The issue of sudden increase in pressure in the ethylene tower
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The ethylene distillation tower in my facility sometimes experiences a sudden increase in pressure during operation, rising from 1678 to 1690 kPa. This phenomenon is unavoidable; it’s not caused by occasional operational errors, but occurs regularly. When the pressure suddenly increases, the liquid level in the reflux tank also rises abruptly, until the tank is full. From a trend perspective, it takes about a few minutes for the liquid level in the reflux tank to first rise, then drop slightly, before rising steadily. Over time, as we become accustomed to this pattern, we increase the reflux flow as soon as the pressure rises, up to the maximum level possible; yet the reflux tank still fills up, and this situation is difficult to control. Some colleagues have analyzed that it’s due to liquid carried along by the vapor balance line connecting the ethylene tower and the tank area – when enough liquid accumulates, it flows in, and they attribute this to design issues. When pressure rises suddenly, the opening degree of the condenser refrigerant first decreases and then increases. I’m not sure if I explained it clearly; I hope the teachers can help me understand.
Does the reflux tank fill up first and then the pressure rises, or does the pressure rise first and then the reflux tank fills up?
It is caused by an excessive tower load, a high liquid level on the tray, and delayed extraction; it represents mild flooding. Is the quality of the product stable? The sudden rise in the liquid level in the reflux tank is due to steam breaking through the liquid layer in a short period of time, resulting in massive condensation
Reply to 2# cyl5410: Hello, the pressure rises first, followed by an increase in the liquid level in the return tank; then it drops a bit before rising steadily until the tank is full.
Reply to 3# zzy515: Hello. Due to the sudden increase in pressure, the temperature distribution within the tower increased as well, and the level of alkanes in the product rose; however, the quality remains within acceptable limits. Is the issue you mentioned regarding delayed extraction related to the liquid level in the tower? When the pressure increases, the liquid level in the tower isn’t high. There’s also a strange phenomenon: even when the tank is full and the reflux is set at its maximum, the liquid level in the tower doesn’t rise. In such cases, increasing the extraction rate actually causes the liquid level to drop further. Please provide some guidance.