Submit Search. Successfully reported this slideshow. We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime. Upcoming SlideShare. Like this presentation? Why not share! Embed Size px. Start on. Show related SlideShares at end. WordPress Shortcode. Helena Francis Follow. Published in: Engineering. Full Name Comment goes here. Are you sure you want to Yes No. Naveen Yadav. Show More. The fluid catalytic cracking FCC unit is a major conversion unit present in many refineries throughout the world.
FCC units are highly flexible and able to upgrade feeds comprising many components, ranging from light, sweet hydrotreated vacuum gas oil VGO to heavy, sour residues.
In addition, FCC feed can include heavy streams from other refinery units, such as coker gas oils, as well as low-value slops of ranging composition. In the vast majority of cases, the FCC feed contains a wide range of contaminants, including metals nickel, vanadium, copper, iron, calcium and sodium and heteroatoms sulphur and nitrogen.
The role of the FCC unit is to convert low-value, high molecular weight high boiling point feed to lighter, more valuable products via cleavage of C-C bonds cracking. This is burned in the FCC regenerator, where the heat of combustion is used to provide the energy required to vaporise and crack the feed; the unit is operated in heat balance. Many of the contaminants in the feed end up in the coke being burned in the regenerator.
Their concentration on the catalyst is controlled via catalyst replacement. Some of the feed sulphur- and nitrogen-containing compounds also form coke on the catalyst; these are temporary poisons because they are burned off in the regenerator.
NPRA Q&A-2 CATALYTIC CRACKING RECEIVES HEAVY ATTENTION AT Q&A MEETING
The exact composition of these gases in the flue gas depends upon the detailed reaction conditions in the regenerator. In partial-burn units, much of the carbon is combusted to CO rather than CO2 in order to decrease the heat of combustion and allow the processing of heavier, higher coke-making feeds. Other species are only present at much lower concentrations. Increasing environmental awareness has brought in place stringent regulations to limit emissions of S and N gases to the atmosphere.
There are basically three sources of hydrocarbon into the FCC stripper. Reaction effluent in the interstitial spaces between catalysts. Reaction effluent in the pores of the catalyst.
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Unreacted and unvaporized oil on the catalyst surface and in the catalyst pore. If the stripper outlet vapor contains more than a very small percentage of gasoline on a total sample weight basis, then it is likely that all of the reaction effluent trapped with catalyst does not disengage and flow upward into the reactor. This stripper had no internals of any type and it was clear that some significant portion of reaction effluent flowing to the stripper was reaching the regenerator.
At the opposite end of the spectrum, Unit C contained only 0. Another critical factor in reviewing stripper results is the content of ethane and lighter gas in the stripper vapor. The production of light gases in FCC, especially methane and hydrogen, is recognized as a by-product of thermal cracking.
For these samples, the weight percentage of sample consisting of ethane and lighter gas ranged from a low of 2. The production of light gases in the FCC stripper is believed to result from the thermal decomposition of heavy unvaporized hydrocarbon molecules on the surface of the catalyst along with condensation and polymerization of multi-ring aromatics. Several refineries use an FCC process model to determine optimum operating parameters to maximize profitability and push the unit to multiple constraints. Typical process variables include feed rate, reactor temperature, feed preheat and catalyst activity.
The ability of any model to estimate these optimum conditions is contingent upon its ability to accurately predict the true process response. Unit technology will play a major role in determine yield shifts associated with process changes. A unit with a poor stripper such as unit A above, will have a very different response due to feed preheat changers than a unit with a modern stripper such as unit C.
This is due to the effect of entrained hydrocarbon on delta coke with changers in catalyst circulation. Another example is reactor temperature. Modern rise termination devices have reduced the post-riser contact time and minimized secondary reactions changing the yield response to process variables. The default model was tuned to an open riser termination design that exhibited gasoline overcracking with increasing reactor temperature.
The modern design exhibited less overcracking. The model was tuned to match the commercial data and provide greater confidence in optimizing unit profitability. Another application requiring accurate prediction of process variable effects is the refinery linear program LP.
Most refineries will use the LP to set global operating conditions for the FCC with the process model used to determine location optimums. The LP is also used to evaluate different crudes and feed streams. If the vectors in the LP do not accurately reflect the process, poor economics decisions may be made. Driven by the evolutionary nature of FCC process technology, refiners are continually assessing the performance of the FCC and contemplating implementation of the latest developments.
Reaction effluent testing represents a convenient method for developing the FCC base operating case data by isolating the reactor section yields. This is especially important when modifications are anticipated for the FCC product recovery section. Further, only reaction effluent testing is suitable for exploring conditions at various points in the FCC reaction section where catalyst is present. One recent revamp study was undertaken to determine the impact of upgrading riser termination to one of the advanced designs available.
Reaction effluent testing was performed just before and right after completion of the revamp. Careful planning was undertaken to insure that there were minimal differences in feed quality between the two runs. Key results from the two test runs are presented in Table 4. These results indicate that there was significant yield benefit achieved with the revamp. Accurate yield determination and process variable response are critical to FCC unit optimization.
Reaction Mix Sampling is an efficient tool to define these parameters. The results can be used to tune the FCC process model, update LP vectors, audit revamp or catalyst changes and determine optimum process conditions to maximize unit profitability at multiple constraints. Specific compositions, methods, or embodiments discussed are intended to be only illustrative of the invention disclosed by this specification.
Variation on these compositions, methods, or embodiments are readily apparent to a person of skill in the art based upon the teachings of this specification and are therefore intended to be included as part of the inventions disclosed herein. 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.
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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. A process for controlling on line FCC effluent exhibiting asorption in the near infrared NIR region comprising: a measuring absorbances of the effluent using an NIR spectrometer measuring absorbances at wavelengths within the range of about nm, and outputting an emitted signal indicative of said absorbance;.
The process of claim 1 including the step of using NIR measuring on line to control reaction mixing sampling RMS on line. The process of claim 1 including the step of using NIR measuring on line of reaction effluent to control riser outlet temperature on FCC processing yields. The process of claim 1 including the step of using NIR measuring of reaction effluent to control riser lift velocity. The process of claim 1 including the step of using NIR measuring on line of reactor effluent to control riser lift steam rates to control FCC product yields.
The process of claim 1 including the step of using NIR measuring on line of reactor stripper effluent to control FCC catalyst stripping. The process of claim 1 including the step of using NIR measuring of reaction effluent to provide on-line modeling of FCC processing. The process of claim 1 wherein said absorbances are measured at wavelengths within the range of about nm. The process of claim 1 wherein said absorbances are measured at wavelengths within the range of nm. The process of claim 1 wherein said absorbance is measured in at least one wavelength and includes the steps of: a periodically or continuously outputting a periodic or continuous signal indicative of the intensity of said absorbance in said wavelength, or wavelengths in said two or more bands or a combination of mathematical functions thereof,.
The process of claim 1 wherein the step of controlling on-line allows for real time optimization processing. The process of claim 1 including the steps of: obtaining a first data set of NIR spectroscopic data samples by subjecting the effluent to NIR spectroscopy;. The process of claim 1 including the step of: mathematically converting the signal to an output signal indicative of the parameter.
The process of claim 7 including the steps of: periodically or continuously outputting a periodic or continuous signal indicative of the intensity of the NIR absorbance in the wavelength, or wavelengths in the two or more bands or a combination of mathematical functions thereof,.
- Process Economics Program Report 195.
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The process of claim 1 including the step of using the NIR results in FCC simulation software to control on-line unit yields and qualities. The process of claim 1 which allows sampling of various locations in the reactor such as catalyst stripper vapor, reactor dilute vapor, riser vapor and reactor effluent to quantify yields and optimize the process.
The process of claim 1 which allows an audit of a process or mechanical change on the unit to quantify the magnitude of the change on yields, performance and economics. The process of claim 1 including the step of using NIR measuring on-line of reactor dilute vapors to control riser outlet conditions and vapor quench. The process of claim 3 where yields are used to tune an FCC simulation model and benchmark LP predicted yields.
Method and apparatus for controlling FCC effluent with near-infrared spectroscopy. Method and apparatus for controlling fcc effluent with near-infrared spectroscopy.
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