Issues related to the temperature and liquid level of the liquid nitrogen cooling tank
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RT, the issues encountered with the cold box in our factory are as follows: 1. There is no fluctuation in the system load, and there are no significant fluctuations in the materials entering or leaving the system； 2. Drop in the liquid level of the scrubber tower, decrease in the temperature of the plate exchanger, drop in the temperature at the top of the scrubber tower, increase in the temperature of the feed gas entering the scrubber tower, and increase in the temperature of the washing nitrogen ； We have analyzed the reasons ourselves as follows: Liquid was present in the syngas at the outlet of the scrubber, which caused a drop in the temperature at the top of the scrubber, a decrease in the liquid level, a drop in the temperature of the heat exchanger plates, and a slight increase in the pressure difference across the scrubber ； The treatment method (only provides temporary relief, not a permanent solution) is as follows: 1. Reduce the amount of nitrogen used for washing in the early stages of temperature drop, thereby decreasing the amount of liquid nitrogen carried away by the syngas ； 2. When the temperature drops too rapidly, increase the amount of washing nitrogen and reduce the discharge volume of CO tail liquid. After the system stabilized, we tried to reduce the amount of nitrogen used for washing and increase the temperature of the feed gas entering the washing tower, but the effects were not significant. Looking forward to replies from all the experts!
We have also encountered such a problem; have the amounts of crude nitrogen, refined nitrogen, and washing nitrogen been adjusted? Looking forward to the results.
The current work involves adjusting the precise nitrogen supply rate (originally 8000 m3/h) to match that of the rough nitrogen supply; there have been no significant fluctuations in the system over the past 4 days
This post was last edited by Blocked on 2016-1-27 13:24. I have a few questions for the original poster: 1. Is the nitrogen washing tower equipped with trays or packing? 2. Is the bottom liquid level control valve operated in automatic or manual mode?
1. Tray； 2. The washing tower operates automatically at 80%; the fuel gas separation tank is operated manually at 100%
It is recommended that the poster check the methane content in the process gas fed into the liquid nitrogen washing system. If the methane level is low, the cooling capacity of the cryogenic tank will be insufficient, and internal nitrogen must be used for adjustment. Additionally, if the temperature of the process gas entering the tower is high, more nitrogen will be required for washing
With the increase in the plate exchanger temperature and the increase in the raw gas temperature, which flow path’s temperature is referred to as the plate exchanger temperature? High-pressure nitrogen?
Cyclic hydrogen is the most severe; the others are more or less the same
It feels to me like the heat exchange capacity of the heat exchanger has decreased. This causes the temperature of the feed gas to rise, while the gas returning from the nitrogen washing tower to the heat exchanger does not undergo sufficient heat exchange within the heat exchanger, resulting in a decrease in its temperature.
Has the temperature difference at the hot side of the heat exchanger also increased?
The temperature difference across the hot-side cross-section is basically normal, around 10°C