Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
1999-07-21
2001-01-30
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S127000, C208S153000, C208S157000, C239S008000, C239S398000, C239S429000, C239S431000, C239S433000, C239S434000, C239S589000
Reexamination Certificate
active
06179997
ABSTRACT:
The present invention relates to the atomization of a liquid stream. In another aspect, the invention relates to a method and apparatus for atomizing and uniformly distributing an oil feed stream into a stream of fluidized catalyst in a fluidized catalytic cracking (FCC) unit or a coker unit.
BACKGROUND OF THE INVENTION
The process of atomizing a liquid stream for such purposes as rapid cooling of the liquid (artificial snow making) or enhanced contact of the atomized liquid with another medium, such as a fluidized catalyst, is well known in the art. It would clearly be desirable to provide an improved process and apparatus for atomizing a liquid stream.
A specific example of an atomization process is the atomization of an oil stream in an FCC or coker unit prior to contacting the oil stream with a fluidized catalyst. Typical FCC unit operations are described below.
Fluidized catalytic cracking of heavy petroleum fractions to produce products such as gasoline and heating oils is well known in the art. In fluidized catalytic cracking, heavy petroleum fractions are often preheated prior to contact with hot, fluidized catalyst particles in a riser reactor. The contact time in the riser reactor is generally in the order of a few seconds. The relatively short contact time encourages the production of gasoline and heating oil range hydrocarbons. Longer contact times can result in overcracking to undesirable end products, such as methane and coke. Important aspects of contacting the heavy petroleum fraction with the fluidized catalyst include the atomization of the heavy petroleum fraction and uniform distribution of the atomized heavy petroleum fraction within the fluidized catalyst. Non-uniform distribution of the heavy petroleum fraction in the fluidized catalyst can lead to localized regions of high catalyst-to-oil ratios and overcracking. Also, poor atomization of the heavy petroleum fraction can lead to localized regions of low catalyst-to-oil ratios resulting in wetting of the catalyst which results in increased coke laydown. In addition, if the heavy petroleum fraction is not sufficiently atomized and does not directly contact the fluidized catalyst upon injection into the riser reactor, then thermal cracking can occur instead of catalytic cracking. Thermal cracking can result in the generation of the undesirable end products of methane and coke. Excess coke is undesirable because the process duties of the stripper and regenerator are increased and the coke can be deposited on the surfaces of the equipment involved. It would be clearly desirable to provide a process and apparatus in which an oil feed stream comprising a heavy petroleum fraction is sufficiently atomized and uniformly distributed within a fluidized catalyst in a fluidized catalytic cracking process.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus to be used in the atomization of a liquid stream in a more efficient manner.
A further object of this invention is to provide a method of atomizing a liquid stream in a manner that increases the atomization efficiency.
It is yet another object of the present invention to improve the efficiency of FCC operations.
It is still another object of the present invention to improve the efficiency of coker operations.
Another object of the present invention is to provide a method and apparatus for atomizing an oil feed stream for catalytic conversion.
A yet further object of the present invention is to provide a method and apparatus for atomizing and uniformly distributing an oil feed stream into a fluidized catalyst.
In accordance with the present invention, the atomizer comprises:
a first conduit having a longitudinal axis, an inside wall, an inside diameter D
1
, an upstream end portion, a downstream end portion, and an opening in the inside wall intermediate said upstream end portion and said downstream end portion;
a second conduit having a perforated-pipe sparger at one end thereof for introducing an atomizing enhancing medium to the first conduit; the perforated-pipe sparger having a longitudinal axis and being disposed within the first conduit through the opening in the inside wall of the first conduit with the longitudinal axis of the perforated-pipe sparger being in a generally perpendicular relation to the longitudinal axis of the first conduit; the perforated-pipe sparger having an outside surface, a first end, a closed second end, an outside diameter D
2
, a length L
1
within the first conduit and a plurality of holes facing generally in the direction of the downstream end portion of the first conduit; the outside surface at the first end of the perforated-pipe sparger being in sealing engagement with the opening in the inside wall of the first conduit; and
a third conduit having an inside diameter D
3
, the third conduit being connected in fluid flow communication with the downstream end portion of the first conduit.
The invention further includes a method of operating the inventive atomizer described above. More particularly, the inventive method for atomizing a liquid stream comprises:
providing the atomizer described above;
introducing a liquid stream to the upstream end portion of the first conduit;
introducing an atomizing enhancing medium through the perforated-pipe sparger via the second conduit;
contacting the liquid stream with the atomizing enhancing medium downstream from the plurality of holes of the perforated-pipe sparger thereby forming a turbulent mixture of the liquid stream and the atomizing enhancing medium;
passing the turbulent mixture to the third conduit thereby converting the turbulent mixture into an annular-mist flow mixture;
passing the annular-mist flow mixture to a nozzle; and
withdrawing the annular-mist flow mixture from the nozzle thereby at least partially atomizing the liquid stream to form an atomized liquid stream.
Other objects and advantages of the invention will be apparent from the detailed description of the invention and the appended claims.
REFERENCES:
patent: 3332442 (1967-07-01), Reed
patent: 4103827 (1978-08-01), Kumazawa
patent: 4960502 (1990-10-01), Holland
patent: 5037616 (1991-08-01), Williatte et al.
patent: 5108583 (1992-04-01), Keon
patent: 5173175 (1992-12-01), Steffens et al.
patent: 5673859 (1997-10-01), Haruch
patent: 5979799 (1999-11-01), Chen et al.
patent: 6003789 (1999-12-01), Base et al.
patent: 6098896 (2000-08-01), Haruch
Perry's Chemical Engineers Handbook, 6th Edition, Section 5, pp. 48-49 (No Date Available).
Hemanta Mukherjee, “The University of Tulsa Fluid Flow Projects—An Experimental Study of Inclined Two-Phase Flow”, Dec. 30, 1979, pp. 60 and 102-104.
Vedder, Jr. William J.
Wells Jan W.
Anderson Jeffrey R.
Griffin Walter D.
Phillips Petroleum Company
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