The start-up of an air separation plant includes three stages: cooling, liquid accumulation, and purification. For a certain device, the time required to start is generally a certain amount. For low-pressure air separation equipment, there is no room for adjusting the pressure of the air compressor. Generally, it is necessary to equip two expanders to work simultaneously to increase the cooling capacity during the start-up phase and shorten the start-up time. Even so, according to the maximum cooling capacity and the cooling capacity required for cooling and liquid accumulation of the device, the start-up time of the device also needs to be more than 36 hours.
Large air separation equipment is generally equipped with liquid oxygen storage tanks as emergency backup oxygen. If necessary, can liquid oxygen be filled into the tower to shorten the start-up time of the air separation equipment? In theory, it is completely possible. For example, if 1m3 of liquid oxygen is backfilled into the main cooler, it is equivalent to providing 0.47 from the outside × The cooling capacity of 106kJ is approximately 5000m3 of expanded air, which is the cooling capacity within 2 hours. Some factories have conducted experiments, filling 20m3 of liquid oxygen into the tower during startup, which can shorten the startup time by 16.5 hours for 6500m3/h air separation equipment; For 10000m3/h air separation equipment, the start-up time can be shortened by more than 8 hours.
Of course, when filling the tower with liquid oxygen, one thing to pay attention to is the timing. It is important to wait until the device cools down to the point where liquid begins to be generated in the main cooling chamber before filling it in to avoid damaging the equipment due to thermal stress caused by excessive temperature difference; The second is to pay attention to the filling pressure. Because liquid oxygen can only be injected above the pressure at the bottom of the upper tower, but it cannot exceed the set pressure of the safety valve of the liquid oxygen storage tank to prevent the safety valve from acting.
