SEPARATION OF HYDROGEN, METHANE, ETHANE, AND PROPANE IN NAPHTHA TO ETHANE AND PROPANE FRACTIONATION SECTION BASED ON A DIVIDING WALL FRACTIONATION COLUMN INTEGRATION

In a process of producing ethylene and propylene from naphtha the process a feed stream comprising hydrogen, methane, ethane, and propane and residual C4+ from a naphtha-to-ethane-and-propane reactor is fed to a dividing wall fractionation column.

TECHNICAL FIELD

This invention relates generally to separating ethane and propane from an effluent stream, containing ethane, propane and also hydrogen, methane, and some C4+ material, of a naphtha to ethane and propane reactor section. More particularly, the invention relates to separating ethane and propane from the effluent using a dividing wall fractionation column.

BACKGROUND

Naphtha fed to a naphtha cracker produces olefins, namely ethylene and propylene. There is an industry trend towards shifting refining capacity to make increased petrochemicals due to the high value and market demand of ethylene and propylene compared to fuels. Naphtha steam cracking is the industry standard for making ethylene and propylene from naphtha, but ethylene plus propylene yields are low—less than 60% and typically less than 50% by weight depending on naphtha composition.

The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior process and apparatuses of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.

SUMMARY

The disclosure is directed to a process of producing light paraffins from naphtha from a stream comprising hydrogen, methane, ethane, propane and C4+ produced in a reactor section of a naphtha-to-ethane-and-propane (NEP) processing unit. The process includes passing a NEP reactor effluent stream comprising hydrogen, methane, ethane, and propane and residual C4+ to the NEP fractionation section for efficiently separating the effluent stream into components. The NEP fractionation section comprises, among other equipment, coldbox (cryogenic) exchangers, and dividing wall fractionation column.

DETAILED DESCRIPTION

The term “downstream” means that at least a portion of fluid flowing to the subject in downstream may operatively flow from the object with which it fluidly communicates.

The term “upstream” means that at least a portion of the fluid flowing from the subject in upstream may operatively flow to the object with which it fluidly communicates.

The term “direct” means that fluid flow from the upstream component enters the downstream component without passing through any other intervening vessel.

The term “indirect” means that fluid flow from the upstream component enters the downstream component after passing through an intervening vessel.

The term “bypass” means that the object is out of downstream communication with a bypassing subject at least to the extent of bypassing.

As used herein, the term “rich” is defined as at least 50 mol %.

As mentioned above, a process and method for separating effluent from a naphtha-to-ethane-and-propane (NEP) reactor section, for which the feed is naphtha, into ethane, propane, and hydrogen/methane rich streams is described. With these general principles in mind, one or more embodiments of the present invention will be described with the understanding that the following description is not intended to be limiting.

This disclosure is directed to a process of producing light paraffins from naphtha and a stream comprising hydrogen, methane, and ethane produced in a reactor section of a naphtha-to-ethane-and-propane processing unit, including a process of separating hydrogen, methane, ethane, propane and C4 hydrocarbons in a deethanizer column configured as a dividing wall column (DWC), which is part of a fractionation section of a naphtha-to-ethane-and-propane (NEP) processing unit. The ethane and propane form feedstocks for an ethane steam cracker (ESC) and a propane de-hydrogenation unit (PDH). The propane dehydrogenation is a process in which light paraffins such as propane can be dehydrogenated to make propylene. Dehydrogenation is an endothermic reaction which requires external heat to drive the reaction to completion. This configuration is part of an overall scheme to feed ethane to the ESC and propane to the PDH, as this enhances an increased efficiency of production of ethylene and propylene (light olefins) from the naphtha than would be possible if naphtha is fed directly to a steam cracker to produce the light olefins.

The NEP processing unit is designed to preferentially produce ethane and propane from naphtha via reacting naphtha with hydrogen. An ethane rich stream is fed to an ethylene producing unit, for example an ESC and a propane rich stream is fed a PDH. This configuration produces higher quantities of olefins, namely ethylene and propylene, than what would be possible if naphtha was directly fed to a naphtha cracker to produce olefins.

An NEP system comprises a reactor section and a fractionation section. In the reactor section, naphtha is reacted with hydrogen. An NEP reactor effluent comprises of hydrogen, methane, and substantial volumes of ethane and propane, as well as C4 paraffins and other C5 to C9+ hydrocarbon components, including C5 paraffins and C6/C7/C8/C9+ aromatics.

The NEP fractionation section separates the reactor effluent stream into the following streams for further processing in downstream units:a) An ethane rich stream, which is passed to the ESC to produce ethylene in cracking heaters of the ESC. The effluent stream from the ESC cracking heaters also contain hydrogen, methane, unreacted ethane, and some C3+ components. The effluent stream is cooled and quenched, caustic scrubbed, and compressed in a cracked gas compressor train. This compressed stream is subsequently fractionated in the fractionation section of the ESC using fractionating columns and refrigeration to cool the streams so that the very light boiling components can be separated. Apart from the main product, ethylene, the other product streams from the ESC include hydrogen, methane, ethane and C3+ stream. The ethane is recycled to the cracking heaters for further production of ethylene.FIG.3shows a schematic of an ESC. An ethane rich stream from the NEP processing unit10is first fed a cracking heater section of the ESC (seeFIG.3).b) A stream comprising of hydrogen, methane, and some ethane, which is also processed in the ESC. This stream joins the ESC in the cracked gas compressor train, upstream of the cold fractionation section of the ESC. The hydrogen and methane leave the cold fractionation section while the ethane is recovered in a C2-splitter of the ESC and is recycled to the ethane cracking heaters.c) A propane rich stream with some C4+ components is fed to a propane dehydrogenation unit (PDH) after separating the propane in a depropanizer.

The above streams a) through c) are separated in a deethanizer column of the NEP. The deethanizer column38is configured as a DWC. In addition to streams a) through c), the NEP fractionation section produces two other streams:d) A C4 rich stream;e) An aromatics byproduct stream.
The separation of these streams are relatively simple and are not part of this invention disclosure

Referring toFIG.1, generally, an NEP processing unit10is designed to preferentially produce an ethane rich stream14and a propane rich stream18from a naphtha stream22via reacting naphtha with hydrogen in a NEP reactor26. An NEP reactor effluent stream30comprising a light paraffin stream is discharged from the NEP reactor26.

The naphtha stream22may comprise C4 to C12 hydrocarbons preferably having a T10between about 0-10° C. and about 60° C. and a T90between about 70 and about 180° C. The naphtha stream22may comprise normal paraffins, iso-paraffins, naphthenes, and aromatics. The naphtha stream22may be heated to a reaction temperature of between about 300° C. and about 550° C. and preferably between about 325° C. and about 525° C.

The NEP reactor effluent30may comprise hydrogen, methane, ethane, propane, and residual C4+. Preferably, the NEP reactor effluent comprises at least 40 wt % ethane or at least 40 wt % propane or at least 70 wt % and preferably at least 80 wt % ethane and propane. The ethane to propane ratio can range from 0.1 to 5. The light paraffin stream can have less than about 15 wt %, suitably less than about 12 wt %, more suitably less than about 10 wt %, preferably less than about 8 wt %, more preferably less than about 6 wt % and most preferably less than about 5 wt % methane. The NEP reactor effluent30is passed through coolers, separators for removing the heavier ends and multiple stages of compression and shown collectively as block31inFIG.1. The cooled vapor stream40from block31passes to a cooling unit, consisting of one or more multi-stream coldbox heat exchangers to produce a feed stream33comprising hydrogen, methane, and substantial volumes of ethane and propane, as well as a minor quantity of C4+ hydrocarbons to NEP separation section34. The deethanizer produces an ethane rich stream (14) and a hydrogen/methane rich stream (72) both of which are routed to ESC58. The deethanizer38DWC also produces a propane rich stream18which is sent to depropanizer66to produce a purified propane stream68and routed to a PDH106.FIG.1is a simplified diagram of the flowscheme. The deethanizer configured as DWC and associated coldbox are the focus of this invention and described in more detail in the following paragraphs.

According to the present disclosure, the NEP separation section34comprises, among other equipment, a deethanizer38and a depropanizer66(seeFIGS.1and4). The deethanizer38is configured as a dividing wall fractionation column and its structure is depicted inFIG.2.FIGS.3and4show the deethanizer38as a DWC in more detail along with its associated reboilers and condenser. WhileFIG.3shows the location of the DWC in the overall flow scheme and how it is linked to the ESC58,FIG.4shows the DWC and its associated cryogenic exchangers in more detail. The deethanizer38DWC is a type of distillation column that can separate mixtures of several components into three or more high-purity streams. The deethanizer38DWC requires much less energy, capital investment, and plant space than conventional columns in series or parallel configurations. The concept of the deethanizer38DWC is well-established, with much literature focusing on the simulation and control. The deethanizer38DWC is a fully thermally coupled distillation column set-up with at least one condenser42and at least one reboiler46regardless of the number of products. The entire sequence is housed into a single shell50by means of one or more vertical partition walls54(seeFIG.2for reference).

Thus, the deethanizer38DWC inputs the feed stream33and outputs the following streams: (1) a side product of the ethane rich stream14, which is passed to an ethane producing unit such as the ESC58, (2) a bottom product18comprising a propane rich stream, as well as other heavy products, which is passed to the depropanizer66, and (3) a top product stream72comprising top product stream comprising hydrogen a methane, some slipped (residual) ethane. The coldbox32associated with the deethanizer38DWC cools the incoming stream to the deethanizer38DWC using the cold streams produced from the deethanizer38DWC (seeFIGS.3and4). The benefits of the feed cooling scheme are shown in Table 1. Example No. 2. The rest of the refrigeration duty of the deethanizer38DWC may be provided by one or more refrigeration fluid streams63(designated by broken/dashed lines) refrigeration streams flowing from a source of refrigeration fluid streams64, which is shown inFIG.3as residing in the ESC58; however, it should be understood that this source of refrigeration fluid streams may reside in the NEP processing unit10or some other locations as desired.

The ethane rich stream14is of relatively high purity and is a vapor side product of the deethanizer38DWC. Withdrawing this ethane rich vapor side product from the deethanizer38DWC lowers a refrigeration requirement for the deethanizer38DWC and reduces energy for vaporization in the ESC58. In a preferred case, the ethane rich stream14is sent to the ESC58, optionally to the ESC58via the coldbox32a,b, and the vapor side product is withdrawn from the DWC eliminates energy for vaporization in the ESC58. The ethane vapor drawn from the DWC is cold with respect to the feed stream40and is therefore utilized to cool the relatively warm (near ambient and approximately 40° C.) feed streams entering the coldbox exchangers in32band32a(seeFIG.4) from the compression system, followed by coolers and separators. The compression system, coolers and separators are described above in the description ofFIG.1.

The ethane rich stream14is passed to the ESC58. Referring toFIG.3, generally, the ESC58includes a cracking heater section74, a cracked gas compressor section78, and a chilling section82. The ethane rich stream14is passed from the deethanizer38DWC wherein an output stream of the ESC58is an ethylene rich stream87.

The ethane rich stream14is initially passed to the cracking heater section74of the ESC58. The ethane rich stream14is cracked under steam in the cracking heater section74to produce a cracked gas stream (cracking heater effluent) including ethylene, unreacted ethane, hydrogen, methane, and other components. The cracked stream exiting the cracking heater section74may be in a superheated state. One or more quench columns84are used for quenching or separating the cracked stream into a plurality of cracked streams. Cracking heater effluent from the quench columns84is then passed to compression and separation.

Compression of the cracking heater effluent is performed in the cracked gas compression section78. Carbon dioxide and acidic sulfur compounds are removed from the cracked gas in a caustic scrubber87. The compressed cracking heater effluent is cooled and subsequently dried in a dryer88by molecular sieves that remove most of the water.

The dried cracking heater effluent89is passed to a cooling unit such as a coldbox90. Hydrogen and light hydrocarbons are removed from the cracked gas in the coldbox90.

Condensates from the coldbox90are fed to a series of separation columns91,92. In a first column91, a methane stream93is obtained from the top and passed to the coldbox90, while a bottom stream is fed to a second column92, which is a deethanizer.

A top product of the second column92, composed primarily of ethylene and ethane, is fed to an acetylene converter94and then fractionated in a C2-splitter96.

An ethylene stream86is withdrawn from the C2-splitter96as a side product. Ethane, from C2-splitter bottom product99, is recycled to the cracking heater section74

The top product stream72of the deethanizer38DWC comprises a stream comprising hydrogen, methane, and some slipped (residual) ethane. Thus, some ethane components are allowed to slip with the top product stream72. The amount of ethane components allowed to slip is adjusted and controlled to optimize overhead temperature and refrigeration requirements. For example, recovering 90% of ethane feed to DWC in side product of DWC vs. 97%—recovery, results in approximately −47° C. (52° F.) overhead temperature of DWC against −71° C. (−96° F.) for the latter case. The result is deeper refrigeration for the latter case, requiring 20-25% higher refrigeration compressor power requirement for the NEP. The top product stream72bypasses the cracking heater section74and is passed to the cracked gas compressor78of the ESC58. In this way, the chilling section82of the ESC58is utilized to recover and separate the hydrogen and methane. This allows additional chilling section equipment for recovery of hydrogen and methane to be eliminated from the NEP separation section34. The slipped (residual) ethane in the top produce stream helps to keep the DWC overhead temperature higher than would be possible with minimum ethane slippage and this in turn helps to reduce refrigeration compressor power attributable to NEP requirements.

As shown inFIG.4, the top product stream72may be passed to the NEP coldbox32bprior to passing to the ESC58.

The ethane in the top product stream72that bypasses the cracking heater section74is recovered in an ESC C2-splitter96downstream from the cracked gas compressor78, the ESC coldbox90, and ESC columns91(demethanizer),92(deethanizer). Ethane slippage with the DWC top product stream72is optimized in conjunction with energy required for separation of additional ethane in the ESC C2-splitter96. It is contemplated that the ethane slippage can be varied between 5% to 20% of the net ethane produced in the NEP processing unit10.

The net bottom product18withdrawn from the deethanizer38DWC comprises a stream comprising propane and C4s as well as other heavy products. As shown inFIG.4, the bottom product18is passed to a depropanizer column66. A propane rich stream68is fed to propane dehydrogenation unit (PDH)106. A propane rich stream68is withdrawn from the depropanizer66and sent to the PDH106, where the desired propylene product110is output.

According to the present disclosure, the ethane rich stream14passed to the ESC58and the propane stream18passed to the PDH106produce higher quantities of olefins (ethylene and propylene) due to the DWC (since it helps to produce ethane and propane rich streams by effective separation), than what would be possible if naphtha was directly fed to a naphtha cracker to produce olefins. The other novelties and advantages of the proposed scheme are elaborated in the subsequent sections.

However, the products of the NEP reactor26contain light products, e.g., hydrogen and methane, along with ethane and propane. As shown inFIG.1, and as discussed in the preceding sections, the NEP processing unit10with incorporation of a DWC type deethanizer38and using shared refrigeration equipment with an ESC (seeFIGS.3-5) is a cost-efficient method of separating H2 and CH4 from ethane and propane produced in NEP reactor26. Careful separation of streams produced in the NEP reactor section26together with using the coldbox90of the ESC58to separate H2 from CH4 which were produced in the NEP processing unit10, makes this scheme of using shared assets between NEP processing unit10and the ESC58optimal regarding both operating and capital expenses.

Advantages of employing the deethanizer38DWC in this process include a reduction in overall energy usage. The DWC system is 15% more efficient than traditional two-column systems. Also, the DWC system reduces the equipment count compared to alternative flow scheme using membrane systems. Utilizing the deethanizer38DWC is an innovative way to achieve the separation of 3 streams of desired purity: (1) hydrogen/H4 rich gas as a top product stream72; (2) an ethane rich14stream as a side product; and (3) a propane rich stream18as the bottom product18in a single column.

It is further contemplated that the principles of this disclosure result in greater carbon efficiency (>70%) that prior processes (45%-55%). Corresponding lower by-product yields and 40%-70% lower fuel gas make the process disclosed herein hydrogen self-sufficient. Finally, the process of this disclosure improves flexibility at design stage for high P:E (ratio of propylene to ethylene) to low P:E with catalyst and processing condition change in NEP reactor section.

Further according to this disclosure, C2 components are allowed to slip with the top product stream72. The amount or volume of C2 allowed to slip is controlled. This allows optimization of the overhead temperature and refrigeration requirements and thus helps to reduce the overall energy usage.

The hydrogen and methane rich stream is passed to the cracked gas compressor section78and further on to the ESC cooling/separation section, bypassing the cracking heater section74since these components are not desired feed for the cracking heaters of the ESC58. In this way the ESC cooling unit (coldbox90, is utilized to recover the H2 and the CH4). Thus, the need for additional cooling units for recovery and separation of H2 and CH4 is eliminated in the NEP separation section34.

The C2s in the hydrogen rich stream which bypass the ESC cracking heater section74are recovered in the ESC C2-splitter96. Optimizing the C2 slippage with deethanizer38DWC top product stream72stream optimizes energy required for separation in the ESC58C2-splitter96. The C2 slippage can be varied between 5% to 20% of the net C2s produced in the NEP processing unit10.

The disclosed process is approximately 15% more energy efficient when compared to a traditional two column process system.

The DWC helps to eliminate hydrogen and CH4 entering the ESC cracking heater section74with feed ethane. This is not possible in other alternative systems. Approximately 10%-15% volumetric flow reduction through the ESC heaters result with consequent benefits in capex of heaters and associated equipment. This also results in separation of components which do not result in ethylene production in cracking heaters in ESC.

According to the present disclosure, cold streams and the deethanizer38DWC side reboiler46may be used for heat recovery. There is additional heat recovery from the cold ethane rich stream14and hydrogen stream72coming out of the deethanizer38DWC. The balance of the cooling may be derived from the refrigeration system which may be common for the ESC58and NEP10and shown as64. Cooling may be shared between the ESC58and the NEP processing unit10. A refrigeration system including compressors can be located in the ESC58and are shown as64, and the NEP coldbox32can derive the refrigerant fluid flow as required. NEP coldbox32refrigeration requirement is approximately 25% of the ESC coldbox90requirement.

The system is flexible towards the refrigeration system selected for the ESC58and both mixed refrigeration system (MR) or cascade (ethylene-propylene) refrigeration system can be used.

This disclosure is further directed to integration of the NEP processing unit10comprising the deethanizer38DWC with the ESC58. The integration disclosed herein achieves a passing of the ethane rich stream14produced in the NEP processing unit10to the cracking heater section74of the ESC58. The integration further achieves passing the top product stream72of hydrogen, methane, and ethane slip from the deethanizer38DWC top to the cracked gas compressor section78of the ESC58. The hydrogen and the methane are separated in the coldbox90of the ESC58while the ethane rich stream is eventually separated in the C2-splitter bottom product99and passed to the ethane cracking heater section74of the ESC58. The ethane content in this stream is about 5% to 20% of the total ethane produced in the NEP reactor26, which is passed to the deethanizer38DWC as feed. The NEP processing unit10and the ESC58can use shared refrigeration equipment.

According to the present disclosure, the NEP processing unit10and the ESC58can share a common refrigeration system with a common source of refrigeration fluid(s)64. One or more refrigeration fluids63are passed from the common source of refrigeration fluid(s)64to a coldbox32of the NEP processing unit10and to a coldbox90of the ESC58.FIG.4shows 2 levels of cascade propylene-ethylene refrigeration (propylene refrigerant may be of approximately −4° C. and drawn 3rdstage suction and of approximately −16° C. and drawn from 2ndstage suction) for NEP coldbox32bwhile the DWC condenser42shows 1 level of ethylene refrigeration (may be of approximately −45° C. drawn from 3rdstage suction) and 1 level of propylene (may be approximately −37° C. and drawn from first stage). The ESC coldbox90has multiple levels of cascade ethylene-propylene refrigeration but not shown, for simplicity and since this coldbox90is not the focus of the present disclosure. The focus and the illustrations are intended to show that NEP refrigeration requirements can make use of available and appropriate refrigeration streams available for the ESC coldbox90, which is the main user of the refrigeration streams, as explained above. Hence, it is emphasized that the cascade refrigeration system of ethylene-propylene and the temperature levels indicated above can vary by approximately ±5° C., and the design of the NEP coldbox32a,band the DWC condenser42can be configured to make use of the available levels of refrigeration. The cascade ethylene-propylene refrigeration system could also be replaced by single mixed refrigeration system for both NEP and ESC.

Alternatively, referring toFIG.5, it is contemplated that the NEP processing unit10and the ESC58can share a common coldbox32/90and a common mixed refrigeration system (MR). This cold box will process all the cold streams of the NEP processing unit10and the ESC58and use these streams to cool the incoming warm streams that need to be cooled. Here, on the NEP processing unit10side of the common coldbox32/90, the NEP reactor section effluent stream40passes through the common coldbox32/90to become the cooled feed stream33to the deethanizer38DWC; the top net vapor product stream72passes through the common coldbox32/90and is warmed prior to passing to the ESC58; the ethane rich stream14passed from the deethanizer38DWC passes through the common coldbox32/90and is warmed prior to passing to the ESC58; the NEP DWC overhead stream (not numbered) is cooled and condensed before entering the NEP DWC reflux drum (not numbered). The ESC58side of the common coldbox32/90receives the dried cracking heater effluent stream89from the dryer88and is cooled to stream189to be fed to ESC demethanizer91; the methane stream93from top of the first column (demethanizer)91enters the common coldbox32/90and is warmed and sent to fuel gas. There are many other streams originating in the ESC58, such as cold hydrogen rich gas originating in the ESC58and sent as warmed hydrogen rich gas, possibly to PSA; an ESC demethanizer overhead stream is condensed and is sent to a demethanizer condenser; an ethane rich stream from the ESC C2 splitter96bottoms and is warmed and sent to ESC Cracking heaters74; liquid ethylene product is vaporized in coldbox32/90and sent to a desired destination. The unbalanced refrigeration requirement can be met by mixed refrigeration system. The intent is to design an integrated common coldbox32/90for both NEP processing unit10and the ESC58and have a common mixed refrigeration system also.

SPECIFIC EMBODIMENTS

A first embodiment of the invention is a process of producing ethylene and propylene from naphtha, the process comprising passing a feed stream comprising hydrogen, methane, ethane, and propane and residual C4+ from a naphtha-to-ethane-and-propane reactor to a dividing wall fractionation column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein a top product stream outputted by the dividing wall fractionation column, the top product stream comprising hydrogen, methane, and some slipped ethane (residual), a side product comprises an ethane rich stream, and a bottom product stream comprises propane and other heavy products. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising controlling an overhead temperature of the dividing wall column and refrigeration energy requirements by controlling an amount of the slipped ethane allowed in the top stream product of the dividing wall column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the top product stream to a cracked gas compressor system of an ethane steam cracker, bypassing a cracking heater section of the ethane steam cracker. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the ethane rich stream from the dividing wall fractionation column to an ethane steam cracker after heat exchange in a plurality of coldbox exchangers with a warm feed stream and thereby reducing a refrigeration requirement for feed cooling. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the ethane rich stream to a cracking heater section of the ethane steam cracker, wherein an ethylene stream is output from the ethane steam cracker. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the stream the ethane rich stream is a vapor side product of the dividing wall fractionation column, and wherein withdrawing the ethane rich stream as a vapor side product from the dividing wall fractionation column lowers a refrigeration requirement for the dividing wall fractionation column and reduces energy for vaporization in the ethane steam cracker. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the energy for vaporization in the ethane rich steam cracker is eliminated by the vapor side product and wherein a further energy reduction takes place by utilizing the ethane rich stream and the top product to cool fluids passing through the plurality of coldbox exchangers. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the propane rich stream from the dividing wall fractionation column to a propane dehydrogenation unit after further fractionation in a depropanizer column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing a top product stream outputted by the dividing wall fractionation column to a cracked gas compressor of an ethane steam cracker; passing an ethane rich stream outputted by the dividing wall fractionation column to the ethane stream cracker, wherein an ethylene stream is output from the ethane steam cracker; and passing a propane rich stream outputted by the dividing wall fractionation column and after fractionation in a depropanizer to a propane dehydrogenation unit, wherein a propylene stream is output from the propane dehydrogenation unit, wherein the top product stream bypasses a cracking heater section of the ethane steam cracker, and thereby reducing a feed flow to the cracking heater section of hydrogen and methane which do not contribute to production of ethylene in the cracking heaters, and wherein a chilling section and cold fractionation section of the ethane steam cracker is configured to recover hydrogen and methane as well as ethane in a C2 splitter. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the feed stream through at least one coldbox prior to passing the feed stream to the dividing wall fractionation column and thereby reducing a refrigeration requirement for cooling the feed stream to the dividing wall fractionation column.

A second embodiment of the invention is an apparatus for producing ethylene and propylene from naphtha comprising an effluent from a naphtha-to-ethane-and-propane processing unit which separates an ethane rich stream and a propane rich stream from a stream comprising ethane, propane, hydrogen, methane, and residual C4+ heavy hydrocarbons, the naphtha-to-ethane-and-propane processing unit comprising a dividing wall fractionation column which receives the effluent stream from an naphtha-to-ethane-and-propane reactor and outputs a top product stream comprising hydrogen and methane, the ethane rich stream as a side product, and the propane rich stream comprising residual C4+ hydrocarbons as a bottom product. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising an ethane steam cracker configured to input the ethane rich stream from the dividing wall fractionation column and output a stream of ethylene. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the ethane rich stream is a vapor side product of the dividing wall fractionation column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein withdrawing the ethane rich stream as a vapor side product from the divided wall fractionation column lowers a refrigeration requirement for the divided wall fractionation column and reduces energy for vaporization in the ethane steam cracker. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising a depropanizer column configured to input the propane rich stream from the divided wall fractionation column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising a propane dehydrogenation unit configured to input an output product from the depropanizer column and output a stream of propylene. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the top product stream output from the dividing wall fractionation column bypasses a cracking heater section of the ethylene steam cracker. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph wherein the naphtha-to-ethane-and-propane processing unit further comprises a coldbox wherein the effluent passes through the coldbox upstream of the dividing wall fractionation column exchanging heat with incoming feed to dividing wall column.20

A third embodiment of the invention is a process of producing ethylene and propylene from naphtha, the process comprising passing a feed stream comprising hydrogen, methane, ethane, and propane and residual C4+ from a naphtha-to-ethane-and-propane reactor through a coldbox; passing the feed stream from the coldbox to a dividing wall fractionation column passing a top product stream from the dividing wall fractionation column, the top product stream comprising hydrogen, methane, and some slipped ethane (residual); passing the top product stream to a cracked gas compressor system of an ethane steam cracker and bypassing a cracking heater section of the ethane steam cracker; passing a side product comprising an ethane rich stream from dividing wall fractionation column; passing the ethane rich stream from the dividing wall fractionation column to a cracking heater section of the ethane steam cracker; passing an ethylene stream from the ethane steam cracker; passing a bottom product stream comprising propane and other heavy products from the dividing wall fractionation column; passing the propane rich stream from the dividing wall fractionation column to a propane dehydrogenation unit after further fractionation in a depropanizer column; and passing a propylene stream is from the propane dehydrogenation unit, wherein the ethane rich stream is a vapor side product of the dividing wall fractionation column, wherein withdrawing the ethane rich stream as a vapor side product from the dividing wall fractionation column lowers a refrigeration requirement for the dividing wall fractionation column and reduces an energy for vaporization in the ethane steam cracker, and wherein the energy for vaporization in the ethane rich steam cracker is eliminated by the vapor side product and wherein a further energy reduction takes place by utilizing the ethane rich stream and the top product stream to cool fluids passing through the coldbox.