化学反应工程Chapter 1.ppt
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1、Chapter 1 Overview of Chemical Reaction Engineering 1.1 Chemical process illustrationEvery industrial chemical process is designed to produce economically a desired product from a variety of starting materials through a succession of treatment steps.Figure 1.1 shows a typical situation.化化 学学 反反 应应 工
2、工 程程化化 学学 反反 应应 工工 程程Fig.1.1 Typical chemical process化化 学学 反反 应应 工工 程程Physical treatment of feed:The raw materials undergo a number of physical treatment steps to put them in the form in which they can be reacted chemically.Then they pass through the reactor.The products of the reaction must then un
3、dergo further physical treatmentseparations,purification,etc.for the final desired product to be obtainedDesign of equipment for the physical treatment steps is studied in the unit operations.化化 学学 反反 应应 工工 程程In this book we are concerned with the chemical treatment step of a process.Economically th
4、is may be an inconsequential(不合理的)unit,perhaps a simple mixing tank.Frequently(常常),however,the chemical treatment step is the heart of the process,the thing that makes or breaks the process economically.化化 学学 反反 应应 工工 程程Design of the reactor is no routine(常规)matter,and many alternatives(二中择一,可供选择的办法
5、)can be proposed for a process.In searching for the optimum it is not just the cost or the reactor that must be minimized.One design may have low reactor cost,but the materials leaving the unit may be such that their treatment requires a much higher cost than alternative designs.Hence,the economics
6、of the overall process must be considered.化化 学学 反反 应应 工工 程程 Reactor design uses information,knowledge,and experience from a variety of areas:Thermodynamics(热力学)(热力学)Chemical kinetics(化学动力学)(化学动力学)Fluid mechanics(流体力学)(流体力学)Heat transfer,mass transfer(传热(传热,传质)传质)Economics(经济学)(经济学)化化 学学 反反 应应 工工 程程1
7、.2 Performance equation:Figure1.2 Information needed to predict what a reactor can do.化化 学学 反反 应应 工工 程程Contacting Pattern or how materials flow through and contact each other in the reactor,how early or late they mix,their clumpiness or state of aggregation.By their very nature some materials are ve
8、ry clumpyfor instance,solids and noncoalescing liquid droplets.Kinetics or how fast things happen.If very fast,then equilibrium tells what will leave the reactor.If not so fast,then the rate of chemical reaction,and maybe heat and mass transfer too,will determine what will happen.化化 学学 反反 应应 工工 程程Ou
9、tput=input,kinetics,contacting (1)This is called the performance equation(or design equation).Why is this important?Because with this expression we can compare different designs and conditions,find which is best,and then scale up to larger units.化化 学学 反反 应应 工工 程程1.3 Classification of Reactions There
10、 are many ways of classifying chemical reactionsIn the view of chemical reaction engineering probably the most useful scheme is the breakdown(=classify)according to the number and types of phases involved.1.3.1 Homogeneous and Heterogeneous reaction systemsHomogeneous reaction,it takes place in one
11、phase alone.(homo-:相同的相同的,hetero-:不同的不同的,相异的相异的)Heterogeneous reaction,it requires the presence of at least two phases to proceed at the rate that it does.化化 学学 反反 应应 工工 程程1.3.2 Catalytic and Non-catalytic reaction systemsCatalytic reaction,whose rate is altered by materials that are neither reactan
12、ts nor products.These foreign materials,called catalysts,need not be present in large amounts.Catalysts act somehow as go-betweens(媒介),either hindering(阻碍)or accelerating(加快)the reaction process.But it does not change the equilibrium of chemical reaction.化化 学学 反反 应应 工工 程程Non-catalytic reaction:absen
13、ce of catalystTablel.1 shows the classification of chemical reactions according to our scheme with a few examples of typical reactions for each type.化化 学学 反反 应应 工工 程程1.3.3 Other ways for reaction classification reactor type(BR,PFR,MFR,fixed-bed,moving-bed,fluidized-bed)heat effects(endothermic,exoth
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