Claudia Irina Koncsag

Waste polystyrene is a burden for the economy, especially when it spreads in environment due to incorrect waste management. In addition, there are toxic pollutants which should not end up in the natural environment. A good way to tackle these problems is to consider recycling polystyrene, through chemical transformation, into an adsorbent for pollutants. This study considers waste polystyrene (PS) and the materials synthetized from it as adsorbents for removal of the pollutant phenol. Dichloroethane polystyrene (DCEPS) and tetrachloromethane polystyrene (TCMPS) were synthesized in the laboratory by crosslinking polystyrene with dichloroethane and tetrachloromethane, using a Friedel–Crafts reaction. The materials were characterized by FTIR to observe the structural modifications induced by crosslinking. Then, the materials were compared for their adsorption capacity at 300 K. The experimental data proved that, for an initial concentration of phenol in water of 517 mg/L, the adsorption capacity is moderate and increases in the following order: PS (13.4 mg phenol/g) < TCMPS (15.7 mg phenol/g) < DCEPS (19.1 mg phenol/g). The adsorption isotherms at 300 K were determined for a large range of concentrations, and the parameters of Freundlich and Langmuir models were calculated, concluding that the Langmuir model fits better. The kinetics were studied and are represented by a pseudo-first order equation, confirmed by high coefficients of determination for all three materials. The adsorption of phenol from an industrial wastewater flux was performed in continuous flow over a laboratory column. PS and DCEPS were tested, with good results. For example, 1.595 L water containing 22 mg phenol/L was adsorbed on 3.76 g DCEPS; the bed capacity in equilibrium with the wastewater is 10 mg/g adsorbent, the removal efficiency was 95% for a treated volume of 1.595 mL, the breakthrough time was 240 min, and the exhaustion time was 270 min. The novelty of the work consists in demonstrating the possibility of applying polystyrene-based materials as adsorbents for the treatment of phenolic wastewater proceeding from oil refineries.

The study investigates, by calculations, some ways to improve the thermal efficiency of plate heat exchangers (PHEs) used in the vegetable oil processing industry. The performance of these heat exchangers is limited by the heat transfer rate of the oil side and by the low thermal conductivity of the plate material. The study starts from a base case with vegetable oils cooled with water in plate heat exchangers, all with a chevron angle of 30° and a different number of channels and plate transfer areas. The change in one geometrical characteristic of the plates, namely the chevron angle, from 30° to 45° then to 60°, led to a significant increase in the overall heat transfer coefficients of 16.0% when changing from 30° to 45° and of 28.1%, on average, when increasing the angle from 45° to 60°. This is a significant increase accompanied by a rise in the pressure drops of the circuits, but the values are acceptable since they do not exceed 1 bar on the oil circuit and 1.4 bar on the cold fluid circuit, respectively. The use of Fe₃O₄–SiO₂/Water hybrid nanofluids with concentrations of 0.5% v/v, 0.75% v/v, and 1% v/v were investigated to replace the cooling water. An increase of 2.2% on average was noticed when using the 1% v/v nanofluid comparatively with water, which is not large but adds to the chevron angle increase. A supplementary 2.6% increase is possible by changing the manufacturing material for plates with aluminum alloy 6060 and also by adding to the performances obtained by previous modifications. The total increase for all sets of modifications can increase the performance by 34.2% on average. Thus, for the design of new PHEs, miniaturization of the equipment becomes possible.

The study investigates, by calculations, some ways to improve the thermal efficiency of plate heat exchangers used in the vegetable oil processing industry. The performance of these heat exchangers is limited by the heat transfer rate on the oil side and by the low thermal conductivity of the plate material. The study starts from a base case with vegetable oils cooled with water in plate heat exchangers, all with chevron angle 30o and different number of channels and plate transfer area. The change of one geometrical characteristic of the plates, namely the chevron angle, from 30o to 45o then to 60o, led to important increasing of the overall heat transfer coefficients, by 16.0 % when changing from 30o to 45o and by 28.1% on average when increasing the angle from 45o to 60o. This is an important increase accompanied by the rise of the pressure drops in circuits, but the values are acceptable since not exceeding 1 bar on oil circuit and 1.4 bar on cold fluid circuit, respectively. The use of Fe3O4–SiO2/Water hybrid nanofluids with concentration 0.5% v/v, 0,75% v/v and 1% v/v were investigated, to replace the cooling water. An increase by 2.2% on average was noticed when using the 1% v/v nanofluid comparatively with water, which is not large but adds to the chevron angle increasing. A supplementary 2.6% increase is possible by changing the manufacture material for plates with aluminum alloy 6060, also adding to the performances obtained by previous modifications. The total increase for all the set of modification can increase the performance by 34.2% on average. Thus, for the design of new PHEs, the miniaturization of the equipment becomes possible.

Biobased greases are derived from renewable resources, are considered more environmentally friendly, and offer comparable performance to petroleum-based greases. In this study, lubricating greases from frying cooking oils were prepared, thus valorizing waste in order to obtain sustainable and environmentally friendly products. Twelve batches (500 g each) were produced from sunflower and palm frying oils, with 20% by weight calcium/lithium stearate soaps prepared in situ and filled with 15 wt.% cellulose or lignin sulfate. The greases were rheologically characterized. Their consistency was assessed by the penetration test performed before and after working the greases. Dropping point determinations offered information about the stability at higher temperatures, and oil bleeding tests were performed. The average values of the friction coefficient (COF), the contact resistance, and the wear scar diameter were measured through mechanical tests. The greases prove to be comparable to those obtained from mineral oils, with good rheological properties, soft consistency, and good antiwearing behavior, e.g., in open or total-loss lubricating systems, like in open gears and certain food processing machinery; they are thermally stable andprone touse in low-loading working mechanisms.

Biobased greases are derived from renewable resources, being considered more environmentally friendly, and offering comparable performance with petroleum-based greases. In this study, lubricating greases from frying cooking oils were prepared, thus valorizing waste, in order to obtain sustainable and environmentally friendly products. 12 batches (500 g each) were produced from sunflower and palm frying oils, with 20% by weight calcium/ lithium stearate soaps prepared in situ, and additivated with 15% wt. cellulose or lignin sulphate. The greases were rheologically characterized. Their consistency was assessed by the penetration test, performed before and after working the greases. Dropping point determinations offered information about the stability at higher temperatures, and oil bleeding tests were performed. The average values of the friction coefficient (COF), the contact resistance and the wear scar diameter were measured, through mechanical tests. Additivated greases prove to be comparable with those obtained from mineral oils, with good rheological properties, soft consistency and good antiwearing behavior, e.g.in open or total- loss lubricating systems, like in open gears and certain food processing machinery; they are thermally stable, and prone for use in low-loading working mechanisms.

Bioethanol and dimetyl carbonate (DMC) are considered alternative fuels and additives to the synthesis compounds used now, since bioethanol is a biofuel and dimethyl carbonate (DMC) is non-toxic, biodegradable and can be produced in a cleaner way. In this study, the effect of adding dimethyl carbonate (DMC) and ethanol to gasoline on the volatility was investigated. The volatility was the main goal of this research but also, the effect on the antiknock properties was studied. Mixtures of gasoline with DMC or with bioethanol were prepared in different proportions of additive: 3%, 6% and 9% v/v. Additionally, mixtures with 3% v/v ethanol plus 3% or 6% v/v DMC, and3% DMC plus 6% v/v ethanol were prepared. For the volatility evaluation, the ASTM distillation curve and vapor pressure of these mixtures were determined experimentally in order to predict the performance of the resulting fuels. When adding oxygenated compounds, the increase in vapor pressure was proportional to the additive quantity. Additionally, modifications of the ASTM distillation curves were observed, with these indicating the formation of minimum boiling point azeotropes and the corresponding increase in volatility, with good effect on the ease of ignition in the engine. Based on the experimental results, the vapor lock index VLI, drivability index DI and vapor–liquid ratio temperature T_(V/L=20) were calculated to quantify the volatility. The experimental results showed that gasoline mixtures with these oxygenated compounds show a significant increase in antiknock properties. Thus, for mixtures with ethanol, the research octane number (RON) increases by up to 2.2 units and the motor octane number (MON) increases by up to 1.2 units. Gasoline mixtures with DMC have another behavior: RON increased by up to 1.5 units, while the MON value increased by up to 2.5 units. For an initial gasoline with RON = 94.7 and MON 84.7, these increases are important and make the difference by exceeding the RON = 95 limit. Adding dimethyl carbonate to gasoline–ethanol blends improves the sensitivity of the fuel.

Many models for accurately predicting the performance of gasket plate heat exchangers were developed in the last decades, grouped in three categories: empirical, semi-analytical or theoretical/numerical, with the view to saving materials and energy through correct design of industrial equipment. This work addresses one such model, namely Lévêque correlation modified by Martin and by Dović, which is promising due to the correct assumption of the flow in sine duct channels and the consideration of energy losses caused by flow reversal at plate edges and the flow path changing when entering the chevron angle. This model was validated by our own experimental data under industrial conditions for vegetable oils processing, both in laminar flow (Re = 8–42) and fully developed turbulent flow (Re = 446–1137). Moreover, in this study, particular values for constants/parameters of the model were determined for the corrugation inclination angle relative to vertical direction equal to 30°. Through statistical analysis, this study demonstrates that this particularized form of the generalized Lévêque correlation can be used with confidence.

The aim of this study is to evaluate the potential of dried Cystoseira barbata alga for ethanol production through alcoholic fermentation. The influence of the main factors affecting the fermentation are studied in the frame of a 23 factorial experimental plan. The main factors influencing the process are the fermentation temperature (t from 25 °C to 35 °C), the solid to liquid ratio (S/L from 0.040 g/g to 0.080 g/g), and the cellulase ratio (R from 8 U/g d.m to 16 U/g d.m.). The maximum volatile compounds yield of 0.2808 g/g d.m and ethanol yield of 0.0158 g/g d.m were favored by the following experimental conditions: process temperature of 35 °C, solid to liquid ratio of 0.0415, and enzyme ratio of 16 U/g d.m. A statistical model was used to correlate the product yield with the process factors. Additionally, 19 interesting bioactive compounds were found in the enzymatic hydrolysis and alcoholic fermentation broths which seem likely to maintain natural defence mechanisms against diseases and physical disorders.

Transesterification is a classical organic synthesis reaction with many uses in both laboratory and industrial applications. In this reaction, one ester is converted to another by the radical alkoxy exchange. In some cases, the transesterification process is more advantageous when used in the manufacturing of esters than their synthesis by direct esterification of the carboxylic acids with alcohols. Based on literature studies, a transesterification study coupled with the reactive distillation (RD) was performed in order to obtain isopropyl lactate (IPL) by methyl lactate (ML) with isopropanol (IPA). The independent variables studied were: the alcohol / methyl lactate molar ratio (R), the number of the theoretical stages in the fractionation zone (NTS) and the reactive distillation column reflux ratio (RR). The experimental matrix was set for a 23 factorial experiment with three variables at two levels: R = 2 and 4; NTS = 1.7, respectively 2.4 and RR = 2 and 7. A linear mathematical model was proposed to correlate the methyl lactate conversion with all three variables. The model is reliable as the statistical analysis proved.

In this paper, we present comparatively different methods of pressure drop calculation in the gasket plate heat exchangers (PHEs), using correlations recommended in literature on industrial data collected from a vegetable oil refinery. The goal of this study was to compare the results obtained with these correlations, in order to choose one or two for practical purpose of pumping power calculations. We concluded that pressure drop values calculated with Mulley relationship and Buonopane & Troupe correlation were close and also Bond’s equation gave results pretty close to these but the pressure drop is slightly underestimated. Kumar correlation gave results far from all the others and its application will lead to oversize. In conclusion, for further calculations we will chose either the Mulley relationship or the Buonopane & Troupe correlation.