Slurry bubble column (C-2391)

Abstract

The present invention is a method for optimally operating a three phase slurry bubble column. The constituents of the three phases, gas, liquid, and solids, are determined by the chemical reaction in the column. The method includes injecting the gas phase into the column with an appropriate velocity so that the solid phase is fluidized while still maintaining “plug flow” over the column length.

1. A method for optimally operating a large diameter three phase (gas, liquid, solid) slurry bubble column having a diameter greater than 15 cm for Fischer-Tropsch synthesis over a supported cobalt catalyst in which solid particles are fluidized in the liquid phase by bubbles of the gas phase, comprising:
 (a) injecting the gas phase into said column at an average gas velocity along said column, U g >2 cm/sec, such that the flow regime is in the substantial absence of slug flow;  
 (b) fluidizing the solid supported cobalt catalyst particles of average diameter, d p >5 μm, to the height, H>3m, of the expanded liquid in the column by operating with a catalyst settling velocity, U s , and dispersion coefficient, D, such that 
           0.5   ⁢     (       U   s     -     U   L       )       ≤     D   H       ,       where   ⁢           ⁢   H     >     3   ⁢           ⁢   m           
           U   s     =       1   18     ⁢     d   p2     ⁢         ρ   s     -     ρ   l       μ     ⁢     gf   ⁡     (     C   p     )           ,       where   ⁢           ⁢     d   p       >     5   ⁢           ⁢   µ   ⁢           ⁢   m           
 
 
       and
 (c) maintaining plug flow in said column by operating with a gas phase velocity, U g , expanded liquid height, H, and dispersion coefficient, D, such that 
   U g ≧0.2D/H, where H>3 m, U g >2 cm/sec  
 
 
       wherein
 ρ s =effective density of the particles  
 ρ l =density of the liquid  
 μ=viscosity of the liquid  
 f(C p )=hindered settling function  
 C p =volume fraction of solids in the slurry (liquid plus solids)  
 U L =liquid velocity along the column  
 H=height of the expanded liquid in said reactor  
 g=gravitational constant  
 d p =diameter of particles  
 m=meters.  
 
     
     
       2. The process of  claim 1  wherein said supported catalysts comprises additional promoters selected from the group consisting of Group I, Group II, Group V, and Group VII metals. 
     
     
       3. The method of  claim 1  wherein the stochiometric consumption ratio (H 2 /CO) is between
   (1.8−2.2)H 2 :CO.  
 
     
     
       4. The method of  claim 3  wherein said support contains TiO 2 , SiO 2 , Al 2 O 3 , HiO 2  or mixtures thereof. 
     
     
       5. The method of  claim 4  wherein said catalyst further contains promotors selected from Group I, II, V and VII and combinations thereof of the periodic table. 
     
     
       6. The method of  claim 5  wherein said catalyst comprises Co, and a TiO 2  support. 
     
     
       7. The method of  claim 1  wherein said liquid phase is the indigenous product generated in the CO hydrogenation reaction. 
     
     
       8. The method of  claim 1  wherein said liquid is hydrocarbon synthesis wax, said solid is a supported cobalt suitable for the synthesis of such wax at typical Fischer-Tropsch conditions, and U s =1.1×10 −4  d. 
     
     
       9. The method of  claim 1  wherein said gas velocity, U g ≧1 D/H. 
     
     
       10. The method of  claim 9  wherein said gas velocity, U g ≧10 D/H. 
     
     
       11. The method of  claim 1  wherein said catalyst particles have a diameter greater than 30 microns. 
     
     
       12. The method of  claim 1  wherein H is greater than 10 meters. 
     
     
       13. The method of  claim 1  wherein U L ≦½ U p . 
     
     
       14. The method of  claim 1  wherein U L ≧0.5 cm/second. 
     
     
       15. The method of  claim 7  wherein U L  is determined in the absence of liquid recycle. 
     
     
       16. The method of  claim 1  wherein said bubble column diameter is greater than 20 cm. 
     
     
       17. The method of  claim 1  further including recycling the liquid in the column. 
     
     
       18. A method for optimally operating a large diameter three phase ( gas, liquid, solid )  slurry bubble column having a diameter greater than  15  cm for Fischer - Tropsch synthesis over a supported cobalt catalyst in which solid particles are fluidized in the liquid phase by bubbles of gas phase comprising:    ( a )  injecting the gas phase into said column at an average gas velocity along said column U   g   > 8  cm/sec, such that the flow regime is in the substantial absence of slug flow;      ( b )  fluidizing the solid supported cobalt catalyst particles of average diameter d   p   > 5  μm, to the height, H> 3  m, of the expanded liquid in the column such that the value of the profile of the concentration of the catalyst particles at the height of the expanded liquid is no less than about  13 . 5   %  of the value of the profile of the catalyst concentration at the bottom of the expanded liquid; and      ( c )  maintaining plug flow in said column by operating with a gas phase velocity, U   g   , expanded liquid height, H, and gas phase dispersion coefficient, D, such that U   g   ≧ 0 . 2  D/H.     
     
     
       19. A method for optimally operating a large diameter three phase ( gas, liquid, solid )  slurry bubble column having a diameter greater than  15  cm for Fischer - Tropsch synthesis over a supported cobalt catalyst in which solid particles are fluidized in the liquid phase by bubbles of gas phase comprising:    ( a )  injecting the gas phase into said column at an average gas velocity along said column such that the flow regime is churn turbulent in the substantial absence of slug flow;      ( b )  fluidizing the solid supported cobalt catalyst particles of average diameter d   p   > 5  μm, to the height, H> 3  m, of the expanded liquid in the column such that the value of the concentration profile of the catalyst particles at the height of the expanded liquid is no less than about  13 . 5   %  of the value of the catalyst concentration profile at the bottom of the expanded liquid; and      ( c )  maintaining plug flow in said column by operating with a gas phase velocity, U   g   , expanded liquid height, H, and gas phase dispersion coefficient, D, such that U   g   ≧ 0 . 2  D/H.     
     
     
       20. A method for optimally operating a large diameter three phase ( gas, liquid, solid )  slurry bubble column having a diameter greater than  15 cm for Fischer- Tropsch synthesis over a supported cobalt catalyst in which solid particles are fluidized in the liquid phase by bubbles of gas phase comprising:    ( a )  injecting the gas phase into said column at an average gas velocity along the column U   g   > 8  cm/sec such that the flow regime is churn turbulent in the substantial absence of slug flow;      ( b )  fluidizing the solid supported cobalt catalyst particles of average diameter d   g   > 5  μm, to the height, H> 3  m, of the expanded liquid in the column such that the value of the concentration profile of the catalyst particles at the height of the expanded liquid is no less than about  13 . 5   %  of the value of the catalyst concentration profile at the bottom of the expanded liquid; and      ( c )  maintaining plug flow in said column by operating with a gas phase velocity, U   g   , expanded liquid height, H and gas phase dispersion coefficient, D, such that U   g   ≧ 0 . 2  D/H.     
     
     
       21. The method of  claim 18  further including recycling the liquid in the column. 
     
     
       22. The process of  claim 18  wherein hydrogen synthesis wax is a product of the process and the catalyst particles are separated from said hydrocarbon synthesis wax by filtration or decantation or other methods. 
     
     
       23. The method of  claim 19  further including recycling the liquid in the column. 
     
     
       24. The process of  claim 19  wherein hydrocarbon synthesis wax is a product of the process and the catalyst particles are separated from said hydrocarbon synthesis wax by filtration or decantation or other methods. 
     
     
       25. The method of  claim 20  further including recycling the liquid in the column. 
     
     
       26. The process of  claim 20  wherein hydrocarbon synthesis wax is a product of the process and the catalyst particles are separated from said hydrocarbon synthesis wax by filtration or decantation or other methods.