Design method of floating oil collector and floating oil collector

Abstract

The invention discloses a design method of a floating oil collector and the floating oil collector, and the design method comprises the following steps: judging whether floating oil is a dispersed phase or a continuous phase, and judging the type of a flow state; determining the inner length and the inner height of the collector; analyzing internal flow field characteristics of the collector, performing numerical simulation, and establishing a numerical calculation model capable of describing the internal flow field characteristics of the collector; from the outlet separation efficiency, different inlet shapes are subjected to analog calculation, and the inlet shape of the collector is selected. The obtained floating oil collector comprises a collector inlet, a collector cavity and a collector outlet, the collector inlet is formed in one side of the collector cavity, the collector outlet is formed in the top of the collector cavity, the section of the collector inlet is a semicircular section or a rectangular section or a circular-groove-shaped section, and the collector cavity is of a streamline structure. According to the invention, the pressure distribution is effectively optimized, the emulsification risk is reduced, the dynamic separation efficiency and quality are improved, the stability and durability of equipment are enhanced, and the maintenance demand and the operation cost are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of floating oil recovery, in particular to a design method of a floating oil collector and the floating oil collector. Background Art

[0002] Marine oil spills, such as tanker leaks and offshore drilling accidents, seriously damage the marine ecology and coastal economy. At present, mechanical collection, chemical dispersion and biodegradation are common methods for oil spill treatment. Although these methods are widely used, with the increase in global fossil fuel development, it is particularly important to improve oil-water separation technology to deal with large areas or high-viscosity oil films on the sea surface, improve separation efficiency and reduce maintenance costs. Existing technologies have significant deficiencies in adaptability, separation efficiency, equipment cost and processing speed.

[0003] Current oil-water separation and recovery technologies for oil spills on the sea are often inefficient when faced with large-area or high-viscosity oil films, making it difficult to achieve rapid and thorough separation. In addition, the complexity of the equipment and its reliance on chemical treatment agents also increase operating costs and potential environmental risks. Summary of the invention

[0004] In order to overcome the above problems existing in the prior art, the present invention provides a design method of a floating oil collector and a floating oil collector.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a design method of a floating oil collector, comprising the following steps: Step 1, determining whether the oil spill is a dispersed phase or a continuous phase, and determining the type of flow state; Step 2, determining the inner length and inner height of the collector; Step 3, analyzing the flow field characteristics inside the collector, performing numerical simulation, and establishing a numerical calculation model that can describe the flow field characteristics inside the collector; Step 4, starting from the outlet separation efficiency, simulate and calculate different inlet shapes to select the collector inlet shape; the inlet shape includes a semicircular cross section, a rectangular cross section, and a circular groove cross section.

[0006] In the above-mentioned design method of a floating oil collector, the numerical simulation in step 3 includes: three-dimensional modeling of the fluid domain; discretization of the fluid domain; establishing a control equation; determining boundary conditions and initial conditions; establishing a discrete equation; solving control parameter settings; making a convergence judgment, if it meets the convergence, displaying and outputting the calculation results, if it does not meet the convergence, repeatedly solving the control parameter settings until it meets the convergence.

[0007] In the above-mentioned design method of a floating oil collector, the discrete processing of the fluid domain specifically includes: using three-dimensional software to establish a cylindrical oil-water separation outlet, performing network division, and using a local encryption method to perform grid refinement processing on the inlet, outlet and outlet wall.

[0008] In the above-mentioned design method of a floating oil collector, the numerical calculation model that can describe the internal flow field characteristics of the collector in step 3 is specifically: studying the influence of oil concentration on the internal flow field and separation performance of the outlet through the Mixture model; and numerically simulating the internal flow field of the collector through the RSM model.

[0009] In the above-mentioned design method for a floating oil collector, step 4 specifically includes: setting inlets of different shapes, and analyzing the velocity, pressure, oil phase distribution, and separation efficiency of the collectors with inlets of different shapes, and finding an inlet with a small velocity value and relatively stable flow in the sedimentation and stratification zone of the collector, a small pressure drop at the collector outlet, a strong oil discharge capacity of the collector, and a high separation efficiency of the collector as the inlet shape of the floating oil collector.

[0010] A floating oil collector, an oil floating collector obtained based on the above-mentioned design method of a floating oil collector, includes a collector inlet, a collector cavity, and a collector outlet, wherein the collector inlet is located on one side of the collector cavity, the collector outlet is located on the top of the collector cavity, the collector inlet cross-section is a semicircular cross-section or a rectangular cross-section or a circular groove cross-section, and the collector cavity has a streamlined structure.

[0011] The beneficial effect of the present invention is that the present invention effectively improves the dynamic separation efficiency: by adjusting the geometry and internal structure of the separator and optimizing the internal flow field, the hydraulic retention time is extended, and the oil-water separation efficiency during dynamic operation is significantly improved. Numerical simulation results show that the separator can more effectively handle changing flow rates and pressure conditions and achieve faster oil-water separation. This optimization is particularly suitable for responding to sudden large-scale oil spills and can quickly reduce environmental impacts.

[0012] The invention effectively optimizes pressure distribution and reduces emulsification risk: This patent optimizes the pressure distribution in the oil-water separator by precisely controlling the inlet shape and internal flow field design, significantly reducing the risk of emulsification caused by high shear force. The uniform pressure environment reduces turbulence and rapid movement, avoiding the occurrence of emulsification, especially when dealing with high-viscosity oils. This improvement not only improves the efficiency and quality of oil-water separation, but also enhances the stability and durability of the equipment, thereby reducing maintenance requirements and operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG1 is a top view of an oil floating collector of the present invention; Figure 2 is a side view of the oil floating collector of the present invention; Figure 3 Schematic diagram of the cross section of the inlet of the floating oil collector of the present invention; wherein (a) is a schematic diagram of a circular cross section, (b) is a schematic diagram of a rectangular cross section, and (c) is a schematic diagram of a circular groove cross section; Figure 4 It is the basic form of fluid movement inside the collector of the present invention; Figure 5 It is the basic step of numerical simulation of the present invention; Figure 6 It is a schematic diagram of the collector fluid domain model and grid division of the present invention; Figure 7 It is a cloud diagram of the velocity variation of the collector cross section under different inlet structures of the present invention; Figure 8 The collector outlet pressure drop and pressure drop utilization efficiency curves under different inlet structures of the present invention; Fig. 9 The oil phase distribution of the collector under different inlet structures of the present invention; Fig.10 The variation law of the collector separation efficiency with the inlet velocity under different inlet structures of the present invention; Fig.11 Schematic diagram of the planar oil spill closure area of ​​the present invention; Fig.12 It is a schematic diagram of the strip-shaped oil spill sealing area of ​​the present invention.

[0014] Among them, 1. Collector inlet, 2. Collector cavity, 3. Collector outlet DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0016] The present invention proposes a novel marine oil spill collector, which is specially designed for efficiently recovering oil spills from the sea surface. This device is particularly suitable for handling operations in the marine environment and can quickly and effectively handle widely distributed oil films. The structure of the oil spill collector is shown in Figure 1-2. The oil spill collector includes a collector inlet 1, a collector cavity 2, and a collector outlet 3. The collector inlet 1 is located on one side of the collector cavity 2, and the collector outlet 3 is located on the top of the collector cavity 2. The cross section of the collector inlet 1 is a circular interface or a rectangular cross section or a circular groove cross section (such as Figure 3 As shown in the figure), the collector cavity has a streamlined structure.

[0017] This embodiment also discloses a design method of the above-mentioned floating oil collector, and the specific steps are as follows: Step 1, determining whether the oil spill is a dispersed phase or a continuous phase, and determining the type of flow state; Step 2, determining the inner length and inner height of the collector; Step 3, analyzing the flow field characteristics inside the collector, performing numerical simulation, and establishing a numerical calculation model that can describe the flow field characteristics inside the collector; Step 4, starting from the outlet separation efficiency, simulate and calculate different inlet shapes to select the collector inlet shape; the inlet shape includes a semicircular cross section, a rectangular cross section, and a circular groove cross section.

[0018] 1.1 Determination of dispersed phase and continuous phase For the separation of oil and liquid phases, we must first know the dispersed phase and the continuous phase. Selker and Sleieher proposed a method to determine the dispersed phase and the continuous phase based on the θ value as follows: ; In the formula, Q L , Q H are the volume flow rates of the light phase and the heavy phase, m 3 / s;ρ L , ρ H They are the density of the light phase and the heavy phase, kg / m 3 ;μ L , μ H are the viscosities of the light phase and heavy phase, Pa·s, respectively. The choice of dispersed phase is related to the value of θ, see Table 1.1.

[0019] The operating conditions of the collector are: Q L =2.78×10 -5 m 3 / s;ρ L =880kg / m 3 ;μ L =80×10 -3 Pa·s;Q H =0.528×10 -3 m 3 / s;ρ H =1000kg / m 3 ;μ H =1×10 -3 Pa·s. Substituting θ=0.136<0.3 into the above formula, it can be seen from Table 1.1 that when θ<0.3, it indicates that the light phase is the dispersed phase, that is, the crude oil is the dispersed phase.

[0020] Table 1.1 Dispersed phase and θ value θ result <0.3 Light phase is dispersed phase 0.3~0.5 The light phase may be the dispersed phase 0.5~2.0 Both the light phase and the heavy phase may be dispersed phases, and the design is considered based on two situations 2.0~3.3 The heavy phase may be the dispersed phase >3.3 The heavy phase is the dispersed phase

[0021] 1.2 Flow state determination in the collector

[0022] When calculating the head loss, the type of flow state must be determined first. The average flow velocity of the flow section of the circular pipe when the flow state changes is called the critical flow velocity. The critical flow velocity V when the flow state changes from turbulent flow to laminar flow is c , called the lower critical velocity, the critical velocity V when the laminar flow state changes to the turbulent flow state c ', called the upper critical velocity. Experiments have shown that the lower critical velocity is inversely proportional to the pipe diameter d and directly proportional to the kinematic viscosity υ, as shown in the formula: ; Among them, the proportional factor Re c is a constant of dimension 1. After a series of experiments using values ​​of υ and d, it was found that Re c is almost a constant: Re c =2000; It shows that c , does not vary with fluid properties, pipe diameter or flow rate. c The value depends on the degree of external disturbance. Re is not a constant, but varies within the range of Re = 12000 ~ 40000. Theoretically, when laminar flow satisfies V > V c When the flow enters an unstable state, if the external disturbance is very weak, the laminar flow state can still be maintained. There are always some disturbances in the actual flow. The upper critical velocity V c ' has no practical meaning. In order to easily identify the flow state, Reynolds introduced dimensional parameters: ; is called the Reynolds number, and V = V c The Re value at this time is called the critical Reynolds number: ; After calculation, Re=15.279. By comparing Re and Re c The value of can be used to determine the flow state.

[0023] The flow state criterion commonly used in engineering design is: Laminar flow state: Re < Re c =2000; Turbulent flow regime: Re > Re c =2000; so it is a laminar flow state.

[0024] 2.1 Determine the inner length and inner height Assume height H = 0.3m flow rate Q = 1.5 m 3 / h =4.17×10 −4 m 3 / s, according to Stokes' law, the settling velocity of the oil droplet v s Calculation: ; Where, d L represents the oil droplet radius; ρ L , ρ H They are the density of the light phase and the heavy phase, kg / m 3 ;μ H is the viscosity of the heavy phase, Pa·s.

[0025] Substitute the known parameters: d L =1×10 −6 m、ρ L =880kg / m 3 , H =1000kg / m 3 , μ H =1×10 −3 Pa·s. Substitute v into the above formula s =2.615×10 −7 m / s.

[0026] In order to allow the oil droplets to settle in the collector, the flow rate of the oil-water mixture must be less than the settling velocity v s , and ensure that the flow rate Q can pass through the given collector size.

[0027] Assuming the height of the collector is H = 0.3 m, first calculate the cross-sectional area A, and then deduce the flow velocity v based on the flow rate Q.

[0028] The cross-sectional area A is calculated as follows: ; In the formula, W is the width and H is the height. Temporarily set the width W to 0.7m, which is a reasonable design width and can provide effective space for subsequent calculations. Substitute A=0.21m in the above formula 2 .

[0029] The relationship between flow rate Q and flow velocity v is as follows:

[0030] ; Known flow rate Q = 4.17 × 10 −4 m 3 / s and cross-sectional area A = 0.21m 2 Substituting into the above formula, v=1.98×10 −3 m / s, which is sufficient to ensure that the oil droplets can complete sedimentation.

[0031] The length L of the collector is determined by the flow velocity v, cross-sectional area A, and flow rate Q as follows: ; Substituting L≈1m into the above formula.

[0032] Step 3: Analyze the flow field characteristics inside the collector, perform numerical simulation, and establish a numerical calculation model that can describe the flow field characteristics inside the collector.

[0033] The collector is an important component of the sea surface oil-water separation system, and has the advantages of simple structure and strong overall volume processing capacity. The outlet sedimentation process is essentially a process in which the flow rate of the oil-water mixture is slowed down to increase the hydraulic retention time, so that the oil phase floats and achieves oil-water separation. This embodiment will qualitatively analyze the collector's working principle and internal flow field characteristics, and elaborate on the numerical simulation method used in this embodiment.

[0034] 3.1 Collector flow field The sea surface floating oil collector has low efficiency and small processing volume per unit time. In this embodiment, the outlet shape is improved by numerical simulation to improve the oil collection performance of the collector. The specific research contents are as follows.

[0035] Starting from the basic working principle, the oil-water sedimentation process is revealed, and the force on the oil droplets in the sedimentation field is specifically analyzed; the basic forms of fluid movement inside the collector are briefly introduced, and the pressure and velocity distribution laws of the sedimentation field, as well as the role of each component in the oil-water separation process are clarified; the outlet physical model is established through the Soildworks software, and the appropriate grid type is selected for grid division; the turbulence model and multiphase flow model used in previous literature simulations are summarized, and combined with the internal flow mechanism of the outlet, a mathematical model suitable for this study is established.

[0036] The collector is a device that uses the principle of gravity sedimentation to perform preliminary separation of oil-water two-phase mixed liquid. The separation process is as follows: the mixed liquid is fed from the inlet at a certain speed. When the mixed liquid enters the collector, the flow area increases, and the fluid velocity decreases due to the increase in the flow area, thereby extending the hydraulic retention time, so that the dispersed phase droplets in the mixed liquid float and initially stratify; the dispersed phase medium in the mixed liquid migrates to the upper side wall, and at the same time, under the action of the incoming flow, the heavy phase medium continues to move downward; the oil phase in the mixed liquid is finally discharged along the outlet under the action of the water pump; thus, the preliminary oil-water separation of the mixed liquid is achieved.

[0037] When analyzing the forces acting on the droplets in the collector, the forces acting on the droplets are generally investigated in the horizontal and vertical directions. The vertical force plays an important role in the floating separation of the oil phase. In the oil-water separation process, the dispersed phase droplets are mainly subjected to four forces: F f is the buoyancy of the oil drop, F g is the gravity on the oil drop, F σ is the surface tension of the oil drop, F v is the viscous resistance of the oil droplet.

[0038] According to the principle of force balance, the following force balance equation can be listed as follows: F f + F g + F σ + F v = 0 ; By definition, the buoyancy F f Equal to the weight of the water displaced by the oil drop, calculated using Archimedes' principle as follows: F f = ρ w Vg ; In the formula, ρ w is the density of water, V is the volume of water displaced by the oil droplet, and g is the acceleration due to gravity.

[0039] F g The force can be described by Newton's second law of motion of the oil droplet as follows: F g = ma ; In the formula, F g is the gravity on the oil drop, m is the mass of the oil drop, and a is the acceleration of the oil drop. When floating in water, the mass of the oil drop can be regarded as zero, so the above formula can be simplified as follows: F g = 0; Surface tension F σ It is equal to the tension at the contact point between the oil droplet surface and the water surface, which can be calculated using the Young-Luel law as follows: F σ = 2πrγ ; Where r is the radius of the oil droplet and γ is the surface tension coefficient of the oil-water interface.

[0040] Viscous resistance F v It is related to the movement speed of the oil droplets, the relative speed between the oil droplets and water, the viscosity between the oil droplets and water, etc., as shown in the formula: F v = 6πηrv ; Where η is the viscosity of water, r is the radius of the oil droplet, and v is the velocity of the oil droplet in water.

[0041] It can be seen from the above formula that when other conditions are the same, the oil droplet floats v o The buoyancy F of the oil droplet in the flow field f Proportional to F f The larger it is, the faster the oil droplets float, and the more conducive it is for the oil droplets to migrate to the center.

[0042] When the outlet reaches a stable operating state, the fluid inside the outlet moves in laminar flow, such as Figure 4As shown. Most of the medium in the top area is dispersed phase oil, and the oil droplets migrate from the collection chamber to the top and are finally discharged from the outlet. Due to the limited extraction capacity of the outlet, part of the fluid that is not discharged by overflow moves in an up and down circulation flow between the collection chamber and the wall. In addition to the above fluid forms, there is also the so-called short-circuit flow, which means that after part of the fluid enters the collection chamber from the inlet, it first flows along the surface of the outlet top cover into the collector, then moves along the upper wall of the collection chamber to the outlet, and finally is directly discharged from the outlet. Since the short-circuit fluid has not been separated, it will directly affect the separation performance of the collector.

[0043] (1) Velocity distribution The velocity field of the fluid in the collector is mainly the internal oil drop floating field. The velocity of the oil drop floating field inside the collector can be divided into horizontal velocity v0 and vertical velocity v1; mastering the velocity distribution of the flow field inside the collector is not only helpful in describing the fluid motion, but also can make a reasonable prediction of the separation efficiency of the collector in theory.

[0044] When an oil-water mixture with an oil content of 5% is passed into the sedimentation device, the floating speed of the oil droplets in the sedimentation field can be calculated by Stokes' law. According to Stokes' law, the viscous resistance of the oil droplets in the diluted fluid medium is proportional to its speed, as shown in the formula: F v = 6πηrv ; In the formula, F v is the viscous resistance of the oil drop; η is the viscosity of the fluid medium; r is the radius of the oil drop; v is the velocity of the oil drop.

[0045] When an oil droplet floats in water, it is also necessary to consider factors such as buoyancy, gravity, and surface tension. When calculating the velocity of the oil droplet, these factors need to be taken into account to establish the corresponding motion equation.

[0046] Assuming that the initial velocity of the oil droplet is v0, the floating velocity of the dispersed phase generally conforms to the Sotkes formula: ; In the formula, v represents the floating velocity of the oil droplet; g represents the acceleration due to gravity; d L =1×10 -6 m represents the radius of the oil droplet; ρ L Indicates the density of oil; ρ H Indicates the density of water; μ L Indicates the viscosity of the fluid.

[0047] Substituting into the above formula, we can find v=1.5×10 -2 m / s.

[0048] As far as the above two component speeds play their roles in the oil-water separation process, the floating speed is the most important speed.

[0049] Separation efficiency is an important parameter for evaluating the separation performance of the collector, and is usually used to characterize the degree of perfection of the oil-water separation process in the collector. According to different calculation methods, the outlet separation efficiency can be divided into three types: mass efficiency, simplified efficiency and comprehensive efficiency. The comprehensive efficiency is determined by the simplified efficiency, inlet oil concentration and split ratio.

[0050] Mass efficiency is defined as the ratio of the mass flow rate of the dispersed phase at the outlet to the mass flow rate of the dispersed phase at the feed inlet. It is usually applied to the solid-liquid separation outlet, but is rarely used in the liquid-liquid separation outlet. Its calculation is as follows: ; Where η m is quality efficiency; M o is the mass flow rate of the dispersed phase at the outlet, kg / s; M is the mass flow rate of the dispersed phase at the feed inlet, kg / s.

[0051] Assuming that the effect of split ratio on the separation process is ignored, simplified efficiency is generally used to measure the oil-water separation effect in the outlet, and its calculation is as follows: ; Where η i To simplify efficiency; C is the oil concentration at the outlet feed, mg / L; C u is the oil concentration at the outlet underflow, mg / L; this formula can better express the actual oil-water separation effect in the outlet. The efficiencies mentioned in this embodiment when analyzing the oil-water separation outlet performance are all simplified efficiencies.

[0052] 3.2 Export numerical simulation Computational Fluid Dynamics (CFD) is a multi-disciplinary interdisciplinary subject that has rapidly emerged with the development of computer technology and numerical theory. Its principle is to use numerical calculation methods to discretely solve the flow field control equations, so as to achieve the purpose of studying the laws of fluid motion. The basic steps of numerical simulation research on oil-water separation outlet are as follows: Figure 5 shown.

[0053] When performing numerical simulation, the quality of fluid domain discretization directly affects the accuracy of equation solution. Boundary conditions and initial conditions are necessary to ensure that the control equation has a unique solution, which is often obtained by calculating and measuring the geometric model. In addition, a suitable mathematical model must be established for the motion morphology of the flow field in the collector to solve the equation, and the convergence of the calculation results must be determined based on the residual. Finally, the mass flow rate entering the collector is observed to verify its correctness.

[0054] Meshing is an important method for discretizing the control equations in the fluid domain and an indispensable step in numerical simulation. The quality of the mesh directly determines the solution speed and simulation accuracy of CFD calculations.

[0055] This embodiment chooses to use a hexahedral structured grid to divide the outlet fluid domain. On the one hand, structured grids have the advantages of high computational efficiency, good regional fitting and fast generation speed compared to unstructured grids; on the other hand, hexahedral grids are significantly superior to other types of volume grids in terms of deformation characteristics, computational accuracy, storage space and anti-distortion degree. The specific meshing process is as follows: First, use Solidworks 3D software to establish a classic double-conical oil-water separation outlet; then, import it into the ICEM submodule of ANSYS software for meshing; finally, use local encryption methods to refine the mesh of key locations such as the inlet, outlet and outlet wall to maximize the quality of meshing and better capture boundary features. The fluid domain model and mesh generation effect are shown below. Figure 6 shown.

[0056] 3.3 Selection of numerical calculation model (1) Multiphase flow model

[0057] The inside of the collector is a simple oil-water two-phase turbulent motion, in which water is the main continuous phase and the oil to be separated is the dispersed phase. The Mixture model uses shared momentum and continuity equations and uses the interphase slip velocity to describe the motion of the dispersed phase. It has the characteristics of small calculation amount and strong calculation stability. It is suitable for widely distributed dispersed phases and situations where the interphase drag is unclear. This example selects the Mixture model to study the influence of oil concentration on the internal flow field and separation performance of the outlet.

[0058] The control equations of the Mixture model are as follows: The continuity equation is as follows: ; In the formula, u m is the average velocity of the mixed liquid mass, m / s.

[0059] ; In the formula, ρ m is the density of the mixed liquid, kg / m 3 .

[0060]

[0061] In the formula, α k is the volume fraction of the kth phase; u k is the kth phase velocity vector, m / s; ρ k is the kth phase density, kg / m3 .

[0062] The momentum equation is as follows: ; In the formula, μ m is the viscosity of the mixed liquid, pa·s; F is the volume force of the external force, N; n is the number of phases in the mixed liquid; u dr,k is the kth phase drift velocity, m / s; μ m 、u dr,k Calculation: ; ; In the formula, μ k is the kth phase viscosity, mPa·s.

[0063] (2) Turbulence model

[0064] The fluid movement inside the collector is relatively simple and belongs to laminar flow. Accurately describing the turbulent motion process is the core issue of CFD simulation of the internal flow field at the outlet, so choosing a suitable turbulence model is the key to numerical simulation research. The RSM model does not rely on the eddy viscosity assumption, but directly uses the Reynolds stress transport equation to solve the Reynolds stress. This model not only takes into account the convection and diffusion effects of Reynolds stress, but also automatically adjusts the generation terms and convection terms according to the degree of streamline bending and rotation. Therefore, it is more powerful in turbulence simulation capabilities. Based on the above analysis, this embodiment selects the RSM model to conduct a numerical simulation study on the internal flow field of the collector. The Reynolds stress transport equation is as follows: ; In the formula, the two terms on the left are the stress change rate with time and the convection term C. ij ; The seven items on the right are turbulent diffusion items D T，ij , shear stress generating term P ij 、System generated item F ij , buoyancy generation term G ij , viscous dissipation term ε ij , molecular viscosity term D L，ij 、Pressure generation term φ ij , Custom ItemS User-Defined .

[0065] Step 4: Based on the outlet separation efficiency, simulate and calculate different inlet shapes and select the collector inlet shape.

[0066] Three collectors with the same flow area but different inlet shapes were taken as the research objects. The influence of inlet shape on the inner cavity flow velocity, outlet pressure, oil phase distribution and separation efficiency was simulated with the help of Fluent software. Starting from the outlet separation efficiency, different structures were simulated and calculated with the help of Fluent software, and the appropriate inlet shape was selected according to the simulation results.

[0067] From the working principle of the collector, it can be known that the inlet section plays a role in collecting and guiding the floating oil. Since the inlet shape directly affects the collection of floating oil and the flow speed of floating oil inside the collector, the pressure and the oil phase distribution, and ultimately affects the gravity sedimentation separation efficiency of the collector mixed liquid, it is necessary to reasonably design the inlet structure of the collection device to further improve the separation performance of the collector. In this regard, this embodiment takes a semicircular floating oil collection device with a semicircular inlet length L=100CM and a semicircular inlet height H=30CM as a benchmark, and obtains two sets of new inlet collection devices by changing the inlet shape. Its inlet structure is as follows: Figure 3 shown.

[0068] During the inlet setting process, the inlet shape is changed while ensuring that the inlet flow area remains unchanged. Figure 3 The middle (a) adopts a semicircular inlet type (Type A); Figure 3 The middle (b) adopts a rectangular cross-section type (type B); Figure 3 The middle (c) adopts a circular groove cross-section type (type C).

[0069] In order to make the inlet structure shape the only research variable, the basic structure of the collection device adopts the same geometric dimensions. Among them, the origin O is located at the center of the bottom surface of the outlet cylinder, the central axis of the outlet cylinder is the y-axis, and the flow direction of the mixed liquid in the collector is the x-axis. In order to facilitate the study of the influence of the inlet structure change on the internal flow field of the collector, the x=0 section is selected as the characteristic section for velocity flow field analysis, the radial sections at different heights of the collector outlet are selected as the characteristic sections for pressure field analysis, and the z=0 section is selected as the characteristic section for oil phase distribution analysis.

[0070] The simulated medium is an oil-water mixture with an oil concentration of 5%, and the density of the continuous phase water is 998 kg / m 3 , dynamic viscosity is 1mPa·s, and the dispersed phase oil density is 850 kg / m 3 , the dynamic viscosity is 8 mPa·s. Most of the oil droplets in the sea oil are distributed in the range of 10 μm to 90 μm, and the average particle size of the oil droplets in this embodiment is set to 50 μm.

[0071] The inlet of the collection device is set as "velocity inlet", and the mixed liquid enters the collection chamber along the normal direction of the inlet section at a velocity flow rate of 0.4m / s-1.1m / s; the top outlet is set as "free outlet". The pressure-velocity coupling equation is solved using the SIMPLE algorithm, and the pressure interpolation method uses the PRESTO format. At the same time, the wall boundary is set to be non-slip and non-leakage.

[0072] Velocity analysis of the fluid inside the collector with different inlet shapes. Prolonging the hydraulic retention time of the unit volume of mixed liquid is an important goal for the continuous optimization of the performance of the collection device. It is not only the key basis for calculating the efficiency of the collection device, but also an important indicator for evaluating the performance of different inlet shapes. However, a larger unit time processing volume is another important goal for the optimization of the performance of the collection device. We should avoid blindly pursuing the extension of the unit volume of mixed liquid hydraulic retention time, which will significantly reduce the unit time processing volume.

[0073] Vertical speed v y It is related to the hydraulic retention time of the fluid in the collector. Figure 7 The velocity variation cloud diagram of the x=0 section of the collecting device under different inlet structures is shown. It can be seen from the figure that the vertical velocity v y The outlet is symmetrically distributed along the central axis, and the velocity at the outlet is significantly higher than the flow velocity inside the collector. Among them, the area near the outlet of the collector is the oil discharge area, where the fluid is mostly oil-rich liquid, and its vertical velocity increases rapidly along the y-axis upward, reaching the maximum value at the outlet; the area corresponding to the lower part of the collector is the sedimentation and stratification area, where the fluid is mostly water phase, and its vertical velocity is relatively small. The vertical velocity value follows the distribution law of "high outlet and low bottom", indicating that the oil-water mixture in the lower cavity has more residence time for sedimentation and separation, and the oil core in the outlet oil discharge area can also overflow and discharge quickly, thereby maintaining a high collection efficiency of the collector.

[0074] from Figure 7 It can be seen that the velocity value of the settling stratification zone of the A-type collector is large and the flow is unstable, which is easy to produce strong disturbances, causing the mixed liquid to be stirred, thus affecting the oil-water separation effect. In contrast, the velocity value of the settling stratification zone of the B-type and C-type collectors is small, the flow is relatively stable, and the flow velocity of the C-type collector is the smallest. Therefore, when considering the hydraulic retention time factor alone, the performance of the C-type collector is better.

[0075] The pressure analysis of the internal fluid of the collector with different inlet shapes is carried out. In the oil-water mixture, there is an obvious interface between the two liquids, oil and water. This is because the surface tension between oil and water in the oil-water mixture is very high, making it difficult for them to mix with each other. When the oil-water mixture flows or is subjected to pressure, the shear force between the liquids will reduce the surface tension between oil and water, and the interface between oil and water will be disturbed and deformed, resulting in the occurrence of emulsification, allowing the molecules between oil and water to diffuse with each other, and eventually causing the oil and water to be broken up into tiny droplets and dispersed in the mixture, affecting the oil-water sedimentation separation effect, so reducing the pressure per unit volume of the mixed liquid is also an important goal of the collection performance.

[0076] from Figure 8 It can be seen that the outlet pressures of the A, B, and C type collection devices show a decreasing trend in turn. It is worth noting that the pressure of type A is about 68% higher than that of type C, while the pressure of type B is only slightly higher than that of type C. Under the premise that the overall oil-water separation capacity of the collection device is the same, the C-type inlet collector can reduce the occurrence of oil phase emulsification reaction caused by pressure, which is one of the goals pursued by the collector performance optimization.

[0077] In addition, at the same inlet velocity, the oil phase distribution of the three collectors A, B, and C is as follows: Fig. 9 As shown in the figure, the oil content near the outlet of the three collectors is higher and the oil content at the bottom is lower. Among them, the oil content of type A collector is the highest, and the oil content near the outlet of type C collector is the lowest. The oil discharge capacity of the collectors is C>B>A. The reason is that the transition of type C collector is smooth at the inlet, and the mixed liquid flows smoothly, which increases the floating speed of the oil phase droplets, thereby achieving rapid separation of oil and water. A reasonable inlet type should be comprehensively balanced between separation efficiency and overall energy consumption, so it is most appropriate to choose the inlet type of type C collector.

[0078] Separation efficiency is an important indicator for evaluating the separation effect of the collector, and the inlet shape is an important factor affecting the separation efficiency. In order to reasonably adjust the inlet shape to obtain a higher separation efficiency, a study on the effect of the collector inlet shape on the separation efficiency was carried out. The variation of the oil phase distribution and separation efficiency of the collectors with different inlet shapes with the inlet velocity is shown in the figure. Fig.10 shown.

[0079] like Fig.10As shown in the figure, the separation efficiency of all inlet type collectors shows a trend of first increasing and then decreasing as the flow rate of the mixed liquid increases. This is because the inlet velocity directly affects the horizontal velocity of the fluid after entering the inner cavity of the collector. When the inlet velocity increases, the horizontal velocity increases, which is conducive to the migration of the oil phase to the center of the collector. But this does not mean that increasing the inlet velocity is always beneficial to oil-water separation. On the one hand, when the inlet velocity reaches a certain value, the oil droplets will be subjected to greater stress and broken into smaller particle size oil droplets, which accelerates the emulsification of the oil phase and affects the oil-water sedimentation separation effect; on the other hand, the increase in the inlet velocity shortens the hydraulic retention time of the mixed liquid in the collector. If the retention time is greatly shortened, some oil droplets will not have time to float and will be carried away by the newly entered fluid, resulting in a decrease in the separation efficiency of the collector.

[0080] Based on the oil recovery device disclosed in this embodiment, the operation mode of the oil recovery device is as follows: the pollution cleaning ship should try to choose an area with less wind and waves to operate to ensure the safe use of the equipment. Once the ship sails to the designated area and confirms that the sea surface is relatively calm, the crew begins to prepare for the deployment of the oil boom.

[0081] When the ship reaches the center of the sea, the oil spill spreads from a point to a surface, and the impact area increases. At this time, the pollution-cleaning ship begins to lower the oil boom. The oil boom is lowered to the water surface through the ship's landing device, and the tugboat immediately moves it forward and pulls it, with the two ends of the oil boom fixed between the pollution-cleaning ship and the tugboat. As the ship moves forward, the oil boom gradually surrounds the oil spill area, narrowing the scope of the oil spill and forming a closed area.

[0082] When the boom is deployed and effectively surrounds the oil spill area, the oil-cleaning ship starts the recovery device. The collector is slowly lowered into the sea, and the oil-water mixture is guided into the collector through the optimized inlet. The collector inlet is carefully designed to ensure the efficient inflow of the oil-water mixture and prevent oil spills.

[0083] During this process, the water pump on the pollution-cleaning ship starts and sucks the oil-water mixture into the collector through the pipeline. The oil-water mixture undergoes preliminary separation through the optimized flow field design inside the collector. The oil-water mixture forms a two-phase flow in the collector, and the oil and water are separated by gravity. The oil layer floats on the water surface, and the water pump continues to work to suck the oil layer out from the top of the collector. At the same time, the separated oil is extracted and transported to the oil storage system on the ship for storage.

[0084] In order to ensure the recovery efficiency, the role of the oil boom is to continuously reduce the area of ​​the oil spill, so as to ensure the appropriate thickness of the oil film and improve the working efficiency of the recovery device. The oil-water separation operation in the collector continues in this process until all the oil-water mixture in the entire oil spill area is collected and processed.

[0085] While the oil and water are being separated, the vessel must continue to move. Each time the recovery device has processed a portion of the oil-water mixture, the boom should be adjusted according to the situation. The vessel keeps the boom in line with the oil spill area to ensure that the thickness of the oil film remains at an appropriate level throughout the recovery process. This operation requires the crew to flexibly adjust the movement and position of the boom based on real-time monitoring data.

[0086] When the recovery work in the oily area is completed, the cleaning vessel turns off the pump and lifts the collector back to the ship. At this time, the crew will carry out necessary equipment cleaning and maintenance work. The collector is cleaned to remove residual oil and ensure the normal operation of the equipment in the next operation.

[0087] The recovered oil in the oil storage system needs to be checked and processed regularly to ensure that the recovered oil can be properly stored or subsequently disposed of. Other equipment on the pollution removal vessel also needs routine inspection and maintenance to ensure the efficiency and safety of the equipment.

[0088] When the oil spill cleanup ship arrives at the oil spill area late, the oil spill usually spreads in a linear manner, which greatly increases the difficulty of containment operations. Fig.12 The oil boom is recovered in the manner shown in the figure, by using two tugboats to tow the longer booms to form a U-shaped structure, thereby surrounding the oil spill area. At this time, the shape of the boom can avoid the failure of the boom due to the tugboat's excessive speed, ensuring that the boom is always stable and can effectively contain the oil spill area.

[0089] Once the oil is gathered, the boom driven by the left tugboat docks with the fixed position of the oil-cleaning boat, ensuring that the boom and the oil-cleaning boat always remain in the same position in the oil spill area. In this way, the oil that was originally diffused in a linear manner is gathered into a surface oil film, which is convenient for subsequent recovery operations.

[0090] During the gathering process, the speed of the two tugboats must be consistent to avoid unstable boom shapes due to uneven speeds. The speed of the tugboats must be precisely controlled to ensure that the booms are always deployed on the sea surface in the predetermined shape, thus forming an effective closed area. During this process, the movement speed of the booms is closely related to the spread speed of the oil pollution on the sea surface, and must be adjusted according to the actual situation to prevent further spread of the oil pollution.

[0091] The accumulated oil spill area will be Fig.11 The oil spill recovery process shown in the figure is used for recovery. The pollution cleaning vessel should keep moving steadily to ensure that the oil boom is synchronized with the oil spill area to avoid oil spill leakage caused by inconsistent ship speed. During this process, the recovery device continues to work, guiding the oil-water mixture into the collector through the optimized inlet for separation. The separated oil is extracted by a water pump and transported to the oil storage system.

[0092] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A design method for a floating oil collector, characterized in that: The steps include: Step 1, determining whether the oil spill is a dispersed phase or a continuous phase, and determining the type of flow state; Step 2, determining the inner length and inner height of the collector; Step 3, analyzing the flow field characteristics inside the collector, performing numerical simulation, and establishing a numerical calculation model that can describe the flow field characteristics inside the collector; Step 4, starting from the outlet separation efficiency, simulate and calculate different inlet shapes to select the collector inlet shape; the inlet shape includes a semicircular cross section, a rectangular cross section, and a circular groove cross section.

2. The design method of a floating oil collector according to claim 1, characterized in that: The numerical simulation in step 3 includes: three-dimensional modeling of the fluid domain; discretization of the fluid domain; establishing control equations; determining boundary conditions and initial conditions; establishing discrete equations; solving control parameter settings; making convergence judgments, and if the convergence is met, displaying and outputting the calculation results; if the convergence is not met, repeatedly solving the control parameter settings until the convergence is met.

3. The design method of a floating oil collector according to claim 2, characterized in that: The discrete processing of the fluid domain specifically includes: using three-dimensional software to establish a cylindrical oil-water separation outlet, performing network division, and using a local encryption method to perform grid refinement processing on the inlet, outlet and outlet wall.

4. The design method of a floating oil collector according to claim 1, characterized in that: The numerical calculation model that can describe the characteristics of the internal flow field of the collector in step 3 is specifically: using the Mixture model to study the influence of the oil concentration on the internal flow field and separation performance of the outlet; and using the RSM model to numerically simulate the internal flow field of the collector.

5. The design method of a floating oil collector according to claim 1, characterized in that: The step 4 specifically includes: setting inlets of different shapes, and analyzing the velocity, pressure, oil phase distribution, and separation efficiency of collectors with inlets of different shapes, and finding an inlet with a small velocity value and relatively stable flow in the sedimentation and stratification zone of the collector, a small pressure drop at the outlet of the collector, a strong oil discharge capacity of the collector, and a high separation efficiency of the collector as the inlet shape of the floating oil collector.

6. A floating oil collector, characterized in that: The oil float collector obtained by the design method of an oil float collector according to any one of claims 1 to 6 comprises a collector inlet, a collector cavity, and a collector outlet, wherein the collector inlet is located on one side of the collector cavity, the collector outlet is located on the top of the collector cavity, the collector inlet cross-section is a semicircular cross-section, a rectangular cross-section, or a circular groove cross-section, and the collector cavity has a streamlined structure.

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