When the air temperature exiting the air-cooled tower is the same, why are the air temperatures at the two molecular sieve inlets different?
Thread Content
The equipment in our factory is Hangyang 21000 air separation units. Last night, while filling out reports, I noticed that although the air temperature coming out of the air cooling tower was around 10 degrees Celsius, the inlet temperatures of the two molecular sieve adsorbers were different. The inlet temperature of Adsorber No. 1 was about 13.4 degrees Celsius, while that of Adsorber No. 2 was around 10 degrees Celsius, which is roughly the same as the air temperature coming out of the air cooling tower. Given the current environmental temperature (winter), I wonder why this situation occurs. I hope the experts here can discuss this and help find an answer. I suspect that it might be due to a leak in Adsorber No. 1, causing the air to undergo adsorption processes within the pipes before entering the adsorber; this adsorption process generates heat, thereby raising the temperature. I appreciate any help from the experts. Thank you in advance.
I’m not sure whether your molecular sieves are of vertical or horizontal type; does air enter the molecular sieves from the top? What were the outlet temperature and outlet pressure of the two molecular sieves at that time?
Our molecular sieve is horizontal in design; air enters from the bottom. I’ll check the outlet temperature and pressure when I start working tonight. Sorry, I’ll provide that information tomorrow
You can first use a manual temperature meter to measure the wall temperature of the tubes, to see if there is such a large temperature difference between the two purifiers; it could be due to measurement errors.
It’s probably a problem with the gauge; molecular sieve cannot be present in the inlet pipeline, and even if it were, it’s impossible for there to be such a high adsorption heat
The molecular sieve goes through a regeneration process; one end is used for operation while the other is used for regeneration – the outlet of the regenerator being the latter. What you mentioned might refer to the cold blowing stage, during which the outlet temperature drops. If the system is shut down and the temperatures differ, it may be necessary to recalibrate the thermometers.
Bring up the DCS data to compare – when did this situation start occurring?
There are only pipes from the exit of the air-cooled tower to the molecular sieve; it’s generally not possible for the situation you described to occur. If there were molecular sieve in those pipes, it would create resistance. Moreover, with such a large flow rate and certain pressure, anything in the pipes would be blown away long ago – so it can’t be molecular sieve there. It’s likely that the zero point of your inlet temperature gauge has shifted. After calibrating the gauge, check again; if the problem persists, come back and discuss it further
There may be internal leakage in the valve, resulting in cross-ventilation
It is normal for the inlet air temperatures to differ when air exits the air cooling tower and enters the two molecular sieves. Since one molecular sieve is being regenerated while the other is in use, air enters both molecular sieves simultaneously only when they operate in parallel. The time for parallel operation is generally too short; as a result, the molecular sieve that has just finished regeneration shows a slightly higher inlet air temperature. This is related to the degree of regeneration, the instruments used, as well as the angle and position of installation, among other factors. If, even during normal operation, the air temperature at the inlet of one of the molecular sieves does not match the temperature at the outlet of the air cooling tower, it is possible to determine the issue by comparing the air temperature at the outlet of the molecular sieve with the temperatures of the air entering the cooling box and the compressor.
Okay, thank you all for your strong support and thorough analysis. I plan to take another look at it tonight and discuss it again tomorrow.