Converter for converting sulfur dioxide to sulfur trioxide

Abstract

A converter for converting SO.sub.2 to SO.sub.3, having an exterior shell, a central axial core tube, and a number of annular catalyst beds one above the other, placed on support plates and separated by division plates. The shell, core tube, support and division plates are all of stainless steel. The support and division plates are performed in a domed shape to prevent excessive sagging in use and are welded to the shell and core tubes, except for the support plate of the first bed. The first bed is at the bottom of the converter and its support plate is welded to an encircling plenum through which supply gas enters. The plenum shields the shell from the hot first bed and produces abrupt changes in the flow direction of the supply gas to remove entrained particles therefrom. From the first bed the gas flows through an internal axial heat exchanger in the core tube, where the gas is cooled against gas from the intermediate absorber, eliminating the need to remove the very hot first bed gas from the converter with a bellows piping system. The first bed gas enters a second bed at the top of the converter and then leaves the converter via a large diameter exit opening in the shell, which opening is of larger diameter than the height between the second bed support plate and its adjacent division plate. The height difference is accommodated by a slot cut in the division plate and a transition plate welded between the slot and the lower part of the exit opening.