【Daily Question】Chemical Engineering Principles 549: Distillation Columns (April 11)
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The Chemical Engineering Theory section is launching the \"One Question per Day\" campaign starting today, aimed at helping everyone reinforce their basic knowledge in chemical engineering. Subsequent series will include those on \"Principles of Chemical Engineering\", \"Mass Transfer and Separation\", \"Thermodynamics in Chemical Engineering\", and \"Chemical Process Engineering\". We hope for your active support~~~ Answers to the \"One Question per Day\" questions can be viewed directly here; the topic will be closed after 1 day! ! To encourage continued participation from everyone this year! Participation earns 3 wealth points, with an additional 4 wealth points for correct answers~~~ Short answer: If the structure of the distillation tower remains unchanged and, during operation, the composition, flow rate, heat conditions of the feed, as well as the flow rate at the top of the tower are kept constant, and only the heat load on the bottom of the tower is reduced, then the composition at the top of the tower will ________, while the composition at the bottom of the tower will ________ decrease ； Increase
A distillation tower is a type of columnar vapor-liquid contact device used for distillation. There are two main types: plate towers and packed towers. Based on the mode of operation, they can be further divided into continuous distillation columns and batch distillation columns. Steam enters from the bottom of the tower. The evaporated vapor phase comes into countercurrent contact with the descending liquid. During this contact, the volatile (low-boiling-point) components in the liquid phase are continuously transferred to the vapor phase, while the non-volatile (high-boiling-point) components in the vapor phase are continuously transferred to the liquid phase. The vapor phase contains a higher concentration of volatile components as it moves closer to the top of the tower, whereas the liquid phase becomes richer in non-volatile components as it moves closer to the bottom of the tower, thereby achieving component separation. The vapor rising from the top of the tower enters the condenser; part of the condensed liquid returns to the top of the tower as reflux to enter the distillation column, while the remaining part is taken out as distillate. The liquid that flows out at the bottom of the tower is sent partly to the reboiler, where it is heated and vaporized to return to the tower as a gas phase; the other part of the liquid is taken out as residue. Principle of Rectification: The basic principle of distillation is a unit operation in which a liquid mixture is partially vaporized and partially condensed multiple times; by taking advantage of the difference in volatility among its various components (relative volatility, α), separation is achieved. Distillation can be classified according to its operation methods into: simple distillation, flash distillation, distillation, and special distillation, etc. Supergravity distillation column: The supergravity distillation technology that has emerged in recent years utilizes a supergravity field with gravity levels hundreds to thousands of times higher due to high-speed rotation, replacing the conventional gravity field. This approach significantly enhances the gas-liquid mass transfer process and reduces the height of the mass transfer unit by an order of magnitude. This transforms the massive tower equipment into an ultra-high gravity distiller with a height of less than 2 meters, thereby achieving higher efficiency and a reduced size. Supergravity distillation alters the traditional distillation mode of tower equipment, allowing for a continuous distillation process to be carried out in an indoor facility.