阅读说明：本技术 天然气部分氧化制乙炔工艺中nmp溶剂的回收方法 (Method for recovering NMP solvent in process of preparing acetylene by partial oxidation of natural gas ) 是由 陈天文 王萍萍 柯月亮 周昌福 曹宝山 于 2019-02-15 设计创作，主要内容包括：本发明属于通过使一薄层液体与已加热的表面相接触的蒸发实现分离技术领域,具体涉及一种天然气部分氧化制乙炔工艺中NMP溶剂的回收方法。所述方法包括以下步骤：将NMP溶剂经预热器加热至80-99℃,然后置于薄膜蒸发器中实现气相NMP溶剂和固体干馏渣的分离。该方法能够实现对含有易结晶、热敏组分的NMP溶剂的回收,提高了回收率；能够避免结晶、结焦形成的堵塞问题；能够有效控制生产现场的VOCs散排超量问题,不会造成环境污染及职业健康危害；且不需要人工清渣,提高了NMP溶剂回收装置的自动化水平。(The invention belongs to the technical field of separation realized by evaporation of a thin-layer liquid in contact with a heated surface, and particularly relates to a method for recovering an NMP solvent in a process for preparing acetylene by partial oxidation of natural gas. The method comprises the following steps: heating the NMP solvent to 80-99 ℃ by a preheater, and then putting the NMP solvent in a thin film evaporator to realize the separation of the gas phase NMP solvent and the solid dry distillation residue. The method can realize the recovery of the NMP solvent containing the easily crystallized and thermosensitive components, and improves the recovery rate; the blockage problem caused by crystallization and coking can be avoided; the problem of excessive VOCs emission in a production field can be effectively controlled, and environmental pollution and occupational health hazards cannot be caused; and manual slag removal is not needed, so that the automation level of the NMP solvent recovery device is improved.)

A method for recovering NMP solvent, comprising the steps of: the NMP solvent is heated to 80-99 ℃ by a preheater 1 and then is placed in a thin film evaporator 3 to realize the separation of the gas phase NMP solvent and the solid dry distillation residue.

2. A method for recovering an NMP solvent according to claim 1, characterized in that the preheater 1 is a shell and tube preheater, and the inner wall of the preheater is subjected to polishing treatment.

3. A method for recovering a solvent for NMP according to claim 1 or 2, characterized in that the heating medium of the preheater 1 is steam or heat conducting oil.

4. A method for recovering an NMP solvent according to claim 1, 2 or 3, characterized in that a flow rate adjusting valve 10 is provided on a liquid phase inlet line of the preheater 1.

5. A method for recovering an NMP solvent according to claim 1, 2, 3 or 4, wherein the thin film evaporator 3 is a wiped film evaporator.

6. A method for recovering an NMP solvent according to claim 5, wherein said wiper blade of the thin film evaporator is a movable wiper blade.

7. A method for recovering an NMP solvent according to claim 1, 2, 3, 4, 5 or 6, wherein the temperature of said thin film evaporator is 120-170 ℃ and the absolute pressure is 1-5 KPa.

8. A method for recovering an NMP solvent according to claim 1, 2, 3, 4, 5, 6 or 7, further comprising the steps of: the gaseous phase of NMP exiting the thin film evaporator is condensed to a liquid phase by the condenser 2.

9. A method for recovering an NMP solvent according to claim 8, characterized in that the condenser 2 is a vertical shell-and-tube condenser.

10. A method for recovering an NMP solvent according to claim 8 or 9, characterized in that a drain port is provided in a bottom portion of the condenser 2, and the drain port is connected to the solvent recovery tank 6 via a downcomer through which the NMP solvent condensed into a liquid phase falls into the solvent recovery tank 6.

11. A method for recovering an NMP solvent according to claim 10, wherein the solvent recovery tank 6 is provided with a partition plate which is vertically arranged and which divides the tank body inner chamber into a storage region and a precipitation region with a gap between a top of the partition plate and a top of the tank body.

12. A method for recovering an NMP solvent according to claim 10 or 11, wherein one end of the downcomer is connected to a liquid discharge port of the condenser 2, and the other end of the downcomer is immersed below a liquid level in a downcomer region of the solvent recovery tank 6, and a vertical distance between both ends of the downcomer is 10m or more.

13. A method for recovering an NMP solvent according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, wherein a slag discharge port is provided at a bottom of the thin film evaporator 3, the slag discharge port is communicated with a dry residue collection tank 4 through a slag discharge pipe, the dry residue collection tank 4 is provided below the thin film evaporator 3, the bottom of the dry residue collection tank 4 is communicated with a dry residue storage tank 5 through a slag discharge pipe, and the dry residue storage tank 5 is provided below the dry residue collection tank.

14. A method for recovering an NMP solvent according to claim 13, wherein the condenser 2 and the dry slag collecting tank 4 are connected to a vacuum pump 7 through a line, respectively.

15. A method for recovering an NMP solvent according to claim 14, wherein a vacuum control valve 8 is provided in a line connecting the vacuum pump 7 and the retort 4.

16. A method for recovering an NMP solvent according to claim 13, 14 or 15, characterized in that a nitrogen flow rate regulating valve 13 is provided at the bottom of the dry residue collection tank 4.

17. A method for recovering an NMP solvent according to claim 13, 14, 15 or 16, wherein the slag discharging pipe is provided with a slag discharging valve 11, and the slag discharging pipe is provided with a slag discharging valve 12.

Technical Field

The invention belongs to the technical field of separation realized by evaporation of a thin-layer liquid in contact with a heated surface, and particularly relates to a method for recovering an NMP solvent in a process for preparing acetylene by partial oxidation of natural gas.

Background

Acetylene is a very important organic chemical raw material, and is widely used in the fields of metal processing, welding, cutting and the like, and the preparation of chemical products such as ethylene, vinyl chloride, trichloroethylene, vinyl acetate, acrylonitrile, polyacrylonitrile, 1, 4-butanediol and the like ("the acetylene is newly developed in organic synthetic chemistry", step winning, China chemical trade, No. 7, No. 22, No. 103, published Japanese 2015, 12 and 31 days; "research progress of acetylene preparation by low-carbon alkane pyrolysis by thermal plasma", Subaogen and the like, chemical reaction engineering and processes, No. 29, No. 3, No. 230, 236 pages, and published Japanese 2013, 06 and 30 months). The preparation method of acetylene mainly comprises a non-catalytic partial oxidation method, an electric arc method, a plasma method and the like, wherein the electric arc method is eliminated due to high energy consumption, the plasma method is still in a test stage (the current state of research of natural gas acetylene, thinking, angry, vinylon communication, No. 33, No. 2, No. 15-20, No. 2013, No. 12, No. 31 in 2013), the power consumption is high, the requirements on equipment are harsh, the method is difficult to popularize and apply so far, and the non-catalytic partial oxidation method is a main method for producing acetylene.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for recovering an NMP solvent, which can recover an NMP solvent containing easily crystallized and thermosensitive components, improve the recovery rate, avoid the problem of blockage caused by crystallization and coking, and effectively solve the problems of heavy physical labor caused by manual slag removal and excessive discharge of VOCs and occupational health hazards caused by the heavy physical labor.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a method for recovering NMP solvent comprising the steps of: the NMP solvent is heated to 80-99 ℃ by a preheater and then put into a thin film evaporator for evaporation separation.

The method can realize the recovery of the NMP solvent containing the easily crystallized and thermosensitive components, and improves the recovery rate.

The method can avoid the blockage problem caused by crystallization and coking, realize automatic slag discharge and improve the automation level of the dry distillation device.

The method does not need manual slag removal, and does not cause environmental pollution and occupational health hazards.

In order to further improve the recovery rate of the NMP solvent, the preheater is a tubular preheater, and the inner wall of the preheater is polished.

In order to further improve the recovery rate of the NMP solvent, the heating medium is steam or heat conducting oil.

In order to further improve the recovery rate of the NMP solvent, a flow control valve 10 is provided on a liquid phase inlet line of the preheater 1.

In order to further improve the recovery rate of the NMP solvent, the thin film evaporator is a wiped film evaporator.

In order to further improve the recovery rate of the NMP solvent, the scraping blades of the thin film evaporator are movable scraping blades.

In order to further improve the recovery rate of the NMP solvent, the temperature of the thin film evaporator is 120-170 ℃, and the absolute pressure is 1-5 KPa.

In order to further improve the recovery rate of the NMP solvent, the method also comprises the following steps: the gaseous phase NMP from the thin film evaporator was condensed to a liquid phase by a condenser.

In order to further improve the recovery rate of the NMP solvent, the condenser 2 is a vertical shell-and-tube condenser.

In order to further improve the recovery rate of the NMP solvent, the bottom of the condenser 2 is provided with a liquid outlet which is connected with the solvent recovery tank 6 through a downcomer through which the NMP solvent condensed into a liquid phase falls into the solvent recovery tank 6.

In order to further improve the rate of recovery of the NMP solvent, the solvent recovery tank 6 is provided with a vertically arranged partition board which divides the inner cavity of the tank body into a storage area and a down-flow area, and a gap is reserved between the top of the partition board and the top of the tank body.

In order to further improve the recovery rate of the NMP solvent, one end of the downcomer is connected with a liquid outlet of the condenser 2, the other end of the downcomer is immersed below the liquid level of a liquid descending area of the solvent recovery tank 6, and the vertical distance between the two ends of the downcomer is more than 10 m.

In order to further improve the recovery rate of the NMP solvent, the bottom of the thin film evaporator 3 is provided with a slag discharge port which is communicated with a dry distillation slag collecting tank 4 through a slag discharge pipe, the dry distillation slag collecting tank 4 is arranged below the thin film evaporator 3, the bottom of the dry distillation slag collecting tank 4 is communicated with a dry distillation slag storage tank 5 through a slag discharge pipe, and the dry distillation slag storage tank 5 is arranged below the dry distillation slag collecting tank.

In order to further improve the recovery rate of the NMP solvent, the condenser 2 and the dry distillation residue collection tank 4 are respectively connected with a vacuum pump 7 through pipelines.

In order to further improve the recovery rate of the NMP solvent, a vacuum control valve 8 is arranged on a pipeline connecting the vacuum pump 7 and the dry distillation residue collection tank 4.

In order to further improve the recovery rate of the NMP solvent, the bottom of the dry distillation residue collection tank 4 is provided with a nitrogen flow rate regulating valve 13.

In order to further improve the recovery rate of the NMP solvent, the slag discharging pipe is provided with a slag discharging valve 11, and the slag discharging pipe is provided with a slag discharging valve 12.

NMP solvent gets into preheater 1 from preheater 1's inlet, and this inlet is provided with the control valve, and preheater 1 adopts conduction oil or steam heating, and this preheater 1 is shell and tube preheater, and preheater 1's inner wall is through polishing treatment. The NMP solvent enters a thin film evaporator 3 after being heated by a preheater 1, the thin film evaporator 3 is a scraping film evaporator, and scraping blades of the scraping film evaporator 3 are movable scraping blades. In the thin film evaporator 3, the heated NMP solvent realizes the separation of the gas phase NMP solvent and the solid phase dry distillation slag.

The vapor phase NMP solvent enters a condenser 2 through a pipeline arranged at the top of the thin film evaporator 3, the condenser 2 is a vertical shell-and-tube condenser, and the bottom of the condenser 2 is provided with a liquid outlet which is connected with a solvent recovery tank 6 through a downcomer.

The liquid phase NMP solvent after the condensation falls into the down-flow district of solvent recovery jar 6 through the downcomer by gravity (solvent recovery jar 6 is provided with the baffle of vertical setting, separates jar internal chamber for storage area and down-flow district with the baffle, leaves the clearance between baffle top and the jar body top).

One end of the downcomer is connected with a liquid outlet of the condenser 2, the other end of the downcomer is immersed below the liquid level of a liquid descending area of the solvent recovery tank 6, and the vertical distance between the two ends of the downcomer is more than 10 m.

The bottom of the thin film evaporator 3 is provided with a slag discharge hole which is communicated with the dry distillation slag collecting tank 4 through a slag discharge pipe, and the dry distillation slag collecting tank 4 is arranged below the thin film evaporator 3. The bottom of the dry distillation residue collecting tank 4 is communicated with the dry distillation residue storage tank 5 through a residue discharge pipe, and the dry distillation residue storage tank 5 is arranged below the dry distillation residue collecting tank 4. The slag discharging pipe is provided with a slag discharging valve 11, and the slag discharging pipe is provided with a slag discharging valve 12.

The vacuum pump 7 is respectively connected with the vertical tube gas condenser 2 and the dry distillation residue collecting tank 4 through pipelines, a vacuum control valve 8 is arranged on the pipeline connecting the vacuum pump 7 and the dry distillation residue collecting tank 4, and a pressure regulating valve 9 is arranged on the pipeline connecting the vacuum pump 7 and the vertical gas condenser 2.

The liquid inlet pipeline of the preheater 1 is provided with an NMP flow regulating valve 10, the bottoms of the thin film evaporator 3 and the dry distillation residue collecting tank 4 are provided with mutually matched electromagnetic valves, and the bottom of the dry distillation residue collecting tank 4 is provided with a nitrogen flow regulating valve 13.

The nitrogen flow regulating valve 13 is connected with a nitrogen pipe network through a pipeline. When discharging slag, a slag discharging valve 11 on the slag discharging pipe is closed, a vacuum control valve 8 is closed, a nitrogen flow regulating valve 13 is opened, the dry distillation slag collecting tank recovers positive pressure, a slag discharging valve 12 on the slag discharging pipe is opened, and dry distillation slag is discharged into a dry distillation slag storage tank 5 due to gravity. And after the dry distillation slag is discharged, the slag discharging valve 11 on the slag discharging pipe is closed, the nitrogen flow regulating valve 13 is closed, the vacuum control valve 8 is opened, when the pressure reaches the pressure of the thin film evaporator 3, the vacuum control valve 8 is closed, the slag discharging valve 11 on the slag discharging pipe is closed, and the primary slag discharging process is completed. Through the arrangement, the automatic slag discharging function under continuous operation is realized.

The invention has the beneficial effects that:

the method can realize the recovery of the NMP solvent containing the easily crystallized and thermosensitive components, and improves the recovery rate.

The method can avoid the blockage problem caused by crystallization and coking.

The method of the invention does not need manual slag removal, and improves the automation level of the NMP recovery device.

The method can effectively control the excessive discharge of VOCs in the production field, and cannot cause environmental pollution and occupational health hazards.

Drawings

FIG. 1 is a flow diagram of an acetylene concentration system;

FIG. 2 is a schematic view of a batch retort system;

fig. 3 is a thin film evaporator system of example 1, in which 1 is a preheater, 2 is a condenser, 3 is a thin film evaporator, 31 is a thin film evaporator motor, 4 is a retort slag collection tank, 5 is a retort slag storage tank, 6 is a solvent recovery tank, 7 is a vacuum pump, 71 is a vacuum pump motor, 8 is a vacuum control valve, 9 is a pressure regulating valve, 10 is an NMP flow regulating valve, 11 is a slag discharge valve, 12 is a slag discharge valve, 13 is a nitrogen flow regulating valve, No.5 is nitrogen gas at a pressure of 0.5MPa, Iw33 is circulating cooling water, S1.0 is heat transfer oil or steam at a pressure of 1MPa, NMP is an NMP stock solution, S0.6 is heat transfer oil or steam at a pressure of 0.6MPa, and C0.6 is condensate.

Detailed Description

The examples are provided for better illustration of the present invention, but the present invention is not limited to the examples. Therefore, those skilled in the art should make insubstantial modifications and adaptations to the embodiments of the present invention in light of the above teachings and remain within the scope of the invention.