| Loose coal sample is a kind of porous medium with complicated structure,which contains water and is inflammable.In the process of coal mining,storage and transportation,with the change of environmental conditions,slow oxidation is easy to occur,which will cause the change of temperature and humidity field inside the loose coal sample and lead to spontaneous combustion of coal.Phase change of the moisture migration can change the temperature field of a loose coal samples,and then control the loose coal samples of low temperature oxidation process,so the study and mastery of loose coal samples under different environmental conditions change law of moisture migration on the reduction of coal low temperature oxidation process,explore the loose coal samples within the high temperature formation mechanism has an important guiding role.In this paper,with the support of the key research and development plan(2018YFC0807900)and the National Natural Science Foundation of China(51874007),some basic research work has been carried out on the variation rules of moisture migration within loose coal samples.Based on the theory of heat and mass transfer in porous media and the theory of porous media seepage,the experimental device of seepage water migration in loose coal samples was designed and built independently.In this paper,the moisture characteristics of unconsolidated coal samples were firstly analyzed,and then the experimental study on the variation rules of moisture migration of unconsolidated coal samples with different moisture content(raw coal,9%,16%,23%and 30%)under three conditions of ventilation without heat source,ventilation without heat source,and ventilation with heat source was carried out by using high frequency coal moisture meter.The experimental results show that different external factors have different effects on the phase transition of loose coal samples during the process of seepage water migration.Without heat source with ventilation,the size of the wind to the moisture of coal sample phase change migration plays an important role,romantic leads to the pressure difference of its occurrence in coal sample is the main power,water seepage migration phenomenon of coal moisture distribution on the whole sample at the same time satisfy into FengKouChu moisture content is the lowest,the farther the trend of the higher the moisture content in the coal sample.Heat source is not ventilation,near the heat source water is most obvious change trend,different water content of coal samples are fast peak water first,and then began to decline,the mutual coupling effect of temperature gradient and moisture gradient,the water there will be a slow decline period,and the higher water content,change the more obvious,evaporation-diffusion-condensation mechanism is temperature moisture migration under the action of the main mechanisms.When there is a heat source and ventilation,the water drop rate is the fastest at the inlet side and near the heat source.At the same time,the water in the coal sample column starts to show a trend of increasing-decreasing-increasing-and then decreasing from the inlet side.With the increase of the experimental period,the water in different coal seams of the loose coal sample finally flattens out.The experiments of water migration under different conditions in this paper provide necessary experimental basis for further revealing the nature of water migration in loose coal samples.Figure 29 table 10 reference 71... |
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