Doubts about distillation column operation
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Dear experts: Assuming that the feed temperature, flow rate, and composition of the distillation column remain unchanged, as does the amount taken from the side stream, and all other conditions stay the same, how will the reflux rate change if only the heat source at the bottom is increased? This tower is simply used to separate components A and B.
The backflow increases, while the liquid level at the bottom of the tower decreases relatively
It is best to explicitly state the problems that occurred on site. If the amount of rising steam is increased, the reflux liquid should decrease. Because the amount of rising steam is large, more liquid evaporates during heat exchange with the liquid flowing downstream, resulting in less liquid returning. The components separated by a tower are not necessarily two; it depends on the structure of the tower. For reference.
The statement is inaccurate; with all other conditions remaining unchanged, this term is problematic. It is suggested that the original poster run a test using water and methanol, and then he will naturally understand what’s going on.
The operational experience and theoretical knowledge at the third and second floors are concerning. . . . The answer is utterly horrible
The operational experience and theoretical knowledge at the third and second floors are concerning. . . . The answer is utterly horrible
From the perspective of phase equilibrium in a single-layer tray, adding a reboiler means an increase in the rising vapor phase; accordingly, it is necessary to increase the liquid phase to maintain phase equilibrium in the tray. However, the feed rate to the tower remained unchanged, and such operation increased the load on the tower. Furthermore, it will cause the reconstituted components of the tower to rise. This results in substandard quality of the product at the top of the tower, while there is also a loss in the product at the bottom of the tower.
Also, according to the problem you described, is there anything abnormal with the tower? Just want to add a reboiler?
Lowering the heat source and reflux rate is not necessarily linked to an increase in recombination at the tower top. The reflux volume should be adjusted according to your needs. By adding a heat source at the bottom, the reflux can remain unchanged, increase, or decrease.
Recently, I encountered a problem during operations. In an attempt to increase the reflux ratio (by increasing reflux while keeping the side-stream withdrawal constant), I increased the feed rate as well as the heat input; the column was already operating above its designed capacity. As a result, the reflux ratio decreased, the pressure difference across the column increased, and the temperature at the bottom of the column rose. When I reduced the feed rate and heat input again, the reflux ratio returned to its original level. I believe that the excessive liquid load in the column prevented light components from reaching the top of the column, which led to a decrease in the reflux ratio; meanwhile, the high liquid load also caused an increase in the pressure difference across the column. If I hadn’t withdrawn the feed and heat source at that time, and instead increased the side-stream withdrawal slightly, could that also reduce the pressure difference and increase the reflux?
Since the top temperature remains unchanged, there’s no need to worry about the reflux rate; if excessive evaporation causes the top temperature to rise, then the reflux ratio needs to be adjusted