A device for separating constituents of a fluid mixture includes an elongate vessel oriented at an acute angle to horizontal. The vessel is operable to receive the fluid mixture and direct the fluid mixture to flow in a convection cell spanning substantially a length of the vessel. The convection cell is formed by gravitational forces acting on the fluid mixture and is operable to deposit a heavy constituent of the fluid mixture about a lower end of the vessel and a light constituent of the fluid mixture about an upper end of the vessel.