Processes and apparatuses for reducing molecular weight fluctuation in a tail gas stream from a pressure swing adsorption process

Abstract

Processes and apparatuses for reducing molecular weight fluctuation in a tail gas stream from a pressure swing adsorption process. The steps of the vessels in the PSA separation zone are synchronized such that when one of the vessels is generating a low molecular weight tail gas, there is another vessel generating a high molecular weight tail gas. Additionally, the steps may be split into sub-steps that utilize gas streams with different pressures / flow rates.

Description

PROCESSES AND APPARATUSES FORREDUCING MOLECULAR WEIGHT FLUCTUATIONIN A TAIL GAS STREAMFROM A PRESSURE SWING ADSORPTION PROCESSRELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Non-Provisional Patent Application Ser. No. 18 / 543,957 filed on December 18, 2023 the entire disclosure of which is incorporated herein by way of reference.FIELD OF THE INVENTION

[0002] This invention relates generally to pressure swing adsorption process and more specifically to processes for reducing molecular weight fluctuation in a tail gas stream from a pressure swing adsorption process.BACKGROUND OF THE INVENTION

[0003] A centrifugal gas compressor provides efficiency, cost, and scalability advantages compared to other types of gas compressors, such as oil-flooded screw compressors, for large gas flow rates. This type of compressor may be used for compression of a tail gas stream in pressure swing adsorption (PSA) unit in, for example, steam methane reforming (SMR) or ATR hydrogen plants, gasification processes, steel plant (blast furnace) offgas, etc.

[0004] While effective for their intended purpose, one disadvantage associated with centrifugal gas compressors is their sensitivity to dynamic fluctuations in gas density. This may impact their ability to effectively and efficiently be utilized in configurations with varying gas compositions. One such contemplated configuration is with a PSA unit in which the PSA tail gas has variations of composition / molecular weight during the cycling and transitions between operating modes.

[0005] A PSA unit generally includes a plurality of adsorption vessels, and each vessel includes a plurality of adsorbent layers. In the PSA unit, a multicomponent gas is typically fed to at least one of a plurality of adsorption beds at an elevated pressure effective to adsorb at least one component, while at least one other component passes through. At a defined time, feed to the adsorber is terminated and the bed is depressurized by one or more co-current depressurization steps wherein pressure is reduced to a defined level which permits the separated, less-strongly adsorbed component or components remaining in the bed to be drawn off without significant concentration of the more-strongly adsorbed components. Then, the bed is depressurized by a countercurrent depressurization step wherein the pressure on the bed is further reduced by withdrawing desorbed gas counter- currently to the direction of feed. Finally, the bed is purged and repressurized. The final stage of re-pressurization is with product gas or feed gas. Accordingly, the tail gas stream from the PSA unit is constantly changing in composition and flow rate. Tail gas mixing tanks are typically used to dampen composition and flow rate variations, but significant variation still remains downstream of the mixing tank.

[0006] Therefore, it would be desirable to provide processes which effectively and efficiently reduce the fluctuations of the PSA tail gas.SUMMARY OF THE INVENTION

[0007] The present invention provides processes which reduce the fluctuation of molecular weight of a PSA tail gas, thus offer more efficient and stable compression, reduce power consumption, and better stability to downstream process. In general, the present processes, the operation steps of the vessels are controlled so that one vessel isproducing a high molecular weight tail gas, another is producing a lower molecular weight tail gas. The combined tail gas from the PSA separation zone has a reduced average molecular weight fluctuation.

[0008] Therefore, the present invention may be characterized, in at least one aspect, as providing a method for reducing molecular weight fluctuation in a tail gas stream from a pressure swing adsorption separation zone by: providing a plurality of vessels each containing an adsorbent configured to adsorb a species from a multi-component feed and provide a product stream and a tail gas stream by cycling through a plurality of steps, wherein a molecular weight of the tail gas stream fluctuates between a low molecular weight at the start of a first step and a high molecular weight at the start of a second step; and controlling the plurality of vessels such that while a first vessel is operated in the first step, a second vessel is operated in the second step.

[0009] The plurality of steps may include an adsorption step, a co-current depressurization step, a counter-current depressurization step, a purge step, and a repressurization step. The first step may be the counter-cunent depressurization step. The second step may be the purge step. The controlling may include maintaining the second vessel in the purge step so long as the first vessel is in the counter-current depressurization step.

[0010] At least one step may include two sub-steps, wherein a pressure or an average pressure of a gas stream used in the first sub-step may be different than a pressure or an average pressure of a gas stream used in the second sub-step. Additionally and / or alternatively, an average flow rate of a gas stream used in the first sub-step may be different than an average flow rate of a gas stream used in the second sub-step. An operating time for the first sub-step may be different than an operating time for the second sub-step.

[0011] The method may include combining the tail gas streams from each vessel to provide a net tail gas stream. The process may further include compressing the net tail gas stream in a compression zone. The compression zone may have at least one compressor.

[0012] The present invention may also be broadly characterized as providing a method for operating a pressure swing adsorption separation zone by: passing a multi-component feed to a PSA separation zone, the PSA separation zone comprising a plurality of vessels each containing an adsorbent configured to adsorb a species from the multicomponent feed, the PSA separation zone configured to provide a product stream and a tail gas stream; cycling the plurality of vessels through a plurality of steps, the plurality of steps comprising: an adsorption step, a co-current depressurization step, a counter-current depressurization step, a purge step, and a repressurization step, wherein a molecular weight of the tail gas stream fluctuates between a low molecular weight at the start of a first step and a high molecular weight at the start of a second step; and maintaining at least one first vessel in the first step so long as at least one second vessel is operated in the second step.

[0013] The first step may be the counter-current depressurization step. The second step may be the purge step.

[0014] At least one step may include two sub-steps, wherein a pressure or an average pressure of a gas stream used in the first sub-step may be different than a pressure or an average pressure of a gas stream used in the second sub-step. Additionally, and / or alternatively, an average flow rate of a gas stream used in the first sub-step may be different than an average flow rate of a gas stream used in the second sub-step. An operating time for the first sub-step may be different than an operating time for the second sub-step.

[0015] The method may also include combining the tail gas streams from each vessel to provide a net tail gas stream. The method may include compressing the net tail gas stream in a compression zone. The compression zone may include at least one compressor.

[0016] The present invention may also be generally characterized as providing a method for operating a pressure swing adsorption separation zone by: passing a multicomponent feed to a PSA separation zone, the PSA separation zone comprising a plurality of vessels each containing an adsorbent configured to adsorb a species from the multicomponent feed, the PSA separation zone configured to provide a product stream and a tail gas stream; cycling the plurality of vessels through a plurality of steps, wherein a molecular weight of the tail gas stream fluctuates between a low molecular weight at the start of a first step and a high molecular weight at the start of a second step; and maintaining at leastone first vessel in the first step so long as at least one second vessel is operated in the second step. At least one step may include two sub-steps. A pressure or an average pressure of a gas stream used in the first sub-step may be different than a pressure or an average pressure of a gas stream used in the second sub-step and / or an average flow rate of a gas stream used in the first sub-step may be different than an average flow rate of a gas stream used in the second sub-step. The first step may be a counter-current depressurization step and the second step may be a purge step.

[0017] Additional aspects, embodiments, and details of the invention, all of which may be combinable in any manner, are set forth in the following detailed description of the invention.DETAILED DESCRIPTION OF THE DRAWINGS

[0018] One or more exemplary embodiments of the present invention will be described below in conjunction with the following drawing figures, in which:

[0019] Figure 1 shows a schematic process flow diagram of a PSA separation zone that may be utilized according to one or more aspects of the present invention; and,

[0020] Figure 2 shows a graph comparing molecular weight fluctuation of a combined PSA tail gas stream in a conventional process and in a process according to one or more aspects of the present invention.DETAILED DESCRIPTION OF THE INVENTION

[0021] As mentioned above, processes which reduce the fluctuation of molecular weight of a PSA tail gas have been invented. According to the present invention, the fluctuation of the molecular weight of a PSA tail gas, is reduced by controlling the vessels within a single PSA separation zone so that one vessel is producing a high molecular weight tail gas, another is producing a lower molecular weight tail gas. The combined tail gas from the PSA separation zone has a reduced average molecular weight fluctuation. While prior processes might have an unintended or some overlap of stages between vessels, the present control has a significant and surprising reduction in the fluctuation of the molecularweight of the tail gas. Additionally, the present invention further contemplates separating stages or steps into sub-steps having different gas pressures or flow rates.

[0022] With these general principles in mind, one or more embodiments of the present invention will be described with the understanding that the following description is not intended to be limiting.

[0023] As shown in FIG. 1, the present processes relate to a PSA separation zone 10, or unit. As used herein, the term “zone” refers to an area including one or more equipment items and / or one or more sub-zones. Equipment items can include one or more reactors or reactor vessels, scrubbers, strippers, fractionators or distillation columns, absorbers or absorber vessels, regenerators, heaters, exchangers, coolers / chillers, pipes, pumps, compressors, valves, controllers, and the like. Additionally, an equipment item can further include one or more zones or sub-zones.

[0024] As is known, a PSA separation zone 10 includes a plurality of fixed-bed adsorption vessels 12a, 12b, 12c, 12d each containing layers of an adsorbent. The vessels 12a, 12b, 12c, 12d may be filled with different layers of materials, for example, lower layers may be filled with weaker adsorbent materials, e.g., relatively low affinity for adsorbing gaseous hydrocarbons, and upper layers may be filled with stronger adsorbent materials, e.g., relatively high affinity for adsorbing gaseous hydrocarbons. For example, the lower layer(s) can contain weakly adsorbent materials, such as activated alumina and / or silica gel, while the intermediate layer(s) can contain intermediate strength adsorbent materials, such as activated carbon, and the upper layer(s) can contain strong adsorbent materials, such as zeolite and / or molecular sieve materials.

[0025] As is known, a multicomponent feed gas 14 comprising, for example, hydrogen, hydrocarbons, and carbon dioxide is passed to a first vessel 12a in the PSA separation zone 10 whereby impurities are adsorbed onto the adsorbent and a product 16, such as a hydrogen product, is recovered. Pressure increases as loading increases in the first adsorber vessel 12a. Once the adsorbent is saturated with impurities, the adsorption step is discontinued. Pressure is equalized by passing the product / hydrogen stream over to one or more other adsorber vessels 12b, 12c, 12d via co-cunent depressurization andpurging of the first adsorber vessel 12a. Pressure is decreased in the first adsorber vessel 12a via counter-current depressurization or blowdown. This step removes the impurities from the first adsorber vessel 12a. The first adsorber vessel 12a is purged using co-current depressurization with another adsorber vessel 12b, 12c, 12d. Thus, there are two vessels utilized in a “purge” step. Vessel A, after adsorption and equalizations, will provide purge step where it co currently depressurizes to another vessel that is on the receive purge side. Then vessel A completes blowdown or counter-current depressurization. Subsequently, vessel A will receive purge gas from another vessel providing the purge gas.

[0026] The product from the blow down and the purge stages is a net tail gas stream 18 which is passed to a compression zone 22, having one or more compressors, like a centrifugal compressor. While the invention is contemplated to be utilized with any type of compressors in the compression zone 22, newer, centrifugal compressors are particularly susceptible to molecular weight fluctuations. Although not depicted, the present invention contemplates providing a surge drum to further dampen the molecular weight fluctuations before the tail gas 18 is passed to the compression zone 22.

[0027] As is known, the vessels 12a, 12b, 12c, 12d are connected by conduits and valves (not shown) which control the flow of the steams in the PSA separation zone 10. The opening and closing of the valves, and thus, controlling the steps of the vessels may be done by a controller 20 in communication with the various pieces of equipment.

[0028] Accordingly, the vessels 12a, 12b, 12c, 12d within the PSA separation zone 10 produce the product stream 16 and tail gas streams 18 by cycling through a plurality of steps that includes an adsorption step, a co-current depressurization step, a counter-current depressurization step, a purge step, and a repressurization step. The co-current depressurization, counter-current depressurization and purge steps decrease the pressure in the fixed-bed adsorption unit and purge the unit with high purity gas from the product or co-current depressurization steps, respectively, to remove the hydrocarbons and carbon dioxide and regenerate the adsorption materials. The repressurization step increases the pressure in the PSA separation zone 10 with either feed gas or product gas in preparation for the next adsorption step.

[0029] The two PSA steps that produce tail gas are counter-current depressurization step, or blowdown, and purge. Blowdown starts with a relatively low molecular weight and as the pressure reduces in the vessel 12a, 12b, 12c, 12d the molecular weight increases until the end of blowdown. The purge step operates in the reverse; molecular weight starts high and reduces throughout the step as the vessel 12a, 12b, 12c, 12d reaches maximum regeneration for the cycle.

[0030] Whenever the PSA separation zone 10 is operating in a blowdown or purge step, there is a steep change in the molecular weight of the tail gas 18 produced by the PSA separation zone 10. While conventional processes provide a surge tank or drum, this does not achieve ideal mixing and reducing of molecular weight fluctuations to effectively and efficiently address this issue.

[0031] To reduce the fluctuations, the present invention synchronizes the vessels 12a, 12b, 12c, 12d and controls the step(s) such that while one or more first vessels 12a, 12b, 12c, 12d are operated in a first step, one or more second vessels 12a, 12b, 12c, 12d are operated in a second step. The first step may be the purge step and the second step may the blowdown step, or the first step may be the blowdown step, and the second step may be the purge step. In the present processes, the simultaneous blowdown and purge naturally offset one another.

[0032] Conventional processes controls the vessels 12a, 12b, 12c, 12d such that the purge step was maximized, however this may result in the purge step ending while another vessel 12a, 12b, 12c, 12d is in the blowdown step. To modify this, a step change will be placed in the center of the PSA sub cycle and the low molecular weight receive purge gas will not be overlapping with high molecular weight of the blowdown gas optimally increasing the step change difference at the start of the next blowdown step.

[0033] In order to further reduce the molecular weight fluctuation in the tail gas stream 18, the present invention contemplates separating one or more of the steps into substeps and using gas streams with different pressures or different flow rates during the two sub-steps. By different pressures or different flow rates, it is meant that the values differ by at least 5% or at least 10%.

[0034] For example, to mitigate the initial low molecular weight spike of the blowdown step, and the overall negative slope of molecular weight over the sub cycle, the blowdown step can be separating into to sub-steps. Assuming blowdown is generally controlled to produce a constant flow rate of gas throughout the total step and that the two sub-steps are equal in time, the first sub-step may use gas with 75% of the average rate of blowdown, while the second sub-step may use gas with 125% of the average rate of blowdown. The change between the two sub-steps may be gradual change throughout the blowdown step. Such a process is believed to reduce the light blowdown gas produced during the heavy purge gas portion of the sub-step and vice versa in the second sub-step.

[0035] In addition to the blowdown step being split into sub-steps, the purge step may also be split; however, with the opposite difference, i.e., the first sub-step having a greater value than the second sub-step.

[0036] Moreover, the operation times of the sub-steps of a particular step may be equal or different.

[0037] The controller 20 may synchronize the steps by sending signals to various valves and other pieces of equipment. The controller 20 or a computing device may include a processor and a memory which has stored therein computer-executable instructions for implementing the processes described herein. The controller 20 may comprise any suitable devices configured to cause a series of steps to be performed so as to implement the method such that instructions, when executed by the computing device or other programmable apparatus, may cause the functions / acts / steps specified in the methods described herein to be executed. The controller 20 may comprise, for example, any type of general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, a central processing unit (CPU), an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, other suitably programmed or programmable logic circuits, or any combination thereof.

[0038] The memory may be any suitable known or other machine-readable storage medium. The memory may comprise non-transitory computer readable storage medium such as, for example, but not limited to, an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. The memory may include a suitable combination of any type of computer memory that is located either internally or externally to the device such as, for example, random-access memory (RAM), read-only memoiy (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like. The memory may comprise any storage means (e.g., devices) suitable for retrievably storing the computerexecutable instructions executable by processing unit.

[0039] The methods and systems described herein may be implemented in a high- level procedural or object-oriented programming or scripting language, or a combination thereof, to communicate with or assist in the operation of the controller 20 or computing device. Alternatively, the methods and systems described herein may be implemented in assembly or machine language. The language may be a compiled or interpreted language. Program code for implementing the methods and systems described herein may be stored on the storage media or the device, for example a ROM, a magnetic disk, an optical disc, a flash drive, or any other suitable storage media or device. The program code may be readable by a general or special-purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein.

[0040] Computer-executable instructions may be in many forms, including modules, executed by one or more computers or other devices. Generally, modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Typically, the functionality of the modules may be combined or distributed as desired in various embodiments.

[0041] It will be appreciated that the systems and devices and components thereof may utilize communication through any of various network protocols such as TCP / IP, Ethernet, FTP, HTTP and the like, and / or through various wireless communication technologies such as GSM, CDMA, Wi-Fi, and WiMAX, is and the various computingdevices described herein may be configured to communicate using any of these network protocols or technologies.

[0042] By synchronizing the steps of the vessels 12a, 12b, 12c, 12d the PSA separation zone 10, the molecular weight fluctuations in the net tail gas stream 18 is reduced.EXPERIMENTS

[0043] The examples included hereinafter illustrating the molecular weight variation in the PSA tail gas is generated using an in-house proprietary software package that solves the heat, mass, and momentum balance equation in an adsorption bed.

[0044] In FIG. 2, the expected molecular weight fluctuations from a 10 bed PSA system is depicted.

[0045] In the upper graph, a simulation based on conventional operations shows without any synchronization, the expected molecular weight fluctuation ranges from 30.5 to 32.8. This is a range of 2.3.

[0046] In the simulation based on the present invention, with synchronization and use of sub-steps, the expected molecular weight fluctuation ranges from 31.5 to 32.5. This is a range of 1.0, or + / - of 1.0%. Thus, there is an improvement of at least two times from conventional processes as a result of synchronizing the vessels so that when one of the vessels is in a blowdown, at least one vessel is in a purge, and when one of the vessels in in purge, one of the vessels is in blowdown.SPECIFIC EMBODIMENTS

[0047] While the following is described in conjunction with specific embodiments, it will be understood that this description is intended to illustrate and not limit the scope of the preceding description and the appended claims.

[0048] A first embodiment of the invention is a method for reducing molecular weight fluctuation in a tail gas stream from a pressure swing adsorption separation zone,the method comprising providing a plurality of vessels each containing an adsorbent configured to adsorb a species from a multi-component feed and provide a product stream and a tail gas stream by cycling through a plurality of steps, wherein a molecular weight of the tail gas stream fluctuates between a low molecular weight at the start of a first step and a high molecular weight at the start of a second step; and controlling the plurality of vessels such that while a first vessel is operated in the first step, a second vessel is operated in the second step. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the plurality of steps comprises an adsorption step, a co-current depressurization step, a counter-cunent depressurization step, a purge step, and a repressurization step. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the first step comprises the counter-current depressurization step. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the second step comprises the purge step. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the controlling comprises maintaining the second vessel in the purge step so long as the first vessel is in the counter-current depressurization step. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein at least one step comprises two sub-steps, wherein a pressure or an average pressure of a gas stream used in the first substep is different than a pressure or an average pressure of a gas stream used in the second sub-step, or wherein an average flow rate of a gas stream used in the first sub-step is different than an average flow rate of a gas stream used in the second sub-step, or both. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein an operating time for the first substep is different than an operating time for the second sub-step. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, further comprising combining the tail gas streams from eachvessel to provide a net tail gas stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, further comprising compressing the net tail gas stream in a compression zone. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the compression zone has at least one compressor.

[0049] A second embodiment of the invention is a method for operating a pressure swing adsorption separation zone, the method comprising passing a multi-component feed to a PSA separation zone, the PSA separation zone comprising a plurality of vessels each containing an adsorbent configured to adsorb a species from the multi-component feed, the PSA separation zone configured to provide a product stream and a tail gas stream , cycling the plurality of vessels through a plurality of steps, the plurality of steps comprising an adsorption step, a co-current depressurization step, a counter-cunent depressurization step, a purge step, and a repressurization step, wherein a molecular weight of the tail gas stream fluctuates between a low molecular weight at the start of a first step and a high molecular weight at the start of a second step; and maintaining at least one first vessel in the first step so long as at least one second vessel is operated in the second step. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the first step comprises the counter-current depressurization step. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the second step comprises the purge step. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein at least one step comprises two sub-steps, wherein a pressure or an average pressure of a gas stream used in the first sub-step is different than a pressure or an average pressure of a gas stream used in the second sub-step, or wherein an average flow rate of a gas stream used in the first sub-step is different than an average flow rate of a gas stream used in the second sub-step, or both. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in thisparagraph, wherein an operating time for the first sub-step is different than an operating time for the second sub-step. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, further comprising combining the tail gas streams from each vessel to provide a net tail gas stream. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, further comprising compressing the net tail gas stream in a compression zone. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the compression zone has at least one compressor.

[0050] A third embodiment of the invention is a method for operating a pressure swing adsorption separation zone, the method comprising passing a multi-component feed to a PSA separation zone, the PSA separation zone comprising a plurality of vessels each containing an adsorbent configured to adsorb a species from the multi-component feed, the PSA separation zone configured to provide a product stream and a tail gas stream, cycling the plurality of vessels through a plurality of steps, wherein a molecular weight of the tail gas stream fluctuates between a low molecular weight at the start of a first step and a high molecular weight at the start of a second step; and maintaining at least one first vessel in the first step so long as at least one second vessel is operated in the second step, wherein at least one step comprises two sub-steps, wherein a pressure or an average pressure of a gas stream used in the first sub-step is different than a pressure or an average pressure of a gas stream used in the second sub-step, or wherein an average flow rate of a gas stream used in the first sub-step is different than an average flow rate of a gas stream used in the second sub-step, or both. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph, wherein the first step comprises a counter-current depressurization step and wherein the second step comprises a purge step.

[0051] Without further elaboration, it is believed that using the preceding description that one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of this invention, without departing fromthe spirit and scope thereof, to make various changes and modifications of the invention and to adapt it to various usages and conditions. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limiting the remainder of the disclosure in any way whatsoever, and that it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0052] In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.

[0053] While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.

Claims

CLAIMSWhat is claimed is:

1. A process for separating carbon monoxide from ethylene, the process comprising: cooling an ethylene stream (50) with a refrigerant stream (60) in a cooling zone (58); separating the ethylene stream in a fractionation zone (16) comprising a fractionation column (54) into a liquid stream (22) comprising ethylene and an overhead stream (64) comprising carbon monoxide and ethylene; separating the overhead stream (64) in a vessel (72) into a liquid portion (74) and a gaseous portion (76), wherein the gaseous portion (76) comprises carbon monoxide and ethylene; and, absorbing the ethylene from the gaseous portion (76) in an absorption zone (66) with an absorbing liquid stream (80) to provide an enriched absorbing liquid (82) comprising an increased level of ethylene and an ethylene depleted vapor (84) comprising carbon monoxide.

2. The process of claim 1, further comprising: reboiling a stream from the fractionation column (54) with the ethylene stream (50) before cooling the ethylene stream (50) in the cooling zone (58).

3. The process of claim 1, further comprising: heating the liquid stream (22) from the fractionation column (54) with the ethylene stream (50) before cooling the ethylene stream (50) in the cooling zone (58).

4. The process of claim 1, further comprising: cooling the overhead stream (64) with a refrigerant stream (60) in a cooling zone (68) before separating the overhead stream (64) in a vessel (72).

5. The process of claim 1, further comprising: subcooling the refrigerant stream (60) by transferring heat from the refrigerant stream (60) to a portion of the liquid stream (22) from the fractionation column (54).

6. The process of claim 1, further comprising: subcooling the refrigerant stream (60) by transferring heat from the refrigerant stream (60) to the gaseous portion (76) from the vessel (72).

7. The process of any one of claims 1 to 6, wherein the absorbing liquid stream (80) comprises a hydrocarbon stream.

8. The process of claim 7, wherein the absorbing liquid stream (80) comprises an oligomerized effluent, and / or wherein the ethylene stream (50) comprises a portion of a dehydrated effluent.

9. The process of claim 7, wherein the emiched absorbing liquid (80) is reboiled.

10. The process of any one of claims 1 to 6, wherein the ethylene stream (50) has a pressure between 3,447 to 4,137 kPa (500 to 600 psi(g)) and the liquid stream (22) has a pressure between 2,413 to 3,103 kPa (350 to 500 psi(g)).

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