Fueling a stationary direct injection diesel engine with diesel-used palm oil–butanol blends – An experimental study
Introduction
Internal combustion engines, especially diesel engines occupy a major part in world’s transport and agricultural sector. Diesel engines fueled by fossil diesel fuel are more rigid and fuel efficient than petrol engines. Because of high cost, increased pollution and faster depletion of the fossil fuel, much research has been diverted towards finding and utilizing alternate fuels for diesel engines. A fuel replacing diesel fuel must be readily available, cheap, clean and renewable in nature. Biomass based fuels offers more benefits and are more promising and have wide range of applicability in rural and urban areas [1], [2]. Vegetable oils have fuel property comparable to diesel fuel and are considered as a suitable alternative for diesel fuel. Edible oils are more costly while non-edible oils, animal fats and used oils are cheaper and are more viscous. The viscosity of these oils can be reduced and can be made equivalent to diesel fuel by blending, transesterification and pyrolysis [3]. Transesterification process which uses expensive chemicals and certain process conditions has been regarded as the best route to reduce the viscosity of vegetable oils, but if poor quality feedstocks like used oils and animal fats are used certain pretreatments are necessary, which makes the process more complex [4].
Many researchers have successfully utilized vegetable oils in diesel engines. Shahid and Jamal [5] have critically reviewed the results of engine tests carried out by researchers on vegetable oil based fuels. Most of the researchers have utilized sunflower oil, rapeseed oil, cottonseed oil, soybean oil, palm oil and peanut oil as fuel for diesel engines in different modes. The summarized results show that palm oil has the greater tendency to substitute diesel fuel. Blends containing 20% and 50% vegetable oil has been reported to produce reduced emissions and reduced engine problems. Ramadhas et al. [6] have listed out the advantages, challenges and technical difficulties in using vegetable oil based fuels in diesel engines. Almeida et al. [7] conducted experiments on a diesel generator with preheated palm oil (40 °C & 100 °C). During their study they obtained reduced NOX emission and increased CO, HC, CO2 emissions. Canakci et al. [8] conducted experiments with crude sunflower oil preheated to 75° C in an IDI (Indirect Injection) diesel engine. They observed similar combustion profile for diesel fuel and crude sunflower oil. Reduced CO2, Smoke and HC emissions and increased brake thermal efficiency was noticed for preheated crude sunflower oil while no report was given by them on NOX emission. Hebbal et al. [9] noticed reduced emissions and increased performance with blend containing 50% deccan hemp oil and 50% diesel fuel. Fish oil obtained as byproduct from fish processing industries blended with marine gas oil has been successfully utilized as fuel in diesel engine [10].
Waste frying oils have also been tested for their potential as alternate fuel in many parts of the world because of their huge availability and low cost. Knothe and Steidley [11] studied the variation of acid value, viscosity, fatty acid profile for used oils and fresh oils. They reported increased acid value, increased viscosity, increased cetane number, reduced linoleic acid content, inferior low temperature properties and higher oxidative stability for used oils. Direct utilization of preheated (70 °C) waste cooking oil showed reduced brake thermal efficiency and increased CO, NOX and SO2 emissions [12]. Bari et al. [13] found that lower calorific value and head loss across the fuel filters are the main cause for reduced brake power output with waste cooking oil as fuel. Bari et al. [14] noticed increased NOX emission, increased thermal efficiency and reduced CO emission with advanced injection timing, and reduced NOX emission during retarded injection timing while using waste cooking as fuel in diesel engine. In India, Pugazhvadivu and Jeyachandran [15] noticed improved thermal efficiency, improved brake specific energy consumption, decreased smoke and CO emission with waste frying oil preheated to 135 °C.
Generally, combustion of vegetable oil based fuels produces higher NOX emission [16]. NOX emission can be reduced by emulsification of fuels with water and alcohols. Nanthagopal and Subbarao [17] obtained reduced emissions with emulsions of waste oil–diesel fuel mixture containing 20% water. Effect of addition of 10% methanol with waste cooking oil biodiesel in blended mode and fumigation mode was studied by Cheng et al. [18]. They reported increased brake thermal efficiency and reduced emission with blended mode while methanol added in fumigation mode resulted in increased CO, HC, NO2 and particulate emissions. Ethanol added in fumigation mode also resulted in increased CO, HC and particulate number [19]. Ethanol (5% and 10 vol%) and diesel fuel blends stabilized by a special type of emulsifier showed decreased smoke and increased HC emission, whereas brake thermal efficiency, NOX, and CO emission for both diesel fuel and blends were found to be similar [20].
Among alcohols, butanol has been gaining more importance in the recent years because of its improved properties compared to ethanol. Butanol is mainly produced from petroleum products like propylene. Due to increased cost of petroleum products and larger availability of agricultural residues research has been diverted towards biobutanol production. ABE (Acetone–Butanol–Ethanol) fermentation process is employed for biobutanol production from agricultural residues including lignocellulose materials. Bacteria like Clostridium beijerinckii, Clostridium acetobutylicum, Escherichia coli, Saccharomyces cerevisae and algae have been successfully utilized for biobutanol production [21]. Jin et al. [21] critically reviewed the benefits and directions of using butanol as fuel in Internal Combustion engines. Stoeberl et al. [22] optimized the production of biobutanol from waste-whey using different strains of Clostridia. They noticed reduced HC, acrolein emissions and higher NOX emissions at high load with increasing concentration of biobutanol in biobutanol–rapeseed oil fuel blends. Diesel–butanol blends containing butanol (8, 16 and 24 vol%) and Isobutanol–diesel fuel blends containing isobutanol (5–20 vol%) resulted in reduced exhaust temperature and reduced CO, NOX and smoke emissions [23], [24]. Carbonyl emissions from butanol–diesel blends were found to be lower than bioethanol–diesel blends [25]. The physical properties of butanol–diesel blends and their organic air toxic emissions were reviewed by Giakoumis et al. [26]. Lujaji et al. [27] noticed reduced smoke and CO2 emissions for blends containing Croton oil–diesel–butanol at high loads. They noticed increased CO and HC emissions throughout the test.
In the near future, the opportunity for setting up biobutanol plants in India is high because of increased availability of agricultural residues and in addition, India being a tourist hub, a large number of restaurants and hotels are being opened throughout the country which serves as a great potential for waste oils. Palm oil is widely used for cooking in southern part of Tamilnadu, India because of its cheaper cost. Palm oil after usage is usually dumped outside but it could be reused as fuel there by a considerable amount of diesel fuel could be saved. It could be seen from the literature survey that no studies have been carried out by blending used palm oil, butanol and diesel which remains as a gap. Hence, in the present investigation the potential of Diesel-Used Palm Oil-Butanol blends as fuel for stationary constant speed DI diesel engine was studied and their performance, emission and combustion characteristics were compared with diesel fuel.
Section snippets
Preparation of fuel blends
Used palm oil used in this study was collected from different restaurants, hotels and hostels in Tirunelveli region of Tamilnadu, India. Butanol (99.9% pure) analytical grade was purchased from Spectrum chemicals and reagents, Edayar, Cochin. Diesel fuel was purchased from a local fuel station at Tirunelveli. The chemical analysis of used palm oil was carried out at National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum (Council of Scientific & Industrial Research
Fuel property of the blends
The chemical properties of used palm oil are shown in Table 3 The fuel properties of the test fuels are shown in Table 4. Viscous fuel leads to reduced cone angle of fuel spray and poor atomization of fuel but the addition of diesel and butanol to used palm oil has considerably improved the viscosity and hence better spray characteristics can be obtained with these blends [32]. The kinematic viscosity of blend containing 15% butanol was closer to diesel fuel. Calorific value of the blends was
Conclusion
Improved fuel properties have been obtained by blending used palm oil with butanol and diesel fuel. Diesel engine operated smoothly and no knocking was noticed throughout the test. Higher BSFC and lower BTE were noticed for the blends because of their lower calorific value. BTE of the blends increased with increasing butanol content in the blends because of improved combustion caused by the presence of oxygen molecule in butanol. CO, NOX emissions and smoke opacity of the blends decreased with
Funding acknowledgement
This research received no specific grant from any funding agency in the public, commercial or non-profit sectors.
Acknowledgements
The authors wish to express their appreciation to D.R. Soban Kumar and Dr. A. Sundaresan of NIIST, Trivandrum and Management of NEC, Kovilpatti for providing facilities to carry out the work. Thanks are extended to Mr. Laxmanan of I.C Engine Laboratory, Chennai.
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