U.S. patent application number 11/694309 was filed with the patent office on 2008-10-02 for process and system for redcuing the olefin content of a hydrocarbon feed gas and production of a hydrogen-enriched gas therefrom.
Invention is credited to Harald Klein, Nicholas Musich, Raju S. Natarajan.
Application Number | 20080237090 11/694309 |
Document ID | / |
Family ID | 39792394 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080237090 |
Kind Code |
A1 |
Musich; Nicholas ; et
al. |
October 2, 2008 |
PROCESS AND SYSTEM FOR REDCUING THE OLEFIN CONTENT OF A HYDROCARBON
FEED GAS AND PRODUCTION OF A HYDROGEN-ENRICHED GAS THEREFROM
Abstract
Olefins can impose deleterious effect on hydrocarbon reforming
processes used to generate hydrogen-enriched gas, and thus are
converted into saturated compounds. Since the hydrogenation process
to convert the olefins into saturated compound, difficulties arise
in attempting to regulate the temperature of the hydrogenation. To
facilitate temperature regulation, the hydrogenation reaction is
carried out in a shell-tube reactor, containing catalyst-filled
tubes, which is operated under isothermal or essentially isothermal
conditions. Preferably, the heat exchange medium introduced into
the shell side of the reactor to regulate the hydrogenation
temperature is boiling water.
Inventors: |
Musich; Nicholas; (Marietta,
GA) ; Natarajan; Raju S.; (Acworth, GA) ;
Klein; Harald; (Wolfratsheausen, DE) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD., SUITE 1400
ARLINGTON
VA
22201
US
|
Family ID: |
39792394 |
Appl. No.: |
11/694309 |
Filed: |
March 30, 2007 |
Current U.S.
Class: |
208/89 ;
196/46 |
Current CPC
Class: |
C10G 45/00 20130101;
C10G 45/08 20130101; C01B 2203/1247 20130101; C01B 39/12 20130101;
C01B 39/06 20130101; C01B 2203/1258 20130101; C01B 2203/1241
20130101; C01B 3/34 20130101; C01B 2203/0233 20130101; C07C 5/03
20130101; C01B 2203/0283 20130101 |
Class at
Publication: |
208/89 ;
196/46 |
International
Class: |
C10G 45/26 20060101
C10G045/26 |
Claims
1. A process for subjecting an olefin containing gas to a hydrogen
treatment wherein olefin compounds are converted into saturated
compounds, said process comprising: introducing hydrogen and a
hydrocarbon feed gas comprising olefins, alkanes, hydrogen,
CO.sub.2, and sulfur compounds into a hydrotreater wherein olefins
are converted into saturated compounds and organic sulfur compounds
are converted into H.sub.2S; wherein the hydrotreater is a shell
and tube catalytic reactor containing catalyst filled tubes, the
hydrogen and hydrocarbon feed gas being introduced into the
catalyst filled tubes, and the shell having at least one inlet for
introduction of a heat exchange medium to cool the catalyst filled
tubes, and at least one outlet for removal of the heat exchange
medium, and wherein the hydrocarbon feed gas is introduced into the
catalyst filled tubes at an inlet temperature of about 400 to
525.degree. F.; and removing the hydrocarbon feed gas from the
catalyst filled tubes of the hydrotreater at a temperature that
differs from the inlet temperature by no more than 30.degree.
F.
2. A process according to claim 1, wherein the temperature of the
hydrocarbon feed gas removed from the catalyst filled tubes of the
hydrotreater differs from the inlet temperature by no more than
15.degree. F.
3. A process according to claim 1, wherein the temperature of the
hydrocarbon feed gas removed from the catalyst filled tubes of the
hydrotreater differs from the inlet temperature by no more than
10.degree. F.
4. A process for treating a hydrocarbon gas to reduce the olefin
content and organic sulfur compound content thereof, the process
comprising: introducing hydrogen and a hydrocarbon feed gas
comprising olefins, alkanes, hydrogen, CO.sub.2, and sulfur
compounds, into a hydrotreater wherein olefins are converted into
saturated compounds and organic sulfur compounds are converted into
H.sub.2S; wherein the hydrotreater is a shell and tube catalytic
reactor containing catalyst filled tubes, the hydrogen and
hydrocarbon feed gas being introduced into the catalyst filled
tubes, and the shell having at least one inlet for introduction of
a heat exchange medium to cool the catalyst filled tubes, and at
least one outlet for removal of the heat exchange medium, and
wherein the hydrocarbon feed gas is introduced into the catalyst
filled tubes at an inlet temperature of about 400 to 525.degree.
F.; removing the hydrocarbon feed gas from the catalyst filled
tubes of the hydrotreater at a temperature that differs from the
inlet temperature by no more than 30.degree. F.; and subjecting the
hydrocarbon feed removed from the hydrotreater to a desulfurization
step.
5. A process according to claim 4, wherein the temperature of the
hydrocarbon feed gas removed from the catalyst filled tubes of the
hydrotreater differs from the inlet temperature by no more than
15.degree. F.
6. A process according to claim 5, wherein the temperature of the
hydrocarbon feed gas removed from the catalyst filled tubes of the
hydrotreater differs from the inlet temperature by no more than
10.degree. F.
7. A process according to claim 4, wherein desulfurization is
performed by introducing the hydrotreated gas into one or more
adsorbers containing at least one adsorbent comprising zinc
oxide.
8. A process according to claim 4, further comprising, following
desulfurization, delivering the desulfurized hydrocarbon feed
stream to a hydrocarbon cracking procedure to produce a
hydrogen-enriched synthesis gas.
9. A process according to claim 8, wherein said hydrocarbon
cracking procedure is steam reforming wherein the desulfurized
hydrocarbon feed stream is converted in the presence of steam to
produce a hydrogen-enriched synthesis gas containing H.sub.2 and
CO.
10. A process according to claim 9, further comprising, following
steam reforming, delivering the product gas stream from the steam
reforming to a shift reactor wherein CO is reacted with water to
form hydrogen and CO.sub.2.
11. A process according to claim 1, wherein the heat exchange
medium used in the hydrotreater is boiling water, and the
temperature of the hydrocarbon feed stream within the catalyst
tubes can be controlled by controlling the pressure of the steam
generated in the shell side of the reactor during heat
exchange.
12. A process according to claim 1, wherein the hydrocarbon feed
introduced into the hydrotreater contains 5 to 50 mol %
olefins.
13. A process according to claim 1, wherein the molar ratio of
hydrogen to olefins and organic sulfur compounds introduced into
the hydrotreater is 1.25:1 to 3:1.
14. A process according to claim 1, wherein the catalyst in the
tunes of the hydrotreater comprise at least one Group VI metal or
compound thereof and at least one Group VIII metal or compound
thereof.
15. A process according to claim 14, wherein said catalyst is a
nickel-molybdenum catalyst.
16. A process according to claim 1, wherein said hydrotreater is
operated at a temperature of 450 to 500.degree. F., and a pressure
of 250 to 400 psig.
17. A system for preparing a hydrogen-enriched gas from a
hydrocarbon feed stream, the system comprising: a catalytic
hydrotreater comprising a shell and tube reactor wherein the tubes
contain a catalyst for hydrogenation of olefins, the shell and tube
reactor further having a first inlet for introducing a hydrocarbon
feed, or a mixture of hydrocarbons and hydrogen, into the tube-side
of the reactor, and a first outlet for removing a hydrocarbon
stream having reduced olefin content from the tube-side of the
reactor, the shell and tube reactor further having a second inlet
for introducing a heat exchange medium to the shell-side of the
reactor, and a second outlet for removing the heat exchange medium
from the shell-side of the reactor, an adsorber having an adsorbent
bed containing an adsorbent for removal of hydrogen sulfide from a
hydrocarbon gas stream, the adsorber further comprising an inlet
for introduction of a hydrocarbon gas stream containing sulfur
compounds, and an outlet for discharging a desulfurized hydrocarbon
gas stream, a first conduit in fluid communication with said first
outlet of said reactor and in fluid communication with said inlet
of said adsorber for introducing at least a portion of the
hydrocarbon stream having reduced olefin content to said adsorber,
a hydrocarbon reformer comprising an inlet for introducing a
desulfurized hydrocarbon gas stream and an outlet for discharging a
hydrogen-enriched synthesis gas, and a second conduit in fluid
communication with said outlet of said adsorber and in fluid
communication with said inlet of said reformer for introducing at
least a portion of the desulfurized hydrocarbon gas stream to said
reformer.
Description
FIELD OF THE INVENTION
[0001] This invention relates to processes and systems for
producing enriched hydrogen gas from hydrocarbon fuel sources, such
as natural gas. In particular, the invention relates to processes
and systems for producing enriched hydrogen gas from hydrocarbon
fuel sources involving reducing the olefin content of the olefin
hydrocarbon fuel and then subjecting the resultant hydrocarbon fuel
with reduced olefin content to hydrocarbon conversion such as steam
reforming.
BACKGROUND OF THE INVENTION
[0002] Hydrogen gas is produced for a variety of chemical and
industrial processes. For example, hydrogen is used as a raw
material in ammonia synthesis, methanol synthesis, and hydrogen
chloride synthesis. Additionally, hydrogen is used to manufacture
hydrogen peroxide and is used in the production of oleochemicals.
Further, hydrogen is used to remove sulfur from hydrocarbon fuels
such as gasoline and diesel.
[0003] One use of hydrogen gas that is of increasing importance is
a fuel for is electrochemical fuel cells. An electrochemical fuel
cell coverts hydrogen, using oxygen as an oxidant, to produce
electricity. Being a clean form of energy, it is expected that the
use of hydrogen gas as a fuel source will continue to grow, and
thus demand for hydrogen gas will continue to increase.
[0004] Processes for production of hydrogen gas by conversion of
hydrocarbons are well known in the art such as catalytic steam
reforming, partial oxidation reforming and autothermal reforming
processes. In such processes, the presence of olefins in the feed
stream can be detrimental to the operation of the reformers. The
operating conditions of a reformer reactor and/or an upstream
hydrotreater can, depending on the amount of hydrogen present and
the temperature, lead to saturation of the olefins which in turn
will result in the generation of heat. Thus, steps must be taken to
control heat generation due to saturation of olefins.
[0005] Traditionally procedures for controlling heat generation in
a hydrotreater include controlled addition of hydrogen combined
with cooling, and removing a portion of the product gas, cooling
it, compressing it, and recycling it back to the hydrotreater.
However, such procedures are expensive and not very energy
efficient. Additionally, the use of heat exchangers and compressors
involve additional capital expense, and can be less reliable due to
the use of rotating equipment that can break down.
[0006] One can also control the temperature of the hydrotreater by
controlling the amount of hydrogen present. In a hydrotreatment
step, hydrogen is, of course, a key reactant. If one can control
the amount of hydrogen available for the reaction, by increasing or
decreasing the amount of the hydrogen, one can control the
reaction. In turn, one can control the temperature rise due to the
reaction by controlling the amount of hydrogen available for the
reaction.
[0007] However, keeping the hydrogen content low to reduce the
temperature rise can result in incomplete olefin hydrotreatment. To
address this possibility, the gas exiting the hydrotreater can be
cooled, combined with more hydrogen, and passed through a second
hydrotreatment bed. This multiple stage arrangement, however, can
be expensive. Moreover, this multiple stage procedure can not be
used in situation where the hydrogen content in the hydrocarbon
feed gas is not controllable or not easily controllable.
[0008] Thus, a need exists for improved processes for
hydrotreatment of hydrocarbons such as performed as part of a
hydrogen production process.
SUMMARY OF THE INVENTION
[0009] In accordance with the invention, prior to reforming, the
olefin content of a hydrocarbon feed stream is reduced by
subjecting the hydrocarbon feed to isothermal hydrotreatment, in
the presence of hydrogen, in a shell and tube reactor, the tubes
being filled with catalyst. This arrangement allows for better
control of the temperature of the resultant dehydrogenated
hydrocarbon stream. The dehydrogenated hydrocarbon stream can then
be subjected to desulfurization and subsequent reforming, e.g.,
steam reforming, to produce a hydrogen-enriched gas.
[0010] Additionally, this isothermal arrangement requires less
capital expenditure then above-mentioned multiple stage
arrangement. Moreover, the inventive isothermal arrangement can be
used in situations where the hydrogen content of the feed gas is
not easily controllable, whereas the above-mentioned multiple stage
arrangement can not.
[0011] While the process is generally described below with respect
to a hydrogen production plant, the hydrotreatment procedure of the
invention can be used in other facilities such as carbon monoxide
plants, methanol synthesis plants, and synthesis gas plants.
[0012] Therefore, in accordance with the invention, there is
provided a process for subjecting an olefin containing gas to a
hydrogen treatment wherein olefin compounds are converted into
saturated compounds, the process comprising:
[0013] introducing hydrogen and a hydrocarbon feed gas comprising
olefins, alkanes, hydrogen, CO.sub.2, and sulfur compounds such as
mercaptanes, thiophenes, and H.sub.2S into a hydrotreater wherein
olefins are converted into saturated compounds and organic sulfur
compounds such as mercaptanes and thiophenes are converted into
H.sub.2S;
[0014] wherein the hydrotreater is a shell and tube catalytic
reactor containing catalyst filled tubes, the hydrogen and
hydrocarbon feed gas being introduced into the catalyst filled
tubes, and the shell having at least one inlet for introduction of
a heat exchange medium to cool the catalyst filled tubes, and at
least one outlet for removal of the heat exchange medium, and
wherein the hydrocarbon feed gas is introduced into the catalyst
filled tubes at an inlet temperature of about 400 to 525.degree.
F.; and
[0015] removing the hydrocarbon feed gas from the catalyst filled
tubes of the hydrotreater at a temperature that differs from the
inlet temperature by no more than 30.degree. F. (preferably no more
than 20.degree. F., especially no more than 15.degree. F., in
particular no more than 10.degree. F., for example, not more
5.degree. F.).
[0016] According to a further aspect of the invention there is
provided a process for treating a hydrocarbon gas to reduce the
olefin content and organic sulfur compound content thereof, the
process comprising:
[0017] introducing hydrogen and a hydrocarbon feed gas comprising
olefins, alkanes, hydrogen, CO.sub.2, and sulfur compounds such as
mercaptanes, thiophenes and H.sub.2S, into a hydrotreater wherein
olefins are converted into saturated compounds and organic sulfur
compounds such as mercaptanes and thiophenes are converted into
H.sub.2S;
[0018] wherein the hydrotreater is a shell and tube catalytic
reactor containing catalyst filled tubes, the hydrogen and
hydrocarbon feed gas being introduced into the catalyst filled
tubes, and the shell having at least one inlet for introduction of
a heat exchange medium to cool the catalyst filled tubes, and at
least one outlet for removal of the heat exchange medium, and
wherein the hydrocarbon feed gas is introduced into the catalyst
filled tubes at an inlet temperature of about 400 to 525.degree.
F.;
[0019] removing the hydrocarbon feed gas from the catalyst filled
tubes of the hydrotreater at a temperature that differs from the
inlet temperature by no more than 30.degree. F. (preferably no more
than 20.degree. F., especially no more than 15.degree. F., in
particular no more than 10.degree. F., for example, not more
5.degree. F.); and
[0020] subjecting the hydrocarbon feed removed from the
hydrotreater to a desulfurization step for removal of H.sub.2S.
[0021] According to a further aspect of the invention, following
desulfurization, the desulfurized hydrocarbon feed stream is
delivered to a hydrocarbon cracking procedure, such as a steam
reforming, to produce a hydrogen-enriched synthesis gas.
[0022] According to a further aspect of the invention, the
hydrocarbon cracking procedure is steam reforming wherein the
desulfurized hydrocarbon feed stream is converted in the presence
of steam to produce a hydrogen-enriched synthesis gas containing,
inter alia, H.sub.2 and CO.
[0023] According to a further aspect of the invention, the product
gas stream from the steam reforming procedure is treated in a shift
reactor wherein CO is reacted with water to form hydrogen and
CO.sub.2, thereby increasing hydrogen production.
[0024] According to a further aspect of the invention, the
hydrocarbon feed stream is preheated to about 500.degree. F. before
being introduced into the hydrotreater.
[0025] According to a further aspect of the invention, the heat
exchange medium used in the hydrotreater is boiling water whereby
the temperature of the hydrocarbon feed stream within the catalyst
tubes can be controlled by controlling the pressure of the steam
generated in the shell side of the reactor during heat
exchange.
[0026] In accordance with another aspect of the invention, there is
provided a system for preparing a hydrogen-enriched gas from a
hydrocarbon feed stream, the system comprising:
[0027] a catalytic hydrotreater comprising a shell and tube reactor
wherein the tubes contain a catalyst suitable for hydrogenation of
olefins and organic sulfur compounds,
[0028] the shell and tube reactor further having a first inlet for
introducing a hydrocarbon feed, or a mixture of hydrocarbons and
hydrogen, into the tube-side of the reactor, and a first outlet for
removing a hydrocarbon stream having reduced the olefin content and
organic sulfur compound from the tube-side of the reactor,
[0029] the shell and tube reactor further having a second inlet for
introducing a heat exchange medium to the shell-side of the
reactor, and a second outlet for removing the heat exchange medium
from the shell-side of the reactor,
[0030] an adsorber, the adsorber having an adsorbent bed containing
an adsorbent for removal of hydrogen sulfide (H.sub.2S) from a
hydrocarbon gas stream, the adsorber further comprising an inlet
for introduction of a hydrocarbon gas stream containing sulfur
compounds, and an outlet for discharging a desulfurized hydrocarbon
gas stream,
[0031] a first conduit in fluid communication with said first
outlet of said reactor and in fluid communication with said inlet
of said adsorber for introducing at least a portion of the
hydrocarbon stream having reduced the olefin and organic sulfur
compounds content to said adsorber,
[0032] a hydrocarbon reformer, such as a steam reforming,
comprising an inlet for introducing a desulfurized hydrocarbon gas
stream and an outlet for discharging a hydrogen-enriched synthesis
gas, and
[0033] a second conduit in fluid communication with said outlet of
said adsorber and in fluid communication with said inlet of said
reformer for introducing at least a portion of the desulfurized
hydrocarbon gas stream to said reformer.
[0034] Upon further study of the specification and appended claims,
further aspects and advantages of this invention will become
apparent to those skilled in the art.
[0035] In accordance with the invention a hydrocarbon feed
containing olefins is subjected to an isothermal (or essentially
isothermal) catalytic hydrotreatment within a shell and tube
reactor, the tubes containing hydrotreatment catalyst. The
hydrocarbon feed can be obtained from a variety of sources such as
natural gas, refinery waste gas, waste gas from petrochemical
plants, LPG, naphtha, etc. Generally, the components of the
hydrocarbon feed will, of course, vary depending on the type of
feedstock selected. Alkanes that may be present in the feedstock
include methane, ethane, propane, and butane. Olefins that may be
present in the feedstock include ethylene, propylene, and butylene.
The process of the invention is suitable for treating hydrocarbon
feed containing, for example, 5 to 50 mol % olefins, preferably 5
to 30 mol % olefins, especially 5 to 20 mol % olefins.
[0036] The hydrocarbon feed may contain additional components such
H.sub.2, CO, CO.sub.2, sulfur compounds, and nitrogen compounds. In
the hydrotreatment stage, organic sulfur compounds within the
hydrocarbon feed are also subjected to hydrogenation wherein
organic sulfur compounds are converted into hydrogen sulfide
(H.sub.2S). Prior to being introduced into the isothermal
hydrotreater, the hydrocarbon feed is preferably combined with a
hydrogen stream prior to introduction into the hydrotreater, in
order to enhance mixing. However, it is also possible to introduce
the hydrocarbon feed and hydrogen stream separately into the
hydrotreater via separate inlets.
[0037] The amount of hydrogen delivered to the hydrotreater will
depend on the amount of olefins/organic sulfur compounds present in
the hydrocarbon feed. Preferably, the amount of hydrogen is an
excess of the amount of olefins/organic sulfur compounds present.
In general, it is preferred that the molar ratio of hydrogen to
olefins/organic sulfur compounds introduced into the hydrotreater
be, for example, 1.25:1 to 3:1. Thus, for example, the combined
hydrocarbon/hydrogen feed which is preheated to a temperature of
about 400 to 525.degree. F., particularly about 450 to 500.degree.
F., preferably has a molar ratio of hydrogen to olefins/organic
sulfur compounds of 1.25:1 to 3:1.
[0038] The hydrocarbon feed and hydrogen may also be preheated
prior to introduction into the hydrotreater. Preheating can be
performed by in a heat exchanger by indirect heat exchange against
any suitable heating medium such as steam or a process gas.
Preferably, the hydrocarbon feed and hydrogen are preheated to a
temperature of about 400 to 525.degree. F., particularly about 450
to 500.degree. F.
[0039] Other optional pretreatments include compression with
subsequent condensate removal to remove at least some of the
heavier hydrocarbons.
[0040] Hydrocarbon feed and hydrogen are introduced into a
distribution zone of the hydrotreater. From distribution zone, the
hydrocarbon feed/hydrogen mixture is distributed into a plurality
of tubes (e.g., 50 to 500 or 100 to 250 tubes) wherein each tube
contains a hydrogenation catalyst.
[0041] Suitable hydrogenation catalysts include those comprising at
least one Group VI metal or compound thereof (such as oxides and
sulfides) and at least one Group VIII metal or compound thereof
(such as oxides and sulfides) on a suitable support such alumina or
silica alumina. For example, the catalyst can be a
cobalt-molybdenum or nicke-molybdenum catalyst on an alumina or
silica support. A nickel-molybdenum catalyst is preferred.
[0042] Hydrogenation conditions within the hydrotreater are
preferably a temperature of about 400 to 525.degree. F.,
particularly about 450 to 500.degree. F., and preferably a pressure
of about 150 to 500 psig, particularly about 250 to 400 psig.
[0043] In order to remove the heat generated in the catalysts tubes
as a result of the exothermic hydrogenation reaction, a cooling
heat exchange medium is introduced to the shell side of the tube
and shell hydrotreater reactor. As noted above, the hydrotreater is
intended to operate under isothermal or essentially isothermal
conditions. Thus, the temperature of the hydrocarbon stream removed
from the outlets of the catalyst filled tubes differs from the
temperature of the hydrocarbon feed/hydrogen mixture introduced
into the inlets of the catalyst filled tubes temperature by no more
than 30.degree. F. (preferably no more than 20.degree. F.,
especially no more than 15.degree. F., in particular no more than
10.degree. F., for example, not more 5.degree. F.). To facilitate
isothermal operation and to enhance the effectiveness of the heat
exchange, the heat exchange medium used in the shell side of the
reactor is preferably an evaporating liquid. In other words, the
heat exchange medium is preferably a liquid medium that, during the
course of the heat exchange, undergoes a phase conversion to a gas.
In particular, the liquid heat exchange medium is water that
converts to steam during while removing the heat from the catalytic
hydrogenation reaction. Boiling water has a high heat transfer
coefficient which will aid in keeping the reaction gas temperature
from significantly increasing. Further, the use of a water/steam
heat exchange medium facilities control of the temperature since
the temperature can be controlled by regulating the steam pressure
in the shell side of the reactor. Thus, the use of a water/steam
heat exchange medium provides better control of the reaction
temperature, and also generates a process stream (i.e., steam) that
can be used for other processes, such as in a downstream stream
reformer.
[0044] Upon exiting the outlets of the catalyst-filled tubes, the
hydrotreated gas is introduced into a lower header and then
discharged let from the hydrotreater via an out. The temperature of
the discharged hydrotreated gas is generally about 405 to
540.degree. F., particularly about 455 to 515.degree. F.
[0045] The discharge temperature is sufficient to permit
desulfurization. Therefore, the hydrotreated gas discharged from
the hydrotreater is in introduced into one or more adsorbers or
absorbers for the removal of hydrogen sulfide. As noted above,
during the hydrotreatment, organic sulfur compounds are converted
into hydrogen sulfide by hydrogenation. The adsorbent used in the
beds of the adsorbers can be, for example, activated carbon,
molecular sieves, or oxides of certain metals, such as alumina,
iron oxide and zinc oxide. Zinc oxide is preferred. Alternatively,
the hydrotreated gas can be desulfurized in an absorber that
employs a liquid absorbent such as an aqueous solution of an
alkanolamine, for example, monoethanolamine.
[0046] The adsorbers/absorbers can be arranged in series or in
parallel. If some of the adsorbers/absorbers are arranged in
parallel, this will allow some of the adsorbers/absorbers to be
operating while others are being subjected to maintenance.
[0047] The hydrotreated/desulfurized gas removed from the
adsorbers/absorbers is then delivered to a hydrocarbon reforming
process, such as steam reforming. In the reforming process, the
hydrocarbons are converted to provide a hydrogen-enriched gas that
further contains, for example, CO, CO.sub.2, methane, nitrogen.
[0048] The entire disclosures of all applications, patents and
publications, cited above and below, are hereby incorporated by
reference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] Various other features and attendant advantages of the
present invention will be more fully appreciated as the same
becomes better understood when considered in conjunction with the
accompanying drawings, in which like reference characters designate
the same or similar parts throughout the several views, and
wherein:
[0050] FIG. 1 illustrates a flow chart of the process according to
the invention; and
[0051] FIG. 2 shows a more detailed view of the hydrotreatment
reactor of the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0052] In FIG. 1, a hydrocarbon feed (1) such as a natural gas
(1a), a refinery gas (1b), or both are combined with a hydrogen
stream (2). The resultant mixture is then preheated by indirect
heat exchange against process gas in heat exchanger (3). The
hydrocarbon/hydrogen mixture removed from heat exchanger (3) is
introduced into reactor (4) at a temperature of 500.degree. F. and
a pressure of 350 psig.
[0053] Reactor (4) is a shell and tube reactor having a plurality
of tubes containing Ni-Mo catalyst on a support. The
hydrocarbon/hydrogen mixture passes through the catalyst filled
tubes whereby olefins contained in the hydrocarbon/hydrogen mixture
undergo hydrogenation to form paraffins. Additionally, organic
sulfur compounds present within the hydrocarbon/hydrogen mixture
undergo hydrogenation to form hydrogen sulfide.
[0054] To operate the reactor under isothermal conditions, boiling
water (5) is introduced into the sell side of reactor (4) to absorb
the heat of the exothermic hydrogenation reactor. During the heat
exchange, at least a portion of the water is converted into steam.
This allows the reaction temperature to be controlled by
controlling the steam pressure within the shell side of reactor
(4). The resultant water/steam is removed from the shell side of
the reactor via line 6.
[0055] The hydrotreated gas discharged from the catalyst-filled
tubes is introduced to adsorbers (7) and (8), connected in series.
Each of adsorbers (7) and (8) contains a bed of zinc oxide
particles which remove hydrogen sulfide from the hydrotreated gas.
After discharge from adsorbers (7) and (8), the
desulfurized/hydrotreated gas (9) is sent to a hydrocarbon
reforming stage (10), such as a steam reformer, to generate a
hydrogen-enriched product gas.
[0056] Without further elaboration, it is believed that one skilled
in the art can, using the preceding description, utilize the
present invention to its fullest extent. The preceding preferred
specific embodiments are, therefore, to be construed as merely
illustrative, and not limitative of the remainder of the disclosure
in any way whatsoever.
[0057] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention
and, without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *