Abstract
A method and apparatus for sampling fluid catalytic cracking catalyst wherein catalyst splashing is virtually eliminated, pluggage is reduced, and the temperature and velocity of the catalyst is also reduced.
Claims
1. A system for sampling catalyst during the operation of a fluid catalytic cracking unit, comprising in combination: a sampling line connected to a the catalytic crackign unit; a cyclone sampler connected to the sampling line; a valve contained within the sampling line for opening and closing the sampling line to allow the flow of catalyst into the cyclone sampler; and a colleciton vessel in communicaiton with the cyclone sampler, for collecting the catalyst sample, the collection vessel including a splash guard to reduce catalyst splashing as the catalyst exits an outlet of the cyclone sampler and enters the collection vessel.
2. The system of claim 1 wherein the splash guard is angled upward from the collection vessel toward the outlet of the cyclone sampler without actually engaging the outlet.
3. The system of claim 1 wherein the sampline line includes a valve to allow purging of the sampling line.
4. A system for sampling catalyst from a fluid catalytic cracking unit comprising, in combination: a sampling line connected to the catalytic cracking unit; a valve for opening the closing the flow of catalyst through the sampling line; a cyclone sampler connected to the sampling line, capable of reducing the velocity and temperature of the catalyst flow; a collection vessel, in communication with the cyclone sample, for collecting the catalyst sample from an outlet of the cycle sampler; and a splash guard, attached to the collection vessel, wherein the splash guard is angled upward and inward toward the outlet of the collection vessel to reduce the catalyst splashing as the catalyst exits the cyclone sampler and enters the collection vessel.
5. The system of claim 4 wherein the sampling line is generally horizontally oriented to minimize pluggage.
6. The system of claim 4 wherein the fluid catalytic cracking unit further includes a regenerated catalyst stand pipe (16) and the sampling line is connected to the stand pipe.
7. The system of claim 4 wherein the fluid catalytic cracking unit further includes a spent catalyst stand pipe (46) and the sampling line is connected to the spent stand pipe.
Description
IN THE DRAWINGS
(1) FIG. 1 is a diagram of a prior art FCC unit comprising a reactor and a regenerator.
(2) FIG. 2 is a side view of a prior art FCC unit with a sample line.
(3) FIG. 3 is a diagram of the FCC unit of the present invention incorporating a cyclone sampler.
(4) FIG. 4 is a schematic view of the cyclone sampler seen in FIG. 3.
(5) FIG. 5 is a diagram of an alternative embodiment of the FCC unit of the present invention incorporating a cyclone sampler.
DETAILED DESCRIPTION OF THE INVENTION
(6) Referring now to FIG. 1, a catalytic cracking unit 1 is shown and is comprised of a regenerator 12, and a reactor 50. Catalyst is transferred from the regenerator 12 to the reactor 50 by a regenerator catalyst stand pipe 16. The rate of catalyst transfer from the reactor 50 to the regenerator 12 is regulated by a slide valve 10. A fluidization medium from nozzle 8 transports catalyst upwardly through a lower portion of a riser 14 at a relative high density until a plurality of feed injection nozzles 18 (only one is shown) inject feed across the flowing stream of catalyst particles. The resulting mixture continues upward through an upper portion of riser 14 to a riser termination device. This specific device utilizes at least two disengaging arms 20 which tangently discharge the mixture of gas and catalyst through openings 22 from a top of riser 14 into disengaging vessel 24 that effects separation of gases from the catalyst. Most of the catalyst discharged from opening 22 fall downwardly in the disengaging vessel 24 into bed 44. A transport conduit 26 carries separated hydrocarbon vapors with entrained catalyst to one or more cyclones 28 in the reactor 50 of separator vessel 30. Cyclones 28 separate spent catalyst from the hydrocarbon vapor stream. Collection chamber 31 gathers the separated hydrocarbon vapor streams from the cyclones 28 for passage to an outlet nozzle 32 and into a downtream fractionation zone (not shown). Dip legs 34 discharge catalyst from the cyclones 28 into bed 29 in the lower portion of a disengaging vessel 30 which pass through ports 36 into bed 44 and disengaging vessel 24. Catalyst and adsorbed or entrained hydrocarbons pass from disengaging vessel 24 into stripping section 38. Catalyst from opening 22 is separated in disengaging vessel 24 and passes directly into the stripping section 38. Hence, entrances to the stripping section 38 includes opening 22 and ports 36. Stripping gas, such as steam, enters a lower portion of the stripping section 38 through distributor 40 and rises counter-current to a downward flow of catalyst through the stripping section 38, thereby removing adsorbed and entrained hydrocarbons from the catalyst, The hydrocarbons flow upwardly through and are ultimately recovered with the stream by the cyclones 28. Distributor 40 distributes the stripping gas around the circumference of the stripping section 38. In order to facilitate hydrocarbon removal structured packing may be provided in stripping section 38. The spent catalyst leaves the stripping section 38 through a port 48 to spent catalyst standpipe 46 and passes into regenerator 12. The catalyst is regenerated in regenerator 12 and sent back to the riser 14 through the regenerated catalyst stand pipe 16.
(7) Referring now to FIG. 2, the prior art sampling method is shown. The FCC unit 1 having a sampling line 74, a root valve 76 and a collection vessel 66. The catalyst is routed to the collection vessel 66 through the sampling line when root valve 76 is open. The collection vessel 66 typically has a sample can (not shown) which is placed in a basket 68 in the top of the collection vessel 66. The sample can must be elevated within the basket 68 to contact the sample line 74 and direct the catalyst into the sample can. When root valve 76 is open catalyst travels through sample line 74 and into collection vessel 66 to be sampled.
(8) Referring now to FIGS. 3 and 4, a preferred embodiment of the present invention is shown. Catalyst from the FCC unit 1 is sampled by traveling through a sampling line 62 into a cyclone sampler 60 when a valve 64 (such as a root valve) is opened. When the catalyst enters the cyclone sampler, the velocity and temperature of the catalyst can be reduced, entrained vapors may be vented to a safe location and the catalyst may be better directed into a collection vessel to avoid catalyst splashing. As the catalyst enters the cyclone sampler 60, velocity is reduced, vapors are vented and the catalyst is directed into a sample can (not shown) within a sample basket 68 contained inside a collection vesse 66. A splash guard 72 may be used to further reduce catalyst splashing.
(9) The cyclone sampler 60 and sampling line 52 may be attached to the FCC unit 1 at any sampling location. In the preferred embodiment, the sampling line 62 attaches to the regenerated standpipe 16 so that regenerated catalyst may be sampled, in a different embodiment, the sampling line 62 may be attached to a spent catalyst standpipe 46 so that spent catalyst may be sampled.
(10) If desired, nitrogen may be used to purge the sampling apparatus by injecting nitrogen into a valve 80. Purging of the sampling vessel reduces the risk of pluggage and reduces the temperature of the catalyst sample. In the prior art, nitrogen purging created significant catalyst splashing however by utilizing the cyclone sampler splashing is significantly reduced even during the nitrogen purging.
(11) A vent 70 with a valve may be utilized to vent the cyclone. This vent 70 may also be used to dislodge any piuggage should it occur. The vent 70 also assists in allowing vapor-lock of the catalyst sample during sampling.
(12) The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the scope of the invention. Accordingly, the whole of the foregoing description is to be construed in an illustrative and not a limitative sense, the scope of the invention being defined solely by the appended claims.
