Apparatus to reduce NOx emissions from a fluid catalytic cracking unit

Claim 1

An apparatus for reducing NO x in flue gas from fluid catalytic cracking regeneration of a spent catalyst, comprising: a first regenerator riser having an inlet at a lower portion for a first mixture of said spent catalyst and a first oxygen containing gas wherein said first riser has a lower portion where NO x is formed during regeneration, and having an upper portion, where a portion of said NO x is converted to N 2 means connective with said upper portion of said riser for discharging and separating a first flue gas stream and a catalyst stream from said discharged first mixture, and wherein said separation means passes said catalyst stream to a first dense catalyst bed and means for withdrawing said first flue gas stream from said apparatus, a second regenerator riser having a lower portion containing said first dense bed and an upper portion above said first dense bed p1 means for adding a second oxygen-containing stream to said first bed to form a second mixture of catalyst and gases comprising NO x and wherein said second mixture is discharged up through said upper portion of said second riser and a portion of said NO x in said second mixture is converted to N 2 ; and means for discharging and separating an at least partially regenerated catalyst stream and a second flue gas stream from said second riser.

Claim 2

An apparatus for reducing NO x in flue gas from fluid catalytic cracking regeneration of a spent catalyst, comprising: a first regenerator riser having an inlet at a lower portion for a first mixture of said spent catalyst and a first oxygen containing gas wherein said first riser has a lower portion where NO x is formed during regeneration, and having an upper portion, where a portion of said NO x is converted to N 2 means connective with said upper portion of said riser for discharging and separating a first flue gas stream and a catalyst stream from said discharged first mixture, and wherein said separation means passes said catalyst stream to a first dense catalyst bed and means for withdrawing said first flue gas stream from said apparatus, a second regenerator riser having a lower portion containing said first dense bed and an upper portion above said first dense bed p1 means for adding a second oxygen-containing stream to said first bed to form a second mixture of catalyst and gases comprising NO x and wherein said second mixture is discharged up through said upper portion of said second riser and a portion of said NO x in said second mixture is converted to N 2 ; and means for discharging and separating an at least partially regenerated catalyst stream and a second flue gas stream from said second riser.

Claim 10

An apparatus for reducing NO x in flue gas from a regenerator for regenerating a spent fluid catalytic cracking catalyst stream comprising a mixture of ZSM-5 catalyst and zeolite Y catalyst particles from a fluid catalytic cracking reactor to produce regenerated catalyst, comprising: a first regenerator riser having an inlet in a lower portion thereof for regenerating a first mixture of said spent catalyst stream, a portion of regenerated catalyst and a first oxygen-containing stream by passing said first mixture therethrough and an outlet in an upper portion of said first riser for discharging a mixture of catalyst and first flue gas from said first riser; a second regenerator riser comprising a lower portion adapted to contain a dense bed of catalyst and an upper portion above said lower portion, said lower portion having a larger inside diameter than said upper portion; means for separating and discharging said first mixture from said first riser and downwardly directing catalyst from said first mixture from said first riser to a first catalyst bed located in said lower portion having a larger inside diameter; means for withdrawing from said apparatus said first flue gas stream from said discharged first mixture; means for adding a second oxygen-containing stream to said first bed; means for passing a second mixture of catalyst and gases comprising said NO x from said first bed into said upper portion of said second riser wherein at least a portion of said NO x is converted to N 2 in said second riser upper portion; an enlarged catalyst collecting chamber above said first catalyst bed comprising an upper portion and a lower portion; means for discharging said second mixture from said second riser and downwardly directing said second mixture from said second riser to a second catalyst bed located in said lower portion of said collecting chamber; means for separating a second flue gas stream from said second mixture prior to passing said second mixture into said second bed; means for adding a third oxygen-containing gas stream to said second bed; means for recycling regenerated catalyst from said second bed to said first riser; means for withdrawing regenerated catalyst from said second bed; and means for separating a third flue gas stream from an atmosphere of said collecting chamber above said second bed.

Claim 11

An apparatus for reducing NO x in flue gas from a regenerator for regenerating a spent fluid catalytic cracking catalyst stream comprising a mixture of ZSM-5 catalyst and zeolite Y catalyst particles from a fluid catalytic cracking reactor to produce regenerated catalyst, comprising: a first regenerator riser having an inlet in a lower portion thereof for regenerating a first mixture of said spent catalyst stream, a portion of regenerated catalyst and a first oxygen-containing stream by passing said first mixture therethrough and an outlet in an upper portion of said first riser for discharging a mixture of catalyst and first flue gas from said first riser; a second regenerator riser comprising a lower portion adapted to contain a dense bed of catalyst and an upper portion above said lower portion, said lower portion having a larger inside diameter than said upper portion; means for separating and discharging said first mixture from said first riser and downwardly directing catalyst from said first mixture from said first riser to a first catalyst bed located in said lower portion having a larger inside diameter; means for withdrawing from said apparatus said first flue gas stream from said discharged first mixture; means for adding a second oxygen-containing stream to said first bed; means for passing a second mixture of catalyst and gases comprising said NO x from said first bed into said upper portion of said second riser wherein at least a portion of said NO x is converted to N 2 in said second riser upper portion; an enlarged catalyst collecting chamber above said first catalyst bed comprising an upper portion and a lower portion; means for discharging said second mixture from said second riser and downwardly directing said second mixture from said second riser to a second catalyst bed located in said lower portion of said collecting chamber; means for separating a second flue gas stream from said second mixture prior to passing said second mixture into said second bed; means for adding a third oxygen-containing gas stream to said second bed; means for recycling regenerated catalyst from said second bed to said first riser; means for withdrawing regenerated catalyst from said second bed; and means for separating a third flue gas stream from an atmosphere of said collecting chamber above said second bed.