Studies On The Mechanism And Technologies Of Extraction Of High Purity And Ultra-fine Alumina From The Fly Ash

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...