Device for preparing low-oxygen mild reaction of gas-phase industrial naphthalene

Abstract

This utility model provides a gas-phase industrial naphthalene preparation apparatus using a low-oxygen, mild reaction, including a reactor. The reactor has an input end and an output end. The output end of the reactor is connected to an exhaust mechanism, and the input end is connected to an inlet mechanism. The gas discharge end of the exhaust mechanism is connected to a return distribution pipe, and the end of the return distribution pipe away from the exhaust mechanism is connected to the inlet mechanism to transport part of the exhaust gas discharged by the exhaust mechanism to the inlet mechanism for supplying into the reactor. A feeding device is connected to the inlet mechanism, and a first control valve for controlling the gas flow rate is installed on the return distribution pipe. This technical solution uses the return distribution pipe and the first control valve to return the discharged purified gas to the reactor. The first control valve controls the amount of purified gas used to reduce the oxygen content, indirectly controlling the oxygen content entering the reactor, thereby controlling the intensity of the reaction between the raw materials and oxygen and increasing the product yield.

Description

Technical Field

[0001] This utility model belongs to the field of chemical equipment technology, and in particular relates to a gas-phase industrial naphthalene low-oxygen mild reaction preparation device. Background Technology

[0002] The raw materials for producing phthalic anhydride (hereinafter referred to as "phthalic anhydride") are industrial naphthalene or o-xylene. The raw materials react with oxygen in the air under the action of a catalyst. The reaction gas is condensed to produce crude phthalic anhydride. The crude phthalic anhydride is refined to produce the finished phthalic anhydride. The non-condensable gas is treated by environmental protection facilities before being discharged.

[0003] Existing phthalic anhydride preparation devices utilize the reaction of raw materials with excess oxygen in the air. However, the reaction process generates a large amount of heat. To protect the catalyst temperature (hot spot) from exceeding the specified temperature, the only solution is to reduce the raw material load and decrease the reaction intensity. Utility Model Content

[0004] In view of the above-mentioned problems existing in the prior art, the purpose of this utility model embodiment is to provide a gas-phase industrial naphthalene low-oxygen mild reaction preparation device.

[0005] The technical solution adopted in this embodiment of the utility model is a gas-phase industrial naphthalene low-oxygen mild reaction preparation device, including a reactor. The reactor has an input end and an output end. The output end of the reactor is connected to an exhaust mechanism, and the input end of the reactor is connected to an inlet mechanism. The gas discharge end of the exhaust mechanism is connected to a return pipeline. The end of the return pipeline away from the exhaust mechanism is connected to the inlet mechanism to transport part of the exhaust gas discharged by the exhaust mechanism to the inlet mechanism for supplying into the reactor. A feeding device is connected to the inlet mechanism, and a first control valve for controlling the gas flow rate is installed on the return pipeline.

[0006] Furthermore, the reactor is provided with several tubes, and the catalyst is placed in the tubes.

[0007] Furthermore, multiple thermometers are vertically installed inside the tube, which are used to detect the catalyst temperature at different heights inside the tube.

[0008] Furthermore, the catalyst within the tube is divided into several layers.

[0009] Furthermore, the air intake mechanism includes an air supply pipe, the input end of which is connected to the output end of the return distribution pipe, and the input end of the air supply pipe is also connected to an air input pipe. A second control valve for controlling the air flow is installed on the return distribution pipe and the air input pipe, and the output end of the feeding device is connected to the air supply pipe.

[0010] Furthermore, a gas filter, a blower, a gas heater, and a vaporizer are sequentially arranged along the gas delivery direction on the gas pipeline, and the output end of the feeding device is connected to the gas pipeline between the gas heater and the vaporizer.

[0011] Furthermore, a gas flow meter and an oxygen concentration detector are also installed on the gas pipeline.

[0012] Furthermore, the feeding device includes a naphthalene tank and a feed pump, wherein the feed pump transports the raw material in the naphthalene tank to the gas inlet mechanism for mixing with gas.

[0013] Furthermore, the exhaust mechanism includes an exhaust pipe, the input end of which is connected to the output end of the reactor, and the input end of the recirculation pipe is connected to the output end of the exhaust pipe. A gas cooler and a switching condenser are sequentially installed on the exhaust pipe along the gas output direction. The switching condenser condenses and separates phthalic anhydride from the gas and discharges it.

[0014] Furthermore, the exhaust pipe is also equipped with an exhaust gas purification device, which is located behind the switching condenser so that uncondensed exhaust gas flows through the exhaust gas purification device.

[0015] Compared with existing technologies, the gas-phase industrial naphthalene low-oxygen mild reaction preparation device proposed in this technical solution uses a return pipeline and a first control valve to return the discharged purified gas to the reactor. The first control valve controls the amount of purified gas used to reduce the oxygen content, thereby indirectly controlling the oxygen content entering the reactor, and thus controlling the intensity of the reaction between the raw materials and oxygen, so as not to cause the hot spot to be too high. At the same time, it increases the load on the raw materials and increases the product yield.

[0016] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and are not intended to limit the present invention.

[0017] The overview of various implementations or examples of the technology described in this utility model is not a complete disclosure of the full scope or all features of the disclosed technology. Attached Figure Description

[0018] In drawings that are not necessarily drawn to scale, the same reference numerals may describe similar parts in different views. The same reference numerals with or without letter suffixes may indicate different instances of similar parts. The drawings generally illustrate various embodiments by way of example rather than limitation and, together with the description and claims, serve to explain embodiments of the utility model. Where appropriate, the same reference numerals are used in all drawings to refer to the same or similar parts. Such embodiments are illustrative and not intended to be exhaustive or exclusive embodiments of the apparatus or method.

[0019] Figure 1 This is a structural schematic diagram of an embodiment of the present utility model.

[0020] Figure 2 This is a schematic diagram of the tube structure according to an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the described embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0022] Unless otherwise defined, the technical or scientific terms used in this utility model shall have the ordinary meaning understood by one of ordinary skill in the art to which this utility model pertains. The terms "first," "second," and similar terms used in this utility model do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0023] To keep the following description of the embodiments of this utility model clear and concise, detailed descriptions of known functions and known components are omitted.

[0024] See Figures 1 to 2This utility model provides a gas-phase industrial naphthalene low-oxygen mild reaction preparation device, including a reactor 1. The reactor 1 has an input end and an output end. The output end of the reactor 1 is connected to an exhaust mechanism, and the input end of the reactor 1 is connected to an inlet mechanism. The gas discharge end of the exhaust mechanism is connected to a return distribution pipe 2. The end of the return distribution pipe 2 away from the exhaust mechanism is connected to the inlet mechanism to transport part of the exhaust gas discharged by the exhaust mechanism to the inlet mechanism for supplying into the reactor 1. A feeding device is connected to the inlet mechanism, and a first control valve 21 for controlling the gas flow rate is installed on the return distribution pipe 2. This technical solution returns the discharged purified gas to the reactor 1 through the return distribution pipe 2 and the first control valve 21. The first control valve 21 controls the amount of purified gas used to reduce the oxygen content, indirectly controlling the oxygen content entering the reactor 1, thereby controlling the intensity of the reaction between the raw material and oxygen, preventing excessively high hot spots, and increasing the load on the raw material to increase the product yield.

[0025] In some embodiments, the reactor 1 is provided with a plurality of tubes 11, and the catalyst is placed in the tubes 11.

[0026] In some embodiments, a multi-point thermometer 12 is also vertically disposed within the tube 11 to detect the catalyst temperature at different heights within the tube 11. The catalyst within the tube 11 is divided into several layers. Under normal circumstances, lower hot spot temperatures improve catalyst performance and extend catalyst lifetime. The upper catalyst layer exhibits high selective oxidation, which is necessary to ensure catalyst performance throughout operation; the main hot spots are located in the upper catalyst layer.

[0027] In some embodiments, the air intake mechanism includes an air supply pipe, the input end of which is connected to the output end of the return distribution pipe 2, and the input end of the air supply pipe is also connected to an air input pipe 3. A second control valve 31 for controlling air flow is installed on the air input pipe 3, and the output end of the feeding device is connected to the air supply pipe. The second control valve 31 controls the incoming air flow.

[0028] In some embodiments, a gas filter 32, a blower 33, a gas heater 34, and a vaporizer 35 are sequentially arranged along the gas delivery direction on the gas pipeline. The output end of the feeding device is connected to the gas pipeline between the gas heater 34 and the vaporizer 35. The blower 33 draws in the gas, the gas filter 32 filters the air and the discharged purified gas, the gas heater 34 heats the gas mixture of air and the discharged purified gas, and the vaporizer 35 vaporizes the mixed gas and raw materials.

[0029] In some embodiments, a gas flow meter 36 and an oxygen concentration detector 37 are also installed on the gas pipeline. The gas drawn in by the blower 33 mainly consists of air and purified gas discharged. After the two gases are mixed and compressed, they are detected by the gas flow meter 36 and the oxygen concentration detector 37 and then sent into the reactor 1.

[0030] In some embodiments, the feeding device includes a naphthalene tank and a feed pump, the feed pump conveying the raw material in the naphthalene tank to an air intake mechanism for mixing with gas.

[0031] In some embodiments, the exhaust mechanism includes an exhaust pipe 4, the input end of which is connected to the output end of the reactor 1, and the input end of the return pipe 2 is connected to the output end of the exhaust pipe 4. A gas cooler 41 and a switching condenser 42 are sequentially installed on the exhaust pipe 4 along the gas output direction. The switching condenser 42 condenses and separates phthalic anhydride from the gas before discharge. The reaction gas discharged from the reactor 1 is initially cooled by the gas cooler 41 and then condensed and separated from the gas by the switching condenser 42.

[0032] In some embodiments, a waste gas purification device 43 is also provided on the exhaust pipe 4. The waste gas purification device 43 is located after the switching condenser 42 so that the gas that has not been condensed by the switching condenser 42 flows through the waste gas purification device 43. The waste gas purification device 43 removes organic matter from the uncondensed waste gas through waste gas purification regenerative combustion or catalytic combustion, removes nitrogen oxides and sulfides through desulfurization and denitrification, and purifies particulate matter in the waste gas through a dust removal system. The final oxygen content in the purified waste gas is 14-16%.

[0033] When using:

[0034] The air required for the oxidation of naphthalene to produce phthalic anhydride is supplied from the atmosphere. After filtration, it is compressed to 60 kPa by blower 33. The compressed air is heated to 185-200°C by gas heater 34 and then enters vaporizer 35.

[0035] The feed device delivers naphthalene from the naphthalene tank area via a feed pump. After being heated and vaporized into naphthalene vapor by vaporizer 35, it then enters reactor 1.

[0036] The naphthalene-air mixture from vaporizer 35 enters the reactor at approximately 180–220°C. The mixed gas enters from the top of reactor 1. On the surface of the V-Ti catalyst, naphthalene is oxidized by air to produce phthalic anhydride. This reaction is a strongly exothermic reaction within the explosive range. Most of the heat of reaction is removed by the molten salt circulating in the molten salt cooler and is then used to generate 6.0 MPa high-pressure saturated steam through a high-pressure steam drum.

[0037] The reaction gas at 360-380℃ is discharged from the bottom of the reactor and cooled to 170-175℃ by the gas cooler 41. Then it enters the switching condenser 42, which condenses the crude phthalic anhydride. The gas that is not condensed by the switching condenser 42 enters the waste gas purification treatment device 43 and is finally discharged or reused.

[0038] During the start-up phase of a new catalyst, its activity is relatively high. Higher feed load and oxygen levels lead to a more vigorous reaction with oxygen, resulting in a higher hotspot. However, the hotspot temperature must be kept below 445℃, necessitating a reduction in feed load, which in turn leads to lower phthalic anhydride yield. Controlling the amount of air entering reactor 1 via the gas pipeline controls the intensity of the reaction between the feedstock and oxygen, preventing excessively high hotspots, while simultaneously increasing the feed load to improve product yield.

[0039] Currently, the reaction between the raw materials and oxygen in the air is a superoxide reaction. The catalyst has high initial activity, resulting in a rapid reaction rate and generating a large amount of heat. Reactor 1's heat transfer rate is insufficient, leading to a slow increase in feed load. By introducing purified gas through the return distribution pipeline 2, the oxygen content in the air is reduced, the reaction rate is controlled, and the excessive heat generated by superoxide is avoided, allowing for a rapid increase in feed load.

[0040] As the catalyst's lifespan increases, the low oxygen content in the air is controlled in the early stages to rapidly increase the load. In the middle and later stages, the supply of purified gas is reduced according to the hot spots to slowly increase the oxygen content in the air and maintain high-load operation.

[0041] The reactor has 16,000 tubes; the oxygen content in the air was adjusted during the experiment.

[0042]

[0043] Under the premise of constant single-pipe air volume, hot spot and salt temperature remain constant. As the oxygen content in the air decreases, the feed rate increases, the catalyst load increases, thereby increasing the yield of phthalic anhydride and producing a superior product.

[0044] The above description is intended to be illustrative and not restrictive. Those skilled in the art can make variations, modifications, substitutions, and alterations to the above embodiments within the scope of this disclosure. Moreover, the above examples (or one or more of them) can be used in combination with each other, and these embodiments can be combined with each other in various combinations or arrangements.

Claims

1. A gas-phase industrial naphthalene preparation apparatus using low-oxygen and mild reaction methods, comprising a reactor (1), characterized in that, The reactor (1) has an input end and an output end. The output end of the reactor (1) is connected to an exhaust mechanism, and the input end of the reactor (1) is connected to an air intake mechanism. The gas discharge end of the exhaust mechanism is connected to a return distribution pipe (2). The end of the return distribution pipe (2) away from the exhaust mechanism is connected to the air intake mechanism to transport part of the exhaust gas discharged by the exhaust mechanism to the air intake mechanism for supplying into the reactor (1). The air intake mechanism is connected to a feeding device, and the return distribution pipe (2) is equipped with a first control valve (21) for controlling the gas flow.

2. The gas-phase industrial naphthalene low-oxygen mild reaction preparation apparatus according to claim 1, characterized in that, The reactor (1) is provided with a number of tubes (11), and a catalyst is placed in each tube (11).

3. The gas-phase industrial naphthalene low-oxygen mild reaction preparation apparatus according to claim 2, characterized in that, The tube (11) is also vertically equipped with a multi-point thermometer (12) for detecting the catalyst temperature at different heights within the tube (11).

4. The gas-phase industrial naphthalene low-oxygen mild reaction preparation apparatus according to claim 2, characterized in that, The catalyst inside the tube (11) is divided into several layers.

5. The gas-phase industrial naphthalene low-oxygen mild reaction preparation apparatus according to claim 1, characterized in that, The air intake mechanism includes an air supply pipe, the input end of which is connected to the output end of the return distribution pipe (2), and the input end of the air supply pipe is also connected to an air input pipe (3). A second control valve (31) for controlling the air flow is installed on the air input pipe (3), and the output end of the feeding device is connected to the air supply pipe.

6. The gas-phase industrial naphthalene low-oxygen mild reaction preparation apparatus according to claim 5, characterized in that, The gas pipeline is provided with a gas filter (32), a blower (33), a gas heater (34) and a vaporizer (35) in sequence along the gas delivery direction. The output end of the feeding device is connected to the gas pipeline between the gas heater (34) and the vaporizer (35).

7. A gas-phase industrial naphthalene preparation apparatus with low oxygen and mild reaction according to claim 5 or 6, characterized in that, The gas pipeline is also equipped with a gas flow meter (36) and an oxygen concentration detector (37).

8. The gas-phase industrial naphthalene low-oxygen mild reaction preparation apparatus according to claim 1, characterized in that, The feeding device includes a naphthalene tank and a feed pump, which transports the raw material in the naphthalene tank to the gas inlet mechanism for mixing with gas.

9. The gas-phase industrial naphthalene low-oxygen mild reaction preparation apparatus according to claim 1, characterized in that, The exhaust mechanism includes an exhaust pipe (4), the input end of which is connected to the output end of the reactor (1), the input end of the return pipe (2) is connected to the output end of the exhaust pipe (4), and a gas cooler (41) and a switching condenser (42) are installed sequentially on the exhaust pipe (4) along the gas output direction. The switching condenser (42) condenses and separates phthalic anhydride from the gas and discharges it.

10. The gas-phase industrial naphthalene low-oxygen mild reaction preparation apparatus according to claim 9, characterized in that, The exhaust pipe (4) is also equipped with an exhaust gas purification device (43), which is located behind the switching condenser (42) so that the gas that is not condensed by the switching condenser (42) flows through the exhaust gas purification device (43).

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