Abstract: A submersible liquid circulation apparatus comprises an upright open-ended draft tube and a bubble generator. The bubble generator is coupled to the exterior side of the draft tube, so that it continuously generates bubbles which are introduced into the draft tube for propelling the liquid material up through the draft tube. This continuous and cyclic movement of bubbles inside the draft tube facilitates continuous circulation and mixing of the liquid. A gas supply means is coupled to the bubble generator for supplying the necessary gas to generate the bubbles. The elongated draft tube comprises an upper section and a lower section separated by a slight gap. Thus, liquid entering the inlet end of the lower section is propelled upward and across the gap separating the two sections and is ultimately expelled through the outlet end of the upper section. This gap provides an additional inlet point for liquid located at a point above the bottom of the digester, to flow directly into the draft tube.

Abstract: The invention relates to apparatus for carrying out mixed liquid, gas and solid phase reactions and is intended for use in sewage digestion tanks where the removal of sludge and foam from the tanks is required. A reactor vessel is provided which includes a floating cover vertically movably maintained within the vessel. A device for limiting gas pressure is connected to the vessel below the cover. A buoyancy chamber is provided which is supported by the cover and located therebelow and is intended to be at least partially immersed within the liquid in the vessel. A foam/sludge withdrawal opening is located below the uppermost portion of the buoyancy chamber and connects the interior of the vessel to the exterior. In a preferred embodiment, a ballast member is supported from the cover and extends from the roof to below the buoyancy member.