粉煤灰中非晶态硅赋存形态及定量分析方法研究

粉煤灰作为大型煤电基地的重要固体废弃物,年排放量超过6亿t,目前利用率仅为60%左右,大部分粉煤灰以堆存为主,造成严重污染,其资源化利用意义重大。以山西、内蒙古等大型能源基地产生的高铝粉煤灰为例,通过基础物性分析发现,粉煤灰中主要包括铝、硅、铁、钙等主量元素,主要以莫来石相、非晶相、铁质微珠相三类矿相形式赋存,其中莫来石相结构稳定,非晶相铝硅酸盐反应活性较高,但其配位结构复杂,反应活性不一。目前针对其丰富的铝硅资源,氧化铝提取和铝硅复合材料制备是主要高值化研究方向,其中非晶相硅的深度脱除是关键处理技术。针对非晶相硅的赋存形态及定量分析,首先采用核磁分析结合电子探针手段,明确非晶相中铝硅酸盐赋存结构复杂,其中硅原子主要以Q4(4Al)、Q4(3Al)、Q4(2Al)、Q4(0Al)、Q2(1Al)五种配位结构形式存在,其中Q4(0Al)含量高达56. 5%;其次采用酸碱联合法,通过逐步削弱铝氧硅沸石自发反应可能性,选择性分离活性铝,促进活性作用位点大量暴露,从而实现非晶态铝硅酸盐的逐步梯级分离,进一步通过ICP、XRF、XRD、扫描电镜、电子探针等分析表征,明确莫来石晶相与铝硅酸盐非晶相之间的高效分离,并开展了2组平行试验,试验结果误差较小。结果表明:非晶相中硅含量为57%～58%,非晶相“鼓包峰”消失,其包裹的莫来石晶粒结构显现,证明非晶相二氧化硅得到高效脱除。该方法具有反应条件温和、误差小、操作弹性大等优点,对粉煤灰铝硅资源高值转化利用具有重要的指导意义。 Abstract:Coal fly ash is regarded as the important solid waste in the large coal power base,and above 600 million tons coal fly ash is generated annually.The utilization ratio is only 60% approximately,the most of fly ash is mainly stored in piles,which can cause serious environmental problems,and its resource utilization is of great significance.In this paper,the high alumina coal fly ash (HAFA) generated in Shanxi and the north of Inner Mongolia was adopted and researched.The basic physical property analysis shows that aluminum,silicon,iron,calcium are the main elements in the coal fly ash,which are in the form of mullite,amorphous silica and ferruginous spheres.Mullite is a stable phase.The reactivity of amorphous phase aluminum silicate is high,but its coordination structure is complex and the reactivity is different.Nowadays,in terms of its abundant aluminum/silicon resources,the main high-value research directions focus on the extraction of alumina and preparation of aluminum-siliconcomposite,in which the removal of amorphous silica is the key processing technology.In view of the occurrence morphology and quantitative analysis of amorphous silicon,firstly,the NMR analysis combined with EPMA was used to determine the complex structure of aluminium-silicate in amorphous phase.The silicon atoms mainly exist in five coordination structures:Q4(4Al)/Q4(3Al)/Q4(2Al)/Q4(0Al)/Q2(1Al),and the content of Q4(0Al) is occupied about 56.5% in the amorphous phase.Secondly,by means of acid-base combination method,the possibility of spontaneous reaction in alumina-silica zeolite was gradually weakened,active aluminium was selectively separated,and the active sites were exposed in large quantities,so as to realize the step-by-step separation of amorphous aluminium-silicate.Further,the efficient separation between mullite crystalline phase and aluminium-silicate amorphous phase was identified by ICP,XRF,XRD,SEM and EPMA.Two groups of