System for absorbing and concentrating tail gas hydrofluoric acid in pentafluoroethane production

Abstract

The utility model relates to the technical field of pentafluoroethane production, in particular to a hydrofluoric acid absorption and concentration system for tail gas in pentafluoroethane production. The hydrofluoric acid absorption and concentration system comprises a tail gas absorption tower, a lower gas inlet of the tail gas absorption tower is connected with a tail gas pipeline through a first gas inlet pipe, and a top gas outlet of the tail gas absorption tower is connected with a lower gas inlet of an auxiliary tail gas absorption tower through a second gas inlet pipe. A bottom liquid outlet of the tail gas absorption auxiliary tower is connected with a second backflow pipe through a second liquid outlet pipe, the second backflow pipe is connected with a bottom heating medium inlet of the graphite heat exchanger, a top heating medium outlet of the graphite heat exchanger is connected with a spraying pipe in the tail gas absorption auxiliary tower through a third backflow pipe, and the second liquid outlet pipe is connected with a solution discharging pipe. The hydrofluoric acid concentration device effectively concentrates hydrofluoric acid obtained by tail gas absorption.

Description

Technical Field

[0001] The utility model relates to the technical field of pentafluoroethane production, in particular to a hydrogen fluoride absorption and concentration system for the tail gas of pentafluoroethane production. Background Art

[0002] During the production of pentafluoroethane, the currently recovered concentration of hydrogen fluoride in the liquid-phase water washing system is about 10-13%, slightly higher in winter and slightly lower in summer, affected by the temperature. Hydrogen fluoride in the tail gas dissolves in water to form hydrofluoric acid. However, as the concentration of hydrogen fluoride in hydrofluoric acid increases, the temperature of hydrofluoric acid also rises accordingly. When the concentration of hydrofluoric acid reaches more than 15%, the temperature of the recovered hydrofluoric acid solution can reach above 40°C. With the increase of the external air temperature, the absorption effect is poor and the concentration is difficult. The generated hydrogen fluoride is sent out by a magnetic pump. As the concentration of hydrogen fluoride increases, the temperature of the water washing circulation absorption rises too fast, and the high temperature easily causes the magnetic pump to demagnetize and the equipment to be damaged. In addition, the high temperature leads to poor absorption effect, and the sodium fluoride scale generated by the reaction of the tail gas with alkali after entering the alkali washing tower will cause the pump to be damaged.

[0003] The current measures are as follows:

[0004] 1. Increase the pickling circulation volume and enhance the spraying effect. However, the effect is poor and the concentration capacity is limited.

[0005] 2. Cool down the hydrogen fluoride circulating water, but the circulating water temperature is high in summer, resulting in insignificant cooling effect. Content of the Utility Model

[0006] The technical problem to be solved by the utility model is to provide a hydrogen fluoride absorption and concentration system for the tail gas of pentafluoroethane production, which effectively concentrates the hydrofluoric acid obtained by absorbing the tail gas.

[0007] The hydrogen fluoride absorption and concentration system for the tail gas of pentafluoroethane production described in the utility model includes a tail gas absorption tower. The lower air inlet of the tail gas absorption tower is connected to the tail gas pipeline through a first inlet pipe. The top air outlet of the tail gas absorption tower is connected to the lower air inlet of a secondary tail gas absorption tower through a second inlet pipe. The bottom liquid outlet of the secondary tail gas absorption tower is connected to a second return pipe through a liquid outlet pipe. The second return pipe is connected to the bottom heat medium inlet of a graphite heat exchanger. The top heat medium outlet of the graphite heat exchanger is connected to the spray pipe inside the secondary tail gas absorption tower through a third return pipe. The liquid outlet pipe is connected to a solution discharge pipe.

[0008] Preferably, a first liquid outlet pipe is provided at the bottom of the tail gas absorption tower. The first liquid outlet pipe is connected to a first return pipe through a first magnetic pump. The first return pipe is connected to the spray pipe inside the tail gas absorption tower. The first return pipe is connected to the lower liquid inlet of the secondary tail gas absorption tower through a liquid transfer pipe.

[0009] Preferably, a circulating water inlet pipe is provided at the bottom of the graphite heat exchanger, and a circulating water outlet pipe is provided at the top of the graphite heat exchanger. A water volume regulating valve is provided on the circulating water inlet pipe.

[0010] Preferably, the tail gas pipeline is connected to the second intake pipe.

[0011] Preferably, a flow meter is provided on the second reflux pipe. A bypass reflux pipe is provided in parallel with the flow meter and the flow regulating valve on the second reflux pipe, and a bypass reflux valve is provided on the bypass reflux pipe. The flow meter detects the flow rate of the second reflux pipe in real time. When an abnormality occurs in the second reflux pipe, the data of the flow meter is abnormal, and it can be switched to the bypass reflux pipe for transportation in time, ensuring the continuity of production.

[0012] Preferably, it further includes a liquid outlet branch pipe arranged in parallel with the second liquid outlet pipe. A second magnetic pump and a third magnetic pump are respectively provided on the second liquid outlet pipe and the liquid outlet branch pipe. The outlets of the second magnetic pump and the third magnetic pump are connected through a connecting pipe, and a pressure gauge is provided on the connecting pipe through a root valve. The liquid outlet branch pipe serves as a standby pipeline for the second liquid outlet pipe, which can prevent production accidents caused by poor flow of the second liquid outlet pipe. The pressure gauge can monitor the pressure in the pipeline, increasing the safety of the system.

[0013] Preferably, filters are provided on both the second liquid outlet pipe and the liquid outlet branch pipe.

[0014] Valves can be provided on the pipeline according to control requirements, and the opening and closing of the valves can be used to conveniently control the on-off of the material in the corresponding pipeline and adjust the flow rate of the material.

[0015] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0016] 1. After the tail gas is absorbed by the tail gas absorption tower, it enters the tail gas absorption secondary tower for further absorption. The hydrofluoric acid generated by the tail gas absorption secondary tower is introduced into the graphite heat exchanger through the second reflux pipe for heat dissipation and cooling, and then sprayed out through the spray pipe of the tail gas absorption secondary tower, and is in reverse contact with the gas entering through the air inlet to absorb hydrogen fluoride in the tail gas, and the concentration of hydrofluoric acid is increased; while establishing an acid absorption cycle, the present utility model can cool down, and can increase the concentration of hydrofluoric acid to more than 25%;

[0017] 2. The hydrofluoric acid generated by the tail gas absorption tower enters the tail gas absorption secondary tower, cools down in the graphite heat exchanger together with the hydrofluoric acid generated by the tail gas absorption secondary tower, and the concentration is further increased;

[0018] 3. The present utility model adds a tail gas absorption secondary tower, improves the tail gas treatment capacity, and can be used as an emergency absorption tower at the same time, ensuring the continuity of the production process and improving the work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of the present utility model;

[0020] In the figure: 1. Tail gas absorption tower; 2. Tail gas pipeline; 3. Auxiliary tail gas absorption tower; 4. Second liquid discharge pipe; 5. Second reflux pipe; 6. Graphite heat exchanger; 7. Solution discharge pipe; 8. First liquid discharge pipe; 9. First magnetic pump; 10. First reflux pipe; 11. Circulating water inlet pipe; 12. Circulating water outlet pipe; 13. Water flow regulating valve; 14. Flowmeter; 15. Flow regulating valve; 16. Third reflux pipe; 17. Bypass reflux pipe; 18. Bypass reflux valve; 19. Liquid discharge branch pipe; 20. Second magnetic pump; 21. Third magnetic pump; 22. Connecting pipe; 23. Root valve; 24. Pressure gauge; 25. First air inlet pipe; 26. Filter; 27. Second air inlet pipe; 28. Liquid transfer pipe. Detailed implementation manners

[0021] The present utility model will be clearly and completely described below with reference to the accompanying drawings.

[0022] As Figure 1 shown, the hydrogen fluoride absorption and concentration system for the tail gas in the production of pentafluoroethane according to the present utility model includes a tail gas absorption tower 1. The lower air inlet of the tail gas absorption tower 1 is connected to the tail gas pipeline 2 through a first air inlet pipe 25. The upper air outlet of the tail gas absorption tower 1 is connected to the lower air inlet of an auxiliary tail gas absorption tower 3 through a second air inlet pipe 27. The bottom liquid outlet of the auxiliary tail gas absorption tower 3 is connected to a second reflux pipe 5 through a second liquid discharge pipe 4. The second reflux pipe 5 is connected to the bottom heat medium inlet of a graphite heat exchanger 6. The top heat medium outlet of the graphite heat exchanger 6 is connected to the spray pipe inside the auxiliary tail gas absorption tower 3 through a third reflux pipe 16. The second liquid discharge pipe 4 is connected to a solution discharge pipe 7.

[0023] The bottom of the tail gas absorption tower 1 is provided with a first liquid discharge pipe 8. The first liquid discharge pipe 8 is connected to a first reflux pipe 10 through a first magnetic pump 9. The first reflux pipe 10 is connected to the spray pipe inside the tail gas absorption tower 1. The first reflux pipe 10 is connected to the lower liquid inlet of the auxiliary tail gas absorption tower 3 through a liquid transfer pipe 28.

[0024] The bottom of the graphite heat exchanger 6 is provided with a circulating water inlet pipe 11. The top of the graphite heat exchanger 6 is provided with a circulating water outlet pipe 12. A water flow regulating valve 13 is arranged on the circulating water inlet pipe 11.

[0025] The tail gas pipeline 2 is connected to the second air inlet pipe 27.

[0026] A flowmeter 14 and a flow regulating valve 15 are arranged on the second reflux pipe 5. A bypass reflux pipe 17 is arranged in parallel with the flowmeter 14 and the flow regulating valve 15 on the second reflux pipe 5. A bypass reflux valve 18 is arranged on the bypass reflux pipe 17.

[0027] It further includes a liquid discharge branch pipe 19 arranged in parallel with the second liquid discharge pipe 4. A second magnetic pump 20 and a third magnetic pump 21 are respectively arranged on the second liquid discharge pipe 4 and the liquid discharge branch pipe 19. The outlets of the second magnetic pump 20 and the third magnetic pump 21 are communicated through a connecting pipe 22. A pressure gauge 24 is arranged on the connecting pipe 22 through a root valve 23.

[0028] Filters 26 are provided on both the liquid outlet pipe II 4 and the liquid outlet branch pipe 19.

[0029] The working process is as follows: The tail gas in the tail gas pipe 2 enters the tail gas absorption tower 1 through the inlet pipe I 25 and then enters the tail gas absorption secondary tower 3 through the inlet pipe II 27; the hydrofluoric acid generated in the tail gas absorption secondary tower 3 is introduced into the graphite heat exchanger 6 through the reflux pipe II 5 for heat dissipation and temperature reduction, and then is sprayed out through the spray pipe of the tail gas absorption secondary tower 3, and contacts the tail gas entering through the inlet pipe II 27 in a countercurrent manner to absorb hydrogen fluoride in the tail gas. Since the temperature of the spray liquid drops before spraying, the absorption capacity for hydrogen fluoride increases, and the concentration of hydrofluoric acid is increased; the hydrofluoric acid generated in the tail gas absorption tower 1 enters the tail gas absorption secondary tower 3 through the liquid transfer pipe 28, enters the graphite heat exchanger 6 together with the hydrofluoric acid generated in the tail gas absorption secondary tower 3 for temperature reduction, and the concentration is further increased. The concentrated hydrofluoric acid enters the solution discharge pipe 7 through the liquid outlet pipe II 4 or the liquid outlet branch pipe 19 at the bottom of the tail gas absorption secondary tower 3 and is discharged.

Claims

1. A hydrofluoric acid absorption and concentration system for tail gas from pentafluoroethane production, characterized in that: The invention comprises a tail gas absorption tower (1), wherein the lower air inlet of the tail gas absorption tower (1) is connected to the tail gas pipeline (2) through an air inlet pipe 1 (25), the top air outlet of the tail gas absorption tower (1) is connected to the lower air inlet of the tail gas absorption auxiliary tower (3) through an air inlet pipe 2 (27), the bottom liquid outlet of the tail gas absorption auxiliary tower (3) is connected to a reflux pipe 2 (5) through a liquid outlet pipe 2 (4), the reflux pipe 2 (5) is connected to a heat medium inlet at the bottom of a graphite heat exchanger (6), the top heat medium outlet of the graphite heat exchanger (6) is connected to a spray pipe in the tail gas absorption auxiliary tower (3) through a reflux pipe 3 (16), and the liquid outlet pipe 2 (4) is connected to a solution discharge pipe (7).

2. The hydrofluoric acid absorption and concentration system for tail gas from pentafluoroethane production according to claim 1, characterized in that: A liquid outlet pipe (8) is provided at the bottom of the tail gas absorption tower (1). The liquid outlet pipe (8) is connected to a reflux pipe (10) via a magnetic pump (9). The reflux pipe (10) is connected to a spray pipe in the tail gas absorption tower (1). The reflux pipe (10) is connected to a liquid inlet at the bottom of the tail gas absorption auxiliary tower (3) via a liquid transfer pipe (28).

3. The hydrofluoric acid absorption and concentration system for tail gas from pentafluoroethane production according to claim 1, characterized in that: A circulating water inlet pipe (11) is provided at the bottom of the graphite heat exchanger (6), a circulating water outlet pipe (12) is provided at the top of the graphite heat exchanger (6), and a water volume regulating valve (13) is provided on the circulating water inlet pipe (11).

4. The hydrofluoric acid absorption and concentration system for tail gas from pentafluoroethane production according to claim 1, characterized in that: The tail gas pipeline (2) is connected to the second intake pipe (27).

5. The hydrofluoric acid absorption and concentration system for tail gas from pentafluoroethane production according to claim 1, characterized in that: The second return pipe (5) is provided with a flow meter (14) and a flow regulating valve (15), the second return pipe (5) is provided with a bypass return pipe (17) in parallel with the flow meter (14) and the flow regulating valve (15), and the bypass return pipe (17) is provided with a bypass return valve (18).

6. The hydrofluoric acid absorption and concentration system for tail gas from pentafluoroethane production according to claim 1, characterized in that: The invention also comprises a liquid outlet branch pipe (19) arranged in parallel with the second liquid outlet pipe (4); the second liquid outlet pipe (4) and the liquid outlet branch pipe (19) are respectively provided with a second magnetic pump (20) and a third magnetic pump (21); the outlets of the second magnetic pump (20) and the third magnetic pump (21) are connected through a connecting pipe (22); and a pressure gauge (24) is provided on the connecting pipe (22) through a root valve (23).

7. The hydrofluoric acid absorption and concentration system for tail gas from pentafluoroethane production according to claim 6, characterized in that: The second liquid outlet pipe (4) and the liquid outlet branch pipe (19) are both provided with filters (26).

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