Device and process for efficiently recovering n-butane to produce maleic anhydride

Abstract

The invention discloses a device and a process for efficiently recovering n-butane to produce maleic anhydride. According to the production device, after a humidifier, a condenser and a gas-liquid separator are arranged on a tail gas pipeline to complete deacidification, CO is adsorbed by an adsorption device to prevent the CO from forming a solid eutectic or an inclusion compound with n-butane under a cryogenic condition; according to the method, N-butane is used as a raw material, and N2 is separated through cryogenic liquefaction at-30 to-10 DEG C, so that efficient recovery of the N-butane for circulating feeding can be realized, the impurity content in the recovered N-butane is low, the influence on normal reaction is reduced, meanwhile, the defects of raw material waste and environmental protection pressure in the prior art are overcome, normal production of maleic anhydride is ensured, and cost reduction and efficiency improvement are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of maleic anhydride preparation, and particularly to a device and process for efficiently recovering n-butane to produce maleic anhydride. BACKGROUND

[0002] Maleic anhydride, also known as maleic anhydride, is an important and commonly used organic chemical raw material. Maleic anhydride is very active in chemical properties due to the presence of conjugated maleic acid group, and can be derived into a large number of downstream products through various chemical reactions, and is widely used in plastic, paint, paint, ink, engineering plastic, medicine, pesticide, food, feed, oil additive, papermaking, textile and other industries.

[0003] The existing maleic anhydride device using n-butane oxidation process uses n-butane mixed with air for oxidation to produce maleic anhydride. The conversion rate of n-butane in the reactor is about 85%, and 15% of n-butane does not participate in the reaction. Most devices directly burn the unreacted n-butane with tail gas into a incinerator after the reaction gas is absorbed by the absorption tower to absorb the maleic anhydride, which not only causes a large amount of waste of n-butane, but also increases the tail gas emission of the device.

[0004] However, the current n-butane oxidation catalytic preparation of maleic anhydride contains a small amount of acidic products or by-products, carbon dioxide and nitrogen entering the reaction with air in the tail gas in addition to a large amount of n-butane, which is not conducive to the efficient recovery of n-butane. The yield of n-butane recovered by the existing technology is less than 60%, and the purity is only 90-92%, which still has a lot of gap for improving the recovery efficiency and maintaining normal n-butane catalytic oxidation reaction during recycling.

[0005] Therefore, it is necessary to design a device and process for efficiently recovering n-butane to produce maleic anhydride, to realize the efficient recovery and recycling of n-butane, and to solve the defects of raw material waste and environmental pressure in the prior art. SUMMARY

[0006] The present application aims to provide a device and process for efficiently recovering n-butane to produce maleic anhydride, which solves the defects of raw material waste and environmental pressure in the prior art by recycling and recycling n-butane.

[0007] To achieve the above-mentioned purpose, the scheme of the present application is as follows: The first object of the present application is to improve a device for efficiently recovering n-butane to produce maleic anhydride, which comprises a dosing unit, an oxidation reactor and a post-treatment unit connected in sequence, wherein the post-treatment unit is used for separating maleic anhydride and tail gas; a humidifier I, a condenser I and a gas-liquid separator I are connected in sequence at the tail gas output end of the post-treatment unit; a gas output end of the gas-liquid separator I is connected in sequence with an adsorption device, a condenser II and a gas-liquid separator II, and a liquid discharge end of the gas-liquid separator II is connected to the dosing unit; the adsorption device is used for adsorbing CO; and the condenser II is used for condensing n-butane into liquid.

[0008] Further, the adsorption device is provided with a plurality of and is arranged in parallel; and / or, the adsorption device is filled with a CO adsorbent, which is a cuprous chloride supported adsorbent.

[0009] Further, the humidifier I is filled with a volatile alkaline liquid, preferably low-concentration ammonia water, and more preferably ammonia water with a concentration of 1-5wt%.

[0010] Further, the dosing unit comprises an air compressor, a steam generator and a butane vaporizer, which are respectively connected to a mixer, and the mixer is connected to the oxidation reactor.

[0011] Preferably, a detector I is arranged between the dosing unit and the oxidation reactor.

[0012] Preferably, a heater I is connected to an output end of the air compressor; a humidifier II is connected to an output end of the steam generator; an output end of the heater I is connected to the humidifier II, and an output end of the humidifier II is connected to the mixer.

[0013] Further, a detector II is arranged at an output end of the gas-liquid separator II, which is used for detecting the amount of recovered n-butane and analyzing impurities.

[0014] Further, the post-treatment unit comprises an absorption tower, a stripping tower and a distillation tower connected in sequence; the oxidation reactor is connected to a lower part of the absorption tower; a bottom part of the absorption tower is connected to an upper part of the stripping tower, a lower part of the stripping tower is connected to a lower part of the distillation tower, and a product maleic anhydride is taken out from the lower part of the distillation tower; and the absorption tower and the stripping tower are respectively connected to the humidifier I.

[0015] Preferably, a condenser III is arranged between the oxidation reactor and the absorption tower.

[0016] The second object of the present application is to improve a process for efficiently recovering n-butane to produce maleic anhydride, which comprises the following steps: post-treating the catalytic oxidation product of n-butane to obtain maleic anhydride and tail gas; recovering n-butane in the tail gas, and continuing to use the recovered n-butane for reaction; The n-butane recovery process comprises the steps of sequentially performing lye washing on the tail gas, CO adsorption, and deep condensation separation of n-butane on the adsorbed gas.

[0017] Preferably, the deep condensation operation temperature is -30~-10℃.

[0018] Preferably, the top of the absorption tower and the stripping tower is respectively communicated to a incinerator.

[0019] Preferably, the desorption output end of the adsorption device is communicated to a incinerator.

[0020] Compared with the prior art, the beneficial effects of the present application are: The production device of the present application can realize high-efficiency recovery of n-butane for recycling by setting a humidifier, a condenser and a gas-liquid separator on the tail gas pipeline to prevent the formation of solid-state eutectic or inclusion of n-butane and CO under cryogenic conditions after deacidification, and by separating N2 through deep condensation, and can realize low content of impurities (N2, CO, CO2, etc.) in the recovered n-butane, reduce the influence on normal reaction, solve the defects of waste of raw materials and environmental pressure in the prior art, ensure normal production of maleic anhydride, and realize cost reduction and efficiency increase. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A high-efficiency n-butane recovery device for producing maleic anhydride is provided.

[0022] The reference signs are: AC1, air compressor; AT1, absorption tower; C1, condenser one; C2, condenser two; C3, condenser three; D1, detector one; D2, detector two; DT1, distillation tower; E1, heater one; E2, vaporizer; E3, heater two; H1, humidifier one; H2, humidifier two; LS1, gas-liquid separator one; LS2, gas-liquid separator two; M1, mixer; GA1, adsorption device; R1, oxidation reactor; S1, stripping tower; SG1, steam generator. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0024] It should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", and the like, indicate an orientation or positional relationship based on the orientation or positional relationship as shown in the drawings, and are used only to facilitate the description of the present application and simplify the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0025] It should also be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing", "setting" and the like should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two components or the interaction relationship between two components. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0026] In one embodiment, as shown in Figure 1 A device for efficiently recovering n-butane to produce maleic anhydride is provided, which includes a dosing unit, an oxidation reactor R1 and a post-treatment unit connected in sequence, the post-treatment unit is used for separating maleic anhydride and tail gas; the tail gas output end of the post-treatment unit is sequentially connected with a humidifier H1, a condenser C1 and a gas-liquid separator LS1; the gas output end of the gas-liquid separator LS1 is sequentially connected with an adsorption device GA1, a condenser C2 and a gas-liquid separator LS2, and the liquid discharge end of the gas-liquid separator LS2 is connected to the dosing unit; the adsorption device GA1 is used for adsorbing CO; the condenser C2 is used for deeply condensing n-butane into liquid.

[0027] In the above embodiment, by providing a humidifier H1 on the tail gas pipeline, a small amount of acrylic acid, acetic acid and maleic anhydride present in the tail gas can be dissolved in advance, and then condensed by the condenser C1, separated by the gas-liquid separator LS1, and the CO is adsorbed by the adsorption device to improve the purity of the n-butane in the tail gas, and then separated by deep condensation to realize the efficient recovery of n-butane for recycling. The impurities (N2, CO, CO2, etc.) in the recovered n-butane reduce the influence on the normal reaction, and at the same time solve the defects of waste of raw materials and environmental pressure in the prior art.

[0028] In a preferred embodiment, the humidifier one is filled with a volatile alkaline liquid, such as low concentration (1-5wt%) ammonia water, which can efficiently react with acidic substances and efficiently capture CO2 gas.

[0029] It can be understood that, in addition to the acidic impurities, the gas components contained in the tail gas, such as N2, CO, CO2, etc., will affect the conversion rate of n-butane to maleic anhydride in the oxidation catalysis, and avoiding a large amount of enrichment will affect the reaction conversion rate. Although it is relatively easy to remove each component independently, the sequence of setting different impurity removal units has different effects on the quality of n-butane recovery. In the present scheme, the physicochemical properties of n-butane are fully considered, and its low boiling point characteristics can be used to condense it into a liquid state to separate it from other gases. However, CO2 and other gases have solubility in n-butane, and the removal of CO generally involves copper metal compounds. These defects have to consider the impact of impurity removal sequence on the purity and recovery rate of n-butane recovery. In the present scheme, a small amount of acidic impurities such as acrylic acid, acetic acid, maleic anhydride and CO2 gas are removed first, water is removed by condensation, and then enters the CO adsorption device, reducing the impact on the adsorbent. The gas components in the gas will not affect the adsorption of the adsorbent, and CO can be selectively adsorbed.

[0030] In addition, when the CO-containing hydrocarbon mixture is deep-cooled below -25℃, the solubility of CO decreases sharply, and when the concentration is >500ppm, microcrystals may be precipitated, leading to fouling of the heat exchanger (Deep Cooling Technology), the specific reasons are as follows: The boiling point of CO is -191.5℃ (atmospheric pressure), and the boiling point of n-butane at atmospheric pressure is -0.5℃. When the mixed gas is cooled to the n-butane condensation temperature (such as -30℃), CO is still in a gaseous state, but it will interact with liquid n-butane as follows: ① Forming clathrate hydrate: If there is a small amount of water in the system, CO molecules may be wrapped in the crystal lattice formed by n-butane-water to generate a solid inclusion compound; ② Eutectic formation: CO and n-butane may form a eutectic mixture at low temperatures, and a solid phase is precipitated near -30℃.

[0031] Therefore, in the above embodiments, the sequence of setting each unit in the post-processing unit fully considers the mutual influence of the physicochemical properties of the impurity components on the previous and subsequent processes. By removing a small amount of acidic impurities such as acrylic acid, acetic acid, maleic anhydride and CO2 gas first, removing water by condensation, and then entering the CO adsorption device, the impact on the adsorbent is reduced, and the solidification problem caused by CO in the deep cooling link is avoided. It has a significant synergistic effect on improving the recovery rate and purity of n-butane, and is not simply added up by each unit, so it is beyond the labor scope of the person skilled in the art.

[0032] In the preferred embodiment, the adsorption device GA1 is provided with several and arranged in parallel, which can realize switching use; the adsorption device GA1 is a common isobaric adsorption device, filled with CO adsorbent, such as CuCl supported adsorbent, preferably the adsorbent is PU-1 type (CuCl is loaded on γ-Al2O3, specific surface area ≥ 300 m 2 / g), which can reduce the CO concentration from 1.2% to <50 ppm, which can effectively avoid the risk of affecting the working efficiency of the heat exchanger caused by the solidification of the n-butane deep cooling link.

[0033] In the preferred embodiment, the batching unit includes an air compressor AC1, a steam generator SG1 and a butane vaporizer, which are respectively communicated with a mixer M1, and the mixer M1 is communicated to an oxidation reactor R1. A detector D1 is arranged between the mixer M1 and the oxidation reactor R1, which detects the content of butane and water online to ensure that the feed ratio meets the requirement of high reaction conversion rate.

[0034] In the preferred embodiment, the output end of the air compressor AC1 is communicated with a heater E1; the output end of the steam generator SG1 is communicated with a humidifier H2; the output end of the heater E1 is communicated with the humidifier H2, and the output end of the humidifier H2 is communicated with the mixer M1. The butane vaporizer includes a vaporizer E2 and a heater E3 communicated therewith, the vaporizer E2 is used for vaporizing liquid n-butane, and the heater E3 is used for preheating the n-butane before entering the mixer M1.

[0035] In the preferred embodiment, the liquid discharge end of the gas-liquid separator LS2 is provided with a detector D2 for impurity analysis and flow monitoring of the treated n-butane, which can be combined to control the new feed to meet the raw material ratio requirement of the catalytic oxidation reaction, and stabilize the reaction conversion rate.

[0036] In the above embodiment, the oxidation reactor R1 is filled with a common catalyst, such as a common VPO catalyst. The detector D1 is provided with a n-butane and water content detection probe, such as a TD500S-C4H10 online butane detector probe. The feed ratio control of water and n-butane can be realized by respectively setting the feed valves at the steam generator SG1 and the butane vaporizer and interlocking with the above-mentioned probes.

[0037] In the preferred embodiment, the post-processing unit comprises the communicating absorption tower AT1, stripping tower S1 and distillation tower DT1; the oxidation reactor R1 is communicated to the lower part of the absorption tower AT1; the bottom of the absorption tower AT1 is communicated to the upper part of the stripping tower S1, the lower part of the stripping tower S1 is communicated to the lower part of the distillation tower DT1, and the upper part of the distillation tower DT1 is used to extract the product maleic anhydride; the top of the absorption tower AT1 and the stripping tower S1 are respectively communicated to the humidifier H1. The absorption tower AT1 absorbs the product obtained by the oxidation reaction by solvent method, the absorption product enters the stripping tower S1 to remove the light components, and then enters the distillation tower DT1 to remove the solvent to obtain the target product maleic anhydride.

[0038] In the preferred embodiment, since the temperature of the oxidation reaction process is high, the product needs to be cooled, so a condenser three C3 is arranged between the oxidation reactor R1 and the absorption tower AT1.

[0039] In the preferred embodiment, the desorption output end of the adsorption device GA1 is communicated to the incinerator, and the CO generated by heating and desorption of the filler is incinerated. The desorption of the adsorption device GA1 uses 200°C nitrogen blowing, and the desorption gas is sent to the incinerator.

[0040] It can be understood that the production device also comprises other instruments, meters or valves arranged on each unit or pipeline. The instruments and meters are used to monitor the state parameters of the materials or unit devices, the valves are used to control the start and stop or flow of the materials, the power pump is used to provide the motion power of the materials, and the like, which all belong to the design range of the present scheme and will not be repeated here.

[0041] In another embodiment, a process for producing maleic anhydride by using the above device is provided, and the steps comprise: S1. In the batching unit, after the raw materials are premixed in the mixer M1 from the air compressor AC1, the steam generator SG1 and the butane vaporizer, after the detection instrument one D1 detects that the content of each component is qualified, the raw materials enter the oxidation reactor R1 to generate maleic anhydride under the action of the VPO catalyst; the chemical reaction formula involved in the reaction process is as follows: Main reaction: C4H 10 +7 / 2O2→C4H2O3+4H2O; Side reaction: C4H 10 +5O2→3CO+CO2+5H2O; In addition, a small amount of impurities such as acrylic acid and acetic acid will also be produced; S2. After the reaction product is condensed in the condenser three C3, it enters the absorption tower AT1, and the product maleic anhydride is absorbed by the solvent absorption method, the absorption liquid enters the stripping tower S1 to remove the low-boiling light components, and then enters the distillation tower DT1 to remove the solvent to obtain the target product maleic anhydride; S3. The insoluble substances overflowing from the top of the absorption tower AT1 and the light components discharged from the stripping tower S1 are collected and then enter the tail gas treatment section. First, they pass through the humidifier H1 containing ammonia water for humidification treatment to produce microdroplets to dissolve soluble impurities, and then enter the condenser C1 for condensation. Subsequently, the gas and liquid are separated in the gas-liquid separator LS1, and then the gas enters the adsorption device GA1 for isobaric adsorption of CO. Then, the gas is further condensed to below the boiling point of n-butane in the condenser C2. After condensation, the liquid enters the gas-liquid separator LS2 to remove the gas phase (N2), and then the obtained liquid phase is detected by the detector D2 to obtain high-purity recovered n-butane. S4. The recovered n-butane is connected to the dosing unit through a pipeline to form a supply of n-butane. At this time, the output of n-butane from the butane vaporizer is adjusted so that the content of n-butane, water, and other components detected by the detector D1 is maintained within a normal range. The n-butane can then be recycled to provide raw materials to the oxidation reactor R1 and maintain a high reaction conversion rate of maleic anhydride.

[0042] In the above embodiment, the oxidation reaction temperature is 390-430℃. Under this reaction condition, the reaction conversion rate is 85% when the n-butane is not recycled, and the reaction conversion rate remains unchanged after the n-butane is recycled.

[0043] In a preferred embodiment, the condensation temperature of the condenser C2 is -10 to -30℃. Under this operating temperature, the n-butane recovery rate is >95%, the purity is ≥99.2%, the N2 content in the recovered liquid n-butane is ≤0.5%, the inlet oxygen concentration of the oxidation reactor R1 is stable at 12-14% after recycling, and the explosion risk is reduced by 30%. Through the pre-adsorption step of CO, the CO concentration in the tail gas is reduced to below 50 ppm before deep condensation, completely avoiding the risk of eutectic solid formation of CO and n-butane at a low temperature of -30℃, and ensuring that the continuous operation period of the device is extended to more than 12 months.

[0044] In the above embodiment, the process is calculated based on an n-butane feed rate of 17 t / h and an annual production of 8000 h. The average annual savings of butane are 9000 t, and the economic benefits are obvious.

[0045] In a comparative working condition, when the condensation temperature of the condenser C2 is >0℃ in the above embodiment, the recovery rate of n-butane is <60%, which is not conducive to the efficient recovery of n-butane.

[0046] In another working condition, when the adsorption device GA1 is not used for isobaric adsorption of CO in the above embodiment, the solid phase wraps the n-butane, causing the recovery rate to decrease from 95% to below 60%, the condenser C2 is frequently scaled, the equipment maintenance cost increases dramatically, and the device needs to be frequently stopped for descaling, resulting in a loss of production capacity of 800 hours per year.

[0047] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A device for efficiently recovering n-butane to produce maleic anhydride, characterized in that: The invention comprises a batching unit, an oxidation reactor (R1) and a post-processing unit which are connected in sequence, wherein the post-processing unit is used to separate maleic anhydride and tail gas; the tail gas output end of the post-processing unit is connected in sequence to a humidifier 1 (H1), a condenser 1 (C1) and a gas-liquid separator 1 (LS1); the gas output end of the gas-liquid separator 1 (LS1) is connected in sequence to an adsorption device (GA1), a condenser 2 (C2) and a gas-liquid separator 2 (LS2); the liquid discharge end of the gas-liquid separator 2 (LS2) is connected to the batching unit; the adsorption device (GA1) is used to adsorb CO; and the condenser 2 (C2) is used to condense n-butane into liquid.

2. The maleic anhydride production device according to claim 1, characterized in that The adsorption devices (GA1) are provided in plurality and are arranged in parallel; And / or, the adsorption device (GA1) is filled with a CO adsorbent, and the CO adsorbent is a cuprous chloride-supported adsorbent.

3. The maleic anhydride production device according to claim 1, characterized in that The humidifier 1 (H1) is filled with ammonia water with a concentration of 1-5 wt%.

4. The maleic anhydride production device according to claim 1, characterized in that The batching unit comprises an air compressor (AC1), a steam generator (SG1) and a butane vaporizer, which are respectively connected to a mixer (M1), and the mixer (M1) is connected to an oxidation reactor (R1).

5. The maleic anhydride production device according to claim 4, characterized in that A detector 1 (D1) is provided between the dosing unit and the oxidation reactor (R1).

6. The maleic anhydride production device according to claim 4, characterized in that The output end of the air compressor (AC1) is connected to heater 1 (E1); the output end of the steam generator (SG1) is connected to humidifier 2 (H2); the output end of heater 1 (E1) is connected to humidifier 2 (H2), and the output end of humidifier 2 (H2) is connected to the mixer (M1).

7. The maleic anhydride production device according to claim 1, characterized in that The output end of the gas-liquid separator 2 (LS2) is provided with a detector 2 (D2).

8. The maleic anhydride production device according to claim 1, characterized in that The post-processing unit includes an absorption tower (AT1), a stripping tower (S1) and a distillation tower (DT1) that are connected to each other; the oxidation reactor (R1) is connected to the lower part of the absorption tower (AT1); the bottom of the absorption tower (AT1) is connected to the upper part of the stripping tower (S1), the lower part of the stripping tower (S1) is connected to the lower part of the distillation tower (DT1), and the product maleic anhydride is extracted from the lower part of the distillation tower (DT1); the tops of the absorption tower (AT1) and the stripping tower (S1) are respectively connected to a humidifier (H1).

9. The maleic anhydride production device according to claim 8, characterized in that A condenser three (C3) is provided between the oxidation reactor (R1) and the absorption tower (AT1).

10. A process for efficiently recovering n-butane to produce maleic anhydride, characterized in that the steps include: Post-processing the product of catalytic oxidation of n-butane to obtain maleic anhydride and tail gas; Recover n-butane from the tail gas and use the recovered n-butane for further reaction; The n-butane recovery process includes the steps of sequentially performing alkali liquid humidification treatment on the tail gas, CO adsorption, and deep condensation of the adsorbed gas to separate the n-butane.

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