Zhenzhen Jia

Bio: Zhenzhen Jia is an academic researcher from Hunan University of Science and Technology. The author has contributed to research in topics: Coal mining & Coal. The author has an hindex of 4, co-authored 5 publications receiving 188 citations.

Numerical simulation on tendency mining fracture evolution characteristics of overlying strata and coal seams above working face with large inclination angle and mining depth

Abstract: In order to master the tendency mining-fracture-evolution characteristics of overlying strata and coal seams above working face with large inclination angle and mining depth in mining process, the 1221 working face in Zhao mine is selected as the engineering background and a mathematical model is established. The displacement variation, stress and strain of overlying strata and coal seams are simulated by using ANSYS software. In the mining process, the movement characteristics, displacement variation laws and fracture evolution characteristics of overlying strata and coal seams above working face with large inclination angle and mining depth along inclination direction are discussed. Simulation results show that with the advance of working face, the fracture development of overlying strata and coal seams is larger and larger; the area of gob is gradually expanding and the transverse stress of overlying strata and coal seams is also expanding. Stress contour of overlying strata and coal seams at both ends of gob becomes denser and denser; the activity of the overlying strata and coal seams near the up-roadway side of the gob is violent. The pressure relief zone is formed in the upper part of the strata and the roof above the gob. Large inclination angle of coal seam results in larger supporting pressure in the underside of the gob and smaller supporting pressure in the upper side of the gob. Along the inclination direction of the working face, the pressure relief zone is mainly concentrated in the outlet roadway of the working face; the fracture development and strata separation are obvious, which offer good passage for gas flow and migration.

Application of response surface methodology (RSM) for optimization of leaching parameters for ash reduction from low-grade coal

Abstract: Coal is the world’s most abundant energy source because of its abundance and relatively low cost. Due to the scarcity in the supply of high-grade coal, it is necessary to use low-grade coal for fulfilling energy demands of modern civilization. However, due to its high ash and moisture content, low-grade coal exerts the substantial impact on their consumption like pyrolysis, liquefaction, gasification and combustion process. The present research aimed to develop the efficient technique for the production of clean coal by optimizing the operating parameters with the help of response surface methodology. The effect of three independent variables such as hydrofluoric acid (HF) concentration (10–20% by volume), temperature (60–100 °C), and time (90–180 min), for ash reduction from the low-grade coal was investigated. A quadratic model was proposed to correlate the independent variables for maximum ash reduction at the optimum process condition by using central composite design (CCD) method. The study reveals that HF concentration was the most effective parameter for ash reduction in comparison with time and temperature. It may be due to the higher F-statistics value for HF concentration, which effects to large extent of ash reduction. The characterization of coal was evaluated by Fourier transform infrared spectroscopy (FTIR) analysis and Field-emission scanning electron microscopy with energy-dispersive X-ray (FESEM-EDX) analysis for confirmation of the ash reduction.