MXPA96005262A - Reactor charoles for a verticalme staged policondensation reactor - Google Patents

Abstract

The present invention relates to a polymerization reactor with a vertically arranged outer envelope, an inlet to the liquid polymer reactor near the top of the reactor, a liquid polymer reactor outlet to the bottom of the reactor, and a vapor outlet, which comprises a series of substantially circular tray assemblies, which are entirely contained within said reactor vessel, each carola assembly having a central vapor chimney and a single flow path enclosed by means of a wall having a sufficient height to avoiding spillage of the liquid polymer, said flow path being composed of at least two loops: the liquid polymer flows from one loop to the other loop by means of a substantially semi-circular turning wall wherein the flow of the liquid polymer is reversed; having said a liquid polymer tray inlet and an outlet of the liquid polymer tray to conduct a flow of the liquid polymer, the flow of the liquid polymer is achieved by means of a hydraulic gradient in which the height of the fluid surface at the inlet of the liquid polymer tray is greater than the height of the fluid surface at the outlet of the tray for the liquid polymer, and said tray assemblies extending to said outer envelope in a vertical arrangement one on the other.

Description

REACTOR CHAROLES FOR A VERTICALLY STAGED POLYCONDENSATION REACTOR Field of the Invention This invention relates to a vertically arranged polymerization reactor and which has a series of substantially circular tray assemblies; each tray assembly has an open central steam chimney and a simple flow path composed of at least two loops wherein the flow of liquid polymer is inverted by means of a substantially semi-circular turning wall; said trays having a tray inlet for liquid polymer and a tray outlet for liquid polymer, to drive a flow of the liquid polymer through a hydraulic gradient; each tray assembly being open at the top to allow steam to escape from the flow of the liquid polymer to the open central steam stack; and said trays being arranged in vertical arrangement, one on the other.

BACKGROUND OF THE INVENTION [0002] Pan designs for vertically oriented polymerization reactors generally employ gravity and vertical drop to achieve the desired degree of polymerization without the complexities of mechanical agitation. In such tray designs, the molten polymeric material forms a cascade within the vertical length of the reaction vessel. Baffles or trays are mounted in the container to provide retention of the molten polymer, thereby increasing the residence time of the liquid within the reactor and its exposure to the reaction conditions. The residence time of the liquid is required to allow sufficient time for the polymerization kinetics to keep pace with the increased release rates of secondary product, achieved by the increase in liquid-vapor surface area and by the improvement in its renovation. The Patents of the U.S.A. Nos. 4,196,168; 3,841, 836; 3,509,203; 3,359,074 and 3,787,479, as well as Great Britain Patent No. 1320769, describe reactors in which the reactant media flows by hydraulic gradient. The U.S. Patent No. 4,196,168 discloses a vertical polymerization reactor having a series of rectangular trays inclined downwards, to conduct a flow of liquid polymer along a downward path. The U.S. Patent No. 3,841, 836 discloses a vertical pol condensation reactor with a series of adjustable rectangular trays, with downward inclination and a continuous sensor means for monitoring the viscosity of the polymer. The disadvantage associated with the use of rectangular trays is that the uniformity of polymer distribution across the width of rectangular trays is difficult to achieve with large trays, and that 30% of the cross sectional area of the reaction vessel is lost compared to a circular tray. Conversely, the simple transverse flow in a circular tray mounted within the container will cause large regions of stagnant flow to form on the periphery of the tray, outside the direct currents from the inlet to the outlet. The liquid polymer in the stagnant flow regions tends to overcook, develop a high viscosity, crosslink and / or degrade. The U.S. Patent No. 3,509,203 discloses a vertical reactor with a series of horizontal structures arranged in cascade, containing a plurality of annular passages in each tray for horizontal flow of the liquid polymer therethrough, and a connecting pipe from the center of each horizontal structure for moving the liquid polymer down. The disadvantages associated with the reactor described in U.S. Pat. No. 3,509,203 are that the flow passage is too long for the high viscosity materials, that the corners in the flow passage give rise to regions of stagnant flow, that the upper part inhibits the transmission of vapor and unnecessarily increases the complexity of the flow. the construction, and that the flow tubes between the trays impede the free flow of a film that would promote the release of steam. The U.S. Patent No. 3,359,074 discloses a vertical polycondensation reactor with a series of circular trays containing slits extending in the direction of the rope, substantially separated by equal spaces with each other. The slits work to generate the necessary surface renewal within the relatively more viscous liquid medium that passes through them. The disadvantages associated with the reactor described in U.S. Pat. No. 3,359,074 are that there is a positive retention volume in the trays, that the residence time is controlled by the viscosity of the liquid and the velocity of the flow, and that the slits must be of the proper size for a particular liquid velocity and the particular physical properties of the liquid or the tray could flood or drain completely. In addition, the flow control mechanism can be occluded. The U.S. Patent No. 3,787,479 describes a vertical reactor with a series of circular trays with transverse deflectors, which create several approximately rectangular segments. Accordingly, the trays contain an elongated flow passage, side by side, for the piston-like flow of the reaction medium from one side of the tray to the other. The disadvantages associated with the reactor described in US Pat. No. 3,787,479 are that the corners in the flow passage cause the formation of regions of stagnant flow, and that the tubes for flow or between the trays prevent the formation of a thin film. Free flow to encourage the release of steam. Great Britain Patent No. 1320769 discloses a reactor having substantially horizontal spiral flow channels, open along its upper part, in which the side walls of the flow channel are spirally constructed in the form of ducts. closed flow. The disadvantages associated with the reactor described in British Patent No. 1320769 are that the use of horizontal spiral flow channels, without inversions, impedes equalizing the flow passages, and that the "internal" passage is shorter than the "external". Furthermore, the use of only one tray greatly limits the available free surface area and prevents the formation of a free falling film between the trays, which promotes the release of the vapor. Therefore, the aforementioned references are deficient because they include either (a) regions of stagnant flow caused by material that is being bypassed by the material flowing within a shorter path current, or (b) misuse of the flow. circular space within the horizontal cross section of a vertically oriented cylindrical vessel. In contrast, the reactor of the present invention utilizes a circular tray that efficiently utilizes the cross-sectional area of a cylindrical reactor while offering uniform flow path lengths of the molten liquid polymer that reduce the stagnant flow regions or dead zones to a minimum. In addition, the reactor of the present invention is capable of processing high viscosity liquids and providing a controlled residence time (volumetric retention of the liquid) for chemical reactions to occur. Moreover, the reactor of the present invention is designed to allow the vapor traffic to escape from each tray and travel toward the vapor output of the reactor along an external path to the flow path of the polymer.

Objectives of the Invention Accordingly, an object of the present invention is to provide an apparatus for the production of condensation polymers. Therefore, another object of the present invention is to provide a tray design for a vertical polymerization reactor with gravity-driven flow, which increases the utilization for liquid retention, of the space contained within a substantially cylindrical pressure vessel. . Accordingly, a further object of the present invention is to provide a tray design that minimizes stagnant flow regions and increases liquid travel speeds. Therefore, it is also an object of the invention to provide a tray design that evenly distributes the flow in each tray. Accordingly, it is also another object of the invention to provide a tray design containing channels that reverse the flow of a liquid by approximately 180 ° to obtain similar flow path lengths along the flow streams, without the presence of regions of stagnant flow or whirlpools. Therefore, a further objective of the invention is to provide a tray design that offers large amounts of vapor-liquid surface area and that creates thin liquid films for devolatilization of bubbles. These and other objects are achieved in this invention by a polymerization reactor having a vertically disposed outer shell, an inlet to the reactor for liquid polymer near the top of the reactor, and a reactor outlet for liquid polymer at the bottom of the reactor , comprising a series of substantially circular tilted or flat tray assemblies, which are completely contained within said reactor vessel. Each tray assembly having a central open steam chimney and a single flow path of essentially transverse section, enclosed by means of a wall with sufficient height to prevent spillage of the liquid polymer. Said flow path is composed of at least two curls; the liquid polymer flows from one loop to the other loop by means of substantially semicircular turning walls in which the flow of the liquid polymer is inverted. Said trays having a tray inlet for liquid polymer and a tray outlet for liquid polymer to drive a flow of the liquid polymer; the flow of the liquid polymer achieved by a hydraulic gradient where the height of the fluid surface at the inlet of the tray for the liquid polymer is greater than the height of the fluid surface at the outlet of the tray for the liquid polymer; and said tray assemblies extending towards said outer envelope vertically, one above the other.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and other additional advantages will become clearer when reference is made to the following detailed description of the invention and the accompanying drawings, in which: Figure 1 is a schematic representation of a section vertical of the polymerization reactor. Figure 2 is a schematic representation of a circular tray. The polymer flow starts outside and is indicated by arrows. Figure 3 is a schematic representation of a circular tray. The polymer flow starts inside and is indicated by arrows. This tray forms a pair with the tray of Figure 2. Figure 4 is a schematic representation of a circular tray. The polymer flow starts outside and is indicated by the arrows. Figure 5 is a schematic representation of the orientation of successive circular trays of the type shown in Figure 4. Figure 6 is a schematic representation of a cross-sectional view of an adjacent circular tray. Steam traffic is indicated by the arrows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention relates to a vertically arranged polymerization reactor, which has a series of assemblies of essentially circular trays. With reference to Figure 1, the polymerization reactor 2 has a vertically disposed casing 4, an inlet 6 to the reactor for liquid polymer near the top of the casing 4 to allow a liquid polymer to enter the reactor 2, an outlet 9 of steam and an outlet 8 of the reactor, for the liquid polymer at the bottom of the casing 4, for letting the liquid polymer out of the reactor 2. The improvement in the polymerization reactor 2 consists of the series of assemblies of essentially circular trays 10, which are completely contained within said reactor 2. The enclosure of the outer perimeter of the tray assemblies 10 can be the enclosure 4 of the reaction vessel 2 or a separate coating wall 12, which prevents the liquid polymer from splashing to the outside and over the perimeter of the tray assemblies 10. As seen in Figure 2, the tray assemblies 10 have a tray inlet 14 for liquid polymer, and a s Tray 16 for liquid polymer. Each tray assembly 10 has an open central steam chimney 18, surrounded by an interior wall 20. The liquid polymer flows on a tray floor 11 along a single flow path 26 of uniform cross section, enclosed by a wall outer 12, an inner wall 20, an intermediate wall 22 between the outer wall 12 and the inner wall 20, and a semicircular turning wall 24. The walls have a sufficient height to prevent spillage of the liquid polymer. The floor of the tray 11 can be flat or have a floor sloping downwards and / or vertical drops. Such characteristics of the tray floor can be adjustable to provide control of the depth of the liquid polymer on the tray. Increasing the inclined angle downward and / or increasing the frequency of vertical drops will result in reduced polymer depths that quickly release the byproducts. The transverse flow path 26 is composed of at least two loops, an inner loop 30 and an outer loop 32. The loops can be concentric. The liquid polymer flows from one loop to the other by means of a substantially semi-circular turning wall 24, which results in the flow direction of the liquid polymer being reversed. Preferably, the width 34 of the transverse flow path 26 is decreased by up to 40% by means of a flow restricting element 36 near the center point of the arc of the semi-circular turning wall 24. The flow restricting element 36 may be an extension of the intermediate wall 22, a vertical cylinder, such as a circular cylinder, attached to the end of the intermediate wall 22, or another craggy body having a vertical axis. Optionally, the intermediate wall 22 can be tapered within the flow restricting element. More preferably, the width of the transverse flow path 34 is 20% to 30% less than the width of the transverse flow path 26 in the inner loop 30 and the outer loop 32. Preferably, the flow restricting element 36 causes a temporary, gradual contraction in the width of the transverse flow path 26 and the subsequent gradual expansion towards the original width of the transverse flow path 26.

Preferably, the flow restricting element extends the section of the intermediate wall 22 within the region of the semi-circular turning wall 24 towards at least 20% of the length of the semi-circular outer turning wall 24. After reversing the flow direction, the liquid polymer flows around the inner loop 30 towards the outlet 16 of the tray. Prior to the outlet 16 of the tray, preferably, it is an outlet weir 40. The polymer flows on and / or through the outlet weir 40 which controls the depth of the liquid polymer in tray assembly 10. The liquid polymer flows from assemblies 10 of upper trays towards mounts 10 of lower tray by gravity. The outlet weir 40 is of such length that, as the liquid polymer flows over or through the outlet weir 40, it is broken by shearing in a thin film.

The slimming process shears small bubbles of vaporized by-products and releases that portion of the byproducts trapped in bubbles, which otherwise might be so small as to get rid of the viscous liquid polymer. Preferably, the polymer flows from a tray a to the lower tray as a free falling film and which improves the release of steam. The release of byproducts that are removed as vapor is necessary in the process of pol condensation in order to promote the increase in molecular weight of the polymer. The flow of liquid polymer is achieved by means of a hydraulic gradient in which the height of the fluid surface in the inlet 14 of tray for liquid polymer is greater than the height of the fluid surface in the outlet weir 40. The higher velocity of the liquid polymer, in comparison with the rectangular trays of a single passage, cleans the flow channel, which minimizes the accumulation of polymer in the walls of the channels and decreases the possibility of forming regions of stagnant flow or swirls . In addition, the high speed increases the efficiency of the heat transfer, which reduces the resistance to the transfer of thermal energy and eliminates the overcooking of the polymer in isolated hot spots. The tray assemblies 10 may contain means for heating liquid monomer or polymer. Suitable heating means include electrical resistances, steam and chemical means of heat transfer. Preferably, the heating means are uniform and are located on the lower side of the tray assemblies 10. A preferred heating means consists in the use of a heat transfer fluid in medium tubular sleeves, which are secured to the lower side of tray assemblies 10.

The liquid polymer from the outlet of an upper tray assembly flows into the inlet region of a lower tray assembly. The inlet region is located in the outer loop 32 or in the inner loop 30 of the tray assemblies 10. In case the liquid polymer penetrates the outer loop 32 through the liquid polymer tray inlet 14, as seen in Figure 2, the liquid polymer flows in the flow path 26 through a redistribution weir 42 located in the outer loop 32. The liquid polymer is prevented from flowing in two directions in the flow path 26 to an inclined entry floor having a backrest wall 46. The liquid polymer flows along the exterior ripple 32 until the flow of liquid polymer is reversed within the interior ripple 30 by a substantially semi-circular turning wall 24. The flow of the liquid polymer in the inner loop 30 is continued until the liquid polymer passes over and / or through an outlet weir 40 into the tray outlet 16 to flow by gravity toward a lower tray assembly of the tray. which is immediately below. In the event that the liquid polymer penetrates through the interior loop 30 through the tray inlet 50, as seen in Figure 3, the liquid polymer flows in the flow path 26 through a redistribution weir 52 located at the inside curl 30. The liquid polymer is prevented from flowing in two directions in the flow path 26 due to an inclined entrance floor having a back wall 56. The liquid polymer flows along the interior loop 30 until the flow of the liquid polymer is reversed within the outer loop 32 by a substantially semi-circular turning wall 24. The flow of the liquid polymer in the outer loop 32 is continued until the liquid polymer passes over and / or through an outlet weir 58 within the tray outlet 60 to flow by gravity toward a lower tray assembly of the tray. which is immediately below. In a preferred embodiment, the flow path of each tray assembly 10 is comprised of two curls, an inner curl and an outer curl, and all tray assemblies are essentially identical. In the preferred embodiment, the inner loop extends to the outer wall of the tray assembly, and the inner wall of the inner loop is tangent to the central steam stack and the semicircular turning wall, and the flow of the liquid polymer on each assembly Tray 10 advances from the outside of the tray to the inside of the tray. In each tray assembly 10, the liquid polymer penetrates to the outer loop 32 through the tray inlet 70 and flows through a redistribution weir 74 in the flow path 26. An inclined seat 72 at the inlet of the inlet is recommended. tray 70 to avoid regions of stagnant flow in the flow path 26. The orientation of the tray assemblies 10 could be designed in a similar manner so that the liquid polymer flows from the inside of the tray to the outside of the tray, without However, this would result in a greater likelihood of the liquid polymer splashing or spilling into the central steam stack 18. The lower tray assemblies are rotated relative to the upper tray assembly that precedes it. Preferably, a lower tray assembly 10 is rotated 22 ° to 62 ° if the diameter of the open central steam stack 18 is one third of the diameter of the reactor vessel, more preferably 24 ° to 34 ° around a vertical axis located at the center point of the tray relative to an upper tray assembly 10. The lower tray assembly is rotated relative to the preceding upper tray assembly, so that the liquid polymer flows over and through the outlet weir 76 of the upper tray outlet 78 falls vertically into the tray entrance 70 of the lower tray assembly, as shown in Figure 4 and Figure 5. The relative rotation angle between successive trays must be kept to a minimum so that the liquid polymer falls into the inlet of a lower tray and the stagnant areas opposite the flow direction of the lower tray are minimized. As seen in Figures 4 and 5, the outlet weir 76 is enlarged over the previous exit weir 58 and results in a thin film descending between the trays. The tray outlet weir 76 is preferably located at such an angle that the length over which the liquid polymer flows is maximized. The angle of rotation of successive trays, preferably, is approximately equal to the angle of the tray outlet and the weir with respect to the flow direction, such that the overflow edge projects parallel to the middle wall of the tray. which is below. More preferably, the angle of rotation and the angle of the outlet weir relative to the direction of flow are 24 ° to 34 °. Preferably, the overflow edge of the tray outlet 78 is aligned a short distance away from the bottom tray wall (s) to prevent the liquid polymer from flowing down the wall (s) . Each assembly of trays 10 may be open at the top to allow the vapor of the liquid polymer to escape over the intermediate wall 22 and / or the inner wall 20, and then radially to the central steam chute 18. On the contrary, each assembly of trays 10 can be closed at the top to force the vapor to move together with the flow of liquid polymer through the tray outlet 16. The tray assemblies 10 extend to said outer shell 4 in a vertical arrangement, one on the other. In the case where the trays are opened in the upper part, the tray assemblies 10 are sufficiently separated to allow the steam to escape, and the walls are sufficiently low to allow the steam to escape. Therefore, the steam escapes along passages that do not interfere with those of the liquid polymer flow. The steam from the tray assemblies 10 is gathered in the open central steam chimney 18, and is directed along the chimney 18 to the steam outlet 9 of the reactor vessel 2. The open central steam chimney 18 comprises 1 to 25 percent, preferably from 6 to 12 percent of the total cross sectional area of each tray. The exact size of the central open steam chute 18 for the specific reactor vessel 2 depends on the size of the reactor vessel 2 and the volumetric flow rate of the steam. In the large reactors columns, the central open steam chimney 18 can be used to allow access for inspection, cleaning and modification. Variations of the described reactor will occur to those skilled in the art in view of the above detailed description. All of these obvious modifications are within the intended full scope of the appended claims.

Claims (20)

1. Novelty of the Invention 1. A polymerization reactor with a vertically arranged outer envelope, an inlet to the liquid polymer reactor near the top of the reactor, a liquid polymer reactor outlet to the bottom of the reactor, and a vapor outlet, comprising a series of assemblies of essentially circular trays, which are fully contained within said reactor vessel; each tray assembly has an open central steam chimney and a single flow path enclosed by means of a wall having a sufficient height to prevent spillage of the liquid polymer; said flow path is composed of at least two curls; the liquid polymer flows from one loop to the other loop by means of a substantially semi-circular turning wall wherein the flow of the liquid polymer is reversed; said trays having a liquid polymer tray inlet and an outlet of the liquid polymer tray to conduct a flow of the liquid polymer; the flow of the liquid polymer is achieved by means of a hydraulic gradient in which the height of the fluid surface at the inlet of the liquid polymer tray is greater than the height of the fluid surface at the exit of the tray for the polymer liquid; and said tray assemblies extending to said outer envelope vertically disposed one above the other.
2. 2 A polymerization reactor with a vertically disposed outer shell, an inlet to the liquid polymer reactor near the top of the reactor, a reactor outlet for liquid polymer at the bottom of the reactor, and a steam outlet, comprising a series of essentially circular tray assemblies, which are fully contained within said reactor vessel; each tray assembly has an open central steam chimney and a single essentially uniform cross-sectional flow path enclosed by means of a wall having a sufficient height to prevent spillage of the liquid polymer; said flow path is composed of at least two curls; the liquid polymer flows from one loop to the other loop by means of a substantially semi-circular turning wall wherein the flow of the liquid polymer is reversed; at the intermediate point of the semi-circular turning wall the width of the flow path is reduced by up to 40% by means of a restrictor of flow of the retainer body; said trays having a liquid polymer tray inlet and a liquid polymer tray outlet to conduct a flow of the liquid polymer; the flow of the liquid polymer is achieved by means of a hydraulic gradient in which the height of the fluid surface at the inlet of the liquid polymer tray is greater than the height of the fluid surface at the exit of the tray for the polymer liquid; each tray assembly being open at the top for the escape of vapors from the flow of the liquid polymer towards the open central steam chimney; and said tray assemblies extending to said outer envelope vertically disposed one above the other, wherein the trays are sufficiently separated to allow the steam to escape
3. 3. The reactor of claim 1, wherein the tray assemblies contain heating means.
4. 4. The reactor of claim 3, wherein the heating means is selected from a group comprising electrical resistances, steam and chemical means for heat transfer.
5. 5. The reactor of claim 4, wherein the heating means are uniform and located on the bottom side of the tray assemblies.
6. 6. The reactor of claim 2, wherein the width of the flow path 20 is reduced 20 to 30 percent at the center point of the semicircular turning wall.
7. 7. The reactor of claim 6, wherein the width of the flow path is reduced by 25 percent at the center point of the semicircular turning wall.
8. 8. The reactor of claim 2, wherein the width of the flow path is gradually reduced in the flow restrictor and subsequently increased to its original value.
9. 9. The reactor of claim 1, wherein the central or open steam chimney 3 comprises from 1 to 25% of the total cross-sectional area of each tray.
10. 10. The reactor of claim 9, wherein the open central steam stack comprises from 6 to 12% of the total cross-sectional area of each tray.
11. 11. The reactor of claim 1, wherein the tray assemblies are essentially identical.
12. 12. The reactor of claim 11, wherein the inner curl extends towards the outer wall of the tray assembly, so that the liquid polymer falls from the upper tray outlet towards the tray inlet of a lower tray.
13. 13. The reactor of claim 1, wherein the inner wall of the inner loop is tangent to the central steam chimney and the semi-circular turning wall.
14. 14. The reactor of claim 1, wherein the flow path of each tray assembly is comprised of two loops, an inner loop and an outer loop.
15. 15. The reactor of claim 1, wherein a lower tray assembly is rotated relative to an upper tray assembly, wherein the angle of rotation is such that the liquid polymer falls into the outermost loop of a lower tray assembly.
16. 16. The reactor of claim 15, wherein the lower tray assembly is rotated 22 ° to 62 ° relative to the upper tray assembly.
17. 17. The reactor of claim 15, wherein the lower tray assembly is rotated 24 ° to 34 ° relative to the upper tray assembly.
18. 18. The reactor of claim 15, wherein the liquid polymer of the upper tray flows on or through an outlet weir that is perpendicular to the flow of the polymer.
19. 19. The reactor of claim 15, wherein the liquid polymer flows on or through an outlet weir which is located at an angle of 20 ° to 60 ° relative to the polymer flow.
20. 20. The reactor of claim 19, wherein the outlet weir angle relative to the polymer flow is from 24 ° to 34 °.