The "dilute phase" refers to a stage in a pneumatic conveying system where solid particles are transported through a gas, typically air, at low concentrations. In this phase, the particles are widely spaced apart, allowing for efficient movement without significant collisions. This method is commonly used in industries such as food processing and pharmaceuticals. In the dilute phase, the velocity of the gas is high enough to keep the particles suspended, preventing them from settling. This contrasts with the "dense phase," where particles are transported at higher concentrations and lower velocities. Understanding these phases is crucial for optimizing material handling processes.