Abstract: A process and a structure is described for separating particles in a fluid medium based on a difference in settling velocity. The feed is introduced tangential into the separation zone. The tangential feed system includes a transition box to reduce flow velocity and disperse the slurry across the separator eliminating the efficiency losses associated with other classifiers that introduce feed directly into the separation chamber. This approach offers an improvement in process capacity and efficiency. The fluidization water is introduced to the separation chamber below a baffle plate that disperses the water across the base of the separator. The feed system may include baffles in the upper separation chamber, and a stilling well with an impact plate adjustable side walls and adjustable baffle plates to reduce flow velocity and disperse the slurry across the separator.