Cryogels and Gels for Advanced Technological Processes in Coal Industry
M. S. FUFAEVA1, L. K. ALTUNINA1, I. S. KOZHEVNIKOV1, S. M. NIKITENKO2, V. I. KLISHIN2
1Institute of Petroleum Chemistry, Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia
2Federal Research Center of Coal and Coal Chemistry, Siberian Branch of the Russian Academy of Sciences, Kemerovo, Russia
Keywords: gel, cryogel, elastic modulus, oscillatory rheometry, polyvinyl alcohol, coal, ecology, hydraulic fracturing
Abstract
The rheological (structural-mechanical) properties of gel-forming compositions, gels and cryogels based on polyvinyl alcohol, as well as the compositions developed at the Institute of Petroleum Chemistry SB RAS, which are promising from the viewpoint of preventing endogenous fires and intensifying methane release during interval hydraulic fracturing of coal seams, have been studied. The amplitude and kinetic dependences of the elastic modulus ( G' ), loss modulus ( G'' ) and complex viscosity were obtained in the oscillatory mode using the rheometer with controlled deformation for the compositions differing from each other in the ratio of components at different temperatures. It has been shown that the gel starts to form already at the moment of component mixing, and the elastic properties of the forming structure predominate ( G' > G'' ). The values of gelation points were determined. It is found that with an increase in crosslinker concentration, the strength of the resulting structure increases, and the time of gel formation decreases. As the temperature decreases, the strength of the resulting structure also increases. In the static mode of sample deformation, it is established that the gel is further stabilised after the freeze-thaw cycle. The developed composition has strength properties and good adhesion to the surface of coal. It can be used to protect coal mine faces from spontaneous combustion and as a protection from coal dust on technological roads. The change of the deformation-compression dependence under constant load on time for gel and cryogel was studied. It has been established that under a constant stress of 7 kPa, gel deformation reaches 25 %, while cryogel deformation is 15 %, that is, the elastic properties of the composition increase after a freeze-thaw cycle. In this regard, it is preferable to carry out the work at sites in the autumn and spring time.
|
