【Daily Question】Chemical Engineering Principles 224: Distillation Columns (November 5)
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The last edit to this post was made by Zaihui Kangqiao on 2015-11-10 at 17:14. The Chemical Engineering Theory section is now launching a \"One Question per Day\" activity aimed at helping everyone reinforce their basic knowledge in chemical engineering. Subsequent series such as \"Chemical Engineering Principles\", \"Mass Transfer and Separation\", \"Chemical Engineering Thermodynamics\", and \"Chemical Engineering Processes\" will also be introduced. We hope for your active support! Answers to the questions in the \"One Question per Day\" activity can be viewed directly, and the thread will be closed after 1 day! ! Participation earns 3 wealth points, with an additional 3 wealth points for correct answers. Short answer question: When a distillation column is operated under certain conditions, what changes occur in the composition of the product at the top of the column if the reflux liquid is changed from a saturated liquid to a cold liquid? Why? When changing from bubble point reflux to cold liquid reflux, xD ↑. The reason is that when the cold liquid flows back to the top of the tower, it condenses some of the vapor, and the latent heat released heats the cold liquid to the saturation temperature of the first tray at the top of the tower. The condensation phase contains a high proportion of poorly volatile components, which leads to an increase in the concentration of the more volatile components in the gas phase. At the same time, while keeping the reflux ratio at the top of the tower constant, the internal reflux within the tower was increased, which also contributes to better separation.
When changing from bubble point reflux to cold liquid reflux, the composition of the overhead distillate increases. The reason is that as the cold liquid flows back to the top of the tower, some of the vapor condenses, and the latent heat released heats the cold liquid to the saturation temperature of the first tray at the top of the tower. The condensation phase contains a high proportion of poorly volatile components, which leads to an increase in the concentration of the more volatile components in the gas phase. At the same time, while keeping the reflux ratio at the top of the tower constant, the internal reflux within the tower was increased, which also contributes to better separation.
The distillation column operates under certain conditions. Question: What changes occur in the composition of the product at the top of the column when the reflux liquid is changed from a saturated liquid to a cold liquid? Why? Answer: When changing from bubble point reflux to cold night reflux, XD increases. The reason is that when the cold night air returns to the top of the tower, it condenses some of the steam, releasing latent heat that warms the cold night air to the saturation temperature of the first plate at the top of the tower. At low temperatures, the components that are difficult to vaporize remain in larger quantities, thereby concentrating the volatile components in the gas phase. Meanwhile, with the reflux at the top of the tower remaining unchanged, the internal reflux within the tower increases, which also facilitates separation.
When changing from bubble point reflux to cold liquid reflux, xD ↑. The reason is that when the cold liquid flows back to the top of the tower, it condenses some of the vapor, and the latent heat released heats the cold liquid to the saturation temperature of the first tray at the top of the tower. The condensation phase contains a high proportion of poorly volatile components, which leads to an increase in the concentration of the more volatile components in the gas phase. At the same time, while keeping the reflux ratio at the top of the tower constant, the internal reflux within the tower was increased, which also contributes to better separation.
When changing from bubble point reflux to cold liquid reflux, xD ↑. The reason is that when the cold liquid flows back to the top of the tower, it condenses some of the vapor, and the latent heat released heats the cold liquid to the saturation temperature of the first tray at the top of the tower. The condensation phase contains a high proportion of poorly volatile components, which leads to an increase in the concentration of the more volatile components in the gas phase. At the same time, while keeping the reflux ratio at the top of the tower constant, the internal reflux within the tower was increased, which also contributes to better separation.
The distillation column operates under certain conditions. Question: What changes occur in the composition of the product at the top of the column when the reflux liquid is changed from a saturated liquid to a cold liquid? Why? Answer: When changing from bubble point reflux to cold liquid reflux, the composition of the overhead distillate increases. The reason is that as the cold liquid flows back to the top of the tower, some of the vapor condenses, and the latent heat released heats the cold liquid to the saturation temperature of the first tray at the top of the tower. The condensation phase contains a high proportion of poorly volatile components, which leads to an increase in the concentration of the more volatile components in the gas phase. At the same time, while keeping the reflux ratio at the top of the tower constant, the internal reflux within the tower was increased, which also contributes to better separation.
Answer: When changing from bubble point reflux to cold liquid reflux, xD ↑. The reason is that when the cold liquid flows back to the top of the tower, it condenses some of the vapor, and the latent heat released heats the cold liquid to the saturation temperature of the first tray at the top of the tower. The condensation phase contains a high proportion of poorly volatile components, which leads to an increase in the concentration of the more volatile components in the gas phase. At the same time, while keeping the reflux ratio at the top of the tower constant, the internal reflux within the tower was increased, which also contributes to separation
Answer: When changing from bubble point reflux to cold liquid reflux, xD ↑. The reason is that when the cold liquid flows back to the top of the tower, it condenses some of the vapor, and the latent heat released heats the cold liquid to the saturation temperature of the first tray at the top of the tower. The condensation phase contains a high proportion of poorly volatile components, which leads to an increase in the concentration of the more volatile components in the gas phase. At the same time, while keeping the reflux ratio at the top of the tower constant, the internal reflux within the tower was increased, which also contributes to separation
The distillation column operates under certain conditions. Question: What changes occur in the composition of the product at the top of the column when the reflux liquid is changed from a saturated liquid to a cold liquid? Why? Increased concentration
The distillation column operates under certain conditions. Question: What changes occur in the composition of the product at the top of the column when the reflux liquid is changed from a saturated liquid to a cold liquid? Why? An increase in concentration is equivalent to an indirect increase in the reflux ratio
The distillation column operates under certain conditions. Question: What changes occur in the composition of the product at the top of the column when the reflux liquid is changed from a saturated liquid to a cold liquid? Why? As the concentration increases, the supercooled liquid flows downward, condensing some of the rising vapor and thereby increasing the reflux ratio