Rifled inner nozzle used in gravity gas-liquid separator and its design method

Abstract

The present invention discloses an inner nozzle with rifling applied to a gravity gas-liquid separator and a design method thereof, and belongs to the field of petrochemical equipment. Aiming at the problem that the central inner nozzle of the existing gravity gas-liquid separator is prone to airflow swing and deviation, the present invention designs spiral rifling in all or part of the pipe sections of the inner nozzle. The inner nozzle with rifling can guide and optimize the direction of the airflow, so that the main body of the airflow leaving the inner nozzle can flow downward quickly and stably until it hits the liquid surface, making full use of the space of the gravity gas-liquid separator, producing a better gas-liquid separation effect, and further reducing gas-liquid entrainment. The present invention further proposes a design method for the inner nozzle, taking the target value F as the design target, and designing the inner nozzle through a numerical simulation method. This method can greatly simplify the design steps of the inner nozzle and intuitively display the design effect.

Description

Technical Field

[0001] The invention belongs to the field of petrochemical industry, and in particular relates to an inner nozzle with rifling applied to a gravity gas-liquid separator and a design method thereof. Background Art

[0002] The gravity gas-liquid separator in the existing petrochemical plant has the following appearance and structure: Figure 1 , because the structure of the internal nozzle at the mixed gas inlet does not match the flow rate, it is easy to form a bias flow in the central nozzle of the gravity gas-liquid separator. When the biased gas enters the main space, it is easy to form an extreme bias flow, which then evolves into complex situations such as air flow swing, causing fatigue and vibration of the internal nozzle of the gravity gas-liquid separator, shortening the service life of the internal nozzle, and resulting in poor gas-liquid separation effect of the gravity gas-liquid separator. Among them, Figure 1 The basic working conditions are: the center nozzle velocity inlet is 20-35m / s; the pressure inside the device is 20-30MPa absolute pressure; the gas phase density is 240-350kg / m 3 ; gas phase viscosity is 1×10 -5 -5×10 -5 kg / (m·s); the liquid level at the bottom is normally maintained at 0.6-1.3m.

[0003] Finite element analysis is used to intuitively show the flow state of gas deviation and swing. Figure 2 Gas velocity vector distribution diagram of the inner nozzle.

[0004] from Figure 2 It can be seen from the gas velocity vector distribution diagram of the inner nozzle that the airflow inside the gravity gas-liquid separator under the original design structure is obviously uneven and unstable, which will inevitably cause corresponding uneven force and vibration problems on the inner nozzle. Summary of the invention

[0005] In order to solve the problems in the prior art, the present invention proposes a rifled inner nozzle applied to a gravity gas-liquid separator and a design method thereof. The rifled inner nozzle of the present invention can guide and optimize the direction of the airflow, so that the main body of the airflow leaving the inner nozzle can flow downward quickly and stably until it hits the liquid surface, making full use of the space of the gravity gas-liquid separator, producing a better gas-liquid separation effect, and further reducing gas-liquid entrainment.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention first provides a rifled inner nozzle for use in a gravity gas-liquid separator, wherein the inner nozzle includes a plurality of pipe sections and a plurality of expanded bell mouths along the axial direction; spiral rifling is designed in all or part of the pipe sections, the spiral rifling twist angle range is 3-30°, and the number of spiral rifling is 1 to 20. The twist angle is a well-known concept in the art, and is defined as: after the rifling is unfolded, the angle between the tangent line at a certain point on the rifling and the inner bore axis is called the twist angle of the point, and the twist angle is also the helical angle of the rifling.

[0008] The present invention also discloses a method for optimizing the gas flow state of a gravity gas-liquid separator by using the rifled inner nozzle, which comprises the following steps:

[0009] S1. According to the size of the gravity gas-liquid separator to be optimized, the basic design parameters of the rifled inner nozzle are selected; the basic design parameters include the length of the rifled inner nozzle penetrating into the interior of the cylinder, the angle of the expanded bell mouth cone, and the outer diameter of the outlet end of the rifled inner nozzle;

[0010] S2. According to the basic design parameters selected in S1, a geometric model of the internal nozzle with rifling is constructed; the airflow parameters of the gravity gas-liquid separator during actual operation are used as known parameters, and the number of rifling and the twist angle of the internal nozzle with rifling are used as optimization parameters for numerical simulation; during the numerical simulation, the internal nozzle outlet section is selected as the analysis section, and the position, velocity value and corresponding area value of each point on the section and the center origin are extracted; the target value F is calculated by the following formula,

[0011]

[0012] Among them, n is the number of points in the analysis section, x0 and y0 are the horizontal and vertical coordinates of the center origin, and x i ,y i is the horizontal and vertical coordinates of point i in the analysis section, u i 、s i are the velocity scalar and area of ​​point i, s 总 is the total area of ​​the analyzed section;

[0013] S3. Select the rifling inner nozzle scheme with a target value F less than the set threshold as the inner nozzle design scheme of the gravity gas-liquid separator.

[0014] By assembling the designed rifled inner nozzle into the gravity gas-liquid separator to be optimized, the airflow state of the gravity gas-liquid separator during actual operation can be optimized.

[0015] The numerical simulation process of the present invention can be performed in any numerical simulation software known in the industry. During the numerical simulation process, the geometric model of the inner nozzle is imported into the numerical simulation software, the rifling type (positive rifling or negative rifling), rifling height or depth, cross-sectional shape, number of rifling and twist angle are selected, and the airflow parameters of the actual working of the gas-liquid separator are input, so that the flow state and flow parameters of the airflow inside the entire inner nozzle and the gravity gas-liquid separator can be obtained.

[0016] As an optional solution of the present invention, S1 is specifically as follows: the length of the inner nozzle penetrating into the cylinder is 20% to 55% of the internal height of the gravity gas-liquid separator cylinder, the angle of the expanded bell mouth cone is 4° to 35°, and the ratio of the outer diameter of the inner nozzle outlet end to the inner diameter of the gravity gas-liquid separator cylinder is 0.15 to 0.4.

[0017] As an optional solution of the present invention, the air flow parameters of the gravity gas-liquid separator in S2 during actual operation include air intake velocity, gas viscosity, gas density, gas mass fraction, and gas temperature.

[0018] According to a preferred solution of the present invention, a solution with the smallest target value F is selected as the design solution for the inner nozzle of the gravity gas-liquid separator; a smallest target value F generally indicates smaller airflow swing.

[0019] Compared with the prior art, the present invention designs spiral rifling in the inner nozzle so that the outer part of the main body of the airflow passing through rotates circumferentially under the action of the rifling structure, generating a certain centrifugal force, so that when the airflow enters the bell mouth of the inner nozzle, it can quickly fill the bell mouth under the action of centrifugal force, thereby suppressing the small airflow vortex that may be generated in the bell mouth. This design can make full use of the space of the bell mouth, slow down the main body of the airflow, and maintain the speed direction of the main body of the airflow unchanged. When the main body of the airflow has enough kinetic energy at the same time and enters the internal space of the lower gravity gas-liquid separator vertically downward, the airflow itself can be quickly stabilized while suppressing the formation of gas deviation, reducing the influence of airflow swing on the device, while improving the gas-liquid separation effect, and better realizing the function of the gas-liquid separator. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the existing internal nozzle appearance structure type;

[0021] Figure 2 The gas velocity vector distribution diagram of the existing nozzle, blue 0-2.5m / s, green 2.5-5m / s, yellow 5-7.5m / s, red 7.5-10m / s;

[0022] Figure 3 It is a schematic diagram of the rifled inner nozzle on the gravity gas-liquid separator of the present invention;

[0023] Figure 4 is the cross-sectional velocity distribution diagram;

[0024] Figure 5 It is a schematic diagram of a rifled inner nozzle of the present invention;

[0025] Figure 6 It is the velocity vector diagram under different designs;

[0026] Figure 7 This is a cross-sectional view of the inner nozzle with rifling;

[0027] Figure 8 It is the velocity streamline distribution diagram. DETAILED DESCRIPTION

[0028] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[0029] Figure 3 The figure shows the external structure of the gravity gas-liquid separator with the inner nozzle structure with rifling. The inner nozzle of the present invention includes a plurality of pipe sections and a plurality of expanded bell mouths along the axial direction. Spiral rifling is designed in all or part of the pipe sections. The spiral rifling angle ranges from 3 to 30 degrees, and the number of spiral rifling is 1 to 20. Further preferably, the spiral rifling angle ranges from 3 to 15 degrees, and the number of spiral rifling is 4 to 15. According to the test, within this range, the inner nozzle with rifling can usually be applied to airflows of various different working conditions, and has the effect of improving the deviation flow.

[0030] The spiral rifling of the present invention can be positive rifling or negative rifling; when designed, the rifling depth of the negative rifling does not exceed one-half of the wall thickness of the tube segment, and the rifling height of the positive rifling does not exceed one-half of the inner diameter of the tube segment. The cross-sectional shape of the spiral rifling can be circular, elliptical, triangular or rectangular. The type, depth and height of the spiral rifling, and the cross-sectional shape can all be pre-selected according to actual needs. The present invention has found that the number of rifling and the twist angle are the main parameters affecting the airflow state. Therefore, in the present invention, the type, depth, height and cross-sectional shape of the spiral rifling are usually selected before numerical simulation. These parameters are usually not used as optimization parameters in the numerical simulation process in the present invention.

[0031] Figure 5 and Figure 7An internal nozzle structure in an embodiment of the present invention is illustrated, which includes three pipe sections and an expanded diameter bell mouth, the expanded diameter bell mouth is located at the last stage in the airflow direction, and spiral rifling is designed in the second and third stage pipe sections. It should be noted that the present invention is not limited to the internal nozzle structure illustrated in this embodiment; the number and position distribution of the pipe sections and the expanded diameter bell mouth can be arbitrary. Preferably, each pipe section is an equal diameter pipe, and when two adjacent pipe sections are designed with spiral rifling, the winding angle, number of spiral rifling and cross-sectional shape of the spiral rifling are equal, and the spiral rifling corresponding to the adjacent pipe sections are connected.

[0032] The present invention optimizes the gas flow state of the gravity gas-liquid separator by designing an inner nozzle with rifling. After the inner nozzle design is completed, the designed inner nozzle with rifling is assembled into the gravity gas-liquid separator to be optimized, thereby optimizing the gas flow state of the gravity gas-liquid separator during actual operation.

[0033] This embodiment provides a design scheme of a rifled inner nozzle:

[0034] First, according to the size of the gravity gas-liquid separator, the basic design parameters of the rifled inner nozzle are selected, including the length of the rifled inner nozzle penetrating into the cylinder, the angle of the expanded bell mouth cone, and the outer diameter of the outlet end of the rifled inner nozzle; wherein, the length of the inner nozzle penetrating into the cylinder is 20% to 55% of the internal height of the gravity gas-liquid separator cylinder, the angle of the expanded bell mouth cone is 4° to 35°, wherein, the internal height of the gravity gas-liquid separator cylinder is the sum of the internal heights of the cylinder section and the bottom cone shell. The ratio of the outer diameter of the outlet end to the inner diameter of the gravity gas-liquid separator cylinder is 0.15 to 0.4.

[0035] Secondly, the internal nozzle geometry model is constructed based on the selected basic design parameters; the gas flow parameters of the gravity gas-liquid separator in actual operation are used as known parameters, and the number of rifling and the twist angle are used as optimization parameters for numerical simulation; the gas flow parameters include the intake velocity, gas viscosity, gas density, gas mass fraction, gas temperature, etc. Before the numerical simulation, the spiral rifling type, rifling depth or height, and rifling cross-sectional shape are pre-selected according to the current processing conditions, and added to the constructed internal nozzle geometry model.

[0036] During the numerical simulation, the inner nozzle outlet section is selected as the analysis section, the analysis section is meshed, and the position, velocity value and corresponding area value of each grid point and the center origin on the analysis section are extracted; the target value F is calculated by the following formula:

[0037]

[0038] Among them, n is the number of points in the analysis section, x0 and y0 are the horizontal and vertical coordinates of the center origin, and x i ,yi is the horizontal and vertical coordinates of point i in the analysis section, u i 、s i are the velocity scalar and area of ​​point i, s 总 is the total area of ​​the analysis section; Figure 4 Central Origin P O and other points as shown in P1.

[0039] Finally, the rifling inner nozzle scheme with a target value F less than the set threshold is selected as the inner nozzle design scheme of the gravity gas-liquid separator. Furthermore, since the smaller the target value F, the smaller the airflow swing, the scheme with the smallest target value F is preferred as the design scheme of the rifling inner nozzle.

[0040] The present invention finds that when the inner nozzle airflow deviates, its main high-speed area will deviate from the central area, such as Figure 4 As shown, the F value needs to consider the size of the selected grid area, the distance from the center and the speed of the point. The larger the corresponding value, the more serious the airflow deviation.

[0041] By analyzing various schemes such as the number of rifling grooves and the angle of twist, the data proves that when the F value is greater than 0.182, it can be judged that there is obvious flow deviation at the inner nozzle outlet. Therefore, when designing, 0.182 can be selected as the setting threshold of the target value F to judge the pros and cons of the design scheme.

[0042] Figure 6 The basic working conditions are shown in Table 1: the center nozzle velocity inlet is 20-35m / s; the pressure inside the device is 20-30MPa absolute pressure; the gas phase density is 240-350kg / m 3 ; gas phase viscosity is 1×10 -5 -5×10 -5 kg / (m·s); velocity vector diagram and target value F value under different design schemes of rifled inner nozzles with a normal liquid level of 0.6-1.3m at the bottom. The present invention designs a special rifling structure on the inner nozzle so that the high-speed airflow passing through can rotate circumferentially and provide radial centrifugal force, so that when the high-speed airflow enters the expanded bell mouth, it can quickly fill the entire bell mouth, preventing the introduced reverse airflow from forming a small vortex to deflect the main body of the airflow and quickly stabilize the airflow. Figure 6 The rifling depth used in the study is 10 mm, and the rifling shape is a standard ellipse. Only the effects of the number of rifling grooves and the twist angle on the airflow are studied. Figure 6 In the velocity vector diagram, the speed in the blue area is 0-2.5m / s, the speed in the green area is 2.5-5m / s, the speed in the yellow area is 5-7.5m / s, and the speed in the red area is 7.5-10m / s.

[0043] Table 1 F value in various design cases (the rifling depth used is 10mm and the rifling shape is a standard ellipse)

[0044]

[0045] Figure 8 The velocity streamline distribution diagram under the scheme of 5 rifling lines and 7.8° twist angle is shown, and the corresponding cross-section diagram of the inner nozzle is as follows Figure 7 As shown in the figure, blue is 0-6m / s, green is 6-14m / s, yellow is 14-19m / s, and red is 19-28m / s. Finite element analysis software is used to verify the improvement of the airflow in the gravity gas-liquid separator by the rifling inner nozzle. Figure 7 As shown in the gas velocity distribution diagram of the inner nozzle with rifling, the high-speed airflow can fully fill the space of the inner nozzle bell mouth after passing through the inner nozzle with rifling, so that the airflow leaving the inner nozzle can still maintain a downward direction. The main body of the airflow flows downward, and under the action of the pressure gradient, it slows down and then leaves the gravity gas-liquid separator upward along the wall.

[0046] Calculations have shown that the rifling structure of the inner nozzle can improve and stabilize the main airflow, making the operation of the gravity gas-liquid separator stable and significantly improving the gas-liquid separation efficiency.

[0047] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for optimizing the gas flow state of a gravity gas-liquid separator by means of a rifled inner nozzle, wherein the rifled inner nozzle comprises a plurality of pipe sections and a plurality of expanded diameter bell mouths along the axial direction; spiral rifling is designed in all or part of the pipe sections, the spiral rifling has a winding angle range of 3-30°, and the number of spiral rifling is 1 to 20, characterized in that: The method comprises the following steps: S1. According to the size of the gravity gas-liquid separator to be optimized, the basic design parameters of the rifled inner nozzle are selected; the basic design parameters include the length of the rifled inner nozzle penetrating into the interior of the cylinder, the angle of the expanded bell mouth cone, and the outer diameter of the outlet end of the rifled inner nozzle; S2. According to the basic design parameters selected in S1, a geometric model of the internal nozzle with rifling is constructed; the airflow parameters of the gravity gas-liquid separator during actual operation are used as known parameters, and the number of rifling and the twist angle of the internal nozzle with rifling are used as optimization parameters for numerical simulation; during the numerical simulation, the internal nozzle outlet section is selected as the analysis section, and the position, velocity value and corresponding area value of each point on the section and the center origin are extracted; the target value F is calculated by the following formula, Among them, n is the number of points in the analysis section, x0 and y0 are the horizontal and vertical coordinates of the center origin, and x i ,y i is the horizontal and vertical coordinates of point i in the analysis section, u i 、s i are the velocity scalar and area of ​​point i, s 总 is the total area of ​​the analyzed section; S3. Select the rifling inner nozzle scheme with a target value F less than the set threshold as the inner nozzle design scheme of the gravity gas-liquid separator.

2. The method according to claim 1, characterized in that Specifically, S1 is as follows: the length of the inner nozzle penetrating into the cylinder is 20% to 55% of the inner height of the gravity gas-liquid separator cylinder, the angle of the expanded bell mouth cone is 4° to 35°, and the ratio of the outer diameter of the inner nozzle outlet end to the inner diameter of the gravity gas-liquid separator cylinder is 0.15 to 0.

4.

3. The method according to claim 1, characterized in that The gas flow parameters of the gravity gas-liquid separator in S2 during actual operation include air intake velocity, gas viscosity, gas density, gas mass fraction, and gas temperature. Before the numerical simulation in S2, the spiral rifling type, the depth or height of the rifling, and the cross-sectional shape of the rifling are pre-selected and added to the constructed inner nozzle geometry model.

4. The method according to claim 1, characterized in that: The set threshold is 0.

182.

5. The method according to claim 1, characterized in that The scheme with the smallest target value F is selected as the internal nozzle design scheme of the gravity gas-liquid separator.

6. The method according to claim 1, characterized in that The spiral rifling is either positive rifling or negative rifling; the rifling depth of the negative rifling does not exceed half of the wall thickness of the tube section, and the rifling height of the positive rifling does not exceed half of the inner diameter of the tube section.

7. The method according to claim 1, characterized in that The number of the spiral rifling is 4-15; the spiral rifling winding angle is preferably 3-15°.

8. The method according to claim 1, characterized in that The cross-sectional shape of the spiral rifling is circular, elliptical, triangular or rectangular.

9. The method according to claim 1, characterized in that: Each pipe section is a pipe of equal diameter. When two adjacent pipe sections are designed with spiral rifling, the winding angle, number of spiral rifling and cross-sectional shape of the spiral rifling are equal, and the spiral rifling corresponding to the adjacent pipe sections are connected.

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