Abstract: Improvements in horizontal, continuously internally circulating contacting-mixing devices of the type having therewithin an impeller, a circulating tube and (usually) an indirect heat exchanging tube bundle; providing baffles or baffling in large volume low velocity zones in the circulation path of such devices in order to increase velocity therewithin and create shear and turbulence, thus to improve mixing; providing baffles or baffling in the annulus or circulating tube (or both) of such devices which extend substantially normal to the conventional axial direction of flow in such vessels in order to markedly change the flow patterns and flow characteristics in the baffled zones.