Abstract: The apparatus provides a unique and novel vessel and process that concentrate solids, produces paste and stores paste from mixtures of solids and liquids. The vessel or tank includes a vertical shaft mounted within the tank and a variable speed drive for rotating the shaft for circulating paste. The shaft includes a helical pump for lifting the paste and a rake arm extending outwardly from a lower portion of the shaft for moving the paste radially inward. A vertical flow director within the tank is connected to the shaft for maintaining paste flow and facilitating paste circulation at outer portions of the tank. A paste exit port through a lower portion of the tank is used for removing paste. The method forms a paste by first introducing a mixture of solids and liquids into a tank. A portion of the solids and liquids are lifted vertically to establish a circulation pattern within the tank.