Nonreactive Processes

Hanson, D. R., and A. R. Ravishankara, Investigation of the Reactive and Nonreactive Processes Involving CIONOj and HCI on Water and Nitric Acid Doped Ice, J. Phys. Chem., 96, 2682-2691 (1992b). 

Using the transformed variables the reactive problem (Eq. (5)) is completely equivalent to a nonreactive problem (Eq. (4)) of reduced dimension. Hence, in the limit of chemical equilibrium the dynamic behavior of reaction separation processes is equivalent to the dynamic behavior of nonreactive processes. 

The illustration in Fig. 5.14 is for a simple nonreactive process. However, according to the theory developed above we can expect similar results for SMB processes with fast chemical reactions. 

Handon DR, Ravishankara AR (1992) Investigation of the reactive and nonreactive processes involving nitryl hypochlorite and hydrogen chloride on water and nitric acid doped ice. J Phys Chem 96 2682-2691... 

Fig. 5. A pictorial representation of the limiting cases for the interaction of a gaseous atom with a surface. Both thermal and nonthermal, reactive and nonreactive processes are shown. A process that occurs in thermal equilibrium with the surface is referred to as thermal.

Material balance equations for this nonreactive process all have the simple form input = output. Three possible balances can be written—on total mass, benzene, and toluene—any two of which provide the equations needed to determine m and x. For example. 

The answers to these questions are not at all obvious when chemical reactions are involved in the process, and we will temporarily postpone consideration of this subject. The following rules apply to nonreactive processes. 

Material balances. For a nonreactive process, no more than independent material balances may be written, where ms is the number of molecular species (e.g., CH4, O2) involved in the process. For example, if benzene and toluene are the species in the streams entering and leaving a distillation column, you could write balances on benzene, toluene, total mass, atomic carbon, atomic hydrogen, and so on, but at most two of those balances would be independent. If additional balances are written, they will not be independent of the first ones and so will provide no new information. 

The calculations are straightforward. Note that all balances on this steady-state nonreactive process have the form input — output, and also note that the balances are written in an order that does not require solution of simultaneous equations (each equation involves only one unknown variable). 

When we first described degree-of-freedom analysis in Section 4.3d, we said that the maximum number of material balances you can write for a nonreactive process equals the number of independent species involved in the process. It is time to take a closer look at what that means and to see how to extend the analysis to reactive processes. 

To perform a degree-of-freedom analysis on a single-unit nonreactive process, count unknown variables on the flowchart, then subtract independent relations among them. The difference, which equals the number of degrees of freedom for the process, must equal zero for a unique solution of the problem to be determinable. Relations include material balances (as many as there are independent species in the feed and product streams), process specifications, density relations between labeled masses and volumes, and physical constraints (e.g., the sum of the component mass or mole fractions of a stream must add up to 1.)... 

You may analyze reactive processes using (a) molecular species balances (the only method used for nonreactive processes), (b) atomic species balances, or (c) extents of reaction. Molecular species balances on reactive processes are often cumbersome they must include generation and consumption terms for each species, and one degree of freedom must be added for each independent reaction. Atomic species balances have the simple form input = output and are usually more straightforward than either of the other two methods. Extents of reaction are particularly convenient for reaction equilibrium calculations. 

Given a description of any nonreactive process for which tabulated specific internal energies or specific enthalpies are available at all input and output states for all process species, (a) draw and completely label a flowchart, including Q and W (or Q and for an open system) if their values are either specified or called for in a problem statement (b) perform a degree-of-freedom analysis and (c) write the necessary equations (including the appropriately simplified energy balance) to determine all requested variables. 

Given any nonreactive process for which the required heal transfer Q or heat transfer rate Q is to be calculated, (a) draw and label the flowchart, including Q oi Q m the labeling (b) carry out a degree-of-freedom analysis (c) write the material and energy balances and other equations you would use to solve for all requested quantities (d) perform the calculations and (e) list the assumptions and approximations built into your calculations. 

Given an adiabatic process or any other nonreactive process for which the value of Q (closed system) or Q (open system) is specified, write material and energy balance equations and solve them simultaneously for requested quantities. 

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