Patent Publication Number: US-2023160633-A1

Title: Process for Separating Hydrogen from an Olefin Hydrocarbon Effluent Vapor Stream

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 17/966,314 filed on Oct. 14, 2022, which is a continuation-in-part of U.S. application Ser. No. 17/377,895 filed on Jul. 16, 2021, which is a continuation-in-part of U.S. application Ser. No. 17/191,427 filed on Mar. 3, 2021, which is a continuation of U.S. application Ser. No. 17/191,373 filed on Mar. 3, 2021, which is a continuation-in-part of U.S. application Ser. No. 17/113,640 filed on Dec. 7, 2020, which is a divisional of U.S. application Ser. No. 15/988,601 filed on May 24, 2018, which is a continuation-in-part of U.S. application Ser. No. 15/600,758 filed on May 21, 2017, the disclosures of which are herein incorporated by reference in their entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND 
     1. Field of Inventions 
     The field of this application and any resulting patent is processes and systems for separating hydrogen from an olefin hydrocarbon vapor stream. 
     2. Description of Related Art 
     Various processes and systems have been proposed and utilized for separating hydrogen from an olefin hydrogen rich compressed effluent vapor stream, including some of the processes and systems disclosed in the references appearing on the face of this patent. However, those processes and systems lack all the steps or features of the processes and systems covered by any patent claims below. As will be apparent to a person of ordinary skill in the art, any processes and systems covered by claims of the issued patent solve many of the problems that prior art processes and systems have failed to solve. Also, the processes and systems covered by at least some of the claims of this patent have benefits that could be surprising and unexpected to a person of ordinary skill in the art based on the prior art existing at the time of invention. 
     SUMMARY 
     One or more specific embodiments disclosed herein includes a process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit, comprising cooling a compressed effluent vapor stream in a heat exchanger; separating hydrogen from olefin and heavy paraffinic components in the cooled compressed effluent vapor stream in a first separator to provide a first vapor stream and a first liquid stream; cooling the first vapor stream in the heat exchanger; separating hydrogen from olefin and heavy paraffinic components in the cooled first vapor stream in a second separator to provide a second vapor stream and a second liquid stream; warming the second vapor stream in the heat exchanger; isentropically expanding, in a high-pressure expander, the second vapor stream, wherein the pressure and temperature of the second vapor stream are lowered; warming the second vapor stream in the heat exchanger; compressing, in a high-pressure compressor, the second vapor stream; cooling the second vapor stream in a first discharge cooler; dividing the second vapor stream into a gas product and a split stream; withdrawing the gas product; compressing, in a low-pressure compressor, the split stream; cooling the split stream in a second discharge cooler and further cooling the split stream in the heat exchanger; isentropically expanding, in a low-pressure expander, the split stream, wherein the pressure and temperature of the split stream are lowered; cooling a liquid paraffinic stream in the heat exchanger; combining the cooled liquid paraffinic stream with the expanded split stream to provide a combined feed, vaporizing the combined feed in the heat exchanger; withdrawing the vaporized combined feed; lowering the pressure of the first liquid stream in a control valve; partially vaporizing the first liquid stream in the heat exchanger; flashing the partially vaporized first liquid stream in a liquid product drum to provide a hydrogen-rich gas, which travels to a rectifier connected to the liquid product drum; combining the hydrogen-rich gas and the second liquid stream in the rectifier, further purifying the hydrogen-rich gas; warming the hydrogen-rich gas from the rectifier in the heat exchanger to provide a flashed vapor stream; pumping a third liquid stream from the liquid product drum to the heat exchanger, wherein it is warmed; and providing a liquid product. 
     One or more specific embodiments disclosed herein includes a process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit, comprising separating hydrogen from olefin and heavy paraffinic components in the compressed effluent vapor stream to provide a first vapor stream and a first liquid stream; separating hydrogen from olefin and heavy paraffinic components in the first vapor stream to provide a second vapor stream and a second liquid stream; expanding and compressing the second vapor stream; dividing the second vapor stream into a gas product and a split stream; compressing and expanding the split stream; lowering the pressure of the first liquid stream; partially vaporizing the first liquid stream; flashing the partially vaporized first liquid stream in a liquid product drum to provide a hydrogen-rich gas; and combining the hydrogen-rich gas and the second liquid stream in a rectifier. 
     One or more specific embodiments disclosed herein includes a process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit, comprising separating hydrogen from olefin and heavy paraffinic components in the compressed effluent vapor stream to provide a first vapor stream and a first liquid stream; separating hydrogen from olefin and heavy paraffinic components in the first vapor stream to provide a second vapor stream and a second liquid stream; isentropically expanding, in a high-pressure expander, the second vapor stream; compressing, in a high-pressure compressor, the second vapor stream; dividing the second vapor stream into a gas product and a split stream; compressing, in a low-pressure compressor, the split stream; and isentropically expanding, in a low-pressure expander, the split stream. 
     One or more specific embodiments disclosed herein includes a process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit, comprising cooling a compressed effluent vapor stream in a heat exchanger; separating hydrogen from olefin and heavy paraffinic components in the cooled compressed effluent vapor stream in a first separator to provide a first vapor stream and a first liquid stream; cooling the first vapor stream in the heat exchanger; separating hydrogen from olefin and heavy paraffinic components in the cooled first vapor stream in a second separator to provide a second vapor stream and a second liquid stream; warming the second vapor stream in the heat exchanger to provide a gas product. 
     One or more specific embodiments disclosed herein includes a process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit, comprising cooling a compressed effluent vapor stream in a heat exchanger; separating hydrogen from olefin and heavy paraffinic components in the cooled compressed effluent vapor stream in a first separator to provide a first vapor stream and a first liquid stream; cooling the first vapor stream in the heat exchanger; separating hydrogen from olefin and heavy paraffinic components in the cooled first vapor stream in a second separator to provide a second vapor stream and a second liquid stream; warming the second vapor stream in the heat exchanger to provide a gas product; lowering the pressure of the first liquid stream in a control valve; flashing the first liquid stream in a liquid product drum to provide a hydrogen-rich gas, which travels to a rectifier connected to the liquid product drum; dividing the second liquid stream into a first liquid split stream and a second liquid split stream; lowering the pressure of the first liquid split stream in a control valve; partially vaporizing the first liquid split stream in the heat exchanger; flashing the partially vaporized first liquid split stream in the liquid product drum to provide additional hydrogen-rich gas, which travels to the rectifier connected to the liquid product drum; combining the hydrogen-rich gas and the second liquid split stream in the rectifier, further purifying the hydrogen-rich gas; warming the purified hydrogen-rich gas from the rectifier in the heat exchanger to provide a flashed vapor stream; pumping a third liquid stream from the liquid product drum to the heat exchanger, wherein it is warmed to provide a liquid product; dividing a liquid paraffinic stream into a plurality of liquid paraffinic streams; lowering the pressure of each of the plurality of liquid paraffinic streams in respective control valves; introducing each of the plurality of liquid paraffinic streams into respective thermosiphon vessels to provide a plurality of vapor paraffinic streams and a plurality of secondary liquid paraffinic streams; circulating each of the plurality of secondary liquid paraffinic streams from the bottom of each thermosiphon vessel, through the heat exchanger, and back to each respective thermosiphon vessel as a plurality of two-phase paraffinic streams, wherein a vapor phase of each of the plurality of two-phase paraffinic streams combines with each of the plurality of vapor paraffinic streams, and wherein a liquid phase of each of the plurality of two-phase paraffinic streams combines with each of the plurality of secondary liquid paraffinic streams; heating each of the plurality of vapor paraffinic streams in the heat exchanger; and combining each of the plurality of heated vapor paraffinic streams to provide an alternative combined feed stream, wherein each of the plurality of heated vapor paraffinic streams are optionally compressed via a compressor prior to being combined. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic illustration, block flow diagram of a system for hydrogen separation shown as a part on and in an overall dehydrogenation system. 
         FIG.  2    is a schematic illustration, flow diagram of a system for hydrogen separation. 
         FIG.  2 A  is a schematic illustration, flow diagram of  FIG.  2   , but showing the optional use of a booster compressor. 
         FIG.  2 B  is a schematic illustration, flow diagram of  FIG.  2   , but showing the optional use of a non-driver I-Compander. 
         FIG.  2 C  is the schematic illustration, flow diagram of  FIG.  2 B , but showing the optional use of a motor-driver I-Compander. 
         FIG.  2 D  is a schematic illustration, flow diagram showing a system for hydrogen separation using two separate expander/compressor sets in series. 
         FIG.  3    is a schematic illustration, flow diagram of  FIG.  2   , but showing the optional use of an expander/electric generator system. 
         FIG.  4    is the schematic illustration, flow diagram of  FIG.  2    with the alternative embodiment of the integrated main heat exchanger split into a warm section and a cold section. 
         FIG.  5    is the schematic illustration, flow diagram of  FIG.  2 A  with the alternative embodiment of the integrated main heat exchanger split into a warm section and a cold section. 
         FIG.  6    is the schematic illustration, flow diagram of  FIG.  2 B  with the alternative embodiment of the integrated main heat exchanger split into a warm section and a cold section. 
         FIG.  7    is the schematic illustration, flow diagram of  FIG.  2 C  with the alternative embodiment of the integrated main heat exchanger split into a warm section and a cold section. 
         FIG.  8    is the schematic illustration, flow diagram of  FIG.  2 D  with the alternative embodiment of the integrated main heat exchanger split into a warm section and a cold section. 
         FIG.  9    is the schematic illustration, flow diagram of  FIG.  3    with the alternative embodiment of the integrated main heat exchanger split into a warm section and a cold section. 
         FIG.  10    is a schematic illustration, flow diagram of  FIG.  9   , but showing the optional use of an external refrigeration system using a mixed refrigerant. 
         FIG.  11    is a schematic illustration, flow diagram of  FIG.  9   , but showing the optional use of an external cascade refrigeration system having two or more refrigeration cycles. 
         FIG.  12    is a schematic illustration, flow diagram of  FIG.  10   , but showing an alternative “no recycle gas” embodiment that does not utilize a recycled gas stream. 
         FIG.  13    illustrates an additional embodiment of the separation system of the processing unit shown in  FIG.  12   , further comprising a deethanizer system and a propylene/propane splitter system. 
         FIG.  14    illustrates an alternative embodiment of a refrigeration process for a rectifier column condenser. 
         FIG.  15    illustrates an alternative embodiment of a refrigeration process wherein refrigeration may be obtained from a cold section of an integrated main heat exchanger. 
     
    
    
     DETAILED DESCRIPTION 
     1. Introduction 
     A detailed description will now be provided. The purpose of this detailed description, which includes the drawings, is to satisfy the statutory requirements of 35 U.S.C. § 112. For example, the detailed description includes a description of the inventions defined by the claims and sufficient information that would enable a person having ordinary skill in the art to make and use the inventions. In the figures, like elements are generally indicated by like reference numerals regardless of the view or figure in which the elements appear. The figures are intended to assist the description and to provide a visual representation of certain aspects of the subject matter described herein. The figures are not all necessarily drawn to scale, nor do they show all the structural details of the systems, nor do they limit the scope of the claims. 
     Each of the appended claims defines a separate invention which, for infringement purposes, is recognized as including equivalents of the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the “invention” will refer to the subject matter recited in one or more, but not necessarily all, of the claims. Each of the inventions will now be described in greater detail below, including specific embodiments, versions, and examples, but the inventions are not limited to these specific embodiments, versions, or examples, which are included to enable a person having ordinary skill in the art to make and use the inventions when the information in this patent is combined with available information and technology. Various terms as used herein are defined below, and the definitions should be adopted when construing the claims that include those terms, except to the extent a different meaning is given within the specification or in express representations to the Patent and Trademark Office (PTO). To the extent a term used in a claim is not defined below or in representations to the PTO, it should be given the broadest definition persons having skill in the art have given that term as reflected in any printed publication, dictionary, or issued patent. 
     2. Selected Definitions 
     Certain claims include one or more of the following terms which, as used herein, are expressly defined below. 
     The term “olefin hydrocarbon” as used herein is defined as an unsaturated hydrocarbon that contains at least one carbon-carbon double bond. The term “compressed effluent vapor stream” as used herein is defined as an olefin-hydrogen effluent gas stream from a feed compressor. In certain embodiments disclosed herein, a combined feed enters a dehydrogenation unit to create an effluent gas stream that contains hydrogen, olefins, and heavy hydrocarbon components. The effluent gas stream in these embodiments is a low-pressure effluent stream. An example of a dehydrogenation unit is OLEFLEX™, which is a brand name for a dehydrogenation unit (OLEFLEX™ is a trademark of UOP Inc. of Des Plaines, Ill.). 
     In certain embodiments disclosed herein, the compressed effluent vapor stream is referred to as a reactor effluent. Further, in certain embodiments, the reactor effluent enters a process for hydrogen separation at 35° C.-52° C. and 0.5-1.2 MPa(g). 
     The term “compressor” as used herein is defined as a mechanical device that increases the pressure of a gas by reducing its volume. In certain embodiments disclosed herein, the feed compressor is also referred to as the reactor effluent compressor unit. 
     The term “heat exchanger” as used herein is defined as a device that transfers or “exchanges” heat from one matter to another. In certain embodiments disclosed herein, the heat exchanger is referred to as the integrated main heat exchanger. Further, in certain embodiments disclosed herein, there may be more than one heat exchanger or only one heat exchanger. Also, in certain embodiments, the heat exchanger may be composed of brazed aluminum heat exchanger cores. In at least one specific embodiment disclosed herein, the integrated main heat exchanger has warm stream passes, and it has cold stream passes. Additionally, in certain embodiments with more than one heat exchanger, the heat exchangers may be configured in series or parallel. 
     The term “separator” as used herein is defined as a device used to separate hydrogen from olefin and heavy paraffinic components. In certain embodiments disclosed herein, gravity is used in a vertical vessel to cause liquid to settle to the bottom of the vessel, where the liquid is withdrawn. In the same embodiments, the gas part of the mixture travels through a gas outlet at the top of the vessel. Further, in certain embodiments disclosed herein, there is more than one separator employed. In certain embodiments disclosed herein, each separator results in a majority of the olefin and paraffinic components being condensed to liquid and the hydrogen remaining vapor. A “paraffin hydrocarbon” is a saturated hydrocarbon having a general formula C n H 2n+2 . For example, in one embodiment disclosed herein, an outlet stream enters a second separator and results in 99.8% vapor and 0.2% liquid. 
     The term “first vapor stream” as used herein is mainly hydrogen gas. In one specific embodiment disclosed herein, the first vapor stream is vapor stream from the first stage cold gas-liquid separator. 
     The term “first liquid stream” as used herein is composed of condensed olefin and paraffinic components. In certain embodiments disclosed herein, the first liquid stream is an olefin-rich liquid stream. Further, in certain embodiments disclosed herein, the first liquid stream is liquid stream from the first stage cold gas-liquid separator. 
     The term “second vapor stream” as used herein is composed of mainly hydrogen gas. In certain embodiments disclosed herein, the second vapor stream has a temperature of −115° C. Further, in certain embodiments disclosed herein, the second vapor stream is a vapor stream from the second stage cold gas-liquid separator. 
     The term “second liquid stream” as used herein is composed of olefin and paraffinic components in liquid form. In one specific embodiment disclosed herein, the second liquid stream is a liquid stream from the second stage cold gas-liquid separator. 
     The term “expander” as used herein is defined as a centrifugal or axial flow turbine through which a gas is isentropically expanded. In one specific embodiment disclosed herein, cryogenic temperatures are achieved from refrigeration by expanding a high-pressure effluent gas stream using two-stage expanders. The term “cryogenic” as used herein is an adjective which means being or related to very low temperatures. The term “refrigeration” as used herein is defined as the process of moving heat from one location to another in controlled conditions. 
     An example of one type of expander configuration is an expander/compressor configuration, which can be two independent expander/compressor sets. In this example of an expander/compressor configuration, the two sets may be either two separate magnetic bearing type expander/compressor sets or oil bearing type sets that share a common lube oil system. For the expander configuration with two separate expander/compressor sets, one set may be called a high-pressure expander/compressor set that is configured as “post-compression.” Another set may be called a low-pressure expander/compressor set that is configured as “pre-compression.” “Post-compression” means that the compressor is set to compress the gas stream after expansion. “Pre-compression” means that the compressor is set to compress the gas stream before expansion. In certain embodiments disclosed herein, the composition and mass flow of the stream to the high-pressure expander and the high-pressure compressor remain substantially unchanged. Further, in the same embodiments, the composition and mass flow of the stream to the low-pressure expander and the low-pressure compressor remain substantially unchanged. 
     In other embodiments, a booster compressor may be added at the discharge of a high-pressure compressor. The term “booster compressor” as used herein refers to an additional compressor that provides additional pressure. In one specific embodiment disclosed herein, a booster compressor is added to achieve the required refrigeration for an effluent gas stream. Further, in the same embodiment, the booster compressor may be an independent compressor driven by either electrical motor or another type of driver. The term “motor” as used herein is defined as an electrical machine that converts electrical energy into mechanical energy. 
     In other embodiments, the high-pressure expander, the low-pressure expander, the high-pressure compressor, and the low-pressure compressor are mounted to a common bull gear to form a non-driver I-Compander. The term “bull gear” as used herein is defined as any large driving gear among smaller gears. In yet another embodiment, an electrical motor may be added to the bull gear to provide additional power for the compressor(s) to boost the pressure of a gas stream. 
     Another example of an expander configuration is an expander/electric generator configuration. The term “electric generator” as used herein is defined as a device that converts mechanical energy into electrical energy. In certain embodiments disclosed herein, there may be two separate expander/electric generator sets. Further, in those embodiments, the output power from the high-pressure expander drives its corresponding electric generator to produce electricity. Likewise, in those same embodiments, the output power from the low-pressure expander drives its corresponding electric generator to produce electricity. 
     The term “refrigerant compressor” as used herein refers to an additional compressor that provides additional pressure. In certain embodiments disclosed herein, an external refrigeration system comprising a single or multi-stage refrigerant compressor may be added to the separation system to provide the necessary refrigeration. In one specific embodiment disclosed herein, a refrigerant compressor may be added to the system to achieve the required refrigeration for an effluent gas stream. Further, in the same embodiment, the refrigerant compressor may be an independent compressor driven by either electrical motor or another type of driver. Further still, in the same embodiment, the refrigerant compressor system may include multiple stages of compression with a discharge cooler after each compressor stage and a discharge vapor/liquid separator after each discharge cooler. 
     The term “gas product” as used herein is defined as a hydrogen-rich gas product stream, which is sent to a downstream production facility. In one specific embodiment disclosed herein, the gas product is net gas product. In one example, the gas product contains primarily the hydrogen as well as the methane and ethane lighter hydrocarbons from the reactor effluent stream minus the material produced internally as recycle gas. In this example, the specifications for the gas product are as follows: 
     
       
         
           
               
             
               
                   
               
               
                 PDH Unit 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Hydrogen, mole percent minimum 
                 92.5 
               
               
                   
                 Total C 3+  olefins, mole % maximum 
                 0.055 
               
               
                   
                 Temperature, C. 
                 36 
               
               
                   
                 Pressure, MPa(g) 
                 0.60 
               
               
                   
                   
               
            
           
         
       
     
     The term “split stream” as used herein refers to a hydrogen-rich stream. In one specific embodiment disclosed herein, the split stream is a recycle gas. In one example, the recycle gas meets the following specifications: 
     
       
         
           
               
             
               
                   
               
               
                 PDH Unit 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Hydrogen, mole percent minimum 
                 92.5 
               
               
                   
                 Total Olefins, mole percent 
                  0.1 maximum 
               
               
                   
                 C3+ Olefins, mole percent 
                 0.05 maximum 
               
               
                   
                   
               
            
           
         
       
     
     The term “liquid paraffinic stream” as used herein refers to a liquid hydrocarbon stream of primarily propane, isobutane, or a mixture of primarily both. Propane is a three-carbon alkane with the molecular formula C 3 H 8 . Isobutane is the simplest alkane with a tertiary carbon, and it has the molecular formula C 4 H 10 . In one specific embodiment disclosed herein, the liquid paraffinic stream is the fresh feed. In one example, the liquid paraffinic stream has a temperature of 52° C. and a pressure of 2.06 MPa(g). 
     The term “control valve” as used herein is defined as a valve used to control fluid flow by varying the size of the flow passage. In one specific embodiment disclosed herein, the control valve is used to lower the pressure of the fluid flow. The term “liquid product drum” as used herein is defined as a device used to separate a vapor-liquid mixture. In certain embodiments disclosed herein, a liquid product drum is attached to a rectifier. In these certain embodiments, the liquid product drum is used for flashing a partially vaporized liquid stream. The term “flashing” as used herein refers to “flash evaporation,” which is defined as the partial vapor that occurs when a saturated liquid stream undergoes a reduction in pressure by passing through a throttling valve or other throttling device. In one example, the temperature of the liquid product drum is maintained at around 0° C. so that the liquid product drum may be composed of carbon steel. 
     In one specific embodiment, once in the liquid product drum, light components such as hydrogen, methane, and ethane, flash out from the liquid and travel upward through a rectifier located on top of the liquid product drum. The term “rectifier” as used herein is defined as a packed column used for “rectification.” In “rectification,” vapor and liquid are passed countercurrent to one another through a special apparatus, sometimes known as a rectifier, in which there are multiple points of contact between the two phases. The countercurrent movement is accompanied by heat and mass exchanges. In one example, the rectifier is a hollow vertical cylinder, within which there are irregularly shaped materials, known collectively as packing. The packing is used to enlarge the vapor-liquid interface. 
     The term “final liquid product” as used herein refers to an olefin-rich liquid product stream. In one specific embodiment disclosed herein, the final liquid product is liquid product stream  307 . In one example, the final liquid product contains primarily the propylene and heavier hydrocarbons from a reactor effluent stream, meeting the following specifications: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Propane + propylene recovery, % 
                 99.9 
               
               
                   
                 Temperature, C. 
                 50 ± 5° C. 
               
               
                   
                 Pressure, MPa(g) 
                 4.0 
               
               
                   
                   
               
            
           
         
       
     
     The “flashed vapor stream” is the vapor from the liquid product drum. In certain embodiments disclosed herein, the flashed vapor stream may be recycled back to the reactor effluent compressor unit for recovery of any hydrocarbons in the flashed vapor stream. 
     The term “coldbox” as used herein is defined as a box designed to contain low-temperature and cryogenic equipment and parts. In certain embodiments disclosed herein, the coldbox is filled with insulation material and purged with nitrogen to provide cold insulation. In certain embodiments, the coldbox may contain the heat exchanger, the separators, the liquid product drum and rectifier, as well as the associated piping. In the same embodiments, control valves can either be enclosed within or installed outside of the coldbox. 
     3. Certain Specific Embodiments 
     Now, certain specific embodiments are described, which are by no means an exclusive description of the inventions. Other specific embodiments, including those referenced in the drawings, are encompassed by this application and any patent that issues therefrom. 
     One or more specific embodiments disclosed herein includes a process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit, comprising cooling a compressed effluent vapor stream in a heat exchanger; separating hydrogen from olefin and heavy paraffinic components in the cooled compressed effluent vapor stream in a first separator to provide a first vapor stream and a first liquid stream; cooling the first vapor stream in the heat exchanger; separating hydrogen from olefin and heavy paraffinic components in the cooled first vapor stream in a second separator to provide a second vapor stream and a second liquid stream; warming the second vapor stream in the heat exchanger; isentropically expanding, in a high-pressure expander, the second vapor stream, wherein the pressure and temperature of the second vapor stream are lowered; warming the second vapor stream in the heat exchanger; compressing, in a high-pressure compressor, the second vapor stream; cooling the second vapor stream in a first discharge cooler; dividing the second vapor stream into a gas product and a split stream; withdrawing the gas product; compressing, in a low-pressure compressor, the split stream; cooling the split stream in a second discharge cooler and further cooling the split stream in the heat exchanger; isentropically expanding, in a low-pressure expander, the split stream, wherein the pressure and temperature of the split stream are lowered; cooling a liquid paraffinic stream in the heat exchanger; combining the cooled liquid paraffinic stream with the expanded split stream to provide a combined feed; vaporizing the combined feed in the heat exchanger; withdrawing the vaporized combined feed; lowering the pressure of the first liquid stream in a control valve; partially vaporizing the first liquid stream in the heat exchanger; flashing the partially vaporized first liquid stream in a liquid product drum to provide a hydrogen-rich gas, which travels to a rectifier connected to the liquid product drum; combining the hydrogen-rich gas and the second liquid stream in the rectifier, further purifying the hydrogen-rich gas; warming the hydrogen-rich gas from the rectifier in the heat exchanger to provide a flashed vapor stream; pumping a third liquid stream from the liquid product drum to the heat exchanger, wherein it is warmed; and providing a liquid product. 
     One or more specific embodiments disclosed herein includes a process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit, comprising separating hydrogen from olefin and heavy paraffinic components in the compressed effluent vapor stream to provide a first vapor stream and a first liquid stream; separating hydrogen from olefin and heavy paraffinic components in the first vapor stream to provide a second vapor stream and a second liquid stream; expanding and compressing the second vapor stream; dividing the second vapor stream into a gas product and a split stream; compressing and expanding the split stream; lowering the pressure of the first liquid stream; partially vaporizing the first liquid stream; flashing the partially vaporized first liquid stream in a liquid product drum to provide a hydrogen-rich gas; and combining the hydrogen-rich gas and the second liquid stream in a rectifier. 
     One or more specific embodiments disclosed herein includes a process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit, comprising separating hydrogen from olefin and heavy paraffinic components in the compressed effluent vapor stream to provide a first vapor stream and a first liquid stream; separating hydrogen from olefin and heavy paraffinic components in the first vapor stream to provide a second vapor stream and a second liquid stream; isentropically expanding, in a high-pressure expander, the second vapor stream; compressing, in a high-pressure compressor, the second vapor stream; dividing the second vapor stream into a gas product and a split stream; compressing, in a low-pressure compressor, the split stream; and isentropically expanding, in a low-pressure expander, the split stream. 
     One or more specific embodiments disclosed herein includes a process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit, comprising cooling the compressed effluent vapor stream in a heat exchanger; separating hydrogen from olefin and heavy paraffinic components in the cooled compressed effluent vapor stream to provide a first vapor stream and a first liquid stream; cooling the first vapor stream in the heat exchanger; separating hydrogen from olefin and heavy paraffinic components in the cooled first vapor stream to provide a second vapor stream and a second liquid stream; warming the second vapor stream in the heat exchanger; expanding the second vapor stream; warming the second vapor stream in the heat exchanger; compressing the second vapor stream; dividing the second vapor stream into a gas product and a split stream; compressing the split stream; cooling the split stream in the heat exchanger; expanding the split stream; cooling a liquid paraffinic stream in the heat exchanger; combining the cooled liquid paraffinic stream with the expanded split stream to provide a combined feed; vaporizing the combined feed in the heat exchanger; partially vaporizing the first liquid stream in the heat exchanger; flashing the partially vaporized first liquid stream in a liquid product drum to provide a hydrogen-rich gas; warming the hydrogen-rich gas in the heat exchanger to provide a flashed vapor stream; and pumping a third liquid stream from the liquid product drum to the heat exchanger, wherein it is warmed. 
     In any one of the processes or systems disclosed herein, the heat exchanger may be a single heat exchanger. 
     In any one of the processes or systems disclosed herein, the heat exchanger may be comprised of one or more brazed aluminum heat exchanger cores. 
     In any one of the processes or systems disclosed herein, the compressed effluent vapor stream may be comprised of hydrogen, paraffinic hydrocarbons, and propylene or isobutylene. 
     In any one of the processes or systems disclosed herein, the compressed effluent vapor stream may be comprised of hydrogen, paraffinic hydrocarbons, and a mixture of propylene and isobutylene. 
     In any one of the processes or systems disclosed herein, the liquid paraffinic stream may be comprised of either propane, isobutane, or a combination of propane and isobutane. 
     In any one of the processes or systems disclosed herein, the process may be performed without the employment of external refrigeration. 
     In any one of the processes or systems disclosed herein, a booster compressor may be employed to provide additional pressure to the second vapor stream from the high-pressure compressor. 
     In any one of the processes or systems disclosed herein, the high-pressure expander, the low-pressure expander, the high-pressure compressor, and the low-pressure expander may be mounted to a bull gear. 
     In any one of the processes or systems disclosed herein, a motor may be employed to drive the bull gear. 
     In any one of the processes or systems disclosed herein, one or more electric generators may be driven by the power produced in the high-pressure expander, low-pressure expander, or both expanders. 
     In any one of the processes or systems disclosed herein, the high-pressure expander and the low-pressure expander may be configured in series. 
     In any one of the processes or systems disclosed herein, the high-pressure compressor and the low-pressure compressor may be configured into two or more stages in series. 
     In any one of the processes or systems disclosed herein, the high-pressure compressor may be driven by the power produced in the high-pressure expander. 
     In any one of the processes or systems disclosed herein, the low-pressure compressor may be driven by the power produced in the low-pressure expander. 
     In any one of the processes or systems disclosed herein, a coldbox may be employed to contain all low-temperature and cryogenic equipment and parts. 
     In any one of the processes or systems disclosed herein, the withdrawn combined feed may be employed as a feed stream to a dehydrogenation reactor. 
     In any one of the processes or systems disclosed herein, the withdrawn liquid product may be introduced into a product storage system. 
     In any one of the processes or systems disclosed herein, the flashed vapor stream may be recycled to a feed compressor. 
     In any one of the processes or systems disclosed herein, the liquid product drum may be maintained at a temperature such that the liquid product drum may be composed of carbon steel. 
     In any one of the processes or systems disclosed herein, the composition and mass flow of the second vapor stream to the high-pressure expander and the high-pressure compressor may remain substantially unchanged. 
     In any one of the processes or systems disclosed herein, the composition and mass flow of the split stream to the low-pressure expander and the low-pressure compressor may remain substantially unchanged. 
     In any one of the processes or systems disclosed herein, the high-pressure expander and high-pressure compressor set and the low-pressure expander and low-pressure compressor set may be magnetic bearing type expander/compressor sets. 
     In any one of the processes or systems disclosed herein, the high-pressure expander and high-pressure compressor set and the low-pressure expander and low-pressure compressor set may be oil bearing type sets that share a common lube oil system. 
     One or more specific embodiments disclosed herein includes a separation system which utilizes a process for the separation of hydrogen from an olefin hydrocarbon rich compressed effluent vapor stream from a dehydrogenation unit comprising a heat exchanger for cooling the compressed effluent vapor stream, cooling the first vapor product, warming the second vapor product, reheating the second vapor product, cooling the split stream, cooling a liquid paraffinic feed for use in the reactor, vaporizing the combined stream, partially vaporizing the first liquid product, warming the hydrogen-rich gas from the rectifier, and warming the flashed liquid stream from the liquid product drum; a first separator in which the cooled compressed effluent vapor stream is separated to provide a first vapor product and a first liquid product; a second separator in which the cooled first vapor product is separated to provide a second vapor product and a second liquid product; a high-pressure expander for isentropically expanding the second vapor product; a high-pressure compressor for compressing the second vapor product; a low-pressure compressor for compressing the split stream; a low-pressure expander for isentropically expanding the split stream; a rectifier for flashing the partially vaporized first liquid product to provide a hydrogen-rich gas and combining the hydrogen-rich gas with the second liquid product. 
     4. Specific Embodiments in the Figures 
     The drawings presented herein are for illustrative purposes only and are not intended to limit the scope of the claims. Rather, the drawings are intended to help enable one having ordinary skill in the art to make and use the claimed inventions. 
     Referring to  FIGS.  1 - 3   , a specific embodiment, e.g., version or example, of a system for hydrogen separation from an olefin hydrocarbon rich compressed effluent vapor stream is illustrated. These figures may show features which may be found in various specific embodiments, including the embodiments shown in this specification and those not shown. 
       FIG.  1    shows a system for hydrogen separation, processing unit  100 , with a dehydrogenation unit  102  and a reactor effluent compressor unit  104 . A fresh feed  200  is a liquid paraffinic stream mainly composed of propane, isobutane, or a mixture of propane and isobutane. Fresh feed  200  is mixed with a recycle gas  220  (not shown), which is produced within the processing unit  100 . Recycle gas  220  contains primarily hydrogen. The combination of fresh feed  200  and recycle gas  220  is vaporized within the processing unit  100  and emerges as a combined feed  202 . The combined feed  202  enters the dehydrogenation unit  102 , where the combined feed  202  is dehydrogenated resulting in an effluent gas stream  204 . Effluent gas stream  204  is a low-pressure effluent stream composed of hydrogen, olefins, and other hydrocarbons. Effluent gas stream  204  is then mixed with a flash drum vapor  206 , which is primarily hydrogen, to form a feed gas stream  208 . The feed gas stream  208  enters the reactor effluent compressor unit  104 , where the feed gas stream  208  has its pressure increased and then its temperature lowered before entering processing unit  100 . A reactor effluent  210  exits the reactor effluent compressor unit  104  containing a mixture of hydrogen and hydrocarbons. There are two product streams produced from the processing unit  100 . One is a hydrogen-rich gas product stream, referred to as a net gas product  212 , and the other is an olefin-rich liquid product stream, referred to as a liquid product  214 , which has a boosted pressure. 
     The processing unit  100  is a system design and flow system that can be connected to a propane dehydrogenation (PDH) unit, an isobutane dehydrogenation (BDH) unit, or a propane/isobutane dehydrogenation (PBDH) unit for hydrogen separation from the reactor effluent. The process conditions (temperature, pressure, composition) are different for PDH, BDH, and PBDH, but the basic process flow scheme may be the same. Illustrative process conditions at key points are listed in the tables below. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 An Example of Process Conditions of the Key Streams for a PDH Plant 
               
            
           
           
               
               
            
               
                   
                 Stream No. 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 200 
                 202 
                 204 
                 206 
                 210 
                 214 
                 212 
               
            
           
           
               
               
            
               
                   
                 Stream Name 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Effluent 
                 Flash 
                   
                   
                 Net 
               
               
                   
                 Fresh 
                 Combined 
                 Gas 
                 Drum 
                 Reactor 
                 Liquid 
                 Gas 
               
               
                   
                 Feed 
                 Feed 
                 Stream 
                 Vapor 
                 Effluent 
                 Product 
                 Product 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Pressure 
                 kPa · G 
                 2200 
                 350 
                 5 
                 5 
                 1190 
                 4000 
                 590 
               
               
                 Temperature 
                 ° C. 
                 52 
                 37 
                 43 
                 37 
                 43 
                 49 
                 43 
               
               
                 Hydrogen 
                 Mole % 
                 0.0000 
                 H2/HCBN 
                 45.6105 
                 70.9685 
                 45.6936 
                 0.0545 
                 95.6074 
               
               
                 Methane 
                 Mole % 
                 0.0000 
                 Ratio: 
                 2.6676 
                 24.9248 
                 2.7406 
                 1.3315 
                 4.1340 
               
               
                 Ethylene 
                 Mole % 
                 0.0000 
                 0.42-0.5 
                 0.1062 
                 0.1596 
                 0.1064 
                 0.1820 
                 0.0230 
               
               
                 Ethane 
                 Mole % 
                 0.7089 
                   
                 2.0304 
                 1.3530 
                 2.0282 
                 3.7273 
                 0.1681 
               
               
                 Propylene 
                 Mole % 
                 0.7793 
                   
                 15.9163 
                 1.0486 
                 15.8676 
                 30.3881 
                 0.0339 
               
               
                 Propane 
                 Mole % 
                 98.3613 
                   
                 33.5518 
                 1.5445 
                 33.4469 
                 64.0928 
                 0.0336 
               
               
                 Propadiene 
                 Mole % 
                 0.0000 
                   
                 0.0024 
                 0.0001 
                 0.0024 
                 0.0047 
                 0.0000 
               
               
                 Methyl acetylene 
                 Mole % 
                 0.0000 
                   
                 0.0103 
                 0.0004 
                 0.0102 
                 0.0196 
                 0.0000 
               
               
                 Isobutane 
                 Mole % 
                 0.1407 
                   
                 0.0472 
                 0.0003 
                 0.0470 
                 0.0902 
                 0.0000 
               
               
                 Isobutylene 
                 Mole % 
                 0.0065 
                   
                 0.0263 
                 0.0001 
                 0.0262 
                 0.0503 
                 0.0000 
               
               
                 1-butene 
                 Mole % 
                 0.0000 
                   
                 0.0006 
                 0.0000 
                 0.0006 
                 0.0011 
                 0.0000 
               
               
                 Normal butane 
                 Mole % 
                 0.0034 
                   
                 0.0002 
                 0.0000 
                 0.0002 
                 0.0004 
                 0.0000 
               
               
                 Cis-2-butene 
                 Mole % 
                 0.0000 
                   
                 0.0006 
                 0.0000 
                 0.0006 
                 0.0011 
                 0.0000 
               
               
                 Trans-2-butene 
                 Mole % 
                 0.0000 
                   
                 0.0007 
                 0.0000 
                 0.0007 
                 0.0013 
                 0.0000 
               
               
                 Benzene 
                 Mole % 
                 0.0000 
                   
                 0.0254 
                 0.0000 
                 0.0253 
                 0.0485 
                 0.0000 
               
               
                 Toluene 
                 Mole % 
                 0.0000 
                   
                 0.0034 
                 0.0000 
                 0.0034 
                 0.0065 
                 0.0000 
               
               
                 Xylene 
                 Mole % 
                 0.0000 
                   
                 0.0000 
                 0.0000 
                 0.0000 
                 0.0000 
                 0.0000 
               
               
                 (as p-xylene) 
               
               
                 Heavy 
                 Mole % 
                 0.0000 
                   
                 0.0000 
                 0.0000 
                 0.0000 
                 0.0000 
                 0.0000 
               
               
                 hydrocarbons 
               
               
                 (as anthracene) 
               
               
                   
               
               
                 Notes: 
               
               
                 1. Liquid product 214 to have &gt;99.9% C3 Recovery 
               
               
                 2. Net gas product 212 to have Minimum H2 &gt; 92.5%; Max Total Olefins &lt; 0.1%; C3 + Olefins, &lt;0.05% 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 An Example of Process Conditions of the Key Streams for a BDH Plant 
               
            
           
           
               
               
            
               
                   
                 Stream No. 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 200 
                 202 
                 204 
                 206 
                 210 
                 214 
                 212 
               
            
           
           
               
               
            
               
                   
                 Stream Name 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Effluent 
                 Flash 
                   
                   
                 Net 
               
               
                   
                 Fresh 
                 Combined 
                 Gas 
                 Drum 
                 Reactor 
                 Liquid 
                 Gas 
               
               
                   
                 Feed 
                 Feed 
                 Stream 
                 Vapor 
                 Effluent 
                 Product 
                 Product 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Pressure 
                 kPa · G 
                 783 
                 350 
                 7 
                 7 
                 599 
                 906 
                 481 
               
               
                 Temperature 
                 ° C. 
                 49 
                 37 
                 43 
                 35 
                 39 
                 47 
                 39 
               
               
                 Hydrogen 
                 Mole % 
                 0.0000 
                 H2/HCBN 
                 47.8013 
                 72.8813 
                 47.8426 
                 0.0525 
                 93.9978 
               
               
                 Methane 
                 Mole % 
                 0.0000 
                 Ratio: 
                 2.8804 
                 19.7952 
                 2.9081 
                 0.4244 
                 5.2564 
               
               
                 Ethylene 
                 Mole % 
                 0.0000 
                 0.3-0.4 
                 0.0041 
                 0.0185 
                 0.0041 
                 0.0038 
                 0.0043 
               
               
                 Ethane 
                 Mole % 
                 0.0000 
                   
                 0.1536 
                 0.4872 
                 0.1541 
                 0.1980 
                 0.1106 
               
               
                 Propylene 
                 Mole % 
                 0.0000 
                   
                 0.4072 
                 0.2578 
                 0.4069 
                 0.7790 
                 0.0474 
               
               
                 Propane 
                 Mole % 
                 0.7046 
                   
                 1.4840 
                 0.8252 
                 1.4829 
                 2.8683 
                 0.1446 
               
               
                 Propadiene 
                 Mole % 
                 0.0000 
                   
                 0.0000 
                 0.0000 
                 0.0000 
                 0.0000 
                 0.0000 
               
               
                 Methyl acetylene 
                 Mole % 
                 0.0000 
                   
                 0.0001 
                 0.0000 
                 0.0001 
                 0.0002 
                 0.0000 
               
               
                 Isobutane 
                 Mole % 
                 97.5005 
                   
                 26.1652 
                 3.5254 
                 26.1280 
                 52.9086 
                 0.2912 
               
               
                 Isobutylene 
                 Mole % 
                 0.0018 
                   
                 20.0619 
                 2.1378 
                 20.0324 
                 40.6490 
                 0.1441 
               
               
                 1-butene 
                 Mole % 
                 0.0000 
                   
                 0.1178 
                 0.0116 
                 0.1177 
                 0.2389 
                 0.0007 
               
               
                 Normal butane 
                 Mole % 
                 1.7931 
                   
                 0.5800 
                 0.0408 
                 0.5792 
                 1.1776 
                 0.0019 
               
               
                 Cis-2-butene 
                 Mole % 
                 0.0000 
                   
                 0.1308 
                 0.0075 
                 0.1306 
                 0.2657 
                 0.0003 
               
               
                 Trans-2-butene 
                 Mole % 
                 0.0000 
                   
                 0.1875 
                 0.0117 
                 0.1872 
                 0.3808 
                 0.0005 
               
               
                 Benzene 
                 Mole % 
                 0.0000 
                   
                 0.0044 
                 0.0000 
                 0.0044 
                 0.0089 
                 0.0000 
               
               
                 Toluene 
                 Mole % 
                 0.0000 
                   
                 0.0044 
                 0.0000 
                 0.0044 
                 0.0089 
                 0.0000 
               
               
                 Xylene 
                 Mole % 
                 0.0000 
                   
                 0.0174 
                 0.0000 
                 0.0174 
                 0.0355 
                 0.0000 
               
               
                 (as p-xylene) 
               
               
                 Heavy 
                 Mole % 
                 0.0000 
                   
                 0.0000 
                 0.0000 
                 0.0000 
                 0.0000 
                 0.0000 
               
               
                 hydrocarbons 
               
               
                 (as anthracene) 
               
               
                   
               
               
                 Notes: 
               
               
                 1. Liquid product 214 to have &gt;90% C4 Recovery 
               
               
                 2. Net gas product 212 to have Minimum H2 &gt; 90%; Max C4 + Olefins &lt; 0.03% 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 An Example of Process Conditions of the Key Streams for a PBDH Plant 
               
            
           
           
               
               
            
               
                   
                 Stream No. 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 200 
                 202 
                 204 
                 206 
                 210 
                 214 
                 212 
               
            
           
           
               
               
            
               
                   
                 Stream Name 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Effluent 
                 Flash 
                   
                   
                 Net 
               
               
                   
                 Fresh 
                 Combined 
                 Gas 
                 Drum 
                 Reactor 
                 Liquid 
                 Gas 
               
               
                   
                 Feed 
                 Feed 
                 Stream 
                 Vapor 
                 Effluent 
                 Product 
                 Product 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Pressure 
                 kPa · G 
                 1830 
                 260 
                 5 
                 5 
                 1070 
                 4240 
                 505 
               
               
                 Temperature 
                 ° C. 
                 37 
                 48 
                 43 
                 48 
                 51 
                 35 
                 43 
               
               
                 Hydrogen 
                 Mole % 
                 0.0000 
                 H2/HCBN 
                 45.9920 
                 79.7057 
                 46.0635 
                 0.0497 
                 96.6271 
               
               
                 Methane 
                 Mole % 
                 0.0000 
                 Ratio: 
                 2.1818 
                 18.8848 
                 2.2172 
                 1.1821 
                 3.2835 
               
               
                 Ethylene 
                 Mole % 
                 0.0000 
                 0.3-0.4 
                 0.0159 
                 0.0192 
                 0.0159 
                 0.0274 
                 0.0031 
               
               
                 Ethane 
                 Mole % 
                 0.0013 
                   
                 0.6943 
                 0.3576 
                 0.6936 
                 1.2766 
                 0.0526 
               
               
                 Propylene 
                 Mole % 
                 0.4579 
                   
                 6.1041 
                 0.2484 
                 6.0917 
                 11.6320 
                 0.0115 
               
               
                 Propane 
                 Mole % 
                 56.0496 
                   
                 23.3764 
                 0.7083 
                 23.3283 
                 44.5664 
                 0.0219 
               
               
                 Propadiene 
                 Mole % 
                 0.0000 
                   
                 0.0004 
                 0.0000 
                 0.0004 
                 0.0008 
                 0.0000 
               
               
                 Methyl acetylene 
                 Mole % 
                 0.0000 
                   
                 0.0017 
                 0.0000 
                 0.0017 
                 0.0033 
                 0.0000 
               
               
                 Isobutane 
                 Mole % 
                 42.6054 
                   
                 11.4073 
                 0.0468 
                 11.3832 
                 21.7572 
                 0.0001 
               
               
                 Isobutylene 
                 Mole % 
                 0.0207 
                   
                 9.5945 
                 0.0280 
                 9.5742 
                 18.2998 
                 0.0001 
               
               
                 1-butene 
                 Mole % 
                 0.0000 
                   
                 0.0739 
                 0.0002 
                 0.0737 
                 0.1409 
                 0.0000 
               
               
                 Normal butane 
                 Mole % 
                 0.8652 
                   
                 0.3381 
                 0.0006 
                 0.3374 
                 0.6449 
                 0.0000 
               
               
                 Cis-2-butene 
                 Mole % 
                 0.0000 
                   
                 0.0806 
                 0.0001 
                 0.0804 
                 0.1537 
                 0.0000 
               
               
                 Trans-2-butene 
                 Mole % 
                 0.0000 
                   
                 0.1165 
                 0.0002 
                 0.1163 
                 0.2223 
                 0.0000 
               
               
                 Benzene 
                 Mole % 
                 0.0000 
                   
                 0.0089 
                 0.0000 
                 0.0089 
                 0.0169 
                 0.0000 
               
               
                 Toluene 
                 Mole % 
                 0.0000 
                   
                 0.0022 
                 0.0000 
                 0.0022 
                 0.0041 
                 0.0000 
               
               
                 Xylene 
                 Mole % 
                 0.0000 
                   
                 0.0095 
                 0.0000 
                 0.0095 
                 0.0182 
                 0.0000 
               
               
                 (as p-xylene) 
               
               
                 Heavy 
                 Mole % 
                 0.0000 
                   
                 0.0019 
                 0.0000 
                 0.0019 
                 0.0037 
                 0.0000 
               
               
                 hydrocarbons 
               
               
                 (as anthracene) 
               
               
                   
               
               
                 Notes: 
               
               
                 1. Liquid product 214 to have &gt;95% C3 Recovery 
               
               
                 2. Net gas product 212 to have Minimum H2 &gt; 95%; Max Total Olefins &lt; 0.1%; Max C3 + Olefins &lt; 0.05% 
               
            
           
         
       
     
       FIG.  2    shows the detailed configuration of the processing unit  100  with an integrated main heat exchanger  106 , two separate expander/compressor sets ( 108 / 110  and  112 / 114 ), a first stage cold gas-liquid separator  116 , a second stage cold gas-liquid separator  118 , a liquid product drum  120 , and a liquid product pump  122 . Based on different process conditions, the integrated main heat exchanger  106  may, in the alternative, be configured into two or more heat exchangers in series or parallel. 
     The two separate expander/compressor sets ( 108 / 110  and  112 / 114 ) may be two independent magnetic-bearing type or two sets of oil-bearing type that share a common lube oil system. Each expander/compressor set ( 108 / 110  and  112 / 114 ) may be configured into two or more stages in series setup depending on the pressure ratios of the expansion and compression, the flow rates, and other factors. 
     Fresh feed  200  enters warm pass A 1  at the upper warm end of the integrated main heat exchanger  106  where the fresh feed  200  is cooled to a low temperature and exits pass A 1  at the lower cold end of the integrated main heat exchanger  106  as an outlet stream  216 . The pressure of the outlet stream  216  is then reduced by a flow control valve  124  to a pressure that meets the required pressure of combined feed  202 , which feeds the dehydrogenation unit  102  (not shown). 
     Outlet stream  218  of flow control valve  124  then returns to the integrated main heat exchanger  106  via pass B 1  where it mixes with recycle gas  220  from the discharge of the low-pressure expander  112 . The mixed stream of recycle gas  220  and outlet stream  218  travels upward along the channel of pass B 1 , where heat exchanging occurs between the cold stream pass B 1  and warm stream passes A 1 , A 2 , A 3 , and A 4 . Before exiting through pass B 1 , the mixed stream is completely vaporized and becomes a superheated vapor stream. The superheated vapor stream is referred to as combined feed  202  after exiting pass B 1 . The pressure of combined feed  202  is maintained at a constant value by the feed of the dehydrogenation unit  102  (not shown). The combined feed  202  is the reactor feedstock for dehydrogenation unit  102  (not shown). 
     The reactor effluent  210 , an olefin-hydrogen effluent stream from the reactor effluent compressor unit  104  (not shown), enters pass A 2  at the upper warm end of the integrated main heat exchanger  106 , where the stream is cooled to a low temperature as it flows through and exits pass A 2  in the middle of the integrated main heat exchanger  106 . The cooling of the reactor effluent  210  as it travels through pass A 2  is caused by cold stream passes B 1  through B 6 . Outlet stream  222  from pass A 2  enters the first stage cold gas-liquid separator  116  with a low temperature, at which time a majority, &gt;95%, of the olefin and heavy paraffinic components in outlet stream  222  are condensed to liquid, which is separated out as liquid stream  224 . Further, almost all, &gt;99% of the hydrogen from outlet stream  222  remains vapor, and the first stage cold gas-liquid separator  116  separates out the vapor as vapor stream  226 . 
     The vapor stream  226  then flows back to the integrated main heat exchanger  106  through pass A 3 , where it is cooled to a lower temperature by the time it exits pass A 3  at the lower end of the integrated main heat exchanger  106 . The outlet stream  228  from pass A 3  enters the second stage cold gas-liquid separator  118 , where almost all, &gt;85%, of the olefin and heavy paraffinic components in outlet stream  228  are condensed to liquid stream  230  and almost all, &gt;99.95% of the hydrogen stays in vapor stream  232 . The vapor stream  232  exits second stage cold gas-liquid separator  118  and returns to the integrated main heat exchanger  106  through pass B 4 , where vapor stream  232  is warmed before exiting pass B 4  of the integrated main heat exchanger  106  as outlet stream  234 . Outlet stream  234  is superheated and enters the high-pressure expander  108 , where it is expanded by “isentropic” gas expansion process to a lower pressure and lower temperature to become a cold stream  236 . The output power from the high-pressure expander  108  drives high-pressure compressor  110 . The high-pressure expander  108  is equipped with an IGV (inlet guide vane) and bypass control valve  126  to maintain a constant pressure at the inlet of high-pressure expander  108 . 
     Cold stream  236  may or may not contain liquid. Cold stream  236  flows directly into pass B 3  at the lower cold end of the integrated main heat exchanger  106  and travels up pass B 3 , where it exchanges heat with warm stream passes A 1 , A 2 , A 3 , and A 4 . As cold stream  236  travels through pass B 3 , it is warmed to a temperature close to the inlet temperatures of passes A 1 , A 2 , A 3 , and A 4  by the time it exits pass B 3  at the upper warm end of the integrated main heat exchanger  106 . An outlet stream  238  from pass B 3  then flows to high-pressure compressor  110 , where the pressure of outlet stream  238  is increased to meet the pressure requirement of the net gas product  212 . A discharge stream  240  from high-pressure compressor  110 , which contains primarily hydrogen and other lighter hydrocarbons (e.g. methane and ethane) from the reactor effluent  210 , is cooled down by a high-pressure compressor discharge cooler  128  before being split into two streams. One stream is the net gas product  212 , which is sent to a downstream production facility. The pressure of the net gas product  212  determines the discharge pressure of the high-pressure compressor  110 . A pressure control valve  130  maintains a minimum required discharge pressure of the high-pressure compressor  110  to protect the high-pressure compressor  110  in case the pressure of the net gas product  212  is lost. 
     The second stream from the discharge of the high-pressure compressor discharge cooler  128  is a split stream  242 . Split stream  242  is routed to the low-pressure compressor  114  where its pressure is boosted. Split stream  242  is then cooled by a low-pressure compressor discharge cooler  132 , before entering warm stream pass A 4  at the upper warm end of the integrated main heat exchanger  106 . Split stream  242  is cooled to a low temperature as it flows down and exits pass A 4  at the middle of the integrated main heat exchanger  106 . An outlet stream  244  of pass A 4  then flows back to the low-pressure expander  112 , where it is expanded to a lower pressure and lower temperature through “isentropic” gas expansion process. The output power from the low-pressure expander  112  drives low-pressure compressor  114 . The low-pressure expander  112  discharge stream is recycle gas  220  that mixes with outlet stream  218  to become combined feed  202 . 
     The low-pressure expander  112  is equipped with an IGV (inlet guide vane) and bypass control valve  134  to maintain a constant flow for recycle gas  220  to mix with outlet stream  218  in order to meet the H 2 /hydrocarbon mole ratio specified for combined feed  202 . The H 2 /hydrocarbon mole ratio is defined as (moles of hydrogen in combined feed  202 )/(moles of hydrocarbon in combined feed  202 ). This ratio is typically specified by the license of dehydrogenation reactors, for example the UOP&#39;s OLEFLEX™ dehydrogenation reactor. 
     The pressure of combined feed  202  determines the discharge pressure of the low-pressure expander  112 . A pressure control valve  136  maintains a minimum required pressure of the low-pressure expander  112  to protect the low-pressure expander  112  from “flying out” in case the pressure of the combined feed  202  is lost. 
     Returning to the first stage cold gas-liquid separator  116 , the pressure of the olefin-rich liquid stream  224  is reduced by level control valve  138  before it enters pass B 2  of the integrated main heat exchanger  106  as cold stream  246 . Cold stream  246  enters pass B 2  at the lower cold end of the integrated main heat exchanger  106  where cold stream  246  exchanges heat with the warm passes A 1 , A 2 , and A 4  and becomes partially vaporized. This partially vaporized stream  248  exits pass B 2  in the middle of the integrated main heat exchanger  106  and flows to the liquid product drum  120 . Once in the liquid product drum  120 , light components, mainly hydrogen, methane, ethane, and maybe some C3+ components, flash out from the liquid and travel upward through the rectifier  140  located on the top of the liquid product drum  120 . The upward travelling hydrogen-rich gas in the rectifier  140 , which is a packed column, makes contact with the downward travelling colder liquid stream  230  from the second stage cold gas-liquid separator  118 . Heat and mass transferring occurs in the rectifier  140 , and therefore the hydrogen-rich gas in the rectifier  140  is further purified to meet the minimum hydrogen content specification of the flash drum vapor  206 , before exiting the top of the rectifier  140  as a vapor stream  250 . 
     The pressure of the liquid product drum  120  is maintained by a pressure control valve  142  on vapor stream  250  to a constant pressure to maximize the recovery of olefin and heavy hydrocarbon components in the liquid product  214  and to meet the specification of the maximum allowable hydrogen content in the liquid product  214 . 
     After the pressure control valve  142 , a cold stream  252  contains certain olefin components in addition to the main light components hydrogen, methane, and ethane. The cold stream  252  enters cold stream pass B 6  at the lower cold end of the integrated main heat exchanger  106 . As cold stream  252  travels up pass B 6 , it exchanges heat with the warm stream passes A 1 , A 2 , A 3 , and A 4 , and cold stream  252  is warmed to a temperature close to the inlet temperature of reactor effluent  210  or fresh feed  200  as it exits pass B 6 . The flash drum vapor  206  from pass B 6  then flows back to the inlet of the reactor effluent compressor unit  104  (not shown). 
     The separated cold liquid stream  254  from the liquid product drum  120  is pumped by the liquid product pump  122  to a pressure that meets the required pressure of the liquid product  214 . The liquid level of the liquid product drum  120  is maintained by a level control valve  144 . 
     The cold liquid product stream  256  then enters pass B 5  at the middle of the integrated main heat exchanger  106 . As the liquid product stream  256  travels upward in pass B 5 , it exchanges heat with the warm passes A 1 , A 2 , and A 4  and is warmed to a temperature defined by the liquid product  214  specification as it exits pass B 5  at the upper warm end of the integrated main heat exchanger  106 . The liquid product  214  is then sent to a production facility. 
     The liquid product drum  120  may be maintained at a temperature greater than −15° C., and therefore, liquid product drum  120  and liquid product pump  122  may be constructed of carbon steel for additional cost savings. 
     Liquid product drum  120  is elevated to a height to get enough NPSHa (net positive suction head available) for the liquid product pump  122  to avoid cavitation damage to the liquid product pump  122 . 
     Further, a coldbox  146  is designed to contain all low-temperature equipment including the integrated main heat exchanger  106 , the first stage cold gas-liquid separator  116 , the second stage cold gas-liquid separator  118 , and the liquid product drum  120 , as well as the associated piping. Control valves  138 ,  119 ,  142 , and  124  can either be enclosed within or installed outside of the coldbox  146 . The coldbox  146  is typically filled with insulation material and purged with nitrogen to provide cold insulation for the low-temperature equipment and parts. 
       FIG.  2 A  shows the option of two separate expander/compressor sets ( 108 / 110  and  112 / 114 ) with an additional booster compressor  148  located at the discharge of the high-pressure compressor  110 . The only difference between  FIG.  2    and  FIG.  2 A  is the addition of the booster compressor  148 , which is used to provide additional pressure to discharge stream  258  from high-pressure compressor  110 . Further, booster compressor  148  achieves the required refrigeration for the effluent gas stream  204 , especially when the pressure difference between the reactor effluent  210  and the net gas product  212  is not high enough to achieve the required refrigeration. The booster compressor  148  is an independent compressor driven by either electrical motor or other type of driver. 
       FIG.  2 B  shows the non-driver I-Compander option. The only difference between  FIG.  2    and  FIG.  2 B  is that the high-pressure expander  108 , the low-pressure expander  112 , the high-pressure compressor  110 , and the low-pressure compressor  114  are mounted to a common bull gear  150  to form a so called non-driver I-Compander  152 . Depending on the pressure ratios of expansion, flow rate, and other factors, each expander may also be set up in series with multiple stages available. Each compressor can be configured into two or more stages in serial setup depending on the pressure ratios of the compression, the flow rate, and other factors. 
       FIG.  2 C  shows the motor-driver I-Compander option. The only difference between  FIG.  2 B  and  FIG.  2 C  is the addition of a motor driver, electric motor  154 , to the bull gear  150  of the I-Compander  152 . The power that drives the compressor(s) is from the high-pressure expander  108  and the low-pressure expander  112 , with additional power input from the electric motor  154 . The only difference between the “motor-driver option” and the “non-driver option” is the addition of the electric motor  154  that provides additional power for the compressor(s) to boost the pressure of discharge stream  240  and the pressure of outlet stream  244  high enough to provide the required refrigeration. The power input to the I-Compander  152  by the electric motor  154  is needed especially when the pressure difference between the reactor effluent  210  and the net gas product  212  is not high enough to achieve the required refrigeration. 
       FIG.  2 D  shows the option of two separate expander/compressor sets ( 108   a / 110   a  and  112   a / 114   a ) in series. In this embodiment, the two separate expander/compressor sets ( 108   a / 110   a  and  112   a / 114   a ) replace the high-pressure expander/compressor set ( 108 / 110 ), as shown in  FIG.  2   , and the low-pressure expander/compressor set ( 112 / 114 ) is eliminated. In this embodiment, outlet stream  234  is superheated and enters expander  108   a , where it is expanded by “isentropic” gas expansion process to a lower pressure and lower temperature. Outlet stream  235  then enters expander  112   a , where it is further expanded by “isentropic” gas expansion process to a lower pressure and lower temperature. The output power from expander  108   a  drives compressor  110   a . Expander  108   a  is equipped with an IGV (inlet guide valve) and bypass control valve  126  to maintain a constant pressure at the inlet of expander  108   a . Additionally, the output power from expander  112   a  drives compressor  114   a.    
     As further illustrated in  FIG.  2 D , outlet stream  237  then splits into two separate streams. The first split stream from outlet stream  237  is cold stream  236 . Cold stream  236  may or may not contain liquid. Cold stream  236  flows directly into pass B 3  at the lower cold end of the integrated main heat exchanger  106  and travels up pass B 3 , where it exchanges heat with warm stream passes A 1 , A 2 , A 3 , and A 4 . As cold stream  236  travels through pass B 3 , it is warmed to a temperature close to the inlet temperatures of passes A 1 , A 2 , A 3 , and A 4  by the time it exits pass B 3  at the upper warm end of the integrated main heat exchanger  106 . In this embodiment, an outlet stream  238  from pass B 3  then flows to compressor  114   a , where the pressure of outlet stream  238  is increased. Outlet stream  239  then enters compressor  110   a , where the pressure of outlet stream  239  is increased to meet the pressure requirement of the net gas product  212 . A discharge stream  240  from compressor  110   a , which contains primarily hydrogen and other lighter hydrocarbons (e.g. methane and ethane) from the reactor effluent  210 , is cooled down by a high-pressure discharge cooler  128 , which then becomes net gas product  212 , which is sent to a downstream production facility. The pressure of the net gas product  212  determines the discharge pressure of the compressor  110   a . A pressure control valve  130  maintains a minimum required discharge pressure of the compressor  110   a  to protect the compressor  110   a  in case the pressure of the net gas product  212  is lost. 
     The second split stream from outlet stream  237  is recycle gas  220  that mixes with outlet stream  218  to become combined feed  202 . The pressure of combined feed  202  determines the discharge pressure of expander  112   a . A pressure control valve  136  maintains a minimum required pressure of the expander  112   a  to protect the expander  112   a  from “flying out” in case the pressure of the combined feed  202  is lost. 
       FIG.  3    shows the expander/electric-generator option of the processing unit  100  in  FIG.  1   . It illustrates configuration of the integrated main heat exchanger  106 , two separate expander/electric-generator sets ( 108 / 156  and  112 / 158 ), the first stage cold gas-liquid separator  116 , the second stage cold gas-liquid separator  118 , the liquid product drum  120  and the liquid product pump  122 . The differences between  FIG.  3    and  FIG.  2    include the configurations of the expander sets as well as the details identified below. 
     Stream  234  exits pass B 4  of the integrated main heat exchanger  106  superheated and enters the high-pressure expander  108 , where stream  234  is expanded to a lower pressure and lower temperature through a so-called “isentropic” gas expansion process. The output power from the high-pressure expander  108  drives electric generator  156  to produce electricity. The high-pressure expander  108  is equipped with an IGV (inlet guide vanes) and bypass control valve  126  to maintain a constant pressure at the expander inlet. 
     The cold outlet stream  236  from the high-pressure expander  108  may or may not contain liquid. It flows directly into pass B 3  located at the lower cold end of the integrated main heat exchanger  106  and travels up in pass B 3 , where cold outlet stream  236  exchanges heat with the warm stream passes A 1 , A 2 , and A 3 . A side stream  260  is taken out from the middle of pass B 3  as feed to the low-pressure expander  112 . 
     The outlet stream  262  of pass B 3  flows through pressure control valve  130  as net gas product  212  to a downstream production facility. The pressure of the net gas product  212  determines the discharge pressure of the high-pressure expander  108 . The pressure control valve  130  is to maintain a minimum required discharge pressure of the high-pressure expander  108  to protect the expander from “flying out” in case the pressure of the net gas product stream is lost. 
     The side-stream  260  from pass B 3  is routed to the low-pressure expander  112 , where it is expanded to a lower pressure and lower temperature through “isentropic” gas expansion process. The output power from the low-pressure expander  112  drives electric generator  158  to produce electricity. 
     The low-pressure expander  112  is equipped with an IGV (inlet guide vanes) and bypass control valve  134  to maintain a constant flow for stream  264 , which is the required hydrogen-rich recycle gas flow to mix with the liquid paraffinic stream  218  to meet the H2/HCBN mole ratio specification for the combined feed  202 . The H2/HCBN mole ratio is defined as (moles of hydrogen in the combined feed  202 )/(moles of hydrocarbon in combined feed  202 ). This ratio is typically specified by the license of dehydrogenation reactors, for example the UOP&#39;s OLEFLEX™ dehydrogenation reactor. 
     The pressure of the combined feed  202  determines the discharge pressure of the low-pressure expander  112 . A pressure control valve  136  is installed to maintain a minimum required pressure of the low-pressure expander  112  to protect the expander from “flying out” in case the pressure of the combined feed  202  is lost. The stream  220  from pressure control valve  136  commingles with stream  218  as detailed in the description of  FIG.  2   . The stream  220  is the recycle gas stream that mixes with stream  218  to become the combined feed  202 . 
     Alternatively, certain embodiments may allow for the integrated main heat exchanger  106  to be split into a warm section  106   a  and a cold section  106   b  as shown in  FIG.  4   .  FIG.  4    is the schematic illustration, flow diagram of  FIG.  2    with the alternative embodiment of the integrated main heat exchanger  106  split into the warm section  106   a  and the cold section  106   b . The warm section  106   a  and the cold section  106   b  can be composited of one or more brazed aluminum heat exchanger (BAHX) cores. As shown in  FIG.  4   , a side stream  400  is taken from warm pass A 1  at a point at the upper end of the warm section  106   a . The flow of side stream  400  is regulated by a control valve  300 . The outlet stream  402  from control valve  300  then flows into pass B 1  at the lower end of the warm section  106   a . Further, as shown in  FIG.  4   , another side stream  404  is taken from warm pass A 1  at a point at the lower end of the warm section  106   a . The flow of side stream  404  is regulated by a control valve  302 . The outlet stream  406  from control valve  302  then flows into pass B 1  lower in the warm section  106   a.    
       FIG.  5    is the schematic illustration, flow diagram of  FIG.  2 A  with the alternative embodiment of the integrated main heat exchanger  106  split into the warm section  106   a  and the cold section  106   b . The warm section  106   a  and the cold section  106   b  can be composited of one or more brazed aluminum heat exchanger (BAHX) cores. As shown in  FIG.  5   , a side stream  400  is taken from warm pass A 1  at a point at the upper end of the warm section  106   a . The flow of side stream  400  is regulated by a control valve  300 . The outlet stream  402  from control valve  300  then flows into pass B 1  at the lower end of the warm section  106   a . Further, as shown in  FIG.  5   , another side stream  404  is taken from warm pass A 1  at a point at the lower end of the warm section  106   a . The flow of side stream  404  is regulated by a control valve  302 . The outlet stream  406  from control valve  302  then flows into pass B 1  lower in the warm section  106   a.    
       FIG.  6    is the schematic illustration, flow diagram of  FIG.  2 B  with the alternative embodiment of the integrated main heat exchanger  106  split into the warm section  106   a  and the cold section  106   b . The warm section  106   a  and the cold section  106   b  can be composited of one or more brazed aluminum heat exchanger (BAHX) cores. As shown in  FIG.  6   , a side stream  400  is taken from warm pass A 1  at a point at the upper end of the warm section  106   a . The flow of side stream  400  is regulated by a control valve  300 . The outlet stream  402  from control valve  300  then flows into pass B 1  at the lower end of the warm section  106   a . Further, as shown in  FIG.  6   , another side stream  404  is taken from warm pass A 1  at a point at the lower end of the warm section  106   a . The flow of side stream  404  is regulated by a control valve  302 . The outlet stream  406  from control valve  302  then flows into pass B 1  lower in the warm section  106   a.    
       FIG.  7    is the schematic illustration, flow diagram of  FIG.  2 C  with the alternative embodiment of the integrated main heat exchanger  106  split into the warm section  106   a  and the cold section  106   b . The warm section  106   a  and the cold section  106   b  can be composited of one or more brazed aluminum heat exchanger (BAHX) cores. As shown in  FIG.  7   , a side stream  400  is taken from warm pass A 1  at a point at the upper end of the warm section  106   a . The flow of side stream  400  is regulated by a control valve  300 . The outlet stream  402  from control valve  300  then flows into pass B 1  at the lower end of the warm section  106   a . Further, as shown in  FIG.  7   , another side stream  404  is taken from warm pass A 1  at a point at the lower end of the warm section  106   a . The flow of side stream  404  is regulated by a control valve  302 . The outlet stream  406  from control valve  302  then flows into pass B 1  lower in the warm section  106   a.    
       FIG.  8    is the schematic illustration, flow diagram of  FIG.  2 D  with the alternative embodiment of the integrated main heat exchanger  106  split into the warm section  106   a  and the cold section  106   b . The warm section  106   a  and the cold section  106   b  can be composited of one or more brazed aluminum heat exchanger (BAHX) cores. As shown in  FIG.  8   , a side stream  400  is taken from warm pass A 1  at a point at the upper end of the warm section  106   a . The flow of side stream  400  is regulated by a control valve  300 . The outlet stream  402  from control valve  300  then flows into pass B 1  at the lower end of the warm section  106   a . Further, as shown in  FIG.  8   , another side stream  404  is taken from warm pass A 1  at a point at the lower end of the warm section  106   a . The flow of side stream  404  is regulated by a control valve  302 . The outlet stream  406  from control valve  302  then flows into pass B 1  lower in the warm section  106   a.    
       FIG.  9    is the schematic illustration, flow diagram of  FIG.  3    with the alternative embodiment of the integrated main heat exchanger  106  split into the warm section  106   a  and the cold section  106   b . The warm section  106   a  and the cold section  106   b  can be composited of one or more brazed aluminum heat exchanger (BAHX) cores. As shown in  FIG.  9   , a side stream  400  is taken from warm pass A 1  at a point at the upper end of the warm section  106   a . The flow of side stream  400  is regulated by a control valve  300 . The outlet stream  402  from control valve  300  then flows into pass B 1  at the lower end of the warm section  106   a . Further, as shown in  FIG.  9   , another side stream  404  is taken from warm pass A 1  at a point at the lower end of the warm section  106   a . The flow of side stream  404  is regulated by a control valve  302 . The outlet stream  406  from control valve  302  then flows into pass B 1  lower in the warm section  106   a.    
       FIG.  10    shows the external refrigeration system option of the processing unit  100  in  FIG.  1   . It illustrates configuration of the integrated main heat exchanger  106 , an external refrigeration system, the first stage cold gas-liquid separator  116 , the second stage cold gas-liquid separator  118 , the liquid product drum  120 , and the liquid product pump  122 . Similarly to the aforementioned embodiments, the integrated main heat exchanger  106  may be split into warm section  106   a  and cold section  106   b  and further composited of one or more brazed aluminum heat exchanger (BAHX) cores as shown in  FIGS.  4 - 9   . The differences between the embodiment shown in  FIG.  10    and the embodiments shown in  FIGS.  2 - 9    include the removal of the expander/compressor systems and the addition of the external refrigeration system. 
     The external refrigeration system may be a closed-loop refrigeration system that provides refrigeration to the effluent gas streams entering the processing unit  100 . In embodiments, the external refrigeration system may utilize and circulate a mixed refrigerant (MR) composition comprising one or more hydrocarbon components such as, without limitation, methane, ethane, ethylene, propane, propylene, butanes, or any combinations thereof. An example of an MR composition may be a mixture of methane, ethylene, and propane. Further, the external refrigeration system may comprise at least one mixed refrigerant compressor to pressurize the MR stream. The at least one mixed refrigerant compressor may be a single or multi-stage compressor system comprising a discharge cooler after each compressor stage and a discharge vapor/liquid separator after each discharge cooler. In embodiments, the external refrigeration system may comprise mixed refrigerant compressor  501 , discharge cooler  502 , and discharge vapor/liquid separator  503 . The discharge vapor/liquid separator  503  may separate the MR composition, resulting in two product streams: a pressurized and cooled vapor refrigerant stream  513  and a pressurized and cooled liquid refrigerant stream  512 . 
     The pressurized and cooled vapor refrigerant stream  513  from the discharge vapor/liquid separator  503  may be at a pressure between about 2,500 kPa·G and about 4,000 kPa·G. In embodiments, the discharge vapor/liquid separator  503  may be a standard vapor/liquid flash separation vessel capable of separating the MR composition into a vapor product and a liquid product. Stream  513  may enter at the top of integrated main heat exchanger  106  and travel down through pass C 1  to be cooled and totally liquified by the cold passes B 1 , B 2 , B 3 , B 5 , B 6 , and C 2  to a temperature between about −100° C. and about −120° C. As such, stream  513  may exit the integrated main heat exchanger  106  as cooled liquid stream  514 . Stream  514  may be reduced to a pressure between about 150 kPa·G and about 450 kPa·G and further cooled to a temperature between about −105° C. and about −130° C. via a pressure control valve  504 , resulting in a pressure-reduced, temperature-decreased vapor/liquid mixed stream  515 . Stream  515  may then enter at the bottom of integrated main heat exchanger  106  and travel upward through pass C 2  to provide refrigeration to the warm passes such as A 1 , A 2 , A 3 , and C 1  through vaporization of the MR composition. As such, stream  515  may exit the integrated main heat exchanger  106  as warm, vaporized stream  510  with a pressure between about 50 kPa·G and about 350 kPa·G. Stream  510  may flow to the mixed refrigerant compressor  501 , such that stream  510  comprising the MR composition may be compressed to stream  511 , and then cooled and condensed by the discharge cooler  502 , resulting in stream  518 . In embodiments, the discharge cooler  502  may be an air cooler or a water cooler. Stream  518  may finally enter discharge vapor/liquid separator  503  to provide the pressurized and cooled vapor refrigerant stream  513  and the pressurized and cooled liquid refrigerant stream  512 . In some embodiments, the warm, vaporized stream  510  may first travel through a suction scrubber before entering the mixed refrigerant compressor  501 . 
     The pressurized and cooled liquid refrigerant stream  512  from discharge vapor/liquid separator  503  may also be at a pressure between about 2,500 kPa·G and about 4,000 kPa·G. In embodiments, stream  512  may enter at the top of integrated main heat exchanger  106 , travel down through pass C 3 , and exit as a subcooled liquid stream  516 . Stream  516  may be reduced in pressure and cooled in temperature via a second pressure control valve  505 , resulting in a pressure-reduced, temperature-decreased liquid stream  517 . Stream  517  may then enter the integrated main heat exchanger  106  to combine with stream  515  in pass C 2 . 
       FIG.  11    shows the external cascade refrigeration system option of the processing unit  100  in  FIG.  1   . It illustrates configuration of the integrated main heat exchanger  106 , an external cascade refrigeration system, the first stage cold gas-liquid separator  116 , the second stage cold gas-liquid separator  118 , the liquid product drum  120 , and the liquid product pump  122 . Similarly to the aforementioned embodiments, the integrated main heat exchanger  106  may be split into warm section  106   a  and cold section  106   b  and further composited of one or more brazed aluminum heat exchanger (BAHX) cores as shown in  FIGS.  4 - 9   . The differences between the embodiment shown in  FIG.  11    and the embodiments shown in  FIGS.  2 - 9    include the removal of the expander/compressor systems and the addition of the external cascade refrigeration system. 
     The external cascade refrigeration system may be a composite of multiple closed-loop external refrigeration cycles that provide refrigeration to the effluent gas streams entering the processing unit  100 . In embodiments, the external cascade refrigeration system may comprise a first external refrigeration cycle and a second external refrigeration cycle. The first external refrigeration cycle may utilize and circulate a refrigerant comprising propane, or propylene, or any combinations thereof. Further, the first external refrigeration cycle may comprise a recycle compressor  601 , to pressurize the refrigerant, and a thermosiphon vessel  604 . The recycle compressor  601  may be a single or multi-stage compressor system comprising a discharge condenser  602  at its final compression discharge stage. The final stage discharge condenser  602  may condense the refrigerant resulting in a pressurized and totally condensed saturated liquid refrigerant stream  613 . 
     The pressurized and totally condensed saturated liquid refrigerant stream  613  from the final stage discharge condenser  602  may be at a pressure between about 1,000 kPa·G and about 1,750 kPa·G. In embodiments, the discharge condenser  602  may be an air cooler or a water cooler. Stream  613  may enter the integrated main heat exchanger  106  and travel down through pass D 1  to be sub-cooled by the cold passes B 1 , B 2 , B 3 , B 5 , B 6 , and D 2  to a temperature between about −10° C. and about −25° C. As such, stream  613  may exit the integrated main heat exchanger  106  as sub-cooled liquid stream  614 . Stream  614  may be reduced to a pressure between about 15 kPa·G and about 50 kPa·G and further cooled to a temperature between about −30° C. and about −45° C. via a level control valve  603 , resulting in a pressure-reduced, temperature-decreased vapor/liquid mixed stream  615 . Stream  615  may then enter a thermosiphon vessel  604 , which may be a vertical vessel configured to maintain a steady internal liquid level. The steady internal liquid level may allow for the formation of a thermosiphon that may be capable of circulating a cold liquid refrigerant stream  616  from the bottom of the thermosiphon vessel  604 , through pass D 2  of the integrated main heat exchanger  106 , and then back to an upper inlet of the thermosiphon vessel  604  as a two-phase refrigerant stream  617 . Stream  617  may comprise between about 30% and about 50% vapor in order to maintain a steady operation of the thermosiphon circulation. In embodiments, the cold liquid refrigerant stream  616  which travels upward through pass D 2  may vaporize to provide refrigeration to the warm passes such as A 1 , A 2 , D 1 , and E 1 . Finally, a flashed vapor stream  610  resulting from the thermosiphon vessel  604  may flow to the recycle compressor  601 , such that stream  610  comprising the refrigerant may be compressed to stream  612 , and then cooled and condensed by the final stage discharge condenser  602 , resulting in stream  613 . In some embodiments, the flashed vapor stream  610  may first travel through a suction scrubber before entering the recycle compressor  601 . 
     The second external refrigeration cycle may utilize and circulate an alternate refrigerant comprising ethane, or ethylene, or any combinations thereof. Alternatively, the alternate refrigerant may comprise a mixture of methane and ethylene or ethane. Further, the second external refrigeration cycle may also comprise one or more stages of recycle compressors (e.g., a first recycle compressor  701  and a second recycle compressor  702 ) to pressurize the alternate refrigerant and one or more thermosiphon vessels (e.g., a warm thermosiphon vessel  705  and a cold thermosiphon vessel  707 ). The one or more recycle compressors ( 701 / 702 ) may be a multi-stage compressor system comprising a discharge cooler  703  at its final compression discharge stage. The final stage discharge cooler  703  may cool the alternate refrigerant resulting in a pressurized and cooled refrigerant stream  714 . 
     The pressurized and cooled refrigerant stream  714  from the final stage discharge cooler  703  may be at a pressure between about 1650 kPa·G and about 1,950 kPa·G. In embodiments, the discharge cooler  703  may be an air cooler or a water cooler. Stream  714  may enter the integrated main heat exchanger  106  and travel down through pass E 1  to be cooled and totally condensed by the cold passes B 1 , B 2 , B 3 , B 5 , B 6 , and D 2  to a temperature between about −30° C. and about −40° C. As such, stream  714  may exit the integrated heat exchanger  106  as a cooled and totally condensed liquid stream  715 . Steam  715  may be reduced to a pressure between about 450 kPa·G and about 700 kPa·G and further reduced its temperature to between about −50° C. and about −70° C. via a level control valve  704 , resulting in a pressure-reduced, temperature decreased vapor/liquid mixed stream  716 . Stream  716  may enter the warm thermosiphon vessel  705  which, similar to thermosiphon vessel  604 , may be a vertical vessel configured to maintain a steady internal liquid level. The steady internal liquid level may allow for the formation of a thermosiphon that may be capable of circulating a warm liquid refrigerant stream  718  from the bottom of the warm thermosiphon vessel  705 , through pass E 2  of the integrated main heat exchanger  106 , and then back to an upper inlet of the warm thermosiphon vessel  705  as a two-phase refrigerant stream  719 . Stream  719  may comprise between about 30% and about 50% vapor in order to maintain a steady operation of the thermosiphon circulation. In embodiments, the warm liquid refrigerant stream  718 , which travels upward through pass E 2 , may vaporize to provide refrigeration to the warm passes such as A 1  and A 3 . A flashed vapor stream  720 , resulting from the warm thermosiphon vessel  705 , may flow to and mix with any recycle compressor discharge stream from any compression discharge stage previous to the final compression discharge stage. In embodiments, the flashed vapor stream  720  may flow to and mix with a first stage recycle compression discharge stream  711  from the first recycled compressor  701  to result in a feed stream  712  that may flow to the second recycled compressor  702 , such that stream  712  comprising the alternate refrigerant may be compressed to stream  713 , and then cooled by the final stage discharge cooler  703 , resulting in stream  714 . In some embodiments, the feed stream  712  may first travel through a suction scrubber before entering the second recycle compressor  702 . 
     In further embodiments, an additional warm liquid refrigerant stream  721  may be drawn from stream  718  at the bottom of warm thermosiphon vessel  705 . Stream  721  may be reduced to a pressure between about 5 kPa·G and about 50 kPa·G and further reduced its temperature to between about −95° C. to about −115° C. via a level control valve  706 , resulting in a pressure-reduced, temperature-decreased liquid stream  722 . Stream  722  may enter the cold thermosiphon vessel  707  which, also similar to thermosiphon  604 , may be a vertical vessel configured to maintain a steady internal liquid level. The steady internal liquid level may allow for the formation of a thermosiphon that may be capable of circulating a cold liquid refrigerant stream  723  from the bottom of the cold thermosiphon vessel  707 , through pass E 3  of the integrated main heat exchanger  106 , and then back to an upper inlet of thermosiphon  707  as a two-phase refrigerant stream  724 . Stream  724  may comprise between about 30% and about 50% vapor in order to maintain a steady operation of the thermosiphon circulation. In embodiments, the cold liquid refrigerant stream  723 , which travels upward through pass E 3 , may vaporize to provide refrigeration to the warm passes such as A 1  and A 3 . Finally, a flashed vapor stream  710 , resulting from the thermosiphon vessel  707 , may flow to the first recycle compressor  701 , such that stream  710  comprising the alternate refrigerant may be compressed, resulting in the first stage recycle compression discharge stream  711 . In some embodiments, the flashed vapor stream  710  may first travel through a suction scrubber before entering the first recycle compressor  701 . 
     Further differences between the embodiments shown in  FIGS.  10 - 11   , and the embodiments shown in  FIGS.  2 - 9    include the removal of pass B 4  and the altered path flow of stream  232 . As illustrated in  FIGS.  10  and  11   , stream  232  may enter at the bottom of integrated main heat exchanger  106  and travel upward through pass B 3  such that the stream  232  may be warmed and exit the integrated main heat exchanger  106  as the net gas product  212 . Further, stream  220 , which in previous embodiments was a resulting stream from the expander system, may now be a stream split from stream  232 . In embodiments, stream  220  may be the result of a stream  264  split from stream  232  that may be reduced to a pressure between about 195 kPa·G and about 450 kPa·G and cooled to a temperature between about −95° C. and about −125° C. via a flow control valve  136 . As with previous embodiments, stream  220  may enter the integrated main heat exchanger  106  where it mixes with outlet stream  218  of flow control valve  124 . The mixed stream of stream  220  and outlet stream  218  may travel upward through pass B 1 , where heat exchanging occurs between the cold stream pass B 1  and warm stream passes A 1 , A 2 , A 3 , and A 4 , as well as C 1 , C 3 , D 1 , and E 1 . Before exiting through pass B 1 , the mixed stream is completely vaporized and becomes a superheated vapor stream. The superheated vapor stream is referred to as combined feed  202  after exiting pass B 1 . The pressure of combined feed  202  is maintained at a constant value by the feed of the dehydrogenation unit  102  (not shown). The combined feed  202  is the reactor feedstock for dehydrogenation unit  102  (not shown). 
       FIG.  12    shows the “no recycle gas” option of the processing unit  100  in  FIG.  10   . In  FIG.  10   , the fresh feed  200  and the recycle gas stream  220  may be mixed and vaporized in the heat exchanger  106  of the processing unit  100 , thereby providing the combined feed  202 . However,  FIG.  12    shows an alternative embodiment that processes and/or vaporizes fresh feed  200 , without combining the recycle gas stream  220 , thereby providing an alternative combined feed  202 . It illustrates configuration of the integrated main heat exchanger  106 , the external refrigeration system, the first stage cold gas-liquid separator  116 , the second stage cold gas-liquid separator  118 , the liquid product drum  120 , and the liquid product pump  122 , as well as a plurality of fresh feed control valves  350 , a plurality of fresh feed thermosiphon vessels  352 , and one or more vapor fresh feed compressors  354 . Similarly to the aforementioned embodiments, the integrated main heat exchanger  106  may be split into warm section  106   a  and cold section  106   b  and further composited of one or more brazed aluminum heat exchanger (BAHX) cores as shown in  FIGS.  4 - 9   . The differences between the embodiment shown in  FIG.  12    and the embodiment shown in  FIG.  10    may include the removal of the recycle gas stream  220 / 264  and their corresponding control valve  136 . By this removal of the recycle gas stream  220 , fresh feed  200  may be processed and/or vaporized differently within processing unit  100 . Therefore, further differences between the embodiments may include the removal of control valves  124 ,  300 , and  302 , their corresponding side streams and outlet streams  216 ,  218 ,  400 ,  402 ,  404 , and  406 , and pass A 1 , as well as the addition of the plurality of fresh feed control valves  350 , the plurality of fresh feed thermosiphon vessels  352 , and the one or more vapor fresh feed compressors  354 . 
     As illustrated in  FIG.  12   , fresh feed  200  may be divided into a plurality of split streams  410 , each at any suitable pressure and temperature. In embodiments, each of the plurality of split streams  410  may be reduced to a pressure between about 50 kPa·G and about 200 kPa·G and further cooled to a temperature between about −35° C. and about −15° C., or alternatively between about −15° C. and about 5° C., via the plurality of fresh feed control valves  350 , resulting in a plurality of pressure-reduced, temperature-decreased split streams  411 . Each of the plurality of streams  411  may enter the plurality of fresh feed thermosiphon vessels  352 , respectively. Each of the plurality of fresh feed thermosiphon vessels  352  may be vertical vessels configured to maintain a steady internal liquid level. The steady internal liquid level may allow for the formation of a thermosiphon that may be capable of circulating a cold fresh feed liquid stream  412  from the bottom of each of the plurality of fresh feed thermosiphon vessel  352 , through a pass B 7  at about the middle of the warm section  106   a  of the main heat exchanger  106 , then back into an upper inlet of each of the plurality of fresh feed thermosiphon vessels  352  as a two-phase stream  413 , comprising a vapor phase and a liquid phase. For instance, each of the plurality of two-phase streams  413  may comprise between about 30% and about 50% vapor in order to maintain steady operation of the thermosiphon circulation. In embodiments, the liquid phase of each of the plurality of two-phase streams  413  may be combined to each of the plurality of cold fresh feed liquid streams  412  which travel upward through respective passes B 7  and vaporize to provide cooling to the warm passes such as A 2 , C 1 , and C 3 . In addition, each of the plurality of fresh feed thermosiphon vessels  352  may provide a flashed cold fresh feed vapor stream  414 , which may include the vapor phase of each of the plurality of two-phase streams  413 . Each of the plurality of flashed cold fresh feed vapor streams  414  may enter the integrated main heat exchanger  106  at about the middle of the warm section  106   a  and travel upward through respective passes B 8 , thus providing additional cooling to the warm passes A 2 , C 1 , and C 3 . Furthermore, as each of the plurality of flashed cold fresh feed vapor streams  414  travel through their respective passes B 8 , the streams  414  may be warmed to temperatures close to that of the reactor effluent  210 , thus becoming a plurality of superheated vapor streams  415  upon exit at the upper end of the warm section  106   a  of main heat exchanger  106 . In embodiments, one of the plurality of superheated vapor streams  415  may include a final-stage superheated vapor stream  422 . Each of the plurality superheated vapor streams  415 , excluding the final-stage superheated vapor stream  422 , may be compressed to a pressure between about 200 kPa·G and about 450 kPa·G via the one or more fresh feed vapor compressors  354 , resulting in one or more compressed superheated vapor streams  416 . Finally, the one or more compressed superheated vapor streams  416  may be comingled, along with the final-stage superheated vapor stream  422 , resulting in the alternative combined feed  202 . The pressure of the alternative combined feed stream  202  may be maintained at a constant value by the feed of the dehydrogenation unit  102  (not shown). The alternative combined feed  202  may once again be a reactor feedstock for dehydrogenation unit  102  (not shown). For solely illustrative purposes,  FIG.  12    shows two split streams  410 , two fresh feed control valves  350 , two fresh feed thermosiphon vessels  352 , two passes B 7 , two passes B 8 , one superheated vapor stream  415 , one final-stage superheated vapor stream  422 , and one vapor fresh feed compressor  354 . However, the processing unit  100  may comprise any suitable number of split streams  410 , fresh feed control valves  350 , fresh feed thermosiphon vessels  352 , passes B 7  and B 8 , and vapor fresh feed compressors  354 . 
     As further illustrated in  FIG.  12   , reactor effluent  210 , an olefin-hydrogen effluent stream from the reactor effluent compressor unit  104  (not shown), enters pass A 2  at the upper warm end of the warm section  106   a  of the integrated main heat exchanger  106 , where the stream is cooled to a low temperature as it flows through and exits pass A 2  at the lower end of the warm section  106   a  of the integrated main heat exchanger  106 . The cooling of the reactor effluent  210  as it travels through pass A 2  is caused by cold stream passes B 3 , B 5 , B 6 , B 7 , B 8  and C 2 . Outlet stream  222  from pass A 2  enters the first stage cold gas-liquid separator  116  with a low temperature, at which time a majority, &gt;95%, of the olefin and heavy paraffinic components in outlet stream  222  are condensed to liquid, which is separated out as liquid stream  224 . Further, almost all, &gt;99% of the hydrogen from outlet stream  222  remains vapor, and the first stage cold gas-liquid separator  116  separates out the vapor as vapor stream  226 . 
     The vapor stream  226  then flows back to the upper end of the cold section  106   b  of the integrated main heat exchanger  106  through pass A 3 , where it is cooled to a lower temperature by the time it exits pass A 3  at the lower end of the cold section  106   b  of the integrated main heat exchanger  106 . The outlet stream  228  from pass A 3  enters the second stage cold gas-liquid separator  118 , where almost all, &gt;85%, of the olefin and heavy paraffinic components in an outlet stream  228  are condensed to a liquid stream  245  and almost all, &gt;99.95% of the hydrogen stays in a cold vapor stream  232 . The cold vapor stream  232  exits second stage cold gas-liquid separator  118  and returns to the lower end of the cold section  106   b  of the integrated main heat exchanger  106  at pass B 3 . The cold vapor stream  232  travels up pass B 3 , where it exchanges heat with warm stream passes A 3 , A 2 , C 1  and C 3 . As such cold vapor stream  232  may be warmed as it travels through pass B 3 . Upon exiting pass B 3  at the upper end of the warm section  106   a  of the integrated main heat exchanger  106 , the temperature of cold vapor stream  232  may be a temperature close to the inlet temperature of pass A 2 . The outlet stream  262  from pass B 3  is typically regulated by a control valve  130  to maintain the pressure of the second stage cold gas-liquid separator  118 . The outlet stream of control valve  130  is the net gas product  212 , which may be sent to a downstream production facility. 
     Returning to the first stage cold gas-liquid separator  116 , the pressure of the olefin-rich liquid stream  224  is reduced by level control valve  138  before it enters the liquid product drum  120  as cold stream  246 . 
     Returning to the second stage cold gas-liquid separator  118 , the olefin-rich liquid stream  245  may be split into two streams  241  and  247 , with stream  247  having about 15% to 20% of the total flow of the stream  245 . The pressure of the olefin-rich liquid stream  241  is reduced by level control valve  141 , resulting in a pressure-reduced stream  243  which may enter pass B 2  from the lower end of the cold section  106   b  of the main heat exchanger  106 . In embodiments, the pressure-reduced stream  243  may be a cold stream that exchanges heat with the warm passes A 3  and C 1 , becoming a partially vaporized stream  248 . This partially vaporized stream  248  exits pass B 2  at the upper end of the cold section  106   b  of the integrated main heat exchanger  106  and flows to the liquid product drum  120 , combining with the cold stream  246 . As for stream  247 , flow control valve  119  may reduce the pressure of stream  247 , resulting in a reduced-pressure stream  230  which may enter the top of rectifier  140  as the rectifier&#39;s reflux liquid. 
     A combined liquid stream  249  from stream  246  and  248  may enter the liquid product drum  120 , where light components, mainly hydrogen, methane, ethane, and maybe some C3+ components, flash out from the liquid and travel upward through the rectifier  140  located on the top of the liquid product drum  120  or installed separately from the liquid product drum  120 . The upward traveling hydrogen-rich gas in the rectifier  140 , which may be a packed column, makes contact with the downward traveling colder reflux liquid stream  230  from the second stage cold gas-liquid separator  118 . Heat and mass transferring occurs in the rectifier  140 , and therefore the hydrogen-rich gas in the rectifier  140  is further purified to meet the minimum hydrogen content specification of the flash drum vapor  206 , before exiting the top of the rectifier  140  as a vapor stream  250 . 
     The pressure of the liquid product drum  120  is maintained by a pressure control valve  142  on vapor stream  250  to a constant pressure to maximize the recovery of olefin and heavy hydrocarbon components in the liquid product  254  and to meet the specification of the maximum allowable hydrogen content in the liquid product  254 . 
     After the pressure control valve  142 , a cold stream  252  contains certain olefin components in addition to the main light components hydrogen, methane, and ethane. The cold stream  252  enters cold stream pass B 6  at the lower end of the cold section  106   b  of the integrated main heat exchanger  106 . As cold stream  252  travels up pass B 6 , it exchanges heat with the warm stream passes A 3 , C 1 , A 2 , and C 3 , and cold stream  252  is warmed to a temperature close to the inlet temperature of reactor effluent  210  or fresh feed  200  as it exits pass B 6  from the upper end of the warm section  106   a  of the main heat exchanger  106 . The flash drum vapor  206  from pass B 6  then flows back to the inlet of the reactor effluent compressor unit  104  (not shown). 
     The separated cold liquid stream  254  from the liquid product drum  120  is pumped by the liquid product pump  122  to a pressure that meets the required pressure of the liquid product  214 . The liquid level of the liquid product drum  120  is maintained by a level control valve  144 . The cold liquid product stream  256  then enters pass B 5  at the lower end of warm section  160   a  of the integrated main heat exchanger  106 . As the liquid product stream  256  travels upward in pass B 5 , it exchanges heat with the warm passes A 2 , C 1  and C 3  and is warmed to a temperature defined by the liquid product  214  specification as it exits pass B 5  at the upper end of the warm section  106   a  of the integrated main heat exchanger  106 . The liquid product  214  is then sent to a production facility. In embodiments, liquid product drum  120  is elevated to a height to get enough NPSHa (net positive suction head available) for the liquid product pump  122  to avoid cavitation damage to the liquid product pump  122 . 
     The external refrigeration system illustrated in  FIG.  12    may be the refrigeration system as described in  FIG.  10    of this disclosure. In embodiments, the mixed refrigerant compressor  501  of the external refrigeration system and the aforementioned one or more vapor fresh feed compressors  354  may be independently installed within the processing unit  100 . Alternatively, the mixed refrigerant compressor  501  and the one or more vapor fresh feed compressors  354  may be integrated into one integrally-geared compressor with the processing unit  100 . 
     Further, a coldbox  146  is designed to contain all low-temperature equipment including the integrated main heat exchanger  106 , the first stage cold gas-liquid separator  116 , the second stage cold gas-liquid separator  118 , the liquid product drum  120 , the plurality of fresh feed thermosiphon vessels  352 , as well as the associated piping. Control valves  350 ,  138 ,  141 ,  119 ,  142 , and  124  can either be enclosed within or installed outside of the coldbox  146 . The coldbox  146  is typically filled with insulation material and purged with nitrogen to provide cold insulation for the low-temperature equipment and parts. 
     Generally, the above describes an improved process and system for separation of hydrogen from an effluent by dehydrogenation of propane, isobutane, or a mixture of both. More specifically, the use of an integrated heat exchanger allows for a more balanced process reducing off-design, i.e. not allowed for or expected, flow distributions. This provides improved thermodynamic efficiency and stability. Further, an integrated heat exchanger with a compact design takes up less space, which can be a significant benefit in an industrial setting. 
     Further, the expander configuration with two sets of expanders/compressors improves the process. In the description above, the composition and mass flow of the stream to each set of expander/compressor remains substantially unchanged. This improves the energy benefit by recovering the expander power back to the system. Also, the hydrogen-rich gas in the rectifier is further purified to meet the minimum hydrogen content specification of the flash drum vapor, which in turn improves the C 3  liquid product recovery. 
     Referring to  FIG.  12   , in embodiments liquid product  214  may mainly comprise propylene and propane, as well as small amounts of lighter components such as hydrogen, methane, ethylene, and ethane. An example of the composition of liquid product  214  is shown in the following Table 1000-1: 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 1000-1 
               
               
                   
                   
               
               
                   
                 Components 
                 Mole % 
                 Notes 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Hydrogen 
                 0.0556 
                 May be as high as 
               
               
                   
                   
                   
                 0.1000% 
               
               
                   
                 Methane 
                 0.1413 
                   
               
               
                   
                 Ethylene 
                 0.0835 
                   
               
               
                   
                 Ethane 
                 1.7337 
                   
               
               
                   
                 Propylene 
                 29.5787 
                 May be as high as 35% 
               
               
                   
                 Propane 
                 67.9940 
                   
               
               
                   
                 C4+ Heavy 
                 0.4131 
                   
               
               
                   
                 HC 
                   
                   
               
               
                   
                 Total 
                 100.0000 
               
               
                   
                   
               
            
           
         
       
     
     In embodiments, the light components, such as ethane and all other lighter components, may need to be removed from liquid product  214 , which may be accomplished using a deethanizer system  1000  and a propylene/propane splitter system  800 . In embodiments, polymer-grade propylene typically comprises a minimum purity of 99.5%-99.8% (mole) propylene and may contain impurities such as methane ethylene, ethane, propane, etc. 
       FIG.  13    illustrates an additional embodiment of the separation system of processing unit  100  shown in  FIG.  12   , wherein  FIG.  13    comprises the deethanizer system  1000  and the propylene/propane splitter system  800 . 
     In embodiments, liquid product  214  may flow to the middle stage of a stripper column  1601 . In embodiments, liquid product  214  may have a pressure in a range of between 1,400 kPa·G to 1,600 kPa·G and a temperature in a range of between 30° C. to 45° C. Further, in embodiments, liquid product  214  may comprise mainly propylene and propane, as well as certain amounts of light components such as hydrogen, methane, ethylene, and ethane. An example of a composition of liquid product  214  is shown in Table 1000-1. In embodiments, stripper column  1601  may comprise a tray-type column or a packing-type column. In embodiments, a reflux liquid stream  1633  may be fed into the top stage of stripper column  1601 , and reboiling vapor streams  1643  and  1645  may be fed into the bottom stage of stripper column  1601 . In embodiments, heat and mass transfers may occur while liquid product  214 , reflux liquid stream  1633 , and reboiling vapor streams  1643  and  1645  travel into and contact the trays and/or packing inside stripper column  1601 , which may form a bottom C3+ hydrocarbon stream  1641  with less than 100 ppm ethane and lighter components. In embodiments, a top vapor stream  1630  may still contain amounts of C3+ hydrocarbons, and therefore, the top vapor stream  1630  may require additional purification and recovery by a rectifier column  1603 . In embodiments, the ethane and lighter components in vapor stream  1630  may be significantly enriched with ethane and lighter components greater than 55% (mole). 
     In embodiments, a fresh feed stream  930 , which may be split from the main fresh feed stream  200 , may flow to a fresh feed/vapor heat exchanger  902 , which may reduce the temperature of the fresh feed stream  930  to about 10° C. to 15° C. In embodiments, this reduction in temperature of the fresh feed stream  930  in heat exchanger  902  may be assisted by a cold fresh feed vapor stream  933 . In embodiments, a liquid stream  931  may emerge from heat exchanger  902  and proceed to a control valve  901 . In embodiments, the pressure of liquid stream  931  may be reduced by control valve  901 , which may result in reducing the pressure of liquid stream  931  to a range of between 250 kP·G to 400 kPa·G (depending on the pressure of the combined feed  202  as required by dehydrogenation unit  102 ) to become a liquid/vapor mixture stream  932 , which may have a temperature ranging from about −10° C. to about 1.5° C. In embodiments, stream  932  may be routed to a stripper column condenser  1602 , which may cool the vapor stream  1630 . In embodiments, saturated vapor stream  933  may emerge from the stripper column condenser  1602 , and saturated vapor stream  933  may proceed to heat exchanger  902  where saturated vapor stream  933  may exchange heat with warm fresh feed stream  930 . In embodiments, a vapor stream  934  may emerge from heat exchanger  902 , and vapor stream  934  may proceed to combine with combined feed  202 . 
     In embodiments, a vapor stream  1631  may emerge from stripper column condenser  1602  with a temperature of about 0° C. to 5° C., and vapor stream  1631  may partially (around 90%) condense to liquid. In embodiments, stream  1631  may proceed to the bottom of rectifier column  1603 , wherein any vapor remaining in stream  1631  may be flashed out. In embodiments, once within the rectifier column  1603 , the vapor materials from stream  1631  may travel upwards in the rectifier column  1603  providing stripping to the materials from a liquid stream  1637  fed from the top of the rectifier column  1603 , and further, the liquid from stream  1631  may be separated out and combined with the materials from liquid stream  1637  to form a cold reflux stream  1632 . In embodiments, cold reflux stream  1632  may proceed to a stripper column reflux pump  1604 , wherein cold reflux stream  1632  emerges as stream  1633 . In embodiments, stream  1633  may proceed back to the top stage of stripper column  1601 . 
     Returning to stream  1641 , in embodiments the C3+ hydrocarbon stream  1641  emerging from the bottom of the stripper column  1601  may be split into three streams: a stream  1642 , which may flow to a stripper column main reboiler  1609 ; a stream  1644 , which may flow to a stripper column supplemental reboiler  1610 ; and a C3+ liquid product stream  1646 , which may flow to a pressure control valve  1611 , where it may become a stream  1647 , which then proceeds to the propylene/propane splitter system  800  (detail not shown) to separate the propylene product. 
     In embodiments, stream  1641  may have a temperature range of between 25° C. to 35° C. depending on the operation pressure of stripper column  1601 , which is typically in a range of between 850 kPa·G to 1150 kPa·G. In embodiments, stream  1642  may be heated by a warm gas stream  810  split from a heat pump compressor (HPC) discharge at the propylene/propane splitter system  800  (detail not shown). In embodiments, the typical temperature of stream  810  may range from between 45° C. to 55° C. In embodiments, stream  810  may be cooled by stream  1642  through the stripper column main reboiler  1609  to a temperature range of 28° C. to 32° C., and a stream  811  may flow to the propylene/propane splitter system  800 . In embodiments, stream  1642  may be vaporized in stripper column main reboiler  1609  becoming stream  1643 , which may be routed back to the bottom stage of stripper column  1601  to provide stripping to the down-coming liquid from stream  214  and stream  1633 . In embodiments, stripper column main reboiler  1609  may be designed to provide 90%-95% of the required reboiling duty of stripper column  1601 , while the remaining 5% to 10% of the required reboiling duty may be provided by stripper column supplemental reboiler  1610 . In embodiments, this design may provide operation flexibility and stability for the reboiling section of stripper column  1601 . In embodiments, the heating medium for stripper column supplemental reboiler  1610  may comprise a temperature greater than 40° C. material, such as the plant cooling water return stream. Alternatively, in other embodiments the heating medium may comprise liquid refrigerant stream  512 . 
     In embodiments, stripper column  1601  may be operated at a pressure ranging from between about 850 kPa·G to about 1150 kPa·G, with a temperature of the top of stripper column  1601  ranging from between −5.0° C. to 5° C. and a temperature of the bottom of stripper column  1601  ranging from between 25° C. to 35° C. In embodiments, this may produce less than about 100 ppm ethane and lighter components in the C3+ product stream  1647 . 
     In embodiments, rectifier column  1603  may operate at about the same pressure as stripper column  1601 . In embodiments, rectifier column  1603  may be a tray-type column or a packing-type column, wherein a reflux liquid stream  1637  may flow into the top stage of rectifier column  1603  and further wherein stripping vapor stream  1631  may flow into the bottom stage of rectifier column  1603 . In embodiments, heat and mass transferring may occur when the liquid and vapor in rectifier column  1603  travel through and contact the trays or packing inside rectifier column  1603 , which may form bottom stream  1632 , and overhead vapor stream  1634  composed primarily of ethane and lighter components. In embodiments, overhead vapor stream  1634  may proceed to a rectifier column reflux condenser  1605 , where stream  1634  may be cooled to about −36° C. to −32° C. and emerge as a stream  1635 . In embodiments, the cooling for stream  1634  may be a result of a refrigerant stream  1735  entering rectifier column reflux condenser  1605 . In embodiments, stream  1635  may be partially condensed by rectifier column reflux condenser  1605 , and stream  1635  may flow to a rectifier column reflux drum  1606 , where the vapor and liquid in stream  1635  may be separated. In embodiments, a liquid stream  1636  may emerge from the bottom of rectifier column reflux drum  1606  and may proceed to a rectifier column reflux pump  1608 , after which stream  1636  emerges as stream  1637 , which may be pumped back to the top stage of rectifier column  1603 . In embodiments, a cold vapor stream  1638  emerging from rectifier column reflux drum  1606  may be C3+ hydrocarbon free and therefore comprise mainly ethane and lighter components. In embodiments, stream  1638  may flow to the refrigerant/gas heat exchanger  1703 , where stream  1638  may exchanges heat with a warm refrigerant liquid stream  1732  and may be warmed to a temperature within the range of about 30° C. to 35° C., emerging from heat exchanger  1703  as a stream  1639 . In embodiments, the pressure of stream  1639  may be regulated by a pressure control valve  1607  to maintain the system pressure of stripper column  1601  and rectifier column  1603 . In embodiments, a discharge stream  1640  from pressure control valve  1607  may be routed to a fuel gas system (not shown). 
     In embodiments, rectifier column  1603  may be operated at a pressure ranging from about 850 kPa·G to about 1150 kPa·G with a temperature ranging from −36° C. to −32° C. at top of the rectifier column  1603  and a temperature ranging from −5° C. to 5° C. at the bottom of the rectifier column  1603 . In embodiments, this may result in about 100% C3+ recovery to C3+ product stream  1647 . 
     In embodiments, the cooling of rectifier column condenser  1605  may be due to a vapor-compression refrigeration system. In embodiments, a refrigeration compressor  1701  may boost a saturated refrigerant vapor stream  1730  from rectifier column reflux condenser  1605  to a high pressure. In embodiments, refrigerant vapor stream  1731  may be condensed to a saturated refrigerant liquid stream  1732  by a refrigerant condenser  1702 . In embodiments, refrigerant condenser  1702  may be water cooler or air cooler. In embodiments, stream  1732  may have a temperature ranging from about 30° C. to 50° C. In embodiments, saturated refrigerant liquid stream  1732  may be further cooled by cold vapor stream  1638  in refrigerant/gas heat exchanger  1703  to a subcooled condition and then routed to a refrigerant receiver vessel  1704  as stream  1733 . In embodiments, the pressure of a subcooled refrigerant liquid stream  1734  from refrigerant receiver vessel  1704  may be reduced through a thermal-expansion valve  1705 , resulting in stream  1735 , which may have a cold temperature of about −45° C. to −35° C. through an adiabatic flash evaporation of part of the liquid refrigerant. In embodiments, cold refrigerant stream  1735  may be routed to the rectifier column reflux condenser  1605  to provide refrigeration to rectifier column overhead stream  1634  by vaporizing the cold refrigerant liquid in stream  1735 . In embodiments, stream  1735  may totally vaporize in rectifier column reflux condenser  1605 , which may result in saturated refrigerant vapor stream  1730 , which may be routed to refrigerant compressor  701  for compression. 
     In embodiments, a suitable refrigerant for the refrigeration system may be propane or propylene. In embodiments, the propane may be charged from fresh feed (propane) stream  200 , while the propylene may be charged from propylene product stream from the propylene/propane splitter system  800  (not shown in detail). In embodiments, the refrigeration system may be optimized by adding an economizer (not shown) to lower the compressor energy consumption. Further, in embodiments, the refrigeration compressor  1701  may be a centrifugal type compressor or a screw type compressor. 
     Referring to  FIG.  14   , in embodiments the vapor-compression refrigeration system for the rectifier column condenser  1605  may alternate to a refrigeration process by flashing a part of fresh feed (propane) stream  200 . In embodiments, a fresh feed stream  1741 , which may be split from the main fresh feed stream  200 , may flow to a fresh feed/gas heat exchanger  1711 , which may reduce the temperature of the fresh feed stream  1741  to about −35° C. to −25° C. In embodiments, this reduction in temperature of the fresh feed stream  1741  in heat exchanger  1711  may be assisted by a cold fresh feed vapor stream  1744  and the cold vapor stream  1638 . In embodiments, a liquid stream  1742  may emerge from heat exchanger  1711  and proceed to a control valve  1712 . In embodiments, the pressure of liquid stream  1742  may be reduced by control valve  1712 , which may result in reducing the pressure of liquid stream  1742  to a range of between 10 kP·G to 50 kPa·G (depending on the required temperature of stream  1635 ) to become a liquid/vapor mixture stream  1743 , which may have a temperature ranging about −40° C. to about −35° C. In embodiments, stream  1743  may be routed to the rectifier column condenser  1605 , which may cool the vapor stream  1634 . In embodiments, saturated vapor stream  1744  may emerge from the rectifier column condenser  1605 , and saturated vapor stream  1744  may proceed to heat exchanger  1711  where saturated vapor stream  1744  may exchange heat with warm fresh feed stream  1741 . In embodiments, a vapor stream  1745  with a temperature ranging from 30° C. to about 45° C. may emerge from heat exchanger  1711 , and vapor stream  1745  may be boosted to a pressure same as stream  934  by a fresh feed vapor booster compressor  1713 . In embodiments, a vapor stream  1746  may emerge from the discharge of the fresh feed vapor booster compressor  1713  and proceed to combine with stream  934  and then commingle with the combined feed  202 . In embodiments, the fresh feed vapor booster compressor  1713  may comprise a centrifugal type compressor, a screw type compressor, or a reciprocating type compressor. 
     In embodiments, similar to  FIG.  13   , cold vapor stream  1638  emerging from rectifier column reflux drum  1606  may be C3+ hydrocarbon free and therefore comprise mainly ethane and lighter components. In embodiments, stream  1638  may flow to the fresh feed/gas heat exchanger  1711 , where stream  1638  may exchanges heat with warm fresh feed liquid stream  1741  and may be warmed to a temperature within the range of about 30° C. to 45° C., emerging from heat exchanger  1711  as a stream  1639 . In embodiments, the pressure of stream  1639  may be regulated by a pressure control valve  1607  to maintain the system pressure of stripper column  1601  and rectifier column  1603 . In embodiments, a discharge stream  1640  from pressure control valve  1607  may be routed to a fuel gas system (not shown). 
     In embodiments, the fresh feed/vapor heat exchanger  902  and the refrigerant/gas heat exchanger  1703  may be shell/tube type heat exchangers or brazed aluminum plate-fin type heat exchangers (BAHX), and the latter may significantly increase the system thermal efficiency since it can be designed to have an approaching temperature as low as 1.0° C. In embodiments, the fresh feed/gas heat exchanger  1711  may be brazed aluminum plate-fin type heat exchangers (BAHX), and may significantly increase the system thermal efficiency since it can be designed to have an approaching temperature as low as 1.0° C. In embodiments, the stripper column reflux condenser  1602 , the stripper column main reboiler  1609 , the stripper column supplemental reboiler  1610 , and rectifier column reflux condenser  1605  may be shell/tube type heat exchangers, or brazed aluminum plate-fin in kettle (PFK) type heat exchangers, and the latter may significantly increase the system thermal efficiency since it can be designed to have an approaching temperature as low as 1.0° C. to 2.0° C. 
     In embodiments, the disclosed processes and schemes of the deethanizer system  1000  may operate at lower pressures and temperatures at the columns  1601  and  1603 , which may reduce the overall system energy consumption, equipment sizes, and equipment cost compared to the traditional deethanizer system that typically operates at a higher pressure ranging about from 2500 kPa·G to 3000 kPa·G. 
     In embodiments, the disclosed processes and schemes of the deethanizer system  1000  may operate at a lower pressure and a lower temperature at the bottom of the stripper column  1601 , which may enable using lower temperature heating sources for reboilers  1609  and  1610 , therefore eliminating low-pressure steam as heating medium, which the tradition deethanizer systems typically uses. In embodiments, lower temperature heating sources such as the HPC discharge stream, the MR liquid stream  512 , and/or a plant cooling water return stream may be used as heating mediums for the reboilers  1609  and  1610 . 
     In embodiments, the elimination of low-pressure steam as a heating source in the disclosed process and schemes of the deethanizer system  1000  may reduce the steam consumption by 0.55 metric tons per metric ton of propylene production. This is therefore a significant reduction of plant CO2 emissions given the steam is typically produced by burning fossil fuels. 
       FIG.  15    illustrates an alternative embodiment in which the refrigeration process by flashing a part of the fresh feed (propane) stream  200  to cool the rectifier column reflux condenser  1605  may be replaced by refrigeration obtained from the cold section  106   b  of the integrated main heat exchanger  106 . 
     Referring to  FIG.  15   , in embodiments the overhead vapor stream  1634  may proceed to a pass D 1  in the cold section  106   b  of the integrated main heat exchanger  106 , where overhead vapor stream  1634  may be cooled to a temperature of about −100° C. to about −32° C. and may emerge as stream  1635 . In embodiments, stream  1635  may be partially condensed. Further, in embodiments, stream  1635  may flow to rectifier column reflux drum  1606 , wherein the vapor and liquid in stream  1635  may be separated. In embodiments, liquid stream  1636  may emerge from the bottom of the rectifier column reflux drum  1606  and may proceed to rectifier column reflux pump  1608 . In embodiments, stream  1637  may emerge from the rectifier column reflux pump  1608 , and stream  1637  may be pumped to the top stage of the rectifier column  1603 . In embodiments, cold vapor stream  1638  may emerge from rectifier column reflux drum  1606 . In embodiments, cold vapor stream  1638  may be C3+ hydrocarbon free and may substantially comprise ethane and lighter components. In embodiments, stream  1638  may be regulated by pressure control valve  1607  to maintain the system pressure of stripper column  1601  and rectifier column  1603 . In embodiments, discharge stream  1640  may emerge from pressure control valve  1607 , and discharge stream  1640  may be routed to a fuel gas system after exchanging heat with other warm streams (not shown).