INFLUENCE OF PROCESS PARAMETERS ON FLUIDISED BED DRYING OF POWDERED MATERIALS

The present study reports preliminary characterization about the fluidised bed drying of powdered materials. Tests were carried out in a Lexan® lab-scale fluidised bed with solids selected to effectively surrogate powders of interest in the manufacture of pharmaceuticals. The process was monitored to correlate the temperature and the flow rate of the fluidising gas, the temperature and the moisture level in the bed, the qualitative fluidisation patterns. Bed material was characterized to assess the modifications of the population of agglomerates as a function of the operating conditions

Hydrodynamics of a Loop-seal Operated in a Circulating Fluidized Bed: Influence of The Operating Conditions on Gas and Solid Flow Patterns

Hydrodynamic features of a loop-seal operated as solids re-injection device in a labscale cold CFB apparatus are studied. Gas flow patterns are characterized by means of gas tracing experiments with continuous injection of CO2 in the loop-seal chambers. Solids flow patterns are characterized by impulsive injection of dyecoloured particles into the supply chamber, followed by particle tracking

SHEAR-ASSISTED FLUIDIZED BED POWDER-COATING

This study addresses a novel concept of dense-fluidized bed coating of objects where the effectiveness of coating is promoted by the intentional and controlled establishment of shear flow around the object. The fluidized powder is sheared by the controlled oscillatory motion of the object with respect to the fluidized bed. The proof-of-concept is given with experiments carried out using a commercial powder specifically manufactured for dry coating applications in fluidized bed. Systematic analysis of the effect of different levels of shear rate on particle mobility/adhesion and effectiveness of coverage was performed. A simple descriptive model has been developed to provide a mechanistic framework for the interpretation of the results

Modelling of a chemical looping combustion system equipped with a two- stage fuel reactor

The proper selection of the oxygen carrier and the correct design of the fuel reactor represent the main criticalities for the success of the chemical looping combustion (CLC) process for solid fuels. In a previous work (1) a two-stage fuel reactor (t-FR), consisting of two bubbling beds in series (bottom bed and top bed) (Fig. 1), has been proposed in order to overcome the limitations of a single-stage fuel reactor (poor char conversion, slip of unburnt volatiles, extensive elutriation of char fines). A mathematical model has been developed with the aim of assessing the performances of the two-stage fuel reactor varying operating conditions in comparison with a benchmark case consisting of a single-stage fuel reactor equipped with and without carbon stripper. The t-FR showed the best performances in terms of combustion efficiency, volatile matter and char conversion, carbon-to-CO2 conversion efficiency and loss of elutriated carbon for all the operating conditions investigated. In the present work a further enhancement of the model has been developed in order to study the hydrodynamics of the proposed multiple interconnected fluidized beds (MIFB) system for the CLC of solid fuels. The modelled system consists of the two-stage fuel reactor, a riser (Air Reactor) and non-mechanical valves for the regulation of the solid circulation between the two reactors. The different parts are considered as separate blocks mutually interconnected (Fig. 1). The operation of the system has been simulated by considering chemical looping combustion of a bituminous coal with an oxygen carrier consisting of CuO supported on zirconia. The numerical simulation has been addressed to evaluate (at steady state) the solid circulation rate, the temperature and oxidation degree of solids and concentrations profiles of gaseous species at the exit of both air and fuel reactors, with the utilization of proper constitutive equations for each block. Specific attention has been paid to the fluid dynamic behaviour of the t-FR. Results of the CLC-MIFB system with the t-FR are presented and the effects on the feasibility of the process of a variation in operating conditions are commented. Please click Additional Files below to see the full abstract

Numerical simulation of hydrogen production by chemical looping reforming in a dual interconnected fluidized bed reactor

Although exploitation of dual interconnected fluidized bed systems (DIFB) is currently being explored in various fields (1,2), DIFBs present some criticalities, mainly related to effective control of solids recirculation and to avoidance of gas leakage between the beds, extremely critical in chemical looping reforming (CLR) for hydrogen production. For the latter, the choice of the degree of oxygen carrier oxidation/reduction, operation temperature and loop design makes the design even more challenging. This paper aims at quantitative assessment of the influence of design variables by means of the numerical simulation of a DIFB-CLR process operated at steady state. The model couples a simple hydrodynamic simulation of a DIFB system equipped with non-mechanical valves for bed solids circulation with a 1D, dynamic and non-isothermal CLR model developed to determine temperature and oxidation degree of solids and gaseous species concentrations at the exit of both air and fuel reactors. The DIFB (Fig. 1), consisting of a riser and of a bubbling fluidized bed (BFB) as air and fuel reactors respectively, was modelled as a combination of interconnected blocks (riser, cyclone, downcomers, L-valve, BFB, loop-seal) after selection of constitutive equations. Methane and Nickel(II) oxide were selected as fuel and oxygen carrier. Results corresponding to steady operation are presented and the effects on the expected process performance of operating conditions are assessed. It is concluded that an appropriate choice of both operating temperature and oxidation/reduction degree of oxygen carrier is an essential prerequisite in order to achieve auto-thermal regimes while assuring process feasibility and good performances in terms of CH4 conversion and H2 selectivity. Please click Additional Files below to see the full abstract

Life cycle assessment and feasibility analysis of a combined chemical looping combustion and power-to-methane system for CO2 capture and utilization

The ability to store effectively excess of electrical energy from peaks of production is key to the development of renewable energies. Power-To-Gas, and specifically Power-To-Methane represents one of the most promising option. This works presents an innovative process layout that integrates Chemical Looping Combustion of solid fuels and a Power-to-Methane system. The core of the proposed layout is a multiple interconnected fluidized bed system (MFB) equipped with a two-stage fuel reactor (t-FR). Performances of the system were evaluated by considering a coal as fuel and CuO supported on zirconia as oxygen carrier. A kinetic scheme comprising both heterogeneous and homogeneous reactions occurring in the MFB was considered. The methanation unit was modelled developing a thermodynamic calculation method based on minimization of the free Gibbs energy. The performance of the system was evaluated by considering that the CO/CO2 stream coming from the t-FR reacts over Ni supported on alumina catalyst with a pure H2 stream generated by an array of electrolysis cells. The number of cells to be stacked in the array was evaluated by considering that a constant H2 production able to convert the whole CO/CO2 stream produced by the CLC process should be attained. The environmental performance of the proposed process was quantified using the Life Cycle Assessment (LCA) methodology. The analysis shows i) that the majority originate from the production and disposal of the oxygen carrier used in the t-FR, and ii) that reusing part of the oxygen produced by the electrolysis cells improves significantly the environmental performance of the proposed process

Self-Fluidization of Fastly-Moving Granular Gravity Currents with Implication on Pyroclastic Flows

The fast motion of gravity currents of group A granular solids is studied with a focus on the dynamical structure of the frontal zone. The frontal zone of the current is “immobilized” and observed in a fixed frame of reference by letting the current flow inside a rotary drum, big enough to make curvature effects negligible. The establishment of a variety of flow regimes, including intermittent avalanching, periodic “plunging breaking” and permanent fluidization of the granular solids in the frontal zone, can be related to flow conditions and to the nature of the granular solids

Life cycle assessment and feasibility analysis of a combined chemical looping combustion and power-to-methane system for CO2 capture and utilization

The ability to store effectively excess of electrical energy from peaks of production is key to the development of renewable energies. Power-To-Gas, and specifically Power-To-Methane represents one of the most promising option. This works presents an innovative process layout that integrates Chemical Looping Combustion of solid fuels and a Power-to-Methane system. The core of the proposed layout is a multiple interconnected fluidized bed system (MFB) equipped with a two-stage fuel reactor (t-FR). Performances of the system were evaluated by considering a coal as fuel and CuO supported on zirconia as oxygen carrier. A kinetic scheme comprising both heterogeneous and homogeneous reactions occurring in the MFB was considered. The methanation unit was modelled developing a thermodynamic calculation method based on minimization of the free Gibbs energy. The performance of the system was evaluated by considering that the CO/CO2 stream coming from the t-FR reacts over Ni supported on alumina catalyst with a pure H2 stream generated by an array of electrolysis cells. The number of cells to be stacked in the array was evaluated by considering that a constant H2 production able to convert the whole CO/CO2 stream produced by the CLC process should be attained. The environmental performance of the proposed process was quantified using the Life Cycle Assessment (LCA) methodology. The analysis shows i) that the majority originate from the production and disposal of the oxygen carrier used in the t-FR, and ii) that reusing part of the oxygen produced by the electrolysis cells improves significantly the environmental performance of the proposed process

Preliminary activity on the pyrolysis of a plastic based solid recovered fuel

Plastic is a versatile, lightweight, resistant, and inexpensive material, and an increase of its global demand has been observed in the last years (from 299 milion tonnes in 2013 to 348 in 2017) [1], with the dominant role played by the packaging sector, which absorbs almost 40% of the overall production. Management of post–consumer plastic packaging waste poses a serious environmental problem, and a number of strategies have been devised to reuse/recover these materials, mainly with the aim of recovering useful materials and avoiding landfilling. Among these strategies, pyrolysis can play a significant role for recovering useful products and energy from the post–selection mixed packaging waste, that is not amenable to other uses [1]. A large amount of studies has been developed to assess the possibility to convert waste plastic to oil by pyrolysis processes [1] either catalytic or non catalytic. Nevertheless, only a limited numbers of papers refer to the use of real plastic waste rather than simulated mixtures [2] even if the performances obtained are strongly influenced by the feedstock characteristics. Please click Additional Files below to see the full abstract