Abstract: To sealingly retain a radiant heat exchange tube extending through an opening (5) in a wall (3) of a furnace, and to isolate the atmosphere within the furnace space (2) from outside ambient space, a thin-wall sleeve (25) has a first portion (40) shrinkfitted around the radiant heat exchange tube (7) which, for high temperature resistance, is made of a ceramic, preferably silicon carbide. A second portion (42, 44, 46) of the sleeve (25) which conically expands, is secured to a flange element (23), for example by welding, which, in turn, is secured for examples by screws, to a flange structure (8) on the wall (3) of the furnace. The flange element (23) has an inner diameter which is greater than the outer diameter of the tube (7). The sleeve (25) is preferably made of iron-nickel and has a wall thickness which is about 1/10 of the wall thickness of the ceramic tube (7).

Abstract: Disclosed is a high temperature heat recovery system having a unique high temperature heat exchanger made of refractory and ceramic materials which can operate in gas streams of up to about 1,500.degree. C.

Abstract: Leaks in tube bundles for a heat exchanger are eliminated or minimized by tube interrelated techniques. A floating tube bundle is constructed with separate support elements also secured to the heat dissipating fins and extending through and supported by the support plates. Thin-walled copper tubing similar to that used for the fluid-carrying tubes is used as support tubes, and steel rods are inserted into these support tubes to provide the necessary strength. To minimize leakage in the area where the tube bundle is joined to a header, connector tubes are provided that have one end joined to the header and the other end extending into one of the tubes of the tube bundle sufficiently far that the end of the connector tube passes through the support plate and at least one fin.