Jingru Bai

Geochemical occurrences of rare earth elements in oil shale from Huadian

Abstract Distribution characteristics and occurrence modes of rare earth elements (REE) in oil shale from Huadian, Jilin province were determined by sequential chemical extraction process. Content of REE were determined by inductively coupled plasma-mass spectrometry (ICP-MS). The results show that the enrichment of light rare earth elements (LREE) in Huadian oil shale is richer than that of heavy rare earth elements (HREE), relative to those in coals from China. The REE in oil shale are positively correlated with terrigenous clastic rock, and the supply of terrigenous materials is relatively stable. The fractionation between LREE and HREE is clear and shows a moderate LREE-enriched pattern. The occurrence of rare earth elements are mainly in minerals fractions. The enrichment of sulfide fractions inclines to LREE; besides, carbonate fractions, ferromanganese oxyhydroxides bound fraction and aluminosilicate bound fraction are more inclined to enrich HREE. Moreover, here is lack of the contents of rare earth elements in exchangeable and organic matter fractions. Additionally, the fractionation effects of rare REEs in different substances have some differences under various sedimentary environments.

Study on The Kinetic Characteristics in Pyrolysis Process of Huadian Oil Shales by Isoconversional Method

Thermal analysis is increasingly used to obtain kinetic datum relating to samples decomposition. The popular model-fitting approach gives excellent fits for nonisothermal data but yields highly uncertain values of Arrhenius parameters. On the other hand, the model-free approach represented by the isoconversional method is recommended as a trustworthy way of obtaining reliable information from nonisothermal. So, in this research the thermal decomposition of Huadian oil shale samples was studied on the thermogravimetric analysis (TG, DTG), at heating rates of 10,20,40,100 °C/min under the nitrogen environment. The apparent activation energy in pyrolysis reactions of two kinds of oil shale samples has been analyzed by the isoconversional method of Friedman. The Sestak’s complex mechanism was used to fit liner for the pyrolysis reaction mechanism of oil shales, and the decomposition mechanism and frequency factor (A) were obtained. The results show that the activation energy is not a constant throughout the reaction process. But in the range of 0.1–0.9 for the conversion rate, the activation energy changes slightly. Oil shale pyrolytic mechanisms are complex and mainly attribute to the nuclear mechanism. The reason was discussed.

Volatile Characteristic of Trace Elements During Microwave Pyrolysis of Oil Shale

Oil shale is abundant in the world. Today, the industry of oil shale retorting for producing shale oil is developing owing to high price of oil in the world. In order to study migratory behavior of trace elements in oil shale at microwave pyrolysis, tests were performed in laboratory with oil shale of the Huadian deposit of China at different powers from 400 to 700 W. The trace elements As, Cd, Hg, Mo, Pb, Se, Cr, Cu, Ni, V, Zn, Ba, Co, Mn present in oil shale and shale char were determined by the inductively coupled plasma-mass spectrometry (ICP-MS). By comparing the content of trace elements in oil shale and shale char, distribution characteristics of trace elements at retorting were studied. The overall trends of volatile ratio of trace elements are ascending with higher microwave power and higher than the conventional pyrolysis. The differences in the volatile ratio indicate that the trace elements investigated are bound with the oil shale kerogen and its mineral matter in different manner. So Float-sink experiments (FSE) were performed on oil shale. Huadian oil shale has more included mineral. The volatilization of organic matter is not the main reason for the volatilization of trace elements in oil shale. The trace elements combined with the mineral elements may be also certain volatility.

Study on the Basic Properties of Indonesian Oil Sands

The basic properties of three Indonesian oil sands have been investigated. The results show that since the high content of volatile, heating value and oil yield, Indonesian oil sands could be combusted for power generation and retorting for oil refining. Moreover, oil sand ash with the low content of fixed carbon and high content of CaO, could not only be used as solid heat carrier during retorting, but also comprehensively used as construction material. Based on the thermogravimeric analysis (TGA), pyrolysis and combustion behaviors have been identified. As for pyrolysis, 350–520°C could be regarded as the major oil-producing region, the apparent activation energy E is not a constant obtained by distributed activation energy model (DAEM). For combustion, 620–800°C is the high-temperature oxidation (HTO) stage. TG-DTG extrapolation method was applied to determine the combustion characteristics parameters such as ignition temperature, burn-out temperature, combustion stability and combustion reactivity, and finally gave a comparison with those of oil shale and coal.

Study on Geochemical Occurrences of REE in Wangqing Oil Shale

Sequential chemical extraction experiment (SCEE) and Float- sink experiment (FSE) have been employed on oil shale research from Wangqing, Jilin province China, in order to determine the binding forms of rare earth elements (REE) in oil shale. The REE contents were determined by the inductively coupled plasma-mass spectrometry (ICP-MS). Wangqing oil shale was screened into specific gravity density level: 2.4g/cm3. The mode of occurrences of rare earth elements in Wangqing oil shale was studied by six-step SCEE. FSE results show that REEs in Wangqing oil shale exist mainly in inorganic minerals and more in excluded mineral, while SCEE results show that REEs of Wangqing oil shale is primarily occurred in minerals, including carbonate, Fe-Mn oxide, sulfide, and Si-minerals. FSE and SCEE results fully illustrate excluded mineral is mainly mode of occurrence of REEs in Wangqing oil shale, whereas inorganic minerals and organic matter is not that. The REE distribution pattern curves of FSE density and SCEE fraction products are similar with that of raw oil shale. The REE in different densities products has a close connection with terrigenous clastic rock, and the supply of terrestrial material is stable.

Study on Trace and Rare Earth Elements in Indonesian Oil Sands

Major, trace elements and rare earth and mineral composition of the oil sand samples (ST1, ST2, ST3) and the oil sand retorting residue (semi-coke: SC1, SC2, SC3) from Indonesian were determined by XFS, ICP-MS and XRD methods. The trace elements content in oil sand is pretty much the same thing in Earth’s Clarke value. The trace element is abundantly in earth’s Clarke, in oil sand yet, for Ti, Mn, Ba, Sr, but these elements are lower enrichment. However, the Cr (EF = 16.8) and Mo (EF = 11.8) are “enrichment” in ST1; the Ni (EF =10.5), Se (EF = 17.5), Sr (EF = 28.7), Mo (EF = 106.5), Sc (EF = 12.8) and U (EF = 43.2) are “enrichment” in ST2; the Se (EF = 12.6), Sr (EF = 18.4), Mo (EF = 47.5), and U (EF = 27.8) are “enrichment” in ST3. Calculations show that trace elements in sime-coke have lower evaporation rate during Fischer Assay. Trace elements in raw oil sand are so stable that trace elements can’t move easily to other pyrolysis product but enrich to sime-coke. After retorting, more elements are EF > 10, such as B, V, Ni, As, Se, Sr, Mo, Hg, Cs and U. It is essential to take the pollution produced by trace elements in sime-coke during the sime-coke utilization into consideration. The REEs content had a high correlation with the ash in oil sand. The REE is closely related to terrigenous elastic rocks.

Kinetics and Thermodynamics of Lead(II) and Copper(II) Adsorption onto Oil Shale Fly Ash

The kinetics and thermodynamics characteristics of Pb(II) and Cu(II) adsorption onto fly ash of a oil shale-fired power plant was investigated by using batch adsorption method. The results showed that Langmuir and Freundlich adsorption isotherms were applicable to the adsorption process, while Freundlich equation is more applicable. The mechanistic steps of the adsorption process was studied through data fitting of the experimental data using the equation of Lagergren pseudo-first-order kinetics, the pseudo-second-order kinetics, and the intra-particle diffusion model. All the three equations were found applicable in initial stage of this study, and the absorptions of Pb(II) and Cu(II) onto fly ash from oil shale-fired CFB was in accordance of the pseudo-2nd-order reaction kinetics. The absorption characteristics of metal ions on oil shale fly ash were controlled by both film diffusion and particle diffusion. Thermodynamic analysis showed that the processes of oil shale fly ash adsorption Pb(II) and Cu(II) are endothermic reaction and a spontaneous process.

Study on Thermal Kinetic Mechanism of Oil Shale

Thermogravimetric experiments were performed on Pyris-1 TGA thermal analyzer, and pyrolysis curves of four oil shale samples at different heating rates were obtained. According to Maleks method, the kinetic mechanism function of sample was determined by using the standard curves and experimental curves of y(Â?)-Â?. The influences of heating rates and species of oil shale samples on the kinetic mechanism function were analyzed. The results showed that, at the different heating rates, the heat transfer rates, temperature gradient and the chemical reactions in the interior of oil shale samples are varied, and then the kinetic mechanism function of sample is changed; The kinetic mechanism functions are not unique at the special heating rate for a single sample, which depend on the conversion rate Â?: When a Â? is less than 0.5, the weight loss during pyrolysis process, has been attributed to the loss of moisture, interlayer water from clay minerals and thermal decomposition of minerals; When Â? equals to 0.5 or so, the weight loss is due to cracking of clay minerals; When Â? is greater than 0.5, the decomposition of carbonate minerals (such as calcite, dolomite, ankerite and other carbonates). When the species of samples are different, chemical structure and the physical characteristics (such as heat transfer coefficient, voidage, specific heat capacity) are various, kinetic mechanism functions are also different, the serial numbers of kinetic mechanism functions are advanced with Â? increasing for a special sample.

Kinetics and Thermodynamics of Cadmium(II) and Zinc(II) Adsorption onto Oil shale fly ash

The kinetics and thermodynamics characteristics of Cd(II) and Zn(II) adsorption onto fly ash of a oil shale-fired power plant was investigated by using batch adsorption method. The results showed that Langmuir and Freundlich adsorption isotherms were applicable to the adsorption process, while Freundlich equation is more applicable. The mechanistic steps of the adsorption process was studied through data fitting of the experimental data using the equation of Lagergren pseudo-firstorder kinetics, the pseudo-second-order kinetics, and the intraparticle diffusion model. All the three equations were found applicable in initial stage of this study, and the absorptions of Cd(II) and Zn(II) onto fly ash from oil shale-fired CFB was in accordance of the pseudo-2nd-order reaction kinetics. The absorption characteristics of metal ions on oil shale fly ash were controlled by both film diffusion and particle diffusion. Thermodynamic analysis showed that the processes of oil shale fly ash adsorption Cd(II) and Zn(II) are endothermic reaction, and it is a spontaneous process at higher temperature.

Combustion Characteristics studies of oil shale de-ash-like

Oil shale from the 4th layers of Dachengzi mines in Huadian was treated by the acid-type chemical solution process, and the experiment was optimized by the orthogonal method with three factors and three levels. Combustion characteristics of oil shale de-ash-like and the effect of ash content and temperature rising rate on combustion characteristics was investigated by thermogravimetric analysis method. Result and conclusion: the ash content in the treated oil shale is significantly reduced to 4.13%, the volatile content in the treated oil shale is reduced, and the fixed carbon content in the treated oil shale is increased largely from 5.31% to 67.89%. The thermogravimetric analysis shows that with the decrease of ash in oil shale de-ash-like, diffusion resistance of the oxidation medium spreading to combustible ash layer is greatly reduced, which is more conducive to burning, energy consumption of burning is reduced and its effect on ignition and burnout is also reduced to minimum. Under the same final temperature, the burnout degree of oil shale after removing mineral falls with temperature rising rates. Finally, combustion kinetic parameters of oil shale de-ash-like were calculated by the integral method (Coats and Redfern method).