A tunable microfluidic device toiInvestigate the influence of fluid-dynamics on polymer nanoprecipitation

Polymer drug-embedding nanocapsules are attracting increasing attention as effective tools for the targeted delivery of pharmaceutical molecules on specific biological tissues. Besides, it is well established that an effective selectivity of the delivery dictates that the size of the carrier particles be accurately controlled, thus maintaining the size dispersion of the particle population as low as possible. To this end, microfluidics-assisted precipitation provides a promising alternative to the traditional processes in that the structure of the flow - ultimately controlling the particle size distribution - can be reliably predicted from the solution of Navier-Stokes equations in the laminar regime. Notwithstanding the great potential provided by microfluidics techniques, much about the interaction between fluid-dynamics and polymer transport and precipitation is yet to be understood. In this work, we investigate polymer precipitation in a simple cross-junction inflow-outflow microchannel, which has proven a viable benchmark to gain insight into the physics of nanoprecipitation in that the particle size distribution is sensitively dependent on the flow operating conditions. Specifically, previous experimental work by some of these authors proved that average particle size can vary by an order of magnitude for operating conditions where the solvent flow rate varies by a factor of three, while keeping the non-solvent flow rate constant. The scope of this work is to show that such sensitive dependence on operating conditions finds direct correspondence in the kinematic structure of the flow, which undergoes abrupt qualitative changes in the same range of operating conditions, provided a fully three-dimensional solution of the incompressible Navier-Stokes equation (thus retaining the inertial term in momentum balance) is afforded

Analysis on High Temperature Gasification for Conversion of RDF into Bio-Methanol

Municipal solid waste (MSW) is one of the residue materials considered as a potential source for biofuel production in the EU Renewable Energy Directive (RED), which establishes that a minimum of 10% biofuels for transport shall be used in every Member State by 2020, thus promoting advanced biofuel from waste. A high-temperature gasification technology transforms MSW into a syngas rich in hydrogen and carbon monoxide and free of tar, char and harmful compounds like dioxins appearing as a promising root for methanol production. The overall process including MSW high-temperature gasification, syngas purification and conditioning up to methanol synthesis has been modeled with Aspen Plus analyzing the influence of waste composition and operating conditions on syngas composition and methanol yield. The evaluation of CAPEX and OPEX has been carried out to obtain a cost of production (COP) estimation. The greenhouse gas (GHG) emission has also been estimated and compared with the conventional waste incineration process and methanol production. The technology assessment shows interesting results technically and economically, when compared with waste to energy processes: over 50% of incoming carbon is fixed into methanol molecule, and due to the negative cost paid for RDF disposal, the bio-methanol COP provides a reasonable industrial margin

Chemical Carbon and Hydrogen Recycle through Waste Gasification: The Methanol Route

A large amount of valuable Carbon and Hydrogen is lost in the disposal of the non-recyclable fraction of Municipal Solid Waste (MSW) – particularly unsorted waste fraction and plastics residue from mechanical recycle process. The waste-to-chemical technology allows to exploit the components entrapped in the non-recyclable waste by converting it into new chemicals. The core of waste-to-chemical technology is the gasification process, which is designed to convert waste into a valuable syngas to be used as example for methanol production. Waste to methanol schemes allow to achieve significant environmental and economic benefits, which can be further intensified within the scenario of increasing share of renewable energy

Waste gasification in a melting updraft moving bed reactor. Preliminary analysis on oxidation and melting zone

Waste conversion into valuable chemical products seems to be a good overcoming strategy both for the fossil fuel resources employment and for the current inefficient waste management. The main step related to the production of chemical from waste is its thermochemical conversion via gasification process. Taking into account the variable composition of waste and its high ash amount, among others, the high temperature melting gasifier is the most suitable system for ensuring the required flexibility. Indeed, besides syngas production, this system allows the melting of waste ash fraction in order to produce a vitrified and inert granular material. A simplified transient one-dimensional model of the oxidation zone including melting phenomenon could help in the understanding of process behavior

The effects of alginate encapsulation on NIT-1 insulinoma cells: viability, growth and insulin secretion.

Transplantation of microencapsulated insulin secreting cells is proposed as a promising therapy for the treatment of type I diabetes mellitus. In recent years, important advances have been made in the field of immunoisolation and many studies have shown that alginate provides some major advantages for encapsulation over other systems. Since it is known that the extracellular matrix influences the behaviour of encapsulated cells, the aim of the present work has been to study the consequences of encapsulation on some cell functions. For this purpose, cell growth and dynamics of insulin release of NIT-1 cells entrapped in alginate capsules compared with those exhibited by free NIT-1 cells were investigated by means of growth curves, assays, Trypan blue staining and ELISA test. All investigations performed allowed us to conclude that alginate-entrapped NIT-1 cells maintain their growth features and secretory functions although with some important differences. In particular, alginate encapsulation affects the cellular growth profile and causes the lost of time dependence of insulin secretion profile

Inertia-driven enhancement of mixing efficiency in microfluidic cross-junctions. A combined Eulerian/Lagrangian approach

Mixing of a diffusing species entrained in a three-dimensional microfluidic flow-focusing cross-junction is numerically investigated at low Reynolds numbers, 1 ≤ Re ≤ 150 , for a value of the Schmidt number representative of a small solute molecule in water, Sc = 103 . Accurate three-dimensional simulations of the steady-state incompressible Navier–Stokes equations confirm recent results reported in the literature highlighting the occurrence of different qualitative structures of the flow geometry, whose range of existence depends on Re and on the ratio, R, between the volumetric flowrates of the impinging currents. At low values of R and increasing Re, the flux tube enclosing the solute-rich stream undergoes a topological transition, from the classical flow-focused structure to a multi-branched shape. We here show that this transition causes a nonmonotonic behavior of mixing efficiency with Re at constant flow ratio. The increase in efficiency is the consequence of a progressive compression of the cross-sectional diffusional lengthscale, which provides the mechanism sustaining the transversal Fickian flux even when the Peclet number, Pe = Re Sc , characterizing mass transport, becomes higher due to the increase in Re. The quantitative assessment of mixing efficiency at the considerably high values of the Peclet number considered ( 103 ≤ Pe ≤ 1.5 × 105 ) is here made possible by a novel method of reconstruction of steady-state cross-sectional concentration maps from velocity-weighted ensemble statistics of noisy trajectories, which does away with the severe numerical diffusion shortcomings associated with classical Eulerian approaches to mass transport in complex 3d flows. Keywords X-Junction · Mixing efficiency · Flux tube · Diffusion · Numerical diffusion · Langevin equation · Concentratio

Methanol production from Refuse Derived Fuel. Influence of feedstock composition on process yield through gasification analysis

Currently the production of methanol from Refuse Derived Fuel, a derived product of Municipal Solid Waste, can be deemed as an excellent example of circular economy, by representing a promising alternative both to conventional methods of waste disposal and methanol production from fossil resources. High-temperature conversion of waste in syngas is the main step of the Waste-to-Methanol process. Unfortunately, produced syngas does not directly comply with the requirements for methanol synthesis, in that syngas purification and conditioning steps are required. Moreover, waste, due to its heterogeneous nature, presents a variable composition, leading to the production of variable syngas flowrate and composition. A thermodynamic equilibrium model of gasification unit has been developed in Aspen Plus environment and applied to analyse the effects of feedstock variability; RDF composition has been characterized considering as main parameters: ash, moisture and combustible fractions, carbon to hydrogen and carbon to oxygen ratios, and Lower Heating Value. Then, a simplified simulation of downstream process has been introduced to evaluate the influence of waste composition on overall methanol production. The present study allows the identification of the main parameters affecting the syngas and, accordingly, overall process yield, consumptions and emissions

Methanol production from Refuse Derived Fuel. A preliminary analysis on the influence of the RDF composition on process yield

Currently, the production of methanol via high-temperature gasification of Refuse-Derived-Fuel (RDF) can be deemed as an excellent example of circular economy: it represents a promising alternative to Waste-to-Energy (WtE) and environmental impact improvement, thus leading to the reduction of carbon footprint and greenhouse gas emissions. The Waste to methanol (WtM) process can be divided into four main sections, namely RDF gasification, syngas purification, conditioning, and methanol synthesis. Methanol manufacturing needs a suitable syngas composition; therefore, the ultimate goal is to achieve a tailored gasification unit in order to decrease conditioning step efforts. In this work, a steady-state simulation of gasification unit has been developed using Aspen Plus. Considering that RDF is typically characterized by a remarkable composition variability, an extended parametric study, where RDF composition is represented in terms of ash, moisture, and combustible contents of the waste, has been undertaken as a preliminary approach. A synoptic description of results given in terms of ternary diagrams has been chosen to represent the main process parameters. Hence, this exploratory study allows to assess the process features associated with different feeding characteristics and provides preliminary suggestions to recognize process strategies to simplify design step and improve the process