铬渣的热解无害化处理

Study on the remediation of chromite ore processing residue by pyrolysis process

采用热解工艺无害化处理铬渣,探讨了稻秆在铬渣无害化处理中的作用。研究了热解温度、稻秆与铬渣质量比、铬渣粒径及保温时间对铬渣热解无害化处理的影响,并分析了热解前后热解产物中铬元素形态的变化。结果表明,热解工艺能有效地将铬渣中Cr(Ⅵ)还原,稻秆热解过程中产生的气相挥发分对Cr(Ⅵ)的还原起核心作用。较为适宜的热解条件:热解温度为400℃,稻秆与铬渣质量比为0.10,铬渣粒径<2000μm,保温时间为10min。在该热解条件处理下,热解产物中的Cr(Ⅵ)质量浓度为121mg/kg,低于热解前铬渣中的Cr(Ⅵ)(3400mg/kg)。热解后,可交换态及碳酸盐结合态铬含量降低,大部分铬转化成了稳定的有机结合态和残渣态,极大地降低了铬渣的危害。

The present work developed a novel technique to treat chromite ore processing residue （COPR）. In this process, the COPR was mixed with rice straw and then pyrolyzed at reasonable high temperature. Process variables, such as the mass ratio of rice straw/COPR, heating temperature, particle size and holding time, were systematically analyzed, and their influences on the Cr（ Ⅵ ） reduction and chromium speciation in COPR were investigated. The results showed that the process could effectively reduce Cr（Ⅵ ）. The optimum condition was.. pyrolysis temperature 400℃, mass ratio of rice straw/COPR 0.10, particle size〈2 000μm, and holding time 10 min. In this condition, only 121 mg/kg of Cr（ Ⅵ ） was left, much less than 3 400 mg/kg of untreated COPR. The study proved that the gaseous organic fraction generated during pyrolysis of rice straw was beneficial to Cr（ Ⅵ ） reduction. The speciation analysis showed that chromium in the pyrolyzed residue was quite stable and much less reactive.