$11\mathrm{.}12$ Explore the principles and applications of reactor design in chemical engineering. Discuss the fundamental concepts underlying reactor design, including reaction kinetics, thermodynamics, and transport phenomena. Explain the significance of reactor selection based on the desired reaction mechanisms, such as homogeneous, heterogeneous, and enzymatic reactions, considering factors like selectivity, conversion efficiency, and catalyst stability. Investigate the influence of reactor geometry, configuration, and operating conditions on reactor performance and product quality. Analyze the role of reactor types, such as batch, continuous stirred$-$tank$,$ plug flow, and fluidized bed reactors, in various chemical processes, highlighting their advantages and limitations$.$ Additionally, discuss the importance of safety considerations, environmental impact, and scale$-$up strategies in reactor design and operation for sustainable chemical engineering practices."