Effect of reheating on the morphology and structure of wax crystals in PPD-beneficiated crude oil

The study on the influences of reheating on the macroscopic flowability and microscopic wax crystal morphology of CQ crude oil beneficiated with pour point depressant(PPD)is beneficial to explore how reheating inherently influences the modification effect of PPDs. In this paper, reheating experiments were conducted on PPD-beneficiated CQ crude oil. It is shown that the influential law of reheating on the morphology and structure of wax crystals corresponds to its effect on the flowability of PPD-beneficiated CQ crude oil. After PPD-beneficiated CQ crude oil is preheated to 60 ℃ and then cooled dynamically to 20 ℃, it is reheated to different temperatures. When the reheating temperature is below 35 ℃, the size of wax crystals decreases, the fractal dimension becomes smaller and the macroscopic flowability of modified oil becomes worse with the increase of reheating temperature. When the reheating temperature is 35 ℃, the wax crystal size and fractal dimension reach the minimum value, and the modification effect of PPD is lost completely. When the reheating temperature is over 35 ℃, the size of wax crystals and the fractal dimension increase and the macroscopic flowability of modified oil gets better gradually with the increase of reheating temperature. The temperature range in which reheating deteriorates the modification effect of PPD seriously is corresponding to interval from wax appearance temperature(WAT)to wax dissolution temperature(WDT)of crude oil. The research results provide the theoretical support for the study on the influences of reheating on the flowability of the modified oil.