Patent Description:
This disclosure relates to processes for producing H<NUM>-rich fuel gas from hydrocarbons such as natural gas, and use thereof in heating such as industrial heating in an olefins production plant.

There exist many industrial processes that require the generation of very high temperatures. Many of these processes achieve the required high temperatures by the combustion of hydrocarbon fuel-gas. A fuel-gas commonly used is natural gas, which comprises primarily methane. In the combustion of methane, approximately <NUM> tons of CO<NUM> are generated for each <NUM> MBtu of heat released (lower heating value ("LHV" basis).

One such large scale manufacturing process is the production of light olefins (e.g. ethylene, propylene, etc.). The predominant method of manufacturing light olefins is via steam-cracking, where a hydrocarbon feed is heated to very high temperatures in the presence of steam. The high temperatures of > <NUM> (> <NUM> °F) required to provide rapid heat input to steam-cracking furnaces (also known as pyrolysis reactors) are achieved by the combustion of fuel-gas. In many olefins production facilities the fuel-gas is internally generated as a byproduct of the cracking process, which can comprise primarily methane (e.g., <NUM>-<NUM> mol%) with a moderate hydrogen content (e.g., <NUM>-<NUM> mol%). A modern, world-scale olefins plant may have up to <NUM> steam-cracking furnaces, each of which may consume up to <NUM> MW or <NUM> MBtu/hour of fuel (LHV basis), and each of which has an individual flue-gas exhaust stack. Thus a modern olefins production facility can generate considerable quantity of CO<NUM> emissions over an extended operation period.

Various techniques have been proposed to reduce the net CO<NUM> emissions from steam cracking furnaces and olefins plants. Capturing CO<NUM> from the individual flue-gas stacks using an amine absorption and regeneration process has been proposed. This process has been demonstrated on the flue-gas stacks of electricity generation facilities. Once captured from the flue-gas stack, the CO<NUM> can be compressed, liquefied and can be sequestered in appropriate geological formations (i.e., Carbon Capture and Sequestration, "CCS"). Application of this technology to an olefins plant is extremely expensive given the potential to have <NUM> (or more) flue-gas stacks from which CO<NUM> must be captured, the low CO<NUM> concentration in the flue-gas, and the lack of available plot-space close to the steam-cracking furnaces in existing facilities. In particular, the large, internally insulated flue-gas ducting, with associated fans and isolation facilities required to transfer the large flue-gas volumes from the furnaces to the location of the amine absorption unit greatly increases the cost of the facilities.

An alternative approach has been proposed wherein a high-hydrogen fuel-gas stream is generated for combustion in the steam-cracking furnaces, thus facilitating the generation of the high temperatures required by the process but with appreciably reduced CO<NUM> emissions from the furnaces.

Hydrogen generation from natural-gas is practiced on an industrial scale via the process of steam reforming. A steam-methane reformer passes heated natural-gas (or another suitable hydrocarbon), in the presence of large volumes of steam, through tubes containing a suitable catalyst, to produce a synthesis gas containing hydrogen, carbon-monoxide, carbon-dioxide and unconverted methane. The process is typically practiced at pressures in the range of <NUM> - <NUM> kPa (<NUM> - <NUM> psig). The process requires high temperatures, so it is normal for various waste-heat recovery heat exchangers to be employed in the reformer effluent stream. The waste heat recovery exchangers typically generate high-pressure steam of ~ <NUM> - <NUM> kPa (~ <NUM> - <NUM> psig) which is then superheated in the convection section of the reformer. Also in the reformer effluent stream, located at appropriate temperature conditions, it is normal to employ one or more "shift reactors" where, over a suitable catalyst, CO reacts with steam to produce additional hydrogen and CO<NUM>. Following the shift reactor(s), the reformer effluent is further cooled to condense the contained steam, leaving a stream predominantly containing hydrogen and CO<NUM>, but also containing unconverted methane and CO. In most industrial facilities a pressure-swing-absorption ("PSA") unit is then employed to recover high purity hydrogen (<NUM>+ %) from the effluent stream. A so-called "PSA reject" stream is also generated, composed of CO<NUM>, CO, unconverted methane and some hydrogen. Historically it has been normal to use the PSA reject stream as a portion of the fuel-requirement of the reformer. <CIT> discloses a steam reforming system having a steam cracker and a steam reformer.

While the steam-methane-reforming process for hydrogen production is well established, there remain several drawbacks to its use for large scale production of hydrogen rich fuel-gas for industrial applications. First, from the description above, it is clear that the process has a high capital cost, employing large reforming furnaces and multiple subsequent processing steps. Second, the combustion of fuel-gas to provide the high temperatures required in the reformer itself can be source of considerable amount of CO<NUM> emissions. Third, the PSA reject stream must be sent to a suitable disposition. Historically the PSA reject stream formed part of the fuel-gas supply to the reformer, but this further adds to the CO<NUM> emissions from the reformer itself.

The CO<NUM> emissions from the SMR can be reduced by installing an amine recovery system on the flue-gas discharged from the reformer stack. This approach further adds to the capital cost and operating expense of the system, particularly as the reformer stack gas is at low (ambient) pressure. The low operating pressure translates to large gas volumes and hence the amine contactor required to absorb the CO<NUM> becomes extremely large.

There is a need, therefore, for improved processes and systems for producing H<NUM>-rich fuel gas and processes and systems for producing olefins. This disclosure satisfies this and other needs.

It has been found that, in a surprising manner, a H<NUM>-rich fuel gas can be produced with a considerably improved efficiency compared to existing processes by a process comprising hydrocarbon reforming with waste heat recovery, at least two stages of shift reactions, and a CO<NUM> separation step. The H<NUM>-rich fuel gas stream can be advantageously supplied as fuel to furnaces such as a SMR furnace, a pre-reformer furnace, and to boilers. The separated CO<NUM> can be conducted away, stored, sequestered, or utilized, enabling the production of the H<NUM>-rich fuel gas with considerably reduced CO<NUM> emission to the atmosphere. The H<NUM>-rich fuel gas can be advantageously integrated with an olefins production plant achieving additional, considerably improved energy efficiency and appreciably reduced CO<NUM> emissions from the olefins production plant compared to running the olefins production plant separately.

Thus, a first aspect of this disclosure is directed to a process comprising the following steps: (I) supplying a hydrocarbon feed and a steam feed into a syngas producing unit comprising a reforming reactor under syngas producing conditions to produce a reformed stream exiting the reforming reactor, wherein the syngas producing conditions include the presence of a reforming catalyst, and the reformed stream comprises H<NUM>, CO, and steam; (II) cooling the reformed stream by using a waste heat recovery unit ("WHRU") to produce a cooled reformed stream and to generate a high-pressure steam ("HPS") stream; (III) contacting the cooled reformed stream with a first shifting catalyst in a first shift reactor under a first set of shifting conditions to produce a first shifted stream exiting the first shift reactor, wherein the first shifted stream has a lower CO concentration and a higher CO<NUM> concentration than the cooled reformed stream; (IV) cooling the first shifted stream to obtain a cooled first shifted stream; (V) contacting the cooled first shifted stream with a second shifting catalyst in a second shift reactor under a second set of shifting conditions to produce a second shifted stream exiting the second shift reactor, wherein the second shifted stream has a lower CO concentration and a higher CO<NUM> concentration than the cooled first shifted stream; (VI) abating steam present in the second shifted stream to produce a crude gas mixture stream comprising CO<NUM> and H<NUM>; (VII) recovering at least a portion of the CO<NUM> present in the crude gas mixture stream to produce a CO<NUM> stream and a H<NUM>-rich stream, wherein the H<NUM>-rich stream comprises H<NUM> at a concentration of at least <NUM> mol%, based on the total moles of molecules in the H<NUM>-rich stream; (VIII) combusting a portion of the H<NUM>-rich stream in the presence of an oxidant to generate thermal energy and to produce a flue gas stream; and (IX) operating a steam cracker located in an olefins production plant under steam cracking conditions to convert a steam cracker feed into a steam cracker effluent comprising olefins; (X) producing a CH<NUM>-rich stream from the steam cracker effluent; and (XI) providing the CH<NUM>-rich stream as at least a portion of the hydrocarbon feed in step (I); wherein the H<NUM>-rich stream is supplied to at least one combustion device used in the process for producing the H<NUM>-rich stream.

Various specific embodiments, versions and examples of the invention will now be described, including preferred embodiments and definitions that are adopted herein for purposes of understanding the claimed invention. While the following detailed description gives specific preferred embodiments, those skilled in the art will appreciate that these embodiments are exemplary only, and that the invention may be practiced in other ways.

In this disclosure, a process is described as comprising at least one "step. " It should be understood that each step is an action or operation that may be carried out once or multiple times in the process, in a continuous or discontinuous fashion. Unless specified to the contrary or the context clearly indicates otherwise, multiple steps in a process may be conducted sequentially in the order as they are listed, with or without overlapping with one or more other steps, or in any other order, as the case may be. In addition, one or more or even all steps may be conducted simultaneously with regard to the same or different batch of material. For example, in a continuous process, while a first step in a process is being conducted with respect to a raw material just fed into the beginning of the process, a second step may be carried out simultaneously with respect to an intermediate material resulting from treating the raw materials fed into the process at an earlier time in the first step. Preferably, the steps are conducted in the order described.

Unless otherwise indicated, all numbers indicating quantities in this disclosure are to be understood as being modified by the term "about" in all instances. It should also be understood that the precise numerical values used in the specification and claims constitute specific embodiments. Efforts have been made to ensure the accuracy of the data in the examples. However, it should be understood that any measured data inherently contains a certain level of error due to the limitation of the technique and/or equipment used for acquiring the measurement.

Certain embodiments and features are described herein using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges including the combination of any two values, e.g., the combination of any lower value with any upper value, the combination of any two lower values, and/or the combination of any two upper values are contemplated unless otherwise indicated.

The indefinite article "a" or "an", as used herein, means "at least one" unless specified to the contrary or the context clearly indicates otherwise. Thus, embodiments using "a reactor" or "a conversion zone" include embodiments where one, two or more reactors or conversion zones are used, unless specified to the contrary or the context clearly indicates that only one reactor or conversion zone is used.

The term "hydrocarbon" means (i) any compound consisting of hydrogen and carbon atoms or (ii) any mixture of two or more such compounds in (i). The term "Cn hydrocarbon," where n is a positive integer, means (i) any hydrocarbon compound comprising carbon atom(s) in its molecule at the total number of n, or (ii) any mixture of two or more such hydrocarbon compounds in (i). Thus, a C2 hydrocarbon can be ethane, ethylene, acetylene, or mixtures of at least two of these compounds at any proportion. A "Cm to Cn hydrocarbon" or "Cm-Cn hydrocarbon," where m and n are positive integers and m < n, means any of Cm, Cm+<NUM>, Cm+<NUM>,. , Cn-<NUM>, Cn hydrocarbons, or any mixtures of two or more thereof. Thus, a "C2 to C3 hydrocarbon" or "C2-C3 hydrocarbon" can be any of ethane, ethylene, acetylene, propane, propene, propyne, propadiene, cyclopropane, and any mixtures of two or more thereof at any proportion between and among the components. A "saturated C2-C3 hydrocarbon" can be ethane, propane, cyclopropane, or any mixture thereof of two or more thereof at any proportion. A "Cn+ hydrocarbon" means (i) any hydrocarbon compound comprising carbon atom(s) in its molecule at the total number of at least n, or (ii) any mixture of two or more such hydrocarbon compounds in (i). A "Cn- hydrocarbon" means (i) any hydrocarbon compound comprising carbon atoms in its molecule at the total number of at most n, or (ii) any mixture of two or more such hydrocarbon compounds in (i). A "Cm hydrocarbon stream" means a hydrocarbon stream consisting essentially of Cm hydrocarbon(s). A "Cm-Cn hydrocarbon stream" means a hydrocarbon stream consisting essentially of Cm-Cn hydrocarbon(s).

For the purposes of this disclosure, the nomenclature of elements is pursuant to the version of the Periodic Table of Elements (under the new notation) as provided in <NPL>), Appendix V.

"High-pressure steam" and "HPS" are used interchangeably to mean a steam having an absolute pressure of at least <NUM> kilopascal ("kPa"). "Super-high-pressure steam" and "Super-HPS" are used interchangeably to mean a steam having an absolute pressure of at least <NUM>,<NUM> kPa. Thus, a Super-HPS is an HPS. "Medium-pressure steam" and "MPS" are used interchangeably to mean a steam having an absolute pressure of at least <NUM> kPa but less than <NUM>,<NUM> kPa. "Low-pressure steam" and "LPS" are used interchangeably to mean a steam having an absolute pressure of at least <NUM> kPa but less than <NUM> kPa.

"Consisting essentially of" means comprising ≥ <NUM> mol%, preferably ≥ <NUM> mol%, preferably ≥ <NUM> mol%, preferably ≥ <NUM> mol%, preferably ≥ <NUM> mol%; preferably <NUM> mol%, of a given material or compound, in a stream or mixture, based on the total moles of molecules in the stream or mixture.

This disclosure is directed to a process for producing H<NUM>-rich fuel gas as summarily above. A system for producing such an H<NUM>-rich stream, preferably using a process including steps (I) to (VII) as described summarily above, may be called an H<NUM>-rich fuel gas production plant in this disclosure. Step (I) of this process includes supplying a hydrocarbon feed and a steam feed into a syngas producing unit comprising a reforming reactor under syngas producing conditions to produce a reformed stream exiting the reforming reactor, wherein the syngas producing conditions include the presence of a reforming catalyst, and the reformed stream comprises H<NUM>, CO, and steam. The hydrocarbon feed can consist essentially of C1-C4 hydrocarbons (preferably saturated), preferably consists essentially of C1-C3 hydrocarbons (preferably saturated), preferably consists essentially of C1-C2 hydrocarbons (preferably saturated), and preferably consists essentially of CH<NUM>. The hydrocarbon feed and the steam feed may be combined to form a joint stream before being fed into the syngas producing unit. Alternatively, they may be fed into the syngas producing unit as separate streams, in which they admix with each other to form a mixture. The feed stream(s) can be pre-heated by, e.g., a furnace, a heat exchanger, and the like, before being fed into the syngas producing unit. The syngas producing unit can comprise a pre-reformer first receiving the feed stream(s), especially if the hydrocarbon feed comprises significant amount of C2+ hydrocarbons. In a pre-reformer, the hydrocarbon feed/steam feed mixture contacts a pre-reforming catalyst under conditions such that the C2+ hydrocarbons are preferentially converted into CH<NUM>. The inclusion of a pre-reformer can reduce coking and fouling of the down-stream reforming reactor. The hydrocarbon feed may have a temperature from, e.g., <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, , or even <NUM>, and an absolute pressure from e.g., <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa. The steam feed may have a temperature from, e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or even <NUM>, and an absolute pressure from e.g., <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa. Preferably, the steam feed is a superheated steam.

The effluent from the pre-reformer can be then fed into the reforming reactor operated under syngas producing conditions, wherein the forward reaction of the following is favored and desirably occurs in the presence of the reforming catalyst:
<CHM>.

The syngas producing condition can include a temperature of, e.g., from <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>,<NUM>, <NUM>,<NUM>, <NUM>,<NUM>, to <NUM>, or even <NUM>, and an absolute pressure of, e.g., from <NUM> kPa, <NUM> kPa, <NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa, in the reforming reactor, depending on the type of the reforming reactor and the syngas producing conditions. A lower pressure in the reformed stream, and hence a lower pressure in the reforming reactor, is conducive to a higher conversion of CH<NUM> in reforming reactor and hence a lower residual CH<NUM> concentration in the reformed stream. The reformed stream exiting the reforming reactor therefore comprises CO, H<NUM>, residual CH<NUM> and H<NUM>O, and optionally CO<NUM> at various concentrations depending on, among others, the type of the reforming reactor and the syngas producing conditions. The reformed stream can have a temperature of, e.g., from <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>,<NUM>, <NUM>,<NUM>, <NUM>,<NUM>, to <NUM>, or even <NUM>, and an absolute pressure of, e.g., from <NUM> kPa, <NUM> kPa, <NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa, depending on the type of the reforming reactor and the syngas producing conditions.

A preferred type of the reforming reactor in the syngas producing unit is an SMR. An SMR typically comprises one or more heated reforming tubes containing the reforming catalyst inside. The hydrocarbon/steam feed stream enters the tubes, heated to a desired elevated temperature, and passes through the reforming catalyst to effect the desirable reforming reaction mentioned above. While an SMR can have many different designs, a preferred SMR comprises a furnace enclosure, a convection section (e.g., an upper convection section), a radiant section (e.g., a lower radiant section), and one or more burners located in the radiant section combusting a fuel to produce a hot flue gas and supply thermal energy to heat the radiant section and the convection section. The hydrocarbon/steam feed stream enters the reforming tube at a location in the convection section, winds downwards through the convection section, whereby it is pre-heated by the ascending hot flue gas produced from fuel combustion at the burner(s), and then enters the radiant section proximate the burners combustion flames, whereby it contacts the reforming catalyst loaded in the reforming tube(s) in the radiant section, to produce a reformed stream exiting the SMR from a location in the radiant section. The syngas producing conditions in the reforming tube(s) in the radiant section can include a temperature of, e.g., from <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, or even <NUM>, and an absolute pressure of, e.g., from <NUM> kPa, <NUM> kPa, <NUM> kPa, <NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa. To achieve a high CH<NUM> conversion in the SMR, and a low CH<NUM> concentration in the H<NUM>-rich stream produced from the process, the syngas producing conditions in the SMR preferably includes an absolute pressure of ≤ <NUM>,<NUM> kPa (<NUM> psig), more preferably ≤ <NUM>,<NUM> kPa (<NUM> psig). Description of an SMR can be found in, e.g., The International Energy Agency Greenhouse Gas R&D Program ("IEAGHG"), "Techno-Economic Evaluation of SMR Based Standalone (Merchant) Plant with CCS", February <NUM>; and IEAGHG, "Reference data and supporting literature Reviews for SMR based Hydrogen production with CCS", <NUM>-TR3, March <NUM>, the contents of which are incorporated herein in their entirety.

The reforming reactor in the syngas producing unit may comprise an autothermal reformer ("ATR"). An ATR typically receives the hydrocarbon/steam feed(s) and an O<NUM> stream into a reaction vessel, where a portion of the hydrocarbon combusts to produce thermal energy, whereby the mixture is heated to an elevated temperature and then allowed to contact a bed of reforming catalyst to effect the desirable reforming reaction and produce a reformed stream exiting the vessel. An ATR can be operated at a higher temperature and pressure than an SMR. The syngas producing conditions in the ATR and the reformed stream exiting an ATR can have a temperature of, e.g., from <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>,<NUM>, <NUM>, to <NUM>,<NUM>, <NUM>,<NUM>, or even <NUM>,<NUM>, and an absolute pressure of, e.g., from <NUM> kPa, <NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa. Commercially available ATRs, such as the Syncor™ ATR available from Haldor Topsoe, having an address at Haldor Topsøes Allé <NUM>, DK-<NUM>, Kgs. Lyngby, Denmark ("Topsoe"), may be used in the process of this disclosure.

The syngas producing unit used in step (I) of the process of this disclosure can include one or more SMR only, one or more ATR only, or a combination of one or more of both.

The reformed stream exiting the reforming reactor has a high temperature and high pressure as indicated above. It is highly desirable to capture the heat energy contained therein. Thus, in step (II), the reformed stream passes through a waste heat recovery unit ("WHRU") to produce a cooled reformed stream and to generate a high-pressure steam ("HPS") stream. The cooled reformed stream can have a temperature from, e.g., <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, or even <NUM>. The cooled reformed stream can have a pressure substantially the same as the reformed stream exiting the reforming reactor. The WHRU can include, e.g., one or more heat exchanger and one or more steam drum in fluid communication with the heat exchanger. The steam drum supplies a water/steam stream to the heat exchanger, where it is heated and can be then returned to the steam drum, where steam is separated from liquid phase water. The HPS stream can have an absolute pressure from, e.g., <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa. The thus produced HPS stream is a saturated steam stream. To make the HPS stream more useful, it may be further heated to produce a superheated HPS ("SH-HPS") stream in, e.g., a furnace. In case the syngas producing unit comprises an SMR having a convection section as described above, the saturated HPS stream may be advantageously superheated in the convection section of the SMR and/or in an auxiliary furnace. In case the syngas producing unit comprises one or more ATR but no SMR, the saturated HPS stream can be superheated in an auxiliary furnace. The auxiliary furnace can include one or more burners combusting a fuel gas stream to supply the needed thermal energy as is known to one skilled in the art. The SH-HPS stream can have one of both of: (i) a temperature from, e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, or even <NUM>; and (ii) an absolute pressure from, e.g., e.g., <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa.

In step (III) of the process of this disclosure, the cooled reformed stream contacts a first shifting catalyst in a first shift reactor under a first set of shifting conditions to produce a first shifted stream exiting the first shift reactor. The first set of shifting conditions includes the presence of a first shift catalyst. Any suitable shift catalyst known to one skilled in the art may be used. Non-limiting examples of suitable shift catalyst for the first shifting catalyst are high temperature shift catalysts available from, e.g., Topsoe. The forward reaction of the following preferentially occur in the first shift reactor:
<CHM>.

As such, the first shifted stream has a lower CO concentration and a higher CO<NUM> concentration than the cooled reformed stream. The forward reaction of (R-<NUM>) is exothermic, resulting in the first shifted stream having a temperature higher than the cooled reformed stream entering the first shift reactor. The first shifted stream exiting the first shift reactor can have a temperature from, e.g., <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, or even <NUM>. The first shifted stream can have an absolute pressure substantially the same as the cooled reformed stream.

While a single stage of shift reactor may convert sufficient amount of CO in the cooled reformed stream to CO<NUM> resulting in a low CO concentration in the first shifted stream, at least two stages of shift reactors are included in the processes of this disclosure to achieve a high level of conversion of CO to CO<NUM>, and eventually to produce a H<NUM>-rich fuel gas stream with low CO concentration. It is further preferred that a subsequent stage, such as the second shift reactor downstream of the first shift reactor is operated at a temperature lower than the first shift reactor, whereby additional amount of CO in the first shifted stream is further converted into CO<NUM> and additional amount of H<NUM> is produced. To that end, the first shifted stream is first cooled down in step (IV) to produce a cooled first shifted stream. Such cooling can be effected by one or more heat exchangers using one or more cooling streams having a temperature lower than the first shifted stream. In one preferred embodiment, the first shifted stream can be cooled by the hydrocarbon stream or a split stream thereof to be fed into the syngas producing unit. Alternatively or additionally, the first shifted stream can be cooled by a boiler water feed stream to produce a heated boiler water stream, a steam stream, and/or a water/steam mixture stream. The thus heated boiler water stream can be heated in a boiler to produce steam at various pressure. The thus heated boiler water stream or steam stream can be further heated by another process stream in another heat exchanger to produce steam. In one preferred embodiment, the heated boiler water stream and/or steam stream can be fed into the steam drum of the WHRU extracting heat from the reformed stream as described above, where the boiler feedwater can be sent to the WHRU exchanger for further heating, and any steam separated in the steam drum can be further superheated. The cooled first shifted stream can have a temperature from, e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, or even <NUM>, and a pressure substantially the same as the first shifted stream.

The cooled first shifted stream is then subjected to a low-temperature shifting in a second shift reactor under a second set of shifting conditions to produce a second shifted stream. The second set of shifting conditions includes the presence of a second shift catalyst, which may be the same or different from the first shift catalyst. Any suitable shift catalyst known to one skilled in the art may be used. Non-limiting examples of suitable catalyst for the second shifting catalyst are low temperature shift catalysts available from, e.g., Topsoe. The forward reaction of the following preferentially occur in the second shift reactor:
<CHM>.

As such, the second shifted stream has a lower CO concentration and a higher CO<NUM> concentration than the cooled first shifted stream. The forward reaction of (R-<NUM>) is exothermic, resulting in the second shifted stream having a temperature higher than the cooled first shifted stream entering the second shift reactor. The second shifted stream exiting the second shift reactor can have a temperature from, e.g., e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, to <NUM>, <NUM>, <NUM>, <NUM>, or even <NUM>. The second shifted stream can have an absolute pressure substantially the same as the cooled first shifted stream.

The second shifted stream comprises H<NUM>, CO<NUM>, CO, steam, and optionally CH<NUM>. In step (VI), steam is then abated from it by cooling and separation. Similar to step (IV) of cooling the first shifted stream, such cooling of the second shifted stream can be effected by one or more heat exchangers using one or more cooling streams having a temperature lower than the second shifted stream. In one preferred embodiment, the second shifted stream can be cooled by the hydrocarbon stream or a split stream thereof to be fed into the syngas producing unit. Alternatively or additionally, the second shifted stream can be cooled by a boiler water feed stream to produce a heated boiler water stream, a steam stream, and/or a water/steam mixture stream. The thus heated boiler water stream and/or water/steam mixture stream can be heated in a boiler to produce steam at various pressure. The thus heated boiler water stream can be heated in a boiler to produce steam at various pressure. The thus heated boiler water stream or steam stream can be further heated by another process stream in another heat exchanger to produce steam. In one preferred embodiment, the heated boiler water stream and/or steam stream can be fed into the steam drum of the WHRU extracting heat from the reformed stream as described above, where the boiler feedwater can be sent to the WHRU exchanger for further heating, and any steam separated in the steam drum can be further superheated. Alternatively or additionally, cooling water exchangers or air-fin heat exchangers can be used to at least partly cool the second shifted syngas stream. The cooled second shifted stream can preferably comprise water condensate, which can be separated to produce a crude gas mixture stream comprising steam at a significantly lower concentration than the second shifted stream exiting the second shift reactor.

The crude gas mixture stream thus consists essentially of CO<NUM>, H<NUM>, optionally CH<NUM> at various amounts, and steam and CO as minor components. The crude gas mixture stream can have an absolute pressure from, e.g., <NUM> kPa, <NUM> kPa, <NUM> kPa, <NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa. In step (VII), a portion of the CO<NUM> therein is recovered to produce a CO<NUM> stream and a H<NUM>-rich stream. Any suitable CO<NUM> recovery process known to one skilled in the art may be used in step (VII), including but not limited to: (i) amine absorption and regeneration process; (ii) a cryogenic CO<NUM> separation process; (iii) a membrane separation process; (iv) a physical absorption and regeneration process; and (iv) any combination any of (i), (ii), and (iii) above. In a preferred embodiment, an amine absorption and regeneration process may be used. Due to the elevated pressure of the crude gas mixture stream, the size of the CO<NUM> recovery equipment can be much smaller than otherwise required to recover CO<NUM> from a gas mixture at atmospheric pressure.

The CO<NUM> stream preferably comprises CO<NUM> at a molar concentration of from, e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>%, based on the total moles of molecules in the CO<NUM> stream. The CO<NUM> stream can comprise at least one and preferably all of, on a molar basis: (i) e.g., from <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>% of CO; (ii) e.g., from <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>% of H<NUM>O; and (iii) e.g., from <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>% of CH<NUM>. The CO<NUM> stream can have an absolute pressure from, e.g., <NUM> kPa, <NUM> kPa, <NUM> kPa, <NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa. The CO<NUM> stream can be compressed, liquefied, conducted away, stored, sequestered, or utilized in any suitable applications known to one skilled in the art. In one embodiment, the CO<NUM> stream, upon optional compression, can be conducted away in a CO<NUM> pipeline. In another embodiment, the CO<NUM> stream, upon optional compression and/or liquefaction, can be injected and stored in a geological formation. In yet another embodiment, the CO<NUM> stream, upon optional compression and/or liquefaction, can be used in extracting hydrocarbons present in a geological formation. Another exemplary use of the CO<NUM> stream is in food applications.

The H<NUM>-rich stream can have an absolute pressure from, e.g., <NUM> kPa, <NUM> kPa, <NUM> kPa, <NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, to <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, <NUM>,<NUM> kPa, or even <NUM>,<NUM> kPa. The H<NUM>-rich stream comprises H<NUM> at a molar concentration of from, <NUM>%, e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, or even <NUM>%, based on the total moles of molecules in the H<NUM>-rich stream. The H<NUM>-rich stream can comprise at least one and preferably all of, on a molar basis: (i) e.g., from <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>%, of CO; (ii) e.g., from <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>%, of CO<NUM>; and (iii) e.g., from <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>% of CH<NUM>. One specific example of a H<NUM>-rich stream that may be produced from the process of this disclosure has the following molar composition: <NUM>% of CO<NUM>; <NUM>% of CO; <NUM>% of H<NUM>; <NUM>% of N<NUM>; <NUM>% of CH<NUM>; and <NUM>% of H<NUM>O.

Where an even higher purity H<NUM> stream is desired, a portion of the H<NUM>-rich stream can be further purified by using processes and technologies known to one skilled in the art, e.g., pressure-swing-separation.

Preferably, however, the H<NUM>-rich stream, notwithstanding the optional low concentrations of CO, CO<NUM>, and CH<NUM>, is used as a fuel gas stream without further purification to provide heating in step (VIII) of the process in, e.g., residential, office, and/or industrial applications, preferably industrial applications. Due to the considerably reduced combined concentrations of CO, CO<NUM>, and CH<NUM> therein compared to conventional fuel gases such as natural gas, the flue gas stream produced from combusting the H<NUM>-rich stream can comprise CO<NUM> at a considerably reduced concentration, resulting in appreciably lower CO<NUM> emission to the atmosphere. Thus, the flue gas stream can comprise CO<NUM> at a molar concentration from, e.g., <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%, preferably ≤ <NUM>%, preferably ≤ <NUM>%, preferably ≤ <NUM>%, based on the total moles of CO<NUM> and H<NUM>O in the flue gas stream. The combustion may be in the presence of, e.g., air, O<NUM>-enhanced air, high-purity O<NUM>, and the like, depending on the specific application.

For use as a fuel gas stream, the H<NUM>-rich stream may preferably has an absolute pressure of ≤ <NUM>,<NUM> kPa (<NUM> psig), preferably ≤ <NUM> kPa (<NUM> psig). To achieve such low pressure of the H<NUM>-rich stream, it is feasible to design a syngas producing unit upstream comprising an SMR and/or an ATR operating under syngas producing conditions including a relatively low pressure, e.g., an absolute pressure of ≤ <NUM>,<NUM> kPa (<NUM> psig), preferably ≤ <NUM>,<NUM> kPa (<NUM> psig). As mentioned above, a lower pressure in the reforming reactor results in a higher CH<NUM> conversion in the reforming reactor, and hence a low residual CH<NUM> concentration in the H<NUM>-rich stream.

The H<NUM>-rich stream is supplied to at least one, preferably a majority, preferably all, of the combustion devices used in the process/system for producing the H<NUM>-rich stream. Thus, where the syngas producing unit comprises a pre-reformer including a furnace heated by one or more burners combusting a fuel gas, preferably a portion of the H<NUM>-rich stream is supplied as at least a portion, preferably a majority, preferably the entirety, of the fuel gas to such burners. Where the syngas producing unit includes an SMR comprising one or more SMR burners combusting a SMR fuel, it is highly desirable to supply a portion of the H<NUM>-rich stream as at least a portion, preferably a majority, preferably the entirety, of the SMR fuel. Where the H<NUM>-rich stream production process/system uses an additional boiler or auxiliary furnace combusting a fuel gas, it is desirable to supply a portion of the H<NUM>-rich stream as at least a portion, preferably a majority, preferably the entirety, of the fuel gas. By combusting the H<NUM>-rich stream and capturing the CO<NUM> stream, the H<NUM>-rich stream production process/system of this disclosure can reach an appreciably reduced level of CO<NUM> emission to the atmosphere than conventional H<NUM> production processes combusting natural gas.

Compared to existing syngas and/or H<NUM>-rich fuel gas producing processes, especially those combusting a hydrocarbon-containing fuel, the H<NUM>-rich fuel gas production process of this disclosure has at least one of the following advantages: (i) lower capital investment and production cost due to, e.g., an absence of a PSA unit, a small-size CO<NUM> recovery unit, and operating the syngas producing unit, the first shift reactor, and the second shift gas reactor under relatively low pressure; and (ii) considerably lower CO<NUM> emission if the CO<NUM> stream is captured, stored, sequestered, and/or utilized.

A modern olefins production plant typically operates by feeding a hydrocarbon feed (e.g., ethane, propane, butanes, naphtha, crude oil, and mixtures and combinations thereof) and steam into a steam cracker, heating the hydrocarbon feed/steam mixture to an elevated cracking temperature for a desirable residence time, thereby cracking the hydrocarbon feed to produce a steam cracker effluent comprising H<NUM>, CH<NUM>, ethane, propane, butanes, C2-C4 olefins, C4 dienes, and C5+ hydrocarbons exiting the pyrolysis reactor. The heating can include a preheating step in the convection section of the steam cracker, followed by transfer to the radiant section, where additional heating to the elevated cracking temperature and cracking occur. The thermal energy need for the preheating in the convection section and the heating in the radiant section is typically provided by a plurality of steam cracker burners combusting a steam cracker fuel gas. The high-temperature steam cracker effluent is immediately cooled down by quenching and/or indirect heat exchange, and separated to produce, among others, a process gas stream comprising C1-C4 hydrocarbons. The process gas stream is then typically compressed and supplied to a product recovery section including a chill train and multiple distillation columns such as a demethanizer, a deethanizer, a depropanizer, a C2 splitter, a C3 splitter, to name a few, from which one of more of the following may be produced: (i) a steam-cracker H<NUM> stream, which may preferably comprise H<NUM> at a molar concentration of from, e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, or even <NUM>%, based on the total moles of molecules in the steam-cracker H<NUM> stream; (ii) a CH<NUM>-rich stream (sometimes referred to as a "tailgas stream") comprising CH<NUM> at a molar concentration from, e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>%, based on the total moles of molecules in the CH<NUM>-rich stream; (ii) an ethane stream; (iii) an ethylene product stream; (iv) a propane stream; and (v) a propylene product stream. Many configurations of the recovery sections are possible. The steam-cracker H<NUM> stream may comprise, on a molar basis, e.g., from <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>% of CH<NUM>. Preferably the steam-cracker H<NUM> stream is substantially free of CO<NUM> and CO, e.g., comprising CO<NUM> and CO at a combined concentration from <NUM> to no greater than <NUM>% by mole, based on the total moles of molecules in the steam-cracker H<NUM> stream. The CH<NUM>-rich stream may comprise at least one and preferably all of, on a molar basis: (i) e.g., from <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, to <NUM>%, or even <NUM>%, <NUM>% H<NUM>; (ii) e.g., from <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% ethane; and (iii) e.g., from <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, or <NUM>% CO, based on the total moles of molecules in the CH<NUM>-rich stream.

The H<NUM>-rich fuel gas production processes of this disclosure is integrated with an olefins production plant to achieve an enhanced level of energy efficiency and a reduced level of CO<NUM> emissions to the atmosphere, regardless of the specific configuration of the recovery section in the plant.

In certain preferred embodiments, a portion of the H<NUM>-rich stream may be combined with a portion of the steam-cracker H<NUM> stream to form a joint H<NUM>-rich stream, which can be used as a fuel gas for residential, office, and/or industrial heating applications, including the heat applications described above for the H<NUM>-rich stream.

In one particularly desirable embodiment, a portion of the H<NUM>-rich stream, the steam-cracker H<NUM> stream, or the joint H<NUM>-rich stream can be supplied to one of more of the steam cracker burners as at least a portion, preferably a majority, preferably the entirety, of the steam cracker fuel gas. A steam cracker can consume large quantity of the steam cracker fuel gas, which hitherto tends to comprise substantial quantity of hydrocarbons such as CH<NUM>. By substituting a portion, preferably majority, preferably the entirety, of the steam cracker fuel gas with the H<NUM>-rich stream, the steam-cracker H<NUM> stream, and/or the joint H<NUM>-rich stream, each containing low concentrations of carbon-containing species, considerable reduction of CO<NUM> emission from the steam cracker flue gas can be achieved. In certain embodiments, the steam cracker may preferably be equipped with a combustion air pre-heater to reduce the fuel consumption requirements of the steam cracker. The combustion air pre-heater can preferably provide heating by electrical heating and/or exchanging heat with a warmer stream such as: the flue-gas of the same or different furnace; a steam stream (preferably a low-pressure steam stream), a hot water stream, and/or a hot oil stream.

An olefins production plant may include one or more boilers and/or auxiliary furnaces combusting a fuel gas in addition to the steam cracker. In such case, it is highly advantageous to supply a portion of the H<NUM>-rich stream, the steam-cracker H<NUM> stream, and/or the joint H<NUM>-rich stream to such boilers and/or auxiliary furnaces as a portion, preferably a majority, preferably the entirety, of the fuel gas needed. Doing so can further reduce CO<NUM> emission to the atmosphere from the olefins production plant.

An olefins production plant may comprise a combined-cycle power plant comprising one or more duct burners combusting a duct burner fuel to generate thermal energy. In such case, it is highly advantageous to supply a portion of the H<NUM>-rich stream, the steam-cracker H<NUM> stream, and/or the joint H<NUM>-rich stream to the duct burners as a portion, preferably a majority, preferably the entirety, of the duct burner fuel needed.

In certain embodiments, the H<NUM>-stream and/or the steam-cracker H<NUM> stream can supply from, e.g., <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>%, of the total fuel gas required, on a Btu basis, in the olefins production plant.

Advantageously, the CH<NUM>-rich stream produced from the olefins production plant is fed into the syngas producing unit as at least a portion of the hydrocarbon feed, optionally along with, e.g., a natural gas stream. Since the CH<NUM>-rich stream from the olefins production plant can be substantially free of sulfur, it can be advantageously fed into the syngas producing unit after the sulfur-removal unit, if any. If the CH<NUM>-rich comprises C2+ hydrocarbons (e.g., ethane) at a low molar concentration, e.g., ≤ <NUM>%, ≤ <NUM>%, <<NUM>%, < <NUM>%, < <NUM>%, e.g., from <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or even <NUM>%, based on the total moles of hydrocarbons in the CH<NUM>-rich stream, then the CH<NUM>-rich stream can be supplied to the reforming reactor at a location downstream of the pre-reformer, if any, because of the reduced need to convert the C2+ hydrocarbons in the pre-reformer. The CH<NUM>-rich stream may comprise H<NUM> at various quantities, as indicated above. However, it is not necessary to remove the H<NUM> from the CH<NUM>-rich stream before it is fed to the SMR. Excess hydrogen in the CH<NUM>-rich stream can consume hydraulic capacity in the SMR and hence is undesirable. But a small amount of hydrogen (preferably ≤ <NUM> mol%, preferably ≤ <NUM> mol%, based on the total moles of molecules in the CH<NUM>-rich stream) is acceptable, and may actually serve to minimize the potential for coke or foulant generation in the SMR.

In certain embodiments, the CH<NUM>-rich stream may have a pressure higher than the pressure of the hydrocarbon feed required for feeding into the syngas producing unit. In such case, it is highly advantageous to expand the CH<NUM>-rich stream in a turbo-expander and/or a Joule-Thompson valve to produce a cooled CH<NUM>-rich stream having a pressure in the vicinity of the pressure of the hydrocarbon feed. The cooled CH<NUM>-rich stream may be heated by using, e.g., any stream in the olefins production plant or the H<NUM>-rich production unit having a temperature higher than the cooled CH<NUM>-rich stream, and then supplied to the syngas producing unit.

In certain embodiments, the CH<NUM>-rich stream may have a pressure lower than the pressure of the hydrocarbon feed required for feeding into the syngas producing unit. In such case, it is desirable to compress the CH<NUM>-rich stream to a pressure in the vicinity of the pressure of the hydrocarbon feed before feeding it to the syngas producing unit.

In the following TABLE I, the CO<NUM> footprint of a steam cracker combusting the following fuel gases emitting flue gases produced from the combustion are compared: (i) only a typical natural gas ("Natural Gas"); (ii) only a tailgas produced from a steam cracker receiving a typical naphtha steam-cracking feed ("Tailgas"); (iii) a CO-rich fuel gas produced from a comparison process including a syngas producing unit followed by a single stage of high-temperature shift reactor, and then followed by H<NUM>O abatement and CO<NUM> recovery ("CO-Rich Fuel"); and (iv) a H<NUM>-rich stream made by the process of this disclosure ("H<NUM>-Rich Fuel"). In all cases the following is assumed: <NUM> wet vol% excess O<NUM>, <NUM> °F (<NUM>) air & fuel gas.

As can be seen from TABLE I, compared to all other three fuel gases, the H<NUM>-rich stream made by the process of this disclosure has a considerably smaller CO<NUM> footprint from the emission of the flue gas produced by the combustion. Even though the H<NUM>-Rich Fuel only comprises H<NUM> at a lightly higher concentration and CO at a slightly lower concentration than the comparative CO-Rich Fuel, the H<NUM>-Rich Fuel demonstrated a markedly lower CO<NUM> footprint (<NUM>% lower). This shows a significant advantage of the process of this disclosure utilizing at least two stages of shift reactors compared to using a single stage of high-temperature shift reactor only. While it is possible to purify the CO-Rich Fuel further to produce a fuel gas having a higher H<NUM> concentration and a lower CO concentration comparable to the H<NUM>-Rich Fuel by using additional equipment such as a PSA unit, the installation and operation of a PSA unit add much more investment and operation costs and reduce the energy efficiency of the process than the addition of the second shift reactor. Therefore, the process of this disclosure achieves the production of a H<NUM>-rich fuel gas with low CO<NUM> footprint with a reduced cost and enhanced energy efficiency.

This disclosure is further illustrated by the exemplary but non-limiting embodiments shown in the drawings, which are described below. In the drawings, the same reference numeral may have similar meanings. In the drawings illustrating an inventive process/system, where multiple initially separate streams are shown to form a joint stream supplied to a next step or device, it should be understood to further include, where appropriate, an alternative where at least one of such multiple separate streams is supplied to the next step or device separately. Where multiple initially separate streams having similar compositions and/or use applications (steam streams generated from differing devices) are shown to form a joint stream supplied to multiple next steps or devices, it should be understood to include, where appropriate, alternatives where at least one of the separate streams and the joint stream is supplied to at least one of the multiple next steps or devices. Thus, where a steam stream X and a steam stream Y, initially separate and generated from differing devices but with similar applications, are shown to form a joint stream Z supplied to two separate turbines A and B, it should be understood to include alternatives where at least one of X, Y, and Z is supplied to at least one of A and B, including but not limited to the following: (i) only stream Z is supplied to A and B; (ii) both of X and Y are supplied, separately, to at least one of A and B; (iii) both of X and Z are supplied, separately, to at least one of A and B; (iv) both of Y and Z are supplied, separately, to at least one of A and B; and (v) only one of X and Y is supplied to at least one of A and B. The drawings are only for the purpose of illustrating certain embodiments of this disclosure, and one skilled in the art appreciates that alternatives thereof may fall within the scope of this disclosure.

<FIG> schematically illustrates processes/systems <NUM> including an SMR for producing a H<NUM>-rich fuel stream according to certain preferred embodiments of this disclosure. As shown, a hydrocarbon feed stream <NUM> (e.g., a natural gas stream comprising primarily CH<NUM>), which may contain CH<NUM>, C2+ hydrocarbons at various concentrations, and sulfur-containing compounds at various concentrations, is first fed into an optional sulfur removal unit <NUM> to produce a sulfur-abated stream <NUM>, to prevent poisoning catalysts used in the downstream process steps such as the catalyst used in the SMR unit described below. Upon optional preheating via, e.g., a heat exchanger or a furnace (not shown), stream <NUM> is combined with an HPS stream <NUM> to form a hydrocarbon/steam mixture stream <NUM>. Upon optional preheating via, e.g., a heat exchanger or a furnace (not shown), stream <NUM> can be then fed into a pre-reformer <NUM> which can be an adiabatic reactor containing a pre-reforming catalyst therein. On contacting the pre-reforming catalyst, the heavier C2+ hydrocarbons are preferentially converted into methane (thus preventing the formation of coke in the downstream primary reforming reactor) to produce a pre-reforming effluent <NUM> comprising methane and steam. Stream <NUM> is then fed into a tube 120a in the upper section <NUM>, sometimes called convection section, of an SMR <NUM>, where it is heated. SMR <NUM> comprises a lower section <NUM>, sometimes called radiant section, housing one or more tube 120b which is in fluid communication with tube 120a receiving the stream <NUM> heated in tube 120a. As shown in <FIG>, tube 120a may exit the convection section to the exterior of the SMR furnace, and then re-enters at the entrance to tube(s) 120b, via, e.g., a manifold (not shown). SMR <NUM> comprises one or more burners <NUM> in the radiant section <NUM>, where a SMR fuel combusts to supply energy to the radiant section <NUM> and then the convection section <NUM> of SMR <NUM>. For the convenience of illustration, tubes 120a and 120b in the SMR are shown as comprising multiple straight segments. In practice, certain portions of tubes 120a and 120b, particularly tube 120a, may be curved, or even form serpentine windings.

A reforming catalyst is loaded in tube(s) 120b in the radiant section <NUM>. Due to the proximity to the burner(s) <NUM>, the hydrocarbon feed and steam, and the reforming catalyst in tube(s) 120b are heated/maintained at an elevated temperature. The forward reaction of the following preferentially occurs under syngas producing conditions:
<CHM>.

In addition, various amounts of CO<NUM> may be produced in tube(s) 120b. Thus, a reformed stream <NUM> comprising CO, H<NUM>, residual CH<NUM>, residual H<NUM>O and optionally various amount of CO<NUM> exits the outlet of tube(s) 120b from the SMR at a temperature of, e.g., from <NUM> to <NUM> and an absolute pressure of, e.g., from <NUM> kPa to <NUM>,<NUM> kPa. Stream <NUM> is then cooled at a waste heat recovery unit ("WHRU") including a waste heat boiler ("WHB") <NUM> and a steam drum <NUM> to produce a cooled reformed stream <NUM> and to generate an HPS stream <NUM>. As shown, a water stream <NUM> flows from steam drum <NUM> to WHB <NUM>, and a steam-water mixture stream <NUM> flows from WHB <NUM> to steam drum <NUM>.

Stream <NUM>, preferentially a saturated steam stream, can be then heated in the convection section <NUM> of SMR <NUM> to produce a super-heated, high-pressure steam ("SPHP") steam stream <NUM>, which can be fed into a steam header and supplied to any suitable equipment or process step. For example, as shown and described above, a split stream <NUM> of stream <NUM> can be combined with the sulfur-abated hydrocarbon feed stream <NUM> to form a combined stream <NUM>, which is then fed into the pre-reformer <NUM>. For another example, a split stream <NUM> of stream <NUM> can be fed into a steam turbine <NUM>, where it is expanded to produce an exhaust steam stream <NUM> and shaft power. The shaft power can be transferred, via shaft <NUM>, to any suitable equipment <NUM> to produce useful mechanical work. One example of equipment <NUM> is an electricity generator, which converts the mechanical work into electrical energy transmissible to any suitable local or distant electrical equipment. Exhaust steam stream <NUM> can have various residual pressure and temperature suitable for, e.g., driving additional steam turbines, heating other equipment and/or streams, and the like.

As shown in <FIG>, the cooled reformed stream <NUM>, comprising CO, H<NUM>, H<NUM>O, and optionally CO<NUM>, is then fed into a first shift reactor <NUM>. The first shift reactor can be operated under a first set of shifting conditions comprising the presence of a first shift catalyst loaded therein. Due to the relatively high temperature in the first set of shifting conditions, the first shift reactor <NUM> is sometimes called a high-temperature shift reactor. On contacting the first shift catalyst under the first set of shifting conditions, the forward reaction of the following preferentially occurs:
<CHM>.

Thus, a first shifted stream <NUM> comprising CO at a lower concentration than stream <NUM> and CO<NUM> at a higher concentration than stream <NUM> exits the first shift reactor <NUM>. Because the forward reaction above is exothermic, stream <NUM> has a higher temperature than stream <NUM> assuming the first shift reactor <NUM> is an adiabatic reactor.

The first shifted stream <NUM> is then further cooled down at heat exchanger <NUM> by any suitable stream having a temperature lower than stream <NUM>. As shown in <FIG>, in a preferred embodiment, a boiler feed water stream <NUM>, supplied from a boiler feed water treatment unit <NUM>, is used to cool down stream <NUM>. The thus heated boiler feed water stream <NUM> exiting the heat exchanger <NUM> can be supplied to steam drum <NUM> and at least partly supplied to the WHB <NUM>, to produce high-pressure steam stream <NUM> as described earlier, or to any other suitable steam generator. Alternatively or additionally (not shown), the hydrocarbon feed stream <NUM>, or a portion thereof, may be heated by stream <NUM> at heat exchanger <NUM> or another heat exchanger upstream or downstream of heat exchanger <NUM>.

The cooled first shifted stream <NUM> exiting heat exchanger <NUM>, comprising CO, H<NUM>, H<NUM>O, and CO<NUM>, is then fed into a second shift reactor <NUM>. The second shift reactor can be operated under a second set of shifting conditions comprising the presence of a second shift catalyst loaded therein and a temperature lower than in the first shift reactor <NUM>. Due to the lower temperature, the second shift reactor <NUM> is sometimes called a low-temperature shift reactor. On contacting the second shift catalyst under the second set of shifting conditions, the forward reaction of the following preferentially occurs:
<CHM>.

Thus, a second shifted stream <NUM> comprising CO at a lower concentration than stream <NUM> and CO<NUM> at a higher concentration than stream <NUM> exits the second shift reactor <NUM>. Because the forward reaction above is exothermic, stream <NUM> has a higher temperature than stream <NUM> assuming the second shift reactor <NUM> is an adiabatic reactor.

The second shifted stream <NUM> can then be further cooled down at heat exchanger <NUM> by any suitable stream having a temperature lower than stream <NUM>. In a preferred embodiment, a boiler feed water stream (not shown) supplied from a boiler feed water treatment unit (e.g., unit <NUM>) can be advantageously used to cool down stream <NUM>. The thus heated boiler feed water stream exiting the heat exchanger <NUM> can be supplied (not shown) to steam drum <NUM> and at least partly supplied to the WHB <NUM>, to produce high-pressure steam stream <NUM> as described earlier, or to any other suitable steam generator. Alternatively or additionally (not shown), the hydrocarbon feed stream <NUM>, or a portion thereof, may be heated by stream <NUM> at heat exchanger <NUM> or another heat exchanger upstream or downstream of heat exchanger <NUM>.

The cooled stream <NUM> exiting heat exchanger <NUM> can be further cooled at heat exchanger <NUM> by any suitable cooling medium having a lower temperature than stream <NUM>, e.g., a cooling water stream, ambient air (using an air-fin cooler, e.g.), and the like. Preferably, a portion of the residual steam in stream <NUM> is condensed to liquid water in stream <NUM>, which can be fed into a separator <NUM> to obtain a condensate stream <NUM> and a vapor stream <NUM>. The steam-abated stream <NUM>, a crude gas mixture, comprises primarily H<NUM> and CO<NUM>, and optionally minor amount of residual CH<NUM> and CO.

Stream <NUM> is then supplied into a CO<NUM> recovery unit <NUM> to produce a CO<NUM> stream <NUM> and an H<NUM>-rich stream <NUM>. Any suitable CO<NUM> recovery unit known in the art may be used. A preferred CO<NUM> recovery unit is an amine absorption and regeneration unit, where the crude gas mixture stream <NUM> contacts a counter-current stream of amine which absorbs the CO<NUM>, which is subsequently released from the amine upon heating ("regeneration"). The CO<NUM> stream <NUM> can be supplied to a CO<NUM> pipeline and conducted away. The CO<NUM> stream <NUM> can be compressed, liquefied, stored, sequestered, or utilized in manners known to one skilled in the art.

The H<NUM>-rich stream <NUM> comprises H<NUM> at a molar concentration from, <NUM>%, e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, based on the total moles of molecules in stream <NUM>. In addition to H<NUM>, stream <NUM> may comprise: (i) CH<NUM> at a molar concentration thereof based on the total moles of molecules in stream <NUM>, from, e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%; (ii) CO at a molar concentration thereof based on the total moles of molecules in stream <NUM>, from, e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, or <NUM>%; and (iii) CO<NUM> at a molar concentration thereof based on the total moles of molecules in stream <NUM>, from, e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%. Stream <NUM> can be advantageously used as a fuel gas for residential, office, and/or industrial heating. Due to the high concentration of H<NUM> and low concentration of carbon-containing molecules therein, the combustion of stream <NUM> in the presence of an oxidant such as air, oxygen, and the like, can produce a flue gas stream comprising CO<NUM> at a low concentration. In certain embodiments, the flue gas stream can comprises CO<NUM> at a molar concentration based on the total moles of H<NUM>O and CO<NUM> in the flue gas stream of no greater than <NUM>% (e.g., from <NUM>%, <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM>%, <NUM>%, to <NUM>%, <NUM> mol%, or <NUM>%). The flue gas stream can be advantageously exhausted into the atmosphere without the need to separate and capture CO<NUM> therefrom.

In a preferred embodiment, as shown in <FIG>, a split stream <NUM> of stream <NUM> can be supplied to the SMR <NUM>, where it is combusted in burner(s) <NUM> to supply thermal energy to the SMR <NUM> heating the lower radiant section <NUM> and tube(s) 120b therein and the convection section <NUM> and tube 120a therein. The flue gas stream <NUM> exiting the SMR <NUM> comprises CO<NUM> at a low concentration, and therefore can be exhausted into the atmosphere with considerably reduced CO<NUM> emission without the need to separate and capture CO<NUM> therefrom.

<FIG> schematically illustrates processes/systems <NUM> including an ATR for producing a H<NUM>-rich fuel stream according to certain preferred embodiments of this disclosure. As shown, a hydrocarbon feed stream <NUM> (e.g., a natural gas stream comprising primarily CH<NUM>), which may contain CH<NUM>, C2+ hydrocarbons at various concentrations, and sulfur-containing compounds at various concentrations, is first fed into an optional sulfur removal unit <NUM> to produce a sulfur-abated stream <NUM>, to prevent poisoning catalysts used in the downstream process steps such as the catalyst used in the pre-reformer and the ATR unit described below. Upon optional preheating via, e.g., a heat exchanger (not shown) or a furnace <NUM> a heated stream <NUM> is produced. Stream <NUM> is then combined with an HPS stream <NUM> to form a hydrocarbon/steam mixture stream <NUM>. Upon optional preheating via, e.g., a heat exchanger or a furnace (not shown), stream <NUM> can be then fed into a pre-reformer <NUM> which can be an adiabatic reactor containing a pre-reforming catalyst therein. On contacting the pre-reforming catalyst, the heavier C2+ hydrocarbons are preferentially converted into methane (thus preventing the formation of coke in the downstream primary reforming reactor) to produce a pre-reforming effluent <NUM> comprising methane and steam. Upon optional heating in furnace <NUM>, stream <NUM> becomes a heated stream <NUM>, which is then fed into an ATR <NUM>, an O<NUM> stream <NUM>, which may be produced by air separation, is also fed into ATR <NUM>.

A reforming catalyst is loaded in ATR <NUM>. On contacting the reforming catalyst, the forward reaction of the following preferentially occurs under syngas producing conditions:
<CHM>.

In addition, various amounts of CO<NUM> may be produced in the ATR. Thus, a reformed stream <NUM> comprising CO, H<NUM>, residual H<NUM>O, optionally residual CH<NUM> at various concentrations, and optionally various amount of CO<NUM> exits ATR <NUM> at a temperature of e.g., from <NUM> to <NUM> and an absolute pressure from <NUM> kPa to <NUM>,<NUM> kPa. Stream <NUM> is then cooled at a waste heat recovery unit ("WHRU") including a waste heat boiler ("WHB") <NUM> and a steam drum <NUM> to produce a cooled reformed stream <NUM> and to generate an HPS stream <NUM>. As shown, a water stream <NUM> flows from steam drum <NUM> to WHB <NUM>, and a steam-water stream <NUM> flows from WHB <NUM> to steam drum <NUM>.

Stream <NUM>, preferentially a saturated steam stream, can be then heated in an auxiliary furnace <NUM> to produce a super-heated, high-pressure steam ("SH-HPS") stream <NUM>, which can be fed into a steam header and supplied to any suitable equipment or process step. Furnace <NUM> may be the same furnace as furnace <NUM> or a separate furnace. For example, as shown and described above, a split stream <NUM> of stream <NUM> can be combined with the sulfur-abated hydrocarbon feed stream <NUM> to form a combined stream <NUM>, which is then fed into the pre-reformer <NUM>. For another example, a split stream <NUM> of stream <NUM> can be fed into a steam turbine <NUM>, where it is expanded to produce an exhaust steam stream <NUM> and shaft power. The shaft power can be transferred, via shaft <NUM>, to any suitable equipment <NUM> to produce useful mechanical work. One example of equipment <NUM> is an electricity generator, which converts the mechanical work into electrical energy transmissible to any suitable local or distant electrical equipment. Exhaust steam stream <NUM> can have various residual pressure and temperature suitable for, e.g., driving additional steam turbines, heating other equipment and/or streams, and the like.

The first shifted stream <NUM> is then further cooled down at heat exchanger <NUM> by any suitable stream having a temperature lower than stream <NUM>. As shown in <FIG>, in a preferred embodiment, a boiler feed water stream <NUM>, supplied from a boiler feed water treatment unit <NUM>, can be used to cool down stream <NUM>. The thus heated boiler feed water stream <NUM> exiting the heat exchanger <NUM> can be supplied to steam drum <NUM> and at least partly subsequently supplied to the WHB <NUM>, to produce high-pressure steam stream <NUM> as described earlier, or to any other suitable steam generator. Alternatively or additionally (not shown), the hydrocarbon feed stream <NUM>, or a portion thereof, may be heated by stream <NUM> at heat exchanger <NUM> or another heat exchanger upstream or downstream of heat exchanger <NUM>.

The cooled stream <NUM> exiting heat exchanger <NUM> can be further cooled at heat exchanger <NUM> by any suitable cooling medium having a lower temperature than stream <NUM>, e.g., a cooling water stream, ambient air (using an air-fin cooler, e.g.), and the like. Preferably, a portion of the residual steam in stream <NUM> is condensed to liquid water in stream <NUM>, which can be fed into a separator <NUM> to obtain a condensate stream <NUM> and a vapor stream <NUM>. The steam-abated stream <NUM>, a crude gas mixture stream, comprises primarily H<NUM> and CO<NUM>, and optionally minor amount of residual CH<NUM> and CO.

In a preferred embodiment, as shown in <FIG>, a split stream <NUM> of stream <NUM> (which is a split stream of stream <NUM>) can be supplied to furnace <NUM>, where it is combusted to preheat the de-sulfured hydrocarbon stream <NUM>, and a split stream <NUM> of stream <NUM> can be supplied to furnace <NUM>, where it is combusted to superheat steam stream <NUM>. The flue gas streams <NUM> and <NUM> exiting furnaces <NUM> and <NUM> comprise CO<NUM> at a low concentration, and therefore can be exhausted into the atmosphere without the need to separate and capture CO<NUM> therefrom.

<FIG> is a block diagram schematically illustrating processes and systems integrating an olefins production plant with an H<NUM>-rich fuel gas production unit as described above, according to certain preferred embodiments of this disclosure. The olefins production plant can include a pyrolysis reactor (e.g., a steam cracker) receiving a hydrocarbon feed and steam, preheating the hydrocarbon feed in a convection section, transferring the preheated feed and steam into a radiant section, subjecting the hydrocarbon feed and steam in the radiant section to suitable pyrolysis conditions including an elevated temperature and a short residence time, thereby producing a pyrolysis effluent comprising olefins such as ethylene, propylene, C4 olefins, C4 dienes, and methane, ethane, propane, and C5+ hydrocarbons. The pyrolysis effluent is typically immediately cooled down by quenching and/or indirect heat transfer, and subsequently separated in a primary fractionator and/or a quench tower to produce, among others, a process gas stream <NUM> comprising H<NUM>, CH<NUM>, ethane, propane, and the desirable C2-C4 olefins and dienes. The process gas stream <NUM> is typically compressed in one or more compressor(s) <NUM> to an elevated pressure, and then cooled down in a chill train and separated in a cryogenic product recovery system <NUM>. The product recovery system <NUM> can include a demethanizer, a deethanizer, a depropanizer, and the like, arranged in various configurations. From the product recovery system <NUM>, a steam-cracker H<NUM> stream <NUM>, a CH<NUM>-rich tailgas stream <NUM>, and a C2 hydrocarbon stream <NUM>, among others, can be produced. The C2 hydrocarbon stream <NUM> can be further separated in a C2 splitter tower <NUM> to produce an ethylene product stream <NUM> and an ethane stream <NUM>, the latter of which can be advantageously recycled to the steam cracker and cracked to produce additional quantities of olefin products.

As show in <FIG>, the CH<NUM>-rich stream <NUM> and an optional supplemental hydrocarbon stream <NUM> (e.g., a natural gas stream) is supplied along with steam (not shown) into a H<NUM>-rich fuel gas production unit <NUM> as hydrocarbon feeds. The H<NUM>-rich fuel gas production unit <NUM> includes a reforming reactor such as an SMR or an ATR, a first shift reactor, a second shift reactor, a CO<NUM> recovery unit and ancillary equipment, such as those described above and illustrated in <FIG> and <FIG>. From unit <NUM>, an H<NUM>-rich fuel gas stream <NUM> and a CO<NUM> stream <NUM> can be produced. The H<NUM>-rich fuel gas stream <NUM> can be advantageously combined with the steam-cracker H<NUM> stream <NUM> produced from the recovery system <NUM> of the olefins production plant to form a joint H<NUM>-rich fuel gas stream <NUM>. A portion of streams <NUM>, <NUM>, and/or <NUM>, such as split stream <NUM> as shown in <FIG>, may be fed into the H<NUM>-rich fuel gas production unit <NUM> as industrial fuel needed by various equipment therein, e.g., a furnace heating any pre-reformer, an SMR, any additional furnaces, boilers, and the like. A portion of streams <NUM>, <NUM>, and/or <NUM>, such as split stream <NUM> as shown in <FIG>, may be supplied to the olefins product plant as industrial fuel needed by various equipment therein, e.g., a steam cracker furnace, any supplemental furnace, and boilers. The combustion of the H<NUM>-rich fuel gas in the H<NUM>-rich fuel gas production unit <NUM> and in the olefins production plant can result in appreciably reduced CO<NUM> emission into the atmosphere compared to combustion of hydrocarbons such as natural gas.

The CO<NUM> stream <NUM> can be compressed, liquefied, conducted away, stored, sequestered, or utilized for suitable applications such as underground hydrocarbon extraction. As a result, processes and systems integrating an olefins production plant with an H<NUM>-rich fuel gas production unit as shown in <FIG> can achieve a desirably reduced overall CO<NUM> emission and a desirably improved overall energy efficiency compared to stand-alone processes.

Claim 1:
A process comprising:
(I) supplying a hydrocarbon feed and a steam feed into a syngas producing unit comprising a reforming reactor under syngas producing conditions to produce a reformed stream exiting the reforming reactor, wherein the syngas producing conditions include the presence of a reforming catalyst, and the reformed stream comprises H<NUM>, CO, and steam;
(II) cooling the reformed stream by using a waste heat recovery unit ("WHRU") to produce a cooled reformed stream and to generate a high-pressure steam ("HPS") stream;
(III) contacting the cooled reformed stream with a first shifting catalyst in a first shift reactor under a first set of shifting conditions to produce a first shifted stream exiting the first shift reactor, wherein the first shifted stream has a lower CO concentration and a higher CO<NUM> concentration than the cooled reformed stream;
(IV) cooling the first shifted stream to obtain a cooled first shifted stream;
(V) contacting the cooled first shifted stream with a second shifting catalyst in a second shift reactor under a second set of shifting conditions to produce a second shifted stream exiting the second shift reactor, wherein the second shifted stream has a lower CO concentration and a higher CO<NUM> concentration than the cooled first shifted stream;
(VI) abating steam present in the second shifted stream to produce a crude gas mixture stream comprising CO<NUM> and H<NUM>;
(VII) recovering at least a portion of the CO<NUM> present in the crude gas mixture stream to produce a CO<NUM> stream and a H<NUM>-rich stream, wherein the H<NUM>-rich stream comprises H<NUM> at a concentration of at least <NUM> mol%, based on the total moles of molecules in the H<NUM>-rich stream;
(VIII) combusting a portion of the H<NUM>-rich stream in the presence of an oxidant to generate thermal energy and to produce a flue gas stream;
(IX) operating a steam cracker located in an olefins production plant under steam cracking conditions to convert a steam cracker feed into a steam cracker effluent comprising olefins;
(X) producing a CH<NUM>-rich stream from the steam cracker effluent; and
(XI) providing the CH<NUM>-rich stream as at least a portion of the hydrocarbon feed in step (I);
wherein the H<NUM>-rich stream is supplied to at least one combustion device used in the process for producing the H<NUM>-rich stream.