METHOD FOR DETERMINING THE THERMAL RESISTANCE OF COALS TO THEIR CYCLIC FREEZING AND THAWING

摘要

FIELD: measuring equipment.;SUBSTANCE: invention relates to metrology, in particular to methods for determining the thermal stability of coals during their cyclic freezing and thawing. Essence: cyclical freezing and thawing of the same type of coal samples are performed at M number of cycles equal to the serial number of the corresponding sample in the series. Further, in parallel recording the parameters of acoustic emission, each of the samples is slowly uniformly heated to a temperature in the range of (80–90) ± 5 °C and held at it for at least 4 hours. Boundaries of successive time intervals are then determined, the first of which begins at the time of heating the sample to 30 °C and ends with stabilization of its temperature at a constant value, and the second – of the same duration, begins with an increase in the level of activity of acoustic emission to a value of not less than one and a half times higher than the background noise level. In each of these intervals, average values of acoustic emission activity are calculated. During the slow heating-up of the sample to the holdup temperature, the initially weak structural bonds are destroyed and the source of emission becomes weak, and when the critical stresses are formed in the sample under prolonged thermal loading, the remaining, initially strong bonds become sources of emission. Therefore, the coefficient K, equal to the ratio between the acoustic emission activity in the second and the first of the indicated time intervals, reflects the residual thermal stability of the coal after freezing and thawing. Value of the thermal stability of the coal with respect to cyclic freezing and thawing is defined as the dependence reduction point K(M), which shows the number of cycles after which there are practically no strong structural bonds in the coal under study.;EFFECT: technical result: possibility of determining the thermal stability of coal during its cyclic freezing and thawing.;1 cl, 5 dwg