| Coal is the main primary energy in China and this coal-based energy structure willnot change in a long term. So the development of low energy-consumption, lowemission and less pollution coal power generation technology is of greatsignificance. In order to save energy and reduce environmental pollution, manycountries all over the world have studied and applied supercritical technologies,which generally reduce the emission of nitrogen oxides by the means of airclassification and separated combustion of dense-dilute pulverized coal. However,the supercritical technologies will result in the low oxygen content in the boilerfurnace and form a reducing atmosphere, which will lead to the high-temperaturecorrosion of boiler water wall, and then cause economic losses and muchinconvenience to the normal and safe operation of boiler.In China, the major high-temperature corrosion in boilers is basically caused bythe reducing atmosphere. The study of formation characteristics of H2S in furnaceis beneficial to reduce the concentration and quantity of H2S and prevent thehigh-temperature corrosion.Numerical simulation was conducted on a supercritical boiler with wallarrangement burners. The combustion characteristics and the formationcharacteristics of H2S in near-wall regions inside the main combustion zone werestudied and analyzed by altering the combustion type and the S content in coal.Fluent6.3.26was used in the numerical simulation. The realizable k–ε model,Lagrangian stochastic tracking model, P-1model and Probability Density Function（PDF） method were employed to simulate the gas turbulence, gas-solid two-phase,radiation and volatile combustion respectively.The temperature field and concentration distribution of CO, SO2and H2S weredetermined through the numerical simulation of the combustion characteristics innear-wall regions inside the main combustion zone.The simulation results show that the reducing atmosphere and H2S are easilyformed in the low oxygen concentration and high CO concentration area in bothvertical and horizontal bias combustion. Besides, with the increasing of the Selement content, the concentration and generated areas of H2S are both enhanced,which demonstrated the S content has a certain impact on the generationcharacteristics of H2S.Comparing the vertical and horizontal bias combustion under the premise ofburning the same cola type, it was found that the horizontal combustion type could increase the concentration of oxygen in the near-wall regions, lighten the reducingatmosphere near the water wall, and effectively decrease the generation of reducinggas CO, the concentration and generation areas of H2S, which could then lessen thepossibility of high-temperature corrosion. |
