Fluidized bed injection assembly for coal gasification

#1. Field of the Invention

#This invention relates to fluidized bed coal gasification reactors, and more particularly to arrangements for feeding fluid, including particulate mediums, into the reactor.

#2. Description of the Prior Art

#The advantages, nature and additional features of the invention will become more apparent from the following description, taken in connection with the accompanying drawings, in which:

#FIG. 1 is a partial cross section view, in elevation, of a fluidized bed gasification reactor in accordance with the invention;

#FIG. 2 is a cross-sectional view, in elevation, of a coaxial feed system for the reactor of FIG. 1;

#Referring now to FIG. 1 there is shown a fluidized bed reactor 10 including a vessel 12. The vessel 12 is generally cylindrical including a lower body 14, an enlarged upper body 16, an inlet feed system 18, an ash outlet 20 at the bottom, and a product gas outlet 22 at the top.

#Char particles and other mediums enter the vessel 12 through the feed system 18 forming a recirculating fluidized bed 24 wherein the char is combusted with air or oxygen and gasified with steam producing a combustible product gas and waste ash. FIG. 1 also depicts the combustion jet penetration depth 26 shown as extending from the top of the feed system 18 to an area in which slugging operational characteristics may occur as a result of enlarged bubble formation which can attain the dimension of the inner diameter of the vessel. It is desirable to enhance penetration depth, the overall penetration jet volume, and the time period during which the particulate matter exists within and immediately above the combustion jet in order to ensure complete combustion of the char. It has been found that this condition is enhanced when the annular velocity is between one and two times the minimum fluidization velocity, U.sub.mf, of the solids in the annulus and the jet velocity is 60 ft./sec. or greater.

#FIGS. 2 and 3 show additional details of the feed system 18. It is arranged so as to provide a combined coaxial feed, and a combined coaxial and radial discharge of fluid mediums, particularly providing coaxial vertical upward feed for char or coal particles in a transport gas. The primary structures include three tubular members, an inner tube 28, an intermediate tube 30, and an outer tube 32, respectively surrounding one another radially so as to form an inner annulus 34 and an outer annulus 36. The tubes are preferably concentric. In preferred form for a one-half ton per hour unit, the inner tube 28 is a 1-inch schedule 40 pipe of Incoloy 800. Radially extending from the tube 28, into the intermediate annulus 34, are a plurality, preferably four, spacer plates 38, 7/16 inch wide by 21/2 inch long of type 316 stainless steel. Char fines or coals in a transport gas, which can comprise recycled product gas, steam, air, nitrogen and carbon dioxide, enter the inner tube through nozzle 40 and are injected into the reactor vessel 12 through the open top of the inner tube 28 at a temperature in the range of 500.degree. F. The spacer plates 38 provide for an even distribution at the upper end of the inner annulus. The solid feeds are thus discharged upwardly directly into the combustion jet.