Abstract
The present paper investigates the feasibility of using acetone (ACE) in triple blends with fossil diesel (D) and straight vegetable oils (SVOs) as alternative fuel for diesel engines. In this respect, ACE is selected as an oxygenated additivedue to its favorable propertiesto be mixed with vegetable oils and fossil diesel. In fact, the very low kinematic viscosity allows reduces the high viscosity of SVOs. ACE’s oxygen content, low autoignition temperature, and very low cloud point and pour point values highlight its possibilities as an additive in D/ACE/SVO triple blends. Moreover, ACE can be produced through a renewable biotechnological process, an acetone–butanol–ethanol (ABE) fermentation from cellulosic biomass. The SVOs tested were castor oil (CO), which is not suitable for human consumption, and sunflower oil (SO), used as a standard reference for waste cooking oil. The viscosity measurement of the ACE/SVO double blend was considered crucial to choose the optimum proportion, which better fulfilled the specifications established by European standard EN 590. Moreover, some of the most significant physicochemical properties of D/ACE/SVO triple blends, such as kinematic viscosity, cloud point, pour point, and calorific value, were determined to assess their suitability as fuels. The blends were evaluated in a conventional diesel generator through the study of the following parameters: engine power, smoke emissions, and fuel consumption. Despite the low calorific value of ACE limits its ratio in the mixtures due to engine knocking problems, the experimental results reveal an excellent performance for the blends containing up to 16-18% of ACE and 22-24% of SVO. These blends produce similar engine power as to fossil diesel, but with slightly higher fuel consumption. Considerable reductions in emissions of air pollutants, as well as excellent cold flow properties are also obtained with these triple blends. In summary, the use of these biofuels could achieve a substitution of fossil diesel up to 40%, independently on the SVO employed.
Highlights
In accordance with the processes initiated in the last decade by many countries to reduce anthropogenic greenhouse gas (GHG) emissions [1], and despite the increased effort in the introduction of vehicles that incorporate electric or hydrogen engines, the gradual replacement of fossil fuelsMolecules 2020, 25, 2935; doi:10.3390/molecules25122935 www.mdpi.com/journal/moleculesMolecules 2020, 25, 2935 by biofuels is revealed as an imperative requirement, in order to accomplish the objectives set by international agreements as well as to ensure energy security [2,3].Straight vegetable oils have become a potential alternative to attain a viable energy transition since they can be obtained from living plant sources, making them renewable and available biofuels
The kinematic viscosity values of acetone/sunflower oil and acetone/castor oil blends are shown in ACE to reduce the viscosity of oils, mainly castor oil
Among the different ACE/straight vegetable oils (SVOs) blends tested, it was found that the blends that fulfil with the international fuel standards (2.0–4–5 cSt) are the ACE/ sunflower oil (SO) 40/60 and the ACE/ castor oil (CO) 45/55
Summary
Straight vegetable oils have become a potential alternative to attain a viable energy transition since they can be obtained from living plant sources, making them renewable and available biofuels. Their high viscosity generates poor fuel atomization, leading to carbon deposition on the injector as a consequence of an incomplete combustion. Most vegetable oils exhibit kinematic viscosity values from 10 to 17 times greater than diesel fuel, even far superior in the case of castor oil, which exhibits a viscosity value of 226.2 centistokes (cSt) For this reason, engines of current vehicle fleets (more than one billion) cannot directly operate on triglycerides as drop-in biofuel. Many researchers have developed different methods to transform these SVOs, such as pyrolysis, micro-emulsification, dilution, and transesterification [4]
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