煤矸石焙烧活化-酸浸提取氧化铝的实验研究

Experimental study on extraction of alumina from coal gangue by roasting activation-acid leaching

从煤矸石中提取有价金属元素是实现煤矸石综合利用的重要途径之一。以高铁低铝煤矸石中的Al_(2)O_(3)为研究对象,采用焙烧法活化煤矸石,以盐酸为浸出介质,研究了焙烧温度、焙烧时间、酸浸温度、盐酸体积分数、酸浸时间和液固比(酸浸1 g煤矸石所用盐酸的体积)对活化物料煤矸石中Al_(2)O_(3)浸出的影响,并对煤矸石中Al_(2)O_(3)的浸出动力学进行了研究。其中,焙烧温度设置5个水平(550℃,650℃,750℃,850℃,950℃),焙烧时间设置5个水平(0.5 h,1.5 h,2.5 h,3.5 h,4.5 h),酸浸温度设置5个水平(60℃,80℃,100℃,109℃,120℃),盐酸体积分数设置5个水平(36%,43%,49%,57%,64%),酸浸时间设置5个水平(0.5 h,1.5 h,2.5 h,3.5 h,4.5 h),液固比设置5个水平(2 mL/g,3 mL/g,4 mL/g,5 mL/g,6 mL/g)。利用扫描电镜(SEM)和X-射线衍射仪(XRD)对煤矸石原矿、活化物料及酸浸渣的矿物组成进行了理化表征,进一步探究Al_(2)O_(3)浸出机理。结果表明:在焙烧温度为650℃、焙烧时间为1.5 h、盐酸体积分数为49%、液固比为4 mL/g、酸浸时间为2 h和酸浸温度为109℃的条件下,Al_(2)O_(3)的浸出率可达94.9%。浸出过程可用未反应收缩核模型来描述,反应速率受固态产物层和界面化学反应的混合控制,表观活化能为39.93 kJ/mol。SEM分析显示焙烧活化能有效破坏煤矸石的稳定结构,使其结构变得疏松多孔。XRD分析表明焙烧后煤矸石中氧化铝主要是活性状态的非晶态偏高岭石和勃姆石,通过酸浸能够有效提高煤矸石中Al_(2)O_(3)的浸出特性。

Extracting valuable metal elements from coal gangue is one of the essential ways to realize the comprehensive utilization of coal gangue.Focused on Al_(2)O_(3)from high-iron and low-aluminum coal gangue,the activated roasting method was employed using hydrochloric acid as the leaching medium.The effects of roasting temperature,roasting time,acid leaching temperature,hydrochloric acid concentration,acid leaching time and liquid-solid ratio(volume of hydrochloric acid used for leaching 1 g coal gangue)on the leaching of Al_(2)O_(3)from activated coal gangue were investigated,and the leaching kinetics of Al_(2)O_(3)in coal gangue was also discussed.The experimental conditions encompassed five groups for each parameter:roasting temperature(550℃,650℃,750℃,850℃,950℃),roasting time(0.5 h,1.5 h,2.5 h,3.5 h,4.5 h),acid leaching temperature(60℃,80℃,100℃,109℃,120℃),concentration of hydrochloric acid(36%,43%,49%,57%,64%),acid leaching time(0.5 h,1.5 h,2,5 h,3.5 h,4.5 h),and the liquid-solid ratio(2 mL/g,3 mL/g,4 mL/g,5 mL/g,6 mL/g).The morphology and mineral composition of raw coal gangue,activated material and acid-leaching slag were characterized by scanning electron microscopy(SEM)and X-ray diffractometer(XRD),respectively.The leaching mechanism was further discussed,The results show that the optimum experimental conditions are as follows:the roasting temperature is 650℃,the roasting time is 1.5 h,the volume fraction of hydrochloric acid is 49%,the ratio of liquid volume to solid mass is 4mL/g,the leaching time is 2 h,and the leaching temperature is 109℃.In these conditions,the leaching ratio of alumina can reach 94.9%.The unreacted shrinking core model can preferably describe the leaching process.The reaction rate is controlled by the mixture of solid product layer and interfacial chemical reaction,and the apparent activation energy is 39.93 kJ/mol.SEM analysis manifestes that the roasting activation can effectively destroy the stable structure of coal gangue,resulting in a porous structure;XRD analysis suggestes that the Al_(2)O_(3)in the roasted coal gangue is composed of amorphous meta kaolinite and boehmite in the activated state,and the leaching characteristics of Al_(2)O_(3)in the coal gangue have conspicuously improved through acid leaching.