An apparatus for the measurement of surface tensions at high pressures and temperatures

Abstract

NCUT Natural Resources Canada, Devon, AB T9G lA8, Canada ydrocracking and hydrotreating of heavy petroleum fractions or of hydrocarbon liquids that require desulfurization and/or H denitrification is one of today's major and now quite mature technologies. The reactions of hydrocracking, hydrodesulfurization (HDS) or hydrodenitrification (HDN) are usually carried out at relatively high temperatures (350'C to 45OOC) and high hydrogen pressures of up to 15 or 20 MPa. In most of these processes, a solid catalyst is present or is formed in the course of the reaction, so that the reaction system is always in a gas-liquid or gas-liquid-solid regime. In many cases, mass transfer can be the controlling rate mechanism in the reactor. In designing such reactors, or in the analysis of their performance, the ability to predict the hydrodynamic behaviour and the gas-liquid mass-transfer rate is necessary. One essential parameter for this analysis is a knowledge of gas-liquid interfacial tension values. The surface tension plays a major role in determining bubble sizes and bubble hydrodynamics, and therefore the interfacial transport area.There is another area in which knowledge of the gas-liquid interfacial tension is very important -the recovery of petroleum from reservoir formations. In the normal petroleum reservoir, oil trapping occurs at varying temperatures and at high pressures due to capillary forces resulting from surface tension. Particularly in secondary recovery, in which gas injection may be used, surface tension is a critical parameter. The variation of surface tension with temperature is well-known, and has been found to be essentially linear except in the vicinity of the critical point. The effects of pressure on surface tension are less easily predicted, and conflicting results have been reported. A significant reduction in surface tension has been found to occur at lower temperatures as gas pressure increases. However, the combined effect of high temperature and high pressure on the interfacial tension of hydrocarbon oils in contact with a gas with a high content of hydrogen or methane appears to require further investigation. The primary objective of this study was to make such surface tension measurements a t hydrocracking or hydrotreating conditions, if possible. Because no apparatus appeared to have been developed capable of such measurements a t these extreme 'Author to whom correspondence may be addressed. E-mail address: dscott@ eremail. uwaterlwxaAn apparatus for the measurement of surface tensions of organic liquids in contact with a gas has been developed which is capable of operation to 400°C and to 14 MPa. It is based on the maximum bubble pressure technique, modified for hydrocarbon oils at high pressures and temperatures. Accuracy of measurement is of the order of *3% for non-aqueous systems for values down to 5 mN/m. Only a 20 to 30 mL liquid sample is required, and small gas volumes. In practice, it was found that measurements with most organic liquids could only be made to a maximum of about ...

Laboratory Measurements of CO2-H2O Interfacial Tension at HP/HT Conditions: Implications for CO2 Sequestration in Deep Aquifers

“…We have chosen to use the pendant drop technique for measuring gas-water IFT since it is the most adaptable method not only for high pressure conditions, but also for a wide range of temperatures (Michaels and Hauser, 1951;Adamson, 1960;Millette, et al, 2002). Unlike other IFT measurement techniques that are empirically derived or require corrections applied to the measured data, the pendant drop approach is an absolute method based on a mathematical solution to the Young-Laplace equation (Deam and Maddox, 1970).…”

Measurement of Vacuum Residue and Asphaltene Fluid Properties at Process Conditions

“…Millette et al 7) suggested the use of the maximum bubble pressure method for measuring surface tension at high pressures in opaque liquids. This method is based on the pressure required to create a bubble at the tip of a capillary tube, which is related to the surface tension and the bubble radius: (4) where r is the radius of the bubble.…”

“…The use of two submerged capillaries of different radii allows correction for hydrostatic head, and a correction is used for non-spherical bubble formation at the tip of a capillary. Millette et al 7) reported calibration data on n-octane to 225°C at 13.8 MPa, and claimed useful results on oils up to 350°C. Unfortunately, neither the data nor the validation for the higher temperature results were presented.…”

Surface Tensions of Hydrocarbons and Bitumens at High Temperatures and Pressures

“…The apparatus is shown in Figure 1, and details of its construction, and its operation can be found in our previous publication (Millette et al, 2002). Tests with the two bitumen samples were done in the temperature range of 185° to 350°C to obtain a suffi ciently fl uid sample at the lower temperature, and to avoid thermal cracking at the higher temperature.…”

“…Because no suitable apparatus appeared to have been developed capable of such measurements, the initial part of the work required a survey of existing methods, and the selection and development of one of thesethe maximum bubble pressure method-as one capable of operation at temperatures to 450°C and pressures to 14 MPa. This initial phase of the study has been described earlier (Millette et al, 2002), and the present report gives the results of surface tension measurements on a number of pure paraffi nic hydrocarbons, two highly saturated petroleum cuts, and two heavy oil feeds-an Athabasca coker feed and a Cold Lake vacuum bottoms fraction-both from the northern Alberta bitumen deposits.…”