A chemical process involves a packed bed reactor operating at a specific pressure drop of 1000 Pa. The bed length is 3 meters and has a void fraction of 0.35. The fluid flowing through the bed has a dynamic viscosity of 0.03 Pas and a density of 1200 kg/m. The desired flow rate through the bed is 8 m/hr. Determine the minimum particle size that will ensure a pressure drop of at least 1000 Pa