Adjustment of the feed position in the catalytic cracking stabilizer

Since the feed contains a large amount of gaseous components, lowering the position of the feed inlet appropriately aims to increase the contact time between the gas phase and the liquid phase inside the tower (the reflux in the tower), thereby facilitating better mass exchange. Reducing the heavy components in liquid hydrocarbons also lowers the pressure at the top of the stabilizer

Where was this statement \"lz\" written? Lowering the feed inlet increases the distillation section; since the content of liquid hydrocarbons is high, it becomes difficult to control the vapor pressure of the stable gasoline. I don’t understand it – I hope someone knowledgeable can explain it

This post was last edited by chengkang on 2010-1-28 07:25. A stabilizer column is a standard separation column; feed is introduced at its middle. The upper part of the feed section serves as the distillation section, while the lower part functions as the stripping section. When the feed components are light, the vapor load increases, which in turn increases the load on the distillation section. Therefore, increasing the number of trays in the distillation section – or moving the feed inlet downward – can reduce the load at the top of the stabilizer column, thereby lowering the pressure at the column top. As the feed composition becomes heavier, it indicates an increase in the load at the bottom of the tower; therefore, the number of trays in the stripping section must be increased, and the feed inlet moves upward. The meaning of the sentence above is that the propane content in denatured gasoline increases, which means the gas-phase load rises; therefore, the number of trays in the distillation section should be increased and the feed inlet should be moved downward.

This post was last edited by chengkang on 2010-1-28 07:26. Lowering the feed inlet indeed helps to push the light components in the feed downward, thereby reducing the load on the top of the tower. However, it is important to ensure that the C4 components in the stable gasoline meet the required standards. The most direct and effective way to adjust the pressure at the top of the stabilizer is to regulate the three-valve assembly there; such adjustment has a lesser impact on the stable operation of the entire stabilizer compared to adjusting the feed position.

If the feed rate remains constant: as the feed moves downward, the pressure at the top of the tower decreases. However, to ensure that the gasoline at the bottom of the tower meets the required standards, it is necessary to increase the reboiling capacity at the bottom of the tower. As a result of this increased reboiling, the pressure at the top of the tower rises, thus creating a vicious cycle. Obviously, the operation is unfavorable. Unless the feed load is reduced. The feed has become lighter; the normal procedure is to raise the feed inlet. By adjusting the three-valve assembly at the top of the tower, the pressure at the tower top can be controlled, which also helps to reduce the load on the lower part of the tower and improve the quality of the product at the bottom of the tower.

This sentence is from the book ＜Catalytic Cracking Unit Training Materials＞ for technicians and senior technicians. For example, as mentioned on page 4, I believe I’ve read somewhere that when the feed to the stabilizer becomes heavier, it should be moved downward, while if the feed becomes lighter, it should be moved upward~~~

This post was last edited by chengkang on 2010-1-28 07:29. This statement is correct. Raising the feed position of the stabilizer tower and increasing the number of plates in the stripping section helps to control the vapor pressure of gasoline, but it is not favorable for controlling the C5 content in the liquid hydrocarbons. Below the feed level of the stabilizer tower, an increase in the number of plates in the distillation section helps to control the C5 content in the liquid hydrocarbons, but it hinders the control of the vapor pressure of gasoline. Therefore, assuming that the degasified gasoline contains a high amount of liquefied gas components, this will increase the pressure at the top of the stabilizer; the feed point to the stabilizer can be adjusted downward to reduce this top pressure.

The control of the liquid level at the bottom of the stabilizer is set to automatic; lowering the feed position means reducing the residence time of gasoline in the stabilizer, which in turn reduces the separation efficiency and alters the yield and composition of the liquid hydrocarbons.

It seems to be a balance between product quality and processing capability.