Can flooding, surging, and liquid flooding be understood in this way? If any experts have different views, please feel free to discuss!

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This post was last edited by A Chuan on 2016-8-31 at 10:13. Can flooding, surging, and liquid flooding be understood in this way? If any experts have different views, please feel free to discuss! Tower flooding Definition: During the distillation process, liquid gradually accumulates above a certain tray, eventually filling part of the tower section and obstructing the upward flow of gas. This prevents proper mass and heat transfer between the gas and liquid phases, a condition known as tower flooding. Reason: 1) The sedimentation tube is blocked, preventing the return fluid from flowing downward. At the start of operation, debris such as iron shavings and welding slag, the accumulation of corrosion products on the equipment during normal production, or the precipitation of solids from liquids, along with the self-polymerization of solutions, can all easily cause blockages in the downcomers. 2) The amount of liquid is too large, causing the downcomer to become overloaded. Phenomenon: When the tower is flooded, the temperature at the top of the tower decreases, the liquid level in the reflux tank drops, while the liquid level and pressure at the bottom of the tower increase. Treatment: 1) Appropriately reduce the feed rate and return flow rate. 2) If the equipment fails, operations shall be halted for repair. Definition of tower flooding: Mist entrainment refers to the phenomenon in the operation of a plate distillation tower, where the rising gas phase carries mist-like liquid droplets from one tray to the tray above it. Impact: Mist entrainment causes low-volatility liquids to enter high-volatility liquids, reducing the efficiency of the tray. During a tower surge, the distillation efficiency inside the tower deteriorates, disrupting normal mass and heat transfer. As a result, the temperature and pressure at the top of the tower, as well as the temperature at the side product outlets and the reflux temperature, all increase. Meanwhile, the liquid level at the bottom of the tower drops suddenly, and the color of the distilled oil turns darker. Phenomenon: During normal operation of the fractionation tower, the gas and liquid phase loads remain relatively stable. When both the gas and liquid phase loads are too high, the pressure drop across the tray increases, which leads to an increase in the liquid level in the downcomer ； As the liquid load increases, the liquid level height at the outlet weir rises. When the liquid fills the entire downcomer, the upper and lower trays become connected, completely disrupting the distillation process, which results in column flooding. Factors: Any factor that leads to an excessive gas-liquid load inside the tower can cause flooding. Such as the processing volume of crude oil, excessively light properties of the feed material, water content in the crude oil entering the tower, steam injection volume at the bottom of the tower, excessively high feed temperature, interruption or uneven distribution of reflux, and excessive reflux flow at the top of the tower. Uneven vapor-liquid load, caused by salt caking on the trays or blockage of the downcomers inside the tower, can also lead to color changes in the product. Treatment: The principle of treatment is to reduce the vapor-liquid load, that is, to decrease the amount of crude oil processed. Liquid flooding refers to the situation in a distillation column where, for various reasons, the liquid phase accumulates beyond the available space. Foaming can be divided into downcomer foaming, mist entrainment foaming, etc. Liquid flooding in the downcomer refers to the accumulation of the liquid phase in the downcomer up to the upper tray. The main reasons for liquid flooding in the downcomer include a low clearance height at the bottom of the downcomer and an excessive flow rate of the liquid phase. Foam entrainment flooding occurs when the gas flow velocity in the open spaces on the tray reaches a certain level, causing the liquid phase on the tray to be carried upward with the rising gas to the upper tray. The main cause of foam entrainment and flooding is an excessive gas phase velocity. The operating condition at which flooding occurs is called the flooding point. When designing a distillation column, it is necessary to control and maintain the flooding rate within a certain range to ensure its stable operation.