为实现钢铁行业的绿色循环发展,钢铁厂对含锌粉尘和含铬废水的处置利用均应满足环保和资源高效利用等要求。以某钢铁企业的含锌粉尘和含铬尘泥2种固废为例进行碳热还原协同处置研究,采用FactSage热力学软件平衡计算,分析碳热还原过程中的潜在反应和气-液-固相变化;通过模拟转底炉工艺,在实验室进行碳热还原试验,研究不同原料配比和还原温度对碳热还原效果的影响规律,采用XRD和SEM-EDS对反应后金属化球团的物相组成及形貌进行研究;综合热力学分析与试验研究阐明含锌粉尘协同处置含铬尘泥的碳热还原机理。研究结果表明,铁酸锌和铬铁矿可以有效分解为铁氧化物和铬氧化物,随着温度升高,铁氧化物的还原过程遵循逐级还原规律,最终被还原为金属铁;相较于铁氧化物,铬氧化物在更高温度下还原为金属铬。试验结果与热力学计算趋势一致,控制碳热还原时间为60 min,含铬尘泥和含锌粉尘干基质量比为1∶4,还原温度为1 300 ℃,能够达到较佳的还原效果。采用多种固废协同处置方式,不仅可以解决粉尘大量堆积的问题,而且能够提取含锌粉尘和含铬尘泥中有价金属元素,制备成金属化球团;该方法也可为含铬废水无害化处置提供新途径,实现资源化综合利用,提高企业经济效益。
Abstract
In order to realize the green and circular development of steel industry,the disposal and utilization of zinc-bearing dust and chromium-containing sludge in steel plants should meet the requirements of environmental protection and efficient use of resources. Firstly,taking the zinc-bearing dust and chromium-containing sludge of a steel plant as an example to study the co-processing of carbothermic reduction,the potential reactions occurred in the process and variations of gas-liquid-solid were calculated using the Equilib module of FactSage software. Secondly,the effects of reaction temperature and ratio of zinc-bearing dust and chromium-containing sludge on carbothermic reduction were studied by laboratory experiment for simulating the rotary hearth furnace,and XRD and SEM-EDS methods were used to study the phase composition and morphology of metalized pellets after the reaction. Finally,combined with thermodynamic analysis and experimental results,the reaction mechanism of carbothermic reduction was clarified. The results show that ZnFe2O4and FeCr2O4 can effectively decompose into iron oxide and chromium oxide. As the temperature rising,the iron oxide is reduced to metallic iron and the reduction process follows the law of stepwise reduction. The chromium oxide can be reduced to metallic chromium at a higher temperature compared to iron oxide,and the experimental results are consistent with the thermodynamic calculation trend. When the carbon-containing pellets mixed at a ratio of 1∶4 are roasted at 1 300 ℃ for 60 minutes,the optimum reduction of carbon-containing pellets can be reached. The use of multiple solid waste co-processing methods can not only solve the problem of large amounts of dust accumulation,but also extract valuable metal elements from zinc-bearing dust and chromium-containing sludge to prepare metalized pellets. The method can also provide new ways for the harmless disposal of chromium-containing wastewater,realize comprehensive utilization of resources, and improve the economic benefits of enterprises.
关键词
含锌粉尘 /
含铬尘泥 /
协同处置 /
碳热还原 /
热力学
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Key words
zinc-bearing dust /
chromium-containing sludge /
co-processing /
carbothermic reduction /
thermodynamics
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脚注
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基金
国家重点研发计划资助项目(2019YFC1905702);江苏省高校自然科学基金面上项目(20KJD450001)
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