Device and method for obtaining maleic anhydride from gas phase containing maleic anhydride

Abstract

The present invention relates to the technical field of post-treatment of maleic anhydride, and in particular to a device and method for obtaining maleic anhydride from a gas phase containing maleic anhydride. According to a device for obtaining a maleic anhydride product from a gas phase material flow containing maleic anhydride provided by the present invention, the objectives of simplifying the process, reducing the device investment and reducing the energy consumption can be achieved while effectively controlling the fumaric acid generation amount and the absorbent consumption.

Description

Device and method for obtaining maleic anhydride from a gas phase containing maleic anhydride Technical Field The invention belongs to the technical field of post-processing of maleic anhydride, and particularly relates to a device and method for obtaining maleic anhydride from a gas phase containing maleic anhydride. Background Art Maleic anhydride, also known as maleic anhydride, is a key organic chemical raw material and the world's third-largest organic anhydride after phthalic anhydride and acetic anhydride. It is widely used in the petrochemical, food processing, pharmaceutical, and building materials industries. In recent years, the rapid development of biodegradable plastics has led to a surge in demand for 1,4-butanediol (BDO), a key raw material for biodegradable plastics. This has also driven demand for maleic anhydride production upstream. At present, the post-reaction treatment technology of maleic anhydride unit can be divided into water absorption method and solvent absorption method according to the solvent type. There are two methods. Because maleic anhydride easily reacts with water to form maleic acid, the water absorption method is easily isomerized to fumaric acid as a byproduct during the dehydration process to produce maleic anhydride, resulting in a decrease in maleic anhydride yield. It has been gradually replaced by the solvent absorption method. Currently, there are two solvents used in industrialized solvent absorption devices: dibutyl phthalate and diisobutyl cyclohexyldicarboxylate. Using solvent absorption, the maleic anhydride in the reaction gas is absorbed and then sent to a desorption tower for desorption to obtain crude maleic anhydride, which is then refined to obtain the maleic anhydride product. The solvent absorption method avoids the conversion of maleic anhydride to maleic acid, and thus avoids the conversion of significant amounts of maleic acid to fumaric acid. This results in a maleic anhydride yield approximately 5% higher using the solvent absorption process than using the traditional water absorption process. In the book edited by Sun Lili, Light Hydrocarbon Processing Technology and Engineering (Sun Lili. China Petrochemical Press, The 2020 report systematically introduces the main processes and engineering details of the n-butane oxidation technology for producing maleic anhydride, and also describes the solvent absorption process flowsheets of the leading patent holders Huntsman, ALMA, and Conser (pages 594-599). Huntsman's maleic anhydride preparation and solvent absorption process uses DBP as the solvent. The post-processing flowsheet comprises an absorption tower 1, a desorption tower, an exhaust gas scrubber, a post-flash tower, and a refining tower. This process is disclosed in U.S. Patent No. 563-1-387. Absorption tower 1 absorbs maleic anhydride from the maleic anhydride-containing exhaust gas to produce a rich solvent. This rich solvent is then fed to the post-flash tower for light removal before entering the desorption tower. Crude maleic anhydride is withdrawn from the upper-middle side of the desorption tower and then fed to a refining tower for purification to produce a refined maleic anhydride product. Conser's solvent absorption process uses DBP as the solvent. The post-processing flowsheet comprises an absorption tower 1, a desorption tower, a secondary absorption tower 1, an exhaust gas scrubber, a light removal tower 2, and a refining tower. ALMA's solvent absorption process uses DIBE as the solvent, and the post-processing process includes an absorption tower 1, a desorption tower, a lightness removal tower 2 and a refining tower. Although the above three processes have been industrialized and each process has different characteristics, The processing procedures are relatively complicated, causing inconvenience in operation. Summary of the Invention In view of this, the object of the present invention is to provide a device and method for obtaining maleic anhydride from a gas phase containing maleic anhydride. The device provided by the present invention can achieve the purpose of simplifying the process when obtaining maleic anhydride from a gas phase containing maleic anhydride while effectively controlling the amount of fumaric acid generated and the consumption of organic solvent. In order to achieve the above object, the present invention provides a device for obtaining maleic anhydride from a gas phase containing maleic anhydride. The invention comprises three tower systems: an absorption tower, a light removal tower and a heavy removal tower. The absorption tower system is also provided with a multi-stage absorption tower circulating cooler. The light removal tower system also comprises a light removal tower reboiler. The heavy removal tower system also comprises a heavy removal tower reboiler, a heavy removal tower condenser and a heavy removal vacuum pump. Preferably, a device for obtaining maleic anhydride from a gas phase containing maleic anhydride comprises: The absorption tower has a structured packing at the bottom; the upper and middle parts of the absorption tower are A first tower tray is provided; a multi-stage demister is provided on the top of the absorption tower; Multi-stage absorption tower circulation cooler, the multi-stage absorption tower circulation cooler and the bottom of the absorption tower connect; The light removal tower is connected to the absorption tower; the bottom of the light removal tower is provided with a first inner A second internal is provided in the upper middle portion of the light removal tower; the first internal and the second internal are separated by a second tray; the first internal comprises a tray or a light removal tower structured packing; the second internal comprises a light removal tower structured packing; a lightness removal column reboiler, the lightness removal column reboiler being connected to the bottom of the lightness removal column; The de-weighting tower is connected to the light-removing tower; the de-weighting tower is provided with a regular de-weighting tower filler; a weight removal column reboiler, the weight removal column reboiler being connected to the bottom of the weight removal column; a weight removal tower condenser, the weight removal tower condenser being connected to the top of the weight removal tower; a light removal vacuum pump connected to a light removal tower; De-weighting vacuum pump, the de-weighting vacuum pump is connected to the de-weighting tower; the de-weighting vacuum pump is a non-aqueous distillation Steam jet pump or non-aqueous liquid jet pump; The light removal tower reboiler is a fixed tube sheet heat exchanger, a U-tube heat exchanger or a falling film reboiler; The multi-stage demister includes a folding plate demister and a wire mesh demister; the wire mesh demister is located at above the folded plate demister; The side of the absorption tower is provided with a reflux inlet, and the side wall of the light removal tower is located between the second internal part and the first internal part. A lean solvent reflux inlet is provided between the internals; The deweighting vacuum pump is provided with a deweighting tail gas outlet and a lean solvent outlet; the deweighting tail gas outlet and The lean solvent outlet is connected to the lean solvent reflux inlet; the lean solvent outlet is connected to the lean solvent reflux inlet; The gas phase containing maleic anhydride passes through the absorption tower, and the gas phase containing maleic anhydride and the absorbent are on the first tray and the structured packing. After mass transfer, a rich solvent containing maleic anhydride is obtained in the bottom of the absorption tower; after obtaining the rich solvent containing maleic anhydride, the rich solvent containing maleic anhydride is flowed into the light removal tower for distillation, and a light removal rich solvent and light components are obtained in the bottom of the light removal tower; the light components rise to the second internal part through the second tower plate and are absorbed by the absorbent to obtain a material containing light components and a light removal tower tail gas; the light component-containing material is cooled by a circulating cooler of a multi-stage absorption tower and refluxed to the absorption tower; the light removal tower tail gas is discharged from the top of the tower and flows into a light removal vacuum pump; the light removal tower operates under vacuum conditions; after obtaining the light removal rich solvent, the light removal rich solvent is distilled through a heavy removal tower to obtain maleic anhydride, non-condensable gas and a solvent containing heavy components, respectively. Preferably, the light removal tower reboiler is a fixed tube sheet heat exchanger, a U-tube heat exchanger or a falling film reboiler. Boiler. Preferably, the multi-stage demister includes a folding plate demister and a wire mesh demister; the wire mesh demister The device is located above the folding plate type demister. Preferably, the circulating cooler is a multi-stage absorption tower circulating cooler. The present invention also provides a method for obtaining maleic anhydride from a gas phase containing maleic anhydride using the device, comprising: Follow these steps: Absorption step: Use DBP or DIBE solvent with purity ≥95% to absorb the maleic anhydride in the gas phase flow. anhydride to obtain a rich solvent containing maleic anhydride; Light removal step: remove water, light acid and other impurities lighter than maleic anhydride from the rich solvent by distillation to obtain A light-depleted rich solvent having a water content of ≤100 ppm, a light acid content of ≤200 ppm, and a maleic acid content of ≤1000 ppm; the light acid comprises acetic acid and acrylic acid; Heavy removal step: remove phthalic anhydride, DBP or DIBE solvent, fumaric acid, tar and Other impurities heavier than maleic anhydride are removed by distillation to obtain maleic anhydride product. Preferably, the steps include: The gas phase containing maleic anhydride passes through the absorption tower, and the gas phase containing maleic anhydride and the absorbent transfer mass on the tower tray and structured packing. Finally, a rich solvent containing maleic anhydride is obtained in the bottom of the absorption tower; Part of the rich solvent containing maleic anhydride is cooled by a circulating cooler and then refluxed to the absorption tower. Butyl phthalate and / or diisobutyl hexahydrophthalate; The rich solvent containing maleic anhydride flows into the light removal tower for distillation, and the light removal rich solvent and light components; the light components rise to the second internal part through the second tray and are absorbed by the absorbent to obtain a material containing light components and a light removal tower tail gas; The light component material is cooled by the multi-stage absorption tower circulation cooler and then refluxed to the absorption tower; The gas is discharged from the top of the tower and flows into the light removal vacuum pump; the light removal tower operates under vacuum conditions; The light-removed rich solvent is distilled in a heavy-removal column to obtain maleic anhydride, non-condensable gas and a solvent containing heavy components. Preferably, the reflux of the rich solvent containing maleic anhydride refluxed to the absorption tower through the multi-stage absorption tower circulation cooler The ratio is 1:1 to 10:1. Preferably, the maleic anhydride-containing rich solvent has a maleic anhydride mass concentration of 10-20% and a water mass concentration of The mass concentration of acetic acid is ≤0.2%, the mass concentration of acetic acid and acrylic acid is ≤0.1%, the mass concentration of maleic acid is ≤1%, and the mass concentration of fumaric acid is ≤0.1%. Preferably, the pressure of the lightness removal tower is 10 to 30 kPaA. The present invention provides a device for obtaining maleic anhydride from a gas phase containing maleic anhydride, comprising an absorption tower, a light removal tower, The invention relates to a three-tower system comprising a degassing tower, a degassing tower and a degassing tower. The absorption tower system is further provided with a multi-stage absorption tower circulating cooler. The degassing tower system further comprises a degassing tower reboiler. The degassing tower system further comprises a degassing tower reboiler, a degassing tower condenser and a degassing vacuum pump. The present invention simplifies the steps of stripping, desorption, flash evaporation, tail gas reabsorption and refining in the traditional maleic anhydride post-processing process into two steps of degassing and degassing, thereby simplifying the process flow. The rich solvent degassing step can not only remove water, reduce fumaric acid production and prevent device blockage, but also remove components lighter than maleic anhydride to preliminarily refine maleic anhydride; the maleic anhydride degassing step can not only desorb maleic anhydride from the solvent, but also remove components heavier than maleic anhydride to complete the refinement of maleic anhydride. The light removal tower in the present invention is heated by a reboiler and operated under negative pressure conditions, which can maintain the high temperature and low pressure of the tower kettle, so that the maleic acid in the rich solvent is quickly dehydrated to generate maleic anhydride, greatly reducing the conversion of maleic acid to fumaric acid. At the same time, the introduction of the reboiler can controllably remove impurities lighter than maleic anhydride in the rich solvent. The introduction of the light removal tower and the light removal tower reboiler in the present invention completely removes the components lighter than maleic anhydride in the feed of the degassing tower, avoids a large amount of non-condensable gas brought in by the material from entering the degassing tower, greatly reduces the vacuum exhaust load of the degassing tower, and enables the degassing tower to operate at a lower pressure. At the same time, there is no need to retain maleic anhydride in the degassing tower. Maleic anhydride is removed from the top of the tower, and a lean solvent that can be circulated back to the absorption tower can be directly obtained, saving energy. In addition, the vacuum pump is an absorbent liquid jet vacuum pump, and the traditional steam jet vacuum pump is no longer used. There is no influence of water, and there is no need to set a tail gas washing step to recycle maleic anhydride, which simplifies the process. BRIEF DESCRIPTION OF THE DRAWINGS FIG1 is a schematic diagram of an apparatus for obtaining maleic anhydride from a gas phase containing maleic anhydride provided by the present invention. Among them, 1-absorption tower, 1-1-absorption tower structured packing, 1-2-first tray, 1-3-multi-stage demister, (1-31)--folded plate demister, 1-32--wire mesh demister, 1-4--multi-stage absorption tower circulating cooler, 1-5--raw material inlet, 1-6--first absorbent inlet, 1-7--absorbed tail gas outlet, 1-8--rich solvent outlet containing maleic anhydride, 1-9--reflux inlet; 2-lightness removal tower, 2-1--first internal, 2-2--second internal, 2-3--second tray, 2-4--lightness removal tower reboiler, 2-5--lightness removal tower heat exchanger, 2-6--lightness removal tower cooler, 2-7--rich solvent inlet, 2-8--Second absorbent inlet, 2-9--Lean solvent reflux inlet, 2-10--Light degassing tower tail gas outlet, 2-11--Light degassing rich solvent outlet, 2-12--Dehydrogenation tail gas cooler; 3-Weight degassing tower, 3-1--Weight degassing tower reboiler, 3-2--Weight degassing tower condenser, 3-3--Non-condensable gas outlet, 3-4--Light degassing rich solvent inlet, 3-5--Heavy component-containing solvent outlet; 4-Weight degassing vacuum pump; 5-Weight degassing vacuum pump, 5-1--Weight degassing tail gas outlet, 5-2-Lean solvent outlet, Material direction from S1 to S17. DETAILED DESCRIPTION The present invention provides a device for obtaining maleic anhydride from a gas phase containing maleic anhydride, comprising an absorption tower 1, a lightness removal tower 2, and a heavyness removal tower 3. The absorption tower system is further provided with a multi-stage absorption tower circulating cooler 1-4, the lightness removal tower system further comprises a lightness removal tower reboiler 2-4, and the heavyness removal tower system further comprises a heavyness removal tower reboiler 3-1, a heavyness removal tower condenser 3-2, and a heavyness removal vacuum pump 5. Preferably, the device for obtaining maleic anhydride from a gas phase containing maleic anhydride provided by the present invention comprises an absorption tower 1; The bottom of the absorption tower 1 is provided with an absorption tower structured packing 1-1; the upper and middle parts of the absorption tower 1 are provided with There is a first tray 1-2; the top of the absorption tower 1 is provided with a multi-stage demister 1-3; A multi-stage absorption tower circulating cooler 1-4 connected to the bottom of the absorption tower 1; a light removal tower 2 connected to the absorption tower 1; The bottom of the de-light tower 2 is provided with a first internal part 2-1; the middle and upper part of the de-light tower 2 is provided with a second internal part 2-1. Internals 2-2; the first internals 2-1 and the second internals 2-2 are separated by a second tray 2-3; the first internals 2-1 include trays or structured packing for a lightness removal tower; the second internals 2-2 include structured packing for a lightness removal tower; A light removal tower reboiler 2-4 connected to the bottom of the light removal tower 2; a heavy removal tower 3 connected to the light removal tower 2; The deweighting tower 3 is provided with a deweighting tower structured packing; The deweighting tower reboiler 3-1 is connected to the bottom of the deweighting tower 3; the deweighting tower reboiler 3-1 is connected to the top of the deweighting tower 3 Deweight removal tower condenser 3-2; A light removal vacuum pump 4 connected to the light removal tower 2; The deweighting vacuum pump 5 connected to the deweighting tower 3; the deweighting vacuum pump 5 is a non-water steam jet pump or a non-water steam jet pump. Liquid jet pump for water. As shown in FIG1 , the device for obtaining maleic anhydride from a gas phase containing maleic anhydride provided by the present invention comprises an absorption tower 1 . In the present invention, the bottom of the absorption tower 1 is provided with an absorption tower structured packing 1-1. Preferably, it includes one or more of grid packing, plate corrugated packing and wire mesh packing. In the present invention, the upper middle portion of the absorption tower 1 is provided with a first tray 1-2; the first tray is preferably It is a plate tower tray. In the present invention, the top of the absorption tower 1 is provided with a multi-stage demister 1-3. The stage demister 1-3 preferably includes a folded plate demister 1-31 and a wire mesh demister 1-32, and the wire mesh demister 1-32 is preferably located above the folded plate demister 1-31. In the present invention, the device includes a multi-stage absorption tower connected to the bottom of the absorption tower 1 for circulating cooling. In the embodiment of the present invention, the multi-stage absorption tower circulation cooler 1-4 is preferably divided into two stages. In the present invention, the absorption tower 1 further comprises: a raw material inlet 1-5 is provided at the bottom, and the absorption tower 1 The side wall is provided with a first absorbent inlet 1-6 below the multi-stage demister 1-3; the top of the absorption tower 1 is provided with an absorption tail gas outlet 1-7; the bottom of the absorption tower 1 is provided with a rich solvent outlet 1-8 containing maleic anhydride; and the side of the absorption tower 1 is provided with a reflux inlet 1-9. The device provided by the present invention includes a lightness removal tower 2 connected to an absorption tower 1. In the present invention, the bottom of the lightness removal tower 2 is provided with a first internal part 2-1, which includes The tower tray or the light removal tower structured packing, in the present invention, the tower tray is preferably a floating valve tower tray or a fixed valve tower tray, and the structured packing preferably includes one or more of grid packing, plate corrugated packing and wire mesh packing. In the present invention, a second internal part 2-2 is provided in the upper middle portion of the lightness removal tower 2, and the second internal part 2-2 includes Including structured packing of light removal tower. In the present invention, the first internal part 2-1 and the second internal part 2-2 are separated by a second tray 2-3; The second tray is preferably a chimney tray. The device provided by the present invention includes a light-removal tower reboiler 2-4 connected to the bottom of the light-removal tower 2. In the present invention, the light removal tower reboiler 2-4 is preferably a fixed tube sheet heat exchanger, a U-tube heat exchanger or Falling film reboiler. In the present invention, the device further comprises a de-lightness tower heat exchanger 2-5 connected to the de-lightness tower 2 and a de-lightness tower cooling 2-6; the outlet of the light removal tower cooler 2-6 is connected to the first absorbent inlet 1-6; in the present invention, the heat exchanger 2-5 is preferably a lean-rich solvent heat exchanger; the light removal tower cooler 2-6 is preferably a lean liquid cooler. In the present invention, the lightness removal tower 2 further comprises: The side wall of the light removal tower 2 is provided with a rich solvent inlet containing maleic anhydride between the tower tray and the first internal part 2-1. 2-7; the maleic anhydride-containing rich solvent inlet 2-7 is connected to the outlet of the light removal tower heat exchanger 2-5; In the present invention, the side wall of the lightness removal tower 2 is provided with a second absorbent inlet above the second internal part 2-2. 2-8. In the present invention, the side wall of the lightness removal tower 2 is located between the second internal part 2-2 and the first internal part 2-1. There is a lean solvent reflux inlet 2-9. In the present invention, the top of the light-removing tower 2 is provided with a light-removing tower tail gas outlet 2-10 and a dehydrogenation tail gas cooling Queqi 2-12; In the present invention, a light removal rich solvent outlet 2-11 is provided at the bottom of the light removal tower 2; The device provided by the present invention comprises a de-weighting tower 3 connected to a light de-weighting tower 2, wherein the de-weighting tower 3 is internally provided with There is a structured packing in the deweighting tower; in the present invention, the structured packing preferably includes one or more of grid packing, plate corrugated packing and wire mesh packing. In the present invention, the device includes a de-weighting tower reboiler 3-1 connected to the bottom of the de-weighting tower 3. In the present invention, the deweighting tower reboiler 3-1 is preferably a double-tube plate falling film reboiler. In the present invention, the device further includes a deweighting tower condenser 3 - 2 connected to the top of the deweighting tower 3 . In the present invention, the deweighting tower condenser 3-2 is preferably a double-tube sheet heat exchanger. In the present invention, the deweighting tower 3 further comprises: The top of the deweighting tower 3 is provided with a non-condensable gas outlet 3-3; the non-condensable gas outlet 3-3 is connected to the deweighting tower 3. Heavy vacuum pump 5; In the present invention, the side of the de-weighting tower is provided with a light-rich solvent inlet 3-4; The inlet 3-4 is connected to the light rich solvent removal outlet 2-11; In the present invention, the bottom of the deweighting tower is provided with a solvent outlet 3-5 containing heavy components. The solvent outlet 3-5 is communicated with the inlet of the light removal tower heat exchanger 2-5; The device provided by the present invention also includes a light removal tower 2 connected to the dehydrogenation tail gas cooler 2-12. Vacuum pump 4. In the present invention, the light removal vacuum pump 4 is preferably a liquid ring vacuum pump or a steam jet pump. The device provided by the present invention comprises a deweighting vacuum pump 5 connected to a deweighting tower 3; the deweighting vacuum pump 5 is Non-aqueous steam jet pump or non-aqueous liquid jet pump. In the present invention, the deweighting vacuum pump 5 is preferably a maleic anhydride steam jet pump, a liquid jet pump with an absorbent (DBP or DIBE) as a power source, or a maleic anhydride steam jet + organic solvent liquid ring vacuum pump, and most preferably a liquid jet pump with an absorbent (DBP or DIBE) as a power source. In the present invention, the degravity vacuum pump 5 is provided with a degravity tail gas outlet 5-1 and a lean solvent outlet 5-2; The deweighted tail gas outlet 5-1 is connected to the reflux inlet 1-9; the lean solvent outlet 5-2 is connected to the lean solvent reflux inlet 2-9. The present invention also provides a method for obtaining maleic anhydride from a gas phase containing maleic anhydride using the device, comprising: Next steps: Absorption step: Use DBP or DIBE solvent with purity ≥95% to absorb maleic anhydride in the gas phase stream containing maleic anhydride. obtaining a rich solvent containing maleic anhydride; Light removal step: remove water, light acid and other impurities lighter than maleic anhydride from the rich solvent by distillation to obtain water-containing A light-removed rich solvent having a content of 100 ppm or less, a light acid content of 200 ppm or less, and a maleic acid content of 1000 ppm or less; the light acid includes acetic acid and acrylic acid; Heavy removal step: remove phthalic anhydride, DBP or DIBE solvent, fumaric acid, tar and other The heavy anhydride impurities are removed by distillation to obtain maleic anhydride product. Preferably, the steps include: The gas phase containing maleic anhydride passes through the absorption tower 1, and the gas phase containing maleic anhydride and the absorbent are transferred on the tower tray and the structured packing. A rich solvent containing maleic anhydride is obtained in the bottom of the absorption tower; Part of the rich solvent containing maleic anhydride is cooled by circulating coolers 1-4 and then refluxed to absorption tower 1. is butyl phthalate and / or diisobutyl hexahydrophthalate; The rich solvent containing maleic anhydride flows into the light removal tower 2 for distillation, and the light removal rich solvent and light components are obtained in the tower kettle of the light removal tower. The light component rises through the second tray 2-3 to the second inner part 2-2 and is absorbed by the absorbent to obtain a material containing light components and a light removal tower tail gas; The light component material is cooled by the multi-stage absorption tower circulation cooler 1-4 and then refluxed to the absorption tower; The gas is discharged from the top of the tower and flows into the light removal vacuum pump; the light removal tower operates under vacuum conditions; The light-removed rich solvent is distilled in a heavy-removal tower 3 to obtain maleic anhydride, non-condensable gas and a solvent containing heavy components. In the present invention, the method for obtaining maleic anhydride from a gas phase containing maleic anhydride using the device comprises the following steps: Steps: The present invention passes the gas phase containing maleic anhydride through the absorption tower 1, and the gas phase containing maleic anhydride and the absorbent are arranged on the tower tray and the regular packing. After mass transfer of the materials, a rich solvent containing maleic anhydride is obtained in the bottom of the absorption tower 1. Specifically, the present invention passes the gas phase containing maleic anhydride from the raw material inlet 1-5 through the absorption tower 1, and the gas phase containing maleic anhydride passes through the absorbent inlet 1-6. The absorbent is sprayed out, and the gas phase containing maleic anhydride and the absorbent are mass-transferred in the high-temperature zone 1-2 and the low-temperature zone 1-1, and a rich solvent containing maleic anhydride is obtained in the bottom of the absorption tower 1. The absorbed tail gas is obtained at the top of the tower, and the tail gas is purified by the multi-stage demister 1-3 and discharged from the absorption tail gas outlet 1-7; part of the rich solvent containing maleic anhydride is cooled by the circulating cooler 1-4 and refluxed to the absorption tower 1 through the reflux inlet 1-9. In the present invention, the absorbent is butyl phthalate and / or diisobutyl hexahydrophthalate. In the present invention, the purity of the absorbent is preferably ≥95%, more preferably 96-99%. In the present invention, the absorption rate of the absorbent to maleic anhydride is preferably ≥98%. In the present invention, the mass concentration of maleic anhydride in the maleic anhydride-containing rich solvent is preferably 10-20%; the mass concentration of water is preferably 10-20%. The mass concentration of acetic acid and acrylic acid is preferably ≤0.1%; the mass concentration of maleic acid is preferably ≤1%; and the mass concentration of fumaric acid is preferably ≤0.1%. After obtaining the rich solvent containing maleic anhydride, the present invention flows the rich solvent containing maleic anhydride into the lightness removal tower 2 for distillation. The light removal tower kettle obtains light removal rich solvent and light components; the light components rise to the second internal part 2-2 through the second tower plate 2-3 and are absorbed by the absorbent to obtain light component-containing material and light removal tower tail gas; the light component-containing material is cooled by the multi-stage absorption tower circulation cooler 1-4 and then refluxed to the absorption tower 1; the light removal tower tail gas is discharged from the top of the tower and flows into the light removal vacuum pump; the light removal tower operates under vacuum conditions. Specifically, the rich solvent containing maleic anhydride is heat-exchanged in the heat exchanger 2-5 of the lightness removal tower, and then the rich solvent containing maleic anhydride is The material is cooled by the multi-stage absorption tower circulation cooler 1-4 and refluxed to the absorption tower 1 through the reflux inlet 1-9; the tail gas of the light removal tower 2 is discharged from the top of the tower through the dehydrogenation tail gas cooler 2-12 and then flows into the light removal vacuum pump 4. In the present invention, the light-removing tower 2 works under vacuum conditions. The pressure is 10-30 kPaA. In the present invention, the temperature of the bottom of the lightness removal column 2 is preferably 160-220°C, more preferably 200°C. In the present invention, the temperature of the maleic anhydride-containing rich solvent when entering the distillation zone is preferably 120-165°C, more preferably 130-150°C. In the present invention, the light-removal rich solvent is located in the bottom of the light-removal tower 2. The concentration of water is preferably ≤100 ppm, the concentrations of acetic acid and acrylic acid are preferably ≤200 ppm, and the concentrations of maleic acid are preferably ≤1000 ppm. After obtaining the light-removed rich solvent, the present invention distills the light-removed rich solvent through a heavy removal tower 3 to obtain maleic anhydride, Non-condensable gases and solvents containing heavy components. Specifically, the light-removed rich solvent is distilled in a heavy-removal tower 3 to obtain maleic anhydride, non-condensable gas and a solvent containing heavy components; After the non-condensable gas is treated by the weight removal vacuum pump 5, the resulting lean solvent is refluxed to the distillation zone 2-2 through the reflux inlet 2-9; The solvent containing the heavy component is combined with part of the rich solvent containing maleic anhydride, and then heat exchanged and cooled in sequence. Reflux to the absorption tower 1; the heat exchange and cooling are carried out in the de-lightness tower heat exchanger 2-5 and the de-lightness tower cooler 2-6 respectively. In the present invention, the top pressure of the deweighting tower 3 is preferably ≤1.5 kPaA, more preferably 0.5-1 kPaA; The bottom pressure of the deweighting tower 3 is preferably ≤2.5 kPaA, more preferably 1-2 kPaA; the bottom temperature of the deweighting tower 3 is preferably 180-220°C, more preferably 200°C. Example 1 Taking FIG1 as an example, the method of obtaining maleic anhydride from a gas phase containing maleic anhydride of the present invention is described: The gas phase (S1) containing maleic anhydride is passed through the absorption tower 1 from the raw material inlet 1-5 and is absorbed by the first absorbent DBP (S2). Absorbent is sprayed out of port 1-6. Within absorption tower 1, maleic anhydride in the airflow and DBP solvent are contacted and mass-transferred in the high-temperature and low-temperature zones of absorption tower 1. ≥98% of the maleic anhydride in the airflow is absorbed by the solvent. Impurities such as water, acetic acid, and acrylic acid are also absorbed by the solvent. A rich solvent containing maleic anhydride is obtained in the absorption tower kettle. The absorbed tail gas (S3) obtained at the top of the tower is purified by multi-stage demisters 1-3 (which in turn pass through a folded plate demister and a wire mesh demister) before being discharged from absorption tail gas outlet 1-7. Part of the rich solvent containing maleic anhydride (S14) is cooled by circulating coolers 1-4 (passing through circulating coolers and circulating After circulating solvent heat collector), it refluxes to absorption tower 1 through reflux inlet 1-9 (the material refluxed to absorption tower 1 is recorded as S15). The rich solvent (S4) containing maleic anhydride enters the heat exchanger 2-5 of the de-light tower for heat exchange (the temperature rises to 160℃, after heat exchange The material is recorded as S5), enters the top of the distillation zone 2-2 through the rich solvent inlet 2-7 containing maleic anhydride for distillation, and the water, light acid and other components lighter than maleic anhydride in the rich solvent are distilled and separated, and a light-removed rich solvent (S6) (water concentration ≤1ppm, acetic acid + acrylic acid concentration ≤20ppm) from which the light components are removed is obtained at the bottom of the light-removal tower, and the evaporated light components enter the absorption zone 2-1 through the tower plate 2-3, and are absorbed by the lean solvent (S8). After absorption, a light-component-containing material and a light-removal tower 2 tail gas are obtained, and the light-component-containing material (S9) is cooled by the multi-stage absorption tower circulation cooler 1-4 and refluxed to the absorption tower 1 through the reflux inlet 1-9; the light-removal tower 2 tail gas (S7) (containing light components such as water, acetic acid, acrylic acid, etc.) is discharged from the top of the tower, cooled to 40°C by the dehydrogenation tail gas cooler 2-12, and then flows into the light-removal vacuum pump 4. The light-removed rich solvent (S6) is distilled in the de-weighting tower 3 distillation zone (filled with structured packing) (S6) to obtain anhydride (S10, purity ≥99.8wt%), non-condensable gas (S13) and solvent containing heavy components (S11); the non-condensable gas is treated by a deweighting vacuum pump 5 (the deweighting vacuum pump adopts a liquid jet vacuum pump with DBP solvent as the power fluid) (S13), and the resulting lean solvent (S16, maleic anhydride mass content ≤0.05%) is refluxed to the distillation zone 2-2 through the reflux inlet 2-9 (S17); The solvent containing the heavy component (S11) is combined with a portion of the rich solvent containing maleic anhydride, and then subjected to heat exchange and cooling in sequence. (The cooled material is recorded as S12) (after cooling to 60°C), it is refluxed to the absorption tower 1 through 1-6; the heat exchange and cooling are carried out in the de-lightness tower heat exchanger 2-5 and the de-lightness tower cooler 2-6 respectively. The operating data of Example 1 is shown in Table 1. As can be seen from Table 1, the device and method of the present invention can effectively control the rich The production of maleic acid and the decomposition of the solvent are as follows: in logistics S4, maleic acid <6000ppm, fumaric acid <500ppm, and water <1000ppm, and the solvent feed rate is 6kg / t maleic anhydride. Furthermore, the present invention employs only three steps, streamlining the traditional maleic anhydride post-treatment process of steam stripping, desorption, flash evaporation, tail gas reabsorption, and refining to two steps: light and heavy removal. This simplifies the process and reduces equipment investment. Furthermore, a circulating solvent heat exchanger for recovering low-temperature heat is provided in the process, and the tail gas from the heavy removal vacuum pump is returned to the absorption tower 1 for recycling, thereby reducing the energy and material consumption of the device and achieving the purpose of the present invention.

[0001] Table 1 Operation data of Example 1 Table 2 Operation data of Example 1 Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. An apparatus for obtaining maleic anhydride from a gas phase containing maleic anhydride, characterized in that, Comprising: An absorption tower (1), at the bottom of the absorption tower (1) there is arranged an absorption tower structured packing (1-1); In the upper-middle part of the absorption tower (1) there is arranged a first tray (1-2); at the top of the absorption tower (1) there is arranged a multi-stage demister (1-3); A multi-stage absorption tower circulating cooler (1-4), the multi-stage absorption tower circulating cooler (1-4) is connected to the bottom of the absorption tower (1); A light component removal tower (2), the light component removal tower (2) is communicated with the absorption tower (1); at the bottom of the light component removal tower (2) there is arranged a first internal component (2-1); in the upper-middle part of the light component removal tower (2) there is arranged a second internal component (2-2); the first internal component (2-1) and the second internal component (2-2) are separated by a second tray (2-3); the first internal component (2-1) includes a tray or a light component removal tower structured packing; the second internal component (2-2) includes a light component removal tower structured packing; A light component removal tower reboiler (2-4), the light component removal tower reboiler (2-4) is connected to the bottom of the light component removal tower (2); A heavy component removal tower (3), the heavy component removal tower (3) is communicated with the light component removal tower (2), inside the heavy component removal tower (3) there is arranged a heavy component removal tower structured packing; A heavy component removal tower reboiler (3-1), the heavy component removal tower reboiler (3-1) is connected to the bottom of the heavy component removal tower (3); A heavy component removal tower condenser (3-2), the heavy component removal tower condenser (3-2) is connected to the top of the heavy component removal tower (3); A light component removal vacuum pump (4), the light component removal vacuum pump (4) is connected to the light component removal tower (2); A heavy component removal vacuum pump (5), the heavy component removal vacuum pump (5) is connected to the heavy component removal tower (3); the heavy component removal vacuum pump (5) is a non-aqueous steam jet pump or a non-aqueous liquid jet pump; The light component removal tower reboiler (2-4) is a fixed tube sheet heat exchanger, a U-tube heat exchanger or a falling film reboiler; The multi-stage demister (1-3) includes a corrugated demister (1-31) and a wire mesh demister (1-32); the wire mesh demister (1-32) is located above the corrugated demister (1-31); On the side of the absorption tower (1) there is arranged a reflux inlet (1-9), on the side wall of the light component removal tower (2) there is arranged a lean solvent reflux inlet (2-9), the lean solvent reflux inlet (2-9) is located between the second internal component (2-2) and the first internal component (2-1); The heavy component removal vacuum pump (5) is provided with a heavy component removal tail gas outlet (5-1) and a lean solvent outlet (5-2); the heavy component removal tail gas outlet (5-1) is communicated with the reflux inlet (1-9); the lean solvent outlet (5-2) is communicated with the lean solvent reflux inlet (2-9); The gas-phase over-absorption tower (1) containing maleic anhydride, after the mass transfer of the gas phase containing maleic anhydride and the absorbent on the first tray (1-2) and the structured packing, a rich solvent containing maleic anhydride is obtained at the bottom of the absorption tower (1); after obtaining the rich solvent containing maleic anhydride, the rich solvent containing maleic anhydride flows into the light-component removal tower (2) for distillation, and a light-component-removed rich solvent and light components are obtained at the bottom of the light-component removal tower (2); the light components rise to the second internal part (2-2) through the second tray (2-3) and are absorbed by the absorbent to obtain a material containing light components and the tail gas of the light-component removal tower; the material containing light components is cooled by the multi-stage absorption tower circulating cooler (1-4) and then refluxed to the absorption tower (1); the tail gas of the light-component removal tower (2) is discharged from the top of the tower and flows into the light-component removal vacuum pump (4); the light-component removal tower (2) operates under vacuum conditions; after obtaining the light-component-removed rich solvent, the light-component-removed rich solvent is rectified in the heavy-component removal tower (3) to obtain maleic anhydride, non-condensable gas and a solvent containing heavy components respectively.

2. The device according to claim 1, wherein The multi-stage absorption tower circulating cooler (1-4) is a two-stage circulating cooler.

3. A method for obtaining maleic anhydride from a gas phase containing maleic anhydride by using the device according to claim 1, characterized in that, It includes the following steps: Absorption step: Absorb maleic anhydride in the gas-phase material stream containing maleic anhydride with a DBP or DIBE solvent with a purity ≥ 95% to obtain a rich solvent containing maleic anhydride. Light-component removal step: Rectify and remove water, light acids and other impurities lighter than maleic anhydride in the rich solvent to obtain a light-component-removed rich solvent with a water content ≤ 100 ppm, light acids ≤ 200 ppm, and maleic acid content ≤ 1000 ppm; the light acids include acetic acid and acrylic acid. Heavy-component removal step: Rectify and remove phthalic anhydride, DBP or DIBE solvent, fumaric acid, tar and other impurities heavier than maleic anhydride in the light-component-removed rich solvent to obtain a maleic anhydride product.

4. The method according to claim 3, wherein: The absorption step specifically includes the following steps: Pass the gas phase containing maleic anhydride through the over-absorption tower (1), after the mass transfer of the gas phase containing maleic anhydride and the absorbent on the tray and the structured packing, a rich solvent containing maleic anhydride is obtained at the bottom of the absorption tower (1). The light-component removal step specifically includes the following steps: Part of the rich solvent containing maleic anhydride is cooled by the circulating cooler (1-4) and then refluxed to the absorption tower (1), and the absorbent is butyl phthalate and / or diisobutyl hexahydrophthalate. The rich solvent containing maleic anhydride flows into the light-component removal tower (2) for distillation, and a light-component-removed rich solvent and light components are obtained at the bottom of the light-component removal tower; the light components rise to the second internal part (2-2) through the second tray (2-3) and are absorbed by the absorbent to obtain a material containing light components and the tail gas of the light-component removal tower. The heavy-component removal step specifically includes the following steps: The material containing light components is cooled by the multi-stage absorption tower circulating cooler (1-4) and then refluxed to the absorption tower; the tail gas of the light-component removal tower is discharged from the top of the tower and flows into the light-component removal vacuum pump; the light-component removal tower operates under vacuum conditions. The light-component-removed rich solvent is rectified in the heavy-component removal tower (3) to obtain maleic anhydride, non-condensable gas and a solvent containing heavy components respectively.

5. The method according to claim 4, characterized in that The reflux ratio of the rich solvent containing maleic anhydride refluxed to the absorption tower (1) through the multi-stage absorption tower circulating cooler (1-4) is 1:1 to 10:

1.

6. The method according to claim 4, wherein In the rich solvent containing maleic anhydride, the mass concentration of maleic anhydride is 10-20%, the mass concentration of water is ≤0.2%, the mass concentration of acetic acid and acrylic acid is ≤0.1%, the mass concentration of maleic acid is ≤1%, and the mass concentration of fumaric acid is ≤0.1%.

7. The method according to claim 4, characterized in that, The pressure of the light removal tower (2) is 10-30 kPaA.

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