Cooling of stripped catalyst prior to regeneration in cracking process

Claim 2

A process for controlling the fluid catalytic cracking of a feedstock containing hydrocarbons, comprising the steps of: passing a mixture comprising catalyst and said feedstock through a riser conversion zone under fluid catalytic cracking conditions to crack said feedstock; passing said mixture, having a riser exit temperature, from said riser into a fluid catalytic cracking reactor vessel; separating a portion of catalyst from said mixture, with the remainder of said mixture forming a reactor vessel gaseous stream; heating said separated catalyst portion by a heating step consisting essentially of combining said separated catalyst portion with a portion of regenerated catalyst from a fluid catalytic cracking regenerator vessel to form combined catalyst; stripping said combined catalyst, by contact with a stripping gas stream, consisting essentially of steam at a stripping temperature between 100° F. above said riser exit temperature and 1500° F., said regenerated catalyst portion having a temperature between 100° F. above said stripping temperature and 1600° F. prior to heating said separated catalyst to produce a stripped catalyst; cooling said stripped catalyst, prior to passing it into said regenerator vessel, to a temperature sufficient to cause said regenerator vessel to be maintained at a temperature between 100° F. above said stripping temperature and 1600° F., wherein said cooling step comprises passing said stripped catalyst stream to a heat-exchanger located outside said reactor vessel; and regenerating said cooled catalyst stream in said fluid catalytic cracking regenerator vessel by contact with an oxygen-containing stream at fluid catalytic cracking regeneration conditions.

Claim 3

The process of claim 1, wherein said stripped catalyst stream is indirectly heat-exchanged with a heat-exchange medium in said heat exchanger.

Claim 4

The process of claim 2, wherein said riser exit temperature ranges between 900° and 1100° F., and said heatexchanger cools said stripped catalyst stream to cause said catalyst in said regenerator vessel to be maintained at a temperature between 150° F. above said stripping step temperature and 1600° F.

Claim 5

The process of claim 3, wherein said heating step and said stripping step occur within said reactor vessel and said stripping step occurs at a stripping temperature between 150° F. above said riser exit temperature and 1400° F. and a residence time for said gaseous stream from 0.5 to 5 seconds.

Claim 6

The process of claim 4, wherein said separating step comprises separating the mixture from said riser conversion zone in a closed cyclone system in communication with said riser conversion zone.

Claim 7

The process of claim 5, wherein said riser exit temperature ranges from 1000° to 1050° F. and said stripped catalyst stream is cooled in said heat-exchanger to between 50° and 150° F. below said stripping temperature, said heat-exchanger thereby causing said regenerator vessel temperature to be maintained independently of said stripping temperature.

Claim 8

The process of claim 6, wherein said separated catalyst portion of said combined catalyst contains sulfur-containing compounds and hydrogen-containing compounds derived from said feedstock, and said stripping step removes 45 to 55% of said sulfur-containing compounds and 70 to 80% of said hydrogen-containing compounds in said separated catalyst portion.

Claim 9

The process of claim 7, wherein said combined catalyst passes countercurrently to said stripping gas during said stripping step.

Claim 10

A process for controlling the fluid catalytic cracking of a feedstock containing hydrocarbons and sulfur-containing compounds, comprising the steps of: passing a mixture comprising catalyst and said feedstock through a riser conversion zone at fluid catalytic cracking conditions to crack said feedstock; passing said mixture, having a riser exit temperature between 1000° and 1050° F., from said riser conversion zone to a closed cyclone system located within a fluid catalytic cracking reactor vessel; separating a portion of catalyst from said mixture in said closed cyclone system, with the remainder of said mixture forming a reactor vessel gaseous stream; heating said separated catalyst portion by a heating step consisting essentially of combining said separated catalyst portion of said reactor vessel with a portion of regenerated catalyst from a fluid catalytic cracking regenerator vessel to form combined catalyst; stripping said combined catalyst by contact with a stripping gas stream consisting essentially of steam in said reactor vessel, under stripping conditions comprising a stripping temperature between 150° F. above said riser exit temperature and 1400° F., said regenerated catalyst portion having a temperature between 150° F. above said stripping temperature and 1600° F. prior to heating said separated catalyst, wherein said separated catalyst portion contains sulfur-containing compounds and hydrogen-containing compounds derived from said feedstock, said stripping conditions are sufficient to separate 45 to 55% of said sulfur-containing compounds and 70 to 80% of said hydrogen-containing compounds in said separated catalyst portion of said combined catalyst to produce a gaseous stream, and said gaseous stream comprises stripping gas and molecular hydrogen, hydrocarbons and sulfur-containing compounds separated from said separated catalyst, said stripping conditions further comprising a residence time from 0.5 to 5 seconds for said gaseous stream, wherein said sulfur-containing compounds in said gaseous stream consist essentially of hydrogen sulfide and mercaptans; cooling said stripped catalyst stream to a temperature between 50° and 150° F. below said stripping temperature, by indirect heat-exchange with a heat-exchange medium in a heat exchanger located outside said reactor vessel, causing said catalyst in said regenerator vessel to be maintained at a temperature between 150° F. above said stripping temperature and 1600° F., thereby maintaining said regenerator vessel temperature independently of said stripping temperature; and regenerating said cooled catalyst stream in said fluid catalytic cracking regenerator vessel, by contact with an oxygen-containing stream under fluid catalytic cracking regeneration conditions.

Claim 11

A process for controlling the fluid catalytic cracking of a feedstock containing hydrocarbons and sulfur-containing compounds, comprising the steps of: passing a mixture comprising catalyst and said feedstock through a riser conversion zone at fluid catalytic cracking conditions to crack said feedstock; passing said mixture, having a riser exit temperature between 1000° and 1050° F., from said riser conversion zone to a closed cyclone system located within a fluid catalytic cracking reactor vessel; separating a portion of catalyst from said mixture in said closed cyclone system, with the remainder of said mixture forming a reactor vessel gaseous stream; heating said separated catalyst portion by a heating step consisting essentially of combining said separated catalyst portion of said reactor vessel with a portion of regenerated catalyst from a fluid catalytic cracking regenerator vessel to form combined catalyst; stripping said combined catalyst by contact with a stripping gas stream consisting essentially of steam in said reactor vessel, under stripping conditions comprising a stripping temperature between 150° F. above said riser exit temperature and 1400° F., said regenerated catalyst portion having a temperature between 150° F. above said stripping temperature and 1600° F. prior to heating said separated catalyst, wherein said separated catalyst portion contains sulfur-containing compounds and hydrogen-containing compounds derived from said feedstock, said stripping conditions are sufficient to separate 45 to 55% of said sulfur-containing compounds and 70 to 80% of said hydrogen-containing compounds in said separated catalyst portion of said combined catalyst to produce a gaseous stream, and said gaseous stream comprises stripping gas and molecular hydrogen, hydrocarbons and sulfur-containing compounds separated from said separated catalyst, said stripping conditions further comprising a residence time from 0.5 to 5 seconds for said gaseous stream, wherein said sulfur-containing compounds in said gaseous stream consist essentially of hydrogen sulfide and mercaptans; cooling said stripped catalyst stream to a temperature between 50° and 150° F. below said stripping temperature, by indirect heat-exchange with a heat-exchange medium in a heat exchanger located outside said reactor vessel, causing said catalyst in said regenerator vessel to be maintained at a temperature between 150° F. above said stripping temperature and 1600° F., thereby maintaining said regenerator vessel temperature independently of said stripping temperature; and regenerating said cooled catalyst stream in said fluid catalytic cracking regenerator vessel, by contact with an oxygen-containing stream under fluid catalytic cracking regeneration conditions.