Optimization of the ventilation scheme for increasing production capacity of underground mines

Currently, many underground mines are revising their design solutions to increase their production capacity. This tendency is explained by the decreasing ore grades, as well as by the extensive introduction of mechanization in underground mining operations that has improved the output of mobile equipment by increasing the box capacity and engine power. Dieselpowered mobile vehicles are the most common in underground mining practice. The advantages of such engines are obvious as they generate more power than other types of engines. However, the high air demand for mine ventilation limits their application. This is associated with the need to increase the cross-sections of permanent mine workings in order to comply with the standard air flow rate with account of the increased ventilation capacity along with an increase in the inventory of mobile equipment in order to ensure the specified output of the mine. The specific features of mining operations are defined by the stage-wise character of commissioning various blocks of the deposit. Managing of production and development works provides an opportunity to ventilate the mine sections due to their consecutive commissioning, locally, with an isolated stream of air by means of mine workings that do not have the intersection of air streams. This provides a reduction of critical path of air travel up to 30% and reduction of the general mine ventilating pressure drop by at least 20% at constant air flow rate. The results of the work can be used in designing the ventilation system of underground mines both under construction and in operation.

The effect of oxygen supply and oxygen distribution on single-head tunnel with different altitudes under mixed ventilation

Hypoxia plays a major role in limiting the construction of the high-altitude mine. Understanding the effect and the distribution of diffused oxygen supply at different altitudes is the premise for the design of a mine with oxygen supply system and the full utilization of oxygen resources. For the optimal design of an oxygen supply mode and ventilation system, a multi-component fluid model of the diffused oxygen supply of a single-head tunnel was developed. This study reveals the variation law of the average oxygen mass fraction at different altitudes. The relationship between the distance from the heading face and the oxygen mass fraction at each altitude was fitted. The results show that the distribution of oxygen mass fraction in a single head tunnel at different altitudes presents a similar trend of increasing first and then decline. In addition, the change of the average oxygen mass fraction with the increase of altitude is not linear, and the dispersion loss is larger in high-altitude areas. The largest oxygen enrichment area is distributed at the altitudes of 4000–4500 m. This study provides theoretical support for improving the hypoxic environment of high-altitude metal mines excavation work.

Study of a segmented ventilation system of the brake disc and determination of the aerodynamic and heat exchange characteristics of the airflow

This study aims determine a relationship between the aerodynamic and heat exchange characteristics of the air flow in a segmented ventilation system of the brake disc with improved heat dissipation in the boundary layer of the air flow. Classical equations of heat and mass transfer in the boundary layer of the air flow cooling the brake disc ventilation chamber were used. The cooling performance of the system was assessed using the method of similarity. The obtained theoretical findings were confirmed by CFD-modelling. Mathematical models were developed for vented discs with both continuous grooves and slotted grooves. A criterion for assessing the performance of brake disc ventilation systems was proposed, consisting in turbulization of the air flow inside the device under study. According to the obtained analytical dependencies, a 20-fold acceleration of the air flow decreases the turbulization parameter by 1.24 times. An increase in the temperature difference in the boundary layer by 8 times leads to an increase in the turbulization parame-ter by 86.2 times. Using the criterion proposed for assessing the work performance, the aerodynamic and heat exchange characteristics of the system under study were calculated. As a result, a relationship between the design parameters of the segmented ventilation system and improved heat dissipation in the boundary layer of the cooling air flow is proposed. The conducted CFD modelling confirmed the aerodynamic characteristics of the system under study obtained theoretical-ly. This mathematical model together with the turbulization parameter can be used when both developing modern vented brake discs and assessing the existing cooling systems of friction units in order to minimize the possibility of reduced heat exchange processes.

Study on the Effect of an Intermittent Ventilation Strategy on Controlling Formaldehyde Concentrations in Office Rooms

Material emission and ventilation are two aspects influencing indoor air quality. In this study, a model predictive control (MPC) strategy is proposed for intermittent ventilation system in office buildings, to achieve a healthy indoor environment. The strategy is based on a dynamic model for predicting emissions of volatile organic compounds (VOCs) from materials. The key parameters of formaldehyde from panel furniture in the model are obtained by an improved C-history method and large-scale chamber experiments. The effectiveness of the determined key parameters is validated, which are then used to predict the formaldehyde concentration variation and the pre-ventilation time in a typical office room. In addition, the influence of some main factors (i.e., vacant time, loading ratio, air change rate) on the pre-ventilation time is analyzed. Results indicate that the pre-ventilation time of the intermittent ventilation system ranges from several minutes to several hours. The pre-ventilation time decreases exponentially with the increase in the vacant time, the air change rate, and with the decrease in the loading ratio. When the loading ratio of the furniture is 0.30 m2/m3 and the vacant time is 100 days, the required pre-ventilation time approaches zero. Results further reveal that an air change rate of 2 h−1 is the most effective means for rapid removal of indoor formaldehyde for the cases studied. The proposed strategy should be helpful for achieving effective indoor pollution control.

Selection of Employees for Performing Work Activities in Currently Used Ventilation Systems in Hard Coal Mining

The way in which rescue actions are carried out in a hard coal mine is conditioned by a number of factors, including the type, scale, and location of the hazard; location of employees at the danger and level of their endangerment; and the ventilation system used in the impacted area. In this article, the importance and necessity to take into account a human factor, specifically the propensity for risky behavior, alongside the selection of rescuers for rescue action is pointed out. As an introduction to the key research studies presented in this article, main ventilation systems used in hard coal mines are described and three real cases of natural hazard occurrences in hard coal mines are discussed. An analysis of these events has shown that the degree of difficulty of a rescue action depends, among other aspects, on the ventilation system applied. Next, a study covering a synthetic assessment of 25 mining rescuers taking into account the ‘risky behavior’ parameter is presented. The results were interpreted considering the—described earlier—cases of hazard occurrence in coal mines and ventilation systems applied there. For the research sample, a selection of rescuers to carry out actions in particular types of ventilation systems, taking as a criterion the mark they obtained in the synthetic assessment, is proposed.