Regeneration of cracking catalyst

Claim 2

In a process for regeneration of coke-contaminated fluidized cracking catalyst which has been partially deactivated with coke deposits in a fluidized catalytic cracking zone, wherein said coke-contaminated catalyst is introduced into a single dense catalyst phase contained in the lower portion of a regeneration vessel maintained at a temperature sufficient to support combustion of the coke, wherein said dense catalyst phase is fluidized by an upwardly flowing molecular oxygen-containing regeneration gas which combusts said coke, wherein a single dilute phase comprising regeneration gas containing oxygen and carbon oxides, and entrained catalyst is maintained in the upper portion of said regeneration vessel in direct communication with said dense catalyst phase, wherein a flue gas comprising carbon oxides is recovered from the top of said regeneration vessel, and wherein a regenerated catalyst of reduced coke contamination is recovered from said dense catalyst phase; the improvement for essentially completely combusting said coke to carbon dioxide in said dense catalyst phase and for avoiding afterburning in said dilute phase which comprises: (a) maintaining said dense phase catalyst bed at a temperature of 1420° F. to 1445° F. and greater than the temperature in the dilute phase but sufficient to initiate and substantially complete carbon monoxide combustion within said dense phase bed, wherein said dense phase temperature is less than a temperature which will thermally deactivate said catalyst; (b) maintaining a flow of oxygen-containing regeneration gas to said dense phase bed sufficient for maintaining a molar excess of oxygen in said flue gas; and (c) maintaining an amount of catalyst in said dense phase bed sufficient to provide adequate catalyst residence time for burning coke from said catalyst and absorbing heat of combustion such that said regeneration gas and said catalyst entering said dilute phase are at a temperature sufficient for combustion of carbon monoxide to carbon dioxide and less than a temperature which will thermally deactivate said catalyst.

Claim 3

The method of claim 1, including adjusting oxygen supplied to said dense phase regeneration zone for varying the mole percent excess oxygen in said flue gas, wherein a change in said mole percent excess oxygen is inversely proportional to carbon remaining on regenerated catalyst and to percent carbon monoxide in said flue gas wherein the molar excess of oxygen in said flue gas is maintained within the range of about 1-10 volume percent, wherein residence time of catalyst in said dense phase is within the range of about 3-10 minutes, wherein said dilute phase temperature is maintained within the range of 1375° F. to about 1395° F.; wherein carbon monoxide content of said flue gas is about 500 ppm or less, and wherein carbon on regenerated catalyst is about 0.15 weight percent or less.

Claim 4

In a process for regeneration of coke-contaminated fluidized cracking catalyst which has been partially deactivated with coke deposits in a fluidized catalytic cracking zone, wherein said coke-contaminated catalyst is introduced into a single dense catalyst phase contained in the lower portion of a regeneration vessel maintained at a temperature sufficient to support combustion of the coke, wherein said dense catalyst phase is fluidized by an upwardly flowing molecular oxygen-containing regeneration gas which combusts said coke, wherein a single dilute phase comprising regeneration gas containing oxygen and carbon oxides and entrained catalyst is maintained in the upper portion of said regeneration vessel in direct communication with said dense catalyst phase, wherein a flue gas comprising carbon oxides is recovered from the top of said regenerator vessel, and wherein a regenerated catalyst of reduced coke contamination is recovered from said dense catalyst phase, the improvement for essentially completely combusting said coke to carbon dioxide in said dense catalyst phase and for avoiding afterburning in said dilute phase which comprises: (a) maintaining said dense phase catalyst bed at a temperature of 1420° F. to 1445° F. and greater than the temperature of the dilute phase but sufficient to initiate and to substantially complete carbon monoxide combustion within said dense phase bed, wherein said dense phase temperature is less than a temperature which will thermally deactivate said catalyst; (b) maintaining a flow of oxygen-containing regeneration gas to said dense phase bed sufficient for maintaining a molar excess of oxygen in said flue gas; (c) maintaining an amount of catalyst in said dense phase bed sufficient to provide adequate catalyst residence time for burning coke from said catalyst and absorbing heat of combustion such that said regeneration gas and said catalyst entering said dilute phase are at a temperature sufficient for combustion of carbon monoxide to carbon dioxide and less than a temperature which will thermally deactivate said catalyst; and (d) simultaneously adjusting said dense catalyst phase temperature and the flow of oxygen to said fluidized dense catalyst phase to inhibit afterburn of carbon monoxide to carbon dioxide within said dilute phase, wherein a change in said dense phase temperature is inversely proportional to a change in said dilute phase temperature, wherein a change in mole percent oxygen in said flue gas is inversely proportional to residual carbon on regenerated catalyst and carbon monoxide content of said flue gas, wherein excess oxygen in said flue gas is within the range of about 1-10 mole percent; wherein residence time of catalyst in said dense phase is within the range of about 3-10 minutes, wherein said dilute phase temperature is maintained within the range of about 1375° F. to about 1395° F., wherein carbon monoxide content of said flue gas is about 500 ppm or less, and wherein carbon on regenerated catalyst is about 0.15 weight percent or less.

Claim 5

In a process for regeneration of coke-contaminated fluidized cracking catalyst which has been partially deactivated with coke deposits in a fluidized catalytic cracking zone, wherein said coke-contaminated catalyst is introduced into a single dense catalyst phase contained in the lower portion of a regeneration vessel maintained at a temperature sufficient to support combustion of the coke, wherein said dense catalyst phase is fluidized by an upwardly flowing molecular oxygen-containing regeneration gas which combusts said coke, wherein a single dilute phase comprising regeneration gas containing oxygen and carbon oxides and entrained catalyst is maintained in the upper portion of said regeneration vessel in direct communication with said dense catalyst phase, wherein a flue gas comprising carbon oxides is recovered from the top of said regenerator vessel, and wherein a regenerated catalyst of reduced coke contamination is recovered from said dense catalyst phase, the improvement for essentially completely combusting said coke to carbon dioxide in said dense catalyst phase and for avoiding afterburning in said dilute phase which comprises: (a) maintaining said dense phase catalyst bed at a temperature of 1420° F. to 1445° F. and greater than the temperature of the dilute phase but sufficient to initiate and to substantially complete carbon monoxide combustion within said dense phase bed, wherein said dense phase temperature is less than a temperature which will thermally deactivate said catalyst; (b) maintaining a flow of oxygen-containing regeneration gas to said dense phase bed sufficient for maintaining a molar excess of oxygen in said flue gas; (c) maintaining an amount of catalyst in said dense phase bed sufficient to provide adequate catalyst residence time for burning coke from said catalyst and absorbing heat of combustion such that said regeneration gas and said catalyst entering said dilute phase are at a temperature sufficient for combustion of carbon monoxide to carbon dioxide and less than a temperature which will thermally deactivate said catalyst; and (d) simultaneously adjusting said dense catalyst phase temperature and the flow of oxygen to said fluidized dense catalyst phase to inhibit afterburn of carbon monoxide to carbon dioxide within said dilute phase, wherein a change in said dense phase temperature is inversely proportional to a change in said dilute phase temperature, wherein a change in mole percent oxygen in said flue gas is inversely proportional to residual carbon on regenerated catalyst and carbon monoxide content of said flue gas, wherein excess oxygen in said flue gas is within the range of about 1-10 mole percent; wherein residence time of catalyst in said dense phase is within the range of about 3-10 minutes, wherein said dilute phase temperature is maintained within the range of about 1375° F. to about 1395° F., wherein carbon monoxide content of said flue gas is about 500 ppm or less, and wherein carbon on regenerated catalyst is about 0.15 weight percent or less.