Design for Simplicity

We pointed out earlier in this chapter that simplicity is the key to controllability. What we mean by simplicity is that the list of dominant variables should be kept as short as possible. It is easy to construct reactors where the number of dominant variables far exceed the number of manipulated variables or where the dominant variables interact in a complicated way. 

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Sensors incorporating glass or plastic optical fibers have demonstrated several advantages over electrosensors for biomedical applications. These sensors involve no electrical connections and hence are safe from that standpoint the leads are quite small and flexible they can be incorporated in catheters for multiple sensing where required, they can be implanted for relatively long periods. The fibers are considerably less than 1 millimeter in diameter. Where designed for simplicity, they often can be considered disposable. 

Since the CLCD was designed, for simplicity, without any HI purification step, the lower phase (HI-I2-H2O) was directly fed to the HI cracker and no catalyst was used. 

Startup actually should begin during the plant design. For simplicity, activities can be divided into pre-mechanical completion and post-mechanical completion. See Fig. 18.1. 

The experimental setup was designed for simplicity and reproducibility. It is described in detail elsewhere (Veser and Schmidt. 1996) and will therefore be discussed very briefly here. 

The entire Elan 500 Plasmalok system is designed for simplicity of operation. A typical daily start-up sequence from the standby mode includes turning on the plasma and changing to the operating mode. After a brief warm-up period for the plasma, routine sample analysis can begin. 

The supervisor records the observation on a specific form. Observations are expected to take 5 to 10 minutes. The form in Figure 20-3 is designed for simplicity. The far right column asks that the employee initial the form to verify that an observation took place. Observations are not intended to be hidden in any manner. The supervisor is expected to alert the employee of this activity. The initialing of the form is also enables the worker to be sure that the reported unsafe conditions are placed on the form. 

The cluster of variables-which we designate X for simplicity -is dimension-... 

The Center for Chemical Process Safety (CCPS) has identified the need for a publication dealing with process safety issues unique to batch reaction systems. This book, Guidelines for Process Safety in Batch Reaction Systems, attempts to aid in the safe design, operation and maintenance of batch and semi-batch reaction systems. In this book the terms batch and semi-batch are used interchangeably for simplicity. The objectives of the book are to ... 

For simplicity, the condition considers the conservative case where the pipe acts simply as a support. The normal practice is to solve all these equations simultaneously, then determine the minimum wall thickness that has strains equal to or less than the allowable design strain. Thus, the minimum structural wall thickness is dictated by the longitudinal tensile load. 

The following macroscopic reaction scheme accounts for many of the observed effects (for simplicity PETN will be designated by RCH20N02) ... 

There is a continuing emphasis on numerical solutions. Numerical solutions are needed for most practical problems in chemical reactor design, but sophisticated numerical techniques are rarely necessary given the speed of modern computers. The goal is to make the techniques understandable and easily accessible and to allow continued focus on the chemistry and physics of the problem. Computational elegance and efficiency are gladly sacrificed for simplicity. 

This section concerns the modelling of countercurrent flow, differential mass transfer applications, for both steady-state and non-steady-state design or simulation purposes. For simplicity, the treatment is restricted to the case of a single solute, transferring between two inert phases, as in the standard treatments of liquid-liquid extraction or gas absorption column design. 

In this section, we apply the axial dispersion flow model (or DPF model) of Section 19.4.2 to design or assess the performance of a reactor with nonideal flow. We consider, for example, the effect of axial dispersion on the concentration profile of a species, or its fractional conversion at the reactor outlet. For simplicity, we assume steady-state, isothermal operation for a simple system of constant density reacting according to A - products. 

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