Soft Sensing Method for Solubility of Hydrogen in Lubricating Oil

Abstract

The present invention discloses a soft measurement method for the solubility of hydrogen in lubricating oil. The soft measurement method comprises the following steps: collecting lubricating oil distillation range data for oil product characterization, generating virtual components of lubricating oil, setting two auxiliary variables of temperature and pressure, and completing the simulation of the lubricating oil feed stream and the hydrogen stream. Then, a mixer is modeled, sensitivity analysis is carried out with the mass flow rate of hydrogen as the operating variable, and according to the dissolved amount when hydrogen reaches saturation in the lubricating oil, the solubility of hydrogen is calculated. This method can quickly measure the solubility of hydrogen in lubricating oil, can guide the device operator to understand the mixing effect of the hydrogen mixer in the device, and is suitable for solving the technical problem that it is difficult to measure the solubility of hydrogen in lubricating oil in the petrochemical industry.

Description

Technical Field

[0001] The present invention belongs to the cross - field of petroleum refining and chemical process simulation, and relates to a soft - sensing method for the solubility of hydrogen in lubricating oil during the liquid - phase hydrogenation process of lubricating oil. Background Technique

[0002] Polyalphaolefin (PAO) synthetic oil is currently the synthetic lubricating oil base oil with the best performance, having a high viscosity index, low volatility, low fluidity, good shear performance, and excellent high - temperature oxidation resistance, and has broad application prospects. The liquid - phase hydrogenation technology of PAO synthetic lubricating oil base oil is a technology developed based on the research in fields such as kerosene, diesel, and wax oil. In this process, the liquid - phase PAO synthetic lubricating oil base oil saturated with hydrogen is introduced into the reactor, and the hydrogen dissolved in the liquid oil participates in the hydrogenation reaction. This process will play an important role in energy conservation, consumption reduction, and high - quality development of the lubricating oil hydrogenation unit.

[0003] The static hydrogen - mixing device is an important equipment in the PAO lubricating oil liquid - phase hydrogenation unit, which is the place where hydrogen and PAO synthetic lubricating oil are mixed and can effectively improve the gas - liquid mass transfer efficiency. The solubility of hydrogen in the hydrogen - mixing device is a key inspection index in the lubricating oil liquid - phase hydrogenation unit. The amount of hydrogen dissolved in the lubricating oil directly reflects the hydrogen - dissolving effect of the hydrogen - mixing device in the liquid - phase hydrogenation unit. At present, for the measurement of the solubility of hydrogen in lubricating oil, most still rely on the artificial analysis values in the laboratory. Laboratory analysis requires a high - temperature and high - pressure system environment. Each sample measurement needs to go through steps such as heating and pressurizing, heat - preservation and pressure - preservation, and cooling and depressurizing, and the measurement cycle is relatively long. There are temperature losses and pressure changes during the liquid - phase sampling operation, which will also affect the measurement results.

[0004] To solve the above problems, multiple software are used to establish models for soft - sensing, including Matlab, AspenHysys, Aspen Plus, etc., to calculate and estimate the value of the solubility of hydrogen in PAO synthetic lubricating oil. However, no matter which software is selected, in most of the current soft - sensing methods for the solubility of hydrogen in PAO synthetic lubricating oil, there are the following problems: that is, the establishment of the model is to perform flash calculation on the mixed materials in the flash module. However, for the PAO synthetic lubricating oil with lighter components, flash calculation is likely to flash out the light components, resulting in the distortion of the model calculation results or complex calculations.

[0005] CN102831256A discloses a method for calculating the solubility parameter of a chemical substance by computer simulation. This method constructs a molecular model of the chemical substance to be calculated and performs an energy minimization calculation, constructs a unit cell structure of the amorphous aggregate of the chemical substance to be calculated, performs an energy minimization calculation and a molecular dynamics calculation on this unit cell structure, calculates the cohesive energy density of the chemical substance, and takes the square root of it to obtain the solubility parameter. This method is applicable to solving the technical problem of difficult judgment of the compatibility between different substances in the petrochemical industry. However, the method of this existing technology is only applicable to the calculation of the solubility between pure substances, and the solubility of mixtures and complex systems cannot be accurately calculated.

[0006] CN108803329A discloses a method for optimizing the solubility in a supercritical extraction process. This method combines the PR state release, studies the coupling between temperature and pressure and its decoupling model with new theories and methods to improve the working efficiency of SFE, constructs a non-linear temperature-pressure decoupling model, gives a solubility optimization method, calculates the optimal working pressure according to the set temperature to obtain the maximum solubility in the supercritical extraction process, and solves the problem of low working efficiency of SFE in the supercritical extraction process. However, the applicable conditions of this solubility method are the supercritical state and the extraction process, and it is not applicable to the solubility measurement of other chemical engineering unit operations and non-supercritical conditions.

[0007] CN111008475A discloses a method for solving the hobbing carbon consumption model based on a chaotic Henry gas solubility optimizer. This method first proposes a chaotic Henry gas solubility algorithm, integrates the chaotic mapping method into the Henry gas solubility algorithm to produce a chaotic Henry gas solubility optimizer with more superior performance, continuously optimizes the hobbing processing parameters by using the chaotic Henry gas solubility optimizer, and evaluates them by using the carbon consumption model to make the hobbing processing parameters and the carbon consumption reach an approximately optimal state at the same time. However, this method is only applicable to the solubility calculation of Henry gas. Summary of the Invention

[0008] The purpose of the present invention is to provide a soft-sensing method for simulating the solubility of hydrogen in lubricating oil. This method can quickly calculate the solubility of hydrogen in lubricating oil, and can guide the operators of the device to understand the mixing effect of the hydrogen mixer in the device, and is suitable for solving the technical problem of difficult measurement of the solubility of hydrogen in lubricating oil in the petrochemical industry.

[0009] To achieve the above purpose, the present invention provides a soft-sensing method for the solubility of hydrogen in lubricating oil, and this soft-sensing method includes the following steps:

[0010] Step (1): Collect the lubricating oil distillation data, use Aspen Plus to characterize the lubricating oil, generate virtual components, set the initial flow rate of the lubricating oil as b, and complete the modeling of the lubricating oil stream;

[0011] Step (2): Set the auxiliary variables temperature to T and pressure to P, set the mass flow rate of hydrogen to d, and complete the modeling of the hydrogen flow stream;

[0012] Step (3): Establish a solubility soft measurement model, then use the mass flow rate of hydrogen as the operating variable, define the gas phase fraction calculated by the mixer module as the sample variable, perform sensitivity analysis, and calculate the dissolved hydrogen amount a;

[0013] Step (4): Based on the above simulation calculation results and the definition of solubility, calculate the estimated value c of the solubility of hydrogen in the lubricating oil; where c = a / b.

[0014] Wherein, the unit of b is kg / h, the unit of T is °C, the unit of P is MPa, the unit of d is kg / h, and the unit of a is kg / h.

[0015] The present invention does not particularly limit the type of lubricating oil. The preferred lubricating oil is PAO synthetic lubricating oil base oil or atmospheric and vacuum lubricating oil.

[0016] In step (1) of the present invention, the characterization of the lubricating oil requires selecting several distillation percentages and their corresponding temperatures as input variables. In addition, the specific gravity and distillation curve type of the lubricating oil need to be clarified.

[0017] In step (3) of the present invention, the mixer module is selected as the solubility soft measurement model, and the mixer auxiliary variables T and P need to be set to target values.

[0018] In step (3) of the present invention, when performing sensitivity analysis, the operating variable limit range is preferably set at 0.001 kg / h to 1 kg / h.

[0019] The present invention can also be described in detail as follows:

[0020] First, the static hydrogen mixer of the lubricant liquid-phase hydrogenation unit was modeled using Aspen Plus. The lubricant stream was simulated using the lubricant distillation range data as input. The mass flow rate of hydrogen was then used as the operating variable, and the gas phase fraction calculated by the mixer module was defined as the sample variable for sensitivity analysis. The model calculations revealed the amount of hydrogen dissolved in the lubricant liquid-phase hydrogenation unit's hydrogen mixer. Based on the solubility definition formula, an estimated value for the solubility of hydrogen in the lubricant in the lubricant liquid-phase hydrogenation unit's hydrogen mixer was calculated. The lubricant distillation range data can be obtained through laboratory measurements.

[0021] 1. Simulation and characterization of lubricating oil distillation data

[0022] Collect the specific gravity values of lubricating oils measured manually in the laboratory.

[0023] Laboratory lubricant oil distillation range data was collected. The temperatures corresponding to lubricant oil distillation percentages of 0%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% were selected as input data. AspenPlus software was then run to generate virtual lubricant components, which were used to characterize the lubricant. The distillation range data should be collected as uniformly and thoroughly as possible, including the initial and final distillation points. The lubricant oil feed stream was simulated using the laboratory-derived lubricant oil distillation curve type.

[0024] 2. Selection of soft-sensing auxiliary variables

[0025] The solubility of hydrogen in lubricating oil is related to factors such as the properties of the lubricating oil, the physical properties of hydrogen, temperature, and pressure. When establishing a solubility calculation model, in addition to setting the hydrogen mass flow rate as the manipulated variable, temperature and pressure conditions must also be specified. Therefore, based on data collected from actual equipment and using sensitivity analysis, temperature (T, °C) and pressure (P, MPa) are used as two auxiliary variables in a soft-sensor model for simulating the solubility of hydrogen in lubricating oil in the static hydrogen mixer of a lubricating oil hydrotreating unit.

[0026] 3. Establishment of solubility soft measurement model

[0027] The mixer module of Aspen Plus was selected to simulate the static hydrogen mixer of the lubricating oil liquid phase hydrogenation unit. The physical property method was selected according to the physical properties of the lubricating oil and hydrogen, and the binary interaction parameters were determined.

[0028] Specify auxiliary variables to simulate lubricant streams based on characterized lubricant data.

[0029] A sensitivity analysis was conducted using hydrogen mass flow rate as the manipulated variable. The limits of the manipulated variable should fully consider the magnitude of hydrogen's solubility in lubricating oil, ensuring that the critical point where the gas phase fraction of mixed stream L changes from zero to a positive value in the sensitivity analysis results falls within the calculated range. To minimize errors and improve calculation accuracy, the number of nodes within the restricted range of the restricted variable should be as large as possible. Based on the software's computational capabilities, the hydrogen mass flow rate at the starting point can be set to 0.0001 to 0.001 kg / h, with the end point set to 1 kg / h.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] (1) Aspen Plus software was used to perform a sensitivity analysis on the mass flow rate of hydrogen, and the solubility of hydrogen in lubricating oil was calculated based on the definition of solubility.

[0032] (2) By setting two auxiliary variables, temperature (T, °C) and pressure P (P, MPa), the effects of temperature and pressure on the hydrogen solubility in lubricating oil were investigated, and the variation law of hydrogen solubility in lubricating oil with temperature and pressure was obtained.

[0033] (3) The soft measurement can be completed with the distillation range data of the lubricating oil and the corresponding temperature and pressure parameters. This model is simple and easy to implement. Moreover, the soft measurement method of the present invention uses a hybrid module calculation, avoiding the situation where light components in the lubricating oil are flashed into the gas phase, resulting in inaccurate solubility calculation.

[0034] (4) The comparison between the laboratory manual measurement and the simulated solubility calculation results shows that there is a linear relationship between the laboratory manual measurement value and the simulated value. Description of the Drawings

[0035] Figure 1 It is a schematic diagram of the model for soft measurement of hydrogen solubility in the lubricating oil of the present invention.

[0036] Figure 2 It is a sensitivity analysis diagram of the mass flow rate of hydrogen introduced to the gas phase fraction of the lubricating oil mixed stream. Detailed Embodiments

[0037] The present invention will be further described below with specific examples. The examples are only illustrative of the present invention rather than limiting it.

[0038] The following is a detailed description of the embodiments of the present invention: These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0039] Example 1:

[0040] 1. Lubricating oil data collection and characterization

[0041] The distillation range data of the raw material PAO lubricating oil were collected from the laboratory. The distillation curve type uses the ASTM D86 method. The volume specific gravity value is 0.8482. The distillation percentages are 0%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 100% respectively, and the corresponding temperatures are 173.2 °C, 215.3 °C, 228.5 °C, 237.8 °C, 247.4 °C, 257.3 °C, 267.9 °C, 291.8 °C, 304.9 °C, 319.7 °C, 328.8 °C, 339.9 °C respectively.

[0042] The lubricating oil was characterized based on the above data.

[0043] 2. Establish a soft measurement model

[0044] Set the auxiliary variable temperature T = 360 °C, pressure P = 5 MPa, the initial mass flow rate of lubricating oil b = 100 kg / h, and the initial hydrogen flow rate d = 1 kg / h. The starting point of the sensitivity manipulation variable is 0.001 kg / h, the ending point is 1 kg / h, and the increment is 0.001 kg / h.

[0045] Input the above data into the model, and calculate that the hydrogen mass flow rate corresponding to the critical point at which the gas-phase fraction of the mixed stream changes from zero to a positive value is 0.106 kg / h, that is, the dissolved amount of hydrogen a in the hydrogen mixer of the liquid-phase hydrogenation unit is 0.106 kg / h.

[0046] 3. Solve for the hydrogen solubility

[0047] According to the definition of solubility, the hydrogen solubility c in the lubricating oil is c = a / b. Substitute the above simulation calculation results to obtain: c = 0.00106.

[0048] Comparative Example 1:

[0049] Use the same raw material PAO lubricating oil as in Example 1, and measure the hydrogen solubility on the PAO lubricating oil hydrogen dissolution experimental device. The experimental temperature is 360 °C and the pressure is 5 MPa.

[0050] Result: The experimentally measured solubility is 0.00127.

[0051] Example 2:

[0052] 1. Lubricating oil data collection and characterization

[0053] Collect the distillation range data of the raw material atmospheric and vacuum lubricating oil from the laboratory. The distillation curve type adopts the ASTM D86 method. The volume specific gravity value. The distillation percentages are 0%, 5%, 10%, 30%, 50%, 70%, 90%, 95%, 100% respectively, and the corresponding temperatures are 212 °C, 322 °C, 374 °C, 415 °C, 430 °C, 448 °C, 469 °C, 476 °C, 484 °C respectively.

[0054] Characterize the lubricating oil according to the above data.

[0055] 2. Establish a soft sensor model

[0056] Set the auxiliary variable temperature T = 360 °C, pressure P = 5 MPa, the initial mass flow rate of lubricating oil b = 100 kg / h, and the initial hydrogen flow rate d = 1 kg / h. The starting point of the sensitivity manipulation variable is 0.001 kg / h, the ending point is 1 kg / h, and the increment is 0.001 kg / h.

[0057] Input the above data into the model, and calculate the hydrogen mass flow rate corresponding to the critical point at which the gas-phase fraction of the mixed stream changes from zero to a positive value, which is kg / h. That is, the hydrogen dissolution amount a in the hydrogen mixer of the liquid-phase hydrogenation unit is 0.051 kg / h.

[0058] 3. Solve for the hydrogen solubility

[0059] According to the definition of solubility, the hydrogen solubility c in the lubricating oil is c = a / b. Substitute the above simulation calculation results to obtain: c = 0.00051.

[0060] Comparative Example 2:

[0061] Use the same raw material atmospheric and vacuum lubricating oil as in Example 2, and measure the hydrogen solubility on a lubricating oil hydrogen dissolution experimental device. The experimental temperature is 360 °C and the pressure is 5 MPa.

[0062] Result: The experimentally measured solubility is 0.000609.

Claims

1. A soft measurement method for the solubility of hydrogen in lubricating oil, characterized in that, It includes the following steps: Step (1): Collect lubricating oil distillation data, characterize the lubricating oil using Aspen Plus to generate virtual components, set the initial flow rate of the lubricating oil as b, and complete the modeling of the lubricating oil stream; Step (2): Set the auxiliary variables of temperature as T and pressure as P, set the mass flow rate of hydrogen as d, and complete the modeling of the hydrogen stream; Step (3): Establish a soft sensor model for solubility. Then, taking the mass flow rate of hydrogen as the operating variable, define the gas phase fraction calculated by the mixer module as the sample variable for sensitivity analysis, and calculate the dissolved amount a of hydrogen; Step (4): According to the above simulation calculation results and the definition of solubility, calculate the estimated value c of the solubility of hydrogen in the lubricating oil; where c = a / b; ① Characterization of lubricating oil distillation data, including: Collect the specific gravity value of the lubricating oil measured manually in the laboratory; Collect the distillation range data of the lubricating oil in the laboratory. Select the temperatures corresponding to the lubricating oil distillation percentages of 0%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% as input data, run the Aspen Plus software for calculation, generate virtual components of the lubricating oil, and characterize the lubricating oil with the virtual components; among them, for the collection of distillation range data, it should be collected as evenly and fully as possible on the basis of including the initial boiling point and the final boiling point of the lubricating oil; combined with the type of lubricating oil distillation curve measured in the laboratory, simulate the lubricating oil feed stream; ② Selection of soft sensor auxiliary variables, including: The solubility of hydrogen in the lubricating oil is related to the properties of the lubricating oil, the physical properties of hydrogen, temperature, and pressure factors; when establishing a solubility calculation model, in addition to setting the mass flow rate of hydrogen as the operating variable, it is also necessary to specify the temperature and pressure conditions; therefore, based on the data that can be collected in the actual device and the method of sensitivity analysis, use temperature (T, °C) and pressure P (P, MPa) as the two auxiliary variables of the soft sensor model for the solubility of hydrogen in the lubricating oil in the static hydrogen mixing device of the lubricating oil hydrogenation unit; ③ Establishment of the soft sensor model for solubility, including: Select the mixer module of Aspen Plus to simulate the static hydrogen mixer of the lubricating oil liquid phase hydrogenation device, select the physical property method according to the physical property states of the lubricating oil and hydrogen, and determine the binary interaction parameters; Specify the auxiliary variables and simulate the lubricating oil stream according to the characterized lubricating oil data; Conduct sensitivity analysis with the mass flow rate of hydrogen as the operating variable; for the limit range of the manipulated variable, the order of magnitude of the solubility of hydrogen in the lubricating oil should be fully considered to ensure that the critical point where the gas phase fraction of the mixed stream L changes from zero to a positive value in the sensitivity analysis results falls within the calculation result range; to reduce errors and improve the calculation accuracy, the number of nodes in the limit interval of the limit variable should be as many as possible; combined with the computing power of the software, set the hydrogen mass flow rate at the starting point to the order of 0.0001 - 0.001 kg / h, and the ending point to 1 kg / h.

2. The soft measurement method for the solubility of hydrogen in lubricating oil according to claim 1, characterized in that The lubricating oil is PAO synthetic lubricating oil base oil or atmospheric and vacuum lubricating oil.

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