钙质添加剂作用下废阴极炭还原红土镍矿脱毒机理研究

Study on detoxification mechanism of laterite nickel ore reducing by spent cathode carbon together with calcareous additives

废阴极炭是铝电解工业生产过程中产生的固体废弃物,数量庞大,目前主要处理方法是堆存。废阴极炭成分主要是碳(60%~70%),还含有部分Na_(3) AlF_(6)、NaF、CaF_(2)及NaCN等,其中的氰化物和氟化物会对环境造成严重危害,属于危险废弃物。现已有利用废阴极炭替代碳质还原剂进行炼铁的研究,用来还原红土镍矿的相关研究还没有发现。本文以云南元江红土镍矿为原料,废阴极炭为还原剂,CaCO_(3)为添加剂,对废阴极炭还原红土镍矿的还原效果及固氟效果进行试验研究。试验结果表明:在废阴极炭的添加量14%、还原温度1250℃、还原时间75 min、CaCO_(3)添加量8%的较佳条件下,还原焙烧产物镍和铁品位分别为5.82%和66.23%,镍回收率为94.04%;固氟率为94.9%,此时毒性浸出溶液中F-浓度为30 mg·L^(-1),远小于100 mg·L^(-1)的排放要求;还原焙烧条件下,废阴极炭中的CN-生成CO_(2)和N_(2),F-以CaF_(2)形式留在焙烧矿中,且可作为助熔剂降低镍铁合金熔点,有利于后期焙烧矿的处理。本文研究为废阴极炭的无害化处理提供了一个新思路。

The spent cathode carbon is a large amount of solid waste produced in the industrial production process of aluminum electrolysis.At present,the main treatment method is stockpiling.The spent cathode carbon is mainly composed of carbon(60%~70%),and also contains some Na_(3) AlF_(6),NaF,CaF_(2)and NaCN.The cyanide and fluoride in the spent cathode carbon will cause serious harm to the environment and are hazardous wastes.At present,there are studies on the use of spent cathode carbon instead of carbonaceous reducing agent for ironmaking,and the related research on the reduction of laterite nickel ore has not been found.In this paper,Yunnan Yuanjiang laterite nickel ore was used as raw material,spent cathode carbon was used as reducing agent,and CaCO_(3)was used as additive to study the reduction effect and fluorine fixation effect of spent cathode carbon reduction laterite nickel ore.The results show that under the optimum conditions of spent cathode carbon addition of 14%,reduction temperature of 1250℃,reduction time of 75 min and CaCO_(3)addition of 8%,the nickel and iron grades of the reduction roasting product are 5.82%and 66.23%,respectively,and the nickel recovery rate is 94.04%.The fluorine fixation rate was 94.9%,and the concentration of F-in the toxic leaching solution was 30 mg·L^(-1),which was far less than the emission requirement of 100 mg·L^(-1).Under the condition of reduction roasting,CN-in waste cathode carbon generates CO_(2)and N_(2),F-remains in the form of CaF_(2)in the roasted ore,and can be used as a flux to reduce the melting point of ferronickel alloy,which is beneficial to the treatment of roasted ore in the later stage.This study provides a new idea for the harmless treatment of spent cathode carbon.