Ethanol to ethylene process

Abstract

A process for dehydrating ethanol to produce ethylene is provided. The ethanol is dehydrated to produce ethylene, which is subsequently converted to longer-chain olefins, which are then hydrogenated to produce long-chain paraffins. In some embodiments, a split feed is used to improve efficiency, eliminating the caustic wash column. Advantages of the process include lower steam requirements and a 30-40% reduction in combined reactor volume when using two reactors compared to a single reactor.

Description

Technical Field

[0001] (Cross-reference) This application claims priority from Indian Provisional Patent Application Nos. 202211049527, 202211049520, and 202211049523, filed on August 30, 2022.

[0002] (Field of the Invention) This relates to an ethanol dehydration process for producing ethylene. More particularly, this relates to a flow scheme of an ethanol dehydration process that may not use a caustic scrubber in some cases. In other examples, the flow scheme has a split feed configuration to allow for less steam usage and reactor section size reduction.

Background Art

[0003] Oil and gas refiners worldwide are seeking methodologies and pathways to reduce carbon dioxide emissions and are moving towards sustainable processes. The process of converting bioethanol to green ethylene is one such sustainable process.

[0004] This disclosure relates to the treatment of ethylene.

[0005] In the dehydration of ethanol to produce ethylene, advantages have been found by operating a split flow and / or eliminating the use of a caustic scrubber in the process. For example, producing ethylene for further processing as an olefin feedstock for ethylene oligomerization.

Summary of the Invention

[0006] A process for converting an ethanol feed stream to ethylene is provided, comprising: dividing the aforementioned ethanol feed stream into a first part and a second part; sending the aforementioned first part to a reactor through a charge heater; mixing vapor with the aforementioned first part in the aforementioned charge heater and sending the ethanol / vapor mixture to the aforementioned reactor; subjecting the aforementioned ethanol / vapor mixture to conditions sufficient to dehydrate the aforementioned ethanol to produce an effluent containing ethylene and water; combining the aforementioned effluent with the aforementioned second part to form an effluent / second part mixture; sending the aforementioned mixture to a second reactor to react and produce a product effluent containing ethylene and water, wherein the aforementioned reactor section has a volume reduction of 30-40% compared to a process containing a caustic scrubber, and the aforementioned first and second reactors contain less vapor than a process having a single reactor.

[0007] In another embodiment, a process is provided for converting an ethanol feed stream to ethylene, comprising dividing the aforementioned ethanol feed stream into a first portion and a second portion to be sent to a reactor section comprising a first reactor and a second reactor, wherein the combination of the aforementioned first reactor and the aforementioned second reactor comprises a reactor volume of about 60-70% of the volume of a single reactor system; sending the aforementioned first portion to the aforementioned first reactor through a charge heater; mixing vapor with the aforementioned first portion in the aforementioned charge heater and sending the ethanol / vapor mixture to the aforementioned first reactor; subjecting the aforementioned ethanol / vapor mixture to conditions sufficient to dehydrate the aforementioned ethanol to produce an effluent containing ethylene and water; combining the aforementioned effluent with the aforementioned second portion to form an effluent / second portion mixture; sending the aforementioned effluent / second portion mixture to the aforementioned second reactor to react and produce a product effluent containing ethylene and water. [Brief explanation of the drawing]

[0008] [Figure 1] A flowchart is provided. [Modes for carrying out the invention]

[0009] The ethanol dehydration process unit is divided into six main sections: a feed pretreatment section, a feed purification section, a reactor section, an ethylene compression section, and a water washing section.

[0010] In the feed ethanol pretreatment section, metal can be removed by using an ion exchange resin guard floor. It is configured in a lead / rag flow configuration so that one container can be taken offline and reloaded while one is online. The ion exchange resin supplier recommends a regenerative system using HCl or sulfuric acid as a regenerator. Since the unit has stainless steel metallurgy, the HCl regenerator is not suitable.

[0011] Demetallized products from the ethanol pretreatment section are sent to a feed purification column (FPC) via the tubular side of a fresh feed-top vapor exchanger. This column is designed to purge heavier molecules associated with the ethanol feed passing through the bottom of the column. These heavier molecules may consist of, but are not limited to, components such as C3+ alcohols, acetals, hexadecanoic acid, octadecanoic acid, isopentyl acetate, cyclohexanol, cyclopentanol, phenol, cresol, and acetals. Some of these heavier molecules may 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 purge is expected to be <1.0% of the total feed, consisting of concentrated heavy substances such as free fatty acids like acetic acid, acetals, cresol, phenol, hexadecanoic acid, and octadecanoic acid, and several heavy alcohols.

[0012] Since dissolved light ends are not expected in the ethanol feedstock, a total condensation system is suitable for this column. The receiver pressure, controlled by a nitrogen push-pull system, is set to allow the use of MP vapor as a reboiling medium for the column. The vapor from the top of the column is first condensed on the shell side of the fresh feed top vapor exchanger, then condensed in the feed purification column top condenser, and then enters the feed purification column receiver. At its foaming point, the receiver liquid is pumped by the net top pump of the feed purification column and further supercooled in the net top condenser of the feed purification column. The supercooled material is mixed with the liquid ethanol recirculation flow and cooled in the DEE absorber feed condenser before entering the DEE absorber on the top tray or feed surge drum.

[0013] The DEE absorber floats with the dehydration separator vapor flow entering beneath 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.

[0014] The reactor section includes the following elements: The feed surge drum liquid or the DEE absorber bottom liquid flow is pumped to the reactor section via a dewatering charge pump. The discharge flow is first preheated in an ethanol treated water exchanger. The preheated ethanol is split into two flows by flow control. The first split of the feed flow is heated and vaporized in a first ethanol vapor heater before entering the low-temperature side (tube side) of the combined feed exchanger 1 (CFE1) and subsequently the charge heater. Before entering the CFE1, the vaporized feed is mixed with vapor generated in a vapor generator. The combined flow is heated to the required reaction temperature in the charge heater and sent to the first reactor.

[0015] The second split feed stream is heated and vaporized before entering the cold side (tube side) of the second combined feed exchange (CFE2). At the cold side outlet of the CFE2, the feed stream is mixed with the first reactor effluent and sent to the first intermediate heater, where the flow is further heated to the required reaction temperature. Although the vapor does not participate in the reaction (except for some minor side reactions), the vapor added to the reactor serves a dual purpose: controlling the endothermic reaction of the entire reactor and maintaining catalyst stability (reducing coke laydown). Since diethyl ether formation is more pronounced at the lower reactor outlet temperature, it is important to minimize the overall reactor temperature drop. To ensure that diethyl ether formation is limited, the second reactor effluent is passed through the second intermediate heater 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 is converted to useful ethylene along with unconverted ethanol. The third reactor effluent is divided 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 reboiler and then the dewatering product condenser before entering the dewatering separator.

[0016] The liquid stream of the dewatering separator is mainly water containing some dissolved oxygenates, and this stream is sent to the low-pressure wastewater stripper, while the steam stream is essentially ethylene products. As mentioned above, the dewatering separator steam is sent to the DEE absorber.

[0017] The combustion heaters used in the reactor section are designed as natural draft furnaces, with the main process heating performed in the radiant section, and the convection section of these combustion heaters designed to generate high-pressure steam.

[0018] The ethylene compression section includes the following factors: The pressure requirement for the vapor product flow to the downstream oligomerization unit exceeds 1000 psig, which is achieved by a four-stage or five-stage compressor system. Four stages may be specified for reciprocating machines, and five stages for centrifugal machines. In one embodiment, there is a four-stage reciprocating machine with one stage in operation and one in standby. The number of stages is based on the downstream unit pressure requirements and may limit the compressor discharge temperature to below 90°C.

[0019] Steam from the water scrubbing tower mixes with the first-stage ethylene compressor spillback before entering the first-stage ethylene compressor suction drum to knock 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 flow further mixes with the second-stage ethylene compressor spillback and enters the first-stage ethylene compressor discharge drum. The steam from the first-stage ethylene compressor discharge drum is split into two flows: the first flow is the first-stage ethylene compressor spillback, and the second flow is the net steam flow entering 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 flow further mixes with the third-stage ethylene compressor spillback and enters the second-stage ethylene compressor discharge drum. The steam from the second-stage ethylene compressor discharge drum is split into two flows: the first is the second-stage ethylene compressor spillback, and the second is the net steam flow entering 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 flows: the first is the third-stage ethylene compressor spillback, and the second is the net steam product entering the ethylene dryer to remove saturated moisture.

[0020] The dry steam from the ethylene dryer is mixed with the fourth-stage ethylene compressor spillback 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 steam from the fourth-stage ethylene compressor discharge drum is split into two flows: the first is the fourth-stage ethylene compressor spillback, and the second 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 flow 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 cooler is added on the compressor spillback line.

[0021] The saturated water in the steam from the water scrubbing 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 is due to the increase in pressure and decrease in intermediate temperature. The knocked-out drum liquid is sent to the wastewater stripper.

[0022] Two ethylene dryers, each loaded with molecular sieves, are designated for removing moisture from ethylene vapor products and operate in reed-lag mode. When the reed dryer molecular sieves become saturated with moisture, the dryers need to be regenerated to restore sieve capacity. The dry ethylene vapor coming out of the lag dryers is used as the regenerator medium. The slip flow from the lag dryer outlet is sent to a regenerator superheater, where the regenerator is heated to the required regeneration temperature before entering the dryers under regeneration. Under regeneration, the spent regenerator, carrying moisture desorbed from the molecular sieves from the dryers, is cooled and condensed in a 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 a wastewater stripper.

[0023] The wastewater section consists of a wastewater stripper and a water wash tower. Liquids from the dewatering separator, the bottom of the water wash tower, the regenerator coalescer (intermittent), and the knockout liquid from the ethylene compressor section knockout drum are sent through the shell side of the wastewater stripper feed-bottom exchanger before entering the top tray of the wastewater stripper. The wastewater stripper is designed to remove oxygenates that enter with the feed as top steam products while recovering treated water into the bottom.

[0024] The wastewater stripper operates at 5-10 psig, and the top steam is cooled and condensed in the off-gas condenser before entering the off-gas knockout drum. The off-gas knockout drum liquid contains water along with most of the alcohol carried from the DEE absorber steam, unconverted alcohol from the reactor, and other non-selective oxygenates formed in the reactor, such as acetaldehyde, ether, and acetic acid. These are recycled, mixed with fresh feed, and sent to the reactor section through the feed surge drum or the bottom of the DEE absorber. The off-gas knockout drum steam is a small purge stream, a mixture of olefins (dissolved in the dehydration separator and water wash tower liquid) and oxygenates. The wastewater stripper has two reboiler systems. The wastewater stripper auxiliary reboiler utilizes low-pressure steam as the reboiler medium, while the wastewater stripper reboiler integrates process heat with the high-temperature dehydration reactor effluent upstream of the dehydration product condenser. The net bottom of the wastewater stripper is pumped by the treated water pump through the tubular side of the wastewater stripper feed-bottom exchanger and is divided into three flows downstream. The first flow is treated water used to wash away steam-produced oxygenates in the water wash tower. This flow is sent to the water wash tower via the ethanol treated water exchanger, treated water cooler, and treated water trim cooler.

[0025] 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 the steam generator. The generated steam is sent to the dehydration reactor to meet the requirement of the steam-to-ethanol ratio. 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.

[0026] The third stream is the net treated water generated from various reactions occurring in the reactor section, which is sent to the wastewater treatment facility. This stream is taken from downstream of the treated water trim cooler.

[0027] As described above, the dehydrator separator steam can be sent to the DEE absorber or the water wash tower. The dehydrator separator steam has certain impurities / oxygenates such as acetaldehyde, diethyl ether, dimethyl ether, water, and unconverted alcohol that may need to be removed depending on the further use of the ethylene product.

[0028] In the DEE absorber, the diethyl ether in the separator steam is absorbed into the bottom liquid along with some other oxygenates. Since the ethanol feed is used to wash the separator steam, there is some carry-over of the ethanol feed to the DEE absorber steam. The DEE absorber overhead steam is sent under 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 carry-over from the DEE absorber steam, and acetic acid using the treated water from the bottom of the wastewater stripper. The treated water enters the top tray of the water wash tower, and the absorption of oxygenates occurs in a countercurrent direction over multiple trays. The water wash tower overhead steam 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.

[0029] The process conditions, conversion rates, and selectivities expected based on the dry ethanol feedstock are shown in the following table.

[0030] [Table 1]

[0031] Description of the drawing Figure 1 shows a process 10 for processing an oxygenate feedstock according to an exemplary embodiment. The oxygenate feedstock may contain alcohol, preferably ethanol. The feedstock may contain ethanol as its main component and may be aqueous. Preferably, the oxygenate feedstock is a biorenewable feedstock.

[0032] The supply line 12 transports the oxygenate stream of the oxygenate feedstock to the supply pretreatment section 14. The supply 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 oxygenate stream in the supply line 12. The supply pretreatment section 14 may include an additional container 18 with a bed of the same adsorbent for further removal of metals from the oxygenate stream. The containers 16 and 18 may be in series or lead-lag type arrangement to allow for the regeneration of used adsorbent. Line 17 transports the partially pretreated oxygenate stream from the outlet of container 16 to the inlet of container 18. The pretreated oxygenate stream exits the supply pretreatment section 14 through line 20 from the outlet of the additional container 18 and is supplied to the purification column 22. The feed pretreatment section 14 can be operated at a temperature of approximately 32°C to approximately 105°C and a pressure of approximately 2800 kPa(g) to approximately 3100 kPa(g).

[0033] In the purification column 22, the pretreated oxygenate stream is fractionated to fractionally distill ethanol from heavier oxygenates, also known as fusel oils, such as cyclohexanol, cyclopentanol, and heavier 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 oxygenate stream in the bottom line 26 is removed from the bottom of the purification column 22 for heavy oxygenate 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 is cooled in an air cooler 25 and provides a top gas stream of purified ethanol in the top line 24, which may be fed into the feed surge drum 26 along with the recirculated ethanol stream of line 27. The purification column 22 may be operated at bottom temperatures of about 82°C to about 121°C and top pressures of about 35 kPa(g) to about 140 kPa(g).

[0034] 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 vapor 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 about 400°C to about 550°C. The first heated charge stream obtained in line 36 is supplied to the first dehydration reactor 40. In the first dehydration reactor 40, the ethanol supply material is converted to ethylene and water on a dehydration catalyst at a pressure of about 455 kPa(g) to about 630 kPa(g). The first dehydration stream is discharged from the first dehydration reactor 40 in line 42.

[0035] The second charge flow in line 44 undergoes heat exchange with the second dehydration exchange flow in line 46, is mixed with the first dehydration flow 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 flow to a flow temperature of 400°C to approximately 550°C. The second heated charge flow obtained in line 50 is supplied to the second dehydration reactor 52. In the second dehydration reactor 52, the ethanol feedstock is converted to ethylene and water on a dehydration catalyst at a pressure of approximately 420 kPa(g) to approximately 700 kPa(g). The second dehydration flow is discharged from the second dehydration reactor 52 in line 54.

[0036] The second dehydration flow in line 54 is supplied to an intermediate heater 56. The intermediate heater 56 may be a combustion heater and can heat the second dehydration flow to about 400°C to about 550°C. The third heated charge flow obtained in line 58 is supplied to a third dehydration reactor 60. In the third dehydration reactor 60, the residual ethanol feedstock is converted to ethylene and water on a dehydration catalyst at a pressure of about 420 kPa (g) to about 700 kPa (g). The third dehydration flow is discharged from the third dehydration reactor 60 in line 62.

[0037] The dehydration catalyst is an alumina-based catalyst.

[0038] The third dewatering flow is divided into a first dewatering exchange flow in line 32 and a second dewatering exchange flow in line 46. The first dewatering exchange flow in line 32 undergoes heat exchange with the first charge flow in line 30, the second dewatering exchange flow in line 46 undergoes heat exchange with the second charge flow in line 44, and the cooled dewatering flow is recombined in line 64.

[0039] The cooled dewatered flow in line 64 is supplied to the quench tower 68, where it is quenched by direct contact with water from the first cooling water flow in line 70 and the second cooling water flow in line 72. The quenched ethylene flow exits the quench tower top line 74, and the bottom water flow exits the bottom of the tower in line 76. The bottom water flow is divided into a drain flow in line 78, which can be transported to the wastewater stripper column 80 via a control valve above it, and a quench recirculation flow in line 82. The first portion of the quench recirculation flow is air-cooled in the product condenser 69 and recirculated as a first lower cooled water flow in line 70 via a control valve above it, while the second portion of the quench recirculation flow is heat-exchanged in the trim condenser 71 and recirculated to the quench tower 68 as a second higher cooled water flow in line 72. Quench tower 68 can operate with a bottom temperature of approximately 37°C to 104°C and a pressure at the top of the tower of approximately 280 kPa(g) to 490 kPa(g).

[0040] The ethylene flow quenched in line 74 is supplied to the first-stage suction drum 86. In the first-stage suction drum, the ethylene exits the top line 88 and proceeds to the first-stage compressor 90, while the residual water exits the bottom of the drum in line 92 through a control valve above it and is transported to the wastewater stripper column 80, possibly via line 78. The first-stage compressor 90 compresses the ethylene flow to a first pressure of approximately 350 kPa(g) to approximately 1225 kPa(g), and the waste in line 91 is cooled in the first-stage waste cooler 93 and the first-stage trim cooler 94.

[0041] The cooled and compressed ethylene flow 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 the top line 98 to the second-stage compressor 100, while the residual water exits the bottom of the drum in line 102 through a control valve above it and is transported to the wastewater stripper column 80, possibly via lines 92 and 78. The second-stage compressor compresses the ethylene flow to a second pressure of approximately 455 kPa(g) to approximately 3220 kPa(g), and the waste in line 101 is cooled in the second-stage waste cooler 103 and the second-stage trim cooler 104.

[0042] The twice-cooled and compressed ethylene flow 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 the top line 108 and is transported to the water washing tower 110, while the residual water flow exits the bottom of the drum in line 112 through a control valve above it and is transported to the wastewater stripper column 80, possibly via lines 102, 92, and 78.

[0043] In the water washing tower 110, the twice cooled and compressed ethylene flow is washed countercurrently with cooled and treated water in line 118 from the wastewater stripper column 80, absorbing additional oxygenates to produce the washed ethylene flow present in the top line 120 and the wash water flow in the bottom line 122. The washed ethylene flow in the top line 120 is transported to the product dryer section 140. The wash water flow in line 122 is returned to the water stripper column 80 through a control valve above it. The wash water 110 can be operated with a bottom temperature of approximately 16°C to approximately 82°C and a top pressure of approximately 2800 kPa(g) to approximately 3500 kPa(g).

[0044] In flow systems other than the current flow system, the washed ethylene stream can be sent to a caustic scrubber section to remove oxygenates. However, it has been found that the process can be successfully operated under certain operating conditions without using a caustic scrubber section, and can produce ethylene for further processing as an olefin feedstock, for example, for ethylene oligomerization. Instead, as described below, the wastewater stripper bottom stream is sent to the top tray of the water scrub tower, while the steam from the second-stage compressor discharge is sent below the bottom tray of the water scrub tower. The intention is to wash the ethylene-rich steam stream and remove as much oxygenate as possible from the product stream. The ethylene-rich steam, with trace amounts of CO and ppm levels of CO2, is sent directly to a series of dryers containing molecular sieves in a lead-lag system to remove moisture from the steam stream and then to a cryogenic distillation unit. The steam from the cryogenic distillation unit is further compressed in the third stage of the ethylene compressor to meet the downstream unit cell limit pressure requirements.

[0045] In the product dryer section 140, the ethylene stream washed and scrubbed in line 120 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 bottom line 150 that is supplied to the wastewater stripper column 80 via 122. The dryer inlet stream is fed to the first product dryer 152 in line 148. The first product dryer 152 includes 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 be operated in an upward flow 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 lead-lag operation to facilitate regeneration during continuous operation. The second product dryer 156, like the first product dryer 152, contains an adsorbent for adsorbing water from ethylene. The dry ethylene stream exits the product dryer section 140 in line 158. The product dryer section 140 can be operated at temperatures of about 32°C to about 105°C and pressures of about 2800 kPa(g) to about 3100 kPa(g).

[0046] The dry ethylene flow in line 158 is supplied to the dryer outlet knockout drum 160 to remove residual water, providing the dryer outlet flow in line 162 and a second knockout water flow in bottom line 164, which is possibly supplied to the wastewater stripper column 80 via lines 150 and 122.

[0047] The dryer outlet flow in line 162 is fed to the heavy oxygen removal column 170, where the top flow, mainly containing ethylene but possibly higher olefins, can be separated from heavy ketones and diethyl ether. The olefins are generated in the top line 172 and fed to the third-stage compressor 174, and the bottom heavy oxygen flow is generated in the bottom line 176. The heavy oxygen purge flow can be incorporated into the heavy oxygen treatment in line 178, while the re-boiling portion is re-boiled and returned to column 170. The compressed ethylene flow at a pressure of approximately 2800 kPa(g) to approximately 7000 kPa(g) in the compressor discharge line 176 can be supplied to the dimerization section. The heavy oxygenate removal column 170 can operate with a bottom temperature of approximately -30°C to approximately 120°C and a top pressure of approximately 2415 kPa(g) to approximately 3100 kPa(g).

[0048] The water streams containing oxygenates and volatile substances in lines 92, 102, 112, 122, 150, and 164 may be fed to the wastewater stripper column 80, where the volatile substances and oxygenates are boiled off to provide a top volatile substance stream in line 182 and a stripped water stream in line 184. A portion of the stripped water stream may be re-boiled and returned to the column to provide the necessary heat. The treated water stream in line 186 may be pumped to the water outlet in 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 with a bottom temperature of approximately 90°C to approximately 120°C and a top pressure of approximately 35 kPa(g) to approximately 140 kPa(g).

[0049] The top volatile flow in line 182 is cooled in the air cooler 189 and can be supplied to the off-gas knockout drum 190. The top flow from the knockout drum 190 in line 192 can be sent to a flare, while the ethanol recirculation flow is pumped to the supply surge drum 26 in line 27, possibly via line 24.

[0050] The following will be explained in conjunction with specific embodiments, but it should be understood that this explanation is intended to illustrate the scope of the preceding explanation and the attached claims, and is not intended to limit them.

[0051] Without further detail, it is expected that those skilled in the art will be able to utilize the invention to the fullest extent without departing from the spirit and scope of the invention, and will readily identify its essential characteristics, and will be able to make various changes and modifications to the invention to suit various uses and conditions. Accordingly, the prior preferred specific embodiments should be interpreted as merely illustrative and not to limit the remainder of this disclosure in any way, but are intended to cover various modifications and equivalent configurations that fall within the scope of the appended claims.

[0052] In the above, unless otherwise specified, all temperatures are given in degrees Celsius, all pressures are given in kPa(g), all parts and percentages are given by weight, and in the formulas, n is an integer between 20 and 2000.

[0053] The first embodiment is a process for processing a flow containing ethylene and an oxygenate, the process comprising sending the aforementioned flow to a water scrubbing tower and sending the resulting ethylene-rich vapor flow directly to a dryer without first sending it to a caustic scrubbing section.

[0054] The second embodiment is a process for converting an ethanol supply stream to ethylene, comprising: dividing the aforementioned ethanol supply stream into a first part and a second part; sending the aforementioned first part to a reactor through a charge heater; mixing vapor with the aforementioned first part in the charge heater and sending the ethanol / vapor mixture to the aforementioned reactor; The process involves subjecting the aforementioned ethanol / vapor mixture to conditions sufficient to dehydrate the aforementioned ethanol to produce an effluent containing ethylene and water, and combining the aforementioned effluent with the aforementioned second portion to form an effluent / second portion mixture, and sending the aforementioned mixture to a second reactor to react and produce a product effluent containing ethylene and water. One embodiment of the present invention is one, any, or all of the embodiments described earlier in this paragraph to the first embodiment of this paragraph, wherein the aforementioned first portion or the aforementioned second portion contains a mixture of ethanol and water. Another embodiment of the present invention is one, any, or all of the embodiments described earlier in this paragraph to the first embodiment of this paragraph, wherein the aforementioned water is recirculated and mixed with the aforementioned ethanol supply stream.

[0055] A third embodiment of the present invention is a process for converting an ethanol feed stream to ethylene, comprising: dividing the aforementioned ethanol feed stream into a first portion and a second portion to be sent to a reactor section comprising a first reactor and a second reactor; sending the aforementioned first portion to the aforementioned first reactor through a charge heater; mixing vapor with the aforementioned first portion in the aforementioned charge heater and sending the ethanol / vapor mixture to the aforementioned first reactor; subjecting the aforementioned ethanol / vapor mixture to conditions sufficient to dehydrate the aforementioned ethanol to produce an effluent containing ethylene and water; combining the aforementioned effluent with the aforementioned second portion to form an effluent / second portion mixture; sending the aforementioned effluent / second portion mixture to the aforementioned second reactor to react and produce a product effluent containing ethylene and water. One embodiment of the present invention is one or all of the embodiments described above from the earlier embodiments to the first embodiment of this paragraph, wherein the aforementioned first portion or the aforementioned second portion contains a mixture of ethanol and water. One embodiment of the present invention is one or all of the embodiments described above, from the earlier embodiments of this paragraph to the first embodiment of this paragraph, wherein the aforementioned water is recirculated and mixed with the aforementioned ethanol supply stream. One embodiment of the present invention is one or all of the embodiments described above, from the earlier embodiments of this paragraph to the first embodiment of this paragraph, wherein the aforementioned reactor section has a volume approximately 30-40% less than that of a dehydration process in which the aforementioned ethanol supply stream remains a single flow. One embodiment of the present invention is one or all of the embodiments described above, from the earlier embodiments of this paragraph to the first embodiment of this paragraph, wherein the aforementioned reactor section further comprises a third reactor vessel. One embodiment of the present invention is one or all of the embodiments described above, from the earlier embodiments of this paragraph to the first embodiment of this paragraph, wherein the oxygenate supply material is pretreated to remove contaminants, and then the pretreated oxygenate stream is sent to the aforementioned reactor section. One embodiment of the present invention is one, any, or all of the embodiments described above from the earlier embodiments to the first embodiment of this paragraph, wherein the aforementioned pretreated oxygenate stream is fractionally distilled to separate ethanol from heavier oxygenates, and the aforementioned ethanol is the aforementioned ethanol feed stream.One embodiment of the present invention is one, any, or all of the embodiments described above from the earlier embodiments of this paragraph to the first embodiment of this paragraph, wherein the ethanol feed stream described above, which is sent to the first reactor described above, is heated to about 400°C to about 550°C and converted to ethylene at about 455 kPa (g) to about 630 kPa (g) on ​​a dehydration catalyst. One embodiment of the present invention is one, any, or all of the embodiments described above from the earlier embodiments of this paragraph to the first embodiment of this paragraph, wherein the mixture of the effluent / second portion described above is heated to about 400°C to about 550°C and converted to ethylene at about 420 kPa (g) to about 700 kPa (g) on ​​a dehydration catalyst. One embodiment of the present invention is one, any, or all of the embodiments described above from the earlier embodiments of this paragraph to the first embodiment of this paragraph, wherein the product effluent described above from the second reactor described above is sent to an intermediate heater, and the heated product effluent is then sent to a third reactor. One embodiment of the present invention is one, any, or all of the embodiments described above from the earlier embodiments to the first embodiment of this paragraph, wherein the product effluent of the aforementioned third reactor does not contain measurable diethyl ether. One embodiment of the present invention is one, any, or all of the embodiments described above from the earlier embodiments to the first embodiment of this paragraph, wherein the aforementioned first and second reactors contain less vapor than when the aforementioned ethanol feed stream is sent to a single reactor and the aforementioned first and second reactors operate at increased endothermic levels. One embodiment of the present invention is one, any, or all of the embodiments described above from the earlier embodiments to the first embodiment of this paragraph, wherein the aforementioned product effluent is not sent to a caustic cleaning section.

Claims

1. A process that converts an ethanol supply stream into ethylene, a. Dividing the ethanol supply stream into a first part and a second part, b. Sending the first portion to the reactor through a charge heater, c. Mixing the vapor with the first part in the charge heater and sending the ethanol / vapor mixture to the reactor, d. The ethanol / vapor mixture is subjected to conditions sufficient to dehydrate the ethanol to produce an effluent containing ethylene and water. e. A process comprising combining the effluent with the second portion to form an effluent / second portion mixture, sending the mixture to a second reactor to react and produce a product effluent containing ethylene and water, wherein the reactor section has a volume reduction of 30-40% compared to a process containing a caustic scrubber, and the first and second reactors contain less steam than a process having a single reactor.

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

3. A process that converts an ethanol supply stream into ethylene, a. Dividing the ethanol supply stream into a first portion and a second portion which are sent to a reactor section comprising a first reactor and a second reactor, wherein the combination of the first reactor and the second reactor comprises a reactor volume of approximately 60-70% of the volume of a single reactor system. b. Sending the first portion to the first reactor through a charge heater, c. Mixing the vapor with the first part in the charge heater and sending the ethanol / vapor mixture to the first reactor, d. The ethanol / vapor mixture is subjected to conditions sufficient to dehydrate the ethanol to produce an effluent containing ethylene and water. e. A process comprising combining the effluent with the second part to form an effluent / second part mixture, and sending the effluent / second part mixture to the second reactor to react and produce a product effluent containing ethylene and water.

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