Abstract: An improved apparatus for mixing and reacting materials that include at least one liquid while simultaneously transferring heat to or from the mixture. A rotating centrifugal impeller mounted in a lower chamber of a closed reactor vessel draws the materials to be mixed from an upper chamber through a short central inlet and mixes them with high energy while impelling them between spaced blades extending outward from the eye of the impeller to a high pressure region at its circumference. The mixture then returns to the upper chamber through a plurality of elongated conduits having thin walls. For maximum heat transfer area in relation to cross-sectional flow area, each conduit is arranged with a first inner portion of annular cross section and a second, reverse flow, outer portion separated from the inner portion by a double-walled tube, the tube having passages between its double walls for circulating heat exchanging fluid.

Abstract: A duct for the circulation of a hot fluid under pressure and formed in a cold structure of concrete is lined with rigid heat-insulating material such as pumice concrete. A corrugated lining membrane is applied in close contact with the heat-insulating material by means of radial members which are disposed in uniformly spaced relation and anchored in the cold structure.