Environmentally friendly device and process for efficient solvent recovery of maleic anhydride

Abstract

The invention discloses an environmentally friendly device and process for efficiently recovering maleic anhydride with solvent, relates to the technical field of acid anhydride refining and purification, solves the technical problems of low recovery rate and high equipment corrosion in the recovery process of maleic anhydride, and the key points of the technical scheme are that the device includes an absorption tower, a desorption tower, a post-flash tower, a tail gas recovery tower, a centrifugal extractor, a plurality of heat exchangers, a pump and a storage tank; wherein the absorption tower kettle circulating pump, the oil-rich storage tank production outlet, the post-flash tower kettle pump, the post-flash tower circulating cooling pump and the lean oil storage tank production outlet are provided with a plurality of branches, effectively ensuring the content of maleic anhydride in the desorption tower feed and the content of impurities in the circulating absorbent, and making full use of the heat contained in the system. The process of recovering maleic anhydride by the device effectively ensures that the purity of maleic anhydride reaches 99.9% (wt), the yield of maleic anhydride reaches more than 98%, and the recycling rate of the absorbent reaches more than 99.9%; compared with the existing solvent absorption method treatment process, the process has a lower solvent ratio, better device stability, greatly reduces the generation of waste residue, and has a significant effect, which is conducive to the promotion and application in the field of maleic anhydride recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of acid anhydride refining and purification, and in particular to an environmentally friendly device and process for recovering maleic anhydride with a high-efficiency solvent. Background Art

[0002] Maleic anhydride is a commonly used important organic chemical raw material, and its consumption is second only to phthalic anhydride and acetic anhydride. It is mainly used in the production of unsaturated polyester resins, BDO, coatings, etc. In recent years, the demand for maleic anhydride is strong and the market prospects are good. The price of downstream product BDO continues to rise, and the import volume remains at a high level.

[0003] The production process of maleic anhydride can be generally divided into two parts: oxidation process and post-processing process. The oxidation process can be divided into benzene process and n-butane process according to the raw materials. The post-processing processes mainly include water absorption process and solvent absorption process. Among them, the benzene process accounts for 65% of the production capacity, and the n-butane process accounts for about 35%. This year, the price of maleic anhydride raw material benzene is high, resulting in losses for maleic anhydride enterprises using the benzene process. Nearly half of the units have stopped production, and the operating rate has remained at around 20% for many years, with actual output negative growth; the n-butane process unit has shown a trend of rapid development due to the advantages of low price of raw material n-butane, high product yield, stable product quality, low energy consumption and high profits.

[0004] There are two main processes for recovering maleic anhydride from maleic anhydride reaction gas: water absorption and solvent absorption. The former has the advantages of short process, low equipment investment, and mature process, but the disadvantage is that improper temperature control during absorption and dehydration operations can easily generate fumaric acid impurities. In addition to affecting the maleic anhydride yield of the device, the large-scale generation of fumaric acid is more seriously harmful in that fumaric acid easily polymerizes with acrylic acid to form a colloid, which blocks the tower plate and even causes the tower plate to fall off in severe cases. The presence of the polymerized colloid seriously affects the tower efficiency and increases the energy consumption of the dehydration operation; and because the colloid cannot be removed by washing with water, it must be boiled with alkali solution, which not only increases the amount of wastewater and the difficulty of wastewater treatment, but also makes the dehydration process unable to proceed continuously. The steam of the device is not easy to balance during intermittent operation, and the work intensity of the operators also increases accordingly.

[0005] Solvent absorption is to first send the gaseous mixture containing maleic anhydride obtained by the oxidation process to the absorption tower, absorb it all with an organic solvent with high boiling point, low viscosity, good chemical stability and weak affinity with water, and then send it to the desorption tower for decompression and separation. The absorption process of the solvent absorption process does not have the process of hydrating maleic anhydride to maleic anhydride. Although a small amount of maleic anhydride will still be generated due to the water in the reaction system, and then isomerized into fumaric acid, the amount generated is much less than that of the water absorption process, and the possibility of device blockage is also reduced a lot. This not only makes the recovery rate of maleic anhydride post-treatment process 3 to 5 percentage points higher than that of the water absorption method, but also improves the operating stability of the device, increases production time, and improves economic benefits. In addition, since there is no process of hydrating maleic anhydride to maleic acid, there is no need for a corresponding dehydration process, the steam consumption of maleic anhydride post-treatment operation is reduced, and the device can output more steam for external use; the recovery rate of maleic anhydride is improved and the equipment investment is reduced.

[0006] US Patent US2014 / 0081036A1 is a patent application for using an organic solvent, especially dibutyl adipate, as a selective absorbent for maleic anhydride. The patent states that because maleic anhydride also has a high solubility in dibutyl adipate solvent, dibutyl adipate can be used as an absorbent to absorb maleic anhydride from a gas stream containing maleic anhydride at an appropriate temperature and pressure. Maleic anhydride is then removed from the dibutyl adipate solvent by stripping under vacuum conditions and elevated temperatures, thereby regenerating the solvent.

[0007] Chinese authorized invention patent CN1062344 involves the use of different types of organic solvents such as dioctyl phthalate or dewaxed oil from a refinery to recover maleic anhydride from the catalytic oxidation of hydrocarbons.

[0008] China's authorized invention patent CN102558113B discloses an improved method for recovering maleic anhydride using an organic solvent, especially dibutyl phthalate. The method reduces the absorption temperature by utilizing hot air stripping and line extraction and cooling cycles in an absorption tower, thereby increasing the maleic anhydride absorption recovery rate and reducing the content of light components in the absorbent, such as acetic acid and acrylic acid, but the results of its implementation are not ideal.

[0009] With the call for energy conservation and emission reduction in my country, it is particularly important to change the shortcomings of the traditional solvent absorption method for purifying maleic anhydride. It is particularly important to develop a new and efficient environmentally friendly process for recovering maleic anhydride by solvent absorption, which has stable operation and significant energy-saving and consumption-reducing effects, and can effectively improve the purity, yield and recycling rate of maleic anhydride. Summary of the invention

[0010] The present invention provides an environmentally friendly device and process for efficiently recovering maleic anhydride with a solvent, the technical purpose of which is to effectively improve the purity and yield of maleic anhydride, increase the recycling rate of the absorbent, and ensure low equipment cost, stable operation effect, and energy saving and consumption reduction.

[0011] The above technical objectives of the present disclosure are achieved through the following technical solutions:

[0012] An environmentally friendly device for efficiently recovering maleic anhydride with a solvent, comprising an absorption tower T1, a desorption tower T2, a post-flash tower T3, a tail gas recovery tower T4, an extractor SE1, a reaction gas cooler E1, an absorbent circulating cooler E2, a desorption tower condenser E3, a desorption tower reboiler E4, a post-flash tower preheater E5, a post-flash tower circulating cooler E6, a lean solvent cooler E7, an absorption tower kettle circulating pump P1, a post-flash tower kettle pump P2, a post-flash tower circulating cooling pump P3, an oil-rich storage tank V1, a lean oil storage tank V2 and an extraction premixing tank V3;

[0013] The reaction gas cooler E1, absorbent circulating cooler E2, desorption tower condenser E3, desorption tower reboiler E4, post-flash tower preheater E5, post-flash tower circulating cooler E6, lean solvent cooler E7, absorber kettle circulating pump P1, post-flash tower kettle pump P2, post-flash tower circulating cooling pump P3 all include feed inlets and discharge ports;

[0014] The absorption tower T1 is provided with an exhaust gas outlet at the top, a lean solvent feed inlet at the upper right side, an absorbent circulating cooling material feed inlet at the lower right side, a reactor outlet mixed gas feed inlet at the left side, and a tower kettle material outlet at the bottom;

[0015] The desorption tower T2 is provided with a steam outlet at the top, a reflux port at the upper right side, a qualified maleic anhydride product outlet at the upper left side, a desorption tower rich oil feed port at the lower left side, a desorption tower kettle steam feed port at the lower right side, and a desorption tower kettle material outlet at the bottom;

[0016] The post-flash tower T3 is provided with a gas phase production port at the top, a post-flash tower circulating cooling material feed port at the upper right side, a post-flash tower feed port at the left side, a post-flash tower side line production port at the lower right side, and a tower kettle lean oil production port at the bottom;

[0017] The tail gas recovery tower T4 is provided with a waste gas extraction port at the top, a tail gas recovery tower lean oil feed port on the right, a tail gas recovery tower gas phase feed port on the left, and a tail gas recovery tower kettle material extraction port at the bottom;

[0018] The extractor SE1 is provided with an extractor feed port on the right side, a raffinate discharge port on the left side, and an extracted lean oil discharge port at the bottom;

[0019] The oil-rich storage tank V1 is provided with an oil-rich feed inlet for the absorber kettle on the left, an oil-rich feed inlet for the side line of the post-flash tower on the bottom, and an oil-rich production outlet on the right;

[0020] The lean oil storage tank V2 is provided with a lean oil feed port on the left side, an absorbent supplement feed port on the top, and a lean oil discharge port on the right side;

[0021] The extraction premixing tank V3 is provided with a premixing tank lean oil feed port on the upper left side, an extractant feed port on the lower left side, and a mixed liquid discharge port at the bottom;

[0022] The lean solvent feed port of the absorption tower is connected to the lean oil discharge port and the extracted lean oil discharge port; the absorbent circulating cooling material feed port is connected to the discharge port of the absorbent circulating cooler E2 and the tail gas recovery tower kettle material production port; the reactor outlet mixed gas feed port is connected to the discharge port of the reaction gas cooler E1; the absorbent kettle material outlet is connected to the feed port of the absorption tower circulating pump P1, and the discharge port of the absorption tower circulating pump P1 is connected to the feed port of the absorbent circulating cooler E2, the absorbent kettle production rich oil feed port, and the feed port of the post-flash tower circulating cooler E6;

[0023] The steam extraction port is connected to the feed port of the desorption tower condenser E3; the desorption tower oil-rich feed port is connected to the oil-rich extraction port; the desorption tower kettle steam feed port is connected to the discharge port of the desorption tower reboiler E4; the desorption tower kettle material extraction port is connected to the feed port of the desorption tower reboiler E4 and the feed port of the post-flash tower preheater E5; the discharge port of the desorption tower condenser E3 is connected to the reflux port and the gas phase feed port of the tail gas recovery tower;

[0024] The gas phase production port is connected to the gas phase feed port of the tail gas recovery tower; the circulating cooling material feed port of the post-flash tower is connected to the discharge port of the post-flash tower circulating cooler E6; the post-flash tower feed port is connected to the discharge port of the post-flash tower preheater E5; the side line production port of the post-flash tower is connected to the feed port of the post-flash tower circulating cooling pump P3; the tower bottom lean oil production port is connected to the feed port of the post-flash tower tower bottom pump P2; the discharge port of the post-flash tower tower bottom pump P2 is connected to the feed port of the post-flash tower preheater E5 and the feed port of the lean solvent cooler E7, and the discharge port of the post-flash tower circulating cooling pump P3 is connected to the feed port of the post-flash tower circulating cooler E6 and the post-flash tower side line production rich oil feed port;

[0025] The lean oil feed port of the tail gas recovery tower is connected to the lean oil outlet port; the extractor feed port is connected to the mixed liquid outlet port; the lean oil feed port is connected to the outlet port of the lean solvent cooler E7; the lean oil outlet port is connected to the lean oil feed port of the tail gas recovery tower, the lean solvent feed port and the lean oil feed port of the premixing tank.

[0026] Furthermore, the total number of plates of the absorption tower T1 is 9 to 40, and the plates are counted from top to bottom, wherein the absorbent circulation cooling material feed port is located at 40% to 60% of the total number of plates of the absorption tower T1.

[0027] Furthermore, the total number of plates of the desorption tower T2 is 22-45, and the number of plates is counted from top to bottom, wherein the oil-rich feed inlet of the desorption tower is located at 40%-55% of the total number of plates of the desorption tower T2, and the qualified maleic anhydride product outlet is located at 12%-20% of the total number of plates of the desorption tower T2.

[0028] Furthermore, the number of plates of the post-flash tower T3 is 4 to 9, and the number of plates is counted from top to bottom. The side line production outlet of the post-flash tower is located 1 to 2 plates upward from the bottom of the post-flash tower T3.

[0029] An environmentally friendly process for efficiently recovering maleic anhydride from solvents comprises the following steps:

[0030] S1: The mixed gas at the outlet of the maleic anhydride reactor is cooled by the reaction gas cooler E1 and then enters the bottom of the absorber T1 through the mixed gas feed port at the reactor outlet, the lean solvent enters the top of the absorber T1 through the lean solvent feed port, and the absorbent circulating cooling material enters the middle and lower part of the absorber T1 through the absorbent circulating cooling material feed port. After being absorbed by the absorbent, the rich oil in the bottom of the absorber T1 is extracted from the bottom material outlet through the discharge port of the absorber bottom circulating pump P1. The extraction of the absorber bottom circulating pump P1 is divided into three streams and respectively sent to the feed port of the absorbent circulating cooler E2, the extraction rich oil feed port of the absorber bottom, and the feed port of the post-flash tower circulating cooler E6; the waste gas is discharged from the waste gas discharge port at the top of the absorber T1;

[0031] S2: The bottom oil-rich oil from the bottom material outlet is sent to the absorbent circulating cooler E2, and after being cooled by the absorbent circulating cooler E2, it is mixed with the produced material from the bottom material outlet of the tail gas recovery tower in the pipeline, and then enters the middle and lower part of the absorption tower T1 through the absorbent circulating cooling material feed port;

[0032] S3: The bottom material outlet is sent to the bottom oil of the absorber bottom production oil-rich feed port, and after being mixed with the material produced from the post-flash tower side line production port in the oil-rich storage tank V1, it is produced from the oil-rich production port, and the production from the oil-rich production port is divided into two streams of materials and pumped into the desorption tower oil-rich feed port and the post-flash tower circulating cooler E6 respectively; after distillation in the desorption tower T2, the steam production port at the top of the tower produces light components, and a part of the production from the steam production port is condensed in the desorption tower condenser E3 and then enters the desorption tower T2 through the reflux port, and the other part enters the tail gas recovery tower T4 through the tail gas recovery tower gas phase feed port; the qualified maleic anhydride product production port of the side line of the desorption tower T2 produces qualified maleic anhydride, and the absorbent is produced from the bottom material production port of the desorption tower;

[0033] S4: a part of the absorbent extracted from the material extraction port of the desorption tower is preheated by the post-flash tower preheater E5 and then enters the post-flash tower T3 through the post-flash tower feed port for further desorption, and the other part is reboiled by the desorption tower reboiler E4 and then enters the desorption tower T2 through the desorption tower kettle steam feed port; the light component is extracted from the gas phase extraction port at the top of the post-flash tower T3, and the absorbent is extracted from the side line extraction port of the post-flash tower. The absorbent extracted from the side line extraction port of the post-flash tower is mixed with the tower bottom rich oil extracted from the tower bottom material outlet and the rich oil extracted from the rich oil storage tank V1, and then cooled by the post-flash tower circulating cooler E6, and then enters the top of the post-flash tower T3 as a liquid phase reflux through the post-flash tower circulating cooling material feed port, and the lean solvent is extracted from the tower bottom lean oil extraction port;

[0034] S5: The light components produced from the steam production outlet and the gas phase production outlet are mixed and enter the bottom of the tail gas recovery tower T4 through the gas phase feed port of the tail gas recovery tower; the lean solvent produced from the lean oil production outlet of the tower bottom is cooled by the lean solvent cooler E7, partially produced through the lean oil storage tank V2, and then enter the top of the tail gas recovery tower T4 through the lean oil feed port of the tail gas recovery tower; in the tail gas recovery tower T4, the material is produced from the material production outlet of the tail gas recovery tower bottom, and the tail gas is produced from the waste gas production outlet at the top of the tower;

[0035] S6: a part of the lean oil produced from the lean oil production outlet of the bottom of the post-flash tower T3 is returned to the post-flash tower preheater E5 to preheat the feed, and the other part is cooled by the lean solvent cooler E7 and then sent to the lean oil feed inlet of the lean oil storage tank V2; a part of the absorbent produced from the side line of the post-flash tower enters the post-flash tower circulating cooler E6 for cooling and then returns to the post-flash tower T3 through the post-flash tower circulating cooling material feed inlet, and the other part enters the rich oil storage tank V1 through the side line of the post-flash tower through the rich oil feed inlet;

[0036] S7: the material at the outlet of the lean oil discharge port of the lean oil storage tank V2 is divided into three streams of materials and respectively enters the lean solvent feed port of the absorption tower T1, the lean oil feed port of the tail gas recovery tower and the lean oil feed port of the premixing tank V3 of the extraction; after being mixed with the fresh extractant entering from the extractant feed port of the extraction premixing tank V3, it is taken out from the mixed liquid discharge port and then enters the centrifugal extractor SE1 through the extractor feed port, and centrifugal separation is carried out in the centrifugal extractor SE1, the extractant phase is taken out from the upper part of the centrifugal extractor SE1 and taken out from the raffinate discharge port, and the lean solvent is taken out from the lower part through the extraction lean oil discharge port.

[0037] Furthermore, the absorption tower T1 is operated at normal pressure or pressurized, the temperature of the bottom rich oil extracted from the absorption tower T1 and entering the oil-rich storage tank V1 is not lower than 94°C, and the content of maleic anhydride in the bottom rich oil entering the oil-rich storage tank V1 is not higher than 18.9% (wt).

[0038] Furthermore, the bottom oil-rich material extracted from the bottom material outlet of the absorption tower T1 is divided into three streams and respectively sent to the absorbent circulating cooler E2, the rich oil storage tank V1 and the post-flash tower circulating cooler E6, and the distribution ratio thereof is 0.6:0.15:0.25~0.8:0.05:0.15.

[0039] Furthermore, the material produced from the oil-rich production outlet is pumped into the oil-rich feed inlet of the desorption tower and the post-flash tower circulating cooler E6 respectively, and the distribution ratio thereof is 0.4:0.6~0.8:0.2.

[0040] Furthermore, the materials produced from the lean oil production outlet of the bottom of the post-flash tower T3 are respectively produced to the post-flash tower preheater E5 and the lean oil storage tank V2, and the distribution ratio thereof is 0.57:0.43~0.73:0.27.

[0041] Furthermore, the materials produced from the side line production outlet of the post-flash tower are respectively produced to the post-flash tower circulating cooler E6 and the oil-rich storage tank V1, and the distribution ratio thereof is 0.65:0.35~0.75:0.25.

[0042] Furthermore, the materials produced from the lean oil outlet of the lean oil storage tank V1 are respectively produced to the absorption tower T1, the tail gas recovery tower T4 and the extraction premixing tank V3, and the distribution ratio thereof is 0.1:0.2:0.7~0.35:0.2:0.45.

[0043] Furthermore, the desorption tower T2 and the post-flash tower T3 are operated under reduced pressure, and the operating pressure is -0.001MPa to -0.010MPa, and the operating pressure of the post-flash tower T3 is lower than the operating pressure of the desorption tower T2. The desorption tower T2 is provided with a three-stage steam ejector, and the bottom temperatures of the desorption tower T2 and the post-flash tower T3 are not higher than 205°C.

[0044] Furthermore, the absorbent is selected from one or a mixture of two or more of dimethyl phthalate, diethyl phthalate, dipropyl phthalate, diisopropyl phthalate, dibutyl phthalate, diisobutyl phthalate, hexahydrophthalate, and diethyl tetrahydrophthalate.

[0045] The beneficial effects of the present disclosure are:

[0046] (1) The process of recovering maleic anhydride from maleic anhydride reaction gas adopts a new solvent to purify maleic anhydride through absorption and desorption. Three branches are set at the outlet of the circulating pump P1 of the absorber. One branch effectively ensures that the oil-rich part of the bottom of the absorber T1 is cooled and circulated back to the absorber T1 to further absorb the maleic anhydride in the reaction gas. At the same time, the material produced from the bottom of the absorber T1 is divided into two streams; the material is produced from the side outlet of the post-flash tower and partially returned to the oil-rich storage tank V1. Through flow adjustment, it is blended with the rich oil produced from the bottom of the absorber T1, effectively ensuring the content of maleic anhydride in the rich oil entering the desorption tower T2, ensuring that the bottom temperature of the desorption tower T2 is lower than 210°C, ensuring the stability of the absorbent and maleic anhydride, and reducing the generation of industrial waste residues; it can also avoid the loss of equipment caused by too low operating pressure of the desorption tower T2.

[0047] (2) Two branches are set on the bottom pump P2 of the post-flash tower. The produced material from the lean oil outlet of the bottom of the post-flash tower T3 is mixed with the produced material from the material outlet of the bottom of the desorption tower and then enters the post-flash tower T3 for further desorption. The heat of the produced material from the post-flash tower T3 is fully utilized, and the consumption of the additional steam of the post-flash tower preheater E5 is reduced. In addition, the bottom material of the post-flash tower T3 returns to the post-flash tower T3 to provide rising steam for the bottom of the post-flash tower T3, ensuring the stable operation of the device.

[0048] (3) Three branch extraction buckles are set at the lean oil outlet of the lean oil storage tank V2. On the one hand, they ensure the stable operation of the absorption tower T1 and the tail gas recovery tower T4. On the other hand, they promptly remove the impurities contained in the lean solvent from the system, ensuring the absorption effect of maleic anhydride during the long-term operation of the absorbent.

[0049] (4) The present invention realizes the recovery of maleic anhydride in the reaction gas and the recycling of the solvent. The invention has good effect, high maleic anhydride yield, high solvent recycling rate, the device can operate stably for a long time, and the environmental protection effect is remarkable. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the structure of the device disclosed in the present invention;

[0051] In the figure: T1-absorption tower; T2-desorption tower; T3-post-flash tower; T4-tail gas recovery tower; E1-reaction gas cooler; E2-absorption tower circulation cooler; E3-desorption tower condenser; E4-desorption tower reboiler; E5-post-flash tower preheater; E6-post-flash tower circulation cooler; E7-lean solvent cooler; P1-absorption tower kettle circulation pump; P2-post-flash tower kettle pump; P3-post-flash tower circulation cooling pump; V1-rich oil storage tank; V2-lean oil storage tank; V3-extraction premixing tank; SE1-centrifugal extractor;

[0052] 1-waste gas outlet; 2-lean solvent feed port; 3-absorbent circulating cooling material feed port; 4-reactor outlet mixed gas feed port; 5-bottom material outlet; 6-steam production port; 7-reflux port; 8-qualified maleic anhydride product production port; 9-desorption tower rich oil feed port; 10-desorption tower bottom steam feed port; 11-desorption tower bottom material production port; 12-gas phase production port; 13-post-flash tower circulating cooling material feed port; 14-post-flash tower feed port; 15-post-flash tower side line production port; 16-bottom lean oil production port; 17- Waste gas production port; 18-lean oil feed port of tail gas recovery tower; 19-gas phase feed port of tail gas recovery tower; 20-tail gas recovery tower kettle material production port; 21-extractor feed port; 22-raffinate discharge port; 23-extraction lean oil discharge port; 24-absorption tower kettle production rich oil feed port; 25-post-flash tower side line production rich oil feed port; 26-oil rich production port; 27-lean oil feed port; 28-absorbent supplement feed port; 29-lean oil discharge port; 30-premix tank lean oil feed port; 31-extractant feed port; 32-mixed liquid discharge port. DETAILED DESCRIPTION

[0053] The technical solution of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0054] In the description of the present disclosure, it is to be understood that the terms "top", "bottom", "left side", "right side", "upper left side", "lower left side", "upper right side", "lower right side", "lower middle", "side", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, "inside" and "outside" refer to the inside and outside relative to the outline of each component itself.

[0055] The device for recovering maleic anhydride with efficient solvent disclosed in the present invention is as follows Figure 1 As shown, the device includes an absorption tower T1, a desorption tower T2, a post-flash tower T3, a tail gas recovery tower T4, an extractor SE1, a reaction gas cooler E1, an absorbent circulating cooler E2, a desorption tower condenser E3, a desorption tower reboiler E4, a post-flash tower preheater E5, a post-flash tower circulating cooler E6, a lean solvent cooler E7, an absorption tower kettle circulating pump P1, a post-flash tower kettle pump P2, a post-flash tower circulating cooling pump P3, an oil-rich storage tank V1, a lean oil storage tank V2 and an extraction premixing tank V3.

[0056] The reaction gas cooler E1, the absorbent circulating cooler E2, the desorber condenser E3, the desorber reboiler E4, the post-flash tower preheater E5, the post-flash tower circulating cooler E6, the lean solvent cooler E7, the absorber kettle circulating pump P1, the post-flash tower kettle pump P2, and the post-flash tower circulating cooling pump P3 all include a feed inlet and a discharge outlet.

[0057] The top of the absorption tower T1 is provided with a waste gas outlet 1, a lean solvent feed port 2 is provided on the upper right side, an absorbent circulating cooling material feed port 3 is provided on the lower right side, a reactor outlet mixed gas feed port 4 is provided on the left side, and a tower kettle material outlet 5 is provided at the bottom. The top of the desorption tower T2 is provided with a steam production port 6, a reflux port 7 is provided on the upper right side, a qualified maleic anhydride product production port 8 is provided on the upper left side, a desorption tower rich oil feed port 9 is provided on the lower left side, a desorption tower kettle steam feed port 10 is provided on the lower right side, and a desorption tower kettle material production port 11 is provided at the bottom.

[0058] The top of the post-flash tower T3 is provided with a gas phase production port 12, the upper right side is provided with a post-flash tower circulating cooling material feed port 13, the left side is provided with a post-flash tower feed port 14, the right side is provided with a post-flash tower side line production port 15, and the bottom is provided with a tower bottom lean oil production port 16. The top of the tail gas recovery tower T4 is provided with a waste gas production port 17, the right side is provided with a tail gas recovery tower lean oil feed port 18, the left side is provided with a tail gas recovery tower gas phase feed port 19, and the bottom is provided with a tail gas recovery tower bottom material production port 20.

[0059] The extractor SE1 is provided with an extractor feed port 21 on the right, a raffinate discharge port 22 on the left, and an extraction lean oil discharge port 23 at the bottom. The rich oil storage tank V1 is provided with an absorber bottom extraction rich oil feed port 24 on the left, a post-flash tower side line extraction rich oil feed port 25 at the bottom, and a rich oil extraction port 26 on the right. The lean oil storage tank V2 is provided with a lean oil feed port 27 on the left, an absorbent supplement feed port 28 on the top, and a lean oil discharge port 29 on the right. The extraction premixing tank V3 is provided with a premixing tank lean oil feed port 30 on the upper left, an extractant feed port 31 on the lower left, and a mixed liquid discharge port 32 at the bottom.

[0060] The lean solvent feed port 2 is connected to the lean oil discharge port 29 and the extracted lean oil discharge port 23; the absorbent circulating cooling material feed port 3 is connected to the discharge port of the absorbent circulating cooler E2 and the tail gas recovery tower kettle material production port 20; the reactor outlet mixed gas feed port 4 is connected to the discharge port of the reaction gas cooler E1; the tower kettle material outlet 5 is connected to the feed port of the absorber circulating pump P1, and the discharge port of the absorber circulating pump P1 is connected to the feed port of the absorbent circulating cooler E2, the absorber kettle production rich oil feed port 24, and the feed port of the post-flash tower circulating cooler E6.

[0061] The steam production port 6 is connected to the feed port of the desorption tower condenser E3; the desorption tower oil-rich feed port 9 is connected to the oil-rich production port 26; the desorption tower kettle steam feed port 10 is connected to the discharge port of the desorption tower reboiler E4; the desorption tower kettle material production port 11 is connected to the feed port of the desorption tower reboiler E4 and the feed port of the post-flash tower preheater E5; the discharge port of the desorption tower condenser E3 is connected to the reflux port 7 and the tail gas recovery tower gas phase feed port 19.

[0062] The gas phase production port 12 is connected to the gas phase feed port 19 of the tail gas recovery tower; the post-flash tower circulating cooling material feed port 13 is connected to the discharge port of the post-flash tower circulating cooler E6; the post-flash tower feed port 14 is connected to the discharge port of the post-flash tower preheater E5; the post-flash tower side line production port 15 is connected to the feed port of the post-flash tower circulating cooling pump P3; the tower bottom lean oil production port 16 is connected to the feed port of the post-flash tower bottom pump P2; the discharge port of the post-flash tower bottom pump P2 is connected to the feed port of the post-flash tower preheater E5 and the feed port of the lean solvent cooler E7, and the discharge port of the post-flash tower circulating cooling pump P3 is connected to the feed port of the post-flash tower circulating cooler E6 and the post-flash tower side line production rich oil feed port 25.

[0063] The lean oil feed port 18 of the tail gas recovery tower is connected to the lean oil discharge port 29; the extractor feed port 21 is connected to the mixed liquid discharge port 32; the lean oil feed port 27 is connected to the discharge port of the lean solvent cooler E7; the lean oil discharge port 29 is connected to the lean oil feed port 18 of the tail gas recovery tower, the lean solvent feed port 2 and the lean oil feed port 30 of the premixing tank.

[0064] Embodiment 1:

[0065] Reference Figure 1 The above device is used to recover maleic anhydride from maleic anhydride reaction gas. The specific process is as follows:

[0066] (1) The feed rate is 321900 kg / h, and the feed composition is 5.50% (wt) water, 1.22% carbon monoxide, 73.55% nitrogen, 15.09% oxygen, 1.47% carbon dioxide, 0.60% n-butane, 0.05% acetic acid, 0.04% acrylic acid, and 2.39% maleic anhydride. The mixed gas at the reactor outlet is cooled to 115°C by the reaction gas cooler E1 and enters the 13th tray of the absorption tower T1 through the reactor outlet mixed gas feed port 4; the feed temperature is 55°C, and the feed rate is 41200 kg / h. kg / h, the feed composition is 0.58% (wt) water, 0.04% maleic anhydride, 0.06% maleic acid, 0.06% fumaric acid, 0.12% phthalic anhydride, 97.65% dibutyl phthalate, and 1.42% tar. The lean solvent enters the first tower plate of the absorption tower T1 through the lean solvent feed port 2; the material output from the absorbent circulating cooler E2 after cooling is mixed with the material taken out from the tail gas recovery tower kettle material outlet 20, and then enters the 7th tower plate of the absorption tower T1 through the absorbent circulating cooling material feed port 3. The operating pressure of absorption tower T1 is 0.14MPa. Maleic anhydride and a small amount of impurities are fully absorbed by the absorbent in absorption tower T1. The rich oil containing 13.63% maleic anhydride in the bottom of the tower is produced through the bottom material outlet 5 to the absorption tower circulation pump P1 at a flow rate of 149499 kg / h, and then divided into three streams and sent to the absorbent circulation cooler E2, the rich oil storage tank V1 and the post-flash tower circulation cooler E6 at flow rates of 89699 kg / h, 22126 kg / h and 37674 kg / h respectively; the waste gas with a maleic anhydride content of 0.003% discharged from the waste gas outlet 1 at the top of the absorption tower T1 is sent out of the boundary area for incineration.

[0067] (2) The rich oil produced from the bottom material outlet 5 and entering the oil-rich storage tank V1 is mixed with the material produced from the side line outlet 15 of the post-flash tower and entering the oil-rich storage tank V1. The mixed material is then produced through the rich oil production pump of the oil-rich production outlet 26. The mixed material is then divided into two streams by three-way adjustment. One stream enters the desorption tower T2 at the 13th plate of the desorption tower T2 through the oil-rich feed inlet 9 at a flow rate of 64272 kg / h for distillation. The operating pressure of the desorption tower T2 is 0.003 MPa, and the number of plates is 28. The light components are produced from the steam production outlet 6 at a flow rate of 184 kg / h after condensation at the top of the tower. The qualified maleic anhydride product production outlet 8 of the side line produces qualified maleic anhydride with a maleic anhydride content of 99.97% at a flow rate of 7550 kg / h on the 4th plate of the desorption tower T2. The bottom material production outlet 11 of the desorption tower produces maleic anhydride with a flow rate of 149499 The absorbent having a maleic anhydride content of 1.2% and a dibutyl phthalate content of 97.3% was produced at a flow rate of kg / h. At this time, the temperature of the absorbent produced from the bottom of the desorption tower T2 was 196°C.

[0068] (3) The material produced from the bottom material outlet 11 of the desorption tower is mixed with the material produced from the bottom lean oil outlet 16 of the post-flash tower T3 and then enters the post-flash tower preheater E5 to be preheated to 215°C and then enters the post-flash tower T3 for further desorption. The operating pressure of the post-flash tower T3 is 0.002MPa, the number of tower plates is 6, the gas phase outlet 12 at the top of the tower produces light components at a flow rate of 365 kg / h, and the side line outlet 15 of the post-flash tower at the 5th tower plate produces an absorbent with a maleic anhydride content of 12.9% at a flow rate of 232855 kg / h. After being adjusted by a three-way valve, it is divided into two streams, one of which is 174641 The flow rate of 500 kg / h is cooled by the post-flash tower circulating cooling pump P3, and then mixed with the flow rate of 53742 kg / h of the absorption tower kettle circulating pump P1, and then enters the post-flash tower circulating cooler E6, and then returns to the first tower plate of the post-flash tower T3 after being cooled to 90°C by the post-flash tower circulating cooler E6; another flow rate of 58214 kg / h is produced from the side line of the post-flash tower to the rich oil feed port 25 and enter the rich oil storage tank V1. The tower kettle lean oil production port 16 produces a lean solvent with a dibutyl phthalate content of 97.9% at a flow rate of 172341 kg / h, and is divided into two streams by the three-way adjustment of the post-flash tower kettle pump P2, one of which enters the post-flash tower preheater E5 at a flow rate of 120639 kg / h; the other enters the lean solvent cooler E7 at a flow rate of 51702 kg / h, and enters the lean oil storage tank V2 after being cooled by the lean solvent cooler E7.

[0069] (4) Fresh absorbent is replenished from the absorbent replenishment feed port 28 and enters the lean oil storage tank V2 at a flow rate of 29 kg / h. After being mixed with the input of the lean solvent cooler E7, it is divided into three streams through the valve group adjustment. One stream enters the absorption tower T1 from the lean solvent feed port 2 at a flow rate of 5179 kg / h, one stream enters the tail gas recovery tower T4 from the tail gas recovery tower lean oil feed port 18 at a flow rate of 10389 kg / h, and one stream enters the extraction premixing tank V3 from the premixing tank lean oil feed port 30 at a flow rate of 36221 kg / h.

[0070] (5) The produced material from the steam outlet 6 at the top of the desorption tower T2 is mixed with the produced material from the gas phase outlet 12 at the top of the post-flash tower T3 and then enters the bottom of the tail gas recovery tower T4 through the gas phase feed inlet 19 of the tail gas recovery tower. The tail gas recovery tower T4 is equipped with 3 m structured packing. The maleic anhydride in the gas phase feed at the bottom of the tail gas recovery tower T4 is further absorbed by the dibutyl phthalate in the top feed. The tail gas recovery tower kettle material outlet 20 produces a solvent with a maleic anhydride content of 4.1% at a flow rate of 10781 kg / h; the waste gas outlet 17 at the top of the tower produces 116 kg / h of tail gas and sends it to the boundary area for incineration.

[0071] (6) The material input from the lean oil feed port 30 of the premixing tank and the 8500 kg / h of desalted water input from the extractant feed port 31 are mixed in the extraction premixing tank V3 and then enter the centrifugal extractor SE1 for centrifugal separation. The extractant phase is extracted from the raffinate outlet 22, and 36346 kg / h of the treated lean solvent is extracted from the extraction lean oil outlet 23 and used as a circulating absorbent, wherein the content of dibutyl phthalate is 97.7%.

[0072] In summary, in the process of recovering maleic anhydride from maleic anhydride reaction gas, the yield of maleic anhydride is 98%, the purity of maleic anhydride is 99.97%, and the circulation rate of absorbent dibutyl phthalate is 99.92%.

[0073] Embodiment 2:

[0074] (1) The feed rate is 324625 kg / h, and the feed composition is 5.45% (wt) water, 1.21% carbon monoxide, 72.93% nitrogen, 14.96% oxygen, 1.46% carbon dioxide, 0.59% n-butane, 0.05% acetic acid, 0.04% acrylic acid, 3.21% maleic anhydride. The mixed gas at the outlet of the maleic anhydride reactor is cooled to 138°C by the reaction gas cooler E1 and enters the 30th tray of the absorption tower T1 through the reactor outlet mixed gas feed port 4; the feed temperature is 58°C, and the feed rate is 28442 kg / h, the feed composition is 0.58% (wt) water, 0.04% maleic anhydride, 0.06% maleic acid, 0.06% fumaric acid, 0.12% phthalic anhydride, 77.65% dibutyl phthalate, 20% diethyl tetrahydrophthalate, and 1.42% tar. The lean solvent enters the first tower plate of the absorption tower T1 through the lean solvent feed port 2; the material output from the absorbent circulating cooler E2 after cooling is mixed with the material taken out from the tail gas recovery tower kettle material outlet 20, and then enters the 16th tower plate of the absorption tower T1 through the absorbent circulating cooling material feed port 3. The operating pressure of absorption tower T1 is 0.15MPa. Maleic anhydride and a small amount of impurities in absorption tower T1 are fully absorbed by the absorbent. The rich oil containing 23.32% maleic anhydride in the bottom of the tower is produced through the bottom material outlet 5 to the absorption tower circulation pump P1 at a flow rate of 234397 kg / h, and then divided into three streams and sent to the absorbent circulation cooler E2, the rich oil storage tank V1 and the post-flash tower circulation cooler E6 at flow rates of 187617 kg / h, 18752 kg / h and 28128 kg / h respectively; the waste gas with a maleic anhydride content of 0.001% discharged from the waste gas outlet 1 at the top of absorption tower T1 is sent out of the boundary area for incineration.

[0075] (2) The rich oil produced from the bottom material outlet 5 and entering the oil-rich storage tank V1 is mixed with the material produced from the side line outlet 15 of the post-flash tower and entering the oil-rich storage tank V1. The mixed material is then produced through the rich oil production pump of the oil-rich production outlet 26. The mixed material is then divided into two streams by three-way adjustment. One stream enters the desorption tower T2 at the 18th plate of the desorption tower T2 through the oil-rich feed inlet 9 of the desorption tower at a flow rate of 52052 kg / h for distillation. The operating pressure of the desorption tower T2 is 0.003 MPa, and the number of plates is 35. The light components are produced from the steam production outlet 6 at a flow rate of 254 kg / h after condensation at the top of the tower. The qualified maleic anhydride product production outlet 8 of the side line produces qualified maleic anhydride with a maleic anhydride content of 99.92% at a flow rate of 10230 kg / h at the 5th plate of the desorption tower T2. The bottom material production outlet 11 of the desorption tower produces qualified maleic anhydride with a maleic anhydride content of 41570 kg / h. The absorbent having a maleic anhydride content of 0.6%, a dibutyl phthalate content of 62.35% and a diethyl tetrahydrophthalate content of 34.92% was produced at a flow rate of kg / h. At this time, the temperature of the absorbent produced from the bottom of the desorption tower T2 was 183°C.

[0076] (3) The material produced from the desorption tower bottom material outlet 11 is mixed with the material produced from the bottom lean oil outlet 16 of the post-flash tower T3 and then enters the post-flash tower preheater E5 to be preheated to 215℃ and then enters the post-flash tower T3 for further desorption. The operating pressure of the post-flash tower T3 is 0.002MPa, the number of tower plates is 4, the gas phase outlet 12 at the top of the tower produces light components at a flow rate of 494 kg / h, and the side line outlet 15 of the post-flash tower at the third tower plate produces absorbent with a maleic anhydride content of 19.8% at a flow rate of 310,000 kg / h. After being adjusted by a three-way valve, it is divided into two streams, one of which has a flow rate of 207,700 kg / h and is cooled by the post-flash tower circulating cooling pump P3 and then mixed with the 97,127 kg / h of mixed liquid enters the post-flash tower circulation cooler E6, is cooled to 90°C in the post-flash tower circulation cooler E6, and then returns to the first plate of the post-flash tower T3; another stream of 102300 kg / h is produced from the side line of the post-flash tower to the rich oil feed port 25 and enters the rich oil storage tank V1. The lean oil production port 16 of the tower bottom produces a lean solvent with a dibutyl phthalate content of 76.99% and a diethyl tetrahydrophthalate content of 19.74% at a flow rate of 132977 kg / h, and is divided into two streams by the three-way adjustment of the post-flash tower bottom pump P2, one of which enters the post-flash tower preheater E5 at a flow rate of 97073 kg / h, and the other enters the lean solvent cooler E7 at a flow rate of 35904 kg / h, and enters the lean oil storage tank V2 after being cooled by the lean solvent cooler E7.

[0077] (4) Fresh absorbent is replenished from the absorbent replenishment feed port 28 and enters the lean oil storage tank V2 at a flow rate of 28 kg / h to be mixed with the input of the lean solvent cooler E7. Then, it is adjusted by the valve group to be divided into three streams, one of which enters the absorption tower T1 from the lean solvent feed port 2 at a flow rate of 10932 kg / h, one enters the tail gas recovery tower T4 from the tail gas recovery tower lean oil feed port 18 at a flow rate of 7220 kg / h, and one enters the extraction premixing tank V3 from the premixing tank lean oil feed port 30 at a flow rate of 17836 kg / h.

[0078] (5) The produced material from the steam outlet 6 at the top of the desorption tower T2 is mixed with the produced material from the gas phase outlet 12 at the top of the post-flash tower T3 and then enters the bottom of the tail gas recovery tower T4 through the gas phase feed inlet 19 of the tail gas recovery tower. The tail gas recovery tower T4 is equipped with 2.8 m regular packing. The maleic anhydride in the gas phase feed at the bottom of the tail gas recovery tower T4 is further absorbed by the dibutyl phthalate in the top feed. The tail gas recovery tower kettle material outlet 20 produces a solvent with a maleic anhydride content of 6.4% at a flow rate of 7733 kg / h; the waste gas outlet 17 at the top of the tower produces 234 kg / h of tail gas and sends it to the boundary area for incineration.

[0079] (6) The material input from the lean oil feed port 30 of the premixing tank and the 5452 kg / h of desalted water input from the extractant feed port 31 are mixed in the extraction premixing tank V3 and then enter the centrifugal extractor SE1 for centrifugal separation. The extractant phase is extracted from the raffinate outlet 22, and 17813 kg / h of the treated lean solvent is extracted from the extraction lean oil outlet 23 and used as a circulating absorbent, wherein the content of dibutyl phthalate is 77%, and the content of diethyl tetrahydrophthalate is 19.74%.

[0080] In summary, in the process of recovering maleic anhydride from maleic anhydride reaction gas, the yield of maleic anhydride is 98.1%, the purity of maleic anhydride is 99.92%, and the circulation rate of the absorbent is 99.9%.

[0081] Embodiment three:

[0082] (1) The feed rate is 679678 kg / h, and the feed composition is the maleic anhydride reactor outlet mixed gas of 1.74% (wt) water, 1.57% carbon monoxide, 75.0% nitrogen, 15.79% oxygen, 3.85% carbon dioxide, 0.05% n-butane, and 1.95% maleic anhydride. It is cooled to 130°C by the reaction gas cooler E1 and enters the 22nd tray of the absorption tower T1 through the reactor outlet mixed gas feed port 4; the feed temperature is 58°C, and the feed rate is 60414 kg / h, the feed composition is 0.38% (wt) water, 0.1% maleic anhydride, 0.02% maleic acid, 0.06% fumaric acid, 0.2% phthalic anhydride, 99.0% dibutyl phthalate, and 0.2% tar. The lean solvent enters the first tower plate of the absorption tower T1 through the lean solvent feed port 2; the material output from the absorbent circulating cooler E2 after cooling is mixed with the material taken out from the tail gas recovery tower kettle material outlet 20, and then enters the 12th tower plate of the absorption tower T1 through the absorbent circulating cooling material feed port 3. The operating pressure of absorption tower T1 is 0.14MPa. Maleic anhydride and a small amount of impurities in absorption tower T1 are fully absorbed by the absorbent. The rich oil containing 16.9% maleic anhydride in the bottom of the tower is produced through the bottom material outlet 5 to the absorption tower circulation pump P1 at a flow rate of 350482 kg / h, and then divided into three streams and sent to the absorbent circulation cooler E2, the rich oil storage tank V1 and the post-flash tower circulation cooler E6 at flow rates of 260058 kg / h, 33457 kg / h and 56967 kg / h respectively; the waste gas with a maleic anhydride content of 0.001% discharged from the waste gas outlet 1 at the top of absorption tower T1 is sent out of the boundary area for incineration.

[0083] (2) The rich oil produced from the bottom material outlet 5 and entering the oil-rich storage tank V1 is mixed with the material produced from the side line outlet 15 of the post-flash tower and entering the oil-rich storage tank V1. The mixed material is then produced through the rich oil production pump of the oil-rich production outlet 26. The mixed material is then divided into two streams by three-way adjustment. One stream enters the desorption tower T2 at the 20th plate of the desorption tower T2 through the oil-rich feed inlet 9 of the desorption tower at a flow rate of 86078 kg / h for distillation. The operating pressure of the desorption tower T2 is 0.003 MPa, and the number of plates is 39. The light components are produced from the steam production outlet 6 at a flow rate of 11 kg / h after condensation at the top of the tower. The qualified maleic anhydride product production outlet 8 of the side line produces qualified maleic anhydride with a maleic anhydride content of 99.99% at a flow rate of 13100 kg / h at the 4th plate of the desorption tower T2. The bottom material production outlet 11 of the desorption tower produces maleic anhydride with a flow rate of 72967 The absorbent having a maleic anhydride content of 0.8% and a dibutyl phthalate content of 98.5% was produced at a flow rate of kg / h. At this time, the temperature of the absorbent produced from the bottom of the desorption tower T2 was 201°C.

[0084] (3) The material produced from the desorption tower bottom material outlet 11 is mixed with the material produced from the bottom lean oil outlet 16 of the post-flash tower T3 and then enters the post-flash tower preheater E5 to be preheated to 210°C and then enters the post-flash tower T3 for further desorption. The operating pressure of the post-flash tower T3 is 0.002MPa, the number of tower plates is 8, the gas phase outlet 12 at the top of the tower produces light components at a flow rate of 2062 kg / h, and the side line outlet 15 of the post-flash tower at the 6th tower plate produces an absorbent with a maleic anhydride content of 14.85% at a flow rate of 320,000 kg / h. After being adjusted by a three-way, it is divided into two streams, one of which has a flow rate of 231,360 kg / h and is cooled by the post-flash tower circulating cooling pump P3 and then mixed with the 92,986 kg / h of the absorption tower bottom circulating pump P1. kg / h of mixed liquid enters the post-flash tower circulation cooler E6, is cooled to 80°C in the post-flash tower circulation cooler E6, and then returns to the first tray of the post-flash tower T3; another stream with a flow rate of 88640 kg / h is produced from the side line of the post-flash tower to the rich oil feed port 25 and enters the rich oil storage tank V1. The lean oil production port 16 of the tower bottom produces a lean solvent with a dibutyl phthalate content of 99.0% at a flow rate of 201745 kg / h, which is divided into two streams by the three-way adjustment of the post-flash tower bottom pump P2, one of which enters the post-flash tower preheater E5 at a flow rate of 126494 kg / h, and the other enters the lean solvent cooler E7 at a flow rate of 75251 kg / h, and enters the lean oil storage tank V2 after being cooled by the lean solvent cooler E7.

[0085] (4) Fresh absorbent is replenished from the absorbent replenishment feed port 28 and enters the lean oil storage tank V2 at a flow rate of 52 kg / h. After being mixed with the input of the lean solvent cooler E7, it is divided into three streams by adjustment of the valve group. One stream enters the absorption tower T1 from the lean solvent feed port 2 at a flow rate of 22854 kg / h, one stream enters the tail gas recovery tower T4 from the tail gas recovery tower lean oil feed port 18 at a flow rate of 25050 kg / h, and one stream enters the extraction premixing tank V3 from the premixing tank lean oil feed port 30 at a flow rate of 27347 kg / h.

[0086] (5) The produced material from the steam outlet 6 at the top of the desorption tower T2 is mixed with the produced material from the gas phase outlet 12 at the top of the post-flash tower T3 and then enters the bottom of the tail gas recovery tower T4 through the gas phase feed inlet 19 of the tail gas recovery tower. The tail gas recovery tower T4 is equipped with 5 m structured packing. The maleic anhydride in the gas phase feed at the bottom of the tail gas recovery tower T4 is further absorbed by the dibutyl phthalate in the top feed. The tail gas recovery tower kettle material outlet 20 produces a solvent with a maleic anhydride content of 11.9% at a flow rate of 17065 kg / h; the waste gas outlet 17 at the top of the tower produces 58.6 kg / h of tail gas and sends it to the boundary area for incineration.

[0087] (6) The material input from the lean oil feed port 30 of the premixing tank and the 8000 kg / h desalted water input from the extractant feed port 31 are mixed in the extraction premixing tank V3 and then enter the centrifugal extractor SE1 for centrifugal separation. The extractant phase is extracted from the raffinate outlet 22, and 27346 kg / h of the treated lean solvent is extracted from the extraction lean oil outlet 23 and used as a circulating absorbent, wherein the content of dibutyl phthalate is 99.2%.

[0088] In summary, in the process of recovering maleic anhydride from maleic anhydride reaction gas, the yield of maleic anhydride is 98.9%, the purity of maleic anhydride is 99.99%, and the circulation rate of absorbent dibutyl phthalate is 99.91%.

[0089] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. An environmentally friendly device for efficiently recovering maleic anhydride from solvent, characterized in that: It includes an absorption tower T1, a desorption tower T2, a post-flash tower T3, a tail gas recovery tower T4, an extractor SE1, a reaction gas cooler E1, an absorbent circulating cooler E2, a desorption tower condenser E3, a desorption tower reboiler E4, a post-flash tower preheater E5, a post-flash tower circulating cooler E6, a lean solvent cooler E7, an absorption tower kettle circulating pump P1, a post-flash tower kettle pump P2, a post-flash tower circulating cooling pump P3, a rich oil storage tank V1, a lean oil storage tank V2 and an extraction premixing tank V3; The reaction gas cooler E1, absorbent circulating cooler E2, desorption tower condenser E3, desorption tower reboiler E4, post-flash tower preheater E5, post-flash tower circulating cooler E6, lean solvent cooler E7, absorber kettle circulating pump P1, post-flash tower kettle pump P2, post-flash tower circulating cooling pump P3 all include feed inlets and discharge ports; The absorption tower T1 is provided with an exhaust gas discharge port (1) at the top, a lean solvent feed port (2) at the upper right side, an absorbent circulating cooling material feed port (3) at the lower right side, a reactor outlet mixed gas feed port (4) at the left side, and a tower kettle material outlet (5) at the bottom; The desorption tower T2 is provided with a steam extraction port (6) at the top, a reflux port (7) at the upper right side, a qualified maleic anhydride product extraction port (8) at the upper left side, a desorption tower rich oil feed port (9) at the lower left side, a desorption tower kettle steam feed port (10) at the lower right side, and a desorption tower kettle material extraction port (11) at the bottom; The post-flash tower T3 is provided with a gas phase production port (12) at the top, a post-flash tower circulating cooling material feed port (13) at the upper right side, a post-flash tower feed port (14) at the left side, a post-flash tower side line production port (15) at the lower right side, and a tower bottom lean oil production port (16) at the bottom; The tail gas recovery tower T4 is provided with a waste gas extraction port (17) at the top, a tail gas recovery tower lean oil feed port (18) at the right, a tail gas recovery tower gas phase feed port (19) at the left, and a tail gas recovery tower kettle material extraction port (20) at the bottom; The extractor SE1 is provided with an extractor feed port (21) on the right side, a raffinate discharge port (22) on the left side, and an extracted lean oil discharge port (23) at the bottom; The oil-rich storage tank V1 is provided with an absorption tower kettle production oil-rich feed inlet (24) on the left side, a post-flash tower side line production oil-rich feed inlet (25) at the bottom, and an oil-rich production outlet (26) on the right side; The lean oil storage tank V2 is provided with a lean oil feed port (27) on the left side, an absorbent supplement feed port (28) on the top, and a lean oil discharge port (29) on the right side; The extraction premixing tank V3 is provided with a premixing tank lean oil feed port (30) on the upper left side, an extractant feed port (31) on the lower left side, and a mixed liquid discharge port (32) at the bottom; The lean solvent feed port (2) is connected to both the lean oil discharge port (29) and the extracted lean oil discharge port (23); the absorbent circulating cooling material feed port (3) is connected to both the discharge port of the absorbent circulating cooler E2 and the tail gas recovery tower bottom material outlet (20); the reactor outlet mixed gas feed port (4) is connected to the discharge port of the reaction gas cooler E1; the bottom material outlet (5) is connected to the feed port of the absorber circulating pump P1, and the discharge port of the absorber circulating pump P1 is connected to the feed port of the absorbent circulating cooler E2, the absorber bottom oil-rich feed port (24), and the feed port of the post-flash tower circulating cooler E6; The steam extraction port (6) is connected to the feed port of the desorption tower condenser E3; the desorption tower oil-rich feed port (9) is connected to the oil-rich extraction port (26); the desorption tower kettle steam feed port (10) is connected to the discharge port of the desorption tower reboiler E4; the desorption tower kettle material extraction port (11) is connected to the feed port of the desorption tower reboiler E4 and the feed port of the post-flash tower preheater E5; the discharge port of the desorption tower condenser E3 is connected to the reflux port (7) and the tail gas recovery tower gas phase feed port (19); The gas phase production port (12) is connected to the gas phase feed port (19) of the tail gas recovery tower; the post-flash tower circulating cooling material feed port (13) is connected to the discharge port of the post-flash tower circulating cooler E6; the post-flash tower feed port (14) is connected to the discharge port of the post-flash tower preheater E5; the post-flash tower side line production port (15) is connected to the feed port of the post-flash tower circulating cooling pump P3; the tower bottom lean oil production port (16) is connected to the feed port of the post-flash tower bottom pump P2; the discharge port of the post-flash tower bottom pump P2 is connected to the feed port of the post-flash tower preheater E5 and the feed port of the lean solvent cooler E7, and the discharge port of the post-flash tower circulating cooling pump P3 is connected to the feed port of the post-flash tower circulating cooler E6 and the post-flash tower side line production rich oil feed port (25); The lean oil feed port (18) of the tail gas recovery tower is connected to the lean oil discharge port (29); the extractor feed port (21) is connected to the mixed liquid discharge port (32); the lean oil feed port (27) is connected to the discharge port of the lean solvent cooler E7; the lean oil discharge port (29) is connected to the lean oil feed port (18) of the tail gas recovery tower, the lean solvent feed port (2) and the lean oil feed port (30) of the premixing tank.

2. The environmental protection device for recovering maleic anhydride with high-efficiency solvent as claimed in claim 1, characterized in that: The total number of plates of the absorption tower T1 is 9 to 40, and the number of plates is counted from top to bottom, wherein the absorbent circulation cooling material feed port (3) is located at 40% to 60% of the total number of plates of the absorption tower T1.

3. The environmental protection device for recovering maleic anhydride with high-efficiency solvent as claimed in claim 1, characterized in that: The total number of plates of the desorption tower T2 is 22 to 45, and the number of plates is counted from top to bottom, wherein the desorption tower oil-rich feed port (9) is located at 40% to 55% of the total number of plates of the desorption tower T2, and the qualified maleic anhydride product outlet (8) is located at 12% to 20% of the total number of plates of the desorption tower T2.

4. The environmental protection device for recovering maleic anhydride with high-efficiency solvent as claimed in claim 1, characterized in that: The post-flash tower T3 has 4 to 9 plates, with the plates counted from top to bottom. The side line production outlet (15) of the post-flash tower is located 1 to 2 plates upward from the bottom of the post-flash tower T3.

5. An environmentally friendly process for recovering maleic anhydride using an efficient solvent, characterized in that: The steps include: S1: The mixed gas at the outlet of the maleic anhydride reactor is cooled by the reaction gas cooler E1 and then enters the bottom of the absorption tower T1 through the mixed gas feed port (4) at the outlet of the reactor. The lean solvent enters the top of the absorption tower T1 through the lean solvent feed port (2). The absorbent circulating cooling material enters the middle and lower part of the absorption tower T1 through the absorbent circulating cooling material feed port (3). After being absorbed by the absorbent, the rich oil containing maleic anhydride in the bottom of the absorption tower T1 is extracted from the bottom material outlet (5) through the discharge port of the absorption tower bottom circulating pump P1. The extracted material of the absorption tower bottom circulating pump P1 is divided into three streams and respectively sent to the feed port of the absorbent circulating cooler E2, the extraction rich oil feed port (24) of the absorption tower bottom, and the feed port of the post-flash tower circulating cooler E6; the waste gas is discharged from the waste gas discharge port (1) at the top of the absorption tower T1; S2: The bottom oil-rich oil sent from the bottom material outlet (5) to the absorbent circulating cooler E2 is cooled by the absorbent circulating cooler E2, mixed with the produced material from the bottom material outlet (20) of the tail gas recovery tower in the pipeline, and then enters the middle and lower part of the absorption tower T1 through the absorbent circulating cooling material feed port (3); S3: The bottom material outlet (5) is sent to the bottom oil of the absorber bottom production rich oil feed port (24), and after being mixed with the material produced from the post-flash tower side line production port (15) in the oil-rich storage tank V1, it is produced from the oil-rich production port (26). The production from the oil-rich production port (26) is divided into two streams of materials and pumped into the desorption tower oil-rich feed port (9) and the post-flash tower circulating cooler E6 respectively; after rectification in the desorption tower T2, the light components are produced from the steam production port (6) at the top of the tower, and part of the production from the steam production port (6) is condensed in the desorption tower condenser E3 and then enters the desorption tower T2 through the reflux port (7), and the other part enters the tail gas recovery tower T4 through the tail gas recovery tower gas phase feed port (19); the qualified maleic anhydride product production port (8) of the side line of the desorption tower T2 produces qualified maleic anhydride, and the absorbent is produced from the bottom material production port (11) of the desorption tower; S4: a part of the absorbent extracted from the desorption tower bottom material extraction port (11) is preheated by the post-flash tower preheater E5 and then enters the post-flash tower T3 through the post-flash tower feed port (14) for further desorption, and the other part is reboiled by the desorption tower reboiler E4 and then enters the desorption tower T2 through the desorption tower bottom steam feed port (10); the light component is extracted from the gas phase extraction port (12) at the top of the post-flash tower T3, and the absorbent is extracted from the side line extraction port (15) of the post-flash tower. The absorbent extracted from the side line extraction port (15) of the post-flash tower is mixed with the bottom rich oil extracted from the bottom material outlet (5) and the rich oil extracted from the rich oil storage tank V1, and then cooled by the post-flash tower circulating cooler E6, and then enters the top of the post-flash tower T3 as a liquid phase reflux through the post-flash tower circulating cooling material feed port (13), and the lean solvent is extracted from the bottom lean oil extraction port (16); S5: The light components extracted from the steam extraction port (6) and the gas phase extraction port (12) are mixed and then enter the bottom of the tail gas recovery tower T4 through the tail gas recovery tower gas phase feed port (19); the lean solvent extracted from the bottom lean oil extraction port (16) is cooled by the lean solvent cooler E7, partially extracted from the lean oil storage tank V2, and then enters the top of the tail gas recovery tower T4 through the tail gas recovery tower lean oil feed port (18); in the tail gas recovery tower T4, the material is extracted from the tail gas recovery tower bottom material extraction port (20), and the tail gas is extracted from the waste gas extraction port (17) at the top of the tower; S6: a part of the lean oil produced from the bottom lean oil production port (16) of the post-flash tower T3 is returned to the post-flash tower preheater E5 to preheat the feed, and the other part is cooled by the lean solvent cooler E7 and then sent to the lean oil feed port (27) of the lean oil storage tank V2; a part of the absorbent produced from the side line production port (15) of the post-flash tower enters the post-flash tower circulating cooler E6 for cooling and then returns to the post-flash tower T3 through the post-flash tower circulating cooling material feed port (13), and the other part enters the rich oil storage tank V1 through the post-flash tower side line production rich oil feed port (25); S7: The material at the outlet of the lean oil discharge port (29) of the lean oil storage tank V2 is divided into three streams of materials and respectively enters the lean solvent feed port (2) of the absorption tower T1, the lean oil feed port (18) of the tail gas recovery tower and the lean oil feed port (30) of the extraction premixing tank V3; after being mixed with the fresh extractant entering from the extraction premixing tank V3 and the extractant feed port (31), the mixed liquid is taken out from the mixed liquid discharge port (32) and then enters the centrifugal extractor SE1 through the extractor feed port (21), and centrifugal separation is performed in the centrifugal extractor SE1. The extractant phase is taken out from the upper part of the centrifugal extractor SE1 and taken out from the raffinate discharge port (22), and the lean solvent is taken out from the lower part through the extraction lean oil discharge port (23).

6. The environmentally friendly process for recovering maleic anhydride using an efficient solvent as claimed in claim 5, characterized in that: The absorption tower T1 is operated at normal pressure or pressurized, the temperature of the bottom rich oil extracted from the absorption tower T1 and entering the oil-rich storage tank V1 is not lower than 94°C, and the content of maleic anhydride in the bottom rich oil entering the oil-rich storage tank V1 is not higher than 18.9% (wt).

7. The environmentally friendly process for recovering maleic anhydride using an efficient solvent as claimed in claim 5, characterized in that: The bottom oil-rich material outputted from the bottom material outlet (5) of the absorption tower T1 is divided into three streams and respectively sent to the absorbent circulating cooler E2, the rich oil storage tank V1 and the post-flash tower circulating cooler E6, and the distribution ratio thereof is 0.6:0.15:0.25-0.8:0.05:0.

15.

8. The environmentally friendly process for recovering maleic anhydride using an efficient solvent as claimed in claim 5, characterized in that: The material produced from the oil-rich production port (26) is pumped into the desorption tower oil-rich feed port (9) and the post-flash tower circulating cooler E6 respectively, and the distribution ratio is 0.4:0.6~0.8:0.

2.

9. The environmentally friendly process for recovering maleic anhydride using an efficient solvent as claimed in claim 5, characterized in that: The materials produced from the lean oil production outlet (16) of the bottom of the post-flash tower T3 are respectively produced to the post-flash tower preheater E5 and the lean oil storage tank V2, and the distribution ratio thereof is 0.57:0.43~0.73:0.

27.

10. The environmentally friendly process for recovering maleic anhydride using an efficient solvent as claimed in claim 5, characterized in that: The material produced from the side line production outlet (15) of the post-flash tower is produced to the post-flash tower circulating cooler E6 and the oil-rich storage tank V1 respectively, and the distribution ratio thereof is 0.65:0.35-0.75:0.

25.

11. The environmentally friendly process for recovering maleic anhydride using an efficient solvent as claimed in claim 5, characterized in that: The materials extracted from the lean oil outlet (29) of the lean oil storage tank V1 are respectively extracted to the absorption tower T1, the tail gas recovery tower T4 and the extraction premixing tank V3, and the distribution ratio thereof is 0.1:0.2:0.7-0.35:0.2:0.

45.

12. The environmentally friendly process for recovering maleic anhydride using an efficient solvent as claimed in claim 5, characterized in that: The desorption tower T2 and the post-flash tower T3 are operated under reduced pressure, and the operating pressure is -0.001MPa to -0.010MPa, and the operating pressure of the post-flash tower T3 is lower than the operating pressure of the desorption tower T2. The desorption tower T2 is provided with a three-stage steam ejector, and the bottom temperatures of the desorption tower T2 and the post-flash tower T3 are not higher than 205°C.

13. The environmentally friendly process for recovering maleic anhydride using an efficient solvent as claimed in claim 5, characterized in that: The absorbent is selected from one of dimethyl phthalate, diethyl phthalate, dipropyl phthalate, diisopropyl phthalate, dibutyl phthalate, diisobutyl phthalate, hexahydrophthalate, diethyl tetrahydrophthalate, or a mixture of two or more thereof.

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