CN117209348A - Method and system for dehydrogenating low-carbon alkane - Google Patents
Method and system for dehydrogenating low-carbon alkane Download PDFInfo
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- CN117209348A CN117209348A CN202311151366.4A CN202311151366A CN117209348A CN 117209348 A CN117209348 A CN 117209348A CN 202311151366 A CN202311151366 A CN 202311151366A CN 117209348 A CN117209348 A CN 117209348A
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- 238000000034 method Methods 0.000 title claims abstract description 75
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 59
- 239000003054 catalyst Substances 0.000 claims abstract description 76
- 238000006356 dehydrogenation reaction Methods 0.000 claims abstract description 76
- 230000008569 process Effects 0.000 claims abstract description 63
- 239000007789 gas Substances 0.000 claims abstract description 54
- 238000000926 separation method Methods 0.000 claims abstract description 54
- 238000006243 chemical reaction Methods 0.000 claims abstract description 41
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 34
- 230000008878 coupling Effects 0.000 claims abstract description 21
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- 239000001257 hydrogen Substances 0.000 claims abstract description 14
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 14
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- 239000012495 reaction gas Substances 0.000 claims abstract description 12
- 238000010438 heat treatment Methods 0.000 claims description 30
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- 230000009286 beneficial effect Effects 0.000 description 2
- BTANRVKWQNVYAZ-UHFFFAOYSA-N butan-2-ol Chemical compound CCC(C)O BTANRVKWQNVYAZ-UHFFFAOYSA-N 0.000 description 2
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- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
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- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/584—Recycling of catalysts
Landscapes
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
Abstract
The application provides a method and a system for dehydrogenating low-carbon alkane, belongs to the technical field of low-carbon alkane dehydrogenation, and solves the problems that the temperature distribution and the temperature drop of a catalyst bed layer cannot be uniform in the prior art, and the service life of the catalyst and the yield of low-carbon alkene are affected. The method comprises the steps of inputting heated process gas and low-carbon alkane into a reactor, enabling the process gas and the low-carbon alkane to contact and react with a dehydrogenation catalyst, a thermal coupling auxiliary agent, inert alumina balls and inert alumina porcelain balls in the reactor, separating low-carbon olefin, hydrogen-rich gas, fuel gas and C4 and C4+ from reaction gas generated by the reaction through a separation system, and returning unconverted low-carbon alkane to the reactor for continuous reaction. The dehydrogenation catalyst, the thermal coupling auxiliary agent, the inert alumina balls and the inert alumina porcelain balls are filled in the reactor according to a certain volume ratio, so that the temperature distribution of the catalyst bed layer of the fixed bed reactor is improved, the reaction and regeneration severity is reduced, and the product yield is improved.
Description
Technical Field
The application belongs to the technical field of low-carbon alkane dehydrogenation, and particularly relates to a method and a system for low-carbon alkane dehydrogenation.
Background
Low-carbon olefin is a basic organic raw material with large demand and wide application range in petrochemical industry, for example, propylene is an important basic chemical raw material, and is widely used for producing chemical products such as polypropylene, isopropanol, isopropylbenzene, carbonyl alcohol, propylene oxide, acrylic acid, acrylonitrile and the like; and another important low-carbon olefin butene is widely used, such as producing high-octane gasoline components from mixed butene, and products such as maleic anhydride, sec-butyl alcohol, heptene, polybutene, acetic anhydride and the like.
At present, the demand of China for low-carbon olefin resources still grows, and propylene supply mainly comes from byproducts in the process of preparing ethylene by naphtha cracking and heavy oil catalytic cracking. Due to the increase of propylene demand, the supply of propylene is still insufficient in recent years, a large amount of propylene products are still imported every year, and the original propylene source can not completely meet the actual demand. Among the production processes that expand the source of propylene are propane dehydrogenation processes, olefin interconversion processes, olefin metathesis processes, methanol to olefins, and the like, where propane dehydrogenation to propylene processes are of interest.
Butene is also in short supply with the rapid growth of MTBE (methyl tertiary butyl ether) units, alkylation units and the like, and dehydrogenation is an important preparation method because of the great demand for dehydrogenated olefins which can be used in various chemical products such as cleaners, high-octane gasoline, pharmaceuticals, plastics, synthetic rubber. One direction of application of this process is the dehydrogenation of isobutane to produce isobutene, which is polymerized to provide tackifiers for adhesives, viscosity index additives for motor oils, impact and oxidation resistant additives for plastics and components for oligomeric gasoline, and therefore, processes for the dehydrogenation of isobutane have also received attention.
The method has the advantages that the method has abundant light hydrocarbon resources such as liquefied petroleum gas, condensate and the like, contains a large amount of low-carbon alkanes such as propane, butane and the like, can effectively convert the propane, butane and the like into propylene and butene directly, can fully utilize petroleum resources, can alleviate the problem of insufficient sources of low-carbon alkenes, particularly propylene, butene and the like, and can simultaneously obtain high-value hydrogen. Therefore, there is a need to develop a process for dehydrogenating lower alkanes for industrial use.
In order to meet the practical application requirements of the low-carbon olefin, research and development institutions at home and abroad have developed a plurality of alkane dehydrogenation processes of low-carbon alkane such as propane, butane and the like in the last century, wherein representative processes mainly comprise a Catofin process of ABB Lummus, an Oleflex process of UOP, a Star process of Phillips company, a PDH process of Linde company and the like.
The Catofin process by Lummus corporation is one of the low-carbon alkane dehydrogenation processes that are mainly used, and belongs to the typical HOUDRY cyclic fixed bed dehydrogenation process; adopts cheaper Cr 2 O 3 /A1 2 O 3 The core device of the chromium catalyst is a plurality of fixed bed reactors, the reaction temperature is about 600 ℃, and under the conditions of high temperature and low pressure, propane absorbs a large amount of heat through the bed catalyst to complete dehydrogenation reaction to prepare propylene, and meanwhile, along with some side reactions, the catalyst needs to be regenerated every 15 minutes. The process has the advantages of high propane conversion rate, good propylene selectivity, strong raw material adaptability, high device online rate and the like, so that the process is more and more valued, and particularly, the process is applied to the aspect of isobutane dehydrogenation and is gradually promoted.
At present, in the dehydrogenation reaction process of the low-carbon alkane, due to the pressure drop difference caused by catalyst filling, material bias flow caused by process piping and other factors, when the dehydrogenation reaction of the low-carbon alkane on the surface active site of the catalyst is carried out, the temperature distribution and the temperature drop of the catalyst bed layer cannot be uniform along with the strong heat absorption process, the service life of the catalyst and the product yield of the low-carbon olefin are seriously influenced, and the process has unsatisfactory aspects of severity, stability, operability, operation period and the like, and needs further improvement and improvement.
Disclosure of Invention
Aiming at the problems, the application aims to provide a method and a system for dehydrogenating low-carbon alkane, which are characterized in that a dehydrogenation catalyst, a thermal coupling aid, inert alumina balls and inert alumina porcelain balls are filled in a reactor according to the volume ratio of 1 (0.1-0.2) (0.4-0.7) (0.4-0.6), so that the temperature distribution of a catalyst bed of a fixed bed reactor is improved, the reaction and regeneration severity is reduced, and the product yield is improved.
The technical scheme adopted by the application is as follows:
a process for the dehydrogenation of lower alkanes comprising the steps of:
s1, gas of low-carbon alkane, CO and/or CO 2 The process gas is heated at 200-500 ℃ and then enters a reactor for reaction;
s2, the low-carbon alkane and the process gas enter a reactor to be contacted with a dehydrogenation catalyst, a thermal coupling auxiliary agent, inert alumina balls serving as a heat accumulator and inert alumina porcelain balls serving as support, and the reaction temperature is 500-700 ℃, the reaction pressure is 50-200 KPa (A), the reaction time is 5-30 min, and the mass airspeed is 0.1-5 h -1 Is subjected to dehydrogenation reaction under the condition of (2); wherein the filling volume ratio of the dehydrogenation catalyst, the thermal coupling auxiliary agent, the inert alumina balls used as the heat accumulator and the inert alumina porcelain balls used as the support is 1 (0.1-0.2): (0.4-0.7): (0.4-0.6);
s3, separating the reaction gas generated by the reactor into low-carbon olefin, hydrogen-rich gas, fuel gas and C4 and C4+ through a separation system, and returning unconverted low-carbon alkane to the reactor.
Preferably, the reactor is provided with at least three reactors, and dehydrogenation reaction, steam purging and catalyst regeneration are respectively carried out; when the reactor regenerates the catalyst, the catalyst bed layer is heated first, and then the reactor is vacuumized and subjected to reduction reaction; the time ratio of dehydrogenation reaction, steam blowing, heating catalyst bed and vacuumizing/reducing reaction is 1 (0.2-0.4), 0.8-1.1 and 0.2-0.4.
Preferably, the dehydrogenation catalyst comprises 18 to 30 mole percent Cr 2 O 3 、0.1mol％～3mol％CeO of (2) 2 0.1 to 1mol% of Cl and 67 to 80mol% of Al 2 O 3 The thermal coupling auxiliary agent comprises 5 to 30mol percent of CuO and 0.1 to 3mol percent of CeO 2 10 to 35mol percent of CaO, 0.1 to 1mol percent of Cl and 50 to 80mol percent of Al 2 O 3 。
The system comprises a feeding pipe, a heating furnace, a reactor and a separation system which are sequentially connected, wherein the separation system is communicated with the feeding pipe through a pipeline, a catalyst bed layer is arranged in the reactor, and a dehydrogenation catalyst, a thermal coupling auxiliary agent, inert alumina balls and inert alumina porcelain balls are filled in the catalyst bed layer.
Preferably, a first heat exchanger, a condenser and a first compressor are sequentially arranged on a pipeline connected with the separation system, and the feeding pipe extends into the first heat exchanger.
Preferably, the separation system comprises a flash separation tank connected with the reactor, the top of the flash separation tank is connected with a cold box through a pipeline, the top of the cold box is connected with a hydrogen-rich gas output pipe, the bottoms of the cold box and the flash separation tank are connected with a deethanizer through a pipeline, the top of the deethanizer is connected with a fuel gas output pipe, the bottom of the deethanizer is connected with a separation tower through a pipeline, the top of the separation tower is connected with a heat pump compressor through a pipeline, the outlet of the heat pump compressor is communicated with the separation tower through a pipeline, the outlet of the heat pump compressor is also connected with a low-carbon olefin output pipe, the bottom of the separation tower is connected with a depropanizer through a pipeline, the bottom of the depropanizer is connected with C and C+ output pipes, and the top of the depropanizer is connected with a feed pipe through a pipeline.
Preferably, the deethanizer is connected to a first reboiler, and the reactor is connected to the flash separation tank with a conduit extending into the first reboiler.
Preferably, the heat pump compressor is two-stage compression, an outlet of the first stage is connected with a second reboiler, an outlet of the second stage is connected with a third reboiler, a cooling medium inlet and an outlet of the second reboiler are communicated with the separation tower, and a cooling medium inlet and an outlet of the third reboiler are communicated with the depropanizer.
Preferably, the reactor comprises a shell, a hot air inlet pipe is communicated with the top of the shell, a low-carbon alkane inlet pipe and other gas inlet pipes are connected to the hot air inlet pipe, a hot air outlet pipe and a hydrocarbon product outlet pipe are communicated with the bottom of the shell, and a pumping-out pipe is connected to the hot air outlet pipe and the hydrocarbon product outlet pipe, and valves are arranged in the hot air inlet pipe, the low-carbon alkane inlet pipe, the other gas inlet pipe, the pumping-out pipe, the hot air outlet pipe and the hydrocarbon product outlet pipe.
Preferably, the hot air inlet pipe is connected with an air heating furnace through a pipeline, the air heating furnace is connected with a second heat exchanger, the second heat exchanger is connected with a gasifier, the hot air outlet pipe is connected with a third heat exchanger, the third heat exchanger is connected with a waste heat boiler, and the pipeline connected with the third heat exchanger and the waste heat boiler stretches into the second heat exchanger.
In summary, due to the adoption of the technical scheme, the beneficial effects of the application are as follows:
the dehydrogenation catalyst, the thermal coupling additive, the inert alumina balls and the inert alumina porcelain balls are filled in the reactor according to the volume ratio of 1 (0.1-0.2) (0.4-0.7) (0.4-0.6), so that the temperature distribution of the catalyst bed layer of the fixed bed reactor is improved, the reaction and regeneration severity is reduced, and the product yield is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart provided in an embodiment of the present application;
FIG. 2 is a schematic view of a regeneration status of a reactor according to an embodiment of the present application;
fig. 3 is a schematic view of a reactor structure according to an embodiment of the present application.
Description of the drawings: 1-a heating furnace; 2-a fifth heat exchanger; 3-a reactor; 4-a fourth heat exchanger; 5-a first heat exchanger; 6-a condenser; 7-a first compressor; 8-a second compressor; 9-a flash separation tank; 10-a cold box; 11-deethanizer; 12-a first reboiler; 13-a heat pump compressor; 14-a second reboiler; 15-a third reboiler; 16-a separation column; 17-depropanizer; 18-feeding pipe; 19-a hydrogen-rich gas outlet pipe; 20-fuel gas outlet pipe; 21-C4 and C4+ output tubes; 22-lower olefins take off; 23-a second heat exchanger; 24-an air heating furnace; 25-a third heat exchanger; 26-a waste heat boiler; a 27-gasifier; 301-hot air inlet pipe; 302-low-carbon alkane feeding pipe; 303—a deflector; 304-other gas inlet pipe; 305-three-point thermocouple; 306-a catalyst bed; 307-refractory brick floor; 308-arch support; 309-evacuating the pipe; 310-hot air outlet pipe; 311-hydrocarbon product outlet pipe; 312-housing.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the description of the present application, it should be noted that, if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate an azimuth or a positional relationship based on that shown in the drawings, or an azimuth or a positional relationship in which a product of the application is conventionally put in use, it is merely for convenience of describing the present application and simplifying the description, and it is not indicated or implied that the referred device or element must have a specific azimuth, be constructed and operated in a specific azimuth, and thus should not be construed as limiting the present application.
The present application will be described in detail with reference to fig. 1 to 3.
Examples
A process for the dehydrogenation of lower alkanes comprising the steps of:
s1, gas of low-carbon alkane, CO and/or CO 2 The process gas is heated at 200-500 ℃ and then enters a reactor 3 for reaction, and the preferable heating temperature is 300-450 ℃; CO and CO in process gas 2 The proportion of the low-carbon alkane raw material is 1 to 20mol percent, and the preferable proportion is 1.5 to 5mol percent; the lower alkane preferably uses one or more of propane, isobutane and n-butane;
s2, low-carbon alkane and process gas enter a reactor 3 to be contacted with a dehydrogenation catalyst, a thermal coupling auxiliary agent, inert alumina balls serving as a heat accumulator and inert alumina porcelain balls serving as support, and the reaction temperature is 500-700 ℃, the reaction pressure is 50-200 KPa (A), the reaction time is 5-30 min, and the mass airspeed is 0.1-5 h -1 The dehydrogenation reaction is carried out under the conditions of 540-650 ℃, reaction pressure of 70-150 KPa (A), reaction time of 10-20 min and mass airspeed of 0.3-2 h -1 The method comprises the steps of carrying out a first treatment on the surface of the Wherein the filling volume ratio of the dehydrogenation catalyst, the thermal coupling auxiliary agent, the inert alumina balls used as a heat accumulator and the inert alumina porcelain balls used as a support is 1 (0.1-0.2): (0.4-0.7): (0.4-0.6), and the preferable volume ratio is 1 (0.15-0.18): (0.5-0.6): (0.45-0.55);
s3, separating the low-carbon olefin, the hydrogen-rich gas, the fuel gas and the C4 and C4+ from the reaction gas generated by the reactor 3 through a separation system, and returning unconverted low-carbon alkane to the reactor 3.
The reactor 3 is provided with at least three reactors, and is used for dehydrogenation reaction, steam purging and catalyst regeneration respectively; when the reactor 3 regenerates the catalyst, the catalyst bed is heated (the hot air with the temperature of 560-730 ℃ and the pressure of 0.01-1 MPa (A) is introduced for heating, the hot air with the temperature of 600-700 ℃ and the pressure of 0.05-0.5 MPa (A) is optimized), then vacuumizing is carried out for reduction reaction, hydrogen-rich gas can be adopted for reduction, the time for heating the catalyst bed and vacuumizing/reducing reaction is 10-70 min each time, and the preferable time is 20-35 min; the time ratio of dehydrogenation reaction, steam purging, heating catalyst bed and vacuumizing/reducing reaction is 1 (0.2-0.4), 0.8-1.1, 0.2-0.4, and the preferable time ratio is 1 (0.25-0.35), 0.9-1.05 and 0.25-0.35.
The dehydrogenation catalyst comprises 18 to 30mol percent of Cr 2 O 3 CeO 0.1mol% -3 mol% 2 0.1 to 1mol% of Cl and 67 to 80mol% of Al 2 O 3 The thermal coupling auxiliary agent comprises 5 to 30mol percent of CuO and 0.1 to 3mol percent of CeO 2 10 to 35mol percent of CaO, 0.1 to 1mol percent of Cl and 50 to 80mol percent of Al 2 O 3 . Inert alumina balls as heat accumulator and inert alumina porcelain balls as support, the composition of which is Al 2 O 3 99.5mol% or more, the heat capacity is 0.2-0.35cal/g ℃, the preferable heat capacity is 0.25-0.32 cal/g ℃, and the highest use temperature is 1400 ℃ or more, so as to be used as an effective heat accumulator and ensure the stability under severe use environment. Cl exists in the form of sodium chloride or calcium chloride.
Since the dehydrogenation catalyst is a Cr-based catalyst, the reduction reaction can be selectively not performed in a single reaction-regeneration cycle period, and thus a large amount of hydrogen-rich fuel can be saved. At this time, the time ratio of dehydrogenation reaction, steam purging and heating the catalyst bed by hot air is 1 (0.1-0.2): 0.4-0.6.
A system for dehydrogenating low-carbon alkane is shown in figure 1, and comprises a feeding pipe 18, a heating furnace 1, a reactor 3 and a separation system which are sequentially connected, wherein the separation system is communicated with the feeding pipe 18 through a pipeline, a catalyst bed layer 306 is arranged in the reactor 3, and the catalyst bed layer 306 is filled with a dehydrogenation catalyst, a thermal coupling auxiliary agent, inert alumina balls and inert alumina porcelain balls. The low-carbon alkane is introduced into the heating furnace 1 for heating by the feed pipe 18, then is introduced into the reactor 3 for mixing with the process gas and contacting with the dehydrogenation catalyst, the thermal coupling auxiliary agent, the inert alumina balls and the inert alumina porcelain balls for dehydrogenation reaction, the reaction gas is separated by the separation system, the low-carbon alkene, the hydrogen-rich gas, the fuel gas, the C4 and the C4+ are obtained, and part of unreacted low-carbon alkane is conveyed to the reactor 3 for continuous reaction.
The first heat exchanger 5, the condenser 6 and the first compressor 7 are sequentially arranged on a pipeline connected with the separation system of the reactor 3, and the feeding pipe 18 extends into the first heat exchanger 5. The first heat exchanger 5 is arranged to preheat the low-carbon alkane in the feed pipe 18, so that the heat of the reaction gas is reused, and the work load of the heating furnace 1 is reduced; after the reaction gas exchanges heat through the first heat exchanger 5, the temperature of the reaction gas is reduced again through the condenser 6, so that the service life of the first compressor 7 is shortened due to high temperature while the work load of the separation system is reduced. The dehydrogenation reaction adopts micro positive pressure operation, so that the first compressor 7 can reduce one-stage compression, and the energy consumption of the first compressor 7 is reduced.
The pipeline connecting the reactor 3 and the separation system is also provided with a fourth heat exchanger 4 positioned between the reactor 3 and the first heat exchanger 5, and the fourth heat exchanger 4 utilizes the temperature of the reaction gas to produce steam and recovers a part of heat. The reactor 3 is connected with a fifth heat exchanger 2, and the fifth heat exchanger 2 heats the process gas.
The separation system comprises a flash separation tank 9 connected with a reactor 3, wherein the top of the flash separation tank 9 is connected with a cold box 10 through a pipeline, the top of the cold box 10 is connected with a hydrogen-rich gas output pipe 19, the bottoms of the cold box 10 and the flash separation tank 9 are connected with a deethanizer 11 through a pipeline, the top of the deethanizer 11 is connected with a fuel gas output pipe 20, the bottom of the deethanizer 11 is connected with a separation tower 16 through a pipeline, the top of the separation tower 16 is connected with a heat pump compressor 13 through a pipeline, the outlet of the heat pump compressor 13 is communicated with the separation tower 16 through a pipeline, the outlet of the heat pump compressor 13 is also connected with a low-carbon olefin output pipe 22, the bottom of the separation tower 16 is connected with a depropanizer 17 through a pipeline, the bottom of the depropanizer 17 is connected with a C4 and a C4+ output pipe 21, and the top of the depropanizer 17 is connected with a feed pipe 18 through a pipeline.
The flash separation tank 9 separates the reaction gas, the top gas of the flash separation tank 9 is condensed by the cold box 10, the hydrogen-rich gas is output from the hydrogen-rich gas output pipe 19, and condensate generated by condensation is conveyed to the deethanizer 11 together with the bottom liquid of the flash separation tank 9 for separation again; the top gas of the deethanizer 11 is taken as fuel gas and is output by a fuel gas output pipe 20, the bottom liquid of the deethanizer 11 enters a separating tower 16, the top gas of the separating tower 16 is compressed and conveyed by a heat pump compressor 13, the top gas is divided into two parts, one part is taken as reflux of the separating tower 16, the other part outputs a low-carbon olefin product through a low-carbon olefin output pipe 22, the bottom liquid of the separating tower 16 enters a depropanizer 17 for separation again, the bottom liquid of the depropanizer 17 is C4 and C4+ and is output from the C4 and C4+ output pipes 21 to the outside, the top gas of the depropanizer 17 is low-carbon alkane, and the low-carbon alkane returns to the feed pipe 18 through a pipeline.
The cold box 10 is connected with a circulation pipeline of refrigerant, the circulation pipeline is internally provided with a second compressor 8 for circulating the refrigerant, the refrigerant is a mixed refrigerant composed of a plurality of substances of methane, ethane, ethylene and propylene, and the temperature of the refrigerant after compression throttling can reach-90 ℃. By adopting the refrigeration mode, the process of setting the compressor of the device is simplified, the investment of a refrigeration system is reduced, the refrigeration efficiency is improved, and the refrigeration power consumption is reduced.
A first reboiler 12 is connected to the deethanizer 11, and the piping connecting the reactor 3 with the flash separation tank 9 extends into the first reboiler 12. The first reboiler 12 recovers heat of the reaction gas, and heats the bottom liquid of the deethanizer 11 and further cools the reaction gas.
The heat pump compressor 13 is two-stage compression, the outlet of the first stage is connected with a second reboiler 14, the outlet of the second stage is connected with a third reboiler 15, the cooling medium inlet and outlet of the second reboiler 14 are communicated with the separation tower 16, and the cooling medium inlet and outlet of the third reboiler 15 are communicated with the depropanizer 17. The second reboiler 14 primarily cools the overhead gas, and heats the bottom liquid of the separation column 16 by the heat, and the third reboiler 15 again cools the overhead gas, and heats the bottom liquid of the depropanizer 17 by the heat.
As shown in fig. 3, the reactor 3 includes a housing 312, a hot air inlet 301 is connected to the top of the housing 312, a low-carbon alkane inlet 302 and other gas inlet 304 are connected to the hot air inlet 301, a hot air outlet 310 and a hydrocarbon product outlet 311 are connected to the bottom of the housing 312, an evacuation pipe 309 is connected to the hot air outlet 310 and the hydrocarbon product outlet 311, and valves are provided in the hot air inlet 301, the low-carbon alkane inlet 302, the other gas inlet 304, the evacuation pipe 309, the hot air outlet 310 and the hydrocarbon product outlet 311.
The other gas inlets 304 are provided in plurality and are used to deliver steam, process gas, and reducing gas. At least three reactors 3 are arranged, part of the reactors 3 are in a reaction state, part of the reactors 3 are in a steam purging state, and the other part of the reactors 3 are in a regeneration state, so that the reactors 3 can react at the same time, and continuous production is ensured. When the reactor 3 is in reaction, the light alkane inlet pipe 302, the other gas inlet pipe 304 for conveying process gas and the hydrocarbon product outlet pipe 311 are opened, and other pipelines are closed; when the reactor 3 is subjected to steam purging, other gas inlet pipes 304 and hydrocarbon product outlet pipes 311 for conveying steam are opened, other pipelines are closed, the steam purges the catalyst bed 306 from top to bottom, and residual hydrocarbon is discharged from the hydrocarbon product outlet pipes 311; when the reactor 3 regenerates, the hot air inlet pipe 301 and the hot air outlet pipe 310 are opened, other pipelines are closed, the hot air passes through the catalyst bed 306 from top to bottom, the catalyst and the auxiliary agent are regenerated, the dehydrogenation catalyst, the thermal coupling auxiliary agent, the inert alumina balls and the inert alumina porcelain balls in the catalyst bed 306 accumulate heat, the temperature of the bed is increased, the waste heat air is discharged from the hot air outlet pipe 310 at the lower part of the reaction, after the heating is finished, the hot air inlet pipe 301 and the hot air outlet pipe 310 are closed, the evacuation pipe 309 is opened for evacuation, the other gas inlet pipe 304 for conveying the reducing gas is opened after the evacuation is finished, the dehydrogenation catalyst and the thermal coupling auxiliary agent are subjected to reduction treatment, and the waste gas is discharged from the evacuation pipe 309.
A baffle 303 is also provided in the housing 312 and is located directly below the hot air inlet duct 301. The hot air inlet pipe 301 is provided with an air drying device for drying hot air, and the hot air is heated and dried when required. The reactor 3 is also provided with a three-point thermocouple 305 for detecting a temperature change of the catalyst bed 306. The bottom of the catalyst bed 306 is provided with a refractory brick floor 307, and an arch support 308 is provided below the refractory brick floor 307.
The shell 312 is made of carbon steel, the inner wall of the shell 312 is provided with a lining made of refractory material, the reactor 3 is not maintained for at least 10 years, continuous production is ensured, the reactor 3 also adopts external heat preservation, and the heat preservation effect is good.
As shown in fig. 2, the reactor 3 is a heating stage during regeneration, the hot air inlet 301 is connected with the air heating furnace 24 through a pipeline, the air heating furnace 24 is connected with the second heat exchanger 23, the second heat exchanger 23 is connected with the gasifier 27, the hot air outlet 310 is connected with the third heat exchanger 25, the third heat exchanger 25 is connected with the waste heat boiler 26, and the pipeline connecting the third heat exchanger 25 and the waste heat boiler 26 extends into the second heat exchanger 23. The air is vaporized by the gasifier 27 and then mixed with fuel gas to enter the second heat exchanger 23 for heating, then enters the air heating furnace 24 for further heating to generate hot air, the hot air heats the reactor 3, the third heat exchanger 25 recovers heat of the used hot air, the hot air is used as a heat source of the second heat exchanger 23 for further heat recovery, and the waste heat boiler 26 recovers the final heat and discharges exhaust gas.
The application reduces the highest temperature of the bed and the deactivation probability of the catalyst at the top of the bed on the premise of keeping the total heat unchanged, reduces the temperature drop in one reaction period, and can improve the selectivity under the condition of keeping the conversion rate unchanged, so the application synergistically improves the stability of the alkane dehydrogenation reaction process and the product yield of the low-carbon olefin, prolongs the service life of the catalyst, and is beneficial to the long-period operation and running of the dehydrogenation process.
Experiment one:
preparation of Cr having a composition of 23mol% 2 O 3 CeO of 1mol% 2 1mol% Cl and 75mol% Al 2 O 3 3mm strip dehydrogenation catalyst of (2) having a surface area of 95m 2 Per g, bulk density of 1.05g/ml, crush strength of 65N/mm. Preparation of CeO having a composition of 15mol% and 3mol% 2 17mol% CaO and 65mol% Al 2 O 3 3mm strip thermal coupling aid of 35m surface area 2 Per g, bulk density 1.1g/ml, crush strength 40N/mm.
The 3mm strip dehydrogenation catalyst, 3mm strip thermal coupling auxiliary agent and 5mm inert alumina balls (Al) as a heat accumulator are prepared 2 O 3 99.5mol% or more, heat capacity 0.3cal/g ℃ and melting temperature 1700 ℃ or more) and 8mm inert alumina porcelain balls (Al) as support 2 O 3 99.5mol% or more, a heat capacity of 0.3cal/g ℃ and a use temperature of 1400 ℃ or more) is filled into the catalyst bed 306 according to a volume ratio of 1:0.15:0.5:0.5.
8 reactors 3 were used, and 8 reactors 3 were put into operation in sequence at 3 minute intervals, 3 reactors 3 being in the dehydrogenation reaction process, 3 reactors 3 being in the regenerative heating process, and 2 reactors being in the steam purge or the evacuation/reduction process at any one time. A single cycle period of about 25 to 30 minutes, wherein the dehydrogenation reaction takes 10 to 15 minutes, about 3 minutes of steam purge, about 9 minutes of regeneration and reheating of the catalyst bed, and about 3 minutes of time is used for the evacuation and reduction reactions.
Industrial grade propane was used as a reaction raw material, and the raw material properties of the industrial grade propane are shown in Table 1.
Table 1 raw material properties table of technical grade propane
| Project | Composition/mol% |
| Ethane (ethane) | 1.2 |
| Propane | 95.4 |
| Propylene | 2.5 |
| Diolefins and acetylenes | 0.5 |
| C 4 + | 0.4 |
CO and CO as process gas 2 By separating industrial CO and CO obtained from waste hot gases in the present application 2 And (3) gas.
The dehydrogenation reaction and regeneration operating conditions for technical grade propane are shown in table 2.
TABLE 2 dehydrogenation and regeneration operating conditions Table
| Project | Data |
| Reaction feed temperature/°c | 590 |
| Reactor pressure/KPa (A) | 50 |
| Propane feed mass space velocity/(WHSV) h -1 | 0.5 |
| Process gas feed mass space velocity/(WHSV) h -1 | 0.01 |
| In a single pass reactionInterval/min | 10～15 |
| Regeneration air feed temperature/°c | 670 |
| Regenerated air feed pressure/KPa (A) | 80 |
Comparative example one:
adopts a typical HOUDRY circulating fixed bed dehydrogenation process in the background art, and the reaction raw materials are consistent with those of experiment one, and adopts the commercial Cr/Al 2 O 3 Industrial dehydrogenation catalysts.
Comparative example two:
adopts a typical HOUDRY circulating fixed bed dehydrogenation process in the background art, and the reaction raw materials are consistent with those of experiment one, and adopts the commercial Cr/Al 2 O 3 Industrial dehydrogenation catalyst and commercially available Cu/Al 2 O 3 Commercial industrial heating materials.
The initial and final catalyst life for the first, comparative examples and comparative examples are shown in Table 3 for the propane dehydrogenation run conditions, wherein no less than 3 years of catalyst life is used as initial and final run conditions.
TABLE 3 comparative table of the initial and final catalyst life operating conditions for propane dehydrogenation reactions
| Project | Experiment one | Comparative example one | Comparative example two |
| Initial propane single pass conversion/% | 50 | 44 | 45 |
| End-of-run propane single pass conversion/% | 44 | 40 | 41 |
| Propylene selectivity/%at initial run | 86 | 84 | 84 |
| End of run propylene selectivity/% | 86 | 81 | 82 |
Compared with the typical operation condition of the HOUDRY circulating fixed bed dehydrogenation process and the operation condition of the HOUDRY circulating fixed bed dehydrogenation process combined with the existing heating material, the method has better propane single pass conversion rate and propylene selectivity, and better propane dehydrogenation reaction implementation effect is obtained.
Experiment II:
the same reaction conditions as in experiment one were used to replace the reaction starting material with a mixed starting material of propane and isobutane. The properties of the propane and isobutane blend stock are shown in table 4.
TABLE 4 Properties of propane and isobutane Mixed feed
| Project | Composition/mol% |
| Ethane (ethane) | 0.3 |
| Propyne | 0.02 |
| Allene | 0.02 |
| Propylene | 1.4 |
| Propane | 56.7 |
| Isobutane | 37.2 |
| Isobutene (i-butene) | 0.7 |
| N-butane | 1.1 |
| N-butene | 0.8 |
| 1, 3-butadiene | 0.2 |
| Maleic anhydride | 0.5 |
| Fumaric acid | 1.1 |
The dehydrogenation reaction and regeneration operation conditions of the mixed feed of propane and isobutane are shown in table 5.
TABLE 5 Table 5 dehydrogenation and regeneration operating conditions for propane and isobutane mixed feed
| Project | Data |
| Reaction feed temperature/°c | 592 |
| Reactor pressure/KPa (A) | 50 |
| Mixed feed mass space velocity/(WHSV) h -1 | 0.5 |
| Process gas feed mass space velocity/(WHSV) h -1 | 0.01 |
| Single pass reaction time/min | 10～15 |
| Regeneration air feed temperature/°c | 671 |
| Regenerated air feed pressure/KPa (A) | 80 |
Comparative example three:
the same process as in comparative example one was used, except that the technical grade propane feed of comparative example one was replaced with a mixed feed of propane and isobutane.
Comparative example four:
the same process as in comparative example two was used, except that the technical grade propane feed of comparative example two was replaced with a mixed feed of propane and isobutane.
The initial and final catalyst life for the propane dehydrogenation reactions run versus the second, third and fourth comparative examples are shown in Table 6, with no less than 3 years catalyst life as initial and final operation.
TABLE 6 comparison of the behavior of propane and isobutane mixed dehydrogenation reactions at the beginning and end of catalyst life
| Project | Experiment two | Comparative example three | Comparative example four |
| Total single pass conversion/%of propane+isobutane at initial stage of operation | 55 | 49 | 50 |
| End-of-run propane+isobutane total single pass conversion/% | 45 | 41 | 42 |
| Propane+isobutane selectivity/% | 86 | 82 | 82 |
| End of run propylene+isobutylene selectivity/% | 85 | 81 | 80 |
Compared with the typical operation of the HOUDRY circulating fixed bed dehydrogenation process and the operation of the HOUDRY circulating fixed bed dehydrogenation process combined with the existing heating material, the method has better conversion rate and selectivity of propane and isobutane and obtains better implementation effect in the dehydrogenation reaction of the mixed industrial raw materials of propane and isobutane. The application has good implementation effect on the mixed low-carbon alkane raw materials with more complex composition and the relatively more complex conversion process, and shows good raw material and process adaptability.
The catalyst bed temperature, as well as other operating conditions, and process consumption data are compared as shown in table 7.
TABLE 7 comparison of operating conditions and process consumption
The application effectively reduces the temperature difference and the severity in the catalyst bed layer, and ensures that the temperature distribution is more uniform.
Experiment III:
on the basis of experiment one, the reaction working section is ensured to be unchanged, the heat reflux of the heat pump compressor 13 and the depropanizer 17 is increased, the micro positive pressure operation is performed to reduce the compression stage number of the first compressor 7, the reduction stage of regeneration is canceled, and the process consumption comparison conditions of experiment one and experiment three are shown in table 8.
Table 8 process consumption vs. situation table
| Project | Experiment one | Experiment three |
| Energy consumption kg standard oil/t olefin product | 340 | 320 |
The energy consumption and the material consumption of the process can be reduced by increasing the heat pump compressor 13, the heat reflux of the depropanizer 17, reducing the compression stage number of the first compressor 7 by micro positive pressure operation and eliminating the reduction stage of regeneration.
The above is only a preferred embodiment of the present application, and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (10)
1. A process for the dehydrogenation of light alkanes, comprising the steps of:
s1, gas of low-carbon alkane, CO and/or CO 2 The process gas is heated at 200-500 ℃ and then enters a reactor (3) for reaction;
s2, low-carbon alkane and process gas enter a reactor (3) to be contacted with a dehydrogenation catalyst, a thermal coupling auxiliary agent, inert alumina balls serving as a heat accumulator and inert alumina porcelain balls serving as support, and the reaction temperature is 500-700 ℃, the reaction pressure is 50-200 KPa (A), the reaction time is 5-30 min, and the mass airspeed is 0.1-5 h -1 Is subjected to dehydrogenation reaction under the condition of (2); wherein the filling volume ratio of the dehydrogenation catalyst, the thermal coupling auxiliary agent, the inert alumina balls used as the heat accumulator and the inert alumina porcelain balls used as the support is 1 (0.1-0.2): (0.4-0.7): (0.4-0.6);
s3, separating the low-carbon olefin, the hydrogen-rich gas, the fuel gas and the C4 and C4+ from the reaction gas generated by the reactor (3) through a separation system, and returning unconverted low-carbon alkane to the reactor (3).
2. A process for the dehydrogenation of light alkanes according to claim 1, characterized in that said reactor (3) is provided with at least three reactors, and is subjected to dehydrogenation reactions, steam purge and catalyst regeneration, respectively; when the reactor (3) regenerates the catalyst, the catalyst bed layer is heated first, and then the vacuum pumping is carried out and the reduction reaction is carried out; the time ratio of dehydrogenation reaction, steam blowing, heating catalyst bed and vacuumizing/reducing reaction is 1 (0.2-0.4), 0.8-1.1 and 0.2-0.4.
3. The method for dehydrogenating light alkane according to claim 1, wherein the dehydrogenation catalyst comprises 18 to 30mol% of Cr 2 O 3 CeO 0.1mol% -3 mol% 2 0.1 to 1mol% of Cl and 67 to 80mol% of Al 2 O 3 The thermal coupling auxiliary agent comprises 5 to 30mol percent of CuO and 0.1 to 3mol percent of CeO 2 10 to 35mol percent of CaO, 0.1 to 1mol percent of Cl and 50 to 80mol percent of Al 2 O 3 。
4. The system for dehydrogenating the low-carbon alkane comprises a feeding pipe (18), a heating furnace (1), a reactor (3) and a separation system which are sequentially connected, and is characterized in that the separation system is communicated with the feeding pipe (18) through a pipeline, a catalyst bed layer (306) is arranged in the reactor (3), and a dehydrogenation catalyst, a thermal coupling auxiliary agent, inert alumina balls and inert alumina porcelain balls are filled in the catalyst bed layer (306).
5. The system for dehydrogenating light alkane according to claim 4, wherein the first heat exchanger (5), the condenser (6) and the first compressor (7) are sequentially arranged on a pipeline connected with the separation system of the reactor (3), and the feeding pipe (18) extends into the first heat exchanger (5).
6. The system for dehydrogenating light alkane according to claim 4, wherein the separation system comprises a flash separation tank (9) connected with the reactor (3), wherein the top of the flash separation tank (9) is connected with a cold box (10) through a pipeline, the top of the cold box (10) is connected with a hydrogen-rich gas output pipe (19), the bottoms of the cold box (10) and the flash separation tank (9) are connected with a deethanizer (11) through a pipeline, the top of the deethanizer (11) is connected with a fuel gas output pipe (20), the bottom of the deethanizer (11) is connected with a separation tower (16) through a pipeline, the top of the separation tower (16) is connected with a heat pump compressor (13) through a pipeline, the outlet of the heat pump compressor (13) is communicated with the separation tower (16) through a pipeline, the outlet of the heat pump compressor (13) is also connected with a low-carbon olefin output pipe (22), the bottom of the separation tower (16) is connected with a depropanizer (17) through a pipeline, the bottom of the depropanizer (17) is connected with C4 and a C4+ output pipe (21), and the top of the depropanizer (17) is connected with a feed pipe (18) through a pipeline.
7. A system for the dehydrogenation of light alkanes according to claim 6, characterized in that the deethanizer (11) is connected to a first reboiler (12) and that the piping connecting the reactor (3) with the flash separation tank (9) extends into the first reboiler (12).
8. The system for dehydrogenating light alkane according to claim 6, wherein the heat pump compressor (13) is two-stage compression, the outlet of the first stage is connected with a second reboiler (14), the outlet of the second stage is connected with a third reboiler (15), the cooling medium inlet and outlet of the second reboiler (14) are communicated with the separation tower (16), and the cooling medium inlet and outlet of the third reboiler (15) are communicated with the depropanizer (17).
9. The system for dehydrogenating light alkane according to claim 6, wherein the reactor (3) comprises a housing (312), a hot air inlet pipe (301) is connected to the top of the housing (312), the hot air inlet pipe (301) is connected to a light alkane inlet pipe (302) and other gas inlet pipes (304), a hot air outlet pipe (310) and a hydrocarbon product outlet pipe (311) are connected to the bottom of the housing (312), the hot air outlet pipe (310) and the hydrocarbon product outlet pipe (311) are connected to an evacuation pipe (309), and valves are provided in the hot air inlet pipe (301), the light alkane inlet pipe (302), the other gas inlet pipes (304), the evacuation pipe (309), the hot air outlet pipe (310) and the hydrocarbon product outlet pipe (311).
10. The system for dehydrogenating low-carbon alkane according to claim 9, wherein the hot air inlet pipe (301) is connected with an air heating furnace (24) through a pipeline, the air heating furnace (24) is connected with a second heat exchanger (23), the second heat exchanger (23) is connected with a gasifier (27), the hot air outlet pipe (310) is connected with a third heat exchanger (25), the third heat exchanger (25) is connected with a waste heat boiler (26), and the pipeline connecting the third heat exchanger (25) and the waste heat boiler (26) extends into the second heat exchanger (23).
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