A compressible multiphase CFD model has been developed to simulate the flashing process of the three-phase slurry at high temperatures and pressures. The model is validated with the gas-water flash process in the literature. A comparison of simulation results for gas-liquid and gas-liquid-solid systems indicates that the presence of solids changes important physical characteristics of these systems, including velocity, pressure, and shock location. The simulations indicate that changing the deflection angle, length, and diameter of the blast tube will significantly influence the flashing process. Increased blast tube length can reduce the velocity of the outlet significantly. The performance of the blast tube will be impaired if the deflection angle is too large. Increased tube diameter boosts mass flow rate while decreasing shock strength and increasing velocity at the outlet. These simulation results would be beneficial for the design and operation of flashtubes.