Research On Extracting Silica From Fly Ash By Alkali Soluble

Fly ash is the inevitable product of thermal power generation.China's energy consumption is mainly from coal and electric power is accounted for more than half in coal consumption.That fly ash accumulation amount is increasing every year is not only of serious damage to the local ecological environment,but also a huge threat of human health life.Therefore,this project aims to study the comprehensive utilization of fly ash.It can bring economic benefits,better protection of human beings and their environment for survival.The mainly chemical components in the high-alumina fly ash is Al₂O₃ and SiO₂,whose percentage is up to 85%.The content of SiO₂ could reach as high as 30%⁶0% in fly ash.Therefore,in addition to the development of aluminum products,high value-added silicide product preparation is a key comprehensive utilization of fly ash.And the content of SiO₂ is too high,resulting in being inconsistent with the bauxite alumina ratio indicators.Silicon dioxide is harmful component in the process of aluminium.It is easy to form a unmolten sodium aluminosilicate,increase consumption of alkali and alumina and adversely affect what alumina is extracted from.In order to extract aluminum from coal ash,we should firstly use pre-desilication treatment to reduce the content of silica,secondly we increase alumina-silica ratio.Hence,in order for the high content of silicon in fly ash,desilication is an indispensable step in the process of extracting aluminium.In this paper,we use fly ash of power plant in the Ping Shuo area as a raw material,which has the following effects:?1?In the coal Ping Shuo area,due to its geological origin,the cause of high content of aluminum and mullite in fly ash is that coal seam contains much mineral kaolinite which has enrichment of aluminum.The physical and chemical properties of fly ash have a great relationship with coal minerals.?2?This paper uses fly ash as a raw material in the preparation of sodium silicate solution.Firstly,it puts fly ash in the muffle furnace heated 1h at 950? Then,It has effects on the process of alkali-soluble silica,aluminum,lithium dissolution rate researching on the reaction temperature,concentration of sodium hydroxide solution,the liquid-solid ratio and the reaction time.By single factor and orthogonal experiments,and ultimately determine the optimum parameters for the stage: the reaction temperature of 135 ?,Na OH solution concentration of 70g/l,the dissolution time of 45 min,solid-liquid ratio of 1:30.?3?This paper uses sodium silicate solution as the source of silicon and uses a method that ventilation with carbon dioxide is preparation for white carbon black products.The optimal parameters are as follows: the concentration of the sodium silicate solution of 30g/l,the temperature of 80?,the flow rate of carbon dioxide of 40-45ml/min.During carbonation,the precipitation in the PH = 11 starts generating and about precipitation in PH = 9 ends of the reaction.The silica production rate is above 95%.