A new nitric acid reduction reaction tower

Abstract

The utility model belongs to nitric acid reduction equipment technical field, concretely relates to a novel nitric acid reduction reaction tower, including tower body, the top of tower body is equipped with gas phase export and liquid inlet, the bottom of tower body is equipped with gas phase import and liquid discharge port, be equipped with liquid phase distributor, gas phase distributor and fairing in the tower body, liquid phase distributor and gas phase distributor all are located in the fairing, and liquid phase distributor is located in the upper portion of fairing, and gas phase distributor is located in the lower portion of fairing. The gas-liquid mixture rises in the fairing, and the high gas content and bubble breakage produce a large gas-liquid contact area, accelerate mass transfer to make the reactant fully react, and the low gas content liquid outside the fairing returns to the bottom of the fairing in laminar or turbulent backflow, forming a circulation. Compared with the traditional tray, the utility model fills the scheme, the gas-liquid direct contact, the reaction effect is better, and the concentration of nitric acid in the discharged tower kettle liquid can be controlled to 200ppm. Moreover, the utility model structure is simple, easy to enlarge, and the maintenance cost is lower.

Description

Technical Field

[0001] This utility model belongs to the technical field of nitric acid reduction equipment, specifically relating to a novel nitric acid reduction reaction tower. Background Technology

[0002] The process for producing ethylene glycol from syngas mainly involves reacting nitric oxide, oxygen, and methanol to generate methyl nitrite. Methyl nitrite then reacts with carbon monoxide to produce the intermediate dimethyl oxalate, which is subsequently hydrogenated to obtain ethylene glycol. During the methyl nitrite formation process, a side reaction occurs to generate nitric acid (4NO + 3O₂ + 2H₂O = 4HNO₃), leading to the loss of nitrogen oxides in the system, and consequently, the loss of methyl nitrite. To recover nitric acid and compensate for the loss of methyl nitrite, current processes typically add a portion of nitric acid to the system. This nitric acid reacts with the methanol-containing esterification system bottom liquid and the NO-containing carbonylation coupling system circulating gas to generate methyl nitrite (2NO + 3CH₃OH + HNO₃ → 3CH₃ONO + 2H₂O). This reaction is usually carried out in a nitric acid reduction reactor.

[0003] For example, Chinese utility model patent CN206731083U discloses a nitric acid reduction purification tower for a syngas-to-ethylene glycol process. This nitric acid reduction purification tower mainly adopts a bubble cap tower structure, with a primary reaction section designed in the upper part of the bubble cap tower to mix the nitric acid solution with the methanol-containing esterification system bottom liquid. The mixed liquid and the NO-containing carbonyl coupling system circulating gas complete a sufficient mass transfer process through the bubble cap tower, thereby achieving the reduction and purification of nitric acid. However, this purification tower has a first packing layer, a second packing layer, and several trays, making its internal structure relatively complex, and its maintenance work is difficult and costly. Based on this, we want to develop a nitric acid reduction reaction tower with a simpler structure. Utility Model Content

[0004] The present invention aims to provide a novel nitric acid reduction reaction tower to solve the problems of complex structure and high maintenance cost of bubble cap towers.

[0005] To achieve the above objectives, the present invention provides a novel nitric acid reduction reaction tower, comprising a tower body, wherein the top of the tower body is provided with a gas phase outlet and a liquid inlet, the bottom of the tower body is provided with a gas phase inlet and a liquid outlet, a liquid phase distributor and a gas phase distributor are provided inside the tower body, and a flow guide tube is also provided inside the tower body, wherein the liquid phase distributor and the gas phase distributor are both located inside the flow guide tube, and the liquid phase distributor is located at the upper part of the flow guide tube, and the gas phase distributor is located at the lower part of the flow guide tube.

[0006] The working principle and beneficial effects of this scheme are as follows: In this scheme, the circulating gas of the NO-containing carbonyl coupling system enters the gas phase distributor from the gas phase inlet at the bottom of the tower, contacts the liquid in the tower bottom, and forms a gas-liquid mixture in the guide tube. Its density is much lower than the density of the predominantly liquid fluid in the annular gap (the space between the outer wall of the guide tube and the inner wall of the tower). The density difference between the two creates a static pressure difference, driving the fluid in the guide tube to flow upwards, while the fluid in the annular gap flows downwards, forming a natural circulation. Thus, the gas and liquid rise in the same direction in the guide tube. The gas is dispersed in the liquid as bubbles. As the bubbles rise, they carry the liquid upwards through buoyancy, forming a high-speed gas-liquid two-phase flow. During this process, the bubbles burst, and the agitation and shearing action of the bubbles promotes gas-liquid mixing and enhances mass transfer. After the gas-liquid mixture reaches the top of the guide tube, the gas partially separates (or overflows), and the liquid, due to its higher density, flows back downwards into the annular gap under the influence of gravity and the static pressure difference. During the backflow, the liquid carries a small number of incompletely separated microbubbles, further promoting mass transfer, especially when the annular gap is narrow. The refluxed liquid returns to the bottom of the guide tube, mixes with the newly introduced gas, forming a continuous circulating flow. This allows NO, methanol, and nitric acid to react fully, yielding the product methyl nitrite. Furthermore, the tower structure in this design is simple, easily scaled up, and has low maintenance difficulty and cost.

[0007] Optionally, a redistributor is provided inside the flow guide tube, and the redistributor is located in the middle of the flow guide tube.

[0008] In this scheme, considering the large length-to-diameter ratio of the tower body, such as 10:1, there is a wall flow effect. A redistributor is set in the middle of the guide tube to reduce or even eliminate the wall flow effect.

[0009] Optionally, the ratio of the outer diameter of the guide tube to the inner diameter of the tower body is 1:1 to 3.

[0010] In this scheme, the ratio of the outer diameter of the guide tube to the inner diameter of the tower body is 1:1 to 3, so that the annular gap width is appropriate, thereby controlling the residence time of the fluid in the annular gap appropriately.

[0011] Optionally, the drain port and the inlet port are connected by a pipe.

[0012] In this scheme, the liquid in the bottom of the column is discharged through the drain port, and most of it is returned to the column through the pipeline, realizing multiple circulation of the liquid in the bottom of the column, so that the reactants can react fully in the column.

[0013] Optionally, the lower part of the tower body is provided with a condensate inlet.

[0014] In this scheme, the gas discharged from the gas phase outlet at the top of the tower is cooled and then sent to the next stage for use. During the cooling process, the methanol gas condenses into liquid and returns to the tower through the condensate inlet to continue participating in the reaction.

[0015] Optionally, the tower body is equipped with temperature sensor I and temperature sensor II. Temperature sensor I is used to detect the temperature inside the guide tube, and temperature sensor II is used to detect the temperature inside the annular gap formed between the tower body and the guide tube.

[0016] In this scheme, temperature sensor I is used to detect the temperature inside the guide tube in real time, and temperature sensor II is used to detect the temperature inside the annular gap in real time. Based on the detected temperature data, the temperature of the nitric acid solution and the bottom liquid of the esterification system containing methanol when entering the tower is adjusted to ensure that the reaction temperature inside the tower is maintained stably.

[0017] Optionally, liquid level sensors are provided at both the upper and lower parts of the tower body.

[0018] In this solution, the liquid level in the tower is monitored in real time by a liquid level sensor to prevent the liquid level from being too high or too low.

[0019] Optionally, a pressure sensor is provided at the top of the tower.

[0020] In this scheme, the air pressure inside the tower is monitored in real time by an air pressure sensor to ensure that the air pressure inside the tower is normal.

[0021] Optionally, manholes are provided at both the top and bottom of the tower.

[0022] In this design, manholes facilitate personnel entering the tower for inspection and maintenance work. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a novel nitric acid reduction reaction tower in an embodiment of this utility model. Detailed Implementation

[0024] The following detailed description illustrates the specific implementation method:

[0025] The markings in the accompanying drawings include: tower body 1, gas phase outlet 2, liquid inlet 3, gas phase inlet 4, liquid outlet 5, liquid phase distributor 6, redistributor 7, gas phase distributor 8, guide tube 9, pipe 10, condensate inlet 11, temperature sensor I 12, temperature sensor II 13, annular gap 14, liquid level sensor 15, gas pressure sensor 16, manhole 17.

[0026] Example

[0027] This embodiment is basically as follows: Figure 1As shown: A novel nitric acid reduction reaction tower includes a tower body 1. The top of the tower body 1 has a gas phase outlet 2 and a liquid inlet 3, while the bottom of the tower body 1 has a gas phase inlet 4 and a liquid outlet 5. Inside the tower body 1 are a liquid phase distributor 6, a redistributor 7, a gas phase distributor 8, and a guide tube 9. The liquid phase distributor 6, redistributor 7, and gas phase distributor 8 are all located within the guide tube 9. The liquid phase distributor 6 is located at the upper part of the guide tube 9, the redistributor 7 is located at the middle part of the guide tube 9, and the gas phase distributor 8 is located at the lower part of the guide tube 9. The ratio of the outer diameter of the guide tube 9 to the inner diameter of the tower body 1 is 1:1 to 3. Specifically, in this embodiment, the ratio of the outer diameter of the guide tube 9 to the inner diameter of the tower body 1 is 1:1.3.

[0028] Gas outlet 2 allows gas to leave the column, liquid inlet 3 allows liquid to enter the column, gas inlet 4 allows gas to enter the column, and liquid outlet 5 allows the liquid in the column bottom to leave. The liquid outlet 5 and liquid inlet 3 are connected by a pipe 10, so that the liquid in the column bottom can return to the top of the column through the pipe 10, realizing multiple circulation of the liquid in the column and ensuring that the reactants react completely in the column.

[0029] The lower part of the tower body 1 is equipped with a condensate inlet 11. In addition to CO and methyl nitrite, the gas leaving through the gas phase outlet 2 also contains substances such as methanol. Therefore, the methanol gas needs to be condensed into liquid by cooling. The liquid methanol is returned to the tower through the condensate inlet 11 to continue to participate in the reaction.

[0030] The tower body 1 is equipped with temperature sensors I12 and II13. Temperature sensor I12 is used to detect the temperature inside the guide tube 9, and temperature sensor II13 is used to detect the temperature inside the annular gap 14 formed between the tower body 1 and the guide tube 9. In this embodiment, there are six temperature sensors I12 and two temperature sensors II13, which are arranged vertically along the tower body 1. The temperature of each stage inside the guide tube 9 is monitored in real time by temperature sensor I12, and the temperature of the middle and lower section inside the annular gap 14 is monitored in real time by temperature sensor II13. Based on the detected temperature data, the temperature of the nitric acid solution and the methanol-containing esterification system bottom liquid entering the tower is adjusted to ensure that a stable reaction temperature is maintained inside the tower.

[0031] The upper and lower parts of the tower body 1 are each equipped with two liquid level sensors 15, for real-time detection of the liquid level inside the tower, allowing for timely adjustment to prevent the liquid level from becoming too high or too low. A pressure sensor 16 is installed at the top of the tower body 1 to real-time detect the pressure inside the tower, allowing for timely pressure adjustment to prevent the pressure from becoming too high or too low. Manholes 17 are provided at both the top and bottom of the tower body 1 to allow personnel to enter the tower for inspection and maintenance work.

[0032] In practical use, the nitric acid solution and the methanol-containing esterification system bottom liquid are mixed outside the tower and heated to a suitable temperature before entering the tower through the inlet 3 at the top. Under the action of the liquid phase distributor 6, the liquid is evenly distributed within the guide tube 9. Furthermore, the redistributor 7, located in the middle section of the guide tube 9, further evenly distributes the liquid. The NO-containing carbonyl coupling system circulating gas enters the tower through the gas phase inlet 4 at the bottom and is evenly distributed within the guide tube 9 under the action of the gas phase distributor 8. The gas contacts the liquid (nitric acid solution and methanol-containing esterification system bottom liquid) at the bottom of the guide tube 9, forming a gas-liquid mixture within the guide tube 9. The gas's density is much lower than the density of the predominantly liquid fluid in the annular gap 14 (the space between the outer wall of the guide tube 9 and the inner wall of the tower body 1). This density difference creates a static pressure difference, driving the fluid in the guide tube 9 to flow upwards, while the fluid in the annular gap 14 flows downwards, forming a natural circulation.

[0033] Inside the guide tube 9, the gas and liquid rise in the same direction. The gas is dispersed in the liquid as bubbles. As the bubbles rise, they carry the liquid upward through buoyancy, forming a high-speed gas-liquid two-phase flow. During this process, the bubbles burst, and the agitation and shearing action of the bubbles promotes gas-liquid mixing. The large gas-liquid contact area enhances mass transfer. After the gas-liquid mixture reaches the top of the guide tube 9, the gas partially separates (or overflows), and the liquid, due to its higher density, flows downward back into the annular gap 14 under the influence of gravity and static pressure difference. During the backflow, the liquid carries a small number of incompletely separated microbubbles, further promoting mass transfer, especially when the annular gap 14 is narrow. The backflowing liquid returns to the bottom of the guide tube 9 and mixes with the newly introduced gas, forming a continuous circulation, allowing NO, methanol, and nitric acid to react fully to produce methyl nitrite. In the above process, the bottom liquid is discharged through the drain port 5, and most of the bottom liquid returns to the inlet port 3 through the pipe 10, realizing multiple circulation of the bottom liquid and ensuring that the reactants react fully within the column.

[0034] CO enters the tower through CO inlet 11, and together with the products methyl nitrite, nitrogen, and other gases, exits the tower body 1 through gas phase outlet 2. The mixed gas after leaving the tower body 1 is cooled and then transported to the next stage for use. During the cooling process, the methanol gas in the mixed gas condenses into liquid and returns to the tower through condensate inlet 11 to continue participating in the reaction.

[0035] During the reaction, temperature sensor I12 and temperature sensor II13 monitor the temperature inside the tower in real time, liquid level sensor 15 monitors the liquid level inside the tower in real time, and gas pressure sensor 16 monitors the gas pressure inside the tower in real time, thereby ensuring that the reaction temperature, liquid level, and gas pressure inside the tower meet the requirements.

[0036] In summary, this embodiment demonstrates excellent mass transfer and complete reaction. Compared to bubble cap tower structures, this embodiment features a simpler structure, is easier to scale up, and has lower maintenance difficulty and cost. Furthermore, the nitric acid concentration in the discharged bottom liquid can be controlled to below 200 ppm, achieving an excellent level in the industry.

[0037] The above descriptions are merely embodiments of this utility model, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of this utility model, and these should also be considered within the scope of protection of this utility model. These modifications will not affect the effectiveness or practicality of this utility model. The specific embodiments described in the specification can be used to interpret the claims.

Claims

1. A novel nitric acid reduction reaction tower, comprising a tower body, wherein the top of the tower body is provided with a gas phase outlet and a liquid inlet, the bottom of the tower body is provided with a gas phase inlet and a liquid outlet, and a liquid phase distributor and a gas phase distributor are provided inside the tower body, characterized in that: The tower body is also equipped with a flow guide tube, in which both the liquid phase distributor and the gas phase distributor are located. The liquid phase distributor is located at the upper part of the flow guide tube, and the gas phase distributor is located at the lower part of the flow guide tube.

2. The novel nitric acid reduction reaction tower according to claim 1, characterized in that: The flow guide tube is equipped with a redistributor, which is located in the middle of the flow guide tube.

3. The novel nitric acid reduction reaction tower according to claim 1, characterized in that: The ratio of the outer diameter of the guide tube to the inner diameter of the tower body is 1:1 to 3.

4. The novel nitric acid reduction reaction tower according to claim 1, characterized in that: The drain port and the inlet port are connected by a pipe.

5. The novel nitric acid reduction reaction tower according to claim 1, characterized in that: The lower part of the tower body is provided with a condensate inlet.

6. The novel nitric acid reduction reaction tower according to claim 1, characterized in that: The tower body is equipped with temperature sensor I and temperature sensor II. Temperature sensor I is used to detect the temperature inside the guide tube, and temperature sensor II is used to detect the temperature inside the annular gap formed between the tower body and the guide tube.

7. The novel nitric acid reduction reaction tower according to claim 1, characterized in that: Liquid level sensors are installed at both the upper and lower parts of the tower body.

8. The novel nitric acid reduction reaction tower according to claim 1, characterized in that: A pressure sensor is installed at the top of the tower.

9. The novel nitric acid reduction reaction tower according to claim 1, characterized in that: Manholes are provided at the top and bottom of the tower.

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