A residue evaporation system for methyl isocyanate production

Abstract

The application discloses a residue evaporation system for methyl isocyanate production, which comprises a residue evaporation intermediate tank, a residue evaporation kettle, a residue evaporation circulating pump, a residue evaporation kettle, a centrifugal machine and a residue washing pool. In use, the residue evaporation circulating pump is started to pour the material into the residue evaporation kettle, the residue evaporation kettle is started to stir, the steam adjusting valve is opened to start residue evaporation, then the residue evaporation kettle is started to stir, the material is transported into the residue evaporation kettle, the liquid alkali is added into the residue evaporation kettle through the alkali delivery pipe, the residue evaporation kettle temperature is controlled, a small amount of methylamine hydrochloride and methyl carbamoyl chloride contained in the residue is decomposed, the PH value of the material is increased to 6-7, and the material is cooled to room temperature. The residue evaporation kettle stirring is stopped, a small amount of trichloromethane is separated by layering and is discharged through the discharge pipe and is then put into a barrel for treatment. Then, the material is transported into the centrifugal machine, the isocyanate residue and waste water are separated, the waste residue is sent to a solid waste treatment equipment, the waste water is pumped into the residue washing pool and is then pumped into a sewage main pipe. The trichloromethane can be recycled, and the residue evaporation circulating pump can effectively solve the material blocking problem.

Description

Technical Field

[0001] This utility model relates to the field of methyl isocyanate production and preparation technology, and in particular to a slag distillation system for methyl isocyanate production. Background Technology

[0002] Methyl isocyanate is an organic synthesis intermediate used in the synthesis of polymers such as polyisocyanates, polyurethanes, and polyurea resins, as well as technical materials such as carbaryl and methomyl. In the methyl isocyanate synthesis section, the purification tower separates chloroform (containing a small amount of methyl isocyanate), which overflows from the tower bottom and is recycled to the acyl chloride section. The tail gas (containing chloroform) from the purification tower is absorbed by bubbling in a chilled tail gas tank before being sent to the tail gas section. In actual production, a slag recovery system is needed to recover residual reactants; however, the current process suffers from problems such as the inability to recover chloroform and issues with feed clogging. Utility Model Content

[0003] The purpose of this application is to provide a slag steaming system for the production of methyl isocyanate, in order to solve the problems of the inability to recover chloroform and the blockage of the feed pipe in the current process.

[0004] To solve the above-mentioned technical problems, this application provides a slag distillation system for methyl isocyanate production, comprising: The intermediate slag tank has a discharge end connected to a slag kettle via a feed pipe. A slag circulation pump is installed on the feed pipe, and the feed pipe is connected to a decomposer near the outlet of the slag circulation pump. The bottom of the slag kettle is connected to a slag discharge kettle via a conveying pipe. An alkali solution conveying pipe is connected to one side of the top of the slag discharge kettle. The bottom discharge end of the slag discharge kettle is connected to a centrifuge via a slag discharge pipe. A discharge pipe is connected to the slag discharge pipe. A slag washing tank is connected to one side of the centrifuge. The bottom of the slag washing tank is connected to a sewage main pipe via a slag washing wastewater pump and a wastewater discharge pipe. The bottom waste slag outlet of the centrifuge is connected to solid waste treatment equipment. The top gas outlet pipe of the slag kettle is connected to the gas outlet of a gas-liquid separator. Both the gas outlet pipe and the top of the slag discharge kettle are connected to tail gas emission pipes. The intermediate slag tank is connected to the gas-liquid separator via a circulation pipe, and the liquid phase outlet pipe of the gas-liquid separator is connected to the feed pipe.

[0005] As a preferred embodiment, a slag steaming system for methyl isocyanate production is provided, wherein the wastewater discharge pipe is further provided with a wastewater circulation pipe connected to the slag discharge vessel.

[0006] The solution requires detailed explanation of a slag steaming system for methyl isocyanate production, wherein there are two intermediate slag steaming tanks connected in parallel.

[0007] In a preferred embodiment, a slag steaming system for methyl isocyanate production is provided, wherein a nitrogen conveying pipe is also provided on the conveying pipe, and a nitrogen purging valve is provided on the nitrogen conveying pipe.

[0008] The solution requires further detailed explanation of a slag steaming system for methyl isocyanate production, wherein an overpressure discharge pipe is installed on one side of the top of the slag steaming vessel, a safety valve is installed on the overpressure discharge pipe, and one end of the overpressure discharge pipe is connected to an emergency exhaust gas tower.

[0009] As a preferred embodiment, a slag steaming system for methyl isocyanate production is provided, wherein the feeding pipe is also connected to a slag washing tank.

[0010] Compared with the prior art, the slag steaming system for methyl isocyanate production provided by this utility model includes a slag steaming intermediate tank. The discharge end of the slag steaming intermediate tank is connected to a slag steaming kettle through a feeding pipe. A slag steaming circulation pump is installed on the feeding pipe. The feeding pipe is connected to a decomposer near the outlet of the slag steaming circulation pump. The bottom of the slag steaming kettle is connected to a slag discharge kettle through a conveying pipe. An alkali conveying pipe is connected to one side of the top of the slag discharge kettle. The bottom discharge end of the slag discharge kettle is connected to a centrifuge through a slag discharge pipe. A discharge pipe is connected to the slag discharge pipe. A slag washing tank is connected to one side of the centrifuge. The bottom of the slag washing tank is connected to a sewage main pipe through a slag washing wastewater pump and a wastewater discharge pipe. The waste slag outlet at the bottom of the centrifuge is connected to solid waste treatment equipment. The gas outlet pipe at the top of the slag steaming kettle is connected to the gas outlet of a gas-liquid separator. Both the gas outlet pipe and the top of the slag discharge kettle are connected to tail gas emission pipes. The slag steaming intermediate tank is connected to the gas-liquid separator through a circulation pipe. The liquid phase outlet pipe of the gas-liquid separator is connected to the feeding pipe. In operation, the slag circulation pump is started to pump the material from the intermediate slag tank into the slag kettle. The kettle agitator is then activated, and the steam regulating valve is opened to begin slag steaming. Slag steaming is stopped when the kettle temperature reaches 110-120℃. Next, the slag discharge kettle agitator is activated, and the material is conveyed to the discharge kettle via the feed pipe. Liquid alkali is added dropwise to the discharge kettle via the alkali feed pipe to control the kettle temperature and decompose the small amounts of methylamine hydrochloride and methylcarbamoyl chloride contained in the slag. The pH of the material is increased to 6-7, and then cooled to room temperature. The discharge kettle agitator is then turned off, and the material is allowed to settle and separate into layers. A small amount of chloroform is then discharged through the discharge pipe and stored in drums. The material is then conveyed through the discharge pipe to a centrifuge to separate isoester residue and wastewater. The waste residue is sent to solid waste treatment equipment, and the wastewater is pumped into a slag washing tank and then pumped into the main sewage pipe via a slag washing wastewater pump. This process completes the recovery of chloroform. Furthermore, the slag circulation pump effectively solves the problem of pipe blockage during material feeding. Attached Figure Description

[0011] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0012] Figure 1 This is a schematic diagram of a slag distillation system for methyl isocyanate production provided in an embodiment of this application; In the diagram: 1. Intermediate slag tank; 01. Liquid phase bottom valve; 2. Feed pipe; 02. Manual valve; 3. Slag kettle; 03. Tail gas valve; 4. Slag circulation pump; 04. Inlet valve; 5. Conveying pipe; 6. Slag discharge kettle; 06. Tail gas pipeline manual valve; 7. Alkali solution conveying pipe; 8. Slag discharge pipe; 9. Centrifuge; 10. Discharge pipe; 11. Slag washing tank; 12. Slag washing wastewater pump; 13. Wastewater discharge pipe; 14. Gas outlet pipe; 15. Tail gas emission pipe; 16. Circulation pipe; 17. Liquid phase outlet pipe; 18. Wastewater circulation pipe; 19. Nitrogen conveying pipe; 20. Nitrogen purging valve; 21. Overpressure discharge pipe; 22. Safety valve; 23. Upper sight glass. Detailed Implementation

[0013] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0014] The core of this application is to provide a slag distillation system for the production of methyl isocyanate, which solves the problems of inability to recover chloroform and pipe blockage during material feeding that exist in current processes.

[0015] Figure 1 A schematic diagram of a slag distillation system for methyl isocyanate production provided in this application embodiment is shown below. Figure 1 As shown.

[0016] Example 1 A slag steaming system for methyl isocyanate production includes a slag steaming intermediate tank 1. The discharge end of the intermediate tank 1 is connected to a slag steaming vessel 3 via a feed pipe 2. A slag steaming circulation pump 4 is installed on the feed pipe 2. The feed pipe 2 is connected to a decomposer near the outlet of the circulation pump 4. The bottom of the slag steaming vessel 3 is connected to a slag discharge vessel 6 via a conveying pipe 5. An alkali solution conveying pipe 7 is connected to one side of the top of the slag discharge vessel 6. The bottom discharge end of the slag discharge vessel 6 is connected to a centrifuge 9 via a slag discharge pipe 8. A discharge pipe 10 is connected to the slag discharge pipe 8. A slag washing tank 11 is connected to one side of the centrifuge 9. The bottom of the slag washing tank 11 is connected to the main sewage pipe through a slag washing wastewater pump 12 and a wastewater discharge pipe 13. The waste slag outlet at the bottom of the centrifuge 9 is connected to the solid waste treatment equipment. The gas outlet pipe 14 at the top of the slag steaming kettle 3 is connected to the gas outlet of the gas-liquid separator. Both the gas outlet pipe 14 and the top of the slag discharge kettle 6 are connected to tail gas discharge pipes 15. The intermediate slag steaming tank 1 is connected to the gas-liquid separator through a circulation pipe 16. The liquid phase outlet pipe 17 of the gas-liquid separator is connected to the feed pipe 2.

[0017] Based on Example 1, in order to avoid the failure of the intermediate slag tank 1 and affect the normal operation of the system, a slag steaming system for methyl isocyanate production is provided. Preferably, there are two intermediate slag steaming tanks 1, and the two intermediate slag steaming tanks 1 are connected in parallel.

[0018] Based on Example 1, in order to improve the cleanliness of material discharge in the conveying pipe 5, a slag steaming system for methyl isocyanate production is preferably provided with a nitrogen conveying pipe 19 and a nitrogen purging valve 20 on the nitrogen conveying pipe 19.

[0019] Based on Example 1, a slag steaming system for methyl isocyanate production, to improve system safety, preferably includes an overpressure discharge pipe 21 on one side of the top of the slag steaming vessel 3. A safety valve 22 is installed on the overpressure discharge pipe 21, and one end of the overpressure discharge pipe 21 is connected to an emergency exhaust gas tower. When the slag steaming vessel 3 experiences overpressure, the safety valve 22 automatically opens and discharges exhaust gas through the overpressure discharge pipe 21 to the emergency exhaust gas tower.

[0020] Based on Example 1, a slag steaming system for methyl isocyanate production is provided, wherein a slag washing tank is also connected to the feed pipe 2.

[0021] Before use, first check and confirm that the bottom valve of the intermediate slag tank 1 is closed, the manhole cover at the slag outlet is tight, the slag outlet drain valve is closed, and the gas phase pipeline valve of the intermediate slag tank 1 is open. Open the slag discharge valve of the gas-liquid separator and close the normal discharge valve. When the liquid reaches 1 / 3 of the upper sight glass 23 of the intermediate slag tank 1, close the decomposer circulating liquid inlet valve and open the liquid phase bottom valve 01 of the intermediate slag tank 1. Confirm that the valves from the slag circulation pump 4 to the decomposer, the two flushing valves to the intermediate slag tank 1, the valve to the washing tank, the gas outlet valve from the slag kettle 3 to the gas-liquid separator, and the bottom valve KV-07221 of the slag kettle 3 are closed. Confirm that the two manual valves 02 on the feed pipe 2 from the slag circulation pump 4 to the slag kettle 3, the feed valve KV-07216 of the slag kettle 3, the inlet valve 04 of the slag circulation pump 4, and the tail gas valve 03 on the tail gas discharge pipe 15 of the slag kettle 3 are open. Start the slag circulation pump 4 to pump the material through the feed pipe. 2. Pour material into the slag steaming kettle 3 and start the agitator inside the kettle. Then, after all the material in the intermediate slag steaming tank 1 is poured into the slag steaming kettle 3, shut down the slag steaming circulation pump 4, close the liquid phase bottom valve 01 of the intermediate slag steaming tank 1, and close the inlet valve 04 of the slag steaming circulation pump 4. Open the shut-off valve before the steam trap in the slag steaming kettle 3 and the bypass valve for the steam trap. The central control unit opens the steam feed switch valve KV-07219 and opens the steam pressure regulating valve PV-07218 to 5% to warm up the steam pipeline and the slag steaming kettle 3. The central control unit slowly opens the steam pressure regulating valve PV-07218, contacting on-site personnel during the slow opening process to ensure there is no liquid hammer in the slag steaming kettle 3 and steam pipelines. Close the bypass valve for the steam trap. The slag steaming kettle 3 begins steaming. The central control unit regulates the temperature of the slag steaming kettle 3 through the steam pressure regulating valve PV-07218 to ensure it is ≤120℃.

[0022] Afterwards, add water to the slag discharge vessel 6 to the set liquid level, tentatively set at 5m. 3Slightly open the steam tracing manual valve of the slag steaming kettle 3 discharge pipeline, and open the shut-off valve and bypass valve of the steam trap in the slag steaming kettle 3 discharge pipeline to warm up the pipeline and ensure no liquid hammer. When the temperature of the slag steaming kettle 3 rises to 110-120℃, the slag steaming is finished. Start the agitator of the slag discharge kettle 6, open the cooling water inlet valve of the jacket of the slag discharge kettle 6, slowly open the steam tracing manual valve of the slag steaming kettle 3 discharge pipeline, confirm that the exhaust gas pipeline manual valve 06 of the slag discharge kettle 6 is open, open the bottom valve KV-07221 of the slag steaming kettle 3, and control the kettle temperature of the slag discharge kettle 6 (<80℃) by controlling the opening of the cooling water return valve of the jacket of the slag discharge kettle 6 until all the material in the slag steaming kettle 3 has been discharged. After confirming that all material has been discharged from the slag discharging vessel 3, shut off the agitator in the slag discharging vessel 3, close the bottom valve KV-07221 of the slag discharging vessel 3, and open the nitrogen purging valve 20 on the conveying pipe 5 to purge the remaining material in the conveying pipe 5 (in this embodiment, the purging time is 10 minutes, but the specific time can be determined according to the actual situation). After purging, close the nitrogen purging valve 20; set the alkali inlet flow rate of the slag discharge vessel 6, and add 8% liquid alkali dropwise into the slag discharge vessel 6 through the alkali conveying pipe 7, controlling the temperature of the slag discharge vessel 6 (<80℃) to decompose. The residue contains a small amount of methylamine hydrochloride and methylcarbamoyl chloride. Add the solution until the pH value of the material reaches 6-7, and cool it to room temperature. Turn off the stirring of the slag discharge vessel 6, let it stand for 30 minutes to separate the layers, and first separate a small amount of chloroform. After being discharged through the discharge pipe 10, it is put into a barrel for treatment. Open the bottom valve KV-07217 of the slag discharge vessel 6 and put the material in the slag discharge vessel 6 into the centrifuge 9 to separate the isoester residue and wastewater. The waste residue is sent to the solid waste treatment equipment for treatment, and the wastewater is pumped into the slag washing tank 11 and sent to the sewage main pipe through the wastewater discharge pipe 13 via the slag washing wastewater pump 12.

[0023] Example 2 Based on Example 1, in order to avoid the presence of chloroform in the wastewater, a slag steaming system for the production of methyl isocyanate is preferably provided with a wastewater circulation pipe 18 connected to the slag discharge vessel 6 on the wastewater discharge pipe 13, so that the wastewater can be pumped back into the slag discharge vessel 6 through the wastewater circulation pipe 18 to recover chloroform.

[0024] This utility model provides a slag steaming system for methyl isocyanate production, comprising a slag steaming intermediate tank 1. The discharge end of the slag steaming intermediate tank 1 is connected to a slag steaming vessel 3 via a feeding pipe 2. A slag steaming circulation pump 4 is installed on the feeding pipe 2. The feeding pipe 2 is connected to a decomposer near the outlet of the slag steaming circulation pump 4. The bottom of the slag steaming vessel 3 is connected to a slag discharge vessel 6 via a conveying pipe 5. An alkali conveying pipe 7 is connected to one side of the top of the slag discharge vessel 6. The bottom discharge end of the slag discharge vessel 6 is connected to a centrifuge 9 via a slag discharge pipe 8. A discharge valve is connected to the slag discharge pipe 8. The material pipe 10 and the centrifuge 9 are connected to a slag washing tank 11 on one side. The bottom of the slag washing tank 11 is connected to the sewage main pipe through the slag washing wastewater pump 12 and the wastewater discharge pipe 13. The waste slag outlet at the bottom of the centrifuge 9 is connected to the solid waste treatment equipment. The gas outlet pipe 14 at the top of the slag steaming kettle 3 is connected to the gas outlet of the gas-liquid separator. Both the gas outlet pipe 14 and the top of the slag discharge kettle 6 are connected to the tail gas discharge pipe 15. The slag steaming intermediate tank 1 is connected to the gas-liquid separator through the circulation pipe 16. The liquid phase outlet pipe 17 of the gas-liquid separator is connected to the feed pipe 2. In use, the slag circulation pump 4 can be started to pump the material in the slag intermediate tank 1 into the slag kettle 3, and the stirring of the slag kettle 3 can be turned on and the steam regulating valve can be opened to start slag steaming. When the temperature of the slag kettle 3 rises to 110-120℃, the slag steaming is stopped. Then, the stirring of the slag discharge kettle 6 can be started, and the material can be transported to the slag discharge kettle 6 through the conveying pipe 5. Liquid alkali can be added dropwise into the slag discharge kettle 6 through the alkali conveying pipe 7 to control the temperature of the slag discharge kettle 6 and decompose the small amount of methylamine hydrochloride and methylcarbamoyl chloride contained in the slag. The pH value of the material is increased to 6-7 and then cooled to room temperature. The stirring of the slag discharge kettle 6 is turned off, and a small amount of trichloromethane is separated by static stratification and discharged into barrels through the discharge pipe 10. Then, the material is transported to the centrifuge 9 through the slag discharge pipe 8 to separate the isoester residue and wastewater. The waste residue is sent to the solid waste treatment equipment, and the wastewater is pumped into the slag washing tank 11 and sent to the sewage main through the slag washing wastewater pump 12. This allows for the recovery of chloroform, and the installation of the slag circulation pump 4 can effectively solve the problem of material blockage during feeding.

[0025] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and incorporate common knowledge or customary techniques in the art disclosed herein. The specification and examples are to be considered exemplary only, and the true scope of this application is indicated by the claims.

[0026] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The embodiments of this application described above do not constitute a limitation on the scope of protection of this application.

Claims

1. A slag distillation system for methyl isocyanate production, characterized in that, include: A slag intermediate tank (1) is provided. The discharge end of the slag intermediate tank (1) is connected to a slag kettle (3) via a feed pipe (2). A slag circulation pump (4) is installed on the feed pipe (2). The feed pipe (2) is connected to a decomposer near the outlet of the slag circulation pump (4). The bottom of the slag kettle (3) is connected to a slag discharge kettle (6) via a conveying pipe (5). An alkali conveying pipe (7) is connected to one side of the top of the slag discharge kettle (6). The bottom discharge end of the slag discharge kettle (6) is connected to a centrifuge (9) via a slag discharge pipe (8). A discharge pipe (10) is connected to the slag discharge pipe (8). The centrifuge (9) is connected to a centrifuge. One side of the centrifuge (9) is connected to a slag washing tank (11). The bottom of the slag washing tank (11) is connected to the sewage main pipe through a slag washing wastewater pump (12) and a wastewater discharge pipe (13). The bottom waste slag outlet of the centrifuge (9) is connected to the solid waste treatment equipment. The top gas outlet pipe (14) of the slag steaming kettle (3) is connected to the gas outlet of the gas-liquid separator. The gas outlet pipe (14) and the top of the slag discharge kettle (6) are both connected to tail gas discharge pipes (15). The slag steaming intermediate tank (1) is connected to the gas-liquid separator through a circulation pipe (16). The liquid phase outlet pipe (17) of the gas-liquid separator is connected to the feeding pipe (2).

2. The slag distillation system for methyl isocyanate production according to claim 1, characterized in that, The wastewater discharge pipe (13) is also equipped with a wastewater circulation pipe (18) connected to the slag discharge vessel (6).

3. The slag distillation system for methyl isocyanate production according to claim 1, characterized in that, There are two intermediate slag tanks (1), and the two intermediate slag tanks (1) are connected in parallel.

4. The slag distillation system for methyl isocyanate production according to claim 1, characterized in that, The material conveying pipe (5) is also provided with a nitrogen conveying pipe (19), and the nitrogen conveying pipe (19) is provided with a nitrogen purging valve (20).

5. The slag distillation system for methyl isocyanate production according to claim 1, characterized in that, An overpressure discharge pipe (21) is also provided on one side of the top of the slag steamer (3). A safety valve (22) is provided on the overpressure discharge pipe (21). One end of the overpressure discharge pipe (21) is connected to the emergency exhaust gas tower.

6. The slag distillation system for methyl isocyanate production according to claim 1, characterized in that, The feeding pipe (2) is also connected to a slag washing tank.

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