Radial flow reactor for ethanol dehydration process

Abstract

A process for dehydration of an ethanol feed stream, the process comprising passing the ethanol feed stream and steam to a radial flow reactor to contact a catalyst under reaction conditions and produce an effluent comprising ethylene. By using the runoff reactor, the possible pressure drop problem of a conventional fixed bed down-flow reactor is eliminated.

Description

[0001] Priority declaration

[0002] This application claims priority to Indian provisional patent application No. 202211049528 filed on August 30, 2022. Technical Field

[0003] This relates to an ethanol dehydration process. More specifically, this relates to the use of a radial reactor in an ethanol dehydration process to produce ethylene, which can be further processed to make jet fuel. Background Art

[0004] Oil and gas refineries around the world are exploring methods and routes to reduce carbon footprints and are moving toward sustainable processes. The ethanol to jet fuel process is one of the routes that promises to minimize or eliminate the consumer's carbon footprint. The final products of the process are jet fuel and diesel fuel produced from bioethanol. Jet fuel is a sustainable aviation fuel and is intended to replace jet fuel produced from conventional sources such as crude oil.

[0005] There are typically three main steps in the process of converting ethanol into jet fuel. The first step is to dehydrate the ethanol to produce ethylene. Next the ethylene is converted into long-chain olefins, which are then hydrogenated to produce paraffins. Summary of the invention

[0006] A process for dehydrating an ethanol feed stream comprising passing the ethanol feed stream and steam to a radial flow reactor to contact a catalyst under reaction conditions and produce an effluent comprising ethylene. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A flow scheme of the present disclosure is shown. DETAILED DESCRIPTION

[0008] The ethanol dehydration treatment unit is divided into six sections: feed pretreatment section, feed purification section, reactor section, ethylene compression section and water washing section.

[0009] In the feed pretreatment section, metals can be removed by using an ion exchange resin guard bed. It is configured in a lead / lag flow scheme so that one vessel can be offline and reloaded while one vessel is online. Ion exchange resin suppliers recommend a regenerable system using HCl or sulfuric acid as the regenerator. HCl regenerator is not appropriate because the unit has stainless steel metallurgy. A regenerable system with sulfuric acid would need to be fully reviewed and reviewed if implemented. Ion exchange resins will have the highest capacity. At present, feed pretreatment is not considered necessary for metal levels below <1.0wppm.

[0010] The demetallized product leaving the feed pretreatment section is sent to the feed purification tower (FPC) by the tube side of the new feed-tower top vapor exchanger. The tower is designed to remove the heavier molecules through the bottom of the tower together with the ethanol feed. The heavier molecules may include but are not limited to components such as C3+ alcohols, acetals, hexadecanoic acid, octadecanoic acid, isoamyl acetate, cyclohexanol, cyclopentanol, phenol, cresols, acetals, etc. Some of these heavier molecules can be converted into ketones in the reactor and tend to accumulate without leaving the process, and therefore need to be removed or minimized before the feed can be sent to the reactor section. The bottom discharge material is expected to be <1.0% of the total feed, which is composed of concentrated heavy materials such as acetic acid, acetals, cresols, phenol, free fatty acids such as hexadecanoic acid and octadecanoic acid, some heavy alcohols, etc., and the bottom storage tank can be swaged and designed to keep the heavier discharge material usually 24 hours, and discharged into the ethanol waste liquid tank.

[0011] Since there are no expected dissolved light ends in the ethanol feed raw material, a total condensing system is suitable for this tower. The receiver pressure controlled by the nitrogen push-pull system is set to allow the use of MP steam as the reboiling medium of the tower. The vapor from the overhead product is first condensed on the shell side of the new feed-tower top vapor exchanger, and then condensed on the feed purification column overhead condenser before entering the feed purification column receiver. The receiver liquid at its bubble point is pumped by the feed purification column net tower top pump and further supercooled in the feed purification column net tower top cooler. The supercooled material is mixed with the liquid ethanol circulating stream and cooled in the ether (DEE) absorber feed cooler before entering the tower top tray or the DEE absorber on the feed surge tank (see discussion below).

[0012] The DEE absorber floats with a dehydration separator vapor stream that enters below the bottom tray of the DEE absorber and provides the tower to remove 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 tank with a 15 minute residence time should be provided, and the FPC net overhead liquid mixed with the recycled ethanol will enter the feed surge tank instead of the DEE absorber. If the FPC is not included as part of the design, the new ethanol feed plus the recycled ethanol stream can be sent to the DEE absorber (if it is considered part of the specific design) or the feed surge tank.

[0013] The reactor section includes the following elements. The feed surge tank liquid or the DEE absorber bottom liquid stream is pumped to the reactor section by a dehydration feed pump. The discharge stream is first preheated in an ethanol-treated water exchanger. The preheated ethanol is divided into two streams during flow control. Before entering the cold side (tube side) of the combined feed exchanger 1 (CFE1), the first branch of the feed stream is heated and vaporized in the ethanol-jet product exchanger, the ethanol-hydrogenation reactor feed exchanger (both of which are located in the oligomerization unit) and the first ethanol steam heater, and then enters the feed heater. Before entering CFE1, the vaporized feed is mixed with steam produced in a steam generator placed in a downstream oligomerization unit. The combined stream is heated to the desired reaction temperature in the feed heater and sent to the first reactor.

[0014] The ethanol dehydration reaction is endothermic in nature. Water is the byproduct of the dehydration reaction, and the water produced in the first reactor satisfies the steam demand in the downstream reactor. Before entering the cold side (tube side) of the second combined feed exchanger (CFE2), the second split of the feed stream is heated and evaporated in the ethanol-second stage oligomerization lag reactor feed exchanger, the ethanol-second stage oligomerization advance reactor feed exchanger (these two exchangers are both located in the oligomerization unit) and the second ethanol steam heater. At the cold side outlet of CFE2, the feed stream is mixed with the first reaction effluent and sent to the first intermediate heater, where the stream is further heated to the required reaction temperature. Steam does not participate in the reaction (except that there may be some minor side reactions), but the steam added in the reactor plays a dual purpose of controlling the heat absorption across the reactor and maintaining catalyst stability (reducing coking). Minimizing the temperature drop across the reactor is critical because at a lower reactor outlet temperature, the formation of ether is more significant. In order to ensure the formation of limiting ether, the second reactor effluent is passed through the second intermediate heater and is heated to the required reactor temperature again before entering the third reactor. The third reactor is a finishing reactor, which ensures that the ether is converted into useful ethylene together with the unconverted ethanol. The third reactor effluent is split and passed through the hot side (shell side) of CFE1 and CFE2. The hot side outlet of the combined feed exchanger is further cooled and condensed in the wastewater stripper reboiler and then in the dehydration product condenser before entering the dehydration separator.

[0015] The dehydration separator liquid stream is primarily water with some dissolved oxygenates and is sent to a low pressure wastewater stripper, while the vapor stream is essentially the ethylene product. As described above, the dehydration separator vapor is sent to the DEE absorber. If the DEE absorber is not considered part of the design, the separator vapor is sent to a water scrubber.

[0016] 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 are designed to produce high pressure steam and are constructed similarly to the fired heater convection section of the CCRPlatforming process unit.

[0017] The ethylene compression section involves the following factors. The pressure requirement for the vapor product stream of the downstream oligomerization unit exceeds 1000 psig, which is achieved by a four-stage or five-stage compressor system. A reciprocating machine may have four stages, while a centrifugal machine may have five stages. In one embodiment, there will be a four-stage reciprocating machine with one run and one standby. The number of stages can be based on the downstream unit pressure requirements and limiting the compressor discharge temperature to less than 195°F.

[0018] The vapor from the water scrubber is mixed with the first-stage ethylene compressor overflow before entering the first-stage ethylene compressor suction drum to separate 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 the first-stage discharge trim cooler, and the cooling stream is further mixed with the second-stage ethylene compressor overflow and enters the first-stage ethylene compressor discharge drum. The vapor from the first-stage ethylene compressor discharge drum is divided into two streams, the first stream is the overflow of the first-stage ethylene compressor, and 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 the second-stage discharge trim cooler; the cooling stream is further mixed with the third-stage ethylene compressor overflow and enters the second-stage ethylene compressor discharge drum. The vapor from the second-stage ethylene compressor discharge drum is divided into two streams, the first stream is the overflow of the second-stage ethylene compressor, and 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 the third stage discharge cooler and the 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 divided into two streams, the first stream is the third stage ethylene compressor overflow, and the second stream is the net vapor product entering the ethylene dryer to remove saturated water.

[0019] The dry steam from the ethylene dryer is mixed with the fourth stage ethylene compressor overflow and enters the fourth stage ethylene compressor suction drum. The steam is compressed in the fourth stage ethylene compressor before entering the fourth stage ethylene compressor discharge drum. The fourth stage ethylene compressor discharge drum steam is divided into two streams, the first stream is the fourth stage ethylene compressor overflow, and the second stream is the net vapor product sent to the oligomerization unit. Different from the upstream level, the fourth stage ethylene compressor discharge is not cooled, and the hot vapor stream is directly sent to the oligomerization unit. In order to ensure that the fourth stage ethylene compressor discharge temperature does not exceed the recommended temperature limit, a fourth stage overflow cooler is added on the compressor overflow line.

[0020] The saturated water in the vapor from the water scrubber is partially separated in the first stage ethylene compressor suction drum and discharge drum and the second and third stage ethylene compressor discharge drum. The separated liquid is mostly water, and this condensation is caused by the increase in pressure and the decrease in intermediate temperature. The separation tank liquid is sent to the wastewater stripping tower.

[0021] Two ethylene dryers loaded with molecular sieves are designated to remove moisture from the ethylene vapor product, and these dryers are operated in lead-lag mode. Once the lead dryer molecular sieve is saturated with water, the dryer needs to be regenerated to restore the screening capacity. The dry ethylene vapor from the lag dryer is used as a regenerant medium. The slipstream from the lag dryer outlet is sent to the regenerant superheater, in which the regenerant is heated to the required regeneration temperature before entering the regenerant dryer. Before entering the regenerant coalescer, the waste regenerant from the regenerant dryer is cooled and condensed in the regenerant condenser, and the waste regenerant carries the desorbed moisture leaving the molecular sieve. The regenerant coalescer separates water from the waste regenerant (i.e., ethylene), and the ethylene vapor is sent back to the first stage ethylene compressor suction drum under pressure control, while waste water is sent to the wastewater stripping tower.

[0022] The wastewater section consists of a wastewater stripper and a water scrubber. Liquids from the dehydration separator, water scrubber bottoms, regenerator coalescer (intermittent), and separated liquids from the ethylene compressor section knockout drum are directed through the shell side of the wastewater stripper feed-bottoms exchanger before entering the top tray of the wastewater stripper. The wastewater stripper is designed to strip out oxygenates that enter as overhead vapor product with the feed, while recovering process water in the bottoms.

[0023] The wastewater stripper operates at 5psig-10psig, and the overhead vapor is cooled and condensed in the waste gas condenser before entering the waste gas knockout drum. The waste gas knockout drum liquid has most of the alcohol carryover from the DEE absorber vapor (if the DEE absorber is part of the design), unconverted alcohol from the reactor, water, and other non-selective oxygenates formed in the reactor such as acetaldehyde, ethers, acetic acid, etc., which are recycled and mixed with new feed and sent to the reactor section through the feed buffer tank or the DEE absorber bottom (if included as part of the design). The waste gas knockout drum vapor is a small purge stream, which is a mixture of olefins (dissolved in the dehydration separator and water scrubber liquids) and oxygenates. This purge gas stream is mixed with the low-pressure waste gas stream produced in the downstream oligomerization unit and further compressed in the waste gas compressor to the required fuel gas knockout drum pressure and then burned in the complex combustion heater. The wastewater stripper has two reboiler systems. One reboiler, i.e., the wastewater stripper auxiliary reboiler, utilizes low pressure steam as the reboiling medium (expected to be operated at startup and as an auxiliary standby reboiler), while the other reboiler, i.e., 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 are pumped by a process water pump through the tube side of the wastewater stripper feed bottoms exchanger, and the downstream is divided into three streams. The first stream is the process water for washing the vapor product oxygenates in the water scrubber. The stream is sent to the water scrubber through an ethanol treated water exchanger, a treated water cooler, and a treated water tempering cooler.

[0024] The second stream is the amount of process water corresponding to the steam injected into the dehydration reactor plus 5% blowdown. This stream is sent to a steam generator placed in the downstream oligomerization unit reactor section for heat recovery. The steam produced is recycled to the dehydration reactor to meet the steam to ethanol ratio requirements. The continuous blowdown from the steam generator is sent directly to the wastewater treatment plant. This stream is split upstream of the ethanol treated water exchanger.

[0025] The third stream is net process water resulting from the various reactions occurring in the reactor section and is sent to a wastewater treatment facility and is taken downstream of the process water trim cooler.

[0026] As previously mentioned, the dehydration separator vapor can be sent to a DEE absorber (if included as part of the design) or a water scrubber. The dehydration separator vapor has certain impurities / oxygenates, such as acetaldehyde, diethyl ether, dimethyl ether, water, unconverted alcohol, etc., which need to be removed before sending the vapor product stream to the downstream oligomerization unit.

[0027] With the DEE absorber, the ether in the separator vapor is absorbed into the bottom liquid along with some other oxygenates. Since the ethanol feed is used to wash the separator vapor, there is some ethanol feed left over in the DEE absorber vapor. The DEE absorber overhead vapor is sent to below the bottom tray of the water scrubber. The water scrubber is designed to use the treated water from the bottom of the wastewater stripper to wash away oxygenates, such as acetaldehyde, unconverted alcohol from the reactor section, ethanol carryover from the DEE absorber vapor, acetic acid, etc. The treated water enters the top tray of the water scrubber, and the absorption of oxygenates occurs in a countercurrent direction on multiple trays. The washed water scrubber overhead vapor is sent to the downstream ethylene compression section, and the liquid bottoms stream with all dissolved oxygenates / alcohols is sent to the wastewater stripper.

[0028] The ethanol dehydration reactor section operates at low pressure psig and operates at temperatures as high as 400°C - 550°C.

[0029] In addition to the operating conditions, the molecular weight and

[0030] The density is low. All these factors lead to very high volume flow rates through the reactor. At such high volume flow rates, it is determined

[0031] Conventional downflow reactors become very difficult.

[0032] For a fixed bed downflow reactor, at high volumetric flow rates,

[0033] The pressure drop across the catalyst bed is in the range of 15 psi to 50 psi. Reactor Section

[0034] It is not recommended to operate at lower pressures and increase the bed pressure drop above

[0035] 3psi-5psi. The higher the pressure in the reactor section,

[0036] The lower the conversion rate and ethylene selectivity, the lower the

[0037] Minimize the pressure drop across the reactor bed. Instead of using a fixed bed downflow reactor, a fixed bed radial flow design is being used. For a fixed bed radial flow design, the expected bed pressure drop will be as low as 3psi-5psi, which is required for this process.

[0038] Low bed pressure drop, radial bed design can help improve vapor distribution.

[0039] exist Figure 1 In the present invention, a method 10 for treating an oxygenate feedstock is shown according to an exemplary embodiment. The oxygenate feedstock may contain an alcohol, and preferably contains ethanol. The feedstock may contain mainly ethanol and may be aqueous. Preferably, the oxygenate feedstock is a biorenewable feedstock.

[0040] Feed line 12 delivers the oxygenate stream of the oxygenate feedstock to a feed pretreatment section 14. The feed pretreatment section 14 includes a vessel 16 containing a cation exchange resin adsorbent bed for removing metal contaminants, such as sodium, zinc, phosphate, copper and calcium, from the oxygenate stream in the feed line 12. The feed pretreatment section 14 may include an additional vessel 18 having the same adsorbent bed for further removing metals from the oxygenate stream. The vessels 16, 18 may be arranged in series or in a lead-lag type arrangement to allow regeneration of spent adsorbent. Line 17 delivers a partially pretreated oxygenate stream from the outlet of vessel 16 to the inlet of vessel 18. The pretreated oxygenate stream flows out of the feed pretreatment section 14 from the outlet of the additional vessel 18 in line 20 and is fed to a purification column 22. The feed pretreatment section 14 may be operated at a temperature of 32°C to 104°C and a pressure of atmospheric pressure to 690 kPa(g).

[0041] In the purification tower 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). The purification tower 22 is operated to minimize ethanol, not exceeding 1% of the feed in the bottom stream of the pipeline 26. The heavy oxygenate stream in the bottom pipeline 26 flows out from the bottom of the purification tower 22 for heavy oxygenate treatment. The purification tower 22 can be reboiled by heat exchange with a suitable hot stream such as steam to provide the heat required for distillation. The purification tower 22 provides a gaseous overhead stream of purified ethanol in the top pipeline 24, which can be cooled in the air cooler 25 and fed to the feed buffer tank 26 together with the recycled ethanol stream in the pipeline 27. The purification tower 22 can be operated with a bottom temperature between 82°C and 121°C and a top pressure of 35kPa(g) to 140kPa(g).

[0042] The ethanol in the feed buffer tank 26 can be covered with nitrogen. Feed pump 29 pumps the ethanol feed stream in pipeline 28 into the two feed streams. The first feed stream in pipeline 30 is heat exchanged with the first dehydration exchange stream in pipeline 32, mixed with steam in pipeline 33 and fed to the first feed heater 34. The first feed heater 34 can be a flame heater and can heat the first feed stream to 400°C to 550°C. The first heated feed stream obtained in pipeline 36 is added to the first dehydration reactor 40. In the first dehydration reactor 40, the ethanol feed is converted into ethylene and water on a dehydration catalyst at a pressure of 455kPa(g) to 630kPa(g). The first dehydration stream is discharged from the first dehydration reactor 40 via pipeline 42.

[0043] The second feed 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 fed to the second feed heater 48. The second feed heater 48 can be a fired heater and can heat the second feed stream to 400° C. to 550° C. The resulting second heated feed stream in line 50 is fed to the second dehydration reactor 52. In the second dehydration reactor 52, the ethanol feed is converted into 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 via line 54.

[0044] The second dehydrated stream in line 54 is fed to an intermediate heater 56. The intermediate heater 56 may be a fired heater and may heat the second dehydrated stream to 400° C. to 550° C. The resulting third heated feed stream in line 58 is fed to a third dehydration reactor 60. In the third dehydration reactor 60, the residual ethanol feed is converted to ethylene and water over a dehydration catalyst at a pressure of 420 kPa(g) to 700 kPa(g). The third dehydrated stream is discharged from the third dehydration reactor 60 via line 62.

[0045] The dehydration catalyst is an alumina based catalyst.

[0046] 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 feed stream in line 30, and the second dehydrated exchange stream in line 46 is heat exchanged with the second feed stream in line 44, and the cooled dehydrated streams are recombined in line 64.

[0047] The cooled dehydrated stream in line 64 is fed to a 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 in a quench tower overhead line 74, and a bottoms water stream exits the bottom of the tower in line 76. The bottoms water stream is split between a vent stream in line 78 and a quench recycle stream in line 82, and the vent stream can be sent to a wastewater stripper 80 via a control valve thereon. A first portion of the quench recycle stream is air cooled in a product condenser 69 and circulated as a first lower cooling water stream in line 70 via a control valve thereon, and a second portion of the quench recycle stream is heat exchanged in a trim condenser 71 and circulated to the quench tower 68 as a second higher cooling water stream in line 72. The quench tower 68 may be operated at a tower bottom temperature of 37° C. to 104° C. and a tower top pressure of 280 kPa(g) to 490 kPa(g).

[0048] The quenched ethylene stream in line 74 is fed to the first stage suction drum 86. In the first stage suction drum, ethylene flows out from the top line 88 to the first stage compressor 90, while residual water flows out from the bottom of the drum in line 92 through a control valve thereon and may be sent to the wastewater stripper 80 through line 78. The 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 the first stage discharge cooler 93 and the first stage trim cooler 94.

[0049] The cooled compressed ethylene stream from the first stage trim cooler 94 is fed to the first stage discharge drum 96. Ethylene flows from the first stage discharge drum 96 in overhead line 98 to the second stage compressor 100, while residual water flows from the bottom of the drum in line 102 through a control valve thereon and may be sent to the wastewater stripper 80 via line 92 and line 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 the second stage discharge cooler 103 and the second stage trim cooler 104.

[0050] The secondary cooled compressed ethylene stream from the second stage trim cooler 104 is fed to the second stage discharge drum 106. Ethylene flows out of the second stage discharge drum 106 in overhead line 108 and is sent to a water scrubber 110, while a residual water stream flows out of the bottom of the drum in line 112 through a control valve thereon and may be sent to a waste water stripper 80 via line 102, line 92 and line 78.

[0051] In the water scrubber 110, the secondary cooled, compressed ethylene stream is counter-currently scrubbed with cooled, treated water in line 118 from the wastewater stripper 80 to absorb additional oxygenates, thereby producing a washed ethylene stream flowing out 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 conveyed to the caustic scrubber 116. The wash water stream in line 122 is conveyed back to the water stripper 80 via a control valve thereon. The water scrubber 110 can be operated at a bottoms temperature of 16°C (60°F) to 82°C and a top pressure of 2800 kPa(g) to 3500 kPa(g).

[0052] The caustic scrubber 116 has a lower caustic scrubber section 124 and an upper water scrubber section 132. In the lower caustic scrubber section 124, the scrubbed ethylene stream in line 120 is scrubbed with an alkaline water stream from line 126 to absorb acidic gases such as carbon dioxide from the scrubbed ethylene stream. Spent caustic is pumped from the bottom of the lower section in line 128 to the periphery and replenished with new caustic in line 130 to provide an alkaline water stream 126. The scrubbed gaseous ethylene stream depleted of acidic gases rises from the caustic scrubber section 124 to the upper water scrubber section 132 through a steam inlet. In the water scrubber section 132, the scrubbed ethylene stream contacts the scrubber water stream from line 134. The scrubbed, scrubbed gaseous ethylene stream flows out of the tower top of the water scrubber section 132 in line 136 and is fed to the product dryer section 140. The waste water stream is discharged from the bottom of the water wash section 132 in the liquid storage tank in line 142 and supplemented with a fresh water stream from line 144 to provide a wash water stream in line 134 and pumped to the top of the water wash section 124 to contact the scrubbed gaseous ethylene stream. The caustic scrubber can be operated at a bottom temperature of 38° C. to 43° C. and a top pressure of 2800 kPa(g) to 2975 kPa(g).

[0053] In the 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 separated water stream in a bottoms line 150, which may be fed to a wastewater stripper 80 via line 122. The dryer inlet stream is fed to a first product dryer 152 via line 148. The first product dryer 152 contains an adsorbent for adsorbing water from the ethylene in the dryer inlet stream in line 148 to provide a dry ethylene stream. The adsorbent may be a molecular sieve material having a pore size of 2A-4A. The first product dryer 152 may be operated in an upflow mode. The product dryer section 140 may include a second product dryer 156 operating as the first product dryer 142. The two product dryers may be operated in series, but are preferably arranged in a lead-lag mode of operation to facilitate regeneration during continuous operation. Similar to the first product dryer 152, the second product dryer 156 contains an adsorbent for adsorbing water from ethylene. The dried ethylene stream exits the product dryer section 140 as a dried ethylene stream in line 158. The product dryer section 140 may be operated at a temperature of 32° C. to 49° C. and a pressure of 2750 kPa(g) to 3100 kPa(g).

[0054] 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 separated water stream in bottoms line 164 which may be fed to wastewater stripper 80 via lines 150 and 122 .

[0055] The dryer outlet stream in line 162 can be fed to a heavy oxygenate removal tower 170 to separate a tower top stream containing mainly ethylene but possibly containing higher olefins from heavy ketones and ethers. Olefins are produced in the tower top line 172 and fed to the third stage compressor 174, and a tower bottom heavy oxygenate stream is produced in the tower bottom line 176. The heavy oxygenate purge stream can be subjected to heavy oxygenate treatment in line 178, while the reboiler portion is reboiled and fed back to the tower 170. A compressed ethylene stream at a pressure of 2800 kPa (gauge) (400 psig) to 7000 kPa (g) in the compressor discharge line 176 can be provided to the dimerization reaction section. The heavy oxygenate removal tower 170 can be operated at a tower bottom temperature of -20°F to 250°F and a tower top pressure of 350 psig to 450 psig.

[0056] The water streams containing oxygenates and volatiles in lines 92, 102, 112, 122, 150, and 164 can be fed to a wastewater stripper 80, where the volatiles and oxygenates are vaporized to provide a tower overhead volatile stream in line 182 and a stripping water stream in line 184. A portion of the stripping water stream can be reboiled and sent back to the tower to provide the necessary heat. The treated water stream in line 186 can be pumped to a water outlet in line 188, which includes a cooled treated water stream in line 118 for the water scrubber 110. The wastewater stripper 80 can be operated at a tower bottom temperature of 93° C. to 121° C. and a tower top pressure of 34 kPa(g) to 138 kPa(g).

[0057] The overhead volatile stream in line 182 may be cooled in air cooler 189 and fed to off-gas knockout drum 190. The overhead stream in line 192 from knockout drum 190 may be sent to a flare while the ethanol recycle stream may be pumped via line 24 to feed buffer tank 26 in line 27.

Claims

1. A process for dehydrating an ethanol feed stream, the process comprising passing the ethanol feed stream and steam to a radial flow reactor to contact a catalyst under reaction conditions and produce an effluent comprising ethylene.

2. The method of claim 1, wherein the first part or the second part comprises a mixture of ethanol and water.

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

4. The process of claim 2, wherein the reactor section is 30% to 40% less in volume than a dehydration process wherein the ethanol feed stream remains a single stream.

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

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

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

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