PATENT
United States Patent Application 20120014847
Inventors:
Killen, Ralph E. (San Francisco, CA, US)
Boyak, Craig (El Cerrito, CA, US)
Song X, Steven (Albany, CA, US)
Kemoun, Abdenour (Pleasant Hill, CA, US)
Souers, Steve (Ocean Springs, MS, US)
Parimi, Krishniah (Alamo, CA, US)
Akin, Zackory (Pleasant Hill, CA, US)
Application Number: 12/839227
Publication Date: 01/19/2012
Assignee: Chevron U.S.A. Inc.
Abstract:
BACKGROUND OF THE INVENTION
Many catalytic processes are performed in reactors containing a series of separate catalytic beds. Reactors used in the chemical, petroleum refining, and other industries for passing liquids or mixed-phase liquid/gas mixtures over packed beds of particulate solids are employed for a variety of different processes. Examples of such processes include: catalytic dewaxing, hydrotreating, hydrodesulphurization, hydrofinishing, and hydrocracking. In these processes a liquid phase is typically mixed with a gas or vapor phase and the mixture passed over a particulate catalyst in a packed bed within a downflow reactor.
In downflow reactors, it is necessary that the gas and liquid are properly mixed and uniformly distributed across the horizontal cross section of the reactor prior to contacting each catalyst bed. Such uniform distribution of the gas and liquid provides major advantages, including: efficient utilization of catalyst, reduced catalyst top layer attrition, improved yields, improved product quality, and increased run lengths. Generally in a downflow catalytic reactor, a plurality of catalyst beds are arranged within the reactor, and a distributor system for the efficient mixing of gas and liquids is disposed above each catalyst bed. The region between catalyst beds is normally provided with a gas injection line to provide additional gas to compensate for gas consumed in the previous catalyst bed. The injected gas can also act as a quench gas for cooling the feed exiting a catalyst bed prior to the feed entering the next catalyst bed. Generally, the injected gas is hydrogen or comprises hydrogen. The liquid feed falling from the above-lying catalyst bed is allowed to accumulate on a collection tray. The quench gas and liquid then pass into a mixing chamber where a swirling movement of the liquid is provided. This enables good mixing of the liquid and thereby provides even temperature conditions of the liquid. Gas-liquid mixing also takes place inside the mixing chamber.
The fluid from the mixing chamber flows downward onto a deflector or impingement plate, whereby the flow is redirected onto a distributor tray having a large number of downflow openings for the passage of liquid. For cross-sectional liquid flow distribution, the downflow openings of conventional apparatus can comprise one or more conduits, or chimneys. The chimney is a cylindrical structure with an open top and one or more openings in the upper portion of its height through which a gas phase can enter. The gas phase travels downward through the length of the chimney. The lower portion of the chimney can have one or more lateral openings for liquid flow through which a liquid phase can enter the chimney and contact the gas phase. As liquid continues to accumulate on the distributor tray, the liquid will rise to a level that covers the lateral opening(s) in the chimney so that the passage of gas is precluded and so that the liquid can enter through the lateral opening(s) into the chimney. Gases and liquids egress via an opening in the bottom of the chimney, through the distributor tray, and onto an underlying catalyst bed. A disadvantage of conventional conduits or chimneys is that, due to the low turbulence around liquid streams, only limited mixing between the two phases will occur.
A good flow distribution device for a catalytic reactor should meet the following four basic requirements: provide even distribution of feed to a catalyst bed over a range of gas and liquid feed rates; be tolerant to certain out-of-levelness of the distribution tray; provide good gas-liquid mixing and heat exchange, and require minimum catalyst bed height to fully wet the underlying catalyst bed. Because conventional chimneys rely on the static liquid height on the tray as the driving force for liquid flow into the chimney, they are deficient in meeting these criteria due to poor tolerance for deviations from levelness of the distributor tray, as well as exhibiting suboptimal spray discharge of fluids onto the underlying catalyst bed, and other deficiencies.
One of the key considerations in flow distributor design is the discharge pattern of liquid and gas from the device. A conventional chimney distributor provides a limited number of points of contact of the liquid feed with the catalyst bed. As a result, a larger distance from the chimney to the bed is required to wet the catalyst surface.
U.S. Pat. No. 7,473,405 to Kemoun et al. discloses a nozzle device for coupling with a fluid distribution conduit.
There is a continuing need for hydroprocessing reactor apparatus providing improved hydrogen/oil mixing at the mixing tray, more uniform and consistent liquid distribution on the catalyst bed, a decreased mixing tray height, and decreased amounts of fabrication material, as well as easier maintenance, assembly and disassembly. There is also a need for systems and apparatus that provide improved tolerance for distributor tray out-of-levelness conditions. There is still a further need for fluid distribution apparatus that can provide more uniform distribution of liquid on a catalyst bed under liquid-only conditions.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a reactor system comprising a reactor shell, a primary feed distribution unit disposed within the reactor shell, and at least one secondary feed distribution unit disposed beneath the primary feed distribution unit within the reactor shell. The primary feed distribution unit comprises a primary deflector plate and a first nozzle tray disposed beneath the deflector plate. The at least one secondary feed distribution unit comprises a collection tray and a second nozzle tray disposed beneath the collection tray. Each of the first nozzle tray and the second nozzle tray comprises a plurality of nozzles, the nozzles each comprise a nozzle body including a distal body portion having at least one liquid inlet configured for the passage of liquid therethrough. The distal body portion defines a substantially cylindrical distal void. Each liquid inlet is disposed tangentially to an inner surface of the distal body portion.
In an embodiment, the present invention also provides a reactor system comprising a reactor shell having an inner wall, a primary feed distribution unit disposed within the reactor shell, and at least one secondary feed distribution unit disposed beneath the primary feed distribution unit within the reactor shell. Each secondary feed distribution unit comprises a collection tray, a nozzle tray disposed beneath the collection tray, at least one support ring affixed to the reactor shell inner wall, and a plurality of trusses. Each truss spans the at least one support ring. Each truss has an upper flange and a lower flange, the upper flange supports the collection tray and the lower flange supports the nozzle tray.
In another embodiment of the present invention, there is provided a feed distribution unit for a catalytic reactor, the feed distribution unit comprising a deflector plate and a nozzle tray disposed beneath the deflector plate. The nozzle tray includes a plurality of nozzles. Each nozzle comprises a nozzle body including a distal body portion having at least one liquid inlet configured for the passage of liquid therethrough. The distal body portion defines a substantially cylindrical distal void. Each liquid inlet is disposed tangentially to an inner surface of the distal body portion.
In an embodiment, the present invention further provides a nozzle for the even distribution of a multi-phase fluid mixture, the nozzle comprising a nozzle body having a proximal body portion, an intermediate body portion, and a distal body portion. The proximal body portion defines a substantially cylindrical proximal void, and the proximal body portion has at least one gas inlet configured for the passage of gas therethrough into the proximal body portion. The intermediate body portion defines a substantially cylindrical intermediate void in fluid communication with the proximal void. The distal body portion has a body wall and at least one liquid inlet configured for the passage of liquid therethrough into the distal body portion. The distal body portion defines a substantially cylindrical distal void, and the at least one liquid inlet is disposed tangentially to an inner surface of the distal body portion.
In another embodiment of the present invention, there is provided a fluid distribution apparatus for a reactor, the apparatus comprising a nozzle tray; a plurality of chimneys affixed to, and extending through, the nozzle tray; and a fluid distribution nozzle disposed within each chimney. Each chimney has a chimney wall defining a substantially cylindrical void extending substantially vertically from a lower surface of the nozzle tray to a location above an upper surface of the nozzle tray. The chimney has an open proximal end and an open distal end, and the chimney wall has at least one lateral opening therein. The nozzle comprises a nozzle body comprising a proximal body portion, an intermediate body portion, and a distal body portion having a distal body wall. The proximal body portion defines a substantially cylindrical proximal void, and the open proximal end is configured for the passage of gas therethrough. The intermediate body portion defines a substantially cylindrical intermediate void in fluid communication with the proximal void. The distal body portion has a liquid inlet configured for the passage of liquid therethrough into the distal body portion. The distal body portion defines a substantially cylindrical distal void. The liquid inlet comprises a curved channel within the distal body wall, and the curved channel has an inner terminus disposed tangentially to an inner surface of the distal body portion.
In another embodiment, the present invention still further provides a fluid distribution device comprising a substantially cylindrical hollow nozzle body having a plurality of outer slots disposed circumferentially around the nozzle body; a cap affixed to a proximal portion of the nozzle body, the cap having an axial proximal opening therein; a base affixed to a distal portion of the nozzle body, the base having an axial distal opening therein; and a substantially cylindrical inner conduit disposed axially within a proximal portion of the nozzle body. The inner conduit is disposed within the proximal opening of the cap, and the inner conduit extends proximally from the cap to define a proximal end of the inner conduit. The inner conduit has a plurality of inner slots disposed circumferentially around the proximal end of the inner conduit. A distal end of the inner conduit extends distally to a location proximal to a distal end of each of the outer slots.
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