It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face.Therefore,a numerical simulation of the coal wall cutting process,which revealed the crack expansion,development,evolution i...It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face.Therefore,a numerical simulation of the coal wall cutting process,which revealed the crack expansion,development,evolution in the coal body and the corresponding lump coal formation mechanism,was performed in PFC2D.Moreover,a correlation was established between the cutting force and lump coal formation,and a statistical analysis method was proposed to determine the lump coal rate.The following conclusions are drawn from the results:(1)Based on a soft ball model,a coal wall cutting model is established.By setting the roller parameters based on linear bonding and simulating the roller cutting process of the coal body,the coal wall cutting process is effectively simulated,and accurate lump coal rate statistics are provided.(2)Under the cutting stress,the coal body in the working face underwent three stages—microfracture generation,fracture expansion,and fracture penetration—to form lump coal,in which the fracture direction is orthogonal to the cutting pressure chain.Within a certain range from the roller,as the cutting depth of the roller increased,the number of new fractures in the coal body first increases and then stabilizes.(3)Under the cutting stress,the fractured coal body is locally compressed,thereby forming a compact core.The formation and destruction of the compact core causes fluctuations in the cutting force.The fluctuation amplitude is positively related to the coal mass.(4)Because the simulation does not consider secondary damage in the coal,the simulated lump coal rate is larger than the actual lump coal rate in the working face;this deviation is mainly concentrated in large lump coal with a diameter greater than 300 mm.展开更多
The COREX process is a unique industrialized smelting reduction technology for iron-making presently in the world. One of its striking characteristics is its ability to directly utilize lump coal as its main fuel. The...The COREX process is a unique industrialized smelting reduction technology for iron-making presently in the world. One of its striking characteristics is its ability to directly utilize lump coal as its main fuel. Therefore, the COREX process uses little,or no coke at all. The requirements on lump coal for the COREX process were given in this paper. In order to reduce the coke consumption and give play to the advantages of directly using lump coal ,the appropriate ratio of coke to lump coal needs to be determined. This paper also summerized several advanced methods of using powdered coal generated by the transporting, loading and unloading of lump coal. In order to solve the lack of coal types for COREX and observe the cracking and devolatilization action of lump coal in the melter-gasifier, an experimental device and a new method were proposed to test the cracking and devolatilization characteristics of lump coal. By means of the new method, the devolatilization and cracking behaviors of lump coal can be investigated, which is helpful to the selection of lump coal for the COREX process.展开更多
The rate of lump coal is one of main factors that affects the price of raw coal. The coal mines always puzzle themselves about how to control rate of lump coal effectively. At present, the rate of lump coal is measure...The rate of lump coal is one of main factors that affects the price of raw coal. The coal mines always puzzle themselves about how to control rate of lump coal effectively. At present, the rate of lump coal is measured mainly by manual operation. The process is inaccurate and the efficiency is low. In this paper, a diameter classification method is proposed to measure the size of lump coal based on image processing.展开更多
The volume hypothesis,a theory about the energy scale of comminution,was adopted to analyze the degradation behavior of lump coal under different heating time.The breakage energy of chars was determined by a compressi...The volume hypothesis,a theory about the energy scale of comminution,was adopted to analyze the degradation behavior of lump coal under different heating time.The breakage energy of chars was determined by a compression test,and the results show that the ultimate strength of chars decreased at the early stage during the heating process,resulting in a decrease of the char breakage energy.At the late stage during the heating process,the char breakage energy increased with the increase of heating time.The power consumption coefficients CKof different chars were determined by a drum experiment,and then the char degradation behavior under different power consumptions was predicted.In addition,agasification experiment was conducted to determine the gasification activation energy（with CO_2）of lump coal heated for different time.The results show that the gasification activation energy increased greatly at the early stage during the heating process,which showed opposite change to the breakage energy of chars.Furthermore,the internal temperature and heat changes of the bonded coal briquette were calculated by using an unsteady heat conduction equation.The large difference between the surface and the center temperatures of coal and the large amount of heat absorption at the early stage during the heating process may have a negative effect on the breakage energy of chars.展开更多
基金The funding was supported by National Natural Science Foundation of China(No.51974294).
文摘It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face.Therefore,a numerical simulation of the coal wall cutting process,which revealed the crack expansion,development,evolution in the coal body and the corresponding lump coal formation mechanism,was performed in PFC2D.Moreover,a correlation was established between the cutting force and lump coal formation,and a statistical analysis method was proposed to determine the lump coal rate.The following conclusions are drawn from the results:(1)Based on a soft ball model,a coal wall cutting model is established.By setting the roller parameters based on linear bonding and simulating the roller cutting process of the coal body,the coal wall cutting process is effectively simulated,and accurate lump coal rate statistics are provided.(2)Under the cutting stress,the coal body in the working face underwent three stages—microfracture generation,fracture expansion,and fracture penetration—to form lump coal,in which the fracture direction is orthogonal to the cutting pressure chain.Within a certain range from the roller,as the cutting depth of the roller increased,the number of new fractures in the coal body first increases and then stabilizes.(3)Under the cutting stress,the fractured coal body is locally compressed,thereby forming a compact core.The formation and destruction of the compact core causes fluctuations in the cutting force.The fluctuation amplitude is positively related to the coal mass.(4)Because the simulation does not consider secondary damage in the coal,the simulated lump coal rate is larger than the actual lump coal rate in the working face;this deviation is mainly concentrated in large lump coal with a diameter greater than 300 mm.
文摘The COREX process is a unique industrialized smelting reduction technology for iron-making presently in the world. One of its striking characteristics is its ability to directly utilize lump coal as its main fuel. Therefore, the COREX process uses little,or no coke at all. The requirements on lump coal for the COREX process were given in this paper. In order to reduce the coke consumption and give play to the advantages of directly using lump coal ,the appropriate ratio of coke to lump coal needs to be determined. This paper also summerized several advanced methods of using powdered coal generated by the transporting, loading and unloading of lump coal. In order to solve the lack of coal types for COREX and observe the cracking and devolatilization action of lump coal in the melter-gasifier, an experimental device and a new method were proposed to test the cracking and devolatilization characteristics of lump coal. By means of the new method, the devolatilization and cracking behaviors of lump coal can be investigated, which is helpful to the selection of lump coal for the COREX process.
文摘The rate of lump coal is one of main factors that affects the price of raw coal. The coal mines always puzzle themselves about how to control rate of lump coal effectively. At present, the rate of lump coal is measured mainly by manual operation. The process is inaccurate and the efficiency is low. In this paper, a diameter classification method is proposed to measure the size of lump coal based on image processing.
基金supported by National Natural Science Foundation of China(51604208,51574189)Talent Technology Fund of Xi′an University of Architecture and Technology(RC1610)
文摘The volume hypothesis,a theory about the energy scale of comminution,was adopted to analyze the degradation behavior of lump coal under different heating time.The breakage energy of chars was determined by a compression test,and the results show that the ultimate strength of chars decreased at the early stage during the heating process,resulting in a decrease of the char breakage energy.At the late stage during the heating process,the char breakage energy increased with the increase of heating time.The power consumption coefficients CKof different chars were determined by a drum experiment,and then the char degradation behavior under different power consumptions was predicted.In addition,agasification experiment was conducted to determine the gasification activation energy（with CO_2）of lump coal heated for different time.The results show that the gasification activation energy increased greatly at the early stage during the heating process,which showed opposite change to the breakage energy of chars.Furthermore,the internal temperature and heat changes of the bonded coal briquette were calculated by using an unsteady heat conduction equation.The large difference between the surface and the center temperatures of coal and the large amount of heat absorption at the early stage during the heating process may have a negative effect on the breakage energy of chars.
