Fluidized bed apparatus

Abstract

A fluidized bed apparatus having an outer vessel provided at a lower region with a plenum chamber as well as a grid situated directly above the plenum chamber and carrying a plurality of nozzles through which gas flows from the plenum chamber into the space in the vessel above the grid. These nozzles provide a given pressure drop in the gas flowing therethrough while as the gas flows from the plenum chamber through each nozzle there is also provided by way of a suitable structure a preliminary pressure drop, so that a two-stage pressure drop is provided in the gas flowing through each nozzle from the plenum chamber into the vessel above the grid. In this way it is possible to achieve a flow of gas above the grid sufficient to maintain the particles suspended in the fluidized bed while attrition of the particles is maintained at a minimum so that very little if any fines flow out of the vessel with gas which is formed therein. According to this method, the particles are petroleum coke particles while the gas is a mixture of steam and air maintained in the plenum chamber at a pressure of only 1-5 psig above the pressure in the bed while at the region of the interior of the vessel above the grid the temperature is on the order of 1500.degree.-1800.degree. F. The grid supporting the nozzles is sloped 3.degree. to 5.degree. downwards towards a center well and supporting member to allow solid agglomerations such as lumps of coke and slag to move radially inward into the well for withdrawal.