Abstract
• Ultrafine Ca(OH) 2 combined with microwave was proposed for coal pretreatment. • Around 70% of total sulfur was fixed in coal ash by the combined treatment. • Effects of coal particle size and employed alkalis on sulfur fixation was studied. • A continuous pretreatment system was developed for practical utilization. • Briquette made from treated coal achieved a sulfur fixation rate of 74.97%. Sulfur fixation technology for raw coal can reduce SO 2 emission during coal combustion. A method combining microwave irradiation and ultrafine Ca(OH) 2 slurry was proposed, where raw coal was pulverized to mix with the slurry, and then treated by microwave irradiation. For anthracite coal (sulfur content = 1.90 wt%) with particle size distributed in the range of 75–180 μm, the treatment fixed 67.98 % of the sulfur in coal ash. Results prove that there is a synergy between microwave irradiation and ultrafine Ca(OH) 2 for coal pretreatment, and finer coal particles had higher fixation rate. Under the same treatment condition, the sulfur fixation rate was increased to 74.68 % by adding 1 mol/L NaOH. Applying more NaOH or less Ca(OH) 2 both made the fixation rate decrease. The combined treatment was also applied to bituminous coal (sulfur content = 0.79 wt%), and a fixation rate of 87.93 % was obtained. A continuous pretreatment system was developed for practical utilization of the method. Coal treated by the system was made into honeycomb briquette and burnt in a domestic coal stove, where a sulfur fixation rate of 74.97 % was obtained, compared to that of 4.55 % from untreated coal briquette.
Published Version
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