Search results for "Fluidized bed"

Simulation of a regeneration plant for spent pickling solutions via spray roasting

2015

Nowadays, pyrohydrolysis techniques are widely applied for regeneration of spent pickling liquors providing an excellent environmental and economical strategy to the problem of waste disposal/recovery, also thanks to the high acid recovery efficiencies (>99%) achieved. In fact, in these processes, iron chlorides are converted into iron oxides and hydrogen chloride at high temperature in spray roasting or fluidized bed reactors. Though the state-of-the-art technologies have been successfully applied only to large-scale plants, the development of small-scale units, able to perform a delocalized regeneration of spent solutions where these latter are actually produced, would be strongly needed …

Searching for a robust strategy for minimizing alkali chlorides in fluidized bed boilers during burning of high SRF-energy-share fuel

2015

Abstract To meet the increasing volume of waste to be treated via energy recovery, high SRF-energy-share fuel is being fired in conventional waste-to-energy facilities. In this work, corrosion related risk during firing of 70 e-% share (target fuel) is studied and compared against the base case fuel containing 50 e-% share. Cl and S concentration is highest in the target fuel as a direct result of increasing the proportion of SRF in the fuel mixture. Br, Zn and Pb showed the same trend. Meanwhile, the concentration of Na, K, Al and Si are highly dependent on the type of the SRF fired. The corrosion risk of the base and target fuels are analyzed using the composition of the fine aerosol frac…

Digital Image Analysis Technique for mixing pattern measurements in bi-dispersed 2D gas fluidized beds

2011

This work concerns a new experimental technique based on Digital Image Analysis aimed at the measurement of the mixing behaviour of the granular phase in a 2D fluidized bed. In particular, the preliminary results obtained about the mixing pattern of a bi-disperse 2D gas fluidized bed are reported. Two different kind of particles were fluidized having the same density but different size. The technique is based on suitable colour-field decomposition of the fluidized bed, in which particles of different colours are employed. The technique here proposed can effectively measure the concentration field in the whole bed during operation, thus obtaining data that can be reliably used for CFD simula…

Current Problems in the Modelling of Photochemical Reactors

1985

Photochemical reactors are examined from the point of view of the main problems connected to their modelling. By distinguishing the diverse meanings of kinetic models and the varied objectives in establishing models, a particular attention is devoted to the following aspects of homogeneous photoreactors: steady state condition, effect of stirring and mixing, effect of the shape of the reactor and of the position of the light source, light emission models, scale up. For the heterogeneous systems only general considerations on kinetic models in heterogeneous photocatalysis and on the problems related to the use of fluidized bed photoreactors are done.

Semi-continuous feeding and gasification of alfalfa and wheat straw pellets in a lab-scale fluidized bed reactor

2015

Abstract Small scale air-blown fluidized bed gasification of alfalfa and wheat straw pellets were conducted for semi-continuous solid feeding and range of operating conditions varied due to the modifications in equivalence ratio (ER) (0.20–0.35) achieved both by varying solid and air input. Alfalfa pellets displayed an improvement in several gasification variables such as gas lower heating value (∼4.1 MJ/Nm3), specific gas yield (1.66 Nm3/kg), cold gas efficiency (∼42%) and carbon conversion efficiency (∼72%) as ER maximized to 0.35 which was found optimum for this feedstock for the present course of experiments. Gasification parameters of wheat straw pellets on the other hand were characte…

Air gasification of wood chips, wood pellets and grass pellets in a bubbling fluidized bed reactor

2021

Abstract Gasification is an attractive method for biomass-to-energy conversion and fluidized bed design is one of the best options for large scale operation. A bubbling fluidized bed reactor was used to analyze the effects of biomass type, equivalence ratio (ER) and temperature for product gas compositions. Wood chips, wood pellets and grass pellets were gasified between 650 °C and 800 °C temperature. The ER was varied between 0.08 and 0.16. Gasification of grass pellets was difficult at 800 °C due to agglomeration and the gas composition was poor compared to wood. The reactor performances improved over the temperature and 650 °C was not sufficient to achieve a reasonable carbon conversion.…

CFD prediction of bubbles local gas hold-up in 2-dimensional gas-solid fluidized beds

2008

ADVANCED STATISTICAL ANALYSIS OF LOCAL BUBBLE SIZE DISTRIBUTIONS IN 2D GAS FLUIDIZED BEDS

2009

The principal difficulty in analysing fluidization quality and bubble dynamics is related to the possibility of measuring or predicting the physical and geometrical properties of gas bubbles rising in a granular medium. Even the development of detailed experimental correlations gives poor results, being necessary a fully statistical approach. On the above basis, the present work focuses on the statistical analysis of the behaviour of a 2-D fluidized bed operating under bubbling and slugging conditions, performing measurements of Local Bubble Size Distributions (BSD) along the bed. The analysis allowed to observe a characteristic bimodal shape of BSDs for different particles dimension and fl…

Experimental Analysis of bubbling dynamics in bidisperse gas-solid 2D fluidized beds

2008

Modeling of Magnetic-Field-Assisted Fluidization: Model Development and CFD Simulation of Magnetically Stabilized Fluidized Beds

2014

Magnetic-field-assisted fluidization is starting to be considered as a viable alternative to standard fluidized beds for those operations (such as particle separations, filtration, adsorption) in which the solid phase can be made of magnetic particles or, alternatively, the fluidizing agent is a ferro-fluid; thus the fluid bed responds to the action of magnetic fields, and stabilized fluidization regimes can be generated. One of the major difficulties to be tackled is the development of a predictive model capable of estimating the stabilized-to-bubbling transition velocity for a given magnetic field or, on the other hand, the magnetic field intensity required to stabilize the bed to a quies…