Note: Descriptions are shown in the official language in which they were submitted.
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Method for the production and use of a hydrocarbon mixture
The invention relates to a method for the production and use of a hydrocarbon
mixture made from
natural gas for crude oil refineries. The hydrocarbon mixture can be supplied
without further
processing for use in a crude oil processing refinery.
It is generally known that natural gas, once broken down into the components
hydrogen, carbon
monoxide, and carbon dioxide, can be converted via catalytic synthesis steps
into ammonia and
methanol, but also petrochemical products, such as gasoline, diesel, or
olefins. Already at the
beginning of the 20th century the scientific and technical foundations were
generated for the
Fischer-Tropsch synthesis, which converts synthesis gases of most various
origins (coal, natural
gas, oil, wood) into liquid hydrocarbons. The method was further developed in
many steps,
implemented on an industrial scale, and is still protected today by a
plurality of new patents. An
essential disadvantage of the modern methods is the fact that, according to
the Fischer-Tropsch
synthesis, a mixture of different hydrocarbons is accrued, including a high
percentage of waxes,
which must be subjected to comprehensive refining. Only with the
implementation of such intense
post processing, which is extremely expensive with regards to investments and
costs, can market-
conform products be produced, such as diesel, gasoline, or kerosene.
In connection with the first oil crisis in the middle of the seventies of the
last century, an alternative
method to the Fischer-Tropsch synthesis was developed; the catalytic
conversion of synthesis
gases into methanol and the subsequent catalytic conversion (dehydration) of
methanol into
gasoline. This method, called "methanol to gasoline" was also used on an
industrial scale (as MtG
technology) and was/is used globally in various arrangements. It allows the
production of
standardized gasoline with an octane rating exceeding 92, which fulfills the
specifications of the
major markets in the U.S.A., Europe, and Asia. After dehydration of methanol,
this method
requires a refining/distillation/hydration process, without which the required
qualities of gasoline
cannot be achieved. Therefore, any arrangement of earlier systems for the
conversion of synthesis
gas into gasoline, via the intermediate product methanol, was forced to
integrate this refining step
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in the overall equipment, with approx. 20% of the total investment costs
allocated to this
processing step. Further, in this MtG-method, in order to yield the specified
octane rating in
gasoline, the dwell time in the reactor for converting the dim4hyl ether /
methanol / water ¨
mixture is largely determined with fixed parameters, and therefore allows
hardly any or only minor
variability.
An essential disadvantage of the above-stated solutions is the considerable
expense for converting
the initially obtained crude gasoline into a market-conform product, which
must be generated in a
methanol synthesis that meets highest standards.
The objective of the invention is to provide a simplified method for
converting natural gas into
hydrocarbon mixtures, which allows feeding the generated mixtures without any
further
processing for use in a refinery processing crude oil. Here it shall be
possible to adapt individual
components of the hydrocarbon mixture, based on the respective goals of the
refinery, in their
volumetric portions according to the specific requirements of the respective
refinery.
According to the invention it has been recognized that natural gas can be
converted into a crude
methanol as an intermediate product using a simplified process. This crude
methanol can then be
converted catalytically into a dimethyl ether ¨ methanol ¨ water mixture and
then, also in a
simplified method, into a hydrocarbon mixture which preferably is free from
sulfur and benzene,
and after dehydration and degassing is fed to a refinery processing crude oil,
where it is preferably
converted into products such as gasoline and/or aromatics meeting certain
specifications. The term
"crude oil refinery" shall here be understood as a refinery processing crude
oil.
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By modifying the reaction parameters, such as pressure, temperature, or dwell
time during the
conversion process of the dimethyl ether ¨ methanol ¨ water mixture into a
hydrocarbon mixture,
here individual components (aromatics, paraffins, olefins) can be increased or
reduced in their
volumetric ratio according to the specific requirements of the respective
refinery.
The method according to the invention and use of a hydrocarbon mixture made
from natural gas
for crude oil refineries is characterized in that the hydrocarbon mixture is
anhydrous. Preferably
the hydrocarbon mixture is free from oxygenated compounds.
According to the invention the hydrocarbon mixture made from natural gas is
produced using the
following production steps: a) converting the natural gas into a methanol
water mixture (here and
in the following called "crude methanol") without subsequent distillation. The
method according
to the invention further comprises b) the catalytic conversion of the crude
methanol of step a) into
a dimethyl ether ¨ methanol ¨ water mixture, and then c) the conversion,
preferably by way of
dehydration, of the dimethyl ether ¨ methanol ¨ water mixture of step b) into
an aqueous
hydrocarbon mixture, which primarily comprises paraffins, C6+ olefins, and
aromatics,
particularly methylated benzenes, such as toluene or xylene. It is preferred
that the aqueous
hydrocarbon mixtures are free from sulfur and/or benzene. The method according
to the invention
further comprises d) the degassing and dehydration of the hydrocarbon mixture,
with the
hydrocarbon mixture yielded with the above-stated processing steps a) to d)
now being anhydrous.
According to the invention, the hydrocarbon mixture yielded with the above-
stated processing
steps a) to d) is then fed to a refinery, particularly a nearby one processing
crude oil, particularly
supplied by way of pumping, and here converted in particular into products,
preferably gasoline
and/or aromatics meeting certain specifications.
The term "products meeting certain specifications" shall here and in the
following be understood
as particularly such petrochemical products which, such as gasoline for
example, meet qualities
standards which have been set by the industry or public supervisory
authorities. The fuel standards
"DIN EN 228" for gasoline and "DIN EN 590" are defined as the minimum
requirements for the
most important quality features, as well as the octane rating:
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regular gasoline mm. 91 octane, premium min. 95 octane, premium plus mm. 98
octane. In
Germany, fuels may only be sold if they meet the respective standard. In the
present case, the term
"crude oil" and "crude oil processing" are used synonymously with "petroleum"
and/or "petroleum
processing".
The terms "free from sulfur" and "free from benzene" as well as "free from
oxygenated
compounds" and "anhydrous" are preferably understood such that the product may
still show a
very low residual content of these compounds mentioned, however no further
cleaning process is
required to this regard in order to allow subsequent use thereof
The term "nearby refinery processing crude oil" is here and in the following
understood such that
the refinery processing crude oil is arranged in the proximity of the location
of the execution of at
least one of the processing steps a) to d), preferably all of these processing
steps. In particular it
shall be understood that the refinery processing crude oil is arranged at a
distance of maximally 20
km from the location of execution of one or more of the processing steps a) to
d).
It is preferred that the hydrocarbon mixture yielded according to the
processing steps a) to d) is
pumped via a pipeline to a refinery processing crude oil and here, depending
on the configuration
of said refinery, is either added to the crude oil and/or suitable cleavage
products, e.g., from
"Fluidized Catalytic Cracking" (FCC). During the subsequent treatment of the
hydrocarbon
mixture, preferably in a hydro-treater, the produced quantity of gasoline
and/or gasoline and
aromatics is increased by the quantity of hydrocarbons comprising the
hydrocarbon mixture
yielded according to the processing steps a) to d).
A major Advantage, economically and regarding processing technology on the one
hand, is the
simplification of the technology for producing crude methanol, namely
particularly the omission
of the distillation of the crude methanol and the reduction of requirements to
the methanol
synthesis connected thereto, and on the other hand the complete omission of
the refining of the
developing hydrocarbon mixture in connection with the methanol production. For
example, the
investment costs for converting
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natural gas into petrochemical products can be reduced by up to 35%, and the
technical
requirements for implementing the method are diminished. Due to the fact that
the production
capacity of a refinery processing crude oil is usually much larger than the
volume of hydrocarbon
mixture developed from the method according to the invention, here such a
refinery processing
crude oil can also be used according to the invention for processing the
hydrocarbon mixture
without any increase of the refinery capacity being required. Thus, existing
infrastructure can be
used without this, considerably changing the capacity utilization, and the
expensive erection of a
refinery station, especially for the hydrocarbon mixture, can be waived.
The distillation of the crude methanol in the MtG-method known from prior art
is expensive since
a thermal method must be used for the crude methanol in order to allow
separating water from the
homogenous crude methanol. In the method according to the invention the
removal of the water
can be waived until the hydrocarbon mixture has been yielded. Then, this
removal can occur by
simple deposition, since the water is then present in a separate phase. This
simplification more
than compensates the now required entraining of water through the intermediate
processing steps,
particularly since the water ratio is not excessively high.
Another considerable advantage arises here in the sense that according to the
respective
configuration of the accepting refinery processing crude oil the product
ratios (paraffins,
aromatics, olefins) can be adjusted to the particular requirements of the
refinery processing crude
oil. This adjustment is easily possible by modifying the dwell time in the
reactor for converting
the dimethyl ether ¨ methanol ¨ water mixture into the initially aqueous
hydrocarbon mixture.
Here, preferably dwell times are set from 10 minutes to one hour. This is not
possible with the
previous the MtG-method because the dwell times are already predetermined by
the fact that a
certain octane rating shall be achieved. The method according to the invention
is not subject to this
limitation, but rather allows adjustment of the dwell times to the individual
conditions of the
refinery processing crude oil.
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For example, in such relatively short dwell times of two to three minutes,
after complete
conversion of the dimethyl ether ¨ methanol mixture, a composition of the
hydrocarbon mixture
can be yielded having approx. 19 % by weight C2-05-olefins, approx. 14 % by
weight paraffin,
and C6+ olefin as well as approx. 9 % by weight aromatics, in addition to
water. At relatively long
dwell times from half an hour to one hour the portion of C2-05-olefins drops
and the respective
ratio of paraffin and C6+ olefins as well as aromatics increase. The ratio of
water remains here
essentially unchanged. At a dwell time of approx. one hour, here for example a
distribution of
hydrocarbons of approx. 1 % by weight C2-05-olefin, approx. 17-18 % by weight
aromatics, and
approx. 22 % by weight paraffins, and C6+ olefins can be yielded, with the
remainder being water.
In other words, with the method according to the invention, by selecting the
dwell time, the fraction
of C2-05-olefins can be either adjusted as a preferred fraction or as a by-
product with a low ratio
of approx. 1 % by weight. Respective ratios therebetween can also be adjusted,
here.
The term "C6+ olefins" shall here and in the following represent particularly
alkenes, which are
either branched or unbranched, and show 6 or more than 6 carbon atoms,
preferably ranging from
6 to 20 carbon atoms, particularly from 6 to 15 carbon atoms. Accordingly, the
term "C2-05
olefins" shall represent particularly alkenes, which are either branched or
unbranched and
comprise from 2 to 5 carbon atoms.
Further, the method according to the invention allows that the hydrocarbon
mixture yielded by the
method is fed in another intermediate step to the crude oil processing of the
refinery. The
hydrocarbon mixture therefore does not need to run necessarily through all
processing steps of
crude oil to be processed, but can "skip" some of these processing steps. This
way the additional
workload of the refinery processing the crude oil is even lower by the
hydrocarbon mixture
provided according to the invention than is currently the case.
Another advantage results for the accepting refinery in the sense that the
method according to the
invention produces a hydrocarbon mixture preferably free from sulfur and
benzene, which
contributes by its processing in a refinery to a reduction of the sulfur
and/or benzene content,
particularly in gasoline. The hydrocarbon mixture is preferably also free from
oxygenated
compounds.
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Natural gas is a flammable, gas found in nature, which is obtained from
underground deposits. It
is frequently found together with crude oil, since it develops in a similar
process. Natural gas
comprises primarily methane; however it is distinguished by additional
chemical compounds and
varies considerably, depending on place of origin. Frequently natural gas also
comprises major
portions of ethane (frequently from 1 % to 15 % of the molar fraction),
propane (frequently from
1% to 10 % of the molar fraction), and butane. Additional secondary components
are hydrosulfide,
nitrogen, carbon dioxide, and water vapor, in addition thereto helium and
perhaps elementary
sulfur and mercury.
According to the invention, the respectively yielded crude methanol is
subjected to no further
distillation. In particular it is preferred that the methanol ¨ water mixture
(crude methanol) yielded
without any intermediate distillation, is converted particularly directly in
the processing step b)
into a dimethyl ether ¨ methanol ¨ water mixture, which then is converted in
the processing step
c) into the aqueous hydrocarbon mixture.
This hydrocarbon mixture shows for example the following composition:
- 57 % by weight water
- 5 % by weight propane
- 38 % by weight hydrocarbons, primarily ranging from C4 to C14.
The hydrocarbons comprise paraffins, olefins, and aromatics.
It is preferred that the conversion of the natural gas into the crude methanol
comprises in the above-
mentioned processing step a) the following processing steps:
a') desulfurizing,
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b') saturating with process condensate and steam to form a processing gas
saturated with water,
c') converting the processing gas into synthesis gas, namely a mixture
essentially comprising
hydrogen, carbon dioxide, and carbon monoxide,
d') cooling the synthesis gas, preferably in a waste heat boiler system, and
compressing the
synthesis gas via a compressor,
e') yielding methanol by catalytic conversion of the synthesis gas from the
processing step d')
within the scope of a two-stage methanol synthesis in a reactor arrangement,
particularly in a
water-cooled reactor and a gas-cooled reactor, and
f) yielding the crude methanol by the subsequent multi-stage condensation of
methanol.
As already indicated above, natural gas comprises, depending on the location
of the deposit and/or
the source, a ratio of up to 15 % nitrogen and a ratio of noble gases of up to
1 %. The respective
nitrogen ratio and the respective portion of noble gases is entrained during
the conversion of the
natural gas into the crude methanol according to the above-stated processing
step a) as well as in
the processing gas, in the respective synthesis gas, in the cracked gas
mentioned in the following,
and in all other gaseous mixtures of the processing step a) without this being
explicitly mentioned
each time in the following. To this regard, the above-mentioned compositions
are to be understood
always in consideration of this potential nitrogen ratio and the potential
ratio of noble gases. In
addition to this nitrogen portion and this portion of noble gases, the
synthesis gas may also
comprise, in addition to hydrogen, carbon dioxide, and carbon monoxide, very
minute quantities
of uncracked methane, for example.
A preferred further development provides that the conversion of the processing
gas into synthesis
gas comprises in the processing step c') the pre-cracking of at least a
portion of the processing gas
in a pre-reformer into a cracked gas with methane, hydrogen, carbon dioxide,
and carbon
monoxide. In particular, this cracked gas may consist entirely or essentially
of methane, hydrogen,
carbon dioxide, and carbon monoxide. By such a use of a pre-reformer for pre-
cracking here the
oxygen consumption can be reduced in the method according to the invention.
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Here it is further preferred that the conversion of the processing gas into
synthesis gas in the
processing step c') comprises a catalytic conversion of a processing gas flow,
preformed
downstream the pre-reformer, which processing gas flow comprises a cracked
gas, under elevated
temperature in an auto-thermal reformer into the synthesis gas for the
processing step d') with
addition of preheated oxygen. Here the term "processing gas flow" shall be
understood as any
arbitrary gas flow in the procedural sense, in the process suggested, which is
given based on the
processing gas or its processing and which is given in the processing step
c'). According to this
preferred embodiment this processing gas flow comprises the cracked gas. The
processing gas
flow may also include the processing gas and particularly essentially comprise
the processing gas
and the cracked gas.
According to a preferred embodiment essentially the entire processing gas from
the processing
step b") is fed to the pre-reformer for pre-cracking, and the cracked gas from
the pre-reformer to
the auto-thermal reformer. A preferred variant provides that the cracked gas
is fed from the pre-
reformer, essentially in its entirety, to the auto-thermal reformer.
Preferably then the catalytic
conversion occurs in the auto-thermal reformer at a pressure of at least 50
bar.
According to another preferred variant it is provided that the conversion of
the processing gas into
synthesis gas in the processing step c') comprises a conversion of the cracked
gas in a steam
reformer into another synthesis gas performed procedurally dovvnstream the pre-
reformer. This
additional synthesis gas is here also a mixture essentially comprising
hydrogen, carbon dioxide,
and carbon monoxide. The additional synthesis gas may also, in principle, show
other ratios of
these components than the synthesis gas developing by conversion in the auto-
thermal reformer.
Preferably the additional synthesis gas is fed to the compressor, particularly
via the waste heat
boiler system, as the synthesis gas for the processing step d').
According to a first variant, this steam reformer may be arranged parallel to
the auto-thermal
reformer and procedurally downstream the pre-reformer. Accordingly, it is
preferred that the
cracked gas from the pre-reformer is divided into a first cracked gas flow,
which is fed to the auto-
thermal reformer, and a second cracked gas flow, which is fed to the steam
reformer. In order to
execute the subsequent cooling and compression it is preferably provided that
the additional
synthesis gas from the steam reformer and the synthesis gas of the auto-
thermal reformer are
combined in order to yield the synthesis gas for the processing step d').
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It is preferred that a partial flow of the processing gas is branched out for
feeding the pre-reformer,
the cracked gas from the pre-reformer is preferably fed in its entirety to the
steam reformer, the
additional synthesis gas is returned from the steam reformer to the remaining
processing gas for
mixing, and then it is fed to the auto-thermal reformer. Preferably the
catalytic conversion occurs
in the auto-thermal reformer at a pressure of at least 30 bar.
According to a preferred embodiment, in case of a two-stage methanol
synthesis, in a processing
step e') a first portion of reactor exhaust gas is branched out, the first
portion of the reactor exhaust
is circulated, and here in another compressor compressed to an operating
pressure for the two-
stage methanol synthesis. The term "reactor exhaust gas" shall here and in the
following be
understood as the gas mixture which develops in the reactor arrangement in the
two-stage methanol
synthesis.
Additionally, in the two-stage methanol synthesis in the processing step e') a
second portion of
reactor gas can be branched out and fed to a pressure-swing arrangement (PSA),
in which hydrogen
is separated from the second portion, with the separated hydrogen being fed to
the compressor of
the processing step d') at its suction side. Such a pressure-swing arrangement
is also called
pressure-swing-adsorption arrangement or pressure-change adsorption
arrangement, and is
characterized by providing a physical method for separating gas mixtures under
pressure by way
of adsorption.
To this regard, it is further preferred that the synthesis gas - particle flow
is branched off after
compression via the compressor and also fed to the pressure swing arrangement.
The pressure
swing arrangement therefore serves to compensate the hydrogen balance in the
two-stage methanol
synthesis. In particular it is provided that in the pressure swing arrangement
hydrogen is separated
from the partial flow of the synthesis gas, and that the separated hydrogen is
fed to the compressor
of the processing step d') on the suction side.
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According to a preferred embodiment, the conversion of the crude methanol into
the dimethyl
ether / methanol / water mixture of the processing step b) occurs in a fixed
bed reactor. It is also
preferred that the conversion of the dimethyl ether / methanol / water mixture
into the aqueous
hydrocarbon mixture of the processing step c) occurs in at least one
additional adiabatically
operating reactor at a temperature range from 300 C to 450 C.
It is also preferred that the dimethyl ethyl ¨ methanol ¨ water mixture
developing in the fixed bed
reactor is mixed with recycle gas for temperature adjustment, namely
preferably in the additional
adiabatically operating reactors.
The term "recycle gas" is here, and in the following, understood as a recycled
gas component,
particularly a gas component essentially comprising hydrocarbons, from a
processing step
procedurally arranged downstream, particularly from degassing according to the
processing step
d).
The hydrocarbon mixture, initially still containing water, is now after
degassing and dehydration
transported to a refinery processing crude oil, preferably pumped, namely
particularly via a
pipeline and here added, depending on the configuration of the refinery,
either to the crude oil or
to suitable by-products.
Here it is preferably provided, on the one hand, that the hydrocarbon mixture
yielded according to
the processing steps a) to d) is added in the refinery procedurally upstream
the hydro-treater. In
particular, it can be added directly before a hydro-treater of the refinery.
This hydro-treater may
represent on the one hand a hydro-treater which is located upstream a
"fluidized catalytic cracking"
(FCC)-unit, particularly procedurally directly upstream thereof. Such a hydro-
treater, procedurally
located upstream the FCC-unit, may be arranged directly following the crude
oil distillation.
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On the other hand, the hydro-treater may represent a hydro-treater which is
procedurally arranged
downstream the FCC-unit, particularly directly following it. The hydro-treater
procedurally
arranged downstream the FCC-unit is preferably arranged procedurally upstream
a gasoline
mixing in a gasoline pool of the refinery, namely preferably directly in front
thereof.
On the other hand, it is preferably provided that the hydrocarbon mixture
yielded according to the
processing steps a) to d) is added in the refinery procedurally upstream the
crude oil distillation.
In particular, it may be added to the refinery directly upstream such a crude
oil distillation.
According to another preferred exemplary embodiment it is provided that the
hydrocarbon mixture
yielded via the processing steps a) to d) is moved for feeding to the
refinery. This moved shall be
understood as a separating for pumping and can particularly represent shipping
in which the
hydrocarbon mixture yielded is therefore moved for shipping to water crafts,
e.g., transportation
barges. Alternatively or additionally the hydrocarbon mixture yielded can also
be loaded onto land
vehicles, particularly trucks for the purpose of transportation.
The suggested method for the production and use of a hydrocarbon mixture from
natural gas for
crude oil refineries can alternatively also be described as a method for using
natural gas, converted
into a hydrocarbon mixture, in crude oil refineries or as a method for
utilizing natural gas by
converting it into a hydrocarbon mixture for crude oil refineries.
In the following, the invention is explained in greater detail based on two
exemplary embodiments.
The drawing shows in
Fig. I a flow chart of a first exemplary embodiment of the suggested method,
Fig. 2 a flow chart of a second exemplary embodiment of the suggested method,
and
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Fig. 3 an illustration of measured components of the aqueous hydrocarbon
mixture from the
conversion of the dimethyl ether methanol ¨ water mixture as a function of the
dwell time.
A natural gas (350,000 Nm3/h) with the following composition
- nitrogen 1.5 % by volume
- methane 92 % by volume
- ethane 3.5 % by volume
- propane 1.5 % by volume
- higher hydrocarbons 1.0 % by volume
- sulfur 50 ppm
is converted in a chemical plant, erected nearby a refinery 25 processing
crude oil, which as
described in greater detail in the following based on two exemplary
embodiments, into a
hydrocarbon mixture as follows:
Exemplary embodiment 1:
Fig. 1 shows for the first exemplary embodiment a central oil processing 1 for
crude oil originating
in various well heads 2. The above-mentioned natural gas 3 is obtained here as
a by-product of
crude oil. This natural gas 3 is initially desulfurized at a temperature of
375 C and a pressure of
70 bar via a zinc-oxide bed (desulfurizing unit 4), then saturated with
process condensate and
steam to a process gas saturated with water (saturator 5), and after
adjustment to a steam/carbon
ratio of 1.0 in the pre-reformer 6, an adiabatically operating catalytic
reactor, pre-cracked at 480
C into a cracked gas comprising methane, hydrogen, carbon dioxide, and carbon
monoxide.
After further heating to 630 to 650 C the cracked gas is fed to an auto-
thermal reformer 7. The
auto-thermal reformer 7 represents also an adiabatically operating catalytic
reactor in which by
adding oxygen 9, preheated to 230 C yielded in an air separation unit 8, a
synthesis gas 10 is
generated at 1030 C, which comprises hydrogen, carbon monoxide, and carbon
dioxide and only
comprises a minute quantity of uncracked methane. This synthesis gas 10 is
cooled in a waste heat
boiler system 11.
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Via various stages, which are used for steam generation and/or heating of
several gas/product
flows, now compression occurs with synthesis gas, applied at 55 bar and
cooled, to 75 bar using a
compressor 12. Subsequently, in a dual system comprising a reactor arrangement
13 with a water-
cooled and a gas-cooled reactor, synthesis gas is catalytically converted into
methane at a
temperature range from 220 to 260 C and by condensation crude methanol 14 is
yielded with the
following composition:
- methanol 83 % by weight
- carbon dioxide 3.6 % by weight
- water 11.7 % by weight
- methane 1.5 % by weight
- higher hydrocarbons 0.1 % by weight
- higher alcohols 0.1 % by weight
During the methanol synthesis here a portion of the reactor exhaust gas 15 is
circulated via a
pipeline and here brought to the required pressure using another compressor
16.
Due to the contaminants included in the synthesis gas 10 a second portion of
reactor exhaust gas
17 is branched off as purge gas and passed through via a pressure swing
arrangement (PSA) 18. A
partial synthesis gas flow 19 is also fed to this PSA 18 at high pressure,
branched off after pressure
increase via the compressor 12. The hydrogen 20 generated in the PSA 18 is
returned at the suction
side of the compressor 12 into the synthesis gas flow.
The crude methanol 14 (503 t/h) is subsequently converted catalytically in a
fixed bed reactor 21
(DME-reactor) into a DME (dimethyl ether / methanol I water) mixture. The
reaction product from
the DME-reactor is mixed with the recycled gas 22 for temperature adjustment,
and then in
additional adiabatically operating reactors 23, at a temperature range from
320 to 420 C and at a
dwell time of 60 minutes, converted into an aqueous hydrocarbon mixture. From
the 503 t/h
methanol here 191 t hydrocarbons and 312 t water develop. This aqueous
hydrocarbon mixture is
then dehydrated in a post-processing unit 24 and degassed.
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The dewatered and degassed hydrocarbon mixture (191 t/h) is pumped into a
nearby refinery 25
processing crude oil. The procedurally relevant processing steps of this
refinery 25 comprise, in
the following sequence, a crude oil distillation 26, a first hydro-treater
27a, a FCC-unit 28, a second
hydro-treater 27b, and a gasoline pool 29 for mixing the gasoline. In this
exemplary embodiment
the hydrocarbon mixture is added upstream the second hydro-treater 27b, which
is arranged
procedurally downstream the "Fluidized Catalytic Cracking" (FCC) unit 28. The
advantage of this
feeding comprises that the introduced hydrocarbons, as preferably sulfur and
benzene-free
components, improve the quality of the gasoline produced. Practically 100 % of
the hydrocarbon
mixture is ultimately converted into gasoline. This way, the hydrocarbons
contained in the
hydrocarbon mixture are added to the gasoline pool 29. The dwell time selected
in the adiabatically
operating reactors 23 lead here to a mixture comprising approx. 65 % paraffins
and C6+ olefins as
well as 35 % aromatics (primarily toluene and xylene).
Exemplary embodiment 2:
The second exemplary embodiment shown in Fig. 2 is generally equivalent to the
above-stated
one, however it is distinguished from the first exemplary embodiment described
in reference to
Fig. 1 in the following features:
After the saturator 5, via a first line 29, a first partial flow of approx. 40
% of the processing gas,
saturated with water, desulfurized, and mixed with steam, is added at a
temperature of approx. 480
C to the pre-reformer 6. Here, the processing gas is pre-cracked into a
cracked gas comprising
methane, hydrogen, carbon dioxide, and carbon monoxide.
After an additional heating to 520 C this cracked gas is converted in a steam
reformer 30,
particularly an externally heated pipe-reactor with a nickel catalytic
converter, here into another
synthesis gas 31, namely a mixture of hydrogen, carbon monoxide, and carbon
dioxide.
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This additional synthesis gas 31 is returned in a second line 32 in another
partial flow (approx.
60%) of the processing gas, saturated with water, desulfurized, and mixed with
steam, developing
after the saturator 5, and fed at a mixed temperature of 670 C to the auto-
thermal reformer 7.
In the auto-thermal reformer 7, an adiabatically operating catalytic reactor,
the mixed gas is yielded
by addition of oxygen 9, heated to 240 C, and obtained in an air separation
device 8, completely
converted at 980 C into a second synthesis gas 1 Oa, which comprises only
minute amounts of
uncracked methane. This second synthesis gas 10a is cooled in a waste heat
boiler system 11.
The second synthesis gas 10a, applied with a pressure of 32 bar, is then
further treated in a manner
similar to the synthesis gas 10 of the first exemplary embodiment, as stated
in example 1, in order
to produce an anhydrous hydrocarbon mixture with the above-stated composition,
with the
difference that downstream the compressor 12 no partial synthesis gas flow 19
is branched off and
fed to the pressure swing arrangement (PSA) 18.
With this method it is possible, compared to the procedure according to
example 1, to reduce the
gas consumption, particularly the oxygen consumption, by 10 % for the
production of the
hydrocarbon mixture.
Another difference of the second exemplary embodiment comprises that the
dehydrated and
degassed hydrocarbon mixture, after being pumped to the nearby refinery 25, is
added upstream
the first hydro-treater 27a and thus directly after the crude oil distillation
28. Here, the procedural
point of adding the hydrocarbon mixture may also be switched between the first
and the second
exemplary embodiment.
Fig. 3 shows an illustration of measured components of the aqueous hydrocarbon
mixture of the
conversion of dimethyl ether ¨ methanol ¨ water mixture as a function of the
dwell time. This
illustration
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is based on the interpolation of individual measuring points. In particular,
the dwell time is shown
logarithmically in hours on the abscissa 33, while on the ordinate 34 the
product selectivity is
shown in % by weight. At the start of the process, exclusively dimethyl ether
35 and methanol 36
as well as minor portions of water 37 are present, while in later dwell times
and thus continued
conversion the portion of water 37 largely increases and the respective
portions of the increasingly
formed C2-05 olefins 38, paraffins, and C6+ olefins (here shown jointly) 39,
as well as the
aromatics 40 initially increase slowly. Similarly the portion of the reactants
dimethyl ether 35 and
methanol 36 reduces.
After converting approximately the entire dimethyl ether 35 and methanol 36
the portion of water
37 reaches a constant value and the portion of C2-05 olefins 38 reaches it
maximum. In a dwell
time exceeding this point of time of complete conversion 41 of the reactants
the portion of the C2-
05-olefins 38 reduces again in favor of the aromatics 40 as well as the
paraffins, and the C6+
olefins 39. This trend continues to an almost complete conversion of the C2-05-
olefins 38, thus
the short-chained olefins, into aromatics 40 on the one hand as well as
paraffins and C6+ olefins
39 on the other hand.
