A cyclohexanone oxime distillation tower reboiler material circulation system

Abstract

The present invention discloses a cyclohexanone oxime distillation tower reboiler material circulation system and process, comprising a toluene distillation tower, a toluene distillation tower reboiler and a toluene distillation tower kettle discharge pump, the toluene distillation tower kettle discharge pump outlet is connected to the toluene distillation tower kettle outlet pipeline, the toluene distillation tower and the toluene distillation tower reboiler are connected through a reboiler inlet pipeline, a tower kettle pump outlet to reboiler inlet connecting pipeline is provided between the toluene distillation tower kettle outlet pipeline and the reboiler inlet pipeline, the tower kettle pump outlet to reboiler inlet connecting pipeline replaces the original inert gas nitrogen pipeline that acts as a driving force, and acts as a driving force for the medium in the reboiler inlet pipeline. The present invention utilizes the high pressure of the medium in the tower kettle pump outlet to reboiler inlet connecting pipeline to drive the reboiler material to achieve the purpose of reboiler material circulation, achieve the reboiler heat exchange efficiency, and ensure the optimal operating conditions of the toluene distillation tower.

Description

Technical Field

[0001] The invention relates to the field of cyclohexanone oxime generation, in particular to a cyclohexanone oxime rectification tower reboiler material circulation system and method. Background Art

[0002] The toluene cyclohexanone oxime solution produced by ammoximation and extractant toluene is mainly passed through a negative pressure toluene distillation tower and a cyclohexanone oxime distillation tower to obtain the product cyclohexanone oxime. The extractant toluene is purified by the toluene distillation tower and then recycled. After the toluene is recovered from the top of the toluene distillation tower, the toluene oxime solution is sent to the cyclohexanone oxime distillation tower to further recover the toluene in the material. The bottom of the tower is the cyclohexanone oxime product that meets the target, and the top of the tower is toluene and a small amount of impurities. The reboiler of the toluene distillation tower is a thermal syphon type. During operation, due to the large circulation volume of cyclohexanone oxime and its relatively large viscosity, the circulation is carried out with the help of the inert gas nitrogen in the tower bottom. The inert gas enters the reboiler, which weakens the heat exchange effect of the reboiler, resulting in low toluene content in the effective gas at the top of the tower and high inert gas content; the toluene content at the vent of the non-condensable gas vacuum pump at the top of the tower remains high, the toluene loss is large, the toluene content of the cyclohexanone oxime in the tower bottom increases, the heat exchange efficiency of the reboiler is low, resulting in high energy consumption, which has a certain impact on the environment.

[0003] Traditional distillation reboiler material circulation process Figure 1 As shown, the traditional distillation reboiler material circulation process and system is a thermal syphon reboiler, which relies on the liquid static pressure head in the tower kettle and the density difference of the two-phase flow in the reboiler to generate a driving force to form a thermal syphon movement to achieve material circulation. The reboiler 2 of the toluene distillation tower 1 is a vertical thermal syphon reboiler. During operation, due to the large circulation volume of cyclohexanone oxime, the reboiler resistance is too large when the load increases, resulting in insufficient power and poor circulation. The flow rate of the nitrogen pipeline 3 connecting the reboiler inlet pipeline is adjusted according to the load size to increase the driving force for circulation.

[0004] The disadvantages of the existing process are:

[0005] 1. The material circulation in the reboiler 2 is carried out by increasing the driving force by connecting the nitrogen pipeline 3 with a flow rate. The reboiler 2 is generally composed of two parts: a liquid sensible heat heating section and an evaporation section. In the evaporation tube of the reboiler in a normal state, the liquid is heated by the sensible heat heating section, and then undergoes sub-cooling nucleate boiling and saturated nucleate boiling. During the normal operation stage, the part close to the tube wall is basically covered by a thin layer of liquid, and the heat is transferred from the tube wall to the liquid with nucleate boiling, and these liquids and bubbles are constantly moving upward. However, after being filled with nitrogen, due to the irregularity of the gas flow, the thin layer of liquid covering the part close to the tube wall is easily covered by the inert gas, resulting in poor heat exchange effect of the reboiler 2.

[0006] 2. Inert gas nitrogen enters the reboiler 2 through the nitrogen pipeline 3 and then enters the toluene distillation tower 1. The nitrogen enters the tower, which affects the material balance in the tower and cannot ensure the optimal operation of the distillation tower. The nitrogen is mixed with the effective ingredient toluene through the top of the tower and evaporated, resulting in an increase in the non-condensable gas component at the top of the tower and a decrease in the effective content of toluene, which in turn affects the heat exchange effect of the top condenser 6 of the toluene distillation tower, resulting in poor heat exchange effect of the top condenser 6, and an increase in the amount of toluene carried by the gas at the venting port of the venting pipeline 8 of the non-condensable gas vacuum pump 7 at the top of the tower, resulting in high toluene consumption.

[0007] 3. The inert gas nitrogen enters the reboiler 2 through the nitrogen pipeline 3 and enters the tower, which affects the tower bottom and material balance of the toluene distillation tower 1, and the optimal operation of the toluene distillation tower 1 cannot be guaranteed. The amount of toluene evaporated from the top of the tower is reduced, resulting in an increase in the toluene content of cyclohexanone oxime in the tower bottom, which increases the load and energy consumption of the cyclohexanone oxime distillation tower 10 in the subsequent process.

[0008] 4. Inert gas nitrogen enters the inlet pipeline 4 of the reboiler 2 through the nitrogen pipeline 3. Since the resistance drop of the reboiler is greater than the resistance drop of the pipeline connected to the tower kettle, the inlet pipeline 4 is the connecting pipeline between the tower kettle of the toluene distillation tower 1 and the reboiler 2. The nitrogen filled in may partially enter the tower kettle of the toluene distillation tower 1 and cannot play a driving force role. Summary of the invention

[0009] In order to solve the technical problems existing in the above-mentioned prior art, the present invention provides a cyclohexanone oxime distillation tower reboiler material circulation system and process, using a tower bottom pump outlet to the reboiler inlet connecting pipeline to replace the original inert gas nitrogen pipeline that acts as a driving force, which acts as a driving force for the medium in the reboiler inlet pipeline.

[0010] In order to solve the technical problem, the technical solution adopted by the present invention is: a cyclohexanone oxime distillation tower reboiler material circulation system, comprising a toluene distillation tower, a toluene distillation tower reboiler and a toluene distillation tower kettle discharge pump, the toluene distillation tower kettle discharge pump outlet is connected to the toluene distillation tower kettle outlet pipeline, the toluene distillation tower and the toluene distillation tower reboiler are connected through a reboiler inlet pipeline, a kettle pump outlet to reboiler inlet connecting pipeline is provided between the toluene distillation tower kettle outlet pipeline and the reboiler inlet pipeline, the kettle pump outlet to reboiler inlet connecting pipeline replaces the original inert gas nitrogen pipeline that acts as a driving force, and acts as a driving force for the medium in the reboiler inlet pipeline.

[0011] Furthermore, the connecting pipeline from the tower bottom pump outlet to the reboiler inlet is obliquely inserted into the center of the reboiler inlet pipeline with an obtuse elbow, and the flow direction of the medium in the connecting pipeline from the tower bottom pump outlet to the reboiler inlet is the same as that in the reboiler inlet pipeline.

[0012] Furthermore, the connecting pipeline from the tower bottom pump outlet to the reboiler inlet is obliquely inserted into the center of the reboiler inlet pipeline with a 135° elbow.

[0013] Furthermore, the pressure and flow rate of the medium in the reboiler inlet pipeline are greater than the pressure and flow rate of the medium in the connecting pipeline from the tower bottom pump outlet to the reboiler inlet, and a vacuum zone is formed between the medium in the reboiler inlet pipeline and the medium in the connecting pipeline from the tower bottom pump outlet to the reboiler inlet at the center outlet of the tube where the latter is inserted into the former, and the medium in the connecting pipeline from the tower bottom pump outlet to the reboiler inlet is guided by the medium in the reboiler inlet pipeline to flow along the outlet direction.

[0014] The present invention also discloses a cyclohexanone oxime distillation tower reboiler material circulation process. In this process, a connecting pipeline from the tower kettle pump outlet to the reboiler inlet is arranged between the tower kettle outlet pipeline of the toluene distillation tower and the reboiler inlet pipeline. The tower kettle pump outlet to the reboiler inlet connecting pipeline replaces the original inert gas nitrogen pipeline that serves as a driving force, and serves as a driving force for the medium in the reboiler inlet pipeline.

[0015] Furthermore, the connecting pipeline from the tower bottom pump outlet to the reboiler inlet is obliquely inserted into the center of the reboiler inlet pipeline with an obtuse elbow, and the flow direction of the medium in the connecting pipeline from the tower bottom pump outlet to the reboiler inlet is the same as that in the reboiler inlet pipeline.

[0016] Furthermore, the connecting pipeline from the tower bottom pump outlet to the reboiler inlet is obliquely inserted into the center of the reboiler inlet pipeline with a 135° elbow.

[0017] Furthermore, the pressure and flow rate of the medium in the reboiler inlet pipeline are smaller than the pressure and flow rate of the medium in the connecting pipeline from the tower bottom pump outlet to the reboiler inlet, and a vacuum zone is formed between the medium in the reboiler inlet pipeline and the medium in the connecting pipeline from the tower bottom pump outlet to the reboiler inlet at the center outlet of the tube where the latter is inserted into the former, and the medium in the connecting pipeline from the tower bottom pump outlet to the reboiler inlet is guided by the medium in the reboiler inlet pipeline to flow along the outlet direction.

[0018] Furthermore, the materials in the reboiler inlet pipeline and the pipeline connecting the tower bottom pump outlet to the reboiler inlet all come from the tower bottom of the toluene distillation tower, and the medium composition is exactly the same. After entering the reboiler, the liquid film formed on the tube wall has a uniform composition.

[0019] Beneficial effects of the present invention:

[0020] 1. Use the equipment and pipelines in the existing system. No additional equipment is needed. Only pipeline 9 needs to be configured. The original nitrogen pipeline 3 is retained for start-up and shutdown replacement. Basically, no equipment investment is required.

[0021] 2. After the medium-driven nitrogen pipeline 3 is changed to the outlet pipeline material of the toluene distillation tower kettle discharge pump 11, the heat exchange efficiency of the reboiler 2 is improved, the content of toluene, an effective ingredient at the top of the toluene distillation tower 1, is increased, the influence of the inert gas nitrogen is eliminated, the gas at the venting port of the top vacuum pump of the toluene distillation tower 1 is significantly reduced, the power consumption of the non-condensable gas vacuum pump 7 is saved, and the problem of high toluene consumption is effectively solved.

[0022] 3. Under the same load of the toluene distillation tower 1, the discharge concentration of the effective component cyclohexanone oxime in the bottom of the tower increases and the flow rate decreases, which reduces the load of the cyclohexanone oxime distillation tower 10 and increases the load adjustment range of the distillation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of the existing distillation reboiler material circulation process;

[0024] Figure 2 This is a flow chart of the material circulation process of the distillation reboiler of the present invention;

[0025] Figure 3 This is a schematic diagram of the connection line from the tower kettle pump outlet to the reboiler inlet pipeline connected to the reboiler inlet pipeline;

[0026] In the figure: 1. toluene distillation tower, 2. toluene distillation tower reboiler, 3. nitrogen pipeline, 4. reboiler inlet pipeline, 5. toluene distillation tower kettle pump outlet pipeline, 6. toluene distillation tower top condenser, 7. non-condensable gas vacuum pump, 8. vacuum pump outlet vent pipeline, 9. tower kettle pump outlet to reboiler inlet connecting pipeline, 10. cyclohexanone oxime distillation tower, 11. toluene distillation tower discharge pump. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0028] Example 1

[0029] This embodiment discloses a cyclohexanone oxime distillation tower reboiler material circulation system, such as Figure 2 As shown, it includes a toluene distillation tower 1, a toluene distillation tower reboiler 2 and a toluene distillation tower kettle discharge pump 11, the outlet of the toluene distillation tower kettle discharge pump 11 is connected to the toluene distillation tower kettle outlet pipeline 5, the toluene distillation tower 1 and the toluene distillation tower reboiler 2 are connected through a reboiler inlet pipeline 4, a tower kettle pump outlet to reboiler inlet connecting pipeline 9 is provided between the toluene distillation tower kettle outlet pipeline 5 and the reboiler inlet pipeline 4, the tower kettle pump outlet to reboiler inlet connecting pipeline 9 replaces the original inert gas nitrogen pipeline 3 which plays a driving force role, and plays a driving force role on the medium in the reboiler inlet pipeline.

[0030] During operation, the inert gas nitrogen pipeline 3 which acts as a driving force is closed, and a connecting pipeline 9 is provided from the tower kettle pump outlet pipeline 5 to the reboiler inlet pipeline 4 of the toluene distillation tower. The pressure of the medium in the reboiler inlet pipeline 4 is 0.5MpaG. The toluene distillation tower 1 is a negative pressure tower. The pipeline 9 acts as a driving force for the medium in the pipeline 4, thereby achieving the purpose of optimal heat exchange cycle of the toluene distillation tower reboiler 2.

[0031] like Figure 3 As shown, in order to achieve the effect of medium pushing in pipeline 9. The installation of pipeline 9 must meet certain requirements. If it is directly connected to the bottom of reboiler 2, because the resistance drop of reboiler 2 is greater than the resistance drop of connecting to the kettle of toluene distillation tower 1, the material in pipeline 9 is easy to take a shortcut and return to the kettle of toluene distillation tower 1, which will not play a role. The connecting pipeline from the kettle pump outlet to the reboiler inlet is obliquely inserted into the center of the reboiler inlet pipeline with a 135° elbow, and the flow direction of the medium in the connecting pipeline from the kettle pump outlet to the reboiler inlet is the same as that in the reboiler inlet pipeline.

[0032] The pressure and flow rate of the medium in the reboiler inlet pipeline are both lower than the pressure and flow rate of the medium in the pipeline connecting the tower kettle pump outlet to the reboiler inlet. Specifically, the medium in pipeline 9 comes from the outlet pipeline of the toluene distillation tower kettle discharge pump 11, with a high pressure and a high flow rate, and enters the central part of pipeline 4; the medium in the reboiler inlet pipeline 4 relies on the liquid static pressure head in the toluene distillation tower 1 and the density difference of the two-phase flow in the reboiler 2 to generate a driving force to form a thermal siphon motion to achieve material circulation, with a low flow rate and low pressure; the medium in pipeline 9 with high pressure and high flow rate and the medium in pipeline 4 with low pressure and low flow rate, the two fluids of different pressures are mixed at the outlet of the pipe where pipeline 9 is obliquely inserted into pipeline 4, forming a vacuum zone, and the medium with low pressure in pipeline 4 is guided to flow along the outlet direction by the medium with high pressure in pipeline 9, so as to achieve a driving effect on the medium in pipeline 4, and in the following process, the speed of the mixed fluid is gradually balanced.

[0033] The materials in the inlet pipeline 4 of the reboiler 2 and the outlet pipeline 5 of the toluene distillation tower kettle discharge pump 11 both come from the kettle of the toluene distillation tower 1, and the medium composition is exactly the same. After entering the reboiler 2, the liquid film formed on the tube wall has a uniform composition, which avoids the gas film adhering to the tube wall and reducing the heat exchange efficiency.

[0034] The present embodiment also discloses a cyclohexanone oxime distillation tower reboiler material circulation process. In the present process, a connecting pipeline 9 from the tower bottom pump outlet to the reboiler inlet is provided between the toluene distillation tower bottom outlet pipeline 5 and the reboiler inlet pipeline 4. The tower bottom pump outlet to the reboiler inlet connecting pipeline 9 replaces the original inert gas nitrogen pipeline 3 which serves as a driving force, and serves as a driving force for the medium in the reboiler inlet pipeline.

[0035] In this embodiment, a pipeline 9 is configured from the outlet pipeline of the toluene distillation tower kettle discharge pump 11 of the toluene distillation tower 1 to the reboiler inlet pipeline 4, and the high medium pressure characteristic of the pipeline 9 is utilized to drive the reboiler material to achieve the purpose of reboiler material circulation, thereby achieving the heat exchange efficiency of the reboiler 2, ensuring the optimal operating conditions of the toluene distillation tower 1, and avoiding the inert gas from adhering to the tube wall, thereby reducing the heat exchange efficiency of the reboiler 2 and the operating efficiency of the toluene distillation tower 1.

[0036] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A cyclohexanone oxime distillation tower reboiler material circulation system, comprising a toluene distillation tower, a toluene distillation tower reboiler and a toluene distillation tower kettle discharge pump, wherein the toluene distillation tower kettle discharge pump outlet is connected to the toluene distillation tower kettle outlet pipeline, and the toluene distillation tower and the toluene distillation tower reboiler are connected via a reboiler inlet pipeline, characterized in that: A connecting pipeline from the tower kettle pump outlet to the reboiler inlet is provided between the tower kettle outlet pipeline of the toluene distillation tower and the reboiler inlet pipeline. The tower kettle pump outlet to the reboiler inlet connecting pipeline replaces the original inert gas nitrogen pipeline that plays a driving force role, and plays a driving force role for the medium in the reboiler inlet pipeline; the tower kettle pump outlet to the reboiler inlet connecting pipeline is obliquely inserted into the center of the reboiler inlet pipeline with an obtuse elbow, and the tower kettle pump outlet to the reboiler inlet connecting pipeline has the same flow direction as the medium in the reboiler inlet pipeline; the tower kettle pump outlet The connecting pipeline from the tower kettle pump outlet to the reboiler inlet is obliquely inserted into the center of the reboiler inlet pipeline with a 135° elbow; the pressure and flow rate of the medium in the reboiler inlet pipeline are smaller than the pressure and flow rate of the medium in the connecting pipeline from the tower kettle pump outlet to the reboiler inlet, and a vacuum zone is formed at the outlet of the tube center where the latter is inserted into the former, and the medium in the connecting pipeline from the tower kettle pump outlet to the reboiler inlet is guided by the medium in the reboiler inlet pipeline to flow along the outlet direction.

2. A cyclohexanone oxime distillation tower reboiler material circulation process, characterized in that: This process is implemented based on the system described in claim 1. In this process, a connecting pipeline from the tower kettle pump outlet to the reboiler inlet is provided between the tower kettle outlet pipeline of the toluene distillation tower and the reboiler inlet pipeline. The tower kettle pump outlet to the reboiler inlet connecting pipeline replaces the original inert gas nitrogen pipeline that plays a driving force role, and plays a driving force role for the medium in the reboiler inlet pipeline; the tower kettle pump outlet to the reboiler inlet connecting pipeline is obliquely inserted into the center of the reboiler inlet pipeline with an obtuse elbow, and the tower kettle pump outlet to the reboiler inlet connecting pipeline and the medium in the reboiler inlet pipeline The flow direction is the same; the connecting pipeline from the tower kettle pump outlet to the reboiler inlet is obliquely inserted into the center of the reboiler inlet pipeline with a 135° elbow; the pressure and flow rate of the medium in the reboiler inlet pipeline are smaller than the pressure and flow rate of the medium in the connecting pipeline from the tower kettle pump outlet to the reboiler inlet, and a vacuum zone is formed between the medium in the reboiler inlet pipeline and the medium in the connecting pipeline from the tower kettle pump outlet to the reboiler inlet at the center outlet of the tube where the latter is inserted into the former, and the medium in the connecting pipeline from the tower kettle pump outlet to the reboiler inlet is guided by the medium in the reboiler inlet pipeline to flow along the outlet direction.

3. The cyclohexanone oxime distillation tower reboiler material circulation process according to claim 2, characterized in that: The materials in the reboiler inlet pipeline and the connecting pipeline from the tower bottom pump outlet to the reboiler inlet all come from the tower bottom of the toluene distillation tower. The medium composition is exactly the same. After entering the reboiler, the liquid film formed on the tube wall has uniform composition.

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