DISTILLATION COLUMN

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent

Application No. 62/867,380, filed June 27, 2019, the entire contents of which are hereby incorporated by reference in their entirety.

FIELD OF INVENTION

[0002] The present invention generally relates to systems and methods for separating ethylene glycols from mixtures. More specifically, the present invention relates to systems and methods for separating ethylene glycols from a mixture comprising water and ethylene glycols using a thermally coupled distillation column.

BACKGROUND OF THE INVENTION

[0003] Ethylene glycols, including monoethylene glycol (MEG), diethylene glycol

(DEG), triethylene glycol (TEG), and polyethylene glycol (PEG), are a group of versatile chemicals used in many areas of the chemical industry. For instance, monoethylene glycol (MEG) is used as an antifreeze and coolant for engines and an intermediate for producing polyester fibers and polyethylene terephthalate (PET), which is used for producing plastic bottles. Diethylene glycol (DEG) can be used to produce polyurethanes, plasticizers, and organic solvents. Triethylene glycol (TEG) is often used as a plasticizer and moisture-retaining agent. Polyethylene glycol (PEG) is used in perfumes, cosmetics, lubricants, and plasticizers.

[0004] Conventionally, ethylene glycols can be produced via thermal hydrolysis of ethylene oxide (EO) in a long plug flow reactor. To obtain a high monoethylene glycol selectivity, a high water to ethylene oxide ratio, which is typically in the range of 15: 1 to 25: 1, is used in the feed stream to the ethylene oxide thermal hydrolysis reactor. Thus, the effluent stream from the thermal hydrolysis reactor generally contains a large portion of water along with the products of monoethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol. This leads to a high separation cost to remove the excess water for producing highly purified ethylene glycols. The separation process generally includes a combination of multiple effect evaporators followed by a drying column and a purification column. The drying column typically provides a concentrated ethylene glycol stream up to 95 wt.%, which is further purified in the purification column. The two-column configuration requires high capital costs and results in high energy consumption due to the use of multiple reboilers. Therefore, the overall production costs for ethylene glycols are high.

[0005] Overall, while the systems and methods for separating and purifying ethylene glycols exist, the need for improvements in this field persists in light of at least the aforementioned drawbacks for the conventional methods.

BRIEF SUMMARY OF THE INVENTION

[0006] A solution to at least some of the above-mentioned problems associated with the systems and methods for separating ethylene glycols from a mixture containing water and ethylene glycol(s) has been discovered. The solution resides in a method of separating a mixture containing ethylene glycol and water via a thermally coupled distillation column (e.g., dividing wall distillation column and Petlyuk column). This method, in embodiments, is capable of replacing two or more downstream separation columns used in a conventional ethylene glycol separation process with a thermally coupled distillation column, thereby reducing the capital expenditures required for building the multiple separation columns and the energy consumption for operating the multiple reboilers and overhead condensers in the separation columns. Thus, this method is capable of reducing the production costs and increasing the production efficiency for ethylene glycols.

[0007] Embodiments of the invention include a method of separating a mixture comprising ethylene glycol and water. The method comprises feeding the mixture to a thermally coupled distillation column. The method comprises subjecting the mixture in the thermally coupled distillation column to process conditions sufficient to separate the mixture into a plurality of streams comprising a first stream comprising primarily monoethylene glycol, and a second stream comprising primarily water. The method comprises recovering the first stream from a side draw of the thermally coupled distillation column. The method comprises recovering the second stream. The mixture comprises more than 1 wt.% water.

[0008] Embodiments of the invention include a method of separating a mixture containing ethylene glycol and water. The method comprises feeding the mixture to a thermally coupled distillation column. The method comprises subjecting the mixture in the thermally coupled distillation column to process conditions sufficient to separate the mixture into a plurality of streams comprising a first stream comprising primarily monoethylene glycol, and a second stream comprising primarily water. The process conditions comprise an operating pressure of 0.45 to 6.0 psia, and a thermally coupled distillation column reflux ratio of 1.5 to 9. The method comprises recovering the first stream in a side draw of the thermally coupled distillation column. The method comprises recovering the second stream as an overhead distillation stream of the thermally coupled distillation column. The mixture comprises more than 1 wt.% water.

[0009] Embodiments of the invention include a method of separating a mixture containing ethylene glycol and water. The method comprises feeding the mixture to a dividing wall distillation column. The method comprises more than 1 wt.% water. The method comprises subjecting the mixture in the dividing wall distillation column to process conditions sufficient to separate the mixture into a plurality of streams comprising a first stream comprising primarily monoethylene glycol, a second stream comprising primarily water, a third stream comprising primarily diethylene glycol, and a fourth stream comprising primarily triethylene glycol. The process conditions comprise a dividing wall distillation column theoretical plate number of 45 to 55, an operating pressure of 0.45 to 6.0 psia, and a dividing wall distillation column reflux ratio of 1.5 to 9. The method comprises recovering the first stream from a side draw of the upper half of the dividing wall distillation column. The method comprises recovering the third stream from a side draw of the lower half of the dividing wall distillation column. The method comprises recovering the fourth stream as a bottom stream of the dividing wall distillation column. The method comprises recovering the second stream as an overhead distillate stream of the dividing wall distillation column.

[0010] The following includes definitions of various terms and phrases used throughout this specification.

[0011] The terms “about” or “approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably, within 5%, more preferably, within 1%, and most preferably, within 0.5%.

[0012] 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, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol.% of component.

[0013] The term“substantially” and its variations are defined to include ranges within

10%, within 5%, within 1%, or within 0.5%.

[0014] The terms“inhibiting” or“reducing” or“preventing” or“avoiding” or any variation of these terms, when used in the claims and/or the specification, includes any measurable decrease or complete inhibition to achieve a desired result.

[0015] The term“effective,” as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.

[0016] The term“dividing wall distillation column,” as that term is used in the specification and/or claims, means a distillation column that contains a vertical wall as a partition in the distillation column, dividing the distillation column into two sides.

[0017] The use of the words“a” or“an” when used in conjunction with the term

“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.”

[0018] The words“comprising” (and any form of comprising, such as“comprise” and

“comprises”),“having” (and any form of having, such as“have” and“has”),“including” (and any form of including, such as“includes” and“include”) or“containing” (and any form of containing, such as“contains” and“contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0019] The process of the present invention can“comprise,”“consist essentially of,” or“consist of’ particular ingredients, components, compositions, etc., disclosed throughout the specification.

[0020] The term“primarily,” as that term is used in the specification and/or claims, means greater than any of 50 wt.%, 50 mol.%, and 50 vol.%. For example,“primarily” may include 50.1 wt.% to 100 wt.% and all values and ranges there between, 50.1 mol.% to 100 mol.% and all values and ranges there between, or 50.1 vol.% to 100 vol.% and all values and ranges there between. [0021] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 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.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0023] FIGS. 1A and IB show schematic diagrams of a dividing wall distillation column for separating water and ethylene glycol(s), according to embodiments of the invention; FIG. 1A shows a schematic diagram of a dividing wall distillation column configured to separate a mixture comprising ethylene glycol(s) and water to produce a stream comprising primarily monoethylene glycol and a stream comprising primarily water; FIG. IB shows a schematic diagram of a dividing wall distillation column configured to separate a mixture comprising ethylene glycol(s) and water to produce a stream comprising primarily monoethylene glycol, a stream comprising primarily diethylene glycol, a stream comprising primarily tri ethylene glycol, and a stream comprising primarily water; and

[0024] FIG. 2 shows a schematic flowchart of a method of separating water and ethylene glycol(s), according to embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The conventional method of separating a mixture of water and ethylene glycol(s) includes a separation process using a drying column followed by one or more purification distillation columns. Overall, this process requires high capital expenditures for building multiple distillation columns. Furthermore, due to the use of multiple reboilers and condensers, the reheating of the processing streams demands a large amount of energy. Thus, the production cost for ethylene glycol(s) is high. The present invention provides a solution to this problem. The solution is premised on a method of separating water and ethylene glycol(s) using a thermally coupled distillation column (e.g., dividing wall distillation column and Petlyuk column). This method uses a single column with a single reboiler, thus reducing the energy consumption for reheating the process streams flowed into the multiple distillation columns used in the conventional methods. Additionally, by using a thermally coupled distillation column, the disclosed method is capable of producing ethylene glycol(s) having the purity the same or higher than the ethylene glycol(s) produced by the conventional methods, thereby eliminating the need for building multiple distillation columns. These and other non limiting aspects of the present invention are discussed in further detail in the following sections.

A. System for separating a mixture of ethylene glycol and water

[0026] In embodiments of the invention, the system for separating a mixture of ethylene glycol(s) and water can include a thermally coupled distillation column. In embodiments of the invention, the thermally coupled distillation column includes a dividing wall distillation column. With reference to FIGS. 1 A and IB, schematic diagrams are shown of system 100 for separating a mixture comprising ethylene glycol(s) and water.

[0027] According to embodiments of the invention, system 100 comprises dividing wall distillation column 101 configured to receive feed stream 11 comprising water and ethylene glycol(s). In embodiments of the invention, feed stream 11 comprises more than 1 wt.% water. Non-limiting examples for ethylene glycol(s) in feed stream 11 may include monoethylene glycol, diethylene glycol, triethylene glycol, and other polyethylene glycol(s). In embodiments of the invention, feed stream 11 may be obtained from an ethylene oxide thermal hydrolysis unit. The ethylene oxide thermal hydrolysis unit may include a thermal hydrolysis reactor configured to react water with ethylene oxide to produce ethylene glycol(s). The thermal hydrolysis unit may further include one or more multiple effect evaporators in fluid communication with an outlet of the thermal hydrolysis reactor. The one or more multiple effect evaporators may be configured to remove at least some water from an effluent of the thermal hydrolysis reactor to produce feed stream 11.

[0028] According to embodiments of the invention, as shown in FIG. 1 A, dividing wall distillation column 101 may comprise an overhead outlet, a side draw outlet, and a bottom outlet. Dividing wall distillation column 101 may be further configured to process feed stream 11 that comprises water and ethylene glycols under process conditions sufficient to separate feed stream 11 into a plurality of streams including first stream 21 comprising primarily monoethylene glycol, second stream 22 comprising primarily water, and mixed polyethylene glycol stream 25 comprising diethylene glycol, triethylene glycol, and other polyethylene glycol(s). The overhead outlet is configured to release second stream 22 comprising primarily water from dividing wall distillation column 101. The side draw outlet is configured to release first stream 21 comprising primarily monoethylene glycol from dividing wall distillation column 101. The bottom outlet is configured to release mixed polyethylene glycol stream 25 from dividing wall distillation column 101.

[0029] According to embodiments of the invention, as shown in FIG. IB, dividing wall distillation column 101 may comprise an overhead outlet, a first side draw outlet, a second side draw outlet and a bottom outlet. First side draw outlet may be disposed on an upper half of dividing wall distillation column 101. Second side draw outlet may be disposed on a lower half of dividing wall distillation column 101. Dividing wall distillation column 101 may be further configured to process feed stream 11 that comprises water and ethylene glycols under process conditions sufficient to separate feed stream 11 into a plurality of streams including first stream 21 comprising primarily monoethylene glycol, second stream 22 comprising primarily water, third stream 23 comprising primarily diethylene glycol, and fourth stream 24 comprising primarily triethylene glycol. The overhead outlet is configured to release second stream 22 comprising primarily water from dividing wall distillation column 101. The first side draw outlet is configured to release first stream 21 comprising primarily monoethylene glycol from dividing wall distillation column 101. The second side draw outlet is configured to release third stream 23 comprising primarily diethylene glycol from dividing wall distillation column 101. The bottom outlet is configured to release fourth stream 24 comprising primarily triethylene glycol from dividing wall distillation column 101.

[0030] According to embodiments of the invention, dividing wall distillation column

101 has a theoretical plate number in a range of 45 to 60 and all ranges and values there between including 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, and 60. In embodiments of the invention, dividing wall distillation column 101 comprises a dividing wall spanning from theoretical plates 5 to 25, theoretical plates 10 to 35, or theoretical plates 15 to 40 (counted from the top to the bottom). In embodiments of the invention, an inlet for feed stream 11 may be disposed between theoretical plate number 5 to 40 and all ranges and values there between. In embodiments of the invention, the inlet for feed stream 11 is disposed at a starting theoretical plate number for the dividing wall. The first side draw outlet, which is configured to release first stream 21 from dividing wall distillation column 101, may be disposed between theoretical plate number 10 to 35 of dividing wall distillation column 101 and all ranges and values there between including 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, and 35. The second side draw outlet, which is configured to release third stream 23 from dividing wall distillation column 101, may be disposed between theoretical plate number 30 to 50 and all ranges and values there between including 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, and 50. In embodiments of the invention, the first side draw outlet location and/or the second side draw outlet location are dependent on starting and ending theoretical plate numbers for the dividing wall.

B. Method of separating a mixture of ethylene glycol(s) and water

[0031] Methods of separating a mixture comprising ethylene glycol(s) and water have been discovered. The methods may be capable of reducing the required capital expenditure and energy consumption for purifying ethylene glycol(s) by replacing multiple distillation columns used in a conventional system with a thermally coupled distillation column (e.g., dividing wall distillation column and Petlyuk column). As shown in FIG. 2, embodiments of the invention include method 200 for separating a mixture comprising ethylene glycol and water. Method 200 may be implemented by system 100, as shown in FIGS. 1 A and IB.

[0032] According to embodiments of the invention, as shown in block 201 , method 200 includes feeding feed stream 11 to dividing wall distillation column 101. In embodiments of the invention, feed stream 11 comprising the mixture containing ethylene glycol(s) and water. Feed stream 11 may be obtained from an ethylene oxide thermal hydrolysis unit comprising a thermal hydrolysis reaction unit in fluid communication with one or more multi-effect evaporators. Feed stream 11 may be flowed from the multi-effect evaporator(s) to dividing wall distillation column 101. According to embodiments of the invention, the mixture comprises more than 1 wt.% water. In embodiments of the invention, the mixture of feed stream 11 comprises 1 to 25 wt.% water and all ranges and values there between including 1 to 3 wt.%, 3 to 5 wt.%, 5 to 7 wt.%, 7 to 9 wt.%, 9 to 11 wt.%, 11 to 13 wt.%, 13 to 15 wt.%, 15 to 17 wt.%, 17 to 19 wt.%, 19 to 21 wt.%, 21 to 23 wt.%, and 23 to 25 wt.%. The mixture of feed stream 11 may further comprise 60 to 90 wt.% monoethylene and all ranges and values there between including ranges of 60 to 62 wt.%, 62 to 64 wt.%, 64 to 66 wt.%, 66 to 68 wt.%, 68 to 70 wt.%, 70 to 72 wt.%, 72 to 74 wt.%, 74 to 76 wt.%, 76 to 78 wt.%, 78 to 80 wt.%, 80 to 82 wt.%, 82 to 84 wt.%, 84 to 86 wt.%, 86 to 88 wt.%, and 88 to 90 wt.%. The mixture of feed stream 11 may further comprise 1 to 8 wt.% diethylene glycol and 0.05 to 3 wt.% tri ethylene glycol.

[0033] According to embodiments of the invention, as shown in block 202, method 200 includes subjecting the mixture in dividing wall distillation column 101 to process conditions sufficient to separate the mixture into a plurality of streams comprising first stream 21 comprising primarily monoethylene glycol, second stream 22 comprising primarily water, third stream 23 comprising primarily diethylene glycol, and fourth stream 24 comprising primarily tri ethylene glycol.

[0034] In embodiments of the invention, when system 100 as shown in FIG. 1A is implemented, the plurality of streams further comprises mixed polyethylene glycol stream 25 comprising diethylene glycol, triethylene glycol, and other polyethylene glycol(s). Mixed polyethylene glycol stream 25 may comprise less than 7 wt.% overall monoethylene glycol. First stream 21 may be recovered from the side draw outlet of dividing wall distillation column 101. Second stream 22 may be recovered from the overhead outlet of dividing wall distillation column 101. Mixed polyethylene glycol stream may be recovered from the bottom outlet of dividing wall distillation column 101. In embodiments of the invention, when system 100 as shown in FIG. IB is implemented, the plurality of streams further comprises third stream 23 comprising primarily diethylene glycol, and fourth stream 24 comprising primarily triethylene glycol. In embodiments of the invention, when system 100 as shown in FIG. IB is implemented, mixed polyethylene glycol stream 25 may comprise less than 0.5 wt.% overall monoethylene glycol. In embodiments of the invention, first stream 21 in configuration shown in FIG. 1A may be drawn from a different theoretical plate number from first stream 21 in configuration shown in FIG. IB.

[0035] In embodiments of the invention, the process conditions at block 202 may include an operating pressure of 0.45 to 6.0 psia and all ranges and values there between including ranges of 0.45 to 0.50 psia, 0.50 to 1.0 psia, 1.0 to 1.5 psia, 1.5 to 2.0 psia, 2.0 to 2.5 psia, 2.5 to 3.0 psia, 3.0 to 3.5 psia, 3.5 to 4.0 psia, 4.0 to 4.5 psia, 4.5 to 5.0 psia, 5.0 to 5.5 psia, and 5.5 to 6.0 psia. Process conditions may include a reflux ratio in a range of 1.5 to 9 and all ranges and values there between including ranges of 1.5 to 2.0, 2.0 to 2.5, 2.5 to 3.0, 3.0 to 3.5, 3.5 to 4.0, 4.0 to 4.5, 4.5 to 5.0, 5.0 to 5.5, 5.5 to 6.0, 6.0 to 6.5, 6.5 to 7.0, 7.0 to 7.5, 7.5 to 8.0, 8.0 to 8.5, and 8.5 to 9.0. In embodiments of the invention, the process conditions at block 202 include an overhead temperature range of 30 to 60 °C and all ranges and values there between including ranges of 30 to 32 °C, 32 to 34 °C, 34 to 36 °C, 36 to 38 °C, 38 to 40 °C, 40 to 42 °C, 42 to 44 °C, 44 to 46 °C, 46 to 48 °C, 48 to 50 °C, 50 to 52 °C, 52 to 54 °C, 54 to 56 °C, 56 to 58 °C, and 58 to 60 °C. The process conditions at block 202 may include a reboiler temperature range of 150 to 205 °C and all ranges and values there between including ranges of 150 to 155 °C, 155 to 160 °C, 160 to 165 °C, 165 to 170 °C, 170 to 175 °C, 175 to 180 °C, 180 to 185 °C, 185 to 190 °C, 190 to 195 °C, 195 to 200 °C, 200 to 205 °C. In embodiments of the invention, the process conditions include performing internal reflux at a starting theoretical plate number that is the starting theoretical plate number of the dividing wall.

[0036] According to embodiments of the invention, as shown in block 203, method 200 includes recovering first stream 21 from a side draw of dividing wall distillation column 101. First stream 21 may be recovered from a side draw of the upper half of dividing wall distillation column 101. As shown in block 204, method 200 may further include recovering second stream 22 from the overhead outlet of dividing wall distillation column 101. As shown in block 205, according to embodiments of the invention, method 200 includes recovering third stream 23 from a side draw of dividing wall distillation column 101. Third stream 23 may be recovered from a side draw of lower half of dividing wall distillation column 101. According to embodiments of the invention, as shown in block 206, method 200 further includes recovering fourth stream 24 as a bottom stream of dividing wall distillation column 101. In embodiments of the invention, as shown in block 207, method 200 may include recycling second stream 22 comprising primarily water to the one or more multi-effect evaporators of an ethylene oxide thermal hydrolysis unit. In embodiments of the invention, the one or more multi-effect evaporators may be in series.

[0037] In embodiments of the invention, first stream 21 may comprise more than 99.99 wt.% monoethylene glycol. Second stream 22 may comprise more than 98 wt.% water. Third stream 23 may comprise more than 99.8 wt.% diethylene glycol. Fourth stream 24 may comprise more than 99.8 wt.% triethylene glycol. In embodiments of the invention, dividing wall distillation column 101 can be replaced by any type of thermally coupled distillation column including a Petlyuk distillation column or energy coupled (reboiler coupled) distillation column. [0038] Although embodiments of the present invention have been described with reference to blocks of FIG. 2, it should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIG. 2. Accordingly, embodiments of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIG. 2.

[0039] The systems and processes described herein can also include various equipment that is not shown and is known to one of skill in the art of chemical processing. For example, some controllers, piping, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, and the like may not be shown. [0040] As part of the disclosure of the present invention, specific examples are included below. The examples are for illustrative purposes only and are not intended to limit the invention. Those of ordinary skill in the art will readily recognize parameters that can be changed or modified to yield essentially the same results.

EXAMPLE 1

(Simulations for separating MEG using a dividing wall distillation column)

[0041] A numerical model for separating MEG from a mixture using a thermally coupled distillation column (dividing wall distillation column) was built in ASPEN PLUS (version 9). A comparison model for conventional separation process that includes a drying column and purification column in series for separating MEG and water was also developed in the same platform.

[0042] For the configuration as shown in FIG. 1 A, the operating conditions used in the models for the dividing wall distillation column and conventional drying column and purification column are shown in Table 1.

Table 1. Operating conditions used for the simulations

[0043] Further simulation runs on the thermally coupled distillation column were conducted using varying operational parameters with the fixed feed temperature and feed flowrate to get comparable results as the conventional two-column distillation system. The varied operational parameters including the feed location, operation temperature, and operation pressure The results are shown in Table 2 for the thermally coupled distillation column, Table 3 for conventional drying column and purification column, and Table 4 for direct comparison of MEG purity and energy requirement between the two processes. Table 2. Results for separation process using thermally coupled distillation column

Table. 3 Results for separation process using conventional two-column configuration Table 4. Comparison of MEG purity and energy requirement

[0044] At steady state, the reboiler duties for the thermally coupled distillation column and the conventional two distillation columns configuration were compared. The results indicated the thermally coupled distillation column (dividing wall distillation column) saved about 28% energy compared to the conventional process with the same MEG purity and MEG recovery percentage.

[0045] Energy requirements and MEG purities were further simulated with two different feed compositions (shown in Table 5) in the thermally coupled distillation column. The results are shown in Table 6.

Table 5 Feed compositions used in the MEG purity and energy requirements study

Table 6 Simulation results for the MEG purity and energy requirements study

EXAMPLE 2

(Simulations for the MEG, DEG and TEG separation process

using a dividing wall distillation column)

[0046] A numerical model for separation of MEG, DEG, TEG, water using a dividing wall distillation column was built in ASPEN PLUS (version 9). A comparison model for conventional separation process including four purification columns in series was also developed in the same platform.

[0047] For the configuration as shown in FIG. IB, the operating conditions used in the models for the dividing wall distillation column are shown in Table 7.

Table 7 Operating conditions for dividing wall distillation column

[0048] The simulation results are shown in Table 8 for separation of MEG, DEG, TEG, and water using a dividing wall distillation column. The comparison results of separation of MEG, DEG, TEG, and water using conventional process with four distillation columns are shown in Table 9. The results indicate that the dividing wall distillation column had a better product recovery and higher product purification while consumed less energy than the conventional four distillation columns. Table 8 Simulation results for the separation process using a dividing wall distillation column

Table 9. Simulation results for the separation process using four distillation columns

EXAMPLE 3

(Experiments for the MEG separation process using a dividing wall distillation column)

[0049] Experiments were conducted in a pilot plant for a dividing wall distillation column. The dividing wall distillation column was operated in the configuration as shown in FIG. 1 A. The bottom stream composition from the dividing wall distillation column matched the composition of a stream flowed from a purification distillation column to a MEG splitter column in a conventional MEG separation unit. The results for the experiments are shown in Table 10. Table 10 Experimental results for MEG separation using a dividing wall distillation column

[0050] The experiment was performed at a single pressure of 0.1 bar. Experimental results (Table 10) shows separation of MEG from water and heavy glycols. These results show that a drying column can be coupled with an MEG column to separate water, MEG, and heavy glycols using a single dividing wall distillation column. [0051] In the context of the present invention, at least the following 16 embodiments are disclosed. Embodiment 1 is a method of separating a mixture containing ethylene glycol and water. The method includes feeding the mixture to a dividing wall distillation column. The method further includes subjecting the mixture in the dividing wall distillation column to process conditions sufficient to separate the mixture into a plurality of streams including a first stream containing primarily monoethylene glycol, and a second stream containing primarily water. The method also includes recovering the first stream from a side draw of the dividing wall distillation column, and recovering the second stream, wherein the mixture contains more than 1 wt.% water. Embodiment 2 is the method of embodiment 1, wherein the mixture contains 10 to 25 wt.% water, 60 to 90 wt.% mono ethylene glycol, 1 to 8 wt.% di ethylene glycol, and 0.05 to 3 wt.% triethylene glycol. Embodiment 3 is the method of either of embodiments 1 or 2, wherein the mixture is obtained from an ethylene oxide hydrolysis reactor. Embodiment 4 is the method of embodiment 3, wherein the mixture is obtained by evaporating an effluent from an ethylene oxide hydrolysis reactor. Embodiment 5 is the method of any of embodiments 1 to 4, wherein the mixture contains more than 10 wt.% water. Embodiment 6 is the method of any of embodiments 1 to 5, wherein the process conditions of the dividing wall distillation column include an operating pressure in a range of 0.45 to 6.0 psia. Embodiment 7 is the method of any of embodiments 1 to 6, wherein the process conditions of the dividing wall distillation column include a dividing wall distillation column reflux ratio in a range of 1.5 to 9. Embodiment 8 is the method of any of embodiments 1 to 7, wherein the process conditions of the dividing wall distillation column include an overhead temperature range of 30 °C to 60 °C. Embodiment 9 is the method of any of embodiments 1 to 8, wherein the process conditions of the dividing wall distillation column include a reboiler temperature range of 150 °C to 205 °C. Embodiment 10 is the method of any of embodiments 1 to 9, wherein the dividing wall distillation column includes 45 to 55 theoretical plates. Embodiment 11 is the method of embodiment 10, wherein the dividing wall distillation column has a dividing wall from theoretical plate number 5 to 25, or from theoretical plate number 10 to 25, or from theoretical plate number 15 to 40. Embodiment 12 is the method of any of embodiments 1 to 11, wherein the plurality of streams further includes a third stream containing primarily diethylene glycol, and a fourth stream containing primarily triethylene glycol. Embodiment 13 is the method of embodiment 12, wherein the first stream is recovered from a side draw of an upper half of the dividing wall distillation column, and the second stream is recovered as an overhead distillate stream of the dividing wall distillation column. Embodiment 14 is the method of either of embodiments 12 or 13, further including recovering the third stream from a side draw of a lower half of the dividing wall distillation column, and recovering the fourth stream as a bottom stream of the dividing wall distillation column. Embodiment 15 is the method of any of embodiments 1 to 13, wherein the second stream containing primarily water is recycled to an evaporation unit. Embodiment 16 is the method of any of embodiments 1 to 15, wherein the first stream contains more than 99.99 wt.% monoethylene glycol.

[0052] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.