Spectrum Research on Rheology of High Rank Coal

Abstract

Aiming to discuss the change characteristic of macromolecular structures of high rank coal in different rheological conditions, the high rank undeformed coal from southern Qinshui basin and the coal after variable temperature and variable pressure rheology experiments were investigated and analyzed in detail through Fourier transform infrared spectroscopy (FTIR) and laser Raman spectra analysis. The result shows that the texture and composition of different types of rheological coals under different temperature and pressure exhibit significant differences. Experiments of variable temperature and pressure of high rank coal (temperature: 300-400 °C, confining pressure: 50-100 MPa, strain: less than 10% and strain rate: 10(-4)-10(-7) · s(-1) will distort their macromolecular structures and recombine the chemistry structures. When the temperature is 300 °C or 350 °C, the high rank coal generates brittle or brittle-ductile rheology easily, mechanical energy transforms to heat energy, some branches and functional groups with weaker bond energy break and fall off, which split as dissociative micromolecule, with stress degradation as principal role, and stress polycondensation occurs with aromatic, texture increasing. When the temperature is up to 400 °C, ductile rheology of the high rank coal occurs with the secondary defects increasing, mechanical energy transforms to strain energy which helps the early shedding small molecules be embedded or adsorbed in the defect or on the surface of macromolecular preferentially and change the aliphatic and aromatic structures. It is affected by stress degradation and polycondensation progress, and the latter is dominated. The confining pressure and water injection of coal do not have much effect on the macromolecular structure obviously.