Water in the distillation column overhead
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Dear experts: In the gasoline distillation tower, the bottom temperature is 130°C; the tower is heated using a reboiler, with low-pressure steam as the heat source. The top temperature of the tower is 30°C, and the top pressure is 0.3 Mpa. Samples taken from the tower feed show no water content, and samples taken from the tower bottom also show no water content. However, there is water in the reflux drum at the tower top. It is suspected that there is a leak in the reboiler. But the saturated vapor pressure of water at 130°C is 0.27 Mpa(A); under such temperature and pressure, water should be in liquid form. May I ask, dear experts, how does water end up in the tower top? Help.
This cannot be determined solely by the saturated vapor pressure of water to decide that the water is in liquid form and therefore cannot be carried to the top of the tower. The steam flow rate should be very low; if it is too high, production cannot be maintained as the moisture level drops.
You mean that this small amount of water is carried up there.
It’s possible that the temperature at the source of steam is 130°C; this means that the temperature of the steam must be higher than 130°C. I’m not sure what the low-pressure steam pressure is for the person in question – ours is 1.0 MPa, and the saturated temperature at that pressure should be 180°C. Secondly, if there is suspicion of internal leakage in the reboiler, can a sample be taken from the oil to check whether water is present?
The low-pressure steam pressure is 1.0 Mpa, and the sample taken from the reboiler column is free of water
Then take a sample from the feed to the tower, as well as a sample from the bottom of the tower; cool them to the same temperature as that at the top of the tower and check whether water is present. I’m not sure whether your reflux tank continuously contains water or it takes a long time before water appears in it
Sampling from the bottom of the tower showed no water after waiting for a long time; sampling from the tower’s feed section also revealed no water. There is no water cooler at the top of the tower, only air coolers
It would be better if the problem description could be more detailed: How severe is the water contamination in the reflux tank? How many can be processed per day?
There are two possible components in this case: the raw materials are the easiest to check; if it’s not the raw materials, then it must be the reboiler. Our unit’s distillation tower is equipped with bottom steam injection (1.0 MPa steam), and the product tank at the top of the tower has dedicated drainage facilities
Let’s analyze the sampling point; take samples from the bottom of the pipeline.