The carbonation and microstructure characteristics of pellets containing ferrous dusts were investigated during carbonation consolidation at differem reaction temperatures and CO2 partial pressures. The results indica...The carbonation and microstructure characteristics of pellets containing ferrous dusts were investigated during carbonation consolidation at differem reaction temperatures and CO2 partial pressures. The results indicated that green pellets had loose and network supporting structure with initial strength, and large cracks and pores existed in the pellets. The carbonation reaction was controlled by interracial chemical reaction at the initial fast stage, which limited diffusion and thus caused the reaction rate to decrease. With increasing reaction temperature and CO2 partial pressure, the conversion rates of CaO and the number of microcrystalline CaCO3 particles increased, and the volume expansion of CaCO3 led to a decrease in the open porosity, average pore size and specific surface area of the pellets. Micro pores were occluded, and the number of smaller pores （diameter less than 50 nm） increased, thereby resulting in the more compact and uniform structure of carbonated pellets. Simuhaneously, the dense structure prevented CO2 diffusion into the product layer, affecting the increase in carbonation conversion rate.展开更多
目的基于中国有色金属矿山开采企业探讨矽尘暴露致矽肺的职业健康风险水平。方法于2019年6月至2020年7月,采用典型抽样方法选取七省(自治区)44家有色金属矿山开采企业,最终纳入37家,其中36家(97.30%)属井下开采。通过开展现场职业卫生调...目的基于中国有色金属矿山开采企业探讨矽尘暴露致矽肺的职业健康风险水平。方法于2019年6月至2020年7月,采用典型抽样方法选取七省(自治区)44家有色金属矿山开采企业,最终纳入37家,其中36家(97.30%)属井下开采。通过开展现场职业卫生调查,以及主要矽尘作业岗位现场检测,收集企业基本信息及其关键岗位的矽尘暴露资料。采用改良的国际采矿和金属委员会(International Council on Mining and Mentals,ICMM)风险评级表法,以及职业危害风险指数法(INDEX法)职业健康风险评估模型,从总粉尘和呼吸性粉尘两方面分别分析有色金属矿山矽尘暴露致矽肺的职业健康风险水平。采用二次加权Kappa检验分析两种风险评估方法的一致性。结果中型企业[64.69%(40.38%,73.41%)]、银矿[84.69%(63.38%,86.06%)]和锑矿(72.22%)开采企业工人矽尘暴露率较高(以四分位数表示)。职业卫生学检测结果(以四分位数表示)显示:(1)降尘样本游离二氧化硅含量为21.18%(17.03%,30.47%);(2)总粉尘浓度为1.60(0.86,2.46)mg/m^(3),超出我国8小时时间加权平均容许浓度(简称超标)样本数占比为64.47%;(3)呼吸性粉尘浓度为0.68(0.30,1.18)mg/m^(3),超标样本数占比50.00%;(4)中型企业以及凿岩工和破碎工的矽尘暴露水平较高。矽尘暴露致矽肺的职业健康风险评估结果显示:(1)整体职业健康风险水平为中等:总粉尘方面ICMM风险评级表法和INDEX法的综合评估结果分别为高和中等风险(S_(weighted)分别为3.52和2.79),呼吸性粉尘方面则均为中等风险(S_(weighted)分别为2.78和2.35);(2)中型企业风险水平高于其他企业。整体上ICMM风险评级表法和INDEX法在总粉尘或呼吸性粉尘方面均具有较强的一致性(Kappa≥0.600)。结论七省有色金属矿山矽尘暴露致矽肺的职业健康风险等级为中等,其中尤以中型开采企业,以及凿岩工和破碎工的风险水平较高。展开更多
A thermodynamic analysis on the acid leaching process of germanium oxide dust and discussion on the behaviors of main substances of the dust in the leaching process were carried out. The effects of temperature, acid c...A thermodynamic analysis on the acid leaching process of germanium oxide dust and discussion on the behaviors of main substances of the dust in the leaching process were carried out. The effects of temperature, acid concentration, leaching time and stirring speed on the leaching rate of germanium were investigated. Based on the characteristic of the dust, the kinetics and reactive mechanism of acid leaching were studied. The results show that the leaching of the dust by acid belonged to ＂the unreacted core shrinking model＂ of producing solid outgrowth layer. The chemical reaction was controlled by inner diffusion process. The apparent activation energy of leaching process was 12.60 kJ/mol. The leaching reaction of germanium was determined to be mainly second order reaction. The optimum conditions were the reaction temperature of 363 K, the leaching time of 2.5 h, the stirring speed of 120 r/min, the solid-to-liquid ratio of 1/8 and the acid concentration of 120 g/L. Under these conditions, the leaching rate of germanium can come up to more than 87%.展开更多
基金Sponsored by National Natural Science Foundation of China(51074061)Natural Science Foundation of Hebei Province of China(E2011209039)
文摘The carbonation and microstructure characteristics of pellets containing ferrous dusts were investigated during carbonation consolidation at differem reaction temperatures and CO2 partial pressures. The results indicated that green pellets had loose and network supporting structure with initial strength, and large cracks and pores existed in the pellets. The carbonation reaction was controlled by interracial chemical reaction at the initial fast stage, which limited diffusion and thus caused the reaction rate to decrease. With increasing reaction temperature and CO2 partial pressure, the conversion rates of CaO and the number of microcrystalline CaCO3 particles increased, and the volume expansion of CaCO3 led to a decrease in the open porosity, average pore size and specific surface area of the pellets. Micro pores were occluded, and the number of smaller pores （diameter less than 50 nm） increased, thereby resulting in the more compact and uniform structure of carbonated pellets. Simuhaneously, the dense structure prevented CO2 diffusion into the product layer, affecting the increase in carbonation conversion rate.
文摘目的基于中国有色金属矿山开采企业探讨矽尘暴露致矽肺的职业健康风险水平。方法于2019年6月至2020年7月,采用典型抽样方法选取七省(自治区)44家有色金属矿山开采企业,最终纳入37家,其中36家(97.30%)属井下开采。通过开展现场职业卫生调查,以及主要矽尘作业岗位现场检测,收集企业基本信息及其关键岗位的矽尘暴露资料。采用改良的国际采矿和金属委员会(International Council on Mining and Mentals,ICMM)风险评级表法,以及职业危害风险指数法(INDEX法)职业健康风险评估模型,从总粉尘和呼吸性粉尘两方面分别分析有色金属矿山矽尘暴露致矽肺的职业健康风险水平。采用二次加权Kappa检验分析两种风险评估方法的一致性。结果中型企业[64.69%(40.38%,73.41%)]、银矿[84.69%(63.38%,86.06%)]和锑矿(72.22%)开采企业工人矽尘暴露率较高(以四分位数表示)。职业卫生学检测结果(以四分位数表示)显示:(1)降尘样本游离二氧化硅含量为21.18%(17.03%,30.47%);(2)总粉尘浓度为1.60(0.86,2.46)mg/m^(3),超出我国8小时时间加权平均容许浓度(简称超标)样本数占比为64.47%;(3)呼吸性粉尘浓度为0.68(0.30,1.18)mg/m^(3),超标样本数占比50.00%;(4)中型企业以及凿岩工和破碎工的矽尘暴露水平较高。矽尘暴露致矽肺的职业健康风险评估结果显示:(1)整体职业健康风险水平为中等:总粉尘方面ICMM风险评级表法和INDEX法的综合评估结果分别为高和中等风险(S_(weighted)分别为3.52和2.79),呼吸性粉尘方面则均为中等风险(S_(weighted)分别为2.78和2.35);(2)中型企业风险水平高于其他企业。整体上ICMM风险评级表法和INDEX法在总粉尘或呼吸性粉尘方面均具有较强的一致性(Kappa≥0.600)。结论七省有色金属矿山矽尘暴露致矽肺的职业健康风险等级为中等,其中尤以中型开采企业,以及凿岩工和破碎工的风险水平较高。
基金financially supported by the Guizhou Prov-ince Nomarch Fund for Excellence Educationists, Scientists, and Technicians (No. 2005-363)the Natural Science Fund of Guizhou Provincial Education Department of China (No. 2007-078)
文摘A thermodynamic analysis on the acid leaching process of germanium oxide dust and discussion on the behaviors of main substances of the dust in the leaching process were carried out. The effects of temperature, acid concentration, leaching time and stirring speed on the leaching rate of germanium were investigated. Based on the characteristic of the dust, the kinetics and reactive mechanism of acid leaching were studied. The results show that the leaching of the dust by acid belonged to ＂the unreacted core shrinking model＂ of producing solid outgrowth layer. The chemical reaction was controlled by inner diffusion process. The apparent activation energy of leaching process was 12.60 kJ/mol. The leaching reaction of germanium was determined to be mainly second order reaction. The optimum conditions were the reaction temperature of 363 K, the leaching time of 2.5 h, the stirring speed of 120 r/min, the solid-to-liquid ratio of 1/8 and the acid concentration of 120 g/L. Under these conditions, the leaching rate of germanium can come up to more than 87%.
