Flash evaporation heat removal method and system for alkylation reaction product

Abstract

The embodiment of the invention provides a flash evaporation heat removal method and system for alkylation reaction products. The method comprises the following steps: separating an ionic liquid alkylation reaction product to obtain a hydrocarbon-rich phase and an ionic liquid-rich phase; the ion-rich liquid phase is atomized into liquid drops through a liquid spraying device or a dispersing device, the liquid drops are injected into a flash tank, all or part of hydrocarbons in the injected ion-rich liquid phase are flashed and vaporized into gas-phase hydrocarbons through pressure reduction, reaction heat is absorbed in the vaporization process, cooling of the non-vaporized ion-rich liquid phase is achieved, and a cooled ion-rich liquid phase is obtained; returning the cooled ion-rich liquid phase to the reactor for recycling; and gas-phase hydrocarbons are subjected to gas-liquid separation through a liquid separation tank, pressurized through a compressor and returned to the reactor for continuous reaction. The liquid drop atomization and flash evaporation technology is utilized, the heat exchange efficiency of the ionic liquid is remarkably improved, and meanwhile the cost of the heat exchanger is low.

Description

Technical Field

[0001] The present application relates to the field of petrochemical technology, and in particular to a flash evaporation heat extraction method and system for alkylation reaction products. Background Art

[0002] In the petroleum refining industry, alkylation reactions (such as the C4 alkylation of isobutane with butenes) are key processes for producing high-octane clean gasoline blending components. Traditional alkylation processes generally use anhydrous hydrofluoric acid (HF) or concentrated sulfuric acid as catalysts. While these strong acid catalysts exhibit excellent reactivity, selectivity, and longevity, they pose risks of highly toxic leaks, equipment corrosion, and severe environmental pollution, significantly limiting the safety and sustainability of the process and prompting the industry to urgently seek green alternative technologies.

[0003] To overcome the environmental and safety bottlenecks of traditional processes, ionic liquids are emerging as a new generation of catalytic systems. They offer advantages such as near-zero vapor pressure, low toxicity, low corrosiveness, tunable properties, easy separation from the product, and recyclability. They reduce pollution emissions and safety risks at the source, making them an ideal alternative.

[0004] However, due to the high viscosity and low thermal conductivity of ionic liquids, the heat generated during the reaction is difficult to effectively remove using traditional heat exchangers, such as shell-and-tube heat exchangers. High viscosity increases fluid flow resistance, which, combined with a low heat transfer coefficient, results in low heat transfer efficiency. To meet cooling requirements, the heat exchange area must be significantly increased or multiple sets of equipment must be connected in series, resulting in bulky and costly equipment. Accumulated reaction heat can easily lead to localized overheating, increasing side reactions and accelerating catalyst deactivation, directly impacting product quality and process stability.

[0005] Therefore, there is an urgent need to develop efficient heat extraction technology that is suitable for ionic liquids with high viscosity and low thermal conductivity. Summary of the Invention

[0006] The embodiments of the present application provide a flash evaporation heat extraction method and system for an alkylation reaction product, which introduces a flash evaporation heat extraction method to achieve rapid cooling of the ionic liquid, significantly improve heat transfer efficiency, and reduce heat exchange costs.

[0007] In a first aspect, an embodiment of the present application provides a flash evaporation heat extraction method for an alkylation reaction product, comprising: separating an ionic liquid alkylation reaction product to obtain a hydrocarbon-rich phase and an ion liquid-rich phase; atomizing the ion liquid-rich phase into droplets using a liquid injection device or a dispersion device, and injecting the droplets into a flash tank; flash vaporizing a portion of hydrocarbons in the ion liquid-rich phase into gaseous hydrocarbons by reducing the pressure; absorbing the heat of reaction during the vaporization process to cool the unvaporized ion liquid-rich phase, thereby obtaining a cooled ion liquid-rich phase; returning the cooled ion liquid-rich phase to a reactor for recycling; and performing gas-liquid separation on the gaseous hydrocarbons in a separatory tank and pressurizing them with a compressor before returning them to the reactor to continue the reaction.

[0008] In one possible embodiment, the volume ratio of the ionic liquid to the hydrocarbon in the ion-rich liquid phase is 1:(0.1-1); the volume ratio of the ionic liquid to the hydrocarbon in the cooled ion-rich liquid phase is 1:(0.04-0.8).

[0009] In one possible embodiment, the volume ratio of the ionic liquid to the hydrocarbon in the cooled ionic liquid-rich phase is 1:(0.05-0.2).

[0010] In one possible embodiment, the temperature of the cooled ion liquid-rich phase is 5° C. to 15° C. lower than the temperature of the ion liquid-rich phase.

[0011] In one possible embodiment, the ion-rich liquid phase is atomized into droplets by a liquid injection device or a dispersion device, including: dispersing the ion-rich liquid phase into multiple streams by a porous distributor; and atomizing the multiple streams into droplets with a particle size of 1 to 300 μm by a radial single-fluid nozzle or a radial two-fluid nozzle.

[0012] In one possible embodiment, the ion-rich liquid phase is atomized into droplets by a liquid injection device or a dispersion device, and the method further includes: further atomizing the droplets atomized by a radial single-fluid nozzle or a radial two-fluid nozzle by an ultrasonic sprayer or a liquid jet breakup device to obtain droplets with a particle size of 0.1 to 50 μm.

[0013] In one possible embodiment, the method further includes: introducing the hydrocarbon-rich phase into a settling tank, standing and stratifying, and then sequentially passing the phase through a high-efficiency coalescer and a separator to remove ionic liquid to obtain a purified hydrocarbon-rich phase; introducing the purified hydrocarbon-rich phase into a distillation tower to separate isobutane, n-butane, and alkylate; and returning the separated isobutane to the reactor for further reaction.

[0014] In a second aspect, an embodiment of the present application provides a flash heat extraction system for an alkylation reaction product, comprising: a separation unit, a liquid injection device or a dispersion device, a flash tank, a pressure valve, a separator tank, and a compressor; the separation unit has a liquid inlet, a top flow port, and a bottom flow port; the liquid inlet is connected to the discharge port of the reactor to introduce the ionic liquid alkylation reaction product, and the top flow port and the bottom flow port output a hydrocarbon-rich phase and an ion-rich liquid phase, respectively; the liquid injection device or the dispersion device is used to atomize the ion-rich liquid phase into droplets and inject them into the flash tank; the pressure valve is used to control the operating pressure of the flash tank so that all or part of the hydrocarbons in the ion-rich liquid phase injected into the flash tank flash vaporize into gaseous hydrocarbons, and the vaporization process absorbs reaction heat to cool the unvaporized ion-rich liquid phase to obtain a cooled ion-rich liquid phase; the cooled ion-rich liquid phase is returned to the reactor via a circulation pump at the bottom of the flash tank; the separator tank is connected in series with the compressor to pressurize the gaseous hydrocarbons and return them to the reactor for further reaction.

[0015] In one possible embodiment, the liquid injection device or dispersion device includes: a porous distributor, a radial single-fluid nozzle or a radial two-fluid nozzle; the porous distributor is used to disperse the ion-rich liquid phase into multiple streams; the radial single-fluid nozzle or the radial two-fluid nozzle is used to atomize the multiple streams into droplets with a particle size of 1 to 300 μm.

[0016] In one possible embodiment, the liquid injection device or dispersion device further includes an ultrasonic sprayer or a liquid jet breakup device; the ultrasonic sprayer or the liquid jet breakup device is used to further atomize droplets with a particle size of 1 to 300 μm into droplets with a particle size of 0.1 to 50 μm.

[0017] In one possible embodiment, the apparatus further comprises: a settling tank, a high-efficiency coalescer, and a distillation tower; the feed port of the settling tank is connected to the top flow port of the hydrocyclone separator or the settling unit for static stratification of the hydrocarbon-rich phase; the settling tank, the high-efficiency coalescer, the separator, and the distillation tower are connected in series; the ionic liquid in the hydrocarbon-rich phase flowing out of the settling tank is removed by utilizing the lipophilic and hydrophobic fiber material in the high-efficiency coalescer, and a purified hydrocarbon-rich phase is obtained by passing through the separator; the distillation tower is used to separate the purified hydrocarbon-rich phase into isobutane, n-butane, and alkylate; a first outlet connected to the reactor is provided at the top of the distillation tower for returning the separated isobutane to the reactor for further reaction; a second outlet is provided on the side or bottom of the distillation tower for discharging the separated n-butane and alkylate.

[0018] The flash evaporation heat extraction method and system for the alkylation reaction product provided in the embodiments of the present application are easy to separate from the alkylation reaction product to obtain a hydrocarbon-rich phase and an ion liquid-rich phase due to the large density difference between the ionic liquid catalyst and hydrocarbon substances such as octane and isobutane; the ion liquid-rich phase is dispersed into small, uniform micro-droplets through the atomization step, so that the high-viscosity fluid is converted into a suspended gas-liquid two-phase system, the surface viscosity is greatly reduced, and the flow and heat transfer bottleneck of the high-viscosity fluid in the traditional heat exchanger is broken through; the flash evaporation step, on the one hand, utilizes the latent heat of vaporization of hydrocarbons to efficiently remove the reaction heat, realizing ionic liquid cooling; on the other hand, During the flash evaporation process, gaseous hydrocarbons continuously escape, forming a turbulent vapor-liquid two-phase environment, which causes the droplet surface to be continuously renewed, significantly improving the heat transfer coefficient and enhancing heat exchange efficiency. Through efficient cooling, the stability and activity of the ionic liquid catalyst involved in the reaction are improved, thereby increasing the octane number and product quality of the alkylate oil. The provided process, through the triple synergistic effects of phase interface reconstruction, viscosity regulation, and phase change heat transfer, not only achieves efficient cooling of the particle liquid, but also solves the problems of large equipment size and cost in traditional processes. Under the same heat exchange requirement, this application supports a smaller equipment size and significantly reduces equipment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0020] Figure 1 A schematic diagram of the structure of the system provided in an embodiment of the present application.

[0021] Reference numerals:

[0022] 110-reactor; 120-hydrocyclone separator; 130-flash tank; 140-pressure control valve; 150-sedimentation tank; 160-high-efficiency coalescer; 170-liquid separator; 180-compressor; 190-distillation tower.

[0023] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0024] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0025] Ionic liquids (ILs) are salt compounds composed of organic cations and organic / inorganic anions that are liquid at or near room temperature. In the C4 alkylation reaction in petroleum refining, ionic liquids, such as chloroaluminate-type ionic liquids, are a new generation of catalytic systems. Their safety, environmental friendliness, and affordability make them an ideal green alternative to traditional strong acid catalysts.

[0026] In industrial units that use ionic liquids to catalyze the C4 alkylation reaction, the heat released by the alkylation reaction needs to be cooled and removed through a heat exchanger. However, ionic liquids themselves have high viscosity and low thermal conductivity, which makes traditional heat exchangers face significant heat transfer resistance problems when processing such fluids. This is manifested in increased pressure drop and low heat transfer efficiency, making it difficult to achieve efficient and economical thermal management. In order to meet the process cooling requirements, it is often necessary to increase the heat exchange area and equipment size, which not only makes the equipment bulky, but also significantly increases the investment cost. In addition, if the reaction exotherm cannot be removed efficiently, it may make it difficult to accurately control the reaction temperature, thereby affecting the reaction selectivity and catalyst stability.

[0027] In order to solve this problem, the present application provides a flash heat extraction method for the alkylation reaction product, which effectively reduces the heat transfer resistance of the high-viscosity ionic liquid by separating, atomizing and flash evaporating the reaction product. Specifically, the method uses a special atomizing device to disperse the separated ion-rich liquid phase into micron-sized droplets, greatly increasing the specific surface area of ​​the liquid; then, in the flash tank, efficient heat extraction is achieved through phase change heat transfer. Compared with traditional heat exchange methods, this method does not need to rely on high-cost large-scale heat exchangers, which not only reduces equipment investment and operating energy consumption, but also can quickly and accurately control the reaction temperature, avoid the occurrence of side reactions caused by local overheating, and significantly improve the stability and economy of the ionic liquid-catalyzed carbon four alkylation process, providing a feasible thermal management solution for the industrial promotion of this technology.

[0028] The following specific embodiments describe in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0029] The present invention provides a method for flash evaporation of an alkylation reaction product to obtain heat, comprising the following steps:

[0030] 1. Hydrocyclone separation

[0031] The ionic liquid alkylation reaction product is separated to obtain a hydrocarbon-rich phase and an ionic liquid-rich phase.

[0032] The ionic liquid alkylation reaction product can be separated by at least one of a hydrocyclone, a settling tank, and a centrifugal separation device.

[0033] After the alkylation reaction, the reaction product comprising the alkylation feed (mainly isobutane), the ionic liquid catalyst and the alkylation product (mainly octane) is separated into a hydrocarbon-rich phase and an ionic liquid-rich phase via a hydrocyclone and / or a settling unit.

[0034] The hydrocarbon-rich phase is rich in hydrocarbon compounds such as isobutane and octane, which are components of high economic value and can be further processed and utilized, for example, as a blending component for high-octane gasoline. The ionic liquid-rich phase, on the other hand, primarily contains ionic liquid catalysts and can be recycled for alkylation reactions, reducing production costs and minimizing environmental impact.

[0035] Due to the significant density difference between the ionic liquid catalyst and the hydrocarbon-rich phase—the mixed hydrocarbons of the alkylation product (primarily octane) and reactants (primarily isobutane)—hydrocyclones or centrifugation can be used to achieve rapid phase separation. Hydrocyclones are the preferred method for phase separation. During the separation process, the ionic liquid-rich phase is discharged from the bottom of the hydrocyclone, while the hydrocarbon-rich phase is discharged from the top.

[0036] Specifically, the volume ratio of the ionic liquid to the hydrocarbons in the separated ionic liquid-rich phase is 1:(0.1-1), and the hydrocarbons are mainly isobutane.

[0037] The acid-hydrocarbon volume ratio of the ionic liquid to hydrocarbons in the ionic liquid-rich phase can be adjusted to a set range by multi-stage separation or by adjusting the parameters of the separation device, such as temperature, pressure, rotation speed, residence time, etc.

[0038] If the volume ratio of ionic liquid to hydrocarbons in the ion-rich phase is greater than 1:0.1, the hydrocarbon content is too low, and the ideal cooling effect cannot be achieved. If the volume ratio of ionic liquid to hydrocarbons in the ion-rich phase is less than 1:1, that is, the hydrocarbon volume accounts for more than 50%, there will be a problem of overcooling, resulting in too low an ionic liquid temperature, affecting catalyst activity. In addition, the excess vaporized hydrocarbons need to be recompressed and returned to the reactor, which increases the workload of the compressor and energy consumption. After extensive testing, the optimal range of the volume ratio of ionic liquid to hydrocarbons in the separated ion-rich phase has been determined to be 1:(0.1-1).

[0039] 2. Ion-rich liquid phase atomization

[0040] The ion-rich liquid phase separated in the previous step is atomized into droplets by a liquid injection device or a dispersion device.

[0041] The spraying device may include at least one of a radial single-fluid or two-fluid nozzle, a liquid jet breakup device, and an ultrasonic sprayer; the dispersing device may include at least one of a porous distributor, a rotary atomizer, and an ultrasonic sprayer.

[0042] Preferably, a radial single-fluid or dual-fluid nozzle can be used for droplet atomization, which has a simple structure, stable operation, is suitable for spraying high-viscosity fluids, and is adapted to the material properties of ionic liquids and light hydrocarbons in this application.

[0043] Specifically, radial single-fluid nozzles utilize high-speed shear forces to break up high-viscosity fluids during the injection process. A dual-fluid nozzle, on the other hand, introduces an auxiliary gas to create a shear layer, accelerating the breakage of the high-viscosity ionic liquid and forming smaller, more uniform droplets. The auxiliary gas can be isobutane produced by vaporization. After injection or dispersion, the ion-rich liquid phase forms droplets in the flash tank with an average particle size of 0.1 to 300 μm. More preferably, the average particle size can be controlled to 0.5 to 50 μm through process parameters such as liquid flow rate, gas-liquid ratio, and injection pressure.

[0044] For example, the droplet size may range from 10 to 100 μm.

[0045] Optionally, the ion-rich liquid phase is atomized into droplets by a liquid injection device or a dispersion device, including: dispersing the ion-rich liquid phase into multiple streams by a porous distributor; and atomizing the multiple streams into droplets with a particle size of 1 to 300 μm by a radial single-fluid nozzle or a radial two-fluid nozzle.

[0046] A porous distributor consists of a sieve plate with uniform pores and a porous tube or distribution plate. Its core function is to divide the fluid into multiple independent streams, achieving initial dispersion. The pore size of a porous distributor can range from 0.5 to 10 mm, and a porous distributor can include hundreds or even thousands of pores to separate the ion-rich liquid phase into tens to hundreds of streams. A porous distributor can disperse the ion-rich liquid phase into millimeter-scale streams.

[0047] Radial single-fluid nozzles utilize the high-speed flow of a high-pressure fluid through the nozzle aperture, breaking it into droplets by turbulent shear forces. To atomize droplets with a diameter ranging from 1 to 300 μm, the fluid flow rate can be controlled based on the empirical formula for the Sauter mean diameter (SMD) and the viscosity of the ionic liquid phase, for example, to 20 m / s.

[0048] Radial twin-fluid nozzles utilize the velocity difference between a compressed gas, such as nitrogen, and a liquid to initiate shear forces, breaking the liquid into a fine mist. Droplet size is inversely proportional to the vapor-liquid velocity ratio, and by controlling the vapor-liquid velocity ratio, droplet sizes ranging from 1 to 300 μm can be achieved.

[0049] Exemplarily, the vapor-liquid velocity ratio may be 5:1 to 20:1.

[0050] Optionally, atomizing the ion-rich liquid phase into droplets by a liquid injection device or a dispersion device also includes: further atomizing the droplets atomized by a radial single-fluid nozzle or a radial two-fluid nozzle by an ultrasonic sprayer or a liquid jet breakup device to obtain droplets with a particle size of 0.1~50 μm.

[0051] Ultrasonic sprayers are based on the cavitation effect produced by ultrasonic vibration, which enables the liquid to overcome surface tension and break into tiny droplets. The droplet size is mainly determined by the vibration frequency and the physical properties of the liquid such as viscosity and surface tension.

[0052] In order to obtain droplets with smaller particle size, the ultrasonic frequency of the ultrasonic sprayer is at least 20 kHz, such as 100 kHz.

[0053] When the ultrasonic frequency is 20 kHz, the droplet size obtained is usually 1~100 μm. By increasing the ultrasonic frequency, droplets of 0.1~50 μm can be generated.

[0054] Liquid jet breakup device splits the liquid flow into fine droplets through high-speed jet impact or shearing action. The droplet size is related to the jet velocity, liquid viscosity and device structure such as nozzle aperture and impact angle.

[0055] When the critical Weber number is greater than 12, the jet will break into droplets, and the particle size d is proportional to the inverse of the jet velocity u raised to the nth power, with n ranging from 0.5 to 1. When the jet velocity is 5 to 20 m / s, droplets with an initial particle size of 100 to 300 μm can be broken down to 10 to 50 μm. By further increasing the jet velocity, for example to 50 m / s or 100 m / s, or optimizing the jet pressure and impact angle, a droplet distribution of 0.1 to 50 μm can be achieved. The jet pressure can be 1 to 5 MPa, and the impact angle should be close to 90°.

[0056] The atomization step can include two stages: initial atomization and secondary atomization. In the initial atomization stage, a combination of a porous distributor and a radial single / dual fluid nozzle is used to produce droplets of 1 to 300 μm through pressure atomization (usually 0.1 to 2 MPa). In the secondary atomization stage, the particle size is further reduced by an ultrasonic sprayer or a jet breakup device.

[0057] Through multi-stage atomization, the droplet size is further reduced, thereby increasing the specific surface area of ​​the droplets, shortening the heat conduction path and reducing the viscosity, thereby greatly improving the evaporation rate.

[0058] 3. Flash evaporation heat extraction

[0059] The droplets obtained by atomization in the previous step are injected into the flash tank. By reducing the pressure, part of the hydrocarbons in the injected ion-rich liquid phase are flash vaporized into gaseous hydrocarbons. The vaporization process absorbs the reaction heat to cool the unvaporized ion-rich liquid phase to obtain a cooled ion-rich liquid phase.

[0060] The pressure in the flash tank is lower than the pressure of the liquid injection device or the dispersion device, so that part of the hydrocarbons in the ion-rich liquid phase injected into the flash tank, such as isobutane, is vaporized due to the sudden pressure drop.

[0061] Specifically, the droplets obtained by atomization are injected into the flash tank horizontally or downwardly. The height difference between the injection port and the top of the flash tank body should be limited to a preset height difference, for example, 1 / 3-1 / 2 of the height of the flash tank body, so that the droplets have sufficient residence time and falling kinetic energy, so that the hydrocarbons therein are completely vaporized, sufficient cooling is achieved, and the dispersion efficiency of the ionic liquid is enhanced to avoid concentration at the bottom of the flash tank, which makes it difficult to recover. The angle of droplet injection needs to be controlled within the range of 0° to a preset angle. The preset angle can be determined based on parameters such as the size of the flash tank and the speed of droplet injection to ensure that most of the cooled ion-rich liquid phase can converge at the bottom of the flash tank, thereby avoiding the cooled ion-rich liquid phase from being sprayed onto the inner wall of the flash tank, and ensuring efficient collection of the cooled ion-rich liquid phase.

[0062] Exemplarily, the preset angle can be an angle less than or equal to 30°, such as 25°, 24°, 23°, 22°, 21°, 20°, 19°, 18°, 17°, 16°, 15°, 14°, 13°, 12°, 11°, 10°, etc.

[0063] An ion-rich liquid phase injection or dispersion inlet is provided on the side wall of the flash tank cylinder, and the ion-rich liquid phase injection or dispersion inlet is set at the center point of the flash tank cylinder axis or within the range of 1 / 3 of the height from the center to the top of the cylinder to ensure that most of the injected droplets converge at the bottom of the flash tank.

[0064] The ionic liquid catalysts used in alkylation reactions have a saturated vapor pressure of zero, are virtually nonvolatile, and are highly stable. Dissolved light hydrocarbons, such as isobutane, have low boiling points and high vapor pressures, making them easily vaporized under reduced pressure. Therefore, during the flash vaporization step, a sudden drop in pressure causes some of the hydrocarbons (primarily isobutane) dissolved in the ionic liquid-rich phase to flash vaporize. This vaporization process absorbs the heat of reaction and rapidly cools the ionic liquid.

[0065] To achieve efficient flash cooling and continuous recovery of the ionic liquid, the ion-rich liquid phase is injected into the flash tank at a downward angle ranging from 0° to a preset angle relative to the radial horizontal section of the flash tank cylinder. First, the flash process requires that after the droplets are rapidly vaporized by some hydrocarbons (such as isobutane), the remaining high-density ionic liquid can quickly settle to the bottom of the tank under the action of gravity. If an upward injection method is used, it will not only slow the droplet settling speed, but also easily form stagnation, eddies, and turbulence within the tank, resulting in ionic liquid loss and reduced settling efficiency. In contrast, the downward injection method fully utilizes gravity to accelerate the droplet settling speed, allowing the ionic liquid to quickly gather at the bottom of the tank after the flash evaporation is completed, significantly improving recovery efficiency. Secondly, to ensure the high efficiency of the flash cooling process, the droplets need to be quickly and evenly dispersed within the tank to form sufficient gas-liquid contact. Upward spraying can easily cause droplets to accumulate at the top of the tank, causing localized overcooling or overheating and disrupting the uniformity of heat and mass transfer. Downward or radial spraying ensures that the droplets quickly diffuse along the inner wall or center of the tank, forming a stable gas-liquid contact interface, avoiding localized mass transfer dead zones, and ensuring the efficient flash process. Furthermore, when spraying upward, ionic liquids that have not completely settled are easily entrained by the gas phase flow field and escape through the gas phase outlet, causing catalyst loss and increasing the processing load of subsequent separation steps. The downward spray design, through the synergistic effect of gravity and gas flow direction, minimizes droplet entrainment, ensuring that the gas phase outlet is mainly flash vaporized hydrocarbon gas, namely gaseous hydrocarbons (such as isobutane), reducing ionic liquid loss and maintaining process stability and economy.

[0066] The pressure in the flash tank can be controlled by a pressure-controlled valve, causing some of the isobutane dissolved in the droplets generated by atomization of the ionic liquid-rich phase to flash vaporize. This vaporization of the isobutane absorbs a significant amount of latent heat of vaporization, removing the heat of reaction and thereby directly lowering the temperature of the ionic liquid.

[0067] The temperature of the ion-rich liquid phase before flash evaporation can be 10-50°C, preferably 25-35°C, for example, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, etc. The temperature of the effluent after flash evaporation, i.e., the cooled ion-rich liquid phase, is 10-40°C, more preferably 15-25°C. Within this temperature range, the catalytic activity and stability of the ionic liquid are maintained at optimal levels, which is beneficial for suppressing side reactions and extending the life of the catalyst. For example, the temperature of cooling the ion-rich liquid phase can be 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, etc.

[0068] Optionally, the temperature of the cooled ion liquid-rich phase is 5° C. to 15° C. lower than the temperature of the ion liquid-rich phase.

[0069] The flash tank adopts a vertical cylindrical structure and is equipped with a top hydrocarbon gas outlet, which is connected to the compression reflux system to collect and liquefy the flash gas and return it to the reactor for recycling; a liquid outlet is provided at the bottom of the tank, and the cooled flash effluent (mainly ionic liquid) after sedimentation is returned to the reactor to continue to participate in the catalytic alkylation reaction.

[0070] Due to the vaporization of some hydrocarbons, the volume ratio of the acid hydrocarbons of the ionic liquid and the hydrocarbons in the cooled ion-liquid-rich phase is reduced compared to the original ion-liquid-rich phase. Optionally, when the volume ratio of the acid hydrocarbons of the ionic liquid and the hydrocarbons in the ion-liquid-rich phase is 1:(0.1-1), the volume ratio of the acid hydrocarbons of the ionic liquid and the hydrocarbons in the cooled ion-liquid-rich phase is 1:(0.04-0.8), preferably 1:(0.05-0.2). For example, the volume ratio of the ionic liquid to the hydrocarbons in the ionic liquid phase can be 1:0.9, 1:0.8, 1:07, 1:0.6, 1:0.5, 1:0.4, 1:03, 1:0.2, etc. The volume ratio of ionic liquid to hydrocarbon in the cooled ionic liquid-rich phase can be 1:0.05, 1:0.06, 1:007, 1:0.08, 1:0.09, 1:0.1, 1:0.15, 1:02, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:07, 1:0.75, etc.

[0071] The desired acid-hydrocarbon volume ratio can be achieved by controlling the operating pressure of the flash tank.

[0072] By regulating the acid-hydrocarbon volume ratio, it is possible to ensure that a sufficient amount of hydrocarbons in the ion-rich liquid phase are vaporized, allowing the vaporization endothermic process to proceed fully, thereby achieving the desired cooling effect and keeping the temperature of the cooled ion-rich liquid phase within the desired range, for example, 15°C to 40°C.

[0073] 4. Recycling

[0074] The cooled ion-rich liquid phase is returned to the reactor for recycling; the gaseous hydrocarbons are separated into gas and liquid by a separator and pressurized by a compressor before being returned to the reactor for further reaction.

[0075] After flash evaporation and cooling, the ionic liquid collects at the bottom of the flash tank and is recycled back to the alkylation reactor, achieving catalyst recycling. Meanwhile, the isobutane-rich gaseous hydrocarbons produced in the flash tank are separated in a separatory tank and pressurized by a compressor before returning to the alkylation reactor to continue the reaction.

[0076] This embodiment also provides a treatment step for the hydrocarbon-rich phase. The separated hydrocarbon-rich phase can be separated and removed by sedimentation, hydrocyclone, or high gravity separation methods to remove trace ionic liquid, and further separated to obtain isobutane, n-butane, and alkylate. The isobutane is returned to the reactor to continue the reaction.

[0077] The hydrocarbon-rich phase can be treated in a supergravity separator, a hydrocyclone separator and / or a multi-stage settling tank to remove the entrained trace liquid particles, and separated in a distillation tower to obtain products such as isobutane, normal butane and alkylate oil, among which the isobutane is recycled back to the reactor to continue the reaction.

[0078] Optionally, the method may further comprise the following steps: introducing the hydrocarbon-rich phase into a settling tank, standing and stratifying the phase, and then sequentially passing the phase through a high-efficiency coalescer and a separator to remove the ionic liquid to obtain a purified hydrocarbon-rich phase; introducing the purified hydrocarbon-rich phase into a distillation tower to separate the phase into isobutane, n-butane, and alkylate; and returning the separated isobutane to the reactor for further reaction.

[0079] The settling tank can be a single-stage or multi-stage settling tank. The hydrocarbon-rich phase can rest in the settling tank for 10 to 60 minutes, for example, 30 minutes or 25 minutes. This time window has been proven to ensure that the ionic liquid and hydrocarbons are fully separated due to their density differences while balancing production efficiency and equipment utilization. During the resting process, the ionic liquid, due to its high density, settles to the bottom of the tank, while the hydrocarbon-rich phase floats to the top, forming a preliminary separation interface.

[0080] The hydrocarbon-rich phase flowing out of the settling tank still contains trace amounts of ionic liquid, which must be further removed by a high-efficiency coalescer. The coalescer is packed with oleophilic and hydrophobic fibers or corrugated plate packing. When the hydrocarbon-rich phase passes through, tiny ionic liquid droplets collide and coalesce on the packing surface, gradually forming larger droplets. This process utilizes surface tension and fluid dynamics to increase the particle size of the ionic liquid droplets from the micron level (e.g., 1-10 μm) to the millimeter level (1-5 mm), significantly improving the efficiency of subsequent liquid separation. The processing capacity of a high-efficiency coalescer is closely related to the specific surface area of ​​the packing and the fluid flow rate. By optimizing the packing structure and controlling the flow rate (typically 0.1-0.5 m / s), the ionic liquid content in the hydrocarbon-rich phase can be reduced to 50-200 ppm.

[0081] The hydrocarbon-rich phase that has passed through the high-efficiency coalescer enters the separator, where the final separation is achieved using the dual effects of gravity and centrifugal force. The separator adopts a swirl or static mixing structure to cause the fluid to generate a swirl motion in the tank, further enhancing the separation of the two phases. Centrifugal force accelerates the migration of ionic liquid droplets to the tank wall, and eventually settles to the bottom of the tank and is discharged; the purified hydrocarbon-rich phase flows out from the top outlet, and the residual ionic liquid content can be reduced to 10~50 ppm, meeting the requirements of subsequent distillation. The separation effect of the separator is affected by the residence time (generally ~10 minutes) and the operating pressure (usually 0.2-0.5 MPa), and needs to be precisely controlled according to actual working conditions.

[0082] The purified hydrocarbon-rich phase enters the distillation tower, where multi-stage distillation achieves efficient separation of isobutane, n-butane, and alkylate. The distillation tower typically utilizes a multi-side draw design. Light fractions at the top are condensed to yield isobutane with a purity of ≥ 99%, which can be returned to the reactor for recycling. n-Butane is also drawn off the side draw for use as a chemical feedstock or fuel gas. High-octane alkylate (octane number ≥ 95) is obtained at the bottom of the tower, serving as a blending component for high-quality gasoline. The distillation process requires strict control of the temperature gradient (40-60°C at the top, 120-150°C at the bottom) and the reflux ratio (3-8) to ensure precise separation of the components.

[0083] The separated isobutane is returned to the reactor to participate in the alkylation reaction, forming a raw material recycling system. This cycle not only improves isobutane utilization and reduces raw material costs, but also maintains a stable reactant concentration within the reactor, ensuring the alkylation reaction proceeds continuously and efficiently. During the recycling process, the purity and impurity content of the isobutane must be regularly monitored to prevent impurity accumulation that may affect the reaction performance.

[0084] The flash evaporation heat extraction method for the alkylation reaction product provided in this embodiment has the following significant technical effects:

[0085] (1) Direct flash evaporation is used to cool the ion-rich liquid phase. The latent heat of vaporization of isobutane flash evaporation is used to achieve temperature control. The temperature of the ionic liquid or flash effluent can be reduced to a suitable reaction temperature range. This process can achieve self-cooling without the need for a large external heat exchanger, greatly reducing the investment cost of heat exchange equipment. At the same time, it avoids the problem of easy scaling and difficult maintenance of traditional heat exchangers in high-viscosity systems.

[0086] (2) The spray dispersion of the ion-rich liquid phase is achieved by using the injection and dispersion technology. The specific surface area is increased by 10 to 100 times compared with the traditional liquid flow, which significantly accelerates the flash evaporation rate and heat transfer efficiency of isobutane. At the same time, the temperature uniformity error can be controlled within ±2°C, effectively avoiding the catalyst deactivation or aggravation of side reactions caused by local overheating, improving the stability of the catalyst and extending the catalyst cycle service life;

[0087] (3) Aiming at the heat transfer bottleneck caused by the high viscosity of ionic liquids (usually 100-1000 mPa·s), this method achieves efficient cooling of high-viscosity effluents through the synergistic effect of spray flash evaporation and gravity, which has important industrial application prospects;

[0088] (4) The process flow is simple and reliable, with the characteristics of simple operation and strong reliability. It can be easily integrated into existing or newly built ionic liquid alkylation production units, and can be directly adapted to the mainstream process route, reducing energy consumption per unit production capacity and shortening the process flow length.

[0089] The present application also provides a flash heat extraction system for an alkylation reaction product, for performing the aforementioned method. The system comprises: a separation unit, a liquid injection device or a dispersion device, a flash tank, a pressure valve, a separator tank, and a compressor. The separation unit comprises a liquid inlet, a top flow port, and a bottom flow port. The liquid inlet is connected to the discharge port of the reactor to introduce the ionic liquid alkylation reaction product, and the top flow port and the bottom flow port output a hydrocarbon-rich phase and an ion liquid-rich phase, respectively. The liquid injection device or the dispersion device is used to atomize the ion liquid-rich phase into droplets and inject them into the flash tank. The pressure valve is used to control the operating pressure of the flash tank so that all or part of the hydrocarbons in the ion liquid-rich phase in the flash tank flash vaporize into gaseous hydrocarbons. The vaporization process absorbs reaction heat to cool the unvaporized ion liquid-rich phase, thereby obtaining a cooled ion liquid-rich phase. The cooled ion liquid-rich phase is returned to the reactor via a circulation pump at the bottom of the flash tank. The separator tank is connected in series with the compressor to pressurize the gaseous hydrocarbons and return them to the reactor for further reaction.

[0090] Optionally, the liquid injection device or dispersion device includes: a porous distributor, a radial single-fluid nozzle or a radial two-fluid nozzle, and an ultrasonic sprayer or a liquid jet breakup device; the porous distributor is used to disperse the ion-rich liquid phase into multiple streams; the radial single-fluid nozzle or the radial two-fluid nozzle is used to atomize the multiple streams into droplets with a particle size of 1~300 μm; the ultrasonic sprayer or liquid jet breakup device is used to further atomize the droplets with a particle size of 1~300 μm into droplets with a particle size of 0.1~50 μm.

[0091] Optionally, the system further comprises a settling tank, a high-efficiency coalescer and a distillation tower; the feed port of the settling tank is connected to the top flow port of the hydrocyclone separator or the settling unit for static stratification of the hydrocarbon-rich phase; the settling tank, the high-efficiency coalescer, the separator and the distillation tower are connected in series; the lipophilic and hydrophobic fiber material in the high-efficiency coalescer is used to remove the ionic liquid of the hydrocarbon-rich phase flowing out of the settling tank, and the purified hydrocarbon-rich phase is obtained through the separator; the distillation tower is used to separate the purified hydrocarbon-rich phase into isobutane, n-butane and alkylate oil; a first outlet connected to the reactor is provided at the top of the distillation tower to return the separated isobutane to the reactor for further reaction; a second outlet is provided on the side or bottom of the distillation tower to discharge the separated n-butane and alkylate oil.

[0092] Figure 1 A schematic diagram of a flash heat extraction system for an alkylation reaction product provided in an embodiment of the present application is shown in FIG. Figure 1 As shown, the system includes a hydrocyclone 120 , a flash tank 130 , a pressure control valve 140 , a settling tank 150 , a high-efficiency coalescer 160 , a liquid separator 170 , a compressor 180 and a distillation column 190 .

[0093] The C4 alkylation reaction feedstock and the ionic liquid catalyst enter reactor 110, where they react to produce a reaction effluent or product. The temperature of the reaction effluent ranges from 25°C to 35°C. Reactor 110 provides a location for the alkylation reaction between the feedstock and the ionic liquid catalyst, achieving alkylation conversion of C4 hydrocarbons under a specific temperature, pressure, and catalyst (ionic liquid) environment.

[0094] First, the reaction product is separated into a hydrocarbon-rich phase and an ion liquid-rich phase by a hydrocyclone 120. The hydrocyclone 120 has a liquid inlet, a top flow port, and a bottom flow port. The liquid inlet is connected to the discharge port of the reactor 110 to introduce the ionic liquid alkylation reaction product; the top flow port and the bottom flow port respectively output the separated hydrocarbon-rich phase and ion liquid-rich phase.

[0095] Subsequently, the ion-rich liquid phase is atomized into droplets by a porous distributor, nozzle, atomizer, and the like. These droplets enter the flash tank 130 directly at a downward angle of 0° to 30°, where the downward angle is the angle with respect to the radially horizontal section of the flash tank 130 cylinder. The particle size of the droplets sprayed into the flash tank 130 is controlled to be within a range of 0.1 to 300 μm, more preferably, regulated to a range of 0.5 to 50 μm through process parameters such as liquid flow rate, gas-liquid ratio, and injection pressure. The flash pressure is controlled by a pressure-controlled valve 140, causing a portion of the isobutane dissolved in the ion-rich liquid phase within the flash tank 130 to flash vaporize. The vaporization of the isobutane absorbs a significant amount of latent heat of vaporization, thereby directly reducing the temperature of the ionic liquid and producing a cooled ion-rich liquid phase.

[0096] The cooled ion liquid-rich phase collects at the bottom of flash tank 130 and is circulated back to reactor 110 via a circulation pump to continue the reaction, thus achieving catalyst recycling. Simultaneously, the isobutane-rich gaseous hydrocarbons produced in flash tank 130 are separated by separator 170 and pressurized by compressor 180 before returning to reactor 110 to continue the reaction. The separated hydrocarbon-rich phase is then allowed to stand and separate in settling tank 150. It then passes through a high-efficiency coalescer 160 and separator 170 to further remove trace amounts of entrained ionic liquid. The phase is then separated by distillation tower 190 to produce isobutane, n-butane, and alkylate. The isobutane is returned to reactor 110 as a feedstock to continue the reaction, while the alkylate is discharged through the bottom outlet of distillation tower 190.

[0097] The following examples further illustrate the embodiments of the present invention and the specific beneficial effects thereof, but they should not be construed as limiting the scope of implementation of the present invention.

[0098] Example 1

[0099] 1.1 Process conditions

[0100] An ionic liquid is used as a catalyst for the C4 alkylation reaction. The molar ratio of isobutane to butene in the feed is controlled at 10:1. The reaction temperature is maintained between 15 and 25°C. The resulting effluent is a two-phase mixture of ionic liquid and hydrocarbons, the primary hydrocarbon components being isobutane, n-butane, and octane. The reaction effluent temperature is 35°C, and the acid-hydrocarbon volume ratio of the ionic liquid to hydrocarbons is 1:1. After separation in a hydrocyclone 120, an ionic liquid-rich phase and a hydrocarbon-rich phase are obtained. The injection inlet for the ionic liquid-rich phase is located at the center of the cylindrical axis of a flash tank 130.

[0101] The ion-rich liquid phase is dispersed and atomized using a radial single-fluid nozzle, with the average droplet size controlled between 10 and 300 μm. The atomized droplets are injected into the vertical cylindrical structure of flash tank 130 at a downward angle of 0° to 30° relative to the horizontal plane of the flash tank 130. The internal pressure of flash tank 130 is controlled by pressure control valve 140 and maintained at 350 kPa.

[0102] 1.2 Cooling effect

[0103] During the flash process, isobutane rapidly vaporizes, absorbing the latent heat of vaporization and carrying away the heat released by the reaction, achieving efficient cooling of the effluent stream. Measurements show that the temperature of the ionic liquid phase steadily drops to 25°C after the flash, with a rapid cooling rate and uniform temperature distribution. After the flash, the acid-hydrocarbon volume ratio of the ionic liquid-rich phase decreases from 1:1 to 1:0.78, indicating that some light hydrocarbons have been vaporized and removed. The liquid phase temperature at the bottom of the flash tank is uniform, with a temperature difference of no more than ±0.5°C.

[0104] Example 2

[0105] 2.1 Process conditions

[0106] The temperature of the ion-rich liquid phase effluent was 25° C. The ion-rich liquid phase was injected into the flash tank at a downward angle of 15° relative to the radial section of the flash tank cylinder. The other conditions were the same as those in Example 1.

[0107] 2.2 Cooling effect

[0108] The reaction effluent enters the flash tank 130 through the flash valve. The pressure in the flash tank 130 is maintained at 300 kPa by the pressure control valve 140. The temperature of the reaction effluent after flash evaporation is 20°C. The volume ratio of acid to hydrocarbon in the ion-rich liquid phase is 1:0.89. The temperature of the liquid in the flash tank 130 is uniform, and the temperature difference does not exceed ±0.5°C.

[0109] Example 3

[0110] 3.1 Process conditions

[0111] The ion-rich liquid phase effluent temperature was 25°C, and the acid-to-hydrocarbon volume ratio of the ion-rich liquid phase was 1:0.5. After separation in hydrocyclone 120, the ion-rich liquid phase was dispersed through a radial two-fluid nozzle, with the average droplet size controlled to be between 0.5 and 50 μm. Other conditions were the same as in Example 1.

[0112] 3.2 Cooling effect

[0113] The reaction effluent enters the flash tank 130 through the flash valve. The pressure in the flash tank 130 is maintained at 300 kPa by the pressure control valve 140. The temperature of the reaction effluent after flash evaporation is 20°C. The volume ratio of acid to hydrocarbon in the ion-rich liquid phase is 1:0.412. The temperature of the liquid in the flash tank is uniform, and the temperature difference does not exceed ±0.5°C.

[0114] Example 4

[0115] 4.1 Process conditions

[0116] The volume ratio of acid to hydrocarbon in the ion-rich liquid phase is 1:0.3, and the other conditions are the same as those in Example 1.

[0117] 4.2 Cooling effect

[0118] The reaction effluent enters the flash tank 130 through the flash valve. The pressure in the flash tank 130 is maintained at 300 kPa by the pressure control valve 140. The temperature of the reaction effluent after flash evaporation is 21°C. The volume ratio of acid to hydrocarbon in the ion-rich liquid phase is 1:0.23. The temperature of the liquid in the flash tank is uniform, and the temperature difference does not exceed ±0.5°C.

[0119] Example 5

[0120] 5.1 Process conditions

[0121] The volume ratio of acid to hydrocarbon in the ionic liquid-rich phase was 1:0.15, and the other conditions were the same as those in Example 1.

[0122] 5.2 Cooling effect

[0123] The reaction effluent enters the flash tank 130 through the flash valve. The pressure in the flash tank 130 is maintained at 300 kPa by the pressure control valve 140. The temperature of the reaction effluent after flash evaporation is 20°C. The volume ratio of acid to hydrocarbon in the ion-rich liquid phase is 1:0.075. The temperature of the liquid in the flash tank is uniform, and the temperature difference does not exceed ±0.5°C.

[0124] Example 6

[0125] 6.1 Process conditions

[0126] The molar ratio of isobutane to butene in the reactor was 15:1. The reaction effluent was a mixture of ionic liquid and hydrocarbons, wherein the hydrocarbons mainly contained isobutane, n-butane, and octane. The temperature of the effluent was 25° C. The volume ratio of acid to hydrocarbon in the ionic liquid-rich phase was 1:0.3. The other conditions were the same as in Example 1.

[0127] 6.2 Cooling effect

[0128] The reaction effluent enters the flash tank 130 through the flash valve. The pressure in the flash tank 130 is maintained at 300 kPa by the pressure control valve 140. The temperature of the reaction effluent after flash evaporation is 20°C. The volume ratio of acid to hydrocarbon in the ion-rich liquid phase is 1:0.22. The temperature of the liquid in the flash tank is uniform, and the temperature difference does not exceed ±0.5°C.

[0129] Comparative Example 1

[0130] 7.1 Process conditions

[0131] The volume ratio of acid to hydrocarbon in the ion liquid-rich phase was 1:0.08, and the other process conditions were the same as those in Example 1.

[0132] 7.2 Cooling effect

[0133] The reaction effluent enters the flash tank 130 through the flash valve. The pressure in the flash tank 130 is maintained at 300 kPa by the pressure control valve 140. The temperature of the reaction effluent after flash evaporation is 32°C. The cooling effect of the ion-rich liquid phase is poor, and the alkylation reaction temperature range of 15~25°C cannot be reached.

[0134] Comparative Example 2

[0135] 8.1 Process conditions

[0136] The ion-rich liquid phase effluent temperature was 25°C, and the acid-to-hydrocarbon volume ratio of the ion-rich liquid phase was 1:0.5. After separation in hydrocyclone 120, the ion-rich liquid phase was dispersed through a porous distributor, with the average droplet size controlled to be between 0.5 and 2 mm. Other conditions were the same as in Example 1.

[0137] 8.2 Cooling effect

[0138] The reaction effluent enters the flash tank 130 through the flash valve. The pressure in the flash tank 130 is maintained at 300 kPa by the pressure control valve 140. The temperature of the reaction effluent after flash evaporation is 31°C. The cooling effect of the ion-rich liquid phase is poor and the alkylation reaction temperature range of 15~25°C cannot be reached.

[0139] Comparative Example 3

[0140] 9.1 Process conditions

[0141] The volume ratio of acid to hydrocarbon in the ion liquid-rich phase was 1:1.5, and the other process conditions were the same as those in Example 1.

[0142] 9.2 Cooling effect

[0143] The reaction effluent enters the flash tank 130 through the flash valve. The pressure in the flash tank 130 is maintained at 350 kPa by the pressure control valve 140. The temperature of the reaction effluent after flash evaporation is 13°C. The volume ratio of acid to hydrocarbon in the ion-rich liquid phase is 1:0.95. The ion-rich liquid phase is overcooled. The temperature of the cooled ion-rich liquid phase exceeds the appropriate alkylation temperature range of 15~25°C. The reaction activity of the ionic liquid catalyst is reduced, and the amount of vaporized hydrocarbons is too large, resulting in increased energy consumption of the compressor.

[0144] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. It is not limited to the precise structure described above and shown in the drawings, and various modifications and changes may be made without departing from the scope of this application. The scope of this application is limited solely by the appended claims.

Claims

1. A flash distillation heat extraction method for an alkylation reaction product, characterized in that: include: The ionic liquid alkylation reaction product is separated to obtain a hydrocarbon-rich phase and an ionic liquid-rich phase; The ion-rich liquid phase is atomized into droplets by a liquid injection device or a dispersion device, and is injected into a flash tank. By reducing the pressure, a portion of the hydrocarbons in the injected ion-rich liquid phase is flash vaporized into gaseous hydrocarbons. The vaporization process absorbs the reaction heat to cool the unvaporized ion-rich liquid phase, thereby obtaining a cooled ion-rich liquid phase. returning the cooled ion-rich liquid phase to the reactor for recycling; The gaseous hydrocarbons are separated into gas and liquid by a separator and pressurized by a compressor, and then returned to the reactor to continue the reaction.

2. The method according to claim 1, characterized in that The volume ratio of the ionic liquid to the hydrocarbons in the ion-rich liquid phase is 1:(0.1-1); the volume ratio of the ionic liquid to the hydrocarbons in the cooled ion-rich liquid phase is 1:(0.04-0.8).

3. The method according to claim 2, characterized in that The volume ratio of the ionic liquid to the hydrocarbon in the cooled ionic liquid-rich phase is 1:(0.05-0.2).

4. The method according to claim 1, wherein The temperature of the cooled ion-rich liquid phase is 5° C. to 15° C. lower than the temperature of the ion-rich liquid phase.

5. The method according to claim 1, wherein The step of atomizing the ion-rich liquid phase into droplets by a liquid spraying device or a dispersing device comprises: dispersing the ionic liquid-rich phase into a plurality of streams through a porous distributor; The plurality of streams are atomized into droplets with a particle size of 1 to 300 μm through a radial single-fluid nozzle or a radial two-fluid nozzle.

6. The method according to claim 5, characterized in that The step of atomizing the ion-rich liquid phase into droplets by a liquid spraying device or a dispersing device further comprises: The droplets atomized by the radial single-fluid nozzle or the radial two-fluid nozzle are further atomized by an ultrasonic sprayer or a liquid jet breakup device to obtain droplets with a particle size of 0.1 to 50 μm.

7. The method according to any one of claims 1 to 6, characterized in that The method further comprises: The hydrocarbon-rich phase is introduced into a settling tank for static stratification, and then sequentially passed through a high-efficiency coalescer and a separator to remove the ionic liquid to obtain a purified hydrocarbon-rich phase; introducing the purified hydrocarbon-rich phase into a distillation column to separate isobutane, normal butane and alkylate; The separated isobutane is returned to the reactor to continue the reaction.

8. A flash heat extraction system for alkylation reaction products, characterized in that: include: Separation units, liquid injection or dispersion devices, flash tanks, pressure valves, separators, and compressors; The separation unit has a liquid inlet, a top flow port and a bottom flow port; the liquid inlet is connected to the discharge port of the reactor to introduce the ionic liquid alkylation reaction product, and the top flow port and the bottom flow port output the hydrocarbon-rich phase and the ionic liquid-rich phase respectively; The liquid injection device or dispersion device is used to atomize the ion-rich liquid phase into droplets and inject them into the interior of the flash tank; The pressure valve is used to control the operating pressure of the flash tank so that all or part of the hydrocarbons in the ion-rich liquid phase injected into the flash tank are flash-vaporized into gaseous hydrocarbons. The vaporization process absorbs the reaction heat to cool the unvaporized ion-rich liquid phase to obtain a cooled ion-rich liquid phase. The cooled ion-rich liquid phase is returned to the reactor via a circulation pump at the bottom of the flash tank. The liquid separator is connected in series with the compressor and is used to pressurize the gaseous hydrocarbons and return them to the reactor for further reaction.

9. The system according to claim 8, characterized in that The liquid injection device or dispersion device includes: a porous distributor, a radial single-fluid nozzle or a radial two-fluid nozzle, and an ultrasonic sprayer or a liquid jet breakup device; The porous distributor is used to disperse the ionic liquid-rich phase into multiple streams; The radial single-fluid nozzle or radial two-fluid nozzle is used to atomize the multiple streams into droplets with a particle size of 1 to 300 μm; The ultrasonic sprayer or liquid jet breakup device is used to further atomize droplets with a particle size of 1 to 300 μm into droplets with a particle size of 0.1 to 50 μm.

10. The system according to claim 8 or 9, characterized in that Also includes: Settling tanks, high-efficiency coalescers and distillation columns; The feed port of the settling tank is in communication with the top flow port of the hydrocyclone or the settling unit, and is used for statically stratifying the hydrocarbon-rich phase; The settling tank, high-efficiency coalescer, separator and distillation tower are connected in series; the ionic liquid of the hydrocarbon-rich phase flowing out of the settling tank is removed by utilizing the lipophilic and hydrophobic fiber material in the high-efficiency coalescer, and the purified hydrocarbon-rich phase is obtained by passing through the separator; The distillation tower is used to separate the purified hydrocarbon-rich phase into isobutane, normal butane and alkylate; the top of the distillation tower is provided with a first outlet connected to the reactor to return the separated isobutane to the reactor for further reaction; A second outlet is provided on the side or bottom of the distillation tower to discharge the separated n-butane and alkylate.

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