The expander is the core source of cold energy. If the expansion volume is lower than the design value or the rotational speed is abnormal, there may be insufficient cold energy. The outlet temperature of the expander should be lower than the design value. If the temperature is higher, it may be due to a decrease in expander efficiency or an excessively high inlet temperature. Insufficient sealing gas pressure can lead to lubricant leakage, affecting the efficiency of the expander and indirectly resulting in loss of cold energy.
The temperature difference at the hot end of the main heat exchanger is too large, which may be caused by blockage of the heat exchanger, uneven airflow distribution, or insufficient cooling capacity, resulting in the inability of the reflux gas to fully cool the air entering the tower. The temperature difference at the cold end is too small, which may be caused by excess cooling capacity, or too large, which may be caused by insufficient cooling capacity or a decrease in heat exchanger efficiency.
Pressure fluctuations in the upper column may indicate a problem with cold balance. If the pressure continues to rise, it may be due to insufficient cold, leading to flooding or a decrease in reflux ratio. If the liquid air and liquid oxygen levels are too low, it may be due to insufficient cold, resulting in excessive evaporation. If the liquid levels are too high, it may be due to excess cold or a malfunction in the reflux valve. A decrease in oxygen purity may be due to insufficient cold, leading to poor distillation performance, or a mismatch between the feed rate and expansion rate.
The temperature inside the cold box should decrease gradually. If the temperature in a certain area rises abnormally, it may be due to cold leakage or uneven frosting on the heat exchanger. If the base temperature of the cold box rises too quickly, it may be due to cold loss or damage to the insulation layer. If the exhaust temperature of the air compressor is too high, it may be due to a decrease in the efficiency of the cooler, which leads to an increase in the temperature of the air entering the tower and an increase in the demand for cold. Fluctuations in outlet pressure or insufficient flow of liquid oxygen pumps and liquid nitrogen pumps may be due to cavitation or insufficient cold, leading to liquid evaporation.
