De Ming Wang

Numerical Simulation Research on Gas-Dust Flow Field of Forced-Exhausted Hybrid Ventilation in Whole Rock Mechanized Heading Face

Euler-Euler two-fluid model was used to construct control equations of gas-solid two-phase flow, based on SIMPLE algorithm of collocated grid and FLUENT software, the pressure distribution of air-flowing field and dust field diffusion in fully-mechanized excavation face with different air-draft volume were simulated. The results show that with the increase of exhausted dust ability, diffusion intensity of producing dust pollution in driving head constantly decreases. Compared to air-draft volume of 320m3/min, when it is 600m3/min, the average dust concentration at the driver and whole section positions respectively decrease 51.28% and 56.51%, and high-concentration dust diffusion distance of the other workers position section decrease from 13.6m to 8.5m. Engineering Application indicates that the measured dust concentration is basically anastomosed with simulation result. When air-draft volume of dedusting fan is 600m3/min and dust control system with air curtain formed by forced fan drum is used, the dedusting rates of total coal dust and respirable dust on spot are respectively 95.1% and 96.1%, which achieves a great dedusting effect.

Temperature Dependence of Reaction Rate in the Oxidation of Dafosi Coal

Adiabatic self-heating tests had been conducted on Dafosi coal. Analysis of the relationship of temperature and reaction rate revealed that the dependence of coal sample temperature on reaction rate can be described by a third order polynomial from 40°C up to 155°C. But at a small interval of temperature, the reaction rate still conforms to the Arrhenius kinetic model. When Arrhenius equation is used to solve the kinetic parameters of the coal spontaneous combustion, the coal temperature should be processed in segment.

Effect of Experimental Conditions on Parameters Derived from Micro Calorimeter Measurements of Coal Low-Temperature Oxidation

C80 micro calorimeter was applied to investigate the initial heat release temperature and heat output at low-temperature oxidation process of Kabuliang anthracite coal under the experimental conditions of different coal sample mass, different temperature rising rates and different gas flow, and analyzed the effect of experimental conditions on test results. The results indicate that the coal sample mass and temperature rising rate affect measurement results, while there is no effect of gas flow. Under the same experimental condition, a higher temperature rising rate leads to a higher initial heat release temperature and less output of heat; The initial heat release temperature shows the trend of increase after decrease with the increase of coal sample mass. So, when micro calorimeter is used to investigate the coal low-temperature oxidation process, the experiments under the conditions of appropriate coal sample mass and the lower temperature rising rate can obtain more accurate test parameters.

Study on Low-Temperature Oxidation Process of Low Rank Coal by In Situ FTIR

Low temperature oxidation of two different low rank coals was measured by in-situ FTIR. Curve-fitting analysis was employed to identify functional groups types of raw coals, and series technology was carried out on in-situ infrared spectrum of sample coals at low-temperature oxidation process to analyze the changes of main active functional groups with temperature. The results indicate that -CH3, -CH2, -OH, C=O, COOH are the main active functional groups in low rank coal. In the oxidation process, with temperature increasing, the methyl and methylene show the tendency of increase after decrease and then decrease, and all of hydroxyl, carboxyl and carbonyl group present the tendency of increase after decrease, there exists some differences among the main functional groups in the coal low-temperature process.

Numerical Simulation Study on Air-Flow Migration Law about Vortex Air Curtain of Plane Wall Fan Drum

Vortex air curtain of plane wall fan drum can control the diffusion of air stripping dust effectively. In order to solve the high-concentration dust problem in fully mechanized excavation face, formation mechanism of vortex air curtain was analyzed. According to fluid mechanical control equations of gas phase flow, mathematical model was established to solve air migration law of vortex air curtain in fully mechanized excavation face. By using Simple algorithm based on collocated grid and fluent software, numerical simulation of air spatial migration law of closed-end dust control in fully mechanized excavation face was carried out. The simulation results show that vortex air curtain dust control system can form dust control fan drum along driving head to the front of the roadheader driver. According to the simulation results and actual conditions of working face field, vortex air curtain suction dust control system consisted of plane wall fan drum and exhausted dust purification device in fully mechanized excavation face was designed, and after it was applied in fully mechanized excavation face, the dust concentration decreased effectively in the working face field.

Research of Ventilation and Dust Removal Technology for Whole Rock Fully-Mechanized Excavation Face

The whole rock fully-mechanized excavation with big cross section, high rock hardness and strong cutting intensity of fully-mechanized coal winning machine has a higher dust concentration than coal roadway excavation, so ventilation dust removal technology is in need in whole rock face. Based on the dust migration and distribution numerical simulation in whole rock tunnel excavation, optimization design of long pressing and short pumping hybrid ventilation and dust removal system were carried out. Eventually, the comprehensive dust prevention measures with air curtain closing dust source, dust electromotor exhausting dust and retaining curtain capturing dust were realized in this paper, which achieved a good removal efficiency of dust.

Dust Simulation and Application of Forced and Exhausted Mixed Ventilation System in Half Coal-Rock Fully-Mechanized Excavation Face

The numerical simulation of migration rule about dust flow field in typical long forcing and short exhausting mixed ventilation dust removal system of half-coal rock fully-mechanized excavation face was carried out, and local ventilation system was improved based on the simulation results. The relative position relationship of ventilation facilities and the matching relationship of forcing and exhausting air volume in half-coal roadway were made sure, thus, the new complete sets of ventilation wet dedusting system with the type of KTCS-500L had been developed. According to the application in Nantun coal mine of Yanzhou mining group, the system proved to be very effective.

Computer Simulation on Key Structure Parameters of Foam Generator for Dust Control in Underground Coal Mines

Foam is a high efficient technology for controlling dust in underground coal mine,and foam generator is one of the core components of the technology. Aiming at designing the key structural parameters of foam generator scientifically, the velocity and pressure distribution of foam generator under different parameters were simulated and displayed by CFD (Computational Fluid Dynamics) software. The results show that the intensity of gas-liquid mixture in foam generator reaches the maximum when the vortex generator is 24mm away from the throat and the baffle with a 45° angle. Under the circumstances, the pressure is well-distributed around the vortex generator and the outlet of foam generator, and the foaming effect best.

Arbitrary-Order Spherical Harmonics Method for Coupled Heat Transfer in Semitransparent Materials

An advanced numerical model and its application in thermal processing of nonlinearly anisotropic scattering semitransparent materials are presented in this paper. The decomposition of the radiative transfer equation is deduced using spherical harmonics (PN-approximation) method. Considering the transient problem, coupled radiative and conductive heat transfer model based on arbitrary-order PN-approximation method is established. With the coupled model, the calculation accuracy of high-order PN-approximation method is verified through comparison with theoretical solution and by the simulation results of other methods. Comparison shows that the arbitrary-order PN-approximation method reproduces results with a high accuracy for linear and non-linear anisotropic scattering, while it can easily treat the nonlinear anisotropic scattering phase functions with desired order. Keywords: semitransparent material, coupled heat transfer, numerical simulation, spherical harmonics method

PLS Regression on Coal Infrared Spectrum with Wavelet Pre-Processing

Study on multivariate calibration for infrared spectrum of coal was presented. The discrete wavelet transformation as pre-processing tool was carried out to decompose the infrared spectrum and compress the data set. The compressed data regression model was applied to simultaneous multi-component determination for coal contents. Compression performance with several wavelet functions at different resolution scales was studied, and prediction ability of the compressed regression model was investigated. Numerical experiment results show that the wavelet transform performs an effective compression preprocessing technique in multivariate calibration and enhances the ability in characteristic extraction of coal infrared spectrum. Using the compressed data regression model, the reconstructing results are almost identical compared to the original spectrum, and the original size of the data set has been reduced to about 5% while the computational time needed decreases significantly.