Hydrogen Production via Steam Reforming: A Critical Analysis of MR and RMM Technologies.

'Hydrogen as the energy carrier of the future' has been a topic discussed for decades and is today the subject of a new revival, especially driven by the investments in renewable electricity and the technological efforts done by high-developed industrial powers, such as Northern Europe and Japan. Although hydrogen production from renewable resources is still limited to small scale, local solutions, and R&D projects; steam reforming (SR) of natural gas at industrial scale is the cheapest and most used technology and generates around 8 kg CO2 per kg H2. This paper is focused on the process optimization and decarbonization of H2 production from fossil fuels to promote more efficient approaches based on membrane separation. In this work, two emerging configurations have been compared from the numerical point of view: the membrane reactor (MR) and the reformer and membrane module (RMM), proposed and tested by this research group. The rate of hydrogen production by SR has been calculated according to other literature works, a one-dimensional model has been developed for mass, heat, and momentum balances. For the membrane modules, the rate of hydrogen permeation has been estimated according to mass transfer correlation previously reported by this research group and based on previous experimental tests carried on in the first RMM Pilot Plant. The methane conversion, carbon dioxide yield, temperature, and pressure profile are compared for each configuration: SR, MR, and RMM. By decoupling the reaction and separation section, such as in the RMM, the overall methane conversion can be increased of about 30% improving the efficiency of the system.

A new gastro-intestinal mathematical model to study drug bioavailability.

This work focuses on a new mathematical model which describes the gastro-intestinal absorption of drugs and the effect of food interactions on drugs bioavailability. The model structure consists of five compartments (stomach, duodenum, jejunum feeding, intestine and blood) simulated though different in-series reactors. All the enzymatic reactions taking place in the gastro-intestinal system are described through the Michaelis-Menten kinetic equations. The model has been tested for drug administration (paracetamol and ketoprofen) with and without the meal digestion. The model has been validated through pharmacokinetics curves obtained from in vivo tests (reported in the literature) and used to simulate the drug absorption dynamics in different conditions. The maximum blood concentration were 0.153 mmol L-1 and 0.0243 mmol L-1, respectively for paracetamol and ketoprofen. The time to reach the maximum concentration for the paracetamol and ketoprofen was around 55 min. In case of contemporary meal digestion, the maximum concentration of paracetamol in the blood was 0.100 mmol L-1 and 0.0135 mmol L-1 for ketoprofen; the time to reach the maximum concentration was 3 h and 45 min for paracetamol and 3 h and 35 min for ketoprofen. The drugs showed different pharmacokinetics, in agreement with the literature, during the digestion of food. To show the predictive capacity of the model, the simulations were also compared against additional experimental data (obtained from in vivo tests available in the literature) relative to ketoprofen administration with food.

Mass Transfer Coefficient in Multi-Stage Reformer/Membrane Modules for Hydrogen Production.

Hydrogen is a promising energy carrier, and is exploitable to extract energy from fossil fuels, biomasses, and intermittent renewable energy sources and its generation from fossil fuels, with CO2 separation at the source being one of the most promising pathways for fossil fuels' utilization. This work focuses on a particular configuration called the Reformer and Membrane Module (RMM), which alternates between stages of Steam Reforming (SR) reactions with H2 separation stages to overcome the thermodynamic limit of the conventional SR. The configuration has numerous advantages with respect to the more widely studied and tested membrane reactors, and has been tested during a pilot-scale research project. Although numerous modelling works appeared in the literature, the design features of the material exchanger (in the so-called RMM architecture) of different geometrical configurations have not been developed, and the mass transfer correlations, capable of providing design tools useful for such membrane modules, are not available. The purpose of this work is therefore to apply a physical-mathematical model of the mass transfer, in three different geometries, considering both concentration polarization and membrane permeation, in order to: (i) simulate the cited experimental results; (ii) estimate the scaling-up correlations for the "material exchange modules"; and (iii) identify the mass transfer limiting regime in relation to the gas mass flow rate.

A Novel Three-Compartmental Model for Artificial Pancreas: Development and Validation.

Closed-loop insulin delivery system, also known as artificial pancreas (AP), provides the blood glucose control in diabetic patients, enabling the automatic blood-sugar management and reducing the risks and improving the lives of people with diabetes. A new three-compartmental model of glucose-insulin interaction for AP is presented and tested in this paper. The glucose and insulin "spaces" are split into a plasma compartment and interstitial fluids compartment, respectively. The model includes an additional subcutaneous compartment and provides three explicit delays and three parameters influencing the regulatory system and correlating with the physiopathology of the patients. Two delays are related with hepatic glucose production and insulin secretion; the third delay represents the lag time in the absorption of exogenous insulin in subcutaneous tissue. The parameters regulate the system dynamics acting on the glucose utilization and the insulin secretion. The clinical data (including information on food ingestion and exogenous insulin injection) from five case studies of Type 1 diabetics are presented and used to validate the mathematical model. After training the parameters for each case study, the model well simulates the glucose level during a 4-day test. The estimated values are physiologically meaningful and provide a further insight on the subject's dysfunctions and on the state of the disease. The results have been also compared with a parallel simulation carried out by implementing a previous two-compartmental model. The proposed algorithm produces a lower sum of the squared error between the simulated and the measured glucose concentrations over time.

Thermodynamic features of dioxins' adsorption.

In this paper, the six more poisonous species among all congeners of dioxin group are taken into account, and the P-T diagram for each of them is developed. Starting from the knowledge of vapour tensions and thermodynamic parameters, the theoretical adsorption isotherms are calculated according to the Langmuir's model. In particular, the Langmuir isotherm parameters (K and wmax) have been validated through the estimation of the adsorption heat (ΔHads), which varies in the range 20-24kJ/mol, in agreement with literature values. This result will allow to put the thermodynamical basis for a rational design of different process units devoted to dioxins removal.

Degradation of ibuprofen by hydrodynamic cavitation: Reaction pathways and effect of operational parameters.

Ibuprofen (IBP) is an anti-inflammatory drug whose residues can be found worldwide in natural water bodies resulting in harmful effects to aquatic species even at low concentrations. This paper deals with the degradation of IBP in water by hydrodynamic cavitation in a convergent-divergent nozzle. Over 60% of ibuprofen was degraded in 60 min with an electrical energy per order (EEO) of 10.77 kWh m(-3) at an initial concentration of 200 µg L(-1) and a relative inlet pressure pin=0.35 MPa. Five intermediates generated from different hydroxylation reactions were identified; the potential mechanisms of degradation were sketched and discussed. The reaction pathways recognized are in line with the relevant literature, both experimental and theoretical. By varying the pressure upstream the constriction, different degradation rates were observed. This effect was discussed according to a numerical simulation of the hydroxyl radical production identifying a clear correspondence between the maximum kinetic constant kOH and the maximum calculated OH production. Furthermore, in the investigated experimental conditions, the pH parameter was found not to affect the extent of degradation; this peculiar feature agrees with a recently published kinetic insight and has been explained in the light of the intermediates of the different reaction pathways.