Author: admin
-
Batch and Continuous Reactors
Some chemical reactions are conducted in a batchwise mode [6]: raw material is charged initially into the reactor and the reaction allowed to proceed until such a time that the desired quantity of product is obtained. This is an unsteady state process wherein the conditions within the reactor with respect to the number of moles…
-
Intrinsic Kinetics and Reaction Rate Parameters
The reaction rate for any species i is generally defined as the rate of change of quantity of i (commonly moles of i) per unit time per unit volume of the reactor. Typically, the reaction rate is a function of the concentration of the reacting species and temperature [2]. The mechanism of the reaction, or the exact pathway by which…
-
Fundamental Concepts of Chemical Engineering Kinetics
The essence of reactor design is obtaining economically optimum specifications for a reactor for a specified duty. For example, let us assume that the market demand for a certain chemical product (let us denote it by R) is 3000 tons per year. The specified duty then might be defined as a production rate of 10…
-
Summary
Thermodynamics offers a theoretical framework for the quantification of energy-work interconversions and system equilibrium. The fundamental thermodynamic quantities are introduced in this chapter and the significances of these quantities explained. The importance of accuracy in the volumetric behavior of substances is described and illustrated using the van der Waals equation belonging to the family of EOSs…
-
Basic Computational Problems
Figure 8.7 shows a process on the P-V diagram with an arbitrary process path, wherein a system undergoes a change from its initial state to a final state along the path shown by the solid line. Figure 8.7 An arbitrary thermodynamic process. As stated earlier in the chapter, the types of computational problems, at the elementary level,…
-
Nonideality
As mentioned in the previous section, the volumetric behavior of a real substance rarely conforms to the ideal gas law. This nonideal behavior requires developing an accurate EOS for determining thermodynamic property changes in processes. Most of the process streams in practice typically consist of mixtures. Even pure product streams typically contain (tolerable) levels of…
-
Volumetric Behavior of Substances
The thermodynamic quantities internal energy, entropy, enthalpy, Helmholtz energy, Gibbs energy, and chemical potential provide the framework for the solution of both types of problems previously described. Although the absolute values of the thermodynamic quantities cannot be determined, changes in these properties can be computed accurately. However, these computations require the knowledge of the volumetric behavior of the…
-
Chemical Potential and Equilibrium
All naturally occurring processes proceed spontaneously until the state of equilibrium is reached where no further net change occurs in the system. The implication of the equilibrium conditions is that the system is not interacting with the surroundings [4]. Understanding this implication is crucial to distinguish between a system at equilibrium and an open system at steady state.…
-
Property Changes in Transformations
A system’s properties change when it moves from one state to another. This transformation or process of changing state is inevitably accompanied by heat and work exchange as governed by the first law. When the work and heat effects associated with the process are such that it is feasible to restore the system to its original…
-
Enthalpy and Free Energies
As interconversion between heat and work is the central concern of thermodynamics, it is useful to define thermodynamic properties that are related to the heat content of a system and energy available for conversion to work. This consideration leads to three thermodynamic functions or properties that are mathematically defined as follows: 4. The terms Helmholtz function (or Helmholtz…