Use of rice husk for emission neutral energy generation and synthesis of solar-grade silicon feedstock

The potential use of rice husk as a source of energy and also for producing high-purity silicon has been investigated by a combination of pilot trials, theoretical calculations and laboratory experiments. Rice husk was combusted at 850°C. Mass balance together with the pilot results indicates an electricity generation potential of 1 MWh per tonne rice husk. The process also generates 180 kg rice husk ash (RHA) that is used for production of high-purity silicon through a hybrid pyrometallurgical–hydrometallurgical process. The process consists of three major steps: purification of RHA by leaching and roasting, reduction by magnesium and recovery of silicon through two steps of leaching. The silicon generation process steps were optimized, showing that about 85% of silicon in the RHA can be recovered. The silicon product has a total impurity of <0.7%, hence it may be used as a suitable feedstock for production of solar-grade silicon.