The harmful trace elements will be released during coal utilization, which can cause environment pollution and further endangering human health, especially for heavy metal elements. Compared to combustion, the release...The harmful trace elements will be released during coal utilization, which can cause environment pollution and further endangering human health, especially for heavy metal elements. Compared to combustion, the release of heavy metal elements during coal pyrolysis process, as a critical initial reaction stage of combustion, has not received sufficient attention. In the present paper, a low rank coal, from Xinjiang province in China, was pyrolyzed in a fixed bed reactor from room temperature, at atmospheric pressure, with the heating rate of 10 °C/min, and the final pyrolysis temperature was from 400 to 800℃ with the interval of 100℃. The volatility of heavy metal elements (including As, Hg, Cd and Pb) during pyrolysis process was investigated. The results showed the volatility of all heavy metal elements increased obviously with increasing temperature, and followed the sequence as Hg > Cd > As > Pb, which was mainly caused by their thermodynamic property and occurrence modes in coal. The occurrence modes of heavy metals were studied by sink-andfloat test and sequential chemical extraction procedure, and it can be found that the heavy metal elements were mainly in the organic and residual states (clay minerals) in the raw coal. And most of the organic heavy metals escaped during the pyrolysis process, the remaining elements were mainly in the residual state, and the elements in Fe-Mn state also tended to remain in the char.展开更多
Na-X zeolites were synthesized by Longkou oil shale ash with the alkaline fusion hydrothermal method.The effects of fusion temperature,ash to NaOH ratio,solid-liquid ratio,crystallization time and crystallization temp...Na-X zeolites were synthesized by Longkou oil shale ash with the alkaline fusion hydrothermal method.The effects of fusion temperature,ash to NaOH ratio,solid-liquid ratio,crystallization time and crystallization temperature on the crystallinity of zeolites were investigated.The synthetic products were characterized by Xray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),29Si nuclear magnetic resonance spectroscopy(29Si NMR)and N2 adsorption-desorption.The results showed that the conditions to synthesize Na-X zeolite were:Longkou oil shale ash to sodium hydroxide ratio 1:1.2 g・g^(-1),fusion temperature 600℃,solid-liquid ratio 1:4 g・mL^(-1),crystallization time 24 h and crystallization temperature 80℃.The zeolite with high crystallinity(91.32%)was synthesized:the product exhibiting octahedral particles observed by SEM,and the calculated Si/Al ratio in Na-X zeolite being 1.23 from^(29)Si MAS NMR spectra,which was consistent with the observation from XRD.展开更多
In this study,the Huadian oil shale(HD-R)and Balikun oil shale(BLK-R)were pyrolyzed in a fixed-bed pyrolyzer at 360–530℃.Based on the migration and conversion of organic carbon,their pyrolysis characteristics were i...In this study,the Huadian oil shale(HD-R)and Balikun oil shale(BLK-R)were pyrolyzed in a fixed-bed pyrolyzer at 360–530℃.Based on the migration and conversion of organic carbon,their pyrolysis characteristics were investigated and compared.The aliphaticity of Huadian kerogen(HD-K)and Balikun kerogen(BLK-K)are 80.53%and 52.83%,respectively.The HD-K contains more C=O,which will render the depolymerization and decomposition of kerogen to occur at low temperatures to produce volatile matters.Thus,the cumulative conversion of the Huadian shale oil is greater than the Balikun shale oil at 390–435℃.The aliphatic carbons of the BLK-K are mainly present as short methylene chains attached to aromatic rings.They will leave the kerogen matrix with the breakage of relatively weaker CeC bonds at β-sites from aromatic rings at medium temperatures.By contrast,aliphatic carbons of the HD-K are dominated by long aliphatic chains.High temperature is necessary to break other stronger CeC to form shale oil and gaseous species,which appears to make the oil accumulation conversion of BLK-R exceed that of HD-R at 450–510℃.展开更多
基金The authors are grateful to the financial support of the National Key Research and Development Program of China (2016YFB0600304)the National Natural Science Foundation of China (No. 51804313).
文摘The harmful trace elements will be released during coal utilization, which can cause environment pollution and further endangering human health, especially for heavy metal elements. Compared to combustion, the release of heavy metal elements during coal pyrolysis process, as a critical initial reaction stage of combustion, has not received sufficient attention. In the present paper, a low rank coal, from Xinjiang province in China, was pyrolyzed in a fixed bed reactor from room temperature, at atmospheric pressure, with the heating rate of 10 °C/min, and the final pyrolysis temperature was from 400 to 800℃ with the interval of 100℃. The volatility of heavy metal elements (including As, Hg, Cd and Pb) during pyrolysis process was investigated. The results showed the volatility of all heavy metal elements increased obviously with increasing temperature, and followed the sequence as Hg > Cd > As > Pb, which was mainly caused by their thermodynamic property and occurrence modes in coal. The occurrence modes of heavy metals were studied by sink-andfloat test and sequential chemical extraction procedure, and it can be found that the heavy metal elements were mainly in the organic and residual states (clay minerals) in the raw coal. And most of the organic heavy metals escaped during the pyrolysis process, the remaining elements were mainly in the residual state, and the elements in Fe-Mn state also tended to remain in the char.
基金the National Basic Research Program of China(973 Program,Grant 2014CB744301).
文摘Na-X zeolites were synthesized by Longkou oil shale ash with the alkaline fusion hydrothermal method.The effects of fusion temperature,ash to NaOH ratio,solid-liquid ratio,crystallization time and crystallization temperature on the crystallinity of zeolites were investigated.The synthetic products were characterized by Xray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),29Si nuclear magnetic resonance spectroscopy(29Si NMR)and N2 adsorption-desorption.The results showed that the conditions to synthesize Na-X zeolite were:Longkou oil shale ash to sodium hydroxide ratio 1:1.2 g・g^(-1),fusion temperature 600℃,solid-liquid ratio 1:4 g・mL^(-1),crystallization time 24 h and crystallization temperature 80℃.The zeolite with high crystallinity(91.32%)was synthesized:the product exhibiting octahedral particles observed by SEM,and the calculated Si/Al ratio in Na-X zeolite being 1.23 from^(29)Si MAS NMR spectra,which was consistent with the observation from XRD.
基金the National Basic Research Program of China(Grant 2014CB744301).
文摘In this study,the Huadian oil shale(HD-R)and Balikun oil shale(BLK-R)were pyrolyzed in a fixed-bed pyrolyzer at 360–530℃.Based on the migration and conversion of organic carbon,their pyrolysis characteristics were investigated and compared.The aliphaticity of Huadian kerogen(HD-K)and Balikun kerogen(BLK-K)are 80.53%and 52.83%,respectively.The HD-K contains more C=O,which will render the depolymerization and decomposition of kerogen to occur at low temperatures to produce volatile matters.Thus,the cumulative conversion of the Huadian shale oil is greater than the Balikun shale oil at 390–435℃.The aliphatic carbons of the BLK-K are mainly present as short methylene chains attached to aromatic rings.They will leave the kerogen matrix with the breakage of relatively weaker CeC bonds at β-sites from aromatic rings at medium temperatures.By contrast,aliphatic carbons of the HD-K are dominated by long aliphatic chains.High temperature is necessary to break other stronger CeC to form shale oil and gaseous species,which appears to make the oil accumulation conversion of BLK-R exceed that of HD-R at 450–510℃.
