GB772864A - Process of and apparatus for treating solid or liquid substances with gases - Google Patents

Abstract

<PICT:0772864/III/1> <PICT:0772864/III/2> <PICT:0772864/III/3> In carrying out chemical or physical reactions on solid and/or liquid substances maintained as a fluidized bed in a grateless reactor with the aid of an upwardly directed current of gas or vapour, the reactor has the shape of a diffusor the walls of which flare continuously or discontinuously to an increasing extent with height up to an angle not exceeding 45 degrees, said increase in angle however not being so great that the gas or vapour stream leaves the wall below one-half the height of the reactor, the current of gas or vapour being introduced into the bottom of the reactor from a chamber in axial alignment therewith, said gas or vapour being introduced into said chamber non-axially and non-tangentially thereto. As shown in the drawing (Fig. 2) the reactor consists of a flaring part 39 in which the fluidized bed is formed and an after reaction shaft 40, a gas inlet chamber 41 being placed below the reactor. Carrier gas is introduced laterally from pipe 43 into the chamber 41 and leaves the apparatus at 44. Pipes 45 and 46 are provided for the introduction of various solid or liquid media and a discharge tube 47 is provided. Alternatively the whole of the finished product may be withdrawn through the gas chamber 41 into a seal 42. Such an apparatus may be employed to carry out endothermic reactions with the aid of fuel, for example the burning or calcining of cement, lime, dolomite, sulphates, silicates, phosphates and bauxite in which case the material may be introduced at 45 whilst coal may be introduced at 46. Thus gypsum may be reduced with the production of a cement-like clinker and gases containing sulphur dioxide, or sulphur may be produced by reducing the pyrites with coal in the presence of an oxygen-containing gas, in which case the reaction temperature may be controlled by a cooling jacket around the reactor space 39. The apparatus may also be used to reduce ores or waste products containing metal oxides to metal, which may be obtained as a vapour, a liquid or in the solid state. The reactor of the invention may be combined with a rotary tube furnace as shown in Fig. 3 wherein a rotary tube 28, to which material is to be treated is introduced at 29, is connected to the upper end of a reactor 32 which is similar to that of Fig. 2. Treatment gas is supplied to a chamber 35 below the reactor 32 by a lateral pipe 37, the gas leaving the fluidized reactor 32 passing through an after reaction shaft 33 into the rotary tube 28 to leave at 38. Material to be treated is fed to the rotary tube 28 at 29, passes through a seal 30 and a pipe 31 to the reactor 32 for discharge at 34 or through a discharge lock 36. According to an example (1) a tin containing pyritic concentrate was supplied to the rotary tube 28 where it was contacted with hot roasting gases produced in the fluidized bed reactor whereby a mixture of sulphur and tin sulphide was distilled off. The material now consisting practically of magnetic pyrites was discharged from the rotary tube by pipe 31 to the fluidized bed reactor where it was roasted to form ferric oxide with oxygen containing gases. Pyrites may be similarly roasted. Alternatively an apparatus as shown in Fig. 4 may be employed in which the fluidized reactor of the invention is designated by 21, the after reaction shaft by 22 and the chamber below the reactor, to which the fluidizing gas is fed laterally at 26, by numeral 23. Such a reactor is surmounted by a conventional fluidized bed reactor 15, also with flaring walls, to which material to be treated is fed at 17. Material from the reactor 15 overflows through pipe 18 through a lock 19 to a pipe 20 into the lower reactor 21. In such an apparatus zinc ores containing lead may be roasted, in which case lead sulphide is distilled off in the upper reactor by means of the roasting gas practically free from oxygen which enters from the lower reactor. In the lower reactor the zinc sulphide now free from lead is roasted with an oxygen containing gas to produce zinc oxides which may be withdrawn through an overflow 25 or through a closure 24. The lead sulphide leaving the upper reactor 15 may be recovered by electrostatic precipitation or it may be burned in an after combustion chamber with further oxygen to obtain a lead oxide dust. The apparatus shown in Figs. 2 or 4 may be employed for granulation. Thus according to examples (3), a mixture of kieselguhr and water-glass is introduced into the reactor of Figs. 2 or 4 and formed into a fluidized bed with a current of carrier gas at a temperature of 350 DEG C. Sulphuric acid is introduced into the fluidized bed in the form of a spray whereby the material is granulated and the granules so formed drop downwards to the bottom of the reactor for discharge in the dry state. (4) The granulation process of example 3 is modified in that the solid material to be granulated is sprayed in the form of a solution through an atomizer nozzle located near the top of the reactor, which has previously been filled with granules of other origin and of rather smaller size than that intended to be produced. Such granules are fluidized by a hot carrier gas and the solution sprayed on to them whereby the solid is deposited from the solution on to the granules of the fluidized bed which increase in size until they they are large enough to fall to the bottom of the reactor. At the same time sufficient new nuclei are formed so that the process proceeds continuously. Thus washing soda may be obtained in grain sizes of from 0.05 to 10 mm. by such a process.