Direct feeding process of extraction device

Abstract

The invention discloses a direct feeding process of an extraction device, which comprises a heavy component removal tower, an extraction tower and a reflux pump, and is characterized by comprising the following steps: step S (1): the heavy component removal tower carries out water washing heavy component removal, and materials are recovered in a tower kettle; step S (2): secondary de-weighting is performed after boiling condensation, and the material after complete de-weighting is directly conveyed into an extraction tower; step S (3), performing liquid-liquid extraction and material separation in the extraction tower, and repeatedly washing with water to improve the separation completion degree; and step S (4), after materials in the extraction tower are separated, the materials enter a stripping tower for solvent separation to form system water circulation, after the materials are subjected to de-weighting treatment by a de-weighting tower, the materials are directly conveyed into the extraction tower of the liquid-liquid extraction unit by a reflux pump at the top of the de-weighting tower, the step S (3) and the step S (4) are carried out in the extraction tower, and a closed-loop system is formed by a direct feeding process of the extraction device. The heavy component removal tower, the extraction tower and the reflux pump are mounted, so that closed-loop perfect design of a direct feeding process of the extraction device is realized, and continuous and continuous operation of the device is realized.

Description

Technical Field

[0001] The invention relates to the technical field of extraction, in particular to a direct material feeding process for an extraction device. Background Art

[0002] Extraction, also known as solvent extraction or liquid-liquid extraction, is a unit operation that uses the different solubility of components in the system in the solvent to separate the mixture. That is, it is a method of transferring solute substances from one solvent to another solvent by using the difference in solubility or distribution coefficient of substances in two immiscible (or slightly soluble) solvents. It is widely used in chemical, metallurgical, food and other industries, and is commonly used in petroleum refining industry; using the difference in solubility or distribution coefficient of substances in two immiscible (or slightly soluble) solvents, substances are transferred from one solvent to another solvent. After repeated extractions, most of the compounds are extracted. The solvent extraction process generally consists of extraction, washing and back extraction. Generally, the process of extracting solutes from the aqueous phase by the organic phase is called extraction, the process of removing other solutes or inclusions in the loaded organic phase by the aqueous phase is called washing, and the process of analyzing the solutes in the organic phase by the aqueous phase is called back extraction.

[0003] 1. Patent document CN104293385A discloses an extraction process of aromatic oil, which discloses "The present invention relates to an extraction process of aromatic oil, wherein high aromatic oil and solvent are reversely contacted in an extraction tower, and the refined liquid obtained at the top of the tower is subjected to solvent removal to obtain an environmentally friendly aromatic oil product; the extracted liquid obtained at the bottom of the tower is subjected to solvent removal to obtain a by-product rich in polycyclic aromatic hydrocarbons, and the solvent is recovered and recycled. The present invention uses the existing high aromatic oil for rubber filling as raw material, selectively removes polycyclic aromatic hydrocarbons in the high aromatic oil by solvent refining, thereby obtaining the desired environmentally friendly aromatic oil product, and the solvent is recycled after recovery, and The use of pressurized gas phase solvent to recover heat can effectively improve the yield of environmentally friendly aromatic oil, ensure the quality of environmentally friendly aromatic oil, and reduce the cost of solvent recovery. The aromatic oil prepared by the method of the present invention has less than 1ppm of benzopyrene and less than 10ppm of the total amount of 8 polycyclic aromatic hydrocarbon compounds, which fully meets the environmental protection requirements of the European Union, and the CA value is above 25%. The above patent uses the existing high aromatic oil for rubber filling as raw material, and realizes the recycling of solvent after recovery and reduces the cost of solvent recovery through the method of solvent refining. However, the above patent cannot perform secondary deweighting function on the material, resulting in incomplete deweighting of the material and poor product quality.

[0004] 2. Patent document CN102408914B discloses a process method for slowing down foaming of a stripping tower in an aromatic hydrocarbon extraction liquid-liquid extraction system, which discloses "The present invention discloses a process method for slowing down foaming of a stripping tower in an aromatic hydrocarbon extraction liquid-liquid extraction system, injecting a defoaming agent into the stripping tower, storing a backwashing liquid in a reflux tank at the top of the stripping tower, and the process method also includes filling a water bag in the reflux tank at the top of the stripping tower with water, and the water in the reflux tank water bag is filled and flows into the backwashing liquid in the reflux tank, and water is distributed to the backwashing liquid so that the backwashing liquid carries water, and the backwashing liquid carrying water returns to the bottom of the extraction tower and then enters the stripping tower, and the water in the backwashing liquid in the stripping tower is heated and vaporized to remove the foaming in the tower. The foam layer gradually disappears, avoiding the phenomenon of tower flushing caused by the thickening of the foam layer in the stripping tower and the increase of the tower pressure difference, thereby ensuring the separation effect of the stripping tower and the qualified mixed aromatics produced by the recovery tower. At the same time, the bottom temperature of the stripping tower and the vapor phase resistance in the tower can be reduced during the vaporization of water, so that the heat transfer of the stripping tower returns to normal. This process method can effectively slow down the foaming of the stripping tower and avoid the phenomenon of tower flushing caused by the thickening of the foam layer in the stripping tower and the increase of the tower pressure difference. The above patent effectively slows down the foaming of the stripping tower and avoids the phenomenon of tower flushing caused by the thickening of the foam layer in the stripping tower and the increase of the tower pressure difference, but the above patent cannot directly transport the material to the extraction tower, resulting in the problem of increased safety hazards caused by excessive material storage in the buffer tank.

[0005] 3. Patent document CN110257102B discloses a production system and method for preparing light aromatics by graded hydropyrolysis of raw materials rich in polycyclic aromatics. It discloses "The present invention provides a production system and method for preparing light aromatics by graded hydropyrolysis of raw materials rich in polycyclic aromatics. The production system comprises a raw material fractionation device, a primary hydropyrolysis unit, a secondary hydropyrolysis unit, a separation device, a product fractionation device, a mixed aromatics hydrogenation refining reaction unit and an aromatics extraction device arranged in sequence according to the process flow. The present invention is based on the principle of directional conversion of material structure, and adopts the molecular segmentation technology to graded hydropyrolysis. First, in the primary stage, In the hydropyrolysis reaction, the polycyclic aromatic hydrocarbons-rich raw material is hydropyrolyzed to produce medium oil mainly composed of 2-4-ring aromatic hydrocarbons, and then in the secondary hydropyrolysis reaction, the medium oil is cracked to produce mixed aromatics rich in BTX, and then the mixed aromatics are hydrorefined and the aromatics are extracted to produce light aromatic BTX products. The above patent realizes the process of directly producing light aromatics by hydropyrolysis at high temperature and high pressure and then low-pressure hydrogenation without catalytic reforming, but the above patent device has high electricity consumption and expensive processing cost, which does not meet the requirements of energy saving and consumption reduction.

[0006] To this end, the present application proposes a direct feeding process for an extraction device that can directly transport materials to an extraction tower to reduce material storage and realize a closed-loop perfect design. Summary of the invention

[0007] The object of the present invention is to provide a direct material feeding process for an extraction device to solve the technical problems raised in the above background technology.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a direct feeding process for an extraction device, comprising a deweighting tower, an extraction tower and a reflux pump, step S(1): the deweighting tower performs water washing and deweighting, and recovers the material in the tower kettle; step S(2): secondary deweighting is performed after boiling and condensing, and the completely deweighted material is directly transported into the extraction tower; step S(3): liquid-liquid extraction and separation of the material in the extraction tower, and repeated water washing improves the separation completion degree; step S(4): after the material in the extraction tower is separated, it enters the stripping tower for solvent separation to form a system water circulation, in step S(1), after the deweighting tower performs deweighting treatment on the material, the reflux pump at the top of the deweighting tower of the post-fractionation unit executes step S(2) to directly transport the material to the liquid-liquid extraction unit extraction tower, and steps S(3) and step S(4) are performed in the extraction tower, so that the direct feeding process for the extraction device forms a closed-loop system.

[0009] Preferably, in step S(1), the deweighting tower separates the heavy hydrocarbons in the mixed material by adsorption. The adsorption methods are divided into physical adsorption and chemical adsorption. The method in which the adsorbate molecules are covered on the surface of the adsorbent in a single layer or multiple layers by the action of van der Waals force is called physical adsorption, while the adsorption caused by chemical bonding between the adsorbate and the atoms on the surface of the adsorbent is called chemical adsorption. In step S(1), the material is recovered at the bottom of the tower kettle. By increasing the feed amount of the deweighting tower and raising the tower kettle liquid level, the material in the tower kettle is backflowed from the upper outlet of the reboiler into the reboiler. After the material components in the reboiler become lighter, steam is added, and the tower kettle will gradually resume circulation.

[0010] Preferably, in step S(2), the material is heated and expanded or even vaporized in the reboiler, the density becomes smaller, leaving vaporization space, and smoothly returns to the tower. The gas and liquid phases in the returned tower, the liquid phase falls to the bottom of the tower, and the gas phase is condensed upward through the condenser and then directly transported to the extraction tower by the conveying module, resulting in.

[0011] Preferably, the material in step S(3) is mixed with the raffinate oil pumped out from the raffinate oil circulation pump at the top of the extraction tower under the flow rate control of the first feed line of the extraction tower and then enters the 60th to 88th layers in the middle of the extraction tower. The lean solvent comes from the bottom of the recovery tower and the rich solvent at the bottom of the extraction tower. After heat exchange in the lean-rich solvent heat exchanger, it enters from the first tower plate at the top of the extraction tower. The flow rate is controlled by the second flow controller. A light phase and a heavy phase are formed in the tower, and most of the non-aromatic hydrocarbons are sent out from the top of the tower as the raffinate phase.

[0012] Preferably, in order to improve the purity of aromatic hydrocarbons in step S(3), light non-aromatic hydrocarbons and light aromatic hydrocarbons in the receiving tank at the top of the stripping tower are used as backwash liquid, and the backwash liquid enters the lower part of the extraction tower through the backwash module to replace the heavy non-aromatic hydrocarbons dissolved in the rich solvent. At the same time, in order to recycle the surplus backwash liquid and easily replace the olefins in the backwash liquid, an upper backwash liquid line is added. The upper backwash liquid enters from the upper feed inlet plate at the upper part of the extraction tower after being controlled by the third controller, and the flow rate is controlled by the third controller.

[0013] Preferably, in step (4), in the stripping tower, light non-aromatics and part of the aromatics in the rich solvent are evaporated, and the flow rate of the light non-aromatic gas at the top of the tower is controlled by the fourth controller. After being cooled by the air cooler and the aftercooler, it enters the liquid receiving tank, and the condensed material is the backwash liquid. The oil phase is pumped out by the backwash liquid pump and pumped into the stripping tower.

[0014] Preferably, the water in the receiving tank water bag in step (4) is pumped out by a backwash liquid pump and sent to a water stripping tower to recover the solvent under the control of an interface controller. The heat source of the stripping tower is controlled by a cascade regulation consisting of a bottom reboiler steam condensate flow controller and a tower bottom pressure controller.

[0015] Preferably, aromatic raffinate oil (abbreviated as non-aromatic) is a colorless liquid at room temperature and pressure, volatile, miscible with most organic liquids, relative density (water = 1): (0.700.3); relative vapor density (air = 1): (2.9); melting point (C): (<-60); initial distillation point (C): (>50); flash point (C): (-20); autoignition point (C): (415); heat of combustion (Kj / m1): (11000); explosion limit % (V / V): (1.0~8.4).

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention comprises a deweighting tower, an extraction tower and a reflux pump, wherein step S(1): the deweighting tower is subjected to water washing and deweighting, and materials are recovered in the tower kettle; step S(2): secondary deweighting is performed after boiling and condensing, and the materials after complete deweighting are directly transported into the extraction tower; step S(3): liquid-liquid extraction and separation of materials are performed in the extraction tower, and repeated water washing is performed to improve the separation completion degree; step S(4): after the materials in the extraction tower are separated, they are transported into the stripping tower for solvent separation, thereby forming a system water cycle, wherein the deweighting tower in step S(1) deweights the materials, and the reflux pump at the top of the deweighting tower of the post-fractionation unit executes step S(2) to directly transport the materials into the liquid-liquid extraction unit extraction tower, and steps S(3) and S(4) are performed in the extraction tower, so that the direct feeding process of the extraction device forms a closed-loop system, thereby realizing the closed-loop perfect design of the direct feeding process of the extraction device, and realizing the coherence and continuous operation of the device;

[0018] 2. The present invention is equipped with a deweighting tower, a boiler and a recovery pipeline. In step S(1), the deweighting tower separates the heavy hydrocarbons in the mixed material by adsorption. The adsorption methods are divided into physical adsorption and chemical adsorption. The method in which the adsorbate molecules are covered on the surface of the adsorbent in a single layer or multiple layers by the action of van der Waals force is called physical adsorption, while the adsorption caused by the chemical bonding between the adsorbate and the atoms on the surface of the adsorbent is called chemical adsorption. In step S(1), the material is recovered at the bottom of the tower kettle. By increasing the feed amount of the deweighting tower and raising the tower kettle liquid level, the material in the tower kettle is backflowed from the upper outlet of the reboiler into the inside of the reboiler. After the material components in the reboiler become lighter, steam is added, and the tower kettle will gradually resume circulation, thereby realizing the secondary deweighting function of the material and solving the problem of poor product quality caused by incomplete deweighting of the material.

[0019] 3. The present invention is equipped with a return tower, a conveying module and an extraction tower. In step S(2), the material is heated and expanded or even vaporized in the reboiler, and the density becomes smaller, leaving a vaporization space, and the material is smoothly returned to the tower. The gas and liquid phases in the return tower, the liquid phase falls to the bottom of the tower, and the gas phase is condensed upward by the condenser and directly conveyed to the extraction tower by the conveying module, thereby realizing the function of directly conveying the material to the extraction tower, reducing the material storage in the buffer tank, and solving the problem of increased safety hazards caused by excessive material storage;

[0020] 4. The present invention is equipped with a backwashing liquid pump, an interface controller and a water stripping tower. In step (4), the water in the receiving tank water bag is pumped out by the backwashing liquid pump, and is sent to the water stripping tower to recover the solvent under the control of the interface controller. The heat source of the stripping tower is controlled by a cascade regulation composed of a bottom reboiler steam condensate flow controller and a tower bottom pressure controller, thereby reducing the unit power consumption of the device, reducing the processing cost of the device, and achieving energy saving and consumption reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process structure of the extraction device of the present invention;

[0022] Figure 2 It is a partial structural schematic diagram of the deweighting process of the deweighting tower of the present invention;

[0023] Figure 3 It is a schematic diagram of the structure of the liquid-liquid separation process of the present invention;

[0024] Figure 4 It is a partial structural schematic diagram of the water cycle flow chart of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] See also Figure 1-Figure 2 The present invention provides an embodiment: a direct feeding process for an extraction device, comprising a deweighting tower, an extraction tower and a reflux pump, step S(1): the deweighting tower performs water washing and deweighting, and recovers the material in the tower kettle; step S(2): secondary deweighting after boiling and condensing, and the completely deweighted material is directly transported into the extraction tower; step S(3): liquid-liquid extraction and separation of materials in the extraction tower, and repeated water washing improves the separation completion degree; step S(4): after the material in the extraction tower is separated, it enters the stripping tower for solvent separation to form a system water circulation, the deweighting tower in step S(1) deweights the material, and the reflux pump at the top of the deweighting tower of the post-fractionation unit executes step S(2) to directly transport the material to the liquid-liquid extraction unit extraction tower, and steps S(3) and S(4) are performed in the extraction tower, so that the direct feeding process for the extraction device forms a closed-loop system.

[0029] See also Figure 2-Figure 3In step S(1), the deweighting tower separates the heavy hydrocarbons in the mixed material by adsorption. The adsorption methods are divided into physical adsorption and chemical adsorption. The method in which the adsorbate molecules are covered on the surface of the adsorbent in a single layer or multiple layers by the action of van der Waals force is called physical adsorption, while the adsorption caused by the chemical bonding between the adsorbate and the atoms on the surface of the adsorbent is called chemical adsorption. In step S(1), the material is recovered at the bottom of the tower kettle. By increasing the feed amount of the deweighting tower and raising the tower kettle liquid level, the material in the tower kettle is backflowed from the upper outlet of the reboiler into the reboiler. After the material components in the reboiler become lighter, steam is added, and the tower kettle will gradually resume circulation. The material relies on gravity to flow from the downflow pipe of the upper tower plate to the liquid receiving tray of the lower tower plate, and then flows horizontally through the tower plate and flows to the next tower plate from the downcomer on the other side. The function of the overflow weir is to maintain a certain thickness of liquid layer on the tower plate. Driven by the pressure difference, the gas passes through the gas channels (bubbles, sieve holes or float valves, etc.) of each layer of the tower plate from bottom to top, disperses into small streams, and bubbles through the liquid layer of each layer of the tower plate. On the tower plate, the gas and liquid phases are in close contact to exchange heat and mass. In the plate tower, the gas and liquid phases are in contact step by step, and the composition of the two phases changes stepwise along the tower height. Under normal operation, the liquid phase is the continuous phase and the gas phase is the dispersed phase, realizing the secondary deweighting function of the material and solving the problem of poor product quality caused by incomplete deweighting of the material.

[0030] See also Figure 3-Figure 4 In step S(2), the material is heated and expanded or even vaporized in the reboiler, and its density becomes smaller, leaving a vaporization space, and smoothly returns to the tower. The gas-liquid two phases in the return tower, and the liquid phase falls to the bottom of the tower. The gas phase is condensed upward through the condenser and directly transported to the extraction tower by the conveying module. The interior of the condensation tower is filled with a lot of fillers. The purpose of seasoning is to increase the contact area so that the hot water or steam and the cooling water can exchange heat. The cooling water flows from top to bottom, and when passing through the fillers, it contacts with the rising steam or hot water to absorb heat, so that it is cooled, and at the same time, a part of the water is evaporated and flows into the pool at the bottom of the cooling tower. The cooled material is directly transported to the extraction tower through the conveying module. The conveying module will not produce the problem of adsorption residue on the material, and the function of directly transporting the material to the extraction tower is realized, which reduces the material storage in the buffer tank and solves the problem of increased safety hazards caused by excessive material storage.

[0031] See also Figure 2-Figure 4In step (4), the water in the water bag of the receiving tank is pumped out by the backwash liquid pump, and is sent to the water stripping tower to recover the solvent after being controlled by the interface controller. The heat source of the stripping tower is controlled by the cascade regulation composed of the bottom reboiler steam condensate flow controller and the tower bottom pressure controller. The reboiler steam condensate flow controller and the tower bottom pressure controller form a cascade regulation to realize heat source control of the stripping tower. The backwash liquid pump pumps the water in the water bag of the receiving tank back into the stripping tower to complete solvent recovery, thereby reducing the unit power consumption of the device, reducing the processing cost of the device, and achieving energy saving and consumption reduction.

[0032] Working principle: the reflux pump at the top of the deweighting tower pumps the material into the conveying module, and the conveying module directly conveys the material to the inside of the extraction tower. The flow meter measures and mixes the raffinate oil and the material at the same time. The mixed material enters the intermediate tank and is sent to the extraction tower after adjustment by the feed flow controller regulating valve; the solvent sulfolane enters the top of the extraction tower, and under the selective dissolution of the solvent, the aromatics and non-aromatics in the feed are separated to form a rich solvent phase with a larger specific gravity and a lighter hydrocarbon phase. Because of the different specific gravities of the two, a reverse flow is formed, and the rich solvent phase flows into the distillation tower from the bottom of the tower by self-pressure, and the non-aromatics are pressed into the raffinate oil water washing tower from the top of the extraction tower under the action of pressure; water The washed raffinate oil containing solvent comes out from the top of the tower and is pumped out by a pump to return to the bottom of the tower for circulation reflux, and another part enters the raffinate oil intermediate tank. The washing water is the condensed water from the reflux tank at the top of the solvent recovery tower. The water liquid at the bottom of the raffinate oil washing tower is sent to the water stripping tower to be heated into water vapor and evaporated, and used as the stripping water vapor for the solvent regeneration tower and the recovery tower; the rich solvent at the bottom of the stripping tower is pumped out by the bottom pump and enters the recovery tower, in which the aromatics and solvent are separated, the intermediate reboiler and the bottom reboiler of the recovery tower are heated with 2.3MPa steam, the mixed aromatics and water vapor evaporated from the top of the tower are condensed by the air cooler and the water cooler and then enter the reflux tank of the recovery tower for stratification, and the water layer is cooled by cold water. The condensate is pumped out by the condensate pump and sent to the water washing tower for washing water. The mixed aromatics are pumped out by the reflux pump of the recovery tower. A part of it flows back to the top of the recovery tower, and the rest is extracted and sent to the mixed aromatics tank as the raw material of the fine retention system. The high-temperature solvent in the recovery tower kettle is pumped out by the lean solvent pump, a small part of it is sent to the solvent regeneration tower for regeneration, and most of it is sent to the extraction tower and the distillation tower after heat exchange in the water stripping tower reboiler. The condensate in the water separation tank of the distillation tower and the washing water at the bottom of the raffinate water washing tower are combined as the feed of the water stripping tower. The main body of this feed is water, containing trace hydrocarbons and a small amount of solvent. The water stripping tower is a tower with a tank reboiler, and the body is equipped with a 2-meter-high metal ball ring packing. The feed enters from the top. The steam from the top of the tower contains trace amounts of hydrocarbons, which are combined with the top flow of the distillation tower and condensed together in the water cooler. A large amount of water vapor is discharged from the upper part of the tank reboiler and led to the solvent regeneration tower and then connected in series to the recovery tower as the stripping steam for the two towers. The aqueous solution containing solvent at the bottom of the reboiler is pumped to the lower part of the recovery tower; the stripping steam from the water stripping tower enters the tower from the kettle of the solvent regeneration tower; its reboiler uses 2.3Mpa steam to heat the steam containing solvent at the top of the tower and send it directly to the bottom of the recovery tower as stripping steam. The solvent regeneration tower and the recovery tower are operated in series under vacuum conditions. Impurities in the solvent are gradually accumulated at the bottom of the regeneration tower, which is cleaned from time to time.

[0033] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A direct feeding process of an extraction device, comprising a deweighting tower, an extraction tower and a reflux pump, Features: Step S(1): washing and de-weighting the material in a de-weighting tower, and recovering the material in the tower kettle; Step S(2): de-weighting the material for a second time after boiling and condensing, and directly conveying the completely de-weighted material into an extraction tower; Step S(3): extracting and separating the material in the extraction tower by liquid-liquid extraction, and repeatedly washing with water to improve the separation completion degree; Step S(4): after the material in the extraction tower is separated, it enters a stripping tower for solvent separation, forming a system water circulation, wherein the de-weighting tower in step S(1) de-weights the material, and the top reflux pump of the de-weighting tower of the post-fractionation unit executes step S(2) to convey the material directly to the extraction tower of the liquid-liquid extraction unit, and steps S(3) and S(4) are carried out in the extraction tower, so that the direct feeding process of the extraction device forms a closed-loop system.

2. A direct feeding process of an extraction device according to claim 1, Features: In step S(1), the deweighting tower separates the heavy hydrocarbons in the mixed material by adsorption. The adsorption methods are divided into physical adsorption and chemical adsorption. The method in which the adsorbate molecules are covered on the surface of the adsorbent in a single layer or multiple layers by the action of van der Waals force is called physical adsorption, while the adsorption caused by the chemical bonding between the adsorbate and the atoms on the surface of the adsorbent is called chemical adsorption. In step S(1), the material is recovered at the bottom of the tower kettle. By increasing the feed amount of the deweighting tower and raising the tower kettle liquid level, the material in the tower kettle is backflowed from the upper outlet of the reboiler into the reboiler. After the material components in the reboiler become lighter, steam is added, and the tower kettle will gradually resume circulation.

3. A direct feeding process for an extraction device according to claim 1, Features: In step S(2), the material is heated in the reboiler to expand or even vaporize, and its density decreases, leaving a vaporization space, and smoothly returns to the tower. The gas and liquid phases in the returning tower, the liquid phase falls to the bottom of the tower, and the gas phase is condensed upward through the condenser and directly transported to the extraction tower by the transport module.

4. A direct feeding process for an extraction device according to claim 1, Features: In step S(3), the material is mixed with the raffinate oil pumped out from the raffinate oil circulation pump at the top of the extraction tower under the flow rate control of the first feed line of the extraction tower, and then enters the 60th to 88th layers in the middle of the extraction tower. The lean solvent comes from the bottom of the recovery tower and the rich solvent at the bottom of the extraction tower. After heat exchange in the lean-rich solvent heat exchanger, it enters from the first tower plate at the top of the extraction tower. The flow rate is controlled by the second flow controller. A light phase and a heavy phase are formed in the tower, and most of the non-aromatic hydrocarbons are sent out from the top of the tower as the raffinate phase.

5. A direct feeding process for an extraction device according to claim 1, Features: In order to improve the purity of aromatic hydrocarbons in step S(3), light non-aromatic hydrocarbons and light aromatic hydrocarbons in the receiving tank at the top of the stripping tower are used as backwash liquid. The backwash liquid enters the lower part of the extraction tower through the backwash module to replace the heavy non-aromatic hydrocarbons dissolved in the rich solvent. At the same time, in order to recycle the surplus backwash liquid and easily replace the olefins in the backwash liquid, an upper backwash liquid line is added. The upper backwash liquid enters from the upper feed inlet plate at the top of the extraction tower under the control of the third controller, and the flow rate is controlled by the third controller.

6. A direct feeding process for an extraction device according to claim 1, Features: In step (4), in the stripping tower, light non-aromatics and part of aromatics in the rich solvent are evaporated, and the flow rate of light non-aromatic gas at the top of the tower is controlled by the fourth controller. After being cooled by the air cooler and the aftercooler, it enters the liquid receiving tank. The condensed material is the backwash liquid, and the oil phase is pumped out by the backwash liquid pump into the stripping tower.

7. A direct feeding process for an extraction device according to claim 1, Features: In step (4), the water in the receiving tank water bag is pumped out by the backwash liquid pump and sent to the water stripping tower to recover the solvent under the control of the interface controller. The heat source of the stripping tower is controlled by a cascade regulation consisting of a bottom reboiler steam condensate flow controller and a tower bottom pressure controller.

8. The direct feeding process of the extraction device according to claim 1, Features: Aromatic raffinate oil (abbreviated as non-aromatic) is a colorless liquid at room temperature and pressure, volatile, and miscible with most organic liquids. Relative density (water = 1): (0.700.3); relative vapor density (air = 1): (2.9); melting point (C): (<-60); initial distillation point (C): (>50); flash point (C): (-20); autoignition point (C): (415); heat of combustion (Kj / m1): (11000); upper limit of explosion limit % (V / V): (1.0~8.4).

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