Ivana B. Banković Ilić

This study aims to explore the influence of screw frequency, nozzle diameter, and press head temperature on critical crude fodder radish seed oil (FRSO) yield, throughput, and fatty acid composition. A quadratic equation, developed using response surface methodology, fitted the experimental data for oil yield. It was substantiated by a non‐significant lack‐of‐fit, commendable coefficient‐of‐determination (R² = 0.782), and a modest mean relative percentage deviation (±7.27%). The analysis of variance pinpointed the statistical significance of press head temperature, nozzle size, and the squared term of press head temperature. The highest FRSO yield (17.61%)—corresponding to an extraction efficiency of 51.3% was found with a screw frequency of 50 Hz, at 80°C, and an 8 mm nozzle. A linear model highlighted that all three pressing factors significantly influenced the FRSO throughput. FRSO consists of C18:1 (30.9%), C22:1 (20.8%), C18:2 (14.9%), and C18:3 (11.9%), aligning with the compositions reported in other studies on fodder radish oils.Practical applications: Effective control of cold pressing parameters is paramount to maximize oil yield and throughput during the oil extraction process and to ensure the appropriate oil quality. A comprehensive understanding of the intricacies of this process, while carefully considering key parameters, which is essential to ensure efficiency, is achieved through a combination of experimental and statistical methods. This study marks the inaugural attempt to optimize screw pressing for fodder radish seeds while conducting a comparative analysis with hydraulic pressing and the Soxhlet extraction method, focusing on oil yield, throughput, and fatty acid composition within the system by employing a modeling approach for oil extraction. Through the utilization of the response surface methodology coupled with various experimental designs, the processing conditions are successfully optimized. The valuable data gathered can aid equipment design for an efficient, eco‐friendly oil extraction process. Furthermore, the oil extracted under the optimized conditions met the quality standards.

Fodder radish (Raphanus sativus L. var. oleiformis Pers) is a promising biofuel source. Response surface methodology was used to optimize screw pressing of fodder radish seeds. The key parameters were nozzle diameter, press head temperature, and screw frequency. A quadratic model accurately predicted the minimum residual oil content in the press cake (20.7%), close to the actual one (22.1 ± 0.7%), using an 8 mm nozzle diameter, 80 °C press head temperature, and 40 Hz screw frequencies. All three process factors are statistically significant, but nozzle diameter had the most influence. An extended linear model identified all three process factors as significant for seed throughput, with screw frequency having a greater impact. The maximum seed throughput was achieved with a 12 mm nozzle, 80 °C press head temperature, and 60 Hz screw frequency (predicted 8.17 g/ min, actual 8.08 g/min).

Biodiesel, a renewable and environmentally friendly alternative to conventional fossil fuels, has gained significant attention over the last two decades. Continuous production of biodiesel offers efficiency, productivity, and scalability advantages. This paper provides a concise overview of continuous reactor systems for biodiesel production, focusing on two specific systems?the reciprocating plate reactor and the packed bed reactor?subjects of the authors' extensive research. A thorough comparison of these reactors, spanning biodiesel yield, reaction kinetics, and conversion efficiency, underscores their advantages. The reciprocating plate reactor demonstrates superior mixing characteristics, which improve mass transfer and reaction kinetics. Conversely, the packed bed reactor offers a higher catalyst-to-feedstock ratio and longer residence time, enhancing conversion efficiency. Both reactors exhibit favourable performance for continuous biodiesel production. This research can contribute to understanding continuous biodiesel production using innovative reactor designs. The comparative analysis between the reciprocating plate and packed bed reactors offers valuable insights for process optimization and reactor selection based on specific requirements such as feedstock availability, reaction kinetics, and economic considerations. These insights pave the way for the implementation of sustainable and efficient biodiesel production processes in the future.

In the group of multiphase contactors and reactors, an important place belongs to reciprocat-ing plate columns (RPCs), which consist of a set of perforated plates fixed on a carrier (the so-called reciprocating or vibrating agitator) moving periodically up and down through a column. This construction maximizes the positive effects of mechanical agitation and minimizes or eliminates the adverse effects characteristic of column-type contactors and reactors. In RPCs, the highest dispersed-phase holdup is achieved at a lower dispersed-phase velocity due to the influence of mechanical agitation on the bubble or drop comminution. Therefore, this device can be the most acceptable contactor or reactor for performing complex actions in multiphase systems. The paper reviews the fundamental research and application of RPCs in Serbia in the last fifty years, from 1970 to 2020. Hydrodynamic and mass-transfer characteristics are analyzed, such as the pressure variation at the column bottom, power consumption, dispersed-phase holdup, axial dispersion, liquid mass transfer coefficient, specific interfacial area, and volumetric mass transfer coefficient. The use of RPCs as reactors in bioprocesses and biodiesel production processes is also discussed.

Possibilities of using waste plum stones in biodiesel production were investigated. The plum kernels were used as a source to obtain oil by the Soxhlet extraction method, while the whole plum stones, the plum stone shells that remained after the crashing, and the plum kernel cake that remained after the oil extraction, were burned off to obtain ashes. The collected ashes were characterized by elemental composition, porosity, and base strength and tested for catalytic activity in transesterification of esterified plum kernel oil. Dominant elements were potassium, calcium, and magnesium at different contents in the three obtained ashes. The most active catalyst was the plum stone shell ash, so the effect of temperature (40, 50, and 60?C) on the reaction rate was investigated. The reaction rate constant increased with the reaction temperature with the activation energy value of 58.8 kJ mol-1. In addition, the plum stone shell ash can be reused as a catalyst after recalcination.

Oil methanolysis over modified CaO catalysts was studied to assess the catalytic performance and to define an appropriate kinetic model. CaO was modified by commercial glycerol and a deep eutectic solvent (DES), choline chloride : glycerol (ChCl : Gly), to obtain catalytically active complexes of CaO and glycerol. The main goal was to investigate the effect of the obtained complexes on the reaction rate and fatty acid methyl ester (FAME) content and to describe the variation of the triacylglycerol (TAG) conversion degree during the reaction time. Fourier transform infrared spectroscopy (FTIR) was applied to confirm the formation of CaO complexes with glycerol or the glycerol-based DES. Different catalyst loadings (0.5, 1, and 5 % of oil weight) and methanol-to-oil molar ratios (6 : 1 and 12 : 1) were applied for investigation of the sunflower oil methanolysis at 60 oC. Two kinetic models were employed yielding the kinetic parameters, which depended on the catalyst loading and the methanol-to-oil molar ratio. Both models showed valid applicability for describing the kinetics of the reactions catalyzed by both complexes (the mean relative percent deviation was lower than 10 %).