What is the sequence for introducing the three streams into the tower and opening the throttling valves leading to the upper section of the tower during cold start of an internally compressed air separation unit?
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For internally compressed air separation, during cold start, what should be the sequence in which the three streams enter the tower and the throttling valves leading to the upper section of the tower are opened, in order to minimize process fluctuations and achieve rapid recovery? ? ? ? ?
Whenever air is supplied into the tower, set the night sky liquid and nitrogen throttle valves to their normal positions. This approach is appropriate when the level of the cooling liquid is high during shutdown; otherwise, it will cause too rapid evaporation of the cooling liquid. It’s also important not to open the nitrogen throttle valve too much, as this will raise the level of the night sky liquid in the lower tower, thereby blocking the air inlet and leading to an increase in the pressure of the air compressor as well as a reduction in its exhaust flow rate. The opening degree of the high-pressure night sky throttle valve should be determined based on the temperature of the fluid entering the expander and the temperature of the oxygen exiting the tower; if the temperature of the fluid entering the expander is low, it is sufficient to increase the opening degree of the high-pressure night sky throttle valve