Mr. Norman P. Lieberman – Why does an increase in the tower bottom’s level in my vacuum tower cause a loss in vacuum? Does this indicate an excessively high tower bottom’s level?
George – No. The level is not the problem. It’s that your boot temperature is too hot. The problem is excessive cracked gas formation in the boot. Assuming your level change is within the level span of the boot, increase the level from 30% to 70%. If the vacuum is adversely affected, try lowering the vacuum tower bottom’s temperature, using the circulating boot quench, by 10°F. You are also promoting coke formation in the boot which may coke-up the suction of your vacuum tower bottom’s pumps.