from syngas to methanol and dymethylether
TRANSCRIPT
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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 syn- gas
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. 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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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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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.