4-1专业英语阅读

Lesson 2 Fractional distillation
Fractional distillation is the separation of a mixture of compounds by their boiling point, by heating to high enough temperatures.
Heat transfer
– This unit operation deals with the principles that govern accumulation and transfer of heat and energy from one place to another.
Evaporation
Fractional Βιβλιοθήκη Baiduistillation in a Laboratory
Apparatus
conical flask
1. The apparatus is assembled as in the diagram. The mixture is put into the round bottomed flask along with a few anti bumping granules(沸石), and the fractionating column is fitted into the top.
2. As the mixture boils, vapor rises up the column. The vapor condenses on the glass platforms inside the column, and runs back down into the liquid below, refluxing distillate.
Liquid-liquid extraction
– In this case a solute in a liquid solution is removed by contacting with another liquid solvent which is relatively immiscible(不混溶的) with the solution.
– This is a special case of heat transfer, which deals with the evaporation of a volatile solvent such as water from a nonvolatile solute such as salt or any other material in solution.
3. Only the most volatile of the vapors stays in gaseous(气态) form all the way to the top. The vapor at the top of the column will be almost pure ethanol.
4. This then passes into the condenser, which cools it down until it liquefies(液化). The process continues until all the ethanol boils out of the mixture.
Unit 1 Unit Operations
Arp 26th，2011 Ying, Xiaoguang
lesson 1 Classification of Unit Operations
Fluid flow
– This concerns the principles that determine the flow or transportation of any fluid from one point to another.
– These involves separation of solids, liquids, or gases by mechanical means, such as filtration, settling, and size reduction, which are often classified as separate unit operations.
Absorption
– In this process a component is removed from a gas stream by treatment with a liquid.
Membrane separation
– This process involves the diffusion of a solute from a liquid or gas through a semipermeable membrane barrier to another fluid.
Crystallization
– This concerns the removal of a solute such as a salt from a solution by precipitating(沉淀) the solute from the solution.
Mechanical physical separation
Liquid-solid leaching(浸提)
– This involves treating a finely divided solid with a liquid that dissolves out and removes a solute contained in the solid.
Drying
– In this operation volatile liquids, usually water, are removed from solid materials
Distillation
– This is an operation whereby components of a liquid mixture are separated by boiling because of their differences in vapor pressure.