Author: workhouse123
-
Ideal Gases
You have no doubt been exposed to the concept of the ideal gas in chemistry and physics. Why go over ideal gases again? At least two reasons exist. First, the experimental and theoretical properties of ideal gases are far simpler than the corresponding properties of liquids and solids. Second, use of the ideal gas concept…
-
Basic Computational Problems
Determination of intrinsic kinetics forms an essential and important component of chemical engineering kinetics. Typically, such determinations are carried out by bench-scale batch experiments wherein the concentrations of species are monitored as a function of time and the concentration-time data are subjected to analysis. Example 9.2.1 illustrates such analysis conducted for the determination of rate expression. Example…
-
Other Considerations
The reactor analysis and design acquires another level of complexity when the reactor is operated under nonisothermal conditions; that is, the temperature of the reactor varies with time or position in the reactor, mostly due to the substantial heat effects associated with most reactions. As the temperature varies, the rate constant also changes according to…
-
Conversion
The discussion in section 9.1.3 assumes that the rate expression is dependent only on the concentration of one reactant, reactant A. However, in general, the rate depends on the concentrations of several other species as well. The component balance in equation 9.1 (and its simplifications discussed earlier) can be written for each species involved in the reaction, yielding as…
-
Reactor Design
A typical reactor design problem for batch reactors involves determination of the batch time needed for producing the specified quantity of the product. This batch time is obtained by separating the variables and integrating equation 9.4 as follows: Here, Ni0 are the initial moles of i. Many of the batch reactors operate under constant volume conditions; that is, the volume…
-
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…
-
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,…
-
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…