Particle processes in various industries, including chemical, pharmaceutical, ceramic, and mineral processing, often involve solid-liquid or solid-gas multiphase systems. Achieving efficient operation in such processes requires a thorough understanding of, and appropriate control over, particle behavior under complex multiphase conditions. With continued advances in computer hardware, the discrete element method (DEM) coupled with computational fluid dynamics (CFD) has emerged as a promising approach for simulating particle-fluid interactions. However, conventional DEM-CFD methods face significant challenges in industrial applications due to stringent limitations on the number of computational particles, despite the strong demand for large-scale simulations. To overcome these limitations, we present an integrated numerical approach that couples coarse-grained DEM-CFD with an implicit drag force algorithm and a scalar-field-based wall boundary model for multiphase particle simulations. In the coarse-graining approach, a group of original particles is represented by a single enlarged particle while ensuring conservation of total energy between the coarse-grained and original particles. Through systematic validation in both solid-liquid and solid-gas systems, the proposed model successfully reproduces the macroscopic particle behavior. Specifically, the coarse-grained system shows strong agreement with the original particle system in terms of particle position, particle velocity, and total kinetic energy. These findings demonstrate the applicability of the proposed model to industrial multiphase particle processes and underscore its potential for numerical optimization studies.