Material balance with reaction

Simple combinations of reactor elements can be solved direc tly. Figure 23-8, for instance, shows two CSTRs in series and with recycle through a PFR. The material balances with an /i-order reaction / = /cC are... 

Filling and Emptying Periods Say the pumping rate is V, the full tank volume is and the rate of reaction is r = kCj. For t < Vri/V the material balances with Eq. (7-68) are as follows. 

Translate word problems and the associated diagrams into material balances with properly defined symbols for the unknown variables and consistent units for steady-state processes with and without chemical reaction. 

This algorithm is very convenient, particiilarly for catalytic reactions, since if written as eqn. (2) it accounts for the material balance with respect to the catalyst ... 

Table VIH. Material Balance in Reactions of (C6Hn)2Hg with Th,+Cl04 and...

The central issue in performing the material balance with recycles is the behaviour of the reaction system. Besides conversion, a design variable inherited from the previous level, the molar reactant ratio becomes now a design variable, which will affect the flow rate of the recycle streams. Note that the assumption of 100% overall recovery of unconverted reactants is maintained. 

In this chapter, we describe an algorithm for predicting feasible splits for continuous single-feed RD that is not limited by the number of reactions or components. The method described here uses minimal information to determine the feasibility of reactive columns phase equilibrium between the components in the mixture, a reaction rate model, and feed state specification. This is based on a bifurcation analysis of the fixed points for a co-current flash cascade model. Unstable nodes ( light species ) and stable nodes ( heavy species ) in the flash cascade model are candidate distillate and bottom products, respectively, from a RD column. Therefore, we focus our attention on those splits that are equivalent to the direct and indirect sharp splits in non-RD. One of the products in these sharp splits will be a pure component, an azeotrope, or a kinetic pinch point the other product will be in material balance with the first. 

A legitimate set of these three properties would be T, P, and the equilibrium mole fraction of ammonia 1/3. With these three, we can obtain values for the other equilibrium mole fractions by solving material balance and reaction-equilibrium expressions. This illustrates a typical use of the traditional phase rule (10.3.1) the (F-specification tells us the number of property values needed to identify the final equilibrium state after all reactions are complete. 

To solve reaction equilibrium problems, we must combine material balances with the criteria for reaction equilibria. Consequently, such problems bear a superficial resemblance to isothermal flash calculations, though in the case of reaction equilibria the material balances are applied to elements, not species. For H independent reactions involving C species in a single phase at fixed T and P, the criteria for equilibrium were given in 7.6.1,... 

MATERIAL BALANCE—CHEMICAL REACTIONS INVOLVED 2.3 2.7 USE OF ENERGY BALANCE WITH MATERIAL BALANCE 2.9... 

Temperature gradient normal to flow. In exothermic reactions, the heat generation rate is q=(-AHr)r. This must be removed to maintain steady-state. For endothermic reactions this much heat must be added. Here the equations deal with exothermic reactions as examples. A criterion can be derived for the temperature difference needed for heat transfer from the catalyst particles to the reacting, flowing fluid. For this, inside heat balance can be measured (Berty 1974) directly, with Pt resistance thermometers. Since this is expensive and complicated, here again the heat generation rate is calculated from the rate of reaction that is derived from the outside material balance, and multiplied by the heat of reaction. 

Consider the reversible first order reaction A R. It is possible to determine the minimum reactor volume at the optimum temperature Tgp( that is required to obtain a fractional conversion X, if the feed is pure A with a volumetric flowrate of u. A material balance for a CESTR is... 

The third term on the left side of the equation has significance in reactive systems only. It is used with a positive sign when material is produced as a net result of all chemical reactions a negative sign must precede this term if material is consumed by chemical reactions. The former situation corresponds to a source and the latter to a sink for the material under consideration. Since the total mass of reactants always equals the total mass of products in a chemical reaction, it is clear that the reaction (source/sink) term (R should appear explicitly in the equation for component material balances only. The overall material balance, which is equivalent to the algebraic sum of all of the component balance equations, will not contain any (R term. 

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