Numerical modeling of open pit ventilation when varying the location of the dust and gas cloud

Pavel V Amosov

doi:10.21440/0536-1028-2021-7-5-15

Abstract

Research objective is to estimate the effect of bulk explosion location and the initial height of the dust and gas cloud on open-pit natural ventilation time and the level of air contamination of the upper edge of the open pit down the wind. Methods of research. Computer modeling of aerodynamics and gaseous component transfer in the 2D geometry is carried out with the COMSOL software. To calculate the aerodynamic characteristics, the approximation of the incompressible fluid with the standard k–ε turbulence model was carried out. Gaseous component distribution was modeled using the numerical solution to the convection-diffusion equation of contaminant transfer. Numerical experiments under the fixed initial concentration of the gaseous component and the speed of the incoming wind flow have been carried out for three locations of bulk explosions and six values of the initial height (from 70 to 420 m with a step of 70 m) of the dust and gas cloud. Research results and analysis. Spatial distributions of the model’s aerodynamic characteristics and contaminants gaseous component when reaching the maximum permissible concentration in the modeled area have been obtained. The estimated time of the open-pit natural ventilation and the dynamics of the open-pit upper edge air contamination dynamics down the wind have been analyzed. The complex and diversified nature of open pit ventilation for various locations of bulk explosions has been recorded. The undulating character of contaminant loss has been predicted (with different heights of peaks) conditioned by the presence of vortex formation in the open pit. Conclusion and scope of results. For the recirculation scheme of ventilation, the situations with the bulk explosion locations shifted to the windward edge of the open pit are the longest. It has been shown that the reduction in the dust and gas cloud lift does not always ensure the reduction in the contamination level at the upper edge of the open pit down the wind.

Highlights

S. and others [1–6]) contain rich experimental and theoretical material on the issues of open-pit aeration in the course of blasting operations. These studies contain analytical expressions that make it possible to estimate the dimensions of the dust and gas cloud (DGC), its height dynamics depending on the temperature drop in the atmospheric layer, the depth of the wells blasted, and other meteorological and process parameters
For the recirculation scheme of ventilation, bulk explosion locations shifted to the windward side of the pit are the longest
The air contamination dynamics has been analyzed at the upper edge of the open pit down the wind

Summary

Introduction

Based on the method of numerical modeling, paper [7] analyses the estimated time of open-pit natural ventilation when varying three parameters of the computer model, namely the location of bulk explosions, the initial concentration of the gaseous component in the DGC, and the speed of the incoming wind flow. The research objective is to estimate the effect of bulk explosion location and the initial height of the DGC on open-pit natural ventilation time and the level of air contamination of the upper edge of the open pit down the wind. Calculation stability is ensured by the selection of the indicated solver and damp ratio value (Isotropic diffusion) at the level of 0.75 At this stage, to reach the MPC, multiple numerical experiments had to be carried out to neatly “catch” the estimated time of natural ventilation. Расчетное время проветривания карьера при вариации начального местоположения ПГО, с

Bulk explosions location left central right

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Conclusions