Numerical Study Of The Effect Of Gas Distributors And Baffles On The Bubble Distribution, Gas And Solid Mixing In A Fluidized Bed, Xuelian Xing

Electronic Thesis and Dissertation Repository

In this study, the multi-phase Eulerian-Eulerian two-fluid method (TFM) coupled with the kinetic theory of granular flow (KTFG) was used to investigate hydrodynamics of particle flows (Geldart Group B) in a lab-scale fluidized bed Geldart Group B particles, operating in bubbling and turbulent regimes. The effect of gas distributors and baffles on the distribution of the gas bubbles, and the mixing of gas and solids were investigated under various superficial gas velocities.

The numerical model is validated by experimental results from two different measurement methods with various gas distributor configurations and a superficial gas velocity ranging from 0.4 m/s to …

Multiphase Cfd Modeling In Particle-Laden Flows, Zhizhong Ding

LSU Doctoral Dissertations

Multiphase modeling is prevalent and useful in solving problems involving multiphase interactions such as fluid and solid. Applications conclude but not limited to fluidized bed, hydraulic conveying, and many others. Modeling techniques with multiple scales can provide various states of details with diverse computational resources used. In this dissertation, two CFD multiphase models are used to disclose interaction details in the particulate system. Two-Fluid Model is used to solve pulsed fluidized bed problem and immersed boundary method based direct numerical method is used to solve particle’s behavior in shear flow. Getting a better understanding of these problems to help to …

Correlating Pressure, Fluidization Gas Velocities, Andsolids Mass Flowrates In A High-Pressurefluidized Bed Coal Feed System, Jacob Talailetalalelei Tuia

Theses and Dissertations

The goal of this thesis was to understand what parameters would be most impactful when delivering dry, pulverized coal in a dilute-phase, with a high-pressure feed-system to a pressurized oxy-combustion (POC) reactor. Many studies have conveyed materials in dense-phase plugs at high-pressure or in dilute-phase flows at atmospheric pressure. Very few studies have fluidized and conveyed materials in dilute-phase flows at high pressure, as we needed to. Additionally, studies which might have been applicable based upon system -pressure and -phase delivered findings that were empirically based and therefore not specifically applicable to non-similar systems. 220 different tests were ran using …

Spraying Slurries: Impact Of Slurry Properties On Spray Characteristics And Agglomerate Formation In Fluidized Beds, Joshua Idowu

Electronic Thesis and Dissertation Repository

Abstract

Fluid Coking^TM is a process that upgrades Alberta’s heavy oil. The recycle stream in the process contains unwanted fines which could affect the interaction between the liquid feed and the bed particles and the tendency to form agglomerates. Agglomeration leads to lower product yields and vessel damage.

The impacts of slurry solids on spray stability and angle were measured in open air while the impacts on agglomerate stability and liquid distribution were studied in a fluidized bed. Particle properties were varied to understand the impact of the solids on agglomerates.

In open air, it was observed that the …

Use Of A Baffle To Enhance Distribution Of A Liquid Sprayed Into A Gas-Solid Fluidized Bed, Majid Jahanmiri

Electronic Thesis and Dissertation Repository

Bubbles in gas-solid fluidized beds are generally beneficial as they promote solids mixing, heat transfer and mass transfer. In most fluidized beds, the local bubble gas flux varies greatly over the cross-section. A novel triboelectric method is developed to measure the bubble gas distribution in a fluidized bed. A correlation relates the local bubble gas flux to the triboelectric signal generated by the impact of the gas bubbles on a triboprobe. Several signal analysis tools, such as power spectrum, cycle analysis and signal moments, were used to determine the best experimental fit for the profile of the bubble gas flux. …

Particle Entrainment Studies From Dry And Wet Bed, Saber Ayatollahi

Electronic Thesis and Dissertation Repository

During the Fluid Coking Process™ bitumen is sprayed into a fluidized bed of hot coke particles. The bitumen undergoes thermal cracking and is converted into gasses, condensable vapors, and solid coke, which deposits on the coke particles. These vapors rise through the vessel and result in entrainment of coke particles. Wet fine coke particles from the freeboard region enter the cyclone and contribute to the fouling of the Coker cyclones which can lead to the premature shut-down of Fluid Cokers.

The primary objective of this research is to determine how bed wetness affects entrainment.

First, a new fluidized bed was …

Effect Of Spray Jet Interactions On The Liquid Distribution In A Fluidized Bed, Helal Elkolaly

Electronic Thesis and Dissertation Repository

Many processes use spray nozzles to introduce liquid into a fluidized bed. One such process is the Fluid Coking Process which is used to upgrade bitumen. Poor liquid distribution in a Fluid Coker proves detrimental as agglomerates form which introduce mass and heat transfer limitations. The main objective of this thesis is to determine the effect of interacting spray jets on the liquid distribution in a Fluid Coker. This was accomplished by using a low temperature experimental model of Fluid Coking to estimate the liquid distribution. Preliminary screening of nozzle positions was accomplished by the use of conductance measurements. A …

Effect Of Temperature And Successive Sprays On Liquid Distribution In Fluidized Beds, Liliana Andrea Pardo Reyes

Electronic Thesis and Dissertation Repository

Liquid injection in gas-solid fluidized beds is used in several industrial processes including food additive production, manufacturing of fertilizers, intermediate processing of pharmaceutical capsules and oil refining (i.e., Fluid Coking^TM and Fluid Catalytic Cracking (FCC)). Good quality in the liquid distribution on the fluidized particles is fundamental in these processes either to ensure uniformity in the formation of desirable agglomerates, or to minimize their formation when undesirable. In the Fluid Coking process, for example, improving the liquid distribution and minimizing agglomerate formation will result in increasing the overall yield of the process and avoid operability problems.

A new experimental …

Development And Study Of Measurement Methods For Jets And Bogging In A Fluidized Bed, Majid Hamidi

Electronic Thesis and Dissertation Repository

In the Fluid Coking process, if the local concentration of liquid is very high, particles may stick together which can eventually result in process upset because of poor fluidization or even defluidization, a condition commonly known in industry as "bogging".

Using a capacitance sensor, the void distribution in a bed of coke particles can be visualized. The voidage fluctuations caused by gas bubbles have been shown to change dramatically as the bed becomes bogged. Therefore, capacitance sensors should be able to predict the bogging condition in fluid cokers.

The first part of the thesis focused on designing noiseless capacitance sensors …

Effect Of Nozzle Geometry On Jet Bed Interaction: Experiments With Commercial Scale Nozzles And Eroded Nozzles, Nicholas A. Prociw

Electronic Thesis and Dissertation Repository

Liquid injection into fluidized bed reactors has several industrial applications, such as Fluid Catalytic Cracking, Gas Phase Polyethylene production, and Fluid Coking. High quality liquid distribution is essential to maximize the yield of desirable products, and minimize agglomeration.

The objectives of this thesis are: to develop a method that measures the rate of liquid released from agglomerates formed as a result of liquid injection into a fluidized bed; to use this method to determine the effect of internal erosion on nozzle performance; and to compare the performance of current commercial spray nozzles to nozzles with altered geometries. To achieve these …

Development And Application Of An Experimental Model For The Fluid Coking Process, Carolina B. Morales

Electronic Thesis and Dissertation Repository

Liquid injection into a fluidized bed is used in industrial applications such as the Fluid Coking^TM process for heavy oil thermal cracking. Poor initial liquid-solid contact results in the formation of agglomerates that limit heat and mass transfer processes, reduce the yield of valuable compounds and create operating problems. The present study develops a new experimental model to simulate the complex phenomena that occur when heavy oil is injected in a Fluid Coker through two-phase nozzles. The model is applied in a pilot scale fluidized bed using scaled-down industrial spray nozzles. The experimental results indicate that agglomerate formation slows …

Development Of A Chemical Kinetic Model For A Fluidized-Bed Sewage Sludge Gasifier, Wyatt Champion

Electronic Theses and Dissertations

As the need for both sustainable energy production and waste minimization increases, the gasification of biomass becomes an increasingly important process. What would otherwise be considered waste can now be used as fuel, and the benefits of volume reduction through gasification are seen in the increased lifespan of landfills. Fluidized-bed gasification is a particularly robust technology, and allows for the conversion of most types of waste biomass. Within a fluidized-bed gasifier, thermal medium (sand) is heated to operating temperature (around 1350°F) and begins to fluidize due to the rapid expansion of air entering the bottom of the reactor. This fluidization …

Simultaneous Particle Agglomeration And Attrition In A High Temperature Fluidized Bed, Mithun Saha

Electronic Thesis and Dissertation Repository

Fluid Coking^TM is a major refining process to upgrade heavy crude oil or bitumen from oil sands. In Fluid Coking^TM bitumen is atomized with steam and sprayed inside a high temperature fluidized bed of coke particles where it thermally cracks into smaller molecules. Fluid Coking^TM is a carbon rejection process as solid carbon residues are formed during fragmentation into lighter hydrocarbon vapors. New coke deposits over existing coke particles and, consequently, the particle size increases. In addition, particles agglomeration occurs when the injected liquid does not disperse uniformly on individual hot coke particles but reaches, instead, local …

Developing Novel Methods To Characterize Liquid Dispersion In A Fluidized Bed, Masoumeh Farkhondehkavaki

Electronic Thesis and Dissertation Repository

The performance of several important industrial processes, such as fluid coking or fluid catalytic cracking, is dependent on the good distribution of liquid feed sprayed into a fluidized bed of hot inert or catalytic particles, respectively.

Liquid injected into a fluidized bed is distributed in three different ways: (i) free moisture, or liquid coating individual particles; (ii) wet micro-agglomerates, which are fluidized; and (iii) wet macro-agglomerates, which settle to the bottom of the bed. This study develops and evaluates various methods for the determination of this moisture.

In the study using electrical techniques, two different kinds of electrodes geometries are …

Particle Attrition With Supersonic Nozzles In A High Temperature Fluidized Bed, Feng Li

Electronic Thesis and Dissertation Repository

Fluidized beds are widely used for a variety of processes such as food, pharmaceutical, petrochemical and energy production. As a typical application of fluidized beds, the fluid coking process uses thermal cracking reactions to upgrade heavy oils and bitumen from oil sands. In order to maintain a well fluidized bed and a satisfactory operation, a series of supersonic nozzles are used to inject high pressure steam in the bed to maintain the coke particle within an optimal range. Currently, the attrition nozzles consume a large florwrate of high pressure and superheated steam, which accounts for about 40 % of the …

An Investigation On The Mixing Hydrodynamics Of A Gas-Solid Fluidized Bed, Mario Alberto Ruvalcaba

Open Access Theses & Dissertations

In previous decades, the experimental and numerical studies of multiphase flows have remarkably increased especially gas-solid flows. Research of this type has abundant applications in energy, chemical processes, among others. Moreover, common applications include fluid catalytic cracking for petroleum refineries, fluidized bed reactors (type of chemical reactors), interface modification, such as applying a coating onto solid items, and an important technology breakthrough in coal gasification. The work presented on this thesis concentrates on the investigation of gas-solid flows utilizing Computational Fluid Dynamics (CFD) methods. The gas-solid flows studies performed on this investigation assumed the solid phase as a continuum with …

Evaporating Cross Flow Spray Jets In Gas-Solid Circulating Fluidized Bed, Tong Hoon Lee

Dissertations

Three-phase flow of solid-gas suspension with liquid spray is found in many industrial applications, including fluidized catalytic cracking in petroleum refinery process, and wet scrubbing process. This dissertation study is aimed to understand the gas-solid-liquid three-phase flow structure, phase interactions and transport in a gas-solid circulating fluidized bed where an evaporating cross-flow liquid spray jet from a rectangular nozzle with a fan angle is injected. The investigation is based on both numerical and experimental approaches. The numerical study is for detailed field descriptions of the flow structure, phase interaction and distributions whereas the experimental study is for simulation validations. The …