Why is it -160°C in front of the LNG liquid shut-off valve and -158°C behind it?
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Why is the temperature of the LNG produced by our plant at the cold box -160°C, while it drops to -158°C after passing through the shut-off valve? The temperature should decrease after passing through the throttle; why is it increasing now? What is the reason for this?
There is a high possibility of instrument error
It might not be just a problem with the gauge; there could be other possibilities
Your LNG may contain a relatively high amount of ethane or propane; at -160°C it is already fully liquefied and in a supercooled state, and its temperature may rise after throttling.
---160 already, and you’re still throttling it – you’re really amazing
It’s not a gauge issue! He just gets warmer. Software calculations work the same way. Substances can experience temperature increases after throttling, temperature decreases, or no change in temperature at all. It’s all included in thermodynamics
This situation is equivalent to your JT valve failing to perform its function of throttling, reducing pressure, and lowering temperature; it is likely caused by an excess of heavy components in the system and a shortage of light components. By the way, do you use a single-cycle process or a 3-loop refrigeration system?
This must be the reverse step effect of methane, as mentioned by foreigners from APCI before.