超声电化学浮选膜分离剥离煤中关键有害元素的机理

The harmful elements in Xinjiang coals are complex and various. It’s necessary to study the step removal of the main harmful elements in Xinjiang coals in order to clean coal utilization. The existing state of different forms of sulfur is similar to that of hamful elements in coal. The ash in coal contains lots of harmful alkaline metals and heavy metals. In our preliminary experiment, the different forms of sulfur and ash were effecitively removed by enhancing flotation of coal using sonoelectrochemical method. Therefore, the method of enhancing flotation of coal using sonoelectrochemistry would be feasible to removal harmful nitrogen, halogens, alkaline metals and heavy metals. Ultrasonic cavitation/shear stress enhance electrochemical conversion and flotation separation, the method that enhanced flotation of coal by sonoelectrochemistry designs to study the step removal of main harmful elements in coal. The harmful elements including nitrogen, halogens, alkaline metals and heavy metals in coal that are transfered into solution step by step during electrochemical conversion with different electrolyte as acid, alkaline or salt. The harmful elements in solution are separated from clean coal by flotation separation. The harmful icons are separated from water by membrane filtration. The study focus on mechanism of replacement reaction between alkaline/heavy metals and hydrogen, between halogens and hydroxyl, migratory route of nitrogen. The raw coal is analysed by NMR and XPS, the treated samples include liquid and solid are also analysed. The relationship between coal structure and step removal of main harmful elements are dissected. The study would solve the key topics on removal of main harmful elements in coal. The newly developed technology presents promising prospects for efficient, economic and simple method in industrial application of Xinjiang coal.

新疆煤中有害元素种类多、区域分布差异大，研究煤中关键有害元素的梯度剥离对煤洁净利用尤为必要。硫的结合形态代表有害元素的赋存形态，灰中富集有害碱金属、重金属。我们前期发现超声电化学浮选有效剥离煤中形态硫和降低灰分，这为超声电化学浮选梯度剥离煤中有害氮、卤素、碱金属、重金属提供了可行性。本课题结合超声空化、剪切作用对电化学转化和物理浮选的促进作用，采用超声电化学强化浮选，通过酸、碱、盐类电解质协同有机溶剂分别对煤中氮、卤素、碱金属、重金属进行电化学分级转化和浮选剥离；结合膜过滤对浮选转移至水相的有害离子进行梯度分离。重点研究有机态赋存的碱金属、重金属与氢键置换，卤素与羟基置换规律；氮转移至液相的迁移途径。结合煤样的原位核磁、XPS分析，处理后煤样的液相、固相组分分析，剖析煤结构差异性与关键有害元素梯度剥离的变化规律。该研究将解决煤中关键有害元素的一体化脱除难题，实现新疆煤的清洁化高值利用。

研究煤中关键有害元素的超声电化学浮选膜分离。通过酸、碱、盐类电解质协同有机溶剂分别对煤中硫、卤素、碱金属、重金属进行电化学分级转化和浮选剥离；结合膜过滤对浮选转移至水相的有害离子进行梯度分离。本课题获取了13种新疆不同煤区煤样中关键有害元素的含量分布：硫含量以特低硫为主，少量为低、中硫。氯含量为特低氯，氟含量以低氟、中氟为主，砷含量为一级。汞含量以中、低为主，少量煤样为特低汞。.研究酸性条件下低硫煤中形态硫、灰及伴生的有害金属元素的一体化剥离。确定煤样脱硫的最优组合：硫酸浓度5.5×10-3 mol/L，电解温度30 ℃，电流强度83×10-3 A/cm2，电解时间35 min。该条件下精煤收率90.98%，降硫率65.96%，黄铁矿硫减少95.91%，硫酸盐硫减少90.0%，有机硫减少37.50%，Hg减少80.0%，Pb减少20.0%，灰分减少32.75%，灰中K2O减少14.89%，灰中Na2O减少27.78%。水分减少20.53%，挥发分增加3.65%，发热量增加5.12%，C减少0.22%，H增加9.55%。研究双氧水为清洁电解质下电厂煤超声电解，发现Coal 3煤中硫、氯、汞、灰中氧化钠依次减少11%、25%、63%、46%，热值增加11%；发现Coal 9煤中硫、氮、氯、砷、铅、汞、灰中氧化钾、灰中氧化钠依次减少3%、3%、40%、25%、67%、4%、50%、22%，热值增加2%。通过膜分离、旋蒸可以有效实现水的净化处理和有害元素的浓缩回收。.超声电化学强化浮选能有效增大表面接触角，提高浮选精煤疏水性，提高精煤收率。电化学脱除部分无机态（弱键结合，如黄铁矿硫）、有机态（强键结合，如醇硫）有害元素，主要归因于电化学转化、酸性H+或碱性OH-置换、重金属元素（如汞、铅和砷）阴极沉积；浮选脱除无机态硫、灰、灰中K2O和Na2O。该研究将推进煤中有害元素的一体化剥离和清洁利用。