MATHEMATICAL DESCRIPTION OF THE SOLID FUEL GASIFICATION PROCESS IN A FIXED BED: 1. NUMERICAL RESULTS OF THERMAL-CHEMICAL PROCESSING OF PEAT IN A VAPOR- OXYGEN MIXTURE UNDER A PRESSURE OF 3 MPa
With the help of the developed two-dimensional model presented in the first part of this work, which includes interfacial convective heat transfer, radiation-conductive heat transfer of the solid phase, radiant and conductive heat transfer of the fixed bed with the reactor wall, heterogeneous and homogeneous chemical reactions, gravity and aerodynamic resistance, the non-stationary gasification of Shubarkol long-flame coal in a steam-oxygen mixture under a pressure of 3 MPa in a fixed bed with solid slag removal at a ratio of mass fractions of gas components H2О/O2=72/28 was numerically investigated. It is shown: 1) in this mode, the temperature of coke-ash particles does not exceed 1000 0С due to the prevalence of heat generation of exothermic reactions C+O2=CO2, C+0,5O2=CO, CO+0,5O2=CO2 and H2+0,5O2=H2O over the heat absorption of endothermic reactions C+СO2=2CO and C+H2O=CO+H2 due to the high concentration of water vapor in the gas mixture. Therefore, calorie and quality of the generator gas (at the time τ = 260 s (by volume): CO=16,4%, H2=44,6%, СO2=27,6%, CH4=10,1% and C6H6=1,16%) is significantly inferior to the synthetic gas obtained with the ratio of mass fractions of gaseous components H2О/O2=40/60 (τ = 280 с: CO=65%, H2=25,6%, СO2=3,8%, CH4=5% and C6H6=0,57%) ; 2) To eliminate overheating of the grate due to the low height of the slag pad, due to low ash content of coal 3–9%, it is recommended to add waste ash to the initial fuel, which will increase the height of the protective inert bed. 3) the calculated composition of the synthetic gas at τ = 260 s is in good agreement with the literature data given in : CO=12–21%, H2=37–41%, СO2=27–34% and CH4=10–13,5%. Ref. 1, tab. 1, fig. 10.
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