Owing to the gas content is an important indicator in coal and gas outburst prevention, we set up a gas adsorption and desorption experimental system with temperature controlling, and draw out a method combining with experimental analysis, theoretical calculation and project inspection to determine the critical value of gas content in coal and gas outburst prediction. This paper takes D6 coal seam in Pingdingshan No.1 coal mine as an example, sets up the powder function equations among the gas content, gas pressure and gas desorption of drill-cuttings (Δh2). The gas content minimum is calculated as 5.04m3/t as the gas pressure and Δh2 reach their critical values respectively, which is lower than the critical value of gas content (5.19m3/t) determined by Langmuir formula, considering a deformed coal with a thickness of 0.6m exists in D6 coal seam, the critical value of gas content is determined as 5.0 m3/t finally, and its accuracy is proved well in engineering application.
Keywords: Coal and gas outburst, critical value of gas content, gas adsorption-desorption experiment, basic gas parameters, deformed coal
The coal industry plays a very important role in the process of economic development in China. The efficient operation of the coal industry chain is the important foundation for the development of coal circular economy. In this paper, we mainly discuss the three types of coal industry chains, and establish a model to measure the efficiency of the coal industry chain based on the DEA theory. Then by using the coal industry data from 28 provinces and cities nationwide during 2012-2015, we measure the efficiency of the coal industry chain in China. The results show that the efficiency of the national coal industry chain during 2012-2015 was on steady increase, and that the pure technical efficiency is the main factor affecting the efficiency of the coal industry chain in China.
Keywords: Coal industry, circular economy, DEA model, efficiency evaluation
As India progresses towards higher level of growth and more emphasis is being given in the development of infrastructure and manufacturing sector, the iron and steel industry is poised for a rapid growth in years to come. The demand for steel is increasing at a rate of 10%. The domestic production capacity is required to be higher than 110Mt/Yr and it is expected to rise up to 150Mt/Yr by the year 2016-17. Alternative iron making processes to produce steel may change the pattern of use of material inputs and cause a significant shift in the share of lumps and agglomerated ore i.e. sinter and pellets. As fines constitute around 50% of total iron ore produced, pelletisation is the need of the hour.
Keywords: Iron, steel, sinter, pellet, pelletisation
In Sukinda valley at Kaliapani, Dist Jajpur, Odisha, high grade chromite ore is blocked in barrier pillars between opencast mines of different mining companies. The blocked ore is friable and weak in nature. A underhand cut and fill (UCF) method using cemented rock fill (CRF) is described in detail in this paper. This addresses the design of the mining method, design, preparation, transport and placement of CRF in stope. An economic analysis shows that this venture is profitable.
Keywords: Chromite ore, friable and weak, underhand cut and fill (UCF), cemented rock fill (CRF), economic analysis
Hot forming (quenching and forming at the same time) makes the steel surface oxidation and decarburization. Stamping parts formed in this technique shows low hardness in the exterior and high hardness in the interior. The material properties exhibit the continuous functionally gradient distribution in the thickness direction. The exterior hardness and strength is low, while the interior hardness and strength is high. So, the new type of multi-layer metal composite materials is formed. The microstructure, hardness, strength and plasticity of this new metal composite material is analyzed and taking the reinforced beam for example, the three-point bending experiment is implemented. To investigate the crashworthiness of the new metal composite materials, the finite element analysis (FEA) model of the reinforced beam is established on the basis of the metallographic and three-point bending experiments. To compare the crash force and energy absorption between the metal composite materials and each phase material in the interior, it is found that the metal composite materials have the comprehensive performance of every single-phase material. So, it is a good alternative material in application of bearing impact and absorbing energy.
Keywords: Hot forming, metal composite materials, microstructure, impact force, energy absorption
Based on the theory of key stratum in ground control, a theoretical model is established in which the governing equation of the “O” form circle is exported and a 2D model of the mining-induced fractures “O” form circle is established. Based on the geological conditions of the Yuelt Coal Mine of the Panj Group, a numerical simulation study of the mining-induced fracture “O” form circle is carried out by Ansys. According to the conclusion, the range of the mining-induced fracture “O” form circle decreases with the advancing speed of the working surface and the development of the gas channel. Therefore, the design parameters of high drilling are optimized with the higher working surface drawing speed and the “O” form ring development degree decline, and a high drilling gas drainage test is carried out in Yuelt Coal Mine No.131015’s working surface. The experimental results show that the optimization of the high drilling parameters is reasonable, and also confirms the influence and control effect of the drawing speed on the mining-induced fractures “O” form circle.
Keywords: Mining-induced fractures “O” form circle, drawing speed, high drilling, gas drainage
The variation of iron oxide in different size consists of a bulk coal sample from Kusmunda area, Korba coalfield has been studied in details. The +25 mm material representing 54.9 per cent of the bulk coal retains 47.2 per cent of total iron oxide in bulk coal ash inclusion of -0.5 mm fines increases iron oxide to 61.1 per cent of the bulk coal ash. Incorporating 25-13mm, 13-6mm,6-3 mm and 3-0.5 mm finer coals further increases iron oxide in the constituted samples to 69.4, 81.9 and 87.3 per cent of total oxide in bulk coal ash. This results in depletion of iron oxide in coal ash of finer constituted samples which now analyze 38.9, 30.6, 18.1 and 12.5 per cent iron oxide of the bulk coal ash respectively.
Keywords: Ash constituents, iron oxide