[Q&A] 3/25/2017
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Question: What is the difference between fractional distillation and distillation? Answer: Fractionation: The boiling ranges of the various products are wide, and there are significant differences in boiling points among the different components. Therefore, the fractionation process involves gradual vaporization and gradual condensation, resulting in a relatively coarse separation process. Distillation: The boiling ranges of the various products are narrow, and the boiling points of the different components are close to each other. Therefore, the distillation process is a process of multiple vaporizations and multiple condensations. The separation process is quite detailed. http://bbs.hcbbs.com/static/image/hrline/4.gif The petrochemical deep processing edition – the event to share pictures of chemical equipment has started! A vast amount of wealth, along with HaiChuan coins, is waiting for you to claim! http://bbs.hcbbs.com/thread-1760733-1-1.html Summary post for the Petrochemical Deep Processing section’s 【Question of the Day】 – updated daily by the moderator. http://bbs.hcbbs.com/thread-1496481-1-1.html Summary post of weekly topics for the Petrochemical Deep Processing section~~~ Updated continuously! http://bbs.hcbbs.com/thread-1751483-1-1.html Petrochemical Sector — New Ideas for Energy Saving: The “Creative Thinking” Campaign http://bbs.hcbbs.com/thread-1666758-1-1.html Xiaomi phones are waiting for you! A thread for collecting chemical technology materials in the “Petrochemical Section” http://bbs.hcbbs.com/thread-1654603-1-1.html Many prizes are waiting for you to claim
Distillation is a (mass and heat transfer) process; it has (similarities) with ordinary distillation, but it also has its own (differences). Ordinary distillation yields (mixtures) with different boiling points, whereas distillation produces pure (monomeric hydrocarbons).
The difference lies in their respective devices and purposes. Ordinary distillation involves vaporizing a liquid. If distillation is used to separate components, the separated fractions from distillation generally have a wide temperature range. For two components with boiling points that are close to each other, such as 5 degrees, it is difficult to separate them by distillation. Fractionation, on the other hand, involves precise distillation using a fractionating column; it is generally used to separate fractions with very similar boiling points. The extent to which boiling point differences can be resolved depends on the design of the fractionating column – a well-designed column can separate components with a difference of just 2 degrees in boiling point.
Both fractional distillation and rectification achieve separation through vaporization and condensation. In fractional distillation, the boiling range of each product is wide and there are significant differences in boiling points among the various components; thus, the distillation process involves gradual vaporization and gradual condensation, resulting in a coarser separation process. In distillation, the boiling range of each product is narrow and the boiling points of the various components are close to each other; therefore, the distillation process involves multiple instances of vaporization and condensation, leading to a finer separation process
Fractionation uses partial vaporization and partial condensation to separate a mixture to achieve a certain level of purity, while distillation employs multiple cycles of vaporization and condensation to achieve a higher degree of separation of the mixture.
Distillation takes advantage of the differences in the volatility of various components within a mixture. Through the recycling of liquid and gas phases, the gas and liquid phases come into contact with each other in multiple stages in opposite directions. Driven by thermal energy and governed by phase equilibrium principles, the more volatile components (light components) are continuously transferred from the liquid phase to the gas phase, while the less volatile components move from the gas phase to the liquid phase, thereby enabling the continuous separation of the mixture. This process is known as distillation. In this process, heat transfer and mass transfer occur simultaneously, which falls under mass transfer process control. Distillation takes advantage of the differences in volatility among the components in a liquid mixture; it causes part of the mixture to vaporize, and then allows some of that vapor to condense, thereby enabling the separation of the various components contained within it. It is a unit operation that belongs to mass transfer separation.
The product obtained through distillation is closer to a pure substance than that obtained through fractional distillation, meaning it has a higher purity.
Distillation involves multiple evaporation and condensation steps, with increased reflux, thereby improving product quality (through fine separation)； Fractionation is a rough separation
Distillation is also a type of fractional distillation; in both cases, substances are separated and purified based on the differences in their boiling points. However, distillation requires the use of a distillation column, and by controlling the reflux ratio, it is possible to achieve better separation of components with differing boiling points. Conventional atmospheric distillation can only separate two substances whose boiling points differ by more than 30 degrees, while distillation can separate two substances with a difference of as little as 0.5 degrees. Nevertheless, distillation cannot be used to separate azeotropes
Fractionation: The process of heating a liquid mixture, where the lighter components vaporize and are then led away for condensation, thereby allowing the separation of the light and heavy components in the mixture. Distillation: A mass transfer process in which a liquid mixture is subjected to repeated partial condensation and partial vaporization to achieve thorough separation of the components in the feed liquid.