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The paper addresses the applicability of equilibrium thermodynamics models and the expediency of their employment for analysis of non-equilibrium systems, first of all, when solving the applied computational problems of large dimensionality. A model of extreme intermediate states (MEIS) is suggested for such an analysis. The methods to include the constraints on chemical kinetics and transfer processes are discussed. These constraints are to be presented in a thermodynamic form, i.e. without time variable. The efficiency of the approach is illustrated with the examples of determining the maximum possible nitrogen oxide concentrations in combustion chambers of gas turbines and modeling the non-stationary flow distribution in multi-loop hydraulic networks.

In the present paper, significance of gas-phase chemical reactions occurring in thermal analysis furnace is evaluated. Free radical species form as a result of biomass thermal decomposition and may give rise to chain reactions. Gas portion emitted by the sample analyzed flows to detector (mass spectrometer in our study) in finite time interval, so chemical reactions may change its composition. Quantitative assessment of this change was made based on data about amount of active species that may initiate kinetic chains. Radical trap method was used to determine radical species amount. Toluene vapors was fed to carrier gas and flowed in thermal analysis furnace reacting with radical species produced from biomass thermal decomposition. Stable radical species-benzyl-is reaction product that can be detected by mass spectrometer. Results show that radical species concentration in gas produced from biomass gasification (639 ppm for pyrolysis stage and 3581 ppm for char gasification stage) is too small to change gas-phase composition significantly in time interval for which gas has been achieving detector. Comprehensive kinetic model for toluene oxidation in oxidizer lack conditions is developed based on widely known mechanisms. Radical species amount estimates may be useful as initial information in heterogeneous combustion modeling.

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