Steam integration in the ethanol to jet fuel process.

Abstract

An ethanol dehydration process is provided, in which the steam to ethanol ratio is 1.0-2.0 wt / wt, preferably 1.5 wt / wt. Steam can be taken from outside the dehydration process, for example from an oligomerization or dimerization reaction.

Description

[Technical Field]

[0001] (Priority statement) This application claims priority to Indian Provisional Patent Application No. 202211049526 filed on August 30, 2022.

[0002] FIELD OF THE INVENTION The present invention relates to an ethanol dehydration process. More particularly, the present invention relates to the generation of steam from oligomerization and hydrogenation reaction steam integration throughout the ethanol to jet fuel process. [Background technology]

[0003] Oil and gas refiners worldwide are exploring methodologies and pathways to reduce their carbon dioxide emissions and are moving toward sustainable processes. The ethanol-to-jet fuel process is one promising pathway to minimize or eliminate customers' carbon dioxide emissions. The end product of this process is jet fuel and diesel fuel produced from bioethanol. Jet fuel is a sustainable aviation fuel and is intended to replace jet fuel produced from traditional sources such as crude oil.

[0004] Generally, the process of converting ethanol to jet fuel has three main steps. First, the ethanol is dehydrated to produce ethylene. Next, the ethylene is converted to long-chain olefins, which are then hydrogenated to produce paraffins. This disclosure is primarily concerned with the conversion of an ethanol feedstream to paraffins. Summary of the Invention

[0005] A process for ethanol dehydration is provided, comprising adding an amount of steam to an ethanol feed stream, wherein the steam to ethanol ratio is between 1.0 and 2.0 wt / wt; and reacting the ethanol feed stream under reaction conditions in the presence of a catalyst to produce an ethylene effluent stream. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic process flow diagram of the present disclosure.

[0007] definition The term "communication" means operatively permitting the flow of materials between the listed components.

[0008] The term "downstream communication" means that at least a portion of the material flowing to the object in the downstream communication can operatively flow from the object in communication.

[0009] The term "upstream communication" means that at least a portion of the material flowing from the object in the upstream communication can operatively flow to the communicating object.

[0010] The term "direct communication" means that the stream from the upstream component enters the downstream component without passing through a fractionation or conversion unit and undergoing a change in composition by physical fractionation or chemical conversion.

[0011] The term "indirect communication" means that a stream from an upstream component enters a downstream component after passing through a fractionation or conversion unit and undergoing a change in composition by physical fractionation or chemical conversion.

[0012] The term "bypass" means that an object is out of downstream communication with a bypass subject, at least to the extent that it bypasses.

[0013] The term "column" refers to a distillation column or columns for separating one or more components of different volatility. Unless otherwise indicated, each column includes a condenser at the top of the column for condensing and refluxing a portion of the overhead stream that returns to the top of the column, and a reboiler at the bottom of the column for vaporizing a portion of the bottom stream and returning it to the bottom of the column. The feed to the column 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. The overhead and bottom lines refer to the net lines from column to column downstream of any reflux or reboil. A stripper column may omit the reboiler at the bottom of the column and instead provide the required heat and driving force for separation from a fluidized inert medium such as steam. A stripping column typically feeds the feed to the top tray and removes the main product from the bottom.

[0014] As used herein, the term "component-rich stream" means that the rich stream exiting the vessel has a higher concentration of the component than the feed to the vessel.

[0015] As used herein, the term "component lean stream" means that the lean stream exiting the vessel has a lower concentration of the component than the feedstock to the vessel.

[0016] As used herein, the term "separator" means a vessel having an inlet and at least an overhead vapor outlet and a bottoms liquid outlet, and may also have an aqueous outlet from a boot. A flash drum is a type of separator that may be in downstream communication with a separator that may be operated at a higher pressure.

[0017] As used herein, the term "predominant" or "predominantly" means more than 50%, suitably more than 75%, and preferably more than 90%.

[0018] As used herein, "C x " should be understood to refer to a molecule having the number of carbon atoms represented by the "x" subscript. xThe term "-" refers to a molecule containing less than or equal to x, preferably x and less, carbon atoms. x The term "+" refers to a molecule having more than or equal to x, preferably x and more, carbon atoms.

[0019] As used herein, the term "carbon number" refers to the number of carbon atoms per hydrocarbon molecule, typically a paraffin molecule. DETAILED DESCRIPTION OF THE INVENTION

[0020] Ethanol feeds are obtained from either wet mill or dry mill processes. These ethanol feedstocks may contain various contaminants such as higher alcohols, metals, acetaldehyde, ethyl acetate, etc. In addition, dry mill feedstocks may also contain fusel oils (heavier alcohols and acids). Ethanol feedstocks may be treated to remove metal contaminants by the use of resin treaters. Heavy hydrocarbons from the fresh feedstock may be knocked out in feed purification columns.

[0021] Fresh ethanol feedstock is mixed with unconverted ethanol and split into two equal streams entering a parallel mixed feed exchanger. A split reactor configuration is considered if the desired steam-to-ethanol ratio is maintained at the reactor inlet. This is to maintain the reactor's endothermicity and ensure catalyst stability. Reducing steam intake is essential to minimize the combined reactor feed rate. The ethanol dehydration reaction generates water as a byproduct. The ethanol dehydration process requires steam injection in the process to obtain the desired catalyst life and maintain operation below the maximum endothermic temperature in an adiabatic system. It has been determined that the optimal steam-to-ethanol ratio should be between 1.0 and 2.0 wt / wt (preferably 1.5). In addition, several columns in the unit (including the feed purification column and wastewater stripper) may also be reboiled using steam. Because the ethanol dehydration reactor operates in the gas phase, generating steam from product water can be energy-intensive (condensation and evaporation of product water). To overcome this issue, it has been concluded that it is preferable to intake steam (~100 psig) from outside the dehydration battery limits. The exothermic oligomerization and hydrogenation reactions can be good sources of steam generation, and good integration opportunities exist to meet the demand for steam.

[0022] The oligomerization step of the ethanol-to-jet fuel process uses a high-temperature reactor at an upstream location. Interbed temperature control can be achieved using steam generation. Steam levels can be set at 100 psig to cool the hot effluent to a minimum of 370°F (187°C). The convection section of the jet fractional reboiler can also be a good steam source.

[0023] For a 300 MMGPY ethanol unit, the total steam flow rate is estimated to be ∼140 klb / hr, which can meet the ethanol dehydration steam injection requirements.

[0024] 1 illustrates a process 10 for treating an oxygenate feedstock according to one exemplary embodiment. The oxygenate feedstock may include an alcohol, preferably ethanol. The feedstock may include ethanol as a primary component and may be aqueous. Preferably, the oxygenate feedstock is a biorenewable feedstock.

[0025] Feed line 12 transports the oxygenate stream of the oxygenate feedstock to feed pretreatment section 14. Feed pretreatment section 14 includes vessel 16 containing a bed of cation exchange resin adsorbent for removing metal contaminants, such as sodium, zinc, phosphate, copper, and calcium, from the oxygenate stream in feed line 12. Feed pretreatment section 14 may include an additional vessel 18 containing a bed of the same adsorbent for further removal of metals from the oxygenate stream. Vessels 16, 18 may be in a series or lead-lag configuration to allow for regeneration of spent adsorbent. Line 17 transports the partially pretreated oxygenate stream from the outlet of vessel 16 to the inlet of vessel 18. The pretreated oxygenate stream exits feed pretreatment section 14 from the outlet of additional vessel 18 in line 20 and is fed to purification column 22. Feed pretreatment section 14 may be operated at a temperature of 32°C to 104°C and a pressure of 670 kPa(g) or atmospheric pressure.

[0026] In refinery column 22, the pretreated oxygenate stream is fractionated to separate ethanol from heavier oxygenates, also known as fusel oils, such as cyclohexanol, cyclopentanol, and heavier alcohols and acids. Refinery column 22 is operated to minimize ethanol to 1% or less of the feed in a bottoms stream in line 26. A heavy oxygenate stream in bottoms line 26 is removed from the bottom of refinery column 22 to heavy oxygenate processing. Refinery column 22 may be reboiled by heat exchange with a suitable high-temperature stream, such as steam, to provide the heat necessary for distillation. Refinery column 22 provides an overhead gas stream of purified ethanol in overhead line 24 that may be cooled in air cooler 25 and fed to feed surge drum 26 along with a recycled ethanol stream in line 27. Refinery column 22 may be operated at a bottoms temperature of 82°C to 121°C and an overhead pressure of 35 kPa(g) to 140 kPa(g).

[0027] The ethanol in the feed surge drum 26 may be blanketed with nitrogen. A charge pump 29 pumps the ethanol charge stream in line 28 into two charge streams. The first charge stream in line 30 is heat exchanged with a first dehydration exchange stream in line 32, mixed with steam in line 33, and supplied to a first charge heater 34. The first charge heater 34 may be a fired heater and may heat the first charge stream to 400°C to 550°C. The resulting first heated charge stream in line 36 is supplied to a first dehydration reactor 40. In the first dehydration reactor 40, the ethanol feedstock is converted to ethylene and water over a dehydration catalyst at a pressure of 455 kPa(g) to 630 kPa(g). The first dehydration stream is discharged from the first dehydration reactor 40 in line 42.

[0028] The second charge stream in line 44 is heat exchanged with the second dehydration exchange stream in line 46, mixed with the first dehydration stream in line 42, and supplied to a second charge heater 48. The second charge heater 48 may be a combustion heater and may heat the second charge stream to 400°C to 550°C. The resulting heated second charge stream in line 50 is supplied to a second dehydration reactor 52. In the second dehydration reactor 52, the ethanol feedstock is converted to ethylene and water over a dehydration catalyst at a pressure of 420 kPa(g) to 700 kPa(g). The second dehydration stream is discharged from the second dehydration reactor 52 in line 54.

[0029] The second dehydrated stream in line 54 is supplied to an intermediate heater 56, which may be a fired heater and may heat the second dehydrated stream to between 400°C and 550°C. The resulting third heated charge stream in line 58 is supplied to a third dehydration reactor 60, where the residual ethanol feedstock is converted to ethylene and water over a dehydration catalyst at a pressure between 420 kPa(g) and 700 kPa(g). The third dehydrated stream is discharged from the third dehydration reactor 60 in line 62.

[0030] The dehydration catalyst can be an alumina-based catalyst.

[0031] The third dehydrated stream is split into a first dehydrated exchange stream in line 32 and a second dehydrated exchange stream in line 46. The first dehydrated exchange stream in line 32 exchanges heat with the first charge stream in line 30, the second dehydrated exchange stream in line 46 exchanges heat with the second charge stream in line 44, and the cooled dehydrated streams are recombined in line 64.

[0032] The cooled dehydrated stream in line 64 is fed to quench tower 68 where it is quenched by direct contact with water from a first cooling water stream in line 70 and a second cooling water stream in line 72. A quenched ethylene stream exits through quench tower overhead line 74, and a bottoms stream exits the bottoms in line 76. The bottoms stream is split into a drain stream in line 78 which can be transported to a waste water stripper column 80 via a control valve thereon, and a quench recycle stream in line 82. A first portion of the quench recycle stream is air cooled in product condenser 69 and recycled through a control valve thereon as a first lower cooled water stream in line 70, and a second portion of the quench recycle stream is heat exchanged in trim condenser 71 and recycled to quench tower 68 as a second higher cooled water stream in line 72. Quench column 68 may be operated at a bottom temperature between 37°C (100°F) and 104°C (220°F) and an overhead pressure between 280 kPa (gauge) (40 psig) and 490 kPa (gauge) (70 psig).

[0033] The quenched ethylene stream in line 74 is fed to first-stage suction drum 86. In the first-stage suction drum, ethylene exits overhead line 88 to 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 wastewater stripper column 80, possibly via line 78. First-stage compressor 90 compresses the ethylene stream to a first pressure of 350 kPa (gauge) (50 psig) to 1225 kPa (gauge) (175 psig), and the effluent in line 91 is cooled in first-stage effluent cooler 93 and first-stage trim cooler 94.

[0034] The cooled, compressed ethylene stream from first-stage trim cooler 94 is fed to first-stage discharge drum 96. From first-stage discharge drum 96, ethylene exits overhead line 98 to second-stage compressor 100, while residual water exits the bottom of the drum in line 102 through a control valve thereon and is transported to wastewater stripper column 80, possibly via lines 92 and 78. The second-stage compressor compresses the ethylene stream to a second pressure of between 455 kPa(g) and 3220 kPa(g), and the effluent in line 101 is cooled in second-stage effluent cooler 103 and second-stage trim cooler 104.

[0035] The twice-cooled, compressed ethylene stream from second-stage trim cooler 104 is fed to second-stage discharge drum 106. From second-stage discharge drum 106, ethylene exits overhead line 108 and is transported to water wash column 110, while a residual water stream exits the bottom of the drum in line 112 through a control valve thereon and is transported to wastewater stripper column 80, possibly via lines 102, 92, and 78.

[0036] In water wash tower 110, the twice-cooled and compressed ethylene stream is washed countercurrently with cooled, treated water in line 118 from wastewater stripper column 80 to absorb additional oxygenates and produce a washed ethylene stream exiting in overhead line 120 and a wash water stream in bottoms line 122. The washed ethylene stream in overhead line 120 is transported to caustic scrubber column 116. The wash water stream in line 122 is returned to water stripper column 80 through a control valve thereon. Wash water 110 may be operated at a bottoms temperature of 16°C to 82°C and an overhead pressure of 2800 kPa(g) to 3500 kPa(g).

[0037] Caustic scrubber column 116 has a lower caustic wash section 124 and an upper water wash section 132. In 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 from the bottom of the lower section in line 128 and replenished with fresh caustic in line 130 to provide aqueous caustic stream 126. The scrubbed vapor ethylene stream, with acid gases removed, ascends from caustic wash section 124 through a steam inlet to upper water wash section 132. In water wash section 132, the scrubbed ethylene stream is contacted with a wash water stream from line 134. The washed, scrubbed vapor ethylene stream exits the top of water wash section 132 in line 136 and is fed to product dryer section 140. A spent water stream is removed from the bottom of water wash section 132 from the liquid sump in line 142 and is supplemented with a fresh water stream from line 144 to provide a wash water stream in line 134 which is pumped to the top of water wash section 124 for contact with the scrubbed vapor ethylene stream. The caustic scrubber column may be operated at a bottom temperature of 38°C to 43°C and an overhead pressure of 2800 kPa(g) to 2975 kPa(g).

[0038] In product dryer section 140, the washed and scrubbed ethylene stream in line 136 is fed to a first dryer inlet knockout drum 146 to remove residual water, providing a dryer inlet stream in line 148 and, possibly, a knockout water stream in a bottoms line 150 that is fed to wastewater stripper column 80 via line 122. The dryer inlet stream is fed in line 148 to a first product dryer 152. First product dryer 152 contains an adsorbent for adsorbing water from the ethylene in the dryer inlet stream in line 148 to provide a dried ethylene stream. The adsorbent may be a molecular sieve material having a pore size of 2 to 4 Å. First product dryer 152 may be operated in an upflow mode. Product dryer section 140 may include a second product dryer 156 that operates as first product dryer 142. The two product dryers may be operated in series, but are preferably arranged in lead-lag operation to facilitate regeneration during continuous operation. Second product dryer 156, like first product dryer 152, contains an adsorbent for adsorbing water from the ethylene. A dry ethylene stream exits product dryer section 140 in line 158. Product dryer section 140 may be operated at a temperature between 32°C (90°F) and 49°C (120°F) and a pressure between 2758 kPa (gauge) (400 psig) and 3102 kPa (gauge) (450 psig).

[0039] The dried ethylene stream in line 158 is fed to a dryer outlet knockout drum 160 to remove residual water and provide a dryer outlet stream in line 162 and a second knockout water stream in bottoms line 164 which is possibly fed to wastewater stripper column 80 via lines 150 and 122.

[0040] The dryer effluent stream in line 162 may be fed to a heavy oxygenate removal column 170 to separate an overhead stream containing primarily ethylene, but possibly higher olefins, from heavy ketones and diethyl ether. Olefins are produced in overhead line 172 and fed to a third-stage compressor 174, and a bottom heavy oxygenate stream is produced in bottoms line 176. A heavy oxygenate purge stream may be taken to heavy oxygenate processing in line 178, while the reboil portion is reboiled and returned to column 170. The compressed ethylene stream in compressor discharge line 176, at a pressure of 2800 kPa (gauge) (400 psig) to 7000 kPa (gauge) (1000 psig), may be provided to the dimerization section. Heavy oxygenate removal column 170 It can be operated at bottom temperatures of -20°F to 250°F and overhead pressures of 350 psig to 450 psig.

[0041] The water streams containing oxygenates and volatiles in lines 92, 102, 112, 122, 150, and 164 may be fed to wastewater stripper column 80, where the volatiles and oxygenates are boiled off to provide an overhead volatiles stream in line 182 and a stripped water stream in line 184. A portion of the stripped water stream may be reboiled and returned to the column to provide the necessary heat. The treated water stream in line 186 may be pumped to a water outlet in line 188 containing the cooled, treated water stream in line 118 for water wash tower 110. Wastewater stripper column 80 may be operated at a bottom temperature of 93°C (200°F) to 121°C (250°F) and an overhead pressure of 34 kPa (gauge) to 138 kPa (gauge) (20 psig).

[0042] The overhead volatiles stream in line 182 may be cooled in air cooler 189 and fed to off-gas knockout drum 190. The overhead stream from knockout drum 190 in line 192 may be sent to a flare, while the ethanol recycle stream is pumped to feed surge drum 26 in line 27, possibly via line 24.

Claims

1. 1. A process for ethanol dehydration, comprising: adding an amount of steam to an ethanol feed stream, wherein the steam to ethanol ratio is between 1.0 and 2.0 wt / wt; and reacting the ethanol feed stream under reaction conditions in the presence of a catalyst to produce an ethylene effluent stream.

2. 2. The process of claim 1, wherein the steam to ethanol ratio is 1.

5.

3. 10. The process of claim 1, wherein a portion of the steam is captured from outside the ethanol dehydration process.

4. 10. The process of claim 1, wherein said amount of steam is derived from an oligomerization or hydrogenation reaction.

5. 10. The process of claim 1, wherein a portion of the steam is produced by a wastewater stripper and then heated in an oligomerization section.

6. 6. The process of claim 5, wherein a portion of the water is removed to minimize the buildup of impurities.

7. The process of claim 1 , wherein the steam is generated in a dedicated steam generator.

8. 8. The process of claim 7, wherein the vapor is further heated by heat exchange with the bottom of the olefin splitter in a flow superheater.

9. 10. The process of claim 1, wherein at least five steam generators are used to generate the steam.

10. 10. The process of claim 1, wherein the recycle steam generator cools hot diesel coming from the flash stripper feed-recycle oil exchanger.

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