Design strategies reactors

The mass balance with homogeneous one-dimensional diffusion and irreversible nth-order chemical reaction provides basic information for the spatial dependence of reactant molar density within a catalytic pellet. Since this problem is based on one isolated pellet, the molar density profile can be obtained for any type of chemical kinetics. Of course, analytical solutions are available only when the rate law conforms to simple zeroth- or first-order kinetics. Numerical techniques are required to solve the mass balance when the kinetics are more complex. The rationale for developing a correlation between the effectiveness factor and intrapellet Damkohler number is based on the fact that the reactor design engineer does not want to consider details of the interplay between diffusion and chemical reaction in each catalytic pellet when these pellets are packed in a large-scale reactor. The strategy is formulated as follows  

Account for diffusion and chemical reaction in one isolated catalytic pellet and calculate a volumetrically averaged rate of consumption of reactants within the pellet in terms of conditions on the external surface of the catalyst. 

If concentrations and temperatures on the external catalytic surface are close to the bulk conditions in a packed reactor, then the design engineer can use these bulk conditions to estimate the rate of consumption of reactants within each pellet. 

The volume-averaged rate of reaction in each catalytic pellet is incorporated into plug-flow mass and thermal energy balances to predict the overall performance of the reactor. 

MASS TRANSFER LIMITATIONS IN ISOTHERMAL CATALYTIC PELLETS 

---

Additional discussion regarding reactor design strategies is covered in Section 3.1 on minimization (as an inherently safer design strategy), and in Section 4.4 on Design and Construction. 

In addilion lo Ihe reactor design strategies and the catalyst selection, a number of important operating variables exists, affecting both the rate and the extent of chemical species transformation. These include semiconductor concentration, reactive surface area, particle aggregate size, concentration of electron donors and acceptors, incident light intensity, pH, presence of competitive sorbates and temperature (Augugliai o et al., 1995). 

Verify the claim that both methods of solution produce the same final answers, and hence the same reactor design strategy, when the two alternatives [i.e., stoichiometric (1 1) feed vs. the 3 1 feed ratio] are considered. A more rigorons addendum to both approaches employs the Hagen-Poiseuille equation for laminar flow or the Ergun equation if the tubular reactor is packed with porous solid catalysts to calculate the pressure drop through the reactor instead of assuming that p = constant from inlet to outlet. 

TABLE 4-5 Reactor Design Strategies to Prevent the Phenomenon of Thermal Runaway in Plug-Flow Tabular Reactors... 

Various reactor design strategies are summarized below. Indicate whether each of these statements is true or false. 

As illustrated in Sections 30-1 and 30-2, all intrapellet resistances can be expressed in terms of f-A, surface a, intrapeiiet and Ea mtrapeiiet approaches zero near the central core of the catalyst when the intrapellet Damkohler number is very large. For small values of the intrapellet Damkohler number, effectiveness factor calculations within an isolated pellet allow one to predict Ca, intrapeUet in terms of CA,sur ce via the dimensionless molar density profile. All external transport resistances can be expressed in terms of Ca, buit gas — Ca, surface, and integration of the plug-flow mass balance allows one to calculate the bulk gas-phase concentration of reactant A. The critical step involves determination of Ca, surface via effectiveness factor formalism. Finally, a complete reactor design strategy is... 

Important results from earlier sections are summarized here to develop reactor design strategies when external resistances to heat and mass transfer cannot be neglected. Intrapellet resistances require information about... 

Strategies for enhanced heat control resulting in a new micro reactor design are briefly mentioned in [37]. 

Reactors can be broadly classified as chemical or biochemical. Most reactors, whether chemical or biochemical, are catalyzed. The strategy will be to choose the catalyst, if one is to be used, and the ideal characteristics and operating conditions needed for the reaction system. The issues that must be addressed for reactor design include ... 

A polytropic reaction means the reactor is neither designed to work under isothermal conditions, nor under adiabatic conditions. The reactor control strategy comprises different periods of time, where different modes of temperature control are applied. These different temperature control strategies may include heating to... 

In this lecture, the development of the MTG process will be reviewed. First, the unique aspects of MTG — the catalyst, chemistry, and its special reactor design aspects — will be discussed. Next, the choices for the conversion system will be presented along with the dual-pronged strategy for development of both the fixed- and fluid bed processes. Finally, our future development plans for this general area of technology will be highlighted. 

Monsler, M, J. Meier, W. R. "A Conceptual Design Strategy for Liquid-Metal-Wall Inertial Fusion Reactors Lawrence Livermore National Laboratory Livermore, CA, UCRL-84881, 1980, 28. 

V, Strategies for Process and Product Development A. Reactor Design Consecrations... 

---