Fushun Oil Shale Research Articles

The study of core and particle model of Fushun oil shale based on microwave field

As an unconventional oil and gas resource, oil shale can alleviate the shortage of oil and gas resources. As a new heating process for oil shale retorting and in-situ mining, microwave can effectively exploit and utilize oil shale. In this paper, the Fushun oil shale and particle model under microwave field are studied by means of experiment and numerical simulation. Based on the measurement of the basic physical properties of oil shale, the effects of microwave power and absorbent (semi-coke and graphite) on the pyrolysis of oil shale were investigated. The experimental results show that the heating rate is the fastest when the maximum microwave power is 700 W without adding absorbent or adding the same absorbent. At the same power, the effect of graphite is slightly better than that of semi-coke. In the aspect of numerical simulation, COMSOL simulation software is used to simulate the oil shale core and particles based on the three-dimensional electromagnetic thermal model. The experimental conclusion is verified. At the same time, it is found in the simulation results that microwave heating has better temperature distribution gradient and electric field distribution. Furthermore, the microwave port is extended to the underground for the simulation of microwave in-situ mining. It is found that the reservoir temperature reaches 450 °C after 1000 days of reservoir heating.

Groundwater Environment and Health Risk Assessment in an In Situ Oil Shale Mining Area

To clarify the risk posed to groundwater in oil shale in situ mining areas, we examine five leached pollutants: Fe, Mn, Cr, sulfate, and ammonia nitrogen. Potential groundwater contents of these five pollutants were evaluated using an improved Nemero comprehensive index method and a health risk assessment method. The results show that, compared with the Class III groundwater quality standard (GB/T 14848-2017) used in the People’s Republic of China, average values of Fe, Mn, and sulfate in leaching solution from Fuyu oil shale exceed the standard, while Cr and ammonia nitrogen do not exceed the standard, and the leaching solution is within Class V groundwater quality. The average values of Fe and Mn in the leaching solution from Fushun oil shale exceed the Class III standard, while Cr, sulfate, and ammonia nitrogen values from this oil shale do not exceed the standard, and the leaching solution is Class IV in terms of groundwater quality. The weighting value used in the Nemero assessment method for the heavy metal Cr is the largest as its potential to cause harm to groundwater quality is the largest. The weight value for sulfate is the smallest as the harm degree is the smallest. The chemical carcinogen Cr has the greatest potential impact on human health. The health risk caused by the chemical non-carcinogen Mn is greater than that caused by Fe and ammonia nitrogen. When high pyrolysis temperatures are used, Mn will be released into groundwater in large quantities. Therefore, supervision and control should be strengthened. The results presented here can provide a reference for the comprehensive evaluation of groundwater risks caused by in situ oil shale mining.

Extractable and kerogen-bound hopanoids from typical Eocene oil shales in China

This study conducted a comparative analysis of extractable hopanoid hydrocarbons and those released via stepwise pyrolysis of typical Eocene immature oil shales in China, namely the Huadian, Maoming, and Fushun shales. Both the Huadian and Maoming shales exhibit immature indicators in extractable and kerogen-bound hopanoids (notably, high abundance of C29 to C32 17β,21β-hopanes and unsaturated hopenes). In contrast, the Fushun oil shale's hopanoids from extracts and pyrolyzates suggest a higher maturity level. The absence of neohopenes in the pyrolyzates of the shales underpins that the kerogen-bound hopanoid skeletons resist rearrangement. However, the Huadian oil shale's asymmetric distribution of C29 and C30 hopenes and neohopenes hints at the presence of an additional source. Novel unsaturated hopenes, such as hop-20 (21)-enes, identified in pyrolyzates of the three kerogens at various pyrolysis temperatures, reveal the occurrence of double bonds in kerogen-bound hopanoid skeletons without methyl rearrangements. The absence of hop-20-(21)-ene in extracts suggests that it might act as an intermediate of these novel hopenes during the epimerization of hopanoid skeletons within kerogen. The extractable and pyrolytic hopanoids' stereochemical alignment indicates that epimerization may occur in both ring systems and alkyl side chains of kerogen-bound hopanoid skeletons. Sequential stepwise pyrolysis proves to be a quick screening method for geological hopanoids without causing any significant alteration to the original skeletons even when cracking multiple covalent bonds is necessary.

Influence of original and additive AAEMs on the migration and transformation of N by pyrolysis in Fushun oil shale

Oil shale contains a large amount of nitrogen compounds during pyrolysis, which will lead to a decline in the quality of shale oil and produce a large number of PM2.5 precursors. To study the migration and transformation of N during the pyrolysis, fixed-bed pyrolysis experiments were conducted on oil shale with different pyrolysis temperatures (500 ℃、600 ℃、700 ℃、800 ℃) and residence times (20 min、40 min), meanwhile, the migration and transformation of single AAEMs on the N of oil shale pyrolysis, the acid-wash samples were loaded with the original and higher concentrations of metals (K2CO3, CaCO3, Na2CO3, MgCO3) according to the ICP results and subjected to experiments at 600 °C - 20 min, the obtained products were analyzed by XPS、GC-MS and solution absorption method. The results revealed that higher temperatures promoted the enrichment of nitrogen-containing molecules in tar, and longer residence durations also led to an increase. Some mineral components in oil shale facilitated the conversion of semi-coke nitrogen to oil-phase nitrogen. An elevated loading concentration caused the catalytic cleavage of macromolecular nitrides. With an increase in temperature, NH3 and HCN exhibited two distinct peaks, respectively. AAEMs encouraged the production of NH3 but limited the content of HCN, where Ca played a more important function than K. The N transformation route was identified by contrasting the effects of reaction temperatures、residence times and AAEMs on N distribution.

The non-isothermal thermal decomposition evolution of the Fushun oil shale kerogen based on ReaxFF molecular dynamics simulation

The non-isothermal thermal decomposition evolution of the Fushun oil shale kerogen based on ReaxFF molecular dynamics simulation

Chemical structure characteristics and multidimensional model construction of Fushun oil shale kerogen: An experimental and simulation study

Solid state 13C nuclear magnetic resonance (13C NMR), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) were carried out to characterize the chemical structure characteristics and to establish the average molecular structure of kerogen extracted from Fushun oil shale. NMR predictor was used to calculate the chemical shift of carbon atoms to verify the rationality of the constructed model. And the stability of 3D model was studied by molecular dynamics (MD) simulations. 13C NMR results demonstrate that Fushun kerogen consists of 76.98% of aliphatic structure dominated by long linear methylene and 21.6% of aromatic structure (mainly protonated aromatic carbon). Functional groups observed in 13C NMR spectra were also detected in FT-IR spectra at wavenumber range of 1800-1000 cm−1. XPS analysis indicates that nitrogen-containing groups were pyrrole, pyridine and primary amines, and sulfur existed as sulfoxides, thiophenes and mercaptans. By comparing the calculated 13C NMR and experimental 13C NMR, it was found that the aromatic structure condensed in two aromatic rings and the aliphatic structure without alicyclic and epoxy ether were more rational for the chemical structure model of Fushun kerogen. A new method to evaluate the average methylene chain length was proposed. Finally, a relatively rational 2D molecular structure with a molecular formula of C228H350O10N6S3 was constructed. The most stable 3D periodic structure (20 optimized molecules, 48.44 × 49.63 × 50.28 Å3) with the lowest total potential energy was obtained by MD simulation and density of it was 0.943 g/cm3.

The three-dimensional molecular structure model of Fushun oil shale kerogen, China

Oil shale pyrolysis products mainly derive from the pyrolysis of organic kerogen. In this study, theoretical and experimental data were combined to conceive a reliable three-dimensional (3D) model of kerogen from the Fushun oil shale, China. The fundamental structural information was characterized based on experimental techniques, including 13C nuclear magnetic resonance spectroscopy (13C NMR), elemental analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FTIR), and pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS). Additionally, the molecular model of the two-dimensional structure of the kerogen was also established based on the basic structure and rapid thermal cleavage product information. The obtained formula is C240H322O32N7S5. Twelve isomers were constructed based on the “grid” concept and molecular dynamics methods and were applied to simulate the formed isomers. It has been identified that the number of grids affected the total energy of the kerogen, FS7 being the structure with the lowest total energy from the Fushun kerogen. The density of kerogen is an important index to evaluate the accuracy of the model, and our results indicate that there is a good match between the density calculated by the model and the experimentally obtained density. Also, a favorable relationship exists between the experimental and simulated values of the model covalent bond concentrations which proves the rationality and accuracy of the 3D molecular structure model. By combining theoretical and experimental data, we established a reliable structural model of the Fushun kerogen, which will provide a strong basis for future research on the pyrolysis mechanism of the Fushun oil shale at a molecular level.

Study of the effect of in situ minerals on the pyrolysis of oil shale in Fushun, China.

Herein, the effect of Fushun oil shale minerals on its kerogen has been investigated. The samples were obtained under non-isothermal conditions at different final temperatures. Scanning electron microscope (SEM) analysis revealed that the silicates were layered and the carbonates were tightly bound to each other. The combination of silicates and carbonates led to close combination of minerals and organic matter and the organic matter was contained in the minerals. The Brunner–Emmet–Teller (BET) experiments conclude that during the non-isothermal pyrolysis process, the specific surface area increased, and then, decreased, which proves the adsorption effect of silicates on oil shale pyrolysis products and the adsorption effect of carbonates was weak. The activation energy of four samples was calculated via Flynn–Wall–Ozawa (FWO) and Friedman kinetic analysis under different heating rates in a non-isothermal process, wherein the average activation energy of the sample containing silicate was 177.60 kJ mol−1 at minimum while that of carbonate was 250.45 kJ mol−1 at maximum, which proves that the catalytic promotion effect of silicate was greater than the inhibition effect of carbonate. The pyrolysis products obtained by Flash pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) under isothermal pyrolysis conditions were primarily composed of aliphatic hydrocarbon structures, which had different degrees of impact on the production of heteroatoms. This work provides a reliable theoretical basis for future studies on the influence of minerals on pyrolysis of organic matter in oil shale.

Comparative study on the pyrolysis behavior and pyrolysate characteristics of Fushun oil shale during anhydrous pyrolysis and sub/supercritical water pyrolysis.

Injected steam can be converted to the sub/supercritical state during the in situ exploitation of oil shale. Thus, the pyrolysis behavior and pyrolysate characteristic of Fushun oil shale during anhydrous pyrolysis and sub/supercritical water pyrolysis were fully compared. The results revealed that the discharged oil yields from sub/supercritical water pyrolysis were 5.44 and 14.33 times that from anhydrous pyrolysis at 360 °C and 450 °C, which was due to the extraction and driving effect of sub/supercritical water. Also, sub/supercritical water could facilitate the discharge and migration of shale oil from the pores and channels. The H2 and CO2 yields in sub/supercritical water pyrolysis were higher than that in anhydrous pyrolysis, resulting from the water–gas shift reaction. The component of shale oil was dominated by saturated hydrocarbons in anhydrous pyrolysis, which accounted for 50–65%. In contrast, a large amount of asphaltenes and resins was formed during pyrolysis in sub/supercritical water due to the solvent effect and weak thermal cracking. The shale oil from anhydrous pyrolysis was lighter than that from sub/supercritical water pyrolysis. Sub/supercritical water reduced the geochemical characteristic indices and lowered the hydrocarbon generation potential and maturity of solid residuals, which can be attributed to the fact that more organic matter was depolymerized and released. The pyrolysate characteristic of oil shale in sub/supercritical water pyrolysis was controlled by multiple mechanisms, including solvent and driving effect, chemical hydrogen-donation and acid–base catalysis.

Study on the structure, pyrolysis kinetics, gas release, reaction mechanism, and pathways of Fushun oil shale and kerogen in China

Oil shale is of increasing interest as it is considered as an important alternative to traditional energy sources due to its abundant reserves. In this study, the pyrolysis mechanism of oil shale and kerogen was investigated by structural characterization and pyrolysis experiments. The experiments on the structural properties of the base showed that the minerals of the Fushun oil shale were the main components that influenced the pyrolysis of kerogen. Small differences in activation energy between the two were obtained by thermogravimetry, and the optimum heating rates were different. The gas-phase FTIR spectroscopy results showed that the main volatiles during pyrolysis were C2+ aliphatic hydrocarbons, CO2, CO, CH4, C2H4, and CO and CO bonded substances. The Py-GC/MS results showed that the species and yields of the kerogen and oil shale pyrolysis products from molecular level. Moreover, the reaction pathways for both the pyrolysis mechanism were predicted, which included the aliphatic chain breakage reaction, dehydrogenation to form olefin, and aromatization reaction. Based on these experimental results, this study provides a reliable theoretical basis for the future utilization of Fushun oil shale.

Pyrolytic characteristics of Fushun oil shale and its by-products

Pyrolytic characteristics of Fushun oil shale and its by-products

Experimental Investigation of the Basic Characteristics and Wettability of Oil Shale Dust.

To investigate the influence of basic characteristics of oil shale dust on wet dust removal, oil shales (Longkou oil shales Y1, Y2S2, and Y2S1 and Fushun oil shale) with different oil contents, brown coal (M1), and bituminous coal (M) were selected from a typical mining area in China to test their physiochemical parameters. Their proximate component, chemical structures, surface morphology, and mineral contents were determined. The sedimentation experiments of oil shale dust and coal dust were implemented using three anionic surfactants (AOS, SDS, and SDBS) and a nonionic surfactant (AEO-9), and the wettability of oil shale dust was analyzed and compared with that of coal dust. The experimental results indicate that the moisture content, volatile content, fixed carbon content, and content of oxygen-containing functional groups of oil shale are higher than those of the coal sample; otherwise, contents of ash, SiO2, aliphatic hydrocarbon, and aromatic hydrocarbon are lower. It can be found that oil shale has semiclosed pores, poor connectivity, a small pore size, a large specific surface area, and a rougher surface, which will lead to poorer wettability of oil shale. The wettability of oil shale can be improved by adding surfactants but is still weaker than that of the coal samples. Anionic surfactants are better than nonionic surfactants in improving the wetting performance. Among them, AOS shows strong wetting ability to oil shale dust. The research results of this paper have an important practical significance for analyzing the wettability of oil shale and controlling oil shale dust.

Pyrolysis characteristics of oil shale semi-coke and its extracted bitumen

Fushun oil shale semi-coke and its extracted bitumen were prepared for analyzing their pyrolysis characteristics by TG–DTG, TG–FTIR, and Py–GC/MS. Semi-coke was the residue of oil shale pyrolyzed to 450 °C, and extracted bitumen was the organic matter extracted from semi-coke with [Bmim]Cl/NMP mixed solvents. Gaussian fitting method was used to analyze the proportions of bond cleavage reactions occured during the pyrolysis to 700 °C at a heating rate of 20 °C/min. Results showed that 3–4 kinds of bond cleavages were mainly involved. The outstanding pyrolysis behaviors were contributed by the cleavages of CalCal and weak bonds (including volatilization). The kinetic parameters based on Coats–Redfern method were calculated from the points for each pyrolysis stage and bond cleavage reaction. The evolution processes of typical gaseous products and distributions of flash pyrolysis products were displayed in detail, exhibiting the prominent roles of aliphatic compounds, CH4, and CO2. Moreover, the releases of the typical gaseous products for semi-coke tended to occur at higher temperatures.

Influence of co-processing of coal and oil shale on combustion characteristics, kinetics and ash fusion behaviour

Combustion characteristics and ash fusion behaviours of Qinghai coal (QH) and Fushun oil shale (FS) and their blends were investigated. It was found that ignition index and burnout index of the blends reached maximum for the blend with 10 wt% FS, while its comprehensive combustibility index remained nearly unchanged when compared with the coal sample. With the increase in heating rates, combustion performance of the samples improved significantly. The statistical analysis demonstrated that combustion temperature contributed significantly (about 73% of the impact ratio) to the thermogravimetric mass loss, followed by oil shale blending ratio and heating rate. In addition, there is noticeable deviation between the experimental and theoretical curves of the blends in the temperature range of 410–480 °C, which indicates the existence of synergistic interactions. Moreover, the lowest apparent activation energy, determined using two model-free integral methods, was found to be 64.1 kJ/mol for the blend with 10 wt% FS. In addition, slag formation and mineral transformation of different samples were determined using the thermochemical database package FactSage 6.3. For the blend with 10 wt% of FS, anorthite, hematite, diopside and quartz were found to be the main crystalline phases at high temperatures. It is shown that the addition of FS mitigated the slagging and fouling tendency of the QH coal combustion.

Effect of Double Transition Metal Salt Catalyst on Fushun Oil Shale Pyrolysis.

Shale ash (SA) as the carrier, the ratio of Cu to Ni in the Cu-Ni transition metal salt being, respectively, 1 : 0, 2 : 1, 1 : 1, 1 : 2, 0 : 1, the double transition metal salt catalyst (CumNin/SA) was prepared to explore the effect of such catalysts on the pyrolysis behavior and characteristics of Fushun OS. The research results show that the temperature (Tmax) corresponding to the maximum weight loss rate decreased by 12.9°C, 4.0°C, and 3.6°C; and the apparent activation energy decreased by 35.2%, 33.9%, and 29.6%, respectively, after adding catalysts Cu0Ni1/SA in pyrolysis. The addition of Cu0Ni1/SA and Cu2Ni1/SA further improves the shale oil (SO) yield of 3.5% and 3.1%, respectively. Cu0Ni1/SA produces more aromatic hydrocarbons, which, however, weakens the stability of SO and is of toxicity in use. After analyzing the pyrolysis product—semicoke (SC) and SO—with ATR-FTIR and GC-MS methods, CumNin/SA promotes the secondary cracking and aromatization of OS pyrolysis, increasing the content of the compound of olefins and aromatics in SO, and hastening the decomposition of long-chain aliphatic hydrocarbons to short-chain aliphatic hydrocarbons.

Structural characterization of thermal bitumen extracted from Fushun oil shale semi-coke with ionic liquid/N-methyl pyrrolidone

Thermal bitumen is an organic intermediate during the pyrolysis of oil shale kerogen. In this work, semi-cokes were prepared for obtaining thermal bitumen by pyrolyzing Fushun oil shale to 400–500 °C, followed by extraction with a mixture of an ionic liquid (1-butyl-3-methylimidazolium chloride) and a polar solvent (N-methyl pyrrolidone). The critical thermal bitumen with the highest yield of the 450 °C semi-coke extraction was carefully performed by gas chromatography–mass spectrometry, Fourier transform infrared spectrophotometry, liquid-state 13C nuclear magnetic resonance spectroscopy, and X-ray photoelectron spectroscopy. The thermal bitumen was mainly composed of aliphatic structures, especially methylene chains. The dominant aliphatic hydrocarbons were between C13 and C27, and the alkanes and corresponding alkenes from C14 to C22 were continuously identified in pairs. A small quantity of benzenes and naphthalenes was identified as well as phenols, carboxylic acids, and nitrogen compounds. The oxygen functional groups were mainly carbon and oxygen double bonds, and the nitrogen and sulfur functional groups were characterized as pyrrole and thiophene. Ultimately, a structural formula (C370H570O29N4S) and its atomic distribution were proposed, based on the final analysis of experimental data.

Permeability of Oil Shale Under In Situ Conditions: Fushun Oil Shale (China) Experimental Case Study

Oil shale is a critical strategic energy source with very large reserves, and it is acknowledged as an alternative energy source to crude oil. Oil shale in situ retorting is the only technologically feasible method to achieve large-scale industrial development. In situ permeability is one of the most critical technical parameters for successful implementation of oil shale in situ retorting. In this study, the permeability of Fushun oil shale at different temperatures was investigated using a triaxial permeability testing machine under in situ conditions. The results show that the permeability of the oil shale under three-dimensional stress can be divided clearly into three stages from 20 °C to 600 °C. First, the oil shale remains almost impermeable from 20 °C to 200 °C. Second, in the temperature range from 200 °C to 350 °C, the permeability of the oil shale first increased and then decreased to almost zero at 350 °C owing to the dual constraints of the surrounding stress and additional expansion stress under in situ conditions. Third, from 350 °C to 600 °C, the permeability of the oil shale increased sharply and reached a maximum of 100 × 10−5 μm2 at 600 °C. Thermal cracking and solid organic matter pyrolysis were the main factors controlling the change in oil shale permeability in the test temperature range. The results suggest that the threshold temperature for oil shale permeability change was 350 °C under in situ conditions. In addition, under in situ conditions, the oil shale permeability decreased with increasing pore pressure at different temperatures. This work has direct applications for oil shale in situ large-scale exploitation.

Effect of Shale Ash-Based Catalyst on the Pyrolysis of Fushun Oil Shale

The effect of shale ash (SA)-based catalysts (SA as carriers to support several transition metal salts, such as ZnCl2, NiCl2·6H2O, and CuCl2·2H2O) on oil shale (OS) pyrolysis was studied. Results showed that SA promoted OS pyrolysis, and the optimum weight ratio of OS:SA was found to be 2:1. The SA-supported transition metal salt catalyst promoted the OS pyrolysis, and the catalytic effect increased with increasing load of the transition metal salt within 0.1–3.0 wt%. The transition metal salts loaded on the SA not only promoted OS pyrolysis and reduced the activation energy required but also changed the yield of pyrolysis products (reduced shale oil and semi-coke yields and increased gas and loss yield). SA-supported 3 wt% CuCl2·2H2O catalyst not only exhibited the highest ability to reduce the activation energy in OS pyrolysis (32.84 kJ/mol) but also improved the gas and loss yield, which was 4.4% higher than the uncatalyzed reaction. The supporting transition metal salts on the SA also increased the content of short-chain hydrocarbons in aliphatic hydrocarbons in shale oil and catalyzed the aromatization of aliphatic hydrocarbons to form aromatic hydrocarbons. The catalytic activity of the transition metal salt on the SA-based catalyst for OS pyrolysis decreased in the order of CuCl2·2H2O > NiCl2·6H2O > ZnCl2.

Evolution of Pore Connectivity in the Fushun Oil Shale by Low-Field Nuclear Magnetic Resonance Spectroscopy

Evolution of Pore Connectivity in the Fushun Oil Shale by Low-Field Nuclear Magnetic Resonance Spectroscopy

Effect of pyrolysis on oil shale using superheated steam: A case study on the Fushun oil shale, China

In the in situ pyrolysis of oil shale (OS) with superheated steam (SS), the internal pores and fractures of the OS act as channels for the migration of steam and locations for heat exchange. After a laboratory test of the in situ pyrolysis of OS with SS, 30 OS samples located in different zones between the injection and production wells were collected. The main parameters of pore and fracture structures inside OS samples were investigated. The results first showed that in each position along the bedding planes, the effective porosity was greater than 19.41%. The internal OS fractures were mainly dominated by microfractures, with lengths between 100 µm and 500 µm. The average pore diameter of the orebody was between 52.77 nm and 69.01 nm, and the aperture of the microfractures was between 59.31 µm and 68.85 µm. Then, in the position near the roof bedrock perpendicular to the bedding directions (BD), the effective porosity and pore diameter of the orebody were small. Only a few cracks were observed in the rock mass, and the distribution of the pore groups in the 3D space was fragmented and had poor connectivity. Finally, in the whole studied OS orebody, the proportion of ore layers with permeabilities ranging from 1.8 × 10−17 m2 to 3.0 × 10−17 m2 was 63.51%, which proved that the connectivity of the pores and fractures in the large area was superior to other areas.