Process Design and Optimization

While process synthesis gives qualitative reference points, for industrial implementation we need quantitative results. Therefore, tools for rigorous process simulation including all effects are needed. In practice, the application of staged models with increasing complexity can be reconunended but tools with this complexity are not yet on the market, so that in many cases reactive distillation cannot be simulated so far that a process design is possible without experiments. 

---

The purification of value-added pharmaceuticals in the past required multiple chromatographic steps for batch purification processes. The design and optimization of these processes were often cumbersome and the operations were fundamentally complex. Individual batch processes requires optimization between chromatographic efficiency and enantioselectivity, which results in major economic ramifications. An additional problem was the extremely short time for development of the purification process. Commercial constraints demand that the time interval between non-optimized laboratory bench purification and the first process-scale production for clinical trials are kept to a minimum. Therefore, rapid process design and optimization methods based on computer aided simulation of an SMB process will assist at this stage. 

The estimation of operating and capital costs is an important facet of process design and optimization. In the absence of firm bids or valid historical records, you can locate charts, tables, and equations that provide cost estimates from a wide variety of sources based on given values of the design variables. 

It is possible to directly measure the instantaneous heat output of a nonexplosively reacting system due to chemical or physical processes as a function of the process time. This quantity shows directly whether and how quickly chemical conversions occur in the process phase under consideration. Such an approach can be useful, not only from a safety perspective but also for process design and optimization. 

In most adsorption processes the adsorbent is contacted with fluid in a packed bed. An understanding of the dynamic behavior of such systems is therefore needed for rational process design and optimization. What is required is a mathematical model which allows the effluent concentration to be predicted for any defined change in the feed concentration or flow rate to the bed. The flow pattern can generally be represented adequately by the axial dispersed plug-flow model, according to which a mass balance for an element of the column yields, for the basic differential equation governing llie dynamic behavior,... 

A model based on a modified mixing rule for the Peng-Robinson equation of state was able to reproduce quantitatively all features of the observed phase equilibrium behavior, with model parameters determined from binary data only. The use of such models may substantially facilitate the task of process design and optimization for separations that utilize supercritical fluids. 

However, there is a remarkable disproportion between the three main areas occupied today by RC, namely hazards, process design/optimization and for monitoring the physico-chemical transformations. If there is an extensive activity in the field of hazards, often with little contribution to increased safety, probably less than 20% of the process development laboratories use calorimeters for process design and optimization very little interest is shown for the use of heat released as a tracer for physico-chemical transformations since RC is still barely used in synthesis laboratories where reactions and process procedures are initiated. 

The use of such a model may substantially facilitate the task of process design and optimization for separations that utilize supercritical fluids. 

Rhyder R F, Manufacturing Process Design and Optimization. Marcel Dekker, Inc., New York, 1997. 

To reduce the lost work in industrial process plants, the minimization of entropy production rates in process equipment is suggested as a strategy for future process design and optimization [81]. The method is based on the hypothesis that the state of operation that has a minimum total entropy production is characterized by equipartition of the local entropy production. In this context we need to quantify the entropy sources of the various irreversible unit operations that occur in the industrial system. 

However, even though the application of the entropy equation in chemical reaction engineering is limited today, the understanding and physical interpretations of terms in the equation may be important in future process design and optimization . 

According to the theoretical model for transport kinetics (see above) most preliminary parameters, needed for the BOHLM process design and optimization, may be obtained by a number of known or experimentally obtained data. Individual mass-transfer coefficients of solute species in the feed, carrier, and strip interfacial boundary layers are determined experimentally by feed, carrier, and strip flow rate variations ... 

According to the theoretical model for transport kinetics (see Section 2.2), most preliminary parameters needed for BAHLM process design and optimization may be obtained by a number of known or experimentally obtained data. 

For a particulate application involving SLS, how to choose the best equipment, to use batch or continuous operation, which filter medium to select, and what is the optimum operating conditions are concerns of engineers. Although theories are available for some SLS operations, solutions for equipment selection, process design, and optimization are still very much dependent on test and experience, and are frequently qualitative or semi-qualitative. In this section, strategy and decision networks for selection of SLS equipment, introduction of filter media, centrifugal pumps for filtration operation, and selection of filter aids by cycle analysis will be discussed. 

---