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The principle of conservation of mass is employed by chemical engineers to perform the material balance computations on process units and plants. These computations involve the overall material balance and the balances for components present in the system. Molecular species (compounds) are conserved and hence serve as components in nonreacting systems, whereas for reacting systems,…

The incompleteness of the desired reaction and the occurrence of undesired side reaction introduced additional levels of complexity in the simple combustion process previously described. By now, readers should have developed a sense of the enormity of computational tasks for a chemical process plant, considering that a chemical process typically has a large number of…

Reacting systems are characterized by the disappearance of reactants and appearance of the products. Clearly, molecular species are not conserved in the reaction, and at steady state, the rate of input of a compound participating in the reaction is not equal to the rate of its output. However, as long as no nuclear reactions are occurring…

Material balances in nonreacting systems are illustrated through a simple example involving dilution of a concentrated solution, an operation frequently encountered in a chemical process plant. EXAMPLE 6.2.1 DILUTION OF A CONCENTRATED AQUEOUS SOLUTION The production process for sodium hydroxide (NaOH) yields a 28% (by mass) solution of sodium hydroxide in a membrane cell. A…

Chemical engineers require additional information (apart from the overall material balance) about material flows of components in the process and conduct component material balances over the process units. Let us assume that the process shown in Figure 6.1 is that of simple mixing of a concentrated aqueous solution of salt A (stream 1) with pure water (H2O; stream 2), yielding a…

Consider an arbitrary process represented by the block flow diagram shown in Figure 6.1. The process unit has two influent flows (streams 1 and 2) feeding into a tank and one effluent flow (stream 3) leaving the tank. Figure 6.1 A simple process unit. Physically, the material being fed to the process must either accumulate in it…

A chemical process typically consists of several units that may involve chemical reactions and/or simple physical separation and mixing operations, as described in previous chapters. The process streams may be constituted of a single phase (gas/liquid/solid) or may be multiphase in nature. A unit may or may not be operating at steady state. Regardless of the…