碱烧结法回收二次铝灰中氧化铝

Study on alumina recovery in secondary aluminum ash by alkali sintering method

二次铝灰中蕴含大量的氧化铝、铝和氮化铝等,还有部分氟化物和氯化物盐类,属于危险废弃物。目前常用的铝回收技术有酸浸法和碱浸法,均存在工艺条件苛刻、回收率低、能耗高、物耗大和产品附加值较低等问题。本研究采用碱烧结法从二次铝灰中回收氧化铝,考察烧结温度对氮化铝转化率的影响,碱铝比、烧结时间和成型方式对氧化铝回收率的影响,得到以下主要结论:在烧结温度1423 K、烧结时间40 min、碱铝比1.1、干压成型的试验条件下,氧化铝溶出率最大为94.23%;通过对二次铝灰铝酸钠熟料浸出渣成分以及物相进行分析,得到二次铝灰经过碱烧结法焙烧后熟料主要成分为Al_(2)O_(3)和Na_(2)O,分别占到49.70%和28.06%,熟料标准浸出后残渣主要成分为CaO、Al_(2)O_(3)和MgO,含量分别为25.46%、20.27%和15.80%;二次铝灰中AlN分解率较高,可达到95%以上,最终浸出渣中氟离子浸出毒性在30 mg/L以下。综上所述,本文采用碱烧结法资源化利用二次铝灰,实现了二次铝灰脱氮固氟的无害化处置,具有环境友好、资源利用率高的优势,为后续大规模工业化推广奠定了理论基础。

Secondary aluminum ash contains a large amount of alumina,aluminum and aluminum nitride,as well as some fluorides and chloride salts,which are hazardous wastes.At present,the commonly used aluminum recovery technologies,acid leaching method and alkali leaching method,have the problems of harsh process conditions,low recovery rate,high energy consumption,large material consumption and low added value of products.In this study,alkali sintering method was used to recover alumina from secondary aluminum ash.The effects of sintering temperature on aluminum nitride conversion,alkali aluminum ratio,sintering time and forming method on alumina recovery were investigated,and the main conclusions were obtained as follows.Under the experimental conditions of sintering temperature 1423 K,sintering time 40 min,alkali to aluminum ratio 1.1 and dry pressing,the maximum dissolution rate of alumina is 94.23%.Through the analysis of the composition and phase of the leaching residue of sodium aluminate clinker of secondary aluminum ash,the main components of the clinker after calcination by alkali sintering method are Al_(2) O_(3) and Na2 O,accounting for 49.70%and 28.06%respectively,and the main components of the residue after standard leaching of clinker are CaO,Al_(2)O_(3) and MgO.The contents were 25.46%,20.27%and 15.80%,respectively;The decomposition rate of AlN in secondary aluminum ash is higher,which can reach more than 95%,and the leaching toxicity of resource products is below 30 mg/L.In summary,this paper uses alkali sintering method for resource utilization of secondary aluminum ash,and realizes harmless treatment of secondary aluminum ash for nitrogen removal and fluorine fixation,which has the advantage of high utilization rate of environmentally friendly resources,and lays a theoretical foundation for subsequent large-scale industrialization.