C5 extraction from stabilizer tower
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Due to the increased C5 content, the vapor pressure of the stabilized gasoline at the bottom of the tower exceeded the specified limit; therefore, it was decided to remove C5 from the stabilization tower. There are two options: one is to remove the gas phase from the bottom of the tower, and the other is to remove the liquid phase from the upper part of the feed. It is not clear which approach will be more effective
“The increased C5 content caused the vapor pressure of the stable gasoline at the bottom of the tower to exceed the specified limit.”？ Has the original poster misunderstood? ； The components of gasoline are C5-C11 itself; it is C4, especially n-butane, that affects the vapor pressure of gasoline. That’s why a stabilizer column is also referred to as a butane removal column.
It is necessary to analyze the reasons for the high vapor pressure; an increase in C5 raises the vapor pressure, but C4 has the most significant effect. Additionally, increasing the gasoline dry point will also reduce the vapor pressure. Drawing off a side stream from the stabilizer tower is not a viable solution; the separation accuracy is low, and what is obtained from this process can be used for nothing. We draw light gasoline above the feed to recycle it in the riser; this increases the vapor pressure of gasoline and raises the C3 concentration in the liquefied gas. What is actually reprocessed is a mixture of C4 and C5, which then combines again as it enters the riser. However, the octane rating of gasoline has decreased significantly.