Skeepest descent curve-based devolatilizer outlet structure and design method

Abstract

The invention discloses a devolatilization device outlet structure based on a steepest descent curve and a design method, and the design method comprises the following steps: 1, constructing an outlet pipe section at the bottom of a devolatilization device body, and constructing an inner wall contour line of the outlet pipe section based on the steepest descent curve, the first curved surface structure is distributed in the shortest average residence time of the melt; the outer wall profile of the outlet pipe section is a second curved surface structure constructed based on the first curved surface structure according to the expected wall thickness; and 2, through a melt passing hole plate arranged on the inlet structure of the devolatilization device, enabling the melt to be devolatilized to fall onto the first curved surface structure of the outlet pipe section through the middle pipe section structure, and connecting the devolatilization device body with the outlet pipe section to form an integrated structure for realizing melt devolatilization through temperature. The problem that the overall devolatilization efficiency of the devolatilization device is low due to the fact that the devolatilization residence time of a melt in an outlet pipe section of the devolatilization device cannot be ensured when materials of different parts are under the given pressure difference is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solution method polyethylene preparation, and particularly relates to a devolatilizer outlet structure based on steepest descent curve and a design method. BACKGROUND

[0002] A devolatilizer is a key device in the production process of high polymer materials (such as plastics, rubber, chemical fiber raw materials, adhesives, special resins, etc.). Its core function is to efficiently remove volatile components (such as unreacted monomers, solvents, moisture, low molecular weight oligomers, and reaction by-products) remaining in the polymer melt or solution. The residual volatile components not only significantly reduce the physical and mechanical properties (such as strength, toughness, transparency) of the final product, thermal stability, electrical properties, but also cause bubbles, discoloration, odor, and even affect the safety and environmental protection of the product during subsequent processing or use. Therefore, efficient and thorough devolatilization is an essential process step for producing high-quality and high-value-added polymer products. The devolatilization process is essentially a process of separating and removing volatile components from high-viscosity polymer melts or solutions. The main driving forces include: (1) surface renewal and diffusion: increasing the surface area (such as forming a thin film, strip or droplet), intensifying the surface renewal rate (such as mechanical stirring, scraping), and providing sufficient residence time to diffuse the volatile components to the surface of the melt / solution; (2) reducing the partial pressure / concentration difference: creating and maintaining a low volatile component partial pressure environment in the devolatilization chamber (usually achieved by vacuum pumping), forming a concentration gradient to drive volatilization; (3) temperature control: appropriately increasing the temperature can reduce the melt viscosity and accelerate diffusion, but the thermal degradation of the polymer needs to be avoided. The core challenge of the devolatilization process is how to overcome the low diffusion coefficient limitation of high-viscosity polymer melts in a limited space and equipment size, achieve efficient and uniform removal of volatile components, and as much as possible reduce the final residual content. The performance of the devolatilizer not only depends on the design of the main devolatilization chamber, but also on the structural design of the outlet end, because it directly affects the final flow state and residence time distribution of the material in the devolatilizer.

[0003] The current structure of the industrial devolatilizer has a structure of a conical pipe directly connected to the bottom of the devolatilizer. However, the traditional outlet structure design has a serious defect of wide residence time distribution in the outlet area of the devolatilizer. The material with too long residence time may be subject to thermal degradation, crosslinking or discoloration. The uneven residence time directly leads to significant differences in the quality of the polymer product (such as residual monomer content, molecular weight distribution, color) of different batches or different parts of the same batch, affecting the consistency and stability of the product. Although the existing technology also attempts to optimize the outlet (such as optimizing the cone angle, adding guide vanes, etc.), these improvements are often empirical and local, lack a systematic fluid mechanics theoretical basis, have limited effect, and are difficult to fundamentally solve the above complex flow problems, especially when dealing with polymer melts with high viscosity and non-Newtonian fluid characteristics. In addition, although the umbrella plate applying the steepest descent curve is added inside the devolatilizer to solve the problem of too long residence time of the material in the existing patent document CN118787972A, there are the following disadvantages: 1. The added umbrella plate has redundant structure and needs frequent cleaning, increasing maintenance cost; 2. The umbrella plate is erected in the middle of the devolatilizer, reducing the effective devolatilization height and reducing the devolatilization efficiency, thereby increasing the manufacturing cost. SUMMARY

[0004] The present application provides a devolatilizer outlet structure and design method based on the steepest descent curve to overcome the above technical problems.

[0005] In order to achieve the above purpose, the technical scheme of the present application is:

[0006] A design method of a devolatilizer outlet structure based on the steepest descent curve, specifically comprising the following steps:

[0007] Step 1: constructing an outlet pipe section at the bottom of the devolatilizer body, and the inner wall contour line of the outlet pipe section is a first curved surface structure based on the steepest descent curve for ensuring the shortest average residence time distribution of the melt under a given pressure difference; and the outer wall contour line of the outlet pipe section is a second curved surface structure based on the first curved surface structure and according to the desired wall thickness;

[0008] Step 2: through the melt perforated plate provided on the inlet structure of the devolatilizer, the melt to be devolatilized falls into the first curved surface structure of the outlet pipe section, and the devolatilizer body and the outlet pipe section are connected to form an integrated structure for devolatilizing the melt by temperature.

[0009] Further, the construction method of the first curved surface structure is

[0010] S100: Obtain the design parameters for constructing the first curved surface structure according to the intermediate pipe segment structure; and obtain the first steepest descent curve model equation according to the design parameters to obtain the first steepest descent curve trajectory; and the expression of the first steepest descent curve equation is

[0011]

[0012] In the formula: R m -R b represents the known design parameters; R m represents the inner wall radius of the intermediate pipe segment structure; R b represents the bottom end outlet radius of the bottom end opening of the outlet pipe segment for interfacing with the downstream pre-set post-processing equipment or pipeline; x1, y1 represents the coordinate point of the trajectory formed by the first steepest descent curve equation; t represents the parameter variable;

[0013] S101: Confirm the center of the circle where the bottom end outlet of the bottom end opening of the outlet pipe segment is located, and take the center as the rotation center to obtain the first curved surface structure by rotating the first steepest descent curve trajectory one circle.

[0014] Further, the construction method of the second curved surface structure is

[0015] S200: Define the desired wall thickness of the outlet pipe segment, and construct the second steepest descent curve model equation according to the first steepest descent curve model equation corresponding to the first curved surface structure to obtain the second steepest descent curve trajectory; and the expression of the second steepest descent curve equation is

[0016]

[0017] In the formula: x2, y2 represents the coordinate point of the trajectory formed by the second steepest descent curve equation; D represents the desired wall thickness of the outlet pipe segment;

[0018] S201: Take the center of the circle where the bottom end outlet of the bottom end opening of the outlet pipe segment is located as the rotation center, and obtain the second curved surface structure by rotating the second steepest descent curve trajectory one circle.

[0019] A steepest descent curve-based devolatilizer outlet structure, comprising an outlet pipe segment arranged at the bottom of a devolatilizer body, the inner wall of the outlet pipe segment is provided with a first curved surface structure; and the outer wall of the outlet pipe segment is provided with a second curved surface structure.

[0020] The devolatilizer body comprises a devolatilizer inlet structure and an intermediate pipe segment structure provided with a melt perforated plate connected vertically in sequence, and the inner wall end point of the outlet pipe segment is smoothly connected with the inner wall of the intermediate pipe segment structure.

[0021] Further, the devolatilizer inlet structure comprises a straight pipe segment component and an elliptical pipe segment component;

[0022] And the top end of the straight pipe segment component is provided with a melt through-hole plate, and the inner wall of the bottom end of the straight pipe segment component is smoothly connected with the inner wall of the top end of the elliptical pipe segment component.

[0023] Further, one side of the elliptical pipe segment component is provided with a gas exhaust pipe, and the gas exhaust pipe communicates with the inside of the elliptical pipe segment component.

[0024] Further, a plurality of rows of hole structures are equidistantly arranged on the melt through-hole plate, and the hole structures of adjacent rows are arranged in a regular triangle distribution.

[0025] Beneficial effects: the present application provides a devolatilizer outlet structure and design method based on the steepest descent curve, by designing the inner wall contour line of the outlet pipe segment as a first curved surface structure based on the steepest descent curve; the shortest average residence time of the outlet area under a given pressure difference is realized, and the residence time distribution of the melt in the outlet pipe segment is optimized, ensuring that different parts of the material experience more uniform devolatilization process, which can significantly improve the overall devolatilization efficiency of the devolatilizer; and the outer wall contour line of the outlet pipe segment is a second curved surface structure based on the first curved surface structure and constructed according to the desired wall thickness; the uniformity of the use strength and the absorption performance of the heat used for devolatilizing the solution can be ensured to avoid deformation of the molten polymer of the solution on the inner wall of the outlet pipe segment to affect the devolatilization efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0027] Figure 1 It is the overall schematic diagram of the devolatilizer outlet structure based on the steepest descent curve of the present application;

[0028] Figure 2 It is the bottom schematic diagram of the devolatilizer outlet structure designed by the steepest descent curve in the present embodiment;

[0029] Figure 3 It is the cross-sectional schematic diagram of the devolatilizer outlet structure designed by the steepest descent curve in the present embodiment;

[0030] Figure 4 It is the construction method flow chart of the first curved surface structure in the present embodiment;

[0031] Figure 5 It is the construction method flow chart of the second curved surface structure in the present embodiment.

[0032] Figure: 1, outlet pipe section; 11, first curved surface structure; 12, second curved surface structure; 13, bottom end outlet; 2, devolatilizer inlet structure; 3, intermediate pipe section structure; 21, melt perforated plate; 211, hole structure; 22, straight pipe section component; 23, elliptical pipe section component; 24, gas exhaust pipe. DETAILED DESCRIPTION

[0033] To make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0034] The present embodiment provides a design method of devolatilizer outlet structure based on steepest descent curve, comprising step one: constructing an outlet pipe section 1 at the bottom of the devolatilizer body, the inner wall contour line of the outlet pipe section 1 is a first curved surface structure 11 constructed based on the steepest descent curve for ensuring the shortest average residence time distribution of the melt under a given pressure difference; the structure affecting the devolatilization efficiency of the devolatilizer in the present embodiment is the structure of the devolatilizer outlet pipe section, and the traditional outlet structure design generally has the serious defect that the residence time distribution in the outlet area of the devolatilizer is wide. The material with too long residence time may be thermally degraded, crosslinked or discolored, and the non-uniformity of the residence time of the melt in the devolatilizer outlet pipe section directly leads to significant differences in the quality (such as residual monomer content, molecular weight distribution, color) of the polymer product of different batches or different parts in the same batch, affecting the consistency and stability of the product. Because a new structure of the devolatilizer outlet pipe section is designed in the present embodiment; specifically, as shown in Figure 4 the construction method of the first curved surface structure 11 is

[0035] S100: obtaining design parameters for constructing the first curved surface structure 11 according to the intermediate pipe section structure 3; and obtaining a first steepest descent curve model equation according to the design parameters to obtain a first steepest descent curve trajectory; and the expression of the first steepest descent curve equation is

[0036]

[0037] In the formula: R m -R b represents known design parameters; R m represents the inner wall radius of the intermediate pipe section structure 3; R bRadius of the bottom end outlet 13 opened at the bottom end of the outlet pipe section 1 for the interface or pipeline interface with the downstream preset post-processing equipment; x1, y1 represent the coordinate points of the trajectory formed by the first steepest descent curve equation; t represents a parameter variable;

[0038] S101: Confirm the center of the circle where the bottom end outlet 13 opened at the bottom end of the outlet pipe section 1 is located, and take the center as the rotation center, rotate the first steepest descent curve trajectory around the center axis by 360°, obtain the first formed rotation surface 11, and take the formed rotation surface as the inner wall structure, that is, the first curved surface structure 11;

[0039] And the outer wall contour of the outlet pipe section 1 is the second curved surface structure 12 constructed based on the first curved surface structure 11 according to the desired wall thickness;

[0040] Specifically, as shown in Figure 5 The construction method of the second curved surface structure 12 is

[0041] S200: Define the desired wall thickness of the outlet pipe section 1, and construct a second steepest descent curve model equation according to the first steepest descent curve model equation corresponding to the first curved surface structure 11 to obtain a second steepest descent curve trajectory; and the expression of the second steepest descent curve equation is

[0042]

[0043] In the formula: x2, y2 represent the coordinate points of the trajectory formed by the first steepest descent curve equation; D represents the desired wall thickness of the outlet pipe section 1;

[0044] S201: Take the center of the circle where the bottom end outlet 13 opened at the bottom end of the outlet pipe section 1 is located as the rotation center, rotate the second steepest descent curve trajectory around the center axis by 360° to obtain the second formed rotation surface 12 and take the formed rotation surface as the outer wall structure, that is, the second curved surface structure 12.

[0045] As shown in Figures 1 to 3 The devolatilizer body includes a devolatilizer inlet structure 2 provided with a melt perforated plate 21 and a middle pipe section structure 3 connected vertically in sequence, and the inner wall end point of the outlet pipe section 1 is smoothly connected with the inner wall of the middle pipe section structure 3;

[0046] Specifically, the devolatilizer inlet structure 2 includes a straight pipe section member 22 and an elliptical pipe section member 23; and the top end of the straight pipe section member 22 is provided with a melt perforated plate 21, and the bottom end inner wall of the straight pipe section member 22 is smoothly connected with the top end inner wall of the elliptical pipe section member 23;

[0047] Step two: the melt to be devolatilized is dropped onto the first curved surface structure 11 of the outlet pipe segment 1 through the melt through-hole plate 21 provided on the devolatilizer inlet structure 2, and the devolatilizer body is connected with the outlet pipe segment 1 to form an integrated structure for devolatilization by temperature.

[0048] In this embodiment, the inner wall contour line of the outlet pipe segment 1 is designed as the first curved surface structure 11 based on the steepest descent curve, which realizes the shortest average residence time of the outlet area under a given pressure difference, thereby optimizing the residence time distribution of the melt in the outlet pipe segment 1, ensuring that different parts of the material experience more uniform devolatilization process, and significantly improving the overall devolatilization efficiency of the devolatilizer. The outer wall contour line of the outlet pipe segment 1 is the second curved surface structure 12 based on the first curved surface structure 11 and according to the desired wall thickness, which can ensure the uniformity of the structural strength and the absorption performance of the heat for devolatilizing the melt, so as to avoid deformation of the molten polymer on the inner wall of the outlet pipe segment 1, which affects the devolatilization efficiency.

[0049] In specific embodiments, one side of the elliptical pipe segment member 23 is provided with a gas exhaust pipe 24, and the gas exhaust pipe 24 communicates with the inside of the elliptical pipe segment member 23. In this embodiment, the gas phase generated during the devolatilization process is discharged from the devolatilizer through the gas exhaust pipe 24 to prevent the gas pressure in the fixed volume of the devolatilizer from rising due to the increase in temperature, which reduces the vacuum degree and makes it difficult for the volatile components in the melt to volatilize, thereby reducing the devolatilization efficiency. This is because lower vacuum degree is not conducive to the escape of volatile components from the polymer melt, resulting in poor devolatilization effect.

[0050] In specific embodiments, a plurality of rows of hole structures 211 are evenly spaced on the melt through-hole plate 21, and the hole structures 211 of adjacent rows are arranged in a regular triangular distribution. In this embodiment, the devolatilizer inlet structure 2 is connected to the flash tank, and the arrangement of the plurality of rows of hole structures 211 facilitates the flow of the melt from the flash tank into the interior of the devolatilizer through the hole structures 211 in the through-hole plate, thereby increasing the processing capacity of the melt.

[0051] The flash tank is connected to the devolatilizer in this embodiment, and the melt flows out of the perforated plate and drips on the outlet of the devolatilizer, and the devolatilized gas phase is discharged from the gas outlet. Preferably, the diameter of the perforated plate is 3300 mm, the diameter of the hole structure on the perforated plate is 11.1125 mm, the distance between the holes in the same row is 25.4 mm, and the holes in different rows are arranged in an equilateral triangle; the inner wall diameter of the straight pipe section component in the inlet structure of the devolatilizer is 3300 mm, and the wall thickness of the straight pipe section component is 100 mm; the inner wall diameter of the elliptical pipe section component increases from 3300 mm to 5900 mm, and the wall thickness of the elliptical pipe section component is 100 mm; the inner wall diameter of the gas discharge pipe of the elliptical pipe section component is 400 mm, the wall thickness is 100 mm, and the height is 500 mm; the inner wall diameter of the middle pipe section structure of the devolatilizer is 5900 mm, and the thickness of the middle pipe section structure is 100 mm. The inner wall of the outlet structure is selected to be the brachistochrone curve, and the origin of the brachistochrone curve on one side is selected at the connection point of the inner wall of the outlet and the inner wall of the middle section, and the equation of the first brachistochrone curve is m; at the same time, in order to ensure that the wall thickness is 100 mm, the outer wall of the outlet structure also adopts the brachistochrone curve, that is, the equation of the second brachistochrone curve is m, and the outlet pipe section is provided with an outlet diameter of 800 mm at the bottom end for connecting with the downstream preset post-treatment equipment or pipeline.

[0052] In this embodiment, based on the size parameters of the preset equipment, the inner wall of the outlet pipe section of the devolatilizer is simulated and calculated by using the brachistochrone curve in this embodiment and the inner wall using a conical pipe, respectively. First, the motion process of the devolatilized melt is simplified as the melt particles only under the action of gravity, in a predetermined rectangular coordinate system, from an arbitrary point x on the inner wall curve or the inner wall of the conical pipe, along the brachistochrone curve or a straight line to the desired target point x0(2.55 m, 0); then, the time of the melt particles falling along the brachistochrone curve only under the action of gravity is calculated, R is the brachistochrone curve parameter, that is, the design parameter; g is the acceleration of gravity (usually taken as 9.8 m / s2), so that the motion time of the melt particles on the brachistochrone curve is independent of the initial position, that is, the position of the particles falling on the conical pipe, which can effectively reduce the residence time distribution. When the brachistochrone curve parameter R = 0.812 m, the falling time of the melt particles along the brachistochrone curve is Tc = 26 s. The time of the particles falling along the conical pipe only under the action of gravity is calculated, where s is the length of the inclined surface (unit: m); g is the acceleration of gravity (usually taken as 9.8 m / s2); θ is the inclination angle of the inclined surface (unit: rad). It can be seen that the motion time of the particles on the conical pipe is related to the initial position, that is, the position of the particles falling on the conical pipe, and has a wide residence time distribution. The method of simulating and calculating the residence time of the melt by using the brachistochrone curve and the inner wall using a conical pipe in this embodiment can be realized by using existing known technical means, and the principle process will not be described in detail here.

[0053] In addition, in order to verify that the fluid drops along the brachistochrone curve, the residence time distribution is narrowed compared with falling along the tapered pipe, Fluent fluid simulation software is used for simulation verification, which includes physical model, mathematical model, multiphase flow model and turbulence model for simulation experiment:

[0054] The physical model: respectively verify the fluid along the brachistochrone curve compared with falling along the tapered pipe, because the falling film flow process has symmetry, so the process can be simplified to a two-dimensional flow model, and the origin of the brachistochrone curve on one side of the brachistochrone curve is selected at the connection point of the outlet inner wall and the middle section inner wall, and the first brachistochrone curve equation is The two-dimensional model of the tapered pipe after simplification is a slope with a horizontal length of 2.55m and a height of 1.624m. The liquid inlet is distributed on the inner wall by horizontal distance 10 through multiple simulations, and the horizontal distance from the inlet to the inner wall of the outlet pipe section is 0, 0.25m, 0.5m, 0.75m, 1m, 1.25m, 1.5m, 1.75m, 2m, 2.25m, 2.5m, respectively. The fluid flows to the outlet at the bottom end of the outlet pipe section through the brachistochrone curve or the slope, wherein the selected solvent system for simulation is a molten polyethylene-cyclohexane system.

[0055] Mathematical model: the fluid flow in CFD simulation needs to satisfy the mass conservation law, momentum conservation law and energy conservation law, and the temperature of gas phase and liquid phase remains unchanged during CFD simulation, so the control equation involved in the process is:

[0056] Mass conservation equation:

[0057] In the formula: ρ represents the average density of two phases, with the unit of kg / m -3 ; t represents the flow time, with the unit of s; u represents the velocity vector value of liquid film, with the unit of m·s -1 ;

[0058] Momentum conservation equation:

[0059] In the formula: p represents the pressure of liquid film, with the unit of Pa; μ represents the average viscosity of two phases, with the unit of Pa·s; F represents the momentum source term, with the unit of N;

[0060] Multiphase flow model: In this embodiment, the VOF model is selected. The basic principle of VOF method is to determine the position of free surface by studying the volume fraction of each phase in the grid, and it can track the change of free surface position. VOF method takes pressure and velocity as independent variables, and the viscosity and other parameters in the grid can be calculated by the parameters between two phases. This calculation method requires less computer memory, so it has great advantages in dealing with fluid mechanics problems with unknown free surface; this simulation experiment uses continuous surface force model (CSF) to calculate surface tension source term; in addition, in order to determine the independence of the grid, several different grid number examples are compared, the simulation conditions are fluid viscosity 168.8 Pa·s, flow rate 5 ml / s, and the falling time along the steepest descent curve from the top is selected for comparison. Taking the grid number 26581 as the benchmark, the relative error is calculated, and the results are shown in Table 1. When the grid number reaches 26581, the grid number has little effect on the film thickness. In order to shorten the calculation time, the final calculation grid number is selected as 26581.

[0061] Table 1. Experimental results of different grid number examples

[0062]

[0063] Turbulence model: The flow of fluid can be divided into laminar flow and turbulent flow, but for medium and high viscosity fluid, it is usually laminar flow due to its high viscosity. Therefore, this simulation experiment adopts laminar flow model. However, in the process of free falling film, i.e. the devolatilization of the melt, the surface of gas and liquid will produce fluctuation, which will cause local turbulent phenomenon. This local turbulent process is beneficial to the fluctuation of gas-liquid interface and the removal of small molecules. This simulation experiment considers the falling film flow condition of medium viscosity fluid and the possible surface fluctuation condition, and specifically selects the RNG k-ε turbulence model in the turbulence model for simulation experiment.

[0064] In the simulation experiment, the existing Fluent2024R1 software package is selected, and the existing unsteady calculation method is adopted. In the experiment process, the existing implicit calculation method is selected for the discrete time item calculation, the PRESTO algorithm is adopted for the pressure item, the second-order upwind scheme is adopted for the discrete scheme of the momentum equation, the SIMPLE algorithm is selected for the pressure-velocity coupling calculation, and the time step is set to 0.001s. According to the above existing technology, the experimental platform is pre-built for experimental verification. The simulation results show that the falling time of the conical pipe is Tlmax=35.587s, Tlmin=1.756s, the falling time along the fastest falling curve is Tcmax=28.563s, Tcmin=24.682s. Therefore, since the maximum time of the molten polymer, i.e. the melt, staying in the outlet pipe section of the devolatilizer is reduced, the reaction temperature in the container can be increased to improve the overall devolatilization efficiency. By comparing the average volatile concentration ratio, the reaction temperature can be increased from 503.15K to 578.15K, the temperature used for devolatilization is increased by 2.98%, and the devolatilization effect is increased by 20%. The temperature control method in the falling film devolatilizer: the higher the temperature in the falling film devolatilizer, the more conducive to devolatilization, but subject to the existing technical requirements that the molten polymer cannot be denatured in the falling film devolatilizer, the temperature is not the higher the better, but by using the fastest falling curve in the outlet section, compared with the conical pipe, the maximum time of the molten polymer, i.e. the melt, staying in the devolatilizer can be reduced, in addition, since the heat absorbed by the molten polymer denaturation is certain, and the maximum time of staying in the devolatilizer is reduced, the temperature in the devolatilizer can be increased without denaturing the molten polymer, so as to improve the devolatilization efficiency. Compared with the existing structure, the following advantages are obtained: 1. simple structure, avoiding frequent cleaning and reducing maintenance cost; 2. the effective devolatilization height is increased, the devolatilization efficiency is improved, and the manufacturing cost is reduced. The core purpose of the present embodiment is to: (1) optimize the residence time distribution: make the residence time of all materials in the outlet area as close as possible and as short as possible (under a given pressure difference), avoid degradation of part of the materials due to too long residence time or insufficient devolatilization due to too short residence time; (2) improve the overall devolatilization efficiency and product quality stability: by solving the above local problems, ultimately realize higher monomer / solvent removal rate, lower final residual volatile content, and more uniform product performance (such as molecular weight distribution, color, odor).

[0065] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A design method for the outlet structure of a devolatilizer based on the steepest descent curve, characterized in that, The specific steps include: Step 1: Construct an outlet pipe section (1) at the bottom of the devourer body, and the inner wall profile of the outlet pipe section (1) is a first curved surface structure (11) constructed based on the steepest descent curve to ensure the shortest average residence time distribution of the melt under a given pressure difference; and the outer wall profile of the outlet pipe section (1) is a second curved surface structure (12) constructed based on the first curved surface structure (11) and according to the desired wall thickness. Step 2: The melt to be devoured is dropped into the first curved surface structure (11) of the outlet pipe section (1) through the intermediate pipe section structure (3) via the perforated plate (21) set on the inlet structure (2) of the devourer, and the devourer body and the outlet pipe section (1) are connected to form an integrated structure for realizing melt devouring by temperature.

2. The design method for the devolatilizer outlet structure based on the steepest descent curve according to claim 1, characterized in that, The method for constructing the first curved surface structure (11) is as follows: S100: Obtain the design parameters for constructing the first curved surface structure (11) based on the intermediate pipe section structure (3); and obtain the first steepest descent curve model equation based on the design parameters to obtain the first steepest descent curve trajectory; And the expression for the equation of the first steepest descent curve is: In the formula: R m -R b Represents known design parameters; R m R represents the inner wall radius of the intermediate pipe section structure (3); b The bottom outlet (13) of the outlet pipe section (1) is opened at the bottom and is used to interface with the downstream pre-installed post-treatment equipment or pipeline interface. x1,y1 represent the coordinate points of the trajectory formed by the equation of the first steepest descent curve. t represents the parameter variable. S101: Confirm the center of the circle where the bottom outlet (13) is located at the bottom of the outlet pipe section (1), and take the center of the circle as the rotation center. By rotating the first steepest descent curve trajectory once, obtain the first curved surface structure (11).

3. The design method for the devolatilizer outlet structure based on the steepest descent curve according to claim 2, characterized in that, The method for constructing the second curved surface structure (12) is as follows: S200: Define the desired wall thickness of the outlet pipe section (1), and construct the second steepest descent curve model equation according to the first steepest descent curve model equation corresponding to the first curved surface structure (11) to obtain the second steepest descent curve trajectory. And the expression for the equation of the second steepest descent curve is: In the formula: x2, y2 represent the coordinate points of the trajectory formed by the equation of the second steepest descent curve; D represents the expected wall thickness of the outlet pipe section (1); S201: Using the center of the circle where the bottom outlet (13) is located at the bottom of the outlet pipe section (1) is located as the rotation center, the second curved surface structure (12) is obtained by rotating the second steepest descent curve trajectory once.

4. A devolatilizer outlet structure obtained based on the design method described in claims 1 to 3, characterized in that, It includes an outlet pipe section (1) located at the bottom of the devolatilizer body, the inner wall of the outlet pipe section (1) being provided with a first curved surface structure (11); and the outer wall of the outlet pipe section (1) being provided with a second curved surface structure (12). The devolatilizer body includes a devolatilizer inlet structure (2) and an intermediate pipe section structure (3) connected vertically in sequence with a melt through-hole plate (21). The inner wall end of the outlet pipe section (1) is smoothly connected to the inner wall of the intermediate pipe section structure (3).

5. The devolatilizer outlet structure based on the steepest descent curve according to claim 4, characterized in that, The devourer inlet structure (2) includes a straight pipe section component (22) and an elliptical pipe section component (23); Furthermore, the top end of the straight pipe section component (22) is provided with a melt through-hole plate (21), and the bottom inner wall of the straight pipe section component (22) is smoothly connected to the top inner wall of the elliptical pipe section component (23).

6. The devolatilizer outlet structure based on the steepest descent curve according to claim 5, characterized in that, The elliptical tube segment component (23) has a gas exhaust pipe (24) on one side, and the gas exhaust pipe (24) is connected to the interior of the elliptical tube segment component (23).

7. The devolatilizer outlet structure based on the steepest descent curve according to claim 4, characterized in that, The melt has several rows of holes (211) evenly spaced on the perforated plate (21), and the holes (211) in adjacent rows are arranged in an equilateral triangle distribution.

Images