Continuous flow reactors optimal design

In this chapter, we first consider uses of batch reactors, and their advantages and disadvantages compared with continuous-flow reactors. After considering what the essential features of process design are, we then develop design or performance equations for both isothermal and nonisothermal operation. The latter requires the energy balance, in addition to the material balance. We continue with an example of optimal performance of a batch reactor, and conclude with a discussion of semibatch and semi-continuous operation. We restrict attention to simple systems, deferring treatment of complex systems to Chapter 18. 

Fan, L. T., Erickson, L. E., Sucher, R. W., and Mathad, G. S. (1965). Optimal design of a sequence of continuous-flow stiired-tank reactors with product recycle. Ind Eng Chem., 4, 432—440. 

This chapter treats the effects of temperature on the three types of ideal reactors batch, piston flow, and continuous-flow stirred tank. Three major questions in reactor design are addressed. What is the optimal temperature for a reaction How can this temperature be achieved or at least approximated in practice How can results from the laboratory or pilot plant be scaled up ... 

Many industrial processes which employ bubble column reactors (BCRs) operate on a continuous liquid flow basis. As a result these BCR s are a substantially more complicated than stationary flow systems. The design and operation of these systems is largely proprietary and there is, indeed a strong reliance upon scale up strategies [1]. With the implementation of Computational Fluid Dynamics (CFD), the associated complex flow phenomena may be anal)rzed to obtain a more comprehensive basis for reactor analysis and optimization. This study has examined the hydrodynamic characteristics of an annular 2-phase (liquid-gas) bubble column reactor operating co-and coimter-current (with respect to the gas flow) continuous modes. 

To conclude, the theoretical works combining chemical kinetics and dispersion phenomena in FIA reactors outline the limits of the continuous-flow concept and emphasize the importance of radial mass transfer rate [a, Eqs. (3.55) and (3.56)] on optimization of the reactor design. The... 

Continuous plug flow reactors are also unsuitable for these purposes because it is usually impossible to obtain an isothermic mode in such reactors, even for reactions with a relatively low rate of reaction. Plug flow reactors usually operate in adiabatic or intermediate modes, which are far from isothermic even with an external heat removal modification. In can be stated that almost all industrial reactors employed for fast processes are not optimally designed and are therefore ineffective. The quality of products is also far from optimal and the processes are generally not perfect from an engineering, economical, or social point of view (decrease of final product yield and quality, increase of nonrecyclable wastes, excessively high consumption of raw materials and low energy efficiency). 

Trambouze, P. J., and Piret. E. L. "Continuous Stirred Tank Reactors Designs for Maximum Conversions of Raw Material to Desired Product, AIChE J. 5, 384 (1959). van de Vusse, J. G. "Plug Flow Type Reactor vs. Tank Reactor, Chem. Eng. Sci. 19, 994 (1964). Viswanathan. J. V., and Grossmann, I. E. "A Combined Penalty Function and Outer-Approximation Method for MINLP Optimization, Compul. Chem. Eng. 14, 769-782 (1990). 

---