US20240182801A1

US20240182801A1 - Steam integration in ethanol to jet fuel process

Info

Publication number: US20240182801A1
Application number: US18/443,513
Authority: US
Inventors: Saikrishna Laxmirajam Gosangari; Ashish Mathur; Jeannie Mee Blommel
Original assignee: UOP LLC
Current assignee: Honeywell UOP LLC
Priority date: 2022-08-30
Filing date: 2024-02-16
Publication date: 2024-06-06

Abstract

An ethanol dehydration process is disclosed. The process comprises adding an amount of steam to a feed to the dehydration reactor to provide a charge stream. The steam stream is mixed with the feed to the dehydration reactor such that the steam to ethanol ratio is between about 0.5 to about 5.0 wt/wt. The charge stream is passed to a dehydration reactor to produce a dehydrated stream. Steam can be imported from outside the dehydration process such as from an oligomerization or dimerization reaction. Steam can be produced from the dehydrated stream.

Description

This application claims priority to U.S. application Ser. No. 18/457,222, filed Aug. 28, 2023, which claimed priority to Indian provisional patent application 202211049526, filed Aug. 30, 2022.

FIELD

The invention relates to conversion of olefins to distillate. More particularly, the invention relates to generation of steam during an oligomerization of olefins to distillate fuels through an ethanol to jet fuel process.

BACKGROUND

Oil and gas refiners worldwide are exploring methodologies and routes to reduce the carbon footprint and are moving towards sustainable processes. An ethanol to jet fuel process is one of the routes that holds promise to minimize or eliminate the customer's carbon footprint. The end product of this process is jet and diesel fuel produced out of bio ethanol. The jet fuel is a sustainable aviation fuel and is intended to replace jet fuel produced out of conventional sources such as crude oil.
There are frequently three main steps in the process to convert ethanol to jet fuel. The first is to dehydrate ethanol to produce ethylene. Next the ethylene is converted to long chain olefins and then the long chain olefins are hydrogenated to generate paraffins. The ethanol dehydration step may need steam injection to get desired catalyst life as well as to maintain operation below maximum endotherm in an adiabatic system. The dehydration of ethanol may require a significant amount of steam. Generating steam from the product water may be energy intensive for the overall process. There is a need for efficient ways to address the steam requirements of the ethanol dehydration step.

SUMMARY

The present disclosure is mostly concerning the use of steam that can be generated during the oligomerization process to convert ethylene or other light olefins to longer chain olefins.
A process is provided for operation of a dehydration reactor comprising adding an amount of steam to a feed to said dehydration reactor wherein said steam is taken from an oligomerization section of a hydrocarbon conversion plant.
In an embodiment, a process is provided for ethanol dehydration comprising adding an amount of steam to an ethanol feed stream wherein a steam to ethanol ratio is between 0.3 to 5.0 wt/wt and reacting said ethanol feed stream at reaction conditions in the presence of a catalyst to produce an ethylene effluent stream.
In another embodiment, is provided a process for operation of a dehydration reactor comprising adding a steam stream to a feed to said dehydration reactor to produce a charge stream; dehydrating said charge stream to produce a dehydrated stream; cooling said dehydrated stream to separate a water stream; and producing said steam stream from said separated water stream. A further embodiment provides a process for operation of a dehydration reactor, comprising adding a steam stream to a feed to said dehydration reactor to produce a charge stream; dehydrating said charge stream to produce a dehydrated stream; cooling the dehydrated stream to separate a water stream; and heating the separated water stream with an olefin charge stream of an oligomerization section to generate said steam stream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic process flow diagram including the ethanol dehydration reactor

FIG. 2 shows a schematic including a series of steam generators that provide steam both to an oligomerization reactor and the ethanol dehydration reactor of FIG. 1 .

DEFINITIONS

The term “communication” means that fluid flow is operatively permitted between enumerated components, which may be characterized as “fluid communication”.
The term “downstream communication” means that at least a portion of material flowing to the subject in downstream communication may operatively flow from the object with which it communicates.
The term “upstream communication” means that at least a portion of the material flowing from the subject in upstream communication may operatively flow to the object with which it communicates.
The term “direct communication” means that flow from the upstream component enters the downstream component without passing through a fractionation or conversion unit to undergo a compositional change due to physical fractionation or chemical conversion.
The term “indirect communication” means that flow from the upstream component enters the downstream component after passing through a fractionation or conversion unit to undergo a compositional change due to physical fractionation or chemical conversion.
The term “bypass” means that the object is out of downstream communication with a bypassing subject at least to the extent of bypassing.
The term “column” means a distillation column or columns for separating one or more components of different volatilities. Unless otherwise indicated, each column includes a condenser on an overhead of the column to condense and reflux a portion of an overhead stream back to the top of the column and a reboiler at a bottom of the column to vaporize and send a portion of a bottoms stream back to the bottom of the column. Feeds to the columns may be preheated. The top pressure is the pressure of the overhead vapor at the vapor outlet of the column. The bottom temperature is the liquid bottom outlet temperature. Overhead lines and bottoms lines refer to the net lines from the column downstream of any reflux or reboil to the column. Stripper columns may omit a reboiler at a bottom of the column and instead provide heating requirements and separation impetus from a fluidized inert media such as steam. Stripping columns typically feed a top tray and take main product from the bottom.
As used herein, the term “a component-rich stream” means that the rich stream coming out of a vessel has a greater concentration of the component than the feed to the vessel.
As used herein, the term “a component-lean stream” means that the lean stream coming out of a vessel has a smaller concentration of the component than the feed to the vessel.
As used herein, the term “separator” means a vessel which has an inlet and at least an overhead vapor outlet and a bottoms liquid outlet and may also have an aqueous stream outlet from a boot. A flash drum is a type of separator which may be in downstream communication with a separator that may be operated at higher pressure.
As used herein, the term “predominant” or “predominate” means greater than 50%, suitably greater than 75% and preferably greater than 90%.
As used herein, the term “True Boiling Point” (TBP) means a test method for determining the boiling point of a material which corresponds to ASTM D-2892 for the production of a liquefied gas, distillate fractions, and residuum of standardized quality on which analytical data can be obtained, and the determination of yields of the above fractions by both mass and volume from which a graph of temperature versus mass % distilled is produced using fifteen theoretical plates in a column with a 5:1 reflux ratio.
As used herein, the term “T5”, “T90” or “T95” means the temperature at which 5 mass percent, 90 mass percent or 95 mass percent, as the case may be, respectively, of the sample boils using ASTM D-86 or TBP.
As used herein, the term “initial boiling point” (IBP) means the temperature at which the sample begins to boil using ASTM D-7169, ASTM D-86 or TBP, as the case may be.
As used herein, the term “end point” (EP) means the temperature at which the sample has all boiled off using ASTM D-7169, ASTM D-86 or TBP, as the case may be.
As used herein, the term “diesel” means hydrocarbons boiling in the range of an IBP between about 125° C. (257° F.) and about 175° C. (347° F.) or a T5 between about 150° C. (302° F.) and about 200° C. (392° F.) and the “diesel cut point” comprising a T95 between about 343° C. (650° F.) and about 399° C. (750° F.) using the TBP distillation method or a T90 between 280° C. (536° F.) and about 340° C. (644° F.) using ASTM D-86. The term “green diesel” means diesel comprising hydrocarbons not sourced from fossil fuels.
As used herein, the term “jet fuel” means hydrocarbons boiling in the range of a T10 between about 190° C. (374° F.) and about 215° C. (419° F.) and an end point of between about 290° C. (554° F.) and about 310° C. (590° F.). The term “green jet fuel” means jet fuel comprising hydrocarbons not sourced from fossil fuels.
As used herein, the term “C_x” are to be understood to refer to molecules having the number of carbon atoms represented by the subscript “x”. Similarly, the term “C_x−” refers to molecules that contain less than or equal to x and preferably x and less carbon atoms. The term “C_x+” refers to molecules with more than or equal to x and preferably x and more carbon atoms.
As used herein, the term “carbon number” refers to the number of carbon atoms per hydrocarbon molecule and typically a paraffin molecule.

DETAILED DESCRIPTION

The process disclosed involves dimerizing and oligomerizing an olefin stream comprising ethylene followed by further oligomerizing ethylene oligomers. The process utilizes a zeolitic catalyst for ethylene oligomerization in a first stage and a metal catalyst for olefins oligomerization in a second stage.
In FIG. 1 , in accordance with an exemplary embodiment, a process 10 is shown for processing an oxygenate feedstock. The oxygenate feedstock may comprise alcohol and preferably comprises ethanol. The feedstock may comprise a predominance of ethanol and may be aqueous. Preferably, the oxygenate feedstock is a biorenewable feedstock.
A feed line 12 transports an oxygenate stream of oxygenate feedstock to a feed pretreatment section 14. The feed pretreatment section 14 comprises a vessel 16 comprising a bed of cationic exchange resin adsorbent for removing metal contaminants, such as sodium, zinc, phosphates, copper, and calcium, and any basic compounds from the oxygenate stream in the feed line 12. The feed pretreatment section 14 may comprise an additional vessel 18 with a bed of the same adsorbent for further removing metals from the oxygenate stream. The vessels 16, 18 may be in series or in a lead-lag type of arrangement to allow for regeneration or replacement of the spent adsorbent. Line 17 transports partially pretreated oxygenate stream from an outlet of vessel 16 to the inlet of vessel 18. A pretreated oxygenate stream exits the feed pretreatment section 14 in line 20 from an outlet of the additional vessel 18 and is fed to a purification column 22. The feed pretreatment section 14 may be operated at a temperature of about 32° C. to about 104° C. or of about 32° C. to about 80° C., and a pressure of about atmospheric pressure to about 670 kPa(g).
In purification column 22, the pretreated oxygenate stream is fractionated to separate ethanol from heavier oxygenates also known as fusel oil such as cyclohexanol, cyclopentanol, and heavier alcohols and acids. The purification column 22 is operated to minimize ethanol to no more than 1% of feed in bottom stream in line 26. A heavy oxygenate stream in a bottoms line 26 is taken from a bottom of the purification column 22 to heavy oxygenate treatment. The purification column 22 may be reboiled by heat exchange with a suitable hot stream such as steam to provide the necessary heat for the distillation. Purification column 22 provides an overhead gaseous stream of purified ethanol in an overhead line 24 which may be cooled in an air cooler 25 and fed to a feed surge drum 26 along with a recycle ethanol stream in line 27. Purification column 22 may be operated with a bottoms temperature between about 82° C. and about 121° C. and an overhead pressure of about 35 kPa (g) to about 140 kPa (g).
The ethanol feeds are derived out of either a wet mill or dry mill process. These ethanol feeds can contain a variety of contaminants such as higher alcohols, metals, acetaldehyde, ethyl acetate, etc. In addition, the dry mill feed can also contain fusel oils (heavier alcohols and acids). The ethanol feed may be treated to remove metal contaminants through the use of resin treaters. The heavy hydrocarbon from the fresh feed can be knocked out in a feed purification column.
A fresh ethanol feed may be combined with unconverted ethanol and is split into two equal streams into parallel combined feed exchangers. A split reactor configuration is considered because a desired steam to ethanol ratio is maintained at the reactor inlet to maintain the reactor endothermicity as well as ensuring catalyst stability. In order to minimize the combined feed rate to reactor, it becomes essential that the steam intake is reduced. The ethanol dehydration reaction results in generation of water as a byproduct. The ethanol dehydration process needs steam injection in the process to obtain desired catalyst life as well as to maintain operation below maximum endotherm in an adiabatic system. It has been identified that an optimum steam to ethanol ratio should lie between about 0.5 to about 5.0 or preferably between about 1.0 to 2.0 wt/wt. In addition to this, some columns in the unit (including the feed purification column and the waste water stripper) can also be reboiled using steam. Since ethanol dehydration reactors operate in a vapor phase, generating steam from the product water may be energy intensive (product water condensation and vaporization). To overcome this issue, it has been concluded that it is preferred to import steam at about ˜100 psig from outside of the dehydration battery limit. The oligomerization and hydrogenation reactions, being exothermic may be a good source of generating steam and there is a good integration opportunity existing to satisfy the demand for steam. Steam may be taken from either or both of the oligomerization and hydrogenation reactions section.
The oligomerization step of an ethanol to jet fuel process uses a high temperature reactor in an upfront position. Interbed temperature control may be achieved using steam generation. The steam level can be set to at a pressure of about 100 psig to cool down a hot effluent at a minimum up to about 370° F. (187° C.). A steam generator using hot diesel from the jet fractionator bottoms may be used to ensure sufficient steam is generated for the ethanol dehydration.
For a 300 MMGPY ethanol unit, the combined flow of steam is estimated to be ˜140 k lb/hr which can satisfy ethanol dehydration steam injection requirements.
Ethanol in the feed surge drum 26 may be blanketed with nitrogen. A charge pump 29 pumps an ethanol charge stream in line 28 into two charge streams. A first charge stream in line 30 is heat exchanged with a first dehydrated exchange stream in line 32, mixed with a steam stream in line 33 and fed to a first charge heater 34. The first charge heater 34 may be a fired heater and may heat the first charge stream to about 400° C. to about 550° C. A resulting first heated charge stream in line 36 is charged to a first dehydration reactor 40. In the first dehydration reactor 40, ethanol feed is converted to ethylene and water over a dehydration catalyst at a pressure of about 379 kPa (a) to about 690 kPa (a) or a pressure of about 455 kPa (g) to about 630 kPa (g). A first dehydrated stream is discharged from the first dehydration reactor 40 in line 42.
A second charge stream in line 44 is heat exchanged with a second dehydrated exchange stream in line 46, mixed with the first dehydrated stream in line 42 and fed to a second charge heater 48. The second charge heater 48 may be a fired heater and may heat the second charge stream to about 400° C. to about 550° C. A resulting second heated charge stream in line 50 is charged to a second dehydration reactor 52. In the second dehydration reactor 52, ethanol feed is converted to ethylene and water over a dehydration catalyst at a pressure of about 420 kPa (g) to about 700 kPa (g). A second dehydrated stream is discharged from the second dehydration reactor 52 in line 54.
The second dehydrated stream in line 54 is fed to an interheater 56. The interheater 56 may be a fired heater and may heat the second dehydrated stream to about 400° C. to about 550° C. A resulting third heated charge stream in line 58 is charged to a third dehydration reactor 60. In the third dehydration reactor 60, residual ethanol feed is converted to ethylene and water over a dehydration catalyst at a pressure of about 420 kPa (g) to about 700 kPa (g). A third dehydrated stream is discharged from the third dehydration reactor 60 in line 62.
The dehydration catalyst may be an alumina-based catalyst.
The third dehydrated stream is split between the first dehydrated exchange stream in line 32 and the second dehydrated exchange stream in line 46. The first dehydrated exchange stream in line 32 is heat exchanged with the first charge stream in line 30, and the second dehydrated exchange stream in line 46 is heat exchanged with the second charge stream in line 44 and the cooled dehydrated streams are recombined in line 64.
The cooled dehydrated stream in line 64 are fed to a quench tower 68 in which the cooled dehydrated stream is quenched by direct contact with water from a first cooled water stream in line 70 and a second cooled water stream in line 72. A quenched ethylene stream exits in a quench overhead line 74 and a bottoms water stream exits the tower bottoms in line 76. The bottoms water stream is split between a drain stream in line 78 which may be transported to a waste water stripper column 80 through a control valve thereon and a quench recycle stream in line 82. A first portion of the quench recycle stream is air cooled in a product condenser 69 and recycled as the first, lower cooled water stream in line 70 through a control valve thereon, and a second portion of the quench recycle stream is heat exchanged in a trim condenser 71 and recycled to the quench tower 68 as the second, higher cooled water stream in line 72. The quench tower 68 may be operated with a bottoms temperature of about 37° C. (100° F.) to about 104° C. (220° F.) and a pressure of about 280 kPa (gauge) (40 psig) to about 490 kPa (gauge) (70 psig) in the overhead.
The quenched ethylene stream in line 74 is fed to a first stage suction drum 86. In the first stage suction drum ethylene exits the overhead line 88 to a first stage compressor 90 while residual water exits the bottom of the drum in line 92 through a control valve thereon and is transported to the waste water stripper column 80 perhaps via line 78. The first stage compressor 90 compresses the ethylene stream to a first pressure of about 350 kPa (gauge) (50 psig) to about 1225 kPa (gauge) (175 psig) and the discharge in line 91 is cooled in a first stage discharge cooler 93 and a first stage trim cooler 94.
The cooled, compressed ethylene stream from the first stage trim cooler 94 is fed to a first stage discharge drum 96. From the first stage discharge drum 96 ethylene exits in an overhead line 98 to a second stage compressor 100 while residual water exits a bottom of the drum in line 102 through a control valve thereon and is transported to the waste water stripper column 80 perhaps via lines 92 and 78. The second stage compressor compresses the ethylene stream to a second pressure of about 455 kPa (g) to about 3220 kPa (g) and the discharge in line 101 is cooled in a second stage discharge cooler 103 and a second stage trim cooler 104.
The twice cooled, compressed ethylene stream from the second stage trim cooler 104 is fed to a second stage discharge drum 106. From the second stage discharge drum 106 ethylene exits in an overhead line 108 and is transported to a water wash tower 110 while a residual water stream exits the bottom of the drum in line 112 through a control valve thereon and is transported to the waste water stripper column 80 perhaps via lines 102, 92 and 78.
In the water wash tower 110, the twice cooled, compressed ethylene stream is counter-currently washed with cooled, treated water in line 118 from the waste water stripper column 80 to absorb additional oxygenates to produce a washed ethylene stream exiting in an overhead line 120 and a wash water stream in a bottoms line 122. The washed ethylene stream in the overhead line 120 is transported to a caustic scrubber column 116. The wash water stream in line 122 is transported back to the water stripper column 80 through a control valve thereon. The wash water 110 may be operated with a bottoms temperature of about 16° C. to about 82° C. and a pressure of about 2800 kPa (g) to about 3500 kPa (g) in the overhead.
The caustic scrubber column 116 has a lower caustic wash section 124 and an upper water wash section 132. In the lower caustic wash section 124 the washed ethylene stream in line 120 is scrubbed with an aqueous caustic stream from line 126 to absorb acid gases such as carbon dioxide from the washed ethylene stream. Spent caustic is pumped around from the bottom of the lower section in line 128 and replenished with fresh caustic in line 130 to provide the aqueous caustic stream 126. A scrubbed vaporous ethylene stream depleted of acid gases ascends from the caustic wash section 124 to the upper water wash section 132 through a vapor inlet. In the water wash section 132, the scrubbed ethylene stream is contacted with a wash water stream from line 134. A washed, scrubbed vaporous ethylene stream exits the overhead of the water wash section 132 in line 136 and is fed to the product drier section 140. A spent water stream is taken from the bottom of the water wash section 132 from a liquid sump in line 142 and replenished with a fresh water stream from line 144 to provide the wash water stream in line 134 and pumped to the top of the water wash section 132 to be contacted with the scrubbed vaporous ethylene stream. The caustic scrubber column may be operated with a bottoms temperature of about 38° C. to about 43° C. and a pressure of about 2800 kPa (g) to about 2975 kPa (g) in the overhead.
In the product drier section 140, the washed, scrubbed ethylene stream in line 136 is fed to a first drier inlet knock-out drum 146 to remove residual water and provide a drier inlet stream in line 148 and a knock-out water stream in the bottoms line 150 which is fed to the waste water stripper column 80 perhaps via line 122. The drier inlet stream is fed to a first product drier 152 in line 148. The first product drier 152 comprises an adsorbent for adsorbing the water from ethylene in the drier inlet stream in line 148 to provide a dried ethylene stream. The adsorbent may be a molecular sieve material with pore diameters of 2-4 A. The first product drier 152 may operate in upflow mode. The first product drier 152 may be operated in a downflow mode. The product drier section 140 may include a second product drier 156 that operates as the first product drier 152. The two product driers may be operated in series but are preferably arranged in a lead-lag operation to facilitate regeneration during continuous operation. The second product drier 156 comprises an adsorbent for adsorbing the water from ethylene like in the first product drier 152. A dried ethylene stream exits the product drier section 140 in a dried ethylene stream in line 158. The product drier section 140 may be operated at a temperature of about 32° C. (90° F.) to about 49° C. (120° F.) and a pressure of about 2758 kPa (gauge) (400 psig) to about 3102 kPa (gauge) (450 psig).
The dried ethylene stream in line 158 is fed to a drier outlet knock-out drum 160 to remove residual water and provide a drier outlet stream in line 162 and a second knock-out water stream in a bottoms line 164 which is fed to the waste water stripper column 80 perhaps via lines 150 and 122. The drier outlet stream in line 162 may be fed to a heavy oxygenates removal column 170. In an aspect, the drier outlet knock-out drum 160 may be optionally used and the dried ethylene stream in line 158 may be fed directly to the heavy oxygenates removal column 170.
The drier outlet stream in line 162 may be fed to a heavy oxygenates removal column 170 to separate an overhead stream comprising predominantly ethylene but perhaps higher olefins from heavy ketones and diethyl ether. The olefins are produced in an overhead line 172 and fed to a third stage compressor 174 and a bottoms heavy oxygenate stream is produced in a bottoms line 176. A heavy oxygenate purge stream may be taken in line 178 to heavy oxygenate treatment while a reboil portion is reboiled and fed back to the column 170. A compressed ethylene stream at a pressure of about 2800 kPa (gauge) (400 psig) to about 7000 kPa (gauge) (1000 psig) in a compressor discharge line 177 may be provided to an oligomerization section. The heavy oxygenate removal column 170 may be operated with a bottoms temperature of about −28° C. (−20° F.) to about 122° C. (250° F.) and a pressure of about 2413 kPa (g) (350 psig) to about 3103 kPa (g) (450 psig) in the overhead.
Water streams comprising oxygenates and volatiles in lines 92, 102, 112, 122, 150, 164 may be fed to the waste water stripper column 80 in which volatiles and oxygenates are boiled off to provide an overhead volatile stream in line 182 and a stripped water stream in line 184. A portion of the stripped water stream can be reboiled and fed back to the column to provide necessary heat. A treated water stream in line 186 may be pumped to water outlets in line 188 which includes the cooled, treated water stream in line 118 for the water wash tower 110. The waste water stripper column 80 may be operated with a bottoms temperature of about 93° C. (200° F.) to about 121° C. (250° F.) and a pressure of about 34 kPa (gauge) (5 psig) to about 138 kPa (gauge) (20 psig) in the overhead. In an aspect, a portion or an entirety of the treated water stream in line 186 may be pumped to a steam regenerator to produce the steam stream in line 33.
The overhead volatile stream in line 182 may be cooled in an air cooler 189 and fed to an off-gas knock out drum 190. An overhead stream from the knock out drum 190 in line 192 may be sent to flare while an ethanol recycle stream is pumped to the feed surge drum 26 in line 27 perhaps via line 24. Alternatively, the overhead stream from the knock out drum 190 in line 192 may be compressed and sent to fuel gas.
FIG. 2 shows an oligomerization reactor column together with a series of five steam generators from which a portion of steam is sent to the ethanol dehydration column into line 33.
Turning to the oligomerization section 210 of FIG. 2 , a charge olefin stream in line 212 is provided to the oligomerization section 210. The charge olefin stream may comprise substantial ethylene and propylene. The charge olefin stream may predominantly comprise ethylene and/or propylene. In an aspect, the charge olefin stream may comprise at least 95 mol % ethylene and/or propylene. The charge olefin stream in line 212 may be styled a light olefin stream. Additional olefinic species with carbon numbers ranging from C₄to C₆can be expected in the charge stream. The light olefin stream may be provided by the dehydration of ethanol or provided from a MTO unit. The charge olefin stream may be at a temperature of about 60° C. (140° F.) to about 150° C. (302° F.), preferably about 80° C. (176° F.) to about 100° C. (212° F.), and a pressure of about 3.5 MPag (500 psig), preferably about 5.6 MPag (800 psig) to about 8.4 MPag (1200 psig).
The charge olefin stream may be initially contacted with a first-stage oligomerization catalyst to oligomerize the ethylene and propylene to oligomers and then contacted with a second oligomerization catalyst to oligomerize unconverted ethylene and propylene from the first-stage oligomerization. Alternatively, the olefin stream may be initially contacted with a second stage oligomerization catalyst to oligomerize ethylene and propylene, and then be contacted with the first-stage oligomerization catalyst to oligomerize the oligomerized ethylene and propylene.
The oligomerization reaction generates a large exotherm. For example, dimerization of ethylene can generate 612 kcal/kg (1100 BTU/lb) of heat. Consequently, this large exotherm must be managed. Accordingly, the charge olefin stream in line 212 may be split into multiple olefin streams. In FIG. 2 , the charge olefin stream is split into two separate streams: a first charge olefin stream in a first charge olefin line 212 a and a second charge olefin stream in a second charge olefin line 212 b. More or less separate multiple olefin streams may be used. Up to six charge olefin streams are readily contemplated. The charge olefin stream in line 212 may be split into equal aliquot multiple olefin streams. Alternatively, the charge olefin stream in line 212 may be split into unequal streams. For example, the charge olefin stream may be split into streams of descending flow rates in which a charge olefin stream to a preceding reactor has a larger flow rate than a charge olefin stream to a subsequent reactor. In an embodiment, the charge olefin stream is split into two streams of equal flow rates, each comprising 50 vol % of the charge olefin stream. In another embodiment, the first charge olefin stream in the first charge olefin line 212 a may comprise about 70 to about 90 vol % of the charge olefin stream in line 212 and the second charge olefin stream in the second olefin line 212 b may comprise about 10 to about 30 vol % of the charge olefin stream in line 212.
To manage the exotherm, the charge olefin stream may be diluted with a diluent stream to provide a diluted olefin stream to absorb the exotherm. The diluent stream may comprise a paraffin stream in diluent line 214. The diluent stream in the diluent line 214 may be added to the first charge olefin stream in the first charge olefin line 212 a before it is charged to the first-stage oligomerization reactor 222. Preferably, the diluent stream is added to the first charge olefin stream in line 212 a after the split of the charge olefin stream in line 212 into multiple olefin streams to provide a first diluted olefin charge stream in line 216 a, so the diluent stream passes through all of the first-stage oligomerization reactions. Alternatively, the diluent stream may also be split into multiple streams with each diluent stream added to a corresponding charge olefin stream. The diluent stream may have a volumetric flow rate of about 2 to about 8 times and preferably about 3 to about 6 times the volumetric flow rate of the charge olefin stream in the charge olefin line 212.
A recycle olefin stream in recycle line 226 comprising C₄to C₈olefins may be mixed with the charge olefin stream and oligomerized in the first-stage oligomerization reactor 222. In an embodiment, the recycle olefin stream in line 226 is split into a plurality of recycle olefin streams 226 a, 226 b, 226 c, and 226 d. A recycle olefin stream in a first recycle olefin line 226 a may be mixed with the first charge olefins stream in line 212 a and charged to the first-stage oligomerization reactor 222. In a further embodiment, the first recycle olefin stream in the first recycle olefin line 226 a is mixed with the first charge olefin stream in line 212 a and the diluent stream in line 214 to provide a diluted first charge olefin stream in line 216 a.
The first diluted charge olefin stream may comprise no more than 35 wt % olefins, suitably no more than 30 wt % olefins and preferably no more than 20 wt % olefins. In an embodiment, the first diluted olefin stream comprises about 10 to about 30 wt % C2 to C8 olefins. The first diluted olefin stream may comprise no more than 30 wt % ethylene, suitably no more than 25 wt % ethylene and preferably no more than 20 wt % ethylene. In an embodiment, the first diluted charge olefin stream comprises about 10 to about 20 wt % propylene. The first diluted charge olefin stream may comprise no more than 30 wt % propylene, suitably no more than 25 wt % propylene and preferably no more than 20 wt % propylene. In an embodiment, the first diluted charge olefin stream comprises about 10 to about 20 wt % propylene.
The first-stage oligomerization reactor 222 may comprise a series of first-stage oligomerization catalyst beds 222 a, 222 b, 222 c and 222 d each for charging with a dedicated olefin charge stream. The first-stage oligomerization 222 reactor preferably contains four fixed first-stage oligomerization catalyst beds 222 a, 222 b, 222 c and 222 d. It is also contemplated that each first-stage oligomerization catalyst bed 222 a, 222 b, 222 c and 222 d may be in a dedicated first-stage oligomerization reactor or multiple first-stage oligomerization catalyst beds may be in two or more separate first-stage oligomerization reactor vessels. Up to six, first-stage oligomerization catalyst beds are readily contemplated. In FIG. 2 , two, first stage oligomerization reactor vessels 221 a and 221 b are utilized.
A parallel first-stage oligomerization reactor may be used when the first-stage oligomerization reactor 222 has deactivated during which the first-stage oligomerization reactor 222 is regenerated in situ by combustion of coke from the catalyst. In another embodiment, each first-stage oligomerization reactor may comprise a lead reactor, a lag reactor and a spare reactor to facilitate regeneration. Only two reactor vessels 221 a, 221 b are shown in FIG. 2 .
The diluted first charge olefin stream in line 216 a may be cooled in a first charge cooler 218 a to provide a cooled diluted first charge olefin stream in line 220 a and charged to a first bed 222 a of first-stage oligomerization catalyst in the first, first-stage oligomerization reactor vessel 221 a of the first-stage oligomerization reactor 222. The cooled diluted first charge olefin stream in line 220 a may be charged at a temperature of about 180° C. (356° F.) to about 260° C. (500° F.) and a pressure of about 3.5 MPag (500 psig) to about 8.4 MPag (1200 psig). The charge cooler 218 a may comprise a steam generator.
The diluted first charge olefin stream may be charged to the first, first-stage catalyst bed 222 a in line 220 a preferably in a down flow operation. However, upflow operation may be suitable. As oligomerization of ethylene, propylene and recycle olefins occurs in the first, first-stage oligomerization catalyst bed 222 a, an exotherm is generated due to the highly exothermic nature of the olefin oligomerization reaction. Oligomerization of the first charge olefin stream produces a first oligomerized effluent stream in a first oligomerized effluent line 224 a at an elevated outlet temperature despite the cooling and dilution. The elevated outlet temperature is limited to between 150° C. (302° F.) and about 250° C. (482° F.).
The second charge olefin stream in line 212 b may be mixed with a second recycle olefin stream in a second recycle olefin line 226 b and with the first oligomerized effluent stream in the first oligomerized effluent line 224 a removed from the first, first-stage oligomerization catalyst bed 222 a in the first, first-stage reactor 221 a to provide a mixed second charge olefin stream in line 216 b. The first oligomerized effluent stream in line 224 a includes the diluent stream from diluent line 214 added to the first olefin charge stream in line 212 a. The second charge olefin stream may comprise no more than 35 wt % C2 to C8 olefins, suitably no more than 25 wt % C2 to C8 olefins and preferably no more than 20 wt % ethylene. The second charge olefin stream may comprise no more than 30 wt % ethylene, suitably no more than 25 wt % ethylene and preferably no more than 20 wt % ethylene. The second charge olefin stream may comprise no more than 30 wt % propylene, suitably no more than 25 wt % propylene and preferably no more than 20 wt % propylene. The second charge olefin stream in line 216 b may be cooled in a second charge cooler 218 b which may be located externally to the first, first-stage oligomerization reactor 221 a to provide a cooled second charge olefin stream in line 220 b and charged to a second bed 222 b of first-stage oligomerization catalyst in the first, first-stage oligomerization reactor 221 a. The second charge cooler 218 b removes the heat of reaction from the first oligomerized effluent stream in the first oligomerized effluent line 224 a. The charge cooler 218 b may comprise a steam generator. The first charge coolers 218 a, 218 b, 218 c, 218 d and 218 e may also be referred to as intercooler steam generators where an intercooler steam generator removes heat of reaction from an oligomerized effluent stream before passing the oligomerized effluent stream to the second oligomerization reactor vessel. An intercooler steam generator between oligomerization catalyst beds in the first oligomerization reactor vessel 221 a may remove heat of reaction from an oligomerized effluent stream of a top oligomerization catalyst bed of the first oligomerization reactor vessel 221 a. An intercooler steam generator between oligomerization catalyst beds in the second oligomerization reactor vessel may remove heat of reaction from an oligomerized effluent stream of a top oligomerization catalyst bed of the second oligomerization reactor vessel 221 b. In an embodiment the oligomerization section comprises a first stage oligomerization reactor 222 and a second stage oligomerization reactor 232 and has provided an intercooler steam generator 218 e to remove heat of reaction from an oligomerized effluent stream of the first stage oligomerization reactor 222 before passing the oligomerized effluent stream to the second stage oligomerization reactor 232.
The second charge olefin stream in line 220 b may be charged at a temperature of about 180° C. (356° F.) to about 230° C. (446° F.) and a pressure of about 3.5 MPag (500 psig) to about 8.4 MPag (1200 psig). The second charge olefin stream will include diluent and olefins from the first oligomerized stream. The olefins from the first oligomerized stream will oligomerize in the second catalyst bed 222 b. Oligomerization of ethylene, propylene, recycle olefins and oligomers in the second olefin stream in the second bed 222 b of first-stage oligomerization catalyst produces a second oligomerized olefin effluent stream in a second oligomerized effluent line 224 b at an elevated outlet temperature. The elevated outlet temperature may be limited to between 30° C. (54° F.) and about 50° C. (90° F.) above the inlet temperature to the catalyst bed 222 b.
The second oligomerized effluent stream in line 224 b removed from the second, first-stage oligomerization catalyst bed 222 b in the first, first-stage reactor vessel 221 a may be mixed with a third recycle olefin stream in a third recycle olefin line 226 c to provide a first recycle olefin charge stream in line 216 c. None of the charge olefin stream in line 212 is directly added to the first recycle olefin charge stream in line 216 c. Alternatively, a portion of the charge olefin stream in line 212 may be charged with the second oligomerized effluent stream with the first recycle olefin charge stream in line 216 c. The second oligomerized effluent stream in line 224 b includes the diluent stream from diluent line 214 added to the first charge olefin stream in line 212 a. The first recycle olefin charge stream may comprise no more than 30 wt % ethylene, suitably no more than 25 wt % ethylene and preferably no more than 20 wt % ethylene. The first recycle olefin charge stream may comprise no more than 30 wt % propylene, suitably no more than 25 wt % propylene and preferably no more than 20 wt % propylene. The first recycle olefin charge stream may comprise no more than 30 wt % C₂to C₈olefins, suitably no more than 25 wt % C2 to C8 olefins and preferably no more than 20 wt % C₂to C₈olefins. The first recycle olefin charge stream in line 216 c may be cooled in a third charge cooler 218 c which may be located externally to the oligomerization reactor 222 to provide a cooled first recycle olefin charge stream in line 220 c and charged to a third bed 222 c of first-stage oligomerization catalyst in the first-stage oligomerization reactor 222. The third charge cooler 218 c removes the heat of reaction from the second oligomerized effluent stream in line 224 b. In an embodiment, the third bed 222 c of first-stage oligomerization catalyst is provided in a second, first-stage oligomerization reactor vessel 221 b. The charge cooler 218 c may comprise a steam generator.
The cooled first recycle olefin charge stream in line 220 c may be charged at a temperature of about 180° C. (356° F.) to about 230° C. (446° F.) and a pressure of about 3.5 MPag (500 psig) to about 8.4 MPag (1200 psig). The first recycle olefin charge stream will include diluent and olefins from the second oligomerized olefin stream and the third recycle olefin stream. The olefins will oligomerize in the third catalyst bed 222 c. Oligomerization of ethylene and propylene and oligomerization of oligomers in the first recycle olefin charge stream in the third bed 222 c of first-stage oligomerization catalyst produces a third oligomerized effluent stream in a third oligomerized effluent line 224 c at an elevated outlet temperature. In an embodiment, the third oligomerized effluent stream is a penultimate oligomerized effluent stream and the third oligomerized effluent line 224 c is a penultimate oligomerized effluent line 224 c. The elevated outlet temperature is limited to between 30° C. (54° F.) and about 50° C. (90° F.) above the inlet temperature to the catalyst bed 222 c.
The third oligomerized effluent stream in line 224 c removed from the second, first-stage oligomerization reactor vessel 221 b of the first-stage oligomerization reactor 222 may be mixed with the fourth recycle olefin stream in line 226 d to provide a second recycle olefin charge stream in line 216 d. The third oligomerized effluent stream in line 224 c includes the diluent stream from diluent line 214 added to the first olefin stream in line 212 a. None of the charge olefin stream in line 212 is directly added to the second recycle olefin charge stream in line 216 d. In an embodiment, the third oligomerized effluent stream in line 224 c may also be mixed with an olefin charge stream from the olefin charge line 222 and be oligomerized therewith. The second recycle olefin charge stream may comprise no more than 35 wt % C₂to C₈olefins, suitably no more than 30 wt % C2 to C8 olefins and preferably no more than 25 wt % C₂to C₈olefins. The second recycle olefin charge stream may comprise no more than 30 wt % ethylene, suitably no more than 25 wt % ethylene and preferably no more than 20 wt % ethylene. The second recycle olefin charge stream may comprise no more than 30 wt % propylene, suitably no more than 25 wt % propylene and preferably no more than 20 wt % propylene. The second recycle olefin charge stream in line 216 d may be cooled in a fourth charge cooler 218 d which may be located externally to the second vessel 221 b of the first-stage oligomerization reactor 222 to provide a cooled second recycle olefin charge stream in line 220 d and charged to a fourth bed 222 d of first-stage oligomerization catalyst in the second vessel of the first-stage oligomerization reactor 222. The fourth charge cooler 218 d removes the heat of reaction from the third oligomerized effluent stream in line 224 c. The charge cooler 218 d may comprise a steam generator.
The cooled second recycle olefin charge stream in line 20 d may be charged at a temperature of about 180° C. (356° F.) to about 230° C. (446° F.) and a pressure of about 3.5 MPa (g) (500 psig) to about 8.4 MPa (g) (1200 psig). The cooled second recycle olefin charge stream in line 220 d will include diluent and olefins from the third or penultimate oligomerized effluent stream and C₄-C₈olefins from the fourth recycle olefin stream. The olefins will oligomerize over the fourth catalyst bed 222 d. Oligomerization of ethylene and propylene in the second recycle olefin charge stream in the fourth bed 222 d of first-stage oligomerization catalyst produces a fourth oligomerized stream in a fourth oligomerized effluent line 224 d at an elevated outlet temperature. The elevated outlet temperature is limited to between 30° C. (54° F.) and about 50° C. (90° F.) above the inlet temperature to the catalyst bed 222 d.
The fourth oligomerized effluent stream in line 224 d exits the second reactor vessel 221 b of the first-stage oligomerization reactor 222. In an embodiment, the fourth oligomerized effluent stream in line 224 d is a last oligomerized effluent stream, and the fourth oligomerized effluent line 224 d is a last oligomerized effluent line 224 d.
The first-stage oligomerization reaction takes place predominantly in the liquid phase or in a mixed liquid and gas phase at a LHSV 0.5 to 10 hr-1 on an olefin basis. We have found that across the first-stage oligomerization catalyst beds, typically 10-50 wt % ethylene in the olefin stream converts to higher olefins. The ethylene will initially dimerize over the catalyst to butenes. A predominance of the propylene and butenes in the olefins stream charged to a first-stage oligomerization catalyst bed is oligomerized. In an embodiment, at least 99 mol % of propylene and butenes in the olefins stream are oligomerized.
The first-stage oligomerization catalyst may include a zeolitic catalyst. The first-stage oligomerization catalyst may be considered a solid acid catalyst. The zeolite may comprise between about 5 and about 95 wt % of the catalyst, for example between about 5 and about 85 wt %. Suitable zeolites include zeolites having a structure from one of the following classes: MFI, MEL, ITH, IMF, TUN, FER, BEA, FAU, BPH, MEI, MSE, MWW, UZM-8, MOR, OFF, MTW, TON, MTT, AFO, ATO, and AEL. Three-letter codes indicating a zeotype are as defined by the Structure Commission of the International Zeolite Association and are maintained at http://www.iza-structure.org/databases. UZM-8 is as described in U.S. Pat. No. 6,756,030. In a preferred aspect, the first-stage oligomerization catalyst may comprise a zeolite with a framework having a ten-ring pore structure. Examples of suitable zeolites having a ten-ring pore structure include TON, MTT, MFI, MEL, AFO, AEL, EUO and FER. In a further preferred aspect, the first-stage oligomerization catalyst comprising a zeolite having a ten-ring pore structure may comprise a uni-dimensional pore structure. A uni-dimensional pore structure indicates zeolites containing non-intersecting pores that are substantially parallel to one of the axes of the crystal. The pores preferably extend through the zeolite crystal. Suitable examples of zeolites having a ten-ring uni-dimensional pore structure may include MTT. In a further aspect, the first-stage oligomerization catalyst comprises an MTT zeolite.
The first-stage oligomerization catalyst can be regenerated upon deactivation. Suitable regeneration conditions include subjecting the first-stage oligomerization catalyst, for example, in situ, to hot air at about 400 to about 500° C. To facilitate regeneration without downtime, a swing bed arrangement may be employed with an alternative first-stage oligomerization reactor. A regeneration gas stream may be admitted to the first-stage oligomerization reactor 222 requiring regeneration. The regeneration gas may comprise air with an increased or decreased concentration of oxygen. Activity and selectivity of the regenerated catalyst is comparable to fresh catalyst.
The zeolite catalyst is advantageous as a first-stage oligomerization catalyst. The zeolitic catalyst has relatively low sensitivity towards oxygenates contamination. Consequently, a smaller degree of removal of oxygenates is required of olefinic feed in line 212 if produced from an ethanol dehydration process.
The last first-stage oligomerized stream in the last first-stage oligomerized effluent line 224 d has a decreased concentration of ethylene and propylene oligomers compared to the charge olefin stream in line 212. The last first-stage oligomerized stream in the last first-stage oligomerized effluent line 224 d is cooled by steam generation in a steam generator 218 e or by other heat exchange and further cooled by heat exchange against a second stage oligomerized stream in line 234 and perhaps further cooled such as by an air cooler to provide a charge first-stage oligomerized stream and charged to a second-stage oligomerization reactor 232 in a second-stage oligomerization charge line 228. In an aspect, the steam generator 218 e may be provided to remove the heat of reaction form last first-stage oligomerized effluent line 224 d of the first stage oligomerization reactor 222 before passing it to the second-stage oligomerization reactor 232. To achieve the most desirable olefin product, the second-stage oligomerization reactor 232 is operated at a temperature from about 80° C. (176° F.) to about 180° C. (356° F.). The second-stage oligomerization reactor 232 is run at a pressure from about 2.1 MPa (300 psig) to about 7.6 MPa (1100 psig), and more preferably from about 3.5 MPa (500 psig) to about 6.9 MPa (1000 psig).
The second-stage oligomerization reactor 232 may be in downstream communication with the first-stage oligomerization reactor 222. The second-stage oligomerization reactor 232 preferably operates in a down flow operation. However, upflow operation may be suitable. The second-stage oligomerization charge stream is contacted with the second-stage oligomerization catalyst causing the unconverted ethylene from the first-stage oligomerization reactor 222 to dimerize and trimerize while higher olefins also dimerize, trimerize and tetramerize to provide distillate range olefins. With regard to the second-stage oligomerization reactor 232, process conditions are selected to produce a higher percentage of jet range olefins which, when hydrogenated in a subsequent step as will be described below, result in a desirable jet-range hydrocarbon product. A predominance of the unconverted ethylene from the first-stage oligomerization reactor 222 is dimerized, trimerized and tetramerized. In an embodiment, at least 99 wt % of ethylene in the second-stage oligomerization charge stream is converted to mostly butenes.
The second-stage oligomerization reactor 232 may comprise a first reactor vessel 231 a comprising a first bed 232 a of second-stage oligomerization catalyst and a second reactor vessel 231 b comprising a second bed 232 b of second-stage oligomerization catalyst. A first, second-stage oligomerized stream is discharged from the first, second-stage reactor vessel 231 a, cooled and charged to the second, second-stage reactor vessel 231 b. A second-stage oligomerized stream with an increased average carbon number greater than the charge first-stage oligomerized stream in line 228 exits the second-stage oligomerization reactor 232 in line 234.
The second-stage oligomerization catalyst is preferably an amorphous silica-alumina base with a metal from either Group VIII and/or Group VIB in the periodic table using Chemical Abstracts Service notations. In an aspect, the catalyst has a Group VIII metal promoted with a Group VIB metal. Typically, the silica and alumina will only be in the base, so the silica-to-alumina ratio will be the same for the catalyst as for the base. The metals can either be impregnated onto or ion exchanged with the silica-alumina base. Co-mulling is also contemplated. Catalysts for the present invention may have a Low Temperature Acidity Ratio of at least about 0.15, suitably of about 0.2, and preferably greater than about 0.25, as determined by Ammonia Temperature Programmed Desorption (Ammonia TPD) as described hereinafter. Additionally, a suitable catalyst will have a surface area of between about 50 and about 400 m2/g as determined by nitrogen BET.
A preferred second-stage oligomerization catalyst of the present disclosure has an amorphous silica-alumina base impregnated with about 0.5 to about 15 wt-% nickel in the form of 3.175 mm (0.125 inch) extrudates and a density of about 0.45 to about 0.65 g/ml. It is also contemplated that metals can be incorporated onto the support by other methods such as ion-exchange and co-mulling.
The second-stage oligomerization catalyst can be regenerated upon deactivation. Suitable regeneration conditions include subjecting the catalyst, for example, in situ, to hot air at about 400 to about 500° C. for 3 hours. To facilitate regeneration without downtime, a swing bed arrangement may be employed with an alternative second-stage oligomerization reactor. The regeneration gas may comprise air with an increased or decreased concentration of oxygen. activity and selectivity of the regenerated catalyst is comparable to fresh catalyst.
Second-stage oligomerization reactions are also exothermic in nature. The last oligomerized olefin stream in line 224 d includes the diluent stream from diluent line 214 added to the first olefin stream in line 212 a and carried through the first-stage oligomerization catalyst beds 222 a-222 d. The diluent stream is then transported into the second-stage oligomerization reactor 232 in line 228 to absorb the exotherm in the second-stage oligomerization reactor. A dedicated diluent line to second-stage oligomerization reactor 232 is also contemplated for prompt control of exotherm rise or to cool down the second-stage oligomerization reactor 232 and want to cool down only second stage.
When the oligomerization reaction is performed according to the above-noted process conditions, a C4 olefin conversion of greater than or equal to about 95% is achieved, or greater than or equal to 97%. The resulting second-stage oligomerized stream in line 234 includes a plurality of olefin products that are distillate range hydrocarbons.
An oligomerized olefin stream in line 234 with an increased C8+ olefin concentration compared to the charge first-stage oligomerization stream in line 228 is heat exchanged with the first-stage oligomerized stream in line 224 d, let down in pressure, subsequently heat exchanged with an olefin splitter bottoms stream in line 230 and fed to a dealkanizer column 240. The oligomerized olefin stream in line 234 is at a temperature from about 160° C. (320° F.) to about 190° C. (374° F.) and a pressure of about 3.9 MPa (gauge) (550 psig) to about 7 MPa (gauge) (1000 psig).
We have found that light alkanes such as ethane and/or propane are generated in the first-stage oligomerization reactor 222 and/or the second-stage oligomerization reactor 232 which must be removed from the second-stage oligomerized stream for fuels production particularly to facilitate light olefin recycle to the first-stage oligomerization reactor 222. Light alkanes are inert and would accumulate in the recycle loop. Hence, the second-stage oligomerized stream in line 234 is dealkanized by fractionation in a dealkanizer column 240 to provide a light alkane stream and a dealkanized stream. In an embodiment, the light alkane stream is an ethane stream in which case the dealkanizer column 240 is a deethanizer column. In another embodiment, the light alkane stream is a propane stream in which case the dealkanizer column 240 is a depropanizer column. The alkane stream may also be a mixture of ethane and propane. The alkane stream may be used as fuel for providing heating duty in the process 210.
In the dealkanizer column 240, light alkanes such as C3− and suitably C2− hydrocarbons, are separated perhaps in an alkane overhead stream in an overhead line 242 from perhaps a dealkanized bottoms stream in a bottoms line 244 comprising C4+ and suitably C3+ hydrocarbons. The dealkanizer column 240 may be operated at a bottoms temperature of about 177° C. (350° F.) to about 302° C. (575° F.) and an overhead pressure of about 207 kPa (gauge) (30 psig) to about 690 kPa (gauge) (100 psig) if operated as a deethanizer column. The dealkanizer column 240 may be operated at a bottoms temperature of about 194° C. (381° F.) to about 333° C. (630° F.) and an overhead pressure of about 207 kPa (gauge) (30 psig) to about 1.14 MPa (gauge) (165 psig) if operated as a depropanizer column.
The alkane overhead stream in the overhead line 242 may be cooled and separated in a dealkanizer receiver 246 to provide a dealkanized off-gas in an off-gas line 247 in which it may be chilled and fed to further processing such as to be taken as fuel gas in line 248 along with a net vapor stream in a receiver overhead line 268. Condensate from the dealkanizer receiver 246 may be refluxed back to the dealkanizer column 240 in a dealkanizer overhead liquid line 249. In an embodiment, some of the condensate from the dealkanizer receiver 246 in line 249 may be taken as recycle in line 251 to the first stage oligomerization reactor in lines 272 and 226. The dealkanized stream perhaps in the bottoms line 244 may be split between a reboil stream in line 250 which is reboiled by heat exchange with a first hot diesel stream in line 252 perhaps taken from a jet fractionator bottom heat exchange stream in the jet bottoms heat exchange line 274 and a net bottoms stream in line 254 which is fed directly to an olefin splitter column 260 perhaps without heating. The reboiled bottom stream in line 250 may be returned boiling to the dealkanizer column 240 to provide heating requirements. In another embodiment, feed to dealkanizer column 240 is not preheated by olefin splitter bottoms stream in line 230, but the feed to the olefins splitter column 260 in the net bottoms line 254 would be preheated by olefin splitter bottoms stream.
The dealkanized stream in the dealkanizer net bottoms line 254 is split by fractionation in an olefin splitter column 260 into a light olefin stream perhaps in an olefin splitter overhead line 262 and a heavy olefin stream perhaps in an olefin splitter bottoms line 264. The olefin splitter overhead stream may be cooled to about 66° C. (150° F.) to about 93° C. (200° F.) and a resulting condensate portion refluxed from an olefin splitter receiver 266 back to the olefin splitter column 260. The net vapor stream in the receiver overhead line 268 from the olefin splitter receiver 266 may be chilled and further processed such as fuel gas in line 248 along with the off-gas stream in the off-gas line 247. The light olefin condensate from a bottom of the olefin splitter receiver in line 270 may be split between a reflux stream that is refluxed back to the column in line 271 and a light olefin recycle stream in a recycle line 272 that may be recycled to the first-stage oligomerization reactor 222 or alternatively to the second-stage oligomerization reactor 232. The light olefin stream in line 272 may comprise about 1 to about 15 wt % of the light olefin stream in line 270. The light olefin stream in line 272 may comprise about 40 to about 80 wt % C4-C8 olefins. In an embodiment, the light olefin stream in line 272 may be flashed in a knock-out drum 275 to remove vapors in a light olefin vapor stream which may be transported to the hydrogenation section in an overhead line 277 and the liquid recycle olefin oligomer stream in line 226 may be recycled to the first-stage oligomerization reactor 222 to oligomerize the C4-C8 olefins. A stream 280 is shown exiting after passing through a heat exchanger.
Steam is sent from steam generators, a first steam generator 218 a through a first steam line 233 a, a second steam generator 218 b through a second steam line 233 b, a third steam generator 218 c through a third steam line 233 c, a fourth steam generator 218 d through a fourth steam line 233 d, and a fifth steam generator 218 e through a fifth steam line 233 e into a combined steam line 33 that is shown passing to provide steam to the ethanol dehydration reactor in FIG. 1 . In an aspect, a portion of the treated water stream in line 188 (FIG. 1 ) is taken in line 288 and passed to the first steam generator 218 a, the second steam generator 218 b, the third steam generator 218 c, the fourth steam generator 218 d, and the fifth steam generator 218 c. In an embodiment, the treated water stream in line 288 is separated into five treated water streams, a first treated water stream in line 288 a, a second treated water stream in line 288 b, a third treated water stream in line 288 c, a fourth treated water stream in line 288 d, and a fifth treated water stream in line 288 e. The first treated water stream in line 288 a may be passed to the first steam generator 218 a to produce a first steam stream in line 233 a. The second treated water stream in line 288 b may be passed to the second steam generator 218 b to produce a second steam stream in line 233 b. The third treated water stream in line 288 c may be passed to the third steam generator 218 c to produce a third steam stream in line 233 c. The fourth treated water stream in line 288 d may be passed to the fourth steam generator 218 d to produce a fourth steam stream in line 233 d. The fifth treated water stream in line 288 e may be passed to the fifth steam generator 218 e to produce a fifth steam stream in line 233 e. The first steam stream in line 233 a, the second steam stream in line 233 b, the third steam stream in line 233 c, the fourth steam stream in line 233 d, and the fifth steam stream in line 233 e are combined to provide the combined steam stream in line 33. The combined steam stream in line 33 is mixed with the first charge stream in line 30 and passed to the ethanol dehydration reactor in FIG. 1 . There may be additional steam generators as needed and in one configuration there are seven steam generators which satisfy process steam demand of upstream ethanol dehydration unit. Process steam is generated using treated process water and use of boiler feed water is avoided. This has been done to reduce net wastewater quantity. In an aspect, the entirety of the treated water stream in line 188 (FIG. 1 ) is taken in line 288 and passed to the first steam generator 218 a, the second steam generator 218 b, the third steam generator 218 c, the fourth steam generator 218 d, and the fifth steam generator 218 e to generate steam in line 33.
Total demand of process steam is very high as compared to steam generation by reactor section steam generators. Hence a dedicated hot diesel driven steam generator is provided to generate balance process steam. This steam generator uses hot diesel as heating media which is pumped by the jet fractionator reboiler pumps which returns to the inlet of the jet fractionator reboiler heater.
The combined process steam is superheated by exchanging heat with olefin splitter bottoms in steam superheater and then sent to ethanol dehydration unit on pressure control.
When generating steam with treated process water, there is a potential risk of steam kettle fouling. Once fouling is identified, impacted steam generator can be isolated for maintenance. A common spare steam generator is provided which can take place of the fouled steam generator.

SPECIFIC EMBODIMENTS

While the following is described in conjunction with specific embodiments, it will be understood that this description is intended to illustrate and not limit the scope of the preceding description and the appended claims.
A first embodiment of the present disclosure is a process for operation of a dehydration reactor comprising adding an amount of steam to a feed to the dehydration reactor wherein the steam is taken from an oligomerization section of a hydrocarbon conversion plant. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the steam is generated from a treated process water produced by a wastewater stripper and then the water is sent to at least one steam generator connected to an oligomerization reactor to produce steam and wherein a portion of the steam is sent to the dehydration reactor. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein a portion of feed water is blown down from each of the at least one steam generators. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein a portion of the steam is sent from a hydrogenation reactor. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the steam cools down a hot effluent by a minimum amount up to about 187° C. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein a steam to alcohol ratio in the dehydration reactor is from about 0.3 to about 5.0 wt/wt. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein a portion of the steam is produced in a dedicated steam generator. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the steam is further heated by exchanging heat with an olefin splitter bottoms stream in a steam superheater. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein a plurality of steam generators are used to generate the steam. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein a recycle oil steam generator cools down hot diesel coming from a flash stripper feed-recycle oil exchanger. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the oligomerization section comprises an oligomerization reactor comprising a first oligomerization reactor vessel and a second oligomerization reactor vessel. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising an intercooler steam generator to remove heat of reaction from an oligomerized effluent stream before passing the oligomerized effluent stream to the second oligomerization reactor vessel. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising an intercooler steam generator between oligomerization catalyst beds in the first oligomerization reactor vessel to remove heat of reaction from an oligomerized effluent stream of a top oligomerization catalyst bed of the first oligomerization reactor vessel. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising an intercooler steam generator between oligomerization catalyst beds in the second oligomerization reactor vessel to remove heat of reaction from an oligomerized effluent stream of a top oligomerization catalyst bed of the second oligomerization reactor vessel. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the oligomerization section comprises a first stage oligomerization reactor and a second stage oligomerization reactor, and wherein an intercooler steam generator is provided to remove heat of reaction from an oligomerized effluent stream of the first stage oligomerization reactor before passing the oligomerized effluent stream to the second stage oligomerization reactor.
A second embodiment of the present disclosure is a process for operation of a dehydration reactor comprising adding a steam stream to a feed to the dehydration reactor to produce a charge stream; dehydrating the charge stream to produce a dehydrated stream; cooling the dehydrated stream to separate a water stream; and producing the steam stream from the separated water stream. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing the separated water stream to an oligomerization section to generate the steam stream. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising passing the separated water stream to a wastewater stripper to produce a stripped water stream; and passing the stripped water stream to the oligomerization section to generate the steam stream. An embodiment of the present disclosure is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph further comprising heating the separated water stream with an olefin charge stream of the oligomerization section to generate the steam stream.
A third embodiment of the present disclosure is a process for operation of a dehydration reactor, comprising adding a steam stream to a feed to the dehydration reactor to produce a charge stream; dehydrating the charge stream to produce a dehydrated stream; cooling the dehydrated stream to separate a water stream; and heating the separated water stream with an olefin charge stream of an oligomerization section to generate the steam stream.
Without further elaboration, it is believed that using the preceding description that one skilled in the art can utilize the present disclosure to its fullest extent and easily ascertain the essential characteristics of this disclosure, without departing from the spirit and scope thereof, to make various changes and modifications of the present disclosure and to adapt it to various usages and conditions. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limiting the remainder of the disclosure in any way whatsoever, and that it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.
In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

Claims

1. A process for operation of a dehydration reactor comprising adding an amount of steam to a feed to said dehydration reactor wherein said steam is taken from an oligomerization section of a hydrocarbon conversion plant.

2. The process of claim 1 wherein said steam is generated from a treated process water produced by a wastewater stripper and then said water is sent to at least one steam generator connected to an oligomerization reactor to produce steam and wherein a portion of said steam is sent to said dehydration reactor.

3. The process of claim 1 wherein a portion of feed water is blown down from each of said at least one steam generators.

4. The process of claim 1 wherein a portion of said steam is sent from a hydrogenation reactor.

5. The process of claim 1 wherein said steam cools down a hot effluent by a minimum amount up to about 187° C.

6. The process of claim 1 wherein a steam to alcohol ratio in said dehydration reactor is from about 0.3 to about 5.0 wt/wt.

7. The process of claim 1 wherein a portion of said steam is produced in a dedicated steam generator.

8. The process of claim 7 wherein said steam is further heated by exchanging heat with an olefin splitter bottoms stream in a steam superheater.

9. The process of claim 1 wherein a plurality of steam generators are used to generate said steam.

10. The process of claim 9 wherein a recycle oil steam generator cools down hot diesel coming from a flash stripper feed-recycle oil exchanger.

11. The process of claim 1, wherein the oligomerization section comprises an oligomerization reactor comprising a first oligomerization reactor vessel and a second oligomerization reactor vessel.

12. The process of claim 11 further comprising an intercooler steam generator to remove heat of reaction from an oligomerized effluent stream before passing said oligomerized effluent stream to the second oligomerization reactor vessel.

13. The process of claim 11 further comprising an intercooler steam generator between oligomerization catalyst beds in the first oligomerization reactor vessel to remove heat of reaction from an oligomerized effluent stream of a top oligomerization catalyst bed of the first oligomerization reactor vessel.

14. The process of claim 11 further comprising an intercooler steam generator between oligomerization catalyst beds in the second oligomerization reactor vessel to remove heat of reaction from an oligomerized effluent stream of a top oligomerization catalyst bed of the second oligomerization reactor vessel.

15. The process of claim 1, wherein the oligomerization section comprises a first stage oligomerization reactor and a second stage oligomerization reactor, and wherein an intercooler steam generator is provided to remove heat of reaction from an oligomerized effluent stream of the first stage oligomerization reactor before passing the oligomerized effluent stream to the second stage oligomerization reactor.

16. A process for operation of a dehydration reactor comprising:

adding a steam stream to a feed to said dehydration reactor to produce a charge stream;

dehydrating said charge stream to produce a dehydrated stream;

cooling said dehydrated stream to separate a water stream; and

producing said steam stream from said separated water stream.

17. The process of claim 16 further comprising passing said separated water stream to an oligomerization section to generate said steam stream.

18. The process of claim 17 further comprising:

passing said separated water stream to a wastewater stripper to produce a stripped water stream; and

passing said stripped water stream to the oligomerization section to generate said steam stream.

19. The process of claim 16 further comprising heating said separated water stream with an olefin charge stream of the oligomerization section to generate said steam stream.

20. A process for operation of a dehydration reactor, comprising:

dehydrating said charge stream to produce a dehydrated stream;

cooling said dehydrated stream to separate a water stream; and

heating said separated water stream with an olefin charge stream of an oligomerization section to generate said steam stream.