U.S. patent application number 16/767224 was filed with the patent office on 2020-12-24 for methods and systems for producing light olefins from naphtha.
The applicant listed for this patent is SABIC Global Technologies B.V.. Invention is credited to Joris VAN WILLIGENBURG.
Application Number | 20200399546 16/767224 |
Document ID | / |
Family ID | 1000005119127 |
Filed Date | 2020-12-24 |
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United States Patent
Application |
20200399546 |
Kind Code |
A1 |
VAN WILLIGENBURG; Joris |
December 24, 2020 |
METHODS AND SYSTEMS FOR PRODUCING LIGHT OLEFINS FROM NAPHTHA
Abstract
Methods and systems for producing olefins from a naphtha
feedstock are provided. Methods can include pyrolyzing the naphtha
feedstock in the presence of hydrogen gas to produce a first
effluent, separating the first effluent into light components,
heavy components and one or more olefin product streams, steam
cracking the light components to produce a second effluent, and
extracting aromatics, if any, from the heavy components to produce
a third effluent.
Inventors: |
VAN WILLIGENBURG; Joris;
(Maastruct, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SABIC Global Technologies B.V. |
Bergen op Zoom |
|
NL |
|
|
Family ID: |
1000005119127 |
Appl. No.: |
16/767224 |
Filed: |
November 15, 2018 |
PCT Filed: |
November 15, 2018 |
PCT NO: |
PCT/IB2018/058997 |
371 Date: |
May 27, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62594329 |
Dec 4, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 2400/30 20130101;
C10K 3/04 20130101; C10G 47/22 20130101; C10G 2400/22 20130101;
C10G 2300/1044 20130101; C10G 2400/20 20130101 |
International
Class: |
C10G 47/22 20060101
C10G047/22; C10K 3/04 20060101 C10K003/04 |
Claims
1. A method for producing olefins and aromatics from a naphtha
feedstock, the method comprising the steps of: (a) pyrolyzing the
naphtha feedstock in the presence of hydrogen gas to produce a
first effluent comprising first olefins; (b) separating the first
effluent into light components, heavy components, if any, and one
or more olefin product streams; (c) steam cracking the light
components to produce a second effluent comprising second olefins;
and (d) extracting aromatics, if any, from the heavy components to
produce a third effluent.
2. The method of claim 1, wherein the first effluent comprises
C.sub.2 to C.sub.4 paraffins and iso-paraffins.
3. The method of claim 1, wherein after pyrolyzing, the first
effluent has a temperature of about 700.degree. C. to about
860.degree. C.
4. The method of claim 1, wherein after steam cracking, the second
effluent has a temperature of about 820.degree. C. to about
880.degree. C.
5. The method of claim 1, wherein the separating the first effluent
comprises compressing the first effluent to pressurize the first
effluent and condense the heavy components.
6. The method of claim 5, further comprising treating the first
effluent to remove carbon dioxide and water, if any.
7. The method of claim 1, further comprising combining the first
effluent and the second effluent prior to the separating.
8. The method of claim 1, further comprising the steps of: (e)
extracting hydrogen, if any, from the light components to produce a
hydrocarbon stream and recycling the hydrogen by mixing it with the
naphtha feedstock; (f) extracting methane, if any, from the
hydrocarbon stream to produce a C.sub.2+ stream; (g) extracting
ethylene and ethane, if any, from the C.sub.2+ stream to produce a
C.sub.3+ stream; (h) extracting propylene and propane, if any, from
the C.sub.3+ stream to produce a C.sub.4+ stream; (i) extracting
C.sub.4 components, if any, from the C.sub.4+ stream to produce a
C.sub.5+ stream; and (j) extracting benzene, toluene, xylene,
ethylbenzene, C.sub.9+ aromatics and heavy oil, if any, from the
heavy components and the C.sub.5+ stream to produce a third
effluent.
9. The method of claim 8, further comprising recycling the third
effluent by combining it with the naphtha feedstock.
10. The method of claim 8, further comprising pyrolyzing the third
effluent.
11. The method of any claim 8, further comprising purifying the
hydrogen by removing carbon monoxide and methane, if any.
12. The method of claim 11, wherein the carbon monoxide is
converted to methane and water, wherein the water is removed to
produce a hydrogen stream comprising from about 85 vol-% to about
95 vol-% hydrogen.
13. The method of claim 12, wherein the methane is removed by
pressure swing adsorption to produce a purified hydrogen stream
comprising greater than about 99 vol-% hydrogen.
14. The method of claim 8, further comprising recycling the
hydrogen by combining it with the naphtha feedstock.
15. The method of claim 8, further comprising transferring the
hydrogen to one or more hydrogenation reactors.
16. The method of claim 8, further comprising the separating the
ethylene and ethane into an ethylene product stream and an ethane
stream.
17. The method of claim 8, further comprising separating the
propylene and propane into a propylene product stream and a propane
stream.
18. The method of claim 8, further comprising steam cracking the
ethane stream and the propane stream.
19. The method of claim 8, further comprising the steps of: (k)
extracting C.sub.4 and lighter hydrocarbons, if any, from the heavy
components and the C.sub.5+ stream to produce a C.sub.4- stream;
and (l) recycling the C.sub.4- stream by combining it with the
first effluent and/or the second effluent.
20. A method for producing olefins and aromatics from a naphtha
feedstock, the method consisting of the steps of: (a) pyrolyzing
the naphtha feedstock in the presence of hydrogen gas to produce a
first effluent comprising first olefins; (b) separating the first
effluent into light components and heavy components and an olefin
product streams, wherein the heavy components comprise aromatics;
(c) steam cracking the light components to produce a second
effluent comprising second olefins; and (d) extracting aromatics
from the heavy components to produce a third effluent, wherein the
yield sum of the ethylene and the propylene is greater than about
51%.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of U.S.
Provisional Patent Application No. 62/594,329, filed Dec. 4, 2017,
which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
A. Field of the Invention
[0002] The invention generally concerns methods and systems for
producing light olefins from naphtha.
B. Description of Related Art
[0003] Light olefins, such as ethylene and propylene, are important
petrochemical products which can be used to produce plastics such
as polyethylene, polypropylene, and various co-polymers. Light
olefins can be produced from hydrocarbon feedstocks including
naphtha. Naphtha can be found in petroleum distillate streams and
can contain a variety of components, depending on the composition
of the crude source.
[0004] Light olefins can be produced by the steam cracking of
naphtha. However, steam cracking can be energy-intensive and can
result in low yields of ethylene and propylene from naphtha. For
example, although steam cracking of lighter paraffins can have high
light olefins yield, steam cracking of naphtha containing large
amounts of aromatic compounds and/or naphthenes can have low light
olefins yield.
[0005] Certain methods are known in the art for converting naphtha
to light olefins. For example, European Patent No. EP 0089310
discloses a method of producing olefins by steam cracking
hydrocarbons under pressure and with coexistence of methane and
hydrogen, including making hydrocarbons coexist with a mixed gas of
methane and hydrogen in a methane/hydrogen mole ratio of 0.2 or
more, performing a thermal cracking reaction, and quenching the
reaction product discharge. Russian Patent No. RU 2,249,611
discloses a hydropyrolysis process using a gasoline and
hydrogenated C.sub.9+ fraction feedstock. The C.sub.9+ fraction can
be isolated as side-cut distillate from bottom residue obtained in
fractionation of liquid pyrolysis products. European Patent
Publication No. EP 0068051 discloses a hydropyrolysis process for
upgrading higher molecular weight feedstock to lower molecular
weight liquid products by pressurizing and heating the
feedstock.
[0006] U.S. Pat. No. 3,907,920 discloses an integrated process to
produce ethylene and methane including a first stage hydropyrolysis
of hydrocarbon oil followed by cracking the hydropyrolysis
effluent, separating and recycling the hydrogen and ethane, and
recovering the ethylene and methane. U.S. Patent Publication No.
2013/0228495 discloses a system and process for producing
petrochemicals, including olefins and aromatics, from crude oil
feedstock by a steam pyrolysis process integrated with a
hydroprocessing process. German Patent Publication No. DE 2,708,412
discloses an integrated process to produce ethylene, ethane,
propane, benzene, and syngas including a hydropyrolysis process
followed by an aromatic separation process, a low temperature
separation process, and an ethane cracking process.
[0007] However, there remains a need for techniques of producing
light olefins, e.g., ethylene and propylene, from naphtha
feedstock.
SUMMARY OF THE INVENTION
[0008] The disclosed subject matter provides methods and systems
for producing light olefins from naphtha. Particularly, according
to the disclosed methods and systems, steam cracking and pyrolysis
of naphtha can be combined to improve the yield of light olefins
from naphtha.
[0009] In certain embodiments, an exemplary method of producing
light olefins, e.g., ethylene and propylene, from a naphtha
feedstock includes pyrolyzing the naphtha feedstock in the presence
of hydrogen gas to produce a first effluent including first
olefins, and separating the first effluent into light components,
heavy components and one or more olefin product streams. The method
further includes steam cracking the light components to produce a
second effluent including second olefins, and extracting aromatics
from the heavy components to produce a third effluent.
[0010] In certain embodiments, the first effluent can contain
C.sub.2 to C.sub.4 paraffins and iso-paraffins. After pyrolysis,
the first effluent can have a temperature from about 700.degree. C.
to about 860.degree. C. After steam cracking, the second effluent
can have a temperature from about 820.degree. C. to about
880.degree. C.
[0011] In certain embodiments, the first effluent can be compressed
to pressurize the first effluent to condense the heavy components
from the light components. The first effluent can be treated to
remove carbon dioxide and water, if any. In certain embodiments,
the second effluent can be combined with the first effluent prior
to separating light components and heavy components.
[0012] In certain embodiments, the method can further include
extracting hydrogen from the light components to produce a
hydrocarbon stream and recycling the hydrogen by mixing it with the
naphtha feedstock. The method can include extracting methane from
the hydrocarbon stream to produce a C.sub.2+ stream, extracting
ethylene and ethane from the C.sub.2+ stream to produce a C.sub.3+
stream, extracting propylene and propane from the C.sub.3+ stream
to produce a C.sub.4+ stream, extracting C.sub.4 components from
the C.sub.4+ stream to produce a C.sub.5+ stream, and extracting
benzene, toluene, xylene, ethylbenzene, C.sub.9+ aromatics, and
heavy oil from the heavy components and the C.sub.5+ stream to
produce a third effluent. The method can further include recycling
the third effluent by combining it with the naphtha feedstock. In
certain embodiments, the method can include pyrolyzing the third
effluent.
[0013] In certain embodiments, the hydrogen can be purified by
removing carbon monoxide and methane. For example, the carbon
monoxide can be converted to methane and water. The water can be
removed to produce a hydrogen stream containing from about 85 vol-%
to about 95 vol-% hydrogen. The methane can be removed by pressure
swing adsorption to produce a purified hydrogen stream comprising
greater than about 99 vol-% hydrogen. The hydrogen can be recycled
by combining it with the naphtha feedstock. Alternatively or
additionally, the hydrogen can be transferred to one or more
hydrogenation reactors.
[0014] In certain embodiments, the ethylene and ethane can be
separated into an ethylene product stream and an ethane stream and
the propylene and propane can be separated into a propylene product
stream and a propane stream. The method can include steam cracking
the ethane stream and the propane stream. In certain embodiments,
the method can include extracting C.sub.4 and lighter hydrocarbons
from the heavy components and the C.sub.5+ stream to produce a
C.sub.4- stream, and recycling the C.sub.4- stream by combining it
with the first effluent and/or the second effluent. In accordance
with the disclosed method, the combined yield of ethylene and
propylene can be greater than about 51%.
[0015] The presently disclosed subject matter also provides systems
for producing light olefins from naphtha. In certain embodiments,
an exemplary system includes a pyrolysis unit to pyrolyze the
naphtha feedstock in the presence of hydrogen. The system also
includes a separation system, coupled to the pyrolysis unit, to
separate heavy components, light components and olefin products. A
steam cracking unit, coupled to the separation system, is provided
to crack the light components and produce olefins. The system can
also include an aromatics extraction unit, coupled to the
separation system, to produce aromatics and recycle paraffins
and/or naphthenes from the heavy components.
[0016] In certain embodiments, the system can further include a gas
compression and treatment unit, coupled to the pyrolysis unit, to
separate heavy components and remove carbon dioxide and water. The
separation system can include a hydrogen separator, a demethanizer,
a deethanizer, a depropanizer, and/or a debutanizer. The system can
include a carbon monoxide conversion unit, coupled to the hydrogen
separator, for converting carbon monoxide to a hydrogen stream
comprising hydrogen, methane, and water. The system can further
include a dryer, coupled to the carbon monoxide conversion unit,
for removing water from the hydrogen stream and a pressure swing
adsorption unit, coupled to the carbon monoxide conversion unit,
for separating methane from the hydrogen.
[0017] In certain embodiments, the system can include a C.sub.2
splitter, coupled to the deethanizer, for separating a ethane
stream and an ethylene product stream, a C.sub.3 splitter, coupled
to the depropanizer, for separating a propane stream and an
propylene product stream, and a recycle line, coupled to the
C.sub.2 splitter and the C.sub.3 splitter, for transferring the
ethane stream and the propane stream to the steam cracking
unit.
[0018] As used herein, the term "about" or "approximately" means
within an acceptable error range for the particular value as
determined by one of ordinary skill in the art, which will depend
in part on how the value is measured or determined, i.e., the
limitations of the measurement system. For example, "about" can
mean a range of up to 20%, up to 10%, up to 5%, and or up to 1% of
a given value.
[0019] As used herein, the term "primarily" means greater than 50%,
e.g., 50.1% or greater, 50.1 to 99.9%, or preferably 51% to 99%, or
any range therebetween.
[0020] In the context of the present invention, twenty embodiments
are now described. Embodiment 1 relates to method for producing
olefins and aromatics from a naphtha feedstock. The method includes
the steps of (a) pyrolyzing the naphtha feedstock in the presence
of hydrogen gas to produce a first effluent containing first
olefins; (b) separating the first effluent into light components,
heavy components, if any, and one or more olefin product streams;
(c) steam cracking the light components to produce a second
effluent containing second olefins; and (d) extracting aromatics,
if any, from the heavy components to produce a third effluent.
Embodiment 2 is the method of embodiment 1, wherein the first
effluent contains C.sub.2 to C.sub.4 paraffins and iso-paraffins.
Embodiment 3 is the method of any of embodiments 1 or 2, wherein
after pyrolyzing, the first effluent has a temperature of about
700.degree. C. to about 860.degree. C. Embodiment 4 is the method
of any of embodiments 1 to 3, wherein after steam cracking, the
second effluent has a temperature of about 820.degree. C. to about
880.degree. C. Embodiment 5 is the method of embodiments 1 one to
4, wherein the separating the first effluent includes compressing
the first effluent to pressurize the first effluent and condense
the heavy components. Embodiment 6 is the method of embodiment 5,
further including the step of treating the first effluent to remove
carbon dioxide and water, if any. Embodiment 7 is the method of
embodiments 1 to 6, further including the step of combining the
first effluent and the second effluent prior to the separating.
Embodiment 8 is the method of any of embodiments 1 to 7, further
including the steps of (e) extracting hydrogen, if any, from the
light components to produce a hydrocarbon stream and recycling the
hydrogen by mixing it with the naphtha feedstock; (f) extracting
methane, if any, from the hydrocarbon stream to produce a C2+
stream; (g) extracting ethylene and ethane, if any, from the C2+
stream to produce a C3+ stream; (h) extracting propylene and
propane, if any, from the C3+ stream to produce a C4+ stream; (i)
extracting C4 components, if any, from the C4+ stream to produce a
C5+ stream; and (j) extracting benzene, toluene, xylene,
ethylbenzene, C9+ aromatics and heavy oil, if any, from the heavy
components and the C5+ stream to produce a third effluent.
Embodiment 9 is the method of embodiment 8, further comprising
recycling the third effluent by combining it with the naphtha
feedstock. Embodiment 10 is the method of any of embodiments 8 or
9, further including the step of pyrolyzing the third effluent.
Embodiment 11 is the method of any one of embodiments 8 to 10,
further including the step of purifying the hydrogen by removing
carbon monoxide and methane, if any. Embodiment 12 is the method of
embodiment 11, wherein the carbon monoxide is converted to methane
and water, wherein the water is removed to produce a hydrogen
stream containing from about 85 vol-% to about 95 vol-% hydrogen.
Embodiment 13 is the method of embodiment 12, wherein the methane
is removed by pressure swing adsorption to produce a purified
hydrogen stream comprising greater than about 99 vol-% hydrogen.
Embodiment 14 is the method of any one of embodiments 8 to 13,
further including the step of recycling the hydrogen by combining
it with the naphtha feedstock. Embodiment 15 is the method of any
one of embodiments 8 to 14, further comprising transferring the
hydrogen to one or more hydrogenation reactors. Embodiment 16 is
the method of any one of embodiments 8 to 15, further including the
step of separating the ethylene and ethane into an ethylene product
stream and an ethane stream. Embodiment 17 is the method of any one
of embodiments 8 to 16, further including the step of separating
the propylene and propane into a propylene product stream and a
propane stream. Embodiment 18 is the method of any one of
embodiments 8 to 17, further including steam cracking the ethane
stream and the propane stream. Embodiment 19 is the method of any
one of embodiments 8 to 18, further including the steps of: (k)
extracting C4 and lighter hydrocarbons, if any, from the heavy
components and the C5+ stream to produce a C.sub.4- stream; and (l)
recycling the C4- stream by combining it with the first effluent
and/or the second effluent. Embodiment 20 is the method of any of
embodiments 1 to 19, wherein the yield sum of the ethylene and the
propylene is greater than about 51%.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Advantages of the present invention may become apparent to
those skilled in the art with the benefit of the following detailed
description and upon reference to the accompanying drawings.
[0022] FIG. 1 depicts a method of producing light olefins from
naphtha according to one exemplary embodiment of the disclosed
subject matter.
[0023] FIG. 2 depicts a system for producing light olefins from
naphtha according to one exemplary embodiment of the disclosed
subject matter.
[0024] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof are shown by
way of example in the drawings. The drawings may not be to
scale.
DETAILED DESCRIPTION
[0025] The presently disclosed subject matter provides methods and
systems for producing light olefins from a hydrocarbon feedstock,
particularly, by combining steam cracking and pyrolysis to improve
the yield of ethylene and/or propylene from naphtha. Heavier
hydrocarbons, e.g., paraffins and naphthenes, can be recycled to a
pyrolysis unit, which has a higher yield of olefins from such
heavier molecules than steam cracking. Lighter hydrocarbons, e.g.,
ethane and propane, can be recycled to a steam cracking unit, which
has a higher yield of olefins from such lighter molecules than
hydropyrolyis.
[0026] The disclosed subject matter provides methods of producing
light olefins, e.g., ethylene and/or propylene, from naphtha
feedstock. In certain embodiments, the method can include mixing
naphtha feedstock with hydrogen gas to produce a first effluent,
separating the first effluent into light components, heavy
components and one or more olefin product streams, steam cracking
the light components to produce a second effluent, and extracting
aromatics, if any, from the heavy components to produce a third
effluent.
[0027] For the purpose of illustration and not limitation, FIG. 1
is a schematic representation of a method according to a
non-limiting embodiment of the disclosed subject matter. In certain
embodiments, the method 100 can include mixing naphtha feedstock
with hydrogen gas to produce a first effluent 101. The naphtha
feedstock of the presently disclosed subject matter can originate
from various sources, e.g., natural gas condensates, petroleum
distillates, coal tar distillates and/or peat. For example, the
naphtha feedstock can include light naphtha, heavy naphtha,
straight run naphtha, full range naphtha, delayed coker naphtha,
fluid catalytic cracking (FCC) naphtha, naphtha produced from
syngas (i.e., a stream including carbon monoxide and hydrogen) via
Fischer-Tropsch synthesis, coker fuel oil and/or gas oils, e.g.,
light coker gas oil and heavy coker gas oil.
[0028] The naphtha feedstock can be a hydrocarbon stream that is
rich in paraffins, iso-paraffins, and/or naphthenes. For example,
the naphtha feedstock can contain from about 0 wt-% to about 100
wt-% paraffins and/or from about 0 wt-% to about 100 wt-%
iso-paraffins. The naphtha feedstock can further include aromatics
and/or C.sub.4 and higher olefins. For example, the naphtha
feedstock can contain less than about 30 wt-% aromatics and/or less
than about 30 wt-% C.sub.4 and higher olefins. The naphtha
feedstock can further include other components, such as diolefins,
traces of polyaromatics, and asphaltenes. In certain embodiments,
the naphtha feedstock can be combined with one or more recycle
streams.
[0029] The naphtha feedstock can be mixed with hydrogen gas in a
hydrogen stream. In certain embodiments, the method can include
recycling hydrogen gas from a separation system. However, the
hydrogen gas of the presently disclosed subject matter can
originate from various other sources, including gaseous streams
from other chemical processes, e.g., ethane cracking, methanol
synthesis, the steam reforming of natural gas, natural gas liquids,
or light petroleum fractions, the gasification of coal, tar,
residue from a crude vacuum tower, or petroleum coke, the
conversion of C.sub.4 hydrocarbons to aromatics, as a byproduct
from the dehydrogenation of propane to propylene, or as a byproduct
from the dehydrogenation of butane to produce 1-butene or
isobutylene.
[0030] In certain embodiments, the hydrogen gas can be part of a
purified hydrogen stream. For example, the amount of hydrogen in
the hydrogen stream can be greater than about 50 vol-%, greater
than about 70 vol-%, greater than about 80 vol-%, greater than
about 85 vol-%, greater than about 90 vol-%, greater than about 95
vol-% or greater than about 99 vol-%. In certain other embodiments,
the hydrogen stream can include steam and/or methane (CH.sub.4).
For example, the hydrogen stream can include from about 30 wt-% to
about 90 wt-% steam and/or from about 30 wt-% to about 90 wt-%
methane.
[0031] In certain embodiments, the method includes pyrolyzing the
naphtha feedstock in the presence of hydrogen to form a first
effluent, e.g., via a pyrolysis reaction in a pyrolysis unit. The
pyrolysis reaction can be performed at temperatures ranging from
about 700.degree. C. to about 860.degree. C., i.e., at the exit of
the pyrolysis unit. The pyrolysis reaction can be performed at
pressures ranging from about 0.5 bar (absolute) to about 40 bar
(absolute), i.e., at the exit of the pyrolysis unit. The naphtha
feedstock can have a residence time in the pyrolysis unit from
about 10 ms to about 800 ms. In certain embodiments, it can be
advantageous for the pyrolysis reaction to favor ethane, propane,
ethylene and/or propylene. For example, with respect to the sum
total of ethane, propane, ethylene and propylene, the pyrolysis
reaction can have selectivity of greater than about 50%, greater
than about 55%, greater than about 60%, greater than about 65%, or
greater than about 70%.
[0032] In certain embodiments, the first effluent can include
paraffins, iso-paraffins, olefins, diolefins, acetylenes,
aromatics, naphthenes, hydrogen, methane, carbon dioxide
(CO.sub.2), and/or carbon monoxide (CO). For example, the first
effluent can include C.sub.2 to C.sub.4 paraffins and
iso-paraffins. In certain embodiments, the first effluent can
contain from about 15 wt-% to about 50 wt-% paraffins and/or from
about 20 wt-% to about 50 wt-% olefins and/or from about 2 wt-% to
about 15 wt-% diolefins and/or from about 2 wt-% to about 20 wt-%
aromatics. In certain embodiments, the first effluent can further
include components recycled by combination with other streams. For
example, the first effluent can include from about 10 wt-% to about
50 wt-% methane and/or from about 1 wt-% to about 10 wt-%
hydrogen.
[0033] In certain embodiments, the method 100 further includes
separating the first effluent into light components and heavy
components 102. For example, the method can include compressing the
first effluent and condensing heavy components, e.g., C.sub.5 and
higher olefins, paraffins, aromatics, and naphthenes. For example,
the heavy components can include 2-methyl-butane,
2,2-dimethylbutane, n-pentane, n-heptane, n-octane, n-nonane,
1-hexene, 1-heptene, 1-octyne, cyclopentane, methylcyclopentane,
cyclohexane, 1,1-dimethylcyclohexane, ethylcyclohexane, benzene,
toluene, mixed xylene, styrene, 1-methylindene,
1-methylnaphthalene, and/or pyrene. Compressing the first effluent
can also aid in downstream separation.
[0034] In certain embodiments, the method can include treating the
first effluent to remove carbon dioxide (CO.sub.2). In certain
embodiments, hydrogen sulfide (H.sub.2S) is also removed by
treating the first effluent. For example, CO.sub.2 and/or H.sub.2S
can be removed by an acid-gas removal process, e.g., including a
caustic wash and/or regenerative solvent (MEA) scrubbing. The
method can further include drying the first effluent to remove
water, e.g., by chilling, adsorption, and/or absorption.
[0035] In certain embodiments, the light components from the first
effluent can be cooled and condensed, e.g., in a cold box. For
example, the light components can be cooled to temperatures ranging
from about -180.degree. C. to about -100.degree. C., from about
-170.degree. C. to about -120.degree. C., or from about
-160.degree. C. to about -140.degree. C. The light components can
be combined with a recycle stream, e.g., from an aromatics
extraction unit, prior to cooling.
[0036] In certain embodiments, the method 100 can further include
extracting hydrogen and other materials from the light components
to produce a hydrocarbon stream 103. For example, during cooling,
hydrogen and other materials, e.g., carbon monoxide and methane,
will not condense, and can be removed in gaseous form. This
uncondensed gas can contain greater than about 50 mol-%, greater
than about 70 mol-%, or greater than about 80 mol-% hydrogen. The
amount of hydrogen in the uncondensed gas can depend on the
residence time in the pyrolysis unit, the temperature of the first
effluent when it exits the pyrolysis unit, and the amount of
methane and/or hydrogen dilution. In certain embodiments, the
uncondensed gas can contain from about 50 mol-% to about 90 mol-%
hydrogen. The uncondensed gas can contain less than about 60 mol-%
methane and less than about 10 mol-% carbon dioxide.
[0037] In certain embodiments, the method can include purifying
hydrogen in the uncondensed gas. For example, carbon monoxide in
the uncondensed gas can be converted to methane and water, e.g, by
methanation, to form a stream including hydrogen, water, and
methane. The water can be removed by drying the stream. In certain
embodiments, after drying, the stream can contain from about 85
vol-% to about 95 vol-% hydrogen. The methane can be separated from
the hydrogen by pressure swing adsorption to produce a purified
hydrogen stream. In certain embodiments, the methane can be used as
fuel gas, e.g., in a fuel gas grid. In certain embodiments, the
purified hydrogen stream can contain greater than about 99 vol-%
hydrogen.
[0038] In certain embodiments, the hydrogen can be transferred to
one or more chemical processes. For example, a stream containing
hydrogen can be split one or more times, and transferred to one or
more reactors, e.g., one or more pyrolysis and/or hydrogenation
reactors. In certain embodiments, the method includes recycling
hydrogen by mixing it with the naphtha feedstock such that the
hydrogen is used for the pyrolysis of the naphtha feedstock. In
certain embodiments, only a portion of the hydrogen is recycled by
mixing it with the naphtha feedstock. Alternatively or
additionally, all or a portion of the hydrogen can be used for the
hydrogenation of C.sub.2, C.sub.3, and/or aromatic hydrocarbons.
Alternatively or additionally, all or a portion of the hydrogen can
be used as fuel, e.g., in a pyrolysis furnace.
[0039] In certain embodiments, the method 100 further includes
extracting methane from the hydrocarbon stream to produce a
C.sub.2+ stream 104. For example, the methane can be extracted by
distillation, e.g., in a demethanizer. In certain embodiments, the
methane can be combined with the methane from the uncondensed gas.
The methane can be used as fuel gas, e.g., in a fuel gas grid.
[0040] The C.sub.2+ stream can include C.sub.2 and higher
hydrocarbons, for example ethane, ethylene, acetylene, propane,
propylene, methylacetylene, propadiene, butadiene, 1-butene,
isobutylene, n-butane, isobutane, 2-butene, vinyl-acetylene, and
higher hydrocarbons such as pentane, C.sub.5 olefins, C.sub.5
diolefins, benzene, C.sub.6 olefins, C.sub.6 diolefins,
cyclohexane, and cyclopentane.
[0041] In certain embodiments, the method 100 further includes
extracting ethylene and ethane from the C.sub.2+ stream to produce
a C.sub.3+ stream 105. For example, a C.sub.2 fraction including
ethylene and ethane can be extracted by distillation, e.g., in a
deethanizer. The C.sub.2 fraction can also include acetylene. In
certain embodiments, the C.sub.2 fraction can be selectively
hydrogenated, e.g., in a hydrogenation reactor, to convert
acetylene in the C.sub.2 fraction into ethylene. After
hydrogenation, the C.sub.2 fraction can contain from about 60 wt-%
to about 90 wt-% ethylene and from about 10 wt-% to about 40 wt-%
ethane.
[0042] The C.sub.2 fraction can be further separated, e.g., by
distillation, to produce an ethylene product stream and an ethane
stream. In certain embodiments, the amount of ethylene in the
ethylene product stream can be greater than about 70 wt-%, greater
than about 80 wt-%, greater than about 90 wt-%, greater than about
95 wt-%, or greater than about 99 wt-%. For example, the ethylene
product stream can be polymer grade ethylene, i.e., contain less
than 500 ppm ethane.
[0043] The C.sub.3+ stream can include C.sub.3 and higher
hydrocarbons, for example propane, propylene, methylacetylene,
propadiene, butadiene, 1-butene, 2-butene, vinyl-acetylene,
isobutylene, n-butane, isobutane, and higher hydrocarbons such as
pentane, C.sub.5 olefins, C.sub.5 diolefins, benzene, C.sub.6
olefins, C.sub.6 diolefins, cyclohexane, and cyclopentane.
[0044] In certain embodiments, the method 100 further includes
extracting propylene and propane from the C.sub.3+ stream to
produce a C.sub.4+ stream 106. For example, a C.sub.3 fraction
including propylene and propane can be extracted by distillation,
e.g., in a depropanizer. The C.sub.3 fraction can also include
methylacetylene and/or propadiene. In certain embodiments, the
C.sub.3 fraction can be selectively hydrogenated, e.g., in a
hydrogenation reactor, to convert methylacetylene and/or propadiene
in the C.sub.3 fraction into propylene. After hydrogenation, the
C.sub.3 fraction can contain from about 75 wt-% to about 97 wt-%
propylene and from about 3 wt-% to about 20 wt-% propane.
[0045] The C.sub.3 fraction can be further separated, e.g., by
distillation, to produce a propylene product stream and a propane
stream. In certain embodiments, the amount of propylene in the
propylene product stream can be greater than about 70 wt-%, greater
than about 80 wt-%, greater than about 90 wt-%, greater than about
95 wt-%, or greater than about 99 wt-%. For example, the propylene
product stream can be refinery grade ethylene, i.e., contain
greater than about 70 wt-% propylene. The propylene product stream
can be chemical grade, i.e., contain greater than about 95 wt-%
propylene. The propylene product stream can be polymer grade, i.e.,
contain from about 98 wt-% to about 99.5 wt-% propylene.
[0046] The C.sub.4+ stream can include C.sub.4 and higher
hydrocarbons, for example butadiene, 1-butene, 2-butene,
vinyl-acetylene, isobutylene, n-butane, isobutane, and higher
hydrocarbons such as pentane, C.sub.5 olefins, C.sub.5 diolefins,
benzene, C.sub.6 olefins, C.sub.6 diolefins, cyclohexane, and
cyclopentane. In certain embodiments, the method 100 further
includes extracting C.sub.4 components from the C.sub.4+ stream to
produce a C.sub.5+ stream 107. For example, a C.sub.4 fraction
including butadiene, 1-butene, isobutylene, n-butane, and isobutane
can be extracted by distillation, e.g., in a debutanizer. The
C.sub.5+ stream can include C.sub.5 and higher hydrocarbons. For
example, the C.sub.5+ stream can include 2-methylbutane, n-pentane,
1-hexene, 1-heptene, cyclopentane, methylcyclopentane, cyclohexane,
methylcyclohexane, 1,1-dimethylcyclohexane, ethylcyclohexane,
and/or benzene.
[0047] In certain embodiments, the method 100 further includes
steam cracking light components, e.g., ethane, propane, and/or
butane, to produce a second effluent 108. The ethane can be
recycled from the C.sub.2 fraction and the propane can be recycled
from the C.sub.3 fraction. The ethane and propane can be combined
prior to transfer to a steam cracking unit. Steam cracking can be
performed at temperatures ranging from about 820.degree. C. to
about 880.degree. C. and pressures ranging from about 1.4 bar
(absolute) to about 3.5 bar (absolute), i.e., at the exit of the
steam cracking unit. The light components can have a residence time
in the steam cracking unit from about 50 ms to about 500 ms.
[0048] The second effluent can include olefins, e.g., ethylene and
propylene. In certain embodiments, the amount of ethylene in the
second effluent can be from about 10 wt-% to about 70 wt-%, from
about 20 wt-% to about 60 wt-%, or from about 30 wt-% to about 50
wt-%. The amount of propylene in the second effluent can be from
about 0.1 wt-% to about 20 wt-%, or from about 1 wt-% to about 15
wt-%. The second effluent can further include other components, for
example hydrogen, methane, paraffins, aromatics and/or heavy
oil.
[0049] In certain embodiments, the method 100 further includes
combining the second effluent with the first effluent from the
pyrolysis reaction 109. The second effluent can be combined with
the first effluent before the first effluent undergoes the
separations discussed above. Therefore, in certain embodiments, the
second effluent can undergo compression, washing, drying, and
cooling as described above. Hydrogen, methane, ethylene and ethane,
propylene and propane, and C.sub.4 components can be extracted from
the second effluent as described in the methods above. The second
effluent can be separated into a hydrogen stream, ethylene product
stream, ethane stream, propylene product stream, propane stream,
C.sub.4 fraction, and C.sub.5+ stream as described above.
[0050] In certain embodiments, the method 100 further includes
extracting benzene, toluene, xylene, ethylbenzene, C.sub.9+
aromatics and heavy oil from the heavy components, e.g., the
condensed hydrocarbons from the compressor, and the C.sub.5+ stream
to produce a third effluent 110. The method can include the
selective hydrogenation of olefins and diolefins prior to
extracting aromatics and heavy oil from the heavy components and
the C.sub.5+ stream.
[0051] Extracting benzene, toluene, xylene, ethylbenzene, C.sub.9+
aromatics and heavy oil from the heavy components and the C.sub.5+
stream can be performed using any suitable method known in the art.
For example, the extraction can use the Edeleanu process (i.e.,
using sulfur dioxide), the UDEX process (i.e., using diethylene
glycol and other solvents), a sulfolane process, the Lurgi
Arosolvan process (i.e., using 1-methyl-2-pyrrolidone), and/or the
IFP process or another morphylane process (i.e, using
n-formylmorpoline).
[0052] In certain embodiments, a C.sub.4- stream containing C.sub.4
and lighter hydrocarbons can be separated from the heavy components
and C.sub.5+ stream. The C.sub.4- stream can be recycled by
combining it with the first effluent and/or second effluent. For
example, the C.sub.4- stream can be combined with the combined
first and second effluents prior to cooling the first and second
effluents. In certain embodiments, the C.sub.4- stream can be
dried, i.e., to remove water, before it is recycled.
[0053] In certain embodiments, a heavy oil stream containing
C.sub.12 and higher hydrocarbons can be separated from the heavy
components and C.sub.5+ stream. The heavy components and the
C.sub.5+ stream can be further separated into a benzene product
stream, toluene product stream, xylene and ethylbenzene product
stream, C.sub.9+ aromatics product stream, and third effluent.
[0054] The third effluent can contain primarily C.sub.5+
hydrocarbons, and can include aliphatic hydrocarbons, e.g.,
paraffins and isoparaffins, and naphthenes. In certain embodiments,
the third effluent contains from about 50 wt-% to about 90 wt-%
paraffins and/or from about 10 wt-% to about 40 wt-% naphthenes. In
certain embodiments, the method 100 further includes recycling the
third effluent by combining it with the naphtha feedstock 111. That
is, the third effluent can be recycled to the pyrolysis reaction.
In other certain embodiments, the third effluent can undergo a
pyrolysis reaction in a separate pyrolysis unit.
[0055] According to methods of the presently disclosed subject
matter, the combined yield of ethylene and propylene can be higher
than the combined yield of ethylene and propylene from the steam
cracking of naphtha without a pyrolysis reaction. For example, the
combined yield of ethylene and propylene can be greater than about
40%, greater than about 50%, greater than about 60%, or greater
than about 70%.
[0056] The presently disclosed subject matter further provides
systems for producing light olefins, e.g., ethylene and propylene,
from naphtha feedstock. For the purpose of illustration and not
limitation, FIG. 2 is a schematic representation of a system
according to a non-limiting embodiment of the disclosed subject
matter. The system can include a pyrolysis unit 250 for pyrolyzing
naphtha feedstock and an olefins and a separation system 270,
coupled to the pyrolysis unit, for separating heavy components,
light components, and olefin products. The system can further
include a steam cracking unit 280, coupled to the separation
system, for cracking the light components to produce olefins and an
aromatics extraction unit 290, coupled to the separation system, to
produce aromatics.
[0057] In certain embodiments, the system 200 can include a
pyrolysis unit 250 for pyrolyzing naphtha feedstock in the presence
of hydrogen. The pyrolysis unit can include a reactor. The reactor
for use in the presently disclosed system can be a tubular
reactor.
[0058] The pyrolysis unit can be coupled to a reactor feed expander
and/or reactor effluent expander. For example, an expander can
increase the volume of the feed and/or effluent to reduce
temperature and pressure. The expander can be mechanically coupled
to a compressor, where the mechanical work produced by expansion of
feed and/or effluent can be used to drive the compressor, thereby
efficiently recovering heat to drive other equipment.
Alternatively, the reactor feed expander and/or reactor effluent
expander can be coupled to a generator to produce electricity.
[0059] "Coupled" as used herein refers to the connection of a
system component to another system component by any suitable means
known in the art. The type of coupling used to connect two or more
system components can depend on the scale and operability of the
system. For example, and not by way of limitation, coupling of two
or more components of a system can include one or more joints,
valves, transfer lines, or sealing elements. Non-limiting examples
of transfer lines include pipes, hose, tubing, and ducting, which
can be made of any suitable material, including stainless steel,
carbon steel, cast iron, ductile iron, non-ferrous metals and
alloys, for example including aluminum, copper, and/or nickel, and
non-metallic materials, e.g., concrete and plastic. Non-limiting
examples of joints include threaded joints, soldered joints, welded
joints, compression joints and mechanical joints. Non-limiting
examples of fittings include coupling fittings, reducing coupling
fittings, union fittings, tee fittings, cross fittings and flange
fittings. Non-limiting examples of valves include gate valves,
globe valves, ball valves, butterfly valves and check valves.
[0060] The pyrolysis unit 250 can be coupled to one or more feed
lines 201, 209 for transferring naphtha feedstock and hydrogen to
the pyrolysis unit. In certain embodiments, a recycle line 240 can
also be coupled to the pyrolysis unit for transferring a recycle
stream containing paraffins and/or naphthenes from the aromatics
extraction unit 290.
[0061] In certain embodiments, the system 200 includes a gas
compression and treatment unit 260 coupled to the pyrolysis unit
250, e.g., via one or more transfer lines 202. The transfer line
containing the first effluent 202 can be combined with a second
transfer line containing the second effluent 230 from the steam
cracking unit 280. The gas compression and treatment unit can
contain one or more compressors. In certain embodiments, the one or
more compressors can be mechanically coupled to a reactor feed
expander and/or reactor effluent expander. Additionally or
alternatively, the one or more compressors can be coupled to a
motor. The gas compression and treatment unit can include a
scrubber for removing carbon dioxide from the first and/or second
effluents. The gas compression and treatment unit can also include
a dryer for removing water from the first and/or second effluents.
For example, the dryer can include molecular sieves for adsorbing
water.
[0062] In certain embodiments, a transfer line 203 can be coupled
to the gas compression and treatment unit 260 for transferring
condensed hydrocarbons from the gas compression and treatment unit
to the aromatics extraction unit 290. A second transfer line 204
can be coupled to the gas compression and treatment unit for
transferring uncondensed hydrocarbons to a cold box 261. In certain
embodiments, the second transfer line 204 can be coupled to a
recycle line 239 from the aromatics extraction unit 290.
[0063] The cold box of the presently disclosed subject matter can
include one or more heat exchangers, e.g., plate fin heat
exchangers, shell and tube heat exchangers, plate heat exchangers,
and/or plate and shell heat exchangers, one or more coolers, one or
more expanders, one or more separators, e.g., distillation columns,
and/or one or more drums, e.g., knock-out drums and/or two-phase
injection drums. The cold box can be made of any suitable material,
for example brazed aluminum and/or stainless steel. In certain
embodiments, the cold box is a brazed aluminum plate-fin heat
exchanger.
[0064] The system 200 can further include a separation system 270
coupled to the cold box 261, e.g., via one or more transfer lines
205. In certain embodiments, the separation system can include a
refrigeration system, which can be integrated with an absorption
chiller and/or adsorption chiller. The separation system can
include a hydrogen separator 271 and one or more distillation
columns, e.g., a demethanizer 272, a deethanizer 273, a
depropanizer 276, and/or a debutanizer 279. The distillation
columns for use in the separation system can be any type known in
the art to be suitable for fractional distillation. The one or more
distillation columns can be adapted to continuous or batch
distillation. The one or more distillation columns can be coupled
to one or more condensers and one or more reboilers. The one or
more distillation columns can be stage or packed columns, and can
include plates, trays and/or packing material. The one or more
distillation columns can be coupled to one or more transfer
lines.
[0065] In certain embodiments, the separation system 270 can
include a hydrogen separator 271 for removing hydrogen and other
uncondensed gases from the hydrocarbon stream. A carbon monoxide
conversion unit 262 can be coupled to the hydrogen separator, e.g.,
via one or more transfer lines 206. The carbon monoxide conversion
unit can convert carbon monoxide in the uncondensed gases to
methane and water to produce a hydrogen rich stream. In certain
embodiments, a dryer can be coupled to the carbon monoxide
conversion unit for removing water from the hydrogen rich
stream.
[0066] A transfer line 207 can be coupled to the carbon monoxide
conversion unit 262, and further coupled to a splitter 263 for
dividing the hydrogen rich stream. A first portion of the hydrogen
rich stream can be transferred to the pyrolysis unit 250, e.g., via
a transfer line 208. A second portion of the hydrogen rich stream
can be transferred to a pressure swing adsorption unit 264, e.g.,
via a transfer line 209. In certain embodiments, the pressure swing
adsorption unit is configured to purify the hydrogen rich stream by
extracting methane. The pressure swing adsorption unit can include
one or more adsorbers. The one or more adsorbers can contain an
adsorbent material, e.g., zeolite, alumina, activated carbon,
and/or silica gel.
[0067] A methane transfer line 210 can be coupled to the pressure
swing adsorption unit for transferring methane to a fuel gas grid.
A hydrogen transfer line 211 can also be coupled to the pressure
swing adsorption unit for transferring purified hydrogen. The
hydrogen transfer line 211 can be coupled to one or more splitters
265, 266 for diverting some of the purified hydrogen stream to one
or more hydrogenation reactors 274, 277. A second hydrogen transfer
line 215 can be coupled to a splitter 266 for transferring hydrogen
to a hydrogenation reactor in the aromatics extraction unit
290.
[0068] The hydrogen separator 271 can also be coupled to a
demethanizer 272, e.g., via a hydrocarbon transfer line 216. As
described above, the demethanizer can include one or more
distillation columns. A methane transfer line 217 can be coupled to
the demethanizer for transferring methane to a fuel gas grid. In
certain embodiments, the methane transfer line 217 can be combined
with the methane transfer line 210 from the pressure swing
adsorption unit 264.
[0069] The system 200 can further include a deethanizer 273 coupled
to the demethanizer 272, e.g., via a C.sub.2+ transfer line 219. As
described above, the deethanizer can include one or more
distillation columns. In certain embodiments, a transfer line 220,
coupled to the deethanizer, can transfer a C.sub.2 fraction from
the deethanizer to a first hydrogenation reactor 274. In
alternative embodiments, the first hydrogenation reactor can be
upstream from the separation system 270. The hydrogenation reactors
of the presently disclosed system can be tubular reactors.
[0070] A transfer line 221, coupled to the first hydrogenation
reactor 274, can transfer the C.sub.2 fraction to a C.sub.2
splitter 175. The C.sub.2 splitter can be configured to separate
ethylene and ethane in the C.sub.2 fraction, e.g., by distillation.
An ethylene product line 222 and an ethane transfer line 223 can be
coupled to the C.sub.2 splitter 275.
[0071] A depropanizer 276 can be coupled to the deethanizer 273,
e.g., via a C.sub.3+ transfer line 224. As described above, the
depropanizer can include one or more distillation columns. In
certain embodiments, a transfer line 225, coupled to the
depropanizer, can transfer a C.sub.3 fraction from the depropanizer
to a second hydrogenation reactor 277. In alternative embodiments,
the second hydrogenation reactor can be upstream from the
separation system 270. A transfer line 226, coupled to the second
hydrogenation reactor, can transfer the C.sub.3 fraction to a
C.sub.3 splitter 278. The C.sub.3 splitter can be configured to
separate propylene and propane in the C.sub.3 fraction, e.g., by
distillation. A propylene product line 227 and an propane transfer
line 228 can be coupled to the C.sub.3 splitter 278.
[0072] The system 200 can further include a debutanizer 279 coupled
to the depropanizer 276, e.g., via a C.sub.4+ transfer line 231. As
described above, the debutanizer can include one or more
distillation columns. In certain embodiments, a crude C.sub.4
product line 232 can be coupled to the debutanizer. A C.sub.5+
transfer line 233 can be coupled to the debutanizer for
transferring C.sub.5 and higher hydrocarbons to the aromatics
extraction unit 290.
[0073] The system 200 can further include a steam cracking unit 280
coupled to the separation system 270. In certain embodiments, the
ethane transfer line 223 and the propane transfer line 228 can be
combined into a recycle line 229 for transferring ethane and
propane from the separation system to the steam cracking unit.
[0074] The steam cracking unit of the presently disclosed subject
matter can include a furnace of any type suitable for the steam
cracking of light hydrocarbons. The furnace can include a radiant
section having one or more burners and a convection section. The
furnace can be coupled to one or more stacks and one or more fans.
Multiple furnaces can be coupled to a common stack and/or fan(s)
and/or share a common convection section. Heat from the convection
section can be used to preheat the light hydrocarbons and/or
superheat dilution steam for the steam cracking furnace and/or to
preheat a dilution steam-hydrocarbon mixture and/or to preheat
boiler feed water and/or to superheat high pressure steam to
temperatures ranging from about 440.degree. C. to about 600.degree.
C. The radiant section of the furnace can contain one or more
tubular reactors.
[0075] A transfer line 230 can be coupled to the steam cracking
unit 280 for transferring the second effluent from the steam
cracking unit to the gas compression and treatment unit 260. In
certain embodiments, the transfer line 230 can be combined with the
transfer line containing the first effluent 202.
[0076] In certain embodiments, the system 200 further includes an
aromatics extraction unit 290 coupled to the separation system 270.
The aromatics extraction unit can include one or more hydrogenation
reactors and one or more distillation columns. The hydrogenation
reaction can be any type suitable for the selective hydrogenation
of olefins and diolefins, including fixed bed reactors, such as
tubular fixed bed reactors and multi-tubular fixed bed reactors,
fluidized bed reactors, such as entrained fluidized bed reactors
and fixed fluidized bed reactors, and slurry bed reactors such as
three-phase slurry bubble columns and ebullated bed reactors. The
distillation columns can be any type suitable for the separation of
aromatics known in the art, including, but not limited to,
separation of aromatics by fractional distillation, vacuum
distillation, azeotropic distillation, extractive distillation,
reactive distillation and/or steam distillation. The distillation
columns can be adapted for continuous or batch distillation. The
distillation columns can be coupled to one or more condensers
and/or one or more reboilers. The distillation columns can be stage
or packed columns, and can include plates, trays and/or packing
material.
[0077] In certain embodiments, a C.sub.4- transfer line 239 is
coupled to the aromatics extraction unit 290 for transferring
C.sub.4 and lighter hydrocarbons to the separation system 270. For
example, the C.sub.4- transfer line can be combined with a transfer
line 204 upstream from the cold box 261. The C.sub.4- transfer line
239 can be coupled to a dryer for removing water from the C.sub.4
and lighter hydrocarbons.
[0078] In certain embodiments a heavy oil product line 238
containing C.sub.12 and heavier hydrocarbons is also coupled to the
aromatics extraction unit 290. A benzene product line 234, a
toluene product line 235, xylene and ethylbenzene product line 236,
and/or a C.sub.9+ aromatics product line 237 can also be coupled to
the aromatics extraction unit. A recycle line 240, coupled to the
aromatics extraction unit, can transfer paraffins and/or naphthenes
to the pyrolysis unit 250.
[0079] The presently disclosed systems can further include
additional components and accessories including, but not limited
to, one or more gas exhaust lines, cyclones, product discharge
lines, reaction zones, heating elements and one or more measurement
accessories.
[0080] The one or more measurement accessories can be any suitable
measurement accessory known to one of ordinary skill in the art
including, but not limited to, pH meters, flow monitors, pressure
indicators and/or transmitters, thermowells, temperature-indicating
controllers, gas detectors, analyzers, level indicators and/or
transmitters, rotational speed indicators and/or transmitters,
torque indicators and/or transmitters, (electric) current
indicators and/or transmitters, voltage indicators and/or
transmitters, and viscometers. The components and accessories can
be placed at various locations within the system.
[0081] The methods and systems of the presently disclosed subject
matter provide advantages over certain existing technologies.
Exemplary advantages include efficient production of light olefins
from naphtha and improved yield of ethylene and propylene from
naphtha feedstock by combining pyrolysis of naphtha with steam
cracking of lighter hydrocarbons.
[0082] The following example is merely illustrative of the
presently disclosed subject matter and should not be considered as
a limitation in any way.
Example
[0083] This example describes the overall mass balance of the
system according to one particular embodiment. Table 1 provides the
final mass balance for two simulations carried out using COILSIM 1D
simulations and Aspen+(v. 8.2) simulations. The first simulation
models steam cracking of a naphtha feedstock with an ethane
recycle. The second simulation models the combined pyrolysis and
steam cracking within the system according to one particular
embodiment having the components described herein above with
respect to FIG. 2.
TABLE-US-00001 Simulation Steam Cracking alone Pyrolysis + Steam
Cracking Description Final yield after steam cracking Final yield
after recycling ethane a typical naphtha feedstock with from
hydrogenation unit to steam ethane recycle from cracking reactor
and recycling C.sub.5+ hydrogenation unit. non-aromatics to
pyrolysis reactor. Feed Naphtha t/h 100 100 Effluent Hydrogen t/h
1.1 0.8 Methane t/h 15.5 16.9 Ethylene t/h 27.7 29.3 Propylene t/h
18.4 23.9 Propane t/h 0.4 0.8 iso- &1-Butene t/h 4.1 8.5
1,3-butadiene t/h 5.9 5.0 other C.sub.4 t/h 1.1 2.9 total C.sub.5
t/h 6.3 0.0 Benzene t/h 5.2 3.7 other C.sub.6 t/h 3.1 0.0
C.sub.7-C.sub.8 aromatics t/h 5.3 3.9 other C.sub.7-C.sub.8 t/h 1.4
0.0 total C.sub.9 t/h 1.0 0.8 C.sub.10+ t/h 3.5 3.5
[0084] In accordance with the disclosed subject matter, and
compared to steam cracking alone, combining the pyrolysis of
naphtha and C.sub.5+ non-aromatic hydrocarbons with the steam
cracking of lighter hydrocarbons increases the combined yield of
ethylene and propylene.
[0085] In addition to the various embodiments depicted and claimed,
the disclosed subject matter is also directed to other embodiments
having other combinations of the features disclosed and claimed
herein. As such, the particular features presented herein can be
combined with each other in other manners within the scope of the
disclosed subject matter such that the disclosed subject matter
includes any suitable combination of the features disclosed herein.
The foregoing description of specific embodiments of the disclosed
subject matter has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
disclosed subject matter to those embodiments disclosed.
[0086] It will be apparent to those skilled in the art that various
modifications and variations can be made in the systems and methods
of the disclosed subject matter without departing from the spirit
or scope of the disclosed subject matter. Thus, it is intended that
the disclosed subject matter include modifications and variations
that are within the scope of the appended claims and their
equivalents.
* * * * *