FIELD OF INVENTION
[001] The subject matter in general relates to production of dimethyl ether
(DME). More particularly, but not exclusively, the subject matter relates to production of dimethyl ether (DME) from coal gasification route with less energy consumption as compared to conventional route of producing dimethyl ether (DME) from coal gasification.
BACKGROUND OF INVENTION
[002] Background description includes information that may be useful in
understanding the present subject matter. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed subject matter, or that any publication specifically or implicitly referenced is prior art.
[003] Usage of dimethyl ether (DME) derived from coal gasification is
desired for blending with LPG, for chemical production as well as for fuel. Coal derived DME can reduce oil dependence of the country like India, China by being utilized as a fuel. There are essentially two methods for producing DME from coal gasification. The first is to produce by obtaining methanol from syngas via coal gasification followed by dehydrating methanol over gamma alumina catalyst. The other route is by directly converting syngas generated from coal gasification into DME. The first approach is widely used for producing DME in the industry due to its simplicity and availability of gamma alumina catalyst.
[004] One of the drawbacks of producing from methanol route is its high
energy consumption. The majority of energy consumption comes from sulphur and CO2 removal process for syngas, methanol purification process and methanol vaporization process. All these processes require steam to achieve heating purpose. Existing practice is to utilize steam from gasifier island as well as independent steam generators.
[005] Reference may be made to the following known Patents:
[006] Chinese patent application CN101289373A provides a method of
jointly producing dimethyl ether by using coal based syngas and methane source

gas, which is used for synthesizing the dimethyl ether by the production technology of the preparation of the dimethyl ether by utilizing coal based syngas one-step method. The method comprises the steps that after being pressurized, the carbon dioxide gas produced in the production process is mixed up with the methane source gas for partial oxidation reforming to obtain the reforming syngas; the reforming syngas obtained is returned to the synthesis process of the dimethyl ether to combine with the coal based syngas as the raw material gas for producing the dimethyl ether. The production method of the invention has the advantages of being capable of solving the production of large amount of the greenhouse gas of the carbon dioxide in the production technology of the preparation of the dimethyl ether by the coal based syngas one-step method as well as being capable of solving the problem of carbon supplement owing to the lack of carbon and more hydrogen in the process of the partial oxidation reforming of the methane source gas , thereby being capable of further improving the utilization ratio of the coal based syngas and the methane source gas and reducing the production cost of the dimethyl ether. However, the invention does not discuss about optimizing energy and discusses DME production from syngas directly from coal and natural gas.
[007] Chinese patent application CN104974022A provides a process for
production of dimethyl ether and combined production of natural gas and urea from coal-based synthetic gas and coke oven gas. The process comprises the following steps: introducing coke oven gas and coal-based synthetic gas into a gasometer and carrying out uniform mixing to form crude raw material gas; carrying out compression and then purification and recovering removed hydrogen sulfide after removal of sulfur; and subjecting purified crude raw material gas to cryogenic separation so as to obtain clean raw material gas, preparing liquefied natural gas or compressed natural gas products from separated methane, synthesizing dimethyl ether from the clean raw material gas and subjecting purge gas produced after synthesis of the dimethyl ether to pressure-variable adsorption and separation, wherein separated CO and H2 are returned and purified, and separated CO2 and liquefied ammonia enter a urea synthesis apparatus for synthesis of urea. The process has the advantages of diversification of products and capacity of adjusting excess production power, facilitating energy conservation and emission reduction,

regulating energy structure, increasing the utilization rate of raw material gas and reducing production cost for dimethyl ether. However, this invention relates to producing DME from syngas and separating DME from CO and H2 using pressure swing adsorption where energy optimization is not claimed clearly.
[008] Patent US4098809A discloses a process for the production of dimethyl
ether by feeding a mixture of CO, CO2 and H2, wherein the quantity of CO is in excess of the stoichiometric value, to a reactor containing a methyl alcohol synthesis catalyst, such as a copper base or chrome-zinc base catalyst, and a methyl alcohol dehydration catalyst, such as alumina, whereby methyl alcohol is formed as an intermediate product which is transformed into dimethyl ether in the same reactor at a temperature in the range of 220° to 400° C and a pressure in the range of 30 to 500 kg/cm2. However it does not discuss the aspect of energy reduction.
[009] US patent application US20130030063A1 discloses a process for the
production of fuel grade DME from carbonaceous fuels, including a pressurized multi-stage progressively expanding fluidized bed gasifier and an oxyblown autothermal reformer to produce a synthesis gas (syngas) with desirable hydrogen to carbon monoxide molar ratio, which then undergoes gas-phase DME one-step direct synthesis in a fluid pluralized bed reactor over an attrition resistant bi-functional catalyst. The crude DME thus obtained is purified in a two column distillation unit to produce a fuel grade DME having a purity greater than 99.98 mole %. However, this invention is related to fluidized bed DME reactor with catalyst which is not related to reducing energy consumption.
[0010] The method of DME provided by the above patents focuses on novel
catalyst, catalyst slurry or fluidized bed reactors, utilization of CO2, operating reactor at height temperature and low pressure etc. and do not address the reduction in energy requirement without sacrificing DME production quality and quantity.
[0011] Referring to FIG. 1, disclosed is a conventional method of producing
dimethyl ether. Syngas is generated in a coal gasifier 102 using coal. The syngas thus produced in the coal gasifier 102 is supplied to a particulate and tar removal system 104 for removing the particulate and tar from the syngas. The steam generated in the coal gasifier 102 is supplied to a water gas shift reactor 106 and an

amine/rectisol system 108.
[0012] The syngas is then passed to the water gas shift reactor 106. In the water
gas shift reactor 106 the ratio of hydrogen (H2) to carbon monoxide (CO) is from 0.5-0.7 to 2-2.2 by providing steam from the coal gasifier 102. The syngas is then passed to the amine/rectisol system 108.
[0013] In the amine/rectisol system 108, hydrogen sulphide (H2S) and carbon
dioxide (CO2) from the syngas are removed using rectisol process. Thus, the H2S concentration in the syngas is less than 100 ppm and CO2 concentration in the syngas is in the range of 5-10% by volume.
[0014] The syngas after the removal of H2S and CO2 is fed into a methanol
reactor 110. The outlet of the methanol reactor 110 is fed into a methanol condenser 112, wherein syngas containing methanol is cooled using cooling water from a cooling tower 114. Thus, the methanol in the methanol condenser 112 contains liquid crude methanol containing with methanol content of 85-90 wt%. The uncondensed syngas is in the methanol condenser 112 is recycled back to the methanol reactor 110.
[0015] The crude methanol from the methanol condenser 112 is supplied to a
crude methanol distillation unit 116. In the crude methanol distillation unit 116 the crude methanol is distilled with purity of 99.5 wt% using steam from a boiler 118. Water is separated from the methanol in the crude methanol distillation unit 116 is separated and supplied to a water tank 122.
[0016] The purified methanol is supplied to a methanol evaporator 124 where
the methanol is pressurised at 10-15 bar. Steam from the boiler 118 is supplied to the methanol evaporator 124.
[0017] The methanol is heated in the methanol evaporator 124 at 160-210
degree Celsius and then supplied to a dimethyl ether (DME) reactor 126. In the DME reactor 126, the methanol vapour is contacted with gamma-alumina catalyst. The methanol-DME-water mixture is supplied to a cooler 127 to be cooled to liquid phase and the cooled methanol-DME-water mixture is supplied to a DME

distillation column 128.
[0018] In the DME distillation column 128, the DME is separated from the top
of the column 128 and supplied to a DME storage unit 130 for storage. Methanol water mixture from the bottom of the column 128 is separated and supplied to a methanol distillation column 132. Using the steam from the boiler 118, the water is separated in the methanol distillation column 132 and provided to the water tank 122. The methanol separated in the methanol distillation column 132 is transferred to the methanol evaporator 124.
[0019] Thus, the conventional method of producing dimethyl ether utilises
high energy consumption.
[0020] In view of the above, the present invention has been introduced which
can address the shortcomings of the prior arts and serve the purpose efficiently.
OBJECTS OF INENTION
[0021] In view of the foregoing limitations inherent in the state of the art, some
of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.
[0022] It is an object of the present disclosure to propose a method for
production of dimethyl ether (dme) from coal gasification route with less energy consumption.
[0023] It is another object of the present disclosure to propose a method for the
production of dimethyl ether (DME) by eliminating energy required for pure methanol generation and utilizing waste heat from methanol condenser to heat methanol for DME production.
[0024] It is yet another object of the present disclosure to propose a method for
the production of dimethyl ether (DME) by eliminating the methanol distillation column.
[0025] These and other objects and advantages of the present invention will be
apparent to those skilled in the art after a consideration of the following detailed

description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.
SUMMARY OF INVENTION
[0026] This summary is provided to introduce concepts related to production
of dimethyl ether (DME). The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0027] The present disclosure relates to a method for production of dimethyl
ether (DME) from coal gasification route with less energy consumption. The method comprises the following steps:
- Generating syngas from coal using a coal gasifier;
- Removing particulate and tar from the syngas generated in the coal gasifier using a particulate and tar removal system;
- Adjusting ratio of hydrogen (H2) to carbon monoxide (CO) in the syngas by providing steam using a water gas shift reactor system;
- Removing hydrogen sulphide (H2S) and carbon dioxide (CO2) from the syngas using an amine/rectisol system. Feeding the syngas from the amine/rectisol system into a methanol reactor;
- Condensing the syngas from the methanol reactor using a methanol condenser cum evaporator system;
- Vapourising the methanol and sending the methanol in vapor and superheated vapor form to a dimethyl ether (DME) reactor using the methanol condenser cum evaporator system.
[0028] Other objects, features and advantages of the present disclosure will
become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating

specific embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[0029] While the specification concludes with claims particularly pointing out
and distinctly claiming the subject matter that is regarded as forming the present subject matter, it is believed that the present disclosure will be better understood from the following description taken in conjunction with the accompanying drawings, where like reference numerals designate like structural and other elements, in which:
[0030] FIG. 1 discloses a conventional method of producing dimethyl ether.
[0031] FIG. 2 discloses a method of producing dimethyl ether according to the
present invention.
[0032] The figures depict embodiments of the present subject matter for the
purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION OF INVENTION
[0033] The detailed description of various exemplary embodiments of the
disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein 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 disclosure as defined by the appended claims.
[0034] It is also to be understood that various arrangements may be devised

that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0035] The terminology used herein is for the purpose of describing particular
embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes”, “consisting” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0036] It should also be noted that in some alternative implementations, the
functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0037] In addition, the descriptions of "first", "second", “third”, and the like in
the present invention are used for the purpose of description only, and are not to be construed as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Thus, features defining "first" and "second" may include at least one of the features, either explicitly or implicitly.
[0038] Unless otherwise defined, all terms (including technical and scientific
terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0039] Referring to FIG. 2, disclosed is a method of producing dimethyl ether
using the present invention. Syngas is generated in a coal gasifier 202 using coal. The syngas thus produced in the coal gasifier 202 is supplied to a particulate and tar removal system 204 for removing the particulate and tar from the syngas. The steam generated in the coal gasifier 202 is supplied to a water gas shift reactor 206 and an amine/rectisol system 208
[0040] The syngas is then passed to the water gas shift reactor 206. In the water
gas shift reactor 206 the ratio of hydrogen (H2) to carbon monoxide (CO) is from 0.5-0.7 to 2-2.2 by providing steam from the coal gasifier 102. The syngas is then passed to the amine/rectisol system 208.
[0041] In the amine/rectisol system 208, hydrogen sulphide (H2S) and carbon
dioxide (CO2) from the syngas are removed using rectisol process. In the amine/rectisol system 208, the H2S concentration in the syngas is reduced to less than 100 ppm and CO2 concentration in the syngas is reduced in the range of 0-1% by volume. The low CO2 concentration is achieved through higher amine/rectisol flow and less loading of CO2 in the solvent.
[0042] The syngas after the removal of H2S and CO2 is fed into a methanol
reactor 210. The outlet of the methanol reactor 210 is fed into a methanol condenser cum evaporator 212, wherein syngas containing methanol is condensed with liquid methanol from a methanol tank 218. The methanol received in the methanol tank 218 is from a methanol distillation column 222 (explained later). The condensed methanol with 99.5 wt% from the methanol condenser cum evaporator 212 is supplied to a methanol cooler 216 for cooling, wherein the methanol cooler 216 is cooled using cooling water from a cooling tower 214. The methanol thus cooled is supplied to the methanol tank 218, wherein the methanol received from the methanol distillation column 222 is also cooled. The methanol thus cooled is circulated to the methanol condenser cum evaporator 212.
[0043] The methanol is vapourised in the methanol condenser cum evaporator
system 212 and circulated to a dimethyl ether (DME) reactor 224 in vapor and superheated vapor form. The methanol is pressurised at 10-15 bar.

[0044] The uncondensed syngas in the methanol condenser cum evaporator
system 212 is recycled back to the methanol reactor 210.
[0045] In the DME reactor 224, the methanol vapour is contacted with gamma-
alumina catalyst and methanol-DME-water mixture is cooled to liquid phase and transferred to a DME distillation column 226.
[0046] In the DME distillation column 226, the DME is separated from the top
of the column 226 and supplied to a DME storage unit 228 for storage. Methanol water mixture from the bottom of the column 226 is separated and transferred to a methanol distillation column 222. Using the steam from a boiler 220, the water is separated in the methanol distillation column 222 and supplied to the water tank 230. The methanol separated in the methanol distillation column 222 is provided to the methanol tank 218.
[0047] Using the above process, the DME is produced with less steam and
cooling water consumption with modified process via methanol generation from coal gasification. The steam from the boiler 220 is used only in the methanol distillation column 222, as opposed to in the conventional process, wherein the steam from the boiler is used in the crude methanol distillation unit, methanol distillation column and methanol evaporator, thereby reducing the energy consumption.
TECHNICAL ADVANTAGE
[0048] A simple method for the production of dimethyl ether (DME).
[0049] Production of dimethyl ether (DME) by eliminating energy required for
pure methanol generation and utilizing waste heat from methanol condenser to heat methanol for DME production.
[0050] Production of dimethyl ether (DME) by eliminating the methanol
distillation column.
[0051] WORKING EXAMPLE
[0052] Disclosed herein, is a working example of the present invention.

[0053] Syngas is generated in a coal gasifier 202 using coal. The syngas thus
produced in the coal gasifier 202 is supplied to a particulate and tar removal system 204 for removing the particulate and tar from the syngas.
[0054] The syngas is then passed to a water gas shift reactor 206. In the water
gas shift reactor 206 the ratio of hydrogen (H2) to carbon monoxide (CO) is from 0.6 to 2.1 by providing steam. The syngas is then passed to a rectisol/amine system 208.
[0055] In the rectisol system 208, hydrogen sulphide (H2S) and carbon dioxide
(CO2) from the syngas are removed using rectisol process. In the rectisol system 208, the H2S concentration in the syngas is reduced to less than 100 ppm and CO2 concentration in the syngas is reduced in 0.5% by volume. The low CO2 concentration is achieved through higher rectisol flow and less loading of CO2 in the solvent.
[0056] The syngas after the removal of H2S and CO2 is fed into a methanol
reactor 210. The outlet of the methanol reactor 210 is fed into a methanol condenser cum evaporator 212, wherein syngas containing methanol is condensed with liquid methanol from a methanol tank 218. The methanol received in the methanol tank 218 is from a methanol distillation column 222 (explained later). The condensed methanol with 99.5 wt% from the methanol condenser cum evaporator 212 is supplied to a methanol cooler 216 for cooling, wherein the methanol cooler 216 is cooled using cooling water from a cooling tower 214. The methanol thus cooled is supplied to the methanol tank 218, wherein the methanol received from the methanol distillation column 222 is also cooled. The methanol thus cooled is circulated to the methanol condenser cum evaporator 212.
[0057] The methanol is vapourised in the methanol condenser cum evaporator
system 212 and circulated to a dimethyl ether (DME) reactor 224 in vapor and superheated vapor form. The methanol is pressurised at 12 bar.
[0058] The uncondensed syngas in the methanol condenser cum evaporator
system 212 is recycled back to the methanol reactor 210.

[0059] In the DME reactor 224, the methanol vapour is contacted with gamma-
alumina catalyst. The methanol-DME-water mixture is supplied to a cooler 225 to be cooled to liquid phase and the cooled methanol-DME-water mixture is transferred to a DME distillation column 226.
[0060] In the DME distillation column 226, the DME is separated from the top
of the column 226 and supplied to a DME storage unit 228 for storage. Methanol water mixture from the bottom of the column 226 is separated and transferred to a methanol distillation column 222. Using the steam from a boiler 220, the water is separated in the methanol distillation column 222 and supplied to the water tank 230. The methanol separated in the methanol distillation column 222 is provided to the methanol tank 218.
[0061] TEST RESULT
[0062] Tests were conducted using the conventional method of producing
dimethyl ether as shown in FIG. 1 and the method of producing dimethyl ether according to the present invention as shown in FIG. 2. The test was conducted for the production of 0.16 tonnes per day (TPD) of DME using 1TPD of Coal. The below table shows the comparison of energy requirements in KWh for various operations using the conventional method and the present invention.
[0063]


[0064] Thus, it is observed that in the production of 0.16 TPD of DME from
1TPD of Coal using the present invention, a net energy reduction/saving of 2.1 W/kg of DME is achieved.
[0065] Furthermore, 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.
[0066] 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. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.
[0067] Furthermore, those skilled in the art can appreciate that the terminology
used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0068] The claims, as originally presented and as they may be amended,
encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

[0069] While the foregoing describes various embodiments of the present
disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof. The scope of the present disclosure is determined by the claims that follow. The present disclosure 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.

WE CLAIM:
1. A method for production of dimethyl ether (DME) from coal gasification
route with less energy consumption, the method comprising the steps of:
generating syngas from coal in a coal gasifier (202);
removing particulate and tar from the syngas in a particulate and tar removal
system (204);
adjusting ratio of hydrogen (H2) to carbon monoxide (CO) in the syngas by
providing steam in a water gas shift reactor system (206);
removing hydrogen sulphide (H2S) and carbon dioxide (CO2) from the syngas
in an amine/rectisol system (208);
feeding the syngas from the amine/rectisol system (208) into a methanol
reactor (210);
condensing the syngas from the methanol reactor (210) in a methanol
condenser cum evaporator system (212); and
vapourising the methanol and sending the methanol in vapor and superheated
vapor form to a dimethyl ether (DME) reactor (224).
2. The method as claimed in claim 1, wherein the ratio of hydrogen to carbon monoxide in the syngas is adjusted from 0.5-0.7 to 2-2.2.
3. The method as claimed in claims 1-2, wherein low CO2 concentration is obtained through higher amine/rectisol flow and less CO2 loading is maintained in the amine/rectisol system (208).
4. The method as claimed in claims 1-3, wherein the H2S concentration in the syngas is less than 100 ppm and CO2 concentration is in the range of 0-1% by volume.
5. The method as claimed in claims 1-4, wherein the uncondensed syngas in the methanol condenser cum evaporator system (212) is recycled back to methanol reactor (210).

6. The method as claimed in claims 1-5, wherein condensed methanol from the methanol condenser cum evaporator system (212) is supplied to a methanol cooler (216), wherein the condensed methanol is cooled and supplied to a methanol tank (218); and the methanol from the methanol tank (218) is supplied to the methanol condenser cum evaporator system (212) to cool the syngas received from the methanol reactor (210).
7. The method as claimed in claims 1-6, wherein,
the methanol vapor is contacted with gamma-alumina catalyst using the DME
reactor (224); and
methanol-DME-water mixture is cooled to liquid phase in a cooler (225).
8. The method as claimed in claim 7, wherein the cooled methanol-DME-water mixture is supplied to a DME distillation column (226).
9. The method as claimed in claim 8, wherein, DME is separated from top of the DME distillation column (226) and methanol water mixture is separated from bottom of the DME distillation column (226); and methanol from the methanol water mixture is separated using a methanol distillation column (222).
10. The method as claimed in claim 9, wherein the methanol separated from the methanol water mixture in the methanol distillation column (222) is supplied to a methanol tank (218).