Dehydrogenation device and dehydrogenation method using superheated steam as heat source

Abstract

The invention discloses a dehydrogenation device and a dehydrogenation method using superheated steam as a heat source. The device comprises first to N stages of dehydrogenation reactors which are connected in series, first to N stages of heat transfer medium heaters which are connected in series, and a high-pressure superheated steam conveying pipeline, the high-pressure superheated steam pipeline is connected with the Nth-stage heat conduction heater and exchanges heat with the heat transfer medium in each stage of heat transfer medium heater; each stage of heat transfer medium heater is connected with the corresponding stage of dehydrogenation reactor and is used for supplying heat to the dehydrogenation reactor; n > = 2. High-pressure superheated steam serves as a heat source, reaction heat is provided for dehydrogenation reaction, and compared with electric heat supply and fuel furnace heat supply, good economical efficiency and practicability are achieved.

Description

[0001] This application claims priority to an earlier application filed on August 29, 2024, with patent application number 202411204812.8, entitled "A Dehydrogenation Device and a Dehydrogenation Method Using Superheated Steam as a Heat Source". The entire contents of the earlier application are incorporated herein by reference. Technical Field

[0002] This invention belongs to the field of chemical technology, specifically relating to a dehydrogenation device and a dehydrogenation method using superheated steam as a heat source. Background Technology

[0003] Dehydrogenation is the reverse of hydrogenation. The principle involves applying a certain temperature to a hydrogen-rich organic liquid, causing the carbon-hydrogen bonds to break under the action of a catalyst, thus achieving dehydrogenation. It is an endothermic reaction. Dehydrogenation reactors currently come in three forms: tubular reactors, adiabatic reactors, and multi-stage reactors.

[0004] Patent document CN 116617966 A discloses a dehydrogenation system and method. The dehydrogenation system includes a vaporizer, a superheater, a mixer, a dehydrogenation reactor, a heat transfer medium circulation unit, and a separator. The tube-side inlet of the dehydrogenation reactor is sequentially connected to the outlet of the mixer, the superheater, and the shell-side outlet of the vaporizer. The tube-side outlet of the dehydrogenation reactor is sequentially connected to the tube-side inlets of the superheater and the vaporizer. The shell-side inlet and shell-side outlet of the dehydrogenation reactor are connected to the heat transfer medium circulation unit. The dehydrogenation method includes: vaporizing and superheating the dehydrogenation feedstock, mixing it with a carrier gas, and then introducing it into the dehydrogenation reactor for reaction; circulating heat to the dehydrogenation reactor through the heat transfer medium circulation unit; and after the dehydrogenation reaction, the material enters the superheater and vaporizer to provide heat for the superheating and vaporization of the dehydrogenation feedstock, thereby obtaining the dehydrogenation product and hydrogen.

[0005] Patent document CN 115430367 A discloses a dehydrogenation system and method. The system includes: a dehydrogenation reactor, a heat-conducting medium axial flow pump, and a heat-conducting medium pipeline. The heat-conducting medium pipeline includes an inlet pipeline, an outlet pipeline, and a medium flow pipeline, which is arranged around the dehydrogenation reactor. The inlet pipeline is connected to the outlet of the heat-conducting medium axial flow pump, and the outlet pipeline is connected to the outlet of the medium flow pipeline. A dehydrogenation catalyst and an inert metal heat-conducting material are loaded in the tubes within the dehydrogenation reactor. The method includes: heated reactants entering the reactor, reacting under the action of the catalyst, and absorbing heat; the heat-conducting medium axial flow pump delivers the heat-conducting medium through the inlet pipeline to the inlet of the medium flow pipeline, providing heat to the dehydrogenation reactor; the heat-conducting medium then enters the outlet pipeline from the outlet of the medium flow pipeline; the product and hydrogen flow out from the reactor outlet. The document states that the provided dehydrogenation system and method can enhance heat introduction and ensure the normal progress of the dehydrogenation reaction.

[0006] Patent document CN 115231516 A discloses a method for the dehydrogenation of methylcyclohexane. The method includes: Step 1: supplying electricity to a conductive methylcyclohexane dehydrogenation catalyst to bring it to a first target temperature; Step 2: contacting a feed gas containing methylcyclohexane, preheated to a second target temperature, with the methylcyclohexane dehydrogenation catalyst at the first target temperature to achieve methylcyclohexane dehydrogenation. This technical solution demonstrates that by heating the catalyst and feed gas separately and generating heat through the application of an electric current, the catalyst is heated. This method enhances heat transfer in the methylcyclohexane dehydrogenation reaction, eliminates the temperature gradient present in the catalyst, improves catalyst utilization, and enhances reaction performance.

[0007] Patent documents CN 116617966 A and CN 115430367 A both use natural gas or fuel oil as the heat source for the system, and thermal oil or lava as the heat transfer medium to provide the reactor with the required heat. Patent document CN115231516A uses electricity as the heat source, supplying power to a conductive dehydrogenation catalyst, and the heat transferred to the catalyst serves as the heat source for the reaction. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention provides a dehydrogenation apparatus, comprising:

[0009] The first to Nth stage dehydrogenation reactors, the first to Nth stage heat transfer medium heaters, and the high-pressure superheated steam transmission pipeline are connected in series.

[0010] The high-pressure superheated steam pipeline is connected to the Nth stage heat conduction heater and exchanges heat with the heat transfer medium in each stage of the heat transfer medium heater.

[0011] Each stage of heat transfer medium heater is connected to the corresponding stage of dehydrogenation reactor to supply heat to the dehydrogenation reactor;

[0012] N≥2.

[0013] According to an embodiment of the present invention, the temperature of the heat transfer medium in the Nth stage heat transfer medium heater is higher than the temperature of the heat transfer medium in the first stage heat transfer medium heater; in one embodiment, the temperature of the heat transfer medium in the heat transfer medium heater increases progressively from the first stage to the Nth stage.

[0014] According to an embodiment of the invention, the temperature of the Nth stage dehydrogenation reactor is higher than that of the first stage dehydrogenation reactor; in one embodiment, the temperature of the dehydrogenation reactor increases progressively from the first stage to the Nth stage.

[0015] According to an embodiment of the present invention, 2≤N≤5, for example N=2, 3 or 4.

[0016] According to an embodiment of the present invention, the heat transfer medium is a medium capable of heat transfer with high-pressure superheated steam, such as heat transfer oil.

[0017] In one embodiment, N = 2, meaning the dehydrogenation device includes:

[0018] Two-stage dehydrogenation reactors in series, two-stage heat transfer medium heaters in series, and high-pressure superheated steam delivery pipelines.

[0019] The high-pressure superheated steam pipeline is connected to the second-stage heat conduction heater and is used to heat the heat conduction liquid in each stage of the heat transfer medium heater.

[0020] The temperature of the heat transfer medium in the second-stage heat transfer medium heater is higher than the temperature of the heat transfer medium in the first-stage heat transfer medium heater.

[0021] The first-stage heat transfer medium heater is connected to the first-stage dehydrogenation reactor, and the second-stage heat transfer medium heater is connected to the second-stage dehydrogenation reactor. The heat transfer medium heater is used to supply heat to the dehydrogenation reactor.

[0022] The temperature of the second-stage dehydrogenation reactor is higher than that of the first-stage dehydrogenation reactor.

[0023] According to an embodiment of the present invention, the heating medium outlet of the Nth stage heat transfer medium heater outputs high-pressure steam at near saturation temperature, which is connected to the heating medium inlet of the N-1th stage heat transfer medium heater via a pipeline.

[0024] According to an embodiment of the present invention, the heating medium outlet of the first-stage heat transfer medium heater outputs high-pressure saturated condensate.

[0025] According to an embodiment of the present invention, the dehydrogenation device further includes a high-pressure saturated condensate recycling device, one end of which is connected to the heating medium outlet of the first-stage heat transfer medium heater, and the other end of which is connected to the high-pressure superheated steam pipeline; for example, the high-pressure saturated condensate recycling device is a high-pressure boiler, and the high-pressure saturated condensate is used to generate superheated steam through the high-pressure boiler.

[0026] According to an embodiment of the present invention, the high-pressure superheated steam pipeline is connected to a high-pressure superheated steam conveying device; the high-pressure superheated steam conveying device is, for example, a chemical industrial park, a thermal power plant, or other device capable of generating high-pressure superheated steam. In some embodiments, the high-pressure superheated steam conveying device is the same as a high-pressure saturated condensate recycling device.

[0027] According to an embodiment of the present invention, the dehydrogenation device further includes first to N stage dehydrogenation feed superheaters, which are respectively installed at the front end of the corresponding stage dehydrogenation reactor.

[0028] According to an embodiment of the present invention, the heat transfer medium outlet of each stage of the dehydrogenation reactor is connected to the heat transfer medium inlet of the corresponding stage of the dehydrogenation feed superheater.

[0029] According to an embodiment of the present invention, the dehydrogenation device further includes a heat transfer medium supply end.

[0030] In one embodiment, the heat transfer medium supply end includes first to N stages of heat transfer medium supply ends connected in parallel. Each stage of the heat transfer medium supply end is sequentially connected to a corresponding stage of heat transfer medium heater, dehydrogenation reactor, and dehydrogenation feed superheater, forming a heat transfer medium loop. Further, a heat transfer medium circulation pump can be installed between each stage of the heat transfer medium supply end and the heat transfer medium heater.

[0031] In one implementation, only one heat transfer medium supply end may be provided, which is sequentially connected to the first-stage heat transfer medium circulation pump, the first-stage heat transfer medium heater, the first-stage dehydrogenation reactor, and the first-stage dehydrogenation feed superheater; a heat transfer oil pipeline connected to the second-stage heat transfer medium circulation pump is provided on the connecting pipeline between the first-stage heat transfer medium heater and the first-stage dehydrogenation reactor, and the heat transfer medium outlet of the second-stage dehydrogenation feed superheater is connected to the connecting pipeline between the first-stage heat transfer medium heater and the first-stage dehydrogenation reactor.

[0032] The present invention also provides a dehydrogenation method, comprising: supplying heat to a dehydrogenation reactor with high-pressure superheated steam;

[0033] Preferably, the high-pressure superheated steam exchanges heat with the heat transfer medium, and the heat transfer medium after heat exchange supplies heat to the dehydrogenation reactor.

[0034] According to an embodiment of the present invention, the heat transfer medium has the limitations shown above.

[0035] According to an embodiment of the present invention, the heat exchange with the heat transfer medium is carried out in a heat transfer medium heater. The number of both the heat transfer medium heater and the dehydrogenation reactor is N, where N has the limitations shown above.

[0036] According to an embodiment of the present invention, the high-pressure superheated steam sequentially passes through the Nth, N-1th, ..., first-stage heat transfer medium heaters, and then the heat-exchanged heat transfer medium supplies heat to the corresponding stage dehydrogenation reactor.

[0037] In one embodiment, the high-pressure superheated steam sequentially passes through a second-stage and a first-stage heat transfer medium heater, and then the heat-exchanged heat transfer medium supplies heat to the corresponding stage of the dehydrogenation reactor.

[0038] According to an embodiment of the present invention, the temperature of the heat transfer medium after heat exchange is higher than the activation temperature of the dehydrogenation feedstock in the dehydrogenation reactor.

[0039] According to an embodiment of the present invention, the pressure of the Nth stage (e.g., N=2, the second stage) dehydrogenation reactor is 50 kPaG to 80 kPaG. Methylcyclohexane dehydrogenation is a volume-increasing reaction, and a lower reaction pressure is beneficial for the forward reaction. However, the reacted material requires multiple cooling, gas-liquid separation, and further pressurization of the gas phase to facilitate the delivery of hydrogen products. To ensure a positive pressure at the hydrogen compressor inlet, the dehydrogenation reaction cannot be carried out at excessively low pressures. The dehydrogenation reaction employs a two-stage series configuration, with the second-stage dehydrogenation reaction occurring at 50 kPaG to 80 kPaG, ensuring the entire dehydrogenation system is under positive pressure and effectively avoiding the potential hazards of hydrogen flash explosions. Furthermore, it reduces the electrical power consumed in further hydrogen compression.

[0040] According to an embodiment of the present invention, the dehydrogenation method is carried out in the above-described dehydrogenation apparatus.

[0041] According to an embodiment of the present invention, the heat transfer medium after heat exchange with each stage of the dehydrogenation reactor further enters the corresponding stage of the dehydrogenation feed superheater for heat exchange; preferably, after heat exchange, it returns to the corresponding stage of the heat transfer medium supply end.

[0042] In one embodiment, N = 2, the dehydrogenation method includes:

[0043] The high-pressure superheated steam enters the second-stage heat transfer medium heater for heat exchange, resulting in high-pressure steam at near-saturation temperature and the second-stage heat transfer medium after heat exchange.

[0044] The heat exchanged second-stage heat transfer medium enters the second-stage dehydrogenation reactor for heating.

[0045] The high-pressure steam at near-saturation temperature enters the first-stage heat transfer medium heater for heat exchange, resulting in high-pressure saturated condensate and the first-stage heat transfer medium after heat exchange.

[0046] The heat exchanged first-stage heat transfer medium enters the first-stage dehydrogenation reactor for heating.

[0047] Preferably, the second-stage heat transfer medium, after being heated by the second-stage dehydrogenation reactor, enters the second-stage dehydrogenation feed superheater, and the first-stage heat transfer medium, after being heated by the first-stage dehydrogenation reactor, enters the first-stage dehydrogenation feed superheater; even more preferably, the heat transfer medium exiting from each stage of the dehydrogenation feed superheater returns to the corresponding stage's heat transfer medium supply end.

[0048] Preferably, the high-pressure saturated condensate enters a high-pressure saturated condensate recycling device for reuse, generating high-pressure superheated steam for recycling.

[0049] The present invention also provides the application of the above-described dehydrogenation device in the dehydrogenation of cyclohexane compounds to benzene compounds, for example, the application of the above-described dehydrogenation device in the dehydrogenation of methylcyclohexane to toluene.

[0050] Terminology Definitions and Explanations

[0051] This invention does not impose specific limitations on the temperature and pressure of the high-pressure superheated steam, as long as the temperature of the heat transfer medium after heat exchange is higher than the activation temperature of the dehydrogenation feedstock in the dehydrogenation reactor. For example, high pressure refers to a pressure not lower than 7.3 MPaG and a temperature not lower than 290°C; for example, a pressure of 7.3–15 MPaG and a temperature of 290–590°C; in one embodiment, it is superheated steam with a pressure of 12.5 MPaG and a temperature of 530°C.

[0052] The activation temperature in the dehydrogenation reactor is determined by the dehydrogenation feedstock, which includes, but is not limited to, olefins, alkanes, cycloalkanes, aromatics, alcohols, and amines; for example, cycloalkanes, such as cyclohexane or methylcycloalkanes.

[0053] Beneficial effects

[0054] This invention uses high-pressure superheated steam as a heat source to provide reaction heat for the dehydrogenation reaction, which has good economic efficiency and practicality compared with electric heating and fuel furnace heating.

[0055] The inventors also discovered that using high-pressure superheated steam to directly transfer heat to the dehydrogenation reaction feedstock would introduce the "high-pressure system" into the "low-pressure system" of dehydrogenation, which is detrimental to both equipment investment and process safety. Therefore, a heat transfer medium system was introduced to transfer heat from the high-pressure superheated steam to the dehydrogenation reaction feedstock through the heat transfer medium. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the dehydrogenation device and dehydrogenation process in Example 1;

[0057] Figure 2 For high-pressure superheated steam in Figure 1 A schematic diagram of the heat exchange process in the middle;

[0058] Figures 1-2 The attached figure labels are:

[0059] 11 – Methylcyclohexane feed tank; 12 – Methylcyclohexane feed pump; 13 – Gas-liquid mixer; 14 – Feed and discharge heat exchangers; 15 – First-stage dehydrogenation feed superheater; 16 – First-stage dehydrogenation reactor; 17 – Second-stage dehydrogenation feed superheater; 18 – Second-stage dehydrogenation reactor; 19 – Air cooler; 20 – Water cooler; 21 – Gas-liquid separator; 22 – Circulating hydrogen compressor; 23 – Hydrogen compressor; 24 – Toluene product tank;

[0060] 41 - First-stage heat transfer oil tank; 51 - Second-stage heat transfer oil tank; 42 - First-stage heat transfer oil circulation pump; 52 - Second-stage heat transfer oil circulation pump; 43 - First-stage heat transfer oil heater; 53 - Second-stage heat transfer oil heater;

[0061] 103 – Methylcyclohexane feed; 114 – Recycled hydrogen; 104 – Mixed feedstock; 105 – Gasified feedstock; 106 – Feedstock to the first dehydrogenation reactor; 107 – Incompletely converted dehydrogenated feedstock from the outlet of the first-stage dehydrogenation reactor; 108 – Feedstock to the second-stage dehydrogenation reactor; 109 – Dehydrogenated product; 110 – Dehydrogenated product after preliminary cooling; 111 – Dehydrogenated product after air cooling; 112 – Dehydrogenated product after water cooling; 113 – Recycled hydrogen to the compressor; 114 – Compressed recycled hydrogen; 115 – Reaction dehydrogenation to the hydrogen compressor; 116 – Pressurized hydrogen product; 117 – Cooled and separated toluene; 118 – Compressed and condensed separated toluene; 119 – Toluene product; 120 – Toluene exit zone;

[0062] 201, 211 – Thermal oil goes to thermal oil pump; 202, 212 – Thermal oil goes to thermal oil heater; 203, 213 – Thermal oil goes to dehydrogenation reactor; 204, 214 – Thermal oil goes to dehydrogenation feed superheater; 205, 215 – Thermal oil goes to thermal oil tank.

[0063] 30 - High-pressure superheated steam pipeline; 301 - High-pressure superheated steam; 302 - High-temperature and high-pressure steam; 303 - High-pressure saturated condensate.

[0064] Figure 3 This is a schematic diagram of the dehydrogenation process for Comparative Example 1;

[0065] Figure 3 Figure label:

[0066] 11' – Methylcyclohexane feed tank; 12' – Methylcyclohexane feed pump; 13' – Gas-liquid mixer; 14' – Feed and discharge heat exchangers; 15' – Phase change superheater; 16' – Superheated steam superheater; 17'–23' – Multistage dehydrogenation reactor; 24' – Air cooler; 25' – Water cooler; 26' – Gas-liquid separator; 27' – Circulating hydrogen compressor; 28' – Hydrogen compressor; 29' – Toluene product tank;

[0067] 101'-Methylcyclohexane; 103'-Methylcyclohexane feed; 111'-Recycled hydrogen; 104'-Mixed feedstock; 105'-Preheated reaction system feed; 106'-Reaction system discharge; 107'-Dehydrogenated product after initial cooling; 108'-Dehydrogenated product after air cooling; 109'-Dehydrogenated product after water cooling; 110'-Recycled hydrogen to compressor; 111'-Recycled hydrogen; 112'-Reaction dehydrogenation to hydrogen compressor; 113'-Cooled separation of toluene; 114'-Compression and condensation separation of toluene; 115'-Reaction product exit zone; 116'-Toluene exit zone.

[0068] Figure 4 This is a schematic diagram of the dehydrogenation process in Comparative Example 2;

[0069] Figure 4 Figure label:

[0070] 11” – Methylcyclohexane feed tank; 12” – Methylcyclohexane feed pump; 13” – Gas-liquid mixer; 14” – Feed and discharge heat exchangers; 15” – Raw material superheater A; 16” – Dehydrogenation reactor; 19” – Air cooler; 20” – Water cooler; 21” – Gas-liquid separator; 22” – Circulating hydrogen compressor; 23” – Hydrogen compressor; 24” – Toluene product tank;

[0071] 21” – Thermal oil circulating pump; 31” – Natural gas boiler;

[0072] 101” – Methylcyclohexane; 103” – Methylcyclohexane feed; 114” – Recycled hydrogen; 104” – Mixed feedstock; 105” – Gasified feedstock; 106” – Dehydrogenation reactor feed; 109” – Dehydrogenation product; 110” – Dehydrogenation product after initial cooling; 111” – Dehydrogenation product after air cooling; 112” – Dehydrogenation product after water cooling; 113” – Recycled hydrogen to compressor; 114” – Compressed recycled hydrogen; 115” – Reaction dehydrogenation to hydrogen compressor; 116” – Pressurized hydrogen product; 117” – Cooled and separated toluene; 118” – Compressed and condensed separated toluene; 120” – Toluene product exit zone. Detailed Implementation

[0073] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0074] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0075] Example 1

[0076] Figure 1 A schematic diagram of the structure and process flow of the dehydrogenation unit used to produce toluene from methylcyclohexane. The dehydrogenation unit includes:

[0077] The system consists of a methylcyclohexane feed tank 11, a methylcyclohexane feed pump 12, a gas-liquid mixer 13, an inlet / outlet heat exchanger 14, a first-stage dehydrogenation feed superheater 15, a first-stage dehydrogenation reactor 16, a second-stage dehydrogenation feed superheater 17, a second-stage dehydrogenation reactor 18, a first-stage heat transfer oil tank 41, a first-stage heat transfer oil circulation pump 42, and a first-stage heat transfer oil heater 43, a second-stage heat transfer oil tank 51, a second-stage heat transfer oil circulation pump 52, and a second-stage heat transfer oil heater 53, as well as a high-pressure superheated steam pipeline 30.

[0078] The high-pressure superheated steam pipeline 30, the second-stage thermal oil heater 53 and the first-stage thermal oil heater 43 are connected in series, that is, the high-pressure superheated steam exchanges heat with the thermal oil, thereby using the high-pressure superheated steam as the heat source of the dehydrogenation reactor.

[0079] The first-stage thermal oil heater 43 is connected to the first-stage dehydrogenation reactor 16, and the second-stage thermal oil heater 53 is connected to the second-stage dehydrogenation reactor 18. The thermal oil heater is used to supply heat to the dehydrogenation reactor. The heating medium outlet of the second-stage thermal oil heater 53 outputs high-pressure steam at near-saturation temperature, and the heating medium outlet of the first-stage thermal oil heater 43 outputs high-pressure saturated condensate.

[0080] The heat transfer medium outlet of each dehydrogenation reactor is connected to the heat transfer medium inlet of the corresponding dehydrogenation feed superheater.

[0081] One implementation of the heat transfer oil system is as follows (i.e.) Figure 1 As shown):

[0082] The first-stage heat transfer oil tank 41, the first-stage heat transfer oil circulation pump 42, the first-stage heat transfer oil heater 43, the first-stage dehydrogenation reactor 16, and the first-stage dehydrogenation feed superheater 15 are connected in sequence, forming a heat transfer oil loop, i.e., a low-temperature heat transfer oil system.

[0083] The second-stage heat transfer oil tank 51, the second-stage heat transfer oil circulation pump 52, the second-stage heat transfer oil heater 53, the second-stage dehydrogenation reactor 18, and the second-stage dehydrogenation feedstock superheater 17 are connected in sequence, forming a heat transfer oil loop, i.e., a high-temperature heat transfer oil system.

[0084] Another implementation of the heat transfer oil system is as follows (i.e.) Figure 2 As shown):

[0085] There is no need to install a second-stage heat transfer oil tank 51. Instead, a heat transfer oil pipeline connected to the second-stage heat transfer oil circulation pump 52 is installed on the connecting pipeline between the first-stage heat transfer oil heater 43 and the first-stage dehydrogenation reactor 16. The heat transfer medium outlet of the second-stage dehydrogenation feed superheater 17 is connected to the connecting pipeline between the first-stage heat transfer oil heater 43 and the first-stage dehydrogenation reactor 16. Figure 2 It is a series system of low-temperature heat transfer oil and high-temperature heat transfer oil.

[0086] The dehydrogenation unit also includes a cooling and separation section for toluene products (one exemplary embodiment): an air cooler 19, a water cooler 20, and a gas-liquid separator 21, in addition to the feed and discharge heat exchanger 14 (the disclosure of the prior application is incorporated herein by reference in its entirety according to Chinese Patent Application No. 202311591408.6 filed on November 27, 2023); and a circulating hydrogen compressor 22, a hydrogen compressor 23, and a toluene product tank 24 connected to the cooling and separation section.

[0087] The specific dehydrogenation process is as follows:

[0088] Methylcyclohexane 101 from the boundary area is fed into the methylcyclohexane feed tank 11, where it is mixed with circulating hydrogen 114 pressurized by the methylcyclohexane feed pump 12 and the circulating hydrogen compressor 22. The mixed feedstock 104 is heated and vaporized by exchanging heat with the dehydrogenation product 109 in the feed-in-feed heat exchanger 14. The vaporized feedstock 105 enters the first-stage dehydrogenation feedstock superheater 15, and the feedstock 106 of the first dehydrogenation reactor (i.e., the mixture of superheated methylcyclohexane and hydrogen) is sent to the first-stage dehydrogenation reactor 16.

[0089] The incompletely converted dehydrogenated feedstock 107 from the outlet of the first-stage dehydrogenation reactor enters the second-stage dehydrogenation feedstock superheater 17. It is then sent to the second-stage dehydrogenation reactor 18.

[0090] The dehydrogenated product 109 from the outlet of the second-stage dehydrogenation reactor 18, after heat exchange and cooling with the mixed feedstock 104, passes through air cooler 19 (to obtain air-cooled dehydrogenated product 111) and water cooler 20 (to obtain water-cooled dehydrogenated product 112) before being sent to gas-liquid separator 21 to obtain cooled and separated toluene 117. A small portion of the separated gas (i.e., recycled hydrogen to compressor 113) is pressurized by recycled hydrogen compressor 22 (compressed recycled hydrogen 114) and mixed with methylcyclohexane feedstock 103, then returned to the reaction system; a large amount of hydrogen (i.e., reaction dehydrogenation to hydrogen compressor 115) is pressurized by hydrogen compressor 23 (i.e., pressurized hydrogen product 116) and sent out of the unit. Hydrogen compressor 23 compresses and condenses the separated toluene 118 and cooled and separated toluene 117 to form toluene product 119, which is sent to toluene product tank 24 and then to toluene exit zone 120. The toluene product is then discharged from the unit.

[0091] Figure 1 The heat exchange process of the heat transfer oil system shown is as follows: The low-temperature and high-temperature heat transfer oils (i.e., heat transfer oil to heat transfer oil pumps 201 and 211) in the first-stage heat transfer oil tank 41 and the second-stage heat transfer oil tank 51 are respectively sent to the first-stage and second-stage heat transfer oil heaters 43 and 53 through the first-stage and second-stage heat transfer oil pumps 42 and 52 (i.e., heat transfer oil to heat transfer oil heaters 202 and 212);

[0092] High-pressure superheated steam 301 first heats the thermal oil in the second-stage thermal oil heater, cooling the high-pressure steam to near saturation temperature to obtain high-temperature high-pressure steam 302. The high-temperature high-pressure steam 302 then heats the low-temperature thermal oil in the first-stage thermal oil heater, condensing into high-pressure saturated condensate 303. The high-pressure saturated condensate 303 is then pumped back to the high-pressure boiler via a high-temperature water pump to generate superheated steam again. The thermal oil after heat exchange in the first and second-stage thermal oil heaters 43 and 53 (i.e., thermal oil goes to dehydrogenation reactors 203 and 213) is sent to the first-stage dehydrogenation reactor 16 and the second-stage dehydrogenation reactor 18, respectively, and then to the first-stage dehydrogenation feed superheater 15 and the second-stage dehydrogenation feed superheater 17 (i.e., thermal oil goes to dehydrogenation feed superheaters 15 and 17), finally returning to the first-stage thermal oil tank 41 and the second-stage thermal oil tank 51 (i.e., thermal oil goes to thermal oil troughs 205 and 215).

[0093] Figure 2 The heat exchange process of the heat transfer oil system is described as follows: The heat transfer oil in the first-stage heat transfer oil tank 41 is pressurized by the first-stage heat transfer oil pump 42 and then sent to the first-stage heat transfer oil heater 43. Most of the heated heat transfer oil is sent to the first-stage dehydrogenation reactor 16, and a small portion of the heat transfer oil is pressurized by the second-stage heat transfer oil pump 52 and then sent to the second-stage heat transfer oil heater 53. The heated high-temperature heat transfer oil is cooled by passing through the second-stage dehydrogenation reactor 18 and the second-stage dehydrogenation feed superheater 17, and then sent to the shell side of the first-stage dehydrogenation reactor 16, where it mixes with the low-temperature heat transfer oil and together supplies heat to the first-stage dehydrogenation reactor 16.

[0094] High-pressure superheated steam 301 first heats the thermal oil in the second-stage thermal oil heater, cooling the high-pressure steam to near saturation temperature to obtain high-temperature high-pressure steam 302. This high-temperature high-pressure steam then heats the low-temperature thermal oil in the first-stage thermal oil heater, condensing into high-pressure saturated condensate 303. The high-pressure saturated condensate is then pumped back to the high-pressure boiler by a high-temperature water pump to generate superheated steam again.

[0095] Table 1. Main Logistics Data for Example 1

[0096] Logistics Number 103 104 106 109 113 114 116 120 Temperature (°C) 40.1 48.4 315.0 335.0 40.0 126.4 40.0 40.0 Pressure (MPaG) 0.35 0.24 0.24 0.06 0.04 0.24 2.50 0.04 Mass flow rate (kg / h) 10682 11059 11059 11059 377 377 718 9964 hydrogen 0.00％ 0.89％ 0.89％ 6.43％ 26.19％ 26.19％ 85.26％ 0.00％ CxHy 0.00％ 0.00％ 0.00％ 0.01％ 0.04％ 0.04％ 0.14％ 0.00％ Toluene 0.00％ 2.26％ 2.26％ 86.65％ 66.42％ 66.42％ 11.96％ 92.79％ Methylcyclohexane 100.0％ 96.84％ 96.84％ 6.86％ 7.27％ 7.27％ 2.56％ 7.16％ impurities 0.00％ 0.00％ 0.00％ 0.05％ 0.09％ 0.09％ 0.08％ 0.05％

[0097] use Figure 1 The heat exchange process, heat transfer oil, and high-pressure steam logistics data are shown in Table 1-1 below:

[0098] Logistics Number 201 202 203 204 205 211 212 Temperature (°C) 321.0 321.2 325.0 321.7 321.0 324.3 324.5 Pressure (MPaG) 1.00 1.50 1.00 1.00 1.00 1.00 1.50 Mass flow rate (t / h) 1838 1838 1838 1838 1838 180 180 heat transfer oil 100％ 100％ 100％ 100％ 100％ 100％ 100％ High-pressure steam / water 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ 0.00％

[0099] Logistics Number 213 214 215 301 302 303 Temperature (°C) 340.0 324.5 324.3 530.0 358.0 328.1 Pressure (MPaG) 1.00 1.00 1.00 12.50 12.50 12.50 Mass flow rate (t / h) 180 180 180 12.6 12.6 12.6 heat transfer oil 100％ 100％ 100％ 0.00％ 0.00％ 0.00％ High-pressure steam / water 0.00％ 0.00％ 0.00％ 100％ 100％ 100％

[0100] use Figure 2 The heat exchange process, heat transfer oil, and high-pressure steam logistics data are shown in Table 1-2 below:

[0101]

[0102]

[0103] Logistics Number 213 214 215 301 302 303 Temperature (°C) 340.0 324.5 324.3 530.0 361.3 327.0 Pressure (MPaG) 1.00 1.00 1.00 12.50 12.50 12.50 Mass flow rate (t / h) 180 180 180 12.6 12.6 12.6 heat transfer oil 100％ 100％ 100％ 0.00％ 0.00％ 0.00％ High-pressure steam / water 0.00％ 0.00％ 0.00％ 100％ 100％ 100％

[0104] Comparative Example 1

[0105] Methylcyclohexane 101' from the boundary area is fed into methylcyclohexane feed tank 11', where it is mixed with circulating hydrogen 111' pressurized by methylcyclohexane feed pump 12' and circulating hydrogen compressor 27'. The mixed feedstock 104' exchanges heat with the reaction system discharge 106' in feed-discharge heat exchanger 14', increasing its temperature and vaporizing it. The resulting preheated reaction system feedstock 105' enters phase change superheater 15' and superheated steam superheater 16'. The feedstock that has reached the superheated temperature is then sent to multi-stage dehydrogenation reactors 17' to 23'.

[0106] After dehydrogenation from the reactor, the dehydrogenated product and feedstock are cooled by heat exchange in the feed heat exchanger 14', and then sent to the air cooler 24' and water cooler 25' for further cooling before being sent to the gas-liquid separator 26'. A small portion of the separated gas is pressurized by the circulating hydrogen compressor 27' and mixed with the methylcyclohexane feed 103', then returned to the reaction system; the majority of the hydrogen is pressurized by the hydrogen compressor 28' and sent out of the unit. The hydrogen compressor 28' sends the condensed toluene 114' to the toluene product tank 29'. The final toluene product is sent out of the unit, i.e., the toluene exit zone 116'.

[0107] Phase change superheater 15' and superheated steam superheater 16' are connected in series. The raw materials and dehydrogenation products from different stage reaction outlets are sent to the above heat exchangers for superheating and then sent to the multi-stage dehydrogenation reactors 17' to 23'.

[0108] Superheated steam 301' from the boundary zone is cooled to near saturation temperature in superheated steam superheater 16'. It then condenses into saturated condensate in phase change superheater 15'. The saturated condensate is pressurized by a pump and sent back to the high-pressure boiler system.

[0109] See flowchart Figure 3 .

[0110] Table 2 Comparative Example 1 Main Logistics Data Table

[0111]

[0112]

[0113] Logistics Number 301’ 302’ 303’ Temperature (°C) 530.0 358.0 328.1 Pressure (MPaG) 12.50 12.50 12.50 Mass flow rate (t / h) 10.5 10.5 10.5 High-pressure steam / water 100％ 100％ 100％

[0114] Table 2-1 Comparison of processes between Example 1 and Comparative Example 1

[0115] Example 1 Comparative Example 1 MCH processing capacity t / a 85456 85456 Hydrogen production of the unit t / a 4897 3836.96 MCH conversion rate 100wt% 92.90％ 72.20％ Steam consumption per ton of hydrogen t / t 20.58 21.89

[0116] Both Example 1 and Comparative Example 1 used the same dehydrogenation catalyst and heat source (12.5 MPaG, 530°C superheated steam). This embodiment of the invention uses a low-temperature reactor connected in series with a high-temperature reactor, which better utilizes the energy of the high-pressure superheated steam, enabling the reaction to achieve a higher conversion rate; furthermore, the process setup is simpler, requiring fewer reactors. Comparative Example 1 referenced a continuous reforming process, using an adiabatic fixed-bed reactor, with high-pressure steam as the heat source for the preheater before the reaction.

[0117] Comparative Example 1 has a conversion rate that is much lower than that of Example 1, resulting in lower energy efficiency and economic efficiency of the process compared to Example 1. Furthermore, its low conversion rate also leads to larger equipment size and higher investment costs.

[0118] Comparative Example 2

[0119] This comparative example will use natural gas as the heat source and heat transfer oil (or molten salt) as the heat transfer medium to provide heat to the dehydrogenation reactor.

[0120] Methylcyclohexane 101” from the boundary area is fed into methylcyclohexane feed tank 11”, and mixed with circulating hydrogen 114” pressurized by methylcyclohexane feed pump 12” and circulating hydrogen compressor 22”. After mixing, raw material 104” exchanges heat with dehydrogenation product 109” in feed heat exchanger 14” to increase temperature and vaporize. The vaporized raw material 105” enters dehydrogenation feed superheater 15”, and dehydrogenation reactor feed (i.e., the mixture of superheated methylcyclohexane and hydrogen) 106” is sent to dehydrogenation reactor 16.

[0121] The dehydrogenated product 109” from the outlet of the dehydrogenation reactor 16” is cooled by heat exchange with the mixed feedstock 104” and then sent to the gas-liquid separator 21” after passing through the air cooler 19” and the water cooler 20” respectively. A small portion of the separated gas is pressurized by the circulating hydrogen compressor 22” and mixed with the methylcyclohexane feedstock 103”, and then returned to the reaction system; a large amount of hydrogen is pressurized by the hydrogen compressor 23” and sent out of the unit. The hydrogen compressor 23” sends the condensed and separated toluene 118” to the toluene product tank 24”. The final toluene product is sent out of the unit, namely the toluene product exit zone 120.

[0122] See flowchart Figure 4 .

[0123] Table 3 Comparative Example 2: Key Logistics Data

[0124] Logistics Number 103” 104” 106” 109” 113” 114” 116” 120” Temperature (°C) 40.1 48.4 320.0 320.0 40.0 126.6 40.0 40.0 Pressure (MPaG) 0.35 0.24 0.07 0.06 0.04 0.24 2.50 0.04 Mass flow rate (kg / h) 10682 11057 11057 11057 375 375 724 9958 hydrogen 0.00％ 0.89％ 0.89％ 6.50％ 26.34％ 26.34％ 85.54％ 0.00％ CxHy 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ Toluene 0.00％ 2.29％ 2.29％ 87.69％ 67.49％ 67.49％ 12.26％ 93.94％ Methylcyclohexane 100.00％ 96.82％ 96.82％ 5.81％ 6.18％ 6.18％ 2.20％ 6.06％ impurities 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ 0.00％

[0125] Table 3-1 Comparison of processes between Example 1 and Comparative Example 2

[0126] Example 1 Comparative Example 2 MCH processing capacity t / a 85456 85456 Hydrogen production of the unit t / a 4897 4957 MCH conversion rate 100wt% 92.90％ 94.00％ Steam consumption per ton of hydrogen t / t 20.58 Natural gas consumption per ton of hydrogen <![CDATA[Nm 3 / t]]> 1401

[0127] As shown in Table 3-1, Example 1, which uses high-pressure superheated steam as a heat source, achieves the same MCH conversion rate as Comparative Example 2, which uses natural gas as a heat source, and is also more economical: the unit price of high-pressure steam is 200 yuan / t, while the unit price of natural gas is 3.00 yuan / Nm³. 3 In terms of cost calculation, the heat source price for producing 1 ton of hydrogen in Example 1 is 4116 yuan, and the heat source price for producing 1 ton of hydrogen in Comparative Example 2 is 4208 yuan. That is, the heat source cost can be reduced by 9.2w per kt of hydrogen produced.

[0128] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A dehydrogenation apparatus characterized by comprising: The dehydrogenation device comprises: a first to N-stage dehydrogenation reactor in series, a first to N-stage heat transfer medium heater in series, and a high-pressure superheated steam delivery pipeline; the high-pressure superheated steam pipeline is connected with the N-stage heat transfer medium heater and exchanges heat with the heat transfer medium in each stage of the heat transfer medium heater; each stage of the heat transfer medium heater is connected with the corresponding stage of the dehydrogenation reactor; N≥2。 2. The dehydrogenation apparatus according to claim 1, characterized by the temperature of the heat transfer medium in the N-stage heat transfer medium heater is higher than the temperature of the heat transfer medium in the first-stage heat transfer medium heater; and / or, the temperature of the N-stage dehydrogenation reactor is higher than the temperature of the first-stage dehydrogenation reactor; and / or, 2≤N≤5; and / or, the heat transfer medium is a medium capable of satisfying heat transfer with high-pressure superheated steam.

3. The dehydrogenation apparatus according to claim 1, wherein From the first stage to the N-stage, the temperature of the heat transfer medium in the heat transfer medium heater gradually increases; and / or, from the first stage to the N-stage, the temperature of the dehydrogenation reactor gradually increases; and / or, N=2, 3 or 4; and / or, the heat transfer medium is heat conducting oil.

4. The dehydrogenation apparatus according to claim 1, wherein The dehydrogenation device comprises: two-stage dehydrogenation reactors in series, two-stage heat transfer medium heaters in series, and a high-pressure superheated steam delivery pipeline; the high-pressure superheated steam pipeline is connected with the second-stage heat transfer medium heater and is used for heating the heat transfer medium in each stage of the heat transfer medium heater; the temperature of the heat transfer medium in the second-stage heat transfer medium heater is higher than the temperature of the heat transfer medium in the first-stage heat transfer medium heater; the first-stage heat transfer medium heater is connected with the first-stage dehydrogenation reactor, the second-stage heat transfer medium heater is connected with the second-stage dehydrogenation reactor, and the heat transfer medium heater is used for supplying heat to the dehydrogenation reactor; the temperature of the second-stage dehydrogenation reactor is higher than the temperature of the first-stage dehydrogenation reactor.

5. The dehydrogenation apparatus according to any one of claims 1 to 3, characterized by The heating medium outlet of the N-stage heat transfer medium heater outputs high-pressure steam at a near-saturation temperature, which is connected with the heating medium inlet of the N-1-stage heat transfer medium heater through a pipeline; the heating medium outlet of the first-stage heat transfer medium heater outputs high-pressure saturated condensate.

6. The dehydrogenation apparatus according to any one of claims 1 to 5, characterized by The dehydrogenation device further comprises a high-pressure saturated condensate recycling device, one end of which is connected with the heating medium outlet of the first-stage heat transfer medium heater and the other end of which is connected with the high-pressure superheated steam pipeline; and / or, the high-pressure superheated steam pipeline is connected with a high-pressure superheated steam delivery device; and / or, the dehydrogenation device further comprises a first to N-stage dehydrogenation raw material superheater, which is arranged at the front end of the corresponding stage of the dehydrogenation reactor; preferably, the heat transfer medium outlet of each stage of the dehydrogenation reactor is connected with the heat transfer medium inlet of the corresponding stage of the dehydrogenation raw material superheater; and / or, the dehydrogenation device further comprises a heat transfer medium supply end; for example, the heat transfer medium supply end comprises a first to N-stage heat transfer medium supply end in parallel, each stage of the heat transfer medium supply end is sequentially connected with the corresponding stage of the heat transfer medium heater, the dehydrogenation reactor and the dehydrogenation raw material superheater, and the heat transfer medium forms a loop. For example, only one heat transfer medium supply end is provided, which is connected with the first-stage heat transfer medium circulating pump, the first-stage heat transfer medium heater, the first-stage dehydrogenation reactor and the first-stage dehydrogenation raw material superheater in sequence; a heat conducting oil pipeline connected with the second-stage heat transfer medium circulating pump is arranged on the connecting pipeline between the first-stage heat transfer medium heater and the first-stage dehydrogenation reactor, and the second-stage dehydrogenation raw material superheater heat transfer medium outlet is connected with the connecting pipeline between the first-stage heat transfer medium heater and the first-stage dehydrogenation reactor.

7. A dehydrogenation process characterized by, The dehydrogenation method comprises: supplying high-pressure superheated steam to the dehydrogenation reactor; Preferably, the high-pressure superheated steam exchanges heat with the heat transfer medium, and the heat transfer medium after heat exchange supplies heat to the dehydrogenation reactor; Preferably, the heat exchange with the heat transfer medium is carried out in a heat transfer medium heater; the number of the heat transfer medium heater and the dehydrogenation reactor is N, and N≥2, preferably 2≤N≤5.

8. The dehydrogenation process of claim 7, wherein, The high-pressure superheated steam sequentially passes through the Nth, N-1th,..., first-stage heat transfer medium heaters, and the heat transfer medium after heat exchange supplies heat to the dehydrogenation reactor of the corresponding stage; Preferably, the high-pressure superheated steam sequentially passes through the second-stage and first-stage heat transfer medium heaters, and the heat transfer medium after heat exchange supplies heat to the dehydrogenation reactor of the corresponding stage; Preferably, the temperature of the heat transfer medium after heat exchange is higher than the activation temperature of the dehydrogenation raw material in the dehydrogenation reactor; Preferably, the pressure of the Nth-stage (for example, N=2, second-stage) dehydrogenation reactor is 50kpaG~80kpaG; And / or, the pressure of the high-pressure superheated steam is not less than 7.3MPaG, and the temperature is not less than 290℃.

9. The dehydrogenation method according to claim 7 or 8, characterized by, The heat transfer medium after heat exchange with the dehydrogenation reactor of each stage further enters the dehydrogenation raw material superheater of the corresponding stage for heat exchange; preferably, after heat exchange, it returns to the heat transfer medium supply end of the corresponding stage; Preferably, the dehydrogenation method comprises: The high-pressure superheated steam enters the second-stage heat transfer medium heater for heat exchange, and high-pressure steam close to saturation temperature and the second-stage heat transfer medium after heat exchange are obtained; The second-stage heat transfer medium after heat exchange enters the second-stage dehydrogenation reactor for heat supply; The high-pressure steam close to saturation temperature enters the first-stage heat transfer medium heater for heat exchange, and high-pressure saturated condensate and the first-stage heat transfer medium after heat exchange are obtained; The first-stage heat transfer medium after heat exchange enters the first-stage dehydrogenation reactor for heat supply; Preferably, the second-stage heat transfer medium after heat supply to the second-stage dehydrogenation reactor enters the second-stage dehydrogenation raw material superheater, and the first-stage heat transfer medium after heat supply to the first-stage dehydrogenation reactor enters the first-stage dehydrogenation raw material superheater; further preferably, the heat transfer medium from each-stage dehydrogenation raw material superheater returns to the heat transfer medium supply end of the corresponding stage; Preferably, the high-pressure saturated condensate enters a high-pressure saturated condensate recycling device for recycling, and high-pressure superheated steam is generated for recycling; Preferably, the dehydrogenation method is carried out in the dehydrogenation device of any one of claims 1-6.

10. The dehydrogenation device of any one of claims 1-6 or the dehydrogenation method of any one of claims 7-9 is applied in the dehydrogenation of cyclohexane compounds to produce benzene compounds, for example, the dehydrogenation device or the dehydrogenation method is applied in the dehydrogenation of methylcyclohexane to produce toluene.

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