In order to reasonably determine the control of surrounding rock and drilling and blasting parameters along the thin coal seam under the hard roof, a mine in Shandong 21602 working face haulage lane was taken as the engineering background, and the surrounding rock structure evolution of the lane was considered, the lane was divided into four stages, and the corresponding lane surrounding rock support scheme was given; numerical simulation and field measurement were used to study the key parameters of the top-cutting along the lane in depth. The results show that: the reasonable drilling and blasting height is 4.5 m, and the angle of top cutting is 70°; after blasting, the accumulated deformation of the top plate is 118 mm, the accumulated deformation of the bottom plate is 344 mm, and the accumulated deformation of the solid coal side is 402 mm, which can meet the requirements of the later use of the stay lane. The relevant research results have been applied in the field at 21602 working face, which provides a reference for the implementation of stay-along lane under the same conditions.

Under the influence of crustal stress at the mining depth of 750m in Wuyang Coal Mine, serious deformation occurred during the construction of the underground main roadway. In order to enhance the overall stability of the roadway, improve the construction quality of the underground deep main roadway, and ensure the safe production of the mine, through the classification analysis of the deep crustal stress and underground engineering rock mass, the initial support design of the underground main roadway is proposed. Combined with the support effect, the theory of fastening key bearing rings is used, Propose an optimized design using a combination of anchor mesh, cable spraying, and grouting anchor cable support. The results indicate that the rock mass classification index for underground engineering can serve as an important reference for selecting suitable layers for underground engineering; Relying on the self stability ability of deep rock mass and using grouting anchor cables to support the key bearing ring of the tunnel as plastic support, can ensure the requirements of tunnel support and achieve good support effects.

In view of the fact that the local ventilation system of the heading face cannot monitor in real time and intelligently control the air flow state of the air duct outlet, the wind field distribution is unreasonable, resulting in potential safety problems such as gas overrun and dust accumulation. Based on the intelligent control device of the heading face air flow, the virtual reality and remote monitoring technology are used to design the virtual mapping remote monitoring system of the physical device. Using Unity3D to build the virtual scene model of the system ; based on Sugar BI cloud platform, PC / Android remote monitoring software is developed, including 3D virtual scene preview, real-time data and video monitoring, prediction and early warning mechanism, intelligent control module and support information subsystem. The system is tested on the laboratory simulation experiment test platform. The results show that the system runs reliably and all expected functions can be realized, thus improving the intelligent visualization of ventilation on the heading face.

Based on the technical reform engineering of Wanli No. 1 coal preparation plant, according to?the coal quality characteristics of high external moisture and high content of fine coal, replace the former vibrating screen with a relaxation screen, reform the heavy-medium shallow-trough separation process so that it can be connected in series or parallel, add a centrifugal dehydration process block clean coal after crushing, the moisture content of the product is reduced, the calorific value of the commercial coal is increased, and the clean coal yield is increased by 28% compared with that before the technical transformation. The total moisture of clean coal decreased by about 3.1% and the calorific value increased by about 148kcal/kg ,business turn loss into gain.Reference experience for the design of technical transformation project of large-scale steam coal preparation plant is provided.

To explore the reasonable size of inclined trapezoidal gob side entry pillar in gently inclined coal seams and the control technology of roadway surrounding rock, taking the 72510N working face as the engineering background, the internal and external stress field theory, numerical simulation and field test considering the coal seam dip angle are applied to carry out research. Through theoretical calculation, we determined that the width of the stress field in the 72510N working face is 13.4 m, and the coal pillar reasonable width should not be greater than 8.4 m. Combined with the simulation calculation results, the coal pillar width was determined to be 7 m. On the basis of analyzing the difficulties in controlling the deformation of surrounding rock of inclined trapezoidal gob side entry in gently inclined coal seams, combined with the research results, it is pointed out that asymmetric support is used to control the surrounding rock. The support mode is "high-strength anchor bolt+roof high-strength long anchor cable+pillar side inclined anchor cable+anchor mesh", which has been applied in the field. The field test results show that the large deformation of surrounding rock of roadway along goaf can be effectively controlled by setting a coal pillar size of 7 m and using asymmetric support technology. The measured maximum displacements of the right middle roof, the left middle roof, the coal pillar, the solid coal and the floor measuring points during tunneling are 121, 105, 96, 90 and 82 mm respectively, and the maximum displacements observed during mining are 389, 363, 346, 335 and 325 mm respectively, meeting the on-site production needs.

Aiming at the problem of low anchoring force of the roof of the shallow buried deep thin bedrock roadway in Hong liulin coal mine, the distribution characteristics and mineral composition of the weathered bedrock are analyzed. The grouting reinforcement test of the thin bedrock roadway is carried out in the laboratory, the grouting reinforcement mechanism of the thin bedrock roadway is analyzed, the roadway anchoring reinforcement technology scheme is proposed, the underground engineering practice is carried out, and the engineering application effect is analyzed. The results show that the content of clay minerals in weathered thin bedrock is high, which increases the softening and expansion deformation of roof rock mass and affects the stability of roadway surrounding rock; The underground grouting fills the weathered bedrock cracks, blocks the roof water seepage channel, improves the integrity of the roof, and increases the resistance to damage of the thin bedrock layer; Good grouting consolidation effect is achieved through anchor cable grouting. The initial stress of anchor and able increases slowly, and then basically remains stable. The stress of anchor rod is 55~67kN, the stress of anchor cable is about 92kN, the roof separation is about 3mm, the deformation of roadway surrounding rock is significantly reduced, and good roadway support effect is achieved through anchor cable grouting. It shows that the bolt grouting reinforcement technology can effectively solve the problem of deformation control of shallow deep and thin bedrock roadway.

Taking the 2-205 fully mechanized top coal caving face of Tenghui Mine as the background, combined with the characteristics of the large cross-section and partial roof fragmentation of the 2-2051 mining roadway props, it is proposed to use a composite support method of grouting anchor cables and single hydraulic props combined with π beams to reinforce and support the roof fragmentation area, in order to ensure the safety of the roadway roof during mining. By analyzing the distribution law of advanced support pressure in the 2-2051 mining roadway, guidance is provided for the reinforcement and support design of the 2-2051 mining roadway. Based on the analysis of the principle and strength of grouting anchor cable reinforcement support, and the calculation of the reinforcement support strength of the 2-2051 mining roadway, the design of the roadway support plan was completed. The research results indicate that the composite support method of using grouting anchor cables and single hydraulic props combined with π beams, combined with the structural characteristics of the tunnel surrounding rock, the distribution law of advanced support pressure, the principle of grouting anchor cable reinforcement support, and the calculation of tunnel reinforcement support strength, has analyzed and calculated reasonable support plan parameters, and targeted the implementation of the reinforcement support plan for the broken roof area. The on-site industrial test results show that the use of anchor injection reinforcement support technology in the fractured area of the mining roadway roof effectively controls the deformation of the roadway roof, which can meet the requirements of safety and efficiency in the mining face. It has engineering promotion value for other mines with similar conditions.

In view of the difficult problem that the strong dynamic pressure in Laoshidan Coal Mine affects the deformation of the surrounding rock of the roadway, based on the analysis of the distribution of the roof rock and the geostress field, this paper summarizes the deformation and failure characteristics of the surrounding rock of the dynamic pressure roadway, puts forward the collaborative control technology of weakening the external force source and improving the internal support strength, determines the optimal fracturing height, develops the hydraulic fracturing scheme and the high prestressed bolt support scheme, and carries out the underground engineering application. The results show that hydraulic fracturing effectively stimulates roof rock fracture and fracture expansion, forms large-scale fractures, and blocks the transmission path of lateral abutment pressure; The ground pressure of the roadway is obviously weakened, with the roof and floor approaching 402mm, and the two sides approaching 83mm, significantly reducing the deformation compared with the original support; Under the influence of strong mining, the stress of anchor bolt and cable has been effectively improved. The maximum stress of anchor bolt is 79~96.5kN, the maximum stress of anchor cable is 101kN, and the anchor bolt cable is not broken. This shows that after hydraulic fracturing and high prestressed anchor bolt support, the lateral bearing pressure of roadway surrounding rock is significantly reduced, the stability is significantly improved, and the control effect of roadway surrounding rock under strong dynamic pressure is significant.

Abstract： In view of the large deformation of weakly cemented soft rock roadway in Dananhu No.7 coal mine under alkaline water environment, the deformation mechanism of weakly cemented soft rock roadway surrounding rock under alkaline water erosion was studied by means of field measurement and numerical calculation, the evolution of plastic zone of roadway surrounding rock under different support parameters and the bearing characteristics of anchor rods and ropes were analyzed, and the best support scheme for weakly cemented soft rock roadway was proposed. The results show that under the existing support parameters, the overall shifting amount of the roadway and the anchor rods and ropes bearing tend to increase sharply first and then slowly, and the shallow delamination phenomenon is obvious; the weakly cemented soft rock roadway with rich alkaline water has the characteristics of rapid initial deformation and large shallow delamination, timely support measures should be taken; the anchor rod and anchor rope row distance is the main control factor of the deformation of the surrounding rock and the anchor rod and rope loading value of the roadway; the proposed and verified anchor rod pre-stress of 50N, anchor length The support scheme of anchor pre-stress 50N, anchor length 1.5m, anchor rod row distance 750mm and anchor cable row distance 1500mm is proposed and verified, and the long-time stability of the roadway is achieved.

Based on the theoretical analysis and calculation of the influence radius of gas shock induced fracture in the roof coal of the gob-side roadway, a blasting hole layout scheme and parameters for gas shock induced fracture to enhance top coal caving property of the gob-side roadway were designed. Numerical simulation verification and field engineering application were also carried out. The results show that the roof top coal between the blasting holes enters the plastic yield state due to the phase change gas shock of liquid carbon dioxide along coal pillar side and the middle span of roadway roof, the subsidence deformation of roadway roof along coal pillar side, across the middle, and on the mining side no longer presents a downward convex shape, and the subsidence deformation of the top coal on the coal pillar side and across the middle of roadway near the working face is basically the same and increases significantly. With no affecting the maintenance of the safety entre, the gas shock technique not only significantly improves the caving property of roadway top coal, ensuring the safe and efficient recovery of the roof coal in the roadway, but also eliminates many major security risks with the hanging roof of side working face. This can promote the safe, efficient and sustainable mining of Sanyuan Coal Industry.

To solve the problem of large bearing stress of the roadway, serious deformation of two gangs and roof in the retreating stage, roof cutting is proposed.Taking 2-203 as the research object,key parameters of the cutting hole are studied combined with theoretical analysis, numerical simulation and field tests.The results show that when the elevation angle and depth of the cutting hole are 75°and 9 m respectively, the stress peak of the coal pillar is smallest, the pressure relief effect is obvious, and the stability of the roadway is better. Through field tests, the deformation on the left side of the coal pillar decreased by 60 mm, a decrease of 14.46%, and the right side decreased by 33.71%.Compared with the deformation of adjacent roadway, roof cutting has a better pressure relief effect on the system roadway.

Based on the hydrogeological conditions of the mine field, the Jiulong coal mine proposes to reuse the high salinity mine water treated underground coal mine to solve the problem of high salinity mine water discharge. According to the proposed water quality index, the experiments treating mine water have been carried out with the process of "coagulation + sedimentation + ultrafiltration".The results show that the water quality indexes of ultrafiltration effluent meet the main water quality indexes proposed.Combined with the existing mine water treatment process of the mine, the "ultrafiltration+disinfection" process is proposed for the deep treatment of underground reuse of mine water to meet the water quality indexes proposed.The advanced treatment process can provide reference for relevant high salinity mine water mines because of saving investment and achieving good results.

The immersion ultrafiltration is adopted for the mine water pretreatment system of coal mine in Ningxia province, the ultrafiltration inlet is equipped with a hybrid heater. When the hybrid heater is put in commissioning with incoming steam,the outlet pipe of the heater, viz.the inlet pipe of the submerged ultrafiltration, is in vibration.Especially during the immersion ultrafiltration back-washing, the inlet pipe has extremely vibration. This paper mainly focuses on the problems existing in the vibration of the mine water submerged ultrafiltration inlet pipeline, to analyze and study the operating conditions of existing systems and equipment,compare differences in major equipment to dig out the fundamental cause of pipe vibration,then re-adjusting the relevant equipment and pipes to solve the vibration of the inlet pipe. Further more, to provide reference for the selection of hybrid heaters, the design of submerged ultrafiltration distribution channels, the selection of ultrafiltration feed pumps, valves and the system design of pipelines.

Based on the background of gas extraction in outburst coal seam, the paper introduces the multiple disturbance process of surrounding rock of mining roadway, especially floor roadway, and combs the damage mechanism and stability control method of surrounding rock of mining roadway. This paper introduces the expansion law of the fractures in the extraction boreholes and the distribution characteristics of the pressure relief fractures in the coal seams. This paper summarizes the research progress on the crack propagation law, the instability mechanism of the sliding surface and the action mechanism of the anchor bolt in the anchored layered fractured rock; The damage evolution mechanism of coal samples and anchored coal samples under cyclic loading is discussed. In recent years, the roadway control methods under complex conditions (mining influence, high stress, broken surrounding rock) are reviewed, including grouting reinforcement, bolt-grouting reinforcement and surrounding rock joint control technology. Finally, the shortcomings of the above research are analyzed and the future development trend is prospected; Under the condition of multiple disturbances, the research should be strengthened in the aspects of the development and evolution characteristics of the surrounding rock fractures of the mining roadway, the evolution of the geological strength factors of the surrounding rock, the evolution characteristics of the low-cycle fatigue damage of the fractured rock strata and the anchored fractured rock strata, the constitutive relationship, and the stability control methods and technologies of the surrounding rock of the mining roadway.

Abstract: In order to solve the problem that the existing coal pillar layout method of Shaqu No.2 mine seriously restricts the safe and efficient recovery of the mine, the 4^# and 5^# coal of Shaqu No.2 mine was used as the research object, and the reasonable width of coal pillar was obtained by theoretical analysis and calculation; UDEC numerical simulation was used to determine the layout of 5302 trackway by simulating the roadway associated with different superimposed coal pillar structures in very close coal seams; engineering tests were conducted to The engineering test was used to observe the mine pressure in different test sections. The research results show that: ① The reasonable coal column width of the front section of 5302 trackway is 61.4m, and the reasonable coal column width of the rear section of 5302 trackway is 12.8m; ② The front section of 5302 trackway adopts the small staggered distance internal staggered arrangement, and the internal staggered 4302 trackway is 5m, and the rear section of 5302 trackway is arranged at the position of 12m from the filling body next to the roadway; ③5302 working face back mining roadway top and bottom plate shift up to 286mm, two helpers shift up to 95mm, roadway support pressure in the roadway dug out gradually stabilized, roadway surrounding rock plastic zone range is not large, roadway surrounding rock control effect is good.

In order to improve the energy absorption efficiency and deformation stability of roadway anchor cable suction pressure structure, mechanical testing and finite element numerical simulation were used to study five different energy absorption pressure structures, namely coarse waist drum, straight pipe, wedge groove, long groove and straight pipe V-shaped groove. The results show that the shape and structure characteristics determine the peak compressive strength, ultimate deformation, energy absorption efficiency and the overall stability of the structure. Although the energy absorption efficiency of the straight tube energy absorption structure with 5mm wall thickness is increased by 48%, 66% and 56%, respectively, compared with the coarse waist drum, wedge groove and long groove structure, local stress concentration is easy to occur in the compression process of the straight tube energy absorption structure, and then the bias induces the uneven deformation and structural instability. The energy absorption efficiency of the straight tube structure with deformation induction V-shaped groove inside is 45.29KJ/g, which only reduces the energy absorption efficiency of the pressure structure by 6% compared with that of the straight tube. However, due to the deformation induction effect of the V-shaped groove, the bias problem caused by local stress concentration can be avoided, and the deformation of the pressure structure is more stable than that of the straight tube.By applying the V-shaped groove energy absorption and compression structure to on-site practice, the deformation of the tunnel was well controlled.

n this paper, taking the 20107 working face of Gaojialiang Coal Mine as the engineering background, with the help of the physical similar material test system and the UDEC numerical simulation program, the breaking law of the overlying rock under the mining conditions of the shallow coal seam is studied. Numerical simulation and physical test results are verified. The research results show that: with the continuous advancement of the mining face, the roof collapses directly after the layer is separated to a certain extent, and the collapsed gangue fills part of the goaf, and then the roof basically bends under the action of its own weight and overlying load. A series of processes such as subsidence, periodic breaking, gangue compaction, and final stabilization; after the mining of the working face, the "three-zone" structure of the overlying rock is basically formed; the observation results of staged water injection in the downhole vertical hole show that the overlying rock failure height is about 100m , the fracture zone is highly developed into the fine-grained sandstone layer, and the simulation results of similar materials and numerical simulations are in good agreement with the actual situation in the field.

Taking the weak earthquake near Zhangshuanglou coal mine as the engineering background, the rock burst risk affected by earthquake is analyzed in detail through SOS microseismic monitoring, stress monitoring and seismic wave CT inversion and other technical means. The results show that the mine microseismic monitoring system has a certain response ability to weak earthquakes near the mine field, but the source position is outside the range of the microseismic monitoring network, and the calculated source positions are more and the positioning position error is larger. The overall trend of the monitoring data of mine microseismic monitoring, stress monitoring and seismic wave CT inversion before and after the earthquakes are stable, which indicate that the weak earthquakes near the mine field have no significant impact on the mine rockburst risk. The results of this paper have significant guidance for the in-depth understand of the impact of the natural earthquake near the mine field on the rockburst risk in coal mine, and also provide a reference for the follow-up study of the development of the rockburst monitoring technology and the relationship between the earthquake and the mine rock burst.

In order to effectively improve the permeability of high-gas and low-permeability coal seam and the effect of gas drainage, the influence of gas drainage borehole on the development law of coal blasting fracture was studied by combining theoretical analysis, similar simulation test and numerical simulation. The research shows that the incident compressive stress wave is reflected in the nearby coal body through the extraction hole, causing the coal body to be subjected to both tangential tensile stress and radial tensile stress. When the tangential tensile stress is greater than the dynamic tensile strength of coal body, the coal body is pulled to form radial cracks. When the radial tensile stress intensity is greater than the dynamic tensile strength of coal, the coal fracture produces circumferential cracks. The main cracks around the blasting hole expand to the side of the extraction hole, and form a cross fracture network with the cracks around the extraction hole. Through the field application of a working face in Huainan Coal Mine, the gas extraction concentration is 3 ~ 4 times and 2 ~ 3 times before blasting when the extraction hole is 3 m and 4 m away from the blasting hole. The results show that the influence of gas drainage borehole on the expansion and development of explosive fractures can effectively improve the permeability of coal seam and the effect of gas drainage.

In view of the contradiction between the high filling cost of the mine goaf and the difficulty in the treatment of large quantities of coal based solid waste mainly composed of gasification slag generated by the coal electricity chemical industry, the strength performance of paste filling materials with high content of gasification slag is explored by taking the gasification slag produced by Ningxia Yuanyanghu Power Plant as the research object. In this study, gasification slag is used as aggregate and cement is used as gelling agent. In the early stage, the reasonable range of three factors, namely, the amount of gasification slag in the dry material (X1), the bone glue ratio (X2), and the slurry concentration (X3), has been determined through single factor tests. Using response surface method, 17 groups of central combination tests have been designed to explore the influence of the three factors and the interaction between the three factors on the strength of paste filling materials. The three factors and 7d The functional relationship between the strength of filling materials at the curing age of 14 days optimizes the proportion scheme of paste filling materials. The results show that the bone glue ratio is the primary factor affecting the 7d and 14d strength. The interaction of bone glue ratio and slurry concentration has the largest impact on the 7d strength, and the interaction of the amount of gasification slag in the dry material and bone glue ratio has the largest impact on the 14d strength. The optimum ratio parameters were obtained as follows: the content of gasified slag in dry material was 49.282 %, the bone glue ratio was 4.554 : 1, and the slurry concentration was 81.056 %.

The surface subsidence in western mining area is characterized by fast deformation speed, deep damage degree and wide spread, and the conventional observation stations cannot adapt to the monitoring task of surface damage in high-intensity mining. How to quickly, accurately and comprehensively monitor the surface subsidence and environmental damage caused by high-intensity large-scale mining is a key problem facing mining enterprises. Taking a mine in Ordos as an example, Unmanned Aerial Vehicle (UAV-LiDAR) measurement technology is used to monitor the surface subsidence of high-intensity mining in this mine, and the key technical process of UAV-LiDAR monitoring is given. Ground points were obtained by Kriging interpolation on the measured point clouds and surface DEM was established. The surface subsidence basin was obtained by multi-stage DEM differential processing. The combined median filter and bilateral filter were used to de-noise the subsidence basin, and finally the high-precision subsidence value was obtained. The accuracy of surface DEM measured by UAV-LIDAR is 15mm, and the error of surface subsidence basin model is 39mm. UAV-LiDAR technology can quickly obtain rich surface data and obtain high-precision surface subsidence basin information. Therefore, the application of this method in mining subsidence monitoring is feasible, and provides support for mining ecological environment monitoring, land reclamation and ecological restoration. The research results can provide effective means for monitoring surface damage in western coal mining.

Auxiliary transportation of underground coal mines is an essential link in modern mine mining. The current auxiliary transportation system has some problems, such as high risk, high labor cost, difficult recruitment, low work efficiency, etc. Taking "Intelligent Equipment, Intelligent Transportation and Intelligent Management" as the overall framework, this paper designs the operation process of mine auxiliary transportation vehicles and puts forward a general architecture of intelligent unmanned transportation system for mining auxiliary transportation vehicles. And the complete schemes of the intelligent dispatching management system, unmanned system, V2X vehicle-road cooperative perception system, remote monitoring, emergency takeover system, and auxiliary operation terminal are designed. The whole set of unmanned transportation systems can realize the deep integration of emerging technologies such as deep learning, big data, and V2X. It can significantly reduce potential safety hazards, improve transportation efficiency, and bring economic benefits. And it can guarantee the safe and efficient operation of auxiliary transportation links of underground coal mines and actively contribute to constructing the intelligent mine and transforming and upgrading coal mining.

The sag resistance is the main resistance during the operation of the conveyor belt. In order to reduce the sag resistance, the one-dimensional Winkler viscoelastic basic model and the standard linear solid model were used to deduce the surface stress distribution of the conveyor belt sag resistance, and a new type of 45° idler set of life product was proposed. Its layout advantages were analyzed, and the sag resistance was numerically simulated, and the influence of the load, the running speed of the conveyor belt, and the running distance of different idlers were analyzed, and the correctness of the numerical simulation was verified by the experimental results. The following conclusions were obtained: the sag resistance of the equallife 45° idler group is reduced by about 30% compared with the standard 35° idler group, and the sag resistance is greatly reduced, thereby achieving the purpose of energy saving and consumption reduction of the whole belt conveyor.

Development of CO2 capture, utilization and sequestration technology suitable for coal-fired power plants is of great significance for realizing the carbon peaking and carbon neutrality goals in our country. Solid waste reduction, recycling and harmless utilization is a strategic measure of pollution prevention and control in China at present. In this paper, a fly ash from Sandaogou Power Plant was selected to experimentally investigated the CO2 mineralization and alkali reduction performance through carbonation reactions. The physical and chemical characteristics before and after reaction of the fly ash were also explored, and the potential utilization of the carbonated fly ash were discussed. The results show that increasing the flue gas flow rate can effectively increase the CO2 mineralization and alkali reduction performance of fly ash. However, when the flue gas flow rate exceeds a certain value, CO₂ dissolution became fast while the conversion rate of calcium reach saturation. The introduction of organic amines into the fly ash -water system could significantly improve the utilization efficiency of CO2 and the CO2 sequestration capacity of the fly ash. This is because organic amines could not only improve the solubility of CO2 in the solution, but also enhance the dissolution of calcium phase from fly ash particles. CO2 mineralization can not only significantly reduce the alkalinity of fly ash, but also reduce the leaching amount of some heavy metals in fly ash, thereby promoting the absorption and resource utilization of fly ash．

Mechanical stirring is a very important step in the process of ultra-fine coal separation. Through theoretical calculation and analysis, the necessity and influence mechanism of stirring energy input in floc flotation process are demonstrated, and the effects of stirring speed and stirring time on floccules size and ultra clean coal separation are experimentally analyzed. The floc size formed by coal particles grinded by two different ultra-fine grinding methods and the separation results of ultra clean coal were compared. The results show that there is an energy barrier peak in the interaction potential energy between particles, and the energy input of mechanical stirring endows the coal particles with the kinetic energy to overcome the energy barrier, which enables them to agglomerate under the action of hydrophobic potential energy. The smaller the particle size, the higher the input of stirring energy. With the increase of stirring speed or stirring time, the floccules size and ultra-clean coal yield increases slightly and then decreases gradually for coal particles with smaller particle size. Stronger stirring energy input is beneficial to the separation of ultra-clean coal with lower ash content. Compared with the coal samples grinded by stirring mill, the ultrafine coal pulverized by jet mill has a larger size of flocs and a higher yield and ash content of ultrafine coal.

In view of the problems such as many functional groups on the surface of slime, poor floatability, low yield and large consumption of flotation reagents in a coal preparation plant in Xiaoyi City, a new collector B-H was developed, and two factor multi-level flotation tests were used to explore the optimal dosage of traditional collector diesel, new collector B-H and foaming agent sec octanol, and the floatability test of slime was conducted for the optimal dosage. The results show that when the ash content of flotation cleaned coal is about 15%, the optimal dosage of B-H collector is 700g?t-1, the dosage of secondary octanol is 250g?t-1, and the flotation cleaned coal yield is 80.42%; The optimum dosage of diesel collector is 1100g?t-1, the dosage of secondary octanol is 250g?t-1, and the flotation clean coal yield is 50.76%. Compared with conventional collector diesel oil, the new collector B-H has increased the clean coal yield by about 30% and the flotation perfection by about 18%, which improves the floatability of coal slime and meets the production requirements.

Based on the optimization of cut-off parameters for excavation machines, using discrete element method-multi-body dynamics bi-directional coupling technique, based on numerical simulation, multi-objective optimization method, taking a certain type of roadheading machine cutting mechanism as the engineering object. Joint Pro/E, EDEM and RecurDyn to build a DEM-MBD bi-directional coupling simulation model of the cut-off process of excavation machines, investigating the effect of different working conditions on the load on the cutting head and cutting performance. Using the Box-Bohnken test method in Design Expert to design a three-factor, three-level response surface regression test with cut-off ratio energy consumption, load mean value and load fluctuation coefficient as cut-off performance evaluation indexes, reducing the three-dimensional objective to a truncated integrated evaluation degree one-dimensional merit search model by principal component method. The results show that when the transverse pendulum speed is 1.270 m/min, the speed range is 44.158 r/min, and the vertical pendulum angle is 12.232°, the integrated evaluation degree of truncation reaches 0.903.

In order to improve the performance and life of the electro-hydraulic proportional valve, the design and research of the electro-hydraulic proportional pressure reducing valve were carried out by comparing the design parameters and optimizing the structure of the valve core and valve body. First, the vibration frequency of the electrical signal is selected based on the pressure amplitude of the valve, and the fitting clearance of the valve core and valve body is selected based on the leakage amount of the valve at each position. Then, according to the state of the valve's maximum current and maximum pressure, the performance of the valve is visually analyzed, and it is found that the hydraulic oil has the highest flow rate at the valve port, and the negative pressure at the valve core shoulder is easy to cause cavitation, and the turbulent kinetic energy is also the largest. According to the analysis results, the structure of the pressure reducing valve is optimized. Finally, a test system is designed to test the proportional valve. The research and inspection results show that when the current frequency is 100 Hz and the matching gap between the valve core and the valve body is 5~6 μm, the proportional pressure reducing valve has good step characteristics and current-pressure characteristics; Increasing the bevel and rounding at the shoulder of the valve core and increasing the annular groove at the valve port of the valve body can effectively inhibit the generation of cavitation, reduce the probability of the valve core being clamped, reduce the loss of energy, and improve the performance of the valve.

Accurate prediction of coal prices is of great significance to defuse energy price risks. Aiming at the problem of coal price forecasting, a multi-step forecasting study of coal price based on ensemble model is carried out. This study analyzes the main controlling factors affecting coal prices, and establishes a data set; effectively integrates Particle swarm optimization (PSO) and Long Short-Term Memory (LSTM), and establishes a multi-parameter multi-step prediction model based on PSO-LSTM. Using the multi-parameter and multi-step forecasting model to call the data set to forecast the coal price of Caofeidian Port, the results show that the forecasting effect of the multi-parameter and multi-step forecasting model based on PSO-LSTM is better than the forecasting model based on BP and LSTM. It’s MAPE and R2 values of predicted price and actual price are 0.025 and 0.908 respectively, which can provide help for scientific control of coal market.