Apparatus and method for producing amorphous silica ash

Abstract

The invention provides apparatus and a method for exothermic treatment of siliceous feed material to provide an ash having a predominantly silica content, typically more than 97% by weight. The apparatus includes a cylindrical housing extending about a central axis and having first and second ends, and a central mixing zone adjacent the first end. A material intake carries the feed material into the housing and has an outlet in the mixing zone, and gas enters through a first gas inlet at the first end through guides to create an inner vortex extending axially about said axis. Gas also enters through guides in a second gas inlet at the second end to create an outer vortex which also extends axially but in the opposite direction from that of the inner vortex. However the inner and outer vortices rotate in the same direction. A gas outlet is positioned to receive spent gas from the housing and an ash outlet is positioned remotely from the mixing zone to receive the ash. If preferred, the position of the ash outlet may be incorporated into the gas outlet. A control system is provided to limit the temperature in the feed material in the housing. As a result, in operation, gases can be fed into the first and second gas inlets carrying sufficient oxygen for exothermic combustion of the feed material and having a flow rate to create said inner and outer vortices. The outer vortex meets the inner vortex in the mixing zone to mix both with the inner vortex and with the feed material which will be subjected to exothermic combustion as the feed material is entrained in the inner and outer vortices. The material will pass through the mixing zone repeatedly until the feed material is converted to an ash having a predominantly amorphous silica content and escape criteria needed to reach and exit through the ash outlet.

1 . Apparatus for exothermic treatment of siliceous feed material, the apparatus including: 
 a cylindrical housing extending about a central axis and having first and second ends, and a central mixing zone adjacent the first end;    a material intake for carrying said feed material into the housing and having a bottom outlet in the mixing zone;    a flow rate controller coupled to the material intake to vary the rate of flow of feed material through the intake;    a first gas inlet at said first end and having guides to create an inner vortex extending about said axis;    a second gas inlet at said second end and having guides to create an outer vortex extending about said axis, the inner and outer vortices rotating in the same direction about said axis and moving axially in opposite directions to create a gas stream;    a gas outlet positioned to receive spent gas from the housing;    an ash outlet positioned remotely from the mixing zone;    a control system having temperature sensors in the gas stream and operable in response to changes in temperatures in the gas stream to operate the flow rate controller to vary the rate of flow of the feed material into the mixing zone in accordance with temperature parameters set to limit the temperature in the feed material in the gas stream;    whereby in operation gases are fed into the first and second gas inlets to create the gas stream with sufficient oxygen for exothermic combustion of the feed material and having a flow rate to create said inner and outer vortices, the outer vortex meeting the inner vortex in the mixing zone to mix both with the inner vortex and with the feed material leaving the material intake, so that the feed material will be subjected to exothermic combustion as the feed material is entrained in the gas stream to pass through the mixing zone repeatedly until the feed material is converted predominantly to amorphous silica ash having escape criteria needed to exit through the ash outlet.    
     
     
         2 . Apparatus as claimed in  claim 1  in which the ash outlet and the gas outlet are positioned such that said ash is entrained in the spent gas.  
     
     
         3 . Apparatus as claimed in  claim 1  in which the material intake extends axially about said axis inside the inner vortex.  
     
     
         4 . Apparatus as claimed in  claim 1  in which said guides in the first gas inlet are blades set in an annular array about said axis.  
     
     
         5 . Apparatus as claimed in  claim 1  in which said guides in the second gas inlet are blades set in an annular array about said axis.  
     
     
         6 . Apparatus as claimed in  claim 4  in which said guides in the second gas inlet are blades set in an annular array about said axis.  
     
     
         7 . Apparatus as claimed in  claim 1  in which the ash outlet is adjacent said first end such that ash having said escape criteria will find the ash outlet as such ash moves radially between the inner vortex and the outer vortex.  
     
     
         8 . Apparatus for exothermic treatment of siliceous feed material, the apparatus including: 
 a cylindrical housing extending about a central axis and having first and second ends, and a central mixing zone adjacent the first end;    a material intake for carrying said feed material into the housing and having a bottom outlet in the mixing zone;    a flow rate controller coupled to the material intake to vary the rate of flow of feed material through the intake;    a first gas inlet at said first end and having guides to create an inner vortex extending about said axis;    a second gas inlet at said second end and having guides to create an outer vortex extending about said axis, the inner and outer vortices rotating in the same direction about said axis and moving axially in opposite directions to create a gas stream;    a gas outlet positioned to receive spent gas from the housing;    a control system having temperature sensors in the gas stream and operable in response to changes in temperatures in the gas stream to operate the flow rate controller to vary the rate of flow of the feed material into the mixing zone in accordance with temperature parameters set to limit the temperature in the feed material in the gas stream;    whereby in operation gases are fed into the first and second gas inlets to create a gas stream and carrying sufficient oxygen for exothermic combustion of the feed material and having a flow rate to create said inner and outer vortices, the outer vortex meeting the inner vortex in the mixing zone to mix both with the inner vortex and with the feed material leaving the material intake, so that the feed material will be subjected to exothermic combustion as the feed material is entrained in the gas sream to pass through the mixing zone repeatedly until the feed material is converted predominantly to amorphous silica ash having escape criteria needed to exit through the gas outlet with the spent gas.    
     
     
         9 . Apparatus as claimed in  claim 8  and further including a separator coupled to the gas outlet to separate the ash from the spent gas.  
     
     
         10 . A method of making an ash having a predominantly amorphous silica content, the method including the steps: 
 feeding exothermic siliceous material into a mixing zone for eventual discharge through an ash outlet;    creating inner and outer vortices about an axis, the vortices defining a gas stream containing sufficient oxygen for exothermic combustion of the feed material and being arranged to flow in opposite axial directions and in the same angular direction, the vortices meeting in the mixing zone to carry the feed material axially in the inner vortex with a centrifugal force component to cause the material to move outwardly from the inner vortex into the outer vortex so that the material is entrapped in the gas stream and passed repeatedly through the mixing zone until the feed material is converted predominantly to amorphous silica ash having escape criteria needed to travel axially to the ash exit so that such ash will exit through the ash outlet;    monitoring temperatures in the gas stream;    comparing the temperatures in the gas stream with known information to provide an output signal; and    using the output signal to control the rate of flow of the exothermic feed material into the apparatus so that the feed material in the gas stream is subjected to maximum temperatures selected to result in an ash having a predominantly amorphous silica content.    
     
     
         11 . A method as claimed in  claim 10  in which the ash has a silica content of no less than 97% by weight.  
     
     
         12 . Apparatus for exothermic treatment of siliceous feed material, the apparatus including: 
 a cylindrical housing extending axially about a central axis and having first and second ends, and a central mixing zone adjacent the first end;    a material intake for carrying said feed material into the housing and having an outlet in the mixing zone;    a first gas inlet at said first end and having guides to create an inner vortex extending axially;    a second gas inlet at said second end and having guides to create an outer vortex extending about said axis, the inner and outer vortices rotating in the same direction about said axis and moving axially in opposite directions to define a gas stream;    a gas outlet positioned centrally in said second end to receive spent gas from the housing;    an ash outlet positioned remotely from the mixing zone;    a control system having temperature sensors in the gas flow and operable in response to changes in temperatures in the gas flow to limit the temperature in the feed material in the housing;    whereby in operation gases are fed into the first and second gas inlets carrying sufficient oxygen for exothermic combustion of the feed material and having a flow rate to create said inner and outer vortices, the outer vortex meeting the inner vortex in the mixing zone to mix both with the inner vortex and with the feed material leaving the material intake, so that the feed material will be subjected to exothermic combustion as the feed material is entrained in the gas stream to pass through the mixing zone repeatedly until the feed material is converted predominantly to amorphous silica ash having escape criteria needed to leave the gas stream and exit through the ash outlet.    
     
     
         13 . A method of making amorphous silica ash, the method including the steps: 
 feeding exothermic siliceous material into a mixing zone for eventual discharge through an ash outlet;    creating a gas stream consisting of inner and outer vortices about a common axis and containing sufficient oxygen for exothermic combustion of the feed material, the vortices meeting in the mixing zone to carry the feed material axially in the inner vortex with a centrifugal force component to cause the material to move outwardly from the inner vortex into the outer vortex so that the material is entrapped in the gas stream and passed repeatedly through the mixing zone until the feed material is converted primarily to amorphous silica ash having escape criteria needed to remain in the inner vortex to carry the ash to ash outlet for passage through the ash outlet;    collecting spent gas at a spent gas outlet;    monitoring the temperatures in the gas stream;    comparing the temperatures in the gas stream with known information to provide an output signal; and    using the output signal to control the maximum temperatures in the gas stream to result in a predominantly amorphous silica ash.    
     
     
         14 . Apparatus as claimed in  claim 12  in which the ash outlet and the gas outlet are positioned such that said amorphous silica ash is entrained in the spent gas.  
     
     
         15 . Apparatus as claimed in  claim 12  in which the material intake extends about said axis.  
     
     
         16 . Apparatus as claimed in  claim 12  in which said guides in the first gas inlet are blades set in an annular array about said axis.  
     
     
         17 . Apparatus as claimed in  claim 12  in which said guides in the second gas inlet are blades set in an annular array about said axis.  
     
     
         18 . Apparatus as claimed in  claim 16  in which said guides in the second gas inlet are blades set in an annular array about said axis.  
     
     
         19 . Apparatus as claimed in  claim 12  in which the ash outlet is adjacent and below said top such that ash will find the ash outlet as the ash moves radially outwards to leave the inner vortex and enter the outer vortex.  
     
     
         20 . Apparatus for exothermic treatment of siliceous feed material, the apparatus including: 
 a cylindrical housing extending about a central axis and having a first and second ends, and a central mixing zone adjacent the first end;    a material intake for carrying said feed material into the mixing zone;    a first gas inlet at said first end and having guides to create an inner vortex extending about said axis;    a second gas inlet at said second end and having guides to create an outer vortex extending about said axis, the inner and outer vortices rotating in the same direction about said axis and moving axially in opposite directions, and the first and second vortices creating a gas stream;    a gas outlet positioned centrally in said second end to receive spent gas from the housing;    a control system having temperature sensors in the gas stream and operable in response to changes in temperatures in the gas stream to limit the temperature in the feed material in the housing;    whereby in operation gases are fed into the first and second gas inlets carrying sufficient oxygen into the gas stream for exothermic combustion of the feed material and having a flow rate to create said inner and outer vortices, the outer vortex meeting the inner vortex in the mixing zone to both mix with the inner vortex and with the feed material leaving the material intake, so that the feed material will be subjected to exothermic combustion as the feed material is entrained in the gas stream to pass through the mixing zone repeatedly until the feed material is converted to a predominantly amorphous silica ash having escape criteria needed to move in the gas stream to the gas outlet with the spent gas.    
     
     
         21 . A method as claimed in  claim 20  in which the ash has a silica ash content of at least 97% by weight.  
     
     
         22 . A method as claimed in  claim 20  in which the ash has a silica ash content of at least 98% by weight.