负载有机硫炭质还原剂还原-硫化复合焙烧锡铁精矿锡、铁分离机理与回收机制

Tin-bearing iron ores reserve large in China, and the tin grade is generally about 0.2-1.2%, which are being well worth to be reclaimed. But they are disseminated complicatedly with other gangue minerals, causing them difficult to be utilized. According to occurrence characteristics of tin and iron phases in the tin-bearing iron concentrate, a new method of reduction-sulfurization recombination roasting using the carbon reductant loading organic sulfur for the recovery of tin and iron is proposed in this study. Taking thermodynamic analysis of multicomponent reaction and kinetics strengthening mechanism as the foundation, the action mechanism of magnetite, hematite etc. on the pyrolysis product composition of carbon and sulfur components in the carbon reductant loading organic sulfur, and the quantitative allocation mechanism of oxygen species to sulfur and carbon in different oxygen potentials, are researched. Based on the mechanism of dissociation, reduction and organic sulfur sulfurization of the tin phase, the action mechanism and influence law of iron phases on the tin volatilization rate are explored. Simulating the tin sulfurized products volatilization process in the roasting atmosphere, the strengthening mechanism of tin sulfurized products volatilization is studied. The iron valent state transformation mechanism in iron mineralogical phase and its effect on directed oxidation to sulfur pyrolysis products containing the low valent state surfur are researched. A new technology and theory system of reduction-sulfurization recombination roasting using the carbon reductant loading organic sulfur for the recovery of tin and iron from tin-bearing iron concentrate is constructed, and implementation of this project is meaningful for the innovation and development of new technology and theory for the tin-bearing iron ores utilization.

我国锡铁矿储量丰富，一般锡品位0.2%-1.2%，但矿中锡、铁物相嵌布关系复杂，资源化利用难度大。基于锡铁精矿中锡、铁矿相赋存特征，提出负载有机硫炭质还原剂还原-硫化复合焙烧锡铁精矿回收锡、铁资源新思路。以多元反应热力学分析和动力学强化机制研究为基础，研究锡铁精矿中磁铁矿、赤铁矿等矿相对负载有机硫炭质还原剂碳、硫组分热解产物组成的影响作用机理，探明不同氧势环境中碳、硫两元素的氧组元定量分配机制；探究过程中锡矿相的解离、还原和有机硫硫化作用机理，明晰铁物相形态对锡硫化挥发效率的影响规律和作用机理；模拟锡硫化产物在焙烧气氛中的挥发行为，探究其挥发强化机制；阐明铁矿相中铁的价态转变机理及其对低价态硫热解产物的定向氧化机理，最终构建负载有机硫炭质还原剂还原-硫化复合焙烧锡铁精矿回收锡、铁资源工艺及基础理论体系，为锡铁矿资源化利用的技术发展提供理论支撑。

我国锡铁矿储量丰富，一般含锡0.2-1.2 wt.%，资源化利用价值大，但矿中锡矿相多呈微细粒状嵌布在磁铁矿矿相中，采用传统选矿法难以实现锡、铁资源的高效分离。项目以锡铁精矿矿相结构为基础，以锡、铁矿相还原、硫化热力学区间差异和硫化产物挥发性区别为出发点，以负载有机硫炭质还原剂还原-硫化复合焙烧锡铁精矿高效分离锡、铁为研究主线，系统开展了锡铁精矿作用下负载有机硫炭质还原剂热解机理、锡矿相还原、硫化和挥发机理、铁矿相演变规律及其对锡硫化挥发效率的影响机制等科学问题的研究，主要结论如下：1，还原气氛中，锡铁精矿中Fe2O3、Fe3O4矿相可促使负载有机硫炭质还原剂碳组分热解产物固定C、CO和CH4转变为CO2，同时硫组分转变为FeS、H2S、COS和SO2；2，SnO2还原路径主要与焙烧温度有关。729-1313 K温度区间内，SnO2还原路径为：SnO2→金属Sn；1313 -1900 K温度区间内，SnO2还原路径为：SnO2→液态SnO→金属Sn；3，还原性气氛较弱时，SnO2可转化为气态SnO，并气态氧化亚锡中Sn2+可以掺杂、取代Fe3O4中Fe2+形成铁锡尖晶石(FexSn3-xO4，x = 0-1.0)，同时少量气态SnO也可以与Fe3O4发生氧化还原反应，导致Sn4+取代尖晶石结构中Fe3+，抑制锡的硫化挥发。然CO分压过高可促进Fe-Sn合金生成，亦不利于锡的硫化挥发，还原硫化焙烧脱锡最优的热力学区间为FeO (s) + Sn (l)；4，还原硫化焙烧过程中，Fe2O3和Fe3O4矿相易被过还原为金属Fe，继而与SnO2还原产物金属Sn结合形成Fe-Sn合金，对Sn的硫化解离形成限制。负载有机硫炭质还原剂热解过程中释放的气相H2S、SO2和COS可将Fe-Sn合金硫化为SnS，促进锡的解离回收。焙烧温度1273 K，废橡胶添加量为10%，焙烧时间60 min，混合气体（58%N2 +21%CO+21%CO2）流量100 ml/min条件下，焙烧底物中锡和硫的含量分别降至0.020 wt.%和0.022 wt.%，铁的含量提高到72.25 wt.%，实现了锡铁精矿的资源化利用。此研究为矿物中锡、铁矿相高效分离新方法的开发提供了重要的科学参考，并为低品位锡资源中锡的高效提取回收提供了一种新方法。