The current state of the problem of manufacture and using synthesis gas based on the carbon gasification reaction. Part 2. Mathematical models of the physical fields of the carbon-containing materials gasification

Abstract

The first part of the article showed the practical feasibility and feasibility of partial or full replacement in the energy and energy-intensive industries of natural gas for synthesis gas resulting from the gasification of solid fuels. At the same time, one of the most appropriate ways to determine the structural, technological and environmentally friendly parameters of the gasification process, especially on an industrial scale, is the mathematical modeling of this process and related equipment. This allows you to abandon the costly field experiments and save significant material, energy and human resources.An analysis of mathematical modeling of the processes of generation and practical use of synthesis gas from solid and liquid fuels showed that for the numerical analysis of gasification processes, for the most part, two models are used: continuum-discrete (Euler-Lagrange) and continuum-continuum (Euler-granular Multіphase). In the continuous-discrete model, the Computer Fluid Dynamics (CFD) approach is used to describe the behavior of the gas mixture of reaction components, and for solid particles, the Discrete Phase Models (DPM) or Discrete Element Methods (DEM) are used. In the continuum-continuum model, the CFD approach is used to describe the behavior of both the gas and pseudo-solid phases. Moreover, for the solid phase, on the basis of the kinetic theory of granular flow, additional equations are written. Turbulent gasification modes are described by the Navier-Stokes equations averaged over Reynolds and Favre using standard or realizable models.It is also shown that in the study of gasification processes, an important problem is chemical kinetics and mechanisms that are responsible for combustion processes and can contain a large number of reaction components and elementary reactions. To solve the corresponding problem of chemical kinetics, two main approaches are used: the first is based on detailed multi-stage chemical reactions, and the second is based on the use of simplified global reactions with a significantly smaller number of both components and reactions.In the published works, specialized equipment for the gasification of solid carbon-containing materials is considered and no attention is given to the modernization of existing industrial equipment in order to produce synthetic gas. At the same time, the kinetics of chemical gasification reactions in different studies differs significantly. First of all, this concerns the order of chemical reactions, activation energy, as well as the values and dimensions of the preexponential factors of the kinetic equation Arrhenіus. It is also shown that in a number of existing mathematical formulations of problems there are certain inaccuracies and even gross errors. All this makes the direct use of existing models very problematic.