Method and plant for the heat treatment of sulfidic ores using annular fluidized

Abstract

The invention relates to a method and a plant for the heat treatment of sulfidic ores, in which solids are heated to a temperature of approximately 450 to 1500° C. in a fluidized bed reactor ( 1 ). In order to improve the energy utilization, it is proposed to introduce a first gas or gas mixture from below through a gas supply tube ( 3 ) into a mixing chamber ( 7 ) of the reactor ( 1 ), the gas supply tube ( 3 ) being at least partly surrounded by a stationary annular fluidized bed ( 35 ) which is fluidized by supplying fluidizing gas. The gas velocities of the first gas or gas mixture as well as of the fluidizing gas for the annular fluidized bed ( 35 ) are adjusted such that the particle Froude numbers in the gas supply tube ( 3 ) are between 1 and 100, in the annular fluidized bed ( 35 ) between 0.02 and 2 and in the mixing chamber ( 7 ) between 0.3 and 30.

1 . A method for heat treating sulfidic ores, comprising treating solids at a temperature of 450 to approximately 1500° C. in a fluidized bed reactor, introducing from below a first gas or gas mixture through a gas supply tube into a mixing chamber of the reactor, the gas supply tube being at least partly surrounded by a stationary annular fluidized bed which is fluidized by supplying fluidizing gas, and adjusting gas velocities of the first gas or gas mixture and the fluidizing gas for the annular fluidized bed wherein the gas velocities have a particle Froude number in the gas supply tube between 1 and 100, in the annular fluidized bed between 0.02 and 2, and in the mixing chamber between 0.3 and 30.  
   
   
       2 . The method as claimed in  claim 1 , wherein the fluidized bed reactor or first reactor is provided downstream with a second reactor, into which a gas mixture laden with solids is introduced from the first reactor from below through a gas supply tube into a mixing chamber, the gas supply tube being surrounded at least partly by a stationary annular fluidized bed which is fluidized by supplying fluidizing gas.  
   
   
       3 . The method as claimed in  claim 1 , wherein the particle Froude number in the gas supply tube is between 1.15 and 20.  
   
   
       4 . The method as claimed in  claim 1 , wherein the particle Froude number in the annular fluidized bed is between 0.11 and 1.15.  
   
   
       5 . The method as claimed in  claim 1 , wherein the particle Froude number in the mixing chamber is between 0.37 and 3.7.  
   
   
       6 . The method as claimed in  claim 1 , adjusting the solids in each reactor to have a bed height such that the annular fluidized bed extends beyond the upper orifice end of the gas supply tube and that solids are constantly introduced into the first gas or gas mixture and entrained by the gas stream to the mixing chamber located above the orifice region of the gas supply tube.  
   
   
       7 . The method as claimed in  claim 1 , wherein the sulfidic ore, comprises gold, zinc, silver, copper, nickel and/or iron, as starting material.  
   
   
       8 . The method as claimed in  claim 1 , wherein at least one reactor is supplied with oxygen-containing gas, through the gas supply tube and/or into the annular fluidized bed.  
   
   
       9 . The method as claimed in  claim 1 , wherein heat is supplied to or extracted from at least one reactor in the annular fluidized bed and/or in the mixing chamber.  
   
   
       10 . The method as claimed in  claim 1 , wherein provided downstream of at least one reactor is a cooling device, in which a solids-laden gas mixture from the reactor is cooled to a temperature of below 400° C.  
   
   
       11 . The method as claimed in  claim 1 , wherein provided downstream of at least one reactor is a separator, from which solids separated from exhaust gases are supplied to the first and/or second reactor or to a further cooling device.  
   
   
       12 . The method as claimed in  claim 11 , wherein at least part of the exhaust gases separated from the solids in the separator is supplied to the first and/or the second reactor as fluidizing gas, in particular after treatment in a downstream gas cleaning stage.  
   
   
       13 . The method as claimed in  claim 11  or wherein at least part of the exhaust gases separated from the solids in the separator is supplied to a plant for producing sulfuric acid.  
   
   
       14 . The method as claimed in  claim 11 , wherein the solids comprising coarse-grained solids and/or roasting residue are drawn off, discontinuously, from the annular fluidized bed of the first and/or second reactor and passed on to a further cooling device.  
   
   
       15 . A plant for heat treating sulfidic ores, by the method as claimed in  claim 1 , comprising a reactor constituting a fluidized bed reactor, wherein the reactor has a gas supply system which is formed such that gas flowing through the gas supply system entrains solids from a stationary annular fluidized bed, which at least partly surrounds the gas supply system, into the mixing chamber.  
   
   
       16 . The plant as claimed in  claim 15 , wherein the gas supply system has at least one gas supply tube extending upwards substantially vertically from the lower region of the reactor into a mixing chamber of the reactor, the gas supply tube being at least partly surrounded by an annular chamber in which the stationary annular fluidized bed is formed.  
   
   
       17 . The plant as claimed in  claim 16 , wherein the reactor is provided downstream with a second reactor, which has a gas supply tube, which is connected to a discharge conduit for solids-laden gas mixtures provided at the upper end of the first reactor and is formed such that gas flowing through the gas supply tube entrains solids from a stationary annular fluidized bed, which at least partly surrounds the gas supply tube, into the mixing chamber.  
   
   
       18 . The plant as claimed in  claim 16  wherein the gas supply tube is arranged approximately centrally with reference to the cross-sectional area of the reactor.  
   
   
       19 . The plant as claimed in  claim 18 , wherein a solids separator, is provided downstream of the second reactor, for the separation of solids, and that the solids separator has a solids conduit leading to the annular fluidized bed of the first and/or second reactor.  
   
   
       20 . The plant as claimed in  claim 18  wherein a cooling device, is provided downstream of the second reactor.  
   
   
       21 . The plant as claimed in  claim 18 , wherein temperature-control elements are provided in the first and/or second reactor.  
   
   
       22 . The plant as claimed in  claim 18 , wherein a gas distributor which divides the annular chamber into an upper fluidized bed region and a lower gas distributor chamber is provided in the first and/or second reactor, and that the gas distributor chamber is connected to a supply conduit for fluidizing gas.  
   
   
       23 . The plant as claimed in  claim 19 , wherein the first and/or second reactor has a supply conduit which leads to the annular chamber and is connected to an exhaust-gas conduit of the separator provided downstream of the second reactor.  
   
   
       24 . The plant as claimed in  claim 19 , wherein a dedusting device and/or a plant for producing sulfuric acid is provided downstream of the separator.  
   
   
       25 . The method as claimed in  claim 1 , wherein the gas supply tube is arranged approximately central.  
   
   
       26 . The method as claimed in  claim 3 , wherein the particle Froude number in the gas supply tube is between 3.95 and 11.6.  
   
   
       27 . The method as claimed in  claim 4 , wherein the particle Froude number in the annular fluidized bed is between 0.11 and 0.52.  
   
   
       28 . The method as claimed in  claim 5 , wherein the particle Froude number is between 0.53 and 1.32.  
   
   
       29 . The method as claimed in  claim 8 , wherein the oxygen-containing gas has an oxygen content of approximately 20 vol-%.  
   
   
       30 . The method as claimed in  claim 10 , wherein the solids-laden gas mixture is cooled to a temperature of approximately 380° C.  
   
   
       31 . The method as claimed in  claim 11 , wherein the separator is a cyclone.  
   
   
       32 . The method as claimed in  claim 12 , wherein gas cleaning stage is a hot-gas electrostatic precipitator and/or a wet-gas treatment.  
   
   
       33 . The plant as claimed in  claim 19 , wherein the solids separator is a cyclone.  
   
   
       34 . The plant as claimed in  claim 20 , wherein the cooling device is a waste-heat boiler with banks of cooling tubes.  
   
   
       35 . The plant as claimed in  claim 21 , wherein the temperature-control elements is a natural circulation boiler with cooling elements and membrane walls.