Patent Description:
Catalytic oxidative dehydrogenation of alkanes into corresponding alkenes is an alternative to steam cracking. In contrast to steam cracking, oxidative dehydrogenation (ODH) may operate at lower temperature and generally does not produce coke. For ethylene production, ODH can provide a greater selectivity for ethylene than does steam cracking. The ODH may be performed in a reactor vessel having a catalyst for the conversion of an alkane to a corresponding alkene. The concept of ODH has been known since at least the late <NUM>'s. Since that time, considerable effort has been expended on improving the ODH process and associated catalyst efficiency and selectivity.

<CIT> - refers to an oxidative dehydrogenation chemical complex designed to reduce costs by including integration of an oxygen separation module that allegedly addresses safety concerns and reduces emission of greenhouse gases.

The following aspects are related to an ODH reactor system. The ODH reactor system includes a first reactor having a first ODH catalyst to dehydrogenate an alkane having a number of carbons in the range of <NUM> to <NUM> to a corresponding alkene at a first temperature and facilitate generation of steam. The first reactor has a first-reactor jacket for heat transfer. The ODH reactor system includes a second reactor having a second ODH catalyst to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> in a first-reactor effluent from the first reactor to the corresponding alkene at a second temperature greater than the first temperature and facilitate generation of steam. The second reactor has a second-reactor jacket for heat transfer. The ODH reactor system includes a third reactor having a third ODH catalyst to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> in a second-reactor effluent from the second reactor to the corresponding alkene at a third temperature greater than the second temperature and facilitate generation of steam. The third reactor has a third-reactor jacket for heat transfer.

Another aspect relates to a system for oxidative dehydrogenation. The system includes a first reactor having a first ODH catalyst to dehydrogenate an alkane at a first temperature. The first reactor has a first-reactor jacket to heat a first heat-transfer fluid flowing through the first-reactor jacket to facilitate generation of steam. The system includes a second reactor having a second ODH catalyst to dehydrogenate unreacted alkane from the first reactor at a second temperature greater than the first temperature. The second reactor has a second-reactor jacket to heat a second heat-transfer fluid flowing through the second-reactor jacket to facilitate generation of steam. The system includes a third reactor having a third ODH catalyst to dehydrogenate unreacted alkane from the second reactor at a third temperature greater than the first temperature. The third reactor has a third-reactor jacket to heat a third heat-transfer fluid flowing through the third-reactor jacket to facilitate generation of steam. The third ODH catalyst and the second ODH catalyst are different than the first ODH catalyst.

Yet another aspect relates to a method of oxidative dehydrogenation. The method includes contacting a feed having an alkane having a number of carbons in the range of <NUM> to <NUM> with a first ODH catalyst in a first reactor at a first temperature to dehydrogenate the alkane having a number of carbons in the range of <NUM> to <NUM> into a corresponding alkene and to heat a first heat-transfer fluid flowing through a first-reactor jacket to facilitate generation of steam. The method includes contacting a first-reactor effluent from the first reactor with a second ODH catalyst in a second reactor at a second temperature greater than the first temperature to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> from the first-reactor effluent into the corresponding alkene and to heat a second heat-transfer fluid flowing through a second-reactor jacket to facilitate generation of steam. The method includes contacting a second-reactor effluent from the second reactor with a third ODH catalyst in a third reactor at a third temperature greater than the first temperature to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> from the second effluent into the corresponding alkene and to heat a third heat-transfer fluid flowing through a third-reactor jacket to facilitate generation of steam.

The catalytic oxidative dehydrogenation (ODH) reaction is exothermic. Therefore, steam may be generated as a coproduct in utilizing heat from the ODH reaction. The steam production may be characterized as integrated with or within the ODH reactor system. In addition, the usage of the produced steam may be integrated at the site having the ODH reactor system. The produced steam may be utilized in the overall ODH system or in other unit operations or units at the facility having the ODH system. The produced steam may also be exported for use by other facilities or sites.

Different qualities or pressures of steam may be generated as a coproduct of the ODH reaction. The term "quality" of the steam may refer to the pressure or type of steam. Typical qualities of steam produced are low pressure steam (e.g., <NUM> kPa (<NUM> pounds per square inch gauge [psig]) or less), medium pressure steam (e.g., in the range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig)), high pressure steam (e.g., <NUM> kPa (<NUM> psig) or greater), or very high pressure steam (e.g., <NUM> kPa (<NUM> psig) or greater), and so forth. There may be different applications for the steam. The use of the steam by the consumers or customers receiving the steam may depend on the quality or pressure of the steam. In some implementations, higher steam pressures of the produced steam may give more versatility in the integration of the steam within the facility or plant. For instance, high pressure steam is used to power turbines attached to compressors, while low pressure steam is typically used for heating purposes, and the like.

In some implementations (noting that the use of only two ODH reactors is outside the scope of the invention), two or more ODH reactors in series may operate at progressively higher temperature to generate different qualities of steam. The respective operating temperature of the ODH reactors is increasingly greater along the series of ODH reactors. The second ODH reactor has a higher operating temperature than the first ODH reactor. The third ODH reactor has a higher operating temperature than the second ODH reactor, and so on.

The different reaction temperatures among the respective ODH reactors may be due to utilization of different types or grades of catalysts in the respective ODH reactors. The catalyst in the second ODH reactor may give an ODH reaction at a greater temperature than the catalyst in the first ODH reactor. The catalyst in the third ODH reactor may give an ODH reaction at a greater temperature than the catalyst in the second ODH reactor, and so on.

Three ODH reactors are depicted in the ODH reactor systems of <FIG>. The present ODH reactor systems may have three ODH reactors in series or may have more than three ODH reactors (e.g., four ODH reactors, five ODH reactors, etc.) in series or parallel for the generation of steam. The final ODH reactor in the series may discharge an effluent having a product alkene of the ODH reactor system.

<FIG> is an ODH reactor system <NUM> including a first ODH reactor <NUM>, a second ODH reactor <NUM>, and a third ODH reactor <NUM> operationally disposed in series. In the illustrated embodiment, the ODH reactors <NUM>, <NUM>, <NUM> are tubular reactors having a process side and a cooling jacket. The process side is one or more tubes or conduits for the reaction of the alkane to alkene. The process side has catalyst (e.g., a fixed bed of catalyst) for the conversion of the alkane to the corresponding alkene. The system <NUM> flows water as a heat transfer fluid through the jacket side to control the reaction temperature on the process side. The heat or energy acquired by the heat transfer fluid through the reactor jacket may be utilized to generate steam as a coproduct. For the system <NUM> in operation, the liquid water is depicted with gray shading in <FIG>. Such gray shading for liquid water is also utilized in <FIG>.

The first ODH reactor <NUM> has a process side <NUM> having a first catalyst <NUM>. The second ODH reactor <NUM> has a process side <NUM> having a second catalyst <NUM>. The third ODH reactor <NUM> has a process side <NUM> having a third catalyst <NUM>. As indicated, each process side <NUM>, <NUM>, <NUM> may be one or more conduits or tubes in some examples. The first catalyst <NUM>, second catalyst <NUM>, and third catalyst <NUM> may each be a fixed bed of catalyst. The first catalyst <NUM>, second catalyst <NUM>, and third catalyst <NUM> may be the same catalyst type or different respective catalyst types.

In operation, the process side <NUM> of the first ODH reactor <NUM> receives a feed <NUM> having an alkane. The feed <NUM> as a hydrocarbon feed may also include oxygen for the ODH reaction. However, the oxygen may be added to the first ODH reactor separate from the feed <NUM>. The alkane in the feed <NUM> is an alkane (saturated hydrocarbon) having a number of carbons in the range of <NUM> to <NUM>. The first ODH reactor <NUM> may receive the feed <NUM> via a conduit coupled (e.g., by a flanged connection) to an inlet of the first ODH reactor <NUM> vessel at the process side <NUM>. The first ODH reactor <NUM> may convert the alkane in the feed <NUM> to a corresponding alkene in a catalytic reaction via the catalyst <NUM> on the process side <NUM> of the first reactor <NUM>. Some of the alkane in the feed <NUM> is not converted into the corresponding alkene but remains unreacted. The first ODH reactor <NUM> discharges an effluent <NUM> having the corresponding alkene and unreacted alkane. In one implementation, the alkane is ethane and the corresponding alkene is ethylene. In that implementation, the effluent <NUM> may also include acetic acid. In addition, the effluent <NUM> may include carbon dioxide, water, and so forth.

The process side <NUM> of the second ODH reactor <NUM> may receive (e.g., via a conduit) the effluent <NUM> from the first ODH reactor <NUM>. The second ODH reactor <NUM> may convert the unreacted alkane to the corresponding alkene in a catalytic reaction via the catalyst <NUM> on the process side <NUM> of the second reactor <NUM>. Some of the unreacted alkane is not converted into the corresponding alkene but remains unreacted. The second ODH reactor <NUM> discharges an effluent <NUM> having the corresponding alkene and unreacted alkane.

The process side <NUM> of the third ODH reactor <NUM> may receive (e.g., via a conduit) the effluent <NUM> from the second ODH reactor <NUM>. The third ODH reactor <NUM> may convert the unreacted alkane to the corresponding alkene in a catalytic reaction with the catalyst <NUM> on the process side <NUM> of the third reactor <NUM>. The third ODH reactor <NUM> discharges an effluent <NUM> having the corresponding alkene and any unreacted alkane. The corresponding alkene (e.g., ethylene) may be a product of the ODH reactor system <NUM>.

In some embodiments, the catalyst <NUM>, <NUM>, <NUM> in the reactors <NUM>, <NUM>, <NUM> (process sides <NUM>, <NUM>, <NUM>) is different, respectively, and may give conversion of the alkane to the corresponding alkene at different temperatures, respectively. The first catalyst <NUM> may be different than the second catalyst <NUM> and the third catalyst <NUM>, and the second catalyst <NUM> may be different than the third catalyst <NUM>. The third reactor <NUM> reaction temperature is greater than the second reactor <NUM> reaction temperature, and the second reactor <NUM> reaction temperature is greater than the first reactor <NUM> reaction temperature.

The arrangement of the three ODH reactors <NUM>, <NUM>, <NUM> is a once-through effluent/feed configuration in that the effluent <NUM> from the first ODH reactor <NUM> is feed to the second ODH reactor <NUM>, and the effluent <NUM> from the second ODH reactor <NUM> is feed to the third ODH reactor <NUM>. In certain embodiments, oxygen may be injected into the effluent <NUM> or the second ODH reactor <NUM> to supplement the effluent <NUM> with oxygen to account for consumption (depletion) of oxygen by the first ODH reactor <NUM>. Likewise, oxygen may be injected into the effluent <NUM> or third ODH reactor <NUM> to supplement the effluent <NUM> with oxygen to account for depletion of oxygen by the second ODH reactor <NUM>. Oxygen may also be fed directly to the second reactor <NUM> or the third reactor <NUM>.

In some implementations, the ODH reactor system <NUM> may have a conduit to provide, if desired, feed (e.g., similar or same as feed <NUM>) or fresh alkane having a number of carbons in the range of <NUM> to <NUM> (e.g., ethane) to the second ODH reactor <NUM> to supplement the effluent <NUM> received from the first ODH reactor <NUM>. This additional feed or fresh alkane having a number of carbons in the range of <NUM> to <NUM> may be added to the effluent <NUM> or directly to the reactor <NUM>. Similarly, the ODH reactor system <NUM> may have a conduit to provide feed (e.g., similar or same as feed <NUM>) or fresh alkane having a number of carbons in the range of <NUM> to <NUM> to the third ODH reactor <NUM> to supplement the effluent <NUM> received from the second ODH reactor <NUM>. This additional feed or fresh alkane having a number of carbons in the range of <NUM> to <NUM> may be added to the effluent <NUM> or directly to the reactor <NUM>.

Moreover, any acetic acid in the effluent <NUM> from the first ODH reactor <NUM> may be oxidized into carbon dioxide in the second ODH reactor <NUM>, depending on the operating temperature of the second ODH reactor <NUM>. Any acetic acid in the effluent <NUM> from the second ODH reactor <NUM> may be combusted into carbon dioxide in the third ODH reactor <NUM>, depending on the operating temperature of the third ODH reactor <NUM>.

The first ODH reactor <NUM> has a jacket <NUM>, the second ODH reactor <NUM> has a jacket <NUM>, and the third ODH reactor <NUM> has a jacket <NUM>. In this illustrated example of <FIG>, the heat transfer fluid that flows through the jackets <NUM>, <NUM>, <NUM> is water (e.g., boiler feedwater). Also, in this example, the ODH reaction system <NUM> includes three flash vessels <NUM>, <NUM>, <NUM> for the generation of steam. A liquid level (water) may be maintained in the three flash vessels <NUM>, <NUM>, <NUM>.

Water from a source <NUM> (e.g., a vessel) is supplied via a motive device <NUM> (e.g., pump) through conduits to the flash vessels <NUM>, <NUM>, <NUM>. One or more control components, such as control valves <NUM>, <NUM>, <NUM>, disposed along the respective conduits may maintain or adjust the amount of water conveyed to the flash vessels <NUM>, <NUM>, <NUM>. The control valves <NUM>, <NUM>, <NUM> may maintain or modulate the volumetric flow rate or mass flow rate of the supplied water. The water may be demineralized water, steam condensate, or boiler feedwater, and the like.

Water from the flash vessels <NUM>, <NUM>, <NUM> as the heat transfer fluid may be provided through conduits to the ODH reactors <NUM>, <NUM>, and <NUM>, respectively, to control temperature on the process side of the reactors. Water may circulate from the respective flash vessel <NUM>, <NUM>, <NUM> through the jacket <NUM>, <NUM>, <NUM>. The motive force for the circulation may be by thermosiphon. In other examples, a motive device (e.g., pump) is disposed on each circulation loop to provide motive force (e.g., to pump) the water through the jacket.

The reaction temperature in the reactors <NUM>, <NUM>, <NUM>, may depend on the type of catalyst. Thus, the temperature of the water flowing through the jackets <NUM>, <NUM>, <NUM> may be affected by the type of catalyst <NUM>, <NUM>, <NUM> on the process side of the reactors. Therefore, the pressure of the steam generated in the flash vessels <NUM>, <NUM>, <NUM> may be affected by the type of catalyst in the respective reactor.

For the first ODH reactor <NUM>, water <NUM> from the first flash vessel <NUM> enters and flows through the first-reactor jacket <NUM> to acquire heat from the first-reactor process side <NUM>. The heated water exits the jacket <NUM> as return water <NUM> to the flash vessel <NUM>. The heat acquired by the water promotes flashing of liquid water into steam in the flash vessel <NUM>. Steam <NUM> discharges overhead from the flash vessel <NUM> (e.g., into a conduit). The steam <NUM> may be a coproduct of the ODH reactor system <NUM>.

The pressure of the steam <NUM> may depend on the catalyst <NUM> in first ODH reactor <NUM>. In other words, the reaction temperature driven by the catalyst <NUM> generally affects the temperature of the return water <NUM> discharging from the jacket <NUM> to the flash vessel <NUM>. The temperature of the return water <NUM> may affect the pressure at which the liquid water flashes into the steam <NUM> discharging from the flash vessel <NUM>. In examples, the steam <NUM> may generally be saturated steam. In certain implementations, the catalyst <NUM> in the first reactor <NUM> provides for a reaction temperature of less than <NUM>. The steam <NUM> may be, for example, low pressure steam at less than <NUM> kPa (<NUM> psig) or medium pressure steam in the pressure range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig). The pressure may generally define the temperature of the steam <NUM>. The temperature and enthalpy of the return water <NUM> may limit the pressure at which flashing can occur in the flash vessel <NUM>. Moreover, the amount (and pressure) of steam <NUM> may be correlative to the first reactor duty (heat generated) removed via heat of vaporization of the flashing water in the flash vessel <NUM>. The duty or amount of heat generated by the first ODH reactor <NUM> may be related to the catalyst <NUM> employed in the first reactor <NUM> and to the production rate of the corresponding alkene in the first reactor <NUM>, and so on. In some embodiments, the steam <NUM> may be routed through a heat exchanger (e.g., shell-and-tube heat exchanger) to heat the steam <NUM> to above saturation temperature. In one embodiment, a portion of the return water <NUM> is diverted from entry to the flash vessel <NUM> and is utilized as a heating medium in the heat exchanger to heat the steam <NUM> above saturation temperature. Other sources of a heating medium (heat transfer fluid) are applicable for the heat exchanger. Lastly, the pressure of the flash vessel <NUM> (and similar flash vessels in <FIG>) may be controlled by the downstream backpressure of the steam header or user, by a control valve on the steam discharge conduit from the overhead of the flash vessel, and/or by the amount of makeup water (e.g., water <NUM>) fed to the flash vessel, and so on.

For the second ODH reactor <NUM>, water <NUM> discharges from a bottom portion of the second flash vessel <NUM> and flows through the second-reactor jacket <NUM> to receive heat from the process side <NUM> of the second ODH reactor <NUM>. The heated water exits the jacket <NUM> as return water <NUM> to the flash vessel <NUM>. The heat acquired by the water promotes flashing of liquid water into steam in the second flash vessel <NUM>. Steam <NUM> discharges overhead from the second flash vessel <NUM>. The steam <NUM> may be a coproduct of the ODH reactor system <NUM>.

The pressure of the steam <NUM> may depend on the catalyst <NUM> in the second ODH reactor <NUM>. The reaction temperature driven by the catalyst <NUM> in the second ODH reactor <NUM> generally affects the temperature of the return water <NUM> discharging from the jacket <NUM> to the flash vessel <NUM>. The temperature of the return water <NUM> may affect the pressure at which the liquid water flashes into the steam <NUM> discharging from the second flash vessel <NUM>. Moreover, the amount (and pressure) of the steam <NUM> may be related to the heat generated by the reaction in the second ODH reactor <NUM>, and removed via heat of vaporization of the flashing water in the second flash vessel <NUM>. The amount of heat generated by the second ODH reactor <NUM> may be related to the catalyst <NUM> employed in the second reactor <NUM> and to the amount (rate) of alkane converted to alkene in the second reactor <NUM>, and the like.

In examples, the steam <NUM> may generally be saturated steam. In certain implementations, the catalyst <NUM> in the second reactor <NUM> provides for a reaction temperature of greater than <NUM> (e.g., in the range of <NUM> to <NUM>). In those implementations, the steam <NUM> exiting overhead from the second flash vessel <NUM> may be, for example, medium pressure steam in the range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig) or in the range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig), or high pressure steam in the pressure range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig). The catalyst <NUM> providing for a reaction temperature in the range of <NUM> to <NUM> may lead to steam <NUM> as medium pressure steam but can also give or result in the steam <NUM> as high pressure steam at <NUM> kPa (<NUM> psig) or greater, depending on reactor operating conditions and other factors. The pressure generally defines the temperature of the steam <NUM>. The steam <NUM> may be at saturation temperature. In some embodiments, the steam <NUM> may be routed through a heat exchanger (e.g., shell-and-tube heat exchanger) to heat the steam <NUM> to above saturation temperature. Thus, in certain implementations, the steam <NUM> is superheated high-pressure steam. In examples, a heat transfer fluid providing heat in the heat exchanger that superheats the steam <NUM> is the effluent <NUM> from the third ODH reactor <NUM> routed through the heat exchanger.

For the third ODH reactor <NUM>, water <NUM> flows from the bottom portion of the third flash vessel <NUM> through the third-reactor jacket <NUM> to accumulate heat from the process side <NUM> of the third ODH reactor <NUM>. The heated water exits the jacket <NUM> as return water <NUM> to the third flash vessel <NUM>. The heat acquired by the water promotes flashing of liquid water into steam in the third flash vessel <NUM>. Steam <NUM> exits from an upper portion of the third flash vessel <NUM> into a conduit for distribution. The steam <NUM> may be a coproduct of the ODH reactor system <NUM>.

The pressure of the steam <NUM> may depend on the catalyst in third ODH reactor <NUM>. The reaction temperature associated with the catalyst <NUM> in the third ODH reactor <NUM> may drive the temperature of the return water <NUM> discharging from the jacket <NUM> to the flash vessel <NUM>. The temperature of the return water <NUM> may determine the pressure at which the liquid water flashes into the steam <NUM> discharging from the flash vessel <NUM>.

In examples, the steam <NUM> may generally be saturated steam. The steam <NUM> may be subjected to further processing (e.g., heating) to superheat the steam <NUM>. In certain embodiments, the catalyst <NUM> in the third ODH reactor <NUM> provides for a reaction temperature at <NUM> or greater, and the steam <NUM> is high pressure steam at <NUM> kPa (<NUM> psig) or greater or very high pressure steam at <NUM> kPa (<NUM> psig) or greater.

The amount (and pressure) of the steam <NUM> generated may be correlative with the heat generated in the third ODH reactor <NUM> and removed by the jacket water for temperature control of the third reactor <NUM>. The removed heat may give the heat of vaporization for the flashing water in the third flash vessel <NUM>. The amount of heat generated by the third ODH reactor <NUM> may be related to the catalyst <NUM> employed in the third reactor <NUM>, the amount (rate) of unreacted alkane converted to the corresponding alkene in the third ODH reactor <NUM>, and so forth.

<FIG> is an ODH reactor system <NUM> having the three ODH reactors <NUM>, <NUM>, <NUM> discussed above with respect to <FIG>. The system <NUM> receives the feed <NUM> having an alkane (e.g., ethane). The first ODH reactor <NUM> discharges an effluent <NUM> having a corresponding alkene and unreacted alkane to the second ODH reactor. The first ODH reactor <NUM> provides both (<NUM>) catalytic conversion and (<NUM>) the effluent <NUM> as a preheated feed to the second ODH reactor <NUM>. The second ODH reactor <NUM> discharges an effluent <NUM> having the corresponding alkene and unreacted alkane to the third ODH reactor <NUM>. The second ODH reactor <NUM> provides for both (<NUM>) catalytic conversion and (<NUM>) the effluent <NUM> as a preheated feed to the third ODH reactor <NUM>. The third ODH reactor <NUM> discharges an effluent <NUM> having the corresponding alkene and any unreacted alkane. The corresponding alkene (e.g., ethylene) in the third-reactor effluent <NUM> may be a product of the ODH reactor system <NUM>.

In system <NUM>, the routing of water as the heat transfer fluid is different than in the system <NUM> of <FIG>. The system <NUM> has the flash vessels <NUM>, <NUM>, <NUM>, which may be the same or similar to those depicted in <FIG>. However, the flash vessels <NUM>, <NUM>, <NUM> receive input water from the respective reactor jacket instead of directly from the water source <NUM>. A cascade flow of water is employed. In other words, the second-reactor jacket <NUM> receives water from the first flash vessel <NUM>. Thus, some heat from the first ODH reactor <NUM> system may be utilized by the second ODH reactor <NUM> system. The third-reactor jacket <NUM> receives water from the second flash vessel <NUM>. Thus, some heat from the first ODH reactor <NUM> system and the second ODH reactor <NUM> system may be utilized by the third ODH reactor <NUM> system. The mass flow rates of the coproduct steam streams <NUM>, <NUM>, <NUM> may be affected by the alternative flows of the jacket water shown in <FIG> as compared to <FIG>.

For the first ODH reactor <NUM>, water is conveyed from the water source <NUM> to the first-reactor jacket <NUM> to control temperature of the first-reactor process side <NUM>. In the illustrated embodiment, a pump <NUM> (e.g., centrifugal pump) provides motive force for flow of the water. For temperature control of the first reactor <NUM>, the flow rate of the water may be maintained or modulated via a control valve <NUM> disposed on the conduit conveying the water. The water flowing through the first-reactor jacket <NUM> acquires heat from the first-reactor process side <NUM> and discharges from the jacket <NUM> as heated water <NUM> to the first flash vessel <NUM>. In implementations, the set point of the control valve <NUM> may be specified in response to the temperature of the process side <NUM> or the temperature of the heated water <NUM>, or both. The heat acquired by the water promotes flashing of liquid water into steam in the first flash vessel <NUM>.

Steam <NUM> discharges overhead from the first flash vessel <NUM> into a conduit for distribution. The steam <NUM> may be a coproduct of the ODH reactor system <NUM>. The pressure of the steam <NUM> may depend on the catalyst <NUM> in first ODH reactor <NUM>, as discussed. In one example, the pressure of the steam <NUM> is low pressure steam at <NUM> kPa (<NUM> psig) or less. The temperature of the heated water <NUM> (and the amount of heat acquired from the first ODH reactor <NUM>) may determine the pressure at which the liquid water flashes into the steam <NUM> discharging from the flash vessel <NUM>. The amount of heat acquired by the jacket water may be the heat generated by the first ODH reactor <NUM> in the ODH catalytic conversion reaction in the first ODH reactor <NUM>.

For the second ODH reactor <NUM>, water <NUM> discharges from a bottom portion of the first flash vessel <NUM> to the second-reactor jacket <NUM>. The water <NUM> may be conveyed via a pump <NUM> (e.g., centrifugal pump). For temperature control of the second reactor <NUM>, a control valve <NUM> may control the flow rate of the water <NUM>. The water <NUM> flows through the second-reactor jacket <NUM> and acquires heat from the second-reactor process side <NUM>. The heated water <NUM> exits the jacket <NUM> to the second flash vessel <NUM>. The set point of the control valve <NUM> may be set in response to the temperature of the process side <NUM> or the temperature of the heated water <NUM>, or both. The heat acquired by the water promotes flashing of liquid water into steam in the second flash vessel <NUM>.

Steam <NUM> discharges overhead from the second flash vessel <NUM> to be conveyed to users of the steam <NUM>. The steam <NUM> may be a coproduct of the ODH reactor system <NUM>. The pressure of the steam <NUM> may depend on the catalyst <NUM> in the second ODH reactor <NUM>, as discussed. In one example, the pressure of the steam <NUM> is medium pressure steam in the range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig). In another example, the pressure of the steam <NUM> is high pressure steam at <NUM> kPa (<NUM> psig) or greater.

The temperature of the heated water <NUM> (and the amount of heat acquired from the second ODH reactor <NUM>) may determine the pressure at which the liquid water flashes into the steam <NUM> discharging from the flash vessel <NUM>. The amount of heat acquired in the heated stream <NUM> may be at least the heat generated by the second ODH reactor <NUM> in the ODH catalytic conversion reaction in the second ODH reactor <NUM>. The heated water <NUM> may also contain heat from the first ODH reactor <NUM> system.

For the third ODH reactor <NUM>, water <NUM> flows from the bottom portion of the second flash vessel <NUM> through the third-reactor jacket <NUM> to receive heat from the third-reactor process side <NUM>. The water <NUM> may be transported via a pump <NUM> and a control valve <NUM>. The flow of water <NUM> through the jacket <NUM> as a heat transfer fluid (jacket water) is for temperature control of the third ODH reactor <NUM>. The heated water <NUM> exits the jacket <NUM> to the third flash vessel <NUM>. Optionally, water <NUM> as additional jacket water may flow by thermosiphon from a bottom discharge of the flash vessel <NUM> to the jacket <NUM>. The heat acquired by the jacket water promotes flashing of liquid water into steam in the flash vessel <NUM>.

Steam <NUM> exits from an upper portion of the third flash vessel <NUM> into a conduit. The steam <NUM> may be a coproduct of the ODH reactor system <NUM>. The pressure of the steam <NUM> may depend on the catalyst <NUM> in third ODH reactor <NUM>, as discussed. In one example, the pressure of the steam <NUM> is high pressure steam at <NUM> kPa (<NUM> psig) or greater. The temperature of the heated water <NUM> (and the amount of heat acquired from the third ODH reactor <NUM>) may determine the pressure at which the liquid water flashes into the steam <NUM> discharging from the flash vessel <NUM>. The amount of heat acquired in the heated stream <NUM> may be at least the heat generated by the third ODH reactor <NUM> in the ODH catalytic conversion reaction in the third ODH reactor <NUM>. The heated water <NUM> may also contain heat from the first ODH reactor <NUM> system and the second ODH reactor <NUM> system.

<FIG> is an ODH reactor system <NUM> having the three ODH reactors <NUM>, <NUM>, <NUM> discussed above. The first ODH reactor <NUM> performs as a catalytic conversion reactor and also serves as a feed preheater for the second ODH reactor <NUM>. The second ODH reactor <NUM> performs as a catalytic conversion reactor and also serves as a feed preheater for the third ODH reactor <NUM>.

Each reactor <NUM>, <NUM>, <NUM> may be a reactor vessel having an inlet and an outlet. The inlet may be to a process side of the reactor and the outlet may be from a process side of the reactor. The inlet may be for feed including a hydrocarbon (and oxygen) and the outlet for an effluent including hydrocarbon. The reactor vessel may have a jacket for heat transfer fluid. The jacket may have a jacket inlet to receive heat transfer fluid and a jacket outlet to discharge heat transfer fluid.

The ODH reactor system <NUM> is similar to the ODH reactor system <NUM> of <FIG>, except that the system <NUM> does not include the second flash vessel <NUM> or the associated steam <NUM> as coproduct stream. The third flash vessel <NUM> becomes the second flash vessel in <FIG>. The amount of the coproduct steam <NUM> generated may be increased. As for the jacket water flow, the heated water <NUM> that discharges from the second-reactor jacket <NUM> flows to the third-reactor jacket <NUM>. The upstream pump <NUM> and control valve <NUM> may be sized accordingly. The control valve <NUM> may be tuned for temperature control of both the second ODH reactor <NUM> and the third ODH reactor <NUM>. The optional thermosiphon flow of water <NUM> from the flash vessel <NUM> to the jacket <NUM> may further facilitate the temperature control in the third reactor <NUM>.

The coproduct steam <NUM> discharged overhead from the flash vessel <NUM> may be heated downstream to superheat the steam <NUM>. Therefore, the coproduct steam <NUM> may be superheated steam. In some implementations, the steam <NUM> may be heated in a heat exchanger <NUM> (e.g., cross exchanger, shell-and-tube heat exchanger, etc.) by the third-reactor effluent <NUM>. In one example, the steam <NUM> is superheated high-pressure steam at <NUM> kPa (<NUM> psig) or greater.

<FIG> is an ODH reactor system <NUM> having the three ODH reactors <NUM>, <NUM>, <NUM> discussed above. The system <NUM> is similar to the ODH reactor system <NUM> of <FIG>, except that steam (with little or no liquid water) is flowed through the third-reactor jacket <NUM> as heat transfer fluid.

The heated water <NUM> from the second-reactor jacket <NUM> is routed to the flash vessel <NUM>. The heated water <NUM> may be liquid water or steam, or a mixture (two-phase flow) of steam and liquid water. For service as a heat transfer fluid, steam <NUM> discharges from an upper portion of the flash vessel <NUM> through a conduit to the third-reactor jacket <NUM>. In examples, the steam <NUM> may be high pressure steam (<NUM> kPa (<NUM> psig) or greater) or very high pressure steam (<NUM> kPa (<NUM> psig) or greater). Heated steam exits the third-reactor jacket <NUM> into a conduit as coproduct superheated steam <NUM> for distribution to users.

A control valve (not shown) may modulate and control the flow rate (e.g., mass per time) of the steam <NUM> flowing through the jacket <NUM> for the temperature control of the third-reactor process side <NUM>. The control valve (if employed) may be disposed on the jacket <NUM> discharge conduit or on the inlet conduit upstream of the jacket <NUM>. The steam <NUM> may be superheated high pressure steam or superheated very high pressure steam.

Lastly, in certain embodiments, the feed <NUM> to the first ODH reactor <NUM> may be heated (preheated) prior to entry into the first ODH reactor <NUM>. For example, the feed <NUM> may be routed through a heat exchanger <NUM> (e.g., cross exchanger, shell-and-tube heat exchanger, etc.) and heated by the third-reactor effluent <NUM> routed through the heat exchanger <NUM>.

<FIG> is an ODH reactor system <NUM> having three reactors that are the same or similar as the three ODH reactors <NUM>, <NUM>, <NUM> discussed above. In implementations, the three ODH reactors <NUM>, <NUM>, <NUM> may be fabricated with a heat transfer area (between the process side and jacket) specified based on various factors. Such factors may include the heat transfer fluid that will be utilized, the amount of heat that will be generated by the reactor, the flow rate of the heat transfer fluid through the jacket, and so forth. For the system <NUM> in operation, <FIG> depicts the liquid water with gray shading and the heat transfer fluid with forward slashed lines. Such indications are retained in <FIG>.

In the illustrated embodiment of <FIG>, the heat transfer fluid <NUM>, <NUM>, <NUM> introduced to the respective reactor jackets <NUM>, <NUM>, <NUM> may be treated water (e.g., demineralized water, boiler feedwater, etc.), glycol (e.g., ethylene glycol, propylene glycol, etc.), molten salt, or other type of heat transfer fluid. In embodiments with the heat transfer fluid <NUM>, <NUM>, <NUM> as molten salt, three molten-salt supply systems may be employed to provide molten salt as the heat transfer fluid <NUM>, <NUM>, and <NUM>, respectively.

Examples of the heat transfer fluid include DOWTHERM™ heat transfer fluids (Dow Chemical Company, Midland, Michigan USA), which may have glycol or synthetic organic compounds generally. Examples of the heat transfer fluid may include DW-Therm HT products (Huber USA, Gary, North Carolina USA), Syltherm™ silicon fluids (e.g., Syltherm™ <NUM>) (Dow Chemical Company, Midland, Michigan USA), and Santolube products (e.g., OS-<NUM>™ or OS-<NUM>™) (SantoLubes LLC, Spartanburg, South Carolina USA). Of course, temperature limitations on these various organic heat-transfer fluids are taken into account.

In certain embodiments, each reactor <NUM>, <NUM>, <NUM> is associated with a heat exchanger <NUM>, <NUM>, <NUM> (e.g., shell-and-tube heat exchanger, plate and frame heat exchanger, etc.) that heats water with the heat transfer fluid discharged from the reactor jacket. The water to be heated is pumped via a pump <NUM> from a water source <NUM> to the three flash vessels <NUM>, <NUM>, <NUM>. Control valves <NUM>, <NUM>, <NUM> may be disposed on the conduits conveying the water to modulate the respective flow rate of the water to the flash vessels <NUM>, <NUM>, <NUM>. In embodiments, this water is boiler feedwater. The water is heated in the heat exchanger <NUM>, <NUM>, <NUM> with the heat transfer fluid (discharged from the reactor jacket) so to flash the water into steam in the flash vessel <NUM>, <NUM>, <NUM> to generate steam.

For the first ODH reactor <NUM>, water <NUM> discharges from a bottom portion of the first flash vessel <NUM> and is heated in the first heat exchanger <NUM>. The heated water discharges from the heat exchanger <NUM> as return water <NUM> to the first flash vessel <NUM>. This circulatory flow of the water through the heat exchanger <NUM> may be by thermosiphon.

Liquid water in the first flash vessel <NUM> flashes into steam <NUM> that discharges from the first flash vessel <NUM> as coproduct steam. The conditions (e.g., amount, pressure, temperature, etc.) of the steam <NUM> may depend on the catalyst <NUM> type in the first ODH reactor <NUM>, the operating (reaction) temperature of the first ODH reactor <NUM>, the amount of heat generated by the first ODH reactor <NUM>, and other factors.

The heat transfer fluid <NUM> is heated in the first-reactor jacket <NUM> and discharges as heated heat-transfer fluid <NUM> to the first heat exchanger <NUM>. In the first heat exchanger <NUM>, heat transfer occurs from the heated heat-transfer fluid <NUM> to the water <NUM>. The heat transfer fluid discharges from the heat exchanger <NUM> as cooled heat-transfer fluid <NUM> to the reactor jacket <NUM>. In certain implementations, some or all of the cooled heat-transfer fluid <NUM> may be returned to the heat-transfer fluid supply system instead of returned to the jacket <NUM>.

Moreover, a flow bypass conduit may be provided around the heat exchanger <NUM>. Thus, a first portion of the heated heat-transfer fluid <NUM> may flow through the heat exchanger <NUM>. A second portion of the heated heat-transfer fluid <NUM> bypasses (flows around) the heat exchanger <NUM> through the flow bypass conduit. In examples, the first portion and the second portion may each be in the range of <NUM> weight percent to <NUM> weight percent of the heated heat-transfer fluid <NUM>.

For the second ODH reactor <NUM>, the operation of steam generation may be similar as with the first ODH reactor <NUM> but with the option to generate steam at different pressure. A different pressure steam may be produced, for example, by utilizing a catalyst <NUM> in the second ODH reactor <NUM> that is different than the catalyst <NUM> in the first ODH reactor <NUM>.

In the steam generation for the second ODH reactor <NUM>, water <NUM> discharges from a bottom outlet of the second flash vessel <NUM> and is heated in the second heat exchanger <NUM>. The heated water exits the heat exchanger <NUM> as return water <NUM> to the second flash vessel <NUM>. The motive force for this circulation of water through the second-reactor jacket <NUM> may be by thermosiphon. Liquid water in the second flash vessel <NUM> vaporizes into steam <NUM>. The steam <NUM> may exit overhead from the second flash vessel <NUM> as coproduct steam. The amount, pressure, and temperature of the steam <NUM> may depend on the catalyst <NUM> type in the second ODH reactor <NUM>, the operating (reaction) temperature of the second ODH reactor <NUM>, the amount of heat generated by the second ODH reactor <NUM>, and so forth.

The heat transfer fluid <NUM> is heated in the second-reactor jacket <NUM> and discharges as heated heat-transfer fluid <NUM> from the jacket <NUM> to flow through the second heat exchanger <NUM>. Heat transfer occurs from the heated heat-transfer fluid <NUM> to the water <NUM>. The heat transfer fluid discharges from the heat exchanger <NUM> as cooled heat-transfer fluid <NUM> to the reactor jacket <NUM>. In certain implementations, some or all of the cooled heat-transfer fluid <NUM> may be returned to the heat-transfer fluid supply system instead of to the jacket <NUM>. Also, in some embodiments, a portion of the heated heat-transfer fluid <NUM> may flow around the heat exchanger <NUM> via a flow bypass conduit in parallel with the heat exchanger <NUM>. In examples, the portion routed through the bypass may be at least <NUM> weight percent of the heated heat-transfer fluid <NUM>, at least <NUM> weight percent of the heated heat-transfer fluid <NUM>, or at least <NUM> weight percent of the heated heat-transfer fluid <NUM>.

For the third ODH reactor <NUM>, the operation of steam generation may be similar as with the first ODH reactor <NUM> and the second ODH reactor <NUM> but with the option to generate steam at different pressure. A different pressure steam may be generated, for instance, by utilizing a catalyst <NUM> in the third ODH reactor <NUM> that is different than the catalyst <NUM> in the first ODH reactor <NUM> and different than the catalyst <NUM> in the second ODH reactor <NUM>.

To produce steam with the third ODH reactor <NUM>, water <NUM> discharges from a bottom outlet of the third flash vessel <NUM> and is heated in the third heat exchanger <NUM>. The heated water exits the heat exchanger <NUM> as return water <NUM> to the third flash vessel <NUM> via thermosiphon in this example. Liquid water in the third flash vessel <NUM> vaporizes into steam <NUM>, which may discharge from an upper portion of the third flash vessel <NUM> as coproduct steam. The amount, pressure, and temperature of the steam <NUM> may be correlative with a number of factors. For example, the factors may include the third-reactor catalyst <NUM> type, the reaction temperature on the third-reactor process side <NUM>, and the amount of heat generated by the reaction on the process side <NUM>.

The heat transfer fluid <NUM> is heated in the third-reactor jacket <NUM> and discharges as heated heat-transfer fluid <NUM> to the third heat exchanger <NUM>. Heat transfer occurs from the heated heat-transfer fluid <NUM> to the water <NUM> in the third heat exchanger <NUM>. The heat transfer fluid discharges from the heat exchanger <NUM> as cooled heat-transfer fluid <NUM> to the reactor jacket <NUM>. Some or all of the cooled heat-transfer fluid <NUM> may return to the heat-transfer fluid supply system instead of sent to the jacket <NUM>. Moreover, in embodiments, a portion of the heated heat-transfer fluid <NUM> may flow through a conduit to bypass the heat exchanger <NUM>.

<FIG> is an ODH reactor system <NUM> having three reactors the same or similar as the three ODH reactors <NUM>, <NUM>, <NUM> discussed above. The three ODH reactors <NUM>, <NUM>, <NUM> have a first catalyst <NUM>, a second catalyst <NUM>, and a third catalyst <NUM>, respectively. The first catalyst <NUM>, second catalyst <NUM>, and third catalyst <NUM> may each be a fixed bed of catalyst and be different or same catalyst type with respect to each other.

The system <NUM> receives the feed <NUM> having an alkane (e.g., ethane). The first ODH reactor <NUM> discharges an effluent <NUM> having a corresponding alkene and unreacted alkane. The second ODH reactor <NUM> receives the first-reactor effluent <NUM> and discharges an effluent <NUM> having more corresponding alkene (and less unreacted alkane) than the first-reactor effluent <NUM>. The third ODH reactor <NUM> receives the second-reactor effluent <NUM> and discharges an effluent <NUM> having the corresponding alkene and any remaining unreacted alkane. The corresponding alkene (e.g., ethylene) in the third-reactor effluent <NUM> may be a product of the ODH reactor system <NUM>.

The system <NUM> utilizes a heat transfer fluid as discussed with respect to <FIG>. However, in comparison to the system <NUM>, aspects of the steam generation are altered in system <NUM>, as indicated below. For instance, in the example of <FIG>, the second flash vessel <NUM> is not employed.

For system <NUM>, the water (e.g., boiler feedwater) to be heated to generate steam is pumped from the water source <NUM> via the pump <NUM> to the first flash vessel <NUM>. The control valve <NUM> disposed along the conduit conveying the water may maintain or adjust the flow rate of the water to the first flash vessel <NUM>. Water is fed from the first flash vessel <NUM> to both the first heat exchanger <NUM> (associated with the first ODH reactor <NUM>) and the second heat exchanger <NUM> (associated with the second ODH reactor <NUM>). Water <NUM> is fed from the first flash vessel <NUM> to the first heat exchanger <NUM> by thermosiphon. Water <NUM> is fed from the first flash vessel <NUM> to the second heat exchanger <NUM> via a pump <NUM>. A control valve <NUM> disposed along the conduit conveying the water <NUM> may maintain or adjust the flow rate of the water <NUM> through the second heat exchanger <NUM>. The flow rate of water <NUM> through the second heat exchanger <NUM> may be modulated by the control valve <NUM> for temperature control of the second reactor <NUM>.

The water <NUM> in the first heat exchanger <NUM> is heated with the heated heat-transfer fluid <NUM> from the first reactor jacket <NUM>. Thus, in this reactor temperature control, the water <NUM> receives the heat generated by the first-reactor <NUM> reaction. The heated water discharges from the first heat exchanger <NUM> as return water <NUM> to the first flash vessel <NUM>. Liquid water in the first flash vessel <NUM> flashes into steam <NUM> that exits overhead from the first flash vessel <NUM> as coproduct steam. In some examples, the steam <NUM> is saturated low-pressure steam at <NUM> kPa (<NUM> psig) or less.

The water <NUM> in the second heat exchanger <NUM> is heated with the heated heat-transfer fluid <NUM> from the second reactor jacket <NUM>. In other words, for reactor temperature control, the water <NUM> receives the heat generated by the second-reactor <NUM> reaction. The heated water <NUM> discharges from the second heat exchanger <NUM> to the flash vessel <NUM>. The heated water <NUM> flowing through the conduit to the flash vessel <NUM> may be liquid water or steam, or a mixture thereof (two-phase flow).

Steam <NUM> discharges from an overhead outlet of the flash vessel <NUM> is routed through the third heat exchanger <NUM> for temperature control of the third ODH reactor <NUM>. The steam <NUM> is heated in the third heat exchanger <NUM> with the heated heat-transfer fluid <NUM> from the third-reactor jacket <NUM>. The pressure of the steam <NUM> may be different than the pressure of the steam <NUM> discharged from the first flash vessel <NUM>. The pressure may be different due at least in part to utilizing a catalyst <NUM> in the second ODH reactor <NUM> and a catalyst <NUM> in the third ODH reactor <NUM> that are different than the catalyst <NUM> in the first ODH reactor <NUM>. In implementations, the flow rate of the steam <NUM> through the heat exchanger <NUM> may be modulated by a control valve (not shown) for temperature control of the third reactor <NUM>.

The heated steam discharges from the third heat exchanger <NUM> as superheated steam <NUM>, which may be a coproduct of the ODH reactor system <NUM>. In implementations, a control valve (not shown) may modulate the flow of the steam <NUM> (or steam <NUM>) to control the temperature of the third reactor <NUM>. In some examples, the superheated steam <NUM> is high pressure steam at <NUM> kPa (<NUM> psig) or greater, or very high pressure steam at <NUM> kPa (<NUM> psig) or greater. In implementations, temperature of the steam <NUM> is at least <NUM> above the saturation temperature, or at least <NUM> above the saturation temperature. In one example, the superheated steam <NUM> has a pressure of about <NUM> kPa (<NUM> psig) and a temperature of at least <NUM> or at least <NUM>. In another example, the superheated steam <NUM> has a pressure of about <NUM> kPa (<NUM> psig) and a temperature of at least <NUM> or at least <NUM>.

Referring to <FIG> and <FIG>, a portion of each of the heated heat-transfer fluids <NUM>, <NUM>, <NUM> that discharge from a reactor jacket may bypass the respective heat exchangers <NUM>, <NUM>, <NUM>. See, for example, the dashed line <NUM> in <FIG>. Moreover, a portion of each of the cooled heat-transfer fluids <NUM>, <NUM>, <NUM> discharging from the respective heat exchangers <NUM>, <NUM>, <NUM> may be returned to the heat-transfer fluid supply system instead of sent to the reactor jacket. See, for example, the dashed line <NUM> in <FIG>.

The heat-transfer fluid supply system(s) that provides the heat transfer fluid <NUM>, <NUM>, <NUM> may have a heat exchanger(s) for temporary operation to heat the heat transfer fluid <NUM>, <NUM>, <NUM> supply. The heat exchanger may be put into operation when the three reactors <NUM>, <NUM>, <NUM> are not performing the catalytic reaction of alkane to alkene and thus are not generating heat. This temporary operation of the heat exchanger may therefore provide heat for steam generation in the ODH reactor system <NUM>, <NUM>.

<FIG> is an ODH reactor system <NUM> having the three ODH reactors <NUM>, <NUM>, <NUM> in series each having a catalyst <NUM>, <NUM>, <NUM>. As with the preceding figures, the system <NUM> receives the feed <NUM> having an alkane (e.g., ethane). The first ODH reactor <NUM> converts (via catalyst <NUM>) some of the alkane to a corresponding alkene (e.g., ethylene). The first ODH reactor <NUM> discharges an effluent <NUM> having the corresponding alkene and unreacted alkane to the second ODH reactor <NUM>. The second ODH reactor <NUM> converts (via catalyst <NUM>) some of the unreacted alkane to the corresponding alkene. The second ODH reactor <NUM> discharges an effluent <NUM> having the corresponding alkene and unreacted alkane to the third ODH reactor <NUM>. The third ODH reactor <NUM> converts (via catalyst <NUM>) some unreacted alkane to the corresponding alkene. The third ODH reactor <NUM> discharges an effluent <NUM> having the corresponding alkene and any unreacted alkane. The corresponding alkene in the third-reactor effluent <NUM> may be a product of the ODH reactor system <NUM>.

The system <NUM> includes the three heat exchangers <NUM>, <NUM>, <NUM> associated with the three ODH reactors <NUM>, <NUM>, <NUM>. The three heat exchangers <NUM>, <NUM>, <NUM> may be the same or similar as in <FIG> and <FIG>. The three heat exchangers <NUM>, <NUM>, <NUM> may be configured differently than in <FIG> and <FIG> because of the different arrangement for source of water flow through the heat exchangers <NUM>, <NUM>, <NUM>.

Heat transfer fluid <NUM> is supplied to the first-reactor jacket <NUM>. In the jacket <NUM>, the heat transfer fluid <NUM> receives the heat generated by the ODH catalytic reaction in first ODH reactor <NUM>. Heated heat-transfer fluid <NUM> discharges from the jacket <NUM> through heat exchanger <NUM> and may return as cooled heat-transfer fluid <NUM> to the jacket <NUM>.

Heat transfer fluid <NUM> is supplied to the second-reactor jacket <NUM> where the heat transfer fluid <NUM> receives the heat generated by the ODH catalytic reaction in second ODH reactor <NUM>. Heated heat-transfer fluid <NUM> discharges from the jacket <NUM> through heat exchanger <NUM> and may return as cooled heat-transfer fluid <NUM> to the jacket <NUM>.

Heat transfer fluid <NUM> is supplied to the third-reactor jacket <NUM> where the heat transfer fluid <NUM> receives the heat generated by the ODH catalytic reaction in third ODH reactor <NUM>. Heated heat-transfer fluid <NUM> discharges from the jacket <NUM> through heat exchanger <NUM> and may return as cooled heat-transfer fluid <NUM> to the jacket <NUM>.

In the illustrated embodiment, the system <NUM> as depicted employs a single flash vessel <NUM>. Water to be heated to generate steam is supplied to the flash vessel <NUM> from a water source <NUM> via pump <NUM>. The water source <NUM> may include a vessel holding the water to be supplied. The water may be boiler feedwater. A control valve <NUM> on the conduit conveying the water to the flash vessel <NUM> may control the flow rate of the water from the source <NUM> to the flash vessel <NUM>.

Water is provided from the flash vessel <NUM> to all three depicted heat exchangers <NUM>, <NUM>, <NUM>. The total flow of water discharging from the bottom portion of the flash vessel <NUM> gives the water <NUM> stream for the inlet to the first heat exchanger <NUM>, the water <NUM> stream for the inlet to the second heat exchanger <NUM>, and the water <NUM> stream for the inlet to the third heat exchanger <NUM>. The water streams flow through the respective heat exchangers <NUM>, <NUM>, <NUM> and return to the flash vessel <NUM>. The motive force for the three circulation loops of water may be thermosiphon or pump.

The water <NUM> is heated in the first heat exchanger <NUM> with heat from the heated heat-transfer fluid <NUM> discharged from the first-reactor jacket <NUM>. The water <NUM> is heated in the second heat exchanger <NUM> with heat from the heated heat-transfer fluid <NUM> discharged from the second-reactor jacket <NUM>. The water <NUM> is heated in the third heat exchanger <NUM> with heat from the heated heat-transfer fluid <NUM> discharged from the third-reactor jacket <NUM>.

The heat acquired by these water streams that return to the flash vessel promotes (contributes to) the flashing of liquid water in the flash vessel <NUM> to generate steam <NUM> that may be a coproduct of the ODH reactor system <NUM>. In embodiments, the steam <NUM> is high pressure steam at <NUM> kPa (<NUM> psig) or greater. In those embodiments, a portion of the steam <NUM> may be diverted and let down in pressure via a control valve <NUM> to give low pressure steam <NUM> at <NUM> kPa (<NUM> psig) or less. Similarly, a portion of the steam <NUM> may be diverted and let down in pressure via a control valve <NUM> to give medium pressure steam <NUM> in the range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig) or in the range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig). Both the low pressure steam <NUM> and the medium pressure steam <NUM> may be coproducts of the ODH reactor system <NUM>.

<FIG> is an ODH reactor system <NUM> that is the same as the ODH reactor system of <FIG>, except that a heat exchanger <NUM> is incorporated into the system <NUM> to superheat the high pressure steam <NUM> so that the coproduct with be superheated steam <NUM> (e.g., superheated high-pressure steam at <NUM> kPa (<NUM> psig) or greater). In the illustrated embodiment, heat transfer fluid from third-reactor jacket <NUM> is circulated through the heat exchanger <NUM> to heat the steam <NUM>. In other embodiments, the third-reactor effluent <NUM> is instead sent through the heat exchanger <NUM> as the heat transfer fluid to heat the steam <NUM>. The heat exchanger <NUM> may be a shell-and-tube heat exchanger or other type of heat exchanger.

Referring to <FIG>, the feed <NUM> to the first ODH reactor <NUM> may be heated (preheated) prior to entry into the first ODH reactor <NUM>. For instance, the feed <NUM> may be routed through a heat exchanger (e.g., cross exchanger, shell-and-tube heat exchanger, etc.) and heated by the third-reactor effluent <NUM> routed through the heat exchanger. See, for example, heat exchanger <NUM> in <FIG>. Also, at least one of the steam <NUM>, the steam <NUM>, or the steam <NUM> may be heated in a heat exchanger (e.g., cross exchanger, shell-and-tube heat exchanger, etc.) by the third-reactor effluent <NUM>. The steam <NUM>, steam <NUM>, or steam <NUM> may be heated to superheat the steam or further superheat the steam. See, for example, the heat exchanger <NUM> in <FIG> that heats the steam <NUM> to give superheated steam <NUM>. The various embodiments for configuration of the ODH reactor system and steam generation discussed with respect to <FIG> are given as examples. Other examples for steam generation by the ODH reactor system will be readily apparent to one of ordinary skill in the art with the benefit of the present disclosure.

Referring to <FIG>, the catalysts <NUM>, <NUM>, <NUM> may be the same or different catalyst type. Catalyst types may give different catalytic reaction temperatures in the conversion of the alkane having a number of carbons in the range of <NUM> to <NUM> to the corresponding alkene. For instance, one catalyst type (labeled, for example, as a low temperature catalyst) may give a catalytic reaction temperature of less than <NUM>. Another catalyst type (labeled, for example, as a medium temperature catalyst) may give a catalytic reaction temperature of at least <NUM> (e.g., in the range of <NUM> to <NUM>). Yet another catalyst type (labeled, for example, as a high temperature catalyst) may give a catalytic reaction temperature of at least <NUM>.

In some embodiments, the first catalyst <NUM> is low temperature catalyst (e.g. reaction temperature less than <NUM>), the second catalyst <NUM> is medium temperature catalyst (e.g., reaction temperature of at least <NUM> or in the range of <NUM> to <NUM>), and the third catalyst <NUM> is high temperature catalyst (reaction temperature at least <NUM>). In other embodiments, the first catalyst <NUM> is low temperature catalyst and both the second catalyst <NUM> and third catalyst <NUM> are high temperature catalyst. In yet other embodiments, all three catalysts <NUM>, <NUM>, <NUM> are high temperature catalyst. Other combinations of catalyst types are applicable among the three catalysts <NUM>, <NUM>, <NUM>.

The low temperature catalyst may be conducive for generating low pressure steam (e.g., less than <NUM> kPa (<NUM> psig)). The medium temperature catalyst may be conducive for generating medium pressure steam (e.g., <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig)). The high temperature catalyst may be conducive for generating high pressure steam (e.g., at least <NUM> kPa (<NUM> psig)). However, each catalyst type may generate heat in its catalytic reaction that can contribute to steam generation of different stream pressures or qualities.

An example of the low temperature catalyst is a catalyst that includes molybdenum, vanadium, tellurium, niobium, and oxygen, wherein the molar ratio of molybdenum to vanadium is from <NUM>:<NUM> to <NUM>:<NUM>, the molar ratio of molybdenum to tellurium is from <NUM>:<NUM> to <NUM>:<NUM>, the molar ratio of molybdenum to niobium is from <NUM>:<NUM> to <NUM>:<NUM>, and oxygen is present at least in an amount to satisfy the valency of any present metal oxides. The molar ratios of molybdenum, vanadium, tellurium, niobium can be determined by inductively coupled plasma mass spectrometry (ICP-MS).

An example of a low temperature catalyst is given in <CIT>. The catalyst provides for the ODH reaction to at a temperature of less than <NUM> and is available from NOVA Chemicals Corporation having headquarters in Calgary, Canada. This example of a low temperature catalyst is a mixed metal oxide having the formula MoaVbTecNbdPdeOf, where a, b, c, d, e, and f subscripts are relative atomic amounts of the elements Mo, V, Te, Nb, Pd, O, respectively. When a=<NUM>, then b=<NUM> to <NUM>, c=<NUM> to <NUM>, d=<NUM> to <NUM>, <NUM>≤e≤<NUM>, and f is a number to satisfy the valence state of the catalyst.

An example of a medium temperature catalyst is a catalyst labeled as a moderate temperature catalyst in <CIT>. The catalyst is described as allowing the ODH reaction process to perform in the temperature range of <NUM> to <NUM>. An example of a high temperature catalyst is a high temperature catalyst described in International Application Publication No. <CIT>. The catalyst is described as allowing the ODH reaction process to run at a temperature in the range of <NUM> to <NUM>.

Referring to <FIG>, for certain cases of the first reactor <NUM> having a low-temperature ODH catalyst (e.g., providing for an ODH reaction at a temperature of about <NUM> or less), high pressure steam can be generated by the first-reactor <NUM> system at the first flash vessel <NUM>. However, for other cases of the first reactor <NUM> having a low-temperature ODH catalyst, the reactor process side temperature may not be adequate to efficiently drive formation of high pressure steam. In other words, the available temperature difference (ΔT) or available log-mean temperature difference (LMTD or ΔTLM) for between the reactor jacket water and the reactor process side may not be adequate to effectively provide for formation of high pressure steam.

Referring to <FIG> and <FIG>, in some examples with the first reactor <NUM> having a low-temperature ODH catalyst (e.g., providing for an ODH reaction at a temperature of about <NUM> or less), high pressure steam can be generated by the first-reactor <NUM> system at the first flash vessel <NUM>. However, for other examples of the first reactor <NUM> having a low-temperature ODH catalyst, the reactor process side temperature may not be adequate to efficiently drive formation of high pressure steam. In other words, the available ΔT or LMTD for the temperature difference between the water <NUM>, <NUM> and heat transfer fluid <NUM>, <NUM> (e.g., molten salt) in the heat exchanger <NUM> may not be adequate to effectively provide for formation of high pressure steam.

Referring to <FIG>, implementations employing water (e.g., boiler feedwater) as the heat transfer fluid may be applicable for reactors <NUM>, <NUM>, <NUM> of small scale. To implement reactors <NUM>, <NUM>, <NUM> that are large and operating with water at contemplated pressures and temperatures on the reactor jackets <NUM>, <NUM>, <NUM> (e.g., for the reactor having medium temperature ODH catalyst or high temperature ODH catalyst) may lead to very large or even impractical wall thicknesses of the reactor jackets <NUM>, <NUM>, <NUM>. Therefore, for large reactors, a heat transfer fluid, such as molten salt, may be beneficial for the reactor jackets in certain instances. See, for example, <FIG>.

Referring to <FIG>, the first ODH reactor <NUM>, the second ODH reactor <NUM>, and the third ODH reactor <NUM> may each be a fixed-bed reactor or tubular fixed-bed reactor. For a fixed-bed reactor, reactants may be introduced into the reactor at one end and flow past an immobilized catalyst. Products are formed and an effluent having the products may discharge at the other end of the reactor. The fixed-bed reactor may have one or more tubes (e.g., ceramic tubes) each having a bed of catalyst and for flow of reactants (e.g., alkane having a number of carbons in the range of <NUM> to <NUM> or ethane) and products (e.g., corresponding alkene or ethylene). The tubes may include, for example, a steel mesh. Moreover, a cooling jacket adjacent the tube(s) may provide for temperature control of the reactor.

In other embodiments, the first ODH reactor <NUM>, the second ODH reactor <NUM>, and the third ODH reactor <NUM> may each be a fluidized bed reactor. In implementations, a fluidized bed reactor may have a support for the catalyst. The support may be a porous structure or distributor plate and disposed in a bottom portion of the reactor. Reactants may flow upward through the support at a velocity to fluidize the bed of catalyst (e.g., the catalyst rises and begins to swirl around in a fluidized manner). The reactants are converted to products upon contact with the fluidized catalyst. An effluent having products may discharge from an upper portion of the reactor. A cooling jacket may facilitate temperature control of the reactor.

Lastly, the temperature referenced for each reactor (e.g., first temperature in the first reactor, second temperature in the second reactor, and third temperature in the third reactor) may be the temperature at which the respective catalyst drives the oxidative dehydrogenation and may be labeled as the catalyst temperature. The temperature referenced may be the reactor operating temperature driven by the catalytic oxidative dehydrogenation. The temperature referenced may be the weighted average temperature of the reactor or reactor catalyst bed, e.g., over the temperature profile from reactor inlet to reactor outlet. The temperature referenced may be or otherwise incorporate reactor peak temperatures, heat-transfer fluid temperature, temperature of steam generated, and so forth. In certain embodiments, the temperature referenced for each reactor is the maximum temperature within the reactor.

<FIG> is a method <NUM> of catalytic oxidative dehydrogenation. The method <NUM> may be a method of operating an ODH reactor system having at least two ODH reactors disposed in series (noting that the use of only two ODH reactors is outside the scope of the invention). Three ODH reactors are discussed with respect to the method <NUM>. However, the present methods may accommodate ODH reactors systems having more than three ODH reactors (e.g., four ODH reactors, five ODH reactors, etc.) in series for the generation of steam. The final ODH reactor in the series may discharge an effluent having a product alkene of the ODH reactor system.

At block <NUM>, the method includes contacting a feed having an alkane having a number of carbons in the range of <NUM> to <NUM> with a first ODH catalyst in a first reactor at a first temperature (e.g., less than <NUM>) to dehydrogenate the alkane having a number of carbons in the range of <NUM> to <NUM> into a corresponding alkene and to heat a first heat-transfer fluid flowing through a first-reactor jacket to facilitate generation of steam. The first catalyst may be disposed as a fixed catalyst bed in the first reactor.

At block <NUM>, the method includes contacting a first-reactor effluent from the first reactor with a second ODH catalyst in a second reactor at a second temperature greater than the first temperature to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> from the first-reactor effluent into the corresponding alkene and to heat a second heat-transfer fluid flowing through a second-reactor jacket to facilitate generation of steam. The second catalyst may be disposed as a fixed catalyst bed in the second reactor.

At block <NUM>, the method includes contacting a second-reactor effluent from the second reactor with a third ODH catalyst in a third reactor at a third temperature (e.g., at least <NUM>) greater than the first temperature to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> from the second effluent into the corresponding alkene and to heat a third heat-transfer fluid flowing through a third-reactor jacket to facilitate generation of steam. The third catalyst may be disposed as a fixed catalyst bed in the third reactor.

For the heat transfer fluid as water, the method may include discharging the first heat-transfer fluid from the first-reactor jacket to a first flash vessel and discharging low pressure steam at <NUM> kPa (<NUM> psig) or less from the first flash vessel. See, e.g., <FIG>. The method may include discharging the second heat-transfer fluid from the second-reactor jacket to a second flash vessel and discharging medium pressure steam in the range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig) from the second flash vessel. See, e.g., <FIG>. The method may include discharging the third heat-transfer fluid from the third-reactor jacket to a third flash vessel and discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater from the third flash vessel. See, e.g., <FIG>. The method may include discharging water from the first flash vessel as the second heat-transfer fluid to the second-reactor jacket, and discharging water from the second flash vessel as the third heat-transfer fluid to the third-reactor jacket. See, e.g., <FIG>. In other embodiments, the method may include discharging the second heat-transfer fluid from the second-reactor jacket to the third reactor-jacket as the third heat-transfer fluid, and discharging the third heat-transfer fluid from the third-reactor jacket to a second flash vessel and discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater from the second flash vessel. See, e.g., <FIG>. In yet other embodiments, the method may include discharging the second heat-transfer fluid from the second-reactor jacket to a second flash vessel, and discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater from the second flash vessel through the third-reactor jacket as the third heat-transfer fluid to superheat the high pressure steam. See, e.g., <FIG>.

At block <NUM>, the method includes discharging a third-reactor effluent having the corresponding alkene from the third reactor. The corresponding alkene in the third-reactor effluent may be a product of the ODH reactor system having the third reactor, second reactor, and fourth reactor. In some embodiments, the alkane is ethane and the corresponding alkene is ethylene. The first reactor, the second reactor, and the third reactor may each be labeled as an ODH reactor and may each be a tubular fixed-bed reactor. As mentioned, the heat transfer fluid may be water. The heat transfer fluid may be treated water (e.g., demineralized water, boiler feedwater, etc.), synthetic organic compounds, glycol (e.g., ethylene glycol, propylene glycol, etc.), or molten salt.

The method may include discharging the first heat-transfer fluid from the first-reactor jacket to a first heat exchanger and heating, via the first heat exchanger, a first water with the first heat-transfer fluid from the first-reactor jacket. Similarly, the method may include discharging the second heat-transfer fluid from the second-reactor jacket to a second heat exchanger and heating, via the second heat exchanger, a second water with the second heat-transfer fluid from the second-reactor jacket. Likewise, the method may include discharging the third heat-transfer fluid from the third-reactor jacket to a third heat exchanger and heating, via the third heat exchanger, a third water with the third heat-transfer fluid from the first-reactor jacket. See, e.g., <FIG>. The method may include discharging the first water as heated from the first heat exchanger to a first flash vessel and discharging low pressure steam at <NUM> kPa (<NUM> psig) or less from the first flash vessel. The method may include discharging the second water as heated from the second heat exchanger to a second flash vessel. See, e.g., <FIG>. The method may include discharging medium pressure steam in the range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig) from the second flash vessel, and discharging the third water as heated from the third heat exchanger to a third flash vessel and discharging high steam at <NUM> kPa (<NUM> psig) or greater from the third flash vessel. See, e.g., <FIG>. The method may include discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater from the second flash vessel as the third water through the third heat exchanger to superheat the high pressure steam. See, e.g., <FIG>.

In other embodiments, the method may include discharging the first water as heated by the first heat exchanger to a flash vessel, discharging the second water as heated by the second heat exchanger to the flash vessel, discharging the third water as heated by the third heat exchanger to the flash vessel, and discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater from the flash vessel. See, e.g., <FIG>. The method may include diverting a portion of the high pressure steam through a control valve to reduce pressure of the portion to medium pressure steam in a range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig). The method may include diverting a portion of the high pressure steam through a control valve to reduce pressure of the portion to low pressure steam at <NUM> kPa (<NUM> psig) or less. The method may include superheating the high pressure steam in a heat exchanger with heat from the third heat-transfer fluid or from a third-reactor effluent discharged from the third reactor. See, e.g., <FIG>. The third-reactor effluent may include the corresponding alkene as a product of the ODH reactor system.

An embodiment is an ODH reactor system (e.g., <FIG>) including a first reactor having a first ODH catalyst to dehydrogenate an alkane having a number of carbons in the range of <NUM> to <NUM> to a corresponding alkene at a first temperature and facilitate generation of steam. The first reactor has a first-reactor jacket for heat transfer. The ODH reactor system includes a second reactor having a second ODH catalyst to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> in a first-reactor effluent from the first reactor to the corresponding alkene at a second temperature greater than the first temperature and facilitate generation of steam. The second reactor has a second-reactor jacket for heat transfer. The ODH reactor system includes a third reactor having a third ODH catalyst to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> in a second-reactor effluent from the second reactor to the corresponding alkene at a third temperature greater than the second temperature and facilitate generation of steam. The third reactor has a third-reactor jacket for heat transfer. In implementations, the first ODH catalyst is in a fixed-bed in the first reactor, the second ODH catalyst is in a fixed-bed in the second reactor, the third ODH catalyst is in a fixed-bed in the third reactor, and the third reactor to discharge a third-reactor effluent having the corresponding alkene. In implementations, the first ODH catalyst is different than the second ODH catalyst and the third ODH catalyst, and the second ODH catalyst is different than third ODH catalyst. In some examples, the first temperature is less than <NUM> and the first reactor to facilitate generation of low pressure steam at <NUM> kPa (<NUM> psig) or less, the second temperature is at least <NUM>, and the third temperature is at least <NUM> and the third reactor to facilitate generation of high pressure steam of at least <NUM> kPa (<NUM> psig) or very high pressure steam at <NUM> kPa (<NUM> psig) or greater.

The ODH reactor system may include a first flash vessel (e.g., <FIG>) to receive jacket water from the first-reactor jacket and discharge low pressure steam at <NUM> kPa (<NUM> psig) or less. If so, the ODH reactor system may include a second flash vessel (e.g., <FIG>) to receive jacket water from the second-reactor jacket and discharge medium pressure steam in a range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig) or discharge high pressure steam at <NUM> kPa (<NUM> psig) or greater. A third flash vessel (e.g., <FIG>) may receive jacket water from the third-reactor jacket and discharge high pressure steam at <NUM> kPa (<NUM> psig) or greater or discharge very high pressure steam at <NUM> kPa (<NUM> psig) or greater. In other examples, a second flash vessel (e.g., <FIG>) receives jacket water from the third-reactor jacket and discharges high pressure steam at <NUM> kPa (<NUM> psig) or greater. In yet other examples, a second flash vessel (e.g., <FIG>) receives jacket water from the second-reactor jacket and discharges high pressure steam at <NUM> kPa (<NUM> psig) or greater (or very high pressure steam at <NUM> kPa (<NUM> psig) or greater) and discharges the steam through the third-reactor jacket to superheat the steam.

The ODH reactor system (e.g., <FIG>) may include: a first heat exchanger to heat a first water with heat transfer fluid from the first-reactor jacket; a second heat exchanger to heat a second water with heat transfer fluid from the second-reactor jacket; and a third heat exchanger to heat a third water with heat transfer fluid from the third-reactor jacket. In certain implementations (e.g., <FIG>), the ODH reactor system includes: a first flash vessel to receive the first water as heated from the first heat exchanger and discharge low pressure steam at <NUM> kPa (<NUM> psig) or less; a second flash vessel to receive the second water as heated from the second heat exchanger and discharge medium pressure steam in the range <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig) or high pressure steam at <NUM> kPa (<NUM> psig) or greater; and a third flash vessel to receive the third water as heated from the third heat exchanger and discharge high pressure steam at <NUM> kPa (<NUM> psig) or greater or very high pressure steam at <NUM> kPa (<NUM> psig) or greater. In some implementations (e.g., <FIG>), the ODH reactor system includes: a first flash vessel to receive the first water as heated from the first heat exchanger and discharge low pressure steam at <NUM> kPa (<NUM> psig) or less; and a second flash vessel to receive the second water as heated from the second heat exchanger and discharge high pressure steam at <NUM> kPa (<NUM> psig) or greater as the third water through the third heat exchanger to superheat the high pressure steam. In other implementations (e.g., <FIG>), the ODH reactor system includes a flash vessel to receive the first water as heated by the first heat exchanger, the second water as heated by the second heat exchanger, and the third water as heated by the third heat exchanger, and discharge high pressure steam at <NUM> kPa (<NUM> psig) or greater. If so, the system (e.g., <FIG>) may include a control valve to reduce pressure of a portion of the high pressure steam to medium pressure steam in a range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig), and also include a control valve to reduce pressure of a portion of the high pressure steam to low pressure steam at <NUM> kPa (<NUM> psig) or less. The ODH reactor system (e.g., <FIG>) may have a heat exchanger to superheat the high pressure steam with heat from the heat transfer fluid from the third-reactor jacket or with heat from a third-reactor effluent discharged from the third reactor. The third-reactor effluent may have the corresponding alkene as a product of the ODH reactor system.

Another embodiment is a system for oxidative dehydrogenation, including a first reactor having first ODH catalyst to dehydrogenate an alkane at a first temperature. The alkane may have a number of carbons in a range of two carbons to six carbons. The first reactor has a first-reactor jacket to heat a first heat-transfer fluid flowing through the first-reactor jacket to facilitate generation of the steam. The system includes a second reactor having a second ODH catalyst to dehydrogenate unreacted alkane from the first reactor at a second temperature greater than the first temperature. The second reactor has a second-reactor jacket to heat a second heat-transfer fluid flowing through the second-reactor jacket to facilitate generation of steam. A third reactor has a third ODH catalyst to dehydrogenate unreacted alkane from the second reactor at a third temperature greater than the first temperature. The third reactor has a third-reactor jacket to heat a third heat-transfer fluid flowing through the third-reactor jacket to facilitate generation of steam. The third ODH catalyst and the second ODH catalyst are different than the first ODH catalyst. The third ODH catalyst may be different than the second ODH catalyst. Moreover, the first reactor, the second reactor, and the third reactor may each be a tubular fixed-bed reactor. Lastly, the system for oxidative dehydrogenation may include an ODH reactor system having the first reactor, the second reactor, and the third reactor, and wherein the ODH reactor system to generate high pressure steam at <NUM> kPa (<NUM> psig) or greater, or very high pressure steam at <NUM> kPa (<NUM> psig) or greater.

Yet another embodiment is a method of oxidative dehydrogenation. The method (e.g., <FIG>) includes: contacting a feed having an alkane having a number of carbons in the range of <NUM> to <NUM> (e.g., ethane) with a first ODH catalyst in a first reactor at a first temperature (e.g., less than <NUM>) to dehydrogenate the alkane having a number of carbons in the range of <NUM> to <NUM> into a corresponding alkene (e.g., ethylene) and to heat a first heat-transfer fluid flowing through a first-reactor jacket to facilitate generation of steam; contacting a first-reactor effluent from the first reactor with a second ODH catalyst in a second reactor at a second temperature (e.g., at least <NUM>) greater than the first temperature to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> from the first-reactor effluent into the corresponding alkene and to heat a second heat-transfer fluid flowing through a second-reactor jacket to facilitate generation of steam; and contacting a second-reactor effluent from the second reactor with a third ODH catalyst in a third reactor at a third temperature (e.g., at least <NUM>) greater than the first temperature to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> from the second effluent into the corresponding alkene and to heat a third heat-transfer fluid flowing through a third-reactor jacket to facilitate generation of steam. In examples, the first temperature is less than <NUM>, the second temperature is at least <NUM> (or in the range of <NUM> to <NUM>), and the third temperature is at least <NUM>. The method may include discharging a third-reactor effluent from the third reactor, wherein the third-reactor effluent includes the corresponding alkene. In implementations, the first reactor, the second reactor, and the third reactor are each a tubular fixed-bed reactor.

The method (e.g., <FIG> and <FIG>) may include discharging the first heat-transfer fluid from the first-reactor jacket to a first flash vessel (wherein the first heat-transfer fluid is water or primarily water) and discharging low pressure steam at <NUM> kPa (<NUM> psig) or less from the first flash vessel. If so, the method (e.g., <FIG> and <FIG>) may include: discharging the second heat-transfer fluid (water or primarily water) from the second-reactor jacket to a second flash vessel; discharging medium pressure steam in the range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig) from the second flash vessel; discharging the third heat-transfer fluid (water or primarily water) from the third-reactor jacket to a third flash vessel; and discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater (or very high pressure steam at <NUM> kPa (<NUM> psig) or greater) from the third flash vessel. In certain implementations (e.g., <FIG> and <FIG>), the method includes discharging water from the first flash vessel as the second heat-transfer fluid to the second-reactor jacket; and discharging water from the second flash vessel as the third heat-transfer fluid to the third-reactor jacket. In other implementations (e.g., <FIG> and <FIG>), the method includes: discharging the second heat-transfer fluid from the second-reactor jacket (water or primarily water) to the third reactor-jacket as the third heat-transfer fluid; discharging the third heat-transfer fluid from the third-reactor jacket to a second flash vessel; and discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater (or very high pressure steam at <NUM> kPa (<NUM> psig) or greater) from the second flash vessel. In yet other implementations (e.g., <FIG> and <FIG>), the method include: discharging the second heat-transfer fluid from the second-reactor jacket to a second flash vessel; and discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater (or very high pressure steam at <NUM> kPa (<NUM> psig) or greater) from the second flash vessel through the third-reactor jacket as the third heat-transfer fluid to superheat the high pressure steam (or very high pressure steam).

In some implementations (e.g., <FIG>), the method includes: discharging the first heat-transfer fluid from the first-reactor jacket to a first heat exchanger and heating, via the first heat exchanger, a first water with the first heat-transfer fluid from the first-reactor jacket; discharging the second heat-transfer fluid from the second-reactor jacket to a second heat exchanger and heating, via the second heat exchanger, a second water with the second heat-transfer fluid from the second-reactor jacket; and discharging the third heat-transfer fluid from the third-reactor jacket to a third heat exchanger and heating, via the third heat exchanger, a third water with the third heat-transfer fluid from the first-reactor jacket. The method (e.g., <FIG> and <FIG>) may include discharging the first water as heated from the first heat exchanger to a first flash vessel, discharging low pressure steam at <NUM> kPa (<NUM> psig) or less from the first flash vessel, and discharging the second water as heated from the second heat exchanger to a second flash vessel. If so, the method (e.g., <FIG> and <FIG>) may include discharging medium pressure steam in the range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig) (or high pressure steam at <NUM> kPa (<NUM> psig) or greater) from the second flash vessel, discharging the third water as heated from the third heat exchanger to a third flash vessel, and discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater (or very high pressure steam at <NUM> kPa (<NUM> psig) or greater) from the third flash vessel. The method (e.g., <FIG> and <FIG>) may include discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater (or very high pressure steam at <NUM> kPa (<NUM> psig) or greater) from the second flash vessel as the third water through the third heat exchanger to superheat the high pressure steam.

In implementations (e.g., <FIG>), the method may include: discharging the first water as heated by the first heat exchanger to a flash vessel; discharging the second water as heated by the second heat exchanger to the flash vessel; discharging the third water as heated by the third heat exchanger to the flash vessel; and discharging high pressure steam at <NUM> kPa (<NUM> psig) or greater (or very high pressure steam at <NUM> kPa (<NUM> psig) or greater) from the flash vessel. The method may include diverting a portion of the high pressure steam (or very high pressure steam) through a control valve to reduce pressure of the portion to medium pressure steam in a range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig). The method may include diverting a portion of the high pressure steam (or very high pressure steam) through a control valve to reduce pressure of the portion to medium pressure steam in a range of <NUM> kPa to <NUM> kPa (<NUM> psig to <NUM> psig) to low pressure steam at <NUM> kPa (<NUM> psig) or less. The method (e.g., <FIG>) may include superheating the high pressure steam in a heat exchanger with heat from the third heat-transfer fluid or from a third-reactor effluent discharged from the third reactor. The third-reactor effluent may include the corresponding alkene as a product of the ODH reactor system.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made.

Claim 1:
An oxidative dehydrogenation (ODH) reactor system, comprising:
a first reactor comprising a first ODH catalyst to dehydrogenate an alkane having a number of carbons in the range of <NUM> to <NUM> to a corresponding alkene at a first temperature and facilitate generation of steam, wherein the first reactor comprises a first-reactor jacket for heat transfer;
a second reactor comprising a second ODH catalyst to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> in a first-reactor effluent from the first reactor to the corresponding alkene at a second temperature greater than the first temperature and facilitate generation of steam, wherein the second reactor comprises a second-reactorjacket for heat transfer; and
a third reactor comprising a third ODH catalyst to dehydrogenate unreacted alkane having a number of carbons in the range of <NUM> to <NUM> in a second-reactor effluent from the second reactor to the corresponding alkene at a third temperature greater than the second temperature and facilitate generation of steam, wherein the third reactor comprises a third-reactor jacket for heat transfer.