The reasons why the liquid enters the heat exchanger when the small air separation plant is running are:
1) during the start-up stage, the speed of closing the valve and lowering pressure of the distillation column is too slow, and the liquid oxygen level is too full, which makes the liquid enter the heat exchanger. The symbol at this time is that the pointer of the pressure gauge of the upper tower fluctuates, the oxygen flow meter beats badly, and the temperature of T3 drops, with which the high and middle pressure automatically drops. When encountering this situation, the valve can be shut down and the pressure-down speed can be increased appropriately, and the large section-1 valve can be opened to increase the air flow through the second heat exchanger. And part of liquid oxygen can be discharged properly. When closing the small air, liquid nitrogen throttle or lowering pressure, it is normal for medium pressure to slightly rise (about 0.05MPa rise every 1 hour ). When the liquid oxygen level drops to the normal position, the temperature and pressure will return to normal automatically. However, do not act too hastily, and do not make the medium pressure rise obviously, in order to avoid liquid flooding.
2) caused by liquid flooding in the upper tower. It symbolizes that the liquid oxygen level drops rapidly at first, the pressure on the upper tower rises, the oxygen purity rises temporarily, and the nitrogen purity declines; then the temperature of T3 and the high and medium pressures decrease, and sometimes the nitrogen flow meter will beat; afterwards, due to the decrease of medium pressure, the amount of oxygen evaporation decreases, the pressure of the upper tower decreases, the liquid oxygen level begins to rise rapidly, the liquid in the upper tower decreases or disappears, and the temperature and pressure of the heat exchanger begin to rise, the medium pressure starts to rise slowly; then the liquid oxygen level starts to fall again, and repeat the above process. According to the different degree of liquid Pan, the interval time of the cycle is also different. Short for tens of minutes, long for several hours once. When the liquid pan causes the liquid, the reasons should be analyzed specifically and different methods should be adopted according to different reasons. If the valve is closed or the liquid flow is caused by lowering pressure, the liquid air and liquid nitrogen throttle valve should be reopened, and the adjustment should be made after the liquid oxygen level rises to the normal height. If the adjustment is not good, it can be adjusted by parking for about half an hour before driving. If it still can't be eliminated, you have to stop the car to warm it up and restart the car. If the liquid flow is caused by excessive processing gas, part of the air should be drained, and then be sent into the equipment step by step after the equipment is normal. If at the end of the running cycle, the pan caused by the block of water or carbon dioxide in the small holes of the tower plate can be reduced in production or stopped for heating, Re-drive. However, no matter what kind of reason causes the liquid flooding, if the liquid is serious, in order not to let the liquid enter the expansion machine, the liquid nitrogen throttle valve can be closed temporarily, and the joint-1 valve can be opened as large as possible. When the temperature returns to normal, slowly open the liquid nitrogen throttle valve and close section-1 valve.
