Fluid catalytic cracking system with fines addition system

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.

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. 1is a simplified schematic of a conventional fluid catalytic cracking system130. The fluid catalytic cracking system130generally includes a fluid catalytic cracking (FCC) unit110coupled to a catalyst injection system100, a petroleum feed stock source104, an exhaust system114and a distillation system116. One or more catalysts from the catalyst injection system100and petroleum from the petroleum feed stock source104are delivered to the FCC unit110. The petroleum and catalysts are reacted in the FCC unit110to produce a vapor that is collected and separated into various petrochemical products in the distillation system116. The exhaust system114is coupled to the FCC unit110and is adapted to control and/or monitor the exhausted byproducts of the fluid cracking process.

The FCC unit110includes a regenerator150and a reactor152. The reactor152primarily houses the catalytic cracking reaction of the petroleum feed stock and delivers the cracked product in vapor form to the distillation system116. Spent catalyst from the cracking reaction is transferred from the reactor152to the regenerator150where the catalyst is rejuvenated by removing coke and other materials. The rejuvenated catalyst is reintroduced into the reactor152to continue the petroleum cracking process. By-products from the catalyst rejuvenation are exhausted from the regenerator150through an effluent stack of the exhaust system114.

The catalyst injection system100maintains a continuous or semi-continuous addition of fresh catalyst to the catalyst inventory circulating between the regenerator150and the reactor152. The catalyst injection system100includes a main catalyst source102and one or more additive sources106. The main catalyst source102and the additive source106are coupled to the FCC unit110by a process line122. A fluid source, such as a blower or air compressor108, is coupled to the process line122and provides pressurized fluid, such as air, that is utilized to carry the various powdered catalysts from the sources102,106through the process line122and into the FCC unit110.

One or more controllers120is/are utilized to control the amounts of catalysts and additives utilized in the FCC unit110. Typically, different additives are provided to the FCC unit110to control the ratio of product types recovered in the distillation system116(i.e., for example, more LPG than gasoline) and to control the composition of emissions passing through the exhaust system114, among other process control attributes. As the controller120is generally positioned proximate the catalyst sources106,102and the FCC unit110, the controller120is 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.

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. 2is a simplified schematic of a fluid catalytic cracking system230having a fines addition system240. The fluid catalytic cracking system230generally includes a fluid catalytic cracking (FCC) unit210coupled to a catalyst injection system200and the fines addition system240, a controller220, a petroleum feed stock source204, a fines recovery system214and a distillation system216. One or more catalysts from the catalyst injection system200and petroleum from the petroleum feed stock source204are delivered to the FCC unit210. The petroleum and catalysts are reacted in the FCC unit210to produce a vapor that is collected and separated into various petrochemical products in the distillation system216.

The FCC unit210includes a regenerator250and a reactor252, as known in the art. The reactor252primarily houses the catalytic cracking reaction of the petroleum feed stock and delivers the cracked product in vapor form to the distillation system216. Spent catalyst from the cracking reaction is transferred from the reactor252to the regenerator250, where the catalyst is rejuvenated by removing coke and other materials. The rejuvenated catalyst is reintroduced into the reactor252to continue the petroleum cracking process. By-products from the catalyst rejuvenation process are exhausted from the regenerator250through an effluent stack.

The catalyst injection system200maintains a semi-continuous addition of fresh catalyst to the catalyst inventory circulating between the regenerator250and the reactor252. The catalyst injection system200includes a main catalyst source202and one or more additive sources206. The main catalyst source202and the additive source206are coupled to the FCC unit210by a process line222. A fluid source, such as a blower or air compressor208, is coupled to the process line222and provides pressurized fluid, such as air, that is utilized to carry the various powdered catalysts from the sources202,206through the process line222and into the FCC unit210.

Typically, different additives are specialized catalysts utilized for process control in the FCC unit210. For example, additives may be provided from the addition source206to the FCC unit210to control the ratio of product types recovered in the distillation system216(i.e., for example, more LPG than gasoline) and/or to control the composition of emissions passing through an effluent stack212of the regenerator250, among other process control attributes. The main catalyst source202generally 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 system214is interfaced with the effluent stack212of the regenerator250and is adapted to remove fines entrained in the gas stream exiting the regenerator250through the stack212. In one embodiment, the fines recovery system214includes one or more devices suitable for separating fines from the effluent stream. In the embodiment depicted inFIG. 2, the fines recovery system214includes at least one of a cyclone separator232and an electrostatic precipitator234.

The separated fines are generally collected and transferred from the fines recovery system214to the fines injection system240. The separated fines may be delivered between the fines recovery system214and the fines injection system240through a conduit242, or may be stored in an intermediate container246(shown in phantomFIG. 2) for later delivery to the fines injection system240. Since the separated fines are at an elevated temperature when removed from the stack212, one or more heat transfer devices (shown inFIG. 3and identified by reference numeral358) may be utilized to reduce the temperature of the fines prior to and/or during the delivery to the fines injection system240. The heat transfer devices244are discussed in further detail below.

The controller220is utilized to regulate the addition of catalysts and/or additives made by the injection system200and addition of fines made by the fines addition system240, so that the dynamic equilibrium of catalyst within the FCC unit210, 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 unit210), may be maintained. The fines injection system240is configured to provide a metric of fines added to the FCC unit210. This metric may be provided to the controller220and utilized to balance the amount of fines within the FCC unit210to ensure efficient movement of catalyst between the regenerator250and reactor252, as further described below.

As the controller220is generally positioned proximate the FCC unit210, the controller220is 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 controller220may 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 system240generally includes a pressure vessel258, a pressure control system260, a metering device262and at least one sensor264suitable for providing a metric indicative of fines injected into the FCC unit210through the fines injection system240. In the embodiment depicted inFIG. 2, the fines injection system240includes a first sensor270configured to detect when a level of catalyst within the fines injection system240exceeds an upper and/or lower threshold. The first sensor270may 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 vessel258of the fines injection system240may be resolved. For example, if the first sensor270provides an indication to the controller220that the fines level (or amount) is greater than a predetermined quantity, the controller220may initiate a fines injection by the fines injection system240.

In another embodiment, the sensor264may be a second sensor272which may be utilized to determine the weight of fines within the storage vessel258and/or added to the FCC unit210. In the embodiment depicted inFIG. 2, the second sensor272is a plurality of load cells adapted to provide a metric indicative of the weight of fines in and/or passing through the storage vessel258. The load cells are respectively coupled to a plurality of legs274that support the storage vessel258above a surface276, such as a concrete pad or structural member. Each of the legs274has one load cell (sensor272) coupled thereto. The controller220receives the outputs of the load cells and utilizes sequential data samples obtained therefrom to resolve the net amount of fines added to the FCC unit210after each addition cycle. The amount of fines present within the storage vessel258may also be determined as needed utilizing the load cells. The amount of fines added to the FCC unit210may 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 unit210.

Alternatively, the sensor264for detecting a metric indicative of the amount of fines in the storage vessel258may be a third sensor278that is adapted to detect a flow of fines through the fines injection system240or other conduit for moving fines. The flow sensor (third sensor278) is adapted to detect the flow of fines through one of the components of the fines addition system240. The flow sensor may be a contact or non-contact device and may be mounted to the conduit254, the storage vessel258, the metering device262or a conduit256coupling the storage vessel258to the FCC unit210. In the embodiment depicted inFIG. 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 conduit254, within the storage vessel258and/or the conduit256exiting the system240.

The metering device262is disposed in the conduit256to control the flow of fines into the conduit256and ultimately to the FCC unit210from the fines addition system240. The metering device262may be an on/off valve, pump, displacement device or other device suitable for regulating the amount of fines passing from the storage vessel258and into the FCC unit210. Other suitable metering devices include, but are not limited to, gear pumps, positive displacement devices, valves and the like. One suitable metering device262is a rotating shear disk valve, available from the Everlasting Valve Company, located in South Plainfield, N.J.

The metering device262may 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 unit210, the metering device262may be configured to inject about 0.5 to about 6 tons per day of fines into FCC unit210without interruption of processing. Of course, systems may be configured to provide larger or smaller amounts. The metering device262typically injects fines into the FCC unit210periodically over the course of a planned production cycle, typically24hours, in multiple shots of predetermined amounts spaced over the production cycle. However, fines may also be added to the FCC unit210in an “as needed” basis.

FIG. 3depicts a larger schematic view of one embodiment of the fines addition system240. The storage vessel258of the fines addition system240is typically a metal container suitable for use at elevated pressures having a first fill port314and a first discharge port316. The first discharge port316is positioned at or near a bottom of the storage vessel258and has the metering device262coupled thereto. Optionally, a second discharge port318may be positioned at or near a bottom of the storage vessel258to allow fines to be removed from the storage vessel258while bypassing the metering device262. The second discharge port318may be coupled to a port320formed in the process line222or conduit256, thereby allowing fines exiting the storage vessel258through the second discharge port318to enter the FCC unit210through the process line222in the event catalyst flow is prevented through the first discharge port318. The second discharge port318may also be utilized to empty fines from the storage vessel258into a container340. This feature allows the material present in the fines injection system240to 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 system260is coupled to a pressure port326formed in the storage vessel258and controls the pressure within the storage vessel258. The pressure control system260selectively pressurizes the storage vessel258to between about 5 to about 60 pounds per square inch (about 0.35 to about 4.2 kg/cm2) during fines addition operations. In operation, the pressure control system260provides air at about 60 psi (about 4.2 kg/cm2) into the interior of the storage vessel258to cause fines to flow from the storage vessel258through the actuated metering device262and into the FCC unit210.

In one embodiment, the pressure control system260is configured to provide plant air or other gas into the storage vessel258. Alternatively, the pressure control system260may utilize gas provided by the blower208.

The air or other gas may also be utilized to fluidize, aerate and/or otherwise cool the fines disposed in the storage vessel258. The pressure control system260may additionally be configured to control the flow of the air or other gas provided to the storage vessel258, thereby providing the ability to optimize cooling of the collected fines and control environmental conditions within the storage vessel258. Isolation valves308and check valves322are provided to selectively direct flow through the pressure control system260. Other control valves308are shown to regulate flow on other conduits shown inFIG. 3.

In the embodiment depicted inFIG. 3, the pressure control system260includes a pressure meter350and a pressure transmitter352that are arranged to detect a metric of pressure within the storage vessel258. The pressure transmitter352includes an output that is coupled to the controller220such that real time pressure information is available for process control. A relief valve326is coupled to the storage vessel258to prevent over pressurization.

The system260may intermittently vent the storage vessel258to about atmospheric pressure to accommodate filling the storage vessel258with fines from the fines recovery system214or other source. For example, the pressure within the storage vessel258vented and/or reduced to allow fines to be added to the storage vessel258through a second fill port312, for example from a tote302or other container (shown in phantom).

The pressure control system260vents the storage vessel258through a vent port310. The vent port310is coupled to the regenerator's exhaust stack212or other suitable effluent stack through a first fines removal device380such as a cyclone separator or filter. A control valve308is provided to selectively regulate (or prevent) flow through the vent port310from the storage vessel258.

The first fines removal device380is utilized to minimize fines escaping from the storage vessel258during venting. Fines recovered by the first fines removal device380may be transferred through a return conduit382to the storage vessel258, or alternately transferred to a container354for later addition to the storage vessel258or disposal. An eductor332or other vacuum source is provided between the first fines removal device380and the stack212to pull a vacuum across the first fines removal device380such that fines, entrained with the gases vented from the storage vessel258, do not settle out and obstruct the conduits coupling the first fines removal device380to the storage vessel258.

A second first fines removal device384may be disposed between the storage vessel258and the first fines removal device380to separate larger particulates from the vent stream. The second first fines removal device384may be a cyclone separator or filter. Separated particulates are returned from the second first fines removal device384to the storage vessel258through a return port370formed in the top of the storage vessel258.

A flow indicator390may be positioned between the storage vessel258and the metering device262to provide a metric indicative that fines are flowing from the storage vessel258. In one embodiment, the flow indicator390may be a sight glass. A control valve308may be positioned between the storage vessel258and the metering device262to allow the flow indicator390to be serviced. Other flow indicators390and control valves308are positioned in other locations beneficial to the operation of the system240. For examples, control valves308are positioned between the storage vessel258, metering device262and fines recovery system214. These control valves308are interlocked to prevent simultaneous opening which could disrupt the planned flow of fines within the system240. Other control valves308are 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 dissipaters358are provided to cool the fines before entering and/or while in the fines addition system240. The heat dissipaters358may be coupled to or positioned approximate to the conduit254between the fines recovery system214and the storage vessel258and/or the container246. The heat dissipater358may also be an integral part of the conduit254. The heat dissipater358is configured to extract heat from the fines within conduit254, thereby reducing the temperature of the fines flowing from the regenerator250to the fines addition system240. In another embodiment, the conduit254may be coiled or define a torturous path such that the heat dissipater358may 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 dissipater358may also include one or more temperature regulating features. For example, the heat dissipater358may include heat transfer fins364. In another embodiment, the heat dissipater358may include one or more conduits362coupled to a fluid source360through which a heat transfer fluid is flowed. By reducing the temperature of fines being collected from the effluent stream of the regenerator250, the design constraint of the fines addition system240may be relaxed accordingly with the reduction in catalyst temperature entering the storage vessel258.

Similarly, the storage vessel258may also be equipped with a thermal regulating device368to reduce the temperature of the storage vessel258. The thermal regulating device368may be configured similar to the heat dissipater358described above. For example, the thermal regulating device358may include heat transfer fins364. In another embodiment, the thermal regulating device358may include one or more conduits362coupled to a fluid source360through which a heat transfer fluid is flowed.

The storage vessel258may alternatively and/or additionally be cooled as described above by providing fluid from the pressure control system260into the storage vessel258. The control valve308may also be periodically opened to allow heated gases disposed on the interior volume of the storage vessel258to be removed and replaced by cooler gas provided from the pressure control system260.

The temperature of the gas and/or fines entering vessel258may be monitored using a sensor366. The sensor366is coupled to the vessel258or to the first fill port314. If the controller220determines, in response to a metric of temperature provided by the sensor366, 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 vessel258to allow the system240to cool before restarting, emptying fines from vessel258using the regulating device262or port318, increasing the heat extraction rate of the heat dissipater368, flowing air into the vessel258from the one of the ports (such as the port318formed 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 port386formed in the conduit254.

Returning toFIG. 2, the controller220is provided to control the function of at least the fines addition system240. The controller220may be any suitable logic device for controlling the operation of the fines addition system240. The controller220generally includes memory224, support circuits226and a central processing unit (CPU)228, as is known.

In one embodiment, the controller220is 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 controller220. It is contemplated that the injection system200and the fines addition system240may have separate controllers, which may, or may not, be linked.

The controller220is coupled to the various support circuits226that provide various signals to the controller220. These support circuits226may include power supplies, clocks, input and output interface circuits and the like. Other support circuits couple to the temperature sensor366, the sensors264, metering device262, isolation valves308, the pressure control system260and the like, to the controller220.

The controller220is utilized to cause the fines addition system to perform a sequence of process steps, such as an injection method400described below with reference toFIG. 4. The method400may be stored within the memory224, or may be accessed by the controller220from another memory source, local or remote.

FIG. 4is flow diagram of one embodiment of a method400for adding fines to a FCC unit. The method400begins at step402providing fines to the fines addition system240. In one embodiment, fines collected by the fines recovery system214from the effluent exiting the regenerator250are provided to the storage vessel258. The fines may be provided directly, or temporarily stored in the container246. Alternatively, or in addition to the recovered fines collected by the fines recovery system214, new fines may be provided from another source, such as a tote302. The tote302may contain new fines that have not been used in the FCC unit210, or fines recovered from another FCC unit. The fines for the tote302, or tote302containing fines, may be provided from a catalyst vendor, other refiner or other refinery.

At step404, fines are injected into the FCC unit210from the fines addition system240. During the fines injection step404, a metric indicative of the amount of fines added to the FCC unit210are obtained using the sensor264. The metric of fines addition may be attained in the form of a weight, volume and/or rate of fines added to the FCC unit210, or by other suitable method.

The controller220is configured to determine the amount of fines added to FCC unit210during each addition cycle. The controller220may store addition information to memory224, 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 method400may 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 unit210is determined at step406. The amount of fines lost/present may be determined by utilizing the amount of catalyst and fines being added to the FCC unit210by the catalyst injection system200and the fines injection system240compensated with an amount of fines consumed in the FCC unit210and/or entrained on the product stream. The amount of fines consumed in the FCC unit210and/or entrained on the product stream may be measured, calculated, estimated or approximated. The amount of fines added to the FCC unit210by the fines injection system240may also be correlated to amount of fines in the effluent stream. The amount of new catalyst added from the container302to fines addition system240must also be factored when determining the fines inventory of the FCC unit210. Thus, from this information, the total amount of fines lost from/present in the FCC unit210may be resolved.

At step408, the amount of fines in or lost the FCC unit210is 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 step410. 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 system240collected from the fines recovery system214, the deficient amount of fines may be provided in the form of new fines (e.g., make-up fines) entering the fines addition system240from the container302. The controller220may monitor the amount of fines lost and/or required from the container302such 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 unit230may also be provided to the controller220as 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.