If the temperature after the expander of the air separation unit is too low, it should find out the cause of the low temperature and take measures to increase the temperature after the expander. If the low temperature of expander is caused by liquid air in front of expander, appropriate measures should be taken to reduce the liquid air level of lower column. If it is caused by other reasons, the more effective method is generally throttling in front of the expander. Throttling will not increase the temperature in front of the expander, but throttling will reduce the pressure in front of the expander, so the pressure difference between the front and the back of the expander will be reduced, the expander will do less work and the temperature will be reduced, so the temperature at the after of the expander can be increased.
