Could everyone please analyze this? Thank you (regarding distillation towers)?
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There is a distillation column intended to remove the light components from the top of the column; however, since the concentration of these light components at the top is low, the liquid level in the reflux tank is kept above 70% before sampling begins from that tank. What impact will this abnormal operation have on the distillation tower? Will the purity of the components in the reflux tank increase over time? Personal analysis: Since the feed flow rate, the vapor at the bottom of the tower, and the reflux rate all remain unchanged, the tower should initially be operating normally. However, as the liquid level in the reflux tank at the top of the tower rises (I believe the purity of the components in the reflux tank does not increase), the pressure in that tank will increase. This will create resistance to the flow of liquid downward in the condenser, resulting in poor flow and a reduction in the heat exchange area of the condenser, which in turn leads to an increase in the pressure at the top of the tower. The increase in the top pressure further reduces the relative volatility of the liquid, deteriorating the separation efficiency of the distillation column, and ultimately leading to an increase in the concentration of light components in the product at the bottom of the column.
Why would the pressure in the reflux tank increase?
I forgot to mention that this tower is relatively small; its exhaust pipe is thin or blocked, which results in poor exhaust at the top of the tower. Under such circumstances, the rising liquid level in the return tank compresses the liquid inside it, resulting in an increase in pressure within the return tank. ---Personal understanding
I think your analysis is very accurate and correct.
Under normal circumstances, the liquid level in the reflux tank has no effect on the tower pressure, unless there is non-condensable gas that has not been removed
Generally, reflux tanks are equipped with control valves for venting and filling air in order to stabilize the tower pressure. In our case, it’s likely that the pipelines are too narrow, preventing pressure from being released; over time, the pressure will gradually increase