Reduction of risk of choosing the optimal ventilation mode for the period of elimination of exogenous fire

Abstract

The time from the occurrence of an exogenous fire in a mine to its complete elimination can be conventionally divided into two periods: the operational time of the emergency elimination plan and the period of intensive fire extinguishing or fire cell isolation. In the first period, there is a significant number of working people in the mine, so the emergency ventilation mode must first of all ensure safe conditions for their evacuation. The issue of choosing an emergency ventilation mode in the mine ventilation network for use during the operational time of the emergency liquidation plan has been studied in sufficient detail. At the second stage of fire development, the ventilation mode should ensure the removal of combustion products by the shortest paths to the exit jet or to the workings where there are no people; to provide fresh air supply, normal temperature and minimal smoke in the areas where mining rescue works are carried out; reduce the intensity of fire development; to prevent overturning of ventilation jets in inclined workings. Among the listed requirements, there are both those that satisfy and those that contradict the criterion of the first period. Therefore, in a number of cases, during the liquidation of developed fires, it is necessary to change the ventilation mode to ensure the fulfillment of the considered conditions. A method of transition from the mode of the first period to the mode of the second is proposed, which consists in determining the list of ventilation modes that are subject to optimization. For each of them, workings are defined, in which it is possible to overturn the ventilation jet. Due to the minimization of their number, it is possible to prevent the spread of a fire zone gassed with gaseous products (that is, its minimization) and to complicate the conditions of conducting mine rescue operations. For this purpose, the theory of interrelationship of aerodynamic parameters of mine workings is used, which simplifies multi-fan ventilation calculations. The described algorithm only seems somewhat cumbersome, since it is known from practice that in the area of action of intense thermal depression of the fire cell, several loosely connected workings cannot be located far from each other, with a possible spreading of the ventilation jet. Thus, by achieving the condition of non- spreading of the ventilation jet for one of the working, it is possible to indirectly solve the problem for a number of other workings, incidental to it, which significantly reduces the complexity of the calculation process. Keywords: exogenous fire, emergency ventilation mode, thermal depression, interrelationship of aerodynamic parameters.