There are some issues with two-effect distillation of ethanol; I seek advice from experts.

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At present, our double-effect tower experiences frequent flooding problems. During initial installation, the steam pressure behind the valve, set at 0.2 by the manufacturer, allowed for a smooth start-up, enabling the design output level to be achieved and meeting 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-stage tower gradually becomes empty, and the feed cannot reach the bottom of the tower. 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 towards the characteristics of one-effect towers recently. 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 78–19 degrees is necessary; otherwise, the concentration reaches 93 even when the temperature is maintained around 78.3 degrees. 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, teachers, what are the reasons that lead to this phenomenon? Is it the reboiler, condenser, or the lower tray that is clogged? Thank you.