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Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds

Description: The purpose of this project was to investigate the origin of pressure fluctuations in fluidized bed systems. The study assessed the potential for using pressure fluctuations as an indicator of fluidized bed hydrodynamics in both laboratory scale cold-models and industrial scale boilers. Both bubbling fluidized beds and circulating fluidized beds were evaluated. Testing including both cold-flow models and laboratory and industrial-scale combustors operating at elevated temperatures. The study yielded several conclusions on the relationship of pressure fluctuations and hydrodynamic behavior in fluidized beds. The study revealed the importance of collecting sufficiently long data sets to capture low frequency (on the order of 1 Hz) pressure phenomena in fluidized beds. Past research has tended toward truncated data sets collected with high frequency response transducers, which miss much of the spectral structure of fluidized bed hydrodynamics. As a result, many previous studies have drawn conclusions concerning hydrodynamic similitude between model and prototype fluidized beds that is insupportable from the low resolution data presented.
Date: May 1, 1998
Creator: Bure, Ethan; Schroeder, Joel R.; Cruz, Ramon De La & Brown, Robert C.
Partner: UNT Libraries Government Documents Department

Pressure Fluctuations as a Diagnostic Tool for Fluidized Beds

Description: The purpose of this project is to investigate the origin of pressure fluctuations in fluidized bed systems. The study will asses the potential for using pressure fluctuations as an indicator of fluidized bed hydrodynamics in both laboratory scale cold-models and industrial scale boilers.
Date: April 23, 1998
Creator: Schroeder, Joel R. & Brown, Robert C.
Partner: UNT Libraries Government Documents Department

Fluidized bed electrowinning of copper. Final report

Description: The objectives of the study were to: design and construct a 10,000- amp fluidized bed electrowinning cell for the recovery of copper from acidic sulfate solutions; demonstrate the technical feasibility of continuous particle recirculation from the electrowinning cell with the ultimate goal of continuous particle removal; and measure cell efficiency as a function of operating conditions.
Date: July 1, 1997
Partner: UNT Libraries Government Documents Department

Granular filtration in a fluidized bed

Description: Successful development of advanced coal-fired power conversion system often requires reliable and efficient cleanup devices that can remove particulate and gaseous pollutants from high-temperature, high- pressure gas streams. A novel filtration concept for particulate cleanup has been developed at the U.S. Department of Energy`s Morgantown Energy Technology Center (METC). The filtration system consists of a fine metal screen filter immersed in a fluidized bed of granular material. As the gas stream passes through the fluidized bed, a layer of the bed granular material is entrained and deposited at the screen surface. This material provides a natural granular filter to separate fine particles from the gas stream passing through the bed. Since the filtering media is the granular material supplied by the fluidized bed, the filter is not subjected to blinding like candle filters. Because only the in-flowing gas, not fine particle cohesive forces, maintains the granular layer at the screen surface, once the thickness and permeability of the granular layer are stabilized, it remains unchanged as long as the in-flowing gas flow rate remains constant. The weight of the particles and the turbulent nature of the fluidized bed limits the thickness of the granular layer on the filter leading to a self-cleaning attribute of the filter. The granular filtration testing system consisted of a filter, a two-dimensional fluidized bed, a continuous powder feeder, a laser-based, in-line particle counting, sizing, and velocimeter (PCSV), and a continuous solid feeding/bed material withdrawal system. The two-dimensional, transparent fluidized bed allowed clear observation of the general fluidized state of the granular material and the conditions under which fines are captured by the granular layer.
Date: December 31, 1996
Creator: Mei, J.S. & Yue, P.C.
Partner: UNT Libraries Government Documents Department

Experience with atmospheric fluidized bed gasification of switchgrass

Description: Switchgrass was gasified in a bubbling fluidized bed reactor rated at 800 kW (2.75 MMBtu/hr) thermal input and operating at atmospheric pressure. A combustible gas with higher heating value varying between 4.2--5.9 MJ/Nm{sup 3} (114--160 Btu/scf) was produced. Carbon conversion was approximately 85%. Difficulties in feeding high moisture switchgrass inhibited smooth reactor operation. Several feed systems for switchgrass were tried with varying degrees of success. The results of gasification trials using switchgrass as fuel are described.
Date: December 31, 1998
Creator: Smeenk, J. & Brown, R.C.
Partner: UNT Libraries Government Documents Department

Simulation of coal gasification in a fluidized bed

Description: In this analysis of coal gasification, a fundamental approach is used where a set of multiphase (Eulerian) fluid dynamic equations, obtained either by a suitable averaging technique (Anderson and Jackson, 1976; Drew, 1971) or the formulations of continuum mechanics (Drew, 1983), is used to describe the conservation of mass, momentum, and energy for three interpenetrating phases. The particles, like the fluidizing gas, are described as interpenetrating continua. Different particle types are treated as distinct phases; in this study, the feed coal and the bed char are represented as separate phases in order to account for their different histories. Constitutive laws account for the exchange of momentum between phases (``drag``) and interphase energy transfer. The stresses within the granular phases are determined by a formulation based on the kinetic theory, characterized by a ``granular temperature``. A computer code, based on this multiphase hydrodynamic model, has been developed at the Morgantown Energy Technology Center for the detailed simulation of gas and particle dynamics in heavily loaded coal conversion processes (Syamlal, Rogers, O`Brien, 1994; Syamlal, 1995). The hydrodynamic simulation showed the reactor operated in a jetting/bubbling mode. A gas jet penetrated a considerable distance into the bed, and then detached as ``bubbles`` which rose to the top of the column. The reaction scheme indicated that the feed coal did not begin to devolatilize until it had traversed this region, because of the time required to heat up. Thus, volatiles were not released in the jetting region of the bed, but higher in the bed. The oxygen fed with the coal, however, reacted immediately with the recirculating hot char. The net effect of the char reaction scheme was to created. CO, which burned in the region where.the jet detached, creating a, fairly stable ``flame``. The tar reaction scheme indicated that none of the tar ...
Date: December 31, 1996
Creator: O`Brien, T.J.
Partner: UNT Libraries Government Documents Department

Analysis and control of the METC fluid bed gasifier. Quarterly report, April 1995--June 1995

Description: This document summarizes work performed for the period 4/1/95 to 7/31/95 on contract no. DE-FG21-94MC31384 (Work accomplished during the period 10/1/94 to 3/31/94 was summarized in the previous technical progress report included in the appendix of this report). In this work, three components will form the basis for design of a control scheme for the Fluidized Bed Gasifier (FBG) at METC: (1) a control systems analysis based on simple linear models derived from process data, (2) review of the literature on fluid bed gasifier operation and control, and (3) understanding of present FBG operation and real world considerations. Tasks accomplished during the present reporting period include: (1) Completion of a literature survey on Fluid Bed Gasifier control, (2) Observation of the FBG during the week of July 17 to July 21, and (3) Suggested improvements to the control of FBG backpressure and MGCR pressure.
Date: June 1, 1995
Partner: UNT Libraries Government Documents Department

Analysis and control of the METC fluid bed gasifier. Quarterly progress report, January--March 1995

Description: This document summarizes work performed for the period 10/1/94 to 3/31/95. In this work, three components will form the basis for design of a control scheme for the Fluidized Bed Gasifier (FBG) at METC: (1) a control systems analysis based on simple linear models derived from process data, (2) review of the literature on fluid bed gasifier operation and control, and (3) understanding of present FBG operation and real world considerations. Below we summarize work accomplished to data in each of these areas.
Date: March 1, 1995
Partner: UNT Libraries Government Documents Department

Final report on characterizing the dynamics of spatio-temporal data

Description: One principal goal of the grant was to model and analyze the dynamics of spatially extended chaotic systems. One of the principal tools used in the analysis was KLTOOL, a computer package developed by the principal investigators for Karhunen-Loeve analysis. The package was used to analyze video data from a laboratory experiment on cellular flames. A second goal of the project was to analyze complex time series whose underlying dynamics may be low dimensionally chaotic. Particular emphasis was placed on systems of possible relevance to energy production and distribution. The work attempted to characterize low-dimensional aspects of the dynamics of a fluidized bed, in particular, a transition from periodic to irregular behavior. Finally, collaborators worked on aspects of targeting in chaotic dynamical systems. This work showed that it is possible to switch a moderately high-dimensional chaotic process rapidly between prespecified periodic saddle orbits embedding within the attractor. Additional work extended previously-developed algorithms for the highly accurate computation of stable manifolds of periodic saddle orbits, which is essential to the successful application of targeting algorithms.
Date: September 1, 1998
Creator: Kostelich, E.J. & Armbruster, H.D.
Partner: UNT Libraries Government Documents Department

Ethanol production from dry-mill corn starch in a fluidized-bed bioreactor

Description: The development of a high-rate process for the production of fuel ethanol from dry-mill corn starch using fluidized-bed bioreactor (FBR) technology is discussed. Experiments were conducted in a laboratory scale FBR using immobilized biocatalysts. Two ethanol production process designs were considered in this study. In the first design, simultaneous saccharification and fermentation was performed at 35 C using {kappa}-carageenan beads (1.5 mm to 1.5 mm in diameter) of co-immobilized glucoamylase and Zymomonas mobilis. For dextrin feed concentration of 100 g/L, the single-pass conversion ranged from 54% to 89%. Ethanol concentrations of 23 to 36 g/L were obtained at volumetric productivities of 9 to 15 g/L-h. No accumulation of glucose was observed, indicating that saccharification was the rate-limiting step. In the second design, saccharification and fermentation were carried out sequentially. In the first stage, solutions of 150 to 160 g/L dextrins were pumped through an immobilized glucoamylase packed column maintained at 55 C. Greater than 95% conversion was obtained at a residence time of 1 h, giving a product of 165 to 170 g glucose/L. In the second stage, these glucose solutions were fed to the FBR containing Z. mobilis immobilized in {kappa}-carageenan beads. At a residence time of 2 h, 94% conversion and ethanol concentration of 70 g/L was achieved, giving an overall productivity of 23 g/L-h.
Date: August 1, 1998
Creator: Krishnan, M. S.; Nghiem, N. P. & Davison, B. H.
Partner: UNT Libraries Government Documents Department


Description: This technical report summarizes the research conducted and progress achieved during the period from October 1, 1997 to March 30, 1998. Numerical modeling and simulation on the gas velocity and pressure were continued to predict the flow patterns in the CFB. The renormalization group k-e turbulence model was employed to improve the predictions of the near the wall flow, wall heat/mass transfer, and wake/vortex shedding behavior. This model could provide more accurate prediction of swirl than in standard k-E model. The air velocity profile was predicted in 2-D velocity vector of the slide plate. The aeration (secondary) air flow rate reduced air velocity and caused a strong gas mixing processes. The air flowed from the high pressure region into the low pressure region. The aeration air injection affected on its neighborhood pressure profile. Two eddies are formed at level k=15 which is symmetrical with the aeration air inlet center line. It is very interesting to note that the air stream flows from the lower pressure region into the high pressure region. Experimental measurements will be conducted to understand heat transfer characteristics in the CFB system. In addition, numerical modeling and simulation will be continued to predict the flow patterns, velocity, pressure, temperature, and heat flux with the heat transfer effect in the CFB system.
Date: May 1, 1998
Partner: UNT Libraries Government Documents Department

Neural network-based monitoring and control of fluidized bed. Quarterly progress report, October 1, 1995--December 31, 1995

Description: This report summarizes work on chaotic behavior control in FBC systems. An update is given to the chaos control method designed to control the chaotic behavior in an FBC system; this method inludes a fully recurrent neural network called the Dynamic System Imitator (DSI). DSI mimics the behavior of a wide variety of dynamic systems in the real world; it was used for modeling linear, nonlinear and chaotic systems, and is also used for iterative prediction of chaotic system behavior. A general methodology for using the DSI to control a nonlinear system is applied to control the chaotic behavior of the Lorenz System. A plan is also outlined for using this method to the FBC system for predicting and controlling its chaotic behavior. Chaotic pressure data from an experimental FBC system was obtained (from METC) on normal and abnormal mixing. Results of chaos analysis applied to these data are presented. These techniques are used to identify the system behavior at different conditions, estimate system order, construct the system attractor, and locate the chaotic behavior in the pressure-drop time series data. Preliminary analysis show that both normal and abnormal conditions of FBC have chaotic characteristics. Objective is to develop a neuro-chaos controller to preserve the normal operational performance of the system.
Date: December 31, 1995
Creator: Bodruzzaman, M.
Partner: UNT Libraries Government Documents Department

Application of chaotic time series for the characterization and control of fluidization and combustion systems. CRADA final report for CRADA No. ORNL92-0127

Description: Oak Ridge National Laboratory and Babcock and Wilcox, a prominent U.S. boiler manufacturer, have collaborated under this CRADA to investigate the application of deterministic chaos theory to improve the performance of fossil fuel boilers. The types of boilers investigated were coal-fired fluidized beds and more conventional pulverized coal systems. The results of this investigation demonstrate that chaotic time series analysis of boiler signals (e.g., pressure, acoustic and/or optical signals) can be used to characterize the combustion dynamics with greater accuracy than is possible with conventional signal analysis. Further, it is expected that these new analysis techniques will lead to a new generation of boiler diagnostics and control technology that can make U.S. industry more competitive in the world boiler market. Babcock and Wilcox is initiating follow-on internal and external research to further develop the technology.
Date: February 1, 1996
Creator: Daw, C.S.; Fuller, T.A. & Flynn, T.J.
Partner: UNT Libraries Government Documents Department

AFBC co-firing of coal and hospital waste. Fourth quarterly report, 1997

Description: The project objective is to design, construct, install, provide operator training and start-up a circulating fluidized bed combustion system at the Lebanon Pennsylvania Veteran`s Affairs Medical Center. This unit will co-fire coal and hospital waste providing lower cost steam for heating and possibly cooling (absorption chiller) and operation of a steam turbine-generator for limited power generation while providing efficient destruction of both general and infectious hospital waste. The steam generated is as follows: Steam =20,000 lb/hr; Temperature = 353 F (saturated); Pressure= 125 psig; Steam quality = 98.5%
Date: July 1, 1997
Partner: UNT Libraries Government Documents Department


Description: This report is one of four reports written to provide background information regarding immobilization technologies remaining under consideration for supplemental immobilization of Hanford's low-activity waste. This paper provides the reader a general understanding of fluidized bed steam reforming and its possible application to treat and immobilize Hanford low-activity waste.
Date: April 8, 2011
Creator: WM, HEWITT
Partner: UNT Libraries Government Documents Department

Mutiscale Modeling of Segregation in Granular Flows

Description: Modeling and simulation of segregation phenomena in granular flows are investigated. Computational models at different scales ranging from particle level (microscale) to continuum level (macroscale) are employed in order to determine the important microscale physics relevant to macroscale modeling. The capability of a multi-fluid model to capture segregation caused by density difference is demonstrated by simulating grain-chaff biomass flows in a laboratory-scale air column and in a combine harvester. The multi-fluid model treats gas and solid phases as interpenetrating continua in an Eulerian frame. This model is further improved by incorporating particle rotation using kinetic theory for rapid granular flow of slightly frictional spheres. A simplified model is implemented without changing the current kinetic theory framework by introducing an effective coefficient of restitution to account for additional energy dissipation due to frictional collisions. The accuracy of predicting segregation rate in a gas-fluidized bed is improved by the implementation. This result indicates that particle rotation is important microscopic physics to be incorporated into the hydrodynamic model. Segregation of a large particle in a dense granular bed of small particles under vertical. vibration is studied using molecular dynamics simulations. Wall friction is identified as a necessary condition for the segregation. Large-scale force networks bearing larger-than-average forces are found with the presence of wall friction. The role of force networks in assisting rising of the large particle is analyzed. Single-point force distribution and two-point spatial force correlation are computed. The results show the heterogeneity of forces and a short-range correlation. The short correlation length implies that even dense granular flows may admit local constitutive relations. A modified minimum spanning tree (MST) algorithm is developed to asymptotically recover the force statistics in the force networks. This algorithm provides a possible route to constructing a continuum model with microstructural information supplied from it. Microstructures in ...
Date: August 3, 2007
Creator: Sun, Jin
Partner: UNT Libraries Government Documents Department

Solids Fraction Measurement with a Reflective Fiber Optic Probe

Description: A method has been developed to extract solids fraction information from a reflective fiber optic probe. The commercially available reflective fiber optic probe was designed to measure axial particle velocity (both up and down directions). However, the reflected light intensity measured is related to particle size and particle concentration. A light reflection model is used to relate the reflected light intensity to solids fraction. In this model we assume that the reflected light intensity is a fixed fraction, K1, of the total light intensity lost in penetration of a solid layer. Also, the solids fraction is related to particle concentration, N, in the light path, by N = K2 (1- ε), where (1-ε) is the solids fraction. The parameters K1 and K2 are determined through a calibration and curve fitting procedure. This paper describes this procedure and the steps taken to derive the values of K1 and K2. It is proposed that the reflective fiber optic can be used for real time measurement of solids fraction in a circulating fluid bed.
Date: November 1, 2006
Creator: Seachman, S.M.; Yue, P.C.; Ludlow, J.C. & Shadle, L.J.
Partner: UNT Libraries Government Documents Department

Investigation of Fuel Chemistry and Bed Performance in a Fluidized Bed Black Liquor Steam Reformer

Description: University of Utah's project entitled 'Investigation of Fuel Chemistry and Bed Performance in a Fluidized Bed Black Liquor Steam Reformer' (DOE Cooperative Agreement DE-FC26-02NT41490) was developed in response to a solicitation released by the U.S. Department of Energy in December 2001, requesting proposals for projects targeted towards black liquor/biomass gasification technology support research and development. Specifically, the solicitation was seeking projects that would provide technical support for Department of Energy supported black liquor and biomass gasification demonstration projects under development at the time.
Date: June 30, 2007
Creator: Whitty, Kevin
Partner: UNT Libraries Government Documents Department

Particle Pressures in Fluidized Beds. Final report

Description: This project studies the particle pressure, which may be thought of as the force exerted by the particulate phase of a multiphase mixture, independently of that exerted by other phases. The project is divided into two parts, one concerning gas and the other liquid fluidized beds. Previous work on gas fluidized beds had suggested that the particle pressures are generated by bubbling action. Thus, for these gas fluidized bed studies, the particle pressure is measured around single bubbles generated in 2-D fluidized beds, using special probes developed especially for this purpose. Liquid beds are immune from bubbling and the particle pressures proved too small to measure directly. However, the major interest in particle pressures in liquid beds lies in their stabilizing effect that arises from the effective elasticity (the derivative of the particle pressure with respect to the void fraction): they impart to the bed. So rather than directly measure the particle pressure, we inferred the values of the elasticity from measurements of instability growth in liquid beds the inference was made by first developing a generic stability model (one with all the normally modeled coefficients left undetermined)and then working backwards to determine the unknown coefficients, including the elasticity.
Date: September 1, 1996
Creator: Campbell, C.S.; Rahman, K. & Jin, C.
Partner: UNT Libraries Government Documents Department

Fundamental study on transient bubble (slug) behavior by characterizing transient forces of solid particles in fluidized beds. Topical report, January 1991--June 1992

Description: The objective of this work is to recognize and interpret the signals of transient motion of bubbles (slugs) in fluidized beds (METC/DOE) by measuring and utilizing the signals of transient gas phase pressure fluctuation, and also by taking the video pictures of transient motions of the bubbles and emulsion phase in fluidized beds. The two signals were measured simultaneously in a three dimensional fluidized bed. Correlation study on the voidage signal and pressure fluctuation was carried out. A domain concept was introduced and new bubble classification was suggested. A video recording approach was also developed to record the transient bubble motion in a two dimensional fluidized bed with a special consideration. This new approach enhances the understanding of bubble image and the physical meaning of transient particle forces. The fundamental mechanism of bubble flow was experimentally investigated and interesting new findings of the transient bubble flow were obtained.
Date: October 1, 1992
Creator: Kono, H.
Partner: UNT Libraries Government Documents Department