Apparatus to alleviate thermal cycles in moving bed radial flow reactor

Abstract

A process and arrangement for contacting a moving bed of compact particulate material, usually catalyst, with a radial flow of fluid maintains an unconfined surface of catalyst particles in place by passing fluid axially into the upper surface of the bed and maintaining radial gas flow across an inlet screen at an elevation that is above the upper most elevation of perforations for withdrawing gas flow from the particulate bed. Two vertical screens confine the bed of catalyst. Perforations cover substantially the entire length of the inlet screen. The outlet portion of the screen has perforations that end below the top of the free surface of the catalyst bed and define an upper bed portion therebetween. The inlet screen directs gas flow radially across the inlet screen into an upper portion of the bed and causes at least partial axial flow of gas through the upper portion of the particle bed. The axial gas flow through the upper portion of the particle bed holds the surface of the catalyst in place while also cause the gas to preheat the relatively cold catalyst as it initially enters the particulate bed. Heating of the catalyst in an upper portion moderates transient temperature spikes and depressions that fatigue a critical junction between perforated and unperforated portions of the outlet screen. The preheating of the catalyst in by this method and seal arrangement reduces damage temperature swings on equipment while providing an overall simplified arrangement for a upper seal zone in a bed of compact moving particles.