Gas emission during destruction of coal samples in a mill is measured experimentally. Using the Skochinsky Institute’s procedure, emmitable gas amount is calculated as function of coal particles. Coal samples for the tests were taken in an outburst-hazardous seam. It is found that the decrease in the size of coal particles to 0.1 mm increases gas emission by several times. The authors developed a model of force interaction between methane molecules in micro-porous coal structure and surface of coal macro-molecule, and a calculation procedure for gas emission in coal as function of its degree of breakdown.

Экспериментально измерено газовыделение при разрушении образца угля в мельнице. По методике ИГД им. А. А. Скочинского рассчитано количество газа, которое может выделиться из угля в зависимости от размера его частиц. Образцы отбирались с выбросоопасного угольного пласта. Установлено, что уменьшение размеров частиц угля до 0.1 мм повышает газовыделение в несколько раз. Разработана модель силового взаимодействия молекул метана в микропористой структуре с поверхностью макромолекулы угля и методика расчета газовыделения из угля в зависимости от степени его разрушения. Gas emission during destruction of coal samples in a mill is measured experimentally. Using the Skochinsky Institute’s procedure, emmitable gas amount is calculated as function of coal particles. Coal samples for the tests were taken in an outburst-hazardous seam. It is found that the decrease in the size of coal particles to 0.1 mm increases gas emission by several times. The authors developed a model of force interaction between methane molecules in micro-porous coal structure and surface of coal macro-molecule, and a calculation procedure for gas emission in coal as function of its degree of breakdown.

The paper presents experimental research on physical processes occurring in the black coal – natural gas system when external parameters change. It was shown that when thermobaric conditions corresponding to the area of stable hydrate existence are created, methane hydrate and carbon dioxide hydrate are formed in the internal space of the natural coal. Decomposition of methane hydrate in the coal occurs near the equilibrium curve, and the process of hydrate formation begins in the case of overcooling by 3–7°С and lasts several dozen hours. For the examined cases, the rate of gas hydrate decomposition in the coal is determined by the rate of change in external parameters during linear increase in temperature from 1 to 6°С/h.

Porosity of eight samples of natural coals was measured in which, with increasing degree of metamorphism, the content of carbon in the organic mass grows from 80 to 93%, and that of oxygen decreases from 14 to 2%. The methods of low-temperature sorption of nitrogen and mercury porosimetry were used, and the isotherm of water sorption was examined (+27°C). Each method was used to calculate the pore volume and the monolayer capacity in sorption of water and sorption of nitrogen, and the pore surface area. The Dent sorption equation was used to calculate the amounts of firmly and weakly bound water in each sample. It was shown that that the amount of strongly bound water monotonically depends on the amount of oxygen in the organic mass. For the natural coal samples under study, the volume of sorbed water is close to the total pore volume determined by the method of mercury porosimetry and is an order of magnitude larger than the pore volume measured by the method of low-temperature nitrogen sorption. Reasons for this discrepancy are discussed.

Among the properties of coal that must be studied in order to optimize its preparation for coke production and deep processing are the interactions of adsorbed materials—in particular, water, methane, and carbon dioxide—with its surface. An important aspect of these interactions is phase transformation of the adsorbed materials in the internal porous structure to form hydrate or ordinary ice. In regular coal, a hydrate of carbon dioxide is formed at a CO2 pressure of 2–4 MPa and temperatures below 10°C, when the moisture content of the coal exceeds the threshold value. However, at the same moisture content, no ice is formed at temperatures between +13°C and –13°C, while decomposition of the hydrate is observed close to the equilibrium curve. For gases that do not form hydrates (helium, nitrogen, argon) in the given temperature and pressure ranges, increasing the pressure to 12 MPa has no influence on the solidification of sorbed water and ice formation.

The results of physical modeling of geomechanical processes in outer zones of coal beds with the main roof caveable with difficulty. The scope of the modeling embraces the inlfuence seams on gas release by gas temperature and pressure variation during stage-wise outlet of gas from a pressure bomb, which simulates cyclical mechanical impact on a coal seam in the zones of a gas pocket. It is found that the low-frequency (2.0–4.5 Hz) attenuating vibrations generated in the main roof can induce both secondary rock mass disintegration as well as methane desorption and decomposition of gas hydrates (if present) accompanied by an increases in gas pressure and in number of gas-dynamic events in outer zones of coal beds.

The physical processes occurring in the coal – natural gas system under the gas pressure release were studied experimentally. The possibility of gas hydrates presence in the inner space of natural coal was shown, which decomposition leads to an increase in the amount of gas passing into the free state. The decomposition of gas hydrates can be caused either by the seam temperature increase or the pressure decrease to lower than the gas hydrates equilibrium curve. The contribution of methane released during gas hydrates decomposition should be taken into account in the design of safe mining technologies for coal seams prone to gas dynamic phenomena.

С увеличением глубины ведения горных работ увеличивается вероятность возникновения газодинамических явлений, в том числе внезапных выбросов угля и газа. Несмотря на то, что первый внезапный выброс угля и газа зарегистрирован более 150 лет назад, а внезапные выбросы угля и газа происходят практически во всех угледобывающих странах, в настоящее время нет полного понимания механизма и причин возникновения внезапных выбросов. Перераспределение напряжений в краевой зоне, местная трещиноватость и нарушенность участков угольного пласта являются необходимыми, но не достаточными условиями возникновения внезапных выбросов угля и газа. По мнению многих ученых именно газовый фактор является определяющим в возникновении внезапного выброса угля и газа. Десятилетия исследований сорбированного метана и метана, занимающего свободное пространство пор и трещин угольного пласта, не позволяют дать исчерпывающее объяснение относительно источников аномально высоких количеств газа, а также причин стремительного перехода метана в газообразное состояние при внезапных выбросах угля и газа. Можно предположить нахождение метана в угольном пласте в виде соединений включения: газовых гидратов и интеркалированных соединений графита. With the increase in the depth of mining, the probability of gas-dynamic phenomena, including sudden releases of coal and gas, increases. Despite the fact that the first sudden release of coal and gas was registered more than 150 years ago, and sudden coal and gas emissions occur in virtually all coal-mining countries, there is currently no full understanding of the mechanism and causes of sudden emissions. Redistribution of stresses in the marginal В. Г. Смирнов smirnovvg@kuzstu.ru

Приведены результаты лабораторных экспериментальных исследований по нагнетанию пластических масс в образец углепласта, находящегося в объемном напряженном состоянии. Исходя из измерений эффективного электросопротивления образца «постоянному току», а также изменения его фильтрационных свойств, авторами проведена оценка роста трещиноватости среды при импульсном нагнетании в пробуренную скважину пластической массы. Установлено, что увеличения проницаемости среды вокруг скважины можно добиться с помощью динамических нагрузок, в результате чего возникает сеть дополнительных трещин, способствующих улучшению дегазации призабойной зоны. Таким образом, подбирая пластическое вещество с определенным коэффициентом динамической вязкости, можно получить вокруг скважины более мелкую или густую сеть дополнительных трещин нормированной длины. The results of laboratory experimental research of plastic mass charging in the coal seam sample being in three-dimensional stress state are given. On the assumption of sample measuring of effective electrical resistance to «Direct curren», also its filtration properties, the authors estimated the growth of the medium fracturing (jointing) with pulsed injection into a drilled well of plastic mass. Its determined that the medium permeability increasing around the drill can be achieved using dynamic force, as a result an additional fractional network appears improving methane drainage of borehole zone. Thus, a smaller or dense additional fractional network of rated length can be obtained around the borehole by selecting a plastic mass with the certain dynamic-viscosity coefficient.

In coke production, the moisture content of the initial coal is an important parameter. The moisture present in the pores of coal changes the properties of the coking batch. Note also that, together with methane and/or carbon dioxide, water may form gaseous hydrates in the coal bed. In the present work, to study the state of the moisture in coal, attention focuses on eight samples of natural gas saturated to constant moisture content in an atmosphere where the relative partial pressure of water vapor is 91%. The moisture sorbed from the atmosphere has a U-shaped dependence on the metamorphic stage of the coal, with a minimum at coking coal (K coal). In similar conditions, the more mature T and A coal contains twice as much moisture as K coal, while the younger D and G coal contains about four times as much moisture. Thermogravimetric analysis of coal samples saturated to constant moisture content permits calculation of the rate of mass loss and activation energy for the evaporation of moisture in the heating of the given samples. For each coal sample, the temperature range where the evaporation of moisture may be described by a first-order Arrhenius equation is determined. The upper limit of this range is compared with the temperature corresponding to maximum rate of mass loss and also with the temperature corresponding to the maximum thermal effect.

In the experimental PT diagrams of system coal pore water methane defined areas of high methane gas release, corresponding to the decomposition and formation of clathrate compounds methane gas hydrates. Calculated change in the amount of methane and the rate of decomposition and the formation of hydrates in these areas. We believe that the process of decomposition and formation of hydrates in the pores of natural coal is described by the Arrhenius equation. The activation energy of decomposition and the formation of methane hydrates in the natural pores of coal are several times higher than the activation energy for the decomposition of pure methane hydrate. Methane released during the decomposition of gas hydrates in the marginal zone of the coal seams, can be the cause of gas-dynamic phenomena.

The mathematical model of dissociation of firm solutions of natural gases as gas hydrates is presented and the problem of finding of speed of dissociation of particles of gas hydrates in a coal matrix depending on their sizes is solved.