U.S. patent application number 15/905292 was filed with the patent office on 2019-08-29 for integration of a hot oxygen burner with an auto thermal reformer.
The applicant listed for this patent is Lawrence Bool, Minish Mahendra Shah. Invention is credited to Lawrence Bool, Minish Mahendra Shah.
Application Number | 20190263659 15/905292 |
Document ID | / |
Family ID | 65441103 |
Filed Date | 2019-08-29 |
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United States Patent
Application |
20190263659 |
Kind Code |
A1 |
Shah; Minish Mahendra ; et
al. |
August 29, 2019 |
INTEGRATION OF A HOT OXYGEN BURNER WITH AN AUTO THERMAL
REFORMER
Abstract
The present invention relates to integrating a hot oxygen burner
with an auto thermal reformer of reducing in a system for
generating synthesis gas.
Inventors: |
Shah; Minish Mahendra; (East
Amherst, NY) ; Bool; Lawrence; (East Aurora,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shah; Minish Mahendra
Bool; Lawrence |
East Amherst
East Aurora |
NY
NY |
US
US |
|
|
Family ID: |
65441103 |
Appl. No.: |
15/905292 |
Filed: |
February 26, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01B 3/382 20130101;
C01B 2203/0244 20130101; C01B 3/363 20130101; C01B 2203/1241
20130101; C01B 2203/0811 20130101; C01B 2203/0216 20130101; C01B
2203/0211 20130101; C01B 2203/0827 20130101 |
International
Class: |
C01B 3/36 20060101
C01B003/36 |
Claims
1. A unit operation within a system for generating syngas,
comprising: a hot oxygen burner assembly integrated with an auto
thermal reactor for receiving a first stream of fuel and oxygen in
the hot oxygen burner to combust said fuel and generate a hot
oxygen jet; introducing a hydrocarbon stream in proximity to the
exit of the hot oxygen burner wherein said exit is disposed within
the auto thermal reactor; igniting the hydrocarbon stream with hot
oxygen, performing partial reforming of the hydrocarbon in a
non-catalytic zone of the auto thermal reactor, and completing the
reforming in a catalytic reaction zones of the of the auto thermal
reactor, thereby forming a syngas which exits the reactor at a
temperature below 2000.degree. F. and with minimal soot
formation.
2. The unit operation of claim 1, wherein the first stream of fuel
is an opportunity fuel.
3. The unit operation of claim 1, further comprising: introducing a
second stream of hydrocarbon upstream of the catalytic reaction
zone in the reactor.
4. An integrated system for generating syngas, comprising:
providing a hydrocarbon feed stream without pre-reforming and/or
heating said hydrocarbon feed stream; splitting said hydrocarbon
feed stream between a fuel stream directed to the hot oxygen burner
assembly integrated with an auto thermal reactor and a hydrocarbon
feed stream where said fuel stream is combusted with oxygen in the
hot oxygen burner assembly of an autothermal reactor to form a hot
oxygen jet; mixing the hydrocarbon feed stream with steam, and
introducing said mixture of hydrocarbon feed in a non-catalytic
region of the auto thermal reactor wherein the mixture of
hydrocarbon feed is substantially entrained in the hot oxygen jet;
igniting the hydrocarbon stream with hot oxygen to create a
reactive jet, thereby performing partial reforming of the
hydrocarbon in a non-catalytic zone of the auto thermal reactor;
and further reforming the hydrocarbon in a catalyst bed of the auto
thermal reactor to generate syngas.
5. The integrated system of claim 4, wherein the fuel stream is an
opportunity fuel.
6. The integrated system of claim 4, wherein the syngas exiting the
auto thermal reactor at a temperature below 2000.degree. F. and at
350 to 550 psia.
7. The integrated system of claim 4, wherein the fuel stream is
about 5-10% by volume of the hydrocarbon feed stream.
8. The integrated system of claim 4, wherein the syngas generated
is routed to a process gas reboiler and further downstream unit
operations.
9. An integrated system for generating syngas, comprising:
providing a main hydrocarbon feed stream without pre-reforming
and/or heating said main hydrocarbon feed stream; splitting the
main hydrocarbon feed stream into three fractions, wherein the
first fraction forms a fuel stream, the second fraction forms a
first feed stream, and the third fraction forms a second feed
stream; directing the fuel stream to the hot oxygen burner assembly
integrated with an auto thermal reactor and a hydrocarbon feed
stream where said fuel stream is combusted with oxygen in the hot
oxygen burner assembly of an autothermal reactor to form a hot
oxygen jet; routing the first feed stream to the exit of the hot
oxygen burner wherein said exit is disposed within the auto thermal
reactor, wherein the mixture of hydrocarbon feed is substantially
entrained in the hot oxygen jet; igniting the hydrocarbon stream
with hot oxygen to create a reactive jet, performing partial
reforming of the hydrocarbon in a non-catalytic zone of the auto
thermal reactor, mixing the second feed stream with steam and
routing mixture such that second feed stream mixture is entrained
into the reactive jet after the first stream is predominantly
entrained; and further reforming the hydrocarbon in a catalyst bed
of the auto thermal reactor to generate syngas.
10. The integrated system of claim 9, wherein the fuel stream is an
opportunity fuel.
11. The integrated system of claim 9, wherein the fuel stream is
about 5-10%, the first feed stream is about 50-85% and the second
feed stream is about 10-45% by volume of the main hydrocarbon feed
stream, respectively.
12. An integrated system for generating syngas, comprising: (a)
providing a main desulfurized hydrocarbon feed stream split into at
least two hydrocarbon streams wherein a first hydrocarbon stream is
routed to the hot oxygen burner and utilized therein as a fuel
which is mixed with oxygen to combust said fuel and generate a hot
oxygen jet; (b) routing the second hydrocarbon stream to a fired
heater and pre-reforming the second hydrocarbon stream into a
heated pre-reformed hydrocarbon stream; (c) routing the heated
pre-reformed hydrocarbon stream through the fired heater to
increase the temperature further, and thereafter introducing the
heated pre-reformed hydrocarbon stream in close proximity to the
hot oxygen burner wherein heated pre-reformed hydrocarbon feed is
substantially entrained in the hot oxygen jet to create a reactive
jet, thereby performing partial reforming of the hydrocarbon in a
non-catalytic zone of the auto thermal reactor; and (d) completing
the reforming in a catalytic reaction zones of the of the auto
thermal reactor, thereby forming a syngas.
13. The integrated system of claim 12, wherein the first
hydrocarbon feed stream is an opportunity fuel.
14. The integrated system of claim 12, further comprising:
splitting a third hydrocarbon stream from the desulfurized
hydrocarbon feed stream and introducing said third hydrocarbon
stream in close proximity to the hot oxygen burner disposed in the
auto thermal reformer and introducing said heated pre-reformed
hydrocarbon feed, such that the heated pre-reformed hydrocarbon
feed is entrained into the reactive jet after the second
hydrocarbon stream is predominantly entrained.
15. The integrated system of claim 1, the first and third
hydrocarbon streams are low cost opportunity fuels.
16. The integrated system of claim 10, wherein the heated
pre-reformed hydrocarbon stream of step (b) is introduced directly
in close proximity the hot oxygen burner thereby performing partial
reforming of the hydrocarbon through partial oxidation reactions in
the non-catalytic zone of the auto thermal reactor.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a novel system and process
for integrating a hot oxygen burner with an auto thermal reformer
for reducing capital expenditure as compared to existing partial
oxidation and autothermal reformer systems. The system also reduces
oxygen utilization and soot formation as compared to existing
partial oxidation system and keeps soot formation to at or below
the levels in existing autothermal reformer system. Specifically,
the system reduces the sizes of pre-reformer and fired heater or
eliminates the need for pre-reformers and/or fired heater entirely.
The system further enables the use of `opportunity fuels` (as
defined below) in the ATR.
Description of Related Art
[0002] Hydrocarbons such as natural gas, naphtha, or liquefied
petroleum gas (LPG) can be catalytically converted with steam to
obtain a synthesis gas (i.e., a mixture of hydrogen (H.sub.2) and
carbon monoxide (CO), commonly referred to as synthesis gas or
syngas. This reforming process could be done through the use of a
so-called steam methane reforming, or alternatively, partial
oxidation and auto thermal reforming processes. These generation
systems are known, and are typically utilized to obtain syngas
which may be ultimately utilized in the production of hydrogen,
methanol, ammonia, or other chemicals. These partial oxidation
("POx") and auto thermal reforming ("ATR") systems typically
generating syngas with a low H.sub.2:CO ratio in the range of about
1.5 to 2.5. The ATR system requires multiple process steps and
pieces of equipment to carry out reforming resulting in capital
intensive processes. The POx system, on the other hand, requires
single process step for reforming. However, the POx system consumes
.about.20-30% more oxygen than the ATR system per unit volume of
syngas and it requires more expensive specialized boiler due to
higher temperature of syngas exiting the POx reactor
(2500-2700.degree. F. vs. 1800-1900.degree. F. for ATR) and soot
formation within the reactor.
[0003] For instance, employees of the assignee developed a hot
oxygen burner based POx technology that drives rapid mixing in the
POx reactor using a hot oxygen jet and a patented technique to
minimize soot within the POx reactor. This is shown in U.S. Pat.
No. 9,540,240. However, HOB-based POx systems exhibit the same
disadvantages inherent to conventional POx systems (i.e., high
oxygen consumption in comparison to an ATR and higher capital
expenditures in the form of expensive boilers, and the like.
[0004] With reference to FIG. 1, a related art ATR system for
generating syngas is shown. Hydrocarbon feedstock stream (1) is
mixed with hydrogen (2) and then pre-heated to a temperature
ranging from 600-725.degree. F. in heating coils (102) and then
preheated hydrocarbon stream (5) is fed to desulfurizer (105).
Amount of hydrogen mixed with hydrocarbon is generally in 2-3% of
hydrocarbon feed on a volumetric basis and it is used for aiding
reactions within desulfurizer. Desulfurized hydrocarbon stream (8)
is mixed with steam (35) and a mixed feed (10) is preheated to 700
to 950.degree. F. in heating coils (107). The ratio of steam to
hydrocarbon (by volume) could vary from 0.4 to 1.5 (i.e.,
steam/carbon ratio). Pre-heated mixed feed (12) is fed to a
pre-reformer (110), where any C.sub.2+ hydrocarbons are reacted
with steam so as to convert them into mixture of H.sub.2, CO and
CH.sub.4. Pre-reformed feed stream (14) is further heated to
1000-1200.degree. F. in heating coils (112) within fired heater
(100) and then fed to ATR (120) as pre-heated pre-reformed feed
(16). Oxygen needed in the ATR is produced by air separation unit
("ASU") (130). Air feedstock stream (21) is separated into oxygen
stream (24) and nitrogen (31) in ASU (130). Oxygen is pre-heated to
a temperature ranging from 200 to 400.degree. F. in oxygen
preheater (135) and preheated oxygen (25) is also fed to the ATR
(120). At the heart of the autothermal reforming process is an ATR
unit operation (120) that combines a partial oxidation (POx) step
and a catalytic reforming step. Within ATR (120), preheated
pre-reformed feed (16) and oxygen (25) react to produce a syngas
mixture (20) comprising H.sub.2, CO, CO.sub.2, steam, any
unconverted CH.sub.4 and other trace components. Specifically, the
feed (16) first reacts with oxygen (25) in a POx step to consume
all the oxygen and release heat. The remaining hydrocarbons in the
feed are then reformed autothermally (not catalytically) with
CO.sub.2 and H.sub.2O present in the mixture. Since the reforming
reactions are endothermic this non-catalytic reforming results in a
reduction in gas temperature. As the reaction cools, the rates of
reaction ("kinetics") slow down causing a kinetic limit to the
achievable hydrocarbon conversion. To overcome this kinetic
constraint, the still hot, reactive, mixture is fed to a catalyst
which promotes reforming to achieve a near equilibrium degree of
reforming. Due to the nature of the catalyst bed, it is critical
that soot not enter the catalyst as it could cause fouling.
Therefore, the conditions in the non-catalytic zone of the reactor
must be maintained to prevent soot at the entrance to the catalyst.
This can be accomplished by preventing soot from forming in the
first place, or by promoting soot gasification reactions that would
consume any soot formed before the gas reaches the catalyst. For
this reason a conventional ATR requires a pre-reformer (110) to
convert higher hydrocarbons, which may be prone to sooting in the
POx step, to methane. Further the ATR may use steam injection at
higher levels than needed in the catalytic reforming step just to
reduce soot formation and enhance soot oxidation.
[0005] Syngas (20) exits the ATR at a temperature of
1800-1900.degree. F. and at pressure ranging from 350-550 psia.
Syngas (20) is then passed through process gas boiler (150) boiler
feed water heater (155) and water heater (160) in sequence to
recover thermal energy contained in syngas for steam generation.
Temperature of syngas exiting the process gas boiler ranges from
550 to 700.degree. F. Steam is typically generated at 350 to 750
psia, however, it can be generated at higher pressure if desired.
Finally, syngas is cooled to 80 to 110.degree. F. in a cooler (165)
and sent to a condensate separator (170) to separate any
condensate. Syngas (32) is then routed to a downstream process for
either making chemicals such as methanol or Fischer Trope liquids
or sent to a purification process for separating syngas into
hydrogen and carbon monoxide. Any residual fuel stream from the
downstream process is combined with make-up hydrocarbon fuel stream
to form a fuel stream for the fired heater. Burning of fuel in the
fired heater provides heat for various heating coils disposed
within the fired heater. Process water (50) is combined with
condensate (52) and heated in water heater (160) to a temperature
of 200-210.degree. F. Heated water is fed to deaerator (140) to
remove any dissolved gases. Boiler feed water (55) from deaerator
(140) is pumped to desired pressure (generally >450 psia) and
heated to temperature that is 10 to 50.degree. F. below the boiling
point of water and sent to steam drum (125). Hot boiler feed water
stream (60) from steam drum (125) is circulated through process gas
boiler (150) to generate steam. A portion of saturated steam (62)
from steam drum is superheated in heating coils (114). The
superheated steam (35) is used in the reforming process. The
remainder of saturated steam (70) is exported.
[0006] Turning to FIG. 2, a related art partial oxidation process
for generating syngas is depicted. Hydrocarbon feedstock stream (1)
is mixed with hydrogen (2) and pre-heated to 450-725.degree. F. in
hydrocarbon heating device (104) and the preheated hydrocarbon
stream (5) is fed to desulfurizer device (105). Desulfurized
hydrocarbon stream (8) along with oxygen stream (24) from the ASU
(130) is fed to the POx reactor (115). Syngas (20) from the POx
reactor exits at a temperature of 2500 to 2700.degree. F. and at
pressure ranging from 350-550 psia. Syngas stream (20) may contain
some soot due to cracking of hydrocarbons within the POx reactor.
Due to high temperature and potential presence of soot, a
specialized boiler called syngas cooler (152) is required to cool
syngas and generate steam. If steam has no value, syngas cooler can
be replaced by quench vessel (not shown) to cool syngas using
direct contact with water. Partially cooled syngas (22) at 550 to
750.degree. F. from syngas cooler (152) is used to preheat
hydrocarbon feedstock in the hydrocarbon heating device (104).
Syngas stream (23) is then routed and processed in a soot scrubber
(154). The soot scrubber includes a venturi scrubber for contacting
syngas with large quantity of water, a contact tower for additional
scrubbing section to remove residual soot from syngas and
separating soot containing water from syngas and pump for
circulating water. Soot free syngas (26) at 275 to 350.degree. F.
is then routed through a water heater (160) and cooler (165) to
cool the syngas (30) to 80-110.degree. F. and sent to the
condensate separator (170). The syngas product (32) from condensate
separator is sent to the downstream process. Process water (50) is
combined with condensate (52) and heated in water heater device
(160) to a temperature ranging from 200-210.degree. F. Heated water
is fed to deaerator (140) to remove any dissolved gases. Boiler
feed water (55) is pumped to desired pressure (generally >450
psia) and sent to syngas cooler (152) to generate steam.
Optionally, boiler feed water can be heated (not shown) close to
its boiling point against partially cooled syngas prior to feeding
it to syngas cooler.
[0007] While the partial oxidation system also produces syngas with
low H.sub.2:CO ratio in the range of about 1.5 to 2.5, the oxygen
consumption in the POx reactor is about 25% higher than the ATR
system for a comparable quantity of syngas. High grade heat at the
exit of the POx reactor is either used for steam generation or
rejected to atmosphere via quench cooling. Therefore, in order to
take advantage of the high temperatures (.about.2600.degree. F.) at
the exit of the POx reactor, an expensive boiler (i.e., syngas
cooler) is necessary.
[0008] In a conventional ATR the burner is designed to rapidly mix
the feed(s) and oxygen, often using swirl and other mixing
enhancement strategies. These strategies make staging the burner
difficult, if not impossible. In other words, in the related art
designs all the feed streams are rapidly mixed with the oxygen
without the ability to feed different streams into different parts
of the flame. For instance, in the related art U.S. Pat. No.
7,255,840 owned by the assignee of the present invention, this
rapid mixing was used to mix the hot oxygen-containing gas with the
hydrocarbon feed to reduce the mixture temperature below the
ignition temperature without igniting the mixture, thereby feeding
an oxygen and hydrocarbon containing mixture to the catalyst
bed.
[0009] In contrast, the HOB/ATR reactor of the integrated system of
the invention uses a different mixing strategy. A portion of the
fuel is burned in an oxygen stream upstream of a nozzle. The
resulting `hot oxygen` stream exits the nozzle and mixes quickly
with surroundings. Since the mixing method is that of a simple
reacting jet, it is possible to control how different streams get
mixed into the reactive portion. In the present invention, the
HOB/ATR reactor ignites the oxygen and hydrocarbon containing
mixture to perform partial oxidation reactions prior to the mixture
entering the catalyst bed. Therefore, the HOB is designed to mix
the streams more slowly than that in the related art to ensure
ignition and avoid soot formation.
[0010] To overcome the disadvantages of the related art, such as
soot formation, high oxygen consumption and the need for expensive
boilers (e.g., syngas coolers), it is an object of the present
invention to integrate an HOB with an ATR reactor in the syngas
generation system. It is another object of the invention, to
eliminate the pre-reformer and the fired heater. By using a
catalyst bed to reform a portion of natural gas by using high grade
heat, oxygen consumption per unit volume of syngas will be reduced.
In addition, exit temperature from such a reactor will be below a
temperature of .about.2000.degree. F. and will make it possible to
use less expensive process gas boiler. It is yet another object of
the invention, to improve the conventional ATR process by replacing
the burner in the ATR by HOB and enable reduction in pre-reformer
and fired heater sizes. Further object of the invention is to
enable use of unconventional fuels in a conventional ATR process by
employing HOB in the ATR reactor.
[0011] Other objects and aspects of the present invention will
become apparent to one of ordinary skill in the art upon review of
the specification, drawings and claims appended hereto.
SUMMARY OF THE INVENTION
[0012] According to an aspect of the invention, unit operation
within a system for generating syngas is provided. The unit
operation includes: a hot oxygen burner assembly integrated with an
auto thermal reactor for receiving a first stream of fuel and
oxygen in the hot oxygen burner to combust said fuel and generate a
hot oxygen jet; introducing a hydrocarbon stream in proximity to
the exit of the hot oxygen burner wherein said exit is disposed
within the auto thermal reactor; igniting the hydrocarbon stream
with hot oxygen, performing partial reforming of the hydrocarbon in
a non-catalytic zone of the auto thermal reactor, and completing
the reforming in a catalytic reaction zones of the of the auto
thermal reactor, thereby forming a syngas which exits the reactor
at a temperature below 2000.degree. F. and with minimal soot
formation.
[0013] In another aspect of the invention, an integrated system for
generating syngas, including:
[0014] providing a hydrocarbon feed stream without pre-reforming
and/or heating said hydrocabon feed stream;
[0015] splitting said hydrocarbon feed stream between a fuel stream
directed to the hot oxygen burner assembly integrated with an auto
thermal reactor and a hydrocarbon feed stream where said fuel
stream is combusted with oxygen in the hot oxygen burner assembly
of an autothermal reactor to form a hot oxygen jet;
[0016] mixing the hydrocarbon feed stream with steam, and
introducing said mixture of hydrocarbon feed in a non-catalytic
region of the auto thermal reactor wherein the mixture of
hydrocarbon feed is substantially entrained in the hot oxygen jet;
igniting the hydrocarbon stream with hot oxygen to create a
reactive jet, thereby performing partial reforming of the
hydrocarbon in a non-catalytic zone of the auto thermal reactor;
and
[0017] further reforming the hydrocarbon in a catalyst bed of the
auto thermal reactor to generate syngas.
[0018] In yet another aspect of the invention, an integrated system
for generating syngas is provided, which includes:
[0019] providing a main hydrocarbon feed stream without
pre-reforming and/or heating said main hydrocarbon feed stream;
[0020] splitting the main hydrocarbon feed stream into three
fractions, wherein the first fraction forms a fuel stream, the
second fraction forms a first feed stream, and the third fraction
forms a second feed stream;
[0021] directing the fuel stream to the hot oxygen burner assembly
integrated with an auto thermal reactor and a hydrocarbon feed
stream where said fuel stream is combusted with oxygen in the hot
oxygen burner assembly of an autothermal reactor to form a hot
oxygen jet;
[0022] routing the first feed stream to the exit of the hot oxygen
burner wherein said exit is disposed within the auto thermal
reactor, wherein the mixture of hydrocarbon feed is substantially
entrained in the hot oxygen jet;
[0023] igniting the hydrocarbon stream with hot oxygen to create a
reactive jet, performing partial reforming of the hydrocarbon in a
non-catalytic zone of the auto thermal reactor,
[0024] mixing the second feed stream with steam and routing mixture
such that second feed stream mixture is entrained into the reactive
jet after the first stream is predominantly entrained; and
[0025] further reforming the hydrocarbon in a catalyst bed of the
auto thermal reactor to generate syngas.
[0026] In yet a further aspect of the invention, an integrated
system for generating syngas is provided. The system includes:
[0027] providing a main desulfurized hydrocarbon feed stream split
into at least two hydrocarbon streams wherein a first hydrocarbon
stream is routed to the hot oxygen burner and utilized therein as a
fuel which is mixed with oxygen to combust said fuel and generate a
hot oxygen jet;
[0028] routing the second hydrocarbon stream to a fired heater and
pre-reforming the second hydrocarbon stream into a heated
pre-reformed hydrocarbon stream;
[0029] routing the heated pre-reformed hydrocarbon stream through
the fired heater to increase the temperature further, and
thereafter introducing the heated pre-reformed hydrocarbon stream
in close proximity to the hot oxygen burner wherein heated
pre-reformed hydrocarbon feed is substantially entrained in the hot
oxygen jet to create a reactive jet, thereby performing partial
reforming of the hydrocarbon in a non-catalytic zone of the auto
thermal reactor; and
[0030] completing the reforming in a catalytic reaction zones of
the of the auto thermal reactor, thereby forming a syngas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The objects and advantages of the invention will be better
understood from the following detailed description of the preferred
embodiments thereof in connection with the accompanying figures
wherein like numbers denote same features throughout and
wherein:
[0032] FIG. 1 is a process flow diagram for a related art ATR
reactor based system for generating syngas;
[0033] FIG. 2 process flow diagram for a related art POx reactor
based system for generating syngas; and
[0034] FIG. 3 depicts a process flow diagram of the present
invention where an HOB is integrated with the ATR based reactor
system for generating syngas. The system generates syngas without
employing pre-reformers and fired heater.
[0035] FIG. 3A depicts a sketch of an HOB/ATR reactor used for the
process shown in FIG. 3.
[0036] FIG. 4 depicts a process flow diagram of another embodiment
of the present invention where an HOB is integrated with the ATR
based reactor system for generating syngas. The system generates
syngas without employing pre-reformers and fired heater and two
hydrocarbon containing streams are introduced in two different
locations of an HOB/ATR reactor.
[0037] FIG. 4A depicts a sketch of an HOB/ATR reactor used for the
process shown in FIG. 4.
[0038] FIG. 5 depicts a process flow diagram of another embodiment
of the present invention where an HOB is integrated with the ATR
based reactor system for generating syngas, wherein fuel for HOB
bypasses pre-reformer and fired heater.
[0039] FIG. 5A depicts a sketch of an HOB/ATR reactor used for the
process shown in FIG. 5.
[0040] FIG. 6 depicts a process flow diagram of another embodiment
of the present invention where an HOB is integrated with the ATR
based reactor system for generating syngas, wherein fuel for HOB
and first hydrocarbon feed bypass pre-reformer and fired
heater.
[0041] FIG. 6A depicts a sketch of an HOB/ATR reactor used for the
process shown in FIG. 6.
[0042] FIG. 7 depicts a process flow diagram of another embodiment
of the present invention where an HOB is integrated with the ATR
based reactor system for generating syngas, wherein fuel for HOB
and first hydrocarbon feed bypass pre-reformer and fired heater and
pre-reformed second feed for an HOB/ATR reactor bypasses fired
heater.
DETAILED DESCRIPTION
[0043] The present invention provides for a system and method of
integrating an HOB, such as the one developed by the assignee of
the current invention, into an ATR reactor to design a syngas
generation system that minimizes capital expenditure by either
eliminating some of the process units or by reducing the sizing
thereof. The "HOB/ATR," as utilized herein, will be understood to
be a single unit operation, which is at times referred to as a hot
oxygen burner assembly integrated with an auto thermal reformer or
simply as an HOB-based reactor. The HOB's ability to control mixing
in the ATR reactor such that ignition of the oxygen-containing and
hydrocarbon containing streams and subsequent partial oxidation
reactions are achieved and soot formation is minimized is leveraged
by integrating it into the ATR reactor. In addition, the system
developed does not require a pre-reformer and a fired heater,
thereby simplifying the syngas generation system. The utilization
of a catalyst bed to reform a portion of hydrocarbon feed by
employing high grade heat results in a reduction of oxygen
consumption per unit volume of syngas generated compared to the
related art POx system. As utilized herein, hydrocarbon shall be
understood to mean a natural gas feed, or a refinery-off gas
containing various hydrocarbons as well as hydrogen, CO and
CO.sub.2 or the like. Further, the exit temperature from an HOB/ATR
reactor is below .about.2000.degree. F. and advantageously the
syngas generation system utilizes a far less expensive process gas
boiler.
[0044] In the present invention, various streams, process
conditions, and unit operations in common to the exemplary
embodiments (and denoted by the same numerals) will be omitted for
the sake of simplicity. In addition, the following terms shall be
defined as follows: "total stoichiometric ratio" or ("total SR")
shall mean moles of oxygen supplied to process/moles of oxygen
required to completely combust hydrocarbons supplied for syngas
conversion. It should be noted that in calculation of total SR,
only those hydrocarbons that are supplied for syngas conversion are
accounted and any hydrocarbons that are used as fuel in fired
heater are not counted; "burner stoichiometric ratio" or "burner
SR" shall mean moles of oxygen supplied to burner/moles of oxygen
required to completely combust hydrocarbons supplied to the
burner.
[0045] Now with reference to FIG. 3, an exemplary embodiment of the
invention where the HOB-based ATR system is presented. FIG. 3A
shows a sketch of an HOB/ATR reactor (118) to show non-catalytic
and catalytic reaction zones of the reactor and entry locations of
various feeds to the reactor. This embodiment has several
advantages over the related art discussed above. Compared to the
system of FIG. 2 wherein the integrated system includes either a
conventional or an HOB-based partial oxidation unit, the design of
process gas boiler is simplified due to lower inlet temperature
(.about.1900.degree. F. vs. 2600.degree. F.) and minimization of
soot in the syngas. The soot scrubber is not needed due to
minimization of soot formation. Compared to the system of FIG. 1
wherein an autothermal reformer is employed, the fired heater and
pre-reformer are not needed due to unique design of burner used in
the HOB/ATR reactor that minimizes soot formation without the use
of pre-reforming.
[0046] Specifically, in the exemplary embodiment of FIG. 3,
hydrocarbon feedstock stream (1) is pre-heated to 450-725.degree.
F. in hydrocarbon heating device (104) and the preheated
hydrocarbon stream (5) is routed to desulfurizer device (105) to
form hydrocarbon feed stream (8). In this exemplary embodiment of
the invention main hydrocarbon feed stream (8) is split into two
separate streams referred to as fuel stream (9) and feed stream
(11). Fuel stream (9), usually amounting to about 5-10% of main
feed stream (8), is combusted with oxygen (24) by HOB (180) to
generate a reactive hot oxygen jet. The amount of fuel (9) fed to
HOB is such that burner SR value is between 3 and 6. The combustion
product from HOB is a hot oxygen jet that contains mainly oxygen,
CO.sub.2 and H.sub.2O. The feed stream (11) is combined with a
steam stream (68) from the steam drum (125) and the combined mixed
feed (15) is introduced in close proximity to the HOB (180). One
way to ensure that mixed feed (15) is introduced in close proximity
to the HOB is by providing an annular section around HOB as shown
in FIG. 3A. Other option is to provide feed ports in the HOB/ATR
reactor close to where HOB penetrates the reactor (not shown). The
amount of oxygen is adjusted such that total SR for the reactor is
between 0.28 and 0.33. Thus, oxygen supplied is 0.28 to 0.33 times
the amount needed for complete combustion of stream 8. The reaction
between hot oxygen jet and combined mixed feed (15) in a
non-catalytic zone of the reactor generates syngas. Mixing the
streams in the non-catalytic zone in this manner, the streams (9)
and (15) are mixed sufficiently quick to avoid soot formation by
the hydrocarbons in the reactor, but sufficiently slow to avoid
soot formation by cracking of the hydrocarbons in the hot gas
stream. The syngas than enters the catalyst bed where further
reforming takes place. The syngas (20) exits the reactor at about
1800 to 1900.degree. F. and at about 350 to 550 psia. The syngas
composition depends on relative amounts of hydrocarbon feed stream
(8), oxygen (24) and steam stream (68) are supplied in the system.
Generally, the range of concentrations of various components on a
molar basis could be ranging from 40 to 60% for hydrogen, 20 to 35%
for CO, 10 to 25% for H.sub.2O, 1 to 7% for CO.sub.2, 0 to 2% of
CH.sub.4 and <1% other components including nitrogen, argon,
NH.sub.3, and HCN. The lower exit temperature from the reactor
(118), enables use of a steam generation system comprising process
gas reboiler (150) and steam drum (125) that is similar to that in
embodiment of FIG. 1 and significantly less expensive compared to
more expensive syngas cooler (152) of the embodiment of the related
art shown in FIG. 2. In addition, it eliminates the need of
pre-reformer (110) or the fired heater (100) of the related art
embodiments in FIG. 1 or the soot scrubber (154) in the related art
embodiment of FIG. 2, thereby reducing capital expenditure.
Partially cooled syngas (22) at 550 to 750.degree. F., from process
gas boiler (150) is used to preheat hydrocarbon feed in the
hydrocarbon heating device (104). Syngas stream (27) is then routed
to a boiler feed water heater (155) to preheat boiler feed water to
about 10 to 50.degree. F. below its boiling point. Syngas is
further cooled through water heater (160) and cooler (165). The
cooled syngas (30) is separated in a condensate separator to
generate syngas product (32) for further use in a downstream
process.
[0047] FIG. 4 depicts an alternative exemplary embodiment, in which
main hydrocarbon feed stream (8) is split into three fractions. One
fraction forms first fuel stream (9) with flow ranging from about
5-10% of the main hydrocarbon feed flow of stream (8). Separately,
a second fraction forms a first feed stream (11) for reactor with
flow of 50 to 85% of main hydrocarbon feed stream (8). The third
fraction forms a second feed stream (18) with flow of sufficient
quantity to achieve the total SR desired by the operator. This
second feed is combined with steam (68) to form a second feed
stream (15) for the reactor. First fuel stream (9) is introduced
into the HOB along with oxygen (24) to form a hot oxygen stream and
first feed stream (11) is introduced into a section closest to the
nozzle of the HOB (180) in reactor (118) such that this first feed
stream (11) is preferentially entrained into the hot gas jet over
second feed stream (15). The first feed stream (11) is ignited by
the hot oxygen stream to create a reactive jet, partially reforming
the hydrocarbon in a non-catalytic zone of the auto thermal
reactor. The second feed stream (15) is introduced after first feed
stream (11) has been predominantly entrained into the reactive jet.
One option for introducing second feed stream (15) is just upstream
of catalyst bed in the HOB/ATR reactor (118) as shown in FIG. 4A.
In this manner, the total SR value in the non-catalytic reaction
zone of the reactor would be similar to a conventional HOB reactor
at 0.35 to 0.37 and syngas exiting the non-catalytic reaction zone
would contain minimal soot. Thus, the soot is minimized by mixing
the streams sufficiently quick to avoid soot formation by
hydrocarbons in the reactor, but slow enough to avoid soot
formation by cracking of the hydrocarbons in the hot gas stream, as
described in detail in U.S. Pat. No. 9,540,240 B2, which is
incorporated herein in its entirety.
[0048] The syngas temperature toward the end of the non-catalytic
zone (i.e., in proximity to the non-catalytic and catalytic zone
interface) would be 2500 to 2700.degree. F. This syngas and second
feed stream (18) are mixed just upstream of the catalyst bed and
temperature of the syngas decreases to below 2100.degree. F. as a
result. This syngas then enters the catalyst zone, where thermal
energy from the syngas aids in endothermic reforming of
hydrocarbons in the second feed (18). The syngas exiting the
reactor (118) is similar in temperature, pressure and composition
to those described earlier for FIG. 3. The total SR value for the
entire reactor (non-catalytic and catalytic zones) when all the
hydrocarbon containing stream (9), (11) and (18) are considered
would be similar to that of embodiment of FIG. 3 at 0.28 to
0.33.
[0049] In the event that steam has no other use in the system, the
embodiments of FIGS. 3 and 4 are envisioned where the system
configuration for the embodiments of FIGS. 3 and 4, steam
generation equipment process gas boiler (150) and steam drum (125)
are replaced by a quench vessel (not shown), which utilizes direct
contact with water. Partially cooled syngas (22) at 550 to
750.degree. F., from process gas boiler (150) is used to preheat
hydrocarbon feed in the hydrocarbon heating device (104). Syngas
stream (27) is then routed to a boiler feed water heater (155) to
preheat boiler feed water to about 10 to 50.degree. F. below its
boiling point. Syngas is further cooled through water heater (160)
and cooler (165). The cooled syngas (30) is separated in a
condensate separator to generate syngas product (32) for further
use in a downstream process.
[0050] While FIGS. 3 and 4 shows embodiments with significant
simplifications in systems of prior art, the HOB/ATR reactor can be
deployed in a conventional ATR like system of FIG. 1 to achieve
improvements over the related art.
[0051] As illustrated in FIG. 5, an alternative exemplary
embodiment depicts a system/process configuration change to that of
related art system of FIG. 1. With reference to FIG. 5A, a sketch
of an HOB/ATR reactor (118) including HOB assembly (180) is
depicted. Since the `fuel` fed to the HOB (180) is completely
combusted before it enters HOB/ATR (118) it is possible to use
non-pre-reformed feed, or opportunity fuels as a fuel stream in
HOB. As utilized herein, "opportunity fuels" will be understood to
mean any hydrocarbon that can provide an economic advantage,
including but not limited to refinery off-gases, tail gases, and
other associated gases. As shown in FIG. 5, a portion of
desulfurized NG (8) is split as a slip stream of hydrocarbon fuel
(9), which bypasses pre-reformer (110) and is fed directly to
HOB/ATR (118), specifically into HOB assembly (180). This would
reduce the need for prereforming this portion of the total feed and
associated heating duty within fired heater.
[0052] In the exemplary embodiment of FIG. 6 a variation in the
system of FIG. 5 is provided. Starting from the detailed showing of
the HOB assembly (180) and the HOB/ATR reactor (118) in FIG. 6A the
mixing can be carefully controlled within HOB assembly (180), it is
possible to introduce a specific portion of the feed as first feed
stream (19) a hydrocarbon gas split from the hydrocarbon main
stream (8) is routed near the burner such that this feed is
entrained into the jet prior to introducing the second feed stream
(16) which consists of pre-reformed natural gas. Since reactions in
this portion of the jet are fuel lean enough to avoid soot
formation, it can be possible to feed unreformed feed into this
region without forming soot. The remaining feed can then be mixed
into the later part of the jet, after the first feed stream (19) is
predominantly entrained in the jet, and take the mixture down to
the final stoichiometric ratio. Specifically, with reference to
FIG. 6, in this embodiment, desulfurized hydrocarbon main stream
(8) is split into three fractions: hydrocarbon fuel stream (9)
which is fed to HOB/ATR (118) to support the fuel lean combustion,
specifically into HOB assembly (180); stream of hydrocarbon (19)
which is fed as first feed to HOB/ATR (118), specifically into
close proximity of HOB assembly (180) and a stream of desulfurized
hydrocarbon (18), which is first routed through fired heater (100).
Desulfurized hydrocarbon feedstock stream (18) is mixed with steam
stream (35) and processed through pre-reformer (110) and fired
heater (100) as described with respect to the embodiment of FIG. 1
to generate pre-heated pre-reformed feed stream (16), which is fed
to HOB/ATR (118) as second feed stream. In this embodiment the
reaction of the hydrocarbon fuel stream (9) and the fuel lean
combustion product from the HOB assembly (180) are not likely to
form soot. Therefore, the pre-reformer duty can be reduced, and in
some situations alternative fuels from within or outside the
integrated system could be used, in essence reducing the size of
the fired heater and/or the pre-reformer and enabling use of lower
cost fuel and/or refinery off-gas streams.
[0053] In yet another exemplary embodiment and with reference to
FIG. 7 in this configuration it is not necessary to preheat
pre-reformed feed (14) prior to feeding it to HOB/ATR (118).
Therefore, in this embodiment, pre-reformed hydrocarbon feed (14)
is directly fed to HOB/ATR (118) a second feed. Thus, eliminating
the preheating of this steam reduces the duty of the fired heater.
In addition, the total SR is increased, thereby reducing the soot
forming potential.
[0054] The invention is further explained through the following
examples, which compare the related art embodiments with the
various ones of the present invention, and those based on various
embodiments of the invention, which are not to be construed as
limiting the present invention.
EXAMPLES
[0055] Process simulations were carried out for various embodiments
described above. Main feed and product streams conditions used in
all simulations are listed in Table 1. Natural gas was used as a
hydrocarbon feed in all the simulations. All the embodiments were
compared for a fixed flow of 20 MMscfd for H.sub.2+CO content in
syngas product (32). Amounts of feed and product streams per unit
volume of syngas varied between various embodiments as indicated in
Table 2. Also, syngas compositions were somewhat different for
different embodiments as indicated by H2/CO ratios in Table 2.
TABLE-US-00001 TABLE 1 HC feed Oxygen Syngas Export steam (1) (24)
(32) (65) Temperature [F.] 70.0 100.0 100.0 505.7 Pressure [psia]
613.5 585.0 461.5 716.7 Mole Fractions Methane 0.905900 Ethane
0.036100 Propane 0.007800 i-Butane 0.003100 n-Butane 0.004500
Nitrogen 0.012595 CO2 0.030000 H2S = mercaptans 0.000005 Oxygen
0.996 Argon 0.004 H2O 1.000
[0056] Table 2 summarizes key comparative parameters of syngas
generation systems in the embodiments of FIGS. 1 through 7,
detailed above. All the embodiments of this invention (FIGS. 3
through 7) achieves H2/CO ratio of between 2.2 to 2.4. Embodiments
of FIGS. 3 and 4 consume about the same NG while consuming
.about.10% less oxygen in comparison to relate art embodiment of
FIG. 2. This improved performance is achieved by embodiments of
FIGS. 3 and 4 while simultaneously reducing process complexity by
eliminating soot scrubber and using a lower cost boiler when
compared to FIG. 2. When compared to the related art embodiments of
FIG. 1, the embodiments described with respect to FIGS. 3 and 4
consume slightly less NG and .about.22% more oxygen while
significantly lowering process complexity by eliminating fired
heater and pre-reformer.
TABLE-US-00002 TABLE 2 FIG. 1 FIG. 2 (related (related Emodiment
art) art) FIG. 3 FIG. 4 FIG. 5 FIG. 6 FIG. 7 H2 + CO in SG, 20 20
20 20 20 20 20 MMscfd NG/(H2 + CO) 0.388 0.380 0.377 0.382 0.391
0.396 0.395 O2/(H2 + CO) 0.200 0.272 0.245 0.246 0.204 0.209 0.226
H2/CO ratio 2.4 1.6 2.2 2.2 2.4 2.4 2.4 Steam export, 27584 44281
30668 31068 29921 29738 29589 lb/hr Prereformer size 1 n/a n/a n/a
0.95 0.68 0.68 Fired heater size 1 n/a n/a n/a 0.98 0.89 0.56 Steam
generation PGB SG PGB PGB PGB PGB PGB equipment cooler Soot
scrubber No Yes No No No No No required?
[0057] Embodiments of FIGS. 5, 6 and 7 consumes slightly more NG
and oxygen compared to the related art embodiment of FIG. 1 while
achieving size reduction for the fired heater between 5% and 32%
and that for the pre-reformer between 2% and 44%.
[0058] While the invention has been described in detail with
reference to specific embodiments thereof, it will become apparent
to one skilled in the art that various changes and modifications
can be made, and equivalents employed, without departing from the
scope of the appended claims.
* * * * *