| Chenghe No.5 coal was used in the paper to have a systematical research on the desulfurization and deashing technology. By the analysis of chemical, technological properties and mineral occurrence of raw coal, it was concluded that raw coal had medium ash, high sulfur, high calorific value and moderate grindability. The coal ash had medium fusibility with main components of Al2O3 and Si O2. The organic sulfur in coal had a high percentage over 60%, which was based on thiophene, and the inorganic sulfur was based on pyrite. The main minerals in coal were clay, pyrite and calcite, in which the pyrite was mainly present as impalpable state in coal.The feasibility to remove sulfur and ash was studied by analyzing sinking and floating of screening characteristics of the coal, and it was concluded that the washability was very difficult or extremely difficult, when the ash was less than 14.00%. From the sulfur distribution, it was shown that there was mainly 34.50% organic sulfur in low densities, which was difficult to remove by mechanical methods. To achieve a better dissociation of pyrite and to reduce ash in a certain degree, the raw coal was pulverized to-0.5mm to have a research on the experiment of desulfurization and deashing by flotation method.By the study of optimum flotation conditions, the influence of kerosene, octanol, coal slurry concentration and inflatable amount on sulfur removal and ash reduction effect of flotation was investigated to determine the optimum flotation conditions, which were 800g·t-1, 80g·t-1, 60g·L-1, and 0.2m3·m-2·s-1 of the above four factors respectively. Under the condition, the desulfurization sophistication, flotation sophistication, clean coal yield, sulfur content and ash content were 15.72%, 27.83%, 80.45%, 2.98% and 18.55% respectively. The influence of five kinds of inhibitors(CaO, Na2S2O3, Na6O18P6, K2Cr2O3, H2O2) on desulfurization and deashing effect were studied, from which it was indicated that Ca O had the best result with the 30kg/t of the amount, and the desulfurization sophistication, flotation sophistication, sulfur content and ash content were 18.80%, 45.9%, 2.86%, and 15.32% respectively. Compared with the flotation without inhibitors, the desulfurization sophistication and flotation sophistication was improved by 3.08% and 18.48%, from which it was illustrated that the desulfurization and deashing effect were improved by flotation with the addition of inhibitors, but was not significant.The influence of electrochemical reduction method on flotation to desulfurize and deash was mainly studied in the paper, in which the influence of electrolytic time, electrolytic current, and electrolyte concentration of different electrolytes on desulfurization sophistication and flotation sophistication were investigated. It was shown that H3PO4 had better desulfurization and deashing effect with 30.31%, 45.02% of desulfurization sophistication and flotation sophistication respectively at the optimal condition of 45 min, 1.0A, and 500g·t-1 of the above three factors respectively, improved by 14.59% and 17.19% compared with the flotation without inhibitors. Under the condition, the sulfur and ash content of the clean coal were 2.50% and 15.65%. From the analysis of sulfur forms removal effect, it was concluded that the electrochemical reduction flotation could remove 90% of the pyri tic sulfur, improved by more than 30% comparing with the flotation with inhibitors, and could also remove 8%~14% of the organic sulfur, which indicated that electrochemical reduction could not only greatly improved the inorganic sulfur removal by flotation, but also improved the removal of organic sulfur. It was concluded that electrochemical reduction flotation method could remove sulfur and ash of Chenghe No.5 coal effectively, which would be of great significance to remove the ash and sulfur in coal to broaden its application area and utilization approach of the Chenghe No.5 coal resources. |
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