Catalytic Cracking Regenerator Research Articles

Corrosion resistance of a steel under an oxidizing atmosphere in a fluid catalytic cracking regenerator

In the present work, the corrosion resistance of an ASTM A 387 G11 steel was evaluated under two conditions: an oxidizing atmosphere in a fluid catalytic cracking regenerator of a petroleum processing unit and a simulated atmosphere in the laboratory, at temperatures of 650 °C and 700 °C. The characterization of the phases present in the oxidized layer was carried out by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) with X-ray energy dispersive analysis (EDS). Severe corrosion was observed after exposure to both the real and simulated conditions, with formation of several iron oxides (Fe2O3, Fe3O4 and FeO) in the product scale layer, as well as a slight inner oxidation and sulfidation of chromium in the substrate. Internal nitridation of the silicon and the manganese was observed only in the real condition, probably related to the long-term exposure inside the regenerator.

Evaluation of the corrosion resistance of thermal-spray coatings under oxidant atmosphere in a fluid catalytic-cracking unit

The effectiveness of several thermal-spray coatings for improving the corrosion resistance of a low-alloy steel was evaluated at 650°C under two conditions: an oxidizing atmosphere in a fluid catalytic-cracking regenerator of a petrochemical unit and a simulated laboratory atmosphere. The high porosity present in all coatings studied in the present work, inherent to the thermal-spray technique, allowed the penetration of gaseous species from the atmosphere into the substrate, leading to the formation of nonprotective oxides and sulfides, as well as internal oxidation, sulfidation, and nitridation. A protective alumina and/or chromia layer did not form, probably due to the relatively low temperature used in both the real and simulated conditions. Characterization of the phases present in the oxidized layer was carried out by X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy (SEM) with X-ray energy-dispersive analysis (EDS).

Effect of Aluminum Thermal Spray Coating on the Corrosion Resistance of a Steel Under Oxidant Atmosphere in a Fluid Catalytic Cracking Regenerator

The effectiveness of aluminum thermal spray coating in the corrosion resistance of an ASTM A 387 G11 1 low alloy steel was evaluated under two conditions: an oxidant atmosphere in a fluid catalytic cracking regenerator of a petrochemical unit and a simulating atmosphere in the laboratory, in the temperatures of 650°C and 700°C. To provide a reference for the behavior of the uncoated substrate, samples of G11 steel without coating were also studied on both conditions, real and simulated. The characterization of the phases present in the oxidized layer was carried out by x-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) with X-ray energy dispersive analysis (EDS). The aluminum coated G11 steel, in both real and simulated conditions, presented a complex inner layer containing Fe-Al intermetallic phases and iron rich oxides and sulfides. Internal oxidation and sulfidation were also observed. In the G11 uncoated steel, a severe corrosion was observed in both, real and simulated conditions, with formation of several iron oxides (Fe 2 O 3 , Fe 3 O 4 and FeO). Internal oxidation and sulfidation of chromium in the alloy were also observed.

Nitrogen Chemistry and NOx Control in a Fluid Catalytic Cracking Regenerator

Emission of NOx from the fluid catalytic cracking (FCC) regenerator is increasingly controlled by various state and local regulations. The FCC regenerator poses a very challenging environment for controlling NOx. Other than NO, the high-temperature flue gas contains O2, CO, CO2, SO2, SO3, H2O, and possibly other nitrogen or sulfur species. In this paper, we will first present a complete nitrogen balance around the fluid catalytic cracking unit by using a circulating pilot plant with continuous regeneration. We will also discuss the transformation of nitrogen species during the cracking and catalyst regeneration process, which has direct implications on the formation and reduction of NOx in the regenerator. Pilot plant or commercial data on the effect of operating conditions, cracking feedstocks, and CO combustion promoter usage on NOx emission will be discussed. With both thermodynamic analysis as well as experiments, we will show that the so-called “thermal NOx” does not contribute to the FCC regenerator...

Advanced De-SO x catalyst: Mixed solid solution spinels with cerium oxide

Mixed solid solution spinels impregnated with cerium, Ce/MgO·MgAl 2- x M x O 4 (MFe, V, Cr, x≤0.4), were studied for controlling the SO x emission from the fluid catalytic cracking (FCC) regenerator. An insufficient sulfur release problem inherent to the earlier DeSO x catalyst, Ce/MgO·MgAl 2O 4, was effectively overcome by incorporating a transition metal into the spinel structure. Studies of the SO x pick-up, temperature profile for the sulfate reduction, the thermal analysis, and the DeSO x cycle test in the batch as well as the automated continuous reactor are discussed to define the role of a transition metal in the mixed spinels for the DeSO x performance. These advanced DeSO x catalysts have led to a commercial success for the simultaneous control of SO x and NO x emissions from the FCC regenerator.

FBSim: A model for fluidized bed simulation—II. Simulation of an industrial fluidized catalytic cracking regenerator

The model for fluidized bed simulation (FBSim), developed in Part I [Faltsi-Saravelou and Vasalos, Computers chem. Engng, 15, 639 (1991)] is applied for the simulation of the regenerator of the fluid catalytic cracking (FCC) unit. Experimental data on flue gas concentrations, catalysts composition and temperature profiles in the fluidized bed have been obtained from an industrial FCC unit operating at promoted total CO burn. The predicted temperature profiles are in good agreement with industrial data and so are the predictions of gas and solid conversions. The limiting step in the regenerator operation is the non-catalytic combustion of carbon, which can be enhanced by the enrichment of the combustion air with oxygen. Simulation results show that at high temperatures the steady-state operation of the FCC regenerator is not influenced by the presence of a CO combustion promotor, although the promotor affects the temperature and component distribution between the bubble and emulsion phases. The dynamic response of the regenerator to step changes in operating variables, such as rate, composition and inlet temperature of the combustion air and coke yield is also examined.

Application of the Kunii—Levenspiel model to a multistage baffled catalytic cracking regenerator

The performance of a multistage catalytic cracking regenerator has been computed for various operating conditions using a Kunii-Levenspiel model. The number of stages, the percentage open area of the baffle, controlling the solids back flow from stage to stage, and the catalyst holdup on each baffle were varied. The results obtained made it possible to predict the optimal operating conditions and to compare the performance of a multistage regenerator with the performance of a single-stage unit.

Analysis of fluidized bed catalytic cracking regenerator models in an industrial scale unit

AbstractFluidized bed regenerator models, under steady state conditions, have been reconsidered because of recent significant changes in the technology of fluidized bed regenerators. Zeolitic catalysts, temperatures of the dense bed at about 700°C and lower CO/CO2 relationships are the new characteristics of the units.Following these innovations the operating conditions of the industrial catalytic cracking regenerator of Destileria La Plata, Yacimientos Petroliferos Fiscales, Argentina, were significantly modified. As a result, an important improvement in the coke conversion was observed. Five different conventional fluidized bed models using experimental data from the industrial regenerator have been tested. The analysis considers bubbles and grid jet regions, and for each model, the prediction of the regenerator performance is shown. The CSTR model is the most successful in this regard.

The influence of the freeboard region in a fluidized bed catalytic cracking regenerator

AbstractA model is developed for a fluidized bed reactor with the dense phase region treated by conventional two‐phase models. Conversion in the freeboard is obtained based on particle trajectories predicted from drag considerations. The model is applied to an industrial‐scale catalytic cracking regenerator. It is shown that the freeboard region can have an important influence on the overall conversion in the unit.

A fluidized bed catalytic cracking regenerator model

AbstractA grid model including thermal effects is proposed. The aim is the simulation of a fluidized catalytic cracking regenerator similar to the industrial unit of Destileria La Plata, YPF, Argentina.It is demonstrated that a simple C.S.T.R. model without bypass of gas feed entering the bed provides a good approach for representing the fluidized bed including the grid region.In addition, by means of the C.S.T.R. model, it is shown that there exist two characteristic operating regions: a zone where (Coo – Co) depends on the initial coke concentration and a zone where (Coo – Cc) is controlled by oxygen supply.

Determination of efficiency of utilization of reaction volume in catalytic cracking regenerator

Determination of efficiency of utilization of reaction volume in catalytic cracking regenerator