Semi-industrial Experiment Study On Preparing Directly Nanometer Zinc Oxide By Low-grade Zinc-bearing Materials

The development of disposal technologies for low-grade zinc-bearing materials, blast furnace zinc-lead-bearing dust and low-grade zinc-oxide ore etc, is relatively slow in recent years. Using existing disposal methods, much energy is consumed and only low-grade zinc oxide by direct method is produced. The developmental direction of disposing low-grade zinc-bearing materials is that products with high added value are produced efficiently in low cost. Nanometer zinc oxide has many specific properties which macroscopic materials have not. So it is used widely, and the quantity demanded for it is very large. But the raw material of most existing preparation methods of nanometer zinc oxide is metallic zinc or zinc salt. The processes of these methods are complicated and the cost of raw material is high. The produce of nanometer zinc oxide can't meet the market demand. So it is a beneficial attempt that preparing directly nanometer zinc oxide by low-grade zinc-bearing materials.Using low-grade zinc-bearing materials as raw materials, nanometer zinc oxide is directly prepared in laboratory triumphantly by carbon-containing pellet direct reduction method and a new pyrogenic method, aluminium bath method. So the main tasks of this study are on the basis of further laboratory study, designing semi-industrial experiment facility, carrying out semi-industrial experiment, testing experiment facility, gaining process parameter, opening up process flow.By analyzing the properties of zinc, lead and their oxides, it is discovered, to realize separtion of zinc and lead, zinc oxide and lead oxide must be fast reduced at a low temperature. By analyzing the mechanism of nucleation and growth of nanometer particles, it is discovered that improving the purity of zinc evaporation, reducing heterogeneous nucleation, fast oxidizing zinc evaporation at a low temperature and fast cooling zinc oxide is beneficial to the diminishment of grain size of zinc oxide.Using blast furnace dust or low-grade zinc-oxide ore as raw material, the optimal method by which nanometer zinc oxide is prepared in laboratory is aluminium bath method. By aluminium bath method, using blast furnace dust as raw material, ZnO content in zinc oxide power is more than 90%, PbO content is smaller than 5%, Pb content in slag is around 15%, zinc volatilization ratio and lead enriched ratio are more than 90%; and using low-grade zinc-oxide ore as raw material, ZnO content in zinc oxide power is more than 98%, PbO content is smaller than 1%, zinc volatilization ratiois more than 90%.The predominance of aluminium bath method in semi-industrial experiments is smaller than in laboratory experiments. The recent results show that the mechanical loss of aluminium is severe in semi-industrial experiments. By carbon-containing pellet direct reduction method, the results are better in semi-industrial experiments than in laboratory experiments. The suitable conditions in semi-industrial experiment: pellet diameter 10-15mm, temperature 1100C, lignitic coal content in pellet 5.7%. Using nut coke with pellet is unsuitable. Under these conditions, using blast furnace dust as raw material and by aluminium bath method, ZnO content in zinc oxide power is about 95%, needed time is 90min, zinc volatilization ratio is more than 90%, lead enriched ratio is around 90%, ZnO collected ratio is about 85%; by direct reduction method, ZnO content in zinc oxide power is about 93%, needed time is 100min, zinc volatilization ratio is more than 90%, lead enriched ratio is around 85%, ZnO collected ratio is more than 80%. Low-grade zinc-oxide ore has not been roasted. The experiment conditions have not been controlled strictly. Under these conditions, using zinc-oxide ore as raw material and by direct reduction method, ZnO content in zinc oxide power is about 94%. The results of TEM measurement show that zinc oxide power is claviform, and its diameter is 30~80nrri, so it belongs to nanometer materials.So using low-grade zinc-bearing materials, blast furnace zinc-lead-bearing dust and low-grade z...