U.S. patent application number 16/065295 was filed with the patent office on 2020-01-23 for methods and systems for superheating dilution steam and generating electricity.
The applicant listed for this patent is SABIC Global Technologies B.V.. Invention is credited to Thomas DIJKMANS, Romina RUGGIERO, Joris VAN WILLIGENBURG.
Application Number | 20200024525 16/065295 |
Document ID | / |
Family ID | 58016742 |
Filed Date | 2020-01-23 |
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United States Patent
Application |
20200024525 |
Kind Code |
A1 |
DIJKMANS; Thomas ; et
al. |
January 23, 2020 |
METHODS AND SYSTEMS FOR SUPERHEATING DILUTION STEAM AND GENERATING
ELECTRICITY
Abstract
Methods and system for superheating dilution steam for use in a
steam cracking furnace and generating electricity are provided.
Methods can include combusting fuel in the presence of compressed
air to produce a flue gas, wherein the flue gas drives a turbine to
produce electricity. Methods can further include superheating the
dilution steam with the flue gas, combining the dilution steam with
a feed stream including hydrocarbons to produce a mixed feed
stream, and steam cracking the mixed feed stream to produce a
product stream.
Inventors: |
DIJKMANS; Thomas; (Elsloo,
NL) ; RUGGIERO; Romina; (Elsloo, NL) ; VAN
WILLIGENBURG; Joris; (Elsloo, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SABIC Global Technologies B.V. |
Bergen op Zoom |
|
NL |
|
|
Family ID: |
58016742 |
Appl. No.: |
16/065295 |
Filed: |
January 10, 2017 |
PCT Filed: |
January 10, 2017 |
PCT NO: |
PCT/IB2017/050113 |
371 Date: |
June 22, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62280852 |
Jan 20, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 2400/20 20130101;
C10G 9/36 20130101; C10G 2300/4006 20130101; F22G 1/16
20130101 |
International
Class: |
C10G 9/36 20060101
C10G009/36; F22G 1/16 20060101 F22G001/16 |
Claims
1. A method for superheating dilution steam for use in a steam
cracking furnace using compressed air, the method comprising the
steps of: (a) combusting fuel in the presence of the compressed air
to produce a flue gas, wherein the flue gas drives a turbine to
produce electricity; (b) superheating the dilution steam with the
flue gas; (c) combining the dilution steam with a feed stream
comprising hydrocarbons to produce a mixed feed stream; and (d)
steam cracking the mixed feed stream to produce a product
stream.
2. The method of claim 1, wherein the dilution steam is superheated
to a temperature from about 400.degree. C. to about 600.degree.
C.
3. The method of claim 1, further comprising heating the feed
stream prior to the combining.
4. The method of claim 1, further comprising flash vaporizing the
mixed feed stream such that greater than about 70% of the
hydrocarbons are vaporized prior to the steam cracking.
5. The method of claim 1, further comprising heating the mixed feed
stream prior to the steam cracking.
6. The method of claim 1, wherein the product stream comprises
ethylene.
7. The method of claim 1, further comprising quenching the product
stream.
8. The method of claim 1, further comprising combusting fuel in the
presence of an oxidation agent to heat the steam cracking
furnace.
9. The method of claim 8, wherein the oxidation agent is heated
with the flue gas prior to the combusting.
10. The method of claim 9, wherein the oxidation agent is heated
with the flue gas in a heat exchanger.
11. The method of claim 10, wherein the oxidation agent is ambient
air.
12. The method of claim 10, wherein the oxidation agent is the flue
gas.
13. A system for superheating dilution steam for use in a steam
cracking furnace, the system comprising: (a) a gas turbine
generator for combusting air and fuel to produce electrical power
and a flue gas stream; (b) a superheater, coupled to the gas
turbine generator, for transferring heat from the flue gas stream
to a dilution steam line; (c) a radiant coil for placement within
the steam cracking furnace; and (d) a feed line, wherein the
dilution steam line is combined with the feed line upstream from
the radiant coil to form a mixed feed line, and wherein the mixed
feed line is coupled to the radiant coil.
14. The system of claim 13, wherein the gas turbine generator
comprises a compressor for compressing the air.
15. The system of claim 13, wherein the steam cracking furnace
comprises a radiant section and a convection section, and wherein
the radiant coil is within the radiant section, further comprising:
(a) a feed preheater within the convection section for heating the
feed line; and (b) a mixed preheater within the convection section
for heating the mixed feed line.
16. The system of claim 15, further comprising a second mixed
preheater for heating the mixed feed line.
17. The system of claim 15, further comprising: (a) a product line,
coupled to the radiant coil, comprising steam cracking products;
and (b) a transfer line exchanger, coupled to the product line, for
quenching the steam cracking products by transferring heat to a
water feed line to produce a steam line.
18. The system of claim 17, wherein the water feed line is coupled
to an economizer within the convection section.
19. The system of claim 18, wherein the steam line is coupled to a
superheater within the convection section.
20. The system of claim 17, wherein: (a) the water feed line is
coupled to an economizer within the convection section and a steam
drum; (b) the steam line is coupled to the steam drum for
separating steam from the steam line to generate a second steam
line; and (c) the second steam line is coupled to a superheater
within the convection section.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of U.S.
Provisional Application No. 62/280,852 filed Jan. 20, 2016. The
contents of the referenced application are incorporated into the
present application by reference.
FIELD
[0002] The disclosed subject matter relates to methods and systems
for superheating dilution steam and generating electricity.
BACKGROUND
[0003] During steam cracking operations, a hydrocarbon feedstock
can be diluted with steam and thermally cracked to form lighter
and/or unsaturated hydrocarbons. The presence of dilution steam can
reduce coke formation. Dilution steam can also decrease the partial
pressure of the hydrocarbons and thereby shift the reaction
equilibrium to favor desired products and reduce byproduct
formation. Additionally, dilution steam can be used to vaporize the
hydrocarbon feedstock, which can reduce fouling in certain
downstream heaters and reactors.
[0004] Because dilution steam can be used to vaporize the
hydrocarbon feedstock, it can be desirable to provide high
temperature dilution steam to promote complete vaporization.
Certain methods of heating or superheating dilution steam are known
in the art. For example, certain methods can heat dilution steam
using coils or heat exchangers within the convection section of the
steam cracking furnace. However, this method can be energy
intensive and there is interest in developing efficient methods of
generating superheated dilution steam.
[0005] Electrical energy can be generated, e.g., using a gas
turbine generator, by combusting fuel to produce flue gas to drive
a turbine. Certain methods of generating steam while producing
electrical energy are known in the art. For example, U.S. Pat. No.
5,647,199 discloses a system for combined-cycle power generation in
which each power generation unit includes a gas turbine that
produces flue gas, a steam generator for producing high pressure
steam from the flue gas, and a high pressure steam turbine for
producing electricity from the high pressure steam. U.S. Pat. No.
5,669,216 discloses a process including performing an endothermic
reaction to produce fuel, and then combusting the fuel to drive a
gas turbine to produce mechanical and/or electrical energy. The
process can include generating steam using the flue gas from the
gas turbine. International Patent Publication No. WO2015/128035
discloses integrating a gas turbine and a steam cracking furnace.
The method can include indirectly quenching the product stream from
the steam cracking furnace in a transfer line exchanger to produce
a mixture of water and steam, separating the water and steam in a
steam drum, and using the flue gas from the gas turbine to
superheat the steam from the steam drum.
[0006] However, there remains a need for improved techniques for
efficiently generating and superheating dilution steam for a steam
cracking process.
SUMMARY OF THE DISCLOSED SUBJECT MATTER
[0007] The disclosed subject matter provides techniques for
superheating dilution steam and generating electricity, including
by integrating a steam cracking furnace and a gas turbine
generator.
[0008] In certain embodiments, an exemplary method of superheating
dilution steam for use in a steam cracking furnace includes
combusting fuel in the presence of compressed air to produce a flue
gas and using the flue gas to drive a turbine to produce
electricity. The method can further include superheating dilution
steam using the flue gas, combining the dilution steam with a
hydrocarbon feed stream to produce a mixed feed stream, and steam
cracking the mixed feed stream to produce a product stream.
[0009] In certain embodiments, the method can further include
compressing ambient air for the combustion. The dilution steam can
be superheated to a temperature from about 400.degree. C. to about
600.degree. C. The feed stream can be heated prior to combining the
dilution steam with the feed stream to produce a mixed feed
stream.
[0010] In certain embodiments, the method can further include flash
vaporizing the mixed feed stream such that greater than about 70%
of the hydrocarbons are vaporized prior to steam cracking the mixed
feed stream. The mixed feed stream can be heated prior to steam
cracking. After steam cracking, the product stream can include
ethylene. The method can further include quenching the product
stream.
[0011] In certain embodiments, the method can further include
combusting fuel in the presence of an oxidation agent to heat the
steam cracking furnace. The oxidation agent can be heated using the
flue gas. In particular embodiments, the oxidation agent is ambient
air. In other particular embodiments, the oxidation agent is the
flue gas.
[0012] The presently disclosed subject matter also provides systems
for superheating dilution steam for use in a steam cracking
furnace. In certain embodiments, an exemplary system includes a gas
turbine generator for combusting air and fuel to produce electrical
power and a flue gas stream. The system can further include a
superheater, coupled to the gas turbine generator, for transferring
heat from the flue gas stream to a dilution steam line. The system
can further include a radiant coil within the steam cracking
furnace, and a feed line, where the dilution steam line is combined
with the feed line upstream from the radiant coil to form a mixed
feed line, and where the mixed feed line is coupled to the radiant
coil.
[0013] In certain embodiments, the gas turbine generator can
include a compressor for compressing air. The steam cracking
furnace can include a radiant section and a convection section, and
the radiant coil can be within the radiant section. In certain
embodiments, the convection section of the fired heater can further
include a feed preheater for heating the feed line and a mixed
preheater for heating the mixed feed line. The convection section
can further include a second mixed preheater for further heating
the mixed feed line.
[0014] In certain embodiments, the system can further include a
product line, coupled to the radiant coil, for transferring the
steam cracking products to a transfer line exchanger. The transfer
line exchanger can be for quenching the steam cracking products by
transferring heat to a water feed line to produce a steam line. The
water feed line can be coupled to an economizer within the
convection section of the steam cracking furnace. The steam line
can be coupled to a superheater within the convection section of
the steam cracking furnace. In certain embodiments, the water feed
line can be coupled to both an economizer and a steam drum and the
steam line can also be coupled to the steam drum for separating
steam from the steam line. The steam from the steam line can be
directed to a superheater within the convection section of the
steam cracking furnace.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 depicts a method of superheating dilution steam and
generating electricity according to one exemplary embodiment of the
disclosed subject matter.
[0016] FIG. 2 depicts a system for superheating dilution steam and
generating electricity according to one exemplary embodiment of the
disclosed subject matter.
[0017] FIG. 3 provides a graphical representation of the remaining
liquid fraction in the feed stream after contact with dilution
steam having temperatures from about 200.degree. C. to about
475.degree. C., in accordance with an example embodiment of the
disclosed subject matter.
DETAILED DESCRIPTION
[0018] The presently disclosed subject matter provides techniques
for superheating dilution steam and generating electricity,
including by integrating a steam cracking furnace and a gas turbine
generator.
[0019] 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 includes combusting fuel in the
presence of compressed air to produce a flue gas 101. The air can
be ambient air. The fuel can be a suitable fuel for a combustion
reaction in the presence of air, for example, the fuel can be a
hydrocarbon mixture such as petroleum, gasoline, diesel, natural
gas or a fuel gas, which can be produced as a byproduct from an
ethylene plant. For example, the fuel gas can contain hydrogen and
methane. In certain embodiments, the fuel gas can be syngas, which
contains carbon monoxide and hydrogen. The syngas can be produced
by the gasification of coal or petroleum products.
[0020] The flue gas can include oxygen, carbon dioxide, steam, and
uncombusted fuel. For example, the flue gas can contain from about
5% to about 18%, from about 10% to about 16%, or from about 13% to
about 15% oxygen by volume. The flue gas can drive a turbine to
generate mechanical work and/or electricity. The flue gas can have
a temperature from about 300.degree. C. to about 800.degree. C.,
from about 350.degree. C. to about 700.degree. C., or from about
400.degree. C. to about 650.degree. C. In certain embodiments, the
temperature of the flue gas can be increased, e.g., using a duct
burner. For example, the temperature of the flue gas can be
increased to about 850.degree. C.
[0021] 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.
[0022] The method 100 can further include superheating dilution
steam using the flue gas 102. For example, heat can be transferred
from the flue gas to the dilution steam, e.g., in a boiler or heat
exchanger. The dilution steam can be superheated to temperatures
ranging from about 250.degree. C. to about 750.degree. C., from
about 350.degree. C. to about 650.degree. C., or from about
400.degree. C. to about 600.degree. C.
[0023] While superheating the dilution steam, the flue gas can be
cooled to a temperature from about 110.degree. C. to about
400.degree. C., or from about 150.degree. C. to about 300.degree.
C. The cooled flue gas can be used to preheat the combustion gas
used in the steam cracking furnace. Alternatively, the cooled flue
gas can be used as a combustion gas in the steam cracking furnace.
Additionally or alternatively, the cooled flue gas can be used to
generate low pressure steam.
[0024] The method 100 can further include combining the dilution
steam with a feed stream including a hydrocarbon feedstock to
produce a mixed feed stream 103. The hydrocarbon feedstock can
include paraffins, olefins, naphthenes, and/or aromatics. The
hydrocarbon feedstock can be light or heavy, i.e., can have a
boiling point ranging from about 30.degree. C. to about 500.degree.
C. In certain embodiments, the feedstock can be a hydrocarbon
stream that is rich in olefins, paraffins, isoparaffins, and/or
naphthenes. The feedstock can further include up to about 30 wt-%
aromatics. In certain embodiments, the feedstock can contain from
about 0 wt-% to about 30 wt-% olefins and/or from about 0 wt-% to
about 100 wt-% n-paraffins and/or from about 0 wt-% to about 100
wt-% isoparaffins and/or from about 0 wt-% to about 30 wt-%
aromatics. The hydrocarbon feedstock can originate from various
sources, for example from natural gas condensates, petroleum
distillates, coal tar distillates, peat and/or a renewable source.
For example, the hydrocarbon feedstock can include light naphtha,
heavy naphtha, straight run naphtha, full range naphtha, delayed
coker naphtha, gas condensates, coker fuel oil and/or gas oils,
e.g., light coker gas oil and heavy coker gas oil. For further
example, the hydrocarbon feedstock can include a hydrocarbon
product from the synthesis of syngas, e.g., from Fischer Tropsch
synthesis and/or the gasification of hydrocarbon material.
[0025] The dilution steam can be combined with the feed stream in a
certain steam to hydrocarbon weight ratio. For example, the weight
ratio of steam to hydrocarbons can be from about 0.1:1 to about
1:1. In particular embodiments, the ratio of steam to hydrocarbons
is about 0.35:1.
[0026] In certain embodiments, the feed stream can be heated prior
to combination with the dilution steam. For example, the feed
stream can be heated in the convection section of a steam cracking
furnace. The feed stream can be heated to a temperature of about
100.degree. C. to about 200.degree. C. prior to combination with
the dilution steam.
[0027] The method 100 can further include flash vaporizing the
mixed feed stream 104, i.e., the combination of the hydrocarbon
feedstock and the dilution steam. Liquid in the mixed feed stream
can be vaporized by contact with the superheated dilution steam.
The extent of vaporization can depend in part on the temperature of
the superheated dilution steam. FIG. 3 provides a graphical
representation of the remaining liquid fraction after contact with
dilution steam having temperatures from about 200.degree. C. to
about 475.degree. C. In certain embodiments, after flash
vaporization, the mixed feed stream can be less than about 35%,
less than about 25%, less than about 15%, less than about 10%, less
than about 5%, less than about 3%, or less than about 1% liquid. In
certain embodiments, greater than about 50%, greater than about
60%, greater than about 70%, or greater than about 80% of the
hydrocarbons in the mixed feed stream are vaporized. In certain
embodiments, the mixed stream is completely vaporized.
[0028] In certain embodiments, the method can further include
heating the mixed feed stream. For example, the mixed feed stream
can be heated to a temperature of about 500.degree. C. to about
700.degree. C. In certain embodiments, the mixed feed stream can be
further vaporized as it is heated.
[0029] The method 100 can further include steam cracking the mixed
feed stream to generate a product stream 105. For example, the
mixed feed stream can be steam cracked in the radiant section of a
steam cracking furnace. The mixed feed stream can be steam cracked
at a temperature from about 600.degree. C. to about 1000.degree.
C., from about 700.degree. C. to about 900.degree. C., or from
about 750.degree. C. to about 850.degree. C.
[0030] The product stream can include the steam cracking products.
For example, the product stream can include light olefins, e.g.,
ethylene. The product stream can further include other olefins,
e.g., propylene and butene, paraffins, e.g., methane, ethane,
propane, and butane, dienes, e.g., butadiene, and/or alkynes, e.g.,
acetylene, methylacetylene and vinylacetylene. In certain
embodiments, the product stream can further include other
components, for example, hydrogen, carbon monoxide, carbon dioxide,
hydrogen sulfide, benzene, toluene, xylenes, ethylbenzene, styrene,
pyrolysis gasoline, and/or pyrolysis fuel oil.
[0031] The method 100 can further include quenching the product
stream 106. For example, the product stream can be quenched to cool
the steam cracking products. The product stream can be cooled to a
temperature of about 180.degree. C. to about 500.degree. C.
[0032] In certain embodiments, the product stream can be cooled by
indirect heat transfer, e.g., by transferring heat from the product
stream to another stream. In certain embodiments, heat can be
transferred to a stream containing water, e.g., from a steam drum.
In particular embodiments, the water can be preheated prior to
quenching the product stream. For example, the water can be
preheated in the convection section of the steam cracking furnace.
Any steam produced by quenching the product stream can be further
superheated, e.g., in the convection section of the steam cracking
furnace. In certain embodiments, the product stream can be cooled
to a temperature of about 300.degree. C. to about 500.degree. C. by
indirect heat transfer, and then subsequently cooled by direct oil
quenching, e.g., to a temperature of about 200.degree. C.
[0033] FIG. 2 is a schematic representation of a system according
to another non-limiting embodiment of the disclosed subject matter.
The system 200 can include a gas turbine generator for combusting
air and fuel to produce electrical power. The gas turbine generator
can include a compressor 220, a combustion chamber 221, and a
turbine 222. The compressor and turbine can be operated on a single
shaft 223. A transfer line 201 can be coupled to the compressor for
providing air to the compressor. One or more transfer lines 202 can
be coupled to the combustion chamber for providing compressed air
and fuel for combustion. The combustion can produce a flue gas,
which can be used to drive the turbine. A transfer line 203 can
transfer flue gas from the combustion chamber to the turbine.
[0034] "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.
[0035] The system 200 can further include a superheater 230,
coupled to the gas turbine generator, e.g., via a transfer line
204. A feed line 206 can also be coupled to the superheater for
providing steam. The superheater can include one or more heat
exchangers. The one or more heat exchangers can be any type
suitable for heating gaseous or liquid streams. For example, but
not by way of limitation, such heat exchangers include shell and
tube heat exchangers, plate heat exchangers, plate and shell heat
exchangers, adiabatic wheel heat exchangers, and plate fin heat
exchangers. In certain embodiments, the transfer line 204 for
transferring flue gas to the superheater can include one or more
duct burners to provide additional heat to the flue gas.
[0036] The system can further include a steam cracking furnace 240
coupled to the superheater 230, i.e., via a transfer line 207. An
exhaust line 205 can be coupled to the superheater 230 for removing
cooled flue gas from the superheater. In certain embodiments, the
exhaust line can be coupled to a heat exchanger for heating
combustion air, i.e., a combustion gas line coupled to the steam
cracking furnace 240. In alternative embodiments, the exhaust line
is coupled to the steam cracking furnace and the flue gas is used
as combustion gas in the steam cracking furnace.
[0037] The steam cracking furnace 240 can include a radiant section
and a convection section. The radiant section can include one or
more burners 247, which may be within a firebox. The radiant
section can include a radiant coil 246. The convection section can
also include one or more coils 241, 242, 243, 244, 245. The coils
can be made of any suitable material and have any suitable
thickness for the transfer of heat from the furnace. The coils can
also include extended surfaces, e.g., fins, to increase heat
transfer.
[0038] A feed line 208 can be coupled to the furnace for
transferring hydrocarbons to the convection section. In certain
embodiments, the feed line can be coupled to a feed preheater 241,
i.e., a coil, for heating the hydrocarbons in the convection
section. The feed line 208 can be combined with the transfer line
207 from the superheater 230 to form a mixed feed line 209
containing hydrocarbons and dilution steam.
[0039] The mixed feed line 209 can be coupled to a mixed preheater
243, i.e., a coil, for heating the hydrocarbons and dilution steam.
This preheater can be termed the "upper mixed preheater." In
certain embodiments, the mixed feed line can be coupled to a second
mixed preheater 245, i.e., a coil, for further heating the
hydrocarbons and dilution steam. This preheater can be termed the
"lower mixed preheater." The system 200 can further include a
radiant coil 246 downstream from one or more preheaters 241, 243,
245.
[0040] A product line 210 can be coupled to the radiant coil 246
for transferring the steam cracking products from the furnace 240.
The product line 210 can be further coupled to a transfer line
exchanger 250. The transfer line exchanger can be a heat exchanger,
e.g., a shell and tube heat exchanger. In particular embodiments,
the transfer line exchanger can be a Borsig transfer line
exchanger, an Alstom exchanger, a Shaw quench system, or a KBR
millisecond primary quench exchanger.
[0041] The transfer line exchanger 250 can be coupled to a steam
drum. A water feed line 212 can provide water to the steam drum. In
certain embodiments, the water feed line can transfer steam and/or
water from the transfer line exchanger 250. In certain embodiments,
the water feed line can be coupled to an economizer 242 upstream
from the transfer line exchanger. The economizer can be a coil
within the convection section of the steam cracking furnace 240.
The product line 210 and the water feed line 212 can exchange heat
within the transfer line exchanger. A cooled product line 211 can
remove cooled steam cracking products from the transfer line
exchanger. A transfer line 213 can transfer the heated water (and
steam, if any) to a superheater 244, i.e., a coil, within the
convection section of the steam cracking furnace. Another transfer
line 214 can transfer steam from the superheater 244 to the steam
drum.
[0042] 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. 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, pressure transmitters, thermowells,
temperature-indicating controllers, gas detectors, analyzers and
viscometers. The components and accessories can be placed at
various locations within the system.
[0043] The methods and systems of the presently disclosed subject
matter can provide advantages over certain existing technologies.
Exemplary advantages include efficient superheating of dilution
steam for steam cracking operations and generation of
electricity.
[0044] The following example provides methods of producing
superheated dilution steam and electricity in accordance with the
disclosed subject matter. However, the following example is merely
illustrative of the presently disclosed subject matter and should
not be considered as a limitation in any way.
Example: Dilution Steam Generation with and without Gas Turbine
[0045] Three steam cracking processes were simulated. In each
simulation, the feed stream was preheated in the convection section
of a fired heater. The feed stream was combined with dilution steam
to form a mixed feed stream, and the mixed feed stream was fed to
an upper mixed preheater and lower mixed preheater. In the first
simulation, the dilution steam was not superheated prior to
combination with the feed stream. In the second simulation, the
dilution steam was superheated in a fired heater (having an
efficiency of 90%) to 400.degree. C., 500.degree. C., and
600.degree. C. In the third simulation, the dilution steam was
superheated using flue gas from a gas turbine generator to
400.degree. C., 500.degree. C., and 600.degree. C. All three
simulations were repeated with light feedstock (i.e., having a
boiling point from 30.degree. C. to 260.degree. C.) and heavy
feedstock (i.e., having a boiling point from 30.degree. C. to
390.degree. C.). Table 1 shows comparative data from the
simulations.
TABLE-US-00001 TABLE 1 Comparative data with no dilution steam
superheater, with fired heater, and with gas turbine generator No
DSSH DSSH with heater DSSH with gas turbine Light feedstock with BP
between 30.degree. C. and 260.degree. C. T.sub.steam 200 400 500
600 400 500 600 Fuel furnace (kg hr.sup.-1) 37590 36800 36530 36030
36800 36530 36030 Fuel heater or gas turbine 0 888 1350 1824 1715
2602 3552 (kg hr.sup.-1) Total fuel (kg hr.sup.-1) 37590 37688
37880 37854 38515 39132 39582 Liquid after flash entering upper
14.2 1 0 0 1 0 0 mixed preheater (% dry) Liquid entering lower
mixed 0 0 0 0 0 0 0 preheater (% dry) Electricity (MW) 0 0 0 0 7.27
11.09 15.01 Heavy feedstock with BP between 30.degree. C. and
390.degree. C. T.sub.steam 200 400 500 600 400 500 600 Fuel furnace
(kg hr.sup.-1) 37060 36190 35800 35320 36190 35800 35320 Fuel
heater or gas turbine 0 888 1350 1824 1715 2602 3552 (kg hr.sup.-1)
Total fuel (kg hr.sup.-1) 37060 37078 37150 37144 37905 38402 38872
Liquid after flash entering upper 44.6 30.5 23.6 17.2 30.5 23.6
17.2 mixed preheater (% dry) Liquid entering lower mixed 7.5 2.3
1.0 0.5 2.3 1.0 0.5 preheater (% dry) Electricity (MW) 0 0 0 0 7.27
11.09 15.01
[0046] As shown in Table 1, as the temperature of dilution steam
increases, the liquid fraction entering the upper mixed preheater
decreases for both the light and heavy feedstock. Additionally, the
liquid fraction entering the lower mixed preheater decreases for
the heavy feedstock.
[0047] Although compared to the fired heater, the gas turbine
generator uses more fuel, it also produces electricity. If the
additional fuel is attributed entirely to electricity generation,
the electricity is generated with an efficiency between 60% and
80%.
[0048] 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.
[0049] 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.
* * * * *