VOCs (Volatile Organic Compounds) distribution calculation method in oil receiving and dispatching process of inner floating roof storage tank

Abstract

The invention belongs to the technical field of oil product storage tank evaporation loss, and particularly relates to a VOCs distribution calculation method in the oil product receiving and dispatching process of an inner floating roof storage tank. According to the technical scheme, the method comprises the following steps that 1, structural parameters of the inner floating roof storage tank and technological parameters of oil product receiving and dispatching are determined; 2, physical property parameters of oil products, oil steam and air are determined, and external environment parameters during oil product receiving and sending are mastered; 3, according to the coupling principle of an oil vapor concentration field, a temperature field and a flow field in the oil product receiving and dispatching process of the inner floating roof storage tank, a mass transfer relational expression of oil product receiving and dispatching and oil vapor is established, a momentum equation, an energy equation and a multiphase fluid integral number equation in different external environments are solved, and VOCs distribution of the inner floating roof storage tank in the receiving and dispatching operation process is calculated. According to the method, the interaction of an oil vapor concentration field, a flow field and a temperature field is comprehensively considered, the VOCs distribution of the inner floating roof storage tank in the receiving and dispatching operation process under different environment conditions is calculated, and the accuracy and reliability of VOCs loss accounting are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of evaporation loss of oil products in storage tanks, and particularly relates to a method for calculating VOCs distribution in the process of receiving and delivering oil products in an inner floating roof storage tank. BACKGROUND

[0002] In the petroleum industry, during the operation of receiving and delivering oil in an inner floating roof storage tank, the volume of the gas phase space changes due to the change of the liquid level in the tank, which causes the phenomenon of "heavy breathing" evaporation loss. Frequent exchange of oil gas and air leads to the emission of volatile organic compounds (VOCs) and energy loss. For a petroleum and chemical enterprise, this not only means direct economic loss, but also increases the production cost of the enterprise. With the increasing demand for energy resources worldwide, reducing VOCs emission and energy loss in storage tanks has become a problem to be solved.

[0003] At present, there are many limitations in the research on VOCs distribution in inner floating roof storage tanks. For example, the key factors in the existing formula method depend on the test data of foreign enterprises, and there is a lack of localization research on domestic storage tanks. Due to the special structure of the storage tank, the sampling is greatly affected by the state of the storage tank and environmental factors, and it is difficult to measure. In addition, since the medium stored in the storage tank, such as crude oil and refined oil, is flammable and explosive, the sampling equipment needs to be close to the high-risk area of the breathing valve during measurement, which poses a safety hazard. Therefore, a new method for calculating the VOCs distribution in the process of receiving and delivering oil products in an inner floating roof storage tank is needed to be established, which is supplemented by numerical simulation or model calculation to realize continuous and accurate calculation of the VOCs distribution in the process of receiving and delivering oil products in an inner floating roof storage tank.

[0004] Although there have been some researches on VOCs emission in storage tanks, the existing accounting methods need to be improved in terms of accuracy and convenience. Therefore, further research is needed on VOCs emission in the process of receiving and delivering oil products in an inner floating roof storage tank to fill the technical gap. SUMMARY

[0005] The application provides a method for calculating VOCs distribution in the process of receiving and delivering oil products in an inner floating roof storage tank, which considers the interaction of oil vapor concentration field, flow field and temperature field by constructing a multi-physical field coupling model, calculates the VOCs distribution of the inner floating roof storage tank in the receiving and delivering operation process under different environmental conditions, and improves the accuracy and reliability of VOCs loss calculation.

[0006] The technical scheme of the application is as follows:

[0007] A method for calculating VOCs distribution in the process of receiving and delivering oil products in an inner floating roof storage tank, comprising the following steps:

[0008] Step 1: determining the structure parameters and oil receiving and delivering process parameters of the inner floating roof storage tank;

[0009] Step 2: Determine the physical properties of the oil, oil vapor, and air, and understand the external environmental parameters during oil receiving and dispatching;

[0010] Step 3: Based on the coupling principle of oil vapor concentration field, temperature field and flow field during the oil receiving and dispatching process of internal floating roof tank, establish the mass transfer relationship between oil receiving and dispatching and oil vapor, solve the momentum equation, energy equation and multiphase flow volume fraction equation under different external environments, and calculate the VOCs distribution of internal floating roof tank during the receiving and dispatching operation.

[0011] Furthermore, in the method for calculating VOCs distribution during the oil product receiving and dispatching process of the internal floating roof tank, in step 1, the structural parameters of the internal floating roof tank include: tank inner diameter, tank height, internal floating roof height, tank top vent inner diameter, tank top vent height, and edge vent size and position; the process parameters for receiving and dispatching oil products of the internal floating roof tank include: annual turnover and annual turnover times.

[0012] Furthermore, in the method for calculating VOCs distribution during the oil receiving and dispatching process of the internal floating roof storage tank, in step 2, the physical properties of the oil, oil vapor, and air include: density, specific heat capacity, viscosity, thermal conductivity, saturated vapor pressure, and molar mass; the external environmental parameters during oil receiving and dispatching include: wind direction, wind speed, atmospheric temperature, and solar radiation intensity.

[0013] Furthermore, in the method for calculating VOCs distribution during the oil delivery and receipt process of the internal floating roof tank, step 3 specifically comprises:

[0014] Step 3.1: Formula for calculating the evaporation loss of oil products during internal floating roof tank operations:

[0015] (1)

[0016] In the formula: L w ρ represents the evaporation loss of oil products during the internal floating roof tank's delivery and receipt; Q represents the annual turnover; S represents the adhesion coefficient of the internal floating roof tank wall; ρ represents the annual turnover of oil products during the delivery and receipt of oil products during the internal floating roof tank's ... y Where is the density of the oil; D is the diameter of the internal floating roof tank.

[0017] Q is represented as:

[0018] (2)

[0019] In the formula: K is the annual turnover rate; V s η represents the theoretical volume of the internal floating roof tank; η is a correction factor based on the volatile characteristics of the medium and the tank structure.

[0020] Step 3.2: The energy equation for the temperature field of the internal floating roof tank is:

[0021] (3)

[0022] Where: t is the time of evaporation loss of the oil product; p is the density of the mixed phase; Cp is the specific heat capacity at constant pressure of the mixed phase; T is the temperature of the mixed phase; V is the velocity vector of the mixed phase; λ is the thermal conductivity of the mixed phase; Q R Qs is the solar radiation heat source term, and the solar radiation amount is calculated using the ASHRAE clear sky model;

[0023] Q R is expressed as:

[0024] (4)

[0025] Where: G D is the amount of direct solar radiation; G dθ is the amount of scattered solar radiation; G R is the amount of ground reflected radiation; G h is the amount of radiative heat exchange;

[0026] G D is expressed as:

[0027] (5)

[0028] (6)

[0029] Where: G ND is the intensity of direct radiation at normal incidence; i is the solar incidence angle; A is the solar radiation intensity when the atmosphere has zero mass; B is the extinction coefficient of the atmosphere; h is the solar altitude angle; C N is the atmospheric cleanness;

[0030] Wherein, the solar position parameters can be calculated by the solar declination angle δ, the hour angle ω and the geographic latitude φ, and the calculation formula is as follows:

[0031] (7)

[0032] (8)

[0033] (9)

[0034] (10)

[0035] (11)

[0036] Where: N is the day number; H is the hour number, counted in 24 hours; θ is the surface tilt angle; γ is the surface orientation angle; α is the solar azimuth angle;

[0037] G dθ is expressed as:

[0038] (12)

[0039] (13)

[0040] where C is the scattering radiation factor; G dV is the scattered light intensity in the vertical direction; G dH is the scattered light intensity in the horizontal direction;

[0041] where A, B, and C are coefficients corresponding to different months given by the ASHRAE clear sky model, and the specific values are shown in Table 1;

[0042] Table 1 Coefficients of ASHRAE Clear Sky Model

[0043]

[0044] G R is expressed as:

[0045] (14)

[0046] where p g is the radiation reflectivity of the horizontal plane;

[0047] G h is expressed as:

[0048] (15)

[0049] (16)

[0050] where h d is the radiation heat transfer coefficient; T a is the fluid temperature; T c is the atmospheric temperature; ε0 is the blackness of the tank wall, which changes with the tank wall coating; C0 is the blackbody thermal radiation coefficient, with a value of 5.67×10 -8 W / m 2 ·K 4 ; t bi is the average temperature of the tank wall; t qi is the monthly minimum air temperature;

[0051] When calculating the temperature field, the influence of solar radiation intensity on the inner floating roof tank wall is fully considered in combination with formulas (4-16), and then the energy equation (3) is obtained;

[0052] Step 3.3: The momentum equation of the flow field in the inner floating roof tank is:

[0053] (17)

[0054] Where p is the pressure of the mixed phase; μ is the dynamic viscosity of the mixed phase; is the gravitational acceleration;

[0055] Through the Reynolds number calculation, the gas flow in the tank presents turbulent flow, and the standard k-ε model is used to solve the turbulent kinetic energy k and the turbulent dissipation rate ε:

[0056] (18)

[0057] (19)

[0058] Where: μ t is the turbulent dynamic viscosity; is the turbulent Prandtl number of the turbulent kinetic energy, and the value is 1.0; G k is the turbulent kinetic energy generated by the average velocity gradient; G b is the turbulent kinetic energy generation term caused by buoyancy; is a constant, and the value is 1.44; is a constant, and the value is 1.92; is the Prandtl number of the turbulent dissipation rate, and the value is 1.3;

[0059] μ t is expressed as:

[0060] (20)

[0061] Where: is a constant, and the value is 0.09;

[0062] The distribution of k and ε is determined by equation (18) and equation (19), which provides the closure relationship of turbulent viscosity for the momentum equation, so that equation (17) is closed and can be solved;

[0063] Step 3.4: Calculation of VOCs distribution in the internal floating roof tank;

[0064] During the oil receiving and sending process of the internal floating roof tank, liquid oil, air and oil vapor containing VOCs are involved; the multiphase volume fraction equation can quantitatively describe the volume fraction of each phase:

[0065] (21)

[0066] (22)

[0067] Where: α q is the volume fraction of the qth phase; ρ q is the density of the qth phase; is the velocity vector of the qth phase; S 1-(q+1)is the mass transfer source term; when q = 1, it is oil vapor; when q = 2, it is oil product; when q = 3, it is air; m is the number of phases participating in a certain mass transfer process, j is the total number of phases in the equation;

[0068] The VOCs distribution is calculated by the oil vapor volume fraction, and the concentration unit is ppm, and the calculation formula is as follows:

[0069] (23)

[0070] In the formula, c is the VOCs concentration, a1 is the oil vapor phase volume fraction, p1 is the density of oil vapor, and V1 is the oil vapor volume.

[0071] The VOCs distribution is calculated by formula (23), which is directly compared with the environmental protection standard to evaluate whether it meets the environmental protection requirements, so as to ensure the effectiveness and comparability of the data.

[0072] Formula (22) is used as a constraint condition to ensure that the total volume fraction of all phases in the storage tank is always 1.

[0073] Further, in the oil receiving and sending process of the inner floating roof storage tank, the VOCs distribution calculation method comprises the following steps:

[0074] (1) Tank top: thermal boundary: ; velocity boundary: ; turbulent kinetic energy: ; turbulent kinetic energy dissipation rate: ;

[0075] Wherein, n is the unit vector of the spatial rectangular coordinate system (x, y, z); q1 is the heat flux of the tank top wall;

[0076] (7) Tank top vent hole side wall: thermal boundary: ; velocity boundary: ; turbulent kinetic energy: ; turbulent kinetic energy dissipation rate: ;

[0077] (8) Tank top vent hole top: thermal boundary: T0; velocity boundary: free flow; turbulent kinetic energy: ; turbulent kinetic energy dissipation rate: ;

[0078] Wherein, T0 is the ambient temperature;

[0079] (9) Edge vent hole: thermal boundary: T0; velocity boundary: windward hole: velocity inlet; leeward hole: free flow; turbulent kinetic energy: ; turbulent kinetic energy dissipation rate: ;

[0080] (10) Tank wall: thermal boundary: ; velocity boundary: ; turbulent kinetic energy: ; turbulent kinetic energy dissipation rate: ;

[0081] Wherein, q2 is the wall heat flux of the tank wall;

[0082] (11) Tank bottom: thermal boundary: ; velocity boundary: ; turbulent kinetic energy: ; turbulent kinetic energy dissipation rate: ;

[0083] Wherein, h1 is the convective heat transfer coefficient at the junction of the tank bottom and the ground, h1=2 W·m -2 ·K -1 ; T1 is the ground temperature.

[0084] Further, the oil receiving and sending process VOCs distribution calculation method of the inner floating roof tank, the initial temperature in the tank is the ambient temperature.

[0085] The beneficial effects of the present application are: the present application calculates the VOCs distribution of the tank by constructing a multi-physical field coupling model, comprehensively considers the interaction of the oil vapor concentration field, the flow field and the temperature field, can intuitively present the multi-phase distribution in the inner floating roof tank, find the VOCs emission rule and characteristics, and significantly improve the calculation accuracy. The present application can predict the VOCs distribution under different external environments through parameter regulation, provide data support for the structure optimization of the oil tank, and provide a theoretical basis for the loss assessment of the environmental protection department and the emission reduction of enterprises. BRIEF DESCRIPTION OF DRAWINGS

[0086] Figure 1 It is a nonlinear equation set relationship diagram for solving the coupling of the flow field-temperature field-oil vapor concentration field in the oil receiving and sending process of the inner floating roof tank;

[0087] Figure 2 It is a boundary schematic diagram of oil evaporation loss in the oil receiving and sending process of the inner floating roof tank; wherein, a-b-c-d, e-f-g-h, i-j-k-l, m-n-o-p, q-r-s-t, u-v-w-x are all edge vent holes;

[0088] Figure 3 It is a schematic diagram of VOCs distribution of the inner floating roof tank; wherein, (a) is a vertical cut plane of the tank, (b) is a tank top, (c) is a tank top vent hole and edge vent hole. DETAILED DESCRIPTION

[0089] This paper takes an internal floating roof storage tank, which was converted from a dome-shaped tank, as the research object. It analyzes the oil evaporation loss during the oil receiving and discharging process of the storage tank at 10:00 am on the summer solstice under the action of a southerly wind of level 8 (wind speed up to 20 m / s). The invention is described in detail with reference to the accompanying drawings, but the scope of protection of the invention is not limited by the accompanying drawings and specific embodiments.

[0090] A method for calculating VOCs distribution during the oil product receiving and dispatching process of an internal floating roof storage tank includes the following steps:

[0091] Step 1: Determine the structural parameters of the internal floating roof tank as shown in Table 2, and the oil receiving and dispatching process parameters as shown in Table 3.

[0092] Table 2 Structural parameters of internal floating roof tanks

[0093]

[0094] Table 3 Process parameters for receiving and dispatching oil products

[0095]

[0096] Step 2: Determine the physical properties of the oil, oil vapor, and air as shown in Table 4, and the external environmental parameters during oil receiving and dispatching as shown in Table 5.

[0097] Table 4 Physical properties of oil, oil vapor and air

[0098]

[0099] Table 5 External Environmental Parameters During Oil Receipt and Dispatch

[0100]

[0101] Step 3: Based on the coupling principle of oil vapor concentration field, temperature field, and flow field during the oil receiving and dispatching process of the internal floating roof tank, establish the mass transfer relationship between the oil receiving / discharging and the oil vapor, solve the momentum equation, energy equation, and multiphase flow volume fraction equation under different external environments, and calculate the VOCs distribution of the internal floating roof tank during the receiving / discharging operation; such as Figure 1 The figure shown is a diagram illustrating the nonlinear equations relating the flow field, temperature field, and oil vapor concentration field during the oil delivery and receipt process in an internal floating roof tank. Specifically:

[0102] Step 3.1: Formula for calculating the evaporation loss of oil products during internal floating roof tank operations:

[0103] (1)

[0104] In the formula: L w The evaporation loss during oil delivery and receipt by the internal floating roof tank; Q is the annual turnover, taken as 8.5 × 10. 3 m 3a; S is the wall adhesion coefficient of the internal floating roof tank, and the value is 0.00257; p y p is the density of oil, and the value is 7194 kg / m 3 D is the diameter of the internal floating roof tank, and the value is 15.5 m;

[0105] Q is represented as:

[0106] (2)

[0107] In the formula, K is the annual turnover frequency, and the value is 5; V s is the theoretical volume, and the value is 2000 m 3 η is the correction coefficient based on the medium volatility characteristics and the structure of the tank, and the value is 0.85;

[0108] Step 3.2: The energy equation of the internal floating roof tank temperature field is:

[0109] (3)

[0110] In the formula, t is the time of oil evaporation loss; p is the density of the mixed phase; is the specific heat capacity of the mixed phase at constant pressure; T is the temperature of the mixed phase; is the velocity vector of the mixed phase; λ is the thermal conductivity of the mixed phase; Q R is the solar radiation heat source term, and the solar radiation amount is calculated by using the ASHRAE clear sky model;

[0111] Q R is represented as:

[0112] (4)

[0113] In the formula, G D is the direct solar radiation amount; G dθ is the solar scattered radiation amount; G R is the ground reflected radiation amount; G h is the radiation heat exchange amount;

[0114] G D is represented as:

[0115] (5)

[0116] (6)

[0117] In the formula, G ND is the vertical incident direct radiation intensity; i is the solar incident angle; A is the solar radiation intensity when the atmosphere is zero, and the value is 1088.29; B is the extinction coefficient of the atmosphere, and the value is 0.205; h is the solar elevation angle; C NThe atmospheric cleanliness level is set at 0.75.

[0118] The solar position parameters can be calculated using the solar declination angle δ, the hour angle ω, and the geographic latitude φ (taken as 41.8°N), as shown in the following formula:

[0119] (7)

[0120] (8)

[0121] (9)

[0122] (10)

[0123] (11)

[0124] In the formula, N is the day number, which is 172; H is the hour, which is 10 in 24 hours; θ is the surface tilt angle; γ is the surface orientation angle; and α is the solar azimuth angle.

[0125] G dθ Represented as:

[0126] (12)

[0127] (13)

[0128] In the formula, C is the scattering radiation factor, with a value of 0.134; G dV G represents the intensity of scattered light in the vertical direction. dH The intensity of scattered light in the horizontal direction;

[0129] G R Represented as:

[0130] (14)

[0131] In the formula, ρ g The reflectivity of the horizontal surface is 0.33.

[0132] G h Represented as:

[0133] (15)

[0134] (16)

[0135] In the formula, h d T is the radiative heat transfer coefficient; a T represents the fluid temperature. cε0 is the atmospheric temperature, taken as 300 K; ε0 is the emissivity of the tank wall, taken as 0.8; C0 is the blackbody thermal emissivity, taken as 5.67 × 102 -8 W / m 2 ·K 4 ;t bi The average temperature of the tank wall is taken as 27℃; t qi The lowest temperature of the month is 20.15℃.

[0136] When calculating the temperature field, the influence of solar radiation intensity on each area of ​​the storage tank was fully considered in conjunction with formula (4-16), and the energy equation (3) was obtained.

[0137] Step 3.3: The momentum equation for the flow field in the internal floating roof tank is:

[0138] (17)

[0139] In the formula, p is the pressure of the mixed phase; μ is the dynamic viscosity of the mixed phase; It is the acceleration due to gravity;

[0140] Based on Reynolds number calculations, the gas flow inside the tank exhibits turbulent flow. The standard k-ε model is used to solve for the turbulent kinetic energy k and the turbulent dissipation rate ε.

[0141] (18)

[0142] (19)

[0143] Where: μ t For turbulent dynamic viscosity; G represents the turbulent Prandtl number of turbulent kinetic energy, with a value of 1.0; k G represents the turbulent kinetic energy generated by the average velocity gradient. b This is the turbulent kinetic energy generation term caused by buoyancy; It is a constant, with a value of 1.44; It is a constant, with a value of 1.92; The Prandtl number is the turbulent dissipation rate, with a value of 1.3.

[0144] μ t Represented as:

[0145] (20)

[0146] In the formula: It is a constant, with a value of 0.09;

[0147] The distributions of k and ε are determined by equations (18) and (19), providing a closed relationship for the turbulent viscosity of the momentum equation, making equation (17) closed and solvable;

[0148] Step 3.4: Calculation of VOCs distribution in internal floating roof tanks;

[0149] During the process of receiving and dispatching oil products in internal floating roof tanks, the main components involved are liquid oil, air, and oil vapor containing VOCs; the volume fraction of each phase can be quantitatively described by the multiphase flow volume fraction equation.

[0150] (twenty one)

[0151] (twenty two)

[0152] In the formula, α q ρ is the volume fraction of the q-th phase; q Let be the density of the q-th phase; Let S be the velocity vector of phase q; 1-(q+1) For mass transfer source terms; when q=1, it is oil vapor; when q=2, it is oil; when q=3, it is air; m is the number of phases participating in a specific mass transfer process, and j is the total number of phases in the equation;

[0153] VOCs distribution can be calculated using the volume fraction of oil vapor, with the concentration unit being ppm. The calculation formula is as follows:

[0154] (twenty three)

[0155] In the formula, c is the VOCs concentration, α1 is the volume fraction of oil vapor phase; ρ1 is the density of oil vapor; V1 is the volume of oil vapor.

[0156] The VOCs distribution can be calculated using formula (23) and directly compared with environmental protection standards to assess whether it meets environmental protection requirements, ensuring the validity and comparability of the data.

[0157] Formula (22) serves as a constraint to ensure that the total volume fraction of all phases in the tank is always 1.

[0158] like Figure 2 The diagram shows the boundary of oil evaporation loss during the oil receiving and dispatching process of an internal floating roof tank. In this diagram, the edge vents abcd, efgh, and ijkl are the leeward vents, and mnop, qrst, and uvwx are the windward vents.

[0159] When calculating the VOCs distribution during the oil delivery and receipt process of the internal floating roof tank, the initial temperature inside the tank is the ambient temperature. A VOF (Volatile Flow) model is used to track changes at the gas-liquid interface. The mass transfer rate between the oil phase and the oil vapor phase is represented by the oil evaporation loss in the internal floating roof tank, which is 9.39787 × 10⁻⁶. -5 kg / s; the boundary conditions are set as shown in Table 6.

[0160] Table 6 Boundary Conditions

[0161]

[0162] like Figure 3 The image shows the VOCs distribution in the internal floating roof tank of this embodiment. The selected locations are the vertical cross-section of the tank, the top of the tank, the top vent, and the edge vent. Different shades of gray are used to represent the differences in oil vapor concentration at different locations within the tank, with values ​​expressed in ppm. The black areas correspond to higher VOCs concentrations, with some areas approaching 1575. The VOCs concentration values ​​in the light gray area are relatively low (ppm). Calculation results show that oil vapor distribution at the vertical plane of the storage tank is mainly concentrated in the center of the tank, air is mainly distributed in the upper part of the tank, and oil is distributed at the bottom. Air is concentrated in the top area of ​​the tank, and oil vapor distribution is more scattered. Air enters through the three edge vents, while both oil vapor and air escape through the other three edge vents and the top vent. This distribution is because the flow direction and speed of the flow field will drive the diffusion of oil vapor. In areas with slow flow velocity, oil vapor is more likely to accumulate and form a high concentration area, while in areas with fast flow velocity, the concentration is relatively low. The oil vapor concentration will be higher near the oil volatilization source. Moreover, since the density of oil vapor is greater than that of air, oil vapor tends to sink due to gravity.

[0163] The above description is only a preferred embodiment of the present invention and is not intended to limit the ideas 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 protection scope of the present invention.

Claims

1. A method for calculating VOCs distribution during the oil product receiving and dispatching process of an internal floating roof storage tank, characterized in that, Includes the following steps: Step 1: Determine the structural parameters and oil receiving / delivering process parameters of the internal floating roof tank; Step 2: Determine the physical properties of the oil, oil vapor, and air, and understand the external environmental parameters during oil receiving and dispatching; Step 3: Based on the coupling principle of oil vapor concentration field, temperature field and flow field during the oil receiving and dispatching process of internal floating roof tank, establish the mass transfer relationship between oil receiving and dispatching and oil vapor, solve the momentum equation, energy equation and multiphase flow volume fraction equation under different external environments, and calculate the VOCs distribution of internal floating roof tank during the receiving and dispatching operation.

2. The method for calculating VOCs distribution during the oil product receiving and dispatching process of an internal floating roof storage tank according to claim 1, characterized in that, In step 1, the structural parameters of the internal floating roof tank include: tank inner diameter, tank height, internal floating roof height, tank top vent inner diameter, tank top vent height, and edge vent size and location; the process parameters for receiving and dispatching oil products by the internal floating roof tank include: annual turnover and annual turnover times.

3. The method for calculating VOCs distribution during the oil product receiving and dispatching process of an internal floating roof storage tank according to claim 2, characterized in that, In step 2, the physical properties of the oil, oil vapor, and air include: density, specific heat capacity, viscosity, thermal conductivity, saturated vapor pressure, and molar mass; the external environmental parameters during oil receiving and dispatching include: wind direction, wind speed, atmospheric temperature, and solar radiation intensity.

4. The method for calculating VOCs distribution during the oil product receiving and dispatching process of an internal floating roof storage tank according to claim 3, characterized in that, Step 3 specifically involves: Step 3.1: Formula for calculating the evaporation loss of oil products during internal floating roof tank operations: （1） In the formula: L w ρ represents the evaporation loss of oil products during the internal floating roof tank's delivery and receipt; Q represents the annual turnover; S represents the adhesion coefficient of the internal floating roof tank wall; ρ represents the annual turnover of oil products during the delivery and receipt of oil products during the internal floating roof tank's ... y Where is the density of the oil; D is the diameter of the internal floating roof tank. Q is represented as: （2） In the formula: K is the annual turnover rate; V s η represents the theoretical volume of the internal floating roof tank; η is a correction factor based on the volatile characteristics of the medium and the tank structure. Step 3.2: The energy equation for the temperature field of the internal floating roof tank is: （3） In the formula: t is the time of oil evaporation loss; ρ is the density of the mixed phase; is the isobaric specific heat capacity of the mixed phase; T is the temperature of the mixed phase; λ is the velocity vector of the mixed phase; λ is the thermal conductivity of the mixed phase; Q R For the solar radiation heat source term, the solar radiation is calculated using the ASHRAE clear sky model; Q R Represented as: （4） Where: G D G represents direct solar radiation. dθ G represents the amount of solar diffuse radiation. R G represents the amount of radiation reflected from the ground. h For radiative heat exchange; G D Represented as: （5） （6） In the formula, G ND denoted as , where i is the solar incidence angle; A is the solar radiation intensity when the atmospheric mass is zero; B is the atmospheric extinction coefficient; h is the solar altitude angle; C is the solar radiation intensity when the atmospheric mass is zero; N For atmospheric cleanliness; The solar position parameters can be calculated using the solar declination angle δ, the hour angle ω, and the geographic latitude φ, as shown in the following formula: （7） （8） （9） （10） （11） In the formula, N is the day number; H is the hour, in 24-hour format; θ is the surface tilt angle; γ is the surface orientation angle; and α is the solar azimuth angle. G dθ Represented as: （12） （13） In the formula, C is the scattering radiation factor; G dV G represents the intensity of scattered light in the vertical direction. dH The intensity of scattered light in the horizontal direction; Among them, A, B and C are the coefficients given by the ASHRAE clear sky model for different months, and the specific values ​​are shown in Table 1. Table 1. ASHRAE Clear Sky Model Coefficients ； G R Represented as: （14） In the formula, ρ g The reflectivity of the horizontal surface; G h Represented as: （15） （16） In the formula, h d T is the radiative heat transfer coefficient; a T represents the fluid temperature. c ε0 represents atmospheric temperature; ε0 represents the emissivity of the tank wall, which varies with the coating on the tank wall; C0 represents the blackbody thermal emissivity, with a value of 5.67 × 102. -8 W / m 2 ·K 4 ;t bi t represents the average temperature of the tank wall. qi This is the lowest temperature of the month; When calculating the temperature field, the influence of solar radiation intensity on the wall of the internal floating roof tank is fully considered in conjunction with formula (4-16), and the energy equation (3) is obtained. Step 3.3: The momentum equation for the flow field in the internal floating roof tank is: （17） In the formula, p is the pressure of the mixed phase; μ is the dynamic viscosity of the mixed phase; It is the acceleration due to gravity; Based on Reynolds number calculations, the gas flow inside the tank exhibits turbulent flow. The standard k-ε model is used to solve for the turbulent kinetic energy k and the turbulent dissipation rate ε. （18） （19） Where: μ t For turbulent dynamic viscosity; G represents the turbulent Prandtl number of turbulent kinetic energy, with a value of 1.0; k G represents the turbulent kinetic energy generated by the average velocity gradient. b This is the turbulent kinetic energy generation term caused by buoyancy; It is a constant, with a value of 1.44; It is a constant, with a value of 1.92; The Prandtl number is the turbulent dissipation rate, with a value of 1.

3. μ t Represented as: （20） In the formula: It is a constant, with a value of 0.09; The distributions of k and ε are determined by equations (18) and (19), providing a closed relationship for the turbulent viscosity of the momentum equation, making equation (17) closed and solvable; Step 3.4: Calculation of VOCs distribution in internal floating roof tanks; In the process of receiving and dispatching oil products using internal floating roof tanks, liquid oil, air, and oil vapor containing VOCs are involved; the volume fraction of each phase can be quantitatively described using multiphase flow volume fraction equations. （21） （22） In the formula, α q ρ is the volume fraction of the q-th phase; q Let be the density of the q-th phase; Let S be the velocity vector of phase q; 1-(q+1) For mass transfer source terms; when q=1, it is oil vapor; when q=2, it is oil; when q=3, it is air; m is the number of phases participating in a specific mass transfer process, and j is the total number of phases in the equation; VOCs distribution is calculated using the volume fraction of oil vapor, with concentration units in ppm. The calculation formula is as follows: （23） In the formula, c is the VOCs concentration, α1 is the volume fraction of oil vapor phase; ρ1 is the density of oil vapor; V1 is the volume of oil vapor. The VOCs distribution is calculated using formula (23), and directly compared with environmental protection standards to assess whether it meets environmental protection requirements, ensuring the validity and comparability of the data; Formula (22) serves as a constraint that ensures the total volume fraction of all phases in the tank is always 1.

5. The method for calculating VOCs distribution during the oil product receiving and dispatching process of an internal floating roof storage tank according to claim 4, characterized in that, In step 3, the following boundary conditions are set when calculating the VOCs distribution: (1) Tank top: thermal boundary: Velocity boundary: Turbulent kinetic energy: ; Turbulent kinetic energy dissipation rate: ; Where n is a unit vector in a spatial rectangular coordinate system (x, y, z); q1 is the heat flux through the top wall of the tank; (2) Side wall of the vent at the top of the tank: thermal boundary: Velocity boundary: Turbulent kinetic energy: Turbulent kinetic energy dissipation rate: ; (3) Top of the vent hole at the top of the tank: Thermal boundary: T0; Velocity boundary: Free flow; Turbulent kinetic energy: Turbulent kinetic energy dissipation rate: ; Where T0 is the ambient temperature; (4) Edge ventilation holes: Thermal boundary: T0; Velocity boundary: Windward hole: Velocity inlet; Leeward hole: Free flow; Turbulent kinetic energy: Turbulent kinetic energy dissipation rate: ; (5) Tank wall: thermal boundary: Velocity boundary: Turbulent kinetic energy: Turbulent kinetic energy dissipation rate: ; Where q2 is the heat flux through the tank wall; (6) Tank bottom: thermal boundary: Velocity boundary: Turbulent kinetic energy: Turbulent kinetic energy dissipation rate: ; Where h1 is the convective heat transfer coefficient at the junction of the tank bottom and the ground, h1 = 2 W·m -2 ·K -1 T1 is the ground temperature.

6. The method for calculating VOCs distribution during the oil product receiving and dispatching process of an internal floating roof storage tank according to claim 3, characterized in that, The initial temperature inside the storage tank is the ambient temperature.

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