Characterizing Of Oil Shale Pyrolysis Process With Laser Ultrasonic Detection

Oil shale,considered as a predominant alternative source,has become the focus of research in the field of oil and gas in recent years.The noncontact all-optical laser ultrasonic technique was proposed to characterize the pyrolysis process of the oil shale in the three regions of Longkou,Yaojie and Barkol of China.The pyrolysis parameters of final temperature（T）,heating rate（β）and ventilating rate（V）were studied by controlling variables and the semicoke in different conditions were prepared,which were detected by the laser ultrasonic technology.The relations of the ultrasonic,the pyrolysis parameters and the oil yield in oil shale in Longkou were found.The ultrasonic velocity was explored to characterize the optimal pyrolysis parameters.The main research results are listed as follows.1.The laser ultrasonic technique was proposed to characterize the pyrolysis process of the oil shale.It was found that the ultrasonic velocity was related with the pyrolysis temperature of the oil shale.The pyrolysis process was divided into three stages due to the ultrasonic propagation speed in the oil shale.The ultrasonic velocity had small changes from 20 to 320°C in the first stage,a sharp decline between 320 and470°C in the second stage,and another small change from 470°C to 600°C in the third stage.An empirical equation of the velocity attenuation was proposed to estimate the beginning and the end of the decomposition of the kerogen.And the qualitative explanation about the changes of the ultrasonic velocity in the three stages was given in the thesis.2.The optimal pyrolysis parameters of Longkou oil shale were studied in the thesis,which was the final temperature T of 550°C,the heating rateβof 15°Cmin^-1 and the ventilating rate V of 0.6 Lmin^-1.The oil yield of the oil shale reached the maximum under the optimal pyrolysis parameters.The semicoke in different conditions was prepared to be detected by the laser ultrasonic technology.The ultrasonic P-wave velocity acquired was found to be interrelated with the three pyrolysis parameters of the oil shale.The oil yield of the oil shale may be qualitatively characterized by the P-wave velocity,and the optimum of T,βand V may be also explored by the trend of the P-wave velocity.