Rock control methods around coal mine roadways can be divided into support and reinforcement methods and destressing methods,and the destressing is an effective way for rock control around the roadways with high in-situ stress and intensive mining induced stress. At present,the destressing technical system for rocks around roadways has been formed,which includes roadway layout,rock destressing in near field and in far field. The classification,mechanism,affecting factors and applicable conditions of various roadway destressing methods are introduced in this paper. The essence of roadway layout is to arrange the roadways in stress decreasing areas,such as under or over gob,along the edge of gob,or in gob,which is the first choice and effective destressing method. The rock destressing around roadways in near field mainly contains slotting,drilling,blasting and driving destressing roadways,and its destressing mechanism is to form some deformation space in shallow rock surrounding roadways,reduce rock displacement toward roadways,and transfer the high stress in shallow rock to deep rock. The rock destressing in far field mainly includes blasting with deep boreholes and hydraulic fracturing,which reduces the coal mining activity affect to roadway stability by means of cutting or worsening roof layers above roadways. In recent years,hydraulic fracturing has been widely applied,and become an effective approach for hard rock worsening above coal face and rock destressing around roadways subjected to intensive mining induced stress. In case study,the applications of regional and local hydraulic fracturing technology are introduced,including geological and production conditions,hydraulic fracturing design and destressing effects. Finally,the existing issues associated with roadway destressing methods are analyzed,the technical development prospects in future are put forward.

Aiming at the serious damage of surrounding rock of mining roadway in extra-thick coal seam,the morphological characteristics of mining roadway plastic zone and their evolution law under the action of mining stress was studied by way of theoretical analysis and numerical simulation,taking haulage roadway of No.21141 working face in Qianqiu Coal Mine which locates at Yima Coal Field as the engineering background. The results showed that ①The shape characteristics of plastic zone were related to the bidirectional load ratio. Under different stress conditions,there are three different forms of plastic zone of circular roadway:round,oval and butterfly.②Under the influence of working face mining,the magnitude and direction of the principal stress field in the mining roadway of extra-thick coal seam will change. With the increase of the distance to the working face,the maximum principal stress increases sharply first and then decreases gradually along the axial direction of the mining roadway,and reaches its peak at 15 m away from the working face. The Angle between the maximum principal stress and x-axis increases gradually and approaches the vertical direction. The minimum principal stress reached the maximum at about 25 m away from the working face and then decreased slowly. ③Under the action of mining stress,the plastic zone morphological characteristics of mining roadway in front of working face will change. With the decrease of the distance to the working face,the plastic zone at the shoulder corner of the mining roadway expands to the depth,and its shape gradually evolves from irregular to butterfly shape. Moreover,the direction of butterfly blade in the plastic zone would be deflected with the maximum principal stress. The research results can provide a theoretical basis for the design of mining scheme of extra-thick coal seam and the determination of supporting parameters of mining roadway.〖JP〗

Microalgae CO2 emission reduction technology is an international frontier research hotspot and high-tech competition focus on the field of greenhouse gas control, and is of great significance to the development of low-carbon economy, energy conservation and emission reduction in China.In order to promote the popularization and application of microalgae fixing flue gas CO2 technology in the whole country, an interaction functional model of meteorological factors such as light intensity, average temperature and sunshine duration on the CO2 fixation ability from coal-fired power plant by microalgae was simulated, based on the experimental data of CO2 fixation rate at Ordos Spirulina Cultivation Base, Inner Mongolia. By means of geospatial display, global spatial autocorrelation, and local spatial autocorrelation, the temporal and spatial differentiation characteristics and influencing factors of microalgae's potential to fix CO2 in flue gas in 361 administrative division research units across the country were explored and analyzed. The results showed that:① In the aspect of influencing factors of CO2 fixation rate by microalgae, the effect of light intensity on the CO2 fixation rate by microalgae is the highest,followed by the average temperature and the weakest sunshine duration.② From the perspective of temporal and spatial variation, the CO2 fixation ability from coal-fired power plant by microalgae in different administrative divisions in China presents the characteristics of “great potential in summer and autumn but small potential in winter and spring”. ③ From the perspective of spatial differentiation law and agglomeration characteristics, the CO2 potential of microalgae to fix flue gas in different time periods in different regions presents a spatial pattern of differential distribution, and shows different trends in different regions; In terms of spatial agglomeration characteristics, the CO2 fixation ability from coal-fired power plant by microalgae presents the characteristics of “high-high agglomeration” and “low-low agglomeration”. In this paper, the temporal and spatial pattern and influencing factors of CO2 fixation potential by microalgae in China were comprehensively analyzed, which has guiding significance for the widespread promotion of this technology in China.

With the progress of social and industrial modernization, the emission of carbon dioxide (CO2) and other greenhouse gases is increasing, resulting in serious greenhouse effect and frequent natural disasters. In order to reduce carbon emissions, it is imperative to develop carbon capture, utilization and storage technology (CCUS). At present, the commonly CO2 capture methods and transformation methods include chemical absorption method, adsorption separation method, membrane separation method, and CO2 catalytic reaction, etc. Among them, the development of efficient and stable adsorption and catalytic materials is the key to the optimization of various capture technologies. In this paper, the application of metal-organic frameworks (MOFs) in CO2 capture and conversion is reviewed in detail, the latest progress of current research is analyzed, and the problems and solutions in the application process are revealed. Compared with single metal MOFs, bimetallic MOFs have better metal defect sites and L acid content, showing good advantages in CO2 adsorption separation and catalytic reaction. The functional modification method can be modified according to the needs of different CO2 capture technologies, and has a high success rate, especially the post-functionalization method, which is widely used in CO2 capture due to its simple modification method and good structure maintenance. Pre-functionalization is the most ideal modification method for MOFs, especially ligand functionalization, which can essentially change the affinity of MOFs to CO2. However, the maintenance of MOFs structure is a major difficulty in current research. The preparation of MOFs nanofluid absorbent can effectively increase the heat and mass transfer inside the absorbent, improve the agglomeration of traditional nanoparticles, facilitate the formation of stable suspension, and increase the amount of CO2 absorption. But the viscosity control of absorbent is the barrier of current research. In addition, as a filling material in membrane separation method, MOFs can effectively improve the selectivity of membrane due to its good compatibility and abundant surface functional groups. At the same time, the high CO2 adsorption of MOFs can improve the CO2 capacity of the membrane, but the mechanical properties and cyclic stability of MOFs membrane need to be further optimized. Although there are many studies on CO2 capture technology by MOFs, the literature on CO2 capture system and economic analysis is limited. Starting from the preparation cost, CO2 capture cost and regeneration cost of MOFs, this study attempts to reveal the relationship between the chemical properties of MOFs and the process economy of CO2 capture.

The kinetic study of CO2 adsorption by Li4SiO4 generally takes powder samples as the object, ignoring the basic requirements of the fluidized bed reactor for the adsorption particle size, which greatly weakens its reference value. To this end, Li4SiO4 particles were formed by adding PE, C6H12O6, NH4HCO3 pore-forming agents based on extrusion spheronization, and P particles, C particles and N particles were obtained respectively. Then, the basic characteristics of the three particles were studied by thermogravimetric analysis, compressive strength test and pore structure test. Furthermore, the CO2 adsorption reaction process test and kinetic analysis were carried out based on the P particle with the best adsorption performance. The results show that P particles have the lowest compressive strength and the best adsorption performance, while the performance of N particles is opposite to that of P particles. Pore structure testing found that P particles had the best specific surface area and pore structure, C particles second, and N particles the worst, thus causing the difference in performance. The study on the kinetics of CO2 adsorption of P particles by the grain model and Jander model found that the reaction rate constant increases with the increase of temperature, the increase of CO2 concentration and the decrease of particle size. and the activation energy of P particle adsorption process of CO2 in the kinetic control stage and pre-exponential factors are 41.61 kJ/mol and 4.20 m 0.133·mol-0.289·s-1, respectively, while they are 114.81 kJ/mol and 131.92 s-1 in the diffusion-controlled phase, respectively.

CO2 emissions are the main cause of global climate change and reducing CO2 emissions is being a global consensus. Porous materials，which with higher CO2 adsorption capacity，higher capture efficiency and lower regeneration energy consumption，are considered an effective method to replace the liquid ammonia method for CO2 capture. It is the key to develop porous materials with the chemically stable，high CO2 adsorption capacity and low-cost in the application of porous materials. Aluminum fumarate (AlFu) adsorbent has shown a great application potential in gas separation owing to high specific-surface area and gas adsorption capacity. In present work，in order to simplify the synthesis steps of aluminium fumarate，disodium fumarate as the linker and aluminium nitrate as the metal source were used to synthesis microsphere-like Al-Fumarate MOF (mAlFu) at room temperature CO2 adsorption. The as-synthesized material was characterized by the Scan Electron Microscopy (SEM)，X-ray diffraction (XRD)，Fourier transform infrared spectroscopy (FT-IR)，all the results showed that the synthesized product was mAlFu adsorbent. Thermo gravimetric analysis (TGA) showed that the decomposition temperature of the mAlFu sorbents was 400 ℃，which had high thermal stability. The pore size analysis showed that mAlFu adsorbent had abundant pores. At the same time，the CO2 adsorption performance of mAlFu was investigated，the CO2 uptake of mAlFu was 2.21 mmol/g at 303 K，0.1 MPa. The constructed conformation of mAlFu was used to compute the CO2 adsorption of mAlFu based on the Monte Carlo (GCMC) method. By comparing the experimental and calculated values，the results show that the method of calculating parameters could be used to predict the gas adsorption of mAlFu. Meanwhile，the CO2 selectivity of mAlFu adsorbent was obtained in flue gas，which value was 14. The CO2 cylic regeneration performance of mAlFu had showed the CO2 adsorption capacity remained stable，indicating the sorbents had great potential for CO2 capture.

After the industrial waste gas is treated by desulfurization and ammonia injection, the main component of the gas is N2/CO2. Based on the idea of reducing energy consumption and using shale reservoirs to effectively sequester CO2, the study on the effect of N2/CO2 gas injection on the mechanical properties of shale was carried out. Taking the black outcrop shale of the Longmaxi Formation in Sichuan Province as the experimental research object, under the condition of constant temperature and pressure, the N2/CO2 mixture gas injection test with different concentrations and ratios was carried out. The uniaxial compression test and the Brazilian splitting test were used to analyze the N2/CO2 effect of CO2 concentration in CO2 mixture on mechanical properties of shale. The research results show that: after the shale specimen is soaked in the N2/CO2 binary gas mixture, with the increase of CO2 concentration and phase change in the gas mixture, the pore growth rate of the specimen shows a trend of first increasing and then decreasing, and the pore growth rate is 34.91%-110.6%; the strength and Poisson's ratio of shale specimens decreased first and then increased, and the elastic modulus increased first and then decreased, the loss rate of uniaxial compressive strength was 37.5%-69.1%, the loss rate of tensile strength was 35.3%-85.4%, the elastic modulus increased by 37.5%-54.7%, and the Poisson's ratio loss rate was 11.8%～20.6%; the change of CO2 concentration and phase state in the mixed gas has a great influence on the damage intensity of shale and the damage factor increases first and then decreases. The shale shows obvious brittle failure characteristics, and the main failure mode is splitting failure. Preliminary analysis shows that the pore structure of shale changes under the action of mixed gas. When CO2 is in gaseous state, shale adsorbs CO2, and the pores generate van der Waals force, which expands the shale matrix, expands natural pores and fissures, increases the increase in pore size, and reduces the strength; when CO2 is in a supercritical state, the solubility of SC-CO2 in shale organic minerals in the mixed gas decreases with the increase of SC-CO2 concentration, the increase of pore size decreases, and the rate of strength decay decreases. When the SC-CO2 concentration in the mixed gas is 11.33 mol/L, the ability to dissolve organic matter is the strongest, the shale has the highest porosity, the highest brittleness, and the most obvious deterioration effect of mechanical properties.

Mine fires seriously hinder the safe production of coal, but three-phase foam is an effective approach to prevent the mine fire. At present, the existing two-phase foam generatorsare not suitable for preparing three-phase foams. In order to develop a foam generator suitable for the preparation of three-phase foams, it is necessary to conduct in-depth analysis on the physical foaming characteristics of three-phase foam and optimize the structure of the foam generator. Accordingly, in view of the characteristics of the three-phase foam, this paper takes the self-priming foamer as an example to analyze the foaming characteristics and formation principle of the three-phase foam and its foamer.The distribution law of the 〖JP2〗flow field, pressure and turbulence intensity of the mixed slurry inside the foamer, and an optimization scheme of the self-priming foam generator are proposed. The results show that:① The self-priming foam generator uses the natural pressure difference to inject the flame-retardant gas into the pipeline to realize the full mixing of the gas and the slurry. The difficulty in the design of the self-priming foam generator is to maintain a sufficient natural pressure difference to break the bubbles and particles. ② When the mixed slurry flows through the Venturi tube, the velocity and turbulence intensity both increases first and then decrease along the flow direction, and reach the maximum value near the throat. The negative pressure area in the pipe is distributed in the throat, while the maximum negative pressure is close to the wall of the pipe. It is more favorable to generate three-phase foam by opening holes in the pipe wall near the throat to eject flame retardant gas. ③ Although an appropriate increase in the diffusion angle can increase the maximum velocity and turbulence intensity at the same time, the degree of improvement gradually weakens with the increase of the diffusion angle; in addition, the maximum negative pressure value increases first and then decreases with the increase of the diffusion angle; When the diffusion angle is 55°, and the opening position is near the throat of the pipe wall, it is most favorable for the generation of three-phase foam.

Re-fracturing is an effective means of increasing production when the primary fracture declines in CBM exploitation. In order to study the crack propagation law of re-fracturing in coalbed methane reservoirs and optimize the parameters of temporary plugging, a simulation experiment of indoor temporary plugging and fracturing was carried out. In this study, a large-scale true triaxial fracturing simulation system was used, and the sample size was 30 cm × 30 cm × 30 cm. After collecting coal and rock in the Qinshui Basin, the standard experimental samples were obtained by wrapping concrete. The experiment first simulates the formation environment by loading triaxial stress, and then injects fracturing fluid into the wellbore with a constant displacement to simulate the initial fracturing. The plugging agent was injected into the wellbore and the re-fracturing experiment was carried out; at the end of the experiment, the fracture morphology of the re-fracturing was analyzed by CT scanning. The experimental results show that the temporary plugging effect is greatly affected by the particle size and dosage of the temporary plugging agent. The particle size of the temporary plugging agent is too large, which affects the sand suspension effect of the fracturing fluid. The temporary plugging agent is easy to accumulate in the wellbore, resulting in an abnormal increase in the re-fracturing construction pressure. The particle size of the temporary plugging agent is too small, and it is difficult to form effective plugging, during the re-fracturing, the fractures mainly propagate along the primary fractures. With the increase of the amount of temporary plugging agent, the plugging effect on the primary fracture is enhanced, and the rupture pressure of re-fracturing increases, which promotes the expansion of re-fracturing fractures in the direction perpendicular to the primary fracture; on the other hand, the temporary plugging agent enters the re-fracturing. After fracturing fractures, secondary plugging is formed, which promotes the formation of branched fractures and increases the complexity of re-fracturing. It is believed that temporary plugging and fracturing can promote the formation of branch fractures, improve the complexity of re-fracturing fractures, and increase the fracturing area to improve the effect of re-fracturing. The fracture morphology of the re-fracturing is mainly affected by factors such as the particle size of the temporary plugging agent and the matching degree of the primary fracturing fractures and the amount of the temporary plugging agent.

The coal-measure tight sandstone in the DJ block of the Ordos Basin is an ultra-low porosity and permeability reservoir, and strong heterogeneity is a key problem in reservoir prediction and evaluation. Based on 1 880 rock cores plug porosity and permeability analysis data and 33 sets of mercury intrusion analysis data, the probability cumulative distribution function of the flow interval index and pore throat radius was calculated, and the three flow units classification scheme with FZI was optimized. Tosolve the problem of the imbalance of the number of different types of sandstone samples, 734 sets of macro-rock equivalent type data and numerical logging data were subjected to sub-stratified sampling and homogenization sampling processing, and the data subset was reconstructed;Through the interactive verification method of parameter setting-training-modeling-testing-performance evaluation, the modeling parameters were optimized, and machine learning models of 7 algorithms in two categories, unsupervised and supervised, were constructed. They are K-means clustering, naive Bayes, decision tree, support vector machine, deep learning, random forest and gradient tree boosting respectively, and the two optimal classifications of gradient boosting tree learning and deep learning are determined according to the f1 score value. The research results show thatthe sandstone classification based on FZI flow unit can significantly reduce the influence of heterogeneity on the accuracy of permeability prediction; compared with unsupervised method, the supervised and active machine learning methods are more suitable for the classification principle of flow unit. Gradient boosting tree learning algorithm can use lithofacies, diagenetic facies, sedimentary micro-equal type data modeling, and can be used for basic geological research such as the genetic characteristics of flow units, while deep learning has stronger processing capabilities for numerical data such as well loggingand is suitable for engineering applications such as permeability prediction. The machine learning model with efficient and reasonable classification for flow units is not unique and can be constructed independently according to research purpose and data typesto optimize the algorithm.

Directional drilling technology can accurately control the tracks of borehole and effectively improve the depth of borehole,which has been more and more widely used in gas control of coal mine and geological structure exploration. However,directional drilling tracks in underground coal mine are often different from the design tracks in the construction process. When multiple drilling holes exist in the same working face,the phenomenon of holes collision may occur. Therefore the effect of gas extraction is affected and resulting in potential safety risks,or hole collapse lead to economic losses. For this problem,an anti-collision hole prevention method based on double objective twin support vector machines for directional drilling in coal mine is proposed,and is verified by directional drilling experiment in a coal mine. The method can be integrated into measurement while drilling (MWD) software to judge whether the hole collision may occur in real time by using the measured data of drilling,and real-time guidance to the site construction is provided at the same time. Firstly,the absolute coordinate system is established by the zero-point borehole,all boreholes are contained on the same working face. Then,the dip Angle,azimuth angle and tool facing angle of the newly completed drilling measuring points are selected as input parameters,and the regression model is established by the double-objective twin support vector regression algorithm. Finally,the absolute coordinates of the predicted points are cut by the x axial direction,and the distance between the intersection points and the predicted points is obtained to determine whether there is a risk of preventing the hole collision. The experiments show that this method can guide the construction of directional drilling under coal mine, effectively avoid the risk of hole collision, eliminate the blind area of extraction and mining, and provide technical support for the improvement of the construction quality and drilling efficiency of directional drilling.

Aiming at the key technology problems of three-dimensional environment reconstruction and non-structural environmental movement trajectory planning,a fixed flexible track type suspension inspection robot platform is designed for the movement of special inspection robot in coal mine. The body structure of explosion-proof multi-wheel suspended inspection robot is designed by the idea of modularization. The driving capability of the robot on a flexible track is analyzed by a theoretical calculation,a multi-wheel traction mathematical model is established,and a specific driving capability parameter of a horizontal flexible track and a given climbing angle track is obtained according to a multi-wheel traction mathematical model. According to the acquired driving capability parameters,the double-wheel double-drive robot walking mode is selected. The experiments of a simulation carried out on the installation mode of the foreign-side drive module,and of a physical experiment carried out on the installation mode of the same-side foreign shaft and the foreign-side foreign-shaft drive module show that the walking mode of double-wheel double-drive can guarantee the good horizontal walking ability and climbing ability,in which,the slope angle of the robot under the self-weight of 20 kg can reach 25 degrees;the maximum swing angle of the mounting robot of the different-side foreign-shaft driving module mounting robot in the moving direction is measured to be 2 degrees,but the same-side foreign-shaft driving module is measured to be 5.82 degrees. The swing of the robot fuselage can be reduced by installing the drive module on the opposite side of the double wheel and double drive,but the swing of the fuselage can not be eliminated by the installation mode of the opposite side and the other side of the robot fuselage. In addition to the basic inspection function,the robot can improve the adaptability of unstructured underground environment,improve the flexibility of underground layout and control,can reduce the investment of track laying and recovery,and provide a new special patrol inspection platform for the coal mine environment.

The development of energy and related chemical technologies is closely related to the development of the national economy and national security.In the process of rapid development in China, some technologies with independent intellectual property rights developed in the field of energy and chemical industry have reached the international leading level. Promoting the export of energy and chemical technology plays an important role in promoting economic development, improving the technical content of my country’s export products, optimizing the structure of export products, developing and protecting foreign commodity markets, and driving the export of products and equipment. Studying the potential export capacity of coal chemical technology is a necessary work to promote technological output. At present, China has not yet formed a complete set of indicators for evaluating the potential export capacity of technologies in the coal chemical industry. In this regard, an evaluation index system for the potential export capacity of coal chemical technology was constructed, and a quantitative evaluation method for the potential export capacity of coal chemical technology was proposed using the AHP. On the basis of the existing research results, this method was used to evaluate the representative complete sets of technologies: coal gasification technology - Shenning furnace, methanol to olefin technology - DMTO and coal indirect liquefaction technology package (Zhongke Synthetic Oil). The evaluation result is that coal gasification technology-Shenning furnace ranks first, followed by methanol to olefin technology-DMTO and indirect coal liquefaction complete process technology package (Synfuels China). At the same time, it is found that the key factors restricting the export potential of China’s coal chemical technology are overseas competitiveness, international recognition and technical performance. In this regard, the following suggestions are put forward:① Improve the export policy of energy and chemical technology, strengthen policy support, and create a favorable environment; seize the opportunity, promote transformation and upgrading, and achieve sustainable development; ② Strengthen independent research and development, improve the level of process technology, and establish a International brand image.