Experiment And Simulating Study On Mineral Matter And Heavy Metals Vaporization Under Oxy-coal Combustion

Most of fuel consumed in power stations in China, now and in the future, is coal. Coal combustion supplies a large amount of thermal energy, at the same time it will bring about tons of problems. It is imperative to remove trace elements from coal combustion. And deposition in boiler caused by the minerals is a great problem. Oxy-coal combustion is a kind of new technology which can joint control the pollution. It uses O2 and recycled flue gas(mainly CO2)as medium to replace air in combustion process. It's lack of the research on mineral transformation and trace elements emission.Experiments were taken out in a Drop-tube furnace under the temperatures of 1200℃and 1400℃to study the dynamic oxy-coal combustion. The ash was collected under all conditions to analyzed by XRD as well as XRF to study the mineral transformation. The experimental results indicate that the concentration of non-crystal phase is lower under the oxy-coal combustion with equal oxy-concentration of air combustion compared to it. Non-crystal phase concentration increased with the increase of oxy-concentration, the fusion phase in the boiler may decrease under oxy-coal combustion, which can ease the deposition; the PM can be decreased under the equal oxy-concentration combustion, the vaporization of the mineral and the reaction extent is decreased, but higher oxy-concentration make the trend higher.The technology of micro-wave digesting is used to digest the ash produced by the experiments above, and the ICP-AES method is applied to measured the trace elements concentration precisely. The results indicate oxy-coal combustion we used can restrain the emission of trace elements, and the restrainablility is related to the positive elements and its volatity. The injection of CaO makes the vaporization of As,Se decreased, while it has little influence on Cr; the injection of Fe2O3 makes the vaporization of As,Se lightly lower. And the clean of Cr is showed throughed the results, Thermogravimetric methods is used to investigate the resolved of CaSeO4 after SeO2 is blended with CaO, the calculation shows the active energy is higher under the oxy-combustion than air,which means it is more difficult to resolve under the oxy-coal combustion.Finally the thermal-equilibrium method is used to calculate the vaporization of typical minerals and trace elements, and prediction is made by the calculation.