High Pressure Dilatometer Research Articles

Some aspects of the role of coal thermoplasticity and coke structure in coal gasification. 2. The effects of pressure and heating rate on dilatometric parameters and optical anisotropy development

An examination of the influence of pressure and heating rate on the thermoplastic properties of a weakly coking coal and of coal with various pitch-like additives was carried out using a high pressure dilatometer. Pressure up to 4 MPa markedly increased the swelling properties and increased the plastic range by decreasing the softening temperature, but the effects of pressure were strongly influenced by rate of heating with high heating rates enhancing the effects. Additions of tar or pitch also enhanced swelling at low pressure. The solid carbonization residues from the dilatometer were examined by polarized light microscopy to determine the content and composition of optically anisotropic species. The anisotropic content was increased by increases in pressure and heating rate and pitch additives enhanced the anisotropic content, especially at low pressure, without affecting the composition of the anisotropy. No direct correlations exist between the dilatometric parameters and the optical anisotropy but their dependence on the conditions emphasizes that when considering high pressure gasification of coal, it is necessary to obtain data under appropriate conditions.

A high-temperature (2300K) high-pressure (2 MPa) dilatometer (for sintering mechanism investigation)

A dilatometer specially designed for a study of the sintering of silicon nitride is described. Densification kinetics could be measured at temperatures up to 2300K. Thermodynamic considerations dictated that the specimens be maintained in a N2 gas pressure of up to 2 MPa. Hot-pressed boron nitride was the only material found suitable for the high-temperature parts of the dilatometer. The pressure vessels contained an RF furnace with graphite susceptor thermally insulated with zirconia granules and housed in a vitreous silica tube. This simple arrangement allowed high heating rates and a minimum of maintenance. The dilatometer is readily adaptable to high-temperature properties measurements where inert gas overpressures are desirable.

High-Pressure Dilatometer up to 22 Kilobars

A high-pressure dilatometer was devised to measure the length change of specimens under hydrostatic pressure up to 22 kilobars. The dilatometer uses a linear variable differential transformer and exhibits a hysteresis with pressure cycling. With a careful calibration of the dilatometer vs pressure, instantaneous measurements of the length change of a specimen can be made within a precision of less than 0.025%.