Mechanical shattering of asphaltenes in FCC riser
AssigneeMobil Oil Corporation
InventorMichael F. Raterman
Life of this patent
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Abstract
An FCC process and apparatus for atomizing heavy feed are disclosed. A liquid feed containing stacked asphaltenes is pressurized, and preferably heated, with a gas such as light hydrocarbons. Pressurized gas and liquid discharge at high velocity into an expansion chamber, where shear force and sudden expansion disrupt stacked structures. Preferably, some thermal conversion, visbreaking, occurs in the expansion chamber. The disrupted feed is discharged into an FCC reactor, preferably to the base of a riser reactor, with a lighter feed, such as a gas oil, added higher up in the riser. Improved atomization and vaporization of the heavy feed in the riser increases conversion and reduces coke make.
Claims18
A dual feed injection catalytic cracking process for converting a relatively light feed containing at least 90 wt % distillable hydrocarbons and a heavier resid feed containing at least 10 wt % hydrocarbons boiling above 1000.degree. F. and complex, disruptable species selected from the group of stacked asphaltene molecules and stacked porphyrins, to catalytically cracked products including at least 40 LV % C5 to 400.degree. F. gasoline having an octane number of at least 90.0 RONCL in a single riser reactor having a base and an upper outlet comprising;
- a. pressurizing said resid feed by mixing therewith sufficient compressed vapor selected from the group consisting of steam, hydrogen, and normally gaseous hydrocarbons, to produce a pressurized resid feed of a resid/vapor mixture having a pressure above 200 psig;
- b. mechanically disrupting said pressurized resid feed by discharging said resid through a high pressure drop nozzle into an expansion chamber operating at a pressure of 1 to 100 psig, with a delta P across said nozzle of at least 200 psi, and an exit velocity above 300 fps to produce mechanically disrupted feed;
- c. thermally treating said disrupted feed in said expansion chamber at a temperature above 700.degree. F. for 0.01 to 1.0 seconds to thermally crack said mechanically disrupted feed to produce a mechanically disrupted and thermally cracked resid feed in an expansion region at a pressure of 1 to 100 psig;
- d. discharging said mechanically disrupted and thermally cracked resid from said expansion region into a base section of a riser catalytic cracking reactor having said base section and an upper outlet section, said riser reactor operating at a pressure below said expansion region;
- e. charging a stream of hot, regenerated cracking catalyst from a catalyst regenerator to said base section of said riser reactor and thermally and catalytically cracking said resid in a resid cracking zone in a lower portion of said riser by contact with said hot, regenerated cracking catalyst;
- f. charging said relatively light feed to said riser reactor at a location downstream of said resid cracking zone;
- g. catalytically cracking said relatively light feed and said, mechanically disrupted and thermally cracked resid feed in said riser reactor at catalytic cracking conditions including a cat:feed weight ratio of a least 4:1, a catalyst and combined vaporized feed initial mixture temperature of 950.degree. to 1100.degree. F., to produce a discharged mixture of catalytically cracked products and spent cracking catalyst which are discharged from said outlet of said riser reactor;
- h. separating said discharged mixture of catalytically cracked products and spent cracking catalyst into a cracked product rich vapor phase, which is withdrawn as a product, and a spent catalyst rich phase;
- i. stripping said spent catalyst in a stripping means at stripping conditions to produce stripped catalyst;
- j. regenerating said stripped catalyst in a catalyst regeneration means operating at catalyst regeneration conditions to produce hot regenerated cracking catalyst which is recycled to the base of said riser reactor.
A fluidized catalytic cracking process wherein a heavy hydrocarbon feed having a measured viscosity and containing stacked hydrocarbon structures selected from the group of stacked asphaltenes and stacked porphyrin structures boiling above 1000.degree. F. is catalytically cracked in a riser cracking reactor means to produce cracked products and spent catalyst, spent catalyst is stripped in a stripping means and regenerated in a catalyst regeneration means to produce hot regenerated catalyst which is recycled to said riser reactor, characterized by use of at least one multi-stage atomizing feed nozzle to inject said hydrocarbon feed in a base portion of said riser reactor, said nozzle comprising:
- a pressurizing section wherein a gas, selected from the group consisting of steam, hydrogen, and normally gaseous hydrocarbons, contacts said hydrocarbon feed and is at least partially dissolved in said hydrocarbon feed to produce a gas/liquid mixture having a pressure of 100 to 2000 psig and containing dissolved gas;
- an expansion section wherein pressure of said pressurized mixture is reduced within less than 0.01 seconds to no more than 30% of the pressure in the pressurizing section and sufficient to:
- cause at least a 3 fold expansion of the gas liquid mixture;
- atomize the liquid;
- cause at least a portion of the dissolved gas to come out of solution and mechanically disrupt stacked structures in said liquid;
- thermally crack said heavy feed by providing a time and temperature in said expansion section, as measured by Equivalent Reaction Time at 800.degree. F. (ERT) of 5 to 500 ERT seconds;
- and produce an atomized, thermally cracked liquid feed containing disrupted stacked hydrocarbon structures with a reduced measured viscosity relative to said measured viscosity of said hydrocarbon feed;
- and
- a riser injection section, wherein said atomized, thermally cracked liquid is injected into said riser reactor.
Dependencies are inferred from the claim text.