Systems and methods for separation with a hybrid membrane and distillation process

Abstract

Systems and methods for separating a mixture comprising an organic liquid and water with a separation system comprising a multiple-effect evaporator and a membrane module (hybrid membrane distillation scheme / system). The systems and methods involve finding the optimal location for slip-stream withdrawal from the multiple-effect evaporator system and optimal location of retentate return to the multiple-effect evaporator system.

Description

SYSTEMS AND METHODS FOR SEPARATION WITH A HYBRID MEMBRANE ANDDISTILLATION PROCESSCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of Indian Provisional Patent Application 202341090370, filed December 31, 2023. The contents of the referenced patent application is incorporated into the present application by reference.FIELD OF INVENTION

[0002] The present disclosure generally relates to the separation of mixtures comprising an organic liquid and water. More specifically, the present disclosure relates to the separation of mixtures comprising an organic liquid and water with a separation system comprising a multipleeffect evaporator and a membrane module.BACKGROUND OF THE INVENTION

[0003] Distillation is a separation process that is widely used commercially to separate chemical components. In particular, distillation is used widely to separate components of petroleum. However, distillation has certain drawbacks in that it is energy intensive, has low per pass separation due to clogging, and exhibits a decrease in tray efficiency with time. In the petrochemical industry, multiple-stage distillation is implemented by multiple-effect evaporators as a unit operation commercially used for dehydration of alcohols. In the context of growing environmental concerns, there is a great demand for CO2 neutralization, more economical processes, more energy efficient separation processes, and separation processes with higher separation factors than currently exists.BRIEF SUMMARY OF THE INVENTION

[0004] The systems and methods of the present disclosure address at least some of the above described drawbacks of current separation processes. As disclosed herein, a distillation process implemented by a multiple-effect evaporator is aided by a membrane process to arrive at a hybrid-pervaporation membrane distillation process. The inventors of the present disclosurerecognize that the method of designing the hybrid-pervaporation membrane distillation process in a certain manner can have significant impact on the energy savings that can be achieved when the process is implemented. Disclosed herein are systems and methods that involve finding the optimal location for slip-stream withdrawal from the multiple-effect evaporator system and the optimal location of retentate return to the multiple-effect evaporator system. The locations for slip-stream withdrawal and retentate return can affect the effectiveness of the hybrid-pervaporation membrane distillation process.

[0005] Embodiments of the disclosure include a method to separate a mixture of an organic component and water, the method comprising: (a) introducing the mixture of of organic component and water as an initial feed stream into a first multiple-effect evaporator column to produce a first water stream and a first concentrated slip stream, wherein the first concentrated slip stream has a higher concentration of the organic component than the concentration of the organic component in the feed stream, and wherein the first multiple-effect evaporator column is one of a plurality of multiple-effect evaporator columns arranged in series such that an input to each of said plurality of multiple-effect evaporator columns subsequent to the first multiple-effect evaporator column; (b) withdrawing, at a withdrawal point, a portion of the concentrated slip stream of one of the plurality of multiple-effect evaporator columns and introducing said portion into a membrane module to produce a permeate stream comprising water and a retentate stream comprising the organic component, wherein the retentate stream has a higher concentration of the organic component than the concentration of the organic component in said concentrated slip stream; and (c) reintroducing the retentate stream, at a reintroduction point, into one of the plurality of multiple-effect evaporator columns as an additional input thereto; wherein the last of the plurality of multiple-effect evaporator columns produces a final water stream and a final product stream having a higher concentration of the organic component than the concentration of the organic component of the retentate stream; and wherein one or more of the water streams from the multiple-effect evaporator columns, the permeate stream, or a combination thereof are recycled back to an upstream unit for hydrolysis.

[0006] Embodiments of the disclosure include a method of separating a mixture of a glycol and water by a system comprising (1) a multiple-effect evaporator; (2) a membranemodule; and a connector leading from the multiple-effect evaporator to the membrane module. The method comprises simulating evaporation of (or actual evaporation of) water from the mixture in the multiple-effect evaporator. The method comprises each of the plurality of multiple-effect evaporator columns includes a plurality of separation stages such that the plurality of multipleeffect evaporator columns, arranged in series, has a total number of separation stages between the initial feed stream and the final product stream. The method further comprises determining a first optimal location from which to withdraw a slip-stream from the multiple-effect evaporator for separation by the membrane module and determining a second optimal location for returning a retentate from the membrane module to the multiple-effect evaporator, wherein the first optimal location for withdrawal point to be at 45% to 60% of the total number of separation stages away from the initial feed stream and the second optimal location are locations for withdrawal of the slip-stream and return of the retentate, respectively, that results in the maximum energy savings as compared to other locations, when the membrane module is operated with the multiple-effect evaporator. The method further comprises locating the reintroduction point to be at 80% to 95% of the total number of separation stages away from the initial feed stream. The method further comprises 10% of the slip stream is withdrawn from the first multiple-effect evaporator column.

[0007] Embodiments of the disclosure include a system for separating a mixture of an organic liquid (e.g., a glycol) and water. The system comprises a multiple-effect evaporator, a membrane module, and a connector leading from the multiple-effect evaporator to the membrane module for transferring a slip-stream from the multiple-effect evaporator to the membrane module. The connector is at a first optimal location in the multiple-effect evaporator. The first optimal location is a location for withdrawal of the slip-stream that results in the maximum energy savings as compared to other locations, when the membrane module is operated with the multiple-effect evaporator.

[0008] The following includes definitions of various terms and phrases used throughout this specification.

[0009] 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%.

[0010] For the purposes of this disclosure, “X, Y, and / or Z” can be construed as X only, Y only, Z only, or any combination of two or more items X, Y, and Z (e.g., XYZ, XY, XZ, YZ).

[0011] 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.

[0012] The term “substantially” and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0013] The terms “inhibiting” or “reducing” or “preventing” or “avoiding” or any variation of these terms, when used in the claims and / or the specification, include any measurable decrease or complete inhibition to achieve a desired result.

[0014] The term “effective,” as that term is used in the specification and / or claims, means adequate to accomplish a desired, expected, or intended result.

[0015] 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.”

[0016] 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.

[0017] The process of the present invention can “comprise,” “consist essentially of,” or “consist of’ particular ingredients, components, compositions, etc., disclosed throughout the specification.

[0018] 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.

[0019] 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 disclosure, 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

[0020] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0021] FIG. 1 shows a system that comprises (1) a multiple-effect evaporator and (2) a membrane module for separating a mixture of an organic liquid and water, according to embodiments of the disclosure; and

[0022] FIG. 2 shows a method of determining how to configure a system that comprises (1) a multiple-effect evaporator and (2) a membrane module for separating a mixture of an organic liquid and water, according to embodiments of the disclosure.DETAILED DESCRIPTION OF THE INVENTION

[0023] The present disclosure involves the optimization of energy used in multiple-effect evaporators for the separation of mixtures of organic liquid and water, e.g., mixtures of diols and water. According to this disclosure, to reduce energy consumption in multiple-stage distillation by multiple-effect evaporators, a membrane module is combined with the multiple-effect evaporators to implement the separation process. In operation of the combined multiple-effect evaporator and membrane module, a slip-stream from the multiple-effect evaporator is used as a feed stream for the membrane module. The present inventors recognize that the location of the slip-stream affects the amount of energy saved when the multiple-effect evaporator is operated in conjunction with the membrane module. Consistent with this, embodiments of the present disclosure identify the optimal location of the slip-stream. Similarly, embodiments of the disclosure identify the optimal location of the return of the retentate stream from the membrane module to the multiple-effect evaporator.Systems for separating a mixture of an organic liquid and water

[0024] FIG. 1 shows a system 10 for separating a mixture of an organic liquid and water, according to embodiments of the disclosure. System 10 comprises a multiple-effect evaporator 100 and a membrane module 101. Embodiments of the disclosure employ a hybrid membrane distillation scheme / system, which can involve multiple membrane modular systems. Multipleeffect evaporator 100 comprises a plurality of evaporators, and as depicted in FIG. 1 includes first evaporator 100-1, second evaporator 100-2, third evaporator 100-3, fourth evaporator 100-4, fifth evaporator 100-5, and sixth evaporator 100-6. While multiple-effect evaporator 100 is shown as having six evaporators in FIG. 1, in embodiments of the disclosure, multiple-effect evaporator 100 can comprise two or more evaporators, or at least five evaporators.

[0025] In embodiments of the disclosure, as shown in FIG. 1, multiple-effect evaporator 100 is adapted to receive a mixture of organic liquid and water, such as a mixture 102 that comprises a diol and water, and is adapted to remove water from the mixture using first evaporator 100-1 to sixth evaporator 100-6, arranged in series. According to embodiments of the disclosure, mixture 102 is distilled by first evaporator 100-1 to produce (a) a first top stream 100- It, comprising water, and (b) a first bottom stream 100- lb, comprising diol and water. Theconcentration of diol in first bottom stream 100-lb is higher than the concentration of diol in mixture 102.

[0026] Multiple-effect evaporator 100, according to embodiments of the disclosure, is configured such that there is a fluid connection between first evaporator 100-1 and second evaporator 100-2 such that first bottom stream 100- lb flows from first evaporator 100-1 to second evaporator 100-2. Second evaporator 100-2, according to embodiments of the disclosure, is adapted to evaporate water from first bottom stream 100-lb to produce a second top stream 100- 2t and a second bottom stream 100-2b. Similarly, as shown in FIG. 1, third evaporator 100-3, fourth evaporator 100-4, fifth evaporator 100-5, and sixth evaporator 100-6 are each adapted to receive the bottom stream from the preceding evaporator (second evaporator 100-2, third evaporator 100-3, fourth evaporator 100-4, and fifth evaporator 100-5, respectively) to produce a third top stream 100-3t and a third bottom stream 100-3b, a fourth top stream 100-4t and a fourth bottom stream 100-4b, a fifth top stream 100-5t and a fifth bottom stream 100-5b, and a sixth top stream 100-6t and a sixth bottom stream 100-6b, respectively. In this way, a high percentage of water is removed from mixture 102 to produce sixth bottom stream 100-6b, which is primarily diol. According to embodiments of the disclosure, the concentration of diol in the bottom streams progressively increases from first bottom stream 100-lb to sixth bottom stream 100-6b.

[0027] As shown in FIG. 1, in embodiments of the disclosure, system 10 includes membrane module 101 connected to multiple-effect evaporator 100 such that a portion of a bottom stream of one of the evaporators can flow to membrane module 101. The slip-stream, according to embodiments of the disclosure, can be taken from one or more outputs of any of first evaporator 100-1 to sixth evaporator 100-6. Any combination of outputs from first evaporator 100-1 to sixth evaporator 100-6 to form the slip-stream is possible. One combination, in particular, involves mixing output from first evaporator 100-1 and output from third evaporator 100-3 to form the slipstream that is fed into membrane module 101 and retentate stream 105, in embodiments of the disclosure, can be routed to sixth evaporator 100-6 bottoms with approximately 90 % glycol concentration. According to embodiments of the disclosure and as shown in FIG. 1, a portion of third bottom stream 100-3b forms slip-stream 103 to membrane module 101, with the remainder of third bottom stream 100-3b(remainder stream 100-3bx), being received by fourth evaporator100-4. As disclosed with respect to system 10, the exit point of third bottom stream 100-3b has been determined to be the optimal location for slip-stream 103 to be withdrawn. Membrane module 101, according to embodiments of the disclosure, can include a membrane that operates based on one of the following: pervaporation, ultrafiltration, and nano-filtration. According to embodiments of the disclosure, membrane module 101 is adapted to process slip-stream 103 and remove water therefrom to produce a permeate stream 104 and a retentate stream 105. System 10, is further adapted, according to embodiments of the disclosure, to return retentate stream 105 to multipleeffect evaporator 100 at an optimal location therein, which in the case shown in FIG. 1 is at the input of sixth evaporator 100-6 (i.e., it is combined with fifth bottom stream 100-5b upstream of the sixth evaporator).Methods of determining how to configure a multiple-effect evaporator with a membrane module for separating a mixture of an organic liquid and water

[0028] FIG. 2 shows a method 20 for determining how to configure a system that comprises (1) a multiple-effect evaporator and (2) a membrane module for separating a mixture of an organic liquid and water, according to embodiments of the disclosure. Method 20 can be implemented, for example, to determine how to configure multiple-effect evaporator 100 and membrane module 101 together to save the maximum amount of energy.

[0029] In embodiments of the disclosure, method 20 includes, at block 200, separation of, or separating, a mixture of organic component and water, such as mixture 102, which comprises diol and water, using a multiple-effect evaporator 100 and a membrane module 101. In embodiments of the disclosure, the diol comprises a glycol. At block 201, method 20 involves, in embodiments of the disclosure, introduces the mixture of organic component and water as an initial feed mixture into a multiple effect evaporator column to produce a first water stream and a first concentrated slip stream. At block 202, method 20 involves, in embodiments of the disclosure, withdraw at a withdrawal point which is the first optimal location in the multiple-effect evaporator, for withdrawal of the slip-stream that results in the maximum energy savings as compared to other locations, when membrane module 101 is operated with multiple-effect evaporator 100. The withdrawal point is 45% to 60% away from the total number of separation stages from the initial feed stream.

[0030] In embodiments of the disclosure, the determining at block 202 comprises conducting simulations on a plurality of withdrawal points from the multiple-effect evaporator to determine the first optimal location. According to embodiments of the disclosure, the determining at block 202 comprises simulations carried out in one or more of the following platforms: AspenPlus, Promax, Aspen Custom Modeler (versions 10 and above), Origin, ProSim and GAMS, in combination with JMP, Minitab tools to carry out sensitivity analyses, wherein the simulations entail energy optimization studies carried out by assuming different locations for the withdrawal point and determining the corresponding energy savings when using that withdrawal point. The simulations on the withdrawal points, according to embodiments of the disclosure, include varying / optimizing the following: capital expenditures (CAPEX) / flux of membrane module (higher flux leads to lower CAPEX); operating parameters; energy savings (OPEX); operating conditions, e.g., free flow rate per module, temperature, pressure, condensate temperature, vacuum pressure; permeate purity desired with recirculation; and waste heat recovery / heat integration. In embodiments of the disclosure, involves validating the determined first optimal location from the simulations. Validating may include carrying out pilot experiments that include heat balance.

[0031] According to embodiments of the disclosure, block 203 of method 20 includes introduce a portion of the concentrated slip stream into the membrane module 101 to produce a permeate stream and a retentate stream. The method 20 includes, in embodiments of the disclosure, withdrawing slip-stream 103 (a portion of third bottom stream 100-3b) from the first optimal location (in the illustrated case, third evaporator 100-3). In embodiments of the disclosure involves separating water from slip-stream 103 by membrane module 101 to form (a) retentate stream 105 comprising a higher concentration of diol (e.g., glycol) than mixture 102 and (b) permeate stream 104 comprising a higher concentration of water than mixture 102, according to embodiments of the disclosure.

[0032] According to embodiments of the disclosure, block 204 of method 20 includes reintroduce the retentate stream from the membrane module 101 into one of the plurality of multiple-effect evaporator column (second optimal location). According to embodiments of the disclosure, method 20 includes determining a second optimal location in the multiple-effect evaporator, from a plurality of return locations therein, for returning retentate stream 105 frommembrane module 101 to multiple-effect evaporator 100, where the determining of the second optimal location involves similar techniques as the determining of the first optimal location. According to embodiments of the disclosure, the second optimal location is a location of returning the retentate stream to multiple-effect evaporator 100 that results in the maximum energy savings as compared to other locations, when membrane module 101 is operated with multiple-effect evaporator 100. In embodiments of the disclosure, involves validating the determined second optimal location from the simulations. Validating may include carrying out pilot experiments that include heat balance.

[0033] According to embodiments of the disclosure, method 20, further includes flowing retentate stream 105 to the second optimal location of the multiple-effect evaporator (in the illustrated case, sixth evaporator 100-6). At block 205, method 20 includes flowing, from multipleeffect evaporator 100, a product stream (z.e., sixth bottom stream 100-6b) comprising a higher concentration of diol (e.g., glycol) than mixture 102.

[0034] After the first optimal location and the second optimal location have been determined and validated, method 20 includes implementing and providing system 10 with multiple-effect evaporator 100 operating in conjunction with membrane module 101. According to embodiments of the disclosure, mixture 102 is flowed to multiple effect-evaporator 100, in which mixture 102 is evaporated to remove water by the several stages, namely first evaporator 100-1 to sixth evaporator 100-6. First top stream 100- It to sixth top stream 100-6t and first bottom stream 100-lb to sixth bottom stream 100-6b are produced, as discussed above.

[0035] Although embodiments of the present disclosure have been described with reference to blocks of FIG. 2 it should be appreciated that operation of the present disclosure is not limited to the particular blocks and / or the particular order of the blocks illustrated in FIG. 2. Accordingly, embodiments of the disclosure may provide functionality as described herein using various blocks in a sequence different than that of FIG. 2.

[0036] 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, somecontrollers, piping, computers, valves, pumps, heaters, thermocouples, pressure indicators, mixers, heat exchangers, and the like may not be shown.

[0037] As part of the disclosure of the present disclosure, specific examples are included below. The examples are for illustrative purposes only and are not intended to limit the disclosure. Those of ordinary skill in the art will readily recognize parameters that can be changed or modified to yield essentially the same results.EXAMPLE(Multi Effect Evaporator Slip-stream Simulation)

[0038] The simulation studies carried were carried out using the AspenPlus simulation tool (version 10) on the multiple-effect evaporator to find the optimum point for a slip-stream, with respect to energy savings, by taking a slip-stream from various locations in the evaporator section for the simulations. The slip-stream, in the simulations, is fed to the membrane module and the outlet from the membrane (the retentate stream) is concentrated as per the concentration of the feed flow to a different evaporator reboiler and fed back to the evaporator reboiler as shown in various columns. Table 1 shows energy savings for a 10% slip-stream determined based on tests of slip-streams from various locations in the multiple-effect evaporator. Table 2 shows energy savings for a 20% slip-stream determined based on tests of slip-streams from various locations in the multiple effect evaporator.TABLE 1Energy savings for 10% slip-stream from various locations in multiple-effect evaporatorTABLE 2Energy savings for 20% slip-stream from various locations in multiple-effect evaporator

[0040] In the context of the present invention, at least the following 15 embodiments are disclosed. Embodiment 1 is a method to separate a mixture of an organic component and water, the method comprising (a) introducing the mixture of the method of organic component and water as an initial feed stream into a first multiple-effect evaporator column to produce a first water stream and a first concentrated slip stream, wherein the first concentrated slip stream has a higher concentration of the organic component than the concentration of the organic component in the feed stream, and wherein the first multiple-effect evaporator column is one of a plurality of multiple-effect evaporator columns arranged in series such that an input to each of said plurality of multiple-effect evaporator columns subsequent to the first multiple-effect evaporator column;(b) withdrawing, at a withdrawal point, a portion of the concentrated slip stream of one of the plurality of multiple-effect evaporator columns and introducing said portion into a membrane module to produce a permeate stream comprising water and a retentate stream comprising the organic component, wherein the retentate stream has a higher concentration of the organic component than the concentration of the organic component in said concentrated slip stream; and(c) reintroducing the retentate stream, at a reintroduction point, into one of the plurality of multipleeffect evaporator columns as an additional input thereto. Embodiment 2 is the method of embodiment 1, wherein the each of the plurality of multiple-effect evaporator columns includes a plurality of separation stages such that the plurality of multiple-effect evaporator columns, arranged in series, has a total number of separation stages between the initial feed stream and the final product stream, and further comprising: locating the withdrawal point to be at 45% to 60% of the total number of separation stages away from the initial feed stream. Embodiment 3 is the method of any of embodiments 1 or 2, wherein the method further comprising: locating the withdrawal point to maximize flux, permeate purity, mass transfer for effective distillation, and to minimize cost compared to other potential withdrawal points. Embodiment 4 is the method of any of embodiments 1 to 3, wherein the method further comprising: locating the reintroduction point to be at 80% to 95% of the total number of separation stages away from the initial feed stream. Embodiment 5 is the method of any of embodiments 1 to 4, wherein 10% of the slip stream is withdrawn from the first multiple-effect evaporator column. Embodiment 6 is the method of any of embodiments 1 to 5, wherein 20% of the slip stream is withdrawn from the first multiple-effect evaporator column. Embodiment 7 is the method of any of embodiments 1 to 6, wherein the method further comprising: locating the reintroduction point to be at 85% to 95% of the totalnumber of separation stages away from the initial feed stage. Embodiment 8 is the method of any of the previous embodiments, wherein the plurality of multiple-effect evaporator columns comprises at least three multiple-effect evaporator columns. Embodiment 9 is the method of any of embodiments 1 to 8, wherein the membrane module comprises a membrane that operates based on one of the following: pervaporation, ultrafiltration, and nano-filtration. Embodiment 10 is the method of any of the previous embodiments, wherein the multiple-effect evaporator comprises at least two stages. Embodiment 11 is the method of embodiment 1, wherein the organic component comprises a diol

[0039] Embodiment 12 is a system for separating a mixture of an organic liquid and water. The system includes a multiple-effect evaporator, a membrane module, and a connector leading from the multiple-effect evaporator to the membrane module for transferring a slip-stream from the multiple-effect evaporator to the membrane module, wherein the connector is at a first optimal location in the multiple-effect evaporator, wherein the first optimal location is a location that results in the least energy consumption as compared to other locations on the multiple-effect evaporator, in operation of the system. Embodiment 13 is the system of embodiment 12, further including a retentate stream produced by the membrane module and directed to a second optimal location in the multiple-effect evaporator, wherein the second optimal location results in the maximum energy savings as compared to other locations on the multiple-effect evaporator, in operation of the system. Embodiment 14 is the system of any of embodiments 12 or 13, wherein the multiple-effect evaporator includes at least two stages. Embodiment 15 is the system of any of embodiments 12 to 14, wherein the membrane module includes a membrane that operates based on one of the following: pervaporation, ultrafiltration, and nano-filtration.

[0040] All embodiments described above and herein can be combined in any manner unless expressly excluded.

[0041] 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.

Claims

CLAIMSWhat is claimed is:

1. A method to separate a mixture of an organic component and water, the method comprising:(a) introducing the mixture of organic component and water as an initial feed stream into a first multiple-effect evaporator column to produce a first water stream and a first concentrated slip stream, wherein the first concentrated slip stream has a higher concentration of the organic component than the concentration of the organic component in the feed stream, and wherein the first multiple-effect evaporator column is one of a plurality of multiple-effect evaporator columns arranged in series such that an input to each of said plurality of multiple-effect evaporator columns subsequent to the first multiple-effect evaporator column;(b) withdrawing, at a withdrawal point, a portion of the concentrated slip stream of one of the plurality of multiple-effect evaporator columns and introducing said portion into a membrane module to produce a permeate stream comprising water and a retentate stream comprising the organic component, wherein the retentate stream has a higher concentration of the organic component than the concentration of the organic component in said concentrated slip stream; and(c) reintroducing the retentate stream, at a reintroduction point, into one of the plurality of multiple-effect evaporator columns as an additional input thereto; wherein the last of the plurality of multiple-effect evaporator columns produces a final water stream and a final product stream having a higher concentration of the organic component than the concentration of the organic component of the retentate stream; and wherein one or more of the water streams from the multiple-effect evaporator columns, the permeate stream, or a combination thereof are recycled back to an upstream unit for hydrolysis.

2. The method according to claim 1, wherein each of the plurality of multiple-effect evaporator columns includes a plurality of separation stages such that the plurality of multiple-effect evaporator columns, arranged in series, has a total number of separation stages between the initial feed stream and the final product stream, and further comprising: locating the withdrawal point to be at 45% to 60% of the total number of separation stages away from the initial feed stream.

3. The method according to claim 1 or claim 2, wherein the method further comprising: locating the withdrawal point to maximize flux, permeate purity, mass transfer for effective distillation, and to minimize cost compared to other potential withdrawal points.

4. The method according to any of claims 1 to 3, wherein the method further comprising: locating the reintroduction point to be at 80% to 95% of the total number of separation stages away from the initial feed stream.

5. The method according to any of claims 1 to 4, wherein 10% of the slip stream is withdrawn from the first multiple-effect evaporator column.

6. The method according to any of claims 1 to 5, wherein 20% of the slip stream is withdrawn from the first multiple-effect evaporator column.

7. The method according to any of claims 1 to 6, wherein the method further comprising: locating the reintroduction point to be at 85% to 95% of the total number of separation stages away from the initial feed stage.

8. The method according to any of claims 1 to 7, wherein the plurality of multipleeffect evaporator columns comprises at least three multiple-effect evaporator columns.

9. The method according to any of claims 1 to 8, wherein the membrane module comprises a membrane that operates based on one of the following: pervaporation, ultrafiltration, and nano-filtration.

10. The method according to any of claims 1 to 9, wherein the multiple-effect evaporator comprises at least two stages.

11. The method according to any of claims 1 to 10, wherein the organic component comprises a diol.

12. A system for separating a mixture of an organic liquid and water, the system comprising: a multiple-effect evaporator; a membrane module; and a connector leading from the multiple-effect evaporator to the membrane module for transferring a slip-stream from the multiple-effect evaporator to the membrane module, wherein the connector is at a first optimal location in the multiple-effect evaporator, wherein the first optimal location is a location that results in the least energy consumption as compared to other locations on the multiple-effect evaporator, in operation of the system.

13. The system according to claim 12, wherein the system further comprising: a retentate stream produced by the membrane module and directed to a second optimal location in the multiple-effect evaporator, wherein the second optimal location results in the maximum energy savings as compared to other locations on the multiple-effect evaporator, in operation of the system.

14. The system according to claim 12 or claim 13, wherein the multiple-effect evaporator comprises at least two stages.

15. The system according to claims 12 to 14, wherein the membrane module comprises a membrane that operates based on one of the following: pervaporation, ultrafiltration, and nano-filtration.

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