Oil Shale Residue Research Articles

The adsorption performance of high crystallinity Na-p zeolites prepared from oil shale ash for the waste water treatment

ABSTRACTS The Na-p type zeolite has been prepared by the alkali fusion hydrothermal synthesis method using the pure oil shale ash (OSA) and mixture of OSA and coal fly ash (CFA) as raw materials, which was used for adsorption of methylene blue (MB). The XRD spectra of zeolite synthesized from pure oil shale residue under different conditions indicated that the optimal experimental conditions were determined as follows: acid leaching concentration of 10%, sodium hydroxide dosage of 7 g, crystallization temperature of 130°C, and crystallization time of 12 h. Under the same conditions, zeolite was synthesized using the mixture of OSA and CFA, and its properties were characterized using XRD, SEM, and BET techniques. The results showed that the specific surface area and crystallinity of the zeolite prepared from the mixture were 59.6 m2/g and 86.32%, respectively, which were higher than that of pure OSA (20.6 m2/g and 64.07%). When 0.05 g of zeolite was added to the 35 mg/L MB solution and adsorbed for 180 min, the removal rates of MB by pure OSA, single-source zeolite and zeolite prepared from the mixture were 27.6%, 83.4%, and 99.2%, respectively. The adjusted R square verified that the pseudo-second-order kinetics and Langmuir isotherm model were the best fitting models. The maximum adsorption capacity (Qmax) of zeolite prepared from the mixture for MB was 55.5 mg/g. The above results proved that the novel material prepared in this study could be a potential effective wastewater treatment material.

Innovative synthesis of low-carbon cemented backfill materials through synergistic activation of solid wastes: An integrated assessment of economic and environmental impacts

The accumulation of large amounts of steel slag (SS) and oil shale residue (OSR) causes serious pollution due to the lack of effective ways to utilize them. In this study, OSR, SS, and soda residue (SR) were used to synergistically prepare all-solid-waste low-carbon cemented backfill material (ALCCB). No cement and chemical additives were added to this material, and synergistic activation enabled full utilization of the solid wastes. The total solid waste utilization rate was 100 %. The mechanical characteristics of the ALCCB and the heavy metal leaching rates were determined. The unconfined compression strength of the ALCCB after 28 days was 5.97 MPa, while the slump was 205 mm. These results met the performance requirements for a filling material. The leaching rates for the heavy metals after 28 days conformed to the guidelines for Class III groundwater quality. The mechanism underlying synergistic hydration of the solid wastes was analyzed at the micro- and macroscale with X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The results indicated that hydration of the ALCCB occurred continuously during curing, and the faster early hydration reaction stabilized heavy metal curing at 7 d. In addition, ALCCB offers greater economic and environmental advantages than cementitious materials. Notably, the economic and environmental benefits of ALCCB were found to supersede those of cement-based materials, with a cost reduction of 42.6 % and a CO2 emission reduction of 86.9 %. This innovative low-carbon mine backfill material effectively promotes the utilization of solid waste resources and supports sustainable development.

Carbothermal Reduction of Oil Shale Residue (OSR) in DC Electric Furnace to Prepare Si–Al–Fe Alloy

Carbothermal Reduction of Oil Shale Residue (OSR) in DC Electric Furnace to Prepare Si–Al–Fe Alloy

The effect of acid mine drainage on the properties of an all-solid waste paste backfill body based on oil shale residue

The complex environment of mine water is closely linked to the effect of the backfill body. The goal of this study was to establish a method with which to reduce carbon emissions from cementitious materials while addressing the large amount of unutilized solid waste, such as oil shale residue, which lies on the surface of the planet, and pollutes the environment. Oil shale residue, fly ash, slag and coal gangue were used to produce an oil shale residue-based all-solid waste paste backfill (OSGPB) to study the changes in strength and environmental impact with corrosion time under acid mine drainage conditions. The development of cracks was monitored using digital image correlation (DIC) technology. The corrosion mechanism of OSGPB was analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). This study revealed that in an acid mine drainage environment, the unconfined compressive strength (UCS) decreased by 38.58% and 15.66% after 24 d of wetdry cycling and complete immersion corrosion, respectively. A significant quantity of corrosive gypsum was produced in the OSGPB, which expanded the internal micropores and gradually formed cracks. This led to more severe internal structural damage during wetdry cycles. Changes in the UCS of the OSGPB over 60 d were predicted using established grey models. The leached concentrations of heavy metal ions met the groundwater quality standard (class III) after the OSGPB was completely immersed in acid mine drainage and subjected to wetdry corrosion cycles. OSGPB showed great potential as a green backfilling material for mines.

Bonding performance of reinforced and oil shale residue concrete

Oil shale residue concrete is prepared by utilizing oil shale semi-coke. It has advantages such as low cost and a high solid waste utilization rate. The study of its bonding-slip characteristics with steel bars is a prerequisite for their application in engineering structures. To study the bonding-slip performance of reinforced oil shale residue concrete, 12 half-beam specimens were designed for the bonding performance test. The test parameters included the substitution rate of oil shale residue, bonding length, and cover thickness. The influences of the aforementioned factors and variables on the stress-slip curve and bonding strength were analyzed. The results showed that the anchoring bond length had the greatest impact on the average bonding strengths of the steel bar and concrete. As the bonding length increases from 5d to 10d, the average bonding strength decreased by approximately 18%. The cover thickness had the second-greatest influence on the bonding strength. As the cover thickness increased from 20 to 30 mm, the average bonding strength increased by more than 12%. The substitution rate of the oil shale residue had the least effect on the average bonding strength, and as the substitution rate increased, the bonding strength decrease with a minor magnitude. Through verification, the bonding-slip constitutive model obtained by fitting the experimental data was found to fit the experimental values well.

Research on hydration characteristics of OSR-GGBFS-FA alkali-activated materials

Based on the characteristics of alkali-activated materials (AAMs) in energy saving and emission reduction, as well as giving full play to the complementary advantages of multi-component solid waste. In this study, a new type of AAMs was prepared from oil shale residue (OSR), ground granulated blast furnace slag (GGBFS), and fly ash (FA). Compressive and flexural strength tests, fluidity experiments, setting time, heat of hydration, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), and Thermo-gravimetric analysis (DTG-TG) were used to analyse the mechanical properties, workability, mineral composition, microstructure, and hydration products of the AAMs. The results showed that the microstructure of AAMs was dense, with high early strength, good mechanical and working properties, and no tendency for retrogressive strength with an increase in the age of maintenance. Under the action of NaOH/Na2SiO3, there is a synergistic hydration of the water-hard and volcanic ash materials, and the three raw materials have synergistic hydration properties and indispensable coupling mechanisms. Meanwhile, the effect of the activator content on AAMs is bidirectional. The OSR, GGBFS, and FA in the AAMs exhibited faster hydration reactions under the action of NaOH/Na2SiO3 and abundant hydration products, which mainly included C-S-H, C-A-S-H, N-A-S-H, and small amounts of CaCO3, hydrotalcite (HT), and Ettringite (AFt). The specimens all met the requirements of the 42.5-grade composite silicate cement, and some specimens reached the strength requirements of the 62.5-grade silicate cement or above. OSR has great potential as a silicate-aluminate material, and this study provides a solid foundation for its further development and utilisation.

An experimental investigation of high-temperature thermochemical conversion of oil shale residues into valuable materials

Oil shale residues, a solid waste produced during oil shale mining, extraction, and refining processes, pose a significant challenge to the environment and sustainability. This study aims to develop a thermochemical conversion process to transform oil shale residues into valuable composite materials. Experiments are conducted to investigate the effects of reaction temperature, time, and reactant composition on the reaction behavior and resulting product characteristics. The results demonstrate that mullite-rich composite materials can be prepared at reaction temperatures of around 1300 °C with reaction times of 5 min. Industrial aluminum ash can be used to supplement the aluminum needed for the complete conversion of excess SiO2 in oil shale residue, but it must be thermally treated to eliminate the NaCl content, which hinders mullite formation. Overall, this study offers a viable approach to converting solid waste into valuable resources while simultaneously addressing the environmental concerns associated with oil shale residues.

Changes in the Strength and Leaching Characteristics of Steel Slag-Oil Shale Residue-Based Filling Paste in a Complex Erosive Environment

Our research group prepared a new filling paste consisting of steel slag–oil shale residue and no admixtures. It was used as the research object to explore the combined effect of chloride and dry–wet cycling-driven erosion on the long-term stability of a cemented filling paste made of total solid wastes. Macroscopic experiments and microscopic analyses methods were employed. The influence of solutions with different mass fractions of chloride salts and different cycling periods on the uniaxial compressive strength and toxicity of the steel slag–oil shale residue-based filling paste was studied, and the deterioration mechanisms of the steel slag–oil shale residue-based filling paste under combined erosion from chloride and dry–wet cycling were investigated. The test results showed that in the same cycling conditions, the strength of the steel slag-oil shale residue-based filling paste increased first with the increase in the mass fraction of the chloride solution and then decreased with the increase in the mass fraction of the chloride solution after reaching the peak value; the leached concentrations of heavy metal ions decreased with increasing chloride salt mass fraction. With an increase in the number of dry–wet cycles, the compressive strength of the specimens in the chloride salt solution with a mass fraction of 0 (pure water) first increases and then tends to be stable. The strength of samples in 5% and 10% chloride salt solutions increased first and then decreased with an increase in the number of dry–wet cycles. The leached concentrations of heavy metal ions from the samples in all three solutions first decreased and then stabilized. The prehydration products of the steel slag–oil shale residue-based filling paste were C-S-H gels, AFt and Friedel’s salt, and these increased with increasing chloride salt mass fraction and the number of dry–wet cycles. However, the hydration reactions of the samples in the 0% chloride solution nearly stopped in the later stages of cycling, and the samples in 5% and 10% chloride salt solutions developed local cracks due to the accumulation of hydration products. The results showed that the number of dry–wet cycles and the chloride salt mass fraction affected the strength and leaching characteristics of the steel slag–oil shale residue-based filling paste by changing the type and amount of erosion products. The test results provide a scientific basis for the promotion and application of backfilling pastes made from total solid wastes.

Mitigation of ammonia and greenhouse gases emissions from urea coated with oil shale residues in a silvopastoral system

The objective of this work was to investigate the viability of using retorted oil shale as urea coating (U + ROS) in the decrease of N losses by ammonia (NH3–N) volatilization. The experiment was carried out in a silvopastoral system with a randomized block design with split-plots. The main treatments consisted of spatial arrangements of the trees, while the subdivision of the plots constituted the surface application of common urea (U) and retorted oil shale-coated urea (U + ROS) for the pasture. In addition to NH3 measurements, fluxes of N2O and CH4 in the soil were determined, as well as soil moisture and contents of mineral N (0–5 cm). Independently of tree spacing, the use of ROS along with urea (U + ROS) showed a mean decrease of 15.9% in the accumulated NH3 volatilization and 24.1% in the peaks of emission, although it was not significantly different from the U treatment (P < 0.10). In addition, it did not increase significantly the N2O and CH4 emissions, evidencing a potential to decrease N losses by ammonia volatilization, with no impact on greenhouse gases emissions from the soil.

Recycling of arsenic-containing biohydrometallurgy waste to produce a binder for cemented paste backfill: Co-treatment with oil shale residue.

The high cost of ordinary Portland cement (OPC) limits the broad usage of cemented paste backfill (CPB). Additionally, improper disposal of arsenic-containing biohydrometallurgy waste (BW) can cause tremendous pollution to the environment. Consequently, BW is used to prepare an alternative cementitious material for CPB in this study. The effect of calcined oil shale residue (COSR) on the binder's characteristics was studied. The reaction kinetics of the binder in the presence of COSR were studied via the isothermal calorimeter test and the Krstulovic-Dabic model; mechanical strength and hydration product modifications due to the addition of COSR were also investigated. The leaching of hazardous elements from the binder was also investigated. The results showed that adding COSR reduced the flowability of fresh slurry and early-age compressive strength; however, adding 20wt% COSR resulted in the highest later age compressive strength, thereby reaching ∼43.65MPa after 60 days. The compressive strength of the CPB sample using the COSR20 as a binder may reach ∼87% of the OPC-based CPB sample. Furthermore, the presence of COSR had no significant effect on the phase assembles but changed the amount of ettringite (AFt) and calcium silicate aluminate hydrate (C-A-S-H). The results of this study show that the prepared binder could be used as an alternative to OPC in CPB.

Experimental Study on Microstructure and Erosion Mechanisms of Solid Waste Cemented Paste Backfill under the Combined Action of Dry-Wet Cycles and Sulphate Erosion.

Solid waste cemented paste backfill (SWCPB) meets the needs of coal mining area management. SWCPB is a cementitious paste backfill material without added cement and is made only from oil shale residue (OSR), steel slag (SS), soda residue (SR) and water. In this study, mine water characteristics were simulated by combining dry–wet cycling experiments with sulphate erosion experiments. SWCPB was assessed regarding appearance, mass loss, and unconfined compressive strength (UCS), and the erosion products were microscopically analysed with X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The mechanism for erosion of the SWCPB by sulphate-rich mine water was comprehensively analysed and revealed. Research showed that the erosion mechanism was divided into two parts: chemical and physical erosion. Low concentrations of sodium sulphate promoted hydration, thereby contributing to the increased mass and strength of SWCPB. At high sodium sulphate concentrations, the erosion mainly consumed Ca(OH)2 within the material, and the main generated erosion products were gypsum and ettringite (AFt). This was accompanied by the destructive effects of Na2SO4 crystal expansion, which resulted in damage and the reduced workability of the SWCPB. The whole erosion process was continuous, mainly due to transformations of pits, pores and cracks. The conclusions of this study may provide appropriate guidance for application of SWCPB materials in the treatment of coal mine backfills. In addition, the corresponding theoretical analysis of the erosion mechanism for SWCPB materials is provided.

Preparing a binder for cemented paste backfill using low-aluminum slag and hazardous oil shale residue and the heavy metals immobilization effects

The high cost and carbon emission of ordinary Portland cement (OPC) increase the burden of mining industry and aggravate environmental pollution. In this study, a cheaper and greener binder was prepared using low-aluminum slag and calcined oil shale residue (COSR) as main precursors to provide an alternative cementing material for cemented paste backfill (CPB). The influence of COSR content on the properties of the CPB sample was investigated, including rheological properties, setting time, mechanical strength, and pore structure. Characterization of binder sample was then conducted via isothermal calorimetric analysis, X-ray diffraction (XRD), thermogravimetry (TG), and scanning electron microscope (SEM). The optimal mix proportion of binder was 56 wt% slag, 24 wt% COSR, 15 wt% flue gas desulfurization gypsum (FGDG), and 5 wt% OPC. The solid waste utilization rate in the binder production reached 95%, considered an eco-friendly binder. Besides, the best performance of the binder was mainly due to the optimal Al2O3 and CaO content, leading to large amounts of precipitated ettringite. It then contributed to a denser structure with high mechanical strength. Furthermore, the sequential extraction test showed that the heavy metal in the solidified CPB sample existed mainly as a residual fraction, contributing to the superior immobilization effects.

Mitigation of Ammonia and Greenhouse Gases Emissions from Urea Coated with Oil Shale Residues in a Silvopastoral System

Mitigation of Ammonia and Greenhouse Gases Emissions from Urea Coated with Oil Shale Residues in a Silvopastoral System

Calcined oil shale residue as a supplementary cementitious material for ordinary Portland cement

Oil shale residue (OSR), a ubiquitous by-product of crude oil processing, is usually stacked on the surface and will pollute the environment. In this study thermal activation technology was used to increase the pozzolanic reactivity of OSR, which was used as supplementary cementitious materials (SCM). Different calcination temperature (500, 600 and 700℃) was carried out to discussed the transformation of mineralogy of OSR, after which, the pozzolanic reactivity test was carried out and the hydration products of OSR were analyzed. Finally, the OPC was replaced with OSRs varied from 10% to 50% by weight to analyze the fresh and mechanical behavior of the samples. The results showed that a number of potentially activatable clay minerals content in the OSR such as kaolinite, montmorillonite and illite, calcining OSR at 500–700℃ can improve pozzolanic reactivity and the optimal calcination temperature is about 600℃. The compressive strength of OSR/OPC composites material increased by around 8% (curing for 3 d) and 11% (curing for 28 d) using OSR (calcined at 600℃ and replacement rate at 10%) as SCMs.

Preparation of Cemented Oil Shale Residue-Steel Slag-Ground Granulated Blast Furnace Slag Backfill and Its Environmental Impact.

A new environmentally friendly cemented oil shale residue–steel slag–ground granulated blast furnace slag backfill (COSGB) was prepared using oil shale residue (OSR), steel slag (SS) and ground granulated blast furnace slag (GGBS) as constituent materials. Based on univariate analysis and the Box–Behnken design (BBD) response surface method, the three responses of the 28 days unconfined compressive strength (UCS), slump and cost were used to optimize the mix ratio. Using a combination of scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP), the reaction products, microscopic morphology and pore structure of the specimens with the optimal mix ratio at different curing ages were analyzed. The influence of heavy metal ions from the raw materials and the COSGB mixtures on the groundwater environment was studied by leaching tests. The research demonstrates that the optimal mix ratio is GGBS mixing amount 4.85%, mass ratio of SS to OSR 0.82, and solid mass concentration 67.69%. At shorter curing age, the hydration products are mainly calcium alumino silicate hydrate (C-A-S-H) and calcium silicate hydrate (C-S-H) gels. With the increase of curing age, ettringite (AFt) and C-S-H gels become the main source of the UCS. Meanwhile, the porosity of the filler decreases continuously. The leaching concentration of heavy metal ions from the COSGB mixtures is all lower than the leaching concentration of raw materials and meet the requirements of the Chinese groundwater quality standard (GB/T 14848-2017). Therefore, this new COSGB cannot pollute the groundwater environment and meets backfill requirements. The proposed technology is a reliable and environmentally friendly alternative for recycling OSR and SS while simultaneously supporting cemented paste backfill (CPB).

Study on Cold Resistance Performance of Composite Subgrade Structure in Seasonal Frozen Regions

In order to achieve the purpose of subgrade frost damage control and waste utilization, this paper proposes a specific kind of composite subgrade structure which is suitable for subgrade in seasonal frozen regions, especially wet subgrade. The composite subgrade structure is composed of extruded polystyrene (XPS) plates as a cold resistance layer and modified subgrade soil with excellent frost resistance which can consume a lot of oil shale residue and fly ash. To provide valuable reference for engineering applications, an outdoor model test is designed and carried out based on indoor test results and actual engineering data. The cold resistance performance of this new type subgrade structure is evaluated by comparing the temperature distribution, energy transfer, and freezing index of the composite subgrade and the common subgrade during the freezing process. The results show that, firstly, the cold resistance layer can effectively preserve temperature inside the subgrade and form a positive temperature zone beneath XPS plates, which can ensure that the subgrade soil in a certain range will not freeze during the freezing period. Secondly, the position with the best cold resistance effect of the cold resistance layer is directly under the XPS plate. In actual application, the key position should be covered as completely as possible by XPS plates to ensure the cold resistance effect. Thirdly, the cold resistance layer can not only protect subgrade soil under XPS plates from frost damage, but also raise and keep the service temperature of the structure above XPS plates in a certain range, which is beneficial to the cold resistance durability of the entire road. This means that the composite subgrade can greatly reduce the occurrence of subgrade frost damage, thereby even improving the service capability of roads in seasonal frozen regions.

Experimental Research on Mechanical Property and Environmental Safety of an Industrial Residue Waste Subgrade Material

In order to promote the sustainable use of oil shale residues, a novel subgrade material (SOF) composed of silty clay, oil shale ash residue, and fly ash was developed. The aim of this paper is to study the mechanical behavior and environmental impact of SOF, which is regarded as the safety assessment and prediction for the application of this novel material. To this purpose, the road performance, dynamic properties, and environment impact tests are conducted. In terms of the road performance, the test results of SOF exceed the standard requirement, especially for CBR (California bearing ratio), which can maintain good performance at bad conditions of low compaction degree and being soaked for a long time. The dynamic properties under cyclic loadings are better than most of original and stabilized soils. The shear strength parameters and the anti‐damage mechanism are also discussed; research results show that the friction of SOF mostly contributes to shear strength under high stress conditions, while its cohesion tends to play a more important role under low stress conditions. According to the deformation variation, the accumulation settlement of SOF under vehicle loadings after several years is predicted, which is far lower than the limit of expressway and Grade I highway. Furthermore, the chemical stability and toxicity of SOF leachates are environmentally friendly, which are in line with the benchmarks of Class II surface water and Class III ground water. All the experimental results manifest that SOF used as subgrade filling has good application potential and safety.

Research on dynamic compressive stress response of new type filler subgrade in freezing and thawing processes

In this study, the dynamic compressive stress (DCS) response of a new type filler subgrade, which consists of oil shale residue, silty clay and fly ash, was studied during the freezing and thawing processes. Moisture content sensor, temperature sensors and DCS sensors were embedded in the outdoor subgrade model in the seasonally frozen region. Five loading points and three levels of load were set to investigate the effects of load on the subgrade in the horizontal direction and vertical direction during the freezing and thawing processes. Furthermore, distribution characteristics of DCS were analyzed by combining with the moisture content and temperature distribution diagram. The results show that:(1) The range of horizontal DCS response fluctuated significantly during the freezing and thawing processes. The maximum value emerged in thawing period and the minimum value emerged in frozen period. (2) The vertical DCS response was strongly affected by moisture content and temperature. The maximum value of DCS, the DCS variation rate along depth and the DCS variation caused by load change all occurred in thawing period. (3) Thawing period is the most unfavorable period for subgrade in seasonally frozen regions. Thus, moisture content and temperature conditions during the thawing period must be considered while optimizing and modifying subgrade filler in seasonally frozen regions.

Synthesis and Preparation of Al-MCM-41 Mesoporous Materials Using Oil Shale Residue

An Al-supported cage-like mesoporous silica type MCM-41 has been prepared using a simple one-step synthetic procedure using oil shale residue and CTAB(Hexadecyl trimethyl Ammonium Bromide) as the template. The effects of temperature on the porosity, structure and surface area of Al-MCM-41 mesoporous materials were characterized by X-ray powder diffraction, N2adsorption desorption, scanning electron micrographs (SEM), transmission electron microscopy (TEM) techniques and Fourier transform infrared spectroscopy (FT-IR). The results indicated that temperature was a key to the characteristics of Al-MCM-41 materials, and when the temperature up to 333 K, Al-MCM-41 exhibited excellent characteristics with high degree of order, high surface area and pore volume. The one-step hydrothermal synthesized MCM-41 mesoporous material possessed high BET surface area, high pore size and high pore volume. They are respectively 835.1 m2/g, 32.6 Å and 1.22 cm3/g under the condition of the Si : Al =78:1, pH =10, crystallization temperature was 333K, crystallization time was 48h and calcination at 823 K for 5 h in air. All the results indicated the possibility of using oil shale residue as silicon and aluminum source to produce Al-MCM-41, and gave us a new way to recycle a solid waste. As well as this made it impossible to large-scale production of Al-MCM-41. Keywords: Al-MCM-41 mesoporous materials, oil shale residue, one-step synthesis

Macro and Meso Characteristics of In-Situ Oil Shale Pyrolysis Using Superheated Steam

The efficiency of oil shale pyrolysis is directly related to the feasibility of in-situ mining technology. Taiyuan University of Technology (China) proposed the technology of in-situ convective heating of oil shale, which uses superheated steam as the heat carrier to heat the oil shale’s ore-body and transport the pyrolysis products. Based on the simulated experiments of in-situ oil shale pyrolysis using superheated steam, the changes in fracture characteristics, pyrolysis characteristics and mesoscopic characteristics of the oil shale during the pyrolysis have been systematically studied in this work. The Xinjiang oil shale’s pyrolysis temperature ranged within 400–510 °C. When the temperature is 447 °C, the rate of pyrolysis of kerogen is the fastest. During the pyrolysis process, the pressure of superheated steam changes within the range of 0.1–11.1 MPa. With the continuous thermal decomposition, the horizontal stress difference shows a tendency to first increase and then, decrease. The rate of weight loss of oil shale residue at various locations after the pyrolysis is found to be within the range of 0.17–2.31%, which is much lower than the original value of 10.8%, indicating that the pyrolysis is more adequate. Finally, the number of microcracks (&lt;50 µm) in the oil shale after pyrolysis is found to be lie within the range of 25–56 and the average length lies within the range of 53.9636–62.3816 µm. The connectivity of the internal pore groups is satisfactory, while the seepage channel is found to be smooth. These results fully reflect the high efficiency and feasibility of in-situ oil shale pyrolysis using superheated steam.