Rewarming of the air separation cryogenic tank?
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After the air separation unit is shut down for a month and the drainage is completed, should it be warmed up immediately, or should warming up take place during the next startup? In our unit, we sometimes rewarm the fluid immediately after drainage is completed, and other times we do it during the next startup – which method is more reasonable?
After the air separation unit is shut down and the liquid has been drained, do not start reheating immediately; instead, wait for 2 hours until all residual liquid has evaporated before beginning the reheating process. It’s of course not good to reheat it again the next time you drive, as the equipment being in a cold state can lead to negative pressure that draws in moisture, water accumulation, and the insulation material sinking and crushing the pipelines.
As mentioned above, after waiting for 2 to 4 hours, the air separation unit begins to be heated, with the heating rate controlled at 10 degrees per hour, allowing the temperature to rise gradually to normal levels. The unit is sealed; if possible, dry gas should be introduced into the upper and lower columns as well as the argon column for protection. It is important to prevent overpressure in the lower pressure system columns and the crude argon column. Perform another short-duration heating and blowing process while driving.
If the equipment needs to be shut down for an extended period, it requires thorough heating, as I told the technician upstairs. Additionally, if possible, the heated device (inside the cryostat or its equipment) can be filled with a dry gas at a pressure slightly higher than atmospheric pressure to achieve sealing; this allows the device to start up without the need for further heating/drying, thereby reducing the startup time. (For reference)
During reheating, do not open the valve too wide; be careful to avoid bulging in the cold box