Process for short contact time cracking

• US 5,296,131 A
• Filed: 12/02/1992
• Issued: 03/22/1994
• Est. Priority Date: 12/02/1992
• Status: Expired due to Fees

• Current Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Original Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Inventors: Raterman, Michael F.
• Primary Examiner(s): Bell, Mark L.
• Assistant Examiner(s): Yildirim, Bekir L.
• Application Number:
  US07/984,630
• Time in Patent Office: 475 Days
• Field of Search: 208/153, 208/167, 208/161, 208/153, 208/113, 208/160, 208/168, 208/120, 208/155, 208/156, 208/127, 208/164, 208/112, 208/152, 422/144
• US Class Current: 208/113
• CPC Class Codes: C10G 11/18 according to the "fluidised-bed" technique

Abstract

A process for short contact time cracking of heavy feed. A falling, annular curtain of hot regenerated FCC catalyst, or hot inert solids, is formed over a cone shaped plug valve. Hydrocarbons pass from under the cone, or via a hollow stem, in radial in to out flow to contact the falling curtain of solids. After 0.01 to 1.0 seconds of contact time, solids and cracked vapor are separated, preferably in a bell separator beneath the reaction zone. Downflow of reactants into a contiguous upflowing stripper minimizes attrition.

Claims

1. A process for the fluidized catalytic cracking of a heavy feed to lighter products comprising:

forming a falling, annular curtain of regenerated FCC catalyst by discharging said FCC catalyst down through a vertical, cone shaped plug valve having a base attached to a vertical stem which controls the flow of said catalyst;

contacting said falling annular curtain of catalyst with a heavy feed by discharging from at least one of the base of the cone shaped plug valve or the stem of said valve said hydrocarbon feed in radial in to out flow, forming a downflowing mixture of catalyst and feed and vaporizing at least a majority by weight of said feed;

cracking said feed in a vertical, cylindrical reactor vessel by passing said downflowing mixture as an annulus defined by the walls of said reactor vessel and the stem of said plug valve at catalytic cracking conditions including a superficial vapor velocity of at least 20 feed per second and a total catalyst and hydrocarbon vapor contact time of 0.01 to 1.0 seconds to produce cracked vapor products and spent catalyst;

separating cracked products from spent products in an inertial separation means to produce a cracked product vapor phase and a spent catalyst phase, and wherein said inertial separation means is a cylindrical shaped bell separator contiguous with and beneath said cylindrical reactor, said bell separator comprising;

an annular inlet in an upper portion of said bell separator having a diameter, and defined by the wall of said valve stem and a circumferential lip;

an annular flow expansion and vapor flow reversal section downstream of said annular inlet, defined by the wall of said valve stem and an outer wall of the cylindrical bell shaped separator, said outer wall having a diameter greater than the diameter of the reaction zone or of the diameter of the annular inlet, and having;

in a lower portion thereof an inlet for stripping gas and an outlet for stripped catalyst; and

in an upper portion thereof at least one vapor outlet connective with and passing through said outer wall of said cylindrical separator vessel and connective with an annular, circumferential vapor removal means extending radially about at least 90% of the circumference of said separator, defined by said circumferential lip and said wall of said separator;

recovering cracked products from said cracked product vapor phase as products of the process;

stripping said spent catalyst phase in a catalyst stripping means at catalyst stripping conditions to produce stripped catalyst;

regenerating in a catalyst regeneration means operating at catalyst regeneration conditions said spent catalyst to produce regenerated catalyst; and

charging regenerated catalyst to the top of said plug valve.

2. The process of claim 1 wherein the superficial vapor velocity in the reactor vessel is 20 to 200 fps.

3. The process of claim 1 wherein said annular inlet of said bell separator has a reduced cross sectional area as compared to a cross sectional area of said reactor, and the superficial vapor velocity within said annular inlet is from 25 to 250 feet per second.

4. The process of claim 3 wherein the superficial vapor velocity within said annular inlet is from 50 to 100 feet per second.

5. The process of claim 1 wherein said superficial vapor velocity in said stripper expansion section downstream of said annular inlet is from 20 to 200 feet per second and is reduced as compared to said superficial velocity in said annular inlet.

6. The process of claim 5 wherein superficial vapor velocity in said stripper expansion section is from 40 to 80 feet per second.

7. The process of claim 1 wherein the cat:

oil ratio in said cracking reactor is at least 10;

1.

8. The process of claim 1 wherein the cat:

oil ratio in said cracking reactor is at least 15;

1, and the residence time of both catalyst and hydrocarbon in said cracking reactor is less than 0.15 seconds.

9. The process of claim 1 wherein said inertial separator comprises a cyclone separator.

10. A process for the fluidized catalytic cracking of a heavy feed to lighter products comprising:

forming a falling, annular curtain of regenerated FCC catalyst by discharging said FCC catalyst down through a vertical, cone shaped plug valve having a base attached to a vertical stem which controls the flow of said catalyst;

contacting said falling annular curtain of catalyst with a heavy feed by discharging from at least one of the base of the cone shaped plug valve or the stem of said valve said hydrocarbon feed in radial in to out flow, forming a downflowing mixture of catalyst and feed and vaporizing at least a majority by weight of said feed;

cracking said feed in a vertical, cylindrical reactor vessel having a vertical axis by passing said downflowing mixture as an annulus defined by the walls of said reactor vessel and the stem of said plug valve at catalytic cracking conditions including a superficial vapor velocity of 20 to 200 feet per second and a total catalyst and hydrocarbon vapor contact time of 0.01 to 1.0 seconds to produce cracked vapor products and spent catalyst;

separating cracked products from spent catalyst in a vertical, cylindrical, bell shaped, inertial separation means having a vertical axis axially aligned with said vertical axis of said cracking reactor and contiguous with and beneath said cracking reactor, to produce a cracked product vapor phase and a spent catalyst phase, said inertial separator comprising;

an annular inlet for catalyst and cracked products in an upper portion of said bell separator having a diameter, and defined by the wall of said valve stem and a circumferential lip;

an annular flow expansion and vapor flow reversal section downstream of said annular inlet, defined by the wall of said valve stem and an outer wall of the cylindrical bell shaped separator, said outer wall having a diameter greater than the diameter of the reactor or of the diameter of the annular inlet, and having;

an inlet for stripping gas in a lower portion thereof; and

an outlet for stripped catalyst in a lower portion thereof; and

at least one vapor outlet in an upper portion thereof connective with and passing through said outer wall of said cylindrical separator vessel and connective with an annular, circumferential vapor removal means extending 360 degrees about the wall of said separator, defined by said circumferential lip and said wall of said separator;

regenerating in a catalyst regeneration means operating at catalyst regeneration conditions said spent catalyst to produce regenerated catalyst; and

charging regenerated catalyst to the top of said plug valve.

11. The process of claim 10 wherein said annular inlet of said bell separator has a reduced cross sectional area as compared to a cross sectional area of said reactor, and the superficial vapor velocity within said annular inlet is from 25 to 250 feet per second.

12. The process of claim 11 wherein the superficial vapor velocity within said annular inlet is from 50 to 100 feet per second.

13. The process of claim 10 wherein said superficial vapor velocity in said expansion section downstream of said annular inlet is from 20 to 200 feet per second and is reduced as compared to said superficial velocity in said annular inlet.

14. The process of claim 13 wherein the superficial vapor velocity in said expansion section is from 40 to 80 feet per second.

15. The process of claim 10 the cat:

oil ratio in said cracking reactor is at least 15;

1, and the residence time of both catalyst and hydrocarbon in said cracking reactor is less than 0.15 seconds.