Scaleup and scaledown

Chapter 2 developed a methodology for treating multiple and complex reactions in batch reactors. The methodology is now applied to piston flow reactors. Chapter 3 also generalizes the design equations for piston flow beyond the simple case of constant density and constant velocity. The key assumption of piston flow remains intact there must be complete mixing in the direction perpendicular to flow and no mixing in the direction of flow. The fluid density and reactor cross section are allowed to vary. The pressure drop in the reactor is calculated. Transpiration is briefly considered. Scaleup and scaledown techniques for tubular reactors are developed in some detail. 

J.R. Inga, Scaleup and Scaledown of Slurry Reactors A New Methodology. Ph.D. Thesis, University of Pittsburgh, 1997. 

Inga JR. Scaleup and scaledown of slurry reactors a new methodology [Ph.D. thesis]. Pittsburgh (PA) University of Pittsburgh 1997. 

Fig. 2.1 Electrochemical engineering its scale and endeavours. Note that the development of industrial electrochemistry involves both scaleup and scaledown proceduifes.

The major part of the book deals with nonideal reaetors. Chapter 4 on pore diffusion plus reaetion ineludes a new method for analyzing laboratory data and has a more eomplete treatment of the effeets of eomplex kineties, particle shape, and pore structure than most other texts. Catalyst design to minimize pore diffusion effects is emphasized. In Chapter 5 heat transfer correlations for tanks, particles, and packed beds, are reviewed, and the conditions required for reactor stability are discussed. Examples of unstable systems are included. The effects of imperfect mixing in stirred tanks and partial mixing in pipeline reactors are discussed in Chapter 6 with examples from the literature. Recommendations for scaleup or scaledown are presented. 

The reader should note that to scaleup (or scaledown) a process, it is necessary to establish geometric and dynamic similarities between the model and the prototype. These two similarities are discussed below. 

Reaction kinetics, catalyst handling, mass and heat transfer, corrosion and many other practical industrial chemistry and engineering considerations impact the success of scaleup from lab to commercial for batch processing. Since the starting point for scaleup studies is the ultimate intended commercial unit, the professional should scaledown from the design parameters and constraints of the proposed commercial unit. 

Chapters 7 and 8 present models and data for mass transfer and reaction in gas-liquid and gas-liquid-solid systems. Many diagrams are used to illustrate the concentration profiles for gas absorption plus reaction and to explain the controlling steps for different cases. Published correlations for mass transfer in bubble columns and stirred tanks are reviewed, with recommendations for design or interpretation of laboratory results. The data for slurry reactors and trickle-bed reactors are also reviewed and shown to fit relatively simple models. However, scaleup can be a problem because of changes in gas velocity and uncertainty in the mass transfer coefficients. The advantages of a scaledown approach are discussed. 

---