scholarly journals CFD Study of Industrial FCC Risers: The Effect of Outlet Configurations on Hydrodynamics and Reactions

2012 ◽  
Vol 2012 ◽  
pp. 1-16 ◽  
Author(s):  
Gabriela C. Lopes ◽  
Leonardo M. Rosa ◽  
Milton Mori ◽  
José R. Nunhez ◽  
Waldir P. Martignoni
Keyword(s):  
Catalytic Cracking ◽  
Flow Model ◽  
Numerical Study ◽  
Three Dimensional ◽  
Kinetic Scheme ◽  
Operating Conditions ◽  
Fluid Catalytic Cracking ◽  
Geometric Configurations ◽  
Three Phase ◽  
Three Phase Flow

Fluid catalytic cracking (FCC) riser reactors have complex hydrodynamics, which depend not only on operating conditions, feedstock quality, and catalyst particles characteristics, but also on the geometric configurations of the reactor. This paper presents a numerical study of the influence of different riser outlet designs on the dynamic of the flow and reactor efficiency. A three-dimensional, three-phase flow model and a four-lump kinetic scheme were used to predict the performance of the reactor. The phenomenon of vaporization of the liquid oil droplets was also analyzed. Results showed that small changes in the outlet configuration had a significant effect on the flow patterns and consequently, on the reaction yields.

Numerical Simulation of Gas Flow and Heat Transfer in Cross-Wavy Primary Surface Channel for Microtubine Recuperators

2005 ◽  
Author(s):  
H. X. Liang ◽  
Q. W. Wang ◽  
L. Q. Luo ◽  
Z. P. Feng
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Gas Turbine ◽  
Numerical Study ◽  
High Reliability ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
The Cross

Three-dimensional numerical simulation was conducted to investigate the flow field and heat transfer performance of the Cross-Wavy Primary Surface (CWPS) recuperators for microturbines. Using high-effective compact recuperators to achieve high thermal efficiency is one of the key techniques in the development of microturbine in recent years. Recuperators need to have minimum volume and weight, high reliability and durability. Most important of all, they need to have high thermal-effectiveness and low pressure-losses so that the gas turbine system can achieve high thermal performances. These requirements have attracted some research efforts in designing and implementing low-cost and compact recuperators for gas turbine engines recently. One of the promising techniques to achieve this goal is the so-called primary surface channels with small hydraulic dimensions. In this paper, we conducted a three-dimensional numerical study of flow and heat transfer for the Cross-Wavy Primary Surface (CWPS) channels with two different geometries. In the CWPS configurations the secondary flow is created by means of curved and interrupted surfaces, which may disturb the thermal boundary layers and thus improve the thermal performances of the channels. To facilitate comparison, we chose the identical hydraulic diameters for the above four CWPS channels. Since our experiments on real recuperators showed that the Reynolds number ranges from 150 to 500 under the operating conditions, we implemented all the simulations under laminar flow situations. By analyzing the correlations of Nusselt numbers and friction factors vs. Reynolds numbers of the four CWPS channels, we found that the CWPS channels have superior and comprehensive thermal performance with high compactness, i.e., high heat transfer area to volume ratio, indicating excellent commercialized application in the compact recuperators.

A Historic Review on R&D of China’s FCC Riser Termination Device Technologies

2013 ◽  
Vol 11 (1) ◽  
pp. 225-242 ◽  
Author(s):  
Chunxi Lu ◽  
Yongmin Zhang ◽  
Mingxian Shi
Keyword(s):  
Catalytic Cracking ◽  
Geometry Optimization ◽  
Operating Conditions ◽  
Fluid Catalytic Cracking ◽  
Processing Capacity ◽  
Centrifugal Separation ◽  
Recovery Efficiency ◽  
The World ◽  
Historic Review ◽  
Fcc Technology

Abstract Fluid catalytic cracking (FCC) is a dominant refining conversion process in China’s most refineries. After decades of development, China has already become one of the major FCC technology licensors in the world. In this review, the research and development (R&D) activities on FCC riser termination device (RTD) technologies in China are reviewed and discussed. Emphasis is put on the R&D of a series of advanced RTD technologies led by China University of Petroleum, Beijing, which initiated in the early 1990s when more and more China’s FCC units chose to process more residue feedstock. Followed by the guideline of three “quick”s and two “high”s, two early types of RTD systems with coupled zones for gas–solids centrifugal separation and pre-stripping were developed and applied successfully in commercial units. Significantly reduced yields of coke and dry gas due to restrained post-riser reactions and satisfactory particle recovery efficiency were achieved. These were the fender-stripper cyclone and vortex quick separator systems designed for external- and internal-riser FCC units, respectively. Later, further improvement efforts led to the development of another two RTD systems, i.e. the circulating-stripper cyclone system for external-riser units and super vortex quick separator system for internal-riser units. By now, nearly 50 applications were commissioned with a sum FCC capacity of 40.0 Mton/a, nearly one-third of China’s total FCC processing capacity. Besides, other research efforts, such as the geometry optimization efforts on LD2 type separator, the studies on RTD for down-flow riser FCC units, and the idea of non-disengager FCC unit are also discussed in this review. To accommodate to degraded feedstock, more stringent environmental regulations and new FCC process technologies, future R&D efforts on RTD technologies should be put on improvements to further satisfy the three-“quick”s and two-“high”s requirements with changing FCC operating conditions and different process requirements.

Experimental and Numerical Study of Cold Gas-Solid Flow Regimes in a Fluidized Bed Gasifier

2017 ◽  
Author(s):  
Anton Pylypenko ◽  
Yevgenii Rastigejev ◽  
Lijun Wang ◽  
Abolghasem Shahbazi
Keyword(s):  
Fluidized Bed ◽  
Numerical Study ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Silica Sand ◽  
State University ◽  
Solid Flow ◽  
Fluidized Bed Gasifier ◽  
Isothermal Gas ◽  
Cold Gas

The objective of this work is to analyze the dynamics and regimes of cold gas-solid flow in a biomass gasifier that is built at North Carolina Agricultural and Technical State University and to identify its corresponding ranges of operating conditions. The value of the minimum fluidization velocity Umf ≈ 8 cm/s has been found experimentally in a series of measurements of a pressure drop in the fluidized bed filled with Gledart type-B silica sand for the range of superficial gas velocities between 0 and 40 cm/s. To complement the experimental results, a set of three-dimensional numerical simulations of the isothermal gas-solid flow based on Eulerian-Eulerian approach has been performed. The analysis of the fluidization characteristics such as axial void fraction distributions has allowed us to evaluate the dependence of the bed expansion ratios from the flow superficial velocity. Good agreement between experimental and numerical results for the considered operating conditions of the gasifier has been observed.

scholarly journals A hyperbolic three-phase flow model

2006 ◽  
Vol 342 (10) ◽  
pp. 779-784 ◽  
Author(s):  
Jean-Marc Hérard
Keyword(s):  
Flow Model ◽  
Phase Flow ◽  
Three Phase ◽  
Three Phase Flow

EFFECTS OF OPERATING CONDITIONS ON THE DEPOSITION OF GaAs IN A VERTICAL CVD REACTOR

2008 ◽  
Vol 15 (01n02) ◽  
pp. 111-116 ◽  
Author(s):  
JAE-SANG BAEK ◽  
JIN-HYO BOO ◽  
YOUN-JEA KIM
Keyword(s):  
Fluid Transport ◽  
Numerical Study ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Rotation Velocity ◽  
Operating Conditions ◽  
Deposition Condition ◽  
Three Dimensional Model ◽  
Trimethyl Gallium ◽  
Vertical Cvd Reactor

A numerical study is needed to gain insight into the growth mechanism and improve the reactor design or optimize the deposition condition in chemical vapor deposition (CVD). In this study, we have performed a numerical analysis of the deposition of gallium arsenide ( GaAs ) from trimethyl gallium (TMG) and arsine in a vertical CVD reactor. The effects of operating parameters, such as the rotation velocity of susceptor, inlet velocity, and inlet TMG fraction, are investigated and presented. The three-dimensional model which is used in this investigation includes complete coupling between the thermal-fluid transport and species transport with chemical reaction.

Experimental and Numerical Study of Stall Flutter in a Transonic Low-Aspect Ratio Fan Blisk

2003 ◽  
Author(s):  
A. J. Sanders ◽  
K. K. Hassan ◽  
D. C. Rabe
Keyword(s):  
Aspect Ratio ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Strain Gages ◽  
Pressure Transducers ◽  
Low Aspect Ratio ◽  
Benchmark Data

Experiments are performed on a modern design transonic shroudless low-aspect ratio fan blisk that experienced both subsonic/transonic and supersonic stall-side flutter. High-response flush mounted miniature pressure transducers are utilized to measure the unsteady aerodynamic loading distribution in the tip region of the fan for both flutter regimes, with strain gages utilized to measure the vibratory response at incipient and deep flutter operating conditions. Numerical simulations are performed and compared with the benchmark data using an unsteady three-dimensional nonlinear viscous computational fluid dynamic (CFD) analysis, with the effects of tip clearance, vibration amplitude, and the number of time steps-per-cycle investigated. The benchmark data are used to guide the validation of the code and establish best practices that ensure accurate flutter predictions.

Solids-Loading Measurements in a Gas-Solid Riser

Volume 1 ◽  
2004 ◽  
Author(s):  
T. J. O’Hern ◽  
S. M. Trujillo ◽  
J. B. Oelfke ◽  
P. R. Tortora ◽  
S. L. Ceccio
Keyword(s):  
Catalytic Cracking ◽  
Volume Fraction ◽  
Electrode System ◽  
Operating Conditions ◽  
Fluid Catalytic Cracking ◽  
Gas Velocity ◽  
Cross Sectional ◽  
Solids Loading ◽  
Special Cases ◽  
Superficial Gas Velocity

Gas-solid multiphase flows are commonly used in chemical processing, petroleum fluid catalytic cracking, and other industrial applications. The distribution of the solid phase in gas-solid flows (generally in the form of small particles) is seldom uniform, but more commonly involves clusters, streamers, and core-annular distributions, depending on the flow orientation and the overall gas and solid flowrates and their ratio. For this reason, tomographic techniques are of great interest for measurement of cross-sectional solids distributions in such flows. The cross-sectional profiles of solids loading can be integrated to yield a cross-sectionally averaged solids loading. Determination of this averaged solids loading is needed to understand the axial variations of solids loading and its sensitivity to flow parameters and to optimize performance. A common technique for determining volume-averaged solids loading in vertical flows like the riser section of a circulating fluidized bed (CFB) is by measurement of the time-averaged axial pressure gradients along the riser axis (differential pressure or ΔP method). Neglecting acceleration and wall friction, the axial momentum balance simplifies to equate the multiphase hydrostatic pressure term with the pressure gradient along the axis. Many authors (e.g., Louge and Chang, 1990) have pointed out the neglected terms in this approach and generally show that ΔP is applicable in the special cases of no solids-loading gradient (fully developed flow) or small solids flux. A more generally applicable technique for measuring solids loading in gas-solid flows is gamma tomography. A gamma tomography system using a 100-mCi Cs-137 source collimated into a fan beam and an array of scintillation detectors, has been developed and implemented for application to a cold-flow (non-reacting) CFB. The CFB has a 14-cm-ID 6-m tall riser, and is currently operated with a multiphase mixture of air and fluid catalytic cracking (FCC) catalyst particles. Typical operating conditions include mean superficial gas velocities up to 7.4 m/s and solids fluxes up to approximately 100 kg/m2·s. Quantitative comparison of gamma- and ΔP-determined solids loadings was made over a range of operating conditions (combination of superficial gas velocity and solids flux). Results indicate that the differences between gamma and ΔP-determined cross-sectionally averaged solids loading are most pronounced near the base of the riser, where solids concentration is highest and the mixture is accelerating. Higher in the riser, the agreement is better. Additionally, the difference is larger in cases of higher superficial gas velocity. In addition, several studies were performed to design an electrical-impedance tomography (EIT) system for a gas-solid flow to collect data suitable for validating computational models. A two-electrode bulk impedance system was studied experimentally. The required accuracy, spatial resolution and temporal resolution of an EIT system are addressed, and modeling and reconstruction are discussed. Bulk solid volume fractions measured by the two-electrode system and by gamma-densitometry tomography are in general agreement. Experiments with the two-electrode system also show that the Maxwell-Hewitt relation, used to convert the mixture impedance to solid volume fraction, must be applied carefully, paying attention to the identity of the dispersed and continuous phases. The design of a 16-electrode system is also described.

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