Safety working condition design method for offshore gas-liquid separator

Abstract

The invention provides a safe working condition design method for an offshore gas-liquid separator. The safe working condition design method comprises the following steps that different sloshing working conditions related to the gas-liquid separator are determined; establishing a geometric model of the gas-liquid separator, establishing a corresponding computational domain, and determining a complex flow area; finely simulating the liquid tank flow field of the gas-liquid separator in a rolling state according to the geometric model of the gas-liquid separator, and monitoring the water level change of each point to obtain the lowest safe water level position; according to the lowest safe water level position, the corresponding relation between different sloshing working conditions and the lowest safe water level is obtained, and according to the corresponding relation, safe water level working conditions under different sloshing conditions are designed; the method has the advantages that the lowest safe water level can be accurately calculated, so that the safe water level working condition is forecasted, a method and modeling technical support is provided for sloshing safe work and working condition design of a gas-liquid separation device of an offshore hydrogen production system, and the method has important guiding significance for efficient development of new energy hydrogen production.

Description

Technical Field

[0001] The present invention relates to the technical field of working safety of offshore gas-liquid separators, and in particular to a safe working condition design method for offshore gas-liquid separators. Background Art

[0002] As global climate change triggers increasingly frequent and significant weather anomalies, there's an urgent need to develop more clean energy sources to replace traditional fossil fuels. Hydrogen, as an important clean energy source, offers advantages such as versatility, cleanliness, and flexibility, with an energy density three times that of traditional petroleum. As the world accelerates the transition to clean, low-carbon energy and actively responds to climate change, offshore hydrogen production using renewable energy has become a focus of attention in the new energy sector, recognized as a key solution to addressing power transmission, peak load regulation, and power consumption.

[0003] Typically, offshore hydrogen production equipment installed on a floating platform experiences sloshing motion, which in turn causes the liquid in the gas-liquid separator installed on the deck to slosh. Different sloshing cycles and amplitudes correspond to different water level changes. An increase in sloshing amplitude causes an increase in the contact area between the free liquid surface and the tank wall, reducing the minimum safe water level. The sloshing cycle also affects the minimum safe water level. Currently, there is a lack of methods for assessing the minimum safe water level of a gas-liquid separator under sloshing conditions, which seriously affects work safety in engineering. The present invention provides a prediction method for assessing the minimum safe water level of a gas-liquid separator under sloshing conditions. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a safe operating condition design method for an offshore gas-liquid separator, which is used to solve the current problem of lack of an assessment method for the minimum safe water level of a gas-liquid separator under sloshing conditions, which seriously affects work safety in engineering.

[0005] To achieve the above-mentioned and other related purposes, the present invention provides the following technical solutions:

[0006] A method for designing safe operating conditions of an offshore gas-liquid separator comprises the following steps: determining different sloshing operating conditions of the gas-liquid separator; establishing a geometric model of the gas-liquid separator, establishing a corresponding calculation domain for the geometric model of the gas-liquid separator, and determining a complex flow area; finely simulating the liquid tank flow field of the gas-liquid separator in a roll state according to the geometric model of the gas-liquid separator, and monitoring the water level changes at each point to obtain a minimum safe water level position; obtaining a correspondence between different sloshing conditions and the minimum safe water level according to the minimum safe water level position, and designing safe water level conditions under different sloshing conditions according to the correspondence.

[0007] In one embodiment of the present invention, the sloshing operating conditions include a sloshing period and a sloshing amplitude, and the sloshing amplitude and the sloshing period can be freely combined crosswise.

[0008] In one embodiment of the present invention, the geometric model of the gas-liquid separator is a cylindrical structure, and the shape of the complex flow region is a cylinder.

[0009] In one embodiment of the present invention, after establishing the geometric model of the gas-liquid separator, establishing the corresponding calculation domain for the geometric model of the gas-liquid separator, and determining the complex flow area, the liquid tank flow field of the gas-liquid separator in the roll state is finely simulated according to the geometric model of the gas-liquid separator, and the water level changes at each point are monitored to obtain the minimum safe water level position, it also includes: using an unstructured body grid to divide the calculation domain, and then using a surface reconstruction model to refine the grid division, and performing grid encryption processing on the complex flow area, so as to obtain a complex flow encryption area.

[0010] In one embodiment of the present invention, the liquid tank flow field of the gas-liquid separator in the roll state is finely simulated based on the geometric model of the gas-liquid separator, and the water level changes at each point are monitored to obtain the minimum safe water level position, including: using the turbulence model closed control equation, the free surface tracking method and the finite volume method to discretize the fluid control equation, and based on the CFD method, the liquid tank flow field of the gas-liquid separator in the roll state is finely simulated, and the water level changes at each point are monitored to obtain the minimum safe water level position.

[0011] In one embodiment of the present invention, the turbulence model may adopt a K-Epsilon two-layer model, a standard K-Epsilon two-layer model, an SST K-Omega model, or a standard K-Omega model.

[0012] In one embodiment of the present invention, considering that liquid tank sloshing involves complex nonlinear phenomena such as gas-liquid mixing, the Euler multiphase flow model, VOF model and other models are also used in the detailed simulation of the liquid tank flow field of the gas-liquid separator in the rolling state.

[0013] In one embodiment of the present invention, the use of the finite volume method to discretize the fluid control equations to perform a detailed simulation of the liquid tank flow field of the gas-liquid separator in a rolling state, and monitoring the water level changes at each point to obtain the minimum safe water level position, includes: using the finite volume method to discretize the fluid control equations, using a central difference format to process the linear diffusion term, using a second-order upwind format to process the nonlinear convection term, and solving it with the SIMPLE algorithm, performing a detailed simulation of the liquid tank flow field of the gas-liquid separator in a rolling state, and monitoring the water level changes at each point to obtain the minimum safe water level position.

[0014] As described above, the safe operating condition design method for an offshore gas-liquid separator of the present invention has the following beneficial effects:

[0015] The present invention first sets different sloshing operating conditions for the gas-liquid separator, then establishes a geometric model of the gas-liquid separator, establishes a corresponding calculation domain and sets a complex flow area, and then uses the turbulence model closed control equation, the free surface tracking method, the finite volume method discrete fluid control equation and the multiphase flow model to simulate the gas-liquid two-phase flow, and finely simulates the liquid tank flow field of the gas-liquid separator under the sloshing state, monitors the changes in the minimum water level and thus designs safe water level operating conditions under different sloshing conditions; compared with the existing technology, the present invention can accurately calculate the minimum safe water level, thereby predicting the safe water level operating conditions, and provide method and modeling technology support for the sloshing safety operation and operating condition design of the gas-liquid separation device of the offshore hydrogen production system, which has important guiding significance for the efficient development of new energy hydrogen production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Shown is an overall flow chart of a safe operating condition design method for an offshore gas-liquid separator disclosed in an embodiment of the present invention;

[0017] Figure 2 A schematic diagram showing the impact of different sloshing amplitudes on the minimum safe water level in the safe operating condition design method for an offshore gas-liquid separator disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless there is a conflict.

[0019] The present invention relates to a method for designing safe working conditions of an offshore gas-liquid separator. In view of the influence of different sloshing working conditions on the minimum safe water level, a method for designing safe working conditions of a gas-liquid separator under sloshing conditions at sea is specifically provided. The method can reasonably and safely assess the minimum safe waterline position of the gas-liquid separator during offshore operation, thereby avoiding safety hazards. The process is as follows: Figure 1 As shown, the details are as follows:

[0020] Step 101: Determine different sloshing operating conditions of the gas-liquid separator.

[0021] Specifically, different sloshing operating conditions for the gas-liquid separator are artificially set and made into an operating condition table. Please refer to Table 1 for details. The sloshing operating conditions include sloshing period and sloshing amplitude, and the sloshing amplitude and sloshing period can be freely combined crosswise.

[0022] Table 1: Gas-liquid separation conditions

[0023] Working conditions Sloshing period Sway amplitude Case 1-Case 3 T1 A1, A2, A3 Case 4-Case 6 T2 A1, A2, A3 Case 7-Case 9 T3 A1, A2, A3 … … …

[0024] Step 102 : establishing a geometric model of the gas-liquid separator, establishing a corresponding calculation domain for the geometric model of the gas-liquid separator, and determining a complex flow area.

[0025] Specifically, a complex flow region is artificially set, wherein the geometric model of the gas-liquid separator is a cylindrical structure and the shape of the complex flow region is a cylinder.

[0026] Step 103 : Use unstructured volume mesh to divide the computational domain, then use the surface reconstruction model to refine the mesh division, and perform mesh encryption processing on the complex flow area, thereby obtaining a complex flow encryption area.

[0027] Specifically, the unstructured grid adopts the cut volume grid.

[0028] In practical applications, a time-domain simulation is performed using CFD multiphase modeling methods, coupled six-degree-of-freedom motion equations, and the NS equations to solve the sloshing problem in the liquid tank of a gas-liquid separator. A physical model is set up, and the Navier-Stokes equations (NS equations) are used as the governing equations. In the Cartesian coordinate system, the equations are expressed as follows: Among them, u i 、u j are the velocity components in the three dimensions (i, j = 1, 2, 3); x i 、x j are the coordinate components in three dimensions (i, j = 1, 2, 3); t is time; ρ is fluid density; p is pressure; v is kinematic viscosity coefficient; f i is the body force component.

[0029] Step 104 , based on the geometric model of the gas-liquid separator, a detailed simulation is performed on the flow field of the liquid tank of the gas-liquid separator in the rolling state, and the water level change at each point is monitored to obtain the minimum safe water level position.

[0030] Specifically, we use the gas two-phase flow and free surface capture models, and establish a sloshing model of the gas-liquid separator tank based on the CFD method. We simulate the dynamic changes of the gas-liquid separator tank under sloshing conditions, monitor the water level history at different locations, and determine the minimum safe water level after comparison. For details, please refer to Figure 2 .

[0031] More specifically, the closed control equations of the turbulence model, the free surface tracking method, and the finite volume method are used to discretize the fluid control equations. The liquid tank flow field of the gas-liquid separator in the rolling state is simulated in detail based on the CFD method, and the water level changes at each point are monitored to obtain the minimum safe water level position. Among them, the sloshing process of the gas-liquid separator is numerically simulated by the CFD method, and the water level changes at different points are monitored to determine the minimum water level h. i =min(H i ).

[0032] Furthermore, the turbulence model can adopt the K-Epsilon two-layer model, the standard K-Epsilon two-layer model, the SSTK-Omega model or the standard K-Omega model; and in view of the fact that the liquid tank sloshing involves complex nonlinear phenomena such as gas-liquid mixing, the Euler multiphase flow model, VOF model and other models are adopted; and the finite volume method is used to discretize the fluid control equations, the central difference format is used to deal with the linear diffusion term, the second-order upwind format is used to deal with the nonlinear convection term, and the SIMPLE algorithm is used to solve it, so as to perform a detailed simulation of the liquid tank flow field of the gas-liquid separator in the rolling state.

[0033] Step 105 , obtaining corresponding relationships between different sloshing conditions and the minimum safe water level according to the position of the minimum safe water level, and designing safe water level conditions under different sloshing conditions according to the corresponding relationships.

[0034] Specifically, please refer to Table 2;

[0035] Table 2: Minimum safe water level corresponding to each working condition

[0036] Working conditions Minimum safe water levelhi Case 1 h1 Case 2 h2 Case 3 h3 Case 4 h4 Case 5 h5 Case 6 h6 Case 7 h7 Case 8 h8 Case 9 h9

[0037] In summary, the present invention first sets different sloshing operating conditions for the gas-liquid separator; then establishes a geometric model of the gas-liquid separator, and uses an unstructured body grid to divide the calculation domain; then uses a gas two-phase flow and free liquid surface capture model, and establishes a liquid tank sloshing model of the gas-liquid separator based on the CFD method, simulates the dynamic changes of the liquid tank of the gas-liquid separator under sloshing conditions, monitors the water level history at different positions, and determines the lowest water level position after comparison; finally, based on the lowest safe position, summarizes the correspondence between different sloshing conditions and the lowest position, and designs safe water level conditions under different sloshing conditions according to the correspondence; therefore, the method of the present invention can accurately evaluate the changes in the lowest safe liquid level caused by sloshing, ensure the normal operation of the gas-liquid separator, and improve the stability and safety of the system.

[0038] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any equivalent modifications or variations made by persons skilled in the art without departing from the spirit and technical concepts disclosed herein shall be encompassed by the claims of the present invention.

Claims

1. A safe working condition design method for an offshore gas-liquid separator, characterized in that: The following steps are involved: Determine different sloshing conditions related to gas-liquid separators; Establishing a geometric model of the gas-liquid separator, establishing a corresponding calculation domain for the geometric model of the gas-liquid separator, and determining a complex flow area; The flow field of the liquid tank of the gas-liquid separator in the rolling state is simulated in detail according to the geometric model of the gas-liquid separator, and the water level changes at each point are monitored to obtain the minimum safe water level position; The corresponding relationship between different sloshing conditions and the minimum safe water level is obtained according to the position of the minimum safe water level, and the safe water level conditions under different sloshing conditions are designed according to the corresponding relationship.

2. The safe operating condition design method for an offshore gas-liquid separator according to claim 1, characterized in that: The sloshing operating conditions include a sloshing period and a sloshing amplitude, and the sloshing amplitude and the sloshing period can be freely combined crosswise.

3. The method for designing safe operating conditions of an offshore gas-liquid separator according to claim 1, characterized in that: The geometric model of the gas-liquid separator is a cylindrical structure, and the shape of the complex flow area is a cylinder.

4. The method for designing safe operating conditions of an offshore gas-liquid separator according to claim 1, characterized in that: After establishing a geometric model of the gas-liquid separator, establishing a corresponding calculation domain for the geometric model of the gas-liquid separator, and determining a complex flow area, a detailed simulation of the liquid tank flow field of the gas-liquid separator in a rolling state is performed based on the geometric model of the gas-liquid separator, and before monitoring the water level changes at each point to determine the minimum safe water level position, the method further includes: The computational domain is divided using an unstructured body grid, the grid division is refined using a surface reconstruction model, and the complex flow region is subjected to grid encryption processing, thereby obtaining a complex flow encryption region.

5. The method for designing safe operating conditions of an offshore gas-liquid separator according to claim 1, characterized in that: The method of finely simulating the flow field of the liquid tank of the gas-liquid separator in the rolling state according to the geometric model of the gas-liquid separator and monitoring the water level changes at each point to obtain the minimum safe water level position includes: The closed control equations of the turbulence model, the free surface tracking method and the finite volume method are used to discretize the fluid control equations. The liquid tank flow field of the gas-liquid separator under the rolling state is simulated in detail based on the CFD method, and the water level changes at each point are monitored to obtain the minimum safe water level position.

6. The method for designing safe operating conditions of an offshore gas-liquid separator according to claim 5, characterized in that: The turbulence model may adopt a K-Epsilon two-layer model, a standard K-Epsilon two-layer model, an SST K-Omega model or a standard K-Omega model.

7. A safe operating condition design method for an offshore gas-liquid separator according to claim 6, characterized in that: Since tank sloshing involves complex nonlinear phenomena such as gas-liquid mixing, the Euler multiphase flow model, VOF model and other models are also used in the detailed simulation of the tank flow field of the gas-liquid separator in the rolling state.

8. The method for designing safe operating conditions of an offshore gas-liquid separator according to claim 5, characterized in that: The finite volume method is used to discretize the fluid control equations to perform a detailed simulation of the liquid tank flow field of the gas-liquid separator in the rolling state, and the water level changes at each point are monitored to obtain the minimum safe water level position, including: The finite volume method is used to discretize the fluid control equations, the central difference format is used to deal with the linear diffusion term, the second-order upwind format is used to deal with the nonlinear convection term, and the SIMPLE algorithm is used to solve the equations. The liquid tank flow field of the gas-liquid separator in the roll state is simulated in detail, and the water level changes at each point are monitored to obtain the minimum safe water level position.

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