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Applications of kinetic theory

Description: The overall objective of this investigation is to develop experimentally verified models for circulating fluidized bed (CFB) combustors. This report presents the author's derivation of analytical solutions useful in understanding the operation of a CFB. The report is in a form of a chapter that reviews the kinetic theory applications.
Date: January 1, 1992
Creator: Gidaspow, D.
Partner: UNT Libraries Government Documents Department

Computation of hydrodynamics using kinetic theory

Description: Rigorous methods of kinetic theory were used to derive particular phase viscosities and granular conductivities. This new kinetic theory predicted flow behavior and oscillations in a complete loop of a CFB. The results were compared to computations with imposed gas phase turbulence in the riser. The computations were repeated for production of synthesis gas from char.
Date: December 1, 1991
Creator: Gidaspow, D.
Partner: UNT Libraries Government Documents Department

Hydrodynamic models for slurry bubble column reactors. Sixth technical progress report

Description: The objective of this investigation is to convert the gas-solid-liquid fluidization model into a predictive design model. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid and particulate phases. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. This report presents measurements of granular temperature of Air Products catalyst. The report is in the form of a preliminary paper, entitled ``Dynamics of Liquid-Solid Fluidized Beds with Small Catalyst Particles.`` The principal results are as follows: (1) For the liquid-solid system the granular temperature is much smaller than for a corresponding gas-solid system. This may be due to the larger viscosity of the liquid in comparison to air. (2) The collisional viscosity of the catalyst is correspondingly much smaller than that of catalyst particles in the air. (3) The dominant frequency of density oscillations is near two Hertz, as expected for a gas-solid fluidized bed. There exists a link between this low frequency and the high frequency of catalyst particle oscillations. The Air Products fluidized bed reactor is designed to produce methanol and synthetic fuels from synthesis gas.
Date: January 1, 1996
Creator: Gidaspow, D.
Partner: UNT Libraries Government Documents Department

Hydrodynamic models for slurry bubble column reactors. Third technical progress report, January 1995--March 1995

Description: The objective of this investigation is to convert our {open_quotes}learning gas-solid-liquid{close_quotes} fluidization model into a predictive design model. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid and particulate phases. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. After a discussion of our research with the DOE-Air Products team in January, we decided to concentrate on the slurry configuration of interest to DOE-Air Products which has no recirculation of liquid. In such a system the gas is the continuous phase, rather than the liquid that we had used in our model in the past. We have built such a cold flow two dimensional plastic model. We have also changed our computer code. At the request of Air Products and DOE we have started a simulation of LaPorte RUN E-8.1 (1991) for production of methanol as described in the Air Products report sent to us. For isothermal operation, there is good mixing, and the preliminary results shown in this report indicate that we should obtain an agreement between the experiment and the simulations. A final report will be prepared upon completion of the simulation.
Date: April 1, 1995
Creator: Gidaspow, D.
Partner: UNT Libraries Government Documents Department

Hydrodynamic models for slurry bubble column reactors. Fifth technical progress report

Description: The objective of this work is to convert our `learning gas-solid-liquid` fluidization model into a predictive design model. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid, and particulate phases. Model verification involves a comparison of these computed velocities and volume fractions to experimental values.
Date: October 1, 1995
Creator: Gidaspow, D.
Partner: UNT Libraries Government Documents Department

Separation of particles from coal-derived liquids via surface charge properties. Quarterly progress report, September 15, 1977--December 15, 1977. [Electrofilters]

Description: A novel device called a cross-flow electrofilter was constructed and tested with a synthetic slurry. Preliminary data indicate that it should be an alternate device for removing particles from coal derived slurries and be able to compete with pressure precoat filters and hydroclones in its ability to remove particles from liquefaction and solvent refined coal process streams.
Date: January 1, 1977
Creator: Gidaspow, D.; Wasan, D.T. & Lee, C.
Partner: UNT Libraries Government Documents Department

Hydrodynamics of circulating fluidized beds: Kinetic theory approach

Description: Rigorous methods of kinetic theory were used to derive particular phase viscosities and granular conductivities. This new kinetic theory predicted flow behavior and oscillations in a complete loop of a CFB. The results were compared to computations with imposed gas phase turbulence in the rise. The computations were repeated for production of synthesis gas from char. 6 refs., 12 figs., 3 tabs.
Date: January 1, 1991
Creator: Gidaspow, D.; Bezburuah, R. & Ding, J.
Partner: UNT Libraries Government Documents Department

Dynamic performance characterization of bound, porous silica gel desiccant

Description: Drying of air with silica gel is a well established procedure. However, for the specific use of silica gel in a novel desiccant air conditioning system, which continually cools the silica gel and utilizes solar energy for silica gel regeneration, conventional packed bed devices are not suitable. For this system to operate effectively the silica gel must not rise in its temperature or its capacity will be greatly diminished. Dynamic dehumidificatuion performance was investigted for a silica gel desiccant fabricated in bound, porous paper-like sheets. Sheets of various thickness (0.7 to 3 mm) were fabricated and tested under several dynamic flow conditions in a flat rectangular channel apparatus. During each experiment conditions of inlet moisture, air flowrate, and sheet temperature were maintained constant. Comparisons were also made with conventional silica gel pellets and with other forms of bound silica gel. The sheets show superior utilization of silica gel in short times (30 minutes or less). Tests were also made to examine the sheet structure in order to explore the effect of temperature on the porous structure, and to obtain pore size distributions.
Date: October 1, 1979
Creator: Onischak, M.; Gidaspow, D.; Perkari, S. & Sasaki, T.
Partner: UNT Libraries Government Documents Department

Hydrodynamic models for slurry bubble column reactors. Eighth technical progress report, April 1996--June 1996

Description: The objective of this investigation is to convert our {open_quotes}learning gas - solid - liquid{close_quotes} fluidization model into a predictive design model. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid and particulate phases. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. As promised in the SIXTH TECHNICAL PROGRESS REPORT, January 1996, this report presents our measurements of granular temperature of Air Products catalyst in our new two dimensional bubble column with controlled jets that roughly approximates the Air Products methanol reactor. We have observed much higher granular temperatures with gas flow than was the case for liquid flow with Air Products catalyst. This means there is much better stirring caused by the high gas flow; clearly a desirable feature in a reactor. We have also observed that there exists a maximum in granular temperature at low solids loading. Operationally this means it may not be desirable to operate at very high catalyst concentrations due to reduced stirring at the high catalyst concentrations. This behavior is very similar to that observed by us in a circulating fluidized bed used to make gasoline from coal, a study to appear in the AIChE Journal.
Date: July 1, 1996
Creator: Gidaspow, D.
Partner: UNT Libraries Government Documents Department

Hydrodynamic models for slurry bubble column reactors. Seventh technical progress report, January--March 1996

Description: The objective of this investigation is to convert our ``learning gas solid-liquid`` fluidization model into a predictive design model. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid and particulate phase. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. A hydrodynamic model for multiphase flows, based on the principles of mass, momentum and energy conservation for each phase, was developed and applied to model gas-liquid, gas-liquid-solid fluidization and gas-solid-solid separation. To simulate the industrial slurry bubble column reactors, a computer program based on the hydrodynamic model was written with modules for chemical reactions (e.g. the synthesis of methanol), phase changes and heat exchangers. In the simulations of gas-liquid two phases flow system, the gas hold-ups, computed with a variety of operating conditions such as temperature, pressure, gas and liquid velocities, agree well with the measurements obtained at Air Products` pilot plant. The hydrodynamic model has more flexible features than the previous empirical correlations in predicting the gas hold-up of gas-liquid two-phase flow systems. In the simulations of gas-liquid-solid bubble column reactors with and without slurry circulation, the code computes volume fractions, temperatures and velocity distributions for the gas, the liquid and the solid phases, as well as concentration distributions for the species (CO, H{sub 2}, CH{sub 3}0H, ... ), after startup from a certain initial state. A kinetic theory approach is used to compute a solid viscosity due to particle collisions. Solid motion and gas-liquid-solid mixing are observed on a color PCSHOW movie made from computed time series data. The steady state and time average catalyst concentration profiles, the slurry height and the rates of methanol production agree well with the measurements obtained at an Air Products` pilot plant.
Date: April 1, 1996
Creator: Gidaspow, D.
Partner: UNT Libraries Government Documents Department

Predictive models for circulating fluidized bed combustors

Description: The overall objective of this investigation is to develop experimentally verified models for circulating fluidized bed (CFB) combustors. The purpose of these models is to help American industry, such as Combustion Engineering, design and scale-up CFB combustors that are capable of burning US Eastern high sulfur coals with low SO{sub x} and NO{sub x} emissions. In this report, presented as a technical paper, solids distributions and velocities were computed for a PYROFLOW circulating fluidized bed system. To illustrate the capability of the computer code an example of coal-pyrite separation is included, which was done earlier for a State of Illinois project. 24 refs., 20 figs., 2 tabs.
Date: November 1, 1989
Creator: Gidaspow, D.
Partner: UNT Libraries Government Documents Department

Characteristics and stability analyses of transient one-dimensional two- phase flow equations and their finite difference approximations

Description: Equation systems describing one-dimensional, transient, two-phase flow with separate continuity, momentum, and energy equations for each phase are classified by use of the method of characteristics. Little attempt is made to justify the physics of these equations. Many of the equation systems possess complex-valued characteristics and hence, according to well-known mathematical theorems, are not well-posed as initial-value problems (IVPs). Real-valued characteristics are necessary but not sufficient to insure well-posedness. In the absence of lower order source or sink terms (potential type flows), which can affect the well-posedness of IVPs, the complex characteristics associated with these two-phase flow equations imply unbounded exponential growth for disturbances of all wavelengths. Analytical and numerical examples show that the ill-posedness of IVPs for the two-phase flow partial differential equations which possess complex characteristics produce unstable numerical schemes. These unstable numerical schemes can produce apparently stable and even accurate results if the growth rate resulting from the complex characteristics remains small throughout the time span of the numerical experiment or if sufficient numerical damping is present for the increment size used. Other examples show that clearly nonphysical numerical instabilities resulting from the complex characteristics can be produced. These latter types of numerical instabilities are shown to be removed by the addition of physically motivated differential terms which eliminate the complex characteristics. (auth)
Date: January 1, 1975
Creator: Lyczkowski, R.W.; Gidaspow, D.; Solbrig, C.W. & Hughes, E.D.
Partner: UNT Libraries Government Documents Department

Hydrodynamic models for slurry bubble column reactors. Fourth technical progress report

Description: The objective of this investigation is to convert our ``learning gas-solid-liquid`` fluidization model into a predictive design model. The IIT hydrodynamic model computes the phase velocities and volume fractions of gas, liquid and particulate phases. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. The simulation of Air Product methanol reactors described in this paper are continuing. Granular temperatures and viscosities have been computed. Preliminary measurements of granular temperatures using the Air Product catalysts were obtained using our CCD camera.
Date: July 1, 1995
Creator: Gidaspow, D.
Partner: UNT Libraries Government Documents Department

Spectral analysis of CFB data: Predictive models of Circulating Fluidized Bed combustors

Description: The overall objective of this investigation is to develop experimentally verified models for circulating fluidized bed (CFB) combustors. Spectral analysis of CFB data obtained at Illinois Institute of Technology shows that the frequencies of pressure oscillations are less than 0.1 Hertz and that they increase with solids volume fraction to the usual value of one Hertz obtained in bubbling beds. These data are consistent with the kinetic theory interpretation of density wave propagation.
Date: April 1, 1992
Creator: Gamwo, I.K.; Miller, A. & Gidaspow, D.
Partner: UNT Libraries Government Documents Department

Predictive models of circulating fluidized bed combustors: SO[sub 2] sorption in the CFB loop

Description: The overall objective of this investigation is to develop experimentally verified models for circulating fluidized bed (CFB) combustors. Sorption of S0[sub 2] with calcined limestone was studied in a PYROFLOW type CFB loop at conditions approximating those found in a CFB combustor. Initially the CFB loop contained 150 micron CaO particles of a density of 3.3 g/cm[sup 3] and air at 1143[degrees]K and 3.25 atm. Atzero time, air containing 600 ppm SO[sub 2], was introduced into the riser bottom at 1143[degrees]K. The effect of gas velocity, sorbent inventory and inlet pressure on the sorption of SO[sub 2], were studied isothermally by running our hydrodynamic code with the S0[sub 2] sorption conservation of species equation. At a velocity of 5m/sec., reported to be a typical velocity by PYROPOWER, there is reasonably good S0[sub 2] removal. At 10 m/sec the S0[sub 2] removal is poor. The best SO[sub 2], removal is for a velocity of 5 m/s and a high bed inventory, initial bed height, H = 9m. Most of the S0[sub 2] is removed in the first two meters of the reactor. However, the S0[sub 2] removal is not complete at the bed outlet. This is due to mixing. At the left wall of the reactor (wall opposite the solids inlet) the S0[sub 2] removal was poor due to gas bypassing caused by the asymmetrical solids inlet. Simulation of the PYROPOWER loop with a symmetrical inlet gave us an order of magnitude improvement over the conventional PYROPOWER system. These results demonstrate the practical utility of the predictive model that we have developed over the last three years.
Date: February 1, 1993
Creator: Gidaspow, D. & Therdthianwong, A. (Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Chemical Engineering)
Partner: UNT Libraries Government Documents Department

Pressurized fluidized-bed hydroretorting of Eastern oil shales oil dedusting

Description: This Topical Report on Shale Oil Dedusting'' presents the results of a research program conducted by the Illinois Institute of Technology (IIT, Chicago) to determine the suitability and effectiveness of the lamella electrosettler -- a novel solid-liquid separation device -- for removing fine shale particles from shale oil via the application of an electric field. The work was conducted by IIT from November 1989 through December 1990 as a subcontractor to the Institute of Gas Technology. The overall objective of the larger program was to develop the Pressurized Fluidized-Bed Hydroretorting (PFH) Process for EasternOil Shales.'' The subtask undertaken by IIT was part of a larger task entitled Testing of Process Improvement Concepts.'' The lamella electrosettler has been shown to be an effective method for separating fine particulate (including colloidal) matter from a liquid using the application of an electric field. Using the walls of the settler as electrodes and during continuous operation, solids migrate preferentially toward one of the electrodes and become concentrated in the refuse stream. The product stream is clarified of particulates. The success of the process depends upon the physical properties of the solids and liquids being tested. A sample with a high specific conductance is not suitable for separation in the lamella electrosettler. The liquid begins to heat up under the influence of the electric field and, eventually, may short. Also, under these conditions, the particles cannot maintain a charge. The high conductivity of the shale oil samples tested rendered them unsuitable for further testing in the lamella electrosettler.
Date: November 1, 1991
Creator: Lau, F.S. (Institute of Gas Technology, Chicago, IL (United States)); Gidaspow, D.; Jayaswal, U. & Wasan, D.T. (Illinois Inst. of Tech., Chicago, IL (United States))
Partner: UNT Libraries Government Documents Department

Pressurized fluidized-bed hydroretorting of Eastern oil shales -- Sulfur control

Description: This topical report on Sulfur Control'' presents the results of work conducted by the Institute of Gas Technology (IGT), the Illinois Institute of Technology (IIT), and the Ohio State University (OSU) to develop three novel approaches for desulfurization that have shown good potential with coal and could be cost-effective for oil shales. These are (1) In-Bed Sulfur Capture using different sorbents (IGT), (2) Electrostatic Desulfurization (IIT), and (3) Microbial Desulfurization and Denitrification (OSU and IGT). The objective of the task on In-Bed Sulfur Capture was to determine the effectiveness of different sorbents (that is, limestone, calcined limestone, dolomite, and siderite) for capturing sulfur (as H{sub 2}S) in the reactor during hydroretorting. The objective of the task on Electrostatic Desulfurization was to determine the operating conditions necessary to achieve a high degree of sulfur removal and kerogen recovery in IIT's electrostatic separator. The objectives of the task on Microbial Desulfurization and Denitrification were to (1) isolate microbial cultures and evaluate their ability to desulfurize and denitrify shale, (2) conduct laboratory-scale batch and continuous tests to improve and enhance microbial removal of these components, and (3) determine the effects of processing parameters, such as shale slurry concentration, solids settling characteristics, agitation rate, and pH on the process.
Date: May 1, 1992
Creator: Roberts, M.J.; Abbasian, J.; Akin, C.; Lau, F.S.; Maka, A.; Mensinger, M.C. et al.
Partner: UNT Libraries Government Documents Department