The ethanol double-effect distillation tower is encountering some problems; I would appreciate the advice from all the experts.
Thread Content
At present, our double-effect tower experiences frequent flooding problems. During initial installation, the steam pressure behind the valve was set by the manufacturer at 0.2, which allowed for a smooth start-up and enabled the achievement of the designed output to meet production requirements. In the past six months, only output within the range of 0.12–15 has been sufficient to produce products that meet the requirements. The amount of concentrated liquor obtained from the atmospheric pressure distillation column has also decreased by about 60%, which severely impacts production. When the main steam pressure is increased to 0.17–0.2, the bottom of the first-effect column gradually becomes empty, and feed cannot reach the bottom of the column. If the feed flow rate is maintained, it will result in waste liquid being poured directly into the reflux tank, which affects product quality. Two-effect towers are also gradually moving toward the characteristics of one-effect towers these days. During feeding, the liquid level in the bottom of the tower is not reflected proportionally right away. The first-stage tower requires pressure reduction before feeding can take place, while the second-stage tower takes some time for its liquid level to rise gradually. Moreover, the concentration in the second-stage tower remains below the required standard. Keeping the temperature at the top of the tower between 78 and 19 degrees Celsius results in a concentration of 80–90; whereas previously, a concentration of 93 was achieved when the temperature was maintained around 78.3 degrees Celsius. The tray at the feed inlet of the first effect tower is currently open, and dirt has been observed, but it has not reached a level that would cause blockage. The next step is to disassemble the reboiler to check for any blockages. May I ask, dear teachers, what are the reasons that lead to this phenomenon? Is it the reboiler, condenser, or the lower tray that is blocked? Thank you.
On one hand, the sedimentation tube is blocked, preventing the return fluid from flowing downward； Another aspect is that the amount of liquid in the distillation tower is too large, causing the downcomer to operate under overload. Appropriately reduce the feed rate and reflux volume of the distillation tower; if necessary, suspend feeding and turn off the heating steam at the bottom of the tower. Once the temperatures of each tray return below normal levels, resume heating and feeding to restore normal operation.
Based on the phenomena you described, it seems that the tower is operating in a flooded condition. However, since it is a double-effect distillation system, the operation of the two towers influences each other; therefore, detailed PID data as well as information on the tower internals are necessary to determine where the problem lies
Upload a flow diagram of the first and second effect towers to facilitate analysis