Study Of The Characteristics Of Ash Obtained Duiring Biomass And Coal Co-Firing

With the shortage and environmental pollution of coal, it is widely concerned about utilization of clean and renewable biomass energy, but the biomass has low calorific and the content of alkali metal is high. It is effective to reduce the content of alkali by co-firing biomass and coal. However, it is inevitable to produce slagging and fouling in the combustion, then impede heat transfer and cause corrosion of equipment, which greatly threatens the safety of the boiler, economic running and reliable of equipment. So the paper studied the characteristics of ash obtained during biomass and coal co-firing in detail.First of all, obtain ash samples in muffle, and then compare the differences between the tested value and calculated value based on pure materials. The results showed the content of ash was mainly affected by mixed ratio and decreased with the increase of biomass in the mixtures. By the comparison between the tested value and calculated value, it showed that tested value was only higher at 900℃and 1000℃.Followed by analyzed the ash component and discussion about the tendency of fouling and slagging by six indexes, the results showed that it was non-linear between the ash component and the content of stalks in the mixtures, while the temperature and residence time have no significant effects. The results also showed that Fe2O3/CaO and S/A were not suitable for judging the slagging and fouling tendency of co-firing biomass and coal. The results indicated that it was possible to burn up to 70% straw stalks and up to 50 % corn stalks in mixtures with coal without encountering notability increased fouling and slagging.Next analyze the ash-fusion temperature, structures and morphologies by ash melting point, XRD and SEM. The results indicated that the melting temperatures of stalks were much higher than that of coal, soft temperature non-linely decreased with the increase of stalks content in the mixtures, the soft temperature of mixtures was higher in the Oxidation atmosphere than that in the weak restore atmosphere. The melting point and the content of alkali metals changed non-linely with the addition content of alkali metals and inorganic sulphur. Finally, establish regression model of ash content and soft temperature of co-firing biomass and coal, then analyzed residuals and optimized the model. At the same time, forecasted the soft temperature of other samples with the obtained model, the difference was little between the determination value and forecast value.