A system for separating heavy aromatics

Abstract

A system for separating heavy aromatics includes a heavy aromatics separation tower and a flash tower, the flash tower having a product outlet at the bottom; a first wound-tube heat exchanger having a first shell side and at least two tube sides, the inlet of the first shell side communicating with the top outlet of the heavy aromatics separation tower, and the outlet communicating downstream, the two tube sides being respectively the first tube side and the second tube side, and along the direction of the shell side medium from the inlet to the outlet of the first shell side, the first tube side is located upstream of the second tube side, the inlet of the first tube side is for hot water input, the outlet of the first tube side is for steam output, and the inlet of the second tube side is for heavy aromatics feedstock input; a second wound-tube heat exchanger having a second shell side and at least a fourth tube side; the first outlet at the bottom of the heavy aromatics separation tower is connected to the middle inlet of the flash tower via a second pipeline, and the second pipeline is provided with a second heater. Compared with the prior art, the present invention can improve heat utilization efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of gasoline processing, and in particular relates to a system for separating heavy aromatics. Background Art

[0002] Existing systems for separating heavy aromatics, such as the invention patent application with application number 202010882077.1 "A high-efficiency and energy-saving heavy aromatics separation process" (application publication number CN112047800A), use a C9 removal tower and a tetramethyl benzene tower to purify heavy aromatics. Tetramethyl benzene-enriched materials can be extracted from the heavy aromatic materials produced as a by-product of the reforming unit reaction. The double-effect distillation and next-wall distillation thermal coupling technology are used to greatly reduce operating energy consumption. Compared with the conventional double-tower distillation process, it can save more than 45% energy.

[0003] Another example is the invention patent application with application number 201911141949.2, "A method for separating C9 heavy aromatics" (application publication number CN112824366A). It uses reformed heavy aromatics as raw materials and adopts distillation to separate the raw oil. The light components can be distilled to obtain mesitylene and para-trimethylbenzene, both of which have a purity greater than 85%. The components in the heavy components with a distillation range of 170-190°C can be distilled to obtain trimethylbenzene with a purity of not less than 85%. Other heavy components can be used as heavy aromatic solvent oil.

[0004] However, the heat utilization rate of existing systems for heavy aromatics separation needs to be further improved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a system for separating heavy aromatics in view of the current status of the existing technology, so as to improve the heat utilization rate.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a system for separating heavy aromatics, comprising a heavy aromatics separation tower and a flash tower, wherein the bottom of the flash tower has a product outlet;

[0007] It is characterized by also including:

[0008] A first wound tube heat exchanger having a first shell side and at least two tube sides, wherein the inlet of the first shell side is connected to the top outlet of the heavy aromatics separation tower, and the outlet of the first shell side is connected to the downstream, the two tube sides are respectively referred to as the first tube side and the second tube side, and along the direction from the inlet to the outlet of the first shell side, the first tube side is located upstream of the second tube side, the inlet of the first tube side is for hot water input, the outlet of the first tube side is for steam output, and the inlet of the second tube side is for heavy aromatics feedstock input;

[0009] A second wound tube heat exchanger having a second shell side and at least one fourth tube side, wherein the inlet of the second shell side is connected to the top outlet of the flash tower, the outlet of the second shell side is connected to the downstream, and the inlet of the fourth tube side is connected to the outlet of the second tube side of the first wound tube heat exchanger; the outlet of the fourth tube side is connected to the middle inlet of the heavy aromatics separation tower via a first pipeline, and a first heater is provided on the first pipeline;

[0010] The first outlet at the bottom of the heavy aromatics separation tower is connected to the middle inlet of the flash tower through a second pipeline, and a second heater is provided on the second pipeline.

[0011] Preferably, the first wound tube heat exchanger further has a third tube pass, and along the direction of the shell-side medium from the inlet to the outlet of the first shell pass, the third tube pass is located downstream of the first tube pass and upstream of the second tube pass.

[0012] Preferably, a first bypass line is also included, whose inlet is used to supply the heavy aromatic hydrocarbon raw material, and whose outlet is connected to the inlet of the fourth tube side of the second wound tube heat exchanger; and a first temperature control valve is provided on the first bypass line, and the first temperature control valve is arranged to adjust the flow rate of the heavy aromatic hydrocarbon raw material in the first bypass line by sensing the temperature of the medium output from the outlet of the first shell side.

[0013] Preferably, it further comprises a first top reflux tank, the inlet of which is connected to the outlet of the first shell side of the first wound tube heat exchanger, and the bottom outlet of which is connected to the upper inlet of the heavy aromatics separation tower;

[0014] It also includes a second tower top reflux tank, the inlet of which is connected to the outlet of the second shell side of the second wound tube heat exchanger, and the bottom outlet of which is connected to the upper inlet of the flash tower.

[0015] Furthermore, it also includes a first circulation pipeline, both ends of which are respectively connected to the two interfaces at the top of the first tower top reflux tank, and a first tower top aftercooler is provided on the first circulation pipeline;

[0016] It also includes a second circulation pipeline, both ends of which are respectively connected to the two interfaces at the top of the second tower top reflux tank, and a second tower top aftercooler is provided on the second circulation pipeline.

[0017] In the above scheme, preferably, the second outlet at the bottom of the heavy aromatics separation tower is connected to the lower inlet of the heavy aromatics separation tower through a third circulation pipeline, and a tower kettle reboiler is provided on the third circulation pipeline;

[0018] The second outlet at the bottom of the flash tower is connected to the lower inlet of the flash tower through a fourth circulation pipeline, and a bottom circulation heater is provided on the fourth circulation pipeline.

[0019] The installation of an external reboiler requires additional space outside the heavy aromatics separation tower. The bottom circulation volume is limited by the installation height of the external reboiler and the pressure drop in the connecting piping, which increases costs. Furthermore, the energy consumption of the heavy aromatics separation tower and the investment in the reboiler need to be further reduced.

[0020] Therefore, in order to further reduce energy consumption and investment, a bottom reboiler is further provided at the lower part of the heavy aromatics separation tower.

[0021] Preferably, the tower bottom reboiler has a spirally wound first heat exchange tube, and both ends of the second heat exchange tube are respectively used for the heat transfer medium outside the heavy aromatics separation tower to enter and exit.

[0022] Preferably, the heavy aromatics separation tower comprises:

[0023] The tower body has a liquid storage chamber at the bottom and a gas-liquid separation chamber above the liquid storage chamber, and a feed pipe is provided on the side wall of the gas-liquid separation chamber;

[0024] The first heat exchange tube is arranged in the liquid storage cavity at the lower part of the tower body along the vertical direction, and is spirally wound from the inside to the outside to form multiple layers of spiral tubes, and a first gap that runs vertically through is formed between adjacent layers of spiral tubes;

[0025] The heavy aromatics separation tower also includes:

[0026] The pipe inlet pipe for the heat transfer medium is provided on the side wall of the tower body and is connected to the upper end of the first heat exchange pipe;

[0027] The pipe outlet pipe for the output of the above-mentioned heat-conducting medium is arranged on the side wall of the tower body and is connected with the lower end pipe opening of the first heat exchange pipe.

[0028] In this way, the first heat exchange tube is arranged in the liquid storage chamber at the lower part of the tower body, which can directly heat the liquid in the liquid storage chamber. The heated liquid can flow upward along the first gap due to the decrease in density, until the boiling gas overflows and enters the gas-liquid separation chamber for gas-liquid separation. The whole process can reduce the energy consumption of the separation tower, make the overall structure more compact, and reduce investment.

[0029] Preferably, the heavy aromatics separation tower further includes a vertically arranged draft tube, which is sleeved around the outermost spiral tube. The outer circumferential wall of the draft tube is spaced from the inner circumferential wall of the tower body to form a second gap. In this way, after heating, the liquid in the draft tube decreases in density and flows upward along the first gap. The liquid outside the draft tube, with its higher density, automatically flows downward, forming a self-circulating flow.

[0030] Preferably, the diameter of the upper port of the guide tube gradually increases from bottom to top, thereby facilitating the diffusion of gas and liquid phases to the surroundings.

[0031] Preferably, the inner circumferential wall of the guide cylinder and the outermost spiral tube are spaced apart from each other, and the spacing distance is consistent with the spacing distance between the adjacent layers of spiral tubes.

[0032] Furthermore, the spiral directions of the spiral tubes in adjacent layers are opposite.

[0033] In each of the above schemes, preferably, the multi-layer spiral tubes formed by winding the first heat exchange tubes are a group of heat exchange units, and there are at least two groups, which are arranged at intervals along the circumferential direction;

[0034] The upper end of the first heat exchange tube of each group of heat exchange units is connected to the tube inlet pipe;

[0035] The lower end of the first heat exchange tube of each group of heat exchange units is connected to the tube outlet pipe.

[0036] Of course, there may be only one set of heat exchange units.

[0037] Preferably, an upper manifold is provided in the tower body above each group of heat exchange units, the input port of the upper manifold is connected to the tube-side inlet pipe, the number of output ports of the upper manifold is consistent with the number of the heat exchange units, and each output port of the upper manifold is connected to the upper end of the first heat exchange tube of the corresponding heat exchange unit;

[0038] A lower collecting pipe is provided in the tower body below each group of heat exchange units, the output port of the lower collecting pipe is connected to the pipe outlet of the tube side, the number of the input ports of the lower collecting pipe is consistent with the number of the heat exchange units, and each input port of the lower collecting pipe is connected to the lower end pipe port of the first heat exchange pipe of the corresponding heat exchange unit.

[0039] Preferably, there are four groups of heat exchange units, which are arranged at equal intervals along the circumferential direction.

[0040] In each of the above schemes, preferably, a condensate outlet pipe is provided on the bottom wall of the liquid storage chamber.

[0041] Preferably, the tube-side inlet pipe is arranged perpendicular to the side wall of the tower body.

[0042] The medium output from the outlet of the first shell side of the first wound tube heat exchanger often needs to be supercooled, and the supercooling usually requires condensation and cooling in the condenser, and then input into the liquid storage tank for gas-liquid separation. The liquid after gas-liquid separation can be returned to the heavy aromatics separation tower again, and the non-condensable gas after gas-liquid separation is discharged. However, since the supercooling of the medium usually requires secondary cooling, that is, at least two condensers are required to be designed in series, or the volume of the condenser is designed to be very large. In addition, the existing liquid storage tank is designed separately from the condenser. The liquid storage tank usually needs to consider a large gas-liquid separation space and liquid storage space as well as various pipes, resulting in a relatively large size of the liquid storage tank. Therefore, the condensing equipment composed of the existing condenser and the liquid storage tank has a large overall footprint and a large investment, and the connecting pipes between the two condensers and the connecting pipes between the condenser and the liquid storage tank increase the pressure loss of the system. Therefore, in order to achieve a compact structure and to realize the condensation, supercooling, gas-liquid separation and liquid storage functions in a smaller space, preferably, the first wound tube heat exchanger includes:

[0043] A first shell-side cylinder extending vertically has a shell-side inlet at its upper portion serving as the first shell-side inlet and an open lower end serving as the first shell-side outlet;

[0044] The second heat exchange tube is axially arranged in the first shell-side cylinder;

[0045] A second shell-side cylinder extending vertically, at least the upper portion of which is sleeved on the outer periphery of the bottom of the first shell-side cylinder;

[0046] a condensation subcooling element disposed within the second shell-side cylinder and below the first shell-side cylinder, the condensation subcooling element comprising a condensation subcooling channel extending vertically, the upper end of the condensation subcooling channel being in communication with the first shell-side outlet of the first shell-side cylinder; an outer peripheral wall of the condensation subcooling channel being opposed to an inner peripheral wall of the second shell-side cylinder to form a third gap;

[0047] A non-condensable gas outlet is provided on the second shell-side cylinder at a position above the condensation subcooling member;

[0048] The space of the second shell-side cylinder below the condensation subcooling member serves as a liquid storage chamber connected to the lower end of the condensation subcooling channel, and the liquid storage chamber is connected to the non-condensable gas outlet through the third gap.

[0049] The bottom of the second shell-side cylinder is provided with a second shell-side outlet as the outlet of the first shell-side and is connected to the upper inlet of the heavy aromatics separation tower.

[0050] In this way, the design of the second heat exchange tube can condense the shell-side medium to be condensed once. The shell-side medium after the primary condensation undergoes secondary condensation and gas-liquid separation in the condensation subcooling channel. The liquid after gas-liquid separation flows into the liquid storage chamber under the action of its own gravity, and the non-condensable gas is discharged from the non-condensable gas outlet through the spiral channel, thereby achieving condensation, gas-liquid separation, and liquid storage functions in a relatively small space. The present invention also integrates condensation, gas-liquid separation, and liquid storage into a single device, eliminating the need for separate connecting pipes. At the same time, the equipment of the present invention is installed vertically, which brings significant economic benefits in terms of investment, floor space, and system operating costs.

[0051] To improve the condensation and gas-liquid separation effects, preferably, the condensation subcooling channel is arranged in a spiral from the inside to the outside, which can increase the contact area between the condensation subcooling channel and the shell-side medium, thereby improving the condensation and gas-liquid separation effects.

[0052] The condensation subcooling channel can generate cooling when powered. Preferably, the condensation subcooling element comprises a central tube and a spiral plate. The central tube extends vertically, with its upper end communicating with the lower end of the second heat exchange tube and its lower end closed. The spiral plate is disposed on the outer circumference of the central tube and has two adjacent spiral channels wound clockwise or counterclockwise along the circumference. The first spiral channel serves as the condensation subcooling channel, while the upper and lower ends of the second spiral channel are closed, and the inner end of the second spiral channel, which is closer to the central tube, communicates with the central tube. A first tube-side inlet pipe is disposed on the sidewall of the second shell-side cylinder and communicates with the outer end of the second spiral channel, which is farther from the central tube. The first tube-side inlet pipe serves as the inlet to one tube side of the first wound tube heat exchanger. Thus, the tube-side medium for condensation first enters the second spiral channel to condense the shell-side medium in the first spiral channel, and then enters the heat exchange tube to condense the shell-side medium in the first shell-side cylinder, thereby achieving condensation and subcooling of the shell-side medium.

[0053] In order to improve the effect of gas-liquid separation, further, the first spiral channel has a central portion relatively close to the central tube and a peripheral portion relatively far away from the central tube;

[0054] The lower port of the first shell-side cylinder is opposite to and connected to the upper port of the central part of the first spiral channel, and the periphery of the lower port of the first shell-side cylinder extends horizontally outward to form a baffle covering the upper port of the outer part of the first spiral channel.

[0055] In this way, the liquid phase in the shell-side medium flows through the central part of the first spiral channel, and the gas phase can spiral outward to the peripheral part, then enter the gap and be discharged from the non-condensable gas outlet.

[0056] Preferably, the portion of the baffle relatively far from the non-condensable gas outlet extends outwardly to the inner peripheral wall of the second shell-side cylinder, so that the non-condensable gas can flow toward the non-condensable gas outlet in a concentrated manner.

[0057] Furthermore, the lower end of the first shell-side cylinder is in the shape of an inverted cone.

[0058] Furthermore, the side wall of the inverted cone is opposite to the non-condensable gas outlet, so as to promote the non-condensable gas to flow out faster.

[0059] In the above schemes, preferably, the side wall of the second shell-side cylinder is provided with a first liquid level gauge and a second liquid level gauge, the first liquid level gauge is arranged corresponding to the central part in the up and down directions of the condensation subcooling channel, and the second liquid level gauge is located below the condensation subcooling channel and above the second shell-side outlet.

[0060] Preferably, a pressure gauge port for detecting system pressure is provided on the side wall of the second shell-side cylinder, and the pressure gauge port is located above the non-condensable gas outlet.

[0061] Compared with the prior art, the advantages of the present invention are: by providing a first wound-tube heat exchanger and a second wound-tube heat exchanger, heat from the gas phase at the top of the heavy aromatics separation tower and the flash tower can be recovered without the need for an additional air cooler; and the first wound-tube heat exchanger is a low-pressure-drop, low-vacuum coil heat exchanger that performs graded and temperature-differentiated heat exchange, while achieving integration of heat exchangers of different diameters;

[0062] In the present invention, the heavy aromatics separation tower adopts negative pressure operation to reduce the vaporization temperature of the feed and adopts a high feed vaporization rate, providing 70% of the heat during feeding, and the tower bottom reboiler only provides 30% of the heat;

[0063] The flash tower is operated in full vacuum, the tower feed adopts a high gasification rate, and the feed provides 100% of the heat for tower operation. The bottom circulation heater is only used as a backup and is used when the second heater is insufficient.

[0064] Moreover, the heat recovery cooling medium of the two towers of the present invention, namely the heavy aromatics separation tower and the flash tower, comes from the materials of the present device or nearby devices, and there is no heat transfer, which belongs to the one-time utilization of heat. This is different from the conventional low-temperature heat recovery, which uses hot water to extract heat and then supplies the heat of the hot water to other devices, resulting in energy loss.

[0065] The heat utilization rate of the system of the present invention reaches more than 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is a schematic structural diagram of embodiment 1 of the present invention;

[0067] Figure 2 for Figure 1Enlarged view of part A in the middle;

[0068] Figure 3 for Figure 1 Enlarged view of middle part B;

[0069] Figure 4 This is a schematic structural diagram of a heavy aromatics separation tower in Example 2 of the present invention;

[0070] Figure 5 Schematic diagram of the partial structure of the heavy aromatics separation tower in Example 3 of the present invention;

[0071] Figure 6 for Figure 5 A top view of

[0072] Figure 7 for Figure 5 Usage status diagram;

[0073] Figure 8 This is the structural intention of a single heat exchange unit in the third embodiment of the present invention;

[0074] Figure 9 Schematic diagram of the partial structure of each layer of spiral tubes in Example 3 of the present invention;

[0075] Figure 10 Schematic diagram of the partial structure of the medium and heavy aromatics separation tower of Example 4 of the present invention;

[0076] Figure 11 for Figure 10 Usage status diagram;

[0077] Figure 12 This is a structural diagram of Embodiment 5 of the present invention;

[0078] Figure 13 for Figure 12 Enlarged view of the middle C section;

[0079] Figure 14 for Figure 12 Enlarged view of the middle D part;

[0080] Figure 15 Schematic diagram of the partial structure of the first wound tube heat exchanger in the fifth embodiment of the present invention;

[0081] Figure 16 for Figure 15 A magnified view of the local structure. DETAILED DESCRIPTION

[0082] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0083] Example 1:

[0084] like Figures 1 to 31 is a preferred embodiment of a system for separating heavy aromatics according to the present invention, the system comprising a first coiled tubular heat exchanger 100 , a heavy aromatics separation tower 200 , a flash tower 300 , and a second coiled tubular heat exchanger 400 .

[0085] The first wound-tube heat exchanger 100 is vertically arranged and comprises a first shell side 101 and three tube sides. The top inlet of the first shell side 101 is connected to the top outlet of the heavy aromatics separation tower 200, and the bottom outlet of the first shell side 101 is connected to the inlet of the downstream first overhead reflux drum 500. The bottom outlet of the first overhead reflux drum 500 is connected to the upper inlet of the heavy aromatics separation tower 200. A first circulation line 501 is also included, with its ends respectively connected to two ports at the top of the first overhead reflux drum 500. A first overhead aftercooler 502 is provided on the first circulation line 501. The first overhead aftercooler 502 is a heat exchanger, and the cooling medium is circulating water, which is used to heat the circulating water.

[0086] The three tube passes of the first wound-tube heat exchanger 100 are designated as the first tube pass 102, the second tube pass 103, and the third tube pass 104. They are arranged sequentially along the direction of the shell-side medium from the inlet to the outlet of the first shell pass 101 (i.e., from top to bottom). The inlet of the first tube pass 102 is for hot water input, and the outlet of the first tube pass 102 is for steam output. The inlet of the second tube pass 103 is for heavy aromatic feedstock input, and the outlet of the second tube pass 103 is for heated heavy aromatic feedstock output. The inlet of the third tube pass 104 is for 40°C medium input (this medium can be from an adjacent device). The outlet of the third tube pass 104 is connected to downstream equipment, and the outlet of the third tube pass 104 outputs a medium at a temperature of 130°C.

[0087] The second wound-tube heat exchanger 400 is horizontally arranged and comprises a second shell side 401 and eight tube sides. The inlet of the second shell side 401 is connected to the top outlet of the flash column 300, and the outlet of the second shell side 401 is connected to the inlet of the downstream second tower top reflux drum 510. The bottom outlet of the second tower top reflux drum 510 is connected to the upper inlet of the flash column 300. A second circulation line 511 is also included, with its ends connected to two ports at the top of the second tower top reflux drum 510. A second tower top aftercooler 512 is installed on the second circulation line 511. The second tower top aftercooler 512 is a heat exchanger, and the cooling medium is circulating water, which is used to heat the circulating water.

[0088] One of the eight tube passes of the second wound tube heat exchanger 400 is the fourth tube pass 402. The fourth tube pass 402 is closest to the inlet of the second shell pass 401 relative to the other seven tube passes, and the inlet of the fourth tube pass 402 is connected to the outlet of the second tube pass 103 of the first wound tube heat exchanger 100. The outlet of the fourth tube pass 402 is connected to the middle inlet of the heavy aromatics separation tower 200 via a first pipeline 403, and the first pipeline 403 is provided with a first heater 404. Along the direction of the shell side medium from the inlet to the outlet of the second shell pass 401, the other seven tube passes are distributed in sequence and respectively supply heavy C9 at a temperature of 40°C, medium 1 at a temperature of 40°C, medium 2 at a temperature of 40°C, medium 3 at a temperature of 40°C, medium 4 at a temperature of 40°C, medium 5 at a temperature of 40°C, and medium 6 at a temperature of 40°C. The temperature of heavy C9 after heat exchange is 115°C, the temperature of medium 1 after heat exchange is 115°C, the temperature of medium 2 after heat exchange is 100°C, the temperature of medium 3 after heat exchange is 100°C, the temperature of medium 4 after heat exchange is 100°C, the temperature of medium 5 after heat exchange is 85°C, and the temperature of medium 6 after heat exchange is 65°C. The heavy C9 and mediums 1 to 6 can be from adjacent devices.

[0089] The system also includes a first bypass line 105, whose inlet is for inputting heavy aromatic feedstock and whose outlet is connected to the inlet of the fourth tube side 402 of the second wound-tube heat exchanger 400. A first temperature-controlled valve 106 is provided on the first bypass line 105. The valve is configured to regulate the flow rate of the heavy aromatic feedstock within the first bypass line 105 by sensing the temperature of the medium output from the outlet of the first shell side 101. Under normal operating conditions, the heavy aromatic feedstock flows entirely through the first bypass line 105 and does not participate in heat exchange. When the top condensation temperature of the first overhead reflux drum 500 does not meet the specified temperature, the bypass line opening is reduced, allowing some of the heavy aromatic feedstock to participate in heat exchange, maintaining the condensate temperature at or below 80°C.

[0090] The first bottom outlet of the heavy aromatics separation tower 200 and the middle inlet of the flash tower 300 are connected via a second pipeline 301 , and a second heater 302 is provided on the second pipeline 301 .

[0091] The second outlet at the bottom of the heavy aromatics separation tower 200 is connected to the lower inlet of the heavy aromatics separation tower 200 via a third circulation line 201, and a bottom reboiler 202 is provided on the third circulation line. The second outlet at the bottom of the flash tower 300 is connected to the lower inlet of the flash tower 300 via a fourth circulation line 303, and a bottom circulation heater 304 is provided on the fourth circulation line. The flash tower 300 has a product outlet at its bottom.

[0092] In this embodiment, the first heater 404, the second heater 302, the bottom reboiler 202, and the bottom circulation heater 304 are all wound-tube heat exchangers, using thermal oil as the heat medium. The use of a wound-tube heat exchanger in the second heater 302 maximizes the vaporization rate of the feed to the flash tower 300.

[0093] The heat exchange process of this embodiment is as follows:

[0094] The C9 raw material separation optimization project process mainly includes feed and normal pressure separation and reduced pressure separation.

[0095] The heavy aromatics raw material in the tank area is transported to the second tube side 103 of the first wound tube heat exchanger 100, exchanges heat with the top gas output from the top of the heavy aromatics separation tower 200, and then exchanges heat with the fourth tube side 402 of the second wound tube heat exchanger 400, and then is heated by the first heater 404 before being sent to the heavy aromatics separation tower 200.

[0096] The heavy aromatics separation tower 200 operates at a slight negative pressure. The overhead gas is first passed through the first tube pass 102 of the first wound-tube heat exchanger 100, heating the water in the first tube pass 102 to steam. The gas is then cooled by the third tube pass 104 and the second tube pass 103 of the first wound-tube heat exchanger 100 before being transferred to the first overhead reflux drum 500. The gaseous phase exiting the bottom outlet of the first overhead reflux drum 500 is pressurized by an overhead extraction pump and then split into two paths: one path returns to the heavy aromatics separation tower 200 as overhead reflux, while the other path is cooled in an air cooler and then delivered as product JQ-1. The gaseous phase exiting the top outlet of the first overhead reflux drum 500 is then connected to the first overhead aftercooler 502, where it is cooled by circulating water. The first overhead aftercooler 502 is controlled by a split-range system, fed with nitrogen and discharged to a flare, retaining the vacuum pump process.

[0097] The bottom circulating liquid output from the second outlet at the bottom of the heavy aromatics separation tower 200 enters the bottom reboiler 202 through the bottom circulating pump and then returns to the tower, with the heat source provided by the heat transfer oil.

[0098] The bottom liquid output from the first outlet at the bottom of the heavy aromatics separation tower 200 is transported to the second heater 302 via a tower kettle extraction pump for heating before entering the flash tower 300. The flash tower 300 operates at a negative pressure. The overhead gas output from the top outlet of the flash tower 300 is cooled by heat exchange in the second wound-tube heat exchanger 400 and then sent to the second overhead reflux tank 510. The medium output from the bottom outlet of the second overhead reflux tank 510 is pressurized by the overhead extraction pump and then split into two paths. One path returns to the flash tower 300 as overhead reflux, while the other path first cools the heavy aromatics output from the first outlet at the bottom of the flash tower 300 via a heavy aromatics / JQ-5 heat exchanger (the heavy aromatics output from the first outlet at the bottom of the flash tower 300 are output after heat exchange). It is then cooled in an air cooler and shipped as product JQ-5. The gaseous medium output from the top outlet of the second overhead reflux tank 510 is connected to the second overhead aftercooler 512 and cooled by circulating water. The top gas phase of the second tower top aftercooler 512 is connected to a vacuum pump.

[0099] The bottom circulating liquid output from the second outlet at the bottom of the flash tower 300 enters the bottom circulating heater 304 through the bottom circulating pump and then returns to the tower, with the heat source provided by the heat transfer oil.

[0100] In this embodiment, the heavy aromatics separation tower 200 adopts a slightly negative pressure operation to reduce the temperature of the feed, reduce the operating temperature of the heat transfer oil, and reduce the operating load of the tower. The top recovery rate is 45 / 72=62.5%, the bottom recovery rate is 39 / 72=54.17%, and the reflux ratio is controlled to R=12 / 33=0.3636.

[0101] Flash tower 300 operates at a high vacuum, lowering both the tower's operating temperature and the tower's feed temperature, reducing the heat transfer oil's operating temperature and the tower's operating load. The overhead recovery rate is 39 / 39 = 100%, while the bottom recovery rate is 3 / 39 = 7.7%. The reflux ratio is controlled at R = 3 / 36 = 0.083.

[0102] Furthermore, this embodiment utilizes a wound tube heat exchanger to achieve low-temperature temperature difference heat exchange, which can reduce the temperature of the heating medium, so that the conventional 300°C thermal oil system of the project can meet the heating requirements, and the heat transfer medium is safe and reliable.

[0103] Example 2:

[0104] like Figure 4 As shown, a preferred embodiment 2 of a system for separating heavy aromatics of the present invention is shown. This embodiment is basically the same as the first embodiment, except that the bottom reboiler 202 is arranged at the lower part of the heavy aromatics separation tower 200, and the bottom reboiler 202 has a spirally wound first heat exchange tube 220, and both ends of the first heat exchange tube 220 are used for the heat transfer medium outside the heavy aromatics separation tower 200 to enter and exit.

[0105] Example 3:

[0106] like Figures 5 to 9As shown, a preferred embodiment 3 of a system for separating heavy aromatics of the present invention is shown. This embodiment is basically the same as the second embodiment, except that the heavy aromatics separation tower 200 in this embodiment includes a tower body 210, a first heat exchange tube 220, a tube side inlet pipe 230, a tube side outlet pipe 240 and a guide tube 250.

[0107] The tower body 210 comprises a liquid storage chamber 211 at its lower portion and a gas-liquid separation chamber 212 above the liquid storage chamber 211. The gas-liquid separation chamber 212 is directly connected to the liquid storage chamber 211 and is equipped with gas-liquid separation trays. These trays are conventional and will not be described in detail here. A feed connection 213 is provided on the sidewall of the gas-liquid separation chamber 212, near the liquid storage chamber 211. A condensate outlet connection 214 is provided on the bottom wall of the liquid storage chamber 211.

[0108] The pipe-side inlet pipe 230 is used for inputting heat transfer medium and is arranged on the side wall of the gas-liquid separation chamber 212 of the tower body 210 near the liquid storage chamber 211 , and the pipe-side inlet pipe 230 is arranged perpendicular to the side wall of the tower body 210 .

[0109] The pipe-side outlet pipe 240 is used for outputting the heat-conducting medium and is disposed on the side wall of the bottom of the liquid storage chamber 211 of the tower body 210 .

[0110] The first heat exchange tube 220 is arranged in the liquid storage chamber 211 at the lower part of the tower body 210 along the vertical direction, and is spirally wound from the inside to the outside to form multiple layers of spiral tubes 221. The spiral directions of adjacent layers of spiral tubes 221 are opposite, and a first gap 222 is formed between adjacent layers of spiral tubes 221. For details, please refer to Figure 9 The guide tube 250 is vertically arranged and sleeved on the outer circumference of the outermost spiral tube 221. The inner circumferential wall of the guide tube 250 and the outermost spiral tube 221 are spaced opposite each other, and the spacing is consistent with the spacing between adjacent layers of spiral tubes 221. At the same time, the diameter of the upper end of the guide tube 250 gradually increases from bottom to top.

[0111] In this embodiment, the multi-layered spiral tubes 221 formed by winding the first heat exchange tubes 220 and the corresponding draft tubes 250 form a set of heat exchange units. There are four sets of these units, circumferentially and evenly spaced within the liquid storage chamber 211. Part of the outer circumferential wall of the draft tubes 250 of each heat exchange unit is spaced apart from the inner circumferential wall of the tower body 210, forming a second gap 251. The upper ends of the first heat exchange tubes 220 of each heat exchange unit are connected to the tube-side inlet pipe 230, and the lower ends of the first heat exchange tubes 220 of each heat exchange unit are connected to the tube-side outlet pipe 240. Specifically, an upper manifold 260 is provided within the tower body 210 above each heat exchange unit. The inlet of the upper manifold 260 is connected to the tube-side inlet pipe 230, and the upper manifold 260 has four outlets, each of which is connected to the upper end of the first heat exchange tube 220 of the corresponding heat exchange unit. A lower manifold 270 is provided below each group of heat exchange units in the tower body 210. The output port of the lower manifold 270 is connected to the pipe outlet pipe 240. The lower manifold 270 has four input ports, and each input port is connected to the lower end of the first heat exchange tube 220 of the corresponding heat exchange unit.

[0112] In this way, under the action of the heat transfer medium in the first heat exchange tube 220, the liquid in the guide tube 250 is heated and can flow upward along the first gap 222 due to the decrease in density, until the boiling gas overflows and enters the gas-liquid separation chamber 212 for gas-liquid separation. The liquid outside the guide tube 250 has a higher density and automatically flows downward, forming a self-circulating flow. Figure 7 .

[0113] Example 4:

[0114] like Figure 10 、 11 As shown, a preferred embodiment 4 of a system for separating heavy aromatics of the present invention is basically the same as the third embodiment, except that there is only one group of heat exchange units in this embodiment, and the upper end of the first heat exchange tube 220 in this group of heat exchange units is directly connected to the tube side inlet pipe 230, and the lower end is directly connected to the tube side outlet pipe 240.

[0115] Embodiment 5:

[0116] like Figures 12-16 FIG. 5 shows a preferred embodiment of a system for separating heavy aromatics according to the present invention. This embodiment is substantially the same as the first embodiment, except that the first top reflux drum 500, the first top aftercooler 502, the second top reflux drum 510, and the second top aftercooler 512 are not required. Specifically, the first wound tube heat exchanger 100 of this embodiment includes a first shell-side cylinder 110, a second heat exchange tube 120, a second shell-side cylinder 130, and a condensing subcooling element 140.

[0117] The first shell side cylinder 110 extends vertically, with a shell side inlet 111 at its upper end serving as the inlet of the first shell side 101 and an open lower end serving as a first shell side outlet 112. The lower end of the first shell side cylinder 110 is in the shape of an inverted cone.

[0118] The second heat exchange tube 120 is axially arranged inside the first shell-side cylinder 110;

[0119] The second shell-side cylinder 130 extends vertically, with at least its upper portion being sleeved around the outer periphery of the bottom of the first shell-side cylinder 110. A non-condensable gas outlet 132 is provided on the sidewall of the second shell-side cylinder 130 at a position corresponding to the inverted cone at the lower end of the first shell-side cylinder 110. The space below the second shell-side cylinder 130 serves as a liquid storage chamber 133. A second shell-side outlet 135 is provided at the bottom of the second shell-side cylinder 130, serving as the outlet from the first shell-side 101 and communicating with the upper inlet of the heavy aromatics separation column 200.

[0120] The condensation subcooling component 140 is arranged in the second shell-side cylinder 130, below the first shell-side cylinder 110, and above the liquid storage chamber 133. The condensation subcooling component 140 has a condensation subcooling channel 141 extending up and down. The upper end of the condensation subcooling channel 141 is connected to the first shell-side outlet 112 of the first shell-side cylinder 110; the lower end of the condensation subcooling channel 141 is connected to the liquid storage chamber 133; the outer peripheral wall of the condensation subcooling channel 141 is opposite to the inner peripheral wall of the second shell-side cylinder 130 to form a third gap 131, so that the liquid storage chamber 133 is connected to the non-condensable gas outlet 132 through the third gap 131.

[0121] In this embodiment, the condensation subcooling member 140 has a central tube 142 and a spiral plate 143. The central tube 142 extends up and down, and the upper end of the central tube 142 is connected to the lower end of the second heat exchange tube 120, and the lower end of the central tube 142 is closed; the spiral plate 143 is arranged on the outer periphery of the central tube 142, and the spiral plate 143 has two spiral channels that are wound clockwise or counterclockwise along the circumferential direction and spirally arranged from the inside to the outside, wherein the first spiral channel 1431 serves as the above-mentioned condensation subcooling channel 141, and the first spiral channel 1431 has a central portion relatively close to the central tube 142 and an outer portion relatively far away from the central tube 142; the upper end of the central portion of the first spiral channel 1431 is opposite to and connected to the lower end of the first shell-side cylinder 110, and the peripheral edge of the lower end of the first shell-side cylinder 110 extends horizontally outward to form a baffle 114 covering the upper end of the outer portion of the first spiral channel 1431. The portion of the baffle 114 relatively away from the non-condensable gas outlet 132 extends outwardly to the inner circumferential wall of the second shell-side cylinder 130 .

[0122] The upper and lower ports of the second spiral channel 1432 are closed, and the inner port of the second spiral channel 1432 close to the central tube 142 is connected to the central tube 142. A first tube-side inlet pipe 134 is provided on the side wall of the second shell-side cylinder 130, which is connected to the outer port of the second spiral channel 1432 away from the central tube 142. The first tube-side inlet pipe 134 serves as the inlet of one of the tube sides of the first wound tube heat exchanger 100.

[0123] That is, the tube-side medium enters the second spiral channel 1432 through the first tube-side inlet pipe 134, and spirally flows from outside to inside to the central tube 142, and then flows into the second heat exchange tube 120, exchanges heat with the shell-side medium in the first shell-side cylinder 110, and is output.

[0124] The shell-side medium is input into the first shell-side cylinder 110 through the shell-side inlet 111, then flows downward and enters the first spiral channel 1431. After heat exchange with the tube-side medium in the second spiral channel 1432, the liquid phase is stored in the liquid storage chamber 133, and the gas phase flows upward and is discharged from the non-condensable gas outlet 132.

[0125] At the same time, a first liquid level gauge 136 and a second liquid level gauge 137 are provided on the side wall of the second shell side cylinder 130. The first liquid level gauge 136 is provided at the central position corresponding to the up-down direction of the condensation subcooling channel 141. The second liquid level gauge 137 is located below the condensation subcooling channel 141 and above the second shell side outlet 135 to monitor the liquid level in the liquid storage chamber 133. The highest point of the liquid level in the liquid storage chamber 133 does not exceed 10% of the width of the spiral plate 143 in the up-down direction. The lowest point of the liquid level is located between the first liquid level gauge 136 and the second liquid level gauge 137. Figure 15 As shown by the double-dotted line in the figure, the double-dotted line on the upper side refers to the highest point of the liquid level, and the double-dotted line on the lower side refers to the lowest point of the liquid level.

[0126] A pressure gauge port 138 for detecting system pressure is provided on the side wall of the second shell-side cylinder 130 , and the pressure gauge port is located above the non-condensable gas outlet 132 .

[0127] The structure of the second wound-tube heat exchanger 400 in this embodiment is designed with reference to the structure of the first wound-tube heat exchanger 100 and is not described in detail here.

[0128] In the present specification and claims, directional terms such as "front," "back," "up," "down," "left," "right," "side," "top," and "bottom" are used to describe various exemplary structural parts and components of the present invention. However, these terms are used herein for convenience of description only and are based on the exemplary orientations shown in the accompanying drawings. Because the embodiments disclosed herein can be arranged in various orientations, these directional terms are intended for illustrative purposes only and should not be construed as limiting. For example, "up" and "down" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

Claims

1. A system for separating heavy aromatics, comprising a heavy aromatics separation tower (200) and a flash tower (300), wherein the bottom of the flash tower (300) has a product outlet; It is characterized by Also included are: A first wound tube heat exchanger (100) having a first shell side (101) and at least two tube sides, wherein the inlet of the first shell side (101) is connected to the top outlet of the heavy aromatics separation tower (200), and the outlet of the first shell side (101) is connected to the downstream, the two tube sides are respectively a first tube side (102) and a second tube side (103), and along the direction of the shell side medium from the inlet to the outlet of the first shell side (101), the first tube side (102) is located upstream of the second tube side (103), the inlet of the first tube side (102) is for hot water input, the outlet of the first tube side (102) is for steam output, and the inlet of the second tube side (103) is for heavy aromatics raw material input; A second wound tube heat exchanger (400) having a second shell side (401) and at least a fourth tube side (402), wherein the inlet of the second shell side (401) is connected to the top outlet of the flash tower (300), the outlet of the second shell side (401) is connected to the downstream, and the inlet of the fourth tube side (402) is connected to the outlet of the second tube side (103) of the first wound tube heat exchanger (100); the outlet of the fourth tube side (402) is connected to the middle inlet of the heavy aromatics separation tower (200) via a first pipeline (403), and the first pipeline (403) is provided with a first heater (404); The first outlet at the bottom of the heavy aromatics separation tower (200) and the middle inlet of the flash tower (300) are connected via a second pipeline (301), and a second heater (302) is provided on the second pipeline (301); A tower bottom reboiler (202) is provided at the lower portion of the heavy aromatics separation tower (200); the tower bottom reboiler (202) has a spirally wound first heat exchange tube (220), and both ends of the first heat exchange tube (220) are respectively used for the heat transfer medium outside the heavy aromatics separation tower (200) to enter and exit; The heavy aromatics separation tower (200) comprises: The tower body (210) has a liquid storage chamber (211) at the bottom and a gas-liquid separation chamber (212) above the liquid storage chamber (211). A feed pipe (213) is provided on the side wall of the gas-liquid separation chamber (212). The first heat exchange tube (220) is arranged in the liquid storage cavity (211) at the lower part of the tower body (210) along the vertical direction, and is spirally wound from the inside to the outside to form multiple layers of spiral tubes (221), with first gaps (222) running vertically formed between adjacent layers of spiral tubes (221); The heavy aromatics separation tower also includes: A pipe-side inlet pipe (230) for inputting the heat-conducting medium is provided on the side wall of the tower body (210) and is in communication with the upper end of the first heat exchange pipe (220); A pipe outlet pipe (240) for outputting the heat transfer medium is provided on the side wall of the tower body (210) and is in communication with the lower end of the first heat exchange pipe (220); The vertically arranged flow guide tube (250) is sleeved on the outer periphery of the outermost spiral tube (221), and the outer peripheral wall of the flow guide tube (250) is spaced apart from the inner peripheral wall of the tower body (210) to form a second gap (251).

2. The system according to claim 1, wherein: The first wound tube heat exchanger (100) further comprises a third tube pass (104), which is located downstream of the first tube pass (102) and upstream of the second tube pass (103) along the direction of the shell-side medium from the inlet to the outlet of the first shell-side (101).

3. The system according to claim 1, wherein: The invention also includes a first bypass line (105), an inlet of which is used to input the heavy aromatic hydrocarbon raw material, and an outlet of which is connected to the inlet of the fourth tube side (402) of the second wound tube heat exchanger (400); and a first temperature control valve (106) is provided on the first bypass line (105), and the first temperature control valve (106) is arranged to adjust the flow rate of the heavy aromatic hydrocarbon raw material in the first bypass line (105) by sensing the temperature of the medium output from the outlet of the first shell side (101).

4. The system according to claim 1, wherein: The first tower top reflux tank (500) is further provided, wherein the inlet thereof is connected to the outlet of the first shell side (101) of the first wound tube heat exchanger (100), and the bottom outlet thereof is connected to the upper inlet of the heavy aromatics separation tower (200); It also includes a second top reflux tank (510), the inlet of which is connected to the outlet of the second shell side (401) of the second wound tube heat exchanger (400), and the bottom outlet of which is connected to the upper inlet of the flash tower (300).

5. The system according to claim 4, characterized in that: It also includes a first circulation pipeline (501), both ends of which are respectively connected to the two interfaces at the top of the first tower top reflux tank (500), and a first tower top aftercooler (502) is provided on the first circulation pipeline (501); The second circulating pipeline (511) is also included, with two ends thereof respectively connected to the two interfaces at the top of the second tower top reflux tank (510), and a second tower top aftercooler (512) is provided on the second circulating pipeline (511).

6. The system according to claim 1, wherein: The second outlet at the bottom of the heavy aromatics separation tower (200) is connected to the lower inlet of the heavy aromatics separation tower (200) through a third circulation pipeline (201), and a tower kettle reboiler (202) is provided on the third circulation pipeline; The second outlet at the bottom of the flash tower (300) is connected to the lower inlet of the flash tower (300) through a fourth circulation pipeline (303), and a bottom circulation heater (304) is provided on the fourth circulation pipeline.

7. The system according to claim 1, wherein: The diameter of the upper port of the guide tube (250) gradually increases from bottom to top.

8. The system according to claim 1, wherein: The inner peripheral wall of the guide tube (250) is spaced apart from the outermost spiral tube (221), and the spacing distance is consistent with the spacing distance between the adjacent spiral tubes (221).

9. The system according to claim 1, wherein: The spiral directions of the spiral tubes (221) in adjacent layers are opposite.

10. The system according to any one of claims 1, 7, 8 and 9, characterized in that: The multi-layer spiral tubes (221) formed by winding the first heat exchange tube (220) are formed into a group of heat exchange units, and there are at least two groups of them, which are arranged at intervals along the circumferential direction; The upper end of the first heat exchange tube (220) of each heat exchange unit group is connected to the tube-side inlet pipe (230); The lower end of the first heat exchange tube (220) of each group of heat exchange units is connected to the tube-side outlet pipe (240).

11. The system according to claim 10, characterized in that: An upper manifold (260) is provided in the tower body (210) above each group of heat exchange units. The input port of the upper manifold (260) is connected to the tube-side inlet pipe (230). The number of output ports of the upper manifold (260) is consistent with the number of the heat exchange units, and each output port of the upper manifold (260) is connected to the upper end of the first heat exchange tube (220) of the corresponding heat exchange unit. A lower collecting pipe (270) is provided in the tower body (210) below each group of heat exchange units. The output port of the lower collecting pipe (270) is connected to the pipe outlet connecting pipe (240). The number of the input ports of the lower collecting pipe (270) is consistent with the number of the heat exchange units, and each input port of the lower collecting pipe (270) is connected to the lower end pipe port of the first heat exchange pipe (220) of the corresponding heat exchange unit.

12. The system according to claim 10, characterized in that: There are four groups of heat exchange units, which are arranged at equal intervals along the circumferential direction.

13. The system according to any one of claims 1, 7, 8, and 9, characterized in that: The bottom wall of the liquid storage chamber (211) is provided with a condensate outlet pipe (214).

14. The system according to any one of claims 1, 7, 8 and 9, characterized in that: The pipe-side inlet pipe (230) is arranged perpendicular to the side wall of the tower body (210).

15. The system according to claim 1, wherein: The first wound tube heat exchanger includes: A first shell-side cylinder (110) extending vertically has a shell-side inlet (111) at its upper portion as the inlet of the first shell-side, and a lower end thereof opened as a first shell-side outlet (112); A second heat exchange tube (120) is axially arranged inside the first shell-side cylinder (110); A second shell-side cylinder (130) extending vertically, at least the upper portion of which is sleeved on the outer periphery of the bottom of the first shell-side cylinder (110); A condensation subcooling element (140) is provided in the second shell-side cylinder (130) and below the first shell-side cylinder (110). The condensation subcooling element (140) has a condensation subcooling channel (141) extending up and down. The upper end of the condensation subcooling channel (141) is connected to the first shell-side outlet (112) of the first shell-side cylinder (110). The outer peripheral wall of the condensation subcooling channel (141) is spaced apart from the inner peripheral wall of the second shell-side cylinder (130) to form a third gap (131). A non-condensable gas outlet (132) is provided on the second shell-side cylinder (130) at a position above the condensation subcooling member (140); The space of the second shell-side cylinder (130) located below the condensation subcooling member (140) serves as a liquid storage chamber (133) that is in communication with the lower end of the condensation subcooling channel (141), and the liquid storage chamber (133) is in communication with the non-condensable gas outlet (132) through the third gap (131); The bottom of the second shell-side cylinder (130) is provided with a second shell-side outlet (135) as the outlet of the first shell-side and is connected to the upper inlet of the heavy aromatics separation tower.

16. The system according to claim 15, characterized in that: The condensation subcooling channel (141) is spirally arranged from inside to outside.

17. The system according to claim 15, characterized in that: The condensing subcooling element (140) has a central tube (142) and a spiral plate (143), wherein the central tube (142) extends up and down, and the upper end of the central tube (142) is connected to the lower end of the second heat exchange tube (120), and the lower end of the central tube (142) is closed; the spiral plate (143) is arranged on the outer periphery of the central tube (142), and the spiral plate (143) has two spiral channels that are rolled clockwise or counterclockwise along the circumference, wherein the first spiral channel (1431) serves as the above-mentioned The condensation subcooling channel (141) and the upper and lower ports of the second spiral channel (1432) are closed, and the inner port of the second spiral channel (1432) close to the central tube (142) is connected to the central tube (142), and the side wall of the second shell-side cylinder (130) is provided with a first tube-side inlet pipe (134) connected to the outer port of the second spiral channel (1432) away from the central tube (142), and the first tube-side inlet pipe (134) serves as the inlet of one of the tubes of the first wound tube heat exchanger.

18. The system according to claim 17, characterized in that: The first spiral channel (1431) has a central portion relatively close to the central tube (142) and a peripheral portion relatively far from the central tube (142); The lower port of the first shell-side cylinder (110) is opposite to and connected to the upper port of the central part of the first spiral channel (1431), and the periphery of the lower port of the first shell-side cylinder (110) extends horizontally outward to form a baffle (114) covering the upper port of the outer part of the first spiral channel (1431).

19. The system according to claim 18, characterized in that: The portion of the baffle (114) relatively far from the non-condensable gas outlet (132) extends outward to the inner peripheral wall of the second shell-side cylinder (130).

20. The system according to claim 18, wherein: The lower end of the first shell-side cylinder (110) is in the shape of an inverted cone.

21. The system according to claim 20, characterized in that: The side wall of the inverted cone is opposite to the non-condensable gas outlet (132).

22. The system according to any one of claims 15 to 21, characterized in that: A first liquid level gauge (136) and a second liquid level gauge (137) are provided on the side wall of the second shell-side cylinder (130). The first liquid level gauge (136) is provided at the central position in the upper and lower directions of the condensation subcooling channel (141), and the second liquid level gauge (137) is located below the condensation subcooling channel (141) and above the second shell-side outlet (135).

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