Simulation Experimental Study On Granulating Molten Blast Furnace Slag By Nozzle Jetting And Analysis Of Slag Solidification

The molten blast furnace slag is a kind of mixture of impurities which can not be integrated into the pig iron during the process of blast furnace smelting. It mainly composes of silicate and aluminate.0.3to1tons of molten blast furnace slag will be formed with1ton pig iron produced. In2013, China has produced more than500million tons of blast furnace slag which contains a huge amount of sensible heat. With the mostly used slag quenching disposal method, the slag sensible heat can not be recovered efficiently. At the same time it pollutes the environment and wastes water. Dry slag granulation process can efficiently recover the sensible heat of the molten blast furnace slag and which has important significance to the sustainable development.Though dry granulation process can effectively recycle the sensible heat, there is still no dry granulation method used widely due to some defects. This paper proposed a novel method to granulate blast furnace slag with a venturi nozzle. Slag mixes with high speed airflow in the throat of the venturi nozzle, and becomes granulated when sprays out. At the same time the molten slag is cooled by the airflow.Paraffin wax and sugar which has similar solidification characters were used to be granulated by jetting experiments. The influence on granulation of the nozzle contraction ratio, nozzle throat size and the jet flow velocity has been probed into. Experiment results show that this method can granulate molten slag and decrease the production of filaments effectively. The molten slag must turn into solid state when it is sprayed into heat-recovering equipments. Otherwise it easily adhere to the equipment wall or bonded with each other, and this will damage the heat-recovery equipment or induce negative influence on heat recovery. This paper has also established physical and mathematical models of molten slag solidification and simulated the cooling process of molten slag by a CFD software. The simulation results are very significant for the blast furnace slag waste heat recovery.