ABSTRACT
The kinetic experiments are carried out in reactors in closed or open systems. There are three common cases:
Batch. Continuous. Semicontinuous.
For kinetic purposes, the variation of the concentration or the pressure with reaction time is accompanied in a batch reactor. In a continuous or open system, the pressure is constant and the concentrations or molar flows of the reactants and products are accompanied in the course of the reaction or along the reactor. The time is substituted by an equivalent variable called space time. The space time takes into account the inlet volumetric flow of the reactants and the volume of the reactor, and, thus, has unit of time, here designated by:
τ = V v0
(h)
The inverse is the space velocity. The molar balance in an open system and for any reaction of the type, initially at
constant temperature, is shown in Scheme 4.1, in which j is a component, reactant, or product:
Moles of reactant that were transformed into products: Rate of transformation or formation of product: rj (mols/h.vol)
Different from other systems, it only exists when a reaction takes place
Molar flow of formed products R, S or not consumed reactants that leaves VdV
dz
Fj + d Fj (mols/h )
Molar flow of reactants A and B that enters in V
Variation of moles of component in a system per time
Fj (mols/h)
A + B ⇔ R + S
Considering Fj the molar flow of the component j, Gj the rate of generation of products or consumption of reactants, and nj the number of moles of component j, we have the following molar balance:
Fj0 − Fj +Gj = dnjdt (4.1)
Note that the balance is carried out to any component, reactant, or product of the reaction, and has the unit of mol/time.
