A low energy aromatics isomerization apparatus

Abstract

This invention proposes a low-energy-consumption aromatics isomerization unit, which makes the following improvements: A heat exchanger is added to the isomerization mechanism to recover waste heat, reduce the air cooling load, and increase the temperature of the cold high-separation oil entering the deheptane tower; a steam generator is installed in the deheptane tower to produce steam first and then preheat the feed, realizing the cascade utilization of the tower top gas energy; the pressure of the circulating tower is reduced, and the circulating tower is changed from being heated by medium-pressure steam to being heated by the bottom oil of the deheptane tower; a mid-section heat extractor is added at an appropriate location in the deheptane tower to extract high-quality heat, reducing the tower top cooling load while simultaneously outputting high-quality heat. This invention first recovers the waste heat from the oil-gas separation section, using the cold high-separation oil as a heat carrier to carry it into the deheptane tower, providing an opportunity for subsequent thermal integration between the deheptane tower and the circulating tower; secondly, the combined effect of top steam production enables the cascade utilization of the deheptane tower top gas energy, and the mid-section heat extractor provides space for thermal integration with adjacent units, significantly reducing the energy consumption of the aromatics unit.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical technology, specifically relating to a low-energy-consumption aromatic hydrocarbon isomerization device. Background Technology

[0002] An aromatics complex is a unit used in petroleum processing to produce para-xylene (PX), toluene, and benzene. It comprises seven units: pretreatment, continuous reforming, isomerization, extraction, disproportionation, adsorption separation, and xylene distillation. The isomerization unit, under hydrogen-containing conditions, isomerizes the lean para-xylene mixed C8 aromatics drawn from the raffinate stream of the adsorption separation unit to produce para-xylene-rich mixed C8 aromatics. It consists of four parts: the isomerization reaction, oil-gas separation, a heptane removal tower, and a recycling tower.

[0003] Existing aromatic hydrocarbon complexes have problems such as incomplete utilization of low-temperature waste heat, large cooling load, and large consumption of reboiling steam in the deheptane tower and circulation tower. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a low-energy-consumption aromatic isomerization device that avoids problems such as unused waste heat, large cooling load, and large consumption of reboiling steam in the deheptane tower and circulation tower.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A low-energy-consumption aromatic hydrocarbon isomerization device includes an isomerization mechanism, a heptane removal mechanism, and a circulation mechanism. The isomerization mechanism includes a reactor, a first heat exchanger, a second heat exchanger, a first air cooler, and a first gas-liquid separator. The reactor is sequentially connected to the first gas-liquid separator via the first heat exchanger, the second heat exchanger, and the first air cooler. The first gas-liquid separator is connected to the second heat exchanger. The heptane removal mechanism includes a third heat exchanger, a fourth heat exchanger, a heptane removal tower, a first steam generator, a fifth heat exchanger, a second air cooler, a mid-section heat extraction component, a second reboiler, a clay tower, and a first pressurization pump. One end of the third heat exchanger is connected to the second heat exchanger, and the other end of the third heat exchanger is connected to the heptane removal tower via the fourth heat exchanger. One end of the fifth heat exchanger is connected to the heptane removal tower via the first steam generator, and the other end of the fifth heat exchanger is connected to the second air cooler via the third heat exchanger. The second air cooler is connected to the circulation mechanism.

[0007] The intermediate heat extraction assembly is connected to the heptane removal tower;

[0008] The deheptane tower is connected to the second reboiler via the first pressurization pump. One end of the second reboiler is connected to the circulation mechanism, and the other end of the second reboiler is connected to the clay tower via the fourth heat exchanger. The clay tower is connected to the xylene removal unit.

[0009] Preferably, the mid-section heat extraction assembly includes a mid-section extraction pump and a second steam generator. One end of the second steam generator is connected to the heat extraction end of the deheptane tower through the mid-section extraction pump, and the other end of the second steam generator is connected to the return end of the deheptane tower. The three form a loop.

[0010] Preferably, the heat extraction end of the deheptane tower is plate 20-25 of the deheptane tower, and the return end of the deheptane tower is plate 23-28 of the deheptane tower.

[0011] Preferably, the deheptane removal mechanism further includes a bypass valve installed between the second reboiler and the first pressurizing pump.

[0012] Preferably, the isomerization mechanism further includes a first feed pump, a first heating furnace, a dehydration tank, and a compressor-turbine unit. The first feed pump is connected to the first heating furnace through the first heat exchanger. The first heating furnace is connected to the reactor. One end of the compressor-turbine unit is connected to the first heat exchanger, and the other end of the compressor-turbine unit is connected to the first gas-liquid separator through the dehydration tank.

[0013] Preferably, the heptane removal mechanism further includes a first reboiler, a second pressurizing pump, and a second heating furnace; the first heating inlet of the heptane removal tower is connected to the first reboiler, the second heating inlet of the heptane removal tower is connected to the second heating furnace, and the first reboiler is connected to the second heating furnace through the second pressurizing pump.

[0014] Preferably, the circulation mechanism includes a second gas-liquid separator, a reflux pump, a third air cooler, a circulating water cooler, a third gas-liquid separator, a second reflux pump, and a circulation tower;

[0015] The first outlet of the second gas-liquid separator is connected to the heptane removal tower via the reflux pump, the second outlet of the second gas-liquid separator is connected to the circulation tower via the fifth heat exchanger, and the inlet of the second gas-liquid separator is connected to the second air cooler.

[0016] The first inlet of the third air cooler is connected to the second gas-liquid separator, the second inlet of the third air cooler is connected to the circulating tower, the outlet of the third air cooler is connected to the third gas-liquid separator through the circulating water cooler, one end of the third gas-liquid separator is connected to the reforming unit, the other end of the third gas-liquid separator is connected to the circulating tower through the second reflux pump, one end of the circulating tower is connected to the first heat exchanger, and the other end of the circulating tower is connected to the second reboiler.

[0017] Preferably, the operating pressure of the circulation tower is 0.56-0.6 MPa.

[0018] The present invention has the following advantages and beneficial effects compared with the prior art:

[0019] (1) By adding a second heat exchanger, the cold high-grade oil generated by the first gas-liquid separator can be preheated a second time by the isomerization product oil generated by the reactor, thereby increasing the temperature of the cold high-grade oil entering the deheptane tower and reducing the air cooling load. The increased temperature of the cold high-grade oil entering the deheptane tower frees up the primary heat of the deheptane tower top gas, which can be used to produce 0.5MPa steam in the newly added steam generator of the deheptane tower, realizing the cascade utilization of the tower top gas energy.

[0020] (2) The main process objective of the circulating tower is to separate C8 non-aromatic hydrocarbons and recycle them back to the isomerization reactor to maintain a certain concentration of C8 non-aromatic hydrocarbons in the reactor. Therefore, there is no need to strictly control the quality of either the top product or the bottom product. Thus, the operating pressure of the circulating tower can be appropriately reduced to 0.56-0.6 MPa to reduce the bottom temperature (the operating pressure of the existing technology is about 0.64 MPa), and other streams can be used as the reboiling heat source (currently, the reboiler uses 2.0 MPa steam with a saturation temperature of 214.9℃ as the heat source).

[0021] (3) A first pressurizing pump is added to pressurize the bottom oil of the deheptane tower and send it into the circulating tower to serve as the reboiling heat source for the circulating tower after depressurization, thus saving steam.

[0022] (4) A bypass valve is added to the bottom oil side of the deheptane tower to regulate the heat exchange load.

[0023] (5) A mid-section reflux is set at an appropriate location in the rectification section of the heptane removal tower. The extraction position is at plates 20-25, and the return position is at plates 23-28. The heat can be recovered to produce 0.5MPa or 1.0MPa steam, or sent out, such as as a reboiling heat source for the extraction distillation tower of the adjacent extraction unit. (In the prior art, the bottom of the extraction distillation tower is 170℃, and 2.0MPa steam is used as the reboiling heat source.) Due to the high temperature of the rectification section of the heptane removal tower and the large air cooling load at the top of the tower, the mid-section heat recovery is added to the rectification section to upgrade the utilization of the waste heat at the top of the heptane removal tower, optimize heat recovery, and reduce its air cooling load. The heat extracted from the mid-section reflux produces 0.5MPa steam. The heat extracted from the mid-section reflux can be used to provide high-quality heat to the heat traps of other aromatic units, such as the extraction distillation unit, to achieve inter-unit thermal integration. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention;

[0025] Figure 2 This is the heterogeneous mechanism in the process flow diagram of Embodiment 1 of the present invention;

[0026] Figure 3 The heptane removal mechanism is shown in the process flow diagram of Embodiment 1 of the present invention;

[0027] Figure 4 The circulating mechanism is shown in the process flow diagram of Embodiment 1 of the present invention;

[0028] Figure 5 This is a process flow diagram of Embodiment 1 of the present invention;

[0029] Figure 6 This is a process flow diagram of Embodiment 2 of the present invention;

[0030] Figure 7 This is a process flow diagram of Embodiment 3 of the present invention;

[0031] Figure 8 The process flow diagram is for Comparative Example 1;

[0032] The markings of the components in the attached diagram:

[0033] 1-Isomerization mechanism, 101-First feed pump, 102-First heat exchanger, 103-First heating furnace, 104-Reactor, 105-Second heat exchanger, 106-First air cooler, 107-First gas-liquid separator, 108 Dehydration tank, 109-Compressor-turbine unit, 2-Heptane removal mechanism, 201-Third heat exchanger, 202-Fourth heat exchanger, 203-Heptane removal tower, 204-First steam generator, 205-Fifth heat exchanger, 206-Second air cooler, 207-Intermediate section Heat extraction component, 2071-intermediate extraction pump, 2072-second steam generator, 208-first reboiler, 209-first pressurization pump, 210-second pressurization pump, 211-second heating furnace, 212-bypass valve, 213-clay tower, 214-second reboiler, 3-circulation mechanism, 301-second gas-liquid separator, 302-first reflux pump, 303-third air cooler, 304-circulating water cooler, 305-third gas-liquid separator, 306-second reflux pump, 307-circulation tower. Detailed Implementation

[0034] The invention's objective will be further described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described in detail here, but the implementation of the invention is not limited to the following embodiments.

[0035] Example 1

[0036] A low-energy-consumption aromatic hydrocarbon isomerization device includes an isomerization mechanism 1, a heptane removal mechanism 2, and a circulation tower mechanism 3. The isomerization mechanism 1 includes a first feed pump 101, a first heat exchanger 102, a first heater 103, a reactor 104, a second heat exchanger 105, a first air cooler 106, a first gas-liquid separator 107, a liquid removal tank 108, and a compressor-turbine unit 109. The heptane removal mechanism 2 includes a third heat exchanger 201, a fourth heat exchanger 202, a heptane removal tower 203, a first steam generator 204, and a fifth heat exchanger 205. 05. Second air cooler 206, intermediate heat extraction assembly 207, first reboiler 208, first pressurizing pump 209, second pressurizing pump 210, second heating furnace 211, bypass valve 212, clay tower 213, and second reboiler 214; the intermediate heat extraction assembly 207 includes an intermediate extraction pump 2071 and a second steam generator 2072; the circulation mechanism 3 includes a second gas-liquid separator 301, a first reflux pump 302, a third air cooler 303, a circulating water cooler 304, a third gas-liquid separator 305, a second reflux pump 306, and a circulation tower 307.

[0037] The discharge end of the adsorption separation unit is connected to the first inlet end of the first heat exchanger 102 via the first feed pump 101. The second inlet end of the first heat exchanger 102 is connected to the oil outlet end of the circulating tower 307. The first discharge end of the first heat exchanger 102 is connected to the inlet end of the first heater 103. The discharge end of the first heater 103 is connected to the inlet end of the reactor 104. The discharge end of the reactor 104 is connected to the fourth inlet end of the first heat exchanger 102. Under the action of a catalyst, C8 aromatics leaning towards p-xylene are converted into C8 aromatics with p-xylene approaching equilibrium.

[0038] The second discharge end of the first heat exchanger 102 is connected to the first feed end of the second heat exchanger 105, and the first discharge end of the second heat exchanger 105 is connected to the feed end of the first air cooler 106. By adding the second heat exchanger 105, the isomerization product oil from the outlet of the isomerization reactor 104 is preheated a second time to increase the temperature of the cold high-grade oil entering the heptane removal tower 203, while reducing the air cooling load.

[0039] The discharge end of the first air cooler 106 is connected to the inlet end of the first gas-liquid separator 107. The first outlet of the first gas-liquid separator 107 enters the inlet of the dehydration tank 108. The second outlet of the first gas-liquid separator 107 is connected to the reforming unit. The liquid outlet of the dehydration tank 108 is connected to the liquid inlet of the compressor-turbine unit 109. The gas outlet of the compressor-turbine unit 109 is connected to the third inlet of the first heat exchanger 102. Most of the gaseous product at the top of the gas-liquid separator enters the dehydration tank 108 as circulating hydrogen; a small portion is discharged to the reforming unit as tail hydrogen. After the trace amount of entrained condensate is separated in the dehydration tank 108, it is pressurized and circulated back to the reaction system by the compressor-turbine unit 109.

[0040] The discharge end of the first gas-liquid separator 107 is connected to the second feed end of the second heat exchanger 105, the second discharge end of the second heat exchanger 105 is connected to the first feed end of the third heat exchanger 201, the first discharge end of the third heat exchanger 201 is connected to the feed end of the fourth heat exchanger 202, and the discharge end of the fourth heat exchanger 202 is connected to the feed end of the deheptane tower 203.

[0041] The outlet of the deheptane tower 203 is connected to the inlet of the first steam generator 204. The outlet of the first steam generator 204 is connected to the inlet of the fifth heat exchanger 205. The outlet of the fifth heat exchanger 205 is connected to the second inlet of the third heat exchanger 201. The second outlet of the third heat exchanger 201 is connected to the inlet of the second air cooler 206. The outlet of the second air cooler 206 is connected to the inlet of the second gas-liquid separator 301. The first outlet of the second gas-liquid separator 301 is connected to the feed end of the deheptane tower 203 via a reflux pump 302. The second outlet of the second gas-liquid separator 301 is connected to the feed end of the fifth heat exchanger 205. The outlet of the fifth heat exchanger 205 is connected to the feed end of the circulating tower 307. The increased temperature of the isomerized oil entering the deheptane tower 203 frees up the primary heat of the overhead gas in the deheptane tower 203, which can be used to produce 0.5MPa steam in the newly added steam generator of the deheptane tower 203, thus realizing the cascade utilization of the overhead gas energy.

[0042] The third discharge end of the second gas-liquid separator 301 and the gas outlet end of the circulating tower 307 are respectively connected to the inlet end of the third air cooler 303. The discharge end of the third air cooler 303 is connected to the inlet end of the circulating water cooler 304. The discharge end of the circulating water cooler 304 is connected to the inlet end of the third gas-liquid separator 305. The first discharge end of the third gas-liquid separator 305 is connected to the inlet end of the circulating tower 307. The second discharge end of the third gas-liquid separator 305 is connected to the reforming unit. The non-condensable gas from the top of the heptane removal tower 203 is led to the third air cooler 303 for cooling and then mixed with the gas from the top of the circulating tower 307 before entering the circulating water cooler 304 for further cooling. After further cooling in the circulating water cooler 304, it enters the third gas-liquid separator 305. The exhaust gas discharged from the top of the tank is discharged to the fuel gas pipeline network. The condensate in the third gas-liquid separator 305 is pressurized by the top product of the circulating tower 307 and the second reflux pump 306. Part of it is returned to the top of the circulating tower 307 as reflux, and the other part is sent to the reforming unit. The bottom oil of the circulating tower 307 is returned to the isomerization reaction section.

[0043] The oil outlet of the heptane removal tower 203 is connected to the feed end of the second reboiler 214 via a first pressurizing pump 209. The first outlet of the second reboiler 214 is connected to the feed end of the circulating tower 307, and the second outlet of the second reboiler 214 is connected to the feed end of the fourth heat exchanger 202. The outlet of the fourth heat exchanger 202 is connected to the feed end of the clay tower 213, and the outlet of the clay tower 213 is connected to the xylene removal unit. The first pressurizing pump 209 is added to pressurize the bottom oil of the heptane removal tower and send it to the circulating tower 307, serving as a reboiler heat source for the depressurized circulating tower 307.

[0044] The inlet of the second steam generator 2072 is connected to the heat release end of the 21st tray of the heptane removal column 203, and the heat release end of the second steam generator 2072 is connected to the inlet of the 23rd tray of the heptane removal column 203 via the intermediate extraction pump 2071. The rectification section of the heptane removal column 203 is equipped with an intermediate reflux, which can recover heat to produce 0.5MPa or 1.0MPa steam.

[0045] The first heating inlet of the deheptane extractor 203 is connected to the heat release end of the first reboiler 208, and the second heating inlet of the deheptane extractor 203 is connected to the heat release end of the second heater 211. The first reboiler 208 is connected to the second heater 211 via a second pressurizing pump 210. A bypass valve 212 is installed between the second reboiler 214 and the second pressurizing pump 210. A new bypass valve 21227 is added for adjusting the heat exchange load.

[0046] The C8 aromatics leaning from p-xylene in the adsorption separation section are pressurized by the first feed pump 101 and mixed with the circulating bottom oil from the circulating tower 307. Then, they are mixed with circulating hydrogen and fresh hydrogen from the isomerization circulating hydrogen compression-turbine unit 109 to form a mixture. The mixture enters the first heat exchanger 102 to exchange heat with the isomerization product oil generated in the reactor. After being heated to the required reaction temperature by the first heater 103, it enters the reactor 104 to react. Under the action of the catalyst, the C8 aromatics leaning from p-xylene are converted into C8 aromatics that are in equilibrium with p-xylene.

[0047] The isomerized oil flows out from the bottom of reactor 104, passes sequentially through the first heat exchanger 102, the second heat exchanger 105, and the first air cooler 106, and finally enters the gas-liquid separator for gas-liquid separation. Most of the gaseous product at the top of the gas-liquid separator is used as circulating hydrogen and enters the dehydration tank 108; a small portion is discharged as tail hydrogen to the reforming unit. After the trace amount of entrained condensate is separated in the dehydration tank 108, it is pressurized and recycled back to the reaction system via the compressor-turbine unit 109.

[0048] The cold high-grade oil flows out from the bottom of the first gas-liquid separator, passes sequentially through the second heat exchanger 105, the third heat exchanger 201, and the fourth heat exchanger 202, and then enters the deheptane tower 203. The task of the deheptane tower 203 is to separate the light components below heptane from the top of the tower. The overhead gas from the heptane tower 203 passes sequentially through the steam generator 26, the fifth heat exchanger 205, the third heat exchanger 201, and the second air cooler 206 before finally entering the second gas-liquid separator 301. The addition of the second heat exchanger 105 recovers the temperature of the isomerized product oil generated in the reactor, raising the temperature of the cold high-grade oil entering the deheptane tower 203, thereby freeing up the primary heat of the overhead gas from the deheptane tower 203 for use in the first steam generator 204 to produce 0.5 MPa steam.

[0049] The non-condensable gas from the top of the heptane remover 203 is led to the third air cooler 303 for cooling, then mixed with the top gas from the circulating tower 307 and further cooled in the circulating water cooler 304. After further cooling in the circulating water cooler 304, it enters the third gas-liquid separator 305. The exhaust gas discharged from the top of the separator is discharged to the fuel gas pipeline. The condensate in the third gas-liquid separator 305 is pressurized by the top product of the circulating tower 307 and the second reflux pump 306. Part of it flows back to the top of the circulating tower 307, and the other part is sent to the reforming unit. The bottom oil of the circulating tower 307 is returned to the isomerization unit and mixed with the C8 aromatics leaning from para-xylene.

[0050] The condensate from the second gas-liquid separator is pressurized by the reflux pump 302. Part of it is returned to the deheptane tower 203 as reflux, and the other part is exchanged with the overhead gas of the deheptane tower 203 through the fifth heat exchanger 205 before entering the circulating tower 307.

[0051] The bottom oil from the heptane dehydrogenator 203 is mixed with the C8 aromatics from the o-xylene unit and then enters the fourth heat exchanger 202 to exchange heat with the feed to the heptane dehydrogenator 203. After being processed by the clay tower 213, it is sent to the xylene fractionation section. A small portion of the reboiling heat of the heptane dehydrogenator 203 is provided by the convection section of the second heater 211, and the majority is provided by the 4.0 MPa steam in the first reboiler 208 at the bottom of the heptane dehydrogenator 203.

[0052] A bypass valve 212 is installed between the second reboiler 214 and the second pressurizing pump 210 to regulate their heat exchange load. The bottom oil pressurizing pump 28 of the heptane stripper 203 pressurizes the bottom oil and sends it to the second reboiler 214 at the bottom of the circulating tower 307. The reboiler 23 at the bottom of the circulating tower 307 is reused. Since the circulating tower 307 does not have strict quality control indicators, its operating pressure is appropriately reduced, and the bottom oil of the heptane stripper 203 can be used as a reboiling heat source for the circulating tower 307.

[0053] Example 2

[0054] The method and components for mid-section heat extraction are missing from Example 1.

[0055] Example 3

[0056] The mid-section heat extraction component is missing from the original embodiment 1.

[0057] Comparative Example 1

[0058] Existing aromatic isomerization equipment.

[0059] Table 1

[0060]

[0061] Table 2

[0062]

[0063] Table 3

[0064]

[0065] Table 4

[0066]

[0067] Table 5

[0068]

[0069] Table 6

[0070]

[0071] Table 7

[0072]

[0073] Table 8

[0074]

[0075] Table 9

[0076]

[0077] Table 10

[0078]

[0079] Table 11

[0080]

[0081] Table 12

[0082]

[0083] Table 13

[0084]

[0085] Table 14

[0086]

[0087] Table 1 shows the parameters of the oil-gas separation part in Example 1. Comparing Table 1 and Table 3, it can be seen that the reaction part in Example 1 is the same as that in Example 2.

[0088] Table 2 shows the main operating parameters of the heptane removal tower and the circulation tower in Example 1. Except for the different purpose of the intermediate heat extraction, the operation of Example 1 is completely consistent with Example 3. The product composition and flow rate of the heptane removal tower and the circulation tower are also basically unchanged compared to the comparative example. The heat extracted in the intermediate stage of Example 1 is used to reboil the extraction distillation tower of the extraction unit, and the reboiling temperature of this tower is 160.1℃. The intermediate heat extraction can be used in the heat traps of other aromatics unit units, including but not limited to the situation in this example. It is worth noting that, unlike Example 3, the reboiling of the extraction distillation tower in Example 1 uses 2.0MPa steam for heating, thus saving 6.5t / h of 2.0MPa steam. Compared to the comparative example, Example 1 produces 9.0 t / h more 0.5 MPa steam, saves 0.7 t / h of 4.0 MPa steam in the heptane removal tower, saves 7.38 t / h of all 2.0 MPa reboiling steam in the circulating tower, and saves 6.5 t / h of 2.0 MPa steam in the extractive distillation tower. The total air cooling load is reduced by 890.9 × 10⁴ kcal / h. Based on the energy price and operating time in Example 1, Example 1 can save 41.544 million yuan in energy costs annually. (Air cooling benefits are not considered, the same applies below.)

[0089] Table 3 shows the main parameters of the oil-gas separation section in Example 2. As can be seen from Table 3, after the isomerized oil is heated and cooled twice in Example 2, the temperature of the isomerized oil entering the air cooler is reduced from 134.9℃ in the comparative example to 115.4℃, reducing the air cooling load of the oil by 1297.3×104kcal / h.

[0090] Table 4 shows the main operating parameters of the heptane removal tower and the circulating tower in Example 2. As can be seen from Table 4, the feed temperature of the heptane removal tower in Example 2 was increased from 192.2℃ in the comparative example to 199.2℃, which reduced the reboiling load at the bottom of the tower by 222.3×104kcal / h, saving 4.5t / h of 4.0MPa steam. The top gas of the heptane removal tower (176.5℃) was fed into the newly added steam generator 26 to produce 9.0t / h of 0.5MPag saturated steam, with a heat recovery of 498.7×104kcal / h. The air cooling load at the top of the heptane removal tower increased by 435.6×104kcal / h, and the air cooling load of the circulating tower decreased by 29.2×104kcal / h. As mentioned earlier, the air cooling load of the isomerization product oil decreased by 1297.3×104kcal / h. Therefore, the overall air cooling load was reduced by 890.9×104kcal / h.

[0091] The pressure at the top of the circulating tower decreased from 0.64 MPa in the comparative example to 0.58 MPa, and the corresponding temperature at the bottom of the tower decreased from 207.9℃ to 203.6℃. The temperature of the reboiled circulating stream returning to the tower decreased from 208.3℃ to 203.8℃. Therefore, the bottom oil of the deheptane tower can be used as the heat source, thus saving 2.0 MPa of reboiler steam (7.38 t / h). Reboiler 23 can be reused.

[0092] Tables 5, 6, and 7 compare the composition of the bottom oil, circulating top oil, and circulating bottom oil of Example 2 with that of the comparative example. As can be seen from Tables 5, 6, and 7, the composition and flow rate of Example 2 are basically the same as those of the comparative example.

[0093] Compared to the comparative example, Example 2 produced 9.0 t / h more 0.5 MPa steam, saved 4.5 t / h of 4.0 MPa steam in the deheptane tower, saved 7.38 t / h of all 2.0 MPa reboiling steam in the circulating tower, and reduced the total air cooling load by 890.9 × 10⁻⁶. 4 kcal / h. According to the plant's internal energy prices: 4.0MPa steam 234 yuan / t, 2.0MPa steam 209 yuan / t, 0.5MPa steam 209 yuan / t, and the plant operates for 8400 hours / year, which can save 37.602 million yuan in energy costs per year.

[0094] Table 8 shows the parameters of the oil-gas separation section in Example 3. Comparing Table 8 and Table 3, it can be seen that the oil-gas separation section in Example 3 is the same as that in Example 2.

[0095] Table 10 shows the composition of the bottom oil of the deheptane removal tower in Example 3 and its comparison with the composition of the comparative example. As can be seen from Table 10, the composition and flow rate of the bottom oil of the deheptane removal tower in Example 2 are basically the same as those of the comparative example.

[0096] Table 9 shows the main operating parameters of the heptane removal tower and the circulating tower in Example 3. In Example 2, the temperature of the overhead gas from the heptane removal tower entering the feed / overhead gas heat exchanger was 176.1℃, and the load on the heat exchanger was 443.3 × 10⁻⁶. 4 kcal / h, producing 9.0 t / h of 0.5 MPa steam. An intermediate heat extraction section is added, extracting 300 t / h of mixed aromatics at 218.8℃ from plate 21 of the heptane stripper, with a return temperature of 194.1℃ and a heat load of 277.1 × 10⁻⁶ kcal / h. 4 kcal / h, which can produce 5.0 t / h of 0.5 MPa steam. As can be seen from Tables 4 and 2, the reboiling load at the bottom of the heptane removal tower is reduced by 34.8 × 10⁻⁶ kcal / h. 4 kcal / h, saving 0.7t / h of 4.0MPa steam; the overhead air cooling load of the de-heptane tower increases by 262.0×10 4 kcal / h, the cooling load at the top of the circulating tower decreased by 28.9 × 10 kcal / h. 4 kcal / h, while the air cooling load of the isomerized oil decreased by 1297.3 × 10 kcal / h. 4 Therefore, the total air-cooled load of the device in Example 3 was still reduced by 1064.2 × 10 kcal / h. 4 kcal / h. The operation of the circulating tower is the same as in Example 2, so it will not be described again.

[0097] Tables 10, 11, and 12 compare the composition of the bottom oil, circulating top oil, and circulating bottom oil of the heptane removal tower in Example 3 with that of the comparative example. As can be seen from Tables 10, 11, and 12, the composition of the bottom oil, circulating top oil, and circulating bottom oil in Example 3 are basically consistent with the flow rates of the comparative example.

[0098] Table 13 shows the main parameters of the oil-gas separation section in the comparative example. As can be seen from Table 13, the isomerized oil produced at 134.9℃ is cooled to 45.6℃ by air cooling, with a total load of 4303.3×104kcal / h, of which the heat at ≥95℃ is 1922.8×104kcal / h.

[0099] Table 14 shows the main operating parameters of the heptane removal tower and the circulating tower in the comparative example. As can be seen from Table 14, the bottom temperature of the circulating tower is 207.9℃, the reboiled circulating stream returning to the tower is 208.3℃, and the bottom temperature of the heptane removal tower is 233.4℃. Appropriately reducing the pressure of the circulating tower can lower its reboiled return temperature, allowing the bottom oil of the heptane removal tower to be used as the reboiler heat source for the circulating tower, thus saving the 2.0 MPa reboiler steam consumption. In the comparative example, the temperature of the cold high-grade oil entering the heptane removal tower is 192.2℃.

[0100] The above-described specific embodiments are preferred embodiments of the present invention and are not intended to limit the present invention. Any other changes or equivalent substitutions made without departing from the technical solution of the present invention are included within the protection scope of the present invention.

Claims

1. A low-energy-consumption aromatic hydrocarbon isomerization device, characterized in that, It includes an isomerization mechanism (1), a heptane removal mechanism (2), and a circulation mechanism (3); the isomerization mechanism (1) includes a reactor (104), a first heat exchanger (102), a second heat exchanger (105), a first air cooler (106), and a first gas-liquid separator (107); the reactor (104) is connected to the first gas-liquid separator (107) in sequence through the first heat exchanger (102), the second heat exchanger (105), the first air cooler (106), and the first gas-liquid separator (107), and the first gas-liquid separator (107) is connected to the second heat exchanger (105); The heptane removal mechanism (2) includes a third heat exchanger (201), a fourth heat exchanger (202), a heptane removal tower (203), a first steam generator (204), a fifth heat exchanger (205), a second air cooler (206), a mid-section heat extraction assembly (207), a second reboiler (214), a clay tower (213), and a first pressure pump (209). One end of the third heat exchanger (201) is connected to the second heat exchanger (105), and the other end of the third heat exchanger (201) is connected to the deheptane tower (203) through the fourth heat exchanger (202); one end of the fifth heat exchanger (205) is connected to the deheptane tower (203) through the first steam generator (204), and the other end of the fifth heat exchanger (205) is connected to the second air cooler (206) through the third heat exchanger (201); the second air cooler (206) is connected to the circulation mechanism (3); The intermediate heat extraction component (207) is connected to the deheptane tower (203); The deheptane tower (203) is connected to the second reboiler (214) via the first pressurization pump (209). One end of the second reboiler (214) is connected to the circulation mechanism (3), and the other end of the second reboiler (214) is connected to the clay tower (213) via the fourth heat exchanger (202). The clay tower (213) is connected to the xylene removal unit. The mid-section heat extraction assembly (207) includes a mid-section extraction pump (2071) and a second steam generator (2072). One end of the second steam generator (2072) is connected to the heat extraction end of the deheptane tower (203) through the mid-section extraction pump (2071), and the other end of the second steam generator (2072) is connected to the return end of the deheptane tower (203). The three form a loop. The heat extraction end of the deheptane tower (203) is plate 20-25 of the deheptane tower, and the return end of the deheptane tower (203) is plate 23-28 of the deheptane tower.

2. The low-energy-consumption aromatic hydrocarbon isomerization device according to claim 1, characterized in that, The heptane removal mechanism (2) also includes a bypass valve (212) installed between the second reboiler (214) and the first pressurization pump (209).

3. The low-energy-consumption aromatic hydrocarbon isomerization device according to claim 1, characterized in that, The isomerization mechanism (1) also includes a first feed pump (101), a first heating furnace (103), a dehydration tank (108), and a compressor-turbine unit (109). The first feed pump (101) is connected to the first heating furnace (103) through the first heat exchanger (102). The first heating furnace (103) is connected to the reactor (104). One end of the compressor-turbine unit (109) is connected to the first heat exchanger (102), and the other end of the compressor-turbine unit (109) is connected to the first gas-liquid separator (107) through the dehydration tank (108).

4. The low-energy-consumption aromatic hydrocarbon isomerization device according to claim 1, characterized in that, The deheptane removal mechanism (2) further includes a first reboiler (208), a second pressurizing pump (210), and a second heating furnace (211); the first heating end of the deheptane removal tower (203) is connected to the first reboiler (208), the second heating end of the deheptane removal tower (203) is connected to the second heating furnace (211), and the first reboiler (208) is connected to the second heating furnace (211) through the second pressurizing pump (210).

5. The low-energy-consumption aromatic hydrocarbon isomerization device according to claim 1, characterized in that, The circulation mechanism (3) includes a second gas-liquid separator (301), a reflux pump (302), a third air cooler (303), a circulating water cooler (304), a third gas-liquid separator (305), a second reflux pump (306), and a circulation tower (307). The first outlet of the second gas-liquid separator (301) is connected to the deheptane tower (203) through the reflux pump (302), the second outlet of the second gas-liquid separator (301) is connected to the circulation tower (307) through the fifth heat exchanger (205), and the inlet of the second gas-liquid separator (301) is connected to the second air cooler (206). The first inlet of the third air cooler (303) is connected to the second gas-liquid separator (301), the second inlet of the third air cooler (303) is connected to the circulating tower (307), the outlet of the third air cooler (303) is connected to the third gas-liquid separator (305) through the circulating water cooler (304), one end of the third gas-liquid separator (305) is connected to the reforming device, and the other end of the third gas-liquid separator (305) is connected to the circulating tower (307) through the second reflux pump (306). One end of the circulating tower (307) is connected to the first heat exchanger (102), and the other end of the circulating tower (307) is connected to the second reboiler (214).

6. The low-energy-consumption aromatic hydrocarbon isomerization device according to claim 5, characterized in that, The operating pressure of the circulating tower (307) is 0.56-0.6 MPa.

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