A pre-hydrogenation butadiene extraction unit and a pre-hydrogenation butadiene extraction method

Abstract

The present invention belongs to the field of cracking C4 treatment, and relates to a pre-hydrogenation butadiene extraction device and a pre-hydrogenation butadiene extraction method. The device includes a selective hydrogenation system, a first extraction tower system, a first stripping tower system, a water washing tower system, and a butadiene refining system arranged in sequence. The selective hydrogenation system includes a selective hydrogenation reactor and a stabilizer tower; the top discharge pipeline of the selective hydrogenation reactor is connected to the stabilizer tower; the side discharge pipeline of the stabilizer tower is connected to the first extraction tower system; the bottom discharge pipeline of the first extraction tower system is connected to the first stripping tower system; the top discharge pipeline of the first stripping tower system is connected to the water washing tower system; the top discharge pipeline of the water washing tower system is connected to the butadiene refining system. By setting up the selective hydrogenation system, the present invention increases the butadiene yield, eliminates the second extraction system and the second stripping tower system, reduces the comprehensive energy consumption, and saves investment.

Description

Technical Field

[0001] The present invention belongs to the field of cracking C4 treatment, and specifically relates to a pre-hydrogenation butadiene extraction device and a pre-hydrogenation butadiene extraction method. Background Art

[0002] Regardless of whether the DMF method or the acetonitrile method is adopted, the butadiene extraction device extracts butadiene through a two-stage extraction and C4 refining process. Taking the DMF method as an example, a typical process is as Figure 1 shown. The first-stage extraction separates monoolefins and alkanes from diolefins and alkynes. The second-stage extraction further separates diolefins and alkynes to remove alkynes. The water washing system removes the solvent, and the refining system removes light and heavy components. Due to the two-stage extraction process, the traditional butadiene extraction device has a long process flow, high energy consumption and investment.

[0003] With the development and maturity of the selective hydrogenation catalyst, first removing the alkynes in the cracked C4 raw material through the selective hydrogenation system, and then producing butadiene through extraction and refining not only improves the utilization efficiency of the raw material, increases the economy of the device, but also can cancel the second extraction tower and the second stripping tower, saving about 10% - 15% of the energy consumption of the whole device. And the selective hydrogenation system is an exothermic reaction, with a small amount of additional energy consumption. Therefore, on the premise of ensuring that the alkyne removal rate and the butadiene loss rate are controlled within a reasonable range, coupling the selective hydrogenation system with the traditional butadiene extraction device will greatly improve the economy and environmental protection of the device, reduce the comprehensive energy consumption of the device, and increase the comprehensive utilization value of C4.

[0004] There are two key steps in the pre-hydrogenation technology. The hydrogenation reactor ensures the selectivity and conversion rate of alkynes through the catalyst and operating conditions, while reducing the loss of butadiene; through the process flow, heavy components (heavy components affect the polymerization of diolefins and alkynes) and purge gas can be removed before the C4 raw material enters the extraction device. CN101172929 realizes the function of removing purge gas through a de-light tower, but does not remove heavy components, and the reaction uses a palladium-based expensive catalyst, with low economic benefits. At the same time, this process does not provide a reflux setting, the reaction temperature rise is large, which affects the performance of the catalyst and is not conducive to long-term operation. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of the existing butadiene device with a long process flow, high energy consumption and low raw material utilization rate. The present invention provides a pre-hydrogenation butadiene extraction device. By coupling the alkyne selective hydrogenation system with the traditional butadiene extraction device, the present invention realizes the purpose of canceling the second extraction system and the second stripping system. It solves the drawbacks of the traditional butadiene device and increases the economic benefits of the device.

[0006] To achieve the above object, a first aspect of the present invention provides a pre-hydrogenation butadiene extraction device, comprising a selective hydrogenation system, a first extraction tower system, a first stripping tower system, a water washing tower system, and a butadiene refining system arranged in sequence. The selective hydrogenation system includes a selective hydrogenation reactor and a stabilizer tower;

[0007] The selective hydrogenation reactor is provided with a selective hydrogenation reactor bottom feed pipeline and a selective hydrogenation reactor top discharge pipeline, and the selective hydrogenation reactor top discharge pipeline is connected to the stabilizer tower;

[0008] The stabilizer tower is provided with a stabilizer tower top discharge pipeline, a stabilizer tower bottom discharge pipeline, and a stabilizer tower side discharge pipeline; the stabilizer tower side discharge pipeline is connected to the first extraction tower system;

[0009] The first extraction tower system is provided with a first extraction tower system top discharge pipeline and a first extraction tower system bottom discharge pipeline, and the first extraction tower system bottom discharge pipeline is connected to the first stripping tower system;

[0010] The first stripping tower system is provided with a first stripping tower system top discharge pipeline and a first stripping tower system bottom discharge pipeline, and the first stripping tower system top discharge pipeline is connected to the water washing tower system;

[0011] The water washing tower system is provided with a water washing tower system top discharge pipeline, and the water washing tower system top discharge pipeline is connected to the butadiene refining system.

[0012] A second aspect of the present invention provides a pre-hydrogenation butadiene extraction method, which is carried out by using the above-mentioned pre-hydrogenation butadiene extraction device, and comprises the following steps:

[0013] After the cracked C4 raw material is mixed with hydrogen, a selective hydrogenation reaction is carried out in the selective hydrogenation reactor, and the reacted material is sent to the stabilizer tower and optionally partially refluxed. The off-gas is separated from the top of the stabilizer tower and sent out, the heavy components are separated from the bottom of the stabilizer tower and sent out, and the stabilizer tower side material is separated from the side and sent to the first extraction tower system;

[0014] The stabilizer tower side material is sent to the first extraction tower system. The monoolefins and paraffin raffinate are drawn out from the top of the first extraction tower system. The material at the bottom of the first extraction tower system is sent to the first stripping tower system. The material at the bottom of the first stripping tower system returns to the first extraction tower system. The material at the top of the first stripping tower system is sent to the water washing tower system. The material at the top of the water washing tower system is sent to the butadiene refining system to obtain a butadiene product.

[0015] Advantages of the present invention:

[0016] 1) By setting up the selective hydrogenation system, the comprehensive utilization efficiency of C4 is increased;

[0017] 2) By setting up a selective hydrogenation system to convert vinyl acetylene into butadiene, the yield of butadiene is increased, and the economic efficiency of the unit is improved;

[0018] 3) By setting up a selective hydrogenation system, the second extraction system and the second stripping tower system are eliminated, reducing the comprehensive energy consumption and saving investment;

[0019] 4) By setting up a stabilizer column, non-condensable gases, C5 and heavy components such as polymers generated during the reaction can be removed, ensuring the stability of the extraction and rectification unit operation and reducing the polymerization risk;

[0020] 5) By setting up the reflux of the reaction materials, the concentration of vinyl acetylene in the raw materials can be reduced, the reaction temperature rise can be decreased, the reaction regeneration time can be extended, and long-term operation can be ensured;

[0021] 6) The nickel-based catalyst is preferably used in the present invention, with prominent economic benefits;

[0022] 7) This device can retrofit all traditional butadiene extraction units.

[0023] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation section. Brief Description of the Drawings

[0024] By describing the exemplary embodiments of the present invention in more detail in conjunction with the drawings, the above and other objects, features, and advantages of the present invention will become more apparent.

[0025] Figure 1 It is a flow chart of a traditional DMF method butadiene extraction unit.

[0026] Figure 2 It is a flow chart of a pre-hydrogenation butadiene extraction unit of the present invention.

[0027] Figure 3 It is a flow chart of an embodiment of the selective hydrogenation system of the present invention.

[0028] Figure 4 It is a flow chart of another embodiment of the selective hydrogenation system of the present invention.

[0029] Description of the Reference Numerals in the Drawings:

[0030] The first extraction column system 1, the first stripping tower system 2, the second extraction column system 3, the second stripping tower system 4, the water washing column system 5, the light component removal tower 6 of the butadiene refining system, the heavy component removal tower 7 of the butadiene refining system, the selective hydrogenation system 8, the selective hydrogenation reactor 9, the stabilizer column 10, the stabilizer top condenser 11, the stabilizer bottom reboiler 12, the hydrogenation separation tank 13, the tail gas condenser 14, the reflux pump 15, the reflux cooler 16; raw material 17, heavy components 18, purge gas 19, C4 product 20, hydrogen 21. Detailed Embodiments

[0031] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0032] The object of the present invention is to solve the problems of long process flow, high energy consumption, and low raw material utilization rate in the existing butadiene plant. The present invention provides a pre-hydrogenation butadiene extraction device. By coupling the alkyne selective hydrogenation system with the traditional butadiene extraction device, the present invention achieves the purpose of canceling the second extraction system and the second stripping system. The disadvantages of the traditional butadiene plant are solved, and the economic benefits of the plant are increased.

[0033] To achieve the above object, a first aspect of the present invention provides a pre-hydrogenation butadiene extraction device, which includes a selective hydrogenation system, a first extraction tower system, a first stripping tower system, a water washing tower system, and a butadiene refining system arranged in sequence. The selective hydrogenation system includes a selective hydrogenation reactor and a stabilizer tower;

[0034] The selective hydrogenation reactor is provided with a selective hydrogenation reactor bottom feed pipeline and a selective hydrogenation reactor top discharge pipeline, and the selective hydrogenation reactor top discharge pipeline is connected to the stabilizer tower;

[0035] The stabilizer tower is provided with a stabilizer tower top discharge pipeline, a stabilizer tower bottom discharge pipeline, and a stabilizer tower side discharge pipeline; the stabilizer tower side discharge pipeline is connected to the first extraction tower system;

[0036] The first extraction tower system is provided with a first extraction tower system top discharge pipeline and a first extraction tower system bottom discharge pipeline, and the first extraction tower system bottom discharge pipeline is connected to the first stripping tower system;

[0037] The first stripping tower system is provided with a first stripping tower system top discharge pipeline and a first stripping tower system bottom discharge pipeline, and the first stripping tower system top discharge pipeline is connected to the water washing tower system;

[0038] The water washing tower system is provided with a water washing tower system top discharge pipeline, and the water washing tower system top discharge pipeline is connected to the butadiene refining system.

[0039] In the present invention, the stabilizer tower can separate more than 99% of C5 in the raw material, and C5 is an important factor causing butadiene polymerization, providing high-quality raw materials for the extraction and refining units.

[0040] In the present invention, a selective hydrogenation system can convert vinylacetylene in the unsaturated components of cracked C4 raw materials into butadiene and a small amount of 1-butene, and convert butyne into 1-butene, obtaining a C4 product rich in butadiene, increasing the yield of butadiene. The setting of the stabilizer column removes light components such as non-condensable gas and heavy components such as C5 and green oil, providing high-quality raw materials for extraction and reducing the polymerization risk. The top discharge pipeline of the selective hydrogenation reactor can be directly connected to the stabilizer column, or a reflux device can be set. The top discharge pipeline of the selective hydrogenation reactor is first connected to the reflux device and then connected to the stabilizer column. For example, an optional reflux pump can be added to select partial reflux of the post-reaction material to reduce the concentration of C4 alkynes at the reactor inlet. It can extend the regeneration frequency and maintain long-term operation. The present invention is applicable to butadiene extraction processes such as acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, N-formylmorpholine, etc., not limited to NMP (N-methylpyrrolidone), and has better applicability and popularization.

[0041] Specifically, a selective hydrogenation system of the present invention is as Figure 3 shown. The cracked C4 raw material is connected to the inlet of the selective hydrogenation reactor and converges with hydrogen. The outlet of the selective hydrogenation reactor is connected to the inlet of the stabilizer column. The top off-gas of the stabilizer column is sent out, and the bottom heavy components of the stabilizer column are sent out. The side line of the stabilizer column is connected to the extraction column system.

[0042] Another selective hydrogenation system of the present invention is as Figure 4 shown, including a selective hydrogenation reactor for hydrogenation and a stabilizer column for removing heavy components and non-condensable gas. A reflux device (including a hydrogenation separation tank, a reflux pump, and a reflux cooler) is set behind the reactor. Among them: the cracked C4 raw material converges with hydrogen and is connected to the inlet of the selective hydrogenation reactor. The outlet of the selective hydrogenation reactor is connected to a gas-liquid separation tank. After separating the non-condensable gas, part of the material is connected to the inlet of the stabilizer column through the reflux pump. The top off-gas of the stabilizer column is sent out, and the bottom heavy components of the stabilizer column are sent out. The side line of the stabilizer column is connected to the extraction column system. Part of the material of the reflux pump is connected to the feed pipeline to dilute the concentration of vinylacetylene in the cracked C4 feed.

[0043] In the present invention, the first extraction column system, the first stripping column system, the water washing column system, and the butadiene refining system in the butadiene extraction device are all typical settings of a conventional butadiene extraction device.

[0044] According to the present invention, preferably, the bottom feed pipeline of the selective hydrogenation reactor includes a hydrogen feed pipeline and a cracked C4 raw material feed pipeline. The top discharge pipeline of the selective hydrogenation reactor is connected to the stabilizer column. The top discharge pipeline of the stabilizer column is connected to a stabilizer column top condenser and then divided into two branches. One branch is used as a product discharge pipeline, and the other branch is connected to the upper part of the stabilizer column. A stabilizer column bottom reboiler is provided at the bottom of the stabilizer column.

[0045] According to the present invention, preferably, the top discharge pipeline of the selective hydrogenation reactor is connected to a hydrogenation separation tank, the hydrogenation separation tank is provided with a top discharge pipeline and a bottom discharge pipeline of the hydrogenation separation tank, the top discharge pipeline of the hydrogenation separation tank is connected to a tail gas condenser, the tail gas condenser is provided with a tail gas condenser discharge pipeline and a tail gas condenser circulation pipeline, the tail gas condenser discharge pipeline converges with the product discharge pipeline of the stabilizer top condenser, and the tail gas condenser circulation pipeline is connected to the hydrogenation separation tank; the bottom discharge pipeline of the hydrogenation separation tank is connected to a reflux pump and then divided into two pipelines, one is connected to the stabilizer, and the other is connected to a reflux cooler and then converges with the bottom feed pipeline of the selective hydrogenation reactor.

[0046] According to the present invention, preferably, the butadiene refining system includes a butadiene refining system light component removal tower and a butadiene refining system heavy component removal tower;

[0047] The butadiene refining system light component removal tower is provided with a top discharge pipeline and a bottom discharge pipeline of the butadiene refining system light component removal tower, and the bottom discharge pipeline of the butadiene refining system light component removal tower is connected to the butadiene refining system heavy component removal tower;

[0048] The butadiene refining system heavy component removal tower is provided with a top discharge pipeline and a bottom discharge pipeline of the butadiene refining system heavy component removal tower.

[0049] The second aspect of the present invention provides a pre-hydrogenation butadiene extraction method, which is carried out by using the pre-hydrogenation butadiene extraction device described above, and includes the following steps:

[0050] After the cracked C4 raw material is mixed with hydrogen, a selective hydrogenation reaction is carried out in the selective hydrogenation reactor, and the reacted material is sent to the stabilizer and optionally partially refluxed. The off-gas is separated from the top of the stabilizer and sent out, the heavy components are separated from the bottom of the stabilizer and sent out, and the side material of the stabilizer is separated and sent to the first extraction tower system;

[0051] The side material of the stabilizer is sent to the first extraction tower system. The raffinate of monoolefins and alkanes is drawn from the top of the first extraction tower system. The bottom material of the first extraction tower system is sent to the first stripping tower system. The bottom material of the first stripping tower system returns to the first extraction tower system. The top material of the first stripping tower system is sent to the water washing tower system. The top material of the water washing tower system is sent to the butadiene refining system to obtain a butadiene product.

[0052] According to the present invention, preferably, the top material of the water washing tower system is sent to the butadiene refining system light component removal tower. The light components are separated from the top and sent out. The bottom material of the butadiene refining system light component removal tower is sent to the butadiene refining system heavy component removal tower. The heavy components are separated from the bottom, and the butadiene product is obtained from the top.

[0053] According to the present invention, preferably, the cracked C4 raw material is a C4 raw material rich in butadiene and vinyl acetylene; wherein, the butadiene content is 20 wt% to 70 wt%, and the vinyl acetylene content is 0.1 wt% to 10 wt%; preferably, the butadiene content is 40 wt% to 55 wt%, and the vinyl acetylene content is 0.5 wt% to 5 wt%.

[0054] According to the present invention, preferably, the catalyst used in the selective hydrogenation reactor is a nickel-based catalyst and / or a palladium-based catalyst, preferably a nickel-based catalyst; the operating conditions of the selective hydrogenation reactor include: the temperature is 20 to 40 °C, the operating pressure is 0.5 to 1.0 MPaG, the reaction temperature rise is 5 to 25 °C, the hydrogen-acetylene molar ratio is 0.5 to 5:1, the recycle ratio is 0 to 3:1, and the catalyst volume space velocity is 0.2 to 3.

[0055] According to the present invention, preferably, the operating conditions of the stabilizer column include: the pressure is 0.4 to 1.0 MPaG, the top operating temperature is 35 to 80 °C, the number of trays is 20 to 80, and the reflux ratio is 5 to 50.

[0056] According to the present invention, preferably, the extraction solvent is at least one of acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, and N-formylmorpholine.

[0057] In the present invention, the effective removal rate of vinyl acetylene (the product of the selectivity and conversion rate of producing butadiene) in the cracked C4 raw material of the selective hydrogenation system is more than 99 wt%, preferably more than 99.9 wt%, and the loss rate of butadiene in the cracked C4 raw material of the selective hydrogenation system shall not exceed 5 wt%, preferably not exceed 3 wt%.

[0058] Example 1

[0059] This example uses as Figure 2The process is carried out using the device shown, which includes a selective hydrogenation system, a first extraction tower system, a first stripping tower system, a water washing tower system, and a butadiene refining system arranged in sequence. The selective hydrogenation system includes a selective hydrogenation reactor, a stabilizer tower, and an optional reflux pump. The selective hydrogenation reactor is provided with a selective hydrogenation reactor bottom feed line and a selective hydrogenation reactor top discharge line. After the selective hydrogenation reactor top discharge line is optionally connected to the reflux pump, it is divided into two pipelines. One is connected to the stabilizer tower, and the other converges with the selective hydrogenation bottom feed line. The selective hydrogenation reactor bottom feed line includes a hydrogen gas line and a cracked C4 feedstock line. The selective hydrogenation reactor top discharge line is optionally connected to a hydrogenation separation tank. The hydrogenation separation tank is provided with a hydrogenation separation tank top discharge line and a hydrogenation separation tank bottom discharge line. The hydrogenation separation tank top discharge line is connected to a tail gas condenser. The tail gas condenser is provided with a tail gas condenser discharge line and a tail gas condenser circulation line. The tail gas condenser circulation line is connected to the side of the hydrogenation separation tank. The hydrogenation separation tank bottom discharge line is connected to the reflux pump and divided into two pipelines. One is connected to the stabilizer tower, and the other is connected to a reflux condenser and then converges with the selective hydrogenation reactor bottom feed line.

[0060] The stabilizer tower is provided with a stabilizer tower top discharge line, a stabilizer tower bottom discharge line, and a stabilizer tower side discharge line. The stabilizer tower side discharge line is connected to the first extraction tower system. The stabilizer tower top discharge line is connected to a stabilizer tower top condenser and then divided into two branches. One converges with the tail gas condenser discharge line, and the other is connected to the upper part of the stabilizer tower. A reboiler is provided at the bottom of the stabilizer tower.

[0061] The first extraction tower system is provided with a first extraction tower system top discharge line and a first extraction tower system bottom discharge line. The first extraction tower system bottom discharge line is connected to the first stripping tower system. The first stripping tower system is provided with a first stripping tower system top discharge line and a first stripping tower system bottom discharge line. The first stripping tower system top discharge line is connected to the water washing tower system. The water washing tower system is provided with a water washing tower system top discharge line. The water washing tower system top discharge line is connected to the butadiene refining system. The butadiene refining system includes a butadiene refining system light component removal tower and a butadiene refining system heavy component removal tower. The butadiene refining system light component removal tower is provided with a butadiene refining system light component removal tower top discharge line and a butadiene refining system light component removal tower bottom discharge line. The butadiene refining system light component removal tower bottom discharge line is connected to the butadiene refining system heavy component removal tower. The butadiene refining system heavy component removal tower is provided with a butadiene refining system heavy component removal tower top discharge line and a butadiene refining system heavy component removal tower bottom discharge line.

[0062] The above-mentioned pre-hydrogenation butadiene extraction method includes the following steps:

[0063] After the cracked C4 raw material is mixed with hydrogen, a selective hydrogenation reaction is carried out in the selective hydrogenation reactor. The reacted material is sent to the stabilizing column and optionally partially refluxed. The off-gas is separated from the top of the stabilizing column and sent out, the heavy components are separated from the bottom of the stabilizing column and sent out, and the side stream of the stabilizing column is separated and sent to the first extraction column system; the cracked C4 raw material is 30 t / h, and its composition is shown in Table 1, where the content of butadiene is 50 wt%, and the content of vinylacetylene is 1 wt%; the selective hydrogenation reaction is controlled by a catalyst and process conditions. The catalyst used is a nickel-based catalyst. The operating conditions of the selective hydrogenation are a temperature of 30 °C, an operating pressure of 0.6 MPaG, a reaction temperature rise of 5 °C, a molar ratio of hydrogen to alkyne (the sum of alkynes and dienes) of 1, a recycle ratio of 1:1, and a catalyst volume space velocity of 0.5; the operating conditions of the stabilizing column include: a pressure of 0.6 MPaG, a top operating temperature of 40 °C, 50 trays, and a reflux ratio of 20;

[0064] The side stream of the stabilizing column is sent to the first extraction column system. The monoolefins and paraffin raffinate are withdrawn from the top of the first extraction column system. The bottom material of the first extraction column system is sent to the first stripping column system. The bottom material of the first stripping column system returns to the first extraction column system. The top material of the first stripping column system is sent to the water washing column system. The top material of the water washing column system is sent to the butadiene refining system to obtain a butadiene product; the top material of the water washing column system is sent to the de-lighting column of the butadiene refining system. The light components are separated from the top and sent out. The bottom material of the de-lighting column of the butadiene refining system is sent to the de-heavy column of the butadiene refining system. The heavy components are separated from the bottom, and the butadiene product is obtained from the top.

[0065] Table 1 Composition of cracked C4 raw material

[0066] Phase state Liquid phase Component unit wt% Allene 0.01 n-Butane 12.70 Isobutane 0.72 1-Butene 11.49 Isobutene 16.52 cis-2-Butene 2.57 trans-2-Butene 3.66 1,3-Butadiene 50.10 1,2-Butadiene 0.52 Methylacetylene 0.19 Water 0.00 Ethylacetylene 0.26 Vinylacetylene 1.040 C5 0.187 Isoprene 0.018 Cyclopentadiene 0.019 Molecular weight 55.100

[0067] In the selective hydrogenation system, vinylacetylene in the unsaturated components of the cracked C4 raw material can be converted into butadiene and a small amount of butene-1, and butyne can be converted into butene-1 to obtain a butadiene-rich C4 product. The effective removal rate of vinylacetylene (the product of the selectivity and conversion rate of producing butadiene) is 99.95 wt%. The loss rate of butadiene in the cracked C4 raw material is 2 wt%.

[0068] Based on this, the product purity of the pre-hydrogenation butadiene extraction unit can be calculated to meet the polymerization grade requirements.

[0069] Purity of butadiene product: 99.9 wt%

[0070] Based on this, the economic benefits of the pre-hydrogenation butadiene extraction unit can be preliminarily calculated. The second extraction tower system and the second stripping tower system account for about 15% of the total unit energy consumption. The energy consumption of the original butadiene extraction unit was 220 kg of standard oil per ton of product. After being transformed into a pre-hydrogenation butadiene extraction unit, the energy consumption can be saved by 220×15% = 33 kg of standard oil per ton of product; the effective removal rate of vinyl acetylene is 99.95 wt%. After the transformation, the butadiene content in the product of the pre-hydrogenation butadiene extraction unit is increased by 0.3 t / h compared with the original butadiene extraction unit; butadiene loss: 30×50%×2% = 0.3 t / h. Therefore, the butadiene loss and the increase can offset each other; the equipment investment cost of the selective hydrogenation system is offset by the second extraction system and the second stripping tower system; the increase in energy consumption of the selective hydrogenation system is limited and can be ignored. Therefore, the pre-hydrogenation butadiene extraction unit can achieve an energy consumption saving of 33 kg of standard oil per ton of product, that is, 33 kg of standard oil per ton of product × 5 yuan / kg of standard oil × 15 t of product × 8000 hours = 19.8 million / year. The energy-saving and consumption-reducing effect and economic benefits are very remarkable.

[0071] Comparative Example 1

[0072] The difference between the device of this comparative example and the device of Example 1 is that the selective hydrogenation system only includes a selective hydrogenation reactor and a light removal tower. The hydrogenation reactor is connected to the light removal tower. The light removal tower is provided with a light removal tower top discharge pipeline and a light removal tower bottom discharge pipeline. The light removal tower bottom discharge pipeline is connected to the first extraction tower system; the difference from the method of Example 1 is that after the cracked C4 raw material is sent into the selective hydrogenation reactor for hydrogenation reaction, it is sent into the light removal tower to remove light components. The top discharge includes light components such as hydrogen, methane, and propane, and the bottom of the tower obtains the C4 fraction with light components removed and is sent into the first extraction tower system.

[0073] The effective removal rate of vinyl acetylene (the product of the selectivity and conversion rate of producing butadiene) is 99.95 wt%. The loss rate of butadiene in the cracked C4 raw material is 3 wt%, and C5 in the cracked C4 raw material is not removed.

[0074] The purity of the butadiene product: 99.7 wt%.

[0075] The embodiments of the present invention have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments.

Claims

1. A pre-hydrogenation butadiene extraction unit, characterized in that, It includes a selective hydrogenation system, a first extraction tower system, a first stripping tower system, a water washing tower system, and a butadiene refining system arranged in sequence. The selective hydrogenation system includes a selective hydrogenation reactor and a stabilizer tower; The selective hydrogenation reactor is provided with a selective hydrogenation reactor bottom feed pipeline and a selective hydrogenation reactor top discharge pipeline. The selective hydrogenation reactor top discharge pipeline is connected to the stabilizer tower; The stabilizer tower is provided with a stabilizer tower top discharge pipeline, a stabilizer tower bottom discharge pipeline, and a stabilizer tower side discharge pipeline; the stabilizer tower side discharge pipeline is connected to the first extraction tower system; The first extraction tower system is provided with a first extraction tower system top discharge pipeline and a first extraction tower system bottom discharge pipeline. The first extraction tower system bottom discharge pipeline is connected to the first stripping tower system; The first stripping tower system is provided with a first stripping tower system top discharge pipeline and a first stripping tower system bottom discharge pipeline. The first stripping tower system top discharge pipeline is connected to the water washing tower system; The water washing tower system is provided with a water washing tower system top discharge pipeline. The water washing tower system top discharge pipeline is connected to the butadiene refining system.

2. The pre-hydrogenation butadiene extraction unit according to claim 1, wherein, The selective hydrogenation reactor bottom feed pipeline includes a hydrogen feed pipeline and a cracked C4 raw material feed pipeline. The selective hydrogenation reactor top discharge pipeline is connected to the stabilizer tower. The stabilizer tower top discharge pipeline is connected to a stabilizer tower top condenser and then divided into two branches. One branch is used as a product discharge pipeline, and the other branch is connected to the upper part of the stabilizer tower; a stabilizer tower kettle reboiler is arranged at the bottom of the stabilizer tower.

3. The pre-hydrogenation butadiene extraction unit according to claim 2, wherein, The selective hydrogenation reactor top discharge pipeline is connected to a hydrogenation separation tank. The hydrogenation separation tank is provided with a hydrogenation separation tank top discharge pipeline and a hydrogenation separation tank bottom discharge pipeline. The hydrogenation separation tank top discharge pipeline is connected to a tail gas condenser. The tail gas condenser is provided with a tail gas condenser discharge pipeline and a tail gas condenser circulation pipeline. The tail gas condenser discharge pipeline converges with the stabilizer tower top condenser product discharge pipeline. The tail gas condenser circulation pipeline is connected to the hydrogenation separation tank; the hydrogenation separation tank bottom discharge pipeline is connected to a reflux pump and then divided into two pipelines. One pipeline is connected to the stabilizer tower, and the other pipeline is connected to a reflux cooler and then converges with the selective hydrogenation reactor bottom feed pipeline.

4. The pre-hydrogenation butadiene extraction unit according to claim 1, wherein, The butadiene refining system includes a butadiene refining system de-lighting tower and a butadiene refining system de-heavying tower; The butadiene refining system de-lighting tower is provided with a butadiene refining system de-lighting tower top discharge pipeline and a butadiene refining system de-lighting tower bottom discharge pipeline. The butadiene refining system de-lighting tower bottom discharge pipeline is connected to the butadiene refining system de-heavying tower; The butadiene refining system de-heavying tower is provided with a butadiene refining system de-heavying tower top discharge pipeline and a butadiene refining system de-heavying tower bottom discharge pipeline.

5. A method for extracting butadiene by pre-hydrogenation, characterized in that, This method is carried out by using the pre-hydrogenation butadiene extraction device described in any one of claims 1-4, and includes the following steps: After the cracked C4 raw material is mixed with hydrogen, a selective hydrogenation reaction is carried out in the selective hydrogenation reactor. The material after the reaction is sent to the stabilizing column and optionally partially refluxed. The purge gas is separated from the top of the stabilizing column and sent out, the heavy components are separated from the bottom of the stabilizing column and sent out, and the side stream of the stabilizing column is separated and sent to the first extraction column system; The side stream of the stabilizing column is sent to the first extraction column system. The monoolefins and paraffin raffinate are withdrawn from the top of the first extraction column system. The material at the bottom of the first extraction column system is sent to the first stripping column system. The material at the bottom of the first stripping column system returns to the first extraction column system. The material at the top of the first stripping column system is sent to the water washing column system. The material at the top of the water washing column system is sent to the butadiene refining system to obtain a butadiene product.

6. The pre-hydrogenation butadiene extraction method according to claim 5, wherein, The material at the top of the water washing column system is sent to the light component removal column of the butadiene refining system. The light components are separated from the top and sent out. The material at the bottom of the light component removal column of the butadiene refining system is sent to the heavy component removal column of the butadiene refining system. The heavy components are separated from the bottom, and the butadiene product is obtained from the top.

7. The pre-hydrogenation butadiene extraction method according to claim 5, wherein, The cracked C4 raw material is a C4 raw material rich in butadiene and vinylacetylene; wherein, the butadiene content is 20 wt% to 70 wt%, and the vinylacetylene content is 0.1 wt% to 10 wt%.

8. The pre-hydrogenation butadiene extraction method according to claim 7, wherein, The butadiene content is 40 wt% to 55 wt%, and the vinylacetylene content is 0.5 wt% to 5 wt%.

9. The pre-hydrogenation butadiene extraction method according to claim 5, wherein, The catalyst used in the selective hydrogenation reactor is a nickel-based catalyst and / or a palladium-based catalyst; The operating conditions of the selective hydrogenation reactor include: the temperature is 20 to 40 °C, the operating pressure is 0.5 to 1.0 MPaG, the reaction temperature rise is 5 to 25 °C, the hydrogen-acetylene molar ratio is 0.5 to 5:1, the recycle ratio is 0 to 3:1, and the catalyst volume space velocity is 0.2 to 3.

10. The pre-hydrogenation butadiene extraction method according to claim 9, wherein, The catalyst used in the selective hydrogenation reactor is a nickel-based catalyst.

11. The pre-hydrogenation butadiene extraction method according to claim 5, wherein, The operating conditions of the stabilizing column include: the pressure is 0.4 to 1.0 MPaG, the top operating temperature is 35 to 80 °C, the number of trays is 20 to 80, and the reflux ratio is 5 to 50.

12. The pre-hydrogenation butadiene extraction method according to claim 5, wherein, The extraction solvent is at least one of acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, and N-formylmorpholine.

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