| Tungsten belongs to the rare metal with high melting point in the field of metallurgy and metal materials.Its high melting point characteristics make it play an important role in military,aerospace,machining,metallurgy and other industries.In China,we mainly use alkali decomposition method to smelt tungsten ore and produce primary product ammonium paratungstate（APT）.The slag produced by decomposition is called alkali wolframite slag.According to the different sources of tungsten ore,tungsten slag can be divided into wolframite slag,scheelite slag and wolframite mixed slag.In the production process of a single product,other metal elements can not be completely separated,such as W,Sn,Ta,Nb,Mn,Fe and other metal elements contained in black and white tungsten slag and black tungsten slag.The metal elements in tungsten slag can be gradually separated from it for recycling,so as to realize the recycling of waste slag.In 2016,alkali slags were listed in the national list of hazardous wastes,with the code of 323-001-48.The total amount of tungsten slags in China has reached the order of million tons,and is still growing every year.Each apt manufacturer builds a hazardous waste dump to stack tungsten slag,which pollutes the air,land and underground water for a long time.It is of great significance to reduce the output of tungsten slag and recycle it in Chinese tungsten smelting industry.Based on the analysis of the chemical composition of wolframite slag,the possibility and sequence of carbothermal reduction of metal oxides in wolframite slag,the proportion of additives and the liquidus temperature of slag are calculated by thermodynamic data.According to the calculated thermodynamic conditions,the effects of the particle size of tungsten slag,the type of carbonaceous reductant,reaction time,reaction temperature,carbon ratio,melting point and the ratio of additives on the carbothermal reduction experiment of tungsten slag were further studied.Using factsage 7.3 to calculate the thermodynamics,the results show that the main metal elements in tungsten slag,Fe and Mn oxides of various valence states,can occur carbothermal reduction reaction at high temperature（1450℃）.Oxides of other metal elements（W,Pb,Ta,Nb,Cu,Sn）in tungsten slag can be reduced.The phase diagram of the oxides of Mn and Si contained in Al2O3 and Cao combined tungsten slag is calculated.The results of calculation are used as a guide to adjust the addition ratio of Al2O3 and CaO,so as to reduce the melting point of slag,reduce energy consumption and save materials.The results show that the alloying rate of W-Slag can reach 35%and the melting effect of slag gold is very good when the test conditions are 1450℃,holding for 120 min,carbon ratio 15%,Al2O3 35%and CaO20%.The recovery of Fe are 93%,Mn 26%.The recovery of W is 30%70%,there was no obvious law.The metal elements Cu and Sn are all in the alloy,part of Ta and Nb are in the alloy,the additives Al2O3 and CaO are not reduced,and they are in the smelting slag. |
