THE INFLUENCE OF PARTICLE ATTRITION ON SORBENT INVENTORY AND PARTICLE SIZE DISTRIBUTION IN AIR-BLOWN CIRCULATING FLUIDIZED BED COMBUSTORS

This paper presents a population balance model aiming at the prediction of sorbent inventory and particle size distribution establishing at steady state in the bed of an air-blown circulating fluidized bed combustor fuelled with a sulphur-bearing solid fuel. The core of the model is represented by population balance equations on sorbent particles which embody terms expressing the extent/rate of sorbent attrition/fragmentation. The effect of the progress of sulphation on attrition and fragmentation is taken into account by selection of appropriate constitutive equations. Model results are presented and discussed with the aim of clarifying the influence of particle attrition/fragmentation on sorbent inventory and particle size distribution, partitioning of sorbent between fly and bottom ash, sulphur capture efficiency. A sensitivity analysis is carried out with reference to relevant operational parameters of the combustor

Sulfur Uptake by Limestone-Based Sorbent Particles in CFBC: The Influence of Attrition/Fragmentation on Sorbent Inventory and Particle Size Distribution

This paper presents a population balance model aiming at the prediction of sorbent inventory and particle size distribution establishing at steady state in the bed of an air-blown CFBC fuelled with a sulphur-bearing solid fuel. The core of the model is represented by population balance equations on sorbent particles which embody terms expressing the extent/rate of sorbent attrition/fragmentation. The effect of the progress of sulphation on attrition and fragmentation is taken into account by selection of appropriate constitutive equations. Model results are presented and discussed with the aim of clarifying the influence of particle attrition/fragmentation on sorbent inventory and particle size distribution, partitioning of sorbent between fly and bottom ash, sulphur capture efficiency. A sensitivity analysis is carried out with reference to relevant operational parameters of the combustor

Development of an experimental test rig for cogeneration based on a Stirling engine and a biofuel burner

A system consisting of a last-generation Stirling engine (SE) and a fuel burner for distributed power generation has been developed and experimentally investigated. The heat generated by the combustion of two liquid fuels, a standard Diesel fuel and a rapeseed oil, is used as a heat source for the SE, that converts part of the thermal energy into mechanical and then electric energy. The hot head of the SE is kept in direct contact with the flame generated by the burner. The burner operating parameters, designed for Diesel fuel, were changed to make it possible to burn vegetable oils, not suitable for internal combustion engines. The possibility of adopting different configurations of the combustion chamber was taken into account to increase the system efficiency. The preliminary configurations adopted allowed to operate this integrated system, obtaining an electric power up to 4.4 kW(el)with a net efficiency of 11.6%

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

Sewage Sludge Gasification in a Fluidized Bed: Experimental Investigation and Modeling

Fluidized bed gasification is a promising process technology to manage the growing amount of sewage sludge (SS) requiring disposal. Two samples of SS, produced in different seasons of the year by a municipal wastewater treatment plant, were subjected to gasification at 850 °C in a bench-scale fluidized bed reactor using, as a gasification agent, a nitrogen/air mixture at different values of oxygen/fuel equivalence ratio (ER = 0.1–0.2). The starting materials and the output streams (syngas, tar, and solid residues) were thoroughly characterized. The fate of specific SS constituents and the characteristics of bottom ashes were addressed, so contributing to the problem of a proper SS management approach in the context of the circular economy. Computer-aided simulations were also performed, which allowed us to predict the composition of the syngas from SS gasification under operating conditions different from those experimentally investigated (i.e., reactor temperature and ER)

Engineering a 3D in vitro model of human skeletal muscle at the single fiber scale

The reproduction of reliable in vitro models of human skeletal muscle is made harder by the intrinsic 3D structural complexity of this tissue. Here we coupled engineered hydrogel with 3D structural cues and specific mechanical properties to derive human 3D muscle constructs ("myobundles") at the scale of single fibers, by using primary myoblasts or myoblasts derived from embryonic stem cells. To this aim, cell culture was performed in confined, laminin-coated micrometric channels obtained inside a 3D hydrogel characterized by the optimal stiffness for skeletal muscle myogenesis. Primary myoblasts cultured in our 3D culture system were able to undergo myotube differentiation and maturation, as demonstrated by the proper expression and localization of key components of the sarcomere and sarcolemma. Such approach allowed the generation of human myobundles of ~10 mm in length and ~120 \u3bcm in diameter, showing spontaneous contraction 7 days after cell seeding. Transcriptome analyses showed higher similarity between 3D myobundles and skeletal signature, compared to that found between 2D myotubes and skeletal muscle, mainly resulting from expression in 3D myobundles of categories of genes involved in skeletal muscle maturation, including extracellular matrix organization. Moreover, imaging analyses confirmed that structured 3D culture system was conducive to differentiation/maturation also when using myoblasts derived from embryonic stem cells. In conclusion, our structured 3D model is a promising tool for modelling human skeletal muscle in healthy and diseases conditions

Production of Q10+B2 nanostructured lipid carriers and optimization of their entrapment capacities

Lipidic carriers are efficient vehicles preserving drugs during cell administration. Several production processes of lipidic nanoparticles were developed to reduce mean size at nanometric level, enhancing homogeneity and process replicability. However, lipidic aggregation has always been considered a huge drawback in terms of high polidispersity and instability. Looking at this problem from a different point of view, specific operating parameters were employed to produce Nanostructured Lipidic Carriers (NLC), whose structure simulates the complexity of cell barrier. NLC present high surface to volume ratio, and improved potential in terms of drug entrapment efficiency and bioavailability. In this work, NLCs were produced by studying the effect of process parameters, such as Drug to Lipid Ratio from 2:1–1:20 w/w. At macroscopic level, the NLCs produced showed these diameters distribution: D(10 %) from 85 nm to 6 µm, D(50 %) of about 10 µm and D(90 %) of about 31 µm. Encapsulation Efficiencies were measured from a minimum of 92.06 % to a maximum of 98.93 %, with mass yield included between 48.8 % and 99 %. Scanning Electron Microscope demonstrated the complexity of the shape of these NLCs, characterized by nanometric structures (100–500 nm) grab on Q10 “pillars” or adsorbed on lipidic external sheet

A population balance model on sorbent in CFB combustors: The influence of particle attrition

A population balance model on sorbent particles in an atmospheric circulating fluidized bed combustor fueled with sulfur-bearing solid fuel is developed. The model aims at the prediction of the following quantities establishing at the steady state in the combustor: sorbent inventory and particle size distribution, partitioning of the sorbent between fly and bottom ash, desulfurization efficiency, and the mass flow rate of the sorbent circulating around the loop of the combustor. The core of the model is represented by the population balance equations on sorbent particles, which embody terms expressing the rate of sorbent attrition/fragmentation. The effect of the progress of sulfation on attrition is taken into account by the selection of appropriate constitutive equations. Model results are presented and discussed with the aim of clarifying the influence of particle attrition. In particular, the effect of attrition on bed sorbent partitioning between lime and sulfated lime and on SO2 capture efficiency is highlighted. The model enables one to assess the balance between opposed effects of attrition on desulfurization: on one hand, attrited fines are characterized by a better reactivity with respect to SO2, when compared with the mother particles; on the other hand, attrition is responsible for larger amounts of unsulfated material reporting to the fly ash. A sensitivity analysis is also carried out with reference to relevant operational parameters of the combustor in order to correlate changes in ash partitioning and desulfurization efficiency with the extent of sorbent attrition and solids circulation