Efficient and energy-saving system for preparing benzene from methylbenzene

Abstract

The utility model discloses a high-efficiency and energy-saving toluene-to-benzene system which is characterized in that toluene and hydrogen are used as raw materials and sequentially pass through a reaction system and a gas-liquid separation system, an obtained liquid-phase product is sequentially subjected to steam stripping by a steam stripping tower system and a carclazyte tank and then enters a benzene tower system to be separated, a gas phase at the top of the benzene tower enters a steam generator, and a byproduct steam is generated; a benzene product is extracted from the side line of the benzene tower and enters a boiler water preheater, and the benzene product is obtained after boiler water is preheated and passes through a benzene product first cooler. The benzene tower system is subjected to heat configuration, the temperature of the benzene tower is increased by increasing the pressure of the benzene tower, high-temperature-level heat is recycled, boiler water preheating and byproduct steam production are conducted, the energy utilization rate is increased, energy consumption is reduced, and the income is increased.

Description

Technical Field

[0001] This invention belongs to the field of toluene-to-benzene technology, and in particular relates to a highly efficient and energy-saving toluene-to-benzene system. Background Technology

[0002] Benzene is an important product of petroleum refining and a crucial raw material for petrochemicals, holding a pivotal position in the petrochemical industry chain. Benzene production and technological level are significant indicators of a country's petrochemical industry development. As a leading product in the aromatics industry chain, it belongs to the "three olefins and three benzenes" category.

[0003] The toluene-to-benzene plant is an industrially highly interconnected facility with a wide range of applications and a significant impact on related industries. It uses toluene as its upstream raw material and produces a diverse range of downstream products, resulting in a long industrial chain and broad market prospects.

[0004] Steam is an important utility medium, used for equipment heating and heat tracing of equipment and pipelines, as well as providing power to equipment. The consumption and byproducts of steam directly determine the energy input of the plant and affect production efficiency. The currently operating mature toluene-to-benzene process utilizes steam generated from the waste heat of the reaction for the use of equipment and pipelines in this plant, achieving a balance between supply and demand. However, energy allocation and utilization are still not optimal.

[0005] In existing technologies, benzene towers are atmospheric pressure towers with low overall tower temperature. The heat in the top material and side stream products is high, but it is low-temperature heat, which is not conducive to recovery and utilization. In addition, a cold source is required to cool the top gas phase and side stream products, which increases energy consumption and production costs. Utility Model Content

[0006] In view of this, the present invention aims to provide a highly efficient and energy-saving toluene-to-benzene system to solve at least one technical problem in the background art.

[0007] To achieve the above objectives, the technical solution of this utility model is implemented as follows:

[0008] A highly efficient and energy-saving method for producing benzene from toluene uses toluene and hydrogen as raw materials. The raw materials pass through a reaction system and a gas-liquid separation system in sequence. The resulting liquid product is stripped through a stripping tower system and a clay tank, and then enters a benzene tower system for separation. The benzene product is collected from the side stream of the benzene tower system and enters a boiler water preheater. After preheating the boiler water, the benzene product is obtained through a first benzene product cooler.

[0009] Furthermore, a portion of the gas phase obtained from the gas-liquid separation system is recycled hydrogen and mixed with the feedstock, while the other portion enters the PSA hydrogen extraction unit.

[0010] Furthermore, fuel gas is discharged from the top of the stripping tower system.

[0011] Furthermore, the vapor phase at the top of the benzene tower system enters the steam generator to produce low-pressure steam; after being cooled to the liquid phase, it returns to the benzene tower system.

[0012] The bottom of the benzene tower system is heated by a heating furnace and a benzene tower reboiler, or the bottom of the benzene tower system is heated by a benzene tower reboiler.

[0013] Furthermore, the material obtained at the bottom of the benzene tower system passes through a heavy aromatics stripping tower and a reboiler or flash tank. The material is then recycled and mixed with the raw material at the top of the heavy aromatics stripping tower and reboiler. Heavy aromatics are obtained at the bottom of the heavy aromatics stripping tower and reboiler, and the material is mixed with the raw material at the top of the heavy aromatics stripping tower and reboiler.

[0014] A highly efficient and energy-saving toluene-to-benzene system includes a reaction system, a gas-liquid separation system, a stripping tower system, a clay tank, and a benzene tower system;

[0015] Toluene and hydrogen are fed into the reaction system through a mixing pipeline. The reaction system is connected to a gas-liquid separation system, which is connected to a stripping tower system. The bottom of the stripping tower system is connected to the bottom of the clay tank, and the top of the clay tank is connected to the benzene tower system.

[0016] Furthermore, the gas-liquid separation system is connected to a mixing pipeline for toluene and hydrogen;

[0017] The gas-liquid separation system is connected to the PSA hydrogen extraction unit via pipeline;

[0018] The bottom of the gas-liquid separation system is connected to the stripping tower system via a pipeline, and the top of the stripping tower system is equipped with a fuel gas discharge pipeline.

[0019] Furthermore, the benzene tower system includes a benzene tower, the bottom of which is connected to a heating furnace via a pipe, and the heating furnace is connected to the bottom of the benzene tower via a pipe.

[0020] Furthermore, the bottom of the benzene tower is connected to the benzene tower reboiler via a pipe, and the benzene tower reboiler is connected to the reboiler of the benzene tower via a pipe.

[0021] Furthermore, the top of the benzene tower is connected to a steam generator via a pipe, the steam generator is connected to a benzene tower reflux tank via a pipe, and the bottom of the benzene tower reflux tank is connected to a benzene tower reflux pump via a pipe.

[0022] One side of the benzene tower is connected to the boiler water preheater via a pipeline, and the boiler water preheater is connected to the first benzene product cooler via a pipeline. The first benzene product cooler outputs benzene product.

[0023] The boiler water preheater and the steam generator are connected by pipes.

[0024] Furthermore, the bottom of the benzene tower is connected to the heavy aromatics stripping tower and reboiler via a pipeline; the bottom of the heavy aromatics stripping tower and reboiler outputs heavy aromatics, and the top of the heavy aromatics stripping tower and reboiler is mixed with toluene and hydrogen via a pipeline.

[0025] Furthermore, the bottom of the benzene tower is connected to the flash tank via a pipeline; the bottom of the heavy aromatics stripping tower and reboiler outputs heavy aromatics, and the top of the heavy aromatics stripping tower and reboiler is mixed with a toluene and hydrogen mixing pipeline via a pipeline.

[0026] The pressure of the benzene tower and the operating pressure can be adjusted according to the specifications of the by-product steam, depending on actual production needs. The vapor phase at the top of the benzene tower exchanges heat with preheated boiler water via a steam generator to produce low-pressure steam for unit use and external distribution. Benzene products from the side stream are preheated in a boiler water preheater and then cooled in a product cooler to obtain the final benzene product. The reboiler in the tower bottom uses waste heat from the convection section of the heating furnace and high-pressure steam as a heat source. The material in the tower bottom enters the heavy aromatics stripping tower and reboiler for separation; depending on production requirements, the heavy aromatics stripping tower and reboiler can be replaced with a flash tank.

[0027] Compared with existing technologies, the high-efficiency and energy-saving toluene-to-benzene system described in this utility model has the following advantages:

[0028] 1. This application increases the operating pressure of the benzene tower, utilizes the high-temperature gas phase byproduct low-pressure steam from the tower top, and uses the heat from the benzene product collected from the side stream to preheat boiler water, reducing boiler heat consumption. The high-temperature material from the tower bottom directly enters the heavy aromatics stripping tower and reboiler for separation, further reducing steam consumption in these components. Thermal configuration is implemented, with the reboiler at the tower bottom heated by a boiler and high-pressure steam. In summary, this invention improves energy utilization, produces low-pressure steam as a byproduct, reduces energy consumption by 10-25%, and increases profitability.

[0029] 2. Compared with existing technologies, this technology can improve energy utilization and produce low-pressure steam as a byproduct. Attached Figure Description

[0030] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0031] Figure 1 This is a schematic diagram of a highly efficient and energy-saving toluene-to-benzene system as described in Comparative Example 1 of this utility model;

[0032] Figure 2 This is a schematic diagram of a high-efficiency and energy-saving toluene-to-benzene system according to Embodiment 1 of this utility model;

[0033] Figure 3This is a schematic diagram of a high-efficiency and energy-saving toluene-to-benzene system according to Embodiment 2 of this utility model;

[0034] Figure 4 This is a schematic diagram of a high-efficiency and energy-saving toluene-to-benzene system according to Embodiment 3 of this utility model;

[0035] Figure 5 This is a schematic diagram of a high-efficiency and energy-saving toluene-to-benzene system according to Embodiment 4 of this utility model.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1. Reaction system; 2. Gas-liquid separation system; 3. Stripping tower system; 4. Clay tank; 5. Benzene tower; 6. Heavy aromatics stripping tower and reboiler; 7. PSA hydrogen extraction unit; 8. Benzene tower reboiler; 9. Heating furnace; 10. Steam generator; 11. Benzene tower reflux tank; 12. Benzene tower reflux pump; 13. Boiler water preheater; 14. Benzene product primary cooler; 15. Flash tank; 16. Benzene tower top condenser; 17. Benzene product secondary cooler; 18. Benzene product transfer pump. Detailed Implementation

[0038] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0039] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0040] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0041] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] Comparative Example 1

[0043] Structure as Figure 1 As shown, toluene and hydrogen are used as raw materials. First, the mixture passes through reaction system 1 and gas-liquid separation system 2. A portion of the gas phase is returned to the cycle as circulating hydrogen, while the other portion enters the PSA hydrogen extraction unit 7. The liquid phase reaction product is stripped through stripping tower system 3 and then passed through clay tank 4 before entering benzene tower 5 for separation. The gas phase at the top of benzene tower 5 is water-cooled by benzene tower top condenser 16 and returned to the benzene tower. Benzene products from the side stream are transferred to the tank area via benzene product second cooler 17 and benzene product transfer pump 12. The bottom material passes through a heavy aromatics stripping tower and reboiler 6, with the top circulating aromatics returning to the cycle, and heavy aromatics obtained from the bottom.

[0044] Following this route, taking a 250,000-ton / year toluene-to-benzene unit (based on toluene) as an example, the benzene tower is an atmospheric pressure tower with a top temperature of 89°C. Its utility consumption is shown in Table 1 below:

[0045]

[0046] Note: If the water cooler at the top of the tower is an air cooler, the amount of circulating water used can be converted into electricity.

[0047] The prices for public utilities are as follows: electricity 0.7 yuan / kW.h, circulating water 0.15 yuan / t, boiler water 6.5 yuan / t, and fuel gas 3.5 yuan / Nm³. 3 The cost of public works is calculated at RMB 5893.0 per hour.

[0048] Example 1

[0049] like Figure 2 As shown, a high-efficiency and energy-saving toluene-to-benzene system includes a reaction system 1, a gas-liquid separation system 2, a stripping tower system 3, a clay tank 4, and a benzene tower system; the benzene tower system includes a benzene tower 5, a heavy aromatic stripping tower and reboiler 6, a benzene tower reboiler 8, a steam generator 10, a benzene tower reflux tank 11, a benzene tower reflux pump 12, and a benzene product first cooler 14.

[0050] Toluene and hydrogen are fed into reaction system 1. Reaction system 1 is connected to gas-liquid separation system 2. Gas-liquid separation system 2 is connected to stripping tower system 3. The bottom of stripping tower system 3 is connected to the bottom of clay tank 4. The top of clay tank 4 is connected to benzene tower 5.

[0051] The gas-liquid separation system 2 is mixed with a mixing pipeline of toluene and hydrogen through a pipeline; the gas-liquid separation system 2 is connected to the PSA hydrogen extraction unit 7 through a pipeline; the bottom of the gas-liquid separation system 2 is connected to the stripping tower system 3 through a pipeline, and the top of the stripping tower system 3 is equipped with a fuel gas discharge pipeline.

[0052] The bottom of the benzene tower 5 is connected to the heating furnace 9 via a pipe, the heating furnace 9 is connected to the bottom of the benzene tower 5 via a pipe, the bottom of the benzene tower is connected to the benzene tower reboiler 8 via a pipe, and the benzene tower reboiler 8 is connected to the bottom of the benzene tower via a pipe.

[0053] The top of the benzene tower is connected to the steam generator 10 via a pipe, the steam generator 10 is connected to the benzene tower reflux tank 11 via a pipe, and the bottom of the benzene tower reflux tank 11 is connected to the benzene tower reflux pump 12 via a pipe. One side of the benzene tower is connected to the boiler water preheater 13 via a pipe, the boiler water preheater 13 is connected to the benzene product first cooler 14 via a pipe, and the benzene product first cooler 14 outputs benzene product. The boiler water preheater 13 and the steam generator 10 are connected via a pipe.

[0054] The bottom of the benzene tower is connected to the heavy aromatic stripping tower and reboiler 6 via a pipeline; the bottom of the heavy aromatic stripping tower and reboiler 6 outputs heavy aromatics, and the top of the heavy aromatic stripping tower and reboiler 6 is mixed with a toluene and hydrogen mixing pipeline via a pipeline.

[0055] Using toluene and hydrogen as raw materials, the mixture first passes through reaction system 1 and gas-liquid separation system 2. A portion of the gas phase is returned to the recycling system as circulating hydrogen, while the other portion enters the PSA hydrogen extraction unit 7. The liquid-phase reaction products are stripped through stripping tower system 3 and then separated in clay tank 4 before entering the benzene tower system. The gas phase at the top of the benzene tower enters steam generator 10 to produce low-pressure steam, which is cooled to the liquid phase and then returned to the benzene tower. Benzene products are collected from the side stream and enter boiler water preheater 13 to preheat the boiler water before entering the tank area via benzene product first cooler 14. The reboiler heat source for the tower bottom is heater furnace 9 and benzene tower reboiler 8. The benzene tower bottom material passes through heavy aromatics stripping tower and reboiler 6. The circulating aromatics at the top of the tower are returned to the recycling system, and heavy aromatics are obtained from the bottom. The steam condensate used for heating the heavy aromatics stripping tower and reboiler 6 is sent to the condensate pipeline network.

[0056] Following this route, taking a 250,000-ton / year toluene-to-benzene unit (based on toluene) as an example, the benzene tower pressure is 0.85 MPaG, the tower top temperature is 156.4℃, and the heat source for the benzene tower reboiler is 4.0 MPaG high-pressure steam. Its utility consumption is shown in Table 2 below:

[0057]

[0058] The prices for public utilities are as follows: electricity 0.7 yuan / kW.h, 4.0MPaG steam 240 yuan / t, 0.4MPaG steam 180 yuan / t, circulating water 0.15 yuan / t, boiler water 6.5 yuan / t, and fuel gas 3.5 yuan / Nm³. 3 The cost of public works is calculated at 5155.1 yuan / hour.

[0059] Compared with Example 1, the benzene tower in the comparative example is an atmospheric pressure tower with a low overall temperature. The waste heat from the material at the top and side outlet cannot be utilized and is condensed and cooled by circulating cooling water. In contrast, the benzene tower in Example 1 has a high pressure and a relatively high overall temperature. The waste heat at the top is used to produce low-pressure steam as a byproduct, and the preheated portion of the benzene product from the side outlet is used for boiler water utilization. This reduces energy consumption costs by 737.87 yuan / h. Based on an annual operating time of 8000 hours, the annual energy saving cost is 5.903 million yuan / year, reducing energy consumption by 12.52% and achieving higher energy utilization.

[0060] Example 2

[0061] like Figure 3 As shown, the structure is the same as in Example 1, using toluene and hydrogen as raw materials. First, the mixture passes through reaction system 1 and gas-liquid separation system 2. A portion of the gas phase is returned to the cycle as circulating hydrogen, while the other portion enters the PSA hydrogen extraction unit 7. The liquid phase reaction product is stripped through stripping tower system 3 and then enters the benzene tower for separation in clay tank 4. The gas phase at the top of the benzene tower enters steam generator 10 to produce low-pressure steam, which is cooled to the liquid phase and then returned to the benzene tower. Benzene product from the side stream enters boiler water preheater 13 to preheat the boiler water, and then enters the tank area via benzene product cooler. The reboiler at the bottom of the tower is heated by the convection section of heater 9 and steam. The material at the bottom of the benzene tower passes through heavy aromatics stripping tower and reboiler 6. The circulating aromatics at the top of the tower are returned to the cycle, and heavy aromatics are obtained at the bottom. The steam condensate used for heating in the heavy aromatics stripping tower and reboiler 6 is flash-evaporated to generate steam for use in the unit and for external distribution.

[0062] Following this route, taking a 250,000-ton / year toluene-to-benzene unit (based on toluene) as an example, the benzene tower pressure is 0.85 MPaG, the top temperature is 156.4℃, and the heat source for the benzene tower reboiler is 4.0 MPaG high-pressure steam. The steam condensate undergoes two-stage flash evaporation to produce 2.0 MPaG steam, 0.4 MPaG steam, and steam condensate, respectively. The 2.0 MPaG steam is used by the unit, while the 0.4 MPaG steam and steam condensate are sent to the pipeline network. The utility consumption is shown in Table 3 below:

[0063]

[0064] The prices for public utilities are as follows: electricity 0.7 yuan / kW.h, 4.0MPaG steam 240 yuan / t, 0.4MPaG steam 180 yuan / t, circulating water 0.15 yuan / t, boiler water 6.5 yuan / t, and fuel gas 3.5 yuan / Nm³. 3 Based on the calculation, the cost of public works is 4583.7 yuan / hour.

[0065] Comparative Example 2 further recovers the waste heat of the high-pressure steam condensate based on Example 1. The steam is generated by two-stage flash evaporation, producing 2.0 MPaG steam and 0.4 MPaG steam respectively, which further improves the utilization rate of heat. Compared with Example 1, the energy consumption cost is reduced by 517.8 yuan / h. Based on an annual operating time of 8000 hours, the annual energy saving cost is 4.1224 million yuan / year.

[0066] Compared with the control group, the energy consumption cost is reduced by RMB 1255.7 / h. Based on an annual operating time of 8000 hours, the annual energy saving cost is RMB 10.0456 million / year, reducing energy consumption by 21.31% and further improving energy utilization.

[0067] Example 3

[0068] like Figure 4 As shown, the difference from Example 1 is that the bottom of the benzene tower is connected to the benzene tower reboiler 8 through a pipe, and the benzene tower reboiler 8 is connected to the bottom of the benzene tower through a pipe, and no heater 9 is provided.

[0069] Using toluene and hydrogen as raw materials, the mixture first passes through reaction system 1 and gas-liquid separation system 2. A portion of the gas phase is returned to the recycling system as circulating hydrogen, while the other portion enters the PSA hydrogen extraction unit 7. The liquid-phase reaction products are stripped through stripping tower system 3 and then separated in clay tank 4 before entering the benzene tower system. The gas phase from the top of the benzene tower enters steam generator 10 to produce low-pressure steam, which is cooled to the liquid phase and then returned to the benzene tower. Benzene products are collected from the side stream and enter boiler water preheater 13 to preheat the boiler water before entering the tank area via benzene product first cooler 14. The reboiler at the bottom of the tower is heated by steam. The material at the bottom of the benzene tower passes through a heavy aromatics stripping tower and reboiler 6. The circulating aromatics at the top of the tower are returned to the recycling system, and heavy aromatics are obtained from the bottom. The condensate from the heating steam is flash-evaporated to generate steam for use in the unit and for external distribution.

[0070] Following this route, taking a 250,000-ton / year toluene-to-benzene unit (based on toluene) as an example, the benzene tower pressure is 0.85 MPaG, the top temperature is 156.4℃, and the heat source for the benzene tower reboiler is only 4.0 MPaG high-pressure steam. The steam condensate undergoes two-stage flash evaporation to produce 2.0 MPaG steam, 0.4 MPaG steam, and steam condensate, respectively. The 2.0 MPaG steam is used by the unit, while the 0.4 MPaG steam and steam condensate are sent to the pipeline network. The utility consumption is shown in Table 4 below:

[0071]

[0072] The prices for public utilities are as follows: electricity 0.7 yuan / kW.h, 4.0MPaG steam 240 yuan / t, 0.4MPaG steam 180 yuan / t, circulating water 0.15 yuan / t, boiler water 6.5 yuan / t, and fuel gas 3.5 yuan / Nm³. 3 The cost of public works is calculated at 5300.2 yuan / hour.

[0073] Comparing Example 3 and Example 2, the heat source for the reboiler at the bottom of the benzene tower is only high-pressure steam. The waste heat from the convection section of the heater 9 is used to produce high-pressure steam. Therefore, the amount of boiler water used increases, and the amount of steam produced increases, but the overall energy utilization efficiency decreases. According to calculations, the energy consumption cost increases by 662.9 yuan / h. Based on an annual operating time of 8000 hours, the annual cost increases by 5.3032 million yuan / year. However, this scheme reduces the high-temperature pipelines of the heater 9 and the benzene tower reboiler, and at the same time reduces heat loss.

[0074] Compared with the control group, the energy consumption cost is reduced by 592.7 yuan / h. Based on an annual operating time of 8,000 hours, the annual energy saving cost is 4.7416 million yuan / year, which is a reduction of 10.01% in energy consumption.

[0075] Example 4

[0076] like Figure 5 As shown, the difference from Example 1 is that the benzene tower is connected to the flash tank 15 via a pipe at the bottom.

[0077] Using toluene and hydrogen as raw materials, the mixture first passes through reaction system 1 and gas-liquid separation system 2. A portion of the gas phase is returned to the recycling system as circulating hydrogen, while the other portion enters the PSA hydrogen extraction unit 7. The liquid-phase reaction products are stripped through stripping tower system 3 and then separated in clay tank 4 before entering the benzene tower system. The gas phase at the top of the benzene tower enters steam generator 10 to produce low-pressure steam, which is cooled to the liquid phase and then returned to the benzene tower. Benzene products from the side stream enter boiler water preheater 13, preheating the boiler water before entering the tank area via benzene product first cooler 14. The bottom material enters flash tank 15, where the circulating aromatics at the top of the tower are returned to the recycling system, and heavy aromatics are obtained from the bottom. The condensate from the heating steam is flashed to generate steam for use in the unit and for external distribution.

[0078] Following this route, taking a 250,000-ton / year toluene-to-benzene unit (based on toluene) as an example, the benzene tower pressure is 0.85 MPaG, the tower top temperature is 156.4℃, and the heat source for the benzene tower reboiler is 4.0 MPaG high-pressure steam. The steam condensate undergoes two-stage flash evaporation to produce 2.0 MPaG steam, 0.4 MPaG steam, and steam condensate, respectively. The 2.0 MPaG steam is used by the unit, while the 0.4 MPaG steam and steam condensate are sent to the pipeline network. The utility consumption is shown in Table 5 below:

[0079]

[0080] The prices for public utilities are as follows: electricity 0.7 yuan / kW.h, 4.0MPaG steam 240 yuan / t, 0.4MPaG steam 180 yuan / t, circulating water 0.15 yuan / t, boiler water 6.5 yuan / t, and fuel gas 3.5 yuan / Nm³. 3 Based on the calculation, the cost of public works is 4583.7 yuan / hour.

[0081] Compared with Example 2, Example 4 can replace the heavy aromatic stripping tower and reboiler 6 with a flash tank according to production needs and requirements for the purity of heavy aromatics. The purity of biphenyl in heavy aromatics is reduced from 99.89% to 80.5%, the steam consumption is reduced, the energy consumption cost is reduced by 53.6 yuan / h, and the annual operating time is calculated as 8000 hours, the annual energy saving cost is 428,800 yuan / year.

[0082] Comparing Example 4 and the comparative example, it can be seen that the energy consumption cost is reduced by 1309.3 yuan / h. Based on an annual operating time of 8000 hours, the annual energy saving cost is 10.4744 million yuan / year, which reduces energy consumption by 22.22%.

[0083] Examples 2 and 4 are applicable to different production needs.

[0084] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A high efficiency energy saving toluene to benzene system characterized by: Includes reaction system, gas-liquid separation system, stripping tower system, clay tank, and benzene tower system; Toluene and hydrogen are fed into the reaction system through a mixing pipeline. The reaction system is connected to a gas-liquid separation system, which is connected to a stripping tower system. The bottom of the stripping tower system is connected to the bottom of the clay tank, and the top of the clay tank is connected to the benzene tower system.

2. A high efficiency energy saving toluene to benzene system as claimed in claim 1 wherein: The gas-liquid separation system is connected to a pipeline for mixing toluene and hydrogen. The gas-liquid separation system is connected to the PSA hydrogen extraction unit via pipeline; The bottom of the gas-liquid separation system is connected to the stripping tower system via a pipeline, and the top of the stripping tower system is equipped with a fuel gas discharge pipeline.

3. The high-efficiency and energy-saving toluene-to-benzene system according to claim 1, characterized in that: The benzene tower system includes a benzene tower, the bottom of which is connected to a heating furnace via a pipe, and the heating furnace is connected to the bottom of the benzene tower via a pipe.

4. The system as claimed in claim 3, wherein the system is a high efficiency energy saving toluene to benzene system. The bottom of the benzene tower is connected to the benzene tower reboiler via a pipe, and the benzene tower reboiler is connected to the bottom of the benzene tower via a pipe.

5. The system as claimed in claim 3, wherein the system is a high efficient energy saving toluene to benzene system. The top of the benzene tower is connected to the steam generator via a pipe, the steam generator is connected to the benzene tower reflux tank via a pipe, and the bottom of the benzene tower reflux tank is connected to the benzene tower reflux pump via a pipe. One side of the benzene tower is connected to the boiler water preheater via a pipeline, and the boiler water preheater is connected to the first benzene product cooler via a pipeline. The first benzene product cooler outputs benzene product. The boiler water preheater and the steam generator are connected by pipes.

6. The system as claimed in claim 1, wherein the system is a high efficient energy saving toluene to benzene system. The bottom of the benzene tower is connected to the heavy aromatics stripping tower and reboiler via a pipeline; the bottom of the heavy aromatics stripping tower and reboiler outputs heavy aromatics, and the top of the heavy aromatics stripping tower and reboiler is mixed with toluene and hydrogen via a pipeline.

7. The system as claimed in claim 1, wherein the system is a high efficient energy saving toluene to benzene system. The bottom of the benzene tower is connected to the flash tank via a pipeline; the bottom of the heavy aromatics stripping tower and reboiler outputs heavy aromatics, and the top of the heavy aromatics stripping tower and reboiler is mixed with toluene and hydrogen via a pipeline.

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