Note: Descriptions are shown in the official language in which they were submitted.
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PROCESSES AND SYSTEMS FOR STEAM CRACKING HYDROCARBON FEEDS
CROSS-REFERENCE TO RELATED APPLICATION
100011 This application claims priority to and the benefit of U.S. Provisional
Application No.
63/286,377 having a filing date of December 06, 2021., the disclosure of which
is incorporated
herein by reference in its entirety.
FIELD
100021 Embodiments disclosed herein generally relate to processes for steam
cracking
hydrocarbons for the production of olefins, particularly low molecular weight
olefins such as
to ethylene and propylene. More particularly, such embodiments relate to
processes for removing
coke deposits that form within radiant coils of a steam cracker and/or within
one or more
quench exchanger inlets during steam cracking of the hydrocarbons under a high
conversion
of ethane and/or propane to one or more other compounds.
BACKGROUND
100031 Steam cracking is a primary means used to generate ethylene and
propylene and other
products from a variety of feedstocks. Modern plants employ optimization
models and controls
to optimize profit. Neither ethane nor propane can be converted entirely to
products in a steam
cracking furnace due to the excessive formation of coke. Despite capital cost,
utility cost,
energy, and environmental benefits for increasing conversion, steam cracking
furnace
operators limit ethane conversion to 70% and limit propane conversion to 90%.
Unconverted
ethane and/or propane in the steam cracker effluent is separated therefrom,
compressed,
refrigerated, and recycled back to the steam cracker furnace for cracking to
extinction. Coking
constraints result in reduced run-lengths between decokes or mechanical
cleanings, causing
operational challenges.
100041 At increased conversion, not only would the rate of coke formation
increase, but also
coking severity changes too. Higher temperatures would result in more
dehydrogenation and
hardening of coke, resulting in coke that is more graphitic and less reactive
to combustion.
These factors would make such coke more resistant to removal via conventional
decoking
processes. If decoking does not remove coke, operators would need to use more
severe
alternative methods of decoking, including mechanical cleaning during costly
and potentially
hazardous furnace outages to remove coke from radiant coils and/or quench
exchangers. The
cost and effort associated with these alternative methods are the primary
reasons operators are
discouraged from pursuing increased conversion of ethane and/or propane to one
or more other
compounds.
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100051 There is a need, therefore, for improved processes for steam cracking
ethane to one
or more other compounds at a conversion of? 75% and/or steam cracking propane
to one or
more other compounds at a conversion of > 93% and for removing coke formed
within radiant
coils of the steam cracker and/or within one or more quench exchanger inlets.
This disclosure
satisfies this and other needs.
SUMMARY
100061 Processes and systems for steam cracking hydrocarbons are provided. In
some
embodiments, the process for steam cracking hydrocarbons can include (A)
providing an
olefins product-ion plant comprising a steam cracking furnace and an olefins
product recovery
section. A first hydrocarbon feed comprising at least one of eth.arre and
propane can be
introduced into a plurality of radiant coils disposed within the steam
cracking furnace under
first steam cracking conditions that produce a first steam cracker effluent
and deposit coke on
an inner surface of the radiant coils. A conversion of ethane, if present at a
molar concentration
in the first hydrocarbon feed equal to or greater than that of propane, to one
or more other
compounds is? 75%. Or a conversion of propane, if present at a molar
concentration in the
first hydrocarbon feed higher than that of ethane feed, to one or more other
compounds is >
93%. The introduction of the first hydrocarbon feed into at least one of the
radiant coils in the
plurality of radiant coils can be periodically stopped. A decoking feed
comprising steam and
optionally air can be introduced into the at least one of the radiant coils
under decoking process
conditions. The decoking process conditions can comprise at least one of: (i)
introducing the
decoking feed into the at least one of the radiant coils to produce a decoking
effluent having a
coil outlet temperature of > 900 C; (ii) introducing the decoking feed into
the at least one of
the radiant coils or into one or more quench exchanger inlets in fluid
communication with the
at least one of the radiant coils at a mass flux rate at the quench exchanger
inlet of > 39 kg= m-
2' second-I ; and (iii) introducing the decoking feed into the at least one of
the radiant coils while
maintaining introduction of the first hydrocarbon feed into one or more of the
radiant coils in
the plurality of radiant coils.
100071 In other embodiments, process for steam cracking hydrocarbons may
comprise
introducing a hydrocarbon feed comprising ethane, propane, or a mixture
thereof into a
plurality of radiant coils disposed within a steam. cracking furnace under
steam cracking
conditions that produce a steam cracker effluent and deposit coke on an inner
surface of the
radiant coils. A conversion of at least one of ethane, if present at a molar
concentration in the
first hydrocarbon feed equal to or greater than that of propane (based on the
total moles of
molecules in the first hydrocarbon feed), to one or more other compounds is ?
75%. Or a
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conversion of propane, if present at a molar concentration in the first
hydrocarbon feed higher
than that of ethane feed (based on the total moles of molecules in the first
hydrocarbon feed),
to one or more other compounds is > 93%. An inner surface of the radiant coils
in the plurality
of radiant coils may comprise a material that is non-catalytic to coke
generation.
[0008j In other embodiments, process for steam cracking hydrocarbons may
comprise (1)
providing an olefins production plant comprising a steam cracking furnace and
an olefins
product recovery section. In a cracking interval, a first hydrocarbon feed
comprising at least
one of ethane and propane is introduced into a plurality of radiant coils
disposed within the
steam cracking furnace under first steam cracking conditions that produce a
first steam cracker
effluent and deposit coke on an inner surface of the radiant coils. A
conversion of ethane, if
present at a molar concentration in the first hydrocarbon feed equal to or
greater than that of
propane, to one or more other compounds is 75%. Or a conversion of propane, if
present at
a molar concentration in the first hydrocarbon feed higher than that of ethane
feed, to one or
more other compounds is 93%. Online decoking in an online decoking interval of
at least
one of the radiant coils can be optionally conducted by introducing a decoking
steam there into.
Periodically introduction of the first hydrocarbon feed into at least one of
the radiant coils in
the plurality of radiant coils maybe stopped. A reference process comprising
the following may
be provided: (a) in a reference cracking interval, introducing a reference
steam cracker feed
(preferably the same as the first hydrocarbon feed) into the plurality of
radiant coils under
reference steam cracking conditions that produce a reference steam cracker
effluent and deposit
coke on the inner surface of the radiant coils, having a reference conversion
of ethane, if present
at higher molar concentration in the reference steam cracker feed than
propane, to one or more
other compounds of 75%, and a reference conversion of propane, if present, to
one or more
other compounds ofS 93%; (b) periodically stopping introduction of a reference
steam cracker
feed into at least one of the radiant coils in the plurality of radiant coils;
and (c) in a reference
offline decoking interval, introducing the decoking feed into the at least one
of the radiant coils
under reference decoking conditions. A decoking feed comprising steam and
optionally air is
introduced into the at least one of the radiant coils under decoking process
conditions such that
-2 millimeter ("mm") < AA < 2 mm, where
AA = RI(rel)*D1(ref) + R(ref)*delta(DI)+ delia(R1)*(D1(ref)+ delia(DI))¨ PI ¨
(P2 --- P2(ref));
delta(RI) R ¨ R(ret), where R is average coke deposition rate in the radiant
coils in
the process during the cracking interval, in millimeter day' (mm = day-1), and
R(ref) is average
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coke deposition rate in the radiant coils in the reference process during the
reference cracking
interval, in min=day-l;
Di(ref) is the duration of the reference cracking interval, in days;
Delta(D1) = Di - Di (ref), where Di is duration of the cracking interval, in
days;
PI is coke removed during the online decoking interval, if any, in mm;
P2 is coke removed during the offline decoking interval, in mm; and
P2(ref) is coke removed during the reference offline decoking interval, in mm.
BRIEF DESCRIPTION OF THE DRAWING
100091 So that the manner in which the above recited features of the present
invention can
be understood in detail, a more particular description of the invention,
briefly summarized
above, may be had by reference to embodiments, some of which are illustrated
in the appended
drawings. It is to be noted, however, that the appended drawings illustrate
only typical
embodiments of this invention and are therefore not to be considered limiting
of its scope, for
the invention may admit to other equally effective embodiments.
100101 The Figure depicts a schematic of an illustrative steam cracking
furnace in operation
to convert first and second hydrocarbon feeds within radiant coils disposed
within a firebox in
the stream cracking furnace, according to one or more embodiments described.
DETAILED DESCRIPTION
[001.1] It is to be understood that the following disclosure describes several
exemplary
embodiments for implementing different features, structures, and/or functions
ofthe invention.
Exemplary embodiments of components, arrangements, and configurations are
described
below to simplify the present disclosure; however, these exemplary embodiments
are provided
merely as examples and are not intended to limit the scope of the invention.
Additionally, the
present disclosure may repeat reference numerals and/or letters in the various
exemplary
embodiments and across the Figure provided herein. This repetition is for the
purpose of
simplicity and clarity and does not in itself dictate a relationship between
the various exemplary
embodiments and/or configurations discussed in the Figure. Moreover, the
exemplary
embodiments presented below can be combined in any combination of ways, i.e.,
any element
from one exemplary embodiment can be used in any other exemplary embodiment,
without
departing from the scope of the disclosure.
[0012] The indefinite article "a" or "an", as used herein, means "at least
one" unless specified
to the contrary or the context clearly indicates otherwise. Thus, embodiments
using "a
separator" include embodiments where one or two or more separators are used,
unless specified
to the contrary or the context clearly indicates that only one separator is
used. Likewise,
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embodiments using "a separation stage" include embodiments where one or two or
more
separation stages are used, unless specified to the contrary.
100131 Certain embodiments and features have been described using a set of
numerical upper
limits and a set of numerical lower limits. It should be appreciated that
ranges including the
combination of any two values, e.g, the combination of any lower value with
any upper value,
the combination of any two lower values, and/or the combination of any two
upper values are
contemplated unless otherwise indicated. Certain lower limits, upper limits
and ranges appear
in one or more claims below. All numerical values are "about" or
"approximately" the
indicated value, and take into account experimental error and variations that
would be expected
by a person having ordinary skill in the art.
[0014] As used herein, the term "hydrocarbon" means a class of compounds
containing
hydrogen bound to carbon. The term "Ca" hydrocarbon means hydrocarbon having n
carbon
atom(s) per molecule, where n is a positive integer. The term "Ca+"
hydrocarbon means
hydrocarbon having at least n carbon atom(s) per molecule, where n is a
positive integer. The
term "Ca." hydrocarbon means hydrocarbon having no more than n number of
carbon atom(s)
per molecule, where n is a positive integer. "Hydrocarbon" encompasses (i)
saturated
hydrocarbon, (ii) unsaturated hydrocarbon, and (iii) mixtures of hydrocarbons,
including
mixtures of hydrocarbon compounds (saturated and/or unsaturated), including
mixtures of
hydrocarbon compounds having different values of n.
[0015] As used herein, the term "hydrocarbon feed" means any feed that
includes
hydrocarbon and is suitable for producing C24- unsaturated hydrocarbons, e.g.,
ethylene and/or
propylene, by pyrolysis, such as by steam cracking. Typical hydrocarbon feeds
include 10%
hydrocarbon (weight basis, based on the weight of the first hydrocarbon feed),
e.g., ? 50%,
such as?. 90%, or? 95%, or 99%.
100161 "Consisting essentially of' a given material means comprising the given
material at a
concentration of? 50 wt%, preferably > 60 vvi%, preferably > 80 wt%,
preferably 90 wi%,
preferably ?: 95 wt%, based on the total weight of an identified mixture
comprising the given
material in question. Thus, a hydrocarbon feed consisting essentially of CS¨
hydrocarbons is a
hydrocarbon feed comprising C5+ hydrocarbons, in total, at an aggregate
concentration of
50 wt%, based on the total weight of the hydrocarbon feed.
[0017] An olefins production plant useful in the processes of this disclosure
can comprise
one or more steam cracker furnaces and an olefins product recovery section. A
steam cracker
furnace can comprises a radiant section and a convection section. A steam
cracker feed
comprising hydrocarbons, after optional combining with dilution steam, upon
pre-heating in
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heat exchangers, e.g., in the convection section of the steam cracker furnace,
is fed into a
plurality of radiant tubes (also known as "radiant coils") located in the
radiant section of the
steam cracker furnace. The radiant coils are heated by the thermal energy
produced by
combustion of a steam cracker fuel to an elevated temperature. Inside the
radiant coils, the first
hydrocarbon feed is subjected to steam cracking conditions including various
steam cracking
temperatures and various residence times, whereby the hydrocarbons undergo
pyrolysis
reactions to produce a steam cracker effluent exiting the steam cracker
furnace comprising
desirable olefins such as ethylene and propylene. Inside the radiant coils,
coke may be formed
and deposited on the inner surface of the radiant coils. The steam cracker
effluent can be
U) immediately quenched to stop additional undesirable reactions. The
quenched cracker effluent
can be separated into fractions, including a process gas stream rich in
hydrogen and C1-C4
hydrocarbons. The process gas stream can be supplied to the olefins product
recovery section,
where the various components are separated to produce the desirable products,
e.g., an ethylene
product stream, a propylene product stream, and the like. An ethane stream
and/or a propane
stream may be produced from the process gas strewn as well, which may be
recycled to the
stream cracker as a portion of the steam cracker hydrocarbon feed. The steam
cracker furnace
may be designed to crack a hydrocarbon feed rich in ethane, propane, naphtha,
gas oil, or even
crude oil. Switching a steam cracker designed to crack a C5+-hydrocarbon-rich
steam cracker
feed to crack an ethane-rich steam cracker feed or a propane-rich steam
cracker feed is not
2o easy.
100181 It has been surprisingly and unexpectedly discovered that one or more
hydrocarbon
feeds containing ethane and/or propane can be subjected to steam cracking
conditions within
one or more radiant coils disposed 'within a steam cracking furnace to produce
a steam cracker
effluent, where a conversion of at least one of ethane, if present at a molar
concentration in the
first hydrocarbon feed equal to or greater than that of propane, to one or
more other compounds
can be > 75%, or a conversion of propane, if present at a molar concentration
in the first
hydrocarbon feed higher than that of ethane feed, to one or more other
compounds can be >
93%, while coke produced during the steam cracking can be sufficiently removed
during a
decoking process such that the coke does not appreciably build-up so that the
steam cracker
does not require frequent (if at all) shut downs due to coke build-up that
necessitates the
mechanical removal of the coke build-up from within the radiant coils and/or
steam cracker
effluent quench exchangers. In some embodiments, steam cracking the one or
more
hydrocarbon feeds can be carried out within the plurality of radiant coils
such that a steam
cracker effluent can be produced for months, e.g., > 1 month, > 2 months, > 3
months, > 4
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months, > 5 months, > 6 months, > 8 months, or > 12 months, with periodic
decoking
operations occurring within all of the radiant coils at the same time or with
periodic decoking
operations occurring within at least one of the radiant coils while
maintaining steam cracking
of the first hydrocarbon feed within at least one other of the radiant coils
without the need to
shut down the steam cracker to mechanically remove coke built up on the inner
surfaces of the
radiant coils and/or the inner surfaces of one or more quench exchangers. In
those embodiments
where online decoking with respect to one or more of the radiant coils is
carried out, the run-
length between offline decoking of the entire furnace can be substantially
extended.
100191 In some embodiments, the one or more hydrocarbon feeds can include one
or more
relatively low molecular weight hydrocarbon (light feedstocks), particularly
those aspects
where relatively high yields of C2 unsaturates, e.g., ethylene and acetylene,
and/or C3
unsaturates, e.g., propylene and methylacetylene, can be desired. Light
feedstocks can include
substantially saturated hydrocarbon molecules having fewer than five carbon
atoms, e.g.,
ethane, propane, and mixtures thereof (e.g., ethane-propane mixtures or "E/P
mix"). For ethane
cracking, a concentration of ethane in the first hydrocarbon feed can be,
e.g., > 50 wt%, > 60
wt%, > 70i,vt%, > 75 wt%, > 80 wt%, > 85%, > 90 wt%, > 95 wt%, up to 100 wt%.
For propane
cracking, a concentration of propane in the first hydrocarbon feed can be,
e.g., 50 wt%, 60
70 wt%, > 75 wt%, 80 wt%, 85%, 90 wt%, 95 wt%, up to 100 wt%. For E/P
mix, a total concentration of ethane plus propane of 50 wt%, > 60 wt%, > 70
wt%, > 75 wt%,
> 80 wt%, > 85%, >. 90 wt%, > 95 wt%, up to 100 wt% can be used, the amount of
ethane in
the E/P mix can be > 20 wt% based on the weight of the E/P mix, e.g., of about
25 wt% to
about 75 wt%. The amount of propane in the E/P mix can be, e.g., 20 wt%, based
on the
weight of the E/P mix, such as of about 25 wt% to about 75 wt%. In some
embodiments, the
first hydrocarbon feed can be or can include, but is not limited to, a
refinery gas stream that
can include one or more C/ to C5, saturated or unsaturated hydrocarbons. In
some
embodiments, a first hydrocarbon feed can include primarily ethane, propane,
or a mixture
thereof, and a second hydrocarbon feed can include a refinery gas stream.
100201 In some embodiments, the steam cracking conditions can include a
residence time of,
e.g., from 0.01 seconds (s), 0.02 s, 0.03 s, 0.04 s, to 0.05 s, 0.06 s, 0.07
s, 0.08 s, 0.09 s, to 0.1
s, 0.2 s, 0.3 s, 0.4 5, to 0.5 S. In some embodiments, the steam cracking
conditions can include
heating the first hydrocarbon feed within the radiant coils sufficiently to
produce a steam
cracker effluent that can have a coil outlet temperature of, e.g., from 815
C, 820 C, 825 C,
830 C, to 840 C, 850 'C, 860 C, 870 C, 880 C, to 890 C, 900 C, 910 C,
920 C, or 925
'C. Generally, to achieve a given conversion of ethane, the higher the coil
outlet temperature,
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the shorter the required residence time. Likewise, to achieve a given
conversion of propane,
the higher the coil outlet temperature, the shorter the required residence
time.
100211 In some embodiments, introduction of th.e first hydrocarbon feed into
at least one of
the radiant coils in the plurality of radiant coils can be stopped
periodically. During this
periodic stoppage in the introduction of the first hydrocarbon feed, a
decoking feed that
includes steam or a mixture of air and steam can be introduced into the at
least one of the
radiant coils under decoking process conditions to remove at least a portion
of any coke
disposed on the inner walls of the at least one radiant coil and/or at least a
portion of any coke
disposed on an inner wall of one or more quench exchanger inlets in fluid
communication with
the at least one radiant coil. In some embodiments the decoking feed can.
include, e.g., from
50 wt%, 55 wt%, 60 wt%, 65 wt%, to 70 wt%, 75 wt%, 80 wt%, 85 wt%, to 90 wt%,
95 wt%,
or 100 wt% of steam, based on a combined weight of steam and the optional air.
100221 In some embodiments, the decoking process conditions can include
introducing the
decoking feed (e.g., a decoking feed comprising a mixture of steam and air)
into the at least
one of the radiant coils to produce a decoking effluent that can have a coil
outlet temperature
of > 900 C. In some embodiments, the decoking effluent can have a temperature
of, e.g., from
910 C, 920 C, 930 C, 940 C, 950 C, to 960 C, 970 C, 980 C, 990 C,
1000 C, to 1010
C, 1020 CC, 1030 C, 1040 CC, or 1050 C.
100231 In some embodiments, the decoking process conditions can include
introducing the
decoking feed (e.g., a decoking feed comprising steam and air) into the at
least one of the
radiant coils or into one or more quench exchanger inlets in fluid
communication with the at
least one of the radiant coils at a mass flux rate at the quench exchanger
inlet of > 39 kg = rn-
2-second-1. In some embodiments, the decoking feed can have a mass flux rate
at the quench
exchanger inlet of, e.g., from 40, 42, 44, 45, to 46, 48, 50, to 52, 54, 55,
to 56, 58, 60, kg-m-
2' second-I, when introduced into the at least one of the radiant coils and/or
into the one or more
quench exchanger inlets.
100241 In some embodiments, the decoking process conditions can include
introducing the
decoking feed (e.g., steam only) into the at least one of the radiant coils
while maintaining
introduction of the first hydrocarbon feed into one or more of the other
radiant coils in the
plurality of radiant coils. Such decoking process conditions can be referred
to as "online
decoking process conditions," where steam cracking of the first hydrocarbon
feed continues
within one or more radiant coils while decoking conditions are present within
one or more
radiant coils. In some embodiments, the decoking effluent can have a coil
outlet temperature
of 5 900 C. In other embodiments, the decoking effluent can have a coil outlet
temperature of
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> 900 C. In some embodiments, the decoking feed can be at a pressure of? 690
kPa-gauge, ?
750 kPa-gauge, ? 800 kPa-gauge, ?_ 850 kPa-gauge, ? 900 kPa-gauge, or ? 930
kPa-gauge
when introduced into the radiant coils. In some embodiments, steam cracking
the one or more
hydrocarbon feeds can be carried out within the plurality of radiant coils
disposed within a
furnace of the steam cracker such that a steam cracker effluent can be
continuously produced
for months, e.g., > 1 month, > 2 months, > 3 months, > 4 months, > 5 months, >
6 months, .2--
months, -? 20 months, ? 40 months.? 60 months, ? 80 months, or?. 100 months,
without
the need to shut down the steam cracker to mechanically remove coke built up
on the inner
surfaces of the radiant coils and/or the inner surfaces of one or more quench
exchangers. In
10 some embodiments, the online decoking process can include the decoking
process described in
WO Publication No. WO 2020/191253.
100251 In some embodiments, the decoking process conditions can include a
combination of
introducing the decoking feed into the at least one of the radiant coils to
produce a decoking
effluent that can have a coil outlet temperature of > 900 C and introducing
the decoking feed
into the at least one of the radiant coils or into one or more quench
exchanger inlets in fluid
communication with the at least one of the radiant coils at a mass flux rate
at the quench
exchanger inlet of > 39 kg-m-2-second4. In other embodiments, the decoking
process
conditions can include a combination of introducing the decoking feed into the
at least one of
the radiant coils to produce a decoking effluent that can have a coil outlet
temperature of >
900 C. and introducing the decoking feed into the at least one of the radiant
coils while
maintaining introduction of the first hydrocarbon feed into one or more of the
radiant coils in
the plurality of radiant coils. In other embodiments, the decoking process
conditions can
include a combination of introducing the decoking feed into the at least one
of the radiant coils
or into one or more quench exchanger inlets in fluid communication with the at
least one of the
radiant coils at a mass flux rate at the quench exchanger inlet of > 39 kg=m-
2..second-' and
introducing the decoking feed into the at least one of the radiant coils while
maintaining
introduction of the first hydrocarbon feed into one or more of the radiant
coils in the plurality
of radiant coils. In still other embodiments, the decoking process conditions
can include a
combination of introducing the decoking feed into the at least one of the
radiant coils to produce
a decoking effluent that can. have a coil outlet temperature of> 900 C,
introducing the decoking
feed into the at least one of the radiant coils or into one or more quench
exchanger inlets in
fluid communication with the at least one of the radiant coils at a mass flux
rate at the quench
exchanger inlet of > 39 kg= second-I, and introducing the decoking
feed into the at least one
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of the radiant coils while maintaining introduction of the first hydrocarbon
feed into one or
more of the radiant coils in the plurality of radiant coils.
100261 In the process of this disclosure, during the cracking interval under
steam cracking
conditions including an ethane conversion > 75% or a propane conversion > 93%,
the steam
cracking condition provides a coking severity; and during the offline decoking
interval under
decoking conditions, the decoking conditions provide a decoking severity. In
certain
embodiments, preferably the decoking severity exceeds the coking severity.
100271 In some embodiments, the process for steam cracking hydrocarbons can
include (C)
operating the olefins production plant by (C I ) first introducing a reference
hydrocarbon feed
(which may be the same as or different from the first hydrocarbon feed as
described above)
into the plurality of radiant coils under reference steam cracking conditions
that produce a
reference steam cracker effluent and convert ethane, if present at an equal or
higher molar
concentration than. propane in the reference hydrocarbon feed, to one or more
other compounds
at <75%, or propane, if present at higher concentration than ethane in the
reference hydrocarbon
feed, to one or more other compounds at <93%; and (D) adjusting step (C) to
carry out step
(13) by, e.g., adjusting the steam cracking conditions such that the
conversion of at least one of
ethane, if present at an equal or higher molar concentration than propane in
the reference
hydrocarbon feed, to one or more other compounds is a.- 75%, and propane, if
present at higher
concentration than ethane in the reference hydrocarbon feed, to one or more
other compounds
is > 93%.
100281 In some embodiments, in step (Cl), the first hydrocarbon feed is
introduced into the
plurality of radiant coils at a first quantity, in step (BI), the reference
hydrocarbon feed is
introduced into the plurality of radiant coils at a second quantity, the first
hydrocarbon feed and
the reference hydrocarbon feed have the same composition, and the second
quantity is higher
than the first quantity. Thus by adjusting the reference steam cracking
conditions to the above
described steam. cracking conditions, and accordingly increasing ethane
conversion from below
75% to at least 75%, or increasing propane conversion from below 93% to at
least 93%, the
olefins production plant processes an increased quantity of the first
hydrocarbon feed without
decreasing the run-length of the steam cracker furnace between adjacent
decoking events
requiring costly mechanical cleaning, achieving a higher productivity and
reducing the
associated potential dangers of mechanical cleaning.
100291 In other embodiments, the first hydrocarbon feed may be different from
the reference
hydrocarbon feed, the quantity of ethane in the first hydrocarbon feed
introduced into the
plurality of radiant coils in step (B1) is higher than the quantity of ethane
in the reference
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hydrocarbon feed introduced into the plurality of radiant coils in step (CI);
and/or the quantity
of propane in the first hydrocarbon feed introduced into the plurality of
radiant coils in step
(B1) is higher than the quantity of propane in the reference hydrocarbon feed
introduced into
the plurality of radiant coils in step (C1). in some of these embodiments, the
first hydrocarbon
feed can comprise ethane and/or propane at a higher concentration than the
reference
hydrocarbon feed. Thus by adjusting the reference steam cracking conditions to
the above
described steam cracking conditions, and accordingly increasing ethane
conversion from below
75% to at least 75%, or increasing propane conversion from below 93% to at
least 93%, the
olefins production plant can be adjusted from processing a reference
hydrocarbon feed
comprising a relatively low concentration of ethane/propane, such as a naphtha
feed or a gas
oil feed, to processing a gas feed such as ethane and/or propane, without
being constrained by
the capacity of the recovery section, if the recovery section was originally
designed to receive
process gas produced by cracking liquid feeds. Thus, in some embodiments, the
reference
hydrocarbon feed may consist essentially of C5+ hydrocarbons such as naphtha,
gas oil, and
the like. Liquid cracking steam cracker furnaces produce some recycle ethane (-
4 wt%) that
must be separated, while for the same amount of ethylene gas cracking plants
produce more
than double (-20-35 wt%) the recycle ethane. Therefore, a liquid cracker
moving from all
liquid feed to all gas feed will require a substantial reduction in recycle
ethane from gas
cracking. By increasing conversion, the recycle ethane rates are reduced and
more gas cracking
can be afforded to a recycle ethane or gas processing constraint.
100301 In other embodiments where step (C) is carried out before step (B),
step (B) may
further comprises: (84) separating a process gas stream comprising Cl-C4
hydrocarbons from
the first steam cracker effluent; (B5) providing a second Cl-C4-hydrocarbon-
containing stream
separate from the process gas stream; and (B6) supplying the process gas
stream and the second
Cl -C4-hydrocarbon-containing stream into the olefins production recovely
section. In certain
embodiments, the second CI-C4-hydrocarbon-containing stream may be obtained
from, e.g., a
petroleum refinery facility. In these embodiments, as a result of adjusting
the reference
cracking conditions in step (C) and implementing step (B), less ethane is
present in the process
gas stream fed into the recovery section, freeing a portion of the capacity of
the recovery section
to receive and process a second Cl -C4-hydrocarbon-containing stream., from
which valuable
products can be recovered.
[0031j In some embodiments, adjusting the steam cracking conditions can
provide an
increased production capability of ethylene, propylene, or a mixture thereof
In other
embodiments, adjusting the steam cracking conditions can provide a capability
of introducing
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or, if already introducing, increasing a throughput capability of one or more
other hydrocarbons
that produce ethane, propane, or a mixture thereof upon steam cracking for
recycle into the
plurality of radiant coils. In other embodiments, adjusting the steam cracking
conditions can
provide a capability of introducing or, if already introducing, increasing a
throughput capability
of one or more refinery gases that can include one or more saturated CI-Cs
hydrocarbons, one
or more unsaturated C1-C4 hydrocarbons, or a mixture thereof that can be
introduced into the
plurality of radiant coils. In still other embodiments, adjusting the steam
cracking conditions
can provide any combination of these benefits.
100321 In some embodiments, in addition to or in lieu of the decoking
conditions, an inner
surface of the radiant coils in th.e plurality of radiant coils and/or an
inner surface within one
or more quench exchangers can include a material that is non-catalytic to coke
generation. In
some embodiments, the radiant coils can be alumina former tubes made of an
alloy that can
include > 1.5 wt% of aluminum that have an aluminum oxide layer disposed on
the inner
surfaces thereof. In other embodiments, the radiant coils can include a layer
comprising silicon
carbide, spinel, or a combination thereof disposed on the inner surfaces
thereof. In other
embodiments, the radiant coils can include a layer comprising a spinel-type
oxide layer
disposed on the inner surfaces thereof. The spinel-type oxide layer can be or
can include, but
is not limited to, compounds having the chemical formula: Mn.Cr3_,(04, wherein
x is from 0.5
to 2, and from 60 wt% to 40 wt% of oxides of Mn and Si selected from the group
consisting of
MnO. MnSiO3, Mn2SiO4 and mixtures thereof provided that the surface contains
less than 5
w-t% of Cr203.
100331 In some embodiments, the process of this disclosure can comprise: (1)
providing an
olefins production plant comprising a steam cracking furnace and an olefins
product recovery
section; (2) operating the olefins production plant by: (2a) in a cracking
interval, introducing a
first hydrocarbon feed comprising at least one of ethane and propane into a
plurality of radiant
coils disposed within the steam cracking furnace under first steam. cracking
conditions that
produce a first steam cracker effluent and deposit coke on an inner surface of
the radiant coils,
wherein a conversion of ethane, if present at a molar concentration in the
first hydrocarbon
feed equal to or greater than that of propane, to one or more other compounds
is 75%, or a
conversion of propane, if present at a molar concentration in the first
hydrocarbon feed higher
than that of ethane feed, to one or more other compounds is 2 93%; (2b)
optionally conducting
online decoking in an online decoking interval of at least one of the radiant
coils by introducing
a decoking steam there into; (2c) periodically stopping introduction of the
first hydrocarbon
feed into at least one of the radiant coils in the plurality of radiant coils;
and (3) providing a
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reference process comprising: (3a) in a reference cracking interval,
introducing a reference
steam cracker feed (preferably the same as the first hydrocarbon feed) into
the plurality of
radiant coils under reference steam cracking conditions that produce a
reference steam cracker
effluent and deposit coke on the inner surface of the radiant coils, having a
reference conversion
of ethane, if present, to one or more other compounds of 75%, and a reference
conversion of
propane, if present, to one or more other compounds of 93%; (3b) periodically
stopping
introduction of the reference steam cracker feed into at least one of the
radiant coils in the
plurality of radiant coils; and (3c) in a reference offline decoking interval,
introducing the
decoking feed into the at least one of the radiant coils under reference
decoking conditions, (4)
introducing a decoking feed comprising steam and optionally air into the at
least one of the
radiant coils under decoking process conditions such that
-2 mm < AA < 2 mm, where
AA ¨ R I (ref.)*D I (ref) + R(ref)* delta(D I ) delta(R1)*(D1(ref) delta(D1))
¨ PI ¨
(P2 ¨ P2(ref));
delta(RI) = RI R1(ref), where RI is average coke deposition rate in the
radiant coils
in the process during the cracking interval, in min day-1, and RI (ref) is
average coke
deposition rate in the radiant coils in the reference process during the
reference cracking
interval, in mm = day -I ;
D (ref) is the duration of the reference cracking interval, in days;
delta(DI) = DI ¨ DI(ref), where DI is duration of the cracking interval, in
days;
PI is coke removed during the online decoking interval, if any, in mm;
P2 is coke removed during the offline decoking interval, in mm; and
P2(ref.) is coke removed during the reference offline decoking interval, in
mm.
10034) In some embodiments, the reference process in step (3) may have been
carried out at
the olefins production plant prior to step (2). In such case P2(ref) can be
measured. PI and P2
can be measured. In some embodiments, the reference hydrocarbon. feed has
substantially the
same composition as the first hydrocarbon feed. We have found that, by
adjusting the reference
steam cracking conditions in step (3) to the steam cracking conditions in step
(2), thus achieving
an elevated ethane conversion > 75% and/or a propane conversion > 93%, a low
coke layer
thickness change, AA, -2 mm :s: AA 2 mm., can be realized, thus achieving a
prolonged run-
length of the steam cracker furnace between adjacent mechanical cleaning of
the radiant coils,
which can be costly and potentially dangerous. Preferably, ¨I mm < AA < 1 mm.
Preferably,
¨0.5 mm < AA < 0.5 mm.
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100351 In some embodiments, the process above can comprise, in addition to
steps (1), (2),
(3), and (4), the following: (5) during a plurality of quench exchanger
decoking intervals,
feeding a quench exchanger decoking feed into a quench exchanger inlet tube
operated under
quench exchanger decoking conditions',
wherein:
the reference process further comprises: during a plurality of reference
quench
exchanger decoking intervals, feeding the quench exchanger decoking feed into
the quench
exchanger inlet tube operated under reference quench exchanger decoking
conditions;
the process further comprises selecting the quench exchanger decoking
conditions such
that:
---2 mm .5_ BB = delta(R2)*(D2(ref) + delta(D2)) (P3 P3(ret)) 2 mm, where:
delta(R2) = R2 - R2(ref), where R2 is average coke deposition rate in the
quench
exchanger inlet tube between two adjacent quench exchanger decoking intervals,
in inm-day-
1; and R2(ref) is average coke deposition rate in the quench exchanger inlet
tube in the
reference process between two adjacent reference quench exchanger decoking
intervals, in
min. day -1 ;
D2(ref) is the duration between two adjacent quench exchanger decoking
intervals, in
days;
delta(D2) - D2 - D2(ref), where D2 is the duration between two adjacent quench
exchanger decoking intervals, in days;
P3 is average coke removed during the plurality of quench exchanger decoking
intervals, in trim; and
P3(ref.) is average coke removed during the plurality of reference quench
exchanger
decoking intervals, in mm.
[00361 P3 and P3(ref) can be measured. BB represents the change of coke
deposition in the
quench exchanger in step (5) relative to the reference process. Preferably, -
1.5 mm BB S.
0.5 mm. Preferably, -1 mm :5: BB 15 mm. Preferably -0.5 mm BB S 0.5 mm. By
adjusting
the reference steam cracking conditions in step (3) to the steam cracking
conditions in step (2),
thus achieving an elevated ethane conversion > 75% and/or a propane conversion
> 93%, and
selecting the quench exchanger decoking conditions, a low coke layer change BB
in the quench
exchanger, -2 mm < BB < 2 trim, can be realized, thus achieving a prolonged
run-length of the
quench exchanger between adjacent mechanical cleaning of the quench exchanger,
which can
be costly and potentially dangerous.
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100371 Similarly, the process of this disclosure comprising steps (1), (2),
(3), (4), and
optionally step (5) can comprise one or more of the following: (i) introducing
the decoking
feed into the at least one of the radiant coils to produce a decoking effluent
having a coil outlet
temperature of > 900 C; (ii) introducing the decoking feed into the at least
one of the radiant
coils or into one or more quench exchanger inlets in fluid communication with
the at least one
of the radiant coils at a mass flux rate at the quench exchanger inlet of > 39
kg.m-2.second-1;
and (iii) introducing the decoking feed into the at least one of the radiant
coils while
maintaining introduction of the first hydrocarbon feed into one or more of the
radiant coils in
the plurality of radiant coils.
100381 The Figure depicts a schematic of an illustrative steam cracking
furnace 100 in
operation to convert a first hydrocarbon feed in line 1001 and a second
hydrocarbon feed in
line 1003, within one or more first radiant coils 1025 and within one or
second radiant coils
1027, respectively, disposed within a radiant section 1029 of the steam
cracking furnace 100,
according to one or more embodiments. A feed rate of the first hydrocarbon
feed in line 1001
can be controlled via a first flow control device 1002 and a feed rate of the
second hydrocarbon
feed in line 1003 can be controlled via a second flow control device 1004.
100391 In some embodiments, the composition of the first hydrocarbon feed in
line 1001 and
the composition of the second hydrocarbon feed in line 1003 can be the same or
different with
respect to one another. In some embodiments, at least one of the first
hydrocarbon feed in line
1001 and the second hydrocarbon feed in line 1003 can. include ethane,
propane, or a mixture
thereof. In some embodiments, the first hydrocarbon feed in line 1001 and the
second
hydrocarbon feed in line 1003 can each include ethane, propane, or a mixture
thereof In some
embodiments, the first hydrocarbon feed in line 1001 and/or the second
hydrocarbon feed in
line 1003 can include 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 75%, 80 wt%, 85
wt%, 90
wt%, 95 wt%, or more of ethane, based on a total weight of all hydrocarbons in
the first
hydrocarbon feed. In other embodiments, the first hydrocarbon reed in line
1001 and/or the
second hydrocarbon feed in line 1003 can include 30 wt%, 40 wt%, 50 wt%, 60
wt%, 70 wt%,
75%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, or more of propane, based on a total
weight of all
hydrocarbons in the first hydrocarbon feed. In some embodiments, the first
hydrocarbon feed
in line 1001 and the second hydrocarbon feed in line 1003 can include a
mixture of ethane and
propane. For example, a hydrocarbon feed that includes ethane and propane can
include at
least 75 wt% of a combined amount of ethane and propane, based on a total
weight of the first
hydrocarbon feed, where the amount of ethane in the ethane and propane mixture
can be 20
wt% based on the combined weight of the ethane and propane in the first
hydrocarbon feed. In
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another example, a hydrocarbon feed that includes ethane and propane can
include at least 75
wt% of a combined amount of ethane and propane, based on a total weight of the
first
hydrocarbon feed, where the amount of propane in the ethane and propane
mixture can be ? 20
wt%, based on the combined weight of the ethane and propane in the first
hydrocarbon feed.
[0040] In some embodiments, the first hydrocarbon feed in line 1001 and the
second
hydrocarbon feed in line 1003 can be mixed, blended, combined, or otherwise
contacted with
steam in lines 1007 and 1009, respectively, to produce first and second
hydrocarbon and steam
mixtures in lines 1011 and 1013, respectively. In some embodiments, the first
and second
hydrocarbon and steam mixtures can independently include steam in an amount in
of about 10
wt% to about 95 wt%, based on the weight of the hydrocarbon and steam mixture.
As shown,
the steam in lines 1007 and 1009 can be provided from a common source, e.g.,
steam in line
1005. In other embodiments, the steam in lines 1007 and 1009 can be provided
from different
sources. A feed rate of the steam contacted with the first hydrocarbon feed in
line 1001 can be
controlled by a third flow control device 1008 and a feed rate of the steam
contacted with the
second hydrocarbon feed in line 1003 can be controlled by a fourth flow
control device 1010.
The amount of steam contacted with the first and second hydrocarbon feeds in
lines 1001 and
1003 can be the same or different with respect to one another.
[0041] The first and second mixtures in lines 1011 and 1013 can each be heated
within one
or more convection coils 1015 and 1017, respectively, disposed within the
convection section
1019 of the steam cracking furnace 100 to produce first and second heated
mixtures via lines
1021 and 1023, respectively. In some embodiments, the first and second
mixtures in lines 1011
and 1013 can be heated to a temperature of 200 C, 300 C, 400', or 450 C to 500
C, 600 C,
700 C, or 750 C within the convection section 1019. The first and second
heated mixtures in
lines 1021 and 1023 can be further heated and subjected to steam cracking
conditions within
the one or more first radiant coils 1025 and within the one or more second
radiant coils 1027,
respectively, disposed within the radiant section 1029 of the steam cracking
furnace 100 to
produce first and second steam cracker effluents via lines 1031 and 1033,
respectively.
100421 The first radiant coil(s) 1025 and the second radiant coil(s) 1027 can
be heated by a
plurality of burners (four are shown ¨ 1035, 1037, 1039, and 1041). The
burners 1035 and
1037 can be considered as being disposed within a first segment of the radiant
section 1029
arid the burners 1039 and 1041 can be considered as being disposed within a
second segment
of the radiant section 1029. As such, the first segment of the radiant section
occupies the left
half of the radiant section 1029 and the second segment of the radiant section
1029 occupies
the right half of the radiant section 1029, as shown in the FIG. In some
embodiments, during
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operation, the burners 1035, 1037, 1039, and 1041 can be operated at
substantially the same
firing rate such that the amount of heat produced by each burner in the first
sand second
segments is substantially the same. In other embodiments, during operation,
one or more of
the burners 1035, 1037, 1039, and 1041 can be operated at different firing
rates with respect to
one or more other burners such that the amount of heat produced by each burner
is not
substantially the same.
100431 In some embodiments, the first steam cracker effluent in line 1031 can
have a first
coil outlet temperature upon exiting the first radiant coil(s) 1025 and the
second steam cracker
effluent in line 1033 can have a second coil outlet temperature upon exiting
the second radiant
coil(s) 1027. The first coil outlet temperature of the first steam. cracker
effluent in line 1.031
can be measured with a first temperature measuring device, e.g., thermocouple,
1043 and the
second coil outlet temperature of the second steam cracker effluent in line
1033 can be
measured with a second temperature measuring device, e.g., thermocouple, 1045.
100441 In some embodiments, the feed rate of the first hydrocarbon feed in
line 1001 and the
feed rate of the second hydrocarbon feed in line 1003 can be controlled based,
at least in part,
on the composition(s) of the first and second hydrocarbon feeds and/or the
first and second coil
outlet temperatures, respectively. In some embodiments, the feed rate of the
first hydrocarbon
feed in line 1001 can be reduced to increase the first coil outlet temperature
of the first steam
cracker effluent in line 1031. In other embodiments, the feed rate of the
first hydrocarbon feed
2o in line 1001 can be increased to reduce the first coil outlet
temperature of the first steam cracker
effluent in line 1031. The feed rate of the second hydrocarbon feed in line
1003 can be
controlled in a similar manner as the feed rate of the first hydrocarbon feed
in line 1001.
100451 Similar to the teed rates of the first and second hydrocarbon feeds,
the feed rate of the
steam in line 1007 and the steam in line 1009 that can be contacted with the
first hydrocarbon
feed in line 1001 and the second hydrocarbon feed in line 1003, respectively,
can be controlled
based, at least in part, on the composition(s) of the first and second
hydrocarbon feeds and the
first and second coil outlet temperatures, respectively. By controlling the
feed rate of the first
and second hydrocarbon feeds and the steam contacted therewith, the feed rate
of the heated
first and second hydrocarbon feeds introduced via lines 1021 and 1023,
respectively, can be
increased or decreased as desired to control or otherwise adjust the first
coil outlet temperature
and the second coil outlet temperature as desired.
10046i In other embodiments, the feed rate of the first hydrocarbon feed in
line 1001 and the
feed rate of the second hydrocarbon feed in line 1003, which can be the same
or different with
respect to one another, can remain substantially constant during steam
cracking. In such
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embodiment, the amount of heat produced via the burners 1035, 1037, 1039, and
1041 can be
independently adjusted to control or otherwise adjust the coil-outlet-
temperatures of the first
and second steam cracker effluents in lines 1031 and 1033. The feed rate of
the steam. in line
1007 and the steam in line 1009 that can be contacted with the first
hydrocarbon feed in line
1001 and the second hydrocarbon feed in line 1003, respectively, which can be
the same or
different with respect to one another, can also remain substantially the same
or can be
independently adjusted with respect to one another during steam cracking.
100471 In some embodiments, the steam cracking conditions can include, but are
not limited
to, one or more of: exposing the heated mixtures of the first hydrocarbon feed
and steam in line
(or a vapor phase product separated therefrom) to a temperature (as measured
at a radiant outlet
of the steam cracking furnace) of > 400 C, e.g., a temperature of about 700 C,
about 800 C,
or about 900 C to about 950 C, about 1,000 C, or about 1050 C, a pressure of
about 10 kPa-
absolute to about 500 kPa-absolute or more, and/or a steam cracking residence
time of about
0.01 second to about 5 seconds, preferably from 0.01 second to 1 second,
preferably from 0.01
second to 0.5 second.
100481 In some embodiments, the steam cracking conditions can be sufficient
produce a
steam cracker effluent and deposit coke on an inner surface of the radiant
coils 1025, 1027,
where a conversion of at least one of ethane, if present at higher
concentration than propane in
the hydrocarbon feed, to one or more other compounds is >75%, and a conversion
of propane,
if present at higher concentration than ethane in the hydrocarbon feed, to one
or more other
compounds is > 93%. Periodically the introduction of the first hydrocarbon
feed in line 1001
and/or introduction of the second hydrocarbon feed in line 1003 can be stopped
by closing the
flow control device 1002 and/or 1010, respectively.
[0049) A decoking feed that can include steam or a mixture of air and steam
can be
introduced into the first and/or second radiant coil(s) 1025, 1027 that does
not have the first
and/or second hydrocarbon feed being introduced thereto. In some embodiments,
when the
flow control device 1002 is closed, flow control device 1012 can be opened
such that air (or
other oxidant) in line 1006 can be mixed, blended, combined, or otherwise
contacted with the
steam in line 1007 to produce th.e decoking feed that can flow through the
radiant coil 1025 to
produce a decoking effluent in line 1031. In some embodiments, the decoking
effluent in line
1031 can be at a temperature of > 900 C, can be introduced into the radiant
coil 1025 and/or a
quench exchanger inlet 1049 of a quench exchanger 1051 at a mass flux at the
quench
exchanger inlet of > 39 kg.m2 second-', introduced into the radiant coil 1025
while flow of the
first hydrocarbon feed in line 1003 is maintained, or any combination thereof.
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100501 In other embodiments, when the flow control device 1004 is closed, flow
control
device 1018 can be opened such that air (or other oxidant) in line 1016 can be
mixed, blended,
combined, or otherwise contacted with the steam. in line 1009 to produce the
decoking feed that
can flow through the radiant coil 1027 to produce a decoking effluent in line
1033. In some
embodiments, the decoking effluent in line 1033 can be at a temperature of >
900 C, can be
introduced into the radiant coil 1027 and/or a quench exchanger inlet 1049 of
the quench
exchanger 1051 at a mass flux at the quench exchanger inlet of > 39 kg-m-
2=second-1,
introduced into the radiant coil 1027 while flow of the first hydrocarbon feed
in line 1001 is
maintained, or any combination thereof
100511 In some embodiments, one or more quench mediums via line 1047 can be
introduced
into the inlet 1049 of the quench exchanger 1051 and can contact the decoking
effluent, and if
present, steam cracker effluent to produce a cooled effluent via line 1053. In
other
embodiments, the quench exchanger 1051 can be an indirect heat exchange stage
such that heat
can be indirection transferred from the decoking effluent, and if present,
steam cracker effluent
to produce the cooled effluent via line 1053. In still other embodiments, the
quench exchanger
1051 can include a direct contact exchange stage and an indirect heat exchange
stage.
100521 In some embodiments, the quench medium in line 1047 that can be
contacted with
the steam cracker effluent and/or the decoking effluent can be or can include
a utility fluid. In
some embodiments, the utility fluid can be the same or similar to the utility
fluids described in
U.S. Patent Nos. 9,090,836; 9,637,694; and 9,777.227; and International Patent
Application
Publication No. WO 2018/111574.
100531 Suitable steam crackers, process gas recovery, configurations, other
equipment, and
process conditions can include those disclosed in U.S. Patent Nos.: 6,419,885;
7,560,019;
7,993,435; 8,105,479; 8,197,668; 8,882,991; 9,637,694; 9,777,227; U.S. Patent
Application
Publication Nos.: 2014/0061096; 2014/0357923; 2016/0376511; 2018/0170832;
2019/0016975; and WO Publication No.: WO 2018/111574; WO/2020/096972;
WO/2020/096974; WO/2020/096977; and WO/2020/096979. Suitable dividing walls
that can
optionally be disposed between two or more segments can include those
disclosed in U.S.
Patent No. 7,718,052.
Hydrocarbon Feeds
100541 in some embodiments, the first and/or second hydrocarbon feeds in lines
1001 and
1003, respectively, can be or can include, but are not limited to, lighter
hydrocarbons such as
Ci-05 alkanes, naphtha distillate, aromatic hydrocarbons, or any mixture
thereof. In some
embodiments, as noted above, two or more hydrocarbon feeds can be introduced
into the steam
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cracker and the two hydrocarbon feeds can be the same or different with
respect to one another.
In other embodiments, the first and/or second hydrocarbon feeds in line 1001
and 1003,
respectively, can be or can. include, but are not limited to, relatively high
molecular weight
hydrocarbons ("heavy feedstocks"), such as those that produce a relatively
large amount of
steam cracker tar ("SCT") during steam cracking. Examples of heavy feedstocks
can include
one or more of steam cracked gas oil and residues, gas oils, heating oil, jet
fuel, diesel, kerosene,
coker naphtha, steam cracked naphtha, catalytically cracked naphtha,
hydrocrackate,
reformate, raffinate reformate, Fischer-Tropsch liquids, Fischer-Tropsch
gases, distillate, crude
oil, atmospheric pipestill bottoms, vacuum pipestill streams including
bottoms, gas oil
condensates, heavy non-virgin hydrocarbon streams from refineries, vacuum gas
oils, heavy
gas oil, naphtha contaminated with crude, atmospheric residue, heavy residue,
Ca/residue
admixture, naphtha/residue admixture, gas oil/residue admixture, crude oil, or
any mixture
thereof.
100551 In some embodiments, the first hydrocarbon feed in line 1001 can
include one or more
lighter hydrocarbons and the second hydrocarbon feed in line 1003 can include
one or more
heavy feedstocks. In some embodiments, the second hydrocarbon feed in line
1003 can have
a nominal final boiling point?. 315 C, ? 399 C, ? 454 C, or? 510 C. Nominal
final boiling
point means the temperature at which 99.5 wt% of a particular sample has
reached its boiling
point. Suitable hydrocarbon feeds can be or can include those described in
U.S. Patent Nos.:
7,138,047; 7,993,435; 8,696,888; 9,327,260; 9,637,694; 9,657,239; and
9,777,227; and
International Patent Application Publication No. WO 2018/111574.
100561 In some embodiments, e.g., when the first and/or second hydrocarbon
feeds in lines
1001 and/or 1003, respectively, include certain heavy feedstocks, the system
100 can include
one or more vapor/liquid separators (sometimes referred to as flash pot or
flash drum)
integrated therewith. When used, the vapor-liquid separator can be configured
to upgrade the
first hydrocarbon feed, e.g., by upgrading the hydrocarbon and steam mixture,
upstream of the
radiant section 1029. In some embodiments, it can be desirable to integrate
the vapor-liquid
separator with the furnace when the first hydrocarbon feed includes > 1 wt% of
non-volatiles,
e.g. , 5 wt%, such as about 5 wt% to about 50 wt% of non-volatiles having a
nominal boiling
point of > 760 C. In some embodiments, it can be desirable to integrate the
vapor/liquid
separator with the furnace when the non-volatiles include asphaltenes, such as
> about 0.1 wt%
asphaltenes based on the weight of the first hydrocarbon feed, e.g., 7-2 about
5 wt%.
Conventional vapor/liquid separation devices can be utilized to do this,
though the process and
systems disclosed herein are not limited thereto. Examples of such
conventional vapor/liquid
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separation devices can include those disclosed in U.S. Patent Nos. 7,138,047;
7,090,765;
7,097358; 7,820,035; 7,311,746; 7,220,887; 7,244,871; 7,247,765; 7351,872;
7,297,833;
7,488,459; 7,312,371; 6,632,351; 7,578,929; and 7,235,705. .A vapor phase can
be separated
from the first hydrocarbon feed in the vapor/liquid separation device. The
separated vapor
phase can be conducted away from the vapor/liquid separator to the radiant
coil(s) for steam
cracking. The liquid-phase separated from the first hydrocarbon feed can be
conducted away
from the vapor/liquid separation device, e.g., for storage and/or further
processing.
Examples:
100571 The foregoing discussion can be further described with reference to the
following
U) non-limiting examples.
100581 In Example 1, ethane was steam cracked at a conversion to other
compounds of 75%
to 80% and a steam-air decoking procedure was periodically used that ensured a
mass flux at
the quench exchanger inlet exceeding 39 kg- m-2- second-I as the steam-air
mixture entered into
the inlet cones of a transfer line exchanger. A steam cracking run length of
19 to 28 days
between implementation of the steam-air decoking procedure was accomplished
with the coke
sufficiently removed during each steam-air decoking procedure such that coke
build-up was
avoided.
100591 In Example 2, ethane was steam cracked at a conversion to other
compounds of 75%
to 82% under steam cracking run lengths that were greater than 20 days between
the periodic
implementation of a steam-air decoking procedure. Radiant tubes composed of
alumina were
installed to enable the steam cracking run lengths and a sufficient amount of
coke was removed
during each steam-air decoking procedure such that coke build-up was avoided.
100601 In. Example 3, ethane was steam. cracked at a conversion to other
compounds of 75%
to 82% under steam cracking run lengths that were greater than 20 days between
the periodic
implementation of a steam-air decoking procedure that used a coil-outlet-
temperature of :>
900 C. The steam-air decoking procedure in this example was able to remove the
coke and
avoided accumulation of coke over multiple steam cracking run lengths.
100611 In Example 4, ethane was steam cracked within a plurality of radiant
coils disposed
in a steam cracker and a conversion of ethane to other compounds of 80% was
obtained and
sustained for months. To accomplish such a long steam cracking run length an
online decoking
process that only implemented a steam-only decoking procedure on a portion of
the radiant
coils at a time while steam cracking continued in the remaining radiant coils
was implemented.
In other words, less than all the radiant coils underwent decoking at any
given time while the
other radiant coils continued to receive the first hydrocarbon feed for steam
cracking. More
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particularly, steam-air decoking in which the steam-air decoking effluent had
a temperature of
> 900 C was only used once during a nearly 7 month run length.
100621 Various terms have been defined above. To the extent a term used in a
claim is not
defined above, it should be given the broadest definition persons in the
pertinent art have given
that term as reflected in at least one printed publication or issued patent.
Furthermore, all
patents, test procedures, and other documents cited in this application are
fully incorporated by
reference to the extent such disclosure is not inconsistent with this
application and for all
jurisdictions in which such incorporation is permitted.
100631 While the foregoing is directed to embodiments of the present
invention, other and
further embodiments of the invention may be devised without departing from the
basic scope
thereof, and the scope thereof is determined by the claims that follow.
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