CN113648931A

CN113648931A - Jacketed autoclave device

Info

Publication number: CN113648931A
Application number: CN202111110581.0A
Authority: CN
Inventors: 利恩·曼斯特; 莱昂纳德斯·J·米伦迪杰克
Original assignee: Invista North America LLC
Current assignee: Invista North America LLC
Priority date: 2013-05-01
Filing date: 2014-04-10
Publication date: 2021-11-16
Also published as: WO2014179043A1; CN104128127A; TW201505708A; EP2991757A1

Abstract

The present invention relates to a polymerization autoclave with an external heating assembly comprising an autoclave vessel body, an autoclave inlet, a pressure relief valve and a heating conduit. The autoclave vessel body defines an internal reaction chamber within which polymerization reactions can occur. The autoclave vessel body was also alloyed steel. The heating conduit surrounds and is connected to the heat transfer portion of the outer surface. The heating conduit has a plurality of coils around the body of the autoclave vessel such that a heating fluid can flow annularly through the heating conduit to transfer heat to the internal reaction chamber through the heat transfer portion. The heating conduit is made of chrome molybdenum alloy steel. A heating conduit is also associated with the heat transfer portion to substantially avoid low cycle fatigue damage resulting from repeated cycle temperature differentials greater than 80 ℃.

Description

Jacketed autoclave device

The present application is a divisional application of an application having an application date of 2014, 10/4, an application number of 201410143881.2 and an invention name of jacketed autoclave device.

Technical Field

The present invention relates to a polymerization autoclave using externally heated helical alloys that substantially avoid low cycle fatigue damage from repeated cycle temperature differentials.

Background

The use of polymers has increased significantly during the past decades, due at least in part to the variation in material properties that can be achieved and the lower costs associated with forming complex shapes. For various polymer production facilities, a continuous polymerization process and a batch polymerization process may be used. Each process has advantages and disadvantages depending on a variety of factors such as cost, throughput, polymer type, polymerization kinetics, and other priorities. Batch polymerization processes typically use a polymerization reactor or autoclave heated to a suitable process temperature. Polymerization autoclaves are typically designed to withstand the high temperatures and pressures during the process. However, the particular polymerization conditions may vary widely depending on the particular polymerization reaction, the choice of additives, the amount of production, and a number of other variables.

Heating of such polymerization reactors typically involves the use of a closed loop heating system that transfers heat from a heating fluid into the reactor. The heating system may include an external heating screw, an internal heating loop, a jacket system, or other similar heat transfer system. Such systems have inherent limitations in thermal distribution, heating rates, reliability, and operational constraints. Therefore, there is a need for an improved heating system on such a polymerization reactor.

Disclosure of Invention

A polymerization autoclave having an external heating assembly may include an autoclave vessel body, an autoclave inlet, a pressure relief valve, and a heating conduit. The autoclave vessel body defines an internal reaction chamber within which polymerization reactions can occur. The container body has an outer surface and an inner surface defining a container wall thickness. The container body is also made of alloy steel. The autoclave inlet is oriented through the autoclave vessel body and is capable of introducing polymerization reactants into the internal reaction chamber. A pressure relief valve is in fluid communication with the internal reaction chamber. More particularly, the pressure relief valve is also capable of selectively venting steam from the internal reaction chamber. The heating conduit is coiled around and connected to the heat transfer portion of the outer surface. The heating conduit has a plurality of coils around the body of the autoclave vessel such that a heating fluid may be circulated through the heating conduit to transfer heat through the heat transfer portion into the internal reaction chamber. The heating conduit also has a heating conduit wall thickness and is made of a chrome molybdenum alloy steel. A heating conduit is also associated with the heat transfer portion to substantially avoid low cycle fatigue damage resulting from repeated cycle temperature differentials of greater than 80 ℃.

In another embodiment, a method of assembling a polymerization autoclave having an external heating assembly may include providing an autoclave vessel body, coiling a heating conduit a plurality of times over a heat transfer portion of an external surface, and welding the heating conduit to the heat transfer portion. The autoclave vessel body may define an internal reaction chamber and may have an outer surface with a heat transfer portion and an inner surface for containing reactants. The autoclave vessel body may also be made of alloy steel and have a vessel wall thickness. Further, the assembly may be such that the heating fluid is circulated through the heating conduit to transfer heat into the internal reaction chamber via the heat transfer portion. Also, the heating conduit may have a heating conduit wall thickness and be made of a chrome molybdenum alloy steel to substantially avoid low cycle fatigue damage resulting from repeated cycle temperature differences greater than 80 ℃.

Additional features and advantages of the invention will become apparent from the detailed description which follows, which illustrates, by way of example, features of the invention.

Drawings

FIG. 1 is a cross-sectional view of a polymerization autoclave according to one embodiment of the present invention.

It should be noted that the drawings are merely examples of various embodiments of the invention and are, therefore, not intended to limit the scope of the invention.

Detailed Description

Although the following detailed description contains many specifics for the purpose of illustrating the invention, those skilled in the art will appreciate that many variations and modifications of the following details are within the scope of the disclosed embodiments.

Accordingly, the following embodiments illustrate the present invention without loss of generality, and without imposing limitations upon the invention. Before the present invention is described in greater detail, it is to be understood that this invention is not limited to particular embodiments described, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, "polyamide" includes a variety of polyamides.

In the present invention, "comprise", "contain", and "have" and the like may have meanings given to them according to the U.S. patent law, and may mean "include" and the like, and are generally interpreted as open-ended terms. The term "consisting of …" is a closed term and is intended to include only the specifically listed devices, methods, components, parts, structures, steps, etc. in accordance with the meaning of U.S. patent law. When used with respect to a device, method, component, means, structure, step, etc., encompassed by the present invention, that "consists essentially of …" or "consists essentially of", etc., it relates to similar compositions as disclosed herein, but it may include additional structural groups, component components, method steps, etc. However, such additional structural groups, compositional components, method steps, and the like do not substantially affect the basic and novel features of the compounds or methods and the like as compared to the corresponding compounds or methods and the like disclosed herein. In further detail, when "consisting essentially of …" or "consisting essentially of", etc., is used in connection with an apparatus, system, method, component, part, structure, step, etc., encompassed by the present invention, it has the meaning ascribed to it in accordance with U.S. patent law and these terms are open ended, except where the basic or novel features being reported are not changed more than what is reported, which allows for the presence of more than what is reported, except in prior art embodiments. When open-ended terms such as "comprising" or "including" are used, it is to be understood that the terms "consisting essentially of …" and "consisting of …" are also directly supported, as is expressly stated.

Phrases such as "suitable for providing", "sufficient to result in" or "sufficient to produce" and the like, in the context of synthetic methods, relate to reaction conditions relating to time, temperature, solvent, reactant concentrations, and the like, which can be varied to provide useful quantities of reaction products or yields of reaction products, which are within the ordinary skill of the artisan. It is not necessary that the desired reaction product be the only reaction product or that the starting materials be completely consumed, and the desired reaction product provided may be isolated or otherwise further used.

It is understood that ratios, concentrations, amounts, or other data may be expressed herein in a range format. It should be understood that such range format is used for convenience and brevity. And thus should be interpreted in a flexible manner to include not only the data parameters as explicitly recited as the endpoints of the ranges, but also to include all the individual data parameters or sub-ranges encompassed within that range as if each numerical value and sub-range includes "about 'X' to about 'Y'". For purposes of this specification, a concentration range of "about 0.1% to about 5%" should be interpreted to include not only the explicitly recited concentration of about 0.1% to about 5% by weight, but also include individual concentrations (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the recited range. In one embodiment, the term "about" may include conventional rounding according to the significant digits of a data parameter. In addition, the phrase "about 'X' to 'Y'" includes "about 'X' to about 'Y'".

The term "about" as used herein, when referring to a data parameter or range, allows for a degree of variation in the value or range, such as within 10% of the stated value or stated range limit or within 5% on the other hand.

In addition, where features or aspects of the invention are described in terms of a list or markush group, those skilled in the art will appreciate that the invention is thus also described in terms of any single element or subgroup of elements of the markush group. For example, if X is described as being selected from the group consisting of bromine, chlorine, and iodine, then the claims that X is bromine and chlorine are fully described as if listed individually. For example, where features or aspects of the invention are described in terms of such a list, those skilled in the art will appreciate that the disclosure is thus also described in terms of any single element or any combination of sub-groups of elements of a markush group. Thus, if X is described as being selected from the group consisting of bromine, chlorine, and iodine, and Y is described as being selected from the group consisting of methyl, ethyl, and propyl, the claims that X is bromine and Y is methyl are fully described and supported.

As used herein, all component amounts are given in weight percent unless otherwise stated. When referring to a component solution, percentages refer to weight percentages of the component including solvent (e.g., water), unless otherwise specified.

It will be apparent to those skilled in the art upon reading this disclosure that each of the individual embodiments described and illustrated herein has individual components and features which may be readily separated from or combined with any of the features of the other several embodiments without departing from the scope or spirit of the present invention. Any described methods may be performed in the order described, or in any other order that is logically possible.

Batch polymerization reactions often involve repeated cycling of temperatures during different steps of the process. Typically, the polymerization reactants are charged to an autoclave, the material is heated sufficiently to initiate polymerization and drive the reaction through during the process. Once completed, the material was extruded or removed from the autoclave. Generally, intermediate cleaning and rinsing steps may also be employed between polymerization batches to provide more consistent product quality. Disadvantageously, such a process can result in significant temperature cycling within the autoclave along the autoclave wall and along adjacent heating systems (e.g., external heating coils). Furthermore, temperature differences at each section through the autoclave and the heating system can result in mechanical stresses at the welded connections and adjacent materials.

As an illustrative example, the formation of a binary polyamide such as nylon-6, 6 involves the conversion/reaction of a nylon salt with an acid at an elevated temperature of about 189 ℃ - > 250 ℃ for several hours. The temperature of the autoclave wall is first below the typical heating fluid temperature. The temperature and pressure conditions in the nylon-6, 6 batch process cycle included changes during the initial stages of the start-up, the nylon salt charge, the reaction phase, the extrusion phase, and the cleaning phase. Between these different stages, temperature variations can result in temperature differences between the autoclave wall and the heating coil.

Table 1 provides an example of cyclic polymerization operating conditions.

Table 1: temperature condition

Notably, the temperature difference between the heating screw and the autoclave wall can vary very dramatically. The externally heated screw is most commonly welded to the outer surface of the autoclave. The expansion of the heating screw during the start of the reaction is limited by the relatively cool autoclave wall. This can result in a pressure load that can exceed the elastic deformation limit of the weld. This permanent deformation can lead to stresses in the weld joint as the autoclave walls are subsequently heated to normal operating temperatures. Similar deformations can be caused during temperature condition changes, such as boiling, steam cleaning, purging, and reactor stopping and starting. In each case, the temperature change results in a varying temperature gradient through the weld as a function of time. Furthermore, for a multi-batch cycle, the container is continually reused during normal use and the temperature is cycled from low to high for different batch cycles.

In the case of nylon 6, 6 production, the batch cycle time may typically be about 100-120 minutes for a standard production volume. Finally, this repeated temperature differential can lead to low cycle fatigue damage at the weld joint between the externally heated screw and the autoclave wall. The degree of heat-induced extrusion and deformation may vary based on the material selection of the autoclave heating vessel, the heating conduits, and the weld alloy used to join the heating conduits. In addition, the relative size and dimensions of each component may also affect the degree of deformation, and thus low cycle fatigue issues may arise over time.

Thus, fig. 1 generally shows a polymerization autoclave 100 that may include an autoclave vessel body 104 and an external heating assembly 102 including a heating conduit 110. Also included are a plurality at the top end of the vessel for transferring reactants and/or additives into the vessel and venting gases and the like. Any of these inlet/outlet ports (which may optionally also include other ports) may be used for these purposes. For example, the vessel may be designed with an autoclave inlet 106, a pressure relief valve 108, and an optional secondary inlet, although other arrangements may be used as they are needed for a given polymerization process. The autoclave vessel body defines an internal reaction chamber 112 within which polymerization can occur. It is of particular note for the present invention that the polymerization reaction may be suitable for preparing polymers such as nylon 6, 6, although other polymerization reactions are also suitable.

The autoclave vessel body 104 may be any vessel capable of carrying out polymerization reactions within its interior. A generally suitable vessel body may comprise an internal reaction chamber enclosed by autoclave walls and capable of withstanding pressure. Although operating conditions may vary, the autoclave vessel body may be adapted to maintain a pressure of at least 300psia, and in some cases at least 600 psia. The autoclave vessel body may have an outer surface 114 and an inner surface 116. The autoclave vessel body has a cylindrical middle portion 118 with a hemispherical top portion 120 and a conical bottom portion 122. Other shapes may be used as well. The autoclave vessel body may be manufactured as a single unitary vessel. Alternatively, the autoclave vessel body may also be formed from multiple parts. These portions of the autoclave vessel body may facilitate production, assembly, cleaning and maintenance of the apparatus. For example, the internal heating assembly 124 may be engaged by a tapered bottom portion of the autoclave vessel body. Although described in more detail below, the polymerization autoclave may also be assembled and disassembled by removing fasteners along flange 126 to allow the internal heating components to be removed as a single unit. Additional features may also be provided as part of the polymerization autoclave for convenience and improved performance. For example, the retainer 127 may be coupled to a fixed structure to provide mechanical stability to the autoclave.

The autoclave vessel body may be made of a material structurally sufficient to withstand the desired operating conditions. However, the autoclave vessel body is typically made of alloy steel. Non-limiting examples of suitable alloy steels may include carbon alloy steels (e.g., HII carbon steel, st35.8, P235GH, P265GH, P295GH, P355GH, etc.), refractory metal alloys, composites thereof, and combinations thereof.

Table 2-1: carbon alloy steel (the balance being Fe)

Alloy (I)

％C

％Si

％Mn

％P

％S

％Mo

％Cr

％Ni/％Cu

St35.8

≤0.17

≤0.35

0.40

≤0.05

-

P235GH

≤0.16

≤0.35

0.6-1.2

≤0.025

≤0.015

≤0.08

≤0.3

P265GH

≤0.2

≤0.40

0.5-1.4

≤0.03

≤0.025

≤0.08

≤0.3

-

P295GH

0.08-0.20

≤0.40

0.90-1.50

≤0.025

≤0.015

≤0.08

≤0.3

P355GH

0.10-0.22

≤0.60

1.10-1.70

≤0.025

≤0.015

≤0.08

≤0.3

P235GH also requires that Cr + Cu + Mo + Ni is less than 0.70%

P295GH also requires Cr + Cu + Mo < 0.70%

In one embodiment, the vessel wall may be made of a chrome molybdenum alloy steel. Suitable chrome molybdenum alloy steels may include, but are not limited to, 16Mo3, 13CrMo4-5, P235GH, P265GH, and combinations thereof. In a particular embodiment, the vessel wall may be made of 16Mo3 that exhibits desirable properties over a wide range of operating conditions. The chemical compositions of these chromium molybdenum alloy steels are listed in tables 2-2.

Tables 2 to 2: chromium molybdenum alloy steel (the balance being Fe)

Alloy (I)

％C

％Si

％Mn

％P

％S

％Mo

％Cr

％Ni/％Cu

16Mo3

0.12-0.20

≤0.35

0.40-0.90

≤0.03

≤0.025

0.25-0.35

≤0.3

-

13CrMo

0.08-0.18

≤0.35

0.40-1.00

≤0.03

≤0.025

0.40-0.60

0.70-1.15

-

P235GH

≤0.16

≤0.35

0.6-1.2

≤0.025

≤0.015

≤0.08

≤0.3

P265GH

≤0.2

≤0.4

0.5-1.4

≤0.03

≤0.025

≤0.08

≤0.3

-

P235GH also has Cr + Cu + Mo + Ni < 0.70%

Depending on the materials selected to make the autoclave vessel body 104, the polymerization process conditions may exhibit corrosive and destructive conditions. Thus, in some alternative embodiments, the autoclave vessel body may be a coating chamber having a base chamber wall and at least one internal coating applied to the interior surface. Such a coating layer may provide an increased corrosion resistance over the corrosion resistance of the material used as the base container wall. Coated walls may generally represent a compromise to achieve mechanical strength (which is characteristic of the underlying container wall) and corrosion resistance (which is characteristic of the coating layer). Thus, at least one inner coating layer may be applied on the inner surface of the base container wall. The coating may be a coating on the base container wall using known techniques, such as explosion welding, although other deposition techniques may also be suitable. The coating material may also provide corrosion protection to the internal surfaces that come into contact with the polymerization reactants and products at high temperatures and pressures.

Thus, the base cavity wall may be made of the alloy steels listed above, in one optional aspect carbon alloy steel, such as HII carbon steel or st35.8. Alternatively, the base vessel wall may be made of a chromium molybdenum alloy steel, such as described above. However, the inner coating may be stainless steel (e.g., SS321, 314, and 306), or the like. Non-limiting examples of stainless steel 321 alloys can include X6CrNiTi18-10, X12CrNiTi8-9, and the like. Table 3 lists the chemical compositions of some suitable stainless steels.

Table 3: chemical composition of stainless steel

Alloy (I)

％C

％Si

％Mn

％P

％S

％Cr

％Ni

X6CrNiTi18-10

≤0.08

≤0.10

≤2.0

≤0.045

≤0.03

17.0-19.0

9.0-12.0

X12CrNiTi8-9

≤0.12

18.5

9.5

X6CrNiTi18-10 also requires Ti% more than or equal to 5X% C but less than or equal to 0.8.

The thickness of the autoclave vessel body 104 may vary. The container thickness may substantially affect the rate of heat transfer during temperature transitions, and may also change the degree of thermal expansion and contraction during such temperature transitions. Accordingly, the container wall thickness may generally vary from about 15mm to about 50mm, and in many cases, from about 20mm to 40 mm. In the case of a coated container, the base container wall may typically have a thickness of from 20mm to 28mm, and the coating may comprise a single layer coating having a thickness of 1.5mm to 5 mm. In one embodiment, the vessel wall may be 24mm thick carbon steel (HII) with an internal coating of 3mm stainless steel 321.

In one aspect, the tapered bottom portion 122 can have a wall thickness that is greater than a wall thickness of the cylindrical middle portion 118. For example, the thickness of the tapered bottom portion may be about 10% to 40% greater than the wall thickness of the cylindrical middle portion.

Various interfaces, inlets and outlets may be fabricated in the autoclave vessel body 104. These features can be provided for controlling feed, product removal, pressure control, venting, introducing additives, introducing staged polymerization reactants, temperature probes, pressure probes, cleaning, and video feeds, among others. The autoclave inlet 106 may be disposed through the autoclave vessel body and capable of introducing polymerization reactants into the internal reaction chamber 112, although the inlet may be configured for any of these purposes. Typically, the autoclave inlet may be wide enough to allow rapid introduction of reactants to reduce fill time. Although any suitable inlet diameter may be used, the autoclave inlet typically has a diameter of from 1 inch to 4 inches, and in many cases about 3 inches.

During processing, it is often desirable to control the pressure within the internal reaction chamber 112. One convenient method is to fill the material and adjust the heating rate while selectively releasing the material to reduce the pressure. For example, the filler material may cause an increase in pressure. Similarly, during the process, heating of the polymerizing reactants and materials may also result in an increase in pressure in the vapor space above the liquid reactants, solids, and polymerized flowable material. As the pressure increases, a suitable mechanism may be used to maintain the pressure within the desired target range. For example, the pressure may vary from about 0psi to about 300psi during the process. The high pressure cycle may typically have an upper limit around 280 psi. Similarly, the extrusion stage typically includes high pressures from about 100psi to 200psi, and typically about 125 psi.

Thus, the pressure relief valve 108 may be in fluid communication with the internal reaction chamber 112. More particularly, the pressure relief valve is also capable of selectively venting vapor from the vapor space of the internal reaction chamber and is generally disposed in the domed top portion 120 of the autoclave vessel body 104. The pressure relief valve may be a flanged pipe; any suitable pressure relief valve may be operatively associated with the flange. The pressure relief valve may generally be adjustable to provide varying pressures to the internal reaction chamber during each polymerization process cycle. Such an adjustable pressure relief valve is operatively connected to the pressure control module to remotely control pressure conditions, among other monitored and controlled conditions.

As another option, the second inlet 128 may be disposed in the hemispherical top portion. Such a second inlet may be used to add additives, staged polymerization reactants, or other components during the process. Non-limiting examples of the additives may include coloring agents, ultraviolet stabilizers, plasticizers, crosslinking agents, antibacterial agents, fibers, process auxiliaries, flame retardants, biodegradability enhancers, and the like. Optionally, a spray nozzle may be provided on the inner end of the inlet as described herein. Typically, the inlet for introducing material into the internal reaction chamber 112 may terminate a distance away from the inner wall surface 116. Thus, in order to more uniformly disperse the material into the internal reaction chamber, nozzles may be used to increase and control the dispersion pattern.

The polymerization process may generally include carefully controlling the reaction temperature within the internal reaction chamber 112. Such temperature control may be achieved by external heating and optionally internal heating. As shown in fig. 1, the external heating assembly 102 may include a heating conduit 110 coiled around the autoclave vessel body 104. The outer surface 114 may include an exposed portion and a heat transfer portion. In particular, the heating conduit may be directly connected to the heat transfer portion of the outer surface. In contrast, the exposed portion of the outer surface is free of heating mechanisms and is exposed to the ambient environment. The heating conduit has a plurality of coils around the body of the autoclave vessel such that a heating fluid may be circulated through the heating conduit to transfer heat to the internal reaction chamber via the heat transfer portion. The number of coils can vary widely, but is typically greater than 10, and in some cases as many as 20 or more than 20. Depending on the particular configuration, the external heating assembly may cover the heat transfer portion of the external surface. Although the degree of coverage may vary, the external heating component may cover 30% to 80%, in some cases 5% to 70%, and typically 40% to 70% of the external surface. For surface coverage, gaps between the windings in the heating conduit are included in these percentages, as they are covered by the external heating assembly.

Each of the coils typically has a small gap such that the outer surface 114 is exposed between successive coils of the heating conduit 110. Such gaps are typically limited to improve heat transfer into the autoclave, but are typically limited to no more than 50% (and in many cases less than 20%) of the width of the surrounding heating conduit. The heating conduit may also have a variety of cross-sectional shapes such as, but not limited to, semi-tubular, full tubular, U-channel, V-channel, and the like. In one aspect, the heating conduit may have a semi-tubular cross-sectional shape. Alternatively, the heating conduit may have an overlapping cross-section where one edge is welded to the outer surface of the autoclave vessel body while the opposite edge is welded to the overhanging portion (i.e. the outer surface) of the adjacent coil of the heating conduit. In this way, only one edge of the heating conduit is welded directly to the outer surface. As a result, the edges of the opposite sides are suspended away from the outer surface of the autoclave vessel body, so that temperature differences during the transition of operating conditions in the polymerization process are reduced. Regardless of the particular configuration, the heating conduit typically may have a uniform cross-sectional shape along the entire length of the heating conduit that is continuous with the outer surface.

The size of the heating conduit 110 is also a factor in the long term reliability and performance of the external heating assembly 102. For example, the wall thickness of the conduit may vary and is typically less than the wall thickness of the container. The corresponding wall thickness of the heating conduit may also affect the degree of stress transferred to the heating screw during temperature changes. The heating conduit wall thickness is typically less than about 25 mm. In one embodiment, the heating conduit wall thickness may be from about 3mm to about 6mm, and in one particular example 4 mm. Similarly, the ratio of container wall thickness to conduit wall thickness can affect performance. As a general rule, the ratio of container wall thickness to conduit wall thickness may be from 2: 1 to 15: 1, and in some cases from 5: 1 to 9: 1.

The heating conduit thickness can affect the stresses in the weld, as well as the heat loss to the surrounding environment. However, the outer width of the heating conduit 110 may also determine the coverage of the outer surface 114 for heat transfer purposes. In addition, the cross-sectional shape of the heating conduit may also determine the pattern of heating fluid within the conduit. While the height of the heating conduit (i.e., the vertical distance from the outer surface to the end portion of the heating conduit) may allow for a larger heating fluid volume, an excessively high height may result in undesirable heat flow and increased heating fluid volume requirements. Similarly, an increased outer width (i.e., the width of the contact area of the heating fluid with the outer surface) may increase the effective heat transfer surface. In addition, reducing the number of contact points with the outer surface results in fewer welds and potential failure points. Conversely, an excessively wide conduit may result in a non-uniform heat flow pattern. Regardless, the outer width of the heating conduit can vary significantly, for example from about 50mm to about 100 mm.

In one aspect, the heating conduit 110 may be integral with or a part of a jacket chamber surrounding at least a portion of the heat transfer portion of the outer surface 114 of the autoclave vessel body 104. Such a jacket chamber may optionally include an inner baffle or wall that directs the heated fluid to flow over a portion of the outer surface. Different baffle arrangements may be used, however complex and/or multiple baffle configurations may result in excessive head pressure. Such increased pressure within the heating assembly may increase the chances of causing a failure within the heating assembly, the need for a high pressure heated fluid pump, or increase operating costs.

Heating conduit 110 may be made of a material that can operate at a temperature of at least 350 ℃ with repeated heating-cooling cycles. Of particular interest is the heating conduit made of chrome molybdenum alloy steel. Non-limiting examples of suitable chrome molybdenum alloy steels include 16Mo3, 13CrMo4-5, P235GH, P265GH, and combinations thereof. The chemical composition of these chromium molybdenum alloy steels is given in table 4.

Table 4: chromium molybdenum alloy steel (the balance being Fe)

Alloy (I)

％C

％Si

％Mn

％P

％S

％Mo

％Cr

％Ni/％Cu

16Mo3

0.12-0.20

≤0.35

0.40-0.90

≤0.03

≤0.025

0.25-0.35

≤0.3

-

13CrMo

0.08-0.18

≤0.35

0.40-1.00

≤0.03

≤0.025

0.40-0.60

0.70-1.15

-

P235GH

≤0.16

≤0.35

0.6-1.2

≤0.025

≤0.015

≤0.08

≤0.3

P265GH

≤0.2

≤0.4

0.5-1.4

≤0.03

≤0.025

≤0.08

≤0.3

-

P235GH also has Cr + Cu + Mo + Ni < 0.7

In one aspect, the heating conduit 110 is made of a different alloy steel than the autoclave vessel body 104 and in particular the outer surface 114. However, in a particular aspect, the heating conduit may be made of the same alloy steel as the alloy steel from which the autoclave vessel body, in particular the outer surface, is made.

Typically, the external heating assembly 102 may be welded to the exterior surface 114 of the autoclave vessel body 104 using a high temperature welding alloy. Non-limiting examples of suitable welding alloys may include Mn — Mo alloys, W2Mo, G46AMG4MO, EMoB32H5, AG42, W425W2Si, or combinations thereof. In one aspect, the welding alloy may be AG 42. In another aspect, the welding alloy may be W2 Mo. Suitable commercially available solder alloys include solders such as, but not limited to, Nertalic

I-Mo or

12G。

Welding the external heating assembly 102 to the outer surface 114 may create a closed heating loop that encloses the heating fluid in the recirculating heating system. For example, the external heating assembly may include an external heating inlet 130 that introduces a heating fluid. As the heating fluid circulates around the autoclave vessel body 104, heat will be transferred into the internal reaction chamber 112 such that the heating fluid will cool in the upper portion of the heating conduit. Thus, the heating conduit may have an external heating outlet 132 that recirculates and reheats the heating fluid.

Any number of welding techniques may be used to weld the external heating assembly 102 to the external surface 114. Non-limiting examples of welding techniques include Gas Tungsten Arc Welding (GTAW), Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW), and the like. The overlay shift weld deposit in the created weld joint may be used to enhance the weld joint strength. Further, the welded connection may be a full penetration weld (i.e., as opposed to a spot weld or a partial penetration weld). For reference, the root gap of the weld joint may be 1mm to 5mm, although other gaps are also suitable.

By a selected combination of materials, heating conduit thickness, vessel wall thickness, and weld alloy materials, the heating conduit may be connected to the heat transfer portion of the outer surface 114 to substantially avoid low cycle fatigue damage resulting from repetitive cycle temperature differentials of greater than 80 ℃, and in some cases greater than 100 ℃.

Although a variety of heating fluids can be used, non-limiting examples include Thermanol

(hydrogenated terphenyls, partially hydrogenated quaterphenyls and higher polyphenyls, and proprietary mixtures of terphenyls),

(mixtures of biphenyl and diphenyl ether) and mixtures thereof. Suitable heating fluids may operate at 330 ℃ to 340 ℃ and may have a vapor pressure of less than 100 psi.

Returning to FIG. 1, the polymerization autoclave 100 may include an internal heating assembly 124 comprising an internal heating manifold. For example, the internal heating manifold may include a conical reservoir 134 having an inlet 136. The conical reservoir may be housed in a conical bottom portion 122 of the autoclave that is connected to the vessel body at a flange 126. The internal heating manifold may also include one or more flow-equalizing heating tubes 138 fluidly connected to the conical reservoir. The heating pipes may be connected to a common outlet 140 for recirculation and/or reheating of the cooled heating fluid. Furthermore, the heating tubes may be vertically arranged and substantially parallel to each other. Furthermore, heating tubes may be disposed in a lower region of the internal reaction chamber 112 to form an axially disposed annular heating manifold. An optional upper shell 142 may be provided to more evenly distribute heat within the internal reaction chamber. The upper housing is shown having an annular shape and a square cross-section with a pointed top.

The internal heating tube may be made of any material capable of operating up to at least 350 ℃, and in some cases up to about 400 ℃. Non-limiting examples of suitable materials may include those listed above for the autoclave vessel wall and external heating conduits, stainless steel, and the like. In one alternative, the internal heating tube may be made of stainless steel. Non-limiting examples of stainless steel include stainless steels 304, 316, and 321.

The internal heating assembly 124 may be integrally connected to a portion of the tapered bottom portion 122 that may be removed as a unit. The split autoclave vessel body may facilitate production, assembly, cleaning or maintenance of the apparatus. In addition, the tapered bottom portion 122 includes an autoclave outlet 144 that allows product to be removed from the internal reaction chamber 112 for further processing (e.g., extrusion, filament forming, molding, etc.). Extrusion can be performed by increasing the pressure and optionally increasing the temperature within the internal reaction chamber 112 to reduce the viscosity of the polymer product.

In another alternative, the polymerization autoclave 100 may be a stirred autoclave including an internal mixer (not shown). The internal mixer may typically be disposed vertically along the centerline of the internal reaction chamber 112. The internal mixer may allow for improved uniformity of polymerization conditions and reduced polymerization time. In this case, the internal heating assembly 124 may be omitted, or the internal heating assembly may be reconfigured to provide clearance for operating the internal mixer.

The polymerization autoclave and structures described herein can provide efficient heat transfer while also minimizing or eliminating the chance of low cycle fatigue. As a result, polymerization autoclaves incorporating these features may provide increased service life, higher reliability, and more uniform heat distribution.

Although the invention has been described in language specific to structural features and/or operations, it is to be understood that the invention defined in the appended claims is not limited to the specific features or operations described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. Numerous modifications and alternative arrangements may be devised without departing from the spirit and scope of the described technology.

Claims

1. A polymerization autoclave having an external heating assembly, comprising:

an autoclave vessel body defining an internal reaction chamber, the autoclave vessel body having an outer surface with a heat transfer portion and an inner surface, the autoclave vessel body being made of alloy steel and having a vessel wall thickness;

an autoclave inlet disposed through the autoclave vessel body and capable of introducing polymerization reactants into the internal reaction chamber;

a pressure relief valve in fluid communication with the internal reaction chamber and capable of selectively venting steam from the internal reaction chamber; and

a heating conduit wrapped around and connected to the heat transfer portion, the heating conduit having a plurality of convolutions around an autoclave vessel body such that heating fluid can circulate through the heating conduit to transfer heat through the heat transfer portion to the internal reaction chamber, the heating conduit having a heating conduit wall thickness, being made of a chromium molybdenum alloy steel and being connected to the heat transfer portion so as to substantially avoid low cycle fatigue damage resulting from repetitive cycle temperature differences of greater than 80 ℃.

2. The polymerization autoclave of claim 1, wherein the autoclave vessel body is a coating chamber having a base chamber wall and at least one internal coating coated on an inner surface.

3. The polymerization autoclave of claim 2, wherein the base chamber wall is made of carbon steel and at least one internal coating is made of stainless steel.

4. The polymerization autoclave of claim 2, wherein the base cavity wall has a thickness of from 20mm to 28mm and the at least one internal coating comprises a single layer coating having a thickness of 1.5mm to 5 mm.

5. The polymerization autoclave of claim 1, wherein the chromium molybdenum alloy steel comprises one selected from the group consisting of 16Mo3, 13CrMo, P235GH, P265GH, and combinations thereof.

6. The polymerization autoclave of claim 5, wherein the chromium molybdenum alloy steel comprises 16Mo 3.

7. The polymerization autoclave of claim 1, wherein the autoclave vessel body is also made of chrome molybdenum alloy steel.

8. The polymerization autoclave of claim 7, wherein the chrome molybdenum alloy steel of the autoclave vessel body comprises one selected from the group consisting of 16Mo3, 13CrMo, P235GH, P265GH, and combinations thereof.

9. The polymerization autoclave of claim 8, wherein the chromium molybdenum alloy steel of the heating conduit is the same material as the autoclave vessel body.

10. The polymerization autoclave of claim 9, wherein the chromium molybdenum alloy steel comprises one selected from the group consisting of 16Mo3, 13CrMo, P235GH, P265GH, and combinations thereof.

11. The polymerization autoclave of claim 9, wherein the chromium molybdenum alloy steel comprises 16Mo 3.

12. The polymerization autoclave of claim 1, wherein the autoclave inlet is disposed in a top portion of the autoclave vessel body.

13. The polymerization autoclave of claim 1, wherein the heat transfer portion of the outer surface covers 40% to 70% of the outer surface.

14. The polymerization autoclave of claim 1, wherein the heating conduit is a half-pipe welded directly to the outer surface of the autoclave by a weld alloy.

15. The polymerization autoclave of claim 14, wherein the welding alloy comprises manganese molybdenum, W2Mo, G46AMG4MO, EMoB32H5, AG42, or combinations thereof.

16. The polymerization autoclave of claim 14, wherein the welding alloy is formed as a full penetration weld.

17. The polymerization autoclave of claim 1, wherein the heating conduit has an outer width of from 50mm to 100 mm.

18. The polymerization autoclave of claim 1, wherein the heating conduit wall thickness is from 3mm to 6 mm.

19. The polymerization autoclave of claim 1, wherein the thickness of the autoclave vessel body is from 20mm to 40 mm.

20. The polymerization autoclave of claim 1, wherein the ratio of the container wall thickness to the conduit wall thickness is from 5: 1 to 9: 1.

21. The polymerization autoclave of claim 1, wherein the heating conduit wall thickness is less than the container wall thickness.

22. The polymerization autoclave of claim 1, wherein the lower portion of the autoclave vessel body has a lower wall thickness that is greater than a vessel wall thickness on the upper portion of the autoclave vessel body.

23. The polymerization autoclave of claim 1, further comprising an internal heating assembly disposed within a lower region of the internal reaction chamber.

24. The polymerization autoclave of claim 23, wherein the internal heating assembly comprises a heating tube made of stainless steel.

25. A method of assembling a polymerization autoclave having an external heating assembly, comprising:

obtaining an autoclave vessel body defining an internal reaction chamber, the autoclave vessel body having an outer surface with a heat transfer portion and an inner surface for containing reactants, the autoclave vessel body being made of an alloy steel and having a vessel wall thickness;

winding a heating conduit around a heat transfer portion of the outer surface a plurality of times;

welding the heating conduit to the heat transfer portion such that heating fluid can circulate through the heating conduit to transfer heat into the internal reaction chamber through the heat transfer portion, the heating conduit having a heating conduit wall thickness and being made of chrome molybdenum alloy steel to substantially avoid low cycle fatigue damage resulting from repetitive cycle temperature differences greater than 80 ℃.

26. The method of claim 25, wherein the autoclave vessel body is a coating chamber having a base chamber wall and at least one internal coating applied to an inner surface, wherein the base chamber wall is made of carbon steel and the at least one internal coating is made of stainless steel.

27. The method of claim 25, wherein the chrome molybdenum alloy steel comprises one selected from the group consisting of 16Mo3, 13CrMo, P235GH, P265GH, and combinations thereof.

28. The method of claim 25, wherein the autoclave vessel body is also made of chrome molybdenum alloy steel.

29. The method of claim 28, wherein the chrome molybdenum alloy steel of the autoclave vessel body comprises one selected from the group consisting of 16Mo3, 13CrMo, P235GH, P265GH, and combinations thereof.

30. The method of claim 28, wherein the chrome molybdenum alloy steel of the heating conduit is the same material as the autoclave vessel body.

31. The method of claim 25, wherein the heat transfer portion of the outer surface covers 40% to 70% of the outer surface.

32. The method of claim 25, wherein the heating conduit is a half-pipe welded directly to the outer surface of the autoclave by a weld alloy.

33. The method of claim 32, wherein the welding alloy comprises manganese molybdenum, W2Mo, G46AMG4MO, EMoB32H5, AG42, or a combination thereof.

34. The method of claim 32, wherein the weld alloy is formed as a full penetration weld.

35. The method of claim 25, wherein the heating conduit has a wall thickness of from 3mm to 6 mm.

36. The method of claim 25, wherein the thickness of the autoclave vessel body is from 20mm to 40 mm.

37. The method of claim 25, wherein the ratio of the container wall thickness to the conduit wall thickness is from 5: 1 to 9: 1.