Pore Structure Evolution Research Articles

Effect of coal tar pitch on highly reactive coke properties and microstructure

ABSTRACT Highly reactive and high-strength cokes are important for developing and producing hydrogen-rich blast furnaces. The work aimed to produce cokes with high reactivity and high post-reaction strength. The coal tar pitch (CP) was added to improve the post-reaction strength of cokes on the premise of adding alkali metals or alkaline earth metals to improve the reactivity of cokes. The chemical reactivity index of coke samples generally decreases by about 1%, while the post reaction strength of coke samples shows a significant improvement after the addition of coal tar pitch, with coke rich in CaO increasing by about 6% and coke rich in K2CO3 and Na2CO3 increasing by about 3% after adding the CP. Besides, the structural strength and micro strength of coke samples from the composite CP were improved. The microstructure analysis of the coke samples before and after the composite CP showed that the addition of the CP could weaken the originally developed pore structure of the coke samples and reduce the surface area of the gasification reaction of coke samples. Therefore, the gasification reaction of coke samples was inhibited. Moreover, the CP reduced the damage of alkali or alkaline earth metals to the dense aromatic-ring structure in the carbon matrix during the carbonization process of coking coal. It increased the amount of qualitative carbon in the coke samples and the order of carbon microcrystals. The effect of the CP on coke samples varied due to differences in coking coal and catalyst types.

Theoretical analysis of shape factor of gas hydrate sediments under stress dependence

The Kozeny-Carman (KC) equation is used extensively to characterize the effective permeability of gas hydrate sediments. However, most existing modeling approaches ignore the changes in the effective stress, hydrate saturation, and pore structures of porous media, which significantly affect the extraction and exploration of gas hydrates. In addition, theoretical models that can accurately describe shape factors during the imbibition process and predict the effective permeability of gas hydrate sediments are rarely reported. This paper proposes a theoretical stress-dependent shape factor model to study the physical relations between the shape factor and relevant parameters (e.g., effective stress, hydrate saturation, effective porosity, and pore fractal dimension). Then, the derived model is extended to study the shape factor during the imbibition process. The two main novel features of the proposed model are: (1) it takes the effective stress, hydrate saturation, and pore structures into account; and (2) it can be used to study the evolution of shape factors during the imbibition process in gas hydrate sediments. The predictions from the developed model provide a good agreement with experimental results, which validates the model. In addition, based on the derived model, the effects of relevant parameters on shape factors are studied theoretically. From a practical standpoint, the model can not only estimate the effective permeability of gas hydrate sediments under stress dependence but also provide insight into the evolution of shape factor, pore structures (e.g., capillary total number, pore fractal dimension, tortuosity fractal dimension, and effective porosity) and hydrate pore habits during the extraction of hydrates.

Modeling and petrophysical properties of digital rock models with various pore structure types: An improved workflow

Pore structure is a crucial factor affecting the physical properties of porous materials, and understanding the mechanisms and laws of these effects is of great significance in the fields of geosciences and petroleum engineering. However, it remains a challenge to accurately understand and quantify the relationship between pore structures and effective properties. This paper improves a workflow to focus on investigating the effect of pore structure on physical properties. First, a hybrid modeling approach combining process-based and morphology-based methods is proposed to reconstruct 3D models with diverse pore structure types. Then, the characteristics and differences in pore structure in these models are compared. Finally, the variation laws and pore-scale mechanisms of the influence of pore structure on physical properties (permeability and elasticity) are discussed based on the reconstructed models. The relationship models between pore structure parameters and permeability/elastic parameters in the grain packing model are established. The effect of pore structure evolution on permeability/elasticity and the microscopic mechanism in three types of morphology-based reconstruction models are explored. The influence degree of pore structure on elastic parameters (bulk modulus, shear modulus, P-wave velocity, and S-wave velocity) is quantified, reaching 29.54%, 51.40%, 18.94%, and 23.18%, respectively. This work forms a workflow for exploring the relationship between pore structures and petrophysical properties at the microscopic scale, providing more ideas and references for understanding the complex physical properties in porous media.

Comparison of sorbents based on Ca(OH)2 for removing HCl from flue gas

Due to EU climate change policy are coal-fired heating and power plant switching their fuel to biomass one. Emissions of flue gas from biomass are more environmentally friendly in general, but emissions of HCl and HF are increasing, and BAT limits are quite low for them. The possible solution is installation of technology DSI (Dry sorbent injection), especially with connection with bag house filter flue gas treatment. Powder of calcium hydroxide is one of suitable solution. Although the chemical composition is same, there are a huge differences in consumption between another types of Ca(OH)2. This article describes two most selling types of Ca(OH)2 in the Czech republic from the lime works in Štramberk (vz.1) and Čertovy schody (vz.2). This article is divided into laboratory part, where characterized both examples, and experimental part – operational test in the heating plant technology. The results of laboratory part were same for both examples in their thermal characteristic (thermogravimetry and DTA) and real density. Elementary and matter composition were quite similar, only sample 1 was a little bit contaminated by CaCO3 from original material. There was big difference in BET specific area – 14.8 m2·g-1 by sample 1 example and 41.273 m2·g-1 by sample 2. Sample 1 had the most of pore volume in pores with diameter 20-80 nm, the second one on had a more developed pore structure through the whole particle, Operational tests in same constructed CFB boilers were realized during two months in the same conditions. Control system of the heating plant mange cleaning technologies by emission limits, input fuel mixture was for both boilers same. Most of focused parameters were same, only data from DSI system were for each sorbent different. Efficiency of removing HF were for both sorbents same around 99%, for HCl around 85%. Consumption sample 1 was 80.63 m3 and 37.74 m3 of sample 2. When comparing the laboratory and operational parts, higher consumption of sample 2 can be caused by more developed porous structure and a larger specific BET surface. This may be due to the purity of the original material (CaCO3), which was also higher in sample 2, as well as the production technology of the sorbents.

Experimental Investigation on Composition and Pore Structure Evolution of Organic-Rich Shale via Supercritical Water

Experimental Investigation on Composition and Pore Structure Evolution of Organic-Rich Shale via Supercritical Water

Study on the evolution of microscopic pore structure of sandstone under freeze-thaw cycles

In cold regions, rocks undergo freeze-thaw (FT) cycles, leading to damage caused by the evolution of pores. This phenomenon significantly influences the rock mass stability. A comprehensive and accurate study of FT damage evolution in rock pores was conducted in this research. The microscopic morphology and pore size distribution (PSD) of sandstone samples subjected to FT cycles were measured utilizing scanning electron microscopy (SEM), nitrogen adsorption/desorption (NAD) method, and mercury intrusion porosimetry (MIP). Multifractal analysis was applied to explore the evolution of PSD. A gradual weakening of the cementation degree of mineral particles under FT cycles was observed based on SEM results, resulting in the formation of larger connected pores. A decrease of 37.3% in the number of pores was recorded after 40 cycles. According to NAD and MIP results, a greater effect on mesopores and large pores were found, with a minimal impact on micropores and transition pores. Multifractal characteristics were identified in the PSD of sandstone samples with different FT cycles. Initially, the connectivity of sandstone pores was found to decrease and then increase gradually after 10 cycles. Uneven PSD was observed to concentrate stress among pores, exacerbate frost heave damage, and drive the PSD towards a more uniform direction. It was concluded that the non-uniform degree of PSD does not consistently increase with FT cycles. The findings of this study can serve as a reference for further research on rock FT damage mechanisms.

Mechanism of gas-phase passivation inhibition during FeS self-ignition based on pore structure and fractal characteristics

Reactive FeS that spontaneously combusts was prepared under field conditions and subjected to gas-phase passivation using various atmospheres and durations. The goal was to uncover how gas-phase passivation inhibits the spontaneous combustion of reactive FeS. The surface characteristics and elemental composition of FeS were analyzed at different gas-phase passivation levels using scanning electron microscopy (SEM) and X-ray energy-dispersive spectroscopy (EDS). The effect of gas-phase passivation on the evolution of the FeS pore structure was investigated using low-temperature liquid nitrogen adsorption, and the FHH fractal theory was employed to address changes in the fractal properties of the FeS surface. The results highlighted the intricate and densely dispersed pore structure of reactive FeS, along with its pronounced surface roughness. With increased levels of gas-phase passivation, the FeS surface became smoother and more regular, the number of oxidation-expanding pores increased, most sulfur elements were converted into sulfur dioxide gas, and iron trioxide passivation films formed on the FeS surface. Gas-phase passivation significantly reduced the specific surface area and cumulative pore volume of reactive FeS. Specifically, the cumulative pore volume decreased by approximately 20.9%, while the specific surface area decreased by 28.5% as gas-phase passivation deepened. The passivation process transformed more micropores into transition pores, with resulting iron-oxygen compounds adhering to the FeS surface. This reduced the number of reactive adsorption sites and substantially slowed down spontaneous combustion. As gas-phase passivation deepened, the volume proportion of FeS micropores decreased to 16.5%, and the micropore area decreased by around 6%. Gas-phase passivation had a significant impact on reducing the spatial fractal dimension and complexity of FeS, with a greater influence on spatial complexity than surface complexity. The passivation effect was initially enhanced by higher oxygen concentrations within the first 6-hours of passivation, but its effectiveness diminished thereafter.

High-performance MgO-CaO/C for H2S oxidation prepared by a facile co-pyrolysis of magnesium gluconate and CaCO3

A low-cost and facile approach to fabricate high-capacity desulfurizers has drawn much interest in the field of H2S removal. In this study, porous carbon materials with dual active components of MgO and CaO were synthesized by a facile co-pyrolysis of magnesium gluconate and CaCO3, and their performance on room temperature H2S oxidation was investigated. The H2S capacity of optimal CaO-MgO/C is 666.5 mg/gcat., more than 50 times that of MgO/C derived from pure magnesium gluconate. The characterization results indicate that compared to MgO/C, the CaO-MgO/C prepared by this co-pyrolysis strategy has a more developed pore structure and abundant basic sites. Consequently, the H2S adsorption and activation over as-prepared materials are promoted by the co-pyrolysis with CaCO3, and the storage space of oxidation products is also increased, resulting in an extraordinary enhancement in the H2S capacity. In addition, the desulfurization and deactivation mechanisms over the as-prepared CaO-MgO/C are illustrated. This work provides a novel and facile route of developing efficient materials for room temperature desulfurization.

Improvement of coal and Petroleum coke combustion in a fluidized bed by using ilmenite ore as bed material

Oxygen carrier-aided combustion (OCAC) is an innovative technology that adopts the reactive oxygen carrier (OC) particles as bed materials instead of inert ones, which improves the uniformity of temporal and spatial oxygen distribution in the fluidized bed combustor. However, the existing research of OCAC mainly focuses on high-volatile fuels, less attention has been paid to high-ash and low-volatile fuels (such as coal), which are widely used in the world. In this work, three kinds of solid fuels have been comprehensively evaluated in a lab-scale fluidized bed reactor. Results show that compared to quartz sands as bed material, the OC as bed material shows an apparent “oxygen buffering capacity”, improving combustion stability and reducing the unburnt gas. The promotion effect of OCAC increases with the increase of volatile content in fuel, which indicates that OCAC mainly improves combustion through the redox reaction between volatile and OC particles. The solid-solid reaction between OC and char was negligible. The OCAC experiment was carried out for more than 20 h and found that due to the abrasion of the OC surface, the generated fly ash has a significantly higher Fe content than that using quartz sand as bed material at the initial stage of the experiment, and the abrasion of OC decreases with the increase of experimental time. Interestingly, during a 20-h continuous operation, the reactivity of ilmenite ore increased gradually, which was attributed to the development of pore structure and Fe diffusion of ilmenite ore. In addition, the content of unburnt carbon in the fly ash is similar regardless of the bed materials.

Influences of Evolution of Pore Structures in Tectonic Coal under Acidization on Methane Desorption.

Experiments on corrosion reactions of pulverized coal with monomeric and polymeric (mixed) acid solutions reveal that monomeric acids are listed in a descending order as HF, HCl, and CH3COOH according to their corrosion effects on tectonic coal collected in Faer Coal Mine (Liupanshui City, Guizhou Province, China). In addition, the optimal mixing ratio of mixed acids is 6% HCl + 6% HF + 3% CH3COOH + 2% KCl. The mineral grains filled in pores in coal samples treated with mixed acid solutions are dissolved, so the porosity increases. The volumes of transition pores and mesopores are obviously affected by acidization, and some transition pores are transformed into mesopores and macropores to form dissolved pores. At the same time, inkbottle-shaped pores reduce, while slit pores or open pores increase. The coal samples after acidization show a higher aromatization degree and an increased relative content of oxygen-containing functional groups, with a generally lower hydroxyl content, so the methane (CH4) adsorption capacity of coal declines, which promotes CH4 desorption. The control effect of pore structures after acidization reactions on CH4 desorption was revealed from perspectives of the diffusion coefficient (Kn), adsorption volume (ω), average pore-throat ratio (PT), and average sinuosity (τav). That is, CH4 molecules in tectonic coal after acidization turn from Knudsen diffusion to transitional diffusion, the adsorption volume of CH4 molecules shrinks, the average pore-throat ratio decreases, and the average sinuosity reduces, which promotes CH4 desorption from tectonic coal.

Effect of H3PO4 content and processing temperature on the structure and mechanical properties of porous Si3N4

Open-porous silicon nitride ceramics have been fabricated via low-temperature processing at 1200 °C using phosphoric acid as an inorganic binder and pore-forming agent. A detailed study of the effect of phosphoric acid content on the microstructure development and an in-depth analysis of the influence of the porosity and pore morphology on compressive strength, flexural strength, and notch-root radius corrected fracture toughness has been performed. Further, the progressive evolution of porosity and the amount and type of crystalline phases as a function of processing temperature were studied by intermittent XRD analysis. For the first time, a detailed analysis of the pore structure evolution on the longitudinal elastic constant of the porous samples was studied using a non-destructive ultrasonic technique. The critical H3PO4 content of 40 vol% yielded a homogeneous nanoporous structure that resulted in the best mechanical properties – compressive strength >120 MPa, flexural strength >70 MPa, and a notch-root radius corrected KIC ∼1 MPa m1/2. Despite the low fabrication temperature and economic processing route, the mechanical properties of the fabricated porous samples are comparable to the values for porous Si3N4 reported in the literature.

Sulfate resistance and degradation mechanism of basalt fiber modified graphite tailings cement-based materials

This paper delves into the modification mechanism and deterioration mechanism of basalt fiber (BF) on the sulfate resistance of graphite tailings (GT) cement-based materials. Initially, the comprehensive properties of basalt fiber modified graphite tailings cement mortar (BFM-GTCM) under different sulfate cycles, such as apparent morphology, water absorption and mechanical characteristics were investigated. Subsequently, the relationship between the evolution of microstructure, interface stability, pore structure, chemical composition and functional groups of BFM-GTCM and its resistance to sulfate erosion under different cycles was revealed by various microscopic characterization and analysis methods (SEM/XRD/MIP/FTIR/DSI). Simultaneously, a corrosion coefficient-pore structure relationship model was also put forth based on multivariate regression theory, and the mechanism enhancing BFM-GTCM resistance to sulfate attack was investigated. The results demonstrated that a suitable blend of BF and GT can prevent sulfate ion penetration, significantly slow down the generation of corrosion products (AFt and gypsum) in cement mortar during sulfate attack, postpone the occurrence of new cracks and the growth of existing ones, improve pore structure, and significantly lessen the degree of durability degradation of BF-GTCM. Among them, 0.3% BF addition and 20% GT replacement was the ideal ratio.

Statistical Modeling of Pore Structures in Fresh Cement Paste Based on Dispersion Theory of Random Two-Phase Media

Pore structures are critical for most properties of cementitious materials. To describe the initial pore structure of fresh cement paste, which is the foundation of the evolution of a pore network induced by hydration of cement particles in hardened concrete, statistical modelling of pore structure is carried out based on a concentric-shell sphere model, by taking cement paste as a random two-phase media. Calculations by the dispersion models agree well with the pore size distributions tested by the low-field H1 nuclear magnetic resonance (NMR) technique. For cement paste that disperses completely with the help of a dispersant, a hard sphere model is practical. However, in most real conditions, an agglomeration of cement particles will occur both before and after mixing with water, which can be characterized by the redistribution of pore size determined by the critical grain size and the hardness parameter in the concentric-shell model, respectively. Calculation results suggest that agglomeration of particles leads to coarser pores. This work will promote the understanding of the formation mechanisms of pore networks and further offers a foundation for modelling the evolution of pore structures in cementitious materials.

Porous biochars with nitrogen defects prepared from hydrogel template-modified food waste for high-performance supercapacitors

The complex composition and heterogeneous nature of food waste limit the application of biochar materials derived from it in supercapacitors. In this study, biochar was prepared from simulated food waste using a hydrogel template and employed to fabricate supercapacitor electrodes. Food waste was first transformed into a soluble state through an advanced oxidation process (potassium persulfate/heat). Small-molecule polymerization was then performed to generate a structurally uniform food waste hydrogel (FWH). Urea was added during the synthesis of FWH to achieve the uniform incorporation of nitrogen into its structure. FWH biochar (FWHB) was obtained from FWH via pyrolysis at different temperatures (500, 700, and 900 °C). Then, we evaluated the physicochemical properties and electrochemical performances of the obtained FWHB samples. The FWHB pyrolyzed at 700 °C (FWHB700) exhibited a unique sponge-like microstructure with a high specific surface area of 693 m2∙g−1, which was 20 times that of untreated food waste biochar. FWHB700 also showed excellent energy storage performance, with a specific capacitance of up to 461 F∙g−1 at a current density of 1 A∙g−1. Based on physicochemical analysis and density functional theory calculations, the energy storage capacity of FWHB700 was found to be related to its high specific surface area, developed pore structure, as well as abundant nitrogen defects and heteroatom active sites. The symmetric FWHB700//FWHB700 supercapacitor delivered a high energy density of 9.99 Wh∙kg−1 at a power density of 125 W∙kg−1, with 88.2 % capacitance retention after 10,000 charge–discharge cycles. In summary, this study introduces a promising electrode material for energy storage and provides a new approach for the efficient utilization of food waste resources.

An electrochemical aptasensor for detection of carbofuran using gold nanoparticles decorated hierarchical porous carbon as an effective sensing platform

In this study, a novel electrochemical aptasensor for carbofuran (CBF) detection is prepared by gold nanoparticles decorated hierarchical porous carbon (Au@HPC). The prepared carbon materials show a three-dimensional hierarchical structure with a large specific surface area and a highly developed porous structure. Aptamers loading significantly improves when gold nanoparticles are embedded into the hierarchical porous carbon skeleton. Besides, Au@HPC modified electrode exhibits a large electroactive area and excellent electrochemical conductivity, serving as a promising platform for highly sensitive and selective electrochemical detection of CBF. The developed CBF electrochemical aptasensor shows a wide linear from 1.0 to 100000 pg/L with a detection limit of 0.5 pg/L, demonstrating an extraordinary sensitivity compared to other sensors for CBF detection. Additionally, the designed aptasensor was used to monitor the CBF in vegetable samples, with a recovery range from 98.4% to 104.8%. The results coincide with the standard test method, revealing its practicability in the food safety analysis.

Real-time pore structure evolution difference between deep and shallow coal during gas adsorption: A study based on synchrotron radiation small-angle X-ray scattering

Coal seam CO2 sequestration is an important option to address global warming. A better knowledge on coal pore structure evolution during gas adsorption can provide guidance for coal seams CO2 sequestration. However, few investigations on the pore structure evolution differences between the deep and shallow coal were conducted during gas adsorption. In this study, based on the real-time synchrotron radiation small-angle X-ray scattering (SAXS) observation, the average pore diameter and pore surface fractal dimension evolution differences between deep and shallow coal were investigated from the aspects of coal compositions and stress history. Two types of coal deformation (inner-swelling and outer-swelling) coexist during gas adsorption. Coal compositions have significant impact on the dominance of deformation type. The dominance of inner-swelling in deep coal is induced by the higher ash contents, and there is the decrease of average pore diameter during gas adsorption. The impact of stress-history (burial depth) on adsorption-induced deformation is more prominent than that of gas adsorption capacity. In deep coal, the surface fractal dimension evolution presents a negative correlation with the evolution of pore diameters. In shallow coal, the surface fractal dimension evolution presents a Langmuir-type correlation with the adsorption time.

Cobalt-supported activated biochar in the co-pyrolysis of cattle manure and rice husk

It is crucial to develop an efficient catalyst for catalytic co-pyrolysis. In this paper, the catalytic co-pyrolysis of cattle manure and rice husk over a catalyst loaded with cobalt (Co) using potassium hydroxide-activated biochar as the support was conducted in a two-stage fixed-bed reactor. The results showed that the cobalt/potassium rice husk char (KRHC) catalyst displayed a good catalytic pyrolysis process with a large specific surface area and a developed pore structure. Loading with cobalt not only improved the quality of syngas but also increased syngas yield. Hydrogen content increased from 4.55 to 13.68% and carbon monoxide content increased from 19.78 to 32.25%, whereas carbon dioxide content decreased from 7.32 to 5.3% and methane content decreased from 8.01 to 6.07%. Syngas yield increased from 3.68 to 4.58 N m3/kg. The catalyst promoted the breaking of C–C and C–O bonds in tar, increased the content of phenols, ketones and aldehydes, and reduced the content of oxygen in the syngas. The catalysts also maintained good performance after five catalytic cycles, with hydrogen and carbon monoxide contents of approximately 10 and 27.5%, respectively.

Multiscale study of microstructural evolution in alkali-activated fly ash-slag paste at elevated temperatures

To promote the high-temperature application of alkali-activated fly ash-slag (AAFS), it is vital to thoroughly understand the performance of AAFS at elevated temperatures. This paper presents a systematic study on the multiscale microstructural evolution in AAFS paste in terms of nanostructure, chemical composition and morphology changes characterised using 29Si nuclear magnetic resonance, X-ray diffraction and Fourier transform infrared spectroscopy, as well as the pore structure evolution by means of mercury intrusion porosimetry, backscattered electron microscopy and X-ray microcomputed tomography. Results indicate that the decomposition of C-A-S-H and N–C-A-S-H gels occurs while gel pores are filled at elevated temperatures up to 800 °C, along with the crack development, whereas micro-cracks are healed by melting and viscous sintering. This study provides an in-depth insight into the damage mechanisms of AAFS paste at elevated temperatures from a multiscale viewpoint, accounting for Level I: solid gel particles, Level II: gel matrix, and Level III: AAFS paste.

Effects of carbon-sequestering coral aggregate on pore structures and compressive strength of concrete

CO2 sequestration/storage shows considerable impacts on the pore structures and compressive strength of concrete. This paper presents a study in which coral aggregates were presoaked in Ca(OH)2 slurries with different solid-to-liquid ratios (i.e. 0.2, 0.4, and 0.6 g/mL) followed by accelerated carbonation. The effects of CO2 sequestration on the particle size distribution, cylinder compressive strength, water absorption, and apparent density of coral aggregate were investigated. The evolution of pore structures in coral aggregate concrete after CO2 sequestration was also studied. Additionally, the effect of CO2 sequestration on the development of compressive strength of coral aggregate concrete was explored. The results showed that CO2 sequestration affected the properties of coral aggregate. Moreover, the porosity of CaCO3 formed by CO2 sequestration was the highest in the concrete. With the increase of solid-to-liquid ratio, the porosity of cement pastes and the CaCO3 increased, and more big pores existed in the cement pastes and CaCO3. Furthermore, the compressive strength of coral aggregate concrete when the solid-to-liquid ratio was 0.2 g/mL increased compared with that before CO2 sequestration, but the compressive strength reduced when the ratio increased to 0.6 g/mL.

Variations in the pore structure and fluid mobility under anionic surfactant assisted matrix acidification of coal based on nuclear magnetic resonance T1-T2 spectra

Matrix acidification is a potential method for increasing the permeability of coalbed methane reservoirs. However, current research on the acid corrosion process is still unclear, and acid solutions can cause water blocking damage to reservoirs. Therefore, this article obtained a T1-T2 joint spectrum through nuclear magnetic resonance (NMR) test and conduct contact angle (CA) test to analyze the pore structure and fluid mobility evolution of bituminous and anthracite coal under sole acidification and Sodium secondary alkyl sulfate (SAS) surfactant assisted acidification. The results show that the acidification process exhibits two distinct stages. Stage 1: acidification mainly expand the pore space of the free fluid, while stage 2: acidification significantly increases both the bound fluid and free fluid space. After sole acidising, the porosity of bituminous and anthracite coal increased by 4.44% and 31.31%, while increased by 18.28% and 38.35% under SAS assisted acidification, respectively. The adding of SAS resulted in better connectivity of coal samples, with pore throat (>0.1 μm) of bituminous and anthracite increasing by 56.02% and 351%, respectively. Under SAS assisted acidification, the maximum decrease of T2cutoff value of bituminous and anthracite coal is 62.79% and 20.28% respectively. Surfactants can effectively alleviate the negative impact of acidification on coal surface wettability. The results can provide references for field application of matrix acidification in coalbed methane reservoir.