化工专业英语复习资料.doc

fundamental principles 基本原理evaporation 蒸发black body 黑体empty space 真空区concentration 浓缩visible light nJ'见光radiation 辐射distillate 憾出液acetonitrile 已睛precipitation 定cation阳离子hydroxide氢氧化物chromatography 层析recrystallization 重结晶sublimation 升华physisorption 物理吸附activated carbon 活性炭hydrophilic 亲水性heat exchanger 换热器fractionating column 精懈柱/塔volatilities 挥发性tray塔板supernate上清液azeotropic distillation 共沸蒸supersaturated 过饱和的silver chloride 氯化银ionic reaction 离了反应pharmaceutical 制药的batch operation 间歇操作Freeze-drying 冷冻干燥Separation process 分离过程crystallization 结晶Filtration 过滤homogeneous 均相的condensation 7令凝thermodynamics 热力学的liquefaction 液化copper 铜separation 分离laminar flow 湍流convection 对•流conduction 传导phonon vibration 声子振动condensation 冷凝thermodynamics processes 热力学过程elastic impact 弹性碰撞thermal energy 热自呂buoyancy forces 浮力1.Heat conduction is directly analogous to diffusion of particles into a fluid, in the situation where there arc no fluid currents・ This type of heat diffusion differs from mass diffusion in behavior, only in as much as it can occur in solids, whereas mass diffusion is mostly limited to fluids.2.In steady state conduction, the amount of heat entering a section is equal to amount of heat coming out. In this conduction, all the laws of direct current electrical conduction can be applied to "heat currents^. In such cases, it is possible to take "thermal resistances as the analog to electrical resistances .Temperature plays the role of voltage and heat tran sferred is the analog of electrical current.3.Conduction is the transfer of heat by direct contact of particles of matter. The transfer of energy could be primarily by elastic impact as in fluids or by free electron diffusion as predominant in metals or phonon vibration as predominant in insulators. In other words, heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from atom to atom. Conduction is greater in solids, where atoms are in constant contact. In liquids (except liquid metals) and gases, themolecules are usually further apart, giving a lower chance of molecules colliding and passing on thermal energy.4、F ractional distillation is one of the unit operations of chemical engineering. Fractionating columns are widely used in the chemical process industries where large quantities of liquids have to be distillcd ・ Such industries arc the petroleum processing, petrochemical production, natural gas processing, coal tar processing, brewing liquified air separation, and hydrocarbon solvents production and similar industries but it finds its widest application in petroleum refineries ・ In such refineries, the crude oil feedstock is a very complex multicomponent mixture that must be separated and yields of pure chemical compounds are not expected, only groups of compounds within a relatively small range of boiling points, also called fractions and that is the origin of the name fractional distillation or fractionation. It is often not worthwhile separating the components in these fractions any further based on product requirements and economics ・5、H eat transfer is the trans让ion of thermal energy from a hotter object to a cooler object (“object" in this sense designating a complex collection of particles which is capable of storing energy in many different ways). When an object or fluid is at a different temperature than its surroundings or another object, transfer of thermal energy, also known as heat transfer, or heat exchange, occurs in such a way that the body and the surroundings reach thermal equilibrium; this means that they are at the same temperature. Heat transfer always occurs from a higher- temperature object to a cooler-temperature one as described by the second law of thermodynamics. Where there is a temperature difference between objects in proximity, heat transfer between them can never be stopped; it can only be slowed ・6、Fractionating columns help to separate the mixture by allowing the mixed vapors to cool, condense, and vaporize again in accordance with Raoult ' s law. With each condensationvaporization cycle, the vapors are enriched in a certain component. A larger surface area allows more cycles, improving separation. This is the rationale for a Vigreux fractionating column or a packed fractionating column ・ Spinning band distillation achieves the same outcome by using a rotating band within the column to force the rising vapors and descending condensate into close contact, achieving equilibrium more quickly.7、 A fractionating column or fractionation column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities. Fractionating columns are used in small scale laboratory distillations as well as for large-scale industrial distillations.&The closed system design required for achieving and maintaining the low-pressure atmosphere insidethe dryer also provides advantages for processing a hazardous material・Examples include toxic chemicals or solvents and explosive materials. The vacuum dryer safely contains and condenses the hazardous vapors from such substances without any threat to your workplace environment or outside atmosphere. With some hazardous materials, you can provide further protection by using inert gas to limit the oxygen level in the vacuum drye匚9.Crystallization is the (natural or artificial process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas. Crystallization is also a chemicalsolid-liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs・10.Radiation is the transfer of heat energy through empty space. All objects with a temperature above absolute zero radiate energy at a rate equal to their emissivity multiplied by the rate at which energy would radiate from them if they were a black body. No medium is necessary for radiation to occur, for it is transferred through electromagnetic waves; radiation works even in and through a perfect vaccum ・ The energy from the Sun travels through the vacuum of space before warming the earth・11.Precipitation reactions can be used for making pigments, removing salts from water in water treatment, and in classical qualitative inorganic analysis. Precipitation is also useful to isolate the products of a reaction during workup・ Ideally, the product of the reaction is insoluble in the reaction solvent. Thus, it precipitates as it is formed, preferably forming pure crystals. An example of this would be the synthesis of porphyrins(nbR||) in refluxing propionic acid. By cooling the reaction mixture to room temperature, crystals of the porphyrin precipitate, and are collected by filtration. 12.Here vacuum drying provides a unique advantage・ By controlling atmospheric pressure, the vacuum dryer increases the effective △ T for a given process. That is, vacuum drying simple reduces the boiling point - or vaporization temperature - required for removing the liquid. By controlling pressure and the heat introduced to the dryer, you can significantly increase the effective △ T and thus dry the material faster than at normal atmosphere・ For this reason, a vacuum dryer is especially suited to drying a heat-sensitive material that degrades above a given temperature and would otherwise require a lengthy drying cycle・ Examples of such materials are vitamins, antibiotics, and many fine chemicals・13.Separation processes can essentially be termed as mass transfer processes. The classification can be based on the means of separation, mechanical or chemical. The choice of separation depends on the pros and cons of each・ Mechanical separations are usually favored 讦possible due to the lower cost of the operations as compared to chemical separations・ Systems that can not be separated by purelymechanical means (e.g. crude oil), chemical separation is the remaining solution. The mixture at hand could exist as a combination of any two or more states: solid-solid, solid-liquid, solid-gas, liquid-liquid, liquid-gas, gas-gas, solid-liquid-gas mixture, etc.14.An important stage of the precipitation process is the onset of nucleation. The creation of a hypothetical solid particle includes the formation of an interface, which requires some energy based on the relative surface energy of the solid and the solution. If this energy is not available, and no suitable nucleation surface is available, supersaturation occurs.15・ In operation, the vessel rotates about the trunnions4 axis. The integrity of the seal around the stationary vacuum line - which extends through the trunnion and is angled upward into the drying chamber's top, above the material in the rotating vessel ・ is critical for maintaining the dryer's vacuum. During rotation, the material cascades inside the chamber, gently tumbling and folding to bring the material into contact with the heated walls. This action makes the dryer especially suitable for handling friable and fragile materials that can't withstand shear from agitation, such as polyethylene terephthalate (聚対苯二甲酸乙二醇酣)pellets. The delumping (粉fi卒白勺)bar can be operated intermittently to break up undesired agglomerates.16.Similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent, or metallic) of the constituent atoms of the material are filled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates. The exact nature of the bonding depends on the details of the species involved, but the adsorption process is generally classified as physisorption (characteristic of weak van der Waals forces) or chemisorption (characteristic of covalent bonding).17.At low driving temperatures, no boiling occurs and the heat transfer rate is controlled by the usual single-phase mechanisms. As the surface temperature is increased, local boiling occurs and vapour bubbles (气［包)nucleation, grow into the surrounding cooler fluid, and collapse・ This is sub-cooled nucleation boiling and is a very efficient heat transfer mechanism・ At high bubble generation rates the bubbles begin to interefere (扰动/干扰)and the heat flux no longer increases rapidly with surface temperature (this is the departure from nucleate boiling DNB). At higher temperatures still, a maximum in the heat flux is reached (the critical heat flux).18.As a liquid mixture in the round bottomed flask is boiled, vapor rises up the fractionating column. The vapor condenses on the glass platforms (known as tray (土荟板)or plates) inside the column, and runs back down into the liquid below and refluxes the upflowing distillate vapor. The hottest tray (塔板)is at the bottom of the column and the coolest tray is at the top. At steady state conditions, the vapor and liquid on each tray is at equilibrium. Only the most volatile of the vapors stays in gas form all the way to the top. The vapor at the top of the column then flows through the water-cooled condenser, which cools the vapor down until it condenses into a liquid distillate （馅出液）.The separation may be enhanced by the addition of more trays （to a practical limitation of heat, flow, etc.）19.Natural methods of precipitation include settling or sedimentation , where the solid forms over a period of time due to ambient forces like gravity or centrifugation. During chemical reactions, precipitation may also occur particularly if an insoluble substance is introduced into a solution and the density happens to be greater （otherwise the precipitate would float or form a suspension. With soluble substances, precipitation is accelerated once the solution becomes supersaterated. In solids, precipitation occurs if the concentration of one solid is above the solubility limit in the host solid, due to e.g. rapid quenching （淬火）or ion implantation, and the temperature is high enough that diffusion can lead to segregation （偏析）into precipitates. Precipitation in solids is routinely used to synthesize nanoclusters・20.Freeze-drying also causes less damage to the substance than other dehydration （脱水）methods using higher temperatures. Frcczc-drying docs not usually cause shrinkagcor tougheningof the material being dried. In addition, flavors, smells and nutritional content generally remain unchanged, making the process popular for preserving food. However, water is not the only chemical capable of sublimation, and the loss of other volatile compounds such as acetic acid （vinegar） and alcohols （醉）can yield undesirable results・。