| Yongzhou in Hunan is the main distribution area and production region of manganese with abundant reserves of manganese ore resources.However,a large number of manganese ore could not meet the reprocessed standard because of the low grade and the high content of impurity,which were stacked on the spot or stockpiled in tailings dam without any disposal,leading to severe waste of manganese resources and serious pollution to the ecological environment.Therefore,it is of great significance to study on the comprehensive utilization of manganese tailings.Regarding the issue above,Lingling district in Yongzhou was regarded as the research area.The resource-recovery,minimization and high-valued of manganese tailings resources was achieved by magnetic separation,curing agent preparation and sludge curing.The main research work and the results are as follows :Self-developed high gradient permanent magnetic roller of horizontal excitation of high gradient with magnetic field strength of 1433.12kA/m was applied in wet and dry magnetic separation of low-grade rhodochrosite and pyrolusite.Under optimal conditions,the manganese grade of low-grade rhodochrosite tailings could reach 19% with manganese recovery of 85%,higher than that of traditional vertical excitation magnetic roller by 7% and 20%,respectively.However,wet and dry magnetic separation of low grade pyrolusite was ineffective for manganese grade increasing by only 4~5%,unable to meet the reprocessed standard.The orthogonal experiment and the progressive superposition test were adopted to selecting the ratio of the hydration reaction compound additives and the early-strength compound additives.The results showed that the four kinds of additives have a role in the potential hydration reaction characteristics.When the two kinds of manganese tailings were mixed by the weight of 1:1,the optimum compressive strength,softening coefficient and porosity were achieved with the optical additives ratio.It was found that the main hydration products of the curing agent were AFt and C-S-H by XRD,SEM and DSC and so on.With the hydration process and hydration period,the hydration products increased and closely intertwined with each other.The internal gap was obviously reduced and the structure was more dense.The compressive strength and softening coefficient was improved and the porosity decreased.The curing agent was applied to curing the dewatered sludge from a sewage treatment plant in Wuhan,then curing dewatered sludge from a sewage treatment plant in Yichang,Hubei Province by the in-situ curing and stabilization treatment.The results showed that the cured sludge could meet the standards of sludge landfill.The compatibilization ratio,water resistance and heavy metal leaching characteristics were better than P.O425 cement.It could be seen from SEM that the hydration products in the solidified sludge were mainly AFt and C-S-H.Network structure was formed by the cross-combination of AFt and C-S-H.The gap of sludge was filled by the sludge particles and unreacted manganese tailings as the fine aggregate and the loose structure of sludge was changed.Compact structure was formed in the solidified sludge,improving the strength,water-resistance and leaching characteristics.Each ton of curing agent of low-grade manganese tailings slag could save ?180 yuan comparing with P.O425 cement through the cost accounting,so the curing agent was of great engineering application prospects. |
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