Research On Influence Of Inherent Mineral Transformation On Biomass Reburning De NO_x Process

As a renewable and low CO₂ emission fuel, biomass is also a potential reburning fuel because of its high volatile content. There are considerable mineral matters in biomass, whose transformation during biomass reburning process will affect NOX reduction. This thesis focuses on the transformation of the mineral matters during biomass reburning process and its effect on NO reduction by char and biogas, aiming to provide fundamental supports to the development of biomass reburning technology.Firstly, NO reduction by biomass char was studied in a fixed bed reactor. The inherent mineral transformation and the development of char reactivity were studied.The results showed that the main mineral that catalyzes char-NO reaction was K. K releases to gas phase or formed acid-insoluble salt during the deNOx process. As a result, the concentration of acid-soluble K decreased significantly. Char reactivity evolution depended on surface area and mineral content. Specific char reactivity increased linealy with acid-soluble K concentration at the research conditions. A model discribing K transformation during char-NO reaction was built, which showed a good coherence with the experimental results. The effect of mineral transformation on char reactivity was introduced to random pore model?RPM?, and a modified RPM was built,which successfully predicted the reactivity evolution of char.Secondly, the isothermal reaction of char with NO and temperature-programmed desorption of rice straw char were studied. The mechanism of K catalyzing char-NO reaction was analyzed. The results showed that K promoted the formation of C?O?during char-NO reation, but did not affect the chemical form of C?O?. No matter K existed or not, the formation of C?N? during char-NO reaction was negligible. The mechanism of K catalyzing char-NO reaction was proposed.Thirdly, the performance of multi-constituent biogas on NO reduction including K and Na salt was studied in a plug flow reactor. The results showed that the main content that reduces NO was CH₄. Though H₂ in biomass did not reduce NO effectively, it inhanced active species concentration, and as a result, promoted NO redution at low temperatue and low excess air coefficient. Adding K and Na salts to the reaction zone promoted NO reduction by biogas at low temperate or low excess air coefficient, whiledepressed NO reduction at high temperate or high excess air coefficient. This is due to the co-effect of K?Na and H₂ on the active species concentration in reaction zone.The effect of alkali metal salt depended on the chemical form of salts, such as the effect of KOH was better than KCl.