Reactor shortcut methods

The shortcut method proposed in Reference 1 may be used only to obtain a preliminary estimate of the height of catalyst required in the reactor. The reactor should be designed from first principles using the rate equation, below, taken from Reference 1 ... 

The computation methods described above require the knowledge of reaction kinetics. Unfortunately, this is not the case in a large number of cases, particularly in an evaluation project. In this case shortcut methods are handy, in which the reactor volume may be estimated from information about the residence time. The following definitions of the reaction time are mostly used ... 

In shortcut methods the reactor volume may be approximated from information about the residence time, expressed either as LHSV, GHSV or WHSV (see section 8.3.1). Technological constraints, as allowable pressure drop, heat and mass transfer, catalyst attrition, etc., are other elements that lead to the final geometric characteristics. An important design parameter is the fluid superficial velocity (phase volumetric flow divided by cross-area). Recommended values are ... 

We also described how concrete equations for critical DSR and CSTRs may be computed. These expressions are complicated to compute analytically, which are derived from geometric controllability arguments developed by Feinberg (2000a, 2000b). These conditions are intricate, and thus it is often not possible to compute analytic solutions to the equations that describe critical reactors. For three-dimensional systems, a shortcut method involving the vDelR condition may be used to find critical a policies. Irrespective of the method used, the conditions for critical reactors are well defined, irrespective of the legitimacy of the kinetics studied, and thus these conditions must be enforced if we wish to attain points on the true AR boundary. 

Various degrees of effort can be applied in process simulation. A simple split balance can give a first overview of the process without introducing any physical relationships into the calculation. The user just defines split factors to decide which way the particular components take. In a medium level of complexity, shortcut methods are used to characterize the various process operations. The rigorous simulation with its full complexity can be considered as the most common case. The particular unit operations (reactors, columns, heat exchangers, flash vessels, compressors, valves, pumps, etc.) are represented with their correct physical background and a model for the thermophysical properties. 

---