GB730347A - Apparatus for the treatment of finely divided fluidizable solid material - Google Patents

Abstract

Apparatus for the heat treatment of finely-divided fluidizable solid materials, comprises an assembly of horizontal heat-resisting metal retorts each having side walls spaced 6-36 inches apart, a porous diaphragm below which pipes 38, 39 supply fluidizing gases, vent pipes 40, 41 in the roof to take off the gases, and an inlet tube 42 and an outlet tube 45 for charge material at opposite ends of the retort. The inlet tube 42 is disposed either over a sloping bottom end wall 43 or over a block with a <PICT:0730347/III/1> <PICT:0730347/III/2> <PICT:0730347/III/3> <PICT:0730347/III/4> <PICT:0730347/III/5> conical top, Fig. 7 (not shown), to prevent fluidization of the material before it enters the retort, and the outlet tube 45 may be replaced by an end horizontal outlet, Figs. 10, 11 (not shown). To prevent buckling of the retorts, side ribs 47 are disposed at the height of the fluidized bed and the roof and/or the bottom of the retorts is rounded, or the retorts are made elliptical in shape, Figs. 2-5 (not shown). When the retorts are assembled in banks the ribs 47 seat on horizontal baffles 54 and hot flue gases circulating in the spaces 55 below the baffles heat the retorts up to 1,000 DEG F. A modification, Fig. 13, suitable for working temperatures over 1000 DEG F. comprises refractory walls defining a treatment chamber flanked by heating chambers 73 in which hot gases from burners 68 follow a tortuous path round baffles 76-79 into a manifold 81 from which they may be supplied to heat low-temperature retorts. The exterior walls are made of firebrick and the heat-conducting walls 60 of silicon carbide or other refractory having a high heat conductivity. In treating relatively coarse materials it may be advantageous to place one or more open burners in the fluidized bed, Fig. 14a (not shown). Where, in a two-stage process, the amounts of heat absorbed at the different stages vary, a bank of parallel retorts is arranged to feed another bank containing a different member of similar paralled retorts through a transverse trough of similar design to the retorts, in which the material is maintained in the fluidized state, Figs. 15-16 (not shown). Vertical retorts, Figs. 17, 18 (not shown), having a diameter in the range 6-36 inches may be conveniently incorporated in plant where there is no evolution of gas at a particular temperature range. Thus a calcination involving a dehydration step at approximately 200 DEG C. and a surface activation step at approximately 550 DEG C. is carried out in the plant shown in Fig. 20, in which the calcining plant is combined with a steam-generating plant around a common pulverulent fuel fired furnace chamber 149. Charge material fed into a distributer trough 131 by a shoot 130 is fluidized therein and then fed in succession through banks of horizontal retorts 137 and 139 wherein it is heated to approximately 200 DEG C., a distributing chamber 141 feeding a third bank of horizontal retorts 142 where it is heated to approximately 550 DEG C., a U-shaped distributing chamber 144 feeding three rows of vertical retorts 145 lining the sides of the combustion chamber 149, in which retorts the reaction is completed, and finally into a U-shaped collecting trough 146 from which it is discharged by shoots 147, 148. The boiler system may include water tubes lining the combustion chamber walls and water-cooled structural members supporting the retorts. Further heat may be recovered by cooling the product in a cooling trough of the type described in Specification 693,868, [Group XXX], Figs. 25 and 26 illustrate a plant suitable for calcining a metallic hydroxide with a finishing temperature of approximately 1000 DEG C. Material entering a fluidizing distributer 176 by a shoot 175 passes in turn through a bank of horizontal retorts 177 operated at 250-350 DEG C., a distributer 178, a bank of eight retorts 179 operated at 350-550 DEG C., a distributer trough 180, a bank of high-temperature retorts 181 where it is heated up to approximately 1000 DEG C., and a collecting trough 182 for discharge to a cooler. Fluidizing medium for the plant comprises flue gases burnt in chambers 188, 189 from which pre-heated air also passes p to combustion chambers 201, separated from the retorts 181 by heat-conducting walls 202. Hot flue gases from the chambers 201 pass through the spaces 203 and 204, heating the medium temperature retorts 179 and finally collect in the channels 205 between the retorts 177 leaving by a flue 206. The invention may be applied to the treatment of finely-ground ores, flotation tailings, metal oxides, mineral pigments, clays and minerals, the low temperature system being particularly applicable to the calcination of kaolin, activated alumina, bauxite, fuller's earth, yellow and brown iron pigments and metallic hydroxides. The high temperature system is applicable to the calcination of alumina, titanium oxide, dark iron pigments, metallic carbonates and sulphide ores. In addition, the apparatus can be adapted to processes involving chemical reactions between gases and solids such as the calcination of petroleum coke, the treatment of semi-coke, and the chlorination or fluorination of solids.