Integrated process for producing light olefins

Abstract

An integrated process for producing light olefins is disclosed. The integrated process includes sending a synthesis gas stream and a hydrogen stream to a methanol synthesis section to provide a methanol-containing reactor effluent. The reactor effluent is separated into a vapor stream and a methanol-containing liquid stream. The methanol-containing liquid stream is sent to a methanol purification section, which includes at least two distillation columns, namely a first distillation column and a second distillation column, to provide a methanol product stream. At least a portion of the methanol product stream is sent to an oxygenate conversion unit to provide an olefin-containing effluent. Reboiling heat for the first and second distillation columns is provided from the separation section of the oxygenate conversion unit.

Description

Technical Field

[0001] This field relates to an integrated process for producing light olefins. This field may relate in particular to integrating a methanol synthesis process with an oxide conversion process.

Background Art

[0002] Olefins have traditionally been produced from petroleum feedstocks by catalytic or steam cracking processes. These cracking processes, particularly steam cracking, produce light olefins such as ethylene and propylene from various hydrocarbon feedstocks. Ethylene and propylene are important general-purpose petrochemicals that are useful in various processes for manufacturing plastics and other compounds.

[0003] In the petrochemical industry, it has long been known that oxides, particularly alcohols, can be converted into light olefins. For example, methanol, an alcohol preferred for light olefin production, can be converted mainly into ethylene and propylene in the presence of a molecular sieve catalyst. This process is called the methanol-olefin (MTO) reaction process and occurs in an MTO reaction system. A highly efficient process for converting methanol to olefins (Methanol to Olefin, MTO) can convert oxides into light olefins that have typically been considered for plastic production. The light olefins produced from the MTO process are concentrated in ethylene and propylene, but include C4-C6 olefins.

[0004] Methanol is typically synthesized from the catalytic reaction of synthesis gas in a methanol reactor in the presence of a catalyst. Synthesis gas is defined as a gas mainly containing carbon monoxide (CO), hydrogen (H2), and preferably carbon dioxide (CO2). Other components may be present. Synthesis gas production processes are well-known and include conventional steam reforming, autothermal reforming, or combinations thereof.

[0005] A typical methanol synthesis system includes a light fraction separation system for separating by-products of the methanol synthesis process. Each of these separation systems may include one or more capital-intensive separation units with heating requirements and / or operation, as well as, for example, distillation columns, pumps, and heat exchangers. Currently, waste heat from strippers and separator columns in the MTO process is discharged into the atmosphere through air cooling. Therefore, there is a need to reduce the number of devices, the overall utilization of heat / steam for the complex, and reduce overall emissions and operating costs. [Overview of the project]

[0006] We devised an integrated process for producing light olefins by integrating the heat generated in the MTO process into the upstream methanol synthesis process. This integrated process can reduce the overall steam utilization for the complex facility, thereby lowering overall emissions and operating costs. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of a methanol synthesis process according to an exemplary embodiment of an integrated process for producing the light olefins of the present disclosure. [Figure 2] This is a schematic diagram of an MTO process according to an exemplary embodiment of an integrated process for producing the light olefins of the present disclosure.

[0008] definition The term "communication" means that fluid flow is operably permitted between the listed components, and this can be characterized as "fluid communication."

[0009] The term "downstream communication" means that at least a portion of the fluid flowing to the downstream-communicating object can be operably flowed from the fluid-communicating object.

[0010] The term "upstream communication" means that at least a portion of the fluid flowing from an upstream communication object can flow operably into a fluid-communicated object.

[0011] The term "direct communication" means that the fluid flow from the upstream component enters the downstream component without passing through any other intervening container.

[0012] The term "indirect communication" refers to the flow of fluid from an upstream component entering a downstream component after passing through an intervening container.

[0013] The term "bypass" means that an object is removed from downstream communication with the object it is bypassing, at least to the extent that it is bypassing it.

[0014] As used herein, the terms “main” or “major” mean more than 50%, preferably more than 75%, and more preferably more than 90%.

[0015] The term “column” refers to one or more distillation columns for separating one or more different volatile components. Unless otherwise specified, each column includes a condenser at the top of the column to condense and reflux a portion of the top flow returning to the top of the column, and a reboiler at the bottom of the column to vaporize a portion of the bottom flow and return it to the bottom of the column. The feed into the column may be preheated. The top pressure is the pressure of the top vapor at the column's vapor outlet. The bottom temperature is the liquid bottom outlet temperature. The top line and bottom line refer to the net lines from column to column downstream of any reflux or reboil. Stripping columns may omit the reboiler at the bottom of the column, but instead may provide heating requirements and the propulsion for separation from fluidizing inert media such as vapor. Stripping columns typically feed to an upper tray and remove the main product from the bottom.

[0016] As used herein, the term “separator” means a vessel having an inlet and at least a top vapor outlet and a bottom liquid outlet, and which may also have an aqueous outlet from the boot. A flash drum is a type of separator that may be downstream-communicated with a separator that may operate at higher pressures. As used herein, the term “boiling temperature” means the atmospheric equivalent boiling point (AEBP) calculated from the observed boiling point and distillation pressure using the formulas provided in ASTM D1160 Appendix A7, entitled “Practice for Converting Observed Vapor Temperatures to Atmospheric Equivalent Temperatures.”

[0017] As used herein, the term “True Boiling Point” (TBP) means a test method for determining the boiling point of a substance, which corresponds to ASTM D-2892 for producing standardized quality liquefied gas, distilled fractions, and residues from which analytical data can be obtained, and for determining the yield of the above fractions by both mass and volume, with a temperature versus mass % graph produced using 15 theoretical stages in a column with a reflux ratio of 5:1.

[0018] As used herein, the terms "T5," "T10," "T90," or "T95" mean the boiling point of 5 mass percent, 10 mass percent, 90 mass percent, or 95 mass percent of the sample, respectively, using ASTM D-86 or TBP.

[0019] As used herein, the term “initial boiling point” (IBP) means the temperature at which the sample begins to boil, using ASTM D-7169, ASTM D-86, or TBP, as applicable.

[0020] As used herein, the term “end point” (EP) means, depending on the context, the temperature at which the sample has completely evaporated, using ASTM D-7169, ASTM D-86, or TBP.

[0021] As used herein, the term “diesel” means hydrocarbons that boil within the “diesel cutpoint” range, including IBP at about 125°C (257°F) to about 175°C (347°F) or T5 at about 150°C (302°F) to about 200°C (392°F), and T95 at about 343°C (650°F) to about 399°C (750°F) using the TBP distillation method, or T90 at 280°C (536°F) to about 340°C (644°F) using ASTM D-86. The term “green diesel” means diesel containing hydrocarbons that are not of fossil fuel origin.

[0022] As used herein, the term “jet fuel” means hydrocarbons that boil at a T10 of about 190°C (374°F) to about 215°C (419°F) and an endpoint of about 290°C (554°F) to about 310°C (590°F). The term “green jet fuel” means jet fuel containing hydrocarbons that are not of fossil fuel origin.

[0023] As used herein, the term “component-rich flow” means that the rich flow exiting the container has a higher concentration of the component than the feed into the container, and preferably than all other flows drawn out of the container.

[0024] As used herein, the term “lean flow of component” means that the lean flow exiting the container has a lower concentration of the component than the feed into the container, and preferably than all other flows drawn out of the container. [Modes for carrying out the invention]

[0025] An integrated process and apparatus for producing light olefins are disclosed. The integrated process and apparatus disclosed herein include integrating the heat generated in the MTO process into the upstream methanol synthesis process. A substantially heated stream of the MTO process can be utilized in the methanol synthesis process to provide the heat load for various units and / or columns. One or more streams from the MTO process can be pumped to the upstream methanol synthesis and / or purification units and cross-exchanged with the process as feed preheating, reboiler heat, etc. The streams after heat exchange circulate back to their respective columns and / or units.

[0026] Referring to FIG. 1, an integrated process and apparatus 101 for producing light olefins includes a methanol synthesis section 111 and a methanol purification section 201. As shown in FIG. 1, a syngas stream in line 122 and a hydrogen gas stream in line 124 are sent to the methanol synthesis section 111. Syngas is defined as a gas mainly containing carbon monoxide (CO), carbon dioxide (CO2), and hydrogen (H2). Optionally, syngas can also contain methane (CH4), as well as small amounts of ethane and propane. Conventional processes for converting carbon components into syngas include steam reforming, partial oxidation, autothermal reforming, and combinations of these processes. According to an embodiment of the present disclosure, the syngas stream in line 122 can be taken in from any suitable source. According to another embodiment of the present disclosure, the hydrogen gas stream in line 124 can be taken in from any suitable source. In an exemplary embodiment, the hydrogen gas stream in line 124 is taken in from a pressure swing adsorption (PSA) unit.

[0027] According to an exemplary embodiment of the present disclosure, the methanol synthesis section 111 includes a first methanol converter 140 and a second methanol converter 160. The syngas stream in line 122 and the hydrogen gas stream in line 124 are sent to the first methanol converter 140 of the methanol synthesis section 111. In an embodiment, the syngas stream in line 122 and the hydrogen gas stream in line 124 may be mixed to provide a mixed feed stream 126, which is sent to the first methanol converter 140. However, the syngas stream in line 122 and the hydrogen gas stream in line 124 may be sent separately to the first methanol converter 140. The mixed feed stream 126 is sent to the syngas boost compressor 130 to compress the syngas to a specific pressure and provide a compressed syngas stream in line 132 before being sent to the first methanol converter 140. In an exemplary embodiment, the syngas may be compressed to a pressure ranging from about 6890 kPa (1000 psia) to about 8970 kPa (1300 psia) in the syngas boost compressor 130. The syngas stream may be heated before passing through the first methanol converter 140. The compressed syngas stream in line 132 can be heat-exchanged in the heat exchanger 133 to provide a heated syngas stream in line 134. The heated syngas stream in line 134 is sent to the first methanol converter 140.

[0028] In the first methanol converter 140 of the methanol synthesis section 111, the syngas is converted into a methanol composition. The methanol synthesis process is achieved in the presence of a methanol synthesis catalyst. In an exemplary embodiment, the syngas stream in line 122 towards the methanol synthesis section 111 has a carbon dioxide to carbon monoxide molar ratio of 1:2 to 1:4 and a hydrogen to carbon monoxide (CO + CO2) molar ratio in the range of about 3:2 to about 3:1.

[0029] A suitable methanol synthesis catalyst may be copper on a zinc oxide and alumina support. The synthesis conditions for the first methanol converter 140 in methanol synthesis section 111 may include a temperature of about 200 to about 300°C and a pressure of about 3.5 to about 10 MPa. Reaction equilibrium typically requires methanol separation and recycling of unreacted reagents into the synthesis reaction.

[0030] According to an exemplary embodiment, the first methanol converter 140 operates at temperatures ranging from approximately 204°C (400°F) to approximately 290°C (550°F). According to another exemplary embodiment, the first methanol converter 140 operates at pressures ranging from approximately 6890 kPa (1000 psia) to approximately 8970 kPa (1300 psia).

[0031] The methanol synthesis reaction is highly exothermic. Boiler feedwater (BFW) in line 148 is sent to the first methanol converter 140 and drawn from the first methanol converter 140 to generate a vapor flow in line 142. The generation of vapor absorbs the heat generated in the methanol synthesis reaction. The vapor flow in line 142 is sent to the top separator 145, which separates the vapor in line 146 from the water flow in line 147. The water flow in line 147 is replenished by recirculated BFW in line 149, providing BFW from line 148 for the first methanol converter 140.

[0032] In the first methanol converter 140, the synthesis gas is converted into a methanol composition in the first reactor effluent containing methanol in line 144. The methanol stream in the first reactor effluent of line 144 may contain methanol, dimethyl ether, ethanol, or a combination thereof. The first reactor effluent of line 144 is heat-exchanged with the compressed synthesis gas stream in line 132 in the heat exchanger 133. The heat-exchanged first reactor effluent in line 135 may be heated in heater 131 to provide heated first reactor effluent in line 136. The heated first reactor effluent in line 136 may be further heated in heater 137 to provide further heated first reactor effluent in line 138. The further heated first reactor effluent in line 138 is separated in the first gas-liquid separator 150 to provide the first vapor stream in line 152 and the first liquid stream in line 154. The first vapor stream in line 152 and the first liquid stream in line 154 can be further processed to recover methanol.

[0033] The first vapor stream in line 152 contains carbon dioxide that has not yet been converted to methanol. The first vapor stream in line 152 can be compressed in the first compressor 155. In an embodiment, the first vapor stream in line 152 can be mixed with the feed hydrogen stream in line 153 to provide the mixed first vapor stream in line 156. The mixed first vapor stream in line 156 is compressed in the first compressor 155 to supply compressed first vapor in line 157 at a pressure of approximately 6890 kPa (1000 psia) to approximately 8970 kPa (1300 psia). In an embodiment, the feed hydrogen stream in line 153 can be taken from any suitable source. According to this disclosure, the feed hydrogen stream in line 153 can be taken from one or more units of process 101.

[0034] The compressed first vapor in line 157 is heat-exchanged with the reactor effluent in heat exchanger 163, providing a heat-exchanged first vapor flow in line 158, which is sent to the second methanol converter 160. In the second methanol converter 160 of methanol synthesis section 111, unconverted carbon dioxide in the synthesis gas is converted into methanol composition. The methanol synthesis process is achieved in the presence of a methanol synthesis catalyst. A suitable methanol synthesis catalyst may be zinc oxide and copper on an alumina support. The synthesis conditions in the second methanol converter 140 of methanol synthesis section 111 may include a temperature of about 200 to about 300°C and a pressure of about 3.5 to about 10 MPa. Reaction equilibrium typically requires methanol separation and recirculation of unreacted reagents into the synthesis reaction.

[0035] The boiler feedwater (BFW) in line 176 is sent to the second methanol converter 160, which generates a vapor flow in line 166 drawn from the second methanol converter 160, absorbing the heat. The vapor flow in line 166 is sent to the top separator 172, which separates the vapor in line 171 from the water flow in line 173. The water flow in line 173 is replenished by the recirculated BFW in line 174, providing BFW in line 176 for the second methanol converter 160.

[0036] In the second methanol converter 160, the first reactor effluent is converted into a methanol composition, providing a second reactor effluent containing methanol in line 162. The methanol stream of the second reactor effluent in line 162 may include methanol, dimethyl ether, ethanol, or a combination thereof. The second reactor effluent in line 162 can be drawn from a side of the second methanol converter 160. The second reactor effluent in line 162 is heat-exchanged with the compressed first vapor in line 157 in a heat exchanger 163. The heat-exchanged second reactor effluent in line 164 may be heated in a heater 165, providing a heated second reactor effluent in line 166. The heated second reactor effluent in line 166 is separated in a second gas-liquid separator 180, providing a second vapor stream in line 182 and a second liquid stream in line 184. The second vapor stream in line 182 and the second liquid stream in line 184 can be further processed to recover methanol.

[0037] According to an exemplary embodiment, the second methanol converter 160 operates at temperatures ranging from approximately 204°C (400°F) to approximately 290°C (550°F). According to another exemplary embodiment, the second methanol converter 160 operates under pressures ranging from approximately 6890 kPa (1000 psia) to approximately 8970 kPa (1300 psia).

[0038] According to this disclosure, the second vapor flow in line 182 is sent to the PSA unit 185, where hydrogen is separated from the second vapor flow in line 182. In an exemplary embodiment, the second vapor flow in line 182 may be separated into a recirculation flow in line 183 and a PSA supply flow in line 184. In another exemplary embodiment, the recirculation flow in line 183 may be sent to the first compressor 155 as a replenishment hydrogen flow. In an embodiment, the replenishment hydrogen flow in line 153 to the first compressor 155 includes the recirculation flow in line 183.

[0039] The PSA feed stream in line 184 is processed in PSA unit 185. Typically, a PSA unit includes a series of adsorption beds, each containing one or a combination of adsorbents suitable for adsorbing specific components to be adsorbed. These adsorbents include, but are not limited to, activated alumina, silica gel, activated carbon, zeolite molecular sieve-type materials, or any combination thereof. The adsorbents are organized in any order required by the adsorption process to adsorb impurities or components. In PSA unit 185, the PSA feed gas flows over the adsorbents, adsorbing impurities that are easily adsorbed during the adsorption process, while hydrogen passes through. Pressure swings allow the adsorbed impurities on the adsorbents to desorb into line 186. The purified hydrogen gas leaves the adsorption beds in the PSA top gas stream 124, where the impurities are lean.

[0040] In the PSA unit 185, hydrogen present in the PSA feed stream in line 184 is separated. As shown in the figure, the purge stream in line 186 is separated from the hydrogen-rich stream in line 187 from the PSA unit 185. The purge stream in line 186 can be used as fuel. In an exemplary embodiment, the hydrogen-rich stream in line 187 can be sent as a hydrogen stream to the synthesis gas booster compressor 130. In an embodiment, the hydrogen stream in line 124 to the synthesis gas booster compressor 130 includes the hydrogen-rich stream in line 187.

[0041] Returning to the second gas-liquid separator 180, the second liquid flow in line 184 is drawn from the bottom of the second gas-liquid separator 180 and sent to the third gas-liquid separator 190. The first liquid flow in line 154 may also be sent to the second gas-liquid separator 180. In an exemplary embodiment, the second liquid flow in line 184 may be mixed with the first liquid flow in line 154 to provide a mixed liquid flow in line 188, which is sent to the third gas-liquid separator 190. In the third gas-liquid separator 190, the first liquid flow in line 154 and the second liquid flow in line 184 are separated into a third vapor flow in line 192 and a third liquid flow in line 194. The third liquid flow in line 194 contains crude methanol. Alternatively, the third liquid flow in line 194 may be a crude methanol flow. The crude methanol stream may contain at least 100 ppmw of carbon oxides and / or at least 100 ppmw of C2+ oxygenates.

[0042] Crude methanol contains methanol, light fractions, and heavier alcohols. Where used and described herein, the terms “crude methanol” or “crude oxygenated feedstock” may include methanol, ethanol, water, light fractions, and fuel off. Light fractions may include ethers, ketones, aldehydes, and dissolved gases such as hydrogen, methane, carbon oxides, and nitrogen. Crude methanol contains fusel oil. Fusel oil in crude methanol typically contains higher alcohols and is commonly burned as fuel in methanol plants. Crude methanol containing fusel oil can be fed to an oxygenated conversion unit for further production of light olefins. According to this disclosure, crude methanol may be fed to an oxygenated conversion unit or an MTO unit.

[0043] According to exemplary embodiments of the present disclosure, crude methanol may have a composition containing carbon monoxide (CO) at a concentration of about 0 to about 1% by weight, carbon dioxide (CO2) at a concentration of about 0.05 to about 2% by weight, methane (CH4) at a concentration of about 0.001 to about 2% by weight, hydrogen (H2) at a concentration of about 0.05 to about 2% by weight, oxygen (O2) at a concentration of about 0 to about 1% by weight, water (H2O) at a concentration of about 5 to about 18% by weight, nitrogen (N2) at a concentration of about 0 to about 1% by weight, methanol (CH3OH) at a concentration of about 75 to about 90% by weight, and alcohols other than methanol at a concentration of about 0.05 to about 4% by weight.

[0044] The third liquid stream in line 194 may be sent to the crude methanol hold-up tank 195. The crude methanol stream in line 196 is drawn from the crude methanol hold-up tank 195. According to the present invention, the crude methanol stream in line 196 may be sent to the oxygenation unit 10, as shown in Figure 2. According to the embodiment, the crude methanol stream in line 196 may be sent to the methanol purification section 201 to separate by-products and / or trace components and provide a methanol product stream for the oxygenation unit 10.

[0045] According to an exemplary embodiment, the crude methanol stream in line 196 may be sent to a methanol purification section 201, which includes at least two distillation columns, a first distillation column 210 and a second distillation column 220. The crude methanol stream in line 196 is heat-exchanged with the product stream in a heat exchanger 197 to provide a heat-exchanged crude methanol stream in line 194 or a heat-exchanged third liquid stream in line 198. The heat-exchanged crude methanol stream in line 198 is sent to the first distillation column 210. In the first distillation column 210, light gases are separated from the crude methanol in the top stream of the first distillation column in line 212. The light gases separated from the crude methanol stream include carbon monoxide, carbon dioxide, methane, hydrogen, and dimethyl ether. The top stream of the first distillation column in line 212 is sent to a first top receiver 215, where the light gases are separated into a first top receiver vapor stream in line 214. The first top receiver vapor stream in line 214 can be sent to the fuel section or used as fuel. From the first top receiver 215, the top receiver liquid stream is drawn in line 216 and sent to the top of the first distillation column 210.

[0046] The first distillation column bottom flow containing methanol in line 218 is drawn for further separation. The first distillation column bottom flow in line 218 is separated into a first reboiling flow in line 218b and a first distillation column outflow flow in line 218a. The first reboiling flow in line 218b is reboiled in reboiler 310 before being sent to the first distillation column bottom section. Typically, the reboiler is the source of considerable heat load consumption and associated operating costs. The applicant has found that the first reboiling flow in line 218b can be reboiled in reboiler 310 with a suitable flow from a downstream oxygenation conversion unit that provides the necessary heating in reboiler 310. The applicant has found that a water-rich flow from the separation section of the downstream oxygenation conversion unit can be appropriately used to reboil the first reboiling flow in line 218b in reboiler 310. Therefore, the first reboiling flow of line 218b is heated / reboiled together with the water-rich flow of the separation section in the reboiler 310 of the first distillation column 210 to provide the first reboiling flow and hot water-rich flow of line 312. The hot water-rich flow is circulated back to the separation section of the downstream oxygenate conversion unit.

[0047] The first distillation column outflow in line 218a contains heavy oxygenated substances such as C2+ alcohols, ketones, and aldehydes that should be removed from the crude methanol stream. Therefore, the first distillation column outflow in line 218a is further separated in the second distillation column 220. In the second distillation column 220, the first distillation column outflow in line 218a is separated into the second distillation column top flow in line 222, which contains methanol, and the second distillation column bottom flow in line 226. The second distillation column top flow in line 222 passes through the heat exchanger 223 to heat the reflux flow in line 221 from the distillation column. The heated reflux flow in line 221' is taken out. From the heat exchanger 223, the partially condensed second distillation column top flow in line 224 is sent to the second top receiver 225. In the second top receiver 225, the partially condensed top flow of the second distillation column in line 224 is separated into the reflux flow in line 228 and the methanol product flow in line 227. The reflux flow in line 228 is recycled to the second distillation column 220.

[0048] According to an exemplary embodiment, the first distillation column 210 operates at a pressure of approximately 172 kPa (25 psia) to approximately 1379 kPa (200 psia). According to another exemplary embodiment, the first distillation column operates at a temperature of approximately -17°C (0°F) to approximately 177°C (350°F).

[0049] The second distillation column bottom flow in line 226 is drawn out of the column. The second distillation column bottom flow in line 226 is separated into a second reboiling flow in line 226b and a second distillation column outflow flow in line 226a. The second reboiling flow in line 226b is reboiled in reboiler 320 before being sent to the second distillation column bottom section. The applicant found that the second reboiling flow in line 226b can be reboiled in reboiler 320 along with another suitable flow from a downstream oxygenation conversion unit that provides the necessary heating in reboiler 320. The applicant found that a product water flow from the separation section of the downstream oxygenation conversion unit can be appropriately used to reboil the second reboiling flow in line 226b in reboiler 320. Therefore, the second reboiling stream of line 226b is heated / reboiled together with the product water stream of the separation section in the reboiler 320 of the second distillation column 220 to provide the second reboiling stream and warm product water stream of line 322. The warm product water stream is circulated back to the separation section of the downstream oxygenate conversion unit.

[0050] According to an exemplary embodiment, the second distillation column operates at a pressure of approximately 3 kPa (5 psia) to approximately 862 kPa (125 psia). Furthermore, according to an exemplary embodiment, the second distillation is operated at a temperature of approximately 38°C (100°F) to approximately 149°C (300°F).

[0051] Returning to the second distillation column 220, the methanol product stream in line 227 undergoes heat exchange with the crude methanol stream in line 196 in the heat exchanger 197 before being sent to the methanol product hold-up tank 202. The methanol product stream is then withdrawn from the methanol product hold-up tank 202 for further processing, as will be disclosed in detail later herein.

[0052] According to embodiments of the present disclosure, the methanol purification section 201 further includes a third distillation column (not shown) for removing heavy oxygenates from the crude methanol stream. According to exemplary embodiments, the third distillation column may operate at pressures from about 35 kPa (5 psia) to about 345 kPa (50 psia). According to another exemplary embodiment of the present disclosure, the third distillation column may be an atmospheric pressure column operating at approximately atmospheric pressure. According to further exemplary embodiments, the second distillation is operated at temperatures from about 38°C (100°F) to about 122°C (250°F).

[0053] If a third column is also used, the second distillation column outflow logistics in line 226a are separated in the third distillation column to provide a top flow and bottom flow containing methanol. The top flow is then sent to the third top receiver to provide a reflux flow and a methanol product flow. The methanol product flow from the third top receiver is sent to the methanol product hold-up tank 202 along with the methanol product flow in line 227. According to an exemplary embodiment of this disclosure, the reflux flow in line 221 is the reflux flow from the third distillation column.

[0054] According to another embodiment of the present disclosure, an integrated process and apparatus for producing light olefins includes an oxygenation conversion unit 110 or MTO unit 110, as shown in Figure 2. The oxygenation conversion unit 110 or MTO unit 110 includes an oxygenation conversion section 11, a separation section 21, and a compression section 80. A methanol product stream in line 204 can be processed in the oxygenation conversion section 11. Alternatively, a crude methanol stream in line 196 can be processed in the oxygenation conversion section 11. The oxygenation conversion unit 110 or MTO unit 110 includes a separation section 21 including a DME stripper column 350, and an extractive distillation column 360 having a water stripper column 30, a quenching column 20, and a product separator column 24.

[0055] As shown in Figure 2, the oxygenation conversion section 11 includes an oxygenation conversion reactor 16 that reacts an oxygenated substance, such as methanol or dimethyl ether (DME), with a fluid catalyst. The superheated feed stream from line 12, including the methanol product stream from line 204 or the crude methanol stream from line 196, is supplied to the oxygenation conversion reactor 16.

[0056] The high-temperature vapor reactor effluent in line 14 is drawn from the oxygenate conversion reactor 16 and, in order to maintain the desired selectivity and conversion rate, the fluidized catalyst is periodically or continuously circulated to the regeneration zone 18 in a conventional manner. Reactor 16 is maintained under conditions effective for oxygenate / methanol conversion, producing light olefin products and by-products containing oxygenates. The high-temperature vapor reactor effluent may contain light olefins, water, and oxygenates.

[0057] The high-temperature steam reactor effluent in line 14 can be pre-cooled in the reactor effluent heat exchanger 15 to recover heat before being sent to the quenching tower 20. In the quenching tower 20, the vapor reactor effluent is brought into direct contact with a water stream supplied in line 19, which may be taken in from a hot water-rich flow in line 47, thereby removing superheat, neutralizing organic acids, and removing catalyst particles. Furthermore, the circulating water stream in the quenching tower system is used in multiple stages to enhance the recovery of catalyst particles. An additional section in the quenching tower 20 may be provided for caustic injection to remove organic acids such as acetic acid and entrained caustic from the caustic contact section. The quenched olefin stream in line 22 is discharged from the quenching tower 20 and supplied to the product separator tower 24 in the separation section 21.

[0058] The product separator column 24 includes two sections for separating the reactor effluent into a product olefin flow at the top line 40, an intermediate liquid flow in the intermediate line 28, and a water flow in the bottom line 25. The water flow in the bottom line 25 can be separated into a circulating product water flow in the bottom line 26, a net product water flow in the bottom line 31, and a pump-around product water flow in line 23. The first, i.e., lower section 24a, receives the quenched reactor effluent into line 22. In the lower section 24a, most of the heat is removed from the quenched reactor effluent into line 22, while partially condensing the water in the quenched reactor effluent into line 26, generating a product water flow in the net bottom line 26, which contains some of the oxygenated by-products in the quenched reactor effluent into line 22. The pump-around product water stream is pumped to the top of the first section 24a of the product separator tower 24 in the cooled and recirculated product water stream 23 to cool the quenched reactor outflow stream in line 22. The product water stream in line 31 is supplied to the water stripper tower 30.

[0059] As disclosed herein above, the applicants have found that the product water stream in line 26 from the separation section 21 of the oxygenate conversion unit 10 can be appropriately used to reboil the second reboiling stream in line 226b in the reboiler 320 from bottom line 226 of the second distillation column 220 of the methanol purification unit 201. Thus, the product water stream in line 26 is sent to the reboiler 320 to provide the second reboiling stream in line 322 and the cooled product water stream in line 27. Alternatively, the circulating product water stream in line 26 can preheat the feed for the second distillation column 220 in line 218a, or the feed for the first distillation column 210 in line 198 of the methanol purification unit 201, or the reboiling stream 218b of the first distillation column 210. The cooled product water stream in line 27 is circulated back to the separation section 21.

[0060] According to embodiments of the present disclosure, the cooled product water flow in line 27, after heating the reboiling flow or other flow in line 226b in the methanol purification unit 201, is cooled back into line 27 and sent to the water stripper column 30. Preferably, the warm product water flow in line 27 is returned to the upper part of the lower section 24a of the product separator column 24. In embodiments, the warm product water flow in line 27 is returned to the product separator column 24 in the pump-around line 23 upstream of the cooler. The water stripper column 30 may communicate downstream with the product separator column 24 and the compression section 80.

[0061] The vapor flow from the first section 24a of the product separator column 24 is sent to the second or upper section 24b of the product separator. The intermediate flow in line 28, containing hydrocarbons, oxygenation by-products, and liquid-phase water, is drawn out at the bottom of the upper section 24b. A portion of the intermediate flow in line 28 is cooled and sent as reflux to the top of the second section of the product separator column 24. The remainder of the intermediate flow in line 28 is sent to the coalescer 29 to separate the hydrocarbon top flow from the aqueous flow in line 34 and can be supplied to the water stripper column 30. The top product olefin flow containing olefins from the second section 24b of the product separator column 24 in line 40 is delivered to the compression section 80. According to an exemplary embodiment, the warm product water flow in line 27, the aqueous flow in line 34, the water return flow in line 32, and the water return flow containing oxygenated by-products from the compression section 80 in the return line 32 are mixed to provide the mixed product water flow in line 36. The mixed product water flow in line 36 is sent to the water stripper tower 30. In addition, the warm product water flow in line 27, the aqueous flow in line 34, and the water return flow in line 32 can be sent separately to the water stripper tower 30.

[0062] The mixed product water stream in line 36 contains diluted hydrocarbon oxygenates such as DME, methanol, acetaldehyde, acetone, and MEK. The water stripper column 30 separates or strips the oxygenates, dividing the stream into a methanol and oxygenate-rich stream in the top line 44, which is rich in methanol and at least one other oxygenate, and a water-rich stream in the bottom line 33. The water-rich stream in the water stripper bottom line 33 is separated into a reboiling stream that is heated and returned to the column, a water stripper circulation stream in line 46, and a stripped water stream 49. In one embodiment, the temperature of the water stripper column 30 may be about 115°C (239°F) to about 180°C (356°F) at the bottom of the water stripper column, and the pressure may be about 75 kPa gauge (11 psig) to about 760 kPa (110 psig) at the top of the water stripper column 30.

[0063] As disclosed in detail above in this specification, the applicants have found that the circulating water-rich flow in line 46 from the water stripper bottom line 33 from the separation section 31 of the oxygenate conversion unit 10 can be appropriately used to reboil the first reboiling flow in line 218b in the reboiler 310 from the bottom flow in the bottom line 218 of the first distillation column 210. Thus, the circulating water-rich flow in line 46 is sent to the reboiler 310 to heat the first reboiling flow in line 218b, providing the first reboiling flow in line 312 and the cooled water-rich flow in line 47. The cooled water-rich flow in line 47 is circulated back to the separation section 31 of the oxygenate conversion unit 10. Alternatively, the circulating water-rich flow of line 46 can preheat the feed for the first distillation column 210 of line 198, or the feed for the second distillation column 220 of methanol purification unit 201 from line 218a, or the reboiling flow 226b of the second distillation column 220.

[0064] The product olefin flow in the product top line 40 carries the valuable olefin product that needs to be recovered. The compression section 80 increases the pressure of the product olefin flow required for downstream processing, as used in conventional light olefin recovery units. The compression section 80 may include a first knockout drum 82 that separates the product olefin flow into a pressurized first olefin-rich flow in the top line 83 at a temperature of about 40°C (104°F) to about 60°C (140°F) and a pressure of about 193 kPa (g) (28 psig) to about 262 kPa (g) (38 psig) and an oxygenate-rich first aqueous flow in the bottom line 84. The olefin-rich flow in the top line 83 may be fed to a compressor 85, cooled, and directed to a second knockout drum 86. The aqueous flow in the bottom line 84 is pumped through the manifold line 76 to the return line 32, where the aqueous flow is returned to the water stripper tower 30 along with the warm product aqueous flow in the mixed product aqueous flow in line 36.

[0065] The compression section 80 may include a second knockout drum 86 that separates the pressurized first olefin-rich flow into a second pressurized olefin-rich flow in the top line 87 at a pressure of approximately 330 kPa(g)(48 psig) to approximately 400 kPa(g)(58 psig) and a temperature of approximately 27°C(80°F) to approximately 54°C(130°F) and an oxygenate-rich second aqueous flow in the bottom line 88. The second olefin-rich flow in the top line 87 may be supplied to a compressor 89, cooled, and directed to a third knockout drum 90. The aqueous flow in the bottom line 88 is pumped to the return line 32 via the manifold line 76, returning the aqueous flow to the water stripper column 30 along with the warm product aqueous flow in the mixed product aqueous flow in line 36.

[0066] The compression section 80 may include a third knockout drum 90 that separates a pressurized second olefin-rich flow into a third pressurized olefin-rich flow in the top line 91 and an oxygenate-rich third aqueous flow in the bottom line 92. The third olefin-rich flow in the top line 91 may be supplied to the oxygenate absorption column 50. The aqueous flow in the bottom line 92 is pumped through the manifold line 76 to the return line 32, where the aqueous flow is returned to the water stripper column 30 along with the warm product aqueous flow in the mixed product aqueous flow in line 36.

[0067] Suitable compressor types may include centrifugal, positive displacement, piston, diaphragm, and screw types. In one embodiment, compressors 85 and 89 in compressor section 80 are centrifugal compressors. The final discharge pressure may be approximately 1 MPa gauge (145 psig) to approximately 2 MPa gauge (290 psig). The compressor discharge may be cooled to near ambient temperature using conventional heat transfer methods.

[0068] As shown in Figure 2, in a preferred embodiment, at least a portion of the compression product flow through the top line 91 is brought into contact in the oxygenation absorption tower 50 with a cooled, water-free, lean water flow directly taken in from the product separator tower 24, under conditions effective for absorbing the oxygenation without prior removal. In an exemplary embodiment, the absorbent flow of line 102, taken from the hot water-rich flow of line 47, may be sent to the oxygenation absorption tower 50. The contact in the oxygenation absorption tower 50 generates an absorption olefin-rich flow in the top line 54 and an absorption water-rich flow containing a certain amount of effluent oxygenation in the bottom line 52. The operating conditions of the oxygenation absorption tower may include a bottom temperature range of about 30°C (86°F) to about 60°C (140°F) and a top pressure range of about 700 kPa gauge (101 psig) to about 1 MPa gauge (145 psig).

[0069] The absorption olefin-containing flow in the top line 54 can be supplied to the absorption column separator 60, where the gaseous olefin flow is taken in from the top line 61 to the third compressor 62, while water and oxygenated material are taken in from the bottom line 59 to the manifold line 76. The gaseous olefin flow in line 61 is compressed in the third compressor, mixed with the flow in the stripper top line 71, partially condensed by cooling in the heat exchanger 64, and supplied to the stripper separator 66 in line 65. The stripper separator separates the aqueous flow containing oxygenated material in the boot in line 67, which supplies to the manifold line 76, the light olefin vapor flow in the top line 68 containing C3-olefins, and the heavy olefin liquid flow in line 69 containing C4+ olefins. The heavy olefin liquid flow in line 69 is stripped in the DME stripper column 70 to remove C3- and lower vapors from the heavy olefin liquid flow in the stripper bottom line 168 in the stripper top line 71. Most of the oxygenated material is stripped into the stripper top line 71 and separated when it is recirculated to the stripper separator 66 after cooling. The stripper separator 66 may operate at a temperature of approximately 30°C (86°F) to approximately 60°C (140°F) and a pressure of approximately 1.7 MPa (g) (250 psig) to approximately 2.1 MPa (g) (300 psig). The light olefin vapor flow in the top line 68 is washed in the caustic scrubber column 73 by countercurrent contact with the caustic solution in line 42, and acidic gases such as carbon dioxide are absorbed from the light olefin vapor before exiting the caustic scrubber 73 in the top line 74. The acidic gas-rich caustic solution exits the scrubber 73 in line 44 and is supplied to the water stripper manifold 76.

[0070] The washed light olefin vapor in the top line 74 is cooled with a propylene refrigerant in the cryogenic cooler 75 to liquefy a portion of the light olefin flow, which is separated in the dry separator 46 to provide an aqueous flow from the boot into the manifold line 76, a vaporized light olefin flow containing C2- hydrocarbons and gas in the top line 77, and a liquid light olefin flow in the bottom line 78 containing C3+ hydrocarbons. The vaporized light olefin flow in the top line 77 is dried in the dryer 79a to provide a vaporized product olefin flow in line 112. The liquid light olefin flow in the bottom line 78 is dried in the dryer 79b to provide a liquid product olefin flow in line 114. The product olefin flows in lines 112 and 114 can be drawn out and further processed.

[0071] The mixed product water stream in line 36, which includes the warm product water stream in line 26, contains dilute hydrocarbon oxygenates such as DME, methanol, acetaldehyde, acetone, and MEK. The water stripper column 30 separates or strips the oxygenates, dividing the flow into a methanol and oxygenate-rich stream in the top line 44, which is rich in methanol and at least one other oxygenate, and a water-rich stream in the bottom line 39.

[0072] A portion of the water-rich flow in bottom line 39 is re-boiled and returned to the water stripping column 30. The net water-rich flow in bottom line 39 can be divided into the extractant flow supplied to the extraction distillation column 60 in line 62, the remaining bottom water-rich flow in bottom line 49, and the side water-rich flow in line 46. The water-rich flow in line 46 is sent to the re-boiler 310 of the methanol purification section 201, which heats the first re-boiling flow in line 218b to provide the first re-boiling flow in line 312 and the hot water-rich flow in line 47. The hot water-rich flow in line 47 is circulated back to the separation section 21' of the oxygenate conversion unit 110. The hot water-rich flow in line 47 can be supplied to the quenching column 20 in line 19 and the oxygenate absorbent in line 102.

[0073] Uncondensed light hydrocarbons can be purged from the top line of the receiver column, while the hydrocarbon lean, methanol and oxygenate-rich flow can be removed at the bottom line 48, which includes methanol, DME, acetaldehyde, acetone, and MEK. A portion of the hydrocarbon lean, methanol and oxygenate-rich flow can be returned to the water stripper column 30 as reflux.

[0074] In one embodiment, the temperature of the water stripper tower 30 may be about 115°C (239°F) to about 150°C (302°F) at the bottom of the water stripper tower, and the pressure may be about 75 kPa gauge (11 psig) to about 345 kPa (50 psig) at the top of the water stripper tower.

[0075] The hydrocarbon lean, methanol, and oxygenate-rich stream can be fed to the extraction distillation column 360 to separate methanol from at least one other oxygenate. However, the hydrocarbon lean methanol and oxygenate-rich stream contains DME, which is readily separated from methanol. Therefore, the hydrocarbon lean, methanol, and oxygenate-rich stream can be fed to the DME stripper column 350 for easy removal of DME. The DME stripper column 350 may be downstream-communicated with the water stripper column 30. The DME stripper column 350 can separate or strip the DME into the DME-rich stream in the top line 352, providing the DME lean, methanol, and oxygenate-rich stream into the bottom line 354. The DME-rich stream in the top line 352 may be recycled to the oxygenate conversion section 11 as a reaction feed. A portion of the DME lean, methanol, and oxygenate-rich stream can be re-boiled and recycled to the DME stripper column 350. The net DME lean methanol and oxygenate-rich flow in the bottom line 354 can be supplied to the extraction distillation column 360. The extraction distillation column 360 is downstream-communicated with the water stripper column 30 and upstream of the communication with the product separator column 24, ensuring that inert oxygenates do not accumulate in the compression section without a return path to the water stripper column 30. Furthermore, in the embodiment, the extraction distillation column may be downstream-communicated with the DME stripper column 350.

[0076] In one embodiment, the temperature of the DME stripper column 350 may be about 85°C (185°F) to about 120°C (248°F) at the bottom of the DME stripper column, and the pressure may be about 75 kPa gauge (11 psig) to about 414 kPa (60 psig) at the top of the column. The DME stripper column 350 can remove light hydrocarbon purge by utilizing a top condenser and receiver separator in addition to or instead of the top condenser and receiver 45 for the water stripper column 30. The top of the DME stripper column can be recycled to the oxygenate conversion section 11.

[0077] The DME lean, methanol and oxygenate-rich stream is fed into a distillation column to separate methanol from at least one other hydrocarbon oxygenate, preferably all other hydrocarbon oxygenates.

[0078] The DME lean, methanol and oxygenate-rich flow in the net bottom line 354 is fed into the extractive distillation column 360 to separate methanol from at least one other hydrocarbon oxygenate, preferably all other hydrocarbon oxygenates. The water extractant flow may also be fed into the extractive distillation column 360 at a position such as the upper quarter of the column, above a position such as the middle quarter of the column, from which the DME lean, methanol and oxygenate-rich flow is fed. The extractant flow may be supplied into line 362, which can be taken out from the water-rich flow in the water stripper bottom line 39.

[0079] The flow rate of the water extractant stream into the extraction distillation column 360 should be 1.5 to approximately 3 times the flow rate of hydrocarbon oxygenates into the extraction distillation column 360 in the DME lean, methanol, and oxygenate-rich stream, and the total flow rate of the DME lean, methanol, and oxygenate-rich stream, 1 to approximately 3 times, may also contain substantial water.

[0080] The extraction distillation column 360 generates an oxygenate-rich stream containing at least one other hydrocarbon oxygenate, such as acetone, acetaldehyde, MEK, and DME, into the top line 364, and a methanol and water-rich extract stream into the bottom line 366. A portion of the methanol and water-rich stream in the bottom line 366 can be re-boiled and returned to the extraction distillation column 360. The oxygenate-rich stream in the top line 364 can be cooled, partially condensed, and fed to the receiver separator 365. Uncondensed light hydrocarbons can be purged from the receiver top line, while the hydrocarbon lean oxygenate-rich stream, containing DME, acetaldehyde, acetone, and MEK, can be removed in the receiver bottom line 368. A portion of the hydrocarbon lean oxygenate-rich stream can be returned to the extraction distillation column 360 as reflux at a position above where the extractant stream is added to the extraction distillation column 360. The light hydrocarbon purge may be fed to the light olefin recovery.

[0081] At least 99% by weight, preferably at least 99.5% by weight, of hydrocarbon oxygenates other than methanol supplied to the extraction distillation column 360 can be recovered in the oxygenate-rich flow in the top line 364 of the extraction distillation column 360 and in the hydrocarbon lean oxygenate-rich flow in the bottom line 368 of the extraction receiver 365. At least 90% by weight, preferably at least 95% by weight, of methanol can be recovered in the methanol and water-rich flow in the net bottom line 366.

[0082] The extraction distillation column 360 may have operating conditions including a bottom temperature in the range of approximately 75°C (167°F) to approximately 150°C (302°F) and a top pressure in the range of approximately 75 kPa gauge (11 psig) to approximately 200 kPa gauge (29 psig). The extraction distillation column 360 may be downstream-communicated with the top line 44 and bottom line 46 of the water stripper column 30.

[0083] The recovered methanol is an MTO reactant that can be recycled to the MTO reactor or oxygenate conversion reactor 16, but it is undesirable to recycle water with methanol. Therefore, the methanol and water-rich flow in the net bottom line 366 can be fed to the methanol stripper column 370 to separate the methanol-rich flow in the top line 372 from the final water-rich flow in the bottom line 374. The methanol-rich flow in the top line 372 can then be recycled to the MTO reactor 16 without reacting and without inert oxygenates that could otherwise accumulate in the process and apparatus 110. A portion of the final water-rich flow in the bottom line 374 can be re-boiled and recycled to the methanol stripper column 370. The final water-rich flow in the net bottom line 374, along with the remaining unrecycled portion of the water-rich flow in the bottom line 49 from the water stripper bottom line 39, can be sent to the water treatment in line 375.

[0084] Specific Embodiments The following will be explained in conjunction with specific embodiments, but it should be understood that this explanation is intended to illustrate the scope of the preceding explanation and the attached claims, and is not intended to limit them.

[0085] A first embodiment of the present invention is a process for producing light olefins, comprising the steps of: sending a synthesis gas stream to a methanol synthesis reactor and providing a reactor effluent containing methanol; separating the reactor effluent into a vapor stream and a liquid stream containing methanol; sending the liquid stream containing methanol to a methanol purification section including a first distillation column and a second distillation column and providing a methanol product stream; sending at least a portion of the methanol product stream to an oxygenate conversion unit and providing an effluent containing olefins; and separating light olefins from the olefin-containing effluent in a separation section of the oxygenate conversion unit, wherein the reboiling heat for the first and second distillation columns is provided from the separation section of the oxygenate conversion unit. Embodiments of the present disclosure are any or all of the embodiments described in the preceding paragraphs to the first embodiment described in this paragraph, wherein the methanol synthesis section includes a first methanol converter and a second methanol converter. Embodiments of the present invention are any or all of the embodiments described in the preceding paragraph to the first embodiment described in this paragraph, and further include the steps of: sending a synthesis gas stream to a first methanol converter to provide a first reactor effluent containing methanol; separating the first reactor effluent into a first vapor stream and a first liquid stream; sending the first vapor stream to a second methanol converter to provide a second reactor effluent containing methanol; separating the second reactor effluent into a second vapor stream and a second liquid stream; separating the first liquid stream and the second liquid stream into a top stream containing light components and a bottom stream containing crude methanol; and sending the bottom stream containing crude methanol to a methanol purification unit.Embodiments of the present invention are any or all of the preceding embodiments to the first embodiment described in this paragraph, wherein the step of supplying a liquid flow includes supplying a liquid flow containing methanol to a first distillation column to provide a first distillation column top flow and a first distillation column bottom flow, separating the first distillation column bottom flow into a first reboiling flow and a first distillation column outflow flow, and heating the first reboiling flow in the reboiler of the first distillation column with a water-rich flow in the separation section to form a first reboiling flow and a hot water-rich flow. The invention includes the steps of providing a flow, sending a first reboiling flow to a first distillation column, sending the first distillation column outflow flow to a second distillation column to provide a second distillation column top flow and a second distillation column bottom flow, separating the second distillation column bottom flow into a second reboiling flow and a second distillation column outflow flow, heating the second reboiling flow in the reboiler of the second distillation column with the product water flow of a separation section to provide a second reboiling flow and a warm product water flow, and sending the second reboiling flow to a second first distillation column. Embodiments of the invention are any or all of the preceding embodiments in this paragraph to the first embodiment in this paragraph, further comprising the step of separating the first distillation column top flow to provide a first reflux flow and a first top liquid flow containing methanol products. Embodiments of the present invention are one or all of the preceding embodiments in this paragraph to the first embodiment in this paragraph, wherein the water-rich flow is obtained from a warm product water flow. Embodiments of the present invention are one or all of the preceding embodiments in this paragraph to the first embodiment in this paragraph, further comprising the step of heating one or both of the water-rich flow and the product water flow before sending the methanol-containing liquid flow to the first distillation column. One embodiment of the present invention is one or all of the preceding embodiments in this paragraph to the first embodiment in this paragraph, further comprising the step of sending the second distillation column outflow flow to the third distillation column to provide a methanol product flow. Embodiments of the present invention are one or all of the preceding embodiments in this paragraph to the first embodiment in this paragraph, wherein the methanol purification unit includes two stripper columns.Embodiments of the present invention are any or all of the preceding embodiments in this paragraph to the first embodiment in this paragraph, and further include the steps of: sending an olefin-containing effluent to a quenching column of a separation section to provide a quenched effluent flow; sending the quenched effluent flow to a product separator column in the separation section to provide an olefin-containing top flow and bottom flow; separating the bottom flow into a reboiling flow and a product flow; sending the product flow to a reboiler of a second distillation column; and sending the warm product flow to the separation section. Embodiments of the present invention are any or all of the preceding embodiments in this paragraph to the first embodiment in this paragraph, and further include the steps of: sending the warm product flow, top flow, and intermediate flow to a water stripper column of a separation section to provide an oxygenate-rich top flow and a water-rich bottom flow; sending at least a portion of the water-rich bottom flow to a reboiler of a first distillation column; and sending the warm water-rich flow to a quenching column of a separation section. Embodiments of the present invention are one or all of the preceding embodiments in this paragraph to the first embodiment in this paragraph, wherein an intermediate water flow is provided from a product separator column and a top water flow is provided from a compression section of the separation section. Embodiments of the present invention are one or all of the preceding embodiments in this paragraph to the first embodiment in this paragraph, further comprising the steps of providing an intermediate liquid flow from a product separator column, separating the intermediate liquid flow into an intermediate reflux flow and an intermediate water flow, and sending a top flow containing olefins to a compression section to separate the olefins and provide a top water flow. Embodiments of the present invention are one or all of the preceding embodiments in this paragraph to the first embodiment in this paragraph, wherein the methanol purification section includes a third distillation column. Embodiments of the present invention are any or all of the preceding embodiments to the first embodiment described in this paragraph, further comprising the steps of: fractionating the flow outflow of the second distillation column in a third distillation column to provide a third distillation column top flow containing methanol; and separating the third distillation column top flow to provide a third reflux flow and a methanol flow.

[0086] Without further detail, it is expected that those skilled in the art will be able to utilize the Disclosure to the fullest extent without departing from the spirit and scope of the Disclosure, readily identify its essential characteristics, and make various changes and modifications to adapt it to various uses and conditions. Accordingly, the prior preferred specific embodiments should be interpreted as merely illustrative examples and not in any way limiting the remainder of the Disclosure, but are intended to cover various modifications and equivalent configurations that fall within the scope of the appended claims.

[0087] In the above, all temperatures are given in degrees Celsius, and all parts and percentages are based on weight unless otherwise indicated.

Claims

1. An integrated process for producing light olefins, A process of supplying a synthesis gas stream to a methanol synthesis reactor and providing a reactor effluent containing methanol, The process involves separating the reactor effluent into a vapor stream and a liquid stream containing methanol. The process involves sending the liquid stream containing methanol to a methanol purification section including a first distillation column to provide a methanol product stream, A step of sending at least a portion of the methanol product stream to an oxygenated conversion unit to provide an effluent containing olefins, The separation section of the oxygenated material conversion unit includes a step of separating light olefins from the effluent containing olefins, The heat to the first distillation column is supplied from the separation section of the oxygenate conversion unit in an integrated process.

2. The process according to claim 1, wherein the methanol synthesis section includes a first methanol converter and a second methanol converter.

3. The process of sending the synthesis gas flow to the first methanol converter and providing a first reactor effluent containing methanol, A step of separating the effluent from the first reactor into a first vapor stream and a first liquid stream, A step of sending the first vapor stream to the second methanol converter and providing a second reactor effluent containing methanol, The process involves separating the effluent from the second reactor into a second vapor stream and a second liquid stream, The process involves separating the first liquid flow and the second liquid flow into a top flow containing light components and a bottom flow containing crude methanol. The process according to claim 2, further comprising the step of sending the bottom flow containing crude methanol to the methanol purification unit.

4. The process of supplying the liquid flow is, A step of sending the liquid stream containing methanol to the first distillation column to provide the top flow and the bottom flow of the first distillation column, The process involves separating the bottom flow of the first distillation column into a first re-boiling flow and a first distillation column outflow flow, In the reboiler of the first distillation column, the first reboil stream is heated with the product water stream taken from the separation section to provide the first reboil stream and the cooled product water stream, Sending the first re-boiling stream to the first distillation column, The process of sending the flow out of the first distillation column to the second distillation column and providing the top flow and bottom flow of the second distillation column, The process involves separating the bottom flow of the second distillation column into a second re-boiling flow and a second distillation column outflow flow, A step of heating the second reboiling stream in the reboiling chamber of the second distillation column with the stripped water stream of the separation section to provide the second reboiling stream and the cooled stripped water stream, The process according to claim 1, further comprising the step of sending a second reboiling flow to the second distillation column.

5. The process according to claim 4, further comprising the step of separating the first distillation column top flow to provide a first reflux flow and a first top liquid flow containing the methanol product.

6. The process according to claim 4, wherein the stripped water stream is obtained from the cooled product water stream.

7. The process according to claim 4, further comprising the step of heating the liquid stream containing methanol together with one or both of the stripped water stream and the product water stream before sending them to the first distillation column.

8. The process according to claim 4, further comprising the step of sending the outflow flow from the second distillation column to a third distillation column to provide the methanol product flow.

9. The process according to claim 1, wherein the methanol purification unit includes two stripper towers.

10. A step of sending the effluent containing olefins to the quenching tower of the separation section and providing the quenched effluent logistics, The process of sending the rapidly cooled outflow to the product separator tower in the separation section and providing a top flow and bottom flow containing olefins, The process of extracting the product water flow from the bottom water flow, The process of sending the product water stream to the reboiler of the first distillation column, The process according to claim 4, further comprising the step of sending a cooled product water stream to the separation section.

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