Claims:1. A process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream (3), said process comprising the steps of:
(a) subjecting the effluent stream (3) to a gas liquid separator (4) to obtain a vapor stream (5) having the dimethyl ether (DME) and the gases, and a first liquid stream (6) having dimethyl ether (DME), methanol and water;
(b) contacting the vapor stream (5) with a reflux liquid (10) in a fine distillation column (7) to obtain a second liquid stream (9) having dimethyl ether (DME), methanol, water and the reflux liquid, and a gas stream (8) containing said gases, wherein said fine distillation column (7) defines a reboiler, a condenser and an inlet for the reflux liquid, and wherein said condenser is operated at a temperature ranging from 5°C to 30°C, further wherein said fine distillation column is operated at a pressure below 15 bar; and
(c) effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid from said first liquid stream (6) and said second liquid stream (9),
said process affording dimethyl ether (DME) with a purity higher than 99%.
2. The process as claimed in claim 1, wherein the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid comprises:
(a) subjecting said first liquid stream (6) and said second liquid stream (9) to a separation column (11) to obtain a stream (15) rich in dimethyl ether (DME), a stream (14) rich in methanol, a stream (12) rich in water and a stream (13) having dimethyl ether (DME) and unreacted gases; and
(b) introducing the stream (13) having dimethyl ether (DME) and unreacted gases in said fine distillation column (7).
3. The process as claimed in claim 1, wherein the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid comprises:
(a) subjecting said first liquid stream (6) and said second liquid stream (9) to a separation column (11) to obtain a stream (12) rich in water, a stream (13) having dimethyl ether (DME) and unreacted gases, and a stream (18) rich in dimethyl ether (DME) and methanol;
(b) subjecting the stream (18) rich in dimethyl ether (DME) and methanol to a flash vessel (16) to obtain a stream (15) rich in dimethyl ether (DME) and a stream (14) rich in methanol.
4. The process as claimed in claim 1, wherein the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid comprises:
(a) subjecting said first liquid stream (6) and said second liquid stream (9) to a separation column (11) to obtain a stream (12) rich in water, a stream (13) having dimethyl ether (DME) and unreacted gases, a stream (14) rich in methanol and a stream (18) rich in dimethyl ether (DME) having minor amount of methanol;
(b) subjecting the stream (18) rich in dimethyl ether (DME) having minor amount of methanol to a flash vessel (16) to obtain a stream (15) rich in dimethyl ether (DME) and a stream (17) rich in methanol, said stream (17) rich in methanol being fed back to said separation column (11).
5. The process as claimed in claim 1, wherein the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid comprises:
(a) subjecting said first liquid stream (6) and said second liquid stream (9) to a separation column (11) to obtain a stream (12) rich in water, a stream (13) having dimethyl ether (DME) and unreacted gases, a stream (15) rich in dimethyl ether (DME), and a stream (18) rich in methanol having minor amount of dimethyl ether (DME);
(b) subjecting the stream (18) rich in methanol having minor amount of dimethyl ether (DME) to a flash vessel (16) to obtain a stream (17) rich in dimethyl ether (DME) and a stream (14) rich in methanol, said stream (17) rich in dimethyl ether (DME) being fed back to said separation column (11).
6. The process as claimed in claim 1, wherein said effluent stream (3) is an effluent stream from a reactor (2) converting syngas to DME.
7. The process as claimed in claim 1, wherein said reflux liquid is selected from water, methanol and mixtures thereof.
8. A process for separating dimethyl ether (DME) from carbon dioxide (CO2), the process comprising: contacting a vapor stream containing dimethyl ether (DME) and carbon dioxide (CO2) with a reflux liquid in a fine distillation column to obtain a liquid stream rich in DME and a gas stream containing carbon dioxide (CO2), wherein said fine distillation column defines a reboiler, a condenser and an inlet for the reflux liquid, and wherein said condenser is operated at a temperature ranging from 5°C to 30°C, further wherein said fine distillation column is operated at a pressure below 15 bar.
, Description:TECHNICAL FIELD
[0001] The present disclosure provides an improved process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream that is economical.

BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] With the increasing demand for cleaner fuel everyone started searching for alternate or cleaner fuels, as part of which gas based fuels are replacing the conventional liquid fuels. At the same time, India being a huge importer of LPG, an alternate fuel which can be blended with LPG or can fully replace LPG is to be explored. DME can be an answer for the above problems.
[0004] There are two processes for producing dimethyl ether (DME): one being direct conversion of syngas to DME, and another being firstly converting syngas to methanol and then effecting dehydration of methanol to produce DME. In both these reactions, the reaction proceeds as below:
………..(1)
……...(2)
…………(3)
[0005] It is noteworthy that at an industrial/commercial scale, the direct conversion of syngas to DME is not preferred, and in-fact, not practiced, owing to the Water Gas Shift reaction occurring simultaneously, significantly lowering the overall yield of DME. Water Gas Shift reaction scheme is shown below:
………..(4)
[0006] As can be seen from the reaction schemes presented hereinabove, whenever direct conversion of syngas to DME is attempted, the water generated at step 1 (along with methanol) upon reacting with carbon monoxide of the syngas, generates CO2 and H2, extent whereof depends on the nature of the catalyst employed for effecting the conversion of syngas to DME and the reactor pressure and temperature conditions. Hence, conventionally, the two step process is used for production of DME from syngas, wherein two different reactors or reactor beds or two different catalysts are employed, and once the first reaction is completed, the methanol and water are separated and the purified stream of methanol is fed to the second reactor for conversion to DME. Since, the water generated during the process is continuously removed (typically, by effecting distillation of methanol and water stream), the equilibrium is tilted towards production of methanol reducing the extent of Water Gas Shift reaction.
[0007] Another bottleneck to successful industrial implementation of direct conversion of syngas to DME is separation of DME and unreacted gases from the reactor effluent stream. Conventionally, the effluent stream is directed towards a gas liquid separator, wherein the liquid stream is separated out from the gaseous stream, the gaseous stream mostly comprises unreacted syngas, CO2 and DME that needs to be separated to obtain DME of requisite purity. Separation of unreacted syngas, CO2 and DME from the gaseous stream requires employment of cryogenics i.e. use of heat transfer media having temperature of -25°C and below, such that the DME, having boiling temp. of about -24°C, can be separated out (as a liquid stream) from the unreacted syngas and CO2. The use of cryogenics not only require huge investment, but also requires manpower/personnel with special operational skills, which makes the conventional processes costly, affecting the overall economics of DME production through direct route. In-fact, partly, owing to the difficulties in separating unreacted syngas and CO2 from DME, two-step process i.e. firstly converting syngas to methanol and then effecting dehydration of methanol to produce DME is implemented industrially, wherein unreacted syngas and/or CO2 is separated from the methanol, and then dehydration of methanol is effected to produce DME (precluding the need of separation of DME and unreacted syngas and/or CO2).
[0008] In an effort to solve the aforesaid technical problem, few reports have been published suggesting utilization of absorption and/or extraction techniques for separation of syngas and/or CO2 and DME. For example, CN1085824A discloses a process for directly preparing dimethyl ether from syngas, characterized in that in addition to the synthesis reaction, it comprises the following two processes: 1) extraction and separation; 2) Desorption and fractionation; the so-called extraction and separation process uses a solvent extraction method to recover the product dimethyl ether from the reaction product tail gas, and the desorption and fractionation process uses a desorption and fractionation method to obtain a higher purity product dimethyl ether from the extract; the extraction requiring operating pressures of not lower than 1.0 MPa; US9856197B2 discloses a method that reforms flare gas or other raw natural gas source, using air without steam, to directly produce dimethyl ether (DME), wherein DME is separated using water as an absorption media at 20 bar pressure and 0°C temperature. However, utilization of absorption or extraction columns/techniques have their own sets of shortcomings including higher initial investments and higher operational costs, inter-alia, others.
[0009] Hence, there remains a long felt need in the art of an improved process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream that is economical, while overcoming (at least in part) the drawbacks associated with the conventional processes/techniques. The present invention satisfies the existing needs, as well as others, and generally overcomes the deficiencies found in the state-of-art.
[0010] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

OBJECTS OF THE INVENTION
[0011] It is an object of the present disclosure to provide an improved process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream that is economical.
[0012] Another object of the present disclosure to provide a process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream that does not require utilization of cryogenics or high pressure.
[0013] Further object of the present disclosure to provide a process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream that affords high purity DME.

SUMMARY
[0014] The present disclosure provides an improved process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream that is economical.
[0015] An aspect of the present disclosure relates to a process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream, said process including the steps of: (a) subjecting the effluent stream to a gas liquid separator to obtain a vapor stream having dimethyl ether (DME) and gases, and a first liquid stream having dimethyl ether (DME), methanol and water; (b) contacting the vapor stream with a reflux liquid in a fine distillation column to obtain a second liquid stream having dimethyl ether (DME), methanol, water and the reflux liquid, and a gas stream containing said gases, wherein said fine distillation column defines a reboiler, a condenser and an inlet for the reflux liquid, and wherein said condenser is operated at a temperature ranging from 5°C to 30°C, further wherein said fine distillation column is operated at a pressure below 15 bar; and (c) effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid from said first liquid stream and said second liquid stream, said process affording dimethyl ether (DME) with a purity higher than 99%. In an embodiment, said effluent stream is an effluent stream from a reactor converting syngas to DME. In an embodiment, the reflux liquid is selected from any or a combination of water and methanol.
[0016] In an embodiment, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream and said second liquid stream to a separation column to obtain a stream rich in dimethyl ether (DME), a stream rich in methanol, a stream rich in water and a stream having dimethyl ether (DME) and unreacted gases; and (b) introducing the stream having dimethyl ether (DME) and unreacted gases in said fine distillation column.
[0017] In an embodiment, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream and said second liquid stream to a separation column to obtain a stream rich in water, a stream having dimethyl ether (DME) and unreacted gases, and a stream rich in dimethyl ether (DME) and methanol; (b) subjecting the stream rich in dimethyl ether (DME) and methanol to a flash vessel to obtain a stream rich in dimethyl ether (DME) and a stream rich in methanol.
[0018] In an embodiment, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream and said second liquid stream to a separation column to obtain a stream rich in water, a stream having dimethyl ether (DME) and unreacted gases, a stream rich in methanol and a stream rich in dimethyl ether (DME) having minor amount of methanol; (b) subjecting the stream rich in dimethyl ether (DME) having minor amount of methanol to a flash vessel to obtain a stream rich in dimethyl ether (DME) and a stream rich in methanol, said stream rich in methanol being fed back to said separation column.
[0019] In an embodiment, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream and said second liquid stream to a separation column to obtain a stream rich in water, a stream having dimethyl ether (DME) and unreacted gases, a stream rich in dimethyl ether (DME), and a stream rich in methanol having minor amount of dimethyl ether (DME); (b) subjecting the stream rich in methanol having minor amount of dimethyl ether (DME) to a flash vessel to obtain a stream rich in dimethyl ether (DME) and a stream rich in methanol, said stream rich in dimethyl ether (DME) being fed back to said separation column.
[0020] Another aspect of the present disclosure relates to a process for separating dimethyl ether (DME) from carbon dioxide (CO2), the process including contacting a vapor stream containing dimethyl ether (DME) and carbon dioxide (CO2) with a reflux liquid in a fine distillation column to obtain a liquid stream rich in DME, and a gas stream containing carbon dioxide (CO2), wherein said fine distillation column defines a reboiler, a condenser and an inlet for the reflux liquid, and wherein said condenser is operated at a temperature ranging from 5C to 30C, further wherein said fine distillation column is operated at a pressure below 15 bar.
[0021] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0023] FIG. 1 illustrates an exemplary schematic for conversion of syngas to dimethyl ether (DME), realized in accordance with an embodiment of the present disclosure.
[0024] FIG. 2 illustrates an exemplary schematic showing separation of dimethyl ether (DME), methanol, water and the reflux liquid, in accordance with an embodiment of the present disclosure.
[0025] FIG. 3 illustrates an exemplary schematic showing separation of dimethyl ether (DME), methanol, water and the reflux liquid, in accordance with an embodiment of the present disclosure.
[0026] FIG. 4 illustrates an exemplary schematic showing separation of dimethyl ether (DME), methanol, water and the reflux liquid, in accordance with an embodiment of the present disclosure.
[0027] FIG. 5 illustrates an exemplary schematic showing separation of dimethyl ether (DME), methanol, water and the reflux liquid, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION
[0028] The following is a detailed description of embodiments of the present invention. The embodiments are in such detail as to clearly communicate the invention. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.
[0029] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0030] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability.
[0031] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0032] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0033] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0034] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0035] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.
[0036] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0037] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0038] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0039] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0040] The present disclosure provides an improved process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream that is economical.
[0041] An aspect of the present disclosure relates to a process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream, said process including the steps of: (a) subjecting the effluent stream to a gas liquid separator to obtain a vapor stream having the dimethyl ether (DME) and the gases, and a first liquid stream having dimethyl ether (DME), methanol and water; (b) contacting the vapor stream with a reflux liquid in a fine distillation column to obtain a second liquid stream having dimethyl ether (DME), methanol, water and the reflux liquid, and a gas stream containing said gases, wherein said fine distillation column defines a reboiler, a condenser and an inlet for the reflux liquid, and wherein said condenser is operated at a temperature ranging from 5°C to 30°C, further wherein said fine distillation column is operated at a pressure below 15 bar; and (c) effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid from said first liquid stream and said second liquid stream, said process affording dimethyl ether (DME) with a purity higher than 99%. In an embodiment, said effluent stream is an effluent stream from a reactor converting syngas to DME. In an embodiment, the reflux liquid is selected from any or a combination of water and methanol. In an embodiment, the reflux liquid is water. In an embodiment, the reflux liquid is methanol. In an embodiment, the reflux liquid is a combination of water and methanol.
[0042] FIG. 1 illustrates an exemplary schematic showing processing of an effluent stream (3) for separating dimethyl ether (DME), methanol, gases and water. As can be seen from FIG. 1, the process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream (3) includes the steps of: (a) subjecting the effluent stream (3) to a gas liquid separator (4) to obtain a vapor stream (5) having dimethyl ether (DME) and gases, and a first liquid stream (6) having dimethyl ether (DME), methanol and water; (b) contacting the vapor stream (5) with a reflux liquid (10) in a fine distillation column (7) to obtain a second liquid stream (9) having dimethyl ether (DME), methanol, water and the reflux liquid, and a gas stream (8) containing said gases, wherein said fine distillation column (7) defines a reboiler, a condenser and an inlet for the reflux liquid, and wherein said condenser is operated at a temperature ranging from 5°C to 30°C, further wherein said fine distillation column is operated at a pressure below 15 bar; and (c) effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid from said first liquid stream (6) and said second liquid stream (9). The advantageous process of the present disclosure affords dimethyl ether (DME) with a purity higher than 99%. In an embodiment, the effluent stream (3) is an effluent stream from a reactor (2) converting syngas to DME.
[0043] As one would appreciate, the advantageous process of the present disclosure affords easy and cost-effective separation of DME from unreacted syngas and/or CO2, which conventionally has been construed to be troublesome. Dimethyl ether (DME), methanol, water and reflux liquid can be separated following any of the conventional or known process techniques, such as by using one or more columns (e.g. distillation columns), flash vessels or such other known instruments to get the dimethyl ether (DME), methanol, reflux liquid and water with requisite purity and/or strength.
[0044] In an embodiment, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream and said second liquid stream to a separation column to obtain a stream rich in dimethyl ether (DME), a stream rich in Methanol, a stream rich in water and a stream having dimethyl ether (DME) and unreacted gases; and (b) introducing the stream having dimethyl ether (DME) and unreacted gases in said fine distillation column. As can be seen from FIG. 1, in accordance with an embodiment, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream (6) and said second liquid stream (9) to a separation column (11) to obtain a stream (15) rich in dimethyl ether (DME), a stream (14) rich in methanol, a stream (12) rich in water and a stream (13) having dimethyl ether (DME) and unreacted gases; and (b) introducing the stream (13) having dimethyl ether (DME) and unreacted gases in said fine distillation column (7). Introducing the stream (13) having dimethyl ether (DME) and unreacted gases in said fine distillation column (7) is advantageous, as the stream (13) includes unrecovered DME, and hence, recycling back the stream (13) to the fine distillation column (7) not only enhances DME concentration, but a definite amount of DME can be recovered from the fine distillation column bottoms and thus enhances DME recovery as well. Methanol separated from the process through stream (14) may be recycled back, in full or in part, to the reactor (2) as per the requirements. Advantageously, the reflux liquid may be selected from the components of reactor effluent stream i.e. water, methanol or mixture thereof, such that the same can be easily recovered without employment of separate instrumentation/processes for separation and/or purification thereof.
[0045] In another embodiment, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream and said second liquid stream to a separation column to obtain a stream rich in water, a stream having dimethyl ether (DME) and unreacted gases, and a stream rich in dimethyl ether (DME) and methanol; (b) subjecting the stream rich in dimethyl ether (DME) and methanol to a flash vessel to obtain a stream rich in dimethyl ether (DME) and a stream rich in methanol.
[0046] FIG. 2 illustrates an exemplary schematic showing separation of dimethyl ether (DME), methanol, water and the reflux liquid, in accordance with an embodiment of the present disclosure. As can be seen from FIG. 2, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream (6) and said second liquid stream (9) to a separation column (11) to obtain a stream (12) rich in water, a stream (13) having dimethyl ether (DME) and unreacted gases, and a stream (18) rich in dimethyl ether (DME) and methanol; and (b) subjecting the stream (18) rich in dimethyl ether (DME) and methanol to a flash vessel (16) to obtain a stream (15) rich in dimethyl ether (DME) and a stream (14) rich in methanol.
[0047] In an embodiment, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream and said second liquid stream to a separation column to obtain a stream rich in water, a stream having dimethyl ether (DME) and unreacted gases, a stream rich in methanol and a stream rich in dimethyl ether (DME) having minor amount of methanol; (b) subjecting the stream rich in dimethyl ether (DME) having minor amount of methanol to a flash vessel to obtain a stream rich in dimethyl ether (DME) and a stream rich in methanol, said stream rich in methanol being fed back to said separation column.
[0048] FIG. 3 illustrates an exemplary schematic showing separation of dimethyl ether (DME), methanol, water and the reflux liquid, in accordance with an embodiment of the present disclosure. As can be seen from FIG. 3, in accordance with an embodiment, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream (6) and said second liquid stream (9) to a separation column (11) to obtain a stream (12) rich in water, a stream (13) having dimethyl ether (DME) and unreacted gases, a stream (14) rich in methanol and a stream (18) rich in dimethyl ether (DME) having minor amount of methanol; and (b) subjecting the stream (18) rich in dimethyl ether (DME) having minor amount of methanol to a flash vessel (16) to obtain a stream (15) rich in dimethyl ether (DME) and a stream (17) rich in methanol, said stream (17) rich in methanol being fed back to said separation column (11).
[0049] In another embodiment, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream and said second liquid stream to a separation column to obtain a stream rich in water, a stream having dimethyl ether (DME) and unreacted gases, a stream rich in dimethyl ether (DME), and a stream rich in methanol having minor amount of dimethyl ether (DME); (b) subjecting the stream rich in methanol having minor amount of dimethyl ether (DME) to a flash vessel to obtain a stream rich in dimethyl ether (DME) and a stream rich in methanol, said stream rich in dimethyl ether (DME) being fed back to said separation column.
[0050] FIG. 4 illustrates an exemplary schematic showing separation of dimethyl ether (DME), methanol, water and the reflux liquid, in accordance with an embodiment of the present disclosure. As can be seen from FIG. 4, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream (6) and said second liquid stream (9) to a separation column (11) to obtain a stream (12) rich in water, a stream (13) having dimethyl ether (DME) and unreacted gases, a stream (15) rich in dimethyl ether (DME), and a stream (18) rich in methanol having minor amount of dimethyl ether (DME); and (b) subjecting the stream (18) rich in methanol having minor amount of dimethyl ether (DME) to a flash vessel (16) to obtain a stream (17) rich in dimethyl ether (DME) and a stream (14) rich in methanol, said stream (17) rich in dimethyl ether (DME) being fed back to said separation column (11).
[0051] FIG. 5 illustrates an exemplary schematic showing separation of dimethyl ether (DME), methanol, water and the reflux liquid, in accordance with an embodiment of the present disclosure. As can be seen from FIG. 5, the step of effecting separation of dimethyl ether (DME), methanol, water and the reflux liquid includes: (a) subjecting said first liquid stream (6) and said second liquid stream (9) to a separation column (11) to obtain a stream (12) rich in water, a stream (13) having dimethyl ether (DME) and unreacted gases, a stream (18) rich in dimethyl ether (DME) having minor amount of methanol, and a stream (20) rich in methanol having minor amount of dimethyl ether (DME); (b) subjecting the stream (18) rich in dimethyl ether (DME) having minor amount of methanol to a flash vessel (16) to obtain a stream (15) rich in dimethyl ether (DME) and a stream (17) rich in methanol, said stream (17) rich in methanol being fed back to said separation column (11); and (c) subjecting the stream (20) rich in methanol having minor amount of dimethyl ether (DME) to a flash vessel (21) to obtain a stream (19) rich in dimethyl ether (DME) and a stream (14) rich in methanol, said stream (19) rich in dimethyl ether (DME) being fed back to said separation column (11).
[0052] Another aspect of the present disclosure relates to a process for separating dimethyl ether (DME) from carbon dioxide (CO2), the process including contacting a vapor stream containing dimethyl ether (DME) and carbon dioxide (CO2) with a reflux liquid in a fine distillation column to obtain a liquid stream rich in DME and a gas stream containing carbon dioxide (CO2), wherein said fine distillation column defines a reboiler, a condenser and an inlet for the reflux liquid, and wherein said condenser is operated at a temperature ranging from 5°C to 30°C, further wherein said fine distillation column is operated at a pressure below 15 bar.
[0053] One would appreciate that feeding the reflux liquid (e.g. water) in the fine distillation column affords maintenance of the liquid flow inside the column, lowering the condenser temperature requirement to about 10°C, which can easily achieved using circulation of chilled water (as a heat transfer media). The reflux liquid (e.g. water) also aids in scrubbing methanol present in the gases, and the resultant methanol and water can be easily separated out in methanol purification section. The reboiler present with the column also aids in removing dissolved gases and maintains maximum DME in the second liquid stream (9), while the unrecovered DME along with unreacted gases leave the column through gas stream (8). Owing to usage of reflux liquid, DME can be separated out as bottoms along with water, which may be purified to obtain DME of about 99.5% purity.
[0054] While the foregoing description discloses various embodiments of the disclosure, other and further embodiments of the invention may be devised without departing from the basic scope of the disclosure. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
[0055] Example 1 – Separating dimethyl ether (DME), methanol, gases and water from an effluent stream using chilled water as heat transfer media and water as the reflux liquid
[0056] Table 1 below provides specifics of the equipment and parameters for separating dimethyl ether (DME), methanol, gases and water from an effluent stream, when chilled water (temperature of about 10°C) was used as heat transfer media.
Table 1: Specifics of equipment and parameters for separating dimethyl ether (DME), methanol, gases and water
Equipment number 4 7 11 16 21
Temperature 35 21 107
Condensor - 9.23 14.44 - -
Reboiler - 81.73 151.74 - -
Pressure 15 10 5 5 5
Number of Stages - 3 30 - -
Distillate rate
(Kmoles / hr) - 27.88 9.01 - -
Reflux rate (Kmoles / hr) - 56.71 92.76 - -
Reflux ratio - 2.03 10.30 - -
Bottoms rate
(kmoles / hr) - 61.40 68.46 - -
Boilup rate (kmoles / hr) - 0.88 63.08 - -
Boilup ratio - 0.01 0.92 - -
Vapor fraction (mole) 0.42 - - 0.89 0.04
Vapor fraction (mass) 0.35 - - 0.89 0.04

[0057] Table 2A and 2B below provides operating parameters along with composition (in mole fraction) of different streams when chilled water was used as heat transfer media.
Table 2A: Operating parameters and composition of different streams
Stream Number 3 5 6 10 8 9 12 13
Flowrate
(Kg / hr) 1811 636.6 1174 900 522.07 1421 1234 406
Flowrate
(Kmoles / hr) 71.55 30.32 41.23 49.96 27.88 61.40 68.46 9.01
Temp. (C) 250.00 35.00 35.00 50.00 9.23 81.73 151.74 14.44
Pressure (Bar) 61 15 15 12 10 10 5 5
Composition (Mole frac)
METHANOL 0.20 0.01 0.35 0.00 0.00 0.00 0.00 0.00
WATER 0.26 0.00 0.45 1.00 0.00 0.81 1.00 0.00
DME 0.17 0.16 0.19 0.00 0.06 0.17 0.00 0.85
H2 0.18 0.42 0.00 0.00 0.46 0.00 0.00 0.00
CO 0.15 0.34 0.01 0.00 0.37 0.00 0.00 0.03
CO2 0.04 0.07 0.01 0.00 0.10 0.01 0.00 0.11

Table 2B: Operating parameters and composition of different streams
Stream Number 15 14 17 18 19 20
Flowrate
(Kg / hr) 490.5 464.54 59.53 550 20.457 485
Flowrate
(Kmoles / hr) 10.66 14.51 1.32 11.98 0.60 15.11
Temp. (C) 21.17 106.94 21.17 19.15 106.94 99.05
Pressure (Bar) 5 5 5 5 5 5
Composition (Mole frac)
METHANOL 0.00 0.99 0.06 0.01 0.87 0.99
WATER 0.00 0.00 0.00 0.00 0.00 0.00
DME 0.99 0.00 0.94 0.99 0.13 0.01
H2 0.00 0.00 0.00 0.00 0.00 0.00
CO 0.00 0.00 0.00 0.00 0.00 0.00
CO2 0.00 0.00 0.00 0.00 0.01 0.00

[0058] As can be seen from Table 2A and 2B above, even when water having temperature of about 10°C is used as a reflux liquid, DME of >99% purity could be separated (stream 18).
[0059] Example 2 – Separating dimethyl ether (DME), methanol, gases and water from an effluent stream using cooled water as heat transfer media and water as the reflux liquid
[0060] Table 3 below provides specifics of the equipment and parameters for separating dimethyl ether (DME), methanol, gases and water from an effluent stream, when cooled water (temperature of about 30°C) was used as heat transfer media.
Table 3: Specifics of equipment and parameters for separating dimethyl ether (DME), methanol, gases and water
Equipment number 4 7 11 16 21
Temperature 35 38
Condensor - 33.45 30.05 - -
Reboiler - 92.57 170.21 - -
Pressure 15 10 8 8 8
Number of Stages - 3 30 - -
Distillate rate (Kmoles / hr) - 29.54 7.20 - -
Reflux rate (Kmoles / hr) - 55.18 100.86 - -
Reflux ratio - 1.87 14.00 - -
Bottoms rate (kmoles / hr) - 57.94 68.38 - -
Boilup rate (kmoles / hr) - 0.70 69.65 - -
Boilup ratio - 0.01 1.02 - -
Vapor fraction (mole) 0.42 - - 0.89 0.05
Vapor fraction (mass) 0.35 - - 0.89 0.05

[0061] Table 4A and 4B below provides operating parameters along with composition (in mole fraction) of different streams when cooled water was used as heat transfer media.
Table 4A: Operating parameters and composition of different streams
Stream Number 3 5 6 10 8 9 12 13
Flowrate
(Kg / hr) 1811 636.61 1174 900 595.58 1265 1233 323.969
Flowrate
(Kmoles / hr) 71.55 30.32 41.23 49.96 29.54 57.94 68.38 7.20
Temp. (C) 248.00 35.00 35.00 50.00 33.45 92.57 170.21 30.05
Pressure (Bar) 61.0 15 15 12 10 10 8 8
Composition (Mole frac)
METHANOL 0.20 0.01 0.35 0.00 0.00 0.00 0.00 0.00
WATER 0.26 0.00 0.45 1.00 0.00 0.86 1.00 0.00
DME 0.17 0.16 0.19 0.00 0.11 0.13 0.00 0.84
H2 0.18 0.42 0.00 0.00 0.44 0.00 0.00 0.00
CO 0.15 0.34 0.01 0.00 0.35 0.00 0.00 0.04
CO2 0.04 0.07 0.01 0.00 0.09 0.00 0.00 0.12

Table 4B: Operating parameters and composition of different streams
Stream Number 15 14 17 18 19 20
Flowrate
(Kg / hr) 419 463.5 50.99 470 25.498 489
Flowrate
(Kmoles / hr) 9.11 14.47 1.13 10.24 0.76 15.24
Temp. (C) 37.61 124.34 37.61 35.36 124.34 117.71
Pressure (Bar) 8 8 8 8 8 8
Composition (Mole frac)
METHANOL 0.01 0.99 0.06 0.01 0.89 0.99
WATER 0.00 0.00 0.00 0.00 0.00 0.00
DME 0.99 0.00 0.94 0.99 0.10 0.01
H2 0.00 0.00 0.00 0.00 0.00 0.00
CO 0.00 0.00 0.00 0.00 0.00 0.00
CO2 0.00 0.00 0.00 0.00 0.00 0.00

[0062] As can be seen from Table 4A and 4B above, even when water having temperature of about 30°C is used as a reflux liquid, DME of >99% purity could be separated (stream 18).
[0063] COMPARISON WITH UTILIZATION OF ABSORPTION COLUMN
[0064] Table 5 below shows comparison of economies when fine distillation column is used versus when absorption column is used.

Table 5: Comparison of economies of fine distillation column versus absorption column
Parameter Units Fine Distillation Absorption
Column top temp °C 9.2 31.6
Column Bottom temp °C 81.7 41.2
Unrecovered DME (w.r.t column feed) % 28 45.6
Overall DME recovery % 85.74 77.20
Separation column Minimum temp. °C 14.4 9.94
Utility cost $/hr 21.22 22.94

[0065] As can be seen from Table 5, employment of fine distillation column affords great economic advantage as compared to usage of absorption column.

ADVANTAGES
[0066] The present disclosure provides an improved process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream that is economical.
[0067] The present disclosure provides a process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream that does not require utilization of cryogenics or high pressure.
[0068] The present disclosure provides a process for separating dimethyl ether (DME), methanol, gases and water from an effluent stream that affords high purity DME.