from syngas to methanol and dymethylether

8/12/2019 From Syngas to Methanol and Dymethylether

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From syngas to methanol

and dimethylether

Ferruccio Trif iro`

Summer School September 2009Bologna


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Content of the lecture

1) Synthesis of methanol from syngas

2) Synthesis of dimethylether (DME) frommethanol

3) Synthesis of DME directly from syngas


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Global production of

methanol The global production of methanol is about 40 million ton

per year, most of which is produced from natural gas.Today, the high price of oil and natural gas has spurrednew interest in alternative feedstocks for the productionof methanol.

Various types of biomass have been considered, but on

the shorter term coal appears to be the only viablealternative raw material for large scale methanolproduction.

In fact, methanol has been produced from

coal for many years in specific geographical areas,notably in China.


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From methanol to fuels 1) Methanol to DME (alternative to Diesel)

2) Methanol for fuel cell

3) Methanol for production of MTBE

4) Methanol as fuel (altenatives togasoline)

5) Methanol for production of hydrogen

6) Synthesis of gasoline (MTG process)


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From methanol to chemicals

MethanolAcetic Acid

Methyl methacrylateMethyl amines

Methyl formiate

Di-methylterephthalateFormaldehyde

chloromethanes


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From methanol to to

olefins The different technologies for the future

SYNGAS

CH3OH

DME

OLEFINS

PROPYLENE

MTP

MTO

SDTO

From

MethaneCoal

Municipal wastes

Recycled plastics

Biomass Organic


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Synthesis of methanol CO+2H2 CH3OH H298k=-90.6kJmol

-1

Methanol synthesis is the second largest

process after ammonia which use catalysts at

high pressure The mechanism is believed to be

CO+H2O-> CO2+H2 H298k=-41.2kJmol-1

CO2+2H2->CH3OH+H2O H298k= -49kJmol-1


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Operative conditions for

methanol synthesis Catalyst : CuO(60-70%)- ZnO(20-30%) Al2O3 (5-

15%)or Cr2O3 (5-15%) Temp 220oC-300oC

Pressure 50-100Atm (5-10MPa)

Composition of the feed 59 -74%H2 27- 15% CO8% C02 3%CH4 Conversion of CO to methanol per pass is normally

16 40 %.

H2 : CO ratio of 2.17.

The selectivity is around 99.8 %


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Ways to improve the yield in

methanol1) The reaction is exothermic and favored at

low temperature, for this reason isnecessary to remove the heat to keep thereaction temperature as low as possible inorder to increase the conversion

2) To remove methanol during the synthesis inorder to shift the equilibrium to higher CO tomethanol conversion per pass (through theDME formation)

3) To develop more active catalysts whichoperate at lower temperature, increasing thethermodynamically allowed conversion


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Equilibrium CO conversion to

methanol (H2/CO=2)

400 450 500 550 600

1

0,5

11

50bar 100 bar

adiabatic

I

s

ot

h

e

r

ma

l

Conversion

Temperature

CO

K

CO +2H2->CH3OH


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The factors affecting on the production

The factors affecting on the production rate in an industrial

methanol reactor are:

1)the thermodynamic equilibrium limitations

2) The catalyst deactivation.Two zones could be distinguished in the methanol

synthesis reactor with imprecise transition point.

A)The first zone starts from reactor entrance and

continues to a point that conversion approaches toequilibrium. In this zone the kinetics controls the

process, so increasing temperature improves the rate of

reaction which leads to more methanol production.

B) In the second zone the process switches to equilibriumand as the temperature increases the deterioratingeffects of equilibrium conversion emerge and decreasesmethanol production


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Factors which influence activity

Methanol synthesis gas is characterised by the

stoichiometric ratio (H2 CO2) / (CO + CO2), oftenreferred to as the module M. A module of 2 defines a

stoichiometric synthesis gas for formation of methanol.

A high CO to CO2 ratio will increase the reaction rate

and the achievable per pass conversion. In addition, theformation of water will decrease, reducing the catalyst

deactivation rate.

High concentration of inerts will lower the partialpressure of the active reactants. Inerts in the methanol

synthesis are typically methane, argon and nitrogen.


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Methanol Megaplant The capacity of methanol plants is increasing to

reduce investments, taking advantage of theeconomy of scale.

The capacity of a world scale plant hasincreased from 2500 MTPD a decade ago toabout 5000 MTPD today.

Even larger plants up to 10,000 MTPD or aboveare considered to further improve economics

and to provide the feedstock for the Methanol-to-Olefin (MTO) process.


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The main sections of methanol

plant

1) In the first section of the plant natural gas

is converted into synthesis gas.

2) In the second section, the synthesis gas

reacts to produce methanol 3) In the tail-end of the plant methanol is

purified to the desired purityl with eventually

the hydrogen recycle 4) utilities


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The role of the syngas

production In the design of a methanol plant the three

sections may be considered independently, andthe technology may be selected and optimisedseparately for each section.

The synthesis gas preparation and compression

typically accounts for about 60% of theinvestment, and almost all energy is consumedin this process section. Therefore, the selectionof reforming technology is of paramount

importance, regardless of the site.


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The production of syngas The preferred technologies are:

1) tubular steam reforming

2) two-step reforming (tubular steam reforming

followed by autothermal or oxygen blown

secondary reforming)

3)Autothermal Reforming (ATR) at low steam to

carbon (S/C) ratio is the preferred technology for

large scale plants by maximising the single linecapacity and minimising the investment.


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Methanol Synthesis and

Purification

Raw methanol is a mixture of methanol, a smallamount of water, dissolved gases, and traces of by-

products.

Typical byproducts include DME, higher alcohols,other oxygenates and minor amounts of acids and

aldehydes

The methanol synthesis catalyst and process arehighly selective. A selectivity of 99.8% is not

uncommon.


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The design of the reactor The methanol synthesis is exothermic and

the maximum conversion is obtained atlow temperature and high pressure.

A challenge in the design of a methanol

synthesis is to remove the heat of reaction

efficiently and economically


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Multiple

Adiabatic Tube cooled

BWR

Quench reactor


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Quench reactor A quench reactor consists of a number of

adiabatic catalyst beds installed in series in onepressure shell. In practice, up to five catalyst

beds have been used. The reactor feed is split

into several fractions and distributed to thesynthesis reactor between the individual catalyst

beds.

The quench reactor design is today consideredobsolete and not suitable for large capacity

plants


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Quench reactor

Conversion CO to methanol

Temperature

Conversion

CO


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Adiabatic reactors .

A synthesis loop with adiabatic reactors

normally comprises a number (2-4) of fixed bedreactors placed in series with cooling betweenthe reactors. The cooling may realized be bypreheat of high pressure boiler feed water,generation of medium pressure steam, and/or bypreheat of feed to the first reactor.

The adiabatic reactor system features good

economy of scale. Mechanical simplicitycontributes to low investment cost. The designcan be scaled up to single-line capacities of

10,000 MTPD or more.


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Multiple layers adiabatic

converters

conversion

CO Equilibrium curve

Maximum reaction rate curve

Temperature

C

O

N

V

ER

S

I

O

N


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BWR REACTOR The BWR(boilng water reactor) is in principle a shell

and tube heat exchanger with catalyst on the tube side.

Cooling of the reactor is provided by circulating boilingwater on the shell side. By controlling the pressure of thecirculating boiling water the reaction temperature iscontrolled and optimised. The steam produced may beused as process steam, either direct or via a falling filmsaturator.

The isothermal nature of the BWR gives a highconversion compared to the amount of catalyst installed.However, to ensure a proper reaction rate the reactor will

operate at intermediate temperatures - say between240C and 260C - and consequently the recycle ratiomay still be significant.


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Equilibrium CO conversion to

methanol (H2/CO=2)

400 450 500 550 600

1

0,5

11

50bar 100 bar

adiabatic

I

s

ot

h

e

r

ma

l

Conversion

Temperature

CO

K

CO +2H2->CH3OH


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Several industrial processesICI adiabatic single bed reactor: the heat ofreaction is removed by adding cold reagent atdifferent heights in the bed

Lurgi two multitubular reactor: the heat ofreaction is removed in the first reactor by boilingwater around bed in the second reactor by gas

Haldor Topsoe several adiabatic reactors:arranged in series intermediate cooler removeheat of reaction

Air product-Chem system three phase fluidized

bed: reactor an inert hydrocarbon liquid insidethe reactor remove the heat

Casale isothermal reactor: the heat is removedby plates immersed in the catalysts


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Lurgi Mega Methanol plant

Lurgis Mega Methanol process is anadvanced technology for converting

natural gas to methanol at low cost in

large quantities.

It permits the construction of highly

efficient single-train plants of at leastdouble the capacity of those built to date.


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The MegaMethanol Concept

The Lurgi MegaMethanol technology has beendeveloped for world-scale methanol plants with

capacities greater than one million metric tons peryear. The main process features to achieve thesetargets are:

1) Oxygen-blown natural gas reforming, either incombination with steam reforming, or as pureautothermal reforming.

2)Two-step methanol synthesis in water- and gas-

cooled reactors operating along the optimum reactionroute.

3) Adjustment of syngas composition by hydrogen

recycle.


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Lurgi reactor


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Lurgi reactorMain features

The Lurgi reactor is nearly isothermal and

the heat of reaction is used to generate high

pressure steam which is used to drive thecompressor and as distillation steam

Advantages

Optimum temperature profileVery high gas synthesis conversion

Large reduction of catalyst volume

Lower gas recycleHigh energy efficiency


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Lurgi reactor- conversion

versus temperature


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The synthesis gas productionThe synthesis gas production section accounts for 60 %of the

capital cost of a methanol plant. Thus, optimisation of thissection yields a significant cost benefit.

Conventional steam reforming is economically applied in smalland medium-sized methanol plants, with the maximumsingle-train capacity being limited to about 3000 mtpd.

Oxygen-blown natural gas reforming, either in combinationwith steam reforming or as pure autothermal reforming, istoday considered to be the best suited technology for largesyngas plants.

The configuration of the reforming process mainly depends on

the feedstock composition which may vary from lightnatural gas (nearly 100% methane content) to oil-associated gases.


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Lurgi autothermal conversion

desulphurization

.

Steam reforming

Methanol synthesis

Autothermal reforming

Methanol distillate

Air separation

PURE METHANOL

oxygen

Light Natural gas Air

Process steam


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Autothermal Reforming

Pure autothermal reforming can be applied for syngas

production whenever light natural gas is available asfeedstock to the process.

The desulfurised and optionally pre-reformed feedstock is

reformed with steam to synthesis gas at about 40 barand higher using oxygen as reforming agent. The

process generates a carbon-free synthesis gas and

offers great operating flexibility over a wide range tomeet specific requirements.

Reformer outlet temperatures are typically in the range o

9501050 C.


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Lurgi combined reforming

desulphurization

.

Pre reforming

Methanol synthesis

Autothermal reforming

Methanol distillate

Hydrogen recovery

Air separation

PURE METHANOL

FUEL GAS

oxygen

Heavy natural gas or oil Air


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Lurgi Combined Reforming

For heavy natural gases and oil-associated gases, the

required stoichiometric number cannot be obtained by pureautothermal reforming, even if all hydrogen available isrecycled. For these applications, the Lurgi MegaMethanolconcept combines autothermal and steam reforming as the

most economic way to generate synthesis gas for methanolplants. After desulfurisation, a feed gas branch stream is

decomposed in a steam reformer at high pressure(3540 bar)and relatively low temperature (700800C).The reformedgas is then mixed with the remainder of the feed gas and

reformed to syngas at high pressure in the autothermalreactor. This concept has become known as the LurgiCombined Reforming Process.


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The dual Lurgi reactorsBased on the Lurgi Methanol Reactor and the highly activemethanol catalyst with its capability to operate at high

space velocities, Lurgi has recently developed a dual reactor

system featuring higher efficiency.The isothermal reactor is combined in series with a gas-cooled

reactor

The first reactor, the isothermal reactor, accomplishes partial

conversion of the syngas to methanol at higher spacevelocities and higher temperatures compared with singlestage synthesis reactors. This results in a significant sizereduction of the water-cooled reactor compared toconventional processes, while the steam raised is available at

a higher pressure..


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Lurgi Mega Reactors


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Lurgi reactor- conversion

versus temperature


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Water cooled reactor


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Gas cooled reactor

Fi t t f M th l


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First reactor for Methanol

Synthesis

The Lurgi Methanol Reactor is basically a verticalshell and tube heat exchanger with fixed tubesheets. The catalyst is accommodated in tubes andrests on a bed of inert material.The water/steam

mixture generated by the heat ofreaction is drawnoff below the upper tube sheet. Steam pressurecontrol permits exact control of the reaction

temperature.This isothermal reactor achieves veryhigh yields at low recycle ratios and minimizes theproduction of by-products.

S d t f th l


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Second reactor for methanol

synthesisThe methanol-containing gas leaving the first reactor is

routed to a second downstream reactor without prior

cooling. In this reactor, cold feedgas for the first reactoris routed through tubes in a countercurrent flow with thereacting gas.

Thus, the reaction temperature is continuously reduced

over the reaction path in the second reactor, and theequilibrium driving force for methanol synthesismaintained over the entire catalyst bed.

As fresh synthesis gas is only fed to the first reactor, no

catalyst poisons reach the second reactor. The poison-free operation and the low operating temperature resultin a virtually unlimited catalyst service life for the gas-cooled reactor.


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Advantages of the Combined Synthesis

Converters High syngas conversion efficiency. At the same

conversion efficiency, the recycle ratio is about half of

the ratio in a single-stage, water-cooled reactor. High energy efficiency. About 0.8 t of 5060 bar steam

per ton of methanol can be generated in the reactor.

In addition, a substantial part of the sensible heat can be

recovered at the gas-cooled reactor outlet. Low investment cost. The reduction in the catalyst volume

for the water-cooled reactor, the omission of the large

feedgas preheater and savings resulting from other

equipment due to the lower recycle ratio translate intospecific cost savings of about 40% for the synthesis loop.

High single-train capacity. Single-train plants with capacities

of 5000 mt/day and above can be built.


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Methanol DistillationThe crude methanol is purified in an energy-saving

3-column distillation unit with the 3-column

arrangement,the higher boiling componentsare separated in two

pure methanol columns.

The first pure methanol column operates atelevated pressure and thesecond column atatmospheric pressure. The overhead vapours ofthe pressurised column heat the sump of

theatmospheric column. Thus, about 40% of theheatingsteam and, in turn, about 40% of thecooling capacity aresaved. The split of therefining column into two columns

allows for very high single-train capacities.


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Lurgi Plant


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ICI Reactor

cold


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Quench reactor Conversion CO to methanol

Temperature

Conversion

CO

ICI process


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ICI process


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ICI

TOPSOE


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TOPSOE

REACTORS

methanol


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Conversion versus temperature


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Topsoe Methanol Process

Based on the unique methanol catalyst, MK-121, HaldorTopse has developed a methanol synthesis process.the heart of the synthesis unit is the methanol reactor, a

tubular reactor with catalyst loaded into several tubessurrounded by a bath of boiling water. The boiling waterefficiently cools the process while at the same timesteam is produced that can be used outside themethanol synthesis unit. The design of the reactor

ensures that the methanol synthesis is carried out at analmost isothermal reaction path at conditions close to themaximum rate of reaction. This ensures a highconversion per pass and a low formation of by-products.

Topse's methanol synthesis


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Topse s methanol synthesis

catalyst MK-121. Based on an optimised copper dispersion

MK-121 ensures a better preservation of the initialhigh catalyst activity as well as an improvedstability compared to its predecessor, MK-101,while at the same time attaining a remarkableselectivity. resulting in low by-product formationover the entire service life. Since the higheractivity of MK-121 allows operation at lowertemperatures, where conditions for by-productformation is less favourable, the total

.


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Topsoe Catalyst MK121


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Topsoe catalyst MK 121


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Catalyst LoadingThe procedure used for catalyst loading is extremely

important, as the catalyst performance depends heavily on

even flow distribution. Therefore, the catalyst should beloaded as uniformly as possible to ensure that the catalystis utilised efficiently. Besides that, the catalyst should bepacked as densely as possible in order to maximise the

installed catalyst activity.Topse has developed new loading methods, which increase

loading density of the catalyst and improve the flowdistribution through the catalyst bed(s) in various types of

methanol converter designs.Furthermore, Topse is continuously studying existing

loading procedures in order to develop new innovativetechniques for installing catalyst.

Fluid bed reactor


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Fluid bed reactor

from Air products


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Air product Chem system Main features

Demonstration plant in Texas

The catalyst is suspended in inert hydrocarbon liquidwhich limits the temperature rise and it adsorbs the heatliberated

Advantages

a higher single pass conversion can be achievedreducing the syngas compression costs

increase of life of catalyst

Contains low amount o water 1% (the gas phase 4-20%

of water It is possible to work with 50% CO entering feedstocks


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Casale Reactor The use of axial-radial flow,e, can solve the

problem, of reducing the pressure drop of a

converter. This design can be obtained easilywith the use of plates as cooling surface area,The flow of cooling gas inside the plates canhave the same direction of the gas in the

catalyst, that is in a horizontal direction, co-current or counter-current (see figure)

It is clear that an axial radial design leads to amuch slimmer vessel for the same catalystvolume, allowing to reach capacities above7000 MTD in a single vessel converter.


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Axial radial plate cooled reactor


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Axial radial catalyst bed


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Methanol Casale reactorsAt present more than 10 million tons per year of methanol

are produced worldwide with Methanol Casale

technologies Methanol Casales synthesis convertertechnology allows substantial and cost-effective capacityincreases in conventional methanol plants

Methanol Casale is currently licensing, providing basic

design and supplying critical equipment for a 7,000 t/dmethanol plant

A 7,000 t/d plant can be built based on a single methanolconverter. They are the only contractors able to build

real single train, efficient plants with this capacity

Casale and the revamping of


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p g

methanol plant .

, Methanol Casale has also become a leader in

revamping complete methanol plants and indesigning and constructing new ones. Keyachievements in plant upgrading includecapacity increase, reduced specific consumption

of synthesis gas, and improvement in the qualityof the raw methanol.

They revamped 21 ICI plants


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Linde reactor The Linde isothermal reactor is a fixed bed reactor with

indirect heat exchange suitable for endothermic and

exothermic catalytic reactions. This reactor provides thebenefits of a tube reactor while simultaneously avoidingthe heat tension problems of a straight tube reactor.Gas/gas, gas/liquid and liquid/liquid reactions can becarried out. The palpable head of gases and liquids as

well as the latent evaporation heat can be used forcooling or heating operations.

The heating or cooling tube bundle embedded in thecatalyst transfers the reaction heat in such a way that the

catalyst can work at an optimum temperature. Thisresults in higher outputs, a longer catalyst lifetime, fewerby-products as well as efficient recovery of the reactionheat and lower reaction costs.


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Linde reactor Linde isothermal reactor, cross-section with

catalyst and tube bundle

The development of the Linde reactor wascarried out with a particular view towardexothermic reaction and steam generation.

The reactor is based on the design of thespecially wound heat exchangers, with whichLinde has been able to collect decades ofexperience in its own production facilities. The

Linde isothermal reactor is in operation world-wide in more than 19 plants, among them eightmethanol plants.


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Linde Reactor Isothermal reactor


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Section Linde reactor


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Linde reactor . The main principle is that the cooling coil in the

catalyst bed removes the heat of reaction

allowing the catalyst to operate at it's optimum

temperature. This results in higher performance,

longer catalyst life, reduction of by-products, as

well as in high efficiency reaction heat recovery

and lower cost of the reactor.

TOYO REACTOR


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Toyo


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Toyo reactor Applicable to 5,000 - 6,000 t/d class large

scale methanol plant with a single traindesign

Low Pressure Drop through Catalyst Bed

and Low Utility Consumption

Mild Operating Conditions for Long

Catalyst Life Maintenability for catalyst exchange

TOYO REACTOR


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Toyo


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DME in two steps


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DME in one step


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From methanol to DME DME synthesis based on methanol dehydration

process is very simple.

2 CH3OH -> 2DME + H2O

The dehydration of methanol is a gas phase andexothermic reaction , the heat of reaction

(approx.23 kj/mol) is considerably smallcompared with methanol synthesis reaction.

The selectivity of DME in methanol

dehydration is very high and is approx. 99.9 %. Dehydration catalyst is of gamma alumina

basis


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Operative conditions for DME Feed methanol is fed to a DME reactor

after vaporization. The synthesis pressure is 1.0 - 2.0 MPa.

The inlet temperature is 220 - 250 C and

the outlet is 300 - 350 C.

Methanol one pass conversion to DME is

70 85 % in the reactor.


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DME Plant 1) Produced DME with by-product water and

unconverted methanol is fed to a DME column

after heat recovery and cooling. 2) In the DME column DME is separated from

the top as a product. Water and methanol aredischarged from the bottom and fed to a

methanol column for methanol recovery.3) The purified methanol from the column is

recycled to the DME reactor after mixing withfeedstock methanol. The methanol consumptionfor DME production is approximately 1.4 ton-methanol per ton-DME.

DME PLANT


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DME

REACTOR

C

H3

OH

D

M

E

DME

TANK

RAW METHANOL

FUEL GAS

WATER

D

ME

C

o

lu

m

n

DME COLUMN

METHANOL

COLUMN

DME from syngas


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y g

. The synthesis of DME from synthesis gas involves threereactions:

1) CO2+3 H2->CH3OH+H2O 2)CO+H2O-> CO2+H2 3) 2 CH3OH ->2CH3OCH3 +H2O

The introduction of Reaction (3), the DME synthesis, serves

to relieve the equilibrium constraints inherent to themethanol synthesis by transforming the methanol into DME.Moreover, the water formed in Reaction (3) is to someextent driving Reaction (2) to produce more hydrogen, which

in turn will drive Reaction (1) to produce more methanol.Thus, the combination of these reactions results in a strongsynergetic effect, which dramatically increases the synthesisgas conversion potential.

From syngas to DME


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The catalyst applied is a proprietary dual-functioncatalyst, catalyzing both steps (i.e., methanol andDME synthesis) in the sequential reaction.Significant advantages arise by permitting the

methanol synthesis, the watergas shift, and theDME synthesis reaction to take placesimultaneously. This methanol synthesis isrestricted by equilibrium, which requires high

pressure in order to reach an acceptableconversion

A dual catalyst system is based on a combination[of Cu/ZnO/Al2O3 catalyst and gamma-alumina

(this issue) catalyst.:

Dalian Institute of Chemical


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Physics In the mid-1990s, DICP was awarded two

patents in the United States concernedwith the conversion of methanol/dimethyl

ether (DME) to light olefins. These

patents are the basis for the syngas viadimethyl ether to olefin process (SDTO).

Catalyst foDME from syngas


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y y g

Bifunctional metal (Cu, Zn, etc.)-zeolite

catalysts have been developed, which can

convert syngas very selectively to DMEwith high carbon monoxide (CO)

conversion (this reaction is far more

favorable thermodynamically than

methanol synthesis from syngas).

. ).

Advantages of SDTO


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g

Syngas to DME breaks the thermodynamic limit

of syngas to methanol system with up to over 90

percent CO conversion, 5-8 percent investment

savings and 5 percent operational cost savings.

Syngas to DME breaks the thermodynamic limit

of syngas to methanol system with up to over 90

percent CO conversion, 5-8 percent investment

savings and 5 percent operational cost savings.

Storage and Handling of methanol


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.

Methanol is stable under normal storage conditions. butcan react violently with strong oxidizing agents.

The greatest hazard involved in handling methanol isthe danger of fire or explosion.. Methanol is aggressivetoward copper, zinc, magnesium, tin, lead, andaluminum, which should therefore be avoided. Similarly,the use of plastics for storage is not recommendedBothfloating- and fixed-roof tanks are used for large-scalemethanol storage.

Blanketing the tank vapor space in combination with aclosed vent recovery system may be required by localenvironmental regulations.

from syngas to methanol and dymethylether

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