A Technical Review Paper On The Scale-Up Of Batch Reactor
Scale-up and dimensionless analysis are required mathematical tools for designer in industrial processes, where chemical or biochemical conversion of feeds, together with various transport processes like momentum, mass, or heat, take place. These processes are depending on scale different of behavior on laboratory, model, or full-scale plants. For example, these processes are homogeneous and heterogeneous reactions, so, the optimizing chemical processes often involves a deep knowledge of their physical and technical elements. The effects of each parameter affect the process need to examine for which sometimes mathematical solutions do not exist. In the case previous, the designer must depend on both model experiments and the theory of similarity between the model and the full-scale plant. This theory improves the planning and execution of experiments and the analysis of the data to produce adequate and valid information on the size and process parameters of the full-scale plant. If the chemical reactions occur slowly and do not exhibit a significant heat of reaction in the homogeneous system (micro kinetics) it follows the rule of chemical kinetic and chemical thermodynamic.
Thermodynamics is the importance role in the scale-up of reactors. It shows the form of rate equations must take in the limiting case where a reaction has achieve equilibrium. Consistency is needed thermodynamically before a rate equation achieves success over the entire range of conversion and chemical reactions do not depend on the theory of similarity rules. However, most industrial reactions occur under heterogeneous systems such as in liquid/solid, gas/solid, liquid/gas, and liquid/liquid, thereby generating high heat of reaction. Therefore, chemical reactions are scale-dependent on mass and heat transfer processes. From pilot plant scale and the full-scale plant can be identical the path of such chemical reactions if the both transfer processes are similar and the chemistry is identical. Pilot plant experiments represent an importance step in the investigation of a process toward formulating specifications for a commercial plant. Usually, a pilot plant uses the micro kinetic data derived by laboratory tests and provides information about the macro kinetics of a process such as the interaction of large conglomerates of molecules, macroscopic fluid elements, the effects of the macroscopic streams of materials and energy on the process, as well as the true residence time in the full-scale plant.
In scaling-up of batch reactor plant to a full-scale commercial plant, every full-size reactor in the plant will have a working volume, which is some multiple of the capacity of a pilot plant reactor and the production of the full-scale plant is usually predicted from cycle times experienced in the small-scale plant. Generally, it is not difficult to maintain the same cycle time when charging the feeds to the reactor but the problems can arise during temperature control, such as the times required to complete temperature adjustment steps in the larger unit. From comparing both model and full-scale plants with the same jacket configurations having the same operating conditions, the same steps take longer at the larger scale because heat transfer area does not scale-up at the same rate as the volume.
The introduced of the concept of the aspect ratio of a reactor (defined as the tangent -to- tangent length of the reactor divided by the reactor diameter) shown that when the aspect ratio (R) is the same for model and prototype reactors, then the increase in the heat transfer area is only a depending of the increase in the volumetric capacity. From the method developed by Steve, and determines the aspect ratio required to make the heat transfer area increase proportionally to the volume.
Nowadays the competitive in development scale up project are increasing regarding to methods, good knowledge in chemistry and the required for multidisciplinary worked. The most critical issues happen are about product quality and yield. It critical issue may causes from several common issue that happen in scale-up such as: reactions slower than expected; selectivity poorer than expected; difficulties with solids handling; fouling or blockages; unexpected corrosion problems. Although, the wrong chemistry design in scale up may forming some of by-product.
