Experimental Investigation of Viscosity Reduction of Heavy Oil via Hydrodynamic Cavitation in Laval Nozzle

Abstract

Hydrodynamic cavitation is rarely studied for viscosity reduction of heavy oil, although ultrasonic viscosity reduction technique has been widely reported. To evaluate the effect of hydrodynamic cavitation on the characters of heavy oil, a home-made setup equipped with a Laval nozzle was assembled. The density and viscosity of heavy oil were investigated. Function groups in heavy oil were determined by fourier transform infrared spectroscopy (FTIR). The results show that the effect of cavitation on the density can be negligible. The viscosity reduction can reach up to 3.8%. Longer circulation time, higher flow rate and upstream pressure lead to more reduction in viscosity continuously. More light compounds can be produced by higher flow rate, the ratio value of infrared absorbance of methylene (=CH2) to methyl (–CH3) can be decreased by 20.42%. However, without sufficient hydrogen donors, cracked compounds will be formed into heavy chains in the closed pipeline during the circulation. Besides of cracking of heavy chains by the energy wave of collapsing bubbles, resonant vibration and bulk nanobubbles (ultrafine bubbles) are introduced to the viscosity reduction of heavy oil.