Radial flow reactor for ethanol dehydration process.

Abstract

A process for the dehydration of an ethanol feed stream comprising passing the ethanol feed stream and steam to a radial flow reactor for contact with a catalyst under reactive conditions to produce an effluent comprising ethylene. The use of a radial flow reactor eliminates pressure drop concerns that can occur in conventional fixed-bed downflow reactors.

Description

[Technical Field]

[0001] (Statement of priority) This application claims priority to Indian Provisional Patent Application No. 202211049528 filed on August 30, 2022.

[0002] FIELD OF THE INVENTION This application relates to an ethanol dehydration process. More specifically, this application relates to the use of a radial reactor in an ethanol dehydration process to produce ethylene that can be further processed to make jet fuel. [Background technology]

[0003] Oil and gas refiners around the world are exploring methodologies and pathways to reduce their carbon footprint and are moving toward sustainable processes. The ethanol-to-jet fuel process is one promising pathway to minimize or eliminate customers' carbon footprints. 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 involves three main steps: first, dehydration of the ethanol to produce ethylene, then conversion of the ethylene to long-chain olefins, which are then hydrogenated to produce paraffins. Summary of the Invention

[0005] 1. A process for the dehydration of an ethanol feed stream, comprising passing the ethanol feed stream and steam to a radial flow reactor for contact with a catalyst under reactive conditions to produce an effluent comprising ethylene. [Brief explanation of the drawings]

[0006] [Figure 1] 1 shows a flow scheme of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0007] The ethanol dehydration process unit is divided into six major sections: feed pretreatment section, feed purification section, reactor section, ethylene compression section, and water wash section.

[0008] The feed pretreatment section can remove metals by using an ion exchange resin guard bed. The feed pretreatment section is configured in a lead / lag flow scheme so that one vessel can be taken offline and reloaded while the other vessel is online. The ion exchange resin supplier recommends a regenerable system using HCl or sulfuric acid as the regenerant. Because the unit has stainless steel metallurgy, HCl regenerant is not suitable. A regenerable system using sulfuric acid, if implemented, would require careful consideration and review. Ion exchange resin would have the highest capacity. Currently, it is not considered necessary to have feed pretreatment for metal contents below <1.0 wppm.

[0009] The demetallized product from the feed pretreatment section is sent through the tube side of a fresh feed-to-overhead steam exchanger to a feed purification column (FPC). This column is designed to purge out heavier molecules that occur with the ethanol feed through the column bottoms. The heavier molecules may consist of components such as, but not limited to, C3+ alcohols, acetals, hexadecanoic acid, octadecanoic acid, isopentyl acetate, cyclohexanol, cyclopentanol, phenol, cresols, and acetals. Some of these heavier molecules may be converted to ketones in the reactor and tend to accumulate without exiting the process; therefore, they need to be removed or minimized before the feed can be sent to the reactor section. The bottoms sparge is expected to be <1.0% of the total feed, consisting of concentrated heavies such as acetic acid, acetals, cresols, phenols, free fatty acids such as hexadecanoic acid and octadecanoic acid, and some heavy alcohols; the column bottoms sump is swaged and designed to hold the heavy purge material for typically 24 hours, which can be purged to an ethanol slop tank.

[0010] Due to the absence of dissolved light ends expected in the ethanol feedstock, a full condensation system is preferred for this column. The receiver pressure, controlled by a nitrogen push-pull system, is set to allow the use of MP steam as the reboil medium for the column. Vapor from the column overhead is condensed first in the shell side of the fresh feed-to-overhead vapor exchanger and then in the feed purification column overhead condenser before entering the feed purification column receiver. The receiver liquid is pumped at its bubble point by the feed purification column net overhead pump and further subcooled in the feed purification column net overhead cooler. The subcooled material is mixed with the liquid ethanol recycle stream and cooled in the diethyl ether (DEE) absorber feed cooler before entering the DEE absorber on the top tray or feed surge drum (see discussion below).

[0011] The DEE absorber is suspended in the dehydration separator vapor stream entering below the bottom tray of the DEE absorber; this column is provided to remove diethyl ether from the dehydration separator vapor. The DEE absorber bottom sump is designed to provide a 15-minute residence time for the liquid feed entering the reactor section. If the DEE absorber is not considered part of the design, a feed surge drum with a 15-minute residence time should be provided, and the FPC net overhead liquid mixed with the recycled ethanol would enter the feed surge drum instead of the DEE absorber. If the FPC is not included as part of the design, the fresh ethanol feed plus the recycled ethanol stream can be sent to either the DEE absorber (if considered part of the specific design) or the feed surge drum.

[0012] The reactor section includes the following elements: The feed surge drum liquid or DEE absorber bottoms liquid stream is pumped to the reactor section via a dehydration charge pump. The discharge stream is first preheated in an ethanol process water exchanger. The preheated ethanol is split into two streams with flow control. The first split of the feed stream is heated and vaporized in an ethanol-jet product exchanger, an ethanol-hydrogenation reactor feed exchanger (both of which are located within the oligomerization unit), and a first ethanol steam heater before entering the cold side (tube side) of combined feed exchanger 1 (CFE1), followed by a charge heater. Before entering CFE1, the vaporized feed is mixed with steam generated in a steam generator located in the downstream oligomerization unit. The combined stream is heated to the required reaction temperature in the charge heater and sent to the first reactor.

[0013] The ethanol dehydration reaction is endothermic in nature. Water is a by-product of the dehydration reaction, and the water produced in the first reactor satisfies the steam requirements of downstream reactors. The second split of the feed stream is heated and vaporized in the ethanol-second-stage oligomerization lag reactor feed exchanger, the ethanol-second-stage oligomerization lead reactor feed exchanger (both located within the oligomerization unit), and the second ethanol steam heater before entering the cold side (tube side) of the second combined feed exchanger (CFE2). At the cold side outlet of CFE2, the feed stream is mixed with the first reactor effluent and sent to the first interheater, where the stream is further heated to the required reaction temperature. While steam does not participate in the reaction (although there may be some minor side reactions), steam added to the reactor serves the dual purpose of controlling the endothermic heat across the reactor and maintaining catalyst stability (reducing coke deposition). Because diethyl ether formation is more pronounced at lower reactor outlet temperatures, it is important to minimize the temperature drop across the reactor. To ensure limited diethyl ether formation, the second reactor effluent is passed through a second interheater and reheated to the required reactor temperature before being sent to the third reactor. The third reactor is a polishing reactor that ensures that the diethyl ether, along with any unconverted ethanol, is converted to useful ethylene. The third reactor effluent is split and passes through the hot side (shell side) of CFE1 and CFE2. The hot side outlet from the combined feed exchanger is further cooled and condensed in a wastewater stripping reboiler followed by a dehydration product condenser before entering the dehydration separator.

[0014] The dehydration separator liquid stream is primarily water with some dissolved oxygenates, and the stream is sent to a low-pressure wastewater stripper, while the vapor stream is essentially ethylene product. As noted above, the dehydration separator vapor is sent to a DEE absorber. If a DEE absorber is not considered part of the design, the separator vapor is sent to a water wash tower.

[0015] The fired heaters used in the reactor section are designed as natural draft furnaces, with the primary process heating occurring in the radiant section, while the convection section of these fired heaters is designed to generate high-pressure steam, similar to the fired heater convection section configuration of the CCR platforming process unit.

[0016] The ethylene compression section includes the following factors: The pressure requirement of the vapor product stream to the downstream oligomerization unit is greater than 1000 psig, which is achieved by a four or five stage compressor system. Four stages may be specified for reciprocating machines, while five stages may be specified for centrifugal machines. In one embodiment, there will be a four stage reciprocating machine, one active and one standby. The number of stages is based on the pressure requirements of the downstream units, and the compressor discharge temperature may be limited to less than 195°F.

[0017] The vapor from the water wash tower mixes with the first-stage ethylene compressor spillback before entering the first-stage ethylene compressor suction drum to knock out any entrained liquid. The vapor from the drum is compressed in the first-stage ethylene compressor, and the compressor discharge is cooled in the first-stage discharge cooler and first-stage discharge trim cooler. The cooled stream further mixes with the second-stage ethylene compressor spillback before entering the first-stage ethylene compressor discharge drum. The vapor from the first-stage ethylene compressor discharge drum is split into two streams: the first stream is the first-stage ethylene compressor spillback, while the second stream is the net vapor stream entering the second-stage ethylene compressor. The vapor is further compressed in the second-stage ethylene compressor, and the compressor discharge is cooled in the second-stage discharge cooler and second-stage discharge trim cooler. The cooled stream further mixes with the third-stage ethylene compressor spillback before entering the second-stage ethylene compressor discharge drum. The vapor from the second-stage ethylene compressor discharge drum is split into two streams: the first stream is the second-stage ethylene compressor spillback, while the second stream is the net vapor stream entering the third-stage ethylene compressor. The vapor is further compressed in the third-stage ethylene compressor, and the compressor discharge is cooled in a third-stage discharge cooler and a third-stage discharge trim cooler before entering the third-stage ethylene compressor discharge drum. The vapor from the third-stage ethylene compressor discharge drum is split into two streams: the first stream is the third-stage ethylene compressor spillback, while the second stream is the net vapor product entering the ethylene dryer to remove saturated moisture.

[0018] Dry vapor from the ethylene dryer is mixed with the fourth-stage ethylene compressor spillback and enters the fourth-stage ethylene compressor suction drum. After being compressed in the fourth-stage ethylene compressor, the vapor enters the fourth-stage ethylene compressor discharge drum. The fourth-stage ethylene compressor discharge drum vapor is split into two streams: the first stream is the fourth-stage ethylene compressor spillback, while the second stream is the net vapor product sent to the oligomerization unit. Unlike the upstream stages, the fourth-stage ethylene compressor discharge is not cooled; the hot vapor stream is sent directly to the oligomerization unit. To ensure that the fourth-stage ethylene compressor discharge temperature does not exceed recommended limits, a fourth-stage spillback cooler is added on the compressor spillback line.

[0019] The saturated water in the vapor from the water wash tower is partially knocked out in the first-stage ethylene compressor suction and discharge drums and the second- and third-stage ethylene compressor discharge drums. The knocked-out liquid is mostly water, and this condensation occurs due to the increase in pressure and decrease in intermediate temperature. The knocked-out drum liquid is sent to the wastewater stripper.

[0020] Two ethylene dryers loaded with molecular sieves are designated for moisture removal from the ethylene vapor product and are operated in lead-lag mode. When the molecular sieves in the lead dryers become saturated with moisture, the dryers must be regenerated to restore sieve capacity. Dry ethylene vapor from the lag dryers is used as the regenerant medium. A slipstream from the lag dryer outlet is sent to a regenerant superheater, where the regenerant is heated to the required regeneration temperature before entering the regenerating dryer. The spent regenerant from the regenerating dryer, carrying moisture desorbed from the molecular sieves, is cooled and condensed in a regenerant condenser before entering a regenerant coalescer. The regenerant coalescer separates water from the spent regenerant, i.e., ethylene. The ethylene vapor is pressure-controlled returned to the first-stage ethylene compressor suction drum, while the spent water is sent to a wastewater stripper.

[0021] The wastewater section consists of a wastewater stripper and a water wash tower. Liquid from the dehydration separator, water wash tower bottoms, regenerant coalescer (intermittent), and knocked-out liquid from the ethylene compressor section knockout drum enter the upper tray of the wastewater stripper after being routed through the shell side of the wastewater stripper feed-to-bottoms exchanger. The wastewater stripper is designed to strip off oxygenates that come with the feed as overhead vapor product while recovering treated water in the bottoms.

[0022] The wastewater stripper operates at 5 to 10 psig, and the overhead vapor enters the off-gas knockout drum after being cooled and condensed in the off-gas condenser. The off-gas knockout drum liquid contains most of the alcohol carried over from the DEE absorber vapor (if a DEE absorber is part of the design), unconverted alcohol from the reactor, and water along with other non-selective oxygenates formed in the reactor, such as acetaldehyde, ethers, and acetic acid. These are recycled, mixed with fresh feed, and sent to the reactor section through the feed surge drum or DEE absorber bottoms (if included as part of the design). The off-gas knockout drum vapor is a small purge stream containing a mixture of olefins (dissolved in the dehydration separator and water wash column liquid) and oxygenates. This purge gas stream is mixed with the low-pressure off-gas stream produced in the downstream oligomerization unit and further compressed in the waste off-gas compressor to the required fuel gas knockout drum pressure before being combusted in a combined-fired heater. The wastewater stripper has a two-reboiler system. One reboiler, the wastewater stripper auxiliary reboiler, utilizes low-pressure steam as the reboil medium (expected to operate during startup and as an auxiliary backup), while the other reboiler, the wastewater stripper reboiler, is process heat integrated with the hot dehydration reactor effluent upstream of the dehydration product condenser. The wastewater stripper net bottoms is pumped by a process water pump through the tube side of the wastewater stripper feed-to-bottoms exchanger and split downstream into three streams. The first stream is process water used for washing the vapor product oxygenates in the water wash tower. This stream is sent to the water wash tower via an ethanol-to-process water exchanger, a process water cooler, and a process water trim cooler.

[0023] The second stream is process water equivalent to the steam injected into the dehydration reactor plus 5% blowdown. This stream is sent to a steam generator located in the downstream oligomerization unit reactor section for heat recovery. The generated steam is recycled back to the dehydration reactor to meet the steam-to-ethanol ratio requirements. The continuous blowdown from the steam generator is sent directly to a wastewater treatment plant. This stream is split upstream of the ethanol-to-process water exchanger.

[0024] The third stream is the net effluent produced from the various reactions occurring in the reactor section and is sent to a wastewater treatment facility; this stream is removed downstream of the effluent trim cooler.

[0025] As previously mentioned, the dehydration separator vapor can be sent to a DEE absorber (if included as part of the design) or a water wash tower. The dehydration separator vapor has certain impurities / oxygenates such as acetaldehyde, diethyl ether, dimethyl ether, water, unconverted alcohols, etc. that need to be removed before the vapor product stream is sent to the downstream oligomerization unit.

[0026] In the DEE absorber, diethyl ether in the separator vapor is absorbed into the bottom liquid along with some other oxygenates. Because ethanol feed is used to wash the separator vapor, there is some carryover of ethanol feed into the DEE absorber vapor. The DEE absorber overhead vapor is sent below the bottom tray of the water wash tower. The water wash tower is designed to wash away oxygenates such as acetaldehyde, unconverted alcohol from the reactor section, ethanol carryover from the DEE absorber vapor, and acetic acid using process water from the wastewater stripper bottoms. Process water enters the top tray of the water wash tower, and oxygenate absorption occurs countercurrently across multiple trays. The washed water wash tower overhead vapor is sent to the downstream ethylene compression section, while the liquid bottom stream containing all dissolved oxygenates / alcohols is sent to the wastewater stripper.

[0027] The ethanol dehydration reactor section is operated at low pressure psig and the operating temperature is high, in the range of 400-550°C. Apart from the operating conditions, the molecular weight and The density is lower. All these factors contribute to This results in a very high volumetric velocity through the reactor. At such a high volumetric velocity, Specifying a conventional downflow reactor becomes very difficult.

[0028] In a fixed-bed downflow reactor, assuming high volumetric velocities, The pressure drop through the catalyst bed ranges from 15 to 50 psi. The reactor section is Operates at lower pressures Increasing the bed pressure drop beyond 3-5 psi is not recommended. The higher the pressure in the reactor section, the Conversion and ethylene selectivity are low. It is necessary to minimize the pressure drop across the reactor bed. Instead of a fixed-bed downflow reactor, a fixed-bed radial flow design is used. In a fixed-bed radial flow design, the expected bed pressure drop will be as low as 3-5 psi, which is the pressure required for the process. Apart from the low bed pressure drop, a radial bed design can help improve vapor distribution.

[0029] 1 illustrates a process 10 for processing 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 or may be aqueous. Preferably, the oxygenate feedstock is a biorenewable feedstock.

[0030] 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 type 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 temperatures between 32°C and 104°C and pressures between atmospheric and 690 kPa(g).

[0031] 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. The 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, which 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).

[0032] 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 the first dehydration exchange stream in line 32, mixed with steam in line 33, and fed to a first charge heater 34. The first charge heater 34 may be a combustion heater and can heat the first charge stream to 400°C to 550°C. The resulting heated first charge stream in line 36 is input to a first dehydration reactor 40. In the first dehydration reactor 40, the ethanol feed 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 into line 42.

[0033] The second charge stream in line 44 is heat exchanged with the 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 combustion heater and is capable of heating the second charge stream to 400°C to 550°C. The resulting second heated charge stream in line 50 is input to a second dehydration reactor 52. In the second dehydration reactor 52, the ethanol feed is converted to ethylene and water over a dehydration catalyst at a pressure of 420 kPa(g) to 700 kPa(g). The second dehydrated stream is discharged from the second dehydration reactor 52 in line 54.

[0034] The second dehydrated stream in line 54 is fed to an interheater 56, which may be a fired heater and is capable of heating the second dehydrated stream to between 400°C and 550°C. The resulting third heated charge stream in line 58 is input to a third dehydration reactor 60, where the residual ethanol feed 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.

[0035] The dehydration catalyst is an alumina-based catalyst.

[0036] 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 is heat exchanged with the first charge stream in line 30, 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.

[0037] 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 cooled water stream in line 70 and a second cooled water stream in line 72. The quenched ethylene stream exits in quench overhead line 74, and a bottoms water stream exits the tower bottoms in line 76. The bottoms water stream is split into a drain stream in line 78 which can be transported to a wastewater stripper column 80 through a control valve on line 78, 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 on line 70 as a first cooler 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 warmer cooled water stream in line 72. The quench tower 68 may be operated at a bottoms temperature of 37°C to 104°C and an overhead pressure of 280 kPa(g) to 490 kPa(g).

[0038] 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 on line 92 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(g) to 1225 kPa(g), and the discharge in line 91 is cooled in first stage discharge cooler 93 and first stage trim cooler 94.

[0039] 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 in overhead line 98 to second-stage compressor 100, while residual water exits the bottom of the drum in line 102 through a control valve on line 102 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 455 kPa (gauge) (165 psig) to 3220 kPa (gauge) (460 psig), and the discharge in line 101 is cooled in second-stage discharge cooler 103 and second-stage trim cooler 104.

[0040] 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 in overhead line 108 and is transported to water wash tower 110, while a residual water stream exits the bottom of the drum in line 112 through a control valve on line 112 and is transported to wastewater stripper column 80, possibly via lines 102, 92, and 78.

[0041] 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, absorbing additional oxygenates to produce a washed ethylene stream exiting 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 transported back to water stripper column 80 through a control valve on line 122. Wash water 110 can be operated at a bottoms temperature of 16°C (60°F) to 82°C and an overhead pressure of 2800 kPa(g) to 3500 kPa(g).

[0042] The caustic scrubber column 116 includes 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 circulated 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. The scrubbed vapor ethylene stream, depleted of acid gases, ascends from the caustic wash section 124 through a vapor inlet to the upper water wash section 132. In the water wash section 132, the scrubbed ethylene stream contacts a wash water stream from line 134. The washed, scrubbed vapor ethylene stream exits the water wash section 132 overhead in line 136 and is supplied to the product dryer section 140. A spent water stream is removed from the liquid sump from the bottom of water wash section 132 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 to contact the scrubbed vapor ethylene stream. The caustic scrubber column may be operated at a bottoms temperature of 38°C to 43°C and an overhead pressure of 2800 kPa(g) to 2975 kPa(g).

[0043] In product dryer section 140, the washed, scrubbed ethylene stream in line 136 is fed to a first dryer inlet knockout drum 146 to remove residual water and provide a dryer inlet stream in line 148 and a knockout water stream in bottoms line 150, which is fed to wastewater stripper column 80, possibly 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 operate in an upflow mode. Product dryer section 140 may also include a second product dryer 156 operating 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. The second product dryer 156, like the first product dryer 152, is equipped with an adsorbent for adsorbing water from the ethylene. The dry ethylene stream exits product dryer section 140 and enters the dry ethylene stream in line 158. Product dryer section 140 may be operated at a temperature of 32 to 49°C and a pressure of 2750 to 3100 kPa(g).

[0044] 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 that is fed to wastewater stripper column 80, possibly via lines 150 and 122.

[0045] The dryer effluent stream in line 162 can be fed to heavy oxygenate removal column 170 to separate the overhead stream, containing primarily ethylene but possibly higher olefins, from the heavy ketones and diethyl ether. Olefins are produced in overhead line 172 and fed to third-stage compressor 174, and a bottoms heavy oxygenate stream is produced in bottoms line 176. A heavy oxygenate purge stream may be removed in line 178 for heavy oxygenate processing, 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(g) may be fed to the dimerization section. Heavy oxygenate removal column 170 can operate at a bottoms temperature of -20°F to 250°F and an overhead pressure of 350 psig to 450 psig.

[0046] The water stream 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 back to the column to provide the necessary heat. The treated water stream in line 186 may be cooled in line 118 for water wash tower 110 and pumped in line 188 to a water outlet containing the cooled treated water stream. Wastewater stripper column 80 may be operated at a bottoms temperature of 93° C. to 121° C. and an overhead pressure of 34 kPa(g) to 138 kPa(g).

[0047] 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 in line 27 to feed surge drum 26, possibly via line 24.

Claims

1. 1. A process for the dehydration of an ethanol feed stream, comprising: passing the ethanol feed stream and steam to a radial flow reactor for contact with a catalyst under reactive conditions to produce an effluent comprising ethylene.

2. 10. The process of claim 1, wherein the first portion or the second portion comprises a mixture of ethanol and water.

3. 3. The process of claim 2, wherein the water is recycled and mixed with the ethanol feed stream.

4. 3. The process of claim 2, wherein the reactor section is 30-40% smaller in volume than in the dehydration process and the ethanol feed stream remains single-stream.

5. 3. The process of claim 2, wherein the reactor section further comprises a third reactor vessel.

6. 3. The process of claim 2, wherein an oxygenate feedstock is pretreated to remove contaminants and then the pretreated oxygenate stream is passed to the reactor section.

7. 7. The process of claim 6, wherein the pretreated oxygenate stream is fractionated to separate ethanol from heavier oxygenates, and the ethanol is then the ethanol feed stream.

8. 3. The process of claim 2, wherein the ethanol feed stream sent to the first reactor is heated to 400°C to 550°C and converted to ethylene over a dehydration catalyst at 455 kPa to 630 kPa.

9. 3. The process of claim 2, wherein the effluent / second portion mixture is heated to 400° C. to 550° C. and converted to ethylene over a dehydration catalyst at 420 kPa to 700 kPa.

10. 3. The process of claim 2, wherein the first and second reactors contain less steam than if all of the ethanol feed stream were sent to a single reactor and the first and second reactors were operated at an increased endothermic level.

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