CN108920807B - Flow anti-corrosion modeling method for high-pressure air cooler system of hydrogenation device - Google Patents
Flow anti-corrosion modeling method for high-pressure air cooler system of hydrogenation device Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 50
- 238000005260 corrosion Methods 0.000 title claims abstract description 33
- 238000005984 hydrogenation reaction Methods 0.000 title claims abstract description 31
- 239000012530 fluid Substances 0.000 claims abstract description 52
- 238000001816 cooling Methods 0.000 claims abstract description 34
- 230000003628 erosive effect Effects 0.000 claims abstract description 18
- 238000002156 mixing Methods 0.000 claims abstract description 14
- 239000000463 material Substances 0.000 claims abstract description 12
- 238000010586 diagram Methods 0.000 claims description 11
- 238000004364 calculation method Methods 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 10
- 238000013178 mathematical model Methods 0.000 claims description 9
- 230000000694 effects Effects 0.000 claims description 7
- 229910000975 Carbon steel Inorganic materials 0.000 claims description 6
- 239000000956 alloy Substances 0.000 claims description 6
- 239000010962 carbon steel Substances 0.000 claims description 6
- 239000000126 substance Substances 0.000 claims description 5
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 229910000851 Alloy steel Inorganic materials 0.000 claims description 3
- 230000001133 acceleration Effects 0.000 claims description 3
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 238000004458 analytical method Methods 0.000 claims description 3
- 230000008878 coupling Effects 0.000 claims description 3
- 238000010168 coupling process Methods 0.000 claims description 3
- 238000005859 coupling reaction Methods 0.000 claims description 3
- 230000005484 gravity Effects 0.000 claims description 3
- 238000010008 shearing Methods 0.000 claims description 3
- 230000007797 corrosion Effects 0.000 abstract description 23
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 abstract description 11
- 150000003863 ammonium salts Chemical class 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 2
- HIVLDXAAFGCOFU-UHFFFAOYSA-N ammonium hydrosulfide Chemical compound [NH4+].[SH-] HIVLDXAAFGCOFU-UHFFFAOYSA-N 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 235000019270 ammonium chloride Nutrition 0.000 description 1
- 239000001284 azanium sulfanide Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004517 catalytic hydrocracking Methods 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000010779 crude oil Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/17—Mechanical parametric or variational design
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2111/00—Details relating to CAD techniques
- G06F2111/10—Numerical modelling
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- Computer Hardware Design (AREA)
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- Mathematical Optimization (AREA)
- Pure & Applied Mathematics (AREA)
- Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
Abstract
The invention discloses a flow anti-corrosion modeling method for a high-pressure air cooler system of a hydrogenation device, which comprises the following steps: (1) selecting air cooler tube bundles and liner tube materials; (2) Establishing a fluid stream according to the operating parameters of the air cooler; (3) Setting initial parameters of a corrugated section of the liner tube, and respectively calculating turbulence by using a k-epsilon turbulence model according to fluid operation parameters, and calculating multiphase flow according to a mixing model; (4) Adjusting the design parameters of the corrugated section of the liner tube, and recalculating until the design parameters meet the requirements; according to the flow anti-corrosion modeling method for the high-pressure air cooler system of the hydrogenation device, disclosed by the invention, the flow field form and the speed distribution in the air cooling tube bundle and on the wall surface of the tube bundle are actively controlled by changing the geometric structure of the liner tube under the condition of not changing the air cooling tube bundle, so that the problems of high-speed flow erosion and low-speed flow ammonium chloride salt scaling corrosion of the high-pressure air cooling tube bundle are simultaneously avoided.
Description
Technical Field
The invention mainly relates to a flow anti-corrosion modeling method for a high-pressure air cooler system of a hydrogenation device, and belongs to the technical field of intelligent control.
Background
The high-pressure air cooling system of the hydrogenation device is one of important equipment of a reaction effluent system of the hydrocracking device and is mainly used for cooling hydrogenation reaction products so as to separate gas from liquid. Because the operation condition of the high-pressure air cooling system of the hydrogenation device is extremely complex, the fluid medium flows in the tube bundle of the high-pressure air cooler, and the related parameters are numerous, the stable and safe environment of the high-pressure air cooling system must be ensured in the operation process. Once safety accidents such as leakage and explosion occur, the economic loss of enterprises is affected, and the life safety of staff is further affected.
In recent years, although the hydrogenation technology of China is continuously improved, most crude oil is introduced from the middle east due to the lack of domestic petroleum resources. The nitrogen content and the sulfur content are extremely high, so that more corrosion leakage accidents occur to the petrochemical enterprise refining device, and the problems of corrosion perforation leakage of the high-pressure air cooler tube bundle of the hydrogenation device are particularly remarkable.
At present, the liner tube at the inlet of the high-pressure air cooler tube bundle of the hydrogenation device adopts a smooth straight tube and right-angle tail structure, and the corrosion probability of the air cooler tube bundle is particularly high due to the irrational property of the liner tube structure. Corrosion problems are focused on two aspects: the inner wall of the sudden expansion section at the tail of the liner tube is severely corroded when the liner tube is eroded by 100-120mm away from the tail of the liner tube, and compared with the inner wall of the middle part and the outlet end pipe section of the tube bundle, the inner wall of the sudden expansion section is slightly damaged. And secondly, the crystallization of ammonium salt on the pipe wall and corrosion under scale occur at a position about 1.5m away from the tail of the liner pipe. In the prior art, the corrosion problem is controlled by improving the material grade, so that the cost is high, and the extreme problems such as under-scale corrosion and the like still cannot be solved; the corrosion problem is controlled by the process parameters, and although the controllability is strong and the cost is low, the problems of high-speed flow erosion and low-speed flow scale corrosion cannot be avoided at the same time. For example, in order to avoid the problems of ammonium salt scaling and the like in the area of about 1.5m at the tail of the liner tube, many factories directly increase the flow velocity of a fluid medium, but the erosion of a tube bundle in the range of 100-120mm at the tail of the liner tube is aggravated by the fact that the tail of the liner tube is suddenly expanded. Therefore, a reasonable and effective liner tube structure is designed, and the problems of erosion corrosion and ammonium salt scaling corrosion of a hydrogenation high-pressure air cooling tube bundle are solved, so that the liner tube structure has great engineering and academic significance.
Disclosure of Invention
In order to overcome the defects existing in the prior art: the invention discloses a flow anti-corrosion modeling method for a high-pressure air cooler system of a hydrogenation device and a corrugated lined pipe structure of the high-pressure air cooler. Through multiple tests, a corrugated liner tube with 6 wave bands and a radian radius of 5mm is disclosed, and the fluid state of the inside of the tube bundle and the boundary layer of the wall surface of the tube bundle is optimized under the condition that the material and the operation parameters of the air cooling tube bundle are not changed for the optimized structural parameters of the corrugated liner tube with the liner tube, and meanwhile the problems of erosion corrosion and ammonium salt scaling corrosion of the hydrogenation high-pressure air cooling tube bundle are solved.
The technical scheme of the invention is as follows:
a hydrogenation device high-pressure air cooler system flow anti-corrosion modeling method comprises the following steps:
s1, selecting a high-pressure air cooling tube bundle and a corrugated belt liner tube material of a high-pressure air cooler;
s2, selecting the flow velocity and medium parameters of fluid in the high-pressure air cooler tube bundle;
the flow velocity range of fluid in the high-pressure air cooler tube bundle is 4.6 m/s-12.2 m/s, the fluid is ammonium bisulfide solution, and the fluid is hydrogenation device reaction effluent;
s3, establishing an analysis model of the influence of the liner tube geometric structure on the flow velocity of the air cooling tube bundle and the wall surface flow;
liner geometry modeling based on Ansys software: analyzing fluid flows in the liner tube, the air cooling tube bundle and the wall surface based on modules Fluent of Ansys software, and determining erosion characteristics of the boundary layer of the wall surface of the air cooling tube bundle and turbulent flow state characteristics of the fluid in the tube bundle, wherein the erosion characteristics of the boundary layer of the wall surface of the air cooling tube bundle comprise phase fraction, shearing stress, pressure distribution diagram and flow velocity vector diagram of the boundary layer fluid of the wall surface of the tube bundle; the turbulent flow regime characteristics of the fluid within the tube bundle include phase fraction, shear stress, pressure profile, and flow velocity vector diagram of the fluid within the tube bundle.
The step S3 specifically comprises the following steps:
(301) Determining a fluid boundary condition;
determining the inlet pressure and flow of the tube bundle and the outlet pressure and flow of the tube bundle according to the operation parameters and the design parameters of the air cooler;
(302) Structural meshing of the fluid mathematical model within the liner tube and tube bundle;
after finishing the shape of the liner tube and the fluid mathematical model in the tube bundle in the Geometry plate, dividing grids in the Mesh plate, and checking that the grid quality is matched with the model size; modeling a liner tube with corrugated strips at the tail part;
(303) Establishing a solution model of a mathematical model of the fluid in the liner tube and the tube bundle;
under the condition of dividing a calculation space by adopting a structured grid, a control equation adopts a three-dimensional unsteady compressible N-S equation, a finite volume method is used when the control equation is calculated, the pressure speed coupling is based on a standard Simple method, a k-epsilon turbulence model is adopted for turbulence calculation, and a mixing model is adopted for multiphase flow calculation; because most of the media flowing in the tube bundle of the hydrogenation air cooling system are liquid-gas mixtures, a mixing model is initially selected, the mixing model is used for solving a Mixture (mixed phase) momentum equation, describing a dispersed phase at a set relative speed, and simulating a homogeneous dispersed multiphase flow without the relative speed;
(304) Analyzing the influence of geometric parameters of the corrugated liner tube on flow states and flow parameters in the tube bundle and on the wall surface;
in order to avoid high-speed flow erosion and low-speed flow ammonium chloride salt scaling erosion, the high-turbulence intensity and high-shear force area should be concentrated in the tube bundle, so that the interior of the tube bundle is in a strong turbulence disturbance state, and therefore ammonium chloride salt in the fluid can be fully stirred and dissolved in the center of the tube bundle due to the strong turbulence disturbance effect in the tube bundle, and finally, nucleation and crystallization of the ammonium chloride salt on the wall surface of the metal tube bundle are avoided, and meanwhile, the flow velocity and the shear force of the boundary layer of the wall surface of the tube bundle are lower, so that erosion thinning of high-speed flow is avoided to the greatest extent; when the high-pressure air cooling tube bundle takes carbon steel as a material, the flow rate of a boundary layer is required to be controlled to be 4.4-5.2m/s, and the Incoloy825 alloy is used as the material of the high-pressure air cooling tube bundle, the flow rate of the boundary layer is required to be controlled to be 4.4-9.1 m/s; otherwise, adjusting the wave band and the wave arc radius of the corrugated pipe, and repeating the steps (301) - (304) until the requirements are met;
(305) And selecting parameters of corrugated lined pipes of the high-pressure air cooler.
Solving a continuity equation, a momentum equation, an energy equation and a volume fraction equation of a second phase of the mixed phase based on the mixing model, wherein the method specifically comprises the following steps:
(a) Continuity equation:
the unit is m/s for mass average velocity; ρ m For the mixing density, the unit is kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the t represents time, the unit is S;is a Laplacian operator;
(b) Momentum equation:
in the method, in the process of the invention,is the gravity acceleration, the unit is m 2 /s；
The unit is N, which is the volume force; mu (mu) m The unit is Pa.s;
p is pressure, in Pa; n is the number of phases; alpha i A volume fraction of the i-th phase;
slip speed in m/s for the i-th phase; ρ i Kg/m 3, the density of the i-th phase; t is the medium temperature, and the unit is K; />Indicating that the mixture is p +.>Is a laplace operator of (c); />Representing the mixture pair->Is a laplace operator of (c);
(c) Energy equation:
K ε the unit is W/(m.K) for effective thermal conductivity; s is S E Is a volumetric heat source containing all substances, in W;
h i enthalpy value for the i-th phase;velocity of the i-th phase, v i The unit is m/s for the speed of the i-th phase;
t is temperature, and the unit is K;a laplace operator representing the medium temperature T;
(d) Volume fraction equation of the second phase:
indicating slip speed in m/s;
(e) Standard k-epsilon turbulence model:
k is turbulent kinetic energy in m 2 S; epsilon is the turbulent dissipation ratio in m 2 /s 2 ；
G k Is a turbulent kinetic energy term caused by laminar flow velocity gradient; g b A turbulent kinetic energy term caused by buoyancy;
Y M the effect of pulsating expansion on the total dissipation ratio for compressible turbulence; c (C) 1 、C 2 、C 3 Is a constant; sigma (sigma) k 、σ ε Is a turbulent prantl;
mu is viscosity in Pa.s; mu (mu) t Is a turbulent viscosity coefficient; x is x i Is in a rectangular coordinate direction;
dk. Depsilon and Dt represent differential operators of k, epsilon, t; ρ represents the density of the substance in kg/m 3 。
The standard k-epsilon model is a turbulence model, and the continuity equation, the momentum equation, the energy equation and the volume fraction equation of the second phase are multiphase flow models and are used for calculating the flow parameter distribution conditions of different types of fluids; the invention realizes the active corrosion protection of the air cooler tube bundle based on the parameters of the corrugated liner tube obtained by the process and the checking method between the steps (301) - (304).
The high-pressure air cooling pipe bundle is made of Incoloy825 alloy or carbon steel, and the liner pipe is made of TA1.
The corrugated lined pipe of the high-pressure air cooler comprises a sudden expansion section, a corrugated section and a liner pipe tail section; the abrupt expansion section is connected with the corrugated section through a first circular arc; the corrugated section is connected with the tail section of the liner tube through a second circular arc;
the corrugated section is 6 sections of corrugations; the radius of the first arc is 5mm; the radius of the second arc is 5mm.
The slope from the entrance of the sudden expansion section to the exit of the corrugated section and the corrugated section to the tail section of the liner is 1:10.
The maximum diameter of the corrugated section is 20mm;
the convex arc radius of the corrugated section is r2=5 mm, and the concave arc radius of the corrugated section is r1=2.5 mm.
The abrupt expansion section is a slope pipe, the gradient is 1:10, and the total length is 50mm;
the diameter of the inlet of the sudden expansion section is 15mm, and the diameter of the outlet is 20mm.
The tail section of the liner tube is a slope tube with the slope of 1:10 and the total length of 30mm.
Compared with the prior art, the invention has the beneficial effects that:
the invention discloses a flow anticorrosion modeling method of a high-pressure air cooler system of a hydrogenation device, which is characterized in that corrugated liner parameters meeting the flow anticorrosion requirement of an air cooler tube bundle are obtained according to the flow state of fluid in the tube bundle and the flow speed of the boundary layer of the wall surface of the tube bundle when the flow speed of the fluid meets the fluid corrosion requirement, and the model for quantitatively analyzing and calculating the geometric parameters of the liner is realized through the fluid modeling method, so that the problems of high-speed flow erosion and low-speed flow ammonium chloride salt scaling corrosion of the high-pressure air cooler tube bundle are solved under the condition that the air cooler tube bundle is not changed, and the active control optimization effect of high-pressure air cooler corrosion in practical application is met.
Drawings
FIG. 1 is a schematic view of a corrugated liner tube of a high-pressure air cooler;
FIG. 2 is a pressure profile of the present invention with a corrugated liner;
FIG. 3 is a velocity profile of the corrugated liner of the present invention;
FIG. 4 right angle tail liner pressure profile.
Detailed Description
The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific examples, so that those skilled in the art can better understand the present invention and implement it, but the examples are not limited thereto.
The invention will be further described with reference to the accompanying drawings.
A hydrogenation device high-pressure air cooler system flow anti-corrosion modeling method comprises the following steps:
s1, selecting a high-pressure air cooling tube bundle and a corrugated belt liner tube material of a high-pressure air cooler;
the high-pressure air cooling pipe bundle is made of Incoloy825 alloy or carbon steel, and the liner pipe is made of TA1;
s2, selecting the flow velocity and medium parameters of fluid in the high-pressure air cooler tube bundle;
the flow velocity range of the fluid in the high-pressure air cooler tube bundle is 4.6 m/s-12.2 m/s, and the fluid is hydrogenation device reaction effluent (containing hydrocarbon, hydrogen sulfide, ammonium hydrogen sulfide and ammonium chloride);
s3, establishing an analysis model of the influence of the liner tube geometric structure on the flow velocity of the air cooling tube bundle and the wall surface flow;
liner geometry modeling based on Ansys software: analyzing fluid flows in the liner tube, the air cooling tube bundle and the wall surface based on modules Fluent of Ansys software, and determining erosion characteristics of the boundary layer of the wall surface of the air cooling tube bundle and turbulent flow state characteristics of the fluid in the tube bundle, wherein the erosion characteristics of the boundary layer of the wall surface of the air cooling tube bundle comprise phase fraction, shearing stress, pressure distribution diagram and flow velocity vector diagram of the boundary layer fluid of the wall surface of the tube bundle; the turbulent flow state characteristics of the fluid in the tube bundle comprise phase fraction, shear stress, pressure distribution diagram and flow velocity vector diagram of the fluid in the tube bundle;
the step S3 specifically comprises the following steps:
(301) Determining a fluid boundary condition;
and determining the inlet pressure and flow of the tube bundle and the outlet pressure and flow of the tube bundle according to the operation parameters and the design parameters of the air cooler.
(302) Structural meshing of the fluid mathematical model within the liner tube and tube bundle;
after finishing the shape of the liner tube and the fluid mathematical model in the tube bundle in the Geometry plate, dividing grids in the Mesh plate, and checking that the grid quality is matched with the model size; modeling a liner tube with corrugated strips at the tail part;
(303) Establishing a solution model of a mathematical model of the fluid in the liner tube and the tube bundle;
under the condition of dividing a calculation space by adopting a structured grid, a control equation adopts a three-dimensional unsteady compressible N-S equation, a finite volume method is used when the control equation is calculated, the pressure speed coupling is based on a standard Simple method, a k-epsilon turbulence model is adopted for turbulence calculation, and a mixing model is adopted for multiphase flow calculation; because most of the media flowing in the tube bundle of the hydrogenation air cooling system are liquid-gas mixtures, a mixing model is initially selected, the mixing model is used for solving a Mixture momentum equation, and a disperse phase is described at a set relative speed and is used for simulating a homogeneous disperse multiphase flow without the relative speed.
Solving a continuity equation, a momentum equation, an energy equation and a volume fraction equation of a second phase of the mixed phase based on the mixing model, wherein the method specifically comprises the following steps:
(a) Continuity equation:
the unit is m/s for mass average velocity; ρ m For the mixing density, the unit is kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the t represents time, the unit is S; />Is a Laplacian operator;
(b) Momentum equation:
in the method, in the process of the invention,is the gravity acceleration, the unit is m 2 /s；
The unit is N, which is the volume force; mu (mu) m The unit is Pa.s;
p is pressure, in Pa; n is the number of phases; alpha i A volume fraction of the i-th phase;
slip speed in m/s for the i-th phase; ρ i Kg/m 3, the density of the i-th phase; t is the medium temperature, and the unit is K; />Indicating that the mixture is p +.>Is a laplace operator of (c); />Representing the mixture pair->Is a laplace operator of (c);
(c) Energy equation:
K e the unit is W/(m.K) for effective thermal conductivity; s is S E To contain all volumetric heat sources;
h i enthalpy value for the i-th phase;is the firstVelocity of i phase, v i The unit is m/s for the speed of the i-th phase;
t is temperature, and the unit is K;representing the Laplacian of the medium under the condition of temperature T;
(d) Volume fraction equation of the second phase:
indicating slip speed in m/s;
(e) Standard k-epsilon turbulence model:
k is turbulent kinetic energy in m 2 S; epsilon is the turbulent dissipation ratio in m 2 /s 2 ；
G k Is a turbulent kinetic energy term caused by laminar flow velocity gradient; g b A turbulent kinetic energy term caused by buoyancy;
Y M the effect of pulsating expansion on the total dissipation ratio for compressible turbulence; c (C) 1 、C 2 、C 3 Is a constant; sigma (sigma) k 、σ ε Is a turbulent prantl; mu is viscosity in units ofPa.s；μ r Is a turbulent viscosity coefficient; x is x i Is in a rectangular coordinate direction;
dk. Depsilon and Dt represent differential operators of k, epsilon, t; ρ represents the density of the substance in kg/m 3 。
The standard k-epsilon model is a turbulence model, and the continuity equation, the momentum equation, the energy equation and the volume fraction equation of the second phase are multiphase flow models and are used for calculating the flow parameter distribution conditions of different types of fluids; the invention realizes the active corrosion protection of the air cooler tube bundle based on the parameters of the corrugated liner tube obtained by the process and the checking method between the steps (301) - (304);
(304) Analyzing the influence of geometric parameters of the corrugated liner tube on flow states and flow parameters in the tube bundle and on the wall surface;
in order to avoid high-speed flow erosion and low-speed flow ammonium chloride salt scaling corrosion, the high-turbulence intensity and high-shear force area should be concentrated in the tube bundle, so that the interior of the tube bundle is in a strong turbulence disturbance state, and therefore ammonium chloride salt in fluid can be fully stirred and dissolved in the center of the tube bundle due to the strong turbulence disturbance effect in the tube bundle, finally, nucleation and crystallization of the ammonium chloride salt on the wall surface of the metal tube bundle are avoided, meanwhile, the flow velocity and the shear force of the wall surface of the tube bundle are low, so that erosion and thinning of high-speed flow are avoided to the greatest extent, the flow velocity of the boundary layer of the high-pressure air cooling tube bundle which uses carbon steel as a material is required to be controlled to be 4.4-5.2m/s, and when Incoloy825 alloy is used as a tube bundle material of a high-pressure air cooler, the flow velocity of the boundary layer is required to be controlled to be 4.4-9.1m/s. Otherwise, adjusting the wave band and the wave arc radius of the corrugated pipe based on the structural parameters of the corrugated liner pipe, and repeating the steps (302) - (305) until the requirements are met.
(305) And selecting parameters of corrugated lined pipes of the high-pressure air cooler.
The invention adopts a method for realizing active corrosion protection by changing the flow state of the inlet of the high-pressure air cooler tube bundle of the hydrogenation device through the liner tube with a novel geometric structure, realizes the quantitative analysis and calculation model of the geometric parameters of the liner tube through a fluid modeling method, solves the problem of actively and synchronously controlling the high-speed flow erosion and the low-speed flow ammonium chloride salt scaling corrosion of the high-pressure air cooler tube bundle under the condition of not changing the air cooler tube bundle, and meets the active control and optimization effect of the high-pressure air cooler corrosion in practical application.
As shown in fig. 1, the corrugated liner tube of the high-pressure air cooler comprises a sudden expansion section 1, a corrugated section 2 and a liner tail section 3; the sudden expansion section 1 is connected with the corrugated section 2 through a first circular arc 4; the corrugated section 2 is connected with the liner tube tail section 3 through a second circular arc 5;
the corrugated section 2 is 6 sections of corrugations; the radius of the first arc 4 is 5mm; the radius of the second arc 5 is 5mm.
The slope from the entrance of the sudden expansion section 1 to the exit of the corrugated section 2 and the corrugated section 2 to the liner tail section 3 is 1:10.
The maximum diameter of the corrugated section 2 is 20mm.
The convex arc radius of the corrugated section 2 is r2=5 mm, and the concave arc radius r1=2.5 mm of the corrugated section 2.
The abrupt expansion section 1 is a sloping pipe with the inclination of 1:10 and the total length of 50mm.
The diameter of the inlet of the sudden expansion section 1 is 15mm, and the diameter of the outlet is 20mm.
The liner tube tail section 3 is a sloping tube with a slope of 1:10 and a total length of 30mm.
As can be seen from fig. 2, the present invention calculates a liner with a corrugated strip where the pressure at the inlet of the liner is greater for fluid flow and the pressure distribution is more uniform for the liner with a corrugated strip than for the right angle tail liner of fig. 4 because of the presence of the corrugated strip where the pressure at the inlet of the liner is relatively greater; in the sudden expansion region, the pressure change is not as high as the change of a right angle tail liner due to the 1:10 bevel. In the rear region of the liner tail, the pressure gradually decreases. As can be seen from the velocity profile of the corrugated liner of fig. 3, the flow velocity at the walls of the corrugated liner and liner tail is relatively low compared to the central tube band,
the foregoing is only a preferred embodiment of the invention, it being noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention.
Claims (8)
1. The flow anti-corrosion modeling method for the high-pressure air cooler system of the hydrogenation device is characterized by comprising the following steps of:
s1, selecting a high-pressure air cooling tube bundle and a corrugated belt liner tube material of a high-pressure air cooler;
s2, selecting the flow velocity and medium parameters of fluid in the high-pressure air cooler tube bundle;
the flow velocity range of fluid in the high-pressure air cooler tube bundle is 4.6 m/s-12.2 m/s, and the fluid is hydrogenation device reaction effluent;
s3, establishing an analysis model of the influence of the liner tube geometric structure on the flow velocity of the air cooling tube bundle and the wall surface flow;
analyzing fluid flows in the liner tube, the air cooling tube bundle and the wall surface based on modules Fluent of Ansys software, and determining erosion characteristics of the boundary layer of the wall surface of the air cooling tube bundle and turbulent flow state characteristics of the fluid in the tube bundle, wherein the erosion characteristics of the boundary layer of the wall surface of the air cooling tube bundle comprise phase fraction, shearing stress, pressure distribution diagram and flow velocity vector diagram of the boundary layer fluid of the wall surface of the tube bundle; the turbulent flow state characteristics of the fluid in the tube bundle comprise phase fraction, shear stress, pressure distribution diagram and flow velocity vector diagram of the fluid in the tube bundle;
the step S3 specifically comprises the following steps:
(301) Determining a fluid boundary condition;
determining the inlet pressure and flow of the tube bundle and the outlet pressure and flow of the tube bundle according to the operation parameters and the design parameters of the air cooler;
(302) Structural meshing of the fluid mathematical model within the liner tube and tube bundle;
after finishing the shape of the liner tube and the fluid mathematical model in the tube bundle in the Geometry plate, dividing grids in the Mesh plate, and checking that the grid quality is matched with the model size; modeling a liner tube with corrugated strips at the tail part;
(303) Establishing a solution model of a mathematical model of the fluid in the liner tube and the tube bundle;
under the condition of dividing a calculation space by adopting a structured grid, a control equation adopts a three-dimensional unsteady compressible N-S equation, a finite volume method is used when the control equation is calculated, the pressure speed coupling is based on a standard Simple method, a k-epsilon turbulence model is adopted for turbulence calculation, and a mixing model is adopted for multiphase flow calculation;
(304) Analyzing the influence of geometric parameters of the corrugated liner tube on flow states and flow parameters in the tube bundle and on the wall surface;
a high-pressure air cooling tube bundle taking carbon steel as a material, wherein the flow speed of a boundary layer is controlled to be 4.4 m/s-5.2 m/s; when the Incoloy825 alloy is used as a tube bundle material of the high-pressure air cooler, the flow speed of a boundary layer is controlled to be 4.4 m/s-9.1 m/s; adjusting the corrugated liner structural parameters based on the boundary layer flow rate control conditions;
(305) And selecting parameters of corrugated lined pipes of the high-pressure air cooler.
2. The method for modeling flow anticorrosion of a high-pressure air cooler system of a hydrogenation device according to claim 1, wherein the method comprises the steps of,
solving a continuity equation, a momentum equation, an energy equation and a volume fraction equation of a second phase of the mixed phase based on the mixing model, wherein the method specifically comprises the following steps:
(a) Continuity equation:
the unit is m/s for mass average velocity; ρ m For the mixing density, the unit is kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the t represents time, the unit is S; />Is a Laplacian operator;
(b) Momentum equation:
in the method, in the process of the invention,is the gravity acceleration, the unit is m 2 /s；
The unit is N, which is the volume force; mu (mu) m The unit is Pa.s;
p is pressure, in Pa; n is the number of phases; oc (oc) i A volume fraction of the i-th phase;
p is pressure, in Pa; n is the number of phases; alpha i A volume fraction of the i-th phase;
slip speed in m/s for the i-th phase; ρi is the density of the i-th phase, kg/m 3; t is the medium temperature, and the unit is K;indicating that the mixture is p +.>Is a laplace operator of (c); />Representing the mixture pair->Is a laplace operator of (c);
(c) Energy equation:
K ε the unit is W/(m.K) for effective thermal conductivity; s is S E Is a volumetric heat source containing all substances, in W;
h i enthalpy value for the i-th phase;velocity of the i-th phase, v i The unit is m/s for the speed of the i-th phase;
t is temperature, and the unit is K;a laplace operator representing the medium temperature T;
(d) Volume fraction equation of the second phase:
indicating slip speed in m/s;
(e) Standard k-epsilon turbulence model:
k is turbulent kinetic energy in m 2 S; epsilon is the turbulent dissipation ratio in m 2 /s 2 ；
G k Is a turbulent kinetic energy term caused by laminar flow velocity gradient; g b A turbulent kinetic energy term caused by buoyancy;
Y M the effect of pulsating expansion on the total dissipation ratio for compressible turbulence; c (C) 1 、C 2 、C 3 Is a constant; sigma (sigma) k 、σ ε Is a turbulent prantl;
mu is viscosity in Pa.s; mu (mu) t Is turbulent viscosityCoefficients; x is x i Is in a rectangular coordinate direction;
dk. Depsilon and Dt represent differential operators of k, epsilon, t; ρ represents the density of the substance in kg/m 3 。
3. The method for modeling flow anticorrosion of a high-pressure air cooler system of a hydrogenation device according to claim 1, wherein the method comprises the steps of,
the high-pressure air cooling pipe bundle is made of Incoloy825 alloy or carbon steel, and the liner pipe is made of TA1.
4. The method for modeling flow anticorrosion of a high-pressure air cooler system of a hydrogenation device according to claim 1, wherein the method comprises the steps of,
the corrugated lined pipe of the high-pressure air cooler comprises a sudden expansion section (1), a corrugated section (2) and a liner pipe tail section (3); the sudden expansion section (1) is connected with the corrugated section (2) through a first circular arc (4); the corrugated section (2) is connected with the liner tube tail section (3) through a second circular arc (5);
the corrugated section (2) is 6 sections of corrugations; the radius of the first arc (4) is 5mm; the radius of the second arc 5 is 5mm.
5. The method for modeling flow anticorrosion of a high-pressure air cooler system of a hydrogenation unit according to claim 4, wherein the method comprises the steps of,
the inclination of 1:10 is from the inlet of the sudden expansion section (1) to the corrugated section (2) and from the corrugated section (2) to the outlet of the liner tail section (3).
6. The method for modeling flow anticorrosion of a high-pressure air cooler system of a hydrogenation unit according to claim 4, wherein the method comprises the steps of,
the maximum diameter of the corrugated section (2) is 20mm;
the convex arc radius of the corrugated section (2) is r2=5 mm, and the concave arc radius of the corrugated section (2) is r1=2.5 mm.
7. The method for modeling flow anticorrosion of a high-pressure air cooler system of a hydrogenation unit according to claim 4, wherein the method comprises the steps of,
the abrupt expansion section (1) is a sloping pipe, the gradient is 1:10, and the total length is 50mm;
the diameter of the inlet of the sudden expansion section (1) is 15mm, and the diameter of the outlet is 20mm.
8. The flow anti-corrosion modeling method for a high-pressure air cooler system of a hydrogenation device according to claim 4, wherein the liner tube tail section (3) is a sloping tube, the slope is 1:10, and the total length is 30mm.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101075270A (en) * | 2007-06-19 | 2007-11-21 | 浙江理工大学 | Method for optimizing pipe bundle liner shape of air cooler |
| CN201110697Y (en) * | 2007-08-24 | 2008-09-03 | 浙江理工大学 | Hydrocracking reaction outrunner apparatus based on unbalance degree analysis |
| CN207123210U (en) * | 2017-08-11 | 2018-03-20 | 中石化广州工程有限公司 | A kind of air cooler tube bundle structure |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101075270A (en) * | 2007-06-19 | 2007-11-21 | 浙江理工大学 | Method for optimizing pipe bundle liner shape of air cooler |
| CN201110697Y (en) * | 2007-08-24 | 2008-09-03 | 浙江理工大学 | Hydrocracking reaction outrunner apparatus based on unbalance degree analysis |
| CN207123210U (en) * | 2017-08-11 | 2018-03-20 | 中石化广州工程有限公司 | A kind of air cooler tube bundle structure |
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| 《加氢热高分空冷器系统流动腐蚀预测及监测管理平台开发》;方华平;《中国优秀硕士学位论文全文数据库工程科技Ⅰ辑》;20151015;参见第二章 * |
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