Reasons for the variable-diameter design of distillation columns
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Some of the distillation columns in ethylene plants are of constant-diameter type, while others are of variable-diameter type. Let’s analyze the reasons behind this: is it determined by the feed condition, or by the gas-liquid phase load?
Could you elaborate more specifically? In fact, towers with subcooled feed are all tapered towers; please analyze the relationship between the two.
It is related to the composition; when the composition of a certain section changes, the quantity changes as well, and thus the gas-liquid phase load also changes
The gas-liquid phase load is related to the empty tower gas velocity
The material balance sheet of the ethylene plant shows the components in the feed to each column; based on these components, along with the temperature gradient from top to bottom of the columns provided by the design team and the design pressures, it is possible to determine the components present on each tray. The gas phase load often determines the size of your tower diameter. This can be seen from the tapered methane column and ethane column.