Simultaneous thermal and plasma chemical activation of conversions in H-2-I-2-HI mixtures

Chemical quasi-equilibria represent the product composition of stable compo nents at the outlet of a nonisothermal plasma chemical reactor under operat ing conditions of very high or vanishing electric power input. The properti es of these quasi-equilibria in relation to the thermodynamic equilibrium a re discussed first of all using an instructive kinetic model. The investiga tions show that for the formation of the quasi-equilibria the existence of two time scales for the chemical conversions in the system is necessary. Th e quasi-equilibrium states are formed on a short time scale by fast relaxat ion and deactivation processes of unstable components. After that the syste m passes into the thermodynamic equilibrium for very long times. The transi tion from a chemical quasi-equilibrium state into the thermodynamic equilib rium was detected in the H-2-I-2-HI system experimentally, too. The analysi s of a detailed microphysical model for this system shows that the transiti on into the thermodynamic equilibrium is caused by the increasing thermal p roduction of unstable components (e.g. iodine atoms) at higher gas temperat ures. Under these conditions the electronic production of atoms is only a s mall correction of the thermal degree of dissociation, and the thermodynami c equilibrium is the only stationary state for the system.