409 / 2018-12-26 10:20:55

Experimental Study on Preparation of Amorphous SiO2 by Fluidized Bed Combustion of Rice Husk

Rice husk ash; Amorphous SiO2; Fluidized bed combustion; Pore characteristics

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Rice husk ash (RHA) contains up to 87%-97% amorphous SiO2, which has large specific surface area and high activity, and has excellent application value. The direct combustion method is the simplest and most direct method for preparing RHA, by which heat generated by the combustion process is used and high-quality RHA is recovered. As a result, we can utilize clean energy and recycle waste. However, in conventional biomass boilers, high-temperature combustion conditions make SiO2 in RHA easily crystallize into cristobalite, losing porosity and pozzolanic properties and affecting recycling. Therefore, it is important to prepare high-quality amorphous SiO2 under the condition of sufficient and stable combustion. In this respect, the subject uses a small fluidized bed experimental system to explore the effect of combustion parameters on the quality of RHA, and studied combustion characteristics of rice husk and pore characteristics of RHA when the combustion parameters such as furnace temperature, excess air coefficient, bed height, primary to secondary air ratio, and wind speed are changed. It is found that a higher primary to secondary air ratio can improve the stability and uniformity of combustion; when the wind speed is 0.6-0.7m/s, the rice husk has a longer residence time and the burnout rate is better, but it may cause the ash particles to agglomerate and sinter; more bed material can strengthen the turbulence in the furnace, but will increase the expansion rate of the bed, so that the RHA is easily elutriated. The fluidized bed combustion method can prepare RHA with a specific surface area of 45m2/g, and the SiO2 remains in an amorphous form, which proves that this scheme has great feasibility.