Reduce the reflux ratio
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This post was last edited by *nyang3390 on 2011-6-30 21:58. Why does the concentration of low-boiling components at the bottom of the tower increase when the reflux ratio is reduced? ? ? Will the concentration of low-boiling components at the tower top decrease? ? ? These are the answers to our daily question; I don’t understand some of them
By reducing the reflux ratio, more product is obtained at the top of the tower; the light components inside the tower decrease, which leads to a drop in tower pressure. The light components at the bottom move upward, resulting in an increase in the heavy components there. At the same time, the excess heavy components rise to the top of the tower, causing an increase in the heavy components there as well.
When reducing the reflux ratio, steam also needs to be taken into consideration; if the amount of steam supplied remains unchanged, reducing the reflux ratio should result in a decrease in the content of light components at the bottom of the tower and an increase in the content of heavy components at the top of the tower
Reply to 3#: By eliminating excess complexities, even if the heating steam volume can be varied, reducing the reflux ratio will still cause the components within the tower to move upward as a whole; this results in a decrease in the concentration of light components at the bottom of the tower, while the concentration of heavy components at the top increases slightly!
Reducing the reflux ratio is not achieved by decreasing D; it is mainly accomplished by reducing the amount of steam entering the column, and this is done by lowering the heating rate at the bottom of the column and the condensation rate at the top of the column
It seems that the people upstairs didn’t directly answer the original poster’s question. In fact, the reason can be determined by performing plate balance calculations for both the top and bottom plates of the tower. A decrease in the reflux at the top of the tower means that less light component is transferred downward; as a result, the concentration of the heavier components increases, which is the direct cause of the decrease in the light component concentration.
Reducing the reflux rate will lead to an increase in the top temperature of the tower, as well as an increase in the amount of heavy components extracted from the tower top； Furthermore, reducing the reflux will lower the pressure difference in the column, causing the heavier components to move upward.
As the reflux ratio decreases, the amount of vapor-liquid exchange is reduced, increasing the likelihood of heavier components escaping from the bottom of the reactor. This also increases the chances of these heavier components being extracted at the top of the tower; as a result, the concentration of heavier components at the top rises while the concentration of lighter components decreases. In contrast, the concentration of lighter components at the bottom of the tower increases.