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] (Priority Claim) This application claims priority to Indian Patent Provisional 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 Art

[0003] Oil and gas refiners around the world are exploring methodologies and pathways to reduce their carbon footprint and are moving towards sustainable processes. The process from ethanol to jet fuel is one of the pathways that has the potential to minimize or eliminate the customer's carbon footprint. The final products of this 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.

[0004] Generally, the process of converting ethanol to jet fuel has three main steps. The first is to dehydrate ethanol to produce ethylene. Next, ethylene is converted to long-chain olefins, and then the long-chain olefins are hydrogenated to produce paraffins. [[ID=********]]

Summary of the Invention

[0005] A process for the dehydration of an ethanol feed stream, the process comprising sending the ethanol feed stream and steam to a radial flow reactor and contacting the ethanol feed stream and steam with a catalyst under reaction conditions to produce an effluent containing ethylene.

Brief Description of the Drawings

[0006] [Figure 1] The flow scheme of this disclosure is shown below. [Modes for carrying out the invention]

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

[0008] In the feed pretreatment section, metals can be removed by using an ion exchange resin guard bed. The feed pretreatment section is configured with a lead / rag flow scheme so that one container can be taken offline and reloaded while one container is online. The ion exchange resin supplier recommends a regenerative system using HCl or sulfuric acid as a regenerator. HCl regenerator is not suitable because the unit has stainless steel metallurgy. A regenerative system using sulfuric acid would need to be carefully examined and considered if implemented. The ion exchange resin would have the highest capacity. Currently, feed pretreatment is not considered necessary due to metal content below <1.0 wppm.

[0009] Demetallation products from the feed pretreatment section are sent through the tubular side of the fresh feed-overhead vapor exchanger to the feed purification column (FPC). This column is designed to purge out heavier molecules that are produced along with the ethanol feed through the column bottom. These heavier molecules may consist of components such as, but are not limited to, C3+ alcohols, acetals, hexadecanoic acid, octadecanoic acid, isopentyl acetate, cyclohexanol, cyclopentanol, phenol, cresol, and acetals. Some of these heavier molecules can be converted to ketones within the reactor and tend to accumulate without leaving the process; therefore, they must be removed or minimized before the feed can be sent to the reactor section. The bottom spur is expected to be <1.0% of the total feed, consisting of concentrated heavy materials such as acetic acid, acetals, cresol, phenol, free fatty acids, e.g., hexadecanoic acid and octadecanoic acid, and several heavy alcohols. The column bottom sump is swaged and designed to hold the heavy purge material for typically 24 hours and can be purged into an ethanol slop tank.

[0010] Since there is no expected dissolved light end in the ethanol feedstock, a total 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 a reboiling medium for the column. The vapor from the column overhead is condensed first on the shell side of the fresh feed-overhead vapor exchanger, then in the feed purification column overhead condenser, before entering the feed purification column receiver. At its foaming point, the receiver liquid is pumped by the feed purification column net overhead pump and further supercooled in the feed purification column net overhead condenser. The supercooled material is mixed with the liquid ethanol recirculation stream and cooled in the diethyl ether (DEE) absorber feed condenser before entering the DEE absorber on the upper tray or feed surge drum (see discussion below).

[0011] The DEE absorber is suspended in the dehydration separator vapor stream that enters below the DEE absorber's bottom tray, and 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 as 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 recirculated ethanol would enter the feed surge drum instead of the DEE absorber. If the FPC is not included as part of the design, a fresh ethanol feed with the recirculated ethanol stream added can be sent to either the DEE absorber (if considered as 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 bottom liquid stream is pumped to the reactor section via a dewatering charge pump. The discharge stream is first preheated in an ethanol treatment 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 these exchangers are located within the oligomerization unit), and a first ethanol steam heater before entering the low-temperature 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 within 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 inherently endothermic. Water is a byproduct of the dehydration reaction, and the water produced in the first reactor satisfies the steam requirements in the downstream reactors. The second split of the feed stream is heated and vaporized in the ethanol-second-stage oligomerized lag reactor feed exchanger, the ethanol-second-stage oligomerized reed reactor feed exchanger (both of these exchangers are located within the oligomerization unit), and the second ethanol steam heater before entering the low-temperature side (tube side) of the second combined feed exchanger (CFE2). At the low-temperature 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. Although steam does not participate in the reaction (though it may be involved in some minor side reactions), the steam added to the reactor serves a dual purpose: controlling the endothermic reaction across the reactor and maintaining catalyst stability (reducing coke buildup). Since diethyl ether formation is more pronounced at lower reactor outlet temperatures, it is important to minimize the temperature drop across the reactor. To ensure that diethyl ether formation is limited, the second reactor effluent is passed through a second interheater, reheated to the desired reactor temperature, and then sent to a third reactor. The third reactor is a polishing reactor that ensures that the diethyl ether, along with the unconverted ethanol, is converted to useful ethylene. The third reactor effluent is split and passes through the high-temperature side (shell side) of CFE1 and CFE2. The high-temperature outlet from the combined feed exchanger is further cooled and condensed in the wastewater stripper boiler, followed by the dewatering product condenser, before entering the dewatering separator.

[0014] The dewatering separator liquid stream is primarily water containing some dissolved oxygenates, and this stream is sent to a low-pressure wastewater stripper, while the steam stream is essentially ethylene products. As mentioned above, the dewatering separator steam is sent to a DEE absorber. If a DEE absorber is not considered as part of the design, the separator steam is sent to a water wash tower.

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

[0016] The ethylene compression section involves the following factors: The pressure requirement for the steam product stream to the downstream oligomerization unit exceeds 1000 psig, which is achieved by a 4-stage or 5-stage compressor system. 4 stages may be specified for reciprocating machines, while 5 stages may be specified for centrifugal machines. In one embodiment, there may be a 4-stage reciprocating machine with one stage active and one standby. The number of stages is based on the pressure requirements of the downstream unit, and the compressor discharge temperature may be limited to less than 195°F.

[0017] Steam from the water scrubbing tower mixes with the spillback of the first-stage ethylene compressor and then enters the first-stage ethylene compressor suction drum, knocking out any entrained liquids. The steam 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 is further mixed with the spillback of the second-stage ethylene compressor and enters the first-stage ethylene compressor discharge drum. The steam from the first-stage ethylene compressor discharge drum is split into two streams: the first stream is the spillback of the first-stage ethylene compressor, while the second stream is the net steam stream that enters the second-stage ethylene compressor. The steam 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 is further mixed with the spillback of the third-stage ethylene compressor and enters the second-stage ethylene compressor discharge drum. The steam 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 steam stream that enters the third-stage ethylene compressor. The steam is further compressed in the third-stage ethylene compressor, and the compressor discharge is cooled in the third-stage discharge cooler and third-stage discharge trim cooler before entering the third-stage ethylene compressor discharge drum. The steam 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 steam product that enters the ethylene dryer to remove saturated moisture.

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

[0019] The saturated water in the steam from the water scrubbing tower is partially knocked out in the suction and discharge drums of the first-stage ethylene compressor and the discharge drums of the second and third-stage ethylene compressors. The knocked-out liquid is mostly water, and this condensation is 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 removing moisture from ethylene vapor products and operate in reed-lag mode. When the molecular sieves in the reed dryers become saturated with moisture, the dryers need to be regenerated to restore sieve capacity. The dry ethylene vapor produced from the lag dryers is used as the regenerator medium. The slipstream from the lag dryer outlet is sent to the regenerator superheater, where the regenerator is heated to the required regeneration temperature before entering the regenerating dryer. The spent regenerator, containing moisture desorbed from the molecular sieves from the regenerating dryer, is cooled and condensed in the regenerator condenser before entering the regenerator coalescer. The regenerator coalescer separates water from the spent regenerator, i.e., ethylene, and this ethylene vapor is returned to the first-stage ethylene compressor suction drum under pressure control, while the spent water is sent to the wastewater stripper.

[0021] The wastewater section consists of a wastewater stripper and a water scrub tower. Liquids from the dewatering separator, water scrub tower bottom, regenerator coalescer (intermittent), and knocked-out liquid from the ethylene compressor section knock-out drum are fed through the shell side of the wastewater stripper feed-bottom exchanger before entering the upper tray of the wastewater stripper. The wastewater stripper is designed to strip off oxygenated materials that come with the feed as overhead steam products, while recovering treated water into the bottom.

[0022] The wastewater stripper operates at 5-10 psig, and the overhead steam enters the off-gas knockout drum after being cooled and condensed in the off-gas condenser. The off-gas knockout drum liquid contains water along with most of the alcohol carried over from the DEE absorber steam (if the DEE absorber is part of the design), unconverted alcohol from the reactor, acetaldehyde, ether, acetic acid, and other non-selective oxygenates formed in the reactor. These are recycled, mixed with fresh feed, and sent to the reactor section through the feed surge drum or the DEE absorber bottom (if included as part of the design). The off-gas knockout drum steam is a small purge stream, which is a mixture of olefins (dissolved in the dewatering separator and water scrubbing tower liquid) and oxygenates. This purge gas stream is mixed with the low-pressure off-gas stream generated 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 the combined combustion heater. The wastewater stripper has two reboiler systems. One reboiler, the wastewater stripper auxiliary reboiler, utilizes low-pressure steam as a reboiling medium (expected to operate during startup and as an auxiliary backup), while the other reboiler, the wastewater stripper boiler, integrates process heat with the high-temperature dehydration reactor effluent upstream of the dehydration product condenser. The wastewater stripper net bottom is pumped by a treated water pump through the tubular side of the wastewater stripper feed-bottom exchanger, and downstream is divided into three streams. The first stream is treated water used to wash steam product oxygenates in the water wash tower. This stream is sent to the water wash tower via an ethanol-treated water exchanger, a treated water cooler, and a treated water trim cooler.

[0023] The second stream is the amount of treated water corresponding to adding a 5% blowdown to the steam injected into the dehydration reactor. 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 requirement. The continuous blowdown from the steam generator is sent directly to the wastewater treatment facility. This stream is split upstream of the ethanol-treated water exchanger.

[0024] The third stream is the net treated water generated from various reactions occurring in the reactor section and is sent to the wastewater treatment facility. This stream is taken from downstream of the treated water trim cooler.

[0025] As described above, 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, and unconverted alcohol that need to be removed before sending the vapor product stream to the downstream oligomerization unit.

[0026] In the DEE absorber, the diethyl 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 carryover of the ethanol feed to the DEE absorber vapor. The DEE absorber overhead vapor is sent under the bottom tray of the water wash tower. The water wash tower is designed to wash out oxygenates such as acetaldehyde, unconverted alcohol from the reactor section, ethanol carryover from the DEE absorber vapor, and acetic acid using the treated water from the wastewater stripper bottom. The treated water enters the upper tray of the water wash tower, and the absorption of oxygenates occurs in a countercurrent direction over multiple trays. The water wash tower overhead vapor after washing is sent to the downstream ethylene compression section, while the liquid bottom stream containing all the dissolved oxygenates / alcohols is sent to the wastewater stripper.

[0027] The ethanol dehydration reactor section operates at low pressure psig and has a high operating temperature in the range of 400 to 550 °C. Apart from the operating conditions, the molecular weight and density of the components are lower. All these factors result in a very high volumetric flow rate through the reactor. At such a high volumetric flow rate, it becomes very difficult to specify a conventional downflow reactor.

[0028] In a fixed bed downflow reactor, assuming a high volumetric flow rate, the pressure drop through the catalyst bed is in the range of 15 to 50 psi. The reactor section operates at a lower pressure, and it is not recommended to increase the bed pressure drop beyond 3 to 5 psi. The higher the pressure in the reactor section, the conversion rate and ethylene selectivity are lower. Therefore, 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 the fixed bed radial flow design, the expected bed pressure drop will be as low as about 3 to 5 psi, which is the pressure required for the process. Apart from the low bed pressure drop, the radial bed design can help improve the vapor distribution.

[0029] FIG. 1 shows a process 10 for treating an oxide feedstock according to an exemplary embodiment. The oxide feedstock may contain alcohol, preferably ethanol. The feedstock may contain ethanol as the main component and may be aqueous. Preferably, the oxide feedstock is a bio-renewable feedstock.

[0030] The supply line 12 transports the oxygenated stream of the oxygenated feedstock to the feed pretreatment section 14. The feed pretreatment section 14 includes a container 16 with a bed of cation exchange resin adsorbent for removing metallic contaminants such as sodium, zinc, phosphate, copper, and calcium from the oxygenated stream in the supply line 12. The feed pretreatment section 14 may also include an additional container 18 with a bed of the same adsorbent for further removal of metals from the oxygenated stream. The containers 16 and 18 may be in series or lead-lug type arrangement to allow for the regeneration of used adsorbent. Line 17 transports the partially pretreated oxygenated stream from the outlet of container 16 to the inlet of container 18. The pretreated oxygenated stream exits the feed pretreatment section 14 from the outlet of the additional container 18 and enters line 20, where it is supplied to the purification column 22. The feed pretreatment section 14 can be operated at temperatures from 32°C to 104°C and pressures from atmospheric pressure to 690 kPa(g).

[0031] In the purification column 22, the pre-treated oxygenated stream is fractionally distilled to separate ethanol from heavier oxygenated substances, also known as fusel oils, such as cyclohexanol, cyclopentanol, and heavier alcohols and acids. The purification column 22 is operated to minimize ethanol to less than 1% of the feed in the bottom stream of line 26. The heavy oxygenated stream in the bottom line 26 is removed from the bottom of the purification column 22 for heavy oxygenated treatment. The purification column 22 may be re-boiled by heat exchange with a suitable high-temperature stream, such as steam, to provide the heat required for distillation. The purification column 22 provides an overhead gas stream of purified ethanol into the overhead line 24, which may be cooled in an air cooler 25 and supplied to the feed surge drum 26 together with the recirculated ethanol stream in line 27. The purification column 22 may be operated at a bottom temperature of 82°C to 121°C and an overhead pressure of 35 kPa(g) to 140 kPa(g).

[0032] The ethanol in the supply surge drum 26 may be covered with nitrogen. The 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 supplied to the 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 first heated charge stream in line 36 is fed into the first dehydration reactor 40. In the first dehydration reactor 40, the ethanol feed is converted to ethylene and water on 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 undergoes heat exchange with the second dehydration exchange stream in line 46, is mixed with the first dehydration stream in line 42, and is supplied to the second charge heater 48. The second charge heater 48 may be a combustion heater and can heat the second charge stream to 400°C to 550°C. The resulting heated second charge stream in line 50 is fed into the second dehydration reactor 52. In the second dehydration reactor 52, the ethanol feed is converted to ethylene and water on 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 into line 54.

[0034] The second dehydration stream in line 54 is supplied to an interheater 56. The interheater 56 may be a combustion heater and can heat the second dehydration stream to 400°C to 550°C. The resulting third heated charge stream in line 58 is fed into a third dehydration reactor 60. In the third dehydration reactor 60, the residual ethanol feed is converted to ethylene and water on a dehydration catalyst at a pressure of 420 kPa (g) to 700 kPa (g). The third dehydration stream is discharged from the third dehydration reactor 60 into line 62.

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

[0036] The third dewatering stream is divided into a first dewatered exchange stream in line 32 and a second dewatered exchange stream in line 46. The first dewatered exchange stream in line 32 exchanges heat with the first charge stream in line 30, the second dewatered exchange stream in line 46 exchanges heat with the second charge stream in line 44, and the cooled dewatered streams are reassembled in line 64.

[0037] The cooled dewatered stream in line 64 is supplied to the quenching tower 68, where it is quenched by direct contact with water from the first cooled water stream in line 70 and the second cooled water stream in line 72. The quenched ethylene stream exits into the quenching overhead line 74, and the bottom water stream exits the bottom of the tower in line 76. The bottom water stream is divided into a drain stream in line 78 and a quenched recirculation stream in line 82, which can be transported to the wastewater stripper column 80 through a control valve on line 78. The first portion of the quenched recirculation stream is air-cooled in the product condenser 69 and recirculated as a first, lower-temperature cooled water stream in line 70 through a control valve on line 70, while the second portion of the quenched recirculation stream undergoes heat exchange in the trim condenser 71 and is recirculated to the quenching tower 68 as a second, higher-temperature cooled water stream in line 72. The quenching tower 68 can be operated at a bottom temperature of 37°C to 104°C and an overhead pressure of 280 kPa(g) to 490 kPa(g).

[0038] The rapidly cooled ethylene stream in line 74 is supplied to the first-stage suction drum 86. In the first-stage suction drum, the ethylene exits the overhead line 88 and goes to the first-stage compressor 90, while the residual water is transported to the wastewater stripper column 80 through a control valve on line 92, exiting the bottom of the drum in line 92 and possibly via 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.

[0039] The cooled and compressed ethylene stream from the first-stage trim cooler 94 is supplied to the first-stage discharge drum 96. From the first-stage discharge drum 96, the ethylene exits into the overhead line 98 and proceeds to the 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 the 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 pressure) (165 psig) to 3220 kPa (gauge pressure) (460 psig), and the discharge in line 101 is cooled in the second-stage discharge cooler 103 and the second-stage trim cooler 104.

[0040] The twice-cooled and compressed ethylene stream from the second-stage trim cooler 104 is supplied to the second-stage discharge drum 106. From the second-stage discharge drum 106, the ethylene exits into the overhead line 108 and is transported to the water scrubbing tower 110, while the residual water stream exits the bottom of the drum in line 112 through a control valve on line 112 and is transported to the wastewater stripper column 80, possibly via lines 102, 92, and 78.

[0041] In the water scrubbing tower 110, the twice-cooled and compressed ethylene stream is washed countercurrently with cooled and treated water in line 118 from the wastewater stripper column 80, absorbing additional oxygen to produce a washed ethylene stream exiting into the overhead line 120 and a wash water stream in the bottom line 122. The washed ethylene stream in the overhead line 120 is transported to the caustic scrubber column 116. The wash water stream in line 122 is transported back to the water stripper column 80 through a control valve on line 122. The wash water 110 can be operated at a bottom temperature of 16°C (60°F) to 82°C and a pressure of 2800 kPa (g) to 3500 kPa (g) in the overhead.

[0042] The caustic scrubber column 116 has a lower caustic washing section 124 and an upper water washing section 132. In the lower caustic washing section 124, the washed ethylene stream in line 120 is scrubbed with an aqueous caustic stream from line 126 to absorb acidic gases such as carbon dioxide from the washed ethylene stream. The spent caustic is pumped from the bottom of the lower section through line 128 and replenished with fresh caustic from line 130 to provide the aqueous caustic stream 126. The scrubbed vaporized ethylene stream, depleted of acidic gases, rises from the caustic washing section 124 to the upper water washing section 132 through a steam inlet. In the water washing section 132, the scrubbed ethylene stream comes into contact with a washing water stream from line 134. The washed and scrubbed vaporized ethylene stream exits the overhead of the water washing section 132 and enters line 136, which is supplied to the product dryer section 140. The used water stream is taken from the bottom of the water washing section 132, from the liquid sump into line 142, replenished with a fresh water stream from line 144 to provide the washing water stream in line 134, and pumped to the top of the water washing section 124 to come into contact with the scrubbed vapor ethylene stream. The caustic scrubber column can be operated at a bottom temperature of 38°C to 43°C and an overhead pressure of 2800 kPa(g) to 2975 kPa(g).

[0043] In the product dryer section 140, the washed and scrubbed ethylene stream from line 136 is fed into 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 bottom line 150, which is possibly fed into a wastewater stripper column 80 via line 122. The dryer inlet stream is fed into the first product dryer 152 in line 148. The first product dryer 152 comprises 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 2-4A. The first product dryer 152 may operate in an upward flow mode. The product dryer section 140 may also 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 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 ethylene. The dry ethylene stream exits the product dryer section 140 and enters the dry ethylene stream in line 158. The product dryer section 140 may be operated at a temperature of 32 to 49°C and a pressure of 2750 kPa(g) to 3100 kPa(g).

[0044] The dry ethylene stream in line 158 is supplied to the dryer outlet knockout drum 160 to remove residual water, and provides a dryer outlet stream in line 162 and a second knockout water stream in bottom line 164, which is supplied to the wastewater stripper column 80, possibly via lines 150 and 122.

[0045] The dryer outlet stream in line 162 is fed into the heavy oxygenation removal column 170, which can separate the overhead stream, which mainly contains ethylene but possibly higher olefins, from heavy ketones and diethyl ether. The olefins are generated in the overhead line 172 and fed into the third-stage compressor 174, and the bottom heavy oxygenation stream is generated in the bottom line 176. The heavy oxygenation purge stream may be taken into line 178 for heavy oxygenation treatment, while the reboiling portion is reboiled and returned to column 170. The compressed ethylene stream in the compressor discharge line 176 at a pressure of 2800 kPa (gauge pressure) (400 psig) to 7000 kPa (g) may be fed into the dimerization section. The heavy oxygenation removal column 170 can be operated at a bottom temperature of -20°F to 250°F and a pressure of 350 psig to 450 psig in the overhead.

[0046] Water streams containing oxygenates and volatile substances in lines 92, 102, 112, 122, 150, and 164 may be fed into a wastewater stripper column 80, where volatile substances and oxygenates are boiled off to provide an overhead volatile substance stream in line 182 and a stripped water stream in line 184. A portion of the stripped water stream can be re-boiled and returned to the column to provide the necessary heat. The treated water stream in line 186 may be pumped towards the water outlet through line 188, which contains a cooled and treated water stream in line 118 for the water washing tower 110. The wastewater stripper column 80 may be operated at a bottom temperature of 93°C to 121°C and an overhead pressure of 34 kPa(g) to 138 kPa(g).

[0047] The overhead volatile substance stream in line 182 may be cooled in an air cooler 189 and supplied to the off-gas knockout drum 190. The overhead stream from the knockout drum 190 in line 192 may be sent to a flare, while the ethanol recirculation stream is pumped through line 27 toward the supply surge drum 26, possibly via line 24.

Claims

1. A process for dehydrating an ethanol supply stream, comprising sending the ethanol supply stream and steam to a radial flow reactor, contacting it with a catalyst under reaction conditions, and producing an effluent containing ethylene.

2. The process according to claim 1, wherein the mixture comprising the ethanol supply stream and steam is divided into two parts, the first part of the mixture being sent to a first reactor of three radial flow reactors, and the second part of the mixture being sent to a second reactor of three radial flow reactors.

3. The process according to claim 2, wherein the effluent from the second of the three radial flow reactors is sent to the third of the three radial flow reactors.

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