Patent Publication Number: US-9890907-B1

Title: FCC catalyst cyclone sampling method and apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present patent application is a divisional of and claims the benefit of U.S. provisional patent application No. 61/910,607 filed Dec. 2, 2013. 
    
    
     BACKGROUND OF THE INVENTION 
     Fluid catalytic cracking (FCC) is a vital process used in the refining of petroleum products. The majority of the refineries in use today utilize the FCC process. Fluid catalytic cracking is used to convert the high boiling, high molecular weight hydrocarbon fractions of petroleum crude oils to more valuable gasoline, olefinic gases and other petroleum products. The FCC process vaporizes and breaks the long-chain molecules of the high boiling hydrocarbon liquids into much shorter molecules by contacting the feedstock at elevated temperatures and pressure in the presence of a catalyst, with the majority of the cracking occurring in the vapor phase. Feedstock is thereby converted into gasoline, distillate, and other liquid cracking products as well as lighter gaseous cracking products. 
     The cracking reactions produce carbonaceous material commonly known as coke, which deposits onto the catalyst. These coke deposits quickly reduce the catalyst&#39;s reactivity, requiring the catalyst to be regenerated. Regeneration is accomplished by burning off the coke which restores the catalyst activity. Fluid catalytic cracking can therefore be distinguished by three specific steps: the cracking step in which the hydrocarbons are converted into the lighter products, a stripping step to remove hydrocarbons absorbed on the catalyst, and a regeneration step to remove coke from the catalyst. The regenerated catalyst may then be reused in the cracking step. 
     FCC catalyst, both spent and regenerated, must be periodically sampled in order to monitor and track FCC unit performance. The sampling also allows the evaluation of the characteristics of the circulating equilibrium catalyst. The catalyst sampling information may be used: to adjust fresh catalyst and catalyst additive addition rates, to track the condition of the catalyst (activity, REO, surface area contaminants, etc.), or to monitor coke on the catalyst to track regenerator performance (note that this list is not intended to be an exhaustive list of the information which may be derived from catalyst samples). 
     Catalyst samples are typically extremely hot, often in the range of 800 to 1000° F. for spent catalyst and 1200 to 1400° F. for regenerated catalyst. Sampling catalyst often produces significant amounts of catalyst dust which can be extremely hot, and is a known skin and eye irritant. Further, catalyst sampling lines are prone to pluggage. These factors pose a risk to personnel taking the samples even when protected by the appropriate personal protective equipment (PPE). 
     The current method for obtaining a catalyst sample is a standard pipe, which is sloped at an angle in an attempt to minimize pluggage. The sampling pipe is directly attached to the FCC unit and, when activated, displaces catalyst sample into a desired container. Typically the catalyst is routed into a sample can which is placed in a basket in the top of a large drum, such as a 55 gallon drum known as a sampling drum. The sample can must be elevated to submerge the sample line into the sample can. This technique reduces catalyst contamination during the initial draw but it also limits the ability of the operator to monitor the flow and the level of catalyst in the sample can. Often the sample can over fills resulting in catalyst “splashing” which poses a risk to personnel taking the samples even when protected by the appropriate PPE. Further, if the sampling line is accidently disconnected from the sample can, hot catalyst is sprayed outward. 
     Removing the hot sample can from under the sample pipe presents another risk to the operator because the operator is exposed to the hot catalyst and the hot sample can. Once the catalyst sample is obtained, the sample line must be closed and purged with nitrogen. The current technique results in nitrogen being blown into the top of the collection drum which creates catalyst dust in the immediate area. Further, ambient conditions such as wind, rain or high heat can cause the catalyst dust to cover anything surrounding the sample can. Therefore, there exists a need for an improved and safer catalyst sampling method and apparatus which reduces catalyst dust, catalyst splashing, and user risk. 
     SUMMARY OF THE INVENTION 
     By upgrading the current sampling line to include a cyclone many of the risks may be greatly reduced or eliminated altogether. The cyclone sampler allows the catalyst to be directed straight into a sampling can, virtually eliminating catalyst splashing and allowing the operator to safely monitor the level of the sampling can, and the flow of the catalyst. The cyclone sampler eliminates the need for the sampling line to descend horizontally. Traditionally the sampling line is slopped to allow the catalyst to enter a sampling can and to reduce pluggage. This slope causes the sampling line to enter the sampling can at angle. This angled entry results in increased splashing and partially blocks the view of the user. The cyclone sampler allows the sampling line to be horizontal, from the FCC to the cyclone sampler. The catalyst enters the cyclone sampler and is directed downward, generally at about a 90-degree angle, into the sampling can. This straight approach allows more of the sample to enter the sampling can and reduces splashing over the prior art model, while allowing the user an unobstructed view of the sampling can. 
     The cyclone sampler also allows the operator to use a nitrogen “chaser” further reducing the risk of pluggage in the sample line and cooling the catalyst sample. The nitrogen can be used to purge the sample line, once the sample valve is closed, without spraying the catalyst uncontrolled into the sample can. The chaser is directed into the cyclone sampler and exits into the sampling can at the same 90-degree angle as the catalyst, thus reducing splashing. 
     The cyclone sampler also eliminates operator exposure to catalyst and catalyst dust by containing and directing the catalyst so that catalyst dust is greatly reduced in the area around the sample station. Further, utilizing a cyclone sample allows the catalyst to cool while in the cyclone vessel reducing risk of personnel exposure to 1300° F. catalyst. By utilizing a cyclone sampler, operator safety is increased while the risk of pluggage is reduced. 
     Other objects and advantages of the present invention become apparent to those skilled in the art upon a review of the following detailed description of the preferred embodiments and the accompanying drawings. 
    
    
     
       IN THE DRAWINGS 
         FIG. 1  is a diagram of a prior art FCC unit comprising a reactor and a regenerator. 
         FIG. 2  is a side view of a prior art FCC unit with a sample line. 
         FIG. 3  is a diagram of the FCC unit of the present invention incorporating a cyclone sampler. 
         FIG. 4  is a schematic view of the cyclone sampler seen in  FIG. 3 . 
         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 
     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 . 
     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. 
     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. 
     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. 
     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. 
     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. 
     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.