Fluidized beds temperature fields

In addition to packed catalyst bed, a fluidized bed irradiated by single and multi-mode microwave field, respectively, was also modeled by Roussy et al. [120]. It was proved that the equality of solid and gas temperatures could be accepted in the stationary state and during cooling in a single-mode system. The single-mode cavity eliminates the influence of particle movements on the electric field distribution. When the bed was irradiated in the multimode cavity, the model has failed. Never-... 

FAA FA FBC FC FEBEX FFFF FGD FP FSU FT FTIR FUETAP Flame atomic absorption Fly ash Fluidized bed combustion Filter cake Full-scale engineered barriers experiment (in crystalline host rock) Flow-field flow fractionation Flue gas desulphurization Fission products Former Soviet Union Fourier transforms Fourier transformed infrared spectroscopy Formed under elevated temperature and pressure... 

Modification of silica gel with volatile or gaseous compounds is performed in the vapour phase. Industrial-scale reactors and laboratory scale gas adsorption apparatus have been used. In the industrial field, fluidized bed and fluid mill reactors are of main importance. In fluidized bed reactors,82 the particles undergo constant agitation due to a turbulent gas stream. Therefore, temperatures are uniform and easy to control. Reagents are introduced in the system as gases. Mass transport in the gas phase is much faster than in solution. Furthermore, gaseous phase separations require fewer procedural steps than solution phase procedures, and may also be more cost-effective, due to independence from the use and disposal of non-aqueous solvents. All these advantages make the fluidized bed reactors preferential for controlled-process industrial modifications. 

Since its foundation the Department of Chemical Engineering and Industrial Chemistry of the V.U.B. acquired considerable experi-eice in the field of high temperature processes, -with studies on steam-reforming of natural gas, pyrolysis of hydrocarbons and catalytic combustion of hydrocarbons. The Department conducted fundamental studies as well as contract work for industry, e.g. in the domain of fluidized bed techniques, incinerator grate mechanisms and small waste-fed boilers. An assessment on current thermal disposal techniques was prepared on behalf of E.E.C.[ 5 57958] ... 

Additional extensive reviews of high-temperature gas cleanup by means of, among other devices, candle filters have been summarized by Di Carlo and Foscolo [51]. Smith and Ahmadi [52] review the field of hot gas filtration in relation to pressurized fluidized bed combustion (PFBC) and integrated combined cycle gasification (IGCC). 

Preparation of filters in slabs or in powders suitable to be placed on air channels in fluidized beds or else as selective adsorbants on process lines. In recent years we made interesting approaches at COGEM A in this field using freeze-dried silica and alumina for the retention of radionuclides, acid droplets, and contaminants in the ventilation ducts of nuclear plants. Besides their great efficiency and low pressure drop the most interesting feature of these freeze-dried filters is that they can withstand extreme pH conditions and high temperatures. 

Dijkhuizen W, Bokkers GA, Deen NG, van Sint Annaland M, Kuipers JAM Extension of PIV for measuring granular temperature field in dense fluidized beds, AIChE J 53 108, 2007. 

The most attractive feature of a turbulent fluidized bed is its uniform temperature field. Thus the conversion can be obviously improved at fully developed turbulent fluidization for most isothermal catalytic fluidized bed reactors compared with bubbling fluidization. At the same time, the solids backmixing is also violent in turbulent fluidization, which in turn intensifies the gas backmixing. A wide gas RTD is very harmful to the selectivity of a chemical process with side reactions. 

Simultaneously, the heat transfer coefficient vvas calculated from Eq. 4.23. To this purpose, the temperature in the core of the fluidized bed, Tbed. was measured. Heater temperature was monitored by a PtlOO placed as dose as possible to the heater surface and kept approximately constant by a PID controller. The temperature of the heater surface, T, was obtained by finite element method (FEM) computations of the temperature field in the heater, being always very dose to the measured temperature. Finally, the heat flow rate was determined from the electrical power consumption of the heater, after minor correction for its thermal inertia upon slight changes during temperature control. 

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