FIELD OF THE INVENTION:
The present disclosure relates to an improved process for a production of Dimethyl Ether (DME) from methanol. The present disclosure also discloses an apparatus for DME production. More specifically, the present disclosure relates to a process for production of DME from methanol using multiple fixed bed reactor and intercooler systems.
BACKGROUND OF THE INVENTION:
There is an ever-increasing demand of Liquid Petroleum Gas (LPG) as cooking fuel. The major factors responsible for this trend is requirement of clean cooking 10 fuel. DME is the simplest ether compound, with a chemical formula of C2H6O. DME is a clean, colourless gas at ambient temperatures, but it can be liquefied under moderate pressure at room temperature. This makes DME quite similar to propane and LPG for handling purposes.
15
DME has been used for decades in the personal care industry, mainly as an environmentally benign propellant in aerosols, as DME is nontoxic and is easily degraded in the troposphere compared to Chlorofluorocarbon (CFCs). As the demand of LPG is increasing, an alternative or a potential blend to LPG is prudent. DME is a potential blend for LPG, which can be produced by 20 dehydration of methanol.
US 2014408 deals with preparation of Methyl ether by passing methanol over a suitable dehydration catalyst at elevated temperature and pressure. According to the disclosure feed methanol is preheated to approximately to 175-500 °C, the 25 preferable operating range being in the neighbourhood of 350-400 °C. Pressure in the reactor may vary from 1 atmosphere to 200 atmospheres with preferable pressure of 15 atmosphere. The disclosure also mentioned about separating the Methyl ether from water and unreacted methanol in liquid phase at substantially lower pressure of reactor. 30
3
US 4605788 proposes enhanced reaction rate and reduced catalyst coking and by-product formation when aluminosilicate containing high level of alumina is used as catalyst. The catalyst described as aluminosilicate preferably containing about 6% silica and about 94% alumina.
5
US 4595785A proposed enhanced reaction rate and reduced catalyst coking and by-product formation when aluminotitanate containing about 0.1-20% of titania and about 80-99.9% alumina is used as catalyst.
EP124078 proposed a process, mainly focused to the separation of product and 10 impurity, for high purity DME synthesis that can be used as propellant. According to the disclosure, with recycle of unreacted methanol to increase yield, impurity having boiling points between DME and methanol (like ethyl methyl ether, methyl formate and formal) starts to build up in the system. These accumulation of impurities in the process increases impurity level in product. It 15 has also been reported that the accumulation level can be as high as 20%. It has been concluded that superior reactor performance high purity of DME can be achieved by modifying distillation columns and specifically by talking side draws from the distillation columns.
20
US 8541630 B2, disclosed a process with fluidized bed reactor for DME synthesis for full use of reaction heat from the DME production. Heat generated in fluidized reactor is used for feed methanol vaporization. The disclosure also relates to the regeneration of fluidized reactor catalyst by burning of carbon deposit in regenerator. Additionally, to reduce impurity, DME column top vapor 25 vent is washed in a wash column by methanol water mixture to reduce product loss.
EP 2888218 B1 disclosed a process for production of purified dimethyl ether from methanol with use of additional Olefin Stripper Column to strip out 30 impurities from reactor product stream. Additionally, vapor vent for both the
4
Methanol column and DME column is mentioned for removal of light fractions in feed methanol (like CH4, CO2, N2) or in reactor product. Vapor vent from DME column top is proposed to be washed in Methanol wash column using a part of reactor feed methanol to reduce DME loss with the vent gas. Additionally, a reactor heat exchanger configuration is proposed where a part of the feed 5 methanol is heated and sent to the first reactor and other part of the feed methanol is used as coolant for first reactor. Heated methanol used as coolant along with the product from first reactor is mixed and sent to a second adiabatic reactor.
WO 2013/041516A2 relates to a reactor system for DME synthesis in cooled gas 10 phase solid catalytic fixed bed reactor for high yield of DME. Reduction of reactor temperature by suitable measure reduces formation of by products like CO, CO2, H2. The reactor system in the disclosure contains one or more combination of adiabatic and cooled reactor section. According to the disclosure the feed stream must be super-heated to kick start the reaction and in the 15 moderator section unreacted gaseous or vaporized or liquid feed is used as heat transfer medium in counter current or concurrent manner before being supplied to the reactor.
The prior arts disclosed the reactor cooling mechanism by using tubular reactor 20 where reaction takes place at catalyst, filled in the tubes of the reactor. Reactor cooling is achieved by coolant in the shell side of the tubular reactor. Challenges associated with catalyst filled tubular reactor are difficulty in filling of catalyst in tubes, monitoring and controlling of hotspots, maldistribution of reactor feed in tubes resulting reduced life of catalyst and increased chance of hot spot 25 formation.
OBJECTIVE OF THE INVENTION:
To overcome the limitation associated with tubular reactor and at the same time to achieve the required cooling, in the present disclosure a novel approach with 30
5
multiple reactors with intercooler and quench is implemented for methanol to DME synthesis.
The proposed novel scheme simplifies process equipment in terms of operation and reactor control, recovers reaction heat and is used in reactor quench heating 5 and thus reducing overall energy requirement of the process. Use of reactors with intercooler and quench have multiple benefits.
The main object of the present disclosure is to provide a process to produce DME from methanol with reactors and inter cooler for better temperature control and 10 heat recovery.
It is another object of the invention to provide a process to produce DME from methanol resulting reduced by-product formation in reactor.
15
It is another object of the invention to provide a process to produce DME from methanol resulting increased life of catalyst.
It is another object of the invention to provide a process to produce DME from methanol with preferable coolant as a part of recycle methanol. 20
SUMMARY OF THE INVENTION:
The present disclosure provides a method for production of DME by dehydration of methanol. The reaction is catalyzed by acidic catalyst in series solid catalytic gas phase reactors with intercoolers. In the present process, quench for reduction 25 of maximum reactor temperature, optimized reactor temperature control which results increased catalyst life was achieved. The present process results in increased DME yield, reduced by-product formation and improved energy utilization.
30
6
The method involves preheating, vaporization and superheating of the feed methanol. The superheated methanol is fed to the first reactor and effluent from first reactor is intercooled by exchanging heat with a part of liquid feed methanol. In the process of cooling the first reactor effluent, liquid methanol gets vaporized and superheated. Both the out streams from the reactor intercooler i.e. cooled first 5 reactor effluent and superheated methanol used for the cooling are mixed and fed to the second reactor which results in distribution of reaction load between two reactors and enhances reaction in second reactor. Methanol in the second reactor feed is converted to DME in the second reactor. Cooled DME and water from the first reactor acts as a coolant in second reactor and keeps the reactor temperature 10 profile low. Reduced temperature profile in second reactor, reduces formation of by products and increases catalyst life.
DETAILED DESCRIPTION OF INVENTION
While the disclosure is susceptible to various modifications and alternative forms, 15 specific aspects thereof have been shown by way of examples and will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the invention. The applicant would like to mention that 20 the examples and comparative studies are mentioned to show only those specific details that are pertinent to understanding the aspects of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
25
One aspect of the present disclosure relates to a process for producing DME by dehydration of methanol, comprises:
(i) Preheating a reactor feed (S2) containing a mixture of fresh feed and condensate from a methanol column (B16) in a preheater (B3) to obtain a preheated stream (S4); 30
7
(ii) vaporizing the preheated stream (S4) in a vaporizer (B4) to obtain a vaporized stream (S5);
(iii) superheating the vaporized stream (S5) in a super heater (B6) to obtain a superheated methanol (S6);
(iv) dehydrating the superheated methanol (S6) in a first reactor (B7) 5 to obtain an effluent (S7), which is cooled in an intercooler (B8) to produce a cooled first reactor effluent stream (S8);
characterized in that, the intercooler (B8) cools the effluent (S7) by exchanging heat with a part of liquid feed methanol stream (S10) which is vaporized and superheated in the process to obtain 10 a stream (S11);
(v) the stream (S11) is mixed with the cooled first reactor effluent stream (S8) to form a mixed stream (S9) which is fed to a second reactor (B9) for further dehydration to produce an effluent stream (S12); 15
(vi) separating the effluent stream (S12) after heat recovery in a DME recovery column (B11) to obtain the product DME from top, and unreacted methanol and water mixture from bottom which is recycled back to the methanol column (B16).
20
Another embodiment of the present disclosure wherein the vaporized stream (S5) is superheated in the feed super heater (B6) by exchanging heat with the second reactor effluent stream (S12), feed in the preheater (B3) is heated by exchanging heat with the stream (S 13).
25
Yet another embodiment of the disclosure, wherein the effluent (S12) is routed to the superheater (B6) for heat recovery, a cold stream (S14) from the preheater (B3) is again cooled in a water cooler (B10) and is fed to product DME recovery column (B11), feed (S6) is maintained in range of 250-280˚C by adjusting bypass of reactor effluent side (S29) of exchanger (B6). 30
8
Further embodiment of disclosure, wherein conversion of methanol in first reactor is limited to 30-40% to limit the reactor outlet temperature in the range of 300-350˚C and first reactor product contains 20-30% dimethyl ether, 60-70 % methanol and 5-15 % water.
5
Yet another embodiment, wherein intercooler (B8) cools the reactor effluent from first reactor to 250-300˚C and mixed stream temperature (S9) is kept in the range of 250-300˚C.
Further embodiment of the present disclosure wherein the two reactors are fixed 10 bed type with only one type of catalyst is used in two reactors.
In another embodiment of the present disclosure, flow rates of the streams is optimized and some part of the streams is by-passed out of the system to maintain heat integration of system. 15
One other embodiment of the present disclosure, wherein DME recovery column operates in the pressure range of 8-12 kg/cm2g, methanol recovery column operates in the range of 1-3 kg/cm2g, DME recovery column bottom temperature is in the range 155-160˚C to minimize DME fraction in methanol water mixed 20 stream (S23) and super heated stream (S11) is in temperature range of 250-300˚C.
One another embodiment of the present disclosure relates to a system for producing dimethyl ether (DME) by dehydration of methanol, comprises a 25 preheater (B3) to heat a mixture (S2) of fresh feed and condensate from a methanol column (B16), to obtain a preheated stream (S4); a vaporizer (B4) to vaporize the preheated stream (S4) to obtain a vaporized stream (S5); a super heater (B6) to superheat the vaporized stream (S5) to obtain a superheated methanol (S6); a first reactor (B7) for dehydrating the superheated methanol (S6) 30 and produce an effluent (S7); an intercooler (B8) to cool the effluent (S7) and
9
produce a cooled first reactor effluent stream (S8), wherein, the intercooler (B8) cools the effluent (S7) by exchanging heat with a part of liquid feed methanol stream (S10) to obtain a stream (S11); a second reactor (B9) for dehydrating mixture of the stream (S11) and the cooled first reactor effluent stream (S8), to produce an effluent stream (S12); second reactor effluent stream (S12) is cooled 5 in the super heater (B6) and is further cooled in the preheater (B3) by exchanging heat with reactor feed methanol to obtain stream (S14); cooled reactor effluent (S14) is further cooled in water cooler (B10); a DME recovery column (B11) is fed with the cooled effluent stream (S15) to separate the product DME (S20) and an unreacted mixture of methanol and water (S23). 10
Referring to figure 1 which illustrates the process of the present disclosure. Feed liquid Methanol from methanol plant is received in feed surge drum cum methanol column condenser drum (B1). Combined reactor feed (S2) methanol i.e. mixed of fresh feed and condensate from methanol rich condensate from 15 methanol column (B16) overhead condenser (B17) is pumped fed to reactor feed preheater (B3). Methanol column (B16) is provided with a reboiler (B18) to vaporize the liquid stream (S27) and return it back to the bottom stage. In reactor feed preheater (B3), feed is heated by exchanging heat with reactor effluent stream (S13). Heated methanol feed (S4) is fully vaporized in vaporizer (B4) 20 using reboiler (B5) operated by steam or electricity or any suitable heating media. The vaporized methanol from vaporizer is again superheated in feed super heater (B6) by exchanging heat from reactor effluent stream (S12) and fed to the first reactor (B7). First Reactor (B7) feed (S6) temperature is maintained in the range of 250°C-280°C by adjusting bypass of reactor effluent side (S29) of exchanger 25 (B6). As the stream S29 bypasses B6 with respect to S12, it is called ‘bypass’. In first reactor (B7), partial conversion of feed methanol is done.
Design of first reactor is done in such a way, that it ensures conversion of methanol in first reactor is limited to 30-40% so as to limit the reactor outlet 30 temperature in the range of 300-350°C. Reactor effluent from first reactor is
10
cooled in reactor intercooler (B8) to 250-300°C by exchanging heat to a part of liquid feed methanol stream (S10). In the process of cooling first reactor effluent (S7), liquid methanol stream is vaporized and super-heated (S11) to a temperature ranging 250-300°C in reactor intercooler (B8). Heated, vaporized methanol stream (S11) is mixed with cooled first reactor effluent stream (S8). 5 The mixed stream (S9) temperature is adjusted by adjusting the split ratio between feed to the first reactor (S6) and the part of liquid methanol used as coolant (S10) in reactor inter cooler (B8). The mixed stream (S9) temperature is kept in the range of 250-300˚C. Unconverted methanol from first reactor along with the methanol used for cooling first reactor effluent is further converted to 10 DME. Conversion of methanol to DME is limited by equilibrium conversion of the reaction and which is in the range of 75-85% of total feed methanol. Reactor effluent (S12) from second reactor (B9) is routed to feed super heater (B6) for heat recovery. Cold stream (S13) from feed super heater is further cooled in feed preheated (B3). Cold stream from feed preheater is again cooled in a water cooler 15 (B10) to an optimum temperature in the range 90˚C-140˚C to minimize methanol column reboiler and condenser duty and is fed to product DME recovery column (B11).
DME recovery column operates in the pressure range of 8-12 kg/cm2g at which 20 liquid DME can be obtained as liquid distillate from column. Unconverted methanol along with the coproduced water is obtained at bottom (S23) of the DME recovery column. DME recovery column bottom temperature is maintained in the range of 155-160˚C to minimize DME fraction in methanol water mixed stream (S23). Overhead vapour fraction (S16) from the DME recovery column 25 (B11) is condensed by overhead condenser (B12) and accumulator (B13) to get the product stream (S20). A reboiler (B15) in which liquid stream (S22) from DME recovery column (B11) is vaporized and returned to the bottom stage. A suitable quantity of reflux (S21) is provided in the DME column to maintain purity of DME in distillate (S20). Water along with unreacted methanol from 30 DME column bottom is fed to methanol recovery column (B16) for recovery of
11
methanol (S25) and is mixed with fresh methanol feed (S1) and is fed to the reactor (B7). Methanol recovery column is operated in the range of 1-3 kg/cm2g. Water produced in the reaction is separated as bottom (S28) of the methanol recovery column (B16).
5
The typical composition of feed methanol is given in Table -1.
Component
wt%
CH3OH
99.9
H2O
0.085
Acetone
0.015
Table 1: Typical composition methanol from methanol unit
Feed liquid methanol from methanol plant is received in feed surge drum cum 10 methanol column condenser drum, which is further preheated, vaporized and superheated. Feed methanol evaporator is used with suitable holdup of liquid to ensure no liquid carryover to the downstream exchanger and reactor system. Liquid methanol after vaporization and super-heating in intercooler is mixed with first reactor effluent and fed to the second reactor which enhances reaction in 15 second reactor. The first reactant effluent comprises 20-30% dimethyl ether, 60-70% methanol and 5-15% water. The quantity of liquid methanol used as cooling media in the intercooler is optimized to reduce the first reactor effluent temperature to limit the maximum temperature in second reactor with maintaining the kick off temperature for the second reactor. The quantity of 20 liquid methanol used as a cooling media in reactor intercooler is optimized for optimal heat integration of system. Kick off temperature is the minimum temperature required at reactor inlet to start the reaction in a feasible manner.
The reactor length and diameter is optimized to limit the maximum reactor 25 temperature resulting in easy reactor design. Reactor diameter is adjusted to get the required gas velocity which meets the design reactor pressure drop. The
12
reactor is at 12-18kg/cm2g resulting in reduced utility requirement to condense DME product and reduced reactor size. First reactor length is set to get enough catalyst volume which gives 30-40% methanol conversion and reactor outlet temperature of 300-350˚C. Second reactor length is set to get an equilibrium conversion of 75-85% and corresponding temperature of 300-350˚C. Keeping the 5 reactor outlet temperature below 350˚C gives an inherently safe system design, as auto ignition temperature of DME is 350˚C. This optimized cooling and mixing give benefit of reduced by-product formation and enhanced catalyst life.
While preferred aspects and an example configuration have been shown and 10 described, it is to be understood that various further modifications and additional configurations will be apparent to those skilled in the art. It is intended that the specific embodiments and configurations herein disclosed are illustrative of the preferred nature of the invention and should not be interpreted as limitations on the scope of the invention. 15
Example:
In a fixed bed catalytic adiabatic reactor, heated methanol is introduced in to the reactor at 260 °C. Reactor outlet temperature increases to 385 °C with a reactor temperature increase of 125 °C. Typical temperature profile of that reactor is 20 presented in Figure 2 where the reactor temperature is presented in form of T-Ti. Where T is temperature at any longitudinal position of the reactor and Ti is reactor inlet temperature.
In the current invention also, the feed temperature of the first reactor is kept at 25 260 °C for comparison purpose. First reactor system is designed to limit the first reactor outlet temperature to 317 °C with a temperature rise of 57 °C. First reactor outlet is cooled in the reactor intercooler to 260 °C. In the process of cooling first reactor effluent in reactor intercooler, a part of liquid methanol feed is vaporized and superheated to 260 °C. Both the stream from reactor intercooler 30 at 260 °C is mixed and send to second reactor. At second reactor temperature
13
increases due to conversion of feed methanol to DME. At second reactor outlet at temperature of 338 °C the equilibrium conversion is achieved. In second reactor temperature increase in reactor is 78 °C. Temperature profile of the two reactor and intercooler is presented in Figure 3 where the temperature is presented in form of T-Ti. Where T is temperature at any longitudinal position of the reactor-5 exchanger and Ti is reactor inlet temperature.
Comparing the two cases, with the fixed bed catalytic adiabatic reactor, a temperature rise of 125 °C with reactor maximum temperature of 385 °C was observed whereas in the present invention, a temperature rise of 57 °C and 78 °C 10 respectively for the reactors with the maximum temperature in the system is 338 °C, which is below the auto ignition temperature of DME (350 °C). Reduction of the temperature rise in reactor and significant reduction of maximum temperature in reactor has benefits in terms of reduction of byproduct formation which further reduces energy consumption in terms of purifying products. Keeping the 15 maximum reactor temperature below 350 °C (auto ignition temperature of DME) in current invention results in inherently safe system design. Reduction of temperature increase in reactors and maximum temperature, increases catalyst life. Key temperatures for both the cases is presented in following table.
20 Parameters Fixed Bed Catalytic adiabatic reactor (Figure 2) Present invention with two reactor and intercooler (Figure 3)
Reactor Inlet Temperature, °C
260
260
Maximum temperature in reactor, °C
385
317 °C and 338 °C
Temperature Rise in Reactor, °C
125
57 °C and 78 °C
Table 2: Comparison between temperature profile between fixed bed catalytic reactor and present invention
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BRIEF DESCRIPTION OF FIGURES
The above and other aspects and advantages of the present invention will become apparent from the following detailed description embodiments, taken in conjunction with drawings, wherein
5
Figure 1 is Schematic representation of Methanol to DME process.
Figure 2 is Temperature profile with single fixed bed catalytic reactor.
Figure 3 is Temperature profile with multiple fixed bed reactors with intercooler.
Advantages: 10
The process and apparatus disclosed in the present disclosure provide the following advantages:
• Better reactor temperature profile monitoring and control.
• Unique way to preheat feed methanol by using multistage exchanger.
• Fixed bed type catalytic reactor resulting in ease of catalyst loading and 15 unloading.
• Fresh feed methanol is introduced in the methanol condenser drum, resulting in no additional requirement of feed surge drum.
• Reduced temperature across the reactors, reduces the formation of byproducts and hence reduction of utility consumption for product 20 purification
• Reduced temperature across the reactors, increases catalyst life and reduces down time.
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15
List of references for the Equipment:
B16
Methanol Column
B17
Overhead Condenser
B18
Reboiler
B1
Methanol column condenser drum
B2
Pump
B3
Pre heater
B4
Vaporizer
B5
Reboiler for vaporizer
B6
Super heater
B7
First reactor
B8
Intercooler
B9
Second Reactor
B10
Water Cooler
B11
DME recovery Column
B12
Overhead Condenser to B11
B13
Accumulator
B14
Pump
B15
Reboiler for DME recovery Column
List of references for the streams:
S1
Fresh feed methanol
S2
Combined reactor feed
S3
Pumped Combined reactor feed to pre heater
S4
Pre heated stream
S5
Vaporized stream
S6
Superheated stream
S7
Effluent from first reactor
S8
Cooled first reactor effluent
S9
Mixed stream
16
S10
Part of liquid feed methanol
S11
Vaporized and superheated methanol from intercooler
S12
Effluent from second reactor
S13
Cooled effluent S12 from B6
S14
Cooled S13 from B3
S15
Feed to DME recovery column
S16
Overhead vapour fraction
S17
Condensed stream from B12
S18
Condensed Overhead stream
S19
Condensed and pumped overhead stream
S20
Product DME
S21
Reflux to DME recovery column
S22
Bottom stream from DME column
S23
Unreacted mixture of methanol and water
S24
Overhead methanol fraction from methanol column
S25
Condensed overhead methanol fraction
S26
Reflux to methanol column
S27
Bottom stream from methanol column
S28
Water separated
S29
Bypass stream

WE CLAIM:

1. A process for producing dimethyl ether (DME) by dehydration of methanol, comprises:
(i) Preheating a reactor feed (S2) containing a mixture of fresh feed (S1) and condensate from a methanol column (B16) in a preheater 5 (B3) to obtain a preheated stream (S4);
(ii) vaporizing the preheated stream (S4) in a vaporizer (B4) to obtain a vaporized stream (S5);
(iii) superheating the vaporized stream (S5) in a super heater (B6) to obtain a superheated methanol (S6); 10
(iv) dehydrating the superheated methanol (S6) in a first reactor (B7) to obtain an effluent (S7), which is cooled in an intercooler (B8) to produce a cooled first reactor effluent stream (S8);
characterized in that, the intercooler (B8) cools the effluent (S7) by exchanging heat with a part of liquid feed methanol stream 15 (S10) which is vaporized and superheated in the process to obtain a stream (S11);
(v) the stream (S11) is mixed with the cooled first reactor effluent stream (S8) to form a mixed stream (S9) which is fed to a second reactor (B9) for further dehydration to produce an effluent stream 20 (S12);
(vi) separating the effluent stream (S12) after heat recovery in a DME recovery column (B11) to obtain the product DME (S20) from top, and unreacted methanol and water mixture (S23) from bottom which is recycled back to the methanol column (B16). 25
2. The process as claimed in claim 1, wherein the vaporized stream (S5) is superheated in the feed super heater (B6) by exchanging heat with the second reactor effluent stream (S12).
30
18
3. The process as claimed in claim 1, wherein feed in the preheater (B3) is heated by exchanging heat with the stream (S 13).
4. The process as claimed in claim 1, wherein the effluent (S12) is routed to the superheater (B6) for heat recovery, a cold stream (S 14) from the 5 preheater (B3) is again cooled in a water cooler (B10) and is fed to product DME recovery column (B11).
5. The process as claimed in claim 1, wherein feed (S6) is maintained in range of 250-280˚C by adjusting bypass of reactor effluent side (S29) of 10 exchanger (B6).
6. The process as claimed in claim 1, wherein conversion of methanol in first reactor is limited to 30-40% to limit the reactor outlet temperature in the range of 300-350˚C. 15
7. The process as claimed in claim 1, wherein first reactor product contains 20-30% dimethyl ether, 60-70 % methanol and 5-15 % water.
8. The process as claimed in claim 1, wherein intercooler (B8) cools the 20 reactor effluent from first reactor to 250-300˚C.
9. The process as claimed in claim 1, wherein mixed stream temperature (S9) is kept in the range of 250-300˚C.
25
10. The process as claimed in claim 1, wherein the two reactors are fixed bed type with only one type of catalyst is used in two reactors.
11. The process as claimed in claim 1, wherein DME recovery column operates in the pressure range of 8-12 kg/cm2g. 30
12. The process as claimed in claim 1, wherein methanol recovery column operates in the range of 1-3 kg/cm2g.
19
13. The process as claimed in claim 1, wherein DME recovery column bottom temperature is in the range 155-160˚C to minimize DME fraction in methanol water mixed stream (S23).
14. The process as claimed in claim 1, wherein super-heated stream (S11) is 5 in temperature range of 250-300˚C.
15. A system for producing dimethyl ether (DME) by dehydration of methanol, comprises:
a preheater (B3) to heat a mixture (S2) of fresh feed (S1) and condensate 10 from a methanol column (B16), to obtain a preheated stream (S4);
a vaporizer (B4) to vaporize the preheated stream(S4) to obtain a vaporized stream (S5);
a super heater (B6) to superheat the vaporized stream (S5) to obtain a superheated methanol (S6); 15
a first reactor (B7) for dehydrating the superheated methanol (S6) and produce an effluent (S7);
an intercooler (B8) to cool the effluent (S7) and produce a cooled first reactor effluent stream (S8), characterized in that, the intercooler (B8) cools the effluent (S7) by exchanging heat with a part of liquid feed methanol 20 stream (S10) to obtain a stream (S11);
a second reactor (B9) for dehydrating mixture of the stream (S11) and the cooled first reactor effluent stream (S8), to produce an effluent stream (S12);
a DME recovery column (B11) to separate the product DME (S20) and an unreacted mixture of methanol and water (S23) from the effluent stream 25 (S12).