Gasification Processes: Modeling and Simulation by Petr A. Nikrityuk & Bernd Meyer

Author:Petr A. Nikrityuk & Bernd Meyer
Language: eng
Format: azw3
ISBN: 9783527673209
Publisher: Wiley
Published: 2014-06-17T16:00:00+00:00

Figure 6.4 (a) Dimensionless concentration as a function of the radial coordinate for and different temperatures and (b) molar flow of as a function of the temperature for (b).

6.3.1 Results and Discussion

Before the analysis of the results, we give a short description of the “physics” of the processes taking place on the particle surface as well as in the gas phase. Figure 6.5 provides a schematic illustration of the process of coal oxidation for the given conditions. Following the analytical modeling for a nonmovable spherical particle in a quiescent dry-gas environment, the combustion of a carbon particle involves the diffusion of through a stagnant film and its reaction at the particle surface to produce and according to the reactions (R1) and (R2), respectively. The produced at the surface diffuses outward and is consumed in the flame sheet, producing according to the reaction (R5). At the same time, the resulting reacts with the carbon surface and produces additional according to the reaction (R3). Since oxidation occurs very fast, both and are zero at the flame sheet. There is no leakage through the flame sheet into the gas phase. The existence of the gas-phase flame also cuts off most of the supply of oxygen to the surface such that reactions (R1) and (R2) are now suppressed. The temperature T and concentration profiles have their peaks at the flame sheet (see, e.g., [16]). Owing to the radiative heat loss, the surface temperature is only slightly higher than the ambient temperature .

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