Optimization of Slurry PH Value for Limestone Wet Desulfurization Technology
Based on limestone wet desulfurization spray scrubber technology, this paper explicitly introduces the ionization process of water in slurry, deduces controlled range of slurry PH value and equation of slurry PH value in slurry droplet by analyzing the main origin of H+ and OH-, and other factors that influence ionization balance of water in slurry, provides theories for simulation of slurry PH value and optimization in practical operation. Besides, it concludes the reasonable range of slurry PH value by analyzing various factors such as increasing SO2 removal efficiency, decreasing operation cost, dissolution of CaCO3, oxidation of SO32- andHSO3-, and relationship of slurry PH values between slurry surface and the undersurface, provides reference for optimization of slurry PH value in practice. Finally, an optimization experiment of slurry PH value is designed for#11FGD in Taiyuan co-generation power plant, and the slurry PH value is optimized effectively.
Desulphurization of SO2–N2 mixtures by limestone slurries
Abstract We studied the absorption of SO 2 from mixtures with N 2 into limestone slurries. The reactor used was a stirred tank with an almost flat gas–liquid interface of area 67.7×10 −4 m 2 at 400 rpm , operated in gas-phase continuous operation mode and batchwise for the slurry. The operating temperatures used were 20°C and 40°C, the content of limestone in the initial slurry was 1, 3 and 5 wt % and the volume fraction of SO 2 in the gas mixture at the inlet to the reactor ranged from 4% to 10%. We determined the overall gas-side SO 2 transfer coefficient, obtaining values of 0.104 and 0.083 mol/s/m 2 / bar at 20°C and 40°C, respectively. By taking into account the individual gas-side SO 2 transfer coefficient and estimating the enhancement factor, we were able to determine the thickness of the interfacial liquid film, 45 and 58 μm at temperatures of 20°C and 40°C, respectively, and the SO 2 physical absorption coefficient, 3.27×10 −5 and 4.01×10 −5 m/s at 20°C and 40°C, respectively. The results obtained are comparable with those reported in previous studies, both by ourselves and by other authors.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.