MXPA00002191A - Aromatics separation process and method of retrofitting existing equipment for same - Google Patents

Abstract

An improved process for the recovery of aromatic compounds from a mixture containing aromatic and non-aromatic compounds and method for retrofitting existing equipment for the same is provided. The improved process comprises the steps of recovering aromatic compounds via parallel operation of a hybrid extractive distillation/liquid-liquid extractor operation and variations thereof. Methods of quickly and economically retrofitting existing recovery process equipment for use with the improved aromatics recovery process are also disclosed.

Description

PROCESS OF SEPARATION OF AROMATIC COMPOUNDS AND METHOD FOR RE-SETTING THE EXISTING EQUIPMENT FOR THIS PURPOSE * RELATED APPLICATION This application is a continuation in part of the copending provisional application Serial Number 60/057889, filed on September 3, 1997, entitled Improved Aromatics Separation Process, whose disclosure is incorporated herein by reference for all purposes. FIELD OF THE INVENTION The present invention relates to chemical separation processes and, more specifically, to an improved process for separating aromatics from a mixture of aromatic and non-aromatic compounds and methods for retro-fitting existing equipment for this purpose. BACKGROUND OF THE INVENTION Aromatic petrochemicals such as, for example, benzene, toluene, and xylenes (collectively "BTX"), serve as important building blocks for various plastics, foams and fibers. Traditionally, these fundamental compounds have been produced through the catalytic reforming of naphtha or through the decomposition of naphtha vapor or gas oils, producing currents such as, for example, pyrolysis gasoline. BTX derived from such traditional methods typically include substantial amounts of non-aromatic compounds having similar boiling points, effectively preventing simple distillation from being used to separate the aromatics from the non-aromatic compounds. Accordingly, various extraction techniques have been developed in an effort to separate aromatic compounds from non-aromatic compounds. Such prior art extraction techniques typically include the use of solvents exhibiting a higher affinity with the aromatic compounds, achieving a selective extraction of the aromatic compounds from the mixture containing aromatic compounds and non-aromatic compounds. An example of an extraction technique of the prior art is the sulfolane process developed by Shell Oil Company. The sulfolane process employs tetrahydrothiophene 1,1 (or sulfolane) as solvent and water as a co-solvent. The process employs a combination of liquid-liquid extraction and extractive separation in a single integrated design. Despite its widespread use, the Sulfolano process suffers from several disadvantages imposed by its design. For example, said process is limited in terms of its available production capacity. This is due to the fact that for the liquid-liquid extraction to occur, a phase separation must be carried out between the solvent / extract and the refined material. The maximum aromatic content of the product fed is limited to approximately 80% -90%. In addition, in traditional sulfolane process designs, the range of feed solution choices is limited. This is due to the fact that the existing sulfolane extraction units were constructed when it was considered that the feed included total aromatic concentrations of approximately 30% to 60%. With the improvements in the new catalysts and the development of continuous catalytic regeneration ("CCR"), the aromatic content of the reforming currents is significantly higher, exceeding the point at which the separation of liquid-liquid phase, and therefore extraction simple, it can happen. An attempt to solve this dilemma has been the artificial recycling of non-aromatic or refined material in order to decrease the total concentration of aromatic compounds and therefore promote phase separation. Alternatively, a co-solvent composition can be increased in an effort to increase the selectivity of the solvent system. Both attempts to integrate recent developments in catalysts and catalyst systems with prior art design significantly decrease the operation efficiency and the capacity of process units. Another drawback associated with the sulfolane process of the prior art is the concentration effect of undesired components present in the reflux stream. Extraction solvents have a group selectivity that favors the extraction of aromatic compounds >naphthalenes / olefins > paraffins and a light composite / heavy compound selectivity that favors components with low carbon numbers. Therefore, the design of the sulfolane process was based on theory in the sense that the extractive separation operation would easily remove lighter non-aromatic compounds, which could flow as reflux to the main extractor and displace heavier aromatics. In practice, the design produces at least two undesired effects: (1) difficulty in recovering the heavier aromatics in the extracted stream; and (2) accumulation of light impurities in the extractive separator and in the reflux system. The first undesired effect associated with said prior art designs is the inability of these designs to completely remove and recover the heavier spices from the aromatic compounds within the mixed feed. For example, an operation employing the prior art design and the processing of a BTX range feed can result in an almost complete recovery of benzene while losing up to 15% or more of the xylenes within the feed in the raffinate of due to the lower affinity of the solvent for xylenes compared to benzene. These results require the use of additional recovery schemes in an effort to more fully recover the xylenes present in the feed. The second unwanted effect results in a significant increase in concentration and lower carbon number components (eg, naphthalenes and C5 and C6 olefins) within the reflux stream, which can cause product contamination of the aromatic compounds with a lower carbon number. Attempts to alleviate this problem include increased efforts by the operator to separate such unwanted components in the reflux stream and / or the use of a pull stream from above the aromatic product fractionator to recycle to the extraction section. Both attempts result in increased power consumption and reduced system capacity. Thus, there remains a need for a recovery process and method for retrofitting the existing recovery process equipment in order to improve compared to prior art aromatics recovery processes and to avoid the disadvantages described above.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided an improved process for separating aromatic compounds from aromatic and non-aromatic mixtures and a method for retro-fitting existing equipment for the use of said improved process. In one aspect, the improved process for separation of the present invention includes an extractive distillation operation as a primary separation step for the recovery of the aromatic compounds. This embodiment of the invention is preferably used with feeds containing BTX fractions, but it is observed that it can also be used with feedstocks containing between 5 and 12 carbons. It was found that the Sulfolane process of the prior art and related systems suffer primarily from design and implementation problems in relation to three main areas: (1) the main extractor; (2) the extractive separator; and (3) the extract recovery operation. Although other incremental improvements were made in other aspects of the prior art process, the main improvements described here focus on these three primary areas. In a first embodiment of the improved separation process of the present invention, a hybrid extraction / distillation extractive system is employed. A portion of the mixed hydrocarbon feedstock is routed to a new separate extractive distillation column ("EDC") that operates in parallel with the main extractor, extractor-extractor, and process water washing operations. The use of an extractive distillation column allows the recovery and purification of the aromatic compounds in a single operation. The optional use of a co-solvent further improves the recoverability of this embodiment of the improved recovery process of aromatic compounds of the present invention. In a second embodiment of the improved aromatics recovery process of the present invention, the hydrocarbon feed originates from a center cut fractionation column ("HFC"), such as a reforming partition column. Additional advantages of the process are obtained by segregating the feed fractions to extraction and extractive distillation operations. The use of a co-solvent can be practiced with this embodiment of the improved aromatics separation process of the present invention to further improve the recovery of aromatic compounds from the feed. In a variation of the third embodiment described above, a side cut of the feed that includes a heavier fraction is taken from the prefractionator column and processed in the EDC. The upper portion is fed to the traditional liquid-liquid extraction portion of the system. The main advantage associated with this variation of the third embodiment is the more complete recovery of heavier aromatics, avoiding the limitations of maximum aromatics associated with prior art designs and described more fully above. In a fourth embodiment of the improved aromatics separation process of the present invention, the hydrocarbon feed is directed directly to the EDC for processing. The upper material is subsequently condensed and directed towards the liquid-liquid extractor, which functions in this mode as a refining extractor. Of practical importance is the fact that this modality can make use of an extractive separation tower modified as the EDC. In accordance with the present invention, the process of improved separation of aromatic compounds that can be derived from the retrofitting of an existing sulfolane-based extraction system. The retrofit is achieved by converting the original liquid-liquid extraction column into a vapor-liquid service and using it as the top portion of an EDC. The extractive separation column of the prior art is used as the lower portion of the EDC. Other elements of the prior art system (e.g., washing column with water) can be eliminated. It is important to note that the hydraulic capacity of the redesigned system will exceed the original capacity of the original system. In accordance with the improved aromatics recovery process of the present invention, a glycol-based extraction system of the prior art design can also be retrofitted to employ the improved aromatics recovery system. To achieve this retrofit, a fresh hydrocarbon feed is fed to the EDC tower (instead of feeding it to the main liquid-liquid extractive column) just with a thin solvent. The upper stream from the EDC contains the non-aromatic comp and can avoid the traditional step of washing with water. The liquid-liquid extraction column becomes a liquid-vapor distillation service. The bottom currents of the EDC are directed towards the liquid-vapor distillation service and further processed. The upper extract product is directed directly into product tanks without any additional washing step. In accordance with the improved aromatics recovery process and method to retrofit an existing equipment for this, an improvement of the extractive distillation process is obtained by converting the original containers used in the liquid-liquid extractive system into a refining extractor , a new EDC, a washing device with refining water and an extraction recovery operation. The primary benefits derived from the modalities identified above of the improved process to recover aromatic comps and method to retro-fit existing equipment for this, and variations of these modalities, can be summarized as follows: The modalities and variations employ either a distillation operation independent extractive or a hybrid combination that includes liquid-liquid extraction to provide process gains, such as capacity and recovery; -all the modalities and variations described here operate without current of aromatic compounds (drag) or refining recycling; - each one of the modalities and variations described here employ an operation of extractive distillation with highly effective solvents and selective addition and / or control of the proportion of co-solvent, if present within the process; - many of the modalities and variations described here segregate food and those coming from intermediate products to gain advantage compared to current limitations on existing equipment and to improve unit efficiency; - many of the modalities and variations described here allow the liquid-liquid extractor operation to be avoided without closing the system to allow maintenance work; f - many of the embodiments and variations described herein can be implemented with a relatively short interruption of the system in such a way that joint operations and other back-matching operations can be carried out; all the modalities and variations of retro-adjustment described here achieve an increase in capacity from 20 to 100% compared to the original configuration with a minimum of reconfiguration; - many of the modalities and variations described here segregate the process streams and direct them towards the most desirable processing operation, offering a greater recovery of light aromatic compounds as well as heavy aromatic compounds; - all the modalities and variations described here optimize the recovery conditions, thus reducing the associated operating costs compared with traditional system designs; - all the modalities and variations described herein more fully employ the liquid-liquid extraction operation, thus requiring a lower solvent inventory compared to the process designs of the prior art; and all the modalities and variations described herein maintain high levels of purity of the fraction extracted from lower boiling point more easily due to the fact that recycling and the associated unwanted accumulation of low weight impurities from the extraction alteration are avoided. liquid-liquid. From the foregoing it can be seen that an object of the present invention is to offer an improved aromatics recovery process as well as a method to retrofit existing equipment for use with a feed containing aromatic compounds and which can significantly increase the recovery of aromatic compounds avoiding the disadvantages associated with the processes and designs of the prior art. The manner in which these objects of the invention as well as other objects are achieved can be learned by taking into account the Detailed Description of the Next Invention, together with the Annex Drawings. BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the improved separation process and method for retro-fitting existing equipment of the present invention can be obtained by reference to the following Detailed Description when taken in combination with the Annex Drawings in which: Figure 1 is a schematic representation of a liquid / liquid extraction system of sulfolane according to the prior art; Figure 2 is a schematic representation of a first embodiment of the improved recovery process of the present invention employing a hybrid extraction / distillation extractive design; Figure 3 is a schematic representation of a second embodiment of the improved recovery process of the present invention employing a prefractionator and segregation of the feed fractions; Figure 4 is a schematic representation of a variation of the second embodiment described above, which employs a heavy feed to an extractive distillation column; Figure 5 is a schematic representation of a third embodiment of the improved recovery process of the present invention employing a hybrid design with a liquid-liquid extractor that operates as a refining extractor; Figure 6 is a schematic representation of a prior art sulfolane-based extraction system retro-fitted to handle an improved recovery process embodiment of the present invention; Figures 7A and 7B are schematic representations of an extraction system based on glycols of the prior art and a retrofit thereof to handle an improved recovery process embodiment of the present invention, respectively; Figure 8 is a schematic representation of a fourth embodiment of the improved recovery process of the present invention employing a hybrid configuration in order to approximately double the extraction unit capacity; and Figure 9 is a schematic representation of a UDEX type retrieval system of the prior art retroequipped to handle an improved recovery process embodiment of the present invention. DETAILED DESCRIPTION OF MODALITIES Compendium of process The present invention refers to the development of an improved process for the recovery of aromatic compounds as well as to a method for retro-fitting specific equipment for the same. In comparison with the processes and systems currently used in the prior art (for example, sulfolane process, UDEX type processes, etc.). The present invention offers a process and method for retrofitting exhaustive equipment to handle such processes that operate without the need for a stream of recycling (entrainment) of aromatics or a refining recycling, and which employs high-efficiency solvent systems with great efficiency. results in improved overall efficiency and capacity of the units. Importantly, the present invention is easily employed in systems of the prior art with a minimum of back-matching operations and associated lost time. Process description The success of the improved aromatic recovery process is based on the development of improvements to several aspects of traditional recovery processes (for example, sulfolano process, UDEX type process, etc). More specifically, the improved aromatics recovery process operates with either an independent extraction and distillation operation or through the hybrid combination of extractive distillation and liquid-liquid extraction to produce process advantages. A liquid-liquid extraction system of sulfolane of the prior art is illustrated in Figure 1. Such prior art systems generally consist of a main extractor 10, an extractive extractant 20, an extract recovery operation 30 and a water washing system 40. The improved process of recovery of aromatic substances and method for retro-fitting an existing equipment of the present invention was developed by analyzing and improving these three components of the system. For example, it was discovered that there is a typically substantial excess of hydraulic capacity within the recovery operation of extracts of these prior art systems when determining to form in which the prior art system could be modified to improve capacity and efficiency, the inventors focused on three of these four primary components: the main extractor 10, the extractive separator 20, and the water washing system 40. It was observed that even when the extractive recovery operation of the system was not typically an Limiting, by its capacity is easily extended by the bonus of a part or all of the internal components to a combination of lower pressure drop device. The modifications to the main extractor 10, the extractive separator 20 and the water washing system 40 were much more important. In the prior art recovery system, a mixed hydrocarbon feed is fed to the main extractor 10 for initial processing. The bottom stream from the main extractor 10 is provided to the extractive separator 20. The upper stream from the main extractor 10 is fed to the washing system with water. E water is fed to the washing system with water in figure 1. Other solvents can be used, if desired. The non-aromatic refined product from the water washing system 40 is removed for further processing or sent for storage. The reflux stream from the extractive separator 20 is recycled back to the lower section of the main extractor 10 for further processing. The bottom stream from the extractive separator 20 is directed towards the recovery operation of extract 30. The stream is added to the recovery operation of extract 30 to facilitate the recovery of aromatic compounds. Aromatic compounds are removed from the top of the extract recovery operation 30 and the bottom stream (poor solvent) is recycled to the upper portion of the main extractor 10. An optional benzene entrainment recycle and an optional refining recycle is they illustrate too. Referring now to Figure 2, a schematic representation of a first embodiment of the aromatics recovery process of the present invention is shown. In a manner similar to the prior art recovery process (Figure 1), the improved recovery system consists of a main extractor 10, an extractive separator 20, an extractive recovery operation 30 and a water washing system 40. However , in contrast to the prior art recovery system (Figure 1), the improved recovery system of the present invention further comprises a separate extractive distillation column ("EDC") 50. In this hybrid extraction / extractive distillation mode, Some of the hydrocarbon feed is directed to the main extractor 10 and a portion of the hydrocarbon feed is directed to the EDC 50 operating * in parallel with the extraction operation presented above. The EDC 50 carries out aromatic recovery and purification in a single operation. A part of the thin solvent that comes out of the extractive recovery operation is routed to an upper section of the EDC 50. In the background current from the EDC 50 it is combined with the bottom stream of the extractive separator 20 and provided to the extract 30 recovery operation. The upper stream from EDC 50 is removed directly for further processing or sent for storage. Since the effect of the solvent is more noticeable in extractive distillation (compared to liquid-liquid extraction), a cosolvent is profitably added to the base of the EDC 50 or in combination with the thin solvent to the EDC 50. Even though the co-solvent is illustrated as water, it is observed that any suitable co-solvent, or combinations of co-solvents, can be used profitably with this embodiment. In a normal operation, a co-solvent (for example water) is pre-mixed with a thin solvent and fed to the upper portion of the EDC 50. The concentration of co-solvent decreases as the solvent lowers -EDC 50. Accordingly the concentration of co-solvent is higher in the upper portion of the EDC 50 and lower to the lower portion of the EDC 50. In order to invert the concentration profile of co-solvent in the EDC 50 and therefore increase For efficiency, additional cosolvent can be added to the bottom of EDC 50, increasing the selectivity of the co-solvent. Improved efficiency and greater capacity are achieved compared to the prior art system design by reducing the bottleneck situation associated with the main extractor 10, the extractive separator 20 and the water refining washing 40 of the prior art system (figure 1). In Figure 3 a second embodiment of the aromatics recovery process of the present invention is illustrated. In this mode, the hydrocarbon feed is fed and originates from a pre-fractionator (for example reforming separation column) 60. Additional advantages are obtained by segregation of feed and providing a current to the main extractor 10 and the other current to the EDC 50. Specifically, a side cut from the pre-fractionator 60 is provided. to the main extractor 10, and an upper fraction (containing lighter materials) is provided to the EDC 50. As in the case of the first embodiment, the selective use of a co-solvent in relation to the EDC 50 can be practiced with this modality . Efficiency and capacity are substantially improved with this embodiment since lighter materials are more easily processed in the EDC 50 (as compared to the extractor / separator operation 10, 20 and 30), and the operation of the EDC 50 is improved due to a narrower range of boiling points for feeding. Alternatively, the light refining stream from the EDC 50 can be processed in a C5 / C6 isomerization unit, and the heavier refining stream is directed to a gasoline blending or gasoline fractionating feed process. A variation of the second embodiment described immediately above is illustrated in Figure 4. In this variation of the second embodiment of the improved aromatics recovery process of the present invention, a feed of mixed hydrocarbons (including heavier materials) is taken to from the pre-fractionator 60 and is provided to the EDC 50 for processing. As in the case of the first variation of the second embodiment, a lateral cut is also provided to the main extractor 10, extractive separator 20, and extractor recovery operation 30 of the system for parallel processing. A clear advantage associated with this variability of the second embodiment is derived from the fact that the heavier aromatics are more completely recovered from the EDC 50 feed (as compared to the extractor / separator portion). Since heavy materials are richer in aromatics (compared to lighter materials), the maximum aromatic limit (described above) achieved with the prior art system is avoided. Another benefit associated with this configuration is that an operator is equipped with the flexibility to selectively purge a part of the average cut of the fraction of aromatics in the raffinate by increasing the cut-off point in the EDC 50 (eg, purge toluene from of a BTX range power). This feature can be used to balance production against octane requirements and downstream limitations. A third embodiment of the improved aromatics recovery process is illustrated in Figure 5. In this third embodiment, a mixed hydrocarbon feed is fed directly to an EDC 50 for processing. The upper stream taken from the EDC 50 is then convinced and subsequently fed to the main extractor 10 for further processing. In this embodiment, the main extractor 10 is operating as a refined product extractor. A bottom stream from the main extractor 10 is alternately offered at various points along the EDC 50, placing the benzene-rich fraction at an optimum location for recovery. In accordance with what is discussed in more detail below, the extractive separator 20 of the prior art design and prior embodiments can be modified to act as the EDC 50 for this embodiment or the extractive separator 20 can be replaced with a new container for its use in the EDC 50. By feeding fresh mixed hydrocarbons directly into the EDC 50, the recovery of the xylenes will be maintained while achieving a substantial reduction in the amount of aromatic compounds present in the reflux stream from the EDC 50 to the main extractor 10 (which operates as a refined product extractor). Additional efficiency and capacity gains are derived in this embodiment since the current fed to the main extractor 10 (which acts as a refined product extractor) will be adjusted for the optimum operation of the liquid-liquid extractor. Figure 6 illustrates the in-process retrofit of sulfolane-type prior art to handle an improved process mode of recovery of aromatic compounds of the present invention. In this retrofit operation, the original liquid-liquid extractor is converted to a vapor-liquid service 10 and is used as the upper portion of an EDC. The original extractive separator is converted for use as the lower portion of the EDC 50. A re-boiler 52 is used for the EDC 50 in its existing state and the condenser 54 for the original extractive separator can be used to condensate the upper vapors from the vapor-liquid service 10. In one embodiment, the washing with refining water 40 is no longer necessary and can be removed from the system or avoided, if desired. A clear advantage of the retrofit illustrated in Figure 6 is that the hydraulic capacity of the liquid-vapor service 10 and the operation of the original extractive separator in series such as EDC 50 is substantially higher than the hydraulic capacity of the original system of the prior art. . As illustrated in Figures 7A and 7B, a glycol-based extraction system of the prior art can also be easily and inexpensively retrofitted to handle one embodiment of the improved recovery process of aromatics of the present invention. In Figure 7A, a recovery system based on original glycol is illustrated. In a system of this type, mixed hydrocarbon feed, thin solvent and reflux are fed into a main extractor 10 (liquid-liquid). A rich solvent taken from the bottom of the main extractor 10 is fed to the extractive separation column / extractive combination recovery. The aromatics are taken through steam extraction to and from the extractive separation column / extract recovery and washed. The thin solvent and reflux are recycled to the main extractor 10. As reference now figure 7B, a retro-adjusted glycol-based recovery system is illustrated, layers of handling an improved process mode of recovery of aromatic compounds of the present invention. In accordance with the retro-fitting, a mixed hydrocarbon feed and thin solvent are fed into an EDC 50 for processing. The extractive separation / recovery column of the combination extract (FIG. 7A) of the original system has been converted to EDC 50. The upper stream from the EDC 50 containing the non-aromatic compounds is effectively free of solvent and can therefore be avoid a washing step. The bottom stream from the EDC 50 is provided to the recovery operation of extract 10, which has been modified from the original liquid-liquid extractor to a liquid-vapor distillation service. The upper stream from the recovery operation of extract 10 is an aromatic product and can be collected without the washing step. The conversion described there is particularly simple and easy to perform since the original extraction unit (Figure 7A) used two capacitors and accumulators, which can be conveniently adapted to the moving system. The re-boilings of the original separation tower (Figure 7A) and a water column (not shown) can also be re-employed conveniently in the new system. As in the case of the previous processes described herein, a co-solvent system or a co-solvent can be added to the base of the EDC 50 or added in combination with the thin solvent to the EDC 50 (Figure 7B) for improve the selectivity of the operation. In Figure 8, a certain embodiment of the improved aromatics recovery process is illustrated. In this embodiment, a hybrid extractive / distillation configuration is employed. In this embodiment, a mixed hydrocarbon feed and thin solvent are provided directly to an EDC 50 for processing. The bottom stream from the EDC 50 is provided to a recovery operation of extract 20 and 30. An aromatic product is taken from the upper portion of the recovery operation of extract 20 and 30. A thin solvent from the bottoms of the extract recovery operation 20 and 30 the EDC 50 and a refining extractor 10 are provided. A higher stream from the EDC 50 is also provided to the refining extractor 10. a higher stream from the refining extractor 10 is provided to the water washing device 40 and non-aromatic compounds from the water washing device 40 are removed for further processing or sent for storage. An easy and convenient retrofit of the original sulfolane process vessels of the prior art is also possible to handle this aromatics recovery process of the present invention. To reconfigure, an original master extractor 10 (figure 1) is converted into the refining extractor 10. The extractive separator 20 and extract recovery operation 30 (figure 1) are converted to operate in parallel as the extraction operations of extract 20 and 30. The washing with refining water 40 (figure 1) remains in washing in water 40 and sed adds a new EDC 50. as illustrated also in figure 5 and as described more fully above, a substantial increase in capacity and efficiencies is achieved by the use of a converted system. It is important to note that the configuration used in Figure 8 substantially increases the unit capacity (up to double capacity through the addition of a new single fractionation column.) As reference now Figure 9, a retrofit of composite recovery system is illustrated. UDEX-type aromatics can handle one embodiment of the improved aromatics recovery process of the present invention For the purposes of this disclosure, the term "UDEX", a trade name for a BTX extraction process employing mixtures of glycols and water as active solvents, will be used to refer to recovery systems that employ two (2) major columns to effect the separation of aromatics from a mixture containing aromatics and non-aromatic compounds. feeding 1 of mixed hydrocarbons in the middle or lower portion of a c liquid-liquid extractor tank 10 and mixed against the stream with a thin solvent 2, which is fed into the upper section of the liquid-liquid extractor column 10. The thin solvent 2 extracts the aromatic compounds leaving a stream of refining 3 Thin aromatics to be collected from the top of the liquid-liquid extractor column 10. The rich solvent 4 containing the extraction solvent, aromatics, and certain non-aromatic residual compounds leaves the liquid-liquid extractor column 10 from the bottom and is routed to the upper portion of a separator column 20. In the separator column 20, the stream is typically subjected to instantaneous distillation (in the single stage or in several stages), the vapors are combined with distillate from the lower sections of the separator column 20 in a reflux stream 5. The reflux stream 5 leaves the column separately r 20 towards the upper portion of the column and condenses and is routed back to the liquid-liquid extractor column 10 for further processing. The thin, separated solvent 7 within the separator column 20 is taken from the upper section of the separator column 20, and directed towards the lower section of the separator column 20 for the recovery of aromatic compounds. In the lower section of the separator column 20, the aromatic compounds are the thin solvent separator in a vapor stream 6, condensates, and subsequently processed in a washing or finishing step in order to produce high purity aromatics. Heat is supplied to the separator column 20 by the reboiler Rl, and, optionally, by the separation stream added to the bottom of the separator column 20. The thin separate solvent 8 can be cooled by heat exchange or by other methods known in the art before being recycled into the liquid-liquid extractor column 10 to repeat the cycle. These basic systems often operate below their efficient capacity due to either an initial unsatisfactory design and / or due to the need to process additional power. It is important to note that these UDEX type recovery systems can be easily and quickly retrofitted to handle an improved aromatics recovery process of the present invention without the requirement for extensive modifications without the need of time wasting associated with conventional methods of adaptation Besides, in some cases, the simple modifications required are reversible, offering additional flexibility to the system and associated equipment. In a retro-adjusted state, a portion of the mixed hydrocarbon feed IA is directed to a new extractive distillation column ("EDC") 50, which separates the aromatics from the non-aromatic compounds in a single operation. A thin solvent 8a is fed into the upper section of the EDC 50. The water content within the EDC 50 can be controlled by pre-distillation of steam 8a before feeding to the EDC 50 and / or by removing the excess water inside the EDC through instantaneous distillation. The upper stream 3a is condensed and optionally refluxed in part and directed to raffinate storage, or combined with the upper stream 3 of the liquid-liquid extractor column 10 and further processed in the refining finishing steps. The background current 7a of the E¿ >C 50 contains primarily aromatics and solvent compounds and is therefore directed to the lower section of separator column 20 for recovery of aromatics. Heat is applied to the EDC 50 through the reboiler R2. If desired, the thermal load in the separator column 20 is rebalanced by the addition of a side re-kettle Rla. The addition of this feature will allow the upper separator vapors to be generated at the midpoint of the separator column 20 and this consequently reduces the vapor in the lower section and the re-kettle load Rl. This retrofit design is especially suitable for applications that require very short closing periods, or in the case of an inactive column located near the UDEX unit. The following solvents were useful in the recovery of aromatic petrochemicals and can be effectively employed with the methods of the present invention described therein: tetraethylene glycol, triethylene glycol, diethylene glycol, ethylene glycol, methoxy glycol ether, diglycolamine, dipropylene glycol, N-formylmorpholine, N-methylpyrrolidone, sulfolane, 3-methylsulfolane and dimethyl sulfoxide, alone, and / or in mixtures with water, and / or in combination with each other and / or water. Improved Separation of Point Components -from Close Boiling System: Heptene / Benzene Solvent Agent: Feeding f Volatility (weight / weight) Relative None 3 0. 8 Tetraethylene glycol / 3 2 .2 methoxytriglycol ether Tetraethylene glycol 3 2. 6 NMP 3 2. 4 NFM 3 3. 0 2-pyrrolidinone 3 3. 1 DMSE 3 3. 3 Sulfolano 3 4. 0 The above table illustrates the improved separation of nearby boiling components employing selective solvents and the improved methods of the present invention. In this example, the relative volatility between heptane (light key non-aromatic compound) and benzene (heavy key aromatic compound) is demonstrated. Generally, the higher the relative volatility, the better the recovery and purity of the aromatic compound. Relative volatility data are used in computer models to produce engineering designs and processes for aromatic compound separation systems. Although illustrated in the appended Drawings and described in the above Detailed Description preferred embodiments of the method of the present invention and method for retro-fitting existing equipment, it will be understood that the invention is not limited to the embodiments presented, but may present numerous adjustments, modifications and substitutions without departing from the spirit of the present invention presented and defined in the appended claims.

Claims (2)

1. CLAIMS A process for the recovery of aromatic compounds from a mixed hydrocarbon feed, containing aromatic compounds and non-aromatic compounds of between 5 and 12 carbon atoms, comprising: supplying a first portion of the mixed hydrocarbon feed to the liquid-liquid extractor, to provide a second portion of the mixed hydrocarbon feed to an extractive distillation column, and to recover aromatic compounds from the first portion of the mixed hydrocarbon feed and from the second portion of the mixed hydrocarbon feed to through the parallel operation of the liquid-liquid extractor and the extractive distillation column The recovery process according to claim 1, wherein the extractive distillation column simultaneously carries out the recovery and purification of aromatic compounds. of recovery of conform The composition according to claim 1, wherein solvent is provided to the upper portion of the extractive distillation column to increase the recovery of aromatic compounds. The recovery process according to claim 1, wherein the bottom stream from the liquid-liquid extractor is provided to an extractive separator for further processing. The recovery process according to claim 1, wherein the bottom stream from the extractive distillation column is provided to an extractive recovery operation for further processing. The recovery process according to claim 4, wherein the bottom stream from the extractive distillation column is combined with a bottom stream from the extractive separator before being supplied to an extractive recovery operation for further processing. The recovery process according to claim 1, wherein an overhead stream containing non-aromatic compounds from the extractive distillation column is removed for further processing or sent for storage. The recovery process according to claim 3, wherein the solvent is selected from the group consisting of: tetraethylene glycol, triethylene glycol, diethylene glycol, ethylene glycol, methoxytriglycol ether, diglycolamine, dipropylene glycol, N-formylmorpholine, N-methylpyrrolidone, sulfolane, 3-methylsulfolane , dimethyl sulfoxide, and mixtures thereof. 9. The recovery process according to claim 3, wherein the solvent is one or more of the following: tetraethylene glycol, triethylene glycol, diethylene glycol, ethylene glycol, methoxytriglycol ether, diglycolamine, dipropylene glycol, N-formylmorpholine, methylpyrrolidone, sulfolane, 3- methylsulfolane and dimethyl sulfoxide. 10. The recovery process according to claim 3, wherein a co-solvent is provided to the recovery process in order to increase the recovery and purity of the recovered aromatic compounds. The recovery process according to claim 10, wherein the co-solvent is provided to a lower portion of the extractive distillation column in order to increase the selectivity of the co-solvent. 12. The recovery process according to claim 10, wherein the co-solvent contains water. The recovery process according to claim 1, wherein the solvent is provided to the extractive distillation column to increase the recovery of aromatic compounds. 14. The recovery process according to claim 13, wherein the solvent is selected within / of the group consisting of: tetraethylene glycol, triethylene glycol, diethylene glycol, ethylene glycol, methoxytriglycol ether, diglycolamine, dipropylene glycol, N-e formylmorpholine, N-methylpyrrolidone, sulfolane, 3-methylsulfolane and dimethyl sulfoxide. 15. The recovery process according to claim 13, wherein the solvent is one or more of the following: tetraethylene glycol, triethylene glycol, diethylene glycol, ethylene glycol, methoxytriglycol ether, diglycolamine, dipropylene glycol, N-formylmorpholine, methylpyrrolidone, sulfolane, 3-methylsulfolane and dimethyl sulfoxide. 16. The recovery process according to claim 13, wherein a co-solvent is provided to the recovery process to increase the recovery of the aromatic compounds and the purity of said recovered aromatic compounds. The recovery process according to claim 1, wherein the supply of mixed hydrocarbons is provided to a prefractionator prior to its segregation in the first portion and the second portion, and said first portion and said second portion are directly fed to said liquid-liquid extractor and said extractive distillation column, respectively. 18. The recovery process according to claim 17, wherein the prefractionator is a reforming separator. The recovery process according to claim 17, wherein the first portion of the mixed hydrocarbon feed is taken from a side portion of the prefractionator. The recovery process according to claim 17, wherein the second portion of the mixed hydrocarbon feed is taken from an upper portion of the prefractionator. The recovery process according to claim 17, wherein the first portion of the mixed hydrocarbon feed and the second portion of the mixed hydrocarbon feed are taken from a side portion of the prefractionator. 2. The recovery process according to claim 1, wherein the light refining current produced by the recovery process is further processed through an isomerization unit. 3. The recovery process according to claim 1, wherein a heavy refining stream produced by the recovery process is further processed through naphtha disintegration. 24. A process for the recovery of aromatic compounds from a mixed hydrocarbon feed containing aromatic compounds and non-aromatic compounds, comprising: supplying the mixed hydrocarbon feed to an extractive distillation column; supplying an upper stream from the extractive distillation column to a liquid-liquid extractor without reflux of any current strife part superior to said extractive distillation column; and providing a bottom stream from the liquid-liquid extractor to at least one location along the length of the extractive distillation column below the feed point of said mixed hydrocarbon feed; and recovering aromatic compounds without washing with water thereof from the mixed hydrocarbon feed. 25. The recovery process according to claim 24, wherein the liquid-liquid extractor operates as a refining extractor. 26. The recovery process according to claim 24, wherein the point at which the bottom stream from the liquid-liquid extractor is provided to the extractive distillation column is predetermined to correspond to a desired composition profile within the extractive distillation column in order to increase the recovery of the aromatic compounds. . The recovery process according to claim 24, wherein additional solvent is provided to the recovery process to increase the recovery of aromatic compounds. . The recovery process according to claim 27, wherein the solvent is selected from a group consisting of: tetraethylene glycol, triethylene glycol, diethylene glycol, ethylene glycol, methoxytriglycol ether, diglyclolamine, dipropylene glycol, N-formylmorpholine, N-methylpyrrolidone, sulfolane, 3- methylsulfolane and 3-methylsulfolane and dimethyl sulfoxide. . The recovery process according to claim 27, wherein the solvent is one or more of the following: tetraethylene glycol, triethylene glycol, diethylene glycol, ethylene glycol, methoxytriglycol ether, diglyclolamine, dipropylene glycol, N-formylmorpholine, -methylpyrrolidone, sulfolane, 3-methylsulfolane and dimethyl sulfoxide. The recovery process according to claim 24, wherein a co-solvent is provided to the recovery process to increase the recovery of aromatics and the purity of the recovered aromatics. . A process for the recovery of aromatic compounds from a mixed hydrocarbon feed containing aromatic compounds and non-aromatic compounds, comprising: supplying the mixed hydrocarbon feed to an extractive distillation column; providing a background stream of rich solvent from the extractive distillation column to an extract recovery operation; providing a background current briefly from the extract recovery operation to a refining extractor; providing an upper stream from the extractive distillation column to the refining extractor without refluxing any part of said stream higher than said extractive distillation column; and recovering aromatic compounds from a higher stream from the extract recovery operation without washing said water with water. The recovery process according to claim 31, wherein the extract recovery operation comprises a single container. 33. The recovery process according to claim 31, wherein the extract recovery operation comprises two containers. 34. The recovery process according to claim 31, wherein an upper stream from the refining extractor is washed. 35. The recovery process according to claim 31, where solvent is provided to the recovery process to increase the recovery of aromatic compounds. 36. The recovery process according to claim 35, wherein the solvent is selected from the group consisting of: tetraethylene glycol, triethylene glycol, diethylene glycol, ethylene glycol, methoxytriglycol ether, diglycolamine, dipropylene glycol, N-formylmorpholine, N-methylpyrrolidone, sulfonan, - methylsulfolane and dimethyl sulfoxide. 37. The recovery process according to claim 35, wherein the solvent is one or more of the following: tetraethylene glycol, triethylene glycol, diethyl glycol, ethylene glycol, methoxytriglycol ether, diglycolamine, dipropylene glycol, N-formylmorpholine, N-methylpyrrolidone, sulfolane, 3- methylsulfolane and dimethyl sulfoxide. 38. The recovery process according to claim 31, wherein a co-solvent is provided to the recovery process to increase the recovery of aromatics and purity of said recovered aromatic compounds. 39. A method for retrofitting existing aromatics recovery equipment from the sulfolane process type to handle a hybrid process based on extractive extraction / distillation to recover aromatic compounds from a feed containing aromatic compounds and non-aromatic compounds, which comprises the steps of: converting an existing liquid-liquid extractor into a vapor-liquid contacting device capable of being used as a top portion of an extractive distillation column; converting an extractive separator into a column capable of being used as a lower portion of an extractive distillation column; and arranging said converted vapor-liquid contacting device and said extractive extractive separator to operate as the extractive distillation column to process a mixed hydrocarbon feed to recover aromatic compounds. The resetting method according to claim 39, further including the step of removing an existing refining washing device. 41. The retrofit method according to claim 39, which includes - in addition the step of avoiding an existing refining washing device. 42. The retrofit method according to claim 39, which includes * 'further the step of using an existing re-kettle for the extractive distillation column. 43. The retrofit method of claim 39, further including the step of using an existing extractive separator condenser to condense higher vapors from the extractive distillation column. 4. A method to retrofit existing aromatics recovery equipment from a glycol-based extraction process for use with an extractive distillation process to recover aromatic compounds from a feed containing aromatic compounds and non-aromatic compounds, which comprises the step of: converting an existing extractive separator and an existing extract recovery column into an extractive distillation column; converting an existing liquid-liquid extractor into a new extract recovery column; and arranging the extractive distillation column and the new extract recovery column to operate together in a process to recover aromatic compounds from a mixed hydrocarbon feed. 45. The retrofit method according to claim 44, further including the step of using at least one existing reboiler with the aromatics recovery process. 46. The retorting method according to claim 44, further including the step of avoiding an existing refining device in aromatic compounds. The retro-fitting method of claim 44, further including the step of removing an existing refining device from aromatics. 8. A method for retrofitting an existing UDEX process-type aromatics recovery equipment to handle a hybrid process based on extractive extraction / distillation to recover aromatic compounds from a feed containing aromatic compounds and non-aromatic compounds, comprising the steps of: providing an extractive distillation column; providing a means for segregating a mixed hydrocarbon feed into a first portion and a second portion; and arranging the extractive distillation column and an existing liquid-liquid extractor to operate in parallel to process a mixed hydrocarbon feed to recover aromatic compounds. 49. The retrofit method according to claim 48, further including the step of providing a reboiler to provide heat to the extractive distillation column. 50. The retrofit method according to claim 48, further including the step of providing a condenser for condensing vapors from the extractive distillation column. 51. The retrofit method according to claim 48, further including the step of providing a side reboiler to balance the thermal load provided to an existing separator column.
2. 2. A process for recovering aromatic compounds from a mixed hydrocarbon feed containing aromatic compounds and non-aromatic compounds, comprising: providing the feed of mixed hydrocarbons to an extractive distillation column; providing a higher stream from the extractive distillation column to a liquid-liquid extractor without refluxing any portion of said stream higher than said extractive distillation column; providing a bottom stream from the liquid-liquid extractor at at least one location along the length of the extractive distillation column; and recover aromatic compounds from the mixed hydrocarbon feed. 53. A process for recovering aromatic compounds from a mixed hydrocarbon feed containing aromatic compounds and non-aromatic compounds, comprising: supplying the mixed hydrocarbon feed to an extractive distillation column; providing a higher stream from the extractive distillation column to a liquid-liquid extractor; providing a bottom stream from the liquid-liquid extractor at at least one location along the length of the extractive distillation column below the feed point of said mixed hydrocarbon feed; and recover aromatic compounds from the mixed hydrocarbon feed. . A process for recovering aromatics from a mixed hydrocarbon feed containing aromatic compounds and non-aromatic compounds, comprising: supplying the mixed hydrocarbon feed to an extractive distillation column; providing a higher stream from the extractive distillation column to a liquid-liquid extractor; providing a bottom current from the liquid-liquid extractor in at least one location along a length of the extractive distillation column; and recovering aromatic compounds without washing with water thereof from the mixed hydrocarbon feed.