Patent GB-1378418-A (GB)
Title: Fluidized bed apparatus and methods
IPC: F23G5/30
Filed: 1972-12-20
Abstract: 1378418 Fluidized bed carbonation BROKEN HILL PTY CO Ltd 20 Dec 1972 [20 Dec 1971] 58949/72 Heading C5E  A fluidized bed apparatus, e.g. for the  carbonization of coal compacts, comprises a treatment channel for containing a bed of  particulate carrier, e.g. silica sand, means at one end of the channel for feeding compacts into the bed of carrier, means for fluidizing the bed of carrier to transport the carrier and compacts to the other end of the channel, a plurality of transfer means of two types disposed in spaced  relationship along the channel, one type being  for the return of carrier to the channel and  including a passage connected to a temperature changing device and having an outlet opening  into the channel at or near the base or floor thereof, and the other type being for the removal  of carrier from the channel and including a  passage having its inlet opening to the channel  just below the top of the bed, whereby the carrier from a temperature changing device passes upwardly through the channel in a direction which is transverse to the direction of transport of the compact and carrier, a device for changing the temperature of the carrier removed from the treatment channel prior to its return thereto, and means at the other end of the treatment channel for discharging compacts and/or carrier. The transfer means may be arranged along the length of the channel with one type alternating with the other type and the return of carrier to the channel may be controlled by a valve arranged to close or throttle the outlet opening of each transfer means to create a desired temperature profile or zones in the bed, e.g. by adopting an intermittent fluidization programme for respective parts of the bed. Transfer means for the return of carrier to the channel may comprise a down-comer passage having an opening to the temperature changing device and a fluidizing means in the passage just below the outlet opening to the channel, and each transfer means for the removal of carrier from the channel includes a down-comer passage having the opening to the channel, and fluidized carrier lifter passage for transporting the carrier to the temperature changing device. The treatment channel and temperature changing device may be part of a single structure and the transfer means are formed in or define a wall separating the channel from the device. In the treatment channel shown, coal compacts are fed via opening 7 and carrier via make-up inlet 8 into feed section 3 which is fluidized by means of distributer pipes 10. Feed section 3 is separated from treatment section 4 by baffle 6 which extends from the roof to below the surface of the fluidized bed to operate as a gas lock between sections 3 and 4 to prevent emission of pollutants at the feed point. The temperature in the feed section is kept low, e.g. 250‹ to 700‹ C. Treatment section 4 which is fluidized by means of distributer pipes 12, extends between baffle 6 and baffle 11 extending from the floor to such a height as to slightly arrest the flow of carrier and compacts into discharge section 5. A grating 14 is positioned above the floor of sections 3 and 4 to create a compacts-free zone of carrier which extends to a level above the outlet openings of the transfer means for the return of carrier such that the returned reheated carrier, e.g. at 650‹ to 900‹ C., is admixed with the resident carrier near the bottom of the bed and below the compacts in the channel thus avoiding thermal shock, and then passes upwardly through the bed in a direction transvese to that of the carrier and compacts in the bed. Baffles 13 extend across the channel between adjacent transfer means for the return of carrier to restrict the horizontal flow of carrier in the compacts-free zone. After treatment, e.g. at between 400‹ and 700‹ C., in Section 4, the compacts and carrier pass over baffle 11 into discharge section 5 which is fluidized by means of distributer pipes 16. The compacts and carrier leave the channel over weir 15 into a separating section comprising grate 17 which extends from weir 15 to the mouth of a shaft furnace; separated carrier being returned to the feeding section 3. Modifications of the construction of the feed section are described.