A short non-effective residence time devolatilization column and its gas-liquid separation internals

Abstract

This invention discloses a devolatilization tower with a short ineffective residence time and its gas-liquid separation internal components. The devolatilization tower includes a heat exchanger, a devolatilization tank located after the heat exchanger, and a gas-liquid separation internal component located inside the devolatilization tank. The gas-liquid separation internal component includes an umbrella plate and a support member supported below the umbrella plate. The support member is a grid support member, which is composed of four crossbeams. The four crossbeams have the same structure, and each crossbeam is equipped with a small umbrella cap on an "I"-shaped crossbeam. They are installed by welding to form a "T"-shaped crossbeam structure. The gas-liquid separation internal component of this invention has an umbrella plate with a surface of the steepest descent curve, which allows the fluid to pass through the umbrella plate more quickly, thereby reducing the ineffective residence time spent by the fluid flowing on the umbrella plate and allocating more of it to the effective residence time of the heat-flash devolatilization, thus improving the devolatilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of polymer material separation technology, specifically to a devolatilization tower with a short non-effective residence time and its gas-liquid separation internal components. Background Technology

[0002] In existing technologies, separation is an important step in chemical production. Its task is to use different methods to achieve processes such as component classification, concentration, enrichment, purification, refining, and isolation of two or more mixed substances.

[0003] Currently, there are various chemical separation methods and a large number of chemical separation devices. The most common method is to separate components based on their different boiling points under varying pressure and temperature conditions. This separation method can also be called the separation of light and heavy components. Components with high boiling points and low vaporization rates are called heavy components, while components with low boiling points and high vaporization rates are called light components. Chemical equipment using this separation method includes flash tanks and devolatilization towers.

[0004] Falling film evaporation is another process that uses this method for separation. In falling film evaporation, the material is added from the top of the heating chamber of the evaporator and evenly distributed into each heat exchange tube via a liquid distribution and film-forming device. The fluid is first distributed by a distribution plate and then flows downwards in a filamentous manner through the film-forming device. During this flow, the lighter components are heated and vaporized, and the resulting vapor enters the condenser for condensation (single-effect operation) or enters the next stage evaporator as the evaporation medium (multi-effect operation). The unvaporized heavier components are discharged through the separation chamber, completing the separation.

[0005] Existing technology CN115920428A discloses an apparatus for polymer devolatilization and a method for devolatilization of polyolefin elastomers, including a pre-stage devolatilizer and a final-stage devolatilizer connected in series. The pre-stage devolatilizer includes a feed distribution plate, a preheater, and a devolatilization tank. The feed distribution plate is fixed to the top of the preheater, and the devolatilization tank is fixed to the bottom of the preheater and connected to the preheater by a flange. After passing through the pre-stage devolatilizer, the melt is transported to the final-stage devolatilizer by a melt pump. This patent adds a feed distribution plate to the top of the pre-stage devolatilizer. The feed distribution plate is conical and has ellipsoidal frustum-shaped holes. The internal components of this design cannot guarantee uniform distribution of the falling fluid. When the fluid reaches the top of the conical distribution plate, it flows towards the edge of the distribution plate under the action of gravity. The time it takes for the fluid at the top to reach the edge, the time it takes for the fluid in the middle to reach the edge, and the time it takes for the fluid near the edge to reach the edge are all different. In addition, the excessively long time for the fluid at the top of the distribution plate to reach the edge significantly affects the overall effect of falling film devolatilization.

[0006] When solution polymerization is carried out, the total residence time of the reaction stock solution in the high-temperature tower is affected by the degradation rate. Although a too long residence time is beneficial to separation mass transfer, it will cause the degradation of the product and lead to a decline in performance indicators. Therefore, when the total residence time is limited, the total residence time can be divided into the time distributed on the conical distribution plate and the time of falling-film flow on the wires outside the plate. However, the distribution on the conical distribution plate is a single-sided diffusion process with low diffusion efficiency, and the falling-film process on the wires is a double-sided diffusion process with high diffusion efficiency. Therefore, when allocating the residence time, the smaller the proportion of the flow time on the conical distribution plate, the better the separation effect. Therefore, we call the flow time on the conical distribution plate the non-effective residence time.

[0007] The triangular conical distribution plate disclosed and used in the prior art has the problem of too long non-effective residence time. In addition, this distribution plate cannot ensure the uniform distribution of the fluid. The material falling in the middle of the conical distribution plate takes longer to flow to the edge than the material falling on the outside, which will lead to uneven distribution of the total residence time of the fluid and unreasonable allocation of the residence time. During high-temperature separation, it will cause serious degradation of the material with a long residence time, a greater decrease in molecular weight, and a broadening of the molecular weight distribution, thereby leading to a decline in the mechanical properties of the product.

[0008] Therefore, in order to solve the above problems, the present invention discloses a devolatilization tower with a short non-effective residence time and its gas-liquid separation internal component. Summary of the Invention

[0009] The purpose of the present invention is to provide a devolatilization tower with a short non-effective residence time and its gas-liquid separation internal component to fill the gap in the current technology.

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] A devolatilization tower with a short non-effective residence time and its gas-liquid separation internal component. The devolatilization tower includes a heat exchanger, a devolatilization tank behind the heat exchanger, and a gas-liquid separation internal component located in the devolatilization tank. The gas-liquid separation internal component includes an umbrella plate and a support member supported below the umbrella plate. The support member is a cross-shaped support member, and the cross-shaped support member is composed of 4 cross beams. The 4 cross beams have the same structure. Each cross beam is equipped with a small umbrella cap on the "I"-shaped cross frame and is installed by welding to form a "仝"-shaped cross beam structure to prevent material accumulation at the top of the "I".

[0012] Preferably, the lower part of the heat exchanger extends into the devolatilization tank, the upper part is connected to the feed pipe, and the lower outlet is a distribution plate. The distribution plate corresponds to the position of the lower umbrella plate. The heat exchanger and the distribution plate are connected by a flange to ensure the sealing of the connection between the two. The distribution plate is provided with equally spaced and equally sized round holes to ensure the uniform distribution of the fluid into the devolatilization tank and onto the umbrella plate.

[0013] Preferably, the upper part of the devolatilization tank includes a heat exchanger, and the tank completely includes a distribution plate and an umbrella plate. The top of the devolatilization tank is connected to temperature and pressure sensors and is equipped with a gas phase conduit for releasing the gas phase from the top of the tank.

[0014] Preferably, a grid-shaped support is installed below the umbrella panel and inside the volatilization tank, and a cylindrical support column is installed above the grid-shaped support. The umbrella panel contains a cylindrical support column, and the diameter of the cylindrical support column inside the umbrella panel is slightly larger than the diameter of the cylindrical support column above the grid-shaped support. The cylindrical support column above the grid-shaped support and the cylindrical support column inside the umbrella panel are nested together and connected by bolts and nuts.

[0015] Preferably, the bottom of the devolatilization tank is equipped with a melt pump, from which liquid products are extruded. A conduit and a discharge vessel are provided after the melt pump for collecting samples. The upper part of the devolatilization tank is cylindrical and the lower part is conical.

[0016] Preferably, the umbrella plate is designed as a conical tray with a bottom diameter of 100-1000 mm.

[0017] Preferably, the umbrella structure is designed such that the outer side of its axial cross-section is the "steepest descent curve", with the vertex of the umbrella's cone angle as the origin and the vertex of the bottom corner of the umbrella as the point (p, q). The analytical expression of the steepest descent curve is y = y(x). Substituting into equation (4), the value of the coefficient r can be determined using the bottom corner vertex (p, q). Equation (4) is...

[0018] The specific derivation process of equation (4) is as follows:

[0019] With the vertex of the cone as the origin and the bottom vertex of the umbrella as the point (p, q), the analytical expression of the steepest descent curve is y = y(x);

[0020] The velocity of any point located on the curve is;

[0021]

[0022] In the formula, g is the acceleration due to gravity;

[0023] Furthermore, since the speed of motion can be expressed as;

[0024]

[0025] Integrating the above equation, we can obtain the time t required for a particle to move from any position on the steepest descent curve to the bottom vertex.

[0026]

[0027] At the same time, the steepest descent curve should satisfy that t in (3) is the smallest t among all y=y(x) curves, that is, t=t min Therefore, the variational method can be used to solve for y in (3), and finally equation (4) is derived.

[0028]

[0029] In the formula, the value of the coefficient r can be determined by the bottom corner vertex (p, q);

[0030] The side edge of the umbrella panel conforms to the above curve. Due to the different sizes of the umbrella panel, the values ​​of p and q in the bottom corner vertices of the analysis are different, so the specific curve parameters are also different.

[0031] Working mechanism of this invention:

[0032] Based on the mathematical characteristics of the steepest descent curve, a particle moves along the curve solely under the influence of gravity, reaching the end of the curve in the shortest time. Furthermore, particles starting from different points on the curve reach the end in the same time. Utilizing this characteristic, fluid can pass through a distribution plate with identical residence times and be evenly distributed, reducing the time spent distributing the fluid within the plate. By using an umbrella-shaped surface with a steepest descent curve, the residence time of the fluid from its initial contact with the umbrella to its departure from the bottom corner is the same, ensuring that the fluid's ineffective residence time on the umbrella is uniform. Moreover, compared to a regular conical umbrella, an umbrella using a steepest descent curve guarantees that the fluid reaches the bottom corner at the fastest speed and in the shortest time, further reducing the ineffective residence time spent on the umbrella.

[0033] Due to the application of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0034] 1. The gas-liquid separation internal component of the present invention is provided with an umbrella plate whose surface has the fastest descent curve. Compared with the traditional triangular cone falling film component, the present invention can make the fluid pass through the umbrella plate faster, thereby reducing the non-effective residence time spent by the fluid flowing on the umbrella plate. In the same residence time, more part is allocated to the effective residence time of heat flash evaporation, thereby improving the volatilization efficiency.

[0035] 2. The umbrella plate of this invention adopts the steepest descent curve design to ensure that the residence time of the fluid at any part is the same when it reaches the bottom corner vertex, and to ensure that the residence time distribution of the fluid is the same everywhere in the devolatilization tank, thus avoiding the possibility of large differences in residence time distribution due to uneven distribution.

[0036] 3. The product structure of the present invention is simple and the cost is low. The cylindrical support column above the grid-shaped support component and the cylindrical support column inside the umbrella board are nested with each other and connected by bolts and nuts, which is convenient for disassembly and cleaning. It also has good commercial significance and is suitable for promotion and application. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, some of the drawings in the following description are some embodiments of the present invention. For those skilled in the art, other drawings can be made based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the devouring tower structure in Embodiment 1 of the present invention;

[0039] Figure 2 This is a schematic diagram of the umbrella board in Embodiment 1 of the present invention;

[0040] Figure 3 This is a schematic diagram of the grid support structure of Embodiment 1 of the present invention;

[0041] Figure 4 This is a schematic diagram of the crossbeam of the grid support member in Embodiment 1 of the present invention;

[0042] Figure 5 This is a left view of the grid support member of Embodiment 1 of the present invention;

[0043] Figure 6 This is the fastest descent curve of Embodiment 1 of the present invention. Detailed Implementation

[0044] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific implementation schemes are now described in detail.

[0045] The present invention will be further described below with reference to embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0046] Example 1

[0047] As attached Figure 1-6 As shown in the figure, this embodiment provides a devolatilization tower with a short ineffective residence time and its gas-liquid separation internal components, the devolatilization tower as shown in the attached figure. Figure 1As shown in the figure, it includes a heat exchanger, a devolatilization tank located behind the heat exchanger, and a gas-liquid separation internal component located inside the devolatilization tank. The gas-liquid separation internal component includes an umbrella plate, as shown in the appendix Figure 2 As shown in the figure, and a support member supported below the umbrella plate. The support member is a cross-shaped support member, and the cross-shaped support member is shown in the appendix Figure 3 As shown in the figure, the side of the cross-shaped support member is shown in the appendix Figure 5 As shown in the figure, the cross-shaped support member is composed of 4 crossbeams. The 4 crossbeams have the same structure. Each crossbeam is equipped with a small umbrella cap on the "I"-shaped cross-frame and is installed by welding to form a "仝"-shaped crossbeam structure, as shown in the appendix Figure 4 As shown in the figure, to prevent materials from accumulating on the top of the "I" shape;

[0048] Furthermore, the lower part of the heat exchanger extends into the devolatilization tank, the upper part is connected to the feed pipe, and the lower outlet is a distribution plate. The distribution plate corresponds to the position of the lower umbrella plate. The heat exchanger and the distribution plate are connected by a flange to ensure the sealing of the connection between the two. The distribution plate is provided with equally spaced and equal-diameter round holes to ensure that the fluid is evenly distributed and enters the devolatilization tank and falls onto the umbrella plate;

[0049] Furthermore, the upper part inside the devolatilization tank includes part of the heat exchanger, completely includes the distribution plate and the umbrella plate. The top of the devolatilization tank is connected with temperature and pressure sensors and is provided with a gas-phase conduit for releasing the gas phase from the top of the tank body;

[0050] Furthermore, a cross-shaped support member is installed inside the devolatilization tank below the umbrella plate, a cylindrical support column is installed above the cross-shaped support member, and a cylindrical support column is included in the umbrella plate. The diameter of the cylindrical support column inside the umbrella plate is slightly larger than the diameter of the cylindrical support column above the cross-shaped support member. The cylindrical support column above the cross-shaped support member and the cylindrical support column inside the umbrella plate are nested with each other and are connected by bolts and nuts;

[0051] Furthermore, a melt pump is provided at the bottom of the devolatilization tank. The liquid product is extruded from the lower part of the melt pump. After the melt pump, there are a conduit and a discharging kettle for collecting samples. The upper part of the devolatilization tank is cylindrical and the lower part is conical;

[0052] As shown in the appendix Figure 6 As shown in the figure, in the polyvinyl alcohol dehydration cold model experiment device, design experiment comparisons are carried out on the falling film conical plate using the steepest descent curve triangular cone plate and the ordinary triangular cone plate. The experiment uses a 20 kg / h, 30% polyvinyl alcohol aqueous solution, and falling film evaporation separation is carried out under the conditions of 120 °C and 0.13 MPa. The designed steepest descent curve triangular cone plate used is the umbrella plate. The bottom diameter of the conical tower plate of the umbrella plate is 300 mm, and the side edges are the steepest descent curve and a straight line respectively. According to theoretical calculations, when the vertex of the distribution plate is the (0, 0) coordinate point, the vertex of the bottom angle is (150, y), and the parameters of the designed steepest descent curve cone plate are satisfied;

[0053]

[0054] The constraint condition is satisfied at the bottom corner vertex:

[0055]

[0056] The calculation yields r = 262.79. Substituting this into equation (4), we get y = 262.79. Therefore, the vertex of the bottom corner is (150, 262.79).

[0057] Substituting the above parameters into equation (3), the time T1 calculated according to the steepest descent curve is:

[0058]

[0059] The falling time T2 using a standard triangular pyramid is:

[0060]

[0061] The calculation results show that T1 is 52s and T2 is 60s;

[0062] After converting the units and substituting the numerical values, it was found that the fastest descent could save 15% of the residence time. Actual experimental results showed that the average residence time calculated by dividing the liquid holding volume by the volumetric flow rate was about 52s, while the average residence time using a common triangular cone plate was about 60s. Compared with the average product concentration, the actual improvement effect was about 5%, and the average residence time was reduced by 8s.

[0063] Example 2

[0064] Based on Example 1, the experiment was repeated by adding a PTFE coating to the triangular pyramid plate to reduce the influence of frictional resistance. The rest of the experiment was the same as in Example 1 and will not be described in detail.

[0065] The calculation results show that T1 is 44s and T2 is 56s.

[0066] The experimental results showed that the average residence time of the product obtained by using the umbrella plate with the steepest descent curve decreased to 44s, while the average residence time of the product obtained by using the triangular pyramid plate decreased to 56s. Compared with the average concentration, the actual improvement effect was about 10%, and the average residence time was reduced by 12s.

[0067] By comparing Example 2 and Example 1, it was found that the main reason for the product quality difference after adopting the cone plate designed with the steepest descent curve is the friction of the cone plate. Reducing the friction can effectively improve the mechanical properties of the product. In addition, the cone plate with the steepest descent curve can achieve better separation effect while using less average residence time than the ordinary triangular cone plate.

[0068] In summary, the gas-liquid separation internal component of this invention is equipped with an umbrella plate whose surface has the steepest descent curve. Compared with the traditional triangular cone falling film component, this invention allows the fluid to pass through the umbrella plate more quickly, thereby reducing the ineffective residence time spent by the fluid flowing on the umbrella plate. In the same residence time, more of it is allocated to the effective residence time of heat flash evaporation, thus improving the volatilization efficiency. The umbrella plate designed with the steepest descent curve ensures that the residence time of the fluid at any part is the same when it reaches the bottom corner, ensuring that the residence time distribution of the fluid is the same everywhere in the volatilization tank, avoiding the possibility of large differences in residence time distribution due to uneven distribution.

[0069] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0070] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to the above embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A devolatilization tower with a short ineffective residence time, characterized in that, The devolatilization tower includes a heat exchanger, a devolatilization tank located behind the heat exchanger, and a gas-liquid separation internal component located inside the devolatilization tank. The gas-liquid separation internal component includes an umbrella plate and a support member supported below the umbrella plate. The support member is a cross-shaped support member, which is composed of 4 cross beams. The 4 cross beams have the same structure. Each cross beam is equipped with a small umbrella cap on an "I"-shaped cross frame and is installed by welding to form a "仝"-shaped cross beam structure; The umbrella structure is designed with the outer side of its axial cross-section as the "steepest descent curve". The origin is the vertex of the umbrella's cone, and the bottom corner vertex is (p, q). The analytical expression of the steepest descent curve is y = y(x). Substituting this into equation (4), the value of the coefficient r can be determined using the bottom corner vertex (p, q). Equation (4) is... .

2. A devolatilization tower with short ineffective residence time as described in claim 1, characterized in that, The lower part of the heat exchanger extends into the devolatilization tank, the upper part is connected to a feed pipe, and the lower outlet is a distribution plate. The distribution plate corresponds to the position of the lower umbrella plate. The heat exchanger and the distribution plate are connected by a flange, and equidistant and equal-diameter round holes are opened in the distribution plate.

3. A devolatilization tower with a short ineffective residence time as described in claim 1, characterized in that, The upper part inside the devolatilization tank includes part of the heat exchanger, completely includes the distribution plate and the umbrella plate. The top of the devolatilization tank is connected with temperature and pressure sensors and is provided with a gas-phase conduit.

4. A devolatilization tower with a short ineffective residence time as described in claim 1, characterized in that, Below the umbrella plate and inside the devolatilization tank, a cross-shaped support member is installed. Above the cross-shaped support member, a cylindrical support column is installed. The umbrella plate contains a cylindrical support column. The diameter of the cylindrical support column inside the umbrella plate is slightly larger than the diameter of the cylindrical support column above the cross-shaped support member. The cylindrical support column above the cross-shaped support member and the cylindrical support column inside the umbrella plate are nested with each other and are connected by bolts and nuts.

5. A devolatilization tower with a short ineffective residence time as described in claim 1, characterized in that, A melt pump is provided at the bottom of the devolatilization tank. The liquid product is extruded from the lower part of the melt pump. After the melt pump, there is a conduit and a discharge kettle. The upper part of the devolatilization tank is cylindrical and the lower part is conical.

6. A devolatilization tower with short ineffective residence time as described in claim 1, characterized in that, The bottom diameter of the umbrella plate is 100~1000mm.

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