A dmto-iic4 recycle feed system

Abstract

The present application relates to a kind of DMTO-IIC4 recycling feed system, including benzene removal column, C4 depropanizer, start-up depropanizer and C4 vaporizer: the benzene removal column is communicated with C4+ raw material pipeline in benzene removal feed line, and the benzene removal feed line of start-up depropanizer is communicated with C4+ raw material pipeline;Benzene removal column is communicated with C4 gas phase feed line;Start-up depropanizer is communicated with C4 liquid phase pipeline of C4 vaporizer by C4 liquid phase feed line;C4 depropanizer is communicated with light hydrocarbon feed line, and C4 depropanizer bottom is communicated with C4 vaporizer by C4 liquid phase pipeline, is communicated with the benzene removal feed line of benzene removal column by C4 liquid phase supplementary pipeline, and is communicated with depropanizer by C4 discharge pipeline;C4 vaporizer is communicated with C4 liquid phase addition pipeline from C4 tank area;The accumulation of C4 reaction oil substance is solved, and C4 reaction can enter stable state as soon as possible in initial stage, guarantee the stability of C4 recycling.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a DMTO-IIC4 remelting feed system. Background Technology

[0002] DMTO-II is a second-generation methanol-to-olefins (MTO) technology and is currently the only operational second-generation production unit in China. The C4 reprocessing unit is a key differentiator from the first-generation MTO technology. The feed system for the C4 reprocessing unit comes from two sources: one is the C4 vapor phase from the top of the olefin separation and benzene removal tower, which is mixed with C4 and fed to the C4 feed vapor phase line; the other is the liquid phase from the bottom of the C4 propane removal tower, which is vaporized in the C4 vaporizer under tower pressure and then added to the C4 feed vapor phase line. The mixed gaseous C4 serves as the feed for the C4 reprocessing unit.

[0003] During the initial startup phase, the C4 reaction was unstable. For extended periods, the C4 depropanizer had no feed material available for the C4 reaction, making it impossible to effectively control the feed flow rate. At low MTO loads, the new catalyst caused insufficient C4 feedstock. When the MTO load dropped to as low as 200 t / h, the C4 reaction became unstable due to insufficient feedstock, making it highly susceptible to deep cracking. During prolonged operation, oils carried in the C4 reactant gas entered the C4 quench water scrubber.

[0004] The oil was washed off with water, causing the oil content in the washing water to exceed the standard. The wastewater stripping tower was unable to handle the excessive oil, resulting in serious exceedance of wastewater indicators and causing the wastewater system to collapse.

[0005] The C4 reaction itself produces small amounts of C6+ (n-methylbenzene) and light oils. Initially, these light oils are short-chain and relatively light, and are not directly washed away by water. Simultaneously, small amounts of short-chain light oils (including long-chain alcohols) in the wash water are also released into the product gas. These gaseous components, mixed with C6+ light oils, enter the C4 compression and separation unit. In the C4 propane stripper, C6+ and light oils remain at the bottom. The original process directly fed the C4 vaporizer from the bottom of the C4 propane stripper, and this portion of C6+ and light oils was then fed back into the C4 reactor to participate in the reaction, further lengthening the reaction chain and causing them to remain in the water system during washing. Over time, the production of long-chain and oily components increases, exceeding the oil balance in the water system and resulting in excessive wastewater discharge.

[0006] The original feed system design, if the reaction proceeded smoothly, would allow the C4 depropanizer material to gradually accumulate over time, reaching the conditions for a recirculation supply. However, in actual start-up, the initial C4 feed was too small, and the reaction depth could not be effectively controlled. A large amount of C4 was reacted into excessively light components, which then accumulated in the C4 depropanizer.

[0007] The inability to accumulate materials results in a vicious cycle where the total feed volume cannot be increased, and the depth of the C4 reaction cannot be controlled, leading to unstable start-up.

[0008] The original design considered early MTO catalysts, but in recent years, MTO catalysts have been updated and replaced, and while diene production has been continuously increasing, the C4+ component has been reduced, resulting in insufficient supply of C4 feedstock under the same load conditions. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a DMTO-IIC4 recycle feed system that separates C5+ components by pre-feeding distillation, solves the problem of C4 reaction oil accumulation, increases the tank area material replenishment line, temporarily replaces the C4 depropanizer bottom material during the initial start-up phase, so that the C4 reaction can quickly enter a stable state, and when the C4 feedstock is insufficient and cannot be maintained at a low MTO load, C4 feedstock is purchased from external sources and replenished to the system through this pipeline, thus ensuring the stability of C4 recycle feedstock.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: a DMTO-IIC4 remelting feed system, comprising a benzene stripping tower, a C4 propane stripping tower, a start-up butane stripping tower, and a C4 vaporizer:

[0011] The benzene removal tower's benzene removal feed line is connected to the C4+ feed line, and the start-up butane removal tower's start-up butane removal tower's feed line is connected to the C4+ feed line.

[0012] The benzene removal tower is connected to the C4 gas phase feed line; the bottom of the benzene removal tower is connected to the C5 product tank area through the C5 product collection pipeline;

[0013] The start-up butane de-butane tower and the C4 vaporizer's C4 liquid phase pipeline are connected via the C4 liquid phase feed pipeline; the bottom of the start-up butane de-butane tower is connected to the C5 collection pipeline that connects to the C5 tank area.

[0014] The C4 depropanizer is connected to the light hydrocarbon feed pipeline. The liquid phase pipeline at the bottom of the C4 depropanizer is connected to the C4 vaporizer through the C4 liquid phase pipeline, to the benzene debenzene feed pipeline of the debenzene tower through the C4 liquid phase replenishment pipeline, and to the butane debutanizer through the C4 discharge pipeline.

[0015] The C4 vaporizer is connected to a C4 liquid phase addition pipeline from the C4 tank area, and the C4 gas phase discharge pipeline on the C4 vaporizer is connected to the C4 gas phase feed line.

[0016] The top of the benzene removal tower is connected to the benzene removal tower reflux tank via a gas phase mixing discharge pipeline, and the top of the benzene removal tower reflux tank is connected to the C4 gas phase feed line.

[0017] The liquid phase mixing discharge pipeline at the top of the start-up butane dehydrogenator is connected to the start-up butane dehydrogenator reflux tank, and the top of the start-up butane dehydrogenator reflux tank is connected to the C4 liquid phase feed pipeline.

[0018] The olefin discharge pipeline at the top of the C4 depropanizer is connected to the C4 depropanizer reflux tank; the C4 depropanizer reflux tank is connected to the light hydrocarbon feed pipeline.

[0019] The benzene removal tower reflux tank is connected to the benzene removal tower via a liquid phase reflux pipeline, and a first reflux pump is connected to the liquid phase reflux pipeline.

[0020] The C4 depropanizer reflux tank is connected to the C4 depropanizer via a C4 reflux pipeline, and a second reflux pump is installed on the C4 reflux pipeline.

[0021] The start-up butane dehydrogenator reflux tank is connected to the start-up butane dehydrogenator via a start-up butane dehydrogenator reflux pipeline, and a third reflux pump is connected to the start-up butane dehydrogenator reflux pipeline.

[0022] A pressure pump is installed on the C4 liquid phase feed line.

[0023] The C4 liquid feed line is connected to a C4 collection line that is connected to the C4 product tank, and the C4 collection line is located downstream of the pressurization pump.

[0024] The beneficial effects of this invention are: 1. By separating C5+ materials through a distillation column, it is ensured that the materials entering the C4 reaction do not contain C6+ light oils, which can effectively reduce the oil content in the washing water and solve the problem of excessive oil in the water system.

[0025] 2. By modifying the top discharge branch of the start-up butane de-butane tower, the start-up butane de-butane tower is made the main liquid feedstock for C4, while the benzene de-butane tower is used as a load balancing measure, allowing the separation and heavy component distillation system to operate more flexibly.

[0026] 3. By introducing mixed C4 from the C4 tank area as the liquid phase feed to the C4 vaporizer, insufficient C4 feed during the initial C4 start-up phase can compensate for unstable deep reactions caused by insufficient C4 feed, allowing the C4 start-up process to reach a steady state as quickly as possible. During normal operation, when the MTO system load is too low and the C4 feed is insufficient, mixed C4 can be purchased externally and supplemented to the system through this process, ensuring the stability of the C4 reaction and increasing revenue. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the pipeline connection of the present invention;

[0028] Explanation of reference numerals in the attached diagram: 34, C5 collection pipeline. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0031] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0032] like Figure 1 The DMTO-IIC4 remelting feed system described above includes a butane stripping tower feed line 7 on one side of the benzene stripping tower 1, a C5 product collection line 12 at the bottom of the benzene stripping tower 1 connected to the C5 product tank area, a gas phase mixing discharge line 9 at the top of the benzene stripping tower 1, a first heater 26 on the gas phase mixing discharge line 9, a benzene stripping tower reflux tank 10 connected to the benzene stripping tower reflux tank 10 connected to the C4 gas phase feed line 11, and the benzene stripping tower reflux tank 10 connected to the benzene stripping tower 1 via a liquid phase reflux line 30, on which a first reflux pump 25 is installed.

[0033] The top of the C4 depropanizer 2 is connected to the C4 depropanizer reflux tank 24 via the olefin discharge pipeline 13. The C4 depropanizer reflux tank 24 is connected to the light hydrocarbon feed pipeline 27. The C4 depropanizer reflux tank 24 is connected to the C4 depropanizer 2 via the reflux pipeline 32. A second reflux pump 31 is installed on the C4 reflux pipeline 32. A second heater 29 is installed on the olefin discharge pipeline 13.

[0034] The bottom of the C4 depropane tower 2 is connected to the C4 vaporizer 4 through the C4 liquid phase pipeline 15. The C4 liquid phase pipeline 15 is connected to the C4 discharge pipeline 14. The C4 gas phase discharge pipeline 17 provided on the C4 vaporizer 4 is connected to the C4 gas phase feed line 11.

[0035] The top of the start-up butane dehydrogenator 3 is equipped with a liquid phase mixing discharge pipeline 18 and a start-up butane dehydrogenator reflux tank 19. A third heater 28 is installed on the liquid phase mixing discharge pipeline 18. The C4 liquid phase feed pipeline 23 connected to the start-up butane dehydrogenator reflux tank 19 is connected to the C4 collection pipeline 22 connected to the C4 product tank. The C4 collection pipeline 22 is located downstream of the pressure pump 21. The start-up butane dehydrogenator reflux tank 19 is connected to the start-up butane dehydrogenator 3 through a start-up butane dehydrogenator reflux pipeline 33. A third reflux pump 20 is installed on the start-up butane dehydrogenator reflux pipeline 33.

[0036] The C4+ feed line 5, drawn from the bottom of the low-pressure propane de-coupling tower, is connected to the feed line 7 of the start-up butane de-coupling tower and the benzene de-coupling tower 6, respectively. The C4+ feed line drawn from the bottom of the low-pressure propane de-coupling tower enters the benzene de-coupling tower 1 and the start-up butane de-coupling tower 3 through the feed line 7 of the start-up butane de-coupling tower and the benzene de-coupling tower 6, respectively, as the feed for the benzene de-coupling tower 1 and the start-up butane de-coupling tower 3.

[0037] A three-way side port is provided on the C4 liquid phase pipeline 15 at the bottom of the C4 depropanizer tower 2. This three-way side port is connected to the inlet of the benzene desulfurizer tower 1 through the C4 liquid phase replenishment pipeline 8. At the same time, a manual valve is added so that the C4 liquid phase at the bottom of the C4 depropanizer tower is used as the feed for the benzene desulfurizer tower. During operation, the feed pipeline from the C4 depropanizer tower to the C4 vaporizer is cut off and switched to the benzene desulfurizer tower. The benzene desulfurizer tower performs distillation separation on the components. The bottom of the benzene desulfurizer tower removes the C6+ and light oil components mixed in the C4 feed. The qualified mixed C4 components at the top of the tower enter the C4 gas phase feed line in a gas phase state.

[0038] The C4 liquid phase pipeline 15, connected to the top of the start-up butane de-butanizer 3, is connected to the C4 vaporizer 4. A tee is installed on the C4 liquid phase feed pipeline 23, and the C4 collection pipeline 22 is connected to this tee. During operation, the start-up butane de-butanizer provides liquid C4 material to the C4 vaporizer. The original olefin separation low-pressure propane de-butanizer, which only feeds material to the benzene de-butanizer during C4 reprocessing startup, is modified to primarily feed to the start-up butane de-butanizer, while simultaneously feeding to the benzene de-butanizer. The amount of material entering the benzene de-butanizer is balanced according to the load condition of the start-up butane de-butanizer.

[0039] A tee line is installed at the end of the C4 liquid phase pipeline 15 near the C4 vaporizer 4. This tee line connects to the C4 tank area via the C4 liquid phase addition pipeline 16. During the initial start-up phase, C4 feedstock is added to the C4 vaporizer based on the C4 vaporization demand. Simultaneously, when the MTO is operating at low load, and the feedstock supply to the start-up butane de-butanizer is insufficient, or when C4 remelting is unstable, the tank area purchases C4 feedstock from external sources, which is also fed into the system through this pipeline.

[0040] During the initial startup phase, C4 feedstock is added to the C4 vaporizer based on the required C4 vaporization volume. This allows the C4 to reach a stable reaction state more than 10 hours earlier than the startup time, reducing the time for light component emissions during startup.

[0041] When the MTO is operating at low load, and the feed to the start-up butane de-butanizer is insufficient, or the C4 reprocessing is unstable, the tank farm purchases C4 feedstock from external sources and feeds it into the system through this pipeline. This ensures optimal efficiency operation of the C4 reprocessing.

[0042] During operation, the butane removal tower line supplies liquid C4 material to the C4 vaporizer. The feed line from the C4 propane removal tower to the C4 vaporizer is then switched to the benzene removal tower, where the components are separated by distillation. The benzene removal tower removes C6+ and light oil components mixed in the C4 feed from the bottom of the tower, and the qualified mixed C4 components at the top of the tower enter the C4 gas phase feed line in a gaseous state.

[0043] When the original olefin separation low-pressure propane de-coupling tower was started up from the C4 remelting, it only fed material to the benzene de-coupling tower. The original olefin separation low-pressure propane de-coupling tower was modified to mainly feed material to the start-up butane de-coupling tower, while simultaneously feeding material to the benzene de-coupling tower. The amount of material entering the benzene de-coupling tower was manually balanced according to the load of the start-up butane de-coupling tower.

[0044] Specifically, during operation, the mixed C4+ feedstock at the bottom of the C4 depropanizer 2 does not directly enter the C4 vaporizer 4, but instead enters the benzene desulfurization tower 1 through a modified pipeline. In the benzene desulfurization tower 1, oily substances of C6+ and above are removed by distillation. The top of the benzene desulfurization tower 1 is a C4-C5 gas phase mixture as the C4 gas phase feed. The liquid phase at the top of the start-up butane desulfurization tower 3 is also a C4-C5 liquid phase mixture without oily substances as the C4 liquid phase feed. The C4 liquid phase from the tank farm is also a high-quality C4 feedstock without oily substances. This combination completely solves the problem of oily substances accumulating in the system after the C4 reaction. The C4 feedstock from the tank farm can ensure that the C4 reaction can quickly reach a stable state at the beginning of start-up, and can ensure the stability of C4 reprocessing when the load is low.

[0045] The above embodiments are merely illustrative examples of the present invention and do not constitute a limitation on the scope of protection of the present invention. Any designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A DMTO-IIC4 recycle feed system, comprising a benzene removal column (1), a C4 depropanizer (2), a debutanizer (3) and a C4 vaporizer (4), characterized in that: the benzene removal column (1) is communicated with a C4+ raw material pipeline (5) through a benzene removal feed pipeline (6), and the debutanizer (3) is communicated with the C4+ raw material pipeline (5) through a debutanizer feed pipeline (7); the benzene removal column (1) is communicated with a C4 gas phase feed line (11); the bottom of the benzene removal column (1) is communicated with a C5 product tank area through a C5 product collection pipeline (12); the debutanizer (3) is communicated with a C4 liquid phase pipeline (15) of the C4 vaporizer (4) through a C4 liquid phase feed pipeline (23); the bottom of the debutanizer (3) is communicated with a C5 collection pipeline (34) communicated with the C5 tank area; the C4 depropanizer (2) is communicated with a light hydrocarbon feed pipeline (27); the bottom of the C4 depropanizer (2) is communicated with the C4 vaporizer (4) through the C4 liquid phase pipeline (15), communicated with the benzene removal feed pipeline (6) of the benzene removal column (1) through a C4 liquid phase supplement pipeline (8), and communicated with a C4 discharge pipeline (14) of a debutanizer; a C4 discharge pipeline (14) is connected to the C4 liquid phase pipeline (15), and a C4 gas phase discharge pipeline (17) provided on the C4 vaporizer (4) is communicated with the C4 gas phase feed line (11); the top of the benzene removal column (1) is communicated with a benzene removal column reflux tank (10) through a gas phase mixed discharge pipeline (9) provided thereon; the top of the benzene removal column reflux tank (10) is communicated with the C4 gas phase feed line (11); an olefin discharge pipeline (13) at the top of the C4 depropanizer (2) is communicated with a C4 depropanizer reflux tank (24); the C4 depropanizer reflux tank (24) is communicated with the light hydrocarbon feed pipeline (27); the C4 liquid phase at the bottom of the C4 depropanizer (2) is used as the feed of the benzene removal column (1); during operation, the feed pipeline of the C4 depropanizer (2) to the C4 vaporizer (4) is cut off and changed to the benzene removal column (1); the components are rectified and separated by the benzene removal column (1); the mixed C6+ and light oil components in the C4 feed are removed from the benzene removal column (1); and the qualified mixed C4 components at the top of the benzene removal column (1) enter the C4 gas phase feed line (11) in a gas phase state. ​ ​ ​ ​ ​ The liquid phase mixing discharge pipeline (18) provided at the top of the start-up debutanizer (3) is connected with the start-up debutanizer reflux tank (19), the top of the start-up debutanizer reflux tank (19) is communicated with the C4 liquid phase feed pipeline (23); the C4 vaporizer (4) is communicated with the C4 liquid phase addition pipeline (16) from the C4 tank area, the main feed of the start-up debutanizer (3) is from the original olefin separation low-pressure depropanizer when the C4 backfiring is started, at the same time, the feed of the debutanizing tower (1) is also from the start-up debutanizer (3), the amount of the material entering the debutanizing tower (1) is balanced according to the load of the start-up debutanizer (3); the C4 gas phase discharge pipeline (17) provided on the C4 vaporizer (4) is communicated with the C4 gas phase feed line (11); the C4 liquid phase feed pipeline (23) is communicated with the C4 liquid phase pipeline (15) on the C4 vaporizer (4).

2. The DMTO-IIC4 recycle feed system of claim 1, wherein, The debutanizing tower reflux tank (10) is communicated with the debutanizing tower (1) through the liquid phase reflux pipeline (30), the first reflux pump (25) is connected on the liquid phase reflux pipeline (30).

3. The DMTO-IIC4 recycle feed system of claim 1, wherein, The C4 depropanizing tower reflux tank (24) is communicated with the C4 depropanizing tower (2) through the C4 reflux pipeline (32), the second reflux pump (31) is provided on the C4 reflux pipeline (32).

4. The DMTO-IIC4 recycle feed system of claim 1, wherein, The start-up debutanizer reflux tank (19) is communicated with the start-up debutanizer (3) through the start-up debutanizer reflux pipeline (33), the third reflux pump (20) is provided on the start-up debutanizer reflux pipeline (33).

5. The DMTO-IIC4 recycle feed system of claim 1 wherein, The C4 liquid phase feed pipeline (23) is provided with the pressurizing pump (21).

6. The DMTO-IIC4 recycle feed system of claim 5, wherein, The C4 liquid phase feed pipeline (23) is communicated with the C4 collection pipeline (22) connected with the C4 product tank, and the C4 collection pipeline (22) is located downstream of the pressurizing pump (21).

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