Results 1 - 10 of 3117
Results 1 - 10 of 3117. Search took: 0.031 seconds
|Sort by: date | relevance|
[en] The fundamental aim of this work is biomass utilization for gas production, which will be used ecologically and with efficiency for obtaining energy. For this reason, a pilot plant was constructed for biomass gasification in a fluidized bed reactor. The practical solution to fluidization of inert material, to fuel supplying, to ash removing and the system for analyzing of produced gas, were presented. The pilot plant is tested on rise hulls from the Kocani region and the fluidization was carried out with air under pressure and the quartz sand was used as inert material. The influence of the temperature and the height of fluidized bed on the minimum fluidized velocity was examined in different working conditions. Also, the influence of the working parameters (granulation and height of the inert bed material, pressure of the gas for fuel supply and the fuel supply) on the composition of gas produced by gasification, was examined. Mathematical model for the complete process was developed and all material flows were calculated. According to the calculated coefficient of over air it can be concluded that the process is carried out with partial fuel combustion i.e. the process of gasification is performed in the reactor. From the obtained results and their analyses, it can be generally said that the aim of this doctoral thesis is accomplished. (Author)
[en] Design, modeling and simulation of fluidized bed risers and reactors depend strongly on the knowledge, operational and hydrodynamic characteristics. In this study effort has been made to describe fluidization phenomenon and its application in fluidized beds is briefly explained. The bubble fluidized bed reactors will be introduced and the computerized calculation needed for simulating of a fluidized bed riser with 0.3m diameter and 5 m height will be given. The effect of bed height on the bubble diameter and mass transfer area is calculated and the result are discussed. Operational; conditions of the bed, type and characteristics of the catalyst, has been selected so to suit the production of Maleic Anhyd ric from the n-Butane oxidation
[en] The RAFAKO Boiler Engineering Company offer of standard and circulation fluidized bed boilers, developed in response to the market demand, is presented. The technology for wet and semi-dry flue gas desulfurization is also included in the offer
[en] Fluidized bed combustion is defined as the burning of fuel solid particles with the contact of hot ash or sand particles into a fluid like state when sufficiently high velocity air or gas is forced to enter through the grate. This method of contacting has a number of characteristics fluidization engineering is concerned with efforts to take advantage of this behavior and put it to good use. A fluidized bed combustor boiler (FBCB) has many advantages over conventional boiler such as high rate of heat transfer coefficient, environmental acceptability and fuel flexibility. With the improved rate of heat transfer in FBC the size of boiler can be substantially reduced. This technology is most suitable for the utilization of low grade Pakistani coal which contain sulfur (4-10%) and ash (20-30%) contents. (author)
[en] Fluidized bed process have been used mostly in the petroleum and paper industries, and for processing nuclear wastes, spent cook liquor, wood chips, and sewage sludge disposal. Even at MINT some of the equipment available used this principal. Before we use or purchase this equipment, it is very grateful if we could understand how the system has been designed. The hydrodynamic fluidization studies is very important in designing of fluidized bed system especially in determining the minimum fluidizing velocity, terminal velocity, flexibility of operation, slugging condition, bubble size and velocity, and transport disengaging height. They can be determined either by calculation or experimentation. This paper will highlight the hydrodynamic study that need to be performed in designing of fluidized bed system so that its can be used appropriately. (Author)
[en] The characteristics of particle movement at the walls of a fluidized bed are important for control of fluidbed reactor systems. For most reactor systems, heat is either introduced or removed through wall surfaces. The presence of walls also affects the characteristics of gas and particle mixing within the reactor. Therefore, knowledge of particle behavior, particularly in the vicinity of reactor walls, is of practical importance to the design of fluid-bed systems.
[en] The thermal-hydraulic behavior of rotating bed reactors is analyzed using the drift-flux model to predict fuel bed expansion. A new correlation for onset of fluidization is developed for this purpose. Parametric effects are discussed and first priority research areas are delineated. Reactor design curves are developed showing small cores between 25- and 50-cm radius should be capable of generating power up to 5000 MW. With exhaust temperatures approaching 3000 K using hydrogen as a propellant, these devices seem especially suited for use in space-tug concepts
[en] Highlights: • We simulated an 8 MWth steam gasification system with the CPFD code Barracuda. • The prediction of the hydrodynamics depends strongly upon the chosen drag law. • The EMMS drag law predicted best the bed material recirculation and pressure drops. • The model of the DFB plant is able to predict the operation accurately. - Abstract: Dual fluidized bed (DFB) systems for biomass gasification consist of two connected fluidized beds with a circulating bed material in between. Inside such reactor systems, rough conditions occur due to the high temperatures and the movement of the bed material. Computational fluid dynamics calculations are a useful tool for investigating fluid dynamics inside such a reactor system. In this study, an industrial-sized DFB system was simulated with the commercial code CPFD Barracuda. The DFB system is part of the combined heat and power (CHP) plant at Güssing, situated in Austria, and has a total fuel input of 8 MW_t_h. The model was set up according to geometry and operating data which allows a realistic description of the hot system in the simulation environment. Furthermore, a conversion model for the biomass particles was implemented which covers the drying and devolatilization processes. Homogeneous and heterogeneous reactions were considered. Since drag models have an important influence on fluidization behavior, four drag models were tested. It was found that the EMMS drag model fits best, with an error of below 20%, whereas the other drag models produced much larger errors. Based on this drag law, further simulations were conducted. The simulation model correctly predicts the different fluidization regimes and pressure drops in the reactor system. It is also able to predict the compositions of the product and flue gas, as well as the temperatures inside the reactor, with reasonable accuracy. Due to the results obtained, Barracuda seems suitable for further investigations regarding the fluid mechanics of such reactors.
[en] Fluidized powder is discharged from a fluidizing vessel into a container. Accurate metering is achieved by opening and closing the valve to discharge the powder in a series of short-duration periods until a predetermined weight is measured by a load cell. The duration of the discharge period may be increased in inverse proportion to the amount of powder in the vessel. Preferably the container is weighed between the discharge periods to prevent fluctuations resulting from dynamic effects. The gas discharged into the container causes the pressures in the vessel and container to equalize thereby decreasing the rate of discharge and increasing the accuracy of metering as the weight reaches the predetermined value. (author)
[en] An improved gas distribution means, which has utility in fluidized bed coaters for depositing pyrolytic carbon, is described. It consists of a plurality of gas-permeable regions within a supporting matrix comprising a relatively thick dimension for structural rigidity and relatively thin sections to inhibit clogging due to decomposition products of the fluidizing gas. A second gas distribution means feeds gas into a plenum below said first gas distribution means to insure a uniform pressurized zone of gas which serves as feed to said gas-permeable regions. (U.S.)