A system for efficiently utilizing the low-temperature heat of the circulating oil from the distillation tower of a catalytic cracking unit

Abstract

The present invention discloses a system for efficiently utilizing the low-temperature heat of the top circulating oil of a catalytic cracking unit fractionation tower. The system comprises a first reboiler and a second reboiler arranged in parallel at the bottom of a gas separation depropanizer. The heat source inlet of the first reboiler of the depropanizer is connected to a catalytic top circulating oil delivery pipe, and the heat source outlet is connected to a post-exchange catalytic top circulating oil pipe. The heat source inlet of the second reboiler of the depropanizer is connected to a depropanizer reboiler steam pipe, and the heat source outlet is connected to a depropanizer condensate return pipe. The inlet of a steam generator is connected to the condensate inlet pipe, and the condensate inlet pipe is directly connected to the depropanizer condensate return pipe or is connected via a steam condensate tank. The heat source inlet of the steam generator is connected to the post-exchange catalytic top circulating oil pipe, and the heat source outlet is connected to a catalytic top circulating oil return pipe. The negative pressure steam outlet of the steam generator is connected to the inlet of a first-stage steam compressor. This system greatly reduces the external steam required for the second reboiler of the depropanizer in the prior art, and has significant economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature heat utilization in chemical enterprises, and in particular to a system for efficiently utilizing low-temperature heat of circulating oil from a fractionation tower top of a catalytic cracking unit. Background Art

[0002] Refining and chemical companies are currently researching the application of heat from lower-temperature products, below 150°C. The catalytic cracking unit (FCC) is a core unit in refining and chemical companies that processes heavy distillates (wax oil and residual oil). It converts heavy distillates into liquefied gas (C3 and C4 components), gasoline, and diesel. The liquefied gas is then separated into propane, propylene, and C4 components by a gas fractionation unit. The C4 component then feeds the MTBE unit as feedstock for MTBE production. The FCC unit, gas fractionation unit, and MTBE unit are typically integrated into a single unit.

[0003] The first and second reboilers are installed in parallel at the bottom of the depropanizer in the gas fractionation unit. The top circulating oil from the catalytic cracking unit fractionation tower (referred to as "catalytic top circulating oil") has a large flow rate and high heat, with an extraction temperature of approximately 128°C-140°C. It serves as the heat source for the first reboiler in the depropanizer. The bottom temperature of the depropanizer is approximately 98°C-108°C. The catalytic top circulating oil and the bottom material are heat-exchanged in the first reboiler of the depropanizer. Due to the limitation of the heat transfer temperature difference, the temperature of the catalytic top circulating oil can only be reduced to approximately 108°C-118°C after heat exchange. The heat provided is generally less than the actual heat load required at the bottom of the depropanizer. A large amount of external steam must be added to the second reboiler of the depropanizer as a heat source, increasing energy consumption and processing costs.

[0004] For the catalytic top-circulating oil returning to the catalytic cracking unit at approximately 108-118°C, existing technology first utilizes its heat to generate heat transfer water at 70-90°C, which is then cooled to approximately 90°C via a catalytic top-circulating oil air cooler and returned to the top of the catalytic fractionation tower for reflux. While this heat transfer water can be used for heat tracing and heating, demand is high in winter and significantly decreases in summer. Seasonally excessive heat is cooled using air or water coolers before being discharged into the atmosphere. This heat is not efficiently utilized, a particularly serious issue in southern refineries, resulting in significant energy waste.

[0005] In an MTBE plant, the bottom temperature of the catalytic distillation column is approximately 130°C-140°C, and the bottom temperature of the methanol recovery column is approximately 105°C-110°C. Despite these relatively low bottom temperatures, existing technologies typically use steam as the reboiler heat source due to a lack of energy-saving measures. This results in high steam consumption, with steam energy accounting for over 90% of the plant's total energy consumption. Summary of the Invention

[0006] Based on the above problems, the present application provides a system for efficiently utilizing the low-temperature heat of the circulating oil from the top of the distillation tower of a catalytic cracking unit. Steam is produced by utilizing the low-temperature heat of the catalytic top circulating oil after heat exchange in the first reboiler of the depropanizer of the gas separation unit, and is used as the heat source for the second reboiler of the gas separation depropanizer (or the reboiler of the MTBE unit). This can effectively reduce the consumption of external steam, reduce the operating costs of refining enterprises, and at the same time reduce pollutant emissions, which is green and environmentally friendly.

[0007] The present application provides a system for efficiently utilizing the low-temperature heat of the circulating oil from the top of a fractionating tower of a catalytic cracking unit, comprising the following steps:

[0008] (1) The catalytic top circulating oil discharged from the first reboiler of the depropanizer is fed into a steam generator to exchange heat with condensed water to generate steam;

[0009] (2) After the steam is compressed by the compressor to increase the pressure and temperature, it is used as a heat source for the second reboiler of the depropanizer (or the reboiler of the MTBE unit).

[0010] The present application provides a system for efficiently utilizing the low-temperature heat of the top circulating oil of the fractionating tower of a catalytic cracking unit, comprising a catalytic fractionating tower, a gas separation depropanizer, a steam generator, a primary steam compressor and a primary steam deoxygenation water pipe, wherein the catalytic fractionating tower is connected to a catalytic top circulating oil delivery pipe and a catalytic top circulating oil reflux pipe, a first reboiler of the depropanizer and a second reboiler of the depropanizer are arranged in parallel at the bottom of the gas separation depropanizer, a heat source inlet of the first reboiler of the depropanizer is connected to the catalytic top circulating oil delivery pipe, and a heat source outlet is connected to the replaced catalytic top circulating oil pipe, a heat source inlet of the second reboiler of the depropanizer is connected to the steam pipe of the depropanizer reboiler, and a heat source outlet is connected to the condensate return pipe of the depropanizer, and the steam generator is arranged at a negative pressure. Steam is generated under high pressure conditions, the heat source inlet of the steam generator is connected to the catalytic top circulation oil pipe after replacement, the heat source outlet is connected to the catalytic top circulation oil return pipe, the liquid inlet of the steam generator is connected to the condensate inlet pipe, the condensate inlet pipe is directly connected to the depropanizer condensate return pipe or is connected through a steam condensate tank, a condensate pump is installed on the condensate inlet pipe, the inlet of the first-stage steam compressor is connected to the negative pressure steam outlet of the steam generator, the outlet of the first-stage steam compressor is connected to the depropanizer reboiler steam pipe through a primary steam pipe, and the primary steam deoxygenation water pipe is connected to the pipe body of the primary steam pipe, so that the superheated steam output from the outlet of the first-stage steam compressor is formed into saturated steam after being sprayed with deoxygenated water.

[0011] In some embodiments, the system further comprises an MTBE methanol recovery tower, the MTBE methanol recovery tower is provided with a methanol recovery tower reboiler, the heat source inlet of the methanol recovery tower reboiler is connected to the methanol recovery tower reboiler steam pipe, the heat source outlet is connected to the methanol recovery tower condensate return pipe, and the methanol recovery tower condensate return pipe is directly connected to the condensate inlet pipe or connected through a steam condensate tank;

[0012] The primary steam pipe is also connected to the steam pipe of the methanol recovery tower reboiler.

[0013] In some embodiments, the system further comprises an MTBE catalytic distillation tower, the MTBE catalytic distillation tower is provided with a catalytic distillation tower reboiler, the heat source inlet of the catalytic distillation tower reboiler is connected to the catalytic distillation tower reboiler steam pipe, the heat source outlet is connected to the catalytic distillation tower condensate return pipe, and the catalytic distillation tower condensate return pipe is directly connected to the condensate inlet pipe or connected through a steam condensate tank;

[0014] The system also includes a two-stage steam compressor, the outlet of the first-stage steam compressor is further connected to the inlet of the second-stage steam compressor through the second-stage compressor inlet pipe, and the outlet of the second-stage steam compressor is connected to the steam pipe of the catalytic distillation tower reboiler through the secondary steam pipe;

[0015] The system also includes a secondary steam deoxygenation water pipe, which is connected to the pipe body of the secondary steam pipe so that the superheated steam output from the outlet of the secondary steam compressor becomes saturated steam after being sprayed with deoxygenated water.

[0016] In some embodiments, where a steam condenser is included, the steam condenser includes a flash vapor phase outlet and a flash liquid phase outlet.

[0017] In some embodiments, the depropanizer reboiler steam line is further configured with a depropanizer make-up steam line.

[0018] In some embodiments, the methanol recovery tower reboiler steam pipe is further configured with a methanol recovery tower supplementary steam pipe.

[0019] In some embodiments, the catalytic distillation column reboiler steam pipe is further configured with a catalytic distillation column supplementary steam pipe.

[0020] In some embodiments, the system further includes a condensate discharge pipe, which is connected to the condensate inlet pipe, and the connection point is arranged after the condensate pump in the flow direction of the condensate inlet pipe.

[0021] In some embodiments, the catalytic top circulating oil delivery pipe is installed with a top circulating oil pump.

[0022] In some embodiments, the operating pressure range of the steam generator is 38.6 kPa(A)-101.3 kPa(A), and the temperature range of the generated steam is 75°C-100°C.

[0023] In some embodiments, the pressure of the superheated steam at the outlet of the first-stage steam compressor is determined based on the bottom temperature of the gas separation and depropanizer tower or the MTBE methanol recovery tower and the corresponding pipeline resistance drop, and the corresponding pipeline is a pipeline connecting the outlet of the first-stage steam compressor and the heat source inlet of the second reboiler of the depropanizer tower or the reboiler of the methanol recovery tower.

[0024] In some embodiments, the pressure of the superheated steam at the outlet of the secondary steam compressor is determined based on the bottom temperature of the MTBE catalytic distillation column and the resistance drop of the corresponding pipeline, which is the pipeline connecting the outlet of the secondary steam compressor and the heat source inlet of the catalytic distillation column reboiler.

[0025] In some embodiments, the catalytic top circulation oil return pipe is connected to the catalytic top circulation oil / heat medium water heat exchanger and the catalytic top circulation oil air cooler in sequence. In the flow direction of the catalytic top circulation oil return pipe, the catalytic top circulation oil first generates heat medium water in the catalytic top circulation oil / heat medium water heat exchanger, and then returns to the top of the catalytic distillation tower for reflux after being cooled in the catalytic top circulation oil air cooler.

[0026] The beneficial effects of the present application are as follows: a system for efficiently utilizing the low-temperature heat of the top circulating oil of the distillation tower of a catalytic cracking unit is provided, comprising a distillation tower of the catalytic cracking unit and a depropanizer of a gas fractionating unit; through the mutual cooperation of a steam condensate tank, a steam generator, a first-stage steam compressor and a primary steam deoxygenation water pipe, the catalytic top circulating oil after heat exchange with the first reboiler of the depropanizer is used as a heat source for the steam generator; condensate from the steam condensate tank is heated and vaporized under negative pressure conditions; the generated negative pressure saturated steam is compressed and pressurized by the first-stage steam compressor to become superheated steam; the superheated steam is sprayed with deoxygenated water to form saturated steam; the saturated steam passes through the primary steam pipe, the depropanizer reboiler and the first steam pipe; the saturated steam passes through the first steam pipe, the depropanizer reboiler and the first steam pipe; the condensate is heated and vaporized under negative pressure conditions; the generated negative pressure saturated steam is compressed and pressurized by the first-stage steam compressor to become superheated steam; the superheated steam is sprayed with deoxygenated water to form saturated steam; the saturated steam passes through the first steam pipe, the depropanizer reboiler and the first steam pipe; the condensate is heated and vaporized under negative pressure conditions; the condensate is heated and vaporized; the condensate is compressed and pressurized by the first-stage steam compressor; the saturated steam passes through the first steam pipe, the depropanizer reboiler and the first steam pipe; the condensate is heated and vaporized; the condensate is heated and vaporized; the condensate is heated and vaporized; the condensate is compressed and pressurized by the first-stage steam compressor; the condensate is compressed and pressurized by the first-stage steam compressor; the condensate is compressed and pressurized by the first-stage steam compressor; The steam is transported through a pipe to the heat source inlet of the second reboiler of the depropanizer, where it exchanges heat with the bottom stream of the gas fraction depropanizer and undergoes a liquefied phase change, with the released heat providing the load required by the second reboiler of the depropanizer. This system fully utilizes the low-temperature heat of the catalytic top circulating oil after heat exchange in the first reboiler of the depropanizer, greatly reducing the external steam required for the second reboiler of the depropanizer in the prior art, thereby saving energy and reducing consumption and carbon dioxide emissions for the enterprise, with significant economic benefits. Moreover, this system can be applied to both new installations and improvements to existing systems. For modified installations, no new pipelines to and from the catalytic cracking unit are required, resulting in low cost and ease of implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention.

[0028] Figure 1 Schematic diagram of a low-temperature heat utilization scheme for catalytic top circulation oil in the prior art;

[0029] Figure 2 This is a schematic structural diagram of the system disclosed in Example 1 for efficiently utilizing the low-temperature heat of the circulating oil from the top of the fractionating tower of a catalytic cracking unit;

[0030] Figure 3This is a schematic structural diagram of the system disclosed in Example 2 for efficiently utilizing the low-temperature heat of the circulating oil from the top of the fractionating tower of a catalytic cracking unit;

[0031] Figure 4 This is a schematic structural diagram of the system disclosed in Example 3 for efficiently utilizing the low-temperature heat of the circulating oil from the distillation tower top of a catalytic cracking unit;

[0032] Figure 5 This is a schematic structural diagram of a system for efficiently utilizing low-temperature heat from the top circulating oil of a catalytic cracking unit fractionation tower disclosed in Example 4;

[0033] Figure 6 This is a schematic structural diagram of the system disclosed in Example 5 for efficiently utilizing the low-temperature heat of the circulating oil from the top of the fractionation tower of a catalytic cracking unit;

[0034] Figure 7 This is a schematic diagram of the structure of the system disclosed in Example 6 for efficiently utilizing the low-temperature heat of the circulating oil from the distillation tower top of a catalytic cracking unit.

[0035] Figure markings: 100-catalytic distillation tower, 110-catalytic top circulating oil delivery pipe, 111-top circulating oil pump, 120-catalytic top circulating oil reflux pipe, 121-catalytic top circulating oil / heat medium water heat exchanger, 122-catalytic top circulating oil air cooler, 123-catalytic top circulating oil pipe after replacement, 200-gas separation depropanizer, 210-depropanizer first reboiler, 220-depropanizer second reboiler, 221-depropanizer reboiler steam pipe, 221a-depropanizer supplementary steam pipe, 222-depropanizer condensate return pipe, 300-steam condensate tank, 310-flash liquid phase outlet, 320-flash steam phase outlet, 321-flash steam pipe, 400-steam generator, 410-condensate inlet, 411-condensate inlet pipe, 412-condensate pump, 420 -Negative pressure steam outlet, 421-negative pressure steam pipe, 500-first-stage steam compressor, 510-second-stage steam compressor, 511-primary steam pipe, 512-second-stage compressor inlet pipe, 513-secondary steam pipe, 600-primary steam deaeration water pipe, 610-secondary steam deaeration water pipe, 700-condensate discharge pipe, 800-MTBE catalytic distillation tower, 810-catalytic distillation tower reboiler, 811-catalytic distillation tower reboiler steam pipe, 811a-catalytic distillation tower supplementary steam pipe, 812-catalytic distillation tower condensate return pipe, 900-MTBE methanol recovery tower, 910-methanol recovery tower reboiler, 911-methanol recovery tower reboiler steam pipe, 911a-methanol recovery tower supplementary steam pipe, 912-methanol recovery tower condensate return pipe. DETAILED DESCRIPTION

[0036] The process of a petroleum refining and chemical enterprise generally includes steps such as heating the raw materials, reacting (or separating), and cooling the products. To conserve the energy consumed by heating the raw materials while also cooling the products, the raw materials are first heated using the heat from the products (or other streams from the reaction and fractionation processes). The raw materials are then heated to the required reaction or separation temperature using a heating furnace (consuming fuel). When excess heat is present within the plant, the heat from the higher-temperature products (generally above 150°C) can be transferred to the outside of the plant through steam generation or other methods.

[0037] Because heat transfer requires a temperature difference, a large amount of low-temperature heat cannot be recovered through heat exchange with raw materials or steam generation. This heat is called low-temperature heat, and its temperature is generally below 150°C. How to fully utilize low-temperature heat has a significant impact on reducing energy consumption, pollutant emissions, and improving economic efficiency for refining and chemical companies.

[0038] The inventors have summarized the existing methods for utilizing low-temperature heat in refining enterprises, as follows:

[0039] It is used for heating process units, heat integration between refining units, and using low-temperature heat as a heat source for the bottom reboiler of the distillation tower of some light component separation units, such as the depropanizer of the gas fractionation unit.

[0040] Used for heating and cooling buildings, or for heating production systems, by exchanging low-temperature heat with heat transfer water. The heat transfer water can be used for heating refinery units or storage and transportation systems, heating the company or surrounding residential buildings in winter, and cooling the refinery's own buildings in summer. This low-temperature heat utilization method can utilize heat above 75°C. However, because heating and cooling demand are affected by the seasons, this utilization method has unstable heat demand.

[0041] Used for cooling process equipment, specifically exchanging low-temperature heat with heat medium water, and then sending it to the refrigeration unit for cooling water. The cold water is used for cooling process that requires low operating temperature. Low-temperature heat cooling is also an inefficient way of utilizing heat.

[0042] It is used for seawater desalination, but other processes are available, such as reverse osmosis, which does not necessarily require low-temperature heat. Moreover, the heat utilization value of seawater desalination is not high. It is only used for seawater desalination when there is no other high-value utilization method for low-temperature heat. In addition, inland refineries do not have the conditions for seawater desalination, and areas with no water shortage do not need to build seawater desalination equipment, so the limitations are relatively large.

[0043] Using low-temperature heat to generate electricity has the disadvantages of high investment and very low energy utilization efficiency, which is about 6%. Few companies adopt this method.

[0044] In summary, the inventors found that under the current conditions of huge low-temperature heat production in refining and chemical enterprises, there is no reasonable way to utilize a large amount of low-temperature heat, and it can only be discharged into the environment through circulating water cooling, air cooler cooling, etc., and the process of discharging energy also consumes energy or other resources.

[0045] The catalytic cracking unit (FCU) is a core unit in refining and petrochemical companies that processes heavy distillates (wax oil and residual oil). It converts heavy distillates into liquefied gas (C3 and C4 components), gasoline, and diesel. The liquefied gas is then separated into propane, propylene, and C4 components by a gas fractionation unit. The C4 component is then fed into the MTBE unit as feedstock to produce MTBE. The FCU, gas fractionation unit, and MTBE unit are typically located within a single complex.

[0046] Taking a refining and chemical enterprise with a processing scale of 5 million tons / year to 10 million tons / year as an example, the scale of its catalytic cracking unit generally reaches about 2.5 million tons / year to 4 million tons / year; the scale of its gas fractionation unit generally reaches about 500,000 tons / year to 1 million tons / year; and the scale of its MTBE unit (measured in MTBE products) generally reaches about 50,000 tons / year to 200,000 tons / year.

[0047] The catalytic cracking unit is one of the most important units for outputting low-temperature heat in refining enterprises. The top circulating oil of the catalytic cracking unit fractionation tower (referred to as "catalytic top circulating oil") has a large flow rate and high heat, and the extraction temperature is around 128℃-140℃. It is a typical low-temperature heat and can be used for heat integration with the gas fractionation unit. Figure 1 Provide detailed explanation.

[0048] Please refer to Figure 1 The catalytic top circulating oil is extracted through the top circulating oil pump 111 and sent to the gas fractionation device as the heat source of the first reboiler 210 of the depropanizer. After heat exchange with the bottom material of the gas separation depropanizer 200, it returns to the catalytic cracking device. After cooling down through the catalytic top circulating oil / heat medium water heat exchanger 121 and the catalytic top circulating oil air cooler 122, it returns to the top of the catalytic distillation tower 100 as reflux; the second reboiler 220 of the depropanizer is set in parallel at the bottom of the gas separation depropanizer 200, using external steam as a heat source to supplement part of the heat for the bottom of the tower.

[0049] While the conventional heat integration method mentioned above rationally utilizes some of the heat from the catalytic top-cycle oil, there is still room for improvement. The temperature at the bottom of the gas separator depropanizer 200 is approximately 98°C-108°C. Due to the limited heat transfer temperature difference in the first reboiler 210 of the depropanizer, the temperature of the catalytic top-cycle oil can only be reduced to approximately 108°C-118°C after heat exchange. This heat is generally insufficient to meet the actual heat load required at the bottom of the gas separator depropanizer 200, necessitating the addition of a large amount of external steam as a heat source in the second reboiler 220 of the depropanizer, increasing energy consumption and processing costs.

[0050] After returning the top circulating oil, which is around 108-118°C, to the catalytic cracking unit, it is first used to generate heat transfer water at 70-90°C. This heat is then cooled to around 90°C by the catalytic top circulating oil air cooler 122 and returned to the top of the catalytic fractionation tower 100 for reflux. This heat is not efficiently utilized. Although heat transfer water can be used for heat tracing and heating, demand is high in winter and significantly decreases in summer. This seasonal excess heat must be cooled using air or water coolers before being discharged into the atmosphere. This situation is particularly serious in southern refineries, resulting in energy waste.

[0051] In an MTBE plant, the bottom temperature of the catalytic distillation column is approximately 130°C-140°C, and the bottom temperature of the methanol recovery column is approximately 105°C-110°C. Despite these relatively low bottom temperatures, existing technologies typically use steam as the reboiler heat source due to a lack of energy-saving measures. This results in high steam consumption, with steam energy accounting for over 90% of the plant's total energy consumption.

[0052] Taking a 600,000 ton / year gas fractionation unit as an example, the first reboiler in the depropanizer uses catalytic top-cycle oil as a heat source, with a flow rate of 570 t / h, reducing the temperature from 128°C to 117°C. The heat load is approximately 4.7 MW, accounting for 37% of the total bottom load. The second reboiler in the depropanizer uses 0.5 MPa(G) steam as a heat source, with a flow rate of 18.5 t / h, condensing saturated vapor at 158°C to saturated liquid. The heat load is approximately 8.0 MW, accounting for 63% of the total bottom load. The unit's rated energy consumption is 52.3 kgoe / t of feedstock, of which steam energy consumption is 19.9 kgoe / t, accounting for 38.0%. The total steam consumption of the unit is 19.6 t / h, of which 18.5 t / h is used in the depropanizer reboiler, accounting for 94.3%. Based on an annual operating time of 8,400 hours, the depropanizer consumes 155,000 tons of steam annually, at a cost of approximately 31.5 million yuan. In the 100,000 ton / year MTBE unit, which is paired with the aforementioned gas fractionation unit, the bottom temperature of the catalytic distillation tower is 131°C, and the bottom temperature of the methanol recovery tower is 107°C. Both towers use 0.5 MPa(G) steam as their heat source, resulting in a total steam consumption of 15.0 t / h. The unit's rated energy consumption is 106.5 kgoe / t MTBE, of which steam consumption accounts for 101.3 kgoe / t of raw material, or 95.2%. The MTBE unit consumes 126,000 tons of steam annually, at a cost of approximately 25.6 million yuan. Steam is energy-intensive and expensive. Replacing some steam with low-temperature heat as a heat source would significantly improve energy efficiency and efficiency for refineries.

[0053] Example 1

[0054] Please refer to Figure 2This embodiment provides a system for efficiently utilizing the low-temperature heat of the catalytic cracking unit fractionation tower overhead circulating oil. The system includes a catalytic fractionation tower 100, a gas separation and depropanizer 200, a steam condenser 300, a steam generator 400, a first-stage steam compressor 500, and a deaeration water pipe 600. The system improves the problem of severe heat waste in the catalytic top circulating oil having a temperature of approximately 108°C-118°C after heat exchange in the first reboiler 210 of the depropanizer.

[0055] Please refer to Figure 2 The catalytic distillation tower 100 is connected to a catalytic top circulating oil delivery pipe 110 and a catalytic top circulating oil return pipe 120. The catalytic top circulating oil delivery pipe 110 serves as the output pipe for the catalytic top circulating oil and generally requires the installation of a top circulating oil pump 111. The catalytic top circulating oil return pipe 120 serves as the return pipe for the catalytic top circulating oil. The bottom of the gas separation depropanizer 200 has a first depropanizer reboiler 210 and a second depropanizer reboiler 220 arranged in parallel. The heat source inlet of the first depropanizer reboiler 210 is connected to the catalytic top circulating oil delivery pipe 110, the heat source outlet of the first depropanizer reboiler 210 is connected to the replaced catalytic top circulating oil pipe 123, the heat source inlet of the second depropanizer reboiler 220 is connected to the depropanizer reboiler steam pipe 221, and the heat source outlet of the second depropanizer reboiler 220 is connected to the depropanizer condensate return pipe 222.

[0056] Please refer to Figure 2 The inlet of the steam condensate tank 300 is connected to the condensate return pipe 222 of the depropanizer, the steam generator 400 is set to generate steam under negative pressure conditions, the heat source inlet of the steam generator 400 is connected to the catalytic top circulation oil pipe 123 after replacement, the heat source outlet of the steam generator 400 is connected to the catalytic top circulation oil return pipe 120, the condensate inlet 410 of the steam generator 400 is connected to the flash liquid phase outlet 310 of the steam condensate tank 300 through the condensate inlet pipe 411, and a condensate pump 412 is installed on the condensate inlet pipe 411. The inlet of the first-stage steam compressor 500 is connected to the negative pressure steam outlet 420 of the steam generator 400 through the negative pressure steam pipe 421, and the outlet of the first-stage steam compressor 500 is connected to the depropanizer reboiler steam pipe 221 through the primary steam pipe 511.

[0057] Please refer to Figure 2 The deoxygenation water pipe 600 is connected to the pipe body of the primary steam pipe 511. The deoxygenation water pipe 600 allows the superheated steam output from the outlet of the first-stage steam compressor 500 to become saturated steam after being sprayed with deoxygenated water.

[0058] The specific working process is as follows:

[0059] The catalytic top-cycle oil from the catalytic cracking unit is delivered via the catalytic top-cycle oil delivery pipe 110 to the first reboiler 210 of the depropanizer in the gas fractionation unit, where it serves as a heat source. In the first reboiler 210, the catalytic top-cycle oil exchanges heat with the material from the bottom of the gas fractionation depropanizer 200, lowering its temperature. The bottom of the gas fractionation depropanizer 200 has a temperature of approximately 98°C-108°C. Due to the heat transfer temperature differential (assuming a 10°C heat transfer temperature differential), the temperature of the catalytic top-cycle oil after heat exchange can only be reduced to approximately 108°C-118°C.

[0060] After heat exchange in the first reboiler 210 of the depropanizer, the catalytic top circulating oil with a temperature of about 108°C-118°C flows by gravity to the steam generator 400, and serves as the heat source of the steam generator 400. The condensate from the steam condensate tank 300 is heated and vaporized under negative pressure conditions to produce negative pressure saturated steam.

[0061] After heat exchange in the steam generator 400, the catalytic top circulating oil returns to the catalytic fractionating tower 100 along the catalytic top circulating oil return pipe 120. The negative pressure saturated steam produced by the steam generator 400 enters the first steam compressor 500 from the inlet thereof. After being compressed and pressurized by the first steam compressor 500, superheated steam is formed. In the process of superheated steam being transported along the primary steam pipe 511 to the steam pipe 221 of the depropanizer, the superheated steam is sprayed with deoxygenated water in the deoxygenated water pipe 600 to form saturated steam, and the minimum saturated temperature of the saturated steam is controlled at 108°C-118°C. It should be noted that the 108°C-118°C here refers to the minimum temperature of the saturated steam formed by spraying with deoxygenated water, and the specific value selected needs to be compatible with the bottom temperature of the gas separation depropanizer 200 of 98°C-108°C, which involves the concept of a minimum heat transfer temperature difference of 10°C between the cold source and the heat source.

[0062] The saturated steam generated by spraying deoxygenated water is transported along the primary steam pipe 511 and the depropanizer reboiler steam pipe 221 to the heat source inlet of the depropanizer second reboiler 220, serving as the heat source for the depropanizer second reboiler 220. In the depropanizer second reboiler 220, the saturated steam exchanges heat with the material from the bottom of the gas separator depropanizer 200, releasing heat through a liquefaction phase change and condensing into condensed water. The condensed water flows by gravity to the steam condensate tank 300. The liquid phase in the steam condensate tank 300 is transported via the condensate pump 412 along the condensate inlet pipe 411 to the steam generator 400. Steam is generated within the steam generator 400 under negative pressure, and its heat source is the catalytic top circulating oil after heat exchange in the depropanizer first reboiler 210.

[0063] By adopting the system for efficiently utilizing the low-temperature heat of the circulating oil from the top of the distillation tower of the catalytic cracking unit provided in this embodiment, the low-temperature heat of the catalytic top circulating oil after heat exchange in the first reboiler 210 of the depropanizer is fully utilized, the potential of the catalytic top circulating oil is fully tapped, its low-temperature heat is transferred and its quality is improved, and self-produced steam is used to replace part of the external steam as the heat source of the second reboiler 220 of the depropanizer, which not only significantly reduces the consumption of external steam, but also reduces the energy consumed by the catalytic top circulating oil in the subsequent cooling process, thereby achieving energy conservation and emission reduction, and significantly improving the economic benefits of the enterprise.

[0064] Please compare Figure 1 and Figure 2 The system provided in this embodiment can be applied to both new installations and improvements to existing systems. For modified installations, no new pipelines to and from the catalytic cracking unit are required, which obviously has the beneficial effects of low cost and ease of implementation.

[0065] The steam generator 400 in the system is further described. The steam generator 400 is a device that vaporizes water into steam under the condition of being heated by a heat source. The vaporization temperature and pressure of water are in a corresponding relationship. To illustrate this relationship, when the vaporization temperatures are 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C and 160°C, the corresponding saturated vapor pressures of water (unit: kPa(A)) are 31.2, 38.6, 47.4, 57.8, 70.1, 84.5, 101.3, 120.8, 143.2, 169.0, 198.5, 232.0, 270.0, 312.9, 361.2, 415.3, 475.7, 543.0 and 617.7 respectively.

[0066] As can be seen, the lower the operating pressure of steam generator 400, the lower the water's vaporization temperature. At the same heat transfer temperature difference, the lower the heat source temperature that can be utilized, and the more heat that can be recovered. A suitable negative pressure environment creates conditions for fully utilizing low-temperature heat. For example, if the water vaporization temperature is set to 90°C, corresponding to a vaporization pressure of 70.1 kPa(A), and the lowest heat transfer temperature difference is set to 10°C, heat above 100°C in the hot material can be utilized. At a heat source temperature of 120°C, heat with a temperature difference of 20°C can be recovered.

[0067] In the present invention, the heat source for steam generator 400 is the catalytic top-cycle oil from the first reboiler 210 of the depropanizer. To properly match the temperature, steam generation is required under negative pressure. In some embodiments, the operating pressure range of steam generator 400 is 38.6 kPa(A)-101.3 kPa(A), and the steam generation temperature range is 75°C-100°C. The specific operating conditions can be determined based on the actual temperature of the catalytic top-cycle oil after heat exchange in the first reboiler 210 of the depropanizer.

[0068] The first-stage steam compressor 500 in the system is further described. As a key component of this system, the first-stage steam compressor 500 pressurizes and heats low-temperature, low-pressure steam to meet the required process temperature and pressure, fully utilizing the steam's latent heat. In this embodiment, the first-stage steam compressor 500 compresses and heats the negative-pressure steam produced by the steam generator 400, achieving conditions compatible with the second reboiler 220 of the depropanizer.

[0069] The bottom temperature of the depropanizer 200 is generally between 98°C and 108°C. Considering a minimum heat transfer temperature difference of 10°C between the heat source and the cold source, the minimum saturated temperature of the steam used as the heat source for the first reboiler 210 of the depropanizer is between 108°C and 118°C, corresponding to a saturated steam pressure of 133.9 kPa(A) to 186.2 kPa(A). Considering the resistance drop of the pipeline from the first steam compressor 500 to the second reboiler 220 of the depropanizer, the outlet pressure of the first steam compressor 500 ranges from approximately 143.9 kPa(A) to 201.2 kPa(A). The actual pressure value should be determined based on the bottom temperature of the depropanizer 200 and the resistance drop of the corresponding pipeline. The corresponding pipeline is the pipeline connecting the outlet of the first steam compressor 500 and the heat source inlet of the second reboiler 220 of the depropanizer.

[0070] Because gas compression converts electrical energy into internal energy, the compressed gas is superheated. To ensure effective heat exchange, the superheated steam should be cooled to a saturated state before use. For example, when steam is compressed from a saturated state of 90°C and 70.1 kPa(A) to 169.0 kPa(A), superheated steam at 180°C is obtained. In some embodiments, spraying this with deoxygenated water can produce saturated steam at 115°C. In addition to the aforementioned benefits, the use of deoxygenated water also takes into account its inherent low impurities and dissolved oxygen content, which helps maintain the quality of the circulating water in the system and mitigates equipment corrosion.

[0071] The steam condensate tank 300 in the system is further described. The purpose of setting up the steam condensate tank 300 is to separate the vapor phase and the liquid phase, stabilize the operation, and alleviate the water hammer phenomenon caused by distance and pressure drop during the condensate transportation process.

[0072] Considering that the condensed water output after heat exchange with the second reboiler 220 of the depropanizer tower may carry some steam, in some embodiments, the steam condensate tank 300 further includes a flash steam phase outlet 320 and a flash liquid phase outlet 310, and the steam is discharged through the flash steam phase outlet 320 and the condensed water is discharged through the flash liquid phase outlet 310.

[0073] In some embodiments, see Figure 2 The flash vapor phase outlet 320 is opened at the top of the steam condensate tank 300 , and the flash liquid phase outlet 310 is opened at the bottom of the steam condensate tank 300 .

[0074] In the detailed description of the specific working process above, it is involved that the condensate flows to the steam condensate tank 300. Specifically, the condensate flashes into steam and liquid phases in the steam condensate tank 300 under the same negative pressure conditions as the steam generator 400. Please refer to Figure 2 In some embodiments, the negative pressure steam outlet 420 of the steam generator 400 is connected to the inlet of the primary steam compressor 500 via a negative pressure steam pipe 421. The flash steam phase outlet 320 is connected to the body of the negative pressure steam pipe 421 via the flash steam pipe 321. Thus, the vapor phase flashed off in the steam condensate tank 300 flows along the flash steam pipe 321 and partially through the negative pressure steam pipe 421 into the primary steam compressor 500. A portion of the flashed liquid phase is pumped out of the condensate discharge pipe 700 to the condensate network via the condensate pump 412, while the remainder is delivered to the steam generator 400 via the condensate inlet pipe 411 for recycling.

[0075] In the above detailed description of the specific working process, self-produced saturated steam is involved as the heat source of the second reboiler 220 of the depropanizer. In some embodiments, considering the limited amount of self-produced saturated steam, the catalytic top circulating oil has not yet established circulation during the start-up and shutdown process, and the possible fluctuations in the flow rate and temperature of the top circulating oil during normal production, the second reboiler 220 of the depropanizer uses self-produced saturated steam as a heat source. It is also equipped with a depropanizer supplementary steam pipe 221a as a means of regulating the supplementary heat and stable operation. Please refer to Figure 2 , an appropriate amount of steam is added to the depropanizer second reboiler 220 through the depropanizer supplementary steam pipe 221a and the depropanizer reboiler steam pipe 221, and is used together with the self-produced saturated steam as the heat source of the depropanizer second reboiler 220.

[0076] Based on the above-mentioned scheme of supplementing an appropriate amount of steam to the second reboiler 220 of the depropanizer through the depropanizer supplementary steam pipe 221a, in some embodiments, the system also includes a condensate discharge pipe 700, which is connected to the condensate inlet pipe 411, and in the flow direction in the condensate inlet pipe 411, the connection point is arranged behind the condensate pump 412, and condensate with the same mass flow rate as the sum of the supplementary steam amount and the sprayed deoxygenated water amount is thrown out from the outlet of the condensate pump 412 to the condensate discharge pipe 700.

[0077] The catalytic top circulating oil that returns to the catalytic fractionation tower 100 along the catalytic top circulating oil return pipe 120 after passing through the steam generator 400 can be further utilized for its residual heat. In some embodiments, please refer to Figure 2 The catalytic top circulating oil return pipe 120 is connected to the catalytic top circulating oil / heat medium water heat exchanger 121 and the catalytic top circulating oil air cooler 122 in sequence. In the flow direction of the catalytic top circulating oil return pipe 120, the catalytic top circulating oil first generates heat medium water in the catalytic top circulating oil / heat medium water heat exchanger 121, and then is cooled in the catalytic top circulating oil air cooler 122 before returning to the top of the catalytic distillation tower 100 for reflux.

[0078] As described above, this system increases the steam pressure to the required temperature through compression, offering high flexibility. This system utilizes the high flow rate and heat capacity of the catalytic top-circulating oil, providing a prerequisite for centralized heat utilization. This system fully utilizes the low-temperature heat of the catalytic top-circulating oil. Under appropriate conditions, this system achieves heat transfer and the conversion of electrical energy into internal energy through water vaporization and steam compression, ultimately improving the quality of the heat. This allows the unit's own steam to replace some external steam as the heat source for the reboiler in the gas separation and depropanization tower 200, achieving significant energy-saving effects.

[0079] Based on the above-mentioned system for efficiently utilizing the low-temperature heat of the catalytic cracking unit fractionation tower overhead circulating oil, this embodiment also uses a 2 million tons / year catalytic cracking unit equipped with a 600,000 tons / year gas fractionation unit as an example to fully illustrate the beneficial effects. The relevant calculations are as follows:

[0080] Total steam production (including steam generator steam, deaerator water pipe spray steam, and condensate tank flash steam) × converted steam energy consumption - electricity consumption × converted electricity energy consumption = 11.5 tons / hour × 66 kg standard oil / ton - 900 kW × 0.22 kg standard oil / kW = 561 kg standard oil / hour. Based on an annual operating time of 8,400 hours, this can save the company 4,712.4 tons of standard oil and reduce carbon dioxide emissions by 14,500 tons per year.

[0081] As a result, the present invention can bring significant economic benefits to enterprises. For example, using a 2 million ton / year catalytic cracking unit equipped with a 600,000 ton / year gas fractionation unit, the construction investment of the present invention is approximately 13 million yuan, with an annual profit of 15 million yuan and a static payback period of only 0.87 years. If implemented nationwide, the system is expected to save 377,000 tons of standard oil annually, increase corporate profits by 1.2 billion yuan, and reduce carbon dioxide emissions by 1.16 million tons annually.

[0082] Example 2

[0083] This embodiment provides a system for efficiently utilizing the low-temperature heat of the circulating oil from the distillation tower of a catalytic cracking unit. The content of this system is basically the same as that of Example 1, except that: Figure 3 , and compared with reference Figure 2 This system eliminates the steam condensate tank 300, and the condensate inlet pipe 411 is directly connected to the depropanizer condensate return pipe 222. This solution is suitable for situations where the steam generator 400 is close to the bottom of the tower.

[0084] Example 3

[0085] This embodiment provides a system for efficiently utilizing the low-temperature heat of the circulating oil at the top of the distillation tower of a catalytic cracking unit. Based on Example 1, the self-produced steam is preferentially supplied to the second reboiler 220 of the depropanizer of the gas fractionation unit (tower bottom temperature 98°C-108°C) as a heat source. If there is surplus, it is supplied to the reboiler 910 of the methanol recovery tower of the MTBE unit (tower bottom temperature 105°C-110°C) as a heat source.

[0086] Based on Example 1, please refer to Figure 4 , further comprising an MTBE methanol recovery tower 900, which is provided with a methanol recovery tower reboiler 910. The heat source inlet of the methanol recovery tower reboiler 910 is connected to the methanol recovery tower reboiler steam pipe 911, and the heat source outlet is connected to the methanol recovery tower condensate return pipe 912. The methanol recovery tower condensate return pipe 912 is connected to the condensate inlet pipe 411 through the steam condensate tank 300. The primary steam pipe 511 is also connected to the methanol recovery tower reboiler steam pipe 911. In some embodiments, the methanol recovery tower reboiler steam pipe 911 is further configured with a methanol recovery tower supplementary steam pipe 911a.

[0087] The bottom temperature of MTBE methanol recovery tower 900 is generally 105°C-110°C. Considering a minimum heat transfer temperature difference of 10°C between the cooling and heating sources, the minimum saturated temperature of the steam used as the heat source for methanol recovery tower reboiler 910 is 115°C-120°C, corresponding to a saturated steam pressure of 169.0 kPa(A)-198.5 kPa(A). Considering the resistance drop of the pipeline from primary steam compressor 500 to methanol recovery tower reboiler 910, the outlet pressure of primary steam compressor 500 ranges from approximately 179.0 kPa(A)-223.5 kPa(A). The actual pressure should be determined based on the bottom temperature of MTBE methanol recovery tower 900 and the resistance drop of the corresponding pipeline. The corresponding pipeline is the pipeline connecting the outlet of primary steam compressor 500 and the heat source inlet of methanol recovery tower reboiler 910.

[0088] Example 4

[0089] This embodiment provides a system for efficiently utilizing the low-temperature heat of the circulating oil from the distillation tower of a catalytic cracking unit. The content of this system is basically the same as that of Example 3, except that: Figure 5 , and compared with reference Figure 4 This system eliminates the steam condensate tank 300, and the methanol recovery tower condensate return pipe 912 is directly connected to the condensate inlet pipe 411. This solution is suitable for situations where the steam generator 400 is close to the bottom of the tower.

[0090] Example 5

[0091] This embodiment provides a system for efficiently utilizing the low-temperature heat of the circulating oil from the distillation tower top of a catalytic cracking unit. Based on Example 3, the self-produced steam is preferentially supplied to the second reboiler 220 of the depropanizer of the gas fractionator (tower bottom temperature 98°C-108°C) as a heat source. If there is any surplus, it is supplied to the reboiler 910 of the methanol recovery tower of the MTBE unit (tower bottom temperature 105°C-110°C) as a heat source. If there is still any surplus, it is supplied to the reboiler 810 of the catalytic distillation tower of the MTBE unit (tower bottom temperature 130°C-140°C) as a heat source.

[0092] Based on Example 3, please refer to Figure 6 The system also includes an MTBE catalytic distillation tower 800, which is provided with a catalytic distillation tower reboiler 810. The heat source inlet of the catalytic distillation tower reboiler 810 is connected to the catalytic distillation tower reboiler steam pipe 811, and the heat source outlet is connected to the catalytic distillation tower condensate return pipe 812. The catalytic distillation tower condensate return pipe 812 is connected to the condensate inlet pipe 411 through the steam condensate tank 300.

[0093] Please refer to Figure 6The system also includes a secondary steam compressor 510. The outlet of the primary steam compressor 500 is connected to the inlet of the secondary steam compressor 510 via a secondary compressor inlet pipe 512. The outlet of the secondary steam compressor 510 is connected to the catalytic distillation column reboiler steam pipe 811 via a secondary steam pipe 513.

[0094] Please refer to Figure 6 The system also includes a secondary steam deoxygenation water pipe 610, which is connected to the secondary steam pipe 513 so that the superheated steam output from the outlet of the secondary steam compressor 510 becomes saturated steam after being sprayed with deoxygenated water.

[0095] In some embodiments, see Figure 6 The catalytic distillation tower reboiler steam pipe 811 is also equipped with a catalytic distillation tower supplementary steam pipe 811a.

[0096] The bottom temperature of the MTBE catalytic distillation tower 800 is generally 130°C-140°C. Considering a minimum heat transfer temperature difference of 10°C between the cold source and the heat source, the minimum saturated temperature of the steam used as the heat source of the catalytic distillation tower reboiler 810 is 140°C-150°C, corresponding to a saturated steam pressure of 361.2 kPa(A)-475.7 kPa(A). The negative pressure steam produced by the steam generator 400 needs to undergo two-stage compression to reach this pressure. Considering the resistance drop of the pipeline from the secondary steam compressor 510 to the catalytic distillation tower reboiler 810, the outlet pressure range of the secondary steam compressor 510 is approximately 371.2 kPa(A)-500.7 kPa(A). The actual pressure value should be determined based on the bottom temperature of the MTBE catalytic distillation tower 800 and the corresponding pipeline resistance drop. The corresponding pipeline is the pipeline connecting the outlet of the secondary steam compressor 510 and the heat source inlet of the catalytic distillation tower reboiler 810.

[0097] Example 6

[0098] This embodiment provides a system for efficiently utilizing the low-temperature heat of the circulating oil from the distillation tower of a catalytic cracking unit. The content of this system is basically the same as that of Example 5, except that: Figure 7 , and compared with reference Figure 6 This system eliminates the steam condensate tank 300, and the catalytic distillation tower condensate return pipe 812 is directly connected to the condensate inlet pipe 411. This solution is suitable for situations where the steam generator 400 is close to the tower bottom.

[0099] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0100] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A system for efficiently utilizing the low-temperature heat of the circulating oil from the distillation tower of a catalytic cracking unit, characterized in that: include: A catalytic distillation tower is connected to a catalytic top circulating oil delivery pipe and a catalytic top circulating oil return pipe; A gas separation depropanizer, a first depropanizer reboiler and a second depropanizer reboiler are arranged in parallel at the bottom of the tower, the heat source inlet of the first depropanizer reboiler is connected to the catalytic top circulating oil delivery pipe, and the heat source outlet is connected to the replaced catalytic top circulating oil pipe, the heat source inlet of the second depropanizer reboiler is connected to the depropanizer reboiler steam pipe, and the heat source outlet is connected to the depropanizer condensate return pipe; A steam generator is configured to generate steam under negative pressure conditions, wherein the heat source inlet of the steam generator is connected to the post-change catalytic top circulation oil pipe, and the heat source outlet is connected to the catalytic top circulation oil return pipe. The liquid inlet of the steam generator is connected to the condensate inlet pipe, and the condensate inlet pipe is directly connected to the depropanizer condensate return pipe or is connected through a steam condensate tank. A condensate pump is installed on the condensate inlet pipe; a first-stage steam compressor, wherein the inlet of the first-stage steam compressor is connected to the negative pressure steam outlet of the steam generator, and the outlet of the first-stage steam compressor is connected to the steam pipe of the depropanizer reboiler through a primary steam pipe; The primary steam deoxygenation water pipe is connected to the pipe body of the primary steam pipe so that the superheated steam output from the outlet of the first-stage steam compressor is converted into saturated steam after being sprayed with deoxygenated water.

2. The system according to claim 1, wherein: The system further includes an MTBE methanol recovery tower, wherein the MTBE methanol recovery tower is provided with a methanol recovery tower reboiler, wherein a heat source inlet of the methanol recovery tower reboiler is connected to a methanol recovery tower reboiler steam pipe, and a heat source outlet is connected to a methanol recovery tower condensate return pipe, and the methanol recovery tower condensate return pipe is directly connected to the condensate inlet pipe or is connected through the steam condensate tank; The primary steam pipe is also connected to the methanol recovery tower reboiler steam pipe.

3. The system according to claim 2, wherein: The system further includes an MTBE catalytic distillation tower, wherein the MTBE catalytic distillation tower is provided with a catalytic distillation tower reboiler, wherein a heat source inlet of the catalytic distillation tower reboiler is connected to a catalytic distillation tower reboiler steam pipe, and a heat source outlet is connected to a catalytic distillation tower condensate return pipe, and the catalytic distillation tower condensate return pipe is directly connected to the condensate inlet pipe or is connected through the steam condensate tank; The system further comprises a secondary steam compressor, wherein the outlet of the primary steam compressor is further connected to the inlet of the secondary steam compressor via a secondary compressor inlet pipe, and the outlet of the secondary steam compressor is connected to the steam pipe of the catalytic distillation column reboiler via a secondary steam pipe; The system further comprises a secondary steam deoxygenation water pipe which is connected to the pipe body of the secondary steam pipe so that the superheated steam output from the outlet of the secondary steam compressor is sprayed with deoxygenated water to form saturated steam.

4. The system according to any one of claims 1 to 3, wherein: In the case where the steam condensate tank is included, the steam condensate tank includes a flash steam phase outlet and a flash liquid phase outlet.

5. The system according to claim 1, wherein: The depropanizer reboiler steam pipe is also equipped with a depropanizer supplementary steam pipe.

6. The system according to claim 2, wherein: The methanol recovery tower reboiler steam pipe is also equipped with a methanol recovery tower supplementary steam pipe.

7. The system according to claim 3, wherein: The catalytic distillation tower reboiler steam pipe is further provided with a catalytic distillation tower supplementary steam pipe.

8. The system according to any one of claims 5 to 7, wherein: The system further includes a condensate discharge pipe, which is connected to the condensate inlet pipe, and in the flow direction of the condensate inlet pipe, the connection point is arranged after the condensate pump.

9. The system according to any one of claims 1 to 3, wherein: The catalytic top circulating oil delivery pipe is equipped with a top circulating oil pump.

10. The system according to any one of claims 1 to 3, wherein: The operating pressure range of the steam generator is 38.6 kPaA-101.3 kPaA, and the temperature range of the generated steam is 75°C-100°C.

11. The system according to any one of claims 1 to 3, wherein: The pressure of the superheated steam at the outlet of the first-stage steam compressor is determined according to the bottom temperature of the gas separation depropanizer or MTBE methanol recovery tower and the corresponding pipeline resistance drop, and the corresponding pipeline is a pipeline connecting the outlet of the first-stage steam compressor and the heat source inlet of the second reboiler of the depropanizer or the reboiler of the methanol recovery tower.

12. The system according to claim 3, wherein: The pressure of the superheated steam at the outlet of the secondary steam compressor is determined according to the bottom temperature of the MTBE catalytic distillation tower and the corresponding pipeline resistance drop. The corresponding pipeline is a pipeline connecting the outlet of the secondary steam compressor and the heat source inlet of the catalytic distillation tower reboiler.

13. The system according to any one of claims 1 to 3, wherein: The catalytic top circulation oil return pipe is connected to the catalytic top circulation oil / heat medium water heat exchanger and the catalytic top circulation oil air cooler in sequence. In the flow direction of the catalytic top circulation oil return pipe, the catalytic top circulation oil first generates heat medium water in the catalytic top circulation oil / heat medium water heat exchanger, and then returns to the top of the catalytic distillation tower for reflux after being cooled in the catalytic top circulation oil air cooler.

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