Mixing apparatus

Abstract

A mixing apparatus ( 100 ) for mixing at least two fluids, the mixing apparatus ( 100 ) comprising a shaft ( 120 ) rotatable about its longitudinal axis ( 121 ), a first ( 122 ) and a second ( 124 ) radially extending impeller mounted on the shaft ( 120 ) and respectively axially spaced apart, characterised in that the first impeller ( 122 ) comprises a plurality of curved blades ( 125 ) operable to move said fluids in an axial direction towards the second impeller ( 124 ), and the second impeller ( 124 ) comprises a plurality of curved blades ( 125 ) operable to move said fluids in an axial direction towards the first impeller ( 122 ).

1 . A mixing apparatus for mixing at least two fluids, the mixing apparatus comprising a shaft rotatable about its longitudinal axis, a first and a second radially extending impeller mounted on the shaft and respectively axially spaced apart, the first impeller comprising a plurality of curved blades operable to move said fluids in an axial direction towards the second impeller, and the second impeller comprising a plurality of curved blades operable to move said fluids in an axial direction towards the first impeller, characterised in that the at least two fluids comprise a liquid and a gas. 
     
     
         2 . A mixing apparatus as claimed in  claim 1 , characterised in that the blades on each impeller are inward pumping into the space between the impellers. 
     
     
         3 . (canceled) 
     
     
         4 . A mixing apparatus as claimed in  claim 1 , characterised in that the first impeller and the second impeller each comprise two or more curved blades. 
     
     
         5 . A mixing apparatus as claimed in  claim 1 , characterised in that the diameter of the first impeller is the same as the diameter of the second impeller. 
     
     
         6 . A mixing apparatus as claimed in  claim 1 , characterised in that the axial distance between the first impeller and the second impeller is at least one impeller diameter apart. 
     
     
         7 . A mixing apparatus as claimed in  claim 1 , characterised in that said impellers operate at a power number substantially 1.75. 
     
     
         8 . A mixing apparatus as claimed in  claim 1 , characterised in that the specific power used when the first impeller and the second impeller rotate is substantially between 100 W/m 3  to 800 W/m 3 . 
     
     
         9 . A mixing apparatus as claimed in  claim 1 , characterised in that when dual opposed Maxflo impellers are used, the arithmetic mean size (d 10 ) is substantially between 250 μm to 550 μm and the surface volume mean diameter (d 32 ) is substantially between 400 μm to 750 μm. 
     
     
         10 . A mixing apparatus as claimed in  claim 1 , characterised in that when BT-6 type impellers are used, the d 10  is substantially between 250 μm to 1500 μm. 
     
     
         11 . A mixing apparatus as claimed in  claim 10 , characterised in that when operating at substantially 765 rpm, the d 10  is substantially 378 μm, and the d 32  is substantially 445 μm. 
     
     
         12 . A mixing apparatus as claimed  claim 1 , characterised in that the sparged gas rate is substantially between 0.05 to 1.0 m 3 /s. 
     
     
         13 . A mixing apparatus as claimed in  claim 12 , characterised in that the sparged gas rate is substantially 0.13 m 3 /s at an impeller speed of substantially 50 rpm to 200 rpm. 
     
     
         14 . A mixing apparatus as claimed in  claim 1 , characterised in that a critical dispersion speed in a vessel having a diameter of substantially between 2 to 5 m, is substantially between 10 to 20 rpm. 
     
     
         15 . A chemical reaction system comprising a liquid phase and a mixing apparatus according to the first aspect of the invention for mixing a fluid into the liquid phase. 
     
     
         16 . A chemical reaction system as claimed in  claim 15 , characterised in that the liquid phase comprises at least one liquid phase reactant for reacting with a gas introduced into the liquid phase, as well as at least one liquid phase reaction product. 
     
     
         17 . A chemical reaction system as claimed in  claim 15 , characterised in that the liquid phase comprises a catalyst system. 
     
     
         18 . A chemical reaction system as claimed in  claim 15 , characterised in that the reaction system is a carbonylation process comprising carbonylating an ethylenically unsaturated compound with carbon monoxide in the presence of a source of hydroxyl groups, and a catalyst system comprising (a) a bidentate phosphine, arsine or stibine ligand, and (b) a catalytic metal selected from a group 8, 9 or 10 metal or a compound thereof. 
     
     
         19 . A mixing apparatus substantially as hereinbefore described with reference to any one of the accompanying drawings.