Process for controlling oxidation of nitrogen and metals in circulating fluidized solids contacting process

Abstract

A fluidized particulate solids contacting process for reducing regenerator flue gas NOx emissions and/or permitting operating with an increased equilibrium solids vanadium level, which process may be an FCC process or a fluidized particulate solid hydrocarbon treating process, wherein spent FCC catalyst or other spent solid is in a regenerator with an oxygen-containing regeneration gas under catalyst (solid) regeneration conditions which include a combination of at least a regeneration temperature and an oxygen level in the regeneration gas which is effective to burn off the spent solid a majority of carbonaceous deposits thereon, while substantially preventing the formation of NOx, and thereby produce a regenerated solid having a carbon level reduced from that of the spent solid and a flue gas; maintaining the regenerated solid in a fluidized state with a fluidizing media that substantially prevents any further oxidation or regeneration; and returning the fluidized regenerated solid to the reactor (contactor) used in the process.

What is claimed is:  
     
         1 . An improved circulating fluidized solids contacting process, which process comprises the steps of: 
 a. contacting a hydrocarbon feed in a fluidized contactor reactor with hot regenerated solid under conditions which convert the hydrocarbon feed into lower molecular weight hydrocarbon product vapors and form a spent solid containing carbonaceous deposits,    b. separating a majority of the lower molecular weight hydrocarbon product vapors from the spent solid to form separated product vapors and separated spent solid containing entrained hydrocarbon vapors,    c. processing the separated product vapors into desired product fractions,    d. subjecting the separated spent solid to stripping to remove therefrom a majority of the entrained hydrocarbon vapors,    e. contacting the resulting stripped spent solid in a regenerator with an oxygen-containing regeneration gas under solid regeneration conditions which include a combination of at least a regeneration temperature and an oxygen level in the regeneration gas which is effective to burn off the spent solid a majority of the carbonaceous deposits, while substantially preventing the formation of NOx, and thereby produce a regenerated solid having a carbon level reduced from that of the spent solid and a flue gas,    f. maintaining the regenerated solid in a fluidized state with a fluidizing media that substantially prevents any further oxidation or regeneration, and    g. returning the fluidized regenerated solid to the contactor.    
     
     
         2 . The process of  claim 1 , wherein the solid regeneration conditions include maintaining the temperature of the regenerated solid exiting the regenerator at not more than 1400° F., and wherein the oxygen level in the regeneration gas is maintained at a level such that the level of excess oxygen in the flue gas exiting the regenerator is not more than 1 mol %.  
     
     
         3 . The process of  claim 1 , wherein the regenerator is a dilute phase regenerator and the stripped spent solid and the regeneration gas are passed co-currently and upwardly in the regenerator.  
     
     
         4 . The process of  claim 1 , wherein the fluidizing media is selected from the group consisting of an inert gas, a non-oxidizing gas and a recycled flue gas.  
     
     
         5 . The process of  claim 1 , wherein the level of carbon on the regenerated solid is from about 0.05 wt % to about 0.4 wt %  
     
     
         6 . The process of  claim 1 , wherein the content of NOx in the flue gas is less than about 150 ppm.  
     
     
         7 . The process of  claim 1 , wherein the spent solid contains vanadium deposited thereon from the hydrocarbon feed and a majority of the vanadium on the spent catalyst is maintained in an oxidation state less than +5.  
     
     
         8 . The process of  claim 1 , wherein the flue gas is cooled, and the cooled flue gas is used as the fluidizing media.  
     
     
         9 . The process of  claim 1 , wherein the flue gas is cooled, and the cooled flue gas is used to fluidize the solid in the regenerator.  
     
     
         10 . The process of  claim 3 , wherein the regenerated solid and flue gas are passed from an exit of the regenerator to a separator vessel and separated in the vessel.  
     
     
         11 . The process of  claim 10 , wherein the fluidizing media is introduced into the separator vessel to fluidize the regenerated solid in the vessel.  
     
     
         12 . The process of  claim 11 , wherein the fluidizing media is an inert gas or cooled recycle flue gas.  
     
     
         13 . The process of  claim 3 , wherein the regenerated solid and flue gas are passed from the regenerator to a separator vessel wherein the flue gas is separated from the regenerated solid, and wherein the separated regenerated solid is maintained in a fluidized state.  
     
     
         14 . An improved fluidized circulating solids process for treating or cracking hydrocarbon feedstocks that contain a significant content of vanadium and/or nitrogen to provide a hydrocarbon product substantially reduced in vanadium content and/or a regenerator flue gas having a low level of NOx, said apparatus comprising: 
 a. contacting said hydrocarbon feedstocks in a contactor with fluidized hot particulate solids under conditions to vaporize the majority of said feedstock and convert said feedstock to a lower molecular weight vapor product and form a spent solid containing carbonaceous deposits which contain the majority of feedstock vanadium,    b. separating a majority of the spent solids from the vaporized product to form separated product vapors and separated spent solids containing entrained hydrocarbon vapors,    c. processing the separated product vapors into desired products,    d. subjecting the separated spent solid to stripping to remove therefrom a majority of the entrained hydrocarbon vapors,    e. contacting the resulting stripped spent solids in a regenerator with an oxygen-containing regeneration lift gas under dilute phase regeneration conditions which include a combination of at least a regeneration temperature and an oxygen level in the regeneration gas which is effective to burn off the spent solids a majority of the carbonaceous deposits while maintaining the majority of vanadium in an oxidation state less than +5 and substantially preventing the formation of NOx,    f. controlling the regenerated solids temperature to not more than 1400° F.,    g. maintaining the resultant controlled temperature regenerated solid in a dense phase fluidized state with a fluidizing media that substantially prevents any further oxidation of the vanadium deposits or the formation of NOx, and    h. returning the fluidized regenerated solid to the contactor.    
     
     
         15 . The process of  claim 14 , wherein the temperature of the regenerated solid exiting the regenerator is not more than 1400° F., the carbon level on the regenerated solid is not more than 0.4 wt %, and excess oxygen in the flue gas is not more than 1 mol %.