常见化工词汇

Half-time 半衰期；batch reactor 间歇式反应器；specific heat 比热；specific surface area 比表面积；boundary layer 边界层；differential pressure 差压；differential thermal analyzer 差热分析仪；air distillation 常压蒸馏；vacuum distillation 减压蒸馏；settling out 沉出；settle, subsidence 沉降；settle, precipitation 沉淀；mass transfer 传质；sensor传感器; coefficient of heat transfer传热系数；catalyze, catalyst, catalyzer catalytic cracking; extraction 萃取；isopleth 等值线isometric等容的, isobath等深线，isothermic等温的；flash闪蒸; titration 滴定；electrolyzing 电解；dynamics 动力学；calcining furnace 煅烧炉；fermentation发酵; flange 发兰；decomposition分解；pulverization粉碎；siccity, drying oven(box) 干燥（箱）;plate tower 板式塔；packing tower填料塔; self-refrigeration(automatic)自动冷凝;filter过滤；rotameter,rotermeter转子流量计;；column temperature gradient温度梯度；crystallization结晶；diffusion扩散；horsepower功率; condenser冷凝器；still釜；tank罐，槽；tower塔；chamber 箱；pump泵；pan锅；tube, pipe管；valve阀; flocculation絮凝；adsorption吸附；absorption 吸收; desorption解吸；dissolve溶解；fusion熔融；melt熔化; swelling溶胀；hydromechanics 流体力学；pressure加压；heating加热；ReactorBathch and semibatch reatorsBatch reactors are generally used for liquid phase reactions. When a solid catalyst has to be kept in suspension or when there are two liquid phases, as in the nitration of aromatics, for instance, an agitator is required. Agitation is also necessary to equalize the temperature in the reator and to keep it at the desired level by efficient hert exchange through a jacket or an internal coil. Consequently, the batch reactor is generally considered to be spatially uniform in composition and temperature. The composition changes with time, however,. Temperature sequencing may be favorable for the selectivity or for achieving complete conversion in a safe way.In pure batch operation the reactants are completely fed into the reator at the beginning. For better control of temperature this type of operation may not be advisable and the reactants may have to be added progressively to the contents of the vessel. The reactor is then said to operate in the semibatch mode. Or, a product maybe withdrawn, for instance, water in an esterification, to reach complete conversion of the reactants.Batch and semibatch reactors are most often used for low production capacities, where the cost of labor and dead time are only a small fraction of the unit cost of the product. They are generally ecountered in the area of special chemicals and polymers and in pharmaceuticals, in particular, in plants with a wide variety of products.Plug flow reatorPlug flow is a simplified and idealized picture of the motion of a fluid, whereby all the fluid elements move with a uniform velocity along parallel streamlines, this perfectly ordered flow is the only transport mechanism accounted for in the pluh flow reactor model.Perfectly mixed flow reatorThis reactor type is the opposite extreme from the plug flow reactor considered above. The essential feature is the assumption of complete uniformity of concentration and temperature throughout the reator, as contrasted with the assumption of no inter mixing of successive fluid elements entering a plug flow vessel. Therefore, in the perfectly mixed flow reactor, the conversion takes place at a unique concentration (and temperature) level which, of course, is also the concentration of the effluent. To approch this ideal mixing pattern, it is necessary that the feed be intimately mixed with the contents of the reactor in a time interval that is very small compared to the mean residence time of the fluid flowing through the vessel. Further discussion of deviations from these ideal flow patterns are given later.The stirred flow reactor is frequently chosen when temperature control is a critical aspect, as in the nitration of aromatic hydrocarbons or glycerin. The stirred flow reactor is also chosen when the conversion must take place at a constant composition, as in the copolymerization of butadiene and styrene, or when areaction between two phases has to be carried out, or when a catalyst must be kept in suspension as in the polymerization of ethylene with Ziegler catalyst, the hydrogenation of a-methylstyrene to cumene, and the air oxidation of cumene toacetone and phenol.Several alternate names have been used for what here is called the perfectly mixed flow reactor. One of the earlist was “continous stirred tank reactor”, or CSTR, which some have modified to “continous flow stirred tank reactor”, or CFSTR. Other names are “backmix reactor”, “mixed flow reactor”, and “ideal stirred tank reactor”. All of these terms appear in the literature and must be recognized.Fixed bed catalytic reactorsThe dicovery of solid catalysts and their application to chemical processes in the early years of this cencury has to a breakthrough of the chemical industry. Since then, this industry has diversified and grown in a spectacular way through the development of new or the rejuvenation of established processes, mostly based on the use of solid catalysta.The main part of these catalytic processes is carried out in a fluidized bed to enable the continuous regeneration of the catalyst, the major solid catalyzed processes of today’ chemical and petroleum refining industries use fixed bed catalytic reactors. Today’s fixed bed reactors are mainly large-capacity units. Such a spectacular rise in reactor capacity is evidently tied to the growing market demand, but its realization undoubtedly also reflects progress in both technological and fundamental areas, pressed by the booming construction activity of the world.Fluidized bedAlthough the fluidized bed technique was introduced as early as 1926, the real breakthrough of fluidized beds was associated with the catalytic cracking of gasoil into gasoline in 1942. before that, catalytic cracking was carried out in fixed bed reactors. Catalytic cracking deposits carbonaceous products in the catalyst, causing rapid deactivation of the latter. To maintain the production capacity, the coke had to be burned off. This regeneration required switching the reactor out of production. In order to eliminate the cycling, attempts were made to circulate the catalyst and burn off the coke in a separate vessel, the regenerator. One approach was to use a moving catalyst bed: in a very compact mass, into the regeneration. From the regenerator thecatalyst was returned to the top of the reactor by a bucket conveyor. Later, the convetor system was replaced by a gas lift. Finally, both the reactor and the regenerator were operated under transport conditions. The high velocities required for pneumatic transport caused considerable attrition of the catalyst. To lower the velocities, very fine solids had to be used. It was then found that the dense mixture of solids and gas behaved in many aspects like a fluid, and this makes the control of streams much more convenent. Since then, fluidized beds have been used in other fields where solids have to be bandled, such as the roasting of ores and in catalytic reactors for highly exothermic reactions. The latter application is based opun another advantage: the high turbulence created in the fluid-solid mixture leads to much higher heat transfer coefficients than those which can be obtained in fixed beds. Therefore, fluidized bed reactors have now also found use in exothermic processes requiring close temperature control such as the oxidation of naphthalene into phthalic anhydride, the ammoxidation of propylene into acrylonitrile, the oxychlorination of ethylene into ethylene dichloride-the first step of vinyl chloride manufacture, and the process for polymerization of ethylene. A new and important application is fluid bed combustion of coal, which permits using low-grade coals rich in mineral matter, less suited for conventional boilers. An additional advantage is the in situ capture of sulsur dioxide by means of injected limestone. Whereas in the above cases only a minor fraction of the catalyst is entrained with the gas, so that the major part is confined in dense bed, with a dilute section and cyclones above it. There are also processes in which the total amount of catalyst is entrained by the gas. The reactors then belong to the category of transport reators.。