Method for producing toluene by using toluene-free tower based on single benzene extraction device
By adjusting the process flow in the monobenzene extraction device and using existing equipment to achieve efficient separation of toluene, the problem of low purity of toluene products under the toluene-free tower is solved, the high-quality production of toluene and the conversion of bisbenzene extraction is achieved, which has alleviated the Gasoline sales pressure and reduces production costs.
Patent Information
- Application Number
- CN202311591606.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-27
- Publication Date
- 2024-12-20
AI Technical Summary
The lack of toluene towers in the existing monobenzene extraction devices leads to low purity of toluene products, which cannot meet the quality requirements, and the recombinant components cannot be effectively separated during the conversion of bisbenzene extraction, affecting the sulfur and C8 aromatic indicators of the product.
By adjusting the process flow in the monobenzene extraction device, using existing equipment, no need to increase the toluene tower, the C8 aromatic hydrocarbon and solvent content of the benzene tower feed is reduced, the benzene tower is used to achieve separation of benzene and toluene, and the benzene tower temperature and feed are controlled. to ensure that the quality of toluene products meets the requirements.
In the absence of toluene tower, high-quality toluene products were successfully produced, achieving the conversion of monobenzene extraction to bisbenzene extraction, and the toluene production reached 10-15%, alleviating the pressure on gasoline sales, reducing production costs and operating costs. Improve the economic benefits of oil refining companies.
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Figure CN119161229A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of petrochemical industry and relates to a method for producing toluene, and in particular to a method for producing toluene without a toluene tower based on a single benzene extraction device. Background Art
[0002] Petroleum toluene, as a basic chemical raw material, is mainly used for dealkylation to produce benzene, nitrotoluene and its derivatives, toluene diisocyanate, benzaldehyde, benzoic acid and its derivatives, toluenesulfonic acid and cresol, etc. It is reported that the proportion of toluene produced by catalytic reforming in my country is 72%, toluene recovered from cracking gasoline accounts for 23%, and the rest is toluene produced as a by-product of coal tar and styrene.
[0003] Toluene is separated from catalytic reforming depentane oil. Currently, the main industrial devices are liquid-liquid extraction and extraction distillation processes. Most of the newly built devices are extraction distillation processes. The extraction distillation process has the advantages of simple process, low investment, and low operating costs. The extraction distillation process is divided into single benzene extraction device and double benzene extraction device according to the target products. The single benzene extraction process has the target product of only petroleum benzene, and no toluene tower is designed. The double benzene extraction process has the target products of petroleum benzene and petroleum toluene. A toluene tower is designed during the construction of the device. According to the national standard "GB / T 3406-2010 Petroleum Toluene", C8 aromatics in petroleum toluene No. 1 product ≯0.05% (wt), total sulfur ≯2mg / kg, when single benzene extraction is converted to double benzene extraction to produce petroleum toluene, the bottom product of the benzene tower is directly used as the petroleum toluene product, because there is no toluene tower, the heavy components cannot be further separated. The presence of trace amounts of C8 aromatics in the feed will cause the benzene tower bottom product to contain C8 aromatics and other impurities, the toluene product purity is low, and indicators such as C8 aromatics do not meet the requirements. When the extraction and separation effect is not good, part of the solvent is carried to the benzene tower, resulting in unqualified sulfur content in toluene. It is necessary to solve the problem of not having a toluene tower to separate the heavy components, so that the C8 aromatics and sulfur content of the petroleum toluene product meet the quality requirements.
[0004] The method of producing petroleum toluene from reformed depentane oil is to purify the extract through a double benzene extraction device, and the extract enters the benzene tower and toluene respectively to produce qualified petroleum toluene, or the extract of double benzene extraction enters the dividing wall tower to produce petroleum toluene. In the single tower extraction device, the problem of no toluene tower needs to be solved.
[0005] CN102942439A discloses a method for separating benzene from mixed hydrocarbons, which is completed by a partition wall extractive distillation tower, wherein the interior of the partition wall tower is divided into three parts, the middle part is a partition wall, which can be a partition extending directly from the top but not in contact with the bottom, or can extend from the upper part of the tower to the lower part of the tower, and the upper and lower parts of the partition wall are not in contact with the top and bottom of the tower, but the upper part of the benzene discharge side of the partition wall is closed and not connected to the top space. The equipment of the present invention is simple and the energy consumption is low. Compared with the conventional process, it can save more than 10% energy.
[0006] CN102942433A discloses a method for separating benzene and toluene from a hydrocarbon mixture. The separation method sets a vertical wall in the middle of a distillation tower for separating non-aromatic hydrocarbons from benzene and toluene. The upper and lower parts of the partition wall are not in contact with the top and bottom of the tower, but the upper part of the benzene and toluene discharge side of the partition wall is closed and not connected to the top space. The tower is divided into three areas: A, B, and C. Non-aromatic hydrocarbons are extracted at the top of area A, benzene and toluene are extracted at the side of B, and C is a common stripping section. There are tower plates or fillers inside the three areas. The partition wall separates the feed and the side line extraction, and components with higher purity are obtained at the top, side line extraction, and bottom of the partition wall extractive distillation tower. The product purity can reach more than 99.7%, which can save more than 20% energy compared with the conventional process. Therefore, the process flow is simple and easy to operate, and the investment cost of saving a tower can also be significantly reduced. The tower used in this method is a partition wall tower, which is more complex in structure and more expensive than an ordinary distillation tower, and needs to be modified for existing devices.
[0007] CN111349459A discloses a mixed aromatic hydrocarbon and a method and device for preparing the same. This invention relates to the field of coal chemical technology, and specifically to a mixed aromatic hydrocarbon and a method and device for preparing the same. The preparation method is a method for increasing the production of aromatic hydrocarbons from coal-based raw materials.
[0008] CN101348405A discloses a method for preparing light aromatics and light alkanes from hydrocarbon raw materials, wherein reforming products, cracked gasoline, mixtures containing C9+ (carbon nine and above) aromatics, naphtha and mixtures thereof are used as raw materials for hydrogenation lightening treatment, so that heavy aromatics undergo dealkylation and transalkylation reactions, and light aromatics undergo isomerization and other reactions to convert into components rich in BTX light aromatics, and the catalyst used contains at least one selected from Pt or Pd and at least one selected from binder-free mordenite, beta zeolite, Y zeolite, ZSM-5 or ZSM-11 zeolite. The technical solution solves the above technical problems well and can be used in the industrial production of aromatics. This invention is directed to catalysts for dealkylation of reforming aromatics and isomerization of light aromatics to produce BTX.
[0009] CN106190289A discloses a method and system for producing aromatics from diversified raw materials. This invention uses one or two of light naphtha and liquefied gas obtained by diesel hydrocracking process, and / or one or a combination of light naphtha, liquefied gas, pentane and raffinate obtained by aromatics combined process as raw materials, and obtains hydrogen-containing gas, propane and mixed aromatics through aromatization of light hydrocarbons. This invention belongs to the production of BTX through aromatization reaction of several raw materials.
[0010] CN1169413A discloses a method for producing pure benzene and pure toluene from an intermediate product containing aromatic hydrocarbons. The purity of benzene is 98.90% and the purity of toluene is 94.85%. The purity of the obtained benzene and toluene is relatively low and cannot meet the factory requirements for the products.
[0011] CN2010102678A discloses a method for producing aromatics from coking gasoline, wherein aromatics are extracted from coking gasoline raw materials, the raffinate oil phase at the top of the extraction tower is separated and the raffinate oil is subjected to aromatization reaction, the liquid product of the aromatization reaction is returned as feed for aromatic extraction, the solvent phase at the bottom of the extraction tower is separated and the mixed aromatics are hydrogenated and refined, and the refined mixed aromatics are subjected to aromatic distillation to obtain aromatic products such as benzene, toluene and xylene. This invention belongs to the process of extracting feed from raffinate oil for aromatization reaction to increase the feed aromatic content and increase the production of aromatics.
[0012] CN102942439A discloses a method for separating benzene from mixed hydrocarbons, which is completed by a dividing wall extractive distillation tower. The tower used in this method is a dividing wall tower, which is more complex in structure and more expensive than a common distillation tower, and requires modification of existing devices.
[0013] CN216837830U discloses an energy-saving aromatics extraction device that is combined with an MTBE device to utilize heat comprehensively, save costs, and reduce energy consumption. This method belongs to the combined comprehensive utilization of heat, recovers heat, and reduces device energy consumption.
[0014] The above-mentioned prior art requires a benzene tower and a toluene tower for separating benzene and toluene using a modified distillation tower. When a partition wall tower is used to separate benzene and toluene, the structure is more complicated than that of an ordinary distillation tower, the cost is higher, and the existing device needs to be modified.
[0015] The rapid development of new energy vehicles has led to a significant decrease in gasoline market demand. At the same time, the increase in refining processing capacity has led to an oversupply of gasoline, making it difficult to sell gasoline products. Fuel-type refineries are still struggling to operate despite significantly reducing their processing loads. The inventory pressure on raw materials and products is high, and the operating model faces huge challenges.
[0016] Under the guidance of the idea of "reducing oil and increasing chemicals, reducing oil and increasing specialties", if the "single benzene extraction" device can quickly realize toluene production by adjusting the operating conditions of the distillation tower on the basis of existing process equipment, and separate the toluene product from the gasoline product and sell it separately as a chemical product, it can achieve the goal of "reducing oil and increasing chemicals", alleviate the sales pressure of gasoline in fuel-type refineries, and improve the economic benefits of refining enterprises. Summary of the invention
[0017] The technical problem to be solved by the present invention is to overcome the above-mentioned problems and provide a single benzene extraction device based on aromatic extraction and distillation. It utilizes the existing process flow without adding a toluene tower, and produces qualified petroleum toluene through operation adjustment. It has the advantages of low production cost, simple production method and no need for system modification.
[0018] The technical solution of the present invention is:
[0019] A method for producing toluene without a toluene tower based on a single benzene extraction device, wherein the method reforms depentanized oil into a dehexanizer of an aromatics device, the C6 and C7 fractions at the top of the dehexanizer are sent to a hydrogenation device to remove olefins, and then enter an extractive distillation device, the extractive distillation tower top produces raffinate oil, the rich solvent at the bottom of the extractive tower enters a solvent regeneration tower, the extract at the top of the tower enters a benzene tower, a benzene product is produced by the side line of the benzene tower, and a toluene product is directly produced by the bottom product of the benzene tower.
[0020] Preferably, the feed rate of the dehexane tower is 145-225 t / h, the reflux rate is reduced to 60-70 t / h, the temperature of the 5th tray is increased to 101-102°C, the temperature of the 36th tray of the benzene tower is controlled at 105-108°C, and the steam output of the steam generator is 1.3-1.4 t / h.
[0021] Specifically, a method for producing toluene without a toluene tower based on a single benzene extraction device of the present invention comprises the following steps:
[0022] Step 1, separating the depentane oil through a dehexane tower step to obtain an aromatic component-rich C7+ fraction;
[0023] Step 2, the aromatics-rich component obtained in step 1 is passed through a hydrogenation device to obtain an aromatics-rich component after hydrogenation;
[0024] Step 3, the aromatics-rich component obtained after hydrogenation in step 2 is passed through an aromatics distillation device to obtain raffinate oil and extract;
[0025] Step 4: The extract obtained in step 3 is passed through a benzene tower to obtain benzene at the top of the tower and toluene at the bottom of the tower.
[0026] Furthermore, in step (1), after the depentanized oil is distilled and separated in a dehexanizer, an aromatics-rich component at the top of the tower and a C7+ fraction at the bottom of the tower are obtained.
[0027] Furthermore, in step (2), a hydrodeolefination reactor is carried out to obtain an olefin-free aromatics-rich component.
[0028] Furthermore, in step (3), after extractive distillation and solvent recovery, aromatics and non-aromatics are separated to obtain non-aromatic component raffinate oil and aromatic component extract.
[0029] Furthermore, in step (4), after distillation separation in the benzene tower, benzene at the top of the tower and toluene at the bottom of the tower are obtained.
[0030] Preferably, in the dehexanizer operation, the reflux rate is reduced to control the C8 aromatic content in the aromatic-rich component at the top of the dehexanizer to be less than 0.01% (wt). The dehexanizer pressure is kept stable by starting and stopping air cooling and fine-tuning the reflux tank pressure, thereby ensuring the stable concentration of the extracted feed toluene.
[0031] More preferably, the temperature of the sensitive plate of the dehexane tower is controlled at 101-103° C. to stabilize the top extraction amount and control the toluene content in the top extraction amount to be between 10% and 15%.
[0032] The mechanism of the present invention is:
[0033] The invention reduces the contents of C8 aromatics and solvent in the benzene tower feed by adjustment, thereby improving the purity of the benzene tower feed. Under the limitation of no toluene tower, the benzene tower is used to separate benzene and toluene, and the toluene quality meets the requirements.
[0034] The beneficial effects of the present invention include:
[0035] The present invention is based on the production of toluene without a toluene tower in a refinery enterprise. On the basis of the existing process flow of a "single benzene extraction" device, high-quality toluene products are successfully produced without a toluene tower, and the production conversion from "single benzene extraction" to "double benzene extraction" is realized. The toluene output can reach 10-15% of the single benzene extraction load. The toluene product is successfully separated from the gasoline product. The toluene product is sold separately as a chemical product, which effectively alleviates the gasoline sales pressure of a fuel-type refinery, achieves the goal of "reducing oil and increasing chemicals", and effectively guarantees the economic benefits of the refinery enterprise.
[0036] Since the present invention is not designed to use a toluene tower, compared with the conventional extraction process of dibenzene, the process is shortened and has the characteristics of low investment. At the same time, the energy consumption of the toluene tower device is low and the operating cost is low. Since the toluene tower is not designed to use, there are fewer heat combinations, and toluene can be flexibly produced according to market conditions, gasoline pool octane number and other conditions. The operation is flexible and the product has strong market adaptability. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The present invention is further described below in conjunction with the accompanying drawings.
[0038] Figure 1 The present invention is a process flow diagram of the method for producing toluene.
[0039] The symbols in the accompanying drawings are described as follows:
[0040] 1-depentanized oil, 2-dehexane tower, 3-aromatic-rich components, 4-C7+ fraction, 5-hydrogenation unit, 6-aromatic-rich components after hydrogenation, 7-extractive distillation unit, 8-raffinate oil, 9-extract liquid, 10-benzene tower, 11-petroleum benzene, 12-petroleum toluene. DETAILED DESCRIPTION
[0041] The present invention is further described in detail below by examples. These examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.
[0042] Example 1
[0043] A method for producing toluene without a toluene tower based on a single benzene extraction device, comprising:
[0044] (1) separating the depentane oil 1 through a dehexane tower 2 to obtain an aromatics-rich component 3 and a C7+ fraction 4;
[0045] (2) The aromatics-rich component 3 obtained in step (1) is passed through a hydrogenation unit step 5 to obtain an aromatics-rich component 6 after hydrogenation;
[0046] (3) The aromatics-rich component 6 obtained after hydrogenation in step (2) is passed through an aromatics distillation unit 7 to obtain a raffinate 8 and an extract 9;
[0047] (4) The extract 9 obtained in step (3) is passed through a benzene tower 10 to obtain a benzene product 11 and petroleum toluene 12.
[0048] The process design flow is as follows: the extract enters the benzene tower, benzene product is obtained at the top of the benzene tower, heavy aromatics are obtained at the bottom of the benzene tower, heavy aromatics enter the toluene tower, toluene is obtained at the top of the toluene tower, and C8 aromatics are obtained at the bottom of the toluene tower.
[0049] The properties of the depentane oil 1 used in this Example 1 are shown in Table 1.
[0050] The properties of the aromatics-rich component 6 after hydrogenation in this Example 1 are shown in Table 2.
[0051] The main operating conditions of this Example 1 are shown in Table 3.
[0052] The main product properties of this Example 1 are shown in Table 4.
[0053] Table 1
[0054] Crude oil number Depentane oil 1 Final distillation point, ℃ 194.1 Normal alkanes, %(v) 5.59 Isoalkanes, %(v) 14.78 Olefins, %(v) 1.64 Cycloalkanes, %(v) 0.97 Aromatic hydrocarbons, %(v) 77.01 Density(20℃),kg / m3 827.8 Bromine index, mgBr / 100g 4020 Feed rate, t / h 201
[0055] Table 2
[0056] Intermediate product number Aromatic component 6 after hydrogenation Bromine index, mgBr / 100g 4.54 Non-aromatic hydrocarbons, % (wt) 63.96 Benzene, % (wt) 22.77 Toluene, % (wt) 13.26 Ethylbenzene, % (wt) <0.01 Xylene, % (wt) <0.01 o-Xylene, % (wt) <0.01 Meta-xylene, % (wt) <0.01 p-Xylene, % (wt) <0.01 Cumene, % (wt) <0.01 C8 aromatics, % (wt) <0.01 C9 aromatics, % (wt) <0.01 Components with carbon content of 10 or above, % (wt) <0.01 Single benzene extraction feed rate, t / h 60
[0057] Table 3
[0058] Operating conditions Example 1 Reflux rate of dehexane tower top, t / h 70 Temperature of the fifth tray of the dehexane tower, ℃ 102 Benzene tower reflux, t / h 28 Temperature control of 36-layer tray of benzene tower,℃ 106 Benzene tower temperature difference, ℃ 3.6
[0059] Table 4
[0060]
[0061]
[0062] As can be seen from Table 4, the C8 aromatics content in the petroleum toluene produced by the method of the present invention meets the index requirements of ≯0.05% (wt) and sulfur content ≯2 mg / kg.
[0063] Example 2
[0064] The preparation process of this embodiment is the same as that of embodiment 1.
[0065] The properties of the depentane oil 1 used in this Example 2 are shown in Table 5.
[0066] The aromatics-rich component 6 after hydrogenation in this Example 2 has properties as shown in Table 6.
[0067] The main operating conditions of this Example 2 are shown in Table 7.
[0068] The main product properties of this Example 2 are shown in Table 8.
[0069] Table 5
[0070]
[0071]
[0072] Table 6
[0073] Intermediate product number Aromatic component 6 after hydrogenation Bromine index, mgBr / 100g 4.65 Non-aromatic hydrocarbons, % (wt) 62.2 Benzene, % (wt) 22.34 Toluene, % (wt) 15.45 Ethylbenzene, % (wt) <0.01 Xylene, % (wt) <0.01 o-Xylene, % (wt) <0.01 Meta-xylene, % (wt) <0.01 p-Xylene, % (wt) <0.01 Cumene, % (wt) <0.01 C8 aromatics, % (wt) <0.01 C9 aromatics, % (wt) <0.01 Components with carbon content of 10 or above, % (wt) <0.01 Single benzene extraction feed rate, t / h 63
[0074] Table 7
[0075] Operating conditions Example 2 Reflux rate of dehexane tower top, t / h 66 Temperature of the fifth tray of the dehexane tower, ℃ 103 Benzene tower reflux, t / h 29 Temperature control of 36-layer tray of benzene tower,℃ 106 Benzene tower temperature difference, ℃ 3.3
[0076] Table 8
[0077]
[0078]
[0079] As can be seen from Table 8, the C8 aromatics content in the petroleum toluene produced by the method of the present invention meets the index requirements of ≯0.05% (wt) and sulfur content ≯2 mg / kg.
[0080] Comparative Example 1
[0081] The single benzene extraction unit normally produces benzene products and does not produce toluene, including:
[0082] (1) separating the depentane oil 1 through a dehexane tower 2 to obtain an aromatics-rich component 3 and a C7+ fraction 4;
[0083] (2) the aromatics-rich component 3 obtained in step 1 is passed through a hydrogenation device in step 5 to obtain an aromatics-rich component 6 after hydrogenation;
[0084] (3) The aromatics-rich component 6 obtained after hydrogenation in step 2 is passed through an aromatics distillation unit 7 to obtain raffinate 8 and an extract 9;
[0085] (4) The extract 9 obtained in step 3 is passed through a benzene tower 10 to obtain a benzene product 11 and a benzene distillation tower bottoms 12.
[0086] The properties of the depentane oil 1 used in this comparative example are shown in Table 9.
[0087] The aromatics-rich component 6 after hydrogenation in this comparative example has properties shown in Table 10.
[0088] The main operating conditions of this comparative example are shown in Table 11.
[0089] The main product properties of this comparative example are shown in Table 12.
[0090] Table 9
[0091]
[0092]
[0093] Table 10
[0094]
[0095]
[0096] Table 11
[0097] Operating conditions Comparative Example 1 Reflux rate of dehexane tower top, t / h 95 Temperature of the fifth tray of the dehexane tower, ℃ 84 Benzene tower reflux, t / h 13 Temperature control of 36-layer tray of benzene tower,℃ 95 Benzene tower temperature difference, ℃ 2.3
[0098] Table 12
[0099] Main Products Benzene distillation tower bottoms 12 Non-aromatic hydrocarbons, % (wt) 0.02 Benzene, % (wt) 93.87 Toluene, % (wt) 4.19 Ethylbenzene, % (wt) 0.29 o-Xylene, % (wt) 0.35 Meta-xylene, % (wt) 0.62 p-Xylene, % (wt) 0.3 C8 aromatics, % (wt) 1.58 C9 aromatics, % (wt) 0.1 Components with carbon content of 10 or above, % (wt) 0.24
[0100] As can be seen from Table 12, when single benzene extraction is in normal production, the purity of toluene 12 in the bottom product of the benzene distillation tower is only 4.19%, which is used as a gasoline blending component.
[0101] Based on the existing process flow of the "single benzene extraction" device, Examples 1-2 simultaneously produce high-quality toluene products without a toluene tower, realizing the conversion of "single benzene extraction" to "double benzene extraction", and the toluene output can reach 10-15% of the single benzene extraction load (for example, the toluene output recorded in Example 2 is 8.5 t / h and the single benzene extraction feed amount is 63 t / h, accounting for about 13.5%), and the toluene product is successfully separated from the gasoline product. The toluene product is sold separately as a chemical product, which effectively alleviates the sales pressure of gasoline in fuel-type refineries, achieves the goal of "reducing oil and increasing chemicals", and effectively guarantees the economic benefits of oil refining enterprises.
Claims
1. A method for producing toluene without a toluene tower based on a single benzene extraction device, characterized in that: The method reforms the depentanized oil into a dehexanizer of an aromatics unit, and the C6 and C7 fractions at the top of the dehexanizer are sent to a hydrogenation unit to remove olefins, and then enter an extractive distillation unit. The extractive distillation tower top produces raffinate oil, and the rich solvent at the bottom of the extractive tower enters a solvent regeneration tower. The extract at the top of the tower enters a benzene tower, and a benzene product is produced by the side line of the benzene tower. The toluene product is directly produced by the bottom product of the benzene tower.
2. The method for producing toluene without a toluene tower based on a single benzene extraction device according to claim 1, characterized in that: The following steps are involved: Step 1, separating the depentane oil (1) through a dehexane tower (2) to obtain an aromatics-rich component (3) and a C7+ fraction (4); Step 2, the aromatics-rich component (3) obtained in step 1 is passed through a hydrogenation unit step 5 to obtain an aromatics-rich component (6) after hydrogenation; Step 3: the aromatics-rich component (6) obtained after hydrogenation in step 2 is passed through an aromatics distillation device (7) to obtain raffinate oil (8) and an extract (9); Step 4: The extract (9) obtained in step 3 is passed through a benzene tower (10) to obtain a benzene product (11) and petroleum toluene (12).
3. The method for producing toluene without a toluene tower based on a single benzene extraction device according to claim 2, characterized in that: In step 1, after the depentanized oil is distilled and separated in a dehexanizer, an aromatics-rich component at the top of the tower and a C7+ fraction at the bottom of the tower are obtained.
4. The method for producing toluene without a toluene tower based on a single benzene extraction device according to claim 2, characterized in that: In step 2, a hydrodeolefination reactor is carried out to obtain an olefin-free aromatics-rich component.
5. The method for producing toluene without a toluene tower based on a single benzene extraction device according to claim 2, characterized in that: In step 3, after extractive distillation and solvent recovery, aromatics and non-aromatics are separated to obtain non-aromatic component raffinate oil and aromatic component extract.
6. The method for producing toluene without a toluene tower based on a single benzene extraction device according to claim 2, characterized in that: In step 4, after distillation separation in the benzene tower, petroleum benzene at the top of the tower and petroleum toluene at the bottom of the tower are obtained.
7. The method for producing toluene without a toluene tower based on a single benzene extraction device according to claim 2, characterized in that: In the operation of the dehexanizer, the reflux rate is reduced to control the weight content of C8 aromatics in the aromatics-rich components at the top of the dehexanizer to be less than 0.01%; the dehexanizer pressure is kept stable by starting and stopping air cooling and fine-tuning the reflux tank pressure, thereby ensuring the stability of the extraction feed toluene concentration.
8. The method for producing toluene without a toluene tower based on a single benzene extraction device according to any one of claims 2 to 7, characterized in that: The temperature of the 5th tray of the dehexane tower is 101-103°C.
9. The method for producing toluene without a toluene tower based on a single benzene extraction device according to any one of claims 2 to 7, characterized in that: The temperature of the 36th plate of the benzene tower is 105-108℃.
10. The method for producing toluene without a toluene tower based on a single benzene extraction device according to any one of claims 2 to 7, characterized in that: The reflux rate of the dehexane tower top is 66-70 t / h, the reflux rate of the benzene tower is 28-29 t / h, and the temperature difference of the benzene tower is 3.3-3.6℃.