With the rapid development of air separation technology and market demand, more and more air separation units adopt hydrogen-free argon production process to produce high purity argon products. Because the operation of argon production is relatively complex, many units with argon air separation do not carry argon, some units put into the argon system due to the fluctuation of oxygen working condition, the limitation of Operation level and other factors cause unsatisfactory operation condition. This article hopes to make operators have a basic understanding of hydrogen-free argon production through the following simple steps.
1. Pre-cooling crude argon Tower
Full-open process argon discharge crude argon Tower inlet Jing argon Tower front vent valve V766; crude argon Tower I bottom liquid blowing off, discharge valve V753, 754 (need 24 ~ 36 hours ).
2. Precooled refined argon Tower
Fully open process argon discharge crude argon Tower I refined argon Tower valve V6; the argon side non-condensable gas discharge valve V760 on the top of the refined argon tower; refined argon Tower, liquid blowing off at the bottom of refined argon measuring cylinder, discharge valve V756, V755 (precooled refined argon tower can be carried out simultaneously with precooled crude argon Tower ).
3. Check argon pump
① Electronic control system -- whether wiring, control and display are correct.
② Sealing air -- whether the pressure, flow and pipeline are correct and do not leak air.
③ Motor rotation direction -- click the motor to make sure the rotation direction is correct.
④ The front and back piping of the pump -- check and confirm that the piping system is unobstructed. Due to the special property of low-temperature liquid, gas is constantly generated during the liquid flowing process, which ensures that the piping can discharge the generated gas smoothly and prevents the appearance of inverted U-shaped piping. While pump before and after blow discharge tube should be main high out of order to exhaust.
4. Comprehensive inspection of argon system instrument
① Whether the resistance (+) (-) pressure tube, transmitter and display instrument of crude argon Tower I and crude argon Tower II are correct.
② Whether the pressure tube (+) (-) of all the level meters of argon system, transmitter and display instrument are correct.
③ Whether the pressure tube, transmitter and display instrument of all pressure points are correct.
④ Process argon flow FI-701 (the pore plate is in the cold box) (+) (-) pressure tube, transmitter and display instrument are correct.
⑤ Check whether all automatic valves and their adjustment and chain are correct.
5. Working condition adjustment of main tower
① Pull down the large oxygen output on the premise of ensuring the purity of oxygen.
② Control the oxygen-enriched liquid level of the tower 36% ~ 38% (liquid nitrogen throttling into the upper tower valve V2 ).
③ Reduce the expansion amount on the premise of ensuring the main cold liquid surface.
6. Hydrops of crude argon Tower
Further precooling to the premise that the argon tower temperature does not drop (blow-off, discharge valve has been closed), slightly open (intermittent) the liquid flow into the coarse argon Tower I condensation evaporator valve V3, make the condenser of the crude argon Tower work intermittently to produce recirculation liquid, make the stuffing of the I tower of the crude argon Tower cool through, and accumulate in a part of the tower bottom.
Note: ① when opening the V3 valve for the first time, pay close attention to the change of PI-701 pressure and do not fluctuate dramatically (≤60kpa ).
② Observe the liquid level at the bottom of crude argon Tower I LIC-701 the liquid level from nothing. Once it rises to 1500mm full scale, finish precooling and close the V3 valve.
7. Pre-cooling argon pump
① Stop valve before opening the pump.
② First open the pump front blow-off valve V741, V742 cold pump front pipe.
③ Slightly open (intermittently) pump back blow-off valve V737, V738 until the liquid sprays out continuously.
Note: ① this work was first conducted under the guidance of argon pump supplier.
② Safety problems to prevent frostbite.
8. Start the argon pump
① Fully open the back flow valve of the pump, fully close the back stop valve of the pump.
② After starting the argon pump, fully open the back stop valve of the argon pump.
③ Observe that the pressure after the pump should be stable at 0.5 ~ 0.7Mpa(G ),
9. Coarse argon column
① After the argon pump is started and before the V3 valve is opened, the liquid level of the LIC-701 will decrease continuously due to the liquid loss. After the argon pump is started, the V3 valve should be opened as soon as possible, make the argon Tower condenser work and produce recirculation liquid.
② The opening degree of the V3 valve should be very slow, otherwise the working condition of the main tower will produce big fluctuation, which will affect the purity of oxygen, after the coarse argon tower works, open the argon pump delivery valve (the opening degree depends on the pressure after the pump), and finally the delivery valve and the return valve cooperate to stabilize the liquid level of the FIC-701.
③ Observe the resistance of two crude argon towers, the normal crude argon Tower II is 3KPa, the crude argon Tower I is 6Kpa. Just input when very little resistance. Resistance value should be slowly increased (on V3), time ~ 6 hours.
④ Input crude argon should be closely observe the main tower conditions. Prevent affecting the purity of oxygen. Expand with V3. The valve V1 of the air throttle entering the upper tower will automatically close down (automatic position ).
⑤ After the resistance is normal, it will take a long time for the main tower to establish, so all the above operations should be small and slow.
⑥After the resistance of the first argon feeding system is normal, the oxygen content of the process argon reaches the standard ~ 36 hours.
⑦ At the initial stage of the establishment of the argon Tower working condition, the removal amount of process argon should be reduced (15 ~ 40m3/H) in order to improve the purity, when the purity is close to normal (when the purity of argon in the middle of two argon towers reaches more than 98%), the process argon flow rate should be appropriately enlarged (60 ~ 100m3/H), otherwise it is easy to cause the imbalance of argon Tower concentration gradient and affect the working condition of the main tower.
10. Jing Jing argon Tower
① After the oxygen content of process argon is normal, the V6 valve should be opened step by step to turn off the small V766 and the process argon should be imported into the refined argon tower. The principle of switching is to control the flow of FI-701 and try to keep the numerical value in front of the refined argon tower.
② The liquid nitrogen steam valve V8 of the refined argon tower is fully open or automatically switched on, and the nitrogen side pressure PIC-8 of the condensing evaporator of the refined argon tower is controlled at 45Kpa. PIC-8 and PIC-760 of the argon side pressure of the refined argon Tower fluctuate at the initial stage. With the normal operation of the Jing argon Tower, the fluctuation of pressure will decrease.
③ Gradually open the condensate evaporator valve V5 of the liquid nitrogen refined argon tower to increase the working load of the condenser of the refined argon tower. In principle, V766 is gradually turned off after V5 is turned on, and the FI-701 traffic is kept within the previous value. After the refined argon tower is stable, V5 can be put into automatic operation.
④ If the V760 is opened properly, the refined argon tower can be fully opened at the initial stage, and if it is normal, the flow rate of the non-condensable gas emission on the top FI-702 the refined argon tower can be controlled at 2 ~ 8M3/h
⑤ Negative pressure is very easy to occur in the fortifying argon Tower PIC-760 when the working condition fluctuates slightly. Negative pressure will cause the wet air outside the cold box to be absorbed into the fortifying argon Tower backward, and the ice freezes on the pipe wall and the surface of the heat exchanger, causing blocking, therefore, the generation of negative pressure should be eliminated (control the opening of V6, V5 and V760 ). If negative pressure has been generated, turn off V760 immediately until the positive pressure is restored.
⑥When the liquid level at the bottom of the Jing argon Tower has ~ When the temperature is 760mm, slightly open the reboiler nitrogen valve V707 and V4 at the bottom of the argon Tower, and master the opening degree according to the situation. If the valve is over, the pressure of PIC-will be increased, which will reduce the flow rate of process argon FI-701. If it is opened too small, the pressure fluctuation range of the refined argon tower is large, and the working condition is unstable, control the pressure of PIC-760 refined argon tower to be 10Kpa ~ 20KPa is the best, and pressure control is comprehensive (V5, V6, V760, V4 all have influence on pressure ).
11. Adjustment of argon content in argon distillation
The content of argon in argon distillation determines the extraction rate of argon, which directly affects the production of argon products. The content of argon in the appropriate argon distillation is 8% ~ 10%. The main factors that affect the argon content of argon distillation are as follows.
① Oxygen production -- the higher the oxygen production, the higher the argon content of argon distillation, but the lower the purity of corresponding oxygen, the higher the nitrogen content in oxygen, and the greater the risk of nitrogen plug.
② Expansion air volume -- the smaller the expansion air volume, the higher the argon distillation content, but the smaller the expansion air volume, the smaller the liquid product output.
③ Argon distillation flow -- Argon distillation flow is the load of crude argon tower. The smaller the load, the higher the argon distillation content, but the smaller the load, the smaller the argon output.
12. The adjustment of the production of argon products
When the argon system works steadily and normally, the production of argon products needs to be adjusted to reach the design condition. The adjustment of the main tower should be conducted according to 5th items. Argon distillation flow rate depends on the opening of the V3 valve, and process argon flow rate depends on the opening of the V6 and V5 valves. The principle of adjustment should be as slow as possible! It can even increase the opening of only 1% of each valve every day, making the working condition experience the change of purification system, the change of oxygen consumption and the fluctuation of power grid. If the purity of oxygen and argon is normal and the working condition is stable, the load can be increased continuously. If there is a tendency of deterioration in a certain working condition, it indicates that the working condition has reached the limit, and it should be adjusted back. Because each adjustment
