Reactor flow characteristics

Detailed descriptions of the chemical reactor flow patterns are given in chaps 8, 10, 7 and 11. Meanwhile, a preliminary overview of the pertinent reactor flow characteristics is given to determine which modeling concepts are available describing the behavior of the relevant flows. 

Flow Regimes in Multiphase Reactors. Reactant contacting, product separations, rates of mass and heat transport, and ultimately reaction conversion and product yields are strong functions of the gas and Hquid flow patterns within the reactors. The nomenclature of commonly observed flow patterns or flow regimes reflects observed flow characteristics, ie, armular, bubbly, plug, slug, spray, stratified, and wavy. 

Scale-Up Principles. Key factors affecting scale-up of reactor performance are nature of reaction zones, specific reaction rates, and mass- and heat-transport rates to and from reaction sites. Where considerable uncertainties exist or large quantities of products are needed for market evaluations, intermediate-sized demonstration units between pilot and industrial plants are usehil. Matching overall fluid flow characteristics within the reactor might determine the operative criteria. Ideally, the smaller reactor acts as a volume segment of the larger one. Elow distributions are not markedly influenced by... 

As their name suggests, these models are based on the physical principles of diffusion and convection, which govern the mixing process. According to the flow pattern, the reactor is divided into different zones with different flow characteristics. 

Plug flow characteristics of aging reactor Stabilization (hydrolysis)... 

Overall numerical RTD provides a quick and relatively simple method to accurately determining the flow characteristics within this type of reactor vessel. 

The determination of the external mass transfer coefficient of CO, k, (see Equation 3) deserves brief comments. Since the complex geometry and flow characteristics in the reactor cell precluded a reliable estimation of k based on correlations given in the literature, the CO oxidation activities of the catalyst... 

At this stage, type (1) is more apparent than type (2), and we provide some preliminary discussion of (2) here. Flow characteristics include relative times taken by elements of fluid to pass through the reactor (residence-time distribution), and mixing character-... 

In this chapter, we focus on the characteristics of the ideal-flow models themselves, without regard to the type of process equipment in which they occur, whether a chemical reactor, a heat exchanger, a packed tower, or some other type. In the following five chapters, we consider the design and performance of reactors in which ideal flow occurs. In addition, in this chapter, we introduce the segregated-flow model for a reactor as one application of the flow characteristics developed. 

Flow characteristics of a continuous reactor are studied by sudden... 

A reactor has flow characteristics given by the nonnormalized C curve in Table P14.ll, and by the shape of this curve we feel that the dispersion or tanks-in-series models should satisfactorily represent flow in the reactor. 

Processes that involve the reaction of gases and solids are extremely difficult to handle mainly due to solid flow difficulties (Knowlton, 2000). The difficulty in the scale-up of these reactors constitutes then main disadvantage. The maximum scale-up factor for fluidized beds is usually between 50 and 100, whereas for fixed beds it could reach the value of 10,000. This is due to the fact that the flow characteristics are very different in the small and the large reactor the bubble diameter does not change upon scale-up, whereas reactor diameter does. 

The location of the CO peak indicates the temperature regime for onset of fast oxidation for each hydrocarbon. At the reaction conditions of the flow reactor, the characteristic temperature regime for oxidation differs widely between fuels. Compared to methane, the C2 hydrocarbons are consumed at much lower temperatures at a given reaction time. This is consistent with the general observation that the C2 hydrocarbons have quite different ignition characteristics compared to methane [427]. As a consequence the presence of ethane (C2H6) and higher hydrocarbons in natural gas has a considerable influence on induction times. 

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