System and method for preparing propylene by means of propane dehydrogenation

Abstract

The present invention belongs to the technical field of propane dehydrogenation. Provided in the present invention are a system and method for preparing propylene by means of propane dehydrogenation, which solve the problems of increased investment cost, high comprehensive energy consumption and increased production operation cost caused by complex structures in the prior art. The system comprises a reaction-regeneration system, the reaction-regeneration system being connected to a separation system used for treating a reaction gas. The separation system comprises a water scrubber; the top of the water scrubber is connected to a compressor suction tank; the top of the compressor suction tank is connected to a reaction gas compressor; the reaction gas compressor is connected to a cold box; the cold box is connected to an ethane tower; the bottom of the ethane tower is connected to a propylene tower; and the bottom of the propylene tower is connected to a propane tower. The water scrubber is provided to wash and cool the reaction gas, so as to prevent subsequent pipes from being blocked by catalyst fine powder and reduce the working load of the cold box; and then the ethane tower, the propylene tower and the propane tower are used to perform separation on the reaction gas. The present invention achieves a low comprehensive energy consumption, a simple structure, a high utilization rate of separated by-products, low investment cost and low production cost.

Description

System and method for producing propylene by dehydrogenating propane Technical Field

[0001] The present invention belongs to the technical field of propane dehydrogenation, and in particular to a system and method for producing propylene by dehydrogenating propane. Background Art

[0002] Propylene is one of the most produced basic organic chemical raw materials in the world, second only to ethylene in usage. Propylene is the raw material for polypropylene plastics, which are commonly used in the automotive and textile industries. They are often used in packaging plastic films and many other products. In addition to being used to produce polypropylene, it is also used to produce derivatives such as acrylonitrile, butanol, and octanol. With the rapid growth in demand for downstream products, the demand for propylene has also increased year by year. Propane dehydrogenation technology to produce propylene has been one of the main technical routes for industrial production of propylene in recent years.

[0003] Propane dehydrogenation is an important process step in the production of propylene and is crucial to the petrochemical industry. Since its discovery in the early 1990s, propane dehydrogenation technology has become increasingly mature in industry, with fixed bed, moving bed and fluidized bed processes. Currently, all three propane dehydrogenation technologies have been industrialized.

[0004] In recent years, propane dehydrogenation technology has developed rapidly, and the scale of industrial equipment has also been gradually expanded. The propane dehydrogenation technologies that have been industrialized and occupy the mainstream of the market are mainly the Catofin fixed bed process and the Oleflex moving bed process. They each have their own advantages and are undergoing continuous technical improvements. For example, the Catofin process now uses a dehydrogenation catalyst Catofin311 with a lower bulk density and is used in conjunction with HGM (heat-generating material) to further improve selectivity; in addition to ensuring that the catalyst performance remains unchanged, the Oleflex process further reduces the platinum content in the catalyst and improves the catalyst's resistance to carbon deposition, allowing the dehydrogenation reaction to maintain operation for a longer period of time.

[0005] China's propane dehydrogenation technology has also made rapid progress in the development of both catalysts and complete processes. In recent years, it has entered the industrialization stage. Chinese research teams have further accelerated the development of propane dehydrogenation technology, continuously improved the technical level, and enhanced technological competitiveness. China's propane dehydrogenation technology has achieved catalysts and complete technology.

[0006] In the coming period, as the trend toward lighter raw materials intensifies, the diversification of propylene feedstocks will become a trend in the industry. Compared with propylene production technologies such as steam cracking and catalytic cracking, propane dehydrogenation technology, due to its single raw material and easy product separation, can significantly increase propylene yields, with total propylene yields reaching over 80%. The production cost of propane dehydrogenation is closely related only to fluctuations in propane prices, which are directly linked to naphtha prices and the propylene market. Propane dehydrogenation technology can convert low-value propane into high-value propylene, thereby improving profitability. Existing propane dehydrogenation systems for propylene production are complex in structure, leading to increased investment costs. During operation, the overall energy consumption is high, and production and operating costs are also increased accordingly.

[0007] Summary of the Invention

[0008] In response to the above problems, the present invention aims to provide a system and method for producing propylene by dehydrogenating propane. A water scrubber is provided to wash and cool the reaction gas, thereby preventing fine catalyst powder from clogging subsequent pipelines and reducing the workload of the cold box. The reaction gas is then separated by an ethane tower, a propylene tower, and a propane tower. The system has low overall energy consumption, a simple structure, a high utilization rate of separated by-products, low investment cost, and low production cost.

[0009] The technical solution adopted in the present invention is as follows:

[0010] A system for producing propylene by dehydrogenating propane comprises a reaction regeneration system connected to a separation system for processing reaction gas; the separation system comprises a water scrubber connected to the reaction regeneration system, the top of the water scrubber being connected to a compressor suction tank via a pipeline, the top of the compressor suction tank being connected to a reaction gas compressor, the reaction gas compressor being connected to a cold box, the cold box being connected to an ethane tower, the bottom of the ethane tower being connected to a propylene tower via a pipeline, and the bottom of the propylene tower being connected to a propane tower via a pipeline.

[0011] Preferably, washing circulation pipelines for circulating washing water are provided at the top, middle and bottom of the water washing tower. The washing circulation pipelines located in the middle and bottom of the water washing tower are connected, and the washing circulation pipeline at the bottom diverts part of the washing water to the washing circulation pipeline in the middle. A catalyst clarification tank and a clarified water tank are provided in the washing circulation pipeline in the middle, and the bottom of the catalyst clarification tank is connected to a sedimentation tank.

[0012] Preferably, the compressor suction tank and the reaction gas compressor are provided in two sets and are connected in series to perform two-stage compression, and the bottom of the compressor suction tank is connected to the water washing tower.

[0013] Preferably, the top of the ethane tower is connected to an ethane tower top reflux tank, and the pipe connecting the ethane tower and the ethane tower top reflux tank extends into the cold box, and the bottom of the ethane tower top reflux tank is connected to two pipes, one of which is connected to the ethane tower, and the other pipe discharges ethane to the outside.

[0014] Preferably, the top of the propylene tower is connected to a propylene tower top reflux tank, and the pipe connecting the propylene tower and the propylene tower top reflux tank extends into the cold box. The bottom of the propylene tower top reflux tank is connected to two pipes, one of which is connected to the propylene tower and the other discharges propylene.

[0015] Preferably, the top of the propane tower is connected to a propane tower top reflux tank, and the pipe connecting the propane tower and the propane tower top reflux tank extends into the cold box, and the bottom of the propane tower top reflux tank is connected to two pipes, one of which is connected to the propane tower, and the other is connected to the feed end of the reaction regeneration system.

[0016] Preferably, the reaction regeneration system includes a feed heat exchanger, a heating furnace, and a reactor connected in sequence, the bottom of the reactor is connected to the regenerator through a pipeline, the bottom of the regenerator is connected to the reactor through a pipeline, the top of the reactor is connected to the heat source inlet of the feed heat exchanger through a pipeline, the heat source outlet of the feed heat exchanger is connected to the steam generator through a pipeline, and the steam generator is connected to the water washing tower through a pipeline.

[0017] Preferably, the reactor is provided with first and second reaction cyclone separators, a third reaction cyclone separator is provided on the pipeline connecting the reactor and the feed heat exchanger, the bottom of the third reaction cyclone separator is connected to the fourth reaction cyclone separator, the top of the fourth reaction cyclone separator is connected to the heat source inlet of the feed heat exchanger through a pipeline, the bottom of the fourth reaction cyclone separator is connected to a reaction fine powder collection tank, the reaction fine powder collection tank is connected to a waste catalyst tank, and a loader is provided below the waste catalyst tank.

[0018] Preferably, the regenerator is provided with a first- and second-stage regeneration cyclone separator, the top of the regenerator is connected to a third-stage regeneration cyclone separator, the top of the third-stage regeneration cyclone separator is connected to a waste heat steam generator through a pipeline, and a double-acting slide valve is provided in the pipeline, the waste heat steam generator is connected to a flue gas dust collector, the flue gas dust collector is connected to a chimney, the bottom of the third-stage regeneration cyclone separator is connected to a fourth-stage regeneration cyclone separator, the top of the fourth-stage regeneration cyclone separator is connected to the waste heat steam generator through a pipeline, the bottom of the fourth-stage regeneration cyclone separator is connected to a regeneration fine powder collection tank, and the regeneration fine powder collection tank is connected to the waste catalyst tank.

[0019] A method for preparing propylene by dehydrogenating propane comprises the following steps:

[0020] S1. Propane is fed from the feed heat exchanger. After being heated in a heating furnace, the propane enters the reactor and contacts the catalyst to react and generate reaction gas. The spent catalyst in the reactor is transported to a regenerator for charring and regeneration to obtain regenerated catalyst. The regenerated catalyst is then returned to the reactor for continued use. The flue gas generated during the regeneration process in the regenerator passes through the regeneration first and second cyclone separators, the regeneration third cyclone separator, and the regeneration fourth cyclone separator in sequence to separate the catalyst fines. The flue gas finally passes through a waste heat steam generator to recover heat and a flue gas dust collector to remove dust before being discharged from a chimney.

[0021] S2, the reaction gas passes through the first and second stage cyclone separators, the third stage cyclone separator and the fourth stage cyclone separator in sequence to separate the catalyst fine powder, which is then input into the feed heat exchanger as a heat source, and then input into the steam generator for cooling;

[0022] S3. The cooled reaction gas enters the water scrubber for washing. The water scrubber is equipped with three sections of washing circulation pipelines. The washing circulation pipeline located in the middle of the water scrubber uses a catalyst clarifier to separate the catalyst and transport it to the sedimentation tank for further separation.

[0023] S4, the washed reaction gas enters the compressor suction tank, is compressed by the reaction gas compressor and transported to the cold box to separate methane hydrogen and condensate;

[0024] S5. The condensate passes through the ethane tower, propylene tower and propane tower in sequence to separate ethane, propylene and propane, and the propane is then fed into the feed end of the feed heat exchanger to react again.

[0025] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0026] A water washing tower is set up to wash and cool the reaction gas to prevent fine catalyst powder from clogging subsequent pipelines and reduce the workload of the cold box. The reaction gas is then separated through an ethane tower, a propylene tower and a propane tower. The overall energy consumption is low, the structure is simple, the utilization rate of the separated by-products is high, the investment cost is low, and the production cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0028] FIG1 is a schematic diagram of a process according to an embodiment of the present invention;

[0029] FIG2 is a schematic diagram of the cold box structure provided by an embodiment of the present invention.

[0030] Description of the drawings: 1-reaction regeneration system; 2-separation system; 3-reaction first and second stage cyclone separators; 4-regeneration first and second stage cyclone separators; 5-reaction third stage cyclone separator; 6-reaction fourth stage cyclone separator; 7-reaction fine powder collection tank; 8-regeneration third stage cyclone separator; 9-regeneration fourth stage cyclone separator; 10-regeneration fine powder collection tank; 11-reaction internal heat extraction pipe; 12-regeneration internal heat extraction pipe; 13-heating furnace; 14-heat extraction pipe of heating furnace; 15-feed heat exchanger; 16-steam generator; 17-waste heat steam generator; 18-flue gas dust collector; 19-chimney; 20-fresh catalyst tank; 21-waste catalyst tank; 22-small dosing instrument; 23-loader; 24-main fan; 25-auxiliary combustion chamber; 26-double-acting slide valve; 27-regenerator; 28-reactor; 201-water scrubber; 202-top Circulation pump; 203-bottom circulation pump; 204-catalyst clarification tank; 205-clarified water tank; 206-catalyst delivery pump; 207-middle circulation pump; 208-sedimentation tank; 209-compressor suction tank; 210-reaction gas compressor; 211-cold box; 212-ethane tower; 213-ethane tower top reflux tank; 214-ethane tower top reflux pump; 215-ethane tower bottom pump; 216-propylene tower; 217-propylene tower top reflux tank; 218-propylene tower top reflux pump; 219-propylene tower bottom pump; 220-propane tower; 221-propane tower top reflux tank; 222-propane tower top reflux pump; 223-depropanizer bottom pump; 224-separation tank; 225-first stage compression pipe; 226-second stage compression pipe. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0033] In the description of the present invention, it should be noted that if the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the application is usually placed when in use. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0034] The present invention will be described in detail below with reference to FIG1-FIG. 2 .

[0035] Example

[0036] A system for producing propylene by dehydrogenating propane, as shown in FIG1 , includes a reaction and regeneration system 1 connected to a separation system 2 for processing reaction gas. Separation system 2 includes a water scrubber 201 connected to reaction and regeneration system 1. The top of water scrubber 201 is connected to a compressor suction tank 209 via a pipeline. The top of compressor suction tank 209 is connected to a reaction gas compressor 210. Reaction gas compressor 210 is connected to a cold box 211. Cold box 211 is connected to an ethane tower 212. The bottom of ethane tower 212 is connected to a propylene tower 216 via a pipeline. The bottom of propylene tower 216 is connected to a propane tower 220 via a pipeline. An ethane tower bottom pump 215 is provided in the pipeline connecting ethane tower 212 and propylene tower 216, and a propylene tower bottom pump 219 is provided in the pipeline connecting propylene tower 216 and propane tower 220.

[0037] As shown in Figure 1, wash water circulation lines are installed at the top, middle, and bottom of water scrubber 201. The wash water circulation lines in the middle and bottom of water scrubber 201 are connected, and the bottom wash water circulation line diverts some of the wash water to the middle wash water circulation line. The middle wash water circulation line is equipped with a catalyst clarification tank 204 and a clarified water tank 205. The bottom of catalyst clarification tank 204 is connected to a settling tank 208. The three wash water circulation lines of water scrubber 201 are respectively equipped with a top circulation pump 202, a middle circulation pump 207, and a bottom circulation pump 203. The outlet of bottom circulation pump 203 is connected to the middle wash water circulation line, thereby delivering the wash water containing catalyst fines at the bottom to catalyst clarification tank 204 for separation. The separated catalyst is then transferred to settling tank 208 by catalyst transfer pump 206 for further separation. The clarified water in catalyst clarification tank 204 is collected in clarified water tank 205 and transported by middle circulation pump 207. Set three-stage cycle washing to make the washing effect obvious.

[0038] The compressor suction tank 209 and the reaction gas compressor 210 are provided with two sets and are connected in series to perform two-stage compression. Under the condition of ensuring the compression ratio, damage to the reaction gas compressor 210 is avoided. As shown in Figure 2, the reaction gas compressor 210 of the first section first compresses the reaction gas in the compressor suction tank 209 and extends into the cold box 211 through a compression pipe 225 for cooling. The condensate and the reaction gas enter the compressor suction tank 209 of the second section. The reaction gas compressor 210 of the second section then compresses the reaction gas and transports it to the separation tank 224 located in the cold box 221 through a two-stage compression pipe 226 for separation. Methane hydrogen and condensate are separated. The methane hydrogen can be used as fuel for the heating furnace, reducing fuel consumption. The condensate is then subjected to subsequent separation operations. The bottom of the compressor suction tank 209 is connected to the water scrubber 201, and the collected condensate is returned to the water scrubber 201 for reuse, which can also reduce the temperature of the washing water.

[0039] The top of ethane tower 212 is connected to an ethane tower overhead reflux tank 213, and the pipe connecting ethane tower 212 and ethane tower overhead reflux tank 213 extends into cold box 211. The bottom of ethane tower overhead reflux tank 213 is connected to two pipes, one of which is connected to ethane tower 212, and the other is used to discharge ethane. Ethane tower 212 separates the condensate into gas and liquid phases. The gas is discharged from the top of ethane tower 212 and condensed in cold box 211 to form a liquid phase, which is finally collected in ethane tower overhead reflux tank 213. The ethane is then transported to the outside world and to ethane tower 212 by ethane tower overhead reflux pump 214. Some of the ethane is transported to the outside world for direct recovery, while the rest is returned to the top of ethane tower 212 for reflux. The liquid phase at the bottom of ethane tower 212 is transported to propylene tower 216 via ethane tower bottom pump 215. The ethane tower 212 has a simple structure, low investment cost, high by-product utilization rate, and low production cost.

[0040] The top of propylene tower 216 is connected to a propylene tower overhead reflux tank 217. The pipe connecting propylene tower 216 and propylene tower overhead reflux tank 217 extends into cold box 211. The bottom of propylene tower overhead reflux tank 217 is connected to two pipes: one pipe connects to propylene tower 216, and the other pipe discharges propylene. Propylene tower 216 separates the liquid at the bottom of ethane tower 212 into two phases. The gas is discharged from the top of propylene tower 216 and condensed in cold box 211 to form a liquid phase, which is eventually collected in propylene tower overhead reflux tank 217. A propylene tower overhead reflux pump 218 then transports propylene to the outside world and to propylene tower 216. Some of the propylene is transported directly to the outside world for recycling, while the remaining propylene returns to the top of propylene tower 216 for reflux. The liquid phase at the bottom of propylene tower 216 is transported to propane tower 220 via a propylene tower bottom pump 219. Propylene tower 216 has a simple structure, low investment cost, high by-product utilization rate, and low production cost.

[0041] The top of the propane tower 220 is connected to a propane tower overhead reflux tank 221, and the pipe connecting the propane tower 220 and the propane tower overhead reflux tank 221 extends into the cold box 211. The bottom of the propane tower overhead reflux tank 221 is connected to two pipes, one of which is connected to the propane tower 220, and the other is connected to the feed end of the reaction and regeneration system 1. The propane tower 220 performs gas-liquid two-phase separation on the bottom liquid of the propylene tower 216. The gas is discharged from the top of the propane tower 220 and condensed in the cold box 211 to form a liquid phase, which is finally collected in the propane tower overhead reflux tank 221. The propane tower overhead reflux pump 222 then transports propane to the reaction and regeneration system 1 and the propane tower 220. Part of the propane is transported to the reaction and regeneration system 1 to continue participating in the reaction, and the rest of the propane is returned to the top of the propane tower 220 for reflux. The bottom liquid phase of the propylene tower 216 is transported to the outside world by the depropanizer bottom pump 223 to remove the heavy component phase. The propane tower 220 has a simple structure, low investment cost, high by-product utilization rate, and low production cost.

[0042] As shown in Figure 2, cold box 211 uses three streams of propylene as refrigerant: propylene 1 (5-15°C), propylene 2 (-25--7°C), and propylene 3 (-50--30°C). A combination of two of these streams can also be used. Cold box 211 also cools the circulating water from the water wash tower. Cold box 211 offers high utilization, effective heat exchange, a simple structure, low energy consumption, and low production costs. Propylene 1, propylene 2, and propylene 3 are compressed in three stages by a propylene refrigeration compressor: the first stage inlet: temperature 5-15°C, pressure 0.5-0.8 MPa; the second stage inlet: temperature -25--7°C, pressure 0.15-0.4 MPa; and the third stage inlet: temperature -50--30°C, pressure 0.03-0.2 MPa. The outlet of the propylene refrigeration compressor can serve as the heat source for the reboiler in each tower, or the superheated steam produced within the unit can be combined with the outlet of the propylene refrigeration compressor to serve as the reboiler for each tower, adjusted according to the tower's required process conditions.

[0043] The reaction and regeneration system 1 comprises a feed heat exchanger 15, a heating furnace 13, and a reactor 28, connected in sequence. The bottom of reactor 28 is connected to a regenerator 27 via a pipeline, which in turn communicates with reactor 28 via a pipeline. The top of reactor 28 is connected to the heat source inlet of feed heat exchanger 15 via a pipeline. The heat source outlet of feed heat exchanger 15 is connected to a steam generator 16 via a pipeline, which in turn is connected to a water scrubber 201 via a pipeline. Propane enters feed heat exchanger 15 for initial heating. The heat source of feed heat exchanger 15 is the reaction gas. Steam generator 16 is used to further cool the reaction gas, lowering the temperature of the reaction gas while reducing the load on heating furnace 13 and water scrubber 201, thereby reducing production costs. Furnace 13 is also equipped with a furnace heat extraction pipe 14, which utilizes waste heat from furnace 13 exhaust to generate steam, comprehensively utilizing thermal energy and reducing the temperature of the furnace exhaust. Regenerator 27 recycles the catalyst in reactor 28 to ensure its normal and continuous operation.

[0044] Reactor 28 is equipped with 4 to 8 sets of internal reaction heat extraction pipes 11 in the dilute phase section, generating steam while lowering the dilute phase temperature, reducing side reactions and improving reaction yield. Regenerator 27 is equipped with 6 to 12 sets of internal regeneration heat extraction pipes 12 in the dense phase section. This simple structure offers low investment costs, reduces the dense phase temperature, and produces saturated steam, thus lowering production costs. The number of internal reaction heat extraction pipes 11 and regeneration heat extraction pipes 12 can be adjusted according to the production scale of the device.

[0045] The regenerator 27 is also connected to a fresh catalyst tank 20. During startup, fresh catalyst is added to the regenerator 27 through the fresh catalyst tank 20, and then transferred to the reactor 28. This saves startup time and effectively increases the catalyst temperature. During normal production, fresh catalyst is added to the regenerator 27 through a small catalyst dosing device 22. The regenerator 27 is connected to an auxiliary combustion chamber 25, which replenishes coke into the regenerator 27 via a main blower 24.

[0046] Reactor 28 is equipped with primary and secondary cyclone separators 3. A tertiary cyclone separator 5 is installed on the pipeline connecting reactor 28 to feed heat exchanger 15. The bottom of tertiary cyclone separator 5 is connected to a tertiary cyclone separator 6. The top of tertiary cyclone separator 6 is connected to the heat source inlet of feed heat exchanger 15 via a pipeline. The bottom of tertiary cyclone separator 6 is connected to a reaction fines collection tank 7, which is connected to a waste catalyst tank 21. A loader 23 is installed below waste catalyst tank 21. The primary and secondary cyclone separators 3 separate the catalyst fines carried by the reaction gas and drop them into reactor 28 for easy recycling. The tertiary cyclone separator 5 and the tertiary cyclone separator 6 further separate the reaction gas exiting reactor 28, further reducing the amount of catalyst fines carried. The reaction gas discharged from the tertiary cyclone separator 5 and the tertiary cyclone separator 6 is then fed into feed heat exchanger 15, improving product yield. The collected catalyst fine powder is collected in the reaction fine powder collection tank 7 and finally transported to the waste catalyst tank 21. The catalyst fine powder is loaded into the transport vehicle through the loader 23 for easy transportation.

[0047] The regenerator 27 is provided with a regeneration first and second stage cyclone separator 4, the top of the regenerator 27 is connected to the regeneration third stage cyclone separator 8, the top of the regeneration third stage cyclone separator 8 is connected to the waste heat steam generator 17 through a pipeline and a double-acting slide valve 26 is provided in the pipeline, the waste heat steam generator 17 is connected to the flue gas dust collector 18, the flue gas dust collector 18 is connected to the chimney 19, the bottom of the regeneration third stage cyclone separator 8 is connected to the regeneration fourth stage cyclone separator 9, the top of the regeneration fourth stage cyclone separator 9 is connected to the waste heat steam generator 17 through a pipeline, the bottom of the regeneration fourth stage cyclone separator 9 is connected to the regeneration fine powder collection tank 10, and the regeneration fine powder collection tank 10 is connected to the waste catalyst tank 21. The catalyst fine powder in the flue gas of the regenerated first and second stage cyclone separators 4 is separated and dropped into the regenerator 27 for easy recycling; the regenerated third stage cyclone separator 8 and the regenerated fourth stage cyclone separator 9 separate the flue gas discharged from the regenerator 27 again, and the flue gas discharged from the regenerated third stage cyclone separator 8 passes through the double-acting slide valve 26 and is merged into the waste heat steam generator 17 together with the flue gas discharged from the regenerated fourth stage cyclone separator 9. The waste heat steam generator 17 uses the heat of the flue gas to generate steam and superheat the saturated steam produced in several other places, with low comprehensive energy consumption and low production cost; the flue gas is removed from the flue gas dust collector 18 to remove the catalyst fine powder finally carried by the flue gas and then discharged from the chimney 19, which is environmentally friendly.

[0048] There are 8 to 20 groups of reaction first and second stage cyclone separators 3, and 6 to 16 groups of regeneration first and second stage cyclone separators 4; the bottoms of the regenerator 27 and the reactor 28 are both provided with stripping sections, and 2 to 5 stripping sections can be provided. The number of cyclone separators and the number of stripping sections can be adjusted according to the production scale of the device.

[0049] A method for preparing propylene by dehydrogenating propane comprises the following steps:

[0050] S1. Propane is input from the feed heat exchanger 15. After being heated by the heating furnace 13, the propane enters the reactor 28 and contacts with the catalyst to react and generate reaction gas. The catalyst to be regenerated in the reactor 28 is transported to the regenerator 27 for charring and regeneration to obtain regenerated catalyst. The regenerated catalyst is then returned to the reactor 28 for continued use. The flue gas generated during the regeneration process of the regenerator 27 passes through the regeneration first and second stage cyclone separators 4, the regeneration third stage cyclone separator 8 and the regeneration fourth stage cyclone separator 9 in sequence to separate the catalyst fine powder. The flue gas finally passes through the waste heat steam generator 17 to recover heat and The flue gas dust collector 18 removes dust and is discharged from the chimney 19; the heating furnace 13 heats the propane to 500-600°C, the reaction temperature in the reactor 28 is 550-650°C, the pressure is 0.03-0.1Mpa, the catalyst-propane ratio (the ratio of the content of catalyst to propane) is 1-20, the preferred reaction temperature is 560-610°C, the pressure is 0.03-0.05Mpa, and the catalyst-propane ratio is 7-16; the preferred reaction conditions of the regenerator 27 are: temperature 600-690°C, pressure 0.025-0.045Mpa.

[0051] S2, the reaction gas passes through the first and second stage cyclone separators 3, the third stage cyclone separator 5 and the fourth stage cyclone separator 6 in sequence to separate the catalyst fine powder, which is then input into the feed heat exchanger 15 as a heat source, and then input into the steam generator 16 for cooling;

[0052] S3, the cooled reaction gas enters the water scrubber 201 for scrubbing. The water scrubber 201 is provided with three sections of scrubbing circulation pipelines. The scrubbing circulation pipeline in the middle of the water scrubber 201 uses the catalyst clarification tank 204 to separate the catalyst and transport it to the settling tank 208 for further separation. The top pressure of the water scrubber 201 is 0.02-0.04 MPa.

[0053] S4, the washed reaction gas enters the compressor suction tank 209, is compressed by the reaction gas compressor 210 and transported to the cold box 211 to separate methane hydrogen and condensate; the reaction gas compressor 210 compresses to 1.1-2.1 MPa;

[0054] S5. The condensate passes through the ethane tower 212, the propylene tower 216 and the propane tower 220 in sequence to separate ethane, propylene and propane, and the propane is then fed into the feed end of the feed heat exchanger 15 for further reaction. The pressure of the ethane tower 212 is 0.5-2.0 MPa, the pressure of the propylene tower 216 is 0.5-1.5 MPa, and the pressure of the propane tower 220 is 0.3-1.3 MPa.

[0055] The present application is also suitable for producing olefins from liquefied gas, and is also suitable for producing olefins from the dehydrogenation of a mixture of one or more of propane low-carbon hydrocarbons, isobutane, and isobutane-rich low-carbon hydrocarbons, and has a wide range of applications.

[0056] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A system for producing propylene by dehydrogenating propane, comprising a reaction regeneration system (1), characterized in that: The reaction regeneration system (1) is connected to a separation system (2) for processing reaction gas; the separation system (2) comprises a water washing tower (201) connected to the reaction regeneration system (1); the top of the water washing tower (201) is connected to a compressor suction tank (209) via a pipeline; the top of the compressor suction tank (209) is connected to a reaction gas compressor (210); the reaction gas compressor (210) is connected to a cold box (211); the cold box (211) is connected to an ethane tower (212); the bottom of the ethane tower (212) is connected to a propylene tower (216) via a pipeline; the bottom of the propylene tower (216) is connected to a propane tower (220) via a pipeline.

2. A system for producing propylene by dehydrogenating propane according to claim 1, characterized in that: The top, middle and bottom of the water washing tower (201) are all provided with washing circulation pipelines for circulating washing water. The washing circulation pipelines located in the middle and bottom of the water washing tower (201) are connected, and the washing circulation pipeline at the bottom diverts part of the washing water to the washing circulation pipeline in the middle. The washing circulation pipeline in the middle is provided with a catalyst clarification tank (204) and a clarified water tank (205), and the bottom of the catalyst clarification tank (204) is connected to a sedimentation tank (208).

3. The system for producing propylene by dehydrogenating propane according to claim 1, characterized in that: The compressor suction tank (209) and the reaction gas compressor (210) are provided in two sets and are connected in series to perform two-stage compression. The bottom of the compressor suction tank (209) is connected to the water washing tower (201).

4. The system for producing propylene by dehydrogenating propane according to claim 1, characterized in that: The top of the ethane tower (212) is connected to an ethane tower top reflux tank (213), and the pipeline connecting the ethane tower (212) and the ethane tower top reflux tank (213) extends into the cold box (211). The bottom of the ethane tower top reflux tank (213) is connected to two pipelines, one of which is connected to the ethane tower (212), and the other pipeline discharges ethane to the outside.

5. The system for producing propylene by dehydrogenating propane according to claim 1, characterized in that: The top of the propylene tower (216) is connected to a propylene tower top reflux tank (217), and the pipeline connecting the propylene tower (216) and the propylene tower top reflux tank (217) extends into the cold box (211). The bottom of the propylene tower top reflux tank (217) is connected to two pipelines, one of which is connected to the propylene tower (216) and the other one discharges propylene to the outside.

6. The system for producing propylene by dehydrogenating propane according to claim 1, characterized in that: The top of the propane tower (220) is connected to a propane tower top reflux tank (221), and the pipeline connecting the propane tower (220) and the propane tower top reflux tank (221) extends into the cold box (211). The bottom of the propane tower top reflux tank (221) is connected to two pipelines, one of which is connected to the propane tower (220) and the other is connected to the feed end of the reaction regeneration system (1).

7. The system for producing propylene by dehydrogenating propane according to claim 1, characterized in that: The reaction regeneration system (1) comprises a feed heat exchanger (15), a heating furnace (13), and a reactor (28) which are connected in sequence. The bottom of the reactor (28) is connected to a regenerator (27) via a pipeline. The bottom of the regenerator (27) is connected to the reactor (28) via a pipeline. The top of the reactor (28) is connected to a heat source inlet of the feed heat exchanger (15) via a pipeline. The heat source outlet of the feed heat exchanger (15) is connected to a steam generator (16) via a pipeline. The steam generator (16) is connected to a water washing tower (201) via a pipeline.

8. A system for producing propylene by dehydrogenating propane according to claim 7, characterized in that: The reactor (28) is provided with a first and second reaction cyclone separator (3); a third reaction cyclone separator (5) is provided on the pipeline connecting the reactor (28) and the feed heat exchanger (15); the bottom of the third reaction cyclone separator (5) is connected to a fourth reaction cyclone separator (6); the top of the fourth reaction cyclone separator (6) is communicated with the heat source inlet of the feed heat exchanger (15) through a pipeline; the bottom of the fourth reaction cyclone separator (6) is connected to a reaction fine powder collection tank (7); the reaction fine powder collection tank (7) is connected to a waste catalyst tank (21); and a loader (23) is provided below the waste catalyst tank (21).

9. The system for producing propylene by dehydrogenating propane according to claim 7, characterized in that: The regenerator (27) is provided with a regenerated first and second stage cyclone separator (4), the top of the regenerator (27) is connected to a regenerated third stage cyclone separator (8), the top of the regenerated third stage cyclone separator (8) is connected to a waste heat steam generator (17) via a pipeline and a double-acting slide valve (26) is provided in the pipeline, the waste heat steam generator (17) is connected to a flue gas dust collector (18), the flue gas dust collector (18) is connected to a chimney (19), the bottom of the regenerated third stage cyclone separator (8) is connected to a regenerated fourth stage cyclone separator (9), the top of the regenerated fourth stage cyclone separator (9) is connected to the waste heat steam generator (17) via a pipeline, the bottom of the regenerated fourth stage cyclone separator (9) is connected to a regenerated fine powder collection tank (10), and the regenerated fine powder collection tank (10) is connected to a waste catalyst tank (21).

10. A method for preparing propylene by dehydrogenating propane, characterized in that: The following steps are involved: S1, propane is input from the feed heat exchanger (15), and after being heated by the heating furnace (13), the propane enters the reactor (28) and contacts with the catalyst and reacts to generate reaction gas; wherein the catalyst to be regenerated in the reactor (28) is transported to the regenerator (27) for charring and regeneration to obtain a regenerated catalyst, and the regenerated catalyst is then returned to the reactor (28) for continued use, and the flue gas generated during the regeneration process of the regenerator (27) passes through the regeneration first and second stage cyclone separators (4), the regeneration third stage cyclone separators (8) and the regeneration fourth stage cyclone separators (9) in sequence to separate the catalyst fine powder, and the flue gas finally passes through the waste heat steam generator (17) to recover heat and the flue gas dust collector (18) to remove dust, and then is discharged from the chimney (19); S2, the reaction gas passes through the first and second stage cyclone separators (3), the third stage cyclone separator (5) and the fourth stage cyclone separator (6) in sequence to separate the catalyst fine powder, which is then input into the feed heat exchanger (15) as a heat source, and then input into the steam generator (16) for cooling; S3, the reaction gas after cooling enters the water scrubber (201) for washing. The water scrubber (201) is provided with three sections of washing circulation pipelines, wherein the washing circulation pipeline located in the middle of the water scrubber (201) uses a catalyst clarification tank (204) to separate the catalyst and transport it to a sedimentation tank (208) for further separation; S4, the washed reaction gas enters the compressor suction tank (209), is compressed by the reaction gas compressor (210) and transported to the cold box (211) to separate methane hydrogen and condensate; S5. The condensate passes through the ethane tower (212), the propylene tower (216) and the propane tower (220) in sequence to separate ethane, propylene and propane, and the propane is then introduced into the feed end of the feed heat exchanger (15) to react again.

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