Device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate

Abstract

The utility model relates to a device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate. The device comprises a sodium nitrite dissolving and feeding kettle; a dimethyl sulfate feeding tank; the dynamic tubular reactor is provided with a first feed port, a second feed port and a first discharge port, the first feed port is connected with the sodium nitrite dissolving and feeding kettle, and the second feed port is connected with the dimethyl sulfate feeding tank; the reaction intermediate kettle is at least provided with a first top discharge port, a first bottom discharge port and a third feed port, and the third feed port is connected with the first discharge port of the dynamic tubular reactor; the water separation tank is connected with the first top discharge hole of the reaction middle kettle through a reaction condenser. A conventional reaction kettle is replaced with the dynamic tubular reactor, a conventional coarse steaming kettle is replaced with the scraper evaporator, continuous production of nitromethane is achieved, energy consumption is low, the product yield is high, and economical efficiency is good.

Description

Technical Field

[0001] The utility model belongs to the field of chemical equipment and relates to a nitromethane production device, in particular to a device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate. Background Art

[0002] Nitromethane is an important organic chemical product that can be used to synthesize hydroxylamine hydrochloride, pesticide chloropicrin, nitro alcohol, etc. It can also be used to prepare explosives, rocket fuel, medicine, dyes, pesticides and gasoline additives. At present, domestic manufacturers generally use dimethyl sulfate and sodium nitrite substitution method to produce nitromethane. The reaction formula is as follows:

[0003] Main reaction: (CH3)2SO4 + 2NaNO2 → 2CH3NO2 + Na2SO4 (1);

[0004] Side reaction: (CH3)2SO4 + 2NaNO2→ CH3ONO↑+ Na2SO4 (2);

[0005] (CH3)2SO4+ 2H2O→ 2CH3OH+H2SO4 (hydrolysis of dimethyl sulfate) (3);

[0006] H2SO4+ 2NaNO2→ Na2SO4+ H2O + NO↑ (4);

[0007] H2SO4+ Na2CO3→ Na2SO4+ H2O + CO2↑ (5);

[0008] 2CH3NO2 + 2H2O→ 2CH3OH+ H2O + NO↑+ NO2↑ (nitromethane hydrolysis) (6).

[0009] The document "Process Optimization for Improving the Yield of Nitromethane Products" [Sun Deqian, Shandong Chemical Industry, 1999] disclosed that the average yield of nitromethane by manufacturers is currently 50% and the product purity is less than 98%, mainly due to the hydrolysis of dimethyl sulfate and nitromethane.

[0010] At present, the reaction device for synthesizing nitromethane from sodium nitrite and dimethyl sulfate is generally an intermittent kettle reactor. Due to the solubility limitation of sodium nitrite at room temperature and the fact that there cannot be too much water in the reaction system (to reduce the hydrolysis of dimethyl sulfate and nitromethane), the sodium nitrite, water and sodium carbonate added to the reactor form a sodium nitrite slurry. When transporting sodium nitrite to the reactor, pipeline blockage is prone to occur. The Chinese utility model patent with the authorization announcement number CN211562015U discloses a raw material feeding device for nitromethane synthesis reaction, including a base, a mixing box and a reaction box are installed in the middle of the top surface of the base from left to right, a stirring device is provided in the mixing box and the reaction box, a feeding port is respectively provided on the left and right sides of the middle of the top of the mixing box, a first circular plate is fixedly installed in the mixing box, the first circular plate is located below the corresponding stirring device, a plurality of uniformly distributed first through holes are provided on the top surface of the first circular plate, a circle of slots is provided in the mixing box, a second circular plate is provided in the slot, the second circular plate can rotate in the slot, and the top surface of the second circular plate contacts the bottom surface of the first circular plate, and a plurality of uniformly distributed second through holes are provided on the top surface of the second circular plate. The application filters the aqueous solution after the mixed dissolution of sodium nitrite and soda ash through a filter screen, so that the sodium nitrite and soda ash that are not fully dissolved remain on the filter screen, thereby avoiding the problem of insufficient dissolution of sodium nitrite and soda ash in water and causing pipeline blockage. However, filtering out the undissolved sodium nitrite solid affects the original reaction system ratio and is equivalent to increasing the amount of water in the system, which is not conducive to the precise control of the reaction.

[0011] The Chinese utility model patent with the authorization announcement number CN215429011U discloses a raw material feeding device for nitromethane synthesis reaction, wherein the crushing mechanism includes a connecting pipe, a crushing box and a supporting assembly, the bottom of the crushing box is fixedly connected to the top of the reaction box, the inner surface of the crushing box is connected to the inner surface of the reaction box, the inside of the crushing box is fixedly connected to the outer surface of the connecting pipe, one end of the connecting pipe is fixedly connected to the outer surface of the feeding pipe, the inner wall of the feeding pipe is fixedly connected with a filter screen, the outer surface of the supporting assembly is movably connected to the inner surface of the crushing box, and the inner surface of the crushing box is fixedly connected with a connecting plate. The utility model sets a crushing mechanism, and the telescopic end of the hydraulic rod reciprocates to push the filter plate to move. The filter plate is vibrated by force, and the sodium nitrite powder falls into the reaction box to continue to dissolve. The combination of the above structures solves the problem that sodium nitrite is easy to block the feeding pipeline due to insufficient dissolution; however, the nitromethane needs to be crushed into small particles, resulting in a complex equipment structure.

[0012] The Chinese utility model patent with the authorization announcement number CN218901838U discloses a device for synthesizing nitromethane from sodium nitrite and dimethyl sulfate, which includes a synthesis kettle, several crude steaming kettles and a controller. The synthesis kettle is provided with an agitator, and the agitator shaft of the agitator is connected to the output shaft of the drive motor. The controller controls the speed of the drive motor based on the pressure and / or temperature and / or reaction time in the synthesis kettle. This application uses one synthesis kettle to correspond to multiple crude steaming kettles, and only realizes the continuity of a single process; the crude steaming still takes 1.5 hours.

[0013] In the above intermittent reaction, sodium nitrite slurry and dimethyl sulfate undergo solid-liquid-liquid reaction, the reaction continuity is poor, the high-temperature rough steaming process takes a long time, resulting in nitromethane hydrolysis, low reaction yield, and high energy consumption. Improving the mass transfer and heat transfer capacity of the nitromethane reaction process, improving the nitromethane recovery rate in the post-treatment process, inhibiting the hydrolysis of dimethyl sulfate, the raw material in the reaction process, and reducing the hydrolysis of nitromethane, the product in the post-treatment process, so as to produce nitromethane continuously, quickly, safely, and with high yield is a problem to be solved. Summary of the invention

[0014] The utility model aims to overcome the deficiencies of the prior art and to provide a device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate.

[0015] To achieve the above object, the technical solution adopted by the utility model is: a device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate, which comprises:

[0016] Sodium nitrite dissolving and feeding kettle;

[0017] Dimethyl sulfate feeding tank;

[0018] A dynamic tubular reactor, wherein the dynamic tubular reactor has a first feed port, a second feed port and a first discharge port, wherein the first feed port is connected to the sodium nitrite dissolving feed kettle, and the second feed port is connected to the dimethyl sulfate feed tank;

[0019] A reaction kettle, wherein the reaction kettle has at least a first top discharge port, a first bottom discharge port and a third feed port, and the third feed port is connected to the first discharge port of the dynamic tubular reactor;

[0020] A water separation tank is connected to the first top discharge port of the reaction intermediate kettle through a reaction condenser.

[0021] Optimally, it also includes a reaction receiving tank, and the water separation tank is connected to the reaction condenser through the reaction receiving tank.

[0022] Optimally, it further comprises a scraper evaporator, wherein the scraper evaporator has at least a fourth feed port, a second top discharge port and a second bottom discharge port, wherein the fourth feed port is connected to the first bottom discharge port of the intermediate reaction vessel.

[0023] Furthermore, it also includes an evaporation receiving tank connected to the second top discharge port of the scraper evaporator through an evaporation condenser, and the water separation tank is also connected to the evaporation receiving tank.

[0024] Furthermore, it also includes a mother liquid water tank connected to the water separation tank, and the scraper evaporator also has a return port, and the mother liquid water tank is connected to the return port through a lifting pump.

[0025] Optimally, the dynamic tubular reactor is also connected to a reaction temperature control unit for controlling the temperature and pressure thereof.

[0026] Furthermore, the reaction temperature control unit includes a pressure transmitter and a temperature transmitter arranged in the dynamic tubular reactor.

[0027] Furthermore, the outer wall of the sodium nitrite dissolving and feeding kettle is provided with a first heating jacket, the outer wall of the dynamic tubular reactor is provided with a first cooling jacket, the outer wall of the reaction intermediate kettle is provided with a second cooling jacket, and the outer wall of the scraper evaporator is provided with a second heating jacket.

[0028] Optimally, the water diversion tank is provided with a liquid level transmitter and an interface position transmitter for detecting the liquid level and the interface position respectively.

[0029] Due to the application of the above technical scheme, the utility model has the following advantages compared with the prior art: the utility model has the following advantages: the device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate makes the sodium nitrite dissolving feeding kettle, the dimethyl sulfate feeding tank and the dynamic tubular reactor input sodium nitrite and dimethyl sulfate into the reactor for reaction, so that the dynamic tubular reactor liquid-liquid phase continuous flow process is adopted, and the nitromethane yield can be increased by 10-20% compared with the original kettle type intermittent solid-liquid-liquid phase reaction process; the reaction time is shortened from the original 30min to 0.5-5min, shortened by 83-98%; the rough steaming time is shortened from the original 1.5h to 5-15min, shortened by 83-94%; the reaction and rough steaming time are greatly shortened, and the production efficiency and the nitromethane yield are improved; at the same time, the channel content volume of the dynamic tubular reactor is small, the equipment occupies a small area, and the reaction is safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The utility model is a schematic diagram of the structure of a device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate. DETAILED DESCRIPTION

[0031] The utility model is further described below in conjunction with the embodiments shown in the accompanying drawings.

[0032] like Figure 1 The device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate shown in the figure mainly comprises a sodium nitrite dissolving and feeding kettle 1, a dimethyl sulfate feeding tank 2, a dynamic tubular reactor 3, a reaction intermediate kettle 5 and a water separation tank 11, etc.

[0033] The sodium nitrite dissolving and feeding kettle 1 is used to dissolve sodium nitrite to obtain a uniform sodium nitrite solution (sodium nitrite aqueous solution) and transport it to the dynamic tubular reactor 3; in this embodiment, the sodium nitrite solution is maintained as a uniform solution at 60-110°C, which effectively avoids the blockage defect of the solid-liquid-liquid reaction process of the sodium nitrite slurry and dimethyl sulfate, thereby reducing maintenance and production costs. The dimethyl sulfate feeding tank 2 is used to store dimethyl sulfate and transport it to the dynamic tubular reactor 3. The dynamic tubular reactor 3 has a first feed port, a second feed port and a first discharge port. The first feed port is connected to the sodium nitrite dissolving feeding kettle 1 (here the connection is through a pipeline, the same below), and the second feed port is connected to the dimethyl sulfate feeding tank 2; usually, feed valves are installed on the above-mentioned pipelines respectively, and the feed flow rates of the sodium nitrite solution and dimethyl sulfate are controlled by controlling the opening of the feed valves, so that the sodium nitrite solution and dimethyl sulfate are smoothly added to the dynamic tubular reactor 3 at a specified flow rate (flow transmitters can also be installed on the above-mentioned pipelines as needed to detect their flow rates respectively).

[0034] The intermediate reactor 5 at least has a first top discharge port, a first bottom discharge port and a third feed port, and the third feed port is connected to the first discharge port of the dynamic tubular reactor 3, so that the intermediate reactor 5 can receive the discharge of the dynamic tubular reactor 3; the production of nitromethane by sodium nitrite and dimethyl sulfate belongs to the nitration reaction, which has the characteristics of fast reaction speed and large heat release. The high-speed rotation of the stirring shaft of the dynamic tubular reactor 3 can carry out good mass transfer and heat exchange for the reaction materials, and 90-95% of the reaction and heat release are completed in the dynamic tubular reactor. The dynamic tubular reactor is connected to the intermediate reactor 5 after 3, which is equivalent to the aging reactor, and can play the role of complete conversion of raw materials and buffer tank.

[0035] The water separation tank 11 is connected to the first top discharge port of the reaction intermediate kettle 5 through the reaction condenser 6, and is used to receive the discharge of the reaction intermediate kettle 5; the mixed condensate obtained after condensation is introduced into the water separation tank 11, and after standing in the water separation tank 11, the nitromethane and water are separated into layers, with nitromethane in the lower layer and water in the upper layer, so as to further separate the crudely evaporated nitromethane from the water (that is, the gas phase outlet at the top of the reaction intermediate kettle 5 is connected to the feed port of the water separation tank 11 through a pipeline after passing through the reaction condenser 6, and the gas phase outlet at the top of the scraper evaporator 8 is connected to the feed port of the water separation tank 11 through a pipeline through the evaporative condenser 9).

[0036] In this embodiment, the device further includes a reaction receiving tank 7, so that the water separation tank 11 is connected to the reaction condenser 6 through the reaction receiving tank 7; at the same time, the device also includes an evaporation receiving tank 10 connected to the second top discharge port of the scraper evaporator 8 through the evaporation condenser 9, and the water separation tank 11 is also connected to the evaporation receiving tank 10 (that is, the top of the reaction receiving tank 7 is connected to the discharge port of the reaction condenser 6, and the bottom is connected to the feed port of the water separation tank 11, and the top of the evaporation receiving tank 10 is connected to the discharge port of the evaporation condenser 9, and the bottom is connected to the feed port of the water separation tank 11). The reaction receiving tank 7 and the evaporation receiving tank 10 are used to receive and buffer the condensate in the reaction condenser 6 and the evaporation condenser 9, respectively.

[0037] In this embodiment, the device further includes a scraper evaporator 8 (the fraction obtained by distillation in the scraper evaporator 8 is a mixture of nitromethane, water and methanol, etc.), the scraper evaporator 8 has at least a fourth feed port, a second top discharge port and a second bottom discharge port, and the fourth feed port is connected to the first bottom discharge port of the reaction intermediate kettle 5 (that is, the discharge port at the bottom of the reaction intermediate kettle 5 is connected to the feed port at the top of the scraper evaporator 8 through a pipeline). The reaction intermediate kettle 5 is connected to the scraper evaporator 8, and the reaction completed liquid in the reaction intermediate kettle 5 enters the scraper evaporator 8 for rapid steaming to evaporate nitromethane and water, effectively avoiding the reduction of nitromethane yield (side reaction 6) due to hydrolysis of nitromethane during the long-term high-temperature rough steaming process, thereby improving the nitromethane yield, improving production efficiency and reducing system energy consumption. The scraper evaporator 8 quickly evaporates the azeotrope of nitromethane and water (azeotrope boiling point 89.5°C), which enters the water separation tank 11 through the evaporation condenser 9 and the evaporation receiving tank 10. Nitromethane is immiscible with water and has a greater density than water. It is automatically stratified when standing in the water separation tank. Nitromethane and water are discharged from the water separation tank respectively according to the interface position obtained by the interface transmitter. The crude nitromethane is distilled, and the wastewater containing nitromethane returns to the scraper evaporator to continue to evaporate nitromethane. The utility model solves the defects of the traditional batch reactor, which is complicated to operate, and the rough steaming time of the rough steaming reactor is long, resulting in low yield of nitromethane hydrolysis, by carrying out the two processes of nitromethane synthesis and rough steaming in the dynamic tubular reactor 3 and the scraper evaporator 8 respectively. The synthesis reaction in the dynamic tubular reactor 3 takes about 0.5 to 5 minutes, and the rough steaming process of the scraper evaporator 8 takes about 5 to 15 minutes. The materials in the dynamic tubular reactor 3 are exported to the intermediate reaction kettle 5, and the materials in the intermediate reaction kettle 5 are exported to the scraper evaporator 8 for rapid steaming, so that the synthesis and rapid steaming processes are continuously carried out. Preferably, the water separation tank 11 is provided with a level transmitter and an interface transmitter for detecting the liquid level and the interface position, respectively. The nitromethane liquid level position is detected by the interface level meter. The bottom of the water separation tank 11 is connected with a discharge regulating valve for discharging the nitromethane in the lower layer from the water separation tank 11. While the mixed condensate is slowly introduced into the lower part of the water separation tank, the opening of the discharge regulating valve at the bottom is adjusted in combination with the interface position obtained by the interface transmitter to control the discharge flow of nitromethane, so that the liquid level of nitromethane is stabilized at a specified height. The mother liquid water in the upper layer overflows from the overflow port at the top of the water separation tank and is sent to the scraper evaporator 8.

[0038] In this embodiment, the device also includes a mother liquid water tank 12 connected to the water separation tank 11, and the scraper evaporator 8 also has a return port. The mother liquid water tank 12 is connected to the return port through a lifting pump (that is, the top of the mother liquid water tank 12 is connected to the discharge port on the upper part of the water separation tank 11, and the bottom of the mother liquid water tank 12 is connected to the top of the scraper evaporator 8 through a pump); the mother liquid water obtained by stratification in the water separation tank 11 is introduced into the mother liquid water tank 12 for buffering, and the mother liquid water in the mother liquid water tank 12 is pumped to the scraper evaporator 8 to further separate the nitromethane carried.

[0039] In this embodiment, the dynamic tubular reactor 3 is also connected to a reaction temperature control unit 4 for controlling its temperature and pressure, and the reaction temperature control unit 4 includes a pressure transmitter and a temperature transmitter arranged in the dynamic tubular reactor 3. The pressure and temperature in the dynamic tubular reactor 3 can reflect the intensity of the reaction. The present application adopts the existing DCS control system to realize the control of the reaction based on the reaction temperature control unit 4, so that the reaction process proceeds smoothly. For example, when the reaction pressure is small, increasing the temperature of the reaction temperature control unit can speed up the reaction; when the reaction pressure is too large, reducing the temperature of the reaction temperature control unit slows down the intensity of the reaction. That is, a controller based on a DCS control system is used, which can make judgments based on the signals of the collected field instruments (temperature, pressure, flow, liquid level, etc.), and output signals to control the corresponding actuators, and can also be controlled by manual values. In this way, based on the sodium nitrite dissolving and feeding kettle, the dynamic tubular reactor, the reaction intermediate kettle and the scraper evaporator, the automatic control of the whole process from material preparation, synthesis to post-processing is realized, the operation of personnel is reduced, the reaction process is stable and controllable, and the yield is stable.

[0040] In this embodiment, the outer wall of the sodium nitrite dissolving and feeding kettle 1 is provided with a first heating jacket, the outer wall of the dynamic tubular reactor 3 is provided with a first cooling jacket, the outer wall of the reaction intermediate kettle 5 is provided with a second cooling jacket, and the outer wall of the scraper evaporator 8 is provided with a second heating jacket, so as to cool or heat the products in each of them respectively.

[0041] The system for continuously producing nitromethane from sodium nitrite and dimethyl sulfate provided by the present application has sodium nitrite in a uniform solution at 60-110°C and adopts a liquid-liquid phase continuous flow process in a dynamic tubular reactor. Compared with the original kettle-type intermittent solid-liquid-liquid phase reaction process, the yield of nitromethane can be increased by 10-20%; the reaction time is shortened from the original 30min to 0.5-5min, shortened by 83-98%; the crude steaming time is shortened from the original 1.5h to 5-15min, shortened by 83-94%. The reaction and crude steaming post-processing time are greatly shortened, and the production efficiency and nitromethane yield are improved; at the same time, the channel content of the dynamic tubular reactor is small, the equipment occupies a small area, and the reaction is safer.

[0042] The above embodiments are only for illustrating the technical concept and features of the utility model, and their purpose is to enable people familiar with the technology to understand the content of the utility model and implement it accordingly, and they cannot be used to limit the protection scope of the utility model. Any equivalent changes or modifications made according to the spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. A device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate, characterized in that it include: Sodium nitrite dissolving and feeding kettle (1); Dimethyl sulfate feed tank (2); A dynamic tubular reactor (3), the dynamic tubular reactor (3) having a first feed port, a second feed port and a first discharge port, the first feed port being connected to the sodium nitrite dissolving feed kettle (1), and the second feed port being connected to the dimethyl sulfate feed tank (2); A reaction intermediate kettle (5), wherein the reaction intermediate kettle (5) has at least a first top discharge port, a first bottom discharge port and a third feed port, wherein the third feed port is connected to the first discharge port of the dynamic tubular reactor (3); A water separation tank (11), wherein the water separation tank (11) is connected to the first top discharge port of the reaction intermediate kettle (5) via a reaction condenser (6).

2. The device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate according to claim 1, characterized in that: It also includes a reaction receiving tank (7), and the water separation tank (11) is connected to the reaction condenser (6) through the reaction receiving tank (7).

3. The device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate according to claim 1, characterized in that: It also comprises a scraper evaporator (8), wherein the scraper evaporator (8) has at least a fourth feed port, a second top discharge port and a second bottom discharge port, wherein the fourth feed port is connected to the first bottom discharge port of the intermediate reaction vessel (5).

4. The device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate according to claim 3, characterized in that: It also includes an evaporation receiving tank (10) connected to the second top discharge port of the scraper evaporator (8) via an evaporation condenser (9), and the water separation tank (11) is also connected to the evaporation receiving tank (10).

5. The device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate according to claim 4, characterized in that: It also includes a mother liquid water tank (12) connected to the water separation tank (11), and the scraper evaporator (8) also has a return port, and the mother liquid water tank (12) is connected to the return port via a lifting pump.

6. The device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate according to claim 1, characterized in that: The dynamic tubular reactor (3) is also connected to a reaction temperature control unit (4) for controlling the temperature and pressure thereof.

7. The device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate according to claim 6, characterized in that: The reaction temperature control unit (4) comprises a pressure transmitter and a temperature transmitter which are arranged in the dynamic tubular reactor (3).

8. The device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate according to claim 3, characterized in that: The outer wall of the sodium nitrite dissolving and feeding kettle (1) is provided with a first heating jacket, the outer wall of the dynamic tubular reactor (3) is provided with a first cooling jacket, the outer wall of the intermediate reaction kettle (5) is provided with a second cooling jacket, and the outer wall of the scraper evaporator (8) is provided with a second heating jacket.

9. The device for continuously producing nitromethane from sodium nitrite and dimethyl sulfate according to claim 1, characterized in that: The water separation tank (11) is provided with a liquid level transmitter and an interface position transmitter for detecting the liquid level and the interface position respectively.

Images