RU2100612C1 - Method for prevention of gas explosion in mine worked-out space - Google Patents

Abstract

FIELD: mining industry, in particular, methods for prevention and decrease of probability of explosion of dust-gas-air mixture in worked-out space and adjacent workings of coal mines. SUBSTANCE: method includes supply of foam to worked-out space. Novelty consists in that foam is supplied in state of limited stability by cycles before caving of immediate roof to fully fill hollows. In so doing, foam is poured from below upward in face for a distance of length of foamed zone which is determined from a mathematical expression. EFFECT: higher efficiency. 1 dwg

Description

 The invention relates to the mining industry, in particular to methods for preventing and reducing the likelihood of explosions of a dusty-gas mixture in a mined space and adjacent mine workings of coal mines.

A known method of localizing the explosion of a dusty gas mixture in a worked-out space, which consists in the construction of a safety rubble strip isolating the worked-out space from a network of existing mine workings [1]
The disadvantages of the method are its complexity and the inability to use in the developed space behind the lining of the working face.

 There is a method of localization of a gas explosion when extinguishing underground fires [2] adopted as a prototype, which consists in filling the mine with air-mechanical foam with the formation of a foam plug, and the foam plug is formed by a gel-like foam with variable multiplicity.

 The disadvantages of the method are the narrow focus of the depreciation plug under dynamic loads and insufficient stability during long-term static loads.

 The objective of the invention is to reduce the likelihood and prevent gas explosions by controlling air leaks in the exhausted space, evenly distributing leaks along the length of the ventilation outlet, reducing the amount of methane entering the outlet with air leaks.

This is achieved by the fact that a foam of limited stability is fed into the worked-out space for the mechanized support, cyclically before planting the immediate roof, until the voids are completely filled, and the foam is spilled from the bottom of the lava up to a distance L _p , determined by the formula:
L _p = L _l (1-τ _p v _l / L _max ) (m),
where L _{l the} length of the face, m;
τ _p foam stability time, h;
V _{l the} speed of lava movement, m / h;
L _max zone of maximum specific leaks or maximum concentration of explosive gases, m

 Thanks to this solution, the likelihood of gas and dust explosions in the exhausted space and ventilation outlet is reduced, and the mass flow rate of air leaks from the treatment outlet is reduced and its delivery coefficient to its lower part is increased.

 The drawing shows a diagram of the action of the foam in the area hazardous for explosion.

 The method is carried out during the development of coal seams with the complete collapse of the rocks of the immediate and main roof behind the lining 1 during direct-flow ventilation of the site (air movement is indicated by arrows 2) along the air supply drift 3, the treatment face 4, and the ventilation drift 5. At the same time, part of the air (leakage) passes through the free zone between the lining and collapsed rocks 6 and through the caving zone 7, entering the ventilation drift 5. Depending on the step of collapse of the immediate roof, the width of the free zone between the lining of the treatment plant oya 1 and caving can vary from a few tenths to a few meters.

 With a maximum width of free space of 6, it is filled with elastic foam, for example, water-air with stabilizers, supplied through a flexible hose from the ventilation drift from the foam generator to the distribution shafts, which are led out to the roof support at specified intervals along the length of the working face (5-10 m).

 Filling the foam with free space within the removed coal seam allows it to float between pieces of the direct roof collapsing then onto it, filling voids and even the collapsing cavity between the direct and main roof due to rarefaction of air in this space. As a result of these processes, the resistance to the movement of air leaks increases and their consumption decreases, up to the complete isolation of the worked out space (rigid foams).

The foam stability time τ _p for air-mechanical foams is limited to dozens of hours or days, which is less than the time of the working face movement at a distance L _max corresponding to the maximum concentration of explosive gases in leaks, often coinciding with the maximum specific air leaks entering the ventilation drift, t. e. τ _p <L _max / V _l , where V _{l the} speed of lava movement (face).

The time τ _p determines the length of the foaming zone of the free space L _p in the lower part of the face, inversely proportional to the relative distance of the stable state of the foam τ _p • V _l , ie

откуда
L_п = L_л(1-τ_пv_л/L_max)
При устойчивости пены, соответствующей L_max, длина ее полосы вдоль лавы минимальна (L_п → 0). При весьма неустойчивой пене (τ_п → 0) длина ее полосы L_п соответствует длине лавы (L_п → L_л).

where from
L _p = L _l (1-τ _p v _l / L _max )
With the stability of the foam corresponding to L _max , the length of its strip along the lava is minimal (L _p → 0). With a very unstable foam (τ _p → 0), the length of its strip L _p corresponds to the length of the lava (L _p → L _l ).

Claims (1)

A method of preventing gas explosions in the worked-out space of coal mine faces, which consists in supplying foam to the worked-out space, characterized in that for the mechanized support in the worked-out space, foam of limited stability is fed cyclically before planting the immediate roof until the voids are completely filled, and the foam spills from the bottom lava up the distance of the length of the foaming zone L _p , determined by the formula
L _p = L _l (1-τ _p v _l / L _max ),
where L _{l the} length of the face, m;
τ _p - foam stability time, h;
v _{l the} speed of lava movement, m / h;
L _{m a x} zone of maximum specific leakage or maximum concentration of explosive gases, m