MATHEMATICAL MODELING AND NUMERICAL STUDY OF BIOMASS FIXED CARBON GASIFICATION IN A DENSE BED AT ATMOSPHERIC PRESSURE. PART 2. ANALYSIS OF NUMERICAL RESULTS

Abstract

Using the constructed two-dimensional model of aerodynamics, heat-mass transfer and chemical reaction of coke-ash residue in a steam-air mixture at a pressure of 1 atm, taking into account interphase convective heat transfer, radiative-conductive heat transfer of the solid phase, radiative and conductive heat transfer of the bed with the reactor wall, gravitational forces and aerodynamic resistance, the unsteady process of lignin gasification in a fixed bed was theoretically investigated. It is shown that: 1) the maximum value of biomass temperature of 887 °С is reached in the oxidation zone, where exothermic reactions prevail over endothermic reactions; 2) the specified temperature turns out to be lower than the temperature of the beginning of ash deformation of 1050 °С, which indicates the slag-free operation of the gas generator; 3) the largest yield of gasification products occurs in the redox reaction zone, where heat absorption dominates over heat release; 4) a slag pad is formed near the grate, protecting the grate from overheating; 5) the largest changes in discrete phase movement speeds are observed in the oxidizing and reducing zones of the gas generator from –5.791.10−5 m/s до  –1.86.10−5 m/s due to the change in particle diameter from 10 mm to 6.83 mm (ash). Bibl. 12, Fig. 6.