Optimize reactor design

Due to the complexity of the problem, it is generally accepted that we will not reach the optimal reactor design and ojjerating variables, but still we would like to design and operate the reactor safely and near the optimum. Further in this section, we will give a general discussion of. scale-up methods for chemical processes, in particular with respect to chemical reactors suitable for the manufacture of fine chemicals. Next, we will discuss how to obtain reasonable quantitative relationships necessary for optimal and safe scale-up according to the art. The reader can find an extensive treatment of scale-up problems in the book of Bisio and Kabel(1985). 

Feinberg, M. and D. Hildebrandt. Optimal Reactor Design from a Geometric Viewpoint I. Universal Properties of the Attainable Region. Chem Eng Sci 52(10) 1637-1666 (1997). 

Feinberg M, Hildebrandt D. Optimal reactor design from a geometric viewpoint. I. Universal properties of the attainable region. Chem Eng Sci 1997 52 1637. 

Hildehrandt, D.. and Feinberg. M. "Optimal Reactor Design from a Geometric Viewpoint." Paper 142c. AIChE Annual Meeting. Miami Beach. FL (1992). 

Investigations with different geometric and operating parameters have aided to optimize reactor design and process operating conditions. The measurements obtained indicate sufficient specific solids circulation rates to achieve adequate heat tranfer to biomass incoming feed and close to the optimum required gas residence time in the riser of the corresponding fast pyrolyser even with a 1000 kg/h biomass feed (7). 

To optimize reactor design and minimize byproduct formation, the conversion of a particular reagent is often less than 100%. If more than one reactant is used, the reagent on which the conversion is based must be specified. 

The availability of good, reliable membranes will not, of course, eliminate the need for optimal reactor design and process analysis, necessary to determine the t) e of membrane to be used and the optimal operating conditions. As was discussed previously, some reactions do not need permselective membranes. Other process parameters like the reactor configuration or the amount of sweep gas utilized can affect dramatically the observed performance. 

There is still a dispute among experts as to the place in which the biphasic aqueous reaction actually takes place, although it is very probably not the bulk of the liquid but the interfacial layer between the aqueous and organic phases. In the case of aqueous biphasic hydroformylation, this question has been decided by methods of reaction modeling and comparison with experimentally proven facts, thus leading to scale-up rules and appropriate kinetic models as a basis for optimal reactor design [34]. 

By comparison between the calculated and measured pressure and heat flux vs. time curves it was shown that the site of this hydroformylation reaction could not be the bulk of the liquid. Only the assumption of a reaction in the liquid boundary layer at the gas-liquid interface gave satisfactory agreement of the data under all experimental conditions. Thus, on this basis scale-up rules for the aqueous bipha-sic hydroformylation and appropriate kinetic models can be developed for optimal reactor design. The principle of both models applied to the general equation (Eq. 10) is shown in Figure 5. 

The concept of a highly automated scale-up process is enticing. One vision of such a process for homogeneous (liquid phase, non-catalytic) reactions starts with little more than a list of reactants, solvents, and desired products. Given this information as well as constraints imposed by economic, environmental, safety, and practical factors, a highly automated system could include both software and hardware components to generate an optimal reactor design. The necessary software components would ... 

Clearly, the optimal reactor design minimizes the annualized cost, computed to account for the capital and operating costs, and not simply the design that maximizes the yield or selectivity. Nonetheless, the maximum attainable region identifies the entire space of feasible concentrations. The following example shows how the attainable region is used to select the most appropriate reactor network to maximize the yield of a desired product where a number of competing reactions occur. 

F. Gallucci, M. Van Sint Annaland and J. A. M. Kuipers, High performance hydrogen membranes deserve optimal reactor design, NPT, 2010,2, 14-15. 

Feinberg, M., 2000a. Optimal reactor design from a geometric viewpoint—III. Critical CFSTRs. Chem. Eng. Sci. 55, 3553-3565. 

Third, no less important aspect for technical reformers is the supply of heat to drive the endothermic reaction. In conventional systems, gas-fired burners are used to heat the outside surface of the reformer mbes. For large tubes used in world-scale reformer plants, the reaction is strongly heat transfer limited, which increases the fuel consumption by the burners. And also at smaller scale, the consequences of concentration and temperature gradients for system performance can be remarkable pointing out the need for optimal reactor design. 

In summary it seems that the ideal catalyst layer design in a microstructured devices is achieved by solving quantitatively the opposite trends between (i) porosity, which means effective diffusion and high specific activity, and (ii) denseness, which means high thermal conductivity and layer stability. The resulting maximum should lead to an optimal reactor design in terms of heat transfer and productivity determined by intrinsic kinetics. 

Chemical Engineering Science, Vol.54, No.7, pp. 2535-2543, ISSN 0009-2509 Feinberg, M, Hildebrand, D. (1997). Optimal reactor design from a geometric viewpoint -1. Universal properties of the attainable region. Chemical Engineering Science, Vol.52, No.lO, pp. 1637-1665, ISSN 0009-2509... 

Control and optimization of reaction yields through stoichiometry and thermodynamics, and reaction kinetics integrated with an optimized reactor design, will strengthen and enhance bioproduct production (Guillard and Tragardh 1999). 

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