Fluid mechanics for fluidized beds uw faculty web server. Fluidized bed reactors are capable of handling large amounts of feed and catalyst. When a gas flow is introduced through the bottom of a bed of solid particles, it will move upwards through the bed via the empty. The primary function of a circulating fluidized bed cfb boiler is to transform the chemical energy in a fuel into useful heat in steam using the cfb mode of gassolid contacting. In the case of a fluidized bed that is slightly nonuniform this equation contains two dependent variables, the local mean particle velocity v and the local concentration. Pdf fluidization characteristics of a prototype fluidized bed. In fluidizedbed combustion, a bed of crushed solid particles usually six millimetres or less is made to behave like a fluid by an airstream passing from the bottom of the bed at sufficient velocity to suspend the material in it. If the ratio of the height to the diameter of the bed is high enough, the size of bubbles may become almost the same as diameter of the bed. Use of fluidized bed technology details later in the course. Before we discuss reactorengineering issues of fluidized bed reactors, we briefly. The fluidized bed reactor has the ability to process large volumes of fluid. An introduction to parameterizing geometric models, vijay srinivasan.
An experimental study on air gasification of polypropylene was conducted in a fluidized bed gasifier with an insider diameter id of 100mm and a height of 4. University of groningen particle transport in fluidized. Fluidized beds are a very important and common process technology used for everything from roasting coffee beans and drying agricultural grains to fluid catalytic cracking and pharmaceutical granulation. Computational fluid dynamics simulation of fluidized bed. A circulating bed usually has a superficial velocity greater than ft. It operates on the principal that when an evenly distributed air is passed upward through a finely divided bed of solid particles at low velocity, the particles remain undisturbed, but if the velocity of air flow is. Distillation column theory and live experiment duration. The text contains various studies, facts, and discussions on fluidized beds. Plant theory fluidized bed combustion flashcards quizlet. In fluidization process, hot air is introduced at high. The workshop provides the basics of drying, granulating, coating and pelletizing and outlines their applications in thepowder processing industry. The twophase theory is represented by the equation. A fluidized bed is formed when a fixed mass of solid particulate is situated in appropriate conditions to support a solidfluid mixture uniformity to behave as a fluid. Chemical engineering laboratory 3, ce 427 packed and fluidized bed experiment introduction packed and fluidized beds play a major role in many chemical engineering processes.
The concept of two fluid phases in a bubbling fluidised bed and its application to a reactor model originates in the work of johnstone and colleagues at the university of illinois 1,2. Introduction drying is utilized to remove moisture from a moist solid by converting the moisture into a gaseous state. The effect of the equivalence ratio, bed height and fluidization velocity on various. Fluidized beds are used widely in chemical processing industries for separations, rapid mass and heat transfer operations, and catalyic reactions. A fluidised bed is a physical phenomenon occurring when a quantity of a solid particulate substance is placed under appropriate conditions to cause a solidfluid mixture to behave as a. The movement of a gas through a fluidized bed can best be described using the twophase theory 5. A labscale fluidized bed made in plexiglass, with a diameter of 146 mm and a uniform air. Fluidized bed combustion types and advantages electrical4u. Using higbies penetration theory and his analogy for mass transfer from a. Fluidized bed reactor basic mechanism, mass transfer in fluidized beds, reaction behaviour in a fluidized bed, mole balance on the bubble, the cloud, and the slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Fundamentals of fluidizedbed chemical processes presents a survey of the design, operation, and chemical processes of fluidized bed reactors. Circulating fluidized beds cfb, where gases are at a higher velocity sufficient to suspend the particle bed, due to a larger kinetic energy of the fluid. Fluid mechanics for fluidized beds to better understand fluidization of a particle bed, it is necessary to determine what range of flow rates allow fluidization, and also, what flow rates will begin to carry the particles out the top of the particle chamber. A new theory of the instability of a uniform fluidized bed.
Compared to a bubbling bed, a circulating bed has significantly higher solids concentration throughout the combustor. This article explains the basics of fluidization theory and outlines how to design a typical fluidized bed. Pdf the fluidization characteristics of a prototypefluidized bed. Fluidized bed combustion fbc is a wellestablished commercial combustion technology, in which combustion occurs in the presence of high concentrations of solids, typically sand, ash or that derived from limestone, if insitu sulphur capture is required i. A result of the mixing is excellent temperature stability and increased masstransfer and reaction rates. Data for fluidtzed bed drying were obtained from the monsanto companys fluid bed dryer. Unit design data fluidized bed combustion voluntary. Experimental and theoretical study of minimum fluidization. Air lift fluidized bed bioreactor for waste water treatment using marine sponges as adsorbent duration. For the catalytic cracking of petroleum naphthas to form gasoline blends, for example, the virtues of the fluidized bed reactor drove its competitors from the market. These pages were constructed to convey the importance of fluidized bed reactors fbrs in todays petroleum and chemical process industries. Pdf air gasification of polypropylene plastic waste in. Multiphase heat transfer with fluidized bed temperature control, heat addition, extraction in fluidized beds example co 2 capture and regeneration post combustion temperature control is essential for optimal operation capture is exothermic regeneration is endothermic experimental studies and mechanistic theory.
Wen west virginia university morgantown, west virginia 26506. Drying of materials which are granular, free flowing, not agglomerating, not fragile, not vulnerable to. Mechanisms for the passage of electric current through a fluidized bed are discussed, and corresponding estimates for the effective electrical conductivity are given. Fluidized bed combustion an overview sciencedirect topics.
According to the twophase theory of fluidization proposed by toomey and. In fluidized bed combustion boiler technology when air or gas is passed through an inert bed of solid particles such as sand supported on a fine mesh or grid, the air initially will seek a path of least resistance and pass upward through the sand. Heat transfer in fluidized bed tube heat exchanger. Stationary or bubbling bed sb circulating fluidized beds cfb vibratory fluidized beds vfb. A fluidized bed is a wellstirred reactor, characterized by excellent gassolid contact, and uniformity of temperature and composition across the bed. Fluidized bed reactors are heterogeneous catalytic reactors in which the mass of catalyst is fluidized. The fluidized bed reactor page university of washington. It is used in the granulation process for drying the material to get desired moisture content in the tablet formulation granules required for perfect compression of tablets. Circulating fluidized bed technology ii is a result of a series of sciencerelated conferences in the 1980s. Fluidized bed dryer also called fluid bed dryer is a kind of equipment used extensively in the pharmaceutical industries to reduce moisture content of pharmaceutical powder and granules.
This process occurs when a fluid liquid or gas is passed up through the granular material. A study of efficient drying parameters for bed dryers. Fluidization or fluidisation is a process similar to liquefaction whereby a granular material is converted from a static solidlike state to a dynamic fluidlike state. Fbc fluidized bed combustion is a combustion technology used to burn solid fuels in steam boilers. Bed height and material density effects on fluidized bed iowa state. According to this theory, gas moves through the bed in two ways as bubbles, and as part of an emulsion or dense phase as illustrated in figure 2. Packedbed situations include such diverse processes as filtration, wastewater treatment, and the flow of crude oil in a petroleum reservoir. A fluidized bed may be defined as the bed of solid particles behaving as a fluid. This allows for extensive mixing in all directions. Fluidized bed dryer fbd is well known and widely used equipment in granulation area of pharmaceutical manufacturing.
The book begins by going through the rise and fall of circulating systems, specifically fluid dynamics. Our pilot plant group wishes to insert a fluidized bed reactor in one of the tail gas. Fluidization chemical engineering at the university of floridahome. This webinar explores the fundamentals of fluidization. Results agreed when using both theoretical models and experimental. Koch dl, sangani as 1999 particle pressure and marginal stability limits for a homogeneous monodisperse gas fluidized bed. Pdf design theory of circulating fluidized bed boilers. Wheat drying, fluidized bed dryer, high efficiency drying parameter, allotted drying time, energy efficiency, exergy efficiency, mathematical model 1. As the velocity is increased further still, the bubbles in a bubbling fluidized bed will coalesce and grow as they rise. As such the surface of the bed is less smooth and larger particles can be entrained from the bed than for stationary beds. At this point, a bubbling fluidized bed occurs as shown in figure 2. This workshop on fluidized bed technology is a perfect combination of theory, handson training and demonstrations. The first chapter examines the basic physics of gassolid fluidization.
Other articles where fluidizedbed combustion is discussed. Fluidized beds are classified by their flow behavior. Since then numerous and different modifications have been made to. Fundamentals of fluidizedbed chemical processes 1st edition. Fluidization is a method of mixing fuel and air in a specific proportion, for obtaining combustion. The purpose of this work thus is to put up a general theoretical framework.
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