FCC regenerator

A schematic diagram of a typical industrial FCC regenerator is shown in Fig. 9.23. The spent catalyst particles are circulated through the regenerator. The orientation, size and location of the spent catalyst distributor are important parameters controlling solids mixing. The regenerated catalyst is withdrawn from the outlet located at the 

FIGURE 9.21 Typical predicted results for the loop reactor (excluding vapor space), (a) Vector plots (liquid phase), (b) contours of gas volume fraction (legend not shown due to confidentiality constraints). Reproduced in colour plate section between pages 210 and 211. 

FIGURE 9.23 Schematic diagram of typical industrial FCC regenerator. 

Global Regenerator Mode) Mixing cell framework. 

---

Example 1 shows the expander inlet conditions typical of past FCC applications with an expander inlet pressure of 30 psia and inlet temperature of 1,200°F. Example 2 shows the conditions prevalent in more recent FCC regenerator technology, where most of the CO is... 

FCC regeneration can be further subdivided into low, intermediate, and high temperature regeneration. In low temperature regeneration (about I,190°F or 640°C), complete combustion is impossible. One of the characteristics of low temperature regeneration is that at 1,190°F, all three components (Oj, CO, and COj) are present in the flue gas at... 

ERA S New Source Performance Standards (NSPS) for Gaseous Emissions from the FCC Regenerators... 

Johnson, T. E., Resid FCC Regenerator Design, presented at the M.W. Kellogg Co. Refiing Technology seminar, Houston, Texas, February 9-10, 1995. 

For the discrete bubble model described in Section V.C, future work will be focused on implementation of closure equations in the force balance, like empirical relations for bubble-rise velocities and the interaction between bubbles. Clearly, a more refined model for the bubble-bubble interaction, including coalescence and breakup, is required along with a more realistic description of the rheology of fluidized suspensions. Finally, the adapted model should be augmented with a thermal energy balance, and associated closures for the thermophysical properties, to study heat transport in large-scale fluidized beds, such as FCC-regenerators and PE and PP gas-phase polymerization reactors. 

Calcined LDHs have been investigated as potential materials for the reduction of SOx and NOx emissions from FCCU in oil refineries [75,76]. Corma et al. found that mixed oxides obtained from a Cu/Mg/Al LDH precursor were the most effective at catalyzing both the oxidation of SO2 to S04 in the FCC regenerator and the reduction of sulfates to H2S, which may be recovered, in the reducing atmosphere of the cracking zone [76]. Calcined Cu/Mg/Al LDHs [77] and Co/Mg/Al LDHs [78], subsequently activated by heating under H2, can simultaneously remove SOx and NOx. In both cases, reduced transition metal species have been proposed as the active sites. 

Table IX shows the effect of regenerator temperature on the relative fractional ZSM-5 replacement rate required to achieve a 1 RON boost. The model prediction shows that ZSM-5 is relatively insensitive to FCC regenerator temperature.

The fluid catalytic cracking (FCC) is a very dynamic nnit that is typically the major conversion process in a refinery. Proper modeling and nnderstanding of unit capabilities represents a tremendons opportunity to improve the overall nnit operation and minimize unit emissions. The combustion chemistry in the FCC regenerator that produces environmental pollntants is extremely complex as nnmerons interactions and reactions occnr between the various chemical species. 

As indicated above, the heat prodnced in the FCC regenerator is ultimately balanced against the reqnirements of the reaction side. In addition to providing catalytic reaction sites, FCC catalyst also absorbs the heat of combustion and carries it to the riser to provide the heat required to vaporize and crack the feed. As catalyst circulation increases, the amonnt of heat transfer snrface available in the feed vaporization zone increases proportionately. 

Magnesium-based materials are used as the pick-up agent in currently available additives. In the FCC regenerator, the additive reacts with SO3 to form magnesium sulfate ... 

The selective Noncatalytic reduction (SNCR) process is a postcombustion NO reduction technology. NO is reduced through the controlled injection of a reagent, either ammonia or urea, into the combustion products of boiler, heater, or FCC regenerator. This process is typically applied on partial burn applications with a CO boiler (COB). 

The majority of these units have a Third Stage Separator (TSS) or electrostatic precipitator (ESP) located before the SCR catalyst bed to protect against upsets in the FCC regenerator. The catalyst can easily be designed to handle the normal dust loading (60 mg-700 mg/Nm ), which is much lower than the typical coal fired boiler (5 g-9 g/Nm ). To handle a FCC upset (>15 g/Nm ) without a PM removal device, the catalyst volume would need to increase. 

The ESP has been used to control particulate emissions in the flue gas following an FCC regenerator since the 1940s with well over 200 FCCU applications. The... 

It is clear that the zeolite delta coke will have a strong effect on the regenerator temperature and hence on the catalyst deactivation. Depending on the trend in FCC regenerator temperatures, the aspect of hydrothermal stability might become of greater importance. 

Gamblin, B., Newton, D., and Grant, C. X-Ray Characterization of the Gas Flow Patterns from FCC Regenerator Air Rising Nozzles, in Circulating Fluidized Bed Technology IV (Amos A. Avidan, ed.), pp. 595-600. Somerset, Pennsylvania (1993). 

The consequence of this is that since there is a correlation between the propylene yields and coke higher propylene yields are associated with higher carbon dioxide emissions as the coke is bumt-off in the FCC regenerator. 

In order to explore this hypothesis, we examined the oxidation state of the metals on the catalyst after CPS as compared to Ecats using temperature programed reduction (TPR). We found diat the metals on the CPS catalysts (both V, and to a lesser extent Ni) were in a higher oxidation state than the metals on Ecat, even for a high excess oxygen FCC regenerator. Based on this result, the standard CPS procedure was... 

---