Light diesel distillation column level control flash point
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It is stated in the Catalyst Cracking Operator’s Guide that when the liquid level in the stripping tower is high and the flash point is high, it is necessary to properly control the cold surface of the stripping tower to ensure sufficient space for vaporization. My understanding: 1. If the liquid level in the stripping tower is high, the residence time increases, allowing more light components to be stripped out, which raises the flash point. 2. If the liquid level in the stripping tower is high, with all other conditions remaining unchanged (such as steam and pressure), then the original vapor-liquid equilibrium pressure should increase, and the flash point should decrease. Viewpoint in the book: High liquid level in the stripper means a high flash point. Then isn’t there a contradiction in the analysis of 1 and 2? Was it still the misunderstanding of point 2? What is the correct understanding of a high liquid level in a stripping tower in terms of residence time, gasification space, and gasification rate? As stated in the book: it is necessary to control the cold surface of the stripping tower to ensure sufficient space for vapor evaporation. How does this evaporation space affect the flash point?
Viewpoint 1 is correct. A high liquid level in the stripper results in a longer residence time for diesel, leading to better stripping effects; more light components are stripped off, which in turn raises the flash point of the diesel. A high liquid level in the diesel stripping tower does not mean a high vapor pressure of oil and gas, as diesel is a liquid. Therefore, Viewpoint 2 is incorrect.
I believe that when the liquid level in the stripping tower is high, a larger amount of extraction is required; since the discharge volume must be increased to maintain that liquid level, a higher extraction volume leads to a higher extraction temperature, and consequently a higher flash point.
When the liquid level is high, the vapor pressure of oil and gas also increases accordingly. If the amount of gas vapor does not increase, then less light components will be carried away by the gas, and the flash point will remain high as well.
I think: 1. With a high liquid level in the stripping tower and an excess amount of diesel present, and given that the pumping volume remains essentially constant, the time required for diesel degassing increases; as a result, the flash point of the diesel rises. Therefore, viewpoint 1 is correct. . . 2. With the liquid level at the bottom of the stripping tower remaining constant, increasing the amount of stripping steam enhances the degassing of light components, resulting in an increase in the flash point. . . 3. Viewpoint 2 is incorrect. . . :lol
Because it is assumed that all conditions except the liquid level remain constant, and the partial pressure is primarily determined by pressure and temperature; since these two factors are held constant, the partial pressure remains unchanged. So I think the impact of dwell time should be the main factor to consider
The liquid level in the stripping tower should be a constant value, controlled by stripping steam. The amount of stripping steam used is relatively small; it is generally introduced above the tray levels in the tower. A high liquid level results in greater resistance, leading to poor stripping efficiency.
I think that, with all other conditions constant and considering only the liquid level, a higher liquid level results in less heat per unit volume of oil removed by the stripping steam, leading to a decrease in overall temperature; as a result, fewer light components escape, which should lower the flash point
The residence time of liquid stripping also needs to be considered.