Process for separating olefin stream from methane

Abstract

A process for separating an olefin stream from a methane stream is disclosed. The process comprises providing an olefin stream comprising C2 and / or C3 olefins. The olefin stream is cooled with a mixed refrigerant stream in a heat exchanger to provide a cooled olefin stream. The cooled olefin stream is passed to a demethanizer operating at an overhead pressure of from about 344 kPa gauge pressure (50 psig) to about 2069 kPa gauge pressure (300 psig). The cooled olefin stream is fractionated in the demethanizer to provide a demethanizer overhead vapor stream and a demethanizer bottom liquid stream. The process provides improved olefin recovery / yield, and also optimizes cooling and / or heating of other process streams.

Description

TECHNICAL FIELD

[0001] The field relates to methods for separating an olefin stream from a methane stream. The field can particularly relate to methods for cooling an olefin stream with a mixed refrigerant. BACKGROUND

[0002] There is a growing global support and demand for sustainable aviation fuel (SAF) with governments offering subsidies and requiring the production of carbon neutral jet fuel. In recent years, considerable research has been devoted to finding effective and efficient ways to produce SAF. Several different approaches can be taken to address this demand, including the methanol-to-olefins approach.

[0003] Olefins have traditionally been produced from petroleum feedstocks through catalytic or steam cracking processes. These cracking processes, especially steam cracking, produce light olefins, such as ethylene and propylene, from various hydrocarbon feedstocks. Ethylene and propylene are important commodity petrochemicals that can be used in various processes for making plastics and other compounds.

[0004] For some time, the petroleum chemical industry has known that oxygenates, especially alcohols, can be converted to light olefins. For example, as a preferred alcohol for light olefin production, methanol can be converted primarily to ethylene and propylene in the presence of a molecular sieve catalyst. This process is known as the methanol-to-olefins (MTO) process, which occurs in an MTO reaction system. An efficient MTO process can convert oxygenates to light olefins that are commonly used in plastic production. The light olefins produced by the MTO process are concentrated in ethylene and propylene, but include C4-C6 olefins.

[0005] Generally, the ethylene-rich stream is separated from the light olefins by employing a process that recovers the ethylene component in the desired ethylene-rich stream by separating the ethylene component from other components and impurities. For example, depending on the feedstock composition, reaction conditions, and extent of side reactions, the MTO effluent can contain other light olefins and diolefins, as well as light paraffins, such as methane and ethane. Some separation processes involve the use of a flash stage and distillation at cryogenic temperatures. While some separation processes involve separation and recovery of ethylene at non-cryogenic temperatures.

[0006] Cryogenic separation can be capital intensive due to the capital cost of specialized vessel metallurgy and refrigeration equipment, as well as operating costs from compression and cooling. Compression and cooling can be provided by, for example, ethylene refrigerant provided by an ethylene refrigeration compressor. On the other hand, non-cryogenic temperatures can limit the extent of ethylene recovery.

[0007] The methanol-to-jet process produces a large amount of a light olefin intermediate stream at low pressure. A light olefin recovery process (LORP) compresses the stream and removes contaminants before the light olefins can oligomerize into jet fuel. Refrigeration and compression consume a large amount of energy in the LORP.

[0008] There is a need to improve olefin recovery, reduce the number of equipment, reduce total heat consumption in the complex, and reduce total emissions and operating costs. Summary of the Invention

[0009] Methods and apparatus have been developed for separating olefin and methane streams using a mixed refrigerant system, providing an alternative to cascade refrigeration for light olefin recovery. The method involves using a mixed refrigerant comprising several components with different molecular weights, which can be tailored for specific process environments and conform to different boiling and cooling profiles. Furthermore, the mixed refrigerant system includes an integrated heat exchanger for exchanging heat between other process streams and the mixed refrigerant stream. Attached Figure Description

[0010] The accompanying drawing is a schematic diagram of a method for separating an olefin stream from a methane stream according to an exemplary embodiment of the present disclosure.

[0011] Definitions

[0012] The term "connectivity" refers to the operative permission for fluid flow between enumerated components, which can be characterized as "fluid connectivity".

[0013] The term "downstream connectivity" means that in downstream connectivity, at least a portion of the fluid flowing toward the body can be operatively flowed from the object with which it is fluidly connected.

[0014] The term "upstream connectivity" means that at least a portion of the fluid flowing out of the main body can be operatively directed to an object in fluid communication with it.

[0015] The terms “direct connection” or “direct” mean that fluid flow from an upstream component enters a downstream component without passing through any other intermediary container.

[0016] The term "tower" refers to one or more distillation columns used to separate one or more components with different volatility. Unless otherwise specified, each column includes a condenser at the top of the column for condensing a portion of the overhead feed and refluxing it back to the top of the column, and a reboiler at the bottom of the column for vaporizing a portion of the bottom feed and returning it to the bottom of the column. The feed to the column can be preheated. The top pressure is the pressure of the vapor at the top of the column at the vapor outlet. The bottom temperature is the liquid temperature at the bottom outlet. Top and bottom lines refer to the net lines from any downstream reflux or reboiler to the column. Stripping columns may omit the reboiler at the bottom of the column and instead provide the heating requirement and power for separating from a fluidized inert medium such as steam. Stripping columns typically feed to the top trays and extract the product from the bottom.

[0017] As used herein, the term "separator" means a vessel having an inlet and at least one top vapor outlet and a bottom liquid outlet, and may also have an outlet for an aqueous feed stream from a boot. A flash tank is a type of separator that can be connected downstream of a separator capable of operating at higher pressures. As used herein, the term "boiling point temperature" means the atmospheric equivalent boiling point (AEBP) calculated from the observed boiling temperature and distillation pressure, as provided in Appendix A7 of ASTM D1160, entitled "Practice for Converting Observed Vapor Temperatures to Atmospheric Equivalent Temperatures".

[0018] As used herein, the term “true boiling point” (TBP) refers to a test method conforming to ASTM D-2892 for determining the boiling point of a substance. ASTM D-2892 is used to produce standardized masses of liquefied gases, distillate fractions, and residues for which analytical data are available, and to determine the yield of the aforementioned fractions by both mass and volume, based on which a graph of distillation temperature versus mass% is obtained using fifteen theoretical plates in a column with a reflux ratio of 5:1.

[0019] As used herein, the terms “T5,” “T10,” “T90,” or “T95” refer to the temperatures at which 5%, 10%, 90%, or 95% (as the case may be) of a sample boil using ASTM D-86 or TBP.

[0020] As used in this article, the term “initial boiling point” (IBP) refers to the temperature at which a sample begins to boil using ASTM D-7169, ASTM D-86, or TBP (as applicable).

[0021] As used herein, the term “endpoint” (EP) refers to the temperature at which a sample is brought to a complete boil using ASTM D-7169, ASTM D-86, or TBP (as applicable).

[0022] As used herein, the term “diesel” means a hydrocarbon that boils in the following ranges: IBP between about 125°C (257°F) and about 175°C (347°F), or T5 between about 150°C (302°F) and about 200°C (392°F), and “diesel fractionation point”, including T95 between about 343°C (650°F) and about 399°C (750°F) using the TBP distillation method, or T90 between 280°C (536°F) and about 340°C (644°F) using ASTM D-86.

[0023] As used herein, the term "jet fuel" refers to a hydrocarbon that boils in the T10 range between about 190°C (374°F) and about 215°C (419°F) and whose endpoint (EP) is between about 290°C (554°F) and about 310°C (590°F).

[0024] As used herein, the term “rich component stream” refers to a rich component stream exiting a container that has a higher component concentration than the feed into the container, and preferably higher than all other streams exiting the container. Detailed Implementation

[0025] For light olefin recovery, cascade refrigeration is traditionally used. Cascade refrigeration typically involves four stages of propylene compression and ethylene refrigeration between the first and third stages. Cascade refrigeration is generally one of the largest utility consumers of light olefin recovery processes and involves a significant amount of equipment for individual coolers and auxiliary equipment in the refrigeration section, such as buffer tanks and pumps.

[0026] A method for separating olefin and methane streams is disclosed, providing an alternative to cascaded refrigeration for light olefin recovery. This method involves the use of mixed refrigerants (i.e., refrigerants having several components that can be tailored to a specific process environment). Mixed refrigerants allow multiple exchangers to be combined into a single heat exchanger and involve fewer compression stages. Power requirements are also reduced in this arrangement. The mixed refrigerant system combines multiple heat exchangers based on their temperature. For example, the mixed refrigerant system can be used with a low-pressure demethanizer, which typically uses a reflux compressor. The mixed refrigerant system can also be used with a low-pressure deethanizer. According to this disclosure, a single refrigerant system is used to facilitate the cooling and condensation of other process streams over a wide temperature range. This disclosure employs a mixed refrigerant composition that provides sufficient heat exchange and / or cooling to other process streams across all temperature ranges exhibited in the method and apparatus.

[0027] A typical feed stream for this method includes an olefin stream containing C2 and / or C3 olefins. Molecular sieves, such as microporous crystalline zeolites and non-zeolite catalysts, particularly aluminosilicate silica (SAPO), are known to promote the conversion of oxygen-containing compounds such as methanol into light olefins. Efficient methanol-to-olefins (MTO) processes can convert oxygen-containing compounds into light olefins commonly used in plastics production. The light olefins produced by MTO processes are concentrated in ethylene and propylene, but also include C4-C6 olefins. Olefin streams containing C2 and / or C3 olefins may also contain C4-C6 olefins.

[0028] Depending on the operating conditions in the MTO reactor, the MTO process can produce olefin feed streams containing C2 and / or C3 olefins with varying C3:C2 ratios. An additional advantage of mixed refrigerant arrangements is that the refrigerant composition can be fine-tuned during operation to optimize energy consumption. For example, an MTO process for preparing olefins for oligomerization would operate with a higher C3:C2 ratio, which would correspond to a heavier mixed refrigerant.

[0029] Ethylene can oligomerize into olefins, such as C4, C6, and C8 olefins. Propylene can oligomerize into olefins, such as C6, C9, and C12 olefins. Larger MTO olefins can also oligomerize. Olefin oligomerization is the process of oligomerizing smaller olefins into larger olefins. More specifically, olefin oligomerization can convert olefins into distillates, including products from the jet fuel and diesel range. Oligomeric distillates can be saturated for use as transportation fuels.

[0030] In an exemplary embodiment, the olefin feed stream containing C2 and / or C3 olefins is generated by reacting oxygen-containing compounds with a SAPO catalyst in an MTO process.

[0031] In an exemplary embodiment, the MTO process and demethanizer of this disclosure are part of a renewable fuel and / or renewable olefin complex, wherein the oxygenated compound feedstock of the MTO process is derived from a renewable source. The operating conditions in the demethanizer and mixed refrigerant will depend on the desired blending of renewable products for the unit and will be tailored to the specific needs of the process.

[0032] Turning to the accompanying drawings illustrating a method 101 for separating an olefin stream from a methane stream, the method includes a demethanizer 160, a deethanizer 190, a C2 splitter 150, and a mixed refrigerant system 201. According to this disclosure, the mixed refrigerant system 201 includes a mixed refrigerant loop 211 and a cryogenic heat exchanger 120. According to this disclosure, the methane stream may contain other light components as well as methane. The methane stream may contain nitrogen (N2), carbon monoxide (CO), hydrogen (H2), and methane (CH4).

[0033] In an exemplary embodiment, a wet olefin feed stream containing C2 and / or C3 olefins is delivered to method 101 via line 105. In a typical embodiment, the wet olefin feed stream can be compressed to a pressure of approximately 1378 kPa gauge pressure (200 psig) to approximately 2414 kPa gauge pressure (350 psig) and washed with caustic alkali and water to remove most of the oxygenated compounds and carbon dioxide. The wet olefin feed stream 105 may be passed to a demethanizer 160.

[0034] In one aspect, the wet olefin feed stream in line 105 can be passed to a cryogenic heat exchanger 120. The wet olefin feed stream in line 105 can be passed to the cryogenic heat exchanger 120 at a temperature of approximately 37°C (100℉) to approximately 66°C (150℉). In one embodiment, the wet olefin feed stream in line 105 comprises a light olefin vapor stream from an MTO process. In an exemplary embodiment, the light olefin vapor stream from the MTO process may contain C2 and / or C3 olefins. In another exemplary embodiment, the wet olefin feed stream in line 105 may comprise a washed light olefin vapor stream from an MTO process.

[0035] The wet olefin feed stream in line 105 can be cooled by heat exchange in heat exchanger 120 to liquefy a portion of the stream and provide a cooled wet olefin feed stream in line 115. In an exemplary embodiment, the cooled wet olefin feed stream in line 115 is at a temperature of about 5°C (40℉) to about 32°C (90℉). The cooled wet olefin feed stream in line 115 can be separated in separator 103 to provide an aqueous stream from the storage tank in line 111, a wet olefin vapor feed stream containing C2- hydrocarbons and gases in top line 106, and a wet olefin liquid feed stream containing C3+ hydrocarbons in bottom line 108. The wet olefin vapor feed stream in top line 106 is dried in dryer 107 to provide a first olefin vapor feed stream in line 102. The wet olefin liquid feed stream in bottom line 108 is dried in dryer 109 to provide the first olefin liquid feed stream in line 104. The first olefin vapor feed stream in line 102 and the first olefin liquid feed stream in line 104 are sent to demethanizer 160, as described below.

[0036] In one aspect, the wet olefin feed stream containing C2 and / or C3 olefins in line 105 is separated into a first olefin vapor feed stream in line 102 and a first olefin liquid feed stream in line 104, and both are fed into the method as is. The first olefin vapor feed stream in line 102 and the first olefin liquid feed stream in line 104 can be respectively passed to a demethanizer 160. In another aspect, the first olefin vapor feed stream in line 102 is passed to a cryogenic heat exchanger 120 at a pressure of approximately 1380 kPa gauge pressure (200 psig) to approximately 2414 kPa gauge pressure (350 psig). The first olefin vapor feed stream in line 102 is cooled in the cryogenic heat exchanger 120 via heat exchange to provide the cooled first olefin vapor feed stream in line 112. In an exemplary embodiment, the cooled first olefin vapor feed stream in line 112 is at a temperature of about -56°C (-70°F) to about -90°C (-130°F). The cooled first olefin vapor feed stream in line 112 is then passed to demethanizer 160.

[0037] According to an exemplary embodiment of this disclosure, the cooled first olefin vapor feed stream in line 112 can be separated before being passed to the demethanizer 160. The cooled first olefin vapor feed stream in line 112 can be passed to separator 140 to provide a second olefin vapor feed stream in line 142 and a second olefin liquid feed stream in line 146. The second olefin vapor feed stream in line 142 and the second olefin liquid feed stream in line 146 are then passed to the demethanizer 160. The second olefin vapor feed stream in line 142 can be expanded by expansion valve 143 to provide an expanded second olefin vapor feed stream in line 144. In an exemplary embodiment, the expanded second olefin vapor feed stream in line 144 is at a temperature of about -62°C (-80°F) to about -102°C (-150°F). The expanded second olefin vapor feed stream in line 144 is then passed to the demethanizer 160. Alternatively, the second olefin vapor feed stream in pipeline 142 can be directly transferred to demethanizer 160.

[0038] The second olefin liquid feed stream in line 146 can be expanded via expansion valve 147 to provide an expanded second olefin liquid feed stream in line 148. In an exemplary embodiment, the expanded second olefin liquid feed stream in line 148 is at a temperature of about -51°C (-60°F) to about -90°C (-130°F). The expanded second olefin liquid feed stream in line 148 is passed to demethanizer 160. Alternatively, the second olefin liquid feed stream in line 146 can be passed directly to demethanizer 160. In one aspect of this disclosure, the use of separator 140 for separating the cooled first olefin vapor feed stream in line 112 is optional. Therefore, the cooled first olefin vapor feed stream in line 112 can be passed directly to demethanizer 160 and separated therein.

[0039] The first olefin liquid feed stream in line 104 can be passed to the demethanizer 160. The first olefin liquid feed stream in line 104 can be expanded by expansion valve 107 to provide the expanded first olefin liquid feed stream in line 113. The expanded first olefin liquid feed stream in line 113 is then passed to the demethanizer 160.

[0040] In demethanizer 160, an expanded second olefin vapor feed stream in line 144, an expanded second olefin liquid feed stream in line 148, and an expanded liquid olefin stream in line 113 are fractionated to provide a demethanizer overhead vapor stream containing methane and lighter gases in overhead line 162, and a demethanizer bottom liquid stream containing C2 and larger hydrocarbons in bottom line 164. According to this disclosure, demethanizer 160 operates at a top pressure of approximately 344 kPa (50 psig) to approximately 2069 kPa (300 psig). In an exemplary embodiment, the demethanizer overhead vapor stream in overhead line 162 is at a temperature of approximately -101°C (-150°F) to approximately -135°C (-210°F). In another exemplary embodiment, the demethanizer overhead vapor stream in line 162 is at a temperature of about -112°C (-170°F) to about -129°C (-200°F).

[0041] Traditionally used cascade refrigeration processes employ two separate refrigeration loops. The first loop typically features two to four stages of propylene compression, and the second loop typically features ethylene refrigeration between one and three stages to adequately cool the light olefin feed stream, thereby separating methane from the heavier hydrocarbons. The method of this disclosure employs a mixed refrigerant system 201, which allows the demethanizer 160 to operate at a lower top pressure of approximately 344 kPa (50 psig) to approximately 2069 kPa (300 psig), compared to the higher top pressure of approximately 2896 kPa (420 psig) in a cascade refrigeration demethanizer. However, advantageously, the demethanizer 160 can, in certain circumstances, operate at a higher pressure of approximately 2069 kPa (300 psig) to approximately 3964 kPa (575 psig). In current methods for processing olefin feed streams, demethanizer 160 can operate at lower pressures from about 517 kPa gauge pressure (75 psig) to about 1379 kPa (200 psig) or from about 689 kPa gauge pressure (100 psig) to about 1035 kPa (150 psig). Furthermore, the method utilizing mixed refrigerant system 201 omits the fourth stage of compression for the wet olefin feed stream in line 105 or the first olefin vapor feed stream in line 102, which is typically used in conjunction with a cascaded refrigeration demethanizer because the demethanizer 160 described herein can operate at lower pressures. Moreover, compared to methods utilizing cascaded refrigeration demethanizers, demethanizer 160 cooled by mixed refrigerant system 201 provides approximately 0.5 wt% to about 1.5 wt% additional ethylene recovery. Operating the demethanizer 160 at lower top pressure has several advantages and benefits, including lower capital costs, easier separation, less load or energy requirements, and fewer fractionation stages for separation in the column.

[0042] The top, bottom and sides of the demethanizer 160 are all in fluid and thermal communication with the cryogenic heat exchanger 120 of the mixed refrigerant system 201.

[0043] In one aspect of this disclosure, a first tower-side stream is drawn from the tower side of the demethanizer 160 in line 166. In an exemplary embodiment, the first tower-side stream is a vapor tower-side stream in line 166. In one aspect, the vapor tower-side stream is drawn into the demethanizer 160 from above the inlet location of the expanded second olefin vapor feed stream in line 144 and below the inlet location of the demethanizer reflux stream in line 188. The first tower-side stream is compressed, cooled, and returned to the top of the demethanizer 160 to provide reflux for the tower to meet the required ethylene recovery. As shown, the first tower-side stream in line 166 is separated by the demethanizer 160. The first tower-side stream in line 166 may be passed to a cryogenic heat exchanger 120 to exchange heat with the mixed refrigerant stream in line 246 and other process streams. In one aspect, the first column-side stream in line 166 can be separated in the top impact container (KOD) 170 and then passed to the cryogenic heat exchanger 120. The first column-side stream in line 166 is separated in the top KOD 170 into a KOD top vapor stream in line 172 and a knocked-out liquid stream in line 174. From the top KOD 170, the KOD top vapor stream in line 172 is extracted and passed to the reflux compressor 180 to provide a compressed first column-side stream in line 182. The KOD 170 can be used to separate any liquid present in the first column-side stream in line 166 before passing the first column-side stream to the downstream reflux compressor 180. In another aspect, the first column-side stream in line 166 can be directly passed to the reflux compressor 180 to provide a compressed first column-side stream in line 182.

[0044] In an exemplary embodiment, the KOD overhead vapor stream in line 172 is compressed in reflux compressor 180 to a pressure of approximately 2757 kPa gauge pressure (400 psig) to approximately 3793 kPa gauge pressure (550 psig) to provide a compressed first column-side stream in line 182. In this embodiment, the compressed first column-side stream in line 182 is at a temperature of approximately 2°C (35℉) to approximately 32°C (90℉). The compressed first column-side stream in line 182 is passed to cryogenic heat exchanger 120 to provide a demethanizer reflux stream in line 132. The compressed first column-side stream in line 182 is cooled by heat exchange in cryogenic heat exchanger 120 to provide a demethanizer reflux stream in line 132. In this embodiment, the demethanizer reflux stream in line 132 is at a temperature of approximately -73°C (-100℉) to approximately -129°C (-200℉). On one hand, a portion of the compressed first tower-side feed stream in line 182 can be recycled to KOD 170, and another portion can be cooled by heat exchange in cryogenic heat exchanger 120 to provide the demethanizer reflux feed stream in line 132, but this aspect is not shown.

[0045] The demethanizer overhead vapor stream in line 162 is extracted and transferred to cryogenic heat exchanger 120 for heat exchange with the mixed refrigerant and other process streams. In one embodiment, the demethanizer overhead vapor stream in line 162 is passed through overhead heat exchanger 185 before being transferred to cryogenic heat exchanger 120. In overhead heat exchanger 185, the demethanizer overhead vapor stream in line 162 can be heated by another process stream from demethanizer 160. In another embodiment, the demethanizer overhead vapor stream in line 162 can be heated by a first column-side stream in line 132 of demethanizer 160, and the first column-side stream in line 132 can be cooled by the demethanizer overhead vapor stream in line 162. On one hand, the demethanizer overhead vapor stream in line 162 can be expanded via expansion valve 175 to provide an expanded demethanizer overhead vapor stream in line 176, which is then transferred to the overhead heat exchanger 185.

[0046] Alternatively, the demethanizer overhead vapor stream in line 162 can be expanded in an expander (not shown) for additional cooling and possible power recovery to provide the expanded demethanizer overhead vapor stream in line 176. Expansion can lower the temperature by approximately 3°C (5℉) to approximately 8°C (15℉). Furthermore, the demethanizer overhead vapor stream in line 162 can be directly transferred to the overhead heat exchanger 185. In an exemplary embodiment, the expanded demethanizer overhead vapor stream in line 176 is at a temperature of approximately -112°C (-170℉) to approximately -140°C (-220℉). The heated demethanizer overhead vapor stream in line 186 is transferred from the overhead heat exchanger 185 to the cryogenic heat exchanger 120. On one hand, the expanded demethanizer overhead vapor stream in line 176 can be condensed by exchanging heat with the demethanizer reflux stream from line 132 of demethanizer 160 in the overhead heat exchanger 185. In an exemplary embodiment, the first heated demethanizer overhead vapor stream in line 186 is at a temperature of about 15°C (60°F) to about 32°C (90°F).

[0047] In the overhead heat exchanger 185, the demethanizer reflux stream in line 132 is further cooled after heat exchange with the expanded demethanizer overhead vapor stream in line 176 to provide the heat-exchanged demethanizer reflux stream in line 188. In an exemplary embodiment, the heat-exchanged demethanizer reflux stream in line 188 is at a temperature of about -101°C (-150°F) to about -124°C (-190°F). The heat-exchanged demethanizer reflux stream in line 188 is transferred to demethanizer 160 near the top of demethanizer 160. In an exemplary embodiment, the heat-exchanged demethanizer reflux stream in line 188 may be transferred to demethanizer 160 via expansion valve 31.

[0048] In one embodiment, the cryogenic heat exchanger 120 and the tower top heat exchanger 185 are separate heat exchangers. These heat exchangers can be plate-fin (also known as brazed aluminum), printed circuit, plate-and-frame, or shell-and-tube heat exchangers. In another embodiment, the cryogenic heat exchanger 120 and the tower top heat exchanger 185 can be combined into a single heat exchanger 120. In yet another alternative embodiment, the cryogenic heat exchanger 120 can be divided into two or more heat exchangers. The decision to combine or separate the heat exchangers depends on the thermal characteristics of the constituent flow, the nature of the selected heat exchanger technology, and the construction cost of the heat exchangers.

[0049] The second column-side stream in line 169 is also drawn from the demethanizer 160. In one aspect, the second column-side stream in line 169 is a liquid stream. In an exemplary embodiment, the second column-side stream in line 169 is the reboiler stream of the demethanizer 160. The second column-side stream in line 169 may be reboiled in the cryogenic heat exchanger 120. In an exemplary embodiment, the second column-side stream in line 169 is at a temperature of about -32°C (-26℉) to about 10°C (50℉). The second column-side stream in line 169 is passed to the cryogenic heat exchanger 120, where it is reboiled. The second column-side stream in line 169 is heated by heat exchange in the cryogenic heat exchanger 120 to provide a heated second column-side stream in line 129. The heated second column-side stream in line 129 is drawn from the cryogenic heat exchanger 120. In one embodiment, the heated second column-side feed in line 129 is at a temperature of approximately -23°C (-10℉) to approximately 16°C (60℉). The heated second column-side feed in line 129 can be transferred to demethanizer 160 from a location above where the second column-side feed is obtained in line 169. Alternatively, the heated second column-side feed in line 129 can be transferred to demethanizer 160 from a location below where the second column-side feed is obtained in line 169. Although not shown, another reboiler feed can be drawn from demethanizer 160. This other reboiler feed can be drawn from a suitable location above or below where the second column-side feed is obtained in line 169. This other reboiler feed can undergo heat exchange in cryogenic heat exchanger 120 and be recycled back to demethanizer 160.

[0050] From the bottom of the demethanizer 160, the demethanizer bottoms liquid stream in line 164 is drawn. In an exemplary embodiment, the demethanizer bottoms liquid stream in line 164 is at a temperature of approximately -20°C (-5℉) to approximately -45°C (-50℉). In the cryogenic heat exchanger 120, the demethanizer bottoms liquid stream in line 164 exchanges heat with other process streams and with the mixed refrigerant stream in line 246. The demethanizer bottoms liquid stream in line 164 may be sent to pump 165, and the pumped demethanizer bottoms liquid stream in line 167 is transferred to the cryogenic heat exchanger 120.

[0051] In cryogenic heat exchanger 120, the pumped demethanizer bottoms stream in line 167 exchanges heat with the mixed refrigerant stream in line 246 and other process streams. In one embodiment, the pumped demethanizer bottoms stream in line 167 is heated by heat exchange in cryogenic heat exchanger 120 to provide a heated demethanizer bottoms stream in line 168. The heated demethanizer bottoms stream in line 168 is withdrawn from cryogenic heat exchanger 120. In one embodiment, the heated demethanizer bottoms stream in line 168 is at a temperature of about 5°C (40℉) to about 38°C (100℉). The heated demethanizer bottoms stream in line 168 can be separated and used for further processing. In one aspect of this disclosure, the heated demethanizer bottoms stream in line 168 can be fed as feed to deethanizer 190. In one embodiment, the heated bottom liquid stream from the demethanizer in line 168 can be transferred to the deethanizer 190 via expansion valve 51. According to an embodiment of this disclosure, the deethanizer 190 is downstream of the demethanizer 160. According to another embodiment of this disclosure, the deethanizer 190 is upstream of the demethanizer 160.

[0052] In one aspect of this disclosure, a mixed refrigerant system 201 is used to exchange heat between other process streams and the mixed refrigerant stream in line 246 within a cryogenic heat exchanger 120. In an exemplary embodiment, other process streams that may exchange heat in the cryogenic heat exchanger 120 include a first olefin vapor feed in line 102, a demethanizer overhead vapor stream in line 162, a first column-side stream in line 166, a second column-side stream in line 169, a demethanizer bottom liquid stream in line 164, and a wet olefin feed stream in line 105. Optionally, the net C2 splitter bottom liquid stream in line 154 may be transferred to the heat exchanger and heated together with other process streams.

[0053] In the cryogenic heat exchanger 120, the first heated demethanizer overhead vapor stream in line 186 exchanges heat with the mixed refrigerant stream in line 246 and other streams to provide the second heated demethanizer overhead vapor stream in line 126. The first heated demethanizer overhead vapor stream in line 186 is heated after heat exchange in the cryogenic heat exchanger 120 to provide the second heated demethanizer overhead vapor stream in line 126. The second heated demethanizer overhead vapor stream in line 126 is withdrawn from the cryogenic heat exchanger 120. In an embodiment, the second heated demethanizer overhead vapor stream in line 126 is at a temperature of about 10°C (50℉) to about 38°C (100℉). The second heated demethanizer overhead vapor stream in line 126 can be separated and delivered to the fuel gas manifold. The demethanizer overhead vapor stream in line 126 can also be used for reactor purging in the MTO unit, fuel for the CO boiler in the MTO unit, and / or fuel for the reboiler heater in the oligomerization unit.

[0054] Returning to the mixed refrigerant system 201 in the figure, the mixed refrigerant system 201 is provided for exchanging heat between a mixed refrigerant and other process streams as described above in a cryogenic heat exchanger 120. The mixed refrigerant system 201 operates with a refrigerant stream that may include a mixed refrigerant stream containing an inert gas and some or all of C1 to C5 hydrocarbons. In an exemplary embodiment, the mixed refrigerant composition may contain about 0 mol% to about 25 mol% of C1 hydrocarbons, about 25 mol% to about 40 mol% of C2 hydrocarbons, and about 20 mol% to about 50 mol% of C3 hydrocarbons. The inert gas may include an amount of nitrogen from about 0 mol% to about 20 mol%. The C2 hydrocarbon may be ethane or ethylene, and the C3 hydrocarbon may be propane or propylene. In an exemplary embodiment, the mixed refrigerant system 201 may be operated with a refrigerant stream containing a non-hydrocarbon refrigerant. Other suitable refrigerant components may be used in the mixed refrigerant system 201.

[0055] The mixed refrigerant system 201 includes a mixed refrigerant loop 211 and a cryogenic heat exchanger 120. As shown, a mixed refrigerant flow in line 246 of the mixed refrigerant system 201 is delivered to the cryogenic heat exchanger 120. In an embodiment, the mixed refrigerant flow in line 246 is delivered to the cryogenic heat exchanger 120 after being compressed to a higher pressure. In an exemplary embodiment, the mixed refrigerant flow in line 246 has a pressure of approximately 689 kPa gauge pressure (100 psig) to approximately 2414 kPa gauge pressure (350 psig).

[0056] After heat exchange, the cooled mixed refrigerant stream in line 116 is withdrawn from the cryogenic heat exchanger 120. In an exemplary embodiment, the cooled mixed refrigerant stream in line 116 may be withdrawn at a temperature of approximately -74°C to 101°F to approximately -129°C to 200°F. The cooled mixed refrigerant stream in line 116 may be passed through expansion valve 117 to provide an expanded mixed refrigerant stream in line 118. In an exemplary embodiment, the expanded mixed refrigerant stream in line 118 is expanded via expansion valve 117 to a pressure of approximately 137 kPa gauge pressure (20 psig) to approximately 414 kPa gauge pressure (60 psig). In another exemplary embodiment, the expanded mixed refrigerant stream in line 118 is at a temperature of approximately -84°C to approximately -120°F to approximately -129°C to 200°F. The expanded mixed refrigerant stream in line 118 is returned to the cryogenic heat exchanger 120 for further heat exchange. On one hand, the expanded mixed refrigerant flow in line 118 is heated to a temperature of about 21°C (70°F) to about 93°C (200°F) via heat exchange in cryogenic heat exchanger 120.

[0057] After further heat exchange in the cryogenic heat exchanger 120, the warm, heat-exchanged mixed refrigerant stream in line 119 is withdrawn from the cryogenic heat exchanger 120. The warm, heat-exchanged mixed refrigerant stream in line 119 is processed in the mixed refrigerant loop 211 of the mixed refrigerant system 201 to provide mixed refrigerant stream 246.

[0058] In embodiments of this disclosure, the warm, heat-exchanged mixed refrigerant stream in line 119 is compressed in a multi-stage compressor in refrigerant circuit 211. In an exemplary embodiment, the multi-stage compressor is a two-stage refrigerant compressor comprising a first-stage refrigerant compressor 220 and a second-stage refrigerant compressor 240.

[0059] According to this disclosure, the warm, heat-exchanged mixed refrigerant stream in line 119 is passed to a first suction drum 210 to provide a first top mixed refrigerant stream in line 212 and a first bottom mixed refrigerant stream in line 214. The first top mixed refrigerant stream in line 212 of the first suction drum 210 is compressed in a first-stage refrigerant compressor 220 to provide a first compressed mixed refrigerant stream in line 222. In an exemplary embodiment, the first top mixed refrigerant stream in line 212 is at a pressure of about 40 kPa (g) (10 psig) to about 344 kPa (g) (50 psig). In one aspect, the first top mixed refrigerant stream in line 212 may be compressed in the first-stage refrigerant compressor 220 to provide a first compressed mixed refrigerant stream in line 222. In an exemplary embodiment, the first compressed mixed refrigerant stream in line 222 is at a pressure of approximately 344 kPa (50 psig) to approximately 1379 kPa (200 psig). In an exemplary embodiment, the first compressed mixed refrigerant stream in line 222 is at a temperature of approximately 65°C (150°F) to approximately 121°C (250°F).

[0060] The first compressed mixed refrigerant stream in line 222 can be cooled in cooler 223 to provide a first cooled compressed mixed refrigerant stream in line 224. Cooler 223 can be an air cooler or a water cooler. Alternatively, any suitable stream from the method can be used to cool the first compressed mixed refrigerant stream in line 222. In an exemplary embodiment, the first compressed mixed refrigerant stream in line 222 can be cooled in cooler 223 to a temperature of approximately 21°C (70°F) to approximately 65°C (150°F).

[0061] The first cooled and compressed mixed refrigerant stream in line 224 is passed to the second suction drum 230 to provide a second top mixed refrigerant stream in line 232 and a second bottom mixed refrigerant stream in line 234. The second top mixed refrigerant stream in line 232 is compressed in a second-stage refrigerant compressor 240 to provide a second compressed mixed refrigerant stream in line 242. In one aspect, the second top mixed refrigerant stream in line 232 is compressed in the second-stage refrigerant compressor 240 to a pressure of approximately 1724 kPa gauge pressure (250 psig) to approximately 2758 kPa gauge pressure (400 psig). In an exemplary embodiment, the second compressed mixed refrigerant stream in line 242 is at a temperature of approximately 65°C (150°F) to approximately 121°C (250°F).

[0062] The second bottom-mixed refrigerant flow in line 234 is pumped through pump 235. The pumped second bottom-mixed refrigerant flow in line 236 is passed through expansion valve 237 to provide an expanded second bottom-mixed refrigerant flow in line 238. In an exemplary embodiment, the pumped second bottom-mixed refrigerant flow in line 236 is at a temperature of about 26°C (80°F) to about 65°C (150°F).

[0063] In one aspect, the second compressed mixed refrigerant stream in line 242 and the expanded second bottom mixed refrigerant stream in line 238 can be combined to provide the compressed mixed refrigerant stream in line 244. In an exemplary embodiment of this disclosure, the compressed mixed refrigerant stream in line 244 is at a temperature of about 48°C (120°F) to about 104°C (220°F). In an embodiment, the compressed mixed refrigerant stream in line 244 can be passed through cooler 245 to provide a mixed refrigerant stream in line 246 having a temperature of about 26°C (80°F) to about 40°C (104°F). The mixed refrigerant stream in line 246 is passed to cryogenic heat exchanger 120. Cooler 245 can be an air cooler or a water cooler. Alternatively, any suitable stream from this method can be used to cool the compressed mixed refrigerant stream in line 244. It is also envisioned that the first bottom mixed refrigerant flow in pipeline 214 can be combined with the second bottom mixed refrigerant flow in pipeline 234, and pumped and processed together.

[0064] Referring to deethanizer 190, the heated bottom liquid stream from demethanizer 168 in line 168 is fractionated in deethanizer 190. Deethanizer 190 fractionates the heated bottom liquid stream from demethanizer 168 into a C2 hydrocarbon-rich top vapor stream from deethanizer 191 and a C3+ hydrocarbon-rich bottom liquid stream from total deethanizer 194. The top vapor stream from deethanizer 191 in line 191 can be transferred to C2 fractionator 150. The top vapor stream from deethanizer 191 in line 191 can be separated into liquid and vapor streams before being transferred to C2 fractionator 150. On one hand, the deethanizer overhead vapor stream in line 191, after passing through the deethanizer condenser 21, can be fed to the deethanizer receiver 187, where it is separated into the deethanizer reflux stream in line 197 and the deethanizer receiver overhead vapor stream in line 192. Optionally, a deethanizer cooler 11 may be present to cool the deethanizer overhead vapor stream in line 191 before passing it to the deethanizer condenser 21. The deethanizer condenser 21 may be cooled with a propylene refrigerant stream. Alternatively, the deethanizer condenser 21 may be cooled with a mixed refrigerant stream in line 246. The deethanizer condenser 21 may be combined with a cryogenic heat exchanger 120, or it may be combined with a C2 splitter reboiler exchanger 32. The deethaner reflux stream from line 197 of deethaner receiver 187 can be returned to deethaner 190. In one embodiment, the deethaner receiver overhead vapor stream from line 192 is fed to C2 splitter 150. In another embodiment, the deethaner receiver overhead vapor stream from line 192 can be fed to an oligomerization unit (not shown).

[0065] The total deethanizer bottoms stream in line 194 provides the deethanizer reboiler stream in line 195, which is heated by heat exchange in the deethanizer bottom reboiler exchanger 189. The heated deethanizer reboiler stream in line 198 is fed back to deethanizer 190. The total deethanizer bottoms stream in line 194 also provides the net deethanizer bottoms stream in line 196. In an exemplary embodiment, the net deethanizer bottoms stream in line 196 may be fed to a depropanizer (not shown). Deethanizer 190 operates at a top temperature of about -4°C (25℉) to about -37°C (-35℉) and a bottom gauge pressure of about 1.7 MPa (g) (250 psig) to about 2.9 MPa (g) (425 psig).

[0066] In an exemplary embodiment, the overhead vapor stream from the de-ethaner receiver in line 192 can be combined with the hydrogen stream in line 194 and delivered to acetylene removal unit 193 to convert the acetylene present in the stream in line 192 to ethylene via selective hydrogenation. Suitable operating pressures in acetylene removal unit 193 range widely from about 276 kPag (40 psig) to about 5516 kPag (800 psig) or from about 345 kPag (50 psig) to about 2069 kPag (300 psig). A relatively moderate temperature is typically used between about 25°C (77°F) and about 350°C (662°F) or about 50°C (122°F) to about 200°C (392°F). The vapor hourly space velocity (HHSV) of the reactants used for the selective hydrogenation catalyst can be about 30 hr⁻¹, or more than about 300 hr⁻¹, or more than about 15 hr⁻¹ to about 600 hr⁻¹. To avoid undesirable saturation of large amounts of monoolefins, the molar ratio of hydrogen to polyolefins in the material entering the selective hydrogenation catalyst bed is maintained between 0.75:1 and 1.8:1.

[0067] The selective hydrogenation catalyst can be any suitable catalyst capable of selectively hydrogenating acetylene in a C2-hydrocarbon feed stream. Particularly preferred selective hydrogenation catalysts include copper and at least one other metal, such as titanium, vanadium, chromium, manganese, cobalt, nickel, zinc, molybdenum, and cadmium, or mixtures thereof. The metal is preferably supported on an inorganic oxide support (such as silica and alumina). Preferably, the selective hydrogenation catalyst may comprise copper and nickel metal supported on alumina. The selectively hydrogenated effluent can be dried to remove moisture. An acetylene-free deethaner receiver overhead vapor stream is taken from acetylene removal unit 193. In one aspect, the acetylene-free deethaner receiver overhead vapor stream is expanded via expansion valve 61. The expanded deethaner receiver overhead vapor stream in line 199 can be transferred from expansion valve 61 to C2 splitter 150.

[0068] C2 splitter 150 fractionates the expanded deethaner receiver overhead vapor stream from line 199 of deethaner 190 into a first C2 splitter overhead vapor stream containing hydrogen and light fractions in line 152, an ethylene-rich C2 splitter side stream in line 177, and a total C2 splitter bottom liquid stream rich in ethane in line 153. On one hand, the C2 splitter overhead vapor stream in line 152, after passing through C2 splitter condenser 22, can be fed to C2 splitter receiver 151, where it is separated into a C2 splitter reflux stream in line 159 and a C2 splitter receiver overhead vapor stream in line 157. Optionally, a C2 splitter cooler 12 may be present to cool the C2 splitter overhead vapor stream in line 152 before passing it to the C2 splitter condenser 22. C2 splitter condenser 22 can be cooled with a propylene refrigerant stream. Alternatively, C2 splitter condenser 22 can be cooled with a mixed refrigerant stream in line 246, or C2 splitter condenser 22 can be combined with a cryogenic heat exchanger 120. The C2 splitter return stream in line 159 from C2 splitter receiver 151 is returned to C2 splitter tower 150. The C2 splitter tower side fraction stream in line 177 is sent to storage or downstream processing of ethylene products. The C2 splitter receiver tower overhead vapor stream in line 157 can be sent to the fuel gas header or returned to the upstream MTO unit as reactor purging.

[0069] The total C2 splitter bottom liquid stream in line 153 supplies the C2 splitter reboiler liquid stream in line 155, which is heated by heat exchange in the C2 splitter bottom reboiler exchanger 32. The heated C2 splitter reboiler liquid stream in line 158 is fed back to the C2 splitter 150. The total C2 splitter bottom liquid stream in line 153 also supplies the net C2 splitter bottom liquid stream in line 154. The C2 splitter 190 can operate at a bottom temperature of about -17°C (0℉) to about 5°C (40℉) and a top gauge pressure of about 1 MPa (g) (150 psig) to about 2.4 MPa (g) (350 psig).

[0070] Optionally, the net C2 splitter bottoms stream in line 154 can be transferred to the cryogenic heat exchanger 120. In one aspect, the net C2 splitter bottoms stream in line 154 can be transferred to the cryogenic heat exchanger 120 via an expansion valve 41. In the cryogenic heat exchanger 120, the net C2 splitter bottoms stream in line 154 is heated after heat exchange. In an exemplary embodiment, the net C2 splitter bottoms stream in line 154 can be transferred to the cryogenic heat exchanger 120 at a temperature of about -23°C (-10℉) to about -68°C (-90℉). The heated net C2 splitter bottoms stream in line 156 is removed from the cryogenic heat exchanger 120. In an exemplary embodiment, the heated net C2 splitter bottoms stream in line 156 is at a temperature of about 5°C (40℉) to about 38°C (100℉). The heated net C2 splitter bottom stream in line 156 can be separated and delivered to the fuel gas manifold or further processed or upgraded.

[0071] This disclosure includes several heat exchangers that can be integrated with other process streams in nearby services. In an exemplary embodiment, the deethanizer bottom reboiler exchanger 189 can exchange heat with a hot water stream from the MTO process. In another exemplary embodiment, the deethanizer bottom reboiler exchanger 189 can exchange heat with the effluent from the oligomerization reactor and / or the hydrogenation reactor in the oligomerization unit. In yet another exemplary embodiment, the first-stage refrigeration condenser 223 and / or the second-stage refrigeration condenser 245 can exchange heat with the deethanizer bottom reboiler exchanger 189 and / or the C2 splitter bottom reboiler exchanger 32.

[0072] Specific embodiments

[0073] While the following description is presented in conjunction with specific embodiments, it should be understood that the description is intended to be illustrative and not to limit the scope of the foregoing description and the appended claims.

[0074] A first embodiment of this disclosure is a method for separating an olefin stream from a methane stream, the method comprising: providing an olefin stream comprising C2 and / or C3 olefins; cooling the olefin stream in a heat exchanger with a mixed refrigerant stream to provide a cooled olefin stream; passing the cooled olefin stream to a demethanizer operating at a top pressure of about 344 kPa gauge pressure (50 psig) to about 2069 kPa gauge pressure (300 psig); and fractionating the cooled olefin stream in the demethanizer to provide a demethanizer top vapor stream and a demethanizer bottom liquid stream. Embodiments of this disclosure are any one or all of the embodiments described above in this paragraph up to the first embodiment in this paragraph, wherein the olefin stream is separated into a vapor olefin stream and a liquid olefin stream, which are respectively passed to the demethanizer. Embodiments of this disclosure are one, any, or all of the embodiments described above to the first embodiment described above in this paragraph, and further include passing the vaporized olefin stream to the heat exchanger; cooling the vaporized olefin stream in the heat exchanger to provide a cooled vaporized olefin stream; separating the cooled vaporized olefin stream to provide an overhead vaporized olefin stream and a bottom liquid olefin stream; and fractionating the overhead vaporized olefin stream, the bottom liquid olefin stream, and the liquid olefin stream in the demethanizer. Embodiments of this disclosure are one, any, or all of the embodiments described above to the first embodiment described above in this paragraph, and further include obtaining a first column-side stream from the demethanizer; passing the first column-side stream to the heat exchanger to provide a heat-exchanged first column-side stream; and passing the heat-exchanged first column-side stream to the demethanizer. The embodiments of this disclosure are one, any, or all of the embodiments described above to the first embodiment described above in this paragraph, and further include passing the first column-side feed stream to a reflux compressor to provide a compressed first column-side feed stream; passing the compressed first column-side feed stream to the heat exchanger to provide a heat-exchanged first column-side feed stream; and passing the heat-exchanged first column-side feed stream to the demethanizer. The embodiments of this disclosure are one, any, or all of the embodiments described above to the first embodiment described above in this paragraph, and further include passing the heat-exchanged first column-side feed stream to a top heat exchanger to provide a cooled reflux stream; expanding the cooled reflux stream to provide an expanded reflux stream; and passing the expanded reflux stream to the demethanizer. The embodiments disclosed herein are one, any, or all of the embodiments described above to the first embodiment described in this paragraph, and further include obtaining a second column-side stream from the demethanizer; passing the second column-side stream to the heat exchanger to provide a heated second column-side stream; and passing the heated second column-side stream to the demethanizer.The embodiments of this disclosure are one, any, or all of the embodiments described above to the first embodiment described above in this paragraph, and further include passing the bottom liquid stream of the demethanizer to the heat exchanger to provide a heat-exchanged bottom liquid stream; and passing the heat-exchanged bottom liquid stream to the deethanizer. The embodiments of this disclosure are one, any, or all of the embodiments described above to the first embodiment described above in this paragraph, wherein the olefin stream containing C2 and / or C3 olefins is generated by reacting oxygen-containing compounds with a SAPO catalyst. The embodiments of this disclosure are one, any, or all of the embodiments described above to the first embodiment described above in this paragraph, and further include passing the overhead vapor stream of the demethanizer to the heat exchanger to exchange heat with the olefin stream and the refrigerant stream to provide a heat-exchanged overhead vapor stream. The embodiments of this disclosure are one, any, or all of the embodiments described above to the first embodiment described above in this paragraph, and further include passing the bottom liquid stream of the demethanizer to the heat exchanger to exchange heat with the olefin stream and the refrigerant stream to provide a heat-exchanged bottom liquid stream. The embodiments of this disclosure are one, any, or all of the embodiments described above to the first embodiment described above in this paragraph, and further include passing the mixed refrigerant stream to a refrigerant compressor to provide a compressed mixed refrigerant stream; passing the compressed mixed refrigerant stream to the heat exchanger to provide the cooled olefin stream and the cooled refrigerant stream; and passing the cooled refrigerant stream to the refrigerant compressor. The embodiments disclosed herein are one, any, or all of the embodiments described above to the first embodiment described in this paragraph, and further include expanding the cooled refrigerant stream to provide an expanded refrigerant stream; transferring the expanded refrigerant stream to the heat exchanger to provide a heat-exchanged refrigerant stream; and transferring the heat-exchanged refrigerant stream to the refrigerant compressor.

[0075] A second embodiment of this disclosure is a method for separating an olefin stream from a methane stream, the method comprising: providing an olefin stream containing C2 and / or C3 olefins; cooling the olefin stream in a heat exchanger with a mixed refrigerant stream to provide a cooled olefin stream; and passing a vaporized olefin stream taken from the cooled olefin stream and a liquid olefin stream taken from the cooled olefin stream to a top pressure at a gauge pressure of about 344 kPa (50 psig) to about 2069 kPa (300 psig). The demethanizer operates in a submerged state; in the demethanizer, the overhead vapor olefin stream and the liquid olefin stream are fractionated to provide an overhead vapor stream, a bottom liquid stream, and a first side stream; and the overhead vapor stream, the bottom liquid stream, and the first side stream are passed to the heat exchanger for heat exchange with the olefin stream and the refrigerant stream, providing the heat-exchanged overhead vapor stream, the heat-exchanged bottom liquid stream, and the heat-exchanged first side stream. Embodiments of this disclosure are one, any, or all of the embodiments described in the foregoing embodiments to the second embodiments in this paragraph, wherein the olefin stream is separated into a vapor olefin stream and a liquid olefin stream, which are respectively passed to the demethanizer. The embodiments of this disclosure are one, any, or all of the embodiments described above to the second embodiment described above in this paragraph, and further include passing the vaporized olefin feed stream to the heat exchanger; cooling the vaporized olefin feed stream in the heat exchanger to provide a cooled vaporized olefin feed stream; separating the cooled vaporized olefin feed stream to provide the overhead vaporized olefin feed stream and the bottom liquid olefin feed stream; and passing the overhead vaporized olefin feed stream, the bottom liquid olefin feed stream, and the liquid olefin feed stream to the demethanizer. The embodiments of this disclosure are one, any, or all of the embodiments described above to the second embodiment described above in this paragraph, and further include passing the first column-side feed stream to a reflux compressor to provide a compressed first column-side feed stream; passing the compressed first column-side feed stream to the heat exchanger; passing the heat-exchanged first column-side feed stream to an overhead heat exchanger to provide a cooled reflux feed stream; and passing the cooled reflux feed stream to the demethanizer. The embodiments disclosed herein are one, any, or all of the embodiments described above to the second embodiment described in this paragraph, wherein the step of transferring the bottom liquid stream of the demethanizer to the heat exchanger includes obtaining a second column-side stream and the bottom liquid stream of the demethanizer from the demethanizer; transferring the second column-side stream and the bottom liquid stream of the demethanizer to the heat exchanger to provide a heated column-side stream and a heat-exchanged bottom liquid stream; transferring the heated column-side stream to the demethanizer; and transferring the heat-exchanged bottom liquid stream to the deethaner.The embodiments of this disclosure are one, any, or all of the embodiments described above to the second embodiment described above in this paragraph, wherein the deethanizer is in downstream fluid communication with the demethanizer. The embodiments of this disclosure are one, any, or all of the embodiments described above to the second embodiment described above in this paragraph, wherein the olefin feed stream containing C2 and / or C3 olefins is generated by reacting oxygen-containing compounds with a SAPO catalyst.

[0076] Although no further detailed description has been provided, it is believed that those skilled in the art can readily identify the essential features of this disclosure by utilizing the foregoing description, and thus make various changes and modifications to adapt it to various uses and situations without departing from the spirit and scope of this disclosure. Therefore, the foregoing preferred embodiments should be understood as illustrative only and not as limiting the remainder of this disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0077] In the foregoing, all temperatures are expressed in degrees Celsius, and all portions and percentages are by weight unless otherwise specified.

Claims

1. A method for separating an olefin stream from a methane stream, the method comprising: Provides olefin feed streams containing C2 and / or C3 olefins; The olefin stream is cooled in a heat exchanger using a mixed refrigerant stream to provide a cooled olefin stream; The cooled olefin feed stream is passed to a demethanizer operating at a top pressure of approximately 344 kPa (50 psig) to approximately 2069 kPa (300 psig); and The cooled olefin stream is fractionated in the demethanizer to provide a top vapor stream and a bottom liquid stream.

2. The method according to claim 1, wherein the olefin stream is separated into a vapor olefin stream and a liquid olefin stream, which are respectively fed to the demethanizer.

3. The method according to claim 2, further comprising: The vaporized olefin feed stream is transferred to the heat exchanger; The vapor olefin feed stream is cooled in the heat exchanger to provide a cooled vapor olefin feed stream; The cooled vaporized olefin stream is separated to provide a top vaporized olefin stream and a bottom liquid olefin stream; as well as The demethanizer is used to fractionate the top vapor olefins, the bottom liquid olefins stream, and the liquid olefins stream.

4. The method according to claim 1, further comprising: A first column side stream is obtained from the demethanizer; The first tower-side feed stream is transferred to the heat exchanger to provide the first tower-side feed stream for heat exchange; as well as The first tower-side feed stream of the heat exchange is transferred to the demethanizer.

5. The method according to claim 4, further comprising: The first tower-side feed stream is passed to the reflux compressor to provide compressed first tower-side feed stream; The compressed first tower-side feed stream is passed to the heat exchanger to provide a first tower-side feed stream for heat exchange; The first tower-side feed stream of the heat exchange is transferred to the demethanizer.

6. The method according to claim 5, further comprising: The first tower-side feed stream of the heat exchange is transferred to the top heat exchanger to provide a cooled reflux stream; The cooled reflux stream is expanded to provide an expanded reflux stream; as well as The expanded reflux stream is then passed to the demethanizer.

7. The method according to claim 1, further comprising: A second tower-side feed stream is obtained from the demethanizer; The second tower-side feed stream is transferred to the heat exchanger to provide a heated second tower-side feed stream; as well as The heated second tower side feed stream is transferred to the demethanizer.

8. The method according to claim 1, further comprising: The bottom liquid stream of the demethanizer is transferred to the heat exchanger to provide a bottom liquid stream for heat exchange; as well as The bottom liquid stream from the heat exchange tower is transferred to the deethaner tower.

9. The method according to claim 1, wherein the olefin stream comprising C2 and / or C3 olefins is generated by reacting oxygen-containing compounds with a SAPO catalyst.

10. The method of claim 1, further comprising passing the overhead vapor stream of the demethanizer to the heat exchanger for heat exchange with the olefin stream and the refrigerant stream to provide a heat-exchanged overhead vapor stream.

11. The method of claim 1, further comprising passing the bottom liquid stream of the demethanizer to the heat exchanger for heat exchange with the olefin stream and the refrigerant stream to provide a heat-exchanged bottom liquid stream.

12. The method according to claim 1, further comprising: The mixed refrigerant stream is passed to the refrigerant compressor to provide a compressed mixed refrigerant stream; The compressed mixed refrigerant stream is passed to the heat exchanger to provide the cooled olefin stream and the cooled refrigerant stream; as well as The cooled refrigerant stream is then transferred to the refrigerant compressor.

13. The method according to claim 12, further comprising: The cooled refrigerant stream is expanded to provide an expanded refrigerant stream; The expanded refrigerant stream is passed to the heat exchanger to provide a refrigerant stream for heat exchange; as well as The refrigerant stream from the heat exchange is then transferred to the refrigerant compressor.

14. A method for separating an olefin stream from a methane stream, the method comprising: Provides olefin feed streams containing C2 and / or C3 olefins; The olefin stream is cooled in a heat exchanger using a mixed refrigerant stream to provide a cooled olefin stream; The overhead vapor olefin stream and the liquid olefin stream taken from the cooled olefin stream are passed to a demethanizer operating at an overhead pressure of about 344 kPa (50 psig) to about 2069 kPa (300 psig). The overhead olefin stream and the liquid olefin stream are fractionated in the demethanizer to provide an overhead olefin stream, a bottom liquid stream, and a first column side stream. as well as The overhead vapor stream, the bottom liquid stream, and the first side stream of the demethanizer are passed to the heat exchanger for heat exchange with the olefin stream and the refrigerant stream, and the overhead vapor stream, the bottom liquid stream, and the first side stream are provided for heat exchange.

15. The method of claim 14, wherein the olefin stream is separated into a vapor olefin stream and a liquid olefin stream, which are respectively fed to the demethanizer.

16. The method according to claim 15, further comprising: The vaporized olefin feed stream is transferred to the heat exchanger; The vapor olefin feed stream is cooled in the heat exchanger to provide a cooled vapor olefin feed stream; The cooled vapor olefin stream is separated to provide the top vapor olefin stream and the bottom liquid olefin stream; as well as The vapor olefin stream from the top of the column, the liquid olefin stream from the bottom of the column, and the liquid olefin stream are transferred to the demethanizer.

17. The method of claim 14, further comprising: The first tower-side feed stream is passed to the reflux compressor to provide compressed first tower-side feed stream; The compressed first tower-side feed stream is transferred to the heat exchanger; The first tower-side feed stream of the heat exchange is transferred to the top heat exchanger to provide a cooled reflux stream; as well as The cooled reflux stream is then passed to the demethanizer.

18. The method of claim 14, wherein the step of transferring the bottom liquid stream of the demethanizer to the heat exchanger comprises: Obtain the second column side flow and the bottom liquid flow of the demethanizer from the demethanizer; The second column side stream and the bottom liquid stream of the demethanizer are passed to the heat exchanger to provide a heated column side stream and a heat-exchanged bottom liquid stream; The heated tower-side feed stream is transferred to the demethanizer; as well as The bottom liquid stream from the heat exchange tower is transferred to the deethaner tower.

19. The method of claim 18, wherein the deethanizer is in fluid communication downstream of the demethanizer.

20. The method of claim 14, wherein the olefin stream comprising C2 and / or C3 olefins is generated by reacting an oxygen-containing compound with a SAPO catalyst.

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