CFD Modeling And Experimental Study Of The Pneumatic Drying Process Of Oil Shale

As an unconventional oil and gas resource, oil shale is one of the most important substitutes for conventional resources in the 21th century, and is given extensive attention globally. However, its porous structure and high moisture tend to cause certain unfavorable situations in the oil shale combustion and gasification process, so oil shale dewatering before its pyrolysis becomes necessary. Pneumatic drying is widely used because of advantages like large-scale handling capacity, equipment simplicity, small investment, etc. This thesis applies the new "Computational Fluid Dynamics" technology to simulate the oil shale pneumatic drying process to reveal the detailed distribution and change trends of the flow fields in the pipe, meanwhile, a new calculation method of heat-mass transfer in the drying process is formed with the user-defined functions embodied in software Fluent. While a systematic simulation analysis is conducted, a pilot cold test and a laboratory thermal experiment are performed. The simulation results are compared with and verified by the experimental results, and they essentially agree with each other. Thus the reliability of the simulation and validity of the empirical equations specific to the pneumatic drying process are proved.From the dynamic simulation of the pneumatic drying pipe and its experimental research, the following statements can be concluded:the Discrete Phase Model in Fluent based on the Eulerian-Lagrangian approach should be adopted to analyze the gas-particle flow; both two-side face-to-face gas inlet approach and a cone-shaped shrinkage with suitable angle at the bottom of the pipe can improve the average distribution of gas velocity, but the cone-shaped shrinkage will enormously increase the pressure loss of the pipe.From the comparison and analysis of the thermal simulation and laboratory experiment of oil shale pneumatic drying, following conclusions can be obtained:the drying process corresponds to the first stage of the two-stage drying kinetics model, and therefore the fact that moisture evaporation occurs mainly at the constant rate drying stage in pneumatic drying is further proved; the J. Baeyens empirical co-relation Nu=0.15 Re? is used to calculate the heat transfer coefficient in oil shale drying process, and the results match with experiment generally, with -2.9% relative error for gas outlet temperature (?)?-8.9% relative error for final oil shale particle temperature (?)?35% relative error for gas outlet moisture, and -2.8% relative error for average heat transfer coefficient.