Search

Funding Information: This work was supported by the National Key R&D Program of China (No. 2019YFA0705502 , 2019YFA0705501 ), the Young and Middle-aged Excellent Team Project for Scientific and Technological Innovation of Jilin Province , China, the National Natural Science Foundation of China ( 42202345 ), and the National Natural Science Foundation of China (Grant No. 41972324 , 52074212 ). Publisher Copyright: © 2022 Elsevier Ltd In this study, a temperature optimization strategy for the Huadian oil shale autothermal pyrolysis in-situ conversion process (ATS) was first proposed by systematically investigating the reaction characteristics of various semi-cokes. As the pyrolysis temperature rised, the semi-coke's calorific value was found to undergo three different stages of increasing, decreasing, and flattening, peaking at around 330 °C. Additionally, the semi-cokes formed at different temperatures exhibited similar combustion characteristics, including combustion activation energy, combustion characteristic parameters, and product release characteristics. Due to the serious pore blockage caused by the substantial generation and the ignition coking of the bitumen, the reaction characteristics of semi-cokes were dramatically decreased at about 330 °C. Finally, the relationship between in-situ heat generation and demand at various stages of ATS process was discussed, and a reasonable strategy for the screening of temperature parameters was proposed. According to this strategy, the optimal control temperature for the preheating stage was determined at 350–370 °C and at Tact (defined in 4.3.2) for the retorting zone in the reaction stage. The results of this study provide a new perspective on the theoretical foundation of the ATS process and have crucial guiding implications for practical engineering applications.

In order to meet the requirements for miniaturization detection of oil shale pyrolysis process and solve the problem of low sensitivity of oil and gas detection devices, a small bionic electronic nose system was designed. Inspired by the working mode of the olfactory receptors in the mouse nasal cavity, the bionic spatial arrangement strategy of the sensor array in the electronic nose chamber was proposed and realized for the first time, the sensor array was used to simulate the distribution of mouse olfactory cells. Using 3D printing technology, a solid model of the electronic nose chamber was manufactured and a comparative test of oil shale pyrolysis gas detection was carried out. The results showed that the proposed spatial arrangement strategy of sensor array inside electronic nose chamber can realize the miniaturization of the electronic nose system, strengthen the detection sensitivity and weaken the mutual interference error. Moreover, it can enhance the recognition rate of the bionic spatial strategy layout, which is higher than the planar layout and spatial comparison layout. This bionic spatial strategy layout combining naive bayes algorithm achieves the highest recognition rate, which is 94.4%. Results obtained from the Computational Fluid Dynamics (CFD) analysis also indicate that the bionic spatial strategy layout can improve the responses of sensors.

Oil shale kerogen is a kind of composite nature of fossil energy polymer. Kerogen pyrolysis is a feasible and alternative strategy to produce fossil fuels from shales. However, the disadvantages including the high energy consumption, the high cost, and the low hydrocarbon conversion, significantly hinder the development and utilization of unconventional hydrocarbon resources. Herein, the hexagonal crystal structural layered double hydroxides (LDHs) with the Ni/Fe ratio of 5.64:2.36 is proposed as pyrolysis catalyst to improve the catalytic efficiency, the selectivity of target hydrocarbons, and lower the temperature for the process of kerogen pyrolysis. As a result, needle-like nanoscale NiFe-LDHs are prepared successfully to perform the fast thermal upgrading of Balikun oil shale kerogen. The catalytic pyrolysis performance has been observed that the temperature for maximum conversion (Tmax) is 401.18 °C, presenting a Tmax reduction of 37.84 °C, the yield of shale oil is increased by 7.83 wt%. And during 350°C– 400°C, a progressive increment of 147.67%, 230.86%, and 310.61% is obtained corresponding to the content of C1-C5, C6-C14, and C14 + hydrocarbons, respectively. This finding enriches the catalyst candidates for kerogen pyrolysis and provides new insights into industrial applications of in-situ pyrolysis technology for oil shale recovery processes.

An inrush of groundwater will absorb the heat injected in oil shale in situ pyrolysis exploitation, which will reduce the pyrolysis efficiency and generate a large amount of oil-containing water. This paper proposed a novel method of water-stopping by gas flooding to solve the problem of groundwater infiltration into the in situ pyrolysis zone of oil shale. In this paper, numerical simulation by TOUGH2/EOS3 and field experiment studies were conducted, with the general aim of this study focused on the establishment of the inflatable area and the long-term water-stopping mechanism. The simulation results showed that the resistance of gas to groundwater flow and the pressure balance of the gas-water interface at the inflatable area front were the main mechanisms of water-stopping. The water yield in the pyrolysis zone decreased significantly from 6 m3/h to nearly 0 m3/h after the inflatable area was established, and the effective water-stopping radius exceeded 50 m around a single well. Furthermore, a field-scale water-stopping by gas flooding experiment was carried out in the National Pilot Project for Oil Shale in situ Exploitation of China (NPOSE), with the results demonstrating that the water yield could be reduced from 6 m3/h to 0.5 m3/h after gas injection, which was basically consistent with the numerical simulation results. Cracked oil (2.85 tons) was successfully obtained at high energy efficiency of approximately 6.1. Consequently, it is verified that the method proposed in this paper has the desired effect of water-stopping and practical application value, which provides technical support for large-scale oil shale in situ pyrolysis exploitation around the world.

In this work, Huadian oil shale was extracted by subcritical water at 300 °C over different time periods to better characterize the underground mining of oil shale in situ. The results revealed tha...

The coupling effect of subcritical water and FeCl3 on the extraction of bulk Huadian oil shale was experimentally investigated. The results showed that, with the addition of FeCl3, the yield of shale oil in subcritical water extraction was enhanced by 58.5 % at 20 h and the time required for the maximum shale oil production was reduced by 43 %. The group compositions of shale oil and residual bitumen as well as the elemental analysis of residual kerogen revealed that FeCl3 could trigger the pyrolysis reaction networks of kerogen by promoting the cleavage of heteroatom bonds, and accelerate the decomposition of asphaltenes in residual bitumen. GC-MS analysis of n-alkanes in shale oil and residual bitumen showed that FeCl3 promoted the secondary cracking of saturated hydrocarbons in residual bitumen rather than in shale oil due to the adsorption of Fe3+ in shale matrix. The solid-state 13C NMR analysis of the residual kerogen indicated that the polycondensation of kerogen was inhibited and the ring-opening reaction of aromatic structure was promoted in the presence of FeCl3. In addition, the acidic FeCl3 solution induced the decomposition of carbonate minerals in oil shale matrix to provide additional mass transfer channels for the migration of bitumen products.

In this study, the non-isothermal pyrolysis method was used to investigate the pyrolysis characteristics of oil shale from four areas: namely Nongan, Fuyu, Mongolia, and North Korea, with special emphasis on Fuyu oil shale. X-ray diffraction was performed to determine the mineral composition of the oil shale. The pyrolysis behaviours of the oil shale at different heating rates were determined by thermogravimetric analysis and differential thermogravimetric analysis. During pyrolysis, as the heating rate increased, the oil shale reaction zone moved to a higher temperature due to thermal hysteresis. The activation energies of the oil shale samples from four areas were obtained by the Flynn–Wall–Ozawa (FWO), Starink, and Friedman methods. The results showed that the activation energy was not stable throughout the conversion stage, and the overall trend showed an increase with an increase in temperature. The average activation energy in the second stage was 304, 307, and 342 kJ mol−1 for Fuyu oil shale; 328, 333, and 348 kJ mol−1 for Nongan oil shale; 341, 347, and 422 kJ mol−1 for North Korea oil shale; and 362, 363, and 379 kJ mol−1 for Mongolia oil shale by the FWO, Starink, and Friedman methods, respectively. The fluctuation of activation energy showed that thermal degradation in oil shale was a complicated multistep reaction, regardless of the area. The quality and characteristics of organic matter and mineral impacted the pyrolysis process and kinetic characteristics. The Sestak–Berggren method was used to fit the data from oil shale pyrolysis. The results indicated that the main mass loss phase of oil shale pyrolysis was controlled by a nucleation mechanism.

In this work, Huadian oil shale was extracted by subcritical water at 365 °C with a time series (2–100 h) to better investigate the carbon isotope fractionation characteristics and how to use its fractionation characteristics to constrain the oil recovery stage during oil shale in situ exploitation. The results revealed that the maximum generation of oil is 70–100 h, and the secondary cracking is limited. The carbon isotopes of the hydrocarbon gases show a normal sequence, with no “rollover” and “reversals” phenomena, and the existence of alkene gases and the CH4-CO2-CO diagram implied that neither chemical nor carbon isotopes achieve equilibrium in the C-H-O system. The carbon isotope (C1–C3) fractionation before oil generation is mainly related to kinetics of organic matter decomposition, and the thermodynamic equilibrium process is limited; when entering the oil generation area, the effect of the carbon isotope thermodynamic equilibrium process (CH4 + 2H2O ⇄ CO2 + 4H2) becomes more important than kinetics, and when it exceeds the maximum oil generation stage, the carbon isotope kinetics process becomes more important again. The δ13CCO2−CH4 is the result of the competition between kinetics and thermodynamic fractionation during the oil shale pyrolysis process. After oil begins to generate, δ13CCO2−CH4 goes from increasing to decreasing (first “turning”); in contrast, when exceeding the maximum oil generation area, it goes from decreasing to increasing (second “turning”). Thus, the second “turning” point can be used to indicate the maximum oil generation area, and it also can be used to help determine when to stop the heating process during oil shale exploitation and lower the production costs.

In this work, Huadian oil shale from China was treated by hydrothermal pretreatment at 200 °C with 1.0–2.5 h in order to investigate the effect of hydrothermal pretreatment on pyrolysis product distribution and characteristics of oil. The differences in the elemental composition and thermal behavior between the untreated and treated oil shale were analyzed and compared. The hydrothermal treatment process could decompose oxygen functional groups and remove some water soluble inorganics in oil shale, which decreased the formation of gas and water during the pyrolysis. However, hydrothermal pretreatment was conducive to increasing shale oil yield. The maximum of oil yield was obtained at the pretreatment time of 2.0 h. The enhancement of the free-radical reactions during the pyrolysis and the reduction of the secondary cracking reactions of the generated oil vapors were considered as the main reasons. The oil obtained by the treated oil shale had a higher H/C ratio, indicating it had high energy content. The analysis results of chemical compositions in oils showed that the relative content of aliphatic hydrocarbons significantly increased after hydrothermal pretreatment. The further analysis demonstrated that the increase in the pretreatment time caused the generated long chain hydrocarbons tended to be directly released from oil shale particles, and were condensed into the oil.

The combination of subcritical water and catalyst was proposed for oil shale extraction. The extraction of Huadian oil shale in FeCl2 solution was performed at 350 °C to evaluate the combined method. At 20 h, a high yield of bitumen 1 (the bitumen discharged from shale matrix) was obtained in FeCl2 solution with an optimal concentration of 0.08 mol/L, which was 50.5% higher than that obtained in pure water. The bitumen 1 reached a maximum yield of 18.98 wt% at 40 h in subcritical FeCl2 solution and 19.14 wt% at 70 h in subcritical water, respectively. The time needed for a maximum yield of bitumen 1 was reduced by 43% after the addition of FeCl2. The results indicated that FeCl2 played an important role in the promotion of the cleavage of hetero-atomic bonds in kerogen and the transportation of bitumen 2 (the bitumen remaining in the shale matrix) in the shale matrix. It showed the addition of FeCl2 did not significantly affect the variation trends of the relative content of the major components in bitumen 1 and bitumen 2 with the time. The subcritical FeCl2 solution extraction should be a highly efficient method for in situ extraction of oil shale.

In this work, thermal behaviors of Huadian oil shale, spent mushroom substrate, and their mixture were investigated in a thermogravimetric analyzer. The Coats–Redfern method was adopted to calculate kinetic parameters. The results indicated that there were remarkable synergetic effects during the copyrolysis. In addition, an comparison of the experimental and the calculated yields was carried out over a temperature range of 490–590 °C by a lab-scale retorting reactor. It showed that synergetic effects between raw materials promoted the producing of oil and gas and reduced the formation of solid residues. Besides, characteristics of the obtained oil indicated that the presence of spent mushroom substrate produced significant influences on the chemical component distribution.

In this work, the effects of the coupling between montmorillonite and CoCl2·6H2O on pyrolysis behavior, products distribution and characteristics of liquid fuel were investigated by the combination of pyrolysis experiment and kinetic analysis. The mass fraction of the MMT in oil shale was 3–9%, and the mass fraction of CoCl2·6H2O was 10–25%. The results showed that the coupling effect promoted the formation of shale oil. The maximum yield of shale oil (17.75 wt%) was obtained at 20CoCl2·6H2O5MMT. Catalytic pyrolysis behavior and kinetic analysis indicated that the presence of CoCl2·6H2O and montmorillonite led to the prominent advance of kerogen decomposition temperature and the decrease of apparent activation energy. Significantly, the addition of the 20CoCl2·6H2O5MMT led that the average apparent activation energy was decreased by about 122.42 kJ/mol compared to the catalyst-free pyrolysis. The strong cracking ability produced by their coupling effect was considered to be the main reason. Montmorillonite and CoCl2·6H2O enhanced the decarboxylation and free-radical reaction, resulting in a decrease of acids yield and an increase of aliphatic hydrocarbons yield. The relative content of aliphatic hydrocarbons increased from 41.55% to 51.27%. These results demonstrated that the combined use of montmorillonite and CoCl2·6H2O was beneficial to the generation of saturated hydrocarbon production.

In-situ recovery of oil from oil shale using the convection heating method requires a hydraulic fracturing process to provide transportable channels for thermal carriers and shale oil and gas released by oil-shale pyrolysis. However, flowing groundwater could enter the reaction zone through fissures generated by hydraulic fracturing, causing significant heat loss and blocking the generation and outflow of oil and gas during the heating process of the in-situ conversion of oil shale. Therefore, a continuous water-stop is indispensable. This study optimized the layout of grouting wells in a hexagonal pattern and carried out a series of grouting diffusion simulations according to the hydrogeological data of the Nong'an oil shale stratum. Moreover, a field test was conducted at the site of the Nong'an pilot project of oil shale in-situ processing. The simulation result indicates that the production wells should be kept open during the grouting process, as numerous local high-velocity zones of groundwater between the grouting wells could restrict the expansion and intersection of grouting. An optimized open pattern grouting method for the Nong'an pilot project was proposed, and a well-spacing of 3 m was determined to be appropriate. Finally, in the field grouting test, the fine grout intersection without local high-velocity zones was verified through water pressure tests and according to the initial and ultimate outflow of groundwater in the production well of the field test, which corresponded to the simulation result. Hence, the authenticity of the grouting method determined by numerical simulation has been verified.

The Cretaceous Era has always been a focus of geologic and palaeoenvironmental studies. Previous researchers believed that the impact of the global carbon cycle represents significant short-term global biogeochemical fluctuations, leading to the formation of a large number of organic rich sediments in the marine environment. During the Turonian, a large number of organic-rich oil shales were deposited in the lakes of the Songliao Basin in the Qingshankou Formation. How the depositional environment affected the formation of oil shales in continental lakes and the characteristics of these oil shales remain controversial. In this paper, through sampling of Qingshankou Formation strata, various testing methods are used to provide a variety of new data to study the characteristics of oil shales and palaeoenvironment evolution history in the Songliao Basin. The research of the sediments in the Qingshankou Formation in the Fuyu oilfield, Songliao Basin, via result analysis revealed that the oil shales possess an excellent oil-generation potential with moderate-high total organic carbon (TOC) levels (0.58–9.43%), high hydrogen index (HI) values (265–959 mg hydrocarbons (HC)/g TOC), high extractable organic matter (EOM) levels (2.50–6.96 mg/g TOC) and high hydrocarbon fractions (48–89%). The sources of the organic matter were mainly zooplankton, red algae and higher plants (including marine organisms). The aqueous palaeoenvironment of the Qingshankou Formation was a saline water environment with a high sulfate concentration, which promoted an increase in nutrients and stratification of the water density in the lake basin. Oxygen consumption in the bottom water layer promoted the accumulation and burial of high-abundance organic matter, thus forming the high-quality oil shales in the Qingshankou Formation. The global carbon cycle, warm-humid palaeoclimate, dynamic local biogeochemical cycling and relative passive tectonism were the most likely reasons for the TOC increase and negative δ13Corg deviation.

Co-pyrolysis of oil shale from different regions with spent oil shale from subcritical water extraction experiments is experimentally conducted using thermogravimetric analysis (TG). The mixture samples (oil shale/spent oil shale in blending ratio of 1:1) are heated from 30 up to 850 °C with heating rate of 5, 10 and 30 °C min−1, nitrogen flow rate of 30 mL min−1. Three different stages are identified based on TG curves of the mixture samples. The second stage which is due to the release of volatile matter is the primary reaction stage, and the mass loss discrepancies of the experimental and calculated TG profiles in the second stage are considered as a measurement of the interactions extent during the co-pyrolysis. The experimental mass loss of Nong’an and Fushun oil shale/spent oil shale mixture samples is higher than the calculated data, and the experimental mass loss of Huadian and Mudanjiang oil shale/spent oil shale mixture samples is lower than the calculated data. It is concluded that the interaction effect obviously occurred during the co-pyrolysis of oil shale and spent oil shale. In addition, the effect of kaoline and montmorillonite on the cracking of the kerogen is discussed according to the co-pyrolysis of kerogen and inorganic mineral. The release index of the kerogen, kerogen/kaolinite and kerogen/montmorillonite is 2.06 × 107, 4.58 × 107 and 1.89 × 107 % K−3 min−1, respectively. And the kinetic parameters of the samples are obtained by Kissinger–Akahira–Sunose method based on the thermogravimetric data, and the apparent activation energy of the kerogen, kerogen/kaolinite and kerogen/montmorillonite is 58.4, 25.7 and 95.9 kJ mol−1, respectively. According to the release index and the kinetic parameters of the samples, we can conclude that the kaolinite is helpful for the pyrolysis of kerogen and the montmorillonite inhibits the pyrolysis of kerogen.

Isothermal subcritical water extraction technique was used to extract organic matters from Huadian oil shale under different extraction conditions. The effects of particle size, extraction temperature, extraction time, and water–oil shale mass ratio were investigated on the extracts yield. A series of extraction experiments were carried out with three particle size samples and the water–oil shale mass ratio in the range 1.5–3.5 at five levels of temperature for 5–70 h. As a result, extraction temperature and extraction time were found to have large effect on the extracts yield, and the particle size had large effect on the extracts yield at 335 °C. The maximum extracts yield could be obtained at 365 °C for 30 h with the water–oil shale mass ratio of 3 using middle particle size oil shale samples. Gas chromatography–mass spectrometry (GC-MS) analysis of the n-hexane-soluble maltene in bitumen 1 and the organic matters in the spent aqueous solution demonstrated that large molecular hydrocarbons could be cra...

The pyrolysis kinetics of Huadian oil shale, spent oil shale obtained from near-critical water extraction experiments and their mixtures were investigated using thermogravimetric analysis (TGA). Experiments were performed at four different heating rates of 2, 10, 20 and 50 K min− 1 from ambient temperature to 850 °C at under atmospheric pressure and nitrogen flux. The results demonstrated that the thermal decomposition of oil shale, spent oil shale and their mixtures involved three degradation steps. The temperature of the maximum degradation rate (Tmax) of the oil shale and mixtures shifted toward higher temperature with the increase of heating rate. The extent of interactions during co-pyrolysis was confirmed by comparing the experimental result with the theoretical one. Different thermogravimetric data were analyzed by integral method. According to the pyrolysis kinetic analysis, the apparent activation energy of spent oil shale and mixtures was lower than that of oil shale. The values of the obtained apparent activation energy of the mixtures decreased with an increasing spent oil shale fraction because of the decreasing of the macromolecular organic matters which needed much energy during the thermal decomposition. The results are reasonable to conclude that the spent oil shale was helpful for the degradation of oil shale in the mixture.

Three sizes of Huadian oil shale lumps from 1 cm to 10 cm were extracted by sub-critical water at 350 °C and 16 MPa for 2–70 h. The oil shale lumps were fractured alone the shale texture in sub-critical water that greatly improved the extraction efficiency of bitumen from the large- and middle-sized sample. The extract yields of bitumen from different sized samples were similar when the extraction time is longer than 20 h and stabilized at about 18 wt.% (ad) after 50 h duration. With the increase of extraction time, asphaltene and preasphaltene extracts were gradually decomposed to maltene. The gas chromatography–mass spectrometry (GC–MS) analysis of the extracts showed that n-alkanes, n-alk-1-enes, isoprenoids, n-alk-2-ones and n-alkanoic acids were the major components. In contrast, aromatic extracts were rare and most of them were remained in the shale residue. The pyrolysis gas chromatography–mass spectrometry (Py-GC–MS) analysis of the spent shale showed that the final undecomposed organics in kerogen were some macromolecular linear hydrocarbon, n-alk-2-ones and n-alkanoic acids fragments. The comparison of the classical pyrolyzate and the sub-critical water extracts showed that the water extracts contained more long-chain alkanes than anhydrous pyrolysis and the alkene extracts could transform to alkanes in sub-critical water. Moreover, the n-alkanoic acids could be decomposed to short-chain compounds through the cleavage of carbon carbon bonds.

The possibility of extracting hydrocarbons from Huadian oil shale by sub-critical water was found in a stainless steel vessel. The effects of temperature and pressure on the extraction of hydrocarbons were studied. After extraction experiments, the residual solid, liquid and gas phase samples were collected and characterized, respectively. The extract yield could reach 7 wt.% (ad) when the extraction of oil shale was conducted at 260 °C for 2.5 h with the pressure of 15 MPa. The results of thermogravimetry (TG) showed that the weight loss of residual solid samples was much smaller than that of the original oil shale. It indicated that kerogen components had been decomposed partly by treatment with sub-critical water. Gas chromatography–mass spectrometry (GC–MS) analysis showed that there were more than 300 recognizable peaks in the extracting solution following processing at 330 °C and 18 MPa. Large amounts of high molecular weight hydrocarbons were gradually decompounded by the increase in types and levels of low molecular weight hydrocarbons, and polycyclic and heterocyclic compounds with the rising of pressure and temperature. These indicated that sub-critical water is capable of cracking kerogen into smaller hydrocarbon compounds at relatively low temperatures.

Multi-objective simultaneous prediction of waterborne coating properties was studied by the neural network combined with programming. The conditions of network with one input layer, three hidden layers and one output layer were confirmed. The monomers mass of BA, MMA, St and pigments mass of TiO2 and CaCO3 were used as input data. Four properties, which were hardness, adhesion, impact resistance and reflectivity, were used as network output. After discussing the hidden layer neurons, learn rate and the number of hidden layers, the best net parameters were confirmed. The results of experiment show that multi-hidden layers was advantageous to improve the accuracy of multi-objective simultaneous prediction. 36 kinds of coating formulations were used as the training subset and 9 acrylate waterborne coatings were used as testing subset in order to predict the performance. The forecast error of hardness was 8.02% and reflectivity was 0.16%. Both forecast accuracy of adhesion and impact resistance were 100%.