Efficient nitric acid concentration device in adipic acid production

Abstract

The invention discloses an efficient nitric acid concentration device in adipic acid production. The efficient nitric acid concentration device comprises a first concentration tower, a second concentration tower, a reboiler, a heater, a first preheater, a second preheater, a first cooler, a second cooler, a first condensate tank and a second condensate tank which are sequentially arranged, in the production process of nitric acid double-effect thermal coupling rectification concentration, by balancing the thermal coupling matching degree of the two concentration towers and recycling the heat of secondary gas and liquid, the efficiency of the concentration towers and the secondary gas-thermal coupling utilization rate are improved, the operation flexibility and stability of the concentration towers are improved, and the production cost is reduced. The nitric acid concentration quality is improved, steam is saved, and the production cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of adipic acid production technology, and specifically relates to a highly efficient nitric acid concentration device in adipic acid production. Background Technology

[0002] In the KA oil nitric acid oxidation process for producing adipic acid, nitric acid with a concentration of 50-70 wt% is used as raw material and reacted with a mixture of cyclohexanol and cyclohexanone. To ensure the stability and controllability of the reaction, the molar ratio of the cyclohexanol / cyclohexanone mixture to nitric acid is generally controlled between 1:5.0 and 8.0, i.e., excess nitric acid. During the reaction, a solution mixture with a concentration of 15-30 wt% adipic acid and 20-30 wt% nitric acid is produced. After a crystallization separation process, the separated nitric acid solution is sent to the mother liquor concentration section for heating, evaporation, and concentration.

[0003] In the mother liquor concentration process, a double-effect distillation process is typically employed. The mother liquor acid enters two series-connected concentration towers, a first concentration tower and a second concentration tower. After heating and distillation, the nitric acid can be recovered and reused. Specifically, after the mother liquor acid enters the first concentration tower, steam is used to heat the mother liquor acid solution inside. The bottom liquid phase from the first concentration tower enters the second concentration tower for secondary heating and distillation. The resulting nitric acid solution, with a concentration of 50–58 wt%, is then sent to an oxidizing acid storage tank for use as oxidizing acid. The overhead gas from the first concentration tower is used as a heat source for the second concentration tower. After being processed by a vacuum system, the condensate from both the first and second concentration towers is collected and discharged. However, the double-effect distillation process for mother liquor acid suffers from low steam efficiency and significant secondary heat energy loss. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by providing a highly efficient nitric acid concentration device in adipic acid production. By balancing the thermal coupling matching degree of the two concentration towers and reusing the heat of the secondary gas and liquid, the efficiency of the concentration towers and the thermal coupling utilization rate of the secondary gas are improved.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A highly efficient nitric acid concentration device for adipic acid production includes a first concentration tower and a second concentration tower, a reboiler, a heater, a first preheater, a second preheater, a first cooler, a second cooler, a first condensate tank, and a second condensate tank arranged sequentially. The front end of the first concentration tower is connected to the mother liquor acid feed pipeline, and its bottom is connected to the inlet and outlet of the reboiler tube side through pipelines. The bottom liquid phase is connected to the second concentration tower through pipelines, and the top gas phase is connected to the tube side inlet of the heater installed at the bottom of the second concentration tower through pipelines. The gas phase outlet of the heater tube side is connected to the inlet of the first cooler tube side through a pipeline, and the liquid phase outlet of the heater tube side is connected to the first condensate tank through a pipeline. The liquid phase outlet of the first cooler tube side is connected to the first condensate tank via a pipeline, and the gas phase outlet of the first cooler tube side is connected to NO via a pipeline through the first vacuum pump. X A gas recovery system, and a first regulating valve is provided in parallel on the first vacuum pump as a bypass pipeline; The liquid phase of the first condensate tank is connected to the inlet of the first preheater tube side via a pipeline and centrifugal pump. The liquid phase at the bottom of the second concentration tower is connected to the acid oxidizing tank via a pipeline, while the gas phase at the top of the tower is connected to the second preheater and the second cooler via pipelines respectively. The liquid phase outlet of the second preheater tube side is connected to the second condensate tank via a pipeline, and a fourth temperature sensor is installed on the pipeline. Its gas phase outlet is connected to NO via a pipeline through the second vacuum pump. X Gas recovery system; The liquid phase outlet of the second cooler is connected to the second condensate tank via a pipeline, and its gas phase outlet is connected to NO via the second vacuum pump. X The gas recovery system, and the second vacuum pump is also equipped with a second regulating valve as a bypass pipeline; The condensate outlet of the second condensate tank is connected to the condensate collection tank via the second centrifugal pump.

[0006] The second concentration tower is equipped with a second thermometer at the bottom, which is controlled and connected to a first temperature regulating valve installed on the reboiler shell-side steam pipeline.

[0007] The pipeline between the top gas phase of the first concentration tower and the heater is also equipped with a first pressure gauge, and the first pressure gauge is connected to a second regulating valve installed on the bypass pipeline of the second vacuum pump.

[0008] A second pressure gauge is installed on the gas phase pipeline at the top of the second concentration tower, and the second pressure gauge is connected to the first regulating valve installed on the bypass pipeline of the first vacuum pump.

[0009] A third regulating valve is also installed on the pipeline between the top gas phase of the second concentration tower and the second preheater. The shell-side outlet of the second preheater leads to the hot water tank, and a fifth temperature sensor is installed on the pipeline between the two. The third regulating valve is connected to the fourth and fifth temperature sensors.

[0010] The shell-side inlet of the first preheater is connected to the mother liquor feed pipeline, and its shell-side outlet is connected to the hot mother liquor tank through a pipeline, with a third temperature sensor and a fourth regulating valve installed on the pipeline.

[0011] The outlet of the first preheater tube side is connected to the condensate collection tank.

[0012] The beneficial effects of this invention are: This invention discloses a highly efficient nitric acid concentration device for adipic acid production, comprising a first and second concentration tower, a reboiler, a heater, a first preheater, a second preheater, a first cooler, a second cooler, a first condensate tank, and a second condensate tank arranged sequentially. After concentration by the double-effect thermal coupling concentration tower, the nitric acid can be recycled. In the production process of nitric acid double-effect thermal coupling distillation concentration, by balancing the thermal coupling matching degree of the two concentration towers and reusing the heat of the secondary gas and liquid, the efficiency of the concentration tower and the utilization rate of the secondary gas thermal coupling are improved, the operational flexibility and stability of the concentration tower are improved, the quality of nitric acid concentration is improved, steam is saved, and production costs are reduced. Attached Figure Description

[0013] Figure 1 This is a flowchart illustrating the present invention. Detailed Implementation

[0014] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0015] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0016] This invention provides a highly efficient nitric acid concentration device for adipic acid production, such as... Figure 1 As shown.

[0017] A highly efficient nitric acid concentration device for adipic acid production includes a first concentration tower 1 and a second concentration tower 2, a reboiler 3, a heater 4, a first preheater 5, a second preheater 6, a first cooler 7, a second cooler 8, a first condensate tank 9, and a second condensate tank 10 arranged sequentially. The front end of the first concentration tower 1 is connected to the mother liquor acid feed pipeline, and its bottom is connected to the inlet and outlet of the reboiler 3 via pipelines. The liquid phase at the bottom of the tower is connected to the second concentration tower via a pipeline, and the gas phase at the top of the tower is connected to the inlet of the heater 4 located at the bottom of the second concentration tower via a pipeline. The gas phase outlet of heater 4 is connected to the inlet of the first cooler tube via a pipeline, and the liquid phase outlet of heater 4 is connected to the first condensate tank 9 via a pipeline.

[0018] The liquid phase outlet of the first cooler 7 is connected to the first condensate tank 9 via a pipeline. The gas phase outlet of the first cooler 7 is connected to NO via a pipeline through the first vacuum pump 11. X A gas recovery system, and a first regulating valve 31 is provided in parallel on the first vacuum pump 11 as a bypass pipeline; The liquid phase of the first condensate tank 9 is connected to the inlet of the first preheater tube side via a pipeline and centrifugal pump. The liquid phase at the bottom of the second concentration tower 2 is connected to the acid oxidizing tank via a pipeline, while the gas phase at the top of the tower is connected to the second preheater 6 and the second cooler 8 via pipelines respectively. The liquid phase outlet of the second preheater 6 is connected to the second condensate tank 10 via a pipeline, and a fourth temperature sensor is installed on the pipeline. Its gas phase outlet is connected to NO via a pipeline through the second vacuum pump 12. X Gas recovery system.

[0019] The liquid phase outlet of the second cooler 8 is connected to the second condensate tank 10 via a pipeline, and its gas phase outlet is connected to NO via the second vacuum pump 12. X The gas recovery system, and the second vacuum pump 12 is also equipped with a second regulating valve 32 as a bypass pipeline; The condensate outlet of the second condensate tank 10 is connected to the condensate collection tank via centrifugal pump 14.

[0020] The bottom of the second concentration tower 2 is equipped with a second thermometer, which is connected to the first temperature regulating valve installed on the shell side steam pipeline of the reboiler 3.

[0021] The pipeline between the top gas phase of the first concentration tower 1 and the heater 4 is also equipped with a first pressure gauge, and the first pressure gauge is connected to the second regulating valve 32 installed on the bypass pipeline of the second vacuum pump 12.

[0022] A second pressure gauge is installed on the gas phase pipeline at the top of the second concentration tower 2, and the second pressure gauge is connected to the first regulating valve 31 installed on the bypass pipeline of the first vacuum pump 11.

[0023] A third regulating valve 33 is also provided on the pipeline between the top gas phase of the second concentration tower 2 and the second preheater 6. The shell outlet of the second preheater 6 leads to the hot water tank, and a fifth temperature sensor is provided on the pipeline between the two. The third regulating valve 33 is connected to the fourth and fifth temperature sensors.

[0024] The shell-side inlet of the first preheater 5 is connected to the mother liquor feed pipeline, and its shell-side outlet is connected to the hot mother liquor tank through a pipeline. A third temperature sensor and a fourth regulating valve 34 are installed on the pipeline, while the tube-side outlet of the first preheater 5 is connected to the condensate collection tank.

[0025] The following description, in conjunction with specific embodiments, provides further details: This invention relates to a highly efficient nitric acid concentration device for adipic acid production, comprising a first concentration tower 1 and a second concentration tower 2, a reboiler 3, a heater 4, a first preheater 5, a second preheater 6, a first cooler 7, and a second cooler 8. The system consists of a first condensate tank 9, a second condensate tank 10, a first vacuum pump 11, a second vacuum pump 12, a first centrifugal pump 13, a second centrifugal pump 14, and pipelines. The first concentration tower 1 is connected to the mother liquor acid feed pipeline. A first temperature sensor is installed at the bottom of the first concentration tower 1. The bottom of the first concentration tower 1 is connected to the inlet and outlet of the reboiler 3 via pipelines. The liquid phase at the bottom of the first concentration tower 1 is connected to the second concentration tower 2 via a pipeline. The gas phase at the top of the first concentration tower 1 is connected to the inlet of the heater 4 at the bottom of the second concentration tower 2 via a pipeline. A first pressure sensor is installed on the gas phase pipeline at the top of the first concentration tower 1. The gas phase outlet of the heater 4 is connected to the inlet of the first cooler 7 via a pipeline. The liquid phase outlet of the heater 4 is connected to the first condensate tank 9 via a pipeline. The liquid phase outlet of the first cooler 7 is connected to the first condensate tank 9 via a pipeline. The gas phase outlet of the first cooler 7 is connected to the inlet of the first vacuum pump 11 via a pipeline. The first vacuum pump 11 is connected to the NO... X A gas recovery system is connected. The first vacuum pump 11 is equipped with a bypass pipeline, and a first regulating valve 31 is installed on the bypass pipeline. The liquid phase of the first condensate tank 9 is connected to the inlet of the first centrifugal pump 13 through a pipeline, and the outlet of the first centrifugal pump 13 is connected to the inlet of the tube side of the first preheater 5 through a pipeline. The outlet of the tube side of the first preheater 5 is connected to the condensate tank. The shell side inlet of the first preheater 5 is connected to the mother liquor feed pipeline, and the shell side outlet of the first preheater 5 is connected to the hot mother liquor tank through a pipeline. A third temperature sensor and a regulating valve are installed on the pipeline. The liquid phase at the bottom of the second concentration tower 2 is connected to the oxidizing acid tank through a pipeline. A second temperature sensor is installed at the bottom of the second concentration tower 2; the gas phase at the top of the second concentration tower 2 is connected to the second preheater 6 and the second cooler 8 via pipelines, and a second pressure sensor is installed on the gas phase pipeline at the top of the second concentration tower 2; a regulating valve is installed on the pipeline connecting the gas phase at the top of the second concentration tower 2 to the inlet of the tube side of the second preheater 6; the liquid phase outlet of the tube side of the second preheater 6 is connected to the second condensate tank 10 via a pipeline, and a fourth temperature sensor is installed on the pipeline; the gas phase outlet of the tube side of the second preheater 6 is connected to the second vacuum pump 12 via a pipeline; the outlet of the second vacuum pump 12 is connected to NO via a pipeline. XThe gas recovery system is equipped with a bypass pipeline for the second vacuum pump 12, and a regulating valve is installed on the bypass pipeline. The liquid phase outlet of the tube side of the second cooler 8 is connected to the second condensate tank 10 via a pipeline. The gas phase outlet of the tube side of the second cooler 8 is connected to the inlet pipeline of the second vacuum pump 12. The shell side inlet of the second preheater 6 is connected to a pure water pipeline, and the shell side outlet is connected to a hot water tank. A fifth temperature sensor is installed on the pipeline. The condensate outlet of the second condensate tank 10 is connected to the inlet of the second centrifugal pump 14, and the outlet of the second centrifugal pump 14 is connected to the condensate tank via a pipeline. An absorbent spray device is installed at the top of the first concentration tower 1 and the second concentration tower 2.

[0026] Implementation example: Main equipment specifications: First concentration tower 1 has a diameter of 4000mm and a height of 22000mm; Second concentration tower 2 has a diameter of 5000mm and a height of 23000mm.

[0027] Mother liquor acid with a nitric acid concentration of 20-30 wt% and a flow rate of 80 t / h is sent to the first concentration tower 1. The bottom of the first concentration tower 1 is connected to the tube side of reboiler 3 via a pipeline. Steam at a pressure of 0.4-0.5 MPa.g and a temperature of about 155℃ is introduced into the shell side inlet of reboiler 3. The mother liquor acid in the tubes of reboiler 3 is heated by the shell side steam and rapidly flows along the tube wall in a film-like manner. A large amount of water evaporates from the surface of the liquid film in the tubes, causing the mother liquor acid to be rapidly superheated along the tube wall surface, thereby generating upward thermal force. This drives the mother liquor acid to circulate naturally between the first concentration tower 1 and reboiler 3, continuously heating and evaporating. The steam condensate is sent to the condensate collection tank through the lower outlet pipeline of the shell side of reboiler 3.

[0028] The gas at approximately 110°C generated at the top of the first concentration tower 1 is sent to the shell-side inlet of heater 4. After heat exchange between the first concentration tower 1 and heater 4, the condensate at approximately 90°C enters the first condensate tank 9 from the tube-side outlet of heater 4. The uncondensed gas flows into the first condensate tank 9 as liquid after passing through the tube side of the first cooler 7, and the uncondensed gas phase is sent to NO by the second vacuum pump 12. X In the gas recovery system, the liquid containing trace amounts of nitric acid in the second condensate tank 10 is sent to the condensate collection tank via the second centrifugal pump 14. After entering the tube inlet of the first preheater 5 via the second centrifugal pump 14, it exchanges heat with the mother liquor, which is at a temperature of about 30°C in the shell side, and its temperature drops to about 50°C before entering the condensate collection tank. The mother liquor at about 30°C is then heated to 80°C by the first preheater 5 and enters the hot mother liquor tank. The pressure of the first concentration tower 1 is controlled by a first pressure gauge installed in the pipeline between the gas phase at the top of the first concentration tower 1 and the heater 4. The first pressure gauge is connected to a first regulating valve 31 installed on the bypass of the second vacuum pump 12, and the pressure is controlled at about 880 mmHg.A.

[0029] A second thermometer is installed at the bottom of the second concentration tower 2. A first temperature regulating valve is installed on the steam pipeline of the shell side of the reboiler 3 to control the temperature at the bottom of the first concentration tower 1 at approximately 123°C. The steam flow rate of the reboiler 3 is controlled by the temperature of the liquid at the bottom of the second concentration tower 2. This improves the heat load balance between the first concentration tower 1 and the second concentration tower 2, enhances the thermal coupling matching degree between the first concentration tower 1 and the second concentration tower 2, and reduces the steam consumption of the first concentration tower 1 from 30 t / h to approximately 18 t / h. The nitric acid content in the mother liquor acid coming out of the bottom of the first concentration tower 1 reaches approximately 40 wt%. The approximately 40 wt% mother liquor acid after concentration in the first concentration tower 1 is sent to the second concentration tower 2 for further concentration. The mother liquor acid in the second concentration tower 2 is heated and evaporated by heater 4, so that the bottom of the second concentration tower 2... The nitric acid content in the mother liquor is concentrated to 45-55 wt% and pumped to the oxidizing acid storage tank via the bottom pump of the second concentration tower 2. The gas phase generated at the top of the second concentration tower 2, with a temperature of about 60°C, enters the heater 4 and the second cooler 8. The gas flow rate of the second preheater 6 is controlled by a third temperature sensor installed at the tube outlet of the second preheater 6 and a fifth temperature sensor installed at the shell outlet of the second preheater 6, and is controlled by a third regulating valve 33 on the pipeline between the shell outlet of the second preheater 6 and the hot water tank, with a flow rate of about 12 t / h. After passing through the second cooler 8, the gas phase at the top of the second concentration tower 2 is cooled to about 30°C and flows into the second condensate tank 10. The uncondensed gas phase and the uncondensed gas from the second preheater 6 merge and enter the first vacuum pump 11 to be sent to NO. X Gas recovery system. The absorbent enters the tower through the spray device at the top of the first concentration tower 1 and the second concentration tower 2. The liquid in the second condensate tank 10 is sent to the condensate collection tank by the second centrifugal pump 14. Finally, the gas phase condensate (containing 30ppm trace nitric acid) at the top of the first concentration tower 1 and the second concentration tower 2 flows into the condensate collection tank and is then sent to the biological treatment pond for treatment.

[0030] This invention utilizes the reaction of KA oil with excess nitric acid to produce a solution mixture of 15-20 wt% adipic acid and 30 wt% nitric acid. The nitric acid solution separated by the crystallization process is then concentrated by a double-effect thermal coupling of concentration towers #1 and #2. The nitric acid can be recycled. During the concentration process, by balancing the thermal coupling matching degree of the two concentration towers, the heat of the secondary gas and liquid is reused, which improves the evaporation efficiency of the distillation tower and the thermal coupling utilization rate of the secondary gas, improves the operability of the concentration tower, and enhances the quality of nitric acid concentration. The equipment investment is relatively small, the steam consumption is low, and the amount of coal used to produce steam is reduced, which also reduces environmental pollution and lowers production costs.

[0031] If this patent uses terms such as "first" and "second" to define components, those skilled in the art should know that the use of "first" and "second" is merely for the convenience of describing the invention and simplifying the description, and the above terms have no special meaning.

[0032] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this invention is defined by the appended claims and their equivalents.

[0033] In the description of this invention, it should be understood that the terms "front", "rear", "left", "right", "center", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to facilitate the description of this invention and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0034] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A highly efficient nitric acid concentration device for adipic acid production, characterized in that: It includes a first concentration tower and a second concentration tower, a reboiler, a heater, a first preheater, a second preheater, a first cooler, a second cooler, a first condensate tank and a second condensate tank arranged in sequence; The front end of the first concentration tower is connected to the mother liquor acid feed pipeline, and its bottom is connected to the inlet and outlet of the reboiler tube side through pipelines. The bottom liquid phase is connected to the second concentration tower through pipelines, and the top gas phase is connected to the tube side inlet of the heater installed at the bottom of the second concentration tower through pipelines. The gas phase outlet of the heater tube side is connected to the inlet of the first cooler tube side through a pipeline, and the liquid phase outlet of the heater tube side is connected to the first condensate tank through a pipeline. The liquid phase outlet of the first cooler tube side is connected to the first condensate tank via a pipeline, and the gas phase outlet of the first cooler tube side is connected to NO via a pipeline through the first vacuum pump. X A gas recovery system, and a first regulating valve is provided in parallel on the first vacuum pump as a bypass pipeline; The liquid phase of the first condensate tank is connected to the inlet of the first preheater tube side via a pipeline and centrifugal pump. The liquid phase at the bottom of the second concentration tower is connected to the acid oxidizing tank via a pipeline, while the gas phase at the top of the tower is connected to the second preheater and the second cooler via pipelines respectively. The liquid phase outlet of the second preheater tube side is connected to the second condensate tank via a pipeline, and a fourth temperature sensor is installed on the pipeline. Its gas phase outlet is connected to NO via a pipeline through the second vacuum pump. X Gas recovery system; The liquid phase outlet of the second cooler is connected to the second condensate tank via a pipeline, and its gas phase outlet is connected to NO via the second vacuum pump. X The gas recovery system, and the second vacuum pump is also equipped with a second regulating valve as a bypass pipeline; The condensate outlet of the second condensate tank is connected to the condensate collection tank via the second centrifugal pump.

2. The adipic acid production high-efficiency nitric acid concentration device according to claim 1, characterized in that: The second concentration tower is equipped with a second thermometer at the bottom, which is controlled and connected to a first temperature regulating valve installed on the reboiler shell-side steam pipeline.

3. The adipic acid production high-efficiency nitric acid concentration device according to claim 1, characterized in that: The pipeline between the top gas phase of the first concentration tower and the heater is also equipped with a first pressure gauge, and the first pressure gauge is connected to a second regulating valve installed on the bypass pipeline of the second vacuum pump.

4. The efficient nitric acid concentration device for adipic acid production according to claim 1, characterized in that: A second pressure gauge is installed on the gas phase pipeline at the top of the second concentration tower, and the second pressure gauge is connected to the first regulating valve installed on the bypass pipeline of the first vacuum pump.

5. The efficient nitric acid concentration device for adipic acid production according to claim 1, characterized in that: A third regulating valve is also installed on the pipeline between the top gas phase of the second concentration tower and the second preheater. The shell-side outlet of the second preheater leads to the hot water tank, and a fifth temperature sensor is installed on the pipeline between the two. The third regulating valve is connected to the fourth and fifth temperature sensors.

6. The highly efficient nitric acid concentration device for adipic acid production according to claim 1, characterized in that: The shell-side inlet of the first preheater is connected to the mother liquor feed pipeline, and its shell-side outlet is connected to the hot mother liquor tank through a pipeline, with a third temperature sensor and a fourth regulating valve installed on the pipeline.

7. A highly efficient nitric acid concentration device for adipic acid production according to claim 6, characterized in that: The tube outlet of the first preheater is connected to the condensate collection tank.

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