Turbulent-flow reactor

Most ion-molecule techniques study reactivity at pressures below 1000 Pa however, several techniques now exist for studying reactions above this pressure range. These include time-resolved, atmospheric-pressure, mass spectrometry optical spectroscopy in a pulsed discharge ion-mobility spectrometry [108] and the turbulent flow reactor [109]. 

The models of Chapter 9 contain at least one empirical parameter. This parameter is used to account for complex flow fields that are not deterministic, time-invariant, and calculable. We are specifically concerned with packed-bed reactors, turbulent-flow reactors, and static mixers (also known as motionless mixers). We begin with packed-bed reactors because they are ubiquitous within the petrochemical industry and because their mathematical treatment closely parallels that of the laminar flow reactors in Chapter 8. 

Turbulent flow reactors are modeled quite differently from laminar flow reactors. In a turbulent flow field, nonzero velocity components exist in all three coordinate directions, and they fluctuate with time. Statistical methods must be used to obtain time average values for the various components and to characterize the instantaneous fluctuations about these averages. We divide the velocity into time average and fluctuating parts ... 

This result makes it clear that particle stress is strongly dependent on the interaction between the particles and the interface, so that electrostatic and also hydrophobic and hydrophilic interactions with the phase boundary are particularly important. This means that the stress caused by gas sparging and also by boundary-layer flows, as opposed to reactors with free turbulent flow (reactors with impellers and baffles), may depend on the particle system and therefore applicability to other material systems is limited. 

The stress caused by gas sparging and also by boundary-layer flows, as opposed to reactors with free turbulent flow (reactors with impellers and bafQes), may depend on the particle system. 

As an example, a compact high-throughput turbulent flow reactor/mixer/heat exchanger was used for various applications, including polymer and rubber manufacture [50]. Further applications refer to emulsification and intensified heat exchange. 

Keeler, R. N., E. E. Petersen, and J. M. Prausnitz (1965). Mixing and chemical reaction in turbulent flow reactors. AIChE Journal 11, 221-227. 

FIGURE 3.11 Oxidation of ethane in a turbulent flow reactor showing intermediate and final product formation (after [13]). 

FIGURE 3.13 Molar rates of progress for benzene oxidation in an atmospheric turbulent flow reactor. The thickness of the lines represents the relative magnitudes of certain species as they pass through each reaction pathway. 

There are many different aspects to the field of turbulent reacting flows. Consider, for example, the effect of turbulence on the rate of an exothermic reaction typical of those occurring in a turbulent flow reactor. Here, the fluctuating temperatures and concentrations could affect the chemical reaction and heat release rates. Then, there is the situation in which combustion products are rapidly mixed with reactants in a time much shorter than the chemical reaction time. (This latter example is the so-called stirred reactor, which will be discussed in more detail in the next section.) In both of these examples, no flame structure is considered to exist. 

In the applications that have been discussed here, high rates of transport have, somewhat paradoxically, favored attainment of conditions under which analyses neglecting transport effects can be applied. The rapid transport helps to achieve conditions of uniformity, under which transport no longer is significant, and effects of finite-rate chemistry can be studied. This same kind of situation prevails in various other experiments, such as those employing a suitably designed turbulent-flow reactor [18], [19], [20]. In... 

FIGURE 10 Oxidation of propane in a turbulent flow reactor. 

Experimental results from the Princeton turbulent flow-reactor have... 

Flow systems in use may be classified as heated laminar tubes, or plug flow tube reactors, (PFTR) and burners, or heated turbulent flow reactors and well-stirred reactors, or continuous stirred-tank reactors, (CSTR). 

Studies of benzene and toluene oxidation in the turbulent flow reactor at Princeton University have provided valuable information on the mechanisms of oxidation at temperatures in excess of 1000 K [213]. The first extensive study of benzene and toluene at temperatures of about 750 K was made by Burgoyne [35]. Apart from CO and CO2, the major products of benzene oxidation that were detected were phenols and acids. An autocatalytic reaction was observed by Burgoyne [35] presumably driven by H2O2 formation and decomposition. Amongst the main products of toluene slow oxidation were benzyl alcohol, benzaldehyde and benzoic acid. Phenolic compounds were also reported. This reaction also showed an autocatalytic development. An equilibrium constant for the equilibrium between benzyl and benzylperoxy radicals has been measured by Fenter et al. [214], but this cannot be followed by an isomerization in the way that is possible in alkanes. 

Benzene, toluene and ethylbenzene Adiabatic turbulent flow reactor T = -1200 K 100 kPa t,cs = 0-125 ms = 0.3-1.5. Benzene and phenol and 7 other aliphatic hydrocarbon products identified (for benzene and ethylbenzene) 6 aromatics and 8 other aliphatic hydrocarbons identified (for toluene) as /(tres). 

Examples of chemical process units in this category include plug flow reactors, laminar flow reactors, turbulent flow reactors, plasma reactors, and separation units that are described in terms of the mass transfer concept. To develop a numerical algorithm, the time and spatial derivatives are replaced by finite difference approximations. In general, the time derivative is represented by a forward difference, whereas the second order spatial derivatives are approximated by central differences as follows for the dependent variable Y in Cartesian coordinates ... 

Derive ( ) for a turbulent flow reactor with l/7th power law. 

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