The annual increase of coal production and its demand lead to the necessity in temporary storage places (warehouses) organization to accommodate raw coal materials before the shipment. It is noted that at the open method of coal storing the dust emission from loading/unloading operations and from the pile surface effects negatively the health of the warehouse workers and adjacent territories. An alternative solution is closed-type warehouses . One of the main hazards of such coal storage can be the release of residual methane from coal segregates into the air after degassing processes during mining and extraction to the surface, as well as transportation to the place of temporary storage. The study carries the analysis of methane content change in coal during the processes of extraction, transportation and storage. Physical and chemical bases of mass transfer during the interaction between gas-saturated coal mass and air are studied. It is determined that the intensity of methane emission depends on: the coal seam natural gas content, parameters of mass transfer between coal, and air and the ambient temperature. The dynamics of coal mass gas exchange with atmospheric air is evaluated by approximate approach, which is based on two interrelated iterations. The first one considers the formation of methane concentration fields in the air space of the bulk volume and the second accounts the methane emission from the pile surface to the outside air. It is determined that safety of closed coal warehouses exploitation by gas factor can be ensured by means of artificial ventilation providing volumetric methane concentration in the air less than 1 %. The flow rate sufficient to achieve this methane concentration was obtained as a result of computer modeling of methane concentration fields formation in the air medium at theoretically calculated methane emission from the pile surface.
The problem of managing methane emission in the mined-out space of the mines of the Vorkuta coal deposit is considered. The mining-geological and mining-technical conditions affecting the current gas situation are briefly described. The main problems usually arise at a distance of 100-200 m from the mine workings.The main method used to control gas-air flows - the erection of a chug wall. The disadvantages of this method are revealed, which lie in the possible creation of a situation, when the ventilation scheme “direct flow with sublight” turns into a “return” one. Two new ways of solving the problem of the emergence of local concentrations of methane, carried out by air leaks from the worked-out space to the ventilation mine are proposed. The first way is based on the use of foam strips, the second - in the additional laying of strips of filling material. The second method also involves solving the problem of hard-to-crack roof landings. A method of calculating the optimal volume of stowing material for the proposed method, taking into account the necessary undermining of the “Triple” formation, is proposed.
The results of the analysis of the character of the growth with depth of methane content in beds and host rocks of coal deposits in the Pechora basin and the factors affecting it are presented. On the basis of field measurements of methane emission dynamics in the mine workings of a number of mines of the Vorkuta coal field and their statistical processing the effect of the increase in the relative methane emission by increasing the size of the mined-out space - the number of the waste pillars and the distance of the working face from the cut mine working is shown. The efficiency of the degassing schemes used to reduce gas release from the surrounding rock masses under development is analyzed. Geomechanical and gasdynamic models of a complexly structured undermined rock mass are proposed, allowing to justifiably calculate parameters of permeability distribution over its volume, air leakage fluxes from the cleaning face and gas-air mixture in the mined-out spaces.
