Internal structure of reactor for continuous nitration of dinitrotoluene

Abstract

The utility model belongs to the technical field of nitration machines, and discloses a reactor internal structure for continuous nitration of dinitrotoluene, which comprises a heat exchange cylinder body which is a main body structure of a heat exchange device and is internally provided with a guide cylinder, and the guide cylinder is fixed between an upper tube plate and a lower tube plate and placed in the center of a stirring container. And the interior of the machine is divided into a stirring area with a stirrer and a circulating area which cannot be directly stirred by the stirrer. The baffle is arranged in the guide cylinder, so that the stirring strength can be increased by about 25%, and the reaction speed can be increased. The length of the baffle is consistent with that of the guide cylinder, but the baffle is not arranged at the stirring blade, a radial baffle is additionally arranged above the guide cylinder and below the liquid level, the radial baffle is connected with the machine wall to reduce the vortex of the liquid, and the baffle is welded with the baffle of the guide cylinder. The baffle plates are arranged in the heat exchange barrel and used for supporting the heat exchange tubes, relieving the stress condition of the heat exchange tubes, preventing fluid flowing from causing vibration of the heat exchange tubes, prolonging the length of a medium flow channel and improving the heat transfer efficiency.

Description

Technical Field

[0001] This utility model belongs to the technical field of dinitrotoluene, and mainly relates to the internal structure of a reactor for continuous nitration of dinitrotoluene, specifically to a tubular reaction device for the internal structure of a dinitrotoluene nitrification machine. Background Technology

[0002] Dinitrotoluene, scientifically known as dinitrotoluene, is a raw material for explosives. It is flammable and highly toxic. Its molecular formula is C7H6N2O4.

[0003] In the current production process, dinitrotoluene (DNT) is prepared by nitration with a mixed nitrate-sulfur acid. This nitration reaction is carried out in two steps. First, mononitrotoluene (MNT) is obtained by reacting toluene with the mixed nitrate-sulfur acid. After removing the used sulfuric acid, the second step converts MNT into dinitrotoluene. Both nitration steps are carried out at a low temperature under cooling conditions.

[0004] "The most important indicator of a reactor is its productivity, which is the number of kilograms of product molecules produced per hour per m3 of reactor volume." "The science of studying and improving reactor productivity is mainly chemical kinetics. The part of chemical kinetics that specifically studies reaction mechanisms and reaction rate laws is called microkinetics."

[0005] "Work on improving reactor productivity based on microdynamics, such as flow patterns, heat transfer, and mass transfer processes, falls under the scope of macrodynamics."

[0006] The nitration process conditions, such as temperature, concentration, and feed ratio, are determined by the nature of the reaction. The equipment is the site of the reaction, but it is crucial. While it doesn't determine whether a reaction occurs, it influences the quality, yield, and overall quality of the reaction. Therefore, studying the relationship between the internal structure of the equipment and the process, and identifying the influence of equipment components on the reaction, is essential. The core principle is to ensure uniform mixing so that the overall reaction rate is kinetically controlled, rather than mass-transfer-controlled. Furthermore, nitration is a strongly exothermic reaction with a rapid reaction rate and concentrated heat release. Poor control can lead to explosions. Therefore, heat removal is also a prominent issue in controlling the nitration reaction, typically requiring the nitration reactor to have excellent heat transfer devices. Utility Model Content

[0007] To overcome the shortcomings of existing dinitrotoluene nitrification reactors, such as slow material flow rate, uneven reaction, easy scaling, poor mass transfer, and low heat transfer capacity, this invention proposes an internal reactor structure for continuous dinitrotoluene nitration. The specific technical solution is as follows:

[0008] An internal structure of a reactor for continuous nitration of dinitrotoluene includes a heat exchange cylinder, a guide tube, baffles, a feed pipe, a stirrer, heat exchange tubes, baffles, a spacer tube, a tie rod, an upper tube sheet, and a lower tube sheet. The heat exchange cylinder is the main structure of the heat exchange device. The upper and lower tube sheets are welded to the heat exchange cylinder. The guide tube is fixed between the upper and lower tube sheets and placed at the center of the stirrer. The upper part of the guide tube is welded to the upper tube sheet, and the upper opening of the guide tube is higher than the upper tube sheet. The lower opening of the guide tube is welded to the lower tube sheet, and the lower opening length of the guide tube is lower than the lower tube sheet. The baffles are radially welded inside the guide tube, and the bottom of the baffles is flush with the guide tube. There are three baffles, evenly distributed inside the guide tube. The feed pipe consists of a straight pipe of a certain length, a standard 90-degree elbow, and a pipe flange welded together. One end of the straight pipe section is welded with a pipe flange to connect to an external pipe, and the other end... The feed pipe has a welded elbow, and the straight section of the feed pipe is welded to the heat exchange tube. The elbow of the feed pipe extends into the guide tube, below the top opening of the guide tube. The heat exchange tube is composed of multiple straight tubes of a certain length, with one end welded to the upper tube sheet and the other end welded to the lower tube sheet, arranged in a ring-shaped column inside the tube. The baffle plate is composed of an arc-shaped flat plate of a certain thickness. The spacer tube is a tube of the same specification as the heat exchange tube. The spacer tube passes through the baffle plate and is fixed at a certain distance. The tie rod passes through the spacer tube, with one end embedded in the lower tube sheet and the other end passing through the spacer tube and the baffle plate and connected with a nut. The upper and lower tube sheets are made of circular steel plates of a certain thickness. A circular hole larger than the diameter of the guide tube is opened in the middle of the upper and lower tube sheets to allow the guide tube to be inserted and welded in place. Holes larger than the outer diameter of the heat exchange tube are drilled around the perimeter to allow the heat exchange tube to be inserted and welded in place.

[0009] Furthermore, the agitator is a standard propeller agitator with three blades, the pitch of which is equal to the diameter of the impeller.

[0010] The beneficial effects of this utility model are:

[0011] This invention primarily addresses the problems of slow material flow rate, uneven reaction, easy scaling, poor mass transfer, and low heat transfer capacity in the nitrification of dinitrotoluene. It provides a stable reaction system for dinitrotoluene production characterized by uniform reaction, fast reaction speed, and high production capacity. The vertical tubular heat exchange tubes and the material within the guide tube of the reactor can effectively participate in circulation. The cooling medium circulates within the reactor, achieving not only heat transfer but also optimizing the flow state of the material medium, resulting in excellent mass transfer. Especially for continuous reactions, the flow state not only provides a steady-state continuous reaction process but also ensures equal residence time of reactants within the reaction tubes, leading to fast reaction speed, high flow rate, and high production capacity.

[0012] Since there is no similar equipment to refer to in the dinitrotoluene production industry, the structural design of the reactor for continuous nitration of dinitrotoluene is innovative and practical. Attached Figure Description

[0013] Figure 1 This is a front view of the reactor device of this utility model.

[0014] In the figure: 1. Heat exchanger body; 2. Guide tube; 3. Baffle; 4. Feed pipe; 5. Agitator; 6. Heat exchange tube; 7. Baffle plate; 8. Spacing tube; 9. Tie rod; 10. Upper tube sheet; 11. Lower tube sheet. Detailed Implementation

[0015] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0016] This embodiment is a reactor device, including 1. a heat exchange cylinder; 2. a flow guide cylinder; 3. a baffle; 4. a feed pipe; 5. a stirrer; 6. a heat exchange tube; 7. a baffle plate; 8. a spacer tube; 9. a tie rod; 10. an upper tube sheet; and 11. a lower tube sheet.

[0017] The heat exchange cylinder 1 of the reactor device is made of steel plate of a certain thickness, rolled and welded. The heat exchange cylinder 1 is fixed between the lower tube sheet 11 and the upper tube sheet 10. It is the main structure of the heat exchange device, supporting and fixing the reactor components, so that these components will not deform or shift during operation, and can effectively prevent internal media leakage. Its height and diameter are determined by the reaction liquid volume, the specifications of the accessories in the reactor device, the specifications of the heat exchange tubes, etc. The height of the heat exchange cylinder 1 affects the reaction rate and heat transfer efficiency of the reactor.

[0018] The guide tube 2 of the reactor device is made of rolled and welded sheet metal and is fixed between the upper tube plate 10 and the lower tube plate 11, placed in the center of the stirring container. The upper part of the guide tube 2 is welded to the upper tube plate of the reactor device. The height of the upper opening of the guide tube should not be flush with the upper tube plate, but should be 20-40mm higher to avoid poor material circulation and mixing. The height of the upper opening of the guide tube is also related to the liquid level of the material. The lower opening of the guide tube is welded to the lower tube plate of the reactor device. The length of the lower opening of the guide tube is lower than that of the lower tube plate. The distance between the lower opening of the guide tube and the bottom of the reactor is the fluid lower channel resistance, which needs to be calculated. The resistance is minimized when the fluid passage area remains constant. The inner wall surface of the guide tube is polished to prevent material from adhering to the inner wall and reduce material scaling.

[0019] The baffle 3 of the reactor device is made of a plate with a thickness of 5mm, a width of 80mm, and a total length of 1440mm, radially welded inside the guide tube. The bottom of the baffle is flush with the guide tube, and there are 3 baffles evenly distributed inside the guide tube, but the baffles are disconnected at the stirring blades. The baffles inside the guide tube prevent the liquid from forming vortices due to centrifugal force generated by stirring, which is not conducive to liquid mixing.

[0020] The feed pipe 4 of the reactor device is composed of a straight pipe of a certain length, a standard 90-degree bend, and a pipe flange welded together. One end of the straight pipe section is welded with a pipe flange to connect to the external pipe, and the other end is welded with a bend. The straight part of the feed pipe is welded to the heat exchange cylinder. The bend part of the feed pipe extends into the inside of the guide cylinder, about 50-100mm below the top opening of the guide cylinder. The purpose is to add the material to the area with a high flow rate, so as to achieve a good mixing effect.

[0021] The stirrer 5 of the reactor device is a standard stirrer, which is placed inside the guide tube. Its function is to mix the acid phase and the organic phase evenly, increase the interface between the two phases, increase mass transfer and reaction rate, and improve heat transfer efficiency. Therefore, the nitration reaction of dinitrotoluene is generally carried out by a propeller-type spiral stirrer.

[0022] The heat exchange tubes 6 of the reactor device consist of multiple straight tubes of a certain length, with one end welded to the upper tube sheet and the other end welded to the lower tube sheet, arranged in a ring-shaped tube array inside the cylinder. The nitrified liquid flows inside the heat exchange tubes, optimizing the flow state of the material medium and resulting in good mass transfer.

[0023] The baffle plate 7 of the reactor device is an arc-shaped plate with a thickness of 5mm. The spacer tube passes through the baffle plate and is fixed at a certain distance to prevent the heat exchange tube from vibrating due to fluid flow. Since the cooling medium flows inside the cylinder, the length of the medium flow channel can be extended, the degree of turbulence can be increased, and the heat transfer efficiency can be improved.

[0024] The reactor device has 8 fixed-distance tubes of the same specifications as the heat exchange tubes. They pass through the baffles and are fixed at a certain distance to ensure that the spacing between the baffles remains unchanged.

[0025] The reactor device has nine tie rods made of round steel with a diameter of 16mm. The tie rods pass through the spacer tube, with one end embedded in the lower tube sheet and the other end passing through the spacer tube and connecting to the baffle plate with a nut. This ensures the stability of the spacer tube and the baffle plate, reduces the vibration of the tube bundle, and ensures that the spacing between the baffle plates remains unchanged.

[0026] The upper tube plate of the reactor device is made of a circular steel plate of a certain thickness. A circular hole slightly larger than the diameter of the guide tube is opened in the middle of the upper tube plate so that the guide tube can be inserted and welded and fixed. Holes slightly larger than the outer diameter of the heat exchange tube are drilled around it so that the heat exchange tube can be inserted and welded and fixed.

[0027] The lower tube plate of the reactor device is made of a circular steel plate of a certain thickness. A circular hole slightly larger than the diameter of the guide tube is opened in the middle of the lower tube plate so that the guide tube can be inserted and welded and fixed. Holes slightly larger than the outer diameter of the heat exchange tube are drilled around it so that the heat exchange tube can be inserted and welded and fixed.

Claims

1. An internal structure of a reactor for continuous nitration of dinitrotoluene, characterized in that, The device includes a heat exchange cylinder (1), a guide tube (2), a baffle (3), a feed pipe (4), a stirrer (5), a heat exchange tube (6), a baffle plate (7), a spacer tube (8), a tie rod (9), an upper tube sheet (10), and a lower tube sheet (11). The heat exchange cylinder (1) is the main structure of the heat exchange device. The upper tube sheet (10) and the lower tube sheet (11) are welded to the heat exchange cylinder (1). The guide tube (2) is fixed between the upper tube sheet (10) and the lower tube sheet (11) and placed in the center of the stirrer (5). The upper part of the guide tube (2) is welded to the upper tube sheet. (10) The upper opening of the guide tube (2) is higher than the upper tube plate (10), and the lower opening of the guide tube (2) is welded to the lower tube plate (11). The length of the lower opening of the guide tube (2) is lower than that of the lower tube plate (11). The baffle (3) is radially welded inside the guide tube (2). The bottom of the baffle (3) is flush with the guide tube (2). There are three baffles (3) evenly distributed inside the guide tube (2). The feed pipe (4) is made of a straight pipe of a certain length, a standard 90-degree elbow, and a pipe flange welded together. One end of the straight pipe section is welded with a pipe flange to connect with the external pipe. The other end is welded with an elbow. The straight part of the feed pipe (4) is welded to the heat exchange tube (6). The elbow part of the feed pipe (4) extends into the guide tube (2) and is lower than the top opening of the guide tube (2). The heat exchange tube (6) is composed of multiple straight tubes of a certain length. One end is welded to the upper tube plate (10) and the other end is welded to the lower tube plate (11). They are arranged in a ring-shaped tube array in the cylinder. The baffle plate (7) is composed of an arc-shaped flat plate of a certain thickness. The spacer tube (8) is a tube of the same specification as the heat exchange tube (6). The spacer tube (8) passes through the baffle plate. The flow plate (7) is fixed at a certain distance. The pull rod (9) passes through the spacer tube (8), with one end embedded in the lower tube plate (11) and the other end passing through the spacer tube (8) and the flow plate (7) connected by a nut. The upper tube plate (10) and the lower tube plate (11) are made of circular steel plates of a certain thickness. A circular hole larger than the diameter of the flow guide tube (2) is opened in the middle of the upper tube plate (10) and the lower tube plate (11) so that the flow guide tube (2) can be inserted and welded and fixed. Holes larger than the outer diameter of the heat exchange tube (6) are drilled around it so that the heat exchange tube (6) can be inserted and welded and fixed.

2. The internal structure of the reactor for continuous nitration of dinitrotoluene as described in claim 1, characterized in that, The agitator (5) is a standard propeller agitator with three blades, the pitch of which is equal to the diameter of the impeller.

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