Chemical Engineering Commons^™

Effect Of Steam On The Performance Of Ca-Based Sorbents In Calcium Looping Processes, Fabio Montagnaro, Eduardo Gais, Antonio Coppola, Piero Salatino, Fabrizio Scala

Fluidization XV

Calcium looping, a post-combustion “carbon capture and storage” process (see Figure 1), is usually carried out by means of a limestone-based sorbent in a dual interconnected fluidized bed reactor. The two stages of this process are limestone calcination and carbonation: in the former case, water vapor can be present as a product of the auxiliary fuel combustion needed to drive this endothermal step; in the latter case, water vapor is usually present in the combustion flue gas stream bearing the CO2 to be captured. This work pursues previous research concerning the hydration-induced reactivation of spent sorbents (1,2,3) further and aims …

The Relationship Between Fluidized Bed Electrostatics And Entrainment, John R. Grace, Turki Alsmari, Xiaotao Bi, Farzam Fotovat

Fluidization XV

Existing methods of predicting entrainment from gas-fluidized beds, based exclusively on hydrodynamic variables and mechanisms, show extremely wide discrepancies in their predictions and often deviate by many orders of magnitude from experimental values. Based on simultaneous measurement of electrostatic charges in the freeboard region and entrainment, this paper will show that inter-particle electrostatic forces on relatively fine particles can be at least of the same order of magnitude as the gravity forces that must be overcome for entrainment to take place. Moreover, incorporation of a term for inter-particle electrostatic force leads to substantial improvement in the ability to correlate our …

Influence Of Catalyst Conditioning On Products In A Continuously Operated Fcc Pilot Plant, Matthias Swoboda, Josef Fimberger, Alexander Reichhold

Fluidization XV

In the past, the industrially proven and well established process of FCC has been used primarily to increase the product yield of the gasoline fraction in the refinery process. Economic and political considerations caused a shift of interest to other FCC-products (light olefins and LCO for example (1)) and the use of alternative feedstocks like vegetable oils (2). Another way to obtain the varying desired results is the development of new FCC catalysts.

In this study, one such, as of yet non-commercial catalyst was used. The focus lay on the relation between catalyst activity and related composition of the products …

First Experience In Operation Of Cold Model Of Fb-Clc-Sf (Fluidized-Bed Chemical-Looping-Combustion Solid-Fuels) Facility, Tomasz Czakiert, Krzysztof Kulicki, Jaroslaw Krzywanski, Anna Zylka, Sylwia Jankowska, Wojciech Nowak

Fluidization XV

The first experiences with the cold model of dual fluidized bed unit designed for chemical looping combustion of solid fuels (FB-CLC-SF) will be presented.

The constructed facility combines two different type reactors. The first one, which is the Air Reactor (AR) is operated in a regime of fast fluidized bed, whereas, the second one, which is the Fuel Reactor (FR) works under bubbling fluidized bed conditions. However, the integrated reactors make the whole construction being a CFB-type (Circulating Fluidized Bed) unit. The facility is made entirely of transparent material (Plexiglas). This feature supports effectively the measurements, which enables to conduct …

Effect Of Bed Particle Size On Heat Transfer Between Fluidized Bed Of Group B Particles And Vertical Rifled Tubes, Artur Blaszczuk, Wojciech Nowak, Jaroslaw Krzywanski

Fluidization XV

The effect of bed particle size on the local heat transfer coefficient between a fluidized bed and vertical rifled tubes (38mm-O.D.) has been determined in a large-scale circulating fluidized bed (CFB) reactor. Bed particles with different Sauter mean particle diameter within the range of 0.219-0.411mm and particle density in the range of 2660-2750 kg/m3 were used as bed material in this heat transfer study. A gas fluidized bed furnace with 27.6´10.6m cross-section above refractory line and 48m in height was used. Air coal firing conditions at the membrane wall in the form of water tubes welded with lateral fins corresponded …

Three-Dimensional Cfd Simulation Of The Regeneration Of Mgo-Based Sorbent In A Carbon Capture Process, Hamid Arastoopour

Fluidization XV

Carbon dioxide is the primary greenhouse gas emitted through human activities; therefore, efficient reduction of CO2 is regarded as one of the key environmental challenges of the current century. Different processes have been introduced in the literature for CO2 capture; among these solid sorbent processes have shown potential advantages. In order to achieve steady CO2 capture using solid sorbents, a circulating fluidized bed (CFB) is used that consists mainly of a carbonator reactor (where the CO2 is adsorbed by solid sorbents) and a regenerator (where carbonated sorbents release CO2 and a concentrated CO2-steam mixture is produced). Different solid sorbents have …

Analysis Of Fluctuations In Velocities, Voidage And Gas Concentration In Cfb Conditions, Timo Niemi, Sirpa Kallio, Juho Peltola

Fluidization XV

The purpose of the present study is to evaluate the possibilities to estimate the fluctuation characteristics of gas concentrations in a CFB from the characteristics of velocity and voidage fluctuations. In CFB combustion, the local concentrations of reactant gases strongly fluctuate which affects the reaction rates. In CFD modeling, the effect of turbulent mixing on reaction rates is commonly taken into account by means of mixing descriptions based on fluctuation time scales. For fast reactions the mixing rate can be the rate limiting step. Similar to gas phase reactions, for heterogeneous combustion of solid fuel, fluctuations in gas concentrations should …

Solid Flux In Travelling Fluidized Bed Operating In Square-Nosed Slugging Regime, Sina Tebianian, Kristian Dubrawski, Naoko Ellisa, John R. Grace, Thomas W. Leadbeater, David J. Parker, Rouzbeh Jafari, Jamal Chaouki, Pablo Garcia-Trinanes, Jonathan P. K. Seville

Fluidization XV

The performance of gas-fluidized bed reactors depends significantly on their hydrodynamics. Among the important properties that dictate the characteristics of a gas-fluidized bed, local solid flux plays a significant role, influencing vital parameters such as bed-to-surface heat exchange and solid circulation rate. Developing techniques that can provide accurate measurements of solid flux is extremely important for: 1) assessing the accuracy of other measurement techniques applicable to industrial units, and 2) validation of CFD models.

Comparison of different measurement techniques that provide similar hydrodynamic information is helpful in assessing the errors associated with each methodology. Most measurement techniques for obtaining solid …

Impact Of Local Fluidized Bed Hydrodynamics On Interactions Between Particles And Gas-Liquid Sprays, Maryam Mohagheghi, Franco Berruti, Cedric Briens

Fluidization XV

In the Fluid CokingTM process, heavy oil is sprayed into a downward-flowing fluidized bed of hot coke particles. A good liquid distribution on the particles is essential to achieve a high yield of desirable liquid products and avoid operating problems. This presentation shows how to modify local bed hydrodynamics to improve liquid distribution.

The distribution of the injected liquid in the bed can be improved by either increasing the atomization gas flowrate or, preferably, the local fluidization velocity. Study of nozzles at different locations and inclinations identifies the dominant effects of bed hydrodynamics at the nozzle and jet tips on …

The Effect Of Riser End Geometry On Gas-Solid Hydrodynamics In A Cfb Riser Operating Above Fast Fluidization Regimes, Larry Shadle

Fluidization XV

Riser hydrodynamics are a function of the gas and solids flow rates as well as the exit geometry, particularly when operated above the upper transport velocity. This work compares the exit voidage for multiple geometries and two different Geldart class B solids: glass beads and coke. Geometries were changed by modifying the volume of an abrupt T-shaped exit above the lateral riser exit. This was accomplished by positioning a plunger at various heights above the exit from zero to 0.38 m. A correlation was developed for the exit voidage as a function of the noted length and the following hydrodynamic …

Pickup Velocity Of Nanoparticles, Jia Wei Chew, J. Ruud Van Ommen, Aditya Anantharaman

Fluidization XV

This paper represents the first systematic study of the pneumatic conveying of nanoparticles. The minimum pickup velocity, U_pu, of six nanoparticle species of different materials (i.e., silicon dioxide (SiO₂), aluminum oxide (Al₂O₃) and titanium dioxide (TiO₂)) and surfaces (i.e., apolar and polar) were determined by the weight loss method. Specifically, the weight loss method involves measuring the mass loss from the particle sample at various superficial gas velocities (U), and the U_pu is the U value at which mass loss is zero. Nanoparticles were picked up as …

Spouting Behavior Of Binary Mixtures Of Spherical And Cylindrical Particles, Douglas W. Marshall, Nicholas W. Eimers, Nathan A. Yergenson, David C. Drown

Fluidization XV

Circulation of particles in a spouted bed is influenced by the aspect ratio of the particles. Circulation of high-aspect particles, such as grains, is similar to bulk flow of powders within a hopper, while circulation of spherical particles is better represented by funnel flow.

Deposition of high quality and high integrity coatings on nuclear fuel particles requires good circulation of the fuel particles to ensure a narrow distribution of coating thicknesses and uniform coating properties. Spouting studies were conducted with using air at room temperature in a 2-D model of a nuclear fuel particle coater to investigate the influence of …

Heat Transfer Challenge And Design Evaluation For A Multi-Stage Temperature Swing Adsorption (Tsa) Process, Gerhard Hofer, Tobias Pröll, Johannes Fuchs, Gerhard Schöny

Fluidization XV

Functionalized solid amine-based temperature swing adsorption (TSA) processes have recently been proposed as a potential way to reduce the energy-penalty of post-combustion carbon capture processes (1). If TSA is to be carried out at large scale and with high energy-efficiency, continuously operated counter-current contactors are required for thermodynamic reasons. This could, generally, be achieved by using moving bed contactors. However, the heat exchange requirement of TSA is significant and heat transfer is poor in fixed and moving beds. Therefore, multi-stage fluidized bed contactors with counter-current flow of solids and gas phase and immersed heat exchange surfaces may solve the heat …

Hydrodynamics Of Compartmented Fluidized Beds For Concentrated Solar Power Applications, Roberto Solimene, Riccardo Chirone, Andrea Paulillo, Piero Salatino

Fluidization XV

Application of fluidized beds to collection and thermal storage of solar radiation is beneficial in Concentrated Solar Power (CSP) systems thanks to their well-known inherently good thermal performances. Non-conventional design and operation of fluidized beds based on uneven or unsteady (pulsed) fluidization (1), may further enhance their thermal performances improving the potential for applications in the very demanding CSP systems. Dense gas-fluidized beds have the potential to effectively accomplish three complementary tasks: the collection of incident solar radiation; the heat transfer of the incident power to immersed tube bundles of high-efficiency steam and/or organic Rankine cycles (ORC) and the thermal …

Attrition Rate Of Iron Ore In The Gas-Solid Fluidized Beds With The Wide Size Distribution, Dong-Hyun Kang, Chang Kuk Ko, Dong Hyun Lee

Fluidization XV

The effects of superficial gas velocity (U_g = 1.25 – 3.00 m/s) and distributor hole size (8.0 – 12.4 mm) on the attrition rate of iron ore in a gas-solid fluidized bed with 0.076 m ID ´ 3.7 m height with or without circulation were investigated. The particle density and the Sauter mean diameter of fresh iron ore were 3,705 kg/m³ and 357 m, respectively. When the kinetic energy rate from the orifice was equal or greater than 180 J/s, the trend of attrition rate could be determined. The attrition rate was determined by measuring the fractional mass …

Carbon Dioxide Recovery By Means Of Tsa In A Sound Assisted Fluidized Bed Of Fine Activated Carbon, Raganati Federica, Ammendola P

Fluidization XV

A large decrease in CO₂ emissions through capturing and separation will be required to keep greenhouse gases at tolerable levels (1). Though several CO₂ capture technologies have been proposed, temperature swing adsorption (TSA), consisting in adsorbing the CO₂ on a solid material and, then, inducing the sorbent regeneration and CO₂ recovery by a temperature increase and gas purge, has the potential to become one of the leading techniques by complementing or replacing the current absorption technology due to its low energy requirement (2). With reference to the sorbent, great attention is focused on fine powders (3). …

Predicting Gas-Flow Distribution In Pilot-Scale Fluidized Beds Using Cfd Simulations, Akhilesh Bakshi, C. Altantzis, A. F. Ghoniem, L. R. Glicksman

Fluidization XV

Bubbling fluidized beds are used extensively in energy and chemical industries because of their excellent heat and mass transfer characteristics. Recently, CFD has been identified as a useful tool for predicting reactor performance, but application to large scales continues to be challenging because of limitations on computational resources. Given that the hydrodynamics can largely be characterized by bubbles rising through the bed, a more feasible approach for investigating large-scale reactors is to quantify bubble dynamics and specifically, gas distribution in different phases- visible bubble flow, bubble-through flow and dense-phase flow.

In this study, 3D CFD simulations of bubbling fluidized beds …

Modelling Study Of Two Chemical Looping Reforming Reactor Configurations: Looping Vs. Switching, Joana F. Morgado, Schalk Cloete, John Morud, Thomas Gurker, Shahriar Amini

Fluidization XV

Autothermal Chemical Looping Reforming (CLR) is a promising technology for hydrogen production with integrated CO₂ separation. Conventional CLR employs two fluidized beds (fuel and air reactors) with an oxygen carrier circulating between them. In this way, CLR supplies heat to the endothermic reforming reaction while avoiding fuel/nitrogen mixing. This configuration can achieve steady operation and low gas leakages between reactors, but has some drawbacks. The complex interconnected configuration is challenging to scale up, especially under the pressurized conditions required for high process efficiency. Moreover, the external circulation of particles through cyclones and loop seals increases reactor costs and imposes …

Characterization Of Fuel Segregation In A Fluidized Bed By Magnetic Particle Tracking, David Pallarès, Anna Köhler, Alexander Rasch, Filip Johnsson

Fluidization XV

A Magnetic Particle Tracking (MPT) system is used to experimentally characterize the vertical distribution of fuel particles in a fluidized bed. The measurements are carried out in a fluid-dynamically down-scaled cold unit resembling a 1×1 m2 boiler operating at 850 °C. The MPT system yields spatial and temporal information of the tracer particle with accuracies in the order of 10-3 m and 10-3 s, respectively. The MPT system is used to study how fuel segregation is influenced by physical properties of the fuel (sizes and densities representing different fuel types) and operational conditions, such as fluidization velocity, bed height and …

Novel Method To Meassure Fine Particle Circulation Rates In Draft Tube Conical Spouted Beds, Idoia Estiati, Haritz Altzibar, Mikel Tellabide, Martin Olazar

Fluidization XV

The spouted bed regime is an alternative contact method to fixed and fluidized beds. The ratio between the inlet diameter and particle diameter limits the scaling-up of spouted beds (the inlet diameter should be smaller than 20-30 times the particle diameter). The insertion of a draft tube is the way of overcoming this limitation.

Particle cycle time is defined as the time the particle takes to travel from the top of the annulus downwards and back again to its starting point. Since the proportion of time spent by a particle in the spout is insignificant compared with that spent in …