An official website of the United States government
Here’s how you know
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
... Comprehensive study on hydrodynamics is carried out in a pilot circulating fluidized bed riser of 18 m in height with high solids flux ranging from 800 to 1800 kg/m²s and superficial gas velocity of 5, 7 and 9 m/s. Results show that with such high solids flux, solids holdup can be up to 20–30% in the whole riser. When solids flux reaches up to1800 kg/m²s, both solids holdup and particle velocity b ...
... An under-resolved coupling strategy for the discrete element method (DEM) and the weakly compressible (WC) generalised finite difference method (GFD) is proposed. A novel filtering technique is proposed that allows for the recovery of a continuum porosity field in an arbitrary domain from DEM information. This allows fine spherical DEM particles to be treated in an under-resolved fashion using wel ...
fluidizedbeds, etc ; convection; dispersibility; technology; Show all 4 Subjects
Abstract:
... A novel method for measuring the micro mixing ratio of binary solids in dense fluidizations is developed. The mixing process within a bubbling fluidized bed that can be assumed as one mixing cell is resolved. Dispersion coefficient and mixing index methods are applied to characterize the mixing process. Results show that diffusion has an important effect on mixing at the bottom and top of the flui ...
... As a subsequent paper for “type-A-choking-oriented unified model for fast fluidization dynamics”, the present work aims to provide more systematic mesoscale analyses on clusters. Starting from theoretical derivations on idealized flow patterns of gas and solids around a single falling cluster; the momentum consumption due to particle circulation in clouds and the modification of flows by the const ...
fluidizedbeds, etc ; carbon dioxide; technology; temperature; Show all 4 Subjects
Abstract:
... Mixing of binary mixture with small-sized particles component (SC) and large-sized particles component (LC) is simulated using unequal granular temperature-based kinetic theory (UGT-KT) in supercritical carbon dioxide fluid (S-CO₂) fluidized bed. Synergy angle is applied to identify the tendency of mixing/segregation of SC and LC binary mixture according to the axial distribution of component volu ...
fluidizedbeds, etc ; filtration; mathematical models; technology; Show all 4 Subjects
Abstract:
... Fluidized bed filters exhibit high PM₂.₅ collection efficiency, as shown in our previous work. In this study, a CFD-IBM-DEM simulation was conducted to elucidate the filtration mechanisms for the further development of these filters. A preliminary numerical simulation of a small fixed-bed filter was performed to determine the appropriate CFD grid size for computational accuracy and cost, and the g ...
fluidizedbeds, etc ; models; probability distribution; technology; Show all 4 Subjects
Abstract:
... The clustering phenomenon in gas-solids high-density (Gs ≥ 300 kg/m²s) and low-density circulating fluidized bed (CFB) risers for FCC particles are compared through CFD studies using a cluster-based drag model. Large clouds of clusters can be clearly identified from the contours of local solids holdup distribution from CFD results, which correspond well to experimental observations. The size, shap ...
fluidizedbeds, etc ; algorithms; fluid mechanics; technology; Show all 4 Subjects
Abstract:
... This study compares the results of two commonly used computational fluid dynamics methods for fluidized bed simulation of smooth type-A monodisperse particles. One approach is based on the continuum assumption called the two-fluid-method (TFM), and one discrete particle method (DEM) based on a soft-sphere collision algorithm. Both DEM and TFM are coarsened by either lumping several particles in a ...
fluidizedbeds, etc ; bubbles; fluids; methodology; photography; powders; Show all 6 Subjects
Abstract:
... Flow pattern transition is one of the most important mechanisms in fluidization technology. By employing the computational fluid dynamics-discrete element method simulation and high-speed photography experiments, the influence of the fluidization velocity on the flow pattern in a fluidized bed was studied. With the increase of the fluidization velocity, the flow pattern transformation undergoes th ...
fluidizedbeds, etc ; biomass; models; prototypes; sawdust; torrefaction; Show all 6 Subjects
Abstract:
... A prototype horizontal pulsed fluidized bed (HPFB) has been built for continuous biomass torrefaction in our lab. Solids residence time distribution (RTD) of hemlock sawdust in the HPFB reactor was measured to study particle transport and mixing using a pulse injection of particle tracer. Effects of weir height, gas pulsation frequency, solids feed rate and gas velocity were investigated. A modifi ...
fluidizedbeds, etc ; fluid mechanics; furnaces; models; prediction; Show all 5 Subjects
Abstract:
... This work studies the fluid dynamics of the solids in the splash zone of fluidized bed furnaces, with focus set on solids back-mixing and solids entrainment in order to enhance the understanding and prediction of the solids flow in the bottom region of the furnace. Experimental results show the establishment of a splash zone also for runs in absence of a dense bottom bed. A simple model assuming b ...
fluidizedbeds, etc ; fluid mechanics; mathematical models; technology; uncertainty; Show all 5 Subjects
Abstract:
... Coupled computational fluid dynamics - discrete element method (CFD-DEM) simulations are carried out to investigate the fluidization characteristics of gas-solid fluidized bed reactor (FBR) containing ternary particles (spheres, ideal and elongated cylinders, the latter two are rod-like particles). The mixing efficiency, velocity distribution, orientation distribution and height change of differen ...
fluidizedbeds, etc ; fluid mechanics; sand; technology; terminal velocity; Show all 5 Subjects
Abstract:
... Cyclones are one of the most common types of gas-solid separators used in circulating fluidized bed boilers. However, cyclones typically do not allow ash to leave the system through the cyclone exit, causing ash to build up in the fluidized bed and necessitating additional systems to remove ash that builds up in the bed. In this study, an alternative “disengager” gas-solid separator is proposed as ...
fluidizedbeds, etc ; activation energy; crystallization; evaporation; filtration; hydrogen; synergism; Show all 7 Subjects
Abstract:
... A green process is proposed to produce Na₂S from waste Na₂SO₄ through hydrogen agglomerate fluidized bed reduction of BaSO₄. In the new process, BaSO₄ acts as the circulating medium, and the synthesis of Na₂S from waste Na₂SO₄ is performed via a two-step approach. First, BaSO₄ is reduced to BaS by hydrogen at high temperatures. Then, the reduction product BaS is put into the Na₂SO₄ solution to pre ...
fluidizedbeds, etc ; cohesion; fluid mechanics; liquids; models; porosity; technology; Show all 7 Subjects
Abstract:
... Gas-fluidized beds of wet flexible fibers with small amounts of liquid are investigated using a coupled approach of Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD). A liquid-bridge force model is implemented to account for cohesive contact forces due to formation of liquid bridges among the wet fibers. The effects of initial bed height, degree of cohesion (characterized by a b ...
fluidizedbeds, etc ; cold; energy; fluid mechanics; gasification; oxygen; wavelet; Show all 7 Subjects
Abstract:
... A new staged fuel reactor (FR), which integrates a bubbling bed and a spouted fluidized bed, is proposed in the present work with regard to lowering the pressure drop of the staged FR during chemical looping applications. In order to gain insights into the gas–solid fluid dynamics of the new design, a cold experimental setup was established. The fluidization dynamics of the staged FR was investiga ...
fluidizedbeds, etc ; case studies; process control; technology; water content; Show all 5 Subjects
Abstract:
... This work investigates how process control of moisture content in continuously operated convective dryers for particulate bio-materials influences the product’s activity. As case study drying of baker’s yeast in a fluidized bed dryer is considered. Superiority of controlled process operation over un-controlled operation with respect to uncertainties in the falling-rate drying period as well as pro ...
fluidizedbeds, etc ; heat transfer; industry; systems engineering; technology; temperature; Show all 6 Subjects
Abstract:
... Fluidization engineering and technology are widely used in metallurgical industries, particularly ferrous metal industry, due to its advantages. However, such fluidized processing suffers from problems such as particle attrition and heat transfer. The influence of these problems could be serious in fluidized system design and operation. This paper reviews briefly the fluidized processing in variou ...
fluidizedbeds, etc ; case studies; energy; power generation; support vector machines; Show all 5 Subjects
Abstract:
... Under such a circumstance that the scale of renewable power connected into grids increases companied with more fluctuation, the flexibility and stability in power generation have been focus. Circulating fluidized bed (CFB) has unique merits in deep peak shaving, but its operation presents multi-influencing factors and multi-mode characteristics, which makes it very difficult to monitor the operati ...
fluidizedbeds, etc ; carbon dioxide; chemistry; fluid mechanics; process design; sorbents; Show all 6 Subjects
Abstract:
... Integrated bubbling-transport fluidized bed is a potential reactor for CO₂ capture with solid sorbents. The gas-particle flows in the reactor greatly influence the capture efficiency. This paper studied the gas-particle flow behaviors in this reactor, focusing on the particle circulation and gas entrainment. The results show that the particle circulation rate is mainly limited by the particle-retu ...