is constructed as follows:

[0100] ρ1=-2.06166×10 -8 t 4 +9.83596×10 -6 t 3 -0.003t 2 -0.48341t+1060.80697

[0101] ,like Figure 1 As shown, the fitting degree R 2 ≈1, the unit of temperature t is ℃.

[0102] The function formula of liquid specific heat capacity and temperature is constructed as follows:

[0103] c1=8.25646×10 -6 t 2 +5.23139×10 -4 t+3.04307

[0104] ,like Figure 2 As shown, the fitting degree R 2 =0.99992, the unit of temperature t is ℃.

[0105] The function formula of liquid thermal conductivity and temperature is constructed as follows:

[0106] k1=-1.03941×10 -6 t 2 -7.39211×10 -7 t+0.31681

[0107] ,like Figure 3 As shown, the fitting degree R 2 ≈1, the unit of temperature t is ℃.

[0108] The function formula of liquid viscosity and temperature is constructed as follows:

[0109] μ1=2.35332×10 -8 t 2 -9.83395×10 -6 t+0.0012

[0110] ,like Figure 4 As shown, the fitting degree R 2 ≈1, the unit of temperature t is ℃.

[0111] The function formula of liquid vaporization latent heat and temperature is constructed as follows:

[0112] L=-0.11562t 2 -23.09614t+51565.3274

[0113] ,like Figure 5 As shown, the fitting degree R 2 ≈1, the unit of temperature t is ℃.

[0114] The function formula of liquid surface tension and temperature is constructed as follows:

[0115] σ1=-2.146×10 -8 t 2 -1.42743×10 -4 t+0.056

[0116] ,like Figure 6As shown, the fitting degree R 2 ≈1, the unit of temperature t is ℃.

[0117] The function formula of gas density and temperature is constructed as follows:

[0118] ρ g =2.10033×10 -5 t 2 -0.01381t+4.46427

[0119] ,like Figure 7 As shown, the fitting degree R 2 ≈1, the unit of temperature t is ℃.

[0120] The function formula of gas specific heat capacity and temperature is constructed as follows:

[0121] c g =1.1754×10 -8 t 4 -7.66578×10 -6 t 3 +0.00187t 2 -0.2021t+10.00898

[0122] ,like Figure 8 As shown, the fitting degree R 2 =0.98816, the unit of temperature t is ℃.

[0123] The function formula of gas pressure and temperature is constructed as follows:

[0124] p g =3.19468×10 -8 t 4 -9.97553×10 -6 t 3 +0.00161t 2 -0.1205t+3.55263

[0125] ,like Fig. 9 As shown, the fitting degree R 2 ≈1, the unit of temperature t is ℃.

[0126] The function formula of gas thermal conductivity and temperature is constructed as follows:

[0127] k g =6.31203×10 -8 t 2 +5.70598×10 -5 t+0.01463

[0128] ,like Fig.10As shown, the degree of fit R 2 ≈1, the unit of temperature t is ℃.

[0129] The function formula of gas viscosity and temperature is constructed as follows:

[0130] 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

[0131] ,like Fig.11 As shown, the degree of fit R 2 =0.99888, the unit of temperature t is ℃.

[0132] Specifically, a numerical simulation method is used to simulate the flow field inside the reboiler, and the calculation results of the corrosion-prone parts are obtained. Select a suitable thermodynamic method to calculate the properties of the medium, such as phase equilibrium constants, thermal enthalpy, transport parameters, etc. It is necessary to verify the consistency between the simulation data and the experimental data to ensure that the optimal thermodynamic model is obtained. In this way, the corrosion of the regeneration tower reboiler system can be evaluated, and control measures can be taken to ensure the safe and reliable operation of the system, including optimizing operating parameters, material selection, corrosion monitoring and maintenance, etc. The embodiment of the present invention combines experimental evaluation, digital simulation and on-site monitoring to fully understand the corrosion condition of the system.

[0133] It should be noted that:

[0134] 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;

[0135] Liquid specific heat capacity: Liquid specific heat capacity refers to the energy required to heat or cool the desulfurization solution, based on the temperature change per unit of mass, which facilitates the understanding of heat energy transfer and temperature control;

[0136] Liquid thermal conductivity: Liquid thermal conductivity describes the ability of a liquid to transfer heat, that is, how fast a liquid transfers heat;

[0137] 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;

[0138] Liquid vaporization latent heat: Liquid vaporization latent heat refers to the heat required to convert liquid into gas, which is convenient for understanding the vaporization process and phase change process of desulfurization solution;

[0139] Liquid surface tension: Liquid surface tension describes the interfacial tension between liquid and air, which facilitates understanding of the behavior and phenomena of liquid at the contact interface;

[0140] Gas density, gas specific heat capacity, gas pressure, gas thermal conductivity and gas viscosity: Again, these parameters are physical properties specific to the gas phase and are used to describe the behavior of the gas.

[0141] The calculation of these physical parameters is carried out by professional software based on existing physical property models and data. The choice of temperature range (100-200℃) is determined according to specific process requirements and applications. The accurate calculation of these parameters is conducive to thermodynamic model and process optimization.

[0142] S4: Modeling and optimization: including obtaining the heat transfer boundary conditions of the reboiler heat exchange tube, using professional software to model the reboiler, and carrying out reboiler calculations according to the inlet and outlet conditions in step S1 to obtain the corresponding process parameters, focusing on obtaining the inlet and outlet pressures and the temperature distribution of the heat exchange tube wall. Among them, the reboiler process is modeled and simulated to obtain the key parameters of the medium inlet and outlet, such as flow rate, temperature, pressure, etc. The obtained reboiler axial temperature distribution curve is as follows: Fig.12 As shown in the figure, the temperature distribution of sulfone amine solution and heating steam changes with the position of the heat exchange tube (the position is converted into the percentage of the tube length). At the same time, the rate of change of the steam flow rate generated by vaporization at different positions with the position of the heat exchange tube is given. It can be seen from the figure that the steam released by the sulfone amine solution gradually increases with the increase of the tube length. The temperature distribution of the sulfone amine solution can be used as the boundary condition of the subsequent fluid mechanics simulation to achieve the decoupling and simplification of the heating steam-tube wall-sulfone amine heat and mass transfer process.

[0143] It should be noted that, in the embodiment of the present invention, the following main operating parameters of the reboiler and the working medium parameters of the reboiler are used for calculation, as shown in Table 1 and Table 2 respectively:

[0144] Table 1: Main operating parameters of reboiler

[0145]

[0146] Table 2: Reboiler working medium parameters

[0147]

[0148] Simulation of flow field in heat exchange tubes: Fig.13As shown, numerical simulation software is used to build the model, complete mesh division and optimization; the model is used to numerically simulate the vaporization process of the liquid in the heat exchange tube, and the influence of the vaporization position on the flow field is 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.

[0149] like Fig.14 As shown, the corrosion condition and corrosion risk areas of the reboiler are evaluated and optimized in combination with the calculation results of S3, including optimizing the operating process parameters, temperature and operating pressure of the reboiler and optimizing the liquid level of the medium in the reboiler. As can be seen from the figure, with the increase of the inlet pressure, the velocity increases significantly, and the position where the fluid vaporizes significantly increases. This is because the operating pressure increases, the unsaturation of the liquid entering the heat exchange tube increases, the heat and pressure drop required for the fluid to reach a saturated state increase, and the tube wall needs to provide more heat and friction resistance to the fluid, so the position where significant vaporization occurs increases. It should be noted that r represents the distance in the axial direction of the tube bundle, where r=0 at the inlet, and z is the radial distance.

[0150] Specifically, reboiler process modeling: Use professional software to model the reboiler and perform process simulation. This method can simulate and understand the fluid flow and heat transfer in the reboiler, and obtain key parameters such as flow, temperature, pressure, etc. At the same time, obtaining the axial temperature distribution curve of the liquid in the reboiler can be used as the key to assessing corrosion risks.

[0151] Simulation of the flow field in the heat exchange tubes in the reboiler, that is, establishing a numerical model: using numerical simulation software to model the heat exchange tubes in the reboiler, and complete meshing and optimization, which helps to simulate the flow of liquid and gas in the heat exchange tubes; numerical simulation: using the established model to numerically simulate the liquid vaporization process in the heat exchange tubes, and obtain relevant data through simulation, such as temperature distribution, phase distribution, pressure distribution, wall shear force, gas mass fraction, vaporization rate, etc., which help to understand the complex flow field in the heat exchange tubes.

[0152] Based on the results of the previous steps, the reboiler operating process parameters, such as temperature and operating pressure, can be optimized to reduce the risk of corrosion and improve system performance, and the liquid level in the reboiler can be optimized to ensure operation under appropriate conditions, thereby reducing the risk of corrosion.

[0153] 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, circulation volume, etc. Using the actual production parameters and the results of the previous steps, further optimize the control parameters, which helps to determine the optimal operating range and improve the efficiency and stability of production.

[0154] In the production application process, through the accumulation and calculation of a large amount of existing data, the optimal operating range of various actual operating process parameters can be clarified, such as the control range of acid gas load, temperature, and processing volume. Through this method, on-site technicians can immediately identify abnormal production conditions and make timely adjustments, and can understand the corrosion conditions of on-site equipment, providing a technical basis for the formulation of overhaul plans. In addition, it avoids inconsistencies between laboratory data and actual production. The embodiments of the present invention involve engineering and analysis in multiple fields, including numerical simulation, experimental data analysis, and process optimization, to ensure the reliability of the reboiler system and reduce the risk of corrosion, thereby improving production efficiency and safety.

[0155] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A method for corrosion assessment and control of a natural gas purification plant, the natural gas purification plant comprising a desulfurization device, the desulfurization device comprising a reboiler, characterized in that: The following steps are involved: S1: Obtain confirmation information: confirm the corrosion-related data of the purification plant equipment, including one or more combinations of information of the purification plant desulfurization device information, production parameters of the desulfurization device, design parameters of the reboiler in the desulfurization device, and operation parameters; S2: Simulation evaluation: Based on the corrosion-related data, an indoor corrosion evaluation test is designed to obtain the corrosion behavior of the metal materials of the desulfurization device and determine the parts prone to corrosion; S3: On-site corrosion monitoring: Select the equipment and pipelines of the desulfurization device according to the simulation evaluation, conduct on-site corrosion monitoring, perform numerical simulation of the flow field inside the desulfurization device, and obtain calculation results of the corrosion prone parts; S4: Modeling and optimization: Modeling and process simulation of the desulfurization device are performed, and the corrosion-prone parts of the desulfurization device are optimized in combination with the calculation results of S3.

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

3. A natural gas purification plant corrosion assessment and control method according to claim 1, characterized in that: The desulfurization device information in S1 includes one or a combination of the following information: the name of the purification plant, the source of the raw gas of 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 device include one or a combination of multiple parameters selected from the group consisting of raw gas medium composition, processing volume, circulation volume, acid gas load, temperature, pressure, solution degradation products and the content of thermally stable salts; The design parameters and operation parameters of the reboiler in the desulfurization device include one or a combination of multiple parameters including medium inlet and outlet temperatures, pressure, design structure, specification size and material.

4. A natural gas purification plant corrosion assessment and control method according to claim 1, characterized in that: The environmental conditions for simulation evaluation in S2 include one or more of temperature, pressure, medium composition and flow rate; The simulation evaluation research 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 rate, corrosion product morphology and corrosion product composition.

5. A natural gas purification plant corrosion assessment and control method according to claim 1, characterized in that: The method for on-site corrosion monitoring in S3 includes an online monitoring method, which includes ultrasonic detection and / or probe monitoring. The monitoring process is verified by using corrosion coupons, and after periodically acquiring monitoring data, the corrosion condition of the desulfurization device is analyzed through the monitoring data.

6. A method for corrosion assessment and control of a natural gas purification plant according to claim 1, characterized in that: The object of the flow field numerical simulation in S3 is a reboiler, and the simulation method includes the following steps: S3.1: Selection and verification of thermodynamic methods: Determine the calculation method based on the properties of the medium components inside the reboiler; S3.2: Compare the deviations between the calculated data and the experimental data to determine the thermodynamic model; S3.3: The influence of temperature on the internal parameters of the reboiler is constructed by the calculation method and the thermodynamic model, and a function formula of the internal parameters of the reboiler is established, wherein the temperature range is 100-200°C.

7. A natural gas purification plant corrosion assessment and control method according to claim 6, characterized in that: The internal parameters of the reboiler include one or a combination of multiple parameters of liquid density, liquid specific heat capacity, liquid thermal conductivity, liquid viscosity, liquid vaporization latent heat, liquid surface tension, gas density, gas specific heat capacity, gas pressure, gas thermal conductivity and gas viscosity.

8. A natural gas purification plant corrosion assessment and control method according to claim 7, characterized in that: The function formula of liquid density and temperature is constructed as follows: ρ1=-2.06166×10 -8 t 4 +9.83596×10 -6 t 3 -0.003t 2 -0.48341t+1060.80697, Among them, the degree of fit R 2 ≈1, the unit of temperature t is °C; The function formula of the liquid specific heat capacity and temperature is constructed as follows: c1=8.25646×10 -6 t 2 +5.23139×10 -4 t+3.04307, Among them, the degree of fit R 2 =0.99992, the unit of temperature t is ℃; The function formula of the liquid thermal conductivity and temperature is constructed as follows: k1=-1.03941×10 -6 t 2 -7.39211×10 -7 t+0.31681, Among them, the degree of fit R 2 ≈1, the unit of temperature t is °C; The function formula of liquid viscosity and temperature is constructed as follows: μ1=2.35332×10 -8 t 2 -9.83395×10 -6 t+0.0012, Among them, the degree of fit R 2 ≈1, the unit of temperature t is °C; The functional formula of the liquid vaporization latent heat and temperature is constructed as follows: L=-0.11562t 2 -23.09614t+51565.3274, Among them, the degree of fit R 2 ≈1, the unit of temperature t is °C; The functional formula of the liquid surface tension and temperature is constructed as follows: σ1=-2.146×10 -8 t 2 -1.42743×10 -4 t+0.056 Among them, the degree of fit R 2 ≈1, the unit of temperature t is °C; The function formula of gas density and temperature is constructed as follows: r g =2.10033×10 -5 t 2 -0.O1381t+4.46427, Among them, the degree of fit R 2 ≈1, the unit of temperature t is °C; The function formula of the gas specific heat capacity and temperature is constructed as follows: c g =1.1754×10 -8 t 4 -7.66578×10 -6 t 3 +0.00187t 2 -0.2021t+10.00898, Among them, the degree of fit R 2 =0.98816, the unit of temperature t is ℃; The function formula of gas pressure and temperature is constructed as follows: p g =3.19468×10 -8 t 4 -9.97553×10 -6 t 3 +0.00161t 2 -0.1205t+3.55263, Among them, the degree of fit R 2 ≈1, the unit of temperature t is °C; The function formula of gas thermal conductivity and temperature is constructed as follows: k g =6.31203×10 -8 t 2 +5.70598×10 -5 t+0.01463, Among them, the degree of fit R 2 ≈1, the unit of temperature t is °C; The function formula of gas viscosity and temperature is constructed as follows: 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 , Among them, the degree of fit R 2 =0.99888, the unit of temperature t is ℃.

9. A natural gas purification plant corrosion assessment and control method according to claim 1, characterized in that: In S4, modeling and process simulation analysis are performed to obtain inlet and outlet parameters of the reboiler, and the axial temperature distribution law of the reboiler is obtained, wherein the inlet and outlet parameters include one parameter or a combination of multiple parameters of flow rate, temperature and pressure, and a heat exchange tube is arranged in the reboiler; During the simulation process, numerical simulation is performed to obtain one or a combination of multiple data of temperature distribution data, phase distribution data, pressure distribution data, wall shear force distribution data, gas mass fraction distribution data and gasification rate distribution data in the heat exchange tube; The optimization process includes optimizing one or more parameters of the reboiler operation process conditions, the reboiler operating temperature, the reboiler operating pressure and the liquid level height of the medium in the reboiler.

10. A natural gas purification plant corrosion assessment and control method according to claim 2, characterized in that: The control parameters include one parameter or a combination of multiple parameters among acid gas load, temperature, processing volume and circulation volume.

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