Flow regime Continuously stirred tank reactor

Over 25 years ago the coking factor of the radiant coil was empirically correlated to operating conditions (48). It has been assumed that the mass transfer of coke precursors from the bulk of the gas to the walls was controlling the rate of deposition (39). Kinetic models (24,49,50) were developed based on the chemical reaction at the wall as a controlling step. Bench-scale data (51—53) appear to indicate that a chemical reaction controls. However, flow regimes of bench-scale reactors are so different from the commercial furnaces that scale-up of bench-scale results caimot be confidently appHed to commercial furnaces. For example. Figure 3 shows the coke deposited on a controlled cylindrical specimen in a continuous stirred tank reactor (CSTR) and the rate of coke deposition. The deposition rate decreases with time and attains a pseudo steady value. Though this is achieved in a matter of rninutes in bench-scale reactors, it takes a few days in a commercial furnace. 

It is useful to examine the consequences of a closed ion source on kinetics measurements. We approach this with a simple mathematical model from which it is possible to make quantitative estimates of the distortion of concentration-time curves due to the ion source residence time. The ion source pressure is normally low enough that flow through it is in the Knudsen regime where all collisions are with the walls, backmixing is complete, and the source can be treated as a continuous stirred tank reactor (CSTR). The isothermal mole balance with a first-order reaction occurring in the source can be written as... 

Backmix flow reactor or continuously stirred tank reactor. The conversion rate is lower than for plug-flow reactors because the reagent is immediately diluted on being introduced into the reactor. Many flow reactors, e.g. tubular reactors, and especially in the turbulent regime are in this class. 

Basic Design ofEnv me Reactors Under Ideal Conditions. Batch Reactor Continuous Stirred Tank Reactor Under Complete Mixing Continuous Packed-Bed Reactor Under Plug Flow Regime... 

The selection of reactor type is perhaps the most important problem in SSITKA studies. There are two types of reactors, that is, plug-flow and continuous stirred tank (CSTR), which differ in mass transfer regimes. The decisive advantage of CSTR is that the reaction takes place in gradientless conditions, which considerably simplifies the kinetic studies. However, the rather high response time of gas mixing in the reactor volume may distort the true dynamics of label transfer from reactants to reaction products. 

Any deviations from ideal displacement regime are called stirring or inverse stirring. In that case tank reactors of ideal stirring are the idealized model of continuously operating apparatus in opposition to ideal plug-flow reactors. 

Chemical reactors, particularly for continuous processes, are often custom designed to involve multiple phases (e.g., vapor, liquid, reacting solid, and solid catalyst), different geometries (e.g., stirred tanks, tubular flows, converging and diverging nozzles, spiral flows, and membrane transport), and various regimes of momentum, heat, and mass transfer (e.g., viscous flow, turbulent flow, conduction, radiation, di sion, and dispersion). There... 

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