Abstract:
In order to improve the leaching efficiency of alumina in Jungar pulverized coal ash, the method of applying Jungar coal in the form of coal-water slurry to circulating fluidized bed (circulating fluidized bed, CFB) boiler is proposed, that is, by virtue of the low-temperature combustion characteristics of coal-water slurry, the calcination temperature in the furnace of CFB boiler is further reduced, so as to improve the reactivity of coal ash and the leaching efficiency of subsequent processes. In order to explore the slurry-forming performance and the best slurry-making process of Jungar coal, taking the preparation experiment of coal-water slurry as the main line, the dispersion effects of four common coal-water slurry dispersants, such as NNO, MF, LC and LS, on Jungar coal-water slurry were systematically compared, and the influence of particle size on Jungar coal-water slurry was discussed, and the rheological properties of slurry were analyzed by using rheological data and Herschel-Bulkley model. The results show that the dispersant NNO has the best dispersion effect, and can improve the apparent viscosity and flow diameter of Jungar coal-water slurry from 966 mPa·s (coal slurry concentration 60%) and 9.1 cm without dispersant to 468 mPa·s and 13.2 cm under the condition that the dosage is only 0.4% of the dry basis pulverized coal mass; The particle size has a significant impact on the stability of Jungar coal-water slurry. As the average particle size of coal powder
D50 decreases from 47.2 µm to 20.5 µm, the stability of slurry is improved, and the occurrence time of hard precipitation is prolonged. When
D50≤35.0 µm, the occurrence time of hard precipitation of coal slurry is more than 7 days, meeting the production requirements; The comprehensive performance of coal-water slurry prepared from Jungar coal at
D50=35.0 µm is the best. Under the condition of coal slurry concentration of 60%, the apparent viscosity of the slurry is only 639 mPa·s, and the flow diameter is 11.9 cm, and the flow grade is Bˉ Grade, hard precipitation occurrence time <7 days, low calorific value 10.06 MJ/kg, belonging to high-quality coal water slurry; Jungar coal-water slurry shows shear-thinning rheological characteristics, is a pseudoplastic fluid, and conforms to Herschel-Bulkley model, with rheological property index n<1.