Ultralow-hydrogen-hydrocarbon-ratio propane dehydrogenation cryogenic separation device and propane dehydrogenation system

Abstract

The invention discloses an ultralow-hydrogen-hydrocarbon-ratio propane dehydrogenation cryogenic separation device and a propane dehydrogenation system, and relates to the technical field of petrochemical low-temperature gas separation.The device comprises a cold box separation unit, and a feed A enters a first separator through a first heat exchanger; a liquid phase outlet of the first separator is communicated with the flash tank and the first heat exchanger to discharge a product B after reheating; a gas phase outlet of the first separator is sequentially communicated with a second heat exchanger and a second separator, a gas phase outlet of the second separator is sequentially communicated with the second heat exchanger and the first heat exchanger to discharge a product D after reheating, and the gas phase outlet of the second separator is further communicated with the second heat exchanger to discharge circulating gas; the feed B is divided into two paths through the first heat exchanger, one path is communicated with the first heat exchanger, and the other path is sequentially communicated with the second heat exchanger to be mixed with circulating gas and then communicated with the first heat exchanger to discharge the product A. The reaction raw materials are adopted as a cold source to supplement cold energy lacked by the separation device, the overall energy consumption of the system is greatly reduced, and the system can stably adapt to multiple working conditions.

Description

Technical Field

[0001] The present invention relates to the field of petrochemical low-temperature gas separation technology, and more specifically to an ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device and a propane dehydrogenation system. Background Art

[0002] With the iteration and update of the production process of propane dehydrogenation to propylene, the hydrogen-to-hydrocarbon ratio of the reaction combined feed has a tendency to decrease. The ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation process has many advantages, such as small circulation process flow, small reactor flow, low reaction temperature, greatly reduced coking, and low power consumption of the product compressor. However, the existing low-temperature separation system process requires a large amount of cooling capacity, and the mixed refrigerant compression unit usually needs to increase the compressor power to increase the refrigerant circulation efficiency, thereby meeting the requirements of the deep cold separation process, but this method causes high energy consumption of the separation device.

[0003] Therefore, how to provide an ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device that can not only meet the process cooling demand while reducing the overall energy consumption of the system, but also stably adapt to multiple working conditions is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0004] In view of this, the object of the present invention is to provide an ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device, which can not only reduce the overall energy consumption of the system while meeting the process cooling demand, but also can stably adapt to multiple working conditions.

[0005] Another object of the present invention is to provide a propane dehydrogenation system comprising the above-mentioned ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] An ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device comprises a cold box separation unit, which comprises a first heat exchanger, a first separator, a flash tank, a second heat exchanger and a second separator;

[0008] The hot flow channel b of the first heat exchanger is used to input feed A and is connected to the inlet of the first separator;

[0009] The liquid phase outlet of the first separator is connected to the inlet of the flash tank, and the liquid phase outlet of the flash tank is connected to the cold flow channel a of the first heat exchanger to discharge product B;

[0010] The gas phase outlet of the first separator is connected in sequence to the hot flow channel a of the second heat exchanger and the inlet of the second separator;

[0011] The gas phase outlet of the second separator is connected to the cold flow channel b of the second heat exchanger and the cold flow channel e of the first heat exchanger in sequence to discharge the product D. The gas phase outlet of the second separator is also connected to the cold flow channel e of the second heat exchanger to serve as circulating gas.

[0012] The cold flow channel g of the first heat exchanger is used to input feed B and is divided into two paths, one path is connected to the cold flow channel h of the first heat exchanger, and the other path is connected to the cold flow channel d and its cold flow channel e in sequence to mix with the circulating gas, and then connected to the cold flow channel h of the first heat exchanger to discharge product A.

[0013] Preferably, the liquid phase outlet of the second separator is connected to the cold flow channel g of the second heat exchanger and the inlet of the flash tank in sequence.

[0014] Preferably, the gas phase outlet of the flash tank is connected to the cold flow channel f of the first heat exchanger to discharge the product C.

[0015] Preferably, the heat flow channel i of the second heat exchanger is used to connect the top gas outlet and the top reflux port of the distillation tower.

[0016] Preferably, the cold flow channel h of the second heat exchanger is used to connect the tail gas port of the distillation tower and the cold flow channel j of the first heat exchanger to discharge the product F.

[0017] Preferably, it also includes a mixed refrigerant compression unit, which includes a compressor and a cooler. The exhaust end of the compressor, the cooler, the first heat exchanger, the second heat exchanger and the suction end of the compressor are connected in sequence through pipelines to form a refrigeration cycle loop.

[0018] Preferably, the mixed refrigerant compression unit further comprises a first gas-liquid separator, and an inlet of the first gas-liquid separator is connected to the cooler;

[0019] The gas phase outlet of the first gas-liquid separator is connected in sequence to the cold flow channel c of the first heat exchanger, the cold flow channel f of the second heat exchanger, the cold flow channel g of the second heat exchanger, the cold flow channel i of the first heat exchanger and the suction end of the compressor;

[0020] The liquid phase outlet of the first gas-liquid separator is sequentially connected to the cold flow channel d of the first heat exchanger, the cold flow channel i of the first heat exchanger and the suction end of the compressor.

[0021] Preferably, the mixed refrigerant compression unit further comprises a second gas-liquid separator and a third gas-liquid separator;

[0022] The inlet of the second gas-liquid separator is connected to the cold flow channel f of the second heat exchanger, and the liquid phase outlet and the gas phase outlet are both connected to the cold flow channel g of the second heat exchanger;

[0023] The inlet of the third gas-liquid separator is connected to the cold flow channel d of the first heat exchanger, and the liquid phase outlet and the gas phase outlet are both connected to the cold flow channel i of the first heat exchanger.

[0024] Preferably, it further comprises a pump pressurizing unit, which is arranged on the pipeline between the liquid phase outlet of the flash tank and the cold flow channel a of the first heat exchanger.

[0025] A propane dehydrogenation system comprises a propane dehydrogenation reaction device, a distillation tower and the ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device described in any one of the above items, wherein the reactant outlet of the propane dehydrogenation reaction device is connected to the hot flow channel b of the first heat exchanger so that its reaction product is the feed A.

[0026] The reactant inlet of the propane dehydrogenation reaction device is connected to the cold flow channel h of the first heat exchanger so that its reaction raw material is the product A;

[0027] The top gas outlet and the bottom reflux port of the distillation tower are connected through the cold flow channel i of the second heat exchanger;

[0028] The tail gas outlet of the distillation tower is connected to the cold flow channel h of the second heat exchanger and the cold flow channel j of the first heat exchanger in sequence.

[0029] The ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device provided by the present invention comprises a first heat exchanger, a first separator, a flash tank, a second heat exchanger and a second separator. The first heat exchanger and the second heat exchanger both have a plurality of cold flow channels and hot flow channels, the cold flow channels are used to absorb heat and convert their internal medium into a gas phase, and the hot flow channels are used to release heat and convert their internal medium into a liquid phase, so as to realize the heat exchange function of the two heat exchangers; the first separator and the second separator are used to separate the mixed substances into gas-liquid two phases; the flash tank is used to collect the liquid phase product.

[0030] When the device is used in the propane dehydrogenation cryogenic separation process, feed A is the reaction product of the propane dehydrogenation reaction device, generally including hydrogen, methane, ethylene, ethane, propylene, propane and other dehydrogenation reaction products. Feed A is cooled through the hot flow channel b of the first heat exchanger. It should be noted that since the boiling point of carbon group III in feed A is higher than that of carbon group II, carbon group III gases such as propylene and propane are first condensed into liquid phase. After partial condensation of feed A, it enters the first separator through the inlet of the first separator for gas-liquid phase separation. The liquid phase product flowing out of the liquid phase outlet of the first separator flows into the flash tank through the inlet of the flash tank, rapidly boils and vaporizes, and undergoes two-phase separation. The liquid phase product mainly containing propylene / propane is reheated to room temperature through the cold flow channel a of the first heat exchanger and then discharged as product B. In addition, the gas phase product flowing out of the gas phase outlet of the first separator is cooled through the hot flow channel a of the second heat exchanger to condense the remaining carbon group II of the feed A into a liquid phase. The condensed gas-liquid phase mixture enters the second separator through the inlet of the second separator for gas-liquid phase separation. At this time, the separated gas phase product is hydrogen-rich gas, and a part of the hydrogen-rich gas flows into the cold flow channel e of the second heat exchanger through the gas phase outlet of the second separator as a circulating gas, that is, circulating hydrogen, and the remaining part is successively reheated to room temperature through the cold flow channel b of the second heat exchanger and the cold flow channel e of the first heat exchanger to be discharged as product D. Therefore, the recovery of high-purity propane / propylene products and hydrogen-rich gas is achieved.

[0031] In the above-mentioned dehydrogenation and separation process of feed A, liquid propane is injected into the cold flow channel g of the first heat exchanger in batches to absorb heat and partially vaporize. After vaporization, it is divided into two streams. One stream passes through the cold flow channel d of the second heat exchanger and flows into its cold flow channel e to mix with the circulating hydrogen. The other stream flows into the cold flow channel h of the first heat exchanger and mixes with the mixture input into the cold flow channel e of the second heat exchanger and is discharged as product A. Product A is a mixture of propane and hydrogen. This product A can be used as a reaction raw material for a propane dehydrogenation reaction device.

[0032] In summary, the ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device provided by the present invention has the following beneficial effects:

[0033] 1. The first heat exchanger and the second heat exchanger are used for two-stage cooling. The first heat exchanger first condenses and separates the carbon group 3 in the dehydrogenation reaction product to avoid further consumption of cold in the second heat exchanger for the liquid phase product after the first condensation, so that the second heat exchanger only condenses the carbon group 2 in the dehydrogenation reaction product. This not only reduces the consumption of cold, that is, reduces the energy consumption of the device, and thus helps to reduce the overall energy consumption of the system, but also ensures the recovery of high-purity propane / propylene products and hydrogen-rich gas.

[0034] 2. Injecting propane in batches not only supplements the external cold source to the first heat exchanger and the second heat exchanger to provide sufficient cold capacity for the combined feed evaporation under various working conditions, but also reduces the energy consumption of the device, thereby helping to reduce the overall energy consumption of the system. In addition, the product A discharged from the separation device can be used as a reaction raw material for the propane dehydrogenation reaction device. In the propane dehydrogenation system, there is no need to use additional devices to mix liquid propane and hydrogen, which can greatly reduce the overall energy consumption of the system and meet the large-scale adjustment of the hydrogen-to-hydrocarbon ratio working conditions.

[0035] In summary, the present invention uses the reaction raw materials as a cold source to supplement the separation device to achieve the coldness lacking in the deep cold separation process, greatly reducing the overall energy consumption of the system and being able to stably adapt to multiple working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0037] Figure 1 This is a schematic diagram of an ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device provided by the present invention.

[0038] Reference numerals:

[0039] I-cold box separation unit; 1-first heat exchanger; 2-first separator; 3-flash tank; 4-second heat exchanger; 5-second separator; V1-first throttle valve; V2-second throttle valve; V3-third throttle valve; V4-fourth throttle valve; V5-fifth throttle valve; V6-sixth throttle valve;

[0040] II-mixed refrigerant compression unit; 6-compressor; 7-cooler; 8-first gas-liquid separator; 9-second gas-liquid separator; 10-third gas-liquid separator; V7-seventh throttle valve; V8-eighth throttle valve; V9-ninth throttle valve;

[0041] III-Pump pressurization unit;

[0042] P1-first pipeline; P2-second pipeline; P3-third pipeline; P4-fourth pipeline; P5-fifth pipeline; P6-sixth pipeline; P7-seventh pipeline; P8-eighth pipeline; P9-ninth pipeline; P10-tenth pipeline; P11-eleventh pipeline; P12-twelfth pipeline; P13-thirteenth pipeline; P14-fourteenth pipeline; P15-fifteenth pipeline; P16-sixteenth pipeline; P17-seventeenth pipeline; P18-eighteenth pipeline; P19-nineteenth pipeline; P20-twentieth pipeline; P21-twenty-first pipeline; P22-twenty-second pipeline; P23-twenty-third pipeline; P24-twenty-fourth pipeline; P25-twenty-fifth pipeline; P2 6-the twenty-sixth pipeline; P27-the twenty-seventh pipeline; P28-the twenty-eighth pipeline; P29-the twenty-ninth pipeline; P30-the thirtieth pipeline; P31-the thirty-first pipeline; P32-the thirty-second pipeline; P33-the thirty-third pipeline; P34-the thirty-fourth pipeline; P35-the thirty-fifth pipeline; P36-the thirty-sixth pipeline; P37-the thirty-seventh pipeline; P38-the thirty-eighth pipeline; P39-the thirty-ninth pipeline; P40-the fortieth pipeline; P41-the forty-first pipeline; P42-the forty-second pipeline; P43-the forty-third pipeline; P44-the forty-fourth pipeline; P45-the forty-fifth pipeline; P46-the forty-sixth pipeline; P47-the forty-seventh pipeline. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The core of the present invention is to provide an ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device, which can not only reduce the overall energy consumption of the system while meeting the process cooling demand, but also can stably adapt to multiple working conditions.

[0045] Another core of the present invention is to provide a propane dehydrogenation system including the above-mentioned ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device.

[0046] Please refer to Figure 1 The present invention provides an ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device, including a cold box separation unit I, which includes a first heat exchanger 1, a first separator 2, a flash tank 3, a second heat exchanger 4 and a second separator 5.

[0047] It should be noted that the first heat exchanger 1 and the second heat exchanger 4 are both devices for achieving heat transfer and transfer, and both include multiple hot flow channels and cold flow channels, wherein the hot flow channel is used to release heat (i.e., provide heat to the surroundings) and convert its internal medium into liquid phase, and the cold flow channel is used to absorb heat (i.e., provide cold to the surroundings) and convert its internal medium into gas phase. The first separator 2 and the second separator 5 are both used to separate the mixed substances into gas and liquid phases. The flash tank 3 is used to collect liquid phase products.

[0048] The hot flow channel b of the first heat exchanger 1 is used to input the feed A and is connected to the inlet of the first separator 2 .

[0049] Specifically, the inlet of the hot flow channel b of the first heat exchanger 1 is connected to the feed A through the first pipeline P1, and the outlet of the hot flow channel b of the first heat exchanger 1 is connected to the inlet of the first separator 2 through the second pipeline P2.

[0050] The liquid phase outlet of the first separator 2 is connected to the inlet of the flash tank 3, and the liquid phase outlet of the flash tank 3 is connected to the cold flow channel a of the first heat exchanger 1 to discharge product B.

[0051] Specifically, the liquid phase outlet of the first separator 2 is connected to the inlet of the flash tank 3 through the twentieth pipeline P20, the liquid phase outlet of the flash tank 3 is connected to the inlet of the cold flow channel a of the first heat exchanger 1 through the liquid outlet pipeline, and the outlet of the cold flow channel a of the first heat exchanger 1 is connected to the twenty-fifth pipeline P25 for discharging product B.

[0052] Further preferably, a first throttle valve V1 is provided on the twentieth pipeline P20 to achieve the purpose of pressure regulation by controlling the medium flow in the pipeline.

[0053] Further preferably, a pump pressurizing unit III is provided on the pipeline between the liquid phase outlet of the flash tank 3 and the cold flow channel a of the first heat exchanger 1. Specifically, the liquid phase outlet of the flash tank 3 is connected to the inlet of the pump pressurizing unit III through the twenty-third pipeline P23, and the outlet of the pump pressurizing unit III is connected to the inlet of the cold flow channel a of the first heat exchanger 1 through the twenty-fourth pipeline P24, thereby, the pump pressurizing unit III plays the role of pumping out the product B, and can also adjust the pressure and flow rate of the product B discharged.

[0054] The gas phase outlet of the first separator 2 is connected to the hot flow channel a of the second heat exchanger 4 and the inlet of the second separator 5 in sequence; the gas phase outlet of the second separator 5 is connected to the cold flow channel b of the second heat exchanger 4 and the cold flow channel e of the first heat exchanger 1 in sequence to discharge product D, and the gas phase outlet of the second separator 5 is also connected to the cold flow channel e of the second heat exchanger 4 as a circulating gas.

[0055] Specifically, the gas phase outlet of the first separator 2 is connected to the inlet of the hot flow channel a of the second heat exchanger 4 through the third pipeline P3, the outlet of the hot flow channel a of the second heat exchanger 4 is connected to the inlet of the second separator 5 through the fourth pipeline P4, and the gas phase outlet of the second separator 5 is connected to the fifth pipeline P5 and branches out the sixth pipeline P6 and the ninth pipeline P9. Among them, the sixth pipeline P6 is connected to the inlet of the cold flow channel b of the second heat exchanger 4, the outlet of the cold flow channel b of the second heat exchanger 4 is connected to the inlet of the cold flow channel e of the first heat exchanger 1 through the seventh pipeline P7, and the outlet of the first heat exchanger 1 is connected to the eighth pipeline P8 for discharging the product D; the ninth pipeline P9 is connected to the cold flow channel e of the second heat exchanger 4 through the tenth pipeline P10. Preferably, the sixth throttle valve V6 is provided on the tenth pipeline P10, and / or the ninth throttle valve V9 is provided on the eighth pipeline P8 for adjusting the medium flow and pressure in the pipeline.

[0056] The cold flow channel g of the first heat exchanger 1 is used to input feed B and is divided into two paths, one path is connected to the cold flow channel h of the first heat exchanger 1, and the other path is connected to the cold flow channel d and its cold flow channel e of the second heat exchanger 4 in sequence to mix with the circulating gas, and then connected to the cold flow channel h of the first heat exchanger 1 to discharge product A.

[0057] Specifically, the inlet of the cold flow channel g of the first heat exchanger 1 is connected to the feed B through the thirteenth pipeline P13, and the outlet of the cold flow channel g of the first heat exchanger 1 is connected to the fourteenth pipeline P14, and the fourteenth pipeline P14 branches out the fifteenth pipeline P15 and the seventeenth pipeline P17. Among them, the fifteenth pipeline P15 is connected to the inlet of the cold flow channel h of the first heat exchanger 1 through the sixteenth pipeline P16; the seventeenth pipeline P17 is connected to the inlet of the cold flow channel d of the second heat exchanger 4, and the outlet of the cold flow channel d of the second heat exchanger 4 is connected to the inlet of the cold flow channel e of the second heat exchanger 4 through the eighteenth pipeline P18 and the nineteenth pipeline P19, and the outlet of the cold flow channel e of the second heat exchanger 4 is connected to the inlet of the cold flow channel h of the first heat exchanger 1 through the eleventh pipeline P11, and the outlet of the cold flow channel h of the first heat exchanger 1 is connected to the twelfth pipeline P12 for discharging product A.

[0058] Preferably, a third throttle valve V3 is provided on the sixteenth pipeline P16, and / or a fourth throttle valve V4 is provided on the nineteenth pipeline P19, for adjusting the flow rate and pressure of the medium in the pipeline.

[0059] It should be particularly pointed out that the device also includes a mixed refrigerant compression unit II, and most of the cooling capacity of the first heat exchanger 1 and the second heat exchanger 4 comes from the mixed refrigerant compression unit II. The refrigerant outlet of the mixed refrigerant compression unit II is sequentially connected to the first heat exchanger 1, the second heat exchanger 4 and the refrigerant inlet of the mixed refrigerant compression unit II to form a refrigeration cycle. Therefore, the mixed refrigerant compression unit II continuously supplies refrigerant to the first heat exchanger 1 and the second heat exchanger 4 as the cooling capacity required for the separation of the device, and this refrigerant circulation supply requires the mixed refrigerant compression unit II to consume electrical energy.

[0060] When the above device is used in the propane dehydrogenation cryogenic separation process, the feed A is the reaction product of the propane dehydrogenation reaction device, generally including hydrogen, methane, ethylene, ethane, propylene, propane and other dehydrogenation reaction products, and the feed A is cooled through the hot flow channel b of the first heat exchanger 1. It should be noted that since the boiling point of the carbon group III (i.e., a mixture of propylene, propane, etc.) in the feed A is higher than that of the carbon group II (i.e., a mixture of methane, ethylene, ethane, etc.), the carbon group III gases such as propylene and propane are first condensed into a liquid phase, and the feed A is partially condensed and enters the first separator 2 through the inlet of the first separator 2 for gas-liquid phase separation. The liquid phase product flowing out of the liquid phase outlet of the first separator 2 flows into the flash tank 3 through the inlet of the flash tank 3, rapidly boils and vaporizes, and undergoes two-phase separation, and the liquid phase product mainly containing propylene / propane is reheated to room temperature through the cold flow channel a of the first heat exchanger 1 and discharged as product B. In addition, the gas phase product flowing out of the gas phase outlet of the first separator 2 is cooled through the hot flow channel a of the second heat exchanger 4 to condense the remaining carbon group A of the feed A into a liquid phase. The condensed gas-liquid phase mixture enters the second separator 5 through the inlet of the second separator 5 for gas-liquid phase separation. At this time, the separated gas phase product is hydrogen-rich gas, and a part of the hydrogen-rich gas flows into the cold flow channel e of the second heat exchanger 4 through the gas phase outlet of the second separator 5 as a circulating gas, that is, circulating hydrogen, and the remaining part passes through the cold flow channel b of the second heat exchanger 4 and the cold flow channel e of the first heat exchanger 1 in turn, and is reheated to room temperature and then discharged as product D. Therefore, the recovery of high-purity propane / propylene products and hydrogen-rich gas is achieved.

[0061] In the above-mentioned dehydrogenation and separation process of feed A, liquid propane is injected into the cold flow channel g of the first heat exchanger 1 in batches to absorb heat and partially vaporize, and then is divided into two streams after vaporization, one stream flows into the cold flow channel e of the second heat exchanger 4 through the cold flow channel d to mix with the circulating hydrogen, and the other stream flows into the cold flow channel h of the first heat exchanger 1 and mixes with the mixture input from the cold flow channel e of the second heat exchanger 4 and is discharged as product A, which is a mixture of propane and hydrogen. Therefore, by injecting propane in batches, an external cold source can be added to the first heat exchanger 1 and the second heat exchanger 4 to reduce the overall energy consumption, and this product A can be used as a reaction raw material for the propane dehydrogenation reaction device, which can meet the large-scale hydrogen-to-hydrocarbon ratio operating condition adjustment.

[0062] Based on the above examples, please refer to Figure 1 The liquid phase outlet of the second separator 5 is connected to the cold flow channel g of the second heat exchanger 4 and the inlet of the flash tank 3 in sequence.

[0063] Specifically, the liquid phase outlet of the second separator 5 is connected to the inlet of the cold flow channel g of the second heat exchanger 4 through the twenty-first pipeline P21, and the outlet of the cold flow channel g is connected to the inlet of the flash tank 3 through the twenty-second pipeline P22.

[0064] It can be understood that the carbon group II in the feed A is condensed into liquid phase substances after the second heat exchanger 4, and then flows into the second separator 5 for gas-liquid phase separation to separate the carbon group II from hydrogen in the feed A. The liquid phase mixture composed of methane, ethylene and ethane can be reheated after the second heat exchanger 4 and flow into the flash tank 3, and mixed with the liquid phase mixture composed of propylene and propane to form a combined product, and then reheated after the first heat exchanger 1 and discharged as product B. Therefore, the recovery of methane, ethylene and ethane is achieved.

[0065] Based on the above examples, please refer to Figure 1 The gas phase outlet of the flash tank 3 is connected to the cold flow channel f of the first heat exchanger 1 to discharge product C.

[0066] Specifically, the gas phase outlet of the flash tank 3 is connected to the inlet of the cold flow channel f of the first heat exchanger 1 through the twenty-sixth pipeline P26, and the outlet of the cold flow channel f of the first heat exchanger 1 is connected to the twenty-seventh pipeline P27. Preferably, a fifth throttle valve V5 is provided on the twenty-seventh pipeline P27 to adjust the medium flow and pressure in the pipeline.

[0067] It should be noted that the flash tank 3 can utilize the difference in saturated vapor pressure of the substances to rapidly evaporate the liquid substances by reducing the pressure, thereby realizing the conversion of the liquid into the gaseous substances, that is, realizing the rapid boiling and vaporization of the substances, and performing two-phase separation. In the feed A, the boiling points of methane, ethylene, ethane, propylene and propane increase in sequence. Since the lower the boiling point of the substance, the easier it is to gasify, the flash tank 3 can be used to separate the substances with lower boiling points, such as hydrogen, and used as the discharge device of the product C, which can not only reduce greenhouse gas emissions, but also be converted into energy to create economic value.

[0068] Based on the above examples, please refer to Figure 1 The heat flow channel i of the second heat exchanger 4 is used to connect the top gas outlet and the top reflux port of the distillation tower.

[0069] It should be particularly pointed out that there is a distillation tower in the propane dehydrogenation system. The cold flow channel a of the first heat exchanger 1 in the present device is connected to the distillation tower through the twenty-fifth pipeline P25, and the distillation tower is used for distilling product B.

[0070] Specifically, the inlet of the heat flow channel i of the second heat exchanger 4 is connected to the top gas outlet of the distillation tower through the 43rd pipeline P43, and the material discharged from the top gas outlet is the feed C. The outlet of the heat flow channel i of the second heat exchanger 4 is connected to the top reflux port of the distillation tower through the 44th pipeline P44, and the material flowing into the top reflux port is the product E. Therefore, the separation device is coupled with the distillation tower, and the second heat exchanger 4 replaces the top condenser of the existing distillation tower, and provides the cooling capacity required by the condensing medium to the top of the tower, thereby further reducing the overall energy consumption of the system.

[0071] Based on the above examples, please refer to Figure 1 The cold flow channel h of the second heat exchanger 4 is used to connect the tail gas port of the distillation tower and the cold flow channel j of the first heat exchanger 1 to discharge the product F.

[0072] Specifically, the inlet of the cold flow channel h of the second heat exchanger 4 is connected to the tail gas outlet of the distillation tower through the 45th pipeline P45, the outlet of the cold flow channel h of the second heat exchanger 4 is connected to the inlet of the cold flow channel j of the first heat exchanger 1 through the 46th pipeline P46, and the outlet of the cold flow channel j of the first heat exchanger 1 is connected to the 47th pipeline P47. Thus, the tail gas of the distillation tower, i.e., the feed D, sequentially passes through the second heat exchanger 4 and the first heat exchanger 1 for cold recovery, which can also further reduce the overall energy consumption of the system.

[0073] Based on the above examples, please refer to Figure 1 The mixed refrigerant compression unit II includes a compressor 6 and a cooler 7. The exhaust end of the compressor 6, the cooler 7, the first heat exchanger 1, the second heat exchanger 4 and the suction end of the compressor 6 are connected in sequence through pipelines to form a refrigeration cycle.

[0074] It should be noted that the pipe can be filled with refrigerant, and the refrigerant composition has the following types: 1. Preferably, a five-component refrigerant is used, i.e., a mixture of hydrogen, methane, ethylene, propane and isopentane in a certain proportion; 2. A four-component refrigerant is also used, i.e., a mixture of nitrogen, methane, ethylene and propane in a certain proportion; 3. A three-component refrigerant is also used, i.e., a mixture of methane, ethylene and propane in a certain proportion. In addition, the refrigerant cannot be only one of the above refrigerants.

[0075] Among them, the compressor 6 plays the role of driving the refrigerant. The specific process is to discharge the gaseous refrigerant, the gaseous refrigerant is condensed into liquid refrigerant through the cooler 7, the liquid refrigerant flows through the first heat exchanger 1 and the second heat exchanger 4 in sequence as a cold source, and absorbs heat and vaporizes into gaseous refrigerant, and the gaseous refrigerant then flows back to the compressor 6, thereby realizing the circulation of the refrigerant.

[0076] Based on the above examples, please refer to Figure 1The mixed refrigerant compression unit II also includes a first gas-liquid separator 8, the inlet of the first gas-liquid separator 8 is connected to the cooler 7; the gas phase outlet of the first gas-liquid separator 8 is connected to the cold flow channel c of the first heat exchanger 1, the cold flow channel f of the second heat exchanger 4, the cold flow channel g of the second heat exchanger 4, the cold flow channel i of the first heat exchanger 1 and the suction end of the compressor 6 in sequence; the liquid phase outlet of the first gas-liquid separator 8 is connected to the cold flow channel d of the first heat exchanger 1, the cold flow channel i of the first heat exchanger 1 and the suction end of the compressor 6 in sequence.

[0077] Specifically, the exhaust end of the compressor 6 is connected to the air inlet of the cooler 7 through the twenty-eighth pipeline P28, and the liquid outlet of the cooler 7 is connected to the inlet of the first gas-liquid separator 8 through the twenty-ninth pipeline P29. The gas phase outlet of the first gas-liquid separator 8 is connected to the inlet of the cold flow channel c of the first heat exchanger 1 through the thirty-third pipeline P33, the outlet of the cold flow channel c of the first heat exchanger 1 is connected to the inlet of the cold flow channel f of the second heat exchanger 4 through the thirty-fourth pipeline P34, the outlet of the cold flow channel f of the second heat exchanger 4 is connected to the inlet of the cold flow channel g of the second heat exchanger 4 through the first main pipeline, the outlet of the cold flow channel g of the second heat exchanger 4 is connected to the inlet of the cold flow channel i of the first heat exchanger 1 through the thirty-ninth pipeline P39 and the fortieth pipeline P40, and the outlet of the cold flow channel i of the first heat exchanger 1 is connected to the suction end of the compressor 6 through the forty-second pipeline P42. The liquid phase outlet of the first gas-liquid separator 8 is connected to the inlet of the cold flow channel d of the first heat exchanger 1 through the 30th pipeline P30, and the outlet of the cold flow channel d of the first heat exchanger 1 is connected to the inlet of the cold flow channel i of the first heat exchanger 1 through the second main pipeline.

[0078] It is understandable that after being cooled by the cooler 7, the refrigerant cannot be completely condensed into a liquid phase, and there is a partial gas phase. The refrigerant cooled by the cooler 7 can be separated into gas and liquid phases by the first gas-liquid separator 8. Among them, the liquid phase refrigerant passes through the cold flow channel d and the cold flow channel i of the first heat exchanger 1 in sequence to provide sufficient cooling capacity for the first heat exchanger 1, and after absorbing heat, it is vaporized into a gas phase refrigerant and flows back to the suction end of the compressor 6. The gas phase refrigerant passes through the cold flow channel c of the first heat exchanger 1, the cold flow channel f of the second heat exchanger 4, the cold flow channel g of the second heat exchanger 4 and the cold flow channel i of the first heat exchanger 1 in sequence to provide sufficient cooling capacity for the two heat exchangers, and after absorbing heat, it is vaporized into a gas phase refrigerant and flows back to the suction end of the compressor 6.

[0079] It should be noted that the cooling capacity provided by the refrigerant mainly depends on its latent heat of evaporation, that is, the cooling capacity delivered from the liquid phase to the gas phase. The gas phase refrigerant is characterized by a small molecular weight and a low boiling point, and is suitable for providing cooling capacity in the deep cooling section. The liquid phase refrigerant is characterized by a large molecular weight and a high boiling point, and is suitable for providing cooling capacity in the shallow cooling section. Therefore, the gas phase refrigerant and the liquid phase refrigerant separated by the first gas-liquid separator 8 correspond to two-stage throttling. The more throttling stages of the mixed refrigerant, the less energy consumption, which is conducive to reducing the overall energy consumption of the system.

[0080] It can be understood that the gas phase refrigerant is still in the gas phase after absorbing heat through the cold flow channel c of the first heat exchanger 1 and the cold flow channel f of the second heat exchanger 4, and is in the gas phase after passing through the eighth throttle valve V8, and is in the gas phase after passing through the cold flow channel g of the second heat exchanger 4 and entering the thirty-ninth pipeline P39. It should be pointed out that when the gas phase and the liquid phase flow in the pipeline, they will impact the pipeline and affect the life of the pipeline, and the interaction between the gas phase and the liquid phase will reduce the transmission efficiency.

[0081] In order to evenly deliver the mixed refrigerant to the second heat exchanger 4 and the first heat exchanger 1, a second gas-liquid separator 9 and a third gas-liquid separator 10 are additionally provided, and their specific configurations are as follows.

[0082] Please refer to Figure 1 The inlet of the second gas-liquid separator 9 is connected to the cold flow channel f of the second heat exchanger 4, and the liquid phase outlet and the gas phase outlet are both connected to the cold flow channel g of the second heat exchanger 4; the inlet of the third gas-liquid separator 10 is connected to the cold flow channel d of the first heat exchanger 1, and the liquid phase outlet and the gas phase outlet are both connected to the cold flow channel i of the first heat exchanger 1.

[0083] Specifically, the outlet of the cold flow channel f of the second heat exchanger 4 is connected to the inlet of the second gas-liquid separator 9 through the thirty-fifth pipeline P35 and the thirty-sixth pipeline P36, the gas phase outlet of the second gas-liquid separator 9 is connected to the inlet of the cold flow channel g of the second heat exchanger 4 through the thirty-seventh pipeline P37, and the liquid phase outlet of the second gas-liquid separator 9 is connected to the inlet of the cold flow channel g of the second heat exchanger 4 through the thirty-eighth pipeline P38. In addition, the cold flow channel d of the first heat exchanger 1 is connected to the inlet of the third gas-liquid separator through the thirty-first pipeline P31 and the thirty-second pipeline P32, the liquid phase outlet of the third gas-liquid separator 10 is connected to the inlet of the cold flow channel i of the first heat exchanger 1 through the forty-first pipeline P41, and the gas phase outlet of the third gas-liquid separator 10 is connected to the inlet of the cold flow channel i of the first heat exchanger 1 through the forty-first pipeline P41.

[0084] Thus, after the liquid refrigerant absorbs heat and partially vaporizes through the cold flow channel d of the first heat exchanger 1, the third gas-liquid separator 10 is used to separate the gas and liquid phases, so that the two are respectively transported from different pipelines to the cold flow channel i of the first heat exchanger 1. In addition, after the gas-phase refrigerant absorbs heat and evaporates through the cold flow channel c of the first heat exchanger 1 and the cold flow channel f of the second heat exchanger 4 in turn, the second gas-liquid separator 9 is used to separate the gas and liquid phases, so that the two are respectively transported from different pipelines to the cold flow channel g of the second heat exchanger 4, which is conducive to the uniform transportation of the gas-liquid refrigerant.

[0085] Preferably, an eighth throttle valve V8 is provided on either the thirty-fifth pipeline P35 or the thirty-sixth pipeline P36, and / or a seventh throttle valve V7 is provided on either the thirty-first pipeline P31 or the thirty-second pipeline P32, for adjusting the flow and pressure of the medium in the pipeline.

[0086] Based on any of the above embodiments, please refer to Figure 1 The pump pressurizing unit III is arranged on the pipeline between the liquid phase outlet of the flash tank 3 and the cold flow channel a of the first heat exchanger 1 .

[0087] Specifically, the pump pressurizing unit III includes at least one pump, the inlet of the pump is connected to the twenty-third pipeline P23, and the outlet is connected to the twenty-fourth pipeline P24, so as to pump the liquid phase product in the flash tank 3 out through the first heat exchanger 1. Preferably, the pump adopts a motor-driven vertical centrifugal barrel pump, which has the advantages of small size, light weight, simple installation, low operating noise, and multiple speed regulation modes.

[0088] In the present invention, the first heat exchanger 1 and the second heat exchanger 4 are both high-efficiency plate-fin heat exchangers suitable for gas-liquid two-phase high-density difference working conditions, and have excellent heat transfer efficiency and effect.

[0089] In the present invention, the first separator 2, the second separator 5, the flash tank 3, the first gas-liquid separator 8, the second gas-liquid separator 9 and the third gas-liquid separator 10 all adopt gravity separators with high-efficiency wire mesh demisters, which not only realize gas-liquid separation but also effectively remove impurities.

[0090] The present invention also provides a propane dehydrogenation system, comprising a propane dehydrogenation reaction device, a distillation tower and the ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device disclosed in the above embodiment.

[0091] Among them, the reactant outlet of the propane dehydrogenation reaction device is connected to the hot flow channel b of the first heat exchanger 1, so that its reaction product is feed A, and feed A is a combination of multiple types of hydrogen, methane, ethylene, ethane, propylene, and propane; the reactant inlet of the propane dehydrogenation reaction device is connected to the cold flow channel h of the first heat exchanger 1, so that its reaction raw material is product A, and product A is a combination of hydrogen and propylene; the top gas outlet and the bottom reflux port of the distillation tower are connected through the cold flow channel i of the second heat exchanger 4; the tail gas outlet of the distillation tower is connected to the cold flow channel h of the second heat exchanger 4 and the cold flow channel j of the first heat exchanger 1 in sequence. Please refer to the prior art for the structure of other parts of the propane dehydrogenation system, which will not be repeated in this article.

[0092] In summary, the ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device and propane dehydrogenation system provided by the present invention mainly have the following advantages:

[0093] 1. The first heat exchanger 1 and the second heat exchanger 4 are used for two-stage cooling. The first heat exchanger 1 first condenses and separates the carbon group 3 in the dehydrogenation reaction product to avoid further consumption of cold by the liquid phase product after the first-stage condensation in the second heat exchanger 4, so that the second heat exchanger 4 only condenses the carbon group 2 in the dehydrogenation reaction product. This not only reduces the consumption of cold, that is, reduces the energy consumption of the device, and thus helps to reduce the overall energy consumption of the system, but also ensures the recovery of high-purity propane / propylene products and hydrogen-rich gas, specifically, the purity of hydrogen reaches more than 92.5%, the content of propane + propylene is less than 6000ppm, and the recovery rate of propane + propylene of the device reaches 99.7%.

[0094] 2. By injecting propane in batches, an external cold source can be added to the first heat exchanger 1 and the second heat exchanger 4 to provide sufficient cooling capacity for the combined feed evaporation under various working conditions while reducing the energy consumption of the device, thereby helping to reduce the overall energy consumption of the system.

[0095] 3. Propane can be injected in batches, and the discharged product A can be used as the reaction raw material of the propane dehydrogenation reaction unit. In the propane dehydrogenation system, there is no need to use additional equipment to mix liquid propane and hydrogen, which can greatly reduce the overall energy consumption of the system and meet the large-scale adjustment of the hydrogen-to-hydrocarbon ratio working conditions.

[0096] 4. The separation device is coupled to the distillation tower, and the second heat exchanger 4 replaces the top condenser of the existing distillation tower and provides the cooling capacity required by the condensing medium to the top of the tower, thereby reducing the overall energy consumption of the system.

[0097] 5. Recycle and utilize the cooling capacity of the tail gas from the distillation tower, thereby further reducing the overall energy consumption of the system.

[0098] It should be noted that, in this specification, relational terms such as first and second are merely used to distinguish one entity from other entities, but do not necessarily require or imply any actual relationship or order between these entities.

[0099] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0100] The above is a detailed introduction to an ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device and a propane dehydrogenation system provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A propane dehydrogenation cryogenic separation device with an ultra-low hydrogen-to-hydrocarbon ratio, characterized in that: It comprises a cold box separation unit (I), which comprises a first heat exchanger (1), a first separator (2), a flash tank (3), a second heat exchanger (4) and a second separator (5); The hot flow channel b of the first heat exchanger (1) is used to input feed A and is connected to the inlet of the first separator (2); The liquid phase outlet of the first separator (2) is connected to the inlet of the flash tank (3), and the liquid phase outlet of the flash tank (3) is connected to the cold flow channel a of the first heat exchanger (1) to discharge product B; The gas phase outlet of the first separator (2) is connected in sequence to the hot flow channel a of the second heat exchanger (4) and the inlet of the second separator (5); The gas phase outlet of the second separator (5) is connected in sequence to the cold flow channel b of the second heat exchanger (4) and the cold flow channel e of the first heat exchanger (1) to discharge the product D. The gas phase outlet of the second separator (5) is also connected to the cold flow channel e of the second heat exchanger (4) to serve as circulating gas. The cold flow channel g of the first heat exchanger (1) is used to input feed B and is divided into two paths, one path is connected to the cold flow channel h of the first heat exchanger (1), and the other path is connected to the cold flow channel d and the cold flow channel e of the second heat exchanger (4) in sequence to mix with the circulating gas, and then connected to the cold flow channel h of the first heat exchanger (1) to discharge product A.

2. The ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device according to claim 1, characterized in that: The liquid phase outlet of the second separator (5) is connected in sequence to the cold flow channel g of the second heat exchanger (4) and the inlet of the flash tank (3).

3. The ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device according to claim 2, characterized in that: The gas phase outlet of the flash tank (3) is connected to the cold flow channel f of the first heat exchanger (1) to discharge the product C.

4. The ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device according to claim 1, characterized in that: The heat flow channel i of the second heat exchanger (4) is used to connect the top gas outlet and the top reflux port of the distillation tower.

5. The ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device according to claim 4, characterized in that: The cold flow channel h of the second heat exchanger (4) is used to connect the tail gas outlet of the distillation tower and the cold flow channel j of the first heat exchanger (1) to discharge the product F.

6. The ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device according to claim 1, characterized in that: The invention also comprises a mixed refrigerant compression unit (II), wherein the mixed refrigerant compression unit (II) comprises a compressor (6) and a cooler (7), wherein the exhaust end of the compressor (6), the cooler (7), the first heat exchanger (1), the second heat exchanger (4) and the suction end of the compressor (6) are connected in sequence through pipelines to form a refrigeration cycle.

7. The ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device according to claim 6, characterized in that: The mixed refrigerant compression unit (II) further comprises a first gas-liquid separator (8), an inlet of the first gas-liquid separator (8) being connected to the cooler (7); The gas phase outlet of the first gas-liquid separator (8) is sequentially connected to the cold flow channel c of the first heat exchanger (1), the cold flow channel f of the second heat exchanger (4), the cold flow channel g of the second heat exchanger (4), the cold flow channel i of the first heat exchanger (1) and the suction end of the compressor (6); The liquid phase outlet of the first gas-liquid separator (8) is connected in sequence to the cold flow channel d of the first heat exchanger (1), the cold flow channel i of the first heat exchanger (1) and the suction end of the compressor (6).

8. The ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device according to claim 7, characterized in that: The mixed refrigerant compression unit (II) further comprises a second gas-liquid separator (9) and a third gas-liquid separator (10); The inlet of the second gas-liquid separator (9) is connected to the cold flow channel f of the second heat exchanger (4), and the liquid phase outlet and the gas phase outlet are both connected to the cold flow channel g of the second heat exchanger (4); The inlet of the third gas-liquid separator (10) is connected to the cold flow channel d of the first heat exchanger (1), and the liquid phase outlet and the gas phase outlet are both connected to the cold flow channel i of the first heat exchanger (1).

9. The ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device according to any one of claims 1 to 8, characterized in that: It also comprises a pump pressurizing unit (III), which is arranged on the pipeline between the liquid phase outlet of the flash tank (3) and the cold flow channel a of the first heat exchanger (1).

10. A propane dehydrogenation system, characterized in that: It comprises a propane dehydrogenation reaction device, a distillation tower and the ultra-low hydrogen-to-hydrocarbon ratio propane dehydrogenation cryogenic separation device as described in any one of claims 1 to 9, wherein the reactant outlet of the propane dehydrogenation reaction device is connected to the heat flow channel b of the first heat exchanger (1) so that its reaction product is the feed A. The reactant inlet of the propane dehydrogenation reaction device is connected to the cold flow channel h of the first heat exchanger (1), so that its reaction raw material is the product A; The top gas outlet and the bottom reflux outlet of the distillation tower are connected via the cold flow channel i of the second heat exchanger (4); The tail gas outlet of the distillation tower is connected in sequence to the cold flow channel h of the second heat exchanger (4) and the cold flow channel j of the first heat exchanger (1).

Images