The air dense medium fluidized bed (ADMFB) is an effective clean coal technology for arid regions of China. However, the precise regulation of the separation and fluidization for polydisperse particles, and the complex movement of internal component is critically difficult in industrial application. In this study, the inclined coal separation model (ICSM), rather than the traditional gravity separation principle for ADMFB, is introduced to predict the distributions of coal particles, bed density and residence time more reasonably. Besides, a multiscale computational method is developed by coupling the coarse-grained model and the STL (StereoLithography) construction method to describe coal separation, medium particle circulation, and internal component motion for industrial ADMFB. The simulation results are validated against experimental data and further support the accuracy of the ICSM, where the coal particles with different densities always are separated diagonally in the bed, hence an inclined feeding method is necessary for transporting raw coal into the separation region quickly to avoid particles aggregation, such as the angle of 60 degrees. Besides, the movement of the discharge wheels and scrapers induces a global circulation of the solid phase, resulting into the significant difference of residence time distributions for coal particles with various densities. However, the internal components can enhance bed density uniformity to some extent and promote effective density segregation. The present research makes a great progress in simulating the industrial ADMFB system and provides key theoretical insights into particle separation mechanisms for regulating industrial beneficiation process.