【作者】 吴萍；

【导师】 季惠明；

【作者基本信息】 天津大学 ， 材料学， 2005， 硕士

【摘要】 粉煤灰是由燃煤电厂产生的固体废弃物。近年来,随着电力工业的发展,粉煤灰的排放量急剧增长,由于得不到适当的处理,大量粉煤灰累积堆放,对环境和经济造成严重危害。因此,对粉煤灰进行有效的综合利用,是消除它对环境和经济消极影响的根本途径。粉煤灰中含有很多有用的物质可以回收利用,其中氧化铝的含量一般可达到20%～35%,最高可达50%左右,可代替铝土矿成为一种很好的氧化铝资源。本课题旨在从粉煤灰中提取高纯超细的氧化铝粉体。通过对反应机理、工艺过程及可行性的研究,探索出新的从粉煤灰中提取氧化铝的方法——煅烧—沥滤法。该方法具有提取率高、能耗低、污染小、易于操作、产品附加值高等优点,是较理想的从粉煤灰中提取氧化铝的方法。实验分别对煅烧—沥滤工艺中的活化过程、溶出过程及干燥、煅烧过程进行讨论。从粉煤灰本身的结构和组成出发分析了粉煤灰活性低的原因,通过对粉煤灰的活化机理进行研究,总结出有效的活化粉煤灰的方法——物理—化学复合活化法。选用Na₂CO₃为活化剂,确定了合理的活化条件。对活性粉煤灰中铝盐溶出过程进行研究,选择H₂SO₄为溶出剂,确定了合适的溶出条件,获得氧化铝的最大提取率超过98%。此外,实验采用络合滴定法,以乙二胺四乙酸（EDTA）为络合剂有效除去其中的杂质铁,用蒸馏水洗涤除去钠和其它可溶性杂质,得到纯度高于99.6%的氧化铝粉体。通过添加合适的分散剂、控制Al（OH）₃的结晶、干燥及煅烧的工艺条件,大大提高了氧化铝粉体的细度。在800℃煅烧得到比表面积为287.4㎡/g,具有单一晶型的纤维状的活性γ-Al₂O₃;在1200℃煅烧2h后可得比表面积26.9㎡/g,粒径为30～50nm,分散性好的α-Al₂O₃。通过合理的综合效益的评价分析认为,采用煅烧—沥滤法从粉煤灰中提取高纯超细氧化铝粉体,是一种高附加值综合利用粉煤灰的有效途径,可以产生很好的经济和环境效益。更多还原

【Abstract】 Vast quantities of fly ash originating from thermoelectric power stations have accumulated over the years. The disposal of fly ash causes significant economic and environmental problems. Consequently, eliminate the harm on economy and environment that brought by fly ash, the only effective measure is to utilize them.There are many available materials containing in fly ash, which can be recovered and used as raw materials in other industries. The content of alumina in fly ash range from twenty percent to thirty five percent, the maximal content of alumina can excess fifty percent. So fly ash can substitute bauxite serve as a good alumina resource.The purpose of this work is to extract high purity and ultra fine alumina powder from the fly ash. After investigation, the sintering-leaching process proved to be the highly effective method to extract alumina from the fly ash. This method can produce high alumina extraction efficiency, and it is handy operation. While it takes low cost, causes little pollution. Therefore, the sintering-leaching process is an ideal method for the extraction of alumina from the fly ash.After investigating the processes of activation, extraction of the fly ash, the factors that reduce the activation of the fly ash were found. Experiments educe that physical-chemical mulriple activating method can availably active the fly ash. Introduce Na2CO3 as the activating agent and sulphuric acid as the lixiviant. Under appropriate activating and lixiviating conditions, the alumina extraction efficiency can exceed 98 percent.The unwanted iron ions in the lixivium were removed with ethylenediamine tetra acetic acid (EDTA) and other soluble impurities were stripped by washing with distilled water. Lastly the purity of the alumina product is excess 99.6 percent. Choose right disperser, proper crystallization, drying and sintering conditions, which will reduce the particle size of the alumina. Calcine the aluminum trihydroxide at 800℃, the dispersive fibriformγ-alumina powder was obtained. The specific surface area of the powder is 287.4㎡/g. When calcine the aluminum trihydroxide at 1200℃, high purityα-alumina was prepared. The specific area of theα-alumina is 26.9㎡/g and the particle size of it is range from 30nm to 50nm.After reasonable synthetically benefit estimation on this subject, the conclusion更多还原