HEAT EXCHANGER FOR USE IN HIGH TEMPERATURE APPLICATIONS

摘要

A heat exchanger achieves a more uniform internal temperature gradient within it s scctions during normal operation as well as subsequent to an unexpected power sh utdown. Internal fouling of tubes containing the process gas and entrained solids is red uced. An external shell is utilized which is insulated on its inner surface and optionall y provided with cooling medium flowing within the shell wall. A double bottom tube sheet enclos ing a secondary cooling medium chamber is also provided. The top of the process gas t ube is preferably enclosed within a shielded chamber to facilitate a thermal gradient p roximate thereto. A ferrule is similarly affixed to the bottom of the process gas tube a t the point where it passes through the double bottom tube sheet. Cooling medium flow is diverted and passed directly into the cooling chamber of the double bottom tube sheet. Cooling medi um from the double bottom tube sheet is then vented to the top of the heat exchanger to a po int adjacent the top tube sheet. A secondary blower for propulsion of the cooling medium is provided in line with the normal flow of cooling medium from the primary blower. Under unex pected shutdown conditions, the primary blower operation is discontinued and the second ary blower continues its propulsion of cooling medium through the double bottom tube sheet and the main cooling medium chamber.