Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Fluidized bed
Reexamination Certificate
1999-12-22
2003-01-07
Tran, Hien (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Fluidized bed
C422S139000, C285S039000
Reexamination Certificate
active
06503461
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the dispersing of liquids into fluidized solids. More specifically this invention relates to an apparatus for dispersing a hydrocarbon feed into a stream of fluidized catalyst particles and for joining conduit sections.
2. Description of the Prior Art
There are a number of continuous cyclical processes employing fluidized solid techniques in which fluids are dispersed into a suspension of fluidized particles. One of the more important processes of this nature is the fluid catalytic cracking (FCC) process for the conversion of relatively high-boiling hydrocarbons to lighter hydrocarbons boiling in the heating oil or gasoline (or lighter) range. The hydrocarbon feed is contacted in one or more reaction zones with the particulate cracking catalyst maintained in a fluidized state under conditions suitable for the conversion of hydrocarbons. Carbonaceous materials are deposited on the solids in the reaction zone and the solids are conveyed during the course of the cycle to another zone where carbon deposits are at least partially removed by combustion in an oxygen-containing medium. The solids from the latter zone are subsequently withdrawn and reintroduced in whole or in part to the reaction zone.
It has been found that the method of contacting the feedstock with the catalyst can dramatically affect the performance of the reaction zone. Modern FCC units use a pipe reactor in the form of a large, usually vertical, riser in which a gaseous medium upwardly transports the catalyst in a fluidized state. Ideally the feed as it enters the riser is instantaneously dispersed throughout a stream of catalyst that is moving up the riser. A complete and instantaneous dispersal of feed across the entire cross section of the riser is not possible, but good results have been obtained by injecting a highly atomized feed into a pre-accelerated stream of catalyst particles. Pre-acceleration is often accomplished in a riser conduit with the use of a lift gas to lift the catalyst particles before they contact the feed. After the catalyst is moving up the riser it is contacted with the feed by injecting the feed into a downstream section of the riser. A good example of the use of lift gas in an FCC riser can be found in U.S. Pat. No. 4,479,870.
Most often fluid is injected into the fluidized particles from multiple points with separate injectors. U.S. Pat. No. 4,717,467 shows one method for injecting an FCC feed into an FCC riser from a plurality of discharge points in a non-radial manner. U.S. Pat. Nos. 5,554,341, 5,173,175, 4,832,825, and 3,654,140 all show the use of radially directed feed injection nozzles to introduce feed into an FCC riser. The nozzles are arranged in a circumferential band about the riser and inject feed toward the center of the riser. The angled feed nozzles are typical of those used to inject feed or other fluids at an intermediate portion in the riser conduit.
The angled feed injectors present a number of problems for the operation of the risers. The nozzles typically extend away from the wall of the riser and into the flow path of the catalyst. Passing particles over the nozzles at high velocity can result in erosion. An obvious solution to the problem of nozzle protrusion would be to recess the nozzles completely into the wall of the riser and thereby remove them from the catalyst flow path. This solution is not satisfactory since the feed injector tips are specifically designed to provide a relatively uniform coverage of the hydrocarbon feed over the cross-section of the riser by expanding the pattern of feed injection as it exits from the nozzle. Completely recessing the tips of the injector nozzles within the wall of the riser disrupts the ability to obtain a spray pattern over the majority of the riser cross-sectional area.
In addition, a long recognized objective when injecting liquids into fluidized particles is the maximization of the hydrocarbon feed dispersal into the particulate suspension. Dividing the liquid into small droplets improves dispersion of the feed by increasing the interaction between the liquid and solids. Preferably, the droplet sizes become small enough to permit vaporization of the liquid before it contacts the solids. It is well known that agitation or shearing can atomize a liquid hydrocarbon feed into fine droplets which are then directed at the fluidized solid particles.
A variety of methods are known for shearing such liquid streams into fine droplets. U.S. Pat. No. 3,071,540 discloses a feed injection apparatus for an FCC unit wherein a high velocity stream of steam, converges around a stream of oil upstream of an orifice through which the mixture of steam and oil is discharged. U.S. Pat. No. 4,434,049 shows another device for injecting a fine dispersion of oil droplets into a fluidized catalyst stream wherein the oil is first discharged through an orifice onto an impact surface located within a mixing tube. The mixing tube delivers a cross flow of steam which simultaneously contacts the liquid. In both cases the combined flow of oil and steam exits the conduit through an orifice which atomizes the feed into a dispersion of fine droplets and directs the dispersion into a stream of flowing catalyst particles.
For the most part, the injectors rely on relatively high fluid velocities and pressure drops to achieve atomization of the oil into fine droplets. The use of discharge orifices, spray nozzles and other distribution and atomization equipment is common in such injectors. Providing this high pressure drop and fluid velocity creates a harsh environment that can quickly erode the components of a feed injector. Therefore, it is routinely necessary to replace or refurbish portions of the injector that are exposed to this harsh environment, particularly the tip of the injector that is often exposed to high velocity particulate material. In addition the position or type of nozzle on or within the injector can greatly influence the type of dispersion obtained and can vary with the feed composition or flow rate. Therefore, it would be advantageous to quickly change out the components in a feed injector that need adjustment for particular feeds or replacing due to damage.
In addition, the need to replace damaged components may be reduced by the use of more refractory materials. For example, ceramic materials could greatly improve the durability of many feed distributor components. However, the inability to incorporate such materials into the usual stainless or carbon steel pipe components of the injector by welding or by the use of standard connections makes their use extremely difficult and has eliminated the presence of such materials from large commercial designs.
The usual placement of injectors further complicates the fashioning of suitable connections for easy replacement of components and for joining materials with diverse properties. Positioning feed injectors around a riser requires a minimization of the opening for the feed injector and results in a confined space that leaves little room for the injector components. This limited space provides little extra clearance for supplying connections.
A known type of piping connection uses a series of machined grooves on the ends of pipes that are connected by bridging links that have complementary grooves for engaging the grooves on the pipe ends. A sleeve or other retaining means is used to hold the link members against the pipes and the cooperating grooves in engagement. Different forms of these types of connections can be seen in U.S. Pat. Nos. 5,152,556, 5,265,917, 5,131,632, 3,687,487, and 4,159,132 3,687,487 mentions that it may be used with ceramic materials.
It is an object of this invention to provide an apparatus that incorporates diverse materials of construction into a feed injection nozzle.
It is a further object of this invention to provide a method and apparatus that simplifies the replacement of feed injector components.
SUMMARY OF THE INVENTION
It has now been discovered that low profile pi
Burgard Jeffrey E.
Mitchell Todd P.
Schulz Gary A.
Melick Andrew G.
Paschall James C.
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