The mathematical modeling of a combination of non-thermal technologies for E. coli inactivation is of great interest for describing the dynamic behavior of microorganisms in food, with the goal of process control, optimization, and prediction. This research focused on the design and implementation of a mathematical model to predict the effect of power ultrasound (US), high-pressure processing (HPP), and the combination of both non-thermal technologies on the inactivation kinetics of E. coli (DSM682) inoculated in orange juice. Samples were processed by US, HPP, and a combination of both technologies at varying process parameters, and a mathematical model for microbial inactivation was developed using a System Dynamics approach. The results showed that the combination of these technologies exhibited a synergistic effect, resulting in no detectable colony-forming units per mL of juice. The developed model accurately predicted the inactivation of E. coli following the combination of these technologies (R² = 0.82) and can be used to predict microbial load reduction or optimize it based on process parameters. Additionally, combining both techniques offers a promising approach for extending the shelf life of fresh juices using non-thermal stabilization technology.

The valorization of industrial byproducts is an emerging practice that aims to transform waste materials generated during production processes into valuable resources. In this work, a preliminary study was carried out on the thermal conversion of an industrial solid byproduct resulting from the pickling of metal surfaces, mainly containing iron (II) oxalate. In a fixed-bed reactor, the thermal conversion was investigated as a function of the operating temperature and overall time. The starting material and the products obtained after heat treatment were characterized in detail, using numerous qualitative and semi-quantitative techniques. The aim of this research was to determine the optimal operating conditions for the transformation of the industrial byproduct into a high-quality product. By varying the operating conditions, it was found that complete conversion of iron (II) oxalate to magnetite was achieved at high temperatures (i.e., 773 K and 873 K) after one hour of treatment. The resulting product had a low degree of crystallization, which increased slightly with an increasing reaction time at a temperature of 873 K, reaching a maximum of about 11%. The magnetite obtained can be used in the future as a starting material for chemical looping processes as a chemical/energy carrier for the production of hydrogen.

The use of green hydrogen to reduce iron ore is a promising approach to drastically decrease CO2 emissions in the steel industry. To enable the rapid adoption of this technology, it is essential to start from the fundamentals, namely understanding the intrinsic kinetics of iron oxide reduction. In this work, a kinetic investigation was conducted in a PBR-like system using both pure and commercial iron oxide powders under a wide range of operating conditions. The thermal conductivity of the outlet gas was measured and innovatively correlated with the extent of solid reduction through a rigorous mathematical procedure. To simulate the reduction process and determine the kinetic parameters, a deterministic axial dispersion model was developed in conjunction with a dynamic multistep shrinking core model. The model incorporates the particle size distribution of the solid into the mass balance and includes a reaction-front control mechanism to ensure physical consistency during kinetic parameter estimation. The model successfully reproduced all experimental data, confirming that the controlling mechanisms were predominantly chemical, internal diffusion, or mixed, depending on the type of solid material used. Furthermore, the model not only demonstrates excellent predictive capabilities through the validation of kinetic parameters but also provides new insights into the key phenomena governing iron oxide reduction.

The steel industry plays a key role in society and the global economy, but it also has a significant environmental impact. The fossil-based process utilizes blast furnaces, in which coke acts as a reducing agent and energy source, which is why it accounts for about two gigatons of CO2 emissions on an annual basis. Reducing iron oxides with hydrogen instead of carbon monoxide provides an elegant carbon-free alternative with water as the byproduct. However, the rapid advancement of this technology on the market would require extremely large investments in entirely new reactors and reactor systems. Moreover, the current and foreseeable hydrogen capacity and infrastructure are insufficient to meet the demand, and the price of non-fossil hydrogen is still high. An alternative to reducing emissions would be to adapt current reactor infrastructure to flexibly utilize mixtures of carbon monoxide and hydrogen, depending on hydrogen availability and price. This dynamic approach requires a rigorous understanding of the reduction kinetics of iron oxides with varying gas composition and reaction conditions. The present work studies the kinetics of pure and industrial hematite powders using H2 and CO mixtures in small scale in the laboratory. The reduction process was followed by analyzing the off-gases online, and the physical-chemical behavior of the solid phase during reduction was studied through detailed analysis of partially reduced material obtained at different stages of the reduction process. The experimental data revealed critical factors influencing the reduction of kinetics, both qualitatively and quantitatively, which support understanding of the complex overall process. Moreover, the study revealed significant differences between pure hematite and industrial feedstock.