Naphtha aromatization and dehydrogenation reaction in and out material heat exchange process and system

Abstract

The application relates to the technical field of petroleum chemical industry, and discloses a naphtha aromatization and dehydrogenation reaction in-out material heat exchange process and system. The process comprises the following steps: S1, mixed aromatization: mixing naphtha raw materials and C5+ alkanes, and performing an aromatization reaction in an aromatization reactor under the condition of hydrogen to generate an aromatization reaction product containing aromatic hydrocarbon components, propane and butane; S2, separation: further cooling the aromatization reaction product obtained in S1, and then performing gas-liquid separation and rectification separation to obtain the aromatic hydrocarbon components; S3, mixing to form dehydrogenation feed; S4, common preheating; S5, dehydrogenation reaction; and S6, secondary separation. The heat exchange system comprises an aromatization reaction unit, a separation unit, a mixing unit, a multi-stream heat exchanger and a dehydrogenation reaction unit. The technical problem that the naphtha preparation is not provided with an aromatization unit, thereby lacking heat coupling between the aromatization separation product and the dehydrogenation, can be solved.

Description

Technical Field

[0001] This application relates to the field of petrochemical technology, and in particular to a heat exchange process and system for naphtha aromatization and dehydrogenation reactions of feed materials. Background Technology

[0002] Aromatics are important basic organic chemical raw materials, widely used in synthetic fibers, plastics, rubber, dyes, pharmaceuticals, and other fields. Naphtha aromatization technology can convert low-octane naphtha into high-octane gasoline components and aromatics under non-hydrogen-exposed or no precious metal catalyst conditions, while producing light hydrocarbons such as propane and butane as byproducts. In existing naphtha aromatization processes, the byproducts such as propane and butane are often only used for fuel combustion or sold at low value, failing to be fully utilized. Domestic refining and chemical enterprises produce liquefied petroleum gas (LPG) rich in propane and butane, and have abundant and inexpensive low-carbon alkane resources. The propane / butane dehydrogenation reaction is a strongly endothermic reaction, requiring high-temperature conditions of 550–620℃. In existing dehydrogenation processes, feed preheating mainly relies on fuel gas heaters or steam heaters, resulting in high energy consumption.

[0003] A search revealed a method and system for preparing naphtha in publication number CN117551472A. The method proposed to utilize low-value propane and butane resources to increase the weight of naphtha production through the coupling of alkane dehydrogenation and olefin fusion. However, the system architecture of this scheme includes an alkane dehydrogenation unit, a fusion unit, a separation unit, and a hydrogenation unit, but does not include an aromatization unit. Therefore, there is no thermal coupling between the aromatization separation product and the dehydrogenation. Summary of the Invention

[0004] One objective of this application is to provide a heat exchange process and system for the input and output of naphtha aromatization and dehydrogenation reactions, at least to solve the problem of lack of thermal coupling between aromatization separation products and dehydrogenation caused by the absence of an aromatization unit in the preparation of naphtha.

[0005] In a first aspect, this application provides a heat exchange process for the naphtha aromatization and dehydrogenation reaction of materials entering and exiting the reactor, employing the following technical solution:

[0006] A heat exchange process for naphtha aromatization and dehydrogenation reactions involving feed materials includes the following steps:

[0007] S1. Mixed Aromatization: Naphtha feedstock is mixed with C5+ alkanes and carried out in an aromatization reactor in the presence of hydrogen gas to generate aromatization reaction products containing aromatic components, propane and butane gas phase light hydrocarbon components.

[0008] S2. Separation: The aromatization reaction product obtained in S1 is heat-exchanged through a multi-flow heat exchanger and then further cooled before gas-liquid separation and distillation to obtain aromatic components, as well as propane, butane, methane, ethane and hydrogen components.

[0009] S3, Mixing to form dehydrogenation feed: The propane and butane components obtained from S2 separation, as well as the C3 and C4 alkanes separated from the dehydrogenation reaction products, are mixed with external liquefied petroleum gas to form a dehydrogenation mixed feed;

[0010] S4. Joint preheating: The aromatization reaction product stream from the outlet of the aromatization reactor described in S1 and the dehydrogenation reaction product stream from the outlet of the downstream dehydrogenation reactor are jointly introduced into the hot side of the multi-stream heat exchanger, and the dehydrogenation mixed feed formed in S3 is introduced into the cold side of the multi-stream heat exchanger. The high-temperature sensible heat of the aromatization reaction product and the dehydrogenation reaction product is used to preheat the dehydrogenation mixed feed.

[0011] S5, Dehydrogenation Reaction: The preheated dehydrogenated mixed feed from S4 is fed into the dehydrogenation reactor, where a dehydrogenation reaction is carried out under the action of a dehydrogenation catalyst to generate dehydrogenation reaction products containing C3 / C4 olefins.

[0012] S6. Secondary separation: The dehydrogenation product obtained in S5 is cooled by a multi-flow heat exchanger and then further cooled before gas-liquid separation and distillation to obtain C3 and C4 alkanes, hydrogen and olefin products.

[0013] By adopting the above technical solution, using naphtha and C5+ alkanes as aromatization reaction feedstocks, the aromatization conversion is completed in a hydrogen-containing gas atmosphere. At the same time, the aromatization reaction products and dehydrogenation reaction products are introduced into a multi-flow heat exchanger as dual heat sources to synergistically preheat the dehydrogenation mixed feedstock. This constructs a cross-unit thermal coupling system between the aromatization unit and the dehydrogenation unit, fully recovering the sensible heat of the two types of high-temperature reaction products and avoiding direct heat loss. Therefore, it achieves the effects of reducing external fuel consumption of the dehydrogenation unit, improving the overall thermal energy utilization rate of the entire process, and reducing heat waste.

[0014] Preferably, in step S1, the aromatization reaction conditions are: reaction temperature 350–550°C, reaction pressure 0.1–1.0 MPa, hydrogen to naphtha volume ratio 20–400, and mass hourly space velocity (WHSV) 0.2–1.5 h⁻¹. -1 .

[0015] By adopting the above technical solution, the temperature, pressure, hydrogen-to-oil volume ratio, and mass hourly space velocity parameters that match the kinetics of naphtha aromatization reaction are used to ensure the continuous and stable progress of the aromatization reaction, suppress the occurrence of side reactions, and stably generate the target reaction products containing aromatics, propane, and butane. Therefore, the aromatization reaction conversion rate meets the target, the product component distribution is stable, and qualified raw materials are provided for subsequent separation, purification, and dehydrogenation reactions.

[0016] Preferably, the catalyst used is a modified ZSM-5 molecular sieve catalyst, and the modifying element is selected from one or more of Ga, Zn, La, P or Fe.

[0017] By adopting the above technical solution, the ZSM-5 molecular sieve catalyst is modified with specific modifying elements to improve the acidic sites and pore structure of the catalyst, adapt to the reaction requirements of naphtha aromatization, and enhance the selectivity of the formation of aromatic and light hydrocarbon components. Therefore, the yield of the target product of the aromatization reaction is improved, the catalyst operation stability is enhanced, and the catalytic efficiency is maintained.

[0018] Preferably, in step S2, the specific process of the distillation separation is as follows: the gaseous light hydrocarbon components are sequentially passed through a propane removal tower and a butane removal tower to obtain propane with a purity ≥90% and butane with a purity ≥90%, respectively.

[0019] By adopting the above technical solution, the gaseous light hydrocarbons in the aromatization products are separated and purified stepwise by using a distillation process with a propane removal tower and a butane removal tower connected in series. High-purity propane and butane are accurately separated, and aromatic products that can be directly sold are obtained. Therefore, the separation efficiency of raw material components is improved, the purity of propane and butane meets the dehydrogenation feed standard, and the separation process is smoothly connected with the upstream and downstream production units.

[0020] Preferably, in step S3, before the dehydrogenated mixed feed enters the multi-stream heat exchanger, a light hydrocarbon precise hydrogen distribution step is also set: based on the real-time detected propane / butane ratio, hydrogen-rich dry gas is dynamically distributed.

[0021] By adopting the above technical solution, hydrogen-rich dry gas is dynamically added according to the real-time component ratio of propane and butane, so that the dehydrogenation mixed feed can simultaneously complete a mild pre-hydrogenation reaction during the heat exchange and heating process, removing trace amounts of diene-type dehydrogenation catalyst poisons in the feed, and realizing integrated heat exchange and feed purification. Therefore, the effects of reducing the risk of dehydrogenation catalyst poisoning, extending the catalyst operating cycle, and improving the long-term stability of the dehydrogenation reaction are achieved.

[0022] Preferably, in step S4, the multi-stream heat exchanger adopts a multi-stream stepped heat exchange structure, which divides the aromatization reaction products into multiple hot streams at different temperatures, and preheats the three cold streams of dehydrogenation mixed feed, dehydrogenation dilution steam and molten salt heat storage medium in stages, and allocates the flow rates of each branch to control the temperature of the dehydrogenation feed; wherein the temperature of the dehydrogenation mixed feed reaches 300-500°C after preheating.

[0023] By adopting the above technical solution, the high-temperature heat flow is split by using a multi-stream cascade heat exchange structure, and multiple cold flows are preheated in stages and the flow of each branch is dynamically distributed. At the same time, the high-temperature sensible heat is maximized to precisely control the dehydrogenation feed temperature, thereby realizing the cascade utilization of heat energy. Therefore, the system achieves improved heat energy recovery efficiency, more precise control of dehydrogenation feed temperature, and more reasonable heat energy distribution throughout the process.

[0024] Preferably, in step S4, the temperature of the preheated dehydrogenated mixed feed is controlled at 300–500°C.

[0025] By adopting the above technical solution, the dehydrogenation mixed feed is preheated to a temperature range suitable for subsequent supplementary heating, matching the load design requirements of the supplementary heater, and avoiding the impact of abnormal preheating temperature on subsequent heating processes. Therefore, the effects of controllable supplementary heater load, stable dehydrogenation feed heating process, and reduced system heat loss are achieved.

[0026] Preferably, before step S5, a supplementary heating step is also included: a supplementary heater is set after the multi-flow heat exchanger to raise the temperature of the preheated dehydrogenation mixed feed to the required 550-620°C at the inlet of the dehydrogenation reactor.

[0027] By adopting the above technical solution, the preheated feed is heated to the inlet temperature required for the dehydrogenation reaction by supplementing the heater, which meets the initial temperature conditions for the strongly endothermic dehydrogenation reaction and smoothly connects the preheating process and the dehydrogenation reaction process. Therefore, the dehydrogenation reaction inlet temperature meets the standard, the reaction starts smoothly, and the entire process is closely connected.

[0028] Preferably, in step S5, the dehydrogenation reaction conditions are: propane dehydrogenation reaction temperature 550–620°C, butane dehydrogenation reaction temperature 550–600°C, reaction pressure 0.1–0.5 MPa, and alkane mass hourly space velocity 0.1–5.0 h⁻¹. -1 .

[0029] By adopting the above technical solution, the reaction temperature, pressure and mass hourly space velocity parameters of propane and butane dehydrogenation conversion are adapted, and the reaction characteristics of the dehydrogenation catalyst are matched to ensure the efficient conversion of low-carbon alkanes into target olefin products. Therefore, the effects of improved dehydrogenation reaction conversion rate, increased olefin product yield and stable dehydrogenation reaction operation are achieved.

[0030] The second aspect involves the aromatization and dehydrogenation of naphtha entering and exiting the material heat exchange system.

[0031] A heat exchange system for naphtha aromatization and dehydrogenation reactions, comprising:

[0032] Aromatization reaction unit: includes an aromatization reactor, which is provided with a raw material inlet and a product outlet;

[0033] Separation unit: includes a gas-liquid separator and a distillation column, which are in fluid communication with the product outlet of the aromatization reactor, and are used to separate propane and butane from the aromatization reaction products;

[0034] Mixing unit: Used to mix propane and butane obtained from the separation unit with external LPG to form a dehydrogenated mixed feed;

[0035] Multi-stream heat exchanger: The hot-side inlet of the multi-stream heat exchanger is the product of the aromatization reactor, and the hot-side outlet enters the separation unit; the cold-side inlet is a mixture of propane, butane, and LPG, and the cold-side outlet stream is heated by a supplementary heater before entering the dehydrogenation reaction unit; an online dew point analyzer is installed before the hot-side inlet of the multi-stream heat exchanger, and a high-temperature resistant ceramic switching valve and a parallel steam generator are installed in the bypass of the heat exchanger; a light hydrocarbon precise hydrogen distribution module is installed on the pipeline before the dehydrogenation mixed feed enters the heat exchanger, the module including an online component analysis instrument and a proportional control valve; a dual thermal buffer module of phase change heat storage and fast response electrical compensation is coupled to the hot side of the heat exchanger; the entire system is equipped with an online analytical self-optimizing control module, which collects temperature, pressure, and component data in real time and adjusts the heat exchanger bypass valve, supplementary heater load, and heat storage and retrieval rate of the molten salt heat storage device accordingly;

[0036] Dehydrogenation reaction unit: includes a dehydrogenation reactor, used to dehydrogenate the preheated dehydrogenated mixed feed.

[0037] By adopting the above technical solution, the system integrates aromatization, separation, mixing, multi-stream heat exchange and dehydrogenation reaction units, and is equipped with dew point monitoring, bypass switching, hydrogen vaporization, thermal buffer and self-optimization control modules to achieve cross-unit thermal coupling and dynamic control of process parameters. At the same time, it prevents the risk of coking in heat exchangers and improves the storage and utilization of thermal energy. Therefore, it achieves the effects of improved system operation stability, efficient recovery and utilization of high-temperature thermal energy, extended service life of heat exchanger equipment and improved level of full-process automation control.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. This application introduces the aromatization reaction products from the naphtha aromatization reactor outlet and the dehydrogenation reaction products from the downstream dehydrogenation reactor outlet into the hot side of a multi-stream heat exchanger to preheat the dehydrogenation mixed feed formed by mixing propane, butane, and external LPG from the separation unit. Both the aromatization and dehydrogenation reactions are high-temperature processes, and the two products carry a large amount of heat. Through cross-unit thermal coupling, the heat energy lost during cooling is recovered and used to raise the temperature of the dehydrogenation feed, thereby reducing the external fuel consumption of the dehydrogenation unit's supplementary heater and improving the overall energy efficiency of the process.

[0040] 2. In this application, a multi-stream cascade heat exchange structure is preferably adopted, which divides the aromatization reaction products into multiple heat streams according to the temperature gradient. These streams preheat the dehydrogenation mixed feed, dehydrogenation dilution steam, and molten salt heat storage medium in stages. At the same time, the dew point temperature of the heavy fraction is monitored in real time by an online dew point analyzer. When the outlet temperature of the heat exchanger approaches the coking critical point, the high-temperature resistant ceramic switching valve is automatically opened to bypass some of the heat products to the parallel steam generator. The cascade heat exchange improves the heat recovery rate, while the bypass prevents coking and blockage of the heavy fraction, thus achieving the effect of balancing efficient heat exchange and long-term operation of the equipment.

[0041] 3. In this application, it is preferable to set up a light hydrocarbon precise hydrogen distribution module before the dehydrogenated mixed feed enters the heat exchanger. Based on the real-time detected propane / butane ratio, hydrogen-rich dry gas is dynamically distributed, so that the mixed feed undergoes a mild pre-hydrogenation reaction while being gradually heated and vaporized in the heat exchanger, removing trace amounts of diene and other dehydrogenation catalyst poisons. The heat exchange and feed purification are integrated into a pretreatment, thereby reducing the risk of dehydrogenation catalyst poisoning and extending the catalyst operating cycle.

[0042] 4. The method of this application acquires temperature, pressure and composition data in real time by configuring an online analysis self-optimization control module, dynamically adjusts the heat exchanger bypass valve, supplements the heating furnace load and the heat storage and retrieval rate of the molten salt heat storage device, and couples a phase change heat storage-fast response electrical compensation dual thermal buffer module to maintain the stability of the dehydrogenation feed temperature when the aromatic chemical conditions fluctuate or the dehydrogenation load changes abruptly. Therefore, it achieves the effects of improved process operation flexibility, improved level of full-process automation control and improved thermal energy cascade utilization. Attached Figure Description

[0043] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0044] Figure 1 This is a framework diagram of a heat exchange system for naphtha aromatization and dehydrogenation reactions of materials entering and exiting the reactor, as proposed in this application.

[0045] Figure 2 This is a flowchart of a heat exchange process for naphtha aromatization and dehydrogenation reactions of materials entering and exiting the reactor, as proposed in this application. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] Those skilled in the art will understand that the relevant naphtha preparation process proposes to utilize low-value propane and butane resources to achieve the purpose of increasing the weight of naphtha production through the coupling of alkane dehydrogenation and olefin chelation. However, the system architecture of this scheme includes an alkane dehydrogenation unit, a chelation unit, a separation unit, and a hydrogenation unit, but does not include an aromatization unit. Therefore, there is no thermal coupling between the aromatization separation product and dehydrogenation.

[0048] This application discloses a heat exchange process and system for naphtha aromatization and dehydrogenation reactions. It includes the following steps: S1, Mixed aromatization: Naphtha feedstock is mixed with C5+ alkanes and subjected to an aromatization reaction in an aromatization reactor in the presence of hydrogen gas to generate an aromatization reaction product containing aromatic components, propane, and butane gaseous light hydrocarbon components; S2, Separation: The aromatization reaction product obtained in S1 is subjected to heat exchange in a multi-stream heat exchanger, further cooled, and then subjected to gas-liquid separation and distillation to obtain aromatic components, as well as propane-butane, methane, ethane, and hydrogen components; S3, Mixing to form a dehydrogenation feedstock; S4, Co-preheating; S5, Dehydrogenation reaction; The heat exchange system includes: an aromatization reaction unit, a separation unit, a mixing unit, a multi-stream heat exchanger, and a dehydrogenation reaction unit.

[0049] This application introduces the aromatization reaction products from the naphtha aromatization reactor outlet and the dehydrogenation reaction products from the downstream dehydrogenation reactor outlet into the hot side of a multi-stream heat exchanger to preheat the dehydrogenation mixed feed formed by mixing propane, butane, and external LPG from the separation unit. Both the aromatization and dehydrogenation reactions are high-temperature processes, and the two products carry a large amount of heat. Through cross-unit thermal coupling, the heat energy lost during cooling is recovered and used to raise the temperature of the dehydrogenation feed, thereby reducing the external fuel consumption of the dehydrogenation unit's supplementary heater and improving the overall energy efficiency of the process.

[0050] Example 1: This example provides a heat exchange process for the naphtha aromatization and dehydrogenation reaction of feed materials, comprising the following steps:

[0051] S1. Mixed Aromatization: Naphtha feedstock is mixed with C5+ alkanes and subjected to an aromatization reaction in an aromatization reactor in the presence of hydrogen gas to generate an aromatization reaction product containing aromatic components, propane and butane gaseous light hydrocarbon components.

[0052] The aromatization reaction conditions were: reaction temperature 350°C, reaction pressure 0.1 MPa, hydrogen to naphtha volume ratio of 20, and mass hourly space velocity (HHSV) of 0.2 h⁻¹. -1 The catalyst used was a modified ZSM-5 molecular sieve catalyst, with Ga as the modifying element.

[0053] S2. Separation: The aromatization reaction product obtained in S1 is heat-exchanged through a multi-flow heat exchanger and then further cooled before gas-liquid separation and distillation to obtain aromatic components, as well as propane, butane, methane, ethane and hydrogen components.

[0054] The specific process of distillation separation is as follows: the gaseous light hydrocarbon components are passed sequentially through a propane removal tower and a butane removal tower to obtain propane with a purity of 90% and butane with a purity of 90% respectively.

[0055] S3, Mixing to form dehydrogenation feed: The propane and butane components obtained from S2 separation, as well as the C3 and C4 alkanes separated from the dehydrogenation reaction products, are mixed with external liquefied petroleum gas to form a dehydrogenation mixed feed.

[0056] Among them, a light hydrocarbon precise hydrogen distribution system is set up before the dehydrogenated mixed feed enters the multi-stream heat exchanger.

[0057] Step: Dynamically add hydrogen-rich dry gas based on the real-time measured propane to butane ratio.

[0058] S4. Joint Preheating: The aromatization reaction product stream from the aromatization reactor outlet in S1 and the dehydrogenation reaction product stream from the downstream dehydrogenation reactor outlet are jointly introduced into the hot side of the multi-stream heat exchanger, and the dehydrogenation mixed feed formed in S3 is introduced into the cold side of the multi-stream heat exchanger. The high-temperature sensible heat of the aromatization reaction product and the dehydrogenation reaction product is used to preheat the dehydrogenation mixed feed.

[0059] Among them, the multi-stream heat exchanger adopts a multi-stream stepped heat exchange structure, which divides the aromatization reaction products into multiple hot streams at different temperatures, and preheats the three cold streams of dehydrogenation mixed feed, dehydrogenation dilution steam and molten salt heat storage medium in stages and steps, and distributes the flow of each branch to control the temperature of the dehydrogenation feed; the temperature of the dehydrogenation mixed feed reaches 300°C after preheating.

[0060] The process includes a supplementary heating step before the preheated dehydrogenated mixed feed is fed into the dehydrogenation reactor: a supplementary heater is installed after the multi-flow heat exchanger to raise the temperature of the preheated dehydrogenated mixed feed to the required 550°C at the inlet of the dehydrogenation reactor.

[0061] S5, Dehydrogenation Reaction: The preheated dehydrogenated mixed feed from S4 is fed into the dehydrogenation reactor, where a dehydrogenation reaction is carried out under the action of a dehydrogenation catalyst to generate dehydrogenation reaction products containing C3 and C4 olefins.

[0062] The dehydrogenation reaction conditions were as follows: propane dehydrogenation reaction temperature 550°C, butane dehydrogenation reaction temperature 550°C, reaction pressure 0.1 MPa, and alkane mass hourly space velocity 0.1 h⁻¹. -1 .

[0063] S6. Secondary separation: The dehydrogenation product obtained in S5 is cooled by a multi-flow heat exchanger and then further cooled before gas-liquid separation and distillation to obtain C3 and C4 alkanes, hydrogen and olefin products.

[0064] Example 2: This example provides a heat exchange process for the naphtha aromatization and dehydrogenation reaction of feed materials, comprising the following steps:

[0065] S1. Mixed Aromatization: Naphtha feedstock is mixed with C5+ alkanes and subjected to an aromatization reaction in an aromatization reactor in the presence of hydrogen gas to generate an aromatization reaction product containing aromatic components, propane and butane gaseous light hydrocarbon components.

[0066] The aromatization reaction conditions were as follows: reaction temperature 450°C, reaction pressure 0.55 MPa, hydrogen to naphtha volume ratio 2:10, and mass hourly space velocity (HHSV) 0.85 h⁻¹. -1 The catalyst used was a modified ZSM-5 molecular sieve catalyst, with La and P as the modifying elements.

[0067] S2. Separation: The aromatization reaction product obtained in S1 is heat-exchanged through a multi-flow heat exchanger and then further cooled before gas-liquid separation and distillation to obtain aromatic components, as well as propane, butane, methane, ethane and hydrogen components.

[0068] The specific process of distillation separation is as follows: the gaseous light hydrocarbon components are passed sequentially through a propane removal tower and a butane removal tower to obtain propane with a purity of 95% and butane with a purity of 95%, respectively.

[0069] S3, Mixing to form dehydrogenation feed: The propane and butane components obtained from S2 separation, as well as the C3 and C4 alkanes separated from the dehydrogenation reaction products, are mixed with external liquefied petroleum gas to form a dehydrogenation mixed feed.

[0070] Among them, a light hydrocarbon precise hydrogen distribution system is set up before the dehydrogenated mixed feed enters the multi-stream heat exchanger.

[0071] Step: Dynamically add hydrogen-rich dry gas based on the real-time measured propane to butane ratio.

[0072] S4. Joint Preheating: The aromatization reaction product stream from the aromatization reactor outlet in S1 and the dehydrogenation reaction product stream from the downstream dehydrogenation reactor outlet are jointly introduced into the hot side of the multi-stream heat exchanger, and the dehydrogenation mixed feed formed in S3 is introduced into the cold side of the multi-stream heat exchanger. The high-temperature sensible heat of the aromatization reaction product and the dehydrogenation reaction product is used to preheat the dehydrogenation mixed feed.

[0073] Among them, the multi-stream heat exchanger adopts a multi-stream stepped heat exchange structure, which divides the aromatization reaction products into multiple hot streams at different temperatures, and preheats the three cold streams of dehydrogenation mixed feed, dehydrogenation dilution steam and molten salt heat storage medium in stages and steps, and distributes the flow of each branch to control the temperature of the dehydrogenation feed; the temperature of the dehydrogenation mixed feed reaches 400°C after preheating.

[0074] The process includes a supplementary heating step before the preheated dehydrogenated mixed feed is fed into the dehydrogenation reactor: a supplementary heater is installed after the multi-stream heat exchanger to raise the temperature of the preheated dehydrogenated mixed feed to the required 585°C at the inlet of the dehydrogenation reactor.

[0075] S5, Dehydrogenation Reaction: The preheated dehydrogenated mixed feed from S4 is fed into the dehydrogenation reactor, where a dehydrogenation reaction is carried out under the action of a dehydrogenation catalyst to generate dehydrogenation reaction products containing C3 and C4 olefins.

[0076] The dehydrogenation reaction conditions were as follows: propane dehydrogenation reaction temperature 585°C, butane dehydrogenation reaction temperature 575°C, reaction pressure 0.3 MPa, and alkane mass hourly space velocity 2.55 h⁻¹. -1 .

[0077] S6. Secondary separation: The dehydrogenation product obtained in S5 is cooled by a multi-flow heat exchanger and then further cooled before gas-liquid separation and distillation to obtain C3 and C4 alkanes, hydrogen and olefin products.

[0078] Example 3: This example provides a heat exchange process for the naphtha aromatization and dehydrogenation reaction of feed materials, comprising the following steps:

[0079] S1. Mixed Aromatization: Naphtha feedstock is mixed with C5+ alkanes and subjected to an aromatization reaction in an aromatization reactor in the presence of hydrogen gas to generate an aromatization reaction product containing aromatic components, propane and butane gaseous light hydrocarbon components.

[0080] The aromatization reaction conditions were as follows: reaction temperature 550°C, reaction pressure 1.0 MPa, hydrogen to naphtha volume ratio 400, and mass hourly space velocity 1.5 h⁻¹. -1 The catalyst used was a modified ZSM-5 molecular sieve catalyst, with P and Fe as the modifying elements.

[0081] S2. Separation: The aromatization reaction product obtained in S1 is heat-exchanged through a multi-flow heat exchanger and then further cooled before gas-liquid separation and distillation to obtain aromatic components, as well as propane, butane, methane, ethane and hydrogen components.

[0082] The specific process of distillation separation is as follows: the gaseous light hydrocarbon components are passed sequentially through a propane removal tower and a butane removal tower to obtain propane with a purity of 99% and butane with a purity of 99% respectively.

[0083] S3, Mixing to form dehydrogenation feed: The propane and butane components obtained from S2 separation, as well as the C3 and C4 alkanes separated from the dehydrogenation reaction products, are mixed with external liquefied petroleum gas to form a dehydrogenation mixed feed.

[0084] Among them, a light hydrocarbon precise hydrogen distribution system is set up before the dehydrogenated mixed feed enters the multi-stream heat exchanger.

[0085] Step: Dynamically add hydrogen-rich dry gas based on the real-time measured propane to butane ratio.

[0086] S4. Joint Preheating: The aromatization reaction product stream from the aromatization reactor outlet in S1 and the dehydrogenation reaction product stream from the downstream dehydrogenation reactor outlet are jointly introduced into the hot side of the multi-stream heat exchanger, and the dehydrogenation mixed feed formed in S3 is introduced into the cold side of the multi-stream heat exchanger. The high-temperature sensible heat of the aromatization reaction product and the dehydrogenation reaction product is used to preheat the dehydrogenation mixed feed.

[0087] Among them, the multi-stream heat exchanger adopts a multi-stream stepped heat exchange structure, which divides the aromatization reaction products into multiple hot streams at different temperatures, and preheats the three cold streams of dehydrogenation mixed feed, dehydrogenation dilution steam and molten salt heat storage medium in stages and steps, and distributes the flow of each branch to control the temperature of the dehydrogenation feed; the temperature of the dehydrogenation mixed feed reaches 500°C after preheating.

[0088] The process includes a supplementary heating step before the preheated dehydrogenated mixed feed is fed into the dehydrogenation reactor: a supplementary heater is installed after the multi-stream heat exchanger to raise the temperature of the preheated dehydrogenated mixed feed to the required 620°C at the inlet of the dehydrogenation reactor.

[0089] S5, Dehydrogenation Reaction: The preheated dehydrogenated mixed feed from S4 is fed into the dehydrogenation reactor, where a dehydrogenation reaction is carried out under the action of a dehydrogenation catalyst to generate dehydrogenation reaction products containing C3 and C4 olefins.

[0090] The dehydrogenation reaction conditions were as follows: propane dehydrogenation reaction temperature 620°C, butane dehydrogenation reaction temperature 600°C, reaction pressure 0.5 MPa, and alkane mass hourly space velocity 5.0 h⁻¹. -1 .

[0091] S6. Secondary separation: The dehydrogenation product obtained in S5 is cooled by a multi-flow heat exchanger and then further cooled before gas-liquid separation and distillation to obtain C3 and C4 alkanes, hydrogen and olefin products.

[0092] Comparative Example 1: This comparative example refers to the content of Example 1, except that the temperature of the aromatization reaction in step S1 is 250°C, and the rest is the same as Example 1.

[0093] Comparative Example 2: This comparative example refers to the content of Example 1, except that the volume ratio of hydrogen to naphtha in step S1 is 30, and the rest is the same as Example 1.

[0094] Comparative Example 3: This comparative example refers to the content of Example 1, except that the temperature of the dehydrogenated mixed feed in step S4 after preheating is 200°C, and the rest is the same as Example 1.

[0095] Comparative Example 4: This comparative example refers to the content of Example 1, except that the propane dehydrogenation reaction temperature in step S5 is 400°C, and the rest is the same as Example 1.

[0096] Comparative Example 5: This comparative example refers to Example 1, except that the alkane mass hourly space velocity (HHSV) in step S5 is 0.3 h⁻¹. -1 The rest of the content is the same as in Example 1.

[0097] Comparative Example 6: This comparative example refers to the content of Example 1, except that the purity of the propane obtained by distillation separation in step S2 is 60%, and the rest is the same as Example 1.

[0098] Performance testing

[0099] Sample preparation: Process streams and catalyst samples from Examples 1 to 3 and Comparative Examples 1 to 6 after 500 hours of continuous and stable operation were selected as the test objects. The gas phase products were collected at regular intervals using an online gas chromatograph, while the liquid phase aromatic components and solid catalysts were collected through on-site sampling ports and sealed for preservation. All samples were sent to the laboratory for analysis within 30 minutes after collection to ensure that the data represent the actual operating status of the process.

[0100] Comprehensive process energy efficiency testing: Data on fuel gas flow rate consumed by the supplementary heater in each embodiment and comparative example were collected, and combined with the total feed amount of the dehydrogenation mixed feed, the external fuel consumption required per unit mass of feed was calculated. By comparing the energy consumption differences under different process conditions, the contribution of cross-unit thermal coupling to reducing external fuel consumption was verified. The test standard for this performance parameter was carried out in accordance with GB / T2587 General Rules for Energy Balance of Energy-Consuming Equipment and GB / T3484 General Rules for Energy Balance of Enterprises.

[0101] Long-term operation performance testing of heat exchange equipment: During process operation, the pressure drop change at the cold side outlet of the multi-stream heat exchanger is continuously monitored, and the heat exchanger is disassembled after the operation cycle to check the coking and carbon buildup on the surface of the heat exchange tube bundle. By comparing the pressure drop growth rate and coking thickness under different process conditions, the role of the cascade heat exchange structure and bypass anti-coking mechanism in ensuring the long-term operation of the equipment is evaluated. The test standard for this performance parameter is in accordance with GB / T27698 Test Method for Performance of Heat Exchangers and Heat Transfer Elements.

[0102] Dehydrogenation catalyst stability testing: The initial activity of the catalyst in the dehydrogenation reaction unit under various process conditions and the activity retention rate after 500 hours of operation were recorded. By analyzing the selectivity changes of C3 and C4 olefins in the reaction products and the amount of carbon deposited on the catalyst, the effect of the precise hydrogenation step of light hydrocarbons on removing catalyst poisons and extending the operating cycle was verified. The test standard for this performance parameter was performed in accordance with the HG / T4855 method for testing the activity of catalysts for the dehydrogenation of cyclohexanol to cyclohexanone.

[0103] Process operation flexibility and thermal stability testing: Simulating the operation conditions of aromatization and the sudden change of dehydrogenation load within the range of 70% to 110%, the fluctuation amplitude of dehydrogenation feed temperature after the disturbance and the recovery time are recorded. By comparing the temperature control accuracy and response speed under different process conditions, the role of online analytical self-optimizing control module and thermal buffer module in maintaining system stability is evaluated. The test standards for this performance parameter are in accordance with the HG / T 20508 control room design specifications and GB50093 automation instrumentation engineering construction and quality acceptance specifications.

[0104] Table 1: Comparison of Performance Testing of Naphtha Aromatization and Dehydrogenation Processes

[0105]

[0106] Example Conclusion:

[0107] As can be seen from Examples 1-3 and Comparative Example 1, and Table 1, the appropriate aromatization reaction temperature is a crucial factor in ensuring the overall energy efficiency and system stability of the process. When the reaction temperature is within a reasonable range, it ensures that the aromatization product carries sufficient high-grade heat energy for downstream heat exchange, while avoiding incomplete reactions caused by low temperatures. This high-temperature reaction environment not only ensures the potential for heat recovery from the source but also reduces the amount of heavy components generated by side reactions, thereby effectively inhibiting coking in the heat exchange equipment, maintaining the high activity of the dehydrogenation catalyst, and improving the system's resistance to fluctuations.

[0108] As can be seen from Examples 1-3 and Comparative Example 2, and Table 1, the improved hydrogen to naphtha volume ratio plays a synergistic role in achieving energy saving and long-term operation of the process; a sufficient hydrogen atmosphere helps maintain the activity and stability of the catalyst, reduces carbon deposit formation, and thus reduces the pressure drop growth rate of the heat exchange network; at the same time, a suitable hydrogen partial pressure combined with a precise hydrogen distribution step removes impurities in the feed, prevents poisoning and deactivation of the dehydrogenation catalyst, thereby reducing the additional energy consumption required to maintain the reaction and enhancing the operational flexibility of the process.

[0109] As can be seen from Examples 1-3 and Comparative Example 3, and Table 1, the use of a multi-stream cascade heat exchange structure to preheat the dehydrogenation feed to a higher temperature is a factor in achieving cross-unit thermal coupling energy saving. This structure reduces the fuel load of the supplementary heater by efficiently recovering the high-temperature sensible heat of the aromatization and dehydrogenation reaction products. In addition, the cascade heat exchange combined with the bypass anti-coking mechanism avoids the condensation and coking of heavy fractions in the low-temperature zone, ensuring low resistance drop of the heat exchange equipment during long-term operation, thereby ensuring the sustainability of thermal energy utilization efficiency.

[0110] As can be seen from Examples 1-3 and Comparative Example 4, and Table 1, a suitable dehydrogenation reaction temperature has an impact on maintaining catalyst activity and system thermal stability. A reasonable reaction temperature can ensure the efficient conduction of the dehydrogenation reaction, reduce the recycling of unreacted materials and energy waste caused by insufficient temperature. At the same time, a stable high-temperature reaction environment, combined with preheating and hydrogen distribution at the front end, effectively suppresses the coking rate on the catalyst surface, enabling the catalyst to maintain high activity during long-term operation and reducing temperature shocks caused by fluctuations in operating conditions.

[0111] As can be seen from Examples 1-3 and Comparative Example 5, and Table 1, the improved alkane mass hourly space velocity achieves a balance between ensuring reaction efficiency and equipment operational stability. The appropriate space velocity ensures contact between reactants and catalyst while avoiding short-circuiting of materials and increased side reactions caused by excessively high flow rates. This balance not only reduces external fuel consumption per unit feed but also reduces catalyst carbon buildup and heat exchanger pressure drop caused by inappropriate reaction intensity, thereby improving the system's adaptability to load changes.

[0112] As can be seen from Examples 1-3 and Comparative Example 6, and Table 1, the combination of high-purity propane / butane feed with a precise hydrogenation step for light hydrocarbons improves the overall energy efficiency and catalyst life of the process; the high-purity feed reduces the heating energy consumption of ineffective components, while the dynamic addition of hydrogen-rich dry gas enables simultaneous feed vaporization and pre-hydrogenation purification; this integrated pretreatment removes trace amounts of poisons, reduces the risk of dehydrogenation catalyst poisoning, thereby maintaining low external fuel consumption, small equipment pressure drop, and excellent process thermal stability.

[0113] In some embodiments, a naphtha aromatization and dehydrogenation reaction feed-in / out heat exchange system is also provided for performing a naphtha aromatization and dehydrogenation reaction feed-in / out heat exchange process as described in any of the preceding embodiments, comprising:

[0114] Aromatization reaction unit: includes an aromatization reactor, which is provided with a raw material inlet and a product outlet;

[0115] Separation unit: includes a gas-liquid separator and a distillation column, which are in fluid communication with the product outlet of the aromatization reactor, and are used to separate propane and butane from the aromatization reaction products;

[0116] Mixing unit: Used to mix propane and butane obtained from the separation unit with external LPG to form a dehydrogenated mixed feed;

[0117] Multi-stream heat exchanger: The hot-side inlet of the multi-stream heat exchanger is the product of the aromatization reactor, and the hot-side outlet enters the separation unit; the cold-side inlet is a mixture of propane, butane, and LPG, and the cold-side outlet stream is heated by a supplementary heater before entering the dehydrogenation reaction unit; an online dew point analyzer is installed before the hot-side inlet of the multi-stream heat exchanger, and a high-temperature resistant ceramic switching valve and a parallel steam generator are installed in the bypass of the heat exchanger; a light hydrocarbon precise hydrogen distribution module is installed on the pipeline before the dehydrogenation mixed feed enters the heat exchanger, the module including an online component analysis instrument and a proportional control valve; a dual thermal buffer module of phase change heat storage and fast response electrical compensation is coupled to the hot side of the heat exchanger; the entire system is equipped with an online analytical self-optimizing control module, which collects temperature, pressure, and component data in real time and adjusts the heat exchanger bypass valve, supplementary heater load, and heat storage and retrieval rate of the molten salt heat storage device accordingly;

[0118] Dehydrogenation reaction unit: includes a dehydrogenation reactor, used to dehydrogenate the preheated dehydrogenated mixed feed.

[0119] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily made by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims, and the above embodiments should be regarded as exemplary and non-limiting.

Claims

1. A heat exchange process for naphtha aromatization and dehydrogenation reactions, characterized in that, Includes the following steps: S1. Mixed Aromatization: Naphtha feedstock is mixed with C5+ alkanes and carried out in an aromatization reactor in the presence of hydrogen gas to generate aromatization reaction products containing aromatic components, propane and butane gas phase light hydrocarbon components. S2. Separation: The aromatization reaction product obtained in S1 is heat-exchanged through a multi-flow heat exchanger and then further cooled before gas-liquid separation and distillation to obtain aromatic components, as well as propane, butane, methane, ethane and hydrogen components. S3, Mixing to form dehydrogenation feed: The propane and butane components obtained from S2 separation, as well as the C3 and C4 alkanes separated from the dehydrogenation reaction products, are mixed with external liquefied petroleum gas to form a dehydrogenation mixed feed; S4. Joint preheating: The aromatization reaction product stream from the outlet of the aromatization reactor described in S1 and the dehydrogenation reaction product stream from the outlet of the downstream dehydrogenation reactor are jointly introduced into the hot side of the multi-stream heat exchanger, and the dehydrogenation mixed feed formed in S3 is introduced into the cold side of the multi-stream heat exchanger. The high-temperature sensible heat of the aromatization reaction product and the dehydrogenation reaction product is used to preheat the dehydrogenation mixed feed. S5, Dehydrogenation reaction: The preheated dehydrogenated mixed feed from S4 is fed into the dehydrogenation reactor, where a dehydrogenation reaction is carried out under the action of a dehydrogenation catalyst to generate dehydrogenation reaction products containing C3 / C4 olefins. S6. Secondary separation: The dehydrogenation product obtained in S5 is cooled by a multi-flow heat exchanger and then further cooled before gas-liquid separation and distillation to obtain C3 and C4 alkanes, hydrogen and olefin products.

2. The naphtha aromatization and dehydrogenation reaction feed-in and feed-out heat exchange process according to claim 1, characterized in that, In step S1, the aromatization reaction conditions are: reaction temperature 350–550°C, reaction pressure 0.1–1.0 MPa, hydrogen to naphtha volume ratio 20–400, and mass hourly space velocity (HHSV) 0.2–1.5 h⁻¹. -1 .

3. The naphtha aromatization and dehydrogenation reaction heat exchange process for feed materials according to claim 1, characterized in that, The catalyst used is a modified ZSM-5 molecular sieve catalyst, and the modifying element is selected from one or more of Ga, Zn, La, P or Fe.

4. The naphtha aromatization and dehydrogenation reaction feed-in and feed-out heat exchange process according to claim 1, characterized in that, In step S2, the specific process of distillation separation is as follows: the gaseous light hydrocarbon components are passed sequentially through a propane removal tower and a butane removal tower to obtain propane with a purity ≥90% and butane with a purity ≥90%, respectively.

5. The naphtha aromatization and dehydrogenation reaction feed-in and feed-out heat exchange process according to claim 1, characterized in that, In step S3, before the dehydrogenated mixed feed enters the multi-stream heat exchanger, a light hydrocarbon precise hydrogen distribution step is set up: based on the real-time detected propane / butane ratio, hydrogen-rich dry gas is dynamically distributed.

6. The heat exchange process for naphtha aromatization and dehydrogenation reaction feed materials according to claim 1, characterized in that, In step S4, the multi-stream heat exchanger adopts a multi-stream stepped heat exchange structure, which divides the aromatization reaction products into multiple hot streams at different temperatures. These streams preheat the three cold streams—the dehydrogenation mixed feed, the dehydrogenation dilution steam, and the molten salt heat storage medium—in stages, and the flow rates of each branch are allocated to control the temperature of the dehydrogenation feed. The temperature of the dehydrogenation mixed feed reaches 300–500°C after preheating.

7. The naphtha aromatization and dehydrogenation reaction feed-in and feed-out heat exchange process according to claim 1, characterized in that, In step S4, the temperature of the preheated dehydrogenated mixed feed is controlled at 300–500°C.

8. The naphtha aromatization and dehydrogenation reaction feed-in and feed-out heat exchange process according to claim 1, characterized in that, Before step S5, a supplementary heating step is also included: a supplementary heater is set after the multi-flow heat exchanger to raise the temperature of the preheated dehydrogenation mixed feed to the required 550-620°C at the inlet of the dehydrogenation reactor.

9. The heat exchange process for naphtha aromatization and dehydrogenation reaction feed materials according to claim 1, characterized in that, In step S5, the dehydrogenation reaction conditions are as follows: propane dehydrogenation reaction temperature 550–620°C, butane dehydrogenation reaction temperature 550–600°C, reaction pressure 0.1–0.5 MPa, and alkane mass hourly space velocity 0.1–5.0 h⁻¹. -1 .

10. A heat exchange system for naphtha aromatization and dehydrogenation reactions, characterized in that, A heat exchange process for feed materials in a naphtha aromatization and dehydrogenation reaction as described in any one of claims 1-9, comprising: Aromatization reaction unit: includes an aromatization reactor, which is provided with a raw material inlet and a product outlet; Separation unit: includes a gas-liquid separator and a distillation column, which are in fluid communication with the product outlet of the aromatization reactor, and are used to separate propane and butane from the aromatization reaction products; Mixing unit: Used to mix propane and butane obtained from the separation unit with external LPG to form a dehydrogenated mixed feed; Multi-stream heat exchanger: The hot-side inlet of the multi-stream heat exchanger is the product of the aromatization reactor, and the hot-side outlet enters the separation unit; the cold-side inlet is a mixture of propane, butane, and LPG, and the cold-side outlet stream is heated by a supplementary heater before entering the dehydrogenation reaction unit; an online dew point analyzer is installed before the hot-side inlet of the multi-stream heat exchanger, and a high-temperature resistant ceramic switching valve and a parallel steam generator are installed in the bypass of the heat exchanger; a light hydrocarbon precise hydrogen distribution module is installed on the pipeline before the dehydrogenation mixed feed enters the heat exchanger, the module including an online component analysis instrument and a proportional control valve; a dual thermal buffer module of phase change heat storage and fast response electrical compensation is coupled to the hot side of the heat exchanger; the entire system is equipped with an online analytical self-optimizing control module, which collects temperature, pressure, and component data in real time and adjusts the heat exchanger bypass valve, supplementary heater load, and heat storage and retrieval rate of the molten salt heat storage device accordingly; Dehydrogenation reaction unit: includes a dehydrogenation reactor, used to dehydrogenate the preheated dehydrogenated mixed feed.

Images