• Energy Research

In this study, a novel low power, high frequency piezoelectric-based ultrasonic reactor was developed and evaluated for intensifying the transesterification process. The reactor was equipped with an automatic temperature control system, a heating element, a precise temperature sensor, and a piezoelectric-based ultrasonic module. The conversion efficiency and specific energy consumption of the reactor were examined under different operational conditions, i.e., reactor temperature (40‒60 °C), ultrasonication time (6‒10 min), and alcohol/oil molar ratio (4:1‒8:1). Transesterification of waste cooking oil (WCO) was performed in the presence of a base-catalyst (potassium hydroxide) using methanol. According to the obtained results, alcohol/oil molar ratio of 6:1, ultrasonication time of 10 min, and reactor temperature of 60 °C were found as the best operational conditions. Under these conditions, the reactor converted WCO to biodiesel with a conversion efficiency of 97.12%, meeting the ASTM standard satisfactorily, while the lowest specific energy consumption of 378 kJ/kg was also recorded. It should be noted that the highest conversion efficiency of 99.3 %, achieved at reactor temperature of 60 °C, ultrasonication time of 10 min, and alcohol/oil molar ratio of 8:1, was not favorable as the associated specific energy consumption was higher at 395 kJ/kg. Overall, the low power, high frequency piezoelectric-based ultrasonic module could be regarded as an efficient and reliable technology for intensifying the transesterification process in terms of energy consumption, conversion efficiency, and processing time, in comparison with high power, low frequency ultrasonic system reported previously. Finally, this technology could also be considered for designing, developing, and retrofitting chemical reactors being employed for non-biofuel applications as well.

Due to the fast fossil fuel depletion and at the same time global warming phenomenon anticipated for the next coming years, the necessity of developing alternative fuels e.g. biofuels (i.e. bioethanol, biodiesel, biogas and etc.) has turned into an important concern. Recently, the application of the bio-solvency properties of biodiesel for recycling waste polymers has been highlighted. However, the impact of polymer dissolution on cold flow characteristics of biodiesel was never investigated. The present study was set to explore the impact of different solvents in stabilizing biodiesel-polymer solution. Among them, acetone was proved to be the best fuel stabilizer. Subsequently, cold flow characteristic i.e. cloud point, of the biodiesel-polymer-acetone fuel was found to have improved (decreased) due to the inclusion of acetone. Finally, flash point analysis of the fuel blends containing acetone was done to ensured high safety of the fuel blend by dramatically increasing the flash point values of biodiesel-polymer fuel blends.

Abstract This study was devoted to introducing and experimenting a new waste-derived oxygenated additive, i.e., ethylene glycol diacetate on performance and emission characteristics of a diesel engine fueled with diesel/biodiesel blends. Mineral diesel and its blends with 5 and 20 vol% biodiesel were used in the engine test runs. These fuel blends were doped with ethylene glycol diacetate at three volumetric levels in the range of 1–3%. The engine was run under engine load conditions varying from idle to full load operation at a constant engine speed of 1500 rpm. Overall, the most appealing results were obtained when diesel fuel dosed with 3 vol% ethylene glycol diacetate was combusted under moderate engine load conditions. This oxygenated fuel blend could result in a significant mitigation in both nitrogen oxides and carbon dioxide emissions but could lead to an unfavorable increase in unburned hydrocarbon emissions in comparison with the additive-free diesel fuel. More specifically, nitrogen oxides and carbon dioxide emissions were reduced by 1.9–4.3 and 1.6–3.1 times, respectively, while unburned hydrocarbon emissions for the selected fuel blend under moderate engine loads were increased by 1.9–3.6 times. The carbon monoxide emission for this fuel blend was comparable with that of neat diesel. Furthermore, the significant reductions in nitrogen oxides and carbon dioxide emissions were achieved with a trivial drop in brake thermal efficiency of the engine (≈5%). As a conclusion, the developed oxygenated additive could be used for reformulating diesel fuel with the aim of substantially mitigating nitrogen oxides emissions.

Abstract Global application of biodiesel in the transport sector has rapidly expanded over the last decade, however, efforts to overcome its main shortcoming, i.e., increase in NOx emissions compared with diesel, are still underway. In light of that, parameters/strategies capable of mitigating biodiesel NOx emissions are of wide interest to further enhance the sustainability aspects of this green fuel. Among various options put to test, the use of fuel additives due to its simplicity and cost-effectiveness has attracted a great deal of attention. In this study, the mechanical shaft work produced by a diesel engine fueled with various diesel/biodiesel blends (B5 and B20) containing glycerol-derived triacetin was scrutinized from environmental viewpoint. Neat petro-diesel, B5, and B20 were also considered as control fuels. Two environmental evaluation methodologies, namely discrete emissions analysis and consolidated life cycle assessment (LCA) were considered to assess the impacts of fuel composition, engine speed, and engine load on the environmental burdens of the shaft work produced. According to the results obtained, the outcomes of both methods considered herein were profoundly affected by engine load and speed. Even though triacetin inclusion into both B5 and B20 profoundly affected the outcomes of emissions analysis, its application did not lead to any spectacular differences in the results of LCA method compared with petro-diesel. More specifically, triacetin incorporation into fuel blends neutralized the unfavorable impacts of biodiesel addition in terms of NOx emissions. However, incorporating triacetin into diesel/biodiesel blends in general did not profoundly mitigate the environmental impacts of the shaft work produced in terms of LCA damage categories as well as the total environmental impacts. Overall, using triacetin as combustion improving agent did appear to be an efficient strategy from the LCA viewpoint considering the current production technologies. In addition, LCA approach was found to be more a comprehensive decision-making approach compared with discrete emissions analysis for evaluating the environmental impacts of the shaft work produced by internal combustion engines.

Abstract Exergy analysis of a DI diesel engine running on several biodiesel/diesel blends (B5) containing various quantities of expanded polystyrene (EPS) was carried out. Neat diesel and B5 were also investigated during the engine tests. The biodiesel used was produced using waste oil extracted from spend bleaching earth (SBE). The experiments were conducted to assess the effects of fuel type, engine speed, and load on thermal efficiency, exergetic parameters, and sustainability index of the diesel engine. The obtained results revealed that the exergetic parameters strongly depended on the engine speed and load. Generally, increasing engine speed remarkably decreased the exergy efficiency and sustainability index of the diesel engine. However, increasing engine load initially enhanced the exergy efficiency and sustainability index, while its further augmentation did not profoundly affect these parameters. The maximum exergy efficiency and sustainability index of the diesel engine (i.e. 40.21% and 1.67, respectively) were achieved using B5 containing 50 g EPS/L biodiesel. Generally, the approach presented herein could be a promising strategy for energy recovery from polymer waste, emissions reduction, and performance improvement. The findings of the present study also confirmed that exergy analysis could be employed to minimize the irreversibility and losses occurring in modern engines and to enhance the sustainability index of combustion processes.

A diesel engine running on diesel/biodiesel mixtures containing ethylene glycol diacetate (EGDA) was investigated from the exergoeconomic and exergoenvironmental viewpoints. Biodiesel was mixed with petrodiesel at 5% and 20% volume ratios, and the resultant mixtures were then doped with EGDA at 1-3% volume ratios. The exergetic sustainability indicators of the engine operating on the prepared fuel formulations were determined at varying engine loads. The indicators were selected to support decision-making on fuel composition and engine load following thermodynamic, economic, and environmental considerations. The engine load markedly affected all the studied exergetic parameters. The highest engine exergetic efficiency (39.5%) was obtained for petrodiesel doped with 1 v/v% EGDA at the engine load of 50%. The minimum value of the unit cost of brake power exergy (49.6 US$/GJ) was found for straight petrodiesel at full-load conditions, while the minimum value of the unit environmental impact of brake power exergy (29.9 mPts/GJ) was observed for petrodiesel mixed with 5 v/v% biodiesel at the engine load of 75%. Overall, adding EGDA to fuel mixtures did not favorably influence the outcomes of both exergetic methods due to its energy-intensive and cost-prohibitive production process. In conclusion, although petrodiesel fuel improvers such EGDA used in the present study could properly mitigate pollutant emissions, the adverse effects of such additives on thermodynamic parameters of diesel engines, particularly on exergoeconomic and exergoenvironmental indices, need to be taken into account, and necessary optimizations should be made before their real-world application.

Integrated environmental analysis using life cycle assessment for different fuel blends used in a single-cylinder diesel engine was performed to select the most eco-friendly fuel blend. More specifically, the inventory data in support of the integrated environmental analysis of water-emulsified 5% biodiesel/diesel blends (B5) containing different levels of carbon nanoparticles (i.e., 38, 75, and 150 µM) as a novel fuel nanoadditives at a fixed engine speed of 1000 rpm and four different engine loads (i.e., 25, 50, 75, and 100%) are presented. Neat diesel, B5, and B5 containing water (3 wt.%) were used as controls. Raw data related to the production and combustion of fuel blends were experimentally collected. Industrial (i.e., experiments at large scale) and laboratory (i.e., experiments at small scale) data were used for fuel blends production while experimental data obtained by engine tests were used for the combustion stage. Then raw data were processed with the IMPACT 2002+ methods by using the SimaPro software and EcoInvent database and were then converted into environmental impacts. Accordingly, six supplementary files including the inventory data on integrated environmental analysis of the different fuel blends are presented (Supplementary Files 1-6). The data could be applied for integrated environmental analysis in order to avoid subjective weighting of combustion parameters for selecting the most eco-friendly fuel blend for use in diesel engines. More specifically, by developing a single score indicator obtained through conducting integrated combustion analysis, comparison of various fuel blends is largely facilitated.