Steam Pyrolysis Research Articles

Production of sludge biochar by steam pyrolysis and acid treatment: Study of the activation mechanism and its impact on physicochemical properties

This study addresses the preparation of sludge biochar through a procedure that combines steam pyrolysis in a wide range of temperature (500–900 ºC) and acid treatment with HCl (performed before or after the pyrolysis). The acid washing after the pyrolysis maximizes BET surface area due to pore unblocking, thus making visible the pore structure generated. The drawback of the acid washing is the lower yield obtained (compared to the acid pretreatment), as well as the loss of the magnetic properties of sludge biochar. The acid pretreatment requires temperatures above 700 ºC to have a beneficial effect, due to the occurrence of additional reactions of the incorporated HCl with sludge constituents. The pretreatment results in materials with a high degree of microporosity. Among the reactions favoured, of interest is the development of magnetite in the whole temperature range. The activation protocol used in this study (especially the procedure that includes the acid pretreatment) is effective to generate biochar with magnetic properties through the transformation of the Fe introduced during the water treatment process, without adding a source of Fe. The presence of magnetite is an advantage for the reuse of sludge biochars in wastewater treatment.

Effect of long reaction distance on gas composition from organic-rich shale pyrolysis under high-temperature steam environment

When high-temperature steam is used as a medium to pyrolyze organic-rich shale, water steam not only acts as heat transfer but also participates in the chemical reaction of organic matter pyrolysis, thus affecting the generation law and release characteristics of gas products. In this study, based on a long-distance reaction system of organic-rich shale pyrolysis via steam injection, the effects of steam temperature and reaction distance on gas product composition are analyzed in depth and compared with other pyrolysis processes. The advantages of organic-rich shale pyrolysis via steam injection are then evaluated. The volume concentration of hydrogen in the gas product obtained via the steam injection pyrolysis of organic-rich shale is the highest, which is more than 60%. The hydrogen content increases as the reaction distance is extended; however, the rate of increase changes gradually. Increasing the reaction distance from 800 to 4000 mm increases the hydrogen content from 34.91% to 69.68% and from 63.13% to 78.61% when the steam temperature is 500 °C and 555 °C, respectively. However, the higher the heat injection temperature, the smaller the reaction distance required to form a high concentration hydrogen pyrolysis environment (hydrogen concentration > 60%). When the steam pyrolysis temperature is increased from 500 °C to 555 °C, the reaction distance required to form a high concentration of hydrogen is reduced from 3800 to 800 mm. Compared with the direct retorting process, the volume concentration of hydrogen obtained from high-temperature steam pyrolysis of organic-rich shale is 8.82 and 10.72 times that of the commonly used Fushun and Kivite furnaces, respectively. The pyrolysis of organic-rich shale via steam injection is a pyrolysis process in a hydrogen-rich environment.

Analysing the modifications of carbon black and other fillers after pyrolysis of model tyres

Carbon blacks (CBs) that are used as fillers to reinforce rubber contribute to tyre recycling issues. Although recovered carbon black (rCB) produced from the thermoconversion of waste tyres has poor reinforcing abilities in non-polar rubbers, the exact origin of the difference between rCBs and CBs is not elucidated. The characteristics of the rCBs produced from the steam pyrolysis of model laboratory-reinforced rubbers, with or without silica added, were analysed and compared to the pristine CB. X-Ray Diffraction revealed that the quantity of unorganised carbon in the rCB increased by about 25% after pyrolysis, revealing the occurrence of carbonaceous deposits originating from rubber carbonisation. They affected the filler texture, and part of the ultra-microporosity (i.e., pores within the diameter range 0.34–0.76 nm), which had a three-fold decrease in the rCB sample. The recovered fillers, with and without silica, had more oxygenated functional groups than the CB. The dispersibility and stability of the colloidal suspensions were affected by the increased surface oxygen functional groups. Reductive hydrogenation was utilised to remove the excess oxygen allowing an improved understanding of the rCBs. This is a promising method to maximise material reutilisation in the circular value chain of tyres.

Bromine Migration and Product Analysis of Waste Printed Circuit Boards during Microwave Steam‐Gasification‐Assisted Pyrolysis

AbstractBromine in waste printed circuit boards has caused serious harm to the environment. How to deal with it safely is a problem. In this paper, the debromination of waste printed circuit boards by microwave gasification pyrolysis was studied, and the properties of pyrolysis products and the migration of bromine were analyzed. The optimum pyrolysis conditions of microwave steam atmosphere were 600 °C, 1000 W, 50 min, 2 mL/min. Compared with conventional pyrolysis and conventional steam pyrolysis, less solid products (60.39 wt %) were obtained, and more metal copper was enriched. The content increased from 27.46 % and 28.35 % to 30.63 %, respectively, and the diffraction peak intensity of copper was also enhanced. There is no obvious change in the type of functional groups of the solid product, and its microscopic morphology is smoother. Compared with conventional pyrolysis, the phenolic compounds in pyrolysis oil decreased, and increased compared with conventional steam pyrolysis. The content of H2 in the pyrolysis gas increased significantly, and the content of CO decreased significantly. Compared with conventional pyrolysis, the bromine content in pyrolysis gas and pyrolysis oil decreased from 94.5 % and 5.5 % to 1 %, respectively, and more bromine (98 %) in the raw material entered the aqueous solution.

Analysis of fracture structure evolution of bituminous coal subjected to in situ steam pyrolysis combined with in situ micro-computed tomography technology

ABSTRACT Underground in situ pyrolysis mining of coal will be a new trend for utilizing coal resources in the future. Steam heating is a feasible and key technology used in this process. Investigating the evolution mechanism of microstructural parameters during coal in situ steam pyrolysis is essential. The influence of external stress on microstructural parameters of coal has not been considered in previous studies. Herein, the permeability and fracture structure parameters of bituminous coal subjected to in situ steam pyrolysis were studied using a high-temperature and high-pressure triaxial testing machine combined with in situ micro-computed tomography (micro-CT) technology. Moreover, the advantages of steam pyrolysis were revealed by comparing it with the natural pyrolysis process. Results showed that (1) the evolution law of fracture ratio and the proportion of large fractures (equivalent fracture diameter R >100 μm) with temperature is consistent. The proportion of large fractures has a considerable impact on the fracture ratio. (2) From 25°C to 600°C, the permeability and fracture structure parameters of bituminous coal exhibit an “increase – decrease–increase” trend with increasing temperature. The threshold temperature points for changing fracture structure parameters are 300°C and 400°C. The promoting effect of pyrolysis on fracture structure parameters competes with the inhibition effect of external stress on fracture development, determining the evolution law of fracture structure parameters with temperature. (3) The threshold temperature zone where the microstructural parameters change considerably is 400°C–600°C. The fracture ratio, proportion of large fractures, and permeability of coal increase considerably. (4) Unlike natural pyrolysis, steam pyrolysis promotes the advancement of threshold temperature point. After 450°C, steam pyrolysis promotes the development of large fractures (R >100 μm) and the fracture ratio is about twice that observed in case of natural pyrolysis. These findings provide theoretical support for the engineering practice of coal in situ underground pyrolysis mining and are of great importance to the development of micromechanics.

Developing a parametric system model to describe the product distribution of steam pyrolysis in a Dual Fluidized bed

Steam pyrolysis is a thermochemical process that converts carbon-based materials into valuable gases. In general, the products of the reaction are syngas (H2,CO,CO2), low-molecular-weight hydrocarbon gases (methane, ethylene, and propylene), pyrolytic gasoline and oils, monoaromatic and polyaromatic species (tar), and carbonaceous residues (char) with ashes. However, the intricacy of the reactions comprising the process, the diversity of the product species, and the constraints linked to the sampling and measurement equipment, create a highly complex system. In this work, a method for data representation is presented based on a special Parametric System Model (PSM) that portrays product species measurements in a way that provides relevant information and valuable insights into the process. The method incorporates generic knowledge of the chemical nature of the reactions to create a constrained system in which the data can be expressed in parametric terms with meaningful statistical functions. The evaluated data were obtained from a high-temperature steam pyrolysis process performed in the 2–4-MW Dual Fluidized Bed reactor at Chalmers University using polyethylene as feedstock. The quantities of the hydrocarbon species detected in the gas product were taken for the PSM as a probabilistic system that can be described with a set of distribution functions. The carbon, hydrogen and oxygen balances were taken into account to build a constrained set of equations to find the parameters of the functions. The resulting model was proven to be useful as a prediction tool to quantify unmeasured carbon group species and to estimate process variables, such as the oxygen transport of the bed material. Also, it was demonstrated the potential of the model as a method to identify and estimate inconsistencies in the measurements, which improve the quality of the characterization data. The modeĺs outcomes find application in providing critical information for the control and evaluation of pyrolysis process and downstream operation of biorefineries.

Controlled Manufacture of Heterogeneous Catalysts for the Hydrogenation of CO2 via Steam Pyrolysis of Different Metal–Organic Frameworks

The use of metal–organic frameworks (MOFs) as precursors for the manufacture of heterogeneous catalysts has gained a great deal of attention over the last decade. By subjecting a given MOF to pyrolysis, electrochemical degradation, or other treatments under a controlled atmosphere, (supported) metal (oxide) nanoparticles with very narrow size distributions can be obtained, opening the door to the design of more efficient catalytic solids. Here, we demonstrate the benefits of steam during the controlled decomposition of two different MOF structures (Basolite F300(Fe) and In@ZIF-67(Co)) and the consequences of treatment under this mildly oxidizing atmosphere on the properties of the resulting catalysts for the direct hydrogenation of CO2 to hydrocarbons and methanol. In-depth characterization demonstrates that steam addition helps to control the phase composition both before and after catalysis; additionally, it results in the formation of smaller nanoparticles, thus leading to more efficient catalysts in comparison with conventional pyrolysis.

High-Efficiency Carbon Fiber Recovery Method and Characterization of Carbon FIBER-Reinforced Epoxy/4,4'-Diaminodiphenyl Sulfone Composites.

Globally, the demand for carbon fiber-reinforced thermosetting plastics for various applications is increasing. As a result, the amount of waste from CFRPs is increasing every year, and the EU Council recommends recycling and reuse of CFRPs. Epoxy resin (EP) is used as a matrix for CFRPs, and amine hardeners are mainly used. However, no research has been conducted on recycling EP/4,4'-diaminodiphenyl sulfone (DDS)-based CFRP. In this study, the effect of steam and air pyrolysis conditions on the mechanical properties of re-cycled carbon fiber (r-CF) recovered from carbon fiber-reinforced thermosetting (epoxy/4,4'-diaminodiphenyl sulfone) plastics (CFRPs) was investigated. Steam pyrolysis enhanced resin degradation relative to N2. The tensile strength of the recovered r-CF was reduced by up to 35.12% due to oxidation by steam or air. However, the interfacial shear strength (IFSS) tended to increase by 9.18%, which is considered to be due to the increase in functional groups containing oxygen atoms and the roughness of the surface due to oxidation. The recycling of CFRP in both a steam and an air atmosphere caused a decrease in the tensile strength of r-CF. However, they were effective methods to recover r-CF that had a clean surface and increased IFSS.

Utilization of microwave steam pyrolysis to produce biochar for thermal energy storage

Utilization of microwave steam pyrolysis to produce biochar for thermal energy storage

Analysis of the permeability evolution law of in situ steam pyrolysis of bituminous coal combing with in situ CT technology

The permeability evolution of bituminous coal under in situ steam pyrolysis was studied combing with in situ CT technology. The results showed that: 1) Permeability varied negatively logarithm with pore pressure, which is related to adsorption expansion; 2) Permeability changed in a “V” shape with temperature. In a range of 300–400 °C, the coal sample continues to soften under hydrothermal action, the external stress closed the crack, and permeability decayed; 3) At 400–600 °C, the hydrothermal action promoted the pyrolysis of the coal samples and generated more seepage channels. The continuous compression by the external stress on the coal body suppressed the expansion of the pores and fissures. However, the former played a leading role in promoting permeability, and permeability showed a piecewise linear growth. CT results showed that the porosity trend of the coal samples was consistent with that of permeability; 4) Above 400 °C, superheated steam promotes the pyrolysis of the coal samples and improved permeability due to its excellent convection and thermal conductivity, drive effect, and participation in chemical reactions.

Comparison of the Characteristics of Recycled Carbon Fibers/Polymer Composites by Different Recycling Techniques.

In this study, three recycling methods, namely, mechanical grinding, steam pyrolysis, and the supercritical solvent process, which are used to acquire recycled carbon fibers (RCFs), were compared for their application in synthesizing polymer-matrix composites. RCF-reinforced polyethylene (PE) composites were prepared to compare the mechanical properties of the composites generated using the three recycling methods. The PE/RCF composites exhibited 1.5 times higher mechanical strength than the RCF-reinforced PE composites, probably because of the surface oxidation effects during the recycling processes that consequently enhanced interfacial forces between the RCF and the matrix. Further, the steam pyrolysis process showed the highest energy efficiency and can thus be applied on a large production scale in domestic recycled CF markets.

Experimental study on the effects of steam temperature on the pore-fracture evolution of oil shale exposed to the convection heating

In the convection heating technology for shale oil recovery, steam is used as a transmission medium to pyrolyze oil shale. An experiment was designed to pyrolyze oil shale via steam injection in a large reactor. The samples of oil shale and semi-coke were obtained at different pyrolysis temperatures, and the pore-fracture structure of the samples was studied. The results showed that the average pore diameter and median pore diameter increased by about 10 times when the steam temperature increased from 314 °C to 555 °C. After completion of the steam pyrolysis, we observed that the internal fractures of oil shale were mainly microfractures. At the pyrolysis temperature of 555 °C, the number of microfractures in oil shale was more than 50 times compared with those observed at normal temperature. The micro-CT results indicated that the porosity of oil shale reached 15% after pyrolysis with high-temperature steam. At this porosity, the oil content of samples after pyrolysis was 0.05–0.22%, and the internal organic matter was completely pyrolyzed. Finally, the bedding planes of rock mass exhibited significant ruptures when the oil shale was pyrolyzed with high-temperature steam, thus providing proper channels for steam injection and flows of oil and gas.

Steam Pyrolysis of Oil Sludge for Energy-Valuable Products

Experimental studies of the steam pyrolysis of oil sludge were performed using a flow-type pilot plant with 300 kg/h capacity (raw material) to obtain energy-valuable products, such as liquid hydrocarbons (30.4 wt%), semi-coke (39.6 wt%), non-condensable gas-phase compounds (26.5 wt%), and bitumen (3.5 wt%). The pyrolysis process was conducted at a temperature of 650 ° C and with a steam flow rate of 150 kg/h. Liquid hydrocarbons were considered a target product. Comprehensive studies of their physicochemical characteristics, atomization process, droplet ignition, and combustion were carried out. The studied sample had physicochemical characteristics similar to traditional fuel oil (calorific value—42.6 MJ/kg, sulfur content—0.8 wt%). The jet spraying angle was 25° in view of the improved rheological properties of the test sample, with a homogeneous jet structure and a predominant droplet diameter of no more than 0.4 mm. The flame combustion process was accompanied by the formation of microexplosions, the frequency and intensity of which depended on the temperature of the air (Tg = 450–700 °C). This study, in view of its applied nature, is of interest in the design of new installations and technological systems for hydrocarbon pyrolysis.

Comparative Analysis of the Characteristics of Carbonaceous Material Obtained via Single-Staged Steam Pyrolysis of Waste Tires

ABSTRACT The two-stage technology of porous carbonaceous material obtained via pyrolysis in inert medium with subsequent activation by steam is well known. While steam could be a suitable substance for pyrolysis as well, single-staged technology for waste tire recycling is yet to be developed. A comparative analysis of the characteristics of the carbonaceous materials obtained by the single-staged steam pyrolysis of waste tires was carried out, which could provide a theoretical background for the development of such technology. The steam pyrolysis was performed in a tubular reactor in an overheated steam medium (500°C with 5 kg/h mass flow rate). The technical characteristics of the obtained samples were evaluated in the context of their potential for further application as absorbent and raw material for rubber production according to Chemical s Service No. 1333–86-4. The composition and physico-chemical properties of the obtained samples were studied using BET and thermogravimetric analysis, atomic emission, transmission and scanning electron microscopies, Raman, X-ray diffraction, and photoelectron spectroscopies. The results revealed that the structure and properties of all obtained carbonaceous material samples were similar. The samples consisted of amorphous carbon (with a disordered graphite lattice) and contained a significant amount of metal oxides. According to experimental data, zinc was present in the form of ZnO with a binding energy of 1022.4 eV, while sulfur was observed in the form of sulfide and oxysulfide with binding energies of 161.8 and 163.2 eV, respectively. According to electron microscopy, the morphology of samples was represented by a set of spherical agglomerates comprising nanosized particles. According to the BET analysis of the samples, the specific surface area varied in the range between 52.0 and 66.0 m2/g and the pore volume values were within a range of 0.53–0.87 cm3/g, while the average pore size varied from 412 to 527 Å. Implications: Our paper presents original research in the field of characterization of solid material obtained by single-staged steam gasification of waste tires, which were produced and exploited in conditions of Russia. Modern technology allows thermal utilization of waste tires by obtaining powders of carbonaceous material, which could be used as fuel, adsorbent, etc., but this process usually consists of two stages – pyrolysis in inert medium and activation in steam or carbon dioxide. One of the most promising directions of technological development is simplifying this process into single step, ensuring that the obtained material could be used as carbon black or adsorbent for gas steam cleansing. No data on suitability of carbonaceous material obtained by single-step steam pyrolysis of all-season waste tires to be adsorbent and/or carbon black is present in the literature. In order to evaluate the suitability of the obtained material to be adsorbent, the high specific surface area should be determined, while CAS technical standards specify many chemical and physical properties of industrial carbon black. The aim of the current article is to study the properties of carbonaceous material obtained during single-staged steam gasification of four different all-season tires (due to their widespread application worldwide) and evaluate its fitness as industrial-scale carbon black or adsorbent. The additional problem addressed was the evaluation of the variation in characteristics of carbonaceous material obtained due to different origins of tires. Experiments were conducted in a tubular lab reactor in order to simplify the experimental procedure while ensuring the applicability of the obtained results to practical conditions. The obtained results could be used for the development of the technology for closed-cycle tire processing (because black carbon is used for tire production) and adsorbent production. The characteristics of the materials obtained allow us to choose optimal parameters for such treatment and develop special policies and programs, which will integrate and regulate waste tire utilization via steam gasification.

Liquid Hydrocarbons Production by the Steam Pyrolysis of Used Tires: Energy Characteristics and Environmental Sustainability

Liquid Hydrocarbons Production by the Steam Pyrolysis of Used Tires: Energy Characteristics and Environmental Sustainability

Role of temperature in the biomass steam pyrolysis in a conical spouted bed reactor

The steam pyrolysis of pinewood sawdust has been conducted in a bench scale plant provided with a conical spouted bed reactor (CSBR). This process is of uttermost relevance for the in-line valorisation of pyrolysis volatiles, specifically for their catalytic steam reforming for hydrogen production. The influence of temperature on the product yields has been analyzed in the 500–800 °C range. A detailed analysis of the volatile stream (condensable and non-condensable components) has been carried out by chromatographic techniques, and the char samples have been characterized by ultimate and proximate analyses, N2 adsorption-desorption, and Scanning Electron Microscopy.A high bio-oil yield was obtained at 500 °C (75.4 wt%), which is evidence of the suitable features of the conical spouted bed reactor for this process. As temperature was increased, higher gas and lower liquid and char yields were obtained. Steam was fully inert at low pyrolysis temperatures (500-600 °C), and only had a little influence at 700 °C due to the low gas residence time in the conical spouted bed reactor. At 800 °C, the reaction mechanism was controlled by gasification reactions.The composition of the liquid fraction was considerably influenced by pyrolysis temperature, with a less oxygenated stream as temperature was increased. Thus, phenolic compounds accounted for the major fraction at low pyrolysis temperatures, whereas hydrocarbons prevailed at 800 °C. The char obtained in the whole temperature range can be further used as active carbon or energy source.

Adsorption Analysis of Activated Carbon from Rice Husk and Kepok Banana (Saba Banana) Peel for Treating Ogan River Water

Ogan river has been utilized as source of raw water for various purposes. The quality of water needs to be monitored continuously. Nowadays, the Ogan River was polluted by household waste and industrial wastewater. This study aims to obtain a better adsorber of rice husks or kepok banana peels activated carbon for treating the Ogan river. Activated carbon is used in different states of applications after its discovery as a robust and reliable is adsorbent. The used method to produces activated carbon is pyrolysis, physical-chemical activation, and steam pyrolysis from agricultural waste materials, e.g., rice husk, palm oil shell, and banana peels. Activated carbon is applied in water treatment, significantly to reduce total suspended solids, pH, and heavy metal (iron) of the Ogan river. In this study, rice husk and kepok banana peels activated carbon were produced using chemical activation with H 3 PO 4 0.1 N 20% at a temperature of 450 o C. The morphological and performance test was conducted on prepared activated carbon. The top surface area of both activated carbon was observed using a scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FTIR) analysis. The mean pore size was calculated to describe the adsorption process of the ogan river, which indicated total suspended solids (TSS) and iron (Fe) concentration, then pH value. The results showed that kepok banana peels activated carbon reduced TSS levels of 79.3 to 48.2 mg/L, decreased Fe concentration of 0.63 to 0.07 mg/L, and increased pH value of 5.94 to 7.89. Meanwhile, the adsorption using activated carbon of rice husk could reduce TSS concentration of 79.3 to 36.1 mg/L, decrease Fe concentration of 0.63 to 0.01 mg/L and increase the pH value increased from 5.94 to 7.16. It was concluded that the activated carbon of rice husks has better performance than kepok banana peels.

Role of Temperature in the Biomass Steam Pyrolysis in a Conical Spouted Bed Reactor

The steam pyrolysis of pinewood sawdust has been conducted in a bench scale plant provided with a conical spouted bed reactor (CSBR). This process is of uttermost relevance for the in-line valorisation of pyrolysis volatiles, specifically for their catalytic steam reforming for hydrogen production. The influence temperature in the 500-800 oC range has on the product yields has been analysed. A detailed analysis of the gaseous streamhas been carried out by chromatographic techniques, and the char samples have been characterized by several techniques.A high bio-oil yield was obtained at 500 oC (75.4 wt.%), which is evidence of the suitable features of the CSBR for this process. As temperature was increased, higher gas and lower liquid and char yields were obtained. Steam was fully inert at low pyrolysis temperatures (500-600oC), and only had a little influence at 700oC due to the low gas residence time in the CSBR. At 800 oC, the reaction mechanism was controlled by gasification reactions.The composition of the liquid fraction was considerably influenced by pyrolysis temperature, with a less oxygenated stream as temperature was increased. The char obtained in the whole temperature range can be further used as active carbon or energy source.

Adsorption mechanism and effectiveness of phenol and tannic acid removal by biochar produced from oil palm frond using steam pyrolysis.

In order to meet the growing demand for adsorbents to treat wastewater effectively, there has been increased interest in using sustainable biomass feedstocks. In this present study, the dermal tissue of oil palm frond was pyrolyzed with superheated steam at 500°C to produce nanoporous biochar as bioadsorbent. The effect of operating conditions was investigated to understand the adsorption mechanism and to enhance the adsorption of phenol and tannic acid. The biochar had a microporous structure with a Brunauer-Emmett-Teller surface area of 422m2/g containing low polar groups. The adsorption capacity of 62.89mg/g for phenol and 67.41mg/g for tannic acid were obtained using 3g/L biochar dosage after 8h of treatment at solution pH of 6.5 and temperature of 45°C. The Freundlich model had the best fit to the isotherm data of phenol (R2 of 0.9863), while the Langmuir model best elucidated the isotherm data of tannic acid (R2 of 0.9632). These indicated that the biochar-phenol interface was associated with a heterogeneous multilayer sorption mechanism, while the biochar-tannic acid interface had a nonspecific monolayer sorption mechanism. The residual concentration of 26.3mg/L phenol and 23.1mg/L tannic acid was achieved when treated from 260mg/L three times consecutively with 1g/L biochar dosage, compared to a reduction to 72.3mg/L phenol and 69.9mg/L tannic acid using 3g/L biochar dosage in a single treatment. The biochar exhibited effective adsorption of phenol and tannic acid, making it possible to treat effluents that contain varieties of phenolic compounds.

Study on the Pore and Fracture Connectivity Characteristics of Oil Shale Pyrolyzed by Superheated Steam

The connectivity of the internal pores and fractures in oil shale is the critical factor in determining the success of the insitu pyrolysis of the oil shale with superheated steam. In this paper, using a self-developed superheated steam pyrolysis experimental system, oil shale samples were subjected to pyrolysis experiments at different steam temperatures. Then, the oil shale samples were scanned with high-precision micro-CT equipment to obtain the three-dimensional digital core of oil shale (DCOS). Based on the three-dimensional site percolation theory and renormalization group algorithm, the pore and fracture connectivity characteristics of the DCOSs were studied. The results show that when the steam temperature reached the pyrolysis temperature for oil shale, a series of pores was formed during the pyrolysis process. These pores gradually connected the adjacent fracture and subsequently formed a massive pore-fracture cluster. However, from room temperature to 555 °C, there were always parts with porosity less than 5% in the DCOSs perpendicular to the direction of the sedimentary bedding, forming the bottleneck of the seepage passage. This occurrence is the main reason that the permeability of the oil shale perpendicular to the direction of the sedimentary bedding is far lower than that parallel to the direction of the sedimentary bedding.