This paper studies the stability of crude oil emulsion characterized by conductivity difference between upper and lower layers. According to the changes of conductivity in the upper and lower layers of crude oil emulsion system, combined with optical microscope observation, the methods and conditions to characterize the stability of crude oil emulsion can be studied by the difference of conductivity between the upper and lower layers. Research finds that when the crude oil system is demulsified and phase separated, the composition, morphology and conductivity of the upper and lower emulsions will be different.Therefore, the conductivity difference between the upper and lower emulsions can be used as the characterization parameter of emulsion stability. By measuring the conductivity and the difference values of the upper and lower layers of the system at different electrical test signal frequencies (0.1,1.0,10.0,100.0 kHz), it is found that the conductivity values and the difference values at high frequency are greater than those at low frequency, and the sensitivity is higher. In addition,when the conductivity difference is greater than 15%, the system is unstable. The experimental results show that the method is also suitable for emulsion system containing anionic surfactant.

Taking the gas storage tank in a gas?liquid linkage actuator of a gas transmission pipeline as an example, the software Ansys Fluent was used to establish a 3D model with the same proportion, to simulate the change of pressure and temperature with continuous heat input when external fire occur. Aspen Hysys was used to calculate the minimum PSV diameter required for safe discharge under fire conditions. The results show that the temperature and pressure of the tank rise sharply, reaching to the steel tank collapse temperature and design pressure in a very short time, when the external fire occurs. The time to reach the collapse temperature of steel tank is lagged behind the time to reach the design pressure of the gas tank. From a security perspective, the PSV should be set, which can also help to reduce the damage of the accidents even if the tanks collapse. The minimum diameter of the PSV calculated by Aspen Hysys is 0.13 cm², and the recommended diameter of the PSV is no less than 0.15 cm².