Abstract:
A fines injection apparatus, a fluid catalytic cracking (FCC) system having a fines injection apparatus, and a method for using the same are provided. In one embodiment, a FCC system includes a FCC unit, a fines collector, and a fines injector coupled to the fines collector for retuning the fines recovered in the fines collector to the FCC unit. In another embodiment, an apparatus for injecting fines into a FCC system includes a fines separator coupled to an effluent stream and an injection apparatus coupled to a regenerator. A conduit is provided for delivering collected fines from the fines separator to the injection apparatus. In yet another embodiment, a method for injecting fines into FCC system includes collecting fines from a waste stream of a FCC system, automatically transferring the collected fines to a fines injection apparatus, and periodically injecting the transferred fines into the FCC system.

Description:
FIELD OF THE INVENTION 
     Embodiments of the invention generally relate to a fluid catalytic cracking system, and more specifically to a fluid catalytic cracking system having a fines addition system. 
     DESCRIPTION OF THE RELATED ART 
       FIG. 1  is a simplified schematic of a conventional fluid catalytic cracking system  130 . The fluid catalytic cracking system  130  generally includes a fluid catalytic cracking (FCC) unit  110  coupled to a catalyst injection system  100 , a petroleum feed stock source  104 , an exhaust system  114  and a distillation system  116 . One or more catalysts from the catalyst injection system  100  and petroleum from the petroleum feed stock source  104  are delivered to the FCC unit  110 . The petroleum and catalysts are reacted in the FCC unit  110  to produce a vapor that is collected and separated into various petrochemical products in the distillation system  116 . The exhaust system  114  is coupled to the FCC unit  110  and is adapted to control and/or monitor the exhausted byproducts of the fluid cracking process. 
     The FCC unit  110  includes a regenerator  150  and a reactor  152 . The reactor  152  primarily houses the catalytic cracking reaction of the petroleum feed stock and delivers the cracked product in vapor form to the distillation system  116 . Spent catalyst from the cracking reaction is transferred from the reactor  152  to the regenerator  150  where the catalyst is rejuvenated by removing coke and other materials. The rejuvenated catalyst is reintroduced into the reactor  152  to continue the petroleum cracking process. By-products from the catalyst rejuvenation are exhausted from the regenerator  150  through an effluent stack of the exhaust system  114 . 
     The catalyst injection system  100  maintains a continuous or semi-continuous addition of fresh catalyst to the catalyst inventory circulating between the regenerator  150  and the reactor  152 . The catalyst injection system  100  includes a main catalyst source  102  and one or more additive sources  106 . The main catalyst source  102  and the additive source  106  are coupled to the FCC unit  110  by a process line  122 . A fluid source, such as a blower or air compressor  108 , is coupled to the process line  122  and provides pressurized fluid, such as air, that is utilized to carry the various powdered catalysts from the sources  102 ,  106  through the process line  122  and into the FCC unit  110 . 
     One or more controllers  120  is/are utilized to control the amounts of catalysts and additives utilized in the FCC unit  110 . Typically, different additives are provided to the FCC unit  110  to control the ratio of product types recovered in the distillation system  116  (i.e., for example, more LPG than gasoline) and to control the composition of emissions passing through the exhaust system  114 , among other process control attributes. As the controller  120  is generally positioned proximate the catalyst sources  106 ,  102  and the FCC unit  110 , the controller  120  is typically housed in an explosion-proof enclosure to prevent spark ignition of gases which may potentially exist on the exterior of the enclosure in a petroleum processing environment. 
     In order to facilitate efficient transfer of the catalyst between the reactor and regenerator, the circulating catalyst must be maintained at a size distribution that facilitates efficient transfer between these vessels. When the size distribution is such that catalyst transfer readily occurs, the catalyst is commonly described as being in a fluidized state. Critical to maintaining the catalyst in the fluidizable state is the presence of a minimum number of small media particles or fines. Generally, the fines have an average particle size of about 30 microns, with the majority of fines having a particle size between 20 and 40 microns, although the size distribution will vary from refinery to refinery. 
     During the course of normal refining, fines may be lost in the product stream, consumed in the FCC unit or entrained with the effluents exiting the regenerator. If enough fines are lost, the circulation rate of catalyst between the reactor and regenerator may decrease, thereby rendering the process unstable or out of balance. As these changes in the dynamic equilibrium force the FCC unit away from its optimal operating limits, the desired product mix and/or effluent composition may not be obtained. As the FCC unit is a major profit center in most refineries, a great deal of time and investment is made by refineries to ensure that the FCC unit is always operating against its operating limits, thereby maximizing profitability. Anything that forces the operation of the FCC unit away from these limits reduces profitability to the detriment of the refiner. Thus, it would be highly desirable to stabilize the FCC operation by ensuring the continuous circulation of catalyst within the FCC unit, thus maintaining the dynamic balance of catalyst in the FCC unit. 
     To mitigate the continual loss of fines, refiners may periodically replenish the fines in the FCC unit. Fines are conventionally added by removing catalyst from one of the catalyst injection systems coupled to the FCC unit, and utilizing the emptied injection system to replenish the number of fines in the system with new (e.g., unused) fines provided by a catalyst vendor. This method is cumbersome for refiners, as an empty catalyst injection system is not always available, and the process operation may be temporarily disoptimized while fines instead of catalyst are in the injection system. 
     Therefore, there is a need for a fluid catalyst cracking unit having a fines addition system. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention generally include a fines addition system, a fluid catalytic cracking (FCC) system having a fines addition system, and a method for using the same. In one embodiment, a FCC system includes a FCC unit, a fines collector for recovering fines leaving the FCC unit, and a fines addition system coupled to the fines collectors for returning the recovered fines to the FCC unit. 
     In another embodiment, an apparatus for injecting fines into a FCC system includes a fines separator coupled to an effluent stream of an FCC unit and a fines addition system coupled to the FCC unit. A conduit is provided for delivering collected fines from the fines separator to the addition system. 
     In yet another embodiment, a method for injecting fines into FCC system includes collecting fines from a waste stream of a FCC system, automatically transferring the collected fines to a fines addition system, and periodically injecting the transferred fines into the FCC system. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a simplified schematic view of a conventional fluid catalytic cracking (FCC) system; 
         FIG. 2  is a simplified schematic diagram of a FCC system having a fines addition system in accordance with one embodiment of the present invention; 
         FIG. 3  is a sectional view of on embodiment of the fines addition system of  FIG. 2 ; and 
         FIG. 4  is a flow diagram of one embodiment of a method of injecting fines in a FCC system. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the FIGS. It is contemplated that features from any one embodiment may be beneficially incorporated in other embodiments without additional recitation. 
     DETAILED DESCRIPTION 
     The invention generally provides a fines addition system, a fluid catalytic cracking (FCC) system having a fines addition system, and a method for injecting fines into a FCC unit. Advantageously, the invention facilitates the addition of fines to a catalyst inventory circulating in the FCC unit, allowing amount of fines present in the FCC unit to be balanced with little or no process disruption, thereby allowing the FCC unit to operate at higher efficiency for longer periods, as compared to conventional practices. 
       FIG. 2  is a simplified schematic of a fluid catalytic cracking system  230  having a fines addition system  240 . The fluid catalytic cracking system  230  generally includes a fluid catalytic cracking (FCC) unit  210  coupled to a catalyst injection system  200  and the fines addition system  240 , a controller  220 , a petroleum feed stock source  204 , a fines recovery system  214  and a distillation system  216 . One or more catalysts from the catalyst injection system  200  and petroleum from the petroleum feed stock source  204  are delivered to the FCC unit  210 . The petroleum and catalysts are reacted in the FCC unit  210  to produce a vapor that is collected and separated into various petrochemical products in the distillation system  216 . 
     The FCC unit  210  includes a regenerator  250  and a reactor  252 , as known in the art. The reactor  252  primarily houses the catalytic cracking reaction of the petroleum feed stock and delivers the cracked product in vapor form to the distillation system  216 . Spent catalyst from the cracking reaction is transferred from the reactor  252  to the regenerator  250 , where the catalyst is rejuvenated by removing coke and other materials. The rejuvenated catalyst is reintroduced into the reactor  252  to continue the petroleum cracking process. By-products from the catalyst rejuvenation process are exhausted from the regenerator  250  through an effluent stack. 
     The catalyst injection system  200  maintains a semi-continuous addition of fresh catalyst to the catalyst inventory circulating between the regenerator  250  and the reactor  252 . The catalyst injection system  200  includes a main catalyst source  202  and one or more additive sources  206 . The main catalyst source  202  and the additive source  206  are coupled to the FCC unit  210  by a process line  222 . A fluid source, such as a blower or air compressor  208 , is coupled to the process line  222  and provides pressurized fluid, such as air, that is utilized to carry the various powdered catalysts from the sources  202 ,  206  through the process line  222  and into the FCC unit  210 . 
     Typically, different additives are specialized catalysts utilized for process control in the FCC unit  210 . For example, additives may be provided from the addition source  206  to the FCC unit  210  to control the ratio of product types recovered in the distillation system  216  (i.e., for example, more LPG than gasoline) and/or to control the composition of emissions passing through an effluent stack  212  of the regenerator  250 , among other process control attributes. The main catalyst source  202  generally delivers a Y-Zeolite containing catalyst, which drives the main cracking process. Examples of catalyst injection systems that may be adapted to benefit the invention are described in U.S. Pat. No. 5,389,236, issued Feb. 14, 1995; U.S. Pat. No. 6,358,401, issued Mar. 19, 2002; U.S. patent application Ser. No. 10/304,670 filed Nov. 2, 2002; U.S. Pat. No. 6,859,759 issued Feb. 22, 2005 U.S. Pat. No. 6,974,659 issued Dec. 13, 2005; U.S. patent application Ser. No. 10/445,543, filed May 27, 2003; and U.S. patent application Ser. No. 10/717,250, filed Nov. 19, 2003, all of which are hereby incorporated by reference in their entireties. Other suitable catalyst injection systems that may be adapted to benefit the invention are available from Intercat Equipment Corporation, located in Sea Girt, N.J., among other manufacturers. 
     The fines recovery system  214  is interfaced with the effluent stack  212  of the regenerator  250  and is adapted to remove fines entrained in the gas stream exiting the regenerator  250  through the stack  212 . In one embodiment, the fines recovery system  214  includes one or more devices suitable for separating fines from the effluent stream. In the embodiment depicted in  FIG. 2 , the fines recovery system  214  includes at least one of a cyclone separator  232  and an electrostatic precipitator  234 . 
     The separated fines are generally collected and transferred from the fines recovery system  214  to the fines injection system  240 . The separated fines may be delivered between the fines recovery system  214  and the fines injection system  240  through a conduit  242 , or may be stored in an intermediate container  246  (shown in phantom  FIG. 2 ) for later delivery to the fines injection system  240 . Since the separated fines are at an elevated temperature when removed from the stack  212 , one or more heat transfer devices (shown in  FIG. 3  and identified by reference numeral  358 ) may be utilized to reduce the temperature of the fines prior to and/or during the delivery to the fines injection system  240 . The heat transfer devices  244  are discussed in further detail below. 
     The controller  220  is utilized to regulate the addition of catalysts and/or additives made by the injection system  200  and addition of fines made by the fines addition system  240 , so that the dynamic equilibrium of catalyst within the FCC unit  210 , which is driven at least in part by the size distribution of catalyst (such as the amount of fines present in the catalyst inventory of the FCC unit  210 ), may be maintained. The fines injection system  240  is configured to provide a metric of fines added to the FCC unit  210 . This metric may be provided to the controller  220  and utilized to balance the amount of fines within the FCC unit  210  to ensure efficient movement of catalyst between the regenerator  250  and reactor  252 , as further described below. 
     As the controller  220  is generally positioned proximate the FCC unit  210 , the controller  220  is typically housed in an explosion-proof enclosure to prevent spark ignition of gases which may potentially exist on the exterior of the enclosure in a petroleum processing environment. The controller  220  may be equipped with remote access capability so that activity may be monitored from other locations, such as operations center or by catalyst suppliers. A controller having such capability is described in U.S. Pat. No. 6,859,759, issued Feb. 22, 2005 and U.S. patent application Ser. No. 10/304,670, filed Nov. 26, 2002, both of which are hereby incorporated by reference in their entireties. It is contemplated that suitable controllers may have alternative configurations. 
     The fines injection system  240  generally includes a pressure vessel  258 , a pressure control system  260 , a metering device  262  and at least one sensor  264  suitable for providing a metric indicative of fines injected into the FCC unit  210  through the fines injection system  240 . In the embodiment depicted in  FIG. 2 , the fines injection system  240  includes a first sensor  270  configured to detect when a level of catalyst within the fines injection system  240  exceeds an upper and/or lower threshold. The first sensor  270  may be a differential pressure measurement device, optical transducer, a capacitance device, a sonic transducer or other device suitable for providing information from which the level or volume of fines disposed in the storage vessel  258  of the fines injection system  240  may be resolved. For example, if the first sensor  270  provides an indication to the controller  220  that the fines level (or amount) is greater than a predetermined quantity, the controller  220  may initiate a fines injection by the fines injection system  240 . 
     In another embodiment, the sensor  264  may be a second sensor  272  which may be utilized to determine the weight of fines within the storage vessel  258  and/or added to the FCC unit  210 . In the embodiment depicted in  FIG. 2 , the second sensor  272  is a plurality of load cells adapted to provide a metric indicative of the weight of fines in and/or passing through the storage vessel  258 . The load cells are respectively coupled to a plurality of legs  274  that support the storage vessel  258  above a surface  276 , such as a concrete pad or structural member. Each of the legs  274  has one load cell (sensor  272 ) coupled thereto. The controller  220  receives the outputs of the load cells and utilizes sequential data samples obtained therefrom to resolve the net amount of fines added to the FCC unit  210  after each addition cycle. The amount of fines present within the storage vessel  258  may also be determined as needed utilizing the load cells. The amount of fines added to the FCC unit  210  may be determined by either weight lost or weight gained computations utilizing the data provided by the load cells. Additionally, the net amount of fines added over the course of the production cycle may be monitored so that variations in the amount of fines added may be detected, which are indicative of the amount of fines lost in the system, and conversely, the amount of fines in the catalyst inventory present in the FCC unit  210 . 
     Alternatively, the sensor  264  for detecting a metric indicative of the amount of fines in the storage vessel  258  may be a third sensor  278  that is adapted to detect a flow of fines through the fines injection system  240  or other conduit for moving fines. The flow sensor (third sensor  278 ) is adapted to detect the flow of fines through one of the components of the fines addition system  240 . The flow sensor may be a contact or non-contact device and may be mounted to the conduit  254 , the storage vessel  258 , the metering device  262  or a conduit  256  coupling the storage vessel  258  to the FCC unit  210 . In the embodiment depicted in  FIG. 2 , the flow sensor may be a sonic flow meter or capacitance device adapted to detect the rate of entrained particles (i.e., fines) moving through the conduit  254 , within the storage vessel  258  and/or the conduit  256  exiting the system  240 . 
     The metering device  262  is disposed in the conduit  256  to control the flow of fines into the conduit  256  and ultimately to the FCC unit  210  from the fines addition system  240 . The metering device  262  may be an on/off valve, pump, displacement device or other device suitable for regulating the amount of fines passing from the storage vessel  258  and into the FCC unit  210 . Other suitable metering devices include, but are not limited to, gear pumps, positive displacement devices, valves and the like. One suitable metering device  262  is a rotating shear disk valve, available from the Everlasting Valve Company, located in South Plainfield, N.J. 
     The metering device  262  may determine the amount of fines by weight, volume, timed dispense or by other manners. The fines addition rate will vary according to the size of the FCC unit, and the degree of fines loss that particular refinery is experiencing. Depending on the fines requirements of the FCC unit  210 , the metering device  262  may be configured to inject about 0.5 to about 6 tons per day of fines into FCC unit  210  without interruption of processing. Of course, systems may be configured to provide larger or smaller amounts. The metering device  262  typically injects fines into the FCC unit  210  periodically over the course of a planned production cycle, typically  24  hours, in multiple shots of predetermined amounts spaced over the production cycle. However, fines may also be added to the FCC unit  210  in an “as needed” basis. 
       FIG. 3  depicts a larger schematic view of one embodiment of the fines addition system  240 . The storage vessel  258  of the fines addition system  240  is typically a metal container suitable for use at elevated pressures having a first fill port  314  and a first discharge port  316 . The first discharge port  316  is positioned at or near a bottom of the storage vessel  258  and has the metering device  262  coupled thereto. Optionally, a second discharge port  318  may be positioned at or near a bottom of the storage vessel  258  to allow fines to be removed from the storage vessel  258  while bypassing the metering device  262 . The second discharge port  318  may be coupled to a port  320  formed in the process line  222  or conduit  256 , thereby allowing fines exiting the storage vessel  258  through the second discharge port  318  to enter the FCC unit  210  through the process line  222  in the event catalyst flow is prevented through the first discharge port  318 . The second discharge port  318  may also be utilized to empty fines from the storage vessel  258  into a container  340 . This feature allows the material present in the fines injection system  240  to be switched from fines to catalyst in emergency situations, and back to fines with minimal process disruption or effort by the refiner. 
     The pressure control system  260  is coupled to a pressure port  326  formed in the storage vessel  258  and controls the pressure within the storage vessel  258 . The pressure control system  260  selectively pressurizes the storage vessel  258  to between about 5 to about 60 pounds per square inch (about 0.35 to about 4.2 kg/cm 2 ) during fines addition operations. In operation, the pressure control system  260  provides air at about 60 psi (about 4.2 kg/cm 2 ) into the interior of the storage vessel  258  to cause fines to flow from the storage vessel  258  through the actuated metering device  262  and into the FCC unit  210 . 
     In one embodiment, the pressure control system  260  is configured to provide plant air or other gas into the storage vessel  258 . Alternatively, the pressure control system  260  may utilize gas provided by the blower  208 . 
     The air or other gas may also be utilized to fluidize, aerate and/or otherwise cool the fines disposed in the storage vessel  258 . The pressure control system  260  may additionally be configured to control the flow of the air or other gas provided to the storage vessel  258 , thereby providing the ability to optimize cooling of the collected fines and control environmental conditions within the storage vessel  258 . Isolation valves  308  and check valves  322  are provided to selectively direct flow through the pressure control system  260 . Other control valves  308  are shown to regulate flow on other conduits shown in  FIG. 3 . 
     In the embodiment depicted in  FIG. 3 , the pressure control system  260  includes a pressure meter  350  and a pressure transmitter  352  that are arranged to detect a metric of pressure within the storage vessel  258 . The pressure transmitter  352  includes an output that is coupled to the controller  220  such that real time pressure information is available for process control. A relief valve  326  is coupled to the storage vessel  258  to prevent over pressurization. 
     The system  260  may intermittently vent the storage vessel  258  to about atmospheric pressure to accommodate filling the storage vessel  258  with fines from the fines recovery system  214  or other source. For example, the pressure within the storage vessel  258  vented and/or reduced to allow fines to be added to the storage vessel  258  through a second fill port  312 , for example from a tote  302  or other container (shown in phantom). 
     The pressure control system  260  vents the storage vessel  258  through a vent port  310 . The vent port  310  is coupled to the regenerator&#39;s exhaust stack  212  or other suitable effluent stack through a first fines removal device  380  such as a cyclone separator or filter. A control valve  308  is provided to selectively regulate (or prevent) flow through the vent port  310  from the storage vessel  258 . 
     The first fines removal device  380  is utilized to minimize fines escaping from the storage vessel  258  during venting. Fines recovered by the first fines removal device  380  may be transferred through a return conduit  382  to the storage vessel  258 , or alternately transferred to a container  354  for later addition to the storage vessel  258  or disposal. An eductor  332  or other vacuum source is provided between the first fines removal device  380  and the stack  212  to pull a vacuum across the first fines removal device  380  such that fines, entrained with the gases vented from the storage vessel  258 , do not settle out and obstruct the conduits coupling the first fines removal device  380  to the storage vessel  258 . 
     A second first fines removal device  384  may be disposed between the storage vessel  258  and the first fines removal device  380  to separate larger particulates from the vent stream. The second first fines removal device  384  may be a cyclone separator or filter. Separated particulates are returned from the second first fines removal device  384  to the storage vessel  258  through a return port  370  formed in the top of the storage vessel  258 . 
     A flow indicator  390  may be positioned between the storage vessel  258  and the metering device  262  to provide a metric indicative that fines are flowing from the storage vessel  258 . In one embodiment, the flow indicator  390  may be a sight glass. A control valve  308  may be positioned between the storage vessel  258  and the metering device  262  to allow the flow indicator  390  to be serviced. Other flow indicators  390  and control valves  308  are positioned in other locations beneficial to the operation of the system  240 . For examples, control valves  308  are positioned between the storage vessel  258 , metering device  262  and fines recovery system  214 . These control valves  308  are interlocked to prevent simultaneous opening which could disrupt the planned flow of fines within the system  240 . Other control valves  308  are not be discussed in further detail for the sake of brevity. 
     Due to the high temperature of the fines exiting the exhaust stream, one or more heat dissipaters  358  are provided to cool the fines before entering and/or while in the fines addition system  240 . The heat dissipaters  358  may be coupled to or positioned approximate to the conduit  254  between the fines recovery system  214  and the storage vessel  258  and/or the container  246 . The heat dissipater  358  may also be an integral part of the conduit  254 . The heat dissipater  358  is configured to extract heat from the fines within conduit  254 , thereby reducing the temperature of the fines flowing from the regenerator  250  to the fines addition system  240 . In another embodiment, the conduit  254  may be coiled or define a torturous path such that the heat dissipater  358  may be interfaced with a greater length of conduit than if the conduit was routed in a straight line path, thereby improving the amount of heat transferred therebetween. 
     The heat dissipater  358  may also include one or more temperature regulating features. For example, the heat dissipater  358  may include heat transfer fins  364 . In another embodiment, the heat dissipater  358  may include one or more conduits  362  coupled to a fluid source  360  through which a heat transfer fluid is flowed. By reducing the temperature of fines being collected from the effluent stream of the regenerator  250 , the design constraint of the fines addition system  240  may be relaxed accordingly with the reduction in catalyst temperature entering the storage vessel  258 . 
     Similarly, the storage vessel  258  may also be equipped with a thermal regulating device  368  to reduce the temperature of the storage vessel  258 . The thermal regulating device  368  may be configured similar to the heat dissipater  358  described above. For example, the thermal regulating device  358  may include heat transfer fins  364 . In another embodiment, the thermal regulating device  358  may include one or more conduits  362  coupled to a fluid source  360  through which a heat transfer fluid is flowed. 
     The storage vessel  258  may alternatively and/or additionally be cooled as described above by providing fluid from the pressure control system  260  into the storage vessel  258 . The control valve  308  may also be periodically opened to allow heated gases disposed on the interior volume of the storage vessel  258  to be removed and replaced by cooler gas provided from the pressure control system  260 . 
     The temperature of the gas and/or fines entering vessel  258  may be monitored using a sensor  366 . The sensor  366  is coupled to the vessel  258  or to the first fill port  314 . If the controller  220  determines, in response to a metric of temperature provided by the sensor  366 , that the temperature of the gas and/or fines entering the vessel exceed a predefined limit, then a remedial action may be initiated. For example, remedial actions may include at least one of shutting off the flow into the storage vessel  258  to allow the system  240  to cool before restarting, emptying fines from vessel  258  using the regulating device  262  or port  318 , increasing the heat extraction rate of the heat dissipater  368 , flowing air into the vessel  258  from the one of the ports (such as the port  318  formed in the bottom of the vessel), or adding an extra flow of cold air to the fines leaving the regenerator to cool it down through a port  386  formed in the conduit  254 . 
     Returning to  FIG. 2 , the controller  220  is provided to control the function of at least the fines addition system  240 . The controller  220  may be any suitable logic device for controlling the operation of the fines addition system  240 . The controller  220  generally includes memory  224 , support circuits  226  and a central processing unit (CPU)  228 , as is known. 
     In one embodiment, the controller  220  is a programmable logic controller (PLC), such as those available from GE Fanuc. However, from the disclosure herein, those skilled in the art will realize that other controllers such as microcontrollers, microprocessors, programmable gate arrays, and application specific integrated circuits (ASICS) may be used to perform the controlling functions of the controller  220 . It is contemplated that the injection system  200  and the fines addition system  240  may have separate controllers, which may, or may not, be linked. 
     The controller  220  is coupled to the various support circuits  226  that provide various signals to the controller  220 . These support circuits  226  may include power supplies, clocks, input and output interface circuits and the like. Other support circuits couple to the temperature sensor  366 , the sensors  264 , metering device  262 , isolation valves  308 , the pressure control system  260  and the like, to the controller  220 . 
     The controller  220  is utilized to cause the fines addition system to perform a sequence of process steps, such as an injection method  400  described below with reference to  FIG. 4 . The method  400  may be stored within the memory  224 , or may be accessed by the controller  220  from another memory source, local or remote. 
       FIG. 4  is flow diagram of one embodiment of a method  400  for adding fines to a FCC unit. The method  400  begins at step  402  providing fines to the fines addition system  240 . In one embodiment, fines collected by the fines recovery system  214  from the effluent exiting the regenerator  250  are provided to the storage vessel  258 . The fines may be provided directly, or temporarily stored in the container  246 . Alternatively, or in addition to the recovered fines collected by the fines recovery system  214 , new fines may be provided from another source, such as a tote  302 . The tote  302  may contain new fines that have not been used in the FCC unit  210 , or fines recovered from another FCC unit. The fines for the tote  302 , or tote  302  containing fines, may be provided from a catalyst vendor, other refiner or other refinery. 
     At step  404 , fines are injected into the FCC unit  210  from the fines addition system  240 . During the fines injection step  404 , a metric indicative of the amount of fines added to the FCC unit  210  are obtained using the sensor  264 . The metric of fines addition may be attained in the form of a weight, volume and/or rate of fines added to the FCC unit  210 , or by other suitable method. 
     The controller  220  is configured to determine the amount of fines added to FCC unit  210  during each addition cycle. The controller  220  may store addition information to memory  224 , or export the information to another device, such as a control room computer at the refinery or to a remote device, such as a computer at the fines vendor via modem, wireless communication, land line or other communications protocol. 
     Optionally, the method  400  may continue to provide information regarding processing. In one embodiment, an amount of fines lost from and/or present in the catalyst inventory of the FCC unit  210  is determined at step  406 . The amount of fines lost/present may be determined by utilizing the amount of catalyst and fines being added to the FCC unit  210  by the catalyst injection system  200  and the fines injection system  240  compensated with an amount of fines consumed in the FCC unit  210  and/or entrained on the product stream. The amount of fines consumed in the FCC unit  210  and/or entrained on the product stream may be measured, calculated, estimated or approximated. The amount of fines added to the FCC unit  210  by the fines injection system  240  may also be correlated to amount of fines in the effluent stream. The amount of new catalyst added from the container  302  to fines addition system  240  must also be factored when determining the fines inventory of the FCC unit  210 . Thus, from this information, the total amount of fines lost from/present in the FCC unit  210  may be resolved. 
     At step  408 , the amount of fines in or lost the FCC unit  210  is compared against a threshold value or process window. If the amount of fines is outside of a predefined process window (or exceeds the threshold), appropriate fines additions (or withdrawals) are made at step  410 . If the amount of fines needed to return to a process state within the process window exceeds an amount of fines in the fines addition system  240  collected from the fines recovery system  214 , the deficient amount of fines may be provided in the form of new fines (e.g., make-up fines) entering the fines addition system  240  from the container  302 . The controller  220  may monitor the amount of fines lost and/or required from the container  302  such that the refiner may determine an amount of make-up fines needed on site, and to schedule make-up fines replenishment shipments from a vendor to ensure uninterrupted processing. Information regarding the amount of fines circulating in the FCC unit  230  may also be provided to the controller  220  as the results of an laboratory or other analysis of a representative catalyst sample, which may be utilized to determine the fines content and tune the fines addition calculation. 
     This cycle of monitoring the amount of catalyst is repeated in order to maintain the dynamic equilibrium of fines in the FCC unit. Advantageously, this allows the FCC unit to continue operating at or near processing limits with minimal fluctuation, thereby providing the desired product mix and emissions composition with minimal dis-optimisation, thereby maximizing the profitability of the FCC system refiner. 
     Although the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise other varied embodiments that still incorporate the teachings and do not depart from the scope and spirit of the invention.