partunitlesson

1、化学化工专业英语化学化工专业英语Specialty English for Chemistry and Chemical Engineering主讲主讲 丁明洁丁明洁河南城建学化工学院河南城建学化工学院小测试小测试agitationagitationn.n.激动激动, , 兴奋兴奋, , 煽动煽动, , 搅动搅动buoyancybuoyancyn.n.浮性浮性, ,浮力浮力, ,轻快轻快collisioncollisionn.n.碰撞碰撞, , 冲突冲突emissivityemissivityn.n.发射率，辐射系数，辐射能力发射率，辐射系数，辐射能力manifestmanifestvtvt.

2、 .表明表明, , 证明证明moleculemoleculen.n.分子分子parcelparceln.n.小包小包, , 包裹包裹velocityvelocityn.n.速度速度, , 速率速率, , 迅速迅速, , 周转率周转率viscosityviscosityn.n.粘质粘质, , 粘性粘性Unit 3Unit 3 Reaction Engineering Reaction Engineering /Lesson 12 Lesson 12 Reactor TypesReactor Types 单击此处编辑母单击此处编辑母1 1Stirred tank reactorStirred ta

3、nk reactor（搅拌釜式反应器）（搅拌釜式反应器）A batchbatch（间歇式的）（间歇式的） stirred stirred tank reactortank reactor is the simplest type of reactor. It is composed of a reactor and a mixer（混和器） such as a stirrer（搅拌子，搅拌器）, a turbine wing（涡轮桨） or a propeller（螺旋桨）. The batch stirred tank reactor is illustrated below:单击此处编辑母

4、单击此处编辑母This reactor is useful for substrate（基质） solutions of high viscosity and for immobilized enzymes （固定化酶）with relatively low activity（低活性）. However, a problem that arises（出现，发生，引起） is that an immobilized enzyme tends to decompose （分解）upon physical stirring. The batch system is generally suitabl

5、e for the production of rather small amounts of chemicals. 单击此处编辑母单击此处编辑母A continuous stirred continuous stirred tanktankreactor （连续（连续搅拌釜式反应器）搅拌釜式反应器） is shown below: The continuous stirred tank reactor is more efficient than a batch stirred tank reactor but the equipment is slightly more complicat

6、ed. 单击此处编辑母单击此处编辑母2 Tubular Reactor2 Tubular Reactor（管式反应器）（管式反应器）Tubular reactors are generally used for gaseous reactions, but are also suitable for some liquid-phase reactions.If high heat-transfer rates are required, small-diameter tubes are used to increase the surface area to volume ratio（表面积体

7、积比）. Several tubes may be arranged （被安排，设计成）in parallel（平行）, connected to a manifold（歧管，管汇） or fitted into （安装在）a tube sheet（管板） in a similar arrangement to （与相似的布置）a shell and tube heat exchanger（管壳式换热器）. For high-temperature reactions the tubes may be arranged in a furnace（炉）. 单击此处编辑母单击此处编辑母3 3Flu

8、idized bedFluidized bedReactorReactor （流化床反应器）A fluidized bed reactor (FBR) is a type of reactor device that can be used to carry out a variety of multiphase（多相的） chemical reactions.单击此处编辑母单击此处编辑母In this type of reactor, a fluid (gas or liquid) is passed through a granular（粒状的） solid material (usual

9、ly a catalyst possibly shaped as tiny spheres（微球）) at high enough velocities to suspend the solid and cause it to behave as though it were a fluid. This process, known as fluidization（流化）, imparts （给予，赋予）many important advantages to the FBR. As a result, the fluidized bed reactor is now used in many

10、 industrial applications. 单击此处编辑母单击此处编辑母Basic principlesThe solid substrate（固体基质） (the catalytic material upon which chemical species react) material in the fluidized bed reactor is typically supported by a porous plate（多孔板）, known as a distributor（分配器，分配盘）. The fluid is then forced through the dist

11、ributor up through the solid material. At lower fluid velocities, the solids remain in place as the fluid passes through the voids （空隙）in the material. 单击此处编辑母单击此处编辑母This is known as a packed bed reactor（填充床反应器）. As the fluid velocity is increased, the reactor will reach a stage where the force of t

12、he fluid on the solids is enough to balance the weight of the solid material. This stage is known as incipient （初期的）fluidization and occurs at this minimum fluidization velocity. 单击此处编辑母单击此处编辑母Once this minimum velocity is surpassed（超过，突破）, the contents of the reactor bed begin to expand and swirl （

13、旋涡，打旋）around much like an agitated tank or boiling pot of water. The reactor is now a fluidized bed. Depending on the operating conditions and properties of solid phase various flow regimes （流动变化规律）can be observed in this reactor.单击此处编辑母单击此处编辑母AdvantagesAdvantagesThe increase in fluidized bed reacto

14、r use in todays industrial world is largely due to the inherent advantages of the technology. Uniform Uniform （均一的）（均一的）Particle Mixing:Particle Mixing: Due to the intrinsic（固有的） fluid-like behavior of the solid material, fluidized beds do not experience （经历）poor mixing as in packed beds. This compl

15、ete mixing allows for （虑及，考虑到，使能够）a uniform product that can often be hard to achieve in other reactor designs. The elimination （消除）of radial（径向的） and axial （轴向的）concentration gradients（浓度梯度） also allows for better fluid-solid contact, which is essential for reaction efficiency and quality. 单击此处编辑母单

16、击此处编辑母Uniform Temperature Gradients:Uniform Temperature Gradients: Many chemical reactions produce or require the addition of heat. Local hot or cold spots（局部热点或冷点） within the reaction bed, often a problem in packed beds, are avoided in a fluidized situation such as an FBR. In other reactor types, t

17、hese local temperature differences, especially hotspots, can result in product degradation（降解）. Thus FBRs are well suited to exothermic （放热的）reactions. Researchers have also learned that the bed-to-surface heat transfer coefficients（传热系数） for FBRs are high. 单击此处编辑母单击此处编辑母Ability to Operate Reactor i

18、n Continuous Ability to Operate Reactor in Continuous State:State: The fluidized bed nature of these reactors allows for the ability to continuously withdraw（引出） product and introduce （引入）new reactants （反应物）into the reaction vessel（容器）. Operating at a continuous process state allows manufacturers to

19、 produce their various products more efficiently due to the removal of startup （启动）conditions in batch processes. 单击此处编辑母单击此处编辑母DisadvantagesDisadvantagesAs in any design, the fluidized bed reactor does have it draw-backs, which any reactor designer must take into consideration. Increased Reactor Ve

20、ssel Size:Increased Reactor Vessel Size: Because of the expansion of the bed materials（扩张） in the reactor, a larger vessel is often required than that for a packed bed reactor. This larger vessel means that more must be spent on initial startup costs. 单击此处编辑母单击此处编辑母Pumping Requirements（输送要求）（输送要求） a

21、nd Pressure Drop（压力降）（压力降）: The requirement for the fluid to suspend the solid material necessitates（迫使，需要） that a higher fluid velocity is attained in the reactor. In order to achieve this, more pumping power and thus higher energy costs are needed. In addition, the pressure drop （压力降）associated wi

22、th deep beds （与深层床相关的） also requires additional （附加的）pumping power. 单击此处编辑母单击此处编辑母Particle EntrainmentParticle Entrainment（夹带）（夹带）: : The high gas velocities present in this style of reactor often result in fine particles becoming entrained in the fluid. These captured（被俘获的，被夹持的） particles are then

23、carried out of the reactor with the fluid, where they must be separated.This can be a very difficult and expensive problem to address（提出，从事，忙于） depending on the design and function of the reactor. This may often continue to be a problem even with other entrainment reducing technologies. 单击此处编辑母单击此处编

24、辑母Lack of Current Understanding Lack of Current Understanding （认识缺少）认识缺少） : : Current understanding of the actual behavior of the materials in a fluidized bed is rather limited. （目前，对物质在流化床中的实际行为的认识相当有限）It is very difficult to predict （预测）and calculate （计算）the complex mass and heat flows within the

25、bed. Due to this lack of understanding, a pilot plant（试验厂） for new processes is required. Even with pilot plants, the scale-up （放大）can be very difficult and may not reflect（反映） what was experienced in the pilot trial（先导试验）. 单击此处编辑母单击此处编辑母Erosion of Internal Components:Erosion of Internal Components:

26、 The fluid-like behavior of the fine solid particles within the bed eventually results in the wear of the reactor vessel. This can require expensive maintenance and upkeep for the reaction vessel and pipes. 单击此处编辑母单击此处编辑母4 Packed bed Reactor4 Packed bed Reactor（填充床反应器）（填充床反应器）There are two basic types of