铁矿烧结烟气半干法脱硫灰除杂及水热非均相低温快速氧化

Impurity removal and hydrothermal heterogeneous cryogenic rapid oxidation of semi-dry desulfurization ash from iron ore sintering flue gas

铁矿烧结半干法烟气脱硫灰因含有大量性质不稳定的亚硫酸钙,无法得到有效利用,脱硫灰的氧化改性是实现其大规模或高值化利用的重要手段。脱硫灰中的碳酸钙是限制其氧化改性的主要因素,碳酸钙与亚硫酸钙两者相互包覆,降低了亚硫酸钙氧化反应的比表面积,限制其氧化速度。利用L(+)-抗坏血酸和冰醋酸两种弱酸作为对碳酸钙的脱除剂,其中浓度为0.4 g/g的冰醋酸可将脱硫中亚硫酸钙含量最高提升至81.17%,最大增幅达69.71%。采用亚临界水热非均相氧化法对不同因素对脱硫灰中亚硫酸钙氧化率的影响进行了研究。结果表明除杂后亚硫酸钙的氧化速率明显增加。在温度140℃、时间30 min、初始压力2 MPa、初始固液比1:30、转速300 r/min条件下,亚硫酸钙氧化率达98.72%,实现了脱硫灰低温快速氧化,产物初步具备制备大长径比硫酸钙晶须生长基础条件。

The semi-dry desulfurization ash of iron ore sintering flue gas cannot be effectively utilized because it contains a lot of unstable calcium sulfite.Oxidation modification of desulfurization ash is an important means to realize its large-scale or high-value utilization.The results show that the calcium carbonate in the desulfurization ash is the main factor limiting its oxidation modification.Calcium carbonate and calcium sulfite cover each other,which reduces the specific surface area of calcium sulfite oxidation reaction and limits its oxidation rate.Two weak acids,L(+)-ascorbic acid and glacial acetic acid,were used to remove calcium carbonate.Glacial acetic acid with a concentration of 0.4 g/g could increase the content of calcium sulfite to 81.17%with the maximum increase of 69.71%.The effect of different factors on the oxidation rate of calcium sulfite in desulfurization ash was studied by subcritical hydrothermal heterogeneous oxidation method.The results showed that the oxidation rate of calcium sulfite was significantly increased after removing impurities.The oxidation rate of calcium sulfite can be increased by increasing the initial pressure,the reaction temperature and time,and reducing the solid-liquid ratio.When the reaction temperature was 140℃,the reaction time was 30 min,the initial pressure was 2 MPa,the initial solid-liquid ratio was 1:30 and the rotating speed was 300 r/min,the oxidation rate of calcium sulfite was 98.72%,while the oxidation rate of desulfurized ash without impurity removal was only 78.77%at 180℃(other conditions were the same).In this work,the desulfurization ash was oxidized rapidly at low temperature.From the micro morphology point of view,compared with the desulfurized ash without impurity removal,the calcium sulfite after impurity removal was easier to grow along the radial direction,which had preliminary conditions for the preparation of calcium sulfate whiskers with a large aspect ratio,which was of great significance for the preparation of calcium sulfate whiskers.