Systems and methods for regenerating extractive distillation solvent with enhanced enthalpy

Abstract

Provided herein are solvent regeneration units, systems, and methods that facilitate enhanced regeneration of solvents utilized in extractive distillation. Examples include a solvent regeneration unit having a vessel that receives a lean solvent stream including 1-methylpyrrolidin-2-one (NMP) and impurities and supplies a purified solvent stream to an extractive distillation zone. The solvent regeneration unit includes an agitator operable to mix a solvent fluid within an interior volume of the vessel. The solvent regeneration unit includes one or more external heating coils connected to an outer surface of the vessel and operable to transfer heat through the outer surface and to the solvent fluid within the interior volume. The solvent regeneration unit includes one or more internal heating elements disposed within the vessel and operable to transfer heat to the solvent fluid. The one or more internal heating elements include a heat exchange panel or a heat exchange tube bundle.

Description

23CHEM0027-WO-ORD1SYSTEMS AND METHODS FOR REGENERATING EXTRACTIVE DISTILLATION SOLVENT WITH ENHANCED ENTHALPYTechnical Field

[0001] The disclosure relates to the regeneration of extractive distillation solvent by a regeneration unit having an increased surface area for heat transfer, thereby facilitating enhanced enthalpy delivery and improved solvent regeneration.Background

[0002] Solvents are used within extractive distillation processes to perform separation of components in a mixture that may otherwise be inseparable through traditional distillation. In some examples, butadiene processing plants may use extractive distillation to isolate a desired product stream including buta-l,3-diene from other C4 hydrocarbon compounds with similar boiling points. In such a process, a solvent stream is circulated through a series of distillation columns to achieve the desired separations while accumulating various impurities within the solvent stream. These impurities may be removed from the solvent stream via solvent regeneration to avoid processing issues and maintain operating efficiency. However, the feed rate for solvent regeneration may be limited based on an amount of heat transfer available between a regeneration unit and the solvent, which is in turn limited by the surface area for heat exchange.Summary

[0003] As noted above, existing solvent regeneration systems are limited in the amount of solvent they are able to regenerate based on insufficient surface area available for heat transfer. As such, a major challenge is identified herein as the improvement of heat transfer surface area for such systems. The present disclosure includes examples of a regeneration unit integrated with heat exchange components on an external surface and within an interior volume of a vessel, thus significantly enhancing the surface area of heat transfer available for solvent regeneration and correspondingly increasing solvent regeneration capacity for the regeneration unit. For example, the disclosed systems and methods provide enhanced heat transfer in a regeneration unit, which facilitates an increased solvent regeneration processing capacity and solvent feed rate without23CHEM0027-WO-ORD2relying upon separate regeneration units. Certain examples further resolve issues associated with regeneration units of increased sizes, which can otherwise suffer from an increase in liquid volume that is not suitably addressed from heating components that are associated with vessel walls and thus limited in heat transfer surface area.

[0004] In examples, the solvent regeneration units, systems, and methods disclosed herein include various structures and features that coordinate to provide a comprehensive network of external heating coils and internal heating elements that enable efficient thermal exchange between a high-temperature heating medium and unregenerated solvent streams. The structures can include (i) an agitated vessel that receives a lean solvent stream of l-methylpyrrolidin-2-one (NMP) and produces a purified solvent stream for supply to an extractive distillation zone, (ii) one or more external heating coils positioned to transfer heat to an outer surface of the agitated vessel, and (iii) one or more internal heating elements disposed within the agitated vessel to transfer heat to fluid therein, with the internal heating elements including a heat exchange panel or a heat exchange tube bundle. Accordingly, this disclosure mitigates the need for introducing other heat exchangers, such as solvent regeneration heaters, which are known to suffer from severe fouling issues on the NMP side during preliminary heating and vaporization. In the context of solvent regeneration, the internal panels or tube bundles facilitate the boiling of solvent out of a liquid pool. As such, the regeneration process is carried out far away from critical vapor fraction thresholds, which conversely are approached within the solvent regeneration heaters.

[0005] The disclosure herein provides several embodiments and examples of units and systems for the regeneration of solvent, such as NMP or a mixture of NMP and water, from a butadiene processing system and methods for solvent regeneration. Examples include a solvent regeneration unit that includes a vessel having an inlet for directing a lean solvent stream into an interior volume of the vessel and an outlet for supplying a purified solvent stream to an extractive distillation zone. The lean solvent stream includes 1-m ethyl pyrrolidin-2-one (NMP) and one or more impurities. The solvent regeneration unit includes an agitator operable to mix a solvent fluid within the interior volume. The solvent regeneration unit includes one or more external heating coils connected to an outer surface of the vessel and operable to transfer heat through the outer surface and to the solvent fluid within the interior volume. The solvent regeneration unit includes one or more internal heating elements disposed within the vessel and operable to transfer heat to the solvent fluid within23CHEM0027-WO-ORD3the interior volume. The one or more internal heating elements include a heat exchange panel or a heat exchange tube bundle.

[0006] In some examples, the one or more internal heating elements include a first surface area in contact with the solvent fluid within the interior volume, the one or more external heating coils include a second surface area in contact with the outer surface of the vessel, and the first surface area is larger than the second surface area. In some examples, the one or more internal heating elements include the heat exchange tube bundle and the heat exchange tube bundle includes one or more U-tubes or straight tubes. In some examples, the one or more internal heating elements include the heat exchange panel, and the heat exchange panel includes a rectangular body or a plate. In some examples, the heat exchange panel includes a baffle connected to an inner surface of the vessel.

[0007] In some examples, the one or more internal heating elements are positioned within a first portion of the interior volume, the agitator is positioned within a second portion of the interior volume, and the first portion and the second portion do not overlap. In some examples, the one or more external heating coils and the one or more internal heating elements are fluidly coupled downstream of a shared thermal fluid source. In some examples, the one or more external heating coils include a helical steam coil.

[0008] In some examples, the vessel includes an operating pressure of about 0.1 bar absolute or less and an operating temperature of about 120 °C or less. In some examples, the vessel is configured to direct the heat transferred from the one or more external heating coils and the one or more internal heating elements to vaporize the lean solvent stream and produce the purified solvent stream. In some examples, the solvent regeneration unit is fluidly coupled downstream of a degasser column and upstream of the extractive distillation zone and the extractive distillation zone is configured to produce at least one product stream including crude butadiene.

[0009] Examples include a method that includes supplying a lean solvent stream including NMP and one or more impurities into a vessel of a solvent regeneration unit and mixing a solvent fluid within the vessel with an agitator to distribute heat within the solvent fluid. The method includes transferring heat from one or more external heating coils in thermal contact with an outer surface of the vessel to the solvent fluid within the vessel and transferring heat from one or more internal heating elements disposed within the vessel to the solvent fluid within the vessel. The one or more internal heating elements include a heat exchange panel or a heat exchange tube bundle.23CHEM0027-WO-ORD4The method includes vaporizing a substantially pure portion of the solvent fluid within the vessel with the heat transferred from the one or more external heating coils and the one or more internal heating elements to produce a purified solvent stream. The method includes supplying the purified solvent stream to a butadiene extractive distillation zone.

[0010] In some examples, the one or more external heating coils and the one or more internal heating elements are fluidly coupled downstream of a shared thermal fluid source. In some examples, the one or more external heating coils include a helical steam coil. In some examples, the vessel includes an operating pressure of about 0.1 bar absolute or less and an operating temperature of about 120 °C or less.

[0011] Still other aspects and advantages of these exemplary embodiments and other embodiments are discussed in detail herein. Moreover, it is to be understood that both the foregoing information and the following detailed description provide merely illustrative examples of various aspects and embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations.Brief Description of the Drawings

[0012] Embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements or procedures in a method. Embodiments are illustrated by way of example and not by way of limitation in the accompanying drawings. The present disclosure can be better understood by referring to the following figures. These drawings illustrate the principles of the disclosure and no limitation of the scope of the disclosure is thereby intended.

[0013] FIG. 1 is a schematic representation of a system including a solvent regeneration unit having external and internal heating components for purifying a lean solvent stream, according to an example.

[0014] FIGS. 2A and 2B are side and top-down cross-sectional schematic representations of a solvent regeneration unit including external heating coils and an internal heating tube bundle, according to an example.23CHEM0027-WO-ORD5

[0015] FIG. 3A and 3B are side and top-down cross-sectional schematic representations of a solvent regeneration unit including external heating coils and two internal heating tube bundles, according to an example.

[0016] FIG. 4 is a top-down cross-sectional schematic representation of a solvent regeneration unit including external heating coils and internal heat exchange panels, according to an example.

[0017] FIG. 5 is a top-down cross-sectional schematic representation of a solvent regeneration unit including external heating coils, an internal heating tube bundle, and baffles, according to an example.

[0018] FIG. 6 is a diagrammatic representation of a control system for controlling operation of the disclosed systems for solvent regeneration, according to an example.Detailed Description

[0019] So that the manner in which the features and advantages of the examples of the systems and methods disclosed herein, as well as others that will become apparent, may be understood in more detail, a more particular description of examples of systems and methods briefly summarized above may be had by reference to the following detailed description of examples thereof, in which one or more are further illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only various examples of the systems and methods disclosed herein and are therefore not to be considered limiting to the scope of the systems and methods disclosed herein as it may include other effective examples as well.

[0020] The description may use the phrases “in some embodiments,” “in various embodiments,” “in an embodiment,” or “in certain embodiments,” “in some examples,” “in various examples,” “in an example,” or “in certain examples,” which may each refer to one or more of the same or different embodiments / examples. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments / examples of the present disclosure, are synonymous.

[0021] The term “about” refers to a range of values including the specified value which a person of ordinary skill in the art would consider reasonably similar to the specified value. In embodiments, “about” refers to values within a standard deviation using measurements generally acceptable in the art. In one non-limiting embodiment, when the term “about” is used with a particular value, then “about” refers to a range extending to ±10 % of the specified value,23CHEM0027-WO-ORD6alternatively ± 5 % of the specified value, or alternatively ±1 % of the specified value, or alternatively ± 0.5 % of the specified value. In embodiments, “about” refers to the specified value.

[0022] The use of the words “a” or “an” when used in conjunction with any of the terms “comprising,” “including,” “containing,” or “having,” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” The terms “wt. %”, “vol. %”, or “mol. %” refer to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume of material, or total moles, that includes the component. In a non-limiting example, 10 grams of a component in 100 grams of the material is 10 wt. % of such component. The terms “enriched” or “rich” or their variations mean an amount of at least generally about 20 wt. %, and preferably about 25 wt. %, of a compound or class of compounds in a stream. The term “substantially contains” means that the mixture includes at least 60 %, or even at least 70 %, or even at least 80 % by weight of the relevant hydrocarbon-based compounds. The terms “reducing,” “reduced,” or any variation thereof, when used in the claims and / or the specification, include any measurable decrease or complete removal to achieve a desired result. The terms “increasing,” “increased,” or any variation thereof, when used in the claims and / or the specification, include any measurable increase to achieve a desired result.

[0023] As used herein, the term “zone” can refer to an area including one or more units and / or one or more sub-zones. Units can include one or more reactors or reactor vessels, separators, strippers, extraction columns, fractionation columns, distillation columns, heaters, exchangers, pipes, pumps, valves, compressors, sensors, and controllers. Additionally, a unit, such as a reactor, dryer, or vessel, can further include one or more zones or sub-zones that contain various equipment.

[0024] The present disclosure describes various examples related to systems and methods for enhanced regeneration or purification of a solvent stream based on increased surface area for heat transfer. The examples include provision of heating components that are coupled to an outer surface of a regeneration unit and integrated with further heating components disposed within an interior volume of the regeneration unit. As described, the solvent stream of certain examples is or includes 1-m ethyl pyrrolidin-2-one (or N-methylpyrrolidone), referred to herein as NMP. The examples included herein provide efficient regeneration of solvent streams that recirculate through23CHEM0027-WO-ORD7extractive distillation zones or sections, such as extractive distillation zones for butadiene processing systems.

[0025] For example, the disclosed systems and methods provide enhanced heat transfer to solvent in a regeneration unit, which facilitates an increased regeneration processing capacity and a correspondingly increased solvent feed rate to the regeneration unit. In particular, the integration of internal heating components with external heating components drastically augments the effective heat transfer surface area, ensuring that as NMP throughput scales, the capacity for efficient regeneration scales in tandem. These features reduce the demand for introducing multiple parallel systems or additional heat exchangers, thereby obviating the associated complexities and costs.

[0026] In certain butadiene processing systems, the circulating solvent is regenerated to remove impurities such as process-generated polymers, chemical additives, and / or any other contaminants or residue content buildup within the solvent. The resulting purified solvent thus increases the overall performance and reliability of the butadiene processing. That is, solvent regeneration provides increased operational stability and continuity to the overall system, while preventing fouling issues. As examples, the increased solvent processing efficiency provided herein can reduce or eliminate problems encountered in certain butadiene processing systems, such as bottleneck conditions and / or excessively high polymer buildup that is treated with an increased solvent processing rate. Certain examples of solvent regeneration units, systems, and methods disclosed herein enable improved regeneration of solvents, which can include NMP solvent streams for butadiene processing systems, as described herein.

[0027] FIG. 1 is a schematic representation of a system 100 for regenerating solvent used for extractive distillation, such as extractive distillation within butadiene recovery systems. The system 100 of the illustrated example is a solvent regeneration section or zone that includes a solvent regeneration unit (or NMP regeneration unit) and a heat exchanger (or condenser). In more detail, the system 100 facilitates the regeneration of a lean solvent stream 102 that includes a solvent and one or more impurities. In some examples, the lean solvent stream 102 is a circulated or byproduct stream produced by a degasser column. The degasser column can receive a mixed solvent stream containing the solvent, the impurities, and one or more gases such as hydrocarbon compounds dissolved in the solvent, and can separate the dissolved gases from the solvent to output the lean solvent stream 102. The lean solvent stream 102 of certain examples is lean with respect23CHEM0027-WO-ORD8to hydrocarbons, such as hydrocarbons accumulated during extractive distillation of butadiene (e.g., buta- 1,3 -diene) and / or any other suitable hydrocarbon products.

[0028] In some examples, the lean solvent stream 102 or solvent thereof is or includes NMP. In certain examples, the solvent is or includes a mixture of NMP and water. The mixture of NMP and water can be referred to as NMP for simplicity, in certain examples. The solvent is at least about 90 weight percent (wt. % NMP) and less than about 10 wt. % water, in some examples. For example, the solvent can be about 91.7 wt. % NMP and 8.3 wt. % water. In an example, the system 100 receives the lean solvent stream 102 at a temperature less than about 100 degrees Celsius (°C). In examples, the temperature of the lean solvent stream 102 is about 95 °C, 90 °C, 85 °C, or 80 °C.

[0029] The lean solvent stream 102 is provided to a solvent regeneration unit 104 for purification or regeneration into a purified solvent stream 106. As will be understood, the solvent regeneration unit 104 integrates one or more external heating components with one or more internal heating components to increase or optimize the solvent processing capacity of the system 100. The illustrated example of the solvent regeneration unit 104 includes a vessel 110 (or agitated vessel), an agitator 112, and two different types of heating components 120. For example, the solvent regeneration unit 104 includes external heating coils 122 coupled to an outer surface of the vessel 110 and internal heating elements 124 disposed within the vessel 110. As used herein, the heating components 120 include both the external heating coils 122 and the internal heating elements 124.

[0030] The vessel 110 includes walls that define an interior volume 130, an inlet 132 for receiving fluid within the interior volume 130, and an outlet 134 for supplying vapor from the interior volume 130. As such, the vessel 110 of certain examples directs the lean solvent stream 102 through the inlet 132 and into the interior volume 130 of the vessel 110, where it forms a solvent fluid 136 or contained solvent liquid. The solvent fluid 136 of certain examples is held or maintained within the vessel 110 with at least a threshold liquid level or tank capacity, such as a level corresponding to about 50 percent, 60 percent, or 70 percent of a height of the interior volume 130. The agitator 112 of the solvent regeneration unit 104 can be any suitable mixing device that increases distribution and causes mixing within the vessel 110, without physically interfering with the internal heating elements 124. In some examples, the agitator 112 includes a shaft physically coupled to an impeller or paddle and actuated by a motor, which drives the impeller or paddle to23CHEM0027-WO-ORD9rotate circumferentially around a longitudinal axis of the shaft within the vessel 110 and mix the solvent fluid 136 within the interior volume 130. The walls of the vessel 110 and the heating components 120 and can each be formed of any suitable material having a suitably large thermal conductivity, such as stainless steel or another thermally conductive metal.

[0031] The solvent regeneration unit 104 utilizes thermal energy from both the external heating coils 122 and the internal heating elements 124 to vaporize the solvent fluid 136 within the vessel 110, which is supplied through the outlet 134 as the purified solvent stream 106. The purified solvent stream 106 output by the solvent regeneration unit 104 is free or substantially free of impurities including polymers, chemical additives, and / or any other contaminants or residue content. Within the solvent regeneration unit 104, the solvent is purified by application of heat to vaporize pure or substantially pure solvent such as NMP, while relatively heavier or less volatile impurities remain within the vessel 110.

[0032] The external heating coils 122 are connected, attached, or coupled to an outer surface of the vessel 110. From this position, the external heating coils 122 facilitate heat transfer from a heating fluid (or heat transfer medium), through the outer surface, and into the solvent fluid 136 within the interior volume 130 of the vessel 110. In some examples, the external heating coils 122 include half-tube coils, such as coils having a flattened surface for closer integration or additional surface contact with the outer surface. The external heating coils 122 can include any suitable shape, size, arrangement, and number of coils for transferring thermal energy into the vessel 110.The external heating coils 122 of certain examples are coupled to the vessel 110 along a bottom surface in addition to side walls, further increasing the surface contact for thermal transfer between the external heating coils 122 and the solvent fluid 136.

[0033] The internal heating elements 124 are disposed within the vessel 110 to deliver additional surface area for transferring heat to the solvent fluid 136 within the interior volume 130.The internal heating elements 124 are positioned within a first portion of the interior volume 130, which can be separate from or not overlapped with a second portion of the interior volume 130 containing the agitator 112. In examples, the internal heating elements 124 include one or more individual elements, which can operate in tandem, in selectively controllable sub-groups, or independently from one another. In an example, the internal heating elements 124 include a heat exchange panel. In an example, the internal heating elements 124 include a heat exchange tube bundle. Particular example arrangements of the one or more internal heating elements 124 and the23CHEM0027-WO-ORD10external heating coils 122 are described in more detail with reference to later figures. The internal heating elements 124 can receive a heating fluid having thermal energy that is transferred through a surface or wall of the internal heating elements 124 and into the solvent fluid 136.

[0034] In some examples, the internal heating elements 124 and the external heating coils 122 receive the heating fluid from a shared thermal fluid source 140 that is fluidly coupled to both of the heating components 120. The heating fluid can thus traverse respective flow paths through the internal heating elements 124 and the external heating coils 122 before being routed to a shared thermal fluid sink 142. In certain examples, the heating fluid is a low pressure stream having a preselected threshold temperature. In certain examples, the internal heating elements 124 and the external heating coils 122 are coupled to independent heating fluid sources, independent heating fluid sinks, or both. The heating fluid can be reheated and recycled to the heating components 120 in a loop, in examples.

[0035] In the illustrated example, the heating fluid is schematically illustrated as being supplied to a lower inlet of each heating component 120 and flowing upward to an upper outlet of each heating component 120. In some examples, the heating fluid is supplied to an upper inlet of one or both heating components 120 and flows downward to a lower outlet. Moreover, one or both heating components 120 can include an inlet and outlet that are generally level with one another, which can reduce a complexity of fluid fittings and connections for certain arrangements. Certain examples provide a cross-flow of heating fluid that flows downward in one heating component 120 and upward in the other heating component 120 to expose both an upper portion and a lower portion of the solvent fluid 136 to thermal energy from the heating fluid having the highest temperature.

[0036] In examples, the solvent regeneration unit 104 includes an operating temperature of about 110 °C to evaporate the purified solvent stream 106 from the solvent fluid 136. In certain examples, the operating temperature of the solvent regeneration unit 104 is less than about 130 °C, 125 °C, 120 °C, or 115 °C. The operating temperature of certain examples is between about 100 °C and 120 °C. The solvent regeneration unit 104 can operate at any suitable temperature to facilitate solvent regeneration based on thermal energy provided by the heating fluid, in certain examples. In examples, the solvent regeneration unit 104 includes an operating pressure that is about 0.05 bar(a). In some examples, the solvent regeneration unit 104 operates under vacuum pressure or includes an operating pressure that is less than about 0.10 bar(a).23CHEM0027-WO-ORD11

[0037] In certain examples, the integration of the internal heating elements 124 with the external heating coils 122 provides an additional surface area of about 2 m2per 1 m3of regeneration vessel volume. The internal heating elements 124 can include a first surface area in contact with the solvent fluid 136 that is larger than a second surface area between the external heating coils 122 and the outer surface of the vessel 110. In some examples, the solvent regeneration unit 104 processes the solvent with a heat duty of about 140 kilowatts (kW). In certain examples, the heat duty of the solvent regeneration unit 104 is between about 100 kW and 180 kW, 110 kW and 170 kW, 120 kW and 160 kW, or 130 kW and 150 kW. However, it should be understood that the present techniques are applicable for increasing an available solvent processing rate of any suitable regeneration unit. For example, the integration of the internal heating elements 124 can increase the overall heat duty of the solvent regeneration unit 104 by at least about 20 %, 30 %, 40 %, 50 %, or 60 % compared to units having only external heating.

[0038] Compared to other regeneration units that lack the combination of internal and external heating components, the solvent regeneration unit 104 is equipped for delivering increased heat duty for use within regeneration processes, such as vaporization of purified solvent. In some examples, the processing capacity of the solvent regeneration unit 104 is limited or constrained by an amount of heat that is input to the vessel 110. Moreover, as a vessel is increased in size, the surface area for externally provided heat transfer increases by an amount that is less than proportional with respect to the solvent volume undergoing regeneration. The disclosed examples of the system 100 solve such problems by dramatically increasing the surface area available for transferring thermal energy into the vessel 110, from both outside of and within the vessel 110 itself. This configuration significantly enhances the heat transfer available for solvent regeneration and facilitates a direct increase in a feed rate of the lean solvent stream 102 for improved solvent regeneration, without the use of additional heat exchangers or regeneration units in the system 100.

[0039] In examples, all or substantially all impurities included in the lean solvent stream 102 are retained within the vessel 110, while substantially pure solvent is vaporized by the thermal energy supplied by the heating components 120. Accordingly, certain examples include periodically or intermittently shutting down the solvent regeneration unit 104 to clean and remove accumulated impurities therein. In an example, the accumulated impurities form a residue within the solvent fluid 136 and / or on one or more surfaces within the vessel 110. In certain examples, operation of the solvent regeneration unit 104 is continued until a threshold amount of residue is23CHEM0027-WO-ORD12accumulated, such as in response to detecting a decrease in heat transfer or a de-calibrated liquid level. The supply of the lean solvent stream 102 is stopped to enable solvent evaporation to continue and empty the vessel 110, which is then cleaned with a stream of heated steam before operation of the solvent regeneration unit 104 is restored. As one example, the solvent regeneration unit 104 is cleaned by filling the vessel 110 with water and heating the water to about 90 °C with the agitator 112 running under nitrogen. Examples included herein further include considerations for the internal heating elements 124 that enable the heated water to circulate across heat transfer surfaces and encourage the release of any buildup. In some examples, the internal heating elements 124 are mechanically cleaned and / or temporarily removed to facilitate enhanced cleaning operations.

[0040] The solvent regeneration unit 104 thus delivers enhanced production of the purified solvent stream 106, which can be directed to an extractive distillation zone to perform extractive distillation of butadiene and / or any other suitable hydrocarbon products. The illustrated example includes a condenser 144 (or heat exchanger) coupled downstream of the solvent regeneration unit 104 to further condition the purified solvent stream 106. For example, the condenser 144 removes thermal energy from the purified solvent stream 106 to condense the vapor into a liquid and produce a liquid purified solvent stream 146 suitable for performing extractive distillation. In examples, the condenser 144 also outputs an ejector stream 148 that is supplied to an ejector associated with the system 100. As non-limiting examples, the condenser 144 can be a shell and tube heat exchanger, a plate heat exchanger, or any other heat exchanger type, including any suitable flow arrangement and number of passes. The system 100 can include any additional processing units that prepare the liquid purified solvent stream 146 for subsequent operations.

[0041] In examples, the extractive distillation zone utilizes the liquid purified solvent stream 146 to isolate one or more product streams including buta-l,3-diene based on one or more extractions. For example, the one or more product streams may be rich in buta- 1,3 -diene. In certain examples, the one or more product streams include crude butadiene (or a mixture of buta- 1,3 -diene and other hydrocarbons), which is further purified to isolate pure or substantially pure buta- 1,3 -diene. In some examples, the liquid purified solvent stream 146 is supplied to a cooled lean solvent circulation system and / or directed to a main washer or extractive distillation column of the extractive distillation zone. In certain examples, the main washer also outputs a23CHEM0027-WO-ORD13hydrocarbon-rich solvent stream that is supplied to the degasser column, which produces the lean solvent stream 102 purified herein.

[0042] The heating components 120, such as the external heating coils 122 and the internal heating elements 124, are individually designed to suit the respective operating conditions of the system 100. In certain examples, Computational Fluid Dynamics (CFD) tools or programs are utilized to guide the design of the internal heating elements 124, the agitator 112, baffles, or any other surfaces within the vessel 110, which can include relatively complex geometries. In examples, the CFD tools are leveraged to perform precise heat transfer simulations that evaluate flow and temperature fields within the solvent regeneration unit 104. Adjustments to the design of the solvent regeneration unit 104 and the heating components 120 thereof can be adjusted, finetuned, or optimized based on simulation-based analyses.

[0043] In certain examples, the design of the solvent regeneration unit 104 is determined based on evaluations of the relationship between the wetted area of the internal heating elements 124 and the liquid level in the vessel 110. The unit design can also depend on a calculated number of individual internal heating elements 124 for achieving a desired or target heat transfer surface area, given the associated process targets. The internal heating elements 124 of certain examples include a heat exchange panel and / or a heat exchange tube bundle. In certain examples, the panels can provide a higher surface area density than tube bundles. The panels and tube bundles can include different heat transfer coefficients that affect the number and dimensions of utilized tube bundles compared to panels. In examples, the solvent regeneration unit 104 includes any suitably compatible arrangement of heat exchange tube bundles, heat exchange panels, and / or baffles that provide a desired flow and temperature fields. As such, the specifically utilized arrangement and design of the internal heating elements 124 is determined based on detailed calculations and / or simulations, including CFD analysis, in certain examples. Non-limiting examples of solvent regeneration units 104 including heat exchange tube bundles or heat exchange panels are described with reference to FIGS. 2A-5.

[0044] FIGS. 2A and 2B are side and top-down cross-sectional schematic representations of a solvent regeneration unit 204 including external heating coils and an internal heating tube bundle, according to an example. The solvent regeneration unit 204 includes a vessel 210 that defines an interior volume 230 into which a lean solvent stream is directed to establish a solvent fluid 236 having a liquid level 250. The solvent regeneration unit 204 also includes an agitator 212 to mix23CHEM0027-WO-ORD14the solvent fluid 236 within the vessel 210, as well as two types of heating components 220 for heating the solvent fluid 236. These elements are similarly labeled as, can correspond to, and can include similar features as the elements described above and depicted in FIG. 1.

[0045] In the illustrated example, the solvent regeneration unit 204 includes external heating coils 222 coupled to an outer surface of the vessel 210 as one of the heating components 220. The external heating coils 222 of certain examples include half-tube coils having a flattened surface or profile that enables an inward-facing surface of the external heating coils to be positioned in full contact with the outer surface of the vessel. In some examples, the external heating coils 222 are attached to the vessel 210 in a spiral or helical arrangement. The external heating coils 222 described herein transfer thermal energy from a heating fluid to the solvent fluid 236 within the vessel.

[0046] The solvent regeneration unit 204 includes an internal heating tube bundle 260 as another heating component 220. The internal heating tube bundle 260 is positioned within the interior volume 230 of the vessel 210 to enable heat transfer between the solvent fluid 236 and a heating fluid traversing the internal heating tube bundle 260. The internal heating tube bundle 260 can include any suitable number of tubes having any corresponding shape to provide additional surface area for heat transfer. In an example, the internal heating tube bundle 260 includes a header that traverses a wall of the vessel 210 and supplies heating fluid to multiple tubes of the internal heating tube bundle 260. The internal heating tube bundle 260 can include straight tubes and / or U-shaped tubes (or U-tubes). The U-shaped tubes can route the heating fluid downward and upward through U-shaped flow paths and return heating fluid that has been cooled by the solvent fluid 236 to a manifold that traverses the wall of the vessel 210. In examples, the tube bundle 260 is positioned within the vessel 210 adjacent or next to the agitator 212, without causing physical interference with operation of the agitator 212. For example, the agitator 212 can rotate through a defined space 262 within the interior volume 230, which is separated from the tube bundle 260 by a preselected distance.

[0047] FIG. 3A and 3B are side and top-down cross-sectional schematic representations of a solvent regeneration unit 304 including external heating coils and two internal heating tube bundles, according to an example. The solvent regeneration unit 304 includes a vessel 310 integrated with heating components 320 and an agitator 312 to heat and purify the a solvent fluid23CHEM0027-WO-ORD15336 within an interior volume 330. These elements are similarly labeled as, can correspond to, and can include similar features as the elements described above and depicted in the previous Figures.

[0048] The illustrated example of the heating components 320 include external heating coils 322 coupled to the vessel 310 and two tube bundles 360 disposed within the interior volume 330 of the vessel 310. The tube bundles 360 can be positioned symmetrically on opposite sides of the agitator 312, in some examples. Additionally, the agitator 312 can rotate through a defined space 362 that does not physically contact the tube bundles 360. For example, the impeller or paddle of the agitator 312 operates at a vertical offset relative to the tube bundles 360 to enable simultaneous heating from any suitable number of tube bundles 360 along with mixing from the agitator 312.

[0049] FIG. 4 is a top-down cross-sectional schematic representation of a solvent regeneration unit 404 including external heating coils and internal heat exchange panels, according to an example. The solvent regeneration unit 404 includes a vessel 410 integrated with heating components 420 and an agitator 412 operating within a defined space 462 to heat and purify the a solvent fluid within an interior volume 430, which can each correspond to and include similar features as similarly named elements described above. The solvent regeneration unit 404 includes external heating coils 422, in examples.

[0050] The illustrated example also includes heat exchange panels 470 as the internal heating elements distributed within the vessel 410 to supply thermal energy into the solvent fluid. The heat exchange panels 470 can be any suitable size, shape, and arrangement. In some examples, the heat exchange panels 470 include a rectangular body or a plate. In examples, multiple heat exchange panels 470 are positioned to extend radially inward from an inner surface of the vessel 410. In some examples, one or more heat exchange panels 470 can be positioned adjacent to the inner surface of the vessel and extend substantially parallel to a diameter of the vessel 410. In certain examples, one or more of the heat exchange panels 470 can provide dual functionality by operating as a baffle connected to the vessel 410 to positively affect fluid flow and mixing within the vessel 410

[0051] FIG. 5 is a top-down cross-sectional schematic representation of a solvent regeneration unit 504 including external heating coils, an internal heating tube bundle, and baffles, according to an example. The solvent regeneration unit 504 includes a vessel 510 having multiple heating components 520 and an agitator 512 operating within a defined space 562 of an interior volume 530, which can each correspond to and include similar features as the elements described above.23CHEM0027-WO-ORD16

[0052] In examples, the heating components 520 include external heating coils 522 and a tube bundle 560 as an internal heating element. The tube bundle 560 and the agitator are adjacent to each other and are positioned in respective halves of the interior volume 530, though any suitable positioning can be utilized. Additionally, the solvent regeneration unit 504 of certain examples includes one or more baffles 572 integrated with an inner surface of the vessel 510. The baffles 572 can be provided with any suitable size, shape, and arrangement that coordinates with operation of the agitator 512 and the heating components 520.

[0053] FIG. 6 is a schematic representation of a control system 600 for controlling the examples of the systems discussed above. The control system 600 includes at least one controller 601. Each controller 601 includes at least one processor 602, which may be or include a central processing unit (CPU), a graphics processing unit (GPU), a co-processing unit, a sub-processing unit, or any other suitable electronic data processor. Each controller 601 includes at least one memory 603, which may be or include random access memory (RAM), read-only memory (ROM), or any other suitable electronic memory or storage. For the illustrated example, the controller 601 is communicatively connected to or in signal communication with each of the components present in a particular implementation of the systems discussed above. For example, the controller 601 can be communicatively coupled to controllable features, actuators, valves, and / or pumps associated with external steam coils 622, internal heating element(s) 624, an agitator 612, a condenser 644, and / or one or more sensors 680 (e.g., temperature sensors, pressure sensors, flow sensors, content analyzers). The controller 601 can further be communicatively connected to any other elements that are included in or facilitate operation of the systems discussed above.

[0054] The communicative connection between the controller 601 and the components, units, zones, and devices enables the controller 601 to receive monitoring and operational data from sensors and / or sub-controllers of each of these components, units, zones, and devices present in the embodiments discussed above, and further enables the controller 601 to provide control signals (e.g., electrical signals, instructions, data packets) to modify the operation of each of these units, zones, or devices. For example, the controller 601 may receive monitoring data from sensors (e.g., temperature sensors, pressure sensors, flow sensors) of each operating unit of the system. Based on any predefined threshold values for certain operational parameters, the controller 601 provides suitable control signals to modify the operation of the operating units and / or any components23CHEM0027-WO-ORD17thereof to ensure that these units and components operate within the temperatures, pressures, and residence times disclosed above.

[0055] In examples, the controller 601 instructs the various components of the systems discussed above to receive and purify a liquid solvent stream for use in extractive distillation, such as based on the interoperation of components of the control system 600. For example, the controller 601 can control one or more of the systems described above to perform methods including (i) supplying a lean solvent stream including NMP and one or more impurities into a vessel of a solvent regeneration unit, (ii) mixing a solvent fluid within the vessel with an agitator to distribute heat within the solvent fluid, (iii) transferring heat from one or more external heating coils in thermal contact with an outer surface of the vessel to the solvent fluid within the vessel, (iv) transferring heat from one or more internal heating elements disposed within the vessel to the solvent fluid within the vessel, (v) vaporizing a substantially pure portion of the solvent fluid within the vessel with the heat transferred from the one or more external heating coils and the one or more internal heating elements to produce a purified solvent stream, and (vi) supplying the purified solvent stream to a butadiene extractive distillation zone. The one or more internal heating elements can include a heat exchange panel or a heat exchange tube bundle. In some examples, the one or more external heating coils and the one or more internal heating elements are fluidly coupled downstream of a shared thermal fluid source. In some examples, the one or more external heating coils include a helical steam coil. In some examples, the vessel includes an operating pressure of about 0.1 bar absolute or less and an operating temperature of about 120 °C or less.Examples

[0056] The following examples are put forth to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and / or methods claimed herein are made and evaluated. Therefore, the following examples are intended to be purely exemplary and are not intended to limit the disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some deviations should be accounted for. There are numerous variations and combinations of reaction conditions (for example, component concentrations, desired solvents, solvent mixtures, temperatures, pressures and other reaction ranges and conditions) that can be used to optimize results obtained23CHEM0027-WO-ORD18from the described process. Only reasonable and routine experimentation is needed to optimize such process conditions.

[0057] Example 1: Increased solvent processing capacity

[0058] The systems and methods disclosed herein can regenerate solvent streams at improved processing rates, based on additional heat transfer provided by heating elements integrated both on an outer surface and within an interior volume of a vessel of a solvent regeneration unit. Simulation studies were performed to confirm the benefits of the disclosed systems and methods of solvent regeneration for butadiene processing systems.

[0059] As a non-limiting example, a reference system was considered that generally includes a solvent regeneration unit lacking the multiple heat transfer features disclosed herein. In particular, the reference unit includes a heat exchange coil coupled to an outer surface of a vessel, with no internal heating elements. As such, the regeneration unit of the reference system produces a significantly lower amount of thermal energy compared to the presently disclosed systems. Similar to the examples described above, a tested system was also considered that includes the solvent regeneration unit having both internal and external heating components as described herein. This configuration enables an increased amount of thermal energy to be transferred to solvent undergoing regeneration.

[0060] Solvent regeneration operations were simulated for each of the reference system and the tested system. The operating parameters included a solvent composition of 91.7 wt. % NMP and 8.3 wt. % water, an NMP temperature of 95 °C, an NMP pump outlet pressure of 15 bar(a), and a regeneration unit vessel pressure of 0.05 bar(a). Based on these simulations, the regeneration unit of the reference system produces a heat duty of 89 kW, which corresponds to a processing capacity of 500 kg / h of NMP.

[0061] In contrast, the tested system includes internal heating coils that deliver an additional surface area of 2 m2per 1 m3of regeneration vessel volume. Assuming a fill level of 60 % and assuming the average heat transfer co-efficient does not change, the internal heating coils provide an additional 50 kW of heat duty, totaling 139 kW for the vessel of the tested system. The tested system having internal and external heating can process 780 kg / h of NMP, which delivers a 56 % increase in solvent processing capacity over the reference system, without the use of additional regeneration units or other complex installations.23CHEM0027-WO-ORD19

[0062] When ranges are disclosed herein, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, and ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited. In the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, reference to values stated in ranges includes each and every value within that range, even though not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit to recite a range not explicitly recited.

[0063] Other objects, features and advantages of the disclosure will become apparent from the foregoing drawings, detailed description, and examples. These drawings, detailed description, and examples, while indicating specific embodiments of the disclosure, are given by way of illustration only and are not meant to be limiting. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. It should be understood that although the disclosure contains certain aspects, embodiments, and optional features, modification, improvement, or variation of such aspects, embodiments, and optional features can be resorted to by those skilled in the art, and that such modification, improvement, or variation is considered to be within the scope of this disclosure.

Claims

23CHEM0027-WO-ORD20Claims1. A solvent regeneration unit comprising:a vessel having an inlet for directing a lean solvent stream into an interior volume of the vessel and an outlet for supplying a purified solvent stream to an extractive distillation zone, wherein the lean solvent stream comprises l-methylpyrrolidin-2- one (NMP) and one or more impurities;an agitator operable to mix a solvent fluid within the interior volume;one or more external heating coils connected to an outer surface of the vessel and operable to transfer heat through the outer surface and to the solvent fluid within the interior volume; andone or more internal heating elements disposed within the vessel and operable to transfer heat to the solvent fluid within the interior volume, wherein the one or more internal heating elements comprise a heat exchange panel or a heat exchange tube bundle.

2. The solvent regeneration unit of claim 1, wherein the one or more internal heating elements include a first surface area in contact with the solvent fluid within the interior volume, the one or more external heating coils include a second surface area in contact with the outer surface of the vessel, and the first surface area is larger than the second surface area.

3. The solvent regeneration unit of claim 1 or 2, wherein the one or more internal heating elements comprise the heat exchange tube bundle, and wherein the heat exchange tube bundle comprises one or more U-tubes or straight tubes.

4. The solvent regeneration unit of claim 1 or 2, wherein the one or more internal heating elements comprise the heat exchange panel, and wherein the heat exchange panel comprises a rectangular body or a plate.

5. The solvent regeneration unit of claim 4, wherein the heat exchange panel comprises a baffle connected to an inner surface of the vessel.

6. The solvent regeneration unit of any one of claims 1-5, wherein the one or more internal heating elements are positioned within a first portion of the interior volume, the agitator is23CHEM0027-WO-ORD21positioned within a second portion of the interior volume, and the first portion and the second portion do not overlap.

7. The solvent regeneration unit of any one of claims 1-6, wherein the one or more external heating coils and the one or more internal heating elements are fluidly coupled downstream of a shared thermal fluid source.

8. The solvent regeneration unit of any one of claims 1-7, wherein the one or more external heating coils comprise a helical steam coil.

9. The solvent regeneration unit of any one of claims 1-8, wherein the vessel comprises an operating pressure of about 0.1 bar absolute or less and an operating temperature of about 120 °C or less.

10. The solvent regeneration unit of any one of claims 1-9, wherein the vessel is configured to direct the heat transferred from the one or more external heating coils and the one or more internal heating elements to vaporize the lean solvent stream and produce the purified solvent stream.

11. The solvent regeneration unit of any one of claims 1-10, wherein the solvent regeneration unit is fluidly coupled downstream of a degasser column and upstream of the extractive distillation zone, and wherein the extractive distillation zone is configured to produce at least one product stream comprising crude butadiene.

12. A method comprising:supplying a lean solvent stream comprising l-methylpyrrolidin-2-one (NMP) and one or more impurities into a vessel of a solvent regeneration unit;mixing a solvent fluid within the vessel with an agitator to distribute heat within the solvent fluid;transferring heat from one or more external heating coils in thermal contact with an outer surface of the vessel to the solvent fluid within the vessel;transferring heat from one or more internal heating elements disposed within the vessel to the solvent fluid within the vessel, the one or more internal heating elements comprising a heat exchange panel or a heat exchange tube bundle;23CHEM0027-WO-ORD22vaporizing a substantially pure portion of the solvent fluid within the vessel with the heat transferred from the one or more external heating coils and the one or more internal heating elements to produce a purified solvent stream; and supplying the purified solvent stream to a butadiene extractive distillation zone.

13. The method of claim 12, wherein the one or more external heating coils and the one or more internal heating elements are fluidly coupled downstream of a shared thermal fluid source.

14. The method of claim 12 or 13, wherein the one or more external heating coils comprise a helical steam coil.

15. The method of any one of claims 12-14, wherein the vessel comprises an operating pressure of about 0.1 bar absolute or less and an operating temperature of about 120 °C or less.

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